GENERAL CONCEPT OF "ENCEPHALITIS"
The term "encephalitis," according to Webster's dictionary, means "an inflammation of the brain." Inflammation is defined as "a morbid condition consisting in congestion of blood vessels and exudation of plasma and blood corpuscles at the site of an infection or injury." Most other lexicons concur in such a definition. Confusion has arisen because some pathologists use the term encephalitis as synonymous with infection of the brain. Since, in the group of diseases with which this paper will deal chiefly it is generally admitted that the anatomic changes observed coincide fairly well with the definition in the dictionaries, since the most important point at issue is exactly the question whether or not they are due to the presence of an infective agent within the brain and since, further, instances of these lesions are almost invariably indexed and catalogued under the denomination "encephalitis" or "encephalomyelitis," we shall continue