THE PONS 



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and the cerebellospinal fasciculus or direct cerebellar tract. The dorsal longitudinal fascic- 

 ulus corresponds to the ventral ground-bundle of the spinal cord, displaced dorsally by the decus- 

 sation ot the pyramids and fillet. In the posterior part of the medulla it is not marked off from 

 the hllet, along the dorsal edge of which it lies, From the level of the hypoglossal nucleus forward 

 It IS distinct and can be traced as a conspicuous tract in the ventral margin of the gray matter of the 

 floor of the fourth ventricle and of the central gray matter of the mid-brain. Ventral to the resti- 

 torni body and related laterally to the external arcuate fibers there i.s a considerable bundle of 

 longitudinal fibers, the spinal root (Tractus spinalis) of the fifth nerve; medial to it is the 

 terminal nucleus of the sensory root of the nerve. 



f'- "'?kV 



Fig. 633. — Cross-section of Medulla Oblongata of Horse, Passing through Facial Nucleus. 

 Cr, Corpus restiforme; D, dorsallongitudinal fasciculus; Fa, ascending part of facial nerve; L, fillet; iV7, nucleus 

 of facial nerve; NS, triangular nucleus of of vestibular root of eighth nerve; N8', spinal root of eighth iierve; Py, pyra- 

 mid; iBa, raphe; i27, radicular part of facial nerve; 7^5, vestibular root of eighth nerve; 5(7, substantia gelatinosa; Ta, 

 posterior end of tuberculum acusticum; V, spinal root of trigeminus. (EUenberger-Baum, Anat. d. Haustiere.) 



Fig. 634. — Cross-section of Medulla Oblongata of Horse; Section Passes through Middle of Corpus 



Trapezoideum. 

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

 scending part of facial nerve; L, fillet; i\f, central white matter of cerebellum; N6, abducens nucleus; A'"5, triangular 

 nucleus; NS', nucleus of Deiters; N8", 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 trigemious. (Ellenberger-Baum, Anat. d. Haustiere.) 



The Pons 

 The pons is that part of the brain stem which hes between the medulla and 

 the cerebral peduncles; it is marked off from these ventrally by anterior and 



