. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Skeleton 635 Fern B position enables it, by straightening the legs suddenly, to rise enough from the ground or the perch to take to the air successfully. When a bird "squats" (Fig. 567b), the leg bones jack-knife together, thus pulling the tendons attached to the toes taut and clinching the phalanges around the perch. To unlock the foot it is necessary for the body to be raised, thus straightening the leg and loosening the tendon which has be
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Skeleton 635 Fern B position enables it, by straightening the legs suddenly, to rise enough from the ground or the perch to take to the air successfully. When a bird "squats" (Fig. 567b), the leg bones jack-knife together, thus pulling the tendons attached to the toes taut and clinching the phalanges around the perch. To unlock the foot it is necessary for the body to be raised, thus straightening the leg and loosening the tendon which has been pulled tight over the ankle by the downward weight of the body in perching. When a bird perches, therefore, it is auto- matically locked for the time be- ing upon the perch and can go to sleep without fear of falling off. Among mammals the ankle joint is never between the rows of tarsal bones as in the reptiles and birds. The difference between the hand and foot of man is greater than in any other animal. In apes the functions of grasping and sup- port are partly shared by both the hand and foot (Figs. 568 and 569), whereas in man these two lines of activity have become entirely segregated, although some individuals have the ability to flex the toes enough to grasp awkwardly such an object as a handkerchief as well as to pick it Patella lio-Tarsus //~i Tendon >^ â >V~Mesotarsal i\l Joint At Tarso- ^VMetatarsus Phalanges Fig. 567. The perching mechanism bird, a, standing; b, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
