352 
THOMPSON YATES LABORATORIES REPORT 
In all the animals examined, we have found the ' motor ' area not to at any point 
extend behind sulcus centralis. Feeble reactions can occasionally, under certain 
circumstances, be provoked by strong faradization behind the sulcus centralis, but these 
are equivocal, and appear under conditions that exclude their acceptance as equivalent 
to ' motor-area ' reactions. 
On the mesial surface of the hemisphere the ' motor ' area has extended less 
far down than was expected. It has not extended to the calloso-marginal fissure. 
Certain areas near that fissure have yielded us movements, e.g., of shoulder, body, 
wrist, and fingers ; but we 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 sulcus 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 localized, 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 produced by this cortex, such as described by one of us 
previously in the cortex of the lower apes. 1 
We find the arrangement of the representation of various regions of the muscu- 
lature follow the segmental sequence of the cranio-spinal nerve-series to a very 
remarkable extent. The accompanying figure 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 sulcus centralis, is but little indication of 
detailed constancy of relation between the physiological area and even that sulcus, 
i. Sherrington, ibid., also Sherrington and Hering, ibid., vol. 62, 1897, and Hering anil Sherrington, 
Pfiiigers Archi-v., vol. 71, 1897. 
