On the Interpretation of the Electrocardiogram. 
283 
course for a space in the 
record uncomplicated, be- 
fore the other makes its 
appearance. Fig. 5 is an 
example. The stimulation 
is a break induction shock 
given through non-polar- 
izable electrodes at the left 
margin of the isolated ven- 
tricle, and affecting the 
galvanometer string at x. 
The right electrode is placed 
on the dorsal surface about 
6 mm. from the point of 
stimulation on the trans- 
verse diameter, and the left- 
hand electrode at the middle 
point of the dorsal surface 
20 mm. from the right-hand 
electrode. From the peak 
lettered to Qi the curve 
gives the variation under 
the right - hand electrode 
alone. At the beginning of 
the upward summit Qi the 
variation under the left- 
hand electrode begins, and 
the remainder of the curve 
represents the summation 
of the two. It will be 
noticed that after deflection 
T the curve takes about 
2 sec. to regain the zero 
line. 
Fig. 6 gives a series of 
records from the isolated 
ventricle of the tortoise 
whose heart yielded the 
response in Fig. 2. The 
isolated quiescent ventricle 
was placed on a block of 
vulcanite and kept moist 
by Einger's solution. Non- 
polarizable stimulating 
electrodes, connected with 
