If it were possible for a medical man to mistake or disregard the symptoms of approaching danger, and to go on exhibiting vapour of chloroform, diluted to a proper strength, till the death of the patient, this event would take place slowly and gradually, as in Experiment 23, related above, and every other experiment in which the air did not contain more than five per cent. of vapour. The action of the heart would survive the respiration; there would be a great tendency to spontaneous recovery, and the patient would be easily restored by artificial respiration, if it were performed whilst the heart was still acting; as I have always found it to be successful in animals under these circumstances. In examining the recorded cases of fatal inhalation of chloroform, we shall find, however, that they have none of them taken place in this gradual manner; but that in all cases the fatal symptoms, if not the actual death, have come on very suddenly. Dr. Sibson was, I believe, the first to point out that, in the fatal cases of inhalation of chloroform, death was caused by its paralysing the heart; but he was not at that time aware of the physical conditions under which this agent may act directly on the heart. In commenting on the first four deaths from chloroform, he says:[61] “In all the four cases it is manifest that the immediate cause of the instantaneous death lay in the heart. The heart, influenced by the poison, ceased to contract, not from the cessation of respiration, for the heart in asphyxia will beat from one to three minutes after respiration has ceased, but from immediate death of the heart. There is no doubt a combination of causes operating to destroy the heart’s contractile power: the mental influence, the congestion in the systemic, and that in the pulmonary capillaries, will all have a material influence.” And further on he says: “We are obliged, then, from the experience of these cases, to conclude, that in man the death is usually instantaneous, and due, as every instantaneous death is, to paralysis of the heart. In animals the death is usually due to paralysis of the muscles of respiration. It is chiefly owing to the superior control of the mind over the body in man, that in him the poison acts on the heart more than in dogs.”