On the Cortex Cerebri in the Monkey, 



87 



Mode of Subdivision of the Cortical Surface. — As before, we have 

 again arbitrarily divided the cortical surface into minute areas 2 ram. 

 square, and thus 73 centres were formed and subjected to excitation. 

 Altogether 23 experiments have been made, the animals being in- 

 variably anaesthetised with ether. 



Anatomy. — The region explored comprised the gyrus coursing in 

 front of the whole length of the precentral sulcus ; the posterior third 

 of the middle frontal convolution ; the posterior half of the superior 

 frontal convolution; the upper end of the ascending frontal convolu- 

 tion, aud the whole of the ascending parietal, except the lower half of 

 its anterior border. 



Topography of Representation. 



The parts of the body which are represented in the region thus 

 denned are as follows, viz. : — 

 (a.) The head and eyes. 

 (b.) The lower limb, 

 (c.) The upper limb. 



(a.) Head and Eyes. — The representation of the important move- 

 ment of turning the head and eyes to the opposite side is situated 

 in a broad zone extending up along the whole length of the precentral 

 sulcus and over the posterior half of the middle and superior frontal 

 convolutions respectively as far as the margin of the hemisphere. 



(&.) Loiver Limb. — The movements of the lower limb are repre- 

 sented in the posterior fifth of the superior frontal, the upper third of 

 the ascending frontal, and the upper third of the ascending parietal 

 convolutions. 



(c.) Upper Lifnh. — In our former paper the account of the repre- 

 sentation of the upper limb was necessarily incomplete, owing to its 

 fusion with that of neighbouring centres. This we have now accom- 

 plished, and the area for the movement of the upper limb may conse- 

 quently be defined as being centralised in the middle of the ascending 

 frontal convolution, from which point it reaches into the middle 

 frontal. Upwards it extends slightly into the superior frontal con- 

 volution and backwards over the lower two-thirds of the ascending 

 parietal convolution as far as the intra-parietal sulcus. 



General Conclusions. 



By exploring the above-mentioned areas with minimal stimulation 

 (see previous paper) we have ascertained — 



(1.) The Primary Movement. 



(2.) The March, i.e., the sequence of movements following the 



primary movement. 

 (3.) The Character of the Movements. 



VOL. XLIII. H 



