250 



VETERINARY PHYSIOLOGY 



4-. The work of restoring the potential energy is due to 

 the oxidation of sarcolactic acid and of carbohydrates, 

 proteins, and fats. These also yield the materials in which 

 the energy is latent for reconstruction. From these latter 

 " foods " the muscle molecule is regenerated and the energ}-, 



therefore, ultimately comes from them. 

 This is a process requiring oxidation, 

 and hence CO2 and HoO are liberated 

 and heat is produced (p. 247) in pro- 

 portion to the work done by the 

 muscles. 



5. In the contraction phase the 

 efficiency may be nearly 100 per 

 cent., but, when the process of restitu- 

 tion is included, only at most 50 per 

 cent. In considering the efficiency of 

 muscle in liberating the energy stored 

 in the food this point must be taken 

 into consideration. 



Muscle, like secreting epithelium 



t / 



f — 





90 too UO l» UO U9 



changes in the effici- 

 ency of the muscles as 

 the work done is in- 

 creased. The decrease 

 in efficiency is indi- 

 cated by the divergence 



FiG.^ 131.— To showj^he (p. 35)^ thus does its work by storing 



the material from which energy may be 

 liberated during its resting phase, and 

 this process dominates the metabolism 

 of muscle. For this, muscle requires 

 between the lines. The fg^^ ^q y[Qi^\ ^\^q material and energy 



ordinates on the left ^ "^ . , , , . , 



are Calories per minute, lor restoration and the oxygen which 

 those on the right indi- is ncccssary to carry out the recupera- 



cate work units con- ,• 



tion. 



The efficiency of the muscles of 

 the body may be measured by deter- 

 mining the total energy liberated in 

 doing a measured amount of work 

 upon some form of ergometer by direct or indirect calorimetry 

 (p. 259). It has been found that some 30 per cent, of the 

 total energy liberated is about the maximum mechanical 

 efficiency. 



The efficiency of muscle thus compares favourably with 

 that of an ordinary steam-engine which yields some 



verted to Calories. The 

 abscissae are the num- 

 ber of revolutions of 

 the bicycle at constant 

 work. 



