DIAMETERS OF NERVE CELLS AND FIBERS d49 
entered in the last column. This ratio rises with the increasing 
weight (age) of the rat, being as table 12 shows 6.70 for the 
smallest group and 8.48 for the largest, an increase which is 
definite and also regular. This shows that these cells are not 
only growing in volume, but maturing, as indicated by the in- 
crease in the ratio. 
Contrasted with these results are the relations which appear in 
the case of the ventral horn cells, as shown in table 13. Here, 
as the last column shows, the nucleus-plasma relation is not 
progressive and is only slightly higher in the largest rats as com- 
pared with the smallest—5.68 for the largest as compared with 
5.54 for the smallest. 
TABLE 13 
Giving the relations of the spinal cord cells and their nuclei. In the last column 
appears the ratio of the volume of the cytoplasm (volume of entire cell less the 
volume of the nuleus) to the volume of the nucleus. Data condensed from table 6 
YERVE CELLS NUCLEI 
Sone Hae a a a lll a ge ae 
WEIGHT Sere Mean Ratio of Mean Ratio of ee ta oat oe 
diameter |jenlargement| diameter jenlargement vee DE 
grams days KL Be 
28.9 24 24.5 1.00 13.1 1.00 1: 5.54 
85.1 56 27.9 1.14 15a 1.15 1: 5.31 
149.8 105 29.4 120 15.4 1.18 T5095 
265.3 267 29.2 1.19 ayes) 1.18 1: 5.68 
We infer from this that at twenty-four days the nucleus- 
plasma relation in the ventral horn cells has nearly reached 
equilibrium, although there is some slight increase in volume of 
the entire cell body, as shown in the previous tables 4, 5, and 6. 
The two types of cells here examined have a different nucleus- 
plasma relation, therefore, and the plasma in the case of the 
ganglion cells is not only absolutely more abundant, but increases 
with the size (age) of the rat. 
This seems to be an important difference. As the spinal cord 
cells do not show a change in the nucleus-plasma relation, despite 
the continued growth of the axon in diameter, we should not 
consider the change in the spinal ganglion cell as due to the growth 
