We have, then, the two natural divisions of calorifacient and plastic foods:  the one adapted to sustain the heat of the body, and enable us to maintain a temperature independent of that of the medium we may be in; the other to build up, repair, and preserve in their natural proportions the various tissues, as the muscular, fibrous, osseous, or nervous, which compose our frames.  These two kinds of food we must have in due proportion and quantity in order to live.  Neither the animal nor the vegetable kingdom furnishes the one to the exclusion of the other.  We derive our supplies of each from both.  More than this, we consume and appropriate certain incidental elements, which find their place and use in the healthy system.  Iron floats in our blood, sulphur lies hidden in the hair and nails, phosphorus scintillates unseen in the brain, lime compacts our bones, and fluorine sets the enamelled edges of our teeth.  At least one-third of all the known chemical elements exist in some part of the human economy, and are taken into the stomach hidden in our various articles of food.  This would seem enough for Nature’s requirements.  It is enough for all the brute creation.  As men, and as thinkers, we need something more.

In all the lower orders of creation the normal state is preserved.  Health is the rule, and sickness the rare exception.  Demand and supply are exactly balanced.  The contraction of the voluntary muscles, and the expenditure of nervous power consequent on locomotion, the temperate use of the five senses, and the quiet, regular performance of the great organic processes, limit the life and the waste of the creature.  But when the brain expands in the dome-like cranium of the human being, a new and incessant call is made on the reparative forces.  The nervous system has its demands increased a hundred-fold.  We think, and we exhaust; we scheme, imagine, study, worry, and enjoy, and proportionately we waste.

In the rude and primitive nations this holds good much less than among civilized people.  Yet even among them, the faculties whose possession involves this loss have been ever exercised to repair it by artificial means.  In the busy life of to-day how much more is this the case!  Overworked brains and stomachs, underworked muscles and limbs, soon derange the balance of supply and demand.  We waste faster than enfeebled digestion can well repair.  We feel always a little depressed; we restore the equilibrium temporarily by stimulation,—­some with alcohol and tobacco, others with coffee and tea.  Now it is to these last means of supply that the name has been given of “accessory foods.”