THE 



OF THI-: H.\('i-;i'n.\i.i>\ 



SSI 



eighth nerves, supply their lil>rcs and tin- adjacent parts, and they end in the grey mieli i with 

 which the ner\e lilires are connected. 'I he ml, , nmiiuli tirli rii-x enter the- siirlaee.- of tin- ; 

 irregularly and break up into capillarie- in it-. substance. The veins form :i plexus on the 

 surface. The upper and lateral part <>! this plexus is drained into the liasilar \eiii on each side. 

 and the lower part is connected by efferent channels \\ith the inferior |>etrosal sinus and the 

 cerebellar veins. 



The Blood-vessels of the Medulla Oblongata. - -Tin- arteries of the medulla are derived 

 directly from the vertebral arteries, from their anterior and posterior spinal and [Histerior inferior 

 cerebellar branches, and from the basilar artery. The branches of these vessels form a plexus in 

 the pia mater trom which, and from the arteries themselves, three main groups of vessels pass 

 into the medulla the chorioidal. the central, and the |H>ripheral. The chorioidal arteries are 

 derived chiefly from the posterior inferior cerebellar arteries. Their relation to the medulla is 

 de-cribed on p. MO. The anterior central arteries rise from the anterior spinal arteries, from 

 the basilar arterv, and from the peripheral plexus; thev pass backwards along the raphe, 

 supplying the adjacent parts of the ventral funiculi and the olivary bodies and they break up 

 into fine terminals in the grey substance of the door of the fourth ventricle around the nuclei 

 of the cranial nerves. The posterior central arteries spring from the posterior spinal arteries. 

 they pass down the median septum of the lower part of the medulla and supply the adjacent 



I'M. 654.^SHOW1NG THE CAPILLARY SfPPLY OF THE ("KKKIIKLLAR CORTEX. (After Aby, 



"Journal of Comparative Neurology," Vol. IX.) 



Capilluriii 



ofmvlrcultir 



layer 



Rfcui-rent 



layer 



| Rtturrrnt ro- 



piUariti to 



nujteottar 



latrr 

 i Jl'M-TION 



lit KIKTSI 



A\U MK- 



liri.l.A 



>' of 



mnlccular 



Or' en I :- 



TI-:.\ AKD 

 M/-.-II- 



I /./..I 



Arlfriole 



nervous substance. The peripheral arteries, like those of the spinal cord, are separable into 

 radicular and intermediate groups. The nufteu/ar art eriea pass from the anterior and posterior 



spinal brandies and from the trunks of the vertebral arteries and accompany the fibres of the 

 last four cranial nerves into the substance of the medulla. They supply the nerve-roots and 

 adjacent \\hitesubstancc and they terminate in capillaries in the grey substance of the lateral 

 part of the lloor of the ventricle. The -pritig trom the art. 



previously named and from the peripheral plexus, and they pas> directly into the columns of 

 the medulla, where they terminate in a capillary plexus which supplies t he \\'hite Mibr-l a nee and the 

 grey nuclei: some of these arteries more es|>ecially those derived from the jiostenor inferior 

 cerebellar and the posterior spinal arteries, extend inwards to the lateral part of the floor of tin- 

 fourth ventricle. 



The veins which issue from the medulla form a peripheral plexus in the pia mater in which 

 there are tuo main longitudinal channels, an anterior median and a posterior median vein. 

 The former communicates below with the anterior median vein of the cord, and above with the 

 veins of I he pons and with the veins which accompany the hypoglos-al nerves. The latter \ 

 y into the internal jugular veins. The ])osterior median vein i-. continuous below will. 

 corresponding vein of the cord, and above, in the region of the calamus script orius. it di\ides 

 into branches which join the radicular veins. The blood is carried away from the peripheral 

 56 



