490 
PROFESSORS D. FERRIER AND G. F. YEO ON THE EFFECTS OF 
pletely for two hours in both eyes. But restoration of vision occurred to such an 
extent after this, that no perceptible deficiency could be detected, so far as could be 
ascertained by any tests applicable to the lower animals. Whether vision was perfect 
in such a degree, central and peripheral, as might be ascertained by accurate peri¬ 
metric tests in a human being, did not admit of determination. 
There was no further impairment of vision when the lesion of the left hemisphere 
was extended forwards into the ascending parietal convolution, but there was a 
marked deficiency as regards the motor power of the right hand and foot, which 
continued till the animal’s death many months subsequently. The defect did not 
amount to actual paralysis, but only to paresis, a condition which can be readily 
accounted for by only partial destruction of the centres concerned in the movements 
in question. (See further, Section III., p. 510). 
In the next experiment on the angular gyrus it was considered advisable at the 
same time to divide the corpus callosum, or part of it, with a view to determine 
whether such a lesion would have any influence on the otherwise speedy compensation 
of unilateral lesion of this gyrus. Previous to this an experiment had been made in 
order to determine the effects, if any, of division of the corpus callosum alone. The 
particulars of this experiment are as follows. 
Experiment 6* (Plate 20, fig. 8). 
Two trephine openings were made over the anterior and posterior extremities of 
the corpus callosum, and the two openings joined by an incision with a Hey’s saw 
close to the middle line. The longitudinal sinus was exposed, and the dura mater 
divided along the left margin, so as to allow access to the longitudinal fissure. A 
small aneurism needle, bent at an obtuse angle, was then passed between the 
hemispheres, and the corpus callosum scratched through, so far as could be judged by 
tactics eruditus. There was some haemorrhage welling up between the hemispheres, 
but not to any extent, and ceasing speedily. 
The animal was rather weakly before the operation, and remained prostrate for 
some time. It was not observed for more than an hour, and nothing definite was 
made out. 
Next day it was still rather languid, but it was able to move about, though the 
right arm and leg were somewhat weak. 
Sight was evidently good, and hearing acute. Tactile sensibility was unimpaired, 
judging from the manner in which it attended to and resented cutaneous irritation. 
Smell was evidently also retained, as it seemed fond of the smell of bergamot held 
under its nose. 
Except for the weakness of the right arm and leg, the cause of which is explained 
below, the animal, though feeble, was otherwise in full possession of all its senses and 
motor powers. 
