IMMUNITY AND SUSCEPTIBILITY. 135 



of affecting mice, were injected into guinea pigs they 

 died of tetanus ; therefore, the tetanus toxin was not 

 destroyed. Roux and Vaillard have also found that 

 similar " neutral mixtures," which failed to cause symp- 

 toms in healthy animals, sometimes did so in diseased 

 animals of the same species. 



In his investigations upon serpents' venom Calmette 

 found the protective value of the serum was destroyed at 

 temperatures causing coagulation (about 68° C), while 

 the venom was able to endure temperatures of 70 , 8o°, 

 and even 90 C. When a mixture of venom and anti- 

 veuene was proportioned so as to be harmless for rabbits, 

 it was found that this mixture, if heated to the degree at 

 which the antivenene was discharged, again became 

 poisonous so that the heated mixture killed rabbits. 

 Calmette used these observations to show that the action 

 was not a chemic one, but it may be that certain im- 

 portant considerations were neglected, for Martin and 

 Cherry l found that this return to toxicity only took place 

 when the venom and antivenene were mixed and imme- 

 diately heated. If the mixture was allowed to remain 

 for a short time in the incubating oven at the tempera- 

 ture of 37 C, then heated to 68° C. and injected into 

 rabbits, the animals did not die. These observers, there- 

 fore, conclude that the reaction between the venom and 

 antivenene is a chemic one which is stimulated by heat 

 and requires time for completion. 



Concerning the effects of toxin-antitoxin mixtures upon 

 the body, Mikanorow 2 reasoned that if toxin produced 

 antitoxin by stimulating the cells to produce an anti- 

 dote, neutral mixtures should not only be harmless for 

 the animal, but, in case the toxin is changed by the 

 antitoxin, should leave no immunity behind it. If, how- 

 ever, the antitoxin stimulates the resisting power of the 

 cells, the simultaneous introduction of toxin and anti- 

 toxin should increase resistance. By frequent adminis- 



1 British Med. Journal, 1898, II., p. 1 1 20. 



1 Archiv fiir biol. IVissensckaft, 1897-1898, Bd. vi., p. 56. 



