46 SURGICAL APPLIED ANA TO MY. [Chap. iv. 



of the internal carotid vessel, may produce all the 

 symptoms associated with pulsating orbital tumours. 



The orbital nerves may be damaged in wounds 

 of the orbit, or in fractures of the orbit and of the 

 base of the skull. They may be pressed upon by 

 tumours from various parts, by aneurisms, hsemorr- 

 hagic and inflammatory effusions. Thus Lawson re- 

 cords a case in which the optic nerve was divided by a 

 stab through the upper eyelid, without the globe being 

 injured, and without any bone being fractured. Tho 

 same nerve has also been completely torn across in 

 fractures of the orbit, and has been pressed upon in 

 fractures involving the lesser wing of the sphenoid. 

 The third, fourth, and sixth nerves, and the first divi- 

 sion of the fifth, may be affected in cases of aneurism 

 involving the internal carotid artery, where they lie in 

 relation with the cavernous sinus. They may readily 

 be pressed upon, also, by any growth involving the 

 sphenoidal fissure, such as a periosteal node springing 

 from the margin of the fissure, while the sixth nerve, 

 from its more intimate connection with the base of the 

 skull, has been directly torn across in a fracture in- 

 volving that part (Prescott Hewett). 



In paralysis of the third nerve there is 

 drooping of the upper lid (ptosis) ; the eye is almost 

 motionless, presents a divergent squint form unop- 

 posed action of the external rectus muscle, and cannot 

 be moved either inwards, upwards, or directly down- 

 wards. Rotation, in a direction downwards and out- 

 wards, can still be effected by the superior oblique and 

 outer rectus muscles. The pupil is dilated and fixed ; 

 the power of accommodation is much impaired, there 

 is diplopia, and sometimes a little protrusion of the 

 globe from relaxation of the recti muscles. These 

 symptoms refer to complete paralysis of the nerve. 

 In cases of partial paralysis, only one or two of the 

 above symptoms may be present. 



