ix] Intermediate Prcnufral Area i!11i 



sentations ill' thi 1 extent of what Flechsig calls the " sensory projection centres" are given, 

 ami 1 \\-oulil draw attention to the anterior portion of the great central field, and particularly 

 to the more sparsely dotted zone lying in front of the ascending frontal convolution and 

 its paracentral annexe. Now the area which Flechsig indicates on the mesial surface of the 

 hemisphere cannot be said to coincide with mine; his field proceeds considerably further 

 forwards and he also extends it mi to the subjacent gyms fornicatus; but on the lateral 

 surface the agreement, so far as the anterior border is concerned, is extraordinary : broad 

 over the upper frontal gyms, the area rapidly narrows at the level of the inferior precentral 

 fissure, and finally sweeps forward to cover the frontal and orbital opercula, in just the 

 same manner as my "intermediate precentral" type does; indeed, his diagram might almost 

 be used to illustrate the points in topography which I have previously emphasised. When 

 we give further thought to the working basis on which the embryologist has to rely in 

 defining his cortical areas, we soon discover the reason why results are obtained on all fours 

 with those forthcoming from an analysis of nerve fibres in the adult cortex. It is, that 

 if any of the areas mapped out by Flechsig in the developing human brain, or by Vogt 

 and Dollken in the brains of lower animals, be examined in the adult condition they will 

 be found to be characterised one and all by the possession of fibres of large calibre, not 

 always arranged in the same manner and not to be seen in equal abundance, but always 

 present. And I think Flechsig will admit that the principal working guide in his classical 

 research has been the developmental peculiarities and the appearances in general exhibited 

 by these larger elements; a point which favours the correctness of this surmise is that the 

 method of staining employed by Flechsig, that of Pal, while admirably adapted for the 

 demonstration of fibres of large and medium size is of little value, and certainly far behind 

 the method of Wolters-Kulschitzky, for displaying the more delicate fibre constituents. If 

 then these large fibres have the importance here suggested we have the key to the situation, 

 for the same fibres have also served as one of my guides ; but not the only one, for I have 

 also taken full notice of the accompanying type of cell lamination ; and as to my area on 

 the mesial surface, the confines of which disagree with those laid down by Flechsig, having 

 mapped it out by both its fibre and cell characters I am more than satisfied that it would 

 be incorrect for me to extend it across the calloso-marginal sulcus and on to the gyrus 

 fornicatus, as Flechsig does his. 



OX SOME ASSOCIATION TRACTS OF FIBRES. 



Before proceeding to the consideration of what clinical medicine teaches us of the functions 

 of this area it will be necessary to intercalate something of its anatomical connections. For 

 there is no question that by means of subcortical tracts of fibres this region forms important 

 connections with other parts of the brain, and I think this statement is justified notwith- 

 standing that the exact origin, course, and function of these tracts is not established and our 

 general knowledge of them not so complete as might be wished. 



The Frontal Pontine Tract. 



Deserving of mention in the first place is the frontal cerebrocorticopontal path (Barker) frontalc 

 Grosshirnrinde Briickenbabn of Flechsig. Fleohsig, who studied thi.s tract in the developing braiu and 

 proved that it became medullated later than the main motor tract, maintains that its fibres are centrifugal; 

 having origin in the large pyramidal cells situated in the hinder portion of the three tiers of frontal 

 convolutions (and possibly also in the middle portion of the gyrus fornicatus), its fibres, having collected, enter 



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