CHAPTER II. 



SOME HISTORICAL AND GENERAL CONSIDERATIONS ON CORTICAL FIBRE 

 ARRANGEMENT AND NERVE CELL LAMINATION. 



BEFORE embarking on a detailed consideration of the various cortical subdivisions which 

 histological processes enable us to define, I should like to make preliminary reference to some 

 writings of others who have investigated the cerebral cortex, and whose teachings have done 

 much to smooth my labours ; and perhaps as the study of fibre arrangement has been prosecuted 

 with less industry and attracted far less attention than cell-lamination, it will be a gain to 

 punctuate and advance the first and lesser known theme, leaving a knowledge of cortical 

 cytology more or less on trust. Also, future explanations may be saved if a few pages are 

 devoted to a general consideration of the arrangement of cortical nerve fibres and cells. 



On February 2nd, 1776, Gennari saw, and described with remarkable exactitude, the " lineola 

 albidior admodum eleganter," in the calcarine region, with which his name is now associated. 

 Vicq d'Azyr, evidently unacquainted with German's writings, redescribed the structure 16 years 

 later. The discovery of this line constituted an opening move in the exploration of that 

 delicate network of nerve fibres which has its seat in the cerebral cortex, but lack of methods 

 of coloration proved an effectual bar to further progress, until Weigert and Exner elaborated 

 their processes for the display of nerve fibres and gave to the neuro-histologist the means for 

 a material advance. 



Just as the discovery by Nissl and Golgi of their respective methods for staining the 

 nerve cell, marks an era in the advancement of our knowledge of nervous cytology, so the 

 publication of the above-mentioned processes for the coloration of nerve fibres was a signal 

 for the commencement of a number of brilliant researches on the histology of the nerve fibre 

 constituents of the cerebral cortex, and the result has been an enormous addition to our 

 knowledge of these elements. 



Though we owe much to Exner, yet his method has been overshadowed by the superla- 

 tiveness of that of the Frankfurt professor, and of recent years all workers on this subject, 

 while they may not have adhered to Weigert's original process in detail, have adopted 

 a working technique based on the principles which it embodies, and foremost amongst such 

 investigators must be mentioned the names of Theodor Kaes, S. Ramon y Cajal, Flechsig, 

 Vulpius, Zacher, Passow, Edinger and Vogt. 



The work of Theodor Kaes, of Hamburg, on the medullated nerve fibres of the cortex, 

 is such a monument of patient industry, that in a retrospective view of the literature it is 

 entitled to the place of honour. Up to the present he has contributed four papers ; the first, 

 a relatively unimportant one, consists mainly of a recommendation of the method of Wolters 



