42 SURGICAL APPLIED ANATOMY. [Chap. iv. 



case in which the internal carotid artery was wounded 

 through the orbit. Certain cases of pulsating orbital 

 tumour which depend upon a communication between 

 the carotid artery and the cavernous sinus have a 

 traumatic origin. 



A reference to the relations of the orbital walls will 

 show that a tumour may readily invade the orbit by 

 spreading from (1) the base of the skull, (2) from the 

 nasal fossoe, (3) from the antrum, ami (4) from the 

 temporal or zygomatic fossae. In any of these instances 

 the growth may enter the orbit by destroying the 

 intervening thin layers of bone, and, in tumours of 

 the antrum, this is the usual mode of entry. It 

 may, however, extend more readily from the cranial 

 cavity through the optic foramen or spheiioidal fissure, 

 from the nose through the nasal duct, and from the 

 two fossae named through the spheno-maxillary fissure. 

 After violent blows upon the temple blood has found 

 its way into the orbit through the spheno-maxillary 

 fissure, and has led to subconjunctival ecchymosis. 

 Distension of the frontal sinus by retained mucus or 

 pus may lead to a prominent tumour at the upper and 

 inner margin of the orbit, above the level of the 

 tendo oculi, which may cause- displacement of the 

 globe downwards, outwards, and forwards. The bones 

 of the orbit are peculiarly apt to be the seat of ivory 

 exostoses, which may in time entirely occupy the orbital 

 cavity. At the upper and outer angle of the orbit a 

 congenital sebaceous cyst is sometimes met with. It 

 lies beneath the orbicularis muscle, and is often con- 

 nected at some depth with the orbital periosteum. 



The capsule of Tenon. The best description 

 of this capsule has been given by Mr. Lockwood ; of 

 his researches Prof. Cunningham provides the follow- 

 ing resume : 



The capsule is a firm loose membrane spread over 

 the posterior fths of the globe, the cornea alone being 



