184 



THE CHEMISTRY OF THE FARM 



given in this table, the comparative values of these 

 foods, and the amounts of work to be obtained from 

 1 lb. of each of them are as follows : — 



Zuntz has determined the quantity of food which a 

 horse requires to perform work under various con- 

 ditions. One of the conditions having most influence 

 on the result is pace. A horse, weighing with harness 

 1,144 lbs., will require 1*33 lbs. of available food to 

 walk 10 miles at 2^ miles per hour; 1*69 lbs. when 

 walking at the speed of 3J miles per hour ; and 2*53 



that this correction is insufficient. The energy consumed in digesting 

 fibrous foods varies according to the condition of the fibre, and often 

 exceeds the whole value of the fibre digested. We must not, however, 

 imagine that digestible cellulose cannot produce work, a large part of 

 the digestible carbohydrates of hay consists indeed of cellulose (p. 183). 

 The true view of the matter is simply that the harder kinds of cellu- 

 lose require more energy for their digestion than they can produce 

 when digested. 



