100 The Functions of the Post central Cortex [CHAP. 



occupies a more or less remote and isolated area : foremost among these we find Ferrier, and 

 Schafer and Horsley. 



In reference to Ferrier's work, many years ago he ventured on the statement that because 

 experimentally-produced destruction of the gyi'us hippocampi occasioned impairment or abolition 

 of tactile and general sensibility, together with a condition of the limbs which indicated loss 

 of the sense of movement without motor paralysis, therefore that part was to be regarded as 

 serving a sensory function. Finding, however, that the effects on sensation following the 

 hippocampal lesion were not lasting, he took one of the animals previously operated upon 

 and excised the gyrus fornicatus in the whole of its course round the corpus callosum, and 

 so succeeded in producing " temporary total contralateral analgesia and lasting insensibility 

 to all milder forms of tactile stimulation." As a result of this operation, he stated that " in 

 addition to the hippocampal region proper, we must include the callosal gyrus as forming part 

 of the common sensory centre"; this statement he still adheres to, and from further work done 

 in collaboration with Turner he believes that his results are in harmony with those published 

 by Horsley and Schafer. 



Horsley and Schafer, like Ferrier, experimented upon lower members of the ape family, 

 and found that any extensive lesion of the gyrus fornicatus was followed by more or less 

 marked hemianaesthesia, but in no case could they produce permanent loss of all forms nf 

 sensibility, nor were they able to establish a relationship between special parts of the gyrus 

 and special regions of the body. 



Coming from writers whose eminence entitles them to great respect, the statement that 

 the gyrus fornicatus is endowed with high functional importance is unpleasant to combat, especially 

 by those who, like myself, are unpractised in experimental work, and whose only weapons are 

 the results of clinico-pathological and histological research ; still, as I shall now indicate, there 

 are several important facts in the hands of investigators in the latter domain which can be 

 advanced in opposition to the statement. The first, and I think I may say the most 

 important, of these pertains to the structural composition of the limbic cortex. Now it is a 

 point which I shall emphasise strongly, when considering the structure of known sensory cortical 

 realms those for the reception of impressions of sight, hearing, and smell that they are one 

 and all characterised by the possession of elements of an outstanding nature, differing in some 

 striking manner from those found in what one may call the general or common type of 

 cortex ; thus, some of the nerve fibres which they harbour strike the eye on account of their 

 great size and unusual arrangement, while the nerve cells to which we suppose these fibres 

 proceed are curious either on account of their great size, their reaction to various stains, or 

 their conformation. A like remark applies to the histological appearances presented by the 

 various known centres (posterior root ganglia, posterior column nuclei, ventro-lateral thalamic 

 nuclei) in the chain of neurones laid down for the conveyance of common sensory impressions 

 from the limbs and other peripheral parts. But the same can certainly not be said of the 

 cortex of the gyrus fornicatus, at any rate, the cortex of that part lying above the corpus 

 callosum ; for when I describe the post-limbic and mid-limbic cortex I will point out that 

 it does not contain a single fibre of large size, nor indeed one of a kind not to be found m 

 any other part of the whole cortex, also that the largest of its nerve cells are, comparatively 

 speaking, small and not marked by any peculiarity in form, arrangement or staining reaction, 

 which suggests special physiological function. For these reasons it is hard for the histologist 

 to entertain the suggestion that the cortex of these parts is endowed with such an important 



