650 THE NEKVOUS SYSTEM. 



the hippocampal gyrus, to the uncus and the temporal pole. The cingulum 

 is composed of several systems of fibres which run only for short distances 

 within it. 



The fasciculus longitudinalis superior is an arcuate bundle which is placed on the 

 lateral aspect of the foot or basal part of the corona radiata and connects the 

 frontal, occipital, and temporal regions of the hemisphere. It lies in the base of the 

 superior operculurn and sweeps backwards over the insular region to the posterior 

 end of the lateral cerebral fissure. Here it bends downwards round the posterior 

 end of the putamen and proceeds forwards in the temporal lobe, to reach its anterior 

 extremity. As it turns downwards to reach the temporal lobe numerous fibres 

 radiate from it into the occipital lobe. 



The fasciculus longitudinalis inferior is a very conspicuous bundle which extends 

 along the whole length of the occipital and temporal regions (Fig. 577, B). Curran 

 has recently demonstrated that the fasciculus uncinatus and the inferior longi- 



Acoustic radiation 

 Transverse temporal gyrus | Fasciculus longitudinalis superior passing 



Short association fibres over the lateral side of the 



^^BMfc^ViBAfefeiiiBli^fei^ Fasciculus occipito-frontalis infe: 



Fasciculus longitudinalis 

 superior 



Fasciculus occipito-frontalis inferior 



Fasciculus unciuatus 



Fissura lateralis 



Optic radiation seen in a gap cut put of 

 the inferior occipito-frontal fasciculus 



FIG. 578. DISSECTION TO DISPLAY SOME OF THE PRINCIPAL ASSOCIATION BUNDLES OF THE CEREBRAL 



HEMISPHERE. 



The occipito-temporal extremity of the superior longitudinal bundle has been cut away in order to expose the 

 subjacent inferior occipito-frontal bundle, parts of which in turn have been removed to expose the origin 

 and termination of the still deeper optic radiation (coloured blue) ; (acoustic fibres, yellow). 



tudinal bundle are merely the shorter inferior fibres of a much bigger and longer 

 tract (Fig. 578), to which he has applied the name occipito-frontalis inferior. The 

 arrangement of these longitudinal tracts may be put concisely by saying that fibre 

 connexions of differing lengths link together the various cortical areas in the 

 longitudinal direction, the deeper fibres (i.e. those furthest removed from the 

 cortex, medial, lateral, superior or inferior) being progressively longer than the 

 superficial. The deepest fibres extend the whole length of the hemisphere and 

 are pushed aside by the insula (Fig. 578) and collected into two great bundles, a 

 superior longitudinal and an inferior occipito-frontal bundle. In the occipital 

 lobe the inferior occipito-frontal bundle is placed on the lateral aspect of the 

 optic radiation, which takes a similar direction and from which it is distinguished 

 by the greater coarseness of its fibres (Figs. 576, p. 649 ; 578 ; 559, p. 631). 

 It is not present in the macaque monkey (Ferrier and Turner), but is well 

 developed in the orang and the chimpanzee. 



