520 COLLECTED STUDIES IN IMMUNITY. 



different kind of poison than the Marburg culture. But this proved 

 not to be the case, for v. Behring demonstrated that his tetanus poison 

 when injected into rabbits in large quantities suffers a considerable 

 diminution in toxicity. On testing the properties of the poison 

 contained in the serum of the poisoned animals he found that this 

 residual poison possessed the same constants as Tizzoni's poison. 

 From this it follows that v. Behring's poison contained also a cer- 

 tain proportion of the Tizzoni variety. The Marburg culture must 

 therefore have produced two varieties of poison at the same time. 

 Naturally by mixing the two poisons one can obtain new poisons 

 which, while they manifest the same action on mice, will have any 

 desired relative toxicity for rabbits; this, of course, within certain 

 limits. If one were to take the time and trouble to examine a large 

 number of native poisons from different laboratories, corresponding 

 differences between them would probably be encountered. 



If we recollect that various specimens of the chemically simple 

 poisons manifest the same relative toxicity on different animals, 

 and then consider the behavior of tetanus toxins as just described, 

 we shall conclude that bacterial poisons of different origin, which 

 manifest a variation in their relative toxicity, are not of simple con- 

 stitution, but are made up of several different constituents. It 

 shows very little knowledge of the subject therefore when Gruber 

 says: " v. Behring shows that two. toxin solutions, which in a given 

 unit of volume contain equal f Ms., i.e., whose unit of volume kills 

 a like number of grammes of mouse in four days, may have an entirely 

 different content of f rabbit, t pigeon, t goat, and f horse. This 

 at once disposes of Ehrlich's conclusions." It is just such phenomena 

 which argue in favor of the plurality of poisons; they do not speak 

 against it. 



Gruber bases another of his objections on the interesting obser- 

 vations made by Madsen and Dreyer on toxons (Zeitsch. f. Hygiene, 

 Vol. 37, page 251). In his dictatorial manner he says that " these 

 observations demonstrate conclusively that Ehrlich's method of 

 analyzing toxins is absolutely useless. Only a person ignorant of 

 chemistry could maintain that the different results in guinea-pigs 

 and in rabbits are sufficiently explained by the different susceptL 

 bility of the animals to the toxins." 



To begin, Gruber's premise is absolutely misleading, when he 

 says: 



" But if the poison is neutralized it will be without effect even 



