PHYSIOLOGY FOR BEC.l XMKKS 



Class III. The fulcrum at one end, but nearer to the power 

 than to the weight. 



Let us examine a few of the movements of the body. 



Bending or Flexion of the Forearm. This is caused 

 by the action of the biceps muscle, the large muscle on the front of 

 the arm. The biceps muscle is attached by two tendons to 

 the scapula, close to the articular cup for the humerus. This 

 forms its origin. It has a large belly which lies on the front of 

 the humerus, but is not attached to it. Just above the elbow 

 joint the muscle narrows and passes into a tendon which, passing 



FIG. 35. Diagram to show the action of the biceps muscle of the arm. 

 The two tendons by which the muscle is attached to the scapula are seen at a; P, 

 the point of attachment of the muscle to the radius; F, the elbow joint ; \V, the 

 weight of the hand. 



over the joint, is attached to the radius at a rough elevation, 

 nearly one and a half inch below the head of the radius. When 

 the muscle contracts, the radius, and with it the ulna, is drawn 

 up towards the scapula, and so the forearm is bent on the arm, 

 the radius and ulna turning as on a hinge at the lower end of the 

 humerus. The arrangement is that of a lever of the third 

 class. The fulcrum is at the elbow joint ; the weight is the 

 radius and all that is attached to it, the arm, the hand and any 

 object in it ; and the power is applied by the muscle between the 

 weight and the fulcrum, but close to the latter. Since the 

 biceps muscle is inserted into the radius close to the elbow 



