( 594 ) 



active substances in solution l ) — they certainly do not enter into 

 simple chemical combination with the cardiac substance, by which this 

 latter would become unfit. If this latter were the case, the life- 

 prolonging influence of Ringer's solution and the remarkable anta- 

 gonism of Na and K on one hand and Ca on the other, would be 

 entirely unexplainable. 



By placing the principal weight on the hypothesis that the vagus 

 alters the constant of velocity, of reaction we were led to the applica- 

 tion of the formula for the catalytic acceleration of a chemical reac- 

 tion. The catalytic acceleration is here negative. The explanation of 

 the formula will be found in G. Bredig's work. Tt runs: 



1 1 



£ = k' — k = 



By application to our experiments, the normal duration of the period 



being indicated by (t 2 — t x ) the altered one during the principal retardation 

 by {t\ — t\), a relation became evident which appears to be constantly 

 found between the intensity of l lie vagus stimulus on one hand and 

 the retardation, indicated by ,? on the other. (An examination of the 

 curves, recorded by the heart would show that the retardation affects 

 principally the diastolic part of tlie process, but since for this part, 

 taken separately, the times of equal change cannot be sharply deter- 

 mined, our calculations enclose the whole process). 



When the vagus stimulus increases the retardation increases also 

 very gradually, until a definite degree is reached ; from this moment 

 the reactional velocity of the hypothetical process of the automatism 

 remains the same, independent of any rise in the intensity of the 

 stimulus. Only by increase of the duration of the vagus stimulus, a 

 new retardation may be produced, which is pretty well proportional 

 to the extension of the duration of the stimulus. For a warmed 

 heart all this holds without any alteration. 



l ) H. J. Hamburger. Osmotischer Druck uncTIonenlehre.^Bd. Ill, p. 127. 



