. Outlines of zoology. MUSCULAR SYSTEM. 657 a horny sheath, which is annually moulted in the puffin. A moultingof claws occurs in the grouse. The dermis is thin and vascular, andIS rich in tactile nerve-endings or Pacinian corpuscles, especiallyabundant in the cere. The only skin gland—the preen gland—secretesan oily fluid, which some birds use in preening their feathers. It isabsent in the ostrich, emu, cassowary, and in a few Carinate Fig. 361.—Parts of a feather.—After , Four barbs (5.) bearing anterior l^arbules () and posterior barbules(J^.BB.); //., six barbs (B.)
. Outlines of zoology. MUSCULAR SYSTEM. 657 a horny sheath, which is annually moulted in the puffin. A moultingof claws occurs in the grouse. The dermis is thin and vascular, andIS rich in tactile nerve-endings or Pacinian corpuscles, especiallyabundant in the cere. The only skin gland—the preen gland—secretesan oily fluid, which some birds use in preening their feathers. It isabsent in the ostrich, emu, cassowary, and in a few Carinate Fig. 361.—Parts of a feather.—After , Four barbs (5.) bearing anterior l^arbules () and posterior barbules(J^.BB.); //., six barbs (B.) in section, showing interlocking of barbules;///., anterior barbule with barbicels (/^.). Muscular system.—The largest breast muscle (pectoralismajor) arises from the sternum and its keel, and from theclavicle, is inserted on the ventral surface of the humerus,and depresses the wing. The smaller but longer pectoralisminor or subclavian, exposed when the large one is reflected,raises the wing. It arises from the keel and sides of thesternum, and is continued over the shoulder (through theforame?t triosseum, which serves as a pulley) to its insertionon the dorsal surface of the humerus. Arising chiefly fromthe coracoid, but in part from the sternum, and insertedon the humerus, is a small coraco-brachialis, which helpsa little in depressing the wing. There are several yetsmaller muscles. Interesting also is the mechanism of perching.
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
