^ 



ALBUMINOID EATIO. 287 



The agreement between these two sets of numbers is as close 

 as can be expected. 



Buhner gives the following as the approximate heats of 

 combustion of the three principal classes of food : 



1 gramme of fat yields 9300 thermal units 



1 ,, protein ,, 4100 



1 ,, carbohydrates ,, 4100 ,, ,, 



or, in other words, 1 gramme of fat would, by union with 

 oxygen, evolve heat sufficient to raise the temperature of 9300 

 grammes of water through 1 C., while a gramme of protein or 

 carbohydrates would, on burning, suffice to heat 4100 grammes 

 of water through 1 C. The numbers given are averages, and 

 in any particular case slightly higher or lower values might be 

 obtained. 



The ratios of the heat-producing powers of the three food 

 stuffs thus are approximately 



Starch (and other carbohydrates) ... 1 



Protein ... ... ... ... 1 



Fat ... ... ... ... 2-27 



or 1:1: 2-3. 



The albuminoid or nutritive ratio of a food is therefore 

 calculated from its digestible constituents, thus 



Albuminoids 



Carbohydrates + (fat x 2-3). 



It is found that the nutritive ratio of the food of an animal 

 must not fall outside certain limits (which vary with circum- 

 stances) or either its health and condition suffer, or waste of 

 food is entailed. Before discussing the subject further, how- 

 ever, it is advisable to give a table of the digestible constituents 

 of the important food stuffs. 



Such a table can be calculated from the tables already given, 

 since the two factors governing it are obviously the composi- 

 tion of the foods and the digestibility of their constituents. 



