348 MICROBIOLOGY 



A FEW COMMON NON,PATHOGENIC SPECIES. 



BACILLUS SUBTILIS COHN. 







Synonyms. Vibrio subtilis Ehrenberg x ; Bacillus subtilis 

 Cohn 2 ; hay bacillus. 



Place in nature. This bacillus is widely distributed in 

 external nature, especially on hay and straw and in the soil. 

 Because of this it is liable to be found in or on almost any 

 article or substance. It is very commonly encountered as a 

 contamination in cultures. It does not possess any disease 

 producing power but it has been reported as a secondary in- 

 vader in suppurative lesions. 



Morphology. Short thick rods with rounded ends. It 

 sometimes appears as filaments and again as chains of long 

 and short rods. It is from 0.8 to 1.2 /A broad, 2.0 to 8.0 ^ long. 

 It possesses from 6 to 8 fiagella. The short forms are actively 

 motile but the thread-like forms are immotile. Oval spores 

 form in the presence of air and they germinate at right angles 

 to long diameter. Spores are set free in about 24 hours. They 

 are from 0.6 by 1.2 /* in size. 



Staining. The vegetative form stains readily with the 

 aniline dyes and the spores by the methods for staining spores. 

 It takes the Gram stain. 



Cultivation. It multiplies readily on all ordinary media. 

 It is an obligatory aerobe. There is considerable difference in 

 the character of the growth especially in bouillon. This sug- 

 gests that there are a number of varieties. The so-called 

 potato bacillus (B. mesentericus) and a number of other 

 aerobic, spore-bearing bacilli widely distributed in nature may 

 belong to a group of bacteria including B. subtilis. 



Agar. A grayish, dry, corrugated growth appears on the 

 surface. 



Gelatin. On this medium the colonies have granular cen- 

 ters and folded margins. Surface growth in stab cultures is 



1 Ehrenberg. Infusionsthierchen als volkommene Organismen. 

 Leipsic, 1838. 



2 Cohn. Beitrage zur Biologie, Bd. I (1872) p. 175. 



