Absorbent medicines, (from ab-iorieo, to suck up). This was formerly an important class of medicines, at present it is reduced below its proper level; and it will be useful to appreciate the real value and object of absorbents.
In a general sense these medicines are such as will absorb acrimony; in a more limited one they are styled Antacidr, Antalkalines, and sometimes Antacrids. The simplest view that we can take of their operation, is in the application of dry flour to the skin, in cases of erysipelas: flour, in this case, truly absorbs the acrid matter flowing under the cuticle, and occasionally passing through it, thus extending the inflammation. Its action is consequently mechanical; and dry flour absorbing the blood in slight haemorrhages, and forming an artificial thrombus, a support to a wounded artery, is equally a mechanical effect. We can proceed further: when the mucilage of gum arabic, an unleavened biscuit, or a similar substance, prevents heartburn, each acts by absorbing the acrid matter which before came in contact with the upper orifice of the stomach. In a way, not very different, demulcents sheath the inflamed or abraded surfaces of the alimentary canal, bladder, or epiglottis. See Demulcents.
Their action has, however, been extended further; and acids, alkalines, or other acrids, have been combated by absorbents acting as chemical bodies. The former are neutralized by alkalis, calcareous and mag-nesian earths; the latter by acids of every kind: the acrids, if their nature is known, by their appropriate antagonists. Ancient physicians have fancifully adopted different earths to different acids. We now employ but two kinds, magnesia and"calcareous earths: the former, with an acid, is slightly laxative; the latter, when neutralized, probably an astringent. Chalk or lime miter are the two forms, in which this last earth is employed; for crabs' claws, crabs' eyes, egg and oyster shells, coral, and burnt hartshorn, have no other power than chalk, and are less active as absorbents. Of late, bitters have been employed with the same view; and they seem to succeed, though they probably prevent the formation of acid by strengthening the tone of the stomach, rather than correct it when formed. Yet we cannot deny some antacid power to bitters. Alkalies act more powerfully as absorbents of acids, and they are now employed cither in the common form of carbonates; in their pure state; or joined with oil in the form of soap. The pure alkali is now generally preferred.
Alkalis in the stomach are opposed by acids, and the mineral acids, as they are also tonic, are preferred. There are few instances where this state of the stomach occurs. In the advanced periods of putrid fevers, when the bile regurgitates; or, when absorbed, in jaundice, it again mixes with every secreted fluid; and in scurvy we usually find acids necessary. In the first case, mineral acids are preferable; in the last two, the vegetable. Of the mineral acids we see no ground for preference; the oxygenated muriatic acid has not been employed freely; and oxygen, in the stomach, is certainly not salutary.
Of other, acrids we have no evidence; when poisonous effluvia, particularly in cases where the infection of putrid fever has been received, and a bad taste has been perceived in the mouth, the evacuation of the stomach is the only certain remedy. Viscid phlegm sometimes loads the stomach, and medicines have been employed to "incide" and dissolve it. We know, how -ever, no medicine that has any such power; and from its weight it cannot be very successfully carried downward, since the orifice of the pylorus is above the greater curvature of the stomach. The only remedy is to evacuate it occasionally by emetics; and, by strengthening the stomach, to prevent, at least to retard, its accumulation.
A more difficult part of the subject remains. Acids have been supposed to contaminate the blood and produce numerous diseases; for which alkalis and absorbents have been employed. Acids, however, except in children, do not extend to the alimentary canal; and we take this early opportunity of declaring, that there is not the slightest evidence of acid or any injurious substance in the vital fluid. In no instance, not even in the venereal disease, will the blood convey infection; and though what is discovered in the excreted fluids must exist in the blood, yet it is there involved, concealed, and soon separated. In short, we cannot correct acrimony in the blood; for the same power that involves it, equally involves the medicines intended to oppose it; each may again appear in the secretions.
In many diseases we perceive an acid thrown off as an offensive and injurious substance. Berthollet found it in the perspiration of gouty persons. It is more obvious in gouty chalk stones, and in the calculus. vesicae. This acid probably arises from the stomach; for, by the use of absorbents and bitters, the diseases are mitigated. They correct the forms of the disease in the first passages; and we think that they offer an instance of their power after having passed. through the circulatory system, when they are again evolved in the glands. See Antacids, Antalkalines, and Lithontriptics.
Absorbentia vasa, absorbent vessels. These are vessels which take up any fluid from the surface or any cavity of the body, and carry it into the blood. They are denominated, according to the liquids they convey, Lacteals and Lymphatics; the former conveying the chyle, a milky liquid, from the intestines; the latter lymph, or a thin pellucid liquor, from the places from whence they take their origin; or any fluids that are extravasated, and convey them into the circulating blood: venal ramifications form no part of the absorbent system. See Lactea vasa, and Lymphae ductus. The following kinds of absorption take place in our bodies, viz. the nutritious particles are absorbed from the intestines by the lacteals, which are the same absorbents as are in every other part; secondly, by bibulous orifices over the external parts of our bodies; thirdly, by the same kind on the internal surfaces of all. cavities, as is evident from an ascites being carried off by this absorption.
After rubbing the hand well, it hath in a quarter of an hour imbibed an ounce and a half of warm water; at the same rate, then, the whole body would have received six or seven pounds. As Dr. Hunter hath observed, this matter is demonstrated beyond a doubt by the following experiment made on a living dog: an opening was made into the cavity of his belly, and three quarts of warm water were injected and secured; in about six hours after he was examined, and not above four ounces of the water were remaining there. De Haen,who drowned dogs in coloured fluids, could find no fluid in the lungs, though the colour which it had conveyed was left.
The power of the external vessels to absorb fluids has, however, been denied by several modern authors, and positive experiments adduced where the result was very different, no diminution of the water having been found. It was supposed by the elder Monro (we ought now to say the first Monro,) that the power of absorption lessened with our strength. Though this may be, the fact is more certain that it increases with the wants of the system. Dr. Simson, of St. Andrew's, adduces a strong instance of a rapid decrease of the water in which the legs were bathed in a phrenitic case: and sailors, who in distress put on shirts wetted with salt water, find their thirst greatly lessened. In many cases, however, no absorption from the skin does take place. There is another power in the absorbent vessels which seems not to have been sufficiently attended to; viz. a selection of the substances they absorb. In general, they do not absorb gases, nor effluvia of any kind, fluids of a narcotic nature, and almost all poisonous fluids, except the venereal poison, may be applied to a sound skin with little danger: yet we have good authority (that of Dr. Alexander) for supposing that bark and nitre may be occasionally absorbed; and we think that we have seen in a putrid sore throat, where the power of swallowing was lost, a bath made of a strong decoction of bark highly salutary. The effects of nourishing clysters are well known.
Further satisfaction on this subject may be received from what is said on the power of the external absorption of the human body by Dr. Wilkinson, in the Medical Museum, \ol. ii. p. 117, etc. And with respect to absorption in the internal parts, see Dr. Hun-ter's Medical Commentaries; with the Observations by Dr. Garner, in the Med. Mus. vol. ii. p. -29, etc.