SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 245 



491. Remark, PERSONS USUALLY CANNOT CONTRACT THESK MUSCLES, 

 not because they are wanting in any case, but from not being used, as 

 any one can prove by frequently making an effort to contract them with 

 a determination, and giving the mind direction toward them. Not a few 

 other muscles through disease become equally indolent and deaf to the 

 calls of the mind. Thus by tight dressing and supports the muscles 

 of the chest not only become infirm, but absolute nullities. 



492. THE TEMPORAL can readily be felt while chew- 

 ing, by putting the fingers on the temple (so called from 

 tempus, time, because first showing gray hairs), to the 

 bone of which, and a fascia stretching from its ridge to 

 the zygoma, muscular fasciculi are attached, and from 

 which converging, their lower extremities terminate in a 

 tendon that passes under the yoke or zygoma (an arm or 

 process of bone extending in the line between the ear 

 and eye), and seizes upon the upper part of the lower 

 jaw, just in front of the joint, and assists in drawing it 

 up when chewing ; hence the perceptible action of the 

 muscle at such a time. 



493. THE MASSETER can be felt working at the same 

 time on the side of the face ; it extends from the yoke and 

 the cheek (malar) bone down to the lower jaw. 



494. THE PTERYGOID, internal and external, are two 

 muscles upon each side, within the jaw, against the mas- 

 seter, that assist in raising the jaw, drawing it forward 

 and from side to side, as in grinding. 



FIG. 179. 



Fig. 179 represents a portion of the lower jaw re- 

 moved to expose 1, the internal pterygoid. A por- 

 tion of the zygoma and the temporal bone in front of 

 2 is removed to expose 2, 3, the external pterygoid. 



491. Why ? 492. What said of ? 493. What said of ? 494. What said 

 of-? Describe Fig. 1T9. 



