254 VETERINARY PHYSIOLOGY 



are oftener off work for lameness tlian for any other ailment, 

 and the chief cause of lameness is work that is excessive 

 either in amount or in rate. 



The nature of the chemical changes in muscle— the 

 metabolism of muscle — must next be studied. 



11. The Chemical Changes in Muscle. 



Metabolism of Muscle- 

 It has been already pointed out that, on account of (1) 

 its bulk, (2) its constant action, (3) the extent of its 

 chemical changes, the metabolism of muscle dominates the 

 metabolism of the body as a whole. As already stated, it is 

 to supply energy to muscle that food is taken. It is to 

 oxidise this food and to liberate its energy that air is drawn 

 into the lungs, and it is to get rid of the carbon dioxide 

 formed in muscle that air is breathed out. It is to adjust 

 the reaction of the fluid bathing the muscle and to get rid 

 of the products of muscular metabolism that urine is 

 secreted. It is to prepare food for muscle that the digestive 

 organs work. It is to carry food and oxygen to muscle 

 that the flow of blood is maintained, and it is to regulate 

 the supply of food to the muscle that the liver performs its 

 functions. 



Hence the study of the metabolism of muscle is really the study 

 of the general metabolism of the body. The intake and output 

 of matter and of energy are alike dominated by the 

 requirements of the muscles. 



One caution, however, must be given. The amount of 

 food taken is not always regulated by the requirements of 

 the body, and hence any surplus over what is required must 

 either be stored for future use (p. 351), or be got rid of 

 from the body, just as the coals thrown into a furnace in 

 excess of the requirements of the engines are burned away. 

 In studying the influence of various factors upon muscular 

 metabolism the influence of food has therefore always to be 

 considered, and should either be eliminated by fasting or 

 be kept constant throughout the observations. 



(1) The Oxidation in Muscle: Coefficient of Oxidation. — The 



