The results of transplantation, as recorded in the first section of the paper, are analyzed from the standpoint of the influence of the factors of serial passage, the material used for inoculation, the age and breed of the animals, and the time or season at which the experiments were carried out.

The material used for the inoculation of different groups of animals appeared to have comparatively little effect on the ultimate results.

The character of the animals used was found to be a factor of more importance in that the tumor displayed definite peculiarities of growth and malignancy referable to age and to breed or color markings. Still, it seemed unlikely that any of these factors would account for the variations in growth and malignancy that had been observed.

After considering the various possibilities presented, it appeared that the principal factors concerned in determining the results of transplantation were adaptation to passage and variations in the conditions of season and weather that prevailed during the time the experiments were being carried out—the one affecting the energy of cell growth and the other affecting animal economy.

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