266 DISEASES OF THE HORSE. 



confined to the deeper structures, and the swelling, redness, and ten- 

 derness of the superficial structures will be less marked. When the 

 external coats thus comparatively escape the extreme anterior edge of 

 the white, or sclerotic, coat where it overlaps the border of the trans- 

 parent cornea is in a measure free from congestion, and, in the absence 

 of the obscuring dark pigment, forms a whitish ring around the 

 cornea. This is jDartly due to the fact that a series of arteries (cili- 

 ary) passing to the inflamed iris penetrate the sclerotic coat a short 

 distance behind its anterior border, and there is therefore a marked 

 difi'erence in color between the general sclerotic occupied between 

 these congested vessels and the anterior rim from which they are 

 absent. Unfortunately, the pigment is often so abundant in the 

 anterior part of the sclerotic as to hide this symptom. In internal 

 ophthalmia the opacity of the cornea may be confined to a zone around 

 the outer margin of the cornea, and even this may be a bluish haze 

 rather than a deep fleecy white. In consequence it becomes possible 

 to see the interior of the chamber for the aqueous humor and the 

 condition of the iris and pupil. The aqueous humor is usually turbid, 

 and has numerous yellowish white flakes floating on its substance 

 or deposited in the lower part of the chamber, so as to cut off the 

 view of the lower portion of the iris. The still visible portion of 

 the iris has lost its natural, clear, dark luster, which is replaced by 

 a brownish or yellowish sere-leaf color. This is more marked in 

 proportion as the iris is inflamed, and less so as the inflammation is 

 confined to the choroid. The amount of flocculent deposit in the 

 chamber of the aqueous humor is also in direct ratio to the inflamma- 

 tion of the iris. Perhaps the most marked feature of internal ophthal- 

 mia is the extreme and painful sensitiveness to light. On this 

 account the lids are usually closed, but wdien opened the pupil is 

 seen to be narrowly closed, even if the animal has been kept in an 

 obscured stall. Exceptions to this *are seen when inflammatory effu- 

 sion has overfilled the globe of the eye, and by pressure on the retina 

 has i^aralyzed it, or when the exudation into the substance of the 

 retina itself has similarly led to its j^aralysis. Then the pupil may 

 be dilated, and frequently its margin loses its regular ovoid outline 

 and becomes uneven by reason of the adhesions which it has con- 

 tracted with the capsule of the lens, through its inflammatory exu- 

 dations. In the case of excessive effusion into the globe of the eye 

 that is found to have become tense and hard so that it can not be 

 indented with the tip of the finger, paralysis of the retina is apt to 

 result. With such paralysis of the retina, vision is heavily clouded 

 or entirely lost ; hence, in spite of the open pupil, the finger may be 

 approached to the eye without the animal becoming conscious of it 

 until it touches the surface, and if the nose on the affected side is 

 gently struck and a feint made to repeat the blow the patient makes 



