THE SPORE-BEARING RODS 363 



have gained entrance to the blood stream from the intestinal 

 tract and have localized in some tissue which has been 

 injured or bruised. 



Clostridium welchii 



This organism is taken as the type of a group of bacteria 

 which in recent years have become very prominent because 

 of their apparent relationship to gaseous and malignant 

 edemas of various types in man and in animals. These 

 bacteria are relatively common in many soils and when they 

 gain access to wounds, produce a variety of lesions. 



Clostridium welchii has been isolated repeatedly from 

 men dying from gaseous edema. 



Morphology. — The organism is a large rod about 

 In X 2-6/i. It is frequently found in chains but may occur 

 in pairs or groups. It is nonmotile. Spores may be pro- 

 duced under certain conditions in the laboratory upon 

 culture media but are not produced in the presence of 

 sugars. These spores are centrally located and the cells 

 become considerably swollen and spindle-shaped. Capsules 

 are produced in the body fluid and in some of the artificial 

 media. The cells are usually Gram-positive. 



Cultural Characters. — Colonies produced upon gelatin 

 or agar plates are round, grayish and semiconfluent, resem- 

 bling in many ways those of Clostridium tetani. Gelatin is 

 usually slowly liquefied, bouillon clouded with the forma- 

 tion of abundant precipitate. Milk is quickly coagulated 

 with the formation of gas and acid. 



Physiology. — The organism grows best at blood heat. 

 The thermal death point for organisms without spores, that 

 is, for vegetative rods, is 50° c. for 10 minutes. Spores 

 require boiling temperature for at least 15 minutes. An 

 abundance of gas is produced from many of the carbo- 

 hydrates including dextrose, lactose and sucrose but not 

 from mannitol. 



