TREPHINING THE SUPERIOR MAXILLARY SINUS. i 1 
elevator is applied and tlie piece lifted out. But if this cannot be effected, 
recourse must again be had to the trephine. The lining mucous membiane 
generally remains in situ, or hanging in shreds to the sides of the opening. 
After removing sharp edges with the lenticular knife, the fingei may 
be introduced for examination. Bleeding is usually slight. If it rendeis 
examination difficult, the sinus is syringed out with water and diied 
with a small sponge, when the mucous membrane may be more closely 
examined. In empyema, pus usually flows from the opening spon¬ 
taneously, and whatever remains can be removed by washing. Any new 
Fig. 49.—Lateral view of horse’s skull ; the facial sinuses exposed. 
Posterior portion of frontal sinus ; co, anterior portion of same ; ct", the septum dividing 
+hem • b, posterior portion of the anterior turbinated bone ; c cavity of nostril ; d, ethmoid 
bone ; e. superior maxillary sinus (lower part), which is divided from the upper part hh by 
the thin septum i ; e' bony plate forming the lateral boundary of the posterior turbinated 
bone/- a! infraorbital canal; Jc, line dividing the upper (thin) from the lower (thick) 
portion of the septum ; m, lower margin of the maxillary sums ; n, ductus ad nasam ; 
o, orbit ; p, zygomatic ridge. 
growths can also be taken away. The opening is closed with a plug of 
tow or jute. 
To facilitate drainage Siedamgrotzky has recently suggested a modified 
method of operation. He operates about J to § of an inch in fiont of 
a horizontal line drawn through the two inner angles of the eyes, and 
pi to 1^ inches from the middle line of the face. After washing out the 
sinus cavity he effects a communication between it and that of the nose 
by thrusting a director downwards and inwards at the deepest spot, 
breaking through the thin plate of bone and the mucous membrane 
covering it, and enlarging the opening so made by excising with a 
tenotome an oval fragment | inch long and f inch wide. To avoid 
injuring the septum nasi the knife is only introduced a slioit distance 
and the operation performed at the deepest spot. The resulting bleeding 
ceases in a few minutes ; if not, the cavity may be plugged. To prevent 
