LABOUE DIET 183 



Sheep apparently require more liberal rations per unit 

 of weight than an ox or horse; this is due to the 

 higher temperature of the sheep (103° — 104"), its 

 smaller size, and therefore larger proportion of surface, 

 and to the growth of wool, with its accompanying 

 fat, which is always in progress. 



Labour Diet. — If external work is to be performed, 

 the body weight remaining unaltered, the quantity of 

 food must be considerably increased. A man doing a 

 moderate day's work was found to exhale one-third 

 more carbonic acid than when at rest ; a man doing 

 such work would clearly require one -third more food 

 to maintain the same condition of body. 



An agricultural horse weighing 1,100 lbs., doing 

 regular work at a walking pace, will produce, accord- 

 ing to Zuntz, about 771 foot-tons of work^ for each 

 pound of available foody reckoned as starch, consumed 

 in the body over and above the quantity required for 

 maintenance. By available food ifi to be understood 

 the portion remaining for use in the animal after all 

 the losses of matter and energy occurring during the 

 processes of digestion and excretion. The quantity 

 of food available for use in muscular exertion by the 

 horse, supplied in 1,000 lbs. of ordinary foods, has been 

 calculated by Zuntz from his experiments, and is 

 shown in the table on p. 122.* Taking the figures 



' This amount of work is considerably less than that mentioned in 

 previous editions of this book. In the experiments by Wolfi, then 

 quoted, the quantity of work performed by the experimental horse was 

 over-estimated. 



- Wolff taught that fibre is of no use for the production of external 

 work, and obtained the amount of food available for work by deduct- 

 ing the fibre from the digested organic matter. Zuntz has shown 



