The next time you’ve got something to complain about, consider the plight of the intestinal worm. It not only has to figure out how to eat and breed in the confines of another creature, it has to prevent that creature’s body from dissolving the parasite into a mist of cells. That means dodging the immune system and inflammation, the body’s natural responses to invasion. Meaning, your late car payment ain’t got nothing on spending your entire life in an intestine.