CHAPTER VIII. 

 TIACTERIUM (Microbacterium, Colin). 



BY tliis name Cohn 1 designates a class of minute scliizo- 

 mycetes, which are slightly elongated and oval, or short and 

 cylindrical, with rounded ends. They divide by fission, 

 like the micrococci, the individuals elongating and becom- 

 ing constricted in the middle. They are capable of sponta- 

 neous locomotion, being possessed of a flagellum at one or both 

 ends, with which they perform active spinning and darting 

 movements (Dallinger). Engelmann has shown that these 

 movements are only possible in the presence of oxygen. 

 Bacteria are found also as dumb-bells, i.e. in the act of 

 dividing, and then appear as rods constricted in the middle. 

 Occasionally, after rapid division, several remain connected, 

 thereby forming a short chain. In this state the terminal 

 elements are flagellate. Bacteria, like micrococci, are capable 

 of forming zoogloca, the interstitial gelatinous substance being, 

 as a rule, more copious than in the zooglrea of micrococci. In 

 this state they form pellicles, in which the elements are with- 

 out flagella ; but from the margin of the pellicles one 

 constantly sees elements separating, becoming flagellate, and 

 moving away. In some species the zooglcea is dendritically 

 ramified (Zooglcea ramigera, Itzigsohn), as seen on the surface 

 of fluids containing decomposing algse. 



1. Septic bacteria.- With Cohn we distinguish two kinds : 

 Bacterium tcrmo and Bacterium lineola. 



(a) Bacterium termo. The elements are short and cylindrical, 

 about 0*0015 mm. long, a third less in breadth, and appear 

 generally as du:nb-bells. They are common in putrefying 



' Biologic d. Pjlanzen, ii. (1872), p. 167. 



