346 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



possessing the same organismal differential as the host, does not elicit an 

 antagonistic reaction ; it does not act as a stimulus. 



There are on record, however, some observations which apparently do not 

 agree with these conclusions. (1) According to Murphy, it is possible to 

 influence the growth of transplanted homoiogenous or heterogenous tumors 

 through the application of a method which affects the number and activity 

 of lymphocytes of the host; an increase of the latter is believed to initiate 

 or to intensify the mechanism of defense against the transplanted piece of 

 tumor, while a diminution in the number of lymphocytes makes possible 

 the growth of tumors, which otherwise would not have occurred. But of 

 special interest is the additional finding that the change in lymphocytes is 

 effective not only against homoio- and heterotumors, but also against pieces 

 of autotransplanted tumors. An experimentally produced increase in the 

 number of lymphocytes was found to diminish markedly the ability of the 

 autotransplanted tumors to grow and to develop. However, in this case we 

 may have to deal with a non-specific effect exerted on the tumor cells by 

 lymphocytes without the intervention of organismal differentials. (2) Fibiger 

 and Miller, in the course of experiments, in which they produced carcinomas 

 through often repeated applications of tar to the skin of mice, found in a 

 certain number of instances that metastases of these cutaneous cancers took 

 place spontaneously in the lung and elsewhere. Now if these animals, during 

 the period when the tar was applied, were inoculated several times with 

 mouse embryo-skin, the number of metastases was thereby diminished. There 

 would then be involved, in these experiments, apparently an effect of homoiog- 

 enous material on autogenous tissue. If these observations should be correct, 

 we would have to assume that also in this case we had to deal with conditions 

 of a non-specific nature, which affected unfavorably the growth of the 

 transplant. In this connection we may recall the more recent findings of 

 Murphy and Sturm, who showed that in embryo-skin substances are present 

 which inhibit tumor growth and may cause the regression even of spontaneous 

 tumors. (3) Lumsden found that when he made repeated injections of the 

 euglobulins from the serum of sheep, which had been immunized against 

 either human, rat or mouse tumors, into or around a spontaneous mouse 

 tumor and then extirpated the tumor and autotransplanted a part of it, the 

 autotransplants did not grow in the large majority of cases, although homoio- 

 transplantation of these tumors into other mice would succeed ; furthermore, 

 as a rule the tumor did not recur after excision. He attributed this result 

 to the development of an immunity against its own tumor in the mouse, and 

 believed that this immunity was due to the absorption of tumor material. But, 

 this type of imunity has apparently not yet been tested by inoculating one 

 of the transplantable tumors in such a mouse. In accordance with such an 

 interpretation, it would be necessary to believe that there is present in the 

 autogenous tumor, in addition to the organismal differentials, still another 

 constituent which calls forth this reaction. This constituent might be an 

 organ differential or it might be a specific stimulus to tumor growth, in the 

 latter case an "antimalignancy" constituent, in the sense of Lumsden. 



