BODILY ENERGY LOST PER DAY. 453 



Day of Rest. Day of Work. 



Restl6hrs. Sleep 8 hrs. ' RestShrs. WorkShrs. SleepSlirs! 



\ 



2470 - 4 32 1235 ' 2 2169 ' 6 



( 10,885Fah.-lb. \ q a f 14.528 Fah.-lb. 



The mechanical work done on the working day, repre- 

 sented in addition an expenditure of energy of 213,344 

 kilogrammeters, which is equal to 502 calories. Of the ex- 

 cess heat in the working day, part is directly produced by 

 the increased chemical changes in the quicker working heart 

 and respiratory muscles, and the other muscles set at work; 

 while part is indirectly due to heat arising from increased 

 friction in the blood-vessels as the blood is driven faster 

 around them, and to friction of the various muscles used. 

 The average cardiac work in twenty-four hours is about 

 60,000 kilogrammeters ; that of the respiratory muscles 

 about 14,000 ; and since nearly all of both is turned finally 

 into heat within the Body, we have 74,000 kilogrammeters 

 of energy answering to about 174 calories (6786 Fah.-lb. 

 units) indirectly produced in tre resting Body daily from 

 these source's. 



Of 100 parts of heat lost from the resting Body, about 

 74.7 are carried off in radiation or conduction from the skin. 

 14.5 are carried off in evaporation from the skin. 



5.4 " " " " " lungs. 



3.6 " " " expired air. 



1.8 " " the excretions. 



In a day of average work, of every 100 parts of energy lost 

 in any form from the Body 



1-2 go as heat in the excreta. 



3-4 in heating the expired air. 

 20-30 in evaporating water from the lungs and skin. 

 60-75 in heat radiated or conducted from the surfaces and 

 in external mechanical work. 



The Superiority of the Body as a Working Machine. 



During eight hours of work, we find (table at top of page) 

 the Body loses 2169.6 calories of energy as heat; and can do 



