210 THE HUMAN MOTOR 



that, under these conditions, the quantity of poisons in the 

 muscles, the blood, and the urine increases considerably^ 1 ) 



The blood, by circulating more quickly during work, washes 

 the poisons out of the tissues, and carries them to the suprarenal 

 glands which secrete adrenalin by which they are neutralised ( 2 ) ; 

 it oxydises them itself by the oxygen which it contains. 



A state of repose is therefore necessary for this purification 

 to take place. It allows, in addition, the elimination of the 

 carbonic gas accumulated in the blood in consequence of the 

 inter-organic combusions, which gas also acts as a muscular 

 poison and lowers the power of the subject. ( 3 ) Finally, it allows 

 the irritability to re-establish itself under the action of the oxygen 

 gas.( 4 ) 



Fatigue necessitates rest, and is its determining circumstance ; 

 it progresses with the work, and becomes eventually the cause 

 of stoppage or of inhibition. From this point of view it safe- 

 guards the health of the subject. 



148. Resistance to Fatigue : Endurance. The resistance to 

 fatigue is generally defined, as the product F X t, in which F is 

 the effort expended, the weight lifted, and t, the time, occupied 

 by the effort. Thus, according to Gaillard, one cannot hold the 

 arms stretched out for longer than 19 minutes. Haughton and 

 Nipher ( 5 ) obtained the relation : 



F 2 x t = C. 



From experiments on nearly 80 subjects, we have found that 

 t varies from 20 to 78 seconds when a weight of 5 kilograms is 

 held in each hand with extended arms until fatigue compels the 

 subject to lower them ; t decreases all the quicker, the shorter 

 the intervals of repose. Thus the product, F 2 X t, varies very 

 much from one subject to another, its highest value being found 

 in sailors and dock labourers. Subjects having a strong will 

 have more endurance than others. According to Chauveau, 

 the resistance to fatigue is a function of the muscular elasticity, 

 and according to Treves, it is a functional tonus of the spinal 

 cord, a reserve of nervous energy. ( 6 ) Waller claims that the 

 centres of the spinal cord are the first to feel fatigue, ( 7 ) whilst 

 loteyko holds that it is the motor terminations of the nerves. ( 8 ) 



( l ) Oddi and Carulli (Arch. Ital. Biol., vol. xix., p. 384, 1893) ; Aducco 

 (Ibid., vol. viii., p. 238, 1887) ; Moitessier (C. R. Biol., 1891, p. 573) ; Casciani 

 (La Ri forma Medica, 1896). 



( a ) Abelc .- .(Internat. Med. Congress at Rome, 1894, vol. ii.) ; Langlois ; 

 Thesis, Pat," 1897). 



( 3 ) Lothak~ue Lotha (Comptes Rendus Sciences, Aug., 1902). 



(*) Spaflanzani, Memoires sur la Respiration, p. 352, Edition 1803. 



( 6 ) Haughton and Nipher (Proceed. Roy. Soc., vol. xxiv.) 

 () Treves (Arch. Ital. Biol., vol. xxx., pp. 1-34, 1898). 



( 7 ) A. D. Waller, " The Sense of Effort " (Brain, vol. xiv., p. 179, 1892). 

 (') J. loteyko (Travaux Instit. Solvay, iii., book 2, 1900). 



