POWER OF NORMAL SERUM TO DEFLECT COMPLEMENT. 613 



Decreasing amounts of inactive rabbit serum are digested with 0.05 cc. 

 guinea-pig serum. Then 1 cc. 5% sheep blood washed five times plus 0.0015 cc. 

 amboceptor (serum from a rabbit immunized with ox blood) are added. In 

 the following table 



A denotes native rabbit serum; 



B rabbit serum treated with sheep blood washed once; 



C rabbit serum treated with sheep blood washed five times. 



The experiment by which Gay seeks to explain my results is 

 therefore entirely valueless so far as my experiment is concerned. 

 To be sure, Gay Helieves to have followed my technique exactly, 

 yet in one important point he has not done so. The hsemolytic 

 immune serum with which he worked was markedly weak, the 

 solvent dose being 0.2 cc.,. while 0.001 cc. of my serum still brought 

 about complete solution. Gay employed 0.4 cc. immune serum, 

 while I used but 0.002 cc., i.e., 1-200 of his dose. It is very well 

 possible that the antibodies which sensitize serum albuminous 

 bodies, the precipitating substances as Gay believes, are present 

 in 0.4 cc. immune se'rum; in amounts as small as 0.002 cc. they 

 are almost certainly absent, and I never observed any precipitin 

 action with these amounts. It is evident, therefore, that with the 

 large doses of immune serum employed by Gay the presence of 

 slight amounts of sheep serum might well make a difference in the 

 result, while this would be a negligible factor in my experiments. 



But how are we to explain the fact that Gay after treating the 

 rabbit serum with sheep blood which had been washed five times 

 was unable to demonstrate the inhibiting action described by me? 

 This again is due to the unfortunate employment of the weak immune 

 serum. Gay has evidently been working with normal amboceptors. 

 It is well known that rabbit serum normally dissolves sheep blood, 

 and the ordinary strength of this hamolytic power corresponds 



