652 



CEREBELLOSPINAL CONN ECTIONS. 



not only is the course of the fibres interrupted, but there is in it an increase in the number of 

 fibres, for far more fibres proceed peripherally from the grey matter of the medulla and spinal 

 cord, than are sent to it from the central grey matter of the brain. 



As to the arrangement of the fibres in this second system, the fibres descending from the 

 caudate and lenticular nucleus (8, 8) are grouped into a special channel, which descends 

 through tfie crusta of the cerebral peduncle, and enters the medulla oblongata, or (according to 

 Flechsig) the pons. In the same way there proceeds from the thalamus (S) and corpora quad- 

 rigemina (6, 6) a bundle which descends through the tegmentum (H) of the cerebral peduncle. 

 Both sets of fibres those in the crusta and in the tegmentum come together in the cord. 



According to Wernicke, the lenticular nucleus and caudate nucleus are not the parts of the 

 brain into which, from the cerebral cortex and through the corona, radiate fibres enter; but 

 they are independent parts, analogous to the cortex, and from them fibres proceed. These 

 fibres pass into the crusta and run along with those fibres proceeding from the thalamus and 

 corpora quadrigemina. 



According to Meynert, the fibres which pass from the thalamus and corpora quadrigemina, 

 through the tegmentum of the cerebral peduncle, are reflex channels ; so that these portions of 

 the brain are centres for certain extensive, co-ordinated reflexes. This is shown by the fact 

 that, after destruction of the voluntary motor paths, in animals, the technical completeness of 



movements, so far as these are discharged 

 reflexly, is still intact. These channels 

 run in the spinal cord, at first on the 

 side (m), and probably ultimately cross in 

 the spinal cord itself. 



The Third Projection System. Lastly, 

 from the central tubular grey matter there 

 proceeds the third system, or the peri- 

 pheral nerves, motor and sensory. These 

 are more numerous than the fibres of the 

 second system. 



[While there are three concentric tubes 

 in the spinal cord ( 359), in the part 

 which forms the brain an extra layer of 

 grey matter is added the peripheral 

 grey tube constituting the cortex of the 

 cerebral hemispheres and cerebellum, and 

 the corpora quadrigemina. Thus, the 

 white matter lies between two concentric 

 masses of grey matter (Hill).] 



Connections of the CerebeUum. The 

 cerebellum consists of two somewhat flat- 

 tened hemispheres connected across the 



Floor of the 4th ventricle" ndTthe connections of the mid(ile U by *{?? 1?^ 



cerebellum. On the left side the three cerebellar form . P^l, 1. /wt 



peduncles are cut short ; on the right the connec- P[ tlon , ? f ? h 0IK ??' tv L A til 



tions of the superior and inferior peduncles have lo f\ f *" * T Zt ^t Zlf 



been preserved/while the middle one has been cut the e \ lob ^S^SJS^ZSS hv 



short! 1, median groove of the 4th ventricle with e ^. m hlT f ^ -f^ZlJ^r.Jl 



the fasciculi terete! ; 2, the striae of the auditory sul ^? " *J f ^1*^ W*, M!Zl 



nerve on each side emerging from it ; 3, inferior ? ^^^ S^T^l^^ ^ 



peduncle; 4, posterior p^mid and 'clava, with ^^^J^^^^T^ 



the calamus scriptorius above it : 5, superior ^P 6 " 01 peauncies connect it witn 



peduncle ; 6, finite the side ef the era. cerebri ; ^r^ltT*^ C* 



Fig. 462. 



8, corpora quadrigemina. 



cerebri. The fibres come from the lower 

 part of the cerebellum and from its dentate 

 nucleus, and a number of these fibres decussate in the upper part of the pons and the tegmen- 

 tum, some of them becoming connected with the red nucleus in the tegmentum of the opposite 

 side. Some of the fibres seem to connect the cerebellum with the frontal lobes, constituting a 

 fronto-cerebellar tract, and they are also crossed (Gowers). When the cerebellum is congeni- 

 tally absent, these fibres are absent (Flechsig). By the two inferior peduncles or restiform 

 bodies, it is connected with all the columns of the spinal cord, and it is to be noted that some of 

 the fibres forming these peduncles are connected with the olivary body of the opposite side, so 

 that they decussate. The middle peduncle is formed by the transverse fibres of the pons (figs. 

 462, 503). It is evident that there is a cerebello-spinal, as well as a cerebro-spinal connection 

 to be considered.] 



[The grey matter is external and the white internal, and on section the foliated branched 

 appearance of the cerebellum constitutes the arbor vitce. Within each lateral lobe is a folded 

 mass of grey matter like that in the olivary body, called the corpus dentatum, and from its 



