112 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



of some other organs, because they elicit so weak a reaction on the part of the 

 host and do not, therefore, make possible finer gradations of the individuality 

 differentials in the various strains. 



Transplantation of the adrenal gland and the analysis of the individuality 

 differentials. While some of the principles concerning the nature of the 

 individuality differentials have been established through the experiments on 

 transplantation, which we have already discussed, still, it may be expected 

 that an extension of the type of organs and tissues subjected to transplanta- 

 tion may give additional data. Such further information was obtained by 

 means of transplantation of the adrenal gland. 



As far as the analysis of the individuality differentials is concerned, the 

 most important observation in these experiments concerns the lymphocytic in- 

 filtration, which was found to occur with increasing intensity around degener- 

 ating cortical tissue as late as eight or ten months after transplantation, while, 

 on the contrary, well preserved areas of cortical tissue were not invaded 

 by lymphocytes. This condition corresponds to the action of the lymphocytes of 

 the host towards ovarian transplants from donors whose individuality differ- 

 entials differed from those of the host. Here, also, the lymphocytes invaded 

 mainly degenerating interstitial gland tissue and not at all, or only very rarely, 

 the preserved granulosa of well developed follicles. Therefore, certain struc- 

 tures within several types of transplanted organs behaved not unlike auto- 

 genous transplants, while other structures, especially those undergoing a cer- 

 tain kind of degenerative change, behaved like homoiotransplanted tissue. We 

 have already discussed the possible causes for these peculiar responses of 

 different structures; the possibility exists that certain tissue differential sub- 

 stances may combine with strange individuality differentials to form sub- 

 stances whch attract the lymphocytes ; or some types of growing or well pre- 

 served tissues may give off substances which protect them against an invasion 

 by lymphocytes, which might otherwise occur if disharmonious individuality 

 differentials interact; or lastly, it is conceivable that individuality differen- 

 tials are produced or set free in larger quantity in certain stages of regression 

 in various tissues. However, such a behavior of the lymphocytes is not usual. 

 Thus, we have found very strong indications that well preserved thyroid tissue 

 can be invaded and destroyed by masses of lymphocytes, if there is a slight 

 divergence between the individuality differentials of host and transplant. In 

 autotransplanted organs we have not observed, thus far, a marked invasion by 

 lymphocytes of the degenerating cells, but this point is being investigated still 

 further at the present time in the case of adrenal glands. In non-transplanted, 

 autogenous adrenals frequently degenerative changes occur, similar to those 

 which attract the lymphocytes in transplants, but they do not lead to intensive 

 accumulation of these cells. The time at which accumulations of lymphocytes 

 occur seems to vary in different inbred strains; it apparently takes place 

 earlier in strains in which the differences between the individuality differen- 

 tials of the various members of the inbred strains are as yet considerable. It is 

 also of interest that pronounced infiltration with lymphocytes may be seen in 

 transplants from sisters or brothers in closely inbred strains, but they occurred 



