INGBERT, Dorsal Roots of Spinal Nerves. 61 
although it seems probable from the investigations of DoNnaLp- 
SON (1894) on changes caused in the nervous tissues by re- 
agents, that the departure from the normal is but slight. 
In order better to compare the areas of the cross-sections 
already discussed, I have constructed curves. In Fig. 1, 
Chart I, (page 72) I have constructed curves to compare the 
absolute areas of the cross-sections of the dorsal roots determined 
by KoLLiker for a male, by Sti_i1nG for a female, and by the 
author fora male. In constructing these curves the normal average 
length of the spinal cord, 441.6' mm.,was used as the base line. 
On this line was marked the normal average length of each 
segment, as determined by Donatpson and Davis (1903).™ 
The ordinates were erected at the caudal end of each segment 
and each sq. mm. cf the area of the cross-section of each dorsal 
root was represented by 20 mm. on the axis of the ordinates. 
For publication this chart has been reduced so as to make its 
base line 96 mm. which is a reduction to 0.22 of the original 
linear dimensions. In Table I* are found the data for this 
chart. 
In Chart II, (page 72) I have compared the same data as are 
used in Chart I. The base line is the same as before. The ordi- 
nates, however, were in this case obtained by taking the largest 
area in each instance as 100% and expressing the other areas 3 
as percentages of this standard. Each percent. in the values 
thus obtained is represented by 1 mm. on the axis of the or- 
dinates. For publication this chart has been reduced as in 
Chart I. In Table I? are found the data for this chart. 
1 The discrepancy between 441.6 here used and 441.9 in table 14 is due to 
the fact that the latter is the sum of the numbers after being rounded from two 
decimal places to one. 
