229
was no asphyxia. In the second block of C, there are the most obvious respiratory variations
in the curve, and these continue right on till the rapid fall sets in. This tracing is so
important that we may repeat here our original remarks on this observation:
"It is to be remembered that this animal got chloroform in the usual way, by a cloth
saturated with the agent being held over his mouth and nose. He received no overdose, and
the administration only lasted seventy seconds. As bearing on at least one mode of death
under chloroform, the relation of the heart's action to respiration is of particular significance.
The blood-pressure is enormously reduced, and the pulsations have become so infrequent as to
be virtually ineffectual, yet respiration continues. But respiration stops forty seconds after
the heart has resumed, the pulsations being still, however, so ineffectual that the pressure is
even minus . We believe that the legitimate inference to be drawn is that the stoppage of
respiration was not due directly to the chloroform, the inhalation of which had ceased for
about forty-eight seconds. It seems likely that the failure of the heart in the first instance,
and the insufficiency of its subsequent pulsations, were the cause of the failure of respiration. In
such a state of the circulation, the respiratory centres would probably be insufficiently supplied
with blood, and be consequently liable to cease acting. In this ease, if death had occurred,
it would only apparently have been due to the failure of the respiration, the primary failure
being that of the heart. To what extent this may apply to human cases we do not venture to
speculate."
7. We now come to a very interesting point, namely, that of determining the relative
effects of a diminished activity of the heart or a diminished activity of respiration in bringing
about a fatal result. In this connection, the report of the Hyderabad Commission contains
many valuable suggestions. We both observed that there is still a fall of pressure after the
animal had ceased to inhale chloroform. Thus, in the first recorded experiment of the British
Medical Association Committee, it is noted: "Chloroform was given, and during deep anæs-
thesia a canula was introduced into the carotid artery, and connected with the kymograph.
By the time connection with the kymograph was established, no chloroform had been given
for about two minutes. On first making the connection, the pressure registered 104 milli-
mêtres, which may be regarded as nearly normal; but now, without any fresh dose, the
pressure rapidly fell to zero, with a remarkable retardation of the heart."* We quite agree
with the Hyderabad Commission in the view that "this after-fall is probably due to absorption
of a portion of the residue of chloroform in the air-passages after the stoppage of the inhala-
tion." The Hyderabad Commission, however, hold that "slowing or temporary stoppage of
the heart in chloroform administration is not dangerous", and that the "controlling influence
of the vagus on the heart is a safeguard, and that it is the exhaustion of the nerve which is
dangerous". Their theory is that when the inhibitory action of the vagus (which is known to
be intermittent and not continuous) is called into play, the heart does not beat so quickly nor
so strongly, that less chloroformed blood is transmitted to the respiratory centres, and that
consequently, these centres are not then in danger of sudden arrest. Further, that if
the vagus irritation ceases, or if the vagus becomes exhausted, the heart "bounds on
again", and "the blood then becomes quickly saturated with chloroform, and an over-
* JOURNAL, vol. II., 1880, p. 962.