The neck is found to exist in no animal but those which have both these passages. All the others which have the gullet only, have nothing but a gorge or throat. In those which have a neck, it is formed of several rounded vertebræ, and is flexible, and joined together by distinct articulations, to allow of the animal turning round the head to look. The lion, the wolf, and the hyæna are the only animals in which it is formed of a single[1] rigid bone. The neck is annexed to the spine, and the spine to the loins. The vertebral column is of a bony substance, but rounded, and pierced within, to afford a passage for the marrow to descend from the brain. It is generally concluded that the marrow is of the same nature as the brain, from the fact that if the membrane of exceeding thinness which covers it is pierced, death immediately ensues.[2] Those animals which have long legs have a long throat as well, which is the case also with aquatic birds, although they have short legs, as well as with those which have hooked talons.