Scientific Proceedings. 



(137) 73 



35 (81). " On experimentally produced variations in the energy 

 of tumor growth": LEO LOEB. (Presented by JAMES 

 EWING.) 



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 grow r th 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 sur- 

 rounding 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 



