18 
PROFESSORS V. HORSLEY AND E. A. SCHAPER 
III. — Lesions of the Occipital Lobes. 
We have found that removal of the occipital lobe npon one side is followed, as 
McJNK * was the first to prove, by a condition of hemiopia ; blindness being produced 
in the lateral half of each retina corresponding to the side of the brain which has been 
submitted to the operation. The blindness is at first complete. The animal takes no 
notice of a threatened blow directed from the opposite side, tends to knock against 
obstacles which lie in the way of that side, and only picks up such objects (raisins, 
&c.) as happen to lie upon the same side of the mesial plane of vision. In a few days, 
however, this condition begins to pass off : threats are avoided ; large objects lying on 
the opposite side of the mesial plane are seen and picked up, at first with some 
awkw^avdness ; and eventually it is not possible to substantiate any permanent affec- 
tion of vision. We have performed this operation four times. We have removed the 
occipital lobes of both sides in two cases only, and in these by two successive opera- 
tions, only a short interval of time having elapsed between them ; one only of these 
two cases survived the operation for any length of time. At first complete blindness, 
affecting the whole visual field, was the result, but this appeared to be subsequently 
in great measure recovered from, although it seemed to us that there was some 
permanent impairment of visual perception. For, although objects were undoubtedly 
seen, there was much greater slowness and difficulty manifested in seizing them. 
This was the case at least with such a small object as a currant upon the floor, the 
animal often fumbling about for a moment or two in the attempt to pick it up. More 
conspicuous objects did not appear to offer the same difficulty, for the animal would 
spring from the side of the cage on to a hanging rope with unerring precision. 
In this case, in which we had removed both occipital lobes in previous operations, 
and after the animal had recovered its visual perceptions so far as has just been 
described, we subsequently cut away the cortex of the angular gyrus of one side. This 
lesion was followed by a return of hemiopia, which remained permanent and apparently 
complete until the death of the animal (from dysentery) four months later. This 
is the only experiment we have ma,de upon the angular gyrus. We have also 
sometimes produced hemiopia in consequence of operations involving the under- 
surface of the Jemporo-sphenoidal lobe. These cases are probably to be explained by 
the fact that the optic radiations into the occij)ital lobe have been reached by the 
Movements of the eyes MuNK appears inclined, but on very insufficient grounds, as it seems to us, to 
connect with the angular gyrus. The ear-region he places around the extremity of the Sylvian fissure. 
It must be borne in mind that the plan Avhich Munk has drawn up has been obtained chiefly, if not 
entirely, by ablation, whereas ours is mainly the result of excitation. Unfortunately Munk has not 
given the particulars of his experiments, but has merely stated their general tendency. In our opinion 
their value would be greatly enhanced, were the precise symptoms manifested dnring life, and the exact 
extent of the cortical lesion in each case, as determined by post-mortem investigation, recorded. 
* ' Functionen der Grosshii^nrinde — Erste Mittheilung.' 1877. 
