NATURE OF ANTITOXIC ACTION. 475 



into an animal, no symptoms take place. This shows that after 

 a time neutralisation is complete. These facts are practically 

 conclusive in favour of toxin neutralisation depending upon a 

 chemical union, and such a view would also throw light on the 

 otherwise somewhat puzzling fact that while, e.g. by lapse of 

 time, the toxicity of a toxin may become diminished, it may still 

 require the same proportion of antitoxin to neutralise it as it did 

 before. On the chemical theory this, according to Ehrlich, is 

 due to the disintegration of the toxophorous atom-group of the 

 toxin molecule {vide pp. 179, 478), while the combining (hapto- 

 phorous) group still remains unaltered. Quite analogous cases 

 could be cited from pure chemistry. 



The evidence usually brought forward against the chemical union of toxin 

 and antitoxin rests chiefly on certain observations of Buchner and of Calmette, 

 and to these a reference must be made. Buchner, in a series of experiments, 

 came to the conclusion that it was possible to make a mixture of tetanus toxin 

 and antitoxin which was neutral to the mouse, but which could produce a fatal 

 result in guinea-pigs. It is to be noted, however, that the mixture used in his 

 experiments was not quite neutral to mice, and this circumstance, along with 

 the fact that the guinea-pig, weight for weight, is more susceptible to this toxin 

 than the mouse, may explain the result. In any case these experiments as 

 they stand cannot be considered to constitute a real objection. Calmette found 

 that the antitoxin to snake venom was more easily destroyed by heat than the 

 toxin, and stated that when a neutral mixture of the two was heated at a 

 temperature sufficient to destroy free antivenin, the toxic properties in part 

 returned. Hence he concluded that the two bodies existed in an uncombined 

 condition in the mixture. Martin and Cherry, however, on repeating these 

 experiments, found that the above result was not obtained if sufficient time for 

 complete combination was allowed ; but if this precaution was not taken, then 

 the presence of the free toxin was revealed when the antitoxin was destroyed 

 by heat. Even, however, if Calmette's results were quite correct, they cannot 

 be considered to constitute a proof that chemical union does not occur : they 

 would only prove that the toxin has not been destroyed. If two complicated 

 chemical compounds of unequal stability are in loose chemical union, it is 

 quite conceivable that the less stable may be destroyed (e.g. by heat) whilst 

 the more stable escapes. 



The next question to be considered is the source of antitoxin. 

 The following three possibilities present themselves : {a) antitoxin 

 may be formed from the toxin, i.e. may be a "modified toxin " ; 

 {b) antitoxin may be the result of an increased formation of 

 molecules normally present in the tissues ; {c) antitoxin may be 

 an entirely new product of the cells of the body. It can now be 

 stated that antitoxin is not a modified toxin. It has been shown, 



