THE PHYSIOLOGY OF MUSCULAR WORK 223 



by the lack of it. The child or young animal which is not active 

 for the pure love of activity is unwell. The belief that progress 

 lies chiefly in mental training is less rampant than formerly. The 

 compulsory education of young children has increased the in- 

 fectious diseases to which they are liable, has stunted the growth 

 of their originality as well as their bodies, and has in many cases 

 produced that mental instability which has revealed itself at a 

 later stage of life in crime, insanity, or suicide. The sup- 

 pression of the instinct to play has gone so far that it has become 

 necessary to found societies for the purpose of teaching children 

 how to play. Even the believers in compulsory education of young 

 children have taken alarm, and think they can undo the harm by 

 compulsory systems of monotonous drill, unnatural postures, and 

 breathing exercises. The irony of it is that this kind of physical 

 training is said to be based upon the teachings of physiology. It is 

 a false physiology which does not recognise that natural exercise 

 is the best, that instincts in healthy children ought not to be unduly 

 suppressed, and that heredity is more potent than systems of 

 education. 



TYPES OF MUSCULAR EXERCISE 



Notwithstanding the numerous gradations of muscular exercise 

 between the slightest and the most severe and prolonged exertion, 

 it is convenient to recognise three types ( 18 ) : (1) Exercises of speed 

 are those in which each individual effort is produced rapidly, but 

 the maximum contraction of any single skeletal muscle is not 

 reached ; (2) exercises of endurance are characterised, by long 

 and continuous efforts of moderate strength ; (3) exercises of 

 strength are those in which the muscular exertion is very great 

 for a brief period, such as the lifting of a heavy weight. In these 

 different forms of exercise it can be shown that the effects produced 

 upon the body are not the same, and a different type of physique ( 19 ) 

 is found in men and animals who excel in any one of them. This 

 is well seen in a comparison of a runner with a navvy or of a race- 

 horse with a dray-horse. It is necessary to remember the im- 

 portance of build and heredity in this respect, and to avoid an 

 overestimate of training. 



The general effects of muscular activity have been sufficiently 

 indicated ; its influence upon the different systems of the body 

 must now be considered. 



