MOTOR NUCLEI IN PHYLOGENY 267 
The gustatory organs of birds are but poorly developed (vide 
supra) and the pars intermedius VII in these forms is reduced 
toa minimum. Kappers (36) has shown that but few gustatory 
fibers can enter the brain stem by the latter path in these forms, 
the majority of the special visceral afferent impulses being trans- 
mitted by the glossopharyngeal and vagus nerves. This author 
pointed out further that the gustatory IX—X components termi- 
nate in a nucleus which is evidently the homologue of the mam- 
malian dorso-lateral and dorso-median nuclei of Staderini. 
The IX—X pharyngeal and oesophageal musculature in birds 
acts. coordinately during deglutition or in antiperistaltic move- 
ments of the foregut in practical independence of V—VII effectors. 
This reflex action of the dorsal motor IX-X nucleus is chiefly 
inaugurated by afferent impulses of both general and special 
visceral nature which enter the brain stem almost wholly through 
the sensory roots of the two nerves in question. The close asso- 
ciation of the dorsal motor IX and X nuclei in the immediate 
neighborhood of the terminal special visceral sensory nucleus of 
their own roots is thus another illustration of Kappers’ principle 
of neurobiotaxis.” 
Motor V-VII complex. In Kappers’ earlier publications (see 
especially 7 and 12) special attention has been drawn to the 
remarkable fact that in most birds, in contrast to all other verte- 
brates, the motor VIT nuclei (two or three in number) are situated 
wholly rostrad of the exit level of their motor root and in close 
association with the motor V cell groups. An exception to this 
rule among birds has been encountered only in the case of Casua- 
ris, where the motor VII nucleus lies on the. exit level of its 
motor root. Kappers has further shown that the position of the 
motor VII nucleus of birds rostrad of its root exit and its close 
association with the motor V nucleus is largely due to a dominat- 
ing trigeminal reflex influence in the absence of a well-developed 
gustatory center.” 
2 A similar association of [IX—X motor nuclei due to analogous circumstances 
has already been observed in Cyclostomes (fig. 13 A, p. 257). 
13 For a full discussion of this interesting question reference should be made 
to Kappers’ original communications (l.ec.). - 
