122 CREATIVE EVOLUTION [chap. 



movement or heat. In short, the chief function of the 

 albuminoids is to repair the machine, while the function 

 of the other class of substances is to supply power. It 

 is natural that the albuminoids should have no specially 

 allotted destination, since every part of the machine has 

 to be maintained. But not so with the other substances. 

 The carbohydrates are distributed very unequally, and 

 this inequality of distribution seems to us in the highest 

 degree instructive. 



Conveyed by the arterial blood in the form of glucose, 

 these substances are deposited, in the form of glycogen, 

 in the different cells forming the tissues. We know that 

 one of the principal functions of the liver is to maintain 

 at a constant level the quantity of glucose held by the 

 blood, by means of the reserves of glycogen secreted by the 

 hepatic cells. Now, in this circulation of glucose and 

 accumulation of glycogen, it is easy to see that the effect 

 is as if the whole effort of the organism were directed 

 towards providing with potential energy the elements of 

 both the muscular and the nervous tissues. The organ- 

 ism proceeds differently in the two cases, but it arrives 

 at the same result. In the first case, it provides the muscle- 

 cell with a large reserve deposited in advance: the quantity 

 of glycogen contained in the muscles is, indeed, enormous 

 in comparison with what is found in the other tissues. 

 In the nervous tissue, on the contrary, the reserve is 

 small (the nervous elements, whose function is merely 

 to liberate the potential energy stored in the muscle, never 

 have to furnish much work at one time) ; but the remark- 

 able thing is that this reserve is restored by the blood at 

 the very moment that it is expended, so that the nerve 

 is instantly recharged with potential energy. Muscular 

 tissue and nervous tissue are, therefore, both privileged, 

 the one in that it is stocked with a large reserve of energy, 



