312 THE FEEDING OF ANIMALS 



animal without loss of body substance. The metaboliza- 

 ble energy of this insufficient ration was found to be 5.7 

 therms, and during the time it was fed, the steer lost from 

 his own tissues an amount of protein and fat equivalent 

 to 2.4 therms a day. In another period, the steer ate 

 5.2 kilograms of the same hay, having a metabolizable 

 energy of 9.26 therms, or 3.58 therms more than was con- 

 tained in the smaller ration. By feeding the larger ration, 

 the use of body protein and fat was reduced to .357 

 therms or 2.02 therms less than was the case with the 

 smaller ration. It seems, then, that 3.58 therms of 

 metabolizable energy in the ration replaced 2.02 therms 

 of energy derived from body substance; or, in other words, 

 the metabolizable energy in the hay was only 56.5 per 

 cent as efficient as was the energy derived from the 

 oxidation of body protein and fat. The other 43.5 per 

 cent of the hay energy was used, as we have seen, in the 

 way of mastication, digestion, and other internal fimc- 

 tions requiring the use of energy in order to prepare the 

 food and transmit it to the tissues. 



411. Distribution of maintenance energy. — ^A study 

 of fasting katabolism has made possible not only the 

 energy used in maintenance but also the approximate 

 determuiation of the distribution of the uses of energy. 

 Zuntz, on the basis of observations made witb a fasting 

 man, computed that muscular activity, including circu- 

 lation, respiration, and the voluntary muscles, used about 

 60 per cent of the metabolism and that the internal 

 organs, such as the liver, intestines, kidneys, pancreas, 

 and salivary glands, used about 40 per cent. 



412. Use of nutrients in fasting metabolism. — The 

 studies of fasting metabolism have made it possible to 

 measure accurately the relative use of the nitrogenous 



