NUTRITION. 455 



One gram (15.5 grains) of pure albumen when completely 

 burnt liberates, as heat, an amount of energy equal to 2117 

 kilogrammeters (15,270 foot-pounds). But in the Body pro- 

 teids are not fully oxidized ; part of their carbon is, to form 

 carbon dioxide, and part of the hydrogen, to form water; 

 but some carbon and hydrogen pass out, combined with ni- 

 trogen and oxygen, in the incompletely oxidized state of urea. 

 Therefore all of the energy theoretically obtainable is not de- 

 rived from proteids in the Body: from the above full amount 

 for each gram of proteid we must take the quantity carried 

 off in the urea, which will be the amount liberated when that 

 urea is completely oxidized. Each gram (15.5 grains) of 

 proteid oxidized in the Body gives of a gram (5.14 grains) 

 of urea ; since one gram of urea liberates, on oxidation, 

 energy amounting to 934 kilogrammeters (6740 foot-pounds), 

 each gram of proteid oxidized, so far as is possible in the 

 Body, will yield during the process 2117 *f * = 1805.7 kilo- 

 grammeters (13,037 foot-pounds) of energy. Knowing that 

 urea carries off practically all the nitrogen of proteids broken 

 up in the Body, and contains 46.6 per cent of nitrogen, while 

 proteids contain 16 per cent, it is easy to find that each gram 

 of urea represents the decomposition of about 2.80 grams of 

 proteid and, therefore, the liberation of 5060.00 kilogram- 

 meters (36,533.0 foot-pounds) of energy. If, therefore, we 

 know how much urea a man excretes during a given time, 

 and how much mechanical work he does during the same 

 time, we can readily discover if the latter could possibly have 

 been done by the energy set free by proteid decomposition. 

 Let us take a special case. Tick and Wislecenus, two Ger- 

 man observers, climbed the Faulhorn mountain, which is 

 1956 meters (about 6415 feet) high. Fick weighed 66 kilo- 

 grams and, therefore, in lifting his Body alone, did during 

 the ascent 129,096 kilogrammeters (932,073 foot-pounds) of 

 work. Wislecenus, who weighed 76 kilograms, did similarly 

 148,656 kilogrammeters (1,073,296 foot-pounds) of work. 

 But during the ascent, and for five hours afterwards, Fick 

 secreted urine containing urea answering only to 37.17 grams 

 of proteid, and Wislecenus urea answering to 37 grams. 

 Since each gram of proteid broken up in the Body liberates 

 1805.7 kilogrammeters (13,037 foot-pounds) of energy, the 

 amount that Fick could possibly have obtained from such a 

 source is 1805.7 X 37.17 = 67,117 kilogrammeters (484,584 



