264 DAVIDSON BLACK 
The intrinsic muscles of the syrinx among parrots, though well 
developed, are not so numerous (but three pairs) nor so highly 
differentiated as they are, for example, in Corvus (49) and in 
most Oscine birds (4), where either five or seven pairs of syrin- 
geal muscles are usually present." 
On the other hand, Mudge (42), Kallus (Melopsittacus, 31), 
and others have shown that in contrast to all other birds the 
chief bulk of the tongue in parrots consists of its highly differen- 
tiated intrinsic musculature which extends as well in the anterior 
third as in the caudal portions of this organ. 
The possibility of coordinate lingual action during phonation 
in parrots was noted long ago by Owen (47, p. 225). It would 
seem probable that this surmise is correct (Denker, 20) and that 
the tongue in parrots forms an integral part of the sound pro- 
ducing mechanism in these animals, and by alteration of its 
shape may be capable of modifying in no unimportant manner 
the quality of the tones produced by syringeal vibrations. 
The large size and unique specialization of the nucleus inter- 
medius XII in parrots is thus evidently to be correlated with the 
bulk of their lingual musculature and especially with the com- 
plexity of its arrangement and action, and not with any syringeal 
peculiarities in these forms. 
In the development of its intrinsic musculature and in the 
part it may play in phonation as well as in deglutition the action 
of the tongue in parrots in some respects resembles that of this 
organ in many mammals. It is, of interest, therefore, to note 
the close association of the nucleus intermedius XII with the 
dorsal part of the caudal visceral motor column in parrots in 
view of the analogous motor nuclear association in this region 
in mammals. 
2. Visceral motor nuclet 
Nervus accessorius. In all lower forms so far investigated the 
accessorius nucleus when present is evidently but the caudal 
prolongation of the dorsal motor vagus column (8, 9, and 10). 
"An excellent short summary of the number and arrangement of syringeal 
muscles in various groups of birds is given by Newton and Gadow (44, p. 939). 
See also Weiss (61, p. 297) and Beddard (4). 
