medical essays-第41部分

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Anatomy　studies　the　organism　in　space。　　Physiology　studies　it　also　in　time。　　After　the　study　of　form　and　composition　follows　close　that　of　action；　and　this　leads　us　along　back　to　the　first　moment　of　the　germ；　and　forward　to　the　resolution　of　the　living　frame　into　its　lifeless　elements。　　In　this　way　Anatomy；　or　rather　that　branch　of　it　which　we　call　Histology；　has　become　inseparably　blended　with　the　study　of　function。　　The　connection　between　the　science　of　life　and　that　of　intimate　structure　on　the　one　hand；　and　composition　on　the　other；　is　illustrated　in　the　titles　of　two　recent　works　of　remarkable　excellence；〃the　Physiological　Anatomy〃　of　Todd　and　Bowman；　and　the　〃Physiological　Chemistry〃　of　Lehmann。

Let　me　briefly　recapitulate　a　few　of　our　acquisitions　in　Physiology；　due　in　large　measure　to　our　new　instruments　and　methods　of　research；　and　at　the　same　time　indicate　the　limits　which　form　the　permanent　or　the　temporary　boundaries　of　our　knowledge。　　I　will　begin　with　the　largest　fact　and　with　the　most　absolute　and　universally　encountered　limitation。

The　〃largest　truth　in　Physiology〃　Mr。　Paget　considers　to　be　〃the　development　of　ova　through　multiplication　and　division　of　their　cells。〃　　I　would　state　it　more　broadly　as　the　agency　of　the　cell　in　all　living　processes。　　It　seems　at　present　necessary　to　abandon　the　original　idea　of　Schwann；　that　we　can　observe　the　building　up　of　a　cell　from　the　simple　granules　of　a　blastema；　or　formative　fluid。　　The　evidence　points　rather　towards　the　axiom；　Omnis　cellula　a　cellula；　that　is；　the　germ　of　a　new　cell　is　always　derived　from　a　preexisting　cell。　　The　doctrine　of　Schwann；　as　I　remarked　long　ago　（1844）；　runs　parallel　with　the　nebular　theory　in　astronomy；　and　they　may　yet　stand　or　fall　together。

As　we　have　seen　Nature　anticipating　the　plasterer　in　fibro…cartilage；　so　we　see　her　beforehand　with　the　glassblower　in　her　dealings　with　the　cell。　　The　artisan　blows　his　vitreous　bubbles；　large　or　small；　to　be　used　afterwards　as　may　be　wanted。　　So　Nature　shapes　her　hyaline　vesicles　and　modifies　them　to　serve　the　needs　of　the　part　where　they　are　found。　　The　artisan　whirls　his　rod；　and　his　glass　bubble　becomes　a　flattened　disk；　with　its　bull's…eye　for　a　nucleus。　　These　lips　of　ours　are　all　glazed　with　microscopic　tiles　formed　of　flattened　cells；　each　one　of　them　with　its　nucleus　still　as　plain　and　relatively　as　prominent；　to　the　eye　of　the　microscopist；　as　the　bull's…eye　in　the　old…fashioned　windowpane。　　Everywhere　we　find　cells；　modified　or　unchanged。　　They　roll　in　inconceivable　multitudes　（five　millions　and　more　to　the　cubic　millimetre；　according　to　Vierordt）　as　blood…disks　through　our　vessels。　　A　close…fitting　mail　of　flattened　cells　coats　our　surface　with　a　panoply　of　imbricated　scales　（more　than　twelve　thousand　millions；　as　Harting　has　computed；　as　true　a　defence　against　our　enemies　as　the　buckler　of　the　armadillo　or　the　carapace　of　the　tortoise　against　theirs。　　The　same　little　protecting　organs　pave　all　the　great　highways　of　the　interior　system。　　Cells；　again；　preside　over　the　chemical　processes　which　elaborate　the　living　fluids；　they　change　their　form　to　become　the　agents　of　voluntary　and　involuntary　motion；　the　soul　itself　sits　on　a　throne　of　nucleated　cells；　and　flashes　its　mandates　through　skeins　of　glassy　filaments　which　once　were　simple　chains　of　vesicles。　　And；　as　if　to　reduce　the　problem　of　living　force　to　its　simplest　expression；　we　see　the　yolk　of　a　transparent　egg　dividing　itself　in　whole　or　in　part；　and　again　dividing　and　subdividing；　until　it　becomes　a　mass　of　cells；　out　of　which　the　harmonious　diversity　of　the　organs　arranges　itself；　worm　or　man；　as　God　has　willed　from　the　beginning。

This　differentiation　having　been　effected；　each　several　part　assumes　its　special　office；　having　a　life　of　its　own　adjusted　to　that　of　other　parts　and　the　whole。　　〃Just　as　a　tree　constitutes　a　mass　arranged　in　a　definite　manner；　in　which；　in　every　single　part；　in　the　leaves　as　in　the　root；　in　the　trunk　as　in　the　blossom；　cells　are　discovered　to　be　the　ultimate　elements；　so　is　it　also　with　the　forms　of　animal　life。　　Every　animal　presents　itself　as　a　sum　of　vital　unities；　every　one　of　which　manifests　all　the　characteristics　of　life。〃

The　mechanism　is　as　clear；　as　unquestionable；　as　absolutely　settled　and　universally　accepted；　as　the　order　of　movement　of　the　heavenly　bodies；　which　we　compute　backward　to　the　days　of　the　observatories　on　the　plains　of　Shinar；　and　on　the　faith　of　which　we　regulate　the　movements　of　war　and　trade　by　the　predictions　of　our　ephemeris。

The　mechanism；　and　that　is　all。　　We　see　the　workman　and　the　tools；　but　the　skill　that　guides　the　work　and　the　power　that　performs　it　are　as　invisible　as　ever。　　I　fear　that　not　every　listener　took　the　significance　of　those　pregnant　words　in　the　passage　I　quoted　from　John　Bell；〃thinking　to　discover　its　properties　in　its　form。〃　　We　have　discovered　the　working　bee　in　this　great　hive　of　organization。　We　have　detected　the　cell　in　the　very　act　of　forming　itself　from　a　nucleus；　of　transforming　itself　into　various　tissues；　of　selecting　the　elements　of　various　secretions。　　But　why　one　cell　becomes　nerve　and　another　muscle；　why　one　selects　bile　and　another　fat；　we　can　no　more　pretend　to　tell；　than　why　one　grape　sucks　out　of　the　soil　the　generous　juice　which　princes　hoard　in　their　cellars；　and　another　the　wine　which　it　takes　three　men　to　drink；one　to　pour　it　down；　another　to　swallow　it；　and　a　third　to　hold　him　while　it　is　going　down。　Certain　analogies　between　this　selecting　power　and　the　phenomena　of　endosmosis　in　the　elective　affinities　of　chemistry　we　can　find；　but　the　problem　of　force　remains　here；　as　everywhere；　unsolved　and　insolvable。

Do　we　gain　anything　by　attempting　to　get　rid　of　the　idea　of　a　special　vital　force　because　we　find　certain　mutually　convertible　relations　between　forces　in　the　body　and　out　of　it？　　I　think　not；　any　more　than　we　should　gain　by　getting　rid　of　the　idea　and　expression　Magnetism　because　of　its　correlation　with　electricity。　　We　may　concede　the　unity　of　all　forms　of　force；　but　we　cannot　overlook　the　fixed　differences　of　its　manifestations　according　to　the　conditions　under　which　it　acts。　　It　is　a　mistake；　however；　to　think　the　mystery　is　greater　in　an　organized　body　than　in　any　other。　　We　see　a　stone　fall　or　a　crystal　form；　and　there　is　nothing　stranger　left　to　wonder　at；　for　we　have　seen　the　Infinite　in　action。

Just　so　far　as　we　can　recognize　the　ordinary　modes　of　operation　of　the　common　forces　of　nature；gravity；　cohesion；　elasticity；　transudation；　chemical　action；　and　the　rest；we　see　the　so…called　vital　acts　in　the　light　of　a　larger　range　of　known　facts　and　familiar　analogies。　　Matteuecci's　well…remembered　lectures　contain　many　and　striking　examples　of　the　working　of　physical　forces　in　physiological　processes。　　Wherever　rigid　experiment　carries　us；　we　are　safe　in　following　this　lead；　but　the　moment　we　begin　to　theorize　beyond　our　strict　observation；　we　are　in　danger　of　falling　into　those　mechanical　follies　which　true　science　has　long　outgrown。

Recognizing　the　fact；　then；　that　we　have　learned　nothing　but　the　machinery　of　life；　and　are　no　nearer　to　its　essence；　what　is　it　that　we　have　gained　by　this　great　discovery　of　the　cell　formation　and　function？

It　would　have　been　reward　enough　to　learn　the　method　Nature　pursues　for　its　own　sake。　　If　the　sovereign　Artificer　lets　us　into　his　own　laboratories　and　workshops；　we　need　not　ask　more　than　the　privilege　of　looking　on　at　his　work。　　We　do　not　know　where　we　now　stand　in　the　hierarchy　of　created　intelligences。　　We　were　made　a　little　lower　than　the　angels。　　I　speak　it　not　irreverently；　as　the　lower　animals　surpass　man　in　some　of　their　attributes；　so　it　may　be　that　not　every　angel's　eye　can　see　as　broadly　and　as　deeply　into　the　material　works　of　God　as　man　himself；　looking　at　the　firmament　through　an　equatorial　of　fifteen　inches'　aperture；　and　searching　into　the　tissues　with　a　twelfth　of　an　inch　objective。

But　there　are　other　positive　gains　of　a　more　practical　character。　Thus　we　are　no　longer　permitted　to　place　the　seat　of　the　living　actions　in　the　extreme　vessels；　which　are　only　the　carriers　from　which　each　part　takes　what　it　wants　by　the　divine　right　of　the　omnipotent　nucleated　cell。　　The　organism　has　become；　in　the　words　already　borrowed　from　Virchow；　〃a　sum　of　vital　unities。〃　　The　strictum　and　laxum；　the　increased　and　diminished　action　of　the　vessels；　out　of　which　medical　theories　and　methods　of　treatment　have　grown　up；　have　yielded　to　the　doctrine　of　local　cell…communities；　belonging　to　this　or　that　vascular　district；　from　which　they　help　themselves；　as　contractors　are　wont　to　do　from　the　national　treasury。

I　cannot　promise　to　do　more　than　to　select　a　few　of　the　points　of　contact　between　our　ignorance　and　our　knowledge　which　present　particular　interest　in　the　existing　state　of　our　physiological　acquisitions。　　Some　of　them　involve　the　microscopic　discoveries　of　which　I　have　been　speaking；　some　belong　to　the　domain　of　chemistry；　and　some　have　relations　with　other　departments　of　physical　science。

If　we　should　begin　with　the　digestive　function；　we　should　find　that　the　long…agitated　question　of　the　nature　of　the　acid　of　the　gastric　juice　is　becoming　settled　in　favor　of　the　lactic。　　But　the　whole　solvent　agency　of　the　digestive　fluid　enters　into　the　category　of　that　exceptional　mode　of　action　already　familiar　to　us　in　chemistry　as　catalysis。　　It　is　therefore　doubly　difficult　of　explanation；　first；　as　being；　like　all　reactions；　a　fact　not　to　be　accounted　for　except　by　the　imaginative　appeal　to　〃affinity；〃　and　secondly；　as　being　one　of　those　peculiar　reactions　provoked　by　an　element　which　stands　outside　and　looks　on　without　compromising　itself。

The　doctrine　of　Mulder；　so　widely　diffused　in　popular　and　scientific　belief；　of　the　existence　of　a　common　base　of　all　albuminous　substances；　the　so…called　protein；　has　not　stood　the　test　of　rigorous　analysis。　　The　division　of　food　into　azotized　and　non…azotized　is　no　doubt　important；　but　the　attempt　to　show　that　the　first　only　is　plastic　or　nutritive；　while　the　second　is　simply　calorifacient；　or　heat…producing；　fails　entirely　in　the　face　of　the　facts　revealed　by　the　study　of　man　in　different　climates；　and　of　numerous　experiments　in