100 HENRY H. DONALDSON 
Percentage of water according to sex 
After 60 days of age, a comparison can be made, by the use 
of the data in table 74, of the weights and water content of the 
spinal cords in the males and females at like ages. Such a com- 
parison shows the correction factor between the sexes to be 
about 0.008 per cent of water per milligram. This lies roughly 
between the correction factor values for the two sexes, as pre- 
viously determined. 
Measures of variability in the percentage of water—spinal cord 
As in the case of the brain, it has been possible to obtain for 
the spinal cord, in a number of age groups of both sexes, the 
measures of variability as represented by the standard devia- - 
tion and the coefficient of variability. The formulas used 
have been given on p. 90. In the case of the males, as will be 
seen from table 2, we have from birth to 163 days of age 19 
groups containing 10 or more entries, and averaging 18 obser- 
vations per group. 
Using the uncorrected values we obtained the following: 
Standard deviation 
Range in 19 groups’ = 0.74+0.07 to 1.86+0.26 
Average of 19 groups 1.06+0.12 
Coefficient of variability 
Range in 19 groups _0.96+0.09 to 2.64+0.37 
Average of 19 groups 1.46+0.17 
In the case of the females we have 11 groups, averaging 14 
individuals in a group, and ranging from 48-223 days of age. 
We obtained the following: 
Standard deviation 
Range in 11 groups __0.60+0.08 to 1.13+0.12 
Average of 11 groups 0.81+0.10 
Coefficient of variability 
Range in 11 groups 0.85+0.11 to 1.56+0.17 
Average of 11 groups 1.13+0.14 
