204 THE HUMAN MOTOR 



According to Kronecker and Cutter ( x ) the work of the legs in 

 walking increases the strength of the arms. The merit of all 

 these observations is that they are founded on figures. But the 

 general doctrine of the gain of strength in the organs in the course 

 of, or as the result of, normal activity, was formulated in the 

 xvmth centuiy by Cheyne and Ramazzini as the result of their 

 observations on artisans. ( 2 ) They stated that the artisans must 

 be suitably nourished. 



The internal massage which the muscles undergo in consequence 

 of their repeated movements during exercise has also, doubtless, 

 a beneficial effect. External massage produces a still more appre- 

 ciable effect which will be examined later ( 159). 



The nature of the training itself, ( 3 ) is both mechanical and 

 physiological, mechanical because the work diminishes the 

 natural inertia of the muscular fibre, and physiological because 

 the work increases the irritability of the muscles and of the nerves 

 just as inactivity blunts them and leads to atrophy and degenera- 

 tion. Also it stimulates the circulatory phenomena, the action 

 of the blood and of the lymph, to the point of giving rise to what 

 has been called functional hypertrophy. The mass of the muscles 

 increases, not by the addition of new fibres, but by the thickening 

 of the old ones, which increase in size and form, a larger reserve 

 of nitrogenous substances. ( 4 ) The albumin thus becomes 

 really an energy-supplying food.( 5 ) The economy of expenditure 

 which results from this increase of muscular power has been 

 discussed in connection with the yield ( 137). 



145. The Effects of Work on the General Metabolism. The 



real repercussion caused by the exertion of the muscles in the 

 organism has an entirely general character. This is metabolism, 

 and is what has been called physiological work ( 60) . It includes 

 all the intimate reactions of the cells, which increase in intensity, 

 like a chemical reaction which gains speed in proportion as the 

 temperature rises. 



Work increases the intensity of the cellular reactions, as heat 

 increases the temperature of a body, and it has been seen ( 126) 

 that when the organism returns to a state of repose, its internal 

 reactions and its expenditure decrease according to Newton's 

 law for the cooling of bodies (the law of repose). 



( x ) Kronecker and Cutter (Comptes Rendus Sciences, vol. cxxix., p. 492 ; 

 1900). 



( 2 ) G. Cheyne, Rules for Health and The Method of Prolonging Life ; 

 B. Ramazzini, De Morbis Artificum Diatriba, Modena, 1701 (translated into 

 various languages). 



( 8 ) Boyet-Collard denned " entrainement " as "a disposition to perform 

 certain work" (Bulletin, Acad. Med., 1842). 



(*) Morpurgo (Arch. ItaL Biol., vol. xxix., p. 65, 1898). 



( 6 ) Zuntz and Schumburg (Pfliieger's Archiv., vol. Ixxxviii., p. 557, 1901). 





