200 MECHANISM OF COMPLEMENT ACTION 



When cobra venom is allowed to act upon complement under cer- 

 tain conditions there ensues a change in the serum such that when 

 this cobra serum, as it is called, is combined with either mid- or end- 

 piece of normal complement, or when either fraction of the cobra 

 serum is combined with the supplementary fraction of normal serum 

 the mixture is hemolytic.^"* This is supposed to be due to the action 

 of cobra venom upon a "third component" of complement. Hemoly- 

 sis by complement would then be considered to result from the com- 

 bined action of mid-piece, end-piece, and third component, all of 

 which must be present. 



The writer is inclined to regard the cobra serum as serum from 

 which all the lysin and its precursors have been removed. The third 

 component, which is destroyed by cobra venom, is the lysin and its 

 related substances. This is in accord with the work of Delezenne 

 and Fourneau^^ and with the observed characteristics of cobra serum. 



Phenomena susceptible of explanation in terms of the scheme here 

 proposed abound in the literature, and their descriptions might be 

 multiplied indefinitely if anything were to be gained by so doing. 

 It is of greater significance that search of the voluminous literature on 

 complement has so far failed to discover any well estabhshed .fact 

 which is incompatible with this hypothesis. If such facts are found, 

 the hypothesis must of course be replaced by some better one; but the 

 writer believes that the main ideas underlying it, namely successive 

 transformations of precursor into lysin and then into inactive products, 

 and the dependence of this lysin on the serum proteins, will prove to 

 be valid. At any rate they seem preferable to certain prevailing 

 explanations based upon the rather indefinite concept of a hemolytic 

 power resulting from the colloidal properties or "lability" of serum 

 proteins.^^ 



SUMMARY. 



It has been shown: 



1. That complement exposed to ultra-violet light is not thereby 

 sensitized to the action of heat (which indicates that it is not protein) . 



^■^ Ritz, H., Z. Immunitdtsjorsch., Orig., 1912, xiii, 62. 



^^ Such ideas have been expressed by many investigators and have recently 

 been developed and emphasized by Sachs in a review of the work of his labora- 

 tory (Sachs, H., Roll. Z,, 1919, xxiv, 113). 



