104 HENRY H. DONALDSON 
APPENDIX 
Formulas for the percentage of water in the central nervous 
system (Hatai, in The Rat, Donaldson 715, p. 170-172). 
PERCENTAGE OF WATER IN BRAIN 
The formulas do not apply to rats under 10 days of age. 
The data for the first 10 days are from direct observations. 
Percentage of water in brain—(male) = 
92.122 —0.614 Age +0.00739 Age? (Phase 1) (40) 
[10 <Age <40] 
= 82.756 —2.103 log Age (Phase 2) (41) 
[40 <Age <160] 
= 77.671 +0.00537 Age —0.000016 Age? (Phase 3) (42) 
[160 <Age <365] 
To transform any determination for the male into that for 
the female, the value for the male at a given age (see formulas 
(40) (41) (42) ) is modified by a plus correction (Hatai). 
Correction (plus) =0.0555 log (age +3) —0.0606 (42a) 
[10 <Age <365] 
The foregoing (40)—(42a) replace the formulas given in the 
paper by Donaldson (’10). 
Formulas (40) (41) (42) (42a) were used for table 74. 
PERCENTAGE OF WATER IN SPINAL CoRD 
The formulas do not apply under 10 days of age. The data 
for the first 10 days are from direct observations. 
Percentage of walter in spinal cord—male = 
87.976 —0.494 Age +0.00364 Age? (Phase 1) (43) 
[10 <Age <40] 
= 100.8 +0.0548 Age —17.7 log Age (Phase 2) (44) 
[40 < Age <150] 
= 62.186 —0.0121 Age +4.434 log Age (Phase 3) (45) 
[150 <Age <365| 
To obtain from the values for the male at different ages the 
corresponding value for the female, several corrections are re- 
quired and these differ according to age. 
