, the embryo of the snake and of a
lizard remain like one another longer than do those of a snake and of a
bird; and the embryo of a dog and of a cat remain like one another for a
far longer period than do those of a dog and a bird, or a dog and an
opossum, or even those of a dog and a monkey.

Surely it must be admitted that the short brief history given by the
development of the egg, is far more wonderful than phylogeny or the long
and slow history of the development of the tribe, which has taken
thousands of years. Compare this time with the time required for the
development of the smallest mammals--the harvest mice which develops in
three weeks, or the smallest of all birds, the humming-bird, which quits
the egg on the twelfth day, or with man who passes through the whole
course of his development in forty weeks, or with the rhinoceros who
requires 1-1/2 years, or the elephant who requires ninety weeks. How
insignificant are these various periods to the long period originally
required; yet in these short periods the whole phylogeny is run through
in the ontogeny or the history of the development of the egg.

THE ATTRIBUTES OF MAN.

We must now consider briefly some of the attributes of man, and see if
he really possesses attributes which are in no inferior degree possessed
by animals. Before proceeding directly to the consideration of the
attributes of man, it will be best to show the correlation that exists
between what are called man's vital forces and the physical forces of
nature. To do this let us choose three forms of its manifestation: these
shall be heat evolved within the body; muscular energy or motion; and
lastly, nervous energy or that form of force which, on the one hand,
stimulates a muscle to contract, and on the other appears in forms
called mental. It will not take any extensive argument to demonstrate
that the heat of the body does not differ from heat from any other
source. It is known that the food taken into the body contains potential
energy, which is capable of being in part converted into actual heat by
oxidation; and since we know that the food taken into the body is
oxidized by the oxygen of the air supplied by the lungs, the heat of the
body must be due to the slow oxidation of the carbon, perhaps also
hydrogen, sulphur, and phosphorus in the food. Now since this so-called
vital heat is developed by oxidation, is recognized by the same tests
and applied to the same purposes as an