COMMISSURAL NEURONES 389 
silver preparations sections of the sympathetic trunk were im- 
bedded in brain or spinal cord before being immersed in the fixing 
fluid. 
Every operated specimen was dissected at the end of the de- 
generation period in order to determine the condition of the 
spinal cord and the sympathetic trunks. Unless otherwise noted, 
the spinal cord was completely destroyed as far cephalad as the 
second or third vertebra. Both sympathetic trunks were sev- 
ered in every specimen except the three referred to above. 
III. OBSERVATIONS 
A. On ganglia of normal frogs 
The conditions found in the sympathetic ganglia of normal frogs 
are illustrated in figures 1 to 5. The first three figures represent 
methylene blue preparations, and figures 4 and 5 show prepara- 
tions stained by the pyridine silver method. Both methods 
gave corresponding and uniform results, although the methylene 
blue technique was found to be much more convenient and to 
show, also, a larger number of spirals and pericellular networks 
(especially the latter), for a given area, than could be seen in 
pyridine silver preparations. The latter method was used 
chiefly as a check against the former. 
Figure 1 shows a small section of ganglion at the site of en- 
trance of a white ramus communicans. The darkly stained 
fibers of the white ramus stand out in marked contrast to all other 
nervous elements of the ganglion. A few fibers are seen to divide 
and a great many can be traced to their terminations in spirals 
and pericellular networks on the neuraxes and bodies of the 
autonomic cells. In many methylene blue preparations such 
terminations appeared to be present on practically every auto- 
nomic cell. 
The characteristic relation of fibers to cells is shown in figure 2. 
This represents a longitudinal section of a sympathetic ganglion, 
and it will be noted that the cells are located near the periphery 
cf the ganglion while the nerve fibers form the central part. 
