( :m ) 



llial also ill llic liuinaii licai-i a ■|»ivmaliire" ('(mtraclioii coiniiifi,' lï-oiu 

 tlie auricle is ollcii succeeded \)\ a too short compeiisatorv pause. 

 The possihihlv of (hsliiigiiishiiig in this wav helweeii auricidar and 

 venti'icnUir extra svstoles had not escaped his allention. 



AVhcji rellecting' npon the consequences wliich extra sysloles coming 

 from Ihe auricle must have on the action of the heart and the cir- 

 cidalion of the hiood of man, 1 found the follow ing simple ex[)laiialioii 

 of the ahove mentioned pheinnnenoji, an explanation from which 

 ensues that we have not got anything to do witli a difference in 

 principle between the frog's heart and the mammalian heart and 

 that it is founded on an anatomic difference l)etweeii the two hearts. 



EN(iKi,MANX (5) has shown that in mnscnlar tissue of ecpial com- 

 position tlie stimnliis to contraction is conducted also at an ecpial 

 rate in all directions. So when an artificial stimnlns is given to the 

 auricle, a conti*action stimnlns and with it a contraction \\a\t' will 

 pass from the slimidaled point not only to the lower parts of the 

 auricle and to the ventricle, luit also to the higher jtarts of llie 

 auricle and 1o the vena cava, so to the place where normally the 

 stimulus is formed and the contraction begins. Engelman.n (tj) has 

 already j)ointe<l to the importance which this "antiperistaltic" move- 

 ment may have for the action of the heart, Ci siiNV and .Mattiikws 

 lia\e also seen the possibility of it. 



When a stimnlns is applied late in the irritable period of the 

 auricl(\ so just before the moment when the following physiological 

 stimulus was to come IVom the vena cava, the stimulus (and the 

 contraction) will not be able to reach the vena cava any more 

 before the j)hysiological stimulus has had its effect there: auricle and 

 ventricle will obey the extra stimulus, the spontaneous contraction 

 already begun will not go on, but the rliylhm at the venai' is not 

 disturbed. 



If the extra-systole sets in a little earlier, the extra contraction 

 might reach the vena cava just at the moment that the |)hysiological 

 stimulus had developed to the necessary intensity ; then also auricle 

 and ventricle obey the extra stimulus, the physiological stimulus is 

 neutralized or it finds the whole heart refractory, but here too the 

 rhythm of the formation of the stimulus is not disturbed and the 

 j)ause of auricle and ventricle is completely compensatory. 



When however the auricle is stimulated still earlier, the extra 

 contraction will reach the \'ena cava before the moment, in which the 

 stimulus to contraction forming there, had attained at sufficient strength 

 to cause a contraction. The stimulating matter found there at that 

 moment will be destroved by the extra contraction : from this moment 



