ON THE ANATOMY AND DISEASES OF CATTLE, &C. 11 
principal seat of ophthalmia in the horse is the conjunctiva. This 
fining of the lid becomes intensely led, and the transparency of 
the cornea is diminished, or temporarily destroyed. In periodical 
ophthalmia, that pest of the equine race, and opprobrium of our 
profession, the eye is more extensively affected: the cornea is 
opaque, the iris pale, the aqueous humour turbid, the capsule of 
the lens cloudy, and, at length, the cloudiness extends to the lens 
itself, and blindness is the result. This apparent object of the 
disease being effected, the cornea clears up ; it becomes as blight 
as ever, but the lens continues impervious, and vision is lost. 
Ophthalmia in the dog presents symptoms altogether different. 
The conjunctiva, indeed, is red, and that portion of it winch 
spreads over the sclerotica is highly injected, and the cornea is 
opaque; but as the disease proceeds, or at a very early period. of 
it, an ulcer appears on the centre of the cornea, at first superficial, 
but it enlarges and deepens, until it has penetrated the cornea, 
and the aqueous humour escapes. Granulations then spimg 
from the edges of the ulcer, and rapidly grow, and protrude 
through the fids. Under proper treatment, however, or by a pro¬ 
cess of nature, these granulations cease to sprout; tney begin to 
disappear; the ulcer diminishes; it heals ; scarcely a ti ace of it 
can be seen ; the cornea recovers its perfect transparency, and the 
vision is not in the slightest degree injured. 
This is one instance out of many in which the same organ is 
differently affected in different animals, and the same disease 
assumes different forms, and requires different treatment, and is 
attended by different sequelse. 
Medicines have different effects on different animals, for 
the expulsion of worms, or to assist the action of purgatives, two 
drachms of calomel are often given to the lioise : two grains 
would puke the strongest dog. The reason why sportsmen are 
enabled to give the excessive and preposterous doses of fifteen or 
twenty grains, is, that the stomach very soon rejects the whole, 
or the greater part, or, if a few grains be retained amidst the rugae 
of the stomach, they produce inflammation of the bowels, dis¬ 
charge of blood, and tenesmus. 
Four ounces of spirit of turpentine may be given to the hoi se, 
not only with impunity, but advantage, in spasmodic colic. One 
drachm cannot be administered to the dog but with almost certain 
destruction. 1 lately saw an instance of this. A stout spaniel 
had the tape-worm : a human surgeon ordered half an ounce of 
spirit of turpentine to be given. One or two drachms were ad¬ 
ministered, and that quantity had scarcely been received into the 
stomach, ere the animal staggered, fell, and died. 
From four to eight drachms of aloes are required to purge a 
