INFECTION. 83 



cially by Hallier, Zurn, etc., as in scarlatina, epidemic diarrhoea, 

 typhus, glanders, rinderpest, syphilis, gonorrhoea. 



II. The Second Group of Cohn, the Mickobacteeia. — We have 

 here the single genus bacterium. Cells cylindrical or elliptical, 

 free, or united in pairs during their division, rarely in fours, never 

 in chains, sometimes in zooglgea, having spontaneous movement, os- 

 cillatory and very active, especially in media rich in alimentary 

 material and in the presence of oxygen. 



As with the spherobacteria, we might divide the rod-bacteria 

 into three groups : first, those of putrefaction, B. termo, lineola : 

 second, those of lactic acetic fermentation ; third, the pigment-bac- 

 teria of colored milk and pus. 



B. termo is the most common of all varieties. They are cylin- 

 drical cells, slightly swollen in the middle, isolated, sometimes united 

 in pairs, two to five times as long as wide. Movements oscillatory. 



They can easily be produced in all infusions of animal and vege- 

 table substances. This bacterium is said to have cilia or hair-like 

 projections from each end of the rod. 



It is the veritable agent and first cause of putrefaction, and 

 hence is to be found in all cadavers where this process has com- 

 menced. 



B. lineola is larger and found in various animal and vegetable 

 infusions, but is not definitely known to cause a specific fermenta- 

 tion. 



The other forms of lactic and acetic fermentation are not of es- 

 pecial pathogenetic interest. 



III. Desmobacteria. — This group of Cohn's is of especial inter- 

 est, as it contains the specific germ of anthrax, that germ upon which 

 the germ-infection theory of disease largely depends for support. 



They are filiform bacteria, composed of elongated articulations, 

 isolated, or in chains more or less extended, and resulting from trans- 

 verse division. (In this form they correspond to leptothrix, but 

 differ from torula in that the filaments are not constricted at the 

 point of articulation.) They may be motionless or not, dependent 

 upon the presence or absence of oxygen, the reaction of the medium 

 which contains them, and other unknown conditions. Some forms 

 never exhibit movement. 



We have here but one germ to consider — bacillus. 



The bacilli are characterized as slender filaments, straight, short, 

 or of moderate length, rigid or flexible, and as being with and with- 

 out movement. One species is a pigment bacteria. 



Bacillus subtilis. — Yery slender elongated filaments formed of a 



