FIBRES OF THE IHTERHAL CAPSULE OF THE BOHHET MONKEY. 
G9 
pletely under the influence of ether, and was killed before it recovered from the 
anaesthetic. 
With few exceptions the left hemisphere was the one used for the examination, 
and, as a rule, the cortex had just before been minutely explored. It was found most 
convenient to remove the vault of the cranium for about 1 cm. to the other side of 
the middle line, and laterally as low as the zygoma in front, and behind to a corre¬ 
sponding level. 
The dura mater was reflected over the area thus exjDosed, care being taken not to 
injure the longitudinal sinus ; the hemisphere was then drawn tow'ards the middle 
line so as to allow of the middle cerebral artery being ligatured soon after its origin, 
this was easily done by passing a fine thread beneath the vessel through the con¬ 
tiguous portions of the orbital and temporo-sphenoidal lobes. 
A horizontal incision was then made with a long sharp scalpel through the substance 
of the hemisphere, from the outer surface towards the middle line, but stopping short 
1 or 2 mm. of the mesial plane. In this way section of all arteries, save the branches 
of the ligatured middle cerebral was avoided, and, hence, haemorrhage was in a great 
measure prevented. The only vessel which gave much trouble was the lenticulo- 
striate artery running vertically through the outer zone of the lenticular nucleus. In 
the first two experiments, we sought to arrest this haemorihage by a fine point of an 
actual cautery, but we found, to our surprise, that although the area touched Avas 
extremely small, yet the cut ends of the fibres of the adjacent internal capsule were 
so damaged (by the radiant heat of the cautery) as to be inexcitable; moreover, we 
speedily found that all hremorrhage could be easily arrested liy placing on the bleeding 
point a small cube of amadou. 
When the hsemorrhage had thus been controlled the upper portion of the hemisphere 
which, as described above, had not been completely separated, but merely raised like 
the lid of a box, was replaced, and preparations were made for recording the results 
of the stimulation. 
The plan of recording which appeared to us likely to afford the most accurate 
results, and, at the same time, not to involve so much delay in exposing the capsule 
as to cause the death of the fibres, was as follows :—- 
Upon paper, on which fine lines were engraved by an engine wdth mathematical 
accuracy so as to cover the surface with squares of 1 mm. side, we drew by means 
of compasses the exact outline of the basal ganglia as exposed by the section. 
In this way we obtained at once the cut surface of the internal capsule correctly 
projected on paper, divided into squares of 1 mm. ; these squares we then numbered 
from the front of the anterior limb of the capsule to the posterior end of the lenticular 
nucleus. Finally, we stimulated each of these bundles of fibres thus obtained of 
1 square mm. area, and recorded the effect produced. 
Mode of Stimidation .—The electrodes used were two fine platinum points, 1 mm. 
apart, so that the excitation should be exactly limited to each square excited. The 
