le was
higher than that of the male in all the species examined whose sex had
been determined.

Meals sometimes cause a slight elevation, sometimes a slight
depression--alcohol seems always to produce a fall. Exercise and
variations of external temperature within ordinary limits cause very
slight change, as there are many compensating influences at work,
which are discussed later. Even from very active exercise the
temperature does not rise more than one degree, and if carried to
exhaustion a fall is observed. In travelling from very cold to very
hot regions a variation of less than one degree occurs, and the
temperature of those living in the tropics is practically identical
with those dwelling in the Arctic regions.

[v.02 p.0050]

_Limits compatible with Life._--There are limits both of heat and cold
that a warm-blooded animal can bear, and other far wider limits that a
cold-blooded animal may endure and yet live. The effect of too extreme
a cold is to lessen metabolism, and hence to lessen the production of
heat. Both katabolic and anabolic changes share in the depression, and
though less energy is used up, still less energy is generated. This
diminished metabolism tells first on the central nervous system,
especially the brain and those parts concerned in consciousness.
Both heart-beat and respiration-number become diminished, drowsiness
supervenes, becoming steadily deeper until it passes into the sleep of
death. Occasionally, however, convulsions may set in towards the end,
and a death somewhat similar to that of asphyxia takes place. In some
recent experiments on cats performed by Sutherland Simpson and
Percy T. Herring, they found them unable to survive when the
rectal temperature was reduced below 16 deg. C. At this low temperature
respiration became increasingly feeble, the heart-impulse usually
continued after respiration had ceased, the beats becoming very
irregular, apparently ceasing, then beginning again. Death appeared to
be mainly due to asphyxia, and the only certain sign that it had
taken place was the loss of knee jerks. On the other hand, too high a
temperature hurries on the metabolism of the various tissues at such
a rate that their capital is soon exhausted. Blood that is too warm
produces dyspnoea and soon exhausts the metabolic capital of the
respiratory centre. The rate of the heart is quickened, the beats then
become irregular and finally cease. The central nervous system is also
prof