■m 



FIG. 9 



Trephining the Facial Sinuses 



Cross section obliquely downwards and backwards through the 

 right half of the head of a two-year old colt at the first molar. F, 

 Frontal sinus ; N, nasal passage at point of communication with the 

 maxillary sinus, IM ; IM', median portion of inferior maxillary 

 sinus ; SM, extreme lower end of superior maxillary sinus opened ; 

 Mi, first molar; M2, second molar; P, palatine artery; SZ, sub- 

 z3'gomatic artery. 



