Trachea Diffusion of oxygen and carbon dioxide takes place across the walls of the smallest tubes, called tracheoles, which penetrate tissues and even indent individual cells. Gas may be conducted through the respiratory system by means of active ventilation or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their haemolymph. This is one of the factors that may limit their size. A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices. Taenidia provide strength and flexibility to the trachea. In the head, thorax, or abdomen, tracheae may also be connected
You Are What You Is (song) it from being featured on "Canoe", a 1993 episode of the American television show "Beavis and Butt-Head", also aired on MTV (though the show abruptly switches to "The Animal Song" by The Europeans early on, then returns to Zappa for the tail end of "You Are What You Is", to which Butt-Head replies, "This is still on? That pisses me off!"). "You Are What You Is" contains references to other songs throughout his career and on the album itself, commonly referred as Zappa's "Conceptual Continuity". References include "Gimme a five dollar bill and an overcoat too" from "Wonderful Wino" on