THE PROCESS OF EXCITATION 105 



all conditions and all aerobic organisms. This is more or less the 

 impression which we derive of the functional excitation process 

 as seen today. 



Under normal conditions the functional excitation is at once 

 followed by a succession of secondary processes, the "self- 

 regulation of metabolism." Self-regulation after a functional 

 excitation is a fact demonstrated, by experience. But in what 

 manner does it take place in detail ? 



As the functional constituent members of metabolism involve 

 a disintegration of the nitrogen-free atom groups, the functional 

 self-regulation must necessarily furnish in sufficient quantity and 

 in proper form the carbon, hydrogen and oxygen atoms, which 

 have been removed in the production of carbon dioxide and water. 

 This is accomplished, as is well known, by the food and the intake 

 of oxygen. It is of importance to the maintenance of living sub- 

 stance that after every functional activity it is as soon as possible 

 again capable of reaction. Therefore, it is absolutely necessary 

 that this material is in the proper place, where building up is 

 essential, and is at the same time constantly in proper form. 

 Indeed, the restitution of the original state follows ixnder favor- 

 able conditions with lightning rapidity, although varying in dif- 

 ferent forms of living substance. This occurs in the nerve in 

 an extremely short time. From this it might be supposed that 

 the living system by accumulating a store of the necessary com- 

 pensation substances in suitable form, had made itself independ- 

 ent to a certain degree of the frequently varying supply of 

 material obtained from the medium. 



This may be held as the proper view, first with regard to com- 

 pensation substances. The fact that living organisms can under 

 some conditions remain for a lengthened period in a state of 

 starvation, without losing their capability of activity, can only 

 be explained by the presence of a great quantity of reserve sup- 

 plies of compensation substances. In the course of work in the 

 laboratory every physiologist has become acquainted with the 

 fact that frogs which have been kept without food for a year, 

 although much reduced in weight, are still capable of some 

 muscular activity. 



