BONES, MUSCLES, EXERCISE, AND REST. 



271 



ankles, and there change their direction and pass to the 

 toes. 



626. When the muscles draw up, they increase in size, and 

 swell out at their middle; and when they cease to act, they 

 are again drawn out in length, and their size is reduced. 

 If we place the right hand on the front of the left upper arm 

 when we bend the left elbow, we shall feel the biceps muscle 

 (Fig. LIV. c, d) swelling out and becoming hard. If, at the 

 same time, we place the fingers in the angle of the elbow, 

 we shall feel the cord drawn tight and moving. If we 

 put the hand on the same place when we straighten the 

 elbow, we shall feel the muscle growing soft, the swelling 

 going down on the upper arm, and the cord moving back- 

 ward and becoming loose in the elbow. 



FIG. LIV. Flexor Muscle of tKe Elbow. 



a, Hum-eras, or bone of upper- 

 arm. 



b, Bone of fore-arm. 



c, Hand. 



d, Biceps muscle. 



e, Its upper attachment. 



/, Its cord attached to the lower 

 arm. 



g, Muscle that straightens the 

 elbow. 



h, Its attachment to the elbow. 



627. The muscle on the back of the upper arm that 

 straightens the elbow is broader and larger, so that its swell- 

 ing, and reduction are not squperceptible as ,in case of the 

 bending muscle. Nevertheless, its .action and relaxation 

 may be perceived, when the lower arm moves upon the 



