THE TUNICS OF THE EYE 



1011 



circumference of the lens. In front, they are continuous with the periphery of the 

 iris. Their posterior surfaces are connected with the suspensory ligament of the 

 lens. 



Ora serrata 



Pars ciliaris retinae 

 Ciliary 'process 



Orbiculus 

 ciliaris 



Lens 



Retina 



Choroid 



Sdera 



FIG. 875. Interior of anterior half of bulb of eye. 



Structure. The ciliary processes (Figs. 876, 877) are similar in structure to the choroid, but 

 the vessels are larger, and have chiefly a longitudinal direction. Their posterior surfaces are 

 covered by a bilaminar layer of black pigment cells, 

 which is continued forward from the retina, and is 

 named the pars ciliaris retinae. In the stroma of the 

 ciliary processes there are also stellate pigment cells, 

 but these are not so numerous as in the choroid itself. 



According to Henderson the aqueous humor is a 

 secretion formed by the active intervention of the 

 epithelial cells lining the apices of the ciliary processes. 1 



The Ciliaris muscle (m. ciliaris; Bowman's 

 muscle) consists of unstriped fibers : it forms a 

 grayish, semitransparent, circular band, about 

 3 mm. broad, on the outer surface of the fore- 

 part of the choroid. It is thickest in front, and 

 consists of two sets of fibers, meridional and 

 circular. The meridional fibers, much the more 

 numerous, arise from the posterior margin of 

 the scleral spur (page 1007); they run back- 

 ward, and are attached to the ciliary processes 

 and orbiculus ciliaris. One bundle, according 

 to Waldeyer, is inserted into the sclera. The 

 circular fibers are internal to the meridional 

 ones, and in a meridional section appear as a 

 triangular zone behind the filtration angle and 

 close to the circumference of the iris. They 

 are well-developed in hypermetropic, but are 

 rudimentary or absent in myopic eyes. The 

 Ciliaris muscle is the chief agent in accom- 

 modation, i. e., in adjusting the eye to the vision of near objects. When it con- 

 tracts it draws forward the ciliary processes, relaxes the suspensory ligament of 

 the lens, and thus allows the lens to become more convex. 



1 Henderson. T.. Glaucoma, London. 1910. 



FIG. 876. Vessels of the choroid, ciliary pro* 

 cesses, and iris of a child. (Arnold.) Magnified 

 10 times, a. Capillary net-work of the posterior 

 part of the choroid, ending at b, the ora serrata. 

 c. Arteries of the corona ciliaris, supplying the 

 ciliary processes, d, and passing into the iris e. 

 f. The capillary net-work close to the pupillary 

 margin of the iris. 



