CHAP. XXVI.] VOLUNTARY MOVEMENTS. 577 



The next question that arises is as to the most correct 

 interpretation of the newly discovered facts. What are 

 the functions or modes of activity of these portions of the 

 Cerebral Cortex whence the stimuli emanate which are to 

 excite special Voluntary Movements ? 



Various answers have been given in reply to this ques- 

 tion. We have (a) the hypothesis of Ferrier, that the 

 results depend upon the existence of ' motor centres ' for 

 Volitional Movements in the cerebral convolutions ; (b) the 

 hypothesis of Schiff, that the Movements of the limbs 

 resulting from stimulation of the cortical ' centres ' are of a 

 ' reflex ' nature, and that the affection of Motility depen- 

 dent upon the destruction of the same parts is essentially 

 an ' ataxy ' resulting from loss of Tactile Sensibility ; and 

 (c) the hypothesis of Hitzig and Nothnagel, that the convo- 

 lutional areas in question are either the * muscular sense ' 

 centres, or parts traversed by ' muscular sense' impressions. 



(a.) The hypothesis of Ferrier is so important in itself, 

 has been so ably advocated by him, and already numbers 

 so many adherents, as to make it desirable that we should 

 examine his views pretty closely. 



The following passages have seemed to the writer to 

 embody the most important statements and views adduced 

 by Ferrier in his work on " The Functions of the 

 Brain," in support of his position that ' motor centres ' 

 exist in the Cerebral Convolutions.* 



(1.) " The entire removal of the [cerebral] hemispheres operates 

 differently in different classes. In the fish, the frog, and the 

 pigeon the removal of the hemispheres exercises little or no appre- 

 ciable effect on the faculties of station and locomotion. Under the 

 influence of stimulation from without, these animals swim, jump, 



* The passages have been arranged in paragraphs and num- 

 bered, merely for the purpose of facilitating reference to the various 

 statements contained therein. 



P P 



