106 THE ACUTE SELF-LIMITED INFECTIONS 



cell wall. The spores develop at one end and give the rod 

 a drumstick appearance; they are best seen in old cultures. 

 The spores may leave the parent bacillus and lead an inde- 

 pendent existence. In this state they are not motile and are 

 stained with great difficulty. The vegetative rod, however, 

 stains with comparative ease. The organism can digest 

 gelatin and grows characteristically in it. 



In discussing the resistance of this germ to deleterious 

 agents, the spores only need be considered, because the 

 vegetative rod has the power of going into this resistant 

 stage very quickly when it meets unfavorable environment. 



9 : 



FIG. 33. Tetanus bacilli with spores in distended ends. X 1 100 diameters. 



(Park.) 



The rods grow best at 37 C. or 98 F. The spores are killed 

 at 105 C., 221 F., when exposed ten minutes to streaming 

 stream. They are destroyed by chemicals as follows: 5 

 per cent, carbolic acid in ten hours; 5 per cent, carbolic acid 

 plus 0.5 per cent, hydrochloric acid in two hours; 1 to 1000 

 corrosive sublimate in three hours; 1 to 1000 corrosive sub- 

 limate plus 0.5 per cent, hydrochloric acid in one-half hour; 

 1 per cent, silver nitrate in five minutes. When dried the 

 tetanus spores will live several years. Sunlight very slowly 

 kills them. Most animals are susceptible to the tetanus 

 bacillus or its toxins. Rats and birds are the least, while 

 horses and man are the most sensitive. 



