OF THE MUSCULAR SYSTEM.
The figure (180) here given from Aleckel* il lustrates some of the most instructive peculiari ties of the muscular system of the Ornithorhyn chus. The animal is dissected from the ventral surface; the great cutaneous muscle, the ' pan niculus carnosus' (1), is reflected from the right side, and the deeper-seated muscles are shown on the left. The panniculus carnosus, which is remarkable for its thickness, encompasses nearly the whole body, adhering most firmly to the external skin, but separated from the subjacent muscles, especially where it covers the thorax, abdomen, the arm, and the thigh, by a copious and lax cellular tissue; and in the female, at the abdominal region, by the mammary glands. The fibres are chiefly longitudinal, but at the lower part of the neck become transverse. The obtuse posterior end of the muscle is attached by three or four fasciculi to the dorsal aspect of the transverse processes of the caudal vertebra;. The legs and the arms protrude through oblique apertures in this muscular tunic ; some of the anterior fasciculi are in serted by a short tendon into the pectoral ridge of the humerus; and others, still more anterior, are attached to the cranium, the lower jaw, and lower lip. A strip of fibres, which is cut off at 1*, is attached to the os hyoides ; another fasciculus (1') spreads over the cheek-pouch, and assists in emptying that receptacle of the food.
The trapezius (9) is divided into two muscles; the posterior portion is an oblong slender tri angle arising by a broad tendon from the tenth and eleventh vertebrae and ribs, and inserted by a short strong tendon in the anterior extremity of the spine of the scapula; the anterior portion is shorter, but broader, and is subquadrangular; it arises from the occipnt and tendinous raphd connecting it with its fellow of the opposite side (called ligamen t= nucha?by Meckel), and is inserted into the spine (' margo anterior scapula,' Illeckel) and acrom ion process of the scapula, and into the outer half of the cla vicle.
The latissirnus dorsi, a very long and broad muscle, arises from the spines of all the dorsal and lumbar vertebra.,
and from the eleven posterior ribs; it is in serted by a broad and strong tendon into the distal half of the ulnar margin of the humerus. At its anterior part this muscle may be sepa rated into a superficial and deep stratum.
The rhomboideus is a single muscle, but thick and long, extending from the occiput to the narrow base of the sca pula.
The splenius is united by an intermediate ten don with the opposite muscle, and is inserted into the mastoid pro cess.
The biventer cervicis and the complesus are distinct throughout their whole course, which ex tends from the anterior dorsal and posterior cer vical spines to the occi put ; the complexus is the longest and thickest muscle, and divides into an external, shorter, and deeper-seated portion, and an internal, longer, and superficial portion.
The sacrolumbalis ari ses from the dorsal ex tremity of the ilium, is attached to the ribs, over which it passes in its course to its insertion into the transverse pro cesses of the four or five posterior cervical verte The longissimus dorsi is a much thicker and narrower muscle, and extends from the dorsal aspect of the sacrum along the spine to the third or fourth cervical vertebra.
The transversalis cervicis and trachelo-mas toideus are blended into a single oblong muscle arising from the anterior dorsal and the trans verse processes of the six lower cervical ver tebrae, and inserted into the mastoid process.
The sterno-mastoid is a double muscle on both sides, one portion being superficial (8), the other deep-seated; each arises separately from the episternal bone, and is separately inserted into the mastoid tubercle, behind the tympanic cavity. The omo-hyoideus and mylo hyoideus (10, 10) have a common insertion into the os hyoides. A muscle (1"), arising from the hyoid bone and expanding to be inserted into the lower lip, serves to retract this part. The sterno-hyoickus (11) joins the hyo-glossus. The genio-hyoideus (12) and the stylo-hyoideus (13) have the normal relations : the biventer maxilla (14) is a short thick muscle, inserted near the bend, representing the angle, of the jaw.