4 Material and Methods of Examination [CHAP. 



and lamination were shown to perfection. I cannot too strongly emphasise the advantage 

 in time-saving and general convenience secured by the possibility of staining first cells and 

 then fibres in successive series of large sections, for apart from the obvious advantage in 

 obtaining a ready comparison between cell and fibre constituents in given parts, it converts 

 a comprehensive investigation of cortical cell lamination from a gigantic and almost im- 

 possible task, when small sections are employed, into one of easy accomplishment 1 . 



In those cases in which portions only of the brain were examined, orthogonal tracings 

 of the various surfaces of the hemisphere were made in the same way, and then small 

 transverse sections of gyri, showing not more than 2 ctm. of cortex, were taken from 50 

 or 60 different situations. The exact position from which these blocks were taken was 

 again carefully indicated in the tracings. The sections from these blocks were made at a 

 thickness of 15 fj, only, and it is from them that the account of the more minute details in the 

 histology of the nerve fibres and cells has been compiled, and the microscopic drawings made. 



I am indebted to my colleague Doctor Wilson for nearly all the microscopic drawings 

 which accompany this work, and would say that before deciding on a method of illustration 

 we tested several mechanical contrivances. First, the projection apparatus recommended by 

 Hammarberg, but though we recognised the usefulness of this apparatus in displaying 

 isolated objects lying on a pale ground, such as nerve cells in Nissl specimens, we found 

 that in sections stained for nerve fibres the plexus was too dense and many of the fibres 

 too delicate to be clearly seen ; secondly, the distortion of the image given by the drawing 

 apparatus of Abbe, in spite of the employment with it of Edinger's table, condemned that 

 instrument, and finally we selected the eye-piece drawing apparatus of Leitz. Since drawing 

 with the aid of this apparatus is merely a mechanical task consisting of tracing over the 

 image of the structure, reflected on to the underlying paper, it is possible to obtain per- 

 fectly accurate drawings free from the prejudicial effect of the personal equation, and it is 

 claimed for the lower power drawings submitted herewith, that the position of every fibre, 

 at any rate, in the outer two-thirds of the cortex, is faithfully shown, and that in the 

 high power figures the calibre as well as the relation of the fibres one to another is 

 accurately represented, and that as regards the cells, size, position and number are faith- 

 fully shown. 



All the drawings have been made to scale, the low power ones at a magnification 

 of ^8., the high power at -if fi . 



It may be asked why photographic representations have not been resorted to, and in 

 replying to this I would say that, while I yield to none in my admiration of the general 

 utility of photography for purposes of reproduction, yet when we come to giving repre- 

 sentations of the nerve fibres of the cortex the camera must yield to the drawing pen. To 

 photograph small fields is of course a simple matter, the difficulty arises when an attempt 

 is made to show the structure of the cortex in the whole of its depth in one view, all 

 efforts in this direction are bound to be unsuccessful because a lens which will embrace a 

 view of the whole cortex must be of such low magnifying power as to fail in displaying 

 any but the fibres of large calibre, and the resulting picture is obviously incomplete. Then 

 when a stronger lens which will give a clear and satisfactory view of fine as well as large 



1 By this method the examination of a whole human hemisphere can be accomplished in six mouths, whereas 

 to go over it thoroughly in small blocks would absorb at least two years. 



