A division of the Animal Kingdom, founded upon the presence or the absence of a vertebral column, was first taught publicly by Lamarck, Professor of Natural History at the Musée in Paris, in the eighth year of the first French Republic, a.d. 1800. "All known animals," says he, "may be distinguished in a remarkable manner, I. Into Animals with Vertebrae. II. Into Animals without Vertebrae."

The importance of this distinction, which he claimed to be the first to establish, was speedily recognised by other naturalists, who adopted his views, and introduced his observations into their works, without always acknowledging the source from whence they were derived. Lamarck described the vertebral column as "supporting the head of the animal at its anterior extremity, the pectoral ribs at the sides, and furnished in its entire length with a canal in which is lodged the pulpy chord, known by the name of the ' Spinal Marrow.' "

The attention of Anatomists was soon directed to a closer study than had hitherto been made of the different bony segments, the assemblage of which constitutes the framework, or skeleton, upon which this division of the animal kingdom depends. Unfortunately the vertebra selected as a type was taken either from the human subject, or from one of the higher Mammalia, from which cause it happened that the terms which gradually crept into common use were inapplicable as to meaning, and insufficient as to number, when employed in the description of the bone in the lower vertebrata. Even in the Mammalian class new processes were constantly being discovered, which could not be included under any of the commonly-received terms, and hence arose a necessity for the determination of a typical vertebra, and for the substitution, in place of the old, of a new nomenclature, by which every possible element of a bone would be accurately and graphically designated.