34 SURGICAL APPLIED ANATOMY. [Chap. iv. 



margins of the orbit than it is to the sides, and the 

 greatest interval between the globe and the orbital 

 wall is on the outer side. The interior of the orbit is 

 most conveniently reached by incisions made to the 

 outer side of the globe, and, in excision of the eye- 

 ball, the scissors are introduced on that side when the 

 optic nerve has to be divided. A propos of this last 

 matter, it may be noted that the readiest way to 

 reach the nerve is to follow the line of the outer wall 

 of the orbit, since a continuation of that line across 

 the sphenoidal fissure will hit the outer rim of the 

 foramen. The bones forming the floor, the roof, and 

 the inner wall of the orbital cavity, are very thin, 

 especially in the last-named situation. Thus, foreign 

 bodies thrust into the orbit have readily penetrated 

 into the cranial cavity, into the nose and ethmoidal 

 cells, and, when directed from above, into the aiitrum. 

 In several instances, a sharp pointed substance, such 

 as the end of a stick or foil, has been thrust into the 

 brain through the orbit, and has left but little 

 external evidence of this serious lesion. Nelaton 

 mentions a case in which the internal carotid artery 

 was wounded through the orbit. 



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 fossse, (3) from the antrum, and (4) from the 

 temporal or zygomatic fossse. 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 sphenoidal fissure, 

 from the nose through the nasal duct, and from the 

 two fossa3 named through the spheno-maxillary fissure. 

 Distension of the frontal sinus by retained mucus or 

 pus may lead to a prominent tumour at the upper and 



