206 HUMAN PHYSIOLOGY CHAP, xiv 



15. After exercise muscles need rest and sleep, so that the 

 wastes may be removed and the cells repaired and stored with 

 energy-producing food materials. 



1 6. Stimulants and narcotics make the muscles weak and 

 flabby because of impaired nutrition. They become sluggish 

 and do not respond to ordinary stimuli. 



