HUMOURS. 451 



The connexion between these folds and the ciliary processes may be 

 very easily demonstrated by dividing an eye transversely into two por- 

 tions, then raising the anterior half, and allowing the vitreous humour to 

 separate from its attachment by its own weight. The folds of the zonula 

 will then be seen to be drawn out from between the folds of the ciliary 

 processes. 



HUMOURS. The Aqueous humour is situated in the anterior and poste- 

 rior chambers of the eye; it is a weakly albuminous fluid, having an alka- 

 line reaction, and a specific gravity very little greater than that of distilled 

 water. According to Petit, it scarcely exceeds four or five grains in 

 weight. 



The anterior chamber is the spftce intervening between the cornea in 

 front, and the iris and pupil behind. The posterior chamber is the narrow 

 space, less than half a line in depth,* bounded by the posterior surface of 

 the iris and pupil in front, and by the ciliary processes, zonula ciliaris, 

 and lens behind The two chambers are lined by a thin layer, the secret- 

 ing membrane of the aqueous humour. 



The Vitreous humour forms the principal bulk of the globe of the eye. 

 It is an albuminous and highly transparent fluid, enclosed in a delicate 

 membrane, the hyaloid. From the inner surface of this membrane, nu- 

 merous thin lamellaB are directed inwards, and form compartments in 

 which the fluid is contained. According to Hannover, these lamellae have 

 a radiated arrangement, like those on the transverse section of an orange, 

 and are about 180 in number. In the centre of the vitreous humour is a 

 tubular canal, through which a minute artery is conducted from the arteria 

 centralis retinae to the capsule of the lens. This vessel is injected without 

 difficulty in the foetus. 



The Crystalline humour or lens is situated immediately behind the pu- 

 pil, and is surrounded by the ciliary processes, which slightly overlap its 

 margin. It is more convex on the posterior than on the anterior surface, 

 and is embedded in the anterior part of the vitreous humour, from which 

 it is separated by the hyaloid membrane. It is invested by a peculiarly 

 transparent and elastic membrane, the capsule of the lens, which contains 

 a small quantity of fluid, called liquor MorgagniJ and is retained in its 

 place by the attachment of the zonula ciliaris. Dr. Jacob is of opinion 

 that the lens is connected to its capsule by means of areolar tissue, and 

 that the liquor Morgagni is the result of a cadaveric change. 



The lens consists of concentric layers, of which the external are soft, 

 the next firmer, and the central form a hardened nucleus. These layers 

 are best demonstrated by boiling, or by immersion in alcohol, when they 

 separate easily from each other. Another division of the lens takes place 

 at the same time : it splits into three triangular segments, which have the 

 sharp edge directed towards the centre, and the base towards the circum- 

 ference. The concentric lamellaB are composed of minute parallel fibres, 

 which are united with each other by means of scalloped borders, the con- 



* Winslow and Lieutaud thought the iris to be in contact with the lens; it frequently 

 adheres to the capsule of the latter in iritis The depth of the posterior chamber i 

 greater in old than in young persons. 



f John Baptist Morjjagni was born in 168'2. He was appointed Professor of Medi 

 cine in Bologna, and published the first part of his "Adversaria Amitomioa ' 1.1 1706 

 He died in 1771 



