Hardesty, spinal Nefves'of the Frog, 335 



nerve. The columns of figures in heavier type (columns b and h) represent in 

 each case the number of fibers by which a section taken at the one level of a 

 root or trunk exceeds a section taken at the other level. 



The numbers of fibers found at the two levels of the dorsal and ventral roots 

 are entered in the double column a, and the number of fibers by which the 

 one section of a root exceeds the other, is, in each case, entered in column b 

 opposite the numbers in column a, which give rise to it. The numbers oppo- 

 site each other in columns f and g, are the numbers of fibers found in each 

 nerve trunk at levels 3 and 4, and from these numbers, column h, or the varia- 

 tions found for the trunk, are derived. The number of fibers in the respective 

 dorsal branches as taken at 5, Fig. i, are also recorded in column f, in each 

 case just under the trunk to which they belong. Column e contains the sums 

 of the fibers in the trunk and dorsal branches, and column d contains the vari- 

 ous numbers by which this sum exceeds the sum of the two roots as taken at 

 level 2 and recorded in column c. 



It will be seen that a section of the dorsal root close to 

 the spinal ganglion or that of a ventral root taken close to the 

 spinal cord, is found to contain more fibers than a section in 

 either case taken farther away. The same is true for the nerve 

 trunk. A section taken in close proximity to the spinal gan- 

 glion contains more fibers than are found close to the ramus 

 communicans or at level 4. 



It is also shown (column d), that in every case the number 

 of fibers in the trunk and dorsal branches combined is consid- 

 erably in excess of the sum of those in the two roots. For 

 the sake of convenience the term ^'distal excess " will be used to 

 designate this excess of fibers on the distal side of the ganglion. 



Data as to the intimate structure of the region of the 

 spinal ganglion sufficient to adequately explain the existence of 

 the "distal excess " are wanting at present. An investigation 

 involving this point is now in progress in this laboratory, and a 

 detailed discussion of the causes giving rise to the excess will 

 best be deferred until this investigation has proceeded further. 

 However, some of the relations of the distal excess to the 

 number and grouping of the fibers in the roots, trunk, and 

 dorsal branches, brought out in the present figures, may be 

 mentioned here. 



