438 BACTERIOLOGY. 



that give to it the appearance of a* common mould. (See 

 Fig. 93.) 



In stab-cultures. In stab-cultures made in tubes 

 about three-quarters filled with gelatin growth begins 

 at about 1.5 to 3 cm. below the surface, and gradually 

 assumes the appearance of a cloudy, linear mass, 

 with prolongations radiating into the gelatin from all 

 sides. Liquefaction with coincident gas production 

 results, and may reach almost to the surface of the 

 gelatin. 



Relation to temperature and to chemical agents. It 

 grows best under a temperature of from 36 to 38 C.; 

 gelatin cultures kept at from 20 to 25 C. begin to 

 grow after three or four days. In an atmosphere of 

 hydrogen at from 18 to 20 C. growth does not usu- 

 ally occur before one week. No growth occurs under 

 14 C. At the temperature of the body spores are 

 formed in cultures in about thirty hours, whereas in 

 gelatin cultures at from 20 to 25 C. they do not usu- 

 ally appear before a week, when the lower part of the 

 gelatin is quite fluid. 



Spores of the tetanus bacillus when dried upon bits 

 of thread over sulphuric acid in the desiccator and sub- 

 sequently kept exposed to the air, retain their vitality 

 and virulence for a number of months. Their vitality 

 is not destroyed by an exposure of one hour to 80 C.; 

 on the other hand, an exposure of five minutes to 

 100 C. in the steam sterilizer kills them. They resist 

 the action of 5 per cent, carbolic acid for ten hours, but 

 succumb when exposed to it for fifteen hours. In the 

 same solution, plus 0.5 per cent, hydrochloric acid, 

 they are no longer active after two hours. They are 

 killed when acted upon for three hours by corrosive 



