Chapter l8 



Modification of the Reaction of the Host Against 

 Strange Individuality Differentials by Transplan- 

 tation of Tissues Into the Allantois of Chick 

 Embryos, Into the Brain, or Into the 

 AnteriorlChamber of the Eye 



It has not been possible to prevent the injury or destruction of homoi- 

 ogenous or heterogenous transplants by immunization of the host with 

 blood or tissue extracts of the donor, or, conversely, by treating the 

 donor with similar substances obtained from the prospective host. On the 

 other hand, in a limited way, it was possible to protect the transplant against 

 aggression by the host by inactivating the reticulo-endothelial system of the 

 latter by means of injections of trypan blue. Previous to the last mentioned 

 observations it had been shown that heterogenous mammalian tumors were 

 able to grow in the chorio-allantois of the developing chick (Rous and Mur- 

 phy), and subsequently the mechanism of this condition was analyzed by 

 Murphy and his collaborators in a series of investigations. Murphy could 

 show that after transplantation of a piece of spleen, and to some extent also 

 of bone marrow, previous to or simultaneously with the transplantation of 

 heterogenous tumor or of heterogenous embryonic tissue into the chorio- 

 allantois, the transplants were destroyed in the same way as they were in adult 

 hosts. The spleen tissue initiated the reactions of the embryo-host which, in 

 the fully developed adult host, prevent the growth of heterogenous tumors 

 and embryonal tissues, and correspondingly, the chicken embryo spontaneous- 

 ly became resistant to these strange transplants as soon as the embryonic 

 development had reached the stage when the organs of defense could function. 

 According to Murphy, these defense mechanisms consist largely in the ac- 

 tivity of the lymphocytes, which call forth a state of immunity in the host. 

 The immune processes thus produced acted not only against strange tumors, 

 but they could also inhibit the growth of autogenous tumors and they were 

 the same as those which protected the organism against pathogenic micro- 

 organisms, such as tubercle bacilli. All the means which injure or destroy the 

 lymphocytes, weaken or remove the immune processes in the host and allow, 

 therefore, tumors to grow or tuberculosis to spread, while those mechanisms 

 which tend to stimulate the multiplication and activity of the lymphocyes, tend 

 to intensify the immune processes and to protect the organism. By the applica- 

 tion to the host of X-rays, dry heat, benzene, and certain other means which 

 injure the lymphocytes, it is therefore possible to enhance the growth of 

 malignant tumors in the organism. 



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