206 D. DAVIDSON BLACK 



The ophthalmic division of the fifth nerve is the most dorsally 

 placed nerve trunk in the orbital fossa and at the level of the 

 central tendon it divides into two branches of about equal size. 

 The most mesial branch divides into two parts upon the dorsal 

 surface of a fiat muscular band whose origin is from the common 

 central tendon and whose insertion is into the deep fascia of the 

 skin lateral to the notch representing the inner canthus. The 

 branches of the nerve become related to the mesial and lateral 

 borders of this muscle. 



The more lateral branch courses laterad almost at right angles 

 to the parent trunk upon the anterior border of a second fiat mus- 

 cular band arising from the central tendon and being inserted 

 into the fascia in the region of the external canthus. All the 

 branches of the ophthalmic division of the fifth nerve enter the 

 subcutaneous tissue at the bony margin of the orbit. Although 

 considerable disturbance occurred in this case in the areas usually 

 supplied by the supratrochlear, frontal, and supraorbital nerves, 

 it is possible that the branches of the fifth nerve here described 

 may correspond to these. 



The flattened bands of muscular tissue described in connec- 

 tion with the branches of the fifth nerve are present in essentially 

 similar relations on both sides and probably represent an anom- 

 alous arrangement of the levator palpebrae superioris muscle. 



Both foramen ovale and foramen rotundum, transmitting re- 

 spectively the mandibular and maxillary divisions of the fifth 

 nerve, are illustrated in figure 8, and the course of the maxillary 

 division is indicated in dotted lines till it reaches the space opened 

 for the dissection of the eye. The posterior boundary of the 

 orbital fossa is here seen to be formed by two rounded bony emi- 

 nences having their convex anterior borders inclined to one an- 

 other in such a fashion as to form a V-shaped notch in the mid- 

 line. Examination shows that these apparently represent the 

 bony roofs of the tooth crypts. It is to be noted that the pos- 

 terior boundary of the orbital fossa is a considerable distance 

 behind the region of the central tendon. 



The maxillary division of the fifth nerve passes over the roof 

 of the crypt and is lost sight of at about the middle of the an- 



