chap, vii.i THE FACE. 101 



positions of the supra- and infraorbital foramina and 

 of the mental foramen are indicated as follows. The 

 supraorbital foramen is found at the junction of the 

 inner with the middle third of the upper margin of the 

 orbit. A straight line drawn downwards from this 

 point so as to cross the gap between the two bicus- 

 pids in both jaws, will hit both the infraorbital and 

 mental foramina. The infraorbital foramen is a little 

 over a quarter of an inch below the margin of the 

 orbit. The dental foramen in the adult is midway 

 between the alveolus and the lower border of the 

 jaw, and is a little over a quarter of an inch below 

 the cul-de-sac of mucous membrane between the lower 

 lip and jaw. At puberty the foramen is nearer to the 

 lower border of the maxilla, and in old age it is close 

 to the alveolus. The infraorbital nerve has been 

 divided for neuralgia at its point of exit, the nerve 

 being reached either by external incision or through 

 the mouth by lifting up the cheek. In other cases the 

 floor of the orbit has been exposed, the infraorbital 

 canal (the anterior half of which has a bony roof) has 

 been opened up, and large portions of the trunk of 

 the nerve have been in this way resected. Meckel's 

 ganglion has been repeatedly excised for the relief of 

 neuralgia involving the second division of the fifth 

 nerve. A triangular flap of skin is turned up from 

 the front of the cheek, and the infraorbital canal is 

 exposed. The anterior wall of the antrum is opened 

 with a trephine, and the bone is cut away from the 

 floor of the infraorbital groove so that the nerve lying 

 in that canal is fully exposed. The nerve is followed 

 back to the posterior wall of the antrum. This wall 

 having been trephined, the spheno-maxillary fossa is 

 opened up and Meckel's ganglion exposed. Beyond 

 the ganglion the foramen rotundum can be made out. 

 The infraorbital artery runs with the nerve, and that 

 vessel, together with its anterior dental branch to the 



