170 SPECIAL BACTERIOLOGY 



The bacilli are easily detected in the tissues, especially in pieces of the 

 liver or spleen, where they can be observed massed together in charac- 

 teristic clumps when stained with carbol fuchsin at the ordinary room 

 temperature, or at 40 to 45 C., washed in absolute alcohol, cleaned in 

 xylol, and mounted in xylol balsam. Alkaline methylene blue can also 

 be used. The characteristic clumps in the tissues consist of small ovals 

 or rods closely packed together, individual bacilli being often only visible 

 at the periphery of the mass, usually in the neighbourhood of a capillary. 



Biological Characters. It grows at any temperature between 20 

 and 38 C. on the ordinary nutrient media. The growth is most 

 luxurious at incubator temperature, while at ordinary room temperature 

 the development is very slow. It also grows both with and without 

 oxygen (facultative anaerobe), and fairly well in CO 2 ; and as a contrast 

 to most other pathogenic bacteria, grows luxuriantly on slightly acid 

 media. 



On Gelatine Plates the deep colonies are small, punctiform, and sharply 

 circumscribed ; under a low power they exhibit a brownish colour. The 

 superficial colonies are much larger, forming a bluish-white, iridescent, 

 fine coating with irregular borders, denser in the centre than at the 

 periphery, and under a low power exhibit a brownish colour and wrinkled 

 appearance. The gelatine is not liquefied. 



In Gelatine Stab Cultures the growth is mostly limited to the surface, 

 with limited, thready, granular growths down the track of the needle, 

 often of a yellow or yellowish-brown colour (see Photograph, Fig. 6l). 



On Gelatine Stroke Cultures a fine, iridescent, bluish growth extends 

 from the centre, and soon covers the whole surface of the gelatine. 

 The gelatine is not liquefied. 



On Agar and Blood Serum Media an extrusive, thick coating develops 

 which presents no typical characteristics. 



On Potato. The growth upon the surface of a cut potato appears as 

 if nothing had developed ; but if examined, it will be found that the 

 whole surface of the potato is covered with tufts, which, when examined 

 microscopically, will be found to consist of numerous motile rods. This 

 peculiarity of growth occurs, as far as is known at present, exclusively in 

 this bacillus. Sometimes, though rarely, the growth is visible, for there 

 are some kinds of potatoes upon which the bacilli developed a raised 

 circumscribed tuft of a yellowish or brownish colour. These potatoes 

 possess either a neutral or alkaline reaction, while the typical growth is 

 confined to those exhibiting an acid reaction. 



In Milk Media an acid reaction results from the growth without 

 causing coagulation, whereas the coli commune causes an acid reaction 

 and coagulation in twenty-four to forty-eight hours at 37 C. 



Bouillon is clouded, with a quantity of sediment and slightly acid 

 reaction. 



