in.] CHOLERAIC COMMA-BACILLI. 51 



indefinite time, and when planted in suitable soil germinate 

 again into rods, and these by elongation and transverse divi- 

 sion give origin to two new bacilli, each of which continues 

 to multiply by division. The formation of such spores, 

 possible only under certain favourable conditions, such as 

 free access of oxygen, suitable temperature, and moisture, 

 constitutes the final step in the life-cycle of a bacillus, as it 

 does in that of the higher fungi and higher plants. 



Where owing to the nature of the bacilli or to unfavour- 

 able conditions (such as the absence of free oxygen in the 



S 



FIG. n. FROM A CUITIVATION OF CHOLERAIC COMMA-BACILLI IN LIQUEFIED 

 GELATINE, AFTER SEVERAL WEEKS. 



case of Bacillus subtilis and anihrads] spore-formation 

 does not set in, the bacilli, having multiplied as long as 

 the nutriment lasts, undergo finally a retrograde change, 

 consisting in the breaking-up and disintegration and death 

 of their protoplasm. This is probably due to the poisonous 

 nature of chemical substances produced by the bacilli 

 themselves. Such a culture ultimately becomes devoid of 

 living protoplasm, and is incapable of starting new growths. 

 These conditions are well-known and have been studied 



E 2 



