1899.] Structure of the Brain in Relation to its Functions. 125 



WEEKLY EVENING MEETING, 



Friday, April 21, 1899. 



Sir James Criohton-Bbowne, M.D. LL.D. F.E.S., Treasurer and 

 Vice-President, in the Chair. 



Frederick Walker Mott, M.D. F.R.S. 



Structure of the Brain in Relation to its Functions. 



What we know, even what we believe we know, of the relation of the 

 structure of the brain to its functions is comparatively small indeed 

 to what we do not know. The history of the evolution of our know- 

 ledge of the structure of the nervous system is full of interest, but 

 time will not permit me to mention more than the fact that Descartes 

 although he was never able to see the structure of the nervous system, 

 yet considered the nervous fibres to consist of little tubes along which 

 the " animal spirits " were conveyed from the brain to the muscles ; 

 if we substitute the phrase " nervous impulse " for animal spirits, his 

 conception was not so very far behind our conception of this structure 

 at the present time. 



At the beginning of this century the microscope demonstrated 

 that the nervous fibre was not a hollow tube, but that it contained a 

 central solid axial core. A little later, microscopical research showed 

 that the brain not only contained nerve fibres but myriads of little 

 masses of protoplasm of a regular shape — nerve cells. These are 

 the two essential elements of the nervous system of all animals with 

 a nervous system. At first, microscopical research was unable to 

 determine the relationship of the cells to the fibres in the brain. 

 All that was known was that the fibres were found in the white 

 matter, the cells in the grey matter ; where the fibres came from and 

 where they went to, was not known. Later on, I shall endeavour to 

 show the enormous advance which has been made in our knowledge 

 of the minute structure of the nervous system, by the invention of 

 instruments with which extremely thin slices of the brain can be 

 cut ; so that these delicate sections can be examined with the high 

 magnifying powers of the microscope. These sections are stained 

 with various chemical reagents so that different structural features in 

 the nerve cells and fibres are seen by the affinity they possess for 

 colouring with the reagents used. The brilliant aniline dyes are 

 among the most useful of these reagents. The investigation of the 



