BACILLUS TETANI 607 



reveal the presence of a few tetanus bacilli, recognizable 

 by their shape, viz., that of a small pin, with a spore repre- 

 senting the head. After forty-eight hours at 38 C. the 

 culture is subjected to a temperature of 80 C. in a water- 

 bath for from three-quarters to one hour. At the end of 

 this time series of plates or Esmarch tubes of slightly alkaline 

 gelatin are made with very small amounts of the culture 

 and kept in an atmosphere of hydrogen (see page 242). 

 They are then kept at from 18 to 20 C., and at the end of 

 about a week the tetanus bacillus begins to appear in the 

 form of colonies. After about ten days the colonies should 

 not only be examined microscopically, but each colony 

 that has developed in the hydrogen atmosphere should be 

 obtained in pure culture and again grown under the same 

 conditions. The colonies that grow only without oxygen, 

 and which are composed of the pin-shaped organisms, 

 must be tested upon mice. If they represent growth of the 

 tetanus bacillus, the typical clinical manifestations of the 

 disease will be produced in these animals. 



In obtaining the organism from the soil much difficulty 

 is experienced. Here are encountered a number of spore- 

 bearing organisms that are facultative in their relation to 

 oxygen, and are therefore very difficult to eliminate; and 

 there is, moreover, one in particular that, like the tetanus 

 bacillus, forms a polar spore. This spore is, however, 

 much more oval than that of the tetanus bacillus, and gives 

 to the organism containing it more the shape of a javelin 

 (or clostridium, properly speaking) than that of a round- 

 headed pin, the characteristic shape of the spore-bearing 

 tetanus organism. It is non-pathogenic, and grows both 

 with and without oxygen, and should, consequently, not 



