no Journal of Comparative Neurology. 



3. In Rana virescens brachycephala the relative weight 

 of the brain compared to that of the spinal cord decreases 

 as the frog increases in size. 



4. The weight of the leg muscles compared with the 

 weight of the entire frog increases in small frogs up to about 5 

 grms. of body weight and then slightly decreases as the frog 

 increases in size. In individuals of all sizes, the muscles of the 

 thigh weigh from 1.78 to 1.80 times as much as those of the 

 rest of the leg. 



5. In frogs of all sizes, the sum of the lengths of the leg 

 bones is a nearly constant fraction of the length of the entire 

 frog. The proportional lengths of the several bones are also 

 nearly constant. 



Introduction. 



The reason for repeating on Rana virescens brachycephala 

 (Cope) a series of observations already made on Rana cates- 

 biana/ is the simple one that the former species is much more 

 readily obtained in this locality and hence more often used for 

 study. In the first instance the Bull frog was chosen for exam- 

 ination because of the great range of size offered by it, but it was 

 expressly stated in the paper referred to that the data obtained 

 from the Bull-frog should not be assumed to hold good for other 

 species of Rana until some evidence to that effect had been 

 brought forward. We may say at once that the relations found 

 in Rana virescens brachycephala are surprisingly similar to 

 those found in R. catesbiana, in spite of some broad differences 

 between the two forms — the most striking of which is the lim- 

 ited range of size in the smaller species. 



The general purpose of this investigation was the same as 

 heretofore, namely, to determine how the central nervous sys- 

 tem changed in weight with the change in the wtight of the 

 body, and especially, of the hind legs, as it was thought that 



' Observations on the Weight and Length of the Central Nervous System 

 and of the Legs, in Bull-frogs of different Sizes, By Henry H. Donaldson. 

 Jour. Comp. Neurol., VIII, 4, Dec, 1898. 



