RHYTHMIC NATURE OF ANIMALS AND PLANTS—BROWN 405 
with all the natural periodicities of the atmosphere imbedded in it, 
still impressing itself upon the organism. Living things might con- 
ceivably possess inherited, regular rhythms, but it is quite incon- 
ceivable that they are born with an inherited plan of all the erratic 
temperature, barometric-pressure, and background-radiation fluctua- 
tions which are to occur during their lifetime. So far we don’t know 
what the specific nature of the factcr or factors may be which are 
directly effective on the living organism. This is one of the most 
important and exciting problems before us in our continuing research. 
But to suggest further that the forces involved in our problem may 
be in part determined by other forces arriving on our earth even from 
outside of our own solar system, we have obtained some striking simi- 
larities of our biological metabolic rhythms, with fluctuations in cosmic 
radiation raining on our outer atmosphere predominantly from dis- 
tant outer space. ‘This discovery was the outcome of a comparison of 
metabolic daily cycles in potatoes, seaweed, and fiddler crabs during 
the spring and summer of the two years, 1954 and 1955. Between these 
two years, the daily metabolic cycles of all three species seemed to 
have, in good measure, turned upside down. In the fiddler crabs, for 
example (as shown in the upper solid curve in fig. 9, the highest rate 
of metabolism for the day in July 1954 was about 2 p.m.; in July 
1955, as seen in the lower solid curve of figure 9, this was near the time 
of day of the lowest rate in the daily metabolic cycles. In searching 
for a possible difference that might have occurred in some subtle 
external physical factor between the two years, some data upon the 
fluctuations in cosmic radiation occurring at the specific times of these 
METABOLISM 
RADIATION 
6 AM 12 6PM 
Figure 9.—Comparison of the average daily cycles of cosmic radiation (broken lines) and 
fiddler crab metabolism (solid lines) for a single summer month in each year, 1954 (upper 
pair of curves) and 1955 (lower pair of curves). 
