DIAMETERS OF NERVE CELLS AND FIBERS 545 
a discussion of this point must be reserved until the relation has 
been more carefully examined. The relations between the volume 
of the ganglion cell and the area of the axis cylinder of the fibers 
passing to the periphery were briefly noted by Donaldson (’00), 
and the results of the present study are in good agreement with 
the earlier observations. 
Bringing these observations together, it may be said that in the 
afferent fibers just distal to the ganglion the increase in the area 
of the axis, as the rat increases in size, during the later phases of 
growth tends to be at the same rate as the increase in the surface 
of the body and as the volume of the ganglion cells from which 
the fibers arise. 
CONSIDERATION OF INCIDENTAL RESULTS HERE OBTAINED 
In order to bring the incidental observations made in the course 
of this study into relation with other observations previously 
recorded for the albino rat, it has seemed worth while to compare 
our data with those already published. 
The relations between the diameters of ganglion cell bodies 
and the diameters of the entire fibers cannot be directly compared 
with the results obtained by Hatai (’02, ’07) after osmic acid, on 
account of differences in the fixation methods and in the pro- 
cedure of measurement.' The records most suitable for com- 
parison are those by Dunn (12) on the diameters of the ventral 
root fibers of the econd cervical nerve of the albino rat of differ- 
ent sizes. For 1 ke body weights the ventral root fibers in the 
second cervical nerve run about 2y less in diameter than the 
fibers in the seventh cervical, but the increase in diameter within 
1 A special set of preparations of spinal ganglion cells shows that the mean 
diameter of the nucleus is much less after osmic acid than after fixation in Bouin’s 
fluid. 
DIAMETERS IN yu 
Cells Nuclei 
Fixation ing bouts 15 oasecte ts ease sas be By 14.4 
Hixa tlonpisvosMCeaClGen sect -h ciate chk enc 34.0 10.8 
