THE GENERAL EFFECT OF STIMULATION 85 



secondary effect, which plays a very important part in the activity 

 of the organism. I refer to fatigue. Here a secondary depres- 

 sion is developed in connection with the primary excitation, for 

 fatigue of a living organism must be characterized as a depression 

 of activity. This case shows that we have to distinguish between 

 a primary depression, as for example, produced by temperature 

 reduction, withdrawal of food, deficiency of oxygen, etc., which 

 occurs as a direct effect of stimulation, and secondary depression, 

 which as in fatigue is an indirect result of primary excitation. 



After the cessation of a briefly catalytic stimulus, not exceed- 

 ing the physiological limit of intensity, another secondary result 

 is observed, which is of the greatest importance for the con- 

 tinued existence of the living substance. The catalytic stimulus 

 brings about a disturbance of the equilibrium of metabolism, 

 which after cessation of the stimulus is reestablished by the living 

 substance. In other words : recovery takes place. This funda- 

 mental principle has been known for a long time as the result 

 of observation. If a skeletal muscle of our body has been acti- 

 vated for a prolonged period by nerve impulses, until it has 

 become completely fatigued and incapable of work, a recovery 

 takes place on the cessation of these impulses and the muscle is 

 again capable of action. Likewise, as the result of strong mental 

 activity during the day, we are mentally fatigued in the evening ; 

 recovery, however, occurs during the night, which results from 

 the removal of the source of activity. The next morning finds 

 us refreshed. This restitution occurs in every cell, and the return 

 of its former capability of action, which had disappeared under 

 the influence of stimulation, shows that compensation has taken 

 place of the metabolism of rest, disturbed by the effects of the 

 stimulus. Hering^ has aptly termed this restitution as "the inter- 

 nal self-regulation of metabolism/' All recovery after disease is 

 based on this self-regulation. The physician simply provides, by 

 means of therapy, for the possibility of its taking place. Healing 

 itself is brought about by the organism. "Natura sanat, medicus 

 cur at." 



1 Ewald Hering: "Zur Theorie der Vorgange in der lebendigen Substanz." In 

 Lotos, Bd. 19, Prag. 1888. 



