364 VETERINARY LECTURES 



598. Chorea, Shivering, String-halt, or Clicking, are modified 

 forms of a peculiar derangement of the nervous system (characterized 

 by involuntary spasmodic muscular jerkings, twitchings, and trem- 

 blings) that is analogous to St. Vitus's dance in the human subject. 

 The cause of the derangement is not really known ; some authorities 

 say it is due to lesions of the brain, and others to an affection of the 

 spinal cord. There are, however, various other theories. Although 

 the disease may have a hereditary tendency, my opinion is that, in 

 the majority of cases, retarded dentition has a great deal to do with 

 inducing it [par. 350), as the complaint is seldom noticed before the 

 animal is rising three years old. It is not so common in the mare ; 

 but big, heavy cart-horses are much affected, more particularly in 

 their hind extremities. When the fore -limbs are attacked, the 

 symptoms are of a trembling character, and are best observed while 

 the animal is eating a feed of oats, when the muscles of the shoulders 

 and legs are noticed to be all in a quiver. In other cases, on the 

 horse being put back, it drags its fore-feet on the heels, after the 

 manner of one suffering from acute founder. The drinking of cold 

 water, in suspected cases, usually provokes the nervous twitchings 

 and tremblings above referred to. 



599. Chorea. — I have seen a horse, rising three years old, 

 suddenly attacked with acute chorea when at work in the plough. 

 It would stop, and fall on to its head or side, and sometimes 

 come over backwards ; on rising it seemed to have little or no 

 control over the muscles of the limbs, having both fore and hind 

 legs spread wide apart to keep it from falling, while the head, 

 hanging in a listless manner, was swung from side to side. In these 

 cases, if made to stir, the animal staggers and falls, or steadies 

 itself against a wall, the attack resembling very much that of 

 lightning shock. As the case proceeds, should the patient be 

 turned out to grass, and be made to trot or canter, it pulls the legs 

 up very high, in a jerky fashion. When stopped suddenly, it may 

 perhaps fall on to its head or shoulder, and go tail over head ; or the 

 fore-feet may be planted forward like posts, the body swinging from 

 side to side. These cases never sufficiently recover to be of much 

 service in saddle or harness, but may do ploughing and harrowing 



