44 MILK AND THE PUBLIC HEALTH ch. m 



are for the most part shorter and thicker. Injected into 

 animals, most of them, like the butter bacillus, exert 

 pathological effects with the production of nodules resembling 

 tubercles. The characteristic which essentially differentiates 

 them from the tubercle bacillus is their comparatively rapid 

 growth on culture media. Their growth in days exceeds that 

 of the tubercle bacillus in the same number of weeks. They 

 will also grow at room temperatures. 



As a group, these bacilli have a somewhat lessened re- 

 sistance to decolorisation by mineral acids as compared with 

 the tubercle bacillus. According to Abbott and Gildersleeve 

 they lose their colour almost instantly if treated by the 25 to 

 30 per cent nitric acid solution used in the original Koch- 

 Ehrlich process. 



