CHEMICAL CHANGE AND HEAT PRODUCTION. 835 



following table of isodynamic foodstuffs is taken from Danilewsky's 

 work : 



The above data are for physical values. It is necessary, therefore, 

 to determine how far the different foodstuffs undergo combustion in 

 the living body, and what values they have as producers of heat during 

 that combustion. 



Eubner has shown that some of the products of the combustion of 

 proteid escape in the foeces as well as in the urine ; the heat value of 

 these substances must be determined and deducted from the heat of 

 combustion of proteid. The reduced or physiological heat value of 

 1 grm. of dry proteid is therefore only about 4000 calories. The fats 

 and carbohydrates appear to undergo complete oxidation in the body. 



An important series of experiments on the sources of animal heat 

 has been performed by Eubner. 1 The experiments were carried on for 

 several days in succession upon a dog weighing 12 kilos. The animal 

 was given a known amount of meat once a day ; the urine and faeces 

 were collected and their heat of combustion determined, and the heat 

 given off by the animal was measured by a calorimeter. At the same 

 time the discharge of carbon dioxide and water from the dog were deter- 

 mined, also the total nitrogen lost in the urine and fteces, and the loss 

 or gain in weight of the animal. No external work was done by the 

 dog, for it remained quiet in the calorimeter, and therefore no energy 

 was lost in the form of work. 



The following is an example of the results obtained : 



This result, 278'5 kilo-calories, compares well with the heat, 276*8 kilo- 

 calories, given off by the animal in the calorimeter. 



Ztschr.f. Biol., Miinchen, 1893-94, Bd. xxx. S. 73. 



