Question: Which type of large intestine worm was primarily studied by Ivan Mackerie?

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Basal electrical rhythm: The basal or basic electrical rhythm (BER) or electrical control activity (ECA) is the spontaneous depolarization and repolarization of pacemaker cells in the smooth muscle of the stomach, small intestine, and large intestine.  This electrical rhythm is spread through gap junctions in the smooth muscle of the GI tract.  These pacemaker cells, also called the interstitial cells of Cajal, control the frequency of contractions in the gastrointestinal tract.  The cells can be located in either the circular or longitudinal layer of the smooth muscle in the GI tract; circular for the small and large intestine, longitudinal for the stomach.  The frequency of contraction differs at each location in the GI tract beginning with 3 per minute in the stomach, then 12 per minute in the duodenum, 9 per minute in the ileum, and a normally low one contraction per 30 minutes in the large intestines that increases 3 to 4 times a day due to a phenomenon called mass movement.  The basal electrical rhythm controls the frequency of contraction but additional neuronal and hormonal controls regulate the strength of each contraction.

Large intestine (Chinese medicine): The large intestine (Chinese: 大肠/大腸: pinyin: "dà cháng") is one of the "fu" organs stipulated by traditional Chinese medicine (TCM).  As distinct from the Western medical concept of large intestine, this concept from TCM is more a way of describing a set of interrelated parts than an anatomical organ.  It is a functionally defined entity and not equivalent to the anatomical organ of the same name.

Mongolian death worm: The Mongolian death worm (Mongolian: олгой-хорхой , olgoi-khorkhoi, "large intestine worm") is a creature

Gastrointestinal perforation: Gastrointestinal perforation, also known as ruptured bowel, is a hole in the wall of part of the gastrointestinal tract.  The gastrointestinal tract includes the esophagus, stomach, small intestine, and large intestine.  Symptoms include severe abdominal pain and tenderness.  When the hole is in the stomach or early part of the small intestine the onset of pain is typically sudden while with a hole in the large intestine onset may be more gradual.  The pain is usually constant in nature.  Sepsis, with an increased heart rate, increased breathing rate, fever, and confusion may occur.

Small intestine: The small intestine or small bowel is the part of the gastrointestinal tract between the stomach and the large intestine, and is where most of the end absorption of food takes place.  The small intestine has three distinct regions – the duodenum, jejunum, and ileum.  The duodenum is the shortest part of the small intestine and is where preparation for absorption begins.  It also receives bile and pancreatic juice through the pancreatic duct, controlled by the sphincter of Oddi.  The primary function of the small intestine is the absorption of nutrients and minerals from food, using small finger-like protrusions called villi.

Trichuris trichiura: The human whipworm (Trichuris trichiura or Trichocephalus trichiuris) is a round worm (a type of helminth) that causes trichuriasis (a type of helminthiasis which is one of the neglected tropical diseases) when it infects a human large intestine.  It is commonly known as the "whipworm" which refers to the shape of the worm; it looks like a whip with wider "handles" at the posterior end.

Trichuris vulpis: Trichuris vulpis is a whipworm that lives in the large intestine of canines in its adult stages.  Out of different types of worms, "Trichuris vulpis" is one of the smaller worms with a size ranging from 30–50 mm in length.  As the name suggests, the worm has a whip-like shape with distinct features including a small, narrow anterior head, which is the digestive part of the worm, and a larger posterior tail, which is the reproductive part of the worm.  Eggs from "T. vulpis" are oval shaped with bipolar plugs and contain a thick outer shell.  Their sizes range from 72–90 μm in length and 32–40 μm in width.  Because of their thick outer shell, "T. vulpis" eggs are very resistant to environmental extremes such as freezing or hot temperatures, thus allowing for their long viability in the outside world.

Ivan Mackerle: Ivan Mackerle (March 1942January 3, 2013) was a Czech cryptozoologist, author, design engineer, and explorer.  He organized expeditions to search for the Loch Ness monster of Scotland, the Tasmanian tiger in Australia, and the elephant bird in Madagascar.  He was most notable for his search of the Mongolian death worm, and he conducted three trips to Mongolia in 1990, 1992, and 2004.  He authored numerous books and publications and from 1998 until 2002 he was chief editor of the Czech paranormal magazine "Fantastická fakta" ("Fantastic Facts").

Pancolitis: Pancolitis or universal colitis is a very severe form of ulcerative colitis.  This form of ulcerative colitis is spread throughout the entire large intestine including the right colon, the left colon, the transverse colon, descending colon, and the rectum.  A diagnosis can be made using a number of techniques but the most accurate method is direct visualization via a colonoscopy.  Symptoms are similar to those of ulcerative colitis but more severe and affect the entire large intestine.  Patients with ulcerative colitis generally exhibit symptoms including rectal bleeding as a result of ulcers, pain in the abdominal region, inflammation in varying degrees, and diarrhea (often containing blood).  Pancolitis patients exhibit these symptoms and may also experience fatigue, fever, and night sweats.  Due to the loss of function in the large intestine patients may lose large amounts of weight from being unable to procure nutrients from food.  In other cases the blood loss from ulcers can result in anemia which can be treated with iron supplements.  Additionally, due to the chronic nature of most cases of pancolitis, patients have a higher chance of developing colon cancer.

Hirschsprung's disease: Hirschsprung's disease (HD) is a form of megacolon that occurs when part or all of the large intestine or parts of the gastrointestinal tract have no ganglion cells and cannot function.  During normal prenatal development, cells from the neural crest migrate into the large intestine (colon) to form the networks of nerves called the myenteric plexus (Auerbach plexus) (between the smooth muscle layers of the gastrointestinal tract wall) and the submucosal plexus (Meissner plexus) (within the submucosa of the gastrointestinal tract wall).  In Hirschsprung's disease, the migration is not complete and part of the colon lacks these nerve bodies that regulate the activity of the colon.  The affected segment of the colon cannot relax and pass stool through the colon, creating an obstruction.  In most affected people, the disorder affects the part of the colon nearest the anus.  In rare cases, the lack of nerve bodies involves more of the colon.  In 5% of cases, the entire colon is affected.  The stomach and esophagus may be affected, too.

Supporting paragraphs: Ivan Mackerle Mongolian death worm
Answer: He was most notable for his search of the Mongolian death worm,