130 ESSENTIALS OF BACTERIOLOGY 



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

 ficial cultures found in long threads. Flagella on the side. 



Properties. They are very motile; they take the anilin dyes 

 less deeply than some similar bacilli. Spores have not yet 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. All 

 nutrient media can be used as culture-ground. They develop 

 chiefly on the surface, and very slowly. Repeated freezing and 



Fig. 66. Bacillus typhi, from an agar-agar culture six hours old, showing the 

 flagella stained by Loffler's method (x 1000) (Frankel and Pfeiffer). 



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. 



In five days they attain to 3 millimeters in diameter. 



On Potato Gelatin. The colonies do not have the yellow 



