THE MUSCLES AND HOW TO USE THEM 



53 



77. Some Large Muscles of the Back and Legs. A very 

 broad muscle in the back is the "climbing muscle " (latis- 

 simus dorsi), which serves to pull the arm backwards. 



Three huge muscles make up the greater portion of the 

 fleshy mass in the lower part of the back. They move 

 the thigh backwards and help 

 to keep the body erect. The 

 longest muscle in the body, 

 called the "tailor's muscle" (sar- 

 torius), runs across the thigh in 

 front. It helps us to cross the 

 legs. 



Two strong muscles form 

 the largest part of the calf of 

 the leg. 



These muscles are constantly 

 called into use in walking, cy- 

 cling, standing, dancing, and 

 leaping. They are of great 

 strength, because in raising the 

 heel they have to raise the 

 weight of the body. 



The tendons of these two 

 leg muscles unite to form the tendon of Achilles (Fig. 39). 



FIG. 43. Some of the Larger 

 Muscles on the Back of the 

 Shoulder and the Arm. 



PHYSICAL EXERCISE 



78. Why we need Physical Exercise. To keep the body 

 in good health, a certain amount of physical exercise should 

 be taken every day. The reason for this is plain. As we 

 have learned, the tissues contain a countless number of 

 little cells, to which the ever-changing blood, in its cease- 

 less current, brings oxygen and nutriment. The tissues 



