VITREOUS BODY CRYSTALLINE LENS. 623 



iris ; behind, by the capsule of the lens and its suspensory ligament, and the ciliary 

 processes. 



In the adult, these two chambers communicate through the pupil ; but in the 

 foetus before the seventh month, when the pupil is closed by the membrana pupil- 

 laris, the two chambers are quite separate. 



It has been generally supposed that the two chambers are lined by a distinct 

 membrane, the secreting membrane of the aqueous humor, analogous in struc- 

 ture to that of a serous sac. An epithelial covering can, however, only be found 

 on the posterior surface of the cornea. That the two chambers do, however, 

 secrete this fluid separately, is shown from its being found in both spaces before 

 the removal of the membrana pupillaris. It is probable that the parts concerned 

 in the secretion of the fluid are the posterior surface of the cornea, both surfaces 

 of the iris, and the ciliary processes. 



VITREOUS BODY. 



The Vitreous Body forms about four-fifths of the entire globe. It fills the 

 concavity of the retina, and is hollowed in front for the reception of the lens and 

 its capsule. It is perfectly transparent, of the consistence of thin jelly, and 

 consists of an albuminous fluid inclosed in a delicate, transparent membrane, the 

 hyaloid. This membrane invests the outer surface of the vitreous body ; it is 

 intimately connected in front with the suspensory ligament of the lens ; and is 

 continued into the back part of the capsule of the lens. It has been supposed by 

 Hannover, that from its inner surface numerous thin lamella? are prolonged 

 inwards in a radiating manner, forming spaces in which the fluid is contained. 

 In the adult, these lamella? cannot be detected even after careful microscopic 

 examination ; but in the foetus a peculiar fibrous texture pervades the mass, the 

 fibres joining at numerous points, and presenting minute nuclear granules at their 

 point of junction. The fluid from the vitreous body resembles nearly pure water; 

 it contains, however, some salts, and a little albumen. 



In the foetus, the centre of the vitreous humor presents a tubular canal, through 

 which a minute artery passes along the vitreous body to the capsule of the lens. In 

 the adult, no vessels penetrate its substance ; so that its nutrition must be carried 

 on by the vessels of the retina and ciliary processes, situated upon its exterior. 



CRYSTALLINE LENS AND ITS CAPSULE. 



The Crystalline Lens, inclosed in its capsule, is situated immediately behind 

 the pupil, in front of the vitreous body, and surrounded by the ciliary processes, 

 which slightly overlap its margin. 



The capsule of the lens is a transparent, highly elastic, and brittle membrane, 

 which closely surrounds the lens. It rests, behind, in a depression in front of 

 the vitreous body : in front, it forms part of the posterior chamber of the eye ; and 

 it is retained in its position chiefly by the suspensory ligament of the lens. The 

 capsule is much thicker in front than behind, structureless in texture ; and when 

 ruptured, the edges roll up with the outer surface innermost, like the elastic laminae 

 of the cornea. The lens is connected to the inner surface of the capsule by a single 

 layer of transparent, polygonal, nucleated cells. These, after death, absorb moisture 

 from the fluids of the eye ; and, breaking down, form the liquor Morgagni. 



In the foetus, a small branch from the arteria centralis retina? runs forwards, as 

 already mentioned, through the vitreous humor to the posterior part of the cap- 

 sule of the lens, where its branches radiate and form a plexiform network, which 

 covers its surface, and are continuous round the margin of the capsule, with the 

 vessels of the pupillary membrane, and with those of the iris. In the adult, no 

 vessels enter its substance. 



The kns is a transparent, double convex body, the convexity being greater on 

 the posterior than on the anterior surface. It measures about a third of an inch 

 in the transverse diameter, and about one-fourth in the antero-posterior. It 



