XXXII.] THE EYE. 363 



(c.) The chorio-capillaris, containing numerous sections of capil- 

 laries. 



(d.) A basement or hyaline membrane. 

 (e.) Pigment-cells containing melanin. 



7. Pigment-Cells of the Choroid (L.H.). From the inner cho- 

 roidal surface of an eye hardened in Miiller's fluid or spirit, scrape 

 off a little of the black pigment layer and mount it in balsam. 



(a.) Observe the branched pigmcnted cells, filled with brown or 

 black granules of melanin. The nucleus contains no pigment 

 granules. If the granules be discharged from the cells and float in 

 a watery fluid, they exhibit Brownian movement. The nucleus 

 stains readily with hsematoxylin. 



8. Ciliary Region, Ciliary Muscle, and Iris. Make a meri- 

 dional section through the corneo-scleral junction of a hardened eye 

 (Miiller's fluid), e.g., of an ox, cat, or rabbit, so as to include the 

 ciliary muscle and the iris Stain the section in haematoxylin or 

 eosin-hsematoxylin, and mount in balsam ; or it may be stained in 

 picro-carmine and mounted in Farrant's solution. To preserve all 

 the parts exactly in position cut it in celloidin, or stain in bulk and 

 cut in paraffin. Fix the sections on a slide by a fixative. 



(a.) Observe the cornea passing into the sclerotic, and near it an 

 opening, the canal of Schlemm (fig. 339). 



(b.) From the angle of the iris and cornea, running in a fan- 

 shaped expansion, the radiating fibres of the ciliary muscle, con- 

 sisting of non-striped muscle. The circular fibres cut transversely 

 inside the radiating fibres are not so well marked as in the human eye. 



(c.) The membrane of Descemet splits up into fibres, some of 

 which curve into the iris, others spread into the ciliary processes. 

 This region constitutes the ligamentum pectinatum iridis. 



((?.) The pigmented folds or ciliary processes. A layer of black 

 pigment-cells continuous with those of the retina continued over 

 these processes, and inside the pigment a clear unpigmented layer 

 of columnar epithelium. 



(e.) The iris, composed of five layers from before backwards. 



(i.) A layer of emloilidiuin continuous with that covering the 

 posterior surface of the cornea (fig. 339, r). 



(2.) The anterior boundary layer, chiefly consisting of branched 

 connective tissue-cells. 



(3.) The vascular layer, or body of the iris, composed of a stroma 

 of connective tissue with numerous sections of blood-vessels and 

 branched pigment-cells, and at its deeper part transverse sections of 

 the circular smooth muscular fibres, which constitute the circular 

 muscle or sphincter ]>upilhB of this organ. It is doubtful if a 

 dilator pupillae exists in man. 



(4.) The posterior liyaline layer, of an elastic nature. 



