At first it seems easy to explain the reason why a sudden fall in
temperature should lead to an increase in the number of deaths, and it
is to be admitted that, to a certain extent, the reason is clear.


ANIMAL POWER AT DIFFERENT PERIODS OF LIFE.

Without entering on the question whether heat is the animating
principle of all living organisms, we may accept that in the evolution
of heat in the body we have a measurement of the capacity of the body
to sustain motion, which is only another phrase for expressing the
resistance of the body to death. For example, if we assume that a
healthy man of thirty respires sufficient air per day to produce as
much heat as would raise fifty pounds of water at 32° Fahr. to 212°
Fahr., and if we assume that a man of sixty in the same temperature is
only able to respire so much air as shall cause him to evolve so much
heat as would raise forty pounds of water from 32° to 212°, we see a
general reason why the older man should feel an effect from a sudden
change in the temperature of the air which the younger would not feel;
and if we assume, further, that a man of eighty could in the same time
produce as much heat as would raise only twenty pounds of water from
32° to 212°, we see a good reason why the oldest should suffer more
from a decrease of external temperature than the other two. It is
necessary, however, to know more than this general statement of an
approximate fact; we ought to understand the method by which the
reduction of temperature influences, and the details of the
physiological process connected with the phenomena. When a human body
is living after the age when the period of its growth is completed and
before the period of its decay has commenced, it produces, when it is
quite healthy, by its own chemical processes, so much heat or force as