. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. into the buccal cavity opposite the back teeth, while opposite the second upper molar tooth on either side, is the exit of Stenson's duct that drains the large parotid gland (Fig. 225), from which saliva flows. It is not diffi- cult to locate the openings of these important ducts, for if one sticks the tongue into the cheek, and psychologically aids the flow of saliva by looking at a freshly sliced lemon, or something that "makes the mouth water,"
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. into the buccal cavity opposite the back teeth, while opposite the second upper molar tooth on either side, is the exit of Stenson's duct that drains the large parotid gland (Fig. 225), from which saliva flows. It is not diffi- cult to locate the openings of these important ducts, for if one sticks the tongue into the cheek, and psychologically aids the flow of saliva by looking at a freshly sliced lemon, or something that "makes the mouth water," a tiny stream of saliva may be felt spurting into the buccal cavity. Birds, turtles, and monotremes with beaks, have dry cornified buccal cavities nearly devoid of glands. No one ever saw a bird "; Saliva, containing a digestive enzyme, ptyalin, is produced at the rate of as much as three pints a day, for the most part dur- ing the intake of food. Since saliva is not stored, the glands need periods of rest and recuperation between times of accelerated activity. The reader can draw his own con- clusions about the physiological results of the gum-chewing habit. On the inner face of the upper lip in the middle line, demonstrable by the exploring tip of the tongue, is a vertical fold of mucous membrane which tends to hold the lip close against the gums. This is called a labial frenulum. A second one occupies a similar median position with ref- (P\t^% IJMl-fr^-nr Jaw Bone erence to the lower lip. In some animals, such as the duckbill, Old World monkeys, apes (Fig. 226), gophers, squir- rels, and other rodents, the buccal cavity can be stretched into dis- tinct cheek pouches, which are used for the temporary storage of food when its collection occurs under circumstances of competition such as to make grabbing as much as possible in a minimum of time desirable. Sometimes greedy little children demonstrate their probable rise from ani- mal ancestry by reverting to the
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
