MAKUAL OF CATTLE- FJEEBINa. 217 



Ko calculations seem to have been made regarding tlie re- 

 lations of fat-eonsnmption and work in this respect 



Unfortunately, eonbiderahle nneertaiuty attaches to the 

 very foundation on which all of these results rest, viz., the 

 heat of combustion of protehi. According to Volt, there 

 is good reason to believe that in Frankland's experiments 

 the nitrogenous substances, especially, were incompletely 

 burned, and tliat consequently his results on these bodies 

 were too low, and Zuntz-^ has shown it to be at least 

 probable that the heat of combustion of protein as deter- 

 mined by Frankland should be increased more than 25 per 

 cent., and that even then it may be considerably too low. 

 But Frankland's determinations are the only ones of this 

 kind that we yet possess, and it is therefore evident that, 

 until these are either proved to be accurale or replaced by 

 others, no certain conclusions can be drawn from computa- 

 tions of t:he force-value of food as to the production of 

 muscular power, although such results as have been ob- 

 tained on the present uncertain basis indicate strongly that 

 the non-nitrogenous constituents of the food or body take 

 part in the process. 



It may be added here that the inoream in the protein- 

 consumption observed in Kellner's experiments was not 

 sufScient to supply the extra force exerted in the second 

 and third periods, even if the heat of combustion of pro- 

 tein as corrected by Zuntz be used as the basis of the 

 calculation. 



Conditions of Muscular Exertion. — If we turn from 

 the study of the effects of muscular exertion to that of its 

 conditions, we shall get much new light, and be helped to 

 a more rational' judgment of the theories as to its source. 



* Landw* Jahrbiiclier, VIII,, 73. 

 10 



