424 



PHYSIOLOGY 



pontis, come there in relationship with the fibres forming the middle peduncles 

 of the cerebellum and derived chiefly from the lateral lobes of the cerebellum. 

 These fibres may therefore be regarded as the efferent side of the great 

 cerebro-cerebellar connections of which the afferent side is represented 



by the fibres efferent so far as concerns the 

 cerebellum which pass from the cerebellar 

 cortex to the dentate nucleus and thence by 

 a fresh relay in the superior cerebellar 

 peduncles to the red nucleus, optic thalamus, 

 and cortex of the opposite side. The devel- 

 opment of these fibres, as of the lateral 

 lobes of the cerebellum, is largely proportional 

 to the growth of the cerebral hemispheres. In 

 cases where there has been congenital atrophy 

 of one cerebral hemisphere, the crusta of the 

 same side and the lateral lobe of the cerebellum 

 of the opposite side also fail to develop. 



Fid. 216. Transverse section 

 through mid-brain to show 

 position of fillet and pyramid. 



AQ, anterior corpus quadri- 

 gemmum ; dV, descending root 

 of fifth nerve ; F, fillet (I, lateral, 

 and m, mesial fillet); Pyr, pyra- 

 mid ; Fr. fibres from frontal lobe 

 to pons ; TO, fibres from tem- 

 poral and occipital lobes to 

 pons ; Ne, fibres from nucleus 

 caudatus to pons ; III, root of 

 third nerve ; S, Sylvian iter ; 

 Rn, red nucleus. 



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 * association 

 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 



Fm. 217. Chief association bundles of the cerebral hemispheres. .(CUNNINOH*AM.) 

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



as associated activity between the various portions of the cortex is gradually 

 acquired by education. 



The long association fibres may !>< divided into five groups as follows: 

 (a) The uncinate fasciculus passes t'nmi the orbital convolutions of the frontal lobe 

 to the front part of the temporal lobe round the stem of the Sylvian fissure (Fig. 217). 



