Page:The Scientific Monthly vol. 3.djvu/562

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��IN tiiese days there is hardly a more commonly accepted principle of human conduct than the tendency to supplant inherited in- stincts by experience based upon organized knowledge; nor will the teachings of unorganized knowledge prove an acceptable substitute. Unaided mother-love has brought up most of the babies reared to adult stature since the dawn of creation, yet it must confess that modem methods in medicine have bettered its instructions. No longer is it possible for the singer, the engineer, the nurse, the teacher, to make headway professionally without scientific training; and now the cook, the policeman, the saleswoman and the charity worker are beginning to follow suit.

Moreover, in regard to inherited instincts, it has to be admitted that they are sometimes altogether lacking upon most important occa- sions, or even fundamentally wrong. It is well known that though many animals, thrown into the water for the first time, can save their Uves by swimming, the inexperienced human is usually unable to do so. The instinct for scratching an irritated skin is almost ineradicable, yet ordinarily mischievous and often dangerous. The universal liking for so powerful a poison as alcohol, so easily developed by all races of men, has sometimes been cited to disprove any possible theory of organic evolution. Such instances as these may easily be multiplied.

How does this apply to that absolutely universal, most important, and least considered (from the scientific standpoint) of all human performances, the every-day business of eating?

It is perhaps a self-evident proposition, that the human body is, physiologically speaking, a machine, t. e.^ a complicated system of more or less perfectly coordinated mechanisms, for which foods serve the double purpose of supplying structural material and also fuel which keeps the engines running. It is a deduction which few would care to deny, that any machine will run better and last longer if built of proper materials suitably repaired, and fed with the proper kind of fuel, in amounts suited to the kind of work it has to do. Yet the uni- versal criterion used by the builder, repairer and stoker of this machine is the desire to eat, dignified by some such name as the normal healthy appetite,'* "natural instinct for food.*' And meantime, the tendency of physicians to use "regulation of the diet rather than medicine, as

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