PHYSIOLOGICAL ANATOMY OF THE EYEBALL. 



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Ciliary Processes. The anterior portion of the choroid is arranged in the form of 

 folds or plaits projecting internally, called the ciliary processes. The largest of these 

 folds are about -^ of an inch in length. They are from sixty to eighty in number. The 

 larger folds are of nearly uniform size and are regularly arranged around the margin of 

 the crystalline lens. Between these folds, which constitute about two-thirds of the entire 

 number, are smaller folds, lying, without any regular alternation, between the larger. 

 Within the folds, are received corresponding folds of the thick membrane, continuous an- 

 teriorly with the hyaloid membrane of the vitreous humor, called the zone of Zinn. 



The ciliary processes present blood-vessels, which are somewhat larger than those of 

 the rest of the choroid. The pigmentary cells are smaller and are arranged in several 

 layers. The anterior border of the processes is free and contains little or no pigment. 



Ciliary Muscle. This muscle, formerly known as the ciliary ligament and now 

 sometimes called the tensor of the choroid, is almost universally recognized by physi- 



FIG. 243. Ciliary muscle; magnified 10 diameters. (Sappey.) 



1, 1. crystalline lens- 2, hyaloid membrane; 3, zone of Zinn; 4, iris; 5, 5, one of the ciliary processes ; 6, 6, radiating 

 fibres of the ciliary muscle; 7, section of the circular portion of the ciliary muscle; 8. venous plexus of the ciliary 

 process; 9, 10, sclerotic coat; 11, 12, cornea ; 13, epithelial layer of the cornea; 14, membrane of Descemet; 15, 

 tig-amentum iridis pectinatum ; 16, epithelium of the membrane of Descemet ; 17, union of the sclerotic coat 

 with the cornea ; 18, section of the canal of Schlemm. 



ologists as the agent for the accommodation of the eye to vision at different distances. 

 Under this view, the ciliary muscle is an organ of great importance, and it is essential, 

 in the study of accommodation, to have an exact idea of its relations to the coats of the 

 eye and to the crystalline lens. For this reason, we shall describe its arrangement as 

 exactly as possible. 



The form and situation of the ciliary muscle are as follows : It surrounds the anterior 

 margin of the choroid, in the form of a ring about of an inch wide and -^ of an inch 

 in thickness at its thickest portion, which is its anterior border. It becomes thinner 



