Chap. XXVI.] VOLUNTARY MOVEMENTS. 575 



As an example of the kind of evidence upon which 

 the above-mentioned localizations in regard to Special 

 Movements have been made, one of Ferrier's experimental 

 observations bearing upon this point may be quoted. 



"The left hemisphere of a monkey was exposed in the region 

 of the ascending frontal convolution sufficiently to display the 

 centre of bicipital action [fig. 182, 6j or supination and flexion of 

 the forearm. The exact spot being determined by the application 

 of the electrodes, it was then accurately cauterised, just sufficiently 

 to destroy the cortical grey matter. This operation immediately 

 manifested itself in paralysis of the power of flexing the right fore- 

 arm. All the other movements of the limbs were retained, but 

 when the right arm was placed in an extended position the animal 

 was utterly powerless to flex it, and the limb hung in a state of 



flaccid extension when the animal was lifted It raised 



things to its mouth with the left hand, the movements of the leg 

 were intact, there was no facial paralysis, and cutaneous and other 

 forms of sensation were uuirapaired." 



Whether or not the various details, of which brief indi- 

 cations only have been given, are destined to be confirmed 

 by other investigations, it seems pretty clear (notwith- 

 standing all which has been said in an adverse sense) that 

 experimental observations on Monkeys, as well as clinico- 

 pathological data gathered from the study of the effects of 

 disease in Man alike support the notion that certain ' ex- 

 citable regions ' of the Cerebral Cortex exist in each Hemi- 

 sphere, the irritation of which produces Choreic or Convul- 

 sive Movements of the opposite side of the body, and the 

 destruction of which gives rise to Paralysis of correspond- 

 ing parts of the body. This ' excitable area ' (figs. 172, 

 182) comprises the convolutions which border on or are 

 adjacent to the ' fissure of Rolando,' viz., the ascending 

 frontal and pari, tal convolutions, the postero-parietal 

 lobule, and the posterior portions of the three tiers of 

 frontal convolutions. 



