74 
Proceedings of the Royal Society of Edinburgh. [Sess. 
most difficult to determine accurately. In its lower part it corresponds 
nearly with that figured by Horsley and Schafer. In its upper part it lies 
more posteriorly. 
In the frontal lobe there is an area lying below the horizontal part of 
the precentral sulcus and in the angle of that sulcus, stimulation of which is 
followed by opening of the eyes and deviation of head and eyes to the 
opposite side. Above the horizontal part of the precentral sulcus, between 
it and the margin, there is an ill-defined region within the frontal lobe 
from which movements of the head can be caused. In our experience this 
region gives less definite and constant response to stimulation than the area 
lying in the angle of the precentral sulcus. We were unable to study the 
eye-movements in detail, as we were not fortunate in obtaining monkeys 
with exceptionally large and well-developed brains, a condition which has 
been shown by Mott and Schafer * to be necessary for their precise 
differentiation. 
The area which we have described as lying close to the margin, and 
from which movements of tail, anus, vagina, and of the trunk are obtained, 
requires further mention. It corresponds with the area on the convexity 
of the hemisphere described by Schafer + as responding with movements 
of the trunk and tail, and which is named by him the trunk area. 
The centre for movements of the trunk in monkeys was placed in the 
prefrontal lobe by Munk,| who stated that he obtained contractions of 
the muscles of the back, abdomen, and diaphragm by stimulation of this 
part of the brain. He further stated that extirpations in this region are 
followed by paresis of the trunk muscles. These results were not confirmed 
by Horsley and Schafer, § who found no permanent paralysis to result from 
ablations in the anterior part of the frontal lobes. They pointed out that 
the movements of the trunk observed by Munk are to be attributed to the 
spreading of the strong currents which he employed to other regions of the 
brain. 
Vogt || applies the term trunk centre to the area which we jhave 
described between the areas for the lower and upper extremities at the 
level of the superior genu of the Rolandic fissure. This area is indicated 
in Sherrington’s figured of the monkey’s brain by the word “ Body.” 
Our experiments confirm what is stated by Horsley and Schafer, that 
movements of the trunk can be elicited from an area close to the margin of 
* Brain , vol. xiii. p. 165. t Text-book of Physiology, vol. ii. p. 741. 
X Ueber die Functionen der Grosshirnrinde , Berlin, 1890, p. 51. 
§ Phil. Trans., 1888, p. 4. || Loc. cit. 
TT The Integrative Action of the Nervous System, p. 297. 
