Chromosome polymorphism due to the A/A, A/S and S/S types of the pair no. 3 in the Norway rat (Rattus norvegicus) collected in Osaka prefecture has been observed in 48 specimens. Although these three chromosome types are observed, the frequency of the A/A type is the highest. These results are compared with those obtained in the Misima population published previously (Yosida and Amano 1965).
By isoelectric focusing technique, we found out the age-related protein in human brain which is present in the individuals of younger than approximately 40 years of age. But the protein disappears or remarkably decreases in its content above 40 years of age.