Hemoglobin Levels in Various Degrees of Susceptibility to Spontaneous Tumors

In 1907 ( l ) , Tyzzer clearly emphasized the probable rBle of heredity in the origin of tumors in mice. The advances made since that time, both in the genetic investigation of the spontaneous tumor and in the study of the transplantable tumor rest largely upon his interest and work. In his 1907 paper, Tyzzer wrote: “Are the races of mice which are susceptible to the inoculable tumors more liable to spontaneous tumors than are the races which are insusceptible? Since heredity is so important a factor in the development of the inoculable tumors, its influence should not be disregarded in the occurrence of spontaneous tumors.” He further emphasized the value of selection in the establishment of uniform strains of mice. Whether the tendency to the frequent development of tumors is based on one general or on various specific “ tumor characters ” was a question that he considered. i‘ The occurrence of ‘ cell rests ’ or misplaced tissue,’’ he states, ‘‘ may possibly have some relation to the inherited tumor character,” but the tumor character according to Mendel’s law cannot be a dominant one. Tyzzer then discussed the possibility of a single recessive character and pointed out the possibility that the development of a tumor may depend upon a combination of several inherited characters, rather than upon the presence of a single character. He thus anticipated the theory of multiple factors which plays such an important r81e in more recent discussions on the genetic nature of tumor susceptibility. According to Tyzzer, coat color had apparently no influence on tumor incidence, since mice of any color Combination niay develop spontaneous tumors. Tyzzer’s conclusion at that time was to the effect that the results already obtained were not sufficiently numerous to prove or disprove that the development of a tumor is dependent upon the presence of an inherited character; although the data obtained may appear to favor this view. “ It seems possible by certain lines of experimental breeding, with the principles of Mendel’s law of heredity in mind, to obtain definite results, whether they be positive or negative.” The recent advances in the genetics of cancer immunity and susceptibility have fully justified Tyzzer’s pioneer stand on this question. The investigations of Loeb ( 2 ) ’ Murray ( 3 ) , Lathrop and Loeb (4), Maud Slye ( S ) , W. S. Murray and C. C. Little ( 6 ) , Clara Lynch (7) , Dobrovolskaia-