520 THE SOLIDS. 



them is obtained in the neighbourhood of the zona ciliaris. 

 (Plate LXVIII. fig. 7.) 



Granular nuclei of large size are seen on the walls of the 

 cellated spaces ; these are most probably concerned in the 

 secretion of the vitreous humour. That these several cellated 

 spaces communicate with each other, seems proved by the fact 

 that if the hyaloid membrane be ruptured, the whole of the 

 vitreous humour will gradually escape through the aperture. 



A layer of cells of large size and of such extreme trans- 

 parency as to be discovered only with great difficulty, are 

 described in the " Physiological Anatomy " as situated on the 

 hyaloid membrane between it and the retina : these have not 

 fallen under the observation of the writer. 



The vitreous body, then, consists of the hyaloid membrane, 

 cellated fibrous structure, the zone of Zinn, and of the vitreous 

 humour. Through the centre of this body a branch of the 

 central artery of the retina passes in early life, destined for 

 the posterior part of the capsule of the lens. 



Crystalline Lens. 



The crystalline lens is composed of capsule and body. 



The capsule is formed of a thin lamella of elastic tissue, 

 much thicker before than behind, but in all essential par- 

 ticulars similar to the posterior elastic lamina of the cornea. 

 The manner in which it is attached to the hyaloid membrane 

 has been already pointed out ; it now remains to observe 

 that the cellated fibres of the vitreous body are also inserted 

 into its posterior part. It is perfectly closed on all sides, so 

 that in the adult condition of the eye neither vessels nor 

 nerves pass through it to the lens. 



The body of the lens, transparent and jelly-like as it ap- 

 pears to the unaided sight, is yet full of elaborate and elegant 

 structure. It consists of very many layers or concentric 

 lamellae of flattened fibres, which radiate from the centre and 

 are disposed in a parallel manner with reference to each 

 other; the fibres, however, have a more complicated ar- 

 rangement than this, as will be evident from what follows. 



