CRITERIA OF SUCCESS OR FAILURE 139 



gradual destruction of autogenous tissue under certain unfavorable condi- 

 tions. Autogenous transplants of thymus may remain permanently preserved 

 in the subcutaneous tissue. Here, at first, it is mainly the reticular tissue which 

 withstands the injury of transplantation; but other cells which soon after 

 transplantation degenerate, subsequently regenerate. In a first stage, these 

 processes occur in transplants also in the bone marrow ; however in the latter 

 location the preservation of the grafts is merely temporary, because the bony 

 capsule which, after some time, surrounds them, interferes with their proper 

 nourishment ; they then atrophy and a gradual absorption of the thymus tissue 

 takes place. We have previously discussed another example of destruction of 

 autogenous skin transplants, due to the ingrowth of the host connective tissue 

 into the epidermal cyst, especially along channels prepared by hairs devoid of 

 complete epithelial covering. In this way, secondary factors not connected 

 with the individuality differentials may determine the fate of transplants, as 

 do under some circumstances, growth stimuli, such as those of certain hor- 

 mones, acting on a transplant, which may to some extent counteract more or 

 less accidental, injurious factors, as well as other unfavorable conditions. 



The experiments of Marine and Manley, in which they compared auto- 

 genous and homoiogenous transplantations of various organs in the rabbit, are 

 of interest because they confirm not only the fact that usually the destruction 

 of homoiogenous tissues takes place wifhin 20 to 30 days, but also because 

 they show that in some rare cases such tissues may remain alive for longer 

 periods. Still, their experiments did not reveal the existence of the finer 

 differences in the reactions of the host against the transplants, in accordance 

 with the relations of the individuality differentials of host and donor. These 

 authors recognize the relatively great power of resistance of lipoid cells in 

 ovary and adrenal gland, but they underestimate the injury which lympho- 

 cytes can inflict on the transplant. However, the injurious effects exerted by 

 lymphocytes differ much under different circumstances, as the experiments 

 which we have already reported show. As to the causes of the unfavorable 

 results of homoiotransplantation, Marine and Manley attribute them to the 

 antigenic properties of the transplants; and the differences in the power 

 of resistance of various organs following transplantation they apparently re- 

 gard as being due to the differences in the antigenic capacities of different 

 tissues. Their conclusions were based not only on theoretical grounds but 

 also on the results of successive transplantations, in which they found that 

 a second homoiotransplant is always more rapidly destroyed than a first one. 

 However, these observations and interpretations are not in accord with our 

 own, as we shall discuss still further in a subsequent chapter. 



