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Show 1896.] ANATOMY OF PETROGALE XANTHOPUS. 705 The Thyroid body consists of two separate oval lobes about 2 inch long, lying one on each side of tbe trachea without any isthmus connecting them. The Arch of the Aorta has only twTo branches, the innominate and the left subclavian; the former gives off the right subclavian, soon after which it divides into right and left carotids. The Subclavian arteries pursue a normal course and give off vertebral, internal mammary, and transverse cervical branches, but no inferior thyroid or superior intercostal were seen. The common Carotid gives off the superior thyroid and, at the anterior margin of the larynx, divides into external and internal carotids, the former giving off lingual, facial, and occipital branches, and ending almost entirely in the internal maxillary, the temporal beino- very small. The superior laryngeal branch comes off from the lingual. The Axillary artery gives off well-marked thoracic, subscapular, and circumflex branches. Tbe Brachicd gives off a small superior profunda which accompanies the museulo-spiral nerve, as well as a large nutrient branch to the humerus. About the middle of the arm, at the place where the median nerve is finally formed, a superficial branch comes off, which possibly represents the inferior profunda though it does not accompany the ulnar nerve. The brachial artery then passes through the supra-condylar foramen, after which it gives off some muscular branches and soon divides into posterior interosseous and median. The posterior Interosseous passes to the back of the forearm between the two bones, giving off a large posterior interosseous recurrent branch; while the median accompanies its nerve into the palm of the hand, where it divides into four digital branches for the clefts between the digits. There is no radial or ulnar artery and no deep palmar arch. Owen' describes the artery which I have called median as the ulnar, and says that there is also a radial artery. The Thoracic aorta shows nothing worthy of special notice. The Abdominal aorta gives off the caeliac, mesenteric, and two renal arteries close together, just behind the opening in the diaphragm. Of the two renals the right is a little in front of the left. There is no posterior mesenteric artery, a condition which Owen has noticed in all Marsupials. The aorta trifurcates opposite the disc between the fifth and sixth lumbar vertebrae into the caudal and two external iliacs. The internal iliacs are given off from the caudal opposite the posterior part of the sixth lumbar vertebra, as has been pointed out by Owen. The External Iliac gives off a large ilio-lumbar branch, and, just before reaching the brim of the pelvis, a common trunk, which divides into obturator and deep epigastric. The Common Femoral soon after its commencement gives off an external circumflex branch, which runs outward between the super- 1 ' Anatomy of Vertebrates,' vol. iii. p. 541. |