Human physiology : designed for colleges and the higher classes in schools and for general reading . tschief use is to masticate the food, it has some agency in. the expression of the countenance, in fixing the teeth firmlytogether, as in the expression of rage. There are three muscleswhich move the ear; 19, moving it upward; 17, forward;and 21, backward. These have but little power in man, butin some animals they move the ear considerably, and areprominent agents of expression. 336. In Fig. 131 the muscles about the mouth, which haveso much to do with the expression of the countenance, are ve
Human physiology : designed for colleges and the higher classes in schools and for general reading . tschief use is to masticate the food, it has some agency in. the expression of the countenance, in fixing the teeth firmlytogether, as in the expression of rage. There are three muscleswhich move the ear; 19, moving it upward; 17, forward;and 21, backward. These have but little power in man, butin some animals they move the ear considerably, and areprominent agents of expression. 336. In Fig. 131 the muscles about the mouth, which haveso much to do with the expression of the countenance, are verydistinctly shown. At a is the muscle which draws up the wingof the nose and the lip ; b raises the lip; c raises the corner ofthe mouth; d and e raise the corner of the mouth, and at thesame time carry it outward ; n draws it outward ; m draws itdownward and outward in which it is assisted by a broad thinmuscle, o, which situated just under the skin comes up fromthe neck; I draws the lower lip downward; and i is the cir- 20 230 HUMAN PHYSIOLOGY. Muscles of expression about the mouth. FIG. I 1W MUSCLES ABOUT THE MOUTH. cular muscle which closes the lips, and thrusts them out inpouting. At A is a short muscle which is fastened to the socketsof the teeth, and has its fibres ending in the skin of the chin. Ittherefore draws the chin up when it contracts. It has so muchagency in the expression of scorn and contempt that it has beencalled the superbus. It is by the action of this muscle, togetherAvith the circular muscle i, that the expression termed poutingis produced. The muscles which I have thus described are allin pairs; and in every pair both muscles contract alwaysexactly alike, unless affected by disease. We laugh and frownand weep on both sides alike. All of these muscles of ex-pression in the face are governed in their action by thebranches of one nerve, the respiratory nerve of the this nerve, therefore, is paralyzed on one side, and noton the other, as i
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