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the presence of the salt appeared in the urine by the appropriate tests, which usually required from five to ten minutes after its reception into the stomach,—the animal was killed; and, on examining the blood, the salt was found in the serum taken from the thoracic portion of the vena cava inferior, in the right and left cavities of the heart, in the aorta, the thoracic duct, the mesenteric glands, the kidneys, the joints, and in the mucous membrane of the bronchi.
Magendie, too, states, as the result of his experiments,—First. That whenever prussiate of potassa is injected into the veins, or is exposed to absorption in the intestinal canal, or in a serous cavity, it speedily passes into the bladder, where it can be readily recognised in the urine. Secondly. That if the quantity of prussiate injected be considerable, it can be detected in the blood by reagents; but if the quantity be small, it is impossible to discover it by the ordinary means. Thirdly. That the same thing happens if the prussiate of potassa be mixed with the blood out of the body. Fourthly. That the salt can be detected, in every proportion, in the urine.
The existence, consequently, of any more direct route from the stomach to the bladder than through the venous system is disproved, and the absorption of fluids must be considered to be effected through the vessels described under the absorption of drinks.
Such are the glandular secretions that we shall consider in this place. There are still two important fluids, whose uses will have to be detailed in the next class of functions—the sperm and the milk. There are several organs likewise, as the spleen, thyroid, thymus and supra-renal capsules, which are termed glands by many anatomists; but which Chaussier has termed glandiform ganglions. Of the uses of these we know little or nothing. Yet it is necessary, that the nature of the organs, and the fancied functions should meet with notice. The offices of the thyroid, thymus, and supra-renal capsules, being apparently confined to foetal existence, will not require consideration here.
OF THE FUNCTIONS OF THE SPLEEN.
The spleen is a viscus of considerable size, situated in the left hypochondriac region, (Fig. 122, H,) beneath the diaphragm, above the left kidney, and to the left of the stomach. Its medium length is about four and a half inches; its thickness two and a half inches; and its weight about eight ounces. It is of a soft texture, somewhat spongy to the feel, and easily torn. In a very recent subject, it is of a grayish-blue colour; which, in a few hours, changes to a purple, so that it resembles a mass of clotted blood.
At its inner surface, or that which faces the stomach and kidney, a fissure exists, by which the vessels, nerves, &c. enter or issue from the organ.
The anatomical elements of the spleen are:—1. The splenic artery, which arises from the coeliac, and after having given off branches to the pancreas and the left gastro-epiploic artery, divides into several branches, which enter the spleen at the fissure, and ramify in the tissue of the organ, so that it seems to be exclusively formed by them. (Fig. 101.) Whilst the branches of the artery are still in the duplicature of the gastro-splenic omentum, and before they ramify in the spleen, they furnish the vasa brevia to the stomach. The precise mode of termination of the arteries in the spleen is unknown. The communication of the arteries with the veins does not, however, appear to be as free as in other parts of the body, or the anastomoses between the minute arteries as numerous.
If, according to Assolant, one of the branches of the splenic artery be tied, the portion of the spleen to which it is distributed dies; and if air be injected into one of these branches, it does not pass into the others; so that the spleen would appear to be a congeries of several distinct lobes; and in certain animals the lobes are so separated as to constitute several spleens. A similar appearance is occasionally seen in the human subject. 2. The splenic vein arises by numerous radicles in the tissue of the spleen; these become gradually larger and less numerous, and leave the fissure of the spleen by three or four trunks, which ultimately, with veins from the stomach and pancreas, unite to form one, that opens into the vena portæ. It is without valves, and its parietes are thin. These are the chief constituents. 3. Lymphatic vessels, which are large and numerous. 4. Nerves, proceeding from the cœliac plexus: they creep along the coats of the splenic artery,—upon which they form an intricate plexus,—into the substance of the spleen. 5. Cellular tissue, which serves as a bond of union between these various parts; but is in extremely small quantity. 6. A proper membrane, which envelopes the organ externally; adheres closely to it, and furnishes fibrous sheaths to the ramifications of the artery and vein; keeping the ramifications separated from the tissue of the organ, and sending prolongations into the parenchyma, which give it more of a reticulated than spongy aspect. 7. Of blood, according to many anatomists, but blood differing from that of both the splenic artery and vein; containing, according to Vauquelin, less colouring matter and fibrine, and more albumen and gelatine, than any other kind of blood. This, by stagnating in the organ, is conceived to form an integrant part of it. Malpighi believed it to be contained in cells; but others have supposed it to be situated in a capillary system intermediate to the splenic artery and vein.
Assolant and Meckel believe, that the blood is in a peculiar state of combination and of intimate union with the other organic elements of the viscus, and with a large quantity of albumen; and that this combination of the blood forms the dark brown pulpy substance, contained in the cells formed by the proper coat, and which can be easily demonstrated by tearing or cutting the spleen, and
The hypotheses, that have been indulged on the nature of the spleen, are beyond measure numerous and visionary; and after all, we are in the greatest obscurity as to its real uses.
Many of these hypotheses are too idle to merit notice; such are those, that consider it to be the seat of the soul,—the organ of dreaming,—of melancholy and of laughter,—of sleep and the venereal appetite--the organ that secretes the mucilaginous fluids of the joints, that serves as a warm fomentation to the stomach, and so on.
It was long regarded as a secretory apparatus, for the formation of the atrabilis,—of a fluid intended to nourish the nerves,—of the gastric juice, of a humour intended to temper the alkaline character of the chyle or bile, &c.
The absence of an excretory duct would be a sufficient answer to all these speculations, if the non-existence of these supposititious humours were insufficient to exhibit their absurdity.
MM. Tiedemann and Gmelin consider its function to be identical with that of the mesenteric glands. They regard it as a ganglion of the absorbent system, which prepares a fluid to be mixed with the chyle and effect its animalization. In favour of the view, that it is a part of the lymphatic system, they remark, that it exists only in those animals that have a distinct absorbent system; that its bulk, in animals is in a ratio with the development of the absorbent system; that the lymphatics predominate in the structure of
the organ; that its texture is like that of the lymphatic ganglions; and lastly, that, on dissecting a turtle, they distinctly saw all the lymphatics of the abdomen passing first to the spleen, then leaving that organ of larger size, and proceeding to the thoracic duct.
In support of their second position, that it furnishes some material towards the animalization of the chyle, they adduce;—the large size of the splenic artery, which manifestly, they conceive, carries more blood to the spleen than is needed for its nutrition; and they affirm, that, in their experiments, they have frequently found, whilst digestion and chylosis were going on, the lymphatic vessels of the spleen gorged with a reddish fluid, which was carried by them into the thoracic duct, where the chyle always has the most rosy hue; and they add, that a substance injected into the splenic artery, passes readily into the lymphatics of the spleen. Lastly, after extirpating the spleen in animals, the chyle appeared to them to be more transparent; no longer depositing coagula; and the lymphatic ganglions of the abdomen seemed to have augmented in
Chaussier, as we have seen, classes the spleen amongst the glandiform ganglions, and affirms, that a fluid is exhaled into its interior of a serous or sanguineous character, which, when absorbed, assists in lymphosis.
Many, again, have believed, that the spleen is a sanguineous, not a lymphatic ganglion, but they have differed regarding the blood on which it exerts its action; some maintaining, that it prepares the blood for the secretion of the gastric juice; others for that of the bile. The former of these views is at once repelled by the fact, that the vessels, which pass from the splenic artery to the stomach, leave that vessel before it enters the spleen.
The latter view also rests on very uncertain data and deductions. Since the period of Haller, the blood of the splenic vein has been presumed to differ essentially from that of other veins, which has led to the belief that some elaboration is effected in the spleen so as to fit the blood for the secretion of the bile. It has been described as more aqueous, more albuminous, more unctuous, and blacker than other venous blood; to be less coagulable, less rich in fibrine, and the fibrine it does contain to be less animalized. Yet these affirmations have been denied; and even were they admitted, we have no positive knowledge that such changes better adapt it for the formation of bile by the liver.
The ideas that have existed regarding its acting as a diverticulum for the blood have been mentioned, under the head of Circulation By some, it has been supposed to act as such in the intervals of digestion; or, in other words, to be a diverticulum to the stomach; by others, its agency in this way is believed to apply to the whole circulatory system, so that when the flow of blood is impeded or arrested in other parts, it may be received into the spleen. It is hard to say which of these
speculations is the most ingenious. None can satisfy the judicious physiologist, especially when he considers the comparative impunity consequent on extirpation of the organ.
This was an operation performed at an early period. Pliny affirms that it was practised on runners to render them more swift. On animals the spleen has been repeatedly removed, and although many of these have died in consequence of the operation, several have recovered.
Adelon refers to the case of a man who was wounded by a knife under the last false rib of the left side. Surgical attendance was not had until twelve hours afterwards; and, as the spleen had issued at the wound, and was much altered, it was considered necessary to extirpate it. The vessels were tied; the man got well in less than two months, and has ever since enjoyed good health.
Sir Charles Bell asserts, in his "Anatomy and Physiology," that an old pupil had recently given him an account of his having cut off the spleen in a native of South America. The spleen had escaped through a wound, and had become gangrenous. He could observe no effect to result from the extirpation.
Dr. O'Brien, in an inaugural dissertation, published at Edinburgh in 1818, refers to a case which fell under his own management. The man was a native of Mexico; the spleen lay out, owing to a wound of the abdomen, for two days before the surgeon was applied to. The bleeding was profuse; the vessels and other connexions were secured by ligature, and the spleen separated completely on the twentieth day of the wound. On the forty-fifth day, the man was discharged from the hospital, cured; and he remarked to some one about this time, that "he felt as well as he ever did in his life."
Dulaurens, Kerckring, Baillie, and others, refer, also, to cases, in which the spleen has been found wanting in man, without any apparent impediment to the functions.
The experiments, that have been made on animals by removing the spleen, have led to discordant results. Malpighi says, that the operation was followed by increased secretion of urine; Dumas, that the animals had afterwards a voracious appetite; Mead, and Mayer, that digestion was impaired, that the evacuations were more liquid, and the bile more watery; Tiedemann and Gmelin, that the chyle appeared more transparent and devoid of clot; Professor Coleman, that the dogs,—the subjects of the experiment,—were fat and indolent.
Dupuytren extirpated the spleens of forty dogs on the same day, without tying any vessel, but merely stitching up the wound of the abdomen, yet no hemorrhage supervened. In the first eight days, half the dogs, operated on, died of inflammation of the abdominal viscera induced by the operation, as was proved by dissection. The other twenty got well without any accident at the end of three weeks at the farthest. At first, they manifested a voracious appetite, VOL. II.