This letter was sent in 2007 to the Journal of Toxicology - Clinical Toxicology but was neither printed nor even its receipt acknowledged.


The article recently published in your journal on The Delphic Oracle and the ethylene-intoxication hypothesis (Foster et al, 45:85-89) does not address the question of hypoxaemia and hypercarbia, either or both of which may account for some of the more bizarre behaviour of the priestess. When she was delirious, ataxic and combative, it is certainly possible that she might have been breathing a higher concentration of ethylene and showing signs of the excitement stage of anaesthesia. However increasing concentrations of any gas or gases mixed with air will by simple displacement reduce the oxygen concentration in the final mixture, which will become increasingly hypoxic. In discussion of the historical use of ethylene as an anaesthetic Spiller, Hale and De Boer quote Herb (2) as saying that mixtures of 20% ethylene and 80% oxygen were used successfully, but what she actually said was that 50 – 80% oxygen was used once in a nine year old boy but on two subsequent occasions the percentage of oxygen had to be decreased in order to secure quiet and relaxation. The minimal alveolar concentration of ethylene, i.e. the concentration required to stop 50% of patients responding to a surgical stimulus, is 67% (3). If the Pythia was breathing, for example, 40% ethylene in air she might still have been in the second stage of anaesthesia but would have been getting only 12.6 % oxygen, and perhaps less than this from further displacement of air by other gases. So signs of hypoxaemia might have contributed to the picture. Reluctance shown by the Pythia to enter the chamber may have been due to fear because of previous asphyxial experience. Death a few days after frenzy (4) could have been due to hypoxic brain or other organ damage.

When she was overbreathing, was flushed and felt asphyxiated she may also have been hypercarbic. Carbon dioxide is known to emanate from many geological vents and it has been shown that the blue patina of bronze statues at Delphi as described by Plutarch (5) was due to formation of azurite, which would have required the presence of at least 1 – 4 % carbon dioxide depending on the ambient temperature (6). While high concentrations of carbon dioxide cause narcosis, lower levels cause hyperventilation, peripheral vasodilatation, restlessness, sweating and tremor.

Further it is unlikely that the composition of the vent gases would have remained constant over 1000 years, and also changes might have occurred when the chamber was lowered c. 373 BC, when there may have been less admixture of fresh air with the vent gases, and also a greater possibility of rebreathing due to the confined space. We think therefore that some of the more bizarre behaviour of the Pythia may have been due to multiple factors.

Magda Mircea, Lecturer, "Al. I. Cuza" University of Iaşi, Faculty of Letters, Department of Classical Languages, Italian and Spanish, Blvd.Carol I, Nr. 11, 700506 Iaşi, Romania. e-mail:

John Powell. Consultant Emeritus,  Southmead Hospital, Bristol, BS10 5NR, UK. Email:

Correspondence re classical matters to Magda Mircea; re anaesthetic and related topics to John Powell.

1. Spiller HA, Hale JR, De Boer JZ The Delphic Oracle: A Multidisciplinary Defense of the Gaseous Vent Theory. Journal of ToxicologyClinical Toxicology; 40 (2):189-96.

2. Herb I.C., Ethylene: Notes Taken from the Clinical Records, Anesth. Analg., Dec (1923) 230–232.

3. Miller, R. D., Wahrenbrock, E. A., Schroeder, C. F., Knipstein, T. W., Eger, E. I., and Buechel, D. R. (1969). Ethylene-halothane anesthesia: addition or synergism?
Anesthesiology , 31 : 301.

4. Plutarch. Moralia
438 B-C

5. Plutarch. De Pythiae Oraculis 2-4, 395 B-396 C.

6. Franke WA, and Mircea M. Plutarch’s report on the blue patina of bronze statues at Delphi – a scientific explanation. Journal of the American Institute for Conservation 2005.