Pi,ATii; VI. 



Trephining the Faciai, Sinuses. 



Cross section downwards and backwards 

 oblique through the half ot the head at the first 

 molar in a two year colt. F, frontal sinus ; N, 

 nasal passage at point of communication with 

 the inferior maxillary sinus, IM ; IM\ median 

 portion of inferior maxillary sinus ; SM, ex- 

 treme lower end of superior maxillary sinus 

 opened ; Mi, first molar; M2 second molar; 

 P, palatine artery ; SZ, sub-zygomatic artery. 



