798 



DISSECTION OF THE EYE. 



two of them 

 named long 

 ciliary, 



anterior 

 ciliary. 



Veins are 

 posterior 

 ciliary, 



and anterior 

 ciliary. 



Ciliary 

 nerves 



end in iris 

 and ciliary 

 muscle. 

 Space con- 

 taining 

 aqueous 

 humour 



is partly 

 divided into 

 two by the 

 iris : 



anterior 

 part; 



posterior, 



its bound- 

 aries. 



Retina 



is in two 

 parts. 



choroid, divide into branches which enter its substance at different 

 points. 



Two of this set (long ciliary) are directed forwards between the 

 sclerotic and choroid, one on each side of the eyeball, and form a 

 circle round the iris in the ciliary muscle, as before explained. In 

 the ball the outer one lies rather above, and the inner, rather 

 below the middle. 



The anterior ciliary arteries, five or six in number, are smaller 

 than the posterior, and arise at the front of the orbit from muscular 

 branches ; they pierce the sclerotic coat about a line behind the 

 cornea, supply the ciliary processes ; and join the circle of the long 

 ciliary vessels. In inflammation of the iris these vessels are 

 enlarged, and offsets of them form a ring round the cornea. 



The posterior ciliary veins have a different arrangement from the 

 arteries. The branches form arches (vasa vorticosa ; fig. 289, A) ii 

 the superficial part of the choroid coat, external to the arteries, and 

 converge to four or five trunks, which perforate the sclerotic coat 

 about midway between the cornea and the optic nerve to end in the 

 ophthalmic veins. 



The anterior ciliary veins begin in a plexus within the ciliary 

 muscle, receiving tributaries from the iris and the ciliary processes, 

 and accompany the arteries through the sclerotic to end in the 

 ophthalmic trunks : they communicate with the venous space of 

 the canal of Schlemm. 



The ciliary nerves (fig. 289, /) are derived from the lenticular 

 ganglion, and the nasal nerve. Entering the back of the eyeball 

 with the arteries, they are continued with the vessels between the 

 sclerotic and cboroid as far as the ciliary muscle : at this spot 

 the nerves send offsets to the cornea, and piercing the fibres of the 

 ciliary muscle, enter the iris. Offsets from the nerves supply the 

 ciliary muscle and the choroid, and fine twigs enter the sclerotic. 



CHAMBER OP THE AQUEOUS HUMOUR (fig. 288, p. 791). The 

 space. between the cornea in. front and the lens behind, in which 

 the iris is suspended, contains a clear fluid named the aqueous 

 humour. In the foetus before the seventh month this interval is 

 separated into two by the iris and the pupillary membrane ; but 

 in the adult it is only partly divided, for the two communicate 

 through the- pupil. The boundaries of the two chambers may be 

 seen in the eye on which a vertical section has been made. 



The anterior chamber is the larger of the two ; it is limited in' 

 front by the cornea, and behind by the iris. 



The posterior chamber (i) is a narrow interval behind the iris at 

 the circumference, which is bounded in front by the iris ; behind 

 by the lens capsule, and by a piece of the membrane (suspensory 

 ligament of the lens) on the front of the vitreous humour ; and at 

 the circumference by the ciliary processes. 



THE RETINA (fig. 288, c). This layer is the innermost and most 

 delicate of the coats of the eyeball, and is situate between the 

 choroid coat and the transparent mass (vitreous) in the interior. It 

 consists of two parts, viz., a thin membrane internally, continuous- 



