Page:Proceedings of the Royal Society of London Vol 69.djvu/221

Rh 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