I left off yesterday saying that Cuvier's first employment was as a tutor for the Comte d'Héricy. During this time he became interested in fossil animals and, as he was already interested in the anatomy of extant animals, he began comparing the living and the fossil remains of a variety of animals. Mammoths were known to the scientists of his day and Cuvier studied the bones of mammoths, mastodons, and extant African and Indian elephants. His work on the subject of elephants led to his first paleontological lecture in 1796 (thanks in part to his recognition of a famed and on-the-run agronomist he befriended) and was published in 1800 under the title Mémoires sur les espèces d'éléphants vivants et fossiles (Memoirs on living and fossil elephant species). This publication and lecture set the stage for Cuvier's later paleontological work as well as definitively differentiating African and Indian elephants, mammoths, and mastodons as distinct species. For the first time ever the mammoth was officially declared to be an extinct taxa. Mastodons were officially given their name by Cuvier in 1806; their remains were referred to as the "Ohio animal" before that.
Histoire naturelle des poissons (Natural history of the fishes) and definitely contained a wealth of anatomical comparison between the species of fish. The work of Cuvier did have detractors and negative aspects. Those will be a topic for Monday, however, and tomorrow will remain set aside for younger readers.