22. It prepares the way for the successful use of the bark and other tonic remedies, by destroying, or so far weakening, a morbid action in the blood-vessels, that a medicine of a moderate stimulus afterwards exceeds it in force, and thereby restores equable and healthy action to the system.
23. Bleeding prevents relapses. It, moreover, prevents that predisposition to the intermitting and pleuritic states of fever, which so frequently attack persons in the spring, who have had the bilious remitting fever in the preceding autumn.
But great and numerous as the advantages of blood-letting are in fevers, there have been many objections to it. I shall briefly enumerate, and endeavour to refute the errors upon this subject.
Blood-letting has been forbidden by physicians, by the following circumstances, and states of the system.
1. By warm weather. Galen bled in a plague, and Aræteus in a bilious fever, in a warm climate. Dr. Sydenham and Dr. Hillary inform us, that the most inflammatory fevers occur in, and succeed hot weather. Dr. Cleghorn prescribed it copiously in the warm months, in Minorca. Dr. Mosely cured the yellow fever by this remedy, in Jamaica. Dr. Broadbelt, and Dr. Weston, in the same island, have lately adopted his successful practice. Dr. Desportes speaks in the highest terms of it in all the inflammatory diseases of St. Domingo. He complains of the neglect of it in the rheumatism, in consequence of which, he says, the disease produces abscesses in the lungs[49]. I have never, in any year of my practice, been restrained by the heat of summer in the use of the lancet, where the pulse has indicated it to be necessary, and have always found the same advantages from it, as when I have prescribed it in the winter or spring months.
In thus deciding in favour of bleeding in warm weather, I do not mean to defend its use to the same extent, as to diseases, or to quantity, in the native and long settled inhabitants of hot climates, as in persons who have recently migrated to them, or who live in climates alternately hot and cold.
2. Being born, and having lived in a warm climate. This is so far from being an objection to blood-letting in an inflammatory disease, that it renders it more necessary. I think I have lost several West-India patients from the influence of this error.
3. Great apparent weakness. This, in acute and violent fevers, is always from a depressed state of the system. It resembles, in so many particulars, that weakness which is the effect of the abstraction of stimulus, that it is no wonder they have been confounded by physicians. This sameness of symptoms from opposite states of the system is taken notice of by Hippocrates. He describes convulsions, and particularly a hiccup, as occurring equally from repletion and inanition, which answer to the terms of depression, and debility from action and abstraction. The natural remedy for the former is depletion, and no mode of depleting is so effectual or safe as blood-letting. But the great objection to this remedy is, when a fever of great morbid excitement affects persons of delicate constitutions, and such as have long been subject to debility of the chronic kind. In this state of the system there is the same morbid and preternatural action in the blood-vessels, that there is in persons of robust habits, and the same remedy is necessary to subdue it in both cases. It is sometimes indicated in a larger quantity in weakly than in robust people, by the plethora which is more easily induced in their relaxed and yielding blood-vessels, and by the greater facility with which ruptures and effusions take place in their viscera. Thus it is more necessary to throw overboard a large part of the cargo of an old and leaky vessel in a storm, than of a new and strong one. I know that vomits, purges, sweats, and other evacuating remedies, are preferred to bleeding in weakly constitutions, but I hope to show hereafter, that bleeding is not only more effectual, but more safe in such habits, than any other depleting remedy.
4. Infancy and childhood. This is so far from being an objection to bleeding, that the excitable state of the blood-vessels in those periods of life, renders it peculiarly necessary in their inflammatory diseases. Dr. Sydenham bled children in the hooping cough, and in dentition. I have followed his practice, and bled as freely in the violent states of fever in infancy as in middle life. I bled my eldest daughter when she was but six weeks old, for convulsions brought on by an excessive dose of laudanum given to her by her nurse; and I bled one of my sons twice, before he was two months old, for an acute fever which fell upon his lungs and bowels. In both cases, life appeared to be saved by this remedy.