PRODUCTION OF HEAT IN MUSCLE 223 



limits, when it is excited, the greater the tension and the greater the heat 

 production developed, i.e. we may assume that increased length of muscle 

 fibre increases the chemical changes, ensuing on excitation, which are respon- 

 sible both for the development of mechanical energy and the production of 

 heat. The significance of these results for the essential nature of muscular 

 contraction we shall discuss in a later chapter, 



