ANIMAL MECHANISM. 



65 



conditions, the effort that can be developed at the extremity of 

 the lever is less than that of the muscle ; but the space passed 

 through by this extremity of the lever is proportionately 

 increased, so that the product of the force multiplied by the 

 distance remains the same. 



Thus, we find in a great number of standard treatises, a 

 sort of accusation brought against nature, for having entirely 

 wasted a great part of the force of our muscles by causing 

 them to act under a disadvantageous leverage. It is true, 

 that to extenuate this fault, they are willing to grant that 

 this arrangement, unfavourable in an economical point of 

 view, gives to our muscles an elegance which they would not 

 have possessed, if for example, a long muscular band had 

 extended from the sternum to the wrist. These mechanical 

 and aesthetic notions ought to give place to more correct ideas. 

 We must, above all, remember that a muscle produces work 

 corresponding to its volume or its weight, whatever may be 

 the proportions of the lever to which it is attached. The 

 effect of the latter is only to regulate the form under which it 

 produces the work, without adding to it or subtracting from 

 it. An error of the same kind is often committed in con- 

 sidering the part played by levers made use of by man in his 

 work. It often happens that human force is unable to raise 

 certain weights ; we have recourse in these cases to levers of 

 the first or second order, in which we increase the power of 

 the arm in the ratio of the longer to the shorter arm of the 

 lever. 



In this manner we utilize a motive force which could not 

 produce external work if we endeavoured to bring it to bear 

 directly on the resistance to be overcome. But a lever which 

 amplifies the force exerted, diminishes as much the extent of 

 the work produced; it adds nothing to the work executed by 

 the motive power. 



Before the notion of work had been introduced into 

 mechanics, and when it was not clearly understood that it was 

 impossible to increase by mechanism the amount of force at 

 our disposal, many false ideas were entertained with regard 

 to the part played by machinery. When we consider those 

 gigantic masses of stone the pyramids of Egypt, or those 



