CHAPTER VII. 



OPERATIONS ON THE SKULL AND FACE. 



Trephining. — The operation of trephining the skull or face is 

 occasionally resorted to after severe injuries, in order to remove 

 foreign material from underneath or to raise depressed pieces of 

 bone. It is also of value in some dental cases. 



The instruments required are a sharp scalpel, dissecting for- 

 ceps, artery forceps, a curved piece of metal to use as an 

 elevator, a small sized trephine (Fig. 38), and a strong gimlet. 



The operation is performed as follows : — 



The animal is secured in the abdominal position and anaes- 

 thetised, the hair having been previously removed by shaving 

 from the seat of operation and the parts thoroughly disinfected. 

 A crucial or T-shaped incision is made over the spot, and all 

 tissues between that and the bone carefully removed by cutting 

 or scraping. A hole, intended for the insertion of the central 

 pin, is bored with a gimlet in the middle of the spot to be 

 operated upon and the trephine applied. This instrument is 

 worked steadily and carefully to and fro in a rotatory manner 

 until it is felt to have almost penentrated the bone. One side 

 is then slightly depressed in order to cause the piece of bone 

 in the trephine to become elevated on one side, and so attach 

 itself to the instrument when the latter is withdrawn, instead 

 of falling into the cavity underneath. The foreign body is then 

 sought for, or the purpose of the operation accomplished, the 

 skin afterwards being sutured over the part, and the whole 

 covered with antiseptic dressings and bandaged or left open 

 according to the discretion of the operator. 



