136 



ESSENTIALS OF BACTERIOLOGY 



Form. Rods with rounded ends about three times as long 

 as they are broad. Usually solitary in tissue-sections, but 

 in old artificial cultures found in long threads. Flagella on 

 all sides (Fig. 58). 



Properties. Very motile. Spores have not been found; 

 they do not liquefy gelatin. 



Growth. They are facultative anaerobic; grow best at 37 

 C., but can also develop at ordinary room temperature. They 

 develop chiefly on the surface, and very slowly. Repeated 



Fig. 58. Bacillus typhi, from an agar-agar culture six hours old, 

 showing the flagella stained by Loffler's method (Xiooo) (Frankel and 

 Pfeiffer). 



freezing and thawing do not affect the vitality of the germ, 

 and phenol in i to 2 per cent, solution has no effect on it. 

 A ten-minute exposure to 60 C. is invariably fatal. 



Colonies on Gelatin Plates. Two forms: the ones near the 

 surface spread out like a leaf, transparent, with bluish fluor- 

 escence. The deeper ones resemble whetstone crystals of 

 uric acid, with the same yellowish tinge (Fig. 59). 



In five days they attain to 3 millimeters in diameter 



