216 



ACTION OF THE MUSCLES. 



wards each other by muscular power. If now, the mus- 

 cle pass straight between them, this can be effected only 

 to a. short distance say one third, the muscle shorten- 

 ing itself one third during its contraction. 



Emily. But if the muscle pass from one bone to 

 the other obliquely, it may shorten itself no more, and 

 yet bring them even twice as near. What a simple con- 

 trivance ! but one which I never should have imagined. 



Dr. B.-r-lt is admirably witnessed in the ribs, which, 

 during respiration, are constantly approaching and re- 

 ceding from each other. In the following figure, letters 



R. R. represent the two ribs. If the fibres of the mus- 

 cle by which they are to be approximated, run straight 

 forward across perpendicular to the bones, they will 

 move through only one third of the space between 

 them, supposing the muscle shortens itself only one third 

 during its contraction. But taking an oblique direction, 

 as represented in O, they may contract but one third of 

 their length, and bring the ribs together. 



Another instance too, where beauty and utility are 

 both obtained by a sacrifice of power, may be seen in 

 the arrangement of the tendons that move the toes and 

 fingers. Instead of passing in a straight line from the 

 arm to the hand, which would have been exceedingly 

 clumsy, they are bound down at the wrist by a fibrous 

 band, under which they move with perfect ease, as you 

 may see in this next cut. In this way, though greater 

 force is required, yet greater velocity is obtained. 



