THE BACILLUS OF TETANUS. 435 



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 194-199). 

 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 microscopic- 

 ally, but each colony that has developed in the hydro- 

 gen atmosphere should be obtained in pure culture and 

 again grown under the same conditions. The colonies 

 that grow only without oxygen, and which are com- 

 posed 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, 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 

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

 characteristic shape of the spore-bearing tetanus organ- 

 ism. It is non-pathogenic, and grows both with and 

 without oxygen, and should, consequently, not be mis- 

 taken 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 



