1 68 



:\IICRO-ORGAXISMS AND DISEASE [ch. ix 



mass of protoplasm not more than o'5 or o'S ju, in diameter to 

 tliat of a cylinder or rod several times as long as it is thick. 

 In some species (e.g. stained tubercle-bacilli) the elements 

 of a chain are almost spherical. There are, on the other 

 hand, other species (t'.^T. bacillus typhosus) where the ele- 

 ments are always rods or cylinders. In these cases of short 

 bacilli it sometimes becomes difficult to say whether an 



-Chains of Bacilli (Bacilli's FilamentosL's) in a Stainkd Film 

 Speclme.v. 



individual is or is not a bacillus, but the growth of the 

 bacilli into cylinders and leptothrix, and particularly their 

 pjower of forming spores, is decisive, although neither of 

 these events may happen, owing to peculiar conditions. 



Flagella and motility of bacilli have been treated in a 

 former chapter, and we need therefore not specially further 

 concern ourselves about them. 



Not all bacilli are capable of forming leptothrix-filaments. 



