The character of the 24-hour periodicity of mitosis in the corneal epithelium of various laboratory animals

Summary

The 24-hour periodicity of mitosis was studied in the corneal epithelium of white mice, white rats and guinea pigs. There were species-specific differences both in the intensity of the cellular multiplication, and in its 24-hour rhythm. The 24-hour periodicity of mitotic activity is clearly manifested in mice and rats, the maximal amount of mitoses being observed during morning hours, and the minimal—in the evening. The curve, charaterizing the 24-hour periodicity of mitoses is uniform during all the seasons of the year. The amplitude of the 24-hour variation of mitotic indices in mice is on the average 3 to 4 times greater than in rats. In guinea pigs the 24-hour mitotic periodicity of the corneal epithelium is not manifested so clearly.