Hardesty, spinal Nerves of the Frog. 



85 



root by dividing the area of the transverse section of the root 

 by the number of fibers contained in it. 



Schwalbe ('82) made some determinations of the diameter 

 of the fibers of the two nerve roots of the frog by actually 

 measuring a few fibers of each root and taking the average di- 

 ameter of the fibers thus measured, Schwalbe, like Birge, ob- 

 tains the least diameter for the motor root of the Ilird nerve, 

 but unlike Birge, he finds the greatest average diameter for dor- 

 sal as well as ventral root fibers possessed by the roots of the 

 VII Ith and IXth nerves. The species of frog used by Schwal- 

 be was the same as that used by Birge. 



VIII. The Relation of the Roots to the Trunk. 



In presenting Tables I and II, attention was called to the 

 fact that in every case the sum of the fibers in the trunk and 

 dorsal branches taken just distal to the spinal ganglion, exceeds 

 by a considerable amount the sum of the fibers in the two roots 



Chart IV. Curves showing the relation existing between the sum of the 

 fibers in the two roots taken close up to the spinal ganglia and the sum of the 

 trunk and dorsal branches taken just distal to the spinal ganglion. The lowest 

 curve represents the sum of the dorsal branches alone. 



