IX] BACILLUS 171 



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

 hold that some bacilli possessed of motility are capable of 

 forming a true zoogloea. When one inoculates a fluid 

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

 motile bacillus {e.g. bacillus mesentericus), after keeping it 

 for twenty-four hours in the incubator one notices that the 

 surface of the fluid is covered with a whitish film ; this, as 

 incubation 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. 



Any part of this pellicle examined under the microscope 

 shows itself to be a zooglcea in the true sense of the word, 

 vast numbers of shorter or longer bacilli crossing and inter- 

 lacing and lying embedded in a gelatinous hyaline matrix. 

 As with proteus vulgaris, one occasionally notices at the 

 margin of the mass one or other bacillus wriggling itself free 

 and darting away. And in the case of non-motile bacilli, 

 putrefactive and others, I have also seen distinct formations 

 of zoogloea, having the shape of spherical or oval lumps of 

 various sizes composed of a hyaline jelly-like matrix, in which 

 are embedded the baciUi in active multiplication. 



In those species in which the bacilli are capable of forming 

 leptothrix (leptothrix buccalis, hay-bacillus, anthrax-bacillus) 

 the filaments may form dense convolutions. When in these 

 convoluted filaments spores are formed, and the sheaths of 

 the filaments swell up and become agglutinated into a 

 hyaline jelly-Hke substance, the spores appear to form a sort 

 of zoogloea. 



Bacilli are killed by drying, but it is necessary to bear in 

 mind that they must be exposed to the drying process in 

 thin layers (Koch). At the temperature of boiling water 



