100 PRINCIPLES OF ANIMAL NUTRITION. 
regard the nitrogen excretion as denoting the complete metabo- 
lism to carbon dioxide, water, urea, etc., of a corresponding 
amount of proteids, we get figures for the total evolution of 
energy (heat) in the organism which are entirely incompatible 
with those derived from other considerations. For example, a 
daily diet of 1500 grams of lean meat given to a dog not only suf- 
ficed to supply the demands for energy but produced a storage of fat 
in the body. The total daily production of heat, computed from 
the results of respiration experiments (see Chapter VIII), was 
1060.2 Cals., equivalent to 88.3 Cals. in two hours, which must have 
been derived essentially from the metabolism of proteids. If, how- 
ever, we compute the evolution of energy from the results of the 
nitrogen excretion as determined in two-hour periods, we get strik- 
ingly variable results. 
in: i n. i n * 
Hour. Uri bey WIPES i Hquivate pe Enereys 
GEL) cesses eereodse enone 3.11 80.6 
DS oy duh ssdi Dardoteaa eae ee 5.71 148.2 
DES) | ais, aan eccldnseneevciestyanau a 6.62" 171.6 
SO. cen intcyaitslal alana nape edaseaee 6.98 181.2 
DT ie secs ania ike taeiln sie chaas oe 6.35 165.1 
MOL seccnnteyn ces pioaantcagee paca ss cetele 6.04 156.0 
QED: x aisnecchiedarts excayermes wiiavartear eae 5.08 132.6 
11-7 (Average) ...........5 2.65 68.9 
AO Grama Neaet it avraconattes cody rahe: ate 1.24 32.5 
The heat production as thus computed varies from over twice 
the average two-hour rate to an amount equal to scarcely more than 
one half of the average fasting metabolism of the same animal 
(62 Cals. per two hours). Such fluctuations are entirely inconsistent 
with all data as to the heat production of the body, which, as we 
shall see later, appears to go on with a remarkable degree of uni- 
formity under uniform conditions. The only reasonable conclu- 
sion, then, appears to be that the nitrogen cleavage and the total 
oxidation of the proteids are distinct and at least largely inde- 
pendent processes. 
Gruber’s explanation of these facts is substantially as follows: 
It is well established that a relatively constant composition of the 
blood and of the fluids of the body generally is an essential condi- 
* One gram N equivalent to 26 Cals. See Chapter VIII. 
