MEMBRANA PUPILLARIS. 427 



form the lesser arterial circle of the iris,* which is never seen 

 till after the rupture of the membrane. The lining membranes 

 of the two chambers then form a continuous coat. 



The iris was formerly supposed to be a continuation of the 

 choroid coat ; but it is now generally agreed that it is a 

 distinct membrane ; for when the eye is very slightly affected 

 by putrefaction, it can be pulled off, and the choroides left 

 entire. 



The choroides, on the contrary, cannot be separated from 

 the ciliary processes without laceration ; and when the pig- 

 ment is washed away from its internal surface, it is very 

 obvious that these processes are continued from the substance 

 of the choroides and reflected inwards, so as to form a pro- 

 jection into the cavity of the eye. 



Of the Ciliary Body, and the Ciliary Processes. 



This internal projection forms a ring or a circle, which has 

 the ciliary ligament before described, near its circumference, 

 and anterior to it.f 



It is so disposed, that the whole of its internal or posterior 

 surface appears to be formed into radiated plaits, which extend 

 from the circumference to the central vacuity, where they 

 terminate. 



The whole of this structure, or the membrane thus plaited, 

 is called the ciliary body, while the plaits are called the ciliary 

 processes. 



In a natural state of the eye, .the ciliary body is covered 



* The thickness of the iris, is considered three or four times greater than 

 that of the thinner portions of the choroid. When the pigment is carefully 

 wiped away from the posterior surface of the iris, we see a great number of 

 straight, raised, and converging lines, which are confounded into a membranous 

 zone near the pupil, formed by the circular fibres. These have some resem- 

 blance in shape to the ciliary processes. p. 



f The ciliary ligament or circle, evidently serves as an attaching medium 

 between the iris, cornea, and sclerotica. Its structure is not fully understood. 

 Some modern anatomists, have considered it in the light of a nervous gang- 

 lion ; others as composed of muscular fibres. It forms the inner wall of the 

 canal of Fontana, described p. 414. Vide, Knox on the Muscularity of the 

 Ciliary Ligament. Ed. Philos. f rans. vol. x. p. 



