422 THE NERVOUS SYSTEM. 



while that of others is diminished ; and in many cases one 

 function only of the mind is deranged, while all the rest are 

 performed in a natural manner. 4. The same opinion is sup- 

 ported by the fact that the several mental faculties are devel- 

 oped to their greatest strength at different periods of life, some 

 being exercised with great energy in childhood, others only in 

 adult age; and that, as their energy decreases in old age, 

 there is not a gradual and equal diminution of power in all of 

 them at once, but, on the contrary, a diminution in one or 

 more, while others retain their full strength, or even increase 

 in power. 5. The plurality of cerebral organs appears to be 

 indicated by the phenomena of dreams, in which only a part 

 of the mental faculties are at rest or asleep, while the others 

 are awake, and, it is presumed, are exercised through the me- 

 dium of the parts of the brain appropriated to them. 



These facts have been so illustrated and adapted by phren- 

 ologists, that the theory of the plurality of organs in the cere- 

 brum, thus made probable, has been commonly regarded as 

 peculiar to phrenology, and as so essentially connected with it, 

 that if the system of Gall and Spurzheim be untrue, this 

 theory cannot be maintained. But it is plain that all the 

 system of phrenology built upon the theory may be false, and 

 the theory itself true ; for phrenologists assume not only this 

 theory, but also that they have determined all the primitive 

 faculties, of which the mind consists, i. e., all the faculties to 

 which special organs must be assigned, and the places of all 

 those organs in the cerebral hemispheres and the cerebellum. 

 That this is a system of error there need be no doubt, but it 

 is possibly founded on a true theory : the cerebrum may have 

 many organs, and the mind as many faculties ; but what are 

 the faculties that require separate organs, and where those 

 organs are situate, are subjects of which only the most general 

 and rudimentary knowledge has been yet attained. 



From the apparently greater frequency of interference with 

 the faculty of speech in disease of the left than of the right half 

 of the cerebrum, it has been thought that the nerve-centre for 

 language, including in this term all intellectual expression of 

 ideas, is situated in the left cerebral hemisphere. It cannot 

 be said, however, that the existing evidence for this theory is 

 at present sufficient to have established it. 



Of the physiology of the other parts of the brain, little or 

 nothing can be said. 



Of the offices of the corpus callosum, or great transverse and 

 oblique commissure of the brain, nothing positive is known. 

 But instances in which it was absent, or very deficient, either 

 without any evident mental defect, or with only such as might 



