x.] BACILLUS. 115 



has the same morphological characters as regards length 

 and thickness of the rods, as regards power to form lepto- 

 thrix, and as regards motility, as the bacillus subtilis. It 

 is capable of forming zooglcea, and is anaerobic, since it 

 grows well and forms spores copiously even when not ex- 

 posed to the air. After the rods have gone on dividing and 

 forming chains and filaments for some time, they swell up, 

 become granular and oval with more or less pointed ends, 

 and the formation of oval spores sets in. In this state the 

 oval rods are about 0*002 to 0*003 mm - thick, and the spores 

 are about 0*002 to 0*003 mm - l n g an ^ 0*001 mm. thick. 

 In solutions of starch, dextrin, or sugar the bacillus forms 



FIG. 51. CLOSTRIDIUM BUTYRICUM, OR BACILLUS BUTYRICUS. 

 Some of the spindle-shaped forms include an oval spore. 



butyric acid. The fermentation of butyric acid in old milk 

 and ripening cheese is due to this bacillus. Cellulose is de- 

 composed by it, and hence its great importance in the diges- 

 tive process of herbivorous animals, in whose stomach and 

 intestine it is very common. It is very common also in 

 substances containing starch. 



Iodine produces a characteristic blue staining in the pro- 

 toplasm of the bacillus. In young rods the colour produced 

 by iodine is blue, in older rods it is violet. 



E. Kern described {Biolog. Centralbl. ii. p. 135) a bacillus 

 under the name of dispora caucasica, which he found in the 



I 2 



