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 More Can I Give money for charity, the intended purpose. WKTU-FM received numerous telephone calls and emails from listeners following their unauthorized playing of the song, thanking the station and asking where they could buy a copy of "What More Can I Give".<ref name="Michael Jackson's 9/11 Single Hits Radio One Year Late"></ref> "What More Can I Give" was eventually made available as a digital download on October 27, 2003. The websites whatmorecanigive.com and musicforgiving.com sold the song at a price of $2 per download, with a portion of the proceeds from the fee going towards children's charities such as Oneness, Mr. Holland's Opus Foundation