Hatai, Ganglion Cells in the Rat. 1 19 



V. The Relations of the Number of Spinal Ganglion 

 Cells to the Number of Dorsal Root Fibers. 



TABLE VII. 



Showing the numerical relations between the spinal ganglion cells 

 and the dorsal root fibers. 



On comparing the total number of cells with the total 

 number of fibers in each of three roots, we note first the most 

 important fact that there is always a great excess of nerve cells 

 in the spinal ganglion. Further, it appears that the number of 

 cells corresponding to each fiber diminishes with the growth of 

 the animal. In the case of the cervical nerve of the 167 gram 

 rat thus falls as low as 2.7 cells for each fiber, which indicates 

 that the increasing number of fibers arises by the gradual ma- 

 turing of the spinal ganglion cells. If we regard the ratio in 

 the case of the thoracic and lumbar nerves we find that the 

 number of cells for each nerve fiber is at all ages somewhat 

 greater for the lumbar nerve than for the thoracic, despite the 

 fact that in previous tables we have found the lumbar nerve 

 more like the cervical than the thoracic. If now, we compare 

 the number of fibers in each case with the number of large cells, 

 we find that in the cervical region at all ages the number of 

 fibers is approximately equal to the number of large cells, while 

 in both the thoracic and lumbar regions, there are on the aver- 

 age, a trifle over two large nerve cells for each fiber. This 



