BACILLUS OF TETANUS. 399 



that give to it the appearance of a common mould. 

 (See Fig. 86.) 



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 

 usually 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 subse- 

 quently 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 solu- 

 tion, 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 sublimate, 



