Cancerous ancestry and the incidence of cancer in mice

The purpose of these experiments has been the collection of data sufficiently abundant and accurate to determine whether an enhanced liability to cancer is transmitted in the case of mice from parents to offspring. In a preliminary note in 1909 a short account was given of the manner in which these experiments have been conducted. The animals have all been housed and fed in a uniform manner in one room. They have been kept in large cages,which have been cleaned regularly, and the environment has been as uniform as it has been possible to make it. During the past five years nearly 1600 animals have been bred, the two sexes contributing approximately equal numbers. Of them, 562 females which have lived for six months or more form the material of the present paper. The incidence of the disease is so dependent on the age and sex of the animals that, in order to get comparable groups, only mice of the same sex and of approximately the same age may be reckoned together. They have been arranged in age-periods of three months’ duration, this being the shortest interval which gives reasonably large figures in each group.