Then, too, stimulated by these impressions, certain secretions are instantly emptied from the ductless glands into the blood which, acting like fuel in an engine, generate more power in the machine, fill it with anger or fear and prepare it to respond to the directions to fight or flee, or to any type of action incident to the machine. It is only within a few years that biologists have had any idea of the use of these ductless glands or of their importance in the functions of life. Very often these ductless glands are diseased, and always they are more or less imperfect; but in whatever condition they are, the machine responds to their flow.
The stored-up impressions are more or less awakened under stimulation. As life goes on, these stored impressions act as inhibitions or stimulations to action, as the case may be. These form the material for comparisons and judgments as to conduct. Not only are the impressions imperfect and the record imperfect, but their value and effect depend on the brain which compares and considers the impressions. From all this mechanism, action is born.
That man is the product of heredity and environment and that he acts as his machine responds to outside stimuli and nothing else, seem amply proven by the evolution and history of man. But, quite aside from this, logic and philosophy must lead to the same conclusions. This is not a universe where acts result from chance. Law is everywhere supreme. Every process of nature and life is a continuous sequence of cause and effect. No intelligent person would ever think of an effect in the physical world which did not follow a cause or causes. It has taken man a long time to find this out. The recurrence of the seasons, the seed-time and harvest, the common phenomena of Nature, were once supposed to be outside the realm of cause and effect and due to the whim of some powerful being. But the laws of matter are now coming to be understood. Chance, accident and whim have been banished from the physical world. The acts of men alone are supposed to be outside the realm of law. There is a cause for the eternal revolution of the earth around the sun, for the succession of seed-time and harvest, for growth and decay; but not for the thoughts and actions of man.