152 HABIT AND INTELLIGENCE. [cHAP. 



Muscular simple truth, that muscular action is itself unconscious, 

 essentially ^® produce the motion of a particular set of muscles — 

 uncon- those of the legs, or hands, or mouth, for instance — by a 

 conscious mental determination; we become aware that 

 they move as we intend, by means of the "muscular 

 sense," which is produced in muscles by their action. But 

 between the conscious mental determination and the sense 

 of muscular action, there is an intermediate link of which 

 we are utterly unconscious ; namely, the special combina- 

 tion of muscles which is needed to effect the movement 

 we intend. Of this we know nothing whatever except 

 what anatomy teaches us ; we effect these combinations by 

 a perfectly unconscious instinct. Were consciousness of 

 the required muscular combinations necessary before we 

 could make the combinations, in the same way that, for 

 instance, consciousness of the meaning of words is neces- 

 sary in order to use the words with accuracy, we could not 

 perform any muscular movement until we had learned the 

 anatomy of the muscles.^ It is indeed scarcely a metaphor 

 to say that the brain gives its orders to the muscles with- 

 out knowing the details of the way in which its orders are 

 to be executed. An equally clear proof of the essentially 

 unconscious nature of muscular action is afforded by the 

 fact, that when any set of muscles, especially those used 

 in walking, is set in motion by a determination of the will, 

 and the attention afterwards withdrawn from their action 

 in consequence of the mind falling into a state of abstrac- 

 Insiance tion or reverie, the action of the muscles often continues 

 in revene. ij^Jependently of consciousness or will. And, what is a 

 fact of the same kind, if nervous connexion between the 

 brain and the lower extremities is cut off by accidental 

 injury to the spine in man, or by purposely cutting 

 through the spinal cord in an animal, irritation applied to 

 the feet causes no sensation, but produces convulsive move- 

 ments in the legs, of which the patient is unconscious.^ 

 Summary. To sum up what has been said : — The higher functions 

 are dependent on the lower ones ; the vital functions are 

 dependent on the inorganic, and the conscious, or mental 



1 Carpenter's Human Physiology, p. 559. ^ Ibid. p. 529. 



