TASTE.--The sense of taste is located chiefly in the tongue, over the surface of which are scattered many minute _taste-bulbs_. These can be seen as small red specks, most plentifully distributed along the edges and at the tip of the tongue. The substance tasted must be in _solution_, and come in contact with the nerve endings. The action of the stimulus is _chemical_. The sense of taste recognizes the four qualities of _sour_, _sweet_, _salt_, and _bitter_. Many of the qualities which we improperly call tastes are in reality a complex of taste, smell, touch, and temperature. Smell contributes so largely to the sense of taste that many articles of food become "tasteless" when we have a catarrh, and many nauseating doses of medicine can be taken without discomfort if the nose is held. Probably none of us, if we are careful to exclude all odors by plugging the nostrils with cotton, can by taste distinguish between scraped apple, potato, turnip, or beet, or can tell hot milk from tea or coffee of the same temperature. SMELL.--In the upper part of the nasal cavity lies a small brownish patch of mucous membrane. It is here that the olfactory nerve endings are located. The substance smelled must be volatile, that is, must exist in gaseous form, and come in direct contact with the nerve endings. Chemical action results in a nerve current. The sensations of smell have not been classified so well as those of taste, and we have no distinct names for them. Neither do we know how many olfactory qualities the sense of smell is capable of revealing. The only definite classification of smell qualities is that based on their pleasantness or the opposite. We also borrow a few terms and speak of _sweet_ or _fragrant_ odors and _fresh_ or _close_ smells. There is some evidence when we observe animals, or even primitive men, that the human race has been evolving greater sensibility to certain odors, while at the same time there has been a loss of keenness of what we call scent. VARIOUS SENSATIONS FROM THE SKIN.--The skin, besides being a protective and excretory organ, affords a lodging-place for the end-organs giving us our sense of pressure, pain, cold, warmth, tickle, and itch. _Pressure_ seems to have for its end-organ the _hair-bulbs_ of the skin; on hairless regions small bulbs called the _corpuscles of Meissner_ serve this purpose. _Pain_ is thought to be mediated by free nerve endings. _Cold_ depends on end-organs called the _bulbs of Krause_; and _warmth_ on the _Ruffinian corpuscles_.