The Relation of Inbreeding to Tumor Production: Studies in the Incidence and in-heritability of Spontaneous Tumors in Mice: XIII. Problems in the Behavior of Tumors

Abstract

Throughout the range of cancer research, there seems to be no other point so frequently and so completely misunderstood as the subject of inbreeding in its relation to the incidence of tumor. Since the beginning of this series of publications, these researches into the problem of the inheritability of cancer have been met by the statement that “inbreeding increases the number of tumors in a strain,” or that “inbreeding is responsible for the high incidence of tumors in a strain of mice, and consequently the demonstration of the inheritability of cancer for mice has no bearing upon the human species, since the latter is not characterized by inbreeding.” The latest and most conspicuous example of this misapprehension of biological procedure and fact appears in Ewing9s recent compendium “Neoplastic Diseases,” (1) in which he states that “Bashford attempted by inbreeding to intensify the hereditary influence,” and that “Slye has proven that inbreeding of tumor-bearing animals greatly increases the incidence of tumors.” With this misinterpretation, he dismisses all the exact indisputable experimental evidence for the inheritability of tumors in general and of all types, including cancer, in particular. It is precisely because inbreeding does not characterize the human species that it is impossible to make any even reasonably complete or accurate study of the inheritability of cancer in that species, and hence that experimental evidence becomes absolutely necessary as it is impossible to prove the inheritability of any character without inbreeding. Mendel in his work with peas was not trying to increase roundness or ovalness, yellowness or greeness, tallness or shortness, or any other quality of peas. He was trying to find out whether these characters were hereditary, and in order to find out whether they were hereditary, he had to inbreed his peas .