relation to the synovia. It exhales by numerous orifices this
fluid which remains there for some time, and afterwards re-enters
the circulation by absorption. Its parietes are then the seat of
exhalation, as the kidneys, for example, are that of the secretion of
urine. The reservoir of the exhaled fluid is the sac without opening
which it forms, as the bladder is that of the urine that comes from the
kidneys. The excretory vessels of this same fluid are the absorbents
which carry it into the mass of blood, as the urethra carries the urine
from the bladder. There is under these different relations more analogy
than there at first seems to be, between secretion and exhalation.
The phenomena of the continuance of the synovia in this membranous
reservoir, have relation to the synovia itself or to the articular
surfaces. The first consist in a peculiar but unknown alteration which
it undergoes between the exhalant and absorbent systems. The second
contribute to facilitate the articular motions. The unctuous and
slippery coat which the serous surfaces receive from the synovia, is
remarkably adapted to this use, as I have observed.
_Natural Development._
In the fœtus and in infancy most of the synovial membranes are much
larger in proportion than in the after ages, because the articular
surfaces have a greater extent in the cartilaginous than in the osseous
state; but they are then extremely delicate. The synovia is not,
as the serous fluids are at this age, more unctuous and of greater
consistence; it appears even to be less so. Before birth it is in small
quantity, no doubt because the motions are trifling.
In old age I have observed that the synovial membrane becomes more
dense and compact. It loses in part its white colour and becomes grey;
less synovia is exhaled from it. It is not like the serous surfaces,
exposed to dropsies. The rigidity it acquires makes motion painful.
It never ossifies except preternaturally. The phosphate of lime which
gradually invades cartilage, does not take hold of it. I do not know
an instance of an old person in whom bone has been found naked in an
articulation.
_Preternatural Development._
I have already observed in the article on the fibrous capsules, that
when the head of a bone remains displaced in a luxation, it is not a
membrane analogous to these capsules that is developed around it; it
is a real cyst, smooth on its internal surface, moistened with serum,
formed at the expense of the cellular texture, and presenting, with a
little more thickness, the true appearance of the synovial membranes;
it is a preternatural synovial membrane. The motions imparted to the
displaced limb appear to increase the serous exhalation in this new
membrane; hence no doubt the great advantage of these motions, in
order to re-establish in part the mobility of the bones which remain
out of their sockets. I have seen a dancer, the head of whose humerus
was lodged in the hollow of the axilla, after a luxation that was not
reduced, perform very varied motions with it.
ARTICLE SECOND.
SYNOVIAL SYSTEM OF THE TENDONS.
This system noticed by many authors and described by Fourcroy,
Soemmering, &c. is precisely of the same nature as the preceding, from
which it differs only by its situation; it is often even confounded
with it. Thus the synovial membrane of the tendon of the biceps is
continuous with that of the scapulo-humeral articulation; thus those
of the gemelli are so with the synovial membrane of the femoro-tibial
articulation; it is the same membrane which belongs at the same time to
the tendon and to the articulation. A remarkable example of it is seen
in the extensors of the leg and the ham, to the tendons of which the
same articular synovial membrane of the knee serves for a capsule.
But very few tendinous synovial membranes are found in the trunk;
almost all are on the extremities where they serve to assist the
slipping of the tendons. They are met with, 1st, where a tendon is
reflected at an angle upon a bone, as around those of the great lateral
peroneus, the peroneus medius, the obturator internus, the great
oblique of the eye, &c.; 2d, where a tendon slips upon an osseous
surface without being reflected, as at the extremity of the tendo
Achillis, as under that of the great glutæus, and those of the psoas
and iliacus united; 3d, where a tendon slips in a fibrous capsule,
as in those of all the flexors, &c. Their extent is uniformly in
proportion to that of the tendons upon which they are spread.
_Forms; Relations; Synovial Fluid._
The tendinous synovial membranes, are, like the articular ones, sacs
without an opening, spread on the one hand on the tendon and on
the other upon the neighbouring organs. These sacs are differently
shaped according to the arrangement of the tendon, but their general
conformation is uniform. We see from this that every tendinous synovial
membrane has two faces, one which forms the interior of the sac, which
is everywhere free and contiguous to itself, the other which lines the
adjacent organs.
The free surface is constantly moistened by a fluid precisely similar
to that of the articulations, furnished like it by exhalation, and
not as authors have said by red bodies situated in the neighbourhood,
bodies of which oftentimes there is no trace visible, and which, when
they exist, have nothing glandular in them. This fluid is in general
much less abundant than in the articulations, at least in the dead
body. But there are varieties in the different synovial bags; those of
the tendo Achillis, of the tendons of the psoas and iliacus united, of
that of the obturator internus, &c. are always more moist than those of
the flexor tendons, &c.
Is it to the absence of synovia that must be attributed the species
of crepitation which the tendons sometimes make in their motions? I
know not. I would only observe that this crepitation has some analogy
with the crackling noise of the joints of the fingers when they are
bent quickly, a noise, which does not depend, as might be supposed,
on the friction of the osseous surfaces; in fact, when it has been
once produced, it cannot be again, though there may be friction again.
Besides it is known that this crackling noise arises from the forced
elongation of the phalanges, and consequently from the separation of
their articular surfaces, as well as from the flexion.
The increase of the fluid of the tendinous synovial membranes forms
a species of dropsy which is called ganglion, a tumour which never
exists in the synovial membranes of the fingers, no doubt on account
of the want of extensibility of the fibrous capsules. It should not
be thought however that all these tumours, which are cured by bursting
them by strong pressure and thus effusing the fluid into the cellular
membrane, have for their base a natural synovial membrane. Most
frequently they are preternatural; they are cysts which are formed in
the cellular texture. In fact these tumours are often found in the
course of the great extensor of the thumb, where there is no synovial
membrane. After rheumatic pains I have seen a considerable collection
of fluid in the small synovial membrane of the tendo Achillis; it
gradually disappeared. I have observed another analogous one in the
bag of the psoas of a dead body. The fluid was reddish and of the
consistence of currant jelly. The action of nitric acid immediately
coagulated it into a white mass, analogous to the white of an egg
hardened.
The adhering surface of the tendinous synovial membranes is spread,
1st, on the one hand upon the tendons, with which it is more or less
intimately united. It is easily detached from those of the internal
obturator, the psoas, &c. It is closely connected with those of the
flexors. 2d. On the other hand, it commonly lines the periosteum,
which, in this place, is penetrated with gelatine, and forms a
fibro-cartilage. Its mode of relation is there analogous to that of the
articular synovial membrane with the cartilage of the bone. Sometimes
it is reflected upon a fibrous capsule after having lined the tendon;
such are those which are in the neighbourhood of the scapulo-humeral
articulation. In some cases, after having lined the tendon, they
mount up to the fleshy fibres, as on the obturator internus. 3d. By
reflecting from the tendon upon the neighbouring organs, they answer
in general instead of much cellular texture; but in the grooves of the
flexors, it is the fibrous sheaths which they clothe.
In all the great motions, the tendinous synovial membranes, stretched
more or less, undergo various locomotions, always less however than
those of the serous surfaces.
The very various forms, which the sac without opening of the
tendinous synovial membranes exhibits, can be reduced to two general
modifications. 1st. Some are rounded sacs, species of bladders; such
are those upon the supra-spinatus, the psoas, iliacus, obturator
internus, &c. All these membranes are remarkable for this, that they
never cover the tendon entirely, but only on one side; that they never
form internal folds and that they are never surrounded by fibrous
sheaths. 2d. The others, belonging especially to the flexors, and to
the different tendons which traverse the sole of the foot, form at
first a kind of cylindrical sac which lines the canal half fibrous,
half cartilaginous in which the tendon slips; then they are reflected
around it, cover it wholly and form for it a true sheath which prevents
it from being moistened by the synovia. This kind of tendinous synovial
membrane represents then truly two canals, at the superior and inferior
extremities of which are found two cul-de-sacs which unite them and
complete the sac without an opening. Internal folds are here frequently
found going from one canal to the other. All the synovial membranes of
the flexors have one of them under the tendon.
_Organization; Properties; Development._
The organization of the tendinous synovial membranes is precisely
analogous to that of the articular ones. Principally cellular, the
texture of these membranes is without any apparent fibre; its softness
is very evident; very few blood vessels are distributed to it, though
the contrary has been said; absorbents and exhalants especially
predominate in it. These, filled with blood in inflammation, give to
the membrane, a reddish tinge, more or less deep. In this state the
synovia is not exhaled; sometimes even adhesions are formed, as I have
observed in a subject in whom the fibrous sheaths and their tendons of
the index and the middle finger seemed to be united. The inflammatory
phenomena of the tendinous synovial membranes are especially remarkable
in whitlows, a disease, one species of which has evidently its seat in
the synovial membrane of the fingers, is analogous to the inflammation
of the pleura, the peritoneum, and to that of the articulations. It is
more dangerous than the inflammation of the synovial membranes in the
form of bladders or bags, because the fibrous sheath which surrounds
the inflamed membrane, not being able to stretch and yield to the
swelling, like the cellular texture which surrounds the synovial bags,
produces real strangulations, which it is often necessary to remove. I
do not know whether the synovial texture of the tendons is exposed to
the slow and tubercular inflammations, common to the articular serous
and synovial systems. Its vital properties and those of texture appear
to be precisely the same as those of this last. Like it, it receives
with difficulty the sympathetic influence of the other organs; it
is unaffected during the derangement of the other systems in acute
diseases; it remains sound in their alterations arising from chronic
affections. I would observe also that all its affections are almost
local. For example, there is not, as in the serous system, species of
dropsical diathesis, that is to say of cases in which all the synovial
sacs are filled at the same time.
The tendinous synovial membranes, fine and delicate in the fœtus and in
infancy, readily yield to the numerous motions which constantly succeed
that age. More dense and compact in the adult, they become rigid in old
age, exhale less fluid, are dry, and do not contribute a little, by the
state in which they are, to the general slowness of the motions which
that age brings with it.
There are many synovial membranes the existence of which is variable;
such as, for example, that of the great glutæus, in the place of which
there is often found only a cellular mass. These membranes are in
general very dry when they exist. Synovia can scarcely be discovered in
them. They resemble in this respect the articular synovial membranes of
the vertebræ, the clavicle, &c.
GLANDULAR SYSTEM.
This system, one of the most important in the animal economy, differs
from most others in this, that the texture which is peculiar to it is
not precisely the same in all the organs that compose it. The fibres
of a muscle of animal life would as well serve for the structure
of any other muscle of the same system. The tendinous fibres, the
cartilaginous, osseous textures, &c. are everywhere the same. On the
contrary, the texture of the liver would not serve to compose the
kidney, nor that of this last the salivary glands. The glandular system
then has a resemblance in its different parts only by certain general
attributes which have many exceptions.
Authors have given the name of glands to organs to which it does not
belong; such as the thyroid, the pineal, the lymphatic glands, those
especially that are in the neighbourhood of the bronchia, the thymus,
the suprarenal, &c. We should call by this name only a body from which
flows, by one or many ducts, a fluid which this body separates from
the blood which it receives by the vessels that go to it. 1st. On the
head, the salivary, the lachrymal, the Meibomian and the ceruminous
glands of the ear, and the amygdalæ.; 2d, the mammæ on the thorax; 3d,
in the abdomen, the liver, the pancreas and the kidneys; 4th, in the
pelvis, the prostate and the testicles; 5th, on the whole trunk and the
face, the very numerous collection of mucous glands; these are nearly
all that are dependant upon the glandular system; all the other organs
which belong to it by this name, are foreign to it in their texture,
their properties, their life and their functions. In this point of
view, the division of Vicq d’Azyr is inaccurate.
The extremities contain nothing which belong to this system, no
doubt because the fluids which it separates almost all serve for the
functions of organic life, whilst in the extremities every thing is in
relation to animal functions.
ARTICLE FIRST.
SITUATION, FORMS, DIVISION, &C. OF THE GLANDULAR SYSTEM.
The glands have two different positions. Some of them are
sub-cutaneous, as the mammæ, the salivary glands, &c.; the others
deep seated, as the liver, the kidneys, the pancreas and almost all
the mucous ones are removed from the action of external bodies. The
greatest number occupy places where there is constantly much motion,
as the salivary glands on account of the jaw, the mucous on account of
the neighbouring fleshy layer, the liver on account of the diaphragm,
&c. It is this which has made it believed that this motion, foreign
to their functions, was destined to produce the excretion of their
fluids. But, 1st, the glands of the palatine arch, the pancreas,
the testicles, the kidneys even, can hardly borrow accessory aid on
account of their position. 2d. We know that the sight alone of grateful
food makes the saliva flow. 3d. Sialagogues produce the same effect.
4th. When the bladder is paralytic, the mucous juices pour into it as
before, oftentimes more copiously. 5th. The semen flows involuntarily.
6th. The excretion of the mucous juices is as easy in the pituitary
membrane as any where else, though the fleshy layer, almost everywhere
spread under the mucous system, is wholly wanting here. A thousand
other analogous facts prove this truth placed beyond a doubt by Bordeu,
viz. that the vital action is the essential cause of every excretion.
Accessory aid should not however be entirely rejected. In fact, in
salivary fistulas, there is evidently more fluid thrown out during
mastication than at any other time. It is evident that in the excretion
of urine, the abdominal muscles perform the principal part. When the
gall-bladder is emptied, I believe that the neighbouring motions are
much assistance to it. In general, whenever the fluids are found in
considerable quantities, if the parietes of the organs which contain
them are not very strong, like those of the heart, the motions of the
neighbouring organs are necessary to overcome the resistance which they
offer. On the contrary, in the capillary vessels in which the fluids
are in small quantities, the organ that contains them is sufficient, by
its reaction, for the motion.
There are single glands like the liver, the pancreas, &c.; and others
in pairs, as the kidneys, the salivary, lachrymal glands, &c. These
resemble each other in general on both sides; but their resemblance
is not to be compared for precision to that of the organs in pairs
of animal life. One of the kidneys is lower than the other; their
arteries, veins and nerves are not analogous either in length or size;
frequently fissures exist in one that are wanting in the other, &c.
The same observation is true with respect to the salivary glands.
The glandular forms are not fixed and invariable; they exhibit
a thousand different modifications in their size, direction and
proportions; they have never the precise and exact conformation of the
organs of animal life. This fact can be disputed by no one who has
examined a number of dead bodies. The following are the means by which
I have made this most evident to myself. We know that the organs vary
much in size, in different individuals; now, in these varieties the
proportions are always accurately kept in animal life, whilst it is
rare that they are so in organic life. Let us take an organ for example
in each of the two lives. I have always seen that in a small brain the
corpus callosum, the thalami nervorum opticorum, the corpora striata,
&c. are in proportion to the whole size of the organ. On the contrary,
nothing is more common than to see a large lobe of Spigelius with a
small liver, and vice versa a large liver with a small lobe. There is
no anatomist who has not had frequent occasion to make this remarkable
observation. A kidney is larger sometimes in its superior part,
sometimes in its inferior, &c. It is in the whole of the organ that
these varieties of size take place in animal life; it is oftentimes in
insulated parts only in organic life. The reason of this appears to me
to be that the harmony of action is necessary, as I have demonstrated,
for the animal functions; so that if one side of the brain is more
developed than the other, if one eye, one ear, one pituitary membrane,
&c. are more developed than their corresponding organs, the perception,
the sight, the hearing, the smell, &c. would be inevitably deranged;
whilst the secretion of bile, of urine, &c. takes place equally well,
though one part of these glands may be larger or smaller than the other
parts.
There is a remark to be made respecting the glands with regard to these
varieties of form, it is, that those which are covered by a membrane,
as the liver, the kidneys, even the pancreas, are less exposed to
them than those which are buried in cellular texture without having
around them a membranous covering, as the salivary, the lachrymal, the
mucous glands, &c. I have often examined these last in the mouth and in
the course of the trachea; I never found them alike in two subjects.
We know that the parotid sometimes extends upon the masseter, and
sometimes does not, that it descends more or less into the neck, that
it is of a greater or less size there, &c.
When one gland of a pair is wanting or becomes diseased, sometimes the
other increases considerably in size, as I have seen in the kidneys.
This takes place also in the treatment by compression of salivary
fistulas, a treatment which does not however always succeed. In other
cases, the sound gland increases its action and secretes more fluid,
without increasing in size.
The exterior of the glands not covered by membranes is unequal and
lobulated; it conforms to the muscles, the vessels, the nerves, and
even the bones, as the parotid which is placed under the angle of the
jaw. Less cellular texture is in general found around them, than around
organs with great motion. That which is in contact with them is more
dense and compact than that of the organic interstices. It closely
resembles the sub-mucous texture, that exterior to the arteries, the
veins, the excretories, &c. but it is not however so resisting. It
receives fat with difficulty, and forms a kind of membrane, which,
insulating to a certain extent the vitality of the gland, performs in
great measure in this respect the functions of the peritoneum around
the liver, of the peculiar membrane of the kidneys, the spleen, &c.
ARTICLE SECOND.
ORGANIZATION OF THE GLANDULAR SYSTEM.
I. _Texture peculiar to the Organization of this System._
The glandular texture is distinct from most of the others in this, that
the fibrous arrangement is wholly foreign to it. The elements that
compose it are not placed at the side of each other, in longitudinal or
oblique lines, as in the muscles, the fibrous bodies, the bones, the
nerves, &c. They are found agglomerated, united by cellular texture,
and adhere but very slightly. Thus whilst the organs with distinct
fibres resist much, especially in the direction of their fibres,
these are torn with the least effort, and break even with ease. Their
rupture is unequal, full of prominences and depressions, a difference
which distinguishes them from cartilage, the rupture of which is in
general smooth. This rupture is not equally easy in all the glands.
The prostate, the amygdalæ, the mucous glands resist much more than
the liver or the kidneys, which principally exhibit this phenomenon.
The pancreas and salivary glands yield a little without breaking, when
they are pulled; but it is not their texture which is the seat of this
phenomenon, it is the abundant cellular texture that penetrates them;
thus their different lobes are then separated, in proportion as the
filaments which are between them become longer.
The glandular texture, which is very commonly called parenchyma, is in
general arranged in three different ways. 1st. In the pancreas, the
salivary and lachrymal glands, there are distinct lobes, separated by
cellular texture, resulting from smaller lobes which are agglomerated
together and which are composed of still less lobes, that are called
glandular grains; the scalpel traces with ease the first, second, third
and even fourth divisions. 2d. In the liver and the kidneys there is
found no trace of the first of these divisions, of those into principal
and even secondary lobes. The glandular grains all in juxta-position,
having between them an equal quantity of cellular texture, a quantity
which is very small, as we shall see, present an uniform texture
without inequality, which is broken with ease, as I have said, and the
rupture of which exhibits species of granulations. 3d. The prostate,
the amygdalæ and all the mucous glands have a soft parenchyma, like
pulp, without the appearance of principal or secondary lobes, or
even glandular grains, not breaking, yielding much more under the
finger that compresses it, than that of the other glands. The simple
inspection of the glandular system is sufficient to enable any one to
perceive the triple difference which I have just pointed out, and which
is essential. The testicles and the mammæ have a peculiar texture which
cannot be referred to these differences.
Authors have been much occupied with the intimate structure of the
glands. Malpighi admitted that there were small bodies in them, which
he believed were formed of a peculiar nature. Ruysch determined that
they were all vascular. Let us neglect all these idle questions, in
which neither inspection nor experiment can guide us. Let us begin to
study anatomy where the organs can be subjected to our senses. The
exact progress of the sciences in this age is not accommodated to all
these hypotheses, which made general anatomy and physiology but a
frivolous romance in the last.