

NUTRITION. 91 



pense as about equal, but it must be borne in mind that the plan 

 only represents an average result of both. 



How are variations in the rate of income and expenditure shown ? 

 By changes in the bodily weight. 



What is the result of the expenditure ? 



(1) The growth of the body and secretion of its necessary mate- 

 rials, as well as the maintenance of the tissues, subjected as they 

 are to the wear incident to the continuance of life and function. 



(2) The continuance of physical conditions suitable to life in the 

 form of heat and motion. The actual combustion of carbon (i. e. oxi- 

 dation) must be sufficient to maintain the animal heat and the nour- 

 ishment of the muscles upon which the continuance of life depend. 



(3) Nervous energy, as in the regulation of all physiological pro- 

 cesses by the reflexes, as well as in voluntary mental and nervous 

 action. 



What is the amount of energy resulting from the bodily expend- 

 iture? 



The daily work of the body has been calculated to be about 

 3400 foot-tons. Of this about one-tenth has been considered to be 

 exhausted in involuntary muscular action (circulation, respiration, 

 etc.) and in voluntary motion, while the remainder (nine-tenths) is 

 expended in maintaining the body -heat. Another method of con- 

 sidering this enormous force may be of use : it is equivalent in 

 heat to that required to raise nearly 50 pounds of water from the 

 freezing to the boiling-point, or in mechanical force it is sufficient 

 to raise the body of a man weighing 150 pounds to a height of 8 

 miles. 



Does this calculation include all the energy developed in the 

 body? 



No. It takes no account of energy exerted in nervous manifes- 

 tations, nor does it take into consideration the utilization of the 

 heat absorbed by the body. 



What is "nitrogenous equilibrium"? 



When an animal is fed exclusively upon a nitrogenous diet, it is 

 found that after a time the egested nitrogen approaches and finally 

 balances that taken in as food. This is known as the " nitrogenous 



