The author investigated the thyroid glands of 1480 school children (aged from 6 to 14) living in the vicinity of Yakage, the south-western rural district of Okayama Prefecture, and 1516 out-patients of Yakage Hospital, in 1950. The incidence of struma among the school children was 4.6 per cent and among the out-patients 4.7% on an average, and the percentage of struma in the spring (7.8%) was higher than in the summer (2.98%). This result suggests that thyroid
glands are in some way susceptible to seasonal influences, and it is therefore necessary to consider the effect of season during investigation. The white blood pictures of seven patients showed no specific findings.