504 DAVIDSON BLACK 
Motor facial, glossopharyngeal and vagal nuclei and roots (Nu. 
et rad. mot. Nn. VII-IX—X). In Polyodon the caudal viscero- 
motor column lies throughout within the ventricular gray and 
extends from a level about midway between the emergent motor 
roots of the facial and glossopharyngeal nerves, to a point some 
distance caudad of the first spino-occipital motor rootlet (figs. 
18,19 and 25 A). As in Selache, within the limits of this column 
are included all the cells of origin of the motor VII-IX—X 
roots. 
R.VII.m.asc 
vas 
Fib.arc.int. 23 
“er \R.desc.V 
Trt. beet \R.ViLm 
Tr.sec.com. 
20 20 a 
Fig. 20 Polyodon spathula. Transverse section of brain stem at the exit 
level of motor facial root. 
Fig. 20a Portion of transverse section of brain stem at somewhat more 
caudal level than the preceding to illustrate the relations of the ascending motor 
facial root. Abbreviations: N.1.1.VII., nervus lineae lateralis; R.VII.m., emer- 
gent fibers of motor facial root; R.VII.m.asc., ascending bundle of motor facial 
root; R.VII.s., sensory facial root. Other abbreviations as in figures 18 and 19. 
The fibers of the motor VII root arise from cells occupying 
the rostral end of the caudal visceral motor column. They 
collect to form a compact bundle which courses rostrad for a 
considerable distance in the ventricular gray beside the fasciculus 
longitudinalis medialis, before they arch laterally and emerge 
on the ventro-lateral periphery of the medulla (figs. 19, 20 
and 20 A). 
The glossopharyngeus motor root arises from cells of the 
viscero-motor column situated immediately caudad of the motor 
