Evening star., 1935-05-04
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
TuOMIS HENRY
BY THOMAS r. HENRY.

organs atrophy. The liver shrinks to
half its normal weight, although its
functioning may not be impaired.
The blood pressure tends to increase
until about the SEVENTEEN year, when
it starts to drop. Low blood pressure
is more serious than high for the
aged, since the danger Of thrombosis
is greater. Many of the peripheral
capillaries are obliterated, resulting in
the characteristic pallor Of the aged.
The senile tremor develops, which Is
not serious sign in itself and has
its own characteristic rate per min
ute. The old almost invariably lose
appetite.
Some persons. DR.. Pepper pointed
out, actually may die of "old age
that is, of normal atrophy Of the body
organs without any particular patho-
logical condition Of any Of them. Such
deaths are usually reported as heart
failure" But the atrophy is a normal
physiological process through which
all who live long enough must pass
A new device for peering into the
mysteries Of life Is being adapted and
brought to higher degrees of usefulness
| at the Smithsonian Institution. This
is the so-called Christensen filter,
based upon principle discovered a
half century ago by a Denish physicist.
1t makes possible the experimental
study Of the precise effects of narrow
bands Of the solar spectrum upon living
organisms. The biological behavior of
every living thing Is intricately inter-
woven with light-both with the light
| spectrum as whole and with in
dividual wave lengths. It Is well known.
for example, that a plant irradiated
solely with green light grows quite
differently from one irradiated with
the entire spectrum or only with red
light. The differences are astonishing.
In the phenomenon of phototropism.
for example, a seeding Is thousands of
times more sensitive to one part of the
visible light spectrum than to another,
as shown by Its manner of bending.
But such expressions as green" or
yellow" applied to light, are psy-
Geological rather than physical. The
color sensation designated green" is
the human response to wave lengths
OF light within certain narrow range
which fall on the retina. It so hap
pens that this sensation Is produced
by light Of wave lengths between 1900
and 5,400 Angstrom units. The
Angstrom unit is one ten-millionth of
q millimeter, or about four billionths
Of an inch.
But light does not exist solely for
mans use in vision and discrimina-
tlon. 1t has numerous other func-
tions, and In the performance Of these
dinerent ranges Of wave lengths diff
fer as profoundly as they do in the
production Of color sensations. Hence
1t Is OF great importance, both practi-
cal and theoretical, to arrange the
spectrum in various ways that have
no visible associaion-that Is, to study
the effects Of as narrow ranges Of
wave lengths as possible on all sorts
Of phenomena, such as growth, pho
tosymthesis, respiration, lethal and
toxic effects, etc.
This requires the irradiating Of OBJ
jects for considerable periods with
restricted ranges Of wave lengths at
high light intensities. How to do this
has been q very difficult technical
problem. One way was through the
light filter devised by the Danish
physicist.
Unfortunately, the wave lengths
transmitted by this filter depend upon
its temperature and when exposed to
o strong source of radiation-the sun,
for example-it heated rapidly so that
the transmitted wave lengths chang
ed. BY complicated technical i'm
provements In the filter device
which is little known in this coun-
try-thjs Lsatiug prohlem hrHaly eAs