32 JOURNAL OF COMPARATIVE NEUROLOGY. 
TABLE VII. 
Showing the sums of the total areas in the three immature and one 
(composite) adult cord, as tabulated in Table VI. 
Age. Sum of 31 Areas. 
I year 1078.53 sq. mm. 
2 years 1060.45 sq. mm. 
5 years 1069.45 sq. mm. 
Maturity 1866.00 sq. mm. 
These figures show that from one to five years, there is 
very little variation in the sum of the total areas. It ranges 
from 1078.53 sq.mm. to 1060.45sq.mm. Since this difference 
appears as a deficit in the two year cord, it is probably the ex- 
pression of an individual variation. The extreme cases, 1 and 
3 years, differ by less than 2%, whereas between five years and 
maturity, there is an increase in the total area of the sections 
of nearly 74%. From this it is inferred that the growtli changes 
leading to the larger area at maturity occur at some time subse- 
quent to the fifth year of life. 
The analysis can be carried a step further by comparing 
the relative areas of gray and white substance in the several 
cases. 
TABLE VIII. 
To show the percentage values of the sums of all the areas occupied by 
gray and by white substance at different ages. 
White Substance Gray Substance 
Percentage Percentage 
Sums of Areas of sums of Sums of Areas of sums of 
Age. in sq.mm. total areas in sq mm. total areas 
I year 766.00 71% 312553 29% 
2 years 741.97 70% 318.48 30% 
5 years 734-80 69% 334-65 31% 
Maturity 1455-07 78% 410.93 22% 
A glance at this table shows that during the first five 
years, the proportional value of the white substance in the sec- 
tion is about 70%, whereas at maturity it reaches 78%, the 
gray substance of course showing a correlated variation. 
It appears then that from the first to the fifth year, there 
