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. [Sidenote: 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. Our entire system of education, our ideas of health and dis-ease, our social customs, the principles of our form of government; our ideas of right and wrong, of rewards and punishments, are all fundamentally concerned with the evolution of man, and when this knowledge is studied with as much application as are the ancient languages, we may expect to see humanity progress at a rate hitherto unknown. [Sidenote: Significance of the term "evolution"] The evolution of man has been very much misunderstood. The term "evolution" is a broad one. It may refer to the growth of the individual, or to the race. It may mean the development of strictly physical organs, or of mental habits, of social customs, or of material products of man's genius, as the great works of civilization in the form of recorded learning, and the wonderful products of man's building ingenuity as seen in modern cities. The subject of the evolution of the human race may be grouped into three general kinds of development or growth: 1 The development of the physical man 2 The development of the mind 3 The development of custom and of external civilization Evolution in these three directions has taken place simultaneously. The mind and the body depend upon each other for their life and actions; while customs are merely the product of many minds working together and communicating their ideas to each other. * * * * * The human race is but the sum of the individuals composing it. We cannot consider the development of the individual without considering him in his relation to the race, neither can we understand the development of the race without understanding the growth of the individual. [Sidenote: Difference between inherited and acquired characteristics]