34 JOURNAL OF COMPARATIVE NEUROLOGY. 
in length. From the measurements of RAVENEL (p. 350), we 
have calculated that the length of the medulla spinalis at one 
year of age would be about 200 mm., whereas he found ina 
five-year old boy the length to be 300 mm. “Yet, despite this 
increase in length, the measurements just given show that the 
transverse diameters remain practically constant. Apparently 
we have here another example of the tendency of structures to 
grow first in their long axis before enlarging at right angles to 
it. It must be remembered, however, that we are without ob- 
servations on the changes which occur within the limits of the 
first year. Y | 
On looking at Table VI, it is to be noted that the area of 
the white substance at maturity is nearly 95 % greater than it 
was at five years, while the gray substance is only 23 % greater, 
thus showing the much more rapid enlargement of the white 
substance. This being the case, it is evident that the curves of 
WoroscHILoFF, based on a five-year old child exhibiting in 
cross section hardly more than half of the white substance in 
its cord than is present in the adult, necessarily give a false no- 
tion of the relations at maturity. 
IT. Comparison of a Curve, Representing the Areas in the Chald’s 
Cord, with the Corresponding Curve for the Cord of the Adult. 
It has just been shown that from the first to the fifth year, 
the areas of the cross sections of the spinal cord remain the 
same size. It is therefore only necessary to obtain the mea- 
surements of the lengths of the segments at some period within 
these ages in order to construct a curve for the child’s cord that 
may be compared with that for the adult. 
Liperitz (p.471) gives the length of the segments in the 
cord of a female child of three and a half years. His measure- 
ments are presented in the following Table X. 
