170 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



discussed, in that in the latter case the transplant is supplied exclusively 

 with the blood of the host. However, in addition experiments have been 

 carried out in which, first, two animals were united by parabiosis and then 

 various organs were transplanted by blood vessel anastomosis from one 

 partner to the other. Likewise, skin has been quite commonly transplanted by 

 means of pedicled flaps to a parabiotic partner. Indeed, the transplantation 

 of pedicled skin flaps from one animal to another represents a rudimentary 

 parabiosis. If a pedicled skin flap is transplanted to another region in the 

 same individual, and the pedicle is cut after healing has taken place, the 

 transplant may continue to live during the lifetime of the person or animal. 

 In the case of homoiogenous transplantation the skin graft remains pre- 

 served usually as long as the skin is united by the pedicle with the circulation 

 of the donor and the transplanted tissue receives, through the blood, sub- 

 stances carrying its own individuality differentials. During that period it 

 is sufficiently under the influence of autogenous substances to be able to 

 resist the action of homoiotoxins which are active at the point of union. 

 But if, after healing has taken place, the pedicle is cut, the transplant is 

 fully exposed to the antagonistic reaction of the host cells, as well as to the 

 homoiotoxins of the bodyfluids of the host, and its fate does not differ from 

 that of the ordinary homoiogenous transplant, the advantage gained by the 

 flap method being merely temporary. It seems that, as in skin transplantation 

 by the ordinary method, so also by the pedicle-flap method, after the pedicle 

 is cut, the transplant may, at least in some cases, survive for a longer time, 

 perhaps even permanently, provided the individuality differentials of host 

 and graft are relatively harmonious, which may be expected especially if 

 syngenesiotransplantations are carried out. Thus Lexer succeeded in keeping 

 alive for eight weeks a skin-flap transplant from daughter to father. In 

 this case, the father received daily injections of blood serum from the 

 donor; when these injections were interrupted, the skin flap no longer re- 

 mained preserved but was cast off by the host. Lexer attributed this result 

 to the favorable action of the injections of donor serum, supplying suitable 

 foodstuffs for the transplant; but later experiments in animals by Lexer 

 and Keysser showed that such serum injections do not exert a beneficial 

 effect on the transplant and it may be assumed that the near relationship 

 of the individuality differentials of transplant and host was responsible for 

 the favorable results obtained. 



Transplants of organs by blood vessel pedicles to a parabiotic partner 

 do not behave differently from corresponding pedicled skin transplants ; the 

 grafted organs undergo the fate of ordinary homoiogenous transplants and 

 die after the pedicle has been cut. We see, then, that it is essentially the 

 relationship of the individuality differentials which determines the outcome 

 in these transplantations, as it does in those of the ordinary type. However, 

 it seems that in man, not only strange individuality differentials but also 

 blood group antigens (A) may pass from one partner through the vessels 

 connecting the skin flap to the other partner, causing in the latter the pro- 

 duction of antibodies and leading here to the destruction of the blood cor- 

 puscles possessing the antigen A. This occurrence was observed by Lauer. 



