. On the anatomy of vertebrates [electronic resource] . igin, passes alongthe groove between the occipital condyle and the paroccipital tothe basisphenoid which it pierces. The vertebral arteries aregiven off by the subclavians, and pass to the skull, as usual,through the cervical vertebrarterial foramina. They unite be-neath the medulla oblongata to form the basilar artery, whichsends off at right angles to the cerebellum two branches as largeas itself: it divides opposite the anterior margin of the ponsVarolii, and the diverging branches are connected by two straighttransverse canals, before
. On the anatomy of vertebrates [electronic resource] . igin, passes alongthe groove between the occipital condyle and the paroccipital tothe basisphenoid which it pierces. The vertebral arteries aregiven off by the subclavians, and pass to the skull, as usual,through the cervical vertebrarterial foramina. They unite be-neath the medulla oblongata to form the basilar artery, whichsends off at right angles to the cerebellum two branches as largeas itself: it divides opposite the anterior margin of the ponsVarolii, and the diverging branches are connected by two straighttransverse canals, before they anastomose with the smaller ento-carotids to form the circle of Willis. The brachial artery dividesearly into ulnar and radial branches: in the Koala, Wombat, 540 ANATOMY OF VERTEBRATES. Kangaroos, Potoroos, most Phalangers {Phal. Coohii is an excep-tion), most Petaurists {Pet. Sciureus is an exception), the Opos-sums, Bandicoots, and Phascogales, the ulnar and larger divisionof the brachial perforates the internal condyle of the humerus; it 422. Branches of the abdominal aorta, Kangaroo. passes over that condyle, impressing it with a more or less deepgroove in the Dasyures and Thylacine. In the abdomen, the primary branches of the aorta are sent off ARTERIES OF MAMMALIA. 541 in the same order as in most Mammalia, with the exception ofthe constant absence of an inferior mesenteric artery. Thismodification probably relates to the simplicity of the mesentericattachment of the intestines above described. A more markedrepetition of an oviparous arterial character occurs in the modeof origin of the great arteries of the posterior extremities. Inmost Mammalia these are derived from a single trunk on eachside — the common iliac artery; in Birds from two primarybranches of the aorta, one corresponding with the external iliacand femoral, the other with the internal iliac and ischiadic the Kangaroo and vulpine Phalanger the aorta gives off,opposite the interspace of t
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