Statistical investigations were made on the birth weight of 14, 801 babies which were born in Namie Area in Fukushima prefecture during the period 1952 to 1957. The birth weight were analysed in accordance with such factors that the monthly vatiation, seasanal variation, influence of birth order and mothers age. The occurrence rate of premature birth was 6.6 percent (male 5.8, femal 7.5) of the total number of live births. The mean value of birth weight of male was greater than that of femal. It was suggested that the limit of premature infant in femal must be lower than the in case of male. The occurence rate of birth in January was the highest and the lowest in December. The frequency of premature infant was the highest in the first born and the lowest in mother's age 25 to 29
Statistical investigations were made on relations between the infant mortality and the social biological factors as a previous paper. The infant death rate was 44.3 (male 48.6, femal 39.9), the neonatal death rate was 22.4 (male 24.5, femal 20.3). The neonatal death rate of premature infant was ten times higher than that of mature infant. The death rate fo premature infant was 194.1 and existed obvious difference between in case of male and in case of female. The death rate of premature infant was the lowest in the third born and in the mother's age from 25 to 29.
In this paper, statistical investigations were made on the relations between the cause of infant death and the social, biological factors as report 1. The effect of coldness for neonatal death rate was distinguished but the coldness. The death rate of antenatal deformity and diseases peculiar to early infancy was found to be ten times higher in case of premature infant than in case of mature infant. The neonatal death rate in case of premature delivery was thirteenth times higher than in case of mature delivery. The frequency of antenatal defomity and diseases peculiar to early infancy was the highest in the fifth born, the highest in the mother's age of above 40 age.
We examined on parasite infestation 8101 pupils of 14 elementary and 9 junior high schools at Miyako-Island in Ryukyu. About 60% of pupils of these schools underwent our examination. These 23 schools were divided into 3 groups such as urban are, rural area, and fishing villages. It was found that the incidence of ascaris infection among the pupils lived at fishing villages was the highest (32.6%), and that the incidence of the ancylostomiasis among the pupils in rural area was the highest (25.3%), especially the hookworn incidence of the pupils of rural janior high school showed very high. About the enterobiasis, there is no differrnce among these 3 groups.