80 



ANIMAL MECHANICS 



the cord were put over the ends of the upper 



piece, C D E, and, 

 consequently, directed 

 obliquely to their at- 

 ID ' tachment at A, on 

 drawing the hand back 

 a very little, but with 

 more force, the lower 

 piece of wood would be 

 suddenly drawn up to 



the higher piece, and the object attained. Or we 

 may put it in this form : If a muscle be in the 

 direction of its tendon, the motion of the extrem- 

 ity of the tendon will be the same with that of the 

 muscle itself : but if the attachment of the muscle 

 to the tendon be oblique, it will draw the tendon 

 through a greater space ; and if the direction 

 of the muscle deviate so far from the line of the 

 tendon as to be perpendicular to it, it will then 

 be in a condition to draw the 

 tendon through the greatest 

 space with the least contraction 

 of its own length. Thus, if A B 

 be a tendon, and C D a mus- 

 cle, by the contraction of C to D the extremi- 

 ties of the tendon A B will be brought together, 

 through a space double the contraction of the 

 muscle. It is the adjustment, on the same prin- 

 ciple, which gives the arrow so quick an impulse 



FIG. 23. 



