MUSCLES 36? 



good supply of oxygen be provided, especially during the rest 

 periods at night; this is the time that much of the carbon dioxide 

 formed in the tissues during the day, when hard work is done, is 

 eliminated. 



Rest and Exercise. — It has been discovered that the feeling of 

 muscular fatigue, the feeling of utter weariness which one often 

 has after prolonged muscular exertion, is probably due to the pres- 

 ence of waste matters in the muscle and blood. These wastes are 

 chiefly the products of oxidation, — carbon dioxide and urea. 



Exercise in moderation is directly a benefit to the muscle. 

 Each time a muscle does work, part of it is oxidized. The very^ 

 process of oxidation gives the muscle an opportunity to assimilate 

 new proteid food; this results directly in the building of new 

 muscle cells or the repairing of the w^asted ones. 



The amount and kind of exercise taken depends largely on the 

 situation of the individual. A strong girl or boy, brought up in the 

 country with fresh air in abundance, and an opportunity to do 

 manual labor out of doors, has great advantage over a city child. 

 Exercise in a gymnasium is not nearly of so much benefit as out- 

 of-door work and play; this is because the supply of oxj^gen, even 

 in the best-ventilated room, may soon be at least partially used up 

 and carbon dioxide take its place in the air. The best results are 

 obtained by working the greatest number of muscles during a 

 given period of time. 



When we become moderately warm, after exercise, a tepid bath 

 followed by a cold plunge and a rub down brings the blood to the 

 surface of the body; a feeling of warmth then results after the sud- 

 den cooling of the skin by the cold water. 



The Relation of Alcohol to Muscular Work. — Records, compiled 

 from a number of reliable sources, seem to show that alcohol has 

 a very decided effect upon the ability of a man to perform muscular 

 work. Not only does it affect the man as to the amount of work, 

 but as to the quality of the work that can be performed in a given 

 period of time. The following extracts show plainly the relation 

 of alcohol, even in moderate quantities, to the capacity for muscular 

 work and to the performance of work that requires great accuracy 

 and training of the eye and muscles. 



