TEE EYE. 



823 



covered by a very thick layer of pigment named the uvea: portions of 

 which, supported by a small pedicle, frequently pass through the 

 pupillary aperture and appear in the anterior chamber of the eye, where 



Fig. 386. 



THE ETE (human) WITH THE SCXBEOTIC COAT REMOVED. 



1, Sclerotic coat ; 2, Veins of the choroid ; 3, Ciliary nerves ; 4, Veins of the 



choroid ; 5, Ciliary ligament ; 6, Iris. 



they are known as " soot-balls " or corpora nigra. (There are frequently 

 several of these black spongy masses, which are generally attached to the 

 upper border of the pupil ; on the lower margin, when present, they are 

 much smaller. Their colour is a brownish-black. They are sometimes so 

 large as to give rise to apprehensions of injury to the vision.) 



The larger circumference of the 

 iris is attached to the ciliary liga- 

 ment, which unites it to the 

 choroid; it is also related to the 

 margin of the cornea, as well as to 

 that of the sclerotic opening. 



The lesser, or internal circum- 

 ference, is elliptical, and circum- 

 scribes the pupillary aperture. 



Strttctubi!. — The organisation 

 of the iris has been much dis- 

 cussed ; but at present it is ad- 

 mitted that its principal element 

 is imstriped muscular fibre. A 

 proper membrane and two epi- 

 thelial layers enter into its form- 

 ation. The proper membrane has, 

 for its framework, circular or radia- 

 ting fasciculi of wavy connective 

 tissue, with pigment cells. Be- 

 tween the fasciculi are placed the ", Sphincter of the pupil ; b, b, Radiating fasciculi 

 unstriped fibres ; these are disposed .°f ^j'^'^^';''^^' ' "' '' Co^-^ctive tissue with 

 in a circular manner around the 

 pupil to constitute the pupillary sphincter, and others radiate from the lesser 



MDSC0LAR STBUCTDEE OF THE lEIS OF A 

 WHITE EAEEIT. 



