bundles are often covered with endothelium (connective- tissue
corpuscles), which are continuous and form a complete invest-
ment.

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

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

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



74 MANUAL OF HISTOLOGY.

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

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

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

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

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

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

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

Inter muscular tissue. It has been claimed by some that



THE CONNECTIVE SUBSTANCE GKOUP. 75

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

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

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

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

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

In general, these bodies appear, as stated by Waldeyer, to
be fiat, having a considerable amount of protoplasmic material
about their nuclei (Fig. 30), though in the direction 6f the per-
iphery they gradually caper off into thin expansions, which are
nearly homogeneous, and extending from them are distinct
processes which in part unite with those of other corpuscles,
not materially differing in this respect from tendon-tissue and
the other varieties. In them is the same flattened, oval body,
which, when seen on the side, is rod-shaped, 5, and is sur-
rounded by an irregular envelope that assumes almost any
shape. Thus the corpuscles are not always flat, though they
are usually so. Their shape depends upon many different
causes, such as the method of preparing the tissue, the amount
of laceration to which it is subjected, etc. The best method 6t'
examining the cornea consists in preparing it by the gold me-
thod, already described.



76



MANUAL OF HISTOLOGY.



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

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




FIG. 30. Corneal tissue. From the rabbit.

as they have been called by Recklinghausen and others. These
bodies are disposed at quite regular intervals throughout the
cornea, and are generally flat with rounded contours, though
often they have processes extending from them in various direc-
tions. In the accompanying drawing the spaces may be dis-
tinctly seen, as well as the variously shaped corneal corpuscles.
One, c, is crowded into the prolongation of a corneal space,
while another, 5, is connected by its processes with a neighbor-
ing corpuscle. One corneal space, a, is entirely empty. These
differing conditions are in a measure due, probably, to the



THE CONNECTIVE SUBSTANCE GROUP. 77

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

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

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

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

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

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

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

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



78



MANUAL OF HISTOLOGY.



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




FIG. 31. Elastic tissue networks. From the frog.

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

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

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



THE CONNECTIVE SUBSTANCE GEOUP. 79

adult tissue become extremely small, and are represented by
the dark markings seen in them. Thin, of London, has claimed
that they originate in branching corpuscles, which by their
coalescence form the network, and the remains of the nucleus
may be shown by hsematoxylin. These markings may, it is
true, be seen in the ligamentum nuchse of the ox, but it is
doubtful whether they are nuclei or mere clefts in the tissue.
Examination by the author, with such high powers as Gund-
lach' s No. 15 immersion, and Wale' s T V, have failed to clear
up the matter.

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

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

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

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

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

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



80



MANUAL OF HISTOLOGY.



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

As the corpuscles become smaller their envelope shrinks,
and they recede from one another. Yet, in many cases, they
may retain connection with one another by means of their pro-

cesses. In advanced life these cor-
puscles are generally more or less
flattened, but their form is also con-
siderably modified by the age of the
tissues and various mechanical alter-
ations to which they are subjected,
according to the particular locality
in which they occur or the province
they have to fill.

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

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

sue. Fibroma of the scalp. r

lium. It is becoming more and more

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

Ehrlich has recently described peculiar connective-tissue




BIBLIOGRAPHY. 81

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

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



BIBLIOGRAPHY.

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

FLEMMING. Arch. f. Anat., etc. 1879. 401454.

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

KOLLMANN. Centralbl. f. d. med. Wiss. 1878. XVI., 881.

EHKLICH. Verhandl. d. Berliner phys GeselL Jan. 17, 1879; Arch. f. Anat. u.
Phys. Phys. Abtheil. pp. 166169. 1879.

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

6



CHAPTER VI.

THE CONNECTIVE SUBSTANCE GKOUP Continued.
CARTILAGE.

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

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

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

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

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



THE CONNECTIVE SUBSTANCE GROUP. 83

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

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

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

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

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

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



84 MANUAL OF HISTOLOGY.

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

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




PIG. 33. Fresh cartilage from the triton. (Rollett.)

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

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

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

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



THE CONNECTIVE SUBSTANCE GROUP. 85

from the frog ; strip it of pericliondrium and mount in serum.
The shoulder-girdle of the triton (newt) may also be employed.
It will then be seen that there are numbers of granular cor-
puscles, with nuclei scattered irregularly throughout an ap-
parently homogeneous, i.e., structureless matrix. If now a
little water be added to the preparation, it will be seen that the
corpuscles are made to shrivel, and in so doing they expose
the wall of the cavity or capsule in which they lie. The cor-
puscles do not appear to have any uniform size or shape : some-
times they are single ; again they are double (daughter-cells) ;
occasionally they are united with the corpuscles in adjacent
capsules. The nucleus is apt to be round and full ; the corpus-
cles are apt to be filled with dark spherical bodies which are
usually fatty molecules, as may be shown by employing a di-
lute solution of osmic acid (1 per cent.).

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

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

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