288 



OPERATIONS ON BONES. 



Via. 303. Via. 304. 



Parts of the Head where Trephining is Performed. 



instrument, there are conditions where, the bone being less sub- 

 cutaneous, the operation is less easily performed. Such is the 

 case as to the lateral faces of the parietal bone, where it wiU be 

 necessary to penetrate through where the crotaphite muscle is. 

 This, however, makes a complication of little importance. Again, 

 there are iudications, such as in cases of chronic coryza, with sup- 

 puration of the sinuses, where a double trephining becomes neces- 

 sary, one to enter the frontal, and the other the superior maxUlary 

 sinus. Figure 305, which is borrowed from Peuch & Toussaint, 

 shows the exact location where the trephining can be made. 

 A, entering into the frontal ; B, the upper, and C, the lower max- 

 illary sinuses. 



The modus operandi of this operation is very simple. Unless 

 the animal is very restless, and cannot be controlled by the ordi- 

 nary means of restraint, or by local anesthesia, and must there- 

 fore be cast, or unless the trephining is merely the first step of an 

 operation to remove foreign bodies or growths from the sinuses, or 

 to apply special action upon a displaced bone, as in a fracture, we 

 prefer to operate in the standing posture, and in such cases have 

 found the use of cocaine of great advantage. 



In any case the skin is first divided by either a V, or a T, or a 



