24 



above the level of the first spinal nerve, the n/ammalinn hypo- 

 glossus, these nuclei disappear altogether as continuous col- 

 lections of nerve-cslls. A small number remain associated 

 as the nucleus of the abducens, while the remaining neurones 

 become scattered through the formatio reticularis (Fig.S.c.n. 

 and t. n. ) 



The intermediate 2one and the dorsal cornu of the cord 

 are relatively small in si^e, but as the paired halves diverge 

 to right and left of the fourth ventricle they increase in 

 mass and assume characters and functions of a special order 

 for each region. The intermediate gray matter contributes the 

 lobus vagi and the viscero-motor nucleus of the oblongata; 

 while the dorsal cornu becomes specialized as the general cuta- 

 neous nucleus. We will note each of these in turn. 



The lobus vagi is a longitudinal elevation in the lateral 

 wall of the fourth ventricle ( F'ig. 1, l.vg. ) . Anatomically, it 

 is one of the most striking features of the oblongata because 

 of the row of bead-like prominences into which its surface is 

 thrown. The position of the structure as seen in a transverse 

 section is represented in Pig.?, l.vg. The lobus vagi is the 

 terminal station for communis components of the Vll, IX, and 

 X nerves; see Subsection 4. Certain of these fibres, instead 

 of passirg directly to their termination here, enter- a compact 

 bundle and run posteriorly to the spinal cord. This tract is 

 known as the fasciculus communis. Its position in the oblonga- 

 ta will be seen in Fit-'.?, f.c. 



