404 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



frontal extremity. They belong to the great system of the 

 fasciculus arcuatus, which connects together the most remote 

 provinces of the cortex of the convexity. Some of its fasciculi 

 traverse the uppermost regions of the claustrum. 



. In addition the fasciculi (unc) of the fasciculus uncinatus are 

 seen, which unite by the shortest path the frontal and tem- 

 poral extremities of the cerebral lobes, and are concentrically 

 surrounded by the tract of the fasciculus arcuatus, which 

 similarly connects all the stations between the same terminal 

 points. The fasciculus uncinatus traverses, throughout its 

 whole extent, the mass of the claustrum and the nucleus of the 

 amygdala. With the anterior and uncinate portion of this 

 fasciculus are intimately united tracts of associative or con- 

 necting fasciculi in the form of flat layers, corresponding to the 

 extent of the claustrum. They form an important part of the 

 white matter of the island (of Reil) and the outer capsule, and 

 : there enclosing the fusiform cells of the claustral formation, 

 .unite, as do the fibrse arcuatse, along the whole cortex with 

 the same formation. It is only corresponding to an espe- 

 cially rich aggregation of the connecting systems, that there 

 is an independent development of the innermost layer of the 

 cortex as a special organ. 



At Ig of the same figure, fasciculi are further shown, which, 

 ^constituting the fasciculus longitudinalis inferior, are directed 

 'from the occipital vertex towards the temporal prominence of the 

 hemispheres. Along the median surface, as is well known, the 

 medulla of the gyrus fornicatus encircles the corpus callosum in 

 an arcuate manner, from the frontal to the temporal extremity 

 of the hemispheres, and is thus for the cortex of the inner sur- 

 face, analogous to the fasciculus arcuatus of the convexity. 

 To this belongs the short medullary tract, marked min fig. 241. 

 A portion of the medulla of the olfactory lobe belongs also, as 

 Gratiolet has correctly indicated, to the fibres arcuatce, since 

 just as the cortex, both of the external and of the internal 

 olfactory convolution, fuses with the two extremities of the 

 gyrus fornicatus, so the medulla of the former is continuous 

 with the medulla of the latter. These two regions of the cortex 

 are in the first place connected by the long inferior fasciculi of 

 the medulla of the convolution immediately covering the corpus 



