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
Free as a Bird Beatles songs, such as "Penny Lane", "Paperback Writer", "A Day in the Life", "Eleanor Rigby", "Helter Skelter", "Piggies", "The Continuing Story of Bungalow Bill", "Strawberry Fields Forever", "Doctor Robert", and "The Fool on The Hill". Between 80 and 100 allusions to the Beatles' story, music and lyrics in the video have been estimated. Although the bird can be heard at the beginning of the video, it is never seen. Neil Aspinall (Apple Records executive at the time) said that this was because no-one could agree on what kind of bird it should be. Pytka had to send his ideas to