MOTOR NUCLEI IN PHYLOGENY 243 
The dorsal motor VII nucleus occupies a central position 
within the formatio reticularis, and its entire bulk les rostrad 
of the exit level of the motor VII root. At its rostral end this 
nucleus becomes continuous with a cell group which gives ori- 
gin to a part of the motor V root, so that the cell column may be 
considered as a motor V—VII nuclear complex. Thus relations 
obtain here that are essentially similar to those of the V—VII 
motor nucleus in Chrysomitris which have been described by 
Kappers (32). At its caudal end this nucleus is somewhat en- 
larged and is prolonged ventrad to a level below that of the upper 
margin of the laterally situated nucleus olivaris superior. 
The ventral motor VII nucleus in Cacatua is much smaller 
than the dorsal cell complex and lies very close to the ventro- 
lateral periphery of the medulla just medial to the nucleus oli- 
varis superior (fig. 6). The sagittal relations of the two motor 
VII nuclei are indicated in the reconstruction chart, figure 16 
D, page 260. 
From their nuclei of origin the path of the emergent motor VII 
fibers to the periphery is indirect. From both dorsal and ventral 
cell groups these radicles pass dorso-medial and become collected 
in the dorsal tegmentum above and to the lateral side of the 
abducens nucleus, where their direction changes caudad and 
finally laterad to emerge on the lateral surface of the medulla for 
the most part dorsal to the radix descendens V, though numbers 
of the emergent VII fibers pierce the latter structure before 
making their exit (figs. 5 and 6). 
The origin and relations of the motor VII nerve in Ciconia 
have already been described and figured by Kappers (382, figs. 
46 and 69; 34, fig. 69), and in most essentials they agree with 
those in Cacatua. The dorsal motor VII cell group is, however, 
smaller in Ciconia than in Cacatua, and its cells do not become 
intermingled rostrally with motor V elements; while the ventral 
by Wallenberg and had also been recorded by Kosaka and Hiraiwa (39) in Gallus. 
Indeed, the latter authors have described three facial nuclei in this bird: a chief 
or ventral nucleus, a dorsal or digastric nucleus, and a cell group associated with 
the latter and termed the ‘Nebenkern.’ It is highly probable that this ‘Neben- 
‘kern’ is represented in Cacatua by the caudo-ventral extension of the dorsal 
motor VII nucleus of this form (vide infra). 
