THE RECONSTITUTION OF ISOLATED PIECES 



susceptibility of the headless forms falls below that of the whole 

 animals, but later rises considerably above it. This is simply 

 an expression of the fact that there is no part of the headless piece 

 which has as high a rate of metabolism as the head-region of the 

 whole animal, but that the rate in the headless piece is considerably 

 higher than that of the regions of lowest rate in the whole animal. 

 It is also evident from Fig. 25 that the difference between normal 



Stages 



II 



III 



IV 



V 



Hours 1234567 



FIG. 25. Susceptibility of Planaria dorotocephala to KCN o.ooi mol. after 

 different degrees of reconstitution: unbroken line, uninjured animals like those from 

 which pieces were taken; short dashes, normal forms after reconstitution; long 

 dashes, teratophthalmic forms; alternate long and short dashes, anophthalmic forms; 

 dots, headless forms. 



and teratophthalmic forms is slight and much less than that between 

 teratophthalmic and anophthalmic forms. 



These curves are a graphic presentation in dynamic terms of 

 the degree of rejuvenescence in its relation to the degree of recon- 

 stitution. Similar tests of the susceptibility of the different 

 reconstitutional forms have been made repeatedly with pieces of 

 different size and from different regions of the body and always 

 with essentially the same result. 



