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
Traditional Chinese medicines derived from the human body "Three Corpses; demonic spirits believed to live in the human body and hasten death" and "gǔdú" 蠱毒 "gu poisoning"; a poison produced by venomous insects; cast a black magic spirit possession over someone". The first "Bencao gangmu" prescription for human nails is not from Chinese medical texts but from Daoist rituals for expelling what (Cooper & Sivin (1973: 220) describe as the "Three Corpse-Worms 三尸, the chief of the "inner gods" who are to the individual microcosm what the celestial bureaucracy is to the cosmos." Prescription 52.6.1, the 斬三尸法 "Method of Beheading the Three Corpses", involves supernaturally cutting the nails