360 



TYPHOID FEVER 



colonies present corresponding differences. The former are 

 delicate semi-transparent films, with wavy margin, and are 

 much larger than the colonies in the substance, which appear as 

 small round points (Fig. 110). These appearances, which are 

 well seen on the third or fourth day, resemble those seen in agar 

 plates, as already described in the method of isolation ; but on 

 gelatin the surface colonies are rather more transparent than 



FIG. 109. 



A. Stab culture of the typhoid bacillus in gelatin, five days' growth. 



B. Stroke culture of the typhoid bacillus on gelatin, six days growth. 



C. Stab culture of the bacillus coli in gelatin, nine days' growth"; the gelatin 



is split in its lower part owing to the formation of yas. 



those on agar. Their characters, as seen under a low power 

 of the microscope, also correspond. If a gelatin tube be 

 inoculated and incubated at 37 C., a uniform turbidity is 

 produced (cf. b. coli, p. 351). 



In stroke cultures on agar there is a bluish-grey film of 

 growth, with fairly regular margins, but without any character- 

 istic features. This film is loosely attached to the surface, and 

 can be easily scraped off. 



