384 PRINCIPLES OF ANIMAL NUTRITION. 
Metabolizable | Excess Above | Digestive Work 
Fasting in Per Cent. 
Food. E f * 7 
v POSTE, | Metghalim, | of Melati 
a 93 644 1.12 
: 8 — : 
Experiments on man ....... 1955 aai 3113 
“ “ dog. dice parang adci 1250 +278 1.53 
2902 +1847 2.99 
TA VOR OGG geie stele nce atiee gi [eats prea eS |e Sk anateegreie 2.19 
Chiefly Carbohydrates : 
2121 +1081 10.89 
Experiments on dog........ 2226 +1094 7.19 
999 +8 8.91 
PAOLO D So sieecs cvdlaia ody Sakeeas Brians [te eessuay 2 aus asa tall adne austen tance 8.99 
Proteids : 
338 —692 16.57 
Experiments on dog......... 943 —20 12.30 
1520 +461 16.05 
AVCTAQC wes eee criows actren . [see cease coeleiue sowss aces 14.97 
Mized Diet : 
Experiments on man ......... 4193 ) +2171 11.76 
It is clear that proteids caused the greatest increase in the 
metabolism and fat the least, while the carbohydrates occupied an 
intermediate position. In the case of fat the increase in the heat 
production seems to show a slight tendency to become greater 
with amounts of food largely in excess of the fasting metabolism, 
but with the carbohydrates and proteids no distinct effect of this 
sort is apparent. 
These results, particularly those on proteids, afford a good illus- 
tration of the fact that the increase in the heat production caused 
by the ingestion of food is not due solely to the increased muscular 
work involved, since if we were to suppose the latter to be the case 
it is not apparent why the proteids, which are digested pretty 
promptly and with comparative ease, should cause seven times as 
much work as the fats. The results certainly suggest strongly that 
a large part of the heat production in the former case arises from 
the considerable chemical cleavage which the proteids undergo in 
digestion and still more from the stimulative effect of food proteids 
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