786 REPORT— ] 897. 



the first to become completely formed, whilst the fibres for auditory impulses are 



the last. 



Flechsig names the great sensory centre which receives the impulses 

 associated with touch, pain, temTpeTa.tm-e,m\.iscu[a.T sense, &c., Korperfiihlsphare, 

 the region of general-body-sensation, or the somsesthetic area as translated by 

 Dr. Barker.^ The tracts conducting these impulses myelinate at successive 

 periods after birth. They pass upwards from the inner and outer capsules and the 

 optic thalamus as three systems.^ Some enter the central convolutions of the 

 Bolandic area, others reach the paracentral lobule, the inferior frontal convolution, 

 the insula, and small parts of the middle and superior frontal convolutions ; whilst 

 considerable numbers reach the gyrus fornicatus and the hippocampal gyrus, 

 which Ferrier had previously localised as a centre of common or tactile sensibility. 

 ' The Eolandic area, therefore, is not exclusively a motor area, but is a centre 

 associated also with the general sensibility of the body. The motor fibres in it 

 are not myelinated until after the sensory paths have become developed. As the 

 motor paths become structurally complete, they can be traced downwards as the 

 great pyramidal tract from the pyramidal nerve-ceUs in this area, from which they 

 arise, into the spinal cord, where they come into close relation with the nerve- 

 ceUs in the anterior horn of grey matter, from which the nerve axial fibre* 

 proceed that are distributed to the voluntary muscles. 



Flechsig's observations agree with those of previous observers in placing the 

 visual centre in the occipital lobe ; the auditory centre in and near the superior 

 temporal convolution ; and the olfactory centre in the uncinate and hippocampal 

 convolutions. Of the position of the taste centre he does not speak definitely, 

 although he thinks it to be in proximity either to the centre of general sensation, 

 or to the olfactory centre. 



The centres of special sense in the cortex, and the large Eolandic area, which 

 is the centre both for motion and general sensation, do not collectively occupy so 

 much as one-half of the superficial area of the convolutions of the cortex. In all 

 the lobes of the brain — frontal, parietal, occipito-temporal, and insula — convolutions 

 are situated, not directly associated with the reception of sensory impressions, 

 or as centres of motor activity, the function of which is to be otherwise 

 accounted for. These convolutions lie intermediary to the sensory and motor 

 centres. Flechsig has shown that in them myelmation of the nerve-fibres does 

 not take place until some weeks after birth, so that they are distinctly later in 

 acquiring their structural perfection and functional activity. As the nerve-fibres 

 become differentiated, they are seen to pass from the sense-centres into these inter- 

 mediate convolutions, so as to connect adjacent centres together, and bring them 

 into association with each other.^ Hence he has called them the Association 

 centres, the function of which is to connect together centres and convolutions 

 otherwise disconnected.* 



We have now, therefore, direct anatomical evidence, based upon differences in 

 their stages of development, that, in addition to the sensory and motor areas in the 



' JoJms Hopkins Bulletin, No. 70, January 1897. 



- Drs. Ferrier and Aldren Turner communicated to the Royal Society of London 

 a few weeks ago (Proc. R.S. June 17,1897) an account of an elaborate research on the 

 tracts which convey general and special sensibility to the cerebral cortex of monkeys. 

 Their results were obtained by the aid of destructive lesions and the study of the 

 consecutive degenerations in the nerve- tracts. From the brief abstract in the Pro- 

 ceedings, their research, though conducted by a different method, harmonises with the 

 observations of Flechsig on the human brain, in regard to the course and connections 

 of the great thalamic cortico-petal sensory fibres. They have also traced association 

 fibres in connection with both the visual and auditory systems. 



3 The term association fibres was introduced a number of years ago to express 

 fibres of the cerebrum which connect together parts of the cortex in the same hemi- 

 sphere. Flechsig's fibres belong to this system. 



■• The Association centres had previously been referred to by other observers as 

 ' silent portions ' of the cortex, not responding to electrical stimulus. Their possible 

 function had been discussed by Professor Calderwood in Relations of Mind and 

 Brain, 2nd edit., 1884. 



