arteries veins motor nerves heart sensory nerves skin iii the temperaments belonging to age 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:: 68 periodtitlenameyear of age ithe period of growthadolescenceup to 30 iithe prime of lifeperiod of beautyup to 35 or 40 iiielderly lifeperiod of decline. senescence.up to about 60 ivdecrepit agesenilityto the end of life 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:: 69 sub-divisionnamedistinctive characters firstinfancythe period before the limbs are fitted for walking secondbabyhoodthe period of formation of the teeth. walking has been learnt, but is not steady. the gums are not full of teeth. thirdchildhoodthe body shows strength of movement. the teeth are fully out. pollutions have not yet appeared fourthjuvenility. "puberty"the period up to the development of hair on the face and pubes. pollutions begin. fifthyouththe period up to the limit of growth of the body (to the beginning of adult life). period of athletic power. 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.: 69–74 the humours 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". 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 in different weights, 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. 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 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 . as long as 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". definition of body fluid the canon defines a humour as "that fluid, moist 'body' into which our aliment is transformed",: 77 and lists the four primary types of fluids as sanguineous, serous, bilious, and atrabilious. the secondary fluids are separated into "non-excrementitious" and "excrementitious". the sanguineous humour avicenna calls this humour "the most excellent of all": 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.: 78–79 the serous humour 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.: 809 the bilious humour 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. anatomy or "the members" 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.: 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".: 99 general physiology in the thesis on general physiology or "the faculties of the body", avicenna separates life into three different categories: vital, natural, and animal. 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.: 110–11 book 2 materia medica book 2 (the materia medica) of the canon alphabetically lists about 800 "simple" medical substances that were used at the time. the substances are simple in the sense of not being compounded with other substances. the first part gives general rules about drugs and a treatise on what was called "the science of powers of medicines". the second part is a list of 800 simple floral, mineral, and animal substances. each entry contains the substance's name, its criteria of goodness (which sometimes describes how the substance is found in nature), and its nature or primary qualities. next are listed one or more of 22 possible general actions, followed by specific properties listed according to a grid of 11 disease types. finally, potential substitutes for the substances are given.: 223 the canon contains seven rules for experimenting with new drugs, taken partly from galen. "the drug must be free from any acquired quality"; for example from being exposed to heat or cold or stored in close proximity to other substances. "the experiment must done on a single, not a composite condition"; in other words it should not be tested on a patient who has complex or multiple illnesses. "the drug must be tested on two contrary conditions"; a drug may act directly on a disease but also it may be effective against a different disease by relieving its symptoms. "the quality of the drug must correspond to the strength of the disease...it is best to experiment first using the weakest and then increase it gradually until you know the potency of the drug, leaving no room for doubt." "one should consider the time needed for the drug to take effect. if the drug has an immediate effect, this shows that it has acted against the disease itself." "the effect of the drug should be the same in all cases or, at least, in most. if that is not the case, the effect is then accidental, because things that occur naturally are always or mostly consistent." "experiments should be carried out on the human body the quality of the medicine might mean that it would affect the human body differently from the animal body..." book 3 special pathology book 3 is arranged by body part, progressing from the top of the body to the bottom of the body and covering the function and diseases of each organ, as well as the etiology, symptoms, diagnosis, prognosis, and treatment for each disease discussed. the third book is also divided into several sections, including: 1. head, eye, ear, nose, mouth, throat, teeth 2. chest, lung, heart 3. alimentary tract: stomach, intestines; liver, gall-bladder, and spleen 4. urinary system 5. conception, pregnancy, the uterus, diseases of women. 6. the muscles, the joints, the feet. 7. special subjects: the intemperaments of the brain; headache; diseases of the brain, epilepsy, paralysis. the information presented in book 3 of the canon of medicine represents some of avicenna's most important contributions to several fields of study, including atherosclerosis, pulsology, migraines, cataracts, vasovagal syncope, and neuroscience. stroke 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. the blockage of vessels is then further subdivided into two sub-types: collapse and ischemia. 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. 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. 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". 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. neuroscience 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, … neurological and neuropsychological disorders, including signs and symptoms and treatment strategies". 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. book 3 of the canon of medicine also describes fifteen kinds of headaches,