84 



Various experiments have been made to dis- 

 cover the intimate nature of the motion of the musr- 

 cles. CARLISLE has endeavoured to prove, by se- 

 veral very ingenious methods, that a muscle, while 

 it contracts, increases in weight and volume, and 

 is consequently penetrated by an increased quan- 

 tity of fluids. The most probable account of the in- 

 terior mechanism by which the motion of the mus- 

 cle is produced, seems to be, that the fibres must 



twist themselves round more distended vessels 



> 



whereby the muscle in a particular place becomes 

 shorter and thicker. It is necessary that nature, 

 by the mechanism of this internal action, should 

 endeavour to regain what it loses by that of the 

 external, in w ? hich every thing is conducted ac- 

 cording to principles, altogether contrary to those, 

 by which we are generally governed in mechanics. 

 The muscle, by means of a small contraction, 

 makes an extended motion, and consequently 

 exercisfe its power near the fulcrum of the bone, 

 whilst the counterpoise is on the other remoter 

 end of the bot\e. .Nature seems here to be lavish 

 in the power it bestows, since every muscle must 

 make a far greater effort, than would be necessary 

 under opposite circumstances ; this expenditure 

 of power must, however, certainly be balanced 

 fry the methods employed to shorten the smallest 



