[ 168 ] 



SECT. XVII. 



OF SIGHT. 



255. THE instruments of vision, the eyes,* are two 

 moveable globes, fixed to the optic nerves whose de- 

 cussationwe formerly noticed (211), as it were to stalks, 

 in such a manner, that their insertion is not exactly 

 opposite the centre of the cornea and iris, but behind 

 this imaginary axis, rather nearer to the nose. 



256. They consist of various coats containing pellu- 

 cid humours of different degrees of density, so placed 

 that the rays of light can pass from the transparent 

 anterior segment of the bulb to the opposite part of 

 the fundus. 



257. The external coat is called sclerotic. It is de- 

 ficient in the centre, and that part is filled up by the 

 cornea, which is transparent, lamellated, more or less 

 convex, and projects like the segment of a small globe 

 from one of larger size.f 



258. The interior of the sclerotica is lined by the 

 chorioid, which abounds in blood-vessels, especially 

 vorticose veins, and is died on each side by a black 



* Sommerring, Abbildungen des menschlichen Auges. Franckfurt. 1801. fol. 



f Ad. Jul. Rose, De Morbis Comes ex fabrica ejus declaratis. Lips. 

 1767. 4to. 



G. H. Gerson, De Forma Cornea deque singular* Visits Phasnomenu. Get- 

 ting. 1810. 4to. 



