TRANSPLANTATION OF TUMORS 389 



was apparent, furthermore, that the more actively the tumor grew, the greater 

 was the number of individuals in which it took. Likewise, in the experiments 

 of Chambers, Scott and Russ with a rat carcinoma which had been injured 

 through radiation, there was a parallelism noticeable between the change in 

 growth energy and number of takes. It was also found in the transplantation 

 of leukemic cells into individuals of the strain in which the leukemia had 

 originated. 



There was, moreover, in our experiments a correlation between the 

 growth energy of spontaneous tumors and their transplantability into other 

 individuals, and Woglom, too, noted a parallelism between the number of 

 successful transplantations of spontaneous tumors into other mice and the 

 growth energy of these tumors. However, Woglom also observed that even 

 very slow-growing tumors may yield a high percentage of takes, an observa- 

 tion which corresponds with our above mentioned experiments with the 

 Japanese mouse, and which may be explained essentially by the great simi- 

 larity of the organismal differentials of host and graft. But, in general, a 

 tumor with greater growth energy will be better able to overcome the re- 

 sistance which relatively unfavorable constellations of the individuality 

 differentials present, than a tumor with a lesser growth energy. In addition 

 to this factor, also variations in the resistance of various tumors to injurious 

 conditions and in the rapidity with which organismal differential substances 

 are produced by tumor and host may interfere with the proportionality be- 

 tween growth energy and transplantability. 



The increase in growth energy which so often follows the first trans- 

 plantation of a tumor is limited ; it usually reaches a maximum in the first or 

 in one of the following generations of tumors and from then on remains 

 approximately constant. But, on the other hand, there can be no doubt as to 

 the reality of this change and the great frequency of its occurrence. On the 

 contrary, the rhythmic variations in growth and transplantability of tumors, 

 which, as Bashford, Murray and Cramer assumed, take^f place in successive 

 generations of a transplanted tumor and which they attributed to conditions 

 inherent in the tumor, were probably caused by changes in environmental 

 factors affecting the growth energy of the tumor cells. Bashford believed, 

 furthermore, that through selective transplantation, a tumor may be divided 

 into substrains, which differ in certain characteristics and vary independently 

 of each other in regard to growth rhythms. He held that a tumor represents 

 a conglomeration of cells endowed with different characteristics. These 

 rhythmic changes were not found by Fleisher in the case of carcinoma No. 

 IX, nor by Bittner in his series of transplantations. Bittner holds that varia- 

 tions in the individuality differentials of the hosts, due to the use of mixed 

 strains of animals, are responsible for these apparent rhythms. 



II. Adaptation of Tumor Cells to Environmental Conditions 



In addition to the factors mentioned, we have to consider some special 

 adaptive changes which take place between transplant and host in the course 

 of transplantations, as an occurrence which may influence the transplanta- 



