242 DISEASES OF THE HOESE. 



nail pricks, etc., are especially dangerous. In the majority of in- 

 stances the cause of tetanus can be traced to wounds, especially pricks 

 and wounds of the feet or of tendinous structures. It sometimes fol- 

 lows 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. Horses with a nervous, excitable 

 disposition are more predisposed than those of a more sluggish 

 nature. Stallions are more subject to develop tetanus as the result 

 of wounds than geldings, and geldings more than mares. 



Symptoms. — The attacks may be acute or subacute. In an acute 

 attack 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 the membrana 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 excita- 

 bility 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 consti- 

 pated early in the attack. The temperature and pulse are not much 

 changed. These symptoms in the acute type become rapidly aggra- 

 vated 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 painful from the 

 spasm of the muscles used in respiration; the jaws are completely 

 set, eyeballs retracted, lips drawn tightly over the teeth, nostrils di- 

 lated, and the animal presents a picture 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 Idcked ; the nervous excitability and rigid- 

 ity of the muscles are not so great. There is, however, always some 

 stiffness of the neck or spine manifest in turning ; the haw is turned 

 over the eyeball when the 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 grad- 

 ually 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 characteristics of acute tetanus become developed. In 

 some cases, however, we find the muscular cramps almost solely con- 

 fined to the head or face, perhaps involving those of the neck. In 

 such cases we have complete trismus (lockjaw), and all the head 

 symptoms are acutely developed. On the contrary, we may find the 



