, CHAPTER V. 

 RESPIRATORY APPARATUS, 



TREPHINING THE FACIAL SINUSES. 



This operation is necessary when pns, tumours, or parasites exist 

 within the sinuses, and in some cases where tumours form within 

 the nasal cavities, etc. 



TREPHINING THE HORN CORE. 



This cavity is opened in front, at the base of the horn, about 

 f of an inch above the keratogenous band. 



FRONTAL SINUS. 



The frontal sinus may be trephined at one of two points, that is, 

 either towards its highest or lowest extremity. 



In the former case the point selected is in the direction of the 

 axis of the horn core, about f of an inch nearer the middle line than 

 the base of the horn itself. 



The animal should be cast. 



First stage. A V-shaped incision f of an inch long on each side 

 is made through the skin and subjacent tissues, exposing the bone. 



Second stage. The skin and periosteum are dissected away and 

 reflected up\Yards. 



Third stage. Trepanation. 



The lower portion of the cavity is trephined within the angle 

 formed by a transverse line uniting the upper margin of the orbits 

 and the inner margin of the super-orbital foramen. 



The stages are precisely the same as those above described. 



MAXILLARY SINUS. 



In adult animals the maxillary sinus is opened immediately above 

 the maxillary tuberosity. In the young the point selected is f of an 

 inch higher. 



