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 The principal tastes are only four; namely, sweet (tasted chiefly by tip of tongue), sour and saline (sides of tongue), bitter (tasted on the back of tongue) (Exp. 5).

The nerves of smell end in the mucous membrane of the upper half of the two nasal chambers; the fibers are spread over the upper proportion of the walls. The direct current of air does not pass as high as these nerve endings; hence sniffing aids the perception of odors. This sense is able to bring up the associations of early life more powerfully than any of the senses. The odor of a flower like one that grew in an old garden can almost restore the consciousness of the past. We smell gases only; solids and liquids cannot affect this pair of nerves (Exp. 8).

Flavors.—The tastes that we call flavors are really smells. We confuse them with taste, because they accompany food that is in the mouth. Name some foods that seem "tasteless" when one has a severe cold in the head. Why is this? Some of the most repulsive drugs can be easily swallowed if the nose is held (Exp. 6 and 7).

Hygiene of the Senses of Taste and Smell.—A savage or a beast uses the senses of taste and smell to find out whether things are good to eat or not. If a civilized man's senses are not perverted, and he eats only simple foods that have a pleasant taste, they will not injure him or cause him sickness. Things that are poisonous usually have unpleasant tastes and often have unpleasant odors. These senses are naturally of wonderful delicacy. They can be cultivated to a still more remarkable degree, or they can be blunted and almost destroyed. Chronic catarrh dulls or destroys the sense of smell. The loss or even the weakening of the perception of flavors is an injury to the working of the closely related sense of taste. When a person loses the enjoyment of delicate flavors, he wants food to have strong seasoning and more decided taste to prevent it from being insipid. Everything must be either very greasy or very sweet or very salty or very sour, to please his degenerate senses. Wheat, corn, and other grains have each its own pleasant taste, yet such persons must have lard in their bread because they are not capable of appreciating anything with a delicate taste. In