THE RECONSTITUTION OF ISOLATED PIECES 107 



ment of the new animal from the piece is completed, the suscepti- 

 bility is greater than that in the corresponding region of the parent 

 animal. This means that during reconstitution the rate of metab- 

 olism increases until it is higher than before section. This increase 

 in rate is not the result of a stimulation which soon disappears, but 

 is connected with the process of reconstitution and is relatively 

 permanent. The rate after reconstitution is the rate characteristic 

 of a physiologically young animal, and it undergoes a gradual 

 decrease as the animal grows and becomes physiologically older. 

 Here also size is a factor in the result: the smaller the piece which 

 undergoes reconstitution into a new whole, the greater the increase 

 in rate of reaction during reconstitution. This increase in meta- 

 bolic activity during reconstitution was first discovered by means 

 of the acclimation method with alcohol as a reagent (Child, 'n). 

 In these earlier experiments a marked increase in rate was found 

 in small pieces, but in very large pieces a decrease in rate apparently 

 occurred. As a matter of fact, the rate does not decrease in large 

 pieces during reconstitution, but increases slightly. My error on 

 this point was due to failure to keep the normal animals under the 

 same conditions as the experimental pieces. In the case of the 

 large pieces the effect of the conditions more than compensated the 

 slight increase in rate due to reconstitution, but in the small pieces, 

 where the increase was much greater, it appeared in spite of the 

 external conditions. 



More recent and extended investigation by the direct method 

 with cyanide as reagent has demonstrated beyond a doubt that 

 reconstitution is accompanied by an increase in rate, the amount 

 of increase varying with the size of the piece, the amount of reconsti- 

 tutional change, and various other factors. 



The partial record of one series of experiments will serve to 

 show both the increase in susceptibility, i.e., of rate of metabolism 

 resulting from reconstitution, and the relation between the amount 

 of increase and the size of the piece. In this experiment large, 

 physiologically old worms eighteen to twenty millimeters in length 

 constituted the material. From a part of these worms pieces in- 

 cluding the region ac in Fig. 18, from another part pieces including 

 the region ab, i.e., just half the length of the preceding lot, were 



