Evening star., 1954-05-31
Instinct Center
Of Bugs Described
Harvard Scientists Find
Insect Unit of Behavior
BY Thomos R. Henry

Insect Unit OF Behavior
By Thomos R. Henry
CHARLOTTESVILLE, Va, May ST.
Location of an instinct center" in the
insect brain. contained largely in a
speck Of nerve cells with mass Of less
than millionth of an ounce, was de-
Scribed before the Virginia Academy of
Sciences meeting here by DR.. Carol
Williams, Harvard University biologist.
The center is the microscopic So
called mushroom body" or corpus pc
dunculatum, found in both hemispheres
of the bug brain. This discovery, with
deep philosophical implications. comes
from the most delicate microSurgery
conceivable in which the barely dis
cernable mushroom body in the brain
Of the silkworm was destroyed bit by
bit by means of an invisibly fine electric
needle by DR.. Williams and his associ-
ate, DR.. William van der Kloot Of the
Harvard faculty.
The two worked with an American
silk worm, the cecropia. common along
the Atlantic coast. which spins as
strong and delicate silken threads as
the Japanese or Italian domesticated
Silkworms. The cocoon is marvel Of
apparent ingenuity, made of single
thread more than mile long.
It is made in three layers, roughly
after the design of a thermos bottle.
The outer layer is a tightly woven,
waterproof silk bag. Inside this is
layer of loosely spun material which
serves as in insulating layer. The third
layer, woven around the hody of the
worm itself isa bag of exceedingly fine,
soft silk.
Worm Provides for Escape.
Through each layer "hatchway" is
provided directly in front of the crea-
lures head. These must be placed one
in front of the other with mathematical
exactitude. Through them the impris-
oned creature must escape when the
time comes and the slightest error prob
ably would make it prisoner forever
in coffin Of it's own making.
In this cocoon the worm remains.
adequately protected from cold and
as winged moth whose sole function
produce more silkwormS.
The spinning of such a cocoon with
its three quite different layers. re-
quires great precision of movement.
Nature has not allowed for any posi-
BILE variations. Now, DR.. Williams
points out, the production obviously
is not the result of any thinking, edu-
cation or practice. The little worms
life span, for one thing, would not
allow for any training. Every move
ment must be instructive and uncon-
SciouS, directed by some part of the
brain into whose structure the pattern
has been built by nature.
The house building must start at
precisely the right time. Until that
time, Drs. Williams and van der Kloot
found, the responsible area of the
brain is held in restraint by a hor-
none secreted by two tiny glands situ-
ated directly behind the brain. At
precisely the right time this inhibiting
secretion ceases and the mushroom
body can go into action.
Two Gases Administered.
The two Harvard scientists then tried
the effects of two gases, carbon dioxide
and carbon monoXide Both acted as
potent brain depressants, but in a quite
different fashion. The first eliminated
the behavior entirely. The worms wan
dered about aimlesSly and unhappily,
apparently trying in vain to remember.
The exhaust gas carbon monoxide.
fatal to humans but without any seri-
Gus lasting effect on invertebrates be-
cause they lack the hemoglobin in the
blood with which it combines in higher
animals, caused them to spin a mean
ingless flat layer Of silk as long as the
effect continued.
When this ended the worm started to
spin what remained of its mile-long
silk thread in the customary pattern,
starting at the point which 1t normally
would have reached had it not been
gaSSed.
The effect of both these gases is on
the nervous system. primarily the brain.
1t apparently blocks an engine neces-
sary for the transmission Of impulses
from one nerve cell to another.
The scientists then resorted to their
unbelievably delicate surgery. They
destroyed the silkworm brain q few
cells at time. The destruction had no
effect on the spinning behavior until
they reached the mushroom body.
When a few cells in this area were
killed by the electric current the ami
NAL could no longer spin a cocoon but
continued to weave it's silken thread
into three fiat sheets, corresponding to
the three normal capsules. With the
killing of a few more cells the weaving
continued. but only in a single sheet.
When few more were destroyed the
entire spinning behavior came to an
end.
Dujardin's Discovery Remembered.
More than q century ago. DR.. Will
liams points out. this mushroom body
was discovered by the French physi-
ologist Dujardin who called 1t "the seat
of instinct" At the time this was only
wild speculation on his part, without
any supporting facts.
Is it also the seat of any other In
stinctive behavior of the silkworm?
Drs. Williams and van der Kloot will
try to answer this question with fur