20 MOTION. 



has no power in itself. The muscles have active strength, the 

 bones have passive strength. 



Since there is such an intimate relation between the muscles 

 and the bones, let us turn to the study of the latter. 



Relation of the Muscles and the Bones. Suspend 

 the skeleton from the ceiling in the most open space in the 

 room. Let the pupils study it, book in hand ; not to learn the 

 names of all the bones, but to get a general idea of the forms 

 and relations of the different parts. It is well to have the 

 skeleton constantly at hand, to show the location of the vari- 

 ous organs as they are taken up one at a time during the 

 term. If possible, supply the class with separate bones from 

 another skeleton, and let the pupils place each separate bone 

 alongside the corresponding one in the complete skeleton. 



Pass to the skeleton, and locate the biceps muscle. After 

 examining Fig. 2, show the points of its origin and insertion. 

 Feel the biceps of your arm. Note that its thickest part is 

 opposite the most slender part of the bone. But at the en- 

 larged end of the bone the muscle has narrowed to a slender 

 tendon, which passes over the joint to be attached to the next 

 bone, thus giving more slenderness, flexibility, and freedom of 

 motion to the joint. 



Take the bones of the arm that are articulated (if there is 

 not an artificial hinge at the elbow, one can readily be made 

 of wire) ; put a strong rubber band in place of the biceps 

 muscle; fasten this to the head of the humerus by cords, 

 and by the lower end to the radius and ulna, where the rough 

 places, an inch or so from the elbow joint, show the insertion 

 of the tendons. Have the rubber stretched so that when not 

 held it will flex the forearm. This will serve to show the 

 action of the biceps ; though we must be careful to bear in 

 mind that the muscle does not pull the arm up because it has 

 been stretched, as is the case with the rubber. In the case 



