78 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



lined merely with Sertoli cells, could survive. Testicle tubules were destroyed 

 also after autogenous transplantation; this effect is therefore due to a non- 

 specific injury, by which the more differentiated testicle cells are affected. 



(9) Striated muscle tissue was relatively resistant to unfavorable individu- 

 ality differentials, and even under the action of strong homoiotoxins some 

 muscle fibers could survive and show amitotic nuclear proliferation. 



(10) Fat tissue, at least in part, tended to survive even after homoiogenous 

 transplantation; but it was readily invaded by connective tissue and by cells 

 which acted as phagocytes, but which could in addition form giant cells, and in 

 some cases, by lymphocytes. The tendency to invasion by these cells differed 

 in different species ; it was greatest in the guinea pig, where there was also the 

 greatest tendency to the formation of giant cells, and it was least marked in 

 the mouse; rat tissue, with which we are here more directly concerned, 

 showed an intermediate position. 



(11) Bone, bone marrow and cartilage: As stated previously, cartilage with 

 the surrounding perichondrium is a very resistant tissue, which could survive 

 and undergo regenerative growth processes even under very severe homoio- 

 genous conditions. In bone, the bone cells tend to die, especially in the central 

 parts, owing to a lack of nourishment. In the peripheral parts of transplanted 

 bone it was often difficult to decide whether the cells situated here had come 

 from the surrounding connective tissue, or whether they were actually pre- 

 served bone cells. Under certain conditions, new bone could be formed in 

 transplants around the cartilage as well as in the bone marrow. The bone mar- 

 row, as a rule, survived only under very favorable conditions of syngenesio- 

 transplantation. 



In general, we may conclude that the results of transplantation of various 

 tissues depend upon inner and outer factors, the former situated in the trans- 

 plant and the latter in the host. Among the inner factors localized in the 

 transplant, (a) the most prominent is the constitution of the individuality 

 differential, which in its relation to the individuality differential of the host 

 largely determines the fate of the transplant ; (b) important too, is the degree 

 of sensitiveness to injury or the power of resistance of the transplant or its 

 various constituent parts to injurious conditions ; and (c) also influencing the 

 survival of the graft are certain accessory conditions, such as the presence of 

 hyaline tissue or other resistant tissues in the transplant, which protect the 

 more sensitive parts ; the thickness of the transplant, which affects the size of 

 the central, least nourished parts ; these latter tend to die, while the peripheral 

 parts remain alive. In addition, the age of the transplant may play a certain 

 role, as well as its possession of a peculiar tissue constitution, which influences 

 the activity of the lymphocytes of the host. Among the outer factors affecting 

 the results of transplantation are the constitution of the individuality differen- 

 tials of the host, the reactivity of the host against strange individuality differ- 

 entials, and the presence in the host of immune substances directed against the 

 transplant ; besides, the place of transplantation may be of significance. 



If we make allowance for the variations caused by all these factors, our ex- 

 periments have shown that as a rule pieces of different tissues, transplanted 



