126 ON VARIABILITY AND ADAPTATION 



While acknowledging that these varieties, with rare exceptions, 

 produce in small animals lesions similar to those due to the 

 typical bacillus, he concludes that they are not specific, and that 

 typical and atypical belong to a group possessing similar condi- 

 tions of existence. He notes also that the Bacillus coli communis 

 possesses many natural varieties. Despite this very cautious 

 conclusion, Gaffky (who with Eberth shares the honour of having 

 discovered the typhoid bacillus) criticised Babes severely, and 

 suggested that all his varieties were due to secondary " Ein- 

 wanderung." x To this Babes replied 2 by showing that if 

 so the varieties had wandered in during life, for his autopsies 

 were made upon the fresh corpse very few hours after death. 

 Surely rather than multiply species to the enormous extent that 

 these conclusions would demand it is simpler, as it is more 

 inherently probable, to hold these varieties to be races and of a 

 common origin : races, it may be, produced by the peculiar 

 conditions of the contest between organism and microbe. At 

 the same time I am not prepared to go as far as Arloing, 3 

 who declares that the bacillus of typhoid can be developed from 

 the Bacillus coli communis in the presence of fermenting faecal 

 matter. 



The subject of the bacillus of typhoid cannot be passed over 

 without mentioning also Cassedebat's important paper. 4 The 

 relation of epidemics of enteric fever to the water supply has 

 been so clearly traced that all that was wanting to afford an 

 absolute proof of the relationship was the demonstration of the 

 presence of the specific bacillus in the suspected sources. And 

 this demonstration would seem to have been made by the methods 

 of Vincent, Rodet, Kitasato, Chantemesse and Widal, Thoinot, 

 and yet others. But Cassedebat, working at Marseilles where 

 enteric fever is almost endemic, states that in the water supply — 

 the Durance — he was unable to discover the typical bacillus, 

 although in its place he determined three forms all resembling 

 the bacillus of typhoid in their mode of growth upon potato 

 (which is very characteristic), and in the form of the colonies 

 upon agar-agar plates, all equally polymorphous, and staining 

 with difficulty, all possessing the same movements of transla- 



1 Gaffky, Hygienische Rundschau, 1891, No. 12. 



2 V. Babes, Centralbl. f. Balct. x., 1891, p. 281. 



3 Arloing, International Congress of Hygiene and Demography, London, 1 89 1 . 



4 Cassedebat, Annates de VInst. Pasteur, iv., 1890, p. 625. 



