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POPULAR SCIENCE REVIEW. 
exposing blood in cliambers into which air could pass in and 
out, the blood could be oxidized at temperatures of 70° if the 
distribution of air and blood were effectually secured, and I 
also found a given standard of oxidation from a given tempera- 
ture. Then I proceeded to test for combination at lower 
temperatures, and discovered a gradually decreasing scale 
until I arrived at 40° Fahr., when combination ceased alto- 
gether. Of course, my method was a very rude imitation of 
nature, but it was sufficient to show this fair and reliable result, 
that the oxidation of blood is arrested as the temperature of 
the oxygen decreases. 
From this point I went to animal life itself. I exposed 
animals to pure cold oxygen and to cold atmospheric air, and 
compared the results with other experiments in which animals of 
similar weight and kind were exposed to warm air and warm 
oxygen. The facts gleaned were most important, for they proved 
conclusively that the products of combustion, that is to say, 
the products resulting from the union of oxygen and 
carbon, were reduced in proportion as the temperature of 
the oxygen was reduced. In the course of this inquiry another 
singular and instructive fact was elicited. It has been long 
known that at ordinary temperature, say 60°, pure neutral 
oxygen does not support animal life so well as oxygen that is 
diluted with nitrogen. In the nitrogen the molecules of oxygen 
are more freely distributed under the influence of motion, that 
is the meaning of the observed fact. AVhat, then, would be the 
respective influence of low and high temperatures on the re- 
spiration of pure oxygen ? To settle this question, animals of 
the same size, kind, and weight were placed in equal measures of 
oxygen gas and common air at a temperature of 20° Fahr., 
and with the inevitable result that the animal in the pure 
oxygen ceased to respire one-third sooner than did the animal 
in common air. Carrying the inquiry further, I found that if 
the oxygen gas were warmed to 50° Fahr., the respiration was 
continued six times as long as in the previous experiment, 
while if the warming were carried to 70° it was sustained : 
twenty-four times as long. 
I need not carry this argument further ; it is the easiest 
of the demonstrative facts of physiological science that the 1 
reduction of temperature lessens the combining power of oxygen ! 
for blood, and therewith causes a reduction of animal force, | 
and a tendency to arrest of that force, death. I 
The third element in the action of cold is purely mechanical, | 
and though in a sense secondary is of immense import. When j 
any body, which is capable of expansion by heat, that is to 1 
say, by radiant motion of its own particles, is reduced in tem- 
perature, it loses volume, and contracts or shrinks. The animal 
