A History of the Stomach and Intestines
During medieval times, anatomists had accurate gross physiological knowledge of the physical structure of the stomach, colon, and the intestines. They recognized the importance of digestion as a source of nutrients, suggesting that if the stomach's function was impaired all other functions of the body could be harmed. Indeed, the understanding of the stomach evolved from the view that it was an active, almost thinking agent to the thought that the stomach, colon, and intestines were very important, yet base and natural organs in the body.
Some of the earliest writings we have about the stomach, intestines, and colon come from Galen. Galen saw the stomach as an animate being: it could feel its own emptiness and generate the sensation of hunger, break up food, and carefully separate useful nutrients from the chaff. 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. In contrast, 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, occasionally bringing in his views about the nature of the stomach and intestines in the process. Other writers built on these ideas by later offering complexion theories of the stomach as a cold and dry organ that was a principal one in the body. They began to see the stomach in more passive terms, suggesting that it was the most unspiritual organ, possibly due to its aesthetically unappealing products. However, anatomists still recognized the importance of the stomach to normal functioning, suggesting that the body, as a whole, needed to have both spiritual and natural members.
Leonardo da Vinci gives the most interesting reading on the gastrointestinal tract organs, as he believed the digestive system aided the respiratory system in its function. Similar to the Chain of Being (a popular diagram during the Early Renaissance depicting the order of living things, with humans at the top), a clear cascade of events leading to breathing is shown by da Vinci. According to da Vinci, the stomach muscles contract, which cause elevation of the intestines, leading to a thrusting upward of the diaphragm (from the condensed air in the intestines). This drives the air from the lungs, or in effect allows one to breathe. Interestingly enough, the opening of the lungs is caused by the relaxation of the stomach muscles, which makes the bowels descend, drawing down the diaphragm and then opening the lungs. This is the first and only time that we see this idea in the sources we have examined. Because da Vinci lived during the early Renaissance, one can perhaps explain his reasoning. During this period, writers like Chaucer and John Donne became famous for their accurate portrayal of the times. Rebellion against the Church's strict teachings and authoritarian attitude came in many forms. Ideas, therefore, were not untouchable. Perhaps, da Vinci attempted to formulate auxiliary notions on the human body, and used the digestive system as a guinea pig.
Yet, overall it seems as if anatomists through time have understood the general purposes of the stomach, intestines, and colons very well. Recognizing them as organs of much import allowed interesting speculations and analogies to be drawn by anatomists.
Questions to consider: Why was the stomach thought of as an active, almost thinking agent, and later as more passive?
A Collection of Quotations from Original Sources and Images of the Stomach, Colon, and Intestines:
Galen, 200 A.D.
"This storehouse [the stomach], a work of the divine, not human, art, receives all the nutriment and subjects the food to its first elaboration, without which it would be useless and of no benefit whatever to the animal. 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."
"[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. And this is wisely done; for since parts throughout the body attract nutriments from the veins arising from the vena cave, which in turn attracts it from the veins in the liver, these again from the veins bringing it up to the porta, which have themselves attracted it from the stomach and intestines, and since there is no other part that can furnish nutriments to the stomach, it becomes necessary for the animal to fill its stomach from an outer source."
"The thick intestine has been formed to prevent elimination from being a continuous process. In many of the voracious animals, however, in which the intestine is straight, it may be observed that there is no difference in width at its lower end. But these animals 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 Middle Ages
"A small amount of movement or activity after a meal allows the food to descend to the fundus of the stomach, especially if after this there is a desire to sleep. Mental excitement or emotion; vigorous exercise; these hinder digestion"
"One should remember too that aliment is best which has the most agreeable flavor, for the walls of the stomach and the retentive faculty jointly apply themselves better to a food of good substance, and the efficiency of the retentive power is assisted when the principal members all mutually concur - the temperament of one being not more divergent from that of another than natural."
Master Nicolaus, ca. 1150-1200
"The stomach is cold and dry in complexion, because frigidity and dryness are concentrating qualities and reduce parts to solidity. The stomach is hard and solid and dense in constitution, so that it may retain food and drink while the first digestion is performed. It is long and rounded in shape, because if it were markedly cavernous it would tend to retain undigested food. It is villous inside, in order that what is taken into it may not be discharged at once, but will be held and digested, and what is necessary will be retained. It is hollow in order that it may better contain food and drink. It is formed of two layers, so that if one breaks from overextension, the other will still hold."
"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."
"In the human body there are six intestines. The first is called duodenum, the second jejunum, the third orbus or monoculus or saccus (all these words have the same meaning), the fourth ileum, the fifth colon, the sixth longaon."
"The colon is called "colander" because the feces are strained there; it is the seat of colic passion."
Berengario Da Carpi, 1460-1530
"The intestines are wound and rewound so that they may retain the food a long time for the sake of a good purpose. There are six of them."
"The colon is arched or divided into chambers and abounds in phlegm. Dry, gourd like masses [cucurbitini] and worms [ascaris] are generated in the colon. The feces acquire an unequal shape in it. A rumbling is heard in it before the hour of evacuation.'"
"To this ileum is joined the second of the slender intestines. It is called the jejunum, hire, hilla, sterile, or empty. It is empty because it is near the liver, which empties the jejunum by drawing the chyle from it."
"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."
"The stomach is a single member. Its complexion in any parts of its components is cold and dry. Its services are to show appetite, to retain and digest the food, and to give the gross part to the intestines and the benign and digested part to the other members by means of the liver."
"The principal parts of the body are the head, chest, and stomach."-- Alessandro Benedetti, 1497
" 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
"The stomach on the inside is denticulated or corrugated [rugae] with thick skin in the manner of a blackberry for the purpose of breaking up food, with the scallops or wrinkles decreasing toward the orifices of the stomach. While the stomach is digesting it is conscious of itself since in hunger and thirst it continuously attracts moisture and is the first to be refreshed."-- Alessandro Benedetti, 1497
"Furthermore, the stomach appears to distribute and bestow the food to all the other members; hence all of them, noble and ignoble, seem to depend upon it for their sole source of sustenance. If its function is impaired, all other functions of the body are placed in the greatest danger."-- Andreas de Laguna, 1535
"Hence from the intestines which are like large ships that carry a milky substance very many meseraic veins, like small boats or skiffs, bear away the purer juice and send it to the liver, similar to those tall ships which as soon as they have crossed the ocean come to Rouen with their cargoes on their way to Paris but transfer their cargoes at Rouen into small boats for the last stage of the journey up the Seine. Indeed the intestines are rightly called ships since they carry the chyle and all the excrement through the entire region of the stomach as if through the Ocean Sea."-- Andreas de Laguna, 1535
Leonardo da Vinci, 1452-1519 (illustration from Da Vinci's text)
"We are told that distance is 13 braccia (small intestine), that is, approximately 26 feet."
"The diaphragm, a thick membrane which is interposed between the intestine and the lung, comes to be stretched by the expansion of the ribs and because of its stretching, it decreases the (abdominal) space in which the said intestines are confined. By the decrease and increase of the (abdominal) said space, the intestines themselves are expanded and then contracted when they are compressed; and this effect continues as long as life."
"The compressed intestines with the condensed air which is generated in them, thrust the diaphragm upwards; the diaphragm compresses the lungs and expresses the air."
"The elevation (of the diaphragm) arises from the air compressed and contained in the intestines-- air which arises from the desiccation of the faeces which give off vapors."
"The transverse muscles (side abdominal) squeeze the intestines, but not the longitudinal (rectus abdominus), because if it were so, man when he stands bent and relaxes these muscles, would not have the power to perform the office of squeezing (the intestines)."
"The transverse (abdominal) muscles are those which on contraction, constrict and elevate the intestines, and push the diaphragm upwards and drive the air from the lung; afterwards, on relaxation of these muscles, the bowels descend, draw down the diaphragm and the lungs open."
William Harvey, 1653
"Intestines arise from the stomach and end in the anus. "
"The ileon arises where the intestine begins to redden and ends in the colon under the right kidney; it occupies the whole lower region under the umbilicus and colon. It is 21 feet in length according to Niccolo Massa."
"In man the intestine is 6 times the length of the body."
"All the intestines but one differ in substance, site, shape, quantity, duty, name."
''The use of the intestines is to retain concocted ailment when it is extracted from the mesenterics and to complete coction in the excrement remaining."
"The duty of the large intestine is more to detain excrement, of the small chyle, lest we be compelled to void continually."
"Intestines are, therefore, made up of tunics, and these from fibers, flesh, parenchyma, veins, arterie, mesenterics, mucous crust, and fat."
"Hot inflammation of the intestines produces veins filled and distended."
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