during the golden age of the theory of the four humors in greek medicine after galen. one of those texts was an anonymous treatise called on the constitution of the universe and of man, published in the mid-19th century by j.l. ideler. in this text, the author establishes the relationship between elements of the universe (air, water, earth, fire) and elements of the man (blood, yellow bile, black bile, phlegm). he said that: the people who have red blood are friendly. they joke and laugh about their bodies, and they are rose tinted, slightly red, and have pretty skin. the people who have yellow bile are bitter, short tempered, and daring. they appear greenish and have yellow skin. the people who are composed of black bile are lazy, fearful, and sickly. they have black hair and black eyes. those who have phlegm are low spirited, forgetful, and have white hair. 17th century english playwright ben jonson wrote humor plays, where character types were based on their humoral complexion. blood it was thought that the nutritional value of the blood was the source of energy for the body and the soul. blood was believed to consist of small proportional amounts of the other three humors. this meant that taking a blood sample would allow for determination of the balance of the four humors in the body. it was associated with a sanguine nature (enthusiastic, active, and social).: 103–05 the seasonal association of blood is the spring because the natural characteristics found in individuals was associated with being hot and wet. yellow bile yellow bile was associated with a choleric nature (ambitious, decisive, aggressive, and short-tempered). it was thought to be fluid found within the gallbladder, or in excretions such as vomit and feces. the associated qualities for yellow bile are hot and dry with the natural association of summer and fire. it was believed that an excess of this humor in an individual would result in emotional irregularities such as increased anger or behaving irrationally. black bile black bile was associated with a melancholy nature, the word "melancholy" itself deriving from the greek for "black bile", μέλαινα χολή (melaina kholé). depression was attributed to excess or unnatural black bile secreted by the spleen. cancer was also attributed to an excess of black bile concentrated in a specific area. the seasonal association of black bile was to autumn as the cold and dry characteristics of the season reflect the nature of man. phlegm phlegm was associated with a phlegmatic nature, thought to be associated with reserved behavior. the phlegm of humorism is far from phlegm as it is defined today. phlegm was used as a general term to describe white or colorless secretions such as pus, mucus, saliva, sweat, or semen. phlegm was also associated with the brain, possibly due to the color and consistency of brain tissue. the french physiologist and nobel laureate charles richet, when describing humorism's "phlegm or pituitary secretion" in 1910, asked rhetorically, "this strange liquid, which is the cause of tumours, of chlorosis, of rheumatism, and cacochymia – where is it? who will ever see it? who has ever ever seen it? what can we say of this fanciful classification of humors into four groups, of which two are absolutely imaginary?" the seasonal association of phlegm is winter due to the natural properties of being cold and wet. humor production humors were believed to be produced via digestion as the final products of hepatic digestion. digestion is a continuous process taking place in every animal, and it can be divided into four sequential stages. the gastric digestion stage, the hepatic digestion stage, the vascular digestion stage, and the tissue digestion stage. each stage digests food until it becomes suitable for use by the body. in gastric digestion, food is made into chylous, which is suitable for the liver to absorb and carry on digestion. chylous is changed into chymous in the hepatic digestion stage. chymous is composed of the four humors: blood, phlegm, yellow bile, and black bile. these four humors then circulate in the blood vessels. in the last stage of digestion, tissue digestion, food becomes similar to the organ tissue for which it is destined. if anything goes wrong leading up to the production of humors, there will be an imbalance leading to disease. proper organ functioning is necessary in the production of good humor. the stomach and liver also have to function normally for proper digestion. if there are any abnormalities in gastric digestion, the liver, blood vessels, and tissues cannot be provided with the raw chylous, which can cause abnormal humor and blood composition. a healthy functioning liver is not capable of converting abnormal chylous into normal chylous and normal humors. humors are the end product of gastric digestion, but they are not the end product of the digestion cycle, so an abnormal humor produced by hepatic digestion will affect other digestive organs. relation to jaundice according to hippocratic humoral theory, jaundice is present in the hippocratic corpus. some of the first descriptions of jaundice come from the hippocratic physicians (icterus). the ailment appears multiple times in the hippocratic corpus, where its genesis, description, prognosis, and therapy are given. the five kinds of jaundice mentioned in the hippocratic corpus all share a yellow or greenish skin color. a modern doctor will undoubtedly start to think of the symptoms listed in contemporary atlases of medicine after reading the clinical symptoms of each variety of jaundice listed in the hippocratic corpus. despite the fact that the hippocratic physicians' therapeutic approaches have little to do with contemporary medical practice, nonetheless, their capacity for observation as they described the various forms of jaundice is remarkable. in the hippocratic corpus, the hippocratic physicians make multiple references to jaundice. at that time, jaundice was viewed as an illness unto itself rather than a symptom brought on by a disease. unification with empedocles's model empedocles's theory suggested that there are four elements: earth, fire, water, and air, with the earth producing the natural systems. since this theory was influential for centuries, later scholars paired qualities associated with each humor as described by hippocrates/galen with seasons and "basic elements" as described by empedocles. the following table shows the four humors with their corresponding elements, seasons, sites of formation, and resulting temperaments: humor season age element organ temperaments blood spring infancy air liver warm and moist sanguine yellow bile summer youth fire gallbladder warm and dry choleric black bile autumn adulthood earth spleen cold and dry melancholic phlegm winter old age water brain/lungs cold and moist phlegmatic influence and legacy islamic medicine