Abstract
I have introduced the limiting function l(x) of relative liability in the case where the populations are normal. It has become clear that the function l(x) is instructive in the study on the quantitative relation of total lactation periods and frequencies of breast cancer.
We may safely conclude that in the urban and the rural district, the length of total lactation periods closely affects the frequencies of breast cancer in 45-64 age-group, though there is no particular relation between them in the 35-44 age-group.
In closing my report this time, I want to express my sincerest thanks to Professor Mitsuo Segi for the kind and thoughtful guidance extended to me.
