TRANSPLANTATION AND INDIVIDUALITY. 153 



tion of myoxid into fibrous connective tissue leads secondarily to 

 changes in the epithelium which rests on the connective tissue. 

 We find thus a chain reaction and in addition to the direct results 

 indirect results of the homoiotoxin action. 



MECHANISM OF THE REACTIONS. 



These experiments prove that the introduction of parts of 

 organs or tissues which originated in a strange individual causes 

 disturbances which lead to changes similar to those found as the 

 result of the action of toxic substances. These substances act not 

 unlike those given off by certain microorganisms, as for instance 

 the tubercle bacillus, which cause changes of a not acute char- 

 acter. Lymphocytes are attracted and besides the relations be- 

 tween various tissues are quite markedly altered. We have every 

 reason to assume that these disturbances are due to products of 

 metabolism given off by the introduced tissue, which act as homo- 

 iotoxins. We have learned that the action of these substances 

 is graded in accordance with the relationship between donor and 

 host. It is as yet doubtful, how far these disturbing substances 

 are those given off in the normal metabolism of the transplanted 

 cells substances which are toxic merely because they act on a 

 strange host and how far they are the product of an abnormal 

 metabolism of the introduced cells, the pathological change being 

 due to the action of the body fluids of the new host upon the 

 strange cells. It is probable that the second alternative holds 

 good at least in many cases. Landsteiner, von Dungern and others 

 have shown that in man certain groups of individuals can be dis- 

 tinguished according to the interaction of blood cells on the one 

 hand, and agglutinins preformed in the blood on the other hand. 



While such agglutinins have not been observed in animals, in 

 certain cases it has been found possible through immunization 

 with blood corpuscles belonging to the same species, but to dif- 

 ferent individuals to produce hemolysins which dissolve cor- 

 puscles of the same species and combine especially with the cor- 

 puscles of the individual whose blood had been used for injection. 

 These observations, as well as our own experiments to which we 

 referred already, as w r ell as others to be mentioned later render it 

 at least probable that such an interaction takes place between a 



