THE RECONSTITUTION OF ISOLATED PIECES 



109 



have been essentially the same. When the pieces are very large 

 and include a considerable portion of the body, the increase in 

 susceptibility is slight or inappreciable, but with decrease in size of 

 piece increase in susceptibihty becomes greater, provided the pieces 

 are not so small that they fail to undergo complete reconstitution. 

 RecalHng the age differences in susceptibility shown in the 

 preceding chapter to exist, it is evident that the animals resulting 

 from the reconstitution of pieces are, at least as regards their 



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Fig. ig. — Susceptibility of Planaria dorotocephala to KCN o . 001 mol. : ab, short 

 pieces; cd, long pieces; ef, uninjured worms like those from which pieces were taken. 



susceptibihty, younger than the animals from which the pieces were 

 taken. Apparently the process of reconstitution brings about in 

 some way a greater or less degree of rejuvenescence as regards the 

 susceptibility to cyanide, i.e., the rate of metaboHsm. The smaller 

 the piece, the greater the amount of reorganization in the forma- 

 tion of a whole animal and the greater the degree of rejuvenescence. 

 In this connection it is of interest to note that the new tissue 

 formed at the cut ends of the piece is for a considerable time after 

 its formation distinctly more susceptible to cyanide, i.e., younger 



