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
A Summer Bird-Cage A Summer Bird-Cage A Summer Bird-Cage is the 1963 debut novel by Margaret Drabble published by Weidenfeld & Nicolson. The title of the novel is taken from a quotation from the play "The White Devil" by John Webster: ‘"Tis just like a summer bird-cage in a garden: the birds that are without despair to get in, and the birds within despair and are in a consumption for fear they shall never get out." The novel centres on two characters who are sisters, Sarah and Louise. At the beginning of the story Sarah (who has recently graduated from Oxford University) has