Hardesty, spinal Nerves of the Frog, 



79 



may vary considerably, even in the total number of fibers, it is 

 evidently not reasonable to suppose the variation can account 

 for this difference which amounts to 5, 175 fibers. 



Chart II, more readily than Table I, conveys an idea of 

 the absolute relations existing between the numbers of fibers in 

 the trunk and dorsal branches of the ten spinal nerves and the 

 numbers of fibers in the dorsal and in the ventral roots. It 

 shows (i) the abrupt rise in the number of fibers at those re- 

 gions of the spinal system from which the limbs are supplied ; 

 (2) as might be expected, the curves for the roots follow that 

 for the trunk and dorsal branches fairly closely, and (3) that the 

 curves for the two roots follow each other but roughly, cross- 

 ing between the 1st and Ilnd nerves, between the Ilnd and 

 Ilird, Ilird and IVth, and between the IXth and Xth. The 

 dorsal root of the Ilnd contains the greatest number of root 

 fibers and the dorsal root of the Xth the least number, both of 

 which however are interpolations. 



m 



vm 



Chart II, showing the number of fibers in the dorsal roots, and in the ven- 

 tral roots and the sum of those in the trunk and dorsal branches of the different 

 spinal nerves. The parts of the curves in broken and dotted lines which repre- 

 sent the Ilnd and Xth nerves are interpolations from the records of Birge. 



