THE PONS 775 
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 of the pyramids and fillet. In the posterior part of the medulla it is not marked off from 
the fillet, 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- 
form body and related laterally to the external arcuate fibers there is 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. 
Fic. 633.—Cross-secTION OF MepuLLA OBLoNGATA OF Horse, PassiNG THROUGH FactaL NUCLEUS. 
Cr, Corpus restiforme; D, dorsal longitudinal fasciculus; Fa, ascending part of facial nerve: L, fillet; N7, nucleus 
of facial nerve; NS, triangular nucleus of of vestibular root of eighth nerve; N8’, spinal root of eighth nerve; Py, pyra- 
mid; 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.) 
Fic. 634.—Cross-section oF Mepttta OBLoNGATA oF Horse; SECTION Passes THROUGH MuppLE oF Corpts 
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; M, central white matter of cerebellum; N6, abducens nucleus; NS, 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; 7, corpus 
trapezoideum; JV, spinal root of trigeminus. (Ellenberger-Baum, Anat. d. Haustiere.) 
THE PONS 
The pons is that part of the brain stem which lies between the medulla and 
the cerebral peduncles; it is marked off from these ventrally by anterior and 
