60 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



the skin flaps represents an "all or nothing" test, which cannot give any in- 

 dication of intermediate results which might be found by means of a micro- 

 scopic study of cellular reactions. Experiments in which we used microscopic 

 studies of the cellular reactions against transplants in adult birds showed that 

 there is no identity between individuality differentials even in brothers be- 

 longing to the same inbred race. Likewise, it may be found that in adult lizards 

 homoiotransplantation of skin does not succeed, whereas autotransplantation 

 is successful (May). By means of statistical analysis Kozelka found in skin 

 grafts in Leghorn fowl, within the first few months after hatching, strong 

 indications that the degree of relationship between donor and host, which 

 signifies also the relationship between the individuality differentials of host 

 and donor, is one of the factors which determines the success of the trans- 

 plantations. Thus he found a persistence of grafts between unrelated birds in 

 18 per cent, between half and full brothers and sisters in 27 per cent, between 

 full brothers and sisters in SO per cent, and between offspring from father 

 and daughter matings in 68 per cent of the transplantations. Similar to our 

 experiences, he noted a correspondence in the behavior of several transplants 

 from the same donor to the same host. However, also non-genetic factors, 

 such as size or age of the donor and of the host, helped to determine the fate 

 of the transplants. In accordance with expectation, transplantations between 

 adult birds gave less favorable results than those between very young chicks, 

 but in both instances the relationship between the individuality differentials 

 of host and graft was the essential factor that determined the result of the 

 transplantation. 



In continuing our former experiments in birds, we made use first of inbred 

 races of chickens, which we obtained from the Mount Hope Farm in Williams- 

 town, Mass., through the kindness of Dr. Goodale. In these experiments we 

 observed that notwithstanding close inbreeding, there was a marked lympho- 

 cytic reaction present, even around transplants in nearly related adult animals 

 belonging to the same inbred race. This reaction was so strong that a definite 

 and very distinct differentiation between the degree of similarity of individ- 

 uality differentials in these animals seemed impossible and our investigations 

 remained, therefore, unpublished. According to information given me by Dr. 

 Goodale, these chickens had been inbred only for five or six generations of 

 consecutive brother-sister matings. Likewise in our more recent experiments 

 with guinea pigs, inbred for only a small number of generations of brother- 

 sister matings, we did not yet observe a definite approximation of the in- 

 dividuality differentials in the various members of these families. We may 

 therefore conclude that in order to achieve progress towards an autogenous 

 constitution of the individuality differentials, a larger number of consecutive 

 brother-sister matings is required than those which had been made in the 

 chickens in Williamstown. Resuming these investigations more recently with 

 W. J. Siebert, we confirmed the finding that also in the exchange of tissues be- 

 tween brothers of strains of chickens inbred to a limited extent, a very in- 

 tensive lymphocytic infiltration and destruction of the transplants take place, 

 and that syngenesio-, homoio-, and interracial transplantations in such chick- 



