THE NUMBER AND ARRANGEMENT OF THE 



FIBERS FORMING THE SPINAL NERVES 



OF THE FROG (RANA VIRESCENS). 



By Irving Hardesty. 



(From the Neurological Laboratory of the University of Chicago.) 

 With Plates VI to XIII. 

 I. Summary. 

 II. Introduction. 



III. The Gross Anatomy of the spinal nerves. 



1. Variations in tlie ventral and dorsal roots. 



2. Variations in the dorsal branches of the different spinal nerves. 



3. Variations in the distance between the spinal ganglia and the 



rami communicantes. 



IV. The nerves in which the enumerations were made. 



V. The number and arrangement of the fibers in the dorsal and ventral 

 roots and in the beginning nerve trunk. 

 I. Changes in the number of fibers. 



a. In the roots. 



b. In the trunk. 



c. As affected by growth. 



VI. The role played by the smaller fibers. 

 VII. The relation of the dorsal and ventral roots to each other. 



1. Size of the roots in the different spinal nerves. 



2. The excess of dorsal root fibers. 



3. The increase in the number of dorsal root fibers. 

 VIII. The relations of the roots to the trunk. 



1. The excess of fibers forming the trunk and dorsal branches. 



2. The amount of the excess for the different spinal nerves. 



3. The correlation between the excess of fibers and the size of the 



dorsal branches. 

 IX. Discussion of the observations here made and comparisons with the re- 

 sults of other observers. 



1. The excess. 



2. The variations in number. 

 X. Methods and technique. 



1. General conditions. 



2. Method of dissection. 



3. Histological technique. 



4. Photographic technique. 



5. The method of counting. 

 XI. Bibliography. 



XII. Explanation of the plates. 



