194 C. M. CHILD 



increases, namely, their rate of reaction decreases during the 

 first twenty-four hours after section, until, except in relatively 

 large pieces, it is greater (i.e., the rate of reaction is lower) than 

 that of the corresponding region in the uninjured animal. In such 

 a sequence of events we see first the sudden rise in rate due to the 

 cutting; after this the rate gradually falls as the effect of the cut- 

 ting gradually decreases, until finally the rate in small pieces is 

 lower than when they formed part of the uninjured whole. This 

 low rate of small pieces as compared with the uninjured whole, is, 

 as I shall show later, a result of isolation, viz., of the absence or 

 decrease in the action of physiological correlative factors which 

 before isolation played an important part in maintaining the 

 average rate of reaction at a certain level. Manifestly, such 

 changes in physiological resistance occurring in an isolated piece 

 within twenty-four hours or less, cannot be readily or consistently 

 interpreted on any other basis than that of the rate of reaction, 

 especially when they are compared with results obtained in other 

 ways. 



Moreover, it can be shown by the same method that the decrease 

 in resistance (i.e., the increase in the rate of reaction in pieces 

 following cutting) can be largely prevented by partial anesthesia 

 at the time of cutting. 



And finally, as regulation proceeds in the piece, the resistance 

 gradually decreases, namely, the rate of reaction gradually rises, 

 until in cases where the piece forms a new whole, the resistance 

 becomes much lower, i.e., the rate becomes much higher than 

 it was originally when the piece was a part of the uninjured 

 animal. In short, the new whole is physiologically, as well as 

 morphologically, younger than the part of the animal which it 

 originally represented. 



Again, the change in resistance in a piece as compared with the 

 corresponding region of the uninjured animal, varies with the 

 degree of mutilation, viz., the rate of reaction increases tempora- 

 rily as the degree of mutilation increases. And the greater the 

 amount of regulatory reorganization in a piece, the lower the 

 resistance as measured by the direct method, becomes; in other 

 words, the higher its rate of reaction. 



