THE EYE AND ITS VISUAL STRUCTURE. 
205 
inner angle of the eye, be carried down the duct, which 
would irritate and obstruct it. No sooner do any of these 
annoyances enter the eye but they are carried off by the 
haw, which lies concealed within the inner corner of the 
eye. This haw is a black or pied cartilaginous substance 
of a triangular form, concave within and made exactly 
to suit the globe of the eye; while it is convex externally, 
accurately fitting the membrane lining the lid, while the 
base of it is reduced to a thin or almost sharp edge. The 
horse has the voluntary power of suddenly protruding this 
from its concealment, and passing it rapidly over the eye¬ 
ball, clears off every nuisance mixed with the tears, and 
then being quickly drawn back, the dust or insect is 
wiped off as the cartilage again passes under the corner of 
the eye. 
In treating of disease of the haw, page 44, we mentioned 
the barbarous practice of cutting out this valuable appen¬ 
dage to the eye. This member is destined by nature as 
a substitute for the want of hands for wiping the eye and 
cleansing it from offensive matter. This being removed, 
subjects the poor animal to pain in its eye for life, and 
lays it open to the constant chance of inflammation from 
dust or small pieces of gravel being blown into it. The 
pain they thus inflict on the horse may be easily conceived 
by any one having dust or other extraneous matter lodged 
between the eyelid and eye, and being without hands to 
wipe it out. 
THE EYE AND ITS VISUAL STRUCTURE. 
PLATE X. Fig. 8. 
The eye is of a spherical figure, yet not perfectly globular ; 
or it may rather be considered as composed of the parts of 
o 
