28 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



significance of the lymphocytes and polymorphonuclear leucocytes for the fate 

 of the transplant; (4) the distant actions which, according to Blumenthal, the 

 individuality differentials exert on the host after these differential substances 

 have entered the host circulation. The connective-tissue and blood-vessel reac- 

 tions occur at an early phase following transplantation and the character of 

 these reactions is usually determined within the first two weeks. The lym- 

 phocytic reaction, as a rule, begins within the second week, but in some cases 

 it may exert its full effect only at subsequent periods, and in certain instances, 

 this reaction may appear and increase during the later phases of the inter- 

 action between host and transplant. The lymphocytes usually are indicative of 

 finer differences between the individuality differentials ; they are not found in 

 any considerable numbers if there is complete compatibility between host and 

 transplant, and they do not as a rule appear in very large masses if the incom- 

 patibility between host and graft is so great that the metabolism of the latter 

 is seriously affected within seven to ten days following transplantation. But 

 even in heterotransplantation these cells may accumulate after some time in 

 the periphery of the injured graft. Polymorphonuclear leucocytes are seen in 

 small numbers soon after the grafting of a piece of tissue, owing to circula- 

 tory disturbances and perhaps also to the presence of necrotic tissue, which is 

 found under these conditions ; but they accumulate in larger numbers usually 

 only around and inside of heterogenous transplants. In the distant reactions, 

 lymphocytes and polymorphonuclear leucocytes are activated in the circula- 

 tion, under the same conditions under which they are activated locally around 

 the transplant. 



(b) Differences in the mode of reaction against strange individuality dif- 

 ferentials exhibited by different species. While the factors which are in- 

 volved in the struggle of an organism against strange individuality differen- 

 tials are in principle the same in all the species with which we have worked, 

 still, some quantitative variations exist in this respect. On the whole, rat and 

 guinea pig react in a similar manner, although there may be minor differences 

 in the intensity of the lymphocytic reaction in these species. There is, in addi- 

 tion, a stronger tendency on the part of the connective tissue to invade and 

 replace transplanted fat tissue in the guinea pig than in the rat. There are, 

 however, quite marked differences between the reactions in the guinea pig 

 and rat, on the one hand, and in the mouse, on the other. In the mouse, the 

 lymphocytic and connective-tissue reactions are in many cases less prominent 

 and consequently the direct injurious action of the body fluids becomes more 

 prominent. The amount of surviving tissue and the state of preservation of 

 the transplanted cells are therefore largely indicative of the degree of com- 

 patibility or incompatibility of the individuality (organismal) differentials in 

 this species. However, the lymphocytic and connective-tissue reactions may 

 here also participate in determining the fate of the transplants and under cer- 

 tain conditions this participation in the struggle is quite pronounced and 

 effective. In contrast to these species, in the chicken, in which the relative 

 proportion of lymphocytes in the circulating blood is higher than in other 

 species, the local lymphocytic reaction may be extremely strong even in cases 



