STRUCTURAL ARRANGEMENTS OF CEREBRUM 481 



II. ASSOCIATION FIBRES 



These fibres serve to unite different portions of the cortex of the 

 same hemisphere and may be classified into short and long associa- 

 tion fibres. The short association fibres pass round the bottom 

 of the sulci in U-shaped loops connecting adjacent convolutions. 

 These fibres are some of the latest to acquire a medullary sheath and 

 probably first become functional as associated activity between the 

 various portions of the cortex is gradually acquired by education. 



The long association fibres may be divided into five groups as 

 follows : 



(a) The uncinate fasciculus passes from the orbital convolutions 

 of the frontal lobe to the front part of the temporal lobe round the 

 stem of the Sylvian fissure (Fig. 216). 



ASSOCIATION 

 TlERES 



FIG. 216. Chief association bundles of the cerebral hemispheres. (CUNNINGHAM.) 

 A. Outer aspect of hemisphere. B. Inner aspect of hemisphere. 



(6) The cingulum is closely associated with those parts of the cere- 

 bral cortex known together as the limbic lobe. In front it originates 

 in the neighbourhood of the anterior perforated space, passes round 

 the genu of the corpus callosum, and then is carried backwards over 

 the upper surface of this body to its hinder end, where it turns 

 round and is distributed to the hippocampal gyrus and to the temporal 

 lobe. 



(c) The longitudinal superior fasciculus lies in the base of the 

 frontal and parietal lobes, and passing from before backwards connects 

 the frontal, occipital, and temporal parts of the cerebral cortex. 



(d) The longitudinal inferior fasciculus runs along the whole length 

 of the occipital and temporal lobes, being situated behind on the outer 

 aspect of the optic radiation. 



(e) The occipito-frontal fasciculus lies on the inner aspect of the 

 corona radiata in intimate relation to the caudate nucleus, and pro- 

 jects out over the upper and outer aspect of the lateral ventricle 



immediately outside the ependyma, 



31 



