Chapter IJ 



The Significance of the Individuality Differen- 

 tials in Transplantation by Means of Blood Vessel 

 Anastomosis and in Parabiotic States 



So far, the interaction of the individuality differentials of host and 

 transplant and the effect of various factors on this interaction have 

 been considered under conditions of a complete primary separation of 

 the grafts from the surrounding tissues, only later a union taking place 

 between the transplant and the tissues of the host. Such a transplant lives 

 under unfavorable conditions of nourishment during the first few days 

 following the transplantation and the central parts of the graft, which suffer 

 most from insufficient nourishment, undergo necrosis. This disadvantage is 

 eliminated if directly after separation of an organ or of a part of an animal, 

 the large blood vessels, and perhaps even the nerves, of the transplant are 

 connected with the corresponding structures of the host at the site of trans- 

 plantation. Thus the blood of the host is carried at once to all parts of the 

 transplant, which does not then suffer from lack of nourishment and the 

 central necrosis is prevented. The homoiogenous or heterogenous indi- 

 viduality differentials act, therefore, in this case, on tissues which are well 

 provided with food and should be better able to resist the unfavorable action 

 of the host. Moreover, the individuality differential substances produced in 

 the transplant, instead of diffusing slowly into the adjoining area, have a 

 chance to be carried directly by vessels into the general circulation of the 

 host, where they are much diluted. It may therefore be expected that the 

 local reaction around the transplant, which is so prominent a feature in the 

 ordinary kind of transplantation, is lacking around transplants which are 

 joined to the host by means of blood vessels. 



In parabiosis — a method of transplantation which was first conceived and 

 applied by Paul Bert, but was technically developed in its present form by 

 Sauerbruch and Heyde — two individuals, usually belonging to the same 

 species, but sometimes also to different species, are united by establishing 

 by means of incisions and sutures a connection between the peritoneal cavities 

 as well as between the skins of the two animals. In parabiosis, two indi- 

 viduals are therefore incompletely joined together; essentially, both partners 

 continue their individual metabolism and functions of organs and live their 

 own life, but at the same time some substances, including individuality dif- 

 ferentials, have a chance to pass continuously — although at a slow rate — 

 from one partner to the other; this takes place mainly by way of capillary 

 anastomoses, connections which gradually develop at the site of the peritoneal- 



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