TWITCHING. 



703 



Trephining. 



This is the boring through of a piece of bone. The operation is 

 almost invariably confined to the bones of the skull or upper jaw, 

 and is employed to give vent to diseased products which have 

 accumulated in the sinuses of the head (p. 371), to relieve pressure 

 on the brain, to facilitate the removal of back teeth, etc. It is 

 most conveniently performed by means of a trejjhine, which is a 

 circular saw made for the purpose. The operation is fully 

 described in Peucli and Toussaint's " Chirurgie Veterinaire." 



1S4. — Applying the twitch. 



Twitching. 



The ordinary twitch is a staff about two inches in diameter, two 

 or three feet long; and furnished with a loop of cord which is 

 passed through a hole bored at one end of the stick. The thick- 

 ness of the cord should not be less than that of the little finger of 

 an ordinary man's hand, and should be made of soft material so as 

 not to cut the horse's skin. The loopj should be made large enough 

 to freely admit the hand. 



The best plan for applying the twitch (Fig. 184, p. 703) is for 

 the operator to pass his right hand through the loop of the cord, 

 grasp the off side of the head collar or halter with the left hand, 



