354 
ANATOMY: H. H. DONALDSON 
present in the brain, or to be a Kttle more exact, we should say the 
lipoid and the non-lipoid fractions. The lipoid (in part) represents 
the myeHn sheaths, while the protein, with part of the lipoid, represents 
the cell bodies and their unsheathed axons. 
With the exception of the one day group, the ages for which analyses 
were made are given in Table 3. 
At one day — or practically birth — ^it is found that the lipoid is present 
to the extent of 0.31 or nearly one-third of the weight of the protein. 
There is, however, no visible myelin at this age, so it is concluded that 
this proportion of the total lipoid is normally associated with the protein 
and is not to be included in the Hpoid which forms the myelin sheaths. 
We have treated the data for the later age groups in accordance with this 
relation — and in each case have taken from the total Hpoid found an 
amount equal to 0.31 of the protein found. The remaining amount of 
lipoid is assumed to be that used for the sheaths. 
In Table 3, the column (2) headed 'Corrected Protein' gives the 
observed protein (non-lipoid) plus 0.31 of itself — and the column (3) 
headed 'Corrected Lipoid' gives the observed lipoid less the amount 
of Hpoid added to the protein. 
TABLE 3 
To show for five brains of the Albino rat and for one spinal cord the percentage of water in the 
myelin as computed according to the method described. The protein and lipoid are given in 
percentages of the total dry substance {Based on Table 2. Koch and Kochy^ 
(1) 
(2) 
(3) 
(4) 
(5) 
(6) 
(7) 
PROPORTION OF 
PERCENTAGE OF WATER 
AGE IN 
DAYS 
CORRECTED 
PROTEIN. 
PER CENT 
CORRECTED 
LIPOID. 
PER CENT 
LIPOID FOR 
DIFFERENT 
AGES. 
LIPOID AT 20 
DAYS = 1 
Entire brain 
observed. 
In neurons 
= Protein (C) 
(assumed) . 
In myelin 
= lipoids (C) 
(computed) . 
Brain 
10 
93.80 
6.2 
86.5 
88 
63.8* 
20 
88.88 
11.12 
1. 
82.5 
87 
46. 5 1 
40 
82.86 
17.14 
1.5 
79.4 
87 
42.7 
120 
75.11 
24.84 
2.2 
78.4 
87 
52.4 
210 
76.36 
23.63 
2.1 
78.1 
87 
47.4 
Average of 20 to 210 rla.vs 
47.8 
Spinal Cord 
120 
52.92 
47.08 
4.2 
70.4 
87 
51.0 
* First traces of myelin. f Myelin well shown. 
