. Human physiology : designed for colleges and the higher classes in schools and for general reading . this purpose, he draws in the water, making it to passthrough this sieve, and then expels it from the nostrils or blow-holes. Birds, too, have no teeth. Their place is suppliedby a contrivance in the stomach itself, for the breaking up ofthe food. This will be described in another part of thischapter. 75. While the food is cut and ground by the teeth, it is atthe same time thoroughly moistened by the saliva, which ispoured forth from certain glands in the neighborhood. Thereare three pairs of
. Human physiology : designed for colleges and the higher classes in schools and for general reading . this purpose, he draws in the water, making it to passthrough this sieve, and then expels it from the nostrils or blow-holes. Birds, too, have no teeth. Their place is suppliedby a contrivance in the stomach itself, for the breaking up ofthe food. This will be described in another part of thischapter. 75. While the food is cut and ground by the teeth, it is atthe same time thoroughly moistened by the saliva, which ispoured forth from certain glands in the neighborhood. Thereare three pairs of these glands. Fig. 9 shows the glands onone side. The parotid gland, 1, is the largest. This is situatedin front of the lower part of the ear. It is the seat of theswelling in the disease called mumps. Its duct, 2, passes overone laro-e muscle and between the fibres of another, and poursits contents into the mouth opposite the second small grinder ofthe upper jaw. If you press on this part of the cheek, you can 46 HUMAN PHYSIOLOGY. Formation of the saliva. Three pairs of salivary glands. FIG. SALIVARY GLANDS. feel in the mouth an increased flow of the saliva. The sub-maxillary gland, 3, is situated inside of the lower jaw at itslower part; and its duct, 4, opens into the mouth at the sideof the frgenum of the tongue. The sublingual gland, 5, liesunder the tongue, and discharges its secretion by a duct at theside of that organ. These saliva factories, as we may termthem, are in much more active operation at some times thanat others. They are especially active when we are eating ; andit is commonly estimated that, during an ordinary meal, abouteight ounces of saliva are poured into the mouth. This largeamount is wanted to moisten the food thoroughly before it isswallowed; and it is supposed, also, that it has some chemicalinfluence in preparing the food for the action of the gastricjuice in the stomach. More saliva than usual is needed, also,when we are speaking, in order to
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