Hardesty, Spinal Nen'cs of the Frog. 89 



the spinal ganglion than is contained in the two roots central to 

 it, is very evident. In several instances an excess has been ob- 

 tained by previous observes. 



Holl ('75) counted the fibers in the two roots and in the 

 trunk of three of the lumbar nerves of the frog. In every case 

 his counts showed a slight excess in favor of the trunk. This 

 excess, however, never exceeded 2 % and the author concluded 

 that the number of fibers on the two sides of the spinal gan- 

 glion was the same. He explained the excess as due to errors 

 in counting. 



Freud ('78), in investigating the spinal ganglia of Petromy- 

 zon, reached the general conclusion that the number of dorsal 

 root fibers was equivalent to the number of spinal ganglion 

 cells. However, he barely mentions on page 79 that, in Pe- 

 tromyzon, he found an increase of fibers in the trunk. This 

 increase he regards as occurring within the ganglion and con- 

 siders it of little importance, thinking it due to a splitting of 

 the processes of the spinal ganglion cells. Figures illustrating 

 this splitting are give in his plates. Freud's counts were made 

 from teased preparations. 



Stienon ('80) in studying the relation of the dorsal root 

 fibers to the cells of the spinal ganglion, made two counts of 

 the fibers in the two roots and in the trunk. In one of these 

 counts, a cervical nerve of the dog was used and in the other a 

 lumbar nerve of the frog. In both he obtained a slight excess 

 in the trunk (1.2% for the frog) and, like Holl, explained the 

 excess as due to errors in technique. 



Birge ('82) who, as before mentioned, made counts of the 

 several spinal nerves of the frog, obtained for two of the nerves 

 quite an appreciable excess of fibers in the trunk. In one 

 (Ilnd) there were found nearly 16% more fibers in the trunk 

 than in the two roots, and in the other (IXth) an excess of 

 nearly 14%. Birge is the first to attach a significance to the 

 excess found. While admitting that the differences obtained 

 might lie within the bounds of error in technique, yet he did 

 not think this probable and suggests that the matter be further 

 investigated. 



