The study reported in this book was based on 88 cases in which the patients had had severe infantile atrophy for at least two and a half or three months. Seventy-seven of these patients could be reexamined, most of them at the age of 12 to 14 years, and in 11 instances reports were obtained. The development of these patients was compared, when possible, with that of their siblings, and the mentality of their parents and of other members of their families was considered. The incidence of feeblemindedness in the population at large was also taken into consideration. Cases of severe atrophy involving infants who were seriously retarded were excluded.
The incidence of feeblemindedness was 17, or 19.3 per hundred, exceeding that of the population at large. However, within the families of the patients the incidence of feeblemindedness was also rather high, although such an Anlage could not account entirely