THE MUSCULAR MOTOR AND ALIMENTATION 127 



thing is noticed in the grip of the hand (pressure-dynamometer) ; 

 it is a relation of the same kind, but T 5 o T o according to Manouvriei . 

 An equally important characteristic oi force and of human effort 

 is that man produces it quickly with its maximum value, and 

 woman more slowly (according to Fere) . 



HUMAN STRENGTH. 



Quetelet's diagram shows a reduction of strength between 

 9 and 13 years of age. Grigorescu ( l ) analysing this period of 

 childhood by measurements taken in schools, finds the develop- 

 ment of strength is arrested between 11 and 13. 



Whilst the preceding table shows a maximum renal force at 

 the age of 30 in Europeans, Gould found it at about thirty-four 

 in white Americans (soldiers) and 40 in Indians. He gives the 

 following values : 



WHITES NEGROES MULATTOES INDIANS 



144-400 kg. 146-700 kg. 158-300 kg. 159-200 kg. 



Weisbach has given figures showing the " effort of pressure " 

 of the hands in Asiatic and Negroid peoples ; these figures are 

 inaccurate even as average values. It is interesting to notice, 

 however, that these measurements, and those made by explorers, 

 on various peoples, show that " the civilised nations are more 

 robust than savage nations/' and better developed, if not more 

 resistant to physical pain. Environment has certain effects on 

 human strength, being able to increase or decrease it. Therefore 

 attention must be paid to it, as well as to the age of the subject. 



90. The Periodicity of Voluntary Muscular Contraction. The 



muscle contracts voluntarily in a periodic manner ; and the con- 

 traction, real tetanus, is itself discontinuous, although the various 



(*) Grigorescu (Comptes Rendus Biologic, 1891, p. 547). 



