Hatai, Ganglion Cells in the Rat. 113 



given age contains the same proportional number of the small 

 and large cells. The percentage of the small cells in different 

 regions at the same age holds nearly the same proportion. An 

 adult white rat (167 grams) contains, therefore, in each spinal 

 ganglion still 60 % of the small cells which were left in an unde- 

 veloped condition. 



Since the small cells are increasing in diameter from 10.3 

 grams to 167 grams, the same standard in size cannot be em- 

 ployed in each case. The following table shows the maximum 

 diameters of the small cells at different ages. The small cells, 

 however, cannot be determined by measurement only, for in 

 some cases the cells show evidently the characteristic structures 

 of the large cells in spite of the diameter corresponding to the 

 following table. For this reason, the proper determination of 

 the number of the small cells will not be obtained by measure- 

 ment only. In this case, therefore, the small cells are 

 those having the diameter less than the diameter of the cell 

 recorded in the table, and at the same time showing the struc- 

 ture characteristic of the small cells as previously determined. 



(1901. I)- 



TABLE III. 



Showing the Maximum Diameters of the Small Cells at Different Ages . 



Regions. Body-Weights. 



10.3 24.5 6S.5 167 



VI Cervical 

 IV Thoracic 

 II Lumbar 



The diameters of the small cells here given are slightly 

 larger than those given in the table of the previous papers (i) on 

 the spinal ganglion cells in the white rat. This difference is mainly 

 due to the method of selection of the cells for the measurement. 

 In this case two largest small cells from each section (68.3 and 

 167 grams), and three largest small cells from each section (10.3 

 and 24. 5 grams) were selected for measurement ; while in the 

 previous case five largest small cells from each section were meas- 

 ured. Thus, in the latter instance, reducing the average. 



