

THE MENTAL FACULTIES. 297 



an act be complex and effected by many muscles, like one of the move- 

 ments of the upper limb, or simple, and performed by a single muscle, 

 as occurs in raising the upper eyelid, or turning the eyeball to one 

 side. In either case, the act is performed by willing a result, not'by 

 willing the muscular contraction. The regulation of the muscles of 

 the larynx, for the production of the various vocal tones, is also simi- 

 larly accomplished by the will, not directed to the laryngeal muscles, 

 but to the purpose of producing a definite note, guided by the sense 

 of hearing. The general fact, that most of the automatic movements 

 performed by muscles of animal life, such as those of laughing, yawn- 

 ing, coughing, sneezing, winking, and so forth, can be imitated volun- 

 tarily, also favors the conclusion, that the motor apparatus immediately 

 exciting the motor nerves is, in the two cases, identical. There are 

 undoubtedly, indeed, voluntary movements, w r hich may become, by 

 the force of habit, automatic ; and many ordinarily automatic move- 

 ments may be suggested through ideas, or imitated by the action of 

 the will ; both sets of facts would therefore favor the conclusion that 

 the nervous apparatus immediately directing the movements of the 

 muscles, is the same, whether the act itself be automatic, ideational, 

 or volitional. Thus, coughing and sneezing may be imitated volunta- 

 rily ; yawning, by seeing others yawn ; the convulsions of hydrophobia, 

 by looking at bright objects suggesting the idea of water, or even by 

 hearing water spoken of; and, lastly, vomiting may occur from the 

 remembrance of nauseous tastes, or of the disagreeable feelings of sea- 

 sickness. On the other hand, the action of walking, or even those 

 more complex movements which are performed in playing on musical 

 instruments, may, as already mentioned, become habitual or auto- 

 matic. 



Psychical Functions of the Nervous System. Mental Faculties of 



Man. 



Whether the mind be regarded as a single entity, distinct from the 

 body, or whether the psychical manifestations or mental processes be 

 viewed as the mere result of changes in the nervous substance of the 

 cerebrum, it is certain that the brain is the corporeal organ through 

 which those functions are performed ; for, as we have seen, in order to 

 give rise to those phenomena which we are accustomed to designate 

 mental, either external or internal influences or stimuli must operate 

 upon and excite that organ. Moreover, disturbances in its condition, 

 and interruption of its functions, are attended with essential disturb- 

 ances in, and cessation of, the psychical acts. 



The fact, already mentioned, that, in the ascending scale of animals, 

 the brain is gradually more developed as the mental powers increase, 

 justifies the inference, that the superior mental endowments of man, 

 as compared with those of animals, are related to those parts of the 

 nervous system, the extraordinary development of which distinguishes 

 man structurally from animals. 



The impressions transmitted through the sensory organs and their 

 sensory nerves, to those parts of the brain, whichever they may be, 



