138 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



intermediate stages between success and complete failure of transplantation. 

 If too late a stage is chosen for examination, the impression of an all or 

 nothing result is obtained, when actually intermediate stages of reaction exist. 

 The different degrees to which these rules were adhered to can explain, for 

 instance, differences between the conclusions at which Little and Bittner 

 arrived, and those obtained by us. In contrast to the findings of some other 

 investigators, in the experiments of Appel, who made careful studies of the 

 intermediate stages in the reactions and who considered also the cellular 

 response of the host, the quantitative differences between the results ob- 

 tained in syngenesio- and autotransplantations of testes in fowl came out 

 very clearly. Likewise Perthes, in careful experiments on skin grafting in 

 man, had noted the difference between the results of autogenous and syn- 

 genesiotransplantation, the marked advantage of the former over the latter 

 being quite definite. In these investigations the same host was used for both 

 types of transplants and the experiments were made at the same time; 

 in addition, multiple grafts were used and the method of transplantation 

 being the same in each case, variable factors were excluded as much as possi- 

 ble. The results agree with those in our experiments in non-inbred animals, 

 which show that the reaction against syngenesiotransplants resembles much 

 more closely that noted in homoiogenous than that in autogenous transplanta- 

 tions. It is also possible, in certain cases, to determine in an approximately 

 quantitative manner the differences in the outcome of transplantations by 

 making a large series of skin grafts into many hosts, which are alike in all 

 but a single distinctive factor. In this manner, valid conclusions may be drawn 

 by means of the statistical method, even without the aid of microscopic ex- 

 aminations ; as an example of this kind of experiments, we might refer to the 

 investigation of Kozelka in fowl. 



In some instances the differences between the results obtained by various 

 investigators are apparent only and do not really exist. -Thus, from the ex- 

 periments of Browman the impression might be obtained that heterotransplan- 

 tation of testicles in mice and rats may succeed to a limited extent, although 

 it is in fact always negative. This interpretation was given because the author 

 accentuates the staining of central portions of the testicular graft, which may 

 sometimes be observed, in contrast to the peripheral portions, which are en- 

 tirely necrotic. In the case of a successful graft, it is the peripheral parts 

 which live, while the central parts die. We have observed similar specimens in 

 which apparently the central parts survived. These findings seem to be 

 due to the fact that the heterotoxins act first on the periphery of the trans- 

 plants, which latter, as a result, are destroyed ; the central parts being with- 

 out nourishment, have already died and no longer function, but they have 

 retained some of their staining characteristics. Browman himself recognized, 

 through functional endocrine tests, that these central parts did not exert any 

 vital activities. 



The experiments of Richter and Jaffe on transplantations of thymus into 

 bone marrow and into the subcutaneous tissue, and of lymph glands into the 

 latter area, are of interest because they contribute a further example of the 



