96 HENRY H. DONALDSON 
TABLE 2—Concluded 
MALES FEMALES 
ay res Noee Percentage of water NaWGE Percentage of water 
Cases Cases 
Observed | Corrected | In table Observed | Corrected | In table 
320-325 4 71.02 69.36 69.40 5 70.83 70.14 69.70 
325-330 
330-335 2 71.18 71.05 69.64 
335-340 i 70.67 69.68 69.61 
340-345 
345-350 
350-355 
355-360 5 70.12 68.96 69.48 
360-365 3 71.01 69.93 69.45 
ences depend on histological composition, the sources of variation 
for the spinal cord are similar to those for the brain (p. 83). 
On the other hand, we have the condition of adaptation by 
enlargement emphasized in the cord, and represented there par- 
ticularly by the passive lengthening, whereby the cord adapts 
itself to the varying lengths of the vertebral canal: an adapta- 
tion which seems to be accomplished mainly by changes in the 
quantity of the white substance. 
Factors for the correction of the percentage of water according to 
the spinal cord weight 
Theoretically there can be little question that the conditions 
represented by the relative weight (i.e., relative to the body 
weight) act as in the case of the brain to produce a high per- 
centage of water in the cord which is relatively small, and vice 
versa. But the cord data cannot be used in the same way as 
we used the data for the brain, because the absolute weight of 
the cord is the dominating factor, owing to the fact that the 
increase in the weight of the spinal cord is so largely due to the 
addition of myelinated fibers. ‘To obtain correction factors for 
the cord it has been necessary therefore, to deal with the data 
from the standpoint of absolute weight. Our assumption is 
that at the same age the absolutely heavier spinal cord will 
