242 DISEASES OF THE HORSE. 
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 pulge, 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 
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 
