“Ideal plan of the double-ringed body of a vertebrate. N, neural canal; H, haemal canal; the body separating them is the centrum of any vertebra, bearing e, and epapophysis, and y, a hypapophysis; n, n, neurapophyses; d, d, diapophyses; ns, bifid neural spine; pl, pl, pleurapophyses; h, h, haemapophyses; hs, bifid haemal spine. Drawn by Dr. R. W. Shufeldt, USA, After Owen. The Axial Skeleton of a bird or any vertebrated animal, that is, one having a back-bone, exhibits in cross-section two rings or hoops, one above and the other below a central point, like the upper and lower loops of a figure 8. The upper ring is the neural arch, so called because such cylinder encloses a section of the cerebro-spinal axis, or principal nervous system of a vertebrate (brain and spinal cord, whence arise all the nerves of the body, excepting those of the sympathetic nervous system). The lower ring is the haema arch, which similarly contains a section of the principal blood vessals and viscera.
Keywordsskeleton, birds, ornithology, nervous system, bird anatomy, bird bones, North American birds, internal parts of birds, axial skeleton, bird vertebra, back bone
Elliot Coues Key to North American Birds (Boston, MA: Estes and Lauriat, 1884)