I am extremely diffident, as I have said, in all matters depending on our supposed knowledge of the animal œconomy; but the preceding circumstances seem to countenance the following reasoning:—The bile, according to Dr. Maclurg, who has given one of the best dissertations on its nature and properties, is composed of two parts; the gross part, which is coagulable by acids, and that part in which the bitter principle resides. The first constitutes the principal part in point of quantity, and seems to be that portion of the mass of fluids which loses the property of sound healthy blood, by a tendency to putrefaction, and is thrown out by this secretion. I will not undertake to vouch for the truth of this, but shall assume it as true in the following reasoning:—According to this theory, therefore, the greater part of the bile is what may be called the effete part of the circulating mass, or perhaps only of the red globules or gluten, the watery and saline part, which passes off by urine being the corrupted part of the serum. This part of the bile being very liable to putrefaction, the bitter part is considered by Dr. Maclurg as intended to correct this, and also to answer some good purpose in digestion. One of the effects of the bile in this operation is to extinguish acidity, whether proceeding from substances taken in, or generated in the stomach. The blood in all climates, and in all situations of life, is subject to have part of it thus corrupted, which, being separated from the common mass by the liver, is mingled and discharged with the common feces; but external heat continued for any length of time tends to augment this corruption of the fluids, and therefore to increase the secretion of bile; and it has been observed both by myself and others, that the bile found in those bodies that have been inspected after death, in consequence of fevers in hot climates, is less bitter, and not so penetrating to the fingers, being therefore deficient in the antiseptic principle. But since external heat makes no alteration in the degree of temperature of the fluids themselves, this effect must take place through the medium of the solids, in consequence of that general languor and want of energy which too much external heat induces in the functions, particularly in that power by which the living body preserves itself from putrefaction. Now if this portion of the blood, thus altered and depraved, is readily secreted and speedily thrown out, as in cholera morbus, no harm befals the constitution, nor any inconvenience but what arises from the irritation of the primæ viæ. But this may not take place if the body should be otherwise deranged; for the removal of this noxious matter from the mass of blood depends upon a due irritability of the blood vessels, the liver, and the bowels, whereby they are stimulated to contract, and thereby expel it. According to the principle of Mr. John Hunter, (whose deep and industrious researches into the animal œconomy place him high in the list of those few on whom nature has bestowed real genius, and who are capable of adding something new to the stock of human knowledge,) there is in a state of health a relative habitude or mutual harmony existing between the solids and fluids, whereby they stimulate and produce actions in each other, in which the healthy state of the functions consists, whether employed in the formation of what is found, or the expulsion of what is noxious: so that where it happens that the solids have a morbid insensibility to the impressions of corrupted and acrimonious fluids, the retention of these adds still more to the general derangement. To illustrate this, it may be observed, that the stomach and bowels, when they are endowed, as it were, with their natural perception, immediately expel any preternatural accumulations of bile that may take place; but when they are insensible to this stimulus through disease, no effort is made to relieve nature till it is excited by medicine. The same reasoning may be applied to the various vessels and ducts. Thus when we see the liver gorged with bile, without any free excretion of it into the gall bladder, as I have sometimes found to be the case upon inspecting the body in some of the worst cases of fever, would it not appear that the gall ducts have lost that natural irritability whereby the bile is expelled? Or, in consequence of a depraved state of action, connected with febrile affection, may it not happen that the absorbents, which, in their natural state, only absorb particular substances, and in a given quantity, will suffer a change in this natural action, and absorb whatever happens to be applied to their orifices? In case of jaundice, the bile, which is perhaps not at all absorbed in a state of health, is taken up in large quantities, and mingled with the mass of blood, which proves a seasonable relief in the state of accumulation and distension occasioned by the obstruction. This may happen in cases of fever, not indeed as a relief to nature, but from a depraved state of irritability in the lymphatics, induced by disease. Though no increased quantity of bile, therefore, is found in the gall bladder, there may have been an increased excretion of it, a preternatural absorption having been excited. So that it may admit of a question whether the colour of the skin, in the yellow fever, is owing to this, or if the idea of it given in the text[104] is more just; but in either case it seems probable that the extreme tendency to putrefaction in the whole body is owing either to the presence of bile, in consequence of absorption, or the retention of something in the blood from a defect of its secretion.
This reasoning concerning the bile in hot climates may, in some sort, be illustrated by what happens to the urine in cold climates. The urine is the vehicle of an excrementitious part of the blood, of which an increased proportion is generated in certain fevers, and if it is thrown out in the form of high-coloured, turbid urine, the fever will most probably be slight and short; but if it becomes pellucid, or crude, as it is called, the general derangement will be increased, the fever will be more violent and dangerous, and the first sign of returning health will be a turbid appearance and sediment.
If the reasoning in the above discussion should appear to some readers unsatisfactory, or ill connected, I can only say that if it is deserving of this character, I am willing to have it considered not only as an illustration, but an example of the nicety and fallacy of theoretical disquisitions.
[105] I have been very cautious of admitting any theory into this work; but I cannot help adopting the doctrine of my much-valued master, Dr. Cullen, on this point, viz. that a great part of the symptoms of fever arise from reaction, or that effort which nature makes to overcome the morbid cause. I am happy in any opportunity of acknowledging my obligations to this learned professor, to whom the medical world in general is so much indebted, as well for the rational views of the animal œconomy, which he teaches, as for that spirit of study and inquiry which he infuses into the minds of his pupils.
[106] M. Desportes, who wrote a treatise on the diseases of St. Domingo.
[107] There is a difference in the appearance of the blood when sizy, perhaps not sufficiently insisted on by practical writers; for though there should even be a very thick buff, yet, if the surface is flat, and the crassamentum tender, no great inflammation is indicated, in comparison of that state of the blood wherein the surface is cupped, the crassamentum contracted so as to afford the appearance of a large portion of serum, and where it feels firm and tenacious, though perhaps but thinly covered with buff. This is a distinction well worth attending to in practice; for it is in these last circumstances that blood-letting gives most relief, and where the patient will bear the repetition of it with most advantage.
[108] See the same observation in Mr. Hume’s Essay on this Disease, published by Dr. Donald Monro.
[109] The state of the stomach is very much affected by that of the external surface of the body; and it is sagaciously observed by Sydenham, that the stomach being commonly very irritable in the plague, the most effectual means of making it retain what was administered internally was to excite a sweat.
[110] The red bark was brought to England in a Spanish prize in the year 1781, and a very accurate account of its medical and chemical properties was published the year after by Dr. William Saunders, of Guy’s hospital. None of it had been brought to the West Indies before the peace, so that I had no opportunity of trying it in that climate.