THE CEREBRUM. 321 



nay, even the whole of it may be so received and retained. It is not to 

 be overlooked that, as soon as this effect occurs, the evidences of sensation 

 arise ; and, since sensation necessarily implies the existence of ideas, 

 ideas themselves are doubtless dependent on this partial retention or reg- 

 istry of impressions. We may therefore adopt the doctrine of Dr. Car- 

 penter, as regards the sensorial functions of the cranio-spinal apparatus, 

 not only from the arguments he has presented, but also from other con- 

 siderations. 



There can be no doubt that the cerebral hemispheres constitute the in- 

 strument through which the mind exerts its influences on the General result 

 body. Any injury of sufficient severity inflicted upon them of variations 



j. ^ J J - A l_ x 1 1 f x 11 in the Size and 



is at once attended with a total loss of intellectual power; weight of the 

 any malformation or lesion by disease is attended by a dete- hemis P here s- 

 rioration below the customary mental standard; any unusual develop- 

 ment with correspondingly increased powers of intellection ; and this not 

 only as regards animals of different tribes, or individuals at special peri- 

 ods of their lives, but also of different men when compared with one an- 

 other. The general impression is founded in fact that those who have 

 distinguished themselves for mental attainments or intellectual power 

 have been marked by the unusual development of their cerebral hemi- 

 spheres. 



It is to be understood that, in thus asserting a correspondence between 

 the development of the cerebrum and intellectual capability, i nstrumental 

 we are not to overlook the instrumental nature of that organ, nature of cere- 

 Though imperfections in it may produce a manifest inferior- brum ' 

 Ity, that inferiority is by no means to be referred to the intellectual prin- 

 ciple itself. The mode of action being by an instrument, if that instru- 

 ment becomes imperfect the action becomes imperfect too. Under such 

 circumstances, in any human contrivance, we should never think of im- 

 puting inferiority to the prime mover. 



From this point of view we may therefore consider the intellectual prin- 

 ciple as possessing powers, properties, and faculties of its own ; as being 

 acted on by impressions existing in the thalamus, and delivered through 

 the intervening fibrous structures to the vesicular material of the convolu- 

 tions of the cerebral hemispheres. In this region they act upon the in- 

 tellectual principle and are acted upon by it, the returning influence, if 

 any, coming down through the converging tubular structures to the cor- 

 pus striatum, and by its commissural connections sent off to particular 

 ganglia, passing along the inferior strand of the crus through the meso- 

 cephalon to the anterior pyramids, and by their decussation to the oppo- 

 site side of the cord. 



Having thus spoken of the sensory ganglia and the cerebral hemi- 

 spheres, it remains to add some remarks respecting the cerebellum. It 



X 



