1908. | Minute Structure of the Nervous System. 441 
departments there still remains a great deal to be done before the anatomical 
structure of the parts in question can yield a sure basis for a true conception 
of their several functions. In the first place, the investigations have been 
concerned with discovering the special structure of the sensory centres 
physiologically best known, viz., the optic, olfactory, and auditory centres, 
and here remarkable discoveries have been made. 
The other important line of investigation has been directed towards finding 
out the course taken by the bundlgs of nerve-fibres through the substance of 
the brain and the spinal cord. This problem, so exceedingly important, 
indeed fundamental, for Physiology and Pathology, has long been one of 
those which anatomists were most of all desirous of solving, first by macro- 
scopical dissection of brain substance specially hardened for the purpose, and 
then by an examination of coloured serial sections. In this work the 
colouring method invented by Weigert has played an important part, as 
has that of Marchi, but by no means less momentous have been the 
_ researches, so ingeniously and energetically pursued, first of all, by Flechsig, 
into the myelinisation (ve. the formation of the myelin sheaths) of the 
different bundles of nerve-fibres which takes place at varying times. The 
exceedingly important results at which Flechsig arrived on the basis of these 
investigations have led up, as far as the construction of the cerebral cortex is 
concerned, to his well-known subdivision into different association-centres. 
Time would not allow of my endeavouring to give even a brief survey of 
these association-centres or of the nerve-fibre paths that lead to and from 
them; I must also pass by, in silence, numbers of researches carried out 
by various investigators, some by anatomical, some by experimental, methods, 
and others, again, by a study of cases of disease, though they have yielded a 
large quantity of excellent and, to some extent, brilliant results. 
Among other fields of inquiry in the large domain of modern neurology 
there are deserving of mention here: the remarkable transplantation 
experiments made by Braus, Harrison, Nageotte, and others, which are 
evidently in affinity with the nerve generation experiments. Furthermore, 
there should be mentioned the researches that have been instituted by 
Edinger and his school of investigators into the phylogenetic development of 
the construction of the brain in the lower vertebrata from Amphioxus 
upwards in the chain of animals, researches which have already yielded 
several excellent results and which promise to illuminate many of the 
hitherto dark points in reference to the organisation of the central nervous 
system. 
However much may be said to have been accomplished by the assiduous 
investigations pursued during recent decades to elucidate the minute 
