A Short History of Nearly Everything-第50章

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nearly　everyone；　including　the　authors　of　some　popular　books　on　oceanography；　assumesthat　the　human　body　would　crumple　under　the　immense　pressures　of　the　deep　ocean。　in　fact；this　appears　not　to　be　the　case。　because　we　are　made　largely　of　water　ourselves；　and　water　is“virtually　inpressible；”　in　the　words　of　frances　ashcroft　of　oxford　university；　“the　bodyremains　at　the　same　pressure　as　the　surrounding　water；　and　is　not　crushed　at　depth。”　it　is　thegases　inside　your　body；　particularly　in　the　lungs；　that　cause　the　trouble。　these　do　press；though　at　what　point　the　pression　bees　fatal　is　not　known。　until　quite　recently　it　wasthought　that　anyone　diving　to　one　hundred　meters　or　so　would　die　painfully　as　his　or　her　lungsimploded　or　chest　wall　collapsed；　but　the　free　divers　have　repeatedly　proved　otherwise。　itappears；　according　to　ashcroft；　that　“humans　may　be　more　like　whales　and　dolphins　than　hadbeen　expected。”

plenty　else　can　go　wrong；　however。　in　the　days　of　diving　suits—the　sort　that　wereconnected　to　the　surface　by　long　hoses—divers　sometimes　experienced　a　dreadedphenomenon　known　as　“the　squeeze。”　this　occurred　when　the　surface　pumps　failed；　leadingto　a　catastrophic　loss　of　pressure　in　the　suit。　the　air　would　leave　the　suit　with　such　violencethat　the　hapless　diver　would　be；　all　too　literally；　sucked　up　into　the　helmet　and　hosepipe。

when　hauled　to　the　surface；　“all　that　is　left　in　the　suit　are　his　bones　and　some　rags　of　flesh；”

the　biologist　j。　b。　s。　haldane　wrote　in　1947；　adding　for　the　benefit　of　doubters；　“this　hashappened。”

（incidentally；　the　original　diving　helmet；　designed　in　1823　by　an　englishman　namedcharles　deane；　was　intended　not　for　diving　but　for　fire…fighting。　it　was　called　a　“smokehelmet；”　but　being　made　of　metal　it　was　hot　and　cumbersome　and；　as　deane　soon　discovered；firefighters　had　no　particular　eagerness　to　enter　burning　structures　in　any　form　of　attire；　butmost　especially　not　in　something　that　heated　up　like　a　kettle　and　made　them　clumsy　into　thebargain。　in　an　attempt　to　save　his　investment；　deane　tried　it　underwater　and　found　it　was　idealfor　salvage　work。）the　real　terror　of　the　deep；　however；　is　the　bends—not　so　much　because　they　areunpleasant；　though　of　course　they　are；　as　because　they　are　so　much　more　likely。　the　air　webreathe　is　80　percent　nitrogen。　put　the　human　body　under　pressure；　and　that　nitrogen　istransformed　into　tiny　bubbles　that　migrate　into　the　blood　and　tissues。　if　the　pressure　ischanged　too　rapidly—as　with　a　too…quick　ascent　by　a　diver—the　bubbles　trapped　within　thebody　will　begin　to　fizz　in　exactly　the　manner　of　a　freshly　opened　bottle　of　champagne；clogging　tiny　blood　vessels；　depriving　cells　of　oxygen；　and　causing　pain　so　excruciating　thatsufferers　are　prone　to　bend　double　in　agony—hence　“the　bends。”

the　bends　have　been　an　occupational　hazard　for　sponge　and　pearl　divers　since　timeimmemorial　but　didn’t　attract　much　attention　in　the　western　world　until　the　nineteenthcentury；　and　then　it　was　among　people　who　didn’t　get　wet　at　all　（or　at　least　not　very　wet　andnot　generally　much　above　the　ankles）。　they　were　caisson　workers。　caissons　were　encloseddry　chambers　built　on　riverbeds　to　facilitate　the　construction　of　bridge　piers。　they　were　filledwith　pressed　air；　and　often　when　the　workers　emerged　after　an　extended　period　ofworking　under　this　artificial　pressure　they　experienced　mild　symptoms　like　tingling　or　itchyskin。　but　an　unpredictable　few　felt　more　insistent　pain　in　the　joints　and　occasionally　collapsedin　agony；　sometimes　never　to　get　up　again。

it　was　all　most　puzzling。　sometimes　workers　would　go　to　bed　feeling　fine；　but　wake　upparalyzed。　sometimes　they　wouldn’t　wake　up　at　all。　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’t　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’s　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—a　level；　as　trevor　norton　notes　in　his　entertaining　history　of　diving；　stars　beneaththe　sea；　only　fractionally　removed　from　nearly　certain　lethality。

haldane’s　son　jack；　known　to　posterity　as　j。b。s。；　was　a　remarkable　prodigy　who　took　aninterest　in　his　father’s　work　almost　from　infancy。　at　the　age　of　three　he　was　overhearddemanding　peevishly　of　his　father；　“but　is　it　oxyhaemoglobin　or　carboxyhaemoglobin？”

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　“the　cleverest　man　i　everknew。”　huxley　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　“a　veryenjoyable　experience”　and　freely　admitted　that　he　“enjoyed　the　opportunity　of　killing　people。”

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’s　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　“pressure　pot。”　this　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　“aberrant　atmosphere”　orsubjected　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。　“almost　every　experiment；”　norton　writes；　“ended　withsomeone　having　a　seizure；　bleeding；　or　vomiting。”　the　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