516 A MANUAL OF BACTERIOLOGY 



individuals are Gram-negative. In the exudate it is 

 capsulated, but the capsule is lost under cultivation 

 except in serum, and the organism spores freely, the 

 spores being large and ovoid and central or sub-terminal. 

 Under cultivation, spores are formed only in media rich 

 in protein and poor in fermentable sugar, e.g. serum, fluid 

 or coagulated. The spores are oval in shape, relatively 

 large and sub-terminal or central in position. 



Cultural characters. The B. perfringens grows well 

 anaerobically on all the ordinary culture media, slowly 

 at 20 C., rapidly at blood-heat, but heavy implantations 

 are usually necessary for success. It forms greyish -white 

 colonies on agar, and gelatin is liquefied. In glucose- 

 broth it produces at first a diffuse cloudiness, but later 

 the fluid becomes clear and a whitish viscid sediment 

 settles. Milk is coagulated with a strong odour of butyric 

 acid, the casein forming a thick, stringy, honey-combed 

 mass on the surface of a clear watery whey (Plate 

 XVIII, c) ; growth ceases after a few days and no spores 

 are formed. On potato the growth is almost invisible. 

 There is abundant formation of gas in culture media, the 

 gas both in dextrose media and in milk, according to 

 Theobald Smith, consisting of hydrogen and carbon 

 dioxide in the ratio 2 : 1 or 3 : 2. 



Inspissated serum is never liquefied. In meat broth a 

 bright pink colour is produced with considerable gas 

 formation, the medium becomes acid and there is a sour 

 smell, but no putrefactive odour. All the sugars and 

 starch are actively fermented with gas and acid produc- 

 tion, there is a tendency to ferment both inulin and 

 glycerin, but mannitol, dulcitol and salicin are not 

 fermented. 



The surface colonies on glucose agar are round and 

 raised, but do not grow downwards, and do not develop 

 filamentous outgrowths ; the deep colonies are lenticular. 



