HMMOLYSINS. 53 



dog will at times dissolve the red cells of cats, rab- 

 bits, and guinea-pigs, at other times not. Further- 

 more, the serum of one and the same animal may 

 possess specific haemolytic properties for certain 

 cells, and later on may lose this property entirely. 

 In human serum these same individual and periodic 

 variations may be demonstrated, as I was able by 

 many experiments to prove. However, the cir- 

 cumstances on which these variations depend are as 

 yet entirely unknown to us. Possibly we are deal- 

 ing here with subtle pathological changes. 



Source of the Complements Leucocytes as a Source 

 Other Sources. Where do the complements or alexins 

 originate? This question has been studied particu- 

 larly by Metchnikoff and by Buchner, also by Bail, 

 Hahn, Schattenfroh, and others. These investiga- 

 tors believe that the leucocytes are the source of 

 the complements or alexins. There is, however, 

 this difference between the views of MetchnikofI 

 and Buchner ; whereas Buchner believes the alexins 

 to be true secretory products, Metchnikoff believes 

 that they originate on the breaking up of the leuco- 

 cytes, i.e., that they are decomposition products. 

 Metchnikoff bases his belief chiefly on the work of 

 his pupil, Gengou, who showed that although the 

 serum was rich in alexin (i.e., complement) the 

 plasma contained none at all. 



Other authors, as Pfeiffer and Moxter, as a result 

 of their experiments, are not willing to assume the 

 existence of any relationship between the alexins 



