Evolution of the cochlea and the elongated cochlea allows for better sensitivity for higher frequencies. As in all lepidosaurs and archosaurs, the single-ossicle (columellar) middle ear transmits sound to the footplate of the columella, which sends a pressure wave through the inner ear. In snakes, the basilar papilla is roughly 1mm long and only responds to frequencies below about 1 kHz. In contrast, lizards tend to have two areas of hair cells, one responding below and the other above 1 kHz. The upper frequency limit in most lizards is roughly 5–8 kHz. The longest lizard papillae are about 2mm long and contain 2000 hair
Jock Stirrup plans could be afforded over the coming years. The planning for the invasion of Iraq required new equipment and Stirrup became increasingly involved in planning for urgent operational requirements. A particular difficulty faced by Stirrup was the need to place equipment orders with industry before the Government was prepared to publicly commit to the action. Stirrup briefed ministers on this point but was prevented from placing the orders according to his desired timescale. In the end some critical items such as body armour, boots and desert clothing were not available to all the personnel who needed them when they deployed.