Donaldson, Nervous System of the Ftog, 315 



thigh weigh 1.8 times as much as those of the rest of the leg. 

 (3). In frogs of all sizes, the sum of the lengths of the 

 leg bones is a nearly constant fraction of the length of the en- 

 tire frog. The proportional lengths of the several bones are 

 also nearly constant. 



Introduction. 



In order to carry out another investigation on the innerva- 

 tion of the leg of the frog, it became necessary to determine 

 the relations summarized in the title of this paper. 



Of all our frogs, the Bull-frog (R. catesbiana) exhibits the 

 greatest variation in size. It was therefore chosen for study in 

 this case and all the statements given below are to be restricted 

 to this species until their applicability to other species has been 

 shown. The results in their first form are exhibited in Table 7 

 and Chart i. Accompanying the table are to be found all 

 remarks concerning the methods employed and the conditions 

 observed during the investigation and the reader is referred to 

 that part of the paper for such data. 



We may therefore at once pass to a presentation of the 

 evidence from which the conclusions stated above have been 



drawn. 



I. The Weight of the Brain and Spinal Cord. 



The proportional weight of the brain and spinal cord de- 

 creases as the body-weight of the frog increases. This is shown 

 in the following table : 



TABLE I. 



In this, Table I, as in the other subsidiary Tables, which 

 follow, the cases are take from Table 7, and the calculations 

 are based on the numbers there given. Each case can be be 

 identified in Table 7 by the body weight, as given above. 



In this investigation, no difference in the weight of the 



