The word employed most of the time by Pliny to denote experience is _experimentum_.[158] In many passages the word does not indicate anything like a purposive, prearranged, scientific experiment in our sense of that word, but simply the ordinary experience of daily life.[159] We are also told what _experti_,[160] or men of experience, advise. In a number of passages, however, _experimentum_ is used in a sense somewhat more closely approaching our “experiment.” These are cases where something is being tested. For instance, a method of determining whether an egg is fresh or rotten by putting it in water and watching if it floats or sinks is called an _experimentum_.[161] That horses would whinny at no other painting of a horse than that by Apelles is spoken of as _illius experimentum artis_, a test of, or testimony to, his art.[162] The expression _religionis experimento_ is applied to a religious test or ordeal by which the virginity of Claudia was vindicated.[163] The word is also used of ways of telling if unguents are good[164] and if wine is beginning to turn;[165] and of various tests of the genuineness of drugs, gems, earths, and metals.[166] It is also twice used of letting down a lighted lamp into a huge wine cask or into wells to discover if there is danger at the bottom from noxious vapors.[167] If the lamp was extinguished, it was a sign of peril to human life. Pliny further suggests purposive experimentation in speaking of _experimenta_ to discover water under ground[168] and in grafting trees.[169] [Sidenote: Experiments due to scientific curiosity.] Most of the tests and experiences thus far mentioned have been practical operations connected with husbandry and industry. But Pliny recounts one or two others which seem to have been dictated solely by scientific curiosity. He classifies the following as _experimenta_:[170] the sinking of a well to prove by its complete illumination that the sun casts no shadow at noon of the summer solstice; the marking of a dolphin’s tail in order to throw some light upon its length of life, should it ever be captured again, as it was three hundred years later—perhaps the experiment of longest duration on record;[171] and the casting of a man into a pit of serpents at Rome to determine if he was really immune from their stings.[172] [Sidenote: Medical experimentation.]