The Breeding Behavior and Tumor Incidence of an Inbred Albino Strain of Mice

Abstract

Comparative data on the genetic, physiological, and breeding characteristics of an inbred stock of experimental animals are of value from the biological point of view. Not only should comparisons be made for different strains maintained under the same conditions but for sublilies of the same stocks kept in different eiivironments and receiving different diets. Murray (1934) has made a complete report on the breeding behavior and the mammary gland tumor incidence in the inbred dilute brown strain of mice. Among the observations reported were: the size of successive litters; the age of the mothers at the birth of successive litters; the mortality among the young at birth and before weaning: the effect of the age of the mothers upon litter size. The incidence of tumors among the breeding females was considered according to the age at which they were observed. The percentage of cancerous individuals based on the total number of animals living to the begnining of each month or longer was also computed. The breeding behavior of the cancerous and non-cancerous females was compared as to mortality among the offspring at birth and before weaning. The present report is a similar description of an inbred strain of mice which, like the dilute brown race, has a high tumor incidence. The mortality among the young mice before weaning has not heen considered, however, owing to a sublethal character inherent in the stock.