1 30 CREATIVE EVOLUTION CHAP. 



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 contrary, 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 pre 

 cisely what does take place, as is shown in particular by 

 the experiments of Morat and Dufourt. 1 While the 

 glycogenic function of the liver depends on the action 

 of the excitory nerves which control it, the action of 

 these nerves is subordinated to the action of those 

 which stimulate the locomotor muscles in this sense, 

 that the muscles begin by expending without calculation, 

 thus consuming glycogen, impoverishing the blood of 

 its glucose, and finally causing the liver, which has 

 had to pour into the impoverished blood some of its 

 reserve of glycogen, to manufacture a fresh supply. 

 From the sensori-motor system, then, everything 

 starts ; on that system everything converges ; and we 

 may say, without metaphor, that the rest of the organism 

 is at its service. 



Consider again what happens in a prolonged fast. 

 It is a remarkable fact that in animals that have died of 

 hunger the brain is found to be almost unimpaired, while 

 the other organs have lost more or less of their weight 

 and their cells have undergone profound changes. 2 It 



1 Archives de physiologic, 1892. 



9 De Manaceine, &quot;Quelques Observations experimentales sur [ influence de 



