100 BONE SAWS AND FORCEPS. 



is passed around the bone by means of the needle and thread shown, 

 and is then attached to the handle ; by drawing the chain to and 



Fig. 131. — Bone forceps. 



fro the bone is gradually sawn through. A trephine (Fig. 309) 

 consists of a hollow steel cylinder bearing teeth on its free border. 



Fig. 132. — Frame saw for bone. 



A central terminal steel point is usually added to steady the trephine 

 in position, and by rotating the handle alternately towards the 



Fig. 133.— Chain saw. 



right and left a circular piece of bone is gradually cut through. 

 Trephines are used for opening the facial sinuses, the wall of the hoof, 

 and the cranial roof. 



