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Painless solution
THE LAST WORD Painless solution I cut the inside of my finger on a piece of smooth metal foil, but felt nothing. The first I realised I had done it was when I started leaving patches of blood on things. The cut was quite deep and took a while to staunch, so why was it completely painless? I’ve had similar cuts on sharp objects before and mostly they’ve been very painful, but every so often some cuts don’t seem to hurt at all.
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edges of even the shiniest paper are rough at the microscopic scale. Any contamination of the wound with acidic or salty liquid from the tin contents, or with microscopic debris lodged in the offending edge or on the skin, will further irritate the nerves. Another factor is the number and density of pain receptors on the part of the skin that is cut. Fingers have a very high density of nerve endings, including those for touch and temperature, but even across a given finger tip these are not uniformly distributed. An otherwise identical cut will be more painful
n I’m an anaesthetist, and I “cut” my patients’ hands every day when I insert an intravenous cannula, usually into the back “Tearing of pain receptors of their hand or wrist. Patients makes paper cuts so sore – expect it to hurt, as do I, so I warn even shiny paper is rough them. Sometimes afterwards the at the microscopic scale” patient will ask if I have done it yet, and exclaim that I must be good, as it didn’t hurt a bit. if it occurs at a spot where they I accept this praise modestly, are more densely packed and because I know skin sensation is more endings get damaged. perceived via discrete receptors There is a circadian – or daily – with free nerve endings used for rhythm in pain threshold. detecting pain. If I choose an area Generally, the least pain is that happens not to contain pain experienced in early to midreceptors, the patient may feel the afternoon, with more experienced needle pressure but no pain. in the morning and at bedtime. John Davies Individuals differ in their tolerance Consultant Anaesthetist of pain, and there is evidence that Lancaster, UK people adopt similar coping mechanisms to their parents. n It depends on how cleanly the Other factors can also influence nerves are severed. For example, someone’s perceived pain at a the edges of the tins and lids left given time, through complex by a tin opener are rougher than interactions between chemical those of metal foil, and tear the neurotransmitters, hormones nerve endings. It is this tearing of and the way in which nerves the pain receptors that also makes are hard-wired. Inspecting or paper cuts so sore, because the applying pressure to the injury,
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New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
good health and physical fitness, and being immersed in an activity help reduce pain. Negative moods and sleep deprivation, in contrast, tend to worsen it. About a year ago I had carpal tunnel surgery on my hand, which involved dividing and parting the overlying tissues to access the carpal ligament where the palm joins the wrist. Having expected discomfort as the anaesthetic wore off, I was surprised by the absence of pain. The procedure was carried out by a top surgeon using finest grade instruments. I was even advised to return to my passion for piano quickly to maintain motility of the tendons, and I know at least one person who, after carpal tunnel release on both hands, was back at work the next day. Len Winokur Leeds, UK
lick. Also, practically all herbivores rely on a partnership with gut flora to supply micronutrients or improve digestion. Then again, they need to eat huge volumes of vegetation to ensure they absorb sufficient quantities of minerals from the minute concentrations in plants. After all, plants contain a little iron and manganese as well as macronutrients such as magnesium because these are needed for photosynthesis. Humans trying to match the performance of specialist herbivores would need bellies like proboscis monkeys, and would be eating 18 hours a day just to keep up; never mind the consequent activity at the nether end, nor the tooth wear that, as brachydont herbivores, humans would suffer. Jon Richfield Somerset West, South Africa
Iron plants
This week’s question
Iron deficiency is common among human vegetarians, so how do herbivores cope?
n Vegetarians have dietary difficulties because they force their omnivorous physiology to cope with a herbivorous diet, mineral imbalances being only one of the consequences. Herbivores survive in good health partly because some are not as vegan as we might imagine. They eagerly eat animal dung, old bones, incidental insects and the like. They are also not too proud to eat dirt wherever they find a salt
More on martinis
You recently ran correspondence on how different spoons used for stirring James Bond’s vodka martinis with ice had an effect on its temperature. I have an additional question. Traditionally martinis are stirred using long bar spoons, as your correspondents noted. However, mixologists use the handle end of the spoon, where there is a disc of metal, rather than the spoon bowl. This makes the martini less dilute. But why? Pierre Grogan London, UK
Why are orangutans orange? A new collection: the usual insight, ingenuity and wit – this time with full colour photographs Available from booksellers and at newscientist.com/orangutans
Last words past and present, plus questions, at last-word.com
edges of even the shiniest paper are rough at the microscopic scale. Any contamination of the wound with acidic or salty liquid from the tin contents, or with microscopic debris lodged in the offending edge or on the skin, will further irritate the nerves. Another factor is the number and density of pain receptors on the part of the skin that is cut. Fingers have a very high density of nerve endings, including those for touch and temperature, but even across a given finger tip these are not uniformly distributed. An otherwise identical cut will be more painful
n I’m an anaesthetist, and I “cut” my patients’ hands every day when I insert an intravenous cannula, usually into the back “Tearing of pain receptors of their hand or wrist. Patients makes paper cuts so sore – expect it to hurt, as do I, so I warn even shiny paper is rough them. Sometimes afterwards the at the microscopic scale” patient will ask if I have done it yet, and exclaim that I must be good, as it didn’t hurt a bit. if it occurs at a spot where they I accept this praise modestly, are more densely packed and because I know skin sensation is more endings get damaged. perceived via discrete receptors There is a circadian – or daily – with free nerve endings used for rhythm in pain threshold. detecting pain. If I choose an area Generally, the least pain is that happens not to contain pain experienced in early to midreceptors, the patient may feel the afternoon, with more experienced needle pressure but no pain. in the morning and at bedtime. John Davies Individuals differ in their tolerance Consultant Anaesthetist of pain, and there is evidence that Lancaster, UK people adopt similar coping mechanisms to their parents. n It depends on how cleanly the Other factors can also influence nerves are severed. For example, someone’s perceived pain at a the edges of the tins and lids left given time, through complex by a tin opener are rougher than interactions between chemical those of metal foil, and tear the neurotransmitters, hormones nerve endings. It is this tearing of and the way in which nerves the pain receptors that also makes are hard-wired. Inspecting or paper cuts so sore, because the applying pressure to the injury,
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
good health and physical fitness, and being immersed in an activity help reduce pain. Negative moods and sleep deprivation, in contrast, tend to worsen it. About a year ago I had carpal tunnel surgery on my hand, which involved dividing and parting the overlying tissues to access the carpal ligament where the palm joins the wrist. Having expected discomfort as the anaesthetic wore off, I was surprised by the absence of pain. The procedure was carried out by a top surgeon using finest grade instruments. I was even advised to return to my passion for piano quickly to maintain motility of the tendons, and I know at least one person who, after carpal tunnel release on both hands, was back at work the next day. Len Winokur Leeds, UK
lick. Also, practically all herbivores rely on a partnership with gut flora to supply micronutrients or improve digestion. Then again, they need to eat huge volumes of vegetation to ensure they absorb sufficient quantities of minerals from the minute concentrations in plants. After all, plants contain a little iron and manganese as well as macronutrients such as magnesium because these are needed for photosynthesis. Humans trying to match the performance of specialist herbivores would need bellies like proboscis monkeys, and would be eating 18 hours a day just to keep up; never mind the consequent activity at the nether end, nor the tooth wear that, as brachydont herbivores, humans would suffer. Jon Richfield Somerset West, South Africa
Iron plants
This week’s question
Iron deficiency is common among human vegetarians, so how do herbivores cope?
n Vegetarians have dietary difficulties because they force their omnivorous physiology to cope with a herbivorous diet, mineral imbalances being only one of the consequences. Herbivores survive in good health partly because some are not as vegan as we might imagine. They eagerly eat animal dung, old bones, incidental insects and the like. They are also not too proud to eat dirt wherever they find a salt
More on martinis
You recently ran correspondence on how different spoons used for stirring James Bond’s vodka martinis with ice had an effect on its temperature. I have an additional question. Traditionally martinis are stirred using long bar spoons, as your correspondents noted. However, mixologists use the handle end of the spoon, where there is a disc of metal, rather than the spoon bowl. This makes the martini less dilute. But why? Pierre Grogan London, UK
Why are orangutans orange? A new collection: the usual insight, ingenuity and wit – this time with full colour photographs Available from booksellers and at newscientist.com/orangutans