160 NAOKI SUGITA 
My study of the Norway cortex did not extend to the early life 
of the animal, but, from the courses of the curves shown. in chart 
4, it seems probable that, in early life, before ten days after birth, 
the developmental changes in the cell size would be quite similar 
to those in the Albino, which have been minutely described in 
part I, and that we may therefore apply to the Norway rat also 
the same developmental phases as were formerly applied to the 
Albino. 
Morphological changes in the cytoplasmic and nuclear struc- 
tures in the Norway rat cells are similar to those in the Albino, 
if the comparison is made at like ages, so that figures 3 and 4 
in part I of this paper may be considered to represent Norway 
cells as well. 
Briefly stated, in the case of the Norway rat, the maximum size 
of the pyramids in the lamina pyramidalis (in brains weighing 
1.3 to 1.5 grams) is cell body 21 x 28 uw and nucleus 20 x 21 py; 
values only slightly larger than those in the Albino. The final 
size of the ganglion cells in the lamina ganglionaris (in brains 
weighing 1.9 to 2.3 grams) is cell body 32 x 48 uw and nucleus 
26 x 27 yw, which is much larger than the corresponding measure- 
ments for the Albino. 
Nissl bodies are already seen in brains weighing 1.13 grams— 
the youngest case in my material—but these bodies assume their 
mature appearance first in brains weighing more than 1.6 grams... 
As regards other developmental changes both in the cytoplasm 
and in the nucleus, the statements made for the Albino are all 
applicable to the Norway, if the comparison is made at like ages. 
SUMMARY 
1. In the full-grown Norway rat (Groups N XIX to N XXIII), 
the average size of the pyramids in the lamina pyramidalis is cell 
body 20x 27 u, nucleus 18x 19 y, and the average size of the 
ganglion cells in the lamina ganglionaris is cell body 32 x 43 u, 
nucleus 26 x 27 un. 
2. The cell body and the nucleus of the pyramids attain their 
maximum size (cell body 21 x 28 », nucleus 20 x 21 w) in brains 
weighing 1.3 to 1.5 grams, and after that they slightly diminish 
