The sterilizing effect and hemolytic effect of cornin, extracted from skeletal muscle of rabbit were studied in vivo and in vitro. The results are summarized as follows: 1. Muscle cornin has no effect whatever on sterility when administrated into new born mice and adult mice. 2. There is no difference on the period of pregnancy and on the new born numbers as compared with no treated control. 3. When the erythrocytes are incubated with muscle cornin and then transfered into the hypotonic salt solution, the hemolytic effect occurs below 0.7 per cent salt solution.