76 ANIMAL MECHANICS 



single muscle are connected by a tissue of nerves, 

 which produce a union or sympathy amongst them, 

 so that one impulse causes a simultaneous effort of 

 all the fibres attached to the same tendon. When 

 we have understood that the muscles are dis- 

 tinct organs of motion, we perceive that they 

 must be classed and associated in order that many 

 shall combine in one act ; and that others, their 

 opponents, shall be put in a state to relax, and 

 offer no opposition to those which are active. 

 These relations can be established only through 

 nerves, which are the organs of communication 

 with the brain, or sensorium. The nerves convey 

 the will to the muscles, and at the same time they 

 class and arrange them so as to make them con- 

 sent to the motions of the body and limbs. 



On first looking to the manner in which the 

 muscles are fixed into the bones, and the course 

 of their tendons, we observe everywhere the ap- 

 pearance of a sacrifice of mechanical power, the 

 tendon being inserted into the bone in such a 

 manner as to lose the advantage of the lever. 

 This appears to be an imperfection, until we learn 

 that there is an accumulation of vital power in 

 the muscle in order to attain velocity of move- 

 ment in the member (Fig. 20). 



The muscle D, which bends the forearm, is 

 inserted into the radius E, so near the fulcrum, 

 or centre of motion in the elbow-joint, and so 



