Hatai, Ganglion Cells in the Rat. 1 1 7 



tion the present writer enumerated the two kinds of the fibers 

 separately, and obtained the following results, which are repre- 



sented in Table VI, 



TAHI.E VI. 



Showing the Number of Fibers, Completely Formed as well as 

 Immature. 



On examining Table VI we notice in the first place the 

 relative increase in the number of mature fibers between 10.3 

 and 167 grams is less in the cervical region than in the other 

 two. This means that even at 10.3 grams, there is a larger 

 proportion of the mature fibers in the cervical root than m the 

 other two with which it is compared, and the last column in 

 the table giving the percentage of the immature fibers supports 

 this statement. That is, the cervical root of the 10.3 gram rat 

 contains 48^ of immature fibers, while that of the thoracic 

 and lumbar contains 69% and 58% respectively. Further, at 

 maturity there is in the cervical root a smaller percentage of the 

 immature fibers than in either of the others, showing that this 

 root is most completely developed. In the same way, if we 

 compare the lumbar with the thoracic root we find the lumbar 

 is always more advanced in its development ; that is, it contains 

 smaller percentage of immature fibers. It thus appears that 

 the roots in the cervical and lumbar regions are more completely 



