The Canon of Medicine

Avicenna begins part one by dividing theoretical medicine and medical practice. He describes what he says are the "four causes" of illness, based on Aristotelian philosophy: The material cause, the efficient cause, the formal cause, and the final cause:[13]^: 29–31

1. Material Cause: Avicenna says that this cause is the human subject itself, the "members or the breath" or "the humours" indirectly.
2. Efficient Cause: The efficient cause is broken up into two categories: The first is "Extrinsic", or the sources external to the human body such as air or the region we live in. The second efficient cause is the "Intrinsic", or the internal sources such as our sleep and "its opposite-the waking state", the "different periods of life", habits, and race.
3. Formal Cause: The formal cause is what Avicenna called "the constitutions; the compositions". According to Oskar Cameron Gruner, who provides a treatise within Avicenna's Canon of Medicine, this was in agreement with Galen who believed that the formal cause of illness is based upon the individual's temperament.
4. Final Cause: The final cause is given as "the actions or functions".

Avicenna's thesis on the elements of the cosmos is described by Gruner as "the foundation of the whole Canon".[13]^: 39 Avicenna insists here that a physician must assume the four elements that are described by natural philosophy,[13]^: 34 although Avicenna makes it clear that he distinguishes between the "simple" element, not mixed with anything else, and what we actually experience as water or air, such as the sea or the atmosphere. The elements we experience are mixed with small amounts of other elements and are therefore not the pure elemental substances.[13]^: 202 The "light" elements are fire and air, while the "heavy" are earth and water:

1. The Earth: Avicenna upholds Aristotelian philosophy by describing Earth as an element that is geocentric. The Earth is at rest, and other things tend towards it because of its intrinsic weight. It is cold and dry.[13]^: 35
2. The Water: Water is described as being exterior to the sphere of the Earth and interior to the sphere of the Air, because of its relative density. It is cold and moist. "Being moist, shapes can be readily fashioned (with it), and as easily lost (and resolved)."[13]^: 35
3. The Air: The position of Air above Water and beneath Fire is "due to its relative lightness". It is "hot and moist", and its effect is to "rarefy" and make things "softer".[13]^: 36
4. The (sphere of the) Fire: Fire is higher than the other elements, "for it reaches to the world of the heavens". It is hot and dry; it traverses the substance of the air, and subdues the coldness of the two heavy elements; "by this power it brings the elementary properties into harmony."[13]^: 37

The Canon of Medicine divides the thesis on temperaments into three subsections; a general overview, one based on members of the body, and temperaments based on age.

The temperaments are reported to be the interaction between the four different element's qualities, such as the conflict between dryness, wetness, cold, and hot. Avicenna suggests that these qualities battle between each other until an equilibrium state is reached and this state is known as the temperaments.[13]^: 57–65

The Canon also adopted the ancient theory of Four Temperaments and extended it to encompass "emotional aspects, mental capacity, moral attitudes, self-awareness, movements and dreams". This expanded theory of four temperaments is given in the following table:[15]

The Eight Varieties of Equipoise

Canon describes humans as having eight different "varieties of equipoise", or differing temperaments.[13]^: 59 The temperaments fall under two categories; In relation to beings other than men and in relation to the individual himself.

A. In relation to beings other than men

i. "the equability of the temperament seen in man as compared with other creatures"
ii. the temperament of other human beings

Avicenna describes a hot versus cold / moist versus dry equilibrium between the members of the human body. The heart, for example, is hot and must be in equilibrium of other cold parts of the body such as the brain. When this equilibrium between these members are achieved, the person is considered to be in "ideal equability".[13]^: 59–60

iii. external factors "such as race, climate, atmosphere"

This third gauge for temperament assumes that each race has their own equilibrium. As an example he says, "The Hindus, in health, have a different equability to the Slaves, and so on." Avicenna explains that the differing climates contribute to differing temperaments among the races.[13]^: 60

iv. in relation to extreme climates

B. In relation to the individual himself

v. "as compared to another person"

Although Avicenna had listed the fifth mode "as compared to another person", he seems to contradict that statement by explaining that every individual has a temperament that is unique to themselves and unlike anyone else.[13]^: 59–61

vi. comparison of the individual himself
vii. comparing one member of the body with another member of the body

The Canon here makes the distinction of the members into categories of their individual "moistness", "dryness", "hotness", and "coldness".

viii. comparison of a member to itself

The Canon continues to explain the sun's position in relation to ideal temperament and the role that climate and human skin play. Organs are nowhere near ideal in temperament, but skin comes the closest. Avicenna says that the hand, especially the palm and the tip of the index finger, is the most sensitive of all and attuned to tactile contact. Medicine is described as "hot" or "cold", not based upon its actual temperature but with regard to how it relates to the temperament of the human body.[13]^: 62–63

The Canon then describes when temperaments are unequal, in other words, illness. Avicenna separates these into two categories, which are fairly self explainable within the context of what he had already defined as the temperaments.

A. Simple "intemperaments"[13]^: 63

1. Hot temperament (hotter than normal)
2. Cold temperament (colder than normal)
3. Dry temperament (drier than usual)
4. Moist temperament (more moist than usual)

B. Compound "intemperaments"

The compound intemperaments are where two things are wrong with the temperament, i.e. hotter and moister; hotter and drier; colder and moister; colder and drier. There are only four because something cannot be simultaneously hotter and colder or drier and moister. The four simple temperaments and four compound intemperaments can each be divided into "Those apart from any material substance" and "Those in which some material substance is concerned", for a total of sixteen intemperaments. Examples of the sixteen intemperaments are provided in the "third and fourth volumes."[13]^: 64

Each member of the body is described to be given each its individual temperament, each with its own degree of heat and moisture. Avicenna lists members of the body in "order of degree of Heat", from hottest to coldest.[13]^: 66

1. The breath and "the heart in which it arises";
2. The blood; which is said to be generated from the liver;
3. The liver, which may be looked upon as concentrated blood;
4. The flesh, which would be as hot as the liver were it not for the nervous tissue which pervades it;
5. The muscles, which are cooler than the flesh because of their tendons and ligaments, as well as the nerves;
6. The spleen, which is colder because of the faex of the blood;
7. The kidneys;
8. The wall of the arteries;
9. The veins;
10. The skin of the palms and soles.

Then a list is given of coldest members to hottest.[13]^: 66

1. The serious humour;
2. The hairs;
3. The bones;
4. The cartilage;
5. The ligaments;
6. The tendon;
7. The membranes;
8. The nerves;
9. The spinal cord;
10. The brain;
11. The fat;
12. The oil of the body;
13. The skin.

Then a list is given in order of moisture. Avicenna credits Galen with this particular list.[13]^: 67

1. The serious humour
2. The blood
3. The oil
4. the fat
5. the brain
6. the spinal cord
7. the breasts and the testicles
8. the lung
9. the liver
10. the spleen
11. the kidneys
12. the muscles
13. the skin

Finally, a list is given in order of dryness<[13]^: 67–68

1. the hair
2. the bone
3. cartilage
4. ligaments
5. tendons
6. sereous membranes
7. arteries
8. veins
9. motor nerves
10. heart
11. sensory nerves
12. skin

The Canon divides life into four "periods" and then subdivides the first period into five separate categories.

The following table is provided for the four periods of life:[13]^: 68

Avicenna says that the third period shows signs of decline in vigor and some decline in intellectual power. In the fourth period, both vigor and intelligence decline.

Avicenna divides the beginning stage of life in the following table, according to Oskar Cameron Gruner's edition of the Canon of Medicine:[13]^: 69

Avicenna generalizes youth as having a "hot" temperament, but comments that there is controversy over which periods of youth are hotter. The general notion that youth are "hot" in temperament is due to youth's supposed relationship to members of the body that are hot. For example, blood was considered "hot" as was mentioned earlier, therefore youth is assumed to be hot partially due to blood being more "plentiful" and "thicker", according to Avicenna. Evidence for youth having an excess of blood is suggested by Avicenna's observation that nose bleeds are more frequent within youth. Other contributing factors are the youth's association with sperm and the consistency of their bile. Further description of youth in regards to heat and moisture is given with respect to sex, geographical location, and occupation. The Canon says, for example, that females are colder and more moist.[13]^: 69–74

The Canon of Medicine is based upon the Four Humours of Hippocratic medicine, but refined in various ways. In disease pathogenesis, for example, Avicenna "added his own view of different types of spirits (or vital life essences) and souls, whose disturbances might lead to bodily diseases because of a close association between them and such master organs as the brain and heart".[16] An element of such belief is apparent in the chapter of al-Lawa, which relates "the manifestations to an interruption of vital life essence to the brain." He combined his own view with that of the Four Humours to establish a new doctrine to explain the mechanisms of various diseases in another work he wrote, Treatise on Pulse:

"From mixture of the four [humors] in different weights, Allah Almighty [God the most high] created different organs; one with more blood like muscle, one with more black bile like bone, one with more phlegm like brain, and one with more yellow bile like lung.

Allah Almighty [God the most high] created the souls from the softness of humors; each soul has its own weight and amalgamation. The generation and nourishment of proper soul takes place in the heart; it resides in the heart and arteries, and is transmitted from the heart to the organs through the arteries. At first, it [proper soul] enters the master organs such as the brain, liver or reproductive organs; from there it goes to other organs while the nature of the soul is being modified in each [of them]. As long as [the soul] is in the heart, it is quite warm, with the nature of fire, and the softness of bile is dominant. Then, that part which goes to the brain to keep it vital and functioning, becomes colder and wetter, and in its composition the serous softness and phlegm vapor dominate. That part, which enters the liver to keep its vitality and functions, becomes softer, warmer and sensibly wet, and in its composition the softness of air and vapor of blood dominate.

In general, there are four types of proper spirit: One is brutal spirit residing in the heart and it is the origin of all spirits. Another – as physicians refer to it – is sensual spirit residing in the brain. The third – as physicians refer to it – is natural spirit residing in the liver. The fourth is generative – i.e. procreative – spirits residing in the gonads. These four spirits go-between the soul of absolute purity and the body of absolute impurity".

The Canon defines a humour as "that fluid, moist 'body' into which our aliment is transformed",[13]^: 77[17] and lists the four primary types of fluids as sanguineous, serous, bilious, and atrabilious. The secondary fluids are separated into "non-excrementitious" and "excrementitious".

Avicenna calls this humour "the most excellent of all"[13]^: 78 the humours. This section describes blood and compares its healthy states with its unhealthy states. Avicenna describes healthy blood as "red in colour, has no unpleasant odour, and has a very sweet taste." Abnormality of the blood stems from a change in temperament or an unhealthy humour has polluted it.[13]^: 78–79

The serous humour is described as a sweet fluid that is cold and moist in relation to blood and bilious humours. Serous humour resembles blood and is necessary for body tissues for two reasons: to provide the tissue with nutrients as an auxiliary and to keep the bones and tissues moist.[13]^: 809

The bilious humour is red and clear in colour, light and pungent, and its normal form is the foam of blood. It can pursue two routes, either into the blood or the gallbladder. When it passes into the blood, its function is to attenuate the blood in such a way, that it enables the blood to transverse the very minutest channels of the body. The part which flows to the gallbladder is needed, since it cleanses the entire body of superfluity and nourishes the gallbladder.

In his thesis on "The Members", Avicenna explains that the humours help to make up the members of the body, gives a general description and how to repair them.
Some are "simple members" or "elementary tissue" such as bone, cartilage and tendons. Some are "compound members" such as the heart, the liver, and the brain. He also categorizes these into vital organs and auxiliary organs.[13]^: 93–106
Avicenna continues to classify the organs by different systems. "According to actions" organizes members by what they do. "According to their origin" classifies members by assuming that each member originates from the blood or from male or "female sperm".[13]^: 99

In the thesis on General Physiology or "The Faculties of the Body", Avicenna separates life into three different categories: Vital, Natural, and Animal.[18] He contrasts Galen's view that the brain is the "chief seat of sentient life" with Aristotle's view that the heart is the source of all the body's faculties, saying that if physicians considered the matter carefully they would agree with Aristotle that the heart was the ultimate source of all the faculties, even if (for example) the brain is where the rational faculty manifests itself.[13]^: 110–11

Strokes are described in extensive detail in Book 3 of the Canon of Medicine. First, two causes of stroke are identified: blockage of vessels in the brain, and blockage of the affective spirit of the brain, a cause that can only be explained using theories on humoral medicine.[28] The blockage of vessels is then further subdivided into two sub-types: collapse and ischemia.[28][11]

Following this description of the causes of stroke, Avicenna discusses how the blocking agents are derived from the blood or phlegm humors, and how these are most abundant in people with wet and cold natures.[28] Book 3 of the Canon of Medicine also lists several manifestations of stroke: asphyxia, hemiplegia, "headache with jugular vein engorgement, dizziness, vertigo, darkened vision, tremor, anxiety, weakness, grinding teeth during sleep, and dark urine with particles", and it distinguishes between the different causes and types of stroke: cold stroke, coma, subarachnoid hemorrhage, and trauma.[28] Finally, Book 3 discusses several treatments for stroke including the use of herbal medicines and "non-pharmacological interventions such as venesection and dry or wet cupping on the lower neck and upper back".[28] While the accounts of the causes and treatments of stroke are based upon theories of humoral medicine, these descriptions are still similar to the modern understanding of strokes.[28]

Book 3 also contains an extensive chapter about neuroscience, which "begins by explaining the structure and function of the nervous system, …parts of the brain, the spinal cord, the ventricles, meninges, nerves and roots, … [and] neurological and neuropsychological disorders, including signs and symptoms and treatment strategies".[29]

Furthermore, several specific neurological conditions are described, including: epilepsy, apoplexy and stroke, paralysis, vertigo, spasm, wry mouth, tremor, meningitis, amnesia and dementia, head injuries and traumas, hysteria and conversion disorder, fainting and stupor, nervous tic, sexual disorders, love sickness, delusion and hallucination, insomnia, sopor, nightmare, mania and psychosis, melancholia, paranoia, asthenia, hydrocephalus, and sciatica.[29] Book 3 of the Canon of Medicine also describes fifteen kinds of headaches, as well as descriptions of treatments for each of these conditions that are divided into three steps:[29]

1. Change of lifestyle

2. Simple medicines

3. Compound medicines

Surgical intervention and other non-pharmacological strategies were also recommended in some cases, such as electrical shocks to treat epilepsy.[29]