OCR Text |
Show 274 MR. F. G. PARSONS ON T H E [Mar. 20, Interossei.-There are eight interossei, which all lie in the same plane, rising from the semilunar cartilage and being inserted into the eight sesamoid bones in front of the four metacarpo-phalangeal joints. The most ulnar of these has already been described as the flexor brevis minimi digiti. In Castor only six of these are present. Muscles of Trunk. Panniculus Carnosus.-The panniculus is well marked in Rodents, and consists in many places of two or more layers of fibres running in different directions. The superficial panniculus in the neck rises from some of the face-muscles, more especially the orbicularis oris, and runs back along the side of the neck to be attached to the spine of the scapula ; it probably corresponds to the human platysma. In Spermophilus, in which the cheek-pouches are present, part of this muscle is specially developed, and runs from the end of the pouch to the metacromial process. On the ventral surface of the neck the fibres decussate across the middle line, and run backwards and outwards over the pectoral region; as a rule, these decussating fibres are more or less scattered, but in Octodon they are very well marked, rising from a small origin a little to the side of the symphysis menti, and spreading out in a fan-shaped manner to cover the opposite side of the neck. Deep to these fibres lies the sterno-facialis, which is attached to the anterior part of the sternum and runs forwards to spread out over the masseter, covering the sterno-mastoid in its course; it is very well marked in all the Octodontidae. Fig. 9. Panniculus of Octodon. The panniculus is not well marked on tbe dorsum of the neck, but over the trunk it is found as a thick mass ; over the shoulders |