Zon NAOKI SUGITA 
cerebral cortex the neuroglia, the intercellular tissue and the 
blood-vessels occupy considerable space and these may not be 
reduced in volume in the same proportion as the large nerve cells. 
These facts combined seem to furnish an explanation why the 
largest nerve cells, which have been here studied, deviate some- 
what in size from the figures theoretically to be expected. 
The data here presented show, I think, that the relations 
between the cell density and the cortica! volume in the underfed 
fit with the formulas presented earlier and which represent the 
relations in the normal Albino brains. 
19. A DISCUSSION ON THE PROCESS OF MYELINATION 
Tables 14 and 16 supply the data on which the myelination 
process in the underfed Albino brain may be tentatively dis- 
cussed. s 
In Donaldson’s series (11), which consisted of twenty-two 
litters of albino rats in which the underfeeding was begun at 30 
days of age and in which all were killed after three weeks and 
compared with the controls from the same litter, the average 
brain weight of the underfed was 1.402 grams and the percentage 
of water 79.28, while the average brain weight of the controls 
was 1.519 grams and the percentage of water 79.39. Here the 
underfed had 0.11 per cent less water. By examining the sec- 
tions from the underfed and the controls, the author could not 
discover any recognizable difference in myelination between them. 
Hatai (’04) made a partial starvation experiment, extending over 
three weeks, using the albino rats in the growing stage, about 
thirty days old. In this series, the final average brain weight was 
1.341 grams and the percentage of water 79.15 or 0.21 per cent 
less than in the controls from the same litter and killed at the 
same age and in which the final brain weight was 1.508 grams 
and the percentage of water 79.36. In the same series, the 
solids extracted with alcohol and ether were determined. ‘The 
average amount cf the extractives in the test brains was 46.7 per 
cent, or 0.9 per cent more than in the controls, in which it was 
45.8 per cent. Though higher in percentage in the underfed, 
