( 59J ) 



The negative chronotropy holds good Cor sinus, auricle and ven- 

 tricle to the same extent, the negative inotropy exists exclusively 

 to r the sinus and the auricle, is mostly positive for the ventricle, if 

 it is found ; the tonotropy is met with in auricle and ventricle. 



A latent stage of' the phenomenon, measured by the time-difference 

 between vagus stimulation and vagus action, was always observed. 

 It is smallest for the inotropy ; already the first period often shows 

 an enfeeblement of the contraction, which in the subsequent periods 

 increases still further. The latent stage of the chronotropy is greater, 

 for only in the second, sometimes in the third period, a retardation 

 is noticeable; on the other hand this phenomenon reaches its maximum 

 at once. Inotropy and tonotropy do not coincide. On the contrary, 

 the maxima of effect form the following series as to time: first 

 maximum of chronotropy, then maximum of tonotropy, finally 

 maximum of inotropy. 



In regard to the sensitiveness for vagus stimuli, we remark that 

 for the inotropy the "threshold value" lies below that for the chrono- 

 tropy and for this latter lower again than for the tonotropy. So we have : 



Threshold value for inotropy <^ idem for chronotropy <^ idem 

 for tonotropy. 



From the fact that dromotropy did not occur in our experiments, 

 one would infer that the threshold value of the dromotropy lies 

 higher still in the present case. 



Physiologists are generally convinced that the rhythmic processes 

 at the bottom of the cardiac pulsations, are based on chemical actions 

 in the cardiac muscle. Leaving apart the founder of the myogenic 

 theory Th. W. Engelmann, we mention some authoritative writers, 

 Fano and Botazzi in Richet's Dictionnaire and Hopmann in Nagel's 

 Handbuch, who embrace this point of view r *). 



Also experimental results may be adduced in support of this 

 theory. Snyder a ) showed that the frequency of the contractions with 

 respect to temperature follows exactly the law, formulated by van 

 't Hoff and Arrhenius for chemical reactions 3 ) and experiments, 

 independently made by J. Gewin, entirely confirmed this. ') Whereas 

 the influence of temperature is considerable, that of pressure is \ci-\ 

 small. This agrees with the small significance of external pressure 

 for so-called condensed systems, i. e. systems in which no gaseous 

 phases occur. 



T ) Fano and Botazzi, Richet's Diet, de physiologie t. IV. p. 316. 



~) Snyder, Univ. of California Publications II. p. 125. 1905. 



:; ) E. Cohen, Voordracht en. Biz. 236 1901. 



'i .1. Gewin, Onderzoekingen Physiol. Lab. Utrecht (o). Dl. VII, p. L l±l. 



