It is found that particular conditions of particular sets of organs give rise to certain groups of symptoms: these groups of symptoms have been supposed to form different genera and species, and have received specific names. Were the nomenclature of these genera and species of fever perfect, the name would in each case be expressive of the condition of the organs upon which the assemblage of symptoms it denotes depends, and perhaps in some greatly advanced state of our science, when these conditions have been perfectly ascertained and have become perfectly familiar, an approximation to this desirable classification and naming may be attempted with success. The state of our knowledge, however, enables no one to undertake the task at present, and in the mean time the slightest glance at the divisions which have been attempted of this class of diseases, is but too sufficient to shew the total absence of that kind of information, which, if there be any truth in the preceding observations, it is alone of value to possess. Thus febrile diseases are commonly divided into idiopathic and symptomatic—a division which is liable to the fundamental objection that the diseases included under the second section are not fevers but inflammations. There are no fevers but idiopathic fevers. It has been shewn that fever differs from inflammation both in the individual phenomena forming the train that constitutes the disease, and in the order in which the several phenomena succeed each other. There are, it is true, individual phenomena common to both; but since the series as well as the order in which the several phenomena stand in the series are different, to call both by the same name can only produce confusion and misconception. Of true or idiopathic fevers two great divisions are made; one comprehending intermittent and the other continued fevers: a division founded on the occurrence of the trains of the phenomena in an interrupted or in an uninterrupted series. Intermittent fever is further divided into intermittent and remittent, the interruption in the series being said to be complete in the one and incomplete in the other. In continued fever, on the other hand, the trains of phenomena are supposed to proceed in a perfectly uninterrupted series, whence the name continued. The single fact suggested to the mind of the practitioner by this classification is in the highest degree trivial.