BACTERIACE^E : THE SPOROGENIC AEROBES 



269 



membrane is produced, so characteristic that the name "mesen- 

 tericus" was applied to this species. It is not pathogenic. 



Bacillus Subtilis. Bacillus subtilis, or the hay bacillus, is 

 abundant in the soil and on the surface of plants, and common 

 in surface waters and in the air. It is readily obtained by boiling 

 hay in water and then setting the infusion aside for a few days. 

 The cell is relatively large, about 1.2," wide by 5^ long, with 

 ends somewhat rounded. Long threads are commonly formed. 

 It is motile with peritrichous flagella. Large oval median spores 



FIG. 107. Bacillus subtilis. Xiooo. 



are formed without distortion of the cell and these are almost 

 as resistant as the spores of the potato bacillus. B. subtilis 

 grows rapidly on ordinary media in the presence of air, best at 

 about 30 C. Gelatin is liquefied and milk is digested. The 

 organism is typically saprophytic, but it has been found growing 

 in the intestine by some investigators, and has been found in a 

 few instances in infections of the human eye, cases of pan- 

 ophthalmitis following injury. 1 



1 Silber schmidt: Annales de V I nstitut Pasteur, 1903, Vol. XVII, pp. 268-287; 

 Also see Kneass and Sailer: Univ. Penn. Med. Bull., June, 1903, Vol. XVI, pp. 



