[Monthly distribution of births in the Japanese population before 1900].

possible a comparison with the data in the vital statistics which have been published annually since 1899 by the Japanese Government. Major sources of these data were: 1) 34,115 adult survivors registered in a) registration books of residents in ward offices in Tokyo and Osaka, b) lists of inmates at nursing homes for the aged in Tokyo, Osaka and Kyushu, and c) lists of members of local societies, the Diet and an alumni-association; 2) 6,988 death certificates of adults in a) the general population in Tokyo between 1965 and 1975 and b) a nationwide employees' association, and 3) 2,005 birth records in a) old parishoners' census registration books, known as "Ninbetsu-Cho," for the years between 1755 and 1867 and b) old diaries, documents and descriptions. In the latter half of the 19th century, the seasonal distribution of birth had an early spring peak between January and March and a trough between May and July, similar to the typical distribution of births in the 20th century. From the late 18th to early 19th centuries, a spring peak was not so evident. Instead, a fall peak was rather prominent in most samples. Similarly, from the 9th to the early 18th centuries, a fall peak pattern was also seen in small samples. The seasonal distribution of births in the latter half of the 19th century in Tokyo, Osaka and Kyushu can be used as distributions of normal control populations for studies on the relationship between birth season and morbidity of some particular diseases.