A report is given of the results obtained by intratesticular inoculation of a malignant tumor of the rabbit based on a study of the first twenty generations.

The subject is presented from the standpoint of variations in growth and malignancy as they occurred with continued transplantation. Essential features of the experimental conditions and of clinical and postmortem observations are condensed and recorded graphically.

On analyzing the results of these experiments, it was found that many changes had occurred in the behavior of the tumor during transplantation, but that the changes were of a very irregular character and as a rule did not proceed constantly in any given direction. Moreover, the evidence as to the effect of transplantation on the growth and malignancy of the tumor was contradictory in that there was a great deal of evidence to show that there had been a decided increase in the activity and capacity for growth on the part of the tumor cells. But, with the exception of a few generations, there was an apparent reduction in the incidence and percentage distribution of secondary tumors, while the death rate was unaltered or actually diminished.

It was believed that this paradoxical situation afforded a basis for an explanation of the results that had been obtained by transplantation.

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