196 THE HUMAN SPECIES 



found that in all muscles the maximum is about three-quarters 

 of the natural length in muscle dissected off from its attach- 

 ments, and about one-half of the natural length when the 

 muscle is in its usual position attached to the skeleton. 



Gerstner has made a comparative estimate of the load-draw- 

 ing capacity of man and three domestic animals. For an eight 

 hours' day the following figures were obtained : 



Men with 70 kilo load 316,800 metre kilogrammes 

 Asses 1 80 792,600 



Oxen 300 1,267,200 

 Horses 375 2,016,000 



The mechanism of the muscles is very similar in man and 



FIG. 103. Fore-legs of horse, stepping and supporting. (Munk-Schultz, 

 Physiologic.} 



other mammals in that the majority of bones work as one-arm 

 levers. There are also two-arm levers to be found, as for 

 example, in man and apes, where the triceps muscle attached 

 to the olecranon forms the power, applied to the short arm of 

 the lever, while the rest of the ulna represents the long arm 

 with the weight at the hand : also the gastrocnemius and soleus 

 in flexing the foot where the ankle-joint is the fulcrum, the 

 heel is the short arm and the rest of the foot the long arm 

 of the lever. 1 



Broadly considered, the gait of man, beasts and birds is 

 similar ; a pendulum movement can be seen in them all, and 

 the greater the contraction of the leg the shorter will be the 

 swing. But closer comparison reveals very essential differences. 



1 Munk-Schultz, he. cit., p. 387. 



