Frontal OIK/ Pr< frontal Arcu* 

 Interradiary Plexus and Association Fibres. 



233 



Very intoivsting variations in the behaviour of the elements pertaining to these systems 

 are to be observed. We saw that the radiary zone of the "precentral" area proper (text- 

 figure 1) was parked with large medullated fibres running in all directions and supported by 

 a dense plexus of fibres; we also saw that the "intermediate precentral" cortex (text-figure 21), 

 while poorly supplied in comparison with the "precentral," was rich in comparison with most 

 other fields. Now in the "frontal" area (text-figure 22) there is a still further reduction in 



rt. 



FIG. 22. Radiary zoue in the cortex of the frontal area at a magnification of J J". 



Comparing it with the drawing of the same part in the intermediate precentral cortex, figure 21. page 210, a loss 

 in fibre strength is manifest. The radiary projections are less prominent, and fibres of large size have almost 

 disappeared. 



the general wealth, but it is important to mention that long and moderately stout fibres of 

 the "association" order are occasionally met with; the "prefrontal" plexus (text-figure 2) 

 in turn differs from the " frontal," in being still more open, and in containing no fibres 

 of large calibre. The latter feature is one which I regard as of great histological 

 importance. 



I would add in conclusion that all the above-mentioned gradations fade insensibly into 

 one another, that the diminution in fibre wealth is accompanied, first, by a general 



C. 30 



