ix.] BACILLUS. 99 



thickness of the bacilli; some (e.g. bacillus amylobacter, 

 and some species occurring in ordinary putrefaction) being 

 several times as thick as others, like hay-bacillus, anthrax- 

 bacillus, &c. 



Many bacilli and bacillus-filaments (e.g. hay-bacillus, an- 

 thrax-bacillus) degenerate on growing old, the protoplasmic 

 elements becoming granular and breaking down altogether 

 into debris. This may occur to single elements within a 

 chain or leptothrix ; and then the corresponding part of the 

 sheath of the chain, owing to the subsequent disappearance 

 of the debris, becomes empty and devoid of protoplasm. 

 Longer or shorter portions of a chain or leptothrix may thus 

 degenerate and become deprived of protoplasm, the sheath 

 only persisting. These portions become at the same time 

 thicker, the sheath having swollen up. 



Another mode of degeneration consists in the elements 

 and sheath curling up, swelling up, and ultimately breaking 

 down into debris. According to Cohn, 1 bacilli do not form 

 zooglcea in the same way as micrococcus and bacterium do. 

 With all due deference to the authority of Cohn, I must hold 

 that the bacilli possessed of a flagellum are capable of 

 forming a true zooglcea. When one inoculates a fluid- 

 nourishing medium (e.g. broth) with hay-bacillus or other 

 motile bacillus of common putrefaction, after keeping it for 

 twenty-four hours in the incubator one notices a uniform 

 turbidity. After several days one notices that the surface of 

 the fluid becomes covered with a whitish film ; this, as in- 

 cubation goes on, thickens into a thick resistant not very 

 friable pellicle. By shaking the fluid the pellicle becomes 

 detached from the glass wall and sinks to the bottom of the 

 fluid ; after another day or two a new pellicle is formed, and 

 so on until the material is exhausted. 



1 Beitr. z. Biologie d. Pflanzen, vol. i?. 



H 2 



