164 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



horse serum during the period following the transplantation, and in a third 

 type of experiments, injections were given to the host, both prior to and 

 following transplantation. It was conceivable that the transplanted tissues 

 in some of these instances had been sensitized to horse serum and that a 

 second injection of horse serum would cause an anaphylactic reaction in the 

 transplant, which would alter the state of preservation and the lymphocytic, 

 connective-tissue and blood-vessel reaction of the host towards the transplant. 

 However, this was not the case ; the reactions of the host tissues against the 

 graft were not essentially altered by these procedures. Only in a few cases, 

 in which the general health of the guinea pig serving as host had been 

 affected by the injection of horse serum, was a definite effect on the trans- 

 plant noticeable, but it is not probable that in the last named experiments 

 we had to deal with a specific condition of anaphylaxis in the transplant. 

 As far as our experiments make possible a decision in this respect, it may 

 then be concluded that a state of true anaphylaxis is not one of the factors 

 which underlies the reaction of the host against homoiogenous transplants. 

 As to a possible improvement in the results of homoiogenous transplantation, 

 only one method appeared to be able to exert such an effect, and this was 

 the inactivation of the reticulo-endothelial system by means of injection of 

 trypan blue into the host previous to the transplantation. In the experiments 

 of Lehmann and Tammann, such a procedure seemed to prolong the life of 

 the transplanted piece of skin to a moderate degree. In 16 out of 28 mice so 

 treated, the skin grafts were better preserved after having been in the hosts 

 for four weeks than in controls; also, the staining of the skin to be trans- 

 planted by trypan blue seemed to protect it to some extent against the 

 antagonistic processes which as a rule take place in the host after trans- 

 plantation. Trypan blue was effective presumably because, temporarily, it 

 diminished the cellular response in organs where the lymphocytes are acti- 

 vated by the homoiogenous tissue, and also it may, perhaps, have neutralized 

 primary antagonistic constituents of the bodyfluids which otherwise would 

 have acted on the strange grafts; furthermore, it is possible that the 

 individuality differentials of transplanted skin infiltrated with this dye are 

 rendered ineffective for a certain period. But on the whole, these effects 

 are weak and temporary. The use of trypan blue proved to be ineffective 

 in similar experiments in rabbits, and Villata also obtained negative results 

 with this method when applied to transplantation of bones and joints in 

 rabbits. In similar experiments by Blumenthal with guinea pigs, into which 

 trypan blue was injected, the rise in the number of white blood cells other- 

 wise caused by the implantation of homoiogenous and heterogenous tissues 

 was prevented ; but he noticed that when tryan blue exerted such an effect, the 

 transplant was surrounded by a peripheral ring in which this dye was 

 deposited. He concluded, therefore, that it must be left undecided whether 

 the deposit of the dye in the periphery of the transplant inhibited the diffusion 

 of the organismal differentials into the host, or whether the trypan blue 

 inhibited the reaction on the part of the leucocytes through a blockade of 

 the reticulo-endothelial system. 



