75 
1906-7.] Functions of the Rolandic Cortex in Monkeys. 
the longitudinal fissure. These movements take place in association with 
those of the tail and perineum, and chiefly affect the muscles of the 
hack. 
It is necessary to consider how far the results here detailed are in 
accordance with those obtained by other methods of research. 
With regard to the posterior boundary of the Rolandic motor area, it is 
to be noted that impairment of voluntary movements of groups of muscles 
follows upon extirpation of the corresponding motor centres in the 
cortex. 
Griinbaum and Sherrington have found,* on extirpating areas in the 
ascending frontal convolution in the anthropoid, that severe but diminish- 
ing paralyses result. Thus after destruction of the hand area the hand 
remains paralysed for several days. This paralysis passes off, until after a 
week or two the ape is able to make use of the hand for voluntary move- 
ment. No paralysis, not even of a passing nature, succeeds ablations of 
large portions of the ascending parietal convolution. 
We have performed a number of experiments on monkeys, in which we 
have destroyed one or other of the motor areas as delimited by us in the 
ascending frontal convolution and obtained paralysis of the corresponding 
part of the body, complete at first but passing off as in the experiments of 
Griinbaum and Sherrington. 
Vogtf records eleven extirpation experiments on monkeys. In five of 
these the lesions involved the cortex anterior to the fissure of Rolando, and 
in six the lesions were made posterior to that fissure. Motor paralysis 
followed only upon lesions in front of the fissure. In the other cases, 
while movements of the affected limb could be carried out, the author 
states that these movements were ataxic. 
It is known that lesions of the motor cortex are followed by degenera- 
tion of nerve fibres in the pyramidal tract. Various experimenters have 
described degeneration resulting from lesions in front of, and also behind, 
the fissure of Rolando. 
Melius l describes experiments on Macacus sinicus in which he removed 
a portion of cortex from the ascending parietal convolution between the 
lower extremity of the intraparietal sulcus and the fissure of Rolando and 
a little above the inferior genu of the fissure of Rolando. He found 
degenerated fibres both coarse and fine passing from the lesion downward 
through the centrum semiovale and present in the posterior limb of the 
internal capsule. 
* Proc. Roy. Soc ., London, 1901, vol. lxix. p. 207. t Loc. cit. 
% Proc. Roy. Soc., London, 1895, vol. lviii. p. 206. 
