“On experimentally produced variations in the energy of tumor growth”

Inoculations of different tumors (sarcomas of the thyroid, mixed tumor of the submaxillary gland) through several or many generations have shown that, under the influence of experimental conditions, the energy of tumor growth varies in a definite way. The rate of growth is relatively slow in the animal originally affected by the tumor; after the inoculation into the first generation there is a certain latent period, after which the tumor begins to grow. The growth in the first generation is more rapid than in the original animal. After the inoculation into the second generation the latent period is abbreviated, more or less, and the succeeding growth is likewise more rapid than the growth in the original animal, or in the first generation. A further shortening of the latent period, or an increase in the rapidity of tumor growth, does not take place in the succeeding generations. Duration of the latent period and rapidity of growth may remain stationary through many generations, or the energy of the tumor growth may even somewhat decline.

These facts permit the conclusion that transplantation of a tumor has a tendency at first to increase the energy of tumor growth, and that this increase may be cumulative. That this increase does not continue in succeeding generations may perhaps be explained by the existence of counteracting influences, the actual existence of which can be demonstrated, as will be shown later.

The energy of tumor growth can be increased directly, and not only indirectly, merely by removal of the tension of the surrounding capsule or by better conditions of nourishment. Such a direct stimulating effect of the wound upon the cell growth causes probably a phenomenon not infrequently observed by surgeons, namely, the increase of malignancy in recurrent tumors. It is also possible to diminish the energy of tumor growth. In the course of tumor inoculations it not rarely happens that certain tumors remain stationary or apparently even retrogress spontaneously. This is especially found in the course of later inoculations, and it probably indicates that after many inoculations one or several of the factors determining a vigorous tumor growth become gradually weakened. In such cases one can observe that even a long time after the expansive growth of such a tumor piece has ceased, many mitoses are present in the cells of the stationary or retrogressive tumor.