ðə fɹˈɛntʃ baɪˈɑːlədʒˌɪst klˈɔːd bɜːnˈɑːɹd pɹəvˈaɪdᵻd ðə klˈæsɪkəl ɑːbzɚvˈeɪʃən ʌv ðɪs ɪfˈɛkt wɛn hiː fˈaʊnd ðæt tʃˈeɪndʒɪŋ ðə dˈaɪət ʌv ɹˈæbɪts fɹʌm æn hˈɜːbɪvˌoːɹ mˈeɪnli plˈænt dˈaɪət tʊ ɐ kˈɑːɹnɪvˌoːɹ mˈeɪnli mˈiːt dˈaɪət tʃˈeɪndʒd ðə jˈʊɹɹɪn fɹʌm mˈoːɹ ˈælkəlˌaɪn tə mˈoːɹ ˈæsɪd.
The French biologist Claude Bernard provided the classical observation of this effect when he found that changing the diet of rabbits from an herbivore (mainly plant) diet to a carnivore (mainly meat) diet changed the urine from more alkaline to more acid.