430 



ELIZABETH HOPKINS DUNN 



killed. Presumably complete degeneration was accomplished. 

 The dorsal roots and the spinal ganglia were found intact. 



The bundles of nerve fibers now under consideration extended 

 from the central end of the ventral root into the spinal ganglion. 

 Their position at the central end of the ventral root was near 

 the center of the cross section of the root. At the point where 

 the ventral root became applied against the dorsal root with a 

 connective tissue septum intervening, the fused bundle turned 

 at almost a right angle and plunged through the substance of 

 the dorsal root and into the spinal ganglion. As a bundle it 

 could be followed dorsally into the ganglion and within the gan- 

 glion laterally into a region where the medullated nerve fibers 



Ganglion dorsale 



Nervus spinalis X 



Rana pipiens 

 Figure 1 



were few and the perikarya numerous. The derivation of these 

 fibers from adjacent perikarya seems a fair assumption. The 

 course of these fibers and their relation to the ganglion is shown 

 diagrammatically in figure 1 . W-Tiile following the fibers serially 

 from A to C, their course from B to C was found to be accom- 

 plished within a dozen sections of ten micra thickness. 



In all, some twenty medullated nerve fibers of varying sizes 

 could be traced to the spinal ganglion of the Xth nerve. On 

 direct measurement, the fibers fell into two groups according to 

 their diameter, those with a diameter of more than ten micra, 

 and those with a diameter of less than five and five-tenths micra. 

 Of the first group, those with a diameter of more than ten micra, 



