BIOLOGY OF CLOSTRIDIUM WELCHII 427 



peptone-free media. Spores of Clostridium Welchii can be pre- 

 served indefinitely in all media in the absence of a fermentable 

 substance. 



5. Clostridium Welchii develops best at 37° to 38°C. Growth 

 does not occur above 42°C. nor below 10°C. From 18° to 35°C. 

 growth is abundant but slow. Freezing vegetative and spore 

 forms effects a steady reduction in numbers which leads to 

 complete destruction of vegetative forms in seven or eight days 

 and of spores in ten to twelve days. 



6. Surface colonies of Clostridium Welchii in plain and sugar 

 agar are opaque white, grayish white or brownish white in color, 

 by transmitted light, sometimes with a central darker dot. 

 Deep colonies are spheres or ovals. Colonies vary in size from 

 0.5 to 2 or 3 micra in diameter. 



7. Gelatin and blood serum are liquefied. Gas and acid are 

 produced from glucose, galactose, lactose, maltose, sucrose, 

 dextrin and starch. Milk is coagulated with a characteristic 

 "stormy fermentation' ' in twenty-four to forty-eight hours at 

 37°. The curd is later digested. Clostridium Welchii is chiefly 

 a fermentative organism and attacks proteins only in the absence 

 of a fermentable carbohydrate. 



8. The thermal death point of vegetative forms of Clostridium 

 Welchii varies from 56° to 63° for a fifteen minute period of 

 exposure. The thermal death point of spores shows two distinct 

 groups; one whose thermal death point is from 87° to 90° and the 

 other which survives 100°. 



9. The minimum lethal dose in intraperitoneal injections of 

 vegetative forms is 0.04 cc. of an eight-hour broth culture for 

 a 100-gram guinea-pig, while for subcutaneous and intravenous 

 injections the minimum lethal dose is 0.025 cc. The rabbit is 

 more resistant to infection than is the guinea-pig. Cultures of 

 Clostridium Welchii vary greatly in virulence. Cultures con- 

 taining spores heated to 80° for fifteen minutes are non-pathogenic. 

 Immunity can be produced by the injection of avirulent cultures 

 or sublethal doses of virulent organisms. Feeding vegetative 

 or spore forms has no ill effect. 



