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 reversed the experiment; I made oxygen
with cold produce anæsthetic sleep in a warm-blooded animal.

I need not carry this argument further; it is the easiest of the
demonstrative facts of physiological science that 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, which, in the end, means _death_.


MECHANICAL COLD.

The third element in the action of cold is more purely mechanical, and
this, though in a sense secondary, is of immense import. When any
body, capable of expansion by heat, that is to say, by radiant motion
of its own particles, is reduced in temperature, it loses volume,
contracts, or shrinks. The animal body is no exception to this rule; a
ring that will fit tightly to the warm finger will fall off the same
finger after exposure to cold. The whole of the soft parts shrink, and
the vessels contract and empty themselves of their blood. Cold applied
to the skin in an extreme degree blanches the skin, and renders it
insensible and bloodless, so that if you prick it it does not bleed,
neither does it feel. In cases where the body altogether is exposed to
extreme cold this shrinking of the external parts is universal; the
whole surface becomes pale and insensible; the blood in the small
vessels superficially placed is forced inward upon the heart and
vessels of the interior organs; the brain is oppressed with blood;
sleep, or coma, as it is technically called, follows, and at last life