122 Journal of Comparative Neurology. 



relative increase of the cytoplasm of the cell-body is much more 

 rapid than that of the nucleus, especially in the last stage of the 

 growth — see Table VIII. 



VII. Summary. 



1. The total number of the spinal ganglion cells remains 

 approximately constant between 10.3 and 167 grams; though 

 individual variations in the number of the cells in correspond- 

 ing ganglia exist. It can therefore be stated that this number 

 does not increase or decrease with age — Table I. 



2. The cervical spinai ganglia contain the greatest num- 

 ber of cells, while the lumbar and thoracic follow in the order 

 named — Table I. 



3. Some of the small cells contained in the spinal ganglia 

 are constantly growing, and in all three ganglia, some of them 

 become large cells — Table II. 



4. In all the ganglia the relative number of the large and 

 small cells is nearly the same at the same age — Table II. 



5. The cervical dorsal root-nerves contain the greatest 

 number of fibers, while the lumbar and thoracic rank in the 

 order given — Table IV. 



6. The relative increase of the number of the fibers in 

 the cervical and lumbar nerves is approximately the same, while 

 that of the thoracic shows a more rapid increase than either — 

 Table V. 



7. The dorsal root nerves at different regions in 10.3 

 gram white rat contain a large percertage of immature fibers 

 giving for the cervical 48%, thoracic 69%, lumbar 58%, while 

 in the mature animal the following percentages are found, 

 1.2%, S% and 4% respectively. This indicates the greater 

 numerical completeness of the cervical nerve in both young and 

 the adult. The lumbar nerve follows the cervical, while the 

 thoracic shows the least numerical completeness both in the 

 young and nature — Table VI. 



8. The number of the cells in the spinal ganglia is always 

 more than twice that of the fibers in the corresponding dorsal 

 root nerves. The ratios between the fibers and cells at 10.3 



