The following lessons, while they do not treat directly of either the chemistry of food or the chemistry of the body, are so closely allied to these subjects that this work would not be complete without them.
WHAT IS EVOLUTION?
If a resident of a city, who is not familiar with modern farm machinery, should see a grain-binder at work, he would be impressed with the skill and the ingenuity of man. In all probability he would think that the machine was the product of one inventive mind. In this, however, he would be mistaken. The reaper in its modern form is the result of gradual development or growth.
An example of evolution
The earliest method of gathering grain was pulling it up by the roots. Later, as cutting tools were invented, a rough knife was used to sever the stalks just above the ground. An improvement upon this method was the cycle; then came the scythe, then the cradle; and next came the mower which was operated by horse-power. From the mower was developed the self rake, which bunched the grain so that the hand-binders could work with greater facility. The next improvement was a self-binding machine. In the present machine we have all of these and many other improvements, which give greater speed with less waste of labor and time.
This development of the grain-binder is a process of evolution. In order to understand a machine so as to use it intelligently, or to make improvements upon it, it is necessary not only to know the machine as it actually is, but also to know the history of its development up to its present form.
To know man is to know evolution
The story of the evolution of a machine is, at best, but a crude illustration of the evolution of man. Nevertheless, the conclusion is the same. If we are to understand man, we must study not only his present physical and mental state, but also the history of his development. Yet those whose work is concerned directly with man—whether they be teachers, guiding the growth of the child; statesmen, formulating the laws and regulations by which men are to be controlled in their public actions; or physicians, who are supposed to instruct and to guide men in the care of their physical well-being—are often densely ignorant of the most rudimentary knowledge of the evolution of man as it is now known and understood by the leading scientists of the world.