48 A MANUAL OF ANA TO MY. 



The Gasserian ganglion is developed upon the sensory 

 portion of the fifth nerve, and lies in a shallow depression 

 upon the antero-superior surface of the apex of the petrous 

 portion of the temporal bone. The ganglion receives sym- 

 pathetic filaments from the carotid plexus. 



From the anterior margin of the ganglion three trunks 

 composed of sensory fibres are given off. The upper one 

 is the ophthalmic branch, which traverses the cavernous 

 sinus and takes its exit from the skull through the sphe- 

 noidal fissure, the middle is the superior maxillary, which 

 leaves through the foramen rotundum, and the third branch 

 is the inferior maxillary, which, with the motor root, 

 descends through the foramen ovale ; these two, being 

 joined external to the skull, form the inferior maxillary 

 nerve. 



DISSECTION OF THE ORBIT. 



If the skull is to be preserved intact the contents of the orbital cavity are to 

 be removed as follows : 



Cut through the orbicularis palpebrarum around the margin of the orbit and 

 open the socket of the eye. 



Scratch in the fascia at the upper part until the levator palpebrse superioris 

 is found. Also find the pulley of the superior oblique at the inner, superior, 

 and anterior part of the cavity. 



Below find the origin of the inferior oblique. 



Now the pulley of the superior oblique and the origin of the inferior oblique 

 must be divided, and then after separating the orbital fascia from the bony 

 wall the arteries, nerves, veins, and muscles are to be divided as far posteri- 

 orly as possible, and the eye removed for further study. 



If the brain has been removed as previously directed and the skull is not to 

 be kept, the student should remove the upper wall of the orbit as follows : 



With a fine saw cut through the vertical plate of the frontal bone still left, 

 over the outer and inner angles of the orbit. Break this piece of bone off. 

 Separate the orbital fascia from the roof of the orbit, marking the location of 

 the pulley of the superior oblique, as far posterior as the sphenoidal fissure. 

 With a pair of bone cutters or a chisel cut the roof of the orbit away, leaving 

 the pulley of the superior oblique in place. 



Remove the presenting portion of the orbital fascia, and carefully pick away 

 the fat which covers the several structures pertaining to the eye. 



