CHANGES IN THE REACTION POTENTIAL OF A TRANSPLANTABLE TUMOR.
A transplantable tumor, known as dBrD, gave very uniform results in a series of mice of known pedigree for a period of about a year. See PDF for Structure We may say that the reaction potential existing between the tumor and individuals inoculated was the same during this first part of the experiment. This tumor will grow in a mouse progressively provided there be present simultaneously at least from six to eight independently segregating genetic factors (genes) in the fundamental make-up of the host derived from the zygote that gave rise to the individual. In the course of routine transplantation of this tumor, there was a sudden change in this hitherto constant reaction potential resulting in at least three types of transplantable tumors-new types as far as their physiological activity and reaction potential are concerned. From a single original transplantable mass, I have therefore obtained four masses that remain true to type at least for some months of continued experimentation. These four types are (1) the original tumor, dBrD, still giving a six to eight Mendelian factor ratio, (2) dBrDm giving a two factor ratio, (3) dBrDBl showing another two factor ratio, and (4) dBrDBs giving a one factor ratio. The number of factors involved in the transplantability for the several tumors investigated are given in Table III.
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Bussey Institution of Harvard University, Boston.