VETERINARY OPHTHALMOLOGY. 85 



face of the cornea. On the back of the iris is a thicker 

 layer containing i:»igment, wliich is continuous with 

 that of the ciliary body and choroid. Xow, this layer 

 of pigment, the tcveciy may be frequently seen as 

 small bodies on a pedicle or stem in the pupillary 

 aperture. Indeed, they may pass through and show 

 in the anterior chamber. Called soot-balls (corpora 

 nigra). More often seen at the upper (pupillary) border. 



In color they are brownish- 

 black. Unstriped muscle fiber 

 is the predominating constituent 

 of the iris, contained in a stroma 

 of connective tissue, which also 

 contains the vessels,nerves, lymph 

 spaces and cells. Around the 

 pupil some certain fibers are ar- ^ ^ 



ranged circularly. This is the 



sj^hincter jmjnlhv, and the dilator ai the pupil is formed 

 of radiating fibers. The peculiar disposition or juncture 

 of these two sets of fibers is that they join each 

 other near the pupil in curves, as I here depict. 

 The sphincter governed l)y the third pair, the dilator 

 by the sympathetic. The iris has three dift'erent classes 

 of nerves sent to it from the ciliary ganglion, which 

 ganglion has three roots — sensitive, motor and sympa- 

 thetic. The twigs which emanate from this ganglion 

 pass to the sclera, surrounding the optic nerve. These 

 are named the short ciliary. The two long posterior 



#0 



