Billed as libido in an atomiser, PT-141 will finally offer women the chance to turn on their sexual desire as and when they need it. Or so the science says. But there are concerns. Will sex in a spray usher in an age of 'McNookie' - quick easy couplings low on emotional nutrition? Julian Dibbell reports Horn of rhinoceros. Penis of tiger. Root of sea holly. Husk of the emerald-green blister beetle known as the Spanish fly. So colourful and exotic is the list of substances that have been claimed to heighten sexual appetite that it is hard not to...