20 JouRNAL OF COMPARATIVE NEUROLOGY. 
ume, is explained by the fact that only in the case of the five- 
year old child are the areas for the separate funiculi given, and 
his interest was at that time directed to the funiculus lateralis. 
Since the white substance in the cord of the five-year old child 
is, both absolutely and proportionately, less than in the adult, the 
use of this series of curves to illustrate the gray and white sub- 
stance in the mature spinal cord is necessarily misleading, yet 
these curves are at present employed in the text-books, without 
any accompanying statement to show that they are based on 
the measurements from an immature cord. 
It is intended in this paper to present a chart which shall 
more accurately show the true relations between the gray and 
white matter as they appear in the adult, and thus shall replace 
the older charts now in use. In order to do this, not only 
should the measurements of the areas be those from the adult 
spinal cord, but there is another correction which applies to all 
the charts thus far published, including that of Krause and 
AGUERRE (1), and which consists in representing the segments 
of the cord in their true lengths. 
I. Representation of the Length of the Segments. 
Heretofore, in these charts, the abscissa has always been 
divided into 31 egual parts—each part representing the length 
of a segment of the spinal cord. Manifestly this will give an 
incorrect form to the curve, because the segments of the cord 
are really of unequal length. 
As any ordinate representing the area of a cross section 
applies strictly to the sum of half the distance from it to the or- 
dinates next above and next below the point at which it is 
erected, it follows that by multiplying the areas represented by 
any ordinate by the length of the cord to which it applies, we 
get an approximation of the volume of the segment. It is evi- 
dent, also, that the volume of a segment thus determined when 
the divisions of the abscissa are equal, would be different from 
that determined when the divisions of the abscissa represent 
the segments in their true length. To make a correct con- 
struction, it was therefore necessary to gather data on the 
