MAUTHNER’S CELL 115 
fixatives is very slow. Beceari (’07) observed a fusion of collat- 
erals from Mauthner’s fiber with ventral horn cells in Cajal prep- 
arations fixed in alkaline alcohol but the well fixed material 
studied by Tagliani (05) and my own sections show only a con- 
tact in these synapses. 
SUMMARY 
The nucleus motorius tegmenti may be divided into cell groups 
which correspond to the various motor nuclei of the medulla ob- 
longata and the relations with these nuclei represent the primi- 
tive connections of the groups. 
The groups have secondarily acquired relations with the pri- 
mary sensory nuclei which lie at the same transverse levels and 
have differentiated accordingly. 
This connection is interpreted as an adaptation for rapid re- 
flexes between the sensory centers and motor centers of the so- 
matic musculature. 
The axones of the larger cells of the nucleus motorius tegmenti 
comprise the greater part of that portion of the fasicculus longi- 
tudinalis medialis which goes to the spinal cord. 
The motor tegmental nucleus is best developed in the region 
of the acoustico-lateral nuclei. 
Certain cells here have migrated toward the acoustico-lat- 
eral decussation, from which they receive collateral fibers, and 
they have increased in size. They are homologized with the 
Miiller’s cells of cyclostomes. 
Mauthner’s cell is interpreted as a cell of the same type as 
the Miiller’s cells which has gone much further in its differentia- 
tion as a result of establishing a direct connection with the VIIIth 
root fibers (p. 112). It is the association cell of three-neurone 
reflexes having short latent periods. The perikaryon and den- 
drites are gigantic in their proportions but the nucleus is not 
correspondingly large. 
At least twelve different types of fibers have endings in the 
pericellular net of Mauthner’s cell (see summary on page 109). 
One portion of the pericellular net is particularly highly devel- 
