306 



S. Simpson, 



same, so that a description of one will snfflce for all. It was confined 

 to tlie left cerebral hemispliere, tlie object being to divide all the pro- 

 jection fibres arising- from the motor cortex in their passage through 

 the corona radiata, and not to injure at all the basal ganglia. After 

 all haemorrhage from the bone had been arrested, sheathed platinum 

 electrodes were applied to the exposed cortex, and the motor area lo- 

 calised by stimulation with a fairly weak faradic current. Without 

 going into details, this was found to be situated in the sigmoid gyrus 



(around the crucial sulcus) and the anterior 

 portions of the first, second and third con- 

 volutions. In the earlier operations, and 

 until some practice had been gained, a 

 formol-hardened brain was kept at hand 

 in order that the convolutions and fissures 

 in the living brain might be the more 

 easily identified. Having localised the area, 

 a fine blunt-pointed bistoury was pushed 

 obliquely downwards and forwards through 

 the grey matter, to the depth of about 

 three quarters of an inch into the white 

 matter, close to the supero-mesial border of 

 the hemisphere, and from one eighth to one 

 fourth of an inch behind the posterior limit 

 of the motor area; it was then carried outwards across the anterior 

 portions of the P*, 2"'^ and o^^ convolutions almost to the lateral border 

 of the hemisphere, and in this way a deep incision was made cutting 

 across all projection fibres from the motor cortex of the left hemi- 

 sphere (see fig. 1). The depth of the incision was always gauged on 

 a formol-hardened brain before the knife was pushed into the living 

 brain, and care was taken to avoid injury to the large vessels at the 

 base. After the bleeding had completely stopped, the dura was re- 

 placed, the skin wound closed with horse liair sutures, and llicii co- 

 vered witli antiseptic gauze and sealed witli ioIUmIìoh. 



In the case of the monkeys an incision was made l)eliiii(l the 

 posterior limit of the motor ar(;a on tlie left side, as in the cats, i. e. 



W 





Fig. 1. 



Brain of cat (natural size). — 



Left front view, to show how 



lesions were made. 



