A trout jumped high in midstream and the sunlight flashed on its body. "You must forget," said Monsieur Biotte, "all the nonsense about musk and ambergris and the testicular secretions of the civet cat. We make our perfumes from chemicals these days. If I want a musky odour I will use ethylene sebacate. Phenylacetic acid will give me civet and benzaldehyde will provide the smell of almonds. No sir, I am no longer interested in mixing up chemicals to make pretty smells."
For some minutes his nose had been running slightly, wetting the black hairs in his nostrils. He noticed it and produced a handkerchief and gave it a blow and a wipe. "What I intend to do," he said, "is to produce a perfume which will have the same electrifying effect upon a man as the scent of a bitch in heat has upon a dog! One whiff and that'!! be it! The man will lose all control. He'll rip off his pants and ravish the lady on the spot!"
"We could have some fun with that," I said.
"We could rule the world!" he cried.
"Yes, but you told me just now that smell has nothing to do with the sexual appetite of the human male."
"It doesn't," he said. "But it used to. I have evidence that in the period of the post-glacial drift, when primitive man was far more closely related to the ape than he is now, he still retained the ape-like characteristic of jumping on any right-smelling female he ran across. And later, in the Palaeolithic and Neolithic periods, he continued to become sexually animated by smell, but to a lesser and lesser degree. By the time the higher civilizations had come along in Egypt and China around 10,000 BC, evolution had played its part and had completely suppressed man's ability to be stimulated sexually by smell. Am I boring you?"
"Not at all. But tell me, does that mean an actual physical change has taken place in man's smelling apparatus?"
"Absolutely not," he said, "otherwise there'd be nothing we could do about it. The little mechanism that enabled our ancestors to smell these subtle odours is still there. I happen to know it is. Listen, you've seen how some people can make their ears move a tiny bit?"
"I can do it myself," I said, doing it.
"You see," he said, "the ear-moving muscle is still there. It's a leftover from the time when man used to be able to cock his ears forward for better hearing, like a dog. He lost that ability over a hundred thousand years ago, but the muscle remains. And the same applies to our smelling apparatus. The mechanism for smelling those secret smells is still there, but we have lost the ability to use it."
"How can you be so certain it's still there?" I asked.
"Do you know how our smelling system works?" he said.
"Not really."
"Then I shall tell you, otherwise I cannot answer your question. Attend closely, please. Air is sucked in through the nostrils and passes the three baffle-shaped turbinate bones in the upper part of the nose. There it gets warmer and filtered. This warm air now travels up and over two clefts that contain the smelling organs. These organs are patches of yellowish tissue, each about an inch square. In this tissue are embedded the nerve-fibres and nerve-endings of the olfactory nerve. Every nerve-ending consists of an olfactory cell bearing a cluster of tiny hairlike filaments. These filaments act as receivers. "Receptors' is a better word. And when the receptors are tickled or stimulated by odorous molecules, they send signals to the brain. If, as you come downstairs in the morning, you sniff into your nostrils the odorous molecules of frying bacon, these will stimulate your receptors, the receptors will flash a signal along the olfactory nerve to the brain, and the brain will interpret it in terms of the character and intensity of the odour. And that is when you cry out, "Ah-ha, bacon for breakfast!"
"I never eat bacon for breakfast," I said.
He ignored this.
"These receptors," he went on, "these tiny hair-like filaments are what concern us. And now you are going to ask me how on earth they can tell the difference between one odorous molecule and another, between say peppermint and camphor?"
"How can they?" I said. I was interested in this.
"Attend more closely than ever now, please," he said. "At the end of each receptor is an indentation, a sort of cup, except that it isn't round. This is the "receptor site'. Imagine now thousands of these little hairlike filaments with tiny cups at their extremities, all waving about like the tendrils of sea anemones and waiting to catch in their cups any odorous molecules that pass by. That, you see, is what actually happens. When you sniff a certain smell, the odorous molecules of the substance which made that smell go rushing around inside your nostrils and get caught by the little cups, the receptor sites. Now the important thing to remember is this. Molecules come in all shapes and sizes. Equally, the little cups or receptor sites are also differently shaped. Thus, the molecules lodge only in the receptor sites which fit them. Pepperminty molecules go only into special pepperminty receptor sites. Camphor molecules, which have a quite different shape, will fit only into the special camphor receptor sites, and so on. It's rather like those toys for small children where they have to fit variously shaped pieces into the right holes."
"Let me see if I understand you," I said. "Are you saying that my brain will know it is a pepperminty smell simply because the molecule has lodged in a pepperminty reception site?"
"Precisely."
"But you are surely not suggesting there are differently shaped receptor sites for every smell in the world?"
"No," he said, "as a matter of fact, man has only seven differently shaped sites."
"Why only seven?"
"Because our sense of smell recognizes only seven "pure primary odours'. All the rest are "complex odours' made up by mixing the primaries."
"Are you sure of that?"
"Positive. Our sense of taste has even less. It recognizes only four primaries-sweet, sour, salt, and bitter! All other tastes are mixtures of these."
"What are the seven pure primary odours?" I asked him.
"Their names are of no importance to us," he said. "Why confuse the issue."
"I'd like to hear them."
"All right," he said. "They are camphoraceous, pungent, musky, ethereal, floral, pepperminty, and putrid. Don't look so sceptical, please. This isn't my discovery. Very learned scientists have worked on it for years. And their conclusions are quite accurate, except in one respect."
"What's that?"
"There is an eighth pure primary odour which they don't know about, and an eighth receptor site to receive the curiously shaped molecules of that odour!"
"Ah-ha-ha!" I said. "I see what you're driving at.,, "Yes," he said, "the eighth pure primary odour is the sexual stimulant that caused primitive man to behave like a dog thousands of years ago. It has a very peculiar molecular structure."
"Then you know what it is?"
"Of course I know what it is."
"And you say we still retain the receptor sites for these peculiar molecules to fit in to?"
"Absolutely."
"This mysterious smell," I said, "does it ever reach our nostrils nowadays?"
"Frequently."
"Do we smell it? I mean, are we aware of it?"
"No.11 "You mean the molecules don't get caught in the receptor sites?"
"They do, my dear fellow, they do. But nothing happens. No signal is sent off to the brain. The telephone line is out of action. It's like that ear muscle. The mechanism is still there, but we've lost the ability to use it properly."
"And what do you propose to do about that?" I asked.
"I shall reactivate it," he said. "We are dealing with nerves here, not muscles. And these nerves are not dead or injured, they're merely dormant. I shall probably increase the intensity of the smell a thousandfold, and add a catalyst."
"Go on," I said.
"That's enough."