678 



NON-PATHOGENIC BACILLI. 



ter and not very rapid. Grows rapidly at the room temperature better at 

 30' C. Development may occur at any temperature between 10 and 45 C. 

 Spore formation is favored by a temperature of 30 C. The spores ger- 

 minate most readily at 30 to 40 C. The exosporium is ruptured at one 

 side of the long-oval spore, and the newly formed bacillus takes its exit from 

 this opening in a direction perpendicular to the long axis of the reproductive 

 element. The spores have great resistance to heat and to chemical agents. 

 By boiling a hay infusion for a short time a pure culture may often be ob- 

 tained, as other microorganisms present are killed, while the spores of Ba- 

 cillus subtilis survive and subsequently germinate. Upon gelatin plates 

 small, white colonies are first developed, which under the microscope are 

 seen to be slightly granular, somewhat irregular in outline, and of a green- 

 ish tint; development progresses very rapidly, and liquefaction of the sur- 

 rounding gelatin is quickly induced, forming saucer-like cavities with gray- 

 ish, translucent contents ; the central portion is white and opaque ; frequently 



8 



FIG. 226. Bacillus subtilis; A, bacilli; B shows formation of spores; C shows the germina- 

 tion of a spore, a, and development of a short rod, /, and subsequently of a longer filament, h. 

 X 1,020. (Trazmowski.) 



a radiate appearance of the bacterial growth is observed ; under the micro- 

 scope a dense, grayish-yellow central mass is seen, arid around this a tangled 

 network of filaments and of rods undergoing the characteristic waddling 

 movements ; at the -margins the filaments are seen to radiate into the non- 

 liquefied gelatin, forming a crown-like aureole. In gelatin stick cultures 

 liquefaction quickly occurs along the entire line of puncture ; later a dense, 

 dry. and friable mycoderma forms upon the surface, and the gelatin below, 

 which was at first filled with whitish flocculi, becomes clear as a result of 

 their deposition at the bottom of the tube. Upon the surface of agar a 

 wrinkled, white layer is developed which is easily lifted entire from the cul- 

 ture medium. Blood serum is liquefied by this bacillus, and a wrinkled myco- 

 derma forms upon the surface. Upon potato the entire surface is soon cov- 

 ered with a cream-like, white layer, which in a short time contains an abun- 

 dance of spores. 



