Hardesty, spinal Nerves of the Frog, 35 1 



dorsal root fibers, and 5.24 fibers distal to the ganglion for every 

 gram the animal gains in weight. DoubHng these would give 

 2.70, 4.76, and 10.48 fibers respectively as the approximate 

 figures for the increase of fibers per gram of weight in the 6th 

 pair of spinal nerves. 



TABLE V. 



Table V. — Showing the rate at which the fibers of the ventral root, dorsal 

 root, and trunk and dorsal branches of the 6th spinal nerve of one side increase 

 in number as the frog increases in weight. The weights are those of the aver- 

 age frogs as determined in Table IV. The differences represent the number of 

 grams and the numbers of fibers gained, and the gain of fibers per gram is ob- 

 tained by dividing the numbers of fibers gained in each locality by the number 

 of grams gained. 



The 6th nerve is one of the smaller spinal nerves of the 

 frog. The 2nd, 7th, 8th, and 9th are considerably larger, 

 while the 5 th and loth are more nearly equal to it. The re- 

 maining nerves are smaller. 



Though the proportional number of fibers contributed to a 

 given nerve is not absolutely constant, yet if we could deter- 

 mine what proportion of the entire set of nerves is generally 

 represented by the 6th, this value (applied) might give us 

 some idea of the relations between the total increase of fibers 

 in all the spinal nerves and the increase of the animal in weight. 

 Unfortunately, the counts formerly made in this laboratory did 

 not include the 2nd and loth nerves. If the computation be 

 restricted to the remaining eight nerves, however, using the 

 figures obtained in the previous paper (Table I, page 69), we 

 get, of these eight nerves alone, the following values for the 

 6th nerve : 



Ventral root-fibers 

 5-5% 



Dorsal root-fibers 

 5-9% 



Fibers in trunk and 

 dorsal branches 



7.2/e 



