FIG. 7 



Trephining of Facial Slnnses 



Cross section of the right half of the head of a horse at the posterior 

 border of the last molar. F, frontal sinus ; IM, lateral portion of 

 inferior maxillary sinus at extreme posterior or stiperior part ; IM', 

 median portion do. ; N, nasal chamber opposite the communication 

 between it and the superior maxillary sinus ; NF, conduit of superior 

 maxillary branch of the trifacial nerve ; SM, superior maxillary sinus ; 

 M^, fragment of last molar. 



