CHAPTER I.

IS THE BODY A MACHINE?


The problem before us in this section is to find out to what extent
animals and plants are machines. We wish to determine whether the laws
and forces which regulate their activities are the same as the laws and
forces with which we experiment in the chemical and physical laboratory,
and whether the principles of mechanics and the doctrine of the
conservation of energy apply equally well in the living machine and the
steam engine.

It might be inferred that the proper method of study would be to confine
our attention largely to the simplest forms of life, since the problems
would be here less complicated, and therefore of easier solution. This,
however, has not been nor can it be the method of study. Our knowledge
of the processes of life have been derived largely from the most rather
than the least complex forms. We have a better knowledge of the
physiology of man and his allies than any other animals. The reason for
this is plain enough. In the first place, there is a value in the
knowledge of the life activities of man entirely apart from any
theoretical aspects, and hence human physiology has demanded attention
for its own sake. The practical utility of human physiology has
stimulated its study for centuries; and in the last fifty years of
scientific progress it has been human physiology and that of allied
animals that has attracted the chief attention of physiologists. The
result is that while the physiology of man is tolerably well known, that
of other animals is less understood the farther we get away from man and