462 
DK. D. EEKBIEK ON THE BBAIN OE MONKEYS. 
convolution was destroyed on both sides throughout the greater part of its extent, by 
means of the blowpipe cautery passed along the surface. 
An hour after the operation (6.30 p.m.) it still staggered while walking, and looked 
only half awake. Made no sign when a whistle was made close to its ear or when 
called loudly. 
Acute sensibility existed on both sides, as determined by the application of a hot 
iron. It rubbed vigorously the parts touched. 
Aloes and citric acid placed on the tongue caused great annoyance and movements 
of the mouth and tongue to expel the offending substance. The animal also ground its 
teeth, and then got up and ran about the room, grinding its teeth, and annoyed at the 
unpleasant sensation in its mouth. 
Acetic acid held before its nostrils caused it to start and sneeze and rub its nose. 
When not disturbed sat quietly with its head down. 
8.30 p.m. Found asleep in its cage. Made no sign of perception till I laid hold of it, 
when it started with a shriek. Looked up and ran to a dish of water and drank. 
Again, on trying to rouse its attention, it did not look up when a loud sound was 
made, though its companion looked terrified. 
12.30 a.m. A loud sound made in the immediate vicinity of its cage caused a slight start. 
April 8th . — 10 a.m. Animal alive and active, and jumped out of its cage when the 
door was opened. Sight was good, and tactile sensation unimpaired. Various experi- 
ments were made to ascertain the existence or not of hearing ; but it was difficult to 
devise a test, as the animal was continually on the alert ; and it was not easy to make a 
sound without in any way attracting its attention by sight. The following method was 
tried. While the animal was sitting quietly by the fire, I retired to the other room, 
and while watching through the chink of the half-shut door called loudly, whistled, 
knocked on the door, tinkled glass, &c., without ever causing it to look round or give 
any sign of having heard. I then cautiously approached the animal, and not till it saw 
me did it give any sign of consciousness of my presence. 
When the same experiment was repeated, while the monkey and its companion were 
quietly seated by the fire enjoying the heat, it gave no sign of hearing, while its com- 
panion started with alarm, and came with curiosity to ascertain the cause of the sound. 
At 12 (noon) the test of sight, related under Exp. IX., was made. 
8 p.m. In presence of Dr. Burdon Sanderson I repeated the various tests with the 
view of eliciting signs of hearing. To all it remained without response. It seemed 
unconscious of my presence when speaking close to its ear, and only started when it 
caught sight of me. 
April 9 th . — The animal was found weak and prostrate, and was killed with chloroform. 
Post mortem Examination . — There was a considerable amount of pus underneath the 
scalp and below the detached surface of the left temporal muscle. Pus was found 
beneath the dura mater continuous with the collection beneath the muscle. The surface 
of the brain was otherwise intact, except at the points to be described. 
