VENOMS, TOXINS, ANTIBODIES 361 



that there exist in serum one or more precursors of alexin, or related 

 substances, which become transformed into alexin by irradiation, or 

 at least reenforce its action. We use the word "alexin" here to mean the 

 principal hemolytic molecular species present in serum and acting in 

 conjunction with amboceptors. 



Another suggestive fact is that Schubert (142) found the moist 

 globulin precipitate or "mid-piece" fraction (cf. below) to have its 

 activity increased oftentimes by ultra-violet irradiation. 



Lundberg's work also gives a clear quantitative statement of the 

 acceleration of inactivation by dilution, the rate constant rising with 

 dilution from 0.0364 for undiluted serum, through 0.0447 for 33 per cent, 

 to 0.0882 for 10 per cent solution. Brooks' value for 5 per cent solution, 

 namely, 0.030, is somewhat smaller, probably because of the use of a 

 weaker source of radiation (quartz-mercury arc). 



That the inactivation of alexin by ultra-violet radiation does not 

 depend upon free oxygen is apparent from Hassko's (76) experiments 

 on the effect of bubbling gases through various dilutions of serum (1 to 

 20 per cent) during ultra-violet irradiation. Although alexin inactivation 

 did proceed a little faster with oxygen than with nitrogen, the difference 

 is, in view of his obsolete and highly inaccurate method of titration, quite 

 without significance. It is unfortunate that immunologists do not more 

 generally grasp the possibility of discarding their obsolete methods and 

 doing statistically valid quantitative work. 



Lundberg's mention of increased opalescence upon irradiation suggests 

 a colloidal or coagulative phenomenon. In addition to the large volume 

 of support which this conception receives from other sources, we may 

 mention some which are of particular interest from the point of view of 

 irradiation. 



Coagulation of proteins, which are the principal colloids of serum, is 

 well known to involve at least two steps: denaturation and flocculation. 

 Both of these may be reversible under appropriate conditions."* Egg 

 albumen is denatured by ultra-violet light and then flocculates rapidly 

 and at first reversibly at room temperature (Bovie, 22). Is alexin 

 similarly sensitized so that it goes on to further destruction at room 

 temperature? As a matter of fact, alexin partially inactivated by heat 

 may regain activity (Gramenitzki, 71). This might be thought of as a 

 result of spontaneous reversion of the denaturation phase of protein 

 coagulation. Brooks (27) was able to confirm Gramenitzki's claim that 

 after heating there was a regeneration of alexin, but a considerable 

 number of the same sera partially inactivated by ultra-violet irradiation 

 showed no evidence whatsoever of either regeneration or of increased 

 sensitization to heat (37°). Koopman (100) has claimed to have found 

 regeneration after partial inactivation by ultra-violet light, but his 



* See, for example, Anson and Mirsky (5, 6). 



