22 TREPHINING OF THE FRONTAL SINUSES 



It has been assumed that pus or other contents in con- 

 siderable quantity might pass from the superior maxillary 

 sinus into the nasal cavity through the normal communi- 

 cating slit between the two cavities, but a careful study of 

 the anatomical arrangement of these parts, opposite N, 

 Figs. 7-10, shows very clearly that this is impossible as the 

 margin of the slit acts as a valve and closes it when pressure 

 is applied from within. 



In order to prevent the aspiration by the patient of the 

 contents of the sinuses, whether pus, blood or irrigating 

 fluids, and to facilitate their escape from the nostril, j^y_ 

 irrigation on the recumbent animal should be carried out 

 with the poll elevated and the nose depressed. 



By studying Figs. 4-10 it will be seen that any collec- 

 tion of pus or other pathologic contents in the frontal sinus 

 at F will result in poor drainage so far as may be obtained 

 by trephining through the external wall only. The drain- 

 age should be completed whether the contents have formed 

 within the frontal sinus itself, or have entered it through 

 the fenestrum, FE, Figs. 5 and 6, from the superior maxillary 

 sinuses, by making an artificial communication through 

 the turbinated bone between the frontal sinus and the nasal 

 fossa at ST, Figs. 4, 5 and 1 1. This is to be accomplished 

 by breaking through the thin walls of the turbinated bone 

 by means of a probe or other suitable instrument and en- 

 larging the opening sufficiently with the probe-pointed 

 bistoury or with the finger. In locating the ^xact point 

 for making this opening intheJurbinated bone, it is advis- 

 able to pass a slightly curved heavy probe, a pair of long 

 Curved ^iiterine dressing forceps or some other slightly 

 curved and somewhat rigid instrument up the nostril to 

 the operative region, and having an index finger in the 

 sinus against the median- wall, the movements of the sound 

 can easily be felt and the wall be broken down either by 

 pushing the sound up into the sinus or thrusting the finger 

 downward into the nasal passage. 



