420 BACTERIOLOGY. 



infection, as they are absent from cultures of certain 

 highly pathogenic bacteria. 



In some instances the production of the poisonous 

 principles, even under artificial conditions of cultiva- 

 tion, is of a most astonishing nature, and poisons result 

 that, in the degree of their toxicity, exceed anything 

 hitherto known to us. For instance, the potencies of 

 the poisons that have been isolated from cultures of the 

 bacillus diphtherias and the bacillus of tetanus have been 

 carefully determined by experiments upon animals, and 

 it has been found that 0.4 milligramme of the former is 

 capable of killing eight guinea-pigs, each weighing 400 

 grammes, or two rabbits, each weighing three kilo- 

 grammes (Roux and Yersin 1 ) ; and that 0.0001 milli- 

 gramme of the latter will produce tetanus in a mouse, 

 with all the characteristic manifestations of the disease 

 (Brieger and Cohn 2 ). 



In short, infection may be best conceived as a contest 

 between the invading organisms on the one side and the 

 resisting tissues of the animal body on the other, the 

 weapons of offense of the former being the poisonous 

 products of their growth, the toxins, and the means of 

 defense possessed by the latter being substances which 

 are, so to speak, antidotal to these poisons. To these 

 substances possessed by the animal body for resisting 

 infection the name "alexines" has been given by Buch- 

 ner, while the name " defensive proteids " is suggested 

 by Hankin. If the tissue elements are not of sufficient 

 vigor to neutralize the bacterial poisons, the bacteria are 

 victorious, and infection results, while, if there be failure 

 to establish a condition of disease, the tissues are vic- 



1 Annales de 1'Institut Pasteur, tome iii., 1889, p. 287. 



2 Zeitschr. fur Hygiene u. Infektionskrankheiten, 1893, Bd. xv., Heft i. 



