Idiopathic or essential epilepsy is a chronic disease of the nervous system characterized by periodically recurring convulsions, lapses or abnormal mental states occurring in persons with a personality defect or constitutional inferiority but with no demonstrated pathologic lesion.1 It is estimated that 0.4 per cent of the population is epileptic. The personality defect or the "psychobiologic feature" has been demonstrated by Clarke in his excellent monograph, Clinical Studies in Epilepsy.2 This constitutional inferiority is probably an inherited defect (rather than congenital).
The hereditary predisposition has long been considered a factor in the etiology of epilepsy.3 The accompanying table gives the variations in statistics on the influence of heredity.
It must be remembered that a reliable history is extremely difficult to obtain from an epileptic or from his parents. Also, the statistics will vary greatly in different countries and in different centers of population. In a consideration of