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Proceedings of the Poyal Society of Edinburgh. [Sess. 
made with the object of involving the whole motor area, the ascending 
parietal convolution (which is now known to produce no motor response 
on direct excitation) had been included, we deemed it necessary, in the 
first place, to determine, in one animal, the extent of the degeneration 
following from destruction of the entire motor cortex on the lateral and 
mesial aspects of the cerebral hemisphere, without including the ascending 
parietal gyrus. This area includes practically the whole width of the 
precentral convolution, and extends from a line about 3 millimetres above 
the fissure of Sylvius over the border of the hemisphere on to the marginal 
convolution on its mesial -aspect (fig. 1). The lesion was made on the 
Fig. 1 . — Lateral aspect of right cerebral hemisphere. The area of 
total extirpation (exclusive of “head and eyes”) is included 
within the interrupted line. The shaded parts indicate the 
extent of the destructive lesions of the leg, arm, and face areas 
respectively, while the circles represent the limited lesions made 
within these areas. 
right side. The animal was killed twenty-three days afterwards, and the 
brain and cord were treated in the manner already described. We shall 
first describe in detail the degeneration resulting from this total extirpa- 
tion, and this w T ill serve, in position and extent, as a standard of com- 
parison for the localisation within the pyramidal tract at different levels 
from above downwards of the fibres proceeding from the limited lesions 
of the motor area of the cortex. 
Degeneration following Extirpation of the entire 
Motor Cortex. 
From the area of extirpation numerous fibres, coarse and fine, radiate 
into the subjacent white matter ; many of the fine fibres (association fibres) 
