28 



SHINKISHI HATAI 



c. Mean and Standard Deviation 



As has already been pointed out by both Boycott and Taka- 

 hashi, a determination of the proper average is very difficult on 

 account of possible modifications due to the technique. The 

 larger the animal, the longer is the internode, and vice versa. 

 In the former case, the longer internode is easily broken and as 

 a consequence the shorter internodes are more often measured 

 than the longer ones, while in the smaller frogs such accidents 

 are less frequent, and the resultiug mean will therefore be much 

 nearer to the true value in this case than in the case of the larger 

 frogs. We cannot however eliminate this error but it must be 

 kept in mind when we come to draw the final conclusions. Our 

 observations yield the following mean values for each group: 



GROUP I 



% 



GROUP II 



% inc. 



GROUP III 



% inc . 



GROUP IV 



% inc 



GROUP V 



% Inc. 



t,. Diameter. 



Mean 



Internode 



6.7 



532 2 



0.0 



1.0 



7.612.43 

 670.2 25.04 



8.4 

 706.9 



25.15 

 30.95 



10.3 



1031.2 



52.43 10.6 57.01 

 33.761311.5146.45 



As we should expect, the mean values for both diameter and 

 internode increase from group 1 to group 5. In order to see 

 how much increase both diameter and internode have made 

 during these five stages, the two measurements in group 1 were 

 compared with those of the succeeding stages. As is shown in the 

 same table, the percentage increase for the diameter is far below 

 that for the internode. In fact the total increment in the diame- 

 ter of group 5 over that of group 1 is only slightly more than half 

 of the value of group 1, while in the case of the internode, it 

 amounts to more than one and a half times the value of group 1. 

 This means of course that the internode has grown three times 

 more rapidly than the diameter during the same period. Whether 

 or not this relation of growth is also true for the growth of the 

 thigh itself, when its width and length are compared, is an inter- 

 esting point to be determined. At least one fact is true as will 

 be shown later, that the growth rates of the internode and of the 

 entire nerve are approximately equal. 



