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Show 1894.] ANATOMY OF ORNITHORHYNCHUS. 703 Extensor ossis metacarpi pollicis.-Arises chiefly from ulna; slightly also from radius. It is inserted, in usual position, into base of first metacarpal bone. There is a tendinous band arising from the cuneiform, Avhich crosses the back of the carpus to join the ulnar margin of the tendon. MYOLOGY OF MANUS. There is a small short muscle of the thumb, which is most probably a combined flexor and abductor. There is a small muscle passing to the little finger, which appears to be an abductor. Palmar inter-ossei.-Are fairly well marked and are three in number. MUSCLES OF THE POSTERIOR EXTREMITY. Gluteus maximus.-Is a large flat muscle, which arises from the posterior part of the crest of the ilium, from the sacral, and upper eight caudal vertebrae. It is inserted into the lower end of the tibia, this part being closely united with the inter-tibialis, and into the sole of the foot, this portion going partly to os calcis and partly to bone supporting the heel. The muscle has a very similar origin and insertion in Echidna 1. Meckel mentions its attachment into the bone supporting the heel in the male. Beneath the gluteus maximus is a muscle which arises from the first four caudal vertebrae. It is inserted into the femur about its middle, just beloAv the gluteal ridge. This deeper portion is supplied by a branch from great sciatic. This is the muscle described by Meckel as medius ; Mivart, too, in Echidna describes a muscle having a similar position. The next-mentioned muscle they both look upon as minimus. Mivart, however, mentions that the muscle described above may represent a deep part of maximus. Its insertion would point to that conclusion. Coues describes this muscle as pyriformis: neither its origin nor insertion would indicate that it corresponds to the ordinary pyriformis. Gluteus medius.-This is a large thick muscle divided at its origin into two parts, superior and inferior. The superior, the larger, arises from the crest and posterior surface of the ilium. The anterior has a narrow origin, from the same surface, close to the cotyloid border of the bone. The two portions are united below, at their insertion into the great tuberosity of the femur. The superior part is supplied by a branch from the sacral plexus. The anterior part is supplied by a branch which arises in abdomen from the anterior crural, and, passing under the rectus, is distributed to this portion of the muscle. Meckel and Mivart in Echidna describe this as minimus. From the nerve-supply it would seem that only posterior portion corresponds to ordinary gluteus medius. The anterior portion may be a muscle divorced from the muscles in front of the thigh. There is a small muscle 1 Mivart. |