MECHANICS OF MUSCLE 



367 



second muscle likewise shortens 5 mm. then E f = E F 5 mm., and 

 with the tension of 1000 gms. the bone J B l will take the position J B 3 and the 

 weight or load (L 1 ) will be lifted from H l to H 3 . The question now is to prove 

 that the work done is the same in both cases, namely, 5 X 1000 grammillimeters. 

 If so, 400 X H l H 2 = 230 X H l H 3 = 5000 grammiliimeters. 



Since the two radii Cd and C d r are very long as compared with the arc d d' we 

 may consider this short arc as a line J_ to C D at d', likewise the arc //' may be 

 considered as a straight line J_ to E F. In the same manner we can consider the 

 short arcs F f, D d, H 1 H 2 and H l H 3 _[_ to the line J B\ The sides D d' and F f 

 of the A D d d' and F f f are each 5 mm. 



The lever arm D J = 60 mm. and J F = 30 mm. 



FIG. 367 



The A D d d' is similar to the A D c J 



hence Dd : 5 :: 60 : 40 Dd = 

 also H 1 H 2 : Dd :: 100 : 60 



H 1 H 2 : :: 100 : 60 H 1 H 2 = 



The AFff is similar to F e J 



hence Ff : 5 :: 30 : 23 Ff = 

 also H l H s :Ff :: 100 : 30 



H l H 3 '. ~ n '. : 100 : 30 H 1 H 



400 X f - 230 X 



300 

 40 



300 

 24 



1500 

 69 



- 5000 



Thus we see that the work of the two muscles depends on the size of the contrac- 

 tion and on the tension and not on the lever arm in very small contractions or in 



