( 593 ) 



inotropic changes occur 1 ) and the mechanical resistance which the 

 heart has to overcome, has remained the same. 



These premisses made, we may at once apply the fundamental 

 equation of Guldberg and Waage's law ; 



<p = kC n 



Here h is a constant, the constant of the reactional velocity, 6 is 

 the quantity of the substance, taking pari in the reaction, // is the 

 exponent, determining the so-called order of the reaction, while <p 

 indicates the reactional velocity. About the exponent n nothing can 

 be stated a priori for the heart. Toxicological experiments, in which 

 the quantity of the reacting substance diminishes, might perhaps 

 teach us something in this respect ; perhaps also experiments on 

 fatigue might give us some clue; at present, however, no data at 

 all are available. Whether there are intermediate reactions and in 

 what number, cannot be ascertained. Under these circumstances I 

 assume, quite arbitrarily, that the present case is the simplest and 

 that the exponent is unity. If later this assumption turns out to be 

 wrong, our calculations will still apply, mutatis mutandis, without 

 losing their meaning. In this simple case the formula runs: 



When the vagus is stimulated a very marked alteration of the 

 times of equal change is noticed. The reactional velocity of the 

 hypothetical chemical process, which lies at the bottom of the auto- 

 matism, must consequently undergo a very considerable change 

 Such a change cannot take place unless either /■ or C are modified. 

 In the literature on the subject both views are put forth, but only 

 the conception that k changes, leads to a clear explanation without 

 further auxiliary hypotheses. It also tits in best with a recent paper 

 of Martin 2 ), according to which vagus-inhibition is ascribed to the 

 action of AT-ions and is counter-acted by rise of temperature. The 

 significance of the ions of the alkalies and alkaline earths for the 

 cardiac muscle is indeed by no means fully explained, even after 

 the mumerous investigations of J. Loeb and his followers and critics 

 — they are regarded by some as the cause of the continually 

 excited condition of the cardiac muscle, as the stimulus for the 

 automatism 3 ), by others as the condition, necessary for keeping l lie 



[ ) In the ventricle vagus-stimulation produces no inotropy . 



2 ) Martin. Amer. Journal of Physiol. Vol. XI, p. 370, 1904 (Martin himself seems 

 to assume a compound of K-\ons with C). 

 :i ) Wenckebach. Die Arythmie etc. Eine physiol. -klinische Studie. Leipzig. 1901. 



40 

 Proceedings Royal Acad. Amsterdam. Vol. IX. 



