144 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



differentials was not very striking; if such power existed at all, it was 

 usually slight and in other cases it was lacking. Thus we observed that if 

 ovaries were transplanted in certain inbred strains of mice, the unfavorable 

 effects of relatively slight deviations from the optimum conditions of the in- 

 dividuality differentials could to some extent be remedied by using ovariec- 

 tomized or castrated hosts; but in other strains, these improvements, due to 

 the removal of the hormones secreted by the sex glands of the host, were 

 lacking ; in no instance were the effects very striking. We saw, furthermore, 

 that multiple transplantations of anterior hypophysis succeeded in mice in 

 which the host's own hypophysis was present and functioning, and that 

 these transplants could exert certain hormonal functions and remain alive for 

 considerable periods of time. This result was obtained in cases in which the 

 disharmony between the individuality differentials of host and donor was 

 only very slight; but there were some indications that when the differences 

 between individuality differentials were greater, the transplants did not long 

 survive. Likewise in experiments with thyroid and parathyroid glands, it was 

 possible to transplant these organs successfully into hosts whose individuality 

 differentials differed only to a slight degree, without first removing the hosts' 

 own thyroid and parathyroid glands, and even several glands transplanted 

 simultaneously in such hosts could survive. In the case of the adrenal gland 

 of the mouse, such transplants degenerated to a large extent; but in many 

 instances some part of the cortex survived for a long time if there was no 

 marked disharmony between the individuality differentials of host and donor. 

 It is possible to test the interaction between endocrine effects and individ- 

 uality differentials in still another way, namely, by experimental administra- 

 tion to the host of an excess of certain hormones, in order to determine 

 whether this counteracts or accentuates the effects of not quite adequate in- 

 dividuality differentials. Christiani, it seems, was the first to express the opin- 

 ion that the need of thyroid tissue on the part of the host organism deter- 

 mined the fate of the thyroid transplants. In thyroidectomized animals the 

 grafts healed in better than in those possessing their own thyroids. On the 

 other hand, administration of thyroid substance caused an atrophy of the 

 thyroid transplants. We were unable to observe any marked effect of the oral 

 administration of thyroid tablets on the fate of thyroid transplants; it cer- 

 tainly did not prevent their survival in transplantations which otherwise 

 would have been successful. At most, this procedure may perhaps have re- 

 duced the functional and mitotic activity of the thyroid transplant, as well 

 as that of the host's thyroid, without, however, interfering very noticeably 

 with the action of the individuality differentials, which latter determined 

 essentially the success or lack of success of these transplantations. 



Likewise, Carroll Smith did not notice that administration of potassium 

 iodide had any marked effect on the fate of autogenous or homoiogenous 

 thyroid transplants in guinea pigs. Also, experiments in which injections of 

 extracts of cattle anterior pituitary were made into guinea pigs carrying 

 thyroid transplants should have some bearing on this problem. Such extracts 

 contain the hormone which causes a very marked growth and functional 



