394 COLLECTED STUDIES IN IMMUNITY. 



Next we come to the very important substances in serum which 

 'Cause haemolysis. I have previously dwelt in detail on the fact that 

 in this the action is always due to amboceptors which attract both 

 blood-cells and complement. Hence I may limit myself at this time 

 to some supplementary remarks. It has long been known that the 

 blood serum of one species injures and dissolves the erythrocytes of 

 other animal species. This is the case not only in distantly related 

 types, such as fish and mammals, but, as was shown by therapeutic 

 blood transfusions, occurs also in comparatively near relatives. 

 Buchner was the first to appreciate the significance of this phenomenon, 

 and assumed that the serum contained a substance innocuous for its 

 own body but acting destructively on foreign elements (bacteria and 

 blood-cells). This substance he therefore terms alexin. Not until, 

 in later years, the mechanism of artificially produced lysins became 

 clear was this Unitarian view shown to be untenable. First it was 

 found that the lysins contained in normal blood are not simple in 

 nature, but are composed just like those artificially produced, of 

 two components, the amboceptor and the fitting complement. Further- 

 more, corresponding to the results in the case of agglutinins, and by 

 means of the same methods, it wa$ found that a given serum can con- 

 tain a large number of different amboceptor lysins. If a certain 

 serum (e.g. dog serum) dissolves the erythrocytes of different species, 

 the specific combining method has shown that this property is due 

 to the presence of different amboceptors, each of which is related 

 to only one of these species of blood-cells. In fact it even seems as 

 if different complements may correspond to these amboceptors. 



In view of what has been said we are fortunately able to regard 

 these different agents which injure the blood from a common point 

 of view. Whether we are dealing with vegetable or animal prod- 

 ucts, whether with lysins or agglutinins, whether with substances 

 of toxin-like nature or of the complex amboceptor type, in all of 

 these cases the prerequisite and cause of this poisonous action is the 



thrust off into the blood they constitute agglutinins and precipitins. The 

 toxins also are to be regarded as receptors of the second order thrust off by 

 bacteria. 



3. Receptors of the third order, which possess two haptophore groups, one 

 of which effects the union with the foodstuff, whereas the other lays hold on 

 certain substances circulating in the blood plasma, the complements, which 

 cause ferment-like actions. After they are thrust off these receptors con- 

 situte the "amboceptors." 



