THE UVEAL TRACT. 201 



be attached to the choroid in front of the retina. Consists of meridional fibres 

 drawing the choroid forwards, and circular fibres which relax the zonula 

 and permit the lens to become more convex, from its own elasticity. 

 Annular Muscle of Muller, consists of separate circular bundles at the 



anterior internal angle of the ciliary body. 



Circulus Arteriosus Major and Minor, are arterial circles on the ciliary 

 muscle, formed by branches of the long posterior ciliary and anterior 

 ciliary arteries. 



What is the Iris 6 ? It is a perforated c.urtain, suspended in the aqueous 

 humor behind the cornea and in front of the lens, and is the anterior portion 

 of the middle tunic of the eyeball, being continuous with the ciliary muscle 

 and the choroid coat. It is about \ inch wide, T ^ 7 inch thick, and is com- 



FIG. 99. 



posed of radiating and circular muscular fibres, a fibrous stroma and pigment 

 cells, covered by a layer of irregular cells continuous with those of the mem- 

 brane of Descemet. The 



Pupil, is the central opening in the iris, situated a little to the nasal side 



of the centre, diameter T ^ to inch. 



Ligamentum Pectinatum Iridis, or Dollinger's band, is the suspensory 

 ligament of the iris, connecting its ciliary margin with the corneo- sclerotic 

 junction. It is formed of strong fibrous prolongations from the membrane 

 of Descemet and the posterior surface of the cornea. 



Fontantfs Spaces, are spaces between the prolongations which form the 

 ligamentum pectinatum. In some animals, as the ox, they fornf regular 

 canals. 



