CILIARY PROCESSES. 429 



the appearance of the nervures or vessels of a willow leaf. Their 

 intimate structure and function are unknown. Home, Wallace^ 

 and others from their observations on the inferior animals, believe 

 Fig. ] 92.f them to be muscular af(d to 



aid in adjusting the focal 

 distance of the lens, to the 

 capsule of which they are 

 indirectly connected ; draw- 

 ing it backwards and for- 

 wards like a magnifying 

 glass, with 80 strings attach- 

 ed to its margin. Others, 

 with equal reason have 

 believed them to be erec- 

 tile, altering the posi- 

 tion of the lens by their 

 expansion or contraction. 

 Fishes with spherical lenses, according to Mr. Wallace, have 

 no ciliary processes ; the adjustment of the lens being in them 

 effected by a single membrane or muscle attached at one 

 point : the rolling of the lens, as it is drawn backwards, 

 it being a sphere, can make no difference in regard to its 

 functions. 



The ciliary body, (or the radiated ring formed by all the 

 processes) is about two lines broad in the human subject ; but 

 the part next to the nose is rather narrower than the rest of it. 



The black pigment is spread over the whole of the posterior, 

 or internal surface of the ciliary body ; but it is much more 

 abundant towards the circumference than towards the centre. 

 It is also more abundant in the furrows between the ciliary 

 processes than it is in the processes themselves ; and as the 

 membrane, of which the processes or plaits are formed, is of a 



* Structure of the eye, by W. C. Wallace. New York, 1S36. 



f This figure from Zinn's work, represents the corpus ciliare or circle of 

 ciliary processes in man, on a large scale. In the centre is seen the iris, with 

 its pupillary opening. There is certainly no direct connexion, between the 

 central extremities of the ciliary processes and the capsule of the lens. p. 



