BIOLOGY OF CLOSTRIDIUM WELCHII 383 



Growth in peptone-free media does not occur. A 1 per cent 

 solution of glucose, maltose or lactose without peptone, a phys- 

 iological salt solution with 1 per cent glucose, maltose or lactose, 

 a 1 per cent glucose, maltose or lactose, a physiological salt and 

 a 1 per cent gelatin solution fail to show any perceptible growth 

 after two weeks incubation. 



The spores of Clostridium Welchii can be preserved indefi- 

 nitely in nearly all media in the absence of glucose, galactose, 

 maltose, lactose, sucrose, dextrin and starch. Media which are 

 vigorously fermented by Clostridium Welchii do not permit of its 

 sporulation. 



3. Temperature requirements. The optimum temperature for 

 this organism is 37°, growth occuring from 10° to 42°. Below 

 10° vegetative forms die quickly while spores may remain alive 

 for months if a large quantity are present in the medium. 



When vegetative and spore forms of Clostridium Welchii are 

 exposed to temperatures below the freezing point, an enormous 

 reduction in numbers is observed. In determining this fact for 

 vegetative forms, pure cultures which had been transferred at 

 least twice into freshly sterilized glucose-liver broth were used. 

 A known number of the organisms from these pure cultures 

 were inoculated into freshly sterilized glucose-liver broth and 

 exposed to temperatures ranging from 13° to 36°F. After each 

 twenty-four hours, the actual bacterial content was determined 

 by the dilution method until the organisms failed to develop 

 in a dilution of one per cubic centimeter. In eight days the 

 bacterial content dropped from 50,000,000 per cubic centimeter 

 to less than one per cubic centimeter with a comparatively 

 uniform rate daily. Of the eight cultures tested, all behaved 

 similarly and produced like results. 



With spores grown in peptone-egg media for seven days, a 

 similar reduction occurred, although it took a longer period to 

 cause complete destruction. 



Freezing vegetative and spore forms of Clostridium Welchii 

 effects a steady death rate which leads to the complete destruction 

 of millions of vegetative forms in the course of seven or eight 

 days, while spores fail to develop after ten to twelve days exposure 

 to this environment. 



