1906-7.] Functions of the Rolandic Cortex in Monkeys. 71 
Rolando. A thin plate of vulcanite, one edge of which had been sharpened, 
was then inserted into the cortical substance at the bottom of the fissure of 
Rolando. Stimulation was applied to the posterior wall of this fissure and 
to the ascending parietal convolution. No response was now obtained from 
this part of the cortex, while application of the electrode to the part of the 
ascending frontal convolution in front of the vulcanite plate was followed 
as before by movements of muscles. The isolating plate was inserted to a 
depth which would permit of its dividing the grey matter without pene- 
trating the underlying white substance. In some of these experiments we 
Tail perineum Digits. . - Knee ; 
and trunk. _ - Hip. 
Body. 
Shoulder. 
.Elbow. 
Wrist 
Digits. 
Neck. 
.Upper lip. 
Opening of mouth. 
Closure of mouth. 
. Tongue and mastication. 
Fig. l. 
also employed the bipolar method of stimulation, using platinum points ’5 
mm. apart. 
The same method of isolation was applied to the determination of the 
boundaries of the centres in front of the Rolandic fissure. 
We also, with the object of limiting the spread of current, made use of 
brass plates whose edges were placed on the surface of the cortex and 
which were connected to earth by wires. 
We found, as previous investigators have done, that implicit reliance 
cannot be placed on the sulci as guides in cerebral topography. We 
accordingly measured and sketched the sulci rapidly after exposure of the 
