
a probable epidemic of congenital
hydrocephalus in 1940-1941
a peak in the incidence of congenital hydrocephalus in 1940-41 is described;
reasons are given for believing it to be a genuine phenomenon, though it is too
late to find the cause.
epidemics of malformations are to be detected promptly only if the incidence
of malformations in a defined population is studied continuously; and for some
epidemics the population studied must be very large indeed.
