576 



PATHOGENIC MICROORGANISMS 



described in this connection. It is of importance to workers with patho- 

 genic bacteria, because of the frequency with which it is found as a 

 saprophyte or secondary invader in chronic suppurative lesions. 



Morphology. Straight rod, 2 to 8 micra long, 0.7 micron wide. Spores 

 formed usually slightly nearer one pole than the other. Grows in long 

 chains and only in such chains are spores found. It does not decolor- 

 ize by Gram's method. Is actively motile in young cultures in which 



FIG. 125. BACILLUS SUBTILIS. (Hay Bacillus.) 



the bacilli are single or in pairs. In older cultures chains are formed 

 and the bacilli become motionless. Gelatin is liquefied. On gelatin 

 and agar the bacilli grow as a dry corrugated pellicle. Microscopically, 

 the colonies are made up of interlacing threads, being irregularly round 

 with fringed edges. There is a tendency to confluence. The bacillus 

 is found in brackish water, infusions of vegetable matter, etc., and is 

 practically non-pathogenic, occurring only occasionally as a saprophyte 

 in old sinuses and infected wounds. 



