medical essays-第35章

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ower　of　dissolving　the　glass。　　But　if　for　a　I　take　oxygen；　for　b　hydrogen；　and　for　c　a　piece　of　spongy　platinum；　I　find　the　first　two　combine　with　the　common　signs　of　combustion　and　form　water；　the　third　in　the　mean　time　undergoing　no　perceptible　change。　　It　has　played　the　part　of　the　unwedded　priest；　who　marries　a　pair　without　taking　a　fee　or　having　any　further　relation　with　the　parties。　　We　call　this　catalysis；　catalytic　action；　the　action　of　presence；　or　by　what　learned　name　we　choose。　　Give　what　name　to　it　we　will；　it　is　a　manifestation　of　power　which　crosses　our　established　laws　of　combination　at　a　very　open　angle　of　intersection。　　I　think　we　may　find　an　analogy　for　it　in　electrical　induction；　the　disturbance　of　the　equilibrium　of　the　electricity　of　a　body　by　the　approach　of　a　charged　body　to　it；　without　interchange　of　electrical　conditions　between　the　two　bodies。　But　an　analogy　is　not　an　explanation；　and　why　a　few　drops　of　yeast　should　change　a　saccharine　mixture　to　carbonic　acid　and　alcohol；a　little　leaven　leavening　the　whole　lump；not　by　combining　with　it；　but　by　setting　a　movement　at　work；　we　not　only　cannot　explain；　but　the　fact　is　such　an　exception　to　the　recognized　laws　of　combination　that　Liebig　is　unwilling　to　admit　the　new　force　at　all　to　which　Berzelius　had　given　the　name　so　generally　accepted。

The　phenomena　of　isomerism；　or　identity　of　composition　and　proportions　of　constituents　with　difference　of　qualities；　and　of　isomorphism；　or　identity　of　form　in　crystals　which　have　one　element　substituted　for　another；　were　equally　surprises　to　science；　and　although　the　mechanism　by　which　they　are　brought　about　can　be　to　a　certain　extent　explained　by　a　reference　to　the　hypothetical　atoms　of　which　the　elements　are　constituted；　yet　this　is　only　turning　the　difficulty　into　a　fraction　with　an　infinitesimal　denominator　and　an　infinite　numerator。

So　far　we　have　studied　the　working　of　force　and　its　seeming　anomalies　in　purely　chemical　phenomena。　　But　we　soon　find　that　chemical　force　is　developed　by　various　other　physical　agencies；by　heat；　by　light；　by　electricity；　by　magnetism；　by　mechanical　agencies；　and；　vice　versa；　that　chemical　action　develops　heat；　light；　electricity；　magnetism；　mechanical　force；　as　we　see　in　our　matches；　galvanic　batteries；　and　explosive　compounds。　　Proceeding　with　our　experiments；　we　find　that　every　kind　of　force　is　capable　of　producing　all　other　kinds；　or；　in　Mr。　Faraday's　language；　that　〃the　various　forms　under　which　the　forces　of　matter　are　made　manifest　have　a　common　origin；　or；　in　other　words；　are　so　directly　related　and　mutually　dependent　that　they　are　convertible　one　into　another。〃

Out　of　this　doctrine　naturally　springs　that　of　the　conservation　of　force；　so　ably　illustrated　by　Mr。　Grove；　Dr。　Carpenter；　and　Mr。　Faraday。　　This　idea　is　no　novelty；　though　it　seems　so　at　first　sight。　It　was　maintained　and　disputed　among　the　giants　of　philosophy。　Des　Cartes　and　Leibnitz　denied　that　any　new　motion　originated　in　nature；　or　that　any　ever　ceased　to　exist；　all　motion　being　in　a　circle；　passing　from　one　body　to　another；　one　losing　what　the　other　gained。　　Newton；　on　the　other　hand；　believed　that　new　motions　were　generated　and　existing　ones　destroyed。　　On　the　first　supposition；　there　is　a　fixed　amount　of　force　always　circulating　in　the　universe。　On　the　second；　the　total　amount　may　be　increasing　or　diminishing。　You　will　find　in　the　〃Annual　of　Scientific　Discovery〃　for　1858　a　very　interesting　lecture　by　Professor　Helmholtz　of　Bonn；　in　which　it　is　maintained　that　a　certain　portion　of　force　is　lost　in　every　natural　process；　being　converted　into　unchangeable　heat；　so　that　the　universe　will　come　to　a　stand…still　at　last；　all　force　passing　into　heat；　and　all　heat　into　a　state　of　equilibrium。

The　doctrines　of　the　convertibility　or　specific　equivalence　of　the　various　forms　of　force；　and　of　its　conservation；　which　is　its　logical　consequence；　are　very　generally　accepted；　as　I　believe；　at　the　present　time；　among　physicists。　　We　are　naturally　led　to　the　question；　What　is　the　nature　of　force？　　The　three　illustrious　philosophers　just　referred　to　agree　in　attributing　the　general　movements　of　the　universe　to　the　immediate　Divine　action。　　The　doctrine　of　〃preestablished　harmony〃　was　an　especial　contrivance　of　Leibnitz　to　remove　the　Creator　from　unworthy　association　with　the　less　divine　acts　of　living　beings。　　Obsolete　as　this　expression　sounds　to　our　ears；　the　phrase　laws　of　the　universe；　which　we　use　so　constantly　with　a　wider　application；　appears　to　me　essentially　identical　with　it。

Force　does　not　admit　of　explanation；　nor　of　proper　definition；　any　more　than　the　hypothetical　substratum　of　matter。　　If　we　assume　the　Infinite　as　omnipresent；　omniscient；　omnipotent；　we　cannot　suppose　Him　excluded　from　any　part　of　His　creation；　except　from　rebellious　souls　which　voluntarily　exclude　Him　by　the　exercise　of　their　fatal　prerogative　of　free…will。　　Force；　then；　is　the　act　of　immanent　Divinity。　　I　find　no　meaning　in　mechanical　explanations。　　Newton's　hypothesis　of　an　ether　filling　the　heavenly　spaces　does　not；　I　confess；　help　my　conceptions。　　I　will；　and　the　muscles　of　my　vocal　organs　shape　my　speech。　　God　wills；　and　the　universe　articulates　His　power；　wisdom；　and　goodness。　　That　is　all　I　know。　　There　is　no　bridge　my　mind　can　throw　from　the　〃immaterial　〃　cause　to　the　〃material〃　effect。

The　problem　of　force　meets　us　everywhere；　and　I　prefer　to　encounter　it　in　the　world　of　physical　phenomena　before　reaching　that　of　living　actions。　　It　is　only　the　name　for　the　incomprehensible　cause　of　certain　changes　known　to　our　consciousness；　and　assumed　to　be　outside　of　it。　　For　me　it　is　the　Deity　Himself　in　action。

I　can　therefore　see　a　large　significance　in　the　somewhat　bold　language　of　Burdach　：　〃There　is　for　me　but　one　miracle；　that　of　infinite　existence；　and　but　one　mystery；　the　manner　in　which　the　finite　proceeds　from　the　infinite。　　So　soon　as　we　recognize　this　incomprehensible　act　as　the　general　and　primordial　miracle；　of　which　our　reason　perceives　the　necessity；　but　the　manner　of　which　our　intelligence　cannot　grasp；　so　soon　as　we　contemplate　the　nature　known　to　us　by　experience　in　this　light；　there　is　for　us　no　other　impenetrable　miracle　or　mystery。〃

Let　us　turn　to　a　branch　of　knowledge　which　deals　with　certainties　up　to　the　limit　of　the　senses；　and　is　involved　in　no　speculations　beyond　them。　　In　certain　points　of　view；　HUMAN　ANATOMY　may　be　considered　an　almost　exhausted　science。　　From　time　to　time　some　small　organ　which　had　escaped　earlier　observers　has　been　pointed　out；such　parts　as　the　tensor　tarsi；　the　otic　ganglion；　or　the　Pacinian　bodies；　but　some　of　our　best　anatomical　works　are　those　which　have　been　classic　for　many　generations。　The　plates　of　the　bones　in　Vesalius；　three　centuries　old；　are　still　masterpieces　of　accuracy；　as　of　art。　　The　magnificent　work　of　Albinus　on　the　muscles；　published　in　1747；　is　still　supreme　in　its　department；　as　the　constant　references　of　the　most　thorough　recent　treatise　on　the　subject；　that　of　Theile；　sufficiently　show。　　More　has　been　done　in　unravelling　the　mysteries　of　the　fasciae；　but　there　has　been　a　tendency　to　overdo　this　kind　of　material　analysis。　　Alexander　Thomson　split　them　up　into　cobwebs；　as　you　may　see　in　the　plates　to　Velpeau's　Surgical　Anatomy。　　I　well　remember　how　he　used　to　shake　his　head　over　the　coarse　work　of　Scarpa　and　Astley　Cooper；as　if　Denner；　who　painted　the　separate　hairs　of　the　beard　and　pores　of　the　skin　in　his　portraits；　had　spoken　lightly　of　the　pictures　of　Rubens　and　Vandyk。

Not　only　has　little　been　added　to　the　catalogue　of　parts；　but　some　things　long　known　had　become　half…forgotten。　Louis　and　others　confounded　the　solitary　glands　of　the　lower　part　of　the　small　intestine　with　those　which　〃the　great　Brunner；〃　as　Haller　calls　him；　described　in　1687　as　being　found　in　the　duodenum。　　The　display　of　the　fibrous　structure　of　the　brain　seemed　a　novelty　as　shown　by　Spurzheim。　　One　is　startled　to　find　the　method　anticipated　by　Raymond　Vieussens　nearly　two　centuries　ago。　　I　can　hardly　think　Gordon　had　ever　looked　at　his　figures；　though　he　names　their　author；　when　he　wrote　the　captious　and　sneering　article　which　attracted　so　much　attention　in　the　pages　of　the　〃Edinburgh　Review。〃

This　is　the　place；　if　anywhere；　to　mention　any　observations　I　could　pretend　to　have　made　in　the　course　of　my　teaching　the　structure　of　the　human　body。　　I　can　make　no　better　show　than　most　of　my　predecessors　in　this　well…reaped　field。　　The　nucleated　cells　found　connected　with　the　cancellated　structure　of　the　bones；　which　I　first　pointed　out　and　had　figured　in　1847；　and　have　shown　yearly　from　that　time　to　the　present；　and　the　fossa　masseterica；　a　shallow　concavity　on　the　ramus　of　the　lower　jaw；　for　the　lodgment　of　the　masseter　muscle；　which　acquires　significance　when　examined　by　the　side　of　the　deep　cavity　on　the　corresponding　part　in　some　carnivora　to　which　it　answers；　may　perhaps　be　claimed　as　deserving　attention。　　I　have　also　pleased　myself　by　making　a　special　group　of　the　six　radiating　muscles　which　diverge　from　the　spine　of　the　axis；　or　second　cervical　vertebra；　and　by　giving　to　it　the　name　stella　musculosa　nuchaee。　　But　this　scanty　catalogue　is　only　an　evidence　that　one　may　teach　long　and　see　little　that　has　not　been　noted　by　those　who　have　gone　before　him。　Of　course　I　do　not　think　it　necessary　to　include　rare；　but　already　described　anomalies；　such　as　the　episternal　bones；　the　rectus　sternalis；　and　other　interesting　exceptional　formations　I　have　encountered；　which　have　shown　a　curious　tendency　to　present　themselves　several　times　in　the　same　season；　perhaps　because　the　first　specimen　found　calls　our　attention　to　any　we　may　subsequently　meet　with。

The　anatomy　of　the　scalpel　and　the　amphitheatre　was；　then；　becoming　an　exhausted　branch　of　investigation。　　But　during　the　present　century　the　study　of　the　human　body　has　changed　its　old　aspect；　and　become　fertile　in　new　observations。　　This　rejuvenescence　was　effected　by　means　of　two　principal　agencies；new　methods　and　a　new　instrument。

Descriptive　anatomy；　as　known　from　an　early　date；　is　to　the　body　what　geography　is　to　the　planet。　　Now　geography　was　pretty　well　known　so　long　ago　as　when　Arrowsmith；　who　was　born　in　1750；　published　his　admirable　maps。　　But　in　that　same　year　was　born　Werner；　who　taught　a　new　way　of　studying　the　earth；　since　become　familiar　to　us　all　under　the　name　of　Geology。

What　geology　has　done　for　our　knowledge　of　the　earth；　has　been　done　for　our　knowledge　of　the　body　by　that　method　of　study　to　which　is　given　the　name　of　General　Anatomy。　　It　studies；　not　the　organs　as　such；　but　the　elements　out　of　which　the　organs　are　constructed。　　It　is　the　geology　of　the　body；　as　that　is　the　general　anatomy　of　the　earth。　　The　extraordinary　genius　of　Bichat；　to　whom　more　than　any　other　we　owe　this　new　method　of　study；　does　not　require　Mr。　Buckle's　testimony　to　impress　the　practitioner　with　the　importance　of　its　achievements。　　I　have　heard　a　very　wise　physician　question　whether　any　important　result　had　accrued　to　practical　medicine　from　Harvey's　discovery　of　the　circulation。　　But　Anatomy；　Physiology；　and　Pathology　have　received　a　new　light　from　this　novel　method　of　contemplating　the　living　structures；　which　has　had　a　vast　influence　in　enabling　the　practiti