358 



RESPIRATION. 



and 13*14 of oxygen. The following table will give a clearer 

 representation of these relations : 



If we consider these relations in their bearing on the develop- 

 ment of heat, we shall be able to construct a table such as Liebig 

 long since suggested, which would indicate the different values of 

 these substances in supporting animal heat. Such a calculation 

 may readily be made, if we take as the basis of our computations 

 Dulong's determinations, according to which 1 gramme of carbon 

 develops 7170 units of heat in its combination with oxygen to 

 form carbonic acid, while 1 gramme of hydrogen gives off 34700 

 units of heat during the formation of water. Although it cannot 

 be denied that in an equation of this kind a number of functions 

 must be taken into account which cannot be deduced from the 

 chemical composition alone, it is, nevertheless, perfectly clear 

 that this is the only point of view from which a rational theory 

 of animal heat can be formed. The present, however, is not the 

 fitting place to enter more fully into this subject. If we limit our- 

 selves to the process of respiration, we obtain, from the above 

 tabular exposition of the different amounts of oxygen required 

 for the complete oxidation of these nutrient substances, certain 

 numbers which may be regarded as respiratory equivalents. If, 

 for instance, we assume that an organism in the full performance 

 of its vital functions must absorb 100 grammes of oxygen 

 within a definite time, the following quantities of the above-men- 

 tioned substances would be necessary, in union with 100 grammes 

 of oxygen, to satisfy the requirements of vitality : namely, 34*23 



