128 



ELEMENTS OF PHYSIOLOGY 



collar bone (Fig. 124). It can be felt as a thick band; 



when the head is turned to one side, it stands out as a 



ridge. When one of the two acts alone, 



it tu:ns the face so as to look to the other 



side. When both act they bow the head. 



The deltoid (Figs. 123, 124), or shoulder 



cap muscle, raises the whole arm outward 



and upward from the side. Can you locate 



it by the feeling of fatigue after raising 



the arm twenty times ? The biceps can tilt ' ed upo ' n Atla e s * 



be seen and felt contracting on the front 



of the arm when bent at the elbow. The triceps is on 



the opposite side of the arm and straightens the elbow 



TRAPEZIUS 

 DELT0/& 



FIG. 122. Muscles of Head and 

 Neck. Find the following mus- 

 cles : 



Chewing muscles; scalp muscles; bow- 

 ing muscle of one side; muscle that 

 holds head erect (upper part of 

 trapezius at back of neck) ; muscle 

 that squints the eye ; muscle that 

 pouts the lips; muscle that broadens 

 the mouth in smiling; muscle that 

 raises corners of mouth ; muscle that 

 draws down corner of mouth. 



FIG. 123. Principal Muscles of the 

 Back. 



Trapezius draws shoulder and head back ; 

 deltoid raises whole arm ; latissimus, 

 climbing muscle, bliquus internus and 

 obliquus externus draw abdominal wall 

 in and force abdominal contents against 

 the diaphragm, thus expelling air from 

 lungs. 



