THE NERVOUS SYSTEM 1447 



of the cortex of the same hemisphere, and they are of two kinds, 

 short and long. 



The short association fibres pass between contiguous gyri, ex- 

 tending in their course across the bottom of the sulci. Some of 

 them lie beneath the grey cortex, whilst others are contained within 

 its deep part. 



The long association fibres pass between portions of the grey 

 cortex, which are at some distance from each other. They are 

 arranged in bundles, the chief of which are as follows : (i) the 

 superior longitudinal fasciculus ; (2) the inferior longitudinal 

 fasciculus ; (3) the perpendicular fasciculus ; (4) the uncinate 

 fasciculus ; (5) the cingiilum ; (6) the occipito-frontal fasciculus ; 

 and (7) the fornix. 



The superior longitudinal fasciculus consists of fibres which 

 extend from the frontal to the occipital lobe. Posteriorly many 

 of its fibres sweep downwards and forwards into the temporal 

 lobe, and from this circumstance it is sometimes spoken of as the 

 arcuate fasciculus. 



The inferior longitudinal fasciculus connects the occipital and 

 temporal lobes, its fibres being disposed upon the outer walls of 

 the posterior and descending comua of the lateral ventricle. 



The perpendicular fasciculus connects the inferior parietal gyrus 

 with the occipito-temporal gyrus. 



The uncinate fasciculus crosses the stem of the fissure of Sylvius, 

 and connects the frontal and temporal lobes. 



The cingulum is connected with the limbic lobe, and lies upon 

 the under surface of the calloscd gyrus and the upper surface of 

 the hippocampal gyrus. Its fibres connect the gyri of the limbic 

 lobe with the cerebral cortex. 



The occipito-frontal fasciculus connects the frontal with the 

 occipital and temporal lobes. According to Dejerine the tapetum 

 of the corpus callosum belongs to this fasciculus, and not to the 

 corpus callosmn. The fasciculus Ues internal to the corona radiata, 

 in intimate relation to the nucleus caudatus, and, as the fibres pass 

 backwards, they lie on the outer walls of the descending and pos- 

 terior comua of the lateral ventricle. 



The fornix connects the hippocampus major of one side with the 

 corresponding corpus albicans, and, through the latter, with the 

 optic thalamus by means of the bundle of Vicq d'Azyr, the fibres 

 of which arise in the corpus albic^is. 



Peculiarities of the Cerebral Cortex — i. Calearine Area. — This area is 

 situated on the mesial surface of the occipital lobe, in close proximity to 

 the calearine fissure, and it is known as the visual area. In this region the 

 outer band of Baillarger is very conspicuous, whilst the inner band of Baillarger 

 is absent. 



2. Rolandic Area. — In this region, more especially in the cortex of the 

 precentral gyrus, there are groups of very large pyramidal cells, which are 

 known as the giant-cells of Betz, and nerve-fibres are present in large numbers. 



3. Hippocampal Area. — The hippocampus major corresponds to the hip- 

 pocampal or dentate fissure, and is produced by an infolding of the cerebral 



