CHAP. X 



BACILLI ; SPECIAL 



179 



separate again or may go on dividing, remaining united, 

 and thus forming a longer or sliorter filament. Not all 

 bacilli possess motility, many of them being for a time in a 

 resting state. 



The bacilli form a dense resistant pellicle on the surface 

 of the nourishing medium, and in this copious spore- 

 formation takes place. If shaken when growing in a fluid, 



Fig. 52. — From a CuLTiiNE of U.\cillus slbtilis (Hay-Uacillus). 



Various forms between single bacilli and leptothri.x. 



Magnifying power about 700. 



the pellicle falls to the bottom, and soon a new pellicle is 

 formed. 



Spore-formation is independent of any deficiency of 

 nourishing material. The spores are oval, bright, of about 

 0001 to o'oo2 mm. in length, and about o'ooo6 to cooi 

 mm. in thickness. They do not stain in ordinary dyes, 

 and hence form a great contrast to the bacilli. 



This bacillus is very common and widely distributed ; it 



N 2 



