x THE FOEE-BRAIN 599 



Both experimental research on animals and clinical facts from 

 man therefore support the conclusion that the functions of the 

 corpus striatum are homologous with those of the sensory -motor 

 area of the cerebral cortex. 



XL The localisation of the area of the cortex which serves 

 the perception and memory of visual images has excited much 

 discussion. 



The earliest anatomical studies for the purpose of ascertaining 

 which portion of the cerebral cortex was in relation with the optic 

 nerve, and therefore with vision, are those of B. Panizza (1855). 

 When Hitzig (1874) announced that the lesions of one posterior 

 portion of the dog's hemisphere produced blindness on the opposite 

 side with paralytic dilatation of the pupil, he was unaware that 

 the same fact had been observed many years previously by 

 Panizza. 



In his book on the functions of the brain (1875), Terrier 

 localised the cortical centre of vision, extirpation of which produces 

 blindness in the eye of the opposite side (Figs. 296, 297, 

 pp. 584, 587), in the angular gyrus of the monkey, and the 

 corresponding region of the second external convolution in dogs, 

 cats, and rabbits. 



In his first communications on the visual sphere of the cortex 

 (1877-78), H. Munk maintained that after bilateral removal of the 

 cortex in area A of the dog (Fig. 296), characteristic disturbances 

 of vision occurred, which he termed psychical blindness. In this 

 condition the animal can see, but no longer recognises the objects 

 which it sees, i.e. it receives visual sensations but has lost the 

 memory of previous visual images. If the whole of the occipital 

 lobe is destroyed (A A' A, Fig. 296), then, according to Munk, the 

 blindness is not only psychical, but absolute and permanent, which 

 he terms cortical blindness. In monkeys, too, the visual sphere lies 

 in the occipital lobes. Partial lesion of the latter produces more 

 or less complete psychical blindness, extirpation of a whole occipital 

 lobe produces bilateral homonymous hemianopsia, namely, blindness 

 of the two halves of the retina of the operated side ; removal of 

 both occipital lobes leads to total and permanent cortical 

 blindness. 



In the following year (1879) we found with Tamburini that 

 the visual centre in dogs is not confined to the cortex of the 

 occipital lobe, but spreads forwards to the frontal region; in 

 monkeys it includes the angular gyrus in addition to the cortex 

 of the occipital lobe. We first demonstrated that not only in 

 monkeys, but also in dogs, the visual zone of one side is in 

 relation with both retinae, and not merely with the retina of the 

 opposite side. But the bilateral homonymous hemianopsia or 

 total blindness which results from excision of the visual area on 

 one, or on both sides, is neither absolute nor permanent, even if, in 



