,46 MORPHOLOGY OF THE BACTERIA. 



The petalococcos and petalobacteria of Billroth 

 correspond with the mycoderma of Pasteur. 



4. Swarms. — We have seen that the filiform 

 and spiral bacteria do not, usually, form zooglcea. 

 These microphytes are either disseminated and free, 

 or united in swarms. This formation may be seen, 

 for that matter, in all the bacteria, when, thanks 

 to abundant nourishment, they multiply rapidly 

 and gather together in considerable masses. They 

 are very active in these swarms, whilst in the 

 zooglcea the corpuscles are motionless, because of 

 the intermediary glairy substance. 



Pulverulent precipitate. — When the nutritive 

 elements are exhausted in a liquid, the bacteria 

 cease to multiply, fall to the bottom of the recep- 

 tacle, and the liquid gradually becomes clear. The 

 deposit formed in this manner may acquire a thick- 

 ness very appreciable to the naked eye. The bac- 

 teria which form this precipitate are not dead, but 

 in a state of temporary repose ; and if a new sup- 

 ply of nutritive material is added to the liquid, 

 they are seen to multiply anew, until this has been 

 exhausted (Cohn). 



