Evening star., 1940-01-27
Of Stars, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
Bu Thomas r. Henri.

"'~ Se0Sy
By Thomas r. Henry.
The strange light that shines" from
the eyes Of an animal at night-most
familiar are the glowing eyes of
cat in the alley-has been investigated
for the first time during the past year
by Ernest p. Walker, assistant director
of the National Geological Park.
1t must be reflection from some sur
face Of the eye Of the light that shines
upon it, Mr.. Walker reports In the an
nual Smithsonian Institution Yearbook.
MIR. Walker carried out his investiga-
ton in the Zoo animal houses with fash
lights, aided by Zoo policemen making
regular rounds. At any time it was a
weird experience. Once the flashlight
was turned on weird lights flashed back
from every direction. They were reflec-
tions from the eyes of the animals.
While the shining of eyes is a we'll
known phenomenon, Mr.. Walker points
out IN his report, most of the observa-
tons have been made in the wild. The
name OF the owner Of the eyes is fire.
quently unknown and it is impossible
that the same individual can be OBJ
served again under similar circumstances.
In his study Mr.. Walker used a re-
f1ecting head lamp, similar to a hand
faShlight, worn on the forehead and
connected with a three-cell battery in
his pocket or attached to his belt. This
was necessary because the rays Of re-
flected light must closely parallel the
line Of sight of the observer in order to
get reflections from the greatest number
of species, and with uniform results.
His best results, he reports, were OBJ
tanned with light of moderate intensity.
If the light is too bright the shining Is
less conspicuous. or does not appear at
all.
The eyes of alligators and crocodiles.
Mr.. Walker found, give one the impress
sion that he is looking into brilliantly
glowing pinkish opening in a dull-sur-
faced bed of COAL"
Most eyes of mammals, on the other
hand, have the appearance of highly
polished metal surfaces.
Sometimes" ssys Mr.. Walker. 1T is
like looking into All incandescent globe
of the color indicated. Often pronounced
light rays appear to emanate from the
eyes. In some eyes, such as those Of the
smaller rodents, the effect is that Of
looking into an Illuminated piece Of am
ber. In the case Of animals that have
eyes that glow it appears that we look
into the eye through the pupil as If the
reflection came from the front surface
OF the retina. In those animals that
give reflection as If from polished
metal I gain no impression of looking
into the eye. In most OF these cases.
however, the reflection is not obtaina BILE
closer than from to 20 feet-a distance
which prevents one from observing which
surface reflects. The reflections from
alligators and crocodiles can be seen
when the observer is within foot of the
animal"
Mr.. Walker experimental with the ef-
fects of red and blue light on the "eye
shine" color of 40 species of mammals and
reptiles, but he found little variation in
colors of the reflected light, other than
the expected red and blue tinges.
With red light resulting reflections
varied from dull, reddish amber through
reddish silver to reddish gold. The diff
ferences were chiefly in brilliance, With
blue light the reflections ranged from
dull and pale blush silver to blue
green and blue, with the metallic luster
persisting in those species that gave
brilliant reflections under normal light.
The reflections from the crocodiles we're
partially opalescent.
These colored light experiments, Mr.,
Walker says, show that eye shine is not
due to fuorescence. Reflection is the
only probable source.
Most animals, he found, stare at a
light, or only move the head slightly. He
could find no shine" in the eyes of the
higher apes or the monkeys A faint
suggestion OF shine was detected in the
eyes OF the ring-tailed lemur, q close
relative Of the monkey family. On the
other hand the most brilliant reflections
OF all were from two tiny members of
the lemur tribe, the slow loris and the
potto.
MY observations suggest" says Mr..
Walker, that the majority of rodent
eyes shine but duly in browns, hazel or
amber, but porcupines are an exception.
Their eyes are very brilliant, generally
silvery and rejecting over a wide angle.
In the case of snakes one is sometimes
tempted to mistake the shine from the
surface Of the scale over the eyes for the
true reflection of the eye."
There is some evidence, Mr.. Walker
points out, that the eyes of exceptional
human beings shine. It has even been
reported that men have been shot by
mistake. The hunter sees pair of
shining eyes in the dark and mistakes
them for those Of an animal. The ex-
periments with the higher monkeys and
apes, however, indicate that this is not a
characteristic Of the family of mammals
to which man belongs.