72 IMMUNE SERA 



Buchner, as we have already seen, had studied 

 this bactericidal action carefully and ascribed the 

 action to a substance found in all normal serum, 

 which he called alexin. According to his experi- 

 ments, this is a very unstable substance, decom- 

 posing 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 functions 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 haemo- 

 lytic action of normal serum. They sought par- 

 ticularly 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 haemo- 

 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 

 remained a second substance which could be reacti- 

 vated after the manner of reactivating an old 

 specific haemolytic serum. This had its difficulties, 

 for they could not add normal dog serum. This, 

 as we saw, is already haemolytic for guinea-pig 



