As you're sitting there, reading these words, you're probably breathing. Down the air goes, into your lungs, via the upper respiratory tract that includes your mouth and nose; up it comes again, back out the same way, after delivering its precious oxygen payload. This, we assume, is how most mammals breathe - but maybe it's not actually the complete picture. According to new research, rodents and pigs can also respirate through their butts. Technically, delivery of oxygen via their rectal intestines suggests a new, enema-like means of ventilating patients under respiratory distress - if the same strange ability can be...