220 DISEASES OF THE HOKSE. 



where it is introduced, but its poison is absorbed, and is carried by 

 the blood to all parts of the body, and thus the nervous system is 

 poisoned. Deep wounds infected by this germ are more dangerous 

 than superficial wounds, because in them the germ is more remote 

 from the oxygen of the air. Hence, nail pricks, etc., are especially 

 dangerous. In the majority of instances the cause of tetanus can be 

 traced to wounds, especially pricks and wounds of the feet or of 

 tendinous structures. 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 presump- 

 tion is that it is due to a specific germ. Horses with a nervous, ex- 

 citable disposition are more predisposed than those of a more slug- 

 gish 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, eyebals 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 locked ; 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 



