STRINGHALT 395 



the heels of the foot, and then by means of an expanding screw passing 

 from one heel of the shoe to the other outward, pressure is made on the 

 parts, and by increasing the force from time to time the heels are caused to 

 open. It need hardly be said that the change brought about in this way 

 can only be temporary, and may be mischievous. As the foot contracts by 

 wasting, so it must expand by growth, and to render the change permanent 

 there is necessary the exercise of those natural forces which regulate its vital 

 activities and conduce to re-establish in it a condition of health. 



20. DEFECTIVE ACTION AND INJURIES 

 ARISING OUT OF IT 



This is a spasmodic upward jerk of the limbs during progression. It is 

 chiefly observed in the hind extremities, but rarely also affects the fore ones. 



In the former it is marked by a convulsive flexion of the hock, when the 

 canon is raised high up towards the abdomen, with which it is on occasions 

 brought into contact. This disordered movement may affect one or both 

 hind-legs equally, or in different degrees. 



It is almost exclusively confined to the walk and the trot, and varies 

 from time to time in the suddenness and extent of the morbid movement. 

 It is exaggerated after rest, and also by excitement. In many instances 

 horses are taken to shows which while at home are perfectly free from the 

 defect, but which no sooner get into the show ring than they develop 

 stringhalt in a very marked form. 



In some animals it is very slight, and only observed in turning. In 

 others it is intermittent, and only seen now and again. Hackneys, whose 

 hock action is now so much developed, are more frequently affected by it 

 than any other variety of the horse. 



Stringhalt has been attributed to a variety of causes some anatomical, 

 others pathological and it has been variously located in the stifle, the 

 hock, and the pastern, and attributed to laceration of muscles of the thigh, 

 to rupture of the tendons inserted into the point of the hock, and to ulcera- 

 tion of joints. In this country it is pretty generally regarded by veterin- 

 arians as a nervous affection, but the proof of this, as of all other alleged 

 causes, is still wanting. 



