MUSCLE 271 



fatigue in the highest degree ; but after a long walk the arms 

 also are less ready and less capable than the state of their 

 nutrition warrants. 



The condition of stiffness experienced for a day or two 

 after excessive exercise is due to various causes in combina- 

 tion. The fact that it may be remedied by encouraging the 

 circulation through the muscles most affected, as by hot baths 

 and massage, tempts us to assign it also in large measure to 

 accumulation of products of action ; but the means taken to 

 reduce stiffness favour the nutrition of the muscles both by 

 giving them more food arid by carrying off their waste. 



Equally remarkable with the self -protective disposition of 

 muscle, which forbids it to give, except at the instance of 

 increasingly urgent messages from the central nervous system, 

 more than a part of the work of which it is capable, is its 

 preparation for meeting an increased demand. It grows with 

 use. Running increases the girth of the leg by developing 

 especially the muscles of the calf. Raising weights enlarges the 

 muscles of the shoulder and arm. Use-growth may reach 

 inconvenient proportions. Nothing is more noticeable during 

 the training of young athletes, whose nutritive responsiveness 

 is at its height, than their liability to pass through a stage in 

 which they are " muscle-bound." Their legs grow bigger, but 

 their pace falls off. 



The development by means of exercises of a strong muscular 

 system has received much attention during recent years. 

 Our ancestors cultivated strength and agility in certain 

 movements without paying much attention to the muscles 

 by which the movements were performed. It is fashionable 

 nowadays to lay stress upon the importance of maintaining 

 an abundant musculature, because of its relation to general 

 " fitness." The balance between muscular activity and the 

 organic functions which is observed by everyone who takes an 

 active holiday proves beyond doubt that the nutritive con- 

 dition of the various glands and of the heart and bloodvessels 

 is in some degree dependent upon the condition of the muscles. 

 Possibly they secrete into the blood other " messengers " in 

 addition to fatigue-substance messengers whose call wakes 

 up the organs of digestion. The man who is so fortunate as 

 to be able to use his muscles in the open air has no need of 



