FUNCTIONS OF THE CEREBRUM. 421 



which no mental defect was observed, although one cerebral 

 hemisphere was so disorganized or atrophied that it could not 

 be supposed capable of discharging its functions. The re- 

 maining hemisphere was, in these cases, adequate to the func- 

 tions generally discharged by both; but the mind does not 

 seem in any of these cases to have been tested in very high 

 intellectual exercises ; so that it is not certain that one hemi- 

 sphere will suffice for these. In general, the mind combines, 

 as one sensation, the impressions which it derives from one 

 object, through both hemispheres, and the ideas to which the 

 two such impressions give rise are single. 



In relation to common sensation and the effort of the will, 

 the impressions .to and from the hemispheres of the brain are 

 carried across the middle line : so that in destruction or com- 

 pression of either hemisphere, whatever effects are produced 

 in loss of sensation or voluntary motion, are observed on the 

 side of the body opposite to that on which the brain is injured. 



In speaking of the cerebral hemispheres as the so-called 

 organs of the mind, they have been regarded as if they were 

 single organs, of which all parts are equally appropriate for 

 the exercise of each of the mental faculties. But it is pos- 

 sible that each faculty has a special portion of the brain ap- 

 propriated to it as its proper organ. For this theory the 

 principal evidences are as follows : 1. That it is in accordance 

 with the physiology of the other compound organs or systems 

 in the body, in which each part has its special function ; as, 

 for example, of the digestive system, in which the stomach, 

 liver, and other organs perform each their separate share in 

 the general process of the digestion of the food. 2. That in 

 different individuals the several mental functions are mani- 

 fested in very different degrees. Even in early childhood, 

 before education can be imagined to have exercised any in- 

 fluence on the mind, children exhibit various dispositions 

 each presents some predominant propensity, or evinces a sin- 

 gular aptness in some study or pursuit ; and it is a matter of 

 daily observation that every one has his peculiar talent or pro- 

 pensity. But it is difficult to imagine how this could be the 

 case, if the manifestation of each faculty depended on the 

 whole of the brain : different conditions of the whole mass 

 might affect the mind generally, depressing or exalting all its 

 functions in an equal degree, but could not permit one faculty 

 to be strongly and another weakly manifested. 3. The plu- 

 rality of organs in the brain is supported by the phenomena 

 of some forms of mental derangement. It is not usual for all 

 the mental faculties in an insane person to be equally disor- 

 dered ; it often happens that the strength of some is increased, 



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