TOXINS 121 



now it has come to include the specific poisons of but four of 

 the great group of pathogenic bacteria. 1 



Chemical Properties of Toxins. The chemical nature 

 of the toxins is entirely unknown. By various precipitation 

 methods they may be carried down, but included with them are 

 masses of impurities, chiefly proteids. It is quite certain that 

 toxins are not proteids, since very active toxins have been 

 obtained by purification processes that did not give the proteid 

 reactions. The old name of " toxalbumin" is, therefore, 

 incorrect. Oppenheimer 2 says of the toxins that " we must be 

 contented to assume that they are large molecular complexes, 

 probably related to the proteids, corresponding to them in 

 certain properties, but standing even nearer to the equally 

 mysterious enzymes with whose properties they show the most 

 extended analogies both in their reactions and in their activities. 77 

 These similarities between toxins and enzymes are very striking, 

 and in discussing the nature of the enzymes we have mentioned 

 the reasons for considering them related to the toxins ; we may 

 now take up the other side of the question and consider the 

 relation of the toxins to the enzymes. 



Resemblance to Enzymes. First of all we meet the same 

 difficulty in isolating toxins that we do in isolating enzymes. 

 " A pure toxin is as unknown as a pure enzyme " (Oppenheimer). 

 At first both were believed to be proteids ; now both are con- 

 sidered by many not to be proteids, but molecular complexes of 

 nearly equally great dimensions. That toxins, like enzymes, are 

 colloids, has been abundantly demonstrated. 3 Both pass through 

 porcelain filters, but both lose much of their strength in the 

 process, and they are almost entirely held back by dialyzing 

 membranes. Neither will withstand boiling, and most forms 

 are destroyed at 80 instantly or in a very short time ; on the 

 whole, however, toxins are more susceptible to heat, as well as 

 to most other injurious agencies. Both stand dry heat over 

 100, and extremely low temperature, without much injury. 

 Left standing in solution for some time they gradually lose their 

 specific properties, and in each case this seems to be due to an 

 alteration in the portion of the molecule that produces the 



1 In addition to the ordinary toxins, Ehrlich recognizes other poisons secreted 

 by the diphtheria bacillus which have a less specific and less actively poisonous 

 action; and called toxones. (This conception is contested by Arrhenius and 

 Madsen). The toxins also vary in their affinity for antitoxin, and on this 

 basis have been divided into proto-, deutero-, and tritotoxin. These refinements 

 of division are not necessary for our consideration of the chemical features of 

 immunity. 



2 Kolle and Wassermann's Handbuch, 1903 (1), 351. 



3 See Zangger, Cent. f. Bakt. (ref.), 1905 (36), 239. 



