Hardesty, spinal Ganglion Cells. 35 



V. Further observations on the conditions eietermining the ex- 

 cess of fibers on the distal side of the spinal ganglion. 



The distal excess was described in the previous papers and 

 some attention was given to probable arrangements of the 

 fibers in producing it. It was shown in a series involving all 

 the spinal nerves of one side of a frog, (i) that of all the nerves, 

 those which in proportion to their trunks have the largest num- 

 ber of fibers in their dorsal branches have also the highest per- 

 centage of distal excess ; (2) that in some cas&s the amount of 

 the distal excess may even exceed the number of fibers in the 

 dorsal branches ; (3) that while in a given nerve (Vlth, consid- 

 from a series of 19 frogs) the increase in weight is not accom- 

 panied by a regular increase in the value of the distal excess in 

 this nerve, yet when the results are grouped for the small and 

 large separately, the distal excess for this nerve shows a decided 

 increase with the gain in weight. It was further suggested 

 that the distal excess is due (i) to the medullated fibers from 

 the sympathetic system which terminate in the spinal ganglion, 

 (2) to cells in the ganglion which send processes toward the 

 periphery but not into the dorsal root, (3) to the bifurcation of 

 the peripheral prolongation of the spinal ganglion neurone of 

 Type I and (4) to the bifurcation of ventral root fibers in the 

 region of the spinal ganglion. 



The observations as to the variations and causes of the 

 distal excess made in these papers, one using the several nerves 

 from one specimen and the other the one nerve from several 

 specimens, should gain significance if further based upon the 

 findings in several nerves from each of several specimens. Ta- 

 ble III is constructed with special .reference to the distal excess 

 and is given as indicating further some of the number relations 

 involving it The table is compiled from the numbers in Tables 

 I and II and represents some relations not brought out in the 

 previous work. 



Attention is called to the following relations as shown in 

 Table III. 



