– beyond words

From earliest childhood, we are accompanied by scents and smells. We store the experience of them in such a way that we can recognise them with certainty, even decades later. Many smells remind us of specific experiences – like the fragrances of spring, the scent of cedar trees or violets, the freshness of a forest after a summer downpour, the lightly salty tang of sea air, the unmistakeable aroma of freshly unearthed potatoes, or a roast turkey at Christmas time. Unpleasant odours also leave lasting impressions, for example hot tar on a road surface, a damp musty cellar, rotten eggs, or even the putrid smell of a decaying cadaver. Long forgotten scents, even after lying hidden under the accumulated experiences of many passing years, can suddenly burst into our recollection. The nose is an indispensable organ, with which we perceive many, many details of our surroundings.

Smelling and tasting are chemical senses. Without our olfactory sense we would only be able to taste sweet, salty, bitter, and sour. It is the nose that makes eating and drinking pleasurable.

Through our nose we can detect danger, and also enjoy the fragrances of flowers, spices and perfumes.

Structure and function of the nose: The fan shaped fibres of the olfactory nerve occupy an appreciable volume of the complex human nasal structure. Odour molecules collide with specific receptor molecules, fitting together like a lock and key. There are between 10 and 25 million receptor cells in the olfactory region which covers an area of about 2.5 cm2 on each side. These receptors are part of the nervous system and are known as olfactory neurons. Like the taste cells, they are supported by basal cells and are continually renewed, their half-life being about ten days. The olfactory cells measure only about 5 to 15 μm (1 μm = one thousandth of a millimetre).

Molecules which cause odours are captured by the receptors in the mucous membrane of the nose. The olfactory information is then converted into electrical impulses which are transmitted to the so-called olfactory bulb which distributes them in the brain.

We can distinguish far more than 10,000 different scents. This wide range can be extended even further with practice; professional perfume testers, and coffee and wine tasters excel in this ability. Only substances that are sufficiently volatile to emit minute particles into the air can be smelled. This multitude of odours exceeds the capacity of our vocabulary to describe them all.

The nose is also essential for respiration. Since the lungs prefer damp, warm, clear air, air is moistened and warmed by its long passage over the mucous membranes of the nose. Most of the coarser, harmful particles in air are trapped by the nose’s fine hairs or its thick secretions (mucus).

The olfactory mucous membrane is located fairly deep inside the nose. It contains millions of receptor cells embedded in elongated supporting cells. These sensory nerve cells are stimulated by odours and also transmit the olfactory messages directly to the brain. They are “direct intermediaries” between the outside world and the brain.

From each of their ends, a tuft of fine hair like projections called cilia (Latin cilium = eyelash) extends into the olfactory mucous membrane, in which the molecules that cause odours are dissolved, having found their way through the nasal cavity. These olfactory nerve cells are continuously renewed from basal neuronal (stem) cells.

This is somewhat exceptional, since many nerve cells of humans and other organisms are not replaced when they die.

It has recently been discovered that the number of detectable odours is directly proportional to the number of genes. In the case of human beings (and mammals generally) there are about 1,000 genes which code for the same number of different olfactory receptors, each of which occurs in thousands of the millions of sensory cells. If a mammal has 30,000 genes, then this means around three percent of them code for proteins which can bind with odour-causing molecules. This is the largest group of related genes discovered so far. It is therefore difficult to measure various odours objectively, since every person, apart from identical twins, has his/her own genetically determined olfactory preferences.

This contrasts sharply with the small number of optical receptor pigments in the eye. Only three types of pigments are required to distinguish between thousands of shades of colour, because the principle of recognition is fundamentally different: All three types can receive a wide range of partially overlapping wave lengths of light, each being most sensitive in a different part of the optical spectrum. The brain finally combines and compares the optical stimuli. Olfactory signals cannot be handled in a similar way, because a large number of qualitatively widely different chemical components would have to be compared.

The process used by the brain to decode olfactory information is one of the central and most difficult unsolved problems in neuro-physiology.

The indescribable sense: The sense of smell truly is the sense beyond words. It can be extraordinarily exact, but it is practically impossible to describe a scent to somebody who hasn’t experienced it personally. We move about 12 cubic metres (12 m3) of air per day by breathing in and out 12,000 times. Inhalation requires about 2 seconds, and exhalation 5 seconds. During this time odour molecules also move with the airflow.

We can describe something we have seen in the finest detail, using plenty of images so that the listener can get a clear picture of our experience.

But in the case of odours, we can only express general feelings like pleasant, horrible, wonderful, or exciting. Just try to describe in words the fragrance of your marriage partner, of a shoe shop, a bakery, or an old library! Our memory for odours is astounding – nothing can stir up old memories better than a certain scent.

The scientifically incomprehensible sense: Most smells are a mixture of a large number of odour-causing substances. Wine, for example, contains about 200 and coffee about 500 different ones. It has up to now not been possible to reduce the multiplicity of scents to mixtures of a few primary odours. The phenomenon of smell is still poorly understood scientifically.

Our olfactory sense is extremely sensitive and exceeds the capabilities of most technological measuring instruments. The threshold of detection for ethyl mercaptan is about 10-13 g (one ten million millionth of a gram = 109 molecules). It is not clear why many molecules which are chemically quite different have the same olfactory effect. On the other hand, very similar chemical compounds can smell completely different.

D-carvone smells like cumin, while L-carvone has a mint-like smell. But both have exactly the same chemical formula, except that the former is right-handed and the latter has a left-handed structure. Like your two hands, these are identical, but mirror images of each other (stereoisomers).

Everybody has his/her own very specific personal scent, which is just as unique as a fingerprint.

A baby recognises its mother by smell, and adults can distinguish between male and female. Dogs readily identify individuals by their odour and can even recognise their owner in the case of identical twins. A border collie has about 220 million olfactory cells. As far as humans are concerned, the following traces of odour-causing substance per liter of air are detectable:

0.000 000004 g 0.000 000 0012 g 0.000 000 000 041 g 0.000 000 004 g 0.000 000 000 016 g 0.000 000 000 005 g 0.000 000 000 0004 g

acetone phenol  naphthalene  camphor  nitrobenzol  vanillin  skatol

Perfumes can be beneficial for health (French parfum = pleasant scent): Perfumes began their triumphal progress as incense in Mesopotamia.

The word “perfume” is derived from the Latin per = by or through, and fumus = odour. The first country known to have used perfumes regularly and extravagantly was Egypt. Their pompous burial and embalming rites required spices and ointments. In the time of Queen Hatsheput (1490 – 1468 BC) perfume became a common passion. Cleopatra (69 – 30 BC) was also a fervent lover of perfume. The cedarwood boat on which she received Anthony had perfumed sails.

Incense containers surrounded her throne, and she herself was perfumed from head to toe. The buildings of the kings of antiquity were filled with scents. They preferred cedar wood for constructing their palaces, because of its sweet resinous smell, as well as its ability to repel insects.

The Bible and perfumes: Aromatic substances also play a significant role in the Bible. A mixture of flowers, aromatic seeds and fruit, and olive oil, is described as “precious ointment” in Psalm 133:2, and in Esther 2:12 we read of “six months with oil of myrrh, and six months with sweet odors, and with other things for the purification of the women”.

Aromatic plants and spices are mentioned many times in the Bible: aloe, balm, galbanum, henna, nard, sweet sedge, cinnamon, and myrrh. Aloes (Numbers 24:6, Psalm 45:8, Song of Songs 4:14) were used for preparing Jesus’ body for burial (John 19:39). In Solomon’s Song of Songs very many scents, fragrances, perfumes, and ointments are mentioned. A certain American lady author described this portion of the Old Testament as the most perfumed poem of all times and as a sensual love story saturated with perfumes and ointments. Love is described in terms of fragrant scents: “How fair is thy love... how much better is thy love than wine! and the smell of thine ointments than all spices! ... the smell of thy garments is like the smell of Lebanon” (Song of Songs 4:10-11). Nard is an aromatic and very costly plant listed among fragrant flowers and spices in Song of Songs 4:13-14. The perfume used to anoint Jesus in Bethany, contained nard (Mark 14:3, John 12:3).

According to John 12:5 this perfume was so expensive that its price was equivalent to a year’s wages (300 silver denarii). The gifts brought to Jesus by the wise men from the east, comprised incense, myrrh and gold (Matthew 2:11).

The phrase “And the LORD smelled a sweet savor” is used frequently in the Old Testament (e. g. Gen 8:21, Ex 29:18,25,41, Lev 1:9,13,7). This means that God is pleased with those deeds. When Noah built an altar and sacrificed burnt offerings, “And the LORD smelled a sweet savor ...” (Gen 8:21). God Himself can smell. He gave us this sense to enrich our lives and to be like Him also in this respect.

Perfumes are also employed in another biblical parable (2 Cor 2:14-16). The triumphal entry of Roman generals was accompanied by prisoners who carried jars of incense so that everybody could smell these perfumes expressing the victory.

In the same way everybody who lives in Christ should spread the fragrance of victory.

Paul wrote to the Corinthians: “For we are unto God a sweet savour of Christ, in them that are saved, and in them that perish: To the one we are the savour of death unto death; and to the other the savour of life unto life” (2 Cor 2:15-16).

This gospel message blows over its hearers like an aromatic cloud, but its effect can vary greatly.

Some of them accept the words which then become a blessing – it is for them a fragrance of life which engenders everlasting life. For the indifferent and for those who reject the message proclaimed, it becomes a deadly odour like a poisonous fog bearing the putrid smell of decaying bodies, a harbinger of death, of eternal perdition.

Only a hair’s breadth separates salvation and doom.

Quote: Richard Axel, professor of biochemistry and molecular biophysics at the University of Columbia, New York: “Till now science has only been groping in the dark in trying to discover the rules governing the way our olfactory sense can unlock the immeasurable structure of our memories.”