TREPHINING OF THE FRONTAL SINUSES. 



27 



the thumb and fingers of one hand, constituting a support 

 in which it may turn back and forth. The pressure under 

 which the trephining is carried out must not be too great 

 or the instrument may become wedged and broken. 



When the bony plate which has been isolated begins to 

 loosen, remove the trephine and break, or pry out the piece 

 of bone with the bone gouge or chisel. Smooth any uneven 

 edges of bone with a heavy scalpel or by re-inserting 

 the trephine and using it as a rasp. The abnormal contents 

 of the sinus may now escape through the opening or be re- 

 moved with the curette, forceps or scissors, and the cavity 

 irrigated with an antiseptic fluid. 



Leave the trephine wound entirely open and irrigate the 

 sinuses daily with antiseptics. 



The frontal, being in free communication below with the 

 superior maxillary sinus, the irrigating fluids may fall 

 directly into the latter until it becomes filled. The superior 

 turbinated bone of the same side forming the median wall 

 of the frontal sinus, it is commonly perforated by necrosis, 

 in cases of serious disease establishing a communication be- 

 tween the frontal and nasal cavities, through which pus 

 and irrigating fluids readily escape into the nostril. 



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 

 anatomical arrangement of these parts, opposite N, Plates 

 VII-X, shows very clearly that it is impossible as the 

 margins 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, any 

 irrigation on the recumbent animal should be carried out 

 with the poll elevated and the head flexed. 



