Chapter I 



A Comparison between the Transplantation 

 of Tumors and of Normal Tissues 



We have analyzed by means of transplantation the organismal and 

 organ differentials of the normal tissues, and we shall now proceed 

 to the study of the corresponding differentials in tumors, which 

 latter differ in their behavior, after transplantation, in certain respects from 

 normal tissues. In the introductory statement we have discussed the essential 

 characteristics of tumors, especially of cancers, and wherein they differ from 

 normal tissues. We then inquired into the factors which caused the trans- 

 formation of normal into cancerous tissues. We shall now study the various 

 types of transplantation of tumors and compare the essential results with 

 those obtained after the grafting of normal tissues ; there are some very 

 marked similarities, as well as some differences. In tumors, we shall find 

 certain complications which did not occur in normal tissues, such as an in- 

 creased growth energy, which to some extent may overcome the antagonistic 

 reactions of the host to the transplant; also, there are indications that the 

 tumor cells themselves can undergo changes of an adaptive character during 

 the course of transplantation, and that, in particular, they may acquire re- 

 sistance to certain injurious conditions to which they are exposed in the new 

 hosts. On the other hand, cancerous tissues may call forth in the new hosts, 

 states of immunity or allergic reactions, which tend to injure the transplant; 

 but there are strong indications that against these the cancer tissue may find 

 protection to some extent, by its ability to absorb and to neutralize substances 

 antagonistic to its growth. There exist in addition, the same problems which 

 we had to face also in normal tissues, namely, that of distinguishing between 

 the presence or lack of the various organismal differentials in the tumor cells, 

 and of the manifestation of these differentials, which may depend on the 

 rapidity of the production and discharge of the organismal differentials by 

 the transplanted tumors or host, and on the power of resistance of the 

 tumor cells to the injurious effects of the host. There is still a further com- 

 plication : while in normal tissues we can readily follow the reactions of the 

 host against the transplant and, with certain precautions, use these reactions 

 as a standard with which to gauge the differences in the organismal differ- 

 entials between host and graft, in the case of tumor transplants such an 

 analysis is very difficult on account of the relatively rapid growth of the 

 tumor tissue. Thus the finer reactions, which we used as indicators in the 

 analysis of the organismal differentials, and especially of the individuality 

 differentials, in normal tissues, cannot very well be used in tumors, at least, 

 not in many cases. Instead, most investigators employ as the standard, the 

 growth or lack of growth of the grafted tumors. This is a less finely graded 



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