20 JouRNAL OF CoMPARATIVE NEUROLOGY. 
develop hardly so fast, attaining 15 , in the mean diameter of 
the cell-body and 10, in the mean diameter in the nucleus. In 
the later stages, as in the previous case, only the large cell grow 
rapidly while the small cells remain nearly the same size. 
Finally, in the rats at maturity, the large cell-bodies attain 
50, in the mean diameter while small cells are only 18 , in 
the mean diameter. 
On comparing the cell-size of the matured cells with those 
of animals just born, it appears that the large cells in the adult 
white rat attain about twice the diameter of those of a white 
rat just born. On the other hand, the small cells in the adult 
rat maintain nearly the same size as those in the new born rat, 
showing the difference of about 4, in mean diameter. These 
relations are presented in the following table: 
TABLE VII—The large and small spinal ganglion cells in cervical ganglia 
of the white rat of different weights. 
Large Small 
Weight |Cell-body | Nucieus Cell-body Nucleus 
4.52 25 fe 12 fl 14 8.5 fl 
10.84 35 16 14.1 9.7 
25a1 39 16 15 Io. 
68.8 37 17 14.4 Io. 
pk Si 50 17 18 10. 
From the above observations, the following conclusion is 
reached : 
(1) The differentiation in the size of the cell-bodies ap- 
pears in the rat in early fcetal life. 
(2) The diameter of small cells in an adult efit rat is 
only slightly greater than that at birth. 
(3) The internal structure of the small cells in an adult 
white rat shows the same appearance as that at birth. 
(4) The nucleus remains relatively large: a striking char- 
acter of immature nerve-cells. 
BuEHLER' made the following suggestions concerning the 
1 BUEHLER, A.—Loc, cit., p.16. 
