344 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



and 1916). A similar but more casual observation has been made also by 

 Apolant. In recent experiments from our laboratory, Blumenthal confirmed 

 this difference between the transplantability of spontaneous tumors into 

 normal mice of different strains and into mice which are bearers of other 

 spontaneous tumors. However, this condition was found only if the hosts 

 were below the age of 12 months, while in older mice, the growth of a 

 spontaneous tumor did not enhance the result of homoiotransplantation. 



The importance of the relations between the individuality differentials 

 of host and tumor was quite definite in experiments in which we compared 

 the effects of the extirpation of a spontaneous autogenous and of a homoio- 

 transplanted tumor on the growth of a second homoiogenus tumor. In this 

 connection we must first refer to the important experiment of Uhlenhuth, 

 Haendel and Steffenhagen, who found that if they inoculated a trans- 

 plantable rat tumor into a rat and the transplant took, it was possible to 

 inoculate the same rat successfully with a second homoiogenous tumor. But 

 if previous to the second inoculation the first homoiogenous tumor had 

 been extirpated, the animal was immune and the second inoculation was 

 unsuccessful. However, if the extirpation of the first tumor had been in- 

 complete and the part which had been left behind grew again, then a second 

 inoculation with the homoiogenous tumor was successful. These observa- 

 tions were controverted by some investigators; especially by Russell, and 

 also by Woglom. The effect of the extirpation of the first tumor, if present 

 at all, was attributed by these authors to the non-specific effects of the 

 operation, and the immunity following the extirpation of the first tumor 

 was accordingly designated as an "operative immunity". But, the experi- 

 ments of Fleisher and the writer showed that the observations of Uhlenhuth 

 and his collaborators were essentially correct, at least as far as certain 

 types of tumors are concerned, among which may be included our trans- 

 plantable mouse carcinoma IX. We found that extirpation of this tumor, 

 when growing in a homoiogenous mouse, prevented the successful second 

 inoculation with this tumor. Evidently the growth of the first tumor had pro- 

 duced an immunity, which became noticeable only after the first tumor had 

 been removed. Furthermore, it could be shown that if pieces of carcinoma IX 

 were transplanted, not into a normal mouse but into a mouse which, in ad- 

 dition to a first inoculated tumor, was also the bearer of an autogenous 

 spontaneous tumor, the Uhlenhuth effect was also readily demonstrated as far 

 as the influence of the transplanted tumor was concerned; but if we extir- 

 pated instead of the first homoiogenous tumor, the autogenous spontaneous 

 tumor, no immunity was conferred on the mouse against a second inocula- 

 tion with homoiogenous mouse carcinoma IX. This proves that the immunity 

 conferred by the extirpation of the first tumor is not a non-specific "opera- 

 tive immunity", but must be due to a specific relation between the individuality 

 differentials of the growing tumor and of the host. The individuality dif- 

 ferential of the transplant differs from that of the host and of the spon- 

 taneous autogenous tumor, the autogenous tumor and the normal tissues of 



