152 Temporal Lobe and Auditor;/ Areas [CHAP. 



Interradiary Plexus and Association Fibres. (Plate XIII, fig. 2.) 



The long, stout fibres which constitute such an important feature of the radiary zone 

 in the transverse temporal gyri are not nearly so obvious on the exposed surface of the 

 first temporal convolution, at the same time they are present in considerable number and 

 they also show an inclination to join and proceed surfacewards in the radiary fasciculi. 



The radiary zone has great general depth, and when compared with the same zone in the 

 more outlying convolutions a difference in the general fibre-wealth is manifest. 



White Substance. 



Another point of difference between this intermediate field and more outlying parts is 

 that the depth of staining of the medullary projection immediately underlying the cortex 

 is great, a feature which agrees with its superiority in fibre-wealth. 



Summing up the characters of the fibre-arrangement in this part, we may say that, 

 compared with the transverse temporal area, while the cortical depth is greater, it is above 

 all things wanting in large deeply-placed association fibres, and that compared with more 

 outlying regions, it possesses a pronounced superiority in general fibre-wealth. 



GENERAL FIBRE ARRANGEMENT IN THE TEMPORAL LOBE. TYPE No. 3. (Plate XIV, fig. 1.) 



The types of arrangement above mentioned are quite special, and pertain, as I shall 

 presently show, to definite areas ; I have now to describe the formation which is present 

 in other parts of the temporal lobe, and which we are to regard as the general type. 



Zonal Layer. 



This layer is poorly developed compared with the same layer in the areas previously 

 described ; it is made up of delicate fibrils, coarse varicose fibres are only occasionally seen, 

 and large medullated fibres are absent. 



iS upr a radiary Layer. 



The outer third of the layer is pale and badly supplied with fibres, but in the inner 

 two-thirds there is a thin plexus of delicate fibrils in the midst of which run a few long 

 fibres almost of medium size, so adding to its density. No line of Kaes is recognisable. 



Line of Baillarger. 



The line of Baillarger though plainly visible cannot be described as well-developed ; a 

 few long medium-sized fibres are recognised in it, but it is mainly composed of short fibres 

 delicate in calibre. 



Radiations of Meynert. 



These are peculiar, inasmuch as they frequently pierce the line of Baillarger and spread 

 up into the supraradiary layer ; otherwise they are thin and slender, and the entire absence 

 of fibres of large calibre is an important feature. 



