12 
PROFESSORS V. HORSLEY AND E. A. SCHAFER 
Results of ablation of the external motor areas. — The experiments of Ferrier, both 
alone and in conjunction with Yeo, have yielded distinct and conclusive results from 
the removal of the excitable areas upon the external surface. But we have found it 
necessary to repeat some of their experiments partly for the sake of contrasting the 
effect of removal of these areas with that of removal of those upon the mesial surface ; 
and partly to put to the test the statements of Schiff, Munk, Luciani, and other 
experimental physiologists regarding the sensory functions of these areas. 
We have accordingly performed a certain number of experiments involving more or 
less complete removal of these motor areas, and in some we have at a later period 
followed this up by removal of the mesial areas as. well. In other experiments we 
have first removed the mesial areas and subsequently those of the external sui-face. 
In one or two instances we have cut away the whole of the motor cortex at one opera- 
tion, but, although the haemorrhage from this operation need not be excessive, the 
prostration and shock which accompany the sudden production of such a complete 
condition of unilateral paralysis'"' as results from this extensive lesion has in all our 
cases been so great that the animal has invariably succumbed within a very short 
period after the operation (seven or eight days at the utmost). The extraordinary 
degree of shock which accompanies this absolute hemiplegic condition is well 
exemplified in the case of a large, strong, tame Jew Monkey, from the left side of 
whose brain had been removed, by three successive operations spread over a period of 
several months, the occipital lobe, the prefrontal lobe, including a portion of the 
head-centre, and nearly the whole of the temporo-sphenoidal lobe, including the greater 
part of the hippocampus major. From all these operations, involving collectively, as 
they did, the removal of at least one-half of the whole cortex cerebri, recovery was 
easy and rapid ; and, apart from a certain amount of hemiopic disturbance of vision, 
and a slight degree of facial paralysis (due probably to an accidental lesion in the 
face-area), was unaccompanied by any permanent symptoms whatever. But on 
removing the rest of the cortex, comprising the angular gyrus, the motor areas of the 
external surface, and the gyrus marginalis (but not the gyrus fornicatus), although the 
amount of brain substance removed was considerably less than in the other operations, 
the shock and prostration were so severe as to cause death within a few hours. (See 
'Record of Experiments,' Case 24.) 
The symptoms produced by removal of the external motor areas alone, including 
that part of the leg-area which extends over the margin, are almost complete paralysis 
of the opposite arm, facial paralysis, paresis of the leg-muscles, chiefly involving the 
flexors of the hip and ankle and the extensors of the toes, and greater or less inability 
to rotate the head to the opposite side. But the trunk-muscles are unaffected, and 
* The hemiplegia which is produced hj the complete removal of the whole motor cortex involves not 
only the limbs and face, but the whole opposite side of the trunk. In speaking of such a hemiplegic 
condition as distinguished from that which involves only the limbs, we shall in future use the term 
complete or absolute hemiplegia. 
