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History
of the Digestive System
How We Learned About Our Own Guts
"The stomach is lowest and has a hidden place
in the body because of its uncleanness, as though nature
had spared the principal members and had relegated the stomach
or bowels farther away from the site of reason and of the
mind and fenced it off with the diaphragm in order not to
disturb the rational part of the mind with its importunity.
These members serve the higher ones. Some of them concoct
the food into juice, others digest it into various humors,
others expel the superfluity." -- Alessandro Benedetti,
1497
Pre
11th century
Male figure, showing intestines, terracotta,
Allahabad Municipal Museum, Allahabad, Uttar Pradesh, India
Image
credit exact date unknown, pre-1000 AD.
"Intestine"
in Sumerian cuneiform pictograph and Egyptian hieroglyph;
"stomach" in Chinese
The Sumerian sign (Jaritz #103), depicts
a 'length of intestine filled with contents, showing both
tied ends'; and means 'qa, measure of capacity (approximately
60 in.3)', which I assume is the capacity of a then standard
length of intestine, used as a container.
The Egyptian sign for intestine is (Gardiner
#F46),
It has an unusual number of variants:
meaning: 'intestine/intestinal cavity',
also 'coils of snake' and 'windings of waterway'.
This is the Chinese sign for "stomach."
Claudius Galenus
of Pergamum (129-200 AD)
Ancient and medieval anatomists had fairly
accurate gross physiological knowledge of the structure
of the stomach, colon, and intestines, dividing the later
into six sections whose names are still retained today in
modern anatomy. They recognized the importance of digestion
as a key aspect of maintaining the humoral balance of the
body, suggesting that, if the stomach and intestines' functions
were impaired, other bodily functions would suffer. Initially
medical practitioners viewed the stomach as an active, almost
thinking agent in the body.
Galen saw the stomach as an animate being
that could feel its own emptiness and generate the sensation
of hunger, writing: "[Nature] has granted to the stomach
alone and particularly to the parts of it near its mouth
the ability to feel a lack which rouses the animal and stimulates
it to seek food. " He additionally described it as
a storehouse of nutrition that sorted the wheat from the
chaff:
"For just as workmen skilled in preparing
wheat cleanse it of any earth, stones, or foreign seeds
mixed with it that would be harmful to the body, so the
faculty of the stomach thrust downward anything of that
sort, but makes the rest of the material, that is naturally
good, still better and distributes it to the veins extending
to the stomach and intestines."
The intestines and colon, on the other
hand, were more passive, relying on their physical attributes
of length and thickness to absorb nutrients and contain
waste. Galen further observed that the longer and varied
size of the intestines was a sign of a higher being. He
contrasted this kind of intestine to that of "voracious
animals ... [that] both feed continually and as incessantly
eliminate, leading a life truly inimical to philosophy and
music, as Plato has said, whereas nobler and more perfect
animals neither eat nor eliminate continually." The
continued fascination with the shape of the human intestines
as indicative of their special purpose is apparent in this
early modern Islamic illustration:
Image from (17th century AD copy of versions
from several centuries earlier) Persian manuscript by Mansur
ibn Muhammad Ahmad at the Majles Library, Tehran. From:
Seyyed Hossein Nasr (1976). Islamic Science:An Illustrated
Study, World of Islam Festival Publishing Ltd..
11th Century
In the early eleventh century, the medieval
Islamic medical philosopher Avicenna was much less concerned
about descriptive anatomy. Instead, he recognized the importance
of nutrition and the vulnerability of the stomach to illness,
giving copious advice about diet and some about digestion,
writing primarily about the stomach and intestines in relation
to these two factors. Very practically he observed, "Mental
excitement or emotion; vigorous exercise; these hinder digestion."
Later medieval and Renaissance medical practitioners built
upon these ideas by offering complexion theories of the
stomach as a cold and dry organ that was among the principal
organs of the body. In the Galenic tradition, it was the
site of first digestion, since the body digested nutrients
in multiple ways. Every aspect of its shape and texture
-- even its location -- facilitated this process. Master
Nicolaus in the twelfth century poetically wrote: "The
stomach has the liver below it like a fire underneath a
cauldron; and thus the stomach is like a kettle of food,
the gall-bladder its cook, and the liver is the fire."
Medieval manuscript describing the stomach.
(source unknown)
The illustration above, from a medieval
anatomy book, demonstrates this idea in the way both the
liver and stomach are drawn. Similarly, the names of parts
of the digestive system recalled their specific functions.
Many thought that the colon was a colander that strained
the feces.
15th Century
Image
credit
Among Leonardo Da Vinci's (1452-1519) many
scientific achievements were his discoveries in anatomy.
Besides artistic talent, he possessed the "stomach"
to dissect of both humans and animals. Dissections weren't
common in da Vinci's day, but probably weren't illegal,
either. Though his understanding of the respiratory system
added little to medieval knowledge, his studies of skeletal
and muscle tissue, brain anatomy, and digestive and reproductive
systems advanced human anatomical understanding to a new
level.
Read
more about Da Vinci's anatomy studies here.
Increased dissection led to more detailed
descriptions of the organs involved in digestion, and to
illustrations such as the one above reflecting this new
approach to anatomy.
In 1497, Alessandro Benedetti lingered
over its "denticulated or corrugated [appearance] with
thick skin in the manner of a blackberry." At the end
of the fifteenth century, Berengario da Carpi wrote:
"The stomach's substance is predominantly
sinewy. Its color is evident. Its form is round and arched
like a Moorish gourd. It is connected to the heart by arteries,
to the liver and spleen by veins, to the vein by descending
nerves. It is attached to the anus by intestines and to
the mouth by means of the gullet."
None of this new detail, however, fundamentally
changed the image of the stomach. It was still a cold and
dry organ, situated at the crossroads of the arterial and
venal systems, that was literally roused to life within
the body.
16th Century
The image shown above is a detail taken
from the frontispiece of the 1555 edition of De Fabrica,
in all probability designed by Johannes Stephan van Calcar,
a pupil of Titian. The plate shows Vesalius at one of his
lectures on anatomy. The bearded figure of Vesalius stands
in the middle beside the dissecting table, performing an
autopsy on the cadaver of a woman. The full frontispiece
shows Vesalius surrounded by a crowd of about 70 students
and spectators of all ages. Learn more about Vesalius, the
father of modern medicine, here.
16th Century
Some religious restrictions on dissection
were lifted in the 15th & 16th centuries, leading to
the wider study of anatomy using models like these as extra
teaching aids.
18th Century
This is an anatomical figure of a pregnant
women lying on a cloth-covered bier in a wooden box. It
is made of ivory and the front can be removed to reveal
the internal organs, some of which can themselves be removed.
The figure may have been manufactured in Italy in the early
18th century. Image
source: Science Museum/Science & Society Picture
Library
19th Century
William Beaumont (November
21, 1785 - April 25, 1853) was a surgeon in the U.S. Army
who became known as the "Father of Gastric Physiology"
following his research on human digestion.
On June 6, 1822, an employee of the American
Fur Company on Mackinac Island named Alexis St. Martin was
accidentally shot in the stomach. Dr. Beaumont treated his
wound, and expected St. Martin to die from his injuries.
Despite this dire prediction, St. Martin survived with a
hole in his stomach that never fully healed. Unable to continue
work for the American Fur Company, he was hired as a handyman
by Dr. Beaumont.
Dr. William Beaumont,circa 1821 & Alexis
St. Martin at about age 81 years.
By the August of 1825, Beaumont had been
relocated to Fort Niagara in New York, and Alexis St. Martin
had come with him. It was at this location that Dr. Beaumont
began to perform experiments on digestion using the stomach
of St. Martin. Most of the experiments were conducted by
tying a piece of food to a string and inserting it through
the hole into St. Martin's stomach. Every few hours, Beaumont
would remove the food and observe how well it had been digested.
Beaumont also extracted a sample of gastric acid from St.
Martin's stomach for analysis. In September, Alexis St.
Martin left Dr. Beaumont and moved to Canada, leaving Beaumont
to concentrate on his duties as an army surgeon.
In 1828 he was stationed in Prairie du
Chien, Wisconsin for the next five years. While there, Beaumont
arranged for Alexis St. Martin to come to serve as Beaumont's
handyman again. In early 1831, Dr. Beaumont conducted another
set of experiments on St. Martin, ranging from the simple
observation of normal digestion to the effects that temperature
and even emotions have on the digestive process. In April,
St.Martin again left for Canada. Beaumont left the army
in 1832 and moved to Washington, D.C.
In Washington, Dr. Beaumont met St. Martin
once again, and performed another set of experiments on
how various foods were digested in the stomach. In 1833,
Beaumont left Washington and returned to Plattsburgh, New
York, where he wrote a book about his experiments on digestion
titled Experiments and Observations on the Gastric Juice
and the Physiology of Digestion. ---Wikipedia
Diagram of Alexis
St. Martin's wound (from Dr. Beaumont's book, Experiments
and Observations on the Gastric Juice and the Physiology
of Digestion, 1833)
"This engraving represents the appearance of the aperture
with the valve depressed.
A A A Edges of the aperture through the integuments and
intercostals, on the inside and around which is the union
of the lacerated edges of the perforated coats of the stomach
with the intercostals and skin.
B The cavity of the stomach, when the valve is depresed.
C Valve, depressed within the cavity of the stomach.
E E E E Cicatrice of the original wound."
Details of the foods used in the
Beaumont-St Martin digestion experiments:
It was not until August 1, 1825
that Dr. Beaumont — now stationed at Fort Niagara
— began his experiments with St. Martin, becoming
the first person to observe human digestion as it occurs
in the stomach. Beaumont tied quarter-ounce pieces of food
to the end of a silk string and dangled the food through
the hole into St. Martin's stomach. (The food items were
"high seasoned alamode beef," raw salted lean
beef, raw salted fat pork, raw lean fresh beef, boiled corned
beef, stale bread, and raw cabbage.) St. Martin went back
to his household duties. Beaumont pulled out the string
one, two, and three hours later, to observe the rate of
digestion for the different foods. Five hours after he first
put the food into St. Martin's stomach, Beaumont removed
the food pieces because St. Martin was suffering stomach
distress. The next day, St. Martin still had indigestion,
which Beaumont treated.
On August 7, 1825, Beaumont
had St. Martin fast for 17 hours, and then took the temperature
of St. Martin's stomach (it was 100 degrees) Beaumont removed
gastric juice from St. Martin's stomach, then observed the
rate of digestion of a piece of corned boiled beef "test-tube"
style, while also placing the same-sized piece of meat directly
into St. Martin's stomach. The stomach digested the meat
in two hours; the vial of gastric juice took 10 hours (maintained
at about 100 degrees). The next day, Beaumont repeated the
experiments using boiled chicken, which he found digested
slower than the beef. The experiments showed that gastric
juice has solvent properties
In January 1831, Beaumont
just observed the normal process of digestion in the stomach.
St. Martin would eat a normal meal and resume his work,
and Beaumont would periodically take samples from St. Martin's
stomach. Another experiment compared what happened to food
placed in a vial of gastric juice (temperature not controlled),
food placed in a container of water, and food eaten by St.
Martin; he learned that gastric juice needed heat to digest
(i.e., that cold gastric juice has no effect on food). Beaumont
used more variety of food samples while at Fort Crawford;
he found that vegetables are less digestible than other
foods, and milk coagulates before the digestive process.
St. Martin sometimes became irritable doing experiments
(it was stressful for him to have food removed from his
stomach), and Beaumont observed that being angry can hinder
one's digestion.
Late 1832 in Washington,
D.C., Beaumont again tried different foods with St. Martin,
including raw oysters, sausage, mutton, and "boiled
salted fat pork." Beaumont focused on gastric juice,
but did not study the importance of saliva on digestion;
sometimes, he put food directly into St. Martin's stomach
(once, he put in 12 raw oysters). He also observed that
exercise helped the production and release of gastric juice.
(Another limitation on Beaumont's work is that he could
not obtain a chemical analysis of the gastric juice, as
chemical analysis was severely limited in the mid-nineteenth
century.)
What happened to
both men and how they are remembered?
William Beaumont continued
his private medical practice in St. Louis. In March 1853,
Dr. Beaumont slipped on an icy step while exiting a patient's
home, hitting his head severely. The occipital hematoma
became infected, his condition deteriorated, and he died
on April 25. He was buried in Bellefontaine Cemetery in
St. Louis. He is memorialized now by a number of medical
history organizations and buildings including:
William Beaumont Hospital in Michigan
Beaumont Memorial building on Mackinac Island
Beaumont Life Sciences Building ("Beaumont Hall")
on the SUNY Plattsburgh Campus
William Beaumont Army Medical Center (WBAMC) in El Paso,
Texas
Alexis St. Martin lived 58 years after
his accident. After returning home to Canada for good, he
worked as a farmer and itinerant laborer ("chopping
wood by the cord," he described it). After the doctor's
death, St. Martin did make a brief visit in 1856 to Dr.
Beaumont's home in St. Louis, where he spoke with Deborah
Beaumont. After Deborah's death, St. Martin frequently corresponded
with Dr. Beaumont's son Israel; in 1879, he wrote that he
had "been ill for six years . . . I am suffering a
little from my gastric fistula, and my digestion grows worse
than ever." His lawyer, Judge Baby of Montreal, said
that St. Martin was "very much addicted to drink"
in his 80's.
When St. Martin died at age 86 on June
24, 1880 in St. Thomas de Joliette, Canada, his family deliberately
let his body decompose in the hot sun for four days and
then buried it in the Catholic churchyard in a deep unmarked
grave, with heavy rocks atop the coffin, hoping to prevent
anyone from examining his stomach or performing an autopsy.
Years later, to commemorate St. Martin's contribution to
medical science, a committee finally persuaded one of St.
Martin's granddaughters to disclose the grave's location;
in 1962, a plaque was placed on the church's wall near the
grave, stating Alexis' history, and that "through his
affliction he served all humanity."
The cafeteria at the William Beaumont Army
Medical Center in El Paso, Texas is named the "Saint
Martin Dining Facility."
Learn
more about Dr. Beaumont and Alexis St. Martin here.
Details from two of a set of nine
wax plaques showing different stages in the dissection of
a female figure and the development of the human
embryo, probably made in Vienna, Austria, early 19th century.
Here, the female figure has been superficially dissected
to show the viscera - the heart, stomach, lungs and intestines.
Below, the female figure has been deeply
dissected to show the alimentary canal and arterial supply
to the lower regions.
Science
Museum/Science & Society Picture Library
20th Century
Fluoroscopy is an imaging
technique commonly used by physicians to obtain real-time
images of the internal structures of a patient through the
use of a fluoroscope. In its simplest form, a fluoroscope
consists of an x-ray source and fluorescent screen between
which a patient is placed. However, modern fluoroscopes
couple the screen to an x-ray image intensifier and CCD
video camera allowing the images to be played and recorded
on a monitor. The use of x rays, a form of ionizing radiation,
requires that the potential risks from a procedure be carefully
balanced with the benefits of the procedure to the patient.
While physicians always try to use low dose rates during
fluorscopy procedures, the length of a typical procedure
often results in a relatively high absorbed dose to the
patient. Recent advances include the digitization of the
images captured and flat-panel detector systems which reduce
the radiation dose to the patient still further.
The fluorscopic unit in the SMH Radiology
Dept. was used largely for the examination of the
gastrointestinal tract. In this 1926 image, a patient
is stationed on the unit. Seated before her is Stafford
L. Warren, radiologist. Minnie S. Hollingsworth passes the
patient a cup containing a contrast medium. At the right
of the image stands Walter W. Fray, M.D., asst. radiologist.
--source
"The Fluroscope" 1926 etching by John Sloan (1871-1951)
showing the artist holding a glass of barium which traces
a path through the digestive system.Due to the limited light
produced from the fluorescent screens, early radiologists
were required to sit in a darkened room, in which the procedure
was to be performed, accustomizing their eyes to the dark
and thereby increasing their sensitivity to the light. The
placement of the radiologist behind the screen resulted
in significant radiation doses to the radiologist. Red adaptation
goggles were developed by Wilhelm Trendleenburg in 1916
to address the problem of dark adaptation of the eyes, previously
studied by Antoine Beclere. The resulting red light from
the goggles' filtration correctly sensitized the physician's
eyes prior to the procedure while still allowing him to
receive enough light to function normally.
Learn
more about fluroscopy here.
Gastroenterology or gastrology
is the medical specialty developed in the 20th century concerned
with digestive diseases. Traditionally, these are separated
by anatomic or functional category. For example, disorders
of the esophagus might be listed under "esophagus"
and also included in a description of motility disorders
(disorders of motor function.) Diseases of the liver fall
under the branch of hepatology, which is traditionally classified
under the umbrella of gastroenterology. Learn
more about gastroenterology here.
Endoscopic
equipment can be used to visualize and collect specimens
from:
The gastrointestinal tract (GI tract):
--esophagus, stomach and duodenum (esophagogastroduodenoscopy)
--small intestine, conventional enteroscopy can visualize
the proximal small bowel; double balloon enteroscopy or
the capsule camera can view the entire bowel
--colon (colonoscopy), the endoscope is used to examine
the colon.
--sigmoid colon: (proctosigmoidoscopy)
--Bile duct
Learn more about endoscopy here.
Watch
actual videos of gastrointestinal endoscopy exams at
The DAVE Project, an acronym for the Digital Atlas of Video
Education, is a collection of teaching tools. The project
consists of a gastrointestinal endoscopy video atlas and
medical lectures and presentations. The full spectrum of
endoscopic imaging supported by pathologic, radiologic,
and surgical images is available.
21st Century
The above photo is a digital composite and
coloration by Marty Chobot, Magnetic Resonance Imaging by
GE Medical Systems and St Luke's -Roosevelt Hospital Center.
It was published in National
Geographic Magazine's
report "The Heavy Cost of Fat" August 2004.
Magnetic resonance imaging (MRI),
formerly referred to as magnetic resonance tomography (MRT)
or nuclear magnetic resonance (NMR), is a method used to
visualize the inside of living organisms as well as to detect
the composition of geological structures. It is primarily
used to demonstrate pathological or other physiological
alterations of living tissues and is a commonly used form
of medical imaging. Learn
more about MRI and medical imaging here.
The above image was used to get an inside
look at how fat affects the body's organs. For the article,
two women were asked to spend five hours under a state-of-the-art
open scanner to get a high-resolution magnetic resonance
imaging scan (MRI). The above image was of a morbidly obese
5'6" woman aged 40 weighing 250 lbs with a Body Mass
Index of 40.3.
The MRI clearly reveals the woman's digestive
system. With regard to liver disease---many obese people
develop deposits of fat inside the liver, a condition that
can progress to cirrhosis in about 10% of cases leading
to liver failure. Obese people are at greater risk of colon
cancer. Abdominal fat appars to increase risk more than
fat elsewhere, which may explain why men (who tend to store
fat in their abdomens) have a higher risk.
Learn more about the History of
the Stomach and Intestines here.
Image credits (from left): Digestive
System path; Vesalius
anatomy lesson;
woman with her alimentary canal ; The
Food Museum collection;
The Quest to Digest
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