" The space between the internal and external sphincter muscles is home to a large number of sensor cells. They analyse the product delivered to them, test it to find out whether it is solid or gaseous, and send the resulting information up to the brain. This is the moment when the brain realises: it’s time to go to the toilet! … or maybe it’s just a bit of wind? "

― Giulia Enders , Gut: The Inside Story of Our Body’s Most Underrated Organ