Using the population data for Heian period (about 800. w900 A.D.), 1750 and 1872, the gravity centers of population were computed, the result being as follows: The above result shows that the population center in 1750 fell in the. north-eastern direction of that in 1872. But the population data for 1750 were inacurate, mainly due to the fact that the large feudal clans in western Japan had reported their own population less than the real number. Hence the real population center in Tokugawa era must have situated more in south-western direction than the point indicated above as for 1750.
The senior author, (K.H.) has proposed an Index of Inbreeding representing the probability of producing a homozygous manifest offspring of simple Mendelian recesrsive morbid traits from consanguinous marriages within a population: where mn represents the number of consangUinous marriages of nth, degree and N the total number of the marriages in the population. Expressed in a unit of cousin mariage, this becomes, provided n is not smaller than 4 From a village in Okayama Prefecture, the authors record the following number of consanguinous marriages, both parties of which are living. Degree of consanguinity: 4 5 6 7 Number of families: 50 10 6 4 among 373 families (See Table 1 on p. 17) Hence I=0.00963 I' =0.1541 which means 15.41% of the total families correspond to the consanguity of cousin marriage, a rate veiy high compared to that of Western Countries. Percentage of cousin marriages has not shown any positive, sign of decrease since 1930 up to date, retaining a rate at about 13 or 14% This place is the home village of the junior author, where his father has a medical dispensary and everybody knows everybody. There are no marriages more sanguinous than 4 th, degree. The high rate of consanguinous marriages does not seem to be peculiar to this village, but rather a common phenomenon among some of Japanese farmer's villages.
328 male offenders at the age of 20, -30 were examined immediately after their sentences. They were reinvestigated 7 years (in average) after their discharge, and it was found that 64.9% out of them had become recidivists. Investigating various constitutional and environmental factors supposed to be the causes of recidivism, it was found that the following 7 factors were responsible in the highest ratio for recidivism. 1. Psychopathy (except asthenictype). c. c 2. Misconduct before 18 8a7g. 0e%. c. c79.2% 3. Previous frequent misconduct. c. c77.1% 4. Brken home. c. c72.8% 5. Incomplete ordinary school education. c. c 78.8% 6. Frequent change of occupation. c. c69.4% 7. Abnormal character and delinquency of parent. c. c86.5% Of course some of these matters are separately of little importance and we must estimate them in their dynamic correlations. But for practical purposes I have tried to see the recidivism, and obtained the following result. 6.7. c. c100.0%recdivism 4.5. c. c91.7% 3. c. c79.2% 2. c. c61.0% 1. c. c50.0% 0. c. c 31.1%