BACILLUS WELCHII 529 
features are the "stormy fermentation," a faint pink coloration of the 
casein coaguhim (which is greatly contracted and filled with gas holes, 
but not dissolved to any appreciable extent), gas bubbles, clear whey, 
and an odor of butyric acid. If the milk has not been heated sufficiently 
to remove all the oxygen, the gas bacillus not infrequently i)roduces a 
coagulum, but no stormy fermentation and liberation of gas. 
Fig. 72.— Bacillus welcliii, capsule stain. X 1000. 
Bacillus welchii ferments a variety of carbohydrates with great 
vigor. Of the hexoses, glucose, fructose, mannose and galactose are 
fermented. Of the bioses, maltose, lactose, saccharose. In addition, 
raffinose, starch and dextrin are fermented by practically all strains. 
Simonds^ has grouped strains of B. welchii into four types: 
Sporulation. 
Type. Inulin. Glycerin. Inulin. Glycerin. 
I Gas Gas — — 
II - Gas + 
III Gas - - + 
IV - - + + 
This classification has been confirmed by Henry- who believes, how- 
ever, that the organism tends to lose its ability to ferment inulin, or 
glycerin, or both, upon prolonged cultivation.' 
Conditions of Growth. --B. welchii is an obligate anaerobe which does 
not grow below 1S° C. nor above 44° C. The optimum temperature 
for growth is 38° C. The spores of the organism are quite resistant to 
the action of heat; five minutes' boiling usually fails to kill them in 
neutral solutions. They are also resistant to drying, particularly in 
the absence of sunlight. They do not appear in media containing 
utilizable carbohydrates. Simonds finds'* that an acidity greater than 
I per cent to phenolphthalein inhibits spore formation. 
1 Simonds: Loc. cit. = Jour. Pathol, and Bactoriol., 1916, 21, 344. 
' It may be stated that one strain kept upon artificial media for five years has retained 
its ability to ferment both glycerin and inulin apparently unimpaired, however. Jour. 
Inf. Dis., 1922, 30, No. 2. 
* Loc. cit., p. 31. 
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