30 IMMUNE SERA. 



this carefully and ascribed the action to a substance 

 found in all normal serum, which he called alexin. 

 According to his experiments, this is a very unstable 

 substance, decomposing spontaneously on standing 

 or on heating for a few minutes to 55 C., or readily 

 on the action of chemicals. According to this 

 author all the globulicidal and bactericidal func- 

 tions of normal serum are performed by this one 

 substance, the alexin. 



Active and Inactive Normal Serum. Ehrlich and 

 Morgenroth now took up the study of the hae- 

 molytic action of normal serum. They sought 

 particularly to discover whether in normal serum 

 the haemolytic property depended on the action of 

 a single substance, the complement (Buchner's 

 alexin), or whether here as in the specific hsemo- 

 lytic serum it depended on the combined action 

 of two substances. For this purpose they used 

 guinea-pig blood, which ' is dissolved by normal 

 dog serum. If this serum was heated to 55 C., it 

 lost its haemolytic power. It was necessary now to 

 show that in this inactive dog serum there re- 

 mained a second substance which could be reacti- 

 vated after the manner of reactivating an old spe- 

 cific haemolytic serum. This had its difficulties, 

 for they could not add normal dog serum. This, 

 as we saw, is already haemolytic for guinea-pig 

 blood. " Possibly," said they, " there exists a com- 

 plement of another animal which will fit the hypo- 

 thetical second substance of this dog serum." 



