Evening star. [volume] (Washington, D.C.) 1854-1972, 1907-04-07

DR.. Bruno Muller. was designed to deter
mine the use of certain empty spaces in the
bodies of birds which have puzzled investi-
gators for many years. The second had to
do with the flight of four winged insects.
The air sac investigation is just report
ed to the Smithsonian. Theories filing
pamphlets have in times past been launched
upon the scientific world to account for
these curious cavities near the lungs and
under the skin of birds. Reasons which
would preclude the possibility of mans
ever navigating in the atmosphere have
been put forth. The fertility of the minds
of investigators in giving these spaces
some function iss convincing evidence to
show how at loss they nave been for any
definite proof. To the subskin AIR sacs'
there has separately been assigned two
functions-to help raise the feathers and to
preserve bodily heat. To the empty spaces
near the lungs however, have been at
tributed powers even more wonderful. II
has been said that they serve as reSond-
tory organs for producing certain tones,
that they perform respiratory functions,
that they help reduce the specific gravity
of the body that they act similar to a
barometer in determining height that they
aid in fixing the wings in extended
position, that they assist the digestion, that
they insure equilibrium in flight. and that
they are storehouses for air for respiration
DR.. Muller has considered all these theories.
Nevertheless he reaches very simple con-
cluSion He says:
Dr. Muller's Conclusion
II do not consider the air sac system
a whole = as collection of organs
having special functions. but rather sys-
tenn of emptyinterspaces. Its value lies
in it's vacuity, that is, in its containing
nothing that can offer a great resistance
or that has notable weight.
Flying is the most complete kind of To-
comotion, and as such presupposes a high
degree of bodily efficiency. Our most eff
fective machines are by means those
which are compact and solid, but those
composed of parts that are as strong as
possible and arranged in the most ap
propriate manner, the interspaces being
taken up by air.
There is apparently nothing. therefore, in
the air sac" system in birds which should
prevent the construction of a flying ma
chine upon similar principles.
The findings in the second report just
received are equally vital to the problem
of mechanical night DIR. Leo Walter,
another of Dr. Won Lendenfeld's assistants,
has been examining the working of the
flying apparatus of four winged insects.
The stroke, says DR.. Walter, is curious
one. 1t is like figure s. with a small
upper loop-a stroke which might be re-
produced mechanically. careful study
has been concluded of the method by
which the hind wings are attached to the
fore wings, since the strength of the stroke
seems to come from the front wings. In
some insects a curious set of tiny briStles
on the upper side of the back wing reach
into little band of hair and join to scales
on the under side of the fore wing, making
the two wings practically one. In others
series of hooks on the upper lock with
a corresponding series on the lower.
. Just what principles of nature brought
out in these researches may be applied to
practical use in a flying notwithstanding
the word literally-is yet TO be determined.
The complete discovery, however. of the
secret of suspension and locomotion in
volved in the flight of birds and insects IS
the first step in the solution of mechanical
navigation in the air. The theory once
established without doubt. engineers may
incorporate all practical features in the
construction of a machine. The object of
DIR. Won Lenuenfelds work under the Hodg-
kins grants of the Smithsonian Institution
is to find facts upon which firmly to
establish a theory.