35* Mufcular Force, [Book IX. 



of the center of motion, and confequently leflbns their 

 effect. Many mufcles pafs over projecting bones, 

 which increafe friction. But befides all thefe caufes 

 diminifhing the power of mufcles, one half of their 

 ftrength is exerted on their fixed extremity j for a mufcle 

 in action, like an extended cord, exerts an equal force 

 at both extremities. 



