the intermediation of certain intervertebral pads, and also articulate by small processes at either end at the upper side of the arch, the zygapophyses. The normals to the polished facets of these point, in the case of the anterior zygapophyses, up and in (mnemonic: ant-up-in), and in the case of the posterior, down and out. The student should make this, and the other features of vertebrae, out upon actual specimens.
Text Book of Biology, Part 1: Vertebrata · The Wunder Library — complete classics, free to read, with narration.