Biological Significance of Factors Influencing the Incidence of Mammary Cancer in Mice2

Abstract

Extensive data on the life histories of the breeding and nonbreeding females of 4 inbred mouse stocks and 5 experimental mouse populations are used to illustrate the concept that the nonmammary cancerous animals in such populations die with an unfulfilled tendency to develop breast tumors. Analysis of the cancerous segments of these populations, on the ground that they are representative of the normal tendencies of the stocks when reared under more controlled conditions, further illustrates that mammary tumor incidence in each of them is the result of a complex syndrome involving varying degrees of physiological receptivity to numerous combinations of viral and hormonal stimuli. An attempt is made to separate and measure the contribution each of the three variables makes to the behavior patterns characteristic of the 4 inbred stocks.