I n a previous paper (K. Ide, '30 a) dealing with the sectional areas of the largest fibers in the roots of the lumbar nerves of the albino rat, the values (as there indicated) at level 2 (chart 1) have been reported.
It was noted in the summary of that study that the areas of the root fibers at level 2 were greater than those found for the fibers in the sciatic nerve.
This raised the question of the change in the sectional area of these fibers in their course, and at the suggestion of Dr. H. H. Donaldson, I have taken up the study of this matter.
From the same specimens which furnished the sections at level 2 sections were also made at three other levels and, in addition, the values for the fibers in the midsciatic could be computed from a previous study (K. Ide, '30).
Chart 1 shows the relative position of these four levels together with that for the midsciatic and also gives in millimeters the approximate intervals between the successive levels.
Description of levels 1 to 5 (chart 1). These levels may be designated as follows : level 1 = central, level 2 = preganglionic, level 3 = postganglionic, level 4 = fifth lumbar nerve, level 5 = midsciatic.
IZINICHI IDE
MATERIAL
The material coiisists of both fifth lumbar nerves for each individual from twelve male and ten female albino rats, as described in a previous paper (K. Ide, '30 a).