258 ON VARIABILITY AND ADAPTATION 



Enzymes akd Ectotoxins 



There is one point which, before closing, I must take up, 

 namely, the nature of ectotoxins. 



In the first full study of these ectotoxins, that, namely, by 

 Roux and Yersin a quarter of a century ago upon the diphtheria 

 ectotoxins, it was clearly pointed out how many properties these 

 bodies possess in common with the group of organic enzymes : 

 their activity in extraordinarily minute doses ; the impossibility 

 of isolating them in a pure state ; their destruction by a tempera- 

 ture of 60° centigrade ; their precipitation by phosphates and 

 other salts. It is not a little interesting how, notwithstanding, 

 bacteriologists in general have shown unwillingness to accept 

 this view. Long years ago Sidney Martin in London brought 

 forward further evidence to the same effect, that the diphtheritic 

 membrane was not in itself highly toxic, that it contained an 

 enzyme whose activity gave origin to toxic albumoses, and that 

 the internal organs, while showing no evidence of the toxin proper, 

 might come to contain these toxic bodies. The significance of 

 these observations lies in the fact that, as everybody knows, 

 diphtheria bacilli are present in quantity in the membrane, 

 and are almost absent from the internal organs. I have not 

 come across a single leading German work on bacteriology that 

 has taken any serious notice of these observations of one of 

 the most brilliant and capable English workers. The stumbling- 

 block has evidently been in the prominence obtained by the 

 phenomena of antitoxin production. This reactive production 

 through the agency of ectotoxins of bodies which combine with* 

 the ectotoxins to render them inert, is wholly outside our usual 

 conception of enzyme activities, and yet it deserves pointing 

 out that, if we take solutions containing what we recognize as 

 enzymes foreign to the animal body, enzymes, for instance, 

 obtained from plants, and if we inoculate these into the animal 

 body, anti-enzymes are developed, identical in all their properties 

 to the antitoxins. Dr. Zinsser of Columbia University, in his 

 excellent work upon Infection and Resistance, lays down that there 

 is an important difference between ectotoxins and enzymes in their 

 mode of action. He states : " While the toxins are apparently 

 bound or neutralized by the tissues they attack, the action of 

 an enzyme seems rather to be a process in which the enzyme 



