do not enjoy in the natural state the properties which put the living
organs in relation with external bodies; they have neither animal
sensibility nor contractility. Thus they would be very improper for
external integuments, or for linings of the organs which the mucous
membranes cover; they would give in fact no other sensation than
that of an obscure and indistinct feeling. They answer very well for
envelopes, integuments for internal organs, but not for sensible
envelopes. We have a proof of it in living animals in whom we can
irritate these membranes with impunity. I have many times seen dogs
in whom I had left the spleen drawn out of the abdomen, in order to
observe the phenomena arising from it, tear this organ without being
in a state of fury, eat it even and be thus nourished by their own
substance. They also often tear without pain the exterior of their
intestines when in experiments these are drawn out, and the animals are
left some time to themselves.
When external bodies are in contact with the serous system, they change
its natural state; they inflame it, as we see in the peritoneum, in the
tunica vaginalis laid bare, as we observe also always when a foreign
body introduced into the system acts upon them. Surgeons, as we know,
even employ this means to which they would in vain have recourse in the
mucous membranes, in order to procure artificial adhesions between the
parietes of these membranes. The different morbid irritations inflame
much more frequently the serous surfaces which in this state acquire
a very acute sensibility, greater even than that of the integuments;
so that these inflamed surfaces would be equally improper to serve for
integuments, because external bodies would excite them painfully.
The sensible organic contractility is nothing in the serous system; but
the insensible and the corresponding sensibility are kept in permanent
exercise in it, 1st, by the continual exhalation and absorption that
are going on there; 2d, by nutrition. These two properties are then
those which predominate in this system; thus upon their alterations
all its diseases turn. Acute inflammations, chronic inflammations with
tubercles, adhesions, dropsies, exhalations of pus, of milky serum, &c.
&c. are all derived from an excess, a defect or an alteration of these
two properties of the serous system. It is then also almost exclusively
that sympathies are put into action in it; so that the serous membranes
diseased either idiopathically or sympathetically exhibit always a
series of phenomena all of which suppose an increased internal motion,
or loss of tone in the exhalant and absorbent capillaries, and in the
peculiar texture of those membranes; whilst in the animal muscular, the
organic muscular systems, &c. these predominant affections which are
marked by convulsions and paralysis in one, and by irregular motions of
irritability in the other, do not suppose this internal alteration of
the texture of the diseased organ. Hence why these two last systems,
though frequently disturbed during life, exhibit but few changes
after death, whilst the serous system is a vast field for the morbid
anatomist.
_Sympathies._
The serous surfaces are capable of being influenced by the affections
of the other organs; this is very evident in the organic diseases of
the heart, the lungs, the liver, the spleen, the stomach, the womb,
&c. organs, which without having any known connexion of functions
with the serous surfaces, influence them however so that all their
morbid defects of organization are accompanied, in the latter periods,
by different serous collections in the great cavities, collections
evidently owing to a derangement of the organs which constantly exhale
this fluid. I shall make upon this point two observations; the first
is that the serous surfaces nearest the diseased organ, are in general
the most susceptible of being influenced by it. Thus in the diseases of
the heart and the lungs, the serous collections take place especially
in the thorax, whilst ascites is always the first consequence of
enlargements of the liver, the spleen, &c. the pleura and the
pericardium being filled subsequently. We know that most sarcoceles
are complicated with dropsies of the tunica vaginalis; whence results
hydro-sarcocele, a disease which surgeons consider separately, but
which is the same as those of the preceding cases, which might in
this respect be called hydro-phthisis, chronic hydro-hepatitis,
hydro-carcinoma of the womb, &c.
The second observation that I have to make is, that whenever the serum
is thus collected in the cavities, in consequence of an organic disease
of a viscus foreign to the membrane, this serum is limpid, transparent,
and probably of the same nature as that which circulates in the
lymphatic vessels. The exhalants which form it not being then in fact
diseased, their action not being increased or that of the absorbents
diminished except by sympathy, the fluid must remain the same. Thus
though there is suffering at the end of the glans from a stone in
the bladder, the glans is perfectly sound, and the mucous fluid that
escapes from it is of the same nature as in the ordinary state. On
the contrary, when dropsies depend upon a disease of texture of the
serous surfaces, as for example upon a tubercular inflammation, or even
an acute one, which has degenerated, &c. the effused serum is almost
always altered; it is milky, or there are albuminous flakes in it,
or a false membrane, &c. I have made this observation, which I think
interesting, upon nearly all the bodies I have opened.
In acute diseases, the serous surfaces receive also equally the
sympathetic influence of the affected organs. If we could then see
them, we should find that they were like the skin, more or less moist,
more or less dry, according to the different periods of the disease.
What proves it is, that at the death which follows the disease, the
serum of the pleura, the pericardium, the peritoneum, &c. varies
remarkably. Sometimes it is evidently increased, at others it is almost
nothing; this depends upon the time in which the subject died. If it is
whilst exhalation is very abundant, we find much serum; it is almost
nothing if life has been sufficiently prolonged to allow absorption to
take place. If the surrounding air did not dissolve the sweat, or if
the skin was in the form of a sac, we should find it with very variable
degrees of moisture, according as the subjects had died in sweat, or
with a suppression of the cutaneous exhalation.
ARTICLE FOURTH.
DEVELOPMENT OF THE SEROUS SYSTEM.
I. _State of this System in the First Age._
All the serous surfaces are extremely delicate in the fœtus. In opening
the thorax by a longitudinal section of the sternum and examining the
pleura in the mediastinum where it is free on both sides, it is found
to have less thickness than the transparent layers of the omentum or
the arachnoides in the adult. The peritoneum is a little thicker in
proportion, but yet its delicacy is very great. The comparison of soap
bubbles is hardly sufficient to convey an idea of the fineness of the
texture of the omentum and the arachnoides.
At this period the fluid that lubricates the serous surfaces is much
more unctuous and viscid than it is afterwards; by carrying the fingers
over these surfaces at the different ages, the difference is easily
perceived. It might almost be said that the tangible qualities of the
serous fluids then approximate those of the synovia. I know not to what
this difference belongs.
Besides, the quantity of these fluids does not appear to be so great in
proportion as that of the cellular fluids, with which they have however
so much analogy; which is probably owing to this, that the internal
motions being less numerous, on account of the inaction of most of the
organic muscles, less fluid is necessary to lubricate the surfaces.
The growth of the serous system is always in proportion to that of the
organs which it covers. The arachnoides is larger in proportion than
it will be in the adult; it seems even, like the brain, to become then
the seat of a more active labour; thus diseases are more frequent in
it. The increase of exhalation is more common in it than in all the
other serous sacs; hence hydrocephalus.
At birth, when the internal motions become suddenly very numerous,
on account of respiration, digestion and the excretions, I presume
that the serous surfaces become the seat of a more active exhalation.
Besides, as very little blood penetrates them, the sudden production
of the red blood and its entrance by the arterial system, where it
succeeds the black blood, produces less changes upon them than upon the
mucous surfaces and the muscular system.
The serous membranes grow like the other organs; for a long time
delicate and diaphanous, they gradually thicken as we advance in age,
and become of a dull white. Their suppleness diminishes as their
density increases; they resist the different reagents so much the less
as the subjects are younger. In infants, maceration and ebullition
reduce them much more quickly to a homogeneous pulp.
I have observed that in the fœtus which has become putrid, there is
often collected different gases in the serous cavities, as may be
proved by opening these cavities under water; a phenomenon much less
evident in the adult, in whom the cellular texture is often wholly
emphysematous by the putrefactive motion, without the escape of any
thing by the canula of a trochar which is plunged into the peritoneal
cavity or into that of the pleura, as I have many times ascertained. In
general, there is disengaged much more aeriform fluid from the organs
of the fœtus, than from those of the adult, in the experiments of
maceration.
II. _State of the Serous System in the after Ages._
In the adult, the serous system remains a long time without undergoing
any very sensible change; its membranes follow only the laws of
the organs they surround. Thus in the age nearest youth, the serous
surfaces of the chest are the most frequent seat of inflammations,
dropsies, &c.; whilst in that bordering on old age the inferior
surfaces like the peritoneum, are the more often affected.
In old age, the serous system becomes dense and compact; its adhesions
to the neighbouring parts are more evident; thus it is less capable of
the different locomotions of which we have spoken. Its forces, which
are weakened, render absorption in it less easy; it is the frequent
seat of dropsy. When it is affected with some diseases, its want of
energy imparts to them a remarkable chronic character. There are many
old people at the Hôtel Dieu with tubercular inflammations of the
peritoneum, which they have had for a long time, whilst young persons
are overcome much quicker by the same inflammations. Thus cancers in
aged persons often remain almost inert, they frequently are not even
painful, whilst their periods are usually most rapid in adults.
The serous effusions are more rare than the infiltrations of the
sub-cutaneous cellular texture in old people; but they take place more
commonly than those of the intermuscular texture.
The serous system becomes ossified, but not like the arterial, the
cartilaginous, &c. from the natural effect of age. Its membranes are
not constantly found osseous in old age, and when this phenomenon takes
place, it happens at every age. It is a disease, a real tumour, whilst
in the arteries and the cartilages it appears to belong to a natural
series of functions. I have a preparation in which the arachnoides is
evidently osseous in many points, and as it is upon the dura-mater that
these productions are formed, their existence serves very well to prove
that the arachnoides is distinct from it; for at the place where they
are found, they can be easily separated from each other.
III. _Preternatural Development of the Serous System._
I shall not repeat here what I have said, in speaking of the cellular
texture, upon the formation of the different cysts. These cysts,
completely analogous to the natural serous membranes, should be really
considered as a preternatural development of these membranes in the
economy; they have the same appearance and almost the same texture,
furnish their fluid according to the same laws, and appear to be the
seat of a constant exhalation and absorption; since they are in vain
emptied by puncture, their fluids are always reproduced, until they are
removed. For example compare the cyst which has grown preternaturally
along the spermatic cord, with the tunica vaginalis filled with water
in hydrocele. If the size of these tumours, which are often found
together, is the same, it is impossible to discover any difference in
their form, appearance, texture, properties, functions, &c.
SYNOVIAL SYSTEM.
I place this system at the side of the serous, because it has the
greatest analogy with it, under the relations, 1st, of its form, which
is in each of these organs that of a sac without an opening; 2d, of
its texture, which appears to be essentially cellular; 3d, of its
functions, which consist in an alternation of exhalation and absorption.
What establishes a real line of demarcation between these two systems
is, 1st, that the fluids which lubricate their membranes appear to
differ in their composition, though there is much resemblance between
them. 2d. In dropsical diatheses which affect at the same time the
cellular texture and all the serous surfaces of the peritoneum, the
pleura, &c. the affection does not extend to the synovial membranes,
which indicates a difference of structure, though we do not know
what this difference is. 3d. And reciprocally in dropsies of the
articulations, an affection in general very rare, and in those of the
tendinous synovial capsules, there is no concomitant affection of
the membranes of the great cavities. 4th. The fluid of the articular
dropsies does not resemble that which fills the great cavities in the
same disease. 5th. The synovial membranes are much more rarely than
the serous, the seat of those slow and tubercular inflammations which
the serous surfaces so often exhibit. I have however seen two examples
of it in the synovial membrane of the knee. I believe that these two
systems are the only ones in which this disease is observed; so that
it is by its existence a character of resemblance, and by its rarity
or frequency, a distinguishing attribute. 6th. The different kinds of
adhesions of which I have spoken as taking place on the serous surface,
are not met with on the synovial surfaces, where we see only that which
identifies these two adhering surfaces, a mode which frequently takes
place in anchylosis, which is also as often occasioned by it, as by the
stiffness of the parts surrounding the articulation. 7th. The synovial
surfaces are not as often as the serous, the seat of those remarkable
locomotions of which we have spoken; which depends on this, that the
articular organs are not, like the most of those covered with serous
surfaces, subject to alternate dilatations and contractions.
The synovial system exhibits evidently two great divisions. To one
belongs the articular system, to the other that of the tendinous
grooves. Each shall be examined separately.
ARTICLE FIRST.
ARTICULAR SYNOVIAL SYSTEM.
I believe that I first described this essential portion of the synovial
system. I shall relate here what I have said of it elsewhere. I shall
examine first how it is separated from the blood, afterwards the fluid
itself, and then I shall describe the organ which furnishes it.
I. _How the Synovia is separated from the mass of Blood._
Every fluid differing from the blood, can be separated from it to be
afterwards transmitted to an organ, but in one of the three following
ways; 1st, by secretion, a function characterized by the existence of
a gland intermediate to the blood vessels that bring the materials to
it, and the excretories which carry off the result; 2d, by exhalation,
a function distinguished from the first, by the absence of this
intermediate gland, and by the immediate continuity of the blood
vessel and the exhaling duct; 3d, by transudation, a phenomenon purely
physical, almost always happening after death, rarely observed during
life, a simple transmission of a fluid by the pores of an organ,
towards which it is mechanically determined. Let us examine which of
these three modes is that chosen by nature to deposit the synovia upon
the articular surfaces.
_Is the synovia transmitted by secretion to the articular surfaces?_
We are indebted to Clopton Havers for the system which places in
the glands the sources of the synovia. Many authors had designated
obscurely before him these organs in the articulations; but he
made them the particular object of his researches, described them
in the different articulations, divided them into two classes, the
one principal, the other accessory, and assigned them characters
so evident, that according to him, they could not be forgotten.
Reddish bunches, spongy, formed by membranes folded upon themselves,
situated sometimes without, and sometimes within the articulations,
always arranged so as to be protected from too strong a compression,
and pouring out through ducts in the form of fringe the fluid they
secrete; such are the characters drawn by Havers, which all anatomists
since him admire, and the correctness of which the most modern and
distinguished authors have acknowledged in their works.
Some anatomists of this age have however thrown doubts upon these
glandular bodies. Lieutaud confounds them with the fatty cellular
texture. Desault did not distinguish them from it. Every thing confirms
me in the same opinion, which many considerations appear to establish
in an undoubted manner. The following are these considerations; 1st,
these reddish bunches are met with only in certain articulations. There
are many of them in which their existence cannot be established but by
supposition. 2d. The greatest number of the synovial membranes of the
tendons certainly do not exhibit any of them, though Havers, Albinus,
Juncke and Fourcroy admit them in all, founded no doubt upon analogy
and not upon inspection. Yet the synovia is separated equally in both
cases, and lubricates the surfaces of the articulations and of the
tendinous sheaths; this separation is then independent of glandular
action. 3d. If the best marked synovial glands are examined, such as
that of the cotyloid cavity, no trace can be discovered there of this
parenchyma of an unknown nature, but remarkable for its structure,
which composes in general the glands, and which distinguishes them
from every other part and forms their true organic character. 4th.
No excretory duct can be demonstrated in these organs. Those in the
form of fringes, admitted by Havers, are imaginary. Bertin himself
has acknowledged this truth, though he attributed to these bodies a
glandular structure. The transudation of the fluids injected by the
arteries in the neighbourhood of the articulation, proves the existence
of these ducts no better than it establishes them in the cavities of
the serous membranes in which it also takes place, and yet in which
it is well proved that no gland pours out the albuminous fluid
that constantly lubricates these cavities. 5th. Inflation resolves
completely these fatty bunches into cellular texture. Maceration
produces the same effect. When gradual and long continued ebullition
has removed all the fat from them, there remains only a mass of cells
pressed together, and similar to those of the common cellular texture.
6th. The glandular character is manifested in certain morbid cases, by
a peculiar swelling and hardening, of which the other organs except the
glands, such as the muscles, the tendons, &c. never offer an example.
The liver, the kidneys, the salivary organs, all the considerable
glands are remarkable for this. So true is this character, that it
serves to indicate glands, the delicacy of which conceals them in the
natural state. For example, the existence of the cryptæ of the stomach,
the urethra, and several other mucous membranes, is founded first upon
the analogy of the other membranes of this class, but principally upon
the preternatural development which these cryptæ acquire in certain
diseases. Never, on the contrary, do the pretended synovial glands
present to the observer a similar development. Always in the diseases
of the articulations, a common swelling seems to identify them with the
neighbouring cellular texture. They have not like the other glands,
affections distinct from those of this texture, no doubt because
they have not a peculiar vitality, because being mere elongations of
the neighbouring cellular texture, they partake of its nature and
properties, and ought consequently to partake of all its conditions,
as it in its turn ought immediately to receive the influence of their
affections.
The considerations which I have just offered successively form, I
think, sufficient data to resolve the problem proposed above, by
establishing as an incontestable proposition, that the synovia is not
transmitted by secretion to the articular surfaces.
Let us examine the second mode of transmission stated by authors.
_Is the synovia transmitted by transudation to the articular surfaces?_
It was an opinion anciently received, that the marrow of the long bones
oozes through the pores of their extremities and through those of the
cartilages which terminate them, to lubricate the articular surfaces.
Havers renewed this idea forgotten at the time he wrote, united this
source of the synovia to that which had placed it in the glands, and
thus formed of this fluid a mixture composed of two fluids differently
transmitted to the articulation. The most of those who succeeded him
partook of his opinion upon this point. Those even, such as Desault,
who rejected the existence of the articular glands and the secretion
of synovia, admitted the transudation of it founded upon the following
observations. 1st. A long bone, stripped of its soft parts and exposed
to the air, allows a fatty oozing to pass through the pores of its
cartilages which does not cease till the medullary juice is completely
exhausted. 2d. The mechanical compression of the cartilaginous
extremity of a long bone produces for a moment the same effect. Are
these facts, which are evident in the dead bone, also real in the
living one? Different considerations, which I will now state, induce
one to believe the contrary.
1st. The vital forces, the effect of which is to impart to all the
organs which they animate a degree of tone sufficient to resist the
entrance of the fluids, leave, when they are extinct, the fibres of
these same organs in a state of laxity that renders them everywhere
permeable. Thus transudation is now considered as hardly any thing
else than a phenomenon that takes place only after death, which, if
transformed into a vital one, would offer an evident exception to
the laws of nature that are especially characterized by simplicity
and uniformity. 2d. The fatty oozing takes place in the experiment
noticed above, not only through the pores of the cartilages, but also
through those of the whole surface of the bone; so that by reasoning
from what has been here observed upon the dead body, it is evident that
during life the whole bone would be, if you may so say, immersed in
an atmosphere of synovia, a consequence, which being proved false by
the most simple inspection, demonstrates the falsity of the principle
deduced from it. 3d. The articulations of the cartilages of the larynx
are lubricated like those of the bones, by the synovial fluid; and yet
here all transudation of marrow is impossible, as it does not exist
in the substances of the cartilages. 4th. The marrow is almost always
sound in diseases which, affecting the articulations alter the fluid
that lubricates them. And reciprocally the synovia does not take a
different character in the affections of the interior of the bones,
which have an influence especially upon the medullary organ. 5th.
Finally, the experiment that I have made, and which has been stated in
the article upon the marrow, evidently proves the non-transudation of
this fluid.