_An account of sporadic cases of bilious yellow fever, as they appeared in Philadelphia in 1795 and 1796_ 435
As many of the diseases which are the subjects of these volumes belong to the class of fevers, the following remarks upon their theory are intended to render the principles and language I have adopted, in the history of their causes, symptoms, and cure, intelligible to the reader.
I am aware that this theory will suffer by being published in a detached state from the general view of the proximate cause of disease which I have taught in my lectures upon pathology, as well as from its being deprived of that support which it would receive from being accompanied with an account of the remedies for fever, and the times and manner of exhibiting them, all of which would have served to illustrate and establish the facts and reasonings which are to follow upon this difficult and interesting inquiry.
I shall not attempt to give a definition of fever. It appears in so many different forms, that a just view of it can only be given in a minute detail of all its symptoms and states.
In order to render the theory, which I am about to deliver, more simple and intelligible, it will be necessary to premise a few general propositions.
I. Fevers of all kinds are preceded by general debility. This debility is natural or accidental. The former is the effect of the sanguineous temperament, and exists at all times in many constitutions. The latter is induced,
1. By such preternatural or unusual stimuli, as, after first elevating the excitement of the system above its healthy grade, and thereby wasting a part of its strength, or what Dr. Brown calls excitability, and Darwin sensorial power, afterwards reduces it down to that state which I shall call debility of action. Or,
2. It is induced by such an abstraction of natural stimuli as to reduce the system _below_ its healthy grade of excitement, and thereby to induce what Dr. Brown calls _direct_ debility, but what I shall call debility from abstraction. This general debility is the same, whether brought on by the former or the latter causes. When induced by the latter, the system becomes more excitable than when induced by the former causes, and hence an attack of fever is more frequently invited by it, than by that state of debility which succeeds the application of an undue portion of stimulating powers. To this there is an exception, and that is, when the remote causes of fever act with so much force and rapidity as _suddenly_ to depress the system, without an intermediate elevation of it, and before sufficient time is given to expend any part of its strength or excitability, or to produce the debility of action. The system in this state, is exactly similar to that which arises from a sudden reduction of its healthy excitement, by the abstraction of stimuli. This debility from abstraction, moreover, is upon a footing with the debility from action, when it is of a _chronic_ nature. They both alike expend so much of the quality or substance of excitability, as to leave the system in a state in which irritants are seldom able to excite the commotions of fever, and when they do, it is of a feeble nature, and hence we observe persons who have been long exposed to debilitating causes of both kinds, often escape fevers, while those who are _recently_ debilitated, are affected by them, under the same circumstances of exposure to those causes.