TREPHINING THE MAXILLARY SINUSES. 31 



ing to the lips of the wound. In practice the operation 

 can be best carried out generally with the animal in the 

 standing position the operative area being first anaesthetized 

 by the use of cocaine or by inducing artificial oedema. In 

 the standing position we largely avoid the danger of aspira- 

 tion of fluids and the hemorrhage is greatly lessened. 



4. TREPHINING THE MAXILI/ARY SINUSES. 



Pl^ATBS III-VIII. 



Uses. Empyema, diseased teeth, odontomes, tumors. 



Instruments. Same as for the frontal sinuses. 



Anatomically there are two maxillary sinuses, superior, 

 SM, and inferior, IM, Plates III-VII, having a thin im- 

 perforate bony partition between them. This partition 

 shifts somewhat in position with age and in case of disease 

 undergoes profound changes in location and is frequently 

 totally obliterated in cases of empyema, dental cysts and 

 other affections. If present, good drainage of the superior 

 sinus may demand its surgical destruction so that some 

 authors advise trephining directly over it in order to open 

 the two cavities simultaneously. In extensive disease the 

 prior destruction of the partition renders such an aim super- 

 fluous ; in limited disease the opening of both cavities is ill 

 advised. The partition may be ignored in operating for 

 extensive disease and the trephine opening be aimed at the 

 probable focus of the malady and, if missed, it should be 

 located through the primary, or what now becomes an ex- 

 ploratory opening, and a second operation made to directly 

 reach the seat of the affection and if need be, yet a third to 

 secure proper drainage. Shave and disinfect as much of 

 the area as may be required bounded above by the inferior 

 border of the orbital cavity, laterally by the zygomatic 

 ridge, inferiorly by the lower end of the zygoma and 

 medianwards by the middle line of the face. Determine 



