Next we will travel into the early years of the Medieval Age.
Alchemists had built upon the fragments of Greek writings they got via
translations from the Arabic. Their system of medicine revolved around a belief
that there were humours in the body, four vital fluids that controlled
everything and had to be kept in balance for good health. Inserted here is a
bit of background on this from an associate of de Azcarraga, S. E. Brinamon:

‘The concept of the four humours is an ancient Greek theory
about the makeup of the human body, first proposed by Galen, a Greek physician
and philosopher in the second century CE. Galen compared the structure of the
human body to the structure of the universe, and claimed that within this
system, four different humours, or fluids, flowed through the body. The levels
of these fluids was influenced by a person's diet or activity level. According
to Galen, an imbalance of the proper levels of the four humours was the cause
of disease.

The four humours correspond to four temperaments: Sanguine,
Choleric, Melancholic, and Phlegmatic. Sanguine is happy: it is the humour of
content, cheerfulness, optimism, and is associated with blood. Choleric is
angry: it is the humour of the hot-tempered and irate, and is associated with
yellow bile. Melancholic is sad: the humour of depression, sadness, low
spirits, and is associated with black bile. And Phlegmatic is sluggishness: the
humour of slothfulness, impassivity and apathy, associated with phlegm, or
mucus.

According to the theory of the four humours, a person's
emotion was determined by the levels of these fluids in the body. For example,
anger was caused by a rush of Yellow Bile to the heart, while slothfulness was
caused by an excess of Phlegm.

Galen's theories were so well established that they were
commonly held until the 17th century, when the four humours made an appearance
in literature. Especially in Elizabethan drama, the four humours and their
corresponding temperaments were used as templates for characters. By
classifying a character as Sanguine or Melancholic, the writer already had a
series of personality traits set up for him.”

Looking a little closer into how
the early medieval alchemists viewed these humours, we can again draw parallels
that easily equate to the four Houses of the Founders. I think you’ll find much
below that is familiar.

Sanguine – Hufflepuff

As the blood was thought to originate from the heart and bring
warmth to the body, so too were the possessors of the Sanguine Gift said to bring
diversity to the community of Wizards from the heart of the Realm of Magic. The
Sanguine Gift was considered the most primeval, and potentially the most
powerful. These Wizards and Witches revered nature and this humour was said to
encourage a generous temperament. The possessors of the Sanguine Gift were
often to be found using their powers for the benefit of others. Some of these
Wizards came from the fringes of the Wizarding World, and were most likely to
fall outside of mainstream approaches to magic.

Phlegmatic – Ravenclaw

Phlegm, in physick (medecine), was considered to be an
aerial humour that was generated in the brain, the organ said to be responsible
for cooling the blood. These Gifted individuals had the benefit of cool-headed
reasoning. They were the scholarly and the innovative, and often among the most
obsessive to boot. Many sought to study broadly, while others dedicated
themselves to the understanding of a very narrow discipline. Phlegmatic Wizards
and Witches were the rational power that kept the Wizarding world thriving.
Phlegm was said to encourage a calm temperament, but also lend itself towards
self-absorption and dullness.

Choleric – Gryffindor

Yellow Bile was believed to be generated by the Liver, and
this fiery humour to be the source of the active emotions. This Gift bestowed a
sense of action and these Wizards and Witches were often the movers and shakers
of the Wizarding World. This Gift was rooted in the deep and fiery passions of
its possessors, and was often linked with force of will. The mastery of the
will was of course an important step in the harnessing of the inherent magical
powers of the Choleric Gift. All of the willpower of these Gifted individuals was
channeled into mastering their magic, thus their emotions understandably got
the better of them, for good or ill.

 Melancholic – Slytherin

Black Bile was thought to derive from the action of the
spleen, and to be the source of the more passive emotions. Those who had this
type of Gift were concerned not with immediate action, but with more long term
goals. They were cool, but passionate about their plans. Some were prone to
developing a sense of power-hunger, while others fell into the trap of becoming
overwhelmed by emotions. Melancholy was said to induce a gloomy and sentimental
temperament in humans, and these Wizards and Witches were often the most
brooding and dangerous to cross. They did not flair up in anger like a
Sanguine, but instead planned revenge.