Functions of the Cerebrum. 663 



that the sight or hearing centers themselves are affected, but the trouble 

 may be in the connections between these centers and the motor centers 

 in the speech area. For the motor stimuli are the results of preliminary 

 sensory stimuli, the latter directly or indirectly giving rise to the for- 

 mer. The motor action of articulation will therefore fail if the sensory 

 stimuli are cut off from the co-ordinating speech organ. 



Ferrier is of opinion that whatever may be the case with the inverte- 

 brates, Consciousness in the vertebrates, including man, depends upon 

 the cerebral hemispheres. According to his view, the mesencephalon, 

 the ganglia between the cerebral hemispheres and the medulla oblongata, 

 is subject to impressions from the environment, and to resulting co-or- 

 dinated movements without conscious sensation ; is, in fact, a complete 

 reflex unconscious machine. The term sensory, which is so constantly 

 used with reference to the afferent nerves and ganglions, must be under- 

 stood to imply only that which is afferent, and not as committing our- 

 selves to the idea that their activity necessarily involves consciousness. 



A lower vertebrate, reptile, fish or bird, deprived of his hemispheres, 

 but possessing the sensory organs, will perform all actions, even well 

 co-ordinated ones in obedience to external stimuli, in a purely reflex man- 

 ner, the element of memory ( and therefore of consciousness, according 

 to Ferrier ) not entering into the composition of the action, or modify- 

 ing it at all. A bird thus mutilated can stand, and recover its equili- 

 brium when pushed over. If placed on its back it can get up on its 

 feet again; if thrown into the air it will fly. If a fly alight on its head 

 it will shake it off. If ammonia be held near its nostrils it will start 

 back. It usually seems asleep, but can be roused, when it will open its 

 eyes and look up. Sometimes it rouses up, yawns, shakes itself, dresses 

 its feathers with its beak, moves a little, stops, and stands first on one 

 foot, then the other. It will not take food, and resists being fed, but 

 when the food is once in the mouth it is swallowed. Fed artificially it 

 may live for months, but would never eat if left to itself. Ferrier says, 

 "it is and remains unconscious, and void of sensation." 



If a fish be deprived of its cerebral hemispheres, it continues to move 

 in the water as well as ever. It preserves its equilibrium, swimming 

 straight forward, but turning out to avoid objects placed in its path. 

 Nevertheless the fish is insane, for it no longer perceives food, or at- 

 tempts to feed itself, and would starve in the midst of plenty. It is 

 under an irresistible impulse to go, and it keeps on till physically ex- 

 hausted, or restrained from without. It acts like the frog deprived of 

 its hemispheres, that is, it is subject to the direct impulses of the stim- 

 ulations of the environment through contact. The resistance of the 

 water affords the stimulation necessary to excite action in the muscles 

 of tail and fins and cause it to move. If food were put into its mouth. 



