Evening star., 1939-04-05

enabling them to see. But when
they fed this pigment to hens, the
result was eggs with brilliant red
orange yolks-about as unattracttve
to housewives as the olive ones.
They then fed laying hens on .
diet from which had been removed
all the carotines, the yellow pig
ments found in carrots and many
other plants and which are the pre-
cursors ir the human body Of vita
min A, the substance necessary for
normal vision. They then found
that their hens laid eggs with color
less yolks, but which turned snow
white when hard boiled. They can
produce these apparently yolkless
eggs in any quantity, If housewives
want them.
There are possibilities, in fact, OF
producing egg yolks of almost any
color by combining newly isolated
natural pigments in the diet Of the
hens. Besides the practical value OF
this research, they pointed out, 1t
may answer some fundamental bio
logical questions. For one thing, why
did nature make egg yolks yellow
anyway? The color is due to caro-
tine pigments, but hens, unlike hu-
man beings, remain perfectly healthy
when all carotines are removed from
their diet. When 1t passes into the
egg yolk the caroline apparently
loses most OF its physiological value.
1t no longer is able to produce vita
min A, as does the caroline Of vege-
tables, butter or cream.
A Fascinating Problem.
The most fascinating problem, they
reported, is to find what it is in
chickens that enables them to make
the lobster pigment In the retinas
of their eyes. 1t Is not found in any
normal food ever tested. This is the
only case known of the genesis of
one Of the essential pigments by the
animal.
Causing a hen to lay eggs with
shells almost any color Of the rain
bow is child's play compared to play
ing with its internal color, DR.. Peter
son and his associates reported. It is
simply matter Of mixing the proper
organic dye with the food. They
exhibit red, white. and green eggs
produced in this way.
Discovery in the retinas Of chick
ems eyes Of a light sensitive pig
ment, long sought in vain by physi-
ologists, which may play prominent
part in seeing in bright light and the
ability to see colors, was reported by
DR.. George Wald of Harvard Univer-
sity, who received today the Eli Lilly
& Co. award for distinguished work
in biochemistry.
The retina of the eye contains
two types of light-sensitive organs,
the rods and cones. The former are
concerned with vision in dim light
and the latter with bright light and
color vision. In the rods Of most
animals. including man, there is a
rose -colored substance known as
rhodopsin. When light falls upon 1t
the color changes to orange then
slowly disappears altogether. 1t de-
generates into vitamin A. which is
built up into rhodopsn again.
Appropriate Nerve Impulses.
These color changes are accom-
panied by chemical activity which
sets up the appropriate nerve i'm
pulses to the visual center Of the
brain which enables one to see.
Reptiles, birds, mammals and ma
rine fishes share this way of seeing
in dim light with man.
Chicken eyes, DR.. Wald explained,
are different. They nave very few
rods and great many cones. Their
eyes seem especially adapted to bright
light and bright colors. Hence the
elusive cone pigment. sought so long
elsewhere, was discovered there. 1t Is