PERCENTAGE OF WATER IN BRAIN AND CORD 89 
Moreover a brain of 1.750 grams should be found with the 
above body length, but the observed brain weight was only 
1.681 grams. It is therefore deficient by 0.069 grams. The 
observed percentage of water in the brain was 78.61 per cent. 
The percentage of water to be expected for a female having a 
body weight of 144.4 grams was 78.62 per cent (table 74, here 
appended). As the observed brain weight was 69 mgms. too 
low and the correction factor is 0.0013 per milligram, the total 
correction amounts to 0.09 which is to be subtracted from the 
observed value 78.61 per cent, thus giving 78.52 per cent as the 
corrected value for the percentage of water. 
This result may be interpreted as follows: The growth of the 
brain was retarded in this animal so that although the animal was 
173 days old, it had nearly but not quite the water content of a 
younger rat, the age of which was normal to the body weight. 
In view of the fact that we have a series of computed values 
for the percentage of water found in brains of the standard size 
at various ages, it is possible in this case to determine the prob- 
able percentage of water in the brain under examination, if it 
had reached the size characteristic for its age—173 days. 
At this age the brain, according to table 74, should weigh 
1.835 grams and have 78.18 per cent of water. This tabular 
brain weight is 154 mgm. above the observed weight 1.681 
grams, with a water content of 78.61 per cent. The difference 
154 mgm. multiplied by the correction factor 0.0013 gives a cor- 
rection of 0.2 which is to be subtracted from the water content 
observed, 78.61 per cent, giving as the corrected value 78.41 
per cent against the tabular value of 78.18 per cent. This 
shows a deviation from the tabular value of about 0.23 per cent 
or an amount just outside the range of +0.2 for random sam- 
pling. This somewhat elaborate process seems necessary to re- 
duce the crude data to a form in which they may be compared 
with each other. 
Percentage of water according to sex 
When the values given in table 74—here appended—are ex- 
amined, we note that from the age of 60 days on the body 
