352 IMMUNO-CATALYSIS 



hemolytic phosphocholine and a diglyceride (stearyloleylglyceride). 

 These facts appear to show that the decomposition of lecithin by CI. 

 welchii toxin constitutes a more drastic change in lecithin, since the 

 phosphoric acid group is now present as a water-soluble compound, 

 but the products of the decomposition are stated to be innocuous. 

 On the other hand, considering the activity of toxin from the patho- 

 logical point of view these authors expressed the view that the lec- 

 ithinase of CI. welchii toxin is probably identical with the lethal, 

 hemolytic and necrotic factors of this toxin. This appeared to be 

 evident since the degree of inhibition of the lecithinase by various 

 type A antisera ran parallel with the protective power of the sera 

 in vivo. In two type C sera, the antilecithinase activity was in good 

 agreement with an independent assay of the a-antitoxin content. 

 Although the presented evidence strongly suggested that the leci- 

 thinase and a-toxin are identical, the ultimate proof of this was held 

 to be dependent on the isolation of homogeneous toxin with the requi- 

 site biochemical and pathogenic properties. The lecithinase activity 

 of the toxin examined was found to be so high as to be capable of 

 accounting for the pathological effect; an amount roughly equivalent 

 to 1 M.L.D. for a mouse could at its maximum velocity hydrolyze 

 the whole of the blood lecithin of the animal in two to three hours. 



4. Immunity to the Pharmacological Actions of Toxins 



The enzymatic activities of the various toxins discussed above are 

 more or less directly related to their biological effects. In the first place 

 it has been shown that the neutralization of toxin by antitoxin inhibits 

 the enzymatic activities of the toxins. Secondly, the pharmacological 

 effects of the toxins are likewise related to one or more enzyme 

 activities of the toxins. 



a. The Inhibition by CI. Welchii Toxin of the Oxidation of Suc- 

 cinate by Tissue. In the following pages it will be shown that toxins 

 cause the liberation in animal organs of various substances injurious to 

 tissue. The tissue freshly obtained from an animal is capable of oxidiz- 

 ing certain enzyme substrates. These respiratory enzymes are suscep- 

 tible to various specific and non-specific enzyme poisons. Wooldridge 

 and Higginbottom (1938) found that the toxins of CI. welchii inhibit 

 the oxidation of succinate by aqueous suspensions of minced small 



