248 LAMENESS. 



horsemen. It is not due to any fracture, nor always to any 

 external injury, but is a progressive disease, arising from some 

 alteration of structure in the spinal cord from disease of the 

 vertebra, or from granular degenerative disease of the muscles 

 themselves. 



" Shivering " is another peculiar nervo-muscular affection of 

 the posterior extremities, resembling stringhalt, and manifested 

 more particularly during the acts of " backing " or " turning 

 reund." 



In a case of this kind the animal, when made to back, wiU 

 perform that act with some difficulty; the muscles of the 

 gluteal and femoral regions are thrown into a state of " clonic 

 spasm," contracting and relaxing in a very irregular manner; 

 hence the term " shivering," from the resemblance of the mus- 

 cular action to trembling or shivering. In many cases the 

 tail is spasmodically elevated and depressed in the manner of 

 a pump-handle, and the limbs elevated from the ground by a 

 peculiar rigid or stiff movement ; the foot often suspended for 

 a moment, as if the animal were unable to direct the action of 

 the muscles. 



When moved forwards, the necessary actions will be per- 

 formed tolerably wxll, but the backward movement is done with 

 more or less difficulty, and sometimes it cannot be performed 

 at all. 



Shivering, immohilite, strained back, and their various modi- 

 fications, must be considered as causes of unsoundness, since 

 their tendency is to increase in severity as the animal becomes 

 older. They often interfere with his condition, and generally 

 give him an aged appearance before he has reached his prime ; 

 and they prevent him lying down, particularly if he is confined 

 in a stall. Some horses, while so affected, lie down well 

 enough ; the majority, however, scarcely ever do so, but fall 

 down in their sleep occasionally, and being unable to rise 

 again without assistance, often injure themselves by strugghng. 

 Animals of this kind should always be slung at night. 



Hereditary tendency. — I think there can be no doubt as to 

 hereditary predisposition being one of the causes of the fore^ 

 going diseases ; indeed, I have had sufficient proof, in my own 

 experience, to convince me that such is the case. Very often 

 one form or other will be found in young animals, two or three 



