314 CHI PING 
The technique employed in preparing the specimens is the 
same as that given in my former paper. The trapped rats were 
carefully examined when dissected, and all the specimens used 
were considered normal. As the ages of the trapped rats were 
unknown, the determination of the percentage of water in the 
brain was made in each case, since by this means the approximate 
age of the animal may be estimated, as pointed out by Donald- 
son (10), Donaldson and Hatai (’11, and ’16). 
TABLE 1 
Giving according to body weight the computed diameters of the largest cells and 
nuclei in the superior cervical ganglion of the Norway rat. Sexes separated. 
Data condensed. Thirteen groups . 
FORTY-THREE MALES FORTY-TWO FEMALES 
m 
Number eis Computed diameter Computed diameter eae, Number 
ge Nucleus Cell Cell Nucleus CGE SE 
grams Le ML ML LB grams 
1 6 9.9 17.2 16.5 9.6 6 1 
3 15 12.9 22.8 22.9 12.5 14 3 
5 35 °12.4 23.4 23.2 itr 28 2 
3 76 13.0 2020 PAD) 13.0 31 1 
3 104 1335 i 26.5 24.3 PASO 51 8 
2 117 13.2 Hf 26.0 320 73 2 
3 157 13.3 26731 24.9 13.0 103 4 
3 186 13.4 27.9 28.3 13.3 157 4 
5 220 13.6 29.7 20.0 13.0 179 6 
4 244 14.0 31.3 26.6 12.8 192 3 
3 276 13.5 33.3 27.8 7 214 3 
5 SYA} 14.0 Bie) 31.6 a7 227 2 
3 385 S37 Sled) Beso il 13.9 258 3 
In measuring the cells and the nuclei of the superior cervical 
ganglion I followed the same procedure as in my former study 
of the Albino. The data represented by the computed diameters 
of the cells and nuclei, and their ratios, together with the sex, 
age, body length, and body weight, as well as the percentage 
of water in the brain, were tabulated in the first instance for 
each individual according to increasing body weight, but these 
data have been condensed for the purpose of this paper—and 
only the condensed tables will be used for discussion. The 
