TREPHINING OF THE FRONTAL SINUSES. 25 



from the boue with a scalpel or bone scraper. Control the 

 hemmorhage. With the center-bit extended place the tre- 

 phine accurately upon the denuded area, perpendicular to 

 the surface of the bone, and by revolving it to and fro force 

 the center-bit into the bone and continue until the trephine 

 has cut a distinct furrow, when the center-bit should be 

 withdrawn and the operation continued, being careful to 

 maintain the trephine perpendicular to the bone. The ope- 

 ration is facilitated by grasping the shaft of the trephine be- 

 tween the thumb and fingers of one hand, constituting a 

 support in which it can glide back and forth. The pressure 

 under which the sawing is carried out must not be too great. 

 When the bony plate which has been .sawed around begins 

 to loosen, remove the trephine and insert the bone screw 

 into the centerbit opening and break out the piece of bone 

 or pry it out with the bone gouge or chisel. Smooth any 

 uneven edges of bone with the lens-shaped knife. The ab- 

 normal contents of the frontal sinus can now escape through 

 the opening or be removed with the curette, forceps or .scis- 

 sors, and the cavity irrigated with an antiseptic fluid. Leave 

 the trephine wound entirely open and dre.ss daily with anti- 

 septics. The frontal sinuses are in free communication with 

 the superior maxillary and with the superior turbinated bone 

 of the same .side so that indirectly the irrigating fluid can 

 e,scape through the nasal opening by way of the maxillary 

 sinus or of a perforation through the superior turbinated 

 bone. 



In order to prevent the aspiration of the contents which 

 are generally purulent, or may consi.st of blood or irri- 

 gating fluids, and to facilitate their escape, irrigation 

 must be carried out with the poll elevated and the head 

 flexed. 



By studying Plates IV and V it will be seen that any 

 collection of pus or other disease products at F would 

 result in poor drainage so far as may be obtained by 



