232 Type of Fibre Arrangement [CHAP. 



short and irregularly scattered fibres can be seen. But since nerve cells, although small, are 

 present in abundance in the same situation, and it is impossible to think of nerve cells 

 without accompanying nerve fibres, I should qualify my statement by saying that scarcely 

 any fibres are present which even a delicate method, like that which we owe to the ingenuity 

 of Wolters and Kulschitzky, will reveal. I might add that this layer does not depart from 

 the usual rule in being richer in fibres in the lower than in the upper parts. 



Line of Baillarger. 



It has been noted elsewhere that the distinctness of the line of Baillarger may depend 

 more on imperfect representation of contiguous strata than on constitutional strength of the 

 linear formation itself, and this is well exemplified in the frontal lobe. Thus, in the 

 " prefrontal " area the stripe is visible, even to the naked eye, and at the lip of the con- 

 volutions has the appearance of being reduplicated, but on microscopic examination the 

 formation is found to be very weak, it contains no large fibres at all, scarcely any which 

 can be designated medium-sized, and the delicate elements which do compose it are both 

 short and scarce. 



In the " frontal " area the line is again visible to the naked eye, but on microscopic 

 examination it is found to contain considerably more fibres and occasionally a long one of 

 medium size. Its general representation, however, is a distinct grade below that of the 

 " intermediate precentral " field. 



Presumably on account of the weakly developed internal layer of large pyramidal cells 

 there is no true reduplication of the line 1 . 



Radiations of Meynert. 



Interesting variations are seen in these radiations. In the " intermediate precentral " area 

 they formed stout fasciculi, and fibres of the large evenly-medullated variety helped to 

 strengthen each column. In the " frontal " area there is an appreciable attenuation of the 

 bundles, and fibres of the large order are rare, but those of medium size common. Coming 

 to the " prefrontal " cortex the attenuation is more pronounced, and large and medium-sized 

 fibres having disappeared the fasciculi are composed entirely of delicate varicose elements. 



This change in the constitution of the radiations is a useful guide to territorial 

 differentiation and must have some functional significance. 



Although I have made counts of the number of radiations in a transverse millimetre 

 of substance, I cannot say that the different regions show variations in this respect. 



1 I have stated that in the "prefrontal" cortex a reduplication of the stripe of Baillarger is noticed at the lip 

 of the convolutions. But this appearance is not peculiar to the "prefrontal" cortex, and is, moreover, a spurious 

 formation. In studying the lamination of a given part, the typical arrangement is always to be looked for along 

 the crown or down the wall of the gyrus, never at the lip, for here, probably owing to physical causes, the stratification 

 suffers disturbance ; in particular it may be noticed that the layer of large external pyramidal cells becomes drawn out 

 and acquires an abnormal depth, and believing that the line of Baillarger is in large measure composed of offshoots 

 of the large pyramidal cells I also think that this disturbance accounts for the spurious reduplication of the line 

 in question. 



