Diphtheria and Tetanus 129 



like a tennis racquet, with the shiny spore in 

 the larger end (Fig. 14). 



The horse and some other animals only 

 occasionally develop tetanus, though one 

 great source of the bacillus is horse manure. 



Humans get tetanus by dirty wounds, 

 usually bruised or punctured. Pure cultures 

 or spores of the germ are not apt to induce 

 tetanus in wounds, but when other bacteria 

 or dirt are introduced into a wound with the 

 tetanus bacilli these are apt to grow. Thus 

 it is that although spores of the bacillus of 

 tetanus are very widely distributed in nature, 

 the disease is not common, because it is only 

 in punctured or lacerated wounds, in which 

 spores and dirt are lodged together, that the 

 proper conditions exist for the growth of this 

 finicky citizen. This is why those who care 

 for horses, those who handle manure, and the 

 boy who celebrates the "Fourth" with a 

 toy pistol are the most frequent victims of 

 lockjaw. There are some regions in which the 

 soil contains a great many spores, so that 

 tetanus frequently follows even slight punc- 

 tured wounds. 



