Pi,ate; VII. 



Trephining of Paciai< Sinuses. 



Cross section of the left side of the head 

 anterior to the last molar, and through the 

 widest part of the inferior maxillary sinus. M', 

 last superior molar ; SM, superior maxillary 

 sinus at' its antero-inferior extremity ; IM, in- 

 ferior maxillary sinus, lateral portion ; IM', do. 

 median portion ; N, nasal fossa ; S, sound lodged 

 in lachrymal duct ; NP, trifacial nerve ; F, 

 frontal sinus. 



