To keep the great Machine in order and to handle it, large numbers of men have been educated in specialties pertaining to its various parts. The first men were probably the warriors, who defended whatever little Machines the various tribes had built up, in their little villages and towns. Next, probably, came the kings or rulers who commanded the warriors; and then, the priests who inculcated in the people the various virtues, such as loyalty, courage, honesty, etc., that tended toward the discipline of the individual and the consequent solidarity of the tribe. Probably agriculturists came next, who tilled the soil; and then came the inventors, who assisted the warriors and the agriculturalists by devising implements to help them do their work. It seems probable that the artisans came next; and that it was by the co-operative working of them with the inventors, that the conceptions of the inventors were embodied in implements of practical usefulness and value. As time went on, and implements were produced that consisted of two or more parts, the activities of the artisans were enlarged, so as to take care of those implements and keep them in adjustment. The bow and arrow, for instance, would not work well, unless the cord were maintained at the correct degree of tension, the feathers on the arrows were kept straight, the ends of the cords properly secured to the bow, etc. Similarly, the mechanisms made for spinning and weaving and fabricating pottery had to be kept in proper condition and adjustment; and if we could realize the small amount of mechanical knowledge extant in primeval days, we would probably also realize that the difficulties of keeping these crude appliances in good working order were as great as are the like difficulties now, with the most complicated printing-press. Furthermore, it was not only for keeping mechanisms in good condition that artisans were needed: a higher degree of skill was needed for operating them. We are forced to the conclusion that, as soon as mechanisms were produced, the need of artisans trained to operate them was felt. Not only this: the fact that the mechanisms were operated, the facts that flax was spun and textures were woven, and pottery was fashioned and baked, and that bows and arrows were used in battle, prove that operators were actually trained to skill in the various arts. This means that, as soon as the Machine of Civilization was begun, operators skilled in the kinds of work which that Machine required were trained in their various parts, and did their appointed work. It was not only machines of brass and iron and wood, moreover, that required skilled operators: the individual human machines were continually getting out of order, and men were trained in whatever knowledge the world contained, to keep them in good order. Hence the physician came into being.