8 BACTERIA 



commonly met with in this form in clinical examinations, and in 

 cultures. Hence, we frequently hear of the bacillus of tubercu- 

 losis, and not the Mycobacterium tuberculosis. 



Among the higher bacteria, the differentiation of those belong- 

 ing to the sheathed group, or Chlamydobacteriacea, is difficult, as it 

 depends largely upon the formation of the false branching and 

 the gonidia. When bacteria exhibit many, or various forms, 

 in the same culture, as does the typhoid bacillus, we speak of 



FIG. 5. Spirochaeta of relapsing fever. (Kolle and Wassermann.) 



them as pleomorphic, or as showing pleomorphism. To eluci- 

 date: Man is pleomorphic, because among adult individuals 

 some are tall or short, fat or thin. 



Involution or Degeneration Forms. When the best or opti- 

 mum conditions for bacterial life (see page 18) are not found, 

 bacteria present appearances quite different from those of the 

 young, active or perfect adult type. These changes are called 

 involutionary if temporary, or degenerative if permanent. 

 For example: the diphtheria bacillus under good conditions for 

 life is a straight or slightly bent rod staining in a granular manner. 



