Idiopathic epilepsy may be defined for the purposes of this paper as a tendency, more or less periodic, to convulsions with loss of consciousness, without obvious exogenous factors, and in persons who have an ordinarily well developed brain. Our problem is: what is the distribution in the human species of this tendency to epilepsy?
Three general matters may be discussed at the outset. First, idiopathic epilepsy is not always easy to separate from epilepsy with exogenous factors; for there may be such factors all unknown to the student. Also, even statistics of army recruiting and missionary hospitals do not distinguish epilepsies due to different causes. We shall have to be content with what is available, unsatisfactory as it is. The defect is not so serious, however, since even in cases of epilepsy in which an irritating or inducing "cause" can be distinguished, we can not deny the probable existence of