With us lordly human beings, at the extreme opposite end in the scale of being from the microscopic jelly-specks, the art of feeding and the mechanism which provides for it have both reached a very high state of advanced perfection.  We have slowly evolved a tongue and palate on the one hand, and French cooks and pate de foie gras on the other.  But while everybody knows practically how things taste to us, and which things respectively we like and dislike, comparatively few people ever recognise that the sense of taste is not merely intended as a source of gratification, but serves a useful purpose in our bodily economy, in informing us what we ought to eat and what to refuse.  Paradoxical as it may sound at first to most people, nice things are, in the main, things that are good for us, and nasty things are poisonous or otherwise injurious.  That we often practically find the exact contrary the case (alas!) is due, not to the provisions of nature, but to the artificial surroundings in which we live, and to the cunning way in which we flavour up unwholesome food, so as to deceive and cajole the natural palate.  Yet, after all, it is a pleasant gospel that what we like is really good for us, and, when we have made some small allowances for artificial conditions, it is in the main a true one also.

The sense of taste, which in the lowest animals is diffused equally over the whole frame, is in ourselves and other higher creatures concentrated in a special part of the body, namely the mouth, where the food about to be swallowed is chewed and otherwise prepared beforehand for the work of digestion.  Now it is, of course, quite clear that some sort of supervision must be exercised by the body over the kind of food that is going to be put into it.  Common experience teaches us that prussic acid and pure opium are undesirable food-stuffs in large quantities; that raw spirits, petroleum, and red lead should be sparingly partaken of by the judicious feeder; and that even green fruit, the bitter end of cucumber, and the berries of deadly nightshade are unsatisfactory articles of diet when continuously persisted in.  If, at the very outset of our digestive apparatus, we hadn’t a sort of automatic premonitory adviser upon the kinds of food we ought or ought not to indulge in, we should naturally commit considerable imprudences in the way of eating and drinking—­even more than we do at present.  Natural selection has therefore provided us with a fairly efficient guide in this respect in the sense of taste, which is placed at the very threshold, as it were, of our digestive mechanism.  It is the duty of taste to warn us against uneatable things, and to recommend to our favourable attention eatable and wholesome ones; and, on the whole, in spite of small occasional remissness, it performs this duty with creditable success.