NECESSARY QUANTITY AND VARIETY OF FOOD. 123 



creases the vigor of the system, provided the increased quan- 

 tity of food required be supplied. 



While a certain amount of waste of the system is inevi- 

 table, it is a conservative provision of nature, that when the 

 supply of new material is diminished life is preserved not, 

 indeed, in all its vigor by a corresponding reduction in the 

 quantity of excretions ; and, in the same way, the vital forces 

 are retained after complete deprivation of food much longer 

 than if destructive assimilation proceeded always with the 

 same activity. 



As regards the quantity of food necessary to maintain the 

 system in proper condition, it is evident that this must be 

 greatly modified by habit, climate, the condition of the mus- 

 cular system, age, sex, etc., as well as idiosyncrasies. 



The daily loss of substance which must be supplied by 

 material introduced from without is very great. 1 A consider- 

 able portion of this discharge takes place by the lungs, and the 

 mode of introduction of gaseous principles to supply part of this 

 waste belongs to the subject of respiration. The most abun- 

 dant discharge which is compensated by absorption from the 

 alimentary canal is that of water, both in a liquid and vapor- 

 ous condition. The entire quantity of water daily removed 

 from the system has been estimated at about four and a half 

 pounds ; 2 and, assuming that there is no evidence of its pro- 

 duction in the organism, an equal quantity must necessarily 

 be introduced. The quantity which is introduced in the form 

 of drink varies with the character of the food. When the 

 solid articles contain a large proportion of water, the quan- 

 tity of drink may be diminished ; and it is possible, by taking 

 a large proportion of the watery vegetables, to do without 

 drink altogether. 8 



1 Prof. Dalton estimates that the daily discharges from the body, including 

 the pulmonary and cutaneous exhalations, amount to a little more than seven 

 pounds avoirdupois. (Human Physiology, Philadelphia, 1864, p. 363.) 



a DALTON, op. cit., p. 70. 



8 Prof. Chas. A. Lee gives a number of examples of persons who were not in 

 the habit of taking water, except that which is contained in the food ; but in these 



