128 CLINICAL BACTERIOLOGY. 



terium lactis aerogenes, principally from the gas-phlegmons 

 in the neighborhood of the intestinal canal ; (2) a special 

 bacillus the bacillus emphysematosus. (Fig. 45.) This 

 appears in the form of nonmotile, plump rods, forming fila- 

 ments. These are anaerobic, and they stain by Gram's 

 method. They grow slightly in gelatin, without causing 

 liquefaction. In bouillon, and also in agar, they give rise to 

 the formation of fetid gas. This bacillus is but seldom found 

 alone in gas-abscesses, but almost always in association with 

 the ordinary pyogenic cocci. In experiments on animals a 

 severe nonsuppurative inflammation, with gas-formation, and 

 which at times causes death, is induced in guinea-pigs by sub- 



Fig. 45. Bacillus aerogenes capsulatus (from photograph by Prof. Simon Flexner). 



cutaneous injection of this bacterium. That the bacterium 

 coli and the bacterium lactis aerogenes may at times cause 

 gas-phlegmons is not surprising, as it is known that both are 

 active gas-producers, especially in the absence of oxygen. 



In the bacteriologic investigation of a gas -abscess it is 

 always necessary to be prepared for the presence of anae- 

 robic microorganisms, and the choice of a culture -method 

 must be governed with reference thereto. 



Impetigo. This is a peculiar anatomic form of suppura- 

 tion within the layers of the epidermis that leads to the 

 formation of pustules. From the contents of the pustules 

 the staphylococcus pyogenes albus and aureus and the 



