5O THK cow PKA. 



and support of bone, blood, nerves, and muscles. These 

 constituents of food are grouped under one heading and 

 are known as ' 'The Ash. ' ' Second, materials which contain 

 nitrogen. These are converted into lean meat, skin, hair, 

 the casein and albumen of milk, etc., and are termed by 

 chemists the "Proteins." Third, sugars, starches, oils, fats, 

 and similar materials, often classed chemically as "nitro- 

 gen free" and "ether extracts." Both classes taken to- 

 gether form the "Carbo-Hydrates." 



These three, "ash, protein, and carbo-hydrates," vary 

 in degree of digestibility, which is also affected by the 

 source whence each is derived. Generally speaking, fats 

 and sugars are more easily digested than starches or pro- 

 teins grain, than hay; hay, than straw. In addition to the 

 needs enumerated is that of heat and energy for the animal 

 body, which gets its glow and power, as does a steam engine, 

 by the the consumption of carbon. For producing this heat 

 and energy, "fats" and "ether extracts" are about two and 

 four-tenths times more effective, pound for pound, than 

 starches, sugars and other "nitrogen-free" materials, that 

 is, 2.4 times the digestible parts of each and not their total 

 amounts. This may be stated in the form of a working rule. 

 Ascertain the chemical and digestible composition of the 

 food under investigation, arid multiply the amount of digest- 

 ible fat by 2.4, and to the product add the amounts of 

 digestible fibre, starch, etc. ("nitrogen -free extract") . The 

 sum shows approximately the digestible carbo-hydrates 

 contained, which divided by the digestible proteins gives the 



