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ANIMAL MECHANICS. 



The preceding analysis of the comparative strengths of 

 the flexor tendons of the fl. hall, long, and fl. dig. long., and of 

 the toes, proves, that of thirty-five animals examined, the ten- 

 dons of the toes exceed the tendons of the muscles in thirty 

 instances, and fall short of them in four instances only. This 

 is a result that is, a priori, probable ; for the use of the foot 

 is not, like that of the hand, to grasp an object by means of 

 the flexion of the digits produced by the muscles of the fore- 

 arm ; but, the toes being applied to the ground as a fulcrum, 

 the muscles of the calf acting on the flexor tendons of the 

 toes (which are fixed), resist their own forcible extension by 

 the weight of the body, by means of the tendons passing round 

 the heel, and so act as a spring to prevent the foot reaching 

 the ground with shock. In other words, in the foot, the 

 force is applied from below, upwards, to the muscles through 

 the intervention of the tendons ; whereas, in a grasping organ, 

 such as the hand, the force is applied from above, downwards, 

 from the muscles to the obstacle, or resistance to be overcome. 



The difference of strengths, or cross sections in all cases 

 represents the friction overcome by the tendons ; while the 

 direction in which the force passes is always from the greater 

 towards the lesser cross section of the tendons. 



B. Comparative Anatomy of the Flexor Tendons of the Hand. 



In the following observations on the comparative anatomy 

 and mechanism of the flexor tendons of the fore foot, or hand, I 

 shall confine myself to the deep flexor tendons of the fingers, as 

 this method will furnish an instructive comparison with the cor- 

 responding long flexor tendons of the toes, already discussed. 

 There is one remarkable difference to be noted between the 

 long flexors of the toes and the deep flexors of the fingers ; 

 viz., that although both become simplified, as we descend in 

 the scale of animals, into a common tendon giving off similar 

 slips to each toe or finger ; yet in the leg, the flexor muscles 



