ACTION OF CHLOROFORM UPON THE HEART AND ARTERIES. 323 
| affecting both auricles and ventricles ; but the former are affected much more than the 
‘latter. ‘This is also the case when the cardio-inhibitory centre is reflexly stimulated, 
| even in presence of atropine (fig. 10). On the other hand, when the nervous connections 
are intact, the administration of a strong dose of chloroform not only greatly weakens 
the force of the cardiac contractions, and thereby causes a marked and progressive fall of 
blood-pressure, but often, after a primary acceleration, produces gradual slowing of the 
rhythm, and this is frequently followed by abrupt and complete cardiac arrest (figs. 6 
and 7). The abrupt cessation of contraction may attect both auricles and ventricles 
simultaneously, or the auricles may first stop; the ventricles, either at once or after a 
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/ Fic. 9.—Dog, weighing about 10 kilos. The animal had received some 3 hours previously ‘00054 gramme (73> gr.) atropine 
| sulphate administered hypodermically. The effect of this was to abolish arrest of the heart on stimulation of the cardio- 
inhibitory centre (see fig. 10), whilst permitting a diminution in force of the beats, especially of the auricle. It will be 
seen from these tracings that exactly the same effect is produced in an animal under the influence of atropine by chloro- 
form alone in strong dose as is caused by reflex excitation of the cardio-inhibitory centre, except that the result is attained 
more gradually. 
a, auricular tracing ; 6, ventricular tracing ; c, blood-pressure (femoral) ; d, respiratory movements of the thorax, which 
are continued in spite of the fact that artificial respiration is carried on by perflation ; ¢, time in 10 seconds; /, signal. 
_ short period of arrest, resuming their action with a rhythm of their own (figs. 6, 7, 
and 11). 
The effect entirely resembles that produced by vagal excitation, with the exception 
that vagal excitation does not, as a rule, by itself produce permanent arrest of cardiac 
| action. But at a certain stage of chloroform anesthesia the arrest produced by. 
_ artificial excitation of the vagus may be permanent, or so prolonged as to lead to death. 
The cessation of the heart’s action brings the blood-pressure to zero, and by arresting the 
