274 INFECTION AND IMMUNITY 



was rusty, or that a nerve had been injured, but to 

 the introduction of earth containing the tetanus ba- 

 cillus, which would more readily adhere to the rough 

 surface of a rusty nail than to a new and clean one. 

 The nature of the wound made is also favourable to in- 

 fection, as the bruised tissues are not likely to bleed 

 much, and the deep wound with a narrow orifice is 

 well calculated to retain any foreign matter introduced 

 at the time the injury was inflicted. Unlike the vari- 

 ous pathogenic bacteria heretofore referred to, the 

 tetanus bacillus will not grow in the presence of oxy- 

 gen. It therefore cannot grow in open wounds 

 exposed to the air, and is incapable of develop- 

 ment in the blood of a living animal. It differs in 

 another particular, also, viz., in the formation of 

 "spores," which are developed in the rods one 

 at the end of each bacillus. These are spherical, 

 highly refractive bodies, which resist desiccation, and 

 may retain their vitality for months and probably 

 for years when present in surface soil or in dust. 

 A temperature of 212 Fahr. is required for their 

 destruction. 



When a needle is dipped into a pure culture of the 

 tetanus bacillus, and a mouse is inoculated with it, 

 subcutaneously, the animal falls sick within twenty- 

 four hours and dies of typical tetanus in two or three 

 days. The tetanic symptoms are first developed in 



