114 GEORGE W. BARTELMEZ 
most of the root fibers which end about Mauthner’s cell are 
thick fibers. Mullenix (’09) has found that some ‘giant’ fibers 
end in every crista and macula of the internal ear and I would 
interpret such fibers as paths of relatively low resistance, 1.e., 
the fibers concerned in the most rapid reflexes. Now according 
to Beceari (’07), the lateral dendrite is related exclusively to sac- 
cular fibers in Salmo and in Ameiurus certainly some fibers from 
the macula sacculi end upon the lateral dendrite. It may well 
be then that Mauthner’s cell is concerned in the characteristic 
auditory reflex in teleosts described by Parker (’08). This is a 
“sudden jump forward”’ after strong auditory stimulation. The 
course of such a reflex might be outlined thus: from the giant 
fiber endings in the macula sacculi, which latter Parker has shown 
to be sensitive to auditory stimuli, via the ganglion and posterior 
VIIIth root to the lateral dendrite; thence by way of Mauthner’s 
fiber to the motor nuclei of the tail muscles. 
The two characteristic synapses of Mauthner’s cell in Ameiurus 
are noteworthy because they afford a valuable material for the 
* study of the morphology of the synapse. My material has been 
fixed by methods which are recognized by cytologists who con- 
trol their work by the study of living cells, as producing a mini- 
mum of artefact. The study of this material with a 1.5 mm. 
apochromatic immersion lens reveals no indications of a fusion 
of fibers, either in the very dense neuropil of the axone cap or in 
the enormous synapse between the VIIIth root fibers and the 
lateral dendrite. In the formol-osmic-Zenker and acetic-osmic- 
bichromate (Bensley) preparations of the latter synapse, there 
is a distinct plasma membrane over the root fibers and where 
the lateral dendrite is cut squarely a similar membrane can be 
distinguished around it (fig. 13). If my interpretation of the 
facts be accepted, this synapse is one where there is very little 
delay, and yet we find two synaptic membranes. The need of 
control of the fixation in cases where there seems to be a fusion 
of nerve processes of different neurones cannot be too greatly 
emphasized. Methods which involve the deposition of metallic 
salts give pictures which cannot be implicitly relied upon, espe- 
cially in the central nervous system where the penetration of 
