284 CHI PING 
the boundaries of a cell body were obscure. Furthermore, the 
distribution of the Nissl granules was rather irregular (as will 
be described later), so that neither the longitudinal nor the 
transverse diameter could be measured according to the extent 
of the stainable mass. 
After the measurements had been taken, a sketch of the section 
with the two cells measured therein was made, and the nucleoli 
in these cells were noted, so that in making measurements for 
the second time the same cells could be identified by their location 
and the number of the nucleoli. As a matter of routine, the cells 
in each ganglion were measured twice, a considerable time being 
allowed to elapse between the first and second measurements. 
The procedure in measuring did not follow in the order of age or 
of body weight of the animal, as given in the tables, but was 
purposely haphazard, and in making measurements for the second 
time, the records were taken without referring to those already 
made. ‘The values used are the means of the two series. 
By this procedure prejudice was avoided and a more accurate 
determination of the size of the cells and nuclei obtained. The 
records thus made were tabulated in detail, but the averages of 
the values for the ten cells in each ganglion are those used for 
the tables, charts, and discussion which follow. The individual 
data have been filed in the archives of The Wistar Institute. 
The square roots of the products of the longitudinal and trans- 
verse diameters of the cells and of the nuclei, respectively, for 
each ganglion were averaged, and the mean was multiplied by 
4.47, the value in u of one division of the eyepiece scale. In 
table 1 the diameters of the cells and nuclei thus computed are 
arranged according to age, and in table 2 according to the body 
weight of the animal. 
Based on the records in tables 1 and 2, charts 1 and 2 were 
plotted. Chart 1 shows on age the graphs for the diameter of the 
cells and nuclei in micra and chart 2 the same relations on body 
weight. 
In the graphs for the cells in chart 1 we see in the increase 
before puberty only chance variations between the male and the 
female in diameter of the cell body, but after the rat has attained 
