DR. D. TERRIER ON THE BRAIN OF MONKEYS. 
463 
In the left hemisphere the brain-surface corresponding to the opening in the skull to 
the extent indicated by the dotted line in fig. 20 was elevated above the rest and congested. 
The surface of the angular gyrus and of the superior temporo-sphenoidal convolution 
was disorganized to the extent seen in the figure. The lower part of the shading 
indicates medullary softening, caused by passing a hot wire into the substance. 
In the right hemisphere (fig. 21) a similar dotted line indicates the extent of the 
Fig. 20. 
Fig. 20 represents by the shading the extent of 
destruction of the grey matter of the left hemisphere 
in Exp. XY. The dotted line indicates the extent 
of surface exposed by removal of the bone and dura 
mater. 
Fig. 21. 
Fig. 21 represents the extent of the lesion in the 
right hemisphere in Exp. XY. 
The dotted line has the same signification as in last 
figure. 
opening of the skull, and the extent of congestion and hernia of the surface of the 
brain. The hernia was only slightly elevated above the rest of the hemisphere. The 
lesion was accurately circumscribed. 
The grey matter on the surface of the superior temporo-sphenoidal convolution was 
destroyed throughout the upper two thirds of its extent (i. e. the extent which reacts 
to electrical stimulation). 
The base of the brain, ganglia, and cranial nerves were intact. 
This experiment (besides confirming the fact of loss of sight by destruction of the 
angular gyrus) serves to localize the effects as to hearing, which were observed to result 
from extensive lesions of the temporo-sphenoidal lobe. It is obviously more difficult 
to ascertain the presence or absence of the sense of hearing in the lower animals than in 
man, on account of the difficulty of distinguishing between reflex action and true 
sensory perception. 
In the above experiments, involving destruction of the superior temporo-sphenoidal 
convolution, it will be seen that, with the exception of an occasional start to a shrill 
sound, in general there was an abolition of reaction to sounds which in normal condi- 
tions are sufficient to excite active attention, and this while the animals were on the 
alert and in full possession of their other senses. 
If this absence of reaction, except where it might well he the result of reflex action, 
