REGENERATION AND DEATH 205 



the skin all the time ? always ready to act, to come 

 forward, waiting only for the chance, and that there is 

 besides something which keeps it in, which holds it 

 back, which stops it ? We call this stopping physio- 

 logical function inhibition ; we say that the growth 

 of the skin is inhibited ; though in the deep part of 

 the skin all the time there are the cells ready to grow 

 as soon as that power of inhibition is taken away, while 

 it is active they will not grow. The simple blister 

 tells us all that. There is, then, a power of regulation 

 which expresses itself in this inhibitory effect. When 

 a salamander has its tail cut off by the experimenter 

 and the new tail grows, just enough is produced. The 

 new tail is like the old. The tissues grow out until 

 the volume of that which is lost is replaced, and then 

 they stop. But if the tail should be cut off again, re- 

 generation would occur again. The experiments may 

 be repeated many times over. It indicates to us that 

 always the growing power is there, but it is held in 

 check. What that check may be is one of the great 

 discoveries we are now longing for. The discovery, 

 when made, is likely to prove of great practical im- 

 portance. The phenomenon of things escaping from 

 inhibitory control and overgrowing is familiar. Such 

 escapes we encounter in tumors, cancers, sarcoma, 

 and various other abnormal forms of growth that occur 

 in the body. 1 They are due to the inherent growth 



A semi-popular exposition of this view regarding malignant tumors has been 

 published by V. Dungern and R. Werner, Das Wesen der bosartigen Gesch- 

 wtilste. Eine biologische Studie, 8vo. pp. 159, Leipzig, 1907. 



