SENSORY GANGLIA. 



115 



Fig. 34. 



nerves. The experiments of these gentlemen show, that vision, more 

 than the other senses, requires a connexion with the organ of the intel- 

 lectual faculties the cerebral hemispheres; and this, as M. Magendie 

 has ingeniously remarked, because vision rarely consists in a single im- 

 pression made by light, but is connected with an intellectual process, 

 by which we judge of the distance, size, shape, &c., of bodies. It has 

 been well suggested and maintained by Dr. 

 Carpenter, 1 that whilst the cerebral ganglia 

 are the organs of the higher intellectual and 

 moral acts ; there is a series of ganglia, con- 

 nected with the reception of impressions 

 from without, which are seated near the base 

 of the brain, and are hence, termed by him 

 sensory ganglia. As we descend in the ani- 

 mal scale, these ganglia become more marked; 

 whilst the cerebral hemispheres become less 

 and less; until ultimately the animal appears 

 to have its encephalic organs limited almost 

 wholly to those that are concerned in the 

 reception of impressions from without, and 

 the originating of motor impulsions from 

 within. These ganglia are seated at the 

 base of the brain: from the origin of the 

 auditory nerves to those of the olfactory. 



Brain of Squirrel, laid open. 



The hemispheres, B, drawn to 

 either side to show the subjacent 

 parts, c. The optic lobes. D. Cerebel- 

 lum, thai. Thalamus opticus. c s. 

 Corpus striatum. 



Fig. 35. 



Fig. 36. 

 Pike. 



Brain of Turtle. 



A. Olfactive ganglia. B. Cerebral hemi- 

 spheres, c. Optic ganglia. D. Cerebellum. 



Brains of Fishes. 



.. Olfactive lobes or ganglia. B. Cerebral hemi- 

 spheres, c. Optic lobes. D. Cerebellum. 



Dr. Carpenter is disposed to regard the optic thalami as ganglia for the 

 reception of tactile impressions, and the corpora striata as ganglia cori- 



1 Principles of Human Physiology, 4th Amer. edit., p. 370, Philad., 1850. 



