BONES, MUSCLES, EXERCISE, AND REST. 265 



The vastus internus and externus, XLIX. v, x, LI. n, o, 

 are two muscles that are attached to almost the whole length 

 of the thigh bone, and send tendinous bands to the upper end 

 of the bones of the leg. They assist in straightening the leg. 



619. The trapezius, (Fig. L. a, a, LI./*,) is attached above 

 to the head, and the bones of the neck and back : it extends 

 outward and part downward and part upward, and its op- 

 posite end is attached to the collar-bone and shoulder-blade. 

 Its upper fibres lift the shoulder ; its lower fibres draw it 

 downward and backward ; and its middle fibres, and the 

 whole acting together, draw the shoulder backward. 



The latissimus dorsi, or the broadest muscle of the back, 

 L. b, LI. g, extends from the middle and the lower half of 

 the back bone, and the back part of the pelvis, and extends 

 forward and upward to the upper arm near the shoulder. It 

 draws the arm backward and downward. 



The deltoid, L. c, XLTX. b, lifts the arm. 



The triceps, or three-headed extensor of the fore-arm, L. d, 

 is attached above to the shoulder-blade and humerus, and 

 below to the extreme point of the elbow. It straightens that 

 joint. 



The great glutens, L. e, LI. k, extends from the back part 

 of the pelvis to the upper part of the thigh bone. It straight- 

 ens the hip joint, and raises the body up on the lower limbs 

 from the sitting position. 



The biceps, or two-headed flexor of the leg, L. f, is attached 

 above to the pelvis and the thigh bone, and sends a tendon 

 from its lower end through the outside of the ham to the 

 outer bone of the leg. It bends the knee, and its tendon 

 forms the outer ham-string. 



The semitendinous and the semimcmbranous muscles, L. g^ 

 Ji, are attached above to the lower part of the pelvis, and, ex- 

 tending down the back and inner part of the thigh, send cords 

 through the middle of the ham to the inner bone of the leg. 

 They aid in bending the knee, and their tendons form the 

 inner ham-string. 



The gastrocnemius, or great muscle of the calf, L. f, is at- 



