Ethylene (ethene) . H2C =CH2. A colourless flammable gas with an unpleasant pungent odour.
‘What we need here in Denver,’ said Dave, ‘is something as strong as ethylene which isn’t smelly or explosive. Then we wouldn’t have any trouble from being a mile up in the sky.’
‘Ethylene?’ I asked. ‘Is that really any good as an anaesthetic?’
‘Oh, yes. It’s splendid stuff. Its MAC is 67%, so it is considerably more powerful than nitrous oxide, but it sure smells revolting. Why now, we haven’t used it for many a year simply because of its smell. There may be a cylinder somewhere around the hospital; Vi will probably be able to find it if there is one, but if you want to see it in action you will have to go to the John Hopkins Clinic in Baltimore where I believe they do still use it occasionally.’
I remembered hearing about the John Hopkins when I had been a student at Guy’s all those years ago. It had always sounded such a prestigious place, yet I had not heard the name mentioned again until now. I tried to remember exactly where Baltimore was. Somewhere near Washington DC, I thought, but I did not like to tell Dave that I was not sure. Still as I would probably never go there it did not really matter.
‘It wasn’t only the smell, Dave,’ the professor chipped in. ‘It is still rather too weak for our altitude and it cannot begin to compare with cyclopropane. What we really need in Denver is a nonflammable cyclo.’
‘Sure, Bob, you are right enough. But the ethylene cylinders were such a wonderful violet colour, weren’t they?’
‘Why, yes, they certainly were, but I quite like the colour of the cyclo cylinders as well. It seems warmer somehow, and altogether more friendly.’
‘But not so exciting!’
The conversation moved to more serious matters: what was the department of anaesthesiology going to do when this quarter’s supply of halothane ran out, which would probably be midway through the next week, with three weeks to go before the new quarter? What would the new skiing seasin be like? When were the transplant surgeons going to start up the liver transplant program again? Had anyone noticed the amazing winds that were battering the outside of the hospital over the last half hour, and how dark it had got outside?
Fifteen minutes later Isabel was on the phone.
‘Tell John ,’ she said to Bob, ‘that we have just been in the middle of a tornado here, and that I’m catching the next plane home. When I said I would come to America I did not mean that I would agree to being in a tornado. You tell him that for me.’
The rest of the day was taken up with a departmental seminar and long before this was finished the winds had subsided completely.
When I got back to the apartment block in Cherry St Isabel told me all about it.
‘It was like the League of Nations here this morning. There were children not just from Denver, Utah and Chicago, but also from Japan, England and Mexico. First of all the television went on the blink. I phoned them up and said would they please come and fix it as we had only had it for a fortnight. The bloke asked what a fortnight was, and then added that we had bought it ‘as is’ so that it had been something of a gamble and that therefore it was our problem not his. I told him not to be so silly, if I had wanted to gamble I would have put the money on a horse. He laughed and said ‘OK, Mam’, and someone came round within ten minutes. Later in the morning it got really dark outside, and windy too. When I saw large shrubs and garden chairs travelling down the road at the level of the first floor windows I knew something pretty unusual was happening! I lined the children up against one of the inside walls because I thought I remembered hearing that’s what you should do in a tornado. Apparently it touched down in Birch St near the Virtue’s house and ripped a huge tree right out of the ground. It was very frightening.’
So it had been a real tornado, eh? And last week there had been an earthquake! It had shaken the whole apartment early on the Sunday morning and woken us up. I had gone storming into the kids’ bedroom and had shouted at them to be quiet, only to find out later that it had been an earthquake which had been 6.0 on the Richter scale and had shaken all the bottles off the shelves in the local liquor store. I wondered what would be the next natural disaster to befall us.
That evening, after a supper of kidney stew with rice and asparagus, I fished out my old Synopsis of Anaesthesia and looked up ethylene in the index. I turned to page 117 and read:
ETHYLENE [C2H4] Rarely used in the United Kingdom today, because its advantages over nitrous oxide are very slight, while its explosibility is great.
Explosibility? Was that really a proper word? I doubted it.
Anaesthetic properties first noticed by Hermann in 1864.
That would be just before Lister used antisepsis during surgical operations, I thought, and wasn’t it the year that Toulouse-Lautrec was born?
Crocker and Knight (1980), the botanists, proved that ethylene contained in illuminating gas would prevent carnation buds from opening.
Illuminating gas? That would be acetylene, wouldn’t it? I knew that in the olden days they used to make acetylene by letting water drop onto lime and that as the gas came off they used it in lamps, so producing ‘limelight’( NB this is quite wrong! ). So there was some ethylene in it too.
This work was taken up by A.B .Luckhardt and J.B. Carter of Chicago in 1923, and by W. Easson Brown of Toronto in 1923, and they introduced it into clinical medicine, along with Isabella Herb, who independently employed it in the Presbyterian Hospital, Chicago, in March 1923.
Isabella Herb, eh? What a splendid name! Of course, Isabel had really been meant to be christened Isabella, after her two grannies, Isabella Judge and Isabella Mackay, but her father had had a wee dram before the service and he had got it wrong when the moment came. At least that was the story.
1) dehydration of ethyl alcohol by sulphuric or phosphoric acid.
2) breaking down of propane by heat.
3) passing ethyl alcohol and superheated steam over a catalyst such as aluminium oxide.
Well. that was a funny collection of different ways of making a simple gas. I tried to imagine how you would set about mixing alcohol and superheated steam; with difficulty, no doubt!
Physical Properties - A colourless nonirritating gas of unpleasant odour ... lighter than air... boiling point 103oC... liquifies at 10oC under pressure of 6 atmospheres ... oil/water solubility ratio 14.4... explosive range 2% to 28% with air; 2% to 80% with oxygen.
Pretty flammable stuff!
Eliminated from the lungs unchanged, the greater part in two minutes... not altered soda lime.
So it was OK to use it in the closed circuit then. Good thing too if the smell was as bad as they say!
Analgesia requires from 20 - 35%. Anaesthesia from 80 - 90%.
Sounds a bit hypoxic after all. As Bob had said, not really the thing for Denver where you needed extra oxygen, not less.
Pharmacology - Ethylene has almost no effect on the body’s metabolism, other than causing a slight rise in blood sugar, and an inhibition of bile acid secretion... induction more rapid than with nitrous oxide: no stimulation of respiration.
Funny having a colon there, probably meant to put a semicolon. The book was somewhat telgrammatic in style but I liked that, even though the language was rather quaint at times.
Maintenance - Ethylene is more powerful than nitrous oxide... muscle relaxation is greater... more oxygen can be used so that cyanosis does not play such a part... breathing is quieter.
You could tell that the book was rather out of date because it was still talking about reduction of oxygen during nitrous oxide anaesthesia. Now it was so easy to supplement ‘gas’ with some halothane it only was very old-fashioned anaesthetists who deliberately reduced the oxygen in the mixture their patients were breathing.
Anaesthesia can be carried to lower plane 1. About 10% oxygen can be given during induction, and when the patient is settled and well premedicated, up to 20% will not lighten the anaesthesia. Recovery is rapid, but postoperative nausea and vomiting are more frequent than after nitrous oxide.
I skipped the next section on Methods of Administration, noting in passing that it could be used with the same apparatus that was used for nitrous oxide.
Advantages of ethylene - the same as nitrous oxide: non-toxicity, rapid induction and recovery, with the additional ones of producing greater muscle relaxation with less risk of hypoxia.
Disadvantages - its explosiveness. It slightly increases capillary oozing when compared to nitrous oxide.
Nothing about the smell! Well that was something they forgot when they wrote that bit; still they had mentioned it earlier.
‘What are you reading?’ Isabel asked.
‘Oh, they were talking about ethylene as an anaesthetic at work today and I was just looking it up in the book. Still I’ll probably never even see a cylinder of ethylene, so what the heck? Is there anything on the telly? I feel like a good laugh. When is Oral Roberts on?’
It was Thursday once again, Thursday the 26th May. I enjoyed every day of the week but Thursdays were special as my copy of New Scientist usually arrived at the newsagent on Thursday, even though the date on the cover was for the Friday. Last week’s magazine had been as interesting as ever. There had been a discussion on whether anaesthetics worked by blocking mitochondria, the small things within cells that control the use of oxygen. It seemed that some research scientists in Indianapolis had shown that halothane and chloroform both reversibly blocked the mitochondrial chain at doses that were clinically useful...
How these anaesthetics work in molecular terms cannot be known until the whole question of mitochondrial respiration is tidied up, but presumably is a key protein whose activity is sensitive to local concentrations of halothane and similar molecules.
It had always been of great interest to me to wonder how exactly anaesthetics made people go to sleep; after all I earned my living by using these 'smelly' volatile liquids on my patients. It was strange not to understand the exact mechanisms involved, but of course it was really much more important to be skilled at the practical aspects than to know about unproved theories. Still you could not help wondering.
I stopped the car outside the shop on my way to work.
‘Hello. Has my New Scientist come yet?’
‘I’m not sure. I’ll have a look for you. Yes, here it is.’
I paid over the 12p and walked back to the car. I was not in a hurry this particular morning, so I planned to have a quick glance through the magazine before I went on to the hospital. I clambered back into the trusty (and rusty) old Ford Anglia. It was rather cramped for someone with legs as long as mine, and it was surely on its last legs itself, but I loved it dearly. It had been such a good and faithful friend to the family. I had driven it more than 120,000 miles and it had hardly ever let us down; a new clutch plate at 76,000 miles and some welding to the floor of the boot where the rear springs were coming through at the time of the last MOT test. Otherwise it had only been tyres, batteries, brakes and that sort of thing so that I really could not complain.
I opened the magazine and glanced at the contents page.
Mount Etna erupts... Engineering a cutprice V12 ... Ethylene as a plant growth regulator...
Hm, that sounded odd. I turned the pages until I came to the article itself, which was by the Deputy Director of the Agricultursal Research Council’s Unit of Developmental Botany at Cambridge.
Ethylene as a plant growth regulator... the discovery that ethylene gas radically affects the the growth of plants came as quite a shock. It now seems that plants actually manufacture the gas as a ‘growth’ regulator. This phenomenon is now at the centre of on of the most fertile areas of botanical research.
I glanced at my watch; plenty of time. I read on:
No one is more surprised by the current interest in ethylene and its effects on plants than the plant scientists themselves. For, as long ago as the mid1800s illuminating gas and smokes were known to cause many remarkable growth responses, and by 1901 D. Neljebow had shown that the active principle was the simple unsaturated substance ethylene.
Simple, but smelly and explosive!
Neljebow’s work was a landmark, for not only did he show that the normal upward growing shoot would, instead, grow horizontal... he found that as little as 0.06 parts per million in the air was required to reduce the rate of growth and cause stems to be short and swollen. Clearly this is a quite remarkable phenomenon.
Although plants vary considerably in their response to ethylene, the typical responses of land plants are inhibition of growth, yellowing and premature shedding of leaves, earlier ripening of fruits and fading of flowers, and the twisting and bending responses of young leaves and stems generally referred to as epinasty.
Epinasty? What a strange word!
Other typical effects include loss of the bending responses to light, the breaking of dormany in buds and seeds, enhancement of flowering, stimulation of adventitious rooting, in some species an increase in female sex expression, and in others a stimulation of latex flow. This formidable list implicates every aspect of plant growth.
Well, fancy that. I remembered, of course, reading in Synopsis of Anaesthesia about the carnation buds that would not open when they had been exposed to illuminating gas, but this list was truly amazing. I flipped quickly through the rest of the magazine:
The sleepy battery business wakes up... Sexual appetite leads beetles to sticky end... Is the Universe nearly dead?... Body fluids electrify heart pacemaker... Concorde will fly through bacteria.
Hm, this promised to be good fun. No wonder I enjoyed Thursdays. I put the journal down and started the engine. The A38 was as busy as ever but I managed to slip into the stream of traffic without too much trouble. Ten minutes later I was at the hospital.
I parked the car outside the Medical School Unit. I resisted the impulse to get the golf clubs out of the boot and bang a couple of balls across the field towards the goalposts in the distance. I climbed the stairs to the anaesthetic department’s laboratory.
‘Hello, Sheila,’ I said as I opened the door. ‘What are you up to?’
‘Oh, hello. I’m looking at these beautiful lymphocytes which I have just stained. Come and see them.’
I peered down the microscope.
‘Yes, they certainly are lovely. Are they from the sample of my blood that you took yesterday?’
‘Yes, they are. But that’s not why they are so beautiful. It’s because I stained them so brilliantly. It was my handiwork that I was admiring. not your cells!’
‘Oh, thanks a lot, Sheila. Look here’s a cell in metaphase. It’s a pity you haven’t fully appreciated the poetry of my chromosomes. They are quite exceptional, you know.’
Joking apart, I really was fascinated to see my own lymphocytes under the microscope, particularly those which were in the process of dividing. I could see some cells where the chromosomes were beginning to separate out into long threads and other cells where the chromosomes were thicker and were lining themselves up along the mitotic spindle. It was quite fantastic. It was strange, too, to think that in 1953 I had often cycled past the Cavendish laboratory in Cambridge just at the time when Crick and Watson were working out the structure of DNA and that I had not known for years that anything exciting had been happening the other side of the wall. It had always looked such a lifeless place from the road.
‘I’m off to see the patients for this afternoon’s list, Sheila.’
Later in the morning my thoughts went back to the article on ethylene. It certainly was interesting. Was it possible that the effects of ethylene on plants were anything to do with anaesthesia, or had it just seemed like it to those botanists long ago? I would have to find out.
It was a couple of days before I was able to get to the main library in the Medical School at the top of St Michael’s Hill. In the meantime I had been able to find out that the original papers on ethylene had appeared in the Journal of the American Medical Association in 1923. They would be in the stack room down the stairs. The stack room, though both dim and dusty , was a splendid place in which to spend an occasional half hour or so. I particularly enjoyed looking through old copies of the medical journals to see how things had changed over the interveing years. Today, of course, I was looking for something specific rather than just browsing.
Here we are, JAMA 1923. I lifted the dusty tome off the shelf. Page 765. Yes, here it is:
The Physiologic Effects of Ethylene. A New Gas Anesthetic. A.B. Luckhardt PhD MD and J.B. Carter BS MS
During the early part of 1908 severe losses were sustained by carnation growers shipping their products into Chicago, because of the fact that these flowers, when placed in the greenhouse, would ‘go to sleep’, whereas the buds already showing petals failed to open. Crocker and Knight of the Hull Botanical Laboratory immediately undertook the study of the effect of illuminating gas on flowering carnations, the results of which showed that ethylene, which forms approximately 4% of the gas, is the chief constituent that determine the toxicity of the gas for plants. Their investigations showed that one part of ethylene in 2,000,000 parts of air caused the already open flowers to close, on 12 hours exposure, whereas one part in 1,000,000 prevented the opening of flowers already showing petals.
As I so often did, I started to skip read once I reached the middle of the first paragraph; I knew that it meant that I would have to start all over again in a few minutes but I have never been able to discipline myself enough to read anything from start to finish the first time through.
... several experiments having been performed with various concentrtions of ethylene with no perceptible toxic but, if anything, mildly anaethetising effects, it was decided to use higher concentrations, the results of which willbe given later... bubbled through diluted dog’s blood... frog + 80% ethylene not anesthetized; but 85% for 30 minutes anesthesia after 20 minutes, recovered in 2 minutes... white mouse... white rat... rabbit... guineapig... kitten... dog.!
Anaesthesia had been judged by strong pinches with a pair of artery forceps. Mostly, they reported, 80% ethylene did not anaesthetise animals whereas 85% did; this meant, of course, that there had been a reduction in the amount of oxygen they had been breathing and this must have had some effect in itself on top of any effect that the ethylene might have had. Still the various creatures apparently had not become anaesthetised by being exposed to 85% nitrous oxide so ethylene did seem to have been stronger than laughing gas. What about man, then? Yes, here it was:
Experiment 1. J.B. CARTER, reclining, Jan 21, 1923, held up the mask to his face with one hand and held up the other arm. He was given the gas plentifully mixed with oxygen until the extended arm wavered. Administration was discontinued. Just enough was given to give a sense of welbeing and exhilaration. At no time was there change in the colour of the face.
How interesting! This really was pioneering stuff. I wondered if they had taken out extra life insurance.
Experiment 2. A.B. Luckhardt reclined and held the mask and arm as had Mr Carter. Mr Carter gave the gas mixture. The arm soon wavered and dropped (in less than one minute). There were no asphyxial sensations. There was a strange sense of contentment and wellbeing. There was no apprehension of possible danger. Everything seemed well. Pains from an infected and active frontal sinus infection left. The subject was satisfied to lie there under the inflence of the gas for all time. He did not think that consciousness was lost at anytime. He came out rather rapidly from a half sleep with slight incoordination of gait lasting a few minutes.
Well, it cured his sinus pain, did it? It reminded me of Humphry Davy’s remarks in 1798 about nitrous oxide curing his toothache.
Experiment 3. The authors having tried out on themselves the immediate effect of the gas, the following subjects volunteered and were more or less deeply anesthetized: (a) A.J. Carlson. (b) J. Blumenstock. (c) Archer C. Sudan, N. Kleitman and K. Phillis were anesthetized far past the stage of analgesia, for in two (N.K. and A.C.S.) the safety pin was pushed through the skin without provoking reflex movement of the arm, much less sensation of pain in the subjects. A.C.S. laughed a great deal before complete anesthetization. On recovery, he talked excitedly and incoherently of his experience. Only after several minutes did his speech assume a logical tendency. He had no recollection of having had the blunt safety pin thrust through the skin of his forearm. N.K., while recovering from the anesthetic but while still dazed, vomited up a large breakfast he had taken several hous before. He likewise had no recllection of having vomited. Nausea was not experienced, and the subject ate a hearty meal within the hour.
It sounded as though the authors of the paper had had some pretty gullible volunteers around, but what fantastic names! The paper went on to describe how Carter and Luckhardt had then let themselves, together with some new volunteers, be anaesthetized several times for ten to fifteen minutes at a time.
In all then, we have anesthetized, more or less deeply, twelve subjects. One of the authors (A.B.L.) was anesthetized six times in three days in six weeks. In neither of us did sugar or albumen appear in the urine as a result of our experiences, nor did we experience any other evil after effects except for a slight nausea and loss of appetite, both of a very temporary nature.
Then there was a summary and a list of possible advantages of ethylene over nitrous oxide. These did not seem very convincing to me. Surely the anaesthesia still relied on partial anoxia? But there was a comment on this at the end:
The phenomena produced by the pure gas are, in fact, partly asphyxial; but this factor can be removed by the addition of oxygen, when it can be seen that narcosis results from the ethylene itself. This is shown on frogs, which preserve their reflexes for hours when placed in pure hydrogen, but lose them promptly (within four minutes) when placed in pure ethylene.
For a while I thought that this was the end of the paper and I smiled to myself at the quaintness of the language and the lack of precision of the science. Then I realized that the comment continued over the page.
Evidently... a direct action on the nervous system... no marked stimulation or depression of the vagus centre... relaxation of the sphincters does not occur during the period of the anesthesia, but defecation and micturition take place immediately on recovery, in the case of the dog... we are inclined to the view that the gas is relatively innocuous... This must be considered a preliminary report of experimental work which has not been carried far enugh to warrant general clinical use.
That was it then. This particular paper had appeared on March 17th. By looking at the index I discovered that in the issue of May 19th there had been a report on a clinical trial in 106 patients. These had been undergoing a variety of operations and there had also been four women who had been given ethylene to breathe during childbirth; apparently with great success and to everybody’s satisfaction, though the report finished with a cautionary note:
We warn surgeons and anesthetists not to use the gas in the presence of an electric spark, the actual cautery or a free flame.
In the same issue, in the correspondence section, there was a letter from Luckhardt and Carter which made me smile when I read it.
NEW ANESTHETICS : ETHYLENE AND ACETYLENE
To the Editor: Your editorial, May 12th, 1923, p.1383, called our attention to some early work on ethylene. Twice in the progress of our own work (spring 1918 and summer 1922) we made, as we thought, a thorough search of the literature for possible references to ethylene, assisted the last time by an expert medical librarian. Unfortunately we failed to find this bibliography. We cannot understand why these early results which, according to the editorial statements, seemed so promising, failed to stimulate the original authors or the later pharmacologists and anesthetists to extend the work during the intervening thirtyeight years as we have done; perhaps their interest was in an investigation of the probable toxic and not the anesthetic properties of ethylene.
So it was true that there was nothing new under the sun! I guessed that even in 1923 Luckhardt and Carter would not have been the first people to fail to find and acknowledge earlier work; they were certainly not the last.
I was very busy with clinical work in the following weeks and I forgot all about ethylene and its strange effect on plants until one day late in June when I opened my copy of the British Journal of Anaesthesia, which had been lying unopened on my desk for nearly three weeks. In it was a fascinating paper  by the people at Northwick Park about the effect of halothane on cells that were in the process dividing into new cells (mitosis). Apparently halothane caused what they called ‘c-mitosis’; this was an effect on cell division that was similar to that caused by exposing cells to a drug called colchicine. I was particularly interested because they had used plant material to study the effect, and it reminded me of all the things that I had read about ethylene. I wondered if cell division in the broad bean, which was the plant they had studied, would be a suitable model for comparing ethylene and anaesthetic agents. It was interesting too that they were discussing colchicine; this was a drug used to treat gout, and Isabel’s brother John was taking it for his big toe.
A few days later I phoned the botany department and asked to be put through to the staff coffee room. When the phone was answered I explained that I was looking for someone to help me to look at the hormonal and anaesthetic effects of ethylene and compare them with the action of other anaesthetic agents, in particular their effects on cell division.
‘Oh,’ said the unknown person at the other end of the phone, ‘I should talk to Chris if I were you.’
So that’s exactly what I did. I visited Chris in his room in the botany building and introduced myself. I told him all about ethylene being an anaesthetic as well as the plant hormone with which he was, of course, already familiar, and how the people at Northwick Park had looked at the effect of halothane on cell division. He was most encouraging.
‘I’ll get one of the students to help us,’ he said. ‘It will be a good project for an undergrad.’
That was how Mary came on the scene. A quiet gentle girl who was keen to get started. I got the British Oxygen Company to deliver a cylinder of ethylene; it was just the splendid purple colour that they had told me about in Denver, and they were certainly right about the revolting smell.
‘It reminds me of rotting cabbage,’ I said.
‘More like my brother’s socks,’ Sheila replied. ‘And it’s a good thing you have stopped smoking or I guess you would blow us all up.’
Soon we were under way; we grew broad beans in a bath of running water at a fixed temperature and exposed them to various concentrations of halothane and ethylene. Sheila and I were responsible for preparing the different mixtures of ethylene/air and halothane/air; Chris and Mary harvested the tips of the roots and prepared slides so that they could count the various stages of the cell cycle. It was great fun, though when the water-bath overflowed it was weeks before we got the musty smell out of the carpet.
Eventually we got the results; they confirmed that halothane did have the colchicine-like effect on cell division that had already been described, but we realised that there was depression of all the stages of the cell cycle as well.
‘If there was only an arrest at metaphase like colchicine produces we would have a great accumulation of cells in metaphase, but we do not have that, so there must be a delay in cells reaching metaphase,’ Chris said. ‘It’s like closing all the pedestrian exits at the bus station. If the buses are arriving at the normal rate then there will be a huge build up of passengers inside the station. If the buses also are delayed then the accumulation will not be marked even though the exits are closed.’
‘And they will probably all be poisoned by carbon monoxide from the engines,’ I replied. ‘I read somewhere that carbon monoxide has an ethylene-like action so I expect they will all go horizontal and grow hairs on their toes!’
We found that ethylene too had a colchicine-like effect but this was not seen at the low hormonal levels, only at the high concentrations that would be necessary for producing anaesthesia.
Chris was not satisfied.
‘We should look at germination and seedling growth, and probably flower opening and leaf fall as well as cell division, if we are going to have a full comparison. We know now that ethylene does act as an anaesthetic at high concentrations, but at low concentrations when it is exhibiting its hormonal action it is quite different.’
So we got some mustard seeds and set them growing in air alone, or in air with a trace of ethylene, or in air with 0.5% halothane. The seedlings which had been exposed to halothane were markedly stunted compared to those that had been in contact with air alone, but despite the stunting the roots grew in the normal downwards direction and the stems grew upwards and towards the light. The seedlings that had been exposed to low concentrations of ethylene were also stunted but the roots and stems grew horizontally in a random manner just like the carnations in those greenhouses of long ago. Clearly this was not ‘anaesthesia’ at all even though it had looked like it in the 1920s.
We also looked at the effect of halothane and ethylene on leaf fall. We took some shoots of Euonymus from one of the hedges outside and showed that halothane did not have any obvious effect, but that ethylene in low dose caused all the leaves to drop off after three or four days.
We wrote a paper and sent it off to the British Journal of Anaesthesia. The paper ended with these words:
We are left with the overall conclusion that anaesthesia and ethylene-like activity are not closely related phenomena.
Still, it had been great fun!
I cannot finish this chapter without mentioning the prolonged and fascinating e-mail correspondence I had with Magda Mircea, an academic classicist in Romania. She had been reading the suggestion that the mantic trances of the priestess at Delphi were produced by intoxication with ethylene. Googling she had come across my ethylene chapter and was full of questions for me. She herself was researching, together with a German metallurgist, the role of carbon dioxide in the development of the blue patina seen on vases at Delphi, and she wondered if some of the manifestations shown by the priestess could have been due to carbon dioxide inhalation. We discussed the signs and symptoms of carbon dioxide intoxication, the stages of anaesthesia, the possible role of hypoxia, William James, Banana gas, jumping goats, hysteria and many other topics. In December 2007 we sent a letter1 to the Journal of Clinical Toxicology, which was neither printed nor even its receipt acknowledged. Never mind. In any case by this time the ethylene theory had been thoroughly thrown into doubt2.
In May I had a fascinating e-mail from Warwick Jameson, a brewer in New Zealand. He told me that large amounts of ethene, which is the modern name for for what I still call ethylene, are produced during beer fermentation and conditioning; in traditional beer made using the "dry hopping" process it would not be uncommon to find 150 ml of ethene gas per litre of finished beer. Ethene acts as a yeast nutrient and prevents glucose repression in brewery fermentation. It is responsible for the trans-esterification of hop oils in beer and thus the development of the pleasant hop aroma and flavour. It also acts as a bactericide. Brewers knew hops had an antiseptic effect in beer, but never understood the biological mechanism. Simply, Warwick said, when hops are added to beer, hop enzymes dehydrate alcohol in the beer to produce ethene gas. He found that a kilogram of hops would produce about 100 L of ethene gas in beer. He went on to discuss rhinoviruses and cancer cells and said he was using ethene hydrosol to treat cancer sufferers with great effect on tumours of various types.
I replied that I was very interested in his work. I also told him about the brewery in Broad Street, Soho, which escaped infection during the cholera epidemic of 1854. This was probably because they had their own well inside the brewery which did not become contaminated with evacuations from cholera patients, unlike the public pump in the street a few houses down. I wonder if the brewery well had become contaminated whether the alcohol and the ethene between them would have dealt with it anyway. I assume that the men working there drank beer not water.
 The Minimal Alveolar Concentration of an agent is that which just prevents gross muscular response to a surgical incision in 50% of patients. See Eger EI, Saidman LJ and Brandstater B. (1965) Minimal alveolar anesthetic concentration: a standard of anesthetic potency. Anesthesiology 26, 756.
 I received this email on 19th July 2007:
Dear John, I think that your chemistry is a little off. Acetylene (today called ethyne) was made by dropping water onto Calcium Carbide. True that the calcium carbide might have had its origin in calcium carbonate or limestone and coal. Speleologists used "carbide" lamps before electricity. The lights had a flint mechanism. If the light went out due to draughts or cascading water they just wiped their hand over the open lamp and it relit. Limelight is so called because the gas flame, of whatever gas, was played onto blocks of lime or calcium oxide. These achieved white heat readily, and so were used for lighting. The same principle was used later in the gas mantle where the material glowed brightly in an otherwise invisible flame. Nothing to do with pouring water on to lime, I'm afraid. Otherwise I am enjoying a trip down a different memory lane. Yours sincerely, Murray Wilson.
Thank you, Murray, for putting me right.
 Osborne, Daphne. Ethylene as a plant growth regulator. New Scientist, 1971:
 Epinasty is defined in my dictionary (Chambers 20th Century) as ‘downcurving of an organ, caused by a more active growth on its upper side. [Gr. epi, upon; nastos, pressed close]’.
 Nunn JF, Lovis JD and Kimball KL. Arrest of mitosis by halothane. Brit J Anaesth. 1971; 43: 524.
 to read this letter click here
 Foster J, Lehoux D, 2007. The Delphic Oracle and the ethylene-intoxication hypothesis. J. Toxicology - Clinical Toxicology; 45:85-89.
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