This is definite instruction so given to a life that it is appropriated. A large part of attempted instruction is never taken in. "I have told you over and over again," says the despairing mother, but telling does not always involve receiving. Placing nourishing food before the boy does not necessarily mean stronger muscle and purer blood. He must eat and digest it. Teaching, to be nourishment, requires first, careful adaptation of the subject matter, then presentation in such a way that the mind will voluntarily reach out, lay hold upon and assimilate it. God again gives the key to real teaching in the word "engraft." Its process in the physical and mental world is identical. First, the delicate adjustment, then a vital union, and lastly, new life resulting. 2. The Watch Care over Activity. We have considered nurture in its work of supplying the best nourishment to growing souls, and now its care for activity must be noted. Since the subject will be discussed more fully in a succeeding chapter, only the necessity for the nurture will be considered here. This necessity appears in the four-fold result of activity. (1) New Experiences. This is the first result to the child from ceaseless movement of hands and feet and eager eyes. In early life he is not conscious of seeking the new experience, he only wants to be in motion. In later life, energy is definitely put forth for some desired end. But whatever the motive, experiences helpful or harmful, according to the sort of activity, result, and they enter character at par value. (2) Growth or Increase in Size. Activity is necessary before anything given to the body or the soul can become a part of life. Food must be acted upon by the digestive, circulatory and assimilative organs to make it bone and muscle and nerve. The mind must think upon the fact in order to add it to the store of knowledge. The heavenly vision must be obeyed before Christian experience is enlarged by it. But there is another aspect of this same thought. Just as truly as activity must precede assimilation, so truly does assimilation follow activity. It may be stated more simply in this way. Nothing can become a part of the life until it has been acted upon; when it has been acted upon it can not be taken out of the life. When digestion is finished and the food is bone and muscle, it can not be withdrawn. When the idea has been thought in or acted upon, it has by that process become a part of the life, and though it may fade from memory its influence is abiding. (3) Development or Increase of Power and Skill. Every muscle exercised gains greater freedom. Every knotty problem mastered means increased mental ability. Every victory means greater power in resisting temptation. Whatever the action, whether good or bad, helpful or harmful, greater skill and power in that direction follows it.