Part 20

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.