medical essays-第45部分

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To　these　add　X；　granules；　of　indeterminate　shape　and　size；　Y；　for　inorganic　matters；　such　as　the　salts　of　bone　and　teeth；　and　Z；　to　stand　as　a　symbol　of　the　fluids；　and　you　have　the　letters　of　what　I　have　ventured　to　call　the　alphabet　of　the　body。

But　just　as　in　language　certain　diphthongs　and　syllables　are　frequently　recurring；　so　we　have　in　the　body　certain　secondary　and　tertiary　combinations；　which　we　meet　more　frequently　than　the　solitary　elements　of　which　they　are　composed。

Thus　A　B；　or　a　collection　of　cells　united　by　simple　structureless　solid；　is　seen　to　be　extensively　employed　in　the　body　under　the　name　of　cartilage。　　Out　of　this　the　surfaces　of　the　articulations　and　the　springs　of　the　breathing　apparatus　are　formed。　　But　when　Nature　came　to　the　buffers　of　the　spinal　column　（intervertebral　disks）　and　the　washers　of　the　joints　（semilunar　fibrocartilages　of　the　knee；　etc。）；　she　required　more　tenacity　than　common　cartilage　possessed。　　What　did　she　do？　　What　does　man　do　in　a　similar　case　of　need？　　I　need　hardly　tell　you。　　The　mason　lays　his　bricks　in　simple　mortar。　　But　the　plasterer　works　some　hair　into　the　mortar　which　he　is　going　to　lay　in　large　sheets　on　the　walls。　　The　children　of　Israel　complained　that　they　had　no　straw　to　make　their　bricks　with；　though　portions　of　it　may　still　be　seen　in　the　crumbling　pyramid　of　Darshour；　which　they　are　said　to　have　built。　　I　visited　the　old　house　on　Witch　Hill　in　Salem　a　year　or　two　ago；　and　there　I　found　the　walls　coated　with　clay　in　which　straw　was　abundantly　mingled；the　old　Judaizing　witch…　hangers　copied　the　Israelites　in　a　good　many　things。　　The　Chinese　and　the　Corsicans　blend　the　fibres　of　amianthus　in　their　pottery　to　give　it　tenacity。　　Now　to　return　to　Nature。　　To　make　her　buffers　and　washers　hold　together　in　the　shocks　to　which　they　would　be　subjected；　she　took　common　cartilage　and　mingled　the　white　fibrous　tissue　with　it；　to　serve　the　same　purpose　as　the　hair　in　the　mortar；　the　straw　in　the　bricks　and　in　the　plaster　of　the　old　wall；　and　the　amianthus　in　the　earthen　vessels。　　Thus　we　have　the　combination　A　B　C；　or　fibro…　cartilage。　　Again；　the　bones　were　once　only　gristle　or　cartilage；　A　B。　　To　give　them　solidity　they　were　infiltrated　with　stone；　in　the　form　of　salts　of　lime；　an　inorganic　element；　so　that　bone　would　be　spelt　out　by　the　letters　A；　B；　and　Y。

If　from　these　organic　syllables　we　proceed　to　form　organic　words；　we　shall　find　that　Nature　employs　three　principal　forms；　namely；　Vessels；　Membranes；　and　Parenchyma；　or　visceral　tissue。　　The　most　complex　of　them　can　be　resolved　into　a　combination　of　these　few　simple　anatomical　constituents。


Passing　for　a　moment　into　the　domain　of　PATHOLOGICAL　ANATOMY；　we　find　the　same　elements　in　morbid　growths　that　we　have　met　with　in　normal　structures。　　The　pus…corpuscle　and　the　white　blood…corpuscle　can　only　be　distinguished　by　tracing　them　to　their　origin。　　A　frequent　form　of　so…called　malignant　disease　proves　to　be　only　a　collection　of　altered　epithelium…cells。　　Even　cancer　itself　has　no　specific　anatomical　element；　and　the　diagnosis　of　a　cancerous　tumor　by　the　microscope；　though　tolerably　sure　under　the　eye　of　an　expert；　is　based　upon　accidental；　and　not　essential　points；the　crowding　together　of　the　elements；　the　size　of　the　cell…nuclei；　and　similar　variable　characters。

Let　us　turn　to　PHYSIOLOGY。　　The　microscope；　which　has　made　a　new　science　of　the　intimate　structure　of　the　organs；　has　at　the　same　time　cleared　up　many　uncertainties　concerning　the　mechanism　of　the　special　functions。　　Up　to　the　time　of　the　living　generation　of　observers；　Nature　had　kept　over　all　her　inner　workshops　the　forbidding　inscription；　No　Admittance！　　If　any　prying　observer　ventured　to　spy　through　his　magnifying　tubes　into　the　mysteries　of　her　glands　and　canals　and　fluids；　she　covered　up　her　work　in　blinding　mists　and　bewildering　halos；　as　the　deities　of　old　concealed　their　favored　heroes　in　the　moment　of　danger。

Science　has　at　length　sifted　the　turbid　light　of　her　lenses；　and　blanched　their　delusive　rainbows。

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