PERCENTAGE OF WATER IN BRAIN AND CORD 79 
are 
Tt 
coat 
fi aoaee 
b 
ae 
Ba 
AH 
seeeeeeeet ee 
ei 
eT 
See Cse04e8) 
Chart 1 Showing the percentage of water on age in the central nervous sys- 
tem of the albino rat. The upper graph gives the values for the water in the 
brain as determined by the formulas (Hatai—in ‘The Rat,’ Donaldson, 1915). 
The lower graph gives the corresponding values for the spinal cord, determined 
in the same way. The small black dots indicate for the brain the corrected 
(observed) values for the several age groups, and these corrected values form 
the data on which the formulas have been based. The small black triangles 
have a like significance in relation to the spinal cord. 
water in the several age groups, as these appear in table 1, for the 
brain, and table 2, for the spinal cord. 
If we take the mean of the deviations of all of the corrected 
(observed) values for the several age groups from the corre- 
sponding formula values for the percentage of water, as given in 
table 1, and shown in chart 1 (males only), we obtain the 
following: 
Mean of deviations—Males +0.19 per cent 
Mean of deviations—Females +0.18 per cent 
Thus it appears that for both sexes the observed values, 
when corrected for brain weight, differ on the average approxi- 
mately +0.2 per cent from the corresponding formula values. 
Consequently new observations on random samples, which fall, 
after correction, within +0.2 per cent of the formula values 
