n] General Remark* on Cortical Fibre anil Cell Arrani/einent 



indeed, he was tin- lirst In indic.-iti' llir exislenre of a great system i>t' intergyral association 

 fibres, and to liis enlightened reasoning we owe mncli of our present knowledge of this system. 



We come next to the researches and the extensive publications of Fleehsig on the 



development of the mednllated ner\e fibres of the cortex; a work almost as important as 



his epoch-making discoveries concerning the myelinisation of the spinal cord. After examining 



many foetal brains, he has arrived at the conclusion thai cortical territories mav In 1 divided 

 into three groups, according to their term of development. 



(a) Primordial regions, which become myelinised before the complete maturation of the 

 foetus; in this group are included both central convolutions, the lips of the calcarine fissure, 

 the first occipital convolution, the uncinate gyms, the internal olfactory convolution, the cornu 

 ammonis, the gyms fornicatua (especially its middle third), the transverse temporal gyri (gyri 

 of Heschl), and what he calls the supra-angular gvrus. 



(b) Intermediate areas, which develop one month after birth, and embrace the base of 

 the first frontal convolution, the orbital portion and base of the third frontal convolution, and 

 the gyrus sub-angularis. 



(c) Terminal areas, in which the fibres assume their myelinic investment later than one 

 month after birth: such regions include the first and second frontal, the inferior parietal and 

 serond and third temporal convolutions, and a portion of the gyrus fornicatus. These convo- 

 lutions, he states, are the ones which distinguish the human from the anthropoid brain. 



On developmental grounds, Flechsig now describes 40, instead of 9 originally localised 

 fields, and thinks that further researches will lead to the discovery of even more. This remark- 

 able subdivision of the cortex and the attendant conclusions have been severely criticised by 

 continental workers ; Nissl. Mnratoff, Dejerine and many others joining hands in indicating 

 that Flechsig has been too sweepingly disregardless of the observations of his brother labourers 

 in the realms of physiology, histology and pathology. I shall have frequent occasion to refer 

 to Flechsig's work in later chapters. 



Of researches on cell-lamination one of the most brilliant is that which we owe to the 

 late Carl Hammarberg, a Swedish observer, and to Berger and Henschen who are respon- 

 sible for its posthumous publication. Although Hammarberg only examined the cortex in 

 a partial manner, that is to say he confined his inspection to pieces taken here and there, 

 every line of his work is stamped with thoroughness and reliability : depending chiefly on 

 cell measurements and cell counts, and sparing no pains, he was rewarded by establishing 

 the existence of many remarkable territorial variations in structure previously unsuspected. 

 The points he made are shown in beautiful and obviously faithful illustrations, and these 

 alone will stand as a lasting monument to one whose early death we all lament. 



Finally, I have to mention that Professor and Madame Vogt have for some time been 

 carrying on a most elaborate series of histological observations, in the Neurobiological 

 Institute of Berlin, and I understand that they intend including in their comprehensive 

 programme, an investigation of the cortex, virtually on the same lines as those laid down 

 in the present research. Up to date, their efforts have resulted in the production of an 

 extensive atlas of admirable drawings, demonstrating many points bearing on cerebral inve- 

 linisation : but unfortunately the publication of the illustrations has preceded the major 

 and for me the most valuable part of the letterpress, so that I have not been able to 

 take advantage of it as much as I have wished. I have also lying in front of me, a 



C. 2 



