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Causes. — The causes are classified under two beads, traumatic where 

 it is the result of injury, and idiopathic where it is due to other causes 

 than injuries, such as cold and damp, excessive fright, nervous exhaust- 

 ion from overwork, chronic irritation caused by worms in the intestines, 

 etc. In the majority of instances the cause of tetanus can be traced 

 to wounds, especially pricks or wounds of the feet or of tendinous 

 structiires. It sometimes follows castration, docking, the introduction 

 of setons, inclusion of a nerve in a ligature, etc. It may come on a 

 long time after the wound is healed, three or four months. In some 

 countries where tetanus appears to be enzootic the presumption is that 

 it is due to a specific germ. Horses with a nervous, excitable disposition 

 are more i^redisposed than those of a more sluggish nature. Stallions 

 are more subject to develop tetanus as the result of wounds than geld- 

 ings, and geldings more than mares. 



Synqytoms. — The attacks may be acute or subacute. In an acute at- 

 tack the animal usually dies within four days. The first symptoms 

 which attract the attention of the owner is difficulty in chewing and 

 swallowing, an extension of the head and protrusion over the inner 

 part of the eye of themembrana nictitans or haw. An examination of 

 the mouth will reveal an inability to open the jaws to their full extent, 

 and the endeavor to do so will produce great nervous excitability and 

 increased spasm of the muscles of the jaw and neck. The muscles of 

 the neck and along the spine become rigid and the legs are moved in a 

 stiff manner. The slightest noise or disturbance throws the animal 

 into increased spasm of all the affected muscles. The tail is usually 

 elevated and held immovable; the bowels become constipated early in 

 the attack. The temperature and pulse are not much changed. These 

 symptoms in the acute type become rapidly aggravated until all the 

 muscles are rigid — in a state of tonic spasm — with a continuous tremor 

 running through them ; a cold perspiration breaks out on the body ; 

 the breathing becomes i^ainful from the spasm of the muscles used in 

 respiration ; the jaws are completely set, eye-balls retracted, lijis drawn 

 tightly over the teeth, nostrils dilated, and the animal presents a pict- 

 ure of the most extreme agony until death relieves him. The pulse, 

 which at first was not much affected, will become quick and hard, or 

 small and thready when the spasm affects the muscles of the heart. 

 In the subacute cases the jaws may never become entirely locked; the 

 nervous excitability and rigidity of muscles are not so great. There is, 

 however, always some stiffness of the neck or spine manifest in turn- 

 ing ; the haw is turned over the eye-ball when tbe nose is elevated. It 

 is not uncommon for owners to continue such animals at their work for 

 several days after the first symptoms have been observed. All the 

 symptoms may gradually increase in severity for a period of ten days, 

 and then gradually diminish under judicious treatment, or they may 

 reach the stage wherein all the characters of acute tetanus become de- 

 veloped. In some cases, however, we find the muscular crami^s almost 



