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 cesses, as muscular power, digestive power, animal heat, and so on.

In the first case supposed, the case of a small demand for mental work and excitement, we look for, and we find, a better physique—greater muscular power and endurance, more vigor of digestion, rendering a coarser food sufficient for nourishment, more resistance to excesses of cold and heat; in short, a constitution adapted to physical drudgery and physical hardship.

Take, now, the other extreme. Let there be a great demand for mental work. The oxidation must now be disproportionately expended in the brain; less is given to the muscles, the stomach, the lungs, the skin, and secreting organs generally. There is a reduction of the possible muscular work, and of the ability to subsist on coarser food, and to endure hardship. Experience confirms this inference; the common observation of mankind has recognized the fact—although in a vague, unsteady form—that the head-worker is not equally fitted to be a hand-worker. The master, mistress, or overseer has each more delicacy of sense, more management, more resource, than the manual operatives, but to these belongs the superiority of muscular power and persistence.

There is nothing incompatible with the principle in allowing the possibility of combining, under certain favorable conditions, both physical and mental exertion