DESCRIFHON OF SPECIES. 



535 



On potato a similar colour is 

 produced. 



They were isolated from nasal 

 mucus. 



Bacillus subflavus (Zimmer- 

 mann). Rods 1-5 to 3 p. in length, 

 '11 fj. in width, and in chains. Motile. 



Colonies prominent, yellowish- 

 white. 



On the surface of gelatine they 

 form a yellowish-grey layer, and 

 on the surface of agar and potato 

 the growth is yellow. 



They occur in water. 



Bacillus subtilis (Hay bacillus). 

 Cylindrical rods as much as 6 /x 

 in length. Single forms grow to 

 double their length, and then 

 undergo division. They also form 

 threads which may be composed of 



FIG. 



211. BACILLUS SUBTILIS 

 SPORES (BAUMGARTEN). 



long rods, short rods, and cocci. 

 They are motile, and provided with 

 a flagellum at each end. If the 

 nourishing medium is impoverished, 

 the multiplication of the rods by 

 division gradually ceases, and spore- 

 formation commences. The rods 

 become motionless, and a dark spot 

 is visible, either in the middle or 

 towards one end. This gradually 

 develops into a shining spore with 

 a dark outline. The rods swell 

 slightly during this process ; their 

 contour becomes undefined, and 

 soon disappears entirely ; spores 

 being set free in about twenty- 

 four hours. The spores are 1'2 p. 

 long, and *G /x broad. They develop 

 into rods in the following way : 

 On one side of the spore a swelling 

 appears, at the summit of which 

 an opening in the spore-membrane 

 results, and the germ escapes ; this 

 lengthens into a rod, and remains 

 for a time attached to the empty 

 spore-membrane. 



The spores are widely distributed, 

 and occur in the air, soil, dust, etc. 

 On the excrement of herbivorous 

 animals the bacilli form a white 

 efflorescence, and a thick crumpled 

 skin on liquid manure. 



They flourish equally in liquids 

 and upon damp, solid, nourishing 

 media. They are aerobic ; depriva- 

 tion of oxygen causes the growth 

 of the bacilli to cease, and the rods 

 degenerate. 



In plate-cultivations the colonies 

 are white, and, under a low power, 

 granular and irregular in outline 

 and faintly-greenish. Liquefaction 

 sets in, producing depressions like 

 saucers. The centre is opaque, and 

 is surrounded by a network of 

 filaments, which extend into the 

 gelatine surrounding the colony. 



FIG. 212. PURE-CULTURE OF BACILLI'S 

 SUBTILIS IN NUTRIENT GELATINE 

 (BAUMGARTEN). 



Inoculated in the depth of gela- 

 tine, liquefaction occurs rapidly in 

 the track of the needle, and a film 



