Studies on the Dryopithecus Pattern of the Japanese Residing in Hokuriku District

Abstract

1) The frequency of type Y on the mandibular first molars in Japanese of Hokuriku district is 71 percent, which is very low among all the ethnic groups. 2) The seventh cusp on the first molar was not found in this study, but the sixth cups was found in about 10 percent It is also recognized in 2.4 percent of the mandibular second molars. 3) The frequency of type Y on the second molar s is as low as 4.3 percent, and the appearance of five cusps is 2.8 percent. 4) When the correlation graph between the groov e patterns and the number of cusps is made and compared with that of the other ethnic groups appearing on references, the mandibular first molars belong to the circle of Caucasian and the mandibular second molars belong to the circle of Mongoloid. 5) In general, the g roove patterns on the mandibular first and second molars of Hokuriku Japanese, reveals considerable regression and the number of cusps also shows regressive tendency.