These seem to arise in the same circumstances, and to be owing to the same general causes, as fevers. They may, in some sense, be considered as fevers, attended with peculiar symptoms in consequence of a determination to the bowels, just as fevers in cold climates are sometimes attended with rheumatism and catarrh. We have seen, in the first part of this work, that the dysentery arose chiefly in those ships which had been subject to fevers.
This determination to the bowels is owing to a variety of causes, but is chiefly connected with external heat; for it is most common in hot climates, and towards the end of summer or in the autumns of cold climates, owing probably to a greater acrimony of the secretions of the intestines, and particularly of the bile. Dysenteries arise in camps also at the same seasons, and in the same circumstances as bilious fevers[113].
Besides climate and season, the other circumstances determining to the one disease more than the other are, 1. A difference in the constitutions of different men; for in the same ship it sometimes happens that both diseases prevail equally, though all the men are using the same diet and breathing the same air. 2. The nature of the occasional cause. A dysentery, for instance, is more likely to arise from an irregularity in eating or drinking; a fever from being exposed to the weather, particularly marsh effluvia. 3. The particular species of infection that may happen to be introduced. Suppose, for example, that a ship’s company is predisposed to acute distempers, and one man or more ill of the dysentery should be brought on board, this will become the prevailing disease, as happened in the Torbay in August, 1780. If the like number of fevers should be introduced, then fevers will be the prevailing disease.
These two diseases may therefore be considered as vicarious, the one substituting itself for the other according to particular accidents, and both proceeding from the same general causes; and this is no new idea of mine, but seems to have been Dr. Sydenham’s, when he calls the dysentery a febris introversa. It may be farther added, that dysentery is the latest form in which this cause, which is common to both, can exert itself; for it is a disease more within the reach of art; and some of the most dangerous symptoms attending fevers, particularly delirium, seldom occur in dysentery. When it proves fatal, it is in consequence of violent local affection, and that in general after it has taken a chronic form. When an incipient fever turns into a dysentery, all the symptoms, and particularly the head-ach, delirium, and coma, if there should be any, are immediately relieved. And the most favourable cases of the yellow fever are those in which a bilious diarrhœa comes on, while the most fatal are those in which the bowels are so torpid as to be insensible to any stimulus either from their own contents or from medicine.
I shall not enter into a minute description of this disease in all its stages, as this has been so ably executed by Sir John Pringle, Sir George Baker, and other authors, but shall only give a sketch of some of the most remarkable symptoms, particularly such as are peculiar to the climate and manner of life, so as to explain the varieties that may be necessary in the mode of treatment.
The fluxes that arose in the fleet were either what may be called the acute idiopathic dysenteries, or a dysenteric state of the bowels from neglected diarrhœas, which was most apt to occur in the convalescent state of fevers, or in men labouring under the scurvy. The body is more susceptible of infection in a state of weakness from these or any other causes; and in hot climates the dysentery seems to be more infectious than fevers; for at hospitals it was so frequently communicated to men who were ill of other complaints, that it was in these the principal cause of mortality. For this reason, I was at more pains with regard to this disease than any other, in keeping those who were ill of it in a separate ward.
I have met with some violent and untractable cases which proved fatal in the acute state; but, in general, this disease draws out to a chronic form in this climate, and does not prove mortal for many weeks. The usual cause of death appears, from the inspection of the bodies, to be an ulceration of the great intestines, particularly of the descending colon and the rectum. This part of the intestinal tube is most affected from its being the receptacle of all the acrid secretions from the rest of the canal; and it is naturally more subject to congestions of the fluids and incurable ulcers, as appears from the rectum being so liable to the hæmorrhoids and the fistula. This ulceration of the great intestines is so common, that, out of eight cases which I inspected after death, seven had this appearance. The case in which there was none was not so much a case of dysentery as of inflamed bowels, brought on by the man having drank to excess of spirits while he was recovering from a dysentery. The acute tormina which always occur in the first days of the disease seem owing to an inflammation, which terminates in ulcers; and these being constantly irritated by the sharp humours, produce the tenesmus, which is the symptom most essential to dysentery in the after part of the disease. Any diarrhœa may in this manner become dysenteric. During the acute griping at the beginning, the stools are loose and copious; but as soon as the tenesmus takes place, they are scanty, which is most probably owing to the spasmodic strictures in the great intestines, in consequence of irritation upon their excoriated surface. The inflammatory state is more lasting and violent in a cold than a hot climate, the gripings are more severe, and the danger is also greater in this stage of it.
The state which the great intestines fall into in old dysenteries seems to have something in it peculiar to itself: the several coats become thick and spongy; their texture is obliterated and destroyed; and they become of a black or very dark purple colour. This, however, cannot be called mortification; for the fibres of the gut do not lose their tenacity, nor is there that putrid and dissolved state in which gangrene consists; but it advances in time to such an extreme state of disease as to be entirely incapable of recovering its natural appearance and functions, and proves therefore the cause of death.
The greater frequency and obstinacy of these chronic fluxes in hot than in cold climates seems to be owing to the same weakening of the powers of life which make recovery in general so tedious, and particularly that of wounds and ulcers. The greater quantity of acrid bile will also tend to keep up the ulceration. Dysenteries have this disadvantage, that the Peruvian bark, which is the most powerful restorative in other complaints of this climate, is here found to be inadmissible on account of the heat, thirst, and other febrile symptoms, which it seldom fails to induce in all stages of this disease.