350 CYTOLYSINS 



active serum is one containing complement, and this must, under ordi- 

 nary circumstances, be a fresh serum. On heating or exposure the 

 serum becomes inactive. An inactivated serum may be reactivated by 

 the addition of fresh complement serum. These terms are in general 

 use, especially in testing for hemolytic and bacteriolytic reactions. 



Origin of Complement. Buchner regarded complement as a true 

 secretory product of the leukocytes, and Metchnikoff also maintains 

 that leukocytes are the main source, the complement being liberated 

 upon disintegration of the white cells. There is considerable experi- 

 mental evidence both for and against these views, but at the present 

 time the consensus of opinion would tend to regard the leukocytes as 

 an important, but not necessarily the sole, source of complement forma- 

 tion. 



Complement has been demonstrated in plasma, where its presence 

 is probably due to continual disintegration of leukocytes and liberation 

 of complement during life. It is probably increased to a slight extent 

 as serum is left in contact with the blood-clot, indicating that disintegra- 

 tion of leukocytes may augment the complement supply. 



The liver (Muller and Dick), pancreas, and other organs have been 

 regarded as sources of complement formation, but in general the evi- 

 dence points to the leukocytes as the chief source of supply, the liver 

 being probably concerned through its activity in blood destruction. 



Multiplicity of Complements. Ordinarily, a fresh serum, such as 

 that of the guinea-pig, will furnish complement for either bacteriolytic 

 or hemolytic amboceptors, and the question arises as to whether one 

 complement unites equally well with all amboceptors, or whether several 

 complements are present in one serum that act more or less specifically 

 with different amboceptors. 



Bordet believes that only one complement is present, and bases this 

 opinion mainly on the fact that a complement that can be shown to 

 activate either a hemolytic or a bacteriolytic amboceptor may be 

 absorbed out of a serum by furnishing an excess of either amboceptor. 



Metchnikoff maintains that there are two cytases or complements, 

 one being derived from macrophages and mainly hemolytic, and the 

 second derived from microphages and chiefly bacteriolytic. 



Ehrlich and Morgenroth, Sachs, Wassermann, Wechsberg, and the 

 German school in general believe that many different complements are 

 present in amounts varying with the different serums. These observers 

 have sought to prove this experimentally, and while the evidence is not 

 absolutely convincing, because of the difficulty of working with sub- 



