836 ANIMAL HEAT. 
Thus it is possible to calculate the production of heat in an animal, if the 
quantity and nature of its food and the amount of the discharge of nitrogen in 
the urine and faeces be known. This Rubner has done, and has compared the 
result with the heat given off by the animal to a calorimeter. Thus : — 
„ , , , , . , , I 228-06 grins, proteid. 
Food of dog during 12 days= <j MQ ^ ^ fa * 
In the urine 30*0 grms. N were discharged, and the dry faeces amounted 
to 16 "8 grms. 
Calculation 1, from physiological heat values.* 
Proteid, 228-06 x 4-0 kilo-cal. = 912-24 
Fat, 340-4 x 9'423 „ =3207-0 
4119-2 kilo-cal. in 12 days. 
Calculation 2, from physical heat value with reduction for heat value 
of urine and faeces. 
Proteid . . = 1222 kilo-cal. 
Fat . . . =3207 
4429 
QAFL O f223'5 heat value of urine. 
oUO'J I si -7 „ „ faeces. 
In 12 days 4124 kilo-calories. 
The amount of heat actually given off by the dog during this time was 
3958 kilo-calories. Thus the calorimeter showed that 96 per cent, of the 
energy of the food had appeared as heat. 
Recent work by Rubner 1 has shown that the body of a living 
animal may be looked upon as a calorimeter, and may be used as such 
for the determination of the heat of combustion of food. Thus the heat 
of combustion of 1 grm. of dry meat, determined in this way, is 4007 
calories, that of 1 grm. of dry fat 9353 calories, figures which are practic- 
ally the same as 4000 and 9423 respectively, the results obtained by 
combustion in a Thompson's calorimeter, when allowance is made for 
the heat value of the products of the proteid lost in the urine and 
fasces. 
The following is one of Rubner's examples of such a determination : — A 
small dog fed upon meat discharged daily 10-09 grms. of nitrogen in its urine 
and faeces, and 9 "06 grms. carbon from fat underwent combustion. The heat 
produced, as determined by the calorimeter, was 379*5 kilo-calories. On a diet 
of meat and fat the same dog discharged 2-95 grms. of nitrogen, and 19 -12 grms. 
carbon from fat underwent combustion, while the production of heat was 311 
kilo-calories. Now, if the calorimetric value of the nitrogen be represented by 
x and that of carbon from fat by y, then — 
(1) 10-09* + 9-(% = 379-5 
(2) 2-95ai+19-12// = 311-0 
.*. .r = 26'7 kilo-calories and y - 12-15 kilo-calories. 
The results obtained by direct combustion were 26 -0 and 12 -3 kilo-calories. 
The heat corresponding to 1 grm. nitrogen = 6 -493 grms. dry meat = 26-36 
kilo-calories ; that to 1 grm. carbon from fat= 1*3 grm. fat = 12-16 kilo-calories. 
1 Ztsclir.f. Biol., Miinchen, 1S94, Bd. xxx. S. 140. 
