137] RATE OF REGENERATION— ZELENY 137 



right fore-leg alone is removed, when its mate is also removed and finally 

 when its mate and one-half of the tail are removed. In the last two cases 

 the average of the two fore-legs is taken as the proper value for the 

 regeneration of a fore-leg. A large number of individuals, all hatched 

 from the same lot of eggs, were used and a selection of larvae was made 

 so as to make the experimental animals as nearly alike as possible in 

 this respect. In each of the five sets an individual for each degree of 

 injury was killed at two days after the operation, and also at four, six, 

 eight, ten, twelve, fourteen, sixteen and nineteen days. The data are 

 given in Tables 77 to 88. The three degrees of injury may be represented 

 by (1) R, (2) R+L, (3) R+L+i/ 2 T, in which R=right fore-leg removed, 

 L=left fore-leg removed and i/^T=one-half of the tail removed. The 

 second involves the removal of some additional material of the same 

 kind as that removed in the first. The third as compared with the first 

 involves the removal of some of the same kind of material and some of 

 another kind. In every case it is the regeneration of the fore-leg that is 

 used as the basis of comparison. 



The additional simultaneous injury and regeneration does not de- 

 crease the regeneration of the individual fore-leg. At two days the 

 average regenerated lengths of a fore-leg are respectively 0.13, 0.16 and 

 0.15 mm. for the three degrees of additional injury ; at four days the 

 corresponding values are 0.22, 0.36 and 0.29 ; at six days 0.42, 0.53 and 

 0.55; at eight days 0.66, 0.83 and 0.73; at ten days 0.91, 1.34 and 1.24; 

 at twelve days 1.48, 1.60 and 1.61; at fourteen days 1.98, 2.19 and 2.29; 

 at sixteen days 3.02, 3.01 and 3.08 ; at nineteen days 3.84, 3.64 and 3.90. 

 At only two of the nine periods is the regeneration of the fore-leg without 

 additional injury as rapid as that of a fore-leg with additional injury 

 and at these two times it is less rapid than one of the two other groups. 

 In seven of the nine cases the regeneration of the fore-leg without 

 additional injury is less than either of the two with such injury. 



Among the forty individual comparisons in which all three degrees 

 are present the degree with no additional injury has 6% firsts, the degree 

 with an additional fore-leg 15% firsts and the degree with an additional 

 fore-leg plus one-half of the tail has 17% firsts. Among the nine time 

 groups the degree with no additional injury has 1% firsts and each of 

 the additional injury combinations has 3% firsts. 



Taking up the lowest positions in the three degrees in the same way, 

 among the forty individual comparisons the degree with no additional 

 injury gives the lowest regeneration in 21% cases while the additional 

 injury combinations each have only 9% lowest regenerations. Among 

 the nine time groups the degree with no additional injury has the lowest 

 value 6 times, the one with an additional removal of the other fore-leg 



