tyti 



6 IRRITABILITY 



inadequate stimuli, no matter what one may think of the relations 

 between physical and psychical phenomena. 



The only debatable question is that concerning the limits of the 

 validity of the doctrine of the specific energy of living substances. 

 This question will involve our attention when we have analyzed 

 somewhat more closely the happenings in the living substance 

 taking place under the influence of stimuli. We will, therefore, 

 return later on to a more detailed consideration of the last ques- 

 tion. Nevertheless, we will here refer to a fact which, upon a 

 superficial observation, seems to restrict the validity of the con- 

 ception of the specific energy of living substance. 



In contrast to those reactions to stimuli, which consist merely 

 in the changes of a rapidity of the specific vital process, are 

 another group of reactions in which the influence of stimuli leads 

 to qualitative alterations in the specific vital process. In these 

 instances, the influence of the stimulus directs the metabolism of 

 rest into new channels, so that chemical processes occur in the 

 cell, which under ordinary circumstances do not take place. This 

 group of reactions, which I wish to term "metamorphic stimula- 

 tion and response," are chiefly observed w^here weak stimuli act 

 continuously upon the living substance. These are essentially 

 weak chemical stimuli, which last for a prolonged period or fre- 

 quently reoccur in the life of the cell community. Examples of 

 this are found in the continual ingestion of alcohol and other 

 poisons by the human being, or in the formation of metabolic 

 products of bacteria, etc. The majority of chronic diseases 

 belong to this group of reactions; disease being simply response 

 to stimulation. Disease is life under altered vital conditions and 

 altered vital conditions are stimuli. This simple and self-evident 

 fact shows the immense importance which the knowledge of the 

 general laws of the physiology of stimulation has for pathology. 

 The pathologist, who does not wish to confine his observations 

 to a purely superficial symptomatology or a merely histological 

 morpholog}^ must seek above all to penetrate as deeply as possible 

 into the nature of the general reactions to stimulation in the living 

 organism. It is the essential point which meets him everywhere. 

 In spite of their great interest for pathology, however, it is just 



