Chap, iv.] THE ORBIT AND EYE. 63 



pectiiiatum already alluded to (Fig. 10). It is re 

 inarkable that in nearly every case of glaucoma these 

 gaps are occluded by the complete obliteration of the 

 angle between the periphery of the iris and the cornea, 

 which angle is normally occupied by the ligamentum 

 pectinatum. The importance of the peripheral part of 

 the anterior chamber in relation to the outflow of 

 fluid from the eye is shown in many ways. If this 

 part be blocked by the iris in perforation of the cornea, 

 or by the lens in some dislocations of that body, in- 

 creased tension of the globe is apt to follow. A like 

 increase of tension is said to attend the application of 

 the actual cautery to the sclero-corneal margin and 

 some cases of episcleritis. Dr. Brailey believes that 

 some outflow also takes place along the optic nerve. 

 It is well known that pressure upon that nerve may 

 produce oedema of the disc. The relief given to 

 glaucoma by iridectomy appears to depend upon the 

 circumstance that the operation practically opens up 

 again these channels of communication from the 

 aqueous, since the procedure, to be successful, should 

 involve an incision so far back on the sclerotic as to 

 fully pass through the angle just alluded to. It is 

 needful also that the iris should be removed quite up 

 to its attachment, and that the portion resected should 

 be considerabla The symptoms of glaucoma are all 

 explained by the effects of the abnormal tension. Thus, 

 the ciliary nerves are compressed against the unyield- 

 ing sclerotic, and give rise to intense pain, while the 

 disturbance in their function shows itself in the fixed 

 and dilated pupil and in the anaesthetic cornea. 

 Perhaps the first parts to suffer from compression are 

 the retinal blood-vessels, and the effect upon them will 

 be most obvious at the periphery of the retina, i.e. 

 at the extreme limit of the retinal circulation. Hence 

 follows that gradually narrowing of the visual field 

 which is constant in glaucoma, while the pressure 



