METABOLISM AND FOOD 89 



plants without much stem give a hay which is 

 easily broken up, and it has been found by direct 

 experiment that to masticate it no more work is 

 required than is the case with the same food in a 

 green condition. The more the plants advance in 

 growth, the richer do they become in crude fibre, 

 and when they are over-ripe differ very little in 

 food value from hay which has been made from 

 them without loss. If the energy required for 

 mastication and digestion of the crude fibre were 

 expressed as starch, it would be found that more 

 energy is required in the case of woody green 

 fodder than with young grass or clover. Green 

 plants which contain 16% or more of crude fibre 

 would have to receive an addition of 58 gr. of 

 starch for each 100 gr. consumed. If the amount 

 of crude fibre were only 4%, then half the above 

 quantity of starch (29 gr.) would be necessary, and 

 in the same way 34 gr. of starch for 6% crude fibre, 

 38 gr. for 8%, 43 gr. for 10%, 48 gr. for 12%, and 

 53 gr. for 14%. 



It has been previously shown that there are 

 food-stuffs whose digestible portion acts exactly 

 as the corresponding nutrient in a pure form. If 

 these pure nutrients were fed in finely divided 

 condition, it is certain that they would cause the 

 greatest production of which the animal is capable, 

 and the food-stuffs whose digestible components 

 show this maximum value are said to possess " full 



