BRAIN AND NERVOUS SYSTEM. 339 



the will ; they only move when directed by the brain. These 

 are voluntary organs. There are others, such as the heart, 

 stomach, &,c., which are not under the control of the will. 

 They do not depend on our attention or volition to set them 

 in motion, and no wish of ours can stay their actions. These 

 are involuntary organs. The organs of respiration are both 

 voluntary and involuntary. They act without our cognizance, 

 and yet we can accelerate their motions, or entirely suspend 

 them, by efforts of the will. The involuntary are supplied with 

 nerves, both of sensation and of motion, as well as the volun- 

 tary organs ; but these nerves are not subject to our command. 



777. There are some motions which, though they are 

 usually under the exclusive control of the will, yet at times 

 are involuntary. We snatch the hand from burning by an 

 effort of the will ; yet if the fire be applied to it when we are 

 asleep, and the action of the will is suspended, we snatch it 

 away with a movement as involuntary as that by which the 

 heart beats or the chest expands. The motions of the hand, 

 the mouth, and the lower limbs, are ordinarily voluntary, and 

 require a distinct volition for their execution; yet, in certain 

 states of nervous disease, they become involuntary. They are 

 then beyond the control of the will, and sometimes take place 

 even when the will is opposed to them. In cases of epilepsy, in 

 the St. Vitus's dance, and in convulsions, the muscles are con- 

 tracted, sometimes with great force, without volition, and the 

 limbs are thrown about, although the sufferer struggles to 

 resist it. 



778. There are other motions which are only effected by 

 the direction of the will, which yet, by practice and disci- 

 pline, become apparently, if not really, involuntary. Walk- 

 ing and the playing upon a violin, an organ, or piano, require 

 the constant attention of the mind of the beginner" to excite 

 and direct his movements. But after practice he can walk 

 upon familiar paths, and play familiar tunes, without the ex- 

 ertion of the will, and even while his attention is partially 

 given to other matters. 



779. When motions become so familiar as to be executed 

 without the attention of the mind, they fatigue the body lesa 



