298 CHI PING 
form, but they are distinguishable, owing to their larger size. © 
It is this group of cells which will appear later as the advanced 
cells. 
3. The growing small cells. These cells are small during the 
first five days after birth, but some of them grow very fast toward 
the end of twenty days, to a size equal to that of the other large 
cells. There is a constant increase in the number of these smaller 
cells which are growing. : 
For the determination of the rate of increase in the number of 
the large cells, 19 to 25 » in diameter, counting was undertaken. 
The cells counted comprised those just described under | and 2. 
Since the same large cell does not appear. in two successive sec- 
tions, repetition in counting them is easily avoided. Table 6 
gives the numbers of these cells. Based upon these numbers, 
the graphs in chart 3 were plotted on age. In chart 3 the male 
has a slightly higher rate of increase than has the female after 
twelve days. When the animal reaches sixteen days, both sexes 
show a more rapid increase, and the difference between them 
becomes more evident. If the data are plotted in a like manner 
on the body weight, they show similar relations. On the whole, 
then, the data show that the increase of large cells during the 
first sixteen days is relatively slow and afterward increasingly 
rapid. Between the age limits here given the increase in the 
number of large cells—sexes combined—is about thirteen-fold. 
THE TRANSFORMATION OF THE YOUNG CELLS 
During the later period of development there remain in this 
ganglion a number of young cells which, in contrast with the 
large cells, are slow in growth and which retain their neuroblastic 
appearance for a considerable length of time (fig. 1). As already 
noted, some nerve cells are precocious and many of them have 
attained their maximum size at the end of twenty to twenty-five 
days. It is most probable that the young cells found after 
twenty-five days of age are largely rudimentary elements, and 
some of them will never grow to the same size as the others. 
Yet some development is going on in both their structure and 
size, as is indicated by the constant decrease of their number 
