444 COLLECTED STUDIES IN IMMUNITY 



out by Calmette, 1 namely, that almost all sera after being heated to 

 65 C. and higher usually show even an increased activating power. 

 This we could explain only by ascribing it to the lecithin set free 

 through heating (Kyes, 1. c.). It thus appeared that heating was more 

 likely to effect a splitting off than a combination of the lecithin. 



Our further studies have shown, however, that this view is not 

 correct in all cases. 2 



To begin, we examined the complementing properties of serum, 

 choosing for our analysis the combination ox blood H- cobra venom + 

 guinea-pig serum. The activating property of the fresh guinea-pig 

 serum was destroyed by half an hour's heating to 56 C., and hence 

 was apparently not due to the presence of lecithin, but to some other 

 complement-like substance. Subsequent investigations have con- 

 firmed us in this opinion. The general course of the haemolysis 

 through snake venom is markedly different when lecithin or serum 

 is used for complementing. Lecithin effects rapid solution; with 

 large amounts of cobra venom this is almost instantaneous. When. 

 serum is used as complement a longer or shorter period of incubation 

 is observed, such as we are accustomed to see with the haemolytic 

 sera. Furthermore, haemolysis with cobra venom + lecithin occurs 

 even at C., whereas the action of cobra venom + serum as comple- 

 ment requires a greater degree of heat. 



That the activating substance of the serum belongs to the class 

 of complements was further demonstrated by the fact that it was 

 destroyed by digestion with papain. Following the method of Ehrlich 

 and Sachs, 3 in order to digest the complement, 5 cc. guinea-pig serum 

 were mixed with 1 cc. 10% solution of papain, digested for 1J hours 

 and then centrifuged. The decanted fluid was used to activate the 

 cobra venom. Table I shows that this property was almost com- 

 pletely lost. 



The serum treated with papain had thus almost completely lost 

 its activating property, whereas a solution of lecithin similarly treated 

 preserved its activating property unchanged. (See Table II.) 



1 Calmette, Sur 1'action hemolytique du venin de cobra, Compt. rend, de 

 1' Academic des Sciences, T. 134, No. 24, 1902. 



* We are much indebted to Drs. Lamb and Greig for cobra venom kindly 

 placed at our disposal. 



* Ehrlich and Sachs, The Plurality of Complements in Serum, Berl. klin 

 Wochenschr. 1902, Nos 14 and 15. 



