File:Guide leaflet (1901) (14581882127).jpg

Identifier: scienceguide7692amer (find matches)
Title: Guide leaflet
Year: 1901 (1900s)
Authors: American Museum of Natural History
Subjects: American Museum of Natural History Natural history
Publisher: New York : The Museum
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: IMLS / LSTA / METRO

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s and limbs are modified to enable him to walk on his hind legs and to use hisforelegs as arms and hands rather than as supports. His brain is much larger and morehighly developed than in the apes. THE UPRIGHT POSTURE AND ITS MAINTENANCE (Case IVA) From fish to man there is still a chain of living forms, in spite of all the devastationand wholesale extinction of the present and past ages. As the skeleton of man testifiesto his derivation from lower forms of vertebrates (Fig. 8) so also does his muscularsystem, and through this orderly and intelligible series of stages we can follow themain changes of posture as our ancestors learned first to swim, then to crawl, to run,to climb and finally to walk erect. In the swimming stages (see Fig. 8A) the segmental muscles of the backbone andribs were dominant, the fin-muscles being subordinate extensions of the body. Thenthe paddles grew outward and were eventually moulded into the new and highlyorganized limbs of land-living vertebrates. 1:303
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Fig. 9. MUSCULAR ANATOMY OFCHIMPANZEE AND MAN, showingprincipal muscles used in maintainingupright posture. The model of thechimpanzee, by G. D. Christensen, wasbased on dissections by H. C. Raven These limbs are compound levers with the muscles arranged on opposite sides ofthe pivots and acting in pairs as antagonists to produce extension or flexion, abduc-tion or adduction, twisting and untwisting, etc. In walking and running each limbalternately pulls and pushes on the ground. When in early stages the limbs sprawledwidely at the sides, the muscles were very thick. In the course of ages, as the feet weregradually brought in toward the midline and the body was raised off the ground,the limbs grew longer and more graceful. The Superficial Musculature of the Chimpanzee. When running on the ground thechimpanzee usually goes on all fours, supporting the fore part of the body on thefingers, sharply bent at the middle joints. The muscular anatomy, however, is welladapted also for a semi-er

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