300 CHI PING 
toward the end of one year. A study of the rate in the decrease 
of the young cells will serve as a means of measuring this change 
at later ages. For this purpose counting was undertaken. 
Because of their considerable number during the early prepubertal 
stage, as well as their small size and irregular distribution, it is 
almost impossible to obtain a satisfactory value by a single 
count, so that a second and a third count were usually made. 
The numbers recorded in table 7 represent averages of three. 
counts of young cells in each ganglion. The cells, selected and 
counted as young cells, have the following characters: They 
are 5 to 10 uw in long diameter; more or less pyriform, and the 
cytoplasm is little differentiated. 
The graphs in chart 4 represent the numbers of the cells as 
given in table 7, on age. The decrease in number at first shows 
no tendency for one sex to outrun the other, but a difference 
appears soon after puberty, and such a difference in decrease of 
the young cells between the male and the female persists till the 
end of one year. The young cells of the female rat in relation 
to age are transformed more rapidly than those of the male; 
that is, these cells grow faster in the female. This phenomenon 
is in accord with what has been seen in the growth of large cells 
in diameter, as shown in charts 1 and 2. 
DISCUSSION 
There is reason to think that at birth the full number of cells 
in the superior cervical sympathetic of the albino rat has been 
attained and that no more cells wander in and mitosis is finished. 
These cells appear to persist throughout the span of life. 
Postnatal development of these cells consists in the enlarge- 
ment of all parts of the neuron accompanied by differentiation. 
In the nucleus there is less change in size than in the cell body. 
The increase in number of nucleoli has been frequently noted, 
but it is not within the scope of the present paper to discuss this 
point. 
Bringing the observations together, we see that the male and 
the female do not differ clearly from each other in the growth of 
these nerve cells until the animal has become sexually mature. 
