The middle region of the tongue is the part with which we experience sensations of taste proper—that is to say, of sweetness and bitterness. In a healthy, natural state all sweet things are pleasant to us, and all bitters (even if combined with sherry) unpleasant. The reason for this is easy enough to understand. It carries us back at once into those primæval tropical forests where our “hairy ancestor” used to diet himself upon the fruits of the earth in due season. Now, almost all edible fruits, roots, and tubers contain sugar; and therefore the presence of sugar is, in the wild condition, as good a rough test of whether anything is good to eat as one could easily find. In fact, the argument cuts both ways: edible fruits are sweet because they are intended for man and other animals to eat; and man and other animals have a tongue pleasurably affected by sugar because sugary things in nature are for them in the highest degree edible. Our early progenitors formed their taste upon oranges, mangoes, bananas, and grapes; upon sweet potatoes, sugar-cane, dates, and wild-honey. There is scarcely anything fitted for human food in the vegetable world (and our earliest ancestors were most undoubted vegetarians), which does not contain sugar in considerable quantities. In temperate climates (where man is but a recent intruder), we have taken, it is true, to regarding wheaten bread as the staff of life; but in our native tropics enormous populations still live almost exclusively upon plantains, bananas, breadfruit, yams, sweet potatoes, dates, cocoanuts, melons, cassava, pineapples, and figs. Our nerves have been adapted to the circumstances of our early life as a race in tropical forests; and we still retain a marked liking for sweets of every sort. Not content with our strawberries, raspberries, gooseberries, currants, apples, pears, cherries, plums, and other northern fruits, we ransack the world for dates, figs, raisins, and oranges. Indeed, in spite of our acquired meat-eating propensities, it may be fairly said that fruits and seeds (including wheat, rice, peas, beans, and other grains and pulse) still form by far the most important element in the foodstuffs of human populations generally.