12 MR. percivall’s introductory lecture 
is readily washed off by the tears, and thus discharged out of 
the eye altogether. 
These curious facts and phenomena, gentlemen (to which 
might be added, taking the whole animal creation, others almost 
ad infinitum), are the results of investigations in anatomy and 
physiology : to every one they are interesting, even on the score 
of their philosophical beauty; to us they are not only equally 
interesting in that sense, but become “ part and parcel” of our 
professional knowledge. 
The ultimate object we have in view, in learning the anatomy 
and physiology of an animal, is, that we may be able to discover 
and understand the nature of its diseases; and with this knowledge 
devise such means as are best adapted for their cure. This com¬ 
prehends the pathology of the animal. We find the struc¬ 
ture of a part in a state of health together with the func¬ 
tions it performs to be of such a description; and whenever we 
behold any deviation from these, we say the part is in a state of 
disease. For example, we know that the eye should appear 
transparent: consequently, should it look muddy or opaque, we 
say it has become diseased. We know the pupil—what is com¬ 
monly called, the apple of the eye—should have a French grey 
or whitish blue sort of aspect: should it appear otherwise, we 
suspect disease to be present. The signs and appearances of 
health are, in a measure, peculiar to every animal of its kind ; so 
that we, who are in the habit of attending medically to one ani¬ 
mal in particular, may often be deceived when we come to give 
our opinion of others. Generally speaking, when a surgeon 
comes to look at a horse’s eye, even though in perfect health, he 
suspects the animal to have a cataract . This is an opinion that 
has more than onee been expressed by some of the most cele¬ 
brated oculists of this town; arising from the circumstance of 
the pupil of the horse’s eye having a white or hazy sort of blue¬ 
ness which does not exist in the human eye. This shews, gen¬ 
tlemen, how dangerous it is to draw comparisons between one 
animal and another. For, notwithstanding that one set of general 
principles must direct us all, we shall find their application dif¬ 
ferent in each individual species. What do you think, gentle¬ 
men, of a surgeon writing a work—and really, in every respect 
but one, a very clever work—and giving an account of the “dis¬ 
eases of the gall-bladder of the horse when, unfortunately for 
all his literary labour, at least in that department, the animal 
never had such a thing as a gall-bladder ! 
Everybody has heard of a corn in a horse’s foot; as different 
a thing, gentlemen, from corns in our feet as light is from dark¬ 
ness. It is, however, a very simple disease; though, simple 
