DESCRIPTION OF SPECIES. 



535 



On potato a similar colour is 

 produced. 



They were isolated from nasal 

 mucus. 



Bacillus subflavus (Zimmer- 

 mann). — Rods 15 to 3 /n in length, 

 •77 ^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. 



BaciUus subtilis (Hay hacillus). 

 — Cylindrical rods as much as 6 m 

 in length. Single forms grow to 

 double their length, and then 

 undergo division. They also form 

 threads which may be composed of 



u 



Fig. 211. — Bacillus Subtilis with 

 Spores (B-vuiiG.iRTEK). 



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 r2 /x 

 long, and -6 /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.— Puee-cultuee of Bacillus 

 Subtilis in Nuteient Gelatine 

 (Baumgaeten). 



Inoculated in the depth of gela- 

 tine, liquefaction occurs rapidly in 

 the track of the needle, and a film 



