On the Ci'rclral Cortex of sow of the JfujJier Apes. 207 



wo hesitate, for reasons to be given in a fuller communication, to class 

 these with those of the " motor " area proper. 



We have found the precentral convolution excitable over its free width, 

 and continuously round into and to the bottom of the sulctis centralis, 

 The " motor " area extends also into the depth of other fissures besides 

 the Rolandic, as can be described in a fuller communication than the 

 present. The hidden part of the excitable area probably equals, 

 perhaps exceeds, in extent that contributing to the free surface of the 

 hemisphere. We have in some individuals found the deeper part of 

 the posterior wall of the sulcus centralis to contribute to the " motor " 

 area. 



In the " motor " area we have found localised, besides very numerous 

 other actions, certain movements of the ear, nostril, palate, movements 

 of sucking, of mastication, of the vocal cords, of the chest wall, of the 

 abdominal wall, of the pelvic floor, of the anal orifice, and of the vaginal 

 orifice. We have met with various examples of inhibition effects pro- 

 duced by this cortex, such as described by one of us previously in 

 the cortex of the lower apes.* 



We find the arrangement of the representation of various regions 

 of the musculature follow the segmental sequence of the cranio- 

 spinal nerve-series to a very remarkable extent. The accompanying 

 figure (Plate 4) indicates better than can a verbal description the 

 degree of adherence to this sequence. 



We do not find that the exciting current for the " motor " cortex 

 requires to be extremely strong for the anthropoid brain. " Epilepsy " 

 is easily evoked from the cortex of the anthropoids. 



Our experiments show that the sulci in the region of cortex dealt 

 with can in no sense be considered to signify physiological boundaries. 

 Further, the variation of the sulci in these higher brains is so great 

 from individual to individual that, as our observations show, they prove 

 but precarious, even fallacious, landmarks to the details of the true 

 topography of the cortex. 



[The mere fact that the " motor " area extends in front of but never 

 (so far as our experiments have yet gone) behind the sukus ceninilis, 

 is but little indication of detailed constancy of relation between the 

 physiological area and even that sulcus, though such a fundamental 

 one ; the antero-posterior diameter of the sulcus, being an area often 

 five-and-twenty mm. across, it is, when treated as marking a line on the 

 cerebral surface, but a rough guide for any detailed examination of the 

 functional topography. November 25, 1901.] 



Extirpation of the hand area by itself has been followed by severe 

 paresis of the hand, the hand being for a few days practically useless 

 and seemingly " powerless." In a few weeks use and " power " were 



* Sherrington, Hid.; also Sherrington and Hering, ibid., vol. 62, 1897, and 

 Hering and Sherrington, ' Pfluger's Archly,' vol. 71, 1897. 



