66 
Proceedings of the Eoyal Society of Edinburgh. [Sess. 
elbow, and shoulder, while on the other hand, when the shoulder move- 
ment takes place first, the march proceeds downwards towards the 
digits. 
Broca,* * * § by means of clinical and pathological observations in cases of 
aphasia, localised the function of producing articulate speech in the posterior 
part of the third frontal convolution of the left hemisphere. Doubt has 
recently been cast upon the correctness of this localisation by the observa- 
tions of Marie, f and the question may, in view of his work, be regarded as 
still open. 
To Fritsch and Hitzig £ is due the establishment, upon a basis of ex- 
perimental evidence, of the doctrine of localisation of function within the 
cerebral cortex. To their work also we owe our knowledge that the cortex 
is excitable by electrical stimuli. These observers, who worked on the dog, 
proved that an area of the cortex in the neighbourhood of the crucial 
sulcus might be mapped out by electrical stimulation from the rest of the 
brain. They proved that this area in one hemisphere governs the muscular 
movements of the opposite side of the body, and that the movements of 
different groups of muscles have their source in motor centres lying separate 
from each other within the excitable area. Further, they found that when 
the centre whose excitation elicited definite movements is extirpated, the 
voluntary production of these movements is impaired. 
Fritsch and Hitzig employed the galvanic current, finding that they 
obtained less constant results by the use of the faradic current. The latter 
method of stimulation has, however, been shown to be preferable for 
accurate work, and was the form used by Ferrier. Ferrier § confirmed the 
results of Fritsch and Hitzig on the dog, and applied the method of electrical 
stimulation to the brain of the monkey and other animals. 
According to Ferrier, movements of the limbs and face can be obtained 
by stimulation of an area on the convexity of the hemisphere comprising 
the ascending frontal and parietal gyri and part of the angular gyrus. 
Within this region lay centres which he represented as areas roughly 
circular in outline, stimulation of which produces definite movements of 
groups of muscles. In front of this region Ferrier described an area 
bounded anteriorly by a line drawn at right angles to the anterior extremity 
of the precentral sulcus and posteriorly by a continuation of the precentral 
sulcus upwards to the longitudinal fissure, stimulation of which causes 
* Loc. cit., p. 330. t La Semaine medicate , 1906. 
X “Ueber die elektrische Erregbarkeit des Grosshirns,” Arch. f. Anat., Physiol ., u. 
wissensch. Med., 1870, S. 300. 
§ Proc. Roy. Soc., London, 1874, vol. xxii. p. 229 ; 1875, vol. xxiii. p. 409. 
