440 
DE. D. EEKKIER ON THE BEAIN OE MONKEYS. 
faces were suppurating slightly. The edges of the bone looked healthy, and there was 
no oedema of the scalp or surrounding parts. 
The dura mater was of normal appearance, and stripped readily from the surface of 
the hemispheres, which looked somewhat “ wet ” but otherwise normal. 
On removal of the brain the base and cranial nerves were all found intact. The 
olfactory tracts and bulbs had escaped injury, though the bulbs were slightly covered 
with pus. 
On opening the ventricles slight excess of fluid was found in them, but the ganglia 
were quite normal in appearance. The anterior cornua of the ventricles had not been 
penetrated. 
The abnormal appearances were entirely confined to the frontal lobes. The hernial 
prolongations were of the size of the openings in the frontal bone, and were bounded by 
a sharp line somewhat congested, indicating the line of section of the lobes. 
In the right hemisphere the line of section struck the anterior extremity of the 
supero-frontal sulcus, and sloping somewhat downwards and forwards had struck the 
orbital surface in a plane anterior to the superior line of section. 
In the left hemisphere the line of section was situated slightly posterior to that on 
the right, cutting across the supero-frontal sulcus, and sloping forwards like the right. 
The posterior half of the orbital surface was intact on both sides. 
The softening at the margins of the section did not extend into the antero-parietal 
sulcus. 
There was some softening between the lips of the longitudinal fissure at the base, but 
this did not extend beyond the perpendicular plane of section. 
The septum lucidum was uninjured. 
The rest of the brain was intact. 
An analysis of these three experiments elicits, with individual differences, certain 
common and fundamental facts. They show conclusively that an animal deprived of 
its frontal lobes retains all its powers of voluntary motion unimpaired, and that it con- 
tinues to see, hear, smell, and taste, and to perceive and localize tactile impressions as 
before. It retains its instincts of self-preservation, retains its appetites, and continues 
to seek its food. It is also capable of exhibiting various emotions. The result, therefore, 
is almost negative, and the removal of a part of the brain which gives no external response 
to electric stimulation exercises no striking positive effect ; and yet the facts seem to 
warrant the conclusion that a decided change is produced in the animal’s character and 
disposition. For this operation I selected the most active, lively, and intelligent animals 
which I could obtain. To one seeing the animals after the removal of their frontal 
lobes little effect might be perceptible, and beyond some dulness and inactivity they 
might seem fairly up to the average of monkey intelligence. They seemed to me, after 
having studied their character carefully before and after the operation, to have under- 
gone a great change. While conscious of sensory impressions, and retaining voluntary 
power, they, instead of being actively interested in their surroundings, ceased to exhibit 
