When we consider how many circumstances connected with the origin and the propagation of fever are wholly unknown, which if known might have a most important influence in preventing its occurrence, in arresting its progress or in lessening its mortality; when we consider in what profound obscurity the very nature of the agents that produce it is still involved; when we consider how easy it is to swell the long catalogue of its symptoms, but how difficult it is to discriminate which, even among the most prominent of the train, are the essential and which the adventitious, and how still more difficult it is to ascertain which are the invariable antecedents and which the invariable sequents, or which the causes and which the effects; when we consider how few comparatively of the external appearances have been ascertained to be the sure and certain signs of any known condition of the internal organs, and how often the existence of several known conditions of the organs remains altogether unsuspected until the demonstration of it is afforded by inspection after death, and when finally on all these accounts we consider how vague the objects must be that are aimed at in the treatment, and consequently how uncertain, how indiscriminate, how fruitlessly inert, how perniciously active, how unsuccessful, how fatal that treatment often is, it must be admitted that fever still presents to us a vast field, in the culture of which the difficulties to be overcome are not slight, and the most diligent labour that can be bestowed upon it may by no means be attended with a sure reward. Of many branches of science it is truly observed that much time and labour are necessary to establish a single important fact; of some parts of medical science this is eminently the case, but perhaps of none is the observation so just as of that which relates to febrile diseases. It is remarkable how entirely the most distinguished physicians of all ages who have treated of this subject coincide in the feeling, that with regard to this important class of disease it is impossible in the short life allotted to the most aged to do any thing more than add a little knowledge to the common stock. If there be any foundation for this feeling it can only be by every man faithfully endeavouring to contribute what he may be able, be the amount ever so small, that that stock can speedily become large or ever become complete.