266 DAVIDSON BLACK 
It is well known that both the crop and gizzard musculature of 
birds are under vagus control (Biedermann, 5, p. 1206). Ver- 
meulen (55) has shown that in many forms a definite correspon- 
dence obtains between the size of the dorsal motor X nucleus and 
the development of the stomach, and similar observations had 
earlier been made by Kosaka and Yagita (38) in the case of 
birds. In all parrots a crop is present and, though in cockatoos 
this structure is of no great size, yet it is well developed. A 
small gizzard is also present in these animals (v. Oppel, 45, 46; 
Owen, 47, p. 161 et seq.), so that the specialization and relative 
size of the stomach in Cacatua would compare favorably with 
the development of this organ in Spheniscus and Colymbus 
(23 and 60). It thus becomes difficult to account for the short 
and relatively slightly developed dorsal motor vagus nucleus in 
Cacatua which in the proportions of this cell column differs so 
markedly from the other birds examined. 
The ventro-lateral motor X nucleus of birds in some respects 
resembles that of Varanus and Alligator (cf. fig. 15), but is 
more rostrally placed than in the latter forms. The possible 
significance of this condition will be discussed subsequently. 
It is interesting to note that the motor LX nucleus in all birds 
examined is characteristically associated with the dorsal motor 
vagus cell group and forms thereby the most rostral part of the 
caudal visceral motor column. In discussing the relations of 
the motor nuclei of this region in reptiles (10), it was pointed 
out that in these forms the association of glossopharyngeal with 
facial motor perikaryons rather than with vagal elements would 
seem to be due to a rearrangement of the visceral motor nuclear 
pattern largely as a consequence of the loss of the hyobranchial 
pump mechanism for pulmonary ventilation and, as Kappers 
has noted, under the direct influence of the caudal VIJ-IX taste 
center. 
In birds, also, the motor glossopharyngeal and vagus nerves, 
apart from the control of the simple laryngeal muscles, have 
lost entirely their original function of innervating respiratory 
musculature, the effectors concerned in pulmonary ventilation 
in these forms being wholly of striate somatic character. 
