DISEASES OF THE HORSE. 219 



time to dry tlioroughlj^ before the horses are replaced. A complete 

 change of food is of the very greatest importance, on account of the 

 belief that the cause resides in diseased grain, hay, and grass. 



TETANUS, OR LOCKJAW. 



This disease is characterized by spasms affecting the muscles of the 

 face, neck, body, and limbs, and of all the muscles supplied by the 

 cerebro-spinal nerves. The spasms or muscular contractions are rigid 

 and persistent, yet mixed with occasional more intense contractions of 

 convulsive violence. 



Causes. — This disease is caused b}" a bacillus that is often found in 

 the soil, in manure and in dust. This germ grows only in the absence 

 of oxygen. It produces a powerful nerve poison, which causes the 

 symptoms of tetanus. The germ itself multiplies at the point 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 superfi- 

 cial wounds, because in them the germ is more remote from the 0x3^- 

 gen of the air. Hence, nail pricks, etc., are especiall}^ 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 introduc- 

 tion of setons, inclusion of a nerve in a ligature, etc. It maj^ come 

 on a long time after the wound is healed — three or four months. In 

 som« 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 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 usuall}' dies within four days. The first symptoms 

 which attract the attention of the owner is difiicult}^ in chewing and 

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

 part of the ej'e of the membrana nictitans, or haw. An examination of 

 the mouth will reveal an inabilit}' to open the jaws to their full extent, 

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

 increased sf)asm 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 

 stifl' 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 rapidl}" 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; 



