332 Journal of Comparative Neurology. 



from those kept at the ordinary basement temperature of the 

 laboratory. The fact that these were not in the normal state 

 of hibernation has possibly somewhat influenced the result 

 attained. In most cases, the frogs of a given month were 

 taken at the same time. Occasionally, however, frogs of all the 

 weights required, could not be obtained within the same week. 

 The reference numerals of Figure i, mark the levels at 

 which the sections were taken. ,This figure is made from a 

 camera drawing of a typical 6th. spinal nerve. 



Figure i. — A typical 6th. spinal nerve of Rana virescens. The numerals 

 indicate the localities from which the sections were taken, the fibers in which 

 sections were counted. The sections of the roots were made near the spinal 

 cord at i and near the spinal ganglion at 2. Sections of the nerve trunk were 

 taken at the levels indicated by 3 and 4, while 5 marks the locality at which the 

 fibers in the dorsal branches were enumerated. The ramus communicans is 

 shown on the distal side of level 4. 



It will be seen that level i is near the end of the nerve 

 roots and therefore would be close to the spinal cord, while 2 

 represents the level at which sections were taken as near the 

 spinal ganglion as possible. Level 3 shows where the first sec- 

 tion of the nerve trunk was taken, and 4, where the second 

 section was taken, or the region just before the ramus commu- 

 nicans is given off. Unlike the nerves caudad to it, the 6th. 

 nerve very rarely has more than one ramus communicans. The 

 sections of the dorsal branches were taken at level 5. 



Table I contains a record of the number of nerve fibers 

 found in sections taken at the above levels, from a 6th. spinal 

 nerve of each of the frogs mentioned. The entries are made 

 in the order of the weights of the specimens. No attention is 

 paid here to the season during which the nerves were prepared. 



