International Association Against Painful Experiments on Animals

101 Misleading results from Vivisection Animal Experiments

39: The Chloroform Controvosy

The anaesthetics ether, nitrous oxide and chloroform originated from experiments carried out by physicians and scientists on themselves, and, together with the introduction of hygienic conditions, enabled surgery to emerge from the dark ages.(1) Because of their high safety profile, nitrous oxide and ether have stood the test of time. In the case of chloroform, entrenched attitudes and contradictory animal experiments allowed a toxic drug to outlive its value and remain in use for over 100 years. (2)

Deaths from chloroform were reported almost weekly during the second half of the l9th century and between 1887 and 1896 there were 376 fatalities in England and Wales. Many believed the deaths resulted from respiratory failure but that risks could be minimised by appropriate administration of the drug and by devoting attention to the patient's breathing in order to detect early warning signs. The alternative (correct) explanation, that chloroform has a direct effect on the heart, was discounted.

Unfortunately, animal experiments carried out by the Hyderabad Commissions of 1888 and 1889 supported the view that chloroform affects the respiration rather than the heart.(2) In a famous telegram to the Lancet,(3) Lauder Brunton summarised results from the Second Commission: "Four hundred and ninety dogs, horses, goats, cats and rabbits used...Results most instructive. Danger from chloroform is asphyxia or overdose: none whatever heart direct." Anaesthetists must have been reassured to hear Brunton's conclusion that chloroform “never causes sudden death from stoppage of the heart.” In 1893, clinical observations completely contradicted the conclusions from Hyderabad and showed that heart failure is the commonest cause of death from chloroform.(2) Nevertheless, use of the drug continued until the 1950s and the Hyderabad Commissions were later blamed for failing to recognise species differences.(2)


I ) R.Sharpe, The Cruel Deception: the use of animals in medical research (Thorsons, 1988).
2) K.B.Thomas, Proceedings of the Royal Society of Medicine, 1974, vol.67, 723-730.
3) Lancet, 1889, December 7, 1183.

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