x THE FOKE-BBAIN 613 



We collected (1885) 20 cases of word deafness from clinical 

 and anatomo- pathological observations, which on examination 

 yielded some important facts showing that the region injured in 

 word deafness is the first and part of the second left temporal 

 convolution. 



Two other clinical facts prove the functional connection 

 between the left temporal lobe and the auditory paths of speech : 

 (a) the cases recorded of lesions of the right temporal lobe 

 unaccompanied in life by word deafness ; (b) lesions of the left 

 temporal lobe in left-handed individuals, which were unaccompanied 

 by word -deafness. There are authentic cases of left-handed 

 persons in whom destruction of the left convolution of Broca was 

 not betrayed by any disturbance of speech. The predominance 

 of the left brain in right-handed people is replaced by predomin- 

 ance of the right brain in the left-handed. 



To confirm the theory that the central focus of the auditory 

 components that subserve acoustic perceptions and ideas lies in 

 the first temporal convolution, the fact may be adduced that 

 defective development of the temporal lobes, particularly of the 

 first temporal convolution, as compared with the rest of the brain 

 has frequently been noted at the post-mortem examination of 

 individuals who were deaf-mutes from birth. 



XIII. Comparatively few investigations have been made upon 

 the cortical localisation of the olfactory and gustatory centres. 



Ferrier, starting from the anatomical fact that there is a 

 direct connection between the olfactory tract and the gyrus 

 hippocampi (subiculum cornu Ammonis), regards this region 

 without defining its limits as the olfactory centre. Electrical 

 excitation of the subiculum both in dogs and monkeys (15, Fig. 

 275) produces movements of sniffing in the nostril of the same 

 side, as though the animal perceived a strong smell. This effect, 

 which is not obtained from any other region of the cortex, 

 strengthens the presumption that the hippocampal region forms 

 part of the olfactory area. 



It is probable, according to Ferrier, that the gustatory centre 

 is contiguous with or lies very near the olfactory. He believes 

 it is localised in the lower extremity of the second temporal 

 convolution, since electrical stimulation of this region sometimes, 

 but not always, provokes movements of the tongue and jaw, as 

 though the animal perceived a sensation of taste. 



Ferrier tried to support his hypothesis by destroying this 

 region, in order to see if symptoms of loss of taste and smell 

 resulted. But the effects were few and uncertain ; he found that 

 extensive destruction of the upper temporal region in the ape 

 might in addition to auditory disturbance produce signs of 

 affection of smell and taste. With more extensive cauterisation 

 of both temporal lobes, so as to destroy the whole of it, inclusive 



