stances penetrate the parietes of vessels and other tissues of the body; an action which he found to be singularly accelerated by the galvanic influence. Prussiate of potassa was injected into the cavity of the pleura; and sulphate of iron introduced into that of the peritoneum in a living animal. Under ordinary circumstances, it requires five or six minutes before the two substances meet by imbibition through the diaphragm; but the admixture is instantaneous if the diaphragm be subjected to a slight galvanic current. The same fact is observed, if one of the liquids be placed in the urinary bladder, and the other in the abdomen; or the one in the lung, and the other in the cavity of the pleura. It was further found, that, according to the direction of the current, the union took place in the one or the other cavity. Dr. Bostock,' in commenting on these cases, thinks it must be admitted, that they "go very far to prove that membranes, perhaps even during life, and certainly after death, before their texture is visibly altered, have the power of permitting the transudation of certain fluids." That such imbibition occurs during life is indisputably proved. If the clear and decisive experiments of Magendie and Fodéra had been insufficient to establish it, the additional testimony,-afforded by Lawrence, Coates, and Harlan; by Dutrochet, Faust, Mitchell, Rogers, Draper, and others, -would be ample. By the different rates of penetrativeness of different fluids, and of permeability of different tissues, we can explain why imbibition may occur in one set of vessels and not in another; and the constant current, established in the interior of the vessel is a sufficient reply to the suggestion, that there may not be the same tendency to transude after the fluid has entered it. M. Adelon2 is of opinion, that under the view of imbibition we ought to find substances in the arteries and lymphatics also; but a sufficient objection to this would be,--the comparative tardiness, with which the former admit the action; and the selection, and, consequently, refusal, exerted by the latter; but even here evidences of adventitious imbibition are occasionally met with; as in the case of salts, which--we have seen-have been detected in the thoracic duct, after having been introduced into the cavity of the abdomen. The two following experiments by Prof. J. K. Mitchell, which are analogous to numerous others, performed in the investigation of this subject, well exhibit endosmose in living tissues. A quantity of a solution of acetate of lead was thrown into the peritoneal cavity of a young cat; sulphuretted hydrogen being passed, at the same time, into the rectum. In four minutes, the poisonous gas killed the animal. Instantly on its death, the peritoneal coat of the intestines, and the parietes of the cavity in contact with them, were found lined with a metallic precipitate, which adhered to the surface, and was removable by nitric acid moderately diluted. It was the characteristic precipitate of sulphuretted hydrogen, when acting on lead. In another experiment on a cat, a solution of acetate of lead was placed in the thorax, and sulphuretted hydrogen in the abdomen. Almost immediately after the entrance of the sulphuretted hydrogen into the abdominal cavity, death ensued. Physiology, edit. cit., p. 629. 2 Op. cit. 3 American Journal of the Medical Sciences, vii. 44, Philada., 1830. On inspecting the thoracic side of the diaphragm, which was done as quickly as possible, the tendinous part of it exhibited the leaden appearance of the precipitate thrown down by sulphuretted hydrogen. The experiment of J. Müller, referred to in a preceding page, establishes the same fact. It may be concluded, then, that all living tissues imbibe liquid matters which come in contact with them; and that the same occurs to solids, provided they are soluble in the humours, and especially in the serum of the blood. But although imbibition is doubtless effected by living tissues, too great a disposition has been manifested to refer all the vital phenomena of absorption and exhalation to it. Even dead animal membrane exerts a positive agency in respect to bodies placed on either side of it. In the early part of this work' the phenomena of imbibition were investigated, and it was there explained how endosmose and exosmose are affected through organic membranes. A careful examination of those phenomena would lead to the belief, that in many cases the membrane exerts no agency except in the manner last suggested by M. Dutrochet. This is signally manifested in experiments with porous, inorganic substances; and it has been ingeniously and ably confirmed by Dr. Draper,' of New York, who found, that the phenomena were elicited, when, instead of an organic tissue, fissured glass was employed. Still, as has been demonstrated, the nature of the septum or membrane has in other cases a marked effect on endosmose. Sir David Barry,3-in different memoirs laid before the Académie Royale de Médecine, the Académie Royale des Sciences of Paris, and the Medico-Chirurgical Society of London,-maintained, that the whole function of external absorption is a physical result of atmospheric pres sure; and "that the circulation in the absorbing vessels and in the great veins depends upon this same cause in all animals possessing the power of contracting and dilating a cavity around that point to which the centripetal current of their circulation is directed." In other words, it is his opinion, that, at the time of inspiration, a tendency to a vacuum is produced in the chest by its expansion; and as the atmospheric pressure externally thus ceases to be counterbalanced, the pressure without occasions the flow of blood towards the heart along the veins. The consideration of the forces that propel the blood will afford us an opportunity of saying a few words on this view; at present, we may only observe, that Sir David ascribes absorption,-which he explicitly states to be, in his opinion, extra vital,-to the same cause. In proof of this, he instituted numerous experiments, in which the absorption of poisons from wounds appeared to take place, or to be suspended, according as the wounds were, as he conceived, exposed to atmospheric pressure, or freed from its influence by the application of a cupping-glass. The same quantity of poison, which, under ordinary circumstances, destroyed an animal in a few seconds, was rendered completely innocuous by the exhausted glass; and what is singular, even when the symptoms had commenced, the application of the cupping-glass 1 See p. 66. 2 Amer. Journ. of the Med. Sciences, for Aug. 1836, p. 276; Nov., 1837, p. 122; May, 1838, p. 23, and August, 1838-more especially the last two. 3 Experimental Researches on the Influence of Atmospheric Pressure upon the Circulation, &c., Lond. 1826. had the effect of speedily and completely removing them; a fact of essential importance in its therapeutical relations. In commenting on the conclusions of Sir D. Barry, Messrs. Addison and Morgan,'-who maintain the doctrine, that all poisonous agents produce their specific effects upon the brain, and general system, through the sentient extremities of nerves, and through the sentient extremities of nerves only; and that, when such agents are introduced into the current of the circulation in any way, their effects result from the impression made upon the sensible structure of the blood vessels, and not from their direct application to the brain itself,-contend, that the soft parts of the body, when covered by an exhausted cupping-glass, must necessarily, from the pressure of the edges of the glass, be deprived for a time of all connexion, both nervous and vascular, with the surrounding parts;-that the nerves must be partially or altogether paralysed by compression of their trunks; and that, from the same cause, all circulation through the veins and arteries within the area of the glass must cease; that the rarefaction of the air within the glass being still farther increased by means of the small pump attached to it, the fluids, in the divided extremities of the vessels, are forced into the vacuum, and, with these fluids, either a part or the whole of the poison, which had been introduced; and that, in such a condition of parts, the compression, on the one hand, and the removal of the poison from the wound on the other, will sufficiently explain the result of the experiment, either according to the views of those who conceive the impression to be made on the nerves of the blood vessels, or of those who think, that the agent must be carried along with the fluid of the circulation to the part to be impressed. Thus far allusion has been made only to the passage of tenuous fluids into the veins. It has been already seen, that many albuminous and saccharine solutions after having been exposed to the gastric and intestinal juices pass into the radicles of the portal veins to be conveyed to the liver to undergo assimilation. Insoluble substances, too, have been detected by Professor Oesterlen2 in the mesenteric veins. On administering levigated charcoal to animals for five or six days in succession, the blood of these veins exhibited distinctly particles of charcoal of different sizes, some of them so large, that it was a matter of surprise how they could have made their way into the blood through the mucous membrane and the walls of the blood vessels. We have no difficulty, consequently, in comprehending how the mild chloride and other insoluble preparations of mercury might be able to enter the blood vessels in this manner. The observations of Oesterlen have been confirmed by Mensonides and Donders3 not only with charcoal, but with sulphur, and with starch, which is readily detected in the blood by the iodine test. The latter is inclined to think that they enter the lacteals rather than the veins, as he finds them deposited in the lungs more than the liver. It is difficult to conceive how they effect their passage. The extreme velocity of the blood in the vessels may exert a degree of traction on them 1 An Essay on the Operation of Poisonous Agents upon the Living Body, Lond., 1829. Heller's Archiv., Bd. iv. Heft 1, cited in Lond. Med. Gazette for July, 1847. 3 Canstatt's Jahresbericht, 1851, p. 122, Würzburg, 1852; and Henle und Pfeufer's Zeitschrift, 1851, Bd. i. s. 415-27. which may account for their entrance, when it could not be effected through dead membrane. Such would seem to be the main facts regarding the absorbent action of the veins, which rests on as strong evidence as we possess regarding any of the functions of the body; yet, in the treatise on Animal and Vegetable Physiology by Dr. Roget,' we find it passed by without a comment! We have still to inquire into the agents of internal and adventitious absorption. IV. INTERNAL ABSORPTION. On this point but few remarks will be necessary, after the exposition of the different vascular actions concerned in absorption. The term comprehends interstitial absorption, and the absorption of recrementitial fluids. The first comprises the agency by which the different textures of the body are decomposed and conveyed into the mass of blood. It will be considered more at length under the head of NUTRITION; the second, that of the various fluids effused into cavities; and the third, that which is effected on the excretions in their reservoirs or excretory ducts. All these must be accomplished by one of the two sets of vessels previously described; lymphatics, or veins, or both. Now, we have attempted to show, that an action of selection and elaboration is exerted by lymphatics; whilst we have no evidence of such action in the case of the veins. It would follow, then, that all the varieties of internal absorption, in which the substance, when received into the vessel, possesses different characters from those it had when without, must be executed by lymphatics; whilst those, in which no conversion occurs, take place by the veins. In the constant absorption, and corresponding deposition, incessantly going on in the body, the solid parts must be reduced to their elements, and a new compound be formed; inasmuch as we never find bone, muscle, cartilage, membrane, &c., existing in these states in any of the absorbed fluids; and it is probable, therefore, that, at the radicles of the lymphatic vessels, they are converted into the same fluid--the lymph-in like manner as the heterogeneous substances in the intestinal canal afford to the lacteals the elements of a fluid the character of which is always identical. On the other hand, when the recrementitial fluid consists simply of the serum of the blood, more or less diluted, there can be no obstacle to the passage of its aqueous portion immediately through the coats of the veins by imbibition, whilst the more solid part is taken up by the lymphatic vessels. In the case of excrementitious fluids, there is reason to believe, that absorption simply removes some of their aqueous portions; and this, it is obvious, can be effected directly by the veins, through imbibition. The facts, connected with the absorption of substances from the interior of the intestine, have clearly shown, that the chyliferous vessels alone absorb chyle, and that the drinks and adventitious substances pass into the mesenteric veins. These apply, however, to external absorption only; but similar experiments and arguments have been brought forward by the supporters of the two opinions, in regard to substances 1 Bridgewater Treatise, Lond., 1834; Amer. edit., Philad., 1836. placed on the peritoneal surface of the intestine, and other parts of the body. Whilst some affirm, that they have entered the lymphatics; others have only been able to discover them in the veins. Mr. Hunter, having injected water coloured with indigo into the peritoneal cavity of animals, saw the lymphatics, a short time afterwards, filled with a liquid of a blue colour. In animals, that had died of pulmonary or abdominal hemorrhage, Mascagni found the lymphatics of the lungs and peritoneum filled with blood; and he asserts, that, having kept his feet for some hours in water, swelling of the inguinal glands supervened, with transudation of a fluid through the gland; coryza, &c. M. Desgenettes observed the lymphatics of the liver containing a bitter, and those of the kidneys a urinous, lymph. Sömmering detected bile in the lymphatics of the liver; and milk in those of the axilla. M. Dupuytren relates a case, which M. Magendie conceives to be much more favourable to the doctrine of absorption by the lymphatic vessels than any of the others. A female, who had an enormous fluctuating tumour at the upper and inner part of the thigh, died at the Hôtel Dieu, of Paris, in 1810. A few days before her death, inflammation occurred in the subcutaneous areolar tissue at the inner part of the tumour. The day after dissolution, M. Dupuytren opened the body. On dividing the integuments, he noticed white points on the lips of the incision. Surprised at the appearance, he carefully dissected away some of the skin, and observed the subcutaneous areolar tissue overrun by whitish lines, some of which were as large as a crow's quill. These were evidently lymphatics filled with puriform matter. The glands of the groin, with which these lymphatics communicated, were injected with the same matter. The lymphatics were full of the fluid, as far as the lumbar glands; but neither the glands nor the thoracic duct presented any trace of it. On the other hand, multiplied experiments have been instituted, by throwing coloured and odorous substances into the great cavities of the body; and these have been found always in the veins, and never in the lymphatics. To the experiments of Mr. Hunter, objections have been urged, similar to those brought against his experiments to prove the absorp tion of milk by the lacteals; and sources of fallacy have been pointed out. The blue colour, which the lymphatics seemed to him to possess, and which was ascribed to the absorption of indigo, was noticed in the experiments of Messrs. Harlan, Lawrence, and Coates; but they discovered that this was an optical illusion. What they saw was the faint blue, which transparent substances assume, when placed over dark cavities. Mr. Mayo has also affirmed that the chyliferous lymphatics always assume a bluish tint a short time after death, even when the animal has not taken indigo. The cases of purulent matter, &c., found in the lymphatics, may be accounted for by the morbid action having produced disorganization of the vessel, so that the fluid could enter the lymphatics directly; and, if once within, its progression could be readily understood. M. Magendie asserts, that M. Dupuytren and he performed more Magendie, Précis, &c., 2de édit., ii. 195, et seq.; and Adelon, art. Absorption, Dict. de Méd., 2de (dit., i. 239, and Physiologie de l'Homme; 2de édit., iii. 65, Paris, 1829. Harlan's Physical Researches, p. 459, Philad., 1835. Outlines of Human Physiology, 3d edit., Lond., 1833. 4 Op. cit., ii. 211. |