Feather These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular "calamus" (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus). Hatchling birds of some
The Bird in a Cage The Bird in a Cage The Bird in a Cage, or The Beauties is a Caroline era comedy written by James Shirley, first published in 1633. The play is notable, even among Shirley's plays, for its lushness — what one critic has called "gay romanticism run mad." The play was licensed for performance, under the title "The Beauties," by Sir Henry Herbert, the Master of the Revels, on 21 January 1633. It was published in quarto in the same year, printed by B. Alsop and T. Fawcet for the bookseller William Cooke. The title page of the 1633 quarto states