. Biology; the story of living things. Skeleton of a hippopotamus, showiiif;: the anti- clinal arrangement of \ ertebral spines character- istic of quadrupeds, but not of bipeds. (After Hesse.) At the other end of the spinal column the tail bones, no longer useful in any of the former ways, telescoped together to form the coccyx. This fusion of the caudal vertebrae formed a mass which bent in and became embedded under the skin, forming a part of the floor of the pelvic basin, now a neces- sary underpinning for the support of the shifting visceral weight. So it came about that man in tucking hi
. Biology; the story of living things. Skeleton of a hippopotamus, showiiif;: the anti- clinal arrangement of \ ertebral spines character- istic of quadrupeds, but not of bipeds. (After Hesse.) At the other end of the spinal column the tail bones, no longer useful in any of the former ways, telescoped together to form the coccyx. This fusion of the caudal vertebrae formed a mass which bent in and became embedded under the skin, forming a part of the floor of the pelvic basin, now a neces- sary underpinning for the support of the shifting visceral weight. So it came about that man in tucking his ancestral tail between his legs turned this apologetic performance to advantage. The thorax with its encircling ribs became flattened and widened as a consequence of upright posture, while the sternal bones, relieved from visceral weight, became firmly fused together and shortened, allowing more freedom and effectiveness of motion for the respiratory muscles. The legs of man straightened, with a greater resultant efficiency in leverage, leaving the arms relatively shorter, since, with the passing of locomotion on all fours, legs and arms no longer needed to be of the same approximate length. The human foot met its new responsibilities in a variety of adaptable ways. Being squarely plantigrade on the ground, the bones involved be- came arranged in two arches, one longitudinal and one transverse, to provide sprightliness to the gait, as well as an ade- quate support to body-weight. One of the ankle bones, the calcaneus, projected out behind forming a heel, thus lessening the likelihood that the balancing biped might tend to tip over backward. In the hind foot of a quadruped such a development of a heel was unneces-. The two arches of the human foot. (From Walter, The Unman Skeleton. By permission of The Macmillan Company, publishers.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appe
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