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The viscero-Diotor nucleus is a column of l^iri^e nerve -cells 

 imbedded in the lateral wall of the fourth ventricle (F'i^.?, 

 v.tn.n.). Different portions of this coluan are known as the 

 nucleus ambiguus, and the motor nuclei of the VI] and V, res- 

 pectively. The axones for the motor roots of the V, VII, 

 IX, and X nerves take their origin from these nerve-cells. 

 It is a curious fact, however, that but few of the axones pass 

 directly into their nerve-roots, but take a course first in the 

 fasciculus lon^itudinalis dorsalis. This is a massive, paired 

 tract, the two bundles lyin? side by side beneath the floor of 

 the fourth ventricle (["ig. ?, f . l.d. ). There are present in the 

 dorsal longitudinal bundle nerve-fibres from several sources. 

 Into this crowded highway the axones from the viscero-motor 

 nucleus penetrate, to finally emerge as the motor roots of 

 their respective nerves. 



The dorsal cornu of the cord is continued into the oblon- 

 gata in an enlarged condition, and it becomes associated with 

 sensory fibres of the V, IX, and X nerves to form the general 

 cutaneous nucleus (Big. f', g.c. n. ). The neurones of this nucleus 

 provide a priniary termination for certain general cutaneous 

 fibres; while others turn backward to the cord as the spinal V 

 tract. At the posterior levels of the oblongata this system 

 appears dorsal to all other structural features, the pair form- 

 ing the rounded, crest-like margins to the fourth ventricle. 

 Proceeding anteriorly, the nucleus is pushed into a position 

 both more ventral and more lateral by the superposition of a 



