BONES, MUSCLES, EXERCISE, AND REST. 321 



CHAPTER XX. 



Day is Time for Labor. Experiments. Soldiers. Miller. Sleep. 

 Quantity of Sleep. Night proper Time for Sleep. Deficient 

 Sleep causes Weakness. Circulation feeble, and Pleat less in 

 Sleep. Difficult Digestion disturbs Sleep. 



737. The day is the time for labor, and the night is the 

 time for rest. This seems to be the almost universal law of 

 nature. During the light of day, the air is more pure, and 

 respiration is better sustained, the changes of particles are 

 more easy, and consequently the muscles are better strength- 

 ened. The light of the sun has, in some way or other, a 

 great influence upon the energies of the body and the mind. 

 The effect of a long series of cloudy days upon the spirits 

 is familiar to all ; we then become dull and querulous about 

 the weather, and the return of the sunshine is received 

 with a burst of joy, as if it brought back new life. Miners, 

 who spend most of their daytime within the earth, become 

 bleached and dull. Mechanics and shopmen, who work or 

 transact business in imperfectly-lighted shops, have a lower 

 degree of energy and health. 



738. Night labor is attended with the double disadvantage 

 of bad air and darkness. The evil consequences of this were 

 shown in the experiment of two French regiments. " One 

 of them, although it was in the heat of summer, marched in 

 the day and rested at night, and arrived at the end of a march 

 of 600 miles without the loss of either men or horses ; but 

 the other, who thought it would be less fatiguing to march 

 in the cool of the evening, and part of the night, than in the 

 heat of the day, at the end of the same march had lost most 

 of the horses and some of the men." * 



739. A similar experiment is partially tried by individuals, 

 almost every where, with the same success. Milkmen and 



* Art of Living Long and Comfortable, p. 172. 



