454 



THE EYE. 



their epithelial lining presents here and there evaginations of glan- 

 dular appearance, lined by the unpigmented cells. These evagina- 

 tions are known as ciliary glands, and to them is attributed in 

 part, at least the secretion of the fluid found in the anterior cham- 

 ber of the eye ; it is, however, still a question as to whether these 

 structures are to be regarded as true glands or simply as depressions 

 or crypts in the epithelium. 



The ciliary muscle is bounded anteriorly (toward the anterior 

 chamber) by the ligamentum pectinatum iridis, externally by the 

 cornea and sclera, posteriorly by the orbiculus ciliaris, and inter- 

 nally by the ciliary processes. It consists of nonstriated muscle- 

 fibers in the majority of vertebrates. This muscle is divided into 

 three portions. The outer or meridional division extends from the 

 posterior elastic lamina of the cornea and its continuation, forming 

 the inner wall of the sinus venosus sclerae, to the posterior portion 

 of the ciliary ring. The origin of the middle division is identical with 



Cornea! epithe- 

 lium. 



Substantia pro- 

 pria. 



Descemet's 



membrane. 

 Canal of 

 Schlemm. 



Iris. 

 .-.. Pigment layer. 



Loose connec- 

 tive tissue of 

 the conjunc- 

 tiva. 



Conjunctiva. 



Meridional fibers. 

 Radial fibers. 

 Miiller's fibers. 



Sclera. 



Processus ciliares. 



Fig. 356. Meridional section of the human ciliary body ; X 2O - 



that of the outer, but its fibers (assuming that we have before us a 

 meridional section) spread out like a fan, and occupy a large area 

 at their insertion into the ciliary ring and ciliary processes. The 

 radial course of these fibers is mterrupted by circular bundles. The 

 third or inner division {fibrce circulares, fibers of Mutter} is situated 

 between the ligamentum pectinatum, the ciliary processes, and the 

 middle portion of the muscle just mentioned, and is thus near the 

 base of the iris. 



Between the ciliary muscle and the posterior elastic membrane 

 of the cornea is an intermediate, richly cellular tissue, which maybe 

 regarded as a continuation of this elastic membrane, and which 

 forms a part of the wall of the sinus venosus. Another structure 

 internal to the foregoing and directed posteriorly is foe.' ligamentum 

 pectinatum iridis, which encircles the anterior chamber and is a con- 

 tinuation of Descemet's membrane to the base of the iris. It con- 



