Pin feather protective peripheral sheath, longitudinal barb ridges, and growth plates. Over time these barb ridges lengthen helically, branch to create barbs and barbules, and fuse to form the rachis or central shaft. Moreover, the barb plate further differentiate into hooklets and cilia, while the marginal and axial plate die to form the intervening space within the feather structure. During moulting, a bird may get careless and begin to chew at its feathers and might accidentally damage a blood feather. To prevent this, it is necessary that the bird is given chewing toys so that it does not chew at its own
Acorus calamus Karpos, of Zephyrus (the West Wind) and Chloris (Spring). When Karpos drowned in a swimming race, Kalamos also drowned and was transformed into a reed, whose rustling in the wind was interpreted as a sigh of lamentation. The plant was a favorite of Henry David Thoreau (who called it "sweet flag"), and also of Walt Whitman, who added a section called the "Calamus" poems, to the third edition of "Leaves of Grass" (1860). In the poems the calamus is used as a symbol of love, lust, and affection. Lewis Carroll uses the plant in "Through the Looking-Glass" as a symbol