. Outlines of zoology. Zoology. 598 BIRDS. processes) are directed backwards parallel to the ischia. There is no pubic symphysis except in the African ostrich (Struthio), and no ischiac symphysis except in the American ostrich (Rhea). In the hind-limb, the Jibula is incomplete and united to the tibia ; there are no free tarsal bones, half of them being united to the distal end of the tibia (which is therefore called a tibio- tarsus), the others being united to the proximal end of three united metatarsals (which thus form a tarso-metatarsus). In other words, the ankle joint is intertarsal. The
. Outlines of zoology. Zoology. 598 BIRDS. processes) are directed backwards parallel to the ischia. There is no pubic symphysis except in the African ostrich (Struthio), and no ischiac symphysis except in the American ostrich (Rhea). In the hind-limb, the Jibula is incomplete and united to the tibia ; there are no free tarsal bones, half of them being united to the distal end of the tibia (which is therefore called a tibio- tarsus), the others being united to the proximal end of three united metatarsals (which thus form a tarso-metatarsus). In other words, the ankle joint is intertarsal. The maximum number of toes is four, of which the first is tlu hallux, and if there be four, the metatarsal of the hallux is free from the other three. In regard to the alimentary system, the absence of teeth, the frequent occurrence of a crop and a gizzard, the usual short- ness of the large intestine, the presence of a cloaca, may be noted. The heart is four-chambered; the single aortic arch curves to the right side; only the pulmonary artery rises from the right ven- tricle ; the two valves between the right auricle and the right ven- tricle are in part muscular; the red blood corpuscles are oval and nucleated; the temperature of the body is from 2°-if F. higher than that of Mammals. The lungs are fixed to the dorsal wall of the thorax; the bronchial tubes expand in irre- gular branches in the lungs; the ends of some of these branches are continued into surrounding air sacs; and these are continued info air spaces in the hones. The trachea is supported by bony rings, and has a voiceless larynx at its upper end, and a syrinx or song-box (with vocal cords) at the origin of the bn>>nhi. The kidneys arc thrcc-lobcd, and lie embedded in the pelvis : the ureters open into the cloaca : there is no bladder : the urine is semi-solid, and consists chiejlv of urates. The testes lie beside the kidneys; the T<asa deferentia run. Fig. 207.—Diagrammatic section of young Bird. (After
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
