THE RECONSTITUTION OF ISOLATED PIECES 105 



size of the isolated piece. In the course of the process some parts 

 of the piece atrophy and disappear, new parts arise and differen- 

 tiate, and a large amount of cell division and growth occur. The 

 piece does not, in many cases cannot, feed until the development of 

 the new individual has reached a certain stage, consequently the 

 energy for the changes which occur must be derived from the 

 nutritive reserves and the tissues of the piece itself. In this con- 

 nection it may be noted that the volume of the new animal is al- 

 ways considerably less than that of the piece from which it arose; 

 in other words, the piece undergoes a considerable amount of reduc- 

 tion in producing a new individual. 



The development of the new animal in this process of recon- 

 stitution is not fundamentally different from embryonic develop- 

 ment (Child, 'i2ff, '13) — it merely occurs under rather different 

 conditions; nor is it essentially different from the process of agamic 

 reproduction in nature; it is, in short, an experimental reproduction. 

 Moreover, the new animal thus produced resembles a young ani- 

 mal in its morphological features and is capable, when fed, of growth 

 and development, in fact, of going through aU stages of the life 

 history beyond that which it apparently represents. All these 

 facts raise the question whether such an animal is or may be younger 

 physiologically as well as morphologically than the animal from 

 which the piece was taken. This question is considered in the 

 following section. 



CHANGES IN SUSCEPTIBILITY DtTRING THE RECONSTITUTION 



OF PIECES 



An extensive investigation of the changes during reconstitution 

 in the susceptibility of isolated pieces to cyanide has been made by 

 the direct susceptibihty method. It should be borne in mind that 

 changes in susceptibility as indicated by this method indicate 

 change in the same direction of rate of metaboKsm. The results 

 of these experiments are given here only in general terms. The 

 complete data have appeared elsewhere (Child, '14a). 



The first change follows immediately upon the act of isolation. 

 The susceptibihty of the piece immediately after isolation is greater, 

 i.e., its rate of metaboKsm is higher, than that of the same region 



