

THE MUSCLES 139 



the industrious son, that is most often found loafing in a 

 back alley smoking cigarettes ; and it is not the industri- 

 ous, helpful daughter who is most often found with the 

 " blues," or nursing a headache. 



235. Heredity. The disastrous effect upon the heart 

 of a life of habitual muscular inactivity is apparent in the 

 lives of many people. The disappearance of dyspepsia 

 and many other diseases, with the remarkable restoration 

 to health that follows judicious muscular exercise or 

 physical labor, is likewise often seen. We have received 

 our bodies as an inheritance from an ancestry which dates 

 back at least to a time when the human race lived an 

 active life in the open air. The human body is adapted 

 to such conditions, and an attempt to change these con- 

 ditions too rapidly, as in the case of city dwellers, causes 

 extinction. The health and continuance of the race under 

 conditions of city life are aided by the continual influx of 

 healthy individuals from the country. In a human body 

 weighing one hundred and fifty pounds, there are about 

 sixty pounds of muscle, and we cannot neglect sixty pounds 

 of tissue with impunity and allow it to become unsound 

 from disuse (Fig. 126). 



236. THOUGHT LESSON. Position of the Voluntary Mus- 

 cles. On Figs. 125 and 126 mark the location of the 

 muscles having the functions named in the following 

 list. Locate them first in your body by performing the 

 action and feeling the muscle with your hand ; then mark 

 lightly with pencil. For instance, take question 4 : locate 

 the muscle that bends the elbow. This is found to be in 

 the front of the upper arm, and the figure " 4 " placed 

 on the dotted line drawn from that muscle. 



Locate the muscle (or muscles) that 



1. Lifts the whole arm outward and upward. 



2. Draws it downward and forward. 



3. Draws it downward and backward. 



