ANATOMY OF THE BALL 311 



in the cells on the inner surface of the membrane. Anteriorly 

 the choroid is folded in upon itself to form the ciliary processes, 

 which project inward around the margin of the crystalline lens. 

 The ciliary muscle is important in accommodation. It is in 

 the shape of a muscular ring surrounding the margin of the 

 choroid just outside the ciliary processes. In front it is attached 



FIG. 89. Diagram of a vertical section of the eye. (From Yeo after Holden.) 



i, anterior chamber filled with aqueous humor; 2, posterior chamber; 3, canal of 

 Petit; a, hyaloid membrane; b, retina (dotted line); c, choroid coat (black line); d, 

 sclerotic coat; e, cornea; f, iris; g, ciliary processes; h, canal of Schlemm or Pontana; 

 i, ciliary muscle. 



to the line of junction of the cornea and sclerotic and to the liga- 

 ment on the anterior surface of the iris; behind it is lost in the 

 substance of the choroid. Its contraction, therefore, compresses 

 the vitreous humor and relaxes the suspensory ligament of the 

 lens. The iris is a circular veil hanging in front of the lens. It 

 presents a perforation a little to the nasal side of its center, the 

 pupil. It is attached in the corneo-sclerotic line. It contains 

 circular and radiating fibers. The iris divides the space between 

 the cornea and lens into two chambers, anterior and posterior 



