VENOMS, TOXINS, ANTIBODIES 359 



the process being that of an unimolecular reaction, i.e., an exponential 

 curve of the form 



where Xo is the initial strength of the toxin and x is the strength at time t. 

 Furthermore, the effects of temperature on the rate of inactivation are 

 quite regular and predictable on a physicochemical basis. For alexin, 

 these facts were clearly shown by Madsen and Watabiki (113). It is. 

 therefore, of interest to examine the effects of irradiation on immune 

 bodies from this point of view. Practically all the available data concern 

 alexin which has been carefully studied by Brooks (28) and by Lund- 

 berg (109, 110), entirely independently of each other. The substantial 

 agreement of their findings has, therefore, increased weight. 



In both cases the titration of alexin was carried out with an accuracy 

 not attainable with other immune bodies (26), determinations on a single 

 sample being reproducible to within about 1 per cent. Triplicate 

 irradiations of three samples of a single serum gave the following titers 

 after irradiation: 56.8, 54.4, 54.7 (28). This will serve to give an idea 

 of the statistical validity of the results. 



Both authors report that the inactivation of alexin by ultra-violet 

 light is nearly independent of temperature: Brooks gives Qio values 

 gradually increasing over the range from 0° to 40°C. from 1.02 to 1.18. 

 Lundberg gives values of ju, the so-called Arrhenius temperature charac- 

 teristic, varying between 0.002 and 0.003, which corresponds to a Qio 

 value of about 1.1. These values are typical of photochemical reactions, 

 and show that, at least in the case of ultra-violet radiation, the amount 

 of alexin inactivated is closely proportional to the amount of photo- 

 chemical reaction. 



The course of the reaction was found by Brooks (28), who irradiated 

 solutions of guinea-pig serum (5 per cent in a special physiologically 

 balanced salt solution), to vary rather irregularly from one sample of 

 alexin to another, but to vary around an exponential curve. Table 1 



Table 1. — Values of the Rate Constant k for Inactfvation of Alexin by 

 Ultra-violet Light, Calculated at Various Times during the Process, 



AS FOR A Unimolecular Reaction 



The values are the means of eight experiments 



{After Brooks, 28) 



1 

 A; = - log -- 



Exposure, min. t a — x 



1 0.026 



2 0.032 

 4 0.030 

 7 0.028 



10 0.030 



15 0.028 



20 0.028 



