The Science Behind The X-Files:

The Host

• As the episode begins, a hapless Russian trawler crewman named Dmitri is ordered to go flush out a clog in his ship's waste tanks. He gets more than he bargained for when the "clog" yanks him into the tank. His panicked shipmates order the waste tanks flushed, sending everyone's favorite mutant into the Jersey sewers.
  
  Just how DO ships deal with human waste at sea? The U.S. Navy's Virtual Naval Hospital has all the information you'll ever need on the terminology, procedures and techniques used: http://www.vnh.org/PreventiveMedicine/Chapter7/7.01.html

• Mulder is called to Newark, where a santiation worker has found poor Dmitri floating face-down in the sewer. When Scully examines the body at Quantico, she notes that the skin is mottled from being exposed to such high levels of bacteria. More surprisingly, she finds Dmitri has an uninvited guest inside him-- a mysterious worm poking out of his liver.
  
  We all know that sewers aren't exactly the most hygenic places to be. But some scientists are finding ways to use sewer bacteria to our advantage. See how it may provide a cheap source of plentiful hydrogen gas (http://www.hightechcareers.com/doc498a/perc498a.html).
  When Scully points out the high levels of bacteria in uncooked food, Mulder jokes that the murder weapon might be a rare steak. Not quite, but Scully's not exaggerating: check out the Food and Drug Administration's "bad bug book," with an alarmingly long list of possible food-borne pathogens, at http://vm.cfsan.fda.gov/%7Emow/intro.html
  

• Scully summons Mulder and explains that the parasite was a platyhelminthine, or flatworm, from the class Turbellaria, also known as a fluke. The parasite attached itself inside Dmitri's bile duct and was feeding off the liver. (What is it with X-Files mutants and livers?) According to Scully, forty million people worldwide are infected with these creatures. The Flukeman's latest victim, a Jersey sanitation worker, has a bite mark on his back which looks like it came from a larger version of what Scully calls a scolex, the four-pronged sucker-mouth flukes use to attach to their hosts.
  
  Funk & Wagnall's Knowledge Center has a page full of fluke facts at http://www.fwkc.com/encyclopedia/low/articles/f/f008000811f.html.
  Flatworms are hermaphrodites, which means they have all the necessary equipment to reproduce asexually, creating offspring without the help of another parent. Brittanica.com has all the information at http://www.britannica.com/bcom/eb/article/1/0,5716,119831+5,00.html.
  What exactly is a bile duct, and how does it relate to the liver? Find out at http://medhlp.netusa.net/glossary/new/gls_0669.htm.
  

• Back in New Jersey, Mulder manages to trap the Flukeman within the pipes of the local sewage treatment facility. Sewage treatment plants are designed to separate solid waste from liquid, then disinfect the remaining water so it's safe to be released again.
  
  Find out more about the sewage treatment process from the Johnstown, Pennsylvania plant's virtual tour at http://www.howstuffworks.com/sewer.htm
  Assuming you have nothing better to do, you'll find plenty of links to treatment plants across the country, including one in New Jersey, at http://www.sewage.net

• The Flukeman escapes from a federal marshall as it's being transferred to another prison and hides out in a chemical toilet at a nearby campground. That's as far as police search dogs are able to track it, but by the time they do, it's on its way back to the sewers.
  
  What exactly defines a tracking dog, and how do they do their job? For answers, see Kevin Clouston's search and rescue dog page at http://users.worldgate.com/~dognyard/sarinfo.html

• Mulder tracks the Flukeman back to the sewers, where he manages to trap it under a grate and cut it in half. Later, Scully tells him that the autopsy revealed signs of extreme genetic mutation, probably caused by radiation from the April 26, 1986, Chernobyl nuclear disaster, the world's worst to date.
  
  What can nuclear radiation do to the human body? Well, it won't make you grow 50 feet tall, or turn green when you get angry, but its effects are still frightening. Read the U.S. Nuclear Regulatory Commission's report at http://www.nrc.gov/NRC/EDUCATE/REACTOR/06-BIO/radbioeffects.html
  When Chernobyl reactor number 4 exploded, it sent radiation over parts Belarus, the Ukraine, and Russia. In the months that followed, many children and animals were born with profound deformities and mutations. In 1996, the French government released a comprehensive study on the disaster and its aftereffects; you can read an English-language version at http://www.nea.fr/html/rp/chernobyl/allchernobyl.html