132 Agricultural Bacteriology. 



the docking of horses, the castration of colts, and 

 through the infection of the umbilical cord of colts. 



Symptoms. The organism grows only at the point 

 of introduction. It produces one of the most powerful 

 poisons known. This is absorbed and is carried to all 

 parts of the body and its action on the nerves causes 

 the characteristic symptoms, of spasms in various mus- 

 cles. The muscles of the throat and jaw are often 

 paralyzed, giving rise to the common name of the dis- 

 ease, lockjaw. The muscles of the neck may be in- 

 volved, causing the head to be held in a stiff outstretched 

 manner. Those of the back and tail are also affected. 



On post-mortem examination no marked lesions are 

 found. The disease is usually fatal in sheep and in hogs ; 

 about 75 per cent of the horses affected die. The dura- 

 tion of the disease in the horse may be but a few days or 

 it may continue for several weeks. 



Preventive measures. A preventive and to some ex- 

 tent a curative treatment has been developed in the 

 tetanus antitoxin. This antitoxin is prepared in the 

 same manner as that used for the prevention and cure 

 of diphtheria. A horse is injected with a small amount 

 of the filtrate of a culture of the tetanus organism in 

 broth. This contains the same poison that the organism 

 produces in the body of the animal. A very small dose 

 must be given at first. The horse soon recovers from 

 the effect of the injection and a larger dose is then given. 

 The treatment is continued for some time with larger 

 and larger doses of the poison. Meanwhile the animal 

 is producing a substance in its body to counteract the 

 poison that has been given it. This process of forming 

 the antitoxin does not cease when enough has been made 

 to neutralize the amount of poison given, but an excess 



