Abstract
The purpose of this paper is to present a method whereby two neoplasms, that are histologically identical, can be shown, nevertheless, to be different in their physiological reactions. This experiment was begun June, 1920, and is still being continued. Enough data have been accumulated, however, to warrant a preliminary report.
The tumors employed are two adenocarcinomas of the mammary gland, that arose spontaneously in two female mice of a closely inbred strain, the second one arising some three weeks after the first. The mice have been rigidly inbred, brother to sister matings, for about eleven years. One would expect, in that time, that the strain must have become homozygous in all, or nearly all, genetic factors that no doubt underlie morphological and physiological characters. This conclusion is warranted by evidence obtained from implanting bits of the two tumors into mice of this strain. The trochar method of implanting the neoplastic tissue has been employed throughout the experiment. In this preliminary experiment both tumors grew in 100 per cent. of all mice inoculated, irrespective of whether the two tumors were inoculated into the same mouse or into separate individuals. In case the two were inoculated into the same animal, the first (dBrA) was always inoculated into the right axilla, the second (dBrB) into the left axilla. The growth curves for each were charted from weekly observations. There was apparently no effect of one tumor upon the other when growing in the same mouse, either in percentage of indications or rate of growth. They remained entirely distinct. The question naturally arose, “Are the two tumors actually identical?”
The complexity of the genetic factor system that evidently underlies susceptibility to transplantable tumors makes it highly improbable that two identical tumors could arise independently within three weeks of each other, even in the same relatively homozygous strain of mice.
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