184- Mr. Bell on the motions of the eye, &c. 
eye-lid, their margins were not brought together, and we 
could perceive the motion of the eye-ball ; in his attempt to 
close the eye we saw the pupil elevated, and the white part 
of the eye exposed. 
I shall now attempt the explanation of some of these 
phenomena : 
The impression upon the left eye had been weak from 
infancy, and the retina being unexercised, the recti or volun- 
tary muscles wanted their excitement, and were deficient in 
activity ; the involuntary muscles therefore prevailed, and 
the pupil was turned upwards and inwards, and consequently 
removed from the axis of the other eye. But when that 
other eye became obscured, the left eye being the only inlet 
to sensation, the attention became directed to the impression 
on the retina, the voluntary muscles were excited to activity, 
and they brought the eye to bear upon objects. This eye 
improved daily, because the natural exercise of a part is its 
stimulus to perfection, both in function and in growth. When 
the right eye became transparent and the light was admitted, 
the voluntary muscles of that eye partook of their natural 
stimulus, and commenced that effort in search of the object, 
which in the course of a few days brought the eye to its 
proper axis, and both eyes to parallelism. 
The next thing that attracts our attention in this short 
narrative, is the revolving of the eye-ball. It has been ex- 
plained in a former part of the paper, that when the eye-lids 
are shut, the recti or voluntary muscles resign their office, 
and the inferior oblique muscle gains power, and the eye-ball 
traverses so as to raise the pupil. It will not have escaped 
observation, that the pupil of this eye was depressed, and 
