THE PRESENCE OF MEDULLATED NERVE FIBERS 



PASSING FROM THE SPINAL GANGLION TO 



THE VENTRAL ROOT IN THE FROG, 



RANA PIPIENS' 



ELIZABETH HOPKINS DUNN 



From the Hull Laboratory of Anatomy of the University of Chicago, and The Nelson 

 Morris Institute of Medical Research 



ONE FIGURE 



It seems advisable at the present time to make a brief report 

 of the presence in the nervoufe system of Rana pipiens of a group 

 of medullated nerve fibers appearing in the ventral root which 

 apparently arises in the spinal ganglion. 



Recognition of this group of nerve fibers occurred in the course 

 of a study in the frog (Dunn '09) of the distribution of the pe- 

 ripheral medullated nerve fibers after unilateral section of the 

 ventral roots of the Vlllth, IXth, and Xth spinal nerves, Gaupp's 

 nomenclature. It was found that after degeneration should 

 have occurred in all the ventral root nerve fibers which were 

 out-growths of ventral column neurones in the spinal cord, some 

 intact medullated nerve fibers were found in each root. The 

 medullated nerve fibers in two of the ventral roots were scattered , 

 but fortunately in the ventral root of the Xth spinal nerve some 

 of the fibers were grouped in two bundles and could be traced to 

 the Xth spinal ganglion. 



In this frog the ventral roots had been torn loose at their points 

 of emergence from the spinal cord and were left free in the spinal 

 canal. Because of their preservation by this method of operating 

 the ventral roots could be examined for their full extent. The 

 operation was performed eight months before the frog was 



^ Reported at the meeting of the American Association of Anatomists in the 

 winter of 1910. 



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