PROCESSES OF IMMUNITY 163 



enous and heterogenous tissue may induce immunity reactions against tumor 

 as well as against normal tissue. (3) These secondary immune reactions also 

 are relatively slight as compared with the primary reactions occurring as the 

 direct result of the diffusion of the individuality differentials from a trans- 

 plant into the circulation of the host. The primary individuality differentials 

 are therefore responsible for the major portion of the reaction of the host 

 against homoiogenous tissues ; but secondary, immune reactions may also par- 

 ticipate in this reaction, although only to a lesser extent. 



These investigations as to the nature of the reactions against homoiogenous 

 and heterogenous tissues suggested a second problem, one which was of 

 practical importance and which therefore interested surgeons especially, 

 because its solution might be an aid in the grafting of homoiogenous tissues 

 in human beings. This problem concerned the possibility of improving the 

 results of homoiotransplantations by experimental means. It was thought 

 possible that in animals, through a preliminary treatment of the host with 

 blood serum or plasma, or with tissue extract of the donor, the former 

 might become desensitized to the effect of the homoiogenous tissues. These 

 experiments were, however, unsuccessful. Likewise, the treatment of the 

 transplants with similar substances from the host previous to the grafting 

 did not cause an accommodation of the 'homoiogenous tissue of the donor 

 to the conditions found in the host. Nor was it possible by means of para- 

 biosis between donor and host to prolong noticeably the life of the homoiog- 

 enous tissue, although under these conditions the graft was supplied with 

 some of the blood to which it was adapted. The observation of Murphy and 

 his collaborators, that by the application of Roentgen rays to the host, and 

 by other means which tended to reduce the number of available lymphocytes, 

 a more favorable outcome in the transplantation of homoiogenous tumors 

 could be obtained, induced surgeons to apply the same methods to the 

 homoiotransplantation of normal tissues, but no real improvement was 

 attained. 



In some of the papers of earlier investigators, in which the question as 

 to the causes of the usual failure of homoiogenous transplantations was 

 discussed, frequent reference is made to a state of anaphylaxis, resulting 

 from grafting of tissues, as one of the principal factors involved in this 

 process. However, a statement as to the nature of such an anaphylactic state 

 and its distinction from a condition of immunity against the transplant in 

 the host is not usually made. In order to test this assumption regarding the 

 presence of anaphylaxis in transplantation, experiments were made by us in 

 which conditions were favorable for the development of a state of sensitiza- 

 tion and thus also for a subsequent state of anaphylaxis in the transplant. 

 We sensitized guinea pigs by injecting them with horse serum and after- 

 wards transplanted pieces of uterus, thyroid or ovaries of the sensitized 

 animal into other guinea pigs, which had not previously been injected with 

 horse serum but which were injected sometime after they had received 

 the transplants. In other experiments we transplanted corresponding tissues 

 from non-injected guinea pigs into animals which received an injection of 



