CYTOLYSINS 129 



subsequently Metchnikoff expressed the belief that complement origin- 

 ates in the leucocytes of the body and is only liberated upon thedeath 

 of these cells. Metchnikoff used the term cytase to indicate what we 

 now call complement and believed that the microphages gave rise to 

 a microcytase capable of dissolving blood and other body cells. Pfeiffer 

 and certain other German workers take a diametrically opposed posi- 

 tion and maintain that the leucocytes furnish none of the complement in 

 the blood. A. von Wassermann and also Landsteiner believe that the 

 leucocytes may constitute one source of origin for the complement, 

 and it seems practically certain from modern investigations that several 

 organs play a part in the formation of complement. Before the bac- 

 tericidal action of blood was thoroughly understood as due to the inter- 

 action of amboceptor and complement, certain studies seemed to indicate 

 that exudates rich in leucocytes were active as bactericidal agents, but 

 it is now understood that other constituents of the exudate take part 

 in this phenomenon and more recent experiments show that extracts 

 of leucocytes do not yield a complement. It has been shown further 

 that variations in the total leucocyte count in an animal produce no 

 corresponding variations of complement content. Neuf eld and certain 

 others take the view that even inside the living leucocytes there is no 

 complement because they have found that destruction of red blood- 

 corpuscles within living leucocytes takes place at a distinctly slower 

 rate of speed than is the case in ordinary hemolysis. Furthermore, 

 they point out that the method of destruction is quite different, in that 

 ordinary hemolysis shows simply liberation of hemoglobin without 

 destruction of the stroma. Metchnikoff 's belief that the death -of the 

 leucocytes yields complement was supported by an experiment which 

 apparently showed that complement is present in serum after clotting, 

 but not in plasma. A considerable amount of experimental evidence 

 has been adduced, since this statement of Metchnikoff, to show that 

 plasma contains complement in the same amount as does serum. Some 

 of these experiments appeared to be invalid on the ground that im- 

 munological work with a plasma is likely to lead to coagulation, thus 

 producing a serum for the actual experiments. After these objections 

 had been presented, further experiments were performed which over- 

 came such objection, and it now seems perfectly clear that plasma con- 

 tains complement. This fact has been firmly established by the 

 recent work of Watanabe. 



Nature of Complement. Complement is probably of protein 

 nature, inasmuch as it is destroyed in coagulation of the serum by heat 

 and is digested by trypsin. Noguchi and his co-workers were of the 

 opinion that complement is a combination of soap and a protein, but 

 numerous other workers failed to confirm these studies. This state- 

 ment of Noguchi, as well as the work of Kyes, with cobra venom led 

 to the hope that it might be possible to prepare an artificial complement. 

 Landsteiner and Jagic have investigated the question and have shown 

 that whereas it is possible to substitute for amboceptor a colloidal 

 solution of silicic acid, which nevertheless shows none of the specific 

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