In a lecture to the Chelsea Physic Garden, a haven of herbs buried deep in the heart of London, chemist Anthony Dweck talked of Plants, Perfume and People and took his lessons from history. Here are some highlights
Let's look at the historical background to the development of medicinal plants throughout the world, paying particular attention to those materials which are fragrant, either as essential oils or as herb materials. So let us journey back through time to the very beginnings of medicinal history. A check on our chronometer shows us to be in the year 1300BC.

Much of Egyptian culture centred on the use of essential oils. Throughout the Bible one finds numerous references to the custom of anointing various parts of the body. There are also many illustrations in papyri, on artefacts and in tomb wall paintings of these undoubtedly expensive and precious oils being prepared and applied. If we look closely at Tutankhamen's throne, we can see the young Queen Ankhesenamen applying oils to his collar. In a panel from the gold shrine surrounding his sarcophagus, she is caught in the act of applying oils to the young pharaoh.

In many illustrations and carvings you will notice strange cones on people's heads. These were highly perfumed unguents of low melting point; as the wearer became warm, so the cone would slowly melt and the fragranced oils would run over them.

To make the oils, a man would first chop and fragment a fragrant piece of wood, then macerate the chips in wine. After a few days the liquor would be strained off. Fat and more fragrant herbs were added and then the mixture was slowly heated. The fragrant herbs obviously yielded their virtues more easily to the oily fat than to the hydro-alcoholic wine. The mixture was allowed to cool, so that the fat set and could be skimmed off.

Herbs and spices were then ground and mixed with this fat, which was fashioned into cakes and allowed to stand. The final product would today be called a pomade. Did the ancient pharaohs have an understanding of aromatherapy, or were they using the fragrances purely for the pleasure of their odour?

We do know that the ancient Egyptians used the seeds of the opium poppy, Papaver somniferum, in cooking, but that they were unaware of the narcotic properties of its exudate. There is no evidence that they smoked hemp, either: they were not makers of spliffs or drug abusers as far as we can tell.

We move next to India in 800BC. To a land of patchouli, cedarwood, cinnamon and precious spices, of gardenia and hibiscus and oils of exotic roses, but most of all the sensuous jasmine.

The most interesting use of jasmine oil was as an aphrodisiac. There are many reasons why a plant may heighten sexual stamina or libido, but jasmine is special. It does not work by irritating the genital tract, by stimulating blood flow or by acting as a tonic, nor does it act as a prophylactic or placebo.

What it does do, is heighten the alpha wave activity in the brain. When this activity is increased, so are awareness and perception. So its action is not physically to improve sex, but it may improve the mental stimuli that are required to get things going and, more to the point, keep them going.

Now to AD23, and one of the earliest recorders of herbal medicine. We are in Como in northern Italy just in time to witness the birth of Caius Plinius Secundus, or Pliny the Elder, who wrote many books, of which only one survives, a work of a mere 37 volumes. A passage that I particularly like is: "A poultice is more efficacious if laid upon him by a maiden, herself fasting and naked, who at the same time has to repeat certain special words." I have no doubt that any man would feel immensely better under these conditions, but have been unable to ascertain what the words should be.

On to the 12th century and the small German town of Bingen. Here we find a remarkable lady, a mystic, stateswoman, writer of holy songs and phenomenal herbalist: the Abbess Hildegarde von Bingen. Many of her recipes include fragrant herbal materials.

There is an interesting cure for hay fever, which is to inhale the fumes from smoking yew wood, prepared by placing the shavings in a flowerpot, then heating the pot. A flowerpot seems a strange idea, because it has a hole in the bottom, but the air circulates through the bottom and convects upwards, carrying more vapour than a pot without the hole.

(I tried this at home to see what it smelt like. Apart from setting off smoke alarms all over the house, it certainly had a pungent and eye-watering effect, and seemed to relieve nasal congestion.)

Then we move on to a village near Carmarthen in Wales to meet the physicians of Myddvai, renowned herbalists of the 13th century. They offer this recipe, which I would certainly avoid, for application to "proud flesh", which I interpret as another term for overactive fibroblast activity and the formation of excessive scar tissue:

"Take a toad that can scarcely creep, beat it with a rod, till irritated, it smells, and dies [How irritated can you get?]. Then put it in an earthern pot, closing the same so that no smoke can come out or air enter in. Burn it till it is reduced to ashes, and apply the same to the part." Not exactly animal-friendly.

We now venture timidly into the 15th century and make our way to London, where we discover a pot of Gilbert's ointment. Suffering from sore lips, we apply some of the soothing salve and read the recipe on the label: "Take a very fat puppy dog and skin him; then take the juice of cucumber, rue and pellitory; berries of ivy and juniper; fat of vulture, fox and bear in equal parts; stuff the puppy therewith and boil him. Add wax to the grease that floats on the surface and make therefrom an ointment. This product has not been tested on animals. Signed, Gilbertus Anglicus."

In 1493 we come upon Philipp Theophrastus Bombastus von Hohenheim (mercifully better known to us as Paracelsus). He wrote: "The mind need not concern itself with the physical constitution of the plants and roots. It recognises the powers and virtues intuitively thanks to the signatures they carry."

This may be best explained with a few examples.

Heartsease or wild pansy, Viola tricolor, has heart-shaped lower leaves, so according to Paracelsus's doctrine it should be good for the heart. In fact it is a heart tonic, and has been used in cases of heart failure.

Celandine, or Chelidonium majus, has a bright yellow juice, so should be good for biliary conditions and jaundice. Examination of its properties shows it to be an antispasmodic, reducing inflammation of the biliary ducts, and it has been used successfully to treat jaundice. Walnut, or Juglans regia, looks like a brain, so should be good for headaches or mental disturbances. We discover that the walnut is one of the foods rich in manganese, important for nerves, brain and cartilage.

In 1597 John Gerard, an Elizabethan physician, published his great "herbal or the historie of plants". He refers to a plant not only as valerian, but also as setwall; surprisingly he is using the dry root as an antidote for poison, and for the healing of "sleight cuts". He writes: "They that will have their heale, must put Setwall in their keale." (I don't know whether a keale is some type of pottage or stew, or simply a saucepan).

The excitement of plant discovery begins to tarnish as modern drugs start to replace traditional remedies. This is progress. But the pendulum swings. The teaching of plant pharmacy is again on the increase, public awareness is increasing and clinical scepticism is on the wane.