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
Calamus (DTP) Calamus (DTP) Calamus is a desktop publishing application, built for the Atari ST computer. The first version was released on July 1, 1987 by the former German software company DMC GmbH. Calamus is still supported by its German owner company, invers Software, and also runs under a built-in and transparent Atari emulator on Windows, or on other platforms such as Mac OS 9 and Mac OS X, using any available TOS emulator. Calamus is a software RIP application which generates high-quality output in any resolution. It was one of the first DTP applications supporting an own vector font format, notable