162 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



that also in the case of heterogenous tissues the primary reactions due to the 

 preformed organismal differentials are the more essential factors on which 

 depend the fate of the transplants. 



The data so far discussed suggest, then, the interpretation that the reactions 

 of the host against both homoiogenous and heterogenous tissues are due largely 

 to the direct, primary action of the individuality differentials given off by the 

 transplants, but that, secondarily, these differentials may also act as antigens 

 and induce the formation of immune substances, which then may secondarily 

 intensify the strength of the reactions. However, it is apparent also that by 

 means of successive transplantations it is difficult to decide the question as to 

 how far such immune processes participate in these reactions. This method 

 suffers from the disadvantages that each transplant can be examined only at 

 the end of the experiment and that it is necessary to study the tissue in stained 

 section. The examination of the white blood cells as a method for the analysis 

 of the individuality differentials obviates these disadvantages, although in 

 certain respects the study of the local reactions around the transplanted tissues 

 is preferable. By determining the effects of two successive transplantations on 

 the white blood cells circulating in the peripheral blood, Blumenthal demon- 

 strated the existence of immune reactions also against transplanted tissues. 

 In these experiments, the interval between the two transplantations was 10 or 

 21 days. In the case of successive transplantations of homoiogenous tissues, 

 the second transplant called forth an accelerated increase in the lymphocytes 

 in the blood. The maximum number of these cells appeared from two to four 

 days earlier than after transplantation, but the maximum number of cells 

 counted after the second transplantation was not so high as after the first 

 transplantation in the large majority of cases. This effect of a second trans- 

 plantation was noted only if both the first and second transplant were homoi- 

 ogenous, but not if one of the two grafts was of a heterogenous nature. 



If successive heterogenous transplantations were made, the maximum in 

 the increase of polymorphonuclear leucocytes, as well as of lymphocytes, 

 which took place as the second phase of the reaction of the host against the 

 transplant, was accelerated to about the same extent as after successful 

 homoiogenous transplantations. But, again, the maximum number of cells 

 found in the blood after the second transplantation was lower than that found 

 after the first transplantation. In order to obtain this effect, both the first and 

 second transplant had to be heterogenous ; again a combination of a heterog- 

 enous and a homoiogenous graft did not produce this effect. The immuniz- 

 ing effect of homoiogenous and heterogenous tissue on the lymphocytes and 

 polymorphonuclear leucocytes in the circulating blood is therefore a specific 

 one. Immunization against the growth of transplanted homoiogenous and 

 heterogenous pieces of tumors may, to a certain degree, be accomplished by a 

 first transplantation of normal tissues, and here, also, both the first trans- 

 plant of normal tissue and the second transplant of tumor must be either 

 homoiogenous or heterogenous. We may conclude from these experiments: 

 (1) that the reactions against homoiogenous and heterogenous tissues differ 

 not only quantitatively but also in kind, and (2) that also normal homoiog- 



