62 ILLINOIS BIOLOGICAL MONOGRAPHS [62 



is still a considerable production of new cells by mitotic division except in 

 the individuals with the two shortest removals in which the process is 

 completed. The regenerated lengths for the six levels beginning with the 

 shortest removal are respectively 1.0, 1.3, 1.4, 2.3, 3.7 and 5.1 mm. The 

 data are given in the last two columns of table 37. There is very dis- 

 tinctly an increase in regenerated length with increase in removed 

 length. Dividing the regenerated length by the removed length at each 

 level, the fractions obtained are 



1.0 1.3 1.4 2.3 3.7 5.1 



and 



1.5 2.8 4.9 8.4 13.1 18.1 



which give the specific regenerated lengths or lengths regenerated per 

 unit of removed lengths. These values are 0.67, 0.46, 0.29, 0.28, 0.28 and 

 0.28. They show a remarkable constancy for removed lengths of 4.9 

 mm. and over. The relations between removed lengths and regenerated 

 lengths are further shown in figure 4 which gives the removed lengths 

 along the horizontal axis and the regenerated lengths parallel to the 

 vertical axis. The plotted line of correlation between the two values 

 is straight except for the two lowest removed lengths. The specific 

 lengths are given in Figure 5 in which the removal lengths again are 

 along the horizontal axis and the lengths regenerated per unit of removed 

 length parallel to the vertical axis. The line of correlation is straight 

 and parallel to the horizontal axis for the four highest removals. For 

 these therefore the regenerated length is directly proportional to the 

 removed length or in other words within these limits the same percent- 

 age of the removed length is regenerated in each within the given time 

 of ten clays. 



The two lowest removed lengths give a higher specific rate than the 

 others. They regenerate a higher percentage of the removed length 

 within the given time. 



The ten day period is chosen as the first example because it is the 

 first one to receive the full benefit of the periods of maximum rate of 

 regeneration, the periods during which rapid multiplication of cells 

 takes place. The other periods give results which agree in general 

 features after the first few days with those at ten days but depart from 

 them in certain respects. 



The remaining periods will now be taken up in turn beginning with 

 the shortest. 



During the first four days after the operation the rate of regenera- 

 tion is slow, the new tissue being derived largely from migration of 

 cells over the cut surface. Measurements of regeneration at this time 

 are especially subject to error because of the small amount regenerated 



