264 Mammalia. 



groove is the outer wall of a venous canal (sinus circularis 

 iridis), the Canal of Schlemm ; the inner wall of this canal is 

 to be seen on the middle coat of the eye, just within the 

 thickest part of the white ring which by the removal of the 

 Sclerotic coat has been disclosed (around the eye just beneath 

 the anterior boundary of the Sclerotic). The white ring just 

 named marks the ciliary ligament and muscle, which limit 

 the extent forwards of the black Choroid coat. 



The Ciliary muscle forms a ring of unstriped muscular tissue ; 

 its fibres are attached in front to the inner surface of the Sclerotic 

 coatf and are also connected with the terminal fibres of the 

 posterior elastic layer of the Cornea. The Ciliary ligament, in- 

 ternal to the Ciliary muscle, surrounds the Iris nearly opposite 

 the junction of the Cornea with the Sclerotic tunic : it may 

 serve the purpose of supporting the other coats at the fore 

 part of the Eye. 



It may now be noted that the Iris is connected by its cir- 

 cumferential border with the Choroid, the Cornea, and the 

 Ciliary ligament and muscle ; whilst its inner edge is the 

 boundary of the Pupil : its anterior surface is variously 

 coloured. 



The outer surface of the Choroid is flocculent, and is covered 

 by remnants of a pigmentary areolar tissue (membrana fusca) 

 between it and the Sclerotic coat : in it may be seen small 

 veins arranged in parallel arches (vasa vorticosa) ; and lying 

 upon its surface are the ciliary arteries and nerves. 



Reflection of Half of the Iris. The student should now 

 carefully lift up a portion of the Iris in the forceps, and with 

 the scissors separate it (for half its circumference), from its 

 attachment along the inner margin of the ciliary muscle, and 

 reflect it. 



By this means an anterior view of the Ciliary processes may 

 be obtained. These Ciliary processes are a series of plaits or 

 folds, disposed in a circle, and projecting inwards, at the back 

 of the circumferential portion of the Iris ; they form the an- 



