MUSCULAR MOTION. 119 



attended with a corresponding decrease of force, and that the nearer 

 the power approaches to the parallel line with the lever the weaker 

 its effect, so much of the force being consumed in efforts either to 

 drag the lever against the fulcrum or force it off, it will at once ap- 

 pear evident at what a great disadvantage or sacrifice of power 

 the muscles of the limbs, from their parallelism with the bones, 

 are in general acting. This disadvantage, however, as I said be- 

 fore, is greatly compensated for by the velocity acquired by the 

 length of the resisting arm of the lever, and the comparative short- 

 ness of that to which the power is affixed. Where power, how- 

 ever, is wanted, as in the hock and fetlock joints of the hind ex- 

 tremity, although celerity of motion is still preserved by the dis- 

 tance at which the fulcrum is removed from the power, the requi- 

 site force is gained by the proximity of the latter to the resistance. 

 "We now perceive the advantages derived from length of hock and 

 length of elbow, and from broad or prominent fetlocks ; we may 

 also calculate to how much greater effect the muscles in the haunches 

 and shoulders will act, where the bones are placed at right angles 

 nearly to each other, and when, consequently, the power of the 

 lever operates perpendicularly to its arm. In the case of the flexor 

 muscles of the arm playing over the head of the humerus, and that 

 of the extensors of the thigh playing upon the patella, pulleys are 

 established, which, though of a nature too simple in themselves 

 to afford any advantage as pulleys, yet increase the power of the 

 muscles attached to them by giving a more advantageous direction 

 to the power over the resisting arm of the lever. These beautiful 

 contrivances are likewise attended with the convenience of per- 

 mitting the muscles from which the power originates being placed 

 out of the direct line of action, in situations where they accord with 

 the contour and proportions of the limb. 



