SENSE OF SIGHT. 87 



of the accessory organs of vision, that is, of the protectors and 

 movers of the eye. 



14. The ylobc. of the eye, (Fig. 31.) 

 is a hollow ball, filled with certain 

 humors, and so arranged that the rays 

 of light may penetrate it, and collect 

 upon the nerve which occupies its 

 bottom. 



15. The sides of this globe are com- 

 posed of a very solid membrane which 

 consists of two parts; one, situated in 

 front, and named transparent cornea ; 

 the other, occupying the sides and bot- 

 tom, and called sclerotica, (Fi<j. 31.; 



16. The sdttrntica surrounds the eye in all parts, except in 

 front; it is white, and entirely opaque : it is this part which is 

 vulgarly called the white of tk<> eye. 



17 The tran&pnri'itt cornea is, on the contrary, diaphanous; 

 it is framed into a great hole in the sclerotica, and resembles a 

 somewhat arched watch-glass, set into a hollow white ball. 



18. A short distance behind the transparent cornea, is found a 

 sort of vertical partition, named iris, from its varied colours, 

 which are seen through the cornea. Its centre is pierced by 

 an onening which is susceptible of enlargement and diminution ; 

 it is called the pupil. 



19. The space comprised between the cornea and the iris, is 

 called the anterior cliambrr of the fife, which is tilled with a trans- 

 parent liquid called the <u/in'ous humor. 



20. Behind the pupil we find the chrystnl/iue lens, which is a 

 transparent lens of a globular form, and behind the r.hrystalline 

 we find a diaphanous mass soft as jelly, which is called vitreous 

 liinnnr, and which fills all the interior of the globe of the eye. 



Explanation of Fi. '.II. An open eye, s. the sclerotica, one part ot 

 which is luined back,- ch. the choroid, r the retina, cl. the transparent 

 cornea, en. the anterior chamber, i. fhe irus, the centre of which is pierced 

 by the pupil, cr. the cry*tu;ine lens. v. the vitreous humor, n. the optic 

 nerve. 



14. What is the glohe of the rye ? 



15. Of vv sat parts do the sides of the globe of the eye consist? 



16. What is the i-clerotica ? 



17. What is the transparent cornea? 



3. What is the ins? Why is it so called? What is the pupil ? 

 ) What is that space c.lled which is comprised between the cornea and 

 iris ? What does the anterior chamber of the eye contain ? 



20. What do we find behind the pupil ? What is the form of the chryetal 

 line lens? What fills the interior of the globe of the eye ? 



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