DOI Page / Citation link:
https://doi.org/10.11588/diglit.18825#0129
LECT. V.] PROPORTIONS OF THE HEAD. 103
the shade, or wherever light is deficient, the pupil
expands, admits all it can collect, and exerts itself
to maintain that equilibrium which is equally de-
stroyed by want, and by redundance.
In cats, and other animals that prey in the dark,
the pupil of the eye is so variable as to admit more
than an hundred times the quantity of light at one
time than at another. The human eye admits more
than ten times the quantity of light at one time than
at another ; and it is supposed the difference may
be vet greater in very dark places t it is not impos-
sible but that the iris may then be drawn back, and
the pupil expand to the whole surface of the cornea.
But it should seem, that though the pupil may ex-
pand to this extent, it is not capable of accommo-
dating itself to all cases requiring- close contraction ;
for we are told of the northern Indians in America
(the Esquimaux, &c.) that to prevent injury to their
eyes from the too strong action of light reflected
by the snows of their country, they form a pair of
what we should call blinkers, consisting of an upper
part, and an under, with so small an aperture be-
tween them as permits only a very slender streak of
light to pass through, which yet is sufficient for
their use. Thus, by a kind of advanced pupil, they
assist the natural organ.
In comparing the sensual powers of animals with
the human, we frequently find the advantage appa-
rently in their favour : two eyes, and those very con-
fined in their operations compared with the same
parts in some animals, are sufficient for the use of
man ; while a Bee or a Fly possesses thousands : for
what
the shade, or wherever light is deficient, the pupil
expands, admits all it can collect, and exerts itself
to maintain that equilibrium which is equally de-
stroyed by want, and by redundance.
In cats, and other animals that prey in the dark,
the pupil of the eye is so variable as to admit more
than an hundred times the quantity of light at one
time than at another. The human eye admits more
than ten times the quantity of light at one time than
at another ; and it is supposed the difference may
be vet greater in very dark places t it is not impos-
sible but that the iris may then be drawn back, and
the pupil expand to the whole surface of the cornea.
But it should seem, that though the pupil may ex-
pand to this extent, it is not capable of accommo-
dating itself to all cases requiring- close contraction ;
for we are told of the northern Indians in America
(the Esquimaux, &c.) that to prevent injury to their
eyes from the too strong action of light reflected
by the snows of their country, they form a pair of
what we should call blinkers, consisting of an upper
part, and an under, with so small an aperture be-
tween them as permits only a very slender streak of
light to pass through, which yet is sufficient for
their use. Thus, by a kind of advanced pupil, they
assist the natural organ.
In comparing the sensual powers of animals with
the human, we frequently find the advantage appa-
rently in their favour : two eyes, and those very con-
fined in their operations compared with the same
parts in some animals, are sufficient for the use of
man ; while a Bee or a Fly possesses thousands : for
what