THE SINUSES OF THE SKULL 105 



on a level with the supra-orbital process of the frontal bone, and 

 about one inch from the middle line." At this point the frontal 

 sinus is opened just below its upper extremity. According to 

 Fleming, " the opening may be safely made half an inch or so 

 above this line, or as low as the horizontal line between the inner 

 angle of each eye, though this involves the upper end of the 

 nasal bone. The opening should be in the space between the 

 frontal suture and the eye." The dangers of allowing much variation 

 in the seat selected have already been pointed out. 



The bone is here immediately subcutaneous. The area is shaved 

 and cleansed, and the cutaneous incision, together with the removal 

 of a piece of bone, is carried out in a manner exactly similar to 

 that already described in connection with the preceding operation. 

 The only difference is that in this case the operation is much more 

 simple, since there are here no muscles to be removed or incised, 

 neither are there any important vessels or nerves near the seat. 



If for some reason the operation has been performed with the 

 animal in the recumbent position it should now be allowed to rise 

 in order that the sinuses may be irrigated through the opening 

 which has been made in the frontal sinus. This will usually cause 

 the purulent contents to be driven out through the opening which 

 has been made into the superior maxillary sinus. Various kinds 

 of irrigating solutions are subsequently used. MacQueen recom- 

 mends a solution of boracic acid, followed by a weak solution of 

 lysol. The patency of the openings into both the frontal and superior 

 maxillary sinuses should be maintained until the discharge ceases, and 

 any diseased pieces of bone should be removed by pinching off with 

 the bone forceps. 



In those cases where the communication between the frontal and 

 superior maxillary sinuses is occluded, and when the process of flushing 

 through the frontal sinus, and other methods are ineffective in 

 restoring its patency, it becomes necessary to make a counter-opening 



o 



