85
If, as implied by the studies of Leiner (1943) and
Vallee
(1957),
the zinc in the
however,
the retina is the source of most of
eyes of vertebrates, then consideration of
the geometry of the eye indicates that a negative correlation
between eye zinc concentration and the gize of fish should be
expected.
Materials comprising the retina are distributed in
a thin film
approximately covering the interior of the pos-
terior hemisphere of the eye.
If zinc is assumed to be dis-
tributed uniformly throughout the retina,
its mass in
the
retina may be considered as directly proportional to the area
of the retinal surface
Grr2), and consequently to vary
directly as the square of the radius.
The mass of the whole
eye is directly proportional to its volume (4/371r3)
varies directly as the cube of the radius.
ana
The concentration
(c) of zinc in the eye may be expressed in terms of the radius
of the eye by dividing the area of the retinal surface by the
volume of the whole eye: Ce 41r2
4/343
= 3/8r.
This indicates
that the concentration varies inversely as the radius.
Since
the mass of the eye, which is proportional to the size of the
fish,
varies directly as the cube of the radius,
and the con-
centration of zine in the eye varies inversely with the radius
of the eye,
an inverse correlation between eye zinc concentra-
tion and fish size would be expected.
The expectation derived