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
What Is Life During the verses, Gordon moves to a square, Motown-style beat – or "rock-steady Northern soul backbeat" in Leng's words – before returning to the "galloping rhythm" of the more open, "knockout" choruses, and the song is driven equally by Badfinger drummer Mike Gibbins' powerful tambourine work. On "What Is Life", Spector provided what music critic David Fricke terms "echo-drenched theater", in the form of reverb-heavy brass, soaring strings (arranged by John Barham) and "a choir of multitracked Harrisons". The vocals and Barham's contribution, along with a brief slide-guitar commentary from Harrison over the final verse, were overdubbed at Trident Studios,