Hardesty, spinal Nerves of the Frog. 327 



thought that some interesting and perhaps important light might 

 be thrown on the growth and the arrangement of the nerve 

 fibers as indicated from the examination of the spinal nerves of 

 the two frogs previously employed, if (i) the nerves of a 

 greater number of frogs were investigated ; (2) if these were 

 taken so as to differ more widely in weight ; and (3) if they 

 were taken also at different seasons of the year. This paper is 

 a record of such an investigation. 



III. The Material Employed. 



For the purposes stated, it was necessary to use specimens 

 so chosen as to offer a wide range in weights, and at the same 

 time taken at different seasons of the year. Thus, in order not 

 to confuse whatever influence season might have in the growth 

 processes with differences in the rate of growth occurring in 

 frogs of different weights or stages of growth, it was necessary 

 to group the frogs according to weight and let each season be 

 represented by a frog of as nearly the same weight as possible. 

 In this way the frogs employed fall into three groups of body- 

 weight ; each group containing specimens taken in five different 

 months of the year. The three groups comprise seventeen 

 different specimens, ranging from 4.7 grams to 78.8 grams in 

 weight. The group of smaller frogs contains seven specimens 

 with weights varying between 4.7 and 10.7 grams. A group 

 of medium sized specimens involves 5 frogs weighing from 21 

 to 40 grams, and a group of five larger specimens ranges from 

 48 to 78 grams. 



Since it would have been an almost interminable task to 

 make the necessary counts of the fibers contained in the entire 

 ten spinal nerves, even of one side, only one nerve was exam- 

 ined from each frog, it being assumed that one nerve will show 

 most of the relations which could be obtained from an examin- 

 ation of two or more. 



Moreover, it was not thought necessary that this one be 

 the largest spinal nerve possessed by the frog. 



The 6th. spinal nerve was therefore chosen, both because 

 of its moderate size and because its dorsal and ventral roots are 



