444 
DR. D. FERRIER ON THE BRAIN OE MONKEYS. 
arm hung by the right side in a state of flaccid extension. When urged to move it 
used the left limbs and the right leg as before, but had lost the power of flexing the 
right arm. In trying to walk, it frequently fell over on its right side. 
An hour after the operation the paralytic condition of the right forearm remained 
very marked ; the loss of voluntary power was 
confined to the same action as was excited by 
the electric stimulus. 
The animal died from an overdose of chloro- 
form when about to be subjected to a further 
operation. 
Post mortem Examination . — The only lesion in 
the brain was a cauterized spot of the size of 
a threepenny bit, corresponding to the bicipital 
centre in the ascending frontal convolution (see 
fig. 8). 
These three experiments, besides others where 
the same regions became involved indirectly as 
the result of other experiments*, afford a simple 
and conclusive proof that the movements which 
are excited by the application of the electrodes 
to the surface of the hemispheres in these regions are due to excitation of the grey 
matter of the cortex, seeing that destruction of these same areas causes paralysis of 
the same movements, while sensation remains unafiectedf. 
In the first experiment the more or less complete destruction of the cortex in the 
region of the fissure of Rolando caused complete hemiplegia on the opposite side of 
the body, affecting all the unilateral movements capable of being called into play by 
the electric irritation. In the next two, only those movements were paralyzed which had 
their special centres destroyed in the cortex of the opposite hemisphere. 
Fig. 8. 
Fig. 8 represents the left hemisphere of the 
brain of the monkey. 
The shaded spot on the ascending frontal 
convolution marked by the letter / indicates 
the extent to which the grey matter of the 
surface had been destroyed in Experiment YI. 
* See Experiments VII. and X. 
t I am aware that the conclusion here stated, and which seems to me well established by the above facts, 
apparently stands in diametric contradiction to the conclusions which Hermann (‘Archiv fiir Physiologie,’ 
Band x. Hefte 2 & 3, p. 77) has arrived at from a few similar experiments on the motor centres of the brain of 
dogs. He concludes that because dogs ultimately recover completely from such disturbances of motor func- 
tions as are at first caused by the ablation of cortical centres, these centres cannot be motor in the true sense 
of the term. Experiments on dogs, however, are not strictly comparable with experiments on monkeys ; and 
the relative subordination and association of lower centres in different animals is a fact which ought to be 
carefully considered. The explanation I have elsewhere given (‘West Riding Reports,’ vol. iii.) of how asso- 
ciated movements, such as those of the limbs of dogs, can still be carried out through the associated action of 
lower centres so long as the cortical centres of the other hemisphere are intact, is quite in harmony with the 
facts Hermann gives, and is further demonstrated by the complete paralysis of voluntary motion which follows 
the destruction of corresponding regions in both hemispheres in these animals. 
