QUALITATIVE BACTERIOLOGICAL ANALYSIS. 109 



apparatus is then incubated at 37 C. ; the next day, or at 

 latest after thirty to thirty-six hours, the milk will be found 

 changed in a characteristic manner. The cream is torn or 

 altogether dissociated by the development of gas, so that the 

 surface of the medium is covered with stringy, pinkish-white 

 masses of coagulated casein, enclosing a number of gas bubbles. 

 The main portion of the tube formerly occupied by the milk 

 now contains a colourless, thin, watery whey, with a few casein 

 lumps adhering here and there to the sides of the tube. When 

 the tube is opened the whey has a smell of butyric acid, and is 

 acid in reaction. Under the microscope the whey is found 

 to contain numerous rods, some motile, others motionless." 



The microbe, when obtained from a typical milk culture, con- 

 sists of rods, measuring from 1'6 to 4*8 ju in length and 0'8 u. 

 in breadth ; it may form short chains. In respect of length 

 and thickness the bacilli closely resembles the B. aiithracis ; 

 they are distinctly thicker than the bacilli of malignant oedema. 

 The bacilli form spores, but they are not seen in the milk 

 cultures; in liquefying gelatine cultures, in serum cultures, 

 and in the subcutaneous exudation from inoculated animals, 

 spores under certain conditions are readily formed. When 

 fully developed they are oval bodies, 1'6 fj. in length, and 

 as much as I/O n or even 1'2 /u in thickness. The B. enteritidis 

 sporogenes is pathogenic; if 1 c.c. of the whey produced 

 in the milk culture be injected into the groin of a guinea-pig, 

 weighing from 200 to 300 grammes, swelling appears in the 

 groin after six hours, which gradually extends on to the abdomen 

 and thigh, usually the animal is found dead after eighteen to 

 twenty-four hours. The skin then will be found separated from 

 the muscles over a considerable area, and the subcutaneous 

 tissue gangrenous, containing an offensive sanguineous 

 exudation. If the examination is made immediately after 

 death the exudation will be found to contain numerous 

 cylindrical bacilli ; but if the examination is deferred for 

 twenty-four hours, large, oval or egg-shaped spores will be 

 found, both free in the fluid and at the end of the bacilli. The 

 microbe grows well in 2 per cent, glucose-agar under anaerobic 

 conditions. In this medium there is very marked gas formation ; 

 the colonies in the depth are round, white in reflected light, 



