Donaldson, American and European Frogs, 143 



From a study of Chart 6 we see that the form of the curves for 

 the two species is very similar, even in details, although there are 

 two evident differences. 



In the first place, R. pipiens has regularly more fibers in each 

 instance except in the ventral root of the IV spinal nerve, in which 

 it has only 379 fibers against 446 in R. esculenta. In the second 

 place, there is in R. pipiens a marked excess of fibers in the dorsal 

 root of the IX nerve. In R. esculenta, the corresponding excess 

 is distributed between the IX and X nerves. As a second 

 specimen of R. esculenta, weighing 23 grams, examined by Birge 

 ('82) shows a similar distribution, the possibility is suggested that 

 this arrangement may be characteristic for R. esculenta. 



The foregoing Table 16 also brings out the fact that the number 

 of sensory, as compared with the number of motor fibers, is rela- 

 tively greater in R. pipiens. Thus 



R. pipiens . . 

 R. esculenta. 



However a further analysis of this relation shows that in the 

 lumbar nerves VIII, IX and X the proportions of motor to sensory 

 are nearly alike in the two species. 



Motor. Sensory. 



R. pipiens I 1-833 



R. esculenta i i . 827 



Moreover for the III nerve these proportions have been assumed 

 as similar (see Hardesty '99, p. 78), so that the difference which 

 is found when the total number of fibers is compared, must depend 

 on differences in this relation, which exists in the roots of the II, 

 IV, V, VI, VII - - - XI nerves. 



The ratio in this group of roots is 



Motor. Sensory. 



R. pipiens I o . 674 



R. esculenta . 



0-55S 



Thus showing R. pipiens as superior in this last group, although 

 in both species the ratio is less than unity. 



As a consequence of these relations, it appears that while R. 

 pipiens has everywhere a better sensory innervation, because 

 there are absolutely more afferent fibers present for the same area 



