ashcroft relates a story concerning thedirectors of a new tunnel under the thames who held a celebratory banquet as the tunnelneared pletion。 to their consternation their champagne failed to fizz when uncorked inthe pressed air of the tunnel。 however； when at length they emerged into the fresh air of alondon evening； the bubbles sprang instantly to fizziness； memorably enlivening thedigestive process。
apart from avoiding high…pressure environments altogether； only two strategies are reliablysuccessful against the bends。 the first is to suffer only a very short exposure to the changes inpressure。 that is why the free divers i mentioned earlier can descend to depths of five hundredfeet without ill effect。 they don鈥檛 stay under long enough for the nitrogen in their system todissolve into their tissues。 the other solution is to ascend by careful stages。 this allows thelittle bubbles of nitrogen to dissipate harmlessly。
a great deal of what we know about surviving at extremes is owed to the extraordinaryfather…and…son team of john scott and j。 b。 s。 haldane。 even by the demanding standards ofbritish intellectuals； the haldanes were outstandingly eccentric。 the senior haldane was bornin 1860 to an aristocratic scottish family （his brother was viscount haldane） but spent mostof his career in parative modesty as a professor of physiology at oxford。 he wasfamously absent…minded。 once after his wife had sent him upstairs to change for a dinnerparty he failed to return and was discovered asleep in bed in his pajamas。 when roused；haldane explained that he had found himself disrobing and assumed it was bedtime。 his ideaof a vacation was to travel to cornwall to study hookworm in miners。 aldous huxley； thenovelist grandson of t。 h。 huxley； who lived with the haldanes for a time； parodied him； atouch mercilessly； as the scientist edward tantamount in the novel point counter point 。
haldane鈥檚 gift to diving was to work out the rest intervals necessary to manage an ascentfrom the depths without getting the bends； but his interests ranged across the whole ofphysiology； from studying altitude sickness in climbers to the problems of heatstroke in desertregions。 he had a particular interest in the effects of toxic gases on the human body。 tounderstand more exactly how carbon monoxide leaks killed miners； he methodically poisonedhimself； carefully taking and measuring his own blood samples the while。 he quit only whenhe was on the verge of losing all muscle control and his blood saturation level had reached 56percent鈥攁 level； as trevor norton notes in his entertaining history of diving； stars beneaththe sea； only fractionally removed from nearly certain lethality。
haldane鈥檚 son jack； known to posterity as j。b。s。； was a remarkable prodigy who took aninterest in his father鈥檚 work almost from infancy。 at the age of three he was overhearddemanding peevishly of his father； 鈥渂ut is it oxyhaemoglobin or carboxyhaemoglobin？鈥�
throughout his youth； the young haldane helped his father with experiments。 by the time hewas a teenager； the two often tested gases and gas masks together； taking turns to see howlong it took them to pass out。
though j。 b。 s。 haldane never took a degree in science （he studied classics at oxford）； hebecame a brilliant scientist in his own right； mostly in cambridge。 the biologist petermedawar； who spent his life around mental olympians； called him 鈥渢he cleverest man i everknew。鈥潯uxley likewise parodied the younger haldane in his novel antic hay； but also usedhis ideas on genetic manipulation of humans as the basis for the plot of brave new world。
among many other achievements； haldane played a central role in marrying darwinian principles of evolution to the genetic work of gregor mendel to produce what is known togeneticists as the modern synthesis。
perhaps uniquely among human beings； the younger haldane found world war i 鈥渁 veryenjoyable experience鈥潯nd freely admitted that he 鈥渆njoyed the opportunity of killing people。鈥�
he was himself wounded twice。 after the war he became a successful popularizer of scienceand wrote twenty…three books （as well as over four hundred scientific papers）。 his books arestill thoroughly readable and instructive； though not always easy to find。 he also became anenthusiastic marxist。 it has been suggested； not altogether cynically； that this was out of apurely contrarian instinct； and that if he had been born in the soviet union he would havebeen a passionate monarchist。 at all events； most of his articles first appeared in themunist daily worker。
whereas his father鈥檚 principal interests concerned miners and poisoning； the youngerhaldane became obsessed with saving submariners and divers from the unpleasantconsequences of their work。 with admiralty funding he acquired a depression chamberthat he called the 鈥減ressure pot。鈥潯his was a metal cylinder into which three people at a timecould be sealed and subjected to tests of various types； all painful and nearly all dangerous。
volunteers might be required to sit in ice water while breathing 鈥渁berrant atmosphere鈥潯rsubjected to rapid changes of pressurization。 in one experiment； haldane simulated adangerously hasty ascent to see what would happen。 what happened was that the dentalfillings in his teeth exploded。 鈥渁lmost every experiment；鈥潯orton writes； 鈥渆nded withsomeone having a seizure； bleeding； or vomiting。鈥潯he chamber was virtually soundproof； sothe only way for occupants to signal unhappiness or distress was to tap insistently on thechamber wall or to hold up notes to a small window。
on another occasion； while poisoning himself with elevated levels of oxygen； haldane hada fit so severe that he crushed several vertebrae。 collapsed lungs were a routine hazard。
perforated eardrums were quite mon； but； as haldane reassuringly noted in one of hisessays； 鈥渢he drum generally heals up； and if a hole remains in it； although one is somewhatdeaf； one can blow tobacco smoke out of the ear in question； which is a socialacplishment。鈥�
what was extraordinary about this was not that haldane was willing to subject himself tosuch risk and disfort in the pursuit of science； but that he had no trouble talkingcolleagues and loved ones into climbing into the chamber； too。 sent on a simulated descent；his wife once had a fit that lasted thirteen minutes。 when at last she stopped bouncing acrossthe floor； she was helped to her feet and sent home to cook dinner。 haldane happily employedwhoever happened to be around； including on one memorable occasion a former primeminister of spain； juan negr铆n。 dr。 negr铆n plained afterward of minor tingling and 鈥渁curious velvety sensation on the lips鈥潯ut otherwise seems to have escaped unharmed。 he mayhave considered himself very lucky。 a similar experiment with oxygen deprivation lefthaldane without feeling in his buttocks and lower spine for six years。
among haldane鈥檚 many specific preoccupations was nitrogen intoxication。 for reasons thatare still poorly understood； beneath depths of about a hundred feet nitrogen bees apowerful intoxicant。 under its influence divers had been known to offer their air hoses topassing fish or decide to try to have a smoke break。 it also produced wild mood swings。 inone test； haldane noted； the subject 鈥渁lternated between depression and elation； at onemoment begging to be depressed because he felt 鈥榖loody awful鈥櫋nd the next minutelaughing and attempting to interfere with his colleague鈥檚 dexterity test。鈥潯n order to measure the rate of deterioration in the subject； a scientist had to go into the chamber with thevolunteer to conduct simple mathematical tests。 but after a few minutes； as haldane laterrecalled； 鈥渢he tester was usually as intoxicated as the testee； and often forgot to press thespindle of his stopwatch； or to take proper notes。鈥潯he cause of the inebriation is even now amystery。 it is thought that it may be the same thing that causes alcohol intoxication； but as noone knows for certain what causes that we are none the wiser。 at all events； without thegreatest care； it is easy to get in trouble once you leave the surface world。
which brings us back （well； nearly） to our earlier observation that earth is not the easiestplace to be an organism； even if it is the only place。 of the small portion of the planet鈥檚surface that is dry enough to stand on； a surprisingly large amount is too hot or cold or dry orsteep or lofty to be of much use to us。 partly； it must be conceded； this is our fault。 in terms ofadaptability； humans are pretty amazingly useless。 like most animals； we don鈥檛 much likereally hot places； but because we sweat so freely and easily stroke； we are especiallyvulnerable。 in the worst circumstances鈥攐n foot without water in a hot desert鈥攎ost peoplewill grow delirious and keel over； possibly never to rise again； in no more than six or sevenhours。 we are no less helpless in the face of cold。 like all mammals； humans are good atgenerating heat but鈥攂ecause we are so nearly hairless鈥攏ot good at keeping it。 even in quitemild weather half the calories you burn go to keep your body warm。 of course； we cancounter these frailties to a large extent by employing clothing and shelter； but even so theportions of earth on which we are prepared or able to live are modest indeed： just 12 percentof the total land area； and only 4 percent of the whole surface if you include the seas。
yet when you consider conditions elsewhere in the known universe； the wonder is not thatwe use so little of our planet but that we have managed to find a planet that we can use even abit of。 you have only to look at our own solar system鈥攐r； e to that； earth at certainperiods in its own history鈥攖o appreciate that most places are much harsher and much lessamenable to life than our mild； blue watery globe。
so far space scientists have discovered about seventy planets outside the solar system； outof the ten billion trillion or so that are thought to be out there； so humans can hardly claim tospeak with authority on the matter； but it appears that if you wish to have a planet suitable forlife； you have to be just awfully lucky； and the more advanced the life； the luckier you have tobe。 various observers have identi