WORK PRODUCTION 



539 



of work upon the protein katabolism was repeatedly investi- 

 gated under the most varied conditions with results which ap- 

 peared upon their face to be conflicting. Some observers found 

 a marked increase in the excretion of nitrogen during or following 

 work, while in other investigations no such effect was apparent. 

 The key to these conflicting results seems to have been first 

 discovered by Kellner in 1879 in experiments upon the work 

 horse. 1 He found that so long as the total amount of feed was 

 ample, variations in the quantity of work performed were 

 without effect upon the protein katabolism. If, however, the 

 work was increased to an amount sufficient to cause a falling 

 off in the weight of the animal, thus indicating that the energy 

 supply was insufficient, the excretion of nitrogen in the urine 

 increased promptly. Furthermore, it was found that if either 

 carbohydrates or fat were added to a ration which was just 

 sufficient to enable the animal to perform a given amount of 

 work, the demands upon the animal could be correspondingly 

 increased without causing any increase in the protein katab- 

 olism. This may be illustrated by the following summary of 

 an experiment in which the addition to the ration consisted of 

 starch and in which the amount of work performed is expressed 

 in the number of revolutions of the sweep power dynamometer 

 used. 



TABLE 153. EFFECT OF STARCH ON PROTEIN KATABOLISM OF WORKING 



HORSE 



Landw. Jahrb., 8 (1870), 701 ; 9 (1880), 651. 



