H^lman Physiology. 



But the muscles have of themselves no power of motion. 

 They can be made to contract only by some stimulus, or 

 exciting cause. Every muscle is supplied with nerves of 



Fig. 24. TENDONS OF THE BACK 

 OF THE HAND. 



Fig. 25. TENDONS AND AR- 

 TERIES OF THE HAND. 



several kinds nerves of nutrition, which preside over the 

 circulation of the blood, and the selection and deposition of 

 the matter required to take the place of that destroyed by 

 muscular action ; nerves which direct the absorbents to remove 

 waste matter ; nerves which carry to the brain a sense of the 

 muscular contraction nerves which excite, direct, and govern, 

 that contraction. 



Thus the body of every muscle is full of nerves, reaching 

 every fibre and every microscopic disk, giving off its brain 

 influence apparently from the loops of nerve as shown in 

 Fig. 26, among the muscular fibres. A nerve in my toe informs 

 my brain that a mosquito has inserted the lancet of his pro- 

 boscis; another nerve carries an order to one or several muscles 

 of the foot to expel the intruder. Scores of these telegraphs are 



