=The Sense of Taste.=--The sense of taste lies chiefly in the _taste buds_ as they are called which are filled with _gustatory cells_ and are found in the papillæ of the tongue, principally in the _circumvallate papillæ_ at the back of the tongue, which are few in number and arranged in a V-shape. There is also a certain power of taste in the tip and sides of the tongue but little in the upper surface or dorsum. Only five special tastes can be distinguished: bitter, sweet, acid, sour, and salt, but sometimes more than one can be distinguished at a time, as bitter and sweet. Every one can distinguish between different tastes but the power varies in different people and with different conditions. Certain tastes seem to be better distinguished in certain places, as sweet at the tip and bitter at the back of the tongue. Moreover, the sense of taste is very dependent upon the sense of smell, especially in the case of aromatic and savory substances, which one really does not taste but smell. If one held his nose and closed his eyes he would not know from the taste whether he was eating onion or apple. This leads to the habit of pinching the nose when taking nauseous medicines. To be tasted a substance must be in solution. Friction against the tongue, lips or cheek increase the sense of taste. A temperature of 100° Fahrenheit favors taste, while both great heat and great cold impair it. There are probably at least two nerves of taste, the lingual branch of the trifacial or fifth cranial and the gustatory branch of the glosso-pharyngeal. Along with the sense of taste there are other senses in the mouth which play an important part, such as _pressure_ and the _sense of heat and cold_, and it is often hard to distinguish them from the pure sensation of taste, which indeed is always accompanied by them. =Salivary Glands.=--On either side of the mouth are three racemose glands for the secretion of the _saliva_, which serves to soften and lubricate the food and partially to digest starches by means of its ferment, _ptyalin_. The _parotid gland_ is the largest and is below and in front of the ear, opening by _Stensen’s duct_. The _submaxillary gland_ is below the jaw toward the back on either side and its duct is _Wharton’s duct_. The _sublingual gland_ lies beneath the mucous membrane of the floor of the mouth and opens by eight to twenty tiny ducts beside the frenum, the _ducts of Rivinus_. The activity of the glands depends upon the blood supply; the more blood the greater their activity. [Illustration: FIG. 20.--Dissection of the side of the face, showing the salivary glands: _a_, Sublingual gland; _b_, submaxillary gland, with its duct opening on the floor of the mouth beneath the tongue at _d_; _c_, parotid gland and its duct, which opens on the inner side of the cheek. (After Yeo.)]