24 IRRITABILITY 



for the liberation of carbon dioxide. It is not the presence of 

 hydrochloric acid or sulphuric acid, as such, which is a condition 

 for the process, but rather the separation of the sodium atoms 

 from their combinations with the oxygen in the molecule of the 

 carbonate. This reaction can occur as a partial component in 

 very different complexes of processes. Or to quote another 

 example, taken from the subject with which we are especially here 

 concerned. I allow an induction shock to act on the nerve of 

 a nerve muscle preparation of the frog. The muscle con- 

 tracts. The electric stimulus is the condition for the muscle con- 

 traction. But I can substitute for the induction shock a mechani- 

 cal stimulus by sudden pressure of the nerve. The muscle again 

 contracts. The analysis again shows that the induction shock as 

 such was not the condition for the muscle contraction, but the 

 excitation of the nerve which it produced and which is conducted 

 as a specific impulse to the muscle. This excitation of the nerve 

 can, however, be induced by very different kinds of processes, 

 namely, by all processes which possess in common the condition 

 that they suddenly increase certain disintegration processes in the 

 living nerve substance. Indeed, the further analysis of the whole 

 process shows in addition that the nerve impulse as such likewise 

 does not form a condition for the contraction of the muscle, but 

 it first of all produces the necessary condition for the muscle 

 contraction by suddenly greatly increasing certain chemical pro- 

 cesses, which take place in the living substance of the resting 

 muscle. The nerve impulse can, therefore, also be replaced by 

 other processes, if only these contain the condition for an increase 

 of disintegration of the muscle substance, as in the case of the 

 direct stimulation of the curarized muscle, where the influence 

 of nervous impulses is totally eliminated. In a further analysis 

 of this process we should penetrate even more deeply into the 

 differentiation of the individual constituent processes and the 

 isolating of the special conditions on which each link in the chain 

 is dependent. 



Such an analysis then shows us the following: Every thing, 

 every state or process, is a complex of numerous components, of 

 which one always conditions the other in the manner that the 



