n.i ANIMAL LIFE 123 



the other in that it is always served at the instant it is in 

 need and to the exact extent of its requirements. 



More particularly, it is from the sensori-motor system 

 that the call for glycogen, the potential energy, comes, 

 as if the rest of the organism were simply there in order 

 to transmit force to the nervous system and to the muscles 

 which the nerves control. True, when we think of the 

 part played by the nervous system (even the sensori- 

 motor system) as regulator of the organic life, it may well 

 be asked whether, in this exchange of good offices between 

 it and the rest of the body, the nervous system is indeed 

 a master that the body serves. But we shall already in- 

 cline to this hypothesis when we consider, even in the 

 static state only, the distribution of potential energy 

 among the tissues; and we shall be entirely convinced of it 

 when we reflect upon the conditions in which the energy 

 is expended and restored. For suppose the sensori- 

 motor system is a system like the others, of the same rank 

 as the others. Borne by the whole of the organism, it will 

 wait until an excess of chemical potential is supplied 

 to it before it performs any work. In other words, it 

 is the production of glycogen which will regulate the 

 consumption by the nerves and muscles. On the con- 

 trary, if the sensori-motor system is the actual master, 

 the duration and extent of its action will be independent, 

 to a certain extent at least, of the reserve of glycogen that 

 it holds, and even of that contained in the whole of the 

 organism. It will perform work, and the other tissues 

 will have to arrange as they can to supply it with potential 

 energy. Now, this is precisely what does take place, as is 

 shown in particular by the experiments of Morat and Du- 

 fourt. 1 While the glycogenic function of the liver depends 

 on the action of the excitory nerves which control it, the 



1 Archives de phyaiologie, 1892. 



