LESION" OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 493 
On separating the hemispheres, which were slightly adherent on their median aspect 
along the longitudinal fissure, a cicatrix nearly an inch long was seen in the corpus 
callosum, somewhat nearer the left hemisphere than the right (fig. 9). 
The cicatrix was deepest posteriorly, and reached within a few millimetres of the 
posterior boundary. The exact depth of the original incision which had thus become 
cicatrised was difficult to determine. 
(The photographs were taken by Mr. J. M. Thomson.) 
Remarks .—This case shows that division or injury of the corpus callosum does not 
appreciably affect the rapidity of compensation of the primary results of lesion of the 
angular gyrus. 
The total blindness of the eye opposite the more extensive destruction of the angular 
gyrus, viz. the left, was very manifest; but the subsequent less extensive lesion of the 
other angular gyrus produced only very transient effects, which might have escaped 
observation unless tested for soon after the operation. But here, as in many other 
cases, the facts related show that at a period when all other faculties and powers 
were unimpaired, vision was distinctly defective. The period of reliable observation is 
not to be determined by the mere length of time that has elapsed since the operation, 
for the rapidity of recovery is very variable, but by the indications that the animal is 
on the alert, and otherwise in full possession of its other powers. In this case the 
second operation seemed to have caused so little general prostration that the animal 
was able to run about almost immediately as if nothing had happened to it. 
Experiment 8* (Plate 21, figs. 12, 13, 14). 
In this case both angular gyri were exposed at the same operation and destroyed as 
completely and accurately as possible by means of the galvanic cautery. 
The animal remained apparently sound asleep for nearly two hours. At this time 
it began to sit up and move about a little in a very cautious and shaky manner. Both 
eyes were opened widely, the pupils were large and equal, and the conjunctiva] reflex 
was very distinct in both eyes. 
It turned its head sharply to sounds, but made no sign of perception wffien a light 
was thrust or flashed close to its eyes, or when threatened in various ways. 
Three hours and a half after the operation when urged to move it knocked its head 
against every obstacle in its path. Its motor powers were unimpaired, hearing acute, 
and tactile sensibility evidently fully retained, as it shook off flies when they settled 
anywhere on its body. 
Next day, twenty-four hours after the operation, the eyelids were somewhat 
cedematous, interfering with the full-opening of the right eye especially. The left 
was sufficiently open for distinct vision. 
The animal was very unwilling to move, and when urged to do so knocked its head 
against every obstacle, and occasionally sprawled with its hands in the air as if to 
lay hold of something. 
