MAUTHNER’S CELL 99 
The one objection that can be raised to this interpretation, so 
far as I can see, is that in the cyclostomes the fibers from Miul- 
ler’s cells are uncrossed. This is not a matter of fundamental 
importance in view of the fact that the axones cf the various 
nucleus motorius tegmenti cells (including the Miller cells) show 
every transition from immediate crossing to an uncrossed fiber 
which gives off crossed collaterals from time to time. 
Edinger considers Deiter’s nucleus an integral part of the nu- 
cleus motorius tegmenti. This matter will be taken up in my 
report upon the acoustico-lateral centers. 
MAUTHNER’S CELL 
Position, general relations and size. The position of Mauth- 
ner’s cell is constant in its relation to the motor VIIth root and 
the cerebellum both in the larvae and adults of the teleosts stud- 
. ied. There is even little individual variation except in dorso- 
ventral position, i.e., it is farther from the ventricle and nearer 
the rest of the motor tegmental nucleus in some cases than in 
others. The cell body lies just rostral to the genu of the VIIth 
nerve and at the caudal end of the cerebellar peduncle. At this 
same level in all larval brains and in the adult Menidia, Salmo, 
etc., we find the anterior VIIIth root and the large-celled ventral 
acoustic nucleus (Deiters’ nucleus), as may be seen in figure 6. 
In adult siluroids, however, the ventral VIIIth nuclei do not 
extend so far rostrally as Mauthner’s cell (fig. 3). In so much as 
the principal connections of Mauthner’s cells are with the VIIIth 
roots and nuclei there are certain significant differences between 
the cell and its synapses in Ameiurus and Salmo, as will appear 
below. 
The primitive teleostean Mauthner’s cell is not unlike a spindle 
bent to a right angle at the middle. The lateral limb is directed 
somewhat caudally, the ventral limb rostrally, so that a plane in- 
cluding both must be oblique to the brain axes. The axone 
(Mauthner’s fiber) arises medially, from the apex of the angle, 
turns abruptly caudally and decussates with its fellow. It has 
long been known to extend throughout the spinal cord, giving 
