THE NATURAL FACULTY
Feeding the Body
The Natural Faculty feeds and regenerates the physical structure of the body. It is responsible for all digestion and metabolism, nutrition and growth.
The Natural Faculty is most developed in plants or vegetable life, which can make their own food. And so, the functions of the Natural Faculty are sometimes called the vegetative functions.
The principal organ of the Natural Faculty is the liver, which is the master metabolic chemist of the bloodstream. The liver generates the Four Humors from chyle through the combined action of the Metabolic Heat and the Natural Force, which are the basic thermal and kinetic energies of the Natural Faculty.
All the other organs and vessels of the Natural Faculty are ultimately the servants and attendants of the liver. The entire digestive tract exists to digest food and drink into chyle, which is then sent to the liver from the small intestine via the veins of the hepatic portal system. From the liver, the inferior vena cava takes the fresh humors to the heart, to be infused with the vital principles and pumped out all over the body.
And so, a close relationship exists between the liver and the veins. In Greek Medicine, the veins serve the liver and the Natural Faculty, whereas the arteries serve the heart and the Vital Faculty.
The Thermal Aspect of Digestion
The thermal aspect of digestion is primary, for without it there woud be no digestion. In digestion, the organism uses its own Metabolic Heat to cook or concoct the food into chyle, and chyle into the Four Humors.
In the First Digestion, the Digestive Fire in the stomach and small intestine concocts the raw food into chyle. The chyle is then sent to the liver to be concocted into the Four Humors by the Metabolic Heat in the Second Digestion.
The subtler, more refined pepsis that occurs in the Third and Fourth digestions, through which the humors are transformed into living tissue, is actually called metabolism. Actually, metabolism is nothing more than micro-digestion, which is occurring all throughout the organism, all the way down to the cellular level.
The essential action of heat in digestion works something like a refiner's or smelter's fire. The food, or raw ore, is consumed or digested and the humors, or pure metal, is distilled or extracted; then the dross, or waste products, are cast off. This is the basic process for all stages of digestion and metabolism. Something is consumed or digested, something is produced, distilled, or extracted, and some byproduct is cast off as unusable waste.
The secret to proper digestion or pepsis lies in getting the heat level just right, and cooking the chyle and humors to perfection. Either overcooking or undercooking will result in the production of toxic humors that can poison or clog the organism.
The Kinetic Aspect of Digestion
The Vital Force enters the liver and is converted into the Natural Force, which animates all digestive function. The Natural Force and the Metabolic Heat together generate the Four Humors.
Each one of the Four Humors is then infused with a certain Administering Virtue, which is a specialized form of the Natural Force. These Four Administering Virtues give their respective humors their basic functions in the digestive and metabolic process.
The Sanguine humor is infused with the Attractive Virtue, or force, which enables an organ to attract or draw into itself that which it needs to process and nourish itself with. The Attractive Virtue is also responsible for our tastes and appetites, and the ability to assimilate nutrients.
The Choleric humor is infused with the Digestive Virtue, or force, which enables it to consume and digest things. The digestive organs of the middle GI tract and their secretions are strong in the Digestive Virtue. The Digestive virtue enables an organ to digest or process things in the proper manner.
The Melancholic humor is infused with the Retentive Virtue, which has a drying, condensing, solidifying effect on metabolism. The Retentive Virtue also enables an organ to hold on to the substances it has drawn into itself long enough to process them properly.
The Phlegmatic humor is infused with the Expulsive Virtue, which enables it to expel, transport, smooth, lubricate, and wash away impurities. The Expulsive Virtue enables an organ to release its contents when the time is right to do so, and is necessary for all eliminative functions.
So, the general digestive process or cycle is: each organ in turn attracts, digests and retains, and then expels its contents. The harmonious function of digestion depends on the proper balance and distribution of the Four Humors and their respective Administering Virtues, all working togaether in an orderly fashion. The balanced, harmonious function of all four Administering Virtues ultimately depends on the smooth, harmonious flow and functioning of the Natural Force in the liver.
The basic functions of an organ are determined by its dominant humor and its Administering Virtue. For example, the stomach, which initiates the major part of digestion, is governed manly by the Choleric humor and its Digestive Virtue. In the colon, which absorbs fluids and electrolytes and solidifies the stool, the dominant humor is black bile, with its Retentive Virtue. However, all four Administering Virtues, in the right proportion, are necessary for the proper, balanced functioning of each organ.
The Digestive Process
Subtle vapors of black bile from the spleen enter the stomach to awaken the gastric secretions and the appetite, and one feels hungry. The tongue's taste buds also awaken, and the mouth secretes saliva, a Sanguine fluid that begins the digestion of carbohydrates. The tongue signals to the digestive organs what to secrete through its sense of taste.
In the middle digestive tract, or the stomach and duodenum, the Choleric humor and its Digestive Virtue predominates. The stomach receives the food and initiates the major part of digestion with its caustic, Choleric acids and enzymes, which would digest the stomach itself if it weren't for its protective mucous coat, of the opposite yet complementary Phlegmatic humor. Residues of black bile in the stomach enable it to hold on to its contents long enough to process them properly. When the time is ripe, the pyloric valve opens under the action of the Phlegmatic humor and its Expulsive Virtue.
In the duodenum, yellow bile is secreted into it from the liver and gall bladder. Yellow bile facilitates the digestion and absorption of fats, and also eliminates excess fats and cholesterol from the body. Bile also acts as a natural laxative, stimulating intestinal peristalsis.
Then, the pancreas secretes its digestive enzymes and bicarbonates, which neutralize and tone down the caustic, acidic heat of the middle GI tract, giving the food and digestive juices a more balanced, Sanguine nature, which facilitates absorption. The digestion of food into chyle is completed in the small intestine.
After the digestion of chyle is completed, the villi of the small intestine absorb its nutrients via the Attractive Virtue of the blood that runs through them. These nutrients are then sent to the liver for processing into the Four Humors.
In the colon, black bile and its Retentive Virtue predominate as the remaining fluids and electrolytes are reabsorbed and the stool condensed and solidified. The Retentive Virtue of black bile enables the stool to be held until the time is right for defecation. The drying, hardening action of black bile is tempered and counterbalanced by the moistening, lubricating action of the Phlegmatic humor, which makes the stools soft enough to expel through its Expulsive Virtue. The presence of yellow bile, a natural laxative, tips the balance in favor of excretion.
The Four Wastes
Pepsis isn't complete until the final excretion of waste from the body. The elimination of wastes is usually the last step in a long chain of metabolic events in which many byproducts are reused and recycled. Finally, what can no longer be used is eliminated as waste.
There are four major waste products of the body in Greek Medicine, which correspond to the Four Elements. Each is produced via the thermal energies and eliminated via the kinetic energies of its respective eliminative organ.
Exhalation is the waste product of the Air element and the Vital Faculty. It's the exhaust of cellular metabolism and is eliminated via the lungs, through the process of gas exchange.
Sweat is the waste product of the Fire element, and is eliminated through the skin, which is the largest eliminative organ of the body. Sweat is the body's main vehicle for eliminating excess heat; many fevers are broken by releasing a sweat.
Urine is the waste product of the Water element, and is eliminated by the kidneys and urinary tract. Urine is the main liquid waste of the body.
Feces, also called the stool or Alvine Discharge, is the waste product of the Earth element, and is eliminated via the colon. Feces are the main solid waste of the body.
Since elimination is the end result of the metabolic process, the waste products can yield many valuable clues about the condition of one's metabolism. Humorally, the organism will try to eliminate escesses and superfluities, whatever they may be, through the wastes.
Analysis of the urine and stool are important diagnostic procedures in Greek Medicine. The right balance between the retention and evacuation of wastes is important to proper hygiene.
The Digestive Tract, or Alimentary Canal
The digestive tract is a great central tube running through the core of the organism, from mouth to anus. It's the Great Central Channel of the Natural Faculty, and most of the assimilation and elimination of substances by the organism takes place via this channel.
Although it consists of many different organs, the digestive tract is actually one continuous tube. And so, an intricate network of reflex relationships exists between its various component orgns, through which one part affects others, and the whole of the digestive tract.
This Great Central Channel is able to either assimilate or eliminate via both ends, which makes it very useful, both physiologically and therapeutically. Through the top end, or orally, one can ingest all manner of food, drink and medicine; one can eliminate via the top end either by expectoration, gargling or vomiting. From the bottom end, defecation is the usual means of elimination, although evacuations may also be therapeutic or procured, as in purgatives or enemas. Through enemas and suppositories, one may also assimilate via the bottom end.
Many deep organs of digestion and metabolism, such as the liver, gall bladder, spleen and pancreas, pour their various digestive secretions into this Gret Central Channel. Therapeutically, their secretions can also become vehicles for the ripening and elimination of morbid humors and metabolic residues, or toxins.