616 BACTERIOLOGY OF THE SOIL, WATER, AND AIR 



Morphology. Rod-shaped organisms with rounded ends, occurring 

 usually in chains of greater or lesser length. The individual cells 

 measure from 0.7 to 1.2 microns in diameter, and vary in length from 

 2.5 to 9 microns. The members of the group are actively motile prior 

 to sporulation and possess numerous peritrichic flagella. No capsules 

 are formed, but spore formation is a characteristic feature of the group. 

 The morphological details of spore formation and spore germination 

 are relied upon largely to distinguish the various members of the 

 group, but these details are of no practical significance in this dis- 



cussion. 



Isolation and Culture. The organisms of the Subtilis-Mesentericus 

 Group grow with great luxuriance upon ordinary cultural media. The 

 colonies on agar are irregular in shape, opaque, and spread rapidly. 

 Gelatin colonies are similar in appearance and the medium is rapidly 

 liquefied. Blood serum and casein are also liquefied. Milk is coagu- 

 lated and the coagulum dissolves; the reaction, at first slightly acid, 

 soon becomes alkaline as a rule. Indol, ammonia in considerable 

 amounts, 2 hydrogen sulphide and other products of protein decom- 

 position are formed in dextrose-free media and cultures of the organisms 

 contain very powerful soluble proteases. The addition of dextrose 

 to such media definitely prevents the formation of such proteases, 

 however. 3 



As a rule the Subtilis-Mesentericus bacilli are non-pathogenic, but 

 Silberschmidt 4 and others have described a type of ophthalmia in 

 Switzerland, apparently incited by Bacillus subtilis, and Spiegelberg, 5 

 Fliigge, 6 Ardoin 7 and more recently Vincent 8 have presented evidence 

 in favor of the view that the organisms may become temporarily 

 localized in the intestinal tract and incite severe gastro-intestinal 

 disturbances. 



It is stated that Bacillus subtilis differs from Bacillus mesentericus 

 and other members of the group in its inability to ferment dextrose. 

 The other varieties form acid but no gas from this sugar. 



The foregoing observations have shown that the normal bacterial 

 flora of the soil plays. a prominent part in agriculture; it transforms 

 dead unavailable organic matter and certain minerals as well into 



1 Gottheil, Centralbl. f. Bakt., 1901, vii, II Abt. Arthur Meyer, Practicum d. botan- 

 ischen Bakterienkunde, Jena, 1903. Chester, Delaware College Agricultural Expt. 

 Station, Ann. Kept., 1902-1903. 



2 Kendall, Day and Walker, loc. cit. 3 Kendall and Walker, loc. cit. 



4 Ann. Inst. Past., 1903, xvii, 268. 5 Jahrb. f. Kinderheilk., 1899, xlix, 194. 



6 Ztschr. f. Hyg., 1894, xvii, 272. " These de Paris, 1898, p. 78. 



8 Intestinal Toxemia in Infants, 1911. 



