THE SCLEROTIC COAT. 



15 



Transverse ditto 



Greatest thickness of the ciliary body . . . . . . . . 



Thickness of the iris .......... 



Length of the radius of curvature of the anterior surface of the cornea . 



Radius of the posterior surface of the sclerotic 



Radius of curvature of the anterior surface of the lens 



Radius of the posterior surface ........ 



Distance of the middle of the posterior surface of the lens from the middle of 



retina 

 Distance between the centre of the spot of entrance of the optic nerve and 



middle of the fovea centralis retinaa ........ 



the 



the 



9'1 

 1*1 



O'l 



7*8 



12'5 



lO'O 



G'O 



15'0 

 3-5 



somewhat thickened owing to the attachment and spreading over it of the tendons 

 of the ocular muscles. The optic nerve pierces this coat about 2'5 to 3 mm. in- 



Anterior cJiouriber 



Iris 



Anterior cULcwu 

 - ' " 



Great 



-uortLcase, 

 ueln. 



cLUcuru 

 Fig. 16. DIAGRAM SHOWING THE PRINCIPAL NERVES AND BL.OOD-VESSELS OF THE EYEBALL. (Testut. 



ternal to the posterior pole of the eyeball, and about 1 mm. below a horizontal plane 

 passing through the poles ; the opening is somewhat smaller at the inner than at the 

 outer surface of the coat. The outer fibrous sheath of the nerve blends with the 

 sclerotic at the margin of the aperture : in consequence of this arrangement, when 

 the nerve is cut oif close to the eyeball, the funiculi seem to enter by a group of 

 pores ; and to the part of the sclerotic thus perforated the name of lamina cribrosa 

 is given. Around this cribrous opening are smaller apertures for the posterior 

 ciliary arteries and the ciliary nerves. These are disposed in the manner shown in 

 the accompanying diagram (fig. 16). Nearer the equator of the globe the sclerotic 

 is pierced by four apertures which transmit veins (venae vorticosse). 



