Evening star. [volume] (Washington, D.C.) 1854-1972, 1952-06-16
Heat Radiation Guides
Fongs Of the RottIer
Viper's Special Eye Is Sensitive
To Changes in Temperature
By Thomas R. Henry

VenomouS snakes of the rattlesnake
family have an "infra-red eye"
It is special sense organ, tied up to
the brain by very CT implicated pattern
OF nerve pathways, which enable the
reptiles to strike instantaneously and
accurately when an object of different
temperature than the air around his
head comes within striking distance.
The snakes literally see by heat radia-
ton SO minute that they hardly could
be detected by thermometer.
A study of this third eye has Just been
reported to the American Association for
the Advancement of Science here by
Drs. Theodore H. Bullock and Raymond
B. Cowles Of the University of California.
The organ is located in the facial pit Of
the rattlesnake, copperhead. moccasin.
and supposedly most other members of
the viper family.
They found that sounds. odors, vibra-
tions close to the head. or light from
which the heat waves have been filtered
produce no nerve impulses from the
"eye" to the brain. These could be pro-
duced, however, by mechanical refor-
nation Of the membrane as with wisp
of cotton, brushing the upper lid with
a camel's hair brush. air movement,
temperature changes of the body. and
by common objects the temperature
of which is above or below a neutral
point and which are brought into
receptive field around the face, re-
CARELESS of intervening air temporal
ture. Air movements must be abrupt,
like weak puffs, and close to the face to
EiNnYN
around the face yield no effect Detec-
ton is Of doubtful Importance in life as
a function of this organ"
Response to Various Objects.
They tried changing the temperature
of the snakes whole body and also of
the third eye alone. They found little
response unless there was changed
temperature in the immediate environ
ment. But any warm or any cold object
in the immediate environment causes q
response. Such response is brought
about, for example, by human hand
held ten inches away or by glass Of
water one degree centigrade above the
surrounding air. ..-.
Actually, the California scientists be-
lieve, the threshold Is much lower than
appears from these observations. The
neutral point, where no response is
evoked, is Independent of the snakes
own body temperature and depends on
the average heat radiation from all
objects in the environment. Cold OBJ
jects depress nerve activity even if they
are warmer than the body and thus are
thoroughly as noticeable to the snake
as warm objects.
This is shown. for example, by placing
an ice cube about an inch away from
the reptiles head. The nerve impulses
from the special organ to the brain go
down Immediately in intensity.
Moving a stimulating object within
the field" the experimenters report.
causes notable alteration in nerve &C
tivity." This suggests that there is
localizing ability based on shadows cast
on the deeply situated membrane by the
margins of the pit. The receptive field
is an irregular one. Preliminary expert
tnentS indicate that the spectral sensi-
tivity curve will show sensitivity to be
extremely low to near infrared wave
lengths. probably appreciate to wave
lengths higher in the scale and prob
ably appreciate in the long infrared.
The longer end contains most of the
energy radiating from objects like the
human hand.
There seems little possibility of q
mechanism based on the usual photo
chemical reactions, such as those of the
eye"