270 DAVIDSON BLACK 
The development of subsidiary cell groups within the oculo- 
motor nucleus has attained to a high state of complexity 
among birds in ‘correlation with the perfection of the intrinsic 
and extrinsic oculomotor effectors. In the descriptive portion 
of this paper special attention was drawn to the accessorius 
cell group which in its relations, staining reactions, and in the 
morphology of its elements closely resembles the Edinger-West- 
phal nucleus of mammals with which it had been homologized 
by Brandis. In birds there can be no doubt that certain oculo-. 
motor root fibers arise in this cell group, and for this reason, 
especially, Kappers’ term nucleus accessorius III has been 
retained (vide supra, footnote 9, p. 250). 
Brouwer (17) has recently reinvestigated the Edinger-West- 
phal nucleus both from the clinical and from the comparative 
anatomical and pathological standpoint, and he has concluded 
that there exists the strongest evidence confirming Jacobsohn’s 
view that the Edinger-Westphal nucleus is the nucleus sympa- 
theticus nervi oculomotorii (80). 
In a consideration of the homology of the nucleus accessorius 
III of birds Kappers’ earlier description of a well-developed nu- 
cleus accessorius IIJ in one specimen of Varanus sp.? becomes 
significant, since it is thereby shown that an oculomotor acces- 
sory cell group (probably of sympathetic nature) has been 
evolved among reptiles and is present in certain modern repre- 
sentatives of these forms in a position exactly analogous to that 
of the Edinger-Westphal nucleus of mammals and the nucleus 
accessorius IIT of birds. 
CONCLUSION 
The cerebral motor nuclear pattern in birds, while showing 
some important variations in different avian families, is on the 
whole fundamentally similar in all the forms examined, and 
characteristically different from that obtaining in any other 
vertebrate group. Thus the strikingly specialized nature of 
the modern class Aves is well exemplified also in the topo- 
graphical relations of the motor roots and nuclei of their 
cerebral nerves. 
