loo THE SURGICAL ANATOMY OF THE HORSE 



or frontal sinuses, it has a tendency to gravitate into the superior 

 maxillary, and it is thus possible to drain all three sinuses by opening 

 into the last named ; but to facilitate the removal of the contents, and 

 to remove any probable obstruction which there might be to the free 

 communication between them it is always advisable to open both 

 into the frontal and superior maxillary sinuses. 



It will readily be gathered that inflammation of the mucous 

 membrane lining the sinuses may be consequent upon a similar condition 

 affecting the mucous membrane of the nasal chamber, and also, as already 

 stated, that as the purulent exudate resulting from the process of 

 inflammation accumulates in one or other of the sphenoidal or frontal 

 sinuses, it has a tendency to gravitate into the superior maxillary sinus. 

 In cases of empyema of the facial sinuses there will therefore be a 

 chronic discharge of purulent material from the nostrils owing to 

 the natural communication which exists between the superior maxil- 

 lary sinus and the nasal chamber, and, moreover, this discharge would 

 be augmented if the animal's head were held in the dependent position. 



But from our examination of the nasal chamber it will be re- 

 membered that this communication is by no means a free one, being 

 deeply seated between the two turbinated bones near the upper 

 extremity of the middle meatus. Consequently, as a rule, the escape 

 of the inflammatory exudate does not keep pace with its formation, and 

 as a result we get, in advanced cases the frontal sinus, in addition to the 

 superior maxillarv, filled with purulent matter. Occasionally it happens 

 that on account of great swelling of the Schneiderian membrane in the 

 region of the orifice of communication with the nasal chamber, the 

 escape of the material into the latter chamber is prevented, or the 

 orifice itself may become occluded by the inflammatory products. In 

 such cases therefore a purulent discharge from the nostrils would 

 not be one of the symptoms of empyema of the sinuses. 



Another symptom of empyema of the sinuses is the absence of the 

 resonant sound which is normally heard upon percussing the areas 



