INGBERT, Dorsal Roots of Spinal Nerves. 55 
in the roots of the spinal nerves of man is that made by StiL1- 
ING (1859)”. 
For the purpose of comparison we shall consider the de- 
terminations of the areas of the spinal nerves in detail. 
Ill. Determination of the Areas of the Cross-Sections of the 
Dorsal Roots of the Spinal Nerves of Man. 
1. Kdolhker’s Determination. ‘The areas of the cross-sections 
of the roots of the spinal nerves, as given by KoLLIKER (1850)" 
for a man and a woman, were in all probability obtained from 
fresh tissue, as no statement to the contrary can be found. 
The roots were sectioned between the spinal cord and the 
spinal ganglia at the place where they penetrate the dura mater, 
(i. e., near the ganglia). After removing the blood vessels and 
the arachnoidea, he measured the diameters of the roots, in- 
cluding the perineurium, and from these measurements calcu- 
lated the areas of the cross-sections. That KOLLIKER was cor- 
rect in considering his results too large will be seen on compar- 
ing them with those obtained by SriLiinG and myself (Table 
I*). Although the included connective tissue is the chief 
source of error in his results, yet the fact that he calculated the 
areas from the diameters of the cross-sections of the nerve roots 
as if they were perfect cylinders is, no doubt another source of 
error worth noting. Considering a Paris line (the unit which he 
employed) equal to 2.2558 mm., I have expressed his results in 
square mm. in Table I *. 
Although he determined the areas of the cross-sections of 
the ventral as well as the dorsal roots, the latter only are neces- 
sary for our comparison. 
2. Stillng’s Determination. The material used by STILL- 
ING (1859)" in his determination of the areas of the spinal roots 
was from the spinal cord of a woman, twenty-six years of age. 
The roots had been hardened in chromic acid according to 
STILLING’s method, and sectioned by hand with a razor at the 
place where they penetrate the dura mater. The sections, 
without staining, were mounted in alcohol. By means of a 
compound microscope and a camera lucida projections of the 
