28fi 



nf llic 1(111^- iiii<l llio sliorl |);uisos during the alteriiaüoii. When once 

 pnlsaling in alternation the liearl eontinues of itself to oscillate round 

 tliis avei-age. Every large sy.slole is followed by a shorter pause, so 

 that there are two reasons, why every following systole will be 

 little, namely : 



1. the short [)receding pause. 



2. the fael that the preceding systoles are large. 



And so, conversely, every little systole will be followed by a 

 large one. This will be so, because the preceding systole is little, 

 and the preceding pause long. P'or this reason a once existing 

 alleniation easily continues. 



Now I thought it desirable to study this heart-phenonienon likewise 

 with the string-galvanometer. Tiie communications on this subject 

 are so contradictory that I felt the desire to study the action-currents 

 of the sinijile frog's heart possessing but one ventricle during the 

 allernation. My experiment facilitated my investigations considerably ; 

 1 could now at any lime by any method make hearts pulsate alter- 

 natingiv; I iledncted the action-currents in the usual way from the 

 point and the basis or auricle. I represent here in Fig. H the sus- 

 pension-curve and the electrogram of a frog's heart that by itself 

 was pulsating allernatingly. (Fig. (3. Time in '/. sec.) After the sixth 

 systole I refrigerated the sinus venosus by pouring a little cliloric 

 etiiyl on it. 



We see in the row of curves the /I'-oscillations remain ecjually 

 large. The slow 7-oscillations are for the little systoles considerably 

 larger than for the large ones. The consequence of this is, that the 

 electric curves alternate over against the mechanical ones in an 

 opposite sense. 



And this can easily be exi)lained. The negativities of the basis 

 and of the point are transmitted from the ventricle to the measuring- 

 apparatus. These negativities demonstrate themselves there in opposite 

 signs. In so far as consequently the basis- and the point-negativities 

 coincide, they are subtracted from each other. Li the mechanical 

 curves homever the point and the basisalterations sum up. The greater 

 the mechanical curve is, i.e. the more the point takes part in it, 

 the smaller the electric curve becomes. With the low curves conse- 

 quently is in the electrogram the incision from the top into the 

 electrograms smaller than with the large curves (indicated by two 

 arrows in Fig. 6). The depth of the incision is indicated by the 

 measure in which the point interferes with the basis. 



That indeed during the little curves the point is in rest can espe- 

 cially distinctly be seen, when the diffei'ence in dimension of the 



