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ter.

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 these 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 experiment of Hunter objections have been urged, similar to those adduced against his experiment to prove the absorption of milk by the lacteals; and some 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. Herbert 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 lymphatic directly; and, if once within, its progression can be readily understood.

Lastly, Magendie affirms, that Dupuytren and himself performed more than one hundred and fifty experiments, in which they submitted to the absorbent action of serous membranes a number of different fluids, and never found any of them within the lymphatic vessels. The substances, thus introduced into the serous cavities, produced their effects more promptly, in proportion to the rapidity, with which they are capable of being absorbed. Opium exerted its narcotic influence, wine produced intoxication, &c. and Magendie found, from numerous experiments, that the ligature of the thoracic duct in no respect diminished the promptitude, with which these effects appeared.

The partisans of lymphatic absorption, however, affirm, that even if these substances are met with in the veins, it by no means follows, that absorption has been effected by that order of vessels; for, as we have seen, the lymphatics, they assert, have frequent communications with the veins; and, consequently, they may still absorb and convey their products into the venous system.

In reply to this, is may be urged, that all the vessels—arterial, venous, and lymphatic—appear to have communication with each other; but that there is no reason to believe, that the distinct offices, performed by them, are, under ordinary circumstances, interfered with. And, again, where would be the necessity for these intermediate lymphatic vessels,—the existence of which has never been demonstrated,—seeing that imbibition is so readily effected

by the veins. The axiom—quod fieri potest per pauca, non debet fieri per multa,—is here strikingly appropriate. The lymphatics, too, as we have endeavoured to show, exert an action of selection and elaboration on the substances exposed to their agency; but, in the case of venous absorption, we have not the slightest evidence that any such selection exists,—odorous, and coloured substances retaining, within the vessel, the properties they had without. Lastly, where would be the use of the distinct, lymphatic circulation opening into the thoracic duct, seeing that the absorbed matters might enter the various venous trunks directly through these supposititious, communicating lymphatics; and ought we not occasionally to be able to detect, in the lymphatic trunks, at least some evidence of those substances, which their fellows are supposed to take up and convey into the veins? These carrier lymphatics have obviously been devised to support the tottering fabric of lymphatic absorption; undermined, as it has been, by the powerful facts and reasonings, that have been adduced in favour of absorption by the veins.

It would result, then, from the whole of the preceding history of absorption, that we are of opinion, that the chyliferous and lymphatic vessels form only chyle and lymph, refusing all other substances; that the veins admit every liquid, which possesses the necessary tenuity; and that, whilst all the absorptions, which require the substance, acted upon, to be decomposed and transformed, are effected by the chyliferous and lymphatic vessels; those that demand no alteration are accomplished directly through the coats of the veins by imbibition; and we shall see, that such is the case with several of the transudations or exhalations.

Sect. V.—ACCIDENTAL ABSORPTION.

The various experiments, to which reference has been made, have shown, that many substances, adventitiously introduced into various cavities, or placed in contact with different tissues, have been rapidly absorbed into the blood, without experiencing any transformation.

Within certain limits, the external envelope of the body admits of this function; but by no means to the same extent as its prolongation, which lines the different excretory canals. The absorption of drinks is sufficient evidence of the activity of the function, as regards the gastro-intestinal mucous membrane. The same may be said of the pulmonary mucous membrane. Through it, the oxygen passes to reach the blood in the lungs, as well as the carbonic acid in its way outwards. Aromatic substances, such as spirit of turpentine, breathed for some time, are detected in the urine; proving that their aroma has been absorbed; and it is in this way, that contagious miasmata probably produce their pestiferous agency. Not only do the tissues, as we have seen, suffer imbibition by fluids, but by gases also; the experiments of Chaussier, and MITCHELL

astonishing us by the rapidity and singularity of their passage through the various tissues;—the rapidity varying according to the permeability of the tissue, and the penetrative power of the gas.

On the subject of cutaneous absorption, much difference of opinion has prevailed; some asserting it to be possible to such an extent, that life might be preserved, for a time, by nourishing baths. It has also been repeatedly affirmed, that the rain has calmed the thirst of shipwrecked mariners, who have been, for some time, deprived of a supply of water. It is obvious, from what we know of absorption, that, in the first of these cases, the water only could be absorbed; and even the possibility of this has been denied by many. Under ordinary circumstances, it can happen to a trifling extent only, if at all; but, in these extraordinary cases, where the system has been long devoid of its usual supplies of moisture, and where we have reason to believe, that the energy of absorption is increased, such imbibition may be possible. Sanctorius, Von Gorter, Keill, Mascagni and others believe, that this kind of absorption is not only frequent but easy. It has been affirmed, that, after bathing, the weight of the body has been manifestly augmented; and the last of these individuals has adduced many facts and arguments to support the position. Bichat was under the impression, that, in this way, he imbibed the tainted air of the dissecting-room, in which he passed a large portion of his time. To avoid an objection, that might be urged against this idea,—that the miasmata might have been absorbed by the air-passages,—he so contrived his experiment, as, by means of a long tube, to breathe the fresh outer air, and he found, that the evidence, which consisted in the alvine evacuations having the smell of the miasmata of the dissectingroom, still continued. It is obvious, however, that such an experiment would hardly admit of satisfactory execution. J. Bradner Stuart found, after bathing in infusions of madder, rhubarb, and turmeric, that the urine was tinged with these substances. A garlic plaster affected the breath, when every care was taken, by breathing through a tube connected with the exterior of the apartment, that the odour should not be received into the lungs. Dr. Thomas Sewell found the urine coloured, after bathing the feet in infusion of madder, and the hands in infusions of madder and rhubarb. Dr. Mussey proved, that if the body be immersed in a decoction of madder, the substance may be detected in the urine, by using the appropriate alkaline tests; and Dr. John Edwards of Paris is, also, in favour of absorption being carried on by the skin to a considerable extent.

To deny cutaneous absorption altogether is impossible. It is one of the ways, in fact, by which we introduce one of our most active remedial agents into the system,—and it has not unfrequently happened, where due caution has not been used, that the poisonous effects of different mineral and other poisons have been developed by their application to the surface, but it is by no means common or easy, when the cuticle is sound, unless the substance employed possesses

unusually penetrating properties. Chaussier found, that to kill an animal, it is sufficient to make sulphuretted hydrogen gas act on the surface of the body, taking care that none gets into the airpassages: the researches of Dr. Mitchell have also shown, that this gas is powerfully penetrant. Unless, however, the substances, in contact with the epidermis, are of such a nature as to attack its chymical composition, there is usually no sensible absorption.

It is only of comparatively late years, that physiologists have ventured to deny, that the water of a bath, or the moisture from a damp atmosphere, is taken up under ordinary circumstances; and if, in such cases, the body appears to have increased in weight, it is affirmed, and with great appearance of truth, that this is owing to some diminution in the cutaneous transpiration. It is, indeed, probable, that one great use of the epidermis is to prevent the inconveniences to which we should necessarily be liable, were such absorption easy. This is confirmed by the fact, that if the skin be deprived of the epidermis, and the vessels, which creep on the outer surface of the true skin, be thus exposed, absorption occurs as rapidly as elsewhere. To insure this result in inoculation and vaccination, the matter is always placed beneath the cuticle; and, indeed, the small vessels are generally slightly wounded, so that the virus gets immediately into the venous blood.

Seguin instituted a series of experiments to demonstrate the absorbent or non-absorbent action of the skin. His conclusion was, that water is not absorbed, and that the epidermis is a natural obstacle to that action. To discover whether this was the case as regarded other fluids, he made trial of some individuals labouring under venereal affections. These persons immersed their feet and legs in a bath, composed of sixteen pints of water and three drachms of corrosive sublimate, for an hour or two, twice a day. Thirteen, subjected to the treatment for twenty-eight days, gave no signs of absorption; the fourteenth was manifestly affected, but he had itchy excoriations on the legs; and the same was the case with two others. As a general principle, absorption exhibited itself in those only whose epidermis was not in a state of integrity. At the temperature of 74° Fahrenheit, however, the sublimate was occasionally absorbed, but never the water.

From other experiments of Seguin, it appeared evident, that the most irritating substances, and those most disposed to combine with the epidermis, were partly absorbed, whilst others were apparently not.

Having weighed a drachm, (seventy-two grains, poids de marc,) of calomel, and the same quantity of camboge, scammony, salt of alembroth and tartar emetic, Seguin placed an individual on his back, washed the skin of the abdomen carefully, and applied to it these substances, at some distance from each other, covering each with a watch-glass, and maintaining the whole in situ by a linen roller. The heat of the room was

kept at 65°. Seguin did not leave the patient, in order that the substances should not be displaced; and he protracted the experiment to ten hours and a quarter. The glasses were then removed, and the substances carefully collected and weighed. The calomel was reduced to 71 1-3 grains. The scammony weighed 71 3-9; the camboge, 71; the salt of alembroth, 62 grains;⁕ and the tartar emetic 67 grains.

It requires, then, in order that matters shall be absorbed by the skin, that they shall be kept in contact with it, so as to penetrate through its pores, or through the channels by which the cutaneous transpiration exudes; or else that they shall be forced through it by friction, the mode adopted for introducing mercury into the system. In this way, the substance comes in contact with the cutaneous veins, and enters them, probably by imbibition.

Nearly about the period that Seguin was engaged in his experiments, Dr. Rousseau, of Philadelphia, contested the existence of absorption through the epidermis, and attempted to show, in opposition to the experiments we have detailed, that the pulmonary organs, and not the skin, are the passages by which certain substances enter the system. By cutting off all communication with the lungs, which he effected by breathing through a tube, communicating with the atmosphere on the outside of the chamber, he found, that, although the surface of the body was bathed with the juice of garlic or the spirit of turpentine, none of the qualities of these fluids could be detected, either in the urine, or in the serum of the blood.

From subsequent experiments, performed by Dr. Rousseau, assisted by Dr. Samuel B. Smith, and many of which Professor Chapman witnessed, the following results were deduced. First, That of all the substances employed, madder and rhubarb are those only that affect the urine; the latter of the two more readily entering the system; and secondly, that the power of absorption is limited to a very small portion of the surface of the body. The only parts, indeed, that seemed to possess it, were the spaces between the middle of the thigh and hip, and between the middle of the arm and shoulder.

Topical bathing, with a decoction of rhubarb or madder, and poultices of these substances, applied to the back, abdomen, sides, or shoulders, produced no change in the urine; nor did immersion of the feet and hands in a bath of the same materials, for several hours, afford the slightest proof of absorption.

From all the above facts,—sufficiently discrepant it is true,—we are justified in concluding, with Professor Chapman, that although the subject is not, perhaps, absolutely decided, enough has been done to demonstrate, that cuticular absorption rarely happens, and that whenever it does, it cannot be deemed the effort of a natural function.

⁕ Several pimples were excited on the part to which it was applied.

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