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 : 



-r, , , , , . I 2 28 '06 grms. proteid. 



Food of dog during 12 days = 



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 fceces. 



Proteid . . = 1222 kilo-cal. 

 Fat = 3207 



4429 



OAK o (223-5 heat value of urine. 

 OOD'Z \ 8i-7 M M 



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. 



Eecent work by Kubner 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 grin, 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 

 faces. 



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) 10-09a;+ 9*06?/ = 379*5 



(2) 2-95aj+19-12y = 311-0 



.'. # = 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 '49 3 grms. dry meat = 26*36 

 kilo-calories ; that to 1 grm. carbon from fat= 1*3 grm. fat= 12 '16 kilo-calories, 

 1 Ztschr.f. BioL, Munchen, 1894, Bd, xxx. S. 140. 



