PERCENTAGE OF WATER IN BRAIN AND CORD 93 
discussing the data we shall follow the same order of presenta- 
tion as was followed for the brain. The records for the spinal 
cord run from birth to 365 days of age and may be grouped as 
follows: 
569 male spinal cords comprised in 61 age groups 
363 female spinal cords comprised in 56 age groups 
Thus in the case of the females there are five age groups less for 
the spinal cord than for the brain. 
For the graph representing the course of the loss of water in 
the cord and the relation of the corrected (observed) male values 
to those computed, the reader is referred to chart 1, p. 79. If 
we take the mean of the deviations of all of the corrected values 
for the percentage of water from the corresponding formula 
values for the several age groups as given in table 2, and shown 
in chart 1 (males only), we obtain the following: 
Mean of deviations — males =+0.61 per cent 
Mean of deviations — females +0.55 per cent 
Thus it appears that the corrected observed values for the 
water in the spinal cord deviate on the average approximately 
+ (.6 per cent from the corresponding formula values. This 
deviation is about three times that found for the brain. As a 
consequence new observations on random samples which after 
correction fall within + 0.6 per cent of the formula values may 
be considered as in agreement. Where one is dealing with very 
uniform material less deviation is to be expected and agreement 
may be limited to values that fall within + 0.3 per cent of the 
standard which is used. Where data from test animals are con- 
trasted with those from controls of the same litter deviations of 
0.1 of a per cent, if constant or nearly so, may be regarded as 
significant. 
Sources of variation in the percentage of water—spinai cord 
The gross differences already noted as modifying the per- 
centage of water in the brain do not apply to the cord, because 
of the dissimilarity in its architecture; but so far as the differ- 
