Cave of Dogs

The Cave of Dogs (Italian: Grotta del Cane) is a cave near Naples, Italy. Volcanic gases seeping into the cave give the air inside a high concentration of carbon dioxide. Dogs held inside would faint; at one time this was a tourist attraction.

Illustration of the cave from a 1865 science book. A guide shows a suffocated dog to a man and woman tourist.
Lake Agnano and the Cave of Dogs depicted in an etching by the Sieur de Rogissart, 1706.
The principle of the Cave of Dogs sketched by Alfred Swaine Taylor, 1832. The carbon dioxide (marked with a darker color) gathers in the lower part of the cave.


The Cave of Dogs (Italian: Grotta del Cane, literally "Cave of the Dog")[1][2]) is a cave about ten metres deep on the eastern side of the Phlegraean Fields near Pozzuoli, Naples.[3] Inside the cave is a fumarole that releases carbon dioxide of volcanic origin.

The cave is thought to have been constructed in classical antiquity, possibly as a sudatorium; if so, the CO2 emissions must have been much lower at the time.[1] It may have been known to Pliny the Elder, who, in his Natural History (written 77-79 AD), mentions a location near Pozzuoli where animals die from poisonous fumes. However, the first unambiguous reports about the cave only appear in the 16th century.[1]

It was a tourist attraction for travelers on the Grand Tour. The CO2 gas, being denser than air, tended to accumulate in the deeper parts of the cave. As a result, small animals such as dogs held inside the cave suffered carbon dioxide poisoning, while a standing human was not affected.[1][4] Local guides, for a fee, would suspend small animals (usually dogs) inside it until they became unconscious. The dogs could be revived by submerging them in the cold waters of the nearby Lake Agnano, although in at least one case this led to the dog drowning instead.[5] Tourists who came to see this attraction included Sir Thomas Browne,[6]Richard Mead,[7] Goethe, John Evelyn, Montesquieu,[8] Alexandre Dumas père, and Mark Twain.[9]

Some tourists including Washington Irving (1804),[10] Percy Bysshe and Mary Shelley (1818)[11] and Ralph Waldo Emerson (1833),[12] objecting to the cruelty, refused to pay for the experiment to be performed on the dog. A Scottish scientist who examined the cave for several days (1877) reported:

On carrying a lighted torch into the cave, its smoke gradually falls, till it reaches the layer of gas, upon which it settles; and on looking in, the surface of the gaseous layer is seen, resembling that of water, and appears covered with beautiful undulations.

On holding the head below the level of the gas, holding the breath, and keeping the eyes open, an intolerable prickling sensation is produced upon the eyes by the carbonic acid.

A dog brought into the cave, as is the custom there, appears, as it were, to drink the gas, lapping with its tongue. Then its eyes begin to dilate to an unnatural size, and its lapping becomes more spasmodic; beyond this it does not seem to suffer. While in the cave, also, the dog was able to stand, but when carried and set on its feet outside in the fresh air, it fell, and lay struggling as if in paroxysms of suffocation, but recovered in two or three minutes. I was told, however, that the animal gets into such a nervous state with the prospects of its frequent ordeals, that it has to be killed in three months.[13]

The lake became polluted, was thought to be malarious, and was drained in 1870. At some point the spectacle fell into disuse, although Baedeker's guides in the 1880s were still advertising that to see the dog experiment would cost tourists 1 lire (≈ 20 U.S. cents).[14]. According to one source, it was banned before World War II for cruelty to animals. The cave entrance was blocked to prevent access by children.[15][16][4][17][18]

In 2001 the cave was investigated by Italian speleologists. Nine metres from its entrance the temperature was 52 °C (126 °F) and the CO2 concentration was 80%, with negligible oxygen.[1]

In popular scienceEdit

The cave was often described in nineteenth century science textbooks to illustrate the density and toxicity of carbon dioxide,[19] and its reputation gave rise to a scientific demonstration of the same name, in which stepped candles are successively extinguished by tipping carbon dioxide into a transparent container.


  1. ^ a b c d e Halliday, William R.; Cigna, Arrigo A. (2007). "The Grotta Del Cane (Dog Cave), Naples, Italy" (PDF). Cave and Karst Science. British Cave Research Association. 33 (3): 131–136. ISSN 1356-191X.
  2. ^ Urban, Sylvanus (1753). "The Gentleman's Magazine and Historical Chronicle, Volume XXIII. Page 16. "Grotto Del Cane described, with the cause of its effects"".
  3. ^ "Grotta del Cane: Italy". Geographical Names. Retrieved 26 March 2015.
  4. ^ a b Kroonenberg, Salomon (2013). Why Hell Stinks of Sulfur: Mythology and Geology of the Underworld. London: Reaktion Books. pp. 41–45. ISBN 978-1-78023-045-0.
  5. ^ Astarita, Tommaso (2005). Between Salt Water and Holy Water: A History of Southern Italy. New York: W. W. Norton & Company. p. 224. ISBN 0-393-05864-6.
  6. ^ Wilkin, Simon, ed. (1845). The Works of Sir Thomas Browne. Vol. 1. London: Bohn. Retrieved 18 April 2021., p=78.
  7. ^ Mead, Richard (1762). The Medical Works of Richard Mead. C. Hitch and L Hawes.
  8. ^ Shackleton, Robert (1955). "The Evolution of Montesquieu's Theory of Climate". Revue Internationale de Philosophie. 9 (33/34): 317–329. JSTOR 23936721.
  9. ^ Twain, Mark (1869). "Innocents Abroad". Archived from the original on 2005-08-13. Retrieved 2022-01-16. the Grotto of the Dog claimed our chief attention, because we had heard and read so much about it. Every body has written about the Grotto del Cane and its poisonous vapors, from Pliny down to Smith, and every tourist has held a dog over its floor by the legs to test the capabilities of the place. The dog dies in a minute and a half--a chicken instantly. As a general thing, strangers who crawl in there to sleep do not get up until they are called. And then they don’t either. The stranger that ventures to sleep there takes a permanent contract. I longed to see this grotto. I resolved to take a dog and hold him myself; suffocate him a little, and time him; suffocate him some more and then finish him. We reached the grotto at about three in the afternoon, and proceeded at once to make the experiments. But now, an important difficulty presented itself. We had no dog.
  10. ^ Irving, Washington (1921). Notes and Journal of Travel in Europe 1804-1805. Vol. III. New York: The Grolier Club. Retrieved 18 April 2022., p.16-8
  11. ^ Chapin, Lisbeth Ann (2003). Shelley's Animals and the Landscape of Consciousness (PhD). University of Denver/ProQuest., p.1.
  12. ^ Emerson, Ralph Waldo (1910). Journals 1833-1835. Boston and New York: Houghton Mifflin. Retrieved 18 April 2022., p.67-8.
  13. ^ Young, T. Graham (1878). "The Gas of the Grotta del Cane". Journal of the Chemical Society. XXXIII: 51–52. Retrieved 18 April 2022., p=52. (The author was the son of Paraffin Young.)
  14. ^ Baedeker, Karl (1880). Italy. Handbook for Travellers. Third Part. Leipzig and London: Baedeker. Retrieved 18 April 2022., p.95 and currency chart.
  15. ^ Taylor, Alfred Swaine, An Account of the Grotta del Cane; With Remarks Upon Suffocation by Carbonic Acid, The London Medical and Physical Journal, 1832, 278-285. [1]
  16. ^ Fleming & Johnson, Toxic Airs: Body, Place, Planet in Historical Perspective, Pittsburgh, 255-256.
  17. ^ Jeff Matthews, Naples: Life, Death & Miracles: Agnano & the Grotto of the Dog. [2] Archived 2016-12-20 at the Wayback Machine, visited 26.3.2015. "The area degraded terribly after WWII and became an eyesore from shoddy overbuilding and illegal waste dumping. I drove by the baths hundreds of times over the years and never knew about the lake, never knew that I was 100 yards from the Grotto of the Dog ...".
  18. ^ Grotta del Cane [3] visited 26.3.2015.
  19. ^ The above image is from L'air et le monde aèrien, an 1865 textbook by Arthur Mangin, p.162 [4]

Coordinates: 40°50′00″N 14°10′00″E / 40.833333°N 14.166667°E / 40.833333; 14.166667

External linksEdit