ANATOMY OF THE EYE 25 



the internal base of the muscle body and were discovered 

 by Heinrich Muller; hence, it is called Muller's portion. 

 At the anterior zone are folds of connective-tissue 

 stroma — seventy or more in number — intermixed with 

 numerous blood-vessels and branched pigment-cells. 

 The anterior internal portion of the body is continuous 

 with the iris. 



A layer of pigmented and one of non-pigmented cells 

 lines the body, and these are continuous with the poste- 

 rior layers of the iris forward and the chorioid and 

 retina backward. This intimate association of the 

 pigment, from the optic disk to the pupillary border, 

 has given it the name of the uvea. 



The ciliary muscle is the muscle of accommodation, 

 and by its contraction the lens becomes more convex, 

 shortening its focus, and accommodating vision for 

 near work. This and the sphincter and dilator pupillae 

 are the intrinsic muscles of the eyeball. 



The lens is the principal refractive medium. It is 

 biconvex, perfectly transparent, colorless, circular in 

 shape, and is enclosed in a delicate transparent capsule. 

 It Kes between the iris and the vitreous, where it rests 

 in a fossa in the latter substance— the fossa petellaris. 

 The space between the border of the lens and the ciliary 

 muscle is known as circumlental space. The anterior 

 portion supports the pupillary border of the iris. 



The lens is composed of hexagonal prisms, arranged 

 in concentric layers supported by a cement substance. 



