Science File Information:
Mulder and Scully travel to a Texas trailer town to investigate a few cow exsanguinations (see EVE) and one homicide. In examining the body, Scully finds two puncture wounds on the neck--bitemarks from sharpened incisors--to which she postulates might be the work of a vampire-obsessed serial killer. Perhaps, she says, the killer filed down his incisors to be just like his movie-screen idols. To find this out, she suggests they get a moulage casting on the the bite marks. Her theories don't stop there. Scully discusses haematodipsia, a psychological disorder in which drinking blood gives one sexual pleasure (from the Greek roots for "blood thirst"); porphyria (see 3); and xeroderma pigmentosum (XP), a severe sensitivity to ultraviolet (UV) light. UV light damages the DNA in cells, even in healthy people. Luckily, the human body normally has mechanisms that repair the DNA so that the damage isn't permanent. People who suffer from XP do not have these cellular repair mechanisms, and exposure to sunlight can cause irreversible damage.
How does UV light damage your DNA? A complicated explanation can be found in the MAD Scientist Network archives at http://www.madsci.org/posts/archives/mar99/921641500.Mb.r.html.
The Why Files have a whole article on XP, with a much simpler explanation of the hows (and whys) behind UV light and DNA damage, at http://whyfiles.news.wisc.edu/shorties/dna_repair.html.
For further information on XP and how you can help people afflicted with it, visit the home page of the non-profit Xeroderma Pigmentosum Society at http://www.xps.org/.
Mulder, as usual, believes it's probably a vampire of legend. He offers his own theories of the fantastic, rattling off a litany of vampire myths from around the world. He claims that one common element in many myths is that vampires are obsessive-compulsive creatures. They obsess over keeping things organized or simplified and compulsively will pick up seeds strewn on the ground or will untie knotted shoelaces. (The local sheriff, listening to Mulder's ideas, confuses people suffering obsessive compulsive disorder with autistic savants, like the movie Rain Man's title character. See ELEGY for more on autism, and you'll see that they're quite different conditions.)
Obsessive Compulsive Disorder (OCD) is a mental illness that afflicts over 5 million Americans. Learn more about it by visiting a fact page provided by the OC & Spectrum Disorders Association at http://www.ocdhelp.org/ocdfacts.html.
If you want to find out how autistic savant are different from OCD sufferers, read the short essay the Center for the Study of Autism has on the nature of savants at http://www.autism.org/savant.html.
While Mulder and the sheriff are off in the local cemetary, scattering sunflower seeds, and looking for obsessive compulsive vampires, Scully is back at the funeral parlor, conducting an autopsy on the dead man with the bite marks on his neck. How exactly does a physician conduct an autopsy? What's the difference between a coroner and a medical examiner? Would a human body yield quite so much intestine? Check out the links below to find out.
Ed Friedlander, M.D. (a.k.a., "Ed, the pathology guy"), has an excellent page on the ins and outs of an autopsy, replete with disturbingly educational cartoons to illustrate the steps of the autopsy, at http://worldmall.com/erf/autopsy.htm.
As for the intestines question--the answer is yes, up to 25 feet. You'll find this and other odd facts about the human body at the self-proclaimedYuckiest Site on the Internet's anatomy pages at http://www.yucky.com/body/index.ssf?/systems/.
(This link, if you hadn't guessed, is geared for a younger crowd, but it's still interesting.)
In the course of her autopsies, Scully finds traces of chloral hydrate. Chloral hydrate is a sedative that was administered to children, in times past, as a relaxant or a treatment of insomnia. Incidentally, it's a danger to people who have porphyria--it can cause acute attacks of the disease. I guess that puts a damper on Scully's porphyria argument in this case...
Find out all that you'd ever like to know about chloral hydrate and it's side effects on an informative brochure from WebMD at http://my.webmd.com/drugs_article/DMK_ARTICLE_1452050.
Mulder realizes too late that the pizza he's just been delivered was laced with chloral hydrate; as he slips into dreamland, he sees the delivery boy stalking towards him, eyes glowing green. Human eyes don't glow green (as a general rule), but some nocturnal animals' eyes do. Cats eyes, for example, "glow" in low light (although I'm not sure exactly what color, because I don't happen to own a cat). This glow is a result of a reflective layer on the back of the eye called the tapetum lucidum that reflects light in such a manner as to let the animal's eye get a second chance to interpret the image coming through the lens, improving the animal's night vision. Nifty!
Read about the tapetum lucidum, red eye, and night vision, at How Things Work's page at http://www.howstuffworks.com/question51.htm.