a history of science-1- 第3部分

h　man　might　not　have　learned　to　eat　without　deleterious　effect；　provided　the　experiment　were　made　gradually。　To　a　certain　extent；　then；　the　observed　poisonous　effects　of　numerous　plants　upon　the　human　system　are　to　be　explained　by　the　fact　that　our　ancestors　have　avoided　this　particular　vegetable。　Certain　fruits　and　berries　might　have　come　to　have　been　a　part　of　man's　diet；　had　they　grown　in　the　regions　he　inhabited　at　an　early　day；　which　now　are　poisonous　to　his　system。　This　thought；　however；　carries　us　too　far　afield。　For　practical　purposes；　it　suffices　that　certain　roots；　leaves；　and　fruits　possess　principles　that　are　poisonous　to　the　human　system；　and　that　unless　man　had　learned　in　some　way　to　avoid　these；　our　race　must　have　come　to　disaster。　In　point　of　fact；　he　did　learn　to　avoid　them；　and　such　evidence　implied；　as　has　been　said；　an　elementary　knowledge　of　toxicology。　Coupled　with　this　knowledge　of　things　dangerous　to　the　human　system；　there　must　have　grown　up；　at　a　very　early　day；　a　belief　in　the　remedial　character　of　various　vegetables　as　agents　to　combat　disease。　Here；　of　course；　was　a　rudimentary　therapeutics；　a　crude　principle　of　an　empirical　art　of　medicine。　As　just　suggested；　the　lower　order　of　animals　have　an　instinctive　knowledge　that　enables　them　to　seek　out　remedial　herbs　（though　we　probably　exaggerate　the　extent　of　this　instinctive　knowledge）；　and　if　this　be　true；　man　must　have　inherited　from　his　prehuman　ancestors　this　instinct　along　with　the　others。　That　he　extended　this　knowledge　through　observation　and　practice；　and　came　early　to　make　extensive　use　of　drugs　in　the　treatment　of　disease；　is　placed　beyond　cavil　through　the　observation　of　the　various　existing　barbaric　tribes；　nearly　all　of　whom　practice　elaborate　systems　of　therapeutics。　We　shall　have　occasion　to　see　that　even　within　historic　times　the　particular　therapeutic　measures　employed　were　often　crude；　and；　as　we　are　accustomed　to　say；　unscientific；　but　even　the　crudest　of　them　are　really　based　upon　scientific　principles；　inasmuch　as　their　application　implies　the　deduction　of　principles　of　action　from　previous　observations。　Certain　drugs　are　applied　to　appease　certain　symptoms　of　disease　because　in　the　belief　of　the　medicine…man　such　drugs　have　proved　beneficial　in　previous　similar　cases。　All　this；　however；　implies　an　appreciation　of　the　fact　that　man　is　subject　to　〃natural〃　diseases；　and　that　if　these　diseases　are　not　combated；　death　may　result。　But　it　should　be　understood　that　the　earliest　man　probably　had　no　such　conception　as　this。　Throughout　all　the　ages　of　early　development；　what　we　call　〃natural〃　disease　and　〃natural〃　death　meant　the　onslaught　of　a　tangible　enemy。　A　study　of　this　question　leads　us　to　some　very　curious　inferences。　The　more　we　look　into　the　matter　the　more　the　thought　forces　itself　home　to　us　that　the　idea　of　natural　death；　as　we　now　conceive　it；　came　to　primitive　man　as　a　relatively　late　scientific　induction。　This　thought　seems　almost　startling；　so　axiomatic　has　the　conception　〃man　is　mortal〃　come　to　appear。　Yet　a　study　of　the　ideas　of　existing　savages；　combined　with　our　knowledge　of　the　point　of　view　from　which　historical　peoples　regard　disease；　make　it　more　probable　that　the　primitive　conception　of　human　life　did　not　include　the　idea　of　necessary　death。　We　are　told　that　the　Australian　savage　who　falls　from　a　tree　and　breaks　his　neck　is　not　regarded　as　having　met　a　natural　death；　but　as　having　been　the　victim　of　the　magical　practices　of　the　〃medicine…man〃　of　some　neighboring　tribe。　Similarly；　we　shall　find　that　the　Egyptian　and　the　Babylonian　of　the　early　historical　period　conceived　illness　as　being　almost　invariably　the　result　of　the　machinations　of　an　enemy。　One　need　but　recall　the　superstitious　observances　of　the　Middle　Ages；　and　the　yet　more　recent　belief　in　witchcraft；　to　realize　how　generally　disease　has　been　personified　as　a　malicious　agent　invoked　by　an　unfriendly　mind。　Indeed；　the　phraseology　of　our　present…day　speech　is　still　reminiscent　of　this；　as　when；　for　example；　we　speak　of　an　〃attack　of　fever；〃　and　the　like。　When；　following　out　this　idea；　we　picture　to　ourselves　the　conditions　under　which　primitive　man　lived；　it　will　be　evident　at　once　how　relatively　infrequent　must　have　been　his　observation　of　what　we　usually　term　natural　death。　His　world　was　a　world　of　strife；　he　lived　by　the　chase；　he　saw　animals　kill　one　another；　he　witnessed　the　death　of　his　own　fellows　at　the　hands　of　enemies。　Naturally　enough；　then；　when　a　member　of　his　family　was　〃struck　down〃　by　invisible　agents；　he　ascribed　this　death　also　to　violence；　even　though　the　offensive　agent　was　concealed。　Moreover；　having　very　little　idea　of　the　lapse　of　timebeing　quite　unaccustomed；　that　is；　to　reckon　events　from　any　fixed　eraprimitive　man　cannot　have　gained　at　once　a　clear　conception　of　age　as　applied　to　his　fellows。　Until　a　relatively　late　stage　of　development　made　tribal　life　possible；　it　cannot　have　been　usual　for　man　to　have　knowledge　of　his　grandparents；　as　a　rule　he　did　not　know　his　own　parents　after　he　had　passed　the　adolescent　stage　and　had　been　turned　out　upon　the　world　to　care　for　himself。　If；　then；　certain　of　his　fellow…beings　showed　those　evidences　of　infirmity　which　we　ascribe　to　age；　it　did　not　necessarily　follow　that　he　saw　any　association　between　such　infirmities　and　the　length　of　time　which　those　persons　had　lived。　The　very　fact　that　some　barbaric　nations　retain　the　custom　of　killing　the　aged　and　infirm；　in　itself　suggests　the　possibility　that　this　custom　arose　before　a　clear　conception　had　been　attained　that　such　drags　upon　the　community　would　be　removed　presently　in　the　natural　order　of　things。　To　a　person　who　had　no　clear　conception　of　the　lapse　of　time　and　no　preconception　as　to　the　limited　period　of　man's　life；　the　infirmities　of　age　might　very　naturally　be　ascribed　to　the　repeated　attacks　of　those　inimical　powers　which　were　understood　sooner　or　later　to　carry　off　most　members　of　the　race。　And　coupled　with　this　thought　would　go　the　conception　that　inasmuch　as　some　people　through　luck　had　escaped　the　vengeance　of　all　their　enemies　for　long　periods；　these　same　individuals　might　continue　to　escape　for　indefinite　periods　of　the　future。　There　were　no　written　records　to　tell　primeval　man　of　events　of　long　ago。　He　lived　in　the　present；　and　his　sweep　of　ideas　scarcely　carried　him　back　beyond　the　limits　of　his　individual　memory。　But　memory　is　observed　to　be　fallacious。　It　must　early　have　been　noted　that　some　people　recalled　events　which　other　participants　in　them　had　quite　forgotten；　and　it　may　readily　enough　have　been　inferred　that　those　members　of　the　tribe　who　spoke　of　events　which　others　could　not　recall　were　merely　the　ones　who　were　gifted　with　the　best　memories。　If　these　reached　a　period　when　their　memories　became　vague；　it　did　not　follow　that　their　recollections　had　carried　them　back　to　the　beginnings　of　their　lives。　Indeed；　it　is　contrary　to　all　experience　to　believe　that　any　man　remembers　all　the　things　he　has　once　known；　and　the　observed　fallaciousness　and　evanescence　of　memory　would　thus　tend　to　substantiate　rather　than　to　controvert　the　idea　that　various　members　of　a　tribe　had　been　alive　for　an　indefinite　period。　Without　further　elaborating　the　argument；　it　seems　a　justifiable　inference　that　the　first　conception　primitive　man　would　have　of　his　own　life　would　not　include　the　thought　of　natural　death；　but　would；　conversely；　connote　the　vague　conception　of　endless　life。　Our　own　ancestors；　a　few　generations　removed；　had　not　got　rid　of　this　conception；　as　the　perpetual　quest　of　the　spring　of　eternal　youth　amply　testifies。　A　naturalist　of　our　own　day　has　suggested　that　perhaps　birds　never　die　except　by　violence。　The　thought；　then；　that　man　has　a　term　of　years　beyond　which　〃in　the　nature　of　things；〃　as　the　saying　goes；　he　may　not　live；　would　have　dawned　but　gradually　upon　the　developing　intelligence　of　successive　generations　of　men；　and　we　cannot　feel　sure　that　he　would　fully　have　grasped　the　conception　of　a　〃natural〃　termination　of　human　life　until　he　had　shaken　himself　free　from　the　idea　that　disease　is　always　the　result　of　the　magic　practice　of　an　enemy。　Our　observation　of　historical　man　in　antiquity　makes　it　somewhat　doubtful　whether　this　conception　had　been　attained　before　the　close　of　the　prehistoric　period。　If　it　had；　this　conception　of　the　mortality　of　man　was　one　of　the　most　striking　scientific　inductions　to　which　prehistoric　man　attained。　Incidentally；　it　may　be　noted　that　the　conception　of　eternal　life　for　the　human　body　being　a　more　primitive　idea　than　the　conception　of　natural　death；　the　idea　of　the　immortality　of　the　spirit　would　be　the　most　natural　of　conceptions。　The　immortal　spirit；　indeed；　would　be　but　a　correlative　of　the　immortal　body；　and　the　idea　which　we　shall　see　prevalent　among　the　Egyptians　that　the　soul　persists　only　as　long　as　the　body　is　intactthe　idea　upon　which　the　practice　of　mummifying　the　dead　dependedfinds　a　ready　explanation。　But　this　phase　of　the　subject　carries　us　somewhat　afield。　For　our　present　purpose　it　suffices　to　have　pointed　out　that　the　conception　of　man's　mortalitya　conception　which　now　seems　of　all　others　the　most　natural　and　〃innate〃was　in　all　probability　a　relatively　late　scientific　induction　of　our　primitive　ancestors。　5。　Turning　from　the　consideration　of　the　body　to　its　mental　complement；　we　are　forced　to　admit　that　here；　also；　our　primitive　man　must　have　made　certain　elementary　observations　that　underlie　such　sciences　as　psychology；　mathematics；　and　political　economy。　The　elementary　emotions　associated　with　hunger　and　with　satiety；　with　love　and　with　hatred；　must　have　forced　themselves　upon　the　earliest　intelligence　that　reached　the　plane　of　conscious　self…observation。　The　capacity　to　count；　at　least　to　the　number　four　or　five；　is　within　the　range　of　even　animal　intelligence。　Certain　savages　have　gone　scarcely　farther　than　this；　but　our　primeval　ancestor；　who　was　forging　on　towards　civilization；　had　learned　to　count　his　fingers　and　toes；　and　to　number　objects　about　him　by　fives　and　tens　in　consequence；　before　be　passed　beyond　the　plane　of　numerous　existing　barbarians。　How　much　beyond　this　he　had　gone　we　need　not　attempt　to　inquire；　but　the　relatively　high　development　of　mathematics　in　the　early　histori