142 PATHOGENIC BACTERIA. 



preceding paragraph, and their activities pointed out. 

 Like the antitoxic serums, however, the antimicrobic 

 serums seem to be formed only in high degrees of forced 

 immunity. 



V. Antitoxins. — A few years ago it might have been 

 unhesitatingly declared that acquired immunity de- 

 pended upon the presence of antitoxins in the blood. We 

 have of late accumulated much experimental evidence 

 which, when sifted, seems to indicate that the antitoxins 

 present in the blood of an animal may have very little to 

 do with its immunity. These observations consist of 

 numerous immunities in which no antitoxins can be 

 demonstrated in the blood, as in the various vaccinations 

 against anthrax, typhoid, cholera, symptomatic anthrax, 

 etc., and some very different conditions in which, with a 

 great deal of antitoxin in the blood, animals succumb to 

 specific infection or intoxication. The most forcible 

 illustration of this is seen in the hypersensitivity of 

 horses furnishing diphtheria and tetanus antitoxin, a 

 full discussion of which has been given. 



In the face of such illustrations we must conclude that 

 antitoxin is one of the phenomena or reactions of im- 

 munity, but that the condition does not depend upon it. 



VI. Ehrlich-Wasserman Lateral Chain Theory. 

 — Ehrlich, 1 in his careful studies of the toxins and anti- 

 toxins, finds it convenient to look upon the protoplasm 

 of the body cells as having a complex molecular structure, 

 with lateral chains of different combining powers and 

 affinities for certain specific toxins. He says: "Every 

 antitoxin-producing toxin is specific in the sense that it 

 produces its symptoms by chemical combination of its 

 toxophoric atoms with some cell substance in the body 

 of a susceptible animal." 



Upon this hypothesis, Wasserman 2 has concluded that 

 when a toxin and its specific cell affinity are mixed 

 in a test-tube the mixture should be neutral. He found 

 that when tetanus toxin was mixed in vitro with an 



1 Klinisches Jahrbuch, 1897. * Loc. cit. 



