The pathology of fever comprehends the morbid changes that take place in the solids and the fluids of the body. It is probable that the changes in the fluids are wholly dependent upon those which take place in the solids, although the vitiation of the former must necessarily react upon, and increase the derangement of the latter. If it be true, as is highly probable, that the changes in the solids are beyond all comparison of the greatest importance, as not only antecedents, but _invariable_ antecedents, or causes, it may be considered fortunate that our knowledge of their diseases is so much more advanced than our knowledge of the diseases of the humours. The morbid changes of the solids are ascertained with a great degree of exactness, it may almost be said with a great degree of perfection; while those which occur in the fluids are almost wholly unknown. Until very recently physicians satisfied themselves with framing conjectures about their corruption; and knowing with certainty no one vice that they possess, they attributed to them a thousand. Attention is now awakened to the subject: investigation is going on: and before long we shall probably know, with some degree of precision, whether any changes really take place, and what they are: but the researches which have hitherto been made are so few and so imperfect, that it can hardly be said that a single point is satisfactorily made out and firmly established. In laying before the reader the pathology of the solids, as far as it is yet ascertained, it is my most anxious wish to enable him constantly to make for himself, as he proceeds, the association between the morbid appearances that are found after death, and the symptoms that were present during life. For this reason every case that is adduced to illustrate any morbid change is preceded by a brief account of the symptoms that were observed, day by day, at the bed-side of the patient. For the sake of brevity however, no less than for that of clearness, none but the essential are noticed. The daily reports, of which all the cases cited, are exceedingly condensed forms, are full, and contain, as they necessarily must contain, many repetitions with which it would be worse than useless to burthen this account of them. Even the statement of the remedies that were adopted (excepting in as far as they obviously influenced the symptoms) is omitted, from the conviction that the mind cannot attend without distraction, at one and the same time, to the pathology and the treatment.