THE BACILLUS OF TETANUS. 377 



of this time, series of plates or Esmarch tubes in slightly 

 alkaline gelatin are made with very small amounts of 

 the culture and kept in an atmosphere of hydrogen (see 

 pages 175-178). They are then kept at from 18° to 20° 

 C, and at the end of about one 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 had 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 growths 

 of the tetanus bacillus, the typical clinical manifesta- 

 tions of the disease will be produced in these animals. 

 In obtaining the organism from the soil much diffi- 

 culty is experienced. There are a number of spore- 

 bearing organisms here 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, less round and much more oval than 

 that of the tetanus bacillus, and gives to the organism 

 containing it more the shape of a javelin (or Clos- 

 tridium, properly speaking) than that of a pin, the 

 characteristic shape of the tetanus organism. It is non- 

 pathogenic, and grows both with and without oxygen, 

 and should, consequently, not be mistaken for the latter 

 bacillus. It must also be borne in mind that there are 

 occasionally present in the soil still other bacilli which 

 form polar spores, and which, when in this stage, are 

 almost identical in appearance with the tetanus bacillus, 

 but they will usually be found to differ from it in their 



