THE PONS 



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THE PONS 



The pons (Varolii) is that part of the brain stem which lies between the medulla 

 and the cere])ral i^eduncles; it is marked off from these ventrally by anterior and 



Fig. 502. — Cross -section- of Medui.l.\ Obloxg.\t.\ of Horse, P.\ssing through F.\ci.\l Nucleus. 

 Cr, Corpus restiforme; D, dorsal longitudinal fasciculus; Fa, a.scendiiig part of facial nerve; L, fillet; 

 JVT", nucleus of facial nerve; NS, triangular nucleus of vestibular root of eighth nerve; N8' , spinal root of eighth 

 nerve; Py, pyramid; Ra, raphe; R7, radicular part of facial nerve; R8, vestibular root of eighth nerve; Sg, 

 substantia gelatinosa; Ta, posterior end of tuberculum acusticum; V , spinal root of trigeminus. (Ellenberger- 

 Baum, Anat. d. Haustiere.) 



posterior grooves. Viewed from ])elow it is elongated transversely, convex in both 

 directions, and presents a wide shallow median groove (Sulcus basilaris), which 



f/ R, 



Fig. 503 — Cro.ss-section' of Medull.\ Oblong.vt.*. of Horse; Section P.\sses through Middle of Corpus 



Tr.\pezoideu.\i. 

 Cr, Corpus restiforme; D, dorsal longitudinal bundle; Fa, ascending part of facial nerve; Fa' , emergent or 

 descentling part of facial nerve; R7 , root of facial nerve; L, fillet; M, central white matter of cerebellum; N6, 

 abducens nucleus; XS, triangular nucleus; N8', nucleus of Deiters; S8", tuberculum acusticum; Oo, anterior 

 olive; Py, pyramid; R6, root of abducens nerve; R7, root of facial nerve; Re, cochlear nerve; Rv, vestibular nerve; 

 Sg, substantia gelatinosa; T, corpus trapezoideum; V, spinal root of trigeminus. (Ellenberger-Baum, Anat. d.. 

 Haustiere.) 



lodges the basilar artery. Laterally a large part of its mass curves upward and 

 backward into the base of the cerebellum, forming the middle cerebellar peduncle 

 (Brachium pontis). The superficial origin of the trigeminal (fifth) nerve is at the 



