236 AXI.MAI. I)K\TIS'rR^'. 



Ihigcrs so as to freely drain the frontal sinus into the maxil- 

 lary sinus and nasal cavity. 



nth Step — Empty and irrigate the sinuses in the stand- 

 ing position and wad the openings with oakum or cotton. 



1 2th Step — Suture the transverse incision of the T-shaped 

 wound, leaving the longitudinal one for wadding and drain- 

 age. 



After-care — Irrigate with 3 per cent zinc sulphate solu- 

 tion daily. Prevent food from entering the cavity by wad- 

 ding the tooth cavity. 



Note — The two openings above referred to are the only 

 ones necessary to drain the sinuses of the horse's head. 

 Openings higher up along the frontal sinus serve no useful 

 purpose. The important feature of the operation is to drain 

 the sinuses into the nasal cavity by breaking down the 

 bony septa. Unless there is free flow from the upper opening 

 to the nostrils the trephining operation for nasal catarrh is 

 a useless procedure. 



CHRONIC PERFORATION OF THE SKULL. 



Definition — Under this head we include the openings of 

 the skull covering the facial sinuses or nasal cavities, that 

 persist after the regenerative process has ceased. 



Etiology — The chronic or peristent perforations of the 

 skull of horses follow large surgical openings necessary to 

 remove nasal tumors, severe contusions of the skin compli- 

 cated with comminuted fractures of the skull plate, attended 

 with sloughing of the injured area, and circular trephine 

 openings followed by necrosis of the surrounding bone. The 

 sequel is most liable to occur in old horses from the dimin- 

 ished nutrition of the bone tissue and periosteum. It is 

 seldom seen in young animals, except in accidental perfora- 

 tion of large dimensions, accompanied with loss of a large 

 area of common integument. Surgical perforations, al- 



