PERCENTAGE OF WATER IN BRAIN AND CORD 91 
The uncorrected values for the percentage of water were used 
in this series, as well as in all of the other series examined. The 
differences between the results based on the corrected, and 
those based on the uncorrected values are however negl gible. 
In the case of the males, as will be seen from table 1, we have 
from birth to 163 days of age, 19 groups containing 10 or more 
entries and averaging 18 observations in a group. 
From the treatment of this material we obtained the following: 
Standard Deviation—Males 
Range in 19 groups _—_0.21+0.028 to 0.50+0.080. 
Average of 19 groups 0.320.035 
Coefficient of variabiliiy—Males 
Range in 19 groups 0.26+0.034 to 0.640.090 
Average of 19 groups 0.40+0.047 
In the case of the females we have 11 groups averaging 14 
individuals in a group and ranging from 48 to 223 days of age. 
From the treatment of this material we obtained the following: 
Standard deviation—Females 
Range in1l groups 0.22+0.030 to 0.45+0.016 
Average of 11 groups 0.310.040 
Coefficient of variability—Females 
Rangein 11 groups 0.280.038 to 0.57+0.077 
Average of 11 groups 0.40+0.050 
It appears from the foregoing that the variability in the per- 
centage of water is nearly alike in the two sexes, and that it is 
remarkable small (¢ = 0.31 and C = 0.40 per cent), thus sup- 
porting the conclusion that normally the water content in the 
brain is highly constant when taken in relat’on to age. A num- 
ber of age groups, used for the preceding determinations, contain 
records that belong to one or to several litters. It seemed 
probable that the variability would be less within a given litter 
than in the mixed population, or in a group composed of al] the 
members of the several litters. Among the 19 male groups, 
just examined, 9 contained from one to four litters each com- 
posed of three or more individuals. In all there were 21 litters 
