ix] Intermediate Precentral Area 211 



The doubling of the line, previously alluded to, occurs half-way down the radiary zone, but 

 the second line is not nearly so broad or so prominent as the first. 



Radiations of Meynert. 



The fibre-strength of the radiations must be described as good, for each contains a number 

 of fine wavy varicose fibres, and two or three evenly-medullated fibres of medium size help to 

 strengthen the individual fasciculi. But medullated fibres of great size, like those found in 

 the " precentral " cortex proper, are present only in the hinder parts of the area, and even here 

 are not numerous. 



Interradiary Plexus. 



The interradiary plexus proper is composed of an abundance of fine fibres, and on 

 examination under a high power most are seen to be varicose. 



Association Fibres. 



We have seen that in the " precentral " area the whole radiary zone is filled by an 

 extremely rich plexus of large medullated fibres running in all directions. In the " inter- 

 mediate " area, remnants of that plexus are visible and the constituents are similar as regards 

 size and position, but there is an enormous reduction in their number, for proof of which one 

 has only to take a single glance at sections showing the two fields. 



I would here say that poor though the association system in fact the whole radiary 

 zone is by comparison with that in the " precentral " area, it is still rich by comparison with 

 the same zone in the cortex of other regions : for instance, the remainder of the frontal lobe, 

 the " parietal," " temporal," and " limbic " areas ; indeed its fibre-wealth, in this particular 

 position, does not fall far short of that observed in the " postcentral " and " visuo-psychic " 

 areas, two fields which have been described as particularly well-endowed in this respect. 

 I would further add, that in the position of the inner line of Baillarger there is an appreciable 

 increment of large " association " fibres, and that such fibres are, as usual, more numerous in 

 the immediate vicinity of the white substance than elsewhere. Some of these fibres can be 

 traced for a long distance, and considerable importance is to be attached to their presence, as 

 they may be conveyers of impulses concerned in the execution of movements of an associative 

 kind, to be mentioned hereafter. I might finally state that the total depth of the radiary 

 zone is great, almost equal to that in the precentral area proper; and that, as in the latter, 

 the fibres exhibit an appreciable numerical and volumetrical diminution as the area is 

 descended. 



TYPE OF CELL LAMINATION. (Plate XXI, tig. 2.) 



In describing the type of cell lamination covering this area, I shall again emphasise the 

 features which distinguish it from the " precentral " type. 



The cell architecture has been studied in serial sections, which, in the case of the extent 

 of the area on the mesial surface, ran vertically, and, on the lateral surface, transversely; in 

 this way, the most satisfactory display of the transition from primary to intermediate type is 

 obtained. 



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