450 
DR. D. PERRIER ON THE BRAIN OF MONKEYS. 
Post mortem Examination . — Slight suppuration existed at the margins of the wound 
and under the scalp ; and there was some oedema of the cellular tissue over the orbits. 
The skull was deficient in the region of the parietal eminences. 
The brain-surface corresponding to this opening was slightly elevated above the rest. 
The surface of the brain was everywhere normal, except in the region of the angular 
gyri. 
The surface of these convolutions was destroyed on both sides. Slight softening 
extended about a line into the adjoining margin of the occipital lobe on both sides, 
slightly more on the left than on the right (see figs. 11, 12). 
Fig. 11. Fig. 12. 
Figs. 11 & 12 represent the left and right hemispheres of the monkey respectively. The shaded portions 
indicate the extent of destruction of the surface of the hemispheres in Experiment X. 
The lower part of the ascending parietal convolution of the right side was also 
slightly involved. 
The base of the brain, the ganglia, and the optic tracts were uninjured. 
This experiment completely confirms the other three as to the effect of destruction of 
the angular gyrus or the power of visual perception. 
The slight affection of the left wrist is explained by slight invasion of the right 
ascending parietal convolution by the process of softening. 
These four experiments demonstrate conclusively that unilateral blindness of a complete 
character results from destruction of the angular gyrus of the opposite hemisphere, and 
that this unilateral blindness is only of temporary duration, provided the angular gyrus 
of the other hemisphere remains intact ; while permanent blindness results from the 
destruction of the angular gyrus in both hemispheres. Further proof of this will be 
found in Experiment XXI. 
The loss of visual perception is the only result of this lesion, the other senses and the 
powers of voluntary motion being retained so long as the lesion remains confined to the 
angular gyrus itself. 
By the term visual perception I wish to indicate the consciousness of visual impres- 
sions, and to distinguish this from mere impressions on the optical apparatus and reac- 
tions which are only of a reflex nature, such as the sudden start which an animal really 
