WOUND INFECTIONS 267 



have been living a saprophytic existence. Here it 

 may be necessary to explain that a saprophytic bac- 

 terium is one which exists independently of a living 

 host and which obtains its supply of nutriment from 

 dead animal or vegetable material, while a parasitic 

 bacterium is one which invades the body of a living 

 animal and receives its nourishment at the expense of 



FIG. II. Micrococcus of erysipelas, etc. {Streptococcus pyogenes) ; magnified 

 1000 diameters. 



the tissues and body fluids of its " host." But certain 

 bacteria, like those at present under consideration, 

 may live either as saprophytes or as parasites. 



Their ability to effect a lodgment in the tissues 

 and multiply there, after having led a saprophytic life 

 for some time, is favoured by a reduction in the vital 

 resisting power of the individual as a result of various 



