458 



COLLECTED STUDIES IN IMMUNITY. 



argument for the view that cobra venom and lecithin behave like 

 amboceptor and complement. 



V. The Susceptibility of the Red Blood-cells. 



These observations show that in comparing the susceptibility of 

 the various species of blood to cobra venom the limit of activity of 

 the venom must be determined with the optimum quantity of lecithin. 

 The values thus obtained may be regarded, so to speak, as the " abso- 

 lute susceptibility" of the blood-cells. In Table XIII the minimal 

 complete solvent dose is determined for several species of blood on 

 the addition of an abundant quantity of lecithin (0.2 cc. of a 0.025% 

 lecithin solution). 



TABLE XIII. 



If we compare these values with the susceptibility of the various 

 blood-cells with cobra venom alone (see Table XIV) we shall see 

 that when the latter is used the amount of venom necessary for 

 complete haemolysis is many times greater than when a sufficient 

 amount of lecithin is "added. Thus the absolute susceptibility of 

 guinea-pig blood against cobra venom + lecithin is 500 times greater 

 than that obtained without the addition of lecithin. 



This shows also that although guinea-pig blood heads the list 

 in either case there are marked deviations, so far as the other bloods 

 are concerned, from the results obtained on the addition of lecithin. 

 Ox blood, for example, which is not at all susceptible when lecithin 

 is lacking, is more susceptible than either rabbit or human blood 

 when lecithin is present. Yet the two latter species of blood are 

 dissolved even without the addition of lecithin. 



We thought it would be especially interesting to study the sus- 

 ceptibility of human blood-cells to cobra venom in various diseases. 

 In the few cases thus far observed (several healthy persons, two cases 



