irth. Kittens, rabbits and puppies, if removed from
their surroundings shortly after birth, lose their body heat until
their temperature has fallen to within a few degrees of that of the
surrounding air. But such animals are at birth blind, helpless and in
some cases naked. Animals who are born when in a condition of greater
development can maintain their temperature fairly constant. In strong,
healthy infants a day or two old the temperature rises slightly, but
in that of weakly, ill-developed children it either remains stationary
or falls. The cause of the variable temperature in infants and
young immature animals is the imperfect development of the nervous
regulating mechanism.

The average temperature falls slightly from infancy to puberty and
again from puberty to middle age, but after that stage is passed the
temperature begins to rise again, and by about the eightieth year is
as high as in infancy. A diurnal variation has been observed dependent
on the periods of rest and activity, the maximum ranging from 10 A.M.
to 6 P.M., the minimum from 11 P.M. to 3 A.M. Sutherland Simpson and
J.J. Galbraith have recently done much work on this subject. In their
first experiments they showed that in a monkey there is a well-marked
and regular diurnal variation of the body temperature, and that by
reversing the daily routine this diurnal variation is also reversed.
The diurnal temperature curve follows the periods of rest and
activity, and is not dependent on the incidence of day and night; in
monkeys which are active during the night and resting during the day,
the body temperature is highest at night and lowest through the day.
They then made observations on the temperature of animals and birds of
nocturnal habit, where the periods of rest and activity are naturally
the reverse of the ordinary through habit and not from outside
interference. They found that in nocturnal birds the temperature
is highest during the natural period of activity (night) and lowest
during the period of rest (day), but that the mean temperature is
lower and the range less than in diurnal birds of the same size. That
the temperature curve of diurnal birds is essentially similar to that
of man and other homoiothermal animals, except that the maximum occurs
earlier in the afternoon and the minimum earlier in the morning. Also
that the curves obtained from rabbit, guinea-pig and dog were quite
similar to those from man. The mean temperature of the fema