In man, the introduction of food into the mouth is generally accomplished by artificial means, so that the biting teeth (incisors) and the tearing teeth (canines) (Fig. 46) are comparatively little used for obtaining a suitable morsel of food. In the mouth, the essential act of chewing or mastication is accomplished by means of the motions of the lower jaw, the tongue and the cheeks. This process of breaking up the solid parts of the food ought to be continued until all hard substances are ground into a soft pulp.