THE GENERAL EFFECT OF STIMULATION 77 



these qualitative alterations of the normal vital process produced 

 by continuous stimulation which have up to now been least ana- 

 lyzed. In this field we expect much from pathological inves- 

 tigation which alone has the immense amount of material at its 

 command. This will take place only when pathology adds to the 

 almost exclusively histological direction of investigation, that also 

 of experimental physiology. It is true that the problems of the 

 qualitative alterations of a vital process by chronic stimulation 

 are much more complicated than those of the rapid responses to 

 temporary stimuli, consisting simply in mere alterations of 

 rapidity of the specific vital process. An understanding of the 

 nature of the former can only be expected when a deeper knowl- 

 edge of the latter is gained, for, as will be seen presently, there is 

 the closest relation between the two groups. 



The reactions to catalytic stimuli of short duration, which pro- 

 duce merely an alteration of rapidity in the specific phenomena 

 of a living organism, show on a closer analysis the interesting 

 fact, that it is not always the entire metabolic processes of the 

 cell which are perceptibly quickened, but that only certain con- 

 stituent processes of the same are affected by the action of exci- 

 tation. This is the more noticeable, as, considering the close corre- 

 lation which all the individual links of the chain of metabolism 

 bear to each other, it is to be expected that the alteration in rapid- 

 ity of one would be followed at once by a corresponding change 

 in all the others. An example of the case in question, in which 

 a special constituent process may be predominately affected, is 

 that of the specific activity of a muscle which is repeatedly stimu- 

 lated by nervous impulses. Since the classical investigation of 

 Pick and Wislicenus 1 on themselves, and of Volt 2 on the dog, we 

 know that the nitrogen metabolism is practically unaltered by 

 the functional use of the muscle and there is a remarkable 

 increase only in the breaking down of the nitrogen-free groups 



1 Pick und Wislicenus: "Ueber die Entstehung der Muskelkraft." Vierteljahres- 

 schrift d. Ziiricher Naturforschenden Gesellschaft. Bd. 10, 1865. 



2 Voit: "Ueber die Entwicklung der Lehre der Quelle der Muskelkraft und einiger 

 Theile der Ernahrung seit 25 Jahren." Zeitschrift f. Biologic Bd. VI, 1870. 



Derselbe: Physiologic des allgemeinen Stoffwechsels u. d. Ernahrung. In Her- 

 manns Handbuch d. Physiologic, Bd. VI, 1881. 



