443 



THE PROPERTIES OF STRIPED MUSCLE. 



some 

 ago. 



of the normal variation, which correspond with those described by 

 myself and Mr. Page in the ventricle of the frog. There is, however, 

 one important difference between their results and ours, namely, that in 

 general they observed no interval between the diphasic variation which 

 constitutes Eugelmann's Dop]jelschwa?iJcung, and the later movement 

 which marks the end of the contraction. The absence of this inter- 

 val Bayliss and Starling attribute to the short duration of the beat. 

 Here it must be mentioned that one of these observers (Bayliss, loc. cit., 

 p. 13) has made observations on the heart of the frog and the tortoise, 

 the photographic records of which show that, in his preparations, 

 Engelmann's second phase (see Fig. 249, 6) was apparently much stronger 

 than in ours. This relatively unimportant discrepancy cannot be 

 explained without further investigation.. 



The fact that the electromotive changes which accompany the 



action of the 

 heart can be 

 observed in man 

 was discovered 

 by Waller 

 ten years 

 The effect ob 

 served varies 

 according to the 

 mode of leading 

 off. This may 

 consist either in 

 placing one elec- 

 trode on the 

 chest at the seat 

 of impulse, and 

 the other on 

 the right hand, 

 or the one on 

 the right hand 

 and the other on 

 the left. The 

 former of these 



methods has been employed by Bayliss and Starling, the latter by 

 Einthoven. The form of the photographic record 1 indicates that the 

 variation begins with a strongly marked change, in which the base 

 becomes first negative then positive to the apex, followed by a more 

 prolonged movement in the former direction. In Einthoven 's experi- 

 ments the contacts were on the right and left hands respectively. The 

 character of the photographic record is shown in Fig. 250 {ABCDX). 

 From it the curve {OPQRSTX) is deduced by a process of analysis, 

 which is essentially the same as that of Burch, and leads to similar 

 results. It may therefore be compared with curve 5 of Fig. 249. 

 Einthoven declines to go further in the physiological interpretation of 

 this curve, than to point out that R, which corresponds to the negative 

 phase of Engelmann's Doppelschwankung, denotes the beginning of the 

 ventricular systole, and that its end is indicated by T (or D). 



1 Einthoven "Ueber die Form des menschlichen Electrocardiograms," Arch. f. d. ges. 

 Physiol., Bonn, Bd. lx. S. 101. 



Fig. 250. 



-Einthoven's Electrocardiogram of man. 



