An impulse denotes action, not an entity. Function is the special and normal action of any organ or part of a living animal. This includes the natural action of any mental faculty. Pathological functions are those performed in a greater or lesser degree than normal. Force is that power which produces or arrests motion, that which may be converted into motion, the rate of transforming energy.
Vitality is the vigorous active principle upon which individual life depends.
Vital force is that principle of life which imparts energy. It is inherent in each organ of an organism. Energy is the internal, inherent power, the product of activity, that which is aroused by an impulse. Nerve-vibration carries thoughts, commands, orders, known as impulses when in transit over the nervous system. Thoughts gather force, receive impetus, while being transmitted, the amount depending upon the quantity of nerve vibration.