396 BACTERIOLOGY. 



quarters to one hour. At the end 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 185-191). 

 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 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 growths 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 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, morever, 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 organ- 

 ism containing it more the shape of a javelin (or dos- 

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

 acteristic shape of the spore-bearing tetanus organism. It 

 is non-pathogenic, and grows both with and without oxy- 

 gen, 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, 



