Address to the Anthropological Section / William Turner.

  • William Turner
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Address to the Anthropological Section / William Turner. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    tbe 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, temperature, muscular sense, &c., the region of general-body-senisation, or the somtesthetic area as translated by Dr. Barker.' The tracts conducting the.se impulses myelinate at successive periods alter birth. They pass upwards from the inner and outer capsules and the optic thalamus as thive systems.'' Some enter the central convolutions of the liolandic 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 Rolandic 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-cells in this area, from which they arise, into the spinal cord, where they come into close relation with the nerve- cells in the anterior horn of grey matter, from which the nerve axial fibres proceed that are distributed to tire voluntary muscles. Flechsig's observations agree with tho.se of previous observers in placing the visual centre in the occipital lobe; the auditory centre in and near tlie superior temporal convolution ; and the cll’actory centre in the uncinate and hippocampal convulutioDS. Of tne 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 Rolandic 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 tbe sensory and motor centres. Flechsig has shown that in them myelination 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 difi’erentiated, 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 ' Johns Hopkins Bulletin, No. 70, January 1897. Drs. Ferrier and Aldren 'turner communicated to the Royal Society of London a few weeks ago {Proo. R.t'i. June 17,1897) an account of an elaborate research on the tracts which convey genet al 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 Fiechsig 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 s3’stems. ® 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 ’ ct the cortex, not responding to electrical stimulus. Their possible function had been discussed by Professor Calderwood in Itelations of Mind and Brain, 2nd edit., 1884.
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