46 QUATERCEt^TENARY STUDIES IN PATHOLOGY 



appear to show that this antitoxin is capable of neutralising the toxin, 

 either when mixed with it or when the serum is injected twenty-four 

 hours before the toxin, and when the two substances are injected at 

 different parts of the body. 



It seems doubtful whether it will be possible to maintain a hard 

 and fast line of demarcation between the toxins proper and the endo- 

 toxins. The injections of emulsions of bacilli from agar, as well as of the 

 toxic filtrates from broth cultures, may, in certain cases, stimulate the 

 animal organism to the production of an antitoxic serum as was shown 

 in the Laboratory here, by Todd (1904), in the case of the B. dysenteriae 

 of Shiga. The view that it is a general biological law, as stated by Kolle, 

 that the injection of endotoxins into the animal body does not stimulate 

 to antitoxin production, cannot be unreservedly accepted, but must 

 be subjected to further investigation. 



Whether the toxin and antitoxin in the case of plague differs or not 

 essentially from those obtained in the case of diphtheria and tetanus, 

 it must be admitted that it is impossible to obtain them in anything like 

 the same degree of concentration. 



The neutralisation of toxin by the antitoxin in vitro is not due to the 

 occurrence of a precipitin reaction. The serum of a horse giving a much 

 greater precipitum with a particular toxin may possess a much lower 

 antitoxic value than the serum of a horse which gives a much smaller 

 precipitum with the same toxin. The fact that the neutralisation also 

 takes place in vivo is against the view that a precipitin reaction plays a 

 part in the phenomenon, for Rostoski, Michaelis and Oppenheimer 

 (1902), showed that this reaction never takes place in the blood of 

 the living animal. 



So far as has been demonstrated experimentally, antitoxic and 

 bacteriolytic actions play little part in the protection afforded by the 

 anti-plague serum. The action of the serum can probably be best 

 interpreted as follows : — The serum acts, not by any influence on the 

 cells of the animal body, but directly on the bacilli, which, after being 

 submitted to its action, no longer repel but rather attract the leucocytes, 

 by which the microbes are then englobed and digested. This was first 

 shown in the case of the B. pestis by Markl. 



The change in the microbe has been expressed by stating that the 

 immune serum converts the negative chemiotaxis of the bacillus into 



(ISO) 



