136 ILLINOIS BIOLOGICAL MONOGRAPHS [136 



PART V 



THE EFFECT OF DEGREE OF INJURY UPON THE RATE OF 



REGENERATION 



In a former series of papers the writer gave the results of experi- 

 ments on the effect of degree of injury upon the rate of regeneration. A 

 number of different species of animals and various combinations of 

 injuries were involved. The results then obtained tend on the whole 

 to show that within certain limits the rate of regeneration from an 

 injured surface is not retarded by simultaneous regeneration in other 

 parts of the body. Where a difference exists between the rates with and 

 without additional injury there is usually an advantage in favor of the 

 part with additional injury. The differences are however often slight 

 and in some of the cases come within the limits of probable error. It 

 is only when the data as a whole are taken that it is possible to judge 

 of the correctness of the general conclusion that within fairly wide limits 

 of additional injury there is certainly no decrease in rate of regener- 

 ation but rather a tendency toward an increase. 



Some additional data on these points have been obtained in connec- 

 tion with the present study of the factors of regeneration. On the whole 

 they confirm the previous results. The principal experiment (Experi- 

 ment I) was planned with a view to further analysis of the problem, 

 especially the determination of the effect of additional injury to a like 

 organ as compared with additional injury to an unlike organ. 



Experiment I Amblystoma punctatum Series 4101-4540 



The young were hatched on March 29-April 4, 1913, and the oper- 

 ations were made on May 4 and 5. The measurements of the control 

 individuals at the time of the operations are given in Table 75. The 

 average total length is 31.3 mm., the tail length 14.4 mm., the average 

 length of the fore-legs 3.6 mm. and the average of the hind-legs 1.5 mm. 



The measurements of control individuals at the end of the experi- 

 ment on May 23 are given in Table 76. The total average length is 42.7 

 mm., the tail length 20.0, the average of the fore-legs 6.2 and the average 

 of the hind-legs 4.5 mm. 



The experiment consisted in the determination of the regenerated 

 length of the right fore-leg under three degrees of injury: when the 



