on Muscular Motion . 
11 
the proportion is i~ inch to 1^-. The cornea is larger and 
more prominent; its real thickness is hardly to be determined, 
since, as well as that of the human eye, it readily imbibes 
moisture immediately after death. When dried, it is thinner 
than the sclerotic coat in the same state. In ruminating ani- 
mals, it appears externally of an oval form ; it is not, how- 
ever, really so, the cornea itself being circular, as in other 
animals ; but a portion of it is rendered opaque, by a mem- 
brane which covers its external surface, and produces an oval 
appearance. This circular form of cornea is necessary, that 
when it is stretched it may form a regular curve. 
The ciliary processes, as in the human eye, are connected 
with the choroide coat ; but they are larger, and are united at 
their origin with the iris. 
This structure of the eye in quadrupeds, so far as it differs 
from that of the human eye, appears calculated to increase the 
power of adjusting it to see near objects, and from the nfode of 
life which these animals pursue, such additional powers appear 
necesssary to enable them with ease to procure their food. 
Birds in general procure their food by means of their beak ; 
and the distance between the eye and the point of the beak is 
so small, that they must have a power of seeing very near ob- 
jects. From living in air, and moving through it with great 
velocity, they require for their own defence, as well as to as- 
sist them in procuring food, a power of seeing at great dis- 
tances. 
That birds of prey see objects distinctly at a great distance 
appears to be proved by the following observations. In the 
year 1778, Mr. Baber and several other gentlemen were upon 
a hunting party in the island of Cassimbusar in Bengal, about 
Ce 
