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Show iiiniiiiiinn """tl WHY WE BEHAVE LIKE HUMAN BEINGS Br GEORGE OORSEY, Pa. D, IX- D. a. i. ' ... . . "Bone-Heads" Really Exist IN UPRIGHT gnlt. balanced skull, and anus free at the aides of the body, we differ most from the only animals that ape as. This upright gnlt Is maintained by action of muscle on bone. We bang on a bony skeleton, largely levers. We move by setting those levers in motion. To put us across a hundred yards In ten aec-onds, aec-onds, the skeleton must be mnture. If our bones were cartilage we would be wonderful contortionists, but our upright gait would collapse. Our ancestors went on all fours. In . acquiring the upright gait, the axis of the body changed from horizontal to perpendicular. This necessitated changes In every bone and muscle In the body and a complete overhauling of everything Inside lungs, circulation, circula-tion, abdominal viscera everything. Our pelvic girdle Is a broad, shallow shal-low bRsln ; It supports the viscera. The keystone of tbe girdle Is the sacrum. It supports the backbone and locks tbe sreb behind. Tbe dog's sacrum Is long and narrow; ours, broader than tt Is long. The sacrum at birth varies from four to seven vertebrae. These unite Intc one bone ; but the first, and sometimes the second, never unites with the others. Above the sacrum la the vertebral column proper; seven neck or cervical, twelve thoracic, and live lumbar vertebraetwenty-four In all. But there may be six or eight cervical ; eleven or thirteen thoracic; four to six lumbar. lum-bar. At fclrth, most of us have twelve pairs of ribs; some, only eleven ; some, thirteen. Seven pairs of ribs Join our sternum, or breastbone; there may be only six, there may be eight. Tbe first pair are sometimes mere rudiments. Our floating float-ing ribs are not so Important as when we walked on all fours; they vary in number and size. The sternum Is less important than formerly ; It varies rnormously. Two little bones sometimes some-times found on Its upper border are vestiges of the eplsternal bones of the lowest mammals. No man-made column Is so delicately delicate-ly adjusted, so slender, or so well balanced as our spine. Its sigmoid, or "S" curve, gives elasticity to our body, grace to our carriage, fine lines to onr back, and saves our brain from Jar and shock. The really human curves develop after birth, especially .the lumbar curve In the "small" of our back. . The Infant cannot stand straight np because It has not yet acquired ac-quired a stand-up-straight backbone. Our backbone ends In small rounded bones about the size of pens. They are the coccyx, skeleton of our talL Tbe upper-arm bone assumes Its human form only after birth, when It also begins to twist, as does the femur, to conform to Its new position at the side of the body. Human history may not start with man's foot, but our foot Is as human as our hands. Its bones show coming snd going changes. The big toe Is tbe strongest and Is more powerful In man than tn any ape; It Is coming. But most of It comes after birth; baby's big toe Is a poor affair. Tbe little toe is going. In one Individual out of every three It has lost a Joint Bat not on account of tl.jht shoes they can make corns, bnt cannot change heredity; the third bone of the little toe Is as often absent In feet which were never shod. Our skull Is no more human than are the bones of our foot or of our pelvis. It Is shorter In front longer at the back, better balanced on the spine; adaptations to an upright gait. Man has a flat face and a sizable chin when be has short Jaws. But Jaws vary, and long or prognathic Jaws change the countenance. In fetal life we have a. pair of tn-termaxlllarles tn-termaxlllarles between the npper jaw bones. At birth tbe suture, as skull joints -re called, between them can barely be seen; by maturity, not at all. The suture often persists, obviously obvious-ly atavistic The chia, or mental point of the lower Jaw, has nothing to do with "mentality." It Is a human trait but not of all men equally. Some have "strong" chins, some next to no cbln at all. ; We have two nasal bones. But In some men and all monkeys they become be-come one; no real bridge then to the nose. Sometimes the bones are small and fiat ; no bridge at all. , The brain can grow only as long as the three big sutures of the skull remain open. They begin to close at the age of forty; the one at the back first; the fore part of the brain can keep on growing. In animals tbe sutures su-tures close earlier than tn man, the front ones first They may close early in man; they may persist till old age. When one or another skull suture closes prematurely, cnrlously shaped heads result Tbe "boat-shaped" head Is due to premature closing of the parietal suture. When all the sutures close prematurely, the skull becomes solid as though a single bone. The brain can grow no more. Idiocy results re-sults the "Aztec" people of the circus. ) by Gtorgo A. Doner.) |