Lecture for 1st year medical students on 22nd December 2000-12-19 by Professor Omar Hasan Kasule, Sr.



The Qur'an mentioned the nose but did not refer to its olfactory function (p 278 5:45, 68:16). The sense of smell is mediated through chemoreceptors that are in the epithelium of the nasal cavity. Material in gaseous form dissolves in the nasal fluid and results in exciting some nerve endings. The sense of smell in humans has not been studied very well. The size of the human olfactory lobe is larger than what would be expected from human olfactory potential.



Smell in humans is poorly understood. There is an olfactory threshold below which no smell is possible. The threshold varies with each odoriferous substance. Normal olfactory sensitivity is variable and is unpredictable. There is no causal relation between chemical structure and odor. Adaptation or desensitization occurs when the odor stays for a long time. The senses of smell and taste work together. The flavors of many substances are a combination of taste and smell. Taste has less impact on behavior than smell.



The Qur'anic term for odour is raihat. The Qur'an reports the prophet Yaqub smelling the odour of the shirt belonging to his son Yusuf (p. 462 12:94). Odors may be pleasant or unpleasant. Musk, misk, has been mentioned as a pleasant odour in the Qur'an (83:26) and hadith (Muslim #5578, 5599, 5600, 5601). The Prophet enjoyed the smell of perfumes (KS 479: Nisai K28 B2; Nisai K36 B1; Tayalisi H2042 & H2681). The odour of raw garlic, thum, is unpleasant and the Prophet forbade those who had eaten it from the mosque (KS 119: Tayalisi H53 & H2171; Ahmad V.1 p15 & p3 p85 & V. 5 p413 & p420; MB# 485 p 260, #486 p 261, MUSLIM #1141, 1142, 1143, 1144, 1145, 1146, 11467, 1148, 1149, 1150, 1157). The oral odour of the fasting person is unpleasant to humans but is most pleasant to Allah (KS p. 325: Bukhari K30 B2 & B9; Bukhari K77 B78; Muslim K13 H158 & H162-164; Tirmidhi K6 B54; Tayalisi H2367 & H2413 & H2485). The Prophet used perfumes. Perfume was recommended for pubic places (MB# 493 p. 263). The use of perfumes and incense serves a social purpose. They facilitate social intercourse by making the environs have a pleasant smell creating a feeling of pleasure and satisfaction. In addition they suppress obnoxious odors that may exist in a place of public congregation.



The smell of food raises appetite. It also stimulates salivary and gastric secretions in preparation for digestion of food. The sense of small as a means of self-protection is limited in humans because they generally cannot smell out enemies. Humans have learned to associate some smells with dangerous substances that have to be avoided. For example the smell of rotten food warns humans not to eat it. Odours can be used deliberately for pleasure like perfume and incense.



Smell and gender are related in animals. Females secrete chemicals called pheromones that attract males. No human counter-part to pheromone has been described. Human females have a better sense of smell than males. This smell is more acute during ovulation. Human and animal smells are different. Humans are micro-osmic with small olfactory lobes. Animals are macro-osmic with relatively large olfactory lobes. Humans can distinguish among 2000-4000 different odors; however they have poor ability to distinguish intensity of smells. Dogs have better developed smell. If human smell were more acute social life would become more difficult due to obnoxious odors in the environment that would over-stimulate the cerebral cortex.




The Qur'an concentrates on the tongue, lisaan, as an organ of talking and not tasting. The term taste, dhawq, has been used to refer to Adam tasting the forbidden tree (7:22) or the tasting of punishment by those condemned to hell (38:57). The Qur'an has used this term extensively to refer to metaphorical tasting, dhawq ma'anawi (p.459 3:185, 5:95, 6:65, 17:75, 21:35, 29:57, 44:56). Tasting has been used metaphorically to refer to punishment in the hereafter, dhawq al 'adhaab (p 459 3:106, 3:181, 4:56, 6:30, 6:148, 7:39, 8:14, 8:35, 8:50, 9:35, 10:52, 10:70, 16:94, 16:112, 22:9, 22:22, 22:25, 25:19, 29:55, 30:41, 32:14, 32:20, 32:21, 34:12, 34:42, 35:37, 37:31, 37:38, 38:8, 39:24, 39:26, 41:16, 41:27, 41:50, 44:47-49, 46:34, 51:13-14, 54:37, 54:39, 54:48, 59:15, 64:5, 65:9, 78:30). Taste has also been metaphorically to refer to tasting bounties, dhawq al naim (p? 10:21, 11:9-10, 30:33, 30:36, 30:46).



The taste buds are the sensory end organs for taste. They are distributed on the human tongue. Each part of the tongue seems specialized for particular tastes. Taste sensations are transmitted to the cortex where they are interpreted. 



The sense of taste in humans is poorly understood. Taste chemoreceptors are in the taste buds. Taste discrimination in humans is poor. Some tastes are better appreciated at some parts of the tongue and not others. The same substance may produce different taste at different places on the tongue. Specific hunger for sweet or salty things is possible. The basic taste modalities are: sour, salt, bitter, and sweet. More complex tastes are combinations of these primary taste modalities.



Ordinary table salt is perhaps the commonest substance tasted by humans. It is an essential part of the diet (KS 348: Ibn Majah K29 B32).



The sense of taste like that of smell helps in provoking appetite and preparation for digestion. Dangerous substances can be tasted out and can be avoided. There is wisdom in the poor sense of taste in babies. Their low food discrimination enables them to eat a wide variety of baby food that has little or no taste.




Classification: Hunger can be defined physiologically, psychologically, and morally. In practice a hunger experience may be a combination of all the three or of some of them. Hunger can also be described according to the type of nutrient that is missed.


Physiological hunger: Physiological hunger occurs when the level of glucose and other essential substances are low triggering a response by the hunger center. The sensation of hunger occurs a long time before the level of nutrients reaches danger levels. Thus hunger is a warning mechanism that Allah gave humans and other animals to start looking for food before all nutrients are exhausted. Hunger is associated with stomach and abdominal discomfort or pain in order to fulfill its function of warning of impending starvation. During the period of poverty in Madina the prophet and some of his companions used to put stones on their stomachs to stop the pain due to pangs of hunger. Abu Hurairah was a frequent victim of hunger (MB # 1887).


Psychological hunger: The psychological feeling of hunger has no direct relationship with the actual state of nutrients in the body. People used to taking meals at a certain time of the day may start feeling hungry when that time approaches.


Moral hunger: When a human is so consumed with pursuit of material pleasures and food, they will always feel in need of food irrespective of their physiological state. There is loss of control over appetite that results in over nutrition and the attendant diseases of obesity.


General hunger & Specific hunger: a person may feel hungry overall or they may have hunger for a specific food item. Hunger may be quantitative due to absolute inadequate dietary intake or may be qualitative due to missing essential nutrients.



Hunger can be caused by absolute or relative lack of food. It can also be due to pathophysiological causes that impair ingestion or utilization of food. In many cases there are underlying social factors involving social injustice that are responsible for hunger in the world.



Hunger is a test for humans (p. 310 2:155). Hunger can be a punishment from Allah (p. 310 16:11). There will be no hunger in jannat (p. 310 20:118). The food of the dwellers of hell does not cure or satisfy hunger (p. 310 88:7). Feeding the hungry is a noble act (p. 310  90:14). It is Allah who feeds the hungry (p. 310 106:4).



The sensation of hunger is essentially a warning to the person to replenish food stocks. It does not indicate immediate danger or pathology.



The appetite for food is a very strong human instinct. Human appetite is closely related to security from hunger and food security. Humans eat pre-emptively so that they ma not get hungry or starve later.  They however sometimes overdo this and overeat causing health problems. The Prophet recommended eating little food (MB # 1893 p 915). A person should not eat to fill the stomach or get complete satisfaction (MB # 1889 p 915). Satiety and hunger centers are in the hypothalamus.




The various definitions of hunger mentioned above also apply to thirst. Thirst can be physiological, psychological, or pathological.



The Qur'an uses the term dhama'u to refer to thirst (p. 765 9:120, 20:119, 24:39).  It teaches that water is essential for life.



The Qur'an described the drink of the dwellers of jannat as good (p 619-620 2:60, 2:249, 2:259, 7:160, 16:10, 16:69, 23:33, 35:12, 36:73, 38:42, 56:68). The drink of the dwellers of hell is bad (p. 260 6:70, 10:4, 14:16-17, 18:29, 56:54-55, 78:24-25).



Humans need water (p. 1054 24:39, 2:48-?). Thirst is a warning to start looking for water. It does not indicate immediate danger.



Water is essential for life. It is a great sin to deny water to a thirsty person who asks for it (KS 529 Bukhari K42 B5, Abu Daud K22 B60, Nisai K44 B6, Ibn Majah K12 B30, Ibn Majah K16 B6, Darimi K18 B69, Ahmad V1 p253, V3 p. 480 & 481). Pure fresh water is the best human drink. All other drinks consumed by humans have water as the main constituent. Three terms have been used by the Qur’an for drinking water: mau 'adhab (p. 1055 25:53, 35:12, 56:68-70, 77:27), mau ghadaq (p.1055 72:16), and  mau ma'in (p 1055 23:50, 67:30). Water is described as of a good enjoyable taste, laddhat al sharaab (p1039-1040 37:46, 47:1). The Qur'an described sources of water and fluids for drinking as rainwater (p 619 16:10), honey (p 619 16:69), river water (p 619 2:249),  and groundwater (p 61938:42). Humans also get water from the food that they eat. The prophet recommended using a lot of water in cooking food (KS 348 Ibn Majah K29 B58, Darimi K8 B26). 




The viscera send many types of messages to the central nervous system. Humans are not aware of most of these. There is so much mechanical and metabolic activity in the viscera that the cortical information processing would be overwhelmed if they were all in the realm of the conscious. It is as if Allah wanted the human to concentrate on sensory input from the external and not the internal environment.



Kinaesthetic sensation is from muscles and is part of the unconscious sensory input. The human has many muscles that are active most of the time. If the kinaesthetic sensory input were conscious, cortical processing would be overwhelmed.



Propioception is conscious awareness of the body position in space. Both the cerebellum and the cortex are involved in propioception. This sense provides immediate feedback in the process of muscular movement so that corrections and adjustments can be made.




Revelation was in most cases an extra-sensory perception. Jibril brought the sunnat to the prophet in the same way that he brought Qur'an (KS 286 Darimi Intro B48). The prophet used to receive revelation in many different ways (KS 488 Bukhari K1 B2; Bukhari K25 B17; Bukhari K26 B10; Bukhari K59 B6; Bukhari K65 S24 B6; Bukhari K65 S48 B1; Bukhari K66 B2; Bukhari K97 B43; Muslim K15 H6 & H8; Muslim K29 H13; Muslim K43 H86-88; Abu Daud K15 B19; Tirmidhi K44 S23 H1; Tirmidhi K46 B7; Nisai K11 B37; Muwatta K15 H7; Ahmad V1 p34; Ahmad V2 p176 & 222; Ahmad V3 p71; Ahmad V5 p184, 190, 317, 318, 320, 327; Ahmad V6 p34, 56, 58, 103, 158, 163, 197, 202, 256, 455, 458; Tayalisi H2180, 2628, 2667). Sometimes the only indication that revelation was being inspired was changes in his face (KS 488 Ahmad V1 p218). The prophet (PBUH) was able to see the Al Aqsa Mosque while seated at the Kaaba in Makka (KS 494 K65 S17 B3; Ahmad V1 p309; Ahmad V3 p377). The Prophet's eyes slept but not his heart (KS 489 Bukhari K4 B5; Bukhari K10 B161; Bukhari K19 B16; Bukhari K61 B24; Abu Daud K5 B26; Darimi Introduction B1; Muwatta K7 H9; Ahmad V1 p220, 278; Ahmad V2 p251, 438; Ahmad V6 p36, 73, 105).




Allah inspired every soul to know the right from evil, alhamahah furujaha wa taqwaha


Salat al istikharat:  After salat al istikharat Allah in His way will inspire the person to make the right decision


Basiirat al mu'umin: The believer has extra insight in solving problems based on Allah’s guidance


Feeling of impending death: In our daily experience, many people in their terminal illness can feel that the end is near.




INSTINCT, jabillah



Omar Ibn al Khattab is reported to have used telepathy to communicate with a field commander during a military engagement


TRUE DREAMS, ru'uyat saadiqat

The start of the revelation, bidayat al wahy, were true dreams, ru'uyat saadiqat (KS 488: Bukhari K65 S95 B1-B3; Bukhari K91 B1; Tirmidhi K46 B6; Ahmad V6 p153)

Ibrahim (PBUH) had a true dream about slaughtering his son and did not hesitate in carrying it out because dreams of prophets are always true.


Yusuf (PBUH) had a true dream about sitting on a throne that eventually became true when he gained political power in Egypt.




The jinn could assume or borrow a human corporeal form but only the prophet could see or deal with them. A delegation of jinn came to see the prophet (KS 159: Bukhari K63 B32; Abu Daud K1 B20; Tirmidhi K44 S46 H3; Ahmad V1 p458). The prophet is reported to have arrested one of the jinn (KS 159 Bukhari K8 B75; Bukhari K60 B40; Muslim K5 H39; Tirmidhi K42 B3; Darimi K23 B14; Ahmad V2 p1, p298). Ordinary humans cannot see jinn or interact with them physically because they were created from energy and not matter, khalq al jaan min maarij min naar (KS 159: Muslim K53 H60; Ahmad V6 p15 & 168). They are however around us we just cannot interact with them (KS 106 Darimi K20 B25; Ahmad V1 p385, 397). The jinn can overhear people's conversations (KS 159 Bukhari 65 S15 B1; Bukhari K65 S34 B1; Bukhari K97 B32; Muslim K39 H124; Tirmidhi K44 S72 H2; Ahmad V1 p218, 274, 323). Recitation of the Qur'an has an impact on the jinn (KS 159 Bukhari K10 B105; Bukhari K63 B32; Bukhari K65 S72; Muslim K4 H149-153; Tirmidhi K44 S55 & S72 H1; Muslim K42 B14; Ahmad V1 p167, 252, 416, 436; Ahmad V5 p312; Tayalisi H281). Some of the jinn are Muslim (KS 159 Bukhari K65 S17 B7 & B8; Muslim K54 H28-30). Other jinn are non-Muslim.



Foretelling and foretellers are condemned (KS 451: Bukhari  K34 B113; Bukhari K37 B20; Bukhari K68 B51; Bukhari K96 B46; Muslim K22 H39; Abu Daud K22 B63; Tirmidhi K9 B37; Tirmidhi K26 B33; Nisai K42 B15; Nisai K44 B90; Ibn Majah K12 B9; Darimi K18 B34; Muwatta K31 H68; Ahmad V4 p118,119,120). Consulting foretellers is prohibited (KS 451: Muslim K39 H121&125; Abu Daud K27 B21; Ahmad V2 p408, 429,486; Ahmad V3 p443; Ahmad V5 p447,448,449; Tayalisi H382,1104,1105). Shaitan overhears people's conversation and informs the foreteller (KS 451: Bukhari K59 B6&11; Bukhari K65 S34 B1; Bukhari K97 B57; Muslim K39 H122,123,124; Ibn Majah Introduction B31; Ahmad V7 p87). The foretellers then predict events correctly thus gaining credibility that they use later to misguide people.



Sorcery comes in various forms (KS 275: Abu Daud K27 B23). Sorcery is one of the enormities, major sin, kabair (KS 275 Bukhari K55 B23; Bukhari K76 B47; Bukhari K86 B44; Abu Daud K17 B43; Ahmad V3 p83; Ahmad V4 p399). Sorcery is polytheism, shirk (KS 275: Abu Daud K27 p17&24; Nisai K37 B19; Ahmad V1 p 389 & 438 & 440; Ahmad V2 p 220). Sorcery is prohibited, haram (KS 274-275: Bukhari K76 B17&19, Bukhari K76 B42-45, B54; Bukhari K81 B21 & B50; Muslim K1 H371&372&374&375; Muslim K39 H103, 107, 116, 121; Abu Daud K27 B9&24; Ahmad V1 p271, 321, 401,403,454; Ahmad V4 p436, 441, 443; Ahmad V5 p60,447,448,449).

Professor Omar Hasan Kasule, Sr. December 2000