STRUCTURE <)!' Till-: l'o.\s 



813 



lateral margin of the section external to the lirarhiuni conjunct ivnin. The ine.~en- 

 rephalic rout of the trigeminus occurs in the dorso-lateral margin of transverse sec- 

 tions through this region, and this is the only one of the cranial nerves represented 

 here. 



The transverse (Hires of the ventral part of the .-ectiun (puns proper), and there- 

 fore the lirachia pout is. consist of fibre* coursing in opposite directions. Many are 

 fibres which are outgrowths of the Pnrkinje cells of the cortex of the cerebellar 

 hemispheres, and pass either directly to the hemisphere of the opposite side or turn 

 upwards in the raphe to course longitudinally in the brain-stem both towards the 

 spinal cord and towards the iiiesencephaloii. < Hhers terminate in the grey substance 

 of the pons. ( Hhers are fibres which arise in the prey substance of the pons and pass 

 to the cerebellar hemispheres, and still others are the cerebro-pontile fibres, chiefly 

 from the temporal lobes. 



The grey substance of the pons (nuclei pontis) occurs quite abundantly. At 

 the inferior border of the pons it is found concentrated about the then more ac- 

 cumulated bundles of the emerging pyramids, and serial sections show it to be a 



FIG. 606. DIAGRAM SHOWING CONNECTIONS OF THE FIBRES OF THE PONS. 

 The plane of the section is obliquely transverse or parallel with the direction of the brachia pontis. 



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l-UXTILK J'A Til 



LOXGITI'DIXAL (PYRAMIDAL) FASCICULI 



direct upward continuation of the arcuate nuclei of the medulla oblongata below. 

 Higher up it is dispersed throughout the central area in the interspaces between the 

 transverse pontile and longit udinal pyramidal fasciculi. A large portion of the nerve- 

 fibres passing through it are thought to be interrupted by its cells, which thus serve 

 as links in some of the neurone chains represented by the fibres of the pons. Of the 

 more important of such relations, the following are said to exist : 



(1) Fibres which arise in the cortex of one cerebellar hemisphere and terminate 

 about cells of the nucleus pontis of the same and opposite side of the mid-line. These 

 cells give off axones which pass to the other cerebellar hemisphere. In this relation 

 the nuclei pontis are analogous to the arcuate nuclei, save that the cerebellar fibres 

 interrupted in the former are connected with the cerebellum by way of the brachia 

 pontis instead of the restiform bodies. 



(2) Certain of the descending cerebro-pontile fibres terminate about cells of the 

 nuclei pontis. Such cells give off fibres which probably, for the most part, pass to 

 the cerebellar hemispheres, the impulses from the cerebral hemisphere of one side 

 being conveyed chiefly to the opposite cerebellar hemisphere. 



