132 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



tion against the transplant was absent. (2) In series II-V with increasing 

 length of time during which the grafts were kept in the hosts, the damage 

 inflicted on the transplants became greater ; this might be expected, provided 

 a discrepancy in the individuality differentials existed between hosts and 

 donors ; it did not occur in autogenous transplantations where, on the contrary, 

 signs of injury due to the operation became less and disappeared in the course 

 of time. (3) If we consider the different series, we find that the intensity of 

 the reactions on the whole increased with increasing distance of relationship 

 between host and donor. This is most clearly indicated by comparing the 

 grades at 12. and 16 days, and especially also by comparing the combined 

 grades at 12 and 16 days. The latter were as follows: series II, 3.9; series 

 III, 2.9; series IV, 2.4; series V, 2.2. At 20 days, the difference between these 

 four series had almost disappeared, either because at that time the injury had 

 become very marked in all of them, or because of the smaller number of 

 experiments that were available for the determination of the average grade. 

 The combined grades for thyroid at 20 and at 16 days also suggest an increas- 

 ing deterioration in the preservation of the transplants with increasing dis- 

 tance of relationship. In these series, and especially in series III, IV, and 

 V, the reactions were relatively severe and accordingly, grade 1 was fre- 

 quent in individual transplantations. The reactions were not so strong 

 in some instances in intrarace transplantations, although in other cases they 

 also were severe. This is especially interesting in view of the fact that some 

 of these strains had been inbred for a considerable number of generations, 

 although not necessarily by brother-to-sister breeding; strain Gray Norway, 

 for instance, having been inbred for 45 generations. Although the rats 

 belonging to the same strain were closely related, still, even in series II and 

 III the reactions were, on the whole, severe. (4) While the differences be- 

 tween the grades in the different series seem to be real, they were much less 

 than one might have expected, considering the great differences in relationship 

 between the rats in these different series. It is noteworthy that the reactions 

 even between brothers and sisters were very marked and that they approached 

 much more closely the reactions against distant donors than those against 

 autogenous transplants. We must assume that the individuality differentials 

 even in brothers and sisters showed quite definite differences and that these 

 were great enough to cause injurious reactions against the grafts. At the 

 same time, it appears probable that the sensitiveness of the host and his 

 ability to react against even relatively slight differences in the constitution 

 of the individuality differentials were great. (5) The transplantations within 

 the mutant albino race showed less severe reactions than those within the 

 other mutant race. It is possible that the mutant albino rats reacted less 

 strongly than other mutant races against the individuality differentials of 

 rats belonging to their own strain. (6) There were definite indications that 

 also in rats the bodyfluids reacted on the transplants in accordance with the 

 relationship between transplant and host, and that the reactions of the host 

 cells were superimposed upon the effect of the bodyfluids. However, in many 

 cases the damage done to the graft by the latter was very slight, or not mani- 



