TRANSPLANTATIONS 53 



transplants, to the primary injury which initiates the regenerative processes 

 is added the secondary injury inflicted on the tubules by lymphocytes and con- 

 nective tissue cells; this second factor may cause increased mitotic prolifera- 

 tion, provided enough tubule tissue is left to respond with such activity. 



We may then conclude that the difference between autogenous and homoio- 

 genous transplants of kidney pieces in the later stages is due to the more rapid 

 destruction of the regenerating tubules in the latter grafts, rather than to a 

 primary difference in the actual development and growth of kidney tissue, 

 which almost ceases on or about the 14th day after transplantation, although a 

 slight regenerative process may occur at a still later date. The damage to the 

 tissue begins on about the 9th day and in the homoiotransplant destruction is 

 almost complete 21 days after transplantation. The activity of the connective 

 tissue destroys also the autotransplant, which has been injured through the 

 abnormal conditions in which it lives, especially in the ear; this activity is 

 therefore, at least partly, an injury reaction, which may develop in autogenous 

 as well as in homoiogenous transplants. In contrast to the connective tissue 

 cells, the lymphocytes react more specifically to homoiotoxins which are 

 present in the bodyfluids of the host and in the transplanted tissue itself ; these 

 toxic substances are both involved, partly directly, partly indirectly, in the 

 activity of the lymphocytes, but, to a certain extent, also in that of the con- 

 nective tissue elements. 



