DEMONSTRATION OF INDIVIDUALITY DIFFERENTIALS 517 



stances through immunization with homoiogenous erythrocytes, but that a 

 hemolytic immune serum thus obtained does not hemolyze the red corpuscles 

 of the individual in which the immune serum developed. It is therefore im- 

 possible to elicit a reaction against autogenous cells. Similarly, Ehrlich and 

 Morgenroth have shown that antihemolysins cannot be made to appear by 

 injecting isohemolysins into a goat in which the hemolysins had originated. 

 Likewise in the case of tumor immunity, we have seen that an active im- 

 munity against the growth of a transplanted tumor will not result from 

 inoculating an animal with pieces of its own organs. 



However, it has been held that in certain cases autogenous antibodies may 

 actually be formed, but not all the authors distinguish sharply between sub- 

 stances and reactions of an autogenous and homoiogenous nature, and it is 

 thus difficult to determine whether we have actually to deal with autogenous 

 rather than with homoiogenous reactions. To mention some examples : 

 According to Guyer, an injury to the eye-lens of a rabbit elicits in this animal 

 the production of antibodies against lens tissue which enters the blood serum; 

 these antibodies can be demonstrated by the formation of a precipitate on 

 mixing the serum of the animal which has been injured with homoiogenous 

 lens substance. Similarly, according to Henshaw, antibodies develop against 

 autogenous antigens after exposure of the skin to ultraviolet rays ; either by 

 means of anaphylactic shock or by the precipitin reaction with corresponding 

 homoiogenous skin material, the development of antibodies could apparently 

 be demonstrated. In these cases we may perhaps have to deal with tissues, 

 which, as a result of injury, had undergone chemical changes of a kind which 

 seem to have made possible the formation of auto-antibodies. This applies 

 also to the experiment of Letterer, who, by injection of autogenous venous 

 blood, sensitized a guinea pig against its own blood, which caused a reaction 

 when injected parenterally. Apparently the normal circulating blood does not 

 cause such a sensitization. 



In the case of paroxysmal hemoglobinuria, pathological changes of a specific 

 kind have evidently taken place in the blood of certain individuals. As a 

 consequence of these changes, it seems that autohemolysins develop, and the 

 union between erythrocytes and autohemolysin which follows depends on an 

 exposure of the erythrocytes to a low temperature. But it is not certain that 

 in this instance there is actually involved an antibody formation against 

 autogenous cells. Certain non-specific procedures, such as injection of boiled 

 milk, apparently intensify the autohemagglutination in some rabbits, but 

 injection of erythrocytes, normal or injured, does not have a corresponding 

 effect. 



In general, it may therefore be assumed that the body does not react against 

 its own normal cells with the production of immune substances, while it is 

 able to do so against homoiogenous substances. However, we cannot exclude 

 the possibility that if a body is injected with its own injured cells, in certain 

 cases a reaction may be elicited, but that such a reaction is less strong than one 

 produced by means of injections of homoiogenous, or better still, of heterog- 

 enous material; furthermore, it is possible that substances of an autogenous 



