FURTHER OBSERVATIONS ON THE CONDITIONS 

 DETERMINING THE NUMBER AND ARRANGE- 

 MENT OF THE FIBERS FORMING THE SPINAL 

 NERVES OF THE FROG (RANA VIRESCENS). 



By Irving Hardesty. 



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



I. Summary. 

 II. Introduction. 



III. The material employed. 



1. The size of the animals and the seasons during which they were 



taken. 



2. The nerve chosen for investigation. 



IV. Methods and technique. 



1. Dissection. 



2. Fixing and staining. 



3. Imbedding and sectioning. 



4. The counting technique. 



V, The general results of the counting. 

 VI. The " distal excess " or the excess of fibers on the distal side of the 

 spinal ganglion. 



1. The amount, variation, and proportions of the distal excess. 



2. Some of the conditions that probably affect it. 



VII. The variations in the number of fibers found at different levels of 

 the dorsal root, ventral root, and nerve trunk. 



1. The just values of the variations — how obtained. 



2. The variations dependent on the size of the frog. 



3. Comparison of the variations in the two roots and in the trunk. 

 VIII. The relation between the weight of the frog and the number of fibers 



contained in its spinal nerves. 



1. The number of fibers in proportion to age. 



2. The number of fibers in the three localities per gram of weight. 



3. The rate at which fibers are gained. 



4. Comparison of Rana virescens with Rana esculenta. 

 IX. The Influence of season. 



X. Bibliography. 



