BONES FORESHADOW BRIDGES

Evening Post, Volume CXXIII, Issue 56, 8 March 1937, Page 5

BONES FORESHADOW BRIDGES

Twenty years ago D'Army Wentworth Thompson, Scottish zoologist, expounded the idea that an understanding of bridge engineering fundamentals would be of definite value to students of backboned animals and their bony framework. It remained, however, for Professor William K. Gregory, of the American Museum of Natural History, to trace definitely the history of these "bridges that walk" and produce working models, now on exhibition, says the '.'Christian Science Monitor.I,' ' Thompson pointed out that fundamentally the framework of fourfooted animals might be interpreted as a kind of bridge, combined with a grappling apparatus somewhat like a steam-shovel. Professor Gregory holds that geologic history as told by fossiliferous rocks show the "grappling apparatus" to have preceded the bridge in the very earliest fishes. The beginning of the bridge, he asserts, was an elastic rod running along the back, around the checker-like segments of the backbone, which developed later. The "piers" of the bridge were first foreshadowed by paired "bilge keels," or projections from the lower part of the fish. The keels later developed into two pairs of stout, well-muscled paddles. "When the air-breathing fishes began to wriggle out on the muddy fiats, they used their paddles as primitive limbs. Eventually these were drawn under the body and true running became possible. In certain forms, such as the running dinosaurs land birds, the bridge became pivoted on the rear piers, or hind limbs, and a 'walking beam' or bipedal type developed."