SYMPATHETIC CELLS: NORWAY RAT 337 
3. The morphological changes in the cells are in general similar 
to those found in the Albino, but the stainable substance is 
somewhat less aggregated. The binuclear cells and the cells 
with pigment are present, as in the Albino, but the latter are 
only slightly more numerous in the Norway. Besides, there 
are in the Norway a few vacuolated cells. 
4. The mode of growth of the cells, as in the Albino, shows 
similarity to that of the motor cells of the spinal cord. 
5. The nucleus-plasma ratio is 1 to 5 at birth and 1 to 12 
after maturity. 
6. The cells at birth are about 16 per cent less in diameter 
than those of the Albino. The growth acquired after the 
weaning period is about 10 per cent less than that of the 
Albino, such difference being probably due to domestication. 
7. Comparing with the standard Albino the data for the wild 
Norways, it appears that in the Norways the diameters of the 
nuclei are the same, but those of the cell bodies are slightly 
less. As a consequence, the nucleus-plasma ratios are smaller 
in the Norway. Moreover, there is no clear sex difference in 
the size of these cells. 
8. Comparing the inbreds with the standard albinos in re- 
spect of these cells, it appears that in the inbreds the sex dif- 
ference in size is less marked. The absolute diameters of the 
nuclei are similar to those for the standards and Norways, but 
the diameters of the cells are much less, and in consequence 
the nucleus-plasma ratios are only about half those for the 
standards. 
9. The interpretation of these differences awaits the data 
to be obtained from Norways after long-continued domestica- 
tion and inbreeding. 
