BACILLUS TETANI 



581 



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 relation to oxygen, and they are also without disease- 

 producing properties. 



Morphology. — ^In the vegetating stage it is a slender rod 

 with rounded ends. It may appear as single rods, or, in 



Fig. 100 



cultures, as long threads. It is motile, though not actively 

 so. The motility is rendered somewhat more conspicuous 

 by examining the organism upon a warm stage. 



At the temperature of the body it rapidly forms spores. 

 These are round, thicker than the cell, and usually occupy 

 one of its poles, giving to the rod the appearance of a small 

 pin. (Fig. 100.) When in the spore-stage it is not motile. 



