EXAMINATION OF THE EYES, NOSE, AND MOUTH 



369 



Fig. 595. Interior View of the Eye 



A, Pupil. B, Iris. C, Ciliary Processes. 

 D, Corpora Nigra. 



other hand, they may be very dense and interfere with the function of 

 vision. Sometimes these opacities are presented as white spots, small or 

 large according to the nature and extent of the disease w r hich produced 

 them. Such examples are serious, and 

 unquestionably constitute unsoundness. 



While these observations are being 

 made as to the condition of the cornea 

 or superficial coat of the eye, it will be 

 necessary to note whether the pupil con- 

 tracts when the eye is exposed to light, 

 and dilates when its influence is with- 

 drawn. The latter condition may be pro- 

 duced by covering the eye with the hat 

 for three or four minutes, when the pupil 

 should dilate and contract again when 

 exposed to light. If it is found to re- 

 main widely dilated, with no disposition 



to contract, or to contract feebly and imperfectly, either the light is not 

 reaching the optic nerve, or the nerve or the iris itself is diseased. In 

 such a case the animal is clearly 

 unsound. 



To those unaccustomed to the 

 examination of eyes the appearance 

 of the corpora nigra (fig. 595) may 

 cause some confusion. These are or- 

 dinarily small black bodies attached 

 to the margin of the iris, but in some 

 instances which have come to the 

 writer's notice they have become so 

 far developed as to hang over the 

 pupil as large black masses, and while 

 doing so obstructing the ingress of 

 light and thus impairing vision. 



The crystalline lens (j, fig. 596), 

 enclosed in its capsule and placed 

 behind the pupil, will now come 

 under observation. In a normal 

 condition both these structures are 

 perfectly clear and transparent, 

 but under circumstances of disease dense opaque spots, varying from 

 the size of a pin's point to that of a pea, or a diffused opacity, 



Fig. 596.- Section of Eye 



A, Lachrymal Gland. B, Levator Palpebrse Snperioris. 

 C, Levator Oculi. D, Sclerotic Coat. K, Choroid Coat. 

 F, Retina. G, Optic Nerve. H, Vitreous Humour. 

 I, Capsule of the Lens. J, Crystalline Lens. K, Aqueous 

 Humour. L, Cornea. M, Iris. N, Upper Eyelid. 



