FOOD 99 



Hay is taken as the standard of comparison, and the following table by 

 Boussingault gives the relative values of the different articles of food in 

 comparison with hay: 



In reading the table, the numbers must be taken to indicate the 

 number of parts of each article which will represent the 100 parts of hay, 

 i.e. 45 parts of wheat, 30 of linseed, 350 of barley straw, and so forth, are 

 equivalent to 100 parts of hay. However interesting this information may 

 be, its true value can only be realized by taking it in connection with the 

 fact that the animal's temperament and digestive capacity have a dominant 

 concern in the appropriation of the different articles of diet. It is quite 

 conceivable that the table might be found absolutely correct for a certain 

 number of horses, while in an equal or possibly greater number of animals 

 of different constitution, and under different circumstances, the nutritive 

 equivalents given would have to be considerably modified. 



All the elaborate experiments which have been performed by a large 

 number of investigators have been mainly directed to the important object 

 of discovering the influence of different foods in producing heat and force, or 

 working power. The amount of heat evolved from the oxidation of certain 

 foods is readily converted into its equivalent of mechanical energy. It was 

 found by Frankland that when a dried food mixed with a powerful oxidiz- 

 ing substance, such as chlorate of potash, was placed in an apparatus sur- 

 rounded with water, and burned, the heat developed raised the temperature 

 of the water. 1 gramme (15*432 grains) when raised 1 C. (1*8 Fahr.) is 

 called a heat unit. 1 Ib. of albumen when oxidized raises the temperature 

 of 4263 Ib. of water 1'8 (Fahr.), while 1 Ib. of fat raises the temperature 

 of 9069 Ib. of water to the same extent (1'8 Fahr.). Joule of Manchester 

 demonstrated that the heat required to raise the temperature of 1 Ib. of 

 water 1 (Fahr.) was equivalent to the power required to raise the weight 

 of 1 Ib. 772 feet high. The foot-pound is, therefore, the unit of work, and 

 772 ft. -pounds is the mechanical equivalent of 1 (Fahr.). Knowing the 

 number of heat units each substance is capable of producing, its potential 

 or mechanical value may be calculated; and the author of Veterinary 

 Hygiene suggests that the most simple way of doing this is to multiply 



