ACTION OF CHLOROFORM UPON THE HEART AND ARTERIES. 325 
circulation causes also a failure of the respiratory centre. This cause of respiratory 
failure has been clearly demonstrated by EMBLEy.* 
The complete similarity between the tracings obtained under the influence of 
chloroform alone on the one hand (when a concentrated vapour is inhaled), and of 
in Nii . 
"mi hi 
Fic, 13.—Tracing showing the effect of moderate vagus stimulation (coil 100) during deeper chloroform anesthesia. In this case 
the excitation was not applied until the respiratory movements had nearly ceased. ‘The effect is to produce complete arrest 
of the heart, which, however, shows a beginning of escape from the arrest after the lapse of about a minute, and 20 seconds 
later resumes beating slowly and feebly, and with but little effect upon the blood-pressure. Respirations are not resumed 
spontaneously, but the animal was recovered 5 minutes after the respirations had ceased, by artificial respiration (compression 
of thorax) continued during about 2 minutes. The first signal mark shows the period of strong chloroform administra- 
tion: the second that of vagus stimulation. 
chloroform plus artificial vagus excitation on the other, shows conclusively that in the 
former case, as in the latter, the actual cause of the arrest of the heart (and of the 
NAY AANAARAAA SALAM y 
SUR 
Fic. 14.—Tracing showing the effect upon the heart (1) of weak and (2) of stronger vagus excitation during extreme 
chloroform anesthesia. The first signal mark shows the period of strong chloroform administration: the second that of 
weak vagus stimulation: the third that of stronger vagus stimulation. The chloroform was given until the respiration 
had ceased and the blood-pressure had fallen to 20 mm. Hg, Excitation of the vagus by induction shocks of very 
moderate strength produced only a momentary arrest of the heart, but stronger excitation caused instant and permanent 
arrest. 
respiration as a secondary effect) is inhibition excited through the vagus. Thus 
figs. 5, 6, 7, and 15 show such a cardiac and respiratory arrest produced by strong 
chloroform alone, and figs. 12, 13, and 14 the same phenomenon produced under 
_ varying degrees of chloroform anesthesia by vagal stimulation. In figs. 12 and 13 it 
is seen that the ventricle has escaped from the inhibition and has resumed contraction 
* Op. cit. 
