Compendium of Histology 
TWENTY-FOUR LECTURES 
BY 
HEINRICH FREY 
m 
PROFESSOR OF MEDICINE IN THE UNIVERSITY OF ZURICH. 
®ranslate& from li)* (Eterman, iji permission of Hje ilutfjor 
BY 
GEORGE R. CUTTER, M.D. 
SURGEON NEW YORK EYE AND EAR INFIRMARY; OPHTHALMIC AND AURAL SURGEON TO THE 
ST. CATHERINE AND WILLIAMSBURGH HOSPITALS; SECRETARY OF THE NEW YORK 
OPHTHALMOLOGICAL SOCIETY, ETC., ETC. 
ILLUSTRATED BY 208 ENGRAVINGS ON WOOD. 
THIRD EDITION 
NEWYORK 
G. P. PUTNAM’S SONS 
182 Fifth Avenue 
1879 Copyrighted by 
G. P. PUTNAM’S SONS, 
1876. TRANSLATOR’S PREFACE. 
The science of Histology has made rapid advances of late 
years. and many new facts have been acquired in this depart- 
ment. This will be readily appreciated by those who are 
familiar with the excellent and exhaustive text-books of 
Frey and Strieker. But many are intimidated by the very 
copiousness of such works. 
Even in Germany, where thoroughness is the great excel- 
lence, there is a demand for a compendium. That Professor 
Frey’s little book meets this want, is proved by its enormous 
sale and the favorable notices of the press. 
I hope that this translation may meet with the same kind 
reception as did that of our Author’s work on Microscopic 
Technology. 
GEORGE R. CUTTER, M.D., 
No. 228 East Twelfth Street, New York. 
August, 1876. TRANSLATOR’S PREFACE TO THE THIRD EDITION. 
It has afforded me no small gratification that my 
translation of Professor Frey’s work should have met 
with so very favorable a reception, both by the profes- 
sion at large and by the medical press. Though brought 
into direct competition with several very able and well 
established works on the same subject, it has been 
adopted as a text-book by the more prominent colleges 
of Great Britain, the United States and Japan. 
It was found necessary to make but very slight 
changes in the present edition. 
George R. Cutter, M.D., 
No. 312 Seconp Ave., New York. 
January, 1878. AUTHOR’S PREFACE. 
Histology has, in the course of a few decades, triumphantly 
won its field ; it has become an integral part of medical 
studies. The hand-books have necessarily become constantly 
more voluminous, in consequence of the immense wealth of 
materials. 
A short compend of the most essential facts is desirable for 
students and practicing physicians. I have often heard this 
wish expressed. 
May the attempt, which I herewith venture, be, therefore, 
indulgently received. The defects of this little book are very 
well known to the author. 
H. FREY. 
Zurich, July 10th, 1875. CONTENTS. 
PAGH 
Translator’s Preface iii 
PAGE 
Author’s Preface v 
FIRST LECTURE. 
General: the protoplasma, the cell, and its derivatives I 
Classification of the tissues.—Blood, lymph, chyle 2C 
SECOND LECTURE. 
THIRD LECTURE. 
The epidermis, or the epithelium 28 
The connective-substance group.—Cartilage, gelatinous tissue, reti- 
cular connective tissue, fat 41 
FOURTH LECTURE. 
FIFTH LECTURE. 
Connective tissue * 51 
Bone tissue ; 60 
SIXTH LECTURE. 
Dentine, enamel, lens tissue 73 
SEVENTH LECTURE 
Muscular tissue 75 
EIGHTH LECTURE. 
NINTH LECTURE. 
The blood-vessels 89 
The lymphatics and the lymphatic glands 102 
TENTH LECTURE. 
ELEVENTH LECTURE. 
The remaining lymphoid organs, with the spleen.—The so-called 
blood-vascular glands H2 CONTENTS. 
TWELFTH LECTURE. 
PAGE 
Gland tissue 128 
THIRTEENTH LECTURE. 
The digestive apparatus, with its glands T39 
Pancreas and liver 150 
FOURTEENTH LECTURE. 
FIFTEENTH LECTURE. 
The lungs 157 
SIXTEENTH LECTURE. 
The kidney, with the urinary passages , 163 
The female generative glands, the ovary with the efferent apparatus... 173 
SEVENTEENTH LECTURE. 
The male generative glands, the testicles with the efferent apparatus. 183 
EIGHTEENTH LECTURE. 
NINETEENTH LECTURE. 
Nerve tissue 192 
TWENTIETH LECTURE. 
The arrangement and termination of the nerve fibres 202 
TWENTY-FIRST LECTURE. 
The central organs of the nervous system, the ganglia, and the 
spinal cord.. 215 
TWENTY-SECOND LECTURE. 
The central organs of • the nervous system, continued—the medulla 
oblongata, and the brain 224 
The organs of sense—skin, gustatory, olfactory, and auditory ap- 
TWENTY-THIRD LECTURE. 
paratus 234 
TWENTY-FOURTH LECTURE, 
The organs of sense, continued—the eye 246 
Index 265 Compendium of Histology. 
FIRST LECTURE. 
GENERAL : THE PROTOPLASMA, THE CELL, AND ITS 
DERIVATIVES. 
A DEEP abyss separates the inorganic from the organic, 
the inanimate from the animate. The rock-crystal on the 
one side—vegetable and animal on the other ; how infinitely 
different the image ! 
Is it, then, many will inquire, possible to bridge over 
this gulf? We answer, not at the present time. It is, perhaps, 
reserved for future generations of men to fill up'this yawning 
chasm, by the aid of a more thorough knowledge of nature, 
and to comprehend the sphere of the material world as a 
unit. 
What, we ask further, is the primary beginning of the 
organic? 
An admirable English 
naturalist, Huxley, suc- 
ceeded, in the year 1868, 
in making a marvelous dis- 
covery. 
The bottom of our seas, 
at the most considerable 
depths, is covered over 
large tracts with a strange 
shiny substance. When 
this thing, called the ba- 
thy bins, is drawn up by the 
Fig. 1.—Bathybius. 2 
FIRST LECTURE. 
dredge, and placed under the microscope—under that instru- 
ment’which has conquered the mighty world of minuteness 
for natural science—a very peculiar image is presented to the 
astonished eye. 
We perceive a transparent jelly, with diminutive granules 
in its interior. We also frequently meet with small cor- 
puscles, surrounded by this, consisting of carbonate of lime. 
They look like our modern sleeve buttons. 
And this mass lives ! It changes from one shape to another 
in slow metamorphosis, exhibiting a constant, though sluggish 
restlessness. Separated portions present the same slow mu- 
tability, the same life. —- 
The mass formed by thisHJ.athybiusl is a nitrogenous carbon 
compound, distended in water, and of an extremely compli- 
cated chemical structure. It belongs to the group of albumin- 
ous bodies, and is called protoplasma. It coagulates in death, 
and also at a relatively slight elevation of temperature. The 
granules it encloses consist partly of coagulated albuminous 
substances, partly of fat; mineral substances are also not 
wanting. 
Leaving the dark deep, and turning to the sunny surface 
of the seas, we here meet with numerous small lumps of 
protoplasma, which 
show the same vital 
transformations, 
shooting out process- 
es, sometimes short, 
sometimes longer, and 
drawing them in 
again; such Is the 
protamoeba of our 
Fig. 2. These are the 
simplest organisms or forms of life. They increase by division. 
One of our most distinguished investigators, Haeckel, has 
called such a lowest being a cytode. 
Fig- 2.—Protamoeba. A, undivided : B, commencing, 
and C, completed division. 
We meet with similar organisms intermingled with these 
cytodes in the water ; as, for example, the amoeba (Fig. 8), THE FROTOPLASMA AND THE CELL 
3 
though in the interior of 
this constantly change- 
able protoplasma, to- 
gether with excavations 
{b)y and small foreign 
bodies {c), accidentally 
taken up from the neigh- 
borhood, a roundish 
structure with small 
punctiform contents (a), 
is found. The contained body bears the name of the kernel 
or nucleus ; the small bodies enclosed within the latter are 
called nucleoli. The entire creature has the significance of a 
simple naked cell. What service the nucleus renders the 
amoeba we are, at present, unable to say. We now leave 
these lowest creatures, and pass, at a bound, to the highest 
animal form—to examine the human body. Its parts have 
been called organs since the primitive days of medicine. They 
correspond to the separate pieces of one of our machines. It 
was also long since known that certain substances of our 
bodies, such as bone, cartilage, muscle, and nerves, were re- 
peated in all portions of the organism and, slightly or not at 
all changed, enter into the structure of the most different parts 
of the body. These substances, which may be compared to 
the different materials of which the machine is formed, were 
early known to be composed of still smaller parts. They were 
compared to the products of the loom, and designated as 
tissues. This name has been retained, and that branch of 
anatomical science which treats of these homogeneous parts, 
is called the science of tissues, or Histology. 
Fig. 3.—Amoeba ; a, nucleus ; l>, vacuoli; c% alimentary 
bodies taken in. 
On attempting, with the aid of the knife and scissors, to 
separate such tissues, we, at first, succeed very readily ; the 
fragments permit of a new division, and this may, perhaps, be 
repeated on those thus obtained. But at last—sometimes 
sooner, sometimes later—a period arrives when even the finest 
and sharpest tools become unserviceable ; they are too blunt, 
too coarse. 4 
FIRST LECTURE. 
Here, where the mechanical analysis terminates, the optical 
begins, by means of the microscope. The latter is an extra- 
ordinarily delicate one ; the fragment, which the anatomist’s 
scissors are unable further to divide, now proves to be infi- 
nitely compounded; it may still consist of thousands of the 
smallest elements. 
These elements are again, in their turn, cells or their 
derivatives. 
Thus, this structure, which forms in an independent manner 
the body of an amoeba, now constitutes our tissues, although 
in a very conditional independence. The cell has, therefore, 
entered into the, service of a mighty unity; it has to sub- 
ordinate and conform itself; nevertheless, the thing remains 
a living individual, comparable to the officer of a modern 
state department. As he fulfils his individual duty in the 
service and as a member of a great whole, so, also, does the 
small cell labor unremittingly until its death. 
It appears of interest that these very small living foundation- 
stones in the body of the higher animals always form cells, and 
that the cytodes of Haeckel have disappeared. 
We have just said that the cells of the human organism 
were very small. Their diameter varies, in fact, 
from 0.076, 0.0375, 0.0228 down to 0.0057 mm. 
Thus it becomes possible that a small particle 
of the substance of the body, about a cubic milli- 
metre, may contain an extraordinary multitude 
of them. It has been computed that such a 
particle of space of the human blood is capable 
of containing five million red cells, though it is 
true they only measure 0.0077 mm. 
The cells present very considerable variations. 
The latter are gained subsequently with the devel- 
opment of the body. In the earliest period of 
embryonic life they were all still very similar. 
The primitive form of a cell is that of a globe 
or of a body approximating a sphere. Thus ap- 
pear the cells d, e, g, bof our Fig. 4. The cell, also, from 
ceUsGwkTnucleus 
and protoplasma. THE PROTOPLASMA AND THE CELL. 
5 
which in a momentous manner the bodies of all the higher 
animals have proceeded,the ovum (Fig. 5), 
presents itself as an elegant spheroidal 
structure. 
From this primitive form two other 
forms, resulting from compression and 
adaptation, may be readily traced ; the 
tall, slender, or, as we say, cylindrical cell 
(Fig. 6, b), and the flattened. The latter 
finally assumes the form of a lamella or 
scale (Fig, 7). 
The bodies of other cells grow in two 
opposite directions, like processes. We 
thus obtain the spindle-shaped cell (Fig. 
4. c, f). When such processes are numer- 
ous and are also branched, a singular thing 
appears, the stellate cell (Fig. 8). 
Fig. 5.—Young ova, 
from the ovarium of a 
rabbit. 
Fig. 6.—Cylindrical cells from the human small 
intestine; 6, ordinary elements ; a, so-called 
Becher-cells. 
Fig. 7.—-Epithelial scales from the 
human mouth. 
The quantity of the cell protoplasma, and hence 
the magnitude of the body of the cell, is subject 
to great variation (Fig. 4). 
While protoplasma occurs originally in every cell, 
it may subsequently be replaced by other materials. 
Thus, in the cells of our Fig. 7, a harder, more water- 
less substance keratine—has been substituted. 
Other cells obtain a lodgment of dark, black pig- 
ment granules of great chemical resistance (Fig. 9). 
These dark molecules are called melanin. One of the 
most widely diffused structures of the human body is the 
Fig. B.—Stel- 
late cell from 
a lymphal ic 
gland. 6 
FIRST LECTURE. 
colorless globular lymphoid cell. It also occurs in the blood 
(Fig. 10, d), and is at last transformed into a disc-shaped 
Fig. ip.—Disc-shaped cells 
of human blood, a, a, a. At 6, 
half from the side ; at r, seen 
entirely from the side ; d, lym- 
phoid cell. 
Fig. 9.—Pigmented connective- 
tissue corpuscle (stellate pigment 
cell from the mammalial eye). 
structure {a, b, c), whose cell body contains a homogeneous red 
substance, of an extremely complicated chemical constitution, 
hmmoglobin. Other cells subsequently become reservoirs 
of fatty matters, often in a high degree. 
We now pass to the kernel or nucleus. Its medium 
diameter may be assumed to be from 0.007 to 0.005 mm. It is 
originally a vesicle (Figs. 4 and 5), that is, a structure en- 
veloped by a delicate covering. Nucleoli occur singly, double, 
or in greater number (Auerbach). Attention has very recently 
been directed to a circle of small molecules deposited between 
the nucleolus and the wall of the nucleus, and called the 
granule-sphere. 
The nucleus may subsequently lose this vesicular character 
and assume a different arrangement. Thus it not unfrequently 
changes, later, into a firmer, more homogeneous structure 
(Fig. 7), or becomes granular. Should the growing cell be- 
come considerably lengthened, the nucleus also frequently 
assumes a more elongated form. 
As a rule, the nucleus remains a definite, tolerably con- 
servative constituent of the cell. Nevertheless, we meet with 
others of the latter which have lost by age the nucleus of an 
earlier period of life. Such non-nucleated cells form the most THE PROTOPLASMA AND THE CELL. 
7 
external layers of the epidermis covering our skin (Fig. n)> 
Other cells (Fig. 12) contain, in complete contrast, double 
nuclei. Their signification will occupy us later. Very singu- 
lar structures, of irregular form, and, in part, of extraordinary 
Fig. ii.—Non-nucleated cells 
of the epidermis. 
Fig. 12.—Cells with double nuclei; 
a, from the liver, b from the choroid 
of the eye, and c, from a ganglion. 
Fig. 13.—Multi-nuclear giant 
cell from the bone marrow of the 
new-born. 
dimensions, occur in the bone marrow, and also in many ab- 
normal tumors. They have been called myeloplaxes and 
giant cells (Fig. 13). Their larger specimens may contain a 
multitude of nuclei. 
In these two things, the protoplasm and the nucleus, we 
have become acquainted with the essential constituents of 
the cell. 
The youthful cell shows nothing further. 
Later, it may become different. The surface of the cell 
body hardens, or from this vicinity is formed a firmer envel- 
oping layer. Thus we have, when this remains very thin, 
what is called a cell membrane, while to a thicker covering is 
given the name of the cell capsule. 
We just said, “ this may occur ; ” but it need not. At the 
present time we occupy a standpoint different from that of 8 
FIRST LECTURE. 
our predecessors. Towards 1840, Schwann, the founder of 
modern histology, erroneously ascribed the cell membrane as 
a third essential constituent to every cell, so that the cell 
would have two concentric envelopes, that of the vesicular 
nucleus and the external one of the cell body. The still fre- 
quently used name of “cell contents” is derived from that 
period. 
It is impossible for any one to demonstrate where such a 
membrane really begins ; that the surface of a cell protoplasm 
in contact with the surrounding objects may, and, in fact, often 
does become more solid, would not be denied by any one ac- 
quainted with the great changeability of protoplasm. We 
may only speak of a cell membrane when we are able to iso- 
late the thing, and thus place it with certainty before the mi- 
croscopist’s eye. A smooth, sharp, dark line of demarcation 
on a possibly strongly changed cell corpse gives us neverthe- 
less no proof of a membrane. We shall find later, it is true, that 
the isolation of an envelope on a fat 
cell, for instance, is very easy. Tak- 
ing, by way of example, our Fig. 14, 
the lateral surfaces of the cylindrical 
structure a are provided with a cover- 
ing which is certainly recognizable. 
Above, at the broad part, it is other- 
wise. Here the cell membrane is 
wanting; and a thicker covering piece, 
permeated by very delicate longitudi- 
nal canals, overlays the protoplasm. We perceive a cell cap- 
sule on the mammalial ovum (Fig. $,2), while a more youthful 
ovulum (1) still appears membraneless. In cartilage tissue? 
are quite ordinary occurrences ; we shall there 
be more intimately occupied with them. 
frOTio'theTma}inhues 
jSh'riie thickenedI'"and’Lmewhat 
elevated seam, which is permeated 
by porous canals; b, view of the 
cells from above, whereby the ap- 
ertures of the porous canals appear 
as small points. 
We proceed further; we inquire after the life of the cell. 
A life we have already ascribed to it, although a limited one 
in the service of the whole. 
Can this, however, be demonstrated ? This question is 
asked by many. We answer, yes. We recall to mind that THE PROTOPLASMA hND THE CELL. 
9 
which we remarked above concerning the bathybius and 
protamoeba, that constant mutability, that vital power of 
contraction of the protoplasm. Numerous cells of our body, 
as, for instance, the lymphoid cells (Fig. io, d), show the 
same, and possess an “ amoeboid ” change of shape. 
When, by an artificial experiment, we produce an inflam- 
mation of the eyeball of a frog, instead of the clear aqueous 
of the normal condition, the contents of the anterior chamber 
soon appear more cloudy. In this less transparent fluid, we 
now meet with innumerable lymphoid cells which, in this case, 
are called pus corpuscles. 
If we subject these cells in a 
conservative manner to micro- 
scopical examination, we rec- 
ognize the vital metamor- 
phosis, already familiar to us, 
of the protoplasm. Every 
shape which our Fig. 15 pre- 
sents—and innumerable oth- 
ers also—may, one after the 
other, be assumed by one and 
the same cell, till finally, in 
death, it comes to rest as a 
spherical body (/). Formerly 
only these corpses were 
known. 
Fig. 15.—Pus cells from the inflamed eye of 
the frog ; a, to k, the changes in the form of the 
living cell; /, dead cell. 
Still other remarkable things are connected with these pe- 
culiarities of the protoplasm. 
If to this cloudy aqueous of the eye we add inoffensive col- 
oring matters in a condition of the finest division, indigo or 
carmine, for instance, we see that the always restless proto- 
plasm gradually takes up into the cell body one colored gran- 
ule after the other (#). Even larger structures may be thus 
introduced. Fragments and even whole red blood corpuscles 
may thus enter into the lymphoid cells of the spleen. The 
amceba (Fig. 3), received its small alimentary corpuscles in 
exactly the same way. This introduction may take place, in 
1* FIRST LECTURE. 
both cases, at any portion of the outer surface ; the latter is, 
indeed, similar throughout. 
By means of this vital transformation, our lymphoid cell is 
able, like an amoeba, to shove itself over whatever it rests 
on ; and thus, very slowly and sluggishly, it is true, wander 
about. This may be observed in the pus cell in the cloudy 
aqueous mentioned. In the magnificently transparent cornea 
of the normal eye of a frog, the lymphoid cells may be seen 
to wander through the corneal canals in the most distinct 
manner, so that they gradually pass over the entire micro- 
scopic field. 
This has been rather drastically expressed by the words, 
“ the cells devour and march.” 
Such amoeboid cells may wander into other cell forms 
which have come to rest. The surfaces of the body have cell 
layers which are called epidermis or epithelium. This tis- 
sue participates actively in the catarrhal irritations of the 
mucous membranes. Lymphoid cells then wander from the 
deeper layers of the latter into the bodies of these epithelial 
cells (Fig. 16). These strange cells had already been ob- 
served before the vitality of the 
protoplasma was conjectured. 
The process was then naturally 
not understood. It was then 
imagined that the lymphoid cells 
were produced within those of 
the epithelium. 
A form of cell has long been 
known, a species of epithelium, 
which presents the most strik- 
ing vital phenomena. This is 
the ciliary cell {/)• Very small 
and thin cilia, which cover the 
free surface of the cell body, 
are constantly occupied in a 
to and fro motion. These vibrations are repeated with such 
extraordinary rapidity that the human eye is unable to dis- 
Fig. i6.—Pus corpuscles in the interior of 
epithelial .cells from the human and mam- 
malial body ; a, Simple cylinder cell of the 
human biliary canal; 6, one with two pus 
cells ; c, with four, and d, with many of 
these contained cells ; e, the latter isolated ; 
/, a ciliated cell from the human respiratory 
apparatus with one, and g, a flattened epi- 
thelial cell from the human urinary bladder, 
with numerous pus corpuscles. THE PROTOPLASMA AND THE CELL. 
tinguish the individual ones. It is only on the death of the 
ciliated cell, when these oscillations are retarded, that they 
can be counted. We now know that these fine cilia are pro- 
toplasma threads, and that their movements fall within the 
vital sphere of that remarkable substance. The rapid work 
of these small hairs and the sluggishness of ordinary proto- 
plasm, it is true, present a difference which is still inexplicable. 
Where there is motion in the domain of animal life, there 
is also sensation. Have the cells, the vitalized, minimal cor- 
ner-stones of our bodies, the latter capacity ? We may affirm 
this unreservedly. 
When these changeable figures, as they were represented 
in our Fig. 15, are subjected to a weak electrical irritation, 
they rapidly return to the spherical form, to subsequently 
recommence the old play of forming processes. 
Every organism, even the smallest and most simple, has a 
transmutability ; that is, it gives off altered unserviceable par- 
ticles of matter, it receives into itself new matter, and trans- 
forms it into the constituents of its own body. The mass of 
the organism then increases, it grows. 
All this happens, likewise, to the cell. The perception of 
these vital actions is rendered difficult by the smallness and 
the obscure existence of our structures. That the cells grow 
may be abundantly shown and with the greatest certainty, as, 
for example, in the fat and cartilage tissues. That they take 
up and transmute matter ; that is, mak.e it something chemi- 
cally different, may also be perceived without trouble. Melanin, 
the black pigment we mentioned above, is wanting in the 
blood. It is formed by the cell (Fig. 9). Choleic acid salts 
and biliary pigment, the former, at least, certainly not present 
in the blood, are productions of the living hepatic cell. The 
latter presents us, furthermore, with a striking example of the 
exchange of matter. Both the substances just mentioned 
appear later as ingredients of the bile. We could readily cite 
many such occurrences, but these few remarks may suffice ; 
they show, at least, the coming and going of the materials. 
The law of destruction adheres like a curse to the heels of 12 
FIRST LECTURE. 
the Organic, from the infusoria, whose life is counted by 
hours, to the oak, whose existence lasts centuries, throughout 
this limited duration of life. Concerning the human organ- 
ism, this highest cell-complex, there is a very ancient, well- 
known saying that it lives seveaty years, and at the furthest 
eighty. 
We now encounter the question : Are the cells, those vital 
corner-stones of our body, once for all present, to remain 
with us permanently as faithful companions to the day of 
death ? Or does our body-cell, that delicate little thing, pos- 
sess a more limited and, perhaps, compared with human life, 
only a very short existence ? 
We answer unreservedly in the latter acceptation. 
The life of the body is long, under fortunate circumstances; 
that of our cells is short. We can present but a very defec- 
tive proof of this, however, at the present time. 
We again present a few examples. We have said above 
that the outer surface of our body is covered by layers of cells. 
The superficial layers are in loose connection ; they are cells 
in old age. The friction of our clothing daily removes im- 
mense numbers of them. A cleanly person, who uses sponge 
and towel energetically every day, rubs off still greater quan- 
tities. 
This takes place very actively in our mouth every day. 
We swallow ; our tongue acts in speaking ; drink and food 
pass this entrance of the digestive apparatus. Every one 
knows this. The mucous membrane of the mouth is, again, 
covered with a thick layer of epithelial cells. Here, also, 
many thousand senile cells are rubbed off daily. That which 
began at the entrance is continued throughout the entire di- 
gestive apparatus. An excess of cells is thus lost daily. 
To show the duration of life of a cell variety, let us turn to 
the human nail. The latter, growing from a fold of skin, is 
a cell-complex. In the depth of the furrow, youth prevails ; 
at the upper border—which we trim—old age. The deceased 
physiologist of Gottingen, Berthold, proved that a nail cell 
lives four months in summer and five in winter. A person, THE PROTOPLASMA AND THE CELL. 
dying in his eightieth year, has changed his nail two hundred 
times, at least—and the nail appeared such an inanimate, ap- 
parently, unalterable thing 1 
We consider the nail cell a relatively long-lived constituent 
of the body. We believe that most of the cells of our body 
have a very much shorter existence. We repeat, however, 
that it is a matter of belief, for no one can prove it, at pres- 
ent ; but everything compels the view that, for example, the 
red blood corpuscles, of whose multitude we spoke above, 
have a much shorter existence than the elements of the 
nails, and they are certainly resembled by many other cell- 
varieties. 
Most cells being destined to an early death, how do they 
die ? 
Science can give to this, at present, but an insufficient 
answer. Certain cells, those of the outer surface of the body 
and of many mucous membranes, dry up in their old age ; 
the connection with the vicinity dissolves, the thing falls from 
its bed. The red blood cells die by being dissolved in the 
blood plasma. Others stick fast in the complicated tissue of 
the spleen, and are likewise children of death ; for the blood 
corpuscle lives only in the perpetual motion of the current; 
rest stamps it with the impress of death. 
Other cells show in their old age granules of lime salts. 
They mummify. In this condition they may, as cell corpses, 
possibly remain for a still longer time constituents of the 
body. Generally, however, they soon afterwards become 
dissolved. 
A very disseminated form of death of ani- 
mal cells, in healthy as in unhealthy life, is 
the so-called fat degeneration. In the place 
of the protoplasma, we perceive, in increas- 
ing quantity, molecules of fatty matter 
(Fig. 17). They finally destroy the cell life and cell body. 
The human body daily loses, therefore, immense numbers 
of its living corner-stones. How does it replace this loss ? 
We here enter a very interesting department of our science. 
Fig 17.—Fatty degen- 
erated cells from theGraa- 
fian follicles of the ovary. FIRST LECTURE. 
Schwann, the founder of modern histology, taught: “ What 
the crystal is in regard to the inorganic, so is the cell in the 
sphere of life.” As the former shoots forth from the mother- 
lye, so also, in a suitable animal fluid, are developed the 
constituents of the cell, nucleolus, nucleus, covering, and 
cell contents. 
This view was embraced during many years. It explained 
everything so conveniently! 
This was, however, over-hasty. Two highly endowed in- 
vestigators, Remak and Virchow, exposed the error; the 
former for the embryonic, the latter for the diseased human 
body. 
The organic kingdom forms a continuity from the Bathybius 
to man. We do not hesitate an instant to acknowledge that 
this is also our conviction. 
There is an old well-known saying : “ Omne vivum ex 
ovo,” and in imitation of this sentence : “ Omnis cellula e 
cellula.” The cell arises from the cell; a spontaneous origin, 
in the sense of Schwann, does not occur. 
We know but one certain method of increase of the cells 
of our body. 
The protamceba, Haeckel’s non-nuclear cytode (Fig. 2), 
divides itself into two beings by constriction. Each portion 
grows, by a predominant reception of 
material, to a new protamceba. This is 
also the method of propagation of the 
nucleated cell of the human body. 
Nucleus and protoplasm divide ; from 
one structure are formed two, and so 
forth. Our figure (Fig. 18) shows this 
multiplying process of embryonic blood 
corpuscles. When, however, the cell 
has once become surrounded by an 
envelope or a capsule, when the proto- 
plasma is imprisoned, then (Fig. 19) the 
contrast of the active and the passive is strikingly presented. 
The capsule remains stiff and quiet, the cell in prison 
Fig. 18. Blood corpuscles of 
a young deer embryo ; at a, the 
most globular cells ; b \af, their 
process of division. THE PROTOPLASMA AND THE CELL. 
15 
maintains the old life. This multiplying process was, in 
old times, badly 
enough designated 
“ endogenous cell for- 
mation.” Mother and 
daughter cells were 
sooken of. The so- 
called mother cell is 
nothing but the cell 
capsule. 
Does the process of 
division of the human 
cell take place slowly 
or rapidly ? We be- 
lieve the latter ; al- 
though a proof can 
scarcely be presented 
here. In the lower animal groups, at all events, processes 
of division occur which are completed with great rapidity. 
i Fig. ig.—Diagram of dividing incapsulated bone cells ; 
a, cell body; b, capsule; c, nucleus ; d, endogenous 
cells ; e, supplementary capsule formation. 
We cannot yet leave the process of division, for we now 
encounter the question; Which constituent of the cell, 
nucleus, or protoplasm, here assumes the chief role ? That a 
non-nucleated lump of proroplasma is capable of dividing, is 
shown by the protamoeba. It is possible that the nucleus is 
only passively simultaneously con- 
stricted, an opinion to which we are 
inclined. Meanwhile cells which, in 
the undivided body, present two sep- 
arated nuclei (Figs. 12, 18, 19), and the 
multi-nuclear myeloplaxes (Fig. 13), 
constitute a certain objection. Once 
more, therefore, uncertainty. 
The blood, lymph, and chyle consist 
of cells suspended in a large quantity of fluid ; in the blood, 
as we already know, these bodies are present in enor- 
mous numbers. Something similar is presented by a 
pathological product—pus. Should one speak here of tis- 
Fig. 20.—Simple flattened epi- 
thelium ; a, of a serous mem- 
brane ; b, of the vessels. 16 
FIRST LECTURE. 
sues ? According to our opinion it is permissible; still, 
we readily admit, the opposite view may be defended. 
Other tissues, such as the epithelium or the epidermis (Fig. 
20), present the cellular elements in close conjunction. At 
the same time, even the first examination teaches us that our 
cells are not loosely crowded together ; they are intimately 
united; they are plastered or cemented together. This 
Fig. 2i.—Capillary vessel from 
thtf mesenlerium of the Guinea- 
pig, after the action of the ni- 
trate of silver solution ; a, vascu- 
lar cells ; b, their nuclei. 
Fig. 22.—Cells of the enam- 
el organ of a four months’ hu- 
man embryo. 
substance, which is of very frequent occurrence in a minimal 
thin layer, is called either the tissue cement or the intercellu- 
lar substance. If a portion of such tissue is placed for a short 
time in a very dilute solution of- nitrate of silver and then 
exposed to the light, the tissue cement becomes black. 
This excellent accessory is nowadays very frequently used. 
In this manner we years ago recognized that the finest blood- THE PROTOPLASMA AND THE CELL. 
17 
vessels, the capillaries, were formed of cemented, elongated 
cell lamellse which become curved and joined together as a 
tube (Fig. 21). 
Stellate cells (Fig. 22), may blend together through theii 
processes, and form a very delicate net-work. The meshes 
may be filled up with homogeneous gelatinous matter, and 
also with a multitude of lymphoid cells. In the former case 
we again have a variety of intercellular substance. 
The latter acquires a considerable thickness in many tissues, 
as in cartilage. At first (Fig. 23), this intermediate substance 
is homogeneous throughout. This condition is either main- 
»Fig. 23.—Cartilage of a 
young sheep foetus. 
Fig. 24.—Cartilage from the auricle of a calf’s 
ear; a, cells ; b, intercellular substances; c, 
elastic fibres of the latter. 
tained, or else fibres subsequently shoot out from the inter- 
cellular substance. Frequently (Fig. 24), we 
meet with them crossed in a felt-like or reticu- 
lated manner. They present an obstinate 
power of resistance to reagents. Such fibres 
are called elastic. Therefore—we repeat it 
the elastic fibre is the result of a subsequent 
metamorphosis of an originally homogeneous 
substance. 
Connective tissue is infinitely diffused 
through the human body. A small piece of 
this, taken from the embryonic body, shows us, 
together with cells, bundles of very fine 
fibrillse, the connective-tissue fibres (Fig. 25). 
They have a quite similar origin. Subsequently, the con- 
Fig. 25.—From the 
tendon of a hog’s em- 
bryo ; <r, the cell ; 6, 
connective tissue fi- 
brilla. 18 
FIRST LECTURE. 
nective tissue has also formed those elastic fibres, which we 
have just met with in cartilage. 
From whence, however, does the tissue cement and the 
intercellular substance come? Have they been inserted from 
the neighborhood between the cells, or have the cells them- 
selves produced these substances ? 
The latter is the case. These substances were once con- 
stituents of Ihe cell body, at one time represented protoplasm. 
The formation of these substances was sometimes compared 
more to a secretive act of the cell, at others, more to a meta- 
morphosis of the outer portion of the cell body. We think 
both occur, and the difference between these views is, in fact, 
of little importance. 
A deposition may also take place from without upon a 
single cell or a cell-complex and enter into a closer union 
with it. The mammalial ovum (Fig. 5), shows a capsule. 
It is the elaboration of the small cells (a) covering the ovu- 
lum. 
The capsule of the cartilage cells appears very similar to 
the ovum capsule. Its origin, however, is entirely different. 
The cartilage cells have 
themselves formed the car- 
tilage capsule. We shall 
return to this subject later. 
The glands (Fig. 26), con- 
sist of secretory cell-com- 
plexes surrounded by a 
hyaloid covering, the so- 
called membrana propria. 
This is not a secretory pro- 
duct of the cell-aggrega- 
tion, as was formerly assum- 
ed. The membrane is trans- 
formed from the connective tissue adjacent to the glandular 
cell-aggregation. It may remain structureless, but extremely 
flat stellate cells may also enter into its structure. They then 
appear as delicate, rib-like thickenings of this membrane. 
Fig. 26.—Tubular glands from the large intes- 
tine of the Guinea-pig. At a, a gland with the 
rnembrana propria showing in places ; at b, escape 
of the contents through a rent in the latter. THE PROTOPLASMA AND THE CELL 
19 
We will add one more example of a 
widely diffused cell transformation ; we 
allude to the transversely striated volun- 
tary muscle. 
This, a thi'ck, cylindrical fibre, not 
unfrequently of considerable length, 
consists of a contractile, longitudinal 
and transversely striated substance. In 
the outer portions of the latter lie 
numerous nuclei with adherent proto- 
plasma remains. It is surrounded by 
a hyaloid sheath. The whole, how- 
ever, arises from a single cell (Fig. 27). 
This («),with a continual increase of the 
nuclei, grows into a thread ; the proto- 
plasma is transformed into the longitudi- 
nally and transversely marked substance 
{c); only a scanty remnant surrounds the 
nucleus, forming it into a rudimentary 
cell, and the homogeneous covering of 
the thing is derived from a transforma- 
tion of the adjacent connective tissue. 
The examples presented may suffice. 
They show, at least, how the most het- 
erogeneous may result from what was 
originally similar, through subsequent 
cell metamorphosis, and they attest the 
high signification of the cell in the structure of the organism 
Fig. 27. Development of 
the transversely striated mus 
cular fibre (sheep embryo). SECOND LECTURE. 
CLASSIFICATION OF THE TISSUES.—BLOOD, LYMPH, CHYLE. 
A CLASSIFICATION of the tissues was, in the course of time, 
often attempted; but it is, and remains, a very difficult thing. 
A scientifically adequate arrangement can be founded only 
on the course of development of the elements. The latter is 
unfortunately not yet accurately established throughout. 
One might nevertheless proceed with strictness, by the aid of 
the history of development; the three well-known germinal 
plates from which the embryo arises might be employed as a 
basis of the arrangement. Still the representation of the tis- 
sues thus arranged would be attended with not inconsiderable 
difficulties. 
We will, therefore, employ a preponderating artificial 
classification, which, with all its defectiveness, possesses, at 
least, the advantage of presenting the material in a more 
convenient form to the learner. 
A. Tissues of simple cells with fluid intermediate sub- 
stance : i. Blood; 2. Lymph; 3. Chyle. 
We distinguish : 
B. Tissues of simple cells with scanty, firm, structureless 
intermediate substance: 4. Epithelium; 5. Nails; 6. Hair. 
C. Tissues of simple or metamorphosed cells, with partly 
still homogeneous, partly fibrous, and, not rarely, more firm 
intermediate substances (connective-tissue group): 7. Carti- 
lage ; 8. Gelatinous tissue and reticular connective substance ; 
9. Fat tissue; 10. Connective tissue; 11. Bone tissue; 12, 
Dentinal tissue. 
D. Tissues of metamorphosed, as a rule, unfused, cells, with 
scanty structureless intermediate substance: 13. Enamel tis- 
sue ; 14- Lens tissue; 15. Muscular tissue. CLASSIFICATION OF THE TISSUES. 
21 
E. Compound tissues : 16. Vessels; 17. Glandular tissue ; 
and 18. Nerve tissue. 
We shall, therefore, proceed in this manner, and turn first 
to the blood. 
“ Blood is quite a peculiar sort of juice,” Goethe lets his 
Mephistopheles say. Modern science, after nearly a hundred 
years, endorses the apothegm completely. 
If a little drop of this fluid, which appears homogeneous to 
the naked eye, is spread out in a thin layer under the micro- 
scope, we are surprised by a peculiar image. The homoge- 
neous red has disappeared ; we perceive innumerable yellow- 
colored cells in a colorless fluid. The fluid is called plasma, 
the cells bear the name of the colored or red blood corpuscles 
(Fig. 10, a, b, c). Among the colored companions, still 
another, though not abundant, colorless structure may be 
noticed by closer examination. This is the lymphoid cell of 
the blood, the so-called white blood corpuscle (d). 
The human red blood cells are diminutive structures ; they 
measure only 0.0088 to 0.0054 mm. Their smallness and their 
innumerable quantity renders it possible that a small space—■ 
a cubic millimetre of blood—may contain five millions of 
them. _ 
Their form, as Fig. 10 
showed, is spherical, the 
periphery appears yellow, 
the centre bright and 
nearly colorless. When 
the blood corpuscle rolls 
over the microscopical 
glass slide, the side view 
presents the appearance 
of c. Our cell, conse- 
quently, represents a cir- 
cular disc, with excavated 
central portions of both 
broad surfaces. 
Fig. 28.—Red blood corpuscles of man ; a, treated 
with water ; b, in evaporating plasma ; c, dried ; <i, 
after coagulation ; e, rouleaux-like arrangement. 
The red blood corpuscle is, besides, a very changeable 22 
SECOND LECTURE. 
thing. In evaporating blood it becomes indented (Fig 
28, b). Rapidly dried, it presents the appearance of c. On 
the addition of water, the cell becomes globular and loses its 
color. The coloring material, an extremely complicated sub- 
stance, called haemoglobin, has now become dissolved. 
Something similar is also seen in previously frozen blood. 
The colorless residue is called stroma. 
A series of reagents, which have been applied to our 
structures during many years, act, similarly, some distending, 
others shrinking ; but by no treatment does a nucleus make 
its appearance. The human red blood corpuscle is, therefore, 
a non-nucleated cell. 
Has the thing a membrane—does it possess a covering ? 
we ask further. We answer negatively. An interesting ex- 
periment is here, according to our opinion, decisive. When 
living blood cells are warmed to 52° C., they commence a 
marvelous transformation. Indentations of the border rapidly 
Fig. 29.—Colored blood cells ; 1, from man ;2, camel; 3, pigeon ; 4, proteus ; 5, water salaman- 
der ; 6, frog : 7, cobitis ; 8, ammocoetes. At a, surface view ; b, profile (mostly after Wagner). 
occur, and partial constrictions of the cell body rapidly follow, 
which either immediately break off or remain in connection CLASSIFICATION OF THE TISSUES. 
23 
with the main portion by means of a thin, pedicle-like bridge. 
The strangest appearances are hereby presented to the eye. 
It is plain that only a membraneless cell body can present 
such constrictions. 
The cells, these living corner-stones of our body, are other- 
wise quite similar in the various vertebrate animals ; it is not 
so, however, with the blood. The differences in most of the 
mammalia are certainly slight. The form remains ; only the 
diameters vary somewhat. A few ruminants, the camel, al- 
paca, and llama, have oval cells (Fig. 29, 2). 
The blood corpuscles of birds (3), amphibia, and most 
fishes (3), appear elliptic ; but in the middle of both broad 
surfaces we meet with an elevation. The diameter changes 
in an interesting manner. In birds, it is 0.0184 to 0.0150 mm.; 
in the squamigerous amphibia, 0.0182 to 0.0150; in osseous 
fishes (7), 0.0182 to O.Oi 14. Our cells reach prodigious dimen- 
sions in the ray and shark, 0.0285 to 0.0226 mm.; then among 
the batrachia, the frog (6) and the toad have blood corpuscles 
of 0.0226 ; the triton (5), up to 0.0325 mm.; and the salamander 
has still larger. The group of the pisciform amphibia have the 
largest of all. In the proteus they measure 0.057 mm. The 
cyclostomen, a low group of fishes, have, strangely, again, 
spherical bi-concave discs measuring 0.0113 mm. (8). 
All these blood corpuscles behave, with reagents, similar 
to those of man and the mammalia. But in them all, on the 
contrary, there is a nucleus. Even in the dying cell it is 
visible. Many reagents—for example, water, very dilute 
acetic acid—let it show out from the now discolored cell as a 
granular structure (Fig. 30, a, b). 
The second element of the blood, the 
tymphoid cell, is much more homogeneous. 
The form is, throughout, spherical; the size 
Is, in man (Fig. io, d; Fig. 31, I to 4), rarely 
0-00S> generally 0.0077 to 0.012 mm. The 
ftiost of our structures, according to this, 
exceed the dimensions of the colored corpuscles. It is the 
same in the mammalia. In the remaining classes of the 
Fig. 30. Blood 
cells of the frog with* 
granular nuclei. 24 
SECOND LECTURE. 
vertebrates, however, the lymphoid cell is smaller than the 
colored element. 
They show a molecular proto- 
plasma, with a granular contour, 
A few lymphoid cells harbor, in 
addition, fat molecules (4)., If water 
be allowed to act on them, the 
nucleus immediately begins to de- 
tach itself (5). After this we have 
nuclear forms, such as the cells 6, 7, 
and 8 possess. Other cells show a 
reniform (9), Or triplicate nucleus 
(10, 11). This artificial production 
may finally break up into a number of small fragments (12). 
changed"nucleus 
huolOsixnJeces:; free nuclei 
substance. 
The lymphoid cells adhere readily, they are of a somewhat 
sticky nature. Their specific weight is less than that of the 
red blood corpuscles. During life we meet with the already 
described amoeboid change of form, as well as a locomotion 
thereby induced; this takes place most actively in diluted 
plasma (Thoma). The cells can also be made to take up 
small foreign particles. 
There are one, two to three colorless blood cells to 1,000 red 
ones in man. The number increases after a plentiful meal, after 
the loss of blood, and also under conditions which indicate a 
more active blood formation. An interesting phenomenon is 
presented by the spleen. The blood flowing into it shows the 
usual small number of lymphoid cells, while in the blood of 
the splenic vein 5, 7, 12, 15, and more of them occur. In the 
lower groups of vertebrate animals, the number of the color- 
less cells is more considerable ; in the frog, the proportion of 
lymphoid cells to red blood corpuscles is 1 : 4-10. 
The web of the frog and the tail of its larvae are adapted to 
examinations of the circulation. The wonderful spectacle 
(Fig. 32), shows how the colored blood corpuscles readily and 
rapidly pass along and among each other, while the viscous 
lymphoid cells move much less rapidly, and not unfrequently 
adhere for a time to the inner surface of the vessel. CLASSIFICATION OF THE TISSUES. 
25 
But whence do our lymphoid cells originate ? First, 
from the lymph and chyle, that is, from the lymphatic 
glands, then from the spleen 
and bone marrow’. They are 
carried away from both the 
latter parts by the blood cur- 
rent. 
What becomes of our cells 
in the veins ? 
They become, in part, grad- 
ually transformed into red 
blood corpuscles, and cover 
the loss of the latter. Whether, 
however, a greater or only a 
lesser portion undergoes this 
metamorphosis, we are not 
yet able to say ; for this, we 
must first learn more accurately the duration of the life of the 
red blood corpuscles. 
Fig. 32.—The blood, current in'thewebof 
the frog ;a, the vessel; b, the epithelial cells 
of the tissue. 
The manner of this metamorphosis we can state in some 
degree. The globular form changes to the specific one of the 
red blood cell, and the protoplasma is replaced by a homo- 
geneous colored substance. In mammalia and man, finally, 
there is also a loss of the nucleus. 
Isolated examples of such intermediate forms have been 
recognized in the blood for years, especially in that of the 
spleen, the mammary ducts and the bone medulla. 
The bright red color of the arterial, and the dark of the 
venous blood is caused by a combination of oxygen with the 
haemoglobin, or a reduction of the latter. Prolonged changes 
in the form of the blood corpuscles likewise exert a modifying 
effect on the color. Distended, they lend a darker color to 
our fluid ; shriveled, a brighter one. 
When a drop of blood is left to itself, it coagulates. The 
filiform separation of the fibrine is shown in our Fig. 28, d. 
When blood is beaten, that is, the fibrine caused to coagu- 
late, the cells sink, the red ones more rapidly, the colorless 26 
SECOND LECTURE. 
lighter ones more slowly, the former arranging themselves 
in rolls (<?). 
We come, finally, to the blood formation of the embryo. 
The flat germinal layer, from which the human body arises, 
consists of three membranous cell layers lying one over the 
other, the horn layer (Hornblatt), the middle germinal layer, 
and the intestinal gland layer (Darmdriisenblatt) (Remak). 
The heart, vessels, and blood proceed from this middle layer, 
from which, besides, many.parts of the body originate. 
The first blood appears very early, and consists only of 
colorless cells, formed of protoplasma and a vesicular nucleus. 
The homogeneous yellow substance gradually replaces the 
molecular protoplasma. We have now before us, nucleated 
colored blood corpuscles (Fig. 18, a), of 0.0056 to 0.016 mm. 
At this period an increase also takes place by the way of 
division (a to f). Later, this procedure becomes extinct, and 
the cells assume more and more the specific form, the nucleus 
at the same time disappearing. 
The fluid of the living blood, the plasma, constantly passes 
through the thin capillary walls into the adjacent tissues. It 
brings to the latter the nutrient materials, to the one these ; 
to the second, again, others. The fluid becomes impregnated, 
however, with the products of decomposition of the tissues. 
The latter are again different. 
Let us now proceed to the lymph and chyle. 
The tissue fluids, which are in consequence so variable in 
their chemical constitution, finally collect in the fissures and 
spaces of the body. Thin-walled vessels are gradually de- 
veloped from these; and then, uniting in larger trunks, they 
finally enter the blood passages. These are the lymphatic 
vessels ; and the fluid contents, whose nature we have just de- 
scribed, are called lymph. 
The walls of the intestines also have their lymph districts. 
Towards the close of active digestion they contain tempora- 
rily another cloudy or white fluid, which is very rich in albu- 
men and fat. This is the lacteal juice or chyle. The canals 
bear the name of the chyliferous system of vessels. CLASSIFICATION OF THE TISSUES. 
27 
The lymph appears colorless and clear as water. Taken 
from the smallest vessels, it may be without cells. It con- 
tains large quantities of them when drawn from the larger 
vessels, especially just after the passage of the latter through 
lymphatic glands or allied structures. Nevertheless, it is infi- 
nitely less rich in cells than the blood. They are the same 
lymphoid cells we became acquainted with in the blood (Fig. 
31) ; further description is therefore unnecessary. 
The lymph presents nothing further. In the chyle, on the 
contrary—and they cause the cloudy or whitish appearance 
of the fluid—we meet with innumerable infinitely fine dust- 
like molecules. With a strong magnifying power they show a 
peculiar, dancing, driving about, the so-called Brunonian 
molecular movement. But there is nothing strange in this. 
It is natural to all very small bodies suspended in water, 
small particles of fat, the smallest crystals, carmine granules, 
and the like. These dust-like particles consist of fat, sur- 
rounded by a very thin albuminous covering. 
Red blood corpuscles may be met with in the lymph and 
chyle as incidental constituents, and occasionally as transition 
forms. I have seen the latter in the thoracic duct of the 
rabbit. 
Red blood cells, pressed out from the blood-vessels, may 
also finally reach the lymphatics. There is no doubt that the 
actively emigrated colorless blood cells often penetrate these 
passages, and thus again commence the journey back into the 
blood. THIRD LECTURE. 
THE EPIDERMIS, OR THE EPITHELIUM. 
UNDER epithelium we understand closely-arranged cell lay- 
ers, held together by a minimal quantity of cement (p. 16); it 
covers the surface of the body, the external as well as the 
internal. 
All three plates of the germinal layer (p. 26), participate in 
the production of the tissue under examination. The horn layer 
supplies the covering of the corium, the so-called epidermis. 
The lower germinal plate forms the epithelium of the diges- 
tive apparatus and the organs arising from the latter. Not 
less important is the role of the cell layer. Manifold 
cavities originate in it; the passages of the vascular system, 
the so-called serous sacs, the articular cavities, down to innu- 
merable small and diminutive tissue spaces. All these again 
have their epithelial cell covering. The latter is now called 
endothelium. The principle is correct; but the boundaries 
cannot yet be sharply drawn throughout. 
Epithelium consists either of a simple cell layer, or the 
cells are stratified more or less manifoldly over each other. 
We distinguish, therefore, unstratified and stratified epithe- 
lium. The latter originates in the horn layer. The former 
is due to the intestinal gland, as well as the middle germinal 
plate. 
The form of the cell varies. Many kinds of epithelium 
present only thin, flat, scale-like cells (Figs. 7 and 20). We 
speak now of flattened or pavement epithelium. In other 
varieties the cell is tall and slender. This is called cylindrical 
epithelium (Figs. 6 and 14). When the surface of the cylin- 
drical cells has vibratory ciliae (Fig. 33) we have the vibratile 
or ciliated epithelium. THE EPIDERMIS. 
29 
The simplest unstratified pavement epithelium belongs in 
most, but perhaps not all its occurrences, to the endothelium. 
We find it in this way on the surface of 
the serous sacs, on the posterior wall of 
the cornea of the eye, over the lateral 
surfaces of the synovial capsules of the 
joints. The same endothelia are met 
with on the inner surface of the cardiac 
cavities and the vessels. 
These cells, very thin lamellae, appear 
sometimes broad and short (Fig. 20, a), 
on the serous membranes, again very narrow and long (b) on 
the inner surface of the arteries. The endothelium of the veins 
has a median character. 
fig. 33.—Various forms of 
ciliated epithelium. 
A larger blood-vessel is a complicated thing. In proportion 
as we descend to the smaller and still smaller branches, one 
outer layer after the other disappears from this complicated 
structure, and at last only the inner- 
most endothelial layer remains. Large 
cells with lapped edges, and—induced 
by the position of the vascular tube 
—now much more strongly incurvated 
and in close connection, constitute the 
walls of the capillary (Fig. 21). The 
lymphatic vessels are also formed in 
the same manner, though their finest 
canals—and they occur in immense 
numbers throughout the body—show 
the outer surfaces of these endothelial 
cells grown into an intimate connection 
with the neighboring tissue, so that one might here speak of 
lacunae. 
Fig. 34.—Endothelial cells after 
treatment with nitrate of silver. 
The terminal respiratory portions of the lungs, the air vesi- 
cles or alveoli, have a layer of simple flattened epithelium 
which does not belong to the endothelium. 
We pass over the others at present. 
An interesting variety is found at the outer surface of the 30 
THIRD LECTURE. 
retina. They were formerly called polyhedral pigment cells 
(Fig. 35). Their surface presents a delicate mosaic, as a rule, 
of a hexagonal form, of 0.0135 to 0.0204 mm. The quantity 
of the pigment granules embedded in the 
soft, homogeneous substance of the cell 
body varies, so that the nucleus is some- 
times visible, at others concealed. The 
outer portion of the cell remains free 
from these melanine molecules, which 
appear to form small crystals (Frisch). 
The profile view shows, however, that 
our cell, far from constituting a flat struc- 
ture, possesses, rather, a certain, sometimes a considerable, 
height, which, at least, equals the diameter. It is thus in the 
lower vertebrate animals ; here their body sends downwards 
a number of filamentous and spiny processes. The latter, 
at first, still contain pigment molecules, and surround in a 
sheath-like manner the rods and cones, the marvellous termi- 
nal apparatus of the retina. This is less frequent in mam- 
malial animals. These pigmented cells extend beyond the 
limits of the specially nervous portion of the retina, over the 
so-called ora serrata, where they become smaller, more rich 
in pigment, and are in thin layers. In this manner they then 
cover the ciliary processes and the posterior surface of the 
iris. 
fig. 35. pigment epithe- 
sheepinordinary°Lxa! 
|rlone!; "'alargerocta- 
Certain of the mammalia (the carnivora and ruminantia) 
have a bright, glistening place in the interior of the eye, 
called the tapetum. Our retinal epithelium is here unpig- 
mented. In albinos this is the case throughout, and the 
cells present the appearance of a delicate pavement epithe- 
lium, as, for instance, in the white rabbit. 
Many mucous membranes present material, and sometimes 
very considerable, layers of pavement epithelium. Among 
these are the conjunctiva of the eye, the mucous membrane 
of the nostrils and of the anus, the mouth and pharynx, the 
oesophagus, the urinary passages, and the vagina. 
In the most superficial layers of the conjunctiva (Fig. 36, a) THE EPIDERMIS. 
31 
we meet with flattened, not inconsiderable cells. In the 
middle layers these elements become smaller, but taller, more 
round, and, in the deepest layer (d), at last, cylindrical. 
Fig. 36.—The cornea of the rabbit in vertical transverse section, after treatment with chloride 
of gold ; a, the older, b, the young epithelial cells of the anterior surface ; c, corneal tissue ; d, a 
nerve branch ; e, finest nerve fibres or primitive fibrilhe ; f, their distribution, and termination in 
the epithelium. 
With a greater increase of the epithelial stratification, the 
number of the upper and middle cell layers is much more 
considerable. 
All the cells have a nucleus. The lowermost have a soft 
protoplasma body ; the superficial (Fig. 7) have become more 
solid and harder; they consist of corneous matter, or kera- 
tine, a derivative of the albuminous group. These cornified 
cells absorb weak alkaline solutions with avidity, becoming, 
at the same time, distended to a globular form. 
A vertical transverse section, after the manner of our draw- 
ing, favors the supposition that our cells have a pretty regu- 
lar form. 
When, however, the cell-cement has been dissolved by a 
suitable macerating medium, an entirely different appearance 
is presented. The stratified pavement epithelium now ap- 
pears very much more like extremely polymorphous cells. 
They lock into each other with their pointed and leaf-like 
processes ; the convex surface of one cell is in contact with 
the concave surface of its neighbor ; the surface is rough and 32 
THIRD LECTURE. 
sometimes indented (Lott, Langerhans). This was first seen 
in the epithelium of the urinary bladder. When the epithe- 
lial stratification is more developed, the cells of the lower 
and middle layers lock into each other with their enormous 
spines and ridges, like two brushes pressed together (Fig. 37). 
These ‘‘spinous and dentate cells” 
(Schultze) lead to an intimate clinching. 
This connection is, however, again dis- 
solved upwards, and their deciduousness 
is thus promoted. 
The most dense formation of flattened 
epithelium covers the human corium. It 
has long been known under the name of 
the epidermis. 
This corium projects in small papillae of 
various shapes. They are called the sensi- 
tive or tactile papillae. The epidermis 
forms a smoother covering over the whole ; 
its deeper cell layers must, therefore, fill 
up the valleys between these papillae. 
These younger cell layers, which have a not inconsiderable 
thickness between the papillae, while they are but slightly 
developed over their apices, present all the characteristics of 
a stratified epithelial mucous membrane. Collectively, it is 
called the Malpighian rete mucosum, or rete Malpighii. 
The layers of old cornified cells make their appearance by an 
abrupt transition. They bear the name of the epidermis in 
the strict sense of the word. Its thickness varies considera- 
bly ; it may exceed a Paris line. The number of layers 
varies, in consequence, extraordinarily. The latter are the 
same scales as those on the surface of the mucous membranes, 
though the cells in contact with the atmospheric air have be- 
come dryer and harder. The nucleus, which these cells for- 
merly possessed, has likewise been lost by the old, effete 
epidermis scale. They measure 0.0285 t° 0.0450 mm.; in the 
mucous epithelium of the mouth, 0.0425 to 0.075 mm. 
ceUs!kYfLm“doeepfr0eepfr 
mfsT3,°ceiihfrom\e 
Itongue.mor1tongue.mor °f the human 
We will speak of the color of the human skin. If we THE EPIDERMIS. 
33 
cover a red cloth with a piece of milk-glass, we have the flesh 
color presented to our eyes, and the thicker the piece of glass 
selected, the lighter the tone will be. It is thus with the 
complexions of Europeans. The corium during life appears 
red, in consequence of its extreme richness in blood ; the 
epidermis is semi-transparent, whitish •or whitish-yellow. 
The thinner the latter, the redder the color (lips, cheeks); 
the thicker the cell covering (the foot-sole, frequently the palm 
of the hand also), the paler the surface of the body. 
In the skin of the dark human races, that of the negro, the 
nuclei in the deeper layers of the epidermis are diffuse 
brown ; the cell bodies are also somewhat darker, and may 
also contain pigment molecules. In the darker portions of the 
bodies of the light races (the nipple and its areola) the same 
condition prevails. The coloring matter here conceals the 
red of the cutis. 
All stratified epithelia, as we already know from what has 
preceded, are of a perishable nature. Millions of the super- 
ficial cells fall off daily, from rubbing, pressure, etc. The 
new formation takes place at the deepest layer, by a process 
of division. Between the latter cell layers, finally, immi- 
grated lymphoid cells may also be met with. 
The second form of epithelial tissue, the cylindrical, be- 
longs to the digestive apparatus, from the entrance to the 
stomach to near the anus, likewise to the ducts of the liver 
and pancreas, the ducts of the lacteal and lachrymal glands, 
and also some portions of the sexual apparatus. 
We there (Fig. 6, b, 14, a) meet, as a rule, with a single row of 
narrow, vertically elongated cells, with a sometimes super- 
ficially, sometimes more deeply lying nucleus, which contains 
a nucleolus. A thin layer of cement substance unites our 
cells, which, seen from above (Fig. 14, b) present a fine mosaic. 
Their height and breadth vary. In the human small intes- 
tine, the former is 0.0182 to 0.027, the latter 0.0057 to 0.009 mm. 
The lateral walls show an envelope ; the free base may present 
naked protoplasma, as in the stomach ; it may, also, how- 
ever, show a different character. . This is the case in the 34 
THIRD LECTURE. 
small intestine (Fig. 14, a). There occurs here an already 
mentioned covering piece, 0.0017 to 0.0025 mm. high, formed 
of a firmer, very changeable substance, and permeated by 
very fine canals, the so-called porous canals. We shall have 
to mention the latter later in alluding to the absorption of 
the chyme. 
That the cylindrical epithelial cells, many of them, at least, 
are destroyed by a mucous metamorphosis of their interior 
(“ Becher cells ”) we have shown in Fig. 6, a. The reparation 
remains unclear. It is not accurately determined that there 
is a deeper, younger layer of cells destined to this purpose. 
Vibratory or ciliary epithelium (Fig. 39) is formed of modi- 
fied cylinder cells. The same cell bodies, with similar varia- 
tions in height and diameter, present themselves. Only the 
free surface, which has the those most restless proto- 
plasma filaments (p. 10), causes the peculiarity. 
Ciliary epithelium lines the human respiratory apparatus. 
Commencing at the base of the epiglottis, it covers the 
larynx, with the exception of the lower vocal cords, which 
have stratified pavement epithelium; also the trachea and the 
bronchi, as far as their finest ramifications, but not the respi- 
ratory vesicles of the lungs (p. 29). We meet with it, fur- 
ther, in the olfactory organ, with the exception of limited 
places. The oviducts and uterus of the female, the vascula 
efferentia, the coni vasculosi, and tire canal of the epididymis, 
as well as the upper half of the vas deferens, have this 
variety of epithelium. Finally, to pass over its more limited 
occurrence, the cavernous system of the spinal cord and 
brain “ vibrates ” in the embryo and neonatus. 
The are often of considerable size in the lower ani- 
mals ; in the higher, they become smaller and smaller. They 
appear exceptionally long, measuring 0.0226 to 0.034 mm., on 
the large epithelial cells of the canal of the epididymis, and 
very short, 0.0056 to 0.0038 mm., in the respiratory apparatus. 
A high degree of perishableness is impressed, as a character- 
istic sign, upon them all. Whether compensatory cells occur 
in ciliated epithelium is, perhaps, not yet accurately deter- THE EPIDERMIS. 
35 
mined. They have, at all events, been frequently admitted. 
Mucous metamorphosis, as in the cylinder cells, is also fre- 
quently met with here. 
Lymphoid cells may also occur between the cylinder and 
the ciliated cells ; indeed, they may even penetrate to the in- 
terior of the cell body (comp. Fig. 16). 
Let us here devote a few words to the remarkable ciliary 
motion. 
Discovered in olden times, subsequently, especially of late 
days, frequently investigated, it has not yet been satisfactorily 
explained. Its occurrence in the animal kingdom is quite 
variable. Sometimes this part vibrates, at others that, 
sometimes nearly all the surfaces ; at others, as in the arthro- 
poda, not at all. What purpose does this work of the cilise 
serve ? 
If we fold a suitable detached piece of mucous membrane and 
examine the edge of the fold, we have the appearance of an 
undulating border, of a flickering candle-flame. If we look 
from above downwards on to it, it suggests the comparison to 
a field of grain agitated by the wind. 
Small bodies suspended in the fluid medium, color granules, 
blood cells, sweep past the folded border, when we examine 
with a high magnifying power. When we use very weak 
lenses, the excursion proceeds more slowly; a cell will require 
several minutes to make its course. 
When the ciliary motion is still in full vital energy, and 
several vibrations then take place in a second, the human eye 
is powerless. It is only when the action becomes retarded 
that we perceive the separate motions—the regular, syn- 
chronous, and homogeneous vibrations of the At- 
tempts have been made to distinguish several varieties of 
these vibrations ; as for example, a hook-like and an oscilla- 
tory. 
We pass over this ; but we must here mention an apparently 
strange condition. In the ciliary movement, we see the 
vibrate towards one side, and the small passing bodies take 
the opposite direction ! 36 
THIRD LECTURE. 
The matter is readily explained. We first recognize the 
slower, less energetic direction of the vibration ; the other, 
more rapid and powerful, we do not yet perceive. In which 
direction, however, will the current be driven? Manifestly, 
in the latter. Engelmann explains the more sluggish move- 
ment as a vital act of the protoplasma ; the more rapid, as the 
effect of elasticity. We agree with him. 
Later, as death approaches, both movements become dis- 
tinct. The current finally ceases, only ato and fro fluctuation 
still remains. 
The ciliary movement has nothing to do with the blood 
current, or with nerve life. It perishes rapidly in warm- 
blooded animals, often very slowly in the lower cold-blooded 
creatures. An elevation of the temperature to 44 ° and 450 C. 
kills them, likewise increasing cold. Everything which exerts 
alchemical influence likewise produces a destructive effect,occa- 
sionally with a temporary increase of the vibration—water, 
for example. It is an interesting observation, that dilute 
solutions of potash and soda may temporarily excite the 
paralyzed vibratory phenomenon to renewed energy (Virchow). 
The true epithelium—that is, so far as it originates in the 
corneous and intestinal gland layers—is developed very early. 
Even in the human embryo of five weeks, according to 
Koelliker, the surface of the body is covered by a double 
layer of cells, a deeper one consisting of smaller rounded 
structures, and an upper one of larger, flatter, indented bodies. 
The former represents the primary rudiments of the rete 
Malpighii, the latter, the horny layer. 
Closely related to the epidermis, and arising from it in the 
third month of foetal life, are the human nails. These obtuse 
quadrangular plates are arched outwards, and lie posteriorly, 
with the so-called nail roots, embraced within a deep furrow 
of the skin. At the sides, the furrow becomes from behind 
forwards more and more shallow. The anterior border of the 
nail remains free. The portion of the cutis covered by the 
nail bears the name of the nail-bed. The latter shows lon- 
gitudinal rows of cutaneous papillee. THE EPIDERMIS. 
37 
The nail consists of two strongly demarcated layers, a deep 
and a superficial. The former is the ordinary 
Malpighian mucous reticulum, such as is 
shown by any other part of the skin. The 
superficial layer, corresponding to the horny 
layer of the epidermis, has gone through the 
process of hornification in a much higher 
degree than occurs elsewhere. At the first 
consideration, we perceive only a brittle, 
homogeneous substance. The power of refrac- 
tion of all its constituents has 
become equal. Reagents, and 
above all, solutions of the alka- 
lies, are here of inestimable 
value. With them we dissolve 
the cement substance and re- 
store a recognizable appear- 
ance to the cell. The latter, an 
originally flat thing, measures 
0.0375 0-0425 mm., but, dif- 
fering from the ordinary epider- 
mis cell, contains a lens-shaped 
granular nucleus, as may be 
readily recognized from Fig. 38, 
<2 and b. 
Fig. 38.—Cells of the 
horny layer of the nail; 
a, a, view from above . 
b, b, seen from the side 
Concerning the duration of the 
life of the nail cell, see p. 12. 
The highest variety of epider- 
moidal tissue is represented in 
man, by the hair. 
An extreme complication of 
structure welcomes us here, all 
at once. 
Fig. 39.—Human hair ; a, the sac : h, its 
hyaline inner layer; c, the external, d, the 
inner root-sheath ; e, transition of the outer 
sheath to the hair-bulb ; f, epidermis of the 
hair in the form of transverse fibres) ; 
g, lower portion of the same ; h, cells of the 
hair-bulb ; i, the hair papillae ; k, cells of the 
medulla ;I, cortical layer ; medulla con- 
taining air ; «, transverse section of the lat- 
ter ; o, the cortex. 
Ihe hair (Fig. 39), lies in an 
obliquely directed sac, an invo- 
lution of the corium, and fre- 
quently likewise of the subcutaneous cellular tissue. The 38 
THIRD LECTURE. 
sac shows externally (Fig. 39, a y 40, i) longitudinally, then 
transversely arranged connective tissue (40, h), and, finally, 
internally (39, b; 40, g), a hyaline boundary layer. At the 
bottom it juts forward as a vascular papilla (Fig. 39, i). It 
is the formative and nutritive organ of the whole. 
On the hair itself we distinguish the hair-bulb (Fig. 39, h). 
resting on the papilla .and the shaft (/). Only a slight portion 
of the latter is surrounded by the sac ; 
the larger, often very long, remaining 
portion, projects freely from the skin, 
as, for instance, the hair on women’s 
heads. As the corium is involuted, 
so also does the epidermis with its 
two layers, the rete Malpighii and the 
horny layer, dip down into the sac. 
These depressions are very appropri- 
ately named root-sheaths ; and the in- 
sinuated rete Malpighii is distinguish- 
ed as the external root-sheath (Fig. 
39, c, 40, e), the horny layer of the 
sac as the internal (Fig. 39, d). The 
former requires no further description, 
it presents nothing special; but the 
latter acquires a modified structure. 
It consists of two layers of hyaline 
cells, an external layer of vertically 
arranged non-nucleated elements, of 
0.0377 to 0.0451 mm. (Fig. 40, d), 
between which longitudinal clefts may 
be perceived, and an inner layer of 
radially arranged cells with nuclei (c). 
Downwards, in the depth of the sac, the 
external root-sheath becomes single. 
Fig, 40. Transverse section 
through a human hair and its fol- 
licle ; iz, hair ; b, epidermis of the 
same ; c, inner, and d, outer layer 
of the inner root-sheath ; e, outer 
root-sheath ; /, its peripheral layer 
of elongated cells ; g-, hyaline 
membrane of the hair sac; h. its 
middle, and z, external layer. 
The substance of the hair bulb (Fig. 39, k) shows the same 
cells as the external root-sheath, with colorless or pigmented 
molecules. Upwards the appearance changes; it then 
comes, or at least very frequently, to a differentiation into THE, EPIDERMIS. 
39 
cortex and medulla fff. In the former we see the cells 
becoming longer and flatter, until finally they are quite dry, 
irregular, elongated cortical plates of 0.0751 mm., and fre- 
quently non-nucleated, in close union, forming the outer por- 
tion of the hair shaft. A diffuse coloring matter, light in 
blondes, deeper in dark-haired individuals, permeates the 
whole. Pigment granules and the finest air vesicles may ap- 
pear in the spores and clefts 
The medullary substance does not, by any means, occur in 
every hair, since in all lanugo hairs and also in many of those 
of the head it may be entirely or partially wanting. At first 
(Fig. 39, k), the cells of the 
hair bulb are perceived to be 
transformed into larger polyhe- 
dral elements of o.oi 51 to 0.0226 
mm. Further above follows 
the drying and shrinking of the 
elements, which have in the 
mean time become non-nucleat- 
ed. Very small air vesicles 
enter the innumerable small 
spaces. A white hair thus re- 
ceives its appearance, while in colored hairs the serrated sub- 
stance glistens through the coloring of the cortex, as if 
tinged. 
Fig. 41.—Rudiments of the hair of a hu- 
man embryo of 16 weeks ; a, h, epidermal 
layer; 7n, in, cells of the rudiments of the 
hair; i, structureless membrane covering 
them. 
We have still one structure remaining, the epidermis or 
cuticle of the hair (Fig 39,/", 4°, b). A double layer of hy- 
aline obliquely standing cells covers the hair, as long as it is 
surrounded by the sac. With the latter terminates the outer 
cell layer, but not so the inner one. This covers the free 
hair, as a system of quite obliquely arranged, flat, non-nu- 
deated lamellae, covering each other in a tile-like manner, like 
a scaly coat of mail. Not unfrequently, after pressure and 
maltreatment, the lamellae present the appearance of regular 
transverse fibres (Fig 39, f*). 
Hairs are found over nearly the whole body, as so-called 
lanugo hairs, and in limited places as thicker, coarse hairs 40 
THIRD LECTURE. 
Its smooth or frizzled condition depends on the cross section 
In the former hair it is round, in the latter oval or reniform. 
The growth of the hair takes place by a cell increase from the 
lower portion of the hair bulb. So long as the sac with its 
papilla remains uninjured, it regenerates the lost hairs ; that is, 
such as are stunted in their hair bulbs and are separated from 
the papillae. This power of reproduction is tolerably ener- 
getic, for the physiological loss of hair is not inconsiderable. 
The origin of the embryonic hair commences at the end of 
the third or the beginning of the fourth month (Fig. 41). 
The epidermis forms with its deeper cells (b) a knobby down- 
ward growth. A structureless boundary layer, furnished by 
the impressed corium {i), leads to the formation of the hair 
sac. From the cell aggregations (m, m), are developed both 
the root-sheaths and the entire true hair with its cuticula. 
The hairs, like the nails, are, therefore, secondary epidermoi- 
dal structures. FOURTH LECTURE, 
the connective-substance group.—cartilage, gela 
tinous tissue, reticular connective tissue, fat. 
Connective TISSUE, fat tissue, cartilage, bone, dentine, are 
Well known constituents of the body. Their finer structure 
proved extremely heterogeneous at the commencement 
period of modern microscopy. It was in the year 1845 that 
Reichert recognized all these things as members of a natural 
unity. Science is indebted to him for the exposition of a 
“ connective-substance group.” Here Virchow accomplished 
further-progress in the domain of pathology; and, indeed, 
also committed errors. Much labor has subsequently been 
bestowed upon this group ; we have made further progress, 
but are still far enough removed from a conclusion. 
All these tissues mentioned—and to these are to be added, 
as new acquisitions, gelatinous tissue and the reticular con- 
nective substance—arise from the middle germinal layer (p. 
26). They are originally similar, but then, pressing on to- 
wards maturity, they assume quite variable forms. Connect- 
lng intermediate forms, however, remain. No one can, for 
example, draw a sharp boundary between gelatinous and 
°i*dinary connective tissue, or between the latter and carti- 
lage. We meet in places, therefore, with a continuous tran- 
Sltion of one connective substance form into another. Truly 
different tissues never do this. We meet, furthermore, in 
fhe animal kingdom, very frequently a substitution of one 
tissue of our group by another. That, for example, which 
111 one creature is connective tissue is in another gelatinous 
tissue, or eveq bone, A temporary substitution also occurs. 
The parts of our skeleton were, for the most part, formerly 
cartilage. In morbid growths we meet with extraordinary 
frequency with such substitutions of the one for the other. 42 
FOURTH LECTURE. 
The connective-substance group, occurring throughout, 
forms a large part of our body, the general frame-work, in 
which the other tissues are embedded. They have rightly 
been called the scaffold and supporting substance of the 
body. 
Let us now examine their individual varieties. 
Cartilage tissue makes its appearance very early in the con- 
struction of the body, though frequently to disappear after a 
short duration of life. Most cartilage, accordingly, does not 
become old. Even at the hour birth a considerable por- 
tion of the cartilage has fallen a sacrifice to a new secondary 
tissue, the osteoid or bone tissue. A portion of the cartilage 
lasts, however, till the death of the person, and may thus 
reach a great age. 
The texture is distinguished, according to several varieties 
of the mature tissue, into : a, the hyaline ; b, the elastic; c, 
a rather uncertain variety, the connective-tissue cartilage, an 
intermediate thing between cartilage and connective tissue. 
In its first embryonic appearance, the progressing cartilage 
presents small spherical protoplasmic formative cells with 
vesicular nuclei and rather scanty homogeneous intermediate 
substance. The latter is still soft, and consists of albuminous 
matter. Soon, however, the cells increase in size ; the inter- 
mediate substance is augmented, and becomes more firm (Fig. 
23). A chemical change also takes 
place gradually ; it becomes a gelat- 
inous tissue ; on boiling, it yields 
chondrine. 
When the intercellular substance 
retains its original homogeneous 
character, it forms hyaline cartilage. 
Thin sections appear transparent like 
glass. The cells (Fig. 42) have also, 
in the mean time, assumed quite a 
variation in their appearance. 
Fig. 42.—Diagram of a perfectly 
mature hyaline cartilage, with quite 
a variety of cells. 
They appear larger, round, oval, 
wedge-shaped. A portion of them show capsules, and not THE CONNECTIVE-SUBSTANCE GROUP. 
43 
unfrequently the latter envelop so-called daughter cells (comp. 
Fig- 19)- raw! 
How have these capsules and the intermediate substance 
been formed ? Concerning this there has 
been much discussion. Nowadays we 
must say that both are cell products, are 
substances yielded by the cell, and were 
formerly a part ol the cell body itself. In 
the ensiform process of the sternum of the 
rabbit, it is easy to recognize, without re- 
agents, that the intercellular substance is 
formed only of the cemented capsules of 
the cartilage cells (Remak). By the aid 
°f macerating media this can also, with greater difficulty, it is 
true, be demonstrated in other 
mammalial and human cartilage 
(Fig. 43). Here, also, the appar- 
ently homogeneous intermediate 
substance becomes divided into a 
system of concentric capsule lay- 
ers, which embrace within them 
the cell or the cell group. The 
individual capsular systems are 
Cemented to each other and like- 
wise the external capsules of ad- 
joining cells. From the similarity 
°f the power of Refraction is caused 
the phantasm of homogeneous- 
ness ; the cartilage cell lies in a 
chasm. When the innermost, 
last-formed capsule has preserved 
an additional, peculiar exponent 
°f refraction, we perceive this 
(Figs. 42, 44) as something dif- 
ferent from the remaining intermediate substance. 
Fig. 43.—Xhyroid cartilage 
of the hog The basis sub- 
stance is divided into cell- 
districts. 
Fig. 44.—From the costal cartilage of 
an old man. 
This division of the cells within their cavities, or, which 
arnounts to the same, within their capsules, gains consider- 44 
FOURTH LECTURE. 
able dimensions in many mature cartilages (Fig. 44, a), so 
that we may meet with enormous capsules of 0.1 to 0.2 mm, 
with whole troops of contained cells. Not unfrequently, how- 
ever, this exuberant increase foretells the approaching disap- 
pearance of the tissue. 
Depositions of fat in the cell body, especially in the vicinity 
of the nucleus, then form very common transformations. 
They may begin very early. Later, the nucleus frequently 
becomes invested by a coherent spherical shell of fat (Fig. 
44). 
A subsequent metamorphosis of the apparently homoge- 
neous intercellular substance into firm, delicate fibrillae, which 
resist acetic acid, is frequently observed ; this is especially 
constant in the interior of old costal cartilage (Fig. 44). 
Calcification is, finally, a quite frequent occurrence in car- 
tilage undergoing retrogression. Dark granules or crumbs 
of lime salts surround the cells or cell 
groups, at first in an areolated man- 
ner. They increase in quantity; the 
whole intermediate substance acquires 
a dark, granular appearance ; the cap- 
sules also become implicated in the 
deposition, and all is black and 
opaque ; only the cells glisten through 
as bright gaps. The older investi- 
gators could not master this. Now- 
adays we readily succeed by the aid of decalcification 
with chromic or lactic acids. 
Fig. 45.—Commencing calcifi- 
cation of hyaline cartilage. 
This calcified cartilage is, however, far from being or from 
becoming bone. We shall hereafter return to this subject. 
Hyaline cartilage substance constituted originally almost 
our entire skeleton, with the exception of the portions form- 
ing the vault of the cranium and the bones of the face. This 
is the transitory cartilage. Remains of the same form the 
articular and costal cartilages and others. Other masses of 
cartilage have nothing to do with the skeleton. To these 
belong the larger cartilages of the larynx, and the cartilage THE CONNECTIVE-SUBSTANCE GROUP. 
45 
of the trachea and bronchia. The cartilage of the nose also 
appears to be hyaline. 
The young, healthy, hyaline cartilage, but not that which 
is growing old, is without vessels. 
An interstitial growth is evident; the increasing size of the 
cartilage cells, the expansion of the capsules, and the increase 
of the intermediate substance remove every doubt. Is there, 
besides, an increase of substance by apposition ? This is not 
known. The nutrition takes place either from the blood- 
vessels of a connective-tissue covering, the perichondrium, 
or, when the cartilage envelopes the bone, from the adjacent 
vessels of the latter. 
Elastic or reticular cartilages arise from a supplementary 
metamorphosis, which commences during the embryonic pe- 
riod. Their number is not large. Among these are the epi- 
glottis, the Santorinian and Wrisbergian cartilages of the 
larynx, the Eustachian tube, and the cartilage of the ear. 
The arytenoid cartilages of the larynx and the symphyses of 
the vertebrae present the same peculiarity only partially. 
In reticular cartilage (Fig. 24) we generally meet with more 
abundant cartilage cells, surrounded by a homogeneous area, 
and the remaining intermediate substance permeated by a 
dose net-work of fine elastic fibres. Considerable variations 
°ccur, however, in the different varieties of animals (Hertwig). 
By connective-tissue cartilage is denoted a substance which 
presents small cartilage cells, surrounded by bundles of a con- 
nective tissue which becomes homogeneous in acetic acid. 
This variety is met with, for example, in the cartilaginous 
kps of the joints, and locally in the vertebral symphyses ; 
°ther parts of the latter present hyaline cartilage ; still others, 
only ordinary connective tissue. In the so-called cartilages 
of the eyelids only connective tissue can be recognized. 
We pass to the gelatinous tissue and reticular connective 
tissue. 
Cartilage presented the quality of solidity ; gelatinous tis- 
sue shows the character of softness in the highest degree. 
Its most simple variety, the vitreus of the eye, is the richest 46 
FOURTH LECTURE. 
in water of all the tissues of the body ; it contains only I. 3 
per cent, of solid constituents, of which a part must still be 
referred to a delicate pellicle surrounding and permeating the 
whole. And yet the origin of the cartilage and corpus vit- 
reum are similar. We again meet with rounded, indifferent 
cells with a homogeneous, intercellular substance. In car- 
tilage (Fig. 23) the latter early solidifies ; in the vitreus it 
becomes watery and swells up, so that in a human embryo 
of four months (Fig. 46) the 
protoplasmatic cells, meas- 
uring 0.0104 to 0.0182 mm., 
are separated by considera- 
ble intermediate gelatinous 
tissue. The latter gives the 
reaction of mucous sub- 
stance or mucin, that sub- 
stance with which we have 
already become acquainted (p. 36), as a product of the meta- 
morphosis of the epithelial cells. For this reason our tissue 
has already been given the name of mucous tissue. 
Fig. 46.—Tissue of the vitreous body of a hu- 
man embryo. 
In the vitreus of the mammalia after birth, the formative 
cells become arrested, and, widely separated by the interven- 
ing gelatinous tissue, are only with difficulty recognized. 
A higher development of the gelatinous tissue is consti- 
tuted by the so-called enamel organ of the progressing tooth. 
The teeth, as is known, are formed and concealed in the jaws ; 
the crown is first formed and the root last. The former is 
covered, at its commencement period, by a cap or bell-shaped 
structure, from the concave under surface of which the for- 
mation of the enamel takes place. Hence the name. 
Here (Fig. 22) we meet with a net-work of delicate, nucle- 
ated stellate cells with a varying number of processes. Some- 
thing like a cell division ib) is occasionally seen. The meshes 
are filled with a homogeneous gelatinous tissue containing 
mucus. 
The same condition prevails, at an early period, in the 
Whartonian jelly of the umbilical cord. Later, we meet, in THE CONNECTIVE-SUBSTANCE GROUP. 
47 
addition, with connective-tissue bundles which lie externally 
to the now flattened cells. The system of spaces is again 
filled with gelatinous substance. 
This is a tissue, therefore, which 
early disappears. 
Under reticular connective tissue 
(Fig. 47) we understand a cellular 
tissue, in the meshes of which lie 
innumerable lymphoid cells. His 
lias called this adenoid tissue. It 
appears to be frequently a second- 
ary formation, proceeding from 
rnetamorphosed common connect- 
ive tissue of the foetal body. 
Reticular connective tissue pre- 
sents, in addition, many changes, 
according to age and locality. As 
its element (Fig. 8), we meet with a 
delicate, stellate cell with a nucleus 
°f 0.0059 to 0.0075 rnm. and a 
moderate-sized protoplasma body. 
numerous processes, which repeatedly divide and thereby 
become constantly finer. By the conjunction of such adja- 
cent branches, which have often arisen under a right angle, 
smaller nodal points are frequently formed, in which a nucleus 
is naturally wanting. 
Fig. 47.—From a lymphoid follicle 
of the vermiform appendix of the rab- 
bit. Fig. 1, reticular tissue with the 
meshes, b, and the remainder of the 
lymph cells, a ; most of the latter have 
been artificially removed. Fig. 2, 
more superficial. 
The latter sends out 
The delicate, mostly polyhedral meshes are usually rounded, 
but may also assume an elongated form. They are smaller 
m the new-born than in the adult. In the latter, during the 
period of health, the nucleus and cell body are usually 
shrunken, so that they may be overlooked. In irritated con- 
ditions, however, the former tense condition is rapidly re- 
established in the swelling tissue. 
Such reticular connective tissue is met with in the lymph 
glands, as well as in a series of allied parts of the body, which 
will combine as lymphoid organs, such as the tonsils, 
thymus gland, and Peyer’s follicles. The Malpighian cor- 48 
FOURTH LECTURE. 
puscles of the spleen also belong here. The tissue of the 
spleen pulp is still more strongly modified. 
The mucous membrane of the small intestine also contains 
our tissue ; although the number of lymphoid cells is here much 
less, and the cell processes not unfrequently appear broader, 
lamelliform. In the large intestine, finally, something inter- 
mediate between our tissue formation and ordinary con- 
nective tissue is met with. 
True connective tissue, to the consideration of which we 
shall soon arrive, appears partly as a firm, partly as a loose 
texture. In the latter case, as under the corium, under 
mucous and serous membranes, etc., it 
encloses irregular communicating spaces. 
These are frequently occupied by groups 
of peculiar cells, overladen with fat. 
This is fat tissue (Fig. 48, a). 
We now turn to the adipose tissue. 
The cells appear large, measuring 
0.076 to 0.13 mm., with nuclei of 0.076 
to 0.009 mm. A thin covering closely en- 
velops a single large drop of fat. The 
latter, from its strong refractive power, 
conceals the nucleus and the outlines of 
the envelope. 
Fig. 48.—a, human fat cells, 
lying together in groups; 6, 
free globules of fat; c, empty 
envelopes. 
An appearance is thus caused as if 
there were free drops of fat, with a dark 
periphery by transmitted light, yellow- 
ish, silvery and bright by incident illumination. Still, the 
always considerable diameter, a slight polyhedral flattening 
of the elements which are closely pressed together, avert the 
mistake. Free fat forms spherical drops of every possible 
size (b). 
The envelope, after its rupture and the escape of the con- 
tents, may be demonstrated as a thin, collapsed sac (z), like- 
wise in an intact condition, after drawing out the fatty con- 
tents with alcohol or ether. The nucleus, lying quite excen- 
trically, is readily recognized after tingeing with carmine. THE CONNECTIVE-SUBSTANCE GROUP. 
49 
The fat of the human body is a mixture of an oleaginous 
substance, triolein, which contains in solution certain quanti- 
ties of more solid matter, tripalmitin and tristearin. When 
the latter increase, there are, on the cooling of the body at 
first, depositions of tuberculated forms, and finally of crys- 
talline. We now perceive irregular needles, at one time tuft- 
shaped and stellate, radiating from a central point, again in 
crowded aggregations filling the whole cell. On warming 
they again disappear. 
Adipose tissue takes a very active part in the material 
changes of the body; it is likewise a very vascular substance. 
As a result of prolonged starvation, in exhausting diseases, 
a portion of the fatty contents disappear from the cell 
(Fig. 49), The fat drop (d) 
is at first but slightly re- 
moved from the membrane. 
A spherical cortex of gela- 
tinous, finely granular sub- 
stance (protoplasma?), sur- 
rounds the former; the nu- 
cleus now becomes visible. 
The progressing deprivation 
of fat is shown by the cells ato f and h. Finally (£■), only a 
few fat globules remain; the entire cavity is now occupied by 
the gelatinous matter. Such examples have been designated, 
not especially happily, as fat cells “ containing serum.” 
Fig. 49.—Impoverished fat cells from the sub- 
cutaneous cellular tissue of a human cadaver. 
If the body outlasts this condition of emaciation, and sub- 
sequently, by a more abundant nourishment, resumes the old 
full appearance, the cells have again become filled with the 
fatty contents. 
The massiveness of the adipose tissue varies considerably. 
It is greater in children and women than in men ; more con- 
siderable in the blooming period of life than in senility. 
Here, above all, individuality asserts itself very powerfully. 
In high degrees of obesity, fat cells frequently occur in places 
where they do not belong, as, for example, between the mus- 
cular fibres. In far advanced emaciation, the panniculus adi- 50 
FOURTH LECTURE. 
posus disappears; though certain parts, like the orbital cavity 
and the medulla of the central portion of the hollow bones, 
still obstinately retain the fatty contents 
within their cells. 
Adipose tissue is of a secondary nature. 
It is entirely wanting in the earlier embryo- 
nic life. The fat cell arises from a metamor- 
phosis of the cells of the connective tissue. 
The ordinary flat, lapped and pointed ele- 
ments of the latter (Fig. s°. a) take up fat 
drops in increasing quantity {b); these flow 
together, the cell becomes rounder, losing 
its processes (c), and finally assumes the 
; well-known appearance (d). There is also 
■ another coarsely granular connective-tissue 
cell, to which more attention has only re- 
cently been called, and which may possibly 
be transformed into a fat cell. We regard the so-called cell 
membrane as a boundary layer formed from the adjacent 
connective tissue. 
Fig. 50. Transfor- 
mation of the connect- 
ive tissue corpuscles 
into fat cells, from a 
human muscle, serving 
at the same time as a 
diagram of the embryo- 
nic origin. FIFTH LECTURE. 
CONNECTIVE TISSUE. 
True connective tissue, the “ cellular tissue ” of the oldei 
anatomists, is very extensively diffused throughout the body. 
As a member of the whole tissue group, it also consists of 
cells and intercellular substance. The latter, on boiling, does 
not yield the chondrin of cartilage (p. 42), however, but 
ordinary glue or glutin. The intercellular substance here 
shows a further metamorphosis in a double direction ; firstly, 
into the so-called connective tissue bundles and fibrillae; and 
secondly, into the multiform elastic elements. The latter 
form fibres, reticular fibres, perforated membranes, limiting 
layers around connective- 
tissue bundles, and also 
around spaces which con- 
tain cells. 
The longest.known is the 
gelatine yielding fibrilla, 
the constituent which im- 
mediately attracts the eye. 
It appears in the form of a 
very fine, hyaline, un- 
branched filament, 0.0007 
mm. in diameter, often 
very extensible, and at the 
same time possessing elas- 
ticity (Fig. 51, to the left). 
These very readily isolat- 
able fibrillse very commonly unite into sometimes thinner, 
sometimes thicker bundles (in the figure to the right). Their 
elasticity very frequently produces an undulated or curly 
Fig. 51.—Connective-tissue bundles. 52 
FIFTH LECTURE 
appearance in separated portions of the tissue. The inter- 
weaving of the fibres varies considerably. When loosely in- 
terwoven, the bundles running in one plane are united by 
homogeneous, membranous intermediate substance. 
Acetic acid, an important reagent, causes the bundles to 
swell up rapidly and the fibrous appearance to disappear. By 
washing out, or neutralizing that reagent, the former ap- 
pearance is restored. 
Previously, the excess of connective-tissue fibrilla very fre- 
quently concealed the intermingled elastic elements. Now, 
in the acid preparation, the latter make their appearance 
(Fig. 52). We perceive, firstly, the finest, frequently corru- 
gated fibrillse without ramifications {a). They remind one of 
the connective-tissue fibrillse ; but the darker appearance, 
and the power of resisting acetic acid, permit of no mis- 
take. Other elastic fibres are larger. 
Fig. 52.—Human elastic fibres. 
Very frequently there are ramifications, and by the com- 
munication of the branches an elastic net-work is formed. 
We perceive such an one at b, with large meshes, and fibres 
which measure only 0.0014 to 0.0025 mm. in thickness. CONNECTIVE TISSUE. 
53 
If we search further, we meet with transitions to broader 
and thicker ramified fibres (c), which, in contradistinction to 
the extensible finer ones, gradually assume a considerable 
inflexibility and brittleness. Their diameter may increase to 
0.0056 to 0.0065 mm. 
In other places, the walls of the larger arteries, we find co- 
herent elastic membranes, in which fine fibrillae and reticular 
fibres are embedded as ledge-like thickenings. There also 
occur homogeneous layers of elastic sub- 
stances which are perforated with little holes 
(Fig. 53, i). Between these and a small- 
meshed reticulum of very broad, flat elastic 
fibres (2) it is, indeed, often 
impossible to make a demar- 
cation. 
These changing elastic ele- 
ments are met with in still 
another condition. They 
form a structureless sheath 
around many connective-tis- 
sue bundles. As surely as 
an innumerable quantity of 
these bundles are without 
envelopes, and exhibit only 
a fibrillated cord, even so 
little can the presence of a 
sheath around others be 
doubted ; as on those which 
pass from the arachnoid, at 
the base of the brain, to the 
larger blood-vessels, on the 
fasciculi of the tendons, on 
much of the subcutaneous cellular tissue. If we apply re- 
agents which produce considerable swelling, as acetic acid, a 
strange appearance is caused (Fig. 54). The sheath is torn 
mto transverse portions, and these rapidly contract between 
the protruding portions of the connective-tissue bundle to 
Fig. 53.—Elastic net- 
work from the aorta ; 1, 
of the ox; 2, of the 
horse. 
Fig. 54.:—Acon- 
nective-tissue bun- 
dle, from the base 
of the humanbrain, 
treated with acetic 
acid. 54 
FIFTH LECTURE. 
very delicate rings, which have a striking resemblance to an 
elastic fibre. Cotton fibres undergo a very similar change on 
the addition of ammoniac copper; only, everything is here 
more massive and easier to observe. 
The most difficult part in the investigation of the connective 
tissue is formed by the cellular elements, the connective-tis- 
sue corpuscles of an earlier period. After manifold strayings, 
a greater light has only of late years been disseminated. 
Since the cells were, as a rule, usually concealed by the 
substance of the fasciculi, acetic acid was formerly generally 
used for the recognition of the former. This, and even 
water, immediately distorts the cells into caricatures. The 
latter have been almost universally known and described for 
tens of years ; and capital has been made of them ! 
The cellular elements are distinguished into non-essential 
migratory, and essential fixed. The former are lymphoid 
cells, which, having escaped from the blood and lymphatic 
vessels, slowly wander through the channels of our tissue. 
The ordinary fixed connective-tissue cell appears as a 
simple or complicated lamellar structure. An oval nucleus 
is surrounded by some protoplasma. The thin structure 
becomes extremely pale and veil-like at the periphery, 
and runs out into points or fibrillse. Very frequently, how- 
ever, there is also a vary- 
ing number of lateral plates 
resting at different angles 
over the middle of these 
chief plates (Fig. 55, a), so 
that a certain resemblance 
to an irregular, crumpled 
shovel edge is produced 
(Ranvier, Waldeyer). Such 
cells lie in the firm connec- 
tive tissue, in the spaces 
between the fasciculi, and have, according to our views, as- 
sumed the described forms subsequent to the growth in thick- 
ness of those fasciculi. The procedure may be illustrated by 
Fig. 55.—Cells of human connective tissue ; a, 
fiat and shovel-shaped elements ; i, coarse granu- 
lar cells. CONNECTIVE TISSUE. 
55 
placing a lump of warm, soft wax between the points of 
three fingers and pressing them together. 
There is still another cell formation met with in connective- 
tissue structures ; they are often very rare ; in places, how- 
ever, quite numerous. They are larger, coarse granular 
structures, with a nucleus and an either rounded or spindle- 
shaped body, without that system of lamellae and processes 
°f the previous form (b). They have been met with in the 
vicinity of vessels, especially arteries, and have received the 
name of-plasma cells (Waldeyer). 
Fat cells may proceed from both varieties of cells, the flat 
and the coarse granular (p. 49). 
Connective-tissue cells also assume an extremely peculiar 
appearance from receiving melanine granules into their body 
(Fig-, 9). This is the “stellate pigment cell” of the earlier 
histologists. The coal or brown-black molecules are smaller 
than in the pigmented epithelium (p. 30). In man such cells 
are limited almost exclusively to the eye. In the lower ver- 
tebrates, such as many of the amphibia, this process of pig- 
ment embedding is enormously diffused, so that in every little 
Piece of connective tissue the strangest cells are met with, 
°ccurring in every possible stellate form. 
The flat connective-tissue cells and their colored associates 
(Tig. 56), show a slow, 
but unmistakable vital 
c°ntractile power. This 
ls not yet recognized in 
the plasma cell. 
Connective tissue, whose 
lrnrnense diffusion in the 
human body we have al- 
ready mentioned, by the 
arrangement and interlac- 
Ing of its bundles, by its 
Very dissimilar proportion of elastic elements, the extremely 
triable vascularity, and, finally, by the commingling of insoh 
üble elements, forms substances which appear to the naked 
Fig. change of form of a pigmented, 
connective-tissue corpuscle from a water newt, during 
45 minutes. 56 
FIFTH LECTURE. 
eye as quite dissimilar things, and which in reality are very 
nearly related. 
The usual system of anatomy recognizes primary bundles, 
that is, simple fibrous cords. A portion of these, held 
together by loose connective tissue, constitute secondary 
bundles, and from these latter tertiary are formed. 
We have, firstly, as a badly selected name runs, “form- 
less” connective tissue. Soft and extensible, it forms the 
general filling up substance of the organism. Membraniform 
connective-tissue bundles with homogeneous interstitial sub- 
stance (Fig. 51), form thin lamellae, wdiich superimposed on each 
other at various angles, incompletely limit cavities. These 
are the so-called “ cells” of the older anatomists, who gave 
our tissue the name of cellular tissue. The lamellae are often 
nearly in contact with each other, but the space enclosed by 
them may also be completely filled by collections of fat cells. 
Where structureless connective tissue occurs in greater quan- 
tity it has received special names. Thus, one speaks of sub- 
cutaneous, submucous and subserous connective tissue. 
Elastic elements are here met with, sometimes scanty, some- 
Jmes more profuse, but never in excess. 
We now come to the formed connective tissue, with its nu- 
merous varieties. This constantly arises from the formless 
variety without any sharp demarcation, so that this division 
of the anatomists is entirely artificial. 
We enumerate here : 1. The corneal tissue. The cornea 
has on its anterior surface stratified pavement epithelium, on 
its posterior a simple cell covering. Under both epithelial 
coverings there is a hyaline layer. The anterior is called the 
lamina elastica anterior, the posterior the Descemet’s or De- 
mours’ membrane. The hyaline corneal tissue consists of a 
net-work of decussating bundles, which may be divided into 
fibrillse of extreme delicacy. The whole is permeated by a 
system of passages which have a sort of parietal layer. In 
these lie the “corneal capsules,” which are flattened cells, 
comparable to a paddle-wheel. Wandering lymphoid cells 
are also not wanting. CONNECTIVE TISSUE. 
57 
2. Tendinous tissue. Longitudinal bundles of a fibrillary 
connective tissue with an elastic boundary layer arranged in 
a compact manner are met with. Between them one recog- 
nizes in transverse sections a system of indented and stellate 
spaces. In these lie, arching over the connective-tissue 
bundles, ordinary lamelliform and shovel-shaped connective- 
tissue cells, and also isolated lymphoid corpuscles. Only 
scanty, fine, elastic fibres occur in this extremely bloodless 
tissue. 
3. The ligaments are, with the exception of the elastic, 
formed like the tendons. 
4. The connective-tissue cartilage (see p. 45). 
5- The so-called fibrous membranes. Firmly woven, non- 
vascular structures with a varying intermixture of elastic ele- 
ments. Among these are the dura mater of the brain and 
spinal cord, the sclerotic of the eye ; the firm envelopes of 
many organs, for example, of the kidneys, testicles, and 
spleen ; furthermore, the fascise of the muscles, the coverings 
°f the nerve trunks (the perineurium or neurilemma), the 
covering of the cartilage and bone (the perichondrium and 
periosteum). The latter is permeated by numerous blood- 
vessels, but which serve principally for the nutrition of the 
invested bone. 
6. The serous membranes, which formerly were erroneously 
considered as entirely closed sacs, consist of a but slightly 
Vascular net-work of connective-tissue bundles, occasionally 
with a considerable contingent of elastic-reticular fibres. The 
free surface is covered by endothelium. To this variety be- 
long the pleura, pericardium, peritoneum and tunica vaginalis 
propria of the testicle. As more incomplete structures, we 
mention the arachnoid membrane of the brain and spinal 
cord, the synovial capsules (having a serous membrane only 
at the sides, and here covered by a simple layer of epithelial 
cells), and also the mucous pouches and the sheaths of the 
tendons. The serous cavities, like the passages between the 
connective-tissue bundles, must be regarded as belonging to 
the lymphatic apparatus, as we shall perceive hereafter. FIFTH LECTURE. 
7. The corium. More firmly interwoven, decussating con- 
nective-tissue bundles with numerous elastic fibres. The 
closely interwoven, very vascular tissue projects towards the 
surface in small papillae of varying shape, in the form of the 
tactile bodies. It is continuous below', without any sharp 
demarcation, with the subcutaneous cellular tissue. Other 
foreign constituents consist of hairs, involuntary muscles, 
glands, nerves. As a covering, we are already familiar with 
the epidermis, the thickest pavement epithelium of the body 
(P- 32). 
8. The mucous membranes. Also extremely vascular, but 
less compactly arranged, and with fewer elastic elements. 
In places it is enormously rich in glands. Smooth muscles 
form a widely diffused constituent. The surface frequently 
projects in papillae. The ordinary connective tissue of the 
mucous membranes may, however, be replaced by reticular 
connective tissue (p. 47). We already know that the epithe- 
lial covering differs exceedingly (pp. 30, 33, and 34). 
9. The vascidar membranes of the central nervoiis organs 
and of the eye; that is, the pia mater, choroidal plexus and 
choroid. A thin, soft connective tissue, in the choroid a 
reticulum of pigmented cells, here show's throughout an enor- 
mous wealth of blood-vessels. 
10. In the structure of the vascular walls connective tissue 
plays an important r6le. Nevertheless, the elastic element 
often increases to such an extent, that the connective-tissue 
bundles and cells recede. One speaks then of “elastic” 
tissue. 
11. This predominance of the elastic elements is also pre- 
sented by the ligaments and membranes of the respiratory 
organs, and likewise by the tissue of the lungs. The same is 
also . seen in the outer layer of the oesophagus, the yellow 
ligaments of the vertebral column, and the ligamentum 
nuchae of mammalial animals. Many of the latter structures 
have lost all connective-tissue bundles. 
Connective tissue possesses but slight vital dignity; it 
comes into consideration in the structure of the organism, in CONNECTIVE TISSUE. 
59 
consequence of its physical properties. Only the more vas- 
cular connective-tissue structures take a more active part in 
the normal material changes. 
During abnormal conditions, however, our tissue assumes 
a new and more vigorous life. From the cells other tissue 
elements may be formed. To determine the magnitude of 
this participation more accurate studies 
are indeed necessary, for the wandering 
lymphoid cells also play their part, and, in 
°ur opinion, in a very important manner. 
We also mention the origin of the con- 
nective tissue. The terminations are 
again similar to those of cartilage. Mem- 
braneless protoplasmatic stellate and 
spindle cells are noticed at an early peri- 
od, held together by a scanty intercellular 
substance, which is at first homogeneous. 
A transformation soon takes place in the 
latter and in the cells, the processes of 
the latter dividing into groups of fine 
connective-tissue fibrillae (Fig. 25, b), 
These bundles of fibrillae gradually ap- 
proach the cell nucleus. The original 
cell protoplasma also becomes changed 
lnto bundles of fibrillae ; new protoplas- 
taking the place of the old, surrounds 
the nucleus, to subsequently pass through 
the same process of metamorphosis (Fig. 
57, A), till at last the cells lie outside of 
their children, that is, the bundles formed from them, in the 
shape of lamellae, with notched margins, or irregular, paddle- 
wheel-like structures (see above). 
Fig. 57.—From the liga- 
mentum nuchae of a hog’s 
embryo. A, side view ; a, 
spindle cells in a fibrous ba- 
sis substance, b; B, the 
elastic fibres c, brought out 
by boiling in a solution of 
potash (alcohol preparation). 
In this intercellular substance, the genesis of which we 
n°w understand, the formation of elastic fibres and reticular 
fibres also takes place subsequently (B). How far the cellu- 
ar elements participate in this requires still more accurate 
investigation. SIXTH LECTURE. 
BONE TISSUE. 
We now turn to the most complicated variety of connective 
substance : we refer to the osteoid or bone tissue. 
It is distinguished for its considerable hardness and firm- 
ness. In man, this member of our tissue group is, with the 
exception of a covering to the tooth root, limited exclusively 
to the bones. 
The anatomists divide the latter into long or cylindrical, 
broad or flat, and, finally, short or irregular bones. 
Let us begin with the middle portion or diaphysis of the 
former, taking a radial longi- 
tudinal section sawn out from 
the dry femur (Fig. 58). 
A very peculiar appear- 
ance is presented. The thin 
lamella is permeated by a 
system of longitudinal canals, 
connected, in a reticular man- 
ner, with a medium width of 
0.1128 to 0.0149 mm. {a). 
The transverse branches open 
out onto the surface of the 
bone, as well as inwards into 
the medullary canals, and re- 
ceive the nutrient vessels 
from both sides. They bear 
the name of the medullary 
or Haversian canalieuik- 
Fig. 58.—Vertical section through the human 
femur; a, medullary canals ;b, bone corpuscles. 
Transverse sections (Fig. 59) naturally present an entirely 
different appearance. The rounded and oblique spaces (c) bone tissue. 
are transversely or obliquely opened longitudinal canals. 
Communicating horizontal canals are now also seen opened 
in a longitudinal direction or 
obliquely. 
The bone substance pre- 
sents, as is shown by the 
transverse section, a lamel- 
lated structure. 
There is a double system of 
layers, however. Firstly, we 
meet with plates which pass 
through the entire thickness 
of the bone, in contact ex- 
ternally with the periosteum 
and internally limiting the 
great medullary canals. They 
are called general or funda- 
mental lamellae (a, d). An- 
other uncommonly abundant 
system of lamellae surround, the individual medullary canals 
with a varying number of layers. These are the special or 
Haversian lamellae (around c). The thickness of both varieties 
of lamellae varies from 0.0065 t° 0.0156 mm., and the ar- 
rangement is often far removed from making any claim to 
regularity. This stratification may also be recognized in 
longitudinal sections as a system of lines, though with less 
distinctness. 
Fig. $9.—Transverse section of a human 
metacarpal bone ; a, outer surface ; c. medul- 
lary canals with the special lamellae: d, inter- 
general lamellae ; e, bone corpuscles. 
A plate of dry bone, let it be taken from where we will, 
always presents a further extremely peculiar structural con- 
dition ; it appears black by transmitted and white by incident 
light, and consists of a marvellously complicated very fine 
canal-work with indented and radiated nodal points. The 
former passages are badly enough named calcareous canali- 
culi ; the dilatations bear the name of the bone corpuscles < r 
lacunae (Figs. 58, 59). 
The form of the lacunae (Fig. 60, a) may be illustrated by 
calling them lens-shaped, or by comparing them to the figure 62 
SIXTH LECTURE. 
produced by two human hands when their volar surfaces resl 
over each other. The length is 0.1805 to 0.0541, the breadth 
3.0068 to 0,0135, the thickness 
0.0045 to 0,009 mm. The offshoots 
of this system of cavities, very nar- 
row canals of 0.0014 to 0.0018 mm. 
diameter, permeate the entire tissue 
in innumerable multitudes, ramifying 
irregularly in a radial direction. 
They open (1) in the Haversian 
canals (b), (2) on the surface of the 
bone, and (3) in the large medullary 
cavity in the interior. Transverse 
and longitudinal sections (the tan- 
gential must also be added) teach 
this most distinctly. 
Fig. 6o.—Lacunas (a, a) with their 
numerous offshoots, opening into the 
transversely divided Haversian canal 
(*)• 
In the dried bone, the marvellously complicated system of 
canaliculi has become filled with air in a condition of the 
finest division. An earlier epoch erroneously assumed the 
contents to be inorganic hardening material, to be the finest 
molecules of the so-called bone earths. Hence the name of the 
“ calcareous canaliculi.” If we place the small thin plate in 
turpentine oil, the thousands upon thousands of finest canali- 
culi rapidly fill with the fluid through capillary attraction. 
The bone corpuscle now presents the appearance of a cavity ; 
the fine canaliculi disappear more or less in the basis sub- 
stance. 
But what does this remarkable canal work 
contain during life ? 
We answer to this, there is in the lacunae a 
protoplasmatic membraneless cell (Fig. 61, b). 
Whether this bone cell, the equivalent of the 
connective-tissue corpuscle, sends off capillary 
offshoots into the lacunae, which is very prob- 
able, we do not yet know. The latter canalic- 
ular system is certainly filled, with transuded blood plasma. 
This fluid must, besides, be rather stagnant, for the frictional 
Fig. 61.—From 
the fresh ethmoid 
bone of the mouse; 
basis substance ; 
t, the bone cell. BONE TISSUE. 
63 
resistance here imposes a veto to the circulation which is with 
difficulty removed. 
Are the lacunae and calcareous canals only cavernous sys- 
tems excavated in the hard, solid basis substance,, or have 
they a special parietes ? After energetic macerating media, 
the previously decalcified bone presents a thin resistant 
boundary layer around the lacunae and canaliculi. It appears 
to be a decalcified elastic substance. It was formerly errone- 
ously considered to be a cell membrane. 
Having become familiar with the most essential portion of 
the structure in the diaphysis, let us now turn to a very short 
discussion of the other parts of the skeleton. The beauti- 
ful regularity here disappears, sometimes to a less, sometimes 
to a greater degree. Even in the epiphyses of the cylindrical 
bones, in consequence of the thinness of the osteoid plates, 
the systems of lamellae are present in a far less developed 
condition around the Haversian canals, and the inner funda- 
mental lamellae are absent. In spongy bone tissue the 
Hminar arrangement may still be distinctly recognized in the 
thick trabeculae and plates, while it disappears more and 
more with the decrease in size. In the cortical layers of flat 
bones, the medullary canals run parallel to the surface, gene- 
rally starting from a point and assuming a radiate direction. 
In the short bones the course generally preponderates in one 
direction. Funnel-shaped apertures of the Haversian canali- 
culi may join together and form small medullary cavities, the 
prefigurations of the larger, etc. 
The bones contain but little water, the compact having 3 to 
7, the spongy 12 to 30 per cent. The organic, form-deter- 
mining basis, amounting from 30 to 45 per cent, in the dry 
bone, is transformed by boiling into glutin, that is, the ordi- 
naiy g}ue Qf the connective tissue. This is diffusely hardened 
by the embedded bone earths. By this is understood a mix- 
ture, amounting from 51 to 60 per cent., of lime salts with a 
slight admixture of magnesia salts. The bone earths yield 
nbout 86 per cent, of phosphoric acid, 9 of carbonate of lime, 
3- 5 of fluoride of calcium, and 2 of phosphate of magnesia. 64 
SIXTH LECTURE. 
When the bone is carefully decalcified its texture remains 
as of old. It is easy to cut the mass, which has now become 
semi-transparent. It is badly enough named the bone car- 
tilage. 
In the mechanical construction of the body, the bones 
come into consideration by reason of their solidity. They 
serve as a protection to softer organs, and form systems of 
levers moved by muscles. The less the proportion of bone 
earths contained, the greater the flexibility and cohesion. A 
preponderance of these mineral substances, on the contrary, 
renders the bone inflexible and brittle. The mutability of its 
materials is very considerable. In harmony with this is the 
double system of canals for the blood-vessels and lacunae. 
The larger cavities of the bone become filled with so-called 
bone marrow. This occurs in a double form, though with 
transitions. In the central portion of the long bones it appears 
as a yellow marrow, that is, as fat cells contained in loose 
connective tissue (p. s°)- In the epiphyses, on the contrary, 
as well as in flat and short bones, we find a softer reddish or 
red substance containing, together with scanty connective 
tissue and isolated fat cells, very numerous lymphoid cells of 
0.009 to 0.0113 mm. The latter elements, according to Neu- 
mann and Bizzozero (p. 25), present transitions into red 
blood corpuscles. Finally, we meet in the bone marrow, 
especially towards the surface, the myeloplaxes, which have 
become familiar to us in Fig. 13. The veins are without 
endothelium; they consist only of an adventitia (Hoyer). 
Altogether, the vessels of the medulla promise still further 
interesting conclusions. 
We now turn to the theory of the origin of the bone tissue, 
osteogenesis. It forms a very difficult and complicated sec- 
tion of histology. 
With the exception of a number of the bones of the cranium 
and face, as we have already said, all portions of the skeleton 
are preformed in cartilage. They afterwards present bone 
substance. 
During a long period the direct metamorphosis of the BONE TISSUE. 
former tissue into the latter was unhesitatingly accepted. 
Sharpey, Bruch, H. Mueller, first demonstrated the erro- 
neousness of this hypothesis. 
Disregarding rare exceptions, the facts run, nowadays, in 
this way: The calcified cartilage does not become osteoid 
tissue, but rather melts down, and in the system of cavities 
thus obtained, the bone substance produced by the peri- 
osteum is established as a new tissue. 
If we take a cartilage which is destined to end in this man- 
ner, two different processes are presented : 
I. A local softening of the cartilage tissue (of the cells as 
'veil as of the intercellular substance) has taken place from the 
surface in an inward direction. Very irregular, manifoldly 
ramified passages have thus been formed. Vessels have 
grown into the latter from the perichondrium, accompanied 
hy lymphoid and unripe connective-tissue cells. This sub- 
stance has been not badly named the cartilage marrow. 
Until recently, it was erroneously assumed that the so-called 
cartilage marrow cells represented derivatives from cartilage 
cells which had penetrated the softened portion. 
2. In the centre of such a cartilage, a calcification of the 
mtercellular substance (p. 44) and very generally, also, an 
energetic forma- 
tion of so-called 
daughter cells 
occurs (Fig. 62). 
This place has 
been called the 
Point of ossifi- 
cation badly 
enough, we add. 
Tor, although a further melting down of the calcified tissue 
occurs here forthwith, and, in the spaces thus formed, the first 
deposition of osteoid tissue commences immediately after- 
wards, this calcified cartilage has nothing whatever to do with 
the latter. 
Fig. 62. —Dorsal vertebra of a human foetus of ten weeks in vertical 
section, a, calcified ; b, soft cartilage. 
The two metamorphoses just mentioned proceed rapidly 66 
SIXTH LECTURE. 
side by side and against each other. The calcification of the 
cartilage spreads peripherically; the liquefaction and re-forma- 
tion of the cartilage canals is constantly increasing in extent, 
and likewise in the domain of the calcified cartilage. 
Fig. 63.—Ossifying border of a phalangeal epiphysis of the calf, in vertical section. At the upper 
part, the cartilage, with its irregularly disposed capsules, containing daughter cells ; a, smaller 
medullary spaces, appearing in part as though closed, drawn empty ; 6, the same with yarrow cells ; 
c, remains of the cilcified cartilage; d, larger medullary spaces, on the walls of which are depo- 
sitions of thinner or thicker bone tissue, and in the hitter case stratified ; e, developing bone cell; 
/, an opened cartilage capsule, with an embedded bone cell; g, a partially filled' cavity, covered 
externally with bone substance and containing a harrow cell; /4, apparently closed cartilage capsules 
containing bone cells. 
The latter must naturally first become physiologically 
decalcified before undergoing solution. This removal of a but 
just deposited lime salt is, up to the present time indeed, 
somewhat enigmatical. 
Let us look at Fig. 63. At the upper part, the cartilage BONE TISSUE. 
still presents the old soft appearance. The cartilage cells lie 
here, in an epiphysis, irregularly. In a diapltysis they would 
be seen pressed together in longitudinal rows, or “ ranked,” 
as it has been expressed. Below, however, we meet with a 
cavernous tissue, the spaces of which, as a result of the prepa- 
ration, in places no longer lodge the cartilage marrow con- 
tents (,a), while it still remains preserved in others (3, d). 
Cloudy, dark trabeculae of the most irregular form constitute 
the last remains of the liquefying decalcified cartilage (y). 
Even these trabecular remains are deprived of further re- 
pose. 
Fig. 64.—Transverse section from the femur of a human embryo of about eleven weeks ; a, a 
transverse, and b, a longitudinally divided medullary canal; c, osteoblasts ; d, the more trans- 
parent, younger, e, the older bone substance ;f, lacunae with the cells ; g-, cells still limited 
to the osteoblast. 
If the contents of these cavernous passages are attentively 
examined at this period, their peripheral cells are found to 
have assumed an anomalous shape. They resemble, with 
their cubical bodies (Fig. 64, c), an irregular, badly developed 
cylinder epithelium. Gegenbaur, their discoverer,, has 68 
SIXTH LECTURE. 
called them osteoblasts—and rightly, for they form the osteoid 
tissue. 
As in a line of inordinately crowded soldiers, one or 
another will be pressed out in front, so does it happen to cer- 
tain of these osteoblasts (g). They now assume indented or 
stellate shapes ; homogeneous, but very soon diffusely calci- 
fied intercellular substance then appears around them. The 
latter as a thin layer—we might say, covering the irregular 
surfaces of the still remaining calcified cartilage trabeculm like 
a wax impression—is the first lamella of the osteoid sub- 
stance ; the indented osteoblasts form the first bone cells, 
however. Our Fig. 63 shows this at its upper portion 
[a, a, a), also at the left, half way up [c, d). 
Concerning the conception of the intercellular substance, 
whether it arises from a secretion of the cells or from the 
metamorphosed cell bodies, the same uncertainty of opinion 
prevails as with other members of the connective substance 
group. 
We have here still more peculiar illusive appearances to 
consider. It is comprehended that by the continual lique- 
faction of the cartilaginous trabeculae the cavities of the tissue 
become opened, and must then serve for the deposition ot 
bone cells and homogeneous basis substance. When the 
conditions are as at f of our Fig. 63, the matter is at once 
clear, the places is also, in a measure, appreciable. When, 
however, the cavities are ruptured from below or above, this 
does not fall within the plane of the section, and we have the 
deceptive appearance of closed cartilage cavities with endo- 
genous bone cells. 
This, which thus occurred for the first time, is repeated 
in rapid sequence manifoldly after each other. Lamella 
upon lamella with enclosed bone cells result (Fig. 63 in 
the lower half). We obtain in this way a stratified 
osteoid tissue. The remains of the cartilaginous tabeculae 
disappear more and more with the continuing process of 
liquefaction. 
But this thing, in its wild, confused irregularity is very dif- BONE TISSUE. 
69 
ferent from the bone tissue which appears in such elegant 
regularity at a later day.* 
Now, how does the latter arise from the former? 
Two different opinions exist on this subject. According to 
the first, and we adhere to this for the most part, the osteoid 
tissue, which is formed at the expense of, and within the foetal 
cartilage, the so-called endochondral bone, has not a happy 
life. It yields to an early death, a speedy process of lique- 
faction, in order to permit the formation of the large medul- 
lary canals. On its surface is deposited, by the periosteum, 
into which the perichondrium has now become changed, and 
with the aid of a deeper osteoblastic layer, new bone tissue 
which, with a supplementary loss of its inner layers, persists 
in the outer portions and causes the regular, beautiful struc- 
ture of the bone. This may be denoted as the apposition 
theory of osteogenesis. Koelliker has recently re-entered the 
lists for this with great energy. 
Another view rejects the resorption of the endochondral 
osteoid tissue absolutely, and explains the transformation of 
the irregular cavernous bone of the commencement period 
into the regular of the later period of life, by interstitial 
growth alone. An industrious Russian investigator, Strelzoff, 
supported by German predecessors, has recently endeavored 
to substantiate this with greater accuracy. 
We cannot enter further into this actually burning contro- 
versy. The truth, according to our views, lies more towards 
the former sidfe. Nevertheless, the young bone certainly has 
an interstitial growth, which Koelliker also, naturally, 
acknowledges ; but to what degree this occurs no one can, at 
the present time, state with accuracy. A resorption is surely, 
also, not yvanting in the normal bone. This is proved by the 
Haversian spaces of healthy bone, if we disregard the long 
known abnormal resorption processes. Those who deny the 
demonstrative force of such facts are, in our opinion, not 
to be reasoned with further. 
* The central portion of the cylindrical bone has also once had the same cav> 
ernous structure that is presented by the epiphysis. 70 
SIXTH LECTURE. 
Let us then investigate these Haversian spaces. 
Our figure (Fig. 65), shows us three Haversian lamellar 
systems. The two hatched ones {a, a), present inter- 
nally an indented resorption line (b, b). New bone lamellae, 
maintaining the outline, have been deposited on this. To 
the right [c), a second liquefaction has overtaken the latter, 
for which a new lamellar formation endeavors to compen- 
sate 
Fig. 65.—A human metacarpal bone in transverse section ; a*, a Haversian lamella system of 
the ordinary variety ;a, «, two others which have undergone absorption internally (b, b), and thuj 
form Haversian spaces, which are filled up by new lamellae ; c, supplementary absorption in one of 
these with deposit of new bone substance ; d, irregular, and tf, ordinary intermediate lamellae. 
Koelliker has ascribed to the multi-nuclear giant cells (Fig. 
13), the property of dissolving the bone substance, and called 
them osteoclasts. We do not share in this view. Between 
the bone-producing osteoblasts of Gegenbaur and the bone- 
destroying elements of the first mentioned investigator, transi- 
tion forms exist. 
We hold fast to the absorption of the endochondral bone, 
therefore, and now inquire into the particulars of the peri- 
pherical reparation. This is produced by the periosteal bone ; 
that is, the osteoid tissue, which is subsequently furnished 
from the inner surface of the periosteum. 
An. eminent French observer, Ollier, informs us that the 
detached living periosteum, whether it be retained in the body BONE TISSUE. 
71 
of its owner, or whether it be transplanted into that of another 
animal, again produces new bone tissue, only the deepest 
layer must be uninjured. 
If we examine this deepest layer with the help of the 
microscope, we discover our old friends, the osteoblasts. This 
cell layer then grows downwards in a conical form into a re- 
trogressing, indifferent cell substance. 
With the bone-producing force of the osteoblasts we are 
already familiar. Therefore the osteoblast-cones (sit venia 
verbo) produce the Haversian lamellae, while the general 
lamellae are produced by the flat osteoblast layer, which is 
immediately beneath the periosteum. In this manner is also 
explained the regular structure of the diaphysis and its increase 
in thickness. Concerning the latter, further remarks are 
scarcely necessary. 
We may, therefore, say; The endochondral bone dis- 
appears as an embryonic structure, the periosteal remains 
during the subsequent life. 
As we have already learned above, a number of cranial and 
face bones never were cartilage. 
They arise from a soft, foetal connective substance, and have 
been badly named the “secondary” bones. Here, also, 
when there is to be a production of osteoid tissue, we 
meet with osteoblasts and the same process of origin of the 
bone tissue as when formed from the periosteum. The 
development of the bone substance commences centrically 
m certain places, and advances from these peripherically. 
These are, therefore, true points of ossification, in contra- 
distinction to the false, or the calcifying centres of endo- 
chondral bone. 
That connective-tissue fragments are frequently hardened 
With the periosteal and secondary bones, we readily under- 
hand. These things—they sometimes appear like a board 
With nails driven in—have received the name of Sharpey’s 
fibres. 
Many modern investigations also favor an immediate trans- 
formation of one or another cartilage into osteoid substance, 72 
SIXTH LECTURE. 
and likewise of a connective-tissue structure. Still, a calcified 
connective tissue has not thus become bone. 
The proliferous formative life of bone is met with more 
frequently in the abnormal than in the normal processes. Un- 
fortunately, we cannot here enter into this subject. SEVENTH LECTURE. 
DENTINE.—ENAMEL,—LENS TISSUE 
The tooth as a whole is known to everybody. We distin- 
guish, (a) the crown, the free part, (b) then a middle portion 
surrounded by the gum, the neck, and, finally (c), the simple 
°r multiple fang wedged into the alveolus of the jaw. 
Through the centre of the tooth 
passes a canal which has a caecal 
termination above; and below, 
corresponding to the fang, it is 
simple or multiple in form, and 
has a free opening at the apex 
°f the root. This is filled with 
a soft connective tissue, rich in 
vessels and nerves, the pulp. 
The chief mass of the tooth, 
is limited internally by 
the cavity, and is covered exter- 
Ually by a thin cortical layer, 
consists of the so-called tooth- 
hone or dentine, a modified 
°steoid tissue. The crown is 
invested by the enamel, the 
fang by the cementum ; both 
substances meet at the neck. 
Fig. 66.—Human tooth-fang d, with ce- 
ment covering a. At b the granular or 
Tomes’ layer with interglobular spaces ; at 
c and e the dentinal canals. 
Let us first of all examine 
the dentine (Fig. 66, d). It 
c°ntains in a collagenous matrix a still greater quantity of 
hme salts than the osteoid substance. It is permeated by 
extraordinarily numerous, very fine canaliculi, o.ooi i to 0.0023 
broad, the so-called dentinal canals (e, e). Their course, SEVENTH LECTURE. 
74 
disregarding the most acute-angled ramifications and looped 
communications, is on the whole regular. They are, in gen- 
eral, perpendicular to the surface of the pulp cavity and 
therefore vertical on the vertex of the crown, oblique on its 
marginal portions, horizontal over the neck and fang, and at 
the apex of the latter reassuming an obliquely descending 
direction. A transverse section shows them radially 
arranged. By more careful examination, however, we 
meet with a number of smaller interesting variations (Koll- 
man). 
Filled with air they appear dark, saturated with fluid as 
transparent, readily disappearing canals. The condition 
of the lacunae of bone is, therefore, repeated here. An 
elastic, calcified parietal layer, like that of the bone, is 
also not wanting in the dentinal canals. They are now 
much more easily recognized with the greater diameter of the 
tubuli. 
Our dentinal canals open internally into the central cavity. 
The latter may be very well compared to a Haversian canal 
of the bone. 
The fang is covered by cement, as we have already 
remarked. This {a), is a thin layer of bone substance, 
increasing downwards towards the apex of the root, gen- 
erally without lamellar structure, but with delicate bone cor- 
puscles. 
A portion of the lacunae of the latter communicate with the 
dentinal tubuli which have entered the cement or—more cor- 
rectly said—pass over into the latter. At the margin of the 
bone covering and the dentine, numerous spaces occur, the 
so-called interglobular spaces (b), which may be mistaken for 
bone corpuscles. 
Let us leave the enamel covering of the crown for the 
present, and turn to the contents of the dental cavity, the 
pulp. 
In the progressing bone, as the previous lecture taught, the 
ruptured cavities were filled with unripe tissue, on the surface 
of which the osteoblasts appeared. Now the tooth pulp pos- DENTINE.—ENAMEL.—L ENS TISS UE. 
75 
sesses—and at a later stage as well—a similar cell covering. 
T-hese (Fig. 67, b), are the dentinal cells or, as they have been 
characteristically named (Waldeyer), 
the odontoblasts, the sculptors of the 
tooth bone. Our cells, oblong, 
measuring 0.02 to 0.03 mm., are stra- 
tified. One or more of their fine, 
thread-like processes penetrate the 
dentinal tubuli peripherically. An 
able English investigator, Tomes, first 
saw such “ soft fibres ” here. 
Fig. 67.—Two dentinal cells, b, 
which pass with their processes 
through a portion of the dentinal 
canals at a% and protrude from 
the fragment of dentine at c ; af- 
ter Beale. 
The crown is covered with enamel, 
the hardest substance of the body. The organic form-deter- 
mining basis amounts to only a slight per 
cent. (3.5 to 6), against a prodigious excess 
of bone earths. 
The enamel (Fig. 68), a petrified epithe- 
lial production, consists of long, closely 
crowded polyhedral cylinders, the enamel 
Prisms or enamel columns (b). They fre- 
quently appear to pass through the entire 
thickness of the enamel covering; their di- 
ameter is 0.0034 to 0.0045 mm. 
Fig. 68. Peripheral 
portion of the dentine d, 
from the crown; with 
enamel covering, b; a, 
enamel membrane ; c, the 
cavities filled with air. 
Transverse polished sections of the enamel 
show a delicate hexagonal mosaic (Fig. 69). 
A peculiar transversely striated appearance may be recog- 
nized in the isolated enamel prisms. 
The surface of the enamel, finally, is cov- 
ered by an uncommonly tough membrane. 
This is the cuticle of the enamel (Fig. 68, a). 
Beneath the enamel the dentinal tubules 
form loop-like and reticular transitions (Fig. 
d). In the hard brittle substance of 
the former, there has been a formation of 
numerous clefts (<:)„ which may communicate with the canals 
°f the dentine. 
Fig. 69.—Transverse 
section of the human 
enamel prisms. 
With the tolerably simple structure of the teeth, which has SEVENTH LECTURE. 
been described, is connected a very complicated historjr of 
their origin. We here mention only the chief points. 
That the teeth are formed in the maxillary bones, that in 
the infant the eruption first takes place after months and 
years, that the first teeth are for the greater part replaced by 
permanent ones, is known to all. 
Two of the three germinal plates participate in the produc- 
tion of our structures, the corneous layer and the middle ger- 
minal layer. The former produces the enamel, the latter the 
pulp,dentine and cement. 
On the free borders of 
the embryonic jaw ap- 
pears at first a mound- 
like thickening of the 
pavement epithelium 
(Fig. 70, a). It presses 
Fig. 70.—Tooth formation of a 
hog’s embryo ; a, epithelial 
mound ; b, younger cell layer ; c, 
the lowermost; e, enamel organ ; 
f tooth germ ; g, inner, and h, 
outer layer of the progressing 
tooth sac. 
F'ig. 71.—Tooth sac of an older human embryo, partly 
diagramatic ; a, connective-tissue parietes of the 
tooth sac, with the outer layer at a 1 and the inner at 
a 2 ; b, enamel organ, with its external, c, and inferior 
cells, d; e, dentine cells ;f, dentine with the capillary 
vessels,^-; i, transition of the connective tissue of the 
parietes into the tissue of the dentine germ. 
downwards into the soft substance of the maxillary tissue as a 
vertical elongated ridge. The former has been named the 
tooth papilla, the latter the enamel germ. 
From place to place, springing up from the depths of the 
tissue of the jaw, convex papillar structures, the so-called 
tooth germs (f), grow towards the enamel germ. Here and 
there, increasing in diameter, they press in the under surface DENTINE.—ENA MEL.—LENS TISSUE. 
77 
of the enamel germ, and thus give this locally the form of a 
cap or bell. The latter is called the enamel organ (e). 
Leaving the intermediate forms aside, let us pass at a 
bound to a later period. Here (Fig. 71) the enamel organ 
{b) has long since become separated by constriction from its 
point of origin, the epithelium of the jaw, and also thrown 
off the lateral bridge connecting it with the ridge of the enamel 
germ. It is covered on the upper convex and inferior concave 
surfaces with cylindrical epithelial cells (c, d). In the interior 
{b) we find gelatinous tissue (Fig. 22). Below (Fig. 71, f) 
we perceive the thick tooth germ, the progressing tooth crown. 
Both are enclosed within a connective-tissue capsule (a), the 
so-called tooth sac, with external {a1) and internal (a2) layers. 
The sac and tooth germ finally become continuous with each 
other below. 
The tooth germ bears on its surface the layer of odonto-’ 
blasts (e). From them is produced the first thin cortical layer 
of the dentine. Layer on layer are subsequently formed 
over the longitudinally growing tooth germ. By this growth 
it finally obtains the neck and fang ; 
its soft, vascular tissue remains more 
and more retarded in its further 
development, and becomes the pulp. 
From the epithelium at the concave 
surface of the enamel organ, occurs 
the formation of the enamel prisms 
(below d), whether these represent 
calcified portions of the cell body or 
secreted cell substances. The tooth, 
growing up, kills the enamel organ 
at last, and makes its eruption. Its 
cement may originate from the lower 
portion of the tooth sac. This per- 
sists, for the most part, as the peri- 
osteum of the alveolus. 
Fig. 72.—Crystalline lens ; a, cap- 
sule ; b, epithelium of the anterior 
half; c, lens fibres, with the anterior, 
d, and posterior ends, e ; f, nuclear 
zone. 
For the permanent teeth, a secondary enamel germ appears 
to branch off from the original one at a very early period. 78 
SEVENTH LECTURE. 
To close with the epithelial productions, we here notice 
briefly the tissue of the crystalline lens of the eye. This 
(Fig. 72), arising from an ingrowth of the corneal plate of the 
foetus, is invested by a structureless capsule {a, a), which is 
thicker anteriorly and thinner posteriorly. The inner surface 
of the anterior segment of the capsule has an unstratified, 
low, cubical pavement epithelium (b). 
The marginal zone of the latter, advancing towards the 
equator, undergoes a gradual transition into elongated nuclear 
elements, the so-called lens fibres (c). These are 
pale, hyaline elements, in the external portions 
of the organ, 0.009 to 0.0113 mm. ; in the inter- 
nal, where they appear more firm, only 0.0056 
mm. broad. The lens fibre, surrounded by a 
sort of envelope, has the value of a full-grown 
cell. The nuclei {/) lie adjacent to the equatorial 
zone. The arrangement is, in general, meridional. Trans- 
verse sections of the lens fibres present an elegant band of 
elongated hexagons (Fig. 73). 
Fig- 73-—Fens 
fibres in trans- 
verse section. EIGHTH LECTURE. 
MUSCULAR TISSUE 
We now return to the mid- 
dle germinal layer of the em- 
bryonic germ, and discuss one 
of its most important and 
extensive productions ; we 
refer to the muscular tissue. 
This presents, in man and 
the higher animals, two quite 
different appearances. In the 
one we recognize as elements 
elongated, spindle-shaped cells 
of a homogeneous appear- 
ance (Fig. 74) ; in the other 
"we meet with a longer, larger, 
striated fibre (Fig. 75, a). 
One speaks, accordingly, of 
smooth and transversely stri- 
ated muscles. Do not believe, 
however, that we have here to 
do with two entirely different 
things ! In the first place, we 
meet with quite a number of 
intermediate varieties in the 
great multiform animal world ; 
and then the two different 
representatives of the mus- 
cular tissue originate from ex- 
tremely similar initial struc- 
tures. The smooth element stops at a lower stage; the 
Fig. 74.—Smooth muscular tissue of man 
and the mammalia; a, a developing cell from 
the gastric region of a two-inch long hog's em- 
bryo ; b, a more advanced cell; cto g, various 
forms of the human contractile fibre cell ; h, 
one with fat granules ; z, a bundle of smooth 
muscular fibres ; /£, transverse section through 
such a one from the aorta of the ox, with 
many nuclei in the plane of the section.^ EIGHTH LECTURE. 
transversely striated has become further developed. The 
latter contracts rapidly and energetically, the former slow- 
ly and sluggishly ; the latter constitutes the voluntary mus- 
cle, the former the involuntary acting. The heart, with 
transversely striated involuntary fibres, makes, it is true, an 
exception. 
Pale, nucleated bands were formerly assumed to be the 
elements of the smooth muscles (Fig. 74, i). 
In the year 1847 Koelliker reduced the 
band into a series of cellular elements, lin- 
early arranged behind each other, his con- 
tractile fibre cells. At that time this was 
an important discovery, a proof of the dis- 
tinguished observer’s sharp-sightedness. 
We perceive these contractile fibre cells 
at ato k. They are sometimes short, some- 
times longer, not infrequently immensely 
long, spindle-shaped structures, 0.0282 to 
0.2256 mm. and more in length, and of 
moderate diameter, 0.0074 to 0.0151 mm. 
The appearance of the membraneless cell 
body is, as a rule, entirely homogeneous, 
except when a deposition of fat {lt) has 
taken place within it. An elongated nu- 
cleus (it is called rod-like) is readily seen. 
It contains one or more nucleoli. Occa- 
sionally we find the nucleus double or in 
even greater number. 
Fig. 75.—Two trans- 
versely striated muscular 
fibrillae (a), with the con- 
nective-tissue bundles {b). 
Smooth muscles are widely diffused throughout the human 
body. From the oesophagus till near the end of the rectum 
they form the long known thick muscular layer, and, besides, 
a still finer one-—the muscularis mucosas—in the tissue of the 
mucous membrane. Smooth muscles are met with, further- 
more, in the respiratory apparatus, as in the posterior walls of 
the trachea, in the circular fibrous membrane of the bronchi 
and their ramifications. According to many, our tissue is 
not wanting even in the respiratory vesicles of the lungs, MUSCULAR TISSUE. 
although we never could convince ourselves of this. The 
middle layer of the vessels, especially of the arteries, contains 
smooth muscle. Small bundles of the same occur in the ce- 
rium ; thus, in the hair-sacs, arrectores pilorum, furthermore, 
from the surface of the corium to the subcutaneous cellular 
tissue (J. Neumann), then, more connectedly, on the nipple 
and the areola, and especially in the so-called tunica dartos 
of the testicle. The walls of the gall-bladder are also muscu- 
lar. In the urinary apparatus, in the calices, and pelvis of 
the kidneys, the ureters, and the bladder our tissue acquires 
a greater development. The male generative apparatus is 
likewise abundantly provided with smooth muscular sub- 
stance ; still more so that of the female. Even the ovary, 
according to our view, harbors this tissue. It forms con- 
nected layers in the oviducts. Altogether the most massive 
collection of the tissue is met with in the womb. During 
pregnancy it acquires a still greater increase. The lymphatic 
glands, the eye (sphincter and dilator pupillae, choroid, the 
ciliary, orbital, and palpebral muscles) also have smooth 
muscles. 
We meet with transversely striated tissue in all the muscles 
of the head, trunk, and limbs, the auricle, the external mus- 
cles of the eye, in the tongue, the pharynx, the upper por- 
tions of the oesophagus, the genitals, the termination of the 
rectum. Our tissue likewise forms the diaphragm and, modi- 
fied, the heart. 
As element (Fig. 75, a) we recognize in man at once a long, 
unramified, cylindrical, filamentous element of 0.0113, 0.0187 
to 0.0563 mm., transverse diameter. This is the muscular 
filament, the muscular fibre, or, as is badly said, the primi- 
tive bundle. 
Here, however, we at once notice a peculiarly complicated 
texture. 
We meet with an envelope and contractile contents ; the 
sarcolemma and sarcous element. The former, closely applied 
to the living muscular filament as a constant companion, may, 
in death, become elevated in a vesicular manner by the 82 
EIGHTH LECTURE. 
absorption of water. When the sarcous por- 
tion has been torn by traction, the sarcolemma, 
or primitive sheath (Fig. 76, a), appears most 
distinctly. It is a hyaline, aggregated, elastic 
membrane. 
Directly superimposed on this envelope, one 
meets with numerous oval nuclei (Fig. 77, c), 
measuring 0.0074 to 0.0113 mm. The lateral 
surfaces, and the pole of the latter, are sur- 
rounded by a small quantity of a protoplas- 
matic substance {d). This, a cell rudiment, 
has been called a muscle corpuscle (M. 
Schultze). This is the condition of the human 
muscle. In the lower animals, however, the 
nucleus also lies in the interior, and the same 
is the case in our heart muscle. 
Fig. 76.—Muscu- 
lar fibrilla torn 
across ; b, b, sarcous 
portion ; a, sarco- 
lemma. 
All this is readily understood. 
Extraordinary difficulties are, on 
the contrary, presented by the sub- 
stance surrounded by the sarcolem- 
ma, the sarcous elements. It is, in 
the first place, very changeable, 
and, with its infinitely delicate 
structure, we soon arrive at the 
limits of the microscopic solution 
possible at present. 
In many cases, and regularly 
after the use of certain reagents, 
the sarcous elements appear as a 
bundle of fine, transversely striated, 
elongated fibrillae, measuring 0.0011 
to 0.0022 mm. It would appear, 
therefore (after the manner of the 
connective tissue),, to be a primi- 
tive bundle. 
Fig. 77.—A muscular fasciculus of 
the frog by 800-fold enlargement; 
dark zones, with sarcous elements ; b, 
bright zones ; c, nuclei; d. interstitial 
granules {alcohol preparation). 
With other methods of treatment, 
and also in the living muscle, we MUSCULAR TISSUE. 
see little or nothing of these fibrillae. The filament permits 
the recognition of transverse lines only. It now appears, 
comparable to a Volta’s pile, to consist of discs piled upon 
each other. 
The fibrillae, as well as the transverse discs, were both re- 
garded as normal, pre-existing structures, and in this, accord- 
ing to our view, a double error was committed. In the living 
muscle there are neither fibrillae or discs. 
The first who here trod the correct path, a generation since, 
was the Englishman, Bowman. It is true that, with the opti- 
cal aids of that period, he was unable to exhaust the subject; 
but we are also unable to do so at the present time, although 
we have at our disposal much more perfect microscopes. 
According to the view of this distinguished investigator, 
the muscular filament consists essentially of an aggregation 
of small bodies, the sarcous 
prisms or sarcous elements 
which, united and holding to- 
gether in the transverse direc- 
tion, afford the appearance of 
a disc or a thin plate (disc 
according to Bowman) (Fig. 
77, a) while, disposed in the 
longitudinal direction, they pre- 
sent that of the fibrillse (Fig. 78, 
I, a, b). Accordingly, neither 
fibrillae or discs pre-exist. There 
is merely a disposition present 
in the muscular filament to become divided, sometimes in the 
transverse, sometimes in the longitudinal direction. The 
cohesion in the latter direction is certainly the strongest; for 
the fibrillse in the dead element are met with more fre- 
quently than transverse plates. 
Fig. 78.—Two muscular fibrillas, from 
the proteus, 1, and the ho?, 2, magnified 
1,030 times ; a, sarcous prisms ; b, bright 
longitudinal connecting medium. At a* 
the sarcous elements are further apart, and 
the transverse connecting medium is visi- 
ble ; c, nucleus. 
Let us next examine the muscular filament somewhat more 
closely, with the aid of the highest magnifying powers. 
The transverse lines are readily resolved into dark trans- 
verse zones, separated by more transparent ones (2, a, b), 84 
EIGHTH LECTURE. 
The former consist of sarcous elements («*) placed nearer each 
other. This may also be recognized without trouble by the 
aid of good and strong magnifying powers. They are elon- 
gated prismatic bodies, measuring 0.0017 mm. in the proteus, 
0.0013 in the frog, 0.0011 to 0.0012 mm. in the mammalia and 
man. 
The sarcous elements must, naturally, be joined one to the 
other. 
If we split off one of the finest longitudinal filaments, that 
is a so-called muscular fibrilla (1), the longitudinal series of 
sarcous elements (a) are held together by the transparent 
longitudinal connecting medium (b). If we examine a mus- 
cular filament split up into transverse plates, the dark and 
light transverse zones are found to be connected by a trans- 
verse connecting substance, which extends over the outer 
surface from a and bof our Fig. 78, 2. Here the longitudinal 
connection is naturally, completely dissolved. 
Up to about ten years ago, we thought the matter 
might thus be passably explained; but newer observa- 
tions have been added and further 
doubts have arisen. 
In the year 1863, the Englishman, 
Martyn, had already *een a dark trans- 
verse line in the transparent longitu- 
dinal connecting medium. These ob- 
servations were afterwards corroborat- 
ed and extended by Krause (Fig. 79). 
Let us name this thing (a), therefore, 
Krause's transverse line or disc. 
But with this we have still not 
reached the end. At the same time 
another competent investigator, Hen- 
sen, found the dark transverse zone, the 
transverse series of sarcous elements, 
divided by a transparent transverse 
line, This is the Hensen’s middle disc. Granules which 
were contiguous above and below to Krause’s transverse line 
Fig. ■ 79.—Krause’s transverse 
discs ; a, a, 1, a muscular fibrilla 
without; 2, one with strong longi- 
tudinal traction, both very strong- 
ly enlarged (Martyn) ; 3, muscu- 
lar filament of the dog imme- 
diately after death. MUSCULAR TISSUE. 
were subsequently designated by Engelmann as accessory 
discs (Fig. 80 b). 
From these singular observations, which 
touch and, perhaps, in part, exceed the limits 
of microscopic analysis, we are at present un- 
able to derive an anyways reliable conclusion. 
An old observation of Bruecke’s is also in- 
teresting. The Bowman’s sarcous elements 
refract the light double, the longitudinal con- 
necting medium refracts simply. 
Fig. Bo.—Piece of a 
dead muscular fila- 
ment from the fly, after 
Engelmann ; a, trans- 
verse discs ; b, acces- 
sory discs. 
We pass, finally, to some more simple structural conditions 
of the transversely striated muscle. 
Among these are the so-called interstitial granules, small 
fat molecules (Fig. 77, d), which, commencing at the nuclear 
poles of the muscular corpuscles, permeate the filament in a 
linear longitudinal direction over shorter or longer distances. 
The preparation of transverse sections 
through the frozen muscle (Fig. 81) was taught 
by Cohnheim. Groups of sarcous elements 
{d) are here recognized as a mosaic of small 
areas of transverse to hexagonal shape. 
Enclosing these are noticed a system of 
transparent, glistening lines {c) which must 
belong to the transverse connecting medium. 
A modification of the transversely striated 
muscles is met with in the tongue and heart 
of the mammalia and man. These are rami- 
fied and reticularly connected filaments. In 
the former organ are noticed frequently 
repeated divisions at acute angles. 
Fig. 81.—Trans- 
verse section through 
a frozen muscle of 
the frog; a, groups of 
sarcous elements : c, 
transparent trans- 
verse connecting me- 
dium; b, nucleus. 
In the heart (Fig. 82), a narrow-meshed 
net-work is constituted by the abundant formation of anasto- 
moses. A sarcolemma is probably wanting in these dimin- 
ished filaments. The latter, furthermore, show strongly pro- 
nounced transverse and longitudinal markings. It is an 
interesting circumstance, finally, that this muscular reticulum 
consists of cemented cells (Fig. 82, to the right). 86 
EIGHTH LECTURE. 
The remaining transversely striated muscles show the fila- 
ments arranged parallel, slightly prismatically flattened against 
each other (Fig. 83, a), and in 
man containing the muscular cor- 
& i 
puscles {e) in their periphery. 
Between them occurs a scanty 
amount of connective tissue, the 
highway for vessels (d) and nerves. 
With rich living this may develop 
fat cells (Fig. 50). 
A varying number of muscu- 
lar fibres unite into bundles, 
measuring 0.5 to I mm., which are 
separated from the neighborhood 
by abundant connective tissue. 
Such primary bundles then unite 
into secondary ones. The con- 
nective tissue covering of the 
muscle bears the name of peri- 
mysium externum, in contradistinction to the perimysium 
internum of the inner connecting substance between the fila- 
ments and bundles. 
Fig. 82.—Muscular filaments of the 
heart. To the right appear transparent 
boundaries and nuclei. 
Smooth muscles also show a 
bundle-like grouping. 
We come, finally, to the con- 
nection with the tendons. The 
latter tissue has already been de- 
scribed above, page 57- 
With a rectilinear insertion 
(Fig. 75) the sarcous substance {a) 
appeared to pass immediately 
over into the tendinous bundle 
(&) ; not so, however, with an 
oblique insertion, where an inter- 
rupted muscular end becomes ap- 
parent. 
Fig. 83.—Transverse section through 
the human biceps brachii; a, the muscu- 
lar fibres ; b, section of a larger vessel; 
Cj a fat cell lying in a large connective- 
tissue interstice; d, capillaries cut across 
in the thin connective-tissue layer be- 
Hveen the several fibres; e, the nuclei 
puuskelkorperchen) of the latter lying 
on the sarcolemma. 
Weismann first obtained convincing appearances here by MUSCULAR TISSUE. 
87 
means of potash solutions (Fig. 84). The end of the filament, 
sometimes rounded, at others pointed, and again irregularly 
shaped, is always covered by sarcolemma 
(£). The tendinous bundle is attached 
by a corresponding excavation {c, d). 
During life the whole is united in the 
firmest manner by means of a cement 
substance. 
The muscular filaments are of various 
lengths, but according to Krause do not 
exceed four centimetres. They termin- 
ate, therefore, repeatedly far from the 
end of the entire muscle, in its interior 
and in the form of points. 
The muscular filament consists of vari- 
ous albuminous bodies. The sarcous 
elements, transverse and longitudinal 
connecting medium, are formed of modi- 
fied members of this so little understood 
group of substances. The proportion of 
Water present is considerable, corresponding to the softness 
of the tissue. 
Fig. 84.—Two muscular 
fibrillas [a, i) after treatment 
with solution of potash, the 
one still in connection with 
the tendon (f), the other 
separated from the same [d). 
We turn to the embryonic development of our tissue. 
The elements of the smooth muscles present nothing but 
cells grown into a spindle shape (Fig. 74). The rounded or 
oval developing cells (a, b) simply exchange their protoplasma 
with the homogeneous sarcous substance, the nuclei assume 
the rod form, and an envelope is altogether wanting. 
We have already (Fig. 27) briefly mentioned the origin of 
the transversely striated fibre. After the example of Schwann, 
they were formerly considered to arise from the fusion and 
rnetamorphosis of formative cells arranged in rows. In the 
heart muscles, as we have already seen, something of the 
kind does, in fact, take place ; but not so in the remaining 
voluntary muscles. Here the element is a single cell, which, 
F is true, undergoes a much more extended development than 
the contractile fibre cell of the smooth tissue. 88 
EIGHTH LECTURE. 
In small embryos one obtains thin (0.C045 to 0.0068 mm.), 
but long (0.28 to 0.38 mm.) spindle cells, with one or 
two vesicular nuclei, and in the centre commencing for- 
mations of transverse lines, that is with a transformation 
into sarcous elements. With an increase in nuclei, the 
structure increases not only in length but also in breadth. 
The transverse striation advances towards the ends, but leaves 
the axial portion still free. We still meet here with the old 
protoplasm. Later, however, after the longitudinal markings 
have also appeared, this protoplasma has disappeared, with 
the exception of a slight residue, which surrounds the nucleus 
and thus forms the muscle corpuscle. We find the latter, at 
last, in mammalia and man, displaced towards the periphery. 
We have already above (p. 82), declared the sarcolemma 
of the transversely striated filament to be a homogeneous 
boundary layer furnished by the adjacent connective tissue. 
All investigators do not, however, coincide with our view. 
The muscular filaments of the new born are still much finer 
than those of the adult. The subsequent increase in thick- 
ness explains in great part the growth of the 
muscle in transverse diameter. New fibres 
are also subsequently developed (Budge). 
This has, it is true, been recently disputed. 
Weismann observed that the muscles of 
the frog divide in a longitudinal direction, 
with a prodigious increase in their nuclei. 
One then sees regular columns of nuclei de- 
scending near each other. The filament di- 
vides, one becomes two, which subsequently 
acquire the normal diameter by a growth in 
thickness. The two products of division 
may afterwards repeat the same cleaving pro- 
cess. A single muscular filament may in this 
way finally become a whole group of filaments. 
Fig. 85.—Fatty degen- 
erated human muscular 
fibre; a, slighter; b, 
increased ; c, highest 
degree. 
Among the forms of retrogression of 
our tissue, fatty degeneration is the most frequent (Fig, 85). NINTH LECTURE. 
THE BLOOD-VESSELS. 
One cannot really speak of a vascular tissue. Only the 
mnermost layer consists of a simple layer of closely cemented 
endothelial cells. This is the original stratum ; it forms the 
simplest, finest vascular tube. 
All the remaining layers, on the contrary, which by their 
further aggregation reinforce the walls of the vessel—and 
they commence very soon—belong to tissues which we have 
already discussed ; they consist of connective tissue and elastic 
substances, as well as layers of smooth muscles. 
The blood is conducted from the heart, as is known, 
by immensely ramified systems of arteries. Its return is 
consigned to the not less ramified veins. Between them 
13 intercalated, but without any sharp demarcation, the 
district of the capillaries. They maintain the nutrition 
°f the organs and tissues, as well as the secretion of the 
glands. 
The finest capillaries—they do not by any means occur in 
all parts of the body, however—have a calibre which just 
suffices to permit the passage of the blood cells, one after the 
other, though often with a certain lateral compression. Their 
lumen may, therefore, be assumed to be for man 0.0045 to 
°-0068 mm. In other parts of the body, however, the finest 
capillaries present double this diameter. 
Without being treated with a suitable reagent, their struc- 
ture appears extraordinarily simple. A hyaline, structure- 
less, extensible and elastic membrane contains embedded, 
from place to place, rounded or elongated oval nuclei of 
°-0056 to 0.0074 mm., with nucleoli. In the finest capil- 
laries the nuclei lie in the simplest manner behind each NINTH LECTURE. 
other ; in somewhat larger ones an alternating position begin? 
to take place. 
If, however, we force a stream of dilute nitrate of silvei 
solution through our capillary, it then appears to be com- 
posed of the plates and curved, nucleated, endothelial or vas- 
cular cells represented in Fig. 21. With stronger magni- 
fying powers (Fig. 87), one recognizes in places, between the 
Fig. 86.—i, capillary with a thin wall, and the 
nuclei a and b ; 2, capillary with double contoured 
walls ; 3, small artery, with the endothelial layer a, 
and the middle layer b. 
Fig. 87.—Capillary from the mes- 
entery of the frog. At a and b, small 
apertures, “Stomata.” 
endot elia, larger and smaller, mostly rounded, dark cor- 
puscles {a, a) or light circular markings {b). There are small 
openings here, through which the lymphoid cells, by their 
vital migration (p. 10), probably make an active exit, and the 
colored elements of the blood are passively forced out (p. 2j). 
The former marvellous emigration has been known for years 
(A. Waller, Cohnheim). 
In other capillaries (Fig. 86, 2) the walls are circumscribed 
by a double line. Here, there already appears to be the pri- 
mary rudiments of a so-called tunica interna or serosa. THE BLOOD-VESSELS. 
91 
More frequently, there are capillaries where the endothelial 
tube is surrounded by a connective-tissue layer, a so-called 
adventitia capillaris. The latter is, 
for a certainty, the primary rudi- 
ment of the layer, which with in- 
creasing complexity occurs in all the 
larger vessels as the most external 
layer or adventitia. We here meet 
at first with either ordinary connec- 
tive tissue, which has indeed re- 
mained at an earlier stage, with lon- 
gitudinally arranged nuclei or cell 
remains (Fig. 89, d), or, when capil- 
laries of lymphoid organs are con- 
cerned (Fig. 88, b), the reticular con- 
nective substance has become spread 
over the endothelial tube in an ele- 
gant manner, and the capillary is 
kept distended by this cellular reticu- 
lum, like the embroidery in a frame. 
Fig. 88.—Capillary vessels and fine 
branches of the mammalia ; a, capil- 
lary vessel from the brain ; b. from a 
lymphatic gland; c, a somewhat 
larger branch with a lymph-sheath 
from the small intestine ; and i/, a 
transverse section of a small artery 
of a lymphatic gland. 
Passing, now, to somewhat larger trunks, numerous 
variations of the structure occur. They coincide in part 
the nature of the vessel, whether arterial or venous 
branches; they are also, in part, of a more individual or local 
nature. 
Frequently, when we follow the capillaries towards the 
arterial tubes, we perceive branches where a layer, striking 
the eye by its transversely arranged nuclei (Fig. 86, 3, b), is 
with around the endothelial tube (a). The former con- 
stitutes the very commencement of the muscular middle layer 
0r tunica jnedia of the vessels. An equally large venous 
branch usually has in the place of the latter layer a con- 
nective-tissue adventitia. Still, it often enough occurs in 
tbe finer arterial branches also, spread out over the muscular 
Lyer. 
Let us take a small arterial trunk, after the manner of our 
Tr * 7 
■t<lg- Bg. The endothelial tube is not drawn here. Lying on 92 
NINTH LECTURE. 
this, and consequently as the innermost layer of the figure, 
we recognize at b a homogeneous, longitudinally striated, 
elastic membrane, the tu- 
nica serosa of the older 
anatomy. The same is 
surrounded by a layer of 
transversely running con- 
tractile fibre cells at c. 
The connective-tissue layer 
d, with longitudinally ar- 
ranged cells, forms the last. 
Under certain circumstan- 
ces, it may be very much 
thicker than in our figure. 
Other small arterial 
trunks show the muscular 
layer to be constituted by 
several layers of fibre cells, 
lying over one another, as 
in Fig. 88, d, where the 
adventitia is again formed 
of reticular connective tissue. 
Fig. 89.—A small arterial trunk. At b, the homo- 
geneous, non-nucleated inner layer; c, the middle 
layer, consisting of contractile fibre cells ; d. the con- 
nective tissue external layer. 
Larger trunks, finally, can no longer be surveyed in their 
totality, under the microscope. One must, therefore, exam- 
ine singly the separately prepared layers, or make longi- 
tudinal and transverse sections through the hardened walls. 
The further transformations, from those immediately fol- 
lowing up to the most remote of the largest blood-vessels, 
consist in the following: The' endothelial tube always 
remains a single layer; the connective-tissue adventitia does 
the same, but it increases in thickness; the connective-tissue 
bundles become more distinct, and elastic fibre reticula are 
more and more frequent, especially in the arteries. Both the 
middle layers, the serosa and media, begin on the contrary 
to become stratified ; each of them consists of an increasing 
number of layers lying over each other. On this depends 
the growing thickness of the vascular walls. The inner THE BLOOD-VESSELS. 
93 
group of layers essentially preserve in their membranous 
layers the nature of the elastic tissue, and present the most 
heterogeneous varieties of the same with a longitudinal 
arrangement. The middlemost group changes into a system 
of alternating layers of elastic tissue and smooth muscles, 
both with a transverse direction, or also of connective tissue. 
The tunica media remains much thinner in veins than in 
arteries of similar size, and the result is that the walls of the 
former vessels are thinner. The endothelial cells of the 
arteries appear as narrow, lancet-shaped lamellae ; those of the 
veins are shorter and broader (p. 29). 
Taking a small vein of about 0.25 mm. in calibre, we find 
succeeding the epithelium a serosa with fine, elastic, longi- 
tudinal reticula. The middle layer consists of several mus- 
cular layers, which have between them elastic reticula and 
connective-tissue layers. The adventitia shows longitudinally 
running connective tissue and a contingent of elastic fibres. 
The appearance is different in middle-sized veins. The 
serosa has here become a group of layers. We now meet 
with homogeneous or striped layers with longitudinally 
arranged spindle cells, elastic membranes or elongated reti- 
cula. Indeed, even the elements of the smooth muscles may 
be continued in these inner groups of layers. The middle 
layers consist of connective tissue running transversely, with 
elastic reticula arranged in the same manner, and smooth 
muscles. Nevertheless, isolated elastic layers with longitu- 
dinal fibres also occur here. The adventitia is as usual; still 
it may also harbor contractile fibre cells. 
The largest veins possess a similar serosa, though without 
the smooth muscles, while the media remains undeveloped 
and may he entirely absent. It shows scanty muscular 
elements, permeated by transverse connective tissue. Elastic 
longitudinal fibro-reticula have likewise maintained their posi- 
tion here. In the thick adventitia of many veins, one meets 
toward the interior with thick longitudinal muscles, as, for 
instance, that of the pregnant uterus, while the sinuses of the 
dura mater ar entirely without muscles. 94 
NINTH LECTURE. 
In the smaller arteries, the serosa and adventitia remain toler- 
ably unchanged. Still, there frequently occur in the former 
reticular perforated elastic layers, so-called “ fenestrated mem- 
branes,” or free elastic longitudinal reticula; the media pre- 
sents several layers of transversely directed muscles, lying over 
each other, and an elastic net-work is also developed in the 
fibrillated outer layer. 
In the larger branches, the stratification of the inner and 
middle layers increases. In the latter, elastic plates with 
transverse fibres, are now interpolated between the muscular 
layers, and the elastic reticulum of the adventitia becomes 
thicker. 
The largest arteries (Fig. 90) show under the endothelium 
(a), strongly stratified, the group of the inner vascular mem- 
brane (£). The several lamel- 
lae, in varying texture, present 
the entire multifariousness of 
the elastic tissue. Inwards, 
towards the endothelial cover- 
ing, one may, indeed, meet 
with more homogeneous, or 
more striated layers with cellu- 
lar reticula imbedded overeach 
other (Langhans, von Ebner). 
In the more middle group 
of layers the membranous 
character of the elastic fibrous 
net-work {d) becomes more 
and more prominent. Their 
fibres may be thinner or thick- 
er; the membranous connect- 
ing substance may appear 
whole or perforated. The num- 
ber of these elastic layers may 
increase to 30, 40, 50, and 
more. The muscles of the 
middle layer {e) appear unequally developed ; frequently no) 
Fig. 90.—Transverse section through the 
walls of a large artery ; a, endothelium ; 0, sero- 
sa ; c, outer layer of the same ; d, elastic, e, mus- 
cular layers of the media ; adventitia ; _/J their 
clastic fibro-reticula. THE BLOOD-VESSELS. 
95 
to a high degree. The direction of the fibres is by no means 
exclusively transverse. In the outer portions of the media, 
fibrillated connective tissue occurs (Schultze, von Ebner). In 
the adventitia (g), finally, the elastic fibro-reticulum (/) 
acquires in an inward direction, in large mammalia, a very 
prodigious development. 
The valves of the vessels consist of connective tissue with 
elastic intermixtures, and the endothelial covering. 
Vasa vasorum is the name given to the capillary vessels 
which occur in the middle and outer layers of the larger trunks, 
and supply the nutritive materials to the walls of the vessel. 
The vascular nerves terminate at the muscles of the 
media. 
We pass to the arrangement of the 
capillary vessels in the human body. 
It is known that they do not occur 
everywhere. Thus, the epithelial struc- 
tures, with the crystalline lens, the cornea 
of the eye, and the permanent cartilages 
are non-vascular. 
A peculiarity of the capillary division 
Fig. 91.—-Vascular net- 
work of a transversely stri- 
ated muscle ; a, arterial, 
venous vessel; c, d, 
the capillary net-work. 
Fig. 92.—A pulmonary alveolus of the calf; 
a, larger blood-vessels, wh ch run in the pari- 
etes of the alveoli; b, capil ary net-work ; c, 
epithelial cells. 
consists in this, that the tubes by giving off branches do 
dot become narrowed to a noticeable degree, and that by 96 
NINTH LECTURE. 
the conjunction of the branches there are formed reticula 
of more regular, and frequently of extremely characteristic 
form. 
The diameter of the capillaries (see above) is by no means 
the same in the different portions of the human body. The 
brain and retina present the finest of 0.0068 to 0.0065 mm., 
and less. The muscles have somewhat larger ones of 0.0074 
mm. The calibre is again increased, somewhat, in those of 
the connective tissue, the external integument, and the mu- 
cous membranes. The lumen is greater in the capillaries of 
most of the glands, such as the liver, the kidneys, and the 
lungs. Here we have a diameter of 0.0099 to 0.0135 mm. 
The most considerable ones, finally, of 0.0226 mm., are seen 
in the bone medulla. That, with the larger blood corpuscles, 
even the finest capillaries of animals have a more considerable 
calibre, it is hardly necessary to remark. 
The capillaries are sometimes more profuse, sometimes more 
scanty, in a part of the body. The size of the portion of the 
tissue comprised within their net-work is, accordingly, quite 
variable ; it is small in the vascular, large in the non-vascular 
parts. The former have an energetic, the latter a sluggish 
assimilation. The lungs (Fig. 92) appear uncommonly vas- 
cular. Their capillary net-work,-serving for respiration, is the 
most compact of the organism. The other glands approxi- 
mate. The fibrous membranes, the tendons, the neurilemma 
are quite non-vascular. 
The form of the capillary net-work is determined by the 
shape of the parts to be circumvoluted, the nature of the 
several elements, or of their arrangement. 
We have, firstly, the straight, capillary net-work. A trans- 
versely striated muscle (Fig. 91) may represent this. The 
several filaments are surrounded by the uncommonly elongated 
meshes (c). The involuntary, smooth muscles also possess 
the same capillary net-work. Here, however, from the thin- 
ness of the elements, a bundle of fibres takes the place of 
the transversely striated filament. 
Other parts with elongated elements—for example, the gas- THE BLOOD-VESSELS. 
97 
trie mucus membrane, with its long, thin, tubular glands—■ 
show a similar straight net-work. 
We are familiar, from Fig. 48, with the fat cells, large, 
rounded structures. Their 
capillary reticulum, in 
correspondence with this, 
forms rounded meshes 
(Fig, 93). The small, ar- 
terial branch (a), and the 
small, venous branch (b) 
of an aggregation of these 
fat cells appear very dis- 
tinct. 
We shall later, at the 
glands, become acquaint- 
ed with very extended 
orgarls of a racemose 
structure. A rounded or , 
elongated saccule (acinus) surrounds an aggregation of smaller 
parenchyma cells. The acini are likewise circumvoluted by 
a complete, quite 
similar, round net- 
work, like the indi- 
vidual fat cells. 
Fig. 93.—Vessels, of the fat cells. The arterial (a), 
venous branches (Jy, with the rounded capillary net- 
work of a fat lobule. 
A handsome, very- 
characteristic ar- 
rangement is pre- 
sented by the capil- 
laries of the liver 
(Fig. 94). The liver 
—we shall return to 
it in greater detail 
subsequently—is di- 
vided into so-called 
lobules, into collections of radially arranged cells. The ex- 
tensively developed capillary system maintains the same 
arrangement—a rounded, stellate one. 
Fig. 94.—The capillary net-work of the rabbit’s liver, crossed 
by a branch of the portal vein. 98 
NINTH LECTURE. 
The human corium projects in microscopically small papil- 
lae, which the thick epithelium (p. 32) surrounds with a 
smooth surface. The greater part of these papillae contains 
a capillary vessel, which ascends on one 
side, bends over the top of the papilla, 
and descends on the other side. This is 
the capillary loop. 
Larger papillae occur on many of the 
mucous membranes ; thus, on the dorsum 
of the tongue, as the so-called gustatory 
papillae, the whole small intestine, as intes- 
tinal villi, to omit others. The simple 
capillary loops are here no longer suffi- 
cient (Fig. 95). Between them are inter- 
posed communicating capillaries and capil- 
lary net-works. Thus arises the looped 
net-work. 
A quite peculiar formation is presented 
by the corticallayer of the kidney, in the 
so-called glomerulus or vascular coil (Fig, 
96). 
Fig. 95-—An intestinal vil- 
lus a, the cylindrical epi- 
thelium with its thickened 
seam : b, the capillary net- 
work ; c. longitudinal layers 
of smooth, muscular fibres ; 
nf, central chyle vessel. 
A microscopic arterial branch (to the 
right) divides, and each branch forms a 
convolution of closely crowded capillaries. 
These portions, with educting canals, reunite, at last, into a 
single abducting vascular tube. 
We here speak, therefore, of a 
centripetal (vas afferens) and a 
centrifugal vessel (vas efferens). 
From the latter arises, further 
below, a new capillary reticulum. 
To study the capillaries, they 
must be injected from the larger 
trunks with transparent, colored 
(with carmine, Prussian blue) gel- 
atine, at an elevated temperature. Opaque, granular masses 
(cinnabar, white lead, chrome yellow) were the more imper- 
Fig. 96.—Glomerulus of the hog’s kid- 
ney. THE BLOOD-VESSELS. 
99 
feet accessories of an earlier epoch. They are rarely used 
at present. Other vehicles for the coloring material, resin- 
ous, waxy masses, or etherial oils, are, at the most, only here 
and there employed for very special purposes. 
The embryonic origin of the vessels is still attended with 
many obscurities. 
The heart, a production of the middle germinal layer, is 
formed very early, and enters soon afterwards into activity. 
It is hollow from the commencement, and the large, adjacent 
blood-vessels likewise appear to possess the same charac- 
teristic. 
With regard to the more particular details of this process, 
we must state that our present knowledge is little satisfactory. 
According to Klein, the first large vessels of the hen’s em- 
bryo are formed from cells of the middle germinal layer. 
The contents of the latter soon liquefy. A protoplasma shell 
now invests the enlarged and macerated cell-body with the 
original nucleus. From such cells are derived the first vascu- 
lar wall, or endothelial tube, as well as the first blood corpus- 
cles. The cell is said to swell, and the nuclei increase, and, 
as during this increase the nuclei assume a regular position, 
the protoplasma mantle finally divides into flat, endothelial 
cells. From these endothelial walls the first blood corpuscles 
are also said to take their origin by a process of constriction. 
They are said, however, to have another origin, also. 
The first vascular walls and the first blood corpuscles, 
therefore, derive their origin from the same cells. 
We add to this the important fact that it is only subse- 
quently to the use of nitrate of silver solution that the pri- 
mary vascular wall is resolved into the familiar endothelial 
cells. 
A process of aggregation then leads, in a secondary man- 
ner, to the formation of the additional external vascular 
layers, a serosa, media, and adventitia. There is here, also, 
a great want of accurate observations. 
Capillaries—we assume, at first, a homogeneous, nucleated 
protoplasma tube—are present at an early period. 100 
NINTH LECTURE. 
They soon present further metamorphoses. These may 
be beautifully recognized in the transparent tail of the tad- 
pole (Fig. 97). It is a sort of budding process. 
Fig. 97.—Development of finer capillaries in the tail of the tadpole; p, p, protoplasma bud* 
and cords. 
From the parieties of already mature neighboring capilla- 
ries is supplied a protoplasma, capable of further independent 
development, in the form of pointed cones (Fig. 97, 1, 2, 
p, p). By their confluence (2) the latter are, at first, trans- 
formed into solid cords. If, then, the axial portion of the 
meanwhile enlarged cord melts down, we have the proto- 
plasma tube (3, p). By a further metamorphosis of the lat- THE BLOOD-VESSELS. 
101 
ter, the formation of new nuclei appears to take place. The 
endothelial tube is finally established by the protoplasma 
walls and the young nuclear formation. 
The abnormal new formation of vessels in later life likewise 
follows the old embryonic law. TENTH LECTURE. 
THE LYMPHATICS AND THE LYMPHATIC GLANDS. 
WHAT is understood by lymph we have already mentioned 
in our second lecture (p. 27). It was the blood plasma which 
had passed out through the capillary walls, and which gave 
off the dissolved nutritive constituents to the tissues, and took 
up in exchange the products of the decomposition of the lat- 
ter. We even then mentioned that this fluid, which is unin 
terruptedly supplied from the blood current, must necessarily 
be removed. The arrangement serving this purpose must 
now be discussed. 
Our present course will, however, be the reverse of that 
followed in the previous lecture ; for the large and medium 
lymphatic discharge tubes- are more accurately known, while 
numerous uncertainties still prevail concerning the knowledge 
of the finer and finest elements. 
Let us commence with the ductus thoracicus, the terminal 
large discharge tube of the lymphatics. We here meet with 
a condition corresponding to the walls of the veins. 
The endothelium is surrounded as a serosa by several layers 
of a striated substance, and then by a net-work of longitudi- 
nal elastic fibres. As a middle layer, we have next, longitu- 
dinally running connective tissue, and then transverse mus- 
cles. The adventitia also shows remains of the latter tissue. 
Valves are not wanting here, nor afterwards in the finer 
lymphatics. 
Descending to the latter, the stratification, as in the veins, 
becomes more simple ; but more accurate studies are here 
still necessary. In small trunks of 0.2 to 0.3 mm., the four 
characteristic vascular layers have been found still present. 
The adventitia, media and serosa gradually disappear, and THE LYMPHATICS AND LYMPHATIC GLANDS. 
103 
we have remaining only the endothelial tube with cells simi- 
lar to those of the blood-vessels. Here also we still meet 
with valves and isolated nodal or ampulla-like enlargements. 
Such vessels remain distinctly demarcated from the immedi- 
ate neighborhood. The relation of these passages to the 
blood-vessels varies greatly. For the most part, both vessels 
simply run alongside of each other. Not unfrequently an 
arterial branch is accompanied by a pair of lymphatic canals. 
One may then readily commit an error, namely, the assump- 
tion that the blood current is invested by a lymphatic. The 
latter condition does, indeed, actually take place (Fig. 88, c), 
although rarely, as many assert. 
At last, however, the appearance of the lymphatics changes; 
the outer surface of our vascular cells has now grown firmly 
together with the surrounding tissues; 
thus there arises at the first examination 
the impression of a cavity and cleft. For- 
merly this was generally considered to be 
the true interpretation, until the employ- 
ment of the dilute solution of nitrate of 
silver opened our eyes (Fig. 98, a). 
For the examination of the finest termi- 
nal lymphatics, artificial injections are nat- 
urally again requisite ; and, Indeed, to a 
higher degree than in the capillaries of the 
blood passages, where under favorable 
conditions the colored cells permit the fine 
tubes to stand out. The lymph, a colorless fluid, poor in 
cells, does not do this, as is known, and only the chyle ves- 
sels, overladen with fat, become at times distinctly prominent 
without any further assistance. 
Fig. 98.—Lymphatic ca- 
nal from the large intestine 
of the Guinea-pig: a, vas- 
cular cells; b, spaces be- 
tween the same. 
But, as is known, the lymphatics have 'no affluent tube 
comparable to an artery ; they show merely a capillary divi- 
sion and effluent canals, comparable to the veins. Filling 
the latter downwards is, almost without exception, prevented 
by the resistance of the valves. A highly celebrated modern 
anatomist, Hyrtl, rendered the service of discovering a very 104 
TENTH LECTURE. 
simple and at the same time extremely effective method of 
injection. We allude to his “puncturing method.” 
The point of a fine canule is carefully forced into a tissue 
which is thought to contain lymphatics, and an attempt is 
made to carefully and slowly inject a wounded lymphatic. 
Many of the attempts are, it is true, thoroughly unsuccessful, 
still practice makes the master, and with patience and perse- 
verance the object is finally accomplished. Teichmann’s ele- 
gant work on the lymphatics, not to mention others, has 
shown this. 
Let us commence first with the chyliferous vessels which, 
at the termination of an abundant digestion, by their fatty 
contents stand out as dark canals. 
In the intestinal villus (Fig. 95), there lies, occupying the 
axis, a cascal canal (ff), surrounded by a looped reticulum of 
capillaries {b, b). Its transverse diameter is 0.0187 to 0.0282 
mm. At the first cursory examination it is a lacuna; with 
more accurate investigation one recognizes here, as elsewhere, 
the thin walls formed of plates of cemented endothelial cells. 
The condition just mentioned also characterizes the re- 
maining portion of the lymphatics. The canals of the latter 
are more irregular, angular 
and wider, and situated nearer 
the interior. They are again 
surrounded by the external, 
much finer and more regular 
capillary net-work of the 
blood current. 
Let us now pass from the 
intestinal villi, further down- 
wards, and examine the infe- 
. 
rior flatter portion of the 
mucous membrane of the 
small intestine in which these 
caecal lacteals from the intes- 
tinal villi bury themselves. 
Let us look at Fig. 99. Here, in connective tissue con- 
Fig. 99.—Transverse section through the mu- 
cous membrane of the small intestine of the 
rabbit (near the surface); a, the reticular con- 
nective tissue containing lymph cells ; b, lymph 
canal; c, transverse section of a Lieberkuhn’s 
gland ; the same with the cells ; e, f, g-, blood- 
vessels. THE L YMPHA TICS AND L YMPHA TIC GLANDS. 
taining lymphoid cells (a), we discover the sections of blood- 
vessels (e, f, g) and of glands {d and c). Our attention is 
then attracted by an oblong cleft (b). It is a lymphatic canal 
consisting of endothelium. 
Our three drawings, Figs. 100, ioi and 102, contain 
further representations of such 
lymphatic passages. 
The caecal commencements are 
quite perceptible in the first two 
figures. 
Fig. ioo.-—A colon papilla of the rabbit, 
in perpendicular section ; a, arterial; b, 
venous trunk of the submucous tissue ; 
c, capillary net-work; d, descending 
venous branch ; e, horizontal lymphatic 
(sheathing an artery) ; _/j lymph canals of 
the axial portion; g, their caecal com- 
mencements. 
Fig. ioi.—Trachoma gland from the conjunctiva of 
the ox, with injected lymphatics, in vertical section ; 
a, submucous lymphatic'vessel ; c, its distribution to 
the passages of the follicle b. 
Thus far all is clear and intelligible.' But we now come 
to an uncertain and much disputed territory. 
Fig. 102.—From the testicle of the calf. Seminiferous canals seen in more oblique, a, and 
tnore transverse sections, b; c, blood-vessels; d, lymphatics. 
The connective tissue, this substance which is so infinitely 106 
TENTH LECTURE. 
diffused throughout the human body, is permeated by 
millions of clefts and spaces. They receive nutritious plas- 
matic or lymphatic fluids, and contain wandering lymphoid 
cells. In the serous cavities and sacs we meet with an im- 
mense lymphatic lacunar system ; nevertheless, the quantity 
of fluid is small. 
Now, do these latter lymphatic passages, lined with endothe 
hum, pass over continuously into these connective-tissue canals, 
and do the former open into the system of serous caverns ? 
It is just these questions which we are now to answer. 
Let us tarry for an instant at the latter relations. 
A communication of the lym- 
phatics with the cavity of the 
serous sac has, for several years, 
been recognized with certainty. 
The names of Recklinghausen, 
Ludwig, Dybkowsky, Schweig- 
ger-Seidel and Dogiel deserve 
mention here. 
Recklinghausen discovered at 
the under surface of the centrum 
tendineum of the rabbit (Fig. 103, 
l), between the epithelium, aper- 
tures (a) of not inconsiderable size, 
or at least greater than the diame- 
ter of a red blood corpuscle. He 
saw how the milk and color gran- 
ules entered here and reached the 
lymphatics of the diaphragm. 
Other short lateral passages of the 
lymphatics were then found to 
open into these apertures (2, b). 
No further doubt can, therefore, 
exist here. 
Fig. 103.—1. Epithelium of the under 
surface of the centrum tendineum of the 
rabbit; a, apertures or stomata ;2, sec- 
tion through the pleura of the dog ; 6, 
free opening, short, lateral passage of the 
lymphatic canal; 3, epithelium of the me- 
diastinum of the latter animal; a, pores. 
The question assumes a different shape, however, concern- 
ing the relation of the above mentioned connective-tissue 
chasm to the vascular system. THE LYMPHATICS AND LYMPHATIC GLANDS. 
107 
According to Recklinghausen, these passages are directly 
connected with the lymphatics. He has given them the name 
of the “juice canals,” a denomination which Waldeyer sub- 
sequently changed into “juice clefts.” 
I regret to be obliged to contradict the former investigator. 
The conservative injection teaches nothing of the kind. I 
dare to assert this after numerous personal studies, and I ap- 
peal, besides, to the testimony of distinguished investigators 
in this department of the technology of injection. I mention 
the names of Hyrtl, Teichmann, His and Langer. By immod- 
erate pressure (in normal life it should never be attained), it 
is true, these chasms or stomata become filled with the colored 
mass. For an illustration, we refer to the small spaces be- 
tween the vascular cells of the lymphatics (Fig. 98, b). We 
have distended them inordinately or, perhaps, forced out a 
soft substance filling the spaces. 
The normal blood-vessels act in a similar manner. Here, 
by careful injection, no one fills the “juice clefts” of the 
connective tissue. No one could show a direct transition of 
the vessel into these passages. 
Under abnormal conditions of the living body, however, 
with a vascular tube over-filled with blood, the stomata even 
here become permeable. If, now, the cadaver be artificially 
injected, the colored substance penetrates these juice passages 
(von Winiwarter, Arnold). 
Thus we regard the matter at present. 
Important constituents of the lymphatic apparatus of the 
mammalia are represented by the lymph-nodes or, as they 
Were earlier less happily named, the lymphatic glands. They 
interrupt the course of the vessels simply or manifoldly. 
They are to be denoted as one of the chief forming places of 
the lymphoid cells. Within them takes place, furthermore, 
a lively reciprocative action between the lymph and the 
blood. 
A lymphatic gland may appear globular, oval, or bean-shaped 
(Fig. 104). In the latter case it presents a so-called hilus 
most distinctly. When the former has reached a certain size. TENTH LECTURE. 
induction lymphatic vessels, vasa afferentia, penetrate, for the 
most part manifoldly, into its convex surface The 
educting vessel at the hilus (h) remains, at the same time, 
frequently single. 
Fig. 104.—Section through one of the smaller lymphatic glands, with the current of the 
lymph—half diagramatic figure; a, the capsule; b, septa between the follicles of the cortex 
(d); c, system of septa of the medullary substance as far as the hilus of the organ ; e, lymph 
tubes of the medulla ; f, lymphatic passages, which surround the follicles and flow through 
the spaces of the medulla ;g. union of the latter into an afferent vessel (h) at the hilus. 
It is surrounded by a connective-tissue sheath (Fig. 104, a, 
i°s,/) with a muscular admixture. This capsule continues 
inwards in a similarly constituted but perforated septum (Fig. 
104, b, c, 105, g, k), which finally unites towards the hilus in a 
thicker connective tissue mass (“ hilus-stroma ”of His). In 
the lymphatic glands of large animals this “ septum system ” 
is immensely developed ; in small creatures it is often uncom- 
monly slight. 
We distinguish in the lymphatic glands a cortical and a 
medullary layer. The former consists of rounded or irregular 
bodies of 0.5 to 2 mm. and more, the follicles (d), which in the 
smaller organs are placed in single, and in larger glands in 
double or manifold rows. 
The medullary substance is composed of reticularly united 
strands, which spring from the inner side of the follicle, pass 
through the septum, and thus constitute a connection be- 
tween these structures of the cortical layer (Fig. 
d, e). The transverse diameter of the strands varies extraor- 
dinarily, from 0.04 too. 13 mm. and more. THE L YMFHA TICS AND L YMPHA TIC GLANDS. 
109 
The follicles and medullary strands are never closely applied 
to the sheath and septa (Figs. 104, 105 ) ; a system of clefts is 
always left. We shall soon learn their signification. 
The follicle (Fig. 105) consists of reticular connective tissue 
Fig. 103.—Follicle from a lymphatic gland of the dog, in vertical section; a, reticular frame- 
work of the more external, b, of the internal portion ; c, fine reticulum of the surface of the follicle ; 
d, origin of a larger, and eof a finer lymph tube ; f capsule; £■, septa; k, division of the one ; i, in- 
vestment space and its tenter-fibres ; h, vas afferens ; /, attachment of the lymph tubes to the septa. 
(Fig. 105, b and a), containing an excessive number of lym- 
phoid cells. At the surface the meshes of the connective 
tissue reticulum become much more narrow {c). 
From it arise fibres which, attached to the inner side of the 
capsule and the outer surface of the septa, keep the follicle 
stretched, as the frame does embroidery. I once named them 
“ tenter-fibres,” and the cup-like spaces permeated by them, 
the “investment spaces” of the follicle (z). The follicles 
themselves are held together in numbers, side by side, by 
connecting bridges of their own tissue. 
The same tissue, containing lymphoid cells, and having 
either its own vessel in its axis (Fig. 105, d, e, 106, a) or an 
entire rectilinear capillary reticulum (Fig. 107, a), forms the TENTH LECTURE. 
strands and reticulum of strands of the medullary substance. 
These “lymphatic tubes” are again, according to my dem 
onstration, attached by similar tenter-fibres (b) to the septa 
(Figs. 105, I, and 107, s),and 
also connected together by a 
connective-tissue cellular net- 
work. 
Fig. 106.—Lymph tube 
from a mesenteric gland of 
the dog ; a, capillary vessel; 
b, reticular connective tissue, 
forming the tube. 
Fig. 107.—From the medullary sub- 
stance of an inguinal lymphatic gland 
of the ox ; a, lymph tube with the com- 
plicated system of vessels ; c, piece of 
another; d, septa; b, connecting 
fibres between the tube and septum. 
The lacuna system between the lymphatic tubes we call 
the lymphatics of the medullary substance. That this arises 
from the investment spaces of the follicle is taught by the Fig- 
ures 104, e, and 105, i, I. 
The blood-vessels attain the interior of the organ, for the 
most part, from the hilus. The arterial affluent, and venous 
effluent tubes are contained in isolated lymphatic tubes. In 
the follicles they form a broad-meshed, rounded, capillary net- 
work. 
Besides these, other smaller vascular branches, surrounded 
by tenter-fibres, may enter our organ from the capsule. 
What purpose is served by these spaces or canal-work be- 
tween the capsule and septum system, on the one hand, and 
the follicles and lymph tubes on the other ? 
We have already answered this. It is the path of the 
lymph in the interior of the organ. 
On perforating the capsule, the vasa afferentia lose their 
walls (Fig. 105, h)\ they become lacunar passages, but are, it THE L YMPHA TICS AND L YMPHA TIC GLANDS. 
111 
• 
is true, still lined with the familiar endothelium in the cortex. 
In the medullary substance the latter cells are absent. The 
vas efiferens, with its independent parietes, is again formed 
towards the hilus by the conjunction of the medullary canals. 
The formation of the vas efiferens is not easy to examine, as 
I, the discoverer of this condition, know from former studies. 
Fig, 104,/, h, represents this current. 
Under natural conditions, there are also lying in the cav- 
ernous passages of our organ, numerous lymphoid cells. 
Whence come the latter ? They have simply, we remark, 
emigrated actively and passively through the narrow-meshed, 
reticular surfaces of the follicles and lymphatic tubes. We 
thus comprehend that a vas afferens may present merely a 
few lymphoid cells, while the vas efiferens may subsequently 
appear relatively rich in these cellular elements. 
I do not need to remark that the current of fluid through 
the lymphatic gland can only be determined by the aid of 
troublesome artificial injections, as His and I can affirm. My 
studies m sre, at that time, the first. ELEVENTH LECTURE. 
THE REMAINING LYMPHOID ORGANS WITH THE SPLEEN. 
THE SO-CALLED BLOOD-VASCULAR GLANDS. 
STRUCTURES, which are identical with the follicles of a lym- 
phatic node, and appear partly single, partly grouped, but 
are always without the medullary substance of the former, 
are met with manifoldly in the human and mammalial body. 
In older times they were given the erroneous name of 
“ glands.” 
Among these are included, as isolated occurrences, the 
so-called lenticular glands of the gastric mucous membrane; 
furthermore, the follicles in the mucous membrane of the 
small and large intestine, to which has been assigned the 
name of the solitary glands. Groups of lymphoid follicles 
form the amygdale or tonsils, then the Peyer’s glands of the 
intestinal canal, as well as the so-called trachoma glands or 
lymphoid follu les of the conjunctiva. A large allied organ 
of the earlier period of life is presented in the thoracic gland 
or thymus. Finally, the spleen, with a similar although con- 
siderably modified structure, terminates this series. 
We comprehend all these, including the lymphatic nodes, 
under the denomination of the “ lymphoid” organs. 
Commencing with a so-called solitary gland of the gastric 
or intestinal mucous membrane, we find it to be an ordinary 
lymphoid follicle surrounded by a cup-like cavity. The 
latter is again permeated by connective-tissue fibres which, 
passing to the tissue of the adjacent mucous membrane, con- 
stitute the connection with the neighborhood. The so-called 
solitary glands of the small intestine—as I ascertained years 
ago by injection—are again washed by the lymph. In 
regard to the “lenticular glands” of the stomach, the authen- LYMPHOID OR G A NS. 
113 
tication has not yet been furnished, but the facts are undoubt- 
edly the same. , 
Let us now pass from the simple to the complicated. 
Let us take the amygdale or tonsils (Fig. 108). These, 
subjected to many changes in the mammalia, show in the 
Fig. 108.—Tonsil of the adult (after Schmidt); a, larger excretory duct: b, more simple one; 
c, lymphoid parietal layer, with follicles ; d, lobule, reminding one of a lingual follicle ; e, superficial; 
/, deeper mucous follicle. 
human body a complicated system of fossae in the surface of the 
mucous membrane. The passages of these depressions open 
in part conjointly (a), in part separately (b). At the peri- 
phery of the follicular aggregation, there are often still smaller 
and shallower fossae (£). The cavities are lined with the 
pavement epithelium of the mouth. A thick, lymphoid 
parietal layer (c), surrounded externally by a connective- 
tissue capsule, invests the entire system of fossae. In this 
lymphoid tissue occur rounded bodies of a large-meshed 
structure and a brighter appearance. These are the follicles. 
In the narrow-meshed connecting tissue, one recognizes 
reticular passages which circurnvallate these bodies. They 
form the paths for the lymph, as the injection shows. 
Simplified formations are presented by the lingual follicles 
on the posterior portion of the dorsum of the tongue. Their 
structure reminds one of the place d of our Fig. 108. 
The so-called trachoma glands have a similar structure, but 
spread out flatter, and are without fossae (Fig. 101). They 
likewise present brighter follicles (b), as well as a narrower- 
meshed and therefore, again, more opaque connecting layer. 
In the latter runs a more developed lymphatic canal-work (c), 114 
ELEVENTH LECTURE. 
which surrounds the follicle with a reticular passage, and com 
mences in a caecal manner just beneath the epithelium. 
Let us also discuss the Peyerian glandular plates. They 
belong to the lower portions of the human small intestine, 
and consist, according to their extent, of a very unequal 
number of aggregated lymphoid follicles. In mammals, where 
however great mutability prevails, they may also be met 
with in the large intestine. The human processus vermi- 
formis, and in still higher development that of the rabbit, 
forms an enormously developed continuous Peyer’s plate. 
The shape of our follicle changes according to the species 
of animal. They are rounded in man (Fig. 109) and in the 
Guinea-pig, and strawberry-shaped in the small intestine of 
the rabbit, while in the vermiform process of the latter animal 
Fig. 109.—Vertical section through a human Peyer’s patch ; a, Intestinal villi; h, Lleberkiihn- 
ian glands ; c, muscular layer of the mucous membrane ; d, apex of the follicle ; f basis portion ; 
glymph-passages around the follicle ; i, at the base of the same ; k, lymphatics of the sub-mucous 
tissue; /, lymphoid tissue of the latter. 
an elongated thing, reminding one of the sole of a shoe, is 
met with. A similar appearance is presented by the Peyerian 
follicles in the ileum of the ox. 
Let us now pass to a closer analysis of our structure. LYMPHOID ORGANS. 
115 
In the follicle (Fig. 109), we distinguish three parts, the 
apex (d), covered only by epithelium, and projecting between 
adjacent villi {a) into the lumen of the intestine, then a middle 
zone (at the elevation of c), and, finally, a basis portion (f). 
The middle zone and basis portion are buried in the sub-mu- 
cous cellular tissue. Here—and we are reminded of the tonsils 
and trachoma follicles—the middle and lower portions are 
united by a more narrow-meshed lymphoid tissue. The sur- 
faces of both these parts are again surrounded by a lymphatic 
canal-work in a reticular form. Not so in the follicles in the 
small intestine of the ox, and in the processus vermiformis of 
the rabbit. In these the basis portion is surrounded, similar 
to the follicles of a lymphatic gland, by a connected cup-like 
Fig. xio.—Transverse section, through the equatorial plane of three Peyerian follicles of the 
rabbit; «, the capillary net-work ; b, the larger annular-shaped vessels. 
lymphatic investment space, while in the middle zone, it is 
true, the reticular passages are still retained. 
The lymphatic injection shows interesting conditions, re- 
minding us of those of the lymphatic glands, and the discover- 116 
ELEVENTH LECTURE. 
ies made in the tonsils and trachoma follicles confirm what 
follows. 
The chyle vessels of the intestinal villi (a), are the vasa 
afferentia (p. 108). Passing further down, they form the 
lymphatic net-work {g, i), which surrounds the follicle, as the 
thread does the toy ball of the child. From these arise, at 
the base of the follicle, the efferent lymphatics (h)} compar- 
able to the vas efferens of the lymphatic gland. 
The capillary net-work, of the Peyer’s plates appears extra- 
ordinarily developed. Fine capillaries permeate the follicle 
in a radial direction (Fig. no, a) ; additional tubes (b) form 
a no less elegant interfollicular net-work. 
The thymus consists of lobular groups of a reticular con- 
nective tissue containing lymphoid cells. The interior of the 
lobule is hollow, connected on all sides with a convoluted 
main canal. Here we also meet with an elegant capillary retic- 
ulum, which differs in man and the calf in the arterial and 
venous arrangement. The lymphatic passages require more 
accurate investigation. The retrogression of the enigmatical 
organ begins before and with puberty. Fat cells in great 
quantity are developed at the expense of the lymphoid tissue. 
The spleen constitutes the most difficult organ of the lym- 
phoid group. It has been the object of many researches in old 
and modern times. We have, indeed, progressed further than 
our predecessors, but much still remains a matter of contro- 
versy. I here give only what I, after numerous personal 
studies, regard as correct. 
Similar to a lymphatic gland, our organ is surrounded by a 
fibrous envelope containing sometimes more, sometimes less 
smooth muscular tissue. This sends off again, in an inward 
direction, an interrupted system of septa. The latter, also 
called the trabecular system of the spleen, is extensively de- 
veloped in large mammals, while in small creatures (marmot, 
rabbit, Guinea-pig, rat and mouse) only scanty rudiments of 
it are met with. We are, therefore, once more reminded of 
the lymphatic glands (p. 108). 
It is best to commence the investigation with one of the latter LYMPHOID ORGANS. 
creatures, a rabbit (Fig. m), for instance. In the largei 
mammals, this system of septa considerably impedes our com- 
prehension of the relations, which is already difficult. 
The soft spleen tissue proper consists of two substances. 
In the first place, we find, scattered throughout the entire 
thickness of the organ, rounded, oblong or irregular structures 
Fig. hi.—Rabbit’s spleen ; a, Malpighian corpuscles ; b, reticular frame-work of the pulp, 
of a whitish color. Sometimes they stand out sharply, at 
others they can only be recognized with difficulty. In many 
species of animals they are observed crowded, in others more 
scanty. Their size slowly decreases in the smaller mammalia. 
These are the Malpighian corpuscles of the spleen or—let us 
say at once—the lymphoid follicles of our organ (a). 
Between them appears a very soft, and in consequence of 
its immense wealth of blood, dark red mass, the so-called 
spleen-pulp. The microscopic analysis of the same shows a 
system of reticularly connected canals (p), which connect 
adjacent Malpighian corpuscles with each other, and leave a 
likewise retiform space—01 cavernous system between them. 
The pulp is, therefore, suggestive of the medullary substance 
of the lymphatic glands, as are the Malpighian corpuscles of 
the follicles of the latter. ELEVENTH LECTURE. 
Both portions of the spleen tissue are, however, shoved 
through each other; it is, therefore, impossible to speak here 
of a special, cortical, or medullary layer. 
We next examine the lymphoid follicle ; and here we again 
meet with the old familiar reticular connective tissue, filled 
with an excess of lymphoid cells, forming in the interior a 
larger meshed, on the surface a more narrow meshed reticu- 
lum. The capillaries of the interior are also readily recog- 
nized. 
The tissue—we repeat—of the pulp strands (Fig. 112, a) 
Fig. i 12.—From the pulp of the human spleen brushed preparation (combination); a, pulp 
strand with the delicate reticular frame-work; b, transverse section of the caverni; c, longitudinal 
section of such a one; d, capillary vessel in a pulp tube dividing up at e; f, epithelium of the 
venous canal; g, side view of the latter ; h, its transverse section. 
arising from the surfaces of the Malpighian corpuscles pre- 
sents, on the contrary, a considerable modification of the 
reticular connective substance, of extremely fine delicate tex- 
ture and with very small meshes, so that only one or a few 
lymphoid cells find room in the latter. The surface of this 
pulp tube preserves the same reticular character. If we 
adjust the focus to the fundus of the caverni invested by them, 
wre find numerous transversely arranged fibres (c). These pas- 
sages are lined with flat, spindle-shaped cells (f), which, 
indeed, as the transverse section (b) teaches, have globular 
nuclei. We have once more before us a vascular endothelium ; LYMPHOID ORGANS. 
119 
only its cell borders are, by way of exception, not cemented 
to each other. If we also add to this that capillaries run in 
the axis of the pulp strands, and that in the narrow reticulum 
of its tissue regular red blood corpuscles are met with, some- 
times fresh and unchanged, sometimes shrivelled and in va- 
rious stages of disintegration, we have then described the 
most essential portion of the structure of the tissue of the 
spleen. 
In order, however, to gain a further insight, we must now 
turn to the vascular arrangement of this strange organ. 
This is very complicated and quite peculiar, and it is just 
here that the views of investigators are diametrically opposed 
to each other. 
The arteria lienalis buries itself, in the ruminantia unrami- 
fied, otherwise, as a rule, with several branches, directly into 
the so-called hilus. The latter become further divided in the 
interior, and finally break up, at an acute angle, into a number 
of fine terminal branches. These, called penicilli, and pecu- 
liarly formed, resemble the branches of a willow stripped of 
its foliage. On these branches (but no longer on the penicil- 
lus) sit the familiar Malpighian corpuscles, like the berries on 
the stem of the grape. 
The arteries and the veins are still invested by a connec- 
tive-tissue sheath, which is continuous with the septum sys- 
tem of the organ. This sheath, like the entire vascular 
expansion, is very different in the several varieties of animals; 
it is slight and rudimentary in the small, complicated and 
thick in the large mammalia. 
Pausing now, however, at that of man, we find the arteries 
and veins, already divided into 4 to 6 branches, passing in and 
out of the organ. Up to trunks of 0.2 mm. they are invest- 
ed in common by a connective-tissue sheath. The latter has 
at first a parietal thickness of about 0.25 mm., diminishing 
to o. 1 mm., whereby arteries of 0.2 and veins of 0.4 mm. 
are still invested in common. There is now a gradual sepa- 
ration of the venous from the arterial branches. The sheath 
in its original condition is continuous for a less distance over 120 
ELEVENTH LECTURE. 
the arteries ; it is gradually changed into a reticular connec- 
tive tissue containing lymphoid cells, a metamorphosis in 
which the adventitia soon participates. The sheath struc- 
ture is extended somewhat further over the venous branch ; 
at last its fibres begin to separate, and it is also lost in the sep- 
tum or trabecular system of our organ. 
From this lymphoid metamorphosis of the artery arise the 
already familiar Malpighian corpuscles of the spleen. They 
lie in part on the point of ramification of arterial branches, 
in part laterally on the unramified vascular tube. Finally— 
and it is a frequent occurrence—the arterial branch passes 
through the centre of the follicle. If we examine more 
closely, we find that no line of demarcation can be drawn 
between the separate follicles and this elongated lymphoid 
covering of the arterial branch. Every Guinea-pig’s spleen 
teaches us this. 
In the follicle, we never meet with a venous branch, but, 
rather, a capillary reticulum with rounded meshes, sometimes 
scantily and poorly developed, sometimes more abundantly. 
The source of supply varies ; sometimes it is branches of the 
follicular artery, sometimes it is through the adjacent pulp- 
tubes. 
We have now to follow the further course of the arterial 
offshoots, the so- called penicilli of the spleen. They enter 
the pulp-tubes of our organ, to pass through their axis and 
to become capillaries. The capillary reticulum of the Mal- 
pighian corpuscle also, at last, sends its offshoots down into 
the adjacent pulp-tubes (Fig. 113, e). 
Now, these capillaries of the pulp-tubes are quite peculiar. 
We follow them by the greatest attention for a certain dis- 
tance (on an uninjected spleen or in a good injected prepara- 
tion), then the capillaries (Fig. 112, d) commence to be 
uncertain and indistinct (e). Separated cell-demarcations 
may still be recognized ; but soon even these disappear. We 
are in the presence of a lacuna—a finest blood current with- 
out walls (Fig. 113, 
Let us recall to mind that the tissue of the pulp-tube pre- LYMPHOID ORGANS. 
sents a reticulum with very narrow meshes, in the interspaces 
of which one, or, at the most, a few lymphoid cells find 
place; and let us not forget that the pulp-tubes possess, su- 
perficially, the same reticular character, covered by an en- 
dothelium consisting of separate, uncemented cells. 
Fig. i 13.—From the spleen of the hedgehog ; a, pulp, with the intermediate currents ; 6, fol- 
licle ; c, boundary layer of the same ; g, its capillaries ; e, transition of the same into the Interme- 
diate pulp-current; _/J transverse section of an arterial branch, at the border of the Malpighian 
corpuscles. 
If we adhere to this previously described textural condi- 
tion, the lacunar capillary blood current, which arises after 
the loss of the capillary walls, will present no further con- 
siderable difficulty. As the failing branch of a drying brook 
wanders at last between the pebbles of its bed, slender and 
scanty, so is it with these finest blood currents. The lym- 
phoid cells resemble the pebbles. 
Still, the blood current contains cellular elements and the 
red blood corpuscles in excess. A portion of the latter 
slip through with their pliable, smooth surface ; others stick 
fast. 
For our colored elements, however, as we have already 
learned, movement is life, rest is death. Thus are explained 
those numerous corpses and fragments of the colored blood 
cells in the spleen, which we mentioned above (p. 119). 
Something additional is also satisfactorily explained by 
this. The closely crowded amoeboid lymph cells are capable 
of taking up into themselves the imprisoned blood corpuscle 122 
ELEVENTH LECTURE. 
or the fragments of its corpse (p. 9). These are the blood- 
corpuscle-containing cells of the spleen, occurrences which, 
many years ago, caused so much racking of the brains, and 
yet are, at present, so easy to interpret. Let us remember 
the amoeba of our Fig. 3. 
We have remembered the dead : let us now return to the 
living. What becomes of these finest blood currents after they 
have successfully passed through the narrow mesh-work of 
the pulp-tubes ? 
If our description has thus far been altogether comprehen- 
sible, the answer follows of itself. These currents enter the 
system of caverni, which Fig. 112 shows between the pulp- 
tubes b and c. 
Let us pause for a moment. If we inject a rabbit’s and a 
Guinea-pig’s spleen, or the organ of a new-born child, from 
the vena lienalis, it is a mere child’s 
play to instantly fill these reticular 
spaces between the pulp-tubes 
(Fig. 114, c). 
Thus—we return to the inverted 
course once more—the lacunar 
pulp current passes over into these 
spaces of the pulp, into the “ cav- 
ernous veins ”of Billroth. From 
the latter, presenting many di- 
versities, it is true, according to 
the variety of animal, arise two 
veins (d), enclosed in continuous 
although very thin walls. 
We said previously (p. I2i) the spleen was a burying-place 
of the red blood corpuscles. This requires no further discus- 
sion now. On the other hand, however, the spleen forms a 
generating focus of these elements, since it contributes lym- 
phoid cells, the substitutes of those colored elements, to the 
blood current. This also requires no further discussion ; cer- 
tainly not, when we recall to mind the reticular surfaces of 
the Malpighian corpuscles, and of the pulp-tubes, and when 
Fig. 114.—From the sheep’s spleen 
(double injection) ; «, reticular frame- 
work of the pulp ; b, intermediate pulp 
current; c, its continuation into the ve- 
nous roots, with incomplete walls ; d, 
venous branch. LYMPHOID ORGANS. 
123 
we think that milliards of lymphoid cells are here surrounded 
by perforated surfaces. 
When our organ becomes enlarged in its pulp, the contact 
surfaces between the blood current and the lymphoid tissue 
increase materially. The latter now sends off more con- 
siderable quantities of its cells into the former. The number 
of the colorless blood corpuscles is thus necessarily increased. 
This is the lienal leucaemia, as it is called by the doctors, a 
disturbance of the equilibrium between the blood and spleen 
tissue, with the saddest consequences. 
Lymphatic passages occur with certainty in the capsular 
and trabecular systems of the spleen. As to what is thought 
to have been met with in the true lymphoid tissue, it stands 
on a weak foundation. 
In the embarrassment of our knowledge we here include 
several parts of the body which a former epoch has, like the 
lymphoid organs described, also called “glands,” and for 
which their successors found the likewise very unsatisfactory 
name of the “ blood-vascular glands.” 
We speak of the thyroid gland, the suprarenal capsule and 
the apophysis cerebri, structures which to the present time 
mock all physiological explanation, and once more confirm 
the old saying, that even the trees do not grow up into 
heaven. 
The thyroid gland, the glandula thyroidea of the anatomist, 
lies, as is known, in front of the respiratory passage leading 
to the lungs. Every one in the Canton of Zurich knows 
that it forms the goitre, that national decoration. We physi- 
ologists are, unfortunately, scarcely able to say more con- 
cerning it than the people. 
Let us, then, examine the strange organ somewhat more 
closely. 
In a connective tissue frame-work we meet, closely ap- 
proached to each other, rounded, oblong or even more irreg- 
ular cavities of 0.05 to o. 1 mm. The inner wall is beset 
with a single layer of low cylindrical cells, 0.02 mm. high and 
0.01 wide. The cavity is filled at an early period with a 124 
ELEVENTH LECTURE. 
homogeneous firm mass, an obscure derivative of the albu- 
minous bodies, the so-called colloid. In the interstitial con- 
nective tissue we meet with a developed, 
round-meshed reticulum of blood capil- 
laries 0.02 to 0.023 nam. broad ; together 
with these there is a widely extended 
lymphatic canal-work. How far it 
stretches, whether it finally circumvo- 
lutes each cavity in a cap-like manner, 
as Boechat recently asserted, requires 
more accurate investigation. Previous 
injection studies by myself and Pere- 
meschko showed nothing of the kind. 
At a later period of life—and the 
thyroid gland appears to grow old 
early—this colloid substance seems to 
increase more and more. The cavities 
become distended, the small parietal 
cells are more and more compressed, and with them the in- 
terstitial connective tissue. In the further progress, these 
cavities flow together, forming larger ones. 
Fig. 115.—Colloid metamor- 
phosis of the thyroid gland ; 
a, gland-vesicle of the rabbit; b, 
commencing colloid metamor- 
phosis of the calf. 
It is assumed of the thyroid gland, like the apophysis cere- 
bri and the suprarenal capsule entirely hypothetically, that 
it removes matters from the blood which, when the same are 
further metamorphosed, either indirectly or directly, are 
afterwards restored to the central fluid of the organism. 
Hence the denomination of the “ blood-vascular glands,” a 
proof of our ignorance at that time. 
Just as obscure are the suprarenal capsules, glandulae suc- 
centuriales, structures which once at an earlier foetal period 
possessed an immense size, and subsequently remained more 
and more behind. 
Here, also, we meet with a double mass, a cortical and a 
medullary layer. The former appears to have a radiated dis- 
position, brownish, reddish or yellowish. The latter, much 
softer, is usually more transparent, grayish, red or yellowish. 
The least resistance is possessed by a border zone which in LYMPHOID OP CANS. 
125 
man is clouded and narrow. It liquefies very readily after 
death. 
A connective-tissue envelope, permeated by elastic ele 
ments, surrounds the organ. Inwards it 
forms a frame-work (Fig. 116, b) ; in 
the spaces of the latter lie soft cells. 
The superficial cavities are, as a rule, 
short; further inwards they acquire a 
radial elongation (a). Transverse sec- 
tions of these spaces, which are con- 
nected at acute angles, frequently present 
oblong and bean-shaped formations. In- 
wards, towards the medullary border, 
the spaces again become smaller, more 
rounded, and the frame-work substance 
delicate and reticular, forming a sort of 
reticular connective tissue (Joesten). 
The contents consist of coarse, granu- 
lar, membraneless cells, closely pressed 
against each other, and containing mole- 
cules of albumen and fat. The cells 
measure 0.0135 to 0.0174 mm., with 
nuclei of 0.0056 to 0.0090 mm. In the 
boundary zone, towards the medullary 
substance, our ceils lodge abundant brownish pigment mole- 
cules. A delicate connective tissue fibro-reticulum also per- 
meates these cavities, which have no membrana propria. 
Fig. 116.—Cortex of the hu- 
man suprarenal gland ; ii, 
gland cylinder ; b, interstitial 
connective tissue. 
It is likewise not easy to investigate the soft medullary 
substance. 
The connective-tissue frame-work having again become 
somewhat more resistent, and at last fused with the connec- 
tive tissue surrounding the veins, forms large oval cavities. 
They are larger than the peripheral ones of the cortical layer, 
without the radiated disposition of the latter. They turn 
their broad side, on the contrary, towards the surface of the 
organ. The medullary cavities are, however, rounder and 
smaller in man. 126 
ELEVENTH LECTURE. 
In them occur, closely crowded, delicate granular cells, 
measuring 0.018 to 0.035 mm., with fine vesicular nuclei. 
The cells appear, in contradistinction to the cortical elements, 
very poor in fat molecules. The behavior of these medul- 
lary cells with chromate of potash is very remarkable, as 
Henle discovered. They become deeply browned, while the 
cortical cells are very slightly changed. 
The vascularity is great, and the arrangement of the ves- 
sels peculiar in the suprarenal capsules. Numerous small 
arterial branches arising from various sources form a capillary 
reticulum in the cortex, with elongated meshes. These capil- 
laries first combine in the medulla into considerable, but very 
thin-walled venous canals. The latter, having likewise a ra- 
diated direction, unite at acute angles, and thus largely devel- 
oped occupy a considerable portion of the medulla. The 
latter large trunks finally open into the very wide veins situ- 
ated in the centre of the organ. 
The lymphatics are still little known. 
In many mammals the medullary mass appears very rich 
in nerves, which may form considerable microscopic plexuses. 
There was, therefore, an inclination to consider it as related 
to the sympathetic. 
The pituitary gland, the hypophysis cerebri, is smaller in 
the higher vertebrates than in the lower, and consists of two 
lobes ; a small posterior one, of a nervous texture, and a 
larger anterior one, with the structure of a blood-vascular 
gland. Through the latter passes a canal lined sometimes 
with flattened epithelium (mammals), sometimes with ciliated 
cells, and which sinks into the infundibulum (Peremeschko). 
Rounded and oval, 0.0496 to 0.0699 nim. large gland spaces 
are enclosed by a connective tissue, rich in capillaries. In its 
interstices lie cells measuring 0.014 mm., with a consider- 
able finely granular body. Colloid metamorphosis may be 
noticed. 
The name of the coccygeal gland, glandula coccygea, has 
been bestowed on a small thing situated at the apex of the 
coccyx. It consists of a system of diverticulated arterial LYMPHOID ORGANS. 
127 
branches of capillaries and veins, invested externally by gran- 
ular cells. s 
The so-called ganglion intercaroticum also has a nearly 
related structure. 
The granulated cells, such as we are familiar with in the 
suprarenal capsule, apophysis cerebri, and the two last named 
organs, belong to the form of coarsely granular connective- 
tissue cells that are so often met with in the neighborhood of 
the vessels (Fig. 55> TWELFTH LECTURE. 
GLAND TISSUE. 
In olden times they were very liberal in their conception 
of the glands. We have already learned this in the lym- 
phoid organs, as well as the thyroid gland, suprarenal capsule 
and apophysis cerebri, which preceding generations of anato- 
mists erroneously regarded as glands. A rounded, limited 
form, and a considerable vascularity was at that time suffi- 
cient to stamp a thing as a gland. We thus obtained the 
lymphatic, Peyerian, and thyroid glands, etc. Later, the 
physiological importance came more into the foreground. 
The true glands take materials from the blood, not alone or 
only principally in the interest of an egotistical nutrition, but 
rather in the service of the whole, whether it be to simply 
free the blood from decomposed substances, or to restore the 
latter, more or less metamorphosed, and serving for other pur- 
poses. On this rests the old distinction of excretion and 
secretion. 
The gland requires an efferent canal system to remove its 
contents. We must lay great weight on this canal in connec- 
tion with the gland ; still the former may, under certain cir- 
cumstances, be wanting, or may remain separate from the 
organ. This is shown by the human ovary. Here the wall 
of the glandular cavity is ruptured. The contents of the lat- 
ter now escape through a rent. It does not thereby cease 
to be a gland, for we know of ovaria enough in lower ani- 
mals which contain quite common glandular formations, pro- 
vided with continuous canals. 
No doubt can therefore prevail here. 
How weak the matter is, however, with the so-called 
blood-vascular glands has already been taught by the previ- 
ous lecture. GLAND TISSUE. 
129 
In modern times, however, the so advanced microscopic 
analysis has furnished characteristics which, in our opinion, 
permit of the certain recognition of a gland. 
Each of our organs (Fig. 117) consists of 
two elements : Ist, of an, as a rule, hyaline 
and thin membrane, the so-called gland 
membrane, membrana propria (a); and 2d, 
of cellular contents (b) enclosed within the 
latter. 
Without a blood supply, however, secretion 
does not take place. A non-vascular gland 
would be a nonentity. We therefore meet 
with a vascular net-work (c), circumvoluting 
the membrana propria, as a third integral 
constituent. 
As further constituents, we have lymphatic 
vessels, muscular elements and nerves. 
Let us now pass to the individual analysis. 
The gland membrane appears, at the first 
examination, homogeneous, and, as a rule, 
very delicate. Exceptionally, however, it 
may acquire a thickness of o.ooi to 0.002 mm. 
It may also be replaced by undeveloped con- 
nective tissue (sebaceous glands of the 
skin). Finally, ordinary connective tis- 
sue or a muscular layer may form a re- 
inforcing stratum around this limiting 
membrane. a 
Fig. 117.—A mam- 
malian Lieberkiihnian 
gland ; a, membrana 
propria ; 6, cells ; c. 
capillaries ; d, gland 
aperture. 
In more recent times, a manifold sys- 
tem of quite flat stellate cells (Fig. 118) 
has been met with which, embedded in 
or resting on the homogeneous mem- 
brana propria, form rib-like thickenings 
of the latter, as for example, in the sub- 
maxillary and lachrymal glands. 
Fig. iiB.—Plexus of star- 
shaped, flat, connective-tissue 
cells, from the membrana pro- 
pria, isolated by maceration. 
From the submaxillary gland 
of the dog. 
Firm, extensible, and formed of a very unchangeable mate- 
rial, probably related to the elastic substance, the membrana 130 
TWELF TH LEC7 LEE. 
propria serves for the transudation and filtration of the blood 
plasma. 
Its origin takes place in the nature of a boundary layer, 
formed from the adjacent connective tissue. 
The form of the gland or of its constituents 
is determined by the membrana propria, or the 
connective tissue, by which it is frequently re- 
placed. For the organ may, with microscopic 
dimensions, remain very simple, while, on the 
other hand (think of the liver and kidney), 
with an increased size, it may assume the most 
complicated structure. 
We distinguish : 
1. The tubular glands (Fig. 117). Here, 
the membrana propria forms a csecal tube, 
generally of considerable length and of rela- 
tively slight diameter. Several such caeca! 
tubes, invisible to the naked eye, may come 
together in a common terminal portion, so 
that there is always a more distinct excretory 
duct. 
Extraordinarily long reticular and caecal ele- 
ments, with many peculiarities, united in im- 
mense numbers, constitute the testicle and 
kidney. We speak now of the tubular glands. 
Fig. ng.—A con- 
voluted gland from 
the conjunctiva of 
the calf. 
Another modification is formed by the so-called convo- 
luted glands (Fig. 119). The terminal portion of this small 
organ presents a peculiar convolution like the coil of a pack 
thread. 
2. Another uncommonly diffused form is the racemose 
gland (Fig. 120). The membrana propria here appears as a 
microscopically small, rounded, elongated or irregularly 
formed saccule.* These “ gland vesicles ” are united at their 
openings in groups, and in this manner a lobule or acinus is 
* It has been proposed to include the small racemose structures of the mucous 
membrane among die ictubular” glands, on account of their elongated saccules. GLAND TISSUE. 
131 
formed. It may acquire an excretory duct, and then the race* 
mose gland, in its smallest and most simple form, is complete. 
But these most elementary structures 
are rare. As a rule (Fig. 120), several 
acini form the still small gland body. 
In larger and large organs the num- 
ber of the gland lobules becomes 
very great. 
It is scarcely necessary to remark 
that transitions occur between the 
tubular and racemose glands. 
3. Finally, we have another gland 
with closed rounded gland capsules, 
which latter are contained in abun- 
dant connective tissue. This is the ovary. These rounded 
structures, which are constituted by a connective-tissue wall, 
are called the Graafian follicles. Among the cells it con- 
tains, one is noted for its size. This is the ovum (Fig. 5). 
Fig. 120.—Human racemose pala- 
tine glands. 
That the latter becomes free by the rupture of the follicular 
wall, we have mentioned above. Let us also add that the 
ruptured follicle is incapable of further repair, but rather goes 
to ruin by a process of cicatrization. The conditions are, 
therefore, in contradistinction to those presented by other 
glands, peculiar and anomalous enough. 
The second and much more important constituent of our 
organ is presented by the gland cells. We shall subsequently 
see that they are nearly all derivatives, of Remak’s corneous 
and intestinal-gland layer. Even in subsequent life, this epi- 
thelial character is not renounced. 
The inner surfaces of the membrana propria are thus lined, 
sometimes simply, sometimes in strata. In the excretory 
portion of the gland, an ordinary epithelium subsequently 
makes its appearance. The gland cell may be called a micro- 
scopically small chemical laboratory. With its body it forms 
the secretion, or changes the formative material received 
from the blood into the latter. 
For this purpose our cells require a certain magnitude. 132 
TWELFTH LECTURE 
We shall, therefore, comprehend that those cells, flattened 
into the thinnest plates, such as we previously met with in the 
pavement epithelium, are absent. 
The gland cell is a membraneless, cubical thing, occasion- 
ally somewhat flattened from above downwards, in other 
cases rendered cylindrical by lateral compression. The for- 
mer shape is represented by the cells of the liver, with a size 
of 0.018 to 0.226 mm. (Fig. 121). The cells (Fig. 122, b) of the 
“gastric mucous glands” of the dog are taller and more slen- 
der. The elements of the Tieberkiihnian 
glandular tubes of the small intestine have 
likewise assumed the cylindrical form, as our 
Fig. 117, b (representing a longitudinal sec- 
tion of this tube) teaches. 
Gland cells covered with ciliae are very 
rarely met with in man. They are only 
known in the uterine tubes. 
Many gland cells—we here allude chiefly 
to those of the liver and kidney—appear 
to constitute tolerably permanent structures. 
In others the cellular elements retain the 
great perishability of the epithelium, and 
perish in the formation of the secretion. 
Fig. i2T.—Human 
liver cells. 
Let us take, for example, a sebaceous 
gland of the external integument, a small 
clustered structure. An acinus is shown in 
Fig. 123, A. 
It is covered by several cell layers. In 
the cavity (b) we meet with a fatty mass, 
which subsequently becomes free as sebum 
cutaneum. 
Fig. 122.—From a gas- 
tric mucous gland of the 
dog ; a, lower portion of 
the excretory duct; b, 
commencement of the 
glandular canal. 
How has the latter been formed ? 
In the peripherical cells, those lying im- 
mediately against the wall of the gland 
vesicle, one already notices an increasing deposit of fat 
molecules. This is, therefore, the fatty degeneration which 
we have already mentioned at page 13. It causes the GLAND TISSUE. 
133 
retrogression of the tissue elements in a normal way here, 
as by a pathological process elsewhere. The gland cell 
swells with the increasing embedment of fat, and finally falls 
from its matrix. Suspended in the cavity of the acinus, it 
has now become a corpse. We meet, accordingly, in the 
Fig. 123.—A, the vesicle of a sebaceous gland ; a, the gland-cells resting on the wall; b, 
those which have been cast off, containing fat and filling the cavity; B, the cells more highly mag- 
nified ; a, smaller ones, poorer in fat and belonging to the wall; b, larger ones, more abundantly 
filled with fat; c, a cell with larger fat drops joined together, and d one with a single drop of fat; 
e,f, cells whose fat has partially escaped. 
sebum with these cells fatty degenerated to a high degree, 
with their fragments, their nuclei which have become free, and 
fat molecules with an albuminous connecting substance. This 
is the origin of the sebum cutaneum, a relatively unimpor- 
tant secretion. 
The lacteal gland consists of a group of enlarged sebaceous 
glands, destined for a higher performance. 
Even before the final period of pregnancy, 
the human organ forms the so-called colos- 
trum. We meet in the latter with globular 
cellular elements of 0.0151 to 0.0563 mm. in 
size (Fig. 124, b). 
These “colostrum corpuscles” are simi- 
lar to the detached, highly fatty, sebaceous 
follicle cells. Subsequently, soon after the 
delivery, the milk contains millions of the so- 
called milk globules (a). They are drops of 
fat which have become free, and are surrounded by a very 
thin shell of a coagulated albuminous body, which is usually 
Fig. 124.—Elemen- 
tary forms of human 
milk ; a, miik globule ; 
b, colostrum, corpuscle. 134 
TWELFTH LECTURE. 
called caseine. Their size varies between 0.003 to 0.009 mm. 
The gland cells should now, with a far more energetic secre- 
tion in the acinus, have been early destroyed. A different 
view might, however, be entertained. The membraneless 
cells may have thrown out the elaborated secretion, as the 
crater of the volcano does the lava—only the cells, like the 
volcano, may persist. T regard this as indeed very plausible. 
We have just spoken of probably the most perishable gland 
elements, immediately after the discussion of more permanent 
elements. Let us now return to the latter for an instant, 
taking up the liver cells. One meets in them, from time to 
time, with brownish molecules and drops of fat. Both ap- 
pear subsequently in the bile ; the former is the “ biliary 
coloring matter ” (to repeat a crude expression of former 
days), the latter becomes “ cholesterine.” Therefore, even 
here, the gland cell once enclosed in its body the secretory 
substance which subsequently becomes free. Here the com- 
ing and going of the latter through the permanent cell body 
is not to be doubted. 
A still further confirmation of the persistence of many 
gland cells has been more recently obtained. Extraordinarily 
fine permanent canaliculi, “the gland capillaries” (first found 
in the liver), occur between the gland cells 
as the terminal offshoots of the excretory 
ducts. Our Fig. 125 represents such from 
the pancreas. We shall, later, refer to 
the matter more in detail. 
With the membrana propria and the 
secretory cells we are, therefore, finished. 
Let us now refer to the capillary reticu- 
lum, the art and manner in which the in- 
dispensable blood current reaches the 
surface of the secreting organ. 
Fig. 125.—From the pan- 
creas of the rabbit; a, larger 
excretory duct: 6, finer one 
of an acinus ; c, finest secre- 
tory canal. 
We repeat what we said at page 96. 
The form of the tissue elements deter- 
mines the arrangement of the capillaries. 
With thin and long glandular tubes, such as stand close to GLAND TISSUE. 
each other in the gastric-mucous membrane, the individual 
tubes occupy about the position of the transversely 
striated muscular filament (Fig. 
91). The reticulum (Fig. 126) 
becomes similarly elongated ; 
only the rings around the 
gland apertures, together with 
anomalous arterial and venous 
branches, produce a considera- 
ble difference in the thing. 
Turning to the racemose 
glands, with the generally- 
rounded form of the element, 
the small acinus, the capillary 
net-work must, as we have 
already remarked, correspond 
to the form of a fat lobule (Fig.. 
93). Our Fig. 127 represents 
the capillary arrangement of a 
larger lobular group of the 
pancreas. The figure might, 
with equal propriety, be used 
for the vascular arrangement 
of a conglomeration of the lobules of fat cells. 
Fig. 126.—The vascular net-wprk of the mu- 
cous membrane of the human stomach—semi- 
diagramatic. The (finer) arterial trunk di- 
vides into the elongated, capillary net-work, 
which passes over into the rounded reticulum 
of the gland apertures, from which the vein 
(the wider, darker vessel) arises. 
The immense assimilation of glandular organs renders a 
considerable wealth of lymphatic passages, which are to .re- 
store the superfluous transudation to the blood passage, very 
appreciable. A portion of these lymphatic passages have 
been discovered very recently. Smooth muscular fibres, 
which either invest the gland body or occur in the parieties 
of the excretory ducts, scarcely require a further physiologi- 
cal explanation. They are of great importance for the ex- 
pulsion ot the secretion. 
Concerning the gland nerves, this most obscure portion of 
the structure of the organ in question, we shall speak later. 
The last which remains for discussion is the excretory duct. 
If we take a simple gland tube (Fig. 128), such as are con- 136 
TWELFTH LECTURE. 
tained in infinite numbers in the gastric mucous membrane, 
and examine a so-called “ peptic-gastric gland ” (it may also, 
it is true, be somewhat more complicated), 
we readily recognize from d to b the secre- 
tory cells. Over bwe meet with a cylindri- 
cal epithelium, the same which covers the 
surface of the gastric mucous membrane. 
A further explanation is, therefore, super- 
fluous. 
Let us, furthermore, cast a glance back to 
our Fig. 122. The drawing represents a so- 
called “gastric-mucous gland.” A long, 
Fig. 128.—A lateral 
view of a gastric gland 
of the cat; a, stomach 
cells : b, inner ; c, ex- 
ternal intercalary por- 
tion ; d, the gland tube, 
with . both varieties of 
cells. 
Fig. 127.—The vascular net work of the rabbit’s pancreas. 
excretory duct bears the same cylinder cells (a). It then 
divides into two caecal tubes. These (b) contain lowei 
cubical elements, the suppliers of a tolerably unknown secre- 
tion. 
Let us examine a still earlier figure—our Fig. 120—the 
small racemose glands. No doubt can prevail here concern- GLAND TISSUE. 
137 
ing the excretory duct. Its cell covering is not rarely different 
from that of the acini. 
The wall of the excretory canal is here of a connective-tis- 
sue nature. In larger, and the largest glands of a similar 
structure, the omitted duct acquires an increasing complica- 
tion. We shall later return to the particulars. 
Let us now take a cursory survey of the different glands 
of the human body. 
41.. To the tubular group belong : the Bowman’s glands in 
the regio olfactoria of the organ of smell; the tubes of the 
mucous membrane of the stomach, small and large intestine, 
which bear the names of the gastric juice glands, or peptic- 
gastric glands, or gastric-mucous and Lieberklihnian tubes ; 
finally, the uterine glands. Then, as modified structures, as 
so-called convoluted glands, we have, finally, to mention the 
smaller and larger sudoriparous glands, together with the ce- 
ruminous glands of the ear. 
Very complicated tubular organs are, as we previously 
mentioned, the kindey and testicle. 
b. Among the racemose glands are included a host of our 
organs from the smallest to the largest dimensions. First 
belong here all the small glands of the mucous membranes 
of the body, then the so-called Brunner’s glands of the duo- 
denum, the sebaceous glands of the skin, and the Meibomian 
of the eyelids. As larger and largest, the group includes : 
the lachrymal gland, the various salivary glands, the pancreas, 
the lacteal glands, then the Cowper’s and Bartholinian glands 
of the sexual system; and, furthermore, the prostate. 
Finally, according to their manner of origin, the lungs 
should also be included here. We shall subsequently have 
to refer more particularly to them, as well as to their prede- 
cessors. 
c. The closed gland capsules. We scarcely need to repeat 
that the ovarium forms the only gland of this kind in the hu- 
man body. 
Our organs, with slight exceptions (the primitive kidney 
and the generative glands), originate, in their cellular portions,, TWELFTH LECTURE. 
138 
either from the upper or lower germinal layer, from the cor 
neous and intestinal gland layer of Remak. The membrana 
propria and capillary reticulum are 
aggregated productions of the middle 
layer, which produces so much. 
A previous figure, 41, the primary- 
rudiment of a hair germ, passes as 
well for the glands of the external in- 
tegument as for those of the mucous 
membrane. When, by a continuous 
increase of the cells, lateral buds 
branch off from the cellular cone as 
it grows downwards, there is formed 
at first a solid, slightly berry-shaped 
mass (Fig. 129). It finally becomes a 
complicated racemose system, which 
at last becomes hollow (a), and 
thereby constitutes the completed 
gland. 
Fig. 129.—Developing racemose 
gland ; a, excretory duct, already 
permeable ; b, solid gland bud ; c, 
membrana propria ; d, surrounding 
connective tissue. 
With this we leave the glandular organs in general. 
The subsequent lectures will, however, carry us back to 
certain of them. THIRTEENTH LECTURE 
THE DIGESTIVE APPARATUS WITH ITS GLANDS. 
The digestive apparatus, in its connective-tissue external 
layers and the muscular middle layers, is certainly of a rela- 
tively simple nature. The mucous membrane, however, with 
the immediately adj icent loose connective tissue, and with all 
which is connected with it, presents an abundance of the 
most diversified structural relations. 
Let us therefore briefly examine the long canal work, with 
the varying constituents in its interior. 
The oral cavity contains the already described teeth (p. 73), 
as well as the tongue. In it open the salivary glands, large 
racemose organs, and, together with these, a number of 
smaller associates, the so-called mucous glands. 
From the vascular mucous membrane of the mouth project 
closely crowded papillae. It is covered by the stratified pave- 
ment epithelium spoken of at 
page 30. The latter may here 
acquire a thickness of 0.45 mm. 
The submucous connective tissue 
appears sometimes dense (gums), 
sometimes loose and extensible 
(the floor of the mouth). In 
it lie the bodies of the numer- 
ous small racemose glands. The 
secretion is mucus; the cells 
form a layer of pale, cubical or 
low cylindrical elements (Fig. 
130). They occur as labial, buc- 
cal, palatine and lingual glands. 
Fig. 130.—Gland vesicles of the palatine 
gland of the rabbit; a, rounded, b, an elon- 
gated acinus. 
Among the salivary glands the submaxillary has recently 
undergone an accurate investigation (Pfliiger, Gianuzzi, Hei- 140 
THIRTEENTH LECTURE. 
denhain). Its cells differ in the several animals. The former 
are granular in the rabbit. In the dog and cat, on the con- 
trary, we find a mucous gland. 
The cells (Fig. 131) here consist of two different structures. 
Firstly {a), we meet with large rounded elements, which are 
filled with a homogeneous 
mucous substance. Be- 
sides these, quite granular, 
smaller cells occur in the 
periphery of the gland 
vesicle (z). Pressed closely 
together, and indistinctly 
separated from each other, 
they form a sort of cres- 
cent (Gianuzzi). They 
subsequently change into 
those large mucous cells. 
The finest secretory capil- 
laries, after the manner of 
our Fig. 125, likewise 
make their appearance 
here, as also do the flat 
stellate cells of the membrana propria (see Fig. 118). The 
excretory ducts show cylinder cells (Fig. 131, d), with longi- 
tudinal striations beneath the nucleus. We have, finally, to 
mention a rounded capillary reticulum, and abundant lym- 
phatics around and between the lobules and lobes. 
Fig. 131.—The submaxillary gland of the dog ; 
a, mucous cells ; b, protoplasma cells ; c, crescent; 
d, transverse section of an excretory duct, with the 
peculiar cylindrical epithelium. 
The sublingual appears to be nearly related to the sub- 
maxillary gland. 
We cannot, however, yet leave the latter. As experimen- 
tal physiology teaches, the irritation of the chorda tympani 
produces a profuse watery secretion ; that of the sympa- 
thetic, on the contrary, a scanty quantity of a thick fluid 
substance. 
The continued irritation of the nerves, as Heidenhain ascer- 
tained, produces an important change in the contents of the 
acini (Fig. 132). Nearly all the large round cells (a) have, THE DIGESTIVE APPARATUS. 
141 
in the mean time, given off their mucine as a secretion. A 
granular protoplasmatic substance now fills the altered cell 
body. 
Fig. 132.—Submaxillary gland of the dog, with its contained ciil' : a. changed by the strong 
irritation of the chorda ; i, those remaining unchanged (after, Heidenhain). 
This was altogether the first difference which a quies- 
cent and active gland presented to the eye of the micros- 
copist. 
The parotid gland contains in its acinus (measuring 0.034 
to 0.052 mm.), granular cubical cells (of 0.014 to 0.018 mm.), 
without any mucous metamorphosis. Fine secretory tubes 
have been met with between the latter. Here, again, the ex- 
cretory duct has ordinary cylinder cells. 
The tongue is an essentially muscular organ, with transverse- 
ly striated filaments crossing each other. The dorsum of the 
tongue has innumerable different papillae. Three forms have 
been distinguished here : the filiform (papillae filiformes, s. 
conicae), the fungiform (p. fungiformes, s. clavatae), and, finally, 
the circumvallated (p. circumvallatae). To the latter have also 
been added the so-called papillae foliatae, which were early 
discovered, then forgotten, and recently more accurately in- 
vestigated. Both the latter organs contain the terminations 
of the gustatory nerves. 
Our organ is rich in racemose glands. We meet principally 
with mucous glands, with the contents rendered familiar to us 
by Fig. 130. In the vicinity of the p. circumvallata and the 142 
THIRTEENTH LECTURE. 
p. foliata, quite similarly shaped glands appear, it is true, bul 
they have different anomalous contents, with granular cloudy 
cells (Fig. 133). The same organs 
have been met with in great numbers 
in the nasal mucous membrane, and 
they have received the name of the 
“ serous glands ” (Heidenhain). 
The tissue of the mucous mem- 
brane commences at the posterior 
fourth of the tongue to undergo a 
lymphoid metamorphosis, in which 
the pharynx may also participate. 
We thus have demarcated lymphoid 
organs, the lingual follicles, the ton- 
sils, and the pharyngeal tonsils, discovered by Koelliker 
(compare p. 113). 
Fig. 133.—Acini («, round, b, ob- 
long) of a serous gland from the 
vicinity of a circumvoluted papilla of 
the cat. 
The pharynx, with its transversely striated muscles, has the 
same covering of stratified pavement epithelium as the oral 
cavity. The tough mucous membrane acquires papillae below. 
The upper portion is rich in mucous glands. 
The oesophagus also retains the old epithelial covering. 
The muscular coating consists of a thicker longitudinal ex- 
ternal layer and a thinner internal transverse layer, and, as it 
descends, shows a replacement of the voluntary transversely 
striated fibrous formation by the involuntary smooth tissue. 
The mucous membrane projects in longitudinal folds, and 
contains racemose mucous glands. 
We may touch upon these only cursorily. 
The stomach or ventriculus, on the contrary, requires a 
more careful discussion. Its serous covering, it is true, pre- 
sents nothing worthy of remark, neither do its smooth muscles, 
which consist of layers running in longitudinal, transverse, 
and oblique directions. But the mucous membrane, which is 
lined with cylinder cells 0.0226 to 0.0323 mm. high and 0.0045 
to 0.0056 mm. broad, shows, on the contrary, an abundance 
of interesting and important things. 
Its surface is not smooth, but uneven. Either lower oi THE DIGESTIVE APPARATUS. 
143 
higher isolated prominences (Fig. 134, a), are met with 
there, or projecting folds, which are united in crossing each 
other. 
The glands open only in the valleys, and never on a hill 
or a fold. Numerous differences of the gastric surfaces 
occur according to the variety of animal. In general, the 
cardial half of the stomach presents a thinner and more 
even mucous membrane than the pyloric portion. The 
mucous membrane may here, at last, acquire an elevation 
of 2 mm. 
An enormous quantity of tubular 
glands (Fig. 134, h) permeate the 
mucous membrane. The massiveness 
of the latter is, therefore, in compar- 
ison to this embedment, but slight. 
We find an ordinary soft connective 
tissue (Fig. 135, a). Lymphoid meta- 
morphosis of the latter may, however, 
take place. 
The glandular tubes of the stomach 
have been divided into two differ- 
ent forms; the so-called peptic- 
gastric glands and the gastric-mucous 
gland. 
Fig. 134.—Vertical sectiqn of 
the human gastric mucous mem- 
brane ; a, surface papillae; b, 
glands. 
The former constitute the more dis- 
seminated and more important 
glandular formations (Fig. 134)- 
They open in part singly (Fig. 
128), in part by the conjunction 
of several tubes into a common 
excretory duct (Fig. 136, 1). 
In both cases the aperture 
appears in the transverse sec- 
tion to be rounded (a), and 
lined with the ordinary slender, 
high cylindrical epithelium of the gastric mucous membrane 
(Fig. 128, a, 136, a). 
Fig. 135.—Transverse section through the 
gastric mucous membrane of the rabbit; a, 
tissue of the mucous membrane ; b, trans- 
verse sections of empty and injected blood- 
vessels, c ; d, spaces for the glands. 144 
THIRTEENTH LECTURE. 
The gland body itself appears as a sometimes smooth bor- 
dered, sometimes sinuous tube. The membrana propria 
shows the familiar flattened stellate 
cells. 
Passing, now, from the outlet of 
the gland in a downward direction, 
we meet at b with a new metamor- 
phosed cell formation, broader, 
lower and more granular. Further 
below, at c, we have two large gland 
cells (peptic cells). The latter are, 
however, first met with at d in their 
highest development. Here, lying 
on an uninterrupted series of smaller 
gland cells are isolated larger, gran- 
ular elements (Fig. 128, d), lodged 
in niche-like sinuosities of the mem- 
brana propria. The latter struc- 
tures are the “ overlying cells ” of 
Heidenhain, in .contradistinction to 
his “ chief cells.” 
Fig. 136.—1, a compound peptic- 
gastric gland of the dog; a, the 
wide aperture (stomach cell) with the 
cylinder epithelium ; b, the division ; 
c, the isolated tubes lined with pep- 
tic cells ; d. the escaping contents ; 2, 
the aperture a, in transverse section ; 
3, transverse section through the in- 
dividual glands. 
We have already learned how dif- 
ferent is the appearance presented 
by the quiescent and overworked 
submaxillary gland of the dog. Something similar—and we 
arc again indebted to Heidenhain for the interesting fact—is 
shown by the peptic-gastric glands. In the fasting animal 
they appear smooth bordered, somewhat shrunken, and their 
chief cells are transparent. A few hours after a plentiful meal 
an essentially different appearance is met with. The peptic- 
gastric glands are now swollen, their walls are sinuous, their 
chief cells enlarged, granular and cloudy. At a later period 
they again shrink ; the chief cells, however, remain per- 
ceptibly clouded. 
Now which of the two varieties of cells supply the gastric 
juice, we do not yet know. We are inclined to conjecture 
that it is the peptic-gastric glands. THE DIGESTIVE APPARATUS. 
145 
The second glandular formation, the gastric mucous 
glands, were long since discovered in the hog. In the dog, 
cat, rabbit and Guinea-pig they occupy a large extent of the 
pyloric region ; in man, on the contrary, but a small zone 
here. They are, again, in part ramified, in part unramified 
tubes. One may also recognize here in the excretory duct 
(and it may acquire a very considerable length) the ordinary 
cylindrical epithelium of the gastric mucous membrane (Fig, 
122, a). The lowertrue portion of the gland shows, on the 
contrary, lower cubical cells {b) richer in fine granules. They 
become cloudy in acetic acid, and call to mind the “ chief 
cells ” of the peptic-gastric glands. 
Small racemose glandules appear in the human pyloric re- 
gion. Isolated lymphoid follicles form the lenticular glan- 
dules, familiar to us from p, 112. 
At the border of the mucous membrane, towards the sub- 
mucous tissue, there is a net-work of smooth muscular fibres, 
the muscularis mucosae (p. 80). Thin strips pass up between 
the gland tubes. 
The arrangement of the vessels in the gastric mucous mem- 
brane (Fig. 126) is elegant and characteristic. Thin and slen- 
der arterial branches, rising up through the submucous tissue, 
terminate in a long-meshed capillary net-work, circumvolut- 
ing the gland tubes, and forming rings around the apertures 
of the latter. The transition into venous roots takes place 
on the surface only, and these rapidly unite into large de- 
scending veins. The latter form a broad-meshed reticulum 
of wider tubes beneath the mucous membrane. 
The lymphatic passages were recently discovered by an 
eminent Swedish investigator, Loven, Large net-works, 
situated in the submucous tissue, send upwards considerable 
caecal canals, which pass between the glands and reach nearly 
to the gastric surface. 
The gastric juice, an acid fluid, contains a peculiar fermen- 
tative body, pepsine. The granules in the covering cells (and 
possibly in the chief cells) are this substance, which has been 
formed by the gland cells. The power of the secretion to 146 
THIRTEENTH LECTURE. 
digest albumen must be left for discussion in another lec- 
ture. 
Let us pass to the small intestine. 
Its serous covering and the smooth muscles, forming a double 
layer, we here omit. The mucous membrane, on the con- 
trary, requires an accurate description, for its structure is 
more complicated than in the stomach. 
In the first place, we meet with innumerable large crescen- 
tic folds (increasing downwards in height), the valvulse con- 
niventes Kerkringii. The surface of the small intestine, be- 
sides, projects in millions of complicated papillae, the intes- 
tinal villi. In the mucous membrane we meet, furthermore, 
with an infinite number of small glandular tubes, the Lieber- 
klihnian glands; and in the duodenum, with small racemose 
organs, the Brunonian glands. Finally, the small intestine 
contains solitary and aggregate (Peyerian) lymph follicles. 
The tissue of the mucous membrane of the small intestine 
also shows a muscularis mucosse, but it is thinner than in the 
stomach, and then a reticu- 
lar connective substance 
containing numerous lym- 
phoid cells (Fig. 47, a). 
The villi (Fig. 137)—we 
have already mentioned 
them in a previous lecture 
—also consist of a similar 
tissue. Even the surface 
is distinctly fenestrated, 
although with narrower 
meshes. In the axis we 
find the chyle vessel (Fig. 
95, d), single or multiple, 
Fig. 137.—Lieberkuhnian glands (a) of the cat, 
with the intestinal villi (b) situated over them. 
in the latter case sometimes connected in an arched and 
bridge-like manner, covered by thin slips of smooth muscle 
(c) derived from the muscularis mucosae, and finally circum- 
voluted by a looped net-work of capillaries {b\ We are 
already familiar with this from what has preceded. THE DIGESTIVE APPARATUS. 
That the whole intestinal canal is lined with cylindrical epi- 
thelium, was mentioned in the second lecture. We also de- 
scribed the peculiarity which the cylinder cells of the small 
intestines presented, the thickened seam, permeated by 
porous canals, of the free broad surface. 
We now turn to the glands. By far the more important 
formations are the Lieberkiihnian tubular glands (Fig. 137, a). 
They are infinitely numerous, and occupy not only the mu- 
cous membrane of the small, but also that of the large intes- 
tine. We are thus reminded of the gastric glands ; the 
capillary net-work is also the same, , 
The Lieberkiihnian glands are smaller, however ; they are 
only 0.38 to 0.45 mm. long, and 0.056 to 0.09 mm. broad. 
Their membrana propria also appears more delicate ; the 
tube remains undivided, and is lined by a simple layer of cyl- 
indrical gland cells (Fig. 117, b). The opening occurs regu- 
larly in the narrow vales which are enclosed by the adjacent 
villi. They secrete the intestinal juice. 
The racemose or Brunonian glands (Fig. 138) of the small 
intestine are of far more subordinate importance. They com- 
Fig. 138.—A human Brunner’s gland. 
mence, in man, just beyond the stomach, and form, in a 
crow’ded sequence, a regular glandular cushion embedded in 
the submucous tissue. They thus extend to about the en- 148 
THIRTEENTH LECTURE. 
trance of the biliary duct, becoming more scanty further 
downwards. The mammalia show numerous variations. 
The size varies in man from 0.25 to 2 mm. The acini ap- 
pear rounded, elongated, sometimes regularly tube-like (0.56 
too. 14 mm.) The duct and gland body have the same cover- 
ing of low cylindrical, pale and irregular cells. If lam not 
mistaken, the Brunonian gland stands in the middle, between 
the ordinary racemose mucous gland, the gastric-mucous 
gland and the serous gland. Concerning the secretion we 
know very little. 
Isolated lymphoid follicles (solitary glands) may occur 
throughout the entire small intestine. These, as well as the 
aggregated lymphoid follicles (the Peyer’splates) have already 
been mentioned in the eleventh lecture. 
We have already mentioned that the Lieberkiihnian tubu- 
lar glands have an elongated net-work of blood-vessels. From 
it arise, and to it return, the afferent and efferent vessels of 
the intestinal villi, which form the looped net-work (Fig. 95, h). 
The lymph or chyle vessels of the intestinal villi, having 
descended into the mucous 
membrane, likewise form a net- 
work, very much more incom 
plete it is true, of wider tubes. 
Our Fig. 109 (a, b, c, k, to the 
left) may represent this toler- 
ably. During the resorption 
of the chyme, its fat, in a con- 
dition of the finest division, 
penetrates first the body of 
the cylindrical epithelium ; it 
then enters a wall-less passage 
through the reticular connective 
substance of the villi, and, at 
last, the caecal chyle canal (Fig. 
Fig. 139.—The very slender intestinal 
villus of a kid, killed during digestion, with- 
out epithelium, and with the lymphatic ves- 
sel filled with chlye, in the axis. 
139) occupying the axis of the latter. “ Preformed passages ” 
for this process of wandering have frequently been searched 
for, it is true, and they have often been thought to be found, THE DIGESTIVE APPARATUS. 
149 
but subsequently nothing of all this was confirmed. These 
were simply microscopic observations such as should not be 
made, instituted for the purpose of filling up a gap in the 
present physiological knowledge at any price. 
The Lieberkiihnian tubes continue throughout the mu- 
cous membrane of the whole large intestine, but now receive, 
most superfluously, a new name, 
that of the glands of the large intes- 
tine (Fig. 140). They have not be- 
come changed in the least. 
The reticular connective sub- 
stance of the mucous membrane of 
the small intestine has, however, 
been further transformed into an 
ordinary connective tissue ; the 
reticular character is less pronounc- 
ed, and the number of lymphoid 
cells contained in the tissue has de- 
creased enormously. The intesti- 
Fig. 140.—Glands of the 1a."4- ntes- 
tine of the rabbit. One tube with cells ; 
the others drawn without cells. 
nal villi of the small intestine have finally entirely disappeared. 
If the mucous membrane, as in the upper part of the 
rabbit’s colon, still projects as papillae, the latter appear 
broader and as prominences of the ordinary mucous mem- 
brane permeated by tubular glands (Fig. 100). 
The colon presents isolated lymphoid follicles. In the 
vermiform process of man and the rabbit, on the contrary, 
there is an enormous Peyerian plate, as we remarked at page 
114. 
The blood-vessels of the large intestine correspond with 
those of the stomach (Fig. 126) for an interchange. Lym- 
phatics have also been subsequently met with in the carni- 
vora and herbivora. Those of the upper colon of the rabbit 
are represented by our Fig. 100, g, f, e. 
In the anus the simple cylinder epithelium is sharply de- 
marcated from the modified epidermis. At the lower end 
of the intestine, the smooth and transversely striated muscles 
become intermixed, reminding us of the oesophagus. FOURTEENTH LECTURE. 
PANCREAS AND LIVER, 
We have still left the two largest glandular organs of the 
digestive apparatus, the pancreas and liver. We shall soon 
finish the pancreas ; the liver, on the contrary, requires a more 
accurate discussion, in consequence of its peculiarities. 
The pancreas is an enormous racemose structure. It re- 
minds one of the salivary glands. The rounded acini meas- 
ure 0.06 to 0.09 mm. The membrana propria is likewise 
said to have flat stellate cells. The rounded vascular net- 
work was represented in our Fig. 127. The lymphatics re- 
quire still more accurate investigation. 
The gland vesicles are lined with indistinctly separated, very- 
granular cubical cells. In the adult rabbit the latter show 
fatty molecules in their interior, that is in the parts turned to- 
wards the lumen. The middle and external portions remain 
transparent. Between them appears the net work of finest 
secretory tubes, already familiar to us from Fig. 125 (Sa- 
viotti). 
The thin-walled excretory duct of the human pancreas 
contains no muscular elements. Below, it presents mucous 
glandules. 
It is covered by a low cylindrical epithelium. If followed, 
in animals, into the gland, these cells are found to become 
more and more flat in the branches. Finally, in the gland 
vesicles themselves, we meet with thoroughly flattened ele- 
ments, reminding us of the endothelia of the vessels. These 
are the so-called “ centro-acinary ” cells (Langerhans), which' 
are found widely extended, not only in the pancreas, but also 
in the parotid. 
The character of the gland cells in a quiescent and active 
condition requires further investigation. PANCREAS AND LIVER. 
151 
The liver—as its natural external surface, or that of an arti- 
ficial section teaches—consists of individual, crowded areae, 
the so-called hepatic islets or hepatic lobules. In many crea- 
tures, as the pig, the demarcation of the lobules is very dis- 
tinct. The borders of the lobules appear tolerably distinct 
in the human organ during the infantile period of life, but 
Let us now turn to the liver. 
very indistinct, on the 
contrary, in the adult. 
Our liver islets are as- 
sumed to measure, as a 
mean, 2.2 mm. 
A hepatic lobule (Fig. 
141), however, consists 
essentially of innumera- 
ble gland cells and, cross- 
ing them, an uncommon 
ly complicated capillary 
net-work. The latter 
unite at the central point 
of the lobule to form 
an initial branch of the 
hepatic vein ; the limits 
are shown externally 
Fig. 141.—Hepatic lobule of a boy ten years old, 
vith the transverse section of the central hepatic vein 
trunk. 
by the branches of the portal vein and the fine biliary 
branches. 
The liver cells have already been noticed at Fig. 121. 
These thick, obtuse-angled structures, whose mean measure- 
ment is 0.018 to 0.023 mm., contain nuclei of 0.006 to 0.007 
mm., with nucleoli. The soft, granular cell body remains 
membraneless and endowed with a slow contractility (Leuc- 
kart). The brown molecules of the biliary coloring matter 
in the cell body, as well as the fatty embedments, we have 
already mentioned. The latter occur in the suckling infant, 
in adults whose diet is rich, and also in fattened animals. 
They form the so-failed fatty liver (Fig. 142). The cell sup- 
ports such an overloading with fat (r, d) relatively well. 152 
FOURTEENTH LECTURE. 
With an altered manner of life, the unusual contents soon 
disappear again - 
In the lobule (Fig; 141) the cells he crowded together in 
a radiated manner, forming simple rows. 
Reticular combinations gradually become 
more frequent externally. These are the 
so-called cellular trabeculae and cellulo- 
trabecular reticula of our organ. 
Between the lobules we meet with in- 
terstitial connective tissue, sometimes 
only slightly developed (man), sometimes 
Fig. 142.—Cells of the fat- 
ty liver; a, b, with smaller 
fat molecules and drops ; c, 
d, with large drops. 
abundantly (pig). This connective tissue derives its origin, 
in part, from the investing membrane of the liver ; it is, in 
part, the continuation of a connective-tissue sheath which sur- 
rounds the blood-vessels and biliary passages entering the 
porta hepatis (Glisson’s capsule). 
The liver receives its blood from two unequally developed 
supply tubes, the wide portal vein and the narrow hepatic 
artery. The first forms, around the lobules, partly shorter or 
longer branches (Fig. 94), sometimes, however, nearly and 
actually assuming a ring-shaped arrangement (pig). These 
branches rapidly divide into the compact capillary net-work 
of 0.009 to 0.0126 mm. wide tubes. They approach the cen- 
tre of the lobule in a radial manner to bury themselves in the 
commencing portion of the hepatic vein, which is situated at 
this point. The latter, like its larger trunks, has uncom- 
monly thin walls, and has coalesced externally with the 
parenchyma of the liver. 
The branches of the hepatic artery, running along with the 
portal vein and biliary ducts, form, in the first place, nu- 
tritious vessels for both the last mentioned parts, and then 
capsular capillaries ; finally, they penetrate the lobule itself. 
They either bury themselves here in the branches of the por- 
tal vein, or pass over into the peripheral portion of the capil- 
lary net-work. 
Both varieties of net-work, that of the hepatic cell tra- 
beculae and that of the blood-vessels, are most intimateh PANCREAS AND LIVER. 
153 
interwoven with each other, so that every space of the one 
meshwork is occupied by portions of the other. 
After suitable treatment, 
as Beale and Wagner found, 
thin sections of the hard- 
ened hepatic tissue show an 
uncommonly elegant reticu- 
lar tissue of a right delicate, 
homogeneous, nucleated, 
connective substance (Fig. 
143, a). 
In the last period of foetal 
life, or in the new-born (Fig. 
143), this consists distinctly, 
in places, of a double mem- 
brane. The one layer corresponds to the capillary walls (and 
shows here and there a combination of the flat, vascular cells 
—Eberth); the other, investing the hepatic cell-trabeculae, 
represents a finest membrana propria. 
Fig. 143.—Frame-work substance from the rab- 
bit’s'liver; homogeneous membrane with nu- 
clei : b, thread-like strands of the latter ; e, sev- 
eral hepatic cells still retained. 
Fig. 144.—Biliary capillaries of the rabbit’s liver. 1. A part of the lobule ; <r, vena hepatica ; 
b, branch of the portal vein ; c, biliary ducts ; d, capillaries. 2. The biliary capillaries (b) in their 
relation to the capillary blood-vessels («). _ 3. The relation of the biliary capillaries to the hepatic 
cells; a, capillaries ; b, hepatic cells ; c, biliary ducts ; d, capillary blood-vessels. 
Great difficulty was encountered, during a long period, in 
the investigation of the finest biliary passages (Fig. 144)- A 154 
FOURTEENTH LECTURE. 
reliable result was at last secured here by means of trouble* 
some injections* (Gerlach, Budge, Andrejevic, MacGillavry) 
The finer ramified system of the biliary passages may, it is 
true, be still readily recognized (Fig. 144, 1). They run with 
the branches of the portal vein {b\ in the intervening spaces 
of adjacent hepatic lobules. From them arise fine branches 
which circumvolute the branch of the portal vein (c). 
They are continuous inwards with a marvelously delicate 
net-work of finest canals, the so-called biliary capillaries (d). 
The diameter of the latter is 0.0025 to 0.0018 mm. (rabbit). 
They surround the individual liver cells (3, b) with elegant 
cubical meshes '{a), so that the cellular element comes into 
contact at one point or another of its surface with these finest 
tubules. We thus have, in addition to the two coarse net- 
works of the cellular trabeculae and capillary vessels, this 
third, finest one, of the biliary capillaries. 
They are also not wanting in the other classes of vertebrate 
animals. There is, nevertheless, considerable variation (Her- 
ing, Eberth). 
We now encounter the question: do the biliary capillaries 
possess a proper wall, or are they only the finest lacunar 
canals? Furthermore, what is their more exact relation to 
the hepatic cells ? 
I have not doubted that there was a special, although 
extremely thin wall, from the instant that I began to study 
the biliary capillaries of the rabbit. One sees here, not only 
the artificially injected, but also the adjacent empty tubules 
(often to a considerable extent), regularly demarcated by 
sharp, straight lines. A lacunar system between contractile 
cells would otherwise scarcely present the regularity of the 
biliary net-work. We therefore coincide with Eberth and 
Koelliker in the assumption of a wall. The same is also 
shown by the cat’s liver. 
* These may be made from the biliary passages in the fresh animal cadaver. 
This was the earlier procedure. An injection may also be made into the vein of 
the living animal of indigo sulphate of soda, which is soon (as in the kidney) 
secreted by the liver (Chrzonszczewsky). PANCREAS AND LIVER,. 
155 
Years ago, Andrejevic had already correctly asserted that 
the blood and biliary capillaries never touched each other, 
but rather that the body of a hepatic cell always lies between 
them as a separating structure. 
The livers of the amphibia and reptiles, and even of birds, 
show this most distinctly. Nevertheless, the more compli- 
cated relations of the mam- 
malial liver yield the same 
result (Fig. 145), although 
with more trouble, to the 
attentive observer. We 
see the blood-vessels (a) 
in part transversely, in 
part longitudinally. The 
biliary capillaries {c) are 
in repeated contact with 
the hepatic cells {&); but 
portions of the cell body always remain as intervening parts 
between these and the capillary vessels of the passage. 
Our figure teaches, furthermore, 'that biliary capillaries 
occur only at the contiguous surfaces of two cells. We shall, 
therefore, have to regard the extremely thin walls of the 
capillaries as the product of adjacent cells which has become 
hardened. 
fig. 145.—Finest biliary passages of the rabbit’s 
liver; a, blood-vessels; b, hepatic cells; c, biliary 
capillaries, 
The lymphatics run in the capsule of Glisson in the same 
manner as the portal vein, hepatic artery, and biliary ducts. 
Having entered the lobule, they invest the capillary blood- 
vessels (MacGillavry, Frey, Biesiadecky and Asp). The deli- 
cate external wall of these “ perivascular ” lymph passages is 
without doubt the thin membrana propria of the hepatic cell 
trabeculae. 
These canals also show between the lobules a membrana 
propria covered with low cylinder cells. Later, the walls 
become connective tissue, the cells are higher and have a 
seam which is permeated by porous canals (p. 8). 
Let us, finally, look after the efferent biliary canals. 
In the largest canals passing out from the hepatic paren- FOURTEENTH LECTURE. 
chyma, there is an external fibrous membrane and an internal 
mucous membrane. In the gall bladder there are, in addition, 
smooth muscular fibres. 
The largest biliary canals have numerous excavations 
(probably reservoirs for bile), as well as racemose glandules. FIFTEENTH LECTURE 
THE LUNGS. 
The lungs originate in the same manner as the racemose 
glands, but acquire an essentially different texture. Their 
efferent canal system requires an especial preliminary dis- 
cussion, on account of its peculiarity and complication. 
The cartilages of the larynx are hyaline, as the thyroid and 
cricoid cartilages. In certain parts of the arytenoid cartilages 
there is an elastic metamorphosis. The Wrisbergian and 
Santorinian cartilages, with the epiglottis, are pure reticular 
cartilage. The triticeaen cartilages are formed of hyaline or 
connective-tissue cartilaginous substance. The ligaments of 
the larynx present a considerable wealth of elastic tissue. 
The lower true vocal cords are purely elastic. The muscles 
are transversely striated. The mucous membrane, rather 
compact and likewise not poor in elastic elements, shows 
embedments of lymphoid cells. It contains racemose, true 
mucous glands. 
. Strongly stratified pavement epithelium covers the anterior 
surface of the epiglottis ; there are not so many layers in that 
covering the posterior surface as far as the base; the same is 
also true of the lower vocal cords. Otherwise, we meet with 
slightly stratified ciliated epithelium, which descends far down 
into the lungs. 
The wind-pipe or trachea, with its system of branches, the 
bronchi, presents a fibrous tube, in the anterior wall of which 
are embedded half rings of hyaline cartilage (annuli carti- 
laginei). A deeper layer of transverse smooth muscles con- 
nects the terminal portions of the half rings posteriorly. In 
the mucous membrane we again meet with numerous mucous 
glandules. 158 
FIFTEENTH LECTURE. 
In the lungs themselves the bronchi divide dichotomously 
again and again, and thus become finer and finer passages. 
The cartilaginous half rings disappear, simple lamellae appear- 
ing in their place. Their last remains are still seen in canals 
of 0.23 mm. The thin parietes have a simple ciliated epithe- 
lium of 0.0135 nim. in height. Mucous glandules continue 
far down, as also do the smooth muscles, which form regular 
rings round the bronchial ramifi- 
cations, and possibly till near the 
so-called pulmonary vesicles. 
At the end of the terminal bron- 
chial branches (Fig. 146, a) we 
now arrive at the true respiratory 
portion of our organ. 
We have, first, thin-walled (0.4 
to 0.2 mm. wide) canaliculi, the 
alveolar passages (Schulze). 
Their acute-angled ramifications 
(c) are familiar. Communicating 
with them laterally and also terminally are short, conical hol- 
low structures (b), the primary pulmonary lobules or, as they 
are commonly called, the infundibula. 
Fig. 146.—A portion of the lung of an 
ape (cercoj>ithecus\ injected with quick- 
silver ; a, end of a bronchial twig; c, al- 
veolar canal; b, infundibula. 
As the gland lobule consists of the gland saccules or acini, 
so does the just mentioned infundibulum consist of similar 
structures, the pulmonary vesicles, pulmonary cells or alveoli. 
They are less isolated from each other, however, and to a 
certain extent present more diverticulations of their walls, 
which meet in common cavities. At a later period, indeed, 
there is not unfrequently an absorption of individual portions 
of the walls. Such expansions of the wall of the alveolar 
passage into pulmonary vesicles (c) are met with every- 
where. 
On making a section through the lung tissue, we meet 
with the alveoli in the form of rounded and oval spaces (Fig. 
147, b, b). Their diameter varies from 0.1128 to 0.3760 mm., 
and increases with the age. 
The hermetic enclosure of the respiratory organs in the THE LUNGS. 
thoracic cavity compels the pulmonary alveoli to maintain a 
certain expansion permanently. In consequence of their 
great distensibility, the lungs follow the expansion of the 
thorax. By means of their elastic power, and assisted by 
the muscles of their canals, they contract at each expiration, 
Fig. 147.—Transverse section througn the pulmonary substance of a child of nine months. A 
number of pulmonary cells, b, surrounded by the elastic fibrous net-work, which bound them in a 
trabecula-like manner, and, with the thin structureless membrane, forming their walls [a) ; d, por- 
tions of the capillary net-work with their vessels curved in a tendril-like manner, projecting into 
the cavities of the pulmonary cells ; c, remains of the epithelium. 
as far as the thoracic walls permit. It is only when the tho- 
racic cavity is opened that the lungs with their alveoli com- 
pletely collapse. 
The parietes of the pulmonary vesicles, a continuation of the 
terminal canal system, is a very thin connective-tissue mem- 
brane. It is surrounded by elastic fibres, finer and coarser, 
sometimes single, sometimes aggregated in groups. The latter 
are met with in the interalveolar septa. The fundus of the 
pulmonary alveolus shows only the finest elements, measur- 
ing 0.0011 mm., in part more isolated, in part connected in a 
reticular manner. FIFTEENTH LECTURE. 
The primary pulmonary lobules of the new-born—later the 
nature of the arrangement becomes more indistinct—united 
by connective-tissue intermediate substance, form larger or 
secondary lobules. The latter appear on the surface of the 
organ in the human adult as arese. measuring I to 2 mm. and 
•more, demarcated by a black substance, and often appearing 
quite distinct. They form, at last, the large lobes. Their 
delineation belongs to descriptive anatomy. 
We have just mentioned the black substance in the inter- 
lobular connective tissue ; it may occur between and in the 
walls of the pulmonary vesicles, and even in the bodies of 
their epithelial cells, as we shall mention hereafter. This is 
the so-called black lung pigment. 
We have just used the epithet “so-called.” In fact these 
substances are not melanine, the complicated, dark ferrugi- 
nous coloring matter of the organism. They have rather an 
extraneous origin ; they are carbon, breathed in in a finely 
divided condition, which is induced by our artificial life in 
enclosed places. 
Mammals living wild show nothing of this, but it is seen 
in their kin when domesticated by man. In human beings 
constantly surrounded by smoke and soot, or in laborers in 
coal mines, the lungs may at last become quite black. If we 
shut a dog up in a place in which there is a constant genera- 
tion of soot, a similar change of the respiratory organs takes 
place with relative rapidity. 
In a condition of the finest division, these particles of car- 
bon penetrate the epithelial cells, and from them enter the 
pulmonary tissue. A great portion of them here become 
permanently quiet. Others enter the lymphatics, and pass 
from these into the lymphoid bronchial glands. They also 
become fixed in the latter organs. This is the so-called mela- 
nosis of these structures. 
By the continual division of the pulmonary artery, there 
arises a system of fine blood-vessels, which encircle the in- 
dividual pulmonary vesicles, and frequently combine into 
Let us now examine the vascular arrangement. THE LUNGS. 
161 
incomplete or more complete rings (Fig. 148, a). From them 
arises an uncommonly close capillary net-work of tubes 
0.0056 to 0.0113 mm. wide, 
which are scarcely separated 
from the atmospheric air by the 
thin membrane of the alveolar 
walls (h). The respiratory in- 
terchange of gases takes place 
here. These capillaries appear 
elongated when the lung vesi- 
cles are strongly expanded. 
When less expanded they pro- 
ject, in a tendril-like manner, 
into the cavity, reminding us 
of a relative condition in the 
muscles. The pulmonary veins 
commence with small branches in the interalveolar septa. 
Gradually combining into larger trunks, they accompany the 
ramifications of the bronchia and the divisions of the pulmo- 
nary arteries. 
Fig. 148.—A pulmonary alveolus of the calf; 
a, larger blood-vessels, which run in the alve- 
olar septa ; b, capillary net-work ; c, epithe- 
lial cells. 
The bronchial arteries are regarded as the nutritive vessels 
of the respiratory organ, but there is no very sharp demar- 
cation between them and the respiratory pulmonary arteries. 
The former supply the walls of the larger blood-vessels, the 
adjacent lymphatic glands, the connective tissue between the 
pulmonary lobules and beneath the pleura. Finally, they 
form the capillary net-works of the various parietal layers of 
the efferent bronchial system ; but the most superficial net- 
work of the mucous membrane arises, in a peculiar manner, 
from the respiratory system of vessels. 
The bronchial veins appear to be quite peculiar. They are 
conjectured to be only the reflux vessels of the arterial 
branches from the larger bronchial ramifications, from the 
lymphatic glands and from the pleura nearest the hilus of the 
lungs. The venous roots from the walls of the finer bronchi 
pass, on the contrary, into the respiratory pulmonary veins. 
The lungs are rich in lymphatics, beneath the pleura as well FIFTEENTH LECTURE. 
as in the bronchial system. Lymphatic lacuni also occur in 
the pulmonary vesicles, and their efferent vessels subsequently 
invest the blood-vessels (Wywodzoff). 
We have, finally, to mention the epithelial lining of the 
alveoli. This has occasioned much discussion. In the mam- 
malial and human embryo there is a continuous covering of 
flat, protoplasmatic, nucleated cells. A change occurs after 
birth, however, with the commencement of aerial respiration. 
Fig. 149.—The epithelium from the basis portion of an infundibulum, situated just 
beneath the pleura of the developed cat; treated with nitrate of silver. 
Only a small contingent of our cells now retain their old 
characteristics (Fig. 149)- The epithelial element, over the 
incurvations of the pulmonary vessels, and over all the other 
prominences, has become a much more considerable proto- 
plasmless and non-nucleated scale. SIXTEENTH LECTURE. 
THE KIDNEY, WITH THE URINARY PASSAGES. 
The structure of the mammalial kidney is extremely com- 
plicated. This bean-shaped organ is covered by a not very 
thick, but resistent, connective-tissue envelope. The blood- 
vessels and lymphatics pass in and out at the hilus, and the 
efferent canal, the ureter, also has its exit at this point. 
The kidney (Fig. 150), consists of two 
different layers, a cortical, and a medul- 
lary substance. The former (above, f), 
appears to the naked eye dark and homo- 
geneous ; the latter (a, b), paler, displays 
a radiated fibrous arrangement. In most 
mammals it projects in a single point into 
the pelvis of the kidney (a). In man the 
medullary substance is divided into a num- 
ber of conical portions, with their bases 
turned towards the cortex and their points 
towards the hilus. 
These are the Malpighian or medullary 
pyramids. The columnse Bertini are de- 
pressions of the cortical substance between 
the latter portions of these cones. 
The cortex and medulla are, further- 
more, permeated by a connective-tissue 
frame-work. 
Fig. 150.—Diagram of 
the mammalial kidney; 
a, papilla; b, straight 
uriniferous canals of the 
medulla; c, so-called 
medullary rays of the 
cortex ; ii, outermost 
cortical layer ; e, cortical 
pyramids, with the arte- 
ries connected with the 
glomeruli; f, border 
layer. 
The elements of the cortex, as well as 
of the medulla, are long, glandular tubes, 
the so-called uriniferous canals or Bellinian 
tubes. 
In the medulla they divide frequently, 
and run in a radial direction {b). They continue through the 164 
SIXTEENTH LECTURE. 
cortex from point to point, in the form of straight bundles (c). 
They are here called medullary rays. Between them, al- 
though incompletely demarcated, remain considerable portions 
of the cortical substance (e), comparable to a truncated pyra- 
mid. These are the so-called cortical 
pyramids. In them run the glandular 
tubules, with the most manifold turnings, 
which finally encompass, with their knob- 
like dilatations, the Malpighian vascular 
coil or glomerulus (Fig. 96). The latter 
structures occur in this portion of the 
organ only. 
Let us now commence the discussion 
of the particulars with the most internal 
division, with the apices of the medul- 
lary pyramids, the renal papillae. Here, 
alone, in the form of 10 to 15 apertures, 
the efferent canal-work of this organ, 
which is so complicated in its structure, 
opens as a system of short canals (Fig. 
151, ci:). Very soon afterwards they 
break up, by acute-angled ramifications, 
into branches of the first and second 
order [b, c), and this is repeated several 
times more. The whole thus acquires a 
brush-like appearance. The canals be-, 
come narrowed, in consequence of this 
continual subdivision, from 0.3 and 0.2 
to 0.05 mm. About 4 to 5 mm. from 
the apex of the papilla the process of 
division ceases, however; the straight 
canals now maintain their diameter un- 
changed for a long distance. 
Fig. 151.—Vertical section 
through the medullary pyra- 
mids of the pig’s kidney (semi- 
diagraraatic); a, trunk of a 
uriniferous canal, opening at 
the apex of the pyramid ; b 
and c, its system of-branches ; 
d, loop-shaped uriniferous ca- 
nals ; (?, vascular loop, andy 
ramification of the vasa recta. 
between mem—ana mis was dis- 
covered by Henle—occurs an additional 
system of much finer loop-shaped canals {d). In order to 
facilitate a further insight, let us give to that particular part THE KIDNEY AND URINARY PASSAGES. 
165 
of the tube which descends from the convoluted cortical por- 
tion, and the side of the loop which passes off from this, the 
name of the descending, and that portion which returns 
towards the surface of the organ the name of the ascending 
side. The former usually has the least, and the latter the 
greatest diameter. The number of the looped canals in- 
creases in proportion as we examine the cortical layer further 
upwards towards the medullary layer. 
The terminal trunk of the efferent canal-work .is invested 
by the connective-tissue frame-work of the papillary apices, 
and is without a merabrana propria. The latter gradually 
makes its appearance at the system of branches, and is more 
distinct as well as more compact at the looped canals. Low 
cylinder cells of 0.03 to 0.02 
mm. border the transverse 
section of the efferent canal 
system (Fig. 152,#). In the 
further system of branches 
the lining cells are still lower 
(down to 0.016 mm.) 
Let us now, for an instant, 
leave the efferent apparatus 
and examine the secretory 
portion of the kidney. 
Fig. 152.—Transverse section through a re- 
nal pyramid of the new-born child ; a, collec- 
tive tubes with cylindrical epithelium; b, de- 
scending side of the looped canal with flat 
cells ; c, returning side of the loop with granu- 
lar cells ; d, transverse sections of vessels ; e, 
connective-tissue frame-work substance. 
We will now turn to the 
cortical layer of our organ 
and, first of all, examine more 
closely the so-called cortical 
pyramids (Fig. ln their axis is seen a branch of the 
renal artery, to which the glomeruli are attached by lateral 
branches, like the berries on the stem of the grape (Fig. 
150, e\ Fig. 155). 
A cortical pyramid, however—we repeat what was pre- 
viously said—consists, for the rest, entirely of convoluted 
uriniferous canals. They take their origin with a balloon- 
shaped portion which surrounds the glomerules, as a bag does 
a sponge. This is the Muller’s or Bowman’s capsule. Its con- 166 
SIXTEENTH LECTURE. 
tracted transition into the uriniferous canals (the so-called 
neck) was discovered at a relatively recent period. 
Only the most external cortical portion of our organ (Hyrtl 
named it the cortex corticis) is without this peculiar vascular 
coil (Fig. ISO, d] Fig. 155, d). 
The inner surface of this capsule has a lining of large, flat, 
endothelial cells. 
The external surface of the glomerulus presents an invest- 
ment of smaller cells which are not so flat. I found them 
thus, formerly. According to Heidenhain, however, the lat- 
ter elements are likewise quite flat. 
In the convoluted uriniferous canals we meet with a clouded, 
granular, cubical epithelium, and the lumen is quite narrow. 
Following this'glandular tubule downwards, we find it as- 
suming a straight and direct course. At first it still remains 
wide, and the gland cells are 
unchanged. Then, having en- 
tered the medullary substance, 
it diminishes in width, exceed- 
ingly, and now becomes the 
narrow descending side ol 
Henle’s looped canal. A re- 
markable transformation of the 
epithelial lining has taken 
place at the same time ; quite 
thin, flat scales, appearing like 
vascular endothelium, now 
line the canal (Fig. 152, b.) 
Fig. 153.—From the kidney of the pig (semi- 
diagramatic) ; a, arterial branch ; b, afferent 
vessels of the glomerulus, c ; d, vas efferens ; 
e, breaking up of the same into the straight 
capillary plexus of the medullary ray ; f, 
rounded plexus of the convoluted canals ; i, g, 
commencement of the venous branch. 
Following the loop further, 
we arrive at the ascending 
wider side. Its epithelium is 
again the old, clouded, glandular variety of the convoluted 
uriniferous canals, as we must maintain in contradistinction 
to Ludwig. 
The returning side finally passes over in the cortex—some- 
times deeper, sometimes quite near the surface—into an 
expanded, gut-like convoluted structure, the so-called “inter- THE KIDNEY AND URINARY PASSAGES. 
167 
calary pie'ce.” Several of these intercalary pieces open into 
a collective tube, and the latter combine into larger canals. 
We have thus presented the whole connection of the kidney. 
Heidenhain has quite 
recently made an interest- 
ing discovery concerning 
the epithelium of the con- 
voluted uriniferous canals, 
of the returning side of 
the loop, and of the inter- 
calary piece. Its proto- 
plasm is in great part 
metamorphosed into a con- 
siderable number of very 
fine cylinders or rods. 
Around the nucleus, 
which these “rod cells” 
invest, as well as between 
the rods, there remains a 
residue of unchanged pro- 
toplasm. These rods, with 
which the gland cells rest 
on the membrana, give the 
transverse section of these 
uriniferous canals a radio- 
striated appearance. 
The medullary rays pene- 
trate the cortex, like groups 
of pegs driven close to- 
gether into a board. They 
consist of two different 
elements. In the first 
place we have the cortical branches of the efferent canal-work 
of the medullary substance pushing forwards to near the sur- 
face of the kidney ; these are accompanied by the upper 
portions of the ascending looped canals, which have a smaller 
diameter. 
Fig. 154.—Diagram of the uriniferous canals in a 
vertical section of the kidney; 7?, cortex: Af, 
medulla ; *, border ; a, efferent canal-work, with the 
system of branches b; c. transition canal (or inter- 
calary piece Vin the ascending or returning side' d\ 
e, descending; convoluted uriniferous canal of 
the cortex; g, capsule with the glomerulus. 168 
SIXTEENTH LECTURE. 
I cannot presume that the highly complicated structure ol 
the mammalial and human kidney is hereby rendered appre- 
ciable to every one ; let us, therefore, make a brief repeti- 
tion. From the glomerulus (Fig. 154, g) and convoluted 
cortical canals (f) the secretion reaches the descending (nar- 
rower) side (e), and from this into the ascending (d). From 
the latter, the secretion passes through the intercalary piece 
(c) into the efferent canal system (b and a). Our urine, there- 
fore, passes through this long course. 
The frame-work substance consists, in the cortex, of a 
scanty scaffolding of a connected, undeveloped connective 
tissue. The latter is somewhat thicker in the medullary sub- 
stance, especially below (Fig. 152, e). Cells are not wanting. 
We have the blood-vessels and lymphatics still remaining. 
The arrangement of the former vessels (Fig. 155) is the 
most complicated, and, therefore, certain differences of opinion 
still prevail in regard to it. 
Jn man the arterial and venous branches enter at the hilus 
and pass into the interior, becoming more and more ramified. 
After giving off branches to the capsule, they perforate the 
latter external to the calyx of the kidney, an arterial branch 
being accompanied, as a rule, by a venous branch. They 
thus pass between the medullary pyramids to the bases of 
the latter {a, h). They here assume an arched arrangement, 
which is less complete in the arteries than in the veins. 
From the arteries now arise the coil-bearing branches (b), 
which, keeping in the axis of the cortical pyramids, continue 
as far as the surface, and give off laterally the vasa afferentia 
of the glomeruli (<r). In the lower animals, such as the frog 
and the adder, the latter forms a single coil-shaped convolu- 
tion. In man and the mammalia (Fig. 196), on the contrary, 
we meet within the latter with the already mentioned (p. 98) 
acute-angled divisions, which subsequently unite into the sin- 
gle vas efferens. 
This (Fig. 153, d\ Fig. 155) is now resolved in a peculiar 
manner into a capillary net-work (Key), forming at first an 
elongated reticulum in the medullary rays (Fig. 153, Fig. THE KIDNEY AND URINARY PASSAGES. 
isS,e). Fromtheperiphery 
of the latter a rounded net- 
work of somewhat wider 
vessels extends to the con- 
voluted uriniferous canals 
of the cortical pyramids 
(Fig- 153,/; Fig. 155,/)- 
The most external cor- 
tical layer, Hyrtl’s cortex 
corticis, receives its blood 
from the efferent vessels 
of the uppermost glome- 
ruli and the terminal 
branches of the coil-bear- 
ing arteries (Fig. 155, d). 
Let us pass to the veins 
of the cortex. Stellate 
venous rootlets, the so- 
called stellulae Verheyenii 
(e), appear quite superfi- 
cially. Connected with 
these stars, there is then 
formed in the cortical 
pyramids a long venous 
trunk {h), which lies in 
close apposition to the 
coil-bearing artery. Into 
its regular lateral branches 
open the rounded capil- 
lary net-work of the cor- 
tical pyramids. The vein, 
itself, sinks at the margin 
between the cortex and 
medulla, into the venous 
arched vessel which we 
mentioned above. 
Fig. 155.—'The vascular arrangement of the kidney in 
vertical section; arterial branch at the margin between 
cortex and medulla ; b. coil-bearing artery; c. vasa 
afferentla of the glomeruli; capillary reticulum of the 
external cortical layer ; e, vein of this part \p, elongated 
capillary net-work of the medullary rays; S', rounded 
net-work around the convoluted uriniferous canals of the 
cortical pyramids ; h, venous branch of the cortex ; z, 
efferent vessels of the deepest glomeruli; k, their capil- 
ar>' net-work; I, venous tubes of the medulla: nt, 
capillary net-work of the papilla. 
Thus far all is settled. 170 
SIXTEENTH LECTURE. 
A variety of views prevail, however, concerning the vascular 
relations of the medulla. Elongated vascular tufts, which 
appear in the upper portion of the medullary substance, the 
so-called boundary layer (Fig. 150,/), are called vasa recta 
(Fig. 151, f\ 155, k and I). They pass, sometimes further 
upwards, sometimes further downwards, in a looped or 
noose-like manner, into each other, and may be mistaken 
for the looped canals of the urinary passages (Fig. e). 
Our vasa recta then form an elegant net-work (Fig. 155, m) 
around the apertures of the uriniferous canals at the apex of 
the medullary pyramids. 
These vasa recta have frequently, if not predominantly, a 
venous character (/); they are continuations of the capillary 
net-work of the cortical pyramids. 
Then—and we regard this source of supply as the more 
important—the medullary vessels arise from the breaking 
up of the vasa efferentia of the deepest glomeruli (Fig. 
155, *)• 
Quite isolated arterial branches, which have left the coil- 
bearing arteries before the giving off of the glomerulus 
branches, are, according to our views, of little consequence, 
though many investigators have considered these so-called 
arteriolae rectae to be of great importance. 
The combination of the vasa recta into venous roots (/) 
presents a similar condition. They frequently have a tuft- 
like character. Their affluent tubes are the returning sides 
of the looped vessels and the effluent canals of the papillary 
apices. These venous roots empty in part into the lower 
terminal portion of the cortical veins, in part into the arched 
communications at the margin between the cortex and the 
medulla. 
We are familiar with the lymphatics of the dog’s kidney 
(Ludwig and Zawarykin). They occupy the interstices of a 
connective tissue full of clefts, which is situated beneath the 
capsule, and from here are in communication with the capsu- 
lar passages, and then form in the cortical pyramids finer, 
deeper canals between the uriniferous canals, capsules of the THE KIDNEY AND URINARY PASSAGES. 
glomeruli and blood-vessels. Later, in making the injection, 
the narrower passages of the medullary rays become filled, and 
at last the lymphatics of the medullary substance itself. The 
whole reminds us of the arrangement in the testicle (see be- 
low). True lymphatics with valves first appear, however, at 
the hilus. 
The question now arises, which of the two systems of ves- 
sels, that of the glomerulus or the net-work circumvoluting 
the uriniferous canals, secretes the urine ? This role has been 
assigned to the glomerulus, and only the signification of an 
absorbing arrangement ascribed to the capillary net-work of 
the uriniferous canals (Ludwig). According to another view 
(Bowman), however, the glomeruli secrete the water chiefly, 
and the cells of the uriniferous canals, as true gland cells, fur- 
nish the characteristic solid constituents of the urine, which 
are washed out by the water flowing past. A new, and as I 
can say correct, observation of Heidenhain’s is of signifi- 
cance for this theory of Bowman’s. Indigo sulphate of soda 
injected into the veins of a living mammal is not excreted by 
the glomeruli, but through the convoluted glandular canals 
of the cortical pyramids. 
Let us finally take a hasty glance at the passages which 
convey away the urine. 
The calices and pelvis of the kidney present a connective- 
tissue outer layer, a middle layer of crossed smooth muscles 
(especially in the pelvis of the kidney), then a mucous mem- 
brane with the pavement epithelium mentioned at p. 30. 
Mucous glands may also occur. 
The muscular coating is thicker in the ureter. An external 
layer shows longitudinal, and an inner layer transverse fibres. 
Further downwards, a third, innermost, longitudinal layer is 
added. The urinary bladder has a relative structure. The 
muscular layer, considerably thickened, consists of oblique 
and transverse reticularly connected bundles of fibres. The 
sphincter vesicae appears at the neck of the bladder as a 
thicker annular layer. The longitudinal layers of the detru- 
sor urinse run over the vertex and anterior wall of the organ. SIXTEENTH LECTURE. 
The mucous membrane and epithelium remain the same. 
Simple mucous glandules are likewise met with. 
The female urinary canal, the urethra, presents a longitu- 
dinally folded mucous membrane with papillae. The mucous 
membrane is very vascular, and has numerous mucous gland- 
ules, the largest of which bear the name of Littre’s glands. 
A strongly developed muscular layer consists of longitudi- 
nally and transversely arranged fibres. The epithelium is of 
the stratified flattened variety. SEVENTEENTH LECTURE. 
THE FEMALE GENERATIVE GLANDS.—THE OVARY WITH 
THE EFFERENT APPARATUS. 
The ovary, a peculiarly constructed organ, forms the most 
important portion of the female sexual apparatus. It has a 
flattened oval, occasionally bean-shaped form, and therefore 
has a hilus through which considerable blood-vessels and 
lymphatics enter and leave the organ. 
We may distinguish in the ovary a sort of medullary sub- 
stance, that is, a connective tissue, uncommonly vascular sub- 
stance or the vascular zone of Waldeyer; and then an invest- 
ing glandular layer, the parenchyma zone. 
The medullary substance begins at the hilus. Its large 
vascular canals remind us of the later-to-be-mentioned cav- 
ernous tissue of the urinary and sexual passages. It radi- 
ates outwards into a frame-work permeating the glandular 
cortical layer. At the surface of the organ the frame-work 
reunites into a more solid continuous substance (Fig. 156, b). 
The entire ovary is covered by a simple layer of low cylin- 
drical cells {a). This was formerly erroneously called a serous 
membrane, but now bears the name of the germinal epithe- 
lium, a designation the correctness of which we shall learn 
later. 
We have next to describe the glandular constituents of the 
ovary, which are by far the most important. 
Beneath the firmer connective-tissue border layer we meet 
with an almost non-vascular layer of youngest ovules, the 
cortical or primordial follicle zone (Fig. 156, c). 
We here discover the young ova, already represented in 
Fig. 5. They are small globular elements (0.0587 mm. large), 
with an elegant globular and vesicular nucleus (0.0226 mm.), 174 
SE VENTEENTH LECTURE. 
The cell body is constituted by a membraneless protoplasma 
containing fat granules. Each of these ovules is surrounded 
by a corona of small nucleated cells. The whole is finally 
enveloped in connective tissue. These are the so-called pri- 
mordial follicles which, often occurring quite crowded here, 
present an enormous excess of egg-germs. 
Other primordial follicles (Fig. 5, 2) become larger'; the 
ovule, which has meanwhile also increased somewhat in size, 
appears to be surrounded by a thicker hyaline rind. The 
small investing cells now form a double row (a). 
In the further development, however, both the cell layers 
Fig. 156.—Ovary of the rabbit; a, germinal epithelium (serosa) : b, cortical or external fibrous 
layer ; c, youngest follicles ; d, a somewhat more developed older one. 
are separated from each other ; there is thus formed a smaller 
cavity (Fig. 156, d) filled with a clear albuminous fluid. 
In the growing follicle, this cavity becomes larger and 
larger. The small cells increase and gradually form a strati- 
fied epithelium. The ovum lies at one point crowded against 
the wall, and surrounded and held by a heap of these cells. 
A developed vascular net-work has, in the meanwhile, also 
been formed in the follicular walls. THE FEMALE GENERATIVE APPARATUS. 
175 
The normal ovarium contains besides a small number of 
ripest gland capsules (12 to 20). These are the Graafian fol- 
licles (Fig. 157), discovered long ago by De Graaf. Their size 
is determined, in a measure, by the dimensions of the mam- 
malial ovum. In women they finally attain to 6to 9 mm. 
Fig. 157.—Mature follicle; a, ovum.; epithelial stratum covering the same, h, and lining the 
cavity, c; d, connective-tissue Wall; e, outer surface of the follicle. 
The parietes consist of a double layer, an inner one with a 
close capillary net-work, and an outer one with the ramifica- 
tion of the larger blood-vessels. The wall itself {e, d) is unde- 
veloped connective tissue. We here again meet with the 
granular connective-tissue cells mentioned at page 54. They 
may surround the vessel like a mantle. The small epithelial 
cells of the follicles measure 0.0074 to 0.0113 mm. {c). 
At one point, mostly at the bottom of the follicle (Schrdn, 
His), but occasionally also at the surface that is turned to- 
wards the germinal epithelium (Waldeyer), we meet with the 
mature ovum (a) surrounded by a thicker epithelial stratifica- 
tion (b). 
In the mammalial animal it remains uncommonly small, 0.2 
to 0.3 mm. in diameter. This explains why its discovery was 176 
SEVENTEENTH LECTURE. 
first made in 1827, by an investigator of great merit, K. E. 
von Baer. It appears scarcely conceivable to us ; for a sharp 
eye sees the ovule, removed from the ruptured follicle, as a 
white point, without a magnifying glass. The successor, 
however, stands on the shoulders of the predecessor. 
Let us tarry for an instant at this most important of all 
cells (Fig. 158), without which there would be no higher ani- 
mal world. Let us remove from 
its surface the cells, which have 
now become cylindrical, of the 
epithelial investment, and our at- 
tention will be first of all attracted 
by the thick (0.009 to O.Oi 13 mm.), 
resistant hyaline capsule, the so- 
called zona pellucida or chorion (a). 
It is an inwardly deposited pro- 
duct of the surrounding smaller 
Fig. 158.—Mature ovum of the rabbit; 
zona pellucida : b, yolk; c, germinal 
vesicle; d, germinal spot. 
cells, and, seen with higher magnifying powers, is permeated 
by the finest radial passages, the so called porous canals. 
The cell-body is a thick, fluid, more or less cloudy mass. 
We perceive in it granules of albuminous matter, as well as 
small drops of fat. In many mamrnalial animals, the quanti- 
ty of the latter may become great, and the substance darker 
and darker. This cell body is call the yolk or vitellus. 
The cell nucleus (c) attracts our attention by its elegant 
globular form, bordered by the finest lines. It now lies con- 
centrically; its diameter is 0.0377 to 0.0451 mm. It has 
received the name of the germinal, or Purkinje’s vesicle. 
In it, and almost always single, we finally notice the nu- 
cleolus (d), a fat-like, glistening granule 0.0046 to 0.0068 
mm. in size. It bears the name of the germinal, or Wagner’s 
spot, the macula germinativa.* 
* We have just become familiar with quite ordinary things provided with special 
names. This nomenclature originated in a former epoch of embryology. Further- 
more, the follicular walls are called theca; their epithelial lining has been denomi- 
nated the formatio or membrana granulosa, and the cellular substance surrounding 
the ovum the cumulus proligerus. THE FEMALE GENERA LIVE APPARA TVS. 
177 
The blood-vessels of the ovary pass, as we mentioned above, 
from the hilus into the medullary substance. They at once 
acquire such a development that the connective tissue forms 
a relatively scanty connecting substance. The outer surfaces 
of the veins coalesce with the latter tissue. The spindle cells 
of the connective tissue must be muscular, for the ovary is 
contractile (His, Frey). From the medulla numerous and 
elegant vascular expansions pass between the follicles of the 
cortex, circumvoluting them with the already described net- 
work. The cortical zone, alone, is very poor in blood-vessels, 
as we already know. 
A considerable wealth of lymphatics is also met with in the 
medullary substance. A net-work of the same also circum- 
volutes the follicles. 
The parovarium represents the remains of the embryonic 
primitive kidney or the Wolffian body. It consists of con- 
nective-tissue passages, lined with ciliated cells. 
The ovary also originated from this primitive kidney, and 
the permanent ordinary kidney from the efferent canal of the 
Fig. 159.—The ovary of a human foetus of 32 weeks, in perpendicular section : a, germinal epi- 
thelium ; b, youngest ova cells (primordial ova) lying in this ; c, a growing connective-tissue trabe- 
cula ;d, epithelial cells becoming buried ;e, youngest follicles ; ovum—and germinal epithelial 
cells in groups : g, lymphoid cells. 
latter gland. Unfortunately, we cannot enter further into this 
subject. We merely mention that, according to Waldeyer, 
in the embryonic chicken, at an early period, at the inner side SEVENTEENTH LECTURE. 
of the primitive kidney, an epithelial thickening appears, into 
which the connective tissue of this organ sprouts in a hill-like 
form. The latter becomes the frame-work substance ; from 
the former originate the germinative epithelium, the epithelial 
cells of the Graafian follicle, and, as the favored daughters of 
the latter, the ova. 
This section of the development is represented by our Fig. 
159, a copy from Waldeyer’s excellent monograph. The first 
embryonic ovula, the “primitive ova,” are, therefore, of epi- 
thelial origin. 
Pfliiger had, even before Waldeyer, acquired interesting 
conclusions concerning the ovaries of the creature after birth. 
From time to time, soon after birth, and then towards the 
period of parturition, in the adult mammalial animal, the 
old embryonic affinity reasserts 
itself. The germinal epithelium 
again proliferates downwards 
in a conical form, and is at last 
separated from the point of 
origin. Thus arise irregular, 
occasionally cord-like, and cy- 
lindrical masses. These are 
Pfliiger’s follicular chains. I 
have called them the egg strands 
(Fig. 160). In their axis we 
meet with certain of the epithe- 
lial cells which have grown to 
be ova. By constriction (2, a), 
new Graafian vesicles are 
formed. 
What becomes of the follicles 
of the ovary ? 
Before sexual maturity they 
appear to be frequently de- 
stroyed by fatty degeneration 
and also by colloid metamor- 
phosis (Slavjansky, Frey). During the period of propagation, 
Fig. 160.—Follicular chains from the ovary 
of the calf; i, with ova forming; 2 at a, 
showing constriction into Graafian vesicles. THE FEMALE GENERATIVE APPARATUS. 
179 
also, a similar destruction takes place in a portion of the 
follicles. 
Others, on the contrary, meet with a different fate. The 
ripest follicles, which have reached the surface of the ovary, 
become ruptured, naturally at the place of the least resist- 
ance, and, therefore, towards the surface. The follicular fluid 
with the ovule leaves the organ through the ruptured outlet. 
The ruptured follicle is transformed into the so-called cor- 
pus luteum, that is-—to express ourselves more intelligibly 
—it returns, at last, by a complicated process of cicatriza- 
tion, to a connective-tissue frame-work substance, leaving no 
trace. 
In the human female, the follicle normally ruptures at the 
menstrual period ; in mammalial animals at the period of 
rutting. 
The ovule, liberated from the ovary and received into the 
oviduct, there undergoes the familiar segmentation of the en- 
capsulated cell (p. 15). Without impregnation, however, this 
multiplying action is soon paralyzed. If the former takes 
place, the old life is merrily and energetically continued. The 
encapsulated ovum at last becomes an aggregation of numer- 
ous small cells. From these living building stones is con- 
structed the new animal body, somewhat as the architect 
builds his house with stones. But the latter, the lifeless ones, 
are brought from all directions, the former are the primitive 
offspring of a single cell, members of a living family. It is the 
difference between the living and the lifeless. 
The oviducts, Fallopian tubes, have, beneath the serous 
covering, longitudinal and transversely arranged smooth 
muscles. The mucous membrane is glandless,* and projects 
in a highly developed system of papillae and folds. The in- 
ner surface is covered by ciliated epithelium. 
During menstruation and pregnancy the womb or uterus 
undergoes extremely important anatomical transformations. 
There is scarcely any organ, except the ovary, perhaps, on 
* All attempts to discover nerves here have, thus far, been unsuccessful. 180 
SEVENTEENTH LECTURE. 
which is so thoroughly impressed the stamp of a proliferating 
formative life as the uterus. 
Its fleshy substance is formed of longitudinal, transverse 
and oblique muscles. Developed in an annular form, it at 
last constitutes the sphincter uteri. 
The mucous membrane—its tissue reminds one of lymphoid 
connective substance—is lined with ciliated epithelium. Be- 
low, in the neck, commences the stratified flattened epithe- 
lium of the vagina. The surface of the mucous membrane is 
sometimes smooth (fundus and body), sometimes with trans- 
verse folds (upper portion of the cervix), sometimes projecting 
in papillae (terminal portion of the cervix). 
Tubular, frequently spiral uterine glands, which are sub- 
ject to considerable variation, occur in the fundus and body 
of the uterus. They have a lining of ciliated cylinder cells 
(Lott). Our glands disappear below. 
The uterus has a highly developed system of blood-ves- 
sels. The wide veins coalesce with the tissue of the latter, 
and gape in transverse sections. 
The lymphatic apparatus also acquires a gr6at develop- 
ment, especially in the loose connective tissue of the mucous 
membrane, then in the muscular layer, and finally, in the 
subserous layer (Leopold). This is also in beautiful harmony 
with this proliferating formative life. 
The immense enlargement of the pregnant uterus consists 
in the first line, in an increase of the muscular tissue. The 
old mucous membrane is hereby disposed about the ovum as 
a so-called transient membrane, the decidua, while a new 
mucous membrane, destined to be a substitute, is meanwhile 
formed beneath. Still, much is here obscure, and, in certain 
groups of mammalial animals, we meet with great variations. 
In the vagina we find external annular, and internal longi- 
tudinal muscles. The mucous membrane shows numerous 
rugosities and folds, columnae rugarum. It has no glands, 
and is covered by stratified, flattened epithelium. 
The hymen is a vascular duplicature of the mucous mem 
brane. THE FEMALE GENERATIVE A FRA RATE'S. 
181 
The clitoris has a prepuce of mucous membrane tissue ; 
the female glans is also covered by such a membrane with 
numerous papillae. The corpora cavernosa and bulbi vesti- 
buli remind us of the same tissue in the male. 
The labia minora, nymphae, are folds of mucous mem- 
brane, containing no fat, but numerous papillae and sebaceous 
follicles. 
The labia majora are rich in fat, and have internally the 
characteristics of the mucous tissues, externally those of the 
corium. 
In the vestibulum and the ostium vaginae, numerous 
mucous glands occur. The glands of Duverney or Bartho- 
lini are larger organs of this kind. 
The lacteal glands are primarily of similar formation in the 
male and female body; they do not become developed in the 
former, and in the latter only after a prolonged period of 
quiescence, and even then only when pregnancy commences. 
We recognize in the mammary gland an aggregation of in- 
dividual racemose glands, which open into numerous (18, 20 
and more) canals, the so-called “lactiferous ducts.” 
Examined in the earlier period of life, our organ consists 
merely of a ramified canal-work. It is hollow above ; below 
in its knob-like terminal portion, it is completely plugged by 
closely compressed cellular masses. The special gland-vesi- 
cles or acini destined for secreting are still wanting. This is 
the condition, during the days of childhood, of the male and 
female lacteal gland, though the latter gradually advances 
somewhat in its development. 
The entrance of puberty exerts no influence on the male 
organ, but a great one on that of the female. There is here 
a bud-like production of numerous terminal vesicles. As- 
sisted by a development of fat cells, they produce the curved 
elevation of the maturing female breast. In this manner the 
female gland is prepared for a possibly coming activity ; but 
it is only with pregnancy, and towards the end of the same, 
that the lacteal secreting apparatus acquires its complete de 
velopment. 182 
SEVENTEENTH LECTURE. 
Let us now examine the organ at the height of Its activity 
in the body of the nursing woman 
(Fig. 161). 
The gland vesicles, rounded or 
elongated (o. 1128 to 0.1872 mm.), 
are formed by a membrana propria 
with flat stellate cells. They have 
a simple lining of low cylinder cells 
(of 0.0113 mm.). Those finest se- 
cretory canals between the cells, 
which we have already mentioned 
at p. 134, have also been demon- 
strated here by means of injections. 
The excretory canal-work also 
has a cylindrical epithelium. How 
far the fatty secretion of our organ, 
the milk, depends upon the destruc- 
tion of the gland cell, or whether the latter structure does not 
simply express the produced or received fat substance from 
the membraneless, contractile cell-body—are questions which 
require more accurate investigation. 
Fig. 161.—Gland-vesicles of a nurs- 
ing woman, with cells and capillaries. 
In advanced life, the female mammary gland loses its 
secretory apparatus. It becomes reduced to the old canal- 
system of a long passed period of childhood (Langer). 
The colostrum (already mentioned at Fig. 124) contains, in 
addition to albuminous fat vesicles surrounded by a very thin 
envelope, gland cells and cell fragments, 0.0151 to 0.0564 mm. 
in size. The ordinary milk of a later period contains only 
the former elements, the so-called milk globules. The size of 
the latter varies from about 0.0023 to 0.009 mm. EIGHTEENTH LECTURE. 
THE MALE GENERATIVE GLANDS, THE TESTICLES WITH 
THE EFFERENT APPARATUS. 
The seminal gland or testicle represents in the male organ- 
ism that which the ovary does in the female body. We leave 
its coarser structure, for the greater part, to descriptive 
anatomy. 
A firm connective-tissue envelope, called the albuginea, 
invests our organ. Numerous and incomplete septa radiate 
from it into the interior, where they finally unite above into 
a thickened wedge-shaped mass, the corpus Highmori. The 
interior is thereby divided into conical lobules whose apices 
are turned towards the corpus Highmori. 
A testicle-lobule consists of an aggregation of uncommonly 
long convoluted canals or tubes. They present divisions and 
communications, and finally pass over into each other in the 
form of a loop, but never terminate in a cul-de-sac (Mihal- 
kovics). These tubules are called seminiferous canals. 
At the apex of the lobule, the seminiferous canal becomes 
united into a straight excretory duct (tubulus rectus) which, 
passing into the corpus Highmori, unites with others in a 
reticular manner and forms a further tubular system, the rete 
testis. From the latter continue nine to seventeen larger 
canals, the so-called vascula efferentia. They at first pursue 
a direct course, and thus perforate the albuginea; then, 
becoming narrow, they form with numerous convolutions 
several conical lobes, the so-called coni vasculosi; the latter 
form the caput epididymis. The terminal canals gradually 
come together into a single one 0.3767 to 0.45 mm. in 
diameter. It forms, with numerous convolutions, the cauda 
epididymis. 184 
EIGHTEENTH LECTURE. 
Further below, the efferent canal becomes straighten, and 
its diameter increases to 2 mm. It is now called the vas 
deferens. Not infrequently, a lateral csecal branch, the vas 
aberrans Hailed, has previously entered 
it. This is the coarser structure. 
Having become familiar with this compli- 
cated arrangement, let us investigate the 
histological texture. 
The seminiferous canals (Fig. 162) have 
about the same diameter throughout their 
entire length. Their diameter is. In most 
mammals, o. 1 to 0.25 mm. They are re- 
markably large in the rat (0.4 mm.). In 
small animals the walls consist of a single 
layer of firmly cemented endothelial cells. 
In larger creatures, this inner layer is sur- 
rounded by others which show the same 
construction of flat nucleated scales, but 
are fenestrated (Mihalkovics). As we shall 
subsequently return to the parenchyma 
cells, we merely remark here that the 
efferent ductuli recti, deviating from these, 
have a different epithelial lining, namely, 
cylinder cells. In the rete testis there is 
no gland membrane; 
the cells are pavement 
shaped. Towards the 
end of the rete, how- 
ever, commences the 
cylinder epithelium of 
the epididymis. 
The quiescent semi- 
niferous canal is either 
entirely (Fig, 163, a, 
b), or, up to a narrow 
lumen, filled with 
rounded polygonal 
Fig. 162.—Human semi- 
niferous canal; a, parietes, 
i, cells. 
Fig. 163.—From the testicle of the calf; a, seminiferous 
canals seen in more oblique, b, in more transverse sections ; 
r, blood-vessels; d, lymphatics. THE MALE GENERATIVE GLANDS. 
185 
cells, measuring 0.0 to 0.0142 mm. The peripheral ones 
present a radiated appearance. In man, their cell bodies 
may contain a yellowish pigment. A coagulated, originally 
thick fluid, albuminous substance between the spermatic cells 
has been erroneously regarded as a second cell-work. 
The connective-tissue frame-work substance of the organ is, 
as we have previously said, developed from the inner surface 
of the albuginea and the system of septa. 
In many creatures (man, dog, rabbit) fibrillated connective 
tissue prevails ; in others (rat, male cat, boar) it is much less 
developed. In the rabbit the connective-tissue bundles are 
invested by the first mentioned (Fig. 55, a) forms of cells 
(the thin, nucleated plates, with protoplasma in the centre, 
and a hyaline, cortical portion); there may even be regular, 
endothelial cell membranes spread out over the seminiferous 
canals and the blood-vessels. In the just mentioned second 
group of animals we find the granular connective-tissue cells 
(Fig. 55, b) in immense numbers, while in the first division 
they are more scanty, or are scarcely met with. 
These granular cells (generally rounded or polygonal, rarely 
having processes, rich in protoplasm, fat, and brownish pig- 
ment) remind one of the hepatic cell (Fig. 121). They have 
a strand or column-like arrangement. Very frequently the 
blood-vessels are here regularly ensheathed by such cell 
layers, as we have described them (p. 55) in connection with 
the vicinity of the vessels. 
The blood-vessels (Fig. 163, c) circumvolute the convoluted 
seminiferous canals in close apposition, with a long-meshed, 
tolerably wide capillary net-work. We find this net-work 
more strongly developed and rounded in the epididymis. 
The latter part, also, probably has a secretory glandular ac- 
tivity (Mihalkovics). 
Let us consider, finally, the lymph passages (d) ; for the 
gland tissue is entirely without lymphatic vessels. It was 
Ludwig and Tomsa who founded our knowledge of this sub- 
ject. Subsequent investigations, also a trifle of mine, have 
been added. 186 
EIGHTEENTH LECTURE. 
The lymph passages keep in the spaces of the connective 
tissue, bounded by the membranous but fenestrated combina- 
tions of the flat connective-tissue cells. 
They form a copious reticular canal-work. In transverse 
sections of the seminiferous canals they form regular rings 
around the latter, with large expansions at the nodal points. 
A continued injection finally drives the mass through the 
spaces of the flattened cells, as far as the outer layers of the 
walls of the seminiferous canals. The solid inner layer of 
the latter alone prevents the further advance of the mass 
(Mihalkovics). Here and there a blood-vessel becomes en- 
sheathed by the lymph current, but this is not the rule. 
Larger lymph passages penetrate from the glandular por- 
tion into the septal system and from here, coalescing, pass 
beneath the albuginea. Having entered the latter, they be- 
come valved vessels, which unite with those of the epididy- 
mis. The final removal of the lymph takes place through 
the spermatic cord. 
The testicle arises, similar to the ovary, at the inner side of 
the Wolffian body. From its canal-work arises the epididy- 
mis (equivalent to the parovarium) ; the efferent canal of the 
primitive kidney, disappearing in the female, persists in the 
male generative apparatus, and becomes the vas deferens. 
The remainder must be left to the history of development. 
We have thus far considered only the quiescent gland. 
Let us now, however, examine the same at the height of its 
activity. 
Let us commence with its product, the semen, or sperm. 
It is by no means exclusively the product of the convoluted 
glandular canals of the testicle, but its fluid portions are cer- 
tainly also derived from the epididymis and the accessory 
glands, although its most important and characteristic ele- 
ments originate from the former source. 
The whitish, thickened fluid, spread out in a thin layer on 
the microscopic glass slide, presents a remarkable appearance, 
which has been stared at for two hundred years, and was 
formerly very curiously explained. THE MALE GENET A LIVE GLANDS. 
187 
Innumerable, lively moving, thread-like elements, the so- 
called seminal filaments, seminal animalculse, spermatozoa 
(Fig. 164) are here met with, suspended in a hyaline fluid. 
Their movement was, at an earlier epoch, 
credulously accepted as a proof of an inde- 
pendent animal life. The name of the seminal 
animalculae, spermatozoa, reminds one of that 
period. 
Nowadays we know that the motility of 
the seminal filaments is very nearly related to 
the ciliary motion (p. 35) ; we likewise know 
that the so-called “ seminal animalculae ” rep- 
resent tissue elements, cell derivatives. We 
are now no less familiar with the motley di- 
versity of forms which these filaments present 
in the animal kingdom. 
Fig. 164.— Sper- 
matozoa of the 
sheep ; a, head ; b, 
middle piece; c, tail. 
Let us confine ourselves to the class of mammalia. 
The filamentous, diminutive thing here shows a so-called 
head (a), then a somewhat thicker, thread-like, middle ap- 
pendage, the middle piece (b), and finally, extraordinarily 
thin, and becoming finer, the terminal piece or tail (c), 
There was formerly no distinction made between these fila- 
mentous portions. 
Whether this remarkable structure also has an internal 
complication is not determined, but is improbable. 
The head of the human seminal element appears as an oval 
disk, somewhat widened backwards, 0.0045 mm. long and 
about half as much in breadth, and not more than 0.0013 to 
0.0018 mm. thick. The entire filament may have a length 
of 0.0451 mm. ; but its terminal end is infinitely thin and dif- 
ficult to recognize. 
In the fruitful copulation, the seminal filaments penetrate 
the zona pellucida of the ovum, conducted through the very 
fine porous canals of this envelope (Fig, 158, a), and pass 
into the yolk, that is, into the true ovum cell. They here 
finally disintegrate by fatty degeneration. 
The process of division which we have already mentioned EIGHTEENTH LECTURE. 
at p. 14 may, indeed, commence without spermatozoa, and 
even in the mammalial animal; but it soon ceases. When, 
however, the seminal elerrfents have mingled their expiring 
body with the yolk, then (in an enigmatical manner, it is 
true), the multiplying process of the segmentation of the vi- 
tellus is continued, until at last innumerable building stones 
have been acquired, of which we have already spoken (p. 179). 
Whence comes the seminal filament ? 
For more than one generation this question has been very 
correctly answered ; from the convoluted canals of the testi- 
cle. But the how has called forth the most diversified an- 
swers among the older investigators, their successors, as well 
as the present generation of histologists. The incipient, 
crude and bad methods of examination certainly led the pio- 
neers to the grossest delusions. 
That we at present understand the whole, I certainly doubt 
very much ; still we have made some progress. 
Let us listen, therefore, to the results of the most recent 
studies (Neumann, von Ebner, Mihalkovics), 
We have already mentioned (p. 185) that the most external 
gland-cell layer of the quiescent seminiferous canal presents 
a prismatic radiated form. This 
cell is the spermatozoa-producing 
structure. All the numerous inner 
cells of this glandular canal appear 
to have no future ; they form merely 
an indifferent redundant substance. 
When the seminal gland-becomes 
active—in mammals this is only pe- 
riodically the case, generally once 
a year, in man in uninterrupted se- 
quence throughout the entire pro- 
creative epoch—when, therefore, 
the testicle is active, a remarkable 
metamorphosis occurs in these pris- 
matic parietal cells (Fig. 165, b). 
The epithelial cell-body grows inwards, that is towards the 
Fig. 165.—From the seminiferous 
canals of the rat; a, parietes with the 
cell nuclei; parietal cells and sperma- 
toblasts , c, the latter with small nar- 
row nuclear corpuscles ; d, inner cell 
layer. THE MALE GENERA TIVE GLANDS. 
189 
axis of the glandular canal, into a pedicle or neck-like proto- 
plasma process. It might remind one of a rude and clumsy 
candelabrum—but the comparison is a lame one. 
These modifications of our peripherical cell layer have been 
appropriately named spermatoblasts (von Ebner). 
In each club-like projection there is formed a nucleus (c)— 
how, we do not know. It becomes the head of the seminal 
element. The protoplasma, further inwards, is changed into 
the filament or tail. Thus each of our spermatoblasts pro- 
duces a number (8 to 12) of seminal filaments. At last the 
latter are set free, and lie in the lumen of the convoluted 
canals of the testicle, the caudal end in the axis of the canal, 
and directed downwards (Fig. 166, 1, b, c, 2). 
Ova and spermatozoa are, there- 
fore, according to their origin, quite 
different things. The former repre- 
sent very highly developed cells ; 
the latter proceed from portions of a 
more simple cell body. 
Let us finally turn to the efferent 
apparatus. 
The vas deferens presents an exter- 
nal connective-tissue layer, a middle 
layer consisting of three strata of 
muscles, and, finally, a mucous mem- 
brane covered with cylinder cells. 
The latter acquires below a greater 
development. 
The seminal vesicles and ejacula- 
tory duct have a similar structure. 
The prostate presents a system 
of small racemose glands embedded 
in an abundance of connective tis- 
sue, which first acquire their com- 
Fig. i66.—-Development of the 
rat’s spermatozoa. i. Spermato- 
blast a, with head 3, and filament 
c. 2. Nearly mature seminal fila- 
ment with adherent protoplasma re- 
mains. 
plete development at the period of puberty. The epithelium 
has a double layer (Langerhans). 
The Cowper’s glands likewise belong to the racemose for- 190 
EIGHTEENTH LECTURE. 
mation. Their cells are cylindrical, but become lower in the 
efferent canal-work. 
The male urethra presents a pars prostatica, a consecutive 
membranous middle portion (pars membranacea), and a 
terminal division running through the penis (pars cavernosa). 
The latter portion is surrounded by a cavernous tissue (corpus 
spongiosum urethrae), which takes the shape of the glans an- 
teriorly. Two similar cavernous structures, the corpora cav- 
ernosa penis, are added. 
The mucous membrane of the urethra has at first flattened, 
and further downwards cylindrical cells. It is surrounded 
by loose connective tissue, which might be called cavernous in 
consequence of its great vascularity, and over this there are 
smooth muscles. Racemose glandules occur in the prostatic 
portion, as well as in the colliculus seminalis. The mucous 
membrane presents folds. In the middle and lower portions 
the muscular coating diminishes more and more. The mucous 
membrane of the lower portion contains excavations (lacunae 
Morgagni!) and small, undeveloped Littre’s mucous glandules. 
Towards the orifice of the urethra stratified flattened epithe- 
lium again commences. 
The skin of the penis, thin and flaccid, has a loose subcuta- 
neous cellular tissue, free from fat, and permeated by smooth 
muscular fibres. An extensible connective tissue, free from 
fat, unites the two plates of the prepuce ; it also contains mus- 
cular elements. 
The thin skin of the glans has numerous papillae, which dis- 
appear in the epithelial covering ; the inner, mucous-mem- 
brane-like surface of the prepuce also shows such papillae. 
The Tyson’s glands occur on the inner surface of the pre- 
puce, occasionally also on the glans, especially on the frenu- 
lum. They participate in a very subordinate manner in the 
formation of the fatty smegma praeputii. 
Let us also mention, in conclusion, the structure of the 
corpora cavernosa. These structures are surrounded by a 
firmer, elastic element, which is however poor in muscular 
elements, a so-called albuginea. It sends off innumerable THE MALE GENERA LIVE GLANDS. 
191 
processes in an inward direction, which are sometimes larger 
sometimes smaller, in the form of trabeculae and plates. Con- 
nective tissue, elastic fibres and smooth muscular substance 
combined form the latter. 
This incomplete system of septa, as we must call it, is 
divided and interconnected in the most multifarious manner. 
We have, therefore, a system of spaces and cavities, remind- 
ing one of a bathing sponge, lined with vascular cells, des- 
tined to receive venous blood. Herein consists just the pecu- 
liarity of the so-called cavernous tissue. 
The various “ cavernous bodies ” present small subordinate 
structural peculiarities. We pass over these minutiae. 
Constantly filled with blood, they become periodically over- 
charged with the same, and cause the erection of the male or- 
gan. 
The cavernous bodies receive their blood supply to a slight 
extent from the arteria dorsalis penis, essentially from the 
arteria profundae. These arterial branches, enclosed in the 
tissue of the septum, pass into the cavernous spaces, partly 
through a capillary net-work, partly with an intermediate 
opening (Langer). Corkscrew-like, crooked arterial branches, 
the so-called arterise helicinae of J. Muller, constitute artefacts 
(Bouget, Langer). 
The various vense emissarise serve for the removal of the 
blood from the caverni. 
. Abundant lymphatic net-works are not wanting in the male 
urethra and the organ of copulation (Teichmann, Belajeff). 
The theory of the erection we leave to physiology. NINETEENTH LECTURE. 
NERVE TISSUE. 
We turn to the final and highest histological formation of 
the animal body ; we refer to the nerve tissue. 
This has been included among the so-called “ compound 
tissues,” that is those which possess more than one element. 
And, in fact, we here meet with two such, namely, fibres and 
cells. The former bear the name of the nerve fibres, nerve 
tubes or primitive fibres ; the latter are called nerve cells or 
ganglion bodies. 
The human nerve fibres appear either as dark contoured 
medullated elements (Fig. 167) or as 
pale non-medullated ones (Fig. 172, b). 
Since the former constitute by far 
the most widely extended and impor- 
tant peripheral elements, let us begin 
our discussion with them. 
They are, like the non-medullated, 
for long distances unramified fila- 
ments, but of very unequal diameter, 
from 0.0226 to 0.0018 mm., and less. 
We distinguish, accordingly, broad or 
coarse nerve fibres (Fig. 167, a) and 
fine or narrow ones (c, d, e). Inter- 
mediately between these appear the 
nerve tubes of medium width (b). 
Let us commence our investigations 
of the structure with the coarse, medul- 
lated elements. 
Fresh and living, it appears like a 
thread of a homogeneous milk-glass-like substance. We 
recogni/e in it no further composition. 
Fig. 167-—Human nerve 
fibres ; a, broad ; b, medium 
breadth ; c, d, e, fine. NERVE TISSUE. 
193 
The nerve tube is, however, a marvelously changeable 
tiling. Under our eyes, and against the will of the observer, 
it changes its original appearance most rapidly into a second, 
third cadaveric image. 
It is at present established that every broad nerve tube con- 
sists of three elements. 
It is invested by a, as a rule, very fine homogeneous con- 
nective-tissue envelope, the neurilemma, the Schwann’s or 
primitive sheath (Fig. 169, b, 171, e). The latter contains, from 
point to point, an elongated nucleus. Occasionally the neu- 
rilemma appears considerably thickened (Fig. 171, c). 
In the axis, occupying a fifth to a fourth of the entire 
diameter, we recognize a pale cylindrical filament, formed of 
Fig. 169.—Various nerve fibres ; 
a, after treatment with absolute 
alcohol; b, with collodion; c, 
fibres of the lamprey: d, from the 
olfactory nerve of the calf; e and 
_/5 from the human brain. 
Fig. 168.—Human nerve 
fibres in various stages of 
coagulation. 
an albuminous substance. This is the axis cylinder, the sole 
essential portion of the nerve tube (Fig. 169, a,b, c, e, 171, e). 
It is surrounded by the so-called nerve medulla or medullary 
sheath, a peculiar and very delicate combination of albumin- 194 
NINETEENTH LECTURE. 
ous bodies, as well as lecithin and cerebrin. This investment 
originally conceals the axis cylinder. 
As soon as we isolate broad nerve tubes, we encounter the 
cadaveric form of the medullary sheath (Fig. 168). “They 
are now coagulated,” is a customary expression of the histolo- 
gists. We meet with the most varying stages of coagulation, 
often close to each other, and even in the course of one and 
the same primitive tube. 
As a commencing stage, we discover on both sides a 
double contour, a sharp but dark external, and a closely 
applied finer border (Fig. 167, a, b, 168, b, above). 
Later, the double contours no longer run parallel with each 
other, and the inner one appears frequently interrupted (Fig. 
168, b, below). The latter becomes constantly more and 
more irregular, and in the previously homogeneous axis por- 
tion, dark bordered, lumpy substances are formed {a, b). 
The process of coagulation may, it is true, be arrested at an 
earlier stage. The cortex then forms to a certain extent, a 
protective mantle around the axis portion. In other cases, 
the latter also does not escape its final destiny ; together 
with the cortex it is completely disintegrated into clots (<;). 
It was a long time before the just described structure of 
the nerve tubes could be agreed upon. The existence of the 
axis cylinder, especially, gave rise to heated debates. It is 
to-day a child’s play to recognize the latter in any transverse 
section of a hardened peripheral nerve or—which amounts to 
the same—each primitive tube in a white column of the spinal 
cord (Fig. 170). 
The nerve tubes of medium size have a 
similar constitution. 
A similar structure—envelope, axis cylin- 
der and medullary sheath—is also perceived 
in the fine filaments of the nerve trunks. 
The medullary sheath (Fig. c, d) remains 
clear, and simply demarcated, even with 
advanced post-mortem changes. Osmic 
acid, which rapidly blackens the medulla of the broad nerve 
Fig. 170.—Trans- 
versely divided nerve 
fibres from the posterior 
column of the human 
spinal cord. NERVE TISSUE. 
195 
fibres, as it does other fatty substances, here acts much less 
thoroughly and more slowly ; there must certainly, therefore, 
be a difference in the constitution of these two different 
fibrous substances. 
Our fine nerve tubes present an additional peculiarity. 
Every mistreatment, pressure, pulling or reagent to which it 
is subjected causes a certain displace- 
ment of the medulla, so that unnaturally 
thinned spaces interchange with rounded 
bulgings (e). The latter have been desig- 
nated as varicosities, and varicose nerve 
fibres are spoken of. Nothing of the 
kind exists during life. 
We here touch upon another unsettled 
question. Ranvier, at present the first 
histologist of France, called attention to 
a familiar phenomenon, to constrictions 
which occur in the course of broad 
medullated (peripheral, but not central) 
fibres. Formerly, however, these con- 
strictions were always regarded as a 
product of the methods of preparation. 
Now, these constricted places (Fig. 171) 
are pretty regularly situated, and be- 
tween every two, very nearly at half 
the distance, one meets with a nucleus 
of the sheath of Swann (a). It is thus 
in mammals, birds, and amphibia ; but 
in fishes the number, of nuclei is greater 
between every two of these constric- 
tions. 
Fig. 171.—Nerve fibres of 
the frog; a, after treatment 
with picro carmine; b, c, d, with 
osmlc acid ; e, with nitrate of 
silver. 
These Ranvier’s “ constriction rings,” 
as the Germans have christened them, 
deserve—although we are at present far removed from an 
accurate knowledge of them—every consideration. The 
medullary sheath certainly isolates the axis cylinder ; but 
this medullary space permits the penetration of nutrient 196 
NINETEENTH LECTURE. 
constituents and the giving off of the products of decomposi- 
tion. 
. Originally, in the foetal period, all the primitive tubes of 
the entire nervous system were thus constituted. If we take 
one of the lowest fishes, the lamprey (petromyzon), we meet 
with this condition throughout its entire life (Fig. 169, c). A 
nucleated sheath invests the axis cylinder. Medullated nerve 
fibres are here entirely wanting. 
Let us now pass to the pale non-medullated nerve fibres. 
Let us turn, at a bound, to the highest animal being, to 
man. 
In us, the olfactory nerve, alone, consists throughout of 
pale, non-medullated fibres, as does in great 
part the sympathetic with its ramifications. 
These pale structures have been called 
Remak’s fibres. They appear as delicate 
0.0038 to 0.0068 mm. wide, nucleated fila- 
ments (Fig. 172, b). 
Does what has been mentioned above, 
however, contain the entire structure of the 
nerve fibre ? We now encounter this diffi- 
cult question. 
It does not appear so; nevertheless, we 
are once more at the limits of the microscopy 
of the present day. 
The axis cylinder, the best portion of the 
nerve tube, most probably consists of a 
bundle of extremely fine filaments. 
Fig. 172.—A sympa- 
thetic nerve branch of 
a mammalial animal; 
two dark bordered 
nerve fibres, a, with an 
excess of the Remak’s 
formation, b. 
They (Fig. 173) appear to be embedded in 
a delicate granular substance. They have 
been called axis fibrillae (Waldeyer) or primitive hbrillae 
(Schultze). Here, also, the incitation was furnished by a bril- 
liant investigator, who has by no means been honored by his 
cotemporaries in proportion to his merits, Remak, the 
founder of the modern history of development. Many years 
ago he saw this combination in the nerve fibres of the river- 
crab. NERVE TISSUE. 
197 
Diagnostic weight has subsequently been laid on the finest 
varicosities of these primitive fibrillae (M. Schultze). 
We shall subsequently return to this. 
We are now, so far as it is at present 
possible, familiar with the fibres. Let us 
turn to the cellular elements. They belong 
solely to the gray substance of the nervous 
system (the peripheral, as well as the cen- 
tral) ; the white substance consists through- 
out solely of nerve tubes. 
Fig. 173.—Fibrillated 
arrangement of the 
axis cylinder ; a, a 
thick axis cylinder from 
the spinal cord of the 
ox ; i, nerve fibre from 
the brain of the torpedo. 
Fig. 174.—Ganglion cells of the mamma- 
lia ; cells with connective-tissue envelopes, 
■which are continued in fibres, d, d; «, a cell 
without a nucleus ; b, two single nucleated 
ones ; and c, one with two nuclei ; a gan- 
glion body without an envelope. 
We frequently encounter, in a very characteristic form, 
those cellular elements, the ganglion bodies (Fig. 174, B). It 
is one of the handsomest cell-forms which the organism pos- 
sesses. The dimensions of most of the globular, ovoid or 
pear-shaped elements lies between 0.0992 to 0.0451 and 
0.0226 mm. In a very delicate granular, thickly gelatinous, 
generally colorless, occasionally brown or black pigmented 
mass, we meet with a globular, delicate walled nuclear vesicle, 
0.0180 to 0.009 mm. in diameter. In it occurs, as a rule 
single, a dull glistening granule, the nucleolus, 0.0029 to 
0.0045 mm. in size* 198 
NINETEENTH LECTURE. 
Our structure is surrounded by an envelope. It appears 
thick, a sort of nucleated connective tissue at the first glance ; 
however, the nuclei may have another signification, for, on 
the inner surface of the capsule, a lining of endothelial cells 
has subsequently been noticed. 
This envelope appears more simple and thinner around the 
ganglion cells of the lower vertebrates, fishes (Fig. 175) and 
amphibia. 
At the first, most cursory examination—and the older his- 
tologists, with their bad methods of investigation, arrived no 
further—all the peripheral ganglion cells appear to have no 
processes or, as a scholastic expression runs, are apolar. We 
have subsequently adopted an entirely different view ; apolar 
ganglion cells either do not occur at all, or only exceptionally 
as embryonic, arrested in 
their development, and 
possibly futureless ele- 
ments. 
About 1845, Koelliker, 
one of the most cele- 
brated histologists, dis- 
covered in the sympa- 
thetic of the vertebrates 
ganglion bodies which 
sent off from one of their 
ends a pale filament,which 
after a sometimes shorter, 
sometimes longer course, 
was enveloped in a me- 
dullary sheath, and be- 
came a nerve fibre (Fig. 
175,4 
Fig. 175.—From the peripheral nerve ganglion of a 
fish, godus lota ; a, h, bipolar ganglion 'cells 'I c, uni- 
polar ; d, e. abnormal forms. 
In vertebrate creatures 
something of the kind 
has, it is true, been previously seen. These are the so-called 
unipolar ganglion cells. 
Soon after this, R. Wagner, Robin and Bidder, with Rei- TWENTIETH LECTURE. 
THE ARRANGEMENT AND TERMINATION OF THE NERVE 
FIBRES. 
The spinal nerves and those of the brain appear white 
through the medullary sheaths of their tubular constituents ; 
the trunks of the sympathetic appear gray from the excess 
of non-medullated fibres. 
The former, at their exit from the central organ, become 
invested in a delicate connective-tissue envelope ; they are 
subsequently surrounded by an additional reinforcement of 
connective tissue, furnished by the dura mater. This affords 
together the nerve sheath, perineurium or neurilemma. This 
connective tissue penetrates, in a lamellar or sheath-like man- 
ner, between the bundles of nerve fibres, becoming, at the 
same time, looser and softer. Its modified boundary layer 
forms at last the primitive sheath of the nerve tube. A 
scanty, straight net-work of finest capillary vessels permeates 
the whole. Injections made from the lymph spaces likewise 
penetrate beneath the perineurium and between the nerve 
bundles (Key and Retzius). 
The primitive fibres run alongside of each other in the 
nerve trunk, undivided and indifferent. The nerve trunks 
usually send off their branches at an acute angle, the bundles 
of fibres bending away from the main path to the lateral. 
When anastomoses take place, groups of fibres pass, at the 
point of communication, from the one nerve to the other, or 
we have a double interchange of fibres. 
The perineurium becomes finer and finer in proportion as 
we proceed from the larger trunks to the finest systems of 
branches. Finally, it appears as a striated or more homo- 
geneous connective substance with rather stunted cells. NERVE TISSUE. 
chert, met with other conditions. They discovered the bi- 
polar cells. 
The spinal nerves arise by a double root; an anterior, 
which passes over the spinal ganglion, and a posterior, which 
passes through the ganglion. 
Fig. 176.—Multipolar ganglion cell from the anterior horn of the spinal cord of the ox, with the 
axis cylinder process {a), and the branched protoplasma process, from which, at b, the finest 
filaments arise. E 
As has been known since the days of Charles Bell, the 
former consists of motory, the latter of sensory filaments. 200 
NINETEENTH LECTURE. 
On teasing out the spinal ganglion of a fish (the ray is most 
to be recommended) we recognize (Fig. 175) that each nerve 
fibre penetrates a ganglion cell, to again pass out at the other 
pole (a, b). Broad fibres connect with larger cells, narrow 
nerve tubes with smaller ones. 
The latter nerve fibres are probably sensory constituents 
of the sympathetic. Numerous individual, otherwise consti- 
tuted combinations occur, in addition to these, perhaps as 
anomalous products of development (d, e). 
Both varieties of ganglion cells show distinctly that their 
envelope passes over into the primitive sheath of the nerve 
fibre connected with them. 
As a third form, we have to mention the multipolar gan- 
glion cells. They were seen for the first time in the year 1838 
(Purkinje). They are met with in man in the sympathetic 
ganglia, in the retina of the eye, and in the gray substance 
of the brain and spinal cord. 
In the so-called anterior cornu of the latter is found the 
elegant form of our Fig. 176. 
A membraneless cell body sends off a varying, often quite 
considerable number of delicate granular processes (b), which 
undergo repeated divisions and continual ramifications, until 
they at last disappear from view in the form of the finest fila- 
ments. The finest lateral filaments were regarded as primi- 
tive fibrillas of the axis cylinders (Deiters), but hardly with 
accuracy, for all is here obscure. 
Together with this system of processes—they have been 
called protoplasma processes—we also meet with a long pro- 
cess, which is always single, and usually arises from the cell 
body, more rarely from the origin of another thick offshoot. 
It never ramifies, and is conspicuous from its sharper, homo- 
geneous appearance. This is the axis-cylinder process (a). 
Later it is invested by the medullary sheath, and becomes a 
nerve fibre. This has also, however, been recently doubted 
(Golgi). 
In the sympathetic of the frog Beale and Arnold met with 
an interesting, although not yet accurately determined struc- NERVE TISSUE. 
201 
ture of the cells (Fig. 177). From the interior of its rounded, 
or pear and kidney-shaped body passes a straight axis-cylin- 
der process {c), which subse- 
quently acquires a medullary 
sheath. 
From the surface of the cell 
arises, singly or doubly, with 
close spiral convolutions, an- 
other filament, which surrounds 
the straight axis cylinder with 
wider turns; it may also run 
alongside of the latter (d), and 
subsequently leave it (/), pass- 
ing further in a straight form. 
Whether these spiral fibres are 
elastic or—which we regard as 
more probable—are actually of 
a nervous nature, is still unde- 
cided. Subsequent German in- 
vestigations have, unfortunately, 
not determined this. 
Finally, the fine, fibrillated 
formations, such as are pre- 
sented by the axis cylinder (p, 
196), have also been most re- 
cently observed, continuing into the interior of the cell body, 
and more especially in the cortical portion of the latter. The 
finest fibrillse which stream in from the protoplasma, as well 
as the axis-cylinder process, run sometimes divergently, some- 
times crossing each other. 
Fig. 177.—Ganglion cell from tlie sym- 
pathetic of the hyla or green tree-frog ; a, 
cell body ;b, sheath; c, straight -nerve 
fibre : and d, spiral fibre ; continuation oi 
the former, e; and of the latter, f ARRANGEMENT OF THE NERVE FIBRES. 
203 
The investigation of the peripheral termination of the 
nerve tubes—in the crude, incipient period they were erro- 
neously regarded as a noose or loop-shaped connection be- 
tween each two fibres—cost the histologists much trouble and 
labor, and even at the present day we are still far removed 
from a satisfactory scientific possession. We present only 
the most important facts, and leave numerous, in part very 
uncertain, minutiae to the more comprehensive text-books on 
this subject. 
Let us commence with the termination of the motory nerve 
fibres in the transversely striated muscle. 
If we follow the small nerve branches which have entered 
the latter, in suitable objects, for example, many quite thin 
membranous muscles of the frog, we meet with a few broad, 
double contoured nerve fibres, subsequently surrounded by a 
hyaline sheath. If the branch divides again, we not infre- 
quently perceive that something new comes over the nerve 
tube ; it becomes narrower, forming a Ranvier’s constriction 
ring (p. 195), and, at the same time, divides into branches, 
two as a rule. With the continued division of these smallest 
nerve trunks, this diminution of the nerve branches is con- 
tinued ; they divide into branches of a new order, and so on. 
The latter hereby become finer, but still retain the double 
contours for a distance; at last they are bordered by a simple 
boundary line. 
In the lower vertebrates this ramification of the primitive' 
tubes is very extensive. In fishes, the latter may finally 
divide into fifty and even one hundred branches. Reichert, 
many years ago, examined the so-called thoracic cutaneous 
muscle of the frog. It contains from 160 to 180 muscular 
filaments, but only from 7 to 10 nerve tubes pass in for their 
supply. 
While, therefore, in the lower vertebrates a motory primi- 
tive fibre supplies with its system of branches quite a number 
of transversely striated muscular filaments, the arrangement 
is different and higher in mammals (and even in reptiles and 
birds). The primitive fibre is much less divided; the mis- TWENTIETH LECTURE. 
204 
proportion between the number of the nerve and muscular 
filaments is accordingly very much less. 
In regard to the termination, the lower vertebrates present 
a different condition from that of the higher. The termina- 
tion takes place regularly, however, in the interior of the 
muscular filament, beneath its sarcolemma. We consider 
only the mammalial muscle (Fig. 178). 
Fig. 178.—Two muscular filaments from the psoas of the Guinea-pig, with the nerve terminations ; 
a, b, the primitive fibres and their continuation into the two terminal plates eN\ A neurilemma 
with nuclei, d, d, and passing over into the sarcolemma, g, g\ k, muscular nuclei. 
The nerve fibre {a, d), surrounded by an expanding nucle- 
ated primitive sheath (<r, d), here passes to the muscular fila- 
ment. Its neurilemma becomes the sarcolemma (g). Beneath 
the latter, at the place of entrance, appears a nucleated, deli- 
cate molecular substance, a rounded or oval bent plate with 
nuclei concave within, convex without. This (occur- 
ring only single in the mammalial muscle, and more towards 
the middle) is the terminal plate of Krause, Rouget and Engel- 
mann, or the nerve-mound of Kuehne: At f, we have the ARRANGEMENT OF THE NERVE FIBRES. 
205 
profile view; at e, we see the structure from its broad 
external surface. Its size varies between 0.0399 to 0.0602 
mm. ; the number of the nuclei from 4 to 20. 
The great delicacy and changeableness of the motory ter- 
minal plate impedes its further study considerably. Does the 
axis cylinder actually cease on spreading out into the former? 
Or, does the termination of the axis cylinder first occur in the 
interior of the terminal plate, so that the signification of some- 
thing like a cushion is to be ascribed to the latter? 
In the muscular filament of the lizard (Fig. 179) we obtain, 
under certain circumstances, a peculiar interesting appearance. 
In penetrating the terminal plate, the axis cylinder of the nerve 
fibre (<h, c) divides and, rapidly 
losing its medulla, passes over by a 
continual ramification into a pale, 
obtusely branched, antler-like fig- 
ure (d, d). The molecular nucleated 
substance is just beneath this ex- 
pansion. We are indebted to 
Kuehne for this observation. I 
have seen something similar by 
reexamination ; but we are once 
more at the limits of the present 
microscopy. Kuehne named this 
antler-like formation the true ter- 
minal plate. 
Fig. 179.—Muscular filament (a) o{ 
the lizard ; b, nerve fibre ; c, its branches 
with the peculiar terminal figure, d. 
This is, according to our expe- 
rience, the present state of the 
matter. Others maintain deviating views, as most recently 
Arndt and Gehrlach. It is impossible for us to enter here 
into a polemic, the more so as this lies at the limits of the 
present microscopic perception. 
Concerning the nerve termination in the muscles of the 
heart, only hypotheses exist at present. 
We have also no very satisfactory knowledge of the nerves 
of the smooth muscles. 
Many years ago various observers (Beale, Arnold, His, 206 
TWENTIETH LECTURE. 
Klebs and others) had met in this tissue formation with 
plexuses or net-works of pale, fine nerve fibres with nuclei in 
the nodal points. This net-work was regarded as terminal. 
Others have, however, proceeded further, whether correctly 
we certainly doubt. 
Arnold, who has investigated these things most accurately, 
gives us the following information concerning them : 
The nerve trunks of the smooth muscular tissue (Fig 180) 
consist in part of medullated, in part of non-medullated fi- 
bres. The latter diminish 
into nucleated-filaments mea- 
suring 0.0018 to 0.0023 mm. 
Even externally in the con- 
nective tissue surrounding 
the muscular substance, there 
occurs a wide-meshed plexus, 
having ganglion cells in 
places, Arnold’s so - called 
basis plexus. From the lat- 
ter pass nucleated fibres, 
which become pale, longitu- 
dinally striated, nucleated fil- 
aments, 0.0041 to 0.005 mm. 
in diameter. The latter grad- 
ually diminish to 0.0018 to 
0.0023 mm. 
Fig. iBo.—The termination of the nerves in the 
smooth muscles of a frog’s artery. 
From these—though pale 
and, therefore, non-medullated fibres also enter it from the 
basis plexus—there is formed a second and likewise tolerably 
wide-meshed reticulum, which also has nuclei at the nodal 
points. This is Arnold’s intermediate plexus. It is either 
closely applied to the smooth muscles, or lies in the connec- 
tive tissue between the several layers of the first-mentioned 
tissue. 
From this second plexus pass off fine fibres, which are at 
first still nucleated. They rapidly become finer, and pass be- 
tween the contractile fibre cells. Finally, after repeated divi ARRANGEMENT OF THE NERVE FIBRES. 
sions, they have diminished to fibrillae of only o.ooos to 
0.0003 mm. They are said to form a new, but now very 
narrow-meshed reticulum of the third order, the intramuscu- 
lar plexus, between the spindle ceils of the tissue. 
From the latter proceed extremely fine filaments, 0.0002 
mm. in size, and therefore primitive fibrillae, into the fibre 
cells. Their discoverer, Frankenhaeuser, asserts that they 
terminate in the nucleoli, but Arnold is already doubtful on 
this point. 
A few years ago, as I examined the muscular vascular walls 
of the frog, by the aid of the best customary methods, I saw 
only nerve plexuses. Klein also went no further. I suspect 
that the predecessors—in this most difficult department—have 
also deceived themselves. 
The nerves of the cornea of the eye have been the object 
of very extensive researches for years. We here meet with a 
twofold manner of termination ; one in the proper corneal 
tissue, and another in the epithelial stratum of the free an- 
terior surface The latter is certainly sensory, the former 
most probably of a motory nature. 
The corneal nerves enter at the periphery as a bundle of 
fine, at first medullated fibres. The medullary sheath is soon 
lost ; we have pale filaments to which must here, as in the 
smooth muscles, be at first ascribed the signification of the 
axis cylinder, and subsequently of the primitive fibrillae (p, 
196). In the cornea we also meet, from behind forwards, 
with a series of nerve plexuses, lying one over the other, with 
evident divisions of the fibres. 
A considerable contingent of the latter terminate in the cor- 
neal tissue. How, is unknown. A former statement of 
Kuehne’s, according to which the primitive fibrillae were said 
to finally unite with the corneal cells (p. 56), could not be 
confirmed. 
Cohnheim, after the example of Hoyer, has shown that from 
the most superficial nerve plexus of the cornea the finest nerve 
filaments (primitive fibrillae or fasciculi of the latter) pass into 
the stratified, flattened epithelium of the above mentioned 208 
TWENTIETH LECTURE. 
conjunctiva corneas. Ascending perpendicularly, and rami- 
fying once more, they finally disappear in the most superfi- 
cial layers of flattened cells (Fig 36, d, e,f). 
We have no certain knowledge concerning the termination 
of the nerves of glandular organs. That the secretion of 
the submaxillary gland is very dependent on nervous influ- 
ence (p, 140), is an old physiological experience. What 
Pflueger has communicated concerning the salivary glands 
and the liver has not been confirmed. Other statements of 
Krause’s must likewise be more accurately tested. 
Passing now to the sensory nerves, we meet with three dif- 
ferent conditions : 
a. A portion of the same run out into considerable, and 
in part, right complicated larger or large structures. 
b. Others have their termination in the small corpuscles of 
the epithelium. 
c. The higher nerves of sense, finally, pass into quite pecu- 
liar specific cellular elements, so-called “ sensory cells.” 
We discuss directly the first two terminations. The third 
and last we shall have to mention at the organs of sense, at 
the close of these lectures. 
The larger terminal apparatuses of the sensory nerves 
are : 
1. Krause’s terminal bulbs. 2, The Pacinian corpuscles. 
3. The Wagner-Meissner’s tactile bodies. 
Let us commence with the first. The terminal bulbs, dis- 
covered by Krause, are of isolated occurrence, and are not 
easy to find in the unpropitious tissue of the mucous mem- 
brane ; they are by no means favorites of the histologists. 
For years, only Koelliker and myself maintained their exist- 
ence, which was at that time doubted even by Arnold, Wal- 
deyer, an excellent investigator, recently declared to us that 
he had also been unable to find them. I have seen them 
in the calf, but have not had a sufficiency of human autop- 
sies. 
According to Krause, the terminal bulbs occur in the con- 
junctiva bulbi, in the mucous membrane of the floor of the ARRANGEMENT OF THE NERVE FIBRES. 
209 
mouth, in the papillae fungiformes and circumvallatae of the 
tongue, in the glans penis and clitoridis. The discoverer 
also found them in not inconsiderable extension in mam- 
mals. 
181), and follow the course of the nerve 
through the separated mucous membrane. 
After a long interval, we meet in the first 
place (*) with a dichotomous division of 
the double contoured nerve fibre (c). 
Then, after following the branch for a 
shorter or longer distance, we arrive at a 
striking appearance (a). It is an elongated 
oval, occasionally slightly bent body, 
measuring 0.0751 to 0.1409 mm. in its 
greatest diameter, and about one-third as 
much in its transverse. In man and the 
ape, the structure has a globular form, ac- 
cording to Krause. 
Let us take the sclerotic conjunctiva of a calf’s eye (Fig 
Let us return to the calf. We here 
meet with a dull, nucleated, moderately 
thick envelope, with an enclosed hyaline, 
homogeneous, rather thick fluid contents. 
The primitive sheath of the nerve trunk 
gives off its neurilemma to this mem- 
brane, or, to express ourselves more intelli- 
gibly perhaps, it increases in thickness 
and becomes the parietes of the terminal 
bulb* 
Fig. 181.—Terminal bulb 
from the conjunctiva bulbi 
of the calf; a, terminal bulb ; 
c, nerve fibre, branching at*; 
b, axis cylinder. 
At the first cursory examination, one might suppose that 
the nerve fibre had thus terminated. One would, however, 
be very much deceived ; for, after losing its medullary 
sheath, the most important constituent of the nerve fibre, 
the axis cylinder, passes through the structure to end at 
the opposite pole, occasionally with the slightest intumes* 
cence. 
This is the terminal bulb, so far as I am familiar with it. 210 
TWENTIETH LECTURE. 
Concerning the Pacinian capsules (Fig. 182) we have abun- 
dant and no longer to be doubted material. 
These structures have had a 
peculiar history. 
They have been known for 
more than one, hundred and thirty 
years. 
They were described in 1741, 
in the doctor’s dissertation of a 
certain Lehmann, having already 
been discovered by a professor 
Vater of that period. They were 
forgotten for nearly three genera- 
tions. 
They were rediscovered soon 
after 1830, without any presenti- 
ment of a predecessor, by Pacini 
of Pistoja and, almost simultane- 
ously, on the occasion of an ana- 
tomical concourse, by Parisian 
physicians. The attention of 
the German investigators was 
Fig. 182.—Pacinian body from the mes- 
entery of the cat; a, nerve fibre with its 
envelope, forming the stem ; b, the cap- 
sular system ; c. the axis canal or inner 
bulb, in which the nerve tube ends. 
especially directed to our structure by the monographs of 
Henle and Koelliker, in the year 1844. As a student at 
that time in Goettingen, I had already found them in the 
abdominal cavity of the cat, and had seen the entering 
nerve. 
Let us leave these historical reminiscenes, however, and 
pass to matters of fact. 
The Pacinian bodies appear as elliptic structures, measur- 
ing I to 2 mm. and more, sometimes more elongated, some- 
times more developed in width. Without the microscope, 
we perceive them to be tense, tolerably firm, semi-transpar- 
ent, and with white axial striations. 
They are regularly met with in the human body on the 
nerves of the palm of the hand and the sole of the foot, 
especially of the fingers and toes. Their total number varies ARRANGEMENT OF THE NERVE FIBRES. 
211 
here between 600 and 1,400 examples. They may occur 
manifold or isolated. 
In mammals we meet with them in the sole of the foot. 
An admirable locality is the mesentery of the cat. Many of 
the latter animals contain them in innumerable quantities ; in 
others, on the contrary, one may bother and fret one’s self and 
find only 6 to 12 altogether. 
The capsular system of the Pacinian corpuscle (b) is much 
more complicated in its structure than the simple envelope 
of the terminal bulb. 
It consists of a considerable number of thin, connective- 
tissue membranes, embedded over each other, and kept tense 
by a fluid intermediate substance. They formerly appeared 
to contain nuclei in their parietes. According to the investi- 
gation of Hoyer, however, their inner surfaces are lined by 
a thin covering of nucleated endothelial cells. The outer 
capsular systems are further removed from each other, follow- 
ing the curvature of the entire structure ; the inner ones are 
more nearly approached to each other, their lateral curvature 
is lessened, and they finally surround an axial canal. This, 
the so-called inner bulb (c), may be compared to the Krause’s 
corpuscle. It is filled by a homogeneous, tolerably resistant 
substance. 
The capsular systems unite below, and form a thicker con- 
nective-tissue tube (a). Through it passes a broad or medium 
sized, but always double contoured nerve fibre. Having 
entered the inner bulb, it loses (at c, below) the medullary 
sheath ; it becomes an axis cylinder, and terminates towards 
the upper closed pole, for the most part undivided, occasion- 
ally (and then varying in its details) divided (c, above). This 
axis cylinder is the most beautiful known. It shows a longi- 
tudinally striated structure, and consists of primitive fibrillae. 
Let us turn, finally, to the so-called tactile bodies of the 
human integument (Fig. 183). They belong—no doubt can 
prevail concerning this—to the related series of the terminal 
bulbs and Facinian structures; but the nerve termination is 
not yet known. 212 
TWENTIETH LECTURE. 
In a preceding lecture (p. 58), we remarked that the human 
cerium developed papilla-like projections, which were some- 
times higher,sometimes 
lower. In the volar sur- 
face of the fingers and 
toes, the hollow of the 
hand, and the sole of 
the foot, and, finally, 
the heel, we meet with 
papillae of a double na- 
ture. One portion con- 
tains a vascular loop (b); 
others, non-vascular, 
contain the nerve ter 
mination (above, i): 
The number of these 
nerve papillae is great- 
est at the volar surface 
of the finger point; 
from here they con- 
stantly decrease. The 
toes are less favored; 
but here, also, the same 
law prevails of the diminu- 
tion towards the sole of 
the foot. Without going 
further into this subject, 
we merely remark here 
that only the ape, our 
nearest corporeal relation, 
presents tactile bodies. 
They are wanting in the 
other mammals. 
A tactile body (Fig. 
184) is either oval or, 
with smaller dimensions, 
rounded. Its diameter 
Fig. 183.—Human skin in perpendicular section ; a, 
superficial layers of the epidermis; b, Malpighian■ rete- 
mucosum. Beneath the latter is the corium, forming the 
papillae above at c, and terminating below in the subcu- 
taneous connective tissue, in which at h, aggregations of 
fat cells appear ; g, sudoriparous glands, with their excre- 
tory ducts e and_/; d, vessels ; i, nerves. 
Fig. 184. —Two human nervous papilla: from the 
skin of the volar surface of the index finger. In the 
interior of the papilla is the tactile body, into the 
tissue of which the nerve fibres enter. ARRANGEMENT OF THE NERVE FIBRES. 
213 
varies between 0.0133 and 0.0037 mm. It lies in the axis por- 
tion of the papilla, and consists of homogeneous connective 
substance, with transverse and obliquely disposed nuclei. 
The whole thing acquires thereby a peculiar appearance, 
which reminds one of a fir cone. The nerve fibres (with their 
trunks passing from below upwards) arrive at our structure 
singly, doubly, or three or four together. Their neurilemma 
passes over into the capsule. They themselves, after previous 
curved excursions or looped windings, enter the tactile bodies 
manifoldly. Having become pale and transformed into axis 
cylinders, they soon disappear from the eye. 
We have thus become familiar with this most peculiar man- 
ner of termination of the sensory nerves. 
How do the millions of other simple sensory nerve fila- 
ments terminate ? We now raise this question. 
Unfortunately, we know but little concerning this at the 
present time. Much has been stated concerning the terminal 
plexuses of the finest nerve fibres, in the frog as well as in 
mammals. 
It is, furthermore, settled that occasionally the terminal 
filaments of the sensory nerves pass into the epithelium and 
end in it. We have already become familiar above (p. 207) 
with the most beautiful example of this kind, in the cornea of 
the eye (Fig. 36). The primitive fibrillse here run out between 
the epithelial cells. » 
Others speak of a penetration of these filaments into the 
cells, and of a termination in the nucleolus ; thus Hensen 
concerning the skin of the frog, Lipmann concerning the 
posterior corneal epithelium of the same animal. 
Other cutaneous nerves appear finally in the form of fine 
non-medullated filaments, which terminate in small cells, 
0.0088 to 0.0033 mm. in size, embedded in the human 
rete Malpighii ; a portion of them may also pass further 
downwards. They have been called Langerhans’ corpus- 
cles. 
Something similar has been subsequently observed in quite 
different mucous membranes, where these Langerhans’ struc- 214 
TWENTIETH LECTURE. 
tures have sometimes been met with, and sometimes also not 
found. 
The dental nerves appear to be peculiarly constituted (Boll) 
We have long been familiar with medullated nerve tubes, 
0.0067 to 0.0038 mm. in diameter, situated in the parietes of 
the dental sac. They form below an elongated nerve plexus. 
From the dichotomous separation of these nerve tubes 
arise innumerable very fine primitive fibrillae. They press 
through the covering of the odontoblasts (p. 75), reach the 
inner surface of the dentine, and probably penetrate the den- 
tinal tubules. The latter have, according to this, a double 
variety of contents, one part being the filamentous processes 
of the odontoblasts, and then the remains of these nervous 
filaments. The sensitiveness of the dentine has also been 
long known by the dentists. TWENTY-FIRST LECTURE. 
THE CENTRAL ORGANS OF THE NERVOUS SYSTEM.—THE 
GANGLIA AND THE SPINAL CORD. 
WHEREVER the ganglion cells accumulate, the formation of 
a central nerve organ commences. Therefore, from these 
smallest cells, only to be discovered by means of the micro- 
scope, up to the brain and spinal cord, with their immense, 
frequently combined, gray substances, proceeds a continuous 
series of developments. Our knowledge concerning the latter 
is at present, however, very insufficient; methods for manag- 
ing such complicated structures are wanting. 
Let us discuss, first, the peripheral ganglia or nerve nodules 
(Fig. 185). A connective-tissue envelope, a modified peri- 
neurium, surrounds the organ. It sends into the interior, 
fenestrated, leaf-like processes, the bearers of a tolerably de- 
veloped capillary net-work. 
The irregular and also con- 
nected cavities are filled with 
ganglion cells [d, e, /), placed 
close to each other, and in- 
vested by connective tissue. 
Between them run isolated 
nerve fibres or bundles of the 
same. At an earlier period 
it was believed that both these 
elements, the cellular and the 
fibrous, merely lay alongside 
of each other. At that time 
they distinguished penetrat- 
ing primitive fibres, which 
passed for the most part in 
bundles and straight through 
the nodules, and circumgyrating, which passed singly, with 
Fig. 185.—A sympathetic ganglion of the 
mammalial animal (diagramatic) ; a, b, c, the 
nerve trunks ; d, multipolar cells ; d*, one 
with a dividing nerve fibre ; e, unipolar; f 
apolar. 216 
TWENTY-FIRST LECTURE. 
manifold turnings, through the narrow spaces between the 
ganglion bodies, to subsequently reassociate themselves with 
the out-coming (single or multiple) nerve trunks. 
This arrangement does in reality (combined, it is true, 
with transitions) occur. We already know that the ganglion 
cell enters into communication with the nerve fibre (Fig. 175). 
In the ganglia of fishes and amphibia, the connective tissue 
is weakly developed ; the elements are, therefore, more 
readily isolated, still we have by no means any satisfactory 
results to report. The ganglia of higher animals are, how- 
ever, permeated by an exuberant fulness of firm connective 
tissue ; picking them apart yields us, unfortunately, only the 
fragments of the nervous contents. 
The requirements of the physiologist, who desires an in- 
sight, cannot at present suffice here for the microscopist, and, 
indeed, should not. For he would have to combine an im- 
perfect perception with hypotheses into an abstract image. 
For the coming races of men, the light of a better intelli- 
gence will be kindled at some future day. We grope about 
in the dark. 
Let us take a spinal ganglion of the fish, with its ganglion 
bodies. The greater portion of the latter are certainly bi- 
polar, that is, the cell is interpolated into the course of a 
broad sensory fibre of the spinal cord (Fig. 175, a). 
Since the elements of the sympathetic in fishes exhibit 
narrow medullated nerve fibres, we should accordingly de- 
clare the nerve fibres connected with ganglion bodies to be 
sensory elements of this division of the nervous system (b). 
One meets in our ganglia, furthermore, with smaller uni 
polar cells (c). Their narrow, sympathetic nerve fibre passes 
downwards and spreads out peripherically. The ganglion 
might, with these latter constituents, be one of the many 
centres of the sympathetic, like all the remaining ganglia of 
the fish’s body. 
Even in the frog, however, the matter becomes much more 
difficult. The presence of bipolar ganglion cells, interpo- 
lated into the course of a sensory fibre of the spinal cord, CENTRAL ORGANS OF NERVOUS SYSTEM. 
217 
is not determined with certainty ; neither is that of sympa- 
thetic bipolar ganglion cells. We are only familiar here with 
the unipolar cells with the descending, narrow, sympathetic 
nerve fibres. 
We know next to nothing, at present, about the similar 
nerve ganglia of the mammalial animal. 
Let us now pass to the sympathetic in the sense of the 
older anatomy. In the frog we can, at least, demonstrate 
unipolar ganglion cells. Others give us the impression of 
the apolar, whether rightly or not we leave undecided. 
Sixteen years ago, by the aid of Remak’s investigations, I 
drew the diagramatic figure 185, as a sympathetic ganglion. 
I repeat the figure here ; not because I regard it as complete 
(I am far removed from this), but because I am unable to 
present any better substitute in a more reliable manner. So 
slight has been the advance made during this long epoch ! 
Remak, that excellent observer, here met with multipolar 
ganglion cells. He attributed to them 3to 12 processes, 
which might be increased two or threefold by further ramifi- 
cations. They are said to at last become nerve tubes. Ac- 
cording to what we have learned above (Fig. 176) concerning 
the protoplasma and axis-cylinder processes of the ganglion 
cells, this cannot very well be correct. Repeated, more accu- 
rate investigations appear, in consequence, to be urgently 
necessary ; but who will make them ? 
With the larger sympathetic ganglia are associated a num- 
ber of smaller and smallest ones. This is the case in the 
ciliary muscle and in the choroid of the eye, in the expan- 
sions of the glosso-pharyngeal nerve passing to the oesopha- 
gus, in the lingual branches of the ramus lingualis of the 
fifth nerve. We also meet with similar small ganglionic en- 
largements in the walls of the larynx, and of the bronchi, 
in the interior of the lungs, and in the heart muscles. 
In the walls of the digestive apparatus there is a developed 
plexus of ganglia belonging, in the first place, to the sub- 
mucous tissue ; then there occurs in the muscles, between 
the longitudinal and annular layers of fibres, the plexus my- 218 
TWENTY-FIRST LECTURE. 
entericus, discovered by Auerbach, with its manifoldly mul- 
tipolar cells (L. Gerlach). The former plexus appears to be 
of a motory and sensory constitution ; the latter possesses 
predominantly the former nature. Such small ganglia are 
also encountered in the urinary and generative organs, as 
well as in glandular structures. Our Fig. 186, a ganglion 
Fig. 186.—Ganglion from the submucous plexus of the small intestine of an infant; a. ganglion 
with the ganglion cells; b, c, nerve trunk, with the pale, nucleated fibres : 2, a nerve trunk from a 
boy five years old. 
from the submucous plexus, may represent this. At a, we 
perceive the ganglion with the non-medullated, nucleated 
fibres ; at 2, a similar nerve trunk is isolated. 
Let us now turn to the cerebro-spinal system, to the spinal 
cord and brain. 
The spinal cord (Fig. 187) presents a cylindrical cord, con- 
sisting of an inner gray and an outer wdrite substance. Both 
form connected layers of substance throughout the entire 
length of the spinal cord. The gray substance forms aa 
irregular Latin H, in transverse sections. One distinguishes 
accordingly, anterior {d) and posterior [e) horns. The latter 
are then invested by Rolando’s “ gelatinous ” substance. In 
the centre of the whole we perceive, lined with cylinder cells, 
the axis canal {a), the last remains of a much wider cavity 
in the earlier foetal period. Two deep furrows, the fissura 
anterior {b) and posterior (c), cut nearly into the centre. In CENTRAL ORGANS OF NERVOUS SYSTEM. 
219 
front of this exists a crossing of nervous fibres, the commis- 
sura anterior {/) ; behind the axis canal we meet with a pre- 
dominantly connective-tissue mass, the so-called commissura 
posterior (h), The white investing substance presents the 
Fig. 187.—Transverse section through the lower half of the human spinal cord ; a, central 
canal ; 6, fissura anterior ; c, fissura posterior; d, anterior horn, with the considerable ganglion 
cells ; e, posterior horn, with the smaller ones ; f anterior white commissure ; g, frame-work sub- 
stance around the central canal; h, posterior gray commissure ; i, bundles of the anterior, and k, 
posterior spinal roots ; I, anterior, m, lateral, and n, posterior column. 
anterior column (/), the lateral (in), and the posterior («), 
consisting essentially of longitudinally arranged medullated 
nerve fibres. At the margin of the anterior and lateral col- 
umns, the motory roots of the spinal nerves pass through to 
the gray substance (i) ; between the middle and posterior 
systems of columns we perceive, shining through, the poste- 
rior sensory roots of these nerves (k). , 
A delicate connective tissue permeates the whole organ as 
a supporting and frame-work substance. It is the bearer of 
the nutritive system of blood-vessels. 
Let us first discuss this connective-tissue substratum. 220 
TWENTY-FIRST LECTURE. 
Oar supporting substance comes forward most purely in 
the vicinity of the axis canal; externally, toward the periph- 
ery of the gray substance, it becomes profusely permeated 
by nervous elements. It has been given the name of the 
neuroglia (Virchow). 
As we here naturally pass over the subordinate varieties, 
we will characterize this supporting tissue as a very delicate 
and extremely decomposable, fine reti- 
cular substance, with nuclei at the 
nodal points, so that cell-bodies must 
be present here (Fig. 188). The fine 
clefts are permeated by a chaotic maze 
of the finest nerve fibrillae ; in the larger 
spaces are ganglion cells. 
Fig. 188.—Neuroglia from the 
gray substance of the human cen- 
tral nervous (cerebellum), 
with embedded nuclei. 
Proceeding further towards the peri- 
phery of the spinal cord, we arrive at 
the white columnar systems, and here the connective-tissue 
substratum has become more compact and firmer. Some- 
times appearing more homogeneous, sometimes more striated, 
and again containing nuclei in individual nodal points, it 
forms a system of septa, an incomplete one it is true, which 
surrounds the descending nerve fibres as a fenestrated system 
of sheaths (Fig. 170). Thicker, connective-tissue vascular 
lamellae radiate out to the pia mater which, as is known, sur- 
rounds the surface of the spinal cord. This envelope finally 
sends folds with considerable blood-vessels into the anterior 
and posterior longitudinal clefts of the organ. 
The vascular net-works of the white substance, which main- 
tain a radial arrangement, are scanty and large-meshed. The 
capillary net-work of the gray substance is compact and 
narrow-meshed ; the latter is very vascular. 
Let us now consider the nervous contents of the connective- 
tissue frame-work. 
The white cortical substance consists essentially of vertically 
arranged nerve tubes of 0.0029 UP to 0.009 mm. diameter. 
The thickest fibres are presented by the anterior columns ; 
the finest by the posterior, especially towards the fissura pos CENTRAL ORGANS OF NERVOUS SYSTEM. 
221 
terior. The latter here forms the wedge-shaped or Golfs 
column. The inner nerve fibres, that is, those which are 
adjacent to the gray cornua, are also usually finer than their 
external associates. 
These longitudinally arranged fibrous masses are permeated 
by the bundles of the transversely and obliquely departing 
and entering roots of the spinal cord. 
The anterior or motory roots of the latter reach the anterior 
cornu (Fig. 187, i), and radiate into the latter in every direc- 
tion in a brush-like form. 
Let us now examine this gray substance of the anterior 
cornu. 1 
Here (d) lie groups of large multipolar ganglion cells, after 
the manner of our Fig. 176. The so-called axis-cylinder pro- 
cess (a) is the commencement of the motory nerve fibre, its 
axis cylinder. This is settled, according to my experience, 
although it has recently been doubted (Golgi). It is certainly 
not easy to observe, but it is and remains the best portion of 
our present knowledge concerning the origin of nervous ele- 
ments in this so infinitely complicated organ. 
If we turn further backwards towards the posterior cornu, 
we meet with, for the most part, smaller, not rarely spindle- 
shaped cells (/), with the same duplicity of systems of pro- 
cesses. At the base of the posterior cornu, further inwards, 
there is also a group of smaller rounded ganglion cells. 
These are the Clarke’s columns. 
The cellular elements of the posterior cornu have generally 
been considered as sensory, and brought into relation with 
the origin of the fibres of the posterior roots ; still this cannot 
be demonstrated. 
We now encounter the question: What becomes of the 
second system of processes (Fig. 176), the so-called proto- 
plasma processes ? 
Their lateral finest filaments (b), like the terminal radiations 
of the branch itself, were considered by Deiters, as we already 
knew, to be primitive nerve fibrillae. From them—and they 
might arise from different cells—an axis cylinder was said to TWENTY-FIRST LECTURE. 
222 
be at last composed, Gerlach subsequently came to a dif- 
ferent conclusion. According to him, the terminal ramifi- 
cations of this system of processes unite into a narrow, fine 
net-work, from which the nerve fibres arise by the combi- 
nation of the thinnest filaments. The last-mentioned investi- 
gator absolutely denies that the proper cells of the posterior 
cornu have axis-cylinder processes. A fundamental ana- 
tomical difference is, therefore, maintained for the motory and 
sensory cells. I trust neither the statements of Deiters or 
Gerlach. With the present accessories we can, unfortunately, 
obtain no certain result. Everything remains a conjecture. 
The manner of arrangement of the bundles of the posterior 
sensory root is, unfortunately, still more complicated than 
that of the anterior, and the fibres become considerably nar- 
rower on their entrance into the gray substance. Our knowl- 
edge is, accordingly, here still incomplete. 
The greater portion of the bundles of fibres appear to main- 
tain a chaotic course through the posterior columns, to later 
pass from the side into the convex part, or portion turned 
inwards, of the posterior cornu {k). The substantia gelatinosa 
Rolandi is here seen to be permeated by the finest nerve 
fibres. The latter are said to pass in part to the base of the 
posterior cornu, part of them reaching the Clarke’s columns. 
Furthermore, still other bundles of fibres pass over the latter, 
more in front. Bundles of sensory fibres may even enter 
both commissures. 
We now come to the question, what do the white longitu- 
dinally disposed systems of columns signify ? 
That they do not represent the bent fibrous masses of the 
toots of the spinal cord which pass to the brain, as was as- 
serted at an earlier epoch, requires no further discussion 
after what we have learned concerning these roots. 
According to the views of Deiters, these vertical bundles 
of white fibres come from one transverse plane of the gray 
substance to subsequently sink into another. The roots of 
the spinal cord terminated, therefore, in the ganglion cells, 
and the latter sent off, as a simplified continuation, these ver- CENTRAL ORGANS OF NERVOUS SYSTEM. 
223 
tical fibres of the white columnar system, These cell groups 
were accordingly a provisory centre. 
The further communications of the ganglion bodies, of the 
equivalent between each other, as well as of the motory with 
the sensory cells, are up to the present time veiled in the 
deepest obscurity. 
Let us mention, finally, in the uncertainty of our knowl- 
edge, the transverse commissures of the spinal cord. The 
anterior shows true nerve fibres in the most distinct manner. 
The bundles of the same arise from the gray substance of the 
one half (without our knowledge of the manner of their ori- 
gin), to ascend and descend and gain the fibrous mass of the 
anterior column at the other side. An endeavor has been 
made to deduce from this a total decussation of the motory 
tract of our organ. 
The posterior commissure also contains, together with con- 
nective-tissue constituents, bundles of fine nerve fibres. TWENTY-SECOND LECTURE. 
THE CENTRAL ORGANS OF THE NERVOUS SYSTEM, CON- 
TINUED.—THE MEDULLA OBLONGATA AND THE BRAIN. 
The spinal cord, as we learned, cannot be mastered with 
the present methods of investigation. 
It appears still more dubious with regard to the far more 
complicated medulla oblongata. , As with the subsequently 
to be mentioned brain, it is scarcely possible to here condense 
the existing, in part contradictory material, into a short sum- 
mary view. We limit ourselves, therefore, to a fragmentary 
discussion. 
The most recent investigations of this central structure 
were made by Deiters, of Bonn, and Meynert, of Vienna. 
The axis canal of the spinal cord opens in the medulla ob- 
longata, in a dorsal direction, into the sinus rhomboideus or 
calamus scriptorius, to continue forward as the fourth ventri- 
cle. By this means changes of position occur in the white 
columns, as well as the gray substance of the spinal cord. 
The anterior longitudinal fissure finally closes as the raphe. 
Large portions form anteriorly and inwardly, with their de- 
cussations, the pyramids, externally from these the (lower) 
corpora olivaria. Then follow externally the lateral columns 
and the corpus restiforme, that is, the wedge-shaped and del- 
icate columns (the latter is a continuation of Goll’s column, 
p. 221). 
In the direction of the brain, the pons Varolii rests upon the 
organ. As a connection with the cerebellum we have the 
crura cerebelli (with their two portions, the crura cerebelli ad 
medullam oblongatam and ad pontem). The connection with 
the cerebrum takes place through the peduncles of the brain. 
Finally, ten cerebral nerves arise from the medulla oblongata. 
The homogeneous connected gray substance here changes THE MEDULLA OBLONGATA AND BRAIN. 
225 
becoming permeated by bands of nerve fibres. This arrange- 
ment, the so-called formatio reticularis, gradually extends 
over nearly the whole medulla oblongata. 
Connected masses of gray substance form what haV'been 
called “ nuclei. ” A portion of these are the centres of escap- 
ing nerves ; in others, systems of fibres of the medulla ob- 
longata acquire a provisory termination, to become modified 
at these places, and subsequently pass further on with their 
derivatives. Among the latter, the so-called “specific nuclei,” 
are included the superior and inferior olivary bodies, the 
Deiters’ nucleus, the pyramidal nucleus, the ganglia post 
pyramidalia, the gray substances of the pons Varolii, and in 
further extension also, the corpus dentatum cerebelli, the 
gray masses of the crura cerebelli, and the greater portion of 
the eminentia quadrigeminae (Deiters). 
There is besides a transverse, arched and circular system 
of fibres, Arnold’s stratum zonale. 
In the formatio reticularis, as well as in the nuclei, we meet 
with ganglion cells of the most varied form, and in part of 
considerable size, with axis cylinder and protoplasma pro- 
cesses. In consequence of the penetration of the gray sub- 
stance into the funiculus gracilis, the floor of the fourth ventri- 
cle is almost exclusively formed of gray substance. The 
neuroglia which surrounded the axis canal of the spinal cord 
also undergoes a proliferous increase to subsequently form a 
considerable share of the walls of the aqueductus Sylvii, the 
third ventricle and the infundibulum. 
Now, how do the cerebral nerves arise from the medulla 
oblongata ? 
Deiters found here not only an anterior and a posterior 
centre of origin, as in the spinal cord, but also a third lateral 
one. The latter begins in this organ, at the anterior horn, 
and gradually acquires a mixed character. 
From it arise the accessorius, vagus, glosso-pharyngeus, 
facialis, acusticus and anterior trigeminus root. 
The sensory portion of the trigeminus is said to be derived 
from the posterior system of origin.. 226 
TWENTY-SECOND LECTURE. 
To the anterior roots of the spinal cord correspond, together 
with the hypoglossus, the nerves of the muscles of the eye ; 
the abducens, trochlearis and oculo-motorius. 
We cannot here enter further into the nerve nuclei. The 
centres of the hypoglossus and accessorius, with large multi- 
polar cells, are located furthest below. 
What becomes of the columns of the spinal cord within the 
medulla oblongata ? 
As we have already remarked, there can here be only a 
simplified continuation of the same. 
The anterior columns, passing to the side of the raphe, and 
displaced by the pyramids, may be followed far under the 
pons ; they are perforated by zonal fibres and gray substance, 
and finally, after the intercalation of ganglion cells, are still 
finely fibrillated. They appear to pass towards the cerebrum 
and cerebellum. . 
The lateral columns, forming the funiculus lateralis, reach, 
in part, the cerebrum. Their fibres are interrupted and dis- 
placed by the formatio reticularis, the Deiter’s nucleus, the 
inferior, accessory and superior olivary bodies. 
The posterior columns of the spinal cord do not, as we 
formerly conjectured, continue as the crura cerebelli ad 
medullam oblongatam directly into the cerebellum. Their 
processes in the medulla oblongata, the funiculus gracilis 
and cuneatus, are interrupted by intruded gray substance, 
the so-called ganglia post pyramidalia, and here cease as 
white fibrous masses. The gray continuations pass in 
part into these crura, in part (crossed and uncrossed) to 
the corpora olivia, and, finally, increased in size, to the pyra- 
mids. 
The pyramids commence with fine nerve fibres from the foi 
matio reticularis. With them are associated nerve fibres 
from the lateral and posterior columns. After the decussa- 
tion they pass in the pedunculi cerebri to the cerebrum, 
to probably reach the corpora striata, the nucleus lenticularis, 
and even the cortex of the hemispheres. 
The inferior corpora olivaria, in man, contain in their gray THE MEDULLA OBLONGATA AND BRAIN. 
substance a peculiarly folded leaf (corpus dentatum) which 
encloses white substance. 
The former substance contains small yellowish pigmented 
ganglion cells. A system of fibres arising from the olivary 
bodies is said to pass in part to the cerebellum, in part to the 
cerebrum. 
The crura cerebelli ad medullam oblongatam form in part 
processes of the medulla oblongata into the cerebellum ; they 
probably also send motory fibres from the latter in a down- 
ward direction to the medulla oblongata (Meynert). 
The crura cerebelli ad pontem are of an essentially different 
nature. They form in the first place a transverse commissure 
system between both the cerebellar hemispheres ; then they 
conduct fibrous masses, arising from the cerebellum, up to the 
cerebrum. 
The cerebellum can, however, absorb only a portion of the 
fibrous masses which ascend from below, and subsequently, 
after the passage of gray substances, sends them off trans- 
formed to the cerebrum. It is merely—as we must at present 
assume—an accessory conducting apparatus; for the other 
fibrous masses ascend directly through the pedunculi cerebri. 
The blood-vessels of the medulla oblongata remind us of 
those of the spinal cord. 
We know very little indeed concerning the cerebellum. We 
have already mentioned two of its crura ; a third commissure, 
the crura cerebelli ad corpora quadrigemina, connects the 
organ with the cerebrum. 
The cerebellum consists essentially of aggregations of white 
nerve substance, with fibres 0.0029 to 0.0902 mm. broad. 
Gray substance occurs in the roof of the fourth ventricle, in 
the corpus dentatum, in Stilling’s so-called roof nucleus, and 
as the external covering layer of the convolutions. 
In the folded gray plate of the corpus dentatum lie ganglion 
cells in a threefold stratum. We pass over the entirely un- 
certain course of the fibres. 
The structure of the cortical layer is interesting. It presents 
an internal rust-brown, and an external gray stratum. 228 
TWENTY-SECOND LECTURE. 
The former, I to 0.5 mm. thick, has crowded and stratified 
granules, that is nucleus like structures or, more properly 
said, small cells of 0.0067 mm. They remind one of the sub- 
sequently to be described elements of the retina of the eye, 
and, like the latter, give off the finest filaments from both 
poles (Fig. 189, below). 
Whether these granules of the cerebellum are of a nervous 
or connective-tissue nature is still undecided. 
The gray stratum contains a simple layer of large remark- 
able ganglion cells. Purkinje described them forty years ago. 
They send downwards an axis- 
cylinder process (d), and up- 
wards or outwards a system 
of antler-like ramified proto- 
plasma processes (c). The 
finest terminal branches of the 
latter (Hadlich) are said to 
bend over (a) in a loop-like 
manner at the surface, and 
return to the rust-colored 
layer. 
Connective-tissue support- 
ing fibres (r) form a special 
boundary layer at the surface. 
The pcdunculi cerebri re- 
ceive ascending masses of 
fibres from the medulla ob- 
longata and cerebellum ; they 
also receive others which de- 
scend from the cerebrum to 
the medulla oblongata. Their 
superior rounded portion 
(cap) is separated from the 
inferior semilunar (basis) por- 
tion by a dark substance. 
Black pigmented multipolar ganglion cells occur here. 
The so-called cerebral ganglia consist of the corpora 
Fig. 189.—The cortex of the human cerebellum 
in perpendicular section. Two Purkinje’s cells, 
beneath them a portion of the granular layer; d, 
the lower, c. the upper process of the former. At 
r, supporting fibres ; at a, the loop-shaped 
bends of the finest cell processes; c, tangential 
thinnest nerve fibres. THE MEDULLA OBLONGATA AND BRALN. 
229 
quadrigemina, the thalamus opticus, the corpus striatum, and 
the nucleus dentatus. They are only imperfectly known. 
The crura cerebelli ad corpora quadrigemina simply pass 
off beneath the corpora quadrigemina. They pass to the 
hemispheres of the cerebrum ; they are in truth the crura 
cerebelli ad cerebrum. The histological acquisitions in this 
department remain, up to the present time, scarcely worth 
mentioning. Small cells, larger multipolar, and spindle- 
shaped ganglion bodies have been met with here. 
The thalamus opticus has likewise yielded nothing further 
in a histological direction. A portion of the optic nerve 
radiates into it, as well as into the anterior corpora quadri- 
gemina. The cap of the crus cerebri is intimately connected 
with the thalamus (Meynert). 
Fibrous masses of the basal portions of the cerebral 
peduncles are said to terminate in the corpus striatum and 
nucleus dentatus. Their finer structure likewise requires more 
accurate investigation. 
The so-called rod corona fibres, in their great development 
in man, are probably connected with his mental abilities. 
They consist in the first place of fibrous masses which, 
without having been in contact with the cerebral ganglia, are 
conducted upwards through the peduncle of the brain, and 
secondly of the radiations of the ganglionic substances. 
The trabeculae and anterior commissure are probably true 
simple commissures, which have nothing to do with either 
the crura cerebri or these rod-corona fibres. 
The white substance of the hemispheres consists essentially 
of medullated nerve fibers, measuring 0.0026 to 0.0067 mm. 
The gray cortical stratum of the hemispheres may be 
reduced to a number of single layers. They may be assumed 
to be six in number. 
Smaller cells occur in the more superficial layers. In the 
fourth layer one meets with considerable many rayed gan- 
glion bodies, measuring 0.025 to 0.040 mm. One of their 
processes is usually directed towards the surface, and three 
others inwards. The central one of these three basal pn> 230 
TWENTY-SECOND LECTURE. 
longations is an axis-cylinder process. Then two other cell 
layers follow. This is all that we know at present. 
Here, also, Gerlach assumes the presence of a very fine 
problematical nerve reticulum, such as we have already 
mentioned at page 222, in connection with the gray substance 
of the spinal cord. 
At the apex of the occipital portion, in the vicinity of the 
so-called sulcus hippocampi, the cortical stratum becomes 
still more complicated. The cornu ammonis also has its 
peculiarities. 
A remarkable, although in man considerably stunted por- 
tion, of the cerebral substance is the bulbus olfactorius. The 
cavity, which is lined with ciliated epithelium, presents pa- 
rietes consisting of internal white, and external gray substance. 
The former contains the root bundles, which are two in 
number, a thicker external one, coming in part from the 
anterior inferior cerebral convolution, in part from the corpus 
callosum, and a thinner internal one, which is thought to be 
derived from the corpus striatum, the chiasma nervorum opti- 
corum and the pedunculus cerebri. 
In a strongly developed neuroglia, we meet, in an inward 
direction, with the longitudinally arranged rnedullated root 
fibers, and then, connected with these, a nerve plexus of very 
fine tubes. We finally meet with granules and multipolar 
ganglion cells. 
Below, or rather externally, the gray substance becomes 
strongly altered. One here meets with globular balls of a 
granular substance with nuclei (glomeruli nervi olfactorii, ac- 
cording to Meynert). 
From these lumps are developed the pale nucleated fibres 
of the special olfactory nerves. 
The apophysis cerebri has already been discussed, so far as 
its anterior portion is concerned, in connection with the blood- 
vascular glands (page 126) ; the posterior consists of gray 
cerebral substance. 
The so-called Pineal gland, conarium, has long been remark- 
able on account of its calcareous concretions. In its connec- THE MEDULLA OBLONGATA AND BE AIN. 
231 
tive-tissue substratum it presents rounded cavities which are 
sometimes more and sometimes less complete. We here 
meet with two kinds of cells ; large stellate ones, forming a 
net-work, and smaller ones. In the adult, the latter have pro- 
cesses, in the new-bo.rn child, however, they were at one time 
without these (Bizzozero). 
The blood-vessels of the brain, similar to those of the spinal 
cord, form very compact vascular net-works in the gray sub- 
stance ; in the white substance the meshes are much wider. 
The arrangement in the individual portions of the brain is 
often, however, very characteristic and elegant, as for ex- 
ample in the olfactory lobules, the corpus striatum and the 
cortex of the cerebellum. We cannot here enter into details. 
We have finally to mention the membranes of the cerebro- 
spinal system. 
The dura mater (page 57) of the brain is intimately con- 
nected with the periosteum of the cranial cavity. Around 
the spinal cord, on . the contrary, with the exception of the 
anterior side, it forms a freely suspended tube. The spaces 
of the vertebral canal are filled by connective tissue with fat 
cells. The vascularity is very moderate in the cerebral por- 
tion, and very slight in the spinal portion. The lymphatics of 
the dura mater are very abundant. The dura mater of the 
brain presents nerves of unknown termination. 
The dura mater and arachnoid leave a system of cavities, 
the subdural space (Key and Retzius), between them. 
The latter membrane, the arachnoid, is very poor in blood- 
vessels, is thin, delicate and fenestrated in a reticular manner. 
Over the spinal cord it is separated from the lowermost 
tunic of the pia mater, with the exception of connecting fila- 
ments of connective tissue. There is thus formed a consider- 
able subarachnoidal space. Over the brain, on the contrary, 
the arachnoid and pia mater are for the greater part coalesced 
with each other, and spaces occur only in those places where 
the former membrane stretches over the furrows of the sur- 
face in a bridge-like manner, while the pia mater descends to 
the bottom. The considerable subarachnoidal space of the 232 
TWENTY-SECOND LECTURE. 
spinal cord is therefore broken up into numerous smaller 
spaces. 
The connective-tissue bundles of the arachnoid are invested 
in a sheath-like manner by the familiar flat stellate endothe- 
lial cells (Key and Retzius). The latter also fill the connec- 
tive-tissue spaces, and after treatment with nitrate of silver, 
show the familiar areolations. 
The connected cavities contain a very watery fluid, the 
cerebro-spinal fluid. 
The pia mater likewise appears thin and delicate, with 
similar flat connective-tissue cells. It is characterized, how- 
ever, by its immense wealth of blood-vessels ; it is, also, by 
no means poor in lymphatics. Its numerous nerves are 
probably designed (at least principally) for the vascular 
walls. 
Our pia mater covers, in close apposition, the nervous 
masses of the central organ. His, it is true, formerly as- 
sumed that there was here an epispinal and epicerebral cavity. 
This does not exist, however ; it is an artefact. More recent 
observations teach that the blood-vessels entering the ner- 
vous substance have connective-tissue adventitia, only loosely 
spread over their so-called tunica media, and that they thus 
open into the subarachnoidal space with funnel-shaped dila- 
tations of the outer layers. They may be artificially injected 
from the subarachnoidal space far into the interior of the 
brain. 
The nerve trunks and ganglia have, according to Key and 
Retzius, the same external dural and internal arachnoidal 
sheath, as well as subarachnoidal spaces. The injection also 
succeeds here. All this, like the serous sacs, belongs to the 
lymphatic apparatus. 
The name of the Pacchionian “glands” or granulations 
has been given to small rounded connective-tis-.ue masses 
which occur especially at the upper longitudinal venous si- 
nuses of the brain. 
According to the two frequently mentioned Swedish in- 
vestigators, the just mentioned structures form transition THE MEDULLA OBLONGATA AND BRAIN. 
portes of these lymphatic spaces into the venous blood cur- 
rent. This naturally requires further confirmation. 
The venous plexus, the plexus choroidei, contains an im- 
mense vascular convolution in undeveloped connective tissue. 
Its covering is formed by a low cubical epithelium, which runs 
downwards into numerous points. TWENTY-THIRD LECTURE. 
THE ORGANS OF SENSE.—THE SKIN; THE GUSTATORY, OL- 
FACTORY AND AUDITORY APPARATUS. 
The human external integument presents the apparatus of 
feeling and touch. The tongue alone takes a further share 
in the function of this sense. 
The course of our lectures required that we should discuss 
the individual portions of the general protecting organ in 
different places. We mentioned the epidermis at p. 32, the 
corium at p. 58, the subcutaneous cellular tissue at p. 56, the 
nails and hair at pp. 36 and 37, The tactile nerves were 
alluded to at p. 211, the simple sensory cutaneous nerves at 
p. 212. Additional information may also be obtained from 
our Fig. 183. 
We will also add something here. The corium is thin- 
nest over the eyelids, the prepuce, the glans penis and inner 
surface of the labia majora; it is thickest over the back, 
the palm of the hand, the buttocks and sole of the foot, 
which are the seat of the greatest pressure. The thickness 
of the epidermis (p. 32) varies still more. We have already 
mentioned that the color of the skin of Europeans is deter- 
mined by the latter. 
That the corium is uncommonly vascular is known to 
everybody. In it occurs a highly developed net-work of ca- 
pillary vessels, 0.0074 to 0.01 [3 mm. broad, which send loops 
into by far the greater proportion of the cutaneous papillae. 
We meet with more independent portions of the vascular 
system around the flat lobules of the panniculus adiposus, 
the hair follicles and the bodies of the sudoriparous glands 
(Tomsa). 
Lymphatics, which are said to possess independent parietes, 
are abundant in the corium (Teichmann and J. Neumann), THE ORGANS OF SENSE. 
235 
forming a double flat net-work. They penetrate the papillae 
as culs-de-sac and loops, so that one is reminded of relative 
conditions of the intestinal villi (p. 98). Great variations 
prevail, however, in the individual portions of the skin. 
We have, finally, to discuss the glands of the skin, which 
have thus far been only cursorily mentioned. 
The more important ones are the convoluted, sudoriparous 
glands (Fig. 183, £*, 190, a, b). They remain small, with the 
exception of those of the axilla, where they acquire enor- 
mous dimensions and 
more fatty contents. 
Their convoluted 
gland body is more 
rarely situated in the 
depths of the corium, 
but, as a rule, in the 
subcutaneous cellular 
tissue. The excre- 
tory duct (e, f), some- 
times shorter, some- 
times longer, accord- 
ing to the thickness 
of the part, is slightly 
spiral, and terminates 
in the palm of the 
hand and sole of the 
foot, by way of ex- 
ception, with funnel-shaped dilatations. It has a double 
layer of epithelium. The walls of the convoluted gland 
body present smooth muscles, which apparently increase with 
the size of the gland body. 
Fig. 190.—A human sudoriparous gland ; a, the coil, sur- 
rounded by the commencement of venous vessels ; b, the 
excretory canal; c, the basketrlike capillary plexus, with the 
arterial trunk. 
The gland cells form a simple layer of low, cubical elements. 
An elegant wicker-work of capillary vessels (c) surrounds the 
secretory portion. 
The human skin contains these sudoriparous glands, with 
few exceptions, but they are quite variable as to number and 
position. The older Krause—he was a thorough observer— 236 
TWENTY- THIRD L E CTURE. 
once computed that our body contains nearly two and a half 
millions of these convoluted glands. 
Considerable sudoriparous glands also surround the anus 
(Gay). 
In the external auditory canal, these convoluted glands ac- 
quire a shorter excretory duct, which is no longer convoluted, 
and their secretion is fatty and brownish-yellow. These are 
the glandulae ceruminosae. 
Let us now investigate the submucous follicles, the glandu- 
lae sebaceae of the older anatomists. Their secretion, an es- 
sentially fatty, thickish substance, we have already become 
familiar with in a preceding lecture (p. 132). 
They form racemose organs (Fig. 191), which are some- 
times smaller and more simple, sometimes more voluminous 
and complicated in their structure. They are situated in the 
corium, and are, for the most part, 
but by no means unexceptionally, 
confined to the vicinity of the hair, 
into the sac of which (p. 37) they ex- 
crete the tough, fat substance. We 
also meet with smaller examples of 
our organ connected with thick hairs, 
and larger glands with lanugo hairs. 
At last these open freely externally, 
without the intermediation of a hair 
sac. Their size varies considerably, 
from 0.2 to 1 mm. and more. The 
vesicles differ considerably in dimen- 
sions and form. Young, striated 
connective tissue here replaces the so-called membrana pro- 
pria. 
Fig. 191.—A sebaceous follicle; 
a, the gland vesicle ; b, the excre- 
tory duct; c, the sac of a lanugo 
hair; d, the shaft of the latter. 
Passing now to the gustatory organ, we have again to com- 
bine what has been previously mentioned. Even at that 
time (p. 141) we remarked that the posterior portion of the 
tongue, upwards in the long known papillae circumvallatse, 
and laterally in the subsequently rediscovered papillae foliatae, 
contained terminal fibres of the glosso-pharyngeus serving as THE ORGANS OF SENSE. 
237 
nerves, of taste. Both systems of papillae occur in man, 
though the foliatae are subject to many individual variations. 
The change is great in mammalial animals. Cats have no 
papillae foliatae ; Guinea-pigs have no circumvallatae. 
We have now to examine the above nerve terminations 
more closely. They are more recent histological acquisitions 
(Loven, Schwalbe, and others). Complicated cup or bud- 
shaped organs, the so-called gustatory buds, have been met 
with here. Large 
numbers of them oc- 
cur, as is distinctly 
represented in our 
Fig. 192, in the lateral 
walls of the papillae 
themselves, and in the 
fig. 192.—Vertical section through the so-called papilla 
foliata of the rabbit. 
inner surface of the surrounding 
mounds of mucous membrane. 
The gustatory bud (about 0.08 
mm. high in man) is an epithelial 
structure. It (Fig. 193) permeates 
the entire thickness of this layer, 
and its points lie free. 
We meet, in the first place, 
with flattened, lancet-shaped, 
pointed parietal cells (a). They 
stand like the staves of a barrel. 
Above, possibly running out into 
the finest ciliae, they surround a 
small opening. 
These supporting or cover cells 
(2 a) ensheath an inner cell forma- 
tion, belonging to the axis portion 
of the gustatory bud, the rod cell, 
or, as it has also (hypothetically, 
it is true) been called, the gusta- 
torj’’ cell (2 b). 
Fig. 193.—r.» Gustatory bud of the 
rabbit; 2a, cover cells ; 2b, rod cells ; 
2 c, a rod cell with a fine terminal fila- 
ment. 
Above, there is a sort of styliform or rod-shaped process 238 
TWENTY-THIRD LECTURE. 
(of irregular form, it is true) ; below, there is a filamentous 
process. It is conjectured that the latter passes over as an 
axis cylinder or primitive fibrilla (?) into the gustatory nerve 
fibres, which run beneath the gustatory bud, and, there- 
fore, that the gustatory cells may be terminal nerve structures. 
No one has yet seen this, however. We shall first appreciate 
the consequences subsequently, at the olfactory, auditory, and 
optic nerves. The circumstance is interesting that so-called 
mucous glandules (p. 141) occur in both varieties of papillae 
(von Exner). 
Accurate facts are wanting concerning the nerve termina- 
tions in the other papillae of the tongue. 
The human olfactory apparatus consists of a relatively 
small part, which contains the termination of the specific nerve 
of sense. This is the soft parts over the upper portion of the 
septum, the upper and a portion of the middle turbinated 
bone. The mucous membrane, which is here yellowish or 
brownish, bears the appropriate name of the regio olfactoria. 
All the remainder, the lower divisions of both main cavities, 
as well as the three adjacent cavities, are unimportant acces- 
sory parts, as has also been long since taught by compara- 
tive anatomy. 
The latter division is lined by a very vascular mucous 
membrane having ciliated cells (the Schneiderian membrane). 
It contains an immense wealth of serous racemose glands 
(p. 142). The mucous membrane is thinner in the accessory 
cavities, and the glands begin to disappear. 
We have no intimate knowledge of the terminations of the 
sensory nerves of the latter parts. 
Let us now return to the most essential parts, and exam- 
ine more closely the structure of the regio olfactoria (Fig. 
194). 
The region bordering on the Schneiderian mucous mem- 
brane, which therefore is, unprovided with olfactory fibres, 
presents the old ciliated covering and the old serous glands. 
Here, however, it is different. Bowman’s gland tubes appear 
in the mucous membrane, with yellowish cells. A thickened THE ORGANS OF SENSE. 
239 
(as a rule) non-ciliated epithelial mass finally covers the 
olfactory region. 
Let us first examine this epi- 
thelium. 
We here meet with two differ- 
ent elements. Firstly (a), long 
cylindrical cells (2 a). Their body 
contains yellowish granules and, 
in connection with the Bowman’s 
glands, causes the mentioned 
color of our locality. The lank 
non-ciliated cylinder sends down- 
wards a thin process which 
becomes divided. By the union 
of such systems of processes a 
regular horizontal net-work is 
formed in the connective tissue 
of the mucous membrane. 
The cells just described have 
nothing at all ’ to do with the 
nerve termination. They are a 
modified, but indifferent epithe- 
lium. ■ 
Fir. 194.—1. Cells of the regio olfac- 
toria of the frog ; a, an epithelial cell, 
terminating below in a ramified process ; 
J>, olfactory cells with the descending fila- 
ment ; d, the peripheral rod, c, and the 
long vibratile cilite. e ; 2, cells from the 
same region of man. The references the 
same, only short projections, e, occur 
(as artefacts) on the rods : 3, fibres of 
the olfactory nerve from the dog; at a 
dividing into h.ir fibrillae. 
Between them, however, there 
appears a second cell formation, 
the terminal structure of the olfac- 
tory nerve, the olfactory cell (b) ; at least, it is at present 
thus called, and with probability. Sometimes higher, some- 
times more deeply situated, we meet with a spindle-shaped 
cell body (i, 2, b). Below (1,2, d) the latter gives off an 
exceedingly thin filamentous process. It presents, with cer- 
tain treatment, small varicosities, like a primitive fibrilla of 
the nerve fibre (p. 196). At the upper pole, our spindle 
cell sends off a broader, smooth rod (1, 2, c), 0.0018 to 
0.0009 mm. wide. Ascending between the epithelial cylin- 
ders, it reaches the surface of the parts. 
In many animals, the terminal surface of the rod has TWENTY-THIRD LECTURE. 
single or multiple long cilise, as for example in the frog 
(i, e). 
The olfactory nerve —we are already 
familiar with its pale primitive fibres (Fig. 
194, 3, Fig. 195,/) from p. 196—gives off 
branches as it ascends to the cell layer of 
the regio olfactoria. The axis cylinder (Fig. 
195, e) proves to be finely striated. At last, 
after losing their sheath, the primitive or 
axis-cylinder fibrillae radiate upwards in a 
brush-like manner, as exceedingly thin vari- 
cose filaments {d). It is assumed that they 
are connected with the descending, similarly 
constituted finest processes of the “ olfac- 
tory cells ” (F). 
This theory proceeded from M. Schultze. 
The eminent investigator—he has, unfortu- 
nately, been prematurely torn from us—could 
not, however, bring forward a forcible proof 
here, any more than with regard to the other 
nerves of sense, after years of arduous hon- 
est labor. One cannot avoid certain con- 
clusions, therefore, that by the aid of im- 
proved methods, the matter may subse- 
quently become quite different. However, 
this is my subjective view. 
Fig. 195.—Probable 
termination of the olfac- 
tory nerve in the pike; a, 
olfactory cells ; b, rods ; 
c. lower varicose fila- 
ments ; e, axis fibrillae in 
the sheath f; d, spread- 
ing out of these ; at— 
wanting connection with 
the same fibrillae, c. 
Exner has more recently denied the differ- 
ence between the epithelial and olfactory 
cells. In contradistinction to him, Von 
Brunn has subsequently subscribed to the 
older view of Schultze. Brunn found over the regio olfac- 
toria a homogeneous boundary layer after the manner of 
the retina (see below). It has pores for the olfactory cells 
only. 
Let us now pass to the termination of the nervus acusticus, 
and thus enter the most difficult department of modern his- 
tology. THE ORGANS OF SENSE. 
241 
Let us fiist make a cursory sketch of the unessential acces- 
sory parts. 
The external ear presents the auricle and the external au- 
ditory canal. The former consists of elastic cartilage covered 
with rarefied corium. Its muscles are transversely striated. 
The ceruminous glands of the external auditory canal have 
been previously mentioned (p, 137). 
The drum membrane, or membrana tympani, a fibrous 
diaphragm, is clothed externally by a rarefied cuticular cover- 
ing, internally by the delicate mucous membrane of the tym- 
panic cavity with simple pavement epithelium. The vascular 
net-work of this membrane is complicated (Gerlach). Lym- 
phatics and nerves are likewise abundant. The termination 
of the latter is for the most part unknown. 
The entire “middle ear” is lined with a thin, vascular mu- 
cous membrane. The vascular net-work shows a considera- 
ble development of the venous portion. The nervus tym- 
panicus presents ganglia. The auditory ossicles consist of 
true compact bone substance ; their muscles are transversely 
striated. The Eustachian tubes have stratified ciliated epithe- 
lium and true mucous glandules. Their nerves show small 
ganglia. 
The internal ear, as is known, consists of the vestibule, 
the semi-circular canals and the cochlea. Vesicles filled with 
watery lymphatic fluid occupy the cavities. The auditory 
nerve terminates in the ampulla and in the saccules of the 
vestibule, and then on the spiral plate of the cochlea (ramus 
vestibuli and ramus cochleae). 
The vestibule and the inner surfaces of the semicircular 
canals are lined with periosteum. The fluid contained in 
their interior is called the perilymph. The periosteum and 
the tissue of the mucous membrane of the tympanic cavity 
combined, form the so-called membrana tympani secundaria. 
The parietes of the saccules of the vestibule (sacculus hemi- 
ellipticus and rotundus) and the membranous semicircular 
canals, together with their ampullae, present externally unde- 
veloped connective tissue, internally 1 hyaline nucleated layer 242 
TWENTY-THIRD LECTURE. 
(in the latter, canals with papilla-like incurvations), as well as 
a flattened epithelium. A second watery fluid, the endo- 
lymph, fills this system of cavities. 
The otoliths are enclosed within a special saccule, and form 
columnar-shaped crystals, measuring 0.009 to 0.002 mm. 
They consist of carbonate of 
lime, though they are said to 
have an organic basis. 
Let us pass to the expan- 
sion of the auditory nerve. 
The ampullae and sacculus 
hemi-ellipticus are supplied by 
the vestibular branch, the sac- 
culus rotundus, on the con- 
trary, by a branch of the 
cochlear nerve. It terminates 
in the duplicatures of the pa- 
rietes, that is at the entering 
angle of the same, the crista acustica. 
of^;.196-otoliths’consistins of carbonate 
In fishes (rays), M. Schultze, many years ago, observed 
simple cylinder epithelium and rod cells intermingled with 
them, reminding one of the probable terminal structures of 
the olfactory nerves (p. 239). F. E. Schulze subsequently 
met with a shock of uncommonly long stiff cilias in osseous 
fishes and tritons. The otolith sacs of fishes also presented 
a similar condition. 
In man the salient points of the vestibular saccules are less 
developed (maculae acusticae of Henle), but are more dif- 
fused. Here, also, fine non-medullated nerve fibres penetrate 
the epithelium. Two kinds of cells and cilia-like processes 
have also been noticed. 
We now come to the cochlea. 
This convoluted structure contains two nerveless winding 
canals, the two so-called scala of the older anatomists, the 
scala vestibuli and the scala tympani (Fig. 197, Vy T), sepa- 
rated by an internally osseous, and externally soft membranous 
spiral plate. Reissner has discovered, in addition, a third cen- THE ORGANS OF SENSE. 
243 
tral spiral canal, forming on transverse section an irregular 
triangle, with its apex directed towards the axis of the cochlea. 
This is Reissner’s cochlear canal, canalis cochlearis (C), the 
Fig. 197.—Perpendicular transverse section through the canal of the cochlea and neighborhood, in 
an older embryonic calf; vestibuli; scala tympani ; C, canal of the cochlea; B, 
Reissner’s membrane with-its insertion (a) into a projection at the so-called habenula sulcata (c) ; 
d, connective tissue stratum with a vas spirale at the under surface of the membrana basilaris ; cf, 
teeth of the first series ; d, sulcus spiralis, with thickened epithelium, which extends as far as the 
developing Cortian organ,/*; e, habenula perforata; Cm, Cord’s membrane (1. inner thinner, 2, 
middle thicker portion of the same, 3, its outer end) ; g, zona pectinata ; h, habenula tecta; k, 
epithelium of the zona pectinata ;k\ of the outer wall of the canal of the cochlea ; kf>, of the 
habenula sulcata ; I, ligamentum spirale (£, transparent connecting portion of the same with the 
zona pectinata); m, entering projection ; n, cartilaginous plate ;o, stria vascularis ;p, periosteum 
of the zona ossea ; pf, transparent outer layer of the same ; q, bundle of the cochlear nerve ; 
place of termination of the medullated nerve fibres ; t, place of the axis cylinder in the canalicula 
of the habenula perforata ; r, tympanic periosteum of the zona ossea. 
proper cochlea of the lower groups of amphibia. Here alone, 
at the bottom, terminates the nervus cochlearis. 
It is impossible for us to describe here the infinitely com- 
plicated structure of the fundamental portion of this true 
cochlea, the more so as, unfortunately, in addition to all the 244 
TWENTY-THIRD LECTURE. 
uncertainty, an extremely complicated nomenclature has also 
been developed.* 
The osseous portion of the spiral plate contains the expan- 
sion of the cochlear nerve. At its peripheral exit its bundles 
of fibres meet the so-called organ of Corti (Fig. 198, h). 
Fig. 198.-—The Corti’s organ of the dog in perpendicular section : a, b, homogeneous stratum of the 
membrana basil#ris ; u, vesicular stratum ; v, tympanic stratum with nuclei and protoplasma ; 
n, labium lympanicum of the crista spiralis ; a, continuation of the tympanic periosteum of the 
lamina spiralis ossea : c, thickened commencing portion of the membrana basilaris, together with 
the place of section, h, of the nerve d, and blood-vessels ; _/, the nerve ; g, epithelium of the 
sulcus spiralis externus ; z, inner hair cell with the basal process, k, surrounded by nuclei and pro- 
toplasma (of the “ granule stratum ”), into which the nerve fibres radiate ; n, base or foot of the inner 
pillar of the Cortl’s organ ; in, its “ head piece,” connected with the same part of the outer pillar, 
the lower part of which is wanting, while the next following pillar o, presents the middle part 
and the base : /, y, r, the three outer hair cells ; z, a so-called supporting cell of Hensen ; /, lamina 
reticularis ; w. nerve fibre terminating at the first of the outer hair cells. 
In a transverse section it forms a conical elevation of the 
membranous base of the cochlear canal. It is hollow in its 
interior, and forms collectively, by the cochlear convolutions, a 
spiral tunnel. Its structure is infinitely complicated. 
We here meet with a double row of convergent ascending 
“pillars” (n, m, 0) which meet each other at the top of the Cor- 
tian organ. There are twTo of the “ external pillars ” (<2) to 
three of these internal elements (n, in'). At their base we 
meet with cell rudiments. 
A further diversity is induced by the epithelial cells of the 
cochlear canals. They become from within outwards (that is 
from the axis of the cochlea towards its convex external arch) 
* The cochlear canal has been the object of extraordinarily extensive labors on 
the part of Reissner, Claudius, Boettcher, Schultze, Deiters, Hensen, Waldeyer, 
Gottstein and others. THE ORGANS OF SENSE. 
245 
higher and higher {g). To the inner side of the inner pillar 
of the Cortian organ is applied a long cylinder cell, which is 
covered at the free upper border with short hairs (i). This 
is the “ inner hair cell ” of Deiters. The “ outer hair cells ” 
{p, q, r), which are also obliquely directed, adhere in three or 
fourfold rows to the outer pillars of this Cortian tunnel. Fur- 
ther outwards occur spindle-shaped elements, “supporting 
cells” of Hensen {z), and then, gradually becoming flattened, 
lower cubical epithelial cells. 
The supports of the inner and outer pillars lock into each 
other in a quite peculiar form. From this point is developed 
an extremely remarkable horizontally extended membrane, 
the lamina velamentosa of Deiters (/, /). It is impossible to 
describe here the marvelous reticular structure. 
Where do the primitive fibrillae of the cochlear nerves end ? 
Freed at last from the confinement of the lamina spiralis ossea, 
it passes between the inner pillars in the tunnel of the Cortian 
organ. They are said to have previously become partially 
lost in the inner hair cells. They now terminate in the outer 
hair cells [w). Notwithstanding the infinite pains and labor 
bestowed on this subject, it still stands on a weak foundation. TWENTY-FOURTH LECTURE. 
THE ORGANS OF SENSE, CONTINUED.—THE EYE 
We have still to mention the termination of the optic 
nerve. In doing this we must of course draw into the circle 
of our discussion the entire eye, that magnificent and won- 
derful organ which is so important for the physician. Never- 
theless, in consequence of its extremely complicated structure, 
we can only present a cursory incomplete description. 
The eyeball (Fig. 199) presents first an external capsular 
FIG. 199.—Transverse section of theNeye ;a, sclerotica ;b, cornea; c, conjunctiva ;d, circulus 
venosus iridis ; e, choroid, with the plgAient layer of the retina ; f ciliary muscle ; g, ciliary process ; 
h. iris : i, optic nerve ; i', colliculus opticus; k, ora serrata retina; ; I. crystalline lens; m, tunica 
Oescemetii; n, membrana limitans interna of the retina; o, membrana hyaloidea ; j>, canalis 
Petiti; q, macufa lutea. 
system ; the posterior, opaque, greater portion is formed by 
the sclerotic (a), while the anterior, smaller, transparent seg- THE EYE. 
247 
merit (h) is constituted by the cornea. These membranes 
enclose a black stratum, the so-called uvea. It consists of the 
choroid (e) with the ciliary processes {g) and, applied exter- 
nally to the latter, the ciliary muscle (/) and, finally, a more 
anterior ring-shaped disk, the iris {h). 
The contents of the hollow ball are formed by the various 
light-refracting media. Even the cornea {b) participates in 
this action. Next to it comes the so-called humor aqueus, 
that is, the watery contents of the anterior and posterior 
chambers of the eye (in front of /). Then follows a firmer 
structure, the most important refracting body, the crystalline 
lens (/). The completion is formed by a large globular mass, 
having a concave impression in front, the vitreous body or 
humor vitreus (behind I). 
The greater portion of the latter is covered by the cup- 
shaped expansion of the optic nerve, the retina {i). It termi- 
nates anteriorly, according to the usual impression, in the 
region of the origin of the ciliary processes, with an undulated 
border, the so-called ora serrata {k). 
A very complicated system of vessels, springing almost 
exclusively from the arteria ophthalmica, supplies our organ 
with blood. Lymphatics are, naturally, also not wanting. 
The cornea, with its two homogeneous boundary layers, was 
mentioned at p. 56; the stratified pavement epithelium of the 
anterior surface at p. 31 ; the simple cell layer of the posterior 
at p. 29 ; the nerves at p. 207. 
We mentioned at that time the system of passages of the 
cornea, and ascribed to them a sort of parietes. Differences 
of opinion prevail concerning this, however. The passages 
of this system of juice-clefts (Fig. 200) may be artificially filled 
by the puncturing method, in successful cases, with the pres- 
ervation of their old shapes, in numerous others, however, 
distorted, with the appearance of wide misshapen canals. 
They have been not badly termed “rupture spaces.” The 
circumstance is interesting that a successful injection of the 
juice-spaces finally leads to the lymphatics of the conjunctiva. 
The cellular contents of the canal-work has caused endless 248 
TWENTY-FOURTH LECTURE. 
controversies; not the lymph corpuscles wandering through 
them, but rather the “fixed” corneal cells (Fig. 200, to the 
left and below). They are stellate and water-wheel-like cells, 
the nucleus of which is always invested by some protoplasm, 
while the peripheral portions are metamorphosed into homo- 
Fig. 200.—The human cornea impregnated with silver. The corneal corpuscles, that is, the system 
of juice-spaces, colorless. To the left, below, four metamorphosed parenchyma cells. 
geneous veil-like plates. The cells probably have a limited 
contractility. Their processes do not, according to our views, 
form any connected net-work. Hence, a portion of the juice- 
canals remain filled with fluid. All this is disputed by others, 
however. No one should here leave the decision with confi- 
dence to one reagent, such as gold, for instance. 
The sclerotica (p. 57) is a firm connective-tissue membrane, 
and consists of bundles arranged meridionally, with others 
crossing them in an equatorial direction. In front they pass 
continuously over into the modified hyaline connective tissue 
of the cornea. It also contains regular passages with lymph 
corpuscles and in part colorless, in part pigmented connective- 
tissue cells (Waldeyer). It appears to have nerves only at 
the corneal border. 
At the margin of both membranes, although belonging to 
the inner surface of the sclerotica, we meet with a complicated 
ring-shaped reservoir. This is the sinus Schlemmii (Fig. 
199, d). It has been declared to be a venous reserved THE EYE. 
249 
(Leber). Others regard it as a lymphatic passage (Schwalbe, 
Waldeyer). 
Posteriorly, the sclerotica passes over into the external 
sheath of the optic nerve, derived from the dura mater. This 
membrane is finally strengthened by the insertions of the ten- 
dinous bundles of the ocular muscles. 
The system of the uvea, with the exception of its most 
anterior portion, the iris, is characterized by very considerably 
developed vessels. 
The entire inner surface (and the posterior surface of the 
iris) is covered by the pigmented outer epithelium of the 
retina (p. 30). During a portion of the foetal period, the 
latter extended much further forwards than it does at a more 
mature period. 
The greater portion of the uvea is formed by the posterior 
segment, the choroid. The thin membrane consists of sev- 
eral, not sharply demarcated, connective-tissue layers. 
We recognize a, an inner hyaline boundary layer, 0.0006 to 
0,0008 mm. in thickness, thicker and more uneven in front; b, 
a thin homogeneous layer, with extraordinarily developed 
stellate capillary net-works (choroidea capillaris) ; c, the 
choroid proper of the histologists, with stellate, very generally 
pigmented connective-tissue cells, and a great wealth of arte- 
rial, as well as venous vessels ; and, finally, d, a loose pig- 
mented connective tissue, which forms the connection with 
the inner surface of the sclerotica. It is called the lamina 
fusca, and also the supra-choroidea; it forms a lymphatic 
space. 
The vascular net-work in the ciliary body, and in the ciliary 
processes which project inwards from the latter, is greatly 
developed. The substratum remains similar to that of the 
choroid, though the pigmented connective-tissue cells dis- 
appear. „ ' 
Externally to these processes we meet with a peculiar 
smooth muscular mass, the tensor choroideae, musculus ciliaris, 
or Hgamentum ciliare of an older epoch (Fig. 199, /). 
The human ciliary muscle arises from the inner side of the 250 
TWENTY-FOURTH LECTURE. 
boundary region of the cornea and sclerotica. Meridional 
bundles of the former radiate in a posterior direction into the 
ciliary body. Below and inwards occur interwoven filaments, 
and still further inwards, circular bundles (Mueller’s ring 
muscle). 
We meet with colorless connective-tissue cells in the con- 
nective-tissue substratum of the iris of light eyes, and pig- 
mented cells in that of dark ones. Besides these, smooth 
muscular elements occur. Annular bundles (Fig. 201, a) 
Fig. 201.—Surface of the human iris ; a, the sphincter ; b, the dilator of, the pupil. 
form the constrictor or sphincter of the pupil. From it pro- 
ceeds the dilator pupillse, an object of controversy of later 
years. 
Muscular bundles, which are at first separated, form more 
peripherically a connected radial layer of fibres {b). At the 
ciliary, that is the outer border, we finally meet with an an- 
nular muscular layer. 
This external or ciliary border of the iris gives rise at its 
anterior surface to another peculiar tissue, the ligamentum 
pectinatum iridis (Huek). 
We have already learned (p. 56) that the posterior surface 
of the cornea is covered by a hyaline membrane, the mem 
brana Descemetica or Demoursii. At its periphery, this 
posterior covering layer passes over into a peculiar reticular 
tissue (probably, in man, most intimately connected with the 
elastic tissue), which passes through the outer margin of the THE EYE. 
251 
anterior chamber of the eye. This is the ligamentum pectina- 
tum, which has just been mentioned. Its trabeculae are 
covered with epithelial cells. The anterior surface of the iris 
also has such a layer. An incompletely closed, ring-shaped 
canal, which is bounded by the trabeculae of this ligamentum, 
has been called the canalis Fontanae. 
Small ganglia- of the ciliary nerves occur in the choroid. 
The ciliary muscle and the iris are more plentifully supplied 
with nerve fibres, but their manner of termination we do not 
yet know. 
Concerning the crystalline lens and the vitreous body in 
general, we refer to pages 78 and 45. There is one circum- 
stance which requires more special mention here. According 
to a widely disseminated acceptation, the hyaloid membrane 
(Fig. 199 in the vicinity of k), separates into two leaves, a 
posterior and an anterior, the so-called zonula Zinnii, which 
is impressed in a ruffle-like manner by the ciliary processes. 
Both continue on to the crystalline lens at its equatorial zone. 
The zonula Zinnii presents a peculiar pale and resistant sys- 
tem of fibres. A three-cornered annular sinus, bounded by 
both lamellae, bears the name of the canalis Petiti. Much is 
still obscure here, and the space is, after all, only an artefact 
(Merkel, Mihalcovics). 
Let us now turn to the expansion of the optic nerve into the 
retina. Our membrane has its greatest thickness (0.38 to 
0.23 mm.) at the place of the entrance of the optic nerve. It 
becomes thinner (to about the half) towards the periphery. 
Passing beyond the equator (thinned to 0.09 mm.) it termi- 
nates as the so-called ora serrata (Fig. 199, k). Externally 
from the place of entrance of the optic nerve (f), about 3 to 4 
mm. removed from it, is the macula lutea, the seat of the most 
distinct vision (q). In its centre there is an excavation, the 
so-called fovea centralis. 
The retina, provided with numerous other elements, appears 
to be an extraordinarily complicated structure, and, at the 
same time, of extreme delicacy and variability. It has been 
the object of infinite research in older and more recent times ; 252 
TWENTY-FOURTH LECTURE. 
but, notwithstanding the labors of H. Mueller and M. Schultze, 
we are still exceedingly distant from a conclusion, as Schwal- 
be’s most recent studies show. 
The retina (Fig. 202) is invested externally by the simple 
pigmented epithelial layer already familiar to us (p. 30). 
Then (1) we have the stratum of 
rods and cones ; thereupon follows 
the so-called external limiting mem- 
brane, the membrana limitans ex- 
terna (the transverse line between 1 
and 2). Next comes the external 
granular layer (2), then the inter- 
granular layer (3). Thereupon fol- 
lows the inner granular layer (4), 
then the molecular stratum (5). 
Further inwards we meet with the 
stratum of the ganglion cells (6), 
thereupon the radial expansion of 
the optic nerve fibres (7). The 
termination is formed by the inter- 
nal limiting membrane, the mem- 
brana limitans interna (10). The 
layer of rods and cones, as well as 
Fig. 202.—The human retina in ver- 
tical section : i, layer of the rods 
cones, demarcated below by the mem- 
brana limitans externa; 2, the exter- 
nal granular layer; 3, intergranular 
layer; 4, internal granular layer: 
5, fine granular layer ; 6, layer of gan- 
glion cells; 7, expansion of the optic 
nerve fibres ; 8, Mueller’s supporting 
fibres ; q, their transformation into the 
inner limiting membrane ; 10, the mem- 
brana limitans interna. 
the external granular layer, is called 
by Schwalbe the neuro-epithelial 
stratum, all the rest the cerebral 
stratum. 
In the structure of this thin 
and wonderfully complicated mem- 
brane we must, however, distinguish two different elements, 
connective tissue and nervous. 
Let us first take the former into account (Fig. 203, A), and 
commence at the inner surface. 
The membrana limitans interna (/), an apparently hyaline, 
o.oon mm. thick layer, deserves mention as the first connec- 
tive-tissue boundary layer. In an inward direction (to- 
wards the vitreous body), smoothly demarcated, it passes over THE EYE. 
253 
externally (towards the choroid), commencing with a triangu- 
lar expansion, and then diminishing into a connective-tissue 
radial fibre system (e), which is wanting only in the macula 
lutea. 
Fig. 203.—Diagramatic representation of the retina ; A, connective-tissue frame-work ; a, men- 
brana limitans externa; e, radial or Muellerian supporting fibres with their nuclei, e' ; d, frame- 
work substance of the intergranular, and g, of the molecular layer; /, membrana limitans in- 
terna ; B, nervous elements ; b. rods with outer and inner members ; c, cones with outer member 
and body ; b', rod, and c', cone granule ; d, expansion of the cone fibre into the finest fibrillae in 
the intergranular layer; f. granules of the inner granular layer ;g, confused mass of finest fibres in 
the molecular layer ; h, ganglion cells ; Al, their axis-cylinder processes ; i, layer of nerve fibres. 
These are the Mueller’s supporting fibres (e). They in- 
c.ease more and more towards the anterior terminal portion. 254 
TWENTY-FOURTH LECTURE. 
Lateral branches of the latter lead to manifold communica- 
tions. In the molecular (g) and the intergranular layer (d) 
there is thus formed a very fine reticular frame-work, such as 
we are already familiar with in the gray substance of the cere- 
bro-spinal system (p. 220). 
Nuclei or cell equivalents occur occasionally in the system 
of supporting fibres, as in the external granular layer {e'). 
The supporting substance certainly extends as far as the 
base of the rod and cone layer (a). There is scarcely 
any doubt, however, that it extends still further as a delicate, 
homogeneous connecting substance. At the former locality 
it forms, as the membrana limitans externa, a fenestrated 
boundary layer, further outwards a connecting medium of 
the rods and cones. 
Having thus become familiar with the connective-tissue sub- 
stratum—it should by no means be genetically confounded 
with the ordinary connective tissue—let us pass to the ner- 
vous elements of the retina (B). Let us here select the re- 
versed course, and commence with the outer layer. 
This stratum is formed by the rods and cones. The whole 
layer is called the rod-layer, stratum bacillosum. They are 
terminal nerve cells, similar to those which we previously met 
with at the higher nerves of sense. Those of the retina, 
however, possess many peculiarities, and we have a more ac- 
curate knowledge of them than of their relatives. The cir- 
cumstance is also interesting that the rods and cones vary 
according to animal groups. Their dimensions are propor- 
tionate to that of the red blood cells. 
The rods, bacilli (B, b), are slender cylindrical structures. 
They consist (Mueller, Braun, Krause) regularly of two parts, 
an apparently homogeneous narrower so-called “ outer mem- 
ber,” which refracts the light more strongly, and a shorter 
“ inner member.” The latter appears paler, somewhat granu- 
lar, and of considerable diameter. In the lower vertebrate 
animals the retinal pigment forms regular sheaths around the 
outer member of the rods and cones. In mammals and man 
the pigment sheath is less developed. THE,EYE. 
255 
The rods acquire their greatest length, 0.06 mm. and more, 
at the bottom of the retina. Further forwards they become 
shorter, towards the ora serrata they are only 0.0399 mm. 
high. Their diameter may be estimated at 0.0016 to 
0.0018 mm. 
Downwards or inwards, beneath the membrana limitans 
externa, the rod becomes pointed, and runs out into an ex- 
traordinarily fine filament, a primitive 
nerve fibrilla (Fig. 203, B, Fig. 204, 1, 
4, Fig. 205, 1, 3). The latter passes 
through the outer granular layer verti- 
cally (and also radially). A small cell, 
the so-called “ rod granule” (Fig. 203, 
B, b\ Fig. ,204, 1, 2, 3, Fig. 205, 3) is 
embedded in its course, sometimes 
higher up, sometimes further down- 
wards. This granule forms the single 
element of the outer granular layer. 
Still more complicated textural con- 
ditions have been observed in the rods 
(Fig. 204). At the border of the in- 
ner, member towards the outer mem- 
ber, embedded in the former, a piano- 
Fig. 204.—Final structure of 
the rods; I, from the chicken 
with the outer and inner mem- 
ber, as well as the cone-ellip- 
soid ; 2, from the frog ; 3, the 
outer member of the rod of a 
frog dividing into transverse 
discs; 4. rod with granule 
from the Guinea-pig. 
convex body has been found with its 
plane base directed upwards (1, a, 2). This is the so-called 
“ rod-ellipsoid ” of Krause. 
Furthermore, as has been long known, the outer member 
breaks up into transverse plates (3). These discs may have 
a thickness of 0.0003 to 0.0004 mm. in man (Schultze). 
The outer member shows a longitudinal striation, caused 
by longitudinal, channel-like depressions, with longitudinal 
elevations springing up between them, like a fluted column 
(Fig. 204, 1, 2, and Fig. 205, I a). Longitudinal striations 
have also been subsequently discovered on the inner members 
(Fig. 205, 1, and 3 b). In the axis of the rod a very fine 
filament, a primitive nerve fibrilla, is also said to have been 
noticed (Ritter). 256 
TWENTY-FOURTH LECTURE. 
Our present knowledge concerning the cones (Fig. 203, B, 
c, Fig. 205 2), is uncertain. 
In man, they have the form of a slen- 
der bottle. Their base rests on the 
membrana limitans externa. Upwards, 
the cone passes into a shorter, conical, 
infinitely changeable structure, the so- 
called cone rod (Fig. 203, B, above c, 
Fig. 205, 2 a). It is the equivalent of 
the external member of the rod, charac- 
terized by its great tendency to break 
up into transverse discs. The inner 
member, or the cone body (Fig. 205, 2 
b), also shows the longitudinal striation, 
similar to the equivalent portion of the 
rod. 
At the base of the rod, immediately 
beneath the limitans externa, we meet 
with a cell-like 
body, the so- 
called cone 
granule (Fig- 
-203, B, c', Fig. 
205, 2, below d). 
A broad cone 
filament (up to 
0.0029 mm- in 
thickness) finally 
runs downward, 
passing through 
the outer granular layer (Fig. 203, below d). It is a fascicu- 
lus of primitive fibrillse. 
Fig. 205.—Fibrillated cover- 
ing of the rods and cones ; i, 
rods; 2, cones of man ; a, 
outer; b, inner member ; c, 
rod-filament; d, limitans ex- 
terna ; 3, rod of the sheep. 
The fibrillae project beyond the 
inner member ; the outer mem- 
ber is wanting. 
Fig. 206.—The rod layer 
seen from without; a, cones ; 
b, cone rods ; c, ordinary 
rods ; i, from the macula lu- 
tea : 2, at the margin of the 
same: 3, from the centre of 
the retina. 
Interesting local variations (Fig. 206) in regard to the num- 
ber of cones and rods occur in the human eye. 
In the macula lutea, the seat of the most distinct vision, 
we meet with cones alone, which have become extremely fine 
(1). In the vicinity the latter are still quite crowded, and are THE EYE. 
257 
surrounded by a single circle of rods (2). The further out- 
wards we proceed, the further we find the cones removed 
from each other, and the greater the number of rods situated 
between them (3). 
Apes, and the most of our domestic animals, present an 
analogous condition. Nocturnal animals, such as the cat, 
have only stunted cones ; bats, hedgehogs, moles, are entirely 
deprived of the latter elements. Birds, on the contrary, 
generally have an abundance of cones. In the chameleon 
and lizard there are no rods at all ; we find only cones, as 
in the human macula lutea. The rod appears to be the ter- 
minal apparatus, serving for the objective colorless vision, as 
the cone does for the color perception of the outer world 
(Schultze). 
The membrana limitans externa, the sieve-like fenestrated 
boundary structure, we are already familiar with. The rod 
apices pass downwards through small spaces, the cone gran- 
ules through larger ones. Finally, this membrane sends out- 
wards the already mentioned delicate homogeneous connect- 
ing substance between the rods and cones. 
The external granular layer, stratum granulosum externum, 
is already familiar to us so far as its connective-tissue frame- 
work is concerned. It (Fig. 203, B) consists of layers of 
small cells stratified over each other, a minimal body closely 
surrounding the nucleus. We distinguish here the larger 
higher cone granules (/), measuring 0.009 to 0.012 mm., and 
the smaller rod granules, measuring 0.0045 to 0.0079 mm., 
situated more deeply. The latter alone present a peculiar, 
perhaps normal transverse striation (Fig. 204, 4). 
Thus far the connection of the retinal elements is clear. 
Now, however, on coming to the so-called intergranular 
layer, the stratum intergranulosum, this clearness is lost. 
There exists here a grievous defect of knowledge. 
Schultze, the excellent investigator whom we have thus far 
followed, asserted that the finest rod-fibrilla;, having arrived 
at the intergranular stratum, formed very fine terminal knobs 
(Fig. 203, B, above d). This is decidedly not the case. The 258 
TWENTY-FOURTH LECTURE. 
filament simply bends into another plane, suddenly and at 
a considerable angle. I have convinced myself of this with 
certainty. 
The broad cone fibres divide at the same place into three 
very fine processes (above d). 
In the most delicate connective-tissue frame-work of the 
intergranular layer we meet with a confused mass of fine 
horizontally and obliquely disposed filaments (d), the con- 
tinuations of the rod and cone fibrillm. 
The inner granular layer—the stratum granulosum inter- 
num—contains, in the first place, as we already know {A, e'), 
connective-tissue nuclei or cellules of oval shape. Together 
with these appear layers of sharply demarcated, globular, nu- 
cleated cells (B,f), into the upper pole of which sinks a 
rather fine nervous filament, to again pass out at the lower 
pole, very much finer, and continuing further in a perpen- 
dicular direction. These nervous granules do not show any 
transverse striation. 
The molecular or fine granular layer, stratum moleculare 
(B, g), repeats, although with greater thickness, the fine con- 
nective-tissue spongy structure of the stratum intergranulo- 
sum. We again discover in it a confused mass of primitive 
fibrillse. Ascending fibres from the more deeply situated 
cells of the intergranular layer, having entered this confused 
mass, may be observed here and there; following their course 
is not to be thought of. We have here, therefore, a new de- 
fect in our knowledge of the retina. 
We now arrive at the layer of the ganglion bodies, the 
stratum cellulosum {B, h). These occur stratified (in 10 to 6 
layers) at the bottom of the retina, to gradually appear to- 
wards the periphery as a single layer, and with an increasing 
distance from each other. With the exception of the macula 
lutea, where the ganglion bodies are bipolar, they form fine 
multipolar cells of not inconsiderable size (up to 0.0377 mm.). 
Their protoplasma processes turn outwards, and finally disap- 
pear with their terminal branches in the maze of fibres of the 
molecular stratum ; their axis-cylinder process is directed in- THE EYE. 
wards (/z'). It passes over into a nerve fibre of the optic 
nerve-fibre layer, the stratum fibrillosum (z). 
In order to comprehend the latter we must commence with 
the contents of the optic nerve. It has medullated nerve 
fibres, 0.0045 to 1.0014 mm. thick. Having entered the ball 
of the eye, their medullary sheath is lost, and they become 
pale axis cylinders.* 
Having advanced into the retina, our optic nerve fibres di- 
vide and reunite at acute angles into bundles, forming a nerve 
plexus. In proportion as we follow their further course for- 
wards, the fibre bundles become thinner and thinner, and the 
distance between them is constantly increased. At last we 
meet with only isolated axis cylinders. 
We have grounds for assuming that each optic-nerve fibre 
penetrates the body of a ganglion cell as an axis-cylinder 
process ; still we cannot prove this at the present time. 
The membrana limitans interna, of a connective-tissue na- 
ture, has been previously mentioned. 
The best portion of the retina, the yellow spot or macula 
lutea, requires a short mention. 
The connective-tissue frame-work substance, with the ex- 
ception of the limitans interna, is undeveloped. The nerve- 
fibre layer likewise disappears; the layer of the ganglion 
cells, still largely developed at the periphery, also disappears 
completely in the centre of the fovea. The molecular and 
inner granular layers also suffer the same fate. There re 
mains, therefore, only the (exclusively occurring) cones with 
the stratum granulosum externum. 
The latter (Fig. 207) are no longer as of old. Their body 
has at last become narrowed to 0.0028 to 0.0033 mm. 
(Schultze) ; it has diminished to nearly the thinness of the 
rod, and the cone rod too.ooi to 0.0009 mm. The cone fibre 
appears to have participated but little in this thinning. The 
* It is remarkable that in individual human retinas the medullary sheath of the 
nerve tubes is preserved. In the dog the same not unfrequently occurs; in rab- 
bits and hares it is even the rule. 260 
TWENTY-FO UR TH LECTURE. 
cone granule lies sometimes higher, sometimes deeper (a); 
we might say from necessity. 
We meet with still another 
condition. In the peripheral 
layers of the retina the cone 
fibre passes through our mem- 
brane in an ascending perpen- 
dicular direction. The latter 
now leaves this direction more 
and more, to pass obliquely out- 
wards and downwards {a). This 
induces beneath the outer gran- 
ular layer (that is the cone gran- 
ules), a quite peculiar appear- 
ance. 
Forwards, towards the ora 
serrata, the retina increases in 
thinness, and the nervous ele- 
ments diminish; the connective 
tissue frame-work acquires the 
upper hand more and more; 
finally all the nervous elements 
have disappeared. 
By the ciliary portion of the 
retina is designated a system 
of cylindrical cells which lie on 
the zonula Zinnii beyond the 
ora serrata, and run as far as 
Fig. 207.—Cones from the macula lutea and 
fovea centralis of man : a, with decomposed 
outer membrane ; b, with the lamellar decom- 
position of the same. 
the iris, according to many even to the pupillary border of 
the latter. 
The blood-vessels of the retina, springing from the arteria 
centralis, form an elegant wide-meshed reticulum of very fine 
tubes. They occupy the inner portion of the retina, but pass 
outwards to the inner granular layer, and perhaps still fur- 
ther. The adventitia of the same surrounds the inner layer 
but loosely, leaving a lymphatic space. 
It is impossible for us to enter into the exceedingly com- THE EYE. 
plicated arrangement of the blood-vessels of the eyeball. 
We must leave this to more special works. 
We would add, however, a few words concerning the 
lymphatics of* the eyeball 
(Fig. 208), basing them on 
Schwalbe’s admirable work. 
We may assume with this 
investigator an anterior and 
a posterior system of lym- 
phatics. 
The former, arising from 
the iris and ciliary processes, 
has its central reservoir in 
the anterior chamber of the 
eye. To this division be- 
long also the lymphatics 
of the cornea and conjunc- 
tiva. 
All that lies behind the 
ciliary processes forms the 
posterior lymphatic system. 
The sclerotic and the cho- 
roid are perhaps without 
definite lymphatic canals. 
Fig. 208.—The posterior lymphatics of the hog’s 
eye; c, conjunctiva ; m r, the recti muscles : 
vi retrretractor bulbi; a, layer of fat; v, the 
outer sheath of the optic nerve ; t, the “Tenon’s” 
space, passing backwards into the “supravaginal,” 
spv: sb v, “ subvaginal ” space between the in- 
ner and outer sheath of the optic nerve ; /, “per- 
ichoroideal ” space connected with the Tenon’s 
space by oblique passages. 
The cup-like space between both membranes, with which 
we are already familiar as the lamina fusca, has, on the 
contrary, the signification of a lymph reservoir. This is 
Schwalbe’s perichoroideal space (/). From it (at the eleva- 
tion of m r of our figure) occurs the transition of the lym- 
phatic fluid into the so-called Tenon’s space (/), that is the 
interval between the outer surface of the sclera and the Te- 
non’s capsule of the eyeball. The connecting lymph canals 
surround the vasa vorticosa of the choroid in a sheath-like 
manner. Posteriorly the Tenon’s reservoir continues into 
the supravaginal space p v), a cylindrical sheath membrane 
of the optic nerve. 
Key and Retzius, the two able investigators mentioned in 262 
TWENTY-FOURTH LECTURE. 
connection with the lymphatics of the nervous central organs, 
injected from the subdural space of the brain (p. 231) an 
intermediate space located between the external and internal 
sheath of the optic nerve, the subvaginal space of Schwalbe 
(.s b v), and from this they drove the injection mass into the 
perichoroideal space of Schwalbe. Schwalbe does not, how- 
ever, accept the latter communication. 
Injection masses may be forced beneath the inner sheath of 
the optic nerve, between the bundles of optic-nerve fibres, 
and this may be done from the subarachnoidal space of the 
brain (p. 231). 
The lymphatics of the retina invest its capillaries and veins, 
therefore, in a sheath-like manner. 
We return to the chambers of the eye, the central reservoir 
of the lymph of the anterior portion of the globe. What is 
the relation of its affluent passages ? 
In the first place a cleft system leads from the canal of 
Petit into the posterior, and thus into the anterior chamber 
of the eye. Wider and more important introductory passages 
open from the Fontana’s space in the ligamentum pectinatum 
iridis, probably for the lymph of the iris and ciliary pro- 
cesses. 
Injection masses pass from the periphery of the membrane 
of Descemet into the canal of Schlemm (p. 248). 
Can a communication between the lymphatic and venous 
passages, actually exist here, similar to that which Key and 
Retzius admitted, by the aid of the Pacchionian granulations 
for the membranes of the brain (p. 232) ? Leber, an observer 
who has rendered great service to the anatomy of the eye, 
has, it is true, disputed this, and he may be right. 
We have still to mention, briefly, the external, less import- 
ant appendices of the eyeball. 
The eyelids contain, embedded in the firm connective tis- 
sue of the tarsal cartilage, the so-called Meibomian glands, 
short sinuous tubes with fatty parenchyma cells, but without 
a membrana propria or muscular tissue in the excretory duct. 
Its secretion is the sebum palpebrale. THE EYE. 
263 
The conjunctiva presents a complete mucous membrane 
over the posterior surface of the eyelids and the anterior sur- 
face of the sclera ; only the stratified pavement epithelium 
remains over the cornea, the mucous membrane having 
become metamorphosed into corneal tissue. 
The conjunctival glands are of manifold species. In man 
and in certain mammals we meet with small mucous glandules, 
though the cells contain fat granules. Convoluted glands 
(Fig. 119) occur at the periphery of the cornea in ruminating 
animals (Meissner). Simple culs-de-sac have been recognized 
in the hog, externally to the corneal periphery, towards the 
outer canthus of the eye (Manz). In the tarsal border of the 
human eye we meet with modified sudoriparous glands 
(Waldeyer). 
Concerning the trachoma glands, we have already commu- 
nicated* all that was necessary (p. 113). In man there are 
probably no true lymphoid follicles (Waldeyer), The ter- 
minal bulbs of the conjunctiva have been mentioned at p. 
209. 
The tear-gland, glandula lacrymalis, consists of an aggre- 
gation of single racemose glands. We are not yet familiar 
with the nerve terminations here. The efferent apparatus 
presents differences of structure in its different portions. 
We leave the description of them, like that of so many other 
things, to more comprehensive text-books. INDEX 
Acinus of the glands, 130. 
Adventitia of the capillaries, see Vessels. 
Air cells, see Lungs. 
Alveoli of the lungs, 158. 
Amoeboid changes of form of the cells, 9. 
Anthracosis of the lungs, 160; of the 
bronchial glands, 160. 
Aquula Cotunnii (perilymph) of the audi- 
tory organs, see Artditory apparatus. 
Aquula vitrea auditiva (endolymph), see 
Auditory apparatus. 
Arachnoid, see Nerve centres. 
Arrectores pilorum, 81. 
Arteriae helicinae, 191. 
Arteries, 94. 
Arteriolse rectas of.the kidney, 170. 
Articular cartilage, 44. 
Assimilation by the cell, II. 
Auditory organ, 240 ; external ear, 241 ; 
membrana tympani, 241 ; auditory 
ossicles, 241 ; Eustachian tube, 241 ; 
internal ear, 241; vestibule and semi- 
circular canals, 241 ; otoliths, 242 ; 
cochlea, 242; its structure, 242; 
Reissner’s, or the cochlear canal, 
Corti’s organ, termination of the coch- 
lear nerves, etc., 243. 
Auditory ossicles, see Auditory organ. 
Auerbach’s plexus myentericus, 218. 
Axis canal of the spinal cord, 224. 
Axis cylinder, 193. 
Axis-cylinder process of the ganglion 
cells, 200. 
Axis fibrillse of the nerves, 196. 
Bacilli of the retina, see the Eye. 
Bartholinian glands, 181. 
Bathybius, 1. 
Becher cells, 5. 
Bellini’s tubes, see Kidney. 
Biliary capillaries, see Liver. 
Biliary passages, see Liver. 
Bladder, see Urinary apparatus. 
Blood, 21 ; cells and plasma, 21 ; red 
blood corpuscles and lymphoid cells, 
21 ; nature of the former, 22 ; differ- 
ences of the same according to the 
groups of vertebrate animals, 23; 
lymphoid cells of the blood, 23 ; rela- 
tive number, 24; circulation of the 
blood, 24 ; fate of the lymphoid cells; 
25 ; genesis of the blood in the em- 
bryo, 26. 
Blood-vascular glands, 123 ; thyroid 
gland, 123; structure, 123; colloid 
formation, 124 ; suprarenal capsules, 
124; cortical and medullary layer, 
124; structure, 125; vessels and 
nerves, 126 ; apophysis cerebri, 126 ; 
coccygeal gland, 126; ganglion inter- 
caroticum, 127. 
Blood-vessels, see Vascular system. 
Bone tissue, 60; kinds of bone, 60; 
medullary or Haversian canal, 60; 
Haversian and general lamellae, 61 ; 
canaliculi, 61 ; bone corpuscles or 
lacunae, 62; bone cells, 62 ; composi- 
tion of bone, 63; bone cartilage, 64; 
bone medulla, 64 ; osteogenesis, 64 ; 
cartilage marrow, 65 ; ossification 
points, 65 ; formation of bone at the 
expense of the cartilage tissue, 65 ; 
osteoblasts, 68; endochondral bones, 
69 ; theory of apposition and expan- 
sion, 69 ; Haversian spaces, 70; os- 
teoclasts, 70; periosteal bone forma- 
tion, 70; Sharpey’s fibres, 71. 
Bowman’sglands of the olfactory region, 
see Olfactory organ. 
Brain, cerebrum and cerebellum, see 
Nerve centres. 
Bronchia, see Lungs. 
Bruch’s trachoma follicles, 113, 263. 
Brunner’s glands, 147. 
Buccal glandules, see Digestive appa- 
ratus. 
Bulbus olfactorious, see Olfactory appx- 
ratus. 
Canaliculi, see Bone tissue. 
Canalis cochlearis, see Auditory appara- 
tus. 266 
INDEX. 
Canalis Fontanae, see Eye. 
Canalis Petiti, see Eye. 
Canalis Schlemmii, see Eye. 
Canalis semi-circular of the ear, see 
Auditory apparatus. 
Capillaries, see Vessels. 
Carotid gland, 126. 
Cartilage, 42 ; hyaline, elastic (reticular) 
and connective-tissue cartilage, 42; 
cartilage cavities and cartilage cells, 
43 ; cartilage capsules, 43 ; intercel- 
lular substance, 43; metamorphosis 
of fibres and calcification, 44 ; occur- 
rence of hyaline cartilage, 44 ; reticu- 
lar cartilage, 45 ; connective tissue, 45. 
Cartilage capsules, see Cartilage. 
Cartilage cell, see Cartilage. 
Cartilage medulla, see Bone. 
Cavernous bodies, see Sexual apparatus 
of the male. 
Cavernous passages of the lymphatic 
glands, see Lymphatic glands. 
Cells, 3 ; naked cells, 3 ; cell doctrine, 
3 ; cell and cytode, 4 ; cell forms, 4, 
5 ; globular, flattened and cylindrical 
forms, 5 ; spindle cells, 5 ; proto- 
plasma, 5 ; transformation of the 
same, 5 ; nucleus, 6 ; nucleolus, 6 ; 
non-nuclear cells, 6 ; multinuclear cells 
(myeloplaxes), 7; cell envelope and 
capsule, 7; porous canals, 8; vital 
(amoeboid) changes in form of the cell, 
9; pus corpuscles, 9; nutrition and 
locomotion, 9; penetration of cells 
into cells, 10; ciliated or vibratory 
cells, 10; sensibility of cells, n ; 
assimilation, 11; duration of life, 12; 
kinds of death of the cell, 13; spon- 
taneous genesis, 14 ; processes of divi- 
sion, 14; endogenous cell formation, 
with mother and daughter cells, 15 ; 
intercellular substance, or tissue 
cement, 16; metamorphosis of the 
cells, and production of tissues, 17; 
metamorphosis of the intercellular sub- 
stance, 17 ; elastic fibres, 17 ; glands, 
18 ; transversely striated muscular fila- 
y mentis, 19. 
Cerebellum, see Nerve centres. 
Cerebral ganglia, see Nerve centres. 
Cerebrin, 194. 
Cerebrum, see Nerve centres. 
Cerumen, see Auditory apparatus. 
Ceruminous glands, see Auditory appa- 
ratus. 
Cl jrio-capillaris, see Eye. 
Chorion of the ovum, 176. 
Choroid, see Eye. 
Chyle, 26, 
Chyle vessels, 103, 116. 
Ciliary cells, see Epithelium. 
Ciliary motion, see Epithelium. 
Ciliary muscles, see Eye. 
Circulatory apparatus, see Vessels. 
Clitoris, see Sexual system of the female, 
Coagulation of the blood, 25. 
Coagulation of the nerve medulla, 194. 
Coccygeal gland, 126., 
Cochlea, see Auditory apparatus. 
Cochlear canal, see Auditory apparatus 
Colloid, 124. 
Colloid metamorphosis of the thyroid 
cavities, 124 ; of the apophysis cere- 
bri, 126. 
Colostrum, see Sexual system of the 
female. 
Columnse Bertini, see Kidneys. 
Columns of the spinal cord, see Nerve 
centres. 
Commissura anterior and posterior of the 
spinal cord, see Nerve centres. 
Commissures of the spinal cord, see 
Nerve centres. 
Conarium of the brain, see Nerve centres. 
Coni of the retina, see Eye. 
Coni vasculosi, see Sexual apparatus of 
the male. 
Conjunctiva, see Eye. 
Connective substance, 41. 
Connective substance, lymphoid and 
reticular, 45. 
Connective tissues, 51; fibrillse, bundles, 
elastic elements, 51 ; elastic sheaths, 
53 ; cells of two different forms, 54 ; 
formless connective tissue, 56 ; formed, 
56 ; cornea, 56 ; tendons, 57 ; liga- 
ments, 57 ; connective-tissue cartilage, 
57 5 fibrous membranes, 57 ; serous, 
57; corium, 58; mucous membranes, 
58 ; vascular membranes (pia mater, 
plexus choroides, and choroid), 58; 
connective tissue vascular walls, 58 ; 
elastic structures, 58; pathological, 
59 ; embryonic conditions of the tissue, 
59- . 
Constituents of the body, 3. 
Contour, double, of the nerves, see Nerre 
tissue. 
Contract of the living cell, 9. 
Convoluted glands, 130. 
Cornea, 56, 207, and see Eye. 
Corneal cells, 56, 245. 
Corneal corpuscles, 56, 248. 
Corneal nerves, 207. 
Corneal tubes, see Eye. 
Corneous layer of the epidermis, 32. INDEX. 
267 
Cornification of the pavement epithelium, 
see Epithelium. 
Cornu ammonis of the brain, see Nerve 
centres. 
Corpora cavernosa, 190. 
Corpora quadrigemina of the brain, see 
Nerve centres. 
Corpus callosum, see Nerve centres 
Corpus ciliare, see Eye. 
Corpus epididymis, see Sexual apparatus 
of the male. 
Corpus Highmori, see Sexual apparatus 
' of the male. 
Corpus luteum, see Sexual apparatus of 
the female. 
Corpus striatum of the brain, see Nerve 
centres. 
Corpus vitreum, see Eye. 
Cortex corticis of the kidney, see Kidney. 
Corti’s cells, see Auditory apparatus. 
Corti’s fibres, see Auditory apparatus. 
Corti’s organ, see Auditory apparatus. 
Cowper’s glands, see Sexual apparatus of 
the male. 
Crura cerebri and cerebelli of the brain, 
see Nerve centres. 
Cuticula of the hair, see Epithelium. 
Cytode, 2. 
Daughter cells, 15. 
Dehiscence of the ovarian follicles, see 
Sexual system of the female. 
Deiter’s cells of the cochlea, see Auditory 
apparatus. 
Dental nerves, 214. 
Dentinal cells, 75. 
Dentinal tubes, etc., see Tooth tissue. 
Dentine, 73. 
Desquamation of the cells, 12. 
Digestive apparatus, 139; oral cavity, 
139; mucous glands, 139; salivary 
glands, submaxillary and sublingual, 
139 ; change of the gland cells, 140 ; 
parotid, 141 ; tongue with its various 
papillae, 141 ; serous glands of the 
tongue, 142; pharynx, 142; oesophagus, 
142; stomach, 142 ; tubular glands. 
143 ; frame-work of the mucous mem- 
brane, 143 ; peptic and gastric-mucous 
glands, 143 ; blood-vessels, 145 ; 
lymphatics, 145 ; small intestines, 146; 
intestinal villi and Lieberkiihnian 
glands, 146; Brunner’s glands, 146; 
lymph or chyle passages, 148 ; absorp- 
tion of fat, 148; large intestine and 
its tubular glands, 149; lymphoid 
follicles of the intestines, 149 ; blood- 
vessels, 149; anus, 149. 
Dilator pupilke, see Eye. 
Discs of the transversely striated mus- 
cles, see Muscles. 
Division of the cells, 14. 
Ductus ejaculatorii of the testicle, 189. 
Dura mater, 57 and 231. 
Duverney’s glands, 181. 
Ear, see Auditory apparatus. 
Egg germ, see Sexual organs of the fe- 
male. 
Egg-strands, see Sexual organs of the 
female. 
Elastic tissue, 52. 
Emigration of colored blood-cells through 
the walls of the vessels, 90; of lym- 
phoid cells, 90. 
Emigration of red and colorless blood- 
cells, 90. 
Enamel germ, 76. 
Enamel of the teeth, 75 ; enamel prisms, 
75 ; enamel cuticle, 75 ; transverse sec- 
tion, 75 ; genesis, 76. 
Enamel organ, 46, 76. 
Enamel prisms, etc., see Enamel. 
Endogenous cell formation, 15. 
Endothelium, 28. 
Engelmann’s accessory discs of the trans- 
versely striated muscle, 85. 
Envelopes of the finer nerve trunks, 57, 
202. 
Enveloping structures of the central 
nervous system, 231. 
Epidermis, see Epithelium. 
Epididymis, see Sexual apparatus of the 
male. 
Epithelium, 28 ; endothelium, 28 ; pave- 
ment, cylinder and ciliated epithelium, 
28 ; cement substance, 31 ; pigment- 
ed epithelium, 30; stratified, 30; 
stachel and riff cells. 32 ; epidermis, 
32 ; ciliary movement, 35 ; nail tis- 
sue, 36 ; nail cells, 37; hairs, 38 ; 
hair shaft and root, 38; root sheath, 
38; cortex and medulla of the hair, 
39 ; epidermis, 39 ; appearance of the 
hairs, lanugo hairs, 40, 
Erection, 191. 
Eustachian tubes, see Auditory appara- 
tus. 
Eye, 246; parts of the eyeball, 247; 
cornea, 247 ; sclerotic, 248 ; canalis 
Schlemmii, 249 ; choroid, 249 ; parts 
of the same, 249 ; ciliary body, 249 ; 
ciliary processes, 249 ; ciliary muscle, 
249 ; iris, 250; sphincter and dilator of 
the pupil, 250; ligamentum pectina 
turn iridis, 250; nerves of the iris, etc.. 268 
INDEX. 
251; crystalline lens, 251; vitreous 
body, 251 ; zonula Zinnii, 251 ; cana- 
lis Petiti, 251 ; retina, 251 ; arrange- 
ment, 252 ; macula lutea, 252 ; layers, 
252; frame-work substance, 252; 
membrana limitans interna, 252 ; 
Mueller’s fibres, 253; membrana 
limitans externa, 254 ; rods and cones, 
254; external granular layer, 257; 
intergranular layer, 257 ; inner gran- 
ular layer, 258 ; molecular stratum, 
258; layer of ganglion cells, 258 ; of 
nerve fibres, 259 ; macula lutea, 259 ; 
pars ciliaris, 260; lymphatics of the 
eye, 261 ; eyelids, 262 ; glands of the 
conjunctiva, 262; lachrymal glands, 
263. 
Eyeball, see Eye. 
Fallopian tube, see Sexual organs of the 
female. 
Fat tissue, 48 ; fat cells, 48 ; fat drops, 
48 ; chemical constitution of the tat 
of the body, 49 j cells losing their fat, 
49 ; occurrence of fat tissue, 50 ; gen- 
esis, 50. 
Fatty degeneration, 13, 88. 
Fibre cell, contractile, see Muscular 
tissue. 
Fibro-cartilage, see Cartilage tissue. 
Fibro-reticular cartilage, see Cartilage 
tissue. 
Follicles, Graafian, of the ovary, see 
Sexual organs of the female. 
Follicles, Malpighian, of the spleen, see 
the latter. 
Follicles of the lymphatic glands, see the 
latter. 
Follicular chains of the ovary, see Sexual 
organs of the female 
Follicular rudiments of the ovary, see 
Sexual organs of the female. 
Forked cells, see Gustatory apparatus. 
F'ormatio granulosa of the ovary, see 
Sexual organs of the female. 
Fovea centralis of the retina, see Eye. 
Gall-bladder, see Liver. 
Ganglia, see Nerve centres. 
Ganglion body, see Nerve tissue. 
Ganglion cell layer of the retina, see 
Eye. 
Ganglion cells, see Nerve tissue. 
Gastric glands, see Digestive apparatus. 
Gastric-mucous glands, see Digestive ap- 
paratus. 
Gastric-mucous membrane, see Digestive 
apparatus. 
Gegenbaur’s osteoblasts, see Bone tis- 
sue. 
Gelatinous tissue and reticular connec- 
tive substance, 45 ; vitreous body, 46; 
reticular connective substance, 47 • 
lymphoid cells and modifications of the 
tissue, 47. 
General lamella:, see Bone tissue. 
Germinal plates, 28, etc. 
Germinal spot, see Ovum. 
Germinal vesicle, see Ovum. 
Giant cells, see Myeloplaxes. 
Gland capillaries, 134. 
Gland nerves, 208. 
Gland tissue, 128; definition, 128; con- 
stituents of the glands, 129; various 
forms of glands, 130; gland cells, 131; 
secretions, 132; vessels, 134 ; lymphat- 
ics, 135 ; nerves, 135; excretory 
ducts, 135 ; individual glands of the 
body, 137 ; genesis, 138. 
Glands, mucous, 139. 
Glands, serous, 142. 
Glomerulus of the kidney, 98, 164. 
Gob’s column of the spinal cord, see 
Nerve centres. 
Graafian follicles of the ovary, see 
Sexual organs of the female. 
Granular layer of the retina, see Eye. 
Growth of the cells, n. 
Gustatory apparatus, 236 ; the various 
papillae, 236; papillae circumvallatae 
and foliatae, 236 : gustatory buds, 237 ; 
nerve termination, 238; gustatory 
cells, 238. 
Gustatory buds, see Gustatory appar- 
atus. 
Gustatory organ (tongue), see Gustatory 
apparatus. 
Gustatory papillae of the tongue, see 
Gustatory apparatus. 
Habenulae of the cochlea, see Auditory 
apparatus. 
Haemoglobin, 22. 
Hair bulb, see Epithelium. 
Hair sac, see Epithelium. 
Hair, see Epithelium. 
Haversian canals, see Bone tissue. 
Haversian lamellae, see Bone tissue. 
Haversian spaces, see Bone tissue. 
Heart muscles, 86. 
Hemispheres of the cerebrum and cere- 
bellum. see Nerve centres. 
Henle’s loops of the uriniferous canals, 
see Urinary apparatus. 
Hensen’s middle discs of the transversely 
striated muscles, 84. INDEX. 
269 
Hepatic lobules, see Liver. 
Hepatic vessels, see Liver. 
Hilus-stroma of the lymphatic glands, 
108. 
Histology, 3. 
Horn layer, 28. 
Horn layer of the epidermis, 32. 
Humor aqueus of the eye, see Eye. 
Humor vitreus of the eye, see Eye. 
Hymen, see Sexual apparatus of the 
female. 
Hypophysis cerebri, 126. 
Infundibula of the lungs, see Lungs. 
Interglobular spaces of the dentinal tissue, 
see Teeth. 
Intestinal glands, see Glands, and Diges- 
tive organs. 
Intestinal villi, 104; and Digestive or- 
gans. 
Iris, see Eye. 
Iris nerves, see Eye. 
Keratine, 5. 
Kidney, 163 ; cortex and medulla, 163 ; 
Malpighian or medullary pyramids, 
163; column® Bert ini, 163 ; uriniferous 
canals or Bellini’s lubes, 163 ; medul- 
lary rays, 164; cortical pyramids, 164; 
glomerulus, 164; papillae renales, 
164; looped canals, 164; excretory 
passages and secretory portion of the 
kidney, 165 ; vascular arrangement of 
the cortical pyramids, 165 ; Mueller’s 
or Bowman’s capsule, 165 ; epithelial 
relations, 166; intercalary piece, 167 ; 
frame-work substance of the kidney, 
168 ; blood and lymph vessels, x6B; 
blood passages, x6B ; lymph passages, 
x 70; urinary passages, 17 x ; renal 
calices and pelvis, 171 ; ureter, 171; 
bladder, 171 ; female uretha, 172. 
Krause’s transverse line of the muscles, 
see Muscular tissue. 
Labia, see Sexual organs of the female. 
Lachrymal gland, etc., see Eye. 
Lacunae, see Bone tissue. 
Lamellae of the bones, see Bone tissue. 
Lamina-elastica of the cornea, see Eye. 
Lamina fusca of the choroid, see Eye. 
Lamina recticularis (velamentosa), see 
Auditory apparatus. 
Lamina spiralis of the cochlea, see Audi- 
tory apparatus. 
Large intestine, see Digestive organs. 
Larynx, see Lungs. 
Lens tissue, 78; lens capsule, 78 ; lens 
fibres, 78. 
Lentiform gastric glands, see Lymphoid 
organs. 
Leucaemia, 123. 
Lieberkiihnian glands, see Digestive 
apparatus. 
Ligaments, see Connective tissue. 
Ligaments, elastic, see Connective tis- 
sue. 
Ligamentum ciliare, see Eye. 
Ligamentum pectinatum iridis, see Eye. 
Ligamentum spirale of the cochlea, see 
Auditory apparatus. 
Lingual papillae, 141. 
Liquor folliculi, see Sexual apparatus of 
the female. 
Liver, 150; hepatic lobules, 151 ; hepa- 
tic cells, 151 ; fatty liver, 151 ; hepa- 
tic cell trabeculae, 152; vessels, 152; 
frame-work, 153 ; biliary passages and 
biliary capillaries, 154; lymphatics, 
155- 
Lungs, 157 ; larynx, 157 ; trachea, 157 ; 
lungs, 158; alveolar passages and pul- 
monic lobules, 158 ; pulmonary vesi- 
cles, p. cells, alveoli, 158; structure, 
159; black lung pigment, 160; ar- 
rangement of vessels, 160; pulmo- 
nary epithelium, 162. 
Lymph, 27. 
Lymph corpuscles, see Lymphoid cells. 
Lymph passages, 102 ; ductus thoraci- 
Cus, 102 ; lymphatics, 103 ; injection 
of the lymphatics, 103 ; arrangement 
of the same, 104; clefts, 106; juice 
canals or juice clefts, 107 ; lymphatic 
glands. 107; envelope, cortex and 
medulla, hilus-stroma, 108; follicles, 
108 ; septa and tenter-fibres, 109 ; in- 
vestment spaces, 109 ; lymph canals, 
no; blood-vessels, 110. 
Lymph sheaths of the blood-vessels, see 
Vessels. 
Lymph vessels, see Lymph passages. 
Lymphatic glands, see Lymph passages. 
Lymphoid cells, 5, 9, 23, etc. 
Lymphoid follicles, see Lymphoid or- 
gans. 
Lymphoid organs, 112; lens-shaped 
glandules, solitary and Peyerian fol- 
licles, tonsils and trachoma glands, 
112; structure of the tonsils, Ix 3; 
trachoma glands in particular, 113 ; 
structure of the Peyerian plaques, 114; 
spleen, 116; Malpighian corpuscles, 
and pulp, 117 ; vessels, 119 ; cells 
containing blood corpuscles, X 22; 270 
INDEX. 
leucaemia, 123; lymphatics, 123; 
blood-vascular glands, 123. 
Macula lutea of the retina, see Eye. 
Malpighian bodies of the spleen, see 
Lymphoid organs. 
Malpighian glomerulus, see Kidney. 
Malpighian pyramids of the kidney, see 
Kidney. 
Malpighian rete mucosum, see Epider- 
mis. 
Medulla, see Spinal cord and medulla 
oblongata. 
Medulla oblongata, see Nerve centres. 
Medulla of the nerves, see Nerve tissue. 
Medullary canals of the bones, see Bone 
tissue. 
Medullary substance of the lymphatic 
glands, kidney, etc., see the organs in 
question. 
Meibomian glands, see Eye. 
Melanin, 5, 30, 
Membrana Descemetica (Demourisiana), 
, see Eye. 
Membrana hyaloidea, see Eye. 
Membrana limitans of the retina, see 
Eye. 
Membrana propria of the glands, see 
Glands. 
Membrana tympani, see Auditory ap- 
paratus. 
Membranes, fibrous, serous, etc., see 
Connective tissue. 
Middle germinal layer, 28. 
Milk, see Sexual organs of the female. 
Milk glands, see Sexual organs of the 
female. 
Milk globules, see Sexual organs of the 
female. 
Molecular movement (Brunonian), 27. 
Mother cells, 15. 
Mucous corpuscles, see Lymphoid cells. 
Mucous membrane, see Connective 
tissue. 
Mucous tissue, 46. 
Mueller’s capsule of the kidney, see Kid- 
ney. 
Mueller’s supporting fibres of the retina, 
see Eye. 
Muscle nerves, 203. 
Muscles, see Muscular tissue. 
Muscular filaments, etc., see Muscular 
tissue. v 
Muscular tissue, 79 ; smooth and trans- 
versely striated, 79 > smooth muscles, 
contractile fibre cells, 80; their occur- 
rence, 80; transversely striated, 81; 
muscular filaments (fibres), 81; sar- 
colemma and sarcous elements, Si ; 
fibrillge and discs, 83 ; transverse discs, 
84 ; accessary discs, 85 ; interstitial 
granules, 85 ; heart muscle, 86; 
transverse section of the muscle, 86 ; 
connection with the tendons, 86 
embryonic development, 87 ; increase, 
88 ; fatty degeneration, 88. 
Myeloplaxes, 7. 
Nail tissue, 37. 
Nails, 36. 
Nasal cavities, see Olfactory apparatus. 
Nerve centres, 2x5; ganglia, 215; their 
structure, 215; sympathetic, 217; 
sympathetic ganglia, submucous and 
plexus myentericus, etc., 217, 218 ; 
spinal cord, 218 ; neuroglia, 220; nerve 
roots of spinal cord, 221 ; white 
substance of spinal cord, 222 ; medulla 
oblongata, 224 ; its several parts, 224; 
cerebellum, 227 ; its several parts, with 
the cortex, 227; cerebrum, 229; its 
several parts, 229 ; blood and lymph 
vessels, 231. 
Nerve fibres, etc., see Nerve tissue. 
Nerve plexuses, etc., see Nerves, ar- 
rangement of. 
Nerve sheath, 202. 
Nerve tissue, 192; nerve fibres and 
ganglion cells, 192 ; medullated and 
non-medullated nerve fibres, X 92; 
broad and narrow medullated fibres, 
192; primitive sheaths, 193; axis 
cylinders, 193; nerve medulla (med- 
ullary sheath), 193; coagulation of 
the medulla, 194; transverse section, 
194; varicosities, 195; Ranvier’s 
constriction rings, 195; pale (Ro- 
maic's), nerve fibres, 196; axis or 
primitive fibrillse, 196 ; ganglion cells, 
197; apolar ganglion cells, 198; 
origin of nerve fibres, 198 uni- and 
bipolar ganglion cells, 198, 199 ; mul- 
tipolar ganglia, 200 ; protoplasma and 
axis-cylinder processes, 290. 
Nerve tubes, see Nerve tissue. 
Nerves, arrangement and termination of, 
202 ; nerve sheath (neurilemma), 193, 
202; nerve termination, 203 ; ter- 
minal plates of voluntary muscles, 
204; nerves of the smooth muscles, 
206 ; nerve termination in the cornea, 
207; gland nerves, 208; terminal 
bulbs, 208; Pacinian corpuscles, 2xo; 
tactile bodies, 211 ; other nerve ter- 
minations, 213; Langerhans’ cor- 
puscles, 213. INDEX. 
271 
Nerves* see Nerve tissue. 
Neurilemma (nerve sheath), 202. 
Neuroglia, see Nerve centres. 
Nipple, see Sexual apparatus of the fe- 
male. , 
Nucleus dentatus cerebellp see Cerebel- 
lum. 
Nucleus of the cell, 6. 
Nymphte, see Sexual organs of the fe- 
male. 
Odontoblasts, see Dentine. 
(Esophagus, see Digestive apparatus. 
Olfactory hairs, etc., see Olfactory ap- 
paratus. 
Olfactory nerve, see Olfactory organ. 
Olfactory organ, 238 ; regio olfactoria, 
238; its structure, 238; olfactory 
cells, 239 ; termination of the same, 
240. 
Optic nerve, see Eye. 
Ora serrata retinae, see Eye. 
Oral cavity, see Digestive apparatus. 
Ossification process, see Bone tissue. 
Osteoblasts, etc., see Bone tissue. 
Otoliths, see Auditory organ. 
Ovarian follicles, see Sexual organs of the 
female. 
Ovary, see Sexual organs of the female. 
Oviduct, see Sexual organs of the female. 
Ovulum, see Sexual organs of the female. 
Ovum, S, 175. 
Ovum, primordial, see-Sexual organs of 
the female. 
Pacchionian granulations, see Nerve cen- 
tres. 
Pacinian corpuscles, see Nerve termina- 
tions. 
Palatine glands, see Digestive appara- 
tus. 
Palpebroe, see Eye. 
Pancreas, 150; contents, 150; centro- 
acinary cells, 150. 
Panniculus adiposus. 49. 
Papilla foliata of the tongue, see Gusta- 
tory apparatus. 
Papilla spiralis (Corti’s organ) of the 
cochlea, see Auditory apparatus. 
Papillae circumvallatse of the tongue, see 
Gustatory apparatus. 
Papillae filiformes of the tongue, see Gus- 
tatory apparatus. 
Papillae fungiformes, see Gustatory ap- 
paratus. 
Papillae of the corium, 58, 212. 
Papillae renales, see Kidney. 
Parotid, see Digestive apparatus. 
Parovarium, see Sexual apparatus of the 
female. 
Pavement epithelium, see Epithelium. 
Pedunculi cerebri, see Nerve centres. 
Penicilli of the splenic arteries, see 
Spleen. 
Penis, see Sexual apparatus of the male. 
Peptic-gastric glands, see Stomach. 
Peptic-renic cells, see Stomach. 
Pericardium, see Connective tissue. 
Perichondrium, see Connective tissue. 
Perilymph (aqua Cotunnii), see Auditory 
apparatus. 
Perimysium, see Muscular tissue. 
Perineurium (nerve sheath), 202. 
Periosteum, see Connective tissue and 
Bones. 
Petit’s canal, see Eye. 
Peyer’s glands (follicles), see Lymphoid 
organs. 
Pharynx, see Digestive apparatus. 
Pia mater, see Connective tissue and 
Nerve centres. 
Pigment cells, see Epithelium and Con- 
nective tissue. 
Pigment epithelium of the retina, see 
Epithelium. 
Pineal gland of the brain, 230. 
Pleura, see Connective tissue. 
Plexus choroidei of the brain, see Nerve 
centres. 
Plexus myentericus, see Nerve tissue. 
Plexus of the nerves, see Nerve arrange- 
ment. 
Plica semilunaris, see Eye. 
Pons Varolii, see Nerve centres. 
Porous canals of the cells, 8. 
Primitive fibnllee of the connective tis- 
sue, muscles, and nerves, see these tis- 
sues. 
Primitive sheaths of muscles and nerves, 
see these tissues. 
Primordial kidney, see Kidney. 
Primordial ova, see Sexual organs of the 
female. 
Processus ciliaris of the eye, see Eye. 
Processus vermiformis, 114. 
Prostate, see Sexual organs of the male. 
Protamceba, 2. 
Protoplasma, 2, etc. 
Pulp of the spleen, see Lymphoid or- 
gans. 
Pulpa dentis (tooth germ), 74. 
Purkinje’s ganglion cells, see Central 
nervous system ; germinal vesicle of 
the ovum, see Sexual organs of the 
female. 
Pus corpuscles (lymphoid cells), 9. 272 
INDEX. 
Pyramids of the kidney, see Kidney. 
Pyramids of the medulla'oblongata, see 
Nerve centres. 
Regio olfactoria, see Olfactory apparatus. 
Reissner’s membrane of the cochlea, see 
Auditory apparatus. 
Remak’s nerve fibres, see Nerve tissue. 
Remak’s studies on cell formation, 14. 
Renal papillae, etc., see Kidney. 
Respiratory organs, see Lungs. 
Rete Malpighii, see Epithelium. 
Rete testis, see Sexual organs of the 
male. 
Reticular cartilage, see Cartilage. 
Retina, see Eye. 
Retinal vessels, see Eye. 
Riff cells (stachel cells), see Epithelium. 
Rod corona fibres, see Nerve centres. 
Rods of the retina, see Eye. 
Salivary glands, see Digestive apparatus. 
Sarcolemma, see Muscular tissue. 
Sarcous element, see Muscular tissue. 
Scala media of the cochlea, see Auditory 
apparatus. 
Schlemm’s canal, see Eye. 
Schneiderian membrane, see Olfactory 
apparatus. 
Schwann’s cell doctrine, 14; Schwann’s 
nerve sheath, see Nerve tissue. 
Sclerotic, see Eye. 
Sebaceous follicles, 236. 
Sebum cutaneum, 132, 236. 
Sebum formation of the glands of the 
skin, 132. 
Sebum palpebrse, see Eye. 
Segmentation of the yolk, 179. 
Semen, see Sexual organs of the male. 
Seminal filaments, etc., see Sexual or- 
gans of the male. 
Sexual organs of the female; ovary, 
173 ; cortical and medullary substance 
of the same, 173 ; germinal epitheli- 
um, 173 ; cortical or zone of the pri- 
mordial follicle, 173; ripe Graafian 
follicle, 175 ; ovum with the chorion, 
yolk, germinal vesicle, and germinal 
spot, 176 ; blood and lymph vessels, 
177; parovarium, 177; genesis, 178; 
follicle chains or ovum strands, 178; 
corpus luteum, 179; segmentation of 
the ovule, 179; oviduct, 179 ; uterus, 
179; uterine glands, 180 ; blood and 
lymph passages of the uterus, 180 ; 
pregnancy, 180 ; vagina, 180 ; hymen, 
ciitoiis, nymphse, and labia majora, 
iSx; vestibule, entrance to the vagina, 
181; lacteal glands, 181 ; colftstrurr. 
and milk, 182. 
Sexual organs of the male ; testicle, 183 ; 
corpus Highmori and seminal canals, 
183; epididymis, etc., 183; vas defe- 
rens, 184; vas aberrans Halleri, 184; 
structure of the seminal canals, 184 ; 
blood and lymph vessels, 185 ; genesis, 
186; seminal filaments, 187; copula- 
tion, 187 ; genesis, 188 ; spermato- 
blasts, 189; structure of the vas defe- 
rens, 189; seminal vesicles, ejaculatory 
ducts, prostate, other glands, 189; 
urethra, 190; corpora cavernosa, 
glans 190 ; colliculus seminalis, 190 ; 
Littre’s and Tyson’s glands, 190; 
structure of the cavernous tissue, 190; 
erection, 191 ; vessels, 191. 
Sharpey’s fibres of the bone, see Bone 
tissue. 
Sheath of the nerve fibres, see Nerve 
tissue. 
Skin, see Connective tissue, 58, and or- 
gans of sense, 234; tactile papillae, 
234; blood-vessels and lymphatics, 
234 ; glands, 235. 
Small intestine, see Digestive apparatus. 
Solitary glands of the intestinal canal, 
see Lymphoid organs. 
Sperm (semen), see Sexual organs of the 
male. 
Spermatozoa, see Sexual organs of the 
male. 
Sphincter pupillse, see Eye. 
Spinal cord, see Nerve centres. 
Spinal ganglia, see Nerve centres. 
Spiral fibres of the ganglion cells, see 
Nerve tissue. 
Spiral leaf of the cochlea, see Auditory 
apparatus. 
Spleen, see Lymphoid tissue. 
Splenic follicles, see Lymphoid organs. 
Splenic vessels, see Lymphoid organs. 
Spot, yellow, of the retina, see Visual 
apparatus. 
Stachel cells (riff cells), see Epithelium. 
Stelluke Verheyenii of the kidney, see 
Kidney. 
Stomach, see Digestive apparatus. 
Stomata of the vessels, see Blood and 
lymph vessels. 
Subarachnoidal spaces, see Nerve cen- 
tres. 
Subdural space, see Nerve centres. 
Sublingual glands, see Digestive appara- 
tus. 
Submaxillary gland, see Digestive ap* 
paratus. INDEX. 
273 
Submucous ganglion plexuses of the di- 
gestive organs, see Nerve centres. 
Suprarenal capsule, see Blood-vascular 
glands. 
Sweat glands, see Gland tissue. 
Sympathetic nerve, see Nerve arrange- 
ment. 
Tactile bodies, see Nerve terminations. 
Tactile organs, 234. 
Teeth, 73 
Tendons, see Connective tissue. 
Tensor choroidige, see Eye. 
Terminal bulbs of the nervous system, 
208. 
Terminal plates of the muscular nerves, 
see Nerve terminations. 
Terminal structures of the nerves, see 
Nerve terminations. 
Testicles, see Sexual apparatus of the 
male. 
Thalamus opticus, see Nerve centres. 
Theca of the ovary follicles, see Sexual 
organs of the female. 
Thymus, see Blood-vascular glands. 
Thyroid, see Blood-vascular glands. 
Tissue, 3 ; simple, 20 ; compound, 21. 
Tissue cement, 16. 
Tissue elements, 4. 
Tissues, division of the, 20. 
Tonsils, see Lymphoid organs. 
Tooth tissue, 73 ; dentine, 73 ; enamel 
and cement, 73 ; dentinal tubes, 73 ; 
cement, 74 ; interglobular spaces, 74 ; 
dentinal cells or odontoblasts, 75 ; 
genesis of the teeth, 76 ; tooth mound, 
enamel germ, tooth germ, 76 ; enamel 
organ, tooth sac, 77. 
Trachea, see Lungs. 
Trachoma glands, see Lymphoid organs 
and Eye. 
Tubse Fallopii, see Sexual organs of the 
female. 
Tunica vasculosa of the eye, see Eye. 
Tympanum, etc., see Auditory appar- 
atus. 
Tyson’s glands, see Sexual organs of the 
male. 
Ureter, see Kidney. 
Urethra, 172, 190. 
Urethra, female, see Urinary apparatus ; 
urethra, male, see Sexual organs of the 
male. 
Urinary apparatus, 163 ; kidneys, 163 ; 
cortex and medulla, 163 ; medullary 
pyramids, 163; columnse Bertini, 163; 
uriniferous canals (Bellini’s tubes), 
163 ; cortical pyramids and glomerulus, 
164; papillae renales, 164; looped 
canals, 164; their two sides, 165; 
Mueller’s or Bowman’s capsule of the 
glomerulus, 165 ; course of the urini- 
ferous canals, intercalary portion, etc., 
166; vascular arrangement, 168; 
cortex corticis, 169; vasa recta, 170; 
lymphatics, 170; theory of the urinary 
secretion according to Ludwig, Bow- 
man, 171 ; urinary canals, renal cali- 
ces and pelvis, 171; ureter, 171; urin- 
ary bladder, 171 ; female urethra, 
172. 
Uterine glands, see Sexual organs of the 
female. * 
Uterus, see Sexual organs of the female. 
Uvea of the eye, see Eye. 
Vagina, see Sexual organs of the fe- 
male. 
Varicosities of the nerves, see Nerve tis- 
sue. 
Vas aberrans Halleri of the testicle, see 
Sexual organs of the male. 
Vas afferens and efferens of the lymph- 
atic glands, see Lymphatics. 
Vasa recta of the kidney, see Kidney. 
Vascula efferentia of the testicle, see 
Sexual organs of the male. 
Vascular membranes, see Vessels and 
Connective tissue.: 
Vascular tissue, see Vessels. 
Veins, see Vessels. 
Venae, inter, and intralobulares of the 
liver, see Liver. 
Venae vorticosae of the eye, see Eye. 
Venous plexus (plexus choroides), of the 
brain, see Central organ of the nervous 
system. 
Vesiculae seminales, see Sexual organs of 
the male. 
Vessels, blood, 16; arteries, veins and 
capillaries, 89 ; capillaries, 89 ; vascu- 
lar cells, 90; adventitia capillaris, 
91; lymph sheath, 91 ; structure of 
the large arterial and venous trunks, 
91 ; structure of the veins, 93 ; of the 
arteries, 94; valves, 95; capillary 
system, 95 ; capillary net-work, 96 ; 
various forms of the same, 96 ; genesis 
in the embryo, 99. 
Vessels, lymphatic, 102; intestinal villi, 
104; other localities, 105 ; lymphatic 
apertures, 106 ; juice canals and clefts, 
107 ; lymphatic glands, 107; their 
structure, 108; cortex, medulla, fol- 
licles, medullary strands, septum sys- INDEX. 
tem, investment space, 108, 109; 
lymphatics of the medulla, 110; ves- 
sels, no; lymph current, in. 
Vestibule of the ear, see Auditory ap- 
paratus. 
Visual apparatus, 24.6. 
Vitreous boc' , 4.5, and the Eye. 
Wandering of the cells. 10. 
Wolffian body, i} 7, 186. 
Yolk, see Ovum.