Ml TABOLIKM 





;unoiiiits of nitrogen and carbon excreted and to calculate m 

 known composition of protein how much protein must have undergone 

 metabolism. We then compute how much carbon this quantity of pro- 

 tein would accounl for, and we deduct this from tin- total carbon 

 tion. The remainder of carbon must have come from tin- metabolism of 

 fats and carbohydrates, and although we can nol t«-ll exactly which, 

 we can arrive at a close approximation by observing tin- respiratory quo- 

 tient i K. Q.), which is the ratio "!' the volume of carbon dioxide exhaled 



i- that of oxygen retained by the body in a given time, i.e.- - . By ob- 



serving this quotient, therefore, we can approximately determine the 

 source from which the nonprotein carbon-excretion is derived. 



Having in the above manner computed how much of each of the proxi- 

 mate principles has undergone metabolism, we next pr ied to compare 



intake and output with a view to finding whether there is an equilibrium 

 between the two, or whether retention or loss is occurring. 



It may serve to make clear the methods by which these calculations i 

 made to study the following example: 



Examplt of a Metabolism Investigation. — H is desired to know whether :i d I 

 taining L25 grams protein, 50 grams fatj and 500 grams carbohydrafo 

 man doing a moderate amount of work. 



Intake 



Total, 



gm. 



gm. 



"Retained in Body. 30 gm. carbon and 2.5 gn . i. 

 sent 6.25: :15.6 gm. 75 gm, Now, this amoonl 



nit for B.25 gm. '■••oi ; so thai 



1.3 28 gm. fat. On this .Int. therefore, the nil 

 protein and U^.". gm. tut per diem. 



Furnished with these data we may now proceed to compute how much 



energy must have been Liberated in the body. 



To express the above result in terms n{ energy lil I, we know that 



3027.5 C. were supplied and that all I pi 15.1 



l.l til retained as protein, and -- - •'• 



toto 327.2 C. We find, therefore that 3027 5 — 327 2 2 :• i 

 required. 



