530 THE NERVOUS SYSTEM. 



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

 but it is possibly founded on a true theory : the cere- 

 brum 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 know- 

 ledge has been yet attained. 



From the apparently greater frequency of interference 

 with the faculty of speech in disease of the left than of the 

 rigid half of the cerebrum, it has been thought that the 

 nerve-centre for language, including in this term all intel- 

 lectual expression of ideas, is situate 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 be ascribed to coincident affections of 

 other parts, make it probable that the office which is com- 

 monly assigned to it, of enabling the two sides of the brain 

 to act in concord, is exercised only in the highest acts of 

 which the mind is capable. And this view is confirmed 

 by the very late period of its development, and by its 

 absence in all but the placental Mammalia.* 



To the fornix and other commissures no special function 

 can be assigned; but it is a reasonable hypothesis that 

 they connect the action of the parts between which they 

 are severally placed. 



* See cases of congenital deficiency of the corpus callosura, by Mr. 

 Paget and Mr. Henry, in the twenty-ninth and thirty-first volumes of 

 the Medico- Chimrgical Transactions. 



