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Full text of "The human body; an account of its structure and activities and the conditions of its healthy working"

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l-^ ' Slifi/er Librarians ia pastt sit Catategue Cards. 

NO. — Take oat cutfollj, leaving about quaiicr of on iftdial 
ibe back. To do othciwUe wmtld. In tome oMh, icUosc otber 
teare*. 

MARTIN, H. NEWELL— The Human Body. 
An ALViiuiit of its Structure and Activities, and 
the conditioDs of its hvalihy working, by H. Ncu- 
cll Martin, IJ. S(-,, M. A.,M.B., Professor of Biol- 
ogy in the Johns Hopkins University; Fellow of 
University ( -ullegc, London ; late Fellow ofChrist'* 
College, Cnmhridge. New York: Hcniy Holt & 
Co., tSSi. I^itrgc lamo, pp. xri. 606, Appendix 
33. (American Science Series.) 

HUMAN BODY, THE.— An Account of its 
Slruf ture and Aiilivities and the conditions of itit 
healthy working, hy H. Newell Martin, 1>. Sc, M- 
A., M. B^ ProfesNOr of Biology in the Johns Hop- 
kins University; Fellow of University Collej:;e, 
London; late Fellow of Christ's Colleft^, Cam- 
bridge. New York: Henry Holt i: Co., 18S1. 
Large iinio, pp. xri. 606, Appendix 33. (Ameri- 
can .Science Series.) 

ANATOMY.— The Human Body. An Account 
of its Strui:ture and Activities, and the conditions 
of its healthy working, by H. Newell Martin, D, 
St., M. A,, M. B,, Profe^so^ of Biology in the 
Johns Hopkins Univcrf-ily; Fellow of University 
College, Londim ; btc Fellow of Chri*l"s College, 
Cambridge. NewYork: Henry Holt & Co., 1S81. 
Large umo, pp, xvi. 606. Appendix 33. (Ameri- 
can Science Series.) 

PHYSIOL OGV.—Thc Human Body. An Ac- 
count of it* Structtire and Activities, and the con- 
ditions of its healthy working, by H. Newell Mar- 
tin, I). Sc, M. A-, M. B., Professor of Biology in 
the Johns Hopkins University ; Fellow of Univer- 
sity t'ollegc, London ; late Fellow of Christ's Col- 
lege, Cambridge. New York: Henry Holt & 
Co., tSSi, Large iimo, pp. xvi. 606, Appendix 
33. (American Science Series.) 



rntic 



AMERICAN SCIENCE SERIES 

FOR HlOn SCHOOLS ASI> COLLEGES. 



Tlw priiiciiHi! oliJM-'tii of thisserie« nre to nupply Uio IacU ~-in somr 
tiiliJci'U very great — of aiithnKlalivc t>oolu wliotw prlnfiitlesdrr, so 
fsr OS pnictlfablo, il]ij»lrtii«d by familiar Ami>rlcaii fui'U, and b1»> to 
Bitpply tliu oilirr luck thai ibe aJvunoi- of SticucB iwiviioiuUy cmlce, 
nf icxt-liook« wliich nt Icust do uot conlrrulict Uie )nte*t gnitrsllM- 
tiotia^ 

Tlie ToluinRi arc Inrge ISuux 

The books nn^ii^nil for arn ta f<)!low», Tboy ayMomatleslly oui- 
linu tlie Cc^td of 8c'itnc>-, as lli» \crm Is usually umployi'il with nfpt- 
eacc to general ediiiuaioii. Those markwl * hod b«cu published i:p 
loFeliruary 1, ISftl. 



J. PhuficM. 

By AhtiiirW. Wkioht, Pro- 
ftaaor bi Yulo Collcige. 

ft. CltratMftt. 

liySiMrw. W. JoiiXBttif aud 
WiM.HM G. MixTEii, Venhtam* 
ill Vale Collide. 

By Sixox Nkwcomb. Supl. 
Amrriciui NfttiLknl AliiuLiiar. oud 
l->iH*ARn S. Hiiinr-i, I'rofnww 
ill tkie Unllfd SlBtc« Xntul Ob- 
wrvatory. $3.50. 



PmfciBur ill Harvard Univcraily. 



V. ItotttHii.* 

By C. E. Bembt, ProfeHor la 
tlio Iowa A^rlciiUtinil CoII^h 
■nd liitB l^ciurer In the I'ni- 
Tcniiy of Udiforuiu. $^7S. 



VI. Xoolofff/,* 

By A. S. PACKAnti. Jr.. Pit>. 
fu»H>r of '/.mtUigy and Ocolngy lu 
Brown Unlvri>iliy. Editor of lliti 
AmrHcan A'uCiralt'i. (U. 

ril. Tbr tluiH'iii Jtoflu.* 

By H. Nkwlli. M.ik-ii.n, Pro- 
fi'saor In llip Johns llupkiuii 
Viiircrsily. ♦3.75. ('oiik's with- 
out the Appcnilix on Rcpmduc- 
llon uill be heal vlico specially 
onlereil 



nil. r^i/fjioina!/. 

I' Wii.iii.tu James, 
nrvajil L'niviTJity. 



By Wii.iii.tu James, I'rufewor 
itm 



IX, Potili'^it Kconotnt/, 

By Fiuscw A. Waijibh. Pto- 
ferwor in Ysiii! College. 

A. GorrrHmrnt, 

Bv EuwiK ].. GuuKJK. Edlto^ 
'>f llio A'alivn. 



IlESnV iroLT ft CO.. Pciu-BnirH*. NEW yOBIC 



AMSJiJCAS SVIEyVB ftSJtISS 

THE HUMAN BODY 



iJlf ACCOUNT OF ITS STRUCTUBE AND ACTIVniES 
AND THE CONDITIONS OF ITS HEALTHY WOBKING 



' - • • • 



— _ • • •- 
fcV •■ 



n. NEWELL MARTIN. D..Sr., M.A.. M.B, 

J'Kffwr of IHategg IN tU JnAitf thj^n* Umrrmls : 




NEW YOKK 

HENlty nOLT AXO COMPANY 

1S8I 

1- 



t ,•• • •• : 
- *.* * *. ■•: 



•V 

ncMt U'ii.« « On. 




J. ounwu, 
U VuAfniM St.. X. y. 




PREFACE. 



Is the followidg pagG6 I baro endeavored to give an 
ikcoount of the 6trueturt> and activitiee of the lIunuiD Body, 
which, while iutelligibto tu tUo gcitonl reader, nhall be 
accurate, iiud Kutlicieiicl)' minute in details to meet the 
nMiniremcDlA of studenta who are not makiog Ilunuia 
AnalomjandPhysiolo^subjccUof sp«ciftlmUttDC«<d«ttid7. 
Wherpter it fctrinvd to mc really prolltable, hj'gienic topics 
huvo uIm l>cen discussed, though at first gbu)c« Uier may 
seem less fully trvat«d of than ia miuiy School or CoIIog« 
Text-books of Physiology, Whoever will take the Irtmble, 
howorer, to examine critically vhat passes for Uygiene ia 
tbe majority of nuch c»ses. will I think find tbitt. irheii 
correct, tnui'h of it i» platitude or tniiiim: since there ia so 
roncb that is of iroportsnoe and interest to b« snid it seems 
hanlly worth while to occupy iipaco with inflating on the 
common place or obnons. 

It is hard to writ* a book, not designed for specialista, 
without running the risk of being minuet! of dogmatism, 
and some readers will, no doubt, be inclined to think t Ital, in 
seveiul instaiioos, 1 hare trcatvd oa wtablisbed facts matters: 
which are dtill open to diwnMion. General reiuiers and 
students are. however, only bewildered by the production of 
an array of obwrvatioiis and arguments on each side of every 
quection, and, in the miijority of case*, Die chief reeponsi- 
bility under which the author of a trut-hnok licK u to Mlect 
what eccm to him the best supported views, and then to 
sut« them simply and conciMly: how win the choic« of 
a side has Iwcn in each case can only be determined by the 
discoveries of the futnre. 

Others will, I am inclined to think, mit« the contrary 




■T 

Rnvr Deer A On. 






PREFACE. 



aMout of tite ftncnn 

whkfc. wOb 
accsnte, sdJ 
raqiuKa'ats «f 

Wbvfnerti 

have abe 
cmbIm Uh 
T«zt4»okio( 
h«wow, to en 
th«i mijoatj of mA 
ooneel, mwA •! it • 
mutih ttiAt « rf t , 
hardly wortli *Ui l» 
uoiumna|ilaoe or 

U is hard townto • 
without nmitinx Auid 





fr 



PRBFACB. 



objection, thst too many dUjnited matters have boon die- 
ouitscd : lliU WM diOiboruU'ly <t»ua aetlie re«ult of an expcri- 
eiiCG in teaching i'hj siolugy wiiidi now oxtcndit orcr more 
tlmii ton years, ll would liavp been conifiaratiTely cn«y to 
alip over tliiug» utill iinuorUiiii «ud Bubji'trt* as yet unin- 
vestigated, juid to represent ourlinowlctlgc of the worliingx 
i>f the animal hm\\ il» iR'atly ri>uiidc-d utr at all it« contours 
and compleio in all n« ilt'tJiil*^/'i/M3', Irrci, tl rofutiiitis. 
Itut bf ao doing no adoijuatc idea of the )ii'eaent tilnu! uf 
lilivHiolugical Hoienec noiild have been conv«yod: in many 
ijircetiona it i* much fnrlbor traveUcd and nmro cwm|ilolely 
jinown tban in others; ami. as ever, esaolly the most iu- 
Icresling [loints are lb<>»e whirh He on tbv bouiidury 
between what we know and what we hope to know. In 
gross Anatomy there are now bnt fen- points cidliug 
for n i)tis|iFiiiiinn of judgim'iit; with respect to Micro- 
scopic Anatomy Ihcre aru nioro; but n trwitiso on PhyMologv 
whieh would pn.»>i by, nnnicnliinicd. nil rbingn not known 
but sought, would oonvcy an nltcrly unfaithful and nntrnc 
tdeiL Phyeiology hiu not finishod il« eoui>e: it i» not ont 
and <lnc(i, and ready to be laid aside for reference like a 
specimen in an Herbarium, but is eumpaniblo rather to a 
living, growing ]ilitril, with fionio riUnit and uiieful brandic;< 
well rniaed into the liftht, othera bnt part grown, and 
many still represented by unfolded biulu. To Ihe teacher. 
morei>ver. no jinpil is more diseoiimging tban Ihe one who 
thinks there is nothing to learn; and the buy wlio has 
''finished" Latin and " done" Ceninetry Iind^ nonietimec hift 
eounlerpiirt in the lad who has "gone through" Physiology. 
Kor this nnfnrtunate slate of mind many Text-books arc. I 
believe, much to blame: diflicnltie;^ arc loo uflen ignored, or 
opening vistas of knowledge resolutely kept out of view: tlio 
forbidden regions may be. it is true, too rough for the young 
student to bo guided through, or as yet piithle.^ for the 
pioncer-i of thought; but the opportunity to arouse the rc- 
cc]ttiTe mental attitude apt to be produced by Uie recogni- 
tion of the tart that much morcxlill remains tobeloarnt — 
to excite the esercise of the reasoning faculties u]>on din- 
Dnted mntt«rs — luid. in soineof the betti^ minda, to arouB« 



I 



PHBFAVK. T 

the longing to assist in adding to knowledge, in an ioceti- 
in«)>)c iKlvunUgo, not lu hn- lightly thrown aKide through 
tbfl desiro to make an elegantly sj-mnietrical bonk. While 
I IruDt, tlicrefom, that this volume cMitaiiiiJ all the more 
important facts at ]>rceen1 known about the working of our 
Uodiee, I as earaestlj Jiope tiiat it uiake^ plain that rciy 
much ij yet to bo discovered. 

A work of tbe scope of th« pret*t*iit volume S*, ot conrse, 
not the pruptT niodium for the publication of novel facl«; 
bat, while Pie "Human Body," accordingly, professea to 
be merely a compilation, Uie introduction of i-onstant ref- 
ereuous to authorities would have beeti out of plaoc. I 
tnist, however, that it will be found throughout imbued 
with the inflitonce of my beloved master, Michael Foster; 
and on various hygienic topics I ttavo to ocknowledgv ■ 
special indebtcdneei to the excellent series entitled UetiHh 
Primem. 

The majority of the anatomical illustriitioiis arc from 
Hcule's Ai\atotm« df* Afm/fhrn, and a few from Arendt's 
Jfehuiatl/i^, the publiahers of each furnishing electrotypes. 
A considerable number, mninly liivtolngicul, are from 
Quain's Anatomy, and a few figures are after Bernstein, 
Carpenter. Frcy, Hneckel, Helmholtit. Iluxloy, McEen- 
drick, and Wundt. About thirty, chiefly dingram malic, 
"were drawn s|>coiiJly for tJio work. 

QnnntJticK are throughout ex|'resscd 6rst on the metric 
BTStem, their approximate equivak'nu in Aincrioiiu weight* 
and mcwurcs being added inbrackotM. 



H. Xbwbll Martin. 



DAunMoiut, Oolober, 1880. 




CONTENTS. 



CHAPTER I. 

ntKUKKUULVTRDCTUKK AKDCOMIWatTIOKOrTHS HTOAN 
IIODV, 

■> 

DcAnitUiDn. TiwuM imd orgiutt. HteioloKy, Zoological puui 
ti«ii of inau. Tbe vcrlobnio plaa of struciUK. Tli« ntarn- 
ouiUa. C'beiBlc&l ooBiposiUoB ot UieBody 



CHAPTER U. 



TtlK VVXDAXnTAI. I'ltrnlOLOOtCil. ACTtOK* 

The iwopiTtiai of tlie HvinR Hodr. ritjHologlcftl properilM. 
Oil*. Cdl growtl). ('gII <li(iiion- AMltnilntioD nnil rcpro- 
ductloB. ConlnctilUy. ItriUliiliijr. Cnnitucilvity Spon- 
iMWlljr. PraUifilaMn. Tlie Iuiidiun«ntHl plipiioloclMl proper- 
UM 18 



CHAPTER IH. 



TBB 



tMFniBBKTtATlOX OK TlIK TUHCES, JlX1> THJ! P1IT1W- 

OLooicAt. DirutoH or kmi-i/>tmxxti>. 



UenlopniMit. Tlie pbyiiolofJciU tllvbKin of Mtor. CI&sxIQini. 
tion of llie liMUea. (Ji>illlTur«tiUBi«(l li^wiMMi. Supporiiui; 
lixHir*. Niitrhlirt) UnitM. Storage timucs. Imlnblc llNUea. 
C»onlin.iilng and automalip llniniea. Holor iUsiim. CoDdiiC' 
tlvn livitmt. ProInMiro (i^ui!*. Rt-pmrlticilve li^niM. Or- 
K*iH Pliyirinloftinil Ri(vbiini«iii(. Anniomlrjil syslrmp. Tlw 
Body ei a working whole 86 



Tiii 



COHTBNTS. 



CTTAPTER IV. 



THE rSTBRNil. MEDrCM. 



Tim pxtcrnil meiliiim. Tlin inlomftl miHlinni. Thn blooil. Tli" 
lymph. ilisUilagy of lilomj, IJIixid pcj*«iiiU. Uwlolosy of 
lympb -. 



CIlAPTBIt V. 



TBX CLOmjiO Of THB BUMHt. 



The coagulation of blood. Cuum of coagiilailoD. Whippvd 
blood, Tlip biiffy ctmt. Ubm of coaKuUticoi. Tlio flliiin 
fncton Arliflcul cloL Tlie fibrin fmnrni. Kx^'iiiiig miiscii 
of fougululiim. Itcluliou of blood vtsacle l<i ciin/iihtion. 
Compoxitiuu »t tliv bloinl. Quanlily of btoud. Origiu uti'l fvXv 
of the bVuxl corpuscli-B. Cbuuilauyof Ivuipli 04 



CHAPTEH VI. 



THB aKELKTdX. 



Exo«kel«tou and ondMkelciuu. Tbt- lnniy »kel*toii, SegmMiU 
lion of Ui9 skcktoD. P«culliirltle» of \\» liiiniaii bony akolu 

' ton , 



H 



M- 



f-n AFTER VII. 

THK sTKDcmia kxo co«niBtTiiis ok immik. jomt*. 

OroM Rtruclure of tho hones, Hlcrtwcopic Wniclitre of bont. 
Chcmu-jil mmpo'ltion of bone. Hygiene of Uiu bony akeleWn. 
ArliL-uliiticmi, .loinU. Ilygicaeor ttiejoinla 



CHAPTER Vlll. 

CAKTtl^OE ASD nmUBCTIVB TMSCB. 

Temporary Bud inTtn.iiicnt rnriilimr-t. Vnriutlmi of curllinKT. 
The (^onncetirc li»ucjL Eliwiic curtllo^ nnd ObKhcattlliiKe. 




coyrsxTS. 



]x 



■ of llw mppottin% timnei. Ily^cae of ttw dm'clop- 
AdlpowUwue 100 



CHAPTElt IX. 

THK ffrnccTriiB or tiib motok oitaAm. 

Mntioo in nnlnulii nntl planU. Anupbold cclk CIIlar«(l fldb. 
The muiclc*. Qiilology n( »triiir<l niiitrlc. Untlriiicd miit- 
du. Cnrtlinc munrula)' tiuuR. Tbc chumulry of niuncular 
tiiaue. Bcvf'teaaud LJebig'«cxUw:l UK 



CHAPTER X. 

THK Piioi-KKTiKd or Mi-vcxxjut Times. 

nbucliltlir. Irritnbtlilf of muscle, A simple niuKulnr oou 
iTU-titm. Ttiianiis. Ciiiuis ludui'iicin^ the depeeof mascii- 

larconlrnrli'Mi Tlio nuMUnancnl of muKnilnr work. Hvib- 
Ciilar rl ax lie it]'. I'liyxloloiQ' of pl^n muMTiilur liuue. 11}'' 
gi«no of Uii: niuxcles. Kxcrclao 13S 



CHAPTER XI. 

IKmOK AXn LOCOMOTION. 

[it special plifiioiogjr at miuelos. Ia-tits in thn Body. The 
•net poatuni. Walking Runolng. ]j.>pitig. U't 

OHAPTEK XII. 

TSB AXATOUT OF TltX XBRTnCK KTirmi. 

Nerre-tninkk Ptextiw». Jfervin;entrea. The cpivbro-sphi^l 
coBin arid lu tHcmbriiDO'^ Tlis tqilonl coril. Tlic cpiiwl 
norrofi. Tint brain TbnoranW ncrvp* Guoglia tuui com- 
municatioii* of (he mninl iktvch. Tbc nympalbetic tytivai, 
T)i« Kponulic giuiglui. Thi! liiiUilogi.' of nnrc'fibru. Tliv 
tiittolagyof ()ervc.c«lU. Tke siniciura of lli« (>pliul con! 1*>4 




(•OSTBXTS. 



CHAPTER xni 

Ttui dUiiuiAt. niratoLooi av ttik nriii'oi'* imTRM 

The pniiiiTlii'S ot uervi- lisdiiH. TIxe fiuictions of Dcn-e-ctnlivii 
nod iiiTVi: iruiilu. KxciUiil &iid tiiliibiTory nvrvcs Tbe vlus 
Hiflcation of nerve illwv*. Inii-rt^eniritl iU'rveHlm's. Tint 
slliiiiili of nnrvcB. (irn<Tnl nnil special iicnf Wimiilt Speclllc 
Dcrvc cnprj[ips. Alt n<'rTt-lilir<*' aiit tiiiKhunentnlly alike. 
The iiAtiiro of n arrviim impuiM.- Tlin rale of lRuisinii«iOTi of 
n n^rriiua iiupiitiie- Fiinctiniiii «f Ihii Kplnnl nerrc-rooU. Tlie 
tnIcr<:onuQunica(i<]D uf ucn'iM.'mtns ... I>iO 



CHAITKH XIV. 

THS A»ATO»Y OP TItK BKinT JiKD BhOOV iriaMBlA 

General otaiemeot. Portion of ilie hcan. Tlie nicinbnuief of 

llin lu-jirl. Tlio rjtrilir* of llio hrwl. Tli« lirtirl h* vicwnl 
ftiMinUt! oiitsiilc The iulcrior til llio litfiirt. The vulvua of 
llio li-.arl. Thv uitcrial Rj-^Ivni. TIid eniillisrirs 1'bu vuiiiit. 
The pulmonary elreiiluiioii. TIh' course of the blood. Tlie 
pnrinl eiieiiiailon. Arterial nnA voii(iu« blood. The sirucluiv 
ofnrtcriu»,cji|ullarics,and mux MI 



CHAITER XV. 

TItB WOBUKO t\V THB mUlIT AXD BLOOD-VEMBU. 

Tlw bent of llic lienrl. TUt'Coidiae inipul tu. Events in u tardiAc 
porfod. Cm of ibe papUlury miiwlcs. Sounds of Hit- hean. 
PuQCllonof Ili«&iiriete*. Tlii- work done! Iiy llto liciiit. The 
blooil Bow outdila llic limrt 1'be circuliiUun iw iwnn vrlih 
(bo microscope. InlernnI frieiion m Uu vsaeh. Tlic cnnrn- 
xion of iinlnlermillent inioacoiiUnuouiftow S19 



CUAITEH XVL 



AHTSIttAI. FllE»>l<R& ASn TRK PrUB. 

Wobor'a MlieiniL Aritrrlal prewur^ Mmlrticaiious of arterial 
prcmnrc. anil how lliey mnjr Im produced. Tlia pulM. Th« 



COA'TSyTH. 



nte of tbe blooddow. Bnettnitaj tmtm of Uw dicul&tloo 
ProoboftbecirculaiUiauf the blood S83 



CHAPTER XVII. 



Tint RKfitTij^nax or tuk ntunr akd iuxwi> tkioxui e* 

Tlie »i:itv<>i'H nVHTRU. 

Tbe need of coontloatioD lo ilio tsMUl&r system. Tbo iotrliulc 
uctrra of llir' licarr. Kervcs Hhnwinj; th« liunrl't Ix-jit. Thr 
cardlo-iohilijlory niorbaniun, Tbir nrcclcrntor unrvci of llio 
hrari. Tl^l^ timrs of llwi blood -rcmml*. Tlie viwo-njntor 
oi'iitre. 'I'ukiiis coW. \'a«><lil»lor nerve*. 347 



CIIAPIEK XVIII. 



TMK HBCKKTuny TlwrWi AMD OKMAXa 



DeflaitioiL Orgn&sof flecrvtlnn. OlaiidiL niy^irnl processn 

^tll wrrelioii. tliotnickl p[oc«<9c* In *i!rr«llon Tlin mode of 
lu.tmt)' of twcrelory ccll.-t. liiltviciico at lliB nurvoua ayMvm 
upMi tccrelloii. Bummvjr 
Tlu 
n 




aM 



CUAlTKIl XIX. 



mk ixvoiMii ASU Kxi'KxniTt'RK or tiik bokv. 



The maleriitl ibiljr I'vueii of the D01I7. The <tniiy liiinr* of tbe 
Body In piiiTgj'. Tlu> nmSFTraiiun cif cncrj^v. Pniinilul end 
ltlo«llc«ovt);y, Thv c rn'r^^* ut tlii-ruicnl nlUiiily. Tlii.- rrlutiou 
Iwtmni inaltM' l<rtl by llie Uodyduily and Ilie vimgj' ^pl-Dt by 
It ThDCondltloosoroxUliiii'in in ili« liviu); Boily, TLcfiiel 
(if iliR Body. (lildAilnii by racri'^slvo *lnp>. Tlio ullliuibn 
of eoo^ in the living Body. Siimtniiry 



A 



}P 



8T7 



CUAPTER XX. 

Pood* •* tiwu»'fonD(-n. The food of pliuiln. Kon-»xtdi»b)o 
(ooda. PuAoitton of fuod*. Oondiiinns which n food must 



■ J 



zU 



COAJ-KNTS. 



ftiTAII Alirneatnrjr pllBd]rfe& TIip romrHwUinn of ihn niorv 
iiiipurUit\l tUDcJs. OooklDf. Alcobol. Thp nrlvnnt.-mc of n 
mixed diet S«3 



CKAPTEB XXL 

Tim AUMKXT.VUV l-AKAL A»l> IT« APPKKIiMiEn 



Qcnerul amnsetneut. Tbi- tvcib. Tbe ton^o. Tlic wllvAry 
gUnds. Tbo fauces. Tim pbarynx. Tli« guild. The 
atOBnoeh. Tho fatetolngy nf ilic gaitrlr glnndik Tlic Huall 
jntcKtiun. Tlio large iotcilim' Tliu livi-r. The paucreas . - SWB 



CHAHTEK XXII. 

Tint I.V1II>TUTIC B'ntTKN ANI> THE UVCTLKHS OL.UiM, 

DislribulioB luid elritcluTC <>f iynipb vivavb. Tlic lltanHric duct. 
Tbu wrf'iwciivUira. The lymplmili; kIiiiuIh. TIic mnTemcat 
of ihn lympU. The hiiIrpii. Tim ihvniut, Tlie lUyroiil body, 
Thevupni'ranNlcapiiuIci 32!) 



.^ 



\\ 



t'HAPrKu xxin. 

Tbe object of dlscslion. V*e» of Mliro. Dc^ftuliiioii. The 
gastric JiiiiM!. Ganlriu dlj^wiion- Thcdifle. Tlio pancTcutic 
«nrrvtlon, Tbo bllr, Tlic itid-bllnul Brrrolii>:i« liilntlinal di 
l^iinii. Ab*orpiioii from the iatc*ltnw, Tlio dlgcslion of an 
ordiuurjr niriil. Dy^pepim. SM 



^' 



CHAPTER XXIV. 

TItG RGePIRATORr UBCHAXKN. 

DvUnitioDS. Itcspimtviy orgnaik Tlic iiirpacngM uiid tvtag*. 
TliL' pkura. Tbe n-npiniiiiry mowiiciiPs. The wiructure of 
tlie thorax. Tlie m(.'('h4iii-'ni of iimpiruiion. Bx)nnitioii. 
Ftorc«d rc«plnitinii, Tlio rvHinralor^ souuds. Thi? cai>arlly 
of iho luugH. Il}glcii« of rc^plialtnn. TIk asptmtion of lIll^ 
tlinrnx, Inlliiriic^ of ro4plrnliiry ninvi-nionln Ui>oii Ihr Ai^u' of 
blood and lymph 3.t:^ 




GOSTBinS. 



ZU1 



CHAPTER XXV. 



TUX cmEHtsntt op nxsriitATioii. 



fatuTcof tbe probk-nui. Cbsngi-s produucil m >ir bj- btittg odcc 
ImkUwd. V«itiliiti<ni. Chaaxen undetgninu by blood in tlia 
Idbxh. 'ibi! blood gnSRf. CnasM of wlor Of UTierial aDd 
vcnoiu tilood. Ijiwi gnv«Tciiig Uic ftlnorption o( g»u-s by 
liqutiU. Tbc nliMirpUoa of oxygm by tlie blooit. Cuaw 
quiiuct!* of itac way iu irhicb o.i.vguo b huld in Hit* blood, 
Tlie general oiys^a imercbaiisiB of ibe Mood. The t^arbou 
dioilde of Ui0 bJood. ]iii«ruftl rc^iiimtloQ .,...,,,,..,,.. 



CHAPTKR SSVI. 



TiiK }CKHv<itiii rAcraua or tiir mkniiutuht mbchaxism. 
AnriivxiA. 

Th« resplraiory ceiiln), Is the rwipiratory cenirc Mlliit? The 
■timulufl of Uic rcBpirntoiT cc^ntrc. Tbc- cniuc of ibr ruptm- 
Wrj- rliyibiri. The lulluenee (if lh« |>u«umuga8lrk' it^rrM upon 
ibe rRi|iinitory c^nirr. Tliu cx|)ir,ilorj' cfuliv. Aspliyxin. 
Oarboo moDoxidv bwEaogtobia. Uodilleil rraplralnry moTc- 
meou 390 



f 



CHAPTEK XXVn, 



TRK XIIMRrS X»0 TRK SKID. 



b 



!i* it«n«Jai arntngvnxiit or ih* iirinnrj orfnn* The MracluTe 
of lli« kidnryt. "niu rcnnl wcrclinn, Tiic nurluniiuii of Uic 
n-naliiwTi'lioii- The ftinclioa of ihn rwial epiiheliuni. The 
Mkin. Epidrnnis ami culU vL-ra. lUini. NniU. 01ai)[hnf 
ihp akin. llL-UUon ot oenrua lo mal wciviion. llygicoe of 
ibD akin. Bathlsg 4M 



CHAPTER XXVni. 



KCTitmnx, 



Tlw pioblema of animal milTllton. The uat of lb« oxktatioiu of 
llio Bod)'. Tiamo-lKUictinK nnd roorgyylcldin^ foods. The 
BMrooof (ho energy aptfnl m muscular work. Lukua ton- 
9Uinpti(in. The nntcccttmla of iiroa. Proleld riarralion and 



k 




x3t C'OAr/fATS,^ 

FWIB 

onr-tedliv. Tin! Hioragc tiniMia. Glycogen. DialMea. Tlie 
UeMjr of fata. I>ii!iviii:!i 4-£i 



CHAPTER XXIX. 

TBK niODUCTrOOl AKD aKOrUHTIOH or THE HBAT OF hib 
BODY. 

Cold- and wMTin-lilMMlvdaiiiraals. The tempuraturcot the Body. 
Tlie souTcea uf animal heat Energy lo>'[ liy tlic Body fa 
twcBiy.four Loiira. The guperkirily of tlio Bnily a* n iiinnhinc 
for eitcuilng mc47hnni''Bl work. The imunicnance of an 
iivorigo [emjioraiiirp. l.oc»l ti'mpcniitin-A Tliwniic ucn'ftt 
Clothing , <W 



CHAPTER XXX. 

^miTIOH AXD KBltl»UIWAKB, 

TliL' subjuRlir« functions of ll>o norvoii* apiiimi. ('oinmiin tea- 
Kitiou iitidorganii of uprciul t«iue. Tbc ptrnplicrul ieri;ri.-nci; 
otwiiMtiona. DifTervncci bvtweeii iiciisailotis. Tlic CMWiitinI 
structure ot a suuiw organ. TbocauMuf llie modality otseiiM' 
tloDi. Tliept)'cho-pIiysi<alla<r. PoivupHons. Seosory lllu- 
■iona 401 

OHAPTEU XXXI. 

TIIE XTR AR AX omcAl. tKtrTUMXKT. 

The cmwiiliiil !ilructur« of an oyc Ttv apppndo^* nf the oyc. 
The )iic.-hr}'Diiit npiinrntUH. Tliomuiclca of tljec.veball. Thu 
iiiiHidini of the eyeball. Tbi: .ilructure of the reiiun, I'hc 
irfrni'tiiiji; tiicdiauf Ilii.'1-ye. Tlw [iruiwrtiea of llgli'. Accv)m 
modailon, Bliort gljihi and Ion; »ighl. Hygiene of ^lu. 
Optical ilcfccUof tliccyc 479 

CHAPTEll XXXII. 

TlIB RTB AS A fiP-<<»onv APPAHATra. 

The eicitsiion of llu; viitual apparatus. Idlo-rolinal tiithL I'ke 
parta uf the retina on whlcli liidti directly netii. Tht! vision 
purple. Intonallyof rbunl icnailion*. Diiraiion of liimlnoun 
senanilons. Tlie localixixg |jo«»er i>f Hie Totina. Oolor vlaloii. 





coxTisxTS. xy 



OolOT bliiulneH. F«il![ue of ihe rrtlna and aft^r-tiiuigM. Com 
Iraslii. llfrinK')' tbmirjof riaiou. Vlmal |)GrG«pIioDS. Sln^k- 
Tialon wiUi two cycD 600 



cHAFrEB xxxm 

Tine RAR Aiea iika]iix4i. 

rUo external aa. The ij-mpanuin. Tbu nudtlary oMirle*. Tbc 
luUTiuil RW- Tbi' aiptn uf (^rlj. Tbd Intidmrsa. patch, tuid 
(tHit'v of KouodH. %tn]Hitlii!tic niaotuinci'. Fuuttions of ilw 
tympantc inembnum. of ilic uiiditoiT' OWicI». at Uw cocliltn, 
ud »I Uia T<«LiliuIe. Auiiitur}* percepUons. W 




CHAPTEK XXXIV. 

TODCn, TKB TCMPEIUTUItB fiB^BE. THE ML-SCUI^Il 
COMMON tURaATIOK. fiUBLL, AHD TABTB. 

[«rTft«ndit)|t« In Ihi- »kin. The prctsuro smisc Tlie locftlixiiiit 
power of the ikiii- Tlic tctii|>rriitur« Mn«c. UoiLtlilj <i( skin 
wnution*. Tli« muaculu* wenw. I^in. Hunger and iIiiibI. 
HmuU. 'ftaiu 5M 



I 



OHAITER XXXV 

Tint riTscTWfin r>if nnt iuuin axo spiSAr. ooBn 

The KpM'iiO |i]i}-Muln)t<k' of ivrrrc-cenire*. The ipiniil «>t>l m ■ 
MDlrv. ItvQi-x uclioun. Tlii- liait-rvainlunci' Iij^pothiujs, Tbc 
iwliicalluii of Uie spinal nml The inliibiiiin of rvltrxc*. Psy- 
(.'bical fttliffilica of tho rnnL The coril an n tvndnetor of 
nvrvinut itn|>uWj>. Fuarlioiu of IIht )>r«in in gcncml. Kunc- 
lion* of nicilalln nhloni^tii. runritonii of ccrflwlhim. pons 
Vnrnlli. luid mul-liraln, Scn>inlii>n!i of rqiilliliriura nnil fiinc 
lton« of •emicircular rannl«. Piinriion* of the f on- brum 
Hjgieoc of the brain "'I 



CHAPTER XXXVl 

TotOR A!in apititrn 

■ of larvDX. Thp vneal «mt«. Caiiwn of the paryiBg 
pitch "I il«- Tolc<', Itnniri? of llie hmaan voioc. The ptoiluc- 
tlolt of VDWoU, Cnnaonanla • AOS 



xn 



(WAT^A'TS 



APPENDIX. 

BltPRODCCTtOlC AKD DKTKLOPUEKT. 

Ri-producUoo in geneml. tk'Xual nnd iim-xiikI rriinKliiction. Mak 
niproducUTe orgaua. Fftiuulo n-produclire o^i^ln^ Piil»-riy 
Ovulatiuu. Mciisiruatlon. Hygiene of mfiinirunUoii. Imprrgua- 
ilOD. Prcguanc;. Tlio fecial appeiula^r-i^ 'I'lii- lDira-ui«riue 
DUIrllion of tli« rmlino. rnriiintinii. t^aclaitno. Fwdln^ of 
inbtnia. Ttieaiageii «( life. Dcoib. 



THE HUMAN BODY. 



r 



CHAPTER I. 
Fthe oeneral structure and composition 

OF THK UinHAJt BODY. 

DeflniUoDS. The llring Imman Bndy may be considered 
from eithiT i>f two aspects. lu xtmutarv tun}' bo eepecinl- 
ly «XHiiiiTic<), HiiJ llie fornu, otmncciioiiH nixl mmU of 
grovlli of ilH jiiirU bo stadied, as nUo ilie m^^niblitTmA or 
differonocfi in eiicli rospocU, w)iicli njipcjir wh«ii it u «om> 
{Mrcd with oth«r mitnnl bodice. Or tlie living Body may 
be more especially studied a^ an organism presenting deS- 
nite])r<>|HTlic«iUKl performing certjiin itctionx; wid then it^ 
paru will be inredtigutcd with a riow to discovering wbat 
dnty, if any, each fulfills. The former group of etndiea 
Conirtitalo^ the Acieiicv of Anatomy, niul in s>i far as it deals 
vith the human Uody alono, of llutnnn Analomtf; while 
the lallcr, the Hcience conoomed with the uses — or in tech- 
nicid Unguage tX\o functiona — of «:ioh part i» known lu 
rhyiMopy. Closely connected with physiology is the 
acteiK-o uf lltigXfnf, which is concornwi with the Donditions 
whioh are fui oiiiblo to the hc^ililiv iictinti of the vuHoiik 

■Ut of the Ilo<Iy ; while the itctivilies and structure of the 
diseaa-<l body fonn the subject -matters of the itt^ience^ of 
Patkalo^fl null Piithnhijical A natomi/. 

Tiaauea and Organs. Histology. Examined merely 
from lite outride, our Uodic« prcj^cnta con»idi.>mhlo com* 
plexlty of structure. We easily recognize distinct parbs u» 
liead, neok, trunk and limba; and in those again smaller 




THE JiVHAS BODT. 



OUQstitueiit parte, oB cyea, dosc, ean), mouth; anu, fore* 
ttrni, hand; thigli, leg uiitl foot. We urn, with rooh 
un i;xtt.-ni»l «xiiiiiiii»ti(}ii, go even farther luid rccugiiiee 
differeut materials as eutering into the fonnalioti of the 
larger parts, ftkin, hair, ttailit and toeth are obvioUHly 
different »iibi<uiii.v»i ; t)im|il« ciiuninution by preGsare 
proves that iiiutnially tliera are liardoi' and euftcr i^olid 
parU; while tlio blood that Bowa fi-oni a cut fingvr I'liows 
that liqttid cotutitueat^ also exist in the Body. The con- 
(■cptiou of complcxilv, which may be thus arrived at bxim 
cxterniil "bwrvulioii of the liring, \i greatly extended by 
dissection of the dead Body, which makes manifest that it 
coDusti of a i^at number of divert purU or vrgant, which 
in turn are built up of a hmil(4 number of muli-rialM, lh« 
same material often entering into the com|)OBition of many 
different organs. These primary building materials are 
known a* the tissues, and that branch of anatcimy whieh 
Am\» witli the cbaract«ra of the tissues and their arrange- 
ment in varioai organa i« known aa Histology; or, since it 
is mainly carried on wilh the aid of the microscope, aa 
Mtcroncopic A'tatomt/. If, with the poet, we compare the 
Body to « house, wo may go on to liken the titsiios to the 
bricks, stone, mortar, wood, iron, glsMi and so on used in 
Iwilding; and theu walls and floon, stairs and windows, 
formed by tbo oumbinntion of these, would aoiiwer \q ana' 
tomical orpins. 

Zoological FoMition of Unn. I'Utemal examination of 
the hnmiin Body oliows hIbo tbiit it iircKoiitj* ix-rtain re- 
*einliliiiiiHi« to the hodiM of many othor animals: bead 
and neck, Iniiik and limbs, and vuHooe minor pnrt« enter- 
ing ijito thein, are not at all peculiar to it. Closer gtudy 
and tbo investigation of internal straotnre demonstrates 
fnrthor that thc-»o rfwuibltmces are in many caaes not 6U- 
perlicial only, but that otir BodicM may bo regarded as built 
Bpon « plan common to them and tlte bodies of many 
other cretiturv«: and it soon beoonica further api>arent 
that this renentblaiico is greater botneon the human Body 
and the bodies of ordinary four-footed U-asts, than U'lwoon 
it BJid the budiea of birda, rvptiles or fishes. Ueaoe, from 



TBS PRUHATBiH. 



8 



a MK^^mI poini of rtcw, iniu)'ji Bod^ ntnrkK him mil a« 
belonging to the group of Mnmmali;i («* Jioolufty), which 
includes nil uiiimuU in vliidi the funiuk'KiukU'!! Ihc jrouiig; 
ODft among niaminalA the nnstomWI resoinhUiiioos are 
closer aDtl Iho dUTerencejt leas botwoeu man anil ccTtain 
npe« than WtH-tt'ii umii untt ihc other mnmniiils: i<o Uiat 
xooI'''^k1ji still, with Jjiniiaiaf, include mnn vith the mou- 
keyA and upos in one HnbdiTisioa of the Slummidia, kaowa 
US the Primatti. Tliut oi viliMtd miin 'a mcntiiUr fnr superior 
to aoj other animal i^ no ralid objociion to such a cUasifi- 
cation, (or zuologicaJ jjronps aro dcliiird by Boatomioal luid 
not by phvRlolugioul cluiriu^tcnt ; and mental Iniite, kiuco wo 
know that their raanifeetation depends upon llio »tmctuml 
iutegrit; of certain orgun^ arc eesontially phenomena of 
fnnction and theraforo not available for {lurjweoa of zo- 
ological sfTangemeot. 

Slaii howvTur walkM eroot with tho heiul upward, while 
the great majority of ManimaU go on nil fount willi th9 
hoad forward nnd tho bjitrk upward, and TArioos apu 
wlopt lutormediato piwitionn, to in conridoriiig corre- 
sponding ports in euoh coaes confusion is a])t to arise 
unless a precise meaning be given to such tenuB as "an- 
torior" and "posterior." To avoitl tlii^ diilloulty tuiato- 
nitsts give these words definite arbitrary eiguilications in 
all ca^-s nud these ve ebul] vtna in future. Tlio liond end 
is alvaj's anterior whatcYcr the natural piwition of llw 
animal, aud the n)i)ioflitc end posterior; tlie belly aide is 
epokon of iw rentrtil, and the oppi>cilo siilo as dorttil; right 
and }f/t of course prownt nw difficulty. Slorcovor, that 
vud of a limb iieaivr the trunk is iqwken ot i\a prinimai 
wilh ivferenco to the other or di.ftiil end. The words 
uf'P«r and lover may ho conveniently used for the rehitive 
iwaition of [turtM in Uio natural trtunding jKiititiou of the 
animal. 

The Vortobmtffl Plan of Stmctore. Xes'lpetinp such 
me;vly aii|mri>nl dilVn-iiir* ji* ariKe fr>tm the dilTcninoeK nf 
iionnal posture alxive pointed out, we Hud lliat man's own 
xoologicul clttef, the Mammals, differs very widely in its 
broad atniehiral )>Ian from the gruui>s inoluding aca anem- 




TttE auxAy Bovr. 



one«, inmoU, or oyaters, bat agrcca in nuiny poinbt with 
tlid gi-oupa of liahee, amphibians. Kptiles, and birda. 
Thcfio four Hre therefore pW'c<l with miiu and idl other 
Mummals iu onn gnutt division of tlie animal kingdom 
known aji the VerUhrnlu. The main anafom!cnl characier of 
»ll rcrti'lirnlp aniniulH la tho prcKi-iicu in the trunk of llie 
body uf two cavilicii, a dorsal and a Tentral, separated by a 
solid partition, and in the itrlnlt« of nenrty all vertebrate 
i\n\mi\\fo.\\i\rA.ftx\»,lh^vtrttbral<olHmn{backhon«ort^ne). 
dCT('l(i)H in thiii jiartition and fornix a ocntral iiup]>ort for 
the rest of the body (Fig. 8, e t). The dorsal cavity is con- 
tinned through tho nock, w)ion tlifrv i» one, into the ItDitd, 
and there widenii out. The bony asis is also continued 
thronjth the nwk and extends into the head iu a modifiod 
form. Tho ventral cnvitV) on the othur bniid, is confinc<l 
to the trunk. It contiiins the main organs connont«d with 
the blood'llow ftad is thus oft«n called thf hamal cavity, 

Upoa tho Yoiitrid side of the he«d is the vwHlk opfn- 
ing leading into a tube, the alimentary ennui, /, whicli 
posses back througli ttie nock and trunk and openii again 
on the out-^idc at the poatorior |inrt of the Uittor. In itit 
pasiBgo through tho trunk region this canal lies in the 
ventrul ciivily. 

TbeUaounaUa. In many vcrtchmte nnimalx Iho ven- 
tral eavity is not subdivided, but in the Mammalia it ie; a 
motDhrauoits triknevente partition, the midriff or diophra^n 
(Fig. 1, t), separating it into uii anlorior cht*t or Ihoradc 
caviftf. and a posterior or abdominal cavity. Tlie alimen* 
tary ciuial and wliiilcvcr else posses from one of tbcso cavi- 
iint to tb« other must therefore perforate the diuphmgni. 

In the chest, bojiideii) ])art of tlio alimentary canal, lie 
important organs the hearl, h, and lun^it, In, the lioart 
lieing on the ventral ride of tho alimentary eiuuil. Tlic 
abdominal cavity h mainly occupied by the alimentary 
canal and organs connected with it and concerned in tho 
dige«tion of food, as the ttomaeh. m/f. the Urer, /<•, the 
pancreas and the inli'sfinfs. Among the other more prom- 
Ltient organs in it are the kidney* and the spleen. 

In the dorsid cavity lie soft white orgiuiH, the h-ain nd 



TITK .VAUMAUAX TTTB. 



^HoJ cord, the rormer nccupying; iU auterior entargemeul 
in tlie head. Untln and spinn) cord together form the 
iserfttro-npiiiai H^rmua centrr. hiil iti iiildit.i»n i<i lW\» then^ 
HTo found 111 thi* vt-nlnil cavity a niiuiber of ^mall uoi've oen* 




•how till) oonCmla o( lla Tentrnl 



trw united together bj- couaecting cords, and with their 
offithoots forming ilic ittfinpathttie mrvou* 9tf»t«m. 
The vails of the three mnin csTitieaare lined by ntnooth, 





« 



TttK HVJfAX ROD 7. 



m:-^ 



0—3 






moiaC xeroua mtmbrant*. That lining the donal ceV% 
is Uic arachnoid : that lininjf llio cfiv»t iliv pimra ; that 

liiiiug the abdoineii tlio perito* 
Tuum : tliv K)xluniiuul carity ie in 
coiiwiiiK'iJi* ofl<-ii cjilk-d (lie per- 
itoneal cavity. Kxtcninlly the 
Walls ot these cavitiod are oorered 
bj the fki», whii-li cotiEiste of two 
layers : an oiitvr Imrn y Uyc-r iiilW 
tlie epidemiif, whidi is constantly 
being »heil on the i;urfiic« and rc- 
ucw<-<l fRiiD bulu«r ; ui)d u dvcpef 
lfty<'r, I'lilied the lUrmit and con- 
taiDing blood, which the epider- 
mis does iioL Belwccn the tikin 
and lUe lining wcroiis mcmbrantw 
aro bottti, mutelM (the lean of 
nil-Ill), luid a great niimhcr of 
other structures which we shall 
have to consider hercKftor. All 
cavities inside the body, il>i the 
alimentary canal iind the air ]>a8- 
aages, which open directly or indi- 
rectly on the furfiiCL' are linid by 
Doft and moist pix-Iuiigiilionit of 
the ^kin known a^ nmcova mem- 

._ _ ^ .. I _. hranet. In tbeee the eatuo two 

ndiaai ■HTiioiiuOhc bod^ a. Inycrs arc fonna a« in the ekin, 

lli« neural lulit, ultli ti» irnpi-p , '. , ,. - . i i »i 

MiliinrMUi^ni ill u.r kkuil cnviiy lint thc iniiieificml bloorfless one 

i*t fl'i A\ t}ir< ft*iiiM I'oi-d; ,V. . ,1 * .,t t' t .1 I 

ihff iinun, ". \'i.'i.iw tiToi iBcaJJed epiuieiiHiii and thc acep- 

tbs dan»l ttDd immUwiun' <^^r onc tD<' CWIHUI. 
^l^iSZS' ",trv';^^';'rv: I>ingran>matieally wc may rep- 

IJ-SS^S^uS^r- '"'"IS recent the human Body in longi- 

Sr'i^.3,5 t"hS4'"!i.^^r t»din..lm-H.m.i«i»Fig. «. where 

pbiuTiii from whlcli oar lube an' i-' tilt' (ii>rsal Or NFUrtll ftll'UVi 
Iculi [i>(hDluii>:t,l.BiiaMiouifr , , , ... 

i„ ih.' i.ioi.iiiti,, /; *. uw iK^M; luid And c, respectively, the 

t, ■ kirlnfi'^ >, lliv KnnpaUMiJo ., i i ■ - i ■ i- ■ 

nprvoiw vbniii rramxfietuaa- tlioriteic and HUihiniinHl i^nbdiri- 

m4l /. Ibo iQtcMJnAl lube IdOhI* « i i . i ■ . t 

UunuchibDktKtamiD*] «•*!■; in MOH* 01 the vontral cavity; a rep* 



OBOSS-SECT/Oy OF IBS BOOT. T 

them; m \* tho vert«bni] colnmn with it« niodJBod prolon- 
gatioR into the head beneath tho untorior cnUrgeitieiit of 
the donul curitj; / is tho alimeDtary canal opening in front 
through the no«e, i, und month, o: h a the heart, la lung, 
a the Bjtnpatbetic D«rToiui Rjsteni, and it » kidnev. 

A tninsvcrsf section (hrotigh the chest is rcpreeented 
diignunniaticall)- iu Fig. 3, «hen> x \» the neural canal 
coataining the epinal cord. In the thoracic cAvity are seen 
the heart. A, thv lungs, U, part of the alimeiit;ir-v ftiniil, a, 
(ind llie Hympathetic nerve centres, ,«^; the dotted line on 
each side oovcring tho inside of ihc cheat wall Mid the 
outride of Ute lung Te|>re9eni4 t\iepltHra. 




rn, t.— AdlaoiunraaUa fMdon MtT«*lh* nodr In thi> r-hM rcKl'in. j, tho 
iliii wt [iilii . fmeb oamala* th« mliul cord; thf black nit» •niToiiii'lInK l( In 
a*Mttbm: a.ih«irii11et.«i«rtoflta«aU[iicDiAr7o>niLl; fi, Uwhsan; «v. q-m- 
puhMIe uarmuii nnwin; II. lane*: (ha dotiM lltiu utkukI tOont uv> Uib 
ptranti rr. Ttlw; tt, Qtf imastbona. 

Sections through corresponding parts of any other Sfsm- 
mol would agree in all eneotial pointA with those repre- 
nonted in Figs. 2 and 3. 

Tho Iiimbii. The limbs present no sncli nrmngemcnt of 
oavitiei on eaoh side <'t a tmnv axis ».t is ^een in the tnink. 
They huTe an axis formed at diQerent parts of one or more 
bcniM (m e«en at U and R m Fig. 4. which represents 
a oron-section of the forwinn near the elbow joinl). hut 
around this are closely packed soft parts, chiefly miiscleii, 
and tho whole is enveloped in skin. The only cavities in 
the limlw are branohing tube* which are lilted with lirjuids 
,dn*iDg life, either blood or a watery-looking fluid known aa 
Ijf^ph. Thc«e tubes, the blood itn<l h/mph t'M^cb respoo* 



8 



TBB HUMAN BOOT. 



tiTely, are not however cfaarscteriBtic of the limhn, for thvy 
ftTO pre^nt in itbutidaace in the dorsal und ventral carities 
and in t-heir walls. 




St».4.—AttCtiaB KTo™ thi' forMmi II tjion dlnance below thii dliowjotot. 
JtUkd 17, Ms two ■HpponlnK ^•mi--. ihn nuliwia iilim: t tb<> Fiildnniilit. uxl a 
tlwdmnlf or Uieafebi: LliolaU«l>ooiiHDiiniiil».l')»wlUib»iiitaof oonnrcUTf 
Hmup, (. Hhleh peiMtnto IwIvcpd tot Ininit the mu>ct««. which ore Indmud 
by numben: n. n. niuvm luiil masbk 



Olwmical CompoaiUon Of the Body. In addition to tjiu 
study of the Botiv as (.-'jmixisi'd of lif-siies suii orguns wliicli 
are optically recopiizable, we may consider it as compoeed 
of a number uf different chemical ftiWtaDccs. Thix branch 
of knowl«dgi>, vihich is *lill very iii<riirii|iU'(i>, rtally prce«nt« 
two cUi«8GS of jn'oblpins. On thr one hand we may limit 
ounwivca to the examination of the choniiail enbEtances 
which exi^t ui rir ni»y bo derivod from the dead Body, or, 
if such a thing wi?ro possible, frum tho living Body entirely 
•t rest; Hncli u study is o^Mcnlitdly (>ii« of siructare and 
may bo called Chrmical Anatomi/. Bnt as long m tba 
Body is alive it is the ev&t of constant chemical tranit- 
formationH in ita mntcriid, und thcKC are innpArably con- 
nected with its function!!, tiie ^'at mnjonty of which arc 
in tliG long-run dependent upon chemical changes. From 
this point «f view, then, the chemical vtndy of the Body 
presents physiologipal problems, and it is usual to include 
all the known facts as to the chemical compasition and 
m*^liiraorpho»c# of living matter under llie namcof Physio- 
hgical O/iemiffrtf. For tiie present we nuiv cnufinc our- 
selves to the more important substances <ii'rivod from or 
known to exist in the Budy, leuvinj^ ijiii'stiona onuceruing the 
chemical chanf^i^ taking jiliice within it for consideration 
along with those fuuctioiis which uro ]>erformGd in connec- 
tion with them. 




omsMisTitr OF Tim hody. 

Elementa Compoalng the Body. Of t lid cU-incnU koowti 
to clieiiiifltA only sixteen have been found to uiko ]>nrt in 
the fonuatioD of the Itumaii Body. These ano vui-bou, hy- 
drogen, nitrogen, oKygcn, Hulphar, phositliortw, chlorine, 
Htiorinfl, Mtlicon, Ai^<(]iiim, potaAainni, lithium, caldum, 
miign«siuni, iron, iinti muDgimese. Copper iind U'^ have 
somfltimes bei-n fotintl in sniuU <jn»utiti<w but arc- jirobably 
BCcidenlal and oi-rsKional. 

trnoombtaed Elements. Only a very small number of 
the above e!cmcii[« exi^t in the body uiicombincd. Ox^yett 
it found ill i-mn\l 'jiiaiitily di:<^ulv(;il in tho blood; but even 
there mo.it of it is in a atato of looite chemical combination. 
It is abo found in the cavities «f the lungs and alimentary 
OMiul. Iwjjtg derived from tlio invpiixil air or Hwnlluwed 
vilh food and saliva; hut wlitle contained in these epacex 
it cui hunlly be said to form a part oE the Body. Nitro- 
geti also axisto unconibined in th« Inng^ and alimentary 
canal, and in small quantity in solution in the blood. Free 
hydrogtiH liiw also Ih-cu f-iiincl in iJio alnn«ntary uiuial. be- 
ing tliere OToiviil by the fermentation of certain food«L 

ChemiMl Compousds. The number of these which 
may be obUlilK^i from tlio BckIv is vcn- grout; but with re- 
gard to very many of them we do imt know ihnt the form 
in uhich we extract tbcm is really that in which the ele- 
menta they contain were united while in the living Body: 
unra the methods of chemirnl analysis an such a* always 
break down the more complex fonns of liTing matter and 
IflftTo UR only iU dibris for exam i nation. We know in 
tact, tolerably accurately, what c-ompounds enter the Body 
lis food and what finally leave it as waste: but the inler- 
me<l)al« conditions of the elements contained in tlu'se coin- 
|M>uuda during their sojourn inxide the Body we know ver^' 
little about; more espociiilly their state of combination dur- 
ing that part of their xtay when (bi-y do not exitt distiolTed 
in the bodily liquids, but form part of a solid living 
tiwiie. 



I For pre.'icnt pur|ioi»cs Uio chemical compounds exlftting 
in or derived from the Body may bo cliiMificd ns organio 



10 TUB BVMAS BODY. 

and inorgunic, and the former bfi xubdividod into t1ioK« 
which contain nitrogen and thoso which do not, 

Nitrogenous or A^olizod Organlo Compounds. Thcoc 
UXi into Huvcviil muiii groups: proieide, pepionts, albtf 
minoith, rii/gfalUne tuMaHcet, mid coloring tnaUert. 

ProtoidB uiv by fitr tho inoi^t characteristic »Qb«taDc« ob- 
taiiHtl tiom thv Binlj,', kiucc tbcy are only known as exist- 
ing in or derived from living tliiugi*, either luiimajii or 
plimts. 'I'lte type of tJiis cla^s of bodies may be found in 
lliB white of un egg, where it is stored up as food for 
Uio developing clitek ; from this typicnl fonn, which is 
called effff oIlrHmin, the proteida in general are ofi4!n calUtd 
albuminous bodies, Eacli of thera oootains carbon, lirdio- 
geo, oxygen, Ktdphiir, and nitrogen uuilo^ lo fiinn n very 
coniph^x niuU't^iiie, and although different members of the 
family dttfer from one another in minor poinU they all 
sgrou in their br'.nd fi'jiMirw and have u ^iniihir )ieix:enlag« 
voni]>o<<!lion. The liittcr in difTcrent exami<U-H «p]K-jira to 
vary within tho following limits, hut it i» nlni<x->t im]i03.iibl« 
to get any one of Iticm jture fur analysis: 

Ouhoa 33 toM pcrcoot. 

nydroKra * to 7.S ■" 

Oxygun. 81 to 94.0 " 

Nitrogen IS to IJ.O " 

gnlpltur, o.sto 3.0 " 

Protcida are recognixed by Uko toUuwing charaieterfl: 1, 
Boiled, either in the Eulid state or in solntion, with strong 
nitric aoid they give a yolluw litjnid which bccomos orange 
Mnncntralizatioit with HmmoniiL 'nimiaiharanlAo-proMc 
ie»l. 

%. Boiled will) a solution containing itnbuitratc and jicr- 
uitrate of m^ri^ury they gi^o a pink pr(;(.'i]>it4kte. or, if in 
very Einidl <|UAntily, n pink-coloi'ed solution. This it 
known un .l/iVfonN /ft. 

3. If H eoluiion ontituining a protcid he acidulated with 
strong ueetio acid and be boiled after the addition of an 
erjunl hulk of a KUtuniU'd w.iten,- i^nlittion of eodiitm sul- 
phate, the proteid will be precipitated. 



PROTBim. PBPT0SS8. 



11 



Among thp mon> imporfcaitt proteids obtained from Uis 
hamnn Body iiro tliefollon-jiif;: 

Sernin albumin. This oximU in si>lution in tlie blood and 
is Terr like egg albumin in iUi pro))erlies. It U cuugulntcd 
(liko th« whit« ot OB egg) when boiled, and then passed 
into th« stdteof coagulattil prottid whiuh is. unliko tbc 
original e^nim ulbumiu. iuHoloble in dilute acida or aJkii- 
liM or in irnlor conuiining nuutnil salts in mlution. All 
other proteidii can br approprinto Irealmetit Im turned into 
ooagitlated proteid. 

Fibrin. Thi* furm* in blood when it "flota." eicber in- 
side or outitide of tike body. It ittnuido by the iuteroctioa 
ottwo other proteids known o&JibriRogeH andfibrinoplasfin. 
It it ini<olublo in water. 

Mj/ottH. This is doriTed from tbo musclcH. in wliiob it 
derelops and eoliditi(!!i after death, cunsiug the "death- 
Atiff«ning." 

tffuts in th« red g1<Aul«i of Uio blood and dlii- 
^lA'MilM other li(|uid8 of the hiAy. In tbo blood 
oorpDAvlos it U combined with n colored substance to form 
hmtnitglobin, which i« orj-stullixitlilc. 

CoMtn is found in milk, ft is inaolnblo in irut«r but 
Minble in dilnle acidi* and alkalies \\» aultitionit, nnliko 
those of fibrin or mrosin. do not coagulate apontaneousl;, 
orIik« that of st-nim albumin on boiling. In the milk it 
is httld in solution bv the free alkali prraont: when milk be* 
oomessour thix is neutrulixed nud the nutcin is precipitated 
Its the "curd," Cliucsc i;«n»i*l« mniiily of cjifoin. 

feptooes. These are formed in the alimentary canal 

the action of some of the digestive li<|Uida upon Uie 
aids swallowed as food. Theycontain the same elements 

the proteid* and pve the xmitho-protcic and Millon's 
reactions, but are not precipitated by boiiinfr with acetic 
acid and sodium sulphate. Thvir grciU di~tinctiro charac- 
ter is however their diffufibility. The ]>roteid3 proper will 
not diaiyze (see f'hrsics). btit the peptones in «ilution puss 
remlily throii^h moitt auiniul mi-mbmncK. 

Albuminoids. These oontain carbon, hydrogen, oxy- 
wid nitrogen, hnt rarely any stil{ihur. Like Che 



13 



TitR i/VitAy Bonr. 



proteids, the nearmt cbotuicnl allies of which tbey seem 
to bo, tlioy nrc only knuwu in or derived (mm living 
beings. Oelatin, obtained from bones and lif^tniento by 
boiling, is a typivid ulbniiiinoid; lu is chondrin, wliich is 
obtttiiiiHl similarly from gristle. Mucin, wbicb gives tbcir 
glairy teD:K'ious cliaractor U> tho sn^rotions of tbe mouth 
uiid avi^; is iiiiijllii-r uliiiitiiiiioiil. 

OrTStalUne Hitrogonoiu Substanoes. These are a 
lictorogcneous group, ih© great luajoi-ily of tlicm being 
niiiu^riaU which have done their work iii the Body and are 
about to be got rid of. Nitrogen enters tbe Body in foodn 
for Uic DiyKt. jiarl in the clietnicidly complex form of some 
proieid. In the vital processea these pi-oteidn are broken 
down into simpler Kubstanuec their carbon being partly 
combinetl with oxygen and parsed out through tlie lungs 
S8 carbon dioxide; tbeir hydrogen iti similarly in large ]>art 
combined wit.ln>xyj^n and paie^ed out aa water; while their 
nitrogen, with some carbon and hydrogi-n and osygen, is 
nsuully piLM»<l out in rho form of a cryiHalltne rompound, 
containing what chemists call an "ammonium rei^idue." 

roi 

Of th«o the mo*t important is ttrta (Carbamide H' > X*), 

which is climinntod through tho kidneyx. t'rie acid is an- 
other nitfDgenous waste product, and many otberH, iiueh tw 
krtalin and krmlinin, soem to bo iulermediuto stages l>c- 
tweeu the prtilcid:> which enter tho body and the urea and 
uric acid which leave it. 

In the bilo or gull, two orj-stallixable nitrogen-con min- 
ing bodies, gli/cOKhoHc and taurockoiie ariih, are found com- 
bined wilb soda, 

nitTogonoua Coloring Uatters. These form an arti- 
floial gi'oiip wh<R<e oon^lituliuu ami origin 'u ill known. 
Among the most importunt uri.' tbe fulluwing: 

Uvmalin, derived fnim the red eorpiiselos of tlie blood 
in which a residue of it is combined with u protoid residue 
lo form litpitioiit'i&in. 

liiliritbht and l/iliriT'lin. which exist in the bile; tho 
former predominating la the bile of miui and of camivo- 



FAT8. CAHBOIITnRATKK 



IS 



rooB animals und giring it a roddisli vcllow crolor. whilA 
bilivcrdin prolomtitnUiS in the bile of Uerbirora wliirh if 
greeu. 

Non-nitrogonoiui Orgooto Compounds. Thf«e may 
be odiivenienilj grouped oa fii/tlrocarbonn or fatly bodies; 
atrbohydrafes or amyloids ; and I'crtiiin non-molhed aeid». 

Fats. The/'n/ji all pontain carbon, hydrogen and Dsygoii. 
the oxygcu being proHciit iu smull jiruiRirt ioti as coinpai-ed 
with the bydrogttn. Three fvtM occur in the body in large 
iftiantitira, fJK. : pahnaliH (OtiUi>0>). xftariii (C'xHixOo). 
and olein (C\,1],t,0i). The two former wiieu pure are 
solid nt llic tcmpi^rsture of the llody, but in It are mixed 
vith olein ("btcii is liquid) in sul'Ii pro]Kirtiotis tu to be 
kept Said. The total <]aantitj of fats in the Bodj is mib- 
ject to greut vuriiitiunR, but it« nvenige ({uuntity iu a man 
weighing 7'> kilograms (16.') pounds) is abont H.t^ kilo> 
grwDS (C pounds). 

Eaeli of thntc fate when heatcci with a caustit; alkali, in 
tbfl preseuco of witor, breaks up into a fatty acid (WcwriV, 
palmitic, or oleic as tlio ease may Iw) and t/li/t^rinn. The 
fatty acid iinitojt with the nlkitli present to form a map. 

C&rbohyclntt«B. These also contain carbon, hydrogen 
iiad oxy^yii, liiit tbero Is one atom of oxygen prwont for 
every two of hydrogen in tlio molei'iiie of each of Ihem. 
Ckemicully they are related to starch. Tlic more impor- 
uni of tlit-m found in the Body arc ihi' following: 

Olgcoiftn (C.U„(>() found in large (]iianticies in the 
liver, where it scemM to be a reserve of material nneworiog 
to the starch stored up by mnny plants. It exists in suaDer 
4|uaDtitica in the miisolei). 

Qtveote, or yrape a»<;Mr (C.II,|0.), which cxtittJi in the 
liTor in small ([uantities ; aluo in the blood and lymph. 
It is largely <lcrived from glycogen which in very rtutdily 
converted into it. 

In'uit, or mtudo »ui/ar (C.ni.O, + 2H,0), found iu 
muscles, liver, spleen, kidneys, elc. 

XfffVcw. or sugar of milt (C„I[„0,, -|- H,0), found in 
cotuidcralilr ijiuintity in milk. 

Organic non-Nitro^noua Adds. OC these the most 



u 



r/us BCXAS Boor 



iinportjint ia rarionh dioxide (CO'), wliicli is the form in 
wbich by far the grvutor part of ihe curboD tukcn ioto tlii> 
B<Hl}'iiltiiiiiil«ly teiarea it. United with cmlcium it is found 
in )ht' bones aud teeth in large proportion. 

Formic, Aeefic, »iid liutyrie acids also iipc (onad in llic 
Body; stearic, palmitic, and oleic have been above men- 
tioned a* obtainable from fats. Loftieaeid is fonnd in the 
«u>niiu.'h and dcrolops in milk when ii. turim i»our. A body 
of Uie Ranie ]wrcentage comjiosition. ('>IIiOi (mrralae- 
tie acid), iH formed in mr^tjcles when tbejr work or die. 

Olyi:eri>'pho»phoric acid (CiHePO*) \6 oblftincd ou the 
decomposition of lecithin, a complex nitrogenous fat found 
in ncnous tifsiio. 

Inorganio Conatituents. Of iho simpler KnbHtanceH en- 
t«riD;{ into tlie structure of tlie body tlie following ure the 
InOMt important: 

Walfr ; in all th« tiiwucw in greater or less proportion 
mid forming about two thirds of the weigiit of the whole 
Body. A man woigliing 75 kilos {16ft lbs.), if completely 
dried would tlicrefoi'i- loiic about 50 kilos (110 11m.) from th« 
ovtiporatiou of wat«r. Of the constituents of the Body the 
enamel of the teeth contains least wtiler (about two per 
cent) and the saliva most (about Siii.5 percent); between 
these extremes are all intermediate stops — bones containing 
;Kboul 'i'l per ci-iit. mudcles tb, blood 19. 

Common MU—SotHum ehloridf — (NaCl) : found in all 
the tissnee and licjuids, and in many cases playing on 
important part in keeping otJier substances in solution in 
water. 

Potasiivtn rhloriiir{KQ\)\ in the blood, muscles, ncrvoe, 
and mo«t liquids. 

Caieiutn phi)«ph(t(e (Ciit'JPO.): in the buneeand teeth in 
large quantity. Iii le6a proportion in all the otiicr tiNsuo.". 

Besides the aboTO, ammonium chloride, sodium and 
I potassium phosphnt^ji, mngnc(>ium phusphute. Midinni sul- 
phate, potassium sulphate and oiilcium Auoridc havu hoen 
obtained from the body. 

Uncombined Hydrochlorir acid (HOI) i« rounil in the 
atomaoh. 



CHAPTER II. 

THE FUNUAMKNTAL PUYSIOLOOICAL 
ACTIONS. 

The Propertioe of the Living Bod;. Vfhvn wro (urn 
from llio stniemre iiuii cunifiu^itiuii of the living Bodyto 
consider its pon'or^i itiid ]>i'Ot'crtioH vm meet nilh tbe same 
varifty and t'<nni)l<-xitv. the moai HUjierlK-iiil t-inniinatiun 
being giitlicicDt lo show thnt its jrurUure endowed viilh very 
dUforent fucuUios. Light Tallin^ on ibo vvo aroiues in lu 
a senimtioti of sight but fulling on tbe ekin ha» uo iiacfa 
effect; pincliing Ihc xkin raiisai iiain, but piuching n kair 
or A tinil does not: when the em's ore slopped, Hoiindti 
arousQ iu us no scnsutiou; wo rcndily recognize, l<»>, liiird 
puru fonnfd for ouppoi't, joints to itdmit of movements, 
a[wrUircui to receive food and others to get rid of wasteii. 
We tbus perceive thiil different orguns of onr Bodies ha¥« 
very di(Ti-rciit endowmoutit and serve for very distioct pur- 
]»90«; and here again the study of internal organs shove 
tu that the varietio.^ of quality olwerred on the exterior are 
hut itligbt indicalions of differeDces of property wbioh jwr- 
vade the whole, boms sometJmee dependent on the s|>ecifiG 
obwuutorM of the tiuutw ooncernt-d and ^amctimee upon the 
uuiuner in vhicb these are combinttd ti> form rariouK 
organs. .Some tissues are solid, rigid and of conslwit 
eUape. as tboso coinpoffing tbe hoiiM and teeth: others, as 
1Im> tnuscleii, are soft and capable of changing their form; 
and still others are capable of working chemical cliangoi 
by which such peculiar Buidi ai< the bite or the saliva are 
produce*). We lind elsewhere a number of ti.'iiu<,-s com- 
bined to form a tiibo a'liipted to receive food and carry it 
through the Body for digestion, and again luinilar tifsuei 




19 



THK ItUMAy BODY. 



differently arniuged to receive the air which wc )>roathe-in. 
and expel aftor atratnicting from it part of its oxygen uid 
addinff U> it certain other things; and in Hie h«art and 
blood-vcenels we lind nimoet the same tisanes arnuigH to 
propel luid curry the blood over the whole Bodv. The 
working of tho Body offers clearly even a more (•om))le]t 
Hubject of Htikiy Ihiiu its litnictiire. 

Fh7«ioLogioal Propertiaa. In common with inanimate 
objcota the Body powH^itHes many merely physicHl pra|M>r1ic«, 
as weighty rigidity, eWticitv, color, and oo on; l>nt in ad- 
dition to these we find in it wiiilo alive many others 
which it ceai^e^ to manifest at death. Of these perhaps 
the power of oxociiliiig Kpoutaneous movementii and of 
maintftining a high bodily Ivmponitnre are the moet 
marked. ?is long an the Body is alive it ii« warm uid, 
since the surrounding air U nearly always t^iolci', mual tw 
losing heat all day long to neJghl>onng objects; nererthe- 
Ihb we are at the end of the day as warm as at the begin- 
ning, tho tein)>eratiirc of the Body in health not varying 
much fi-om s:.:.' C. (ftJC F.), so that clearly our Bodies 
must be making he*! somehow idl the time. After death this 
production of heat cc&»ea and thv Body cools down to the 
tempcniture in its neighborhood; but so clowly do wo 
nnsociate with it the idea of warmth tliat the iietisnlioii 
esperienced in lou(;h)ng a corpse produces so jmwerful 
ao impro(*ion iw commonly to bo described as iey cold. 
The other great characteristic of the living Body i« it« 
power of executing moTcmenlB; so long as life lasts it is 
never nt rent; even in the deepest slumber the regular 
breathing, the tap of the heart against the ohest-wall, and 
the boat of the pulse tell us that we are watching sleep and 
not deiith. If to this we add the [>oMsc«8ton of eonscions- 
nesa by the living Body, whether aroused by forces im- 
mediately acting upon sense-organs or not, we mighl do- 
soribc it a« a heat-prodnciiig, moving, eoiucious organism. 

The pro<luetiou of heat in the Body needs fuel of 
Romc kind il* much as its production in a liro; and every 
time we move ourselves or external objecbf some of the 
Body is used up to supply the necessary working power. Just 



0RLL6. 



17 



08 some cools nro harnt in the fumsM of an engine for 
cTorr bit of work it doe^: in the same way cTerj thought 
that arises in lis is nccoDiimniod with the deetamction of 
aome part of tliv Body. Hoiin- thi-xo primury uvtions of 
Vcttjiiiig wann, moving, and being coim'ioiiii ncc«:c«it«to 
many others for the Bupply of neir materi:il3 to the tis- 
isavt conoornvd and (or tbfi mnuval of tlieir vwttiM; still 
otiicn arc no«cs»arT to regulate tlie i>rodiiclion uid Iom of 
heat in a<?coi-dance with changes in the exterior tempera- 
tare, to bring the moving tissues into reUtion with the 
thinking, and »»> on. By nucli iiub.*idiary arnrngemcnU 
the working of the whole Body becomes ao complex that it 
Tonld Bit niiiny piige^ merely to ennmerate what is known 
of the diilic« of it* varion* parts. HywoviT, nil tho projicr 
physiological prvjpiirties depend in ultimate anaipisona 
small number of facnlties whioh are pOMessed by all livbg 
things, their great vuricty in the hiimnn Body depending 
npon D)H>olitl dcTelopment and combination in different 
tiesnea »nd organs; and before attempting to study them in 
their most complex fonns it \* lulvHiitagcous 
to oic.imine them in their .limpleit and moat 
generalized man ifesuit ions as exhibited by 
some of the lowest living things or by tho 
fimplci^t eonKtiiueniA of our own Bo<lie«i. 

Cells. Among the anatomical elements 
which the hisUiIogiift meet* with ha entering 
into llie oomjiosirion of ilie human Body 
are minute granular masses of a soft con- 
sistence, uboiit 0.013 niitlimeler (-f^ui "f <^<> 
inch) in diameior (Fig. A, r). Imbedded in 
uob lies a central poi-tion, not granular 
ud therefore different in appearance from 
the rest, Tlicao anntotniual units arc known 
If the granular substance being the 
hodgmxA thi' imliQildcd clearer portion 
\i\« cttl HHchiin. Inside the nuolciiit may ufton Iwi di«tin- 
goished a still smaller body — t\ie nucUolHS. Cells of this 
kind exist in ubiindance in the blood, where they are known 
M tlio white blood corpittdtt, and each cihibita of it«olf 




Pia.O.— FDnu 
otoeltetrtmUM 
Hod; 



19 



THE nUMAA' BODY. 



certain projwrties wbicli are distinctive of all living ihings 
as compared with iuunimuUt objects. 

Cell Growth. In tbo fml plitcc, onch 8uch cfW am Itiko 
np nintr>rialit from \ts oiiUide and build Ibi'm uji into it« 
own peculiar substance; and this docs not occur bv tlie 
deposit of new luyvrs of matorial Itko itsoiruon tlie surface 
of tbe c«II (aa a ci^stat miglit increase in an ornporntiiig 
solntion of tbe same suit) but in an cutircly different way. 
Tbectdl tak» uji rhemioal elompntii, oitbcr fi-eo or cum- 
bioed in a manner different from that in which iht^' i>su>t 
in it£ own living cubstjuioe, and works chemirjtl change* 
in tlicm by wliich tliey aro made into jiart and parcel of 
itnlf. Jkliireover, tlto new ni»t«i'ial thu.'^ formed is not de> 
posited, at any raU) necessarily or alvayjt, on clic imrface 
of tbe old, bnt is laid down in tbe snbstancc of the already 
ejdstiDgccU among ilitconslilncnt molecules. The new- 
formed mok'c-uli-^ therefore rontrihnte to Ihf growth of the 
cell not by saperficial aceretion, bnt by interstitial dopoot 
or ititus»ufc«piwit. 

Cell Division. The increaae of me, wbieli may be 
brouglit iibuut in the aliOTfl manner, is not indeliuite, but 
La limited in two ways. Alongudc of tbe formation and 
deposit of new niatcrial ibcrc occurs always io the Uring 
cell a breaking down and elimination of the old; and when 
this process equals the ai-oumnlat ion of new matcriid, as it 
docs in all the celle of the Itmly when they attain a certain 
bLm, growth of course ceases. In fact the work of tbe ecll in- 
creases as its mass, imd therefore aa the cube of '\U dinme- 




Ftn. S.-A wUM hload oorniitcln itivhllug. oi obnDnnt HI ■iiivc«ln lii(>niiJ> 
at k f«« iKCODdi with Ihrr miirnMCOiiF. 

tcr; while the receptive powers, dependent primarily ujton 
the snperdcial area, only increase as the #f|uarc of the di- 
ameter. The breaking down in tbe cell increases when it« 



ASSimLATTON. 



19 



work doee and so st lost equale the reception and constrno 
tioD. Tbo second limitation \o iiidctinitv groirih is oon- 
nDCt«d witli t)i« t>aw«r of the cell to givu n»u to ut-w celU 
like iUelf. Under certain circnmstances, which arc not 
wolt kuon-ii, tbo ooll may Weomc uiirruned (Pig- 0) at one 
LOQv: the constriction deojienii until the \\aru on cncli eido 
of it are merely united by a narrow band irbick flnallr 
^ves way and two eelU an- formed, oiioh like tbc paroni 
but for its ifinullei- siKe; or tin- cell may divide into two or 
morv by Hut surfaces of separation, or in 
a way intermediate bctwot-u this mode 
and tlie last (Tig. 1). In <onie ca«» now 
colli; form in the interior of the old and 
are then set free from it. The new cells 
produced in tliese iraye grow as the origi- 
niil cell did, and may in turn multiply in 
Chti same manner. Very commonly the 
noclcii!! dirides before the rest of the 
c«11, and \u jiarU then form the iinoloi of 
the new cells. 

Amimilation: RoproduoUon. These 
two (lowoi-^, ih:U of working up into thttir 
own substance materiulH derived from out«idc. known oa 
aaairniUtlion. and tbat of, in one way or another, giving riw 
to DOW beings like t)iem.wIvo:t. kiionn as repradudioH, are 
p08M88ed by all kinds of living btiing^, whether iininuds or 
plants. There i^ bowevur, this im|)»rta]it dilTerenco be- 
tween the two: the power of tuwimilution is neceuary for 
tbo niainti'nancc of each individual eel), plant, or auimnl, 
«<Hce (he already esisiing living material \^ constantly 
hreiiking down and Wng removed as long »» lifel)uiti<,and 
the tosi miiNt bo mndi) good if each is to oonlinuc iu exist- 
BQoe. The power of reproductaon, on the other hand, ia 
iioceasary only for the continuance of the kind or race, and 
uwd bo, anil often i.-", po«*{-i«cd only by some of the indi- 
viduaU composing it. Working bees, for example, cannot 
reproduce their kind, thai duty being left to tbo qiic«n-beo 
and the .drones of each hive. 

The breaking down of already existing chemical com- 



o 

oooo 

fm.?.— ADoihar 
modi* ef 0*11 dMslOn . 
Araunil«d evil rtitn- 
nles lu oar dlmiv 
Err. Uitn iinulually 
■urTowi In a muluui 
■one. siiil llii>ll> ia 
Mparalnl tnUi tiro 
rarW: thenoPlciwiti. 
«ld« »t Dm 
(Una. 




90 



THE atTJfA.y BODY. 



pounds into simpU'r ones, sometimes called dittutmt'ltidon, 
is as mriirial>le in liring Iwlng^ uh thu building up of uew 
coinpl<^x molecules referred to abore. It is ai>M)c!»t4)d nitk 
(hi> assumption of niicombined oxygen from tiie exterior, 
which i« llicn pombinwi dii-cctly or indirectlv with 
other eleraenu in the cell, as for exnniplc rarbon, 
giving rise to carbon dioxide, or hydrogen [irodaciug 
water. In ihU wny tlio moWule in vrhioti the carbon and 
liydrogcu pravioosly existed is broken doirn, and at the 
sumo time energy in liberated, which in all caseA seems i» 
take in piu-t the form of heal jiijit a« when conX is barn t 
in a lire, but may be used in pare for other parpo«ie« such us 
producing movements. The carbon dioxide is usually got 
rid of by the same mcohanunn u« that which serves to take 
n\i the oxygpn, and (li^e two procejiaca coni'titiitc Ihc 
function 'of n»piration which occurs in all living thingn. 
Asgimilatioii and disijsimilation, going on stdo by «ido and 
btiog to a ccrtftiri extent correlative, are often (ipokcn of 
together «A the i)rocefis of nulri/ion, s term which thei-c- 
(or« includes all the chemical traii^fonnationa occurring in 
living mailer. 

Contractility. Nutrition and (with the above-mentioned 
partial exec] it ion) repruduL-tion charoctpri/e all living crea- 
tures; ami both fiu;ultic3 arc possessed by the simple 
nucleated oelU already referred to as foimd in our blood. 
Bnt these cells possess also certain other pro)>erties which, 
althongh not eo absolutely diagnoalic, are yet verj- charac- 
teristic of living things, 

Kxamincd carefully with a microscope in a frciih.di'iiivn 
drop of blood, they exhibit changes of form independent 
of any pri-<*iirc which might distort them or ulhcrwice 
mcs:hiinicnlly niter their shape. The« chnngCK may some- 
times show themselves as constrictions ultimately leading 
to the division of the cell; hut more c«mmonly(Fig. 12*) 
they have no such reeiiill, the cell flim|>ly nltering it^ form 
by drawing in its substance at one point and tbrosting it 
oat lit another. The portion thus protruded may in turn 
be drawn in and a process lie tlirown out elsewhere ; or the 
rest of the cell may collect around it. and a fresh protru- 

• P. 48. 



mniTABiurr. 



SI 



» 



aioD be then niudo in the xamc rnde; and by repeatiug cliiit 
nuuia'iivro cIksr cellH may change their place and creep 
MTOaa the tield of the microscope. Such ohniigcs of fomi 
from their close rcscmblaiieo tolliose exhibited by the micro* 
)toopic uiiiinal kitowD a^i the Amteba (lico Zoology) ure called 
ttinofdoiil, and the faculty in the living cell tipou which they 
dei>en(l is known in i)liyiiiology as eonlraclHili/. It mngt 
be borno in mind that phyeiologicat coutroctilitv in this 
aeitM is i]uit« different from the «o-called contrttolility of 
ftBtretched indian-rnbhcr bund, which morely toiid* to re- 
HKume iL form from which it has previously been forcibly 
removed. 

JCrritabUit;. Another pro|>prty exhibtt«d by these hlood- 
oell» is known ns irritahiUlij. An Aintebii coming into 
i\>ntiiot with a solid particle calculated to servo it os food 
will ihrow around it processes of its suhetance, and grad- 
lUtlly carry the foreign mas* into it« own body. The 
amount of energy expended by the animal under theac 
circumstimccs is altogetlicr di^preportiouato to the force of 
the external contact, li iit not that tho swollovod mau 
pasties in mechanically the eurface of the Am<i>ba, or bnr- 
rows iuto it, but Iho mere touch arouses in the animal an 
activity i|uilc disproportionate to llie MciUng force,j,ttml 
vom)mrable to that set free by a spark falling inlo gunjww- 
der or by u slight tJip on a piece of gun-cotton. It is this 
di«])roporlion between the excitant (known in i'hygiolugyas 
a xliiHitlu*) and the result, which is the exseiitial character- 
istic of xrrilabililtf when the term is used in a physiological 
connection. The granular ooll» of the blood can take 
foreign matters into themselves iu exactly the same man- 
ner as nn Ameeba dues; and in this and in other ways, as 
by oontrucling into rigid spliercit under the iulluence of 
electrical shocks, thoy show that they aiao arc endowed 
with irritability. 

Conductivity. Further, when an Amcnbaoroneof these 
rJdood-ct'lU fumes into contact with a foreign body and 
proceeds to druw it into its own substanoe, the activity ex- 
cited is it<jt merely dii«pluyed by the parts dctually touched. 
Distant [)ar1s of the coll also co-operate, 8o that tho influ- 




ss 



rnii uvMAX soj>r. 




enoe of the Blimultu is noL locul only, but in ooiuiequence 
of it u chun^ i^ li-ou^Iit abont in ot)iitr {iiirtis nruunng 
tbviu. Thiiiprapertyof txausniittingdistatbaucefi is known 
us condvctifit^. 

Fituilly, Die muvpiDonU oxcitod arc not, m a rule, ran* 
doni, Tlity iin.- not im'gular coiiviil«ion». but arc luiapted 
to iilliiiii a certain end, being so combined no to bring llie 
external particle into the interior of the cell. Thia capo- 
city of all the parti! to wurk togL>tlier in definite strength 
and sequence, to falfl! sonic ]>ur|)osc, H kiionn as co-ortti' 
nation. 

Theae Properties Cbaraotoriatio but not Diagnontio. 
Thcde four faotiliiea. irritaliility. comUictiTity, contractility, 
and co-ordination, arc posseted in a high degree by our 
Bodies as a whole. If the inside of the no;^ he tickled with 
a feather, a snooze will ho prodiice<i. Hero the feather- 
toucb {stimulm) has called forth moTenionts which nr« 
nicchanictdly altogether di^projiortionat« to the energy of 
the oonlaol, so that the tiring body is clearly irritabU. 
The moTeinents, which are tbemselTefi a manifpstjition of 
coHtracHUty, are not exhibited at llio point tonohcd, but at 
more or Ic^m diMtunt parts, among which those of abdomen, 
chest, and faoe are viaible from the exterior; onr Dodice 
therefoi-e poBseas ph^»ii4orficfil condticiii'ity. And finally 
Uicsc movements are not randotn, but oombinod eo as to 
produce a violent current of air through the nose tending 
to remove the irritating object; und in this we have a 
inai)ifc»t»t40» of cO'Ordination. Spcnking broadly, tbeee 
]iroperties are more manifest in animalii than in plantf, 
though they are by no meani< abBolutely confined to the 
former. In the iwnsitire plant touching one leullel will 
cxcile regular raoTemonta of the whole leaf, and many of 
the lower n{]ualic plants exhibit niovementii as active as 
thofe of aniniiik. On Ihe other hand, no one of these fonr 
facilities is absalutely distinctive of living things in the 
way that groirlh bi/ inluMuscffilioH and rvprfidiicfion are. 
Irritability is txit u name for unstable molecular equilibrium, 
and is as marked In nitroglycerine aa in any living c«lls; in 
tlic telephono the infiuonco of the voice is conducted as a 



SPOXTASlilTT. 



r ctiuige Along a wire, iind prodaoc« rei^ults nt » 
dUtance; and many inituinutte nuwliiiMSS afford exiituples of 
the co-ordiuatiou of inorcmenM (or Uio atuiun)«ul uf 
defl»it« 4>tids. 

Spostaaoity. There \e, Kowvvcr, one character belonging 
to m^iiiv of [.lit: muvoiiienUi cxhiliit«d liy amivboid cclK >ii 
wbicb they appear at tirat eight to diSt-r fuudamentally 
from the moremout^ of inanimate objecU. This chnracler 
is thfir iippiiruut t}>onfaneilt/ or itulnmatirit^. The cell* 
frequently cbange tbeir form independently of any ro- 
oognisoble external cause, while a dead va&s^ at rest aud 
unacted on frum outride remains at rcrt. Thi<( difference 
i«, however, only apparent ami d<-poudi) not upon any faculty 
of spontaneous iic-tion peculiar to the living cell, but upon 
it« uutritiTO powers. It uitn be proved that any system of 
material partidcit in equilibrium and at rest will forever 
remain eo if not acted upon by an external force. Snch a 
<jvt«m CAD oany on, under certain conditions, a Kcries of 
chftn^es wlien once a start lias been given; but it cannot 
initiate thcai itself. Each living cell in the long-run U but 
u oomplei Aggregnto of moleculct, com)>o^(id in their turn 
of chemical elemental, and if we suppose thia whole set of 
atoms at rt-tit in titjuilibrium at any moment, no change can 
be starKid in tlie cell from inside; in other words, it will 
possess no read apontaneity. VHien, however, we consider 
the irritability of amu>bnid cells, or. expresaed in mocbonical 
terms, the unstable eijuijibrium of tlteir particles, it be- 
coiDCd obvious that a very lilight external cause, such as 
may eutirely elude our obsenation, may serve lo set going 
ill tbem a very marked ncries of changes, juttt as pnlling 
the trigger will lire off a gun. Once the eipiilibrium of 
the ooll bns been disturtx^d, movcniouU either of some of 
its constituent molecules or of ita whole maa^ will continue 
until all the moleeules have again settled down into a stable 
■t«t«. But in living cells the reattainiiieiit of ihis stAt« is 
commonly indetlniiely postponed by the reoeption of new 

I particles, food in one form or another, from the exterior. 
The nvoroet npproocb to it isproluvhly exhibited by the rest- 
ing stAt« into whiob some of the lower uuiraals, as the wheel 



H 



THE UCVA.V BODY. 




animaloules, pass when dried iilowly iit n loir Ivmpenittire: 
the drying noting by checking the n«tritj\e pnwentes, 
nrhich would otherwise h»vc prevented thv raUtoinmettt 
of tnolecnlar eqnilibriain. All sigiiti of niovemcmt or other 
change diMippeu- nnder these circunutances, but a^ soon 
H Wktcr agwn soaks into their RnbHtance und diftarbs the 
esisting condition, then the so-called " sjiontaiioou*" tnoru- 
mcDta recommence. If, therefore, we use the term spon- 
tsoeity to esprcM a pow«r in n renting i^ttcm of purlicles of 
iniliatiog eltangen in ilm-lf, it \» poneated neither br bring 
nor nut-living thitigB. But if we Bimply employ it to deaig- 
naU) chwigen who»e primary- cause we do not rcoognizfl. and 
which cause was in many ca^ea long anleecdent to the 
obanges whirh we see. then the term is unobjectionable and 
oonvcnicnl, ib< it Kn'C« to oipretu briefly n phenomenon 
prcfenlol by many living Ihingx and fiiiding it^ highest 
manifestation in many hnman actions. It then, bow- 
eror, so longer dceignntcs n projiertv peculiar to them. A 
stoam-en^ne with ita furna^'e lighted and water in it« 
boiler mny be fict in motion by oponiR<; a ralvc, and the 
moTemout« thus started will oontinuc :'|iontancoui>ly, in thu 
aboTO sense, until the oools or water are used np. Tlie dif- 
ference Iwtweeu it and the living cell lies not in any sjHTin- 
taneity of the latter, but in it* nutritive ]>owen(. which 
raable it to rei>1aee continually what anawe.ra to the coalM 
and water of the engine. 

Protoplaiim. Finding all thesv properties poesessed by 
a simple iiiidonlpd oell, wearo nftturHlIylcd to inquire upon 
what purt ii[ ii do thoy depend? It is dear that if they are 
exhibited in Ihc absence of any one it canunt be essen- 
tial t« their manifestation. Now » study of the lower 
forms of life i-hon-s us that these powers are indepL^ndcnt of 
the cell niiclc"*, i^iiice we And them nil exhibited by cells in 
which the uucleuK ia wanting. Moreover, in many cases 
not only the nucleus but all granules are ab««nt, and yet we 
find the remaining miuii nutritive. rRproductive. irritable, 
contractile, conductive, co-oidinative. and automatic. We 
are thus driven to eoncluile that in llu- cuweof tliegranular 
blood-cells, thejie faculties are moat probably endowments 



enoTOPtASX. 



u 



uf iIm) lriuiii|M['ent jjortitms of the cell body, in wiiicli the 
gnaales lie imbedded. Tliis, l^e reaUy workinjg part of the 
cell, is kiiowu (w (lie cell protoplasm. The rile of the 
nuclous and griuiulus m oft«ii [tretcat is not yet well 
uodertitood; poitsibly Ihe granulw in many cnses reprcMiit 
incompletely u««iiiiiliitod food. 

What tbc lu-tual oheiiiical constitution of protoplasm is 
we do Dot know, bat it ia one of great complexity. All 
muthuilfl of chemical anulyfis destroy it, and what we analyze 
la not protoplusm, which is nlway* ulive — which is a form 
of matter endowed with ihoae propertied) which we call 
vital — but a mixture of the products of its docompoEition 
when it cea.iis to live. Such amixtnre ii often called dead 
protoplasm, but the phrase is objectionable as implying a 
contradiction. Wherever there is protopliism there is life, 
aod wherever we meet with life we find protoi)ln»in, so that 
it has been called the " physical basis of life." The name 
protoplasm, too, is rather to be roganlcd ns a general term 
for a number of closely allied substances agreeing with one 
another chemically in main points, as the proteids do, but 
differing in minor dutaila, in consequence of which one cell 
differs slightly from another in faculty. On proximate 
analysis every mass of protoplasm is found to contain mncb 
Iter and a certain amount of mineral salts; the water 
ag in part eonstitnent or entering into tlie structure of 
imolpculos of protoplasm, and in part probably deposited 
in layers between them. Of organic constituents proto- 
plasm always yields one or more prolcids, some fats, and 
•ome stui-chy or Siiccharino body. So that tho origiuul 
protoplasm is probably to bo regarded as containing chemi- 
cal "residues" of proteids, fats, and carbohydrates, com- 
binccl with wilt-i and w(iti*r. 

The Pundamontal Physiological Properties. All living 
animals possess in gn.-aiur or less degree the properties coa- 
«idcred in this cha))tc'r; and since the science of physiology 
is Tirtnally ooncenied with considering how these proper- 
ties are acquiri-d. maintained, and manifested, and for 
what ends they are employed, we may call them the /undo- 
mtntal phj/nohgicai properties. 



CHAPTER III. 

THE DlFFEIUIXTlA'i'ION OF THE TISSUES AND 
THE PHYSIOLOGICAL DIVISION OP EMPLOY- 
MEXTS. 

DerelopaMnt. Kvery httman Body comiueQced its indi- 
Tidual «xi:*loiic,c as a eingle nucleated coll. Tliis cell, 
known as the wum, divides or st^ments nod givea rise to 




F».a~A.anoru>n: U to E. sUAwliro «teeM lo lis Bc«iiuiiiatlun until Uw 

a maaa cuiiatHting of a number of similar units and cailed 
the mullifrrg tnnns or the morula. At this period tlioni 
long boforo tiirtli, there are do diiititigiiishuhle tissues cn- 
toring into the stntcture of the Body, nor are any organs 
rooognixiihlc. 

For a short time the morula iiicrooaes in si:ie by tlic 
growth and division of its cells, but ven* soon new pro- 
oaisoa oociir which ullimut«ly giro rixe to the complex 




DinsiOX OF LABOJt. 



87 



adnlt bo^y with iw many tissues and organs. Groups of 
cells ceasinu to grow and niultiplj' tiko their parents begin 
to grow in witys pi^ciiliikr U> theni.ielvoit, itn<I so come to 
differ botti from the original cells of the moruln and from 
tb« cells of other groups, and Hum iinlikcness becoming 
more iind more miirkcd. » vnn'od vholv \» finally built up 
from one origlnallv alike in all its parlii. Peculiar grovtb 
of tiiis kind, forming a complex from a simple whole, is 
calkyl deivtopnterU; and the procc«>t itself iu this ca<e is 
known a» the Siffrrenlialion of lh» fi»»uM, since by it lh«y 
are, so to speak, separated or specialised from the general 
miuu of mothcr-cdli forming the mornla. 

As the diffcfoiice't in the form and structure of the eon- 
stitnent cells of the mornla become marked, differences In 
property arioc, ai«l it becomes obvious that llie whole cell 
aggregate is not destined to give rise to a collection of in- 
dependent living tilings, but to form a single iiiimuu being, 
in vliom each |>art. vhile maintaiuing its own life, th^l 
have duties to porf<>rni for llio gmul of the whole. In other 
voxd*, a single mmpounil individual is to be built nj) by 
the onion and co-operation of a number of simple ones 
repreaenlcd by the various colls, each of which thotieoforth. 
wliile primarily looking after its own interests and having 
its own pecnliar faculties, has at the same time its activi- 
ties subiirdiiiiitcil t<> the good of the entire community. 

The Physiological Division of Labor. The fundamen- 
tid pliy»i»l"gii;il jinijKtrtitM. originiilly ethibilcd by all the 
wllii. become ulliniatoly distributed between the different 
modified celk which form the tissues of the fully developed 
Body much iu llie Kame way as diffoivtit employments arc 
distributed in a civilised state; for the difference between 
the fully developed human Body and the collection of 
iimoiboid cells from which it started is essentially the same 
a« that between a. nun)l>cr of wandering savages and a civj- 
lixed nittiiiri. In Ilic former, ajutrt from differences de- 
{>ende»t on sex, each imlividual has no one special occu* 
patioii different fri)m (hut of the rci^t, hut hii« all his own 
needs to look after: he must collect liis own food and 
preparu it for wtiug, make bis own clothes if he weans 



i 



s» 



TBB BUM AS BODT. 



any, proride his ovn RhiOlor, and defend himself from wild 
bcafiU or tiis fc-tlow-moii. In llio civilized ouiiiitry, on the 
oUter hand, wc find agncultiirisU to mite food aud cooks 
to prepare it. toiloni to mnkv cloiht^, and policemen and 
soldien to provide protection. Aud jitut sa we Itnd that 
when diHtributioD of cmploiiiiirnU in it t« more minute 
tbfi mora odvaniX'd n nation ii in civiliKution, ro ih an ant- 
mnl higher or lower in the Bcale according to the degree in 
which it exhibits a division of pbyaiologicid dutic« between 
it« different tisfncii. 

From the enbdivimn of Ubor in adranced commnnitieB 
eerenil importnnt contV'iiicnces ari^-. In the lirst place, 
each man devoting hini&clf to one kind of work mainly and 
relying upon olhers for the Knp]>ly of hie other nceda, every 
Bort of work got* better done. The man who U constantly 
making boots booomea more expert than one whose atten- 
tion is coDStantly di»triicte<t \>y other duties, and he will not 
only make more hoots in a given time, but better ones; aud 
80 with Ihe performance of all othur kind^ of work. In 
the second i>liioi.-, a iiece»(itT ansca for a now sort of indos- 
try, in order lu convey the prodnce of one individnal is 
excess of the needs of himiH^lf and his family to those at a 
tlistimce who miiy want it, anA to convey bock in return 
the excess of their prodnce which be needs. The carriage 
of food from the country to cities, and of city produce 
to eonntrj- diMrict^, und the occupation of shopkc«ping, 
are instances of these new kinds of labor whtdi arUe in 
civilized communilics. In addition there is developed a 
need for arningciiK-nt^ by which the work of individual 
shall be regulated in proportion to the wants of the 
whole Community, ;^nch a> is in part effected by the agener 
of large cmployeii* «f lubur who regulate thosotivitios of 
a number of individuals for the production of various 
articles iu the ditlcrcnt (|uantiticg required at different 
Umet!. 

Exactly similar phcnomenu iv-*nU from the subdivision 
of labor in the human Body. By the distribution of em- 
ployment* botwton ill! difTi-rent tiit^ues, each one epeciuUy 
doing one work for the general commonity aud relying on 



Is 



■ 



CLASSIFICATION OF TISSUES. Sfl 

oth«n r»r their aid in turn, cacli ni-ccsBBry work is 
bett«r iwrfuriued. And a nvcd ari.Hv for a distributive 
iiieciiani^m by which the cioeas producis, if any, of various 
(iii:mes shiill he aimed u> others which i^uire thorn, uud 
for a rogiihuive inechaDi^ii hy wliich tlio mrtivitii-^ "f Ihe 
varioiu tiuuca shall bo rendered |>ro])ortiuuuto to tiie ueidf 
of the whole Body at different times mid uoder diSorviilr 
pirounwlaiiiTJi. Accordingly, a« we miiy olHHuify Uie in- 
hiihiiiiiiL-iof ihc Uiiilod SUtca into lawyers, doctor*, clergy- 
men. merehziDts. riumcn, and sn ou, we raiiy 

CUwify tba Tlssaea, hy selecting the most disHnctiTV 
propertieei of each of those entering intu Die coostnti^ 
tion of the adnlt Body iind iirruiiging them iiil*> |)liy»io> 
logical group*; Umsi' of em^h gronp being characterized by 
amno one prominent empluyinimt. No kucIi cUssilicotion, 
however, can l>o more than uiiproxiniately accurate, iiinoi! 
tho same tiH«u« ha.i often moi-e than one well-marked 
physiological property. The following itrningomout, lioir- 
over. ii pracii cully convenient. 

1. UndiObreRtintod TIbsuob. These nro composed of 

Is which hiivo dcvclDpcd along no one epcciid lino, but 
'rjtain very much the fonn and propertiest of the cells form- 
ing the very young Body before different lissiiN were re- 
oognixAblo in iU The lymjili corpitHclcx and tlm coIorloM 
corpuscle!! of the blood belong to this clasR. 

S. Supporting Tlsauea. Including etirtilage (gristle), 
hone, and ivinctiiiv tiseue. Of thu lutt^r there are eotcra] 
i^ub«idiiiry variulies, the two more important being whit* 
fiiroiu eOHNfttivt Imur, cuinptMcd mainly of colorless in- 
extensible fibres, aoA t/tlhic ^irou» /is»uit, composed, mninly 
of yellow cliLitio iibrp^ A11 the xtipportiu^r tissnee are used 
in the Body for mechanical purpooef. the hones iind csiti- 
liigee form the liard framework by which softer tisstiee are 
«Dpporled and proU-clcd; and iho connective tissaes unite 
the various hoiic-s and carlilagea, form inveating mem- 
bmiiei! Around difforout organs, and in the form of fine 
oetworkfl pouotrate their AuKvtitnce and support their coo- 
stituent oella. The functions of Iheae tissaes being for tlio 
mo»l part to pwiively resist strain or preesare, none of 




30 



run aVMAJf BODY. 




tjusm hiu> any very marked j>liyii<>Ingical j>r<)|)crty; iktvy lire 
not, for cxain|>Ic irrilablo or cuutRtrtilc. and their mad is 
chiefly nuuk- ti]> of uii inU'rcvlluIur Hiibxtuiicu which ha.'f 
I1CCJ1 ftiruK'ii by i!n' iiclively living owlls sparsoly :ic-alt«r«U 
through them, as for iustance in curtiliigc, Fig.42,*whcro 
the evils iii« seen imbeddod in ravjtii'S in iitnutrixnhich 
4hey bavK fiiniii.-'l uround Ihcin; tuul which luulrix hy it^ 
firmaesii nnd cludtii^ity furiuG tho rimctiotuilly iiuporlant 
|i:irt <it the ttsBUi\ 

3. Nutritive TisHues. This i» h hirgc group, the meni- 
bcrs of which full ini" thre« main diviaion», Tii.: 

A*»imilafitr tiMtitx, conoerucd ia necuiTing and pro|tar- 
ing food niiUeriiiU, itotl including — [a) Srcrciory (tMUM, 
cuinjioscd t>f oells which make Uie digestive liquido paurcd 
into alimentary cHnal. and brin;png about chemical or othor 
chungC'! in the food. {/') Ji>t-r/jlitr li.-'i'ues, ropreMi-nliHl 
bj uetls whicli tine parta of the alimcutary canal and take 
np tiio digested food. 

/Climinir/irx or Fxcretory titmiM, represented l)^ ooUa 
in the kidmy?, skin, iind clH-whciv, whii»c main buHiiicw 
it is to get rid u( the wante prMiluctit of the various parts of 
the Body. 

Revpimlorg Hnsves. Tlieno are concerned in the pas- 
oons inteii'hangos between tliu Body iitid the surrounding 
air. They iiiv conntitutcd by tlio cells huing the lunga 
and hy the imlored coqntsclcs of the hloud. 

As regards theuutritive tiseucii it re>|nii'os especially to be 
borne in mind that although .>uch a dnMificutinn ui w hero 
given is usi^ful, as helping to show the method j>ur-ued in 
the domvstic economy of tb« Body, it is only imperfect 
and largely uri illciul. Every cell of tlio Body ik tn itself 
assimilative, respiratory, and excretory, and the tissued 
in thi.'' clii«» lire only tho^e concerned in the lirst and 
last iiilerdiangcii of material between it and the esterncd 
world. They provide or get lid of substance for the 
whole Body, leaving the fcctling and breathing and excre- 
tion of its individual tisAuei* to be iilumutely looked after 
hy themselves, jiist ii* even the mandarin described by Itobin- 
son Crusoe who fotutd his dignity promoted by huiiug 



STOHAOK TIS81TES. 



31 



wrraaU to put th« food into his mouUi, had fluHUy to 
giwullow mid digeat it for tiinuelf. Moreover, there ia iio 
logiod dietiDctioii between u xccrvtory itnd «u cxcrclon' 
t-ell: cuch of them is ohiinR-tcrixed by tlie formiition of cer* 
tain snbstsitcct wbi<:h are poured out on a free surface oii 
the exterior or interior of Hio Body. Miiny wtcrctorycclln 
too luivG no oouccni with the digestion uf food, a^ fur 
example those which form the toant and sweiit. 

4. Storago TlsBuea. The Dody does not In i* fi'o::i hand 
to muuth: it Iiu^ ulway^ in hcaltliaflU|>plyuf food nmleriaU 
iiccumulatixl in it boyoiid its immediate needs. This lies 
in i>art ID the individual oolU tbomMlrcs. just ng in ii pros- 
perous Doinmuiiity nearly every one will have some lil4le 
pockft- money. But ajmrt from this reaorvc there are oer- 
tnin celU, aHuM of cuiiilitlii'i-^, which fUivn up ennviilrnihl^ 
quantities of DLateriul and constitute what wc will call the 
'iorage Iushm- Tlic^c uro eirjiectany rcprttwiitod by the 
liver-ocllD and fat-cells, which contain in health u roMTV* 
fund for tbo ri'i'l of tlio RoJy. Since holli ■'( thiw. to- 
f^thcr with oocrelory and excretory cells, are t)io huiIh of 
l^reul dkumical activity, they ore all often (Ailed mrtabolh 

D. Irritable TlBsues. Thi; innintenanoo. or at any rate 
tbo best ]>ii«.-j'eriiy, of a nation is not fully secured when u 
division of labor lia< I^Ocun [iliuxt in food-supply and food- 
diHtrihution employments. It in extremely d(^^rahlc that 
means lihall ho jiroridod by which it may receive informa- 
tioD of cxternul changM which may affect it lus a whole, 
ftuch ta (ho policy of foreign couiiIj-Im ; or which thai) e»- 
able the itiliabitants of one )>art to know the needs of an- 
other, and direct their activity accordingly. Foreipi min- 
Lsten iiud coii^iiIk and newvpupor correspond on to arv em- 
ployed to place it in commanieatiou with other statM and 
keep it infonned as to ils interests; and we find alsoofga- 
niswtious, such wt the meteorological department, to wnrn 
diitant partft of approaching storms or other climatio 
changes which may seriouHly affect the pursuits carried on 
in tbera. In the human Body wo hare u oomparablo «lu8S 
of 'itelligence-gaining tissuci lying in the soose organs. 



TUn nrjfAJT BOOT. 



whose buHineM it is to lufCortHm mid tyimmutiicnU to Uir 
whole. fxti>nial changps which occur nround iL Since 
the usefiilneaa of these tiasiiea dejieuds upou the roadioess 
with which slight cuu«m omle them to Mtinrr, we may 
call them Ihe irriMiJf liitnw'. 

6. Co-ordinating and Automatic Tissuon. 8nch infor- 
initlioii «.« that colW-wd by miiii-turs in foreign jiiirls or hv 
ineteoi'ological ohscrvcrs, is usuuily sent direct to some ceii- 
trij olliue from whiuU it is retiiatrthutod; Ihiji mere rcdij?- 
iribiition is, however, in many cases but a small ]mrt of the 
workcarricd on in stiuU oDiccs. Let us suiijio^^c informa- 
tion to be ohliiiia-d t)i:it »u Indian e)iii>t is collecting lii« 
men for an attiick on some point. The news is probal)ly 
first tr»n»[nittcd to Wiishington, and it bccvniL^j the duty 
of the cxoi'utivo ofHiK^ra thoro to employ oerioin of llio con- 
stituent units of the eocioiy in such definite work aa ii 
needed for it» protection. Troo|»« have to he «nt to the 
place threatened; porhnps recruit* enlisted; food and 
clotbos, wcnpuns and uniintinitt«u must bo provided for 
tlio army; and so on. In olbcr words, the work of tho 
Tariona classes composing the society has to be organized 
for the common good; the mere spreading the news 
of tlio dmiger would nione ho of litllo avuil. So in tho 
Body: tho informution foniardcd lo certjiin centres from 
the irrltiible tiMucit U ii^cd in miicIi n wuy m to arouse to 
orderly iw:tiviiy other tissues whoso services are required^ we 
find thus in those centres a group of co-orttinatinff tisstut, 
rc[>TCfcii\cii hy >uref-cel!M and jiosttihly by ooruiin other con- 
KtitiifUt'' of the nerve centres. Certain nerve-cells are also 
automatic in the physiological sense already pointed out. 
Tho highest tnunifesttalion of this Isttor faculty, shown 
objectively by niuspuhir moTemenls, is suhjcolivoly knonu 
us the "will," !i state of consciousness; and other menial 
phenomena, as semuition* and emotions, are niso asHoeiated 
with the activity of nerve-cell* lying in the bmin. How ii 
is thnt any one stale of a nuilerial cell should give rise to a 
jiurticulur state of l'on«.'tl)u^^css is a matter qnito beyond 
our powers of eouoeiitinn; hiil not really more so than how 
it is that every portion of matter attracts every other por- 



MOTOR TISSXrSS. 



tion according to the law of inverse sqnures. In the 
living Bodj, as clscwheru in tlio nnivcrso, wo can shidj 
phenoinco:i and make out their reUliond of (ieijuen<;c or 
tio-cx into nee; but why ono iihPDinnvniiQ isoccomjiatiiod bj 
aiiothfir, why in fiwt, any cause prtHlm-es an cffi-ot, i* ii 
matter quite bojoml our reach iu cverj' case; nliether it be 
u KCniuttion uoconipanying a niulcculnr chuitgc iu a nerve- 
cell, or tho fall of a stouo to the ginund in obedience to the 
law of gra vital ion. 

7. Uotor Ttaanes. These have the coutiaftility of the 
original protoplasmic mosses highly iKvolopud. Thu more 
important are cHiaUif (flU and num-nlnr tissue. Tho for- 
mer line certain surfaces of th<^ body, and jKissaaa on their 
free awfacoa Stip threads which are in constant movement 
One finds !'ttcb i-tAU. for example (Fig. 47*)lining the iu- 
Btdc uf the windpipe, where their threads or cilia serve, by 
their motion, to sweep any fluid formed there towards the 
throat, whore il can be efiugbcd up and got rid of. Mni>- 
ottlar tissue occurs in two main varieties. Ono kind is 
fonad in the mnscleti attached to the bones, and which an 
nssd in the onlinary voluntary movoinent'i of the body, 
It IB Gnm|iosed of fibres which present crofie-stripos when 
view«d under the microscope (Pig. Silt)^ and is hence 
known Mt striped or sln'nhit miisrnlar ttMui-. The other 
kind of mnscniar tissue is found in the walls of the 
alimpntary canal and KOine other hollow organs, and con- 
tti.it^ of elongated cells (Fig. .^o I) which present no cross 
striation. It is known as plain or umtriatrd mwseutar 

TliO'cells enumerated under the heading of "undiSor- 
eutiatod tissues" might nl^o be included umotig the motor 
tinnoA, aiiicc they aiv cupublc of cliangitig thf-ir form. 

8. Tho Conductive Tisauoo. These are represented by 
the n«rc« fifiTf/i, slender ihrcjids formed by modification 
and fusion of cells, and having the coudiiotivity of the 
•muiboid cells of the morula highly developed: that is to 
say, they readily transmit molecular l]i^tu^banccs. When 
its equilibrium is upset at one end, a norvc-6bre will 
tnutamit to it« other a molecular movement, known as a 



Bi 



TBS iruXAX BODY. 



" survoti$ impuUe," and eo can excite in torn parts distant 
trom tho oripiml exciting forco. Svrvofilm^* pltK*, mi 
lliv one tiAud, the irrilahio lisAUOH in conDL-i-tioii with the 
iUitomatic. (.-o-DnHiiutiii;;. and s^UHury: and on tho oth^r 
])ut tlitt lliivc Iiitlor in i/omumtiicatiou with the amsculur, 
secretory, and other tiuiiee. 

9. Frot«ative Tissuoa. These oon^irt of ceruiin colb 
lining ca^iiici iunide the liodyand called fpilh'li'il lylln, 
find ccWf I'livcritig tlic whole Dxlorior of the Uody and 
forming i^iiilrniii», hairt, mid wnh. The n^tawiW which 
covers the teeth belongs also to this group. 

The cla*a of protfctivo ti«siic« is, howrever. pvm more 
iirtifioial than Hint ui the iiutriitTe tiwuef, uinl cuiirii'L U- 
dofined by positive characters. Many epithelial Pells ars 
Becrctory.. excretory, or receptive; and ciliated coUs have 
nircjidy been included among tho uiolor liKsuc", nlllumgh 
from till- fikcl Uial tho moveniontK nf iheir ciliu go on 
in separated cells and independently uf rLiognizHblv extor- 
Da] :^imit1i. ihoy might well have been put tutmng the mi- 
tomatic. 'I'lip jirotectivc tissnea may be but deJincd as 
inclndingoeilii which line free ifiirfaccs, and wlicwo func- 
tions arc niiiinly mcchimical or physictd. 

10. The R«pn>daotive TiasnAS. These ara concerned 
in the product ion of iictv individuuK and in the human 
Body uro of two kiml^, located in differunt tuxv^ The 
conjunction of the pi-udncts of each aex is necessary for the 
origination of offspring, Hiiico the ovum, or female pro- 
duct which directly dcvch)pii into the new humiiii hciug, 
liM dormnut until it has been /rrlUizetl or actpd upon by 
the product of tho mule. 

The ComblnatlCHi of Ttaaues to Form Orgaiui. Tl'c vit- 
rions ti»ucs iibovo eniimi-riitod forming tlio luiilding mtito- 
ri:il« of the Body, niiatoniy in j>nmarily concerned with 
tlivir Ktructnrc, and pliysiolnf^v with their prupeiiiu*. If 
this, houcTcr, were the whole matter, the jnoblGnis 
of anatomy and physiology would be ninch simpler 
than they actually are. The knowh-dge about tho living 
Body obtained by studying only the forms and functions 



4 



ORG ASS. 



85 



the individual tiiwiieit voiild lie onin|iiiri>b]c to that at- 
tiiiaoil Eihiiiic It grmt fnctorj* hy .itudytng tiopnrntelj' the 
boilers, pistoDa, lovers, wheels, etc., (ound in it, and leav- 
ing oat of account altogether the uity in whicli thnw nro 
oombini^ to fi)rni various nijushine.^: for U\ the Body tiie 
varioiLii lissuoa are for the most part m^socintod to furai 
argaiu, each organ luusivoring to a com)ili.'X niiu,*litiie like n 
Ativan] •engine with it:* iiiiniGroua oonsiittient partii. And 
Just 03 in different machines a co^^ wheel may perform 
very diffort'iit diitii'^, <lepisiiiloiit Upon the way in which it 
i* coiiikei'ted with other paiu, so in the Body any otjc tis- 
sue, although ila essential proiwrties are everywhere the 
nmv, may hy iti* activity giiVcrve very various nso* u«e«r(l- 
ing to the manner in which it is combined with others. 
For example: A nervu-fibro uniting tho eye witJi on« part 
at the brain will, hy mi'an^ of its conductivity, when ilit 
«ud iu Uio eye i« excited by the irritable tissue attached to 
it on which tight acts, cause ahaagGB in the sensory nerve- 
cells conut^ctod with Ita otlior oud and so ftrouHo a eight 
Mettjittiuu; but an exactly similiir ncrvc-Hhre ruuning from 
the brain to the muscles will, aUo by rirtuo of its conduc- 
tivity, when it» ending inthc brain is excito<i hy a diango 
in u aorve-oell connected with it, stir up the muacle to con- 
tract under tJiu c<mtr»l uf tliu will. Tht.' diffei'eiit rMultH 
de[)«ad on the different ymris connccti^d wttii the eiuU of 
tho nerve-flbros in each case, and not on any difference in 
tlie proporlie^ of the ncrvc-fibros themselves. 

It becouKu neijoiwtry then to Ktuily thu arrangement nntl 
lues of the ll^nea >\s combined to form vurioutt orguiiK, and 
this is frequently fur more diffienlt than to make out the 
«tractnroand pro|>ortioe of the tnJividuol tissues. An or- 
dioaiy roiiHclc, such 08 one sen in the lean of moat, i« a 
very complex orgun, conlaining not only contractile miw- 
oular tissue, hut ifupporliti); and uniting connective tissue 
and conductive nerve-Obrei*. and in addition a com|iTox 
commiunriat armngoment, compospd in its turn of sereral 
tinucs. concerned in the fond supiily mid \va«to removal of 
the whole muscle. The anatomical study of a mnaole fasi 



a« 



Tim IHTiTAir ItODY. 



to take into account tlio nrmngcinCTit of nil (lic»^ pnrtx 
witkiii it, and alflo its coiinectioiiB with other oT^iiie of the 
Body. The phyHiologv of any niti«L-lo must take into ac- 
count tho Bvliiiii.s <it nU ih«e imrl.s working logdhiT and 
not meroiy tlie functions of the miiecular fibres tliemsclvts, 
and has also to muko out under wliut conditions the muscle 
it oxcitod tn at-tivity by chnngoa in other organs, and what 
ehange.'' in thfise it brings about when it worka. 

FhyaiologicBl Moohanlams. Kvon Iho »tudy of organs 
added tu tliat of lli<i i^egiiiiate ti.iaucH duv-s not cshautt tlie 
whole matter. In u factory wc frciueully find machine* 
arraugcd so tliiil. I wo or more *hall work together for the 
|ii'i-forimuice of some one work: a si<-ani-<rngiiie mid a loom 
may, for example, be conneetcd and used together to wwive 
cs^l^)Cf5. Similarly in Ihe Body Ktvcral orgims are often 
arranged to work together fo ad to attain some one end by 
their united uctioiis. Such combination!! are known as 
pfitfi^iriliii/intl (tfiparititi.ift. The circulatory npj)amtus, for 
exanijile, consists of various organs (oiieh in turn eompusnl 
of EOTorid tissue!!) known a» heart, arteries, caj'illariea, and 
veins. The AmH forms a fori?e-imnij) Uy which the blood 
is kept flowing through the whole mei'liaiiiirn, and the 
rest, known together us the blood-VM»el.t. distribute ibo 
blood to tho viiridiis organs and reguhile the supply siccord- 
ing to their needs. Again, in tho visual ujipftnUn* wc iind 
Uie oo-operatioH of (a) a set of optimi im^trunients whieh 
bring the light proceeding from external objects to a focus 
npon {b) tho refina, which contains highly irritahle piarM; 
tbesc, changed by the light. Miniiilute (') tho optic nertf, 
wliieh is conduclirc and Iratmniit^ a diftturbanrc which 
arouses finally (d) ecnaoiy parts in the brnin. In tho pro. 
duction of ordinary sight sensations idl these parts arc con- 
rcnied and work together as a risuni nppanitui^ So, too, 
we find a rfypiriitnrii apparatu*. oonsUting primarily of two 
hollow nrgnuit, tho luii'/.i. which lie in the chest and com- 
mnniente by the vinrtpipe with tho luiok of the throat, 
from which air enters them. Rut to complete the respi- 
ratory appiiritfux are many olher organs, bones, musclosr 
nerves, and nerve-centres, whicb work together to renew 



ASATOmCAh STSTRMf. 



87 



Uw air in the lutig» from timn to time; nnd tbe act of 
brftttiiing \a the fioal result of the activity of the whole 
a{>paratn3. 

Many »iiniliir iiiiitaiiix!!!, m lliu nlinien(»ry ftppurntue. the 
nuditory npparaui^ and eo on, will readily be thought of. 
Tli« itludy of the woikiiig of such complicated mechanisms 
farina a very important part of pliysiology. 

Anntomicsl Systems. Kriini tla* iiiiutomicnl side the 
whole txilltiptioii of biidily orgaua agrooing in (structure 
with one aiiother is often epoken of as a system; all Che 
8, for example, are grouped together as the mugeular 
t, and all tho bones &$ Die as^mti^ i<i/»leni, and so on. 
withont any reference to the dilTcivnt iisca of different 
mtucles or bones. The term system is. howerer, often used 
as uqiiivulent U> " apparatus:" odo rc-ails iudiSTcrontly of the 
"circulatory systom" or tho "chvulutory apparatus." It 
is better, however, to i-eserve the term system for a collec- 
tion of organs cliusod together on account of similarity of 
rtrnctope; and "'apparatus" for a cotleccion of organs con- 
Hidcrcd together on occonnt of their co-opcralion to execute 
one funerion. The formor term will then havfl an anatomi- 
cal, the latter a physiological. &ignificance, 

Ttte Body M a Working Whole. Finally it must all 
through be borne in mind llmt not even the moat complex 
system or apparatUH can bo considered altogether alouo as 
an iadcpcndenily living part. All «i-e nnitvrl to muko one 
living Body, in which there is throaghont a mulual intcr- 
d«pondonc«, so that the whole forms one luitnun being, in 
whom tho circiilaLury, respiratory, digestive, eensory, and 
other apparatuses ore constantly influencing one another, 
flocb ffloilifying the activilioe of the I'est. This iutoiuctiou 
is mainly brought nboiit through the conductive and er^. 
ordinating tissnes of Ihe norvons system, which place all 
parte of the Body in commnnication. But in addition to 
thif another bond of union is formed by the blood, which 
by the circulatory apparatus is carried from tiimic to tissue 
and organ to organ, and so, bringing materials derived in 
one region to distant parts, etuiblea ouch organ to inflnonce 
M iht rest for good or il). 



38 



riUC ttUMAN BODY. 



Bendea tlio blood unuiber liquid, called lymph, exiattt in 
tbo Body. Il l* uontuined m \af*c\t distinct from ibosc 
wliicli curry llic bluud, but emptying into lliv blood* v^jj>i.'1m 
at certain points. Thiii liiiuid being aIao in coiiiiiaiit iiiovc- 
ment fornu anothpr agency by which products aiv carried 
fn>in piirt to piirt, niid tho wiilfiiroor tll-fureuf oiic member 
ciiubled to iiiiiueuce &IL 



CHAPTER IV. 

THE INTERNAL MKmUM. 

mal Medium. During llio whole of life int«r- 
cfa&ngee of miiti7ri:il '^>i on botw«i'ii ovury living Iwitig iin<) 
tb9 ftxtonml world; liv theiii! exchangeH niatt-rial particles 
t.hat one time coiiatitiito parts of iniminiute ohjecis coino 
at another to form gmrl of » living; Itcing: iiin) Inter un 
tfaem nine aioma. after hariug been a part of a liviu^ cell, 
are passed out from the Body in the form of Iif«]cjw com- 
poands. A« th« foods and wiu>t«« of tiu-iumt living things 
differ more or less, bo are more or lees diflfn-iit environ- 
ments 6oit«d for their eni^lvnt-c: »ud there is iK^curdingly 
It relationship liotween the plants and animals living iu 
my one place and the conditions of air, earth, and wawr 
prevailing lliore. Eren snch i^implo nnieollular animals ii£ 
the ama>i>ii live only in ukut or mud contnlning iu »olu> 
tiou certain gaaea and, in tin.-<|)ension, solid fond particica; 
and Ihey soon die if the water bo changed either by esien- 
tially altering itM gates or by tjikiug out of it the Holid food. 
So in ycoAt we find a unicolluliir {ilaiit whieli tlirivcii and 
inuUiplies only in li'iuids of certain composition, and whirh 
in the Absence of organic lompoundif of carbon in solution 
will noi, ^row at all. Kacb of tlieM) simple living things, 
which corraaponds to one only of tho innumerable cells 
composing tlm fiilU^j'rown hnmun Body, thus requires for 
the mai)ife.'>l:ttio:i of it4< vila] properties the presence of ii 
surronnding medium suited to iijwlf: the yeast would die, 
or at the bc«t lie dormant, in a ll<|nid containing ouly the 
eolid organic particles on which the amti-lm li»i-s; ii;id 
the amonbii would die in such Bolnlions as those iu which 
jeaat thrives best. 



40 



TBS RVMAX Bonr. 



The Xotoroal Uedium. The snme close rebitionehip 
bctn'ccu the iiving being and ita environment, and the 
tame oyclicnl int«rch»iigc between the two which we flud 
in the amo'lm und ibc jcast-ciOl, wjonr iiUo m even the 
most complex living beings. When, howcTcr, an nninml 
oomcfl lo be comiKwwl of many cells, some of whicli are 
placed far awav fmm the surfiice of its b"ih' Rnd so from 
immediute cotiiaetwiih the environment, tliore uriiws a new 
need — a necessity for an internal inedinm or pUiKnia whicli 
shall play the Nime jiurt toward the individual cells as the 
sHrnitmding air, water, and food to the wliole animal. Tliin 
internal mL-diiiin kupt in movement, and receiving at Kome 
regions of the bodily HnrfiK'es materials from the cilerior, 
while losing otber subetancefi to the exterior at other sor- 
faces, thus forms u eort of middleman bctivci'n the in- 
dividual ti--<'ine.'i and tlio finrrounding world, and nttimls in 
the «ame relationship to cwh of the oclls of the Body a« 
the nnter in wliich an iiimi^lia live^ doe-'« to Ihiit animnl or 
boer-wort does to a yeuMt-ei'll. Wo Bnd accordingly the 
human Body pcr^nilcd by a li'jnid phii-nia. containing gasee 
and f()(jd material in ^uhition, and the prexcnoe of which is 
neccamry for the maintenance of the life of the tissues. 
Any groat change iu thiK mcdinm will ailect injuriously 
few or many of the grnups of cell* in the Body, or may even 
taujic their death: just as altering the media in which 
ther live will kill an amrelm or n ycust-ccll. 

The Blood. In ibe human Body the internal medium is 
primarily fumislicd by the blowl, which, as every one 
knows, is a red lii|nid, very widely diittributed over the 
frame, since it flows from any part when the «kin ii< cut 
through. There are in fact very few portions of the Body 
into which the blood is not carried. Oneof the exceptions 
is the cpidcrmi*, or onter layer nf the skin : if a cnt be 
made throiiRh it only, leaving the dcejier akin-layers in- 
tact, no blood will flow from the wound. Ilaira and imilif 
also contiiin no blood. In the interior of the Body the 
e]iitbnlial cells lining free surfaces, such as the inside of 
the nlimenljiry canal, contain no blood, nor do the hard 
purl« of the teeth, the cartilag«s, and the refracting media 



Tax nrrgRXAL ukmvv. 



41 



: 



of the eye («oo Chap. XXXI.), but tlimte iiil«rior parts are 
moisUtned with liquid of eomo kind, and unlike lliu opi* 
ilermis are protect«d from ni]>id evaporutiou. ^Vll Uiese 
bloodle«8 partm together fonu ft group of nvn-itiscular tis- 
■mes; lliey alone escepted, wounding any ]<art of tlie Itody 
will be followed l>y bleeding. 

In mauy of the lower iuiiniul« there i^ no need Ihut the 
l)<|Uid represi'nting their blood should be renewed very 
rapidly in difforant partx. Their colls liti> slowly, and bo 
reqnirc but little food und produoo hut littlu wiuto. In h 
ees anemone, for exaniple. there is no Bjictnid arningcniviiL 
to keep the blood moving ; ic is just pushed about from 
pari U) part by the general mnvenicnt.-' of the body of the 
animal. But in higher aniniak, c.4j>ecialiy th«»o with an 
elevated temperature, such an arrangement, or rulhcralc 
eencc of arrangement, us litis would not suflicc. In them 
the constituent cells liTcvery faat, mjiking ninth wasto and 
uiiing niiieh food, and so alter the blood in their ut'igh- 
borhood very rapidly. Besides, no have ween thut in com- 
plex animals certain cells are set a}>art to get food for the 
wbolo organism, and uert4kin otherit to fmnlly remove its 
vaates, and there mnet be a mire and rapid inu-nbange of 
materia) between the feeding and escreting tissues and all 
the others. This can only be brought about by a rapid 
movement of the blood in a deflnite course, and this is ac- 
complished by shutting it up in a closed eot of tubes, and 
placing somovhero a pump, which constantly tithes in 
blood from one end of the system of tubes and forces it 
out again into the otJicr. Sent by this pump, tJie heart, 
through all purl« of the Body and back to the heart 
again, the lilood geta food from the receptive colls, takce it 
to the working cells, carries off the waste of those latter to 
the excreting cells : and »a the round goes on. 

The Lymph. The blood, however, lies oTeryrhare in 
closed lubes formed by ihu viu^cubr mtem, and dooa OOt 
come into direct contact with any cells of the Body except 
thodC which float in it and those which lino the interior 
of the blood-vcsscls. At one piLt't of it« coui-»e, however, 
the TOsels through wbich it passes have extremely thin 



48 



TUB UfJfAS OODT. 



A. 



r,r.i I. iHn- 

»iiiK' iii'pnrnMr*, 

llqulda. A wu) 

■ molM bdIioiu 
mnnbnns. 



coaUi (UkI Oirough Uie wuUa of tlie»R atpiUarie» liquid 
Traiiaiidos fnun the lilood uid bntbee the vuriouH tissues. 
Ihe truuEudcd liquid is thv lymph, liiid il is lliis vhicli 
[uniui lliv iuiaiudiuU! uutrieui pluema of the ti;>&uea cxcv]>t 
ihc tisw which tli6 blood inoi^tcjiii diivotly. 

Dialysis. Whcu two Hquidd coiituioiug dilTerent tnut- 
t«r8 in KiluiioQ aro sepanited from one iiiiolhci' by a nioi^l 
aiiimnl mcmbruiio. aii inlcrcliungo of niuU-ml will uikf 
gdnoo iiiKioi- certain i^^iiditiona. If A be n 
vessel (Fig. 9) comjik'toly divided verlit-nlh 
bj Mach It III L-mb nine, und » Miliilimi uf fuu- 
inoii Mdl iu wnter be placed on the eidv b. 
and a aolntion of £Ugar iit wiit^r on the side 
c, it n'ill bo found nfti^r a time thai mnu.- 
nilt lind got into i- and Honio xugar into h, al- 
though there are no viKible iroree in the parti- 
tion. Such im iDlcrdmiigtt it mA to be due 
to t/iiili/*i8ot oamimM, and if the procwawerp 
allowed to go on for euuid liotirit the miuic 
proi>ortioni< of salt and tugar would l>o found in tJie nolu- 
tions on each side of the dividing membrane. 

The Benewal of tbo Lymph. OKuiotie iirocoMiHt plur a 
great jnirl in the nuiiitive prooesses of llie Body. The 
lymph present in any organ gives up things to the ceils there 
and get« things fn»m Uicm; and m, although it may havo 
originally been tolerably like the liquid part of the blood, it 
soon aoi|uireB a different chemical composition. OilTusion 
or dinlvbis then commoncce botwcon tlic lymph oul#idc and 
the blood in.>tidc the cupillaric^, und the hitter givc« up to 
the lymph new materiaU in place of thotie which it has Iwt 
aud \nV<f* from il Iho tnu-te products it ha« received from 
the tissues. When thin blood thus altered by exchanges 
with the lymph g«t« again to the neighborhood of the i-c- 
ccptivo celU, having lost eomo foiid materials it \i poorer 
in those Uian the riehlysup|i]iod lym|>h around those cells, 
and takes up a supply by dialysis from it. When it reachen 
the cterelory «rgait« it ha.t previoiixly pickt-d iip a qnanliiy 
of wiuite mattcT-'i and loses these by dialysis to the lymph 
there pr^enl, wluch is epecially poor in ^iioh nuitl«r«. 



LYMPHATICS. 



43 



since the excretory mIIh coiistimtly deprire it of them. In 
conRijucnvc of (he different wiitit^ iiiitl wiislMuf vanixis 
ccllii, and of the same wUe at dillt'ivut tiuius, tlio tvmjih 
muHt Tiiry conudui-uhlv in cuiii|iu«ittun in viirious orgiuiituf 
the Biidy, and the blood llowing Ihroiigh them will gii or 
\ote different things in different |)Iu(.'q«. But renewing 
during i(« circnit in one whiit it Iusch iu anoilier, ilji avcr- 
Kgo ooniposilion is kejit pretty constjmt, and, tiirongh in- 
terchange with it, the iivorugc o»nipu«iliou uf the lymph 
also. 

Tbe laympbMio Vessels. The blood, oq the whale. 
10903 more li<|uid to the lymph through the capilUury walU 
than it rcctiivo-s back the same wiiy. Thi# deponds tnuinly 
on the fiurt that the jircssure on the lihtod inside llie vee- 
eU ia greater thiui thul on the lymph outiiidu. tind eo H 
ertiiin iimonnt of Hltriilion of liijuid fi'uni within out 
occurs through the vu«cnlnr widl iu addition to Uie dialysis 
proper. The once*)* ijoolk'cteil from the vurions organs of 
fho Bixiy into a set of /r/injJuitir tvtstlt vhich curry jt 
direclly liack into Hunie i)r Iho liirg(T bloi>d-ve.'eel* nwir 
ii'hi'rtrthi.v<cempty into the heart; nud hy this flow of lymph, 
under pr&wure from behind, it is renewed in various oi-- 
gans, fresh li<[uid litti'ring through ihc c-j>j)illariM l» l:iku 
it* pliice 11* fust i%i tlie old is oarrii-d nfl. 

The Locteals. Jo the walls uf the alimenliuy canul cer- 
tuin fuoil ui!iti'i'ial:! afler juivsing through iho receptive cells 
into the lymph luf nut truiisf erred liHidly, like llie rc*l, by 
diolyxiw into the hhiod, hut are carrricd off tiodity in the 
ly in |ili- vessels and poured into UicveinHof » dislanl [lart 
of the Body. The lymphatic vcnk-U concerned in thia 
work, being freijueutly tilled with a white li-iiiid during di- 
gestion, are called the iin'H-)/ or tarttnl venxrlit. 

Summary. To t>inu up: tho Idood and lymph form the 
iutarnat niediinu in which the ti^itucs of the Body lire; the 
lymph i< priniiirily derived from the Mood and forms the 
immediate plii-iHiii for ihe grcjit niujority of thu living coIIb 
of tho Body: and the eieeas of it is linally returned lo tho 
Mood. Tlic lymph moves hut slowly, but is eoiD'tantly 
roitovated by the blood, which is kept in rapid movement, 



u 



THB nVMAX BODT. 



aod whicb, lw*id<,-s containing a store of new food mfttt«r« 
for th« Ij-nipli, caixiea off the wastps whicb the rarioiis cells 
have poured into the lulter.niitl tlui.i \» uI«o awirt of Aevragc 
Ktreiiiu into which the wastes of the whole liody are pri- 
marily policcted. 

Hicrosoopto Cliaracters of Blood. U v. linger hv 
pricked, and Ihc dixip of lilowl fiuwing out be reoeiTed on 
a glasx slide. coTOrcd. protected from evaporation, and ex- 
umiiicd with • mtcroAOope mugnilViDg about 400 diometci!^, 
it will be Bced to f^msiat of innumemhle solid bodiea float- 
ing m a liquid. The imlid Wlie:' are ilic biood eorputdet, 
and the liijuid is the IIoikI plasma oi' liquor mnffiiini*. 

The corpuscles are not all alike. While currents still 
exi»t in the freshly sp^-jul drop of lilood, the grcut majority 
of Lhemaro rejidily cirried to aud fro: hut a certain num- 
ber more commonly stiek to the glass UD(1 remain in one 
pUiCD. The former are the r«f, the latter the pfite or color' 
less blood ii>ri"i.'r/eg. 

Bed Oorptisolea. form and Si'tf. The rci! corpuwksac 
ihcy lloiii. about fnijiii-ntly seem to rmy in form, but by a 
little uttenlioii it uni be made out itmt this appearance is 
duo to their turning round as tlicy flo«tt, and ho prctiontiiig 
different 8«|Jects fo view; just as a siUcr dollar preBent.t a 
difforciit outline according as it U looked at from the front 
or edgewise or in three-quarter prollle, 

Somotimc« the corpuscle (Fig, 10. S) appears circnl*r; 
then it is seen in full face ; somctiron linear {C), and 
cligbUy narrowed in the middle; sometimes othI, ns the 
dollar when hidf-wny between a full and a side Tiew. 
These npiwuraneoii .*how thiit wicli red oorpuMclo i* a circu- 
htr di^k, itlighr.ly hollowed in the middle (or biconcave) and 
about four times as wide !is it is thick. The average trans- 
vcrto diameter is O.11O8 millimelcr (irfim inch). — C\>lor. 
Seen ningly each red corpuscle i* of a pale yellow color; it 
is only when collected in niassi-M that they appear red, 
The blood owes its ivd color to the great numt)er)i of these 
bodies in it; if it be sprmd out in a very thin byer it, too, 
i« yellow. The Inyer niu*t. however, he very Ihiu or the 
drop will still look red on iicooiiut of the immense number 



BLOOD. 




of these corpasclea pretwiit; in a cubic millimelor (^ inch) 
of blood there ure ubotit Gvc millions of ihcm. — Sfruclun. 
Seen fiwin Uio front, the wnti-al jmrt of <yK:li red ourptiscJe 
iu a ocrtaiD focus of tho iiiicroetope ap^vai^ dimmer or 
darker than iho rest (Fig. 10, B), oscopl a niirrow hand 
neiir the oul4;r rim. If the leiw of the uiicnuscojie bu ntiiwd, 
however, Ihis pieviouBly dimnicr t«iurul part becomes 
brighter, and the pruviotwly brighk-r jmrt oUcare {£). 




u. W— Blood corpuHlHi .1. tn«^in«l ■houHWdlnmnWrii, Thprtrimr- 
-M haw HRBBC*! tlivniwim In rouleaux : a. o. coIotIh* oorpiuplm : B. 
- - 1 «on>UMli9« mora inaxnin«<l and Hen In toeut ; S, a rvd corpuiclo ■lichllj 
J DUflt boat. At llu Ftthi-lunil top oomsr ta a rod «on>uKla mdo Id llirr*- 
l|aiwnv taeo. and at Com mvu aOgiwIm. F. O. H, t, whRa cmtmcIm titVif 



This dilToroiice in appoitmnce dot's not indiciito Uio prtjcnco 
of a Getitral part or nutUun dilTorent from the ivitt, hiiL is 
an optioal phenomenou due to the Eba]N> of the corpUEcle, 
in consequence of vhich it ads like n littlv biconcam k-iu 
(se« PhvMicv). Rhvs of h'ght parting ihrntigh noar the 
' centre of the corpuscle are refracted differently from thoMO 
ptuaing through olaevhero; and when the microscope \s 
so (ocasod that tho lattor ruacli Lhe e^-v, Uic furuivr do iitil, 



4e 



TBM HUMAS BODY. 



and vice verm ; llios when th« («iitrul pnrU look bright, 
those uroiind thorn louk uh#curci aud the ootttrarr. 

There ia no wilirfaotury evident* liial llic«c corpiuolM 
have any oiivoloping sac or c-ell-wiiU. ^Ul the mothodii 
used to bring oiio iiit» view umler the micro».-ope are snch 
Bfi would coa{;ulate the outer hiytTx uf Ihv ciilN'tHnvo com- 
poting the oorpuwle and so mAka an iirlillcial cjivcIoiic. 
y« fur M optical aualy*i3 goes, then, each corpuscle in ho- 
niogoncous thruughotit. By other meim^ wc can, however, 
tihon' that At Ica^L two niiiU^rtiit!' anxxt into thi> stniclilixt 
of each red corpiuicle. If the hiood he dihiied with several 
liuicji iU own bulk of water uiid he then examined with the 
microscope it will 1)0 found llutt tin- n& corpufclfH are col- 
orless and tite plasma colored. The dtJution has caused 
the coloring matter to pass out of the corpuscles and dis- 
8oItc in the lifptid. Tbi* colniingconsliliicnt of the oor- 
pnsclo is ha-motflohm, and the lolorless residue which it 
leaves behind und wliicli ewclU up into a sphero in the di- 
luted phunia is tlio AfroHM. In Uio living cor]iuscto the 
two are intimately mingled throughout it, ami so long as 
this is the cai^o tho blood is opaque; but when tlic coloring 
matter dissolves in the pUuinti, Uioii the hloo<l hevouica 
transparent, or, as it is called, lak^. The difference may 
bo very well seen by comparing a thin layer of fresh blood 
diluted wilh ten time* ils volume of ten-per-ceut salt »o- 
luljou Willi a KimiW Ittyer of lilood ililutod with len vol* 
umea of water. The watery mixtitio '\a a dark transparent 
r«l; the other, in which the coloring mutter still lies in 
(he corpusclcK, ia a hrighti>r opaipie Tcd.—Comnglfurj/. 
Kach red oorpuscto is a soft jelly-like mass which can be 
retijiiy crushed onl of shape. Unlew tho pressure be fiich 
an to niptiiro it. the oorpuselo immediately rotuwuniex its 
proper form when the external force is removed. The cor- 
]>ii>»lcK«re. then, highly elastic; lliey frcjueiitlycjin hCR-cu 
mueh dragged out of vhnpc inside the vessels when the 
circulation of thu hli>ud i* wuti'hetl in a living animal 
(riiap, XV.), but immediatolyspringiiig back to their nor- 
mal form when iliey get ii cLunee, 

Blood-Cryatals. Ilasmoglobin U, us ■ibov'e shown, readily 



BLOOD CJtTSTAtA 



4T 



aoluble in water. In this it kwii decompofiM if kept in a 
warm room, breaking up into a proteid subftliincc mllcdi 
jfMnlin and a i-ed-colored t>odif. kanuttiH. By keeping 
ihc ha-rnog)obiii «o1iitioii very cold. iiowcTer, ihiii drcompo- 
TtitiAii oan bi> greatly ictufded, and at tlie e&mo time Die 
liulubilityof the ti!emoi;lo)>iD in thowut«rinucIidimini»<hed. 
In dilute alcohol Iia-mogiobin in fltiti l«!w Holublc, und no if 
tl3 ioe-oold watery solution liavo ooe fourth of iU roliime 
o( cold alcohol atldod to it and the mixluro bu put in a re- 
frigerator for twiMity-four hours, a part of the hn-moglobin 
will often crystallixo out and unk tu tiie bottom of the 
TcMe). where it can bo oolleoted for examination. The 
hemoglobin of the rat ia 
teas soluble than that of 
man. and thereforo crjs- 
lallizes out eapeci^lv 
easily; but theee biemo- 
globin <.-ni'$t4d«, or. as 
they are often called, 
hlood-cryftah, can bo 
nbtained from human 
blood. In 100 parls of 
dri- buniun rwl blowi- cryuiu' 
corpuscle! (here are 90 of hipnioglobin. The bsmoglobin 
is the eeaential constituent of Uio red blood corpuscles, 
enabling them to pick up lars« quantities of osyg«n !n 
the Iung3 and carry II lo all jmru of llio Body. (See Bes- 
pi ml ion. ) 

Hatnoglnbin contjiinH a coniiideniblo qnantity of iron, 
much more than any ollior proximate constituent of the 
«t>.ly, 

The ColorioM Blood Corpuaoles (Fig. 10, F, If, 6). 
Tlie iitlorleti.i, ptile. or t/'Ai/i* rttrpH^rlet of the blood are far 
le>M numuroiis than Iho red; in health there is on the ave- 
rage about one white to three hundred red, but the pro- 
jwrtitin mny rary consideraWy. Kath is finely grannlar 
and L-onsisU of a soft mius of procop)iu<m enveloped in no 
definite mll-wati, but containing a nudeus. The granules 
In ilie proloplaHm i">mmonIy hide iho nucleus in a fresh 




Tm. II.— BJiwd .crrMili. or luuiiio(lul)la 



4S 



TBE UUMAX nODT. 




oorpnsde, bat dilute acetic acid diasoWoa most of tlinn 
ttQd brings llio ntidciu into ricw. These juile corpuscles 
belong \a tho groiii) of tiiidiffcrciiliiitod tissues and differ ia 
no importAiit reisoguizalile ohamctor from the cells which 
Riiiico up llie ivliolv von,' j'ouag human Body, nor indeed 
from such an unicellular animid na uu Aiiiu-lm. Liltv tho 
lutlor. they Imvc the power of slowly changing iheir form 
s|)0»taDCoit.«1y, and m hu*c not tho deliniteness of outlioo 
which belongs to the red oorpu«ol08. At ouo moniont 
(I-'iK- 13) a pale corpuscle will be seen 
M u «phcroi(l»l mass; a few seconds 
later ]>i-ocei»(» will be eccn nuliating 
from this, and soon after these pro* 
cc<W8 may be retracted and others 
tliriist out; and so lli6 ourpUKcIo goea 
111 rhanfring its shape, nicso slow 
am^hoid jnoMrnenla aro greatly pro- 

^SS^citTiXTM*".';;^ ™"'<"l ^y ^'"^V^^S "■« specimen of 
SlSJ.'uri;iu:,',i..' 'C ^^"'"^ '"^ **•" lompt-rattiro of ihe Body 
abaasMof r<nn .uioiuiu uhilc under cxnniinution. Bvlhni«t- 
m^ out a process on one side, then 
drawing tho rest of its body up to it, and then sending out 
a proGcstt again on the «ame side, the corpuscle can xlowly 
change its phico and croep across tho field of the micro- 
scope. Insidt) tho blood-voMcN llte^o vorpuscU's execute 
qnitc simitar movements; and they sometimes bore right 
through tho capillary walls and. gotling out into the lymph 
spaces, creep about among the otlier ti£<ues. This emigra- 
tion i» D«iv)eially frequent in inflamed part«, and Ihc^itM 
or " mailer' which collecta in absceoeB is largely made np 
of white blood corpuscles which have in this way got out of 
tbe blood-vfwi'l*. Tho sixc of the white cor])«.>'olos is not 
ra constant as that of the red; on the whole, however, they 
ore larger, their avoragc dijuneter being about 0.0127 milli- 
meter (n^^rff inch). Tlie general pi-operties of those cor- 
pnsob-s luivi' iih-eady bc^n described in Chup. II. 

Blood of Other Animals. In all animalK with Mood the 
pale corpuscles arc pretty much alike, but tJie red corpoa- 
cles, which with rare uxccptioiu ore found only Jo Vvrte* 




LrntPB. 



49 



brates, raiy considerubly. Ju nil thtt vlue; of tbo mumtniilm 
they are circniar bioonciirc diBlui with the exception of tlio 
tribe, in which thoy are oval. They vary in diam- 
.00'3mm. {mu8kdc«r)to.011 Dim. (i'h-|>liant). In 
the (Igg thi-y nre iicurly the same fliici^ ua those of man. In 
no mamniuU ■](> rlie fully developed red forpiiKclos possccs 
a nncleua. In all other Tertebmte oliMscn llie rwl corpus- 
clus powe** «centnil niick*ii«, and ur(*oviU sUj;hlly bicoiivei 
i-xooju. in A few llwlics in which they are cii-cular. 
Ihey are lat^cul of all in the amphibia, ThoKC of the frog 
M* 0.03 mm. ( u'^n inch ) long and .007 mm. bixifld. 

Histology of Lymph. Pure lymph is a colorlcw watery- 
looking liquid: examined wilh i» micnvsenpe it i« *een to 
contain niimeron« pale corpusclea exactly like those of the 
blood, and no doubt largely consisting of palo blood cor- 
pntides which have emigiiited. It contains none of the 
red cfirpuitelcs. The lymph llowlng from the intestines 
during digeetion \^, ns alrriady mentioned, not cnliirtdM 
but white and milky. It iv known na thylf and will be 
consideFed with the proec>'« of digestion. During fasting 
the lymph from the intestines is colorless like that from 
other parti of the Body. 



diakj 



CHAPTER V. 

THE CU>TTIN(i OK BLOOD. 



The Coagulation of tho Blood. Wlion blood is first 
druwn frmii tin; iivitig B.Hij- il is |icrf(!<;l.h- li(|iii<l. flowing 
in aiiv direction as readily as water. This condilion is, 
however, only temjiorarv ; inn few minutes the Wood be- 
oome« vUcid iitid ittifky. untl llic viscidily bpfomt-s nwn- 
and wore marked until., afler (lie lapse of five or six niiii- 
iitee, the whole mass eeta into n jelly which iidherc^ to 
the TOesclroiituiniugit sothnt thiHiony bt* iiiTi'i'ted without 
an; blood wlmtcvcr being 8i)illed. This triage b known 
as that of gilatiniiatiiiH and is ulao nut permanent. lu 
a few minnk'i< the toj) i>f llic jclty-liko niii.'^ will be eeon 
to be hollowed or "cupped" and in Ibi* cunwivity will be 
KCcn a fmall quantity of ncitrly colorless liquid, the hlood 
»enim. The jelly next shrinkii so an to pull itself loose 
from the fiides and bottom of the Te»se1 containing it, and 
lU it iJiriuk*, sr^uecxcj out more and nmre HTurn. inti- 
mately we get a solid riot, eol()n'd red, and xinallcr in size 
than the tt-s^el in which the blood coa^ilut«d hut retain* 
ing \U furm, flouting in a (juantity of pulo yellow serum. 
It, however, the blood be not ailnwcd to coagnlute in por- 
foet rftst, a cortuio numiwr of red corpuscles will Iw rubbed 
out of tho riot into the Hcnim and the hitter will bv mora 
or loM reddish. The longer the clot is kept the more txriini 
will be olilaiiicd: if the lirst qtuiutity exuded be decanted 
off and thu- clot put aside and protected fmni evujiorution. 
it will in a short time be found to have shnitik to a smaller 
size and to have prcMCil out morf serum; and this goes on 
OS long as it is kept, until pulrcfactivo changeH enmmeuco. 




0AV8ES OF COAOirLATtON. 



6\ 



tbfl 




Oaiue of CoagulntioD. M a drop o[ fresh-drawn blood 
be (<|>Ti--iii <iui .nijil wtit4:li«'il willi « micr<MOu])o mngDifyiiig 
600 or 700 diameters, it will bo ecea tbat tJie <^aagllIntioll ix 
dae to tlie separation of very fine solid tbreadH wbicfa ran 
in etciy direction ftiroii^h (h« fibu^nin mid form u clow 
network cutanglingf all llio oorpusi^ii-s. Thet*e tbrtwiii on; 
cMnpiMod of a prok'id substance known as fibrin. When 
tbcy liret form, llio wbolo drop itt much likeaxpinige soaked 
full of water (represcmted by the soruni) and having solid 
bodies (the (.■orj>usck's) in its cnvitit-s. Aftir tin' fihriri 
Inreajls hate l>t«n foiined they tend to sliiTten ; hencv 
when biood clota in mass in a veeel, the fibrinous network 
teiids lo shrink in «vorjr diredion just iw a network 
Torinbd i>f stretched india-nibbiT hands would, and thin 
idirinkage in gre;tter the longer the clotted blood is kejit. 
At first the threads slick t<>o rtrnily to the bottom und sidcfl 
of the roTistrl to be pnllod away, and tliu8 the first aign of 
contraction of the fibrin Is seen in the cupping of the 

fitco of the gi'hitiTiixc'd hlnod whi^ro tlie threailii Imvc no 

id attiu-hmenl, and there the contracting mass preeaefl 
oat from ila mesbes the first drops of eenim. Finally the 
contniction of the fibrin ovcrcmno* its ndhesion to the vowel 
and the clot pulls itxclt ^)o^e on all sides, pressing ont 
more and more scnmi, in whii-h it ullimjili-ly flouts. The 
f^ul majority of the rod eoqiusclw arc held back \n the 
mcshea of the fibrin, but a good many pale porposoles, by 
their ameeboid movements, work their way out and get 
itito the «ernm. 

Whippod Blood. The eswcntiat point in coagulation 
being Ibe foriuaiioiiuf Ithrin in the plasiiia, and blood only 
forming a rerlaiu tinionnt of fibrin, if thin ho removed «» fast 
A3 it formx the remaining blood will not clot. The (ibrin 
may bo separated hy wlmC is known ai " whipping" the 
blood. For this piir|ioKO fi-ctsh-drawn blood is stirred up vig- 
orously with a bunch of twig*, nndllic sticky fibrin thrcwls 
iM thoy form adhere to these, If (be Iwig« be withdrawn 
afler a few minutes a (|uiuitityof stringy material will Ihi 
found attached to them. This ii at lir^t oili^red red by 
adhering blood corpnsolos: Ihii by washing in water these 



THE HUMAN BODT. 



luay be removed, and tim purv ti1>riii tluis obtainud is {>er- 
fcctly wliilti »nil in tlie form of highly olaijtic threads. It 
u insoluble in water ami in dilute »ciii<, but i°wflls up io u 
transparent jelly in tliv lutlcr. The ■■ whippwl" nr "dofl- 
briuittc^ blood" from which the fibrin has iWa in this way 
removed, looks iiirt like onlinmy blood, but hiw lout it« 
]iow<T of Viiii<^iiHtIiig 8|iontaucously. 

The Bufiy Coat. That the red corpuscles are not an 
effvniid pitrt i>t thi> clot, but lire merely mechiutically 
Cttught up in it, Rcem» clear from the microscopic ob- 
servation of the process of coiigulaliou; and from the £«t 
that perfectly formed fibrin win bo ublitincd free from cor- 
]>u»clot by whijipiug tlie blood and wa^ihing the threads 
which adhere to the twige. Under certuia conditions, 
moreover, uuc gelti a naturally formed clot containing dq 
red oorpudc.leH in one part of it. The corpuscles of human 
blood are a little iR'avicr, bulk for bulk, than tlie plaHnu 
in which they float; hence, when tlie blood is drawn aud 
hift at rest they sink slowly iu it; aud if for imy reason the 
clotting takcH place nioro slowly or the corpuscles sink 
moro r»])i<lly ihuu n»iitil, a coIfirlcM lop stratum of plasma, 
with no red cor|tUBeIes in it. will be left before gelatiuiza- 
tion occiire and Mtopa tlie f u rtiuT linking of lh« corpiMclM- 
Tho upjiermoat part, of the clot formed under these cir- 
cumstances \a colorless or palo yoUuw, and in know n as ibu 
buffy coat; it \* O'lwcially apt to be formed in the blood 
dmwn from febrile patients, and was therefore a point to 
which physiciuuH jwd much iiitontion in Uio uhlcu timiM 
when bloiidli^Uing wo-i tli»u^ht i* jmiiuocti for all ills. In 
horse's bliiotl the diffcrenw bi-tweon the specific gravity of 
the corpii^'U's Kill) thitc <i^ iiii> it> giviitvr thiui in hu- 

man bloml, and liono's biH-l ■ '-■■"""'itea more slowly, 
eo that ild oloUl|UM|Mitt -at. Tho oulor* 

Wtiiii t\ hi' thn air JU 

toj* U"- " 'I in iJii* 

WT '.UVBltof 

. 'i ^uu uf thii nir. 



trSBS OF C0A6ULATI0JF. 



S3 



which forms n bright red cot»{Kiund with the coloring mat- 
ter of th* red (sjrjuiBi-K-s. If tlu'olut b(? turnctl upside down 
«tid left for a short time, tlie jffe^iouslj- dark hottoru layer, 
now expose<l to tli« ntr, will bcL'uino bright; und thti preri- 
iiusly liriglil top layer, uow immersed in the i^CTuni, will 
I II •(.■>' 1 111^ iliirk. 

UsoB of CoAgiilation. T]io clotting uf the blood is so 
iiiijiort^nt u pruit-^.s ihiit it« can.ic \tu* birii frcijiicDtJy in- 
vesti^ted; bnt iis yet it is not perfectly undetHiuoil. The 
liring ciix-nlul iiig blooil in tho hu^llliy bluiHl-vc^wts docs 
not dot; it coiiutins no Holid llbrin, hut Ihiii fonuH in il, 
sooner or later, whea the blood gets by uny means out of the 
ww-icls or if tlio lining of tliewe is injured. In Miii< way the 
moutti.^ of the small vessels opened in a cut are rioggod np, 
tuid the bicedin)^. nliich would otherwise go on indelinitely, 
is stopped. So. loo, when a surgeon lies up un artery be- 
fore dividing it, and (he tight ligature orui<hea or t^-nra its 
delicate inner stirface. the liltKid clol* where this is injured, 
and from tiwire a coiigTiliim is formed readiing up to the 
next higliet't branch of the vcHSi'l. This becomes more und 
more Holid, und by the time the ligature h removed hn« 
formed it, firm ping in the cut end of the artery, which 
gi'iMit,ly <iittiiiii>!u"< i.lio risk of bhinltrig. 

The Fibrin Factors. As reganU the fonnation of 
flbrto the Tullowing ptiints ticcm to bo made out with toler- 
able certainty. I'Vesh-dniwii blnod contuins or develops 
two substance?, fibrinoplnstin jind fihi-iiiogtn, which by 
their iiittTuction form fibrin, under the influence of a third 
body called the fibrin j'rrmeni; moreover, fibrin is only 
fonnod if a certain proportion of neutral mineml tfixMt, 
such ii'<i are found diivulved in the blood plasma, is present. 

Blond wrnm doen not clot of itdclf at ordinary lempt'™- 
tures: it contams flhrinoplastin and fibrin fcnneiit and 
the requisite cjutinlity of eaWt, but not the librinugi-n; tliat 
which originally exi.ited in the pliuima having apparently 
Ixion nscd up with the proper proportion of tibriuoplastin 
to fonn filiiin, Ic.iviiig ovtrr iin excou of tilirinciplasliu in 
solution in the serum. 

^n the other hund, the liqnids found in the cavities of 



Si 



TIIK IW.1fAll BOOT. 



tliR llody whicli arc liood hy serous membranes, commonh' 
contaiu litiniin^vn iiiid ihc huIu but no tlhriiiuplu-^ltii, nriil 
tlicrcfoi'e tliey do nut coagulute s]>oii(ani3ouBh. But if » 
liltle bloot) T'trrntii be added to on« of l)ie»e liqtiidx, cougiilu- 
tion ljikc« jiliuy. 

Artificial Clot, If senim l>c sliglilly diluted wilh water 
Hud kt'iit tc-i'culd wliile it Ktiviim of vurboii diuxtdv giu id 
^ ^ I)a.i()i!d ilirougU it for some huiirs, a white precipitate it 
j^*^ /j|**throwii down wliicli i.:t>iiiuiri» tibriiioj.iliistin iind the tihrrn 
4**^ fciimnil. This prccipitJito aft«r wiishing iiiny be diwohcii 
in cold water coiitaijiing the merest trace of eauslic potash. 
If tliti li(jiiiil moii>i cuing u iwrous cavilv be Irojilod in i\ 
xintiliir way a precipitate in formed, containing' Gbriiiogt'ii 
instead of the fibrinoplu^lin, and but litile of the fermeni. 
If this prticipitatu be wiushcd and diwolvtHl nnd,llii; (^dniioii 
bo (tdded to the Bolntioii of the blood-serum' precipitate, 
no clot is formed; but if about one |ior cent of sodic car- 
bonitto or otlicr nculml Mill In' added lo llic mixture, tli«n 
it clots. Tliia shows the necessity of the siUtf. which is 
perhaps better proved in another way. If ^-nmi l>c put in 
a dijdyxiT (jico Phy»i(w) wilh distilled water on iho other 
side of the membrane, all tlie salts will gradually poes ont 
from the (<enim into the water: iw (lio laet portions of 
them pti.iM oul, the RbrinophiJltn and fennent, which are 
"coUouU" (that is. bodies wliich will not dialyze), are pre- 
cipitated; they Diuy bo rcdiNtohid by the addition of a 
trace of caustic potash. Similaily the salts may be re- 
mored from the liijnid obtjiincd from a serous cavity, and 
the precipitated fibrinogen rcdi^tolvod. If these solutions 
bo now mixed no clot is formed; hut if the stilin which haw 
been dialyKed out, or an c(|uivalent portion of other nen- 
tral salts, be ndded to the mixluiv. it will clot. 

The Fibrin Ferment. Tlio aetixity of the ferment w 
proved as follows: If spnini lie diluted with a large bulk of 
t^, wntcr^ind llien Citibun dioxidi- giw be jMiwcd through it, 
LjfA^ Bbrinojilikitin will bn )>rcci pi tided, wilh litllc or none of 
li** ^^^ ferment. If this ^brinoplastin bo dissolved and added 
to the liipiid from a *itous nnity it will not cuiiw it Ii) 
clot, or only very slowly, nucording an no flbrin ferment or 




Fmnnr pSRifByr. 



w 



IhiI a little ia presenL But if some of the ferment be 
luldcd, tlioii tin* niixtiiTO co»giiliit'-N mjiiillv, Tlie fcnneiit 
nmy be obtuineil hv adding a large iiiiuutity of utrong nl- 
iwbul to Kima tnvh bluod eeniiii. Tlie uluuhot )>i'ecipi- 
tates albumen, lll>riii(>))liiKtiii, and tliu fcrmviu. The piv- 
oipitate is let 8t»r iinder alooho] for ^onie montlLt. during 
ivhich time llic idbumcn uml librinoplfutin an? altered ho 
nn to [M.'come insnloble in wiilvr. T!ic uloobol Ik Uioti d»-- 
caiited off unci the residue treated with water which dia- 
Kiilvi's ihe fernipiit. Thi« (iolntion added to tfau uboTe 
mixture containing llhriim]t]iu«Lin, flhrinogeu, and iuUx, 
will make it clot. 

Of thojso fotir bodies which play it part in the coajpik- 
tioD of tlie blood, tlie tll>riii(i]>hi^lin and flbrInojj;on pri- 
marily determine the qnaniity of fibrin formed. The fer- 
ment seems to act on them in Hi>nic wtiy »o iix to inukt^ llirm 
interact, bitt it docs not eolcr iuti> the lihvin; it U not uiied 
up in the process, and the ijuanttty of fibrin formed is thuii 
Independent of the quuntity of the ferment jTCWnt; but 
the more of it there is, the mor« ([nickly does the coagula- 
tion occur. The pwrt tlie suits play is obscure: probably 
part of them are necessary constituenta of the fibrin, aiace 
it loaves u htrgo proportion of ash when burnt. But tJicy 
seem to act in i»ome other way when jiresent in certain 
proportions, since too lur^ a |H>rcDnta<;e of them slops 
congulution as completoly us their total abtwuee. If fi'e«h 
blood be mixed with an equal bulk of a saturated solution 
of magnesium sulphate (Epsom 8ult«) or of common snit. 
it will not clot; but if tlii^; mixture bo liLrgely diluli'd with 
water, then clotting will tiike place. 

Sxciting CauaOB of Coagulution. The aboro tods show 
clearly vnoiigh that Ihe coiiguhiMon of the blood 18 a 
physico-chemical process, but still leave unexplained why 
it doos not occur in circuliiling blood inside healthy blond- 
vessels. It ia. In 1ml, niueli e:t.<«icr to jioint out what arc 
not the proximate reasons of the coagnUtioa of drawn 
blood than what are. 

Blood when removed from the Body and received in a 
TLiSBul vomos to re«t, cools, and is exposed to the air, bom 



K 



THE BTVAy JiODT. 



which it may rCMivft or U> which it may jprc oft gn«couR 
bcdies. But it ie oiwy to prove that none of tlieae three 
things it the ciiusc fit coMgulntiun. Stirriiig the <Iriiwii 
blood and so ket!)iing it id niovomcnt dops not prevent l«it 
buteos its cougiihilion; mid bluud mri-fully iinpriiroDfd in 
u liTiDg hi 0(1(1- vessel, and ao kept at re^l. will not clot for u 
long time: not until the inner coat of the vessol hegina to 
change from the w tint of frc^li Wood. 8ci'ondiy, keeping tl»? 
bliMid at the temiif raiuro of llic llody baotens coagiilalion. 
and cooling retanlK it: blood receired inlu an ico-cold vcuwcl 
Kill] kvpt «urr(iiiiidt'd with ire will i-lol more &lowIy than 
bliHxi drawn aiid loft exjioaod to ordinary temperatures. 
Finally, if Iho bloi)d be cullcct^d over mercury from u 
blood-vcmcl, witlumt. having been «x)«>ited to tlie air even 
for an innlJinl, it will still clot perfeclly well. 

The formation of fibrin in then due to changes taking 
|Jaco in lli« blood il.'wlf when it ix removed from the 
blood -vesflelB; clottinp depends upon some reaumngeraent 
of the blood conitlituunl^. There '\t & good deal of reason 
to believe that wbat otieiirs is a breaking ti)i of a nnmber 
of the colorless corpuscles; Ihiit these ihi-n form librino- 
plOElin and tibrin fennetit, and, the libriiio^u and »alU 
already exixting in solution in the blond plaamu, librin is 
formed. When Hnids wliioh contniu no red corpuscles 
clot, as for ilwtancO vaeeiiio lym]»li, Ihe fii>t ihtX'adA of 
fibrin dcvelojied can be seen under the microscope to 
radiate from the pule corpuwlen present. 

Balatioa of the Blood-VeflaolB to CoagulBtltHi. Astothe 
role of the vcs^cla with respect to congnlution when the 
blood is flowing in tlieni two view* are hold, betwcin which 
tbe facts at present known do not permit a decisive judg- 
ment to he mode. One theory is lliat the vessels actively 
prevent coagulation by ron!<tHntly nbsorbing from the blowl 
gome siibatance, as for example the flhrin fcnnent, which 
may bo supposed constjinlly to devcloji, and the presence 
of which i;i a necessary condiliau for the formation of 
fibrin. The other view is that the blood-veaseU are [wasive 
and completely neutral. Tlu-y (^iiiijily do not excite those 
changes in tlie blood conalitiicnts which give rl«e to the 



I 



COMPOSITION OF TBK BLOOD. 



»7 



formatiou of &briiiO)il»#tin or tin- rcrTnciit, while for^iga 
bodi«« ill oonlitot with the blood du excite theac oh&ngcA ' 
iind DO cnuac cwi^ulaiion. 

Whatever the piirt whii;h the- blo(Kl-T«S8oli< \Anj, it is only 
exhibited whvii tlioir inner surfaces are healthy and niiin- 
jurad. If this lining be nipturcd or diwoM-d the blood 
clots. Accordingly, after doHt h, wla-n jiiwr-mortcrn c:hai)g«« : 
lutvu aSt'c-ted the bliHiil-ves^Ia, the blood clots in them; 
(nil nfu.'n very slowly, aitice the vcteels onlygraduallyulter. 
If the Dodr be left in ono i>o»itioQ iifttir death, the clot* 
formed ill llii.' heart have oft«u it marked bulTy coat, lieoauso 
the oorpuAclea have had a long time Ut cink in the pluitmA 
before ooiiguUtion on^irri-id. In modico-legal ca»(t« it is 
thu» sometimeK possible to say what was the position of a 
corpse for eonic hours after dciith, although it bus been 
wib«-<|uenlJy moved. The !ym|ih clot* llkt- Ihe blood, but 
not &0 firmly; aiiico it contains no red corpuscles, the clot 
formed is of coarse colorless. 

Composition of the Blood. The average qiooiflcgrarity 
of hiiniiiii blood i" lOJJ. It has an alkaline n-oclion, 
which become^ la<s nnirkcd as rottgnliition oeeum. About 
one half of its mass consists of moist coi-puscles and tlio 
remainder of plasma. Expoi^od in a Tacuum, 100 volnmcs 
of blood yield about fiO of gas <'onxi?ting of a mixture of 
oxygen, carbon dioside, and nitrogen. 

Ohemiatry of the Serum. The blood ptii*ma cannot ivell 
be I'xaniined lu to it6 chciiiicnl constituents, sinoo )t clots 
under manipulation. The scrum is, however, oasentially 
bload pliL^ma minus fibrin, and from mi unalyxi.i of it we 
can draw concttisions as to the plasma. In loO pnrln of 
wrnm there arc uboutOOpartfiof water, 6.5 of protoids, and 
t.R of fats, salts, and other les^-knnwn solid bodies. Of 
the proteids pre&ent the nio^ abundant ii> senim albumin, 
which agree* with I'^gjilbnmin in coagulatingwhcn heated: 
so Unit aeram when boiled .-its into nti opiii|nc while niiiss, 
Jitst us the white of an e^g does. Chemically, serum allm- 
niin differ* from egg albumin in being congnlalod by ether; 
and physiologically, in the fiu-t that althongb present in 
such large ijnantitiM in the blood, it does not pass through 



rap. Brr.VA.\ nonr. 



tlie kidneys, irfaereufl pgg ulbumin wIkmi injects] into tliP 
b)oo<l-vp»i«'l« "f iin niiinial i^ rapidly I'icreted br tbofic 
MrgiuiH. In heiitth thv fiilH iirc on\y iircKCtit in ibr MTUm 
ill HiDall '|iiantily fx<.-«]>t uflvr a iikmI at wbidi fattr iiub- 
fltniKiM have been Eiateu; Hcriim obtiiinvd from the blood of 
nil animal soon after such ii nit-itl i» ofton milky id ii[i}i(-iir- 
mice (roni tbe fuU iin-x-iil, iiisiwul of being perfectly color- 
losa OP pale yellow, and trausparoot as it i» after filiating, 
Tbo mIu diesolrcd in tbo tit-rum aw mainly iMnlium chloride 
und eurbunut^': but Mnidl qiiii!ititi(w of sodinm, calcium, 
and magiieaiiim iihosphittcs nic iilsu jirc-ipnt. 

Chomiatry of tlie Eed Corpuooloit. In \\w*vi in the fresh 
moiet HiaU' xhi-n itrc in 100 part^. "i(i of water and 44 of 
eulid^ Of the solids about one \Kr ccnl is »dl^ chiefly 
p(>|jiN<iitm piiii.«)iliiiU! and irhkiridi'. Tin? n-iiiuiiiing; in-giiQio 
eulids contiiin. in 100 juti'tft. 'JO of htpnioglobin and about S 
uf othur prolciOii; tho residue consiitts of lr«< well-known 
bodies. 

cniemtBtr; of the Wbito Corpuaolon. These ^i^cld be- 
eides much waicr, gorenU proteida, some faU, glycogen 
(see Chap. X^VHI.), and aalt«: and iimallor tjtuuititieK of 
other biKli&«. Tho predominant .'<uJt«, like those uf the red 
oorpuscki^, are pntawtum phoi^pbiik-K. 

Variations in the Composition of the Blood. H^gionic 
llrmitrkf. Tlio uIhjvo sluteiiients refer only to (lie average 
CDmpi)»ition of the liealthy blood, and lu IIh better known 
constituents. Frum what was said in the last chapter it is 
clear that the blnod (lowing tmm any organ will have lost 
or gained, or gaiiiod some tbin^ and lost others, whrii 
compared with tlio bloo<l which entered it. Uul the \n?,m» 
and gains in partie-uhir partjt of tlie Body are in snch small 
amouni as. with the exception of the blood gaae*, lu elude 
analysis fur the m<i»t part: and tho Mood from all partii 
hein;; mixed up in the hear), they hulanco one nnothcr and 
produep 11 tiileml)ly constant arcrage. In health, however, 
the dpeeilli^ gra\ityof Ihcldoifd may vitrj- from 1045 to 
1075; the rod corpuscles also are prc-sent in greater propor- 
tion to the plaxnia after » meal than before it, Ueolthy 
ilccp in pr(i)ier amount also iuori'utv< tho proportion of red 



J 



ntooji coRPUsciss. 



tm 




oorptuck'i!, nml want of it diminiohtw thrirnnmber as maj 
be recogaued In the pallid aspect of a ]>cri4on who lua 1o«t 
sereral nighU' rot. Fi'e«h air utid plenty of it hna the 
«amc oftftct. 

The proportion of these corjjtieclca lias a great iinimrt- 
aiico since, m ve itliall stilntcquonth' wn. llicy ecrvo to can^' 
oxygen, which is neceasary for tho perforninnoc of if« fnnc* 
lioMs. nil over tho Body. Anmmin is a difloaHi'd eondition 
(!hanit;l«riwr<i by pallor due to liclU-ieiKTy of red blood cor- 
pusflf-s aiiii accompanied bylan^or and liMh-MiH-"-*. !t \t 
not unfrequent in young girlB on tiio verge of womanhood, 
and in peri<ons overworked aikd conflntnl within doors. In 
iitioh easoa the best remedies arc opeu-air exerciso and gortd 
food. 

Summary. Pratitically the wmjioif il ion of the blood 
may tie thus stated: It oousints of (I) pla.*tHn, contiijiling 
mainly of water eoutuining in solution scrum albumin, 
«odium ^lt«, »mall«r amonnt.t of thoao of other metals, and 
ixtractiveti of which tlie most ('on;<liintare wretr. trea/i'n. 

d grajic augar; (2) red ooqinaolea. containing rather more 
half theirweight of water, the remainder being main- 
ly hnmoglohin, other protoid», and poiiish «ali;i: (;j) white 
(■or|)«!»dM. consisting of water, various protifiiV, glycogen, 
and polanh wdt*; (4) ga«?«. partly dissolved in the plasma 
or combincil with its sodium Bidt.i, and (oxygon) piurfly 

mbiiied ttitii liio hiBmo|,'lobin of the red corpnacK's. 

Quantity of Blood. Tliu total amount of blood in tho 
Body in difflcult of accurale itetcrmi nation. It l*. hon'- 
ever, about ^ of the whole weight of the Body, so the 
• [uantity in a man weighing TS kilos (165 Ibi^) is about 5.8 
kilos (rj.7 IliK. ). Of this at any given moment about one 
fourth would be found in the heart and big blood-vessels; 
and equal quantities in the c-iipillnnes of the liver, and in 
LhoEeof the mnsolefl which move the skeleton: while the 
remaining fourth is dietributod among the remaining parts 
of the Itody. 

Tho Origin And Fate of the Blood Oorpaaol«8. Tho 
white blood corpuscles vary so rapidly iind frifjuentty in 
number in the blood that they must be constantly in pco- 



<MIR of ftltcrAtioii or removal, niul fnniinlion ; thoirmimher 
is lar^el,v iRorcosed by tttking food, even nior« than that of 
tlie ri-d, «o that tlicir proportion to tho rc-d rues, from 1 
i« luou during fiutiiig, to 1 to 2.10 or 300 uftxir u tuciil. 
They no doubt multiply to a certain extent by divi>iiiM 
while circuluting iti the blooil, l>iit lliii majority come from 
iliu lymphatic gliuids and similar Htriictnre.'i ()tec Oliap. 
XXIL) found in muny ymrts of the Body, wbic^b dou- 
lain many ctHU like puli> bloo^ c'>rpti.TK% and often in 
{trooess of diviMoo. From theee or^aiia the <!or]>u8ck-» en- 
ter the lymph-ves«Ifi and »r© curried on int« the blood. 
From the capillury blood- vcmcU mutiy agiiin migrtitc. and 
it is probable ibut thc-e emigrants take ]>art. ftx'unently in 
th« repair iir regentTatiwi 'if iiijiirt'il tiwucje. Being un- 
diflcrentiuted and sjiu-iiiliitc'd to no line uf work they are 
ready to take np any that comes to hand, and may be com- 
]>arcd to the young men in a commiiiiity who have not yet 
teW'ted an uei-upation an<l are on ihe lookont for an o]ien- 
itig. On tho other liand there cecnix little doubt that a 
great niiuiy white eorpu^-tes give ri^e to red oneii, Mid thi« 
IB perhaps to be regarded as liieir 6[Hicial function. The 
oorpnsclos of iieorly all iriTcrtebnile animal.'' arc eolorloM 
rmly, although the blood plajima of some contaitiit liH'mo- 
Rlobin in ealntion. Amiihioxn«, llio lowest undoabted 
vertebrate iiiiiinnl («pe Zoolop"). h1»o )VK!«entc« only colorlesc 
corpusi'les in it.^ hlood. But higiier and more cinn]ilox ani- 
mals need more oxygen, and im bliXMl plaema dissolves 
very little of that gius '■hey derclop in addition the hiemo- 
glohin-eontaining oorpnsclea which pick it up in the gills 
or lungs and earn,' it In nil [>art.* of the Body, leaving it 
where wanli'd (r^eo ChMjt. XXV. ). In cold-blimded verlohratcn 
the red rorpUBclea are not nearly bo many in proportion n* 
in llio wimn- blooded, which u«e far nioru oxygen. The 
older tiew WB8 that the mannnatinu rpd corpuscle rcpi"e- 
ttcntcd the nuelens of one of the white, in which hiemoglo- 
hin had hcim formed and from about wliicli the rc<l of the 
corpuscle had diruppearcd. This, however, does not seem 
to he the case: but the pale enrpuscle develops or formB 
hmDOglohin in its cell protoplasm, and flatten) nnd as- 



LrUPB. 



61 



xniDes the form of a red coriHiede,wliile iu n»cl«ns di«q>- 
pears. Ouciuioiiul trutuilioiiul fuims between tlie pale nn<t 
the reJ I'Oi'piiM-'le iin- scun in bloud when oxumineil with. 
the nucrwfoojiu; and if blood be pnt fl1■^ll on ii oold liUdQ ' 
and eiaiiiiiiu<l in a culd room theiie liansitional for»i;i ur» 
tnort- iiumcroii-s sinio »l ordinary tcmjicrattirefi tliey very 
nijiiiilv l)reiik down anil full to pit-ofit wh«n blood is drawn. 

Ui>w long an individual red corpnscle IiiM-- is nol known. 
(mr Willi wrtiiiuty liow or when il disajjjH'ars. Tlmio lis 
however, Nonio reason to believe iJtat n great many are de- 
stroyed in Ibe sidnen (^eo Clia]). XXII.). 

Chomistry of Lymph. Lynipb i.^ u colorlcta Qnid wlien 
pure, feebly ulkulinc, iimi wiih a sjiecilio gnivily of abont 
1045. It maybbdoHcribed as blood minnx iU red corpiiscW 
nnd considcmbly diluted, but of course in various [larla of 
the Body it will contiun minute qiiKutiliiM! of tin bti lances 
derived from n«iglibnring tis^in-*. Il <roniJiInii a considera- 
ble (juantity of carbon dioxide jpis which it gives up in a 
vtKuum, but no oxygen, ninco any of that p>a which pasaea 
into it by diffusion from ihe blood is iniinodiut«ly picked 
tip by the living tijaueo dinoug whii'h it down. 



CHAPTER VI. 



TIIK SKELETON. 



Excwkeleton and Endoskeleton. Tho lUtvlcion of an 
iiriiiTial iiK'lmien iill its liiiiil ]>Rileftiiig ur siipporliiig pans, 
ttiid is mot with in two main fitniis in tiic aiiiniMl kingdom. 
First as iin a^oi^kflelon dfvdoj>(.'tl in contKrliun with cither 
tho supLTtiuiul ur diqiur liivcr of the Hkin, and represented 
by th« i^hdl uf ii uluni, ihv ."lali-s of fches, the horny philt* 
of u tiirtlct, thf bony phi t<;s "f nn arHnwlllhi. mid llu' fOHtln^rs 
of birds. In man the cxos^kek'ton is but slightly developed, 
)>nt it U ruprcM-ntod by Uiu hiiirn, nuilx. uiid teeth; for al* 
though the lultor lie williin tho month, the etudy of devel- 
opment shows Ihitt they tire d('velu|H-d from im ofTHJioot of 
t^e »kin which gniwrt in and lines the inotiih long before 
birtb. Hard parts formed from structures deeper thnn 
the skin coniitimto tho emiMkelefoH. which in man is highly 
devolopod imd consistj* of ii jfruat many i«nM Kiid rarlUaga 
or gristles, the Imnea forming the mass of the hard frame- 
work of the Body, whilo lliu uirtilagcs finiMli it oft ut vnri- 
oaa ports. Thia fnunework is what ih commonly nieittit by 
the skeleton, and it primarily supports the softer parts und 
is also unangvd so us to enrroiind cavities in nhidi delicnte 
orgADS, as t]ic bruin, heart, ur fjiinid cord, may lie with 
Rafety. The skeleton thus formed, however, is completed 
iind snpplemcntod by iinulber iniide of tho connective tismie, 
Ti'liich not only, in tho shiipe of longh bnndi* or ligamtntf. 
ties tlio bones and cartilages together, but abo in varioii:- 
forms pervades Iho whole Body as ii sort of eub»idliir\ 
(kdelon runnln); through all the soft orgiirn^ furmiog nei- 
W'Tks of fibre* around their other constitnents: so thot it 
nniko-<, R» it wore, ii mienweopie nkelolon for the individnid 
modified eells of whiok the Body ia so largely composed, 



AXIAL 8XBLBTOK. 



and alao forms pitrtitioiiH botwcoii the mniit^lM. cncrw for 
eatlb, orgHiu ui< the liver nixl kidnoy-i, miii Kliciitlte around 
the blood -tdssoIb. The bony iind cartilaginnns frnmework 
with its li^metits miglit be ciilled the skcldon of the 
organs of llie Body* oml thin Unvi- i^iipportjiig mofhwork tho 
skeleton of the tiaaiicB. Iknitloj* forming a support in the 
eubstauco of rurioiu organs, tho connective til^sllc is uW 
ottun liiiil ibiwn ax » «urt of piioking motcriul in thv orericos 
bt'twcen thorn; and so widely i« it distributed everj-whcro 
from the skin outside t<i the lining of the iilimcntiirj canal 
inside, that if some solvent could be emjiloyi'J which wciuhl 
uurrode iiwiiy ii!l {he rest «nd leave only this tissue, a Tory 
perfect model of the whole Body would bo left; soinethiug 
like 11 " Kkclet-m Ifiif." tml fur niorii miURto in it« tracery. 

Tbe Bony Skoletoa (I'ig. I'l). If the hard framework 
of the Bwiy wore joineiltogelher like Ihe joints and beams of 
a holl.^c, the whole nuL«s wonld ho rigiil; itjt piirt«coiildnot 
move with re1:iiion to ono another, »ud we would iw u»- 
uhle to niUe ii Imnd in tlio month or juit one foot before 
another. 1'o allow of mobility Ihe bony ekcluton is mode 
of ma.ny se)Kirate pieees which are joined together, the 
poiiilH of union being culled articulaliona, and at many 
phw^e* the iKnies ontorin;^ into an articulation aro movubly 
hinged tflgether, funiiiog wlmt are known aa joinh. Tho 
total numljcr of bone:* in the Body is more than two 
hundred in the adult; and the number in children is still 
greater, fir viinims bones wbieli are disliuet in the child 
(and remain distint^t throughoril life in many lower animals) 
grow together so ibii to form ouo hone in the fnll-growii 
man. The adtiH bony skeleton may be described as con- 
sisting of an rxinl iMeton found in the head, neck, and 
trunk; and an iiji/ifHilirtitnr xi-flrloii, eonxii'ling of the 
hones in tlio limhs and in the arches (u and «, Fig, 13) by 
which these aro carried and iitlaclied lo the trunk. 

Axial Skeleton. The axial skeleUm ci>n«isUi primarily 
of the verltbmt column or .ipine. a side view of which is 
ri'pivwnied ill Fif, 14. Tlie upper part »f thi« column i* 
composed of twenty-four separate bones, etveh of which is a 
verltbra. At the posterior part of the trunk, beneath the 



H 



TBB trrT-VAx Bonr, 




Flo, n 



"' trnuMMil canU^noiB 



Flo, IL-aMv *lcw or O* 
■ploaj culumn. 



VERTEBRA. 



«S 




moraMc vertebra. cumo« thv Bncnitn (S 1), miulc u;> ot 
ftro Tcrttibne, which in the adult graw together to form 
one lx>i»e, and below the «acrum \« the cocctfx {Co 1-4), 
coDsisting of fuitr rcrv «mali tail vertcbne, witicb in ad- 
vanced iifo ttlw' iitiiu- Ui form one bone. 

On tint to|i of tile T-rlebrul ccdiimn ia borne the ikuU, 
made up of two parts, via,, ii great Iws abovv which id- 
<Aose» the brain and in eall«il the rranitim, and a \iargf 
nnmbcr of bonw on the ventral side of this which form the 
skeletou of the face. Attnvhcd by lig»m«ni« to the under 
side of the craninm is the hyoid bonty to which tlie root of 
tlio tongiio is fixed. 

Of Ihe twi'ritT-fonr separate vertebrse of the adult the 
seven nearest the fikiill (Fig. U. CI-7) lie in tin: neck 
and arc known an the cervical vtrfririt. Tbeae are fol- 
lowed by twelve otiiera whifili luive ribs attached to them 
(see Fig. 13) and lie at the buck of the chest; they are the 
HorMl vertfbrai (Dl^-Vi). The nbi(>"ig. 25*)uw- Hit-nder 
cnrrcd bones attached by their dorsal ends, called their 
AMdf, to the donuil vertobnv and running thcncv round the 
side.* of Ihe clien. In the ventral median line of the tat- 
ter is the breast-bone or aierHum (rf. Fig 13). Eai-h rib 
near iu sternal end oeo/m to be bony and io coinj)oite<l of 
cartilage. 

These parts — skull, hyoid bone, vertebral column, ribs, 
and Mornum — constitute tlio axial skeleton, and we have 
now to consider ilj< purt.^ more in detail. 

The Sonial Vertobm. If a single vertebra, say Ihe 
eleventh from the skull, bo examined parofuUy it will be 
found to consist of the following parts (Figs. 15 and Ii>): 

Rrjjt a bony miuss, C. rounded on the sides and Hattened 
on each end where it h turned towanis the vertobrip above 
and bulow it. This stont bony cylinder is the "botit/" or 
ri-nimm iif ilio vcrt.cbru, and the series of vertebral bodies 
(Fig. L4) forms in tho trunk thut bony partition between 
the dorsal an<l ventral entities of the body spoken of in 
i^liuptcr I. To till! dorsal side of the body is altached nn 
h — the Hfftfai arch. A, which with Uip l>aok of the body 
iuch)i^8 a epaco. Fi\ the neunti ring. In the tnbe formed 



Tim nrJfA.v novr. 

l>y tlie rings of tho Micoowivo Tcrlobrw lio« Uie npinal conl. 
IVojecting tjiivn t)t« dorual side of the neural nivh is a luug 
boiiy Luir, Px, tlie spinotu pToct*t: and the project ious of tlicet- 
procesBcs from tin; TarKnw vcrlel>nv enn lie foil, ihrongh llio 
dkin nil ilowii iht> middle of the back. Ilinic^ tho nainc of 
tpitial riilamn often ^ven to tlio whole bnck-bone. 

Six other iirucesioaurise from thcnrcli of tlipvcrtehm: twi 
project forwiirdB, i.e. towardfl the bead; lheiic>, P<i». are tlio 
anterior artiatlar proce*»e« and have » *moolb swrfaca, 
oovered vitb curtiluge oa tbeir doraal jiidi^. A pair of sim- 





Fia. n. Flo. I A 

Tm. 10.— A durtal tirtrbra m«ii rrom IwUlUl. Lt. Ibn «iid tunird rram thn 



FW. tS.— Two donol TerMbr* Tic* aI fr»m th>>I*fl alilr, ami In xtivtr tmliiral 
i«1MIt« podtlOD*. Cttw hodfi A. tiKuml nnt'i: >V, I tip m-urnl iinc; /*>. (ill 
now pmiw; Am. anWrforarwulartvormi tW. iKBUrlor a(iL<uL&rpravoi>; 
Ft, WUMnne nn>c«>: n. Uo«C tor nnti^ulailon -iltli Uir iiitH-nli- ul a rili; 
At, FU. ■ttkrulu' mlMca on Ibe conlnuu fur ank-ulallon wltti n iili, 



ilar ;KM/en'nr artieular procestet, Pai, runs luck from tlie 
nennd arch, uud thive have smooth Ktirfnccs ou their tdd- 
Inil nspecia. In the natural position of Ilii? vortebrn, ibc 
Binooth Biirfacfs of its anterior uriieular prou«ftseB fit upon 
the poj^tcrior iirliciilar proctiasen of the vcrt^ebru nest in 
front, forming ii joint, iind tlio two priKvwc* arc united 
by ligaments. Simibirly it« posterior arlicular |)rocesea9 
form joints (Fig. 10) with the anterior articular procesBee 
of the vci'tubree nvxl behind. 



BKGMKXTATION OF SEHLETOS. 



Vt 



The retunining processes are the tranaverif. Pi, wbich 
run oiitwurcU and u littk' (Ior«illjr. £»l-)i of tliese has a 
smooth arlicuUr sarface, M, near its ouwr end. 

On llic "fwdy" i»n) eeon two articular surfaces on each 
*idc: ont>. fVn. at ita ant«rior. iiiy hiIkt, Fri, at its poste- 
rior end, and botb cloflc to the nthiclimeiil of thu nvnnil 
arch. Eacb of tlieso surfaces formed with corrcapondiiig 
axtiu oil the vortubrm in front, tuid Ii<>tiinc1 .1 pit into which 
the etid of a rib litt«d and the rib utiacbed JJi ihi.t way to 
the anterior part of I he "bodv"" iil«o lilLe'l on. » bttte way 
from it.^ dorsal end. to the articular tiurface at tbc end of 
the transverw! proucM. 

The Segments of the Axial Skeleton. If « durMil Terte- 
bra, Kiy tliL- lirsi (I-'ig. 17f. ln-iict^M-'lK^ with tbejuiir of riba, 
Cv. belonging to it an<] tlio 
bit of the ateroum, S, to 
which thoE^t ribs are fixed 
vcntrally, we wutild find n 
bony pai'tilioii f'^rnied by 
Uio body of the vortflbra. 
lying between two arobe.'* 
which tinrround vavition. 
The dorsal cavity ini-lo.ted 
by tbc •' body" and '■ neural 
arch 
part of the spinal rora. llie wiibiiipboiij'aLni] . 

,, I 1.1 nil' vrRelim: S. tlio (■mtMl-DODO. Tba 

olner rin^, made np by the iuihiur<Jiiui«i|iBn twivavD 8ud b 
body of the vertebra ri.,r- "■"^'"""'"^^ 
sully, Ihe slernam ventrally. and the ribs on the aides, sur- 
Cniinds the chest cavity with its contents. All of these 
partj* logetbor form a typical segment <:f the nxinl skeleton, 
whii^b. bflwever. only attains this oomplolen(u» in Uit 
iboracic region of the tmnk. In tbe skull it is c'^atly 
modilied; and in tlie neck and the lower ]mrt nf the trunk 
the ribs lire either absent or very small, aiipearinjr only m 
processes of tbe verlehnn; nnd the stomul portion is wanting 
altogether. 

Kcvertbeleas we may regaitl the whole axiid skeleton a* 
made ap of a series of such segments placed one in front of 




. . ,, Pia IT.-t>iftKn>i»maltenniMraladaa 
contained oiiiiinnllv nra-wmn'i'.tihouiBiiAattoq. r.a 

P .... - rrtivbrn: C (v, tttw arII«uHtlDE abor* 
~ cmnnotw pTDMv Ot 



n 



TBS JffUyAy BODT. 



the otlicr, tint. ImviMj; ilJITi'rcnl porlioiw of the complete 
Mcgmeut much modifiod or riidimeman. or oven nHogiMlicr 
wantiDg ill iruinu rofrions. PurlJi wltich in tliis sori of niiv 
ivjiijt i;uiTtojminl to one another tliou^fli Ihev dilTvr in dc* 
taU, which Jirc so to speak ditTerent v&riclies of one ihiiig. 
arc mid in uniitoniical laiisHRgo tn bo /iftiuologotu to one nn- 
othcr; and when l\w\ miorccd one niiolhci' in u mw, lu (he 
trnnk wjimcnts do, the fwmoio^y in iipokon of as la-n'al. 

The Cervical Vertobraa. lu the cerviod nrgion of the 
vertebral cokimn tiio bodies of the verlehne are fliiialh-r 
UuiD ill the diir^ul, Imt the arches are hirgcr; the epiuous 
processes are short aitd often hifi>l mid the t runs verse pni' 
OOSeee appear perfurat^d hy u canal, the wrtehral I'oram'rn. 

Tlio Uinv liar hounding 
(his a]>crttire on the ventral 
side, howorer. is in reality 
tt very »niall rih vrhii-h hii» 
growD into continuity witli 
the body and true transvense 
procem of the Tertebru, al- 
tliough separate in very early 
life: the irnnsvcrK- proccM 
pro]>cr buunda Uie vcrtehral 
foratuvu dorsnlly. In Ihis latter daring life mns An artory, 
which ultimately enter* the flVnll mvtty. 

The Atlas and Axis. The Ih'Ht and second cervical vcr- 
tcbrwdiflerconsTdcniMyfronitherest. The liiHt. or atlnx 
(Fig- 1U). whii^li cmTit!s the head, has n very #niall body. 
An. and a large neural ring. This ring ia subdivided bv a 
cord, or tlie irann-erxt ligniifiil, L, into a dorwil iiioicly lU 
whicli the spinal coi-d lies and a vi-ntrul into which tho 
bony pvoccs* I) i>roject». This is the oiloHfoiil proef»j'. mid 
arises from llie front of the ix\\t or second corviad rorlcbta 
(Pig. 2U). Around this peg the atlas rotalt-.'< whcnttie head 
i* turned from side to *ide. carrying the sktiU (which ar- 
ticulates with the large Imllow surfaces J-'iifi) with it. 

The odohluid ]>rocef« rcidly rGprc-«onlJ< a largo pioco of 
the body of the uthiii which in early life BOjinrated from its 
own vertebra and grows on the axis. 




Flo. IR— A wirru'al ti>i1*bre. Ftl. 

rmr\in\ tonunra: f\i<. MilMlor«rtlc- 



SAOHUJf. W 

Tho Lumbar Vert«bnB (Fig. 'il) are the largest of all 
th« movable verti-l>ni> mikI tiiivc uu ri))« lUtachvd to them. 
Their spiuee are short aiid stout autl lie in a more horisontal 



A* F«* 




Fal 



I'm 15.— Tlii-flHai Fio M^Thr orit .In, iHidy .if nili»: /', i»li.iiiniil poj- 
uitorlor anii^iilu>ur(*M)Ot »xU; X^lnuuTgne UBOaiooI; fit. vcnebnil rem' 

plane than lliooc ol the vert«bne in front. Thv articular 
and iransTone j>roce»iiM are itlso short and stout. 

Tbo Soorum, which U roprcKcnti><l along with the last 
lumbar vert«bra in Pig. 22, consists in tlic ndiiU of a single 
bone; bat cnwa-ridgeii on its rentnU surface indicate Uie 




Fid. >I —A lumlmr vvrli>bnt ntm iToat tit» Ml ittda, n, iplnouii prvOHO; 
Pu<. Aniarlur unii-iilur |in>F>-M; nu, poMarlor itlrnlw praoi— , 



litnils of th<> Ave separate vert«bne of irhich it-is composed 
in childhood. It ia eomewhut triungniar in form, it« bau 
bting dir(;(;tcd upwarUa aad artivuliitiu|[ irith tlie under 



70 



rJtK uviiAX nonr. 



aurfiioeof (be bodj of tlic (ifi)i liiniliur v<>rlo1>ra. On itji 
mdM mra Inrgi- Kurbces to which the arch beiiring the lover 




TtOL St.— The Ian lumbar TorUbrsand thoaacrainiMn fmmihHrantml rid*. 
no, autvrior un:rti tiiruiiliut. 

limhe is iitlat-licrl (kcp Fig. 13). Its wntral fliirface ia con- 
C&TO and snioolli and presents fonr puire of anterior sacral 
foramina. /Vn. wliich coniinmiicate with 
Die nearal canal. Itii dorsal fliii-facp. convex 
and roughened, haa four similur psursof ;3«»^ 
lerior xarrul fnramiva. 

'Vhn ntfT^j (Fig. 23) calls for no special 
remark. The four bones which grow tc^th- 
er, or aiih/lot^. to form it rciirMont only the 
bodies of vcrlcbnw, and pvcn that imperfectly. 
It U in i-ealily a short tail, although not visi- 
ble as such from the ext«rior. 
The Spinal Column as a Whole. The vertebral columu 




nan.— Tba 



BPiSE AS A WHOLB. 



n 



Miit^:lMa.-o£.nv^inluigt" *''""' t*i'(>nty-«ight inches 
loof^ TieiraS frnta one^deX^g. 14) it prceenU four cur- 
vatures : one with llic c-onvoxity forwiird* in tho ccrrical 
region i» followoil, in tho doraal, by a onrvowilh '\U ooiicav* 
ily towards the cheat. In tb« lutnbHi- region the curTe hiui 
iigain its conToxity turned vcntmlly, while in the mend und 
coccygciil rogionn tho reverse in ( he ctvf. Thosie curvature* 
gire the whole column a good deal of springiness euch as 
would be sbsont won? it » stniiglit rod. und this \t further 
wcurod hy tho presence of roropivasible elastic pads, the 
inleri'erffbral disks, made up of carlilagc and coimiKitlve 
tiMjue, which lie between the bodies of thono vertebra- 
which are not ankylosed together, and illl np completely 
the empty spaces loft between the bodies of tho Tertobre in 
Fig. 14. By nioan.4 of Uic«o pods, moreover, a corlaiti 
amount of movement is allowed between each pair of ver- 
tebne : and so the spinal colunin can be bent to con*idcr- 
able extent in any direclion ; while the movement between 
any two verlchnw in mi limitml lliat no tihurp bend ctui take 
place Ht any <mi* point, such as might tear or injure otlier- 
wi»c the spinal cord coiitaintd in the netiral caoul. The 
amount of Diovemcnt |)erniiUcd is greatest iu the corrioal 
region. 

lo the caw of Ilie movable verlcbriB. where tho arch 
joins tlic body on each t^ido, it it «oniewh>t iiiirrowcd; this 
narrowed stalk being known as the pfdiele (U, V\g. Ifl), 
while the broader remaining portion of the arch is its lam' 
iiui. Between the pedidca of two oontignoiiH vertebrw 
thoro »ro in this way left apertures, tJie inhrverttbral holea 
which form a scriex on each side of the vcrlebml column. 
ittid one of which, Fi, is shown between the two dorsal 
vcTl^'brw in Fig, 1(1. Through these foi-nmina iierTea rw\ 
out from tho i^pinal Lortl to varions regions of tho Body. 
The Ntcral fommina, anterior and posterior, are the repre- 
s«iit«tive8 of these apertures, but mndilied in arrangement, 
on soconnt of tho fusion of the i\n\\M and bodies of the 
verti-bni; bciwi-rn which Ihey lie, 

Stomum. The sifrrtvm or bretut-bone (Fig. ii and d. 
Fig. I'l) is wider from i>idc tn side than dorao-veni rally. Tl 



7» 



THE HntAS BODY. 



consista in the (uiult of llircc piwe.*. arid «ccn from the von 
tral side hus soiniwhut. tlio form (if u d«gg«r. Tlic picw 
-V nearcHt the )iead is called the handle or manubrium. 
and preseuts anteriorily K notch. Id, on enoh «ide, with 
wliicli the roilai'-lwinp articulates (w, Fig, 13); on each side 
are two other iiotchci-. /c 1 and Ic 'i. to which (he sttrnul 
ends of the first and mcoikI ribn arc attached. Tiie middle 
piece, C, of the itternimi is called the ^di/; it complciea 
the uotch for the Ki^ooiid rib and ha§ on 
ilK niiiw others, Jr, 3-7, for llie tliird, 
fourth, fifth, sixth, and seventh ribs. 
The Iiwt piece of tho Kterniim. P, is 
called the enxifonn or zipkoirl procvn; 
it is composed of cartilage, and has nw 
rihii iiltaohed to it. 

The Bibs ( b'ig. 35). There are twelve 
pairs of ribs, oach being a slender ctirred 
bone atlftoliod dortially lo the body and 
transverse process of a, vertebra in the 
manner alrpiidy inontiimcd, and c»n- 
tiniiod ventrally by a coftal cnrlUa^t. 
In tho ciMC of tho aiitorioi' seven pairs, 
the coetal oartilageji are attached direct- 
ly to the sidee of tho breast-hone; the 
next throo oartilagOK are each attached 
to tho cartilage of the preceding rib, 
tvliilo the Djtrtilage« of the tenth and 

'::.wSt^t,^^^^i: '™"r- «■ these are called th« /«. or 
fe. ' "LiiSSlf^ '•" **" fioaling ribs. The convexity of each 
cnrvcd rib i:* tunica outwards so as to 
give rntinitnivii to the sides of the clicRl and incroa«o ita 
cavity, and each slopes downwitrda from ita vertebral at- 
turhnicnt, au that itg sternal end is oonsiderably lower than 
its dorj'iil. 

Tho Skull (Fig. 20) consists of twenty-two bones in 
the a<luli. of which eight, forming the cranium, aro ar- 
i-anged no as to inclose the brain*case and jirotcot the 
auditory urgun, while tho romaiuiiig fourteen support 




4 



TBB 8EVLL. 

Um faco uod sarround the mouth. Uio nose, and tlio eye- 
socketa. 




Pta. SV— Thp ribanf thn InKdFlif. wltb tbo donkl and two luaibar vartobnK 
Uu> hb CAtUlacM ui'l the ■Wmum. 

Oraoiiim. The oraniiim U a box with n tliic-k Boor and 
thinDer walk sind roof. Its floor or i«sfl represpnts ia tlio 
bead (u in ddpicUid diagmomutically ia Fig. 3} that par- 




*l 



THE nVVAK nODT. 



titiflii between the dontal and Tcntrnl i»vit)M which in tlio 
trunk is mnile nt) of the bodiea of the yertcbne. In Tory 
ea,r\j life it presents in the middle hne & »eries of four 
bones, the bttM-occipilat, ban-sphe/ioid, presphmoid, and 




FIOlM.— AiiMn vinwof tlMirdnilL O.oeelplul lx«w: T. Unnpo'*': iV. i»ri»- 
talj F. (roiiltil; K uphvaiM; X. baIu: lUr. iiiiuUla; Y.luuil: KMhmoEd. L. 
UatTfuM; J/d. tiiCprforituuillii. 

ixiai-eihmoid, whioli tuiswer prettj- niiich to the bodii^ of 
four Tortebra>, und have attiiched tu tbem the thin bonos 
vhich inchwo tht- okiiU cavity (uliioh may be likened to 
an enlarged nenral canal) on the sideti and tup. In the 






TTnmnn Bodv, however, llicwc boneti veiy soon ankyloa« 
wiih otherd or wiih one another; although llicy remain 
distinct throughout life iu the skulU of verr many lower 
aniiiiaU On lhi> baae of itiu Rkiill, besides manj small 
aiiertures by which uervea and blood-vettaeU paw in or oot, 
is II largo ftpcrtiirc. the /ortim<-K niaffHum. Uiroagh wbiob 
tbe Hpiuiil cord passes in to join tho braitt. 

Tile rranial bones are the following: 

I. The oeripilal bone (Fig. 'id, 
0) niipaired and having in it iUd 
foTamtK nwgnum. It is niude 
np by tfao fusion of iho biist-oi- 
tiipital (Fig. 27) with olhor fUitlcr 
bonos. 2. TXk froulal bone (Fig. 
%!, F), aW uupdiimi in tb« adult, 
but ia tbe child each halt is a sop- 
arat« bouo. 3. A pnur of thin plate- 
like parithl JaJiM (Fig. 26, P,\ 
which meet one another ulong llie 
iniddlo lino in the top of tiic 
Hknll, mid roof in a great part of 
tbe OTaniul cavity. 4. A piiir of 
tttitp«ral bones (Fig. '^fi. T), one 
on Mob side of tiie tikiill bcnealh 
the parietal On each temporal 
bono '\i a large aperture h<9ding 
into the oar cavity, the eseenljat 
I«rt8 of the organs of hearing 
iwing containmi in thoM boiiCKU 
5. The Kphruoid banf, made up 
by the union of ike ba*i-^j>/tr- 

mn'd and prtuphenoid (lying on the base of skull in front 
of the biui-occipitiil) with one another uiid with Hatler 
(wne». in «eon pnrlly(Kig. 26, if) on the sides of Hiecmnium 
in froni of Uio tein]t..nil«. 6. The rthmoid. likv llie splic- 
noiil, single in the Hdull, i.* really made ujt by llie union of 
a single nu-iliiin btm-tthmoui with a pair of lateral bouw. 
II closes the skull cavity iu front, and lies between it and 
the top of ibe naaal chambers, being perforated by many 




Fid. t: The ■>«« of Ih? ikull 
Till; limur JK" lia.. I-Mu travfuA. 
\\\ht lovrrr |>in uF Il»> llgiu* 
IK ibr hvA iwlniv [orniliut «• 
raof of Che mcnilli «id —ru un d- 
•d tir •!>« uppe Ml of UMk. 
Abot* Oi\» an thr (NLlrad opni- 
Inn of Ui» pn itw iof nwa, MUt 
• dioft naf alKR« Ui» mkldlp of 
(ba Bcurp ■■ ttw ■■nre median 
<lani)ii«ii ■uiimiM.wlui Um iMUiy 
nenvralUf* «or mWMMI ran- 
iMmI alaah artlaulMc irlUi Ibi* 
■UM. on Iu djlcK 



78 



TBK HVXAN BODT. 



small holes throns;!i which the uerrcs of «mcll pMs. A 
little Ml of it is seeu on ilii» inner side of the eye<»ock»t itt 
E i« Fig. 86. 

TMial Skeleton. Tiie majoi-iry of the fiicc bones ore in 
piufB ; two "Illy being single ami median. One of thw« is 
the lower jaw-bone or in/erior vittxilla (Fig. 86, Md): the 
other is the vomei: which forms p«rt of the pnrtltioii 
bctwocii ihf two [ii>«lril«:. 

The imired faoc-bonen aro: 1. The »n«r///(F, or npper jaw- 
bones (J/r, Fig. 20), one on each side, carrying the upper 
row of teeth and forming a great part of the hard palafc 
which sei'iirales the mouth from tlie iioso. 'i- The pala- 
tine lones, completing the skeleton of the hard palate, and 
behind which the nose conimunicutes by IhepMterior nare* 
(Fig. itl) with the throat eavily, so that air ean pass in or 
ont in breathing. 3. The malar boiiex. or cheek-hones, 
(Z, Fig. J!6), lying benfath and on the outside of the orbit 
on eacli side. 4. The na^a! bonea (,V, Fig, 86), rooting in 
the noee. 5. The lachrymal hont* {L, Fig. 'id), rcry :>ma]l 
and thin and lying between the nose and orbit. 6. The 
inferior tvrbiiialf botus tie inside the noso, one in each 
nostril chunihcr. 

The Hyoid. Besides the cranial and facial bones there 
is, a,i already pointed out, one other, the hyoid (Fig. 28), 
which really belongs to the skull, although it lies in the 
neck. li can be fell in front of the throat', just aljove 
"Adam's apple." The hyoid bone \% tJ-ithapod. with ita 
convexity turned rentrally, and oonsista 
of a borly and two puirs of procesaec 
called rorfiua. The smaller cornua (Fig. 
28. 'd) nro atlnchcd to the skull, close to 
T in Fig. 26, hy long ligsnienti!*. Thctte 
ligaments in many animals are represent- 
ed by bone*, BO that llie hyoid, with them, 
forms a bony arch attached to the base 
of the skull much 'm the ribs are uttaehcd to the bodies of 
the rertebra:>. In Hdhes, behind this figoideart arch come 
BCTornI others which bear the gills; and in the very young 
Human Body these alto ore roprcaented, Uiough they almoat 




FM. »— The hyoid 

lionii, 1, lio.ly ; B. 

■ma) I rarnun 



SffOULDSR OIRDLB. 



77 



entinlj cliwippcar long Iwfwri' birMi. The hyoid, then, 
with iU ooroua ami li^iiDieuto aaswcis pretty ronch to & 
gill-arch, or reullT to parts of two gill-urches, Eince the 
groat and small (wnius )>eIoiig to origiiiiilly iicpHr»t« arches 
present at an earl; stage of developmont. It is a remnant 
of a structure which has no longer any ubc in the Human 
Body; bnl io the yoang fwg tadpole parts answering to 
it cany g:ill8 and have clefts between them which extend 
into the throat jii£t as in fishes. The giUs are lost after- 
wunU and the clefts closed np when the frog gets its langs 
and begins to breatlie by them. In the embryonic human 
being the»tf gill-olefts arc al»« present and aereral more 
behind them, but the arche* between them do not bear 
gills, and Ihe clefts themselves are closed long before birtJi. 
As they have no use their presence is hard to account for; 
tho.w who accept iho doetrine of Evolution regard them aa 
developmental reminiscences of an extri'mcly remote ances- 
tor ill which they were of functional importance somewhat 
■8 in the tadpole; of conrsc this doCH not mean tltat men 
were devchi(»cd from tiulpolos. 

The Appendicular Skeleton. This consists of the 
tkoul'ler yirdlf und the bunea of the fore limbs, and the 
pth'ic girdlfi and the boncM of tho posterior limbs. The two 
sapporting girdles in their natural position with referenoo 
to the triink skeleton are reprt-sented iu Fig. 29. 

Tho Shoulder Oirdlo, op Feotorol Aroh. Thin if made 
up ou each side of tho naipuia or ahoultier-dlade, and the 
elavicU or collor-bone. 

The *eapnln (S, Fig. 29) is a flattish trinngnlnr bone 
which can rendily W fett on tlic biiek of the thorax. It is 
not directly arlicolated to the axial skololon. but lies im- 
bedded in the muscles and other parts outside the ribs on 
each «d« of the rertcbral cnhimn. From its dorsal side 
arises a creat to which the outer end of the collur-bonc is 
fixed, and on its onter e<ige isn i^hullow cup into which tho 
top of tho arm-bone flt^; this hollow is known us tho glenoid 
fossa. 

Tha coliar-ione [C, Pig. 'Zd) is cylindrictU and attached 



78 THE BVSfAK BODT. 

at its inner «ncl bo the xtornum m shown in rhi> Rgure, fit- 
iing into ilic notoh repreaentod at Id in Fig. 24, 

The Fore Inmb. In the limb itself (Fig. 30) ure tbirt\' 
bones. The lai-gest, a, lie* in the upper nrni, nnd U oillcd 




« 

Ftn. n -Thf •krU-livi ol tliL- (tuuk (.nil III' lliiili iirrlHi« mrn ttom ih« rronl. 

donftUs And meolkntf lln fellow h£ ihe jfub^r iirmj^hyvlf In the Tonml uetlLtux 
Ha*. 

the humcrun. At llie elbow tlio hiimcnis is gucceedcd 1>j 
two boncf . tlic radxH* and ulna, c mid b, which lie side by 
sido, the ruHiiiB being on the thumb side. At the diatal 
ends of these bones come eight small ones, closely packed 



PBLVIV 0IRDL8. 



TO 



Mid fiirniing ihe wrist. or Qwyiw. Then eomeflvftcylindri- 
cal bniics which cun be felt thi'otij*)i the soft parts in the 
pulm t>f the huixl; orio for thv thuii])>. utid cmo for fiich of 
the fingerfl. Those lire the meiaearpal bones, and are dw- 
tingiiUhed at, tirsU scf.'oiid, thinl. iind so on, the first heing 
lliat of Ihe thiimh. In ihe tJiinnb itself are two Itoneo, and 
iu «ch finger tliree, arraujjett in rows one after the other: 
these bones are all called phaUinge» 

Thn Falvic GiriUa l^'ig- ~^)- Thia conHUu of a large 
bone, ihe on inuomiitalum. Oc. on each side, which U 
firmly lixe'l <htnwlly to th<- «icnini and incctv its follow in 
the middle ventral line. In the child each oa innontinatnm 
consists of titrce bones, n't., tJie iliuto, the ischium, and 
pnbiit- Where i liesc three boae» uicetund finally ankytom' 
there ia a deep socket, the acetabulum, into which the head 
of the thigh-bone fits (MteFtg. 13). Between thepiibioaod 
ischial bones is the largest foramen in the whole skeleton, 
known n* the doorlike or thiftvid forantMi. I'iie pubic 
bone lies above and the ischial bblow it. The ilium forms 
the npper ospsndod portion of the os innominatum to 
which ilie line drawn from Oc m Kig. 29 points. 

Tho Hind Limb. Iu this Ihorfi are thirty bones, as in tlip 
fore linih, but not quiti- :<iniitHrly arranged; there huitig one 
168.1 at the ankle than in the wriBt, and one at the knee 
not pnuent at the elbow-joint. The thigb-bono or femur 
{a. Fig. 31) i.i the hirgejl boiie in the body and extondK 
from the hip to the knee-joint. It presenta above a large 
rounded htad v}\\\:\i &U- into IJio acetAbulum and, below, it 
\« also enlarged aud pre-tcut^i smooth sarfaocs which meot 
the bone« of the leg. Those latter are two in number, 
known as the tibia, r, or diin'boue. anA fibula, d: tho tibia 
being on l\w great'too Aide. Iu from of tJie kn<'C-joint is 
the knec'Cup. or patella, b. 

At the distal end of the log-boneR comes tho fool, con- 
eisting of larsHii, metnlnrsus, and pluilantjes. The tarsus, 
which aowuvr^lo the Ciirpua of the forotirab, is madenp of 
Beven irregular l)orie^', the largest being the hecl-bono. or 
eateantum, h. The metatarsos consists of five bonoa lying 
Mde by aide, and each carries a toe at its distal end. In 



L 



so 



raS HVMAS BOOT. 



tlU|pr«at too (or hallux) lli^ro arv two phalaoges, in each 

of the others tliree, amitigpfl «,« iti ihc fingers, but smaller. 

Comparison of the Anterior and Poetdtior Zimbs. 1 1 





Fin. n 



rio.si. 



rM.)(— 'n<i<)>nn<-anrih>>iinn, n. hiimnnix ^ h. iilrui: r mlliiH^ rf, tlin eafpin: 
«,tMlnUi inpiwnrpjil; t. Ihc ihrpL- [ihalnnvni of itrr linli rililt IIIUlv Bnen). 
0; ttie idWiBuRri or iIif pollci uliumi-i. 

F)a. si,— l!i>tu'« lit lilt' U'^- a. [ruiiir: b. paLclln. r. iilila: d, ftbula: \, Mkft' 
Dvum; r, ivniAiutn^ (aruni^iii^H, /, iiiDUliin«i] baiit«: ii^ phAlanxvA 

is clear that th« skeletons of the ai'm and leg correspond 
pretty c1o»el,v to une unulhcr, Both itro in fact finite nlike 
in very early life, uid th^ir diUi-reuL-cii at birth depend upon 



ffOlfOltHflSS OF TSX LDtBS. 

^flir diverging in different ways as they develop froDHf 
thtir jinmicivc «implioitT; nt both may be regarded m' 
modifications of the same original straclurc, tlicy nro ho- 




i 




rpi n -THr •k?lcl'vii ariheana Kndlcc. H. <1if liumi^nu: CVt. lu snJiiulw I 
hoi>l whli'Ii nil liilu Hid Ktciiolil I-MM at Uid amg^ula; I.'. Ilm ulim. B. Ihn r^ . 
itiiu; U, iliii ulir<-TiUiL>ii ; /V. tlio f«mur: P. Um pilwU>; >', (lie Obulii; r, Uia ' 
UMa- 

mohijous. Tlie pelrie ginllc dourly eorrCji]>on<U generally 
to tlu> ]>cctai'al &rch, the tibiji and flbuhi to the raditu and 



88 TEK UCMAX BODY. 

ulna ; the five metatarsal bonee to the flvc metacarpnl. vlqSt 
the phuIaDgcH of the toe« tu those of the thumb and liugera. 
On the othtT imud, Uu-ie iit tii the arm no wparate hone < 
at the elhuw-joint coiresjioiiding to tlie )NUflIa at the knee ^_ 
but the ulna beurH above a bony procetiB, th« eierranon (0..fll 
Pig. 'i'i), whk'h at lint \» « »cpurato bone sad is the rcp<^ 
rcMutative of the patella. There arc in Ihe ciirpuii eight 
boned and in the tanuH but ttcvva. The atlrxigaluji uf thtt 
tarsoi {Ta, Fig, 33) reprosentA ttoo bonce which, hovi-everj 




FiO. &— DteynuD ibuwluc tha nlUJoo at Iha [wclonil arrh lotlw sxIkI As 

•too. 

bare grown together. The elbow-joint bends forward;^ and^ 
the kuer-joiiit biu.-k«-aii]s. 
Oonpariiij; the linib« m a whole, grevler differences coma j 

to light, differences which are 

Omuinly correlated with the 
different wtt* of the two 
^^ limbs. Thearms. serving a«j 
^fc prehensile oi-gkins, have all 
tbeir porta aa movable m \» 
consifilent with the requisite 
Htrcngth, whil« I he lower 
limbit, having to bear the 
whole weight of the Body. 
re(|uirtt to have thvir parts mmh more firmly knit together. 
Accordingly we find the shoulder girdle, represented red in 
the diagram (Fig. :):i), only directly attached to the axial 
ckeloton by the union of the inner ends of tlic clavicles with 
the ttoniuu, and vajiable of eousidpriible independent move- 
ment, oa seen, for instance, in " sbrngging the shoulders." 
The pelvic ureh, on the contniry, i* (irmly and immovubly 



OMDt id llw fitie arcb lo Uin axial 
(kflatOB. 



BAND Aim FOOT COMPARED. 



SS 



fixod to themdesof thefla^rrum. Th«sockctof thoKapaU, 
into which the head of the biimonis fits, is reiy shallow 
And allows » fur grealor range of moTomeiit thuii is per- 
mittcil bv llio deeper socket on the pelvis, into wliiuh the 
head of the femur fits. Further, if we hold the right 
humerus tightly in tho left huiid «i>d do uot ulluw it to 
move, we cuo Ktill move the forearm konea so a^ to ttini 
(he palm of tho hand either up or down: no such moTe* 
mcnt is possible between the tJbia Mid fibula. PiniOly, in 
Ihe foot the boiif.<i arc mnoh lou movable than in the 
band, and art- arranged to as make a springy arch (Fig. SA) 
which bears behind on the calcanoum, Co, and in front on 
the dixtal cndi> »f thi; taml bonei), Os', and over the erown 
of the arch, at Tb, is the sarfaoe with which the leg-bones 




no. l^Tbn iHiim or Uie fow, (V, (nledwum, or M «aMi,- 1% uUtvlnr 
MrfkM hr Ubia on [he lulnanliui t». Uw tfuboMboM. 

articulate and on which the weight of the Body beara in 
standing. 

Tlie toee, too, are far 1cm niomblc than the finger*, an<l 
this dilToroncv is especially well iniirkcd between the great 
loo and IJie thtimb. The latter ran be made to meet each 
of the finger-tips luid no llie Imml can seiio and manipulate 
very umali objt'cls. while this power of opposing the first 
digit to the rest jji nearly Jibfienl in the foot of civilize*! 
man. In children, however, who have never worn boot«, 
and in savages, tho great t«e is far more movable, though it 
n«ver forms a- comidote a thumb as in many apo-, which 
OKI tlit'ir feel, as well as their haudii, for prehenxion. By 
practic4>, however, our own toes can be miule muoli more 




M 



TBB mrxAy bobt. 



mobile than they iiEiinllj are, so that the foot can to n 
certttin «xt<Mit rcptiiop titv liAnd; m Iium been illustraled in 
the cam of {)eTHou!i bom without baiidi> who liiivv iuinird to 
write and paini with their toes. 

FoouUarlties of tho Human Skeleton. Tho«c iire largely 
fjonnecr«d with the dirision of labor bciwucn thtt fore and 
hind limbs referred to above, which is earriod farUicr in 
tnaa than in any other creature. Even the highest apes 
frcjueiitly use their fore limbs in Iwomolion and their 
hind limba in prehension, and we And aoconliiigly that 
iinatomically tlicy pri-sunt lew- diSereiiiiatioa of hand and 
fool. The other more itiiportanl dinr(ict*TrBti(w of tho 
human skeleton are correlated for Ibe most part with tlie 
iiifiiiilcuHnco of the crtt't }iustiiro. whioh ia in«H« complete 
and iiabitnitl in man than in the anIniulH most cloi^ely allied 
to him anatomically. These pocniiaritiefi, however, only 
Hppeur fully in the udiilt. In tho infunt tho head is pro- 
lioitionately larger, the cnrves of the vertebral column are 
nearly ah«cDl. and the posterior limbe are rehitively very 
MhorU In all tlKW pointji the infunt approiiches mow 
closely to the ape, and they all combine to give the centre 
of gravity of the Body a cuinparutively very high giOMtioii 
and to render tho maintenanoe of tlic erect posture difficult 
and insecure. The subsequent great reUtive length of the 
posterior limbK. which grow di8pro|iortionately fiut in 
ehildliuod Ht) compared with the ant«nor, makes progre^ion 
on them more rapid by giving a longer etride and at the 
Mime time makes it nlmoiit impo^fihle to go on " idl fours" 
except by crawling on the hands and kneea In other Pri- 
tDStea tbia disproportion between the utitcriur nnd po«l(-rior 
limba dooi not occur to nearly tli<t .-uime extent. 

In man the skull is nearly balanced on the top of the 
vertebral column, the occipital londjU* which articulale 
with the attn« being aboat ila middle (Fig. ::i*),so that Imt 
little eSovt is needed to keep the head erect. In fuur-foot- 
ed bcwt^ ou the contrary, the i>kull i> ctuTied on the front 
end of tlie boriKontal vertebral column and need* «pcoinl 
lipnmenta to Hn^luiu it. For iii»tance, in tbeox and sheep 
there ia a great elastic cord ruiuiing from the cervical ver- 




CHABACTHItrsTlCS OF fir. VAX UKRLETOX. 



95 



tobra^ u> tli€ \nc\i. af the Kkiill ami lidiiing to hold up tUfl 
hcAtl. Kvcii ill the highest apos the skull tluc-'< iiol hiiliinco 
on (he tap of the epinni column: tlio fnce p^irt ta inuclli 
henvier lh:m tho bsick, while in iiiim tliu fiK-c p;irU arc rela- 
tively smiillei' and ihe cranium larger, so (hat the two 
noftiiy oquijioific. To kc«p Ihe Iipiid erect »u(t look things 
straight in ihc face-, " like a (nan," i;i for [lie ape* fur more 
fatiguing, nnd so they cannoc long maintain that poitttion. 
Tlie humun spinal colunin, gniilimll}' widening from the 
nwk to the naenini, is well fitted to sustain the weight of 
the heiid, upper limbs, otcn, carried by it, and it^ cumititrev,, 
which are peculiiirlr human, givt- it considerahlo elaeticit 
conibiiiod with strength. The pelviji. lo the gid(!» of which 
the lower limbs are attached, is proportionately very broad 
in mail, so thnt the halaiico can be mom roudily maintained 
during lateral bending of Uic Irunk. Tho arched instep 
iiu<l broad sole of the human foot are also very ohiuracter- 
Utic- The majority of fonr-footod beusts, as boreos, walk 
on the tipo of their toes and fingem, and those animal*, 
bears and apes, which like mnii place tho tarsua also onl 
the ground, or arc plantiijrii'lf in uxlinical langiuige, haTO 
n mueh leas marked aroh there. The vault«d hunuiii tar- 
sus, composed of » number of itmall bonee, each of wliich 
can glido n little over itj iieighhor>i, hut none of which uunj 
move much, ia ndmirally calcnlat«d to break any jar wluc 
might be tran«miltci) to the *pinal column by the cont 
of tho ftole with the gronnd at each atcp. A wulNuTuhc 
instep ia therefore justitiably considered a beauty ; it moke 
progresiion easier, and by iU xpriiigincst givc« ehulicity to 
tju stop. In Ijoiidoii flui-forited candidates for appoint* 
moDl M policemeti are rejected, as tlicy oanaot stand the 
btigne of walking tlie dnily " beat.'' 



CHAPTER VII. 

THE STEUCTtIRK AND OOilPOSITION OF BOKE. 
JOINTS. 



Oroea Structure of the Bonos. Th^ booes of the Bod; 
huvc nil » jsimiliir structure iid<1 compoEilion, but on ao- 
coiint of differetiKC") in shape they aro (livided by anitto- 
Riists into the following gi'ou|>fl: (1) Long bones, more 
or loss cylindrical in form. liki' tlie boucs of tho thigh nnd 
arm, leg and foreiirm, ini-tflrarputf, motaUrHus, fingers 
and toes. (2) TtAiilar bow«, in Ihe form of expanded 
p1iit«8, like the bonija on tin- roof mid isi<lwt of the ekull. luid , 
the shoulder-blades. (3) Short bonex ; rounded or nugniar^ 
in form iind nol. much greater in one diameter than in 
nnother, like Ihi' lionet of the lurAiiA mid [■iirpiiK. (4) Ir- 
regular hones, ineludinj' all which do not get well into any 
of tho preceding grou|i!i,iind lommonly lying in the middle 
line of the Itudy und dirl^ihle into two nimiiar halves, lu 
the vertebras. Living bones havo a blnish-white color and 
poAflCMti con»iidcntble elnaticity, which in best weo iu long 
slender hones such as tJie ribs. 

To get a general idea of tho structure of si bone, we miiy se- 
lect the humerus. Externally in Ihe freph stale il is covered ' 
by a dense whit* fibrous membrane very closely adherent to 
it and ccmt^ning a good many small blood-vessel 
Thiii nicnihrane is called t\ic pfn'osfeuin; on it;< under sidfl 
new osi^cuns ti.^4U(> \a formed while the bone is still growing, 
and all through life it ia concerned in maintaining the un- 
tntion of the bone, which dies if it is etrip))ed off. The 
periosteum covers the whole fiirfiioe of Ihe liorie except it^ 
endx in the elbow and shoulder joint«i; ihe surfaces there 
which come in contact with other bones and glide over them \ 



SmUCTUHE OF A BOXB. 



trr 




in the movements of iho joint have no perioewum, but are 
corered by » liiin layer of 
gmtk-, known as the articu- 
lar eiirtiUgc. Very early in 
the det-elopmcut of tbe Uody 
the bone in fact was repre- 
Mnlcd ciitiroly by curtilu^; 
but aflerwnrdii iioarly all thij 
was repbKwd by oHseoiiK tis- 
81IU. IcaTing only u Ih'iu oartj- 
luginoiiii layer at the ends. 

The bono ilwlf. Fig. 36. 
ooDiiistJi of a central iieiirly 
i;ylinilricH.l portion or if/ia/f, 
^steading between the dot- 
ted linos X and t in the fig- 
ure, and tvo enlarged artic- 
ular exiremilies. 

On the up))er articular ck> 
tremity is the rounded sur- 
face, Cp, wliidi enters into 
the shoulder -joint, lilting 
against the glenoid curityof 
the acapnia; and on the low- 
er are tJie simibir snrfacoii, 
C^ and TV, wlikh articulate 
with th« riuliiu itnd ulna re- 
spent ively. Decided carry- 
ing the articular snrfucos, 
each oxtremily preHeotd scv. 
eriU ]>ronii nonces. On the 
upper are thoec marked Ttnj 
and Tm (the greater and 
wtaller trocJainten), which 
give attachnienl to muscles; 
aud iiiniilar cmincitccs, iho 
fzUrnat and internal con- 




duits, El and 
on Uie lower 



Em. are ecoii 
end. B(i«idea 



Pra. W.— Tb* M:bt bumcniK. >■•>« 
rram (be (roal. t^ir dDuripilon. ■»' 

tltcae, Koreral bony ridges 



88 



TOK ntnfA.v noDT. 



»Dd rough patches on tho nluili iiidictttc ])IaoM to whitih 

musciua of ihu ut'iu wcix: tlxecl. 
XnUmal Struoturo. H the Wne ho divided Jongitndi- 
iiullv, ii will be »tiiia that itj< shaft i« hollow^ 
the >i)>tic6 Iicing kiiuwii us tht: mrJuihry 
ctin'tg, and in ihc Ereeh bono filled villi 
Tiianun*. Fig. 3* r€|j!V"ciii8 ii langitudi- 
iial ^oction of t.li<; fcniur, wiiitOi in thi* n-- 
i<]ifcl is (£iiilc Mmihir to ihc huincnt?. 
Th« niaiTowf oavitv does not roach into iJn' 

* 

articular exLretnitict), but thflro the bout- 
has u loose Kpoiigy fi'xturc, cxcoin » lliin 
kycr oil thf aiirfiu^c. In the shaft, on the 
other hand, the outer compact layer is 
much the thickest, tlio Kjiongy or ctmrrf- 
lated fmiin forming oiilya thin ftratom im- 
mediately iiT'oiiiid the medullar) cavity. 
To ihe naked eyi' llie i-Miii;clInlc<l bone 
appoara made up of n trellis-work of thiu 
bony plates which intcrsoi-l in all direc- 
tions tind aunound eitvitieH rather Wgcr 
Ihuii tho head uf an ordinary pin; the 
compact bone, on the contrary, appears 
to have no cavities in it until it is exam- 
inoil with II niapJifying glnjw. In the 
i*l>iic'i!i of the .ipDngy jmri ion lien, during 
life, a Buhelance knowaa^ the reii itiarrow, 
which is iptilc dilTercnt from the yellow 
fatty nutrrow lying in the central cavity 

of till? .-ililfl. 

Microooopio Structure of Bone. I'le 
microscope ehoivs tliat the conipuct bone 
eontniiiK OAviUes and only dilTers from the 
epongj' portion in the fact tbiit the>o 
are much smaller nnd the hard true bony 
[ilutt-)" surniunding them much more nn- 
merouA in ])roportion tbttn Jn the «porigy 
part^. If a thin lrani?ver*e scethm of llie shaft of tho hu- 
mcruii be esamlncd (Fig. 38) with a micniccopo magnifying 



ria. »r-A iMwi- 
iiulul ■eeUon a( 
IliOfaiUlr, d.inir^ 

bOM;u,c«ii<ulliitt-<1 
buoD; b. niMLuUAi'3' 





msToi.oer of BOim 



69 



twenty Hinmolers, it will bo eocd that nnmcronfl oponings 
exist all OTer the (lomiiact parta of the section and gradu- 
ally become Iiir^r as thin passes into the csincclliited part, 
next tlic iiiftdullar^'caritj'. Thcso ojiciiiiigs »re tlio ctoss- 
BOctions of tubes known oa tlie ilavenian canaU, wbich 
rflmifj ull tliroiigh ibc bone, running muialj iu the diroc- 




Fw.Hl— j1, k Innrenc ■Pi:il')n "t iIiq iiIfio. haIufuI ui>-i tluiwlac Ihe mo-luL- 

tion of ila long axis, bnt iiniliul by numerous oroaa or ob- 
lique branches iw«ocn in the longitudinal section iVif[. 39). 
The outernuwl ones open on the eurfiico ol tbi' i"iiic Im- 
neath the periosteum, and in llio living bone blood-vessels 
run from this through the Haversian canals and convey 



90 



THE ffWAX- B07>T. 



if 






mntf^rials for iU growth iiikI iiniimhtncnt. The avcrngo 
dUoiGter of ibe Uaversian canala U 0.05 mm. (^j^ of aii 
inch). 

Arotmd each UaTcr^iim ctinitl lies a eel of plates, or 
lamtlla, of biiixl bmiy ^ulutanco (see the tninaver.->o Acction 
Fig. 38), each caiial with its lamella forming an Haver- 
sian iftfsiein: and tlio wliolo hone \* malic iij> of s number 
of Mich s\Mi?ni», willi tiie addition of a few lunolla! lying 
ill the cornerg between tliem, und a eertnin iiniolMjr whicli 
run iinnind tlie wholo bone on itn miter siirfiur. In the 
upoiigT yttrU of the bone the Harorsian canala are tevy 
huge and the iutervening lamcllw few in luiinbcr. 

Between Ihe lamelliv ]ic wiiall cavities, tlie liirunai, cuoh 
of which id leulicuW in form. Hotnewhat like iJie ejiace which 

would bo inclosed by two 
wat ell-glasses joined by their 
edges. From the Itienn^ many 
extremely fine branching ck- 
niUs, tbo fanaliaiH, rodiftte 
and ]ienetrale the l«>ny lit- 
melln? in all direetio»». Tbo 
innermoBt ounnliculi uf eaelt 
i"yslem in<en into the oeutrul 
IlHTersiuncnniil; and thon uf 
vtiHotts liicuiia> iiitereonimn- 
ntcaling, these tine tubes forni a Ket of |iii.'«trigc« tlirongh 
which liquid which has tran^tnded from the blood'TeoKoU 
in the Havenfiiin canals enn oo^o all through the bone. 
The lacuns and canaliculi are well Keen in Fig. 3d. 

In the living bono ii granular nucleated etU lies in each 
lucuna. Tlicee c('lli<, ur botie ccrpnsdes, arc the remnants 
of tho»o which btiilt np the bone, the hard {iarta of the Int* 
tiT being really an inteveellnlar Buhatnnce or skeleton 
funned around and by the»G eellK, much in the sume way 
as a calcaremi)- i^kelcton ji* fonnod around each Foraminifer 
(»eo Zoologj') by the activity of ita protopbEm. By the 
eo-ojwration of all the bone coriniscles. and (he union of 
their skeletons, the whole bone i* bnilt np. 
In other bonvit we find the suuiq genei'al arrangement of 



Kio, 3CI.— A n.lii li.njfltuilliiiil wi- 
liun i'f iKtt^", fimt;"^'^*'*^ ii*"Hjt a'»I 
illunulvre. oa. ItnTiTnlnu .:uiuit(. 



COSfPOSlTlOS OF BOXS. 



61 



• 



the pari*, an outer dense layer and an inner spongy por- 
tion. Ill the flat and irregular b«ii«> Uiere is no medullaiy 
cavity, and tliu whole centre is filled tip with caiicoIlal«d 
tisaue with red marrow in its spiuMw. For examplo, in 
the thin bonos rouftng in the Kkull we find an ont«r 
and inuiT har<i layer of eompacl bono known as the outer 
and iriHvr MiU-x respect ively. the inner eiipfcially being very 
dense. Butwccii the two laltUw lies the sjiougy boiie, 
red in color to the naked eye from the marrow within it, 
and ciilled the dipfoe. The interior of the vcrtcbrw aUo ic 
entirely occupied by spongy bom-. Everywhere, exoept 
where 11 bonv joiii.-> some other part of the skeleton, it is 
OOTered with the perioateiim 

ChemiwI Compoaition of Bone. Ai>art from tiie bone 
corpuscles and the soft contents of the Ilaversiau canals 
and of the spaces of the cancellated bone, the bony Hiih- 
iftaiiee proper, a« found in the lamella), \* ooinpO)>«d of 
earthy and organic portions intimately combined, eo that 
the nmalletit di^tinguinliable portion of bono contains Imth. 
The earthy matters form about two thirds uf the total 
weight of :i dried bone, and may he removed by soaking 
the bone in dilute hydrochloric acid. The organic portion 
left after (his treatment constitutes a flexible mass, retain- 
ing porfovtly the form of the origina! bone. By long boil- 
ing, ea{>ecially under pressure at a higher temperature 
than tbut at whieli wnler boiln when exposed freely to the 
air, tlic orgimio portion of the bone i# nearly entirely con- 
verted into gelatiae which dissotvea in the hot water. Much 
of the gelatine of commerce is prepared in this manner hy 
boiling the bones of sUughtered iuiiinuJci, and even well- 
picked bones may be UHcd to form u good thick soup if 
boiled under pressare in a Pa))in's digoster; much nutri- 
tions matter being, in the common mndcd of domeetic 
Ciooking, thrown away in the bones. 

The earthy salts of bone may lie obtained free from or- 
ganic mattcrby calcining a bone in a clear tire, which bums 
away the organic matter. The residue forms a white very 
bridle ma>is, retaining perfectly the shaiw and stnicttiral 
details of U)e originid bone. It consistn mainly of normal 



TUK nVMAX ItODT. 



oaloium pb<Mpbiito. or bone tarth (Cai, 3PO4); biu tberc \» 
hIso prcwoiit II i-oiiiiiilfnihlt^ jituporlioH of ciilciiiiii ciirbotuile 
(CaCOi) and ^mitlltr •luaniiiies of otber trails. 

Hygiene of Uio Bony Skoloton. In curly life the boiic» 
are It'HH rigul, fnnn the tuci tbai the mrtbv iiiutl^Mx then 
|ireaeiii in them bear a les>i proportioR to the *ofler orgiinic 
partv. Itcrice the hona of an agod person ure more britilc 
and easily broken tliiin iboee of a child. Tliv bones of 11 
young child Mc in fuel tolerably flexible and will Iw dis- 
torted by any eontiniied gtrein; therefore ebildren shonld 
never be kcpl nittlng for hours, in feiiocl or el»on-hcre. on a 
bench which im co high that the fi^et arc not snpported. It 
this be niiiieted upon (for no child will continue it volunta- 
rily) the thigh-bones will iilniOKl (vrliiinly Im bent OTor the 
edge of [he seat by the n-ejght of the legti luid feet, and n 
permanent distortion niHV bo produced. For the siinic 
ren«on it, in iniportiiur (but a ihild !h- unide to Kittitruighl in 
writing, to avoid the risk of producing u luteral ciirvulure 
of the iipinid (.Tilunin. Tbi' fiicibty with which the bone* 
may be moulded by prolonged jires'ni'e in early life is well 
men in the distortion of the feel of CliiiitMC ladivsi^. )>ru- 
duocd by keeping iheni in light «ht>ea; and in the vxtraor- 
dinury forms which some iwjes of man produce in their 
skulls, by tying botirdw on the hiitdji of the cliildren. 

Throaghout the whole of life. nioreoTer, the bone* re- 
main among the most I'aaily niodilicd parts of the Body; 
altJiough judging from the fact that dead boaoK are the 
most permanent parts »f fossil animuls we might Iw in- 
clined to think otbcrwieo. The living bono, hotrover, is 
conetanlly undergoing change" under the influence of ihr 
protoplasmic cells inilieddtM] in il. and in the living Body ib 
constantly being abiiorbed and n-cuns^lnicled. The ox|m-- 
ricnw of physicians shows that nny coniiniiod ]tressiiiv. 
sncli iVi that of u tumor, will cause the absorption and dis- 
appearance of bone almost ifuickor than that of any other 
tinue; and the «uinc i* Into of any other ouutinucd pree- 
Bure. Moreover, during life the bones aie (>miDently plas- 
tic; nmler nbiiormul |H'i'*.>urc.« ihcy air found lo i(iiii'kly 
assume abnornnil xbapds, bi'ing absorbed and di6up[>earing 




ABncuiATtoya. 



m 



at points where thfi preunre U most powerfal, and increas- 
ing at other puiuu; ti^ht iHicing inny in this wuj procluce a 
permanent li'wtortion of the ribs. 

Whoti :i boiii- i« friiolurod n Ktirgcon lihould be called in 
H3 soon A» jmn-iiblc, for onco intUimtiiation lias been «i!t itji 
and the parts havo bccomo swollen it te unicb more diffi- 
cult to pliicc ibo brokon cmls of llie bone togcilu-r in their 
proper poHition tlitiu l>cfor<> this baa occurred. <>m-o thi^ 
bon«s arc replaced ihey must be held in position by splints 
or buudugcis, or tho niim-U-^ ultiichi-d lo t)iL-ni will «oon diiu 
plaoo them a;i:uin. With rest, in joung and healthy per- 
sons complete nuion vill commonly occur in tbroc or four 
irccki>: but in old personN th« procew of cure i» slower and 
\» api. to l>e imperfect. 

Artioulationfl. The bones of the akeleion ore joined to- 
gOther in very viirioim vnyt; sumctimcs no »:* to admit of no 
movement at all Ixitween Ihcm; in other cases so as to per- 
mit only a limited range or variety of movement: and el»e- 
wbere so iis to allow of vei-y free moTement iu many dirco 
tiona. AU kinds of unions between bouee are called ar/i'cK- 

Of urticiilal ions permittinfc no movements, IhoM which 
unite tbo majority of the oraiiia! bones afford a good exam- 
ple. Esovpt the lower jiiw, and certain tiny boncM inside the 
temporal bone belonging to the org:in of hearing, all 
the skull-banes are immovably joined together. This union 
in the cuuoof mo^t occtn^ by menus of toothed edge# which 
lit into one another and form jagged lines of nnion known 
HB»uttirt». Somoof lhe«ecini be well seen in Pig. 8tJ* between 
I he frontal and ]>arielnl bones (rnrown/ Kiiliirf) and lielwci;n 
llie parietiil and oeci|»ital bones (lamMoidnJ snlur«): whilo 
another lies along the middle lino in the top of tbc cmwu 
hotwc«n the tun ]iunc-tA] bones, and i« known aa the fiiyU' 
/«/ sulure. In now-ijorn ebildren where the sagittal meets 
tbc c'ronal uud lamlidoldal sutures there are largo spaces 
not yet covered in by the ncitiblmring hones, which sulwe- 
qiiontly extend over thern. Tbese openiiig)^ are known as 
foHianfllf*. At thcni a pulsation eun uflen be felt ^yn- 
dironoiifi with eucii beat of tho heart, which, driving more 

"^. 74." ~ 



M 



TOE nrXAY BODY. 



blood into tlie brfttn, cli»t«nili« it nnd cnuorji it to pn«h out 
the flkin where bone is »b<ieiit. iVnoiher good example 
of an urticiiliitioii lulmitlingof n» muvt^Dicut, is that between 
the rough Hnrfaoe on (he sidee of the saorani uid the in- 
nominate boue. 

Wo find good examples of the second clius of articula- 
tions — tliOM- aiimitliiig of a alight amumit of movement — 
in tlie Tertebi-al column. Between every pair of verlebni* 
from the second ccrvioiU to the sacrum 'n an olaetic pad, 
the iatervfrUbrnl tlisi:, which adheres by ita sinfaoes Iti llic 
bodivs of the vertebrie between which it lies, and only per- 
mits 80 much movement Iwtweon tJiem as can ho brnught 
about by it* own oomiiression or stretching. When U)w 
back-bone is curved to tlic right, for iuxtuuce, each of the 
inlffrvertebral disks is compressed ou ita right eido and 
Btretchcd a httlu on its left, and thi§ combination of move- 
ments, each individuidly but slight, gives eoiisidorablo 
flexibility to the j^pinal column as a whole. 

Joints. ArtictiUtions permitting »f moTcment by the 
gliding of one boite over anotlicr, iire known aa joirUs and 
all have the same ftindiimcnlal structure, although the 
amount of morement permitled in different jointa ia very 
different. 

Hip-Joint. Wo may take tbii* as a good example of n 
true joint permitting a great amount and variety of movo- 
meut. On the ok innominntum is the uivity uf the aeeta- 
bulum (Fig. 40), which ia lined inside by a tbin layer of 
arlicular rurliitige which has an extremely Emooth surfaee. 
The bony oiip is uUo deepened a little by ii eurtilaginouK 
rim. The proximal end of the femur consists of a neurly 
Fpherical emooth head, borne on a somewhat narrower ««vi-. 
and fitling into the lunftiibnUim. Thi« head also ia covered 
wilh articular carlilage; and it rolls in the acetabulum like 
a ball in a socket. To keep the licmes together and limit 
the amount of movement, liganicnt* pasii from one to the 
other. These are comjKiBod of white fibrous connective 
tissue (('liap. VtH.) and are extremely pliiiblo but quite 
inexteiifible and very (jlrong and I'uigh. One i« tJie rap- 
tular iijfameni, which forms a sort of loose bag all round 



arXOVlAL JODfTR 



w 



the joint, und nnntluti' in the rouiul ligtiiMnt, which poisei 
from llic tu^dUbulum to the licnd of the fomnr. Bhoiild 
the Inttor rotuto nbove a cprttiin eitfiit iu ili^ socket, the 
round ligunicnt mid one Kide of th<.- rupi^ulitr lif!:uni''nt Hre 
jml oil the Mtratcb, and any further tnovoment whidi might 
liMocate the femur (thut is remove tlie head from iu 
socket) is chockod. Covering the inside of the capBoUr 
ligitment mid the ont.-ide i>f ilic mnnd ligameiii is u litj«r 
of flat oethi, wbidi we continued in a moditicd form orer 




RS. A— SmUciIi through Ui» hlp-jotol. 

the artiealar cartilages and form the »i/Mviitl membrane. 
Thi», which thus form* tlie lining of the joint, is uliruira 
[uoidtciied in health by it xmoll <juuutil,v of gltiry fyMui'ia/ 
fiwi4, something like the while of a raw egg in consifl- 
tency, and playing the part of the oil with which the cou- 
tigiiouii moving Htirfiaoj iu ti niiu'liino ixra moiKteiiod; it 
mitkes uU run amoothly with very little friction. 

Ill thv imtural stuttf of the ]iiirlH, the head of t]ic femur 
and the bottom and sideis of tlie aoetabuhini lie iu cl<wo 
coutuct, the two sj-nuvial memhriuies rubbing together. 




M 



THE RVMAS BOT>r. 



Tliis crontuct is not nutinUiJnvd by the lig]uii«nts, which aro 
Loo louse and tn-rvc only lu chock cxeciwrvo movement, 
bill by tlie nuniorous stout muiicleB which jiuati fi-uiii lIio 
thigh to the trnnk and bind the two Grmly togniht-r. 
Storwivcr, iho »Liiioii]jheric iirwwurc Cicrteil on the siirface 
of the Body and transmitted tiiruiigh the soft jmrN to Ihi- 
outside of the air-tight joint helps also to keep the parts in 
contact. If all the muscles and ligaments around the 
joint be cut away ll i» «til] found in the dead Body that 
tii« head of iJie femur will ho kejit in its socket by this 
pressure, and so liiialr as to bear the weight of the whole 
limb without dislocation, just as the pressure of the air 
will (TDablo a hoy's " ciK-kDr" to lift a tolerably heavy Glonr. 
Ball4iid40Qket Joints. Such a joint at ihut ut the lii]) 
is called a ball-and-socket joint and allows of more free 
moTcmoiil (hnii any other. Tlirotigh movements occurring 
in it iho tlii^h can hb fivx*^, or bc-iit ta thitt llic knee a)>- 

pTonchwi tlu- chiHtt; or ej-Undtd, that is moved in the oppo- 
site direcliiui. It can he ahtlHclttl, no that llie knee move* 
outwardtj; aud addueUrl, or moved bairk iowardx the other 
knee again. The liiub can also by movements at the hi]»- 
joint l>o cireiimductrd, thut u made to dcscnbe a cono of 
which the ba^te is at iho foot and the ai»'x at thehi]>. Fi- 
nally rotation can oci-iir in the joint, so that with knee and 
foot joints held rigid the toos can be turned in or out, to h 
certain extent, by n rolling aroiiiid of the femur in it:^ socket. 

At the junction of the humerne with the scapula in 
anoiliiT hall-und-.<ocket joint permitting all the above 
luovcriunlA to even a greater exteitl. This greater rango 
of motion nt the shoulder^joint depends tnuinly on the 
nhnllonni'SB i.f the glenoid (tavily tus compared wilh the 
iieelabulum and upon the absence of any ligament nn*wer« 
itig to the round ligament of the hiji-joint. Another ball- 
and-iincket joint exhU between the c^irpiis and the meta- 
earjml bonn of the thumb; and othen with the same Tariety, 
but a mnch less range, of movement between each of the 
remaining melai-nrpal boucH and the ]>i'oxima] phalanx <if 
the linger which arlicnlateJi with it. 

Hingo-JoinU. Another form of snioviid joint is known 



FORifS OP JOIXTB. 



«7 



V k Hagt-joint. In it ttic urticulntiug bony surfacee i 
of Bucii .s1in|>o as to permit of rnQVcmtut, to (iiid fro, In on« 
plane only, like a door on iU hiiigea. The joinLii between 
Uk' (iliiilniigett uf thfi fingera arc good examples of kinge- 
joinla. If no moremcnt ijc iillowiti wliciit Hit liiigci- joiiw 
llic palm uf the liaiiil it. will Ih) fniiiul that each can be 

It and .Hlraightened at its onn two joints, but not moved 
'^a any other wuy. tbc kiicc u hIso a hinge-joint. a.i is thu 
urlicuUtioii iM'twcon the lower jiiw and ti»> base of the 
ukiill which altowH us to open and eluse our uiniitlia. The 
latter is, bowcvcr, not a perfect hinge-joint, nince it jicr- 
mit« of a small amount of lateral movement encb aa occurs 
in cheering, and also of a gliding movomcnt by which tho 
low«i- jiivf can hi! tlirunt forward so as to priitriido the cbiu 
and bring ibe lower row of teeth outside the upper. 

Fivot-Jointa. Id (liis form ooo bunt; rolut<t.-< uround ati* 
other wliirh i-eniuins Atationary. Wo have a good example 
of it between the firrt and second cerrieal TKrtebrdi. Tlio 
first cenlcBl vertebra or ni//fM(Fig. I!>*)lta5 a very email 
body unfl a very birgc arch, and its nennd canal u subdi- 
vided by a ti-iiiiHvcrKC ligument {L, Fig. 19) intoadomal 
land a rentrnl portion; in the latlt-r the spinnl (;ord lies. 
The Moeond vertebra or axis (Fig. 20) has arising from ilM 
body the «ti>iil bony jwg, D, called tbo odimMd proce»». 
This projects into the vcnfral portion of tho ajiace sur- 
rounded by the atla.*. .ind. kept in ]>tace there by the tranx- 
rerse ligainent, forma a pivot around wbii-h the alia.-), ear' 
Tying tb* "kill wiih it, rutateifl when we tuni tbfl h<ad 
bom «ide to aide. The joint* on each side Ivtween tho 
ntln and tlio skull arc hinge-jointa and permit only tJio 
: movements of nmMing and raising tho hcwi. When the 
'li«ad is leaned oter to one side, tfae curvieal )>urt of the 
tpinnl eohnnn is bent. 

Another kind of pivot-joint is seen in the forearm. If 
the limb be bold straight out, with Ihc piilin up and the 
elbow renting on the table, so that Ihi- ifhonhler-joinl bo 
kept Bt«a(ly while the hand U rot^ited until it« biu:k ia 
tnnied upwards, it will bo found thut Ili« rudliis has partly 
rolled ronnd the ulna. When the palm ii upwards and 



08 



THE HUJlAy BOD}'. 



Ua- 



the tbntnb otitwurJu. t.)iu \»vvr end of the nulina can lio 
felt on llic oulcr itiiJe of ihp foreami just al>nve the wrist, 
and if thiH be done while the huod is tiirni^l over, it will 
bo easily ditwernod that during the inorement tbiii end of 
the rniliiis cnrrying the Iisind with it, tiuvclH aronnd the 
luwer end of th« ulna so as to get to itn inner side. The 
relative poeition of Lho bones wlicu the piilm is npwunli! 
b sliown %i A in Fig. 41, and when the pnlni \» down at 
B. The former jwsiiion ia known us gupinalion: ihe lat- 
ter IIS pronation. The elbow 
cud of the humerus (Fig. 3tl*] 
bears a Inrge artienlar eurface: 
on the inu'T two thirds of this, 
Tr, the nlnii fi<K, and Ihe ridgcD 
and {H'ooTes of both banes inter- 
locking form » hingo-juint, al- 
lowing only of bonding or 
straightening tho forrai'ui on 
the arm. Tho radius, fits on 
the roanded outer third, Ci>l, 
and forma there a ball-aud-BOcket 
joint, ttt which tho nioTenient 
lakes ]ilaoc when the Imnd i* 
turned from the iin]nne to tlie 
{irone iio«)tion; the ulna forming 
a fixi'd bttr around which the 
lower end of tho radius is moved. 
Olfding Joints. These per- 
mit aa a rule but liiilo move- 
ment: examples oi-e found be- 
tween tho closely packed bones of the tJimiH (Fig. 35f)nnd 
carptu, whicli elidu u little over one another when subjected 
topTOUore. 

Hysieno of the Jointa. Wtien a bone [« diipkced or 
Uittocaifil tbe ligamoiiU around the joint are mono orle^ 
torn and other soft parln injured. This soon leads to in- 
flammaliou and swelling whieh mukc not only the recogni- 
tion of the injury but, after diaguosis, tho replnoetnent 
of Ibe bone, or tho rfdncUou of fk» diakcaOon, difficult. 



Tlo. 41.— A, anu in >m<ioMlciin; 
B. arm In nniiulUiD; H. bumnnu; 
Jf. nOXaa; V. iHoK 



« 



i 




•P.8T. 



ti*.«a. 



d 



3MBIOVAT10XS Am> fPRArSB. 



M 



MoreoTer the innsclea nttaclied to it oon«tAntly pull on tbc 
ilifplncoii bono am] drag it t-till fititheroiit of pince; to that 
it \s of ^eat impoi'tiinoe lliut u dislocation bo roduoed wt 
«oo» as possible. In most cases this can only bo attempted 
with Hif<^ty bv finu wtiu know* lite form of the boncif, iind 
|KMBM»e^ Niiffii^ietit fttiiirotiiit'al kniiwlo<!|;o M mcogiiixc the 
diivction of the displacement. No injury to a joint should 
lie ni<^U-<'U>d. [nfliimmiitioii nni'o «tart»<I (licre is oflcn difli- 
enit to clienk and niuii on, in a Hiroiiic vay, uniil the 8yno< 
vial ptirfaces arp destroyed, mid the two bones perhapo 
grow together, rendering tJie joint permanently stiff. A 
«pntinod joint mIioiiM gvi immediaU' and ooinploto rottt, for 
weeks if iieoossary. and if there be ranch swelling, or con- 
tinufd pain, medical advice should bo obtained. An im- 
properly carcd-for ipruii is the cau»c of itiiuiy a n«eleiM 
ankle or knee. 



CHAPTER VIII. 

CARTILAGE AXD CONXECTIVE TISSUE. 

Temporary and Fenn&Qent Oaitilagea. In early Ijf^ 
B givut nuiny parU uf thu Kupporting fmmework of Ibo 
Body, whirl) afUirwanls become boue, inrisUtof curliliigv. 
Savii for example is the rase wilh all the Tert«bne, and 
with the bonoe of the limbs. In th<.>»e cariilugos tinbse- 
<[ticutly the proocn known as tuuifir/iliun tiikoji iilnce, by 
vbicli a great portion of the orifpnaJ cartilsginou.'i model a 
romoTftd and rcpluccd by trac osMotit tiuao. Oflcn, how- 
ever, some of the (irimitiTe cartilage is left throuj^hout tbc 
whole of life at the endH of tho bones in joints where it 
forms tho articiilur mrtibtgL-ti; and in various other places 
■till larger miu^M remain, Hiicli lu the eoittal cnrtiliget. 
lho«o in tho oxtennd eara forming their framework, othtrK 
fltiUhing tho ekclotoQ of Iho no^o whit-h ii only incom- 
jiletely bony, «nd many in inlernni |mrUof tho Body, us the 
ourliliigo of " Adam's aj>|ile," which can he tch in the front 
of the noctk, and n number of ring* around Ibe windpipr 
■orring to keep itojicn. These ju-ntintent mtuwesarcknown 
H the jifrmnHrnl, tho olhera as the temporary nirlihffes. 
Id old Hge many 80-oalU>d permanent cartilages become 
catcijttil — Ibat \t. hiinloiicd and made nnyieldiiig by dejionli' 
of linio salu in them — without assuming the hiatological 
elmnu.'tor of liittie, and this cidfiliiiiiion of tbc piTniiinetil 
rarlilagisi in one chief cauae of the want of pliability and 
suppleness of tho frame in advantwl life. 

HTmlino Okrtilage. In It^ \tnrv*i form cartilige \» f1cxi> 
hie and eliL-lio. of a pale lihueh-white color when alive and 
Kocn in liir^tt miu«eA, and cait rviv\\\\ with n knife. In thin 
it is ijiiilo transparent. Kveriwhei-e exeept in the 




CAHrfLAOB. 



101 



JchdU it is invesled by a tough adheri>iil membrane, th« 
perichondrium, which resembles in elructiire and function 
the iwrioaUium of the bones. Wlion boiled for n long timo 
in water rfUcb t-arlilagea yield a solution of ehondrin, wbicU 
ilifforii from gel ntin in minor points but. a'-reeo with it in 
the fact that itA liot wiitcry eolutioiu " twt" or golutinlze on 
cooling. When a thin slice of hyaline rartilago is examined 
with u niicrosfopo it is found (Fifr. 42) to consist of gran- 
ular nucleateil colU, oft«a colleeted into groups of two, 
four, or more, scattered tbroa^b a homogeneoua or faintly 
granular gnnind m\i*iu.DCD or matrix. Essentially, cnrti logo 
resembles bone, being made u|> of )>rotopia»mic cells and a 
proporliouutety large amount of uon-protoplnsmiti intorcel- 




rV) tl. -IlyKllnoOMtlUM. EMQCllwlUiRtmKlniu'ldliADdkbinitladMde', 
b, aorll wlilcli bM divldtil niM I wo; n. n (croup at four r'cJli>ui>li m miutJ ra- 
nill rmin ft rapotnion at thu dMilon »l A The icruulea at Uiu nuirtx an 
nipiwiliil miicli loo cokTM itDd ouuiilcoaiuL 

lolar snbstunce, tho cells being tlio more actively living 
part and the matrix their prodnet. Exanijilea of iIiik hya- 
line variety (so caliod frnm Jtii gliu^y truiK^pitrvnt appear- 
ance} are found In iiU the temjmrory cartilages, and in tlio 
iKwtal and articular tunong the i>ermaaent. 

They rarely contain blood-rcsMlx except at those points 
where a tcniporaiy cartilage is being remorcd and replaced 
by bone; then blood-veesels mn in from the perichondrium 
and form loi>ps in Iho matrix, around which it is absorbed 
and bony tixfuc deimsited. In oonjwviiionoo of the niimit 
abwnce of blood-vesiwls the nntritive processes and ex- 
ohanges of material must he raiaH and Mow in cartilago, aa 



102 



THE UCMAS BODY. 



inigM iiidccil bo <-x]H-i;U'i1 Sittm tlic pai^iive and uerolj 
mec'lianicul rile which this tisane pla>'s. 

Uynlinc mriilugc u tlic type, or in"*l chiiniclcn<ilic«!!y 
dtvolojjod fomi, of a, tissue JFoiind wilh inodiliciltiona eise- 
wliero iu the Body. One of iu ut)ior inodJI]cittioii« in the 
Ko-fjillcd celluhr niriilage, whieh roiisicta of the dcllii with 
hiirdiy any imitTix, only jiist pnuiish to form a thin eapsulo 
uroiiud tuL'h. Thia form is (hut with wliioh all thi- «ir- 
trilagoA com me IK t', tho hyaline variety heing built up by the 
increase of the cell capsulw and their fusion to fonn the 
matrix. It porviMts lliroughout life in the thin eiirtiln^noun 
pUte of a mourti''s external car. Other varicliee »i cai-tilage 
ure roully mixhtres of true oartilagu and coimcctivo tii:<«uei«, 
and will Im> cutir^idiTi'd afitr the latter. 

The Connective Tissues. These complete the ekeieton. 
marked out iu its coarser fcatunw by tho bone^ and car- 
tilages, and constitute tho litiiil group of the eupporting 
tlMuei. They occur in all fums from broad iiK'mbrancit 
and stout cords to the llticit thrctulA, forming networks 
around the other ultimate histological elements of various 
orf^n«. In ndditinn t<i ittihiidiary forms, thrao main varie- 
ties of this tissue are rejidily distinguishable, y\z., areolar, 
%ehiif jibritus, and yfUow ehgti'r. Ench consists of fibres 
and cellf, tho fibres being of two kind^ mixed in nearly 
equal proportions in tJie areolar variely, while one kind 
predominates in one and nnothor in the second of the re- 
maining ehi'f forma. 

Areolar Connective Tissuo. This exists abundantly tw- 
neuth the itkin, wlipre il forms a loo^e flocculeot laj'Cr. 
somewhat like raw outton in appearance but not ao whit«. 
It is on account of its loose texture that the skin can every- 
where be moved, muro or Icait, to and fro over th« subjo- 
cont part* to which it is united by this tissue. Areolar 
tissue consists of innumerable bands and cords interlacing 
in all directions, and run he greatly di<lendod by blowing air 
in ot any point, from whence it travels widely through the 
intercommunicating nieslie*. Tn dropsy of tho legs or feel 
the cavities of tliii) tissue arc distended with lym]>h. From 
beneath the skin the ureohir tianie extends all through the 



OONimCTtVB TISSirHR 



103 



B<kIj between tkc muscles und uro;md the blood-T«SBelB and 
iiwTes; and fftill finer layers of it enter inUi thvfe nod otlivr 
organs nod aoitc ibcir \ariou8 piiru togcLber. It oonsti- 
tat«« ill fuL-l u Aufi jiuc^king niHttriul which fill« up Uid 
liolvii and uui-iicrs of the llodv. ns for iDstnuce arouud the 
blood-vcsiuU and between the niuselcs in Fi™. 4. 

Microscopic Sti-uoture of Areolar Tiasuo. When exain- 
iiKHl wiili ihi; iiiioniiK-DjK- areoW tiaaiie is tuton U> ooiisi«t of 
nndnkti>d cells imbedded in a ground suhsunco whith is 
permeated by fibrt-s. The fibnw cTcrvwheroform the \<te- 
domiuunt ft^mure of lite tiiunc (the bomugcneous matrix 
and the cells being inconspicnoiia) an<i are of tn-o verjr dif< 
ferent kinds. In a strict senae indeed the areolar tiiwue 
ongbt to be considered a* a mixture of two tissues, one 
correxpondiiig t<i e:wli variety of fibres in it. It is charac- 
terised s* a diiittiiiit individual by it-t loone Icxtnrc and by 
the fact that the two forms of fibres «r© present in tolera- 
bly cqnul i|ii»ntiti». In many j)Iik~c.« a iii»\ifi conlatning 
the Garoe Iiifliological elements im the areolar iixsuc la found 
io the form of don#e meinbranea, aa for example porii^iflcum 
and pc rich end num. 

Whito Fibroux TisBue. One of tbo varieties of fibres 
pcrvntliiig ih<' m.'Ltrix i>f areutur tis.inr exi.-<t^ alinoxt un- 
mixed with the other kind in the cords or tmtlom which 
nuite miisoJL'B to the bonat. This form, known a« (he white 
fibrous conHwfirti lif»ue, alao exiKt^ fairly ptiro in tbo 
ligaments around moel joinla. I'hyeically it is very floxi* 
ble but oxirtimely tough and inoxlensible, so ihat it will 
readily bond in any diivclion but iit Tm' hard te break; 
wiMni fresli it has an opa'|tio white color. 

VTIiite fibrouH t)s«iu' (Fi;;, Vi) ounsist* of a matrix, eo»- 
loining cariticit in which ci'lls lie ami pervaded by bnndleii 
of extremely fine Hbre^. These fibres lie in each bundle 
tolerably parallel to one another in u wavy coiiree (Fig. 43) 
•nd nexer branch or unite. Their diameter varies from 
0;000.1 Io 0.001 roillimeter (jslsu to rilai <^' ""» iwYt). 

Chemically Ibiit tJMuo is cltnriK-lorixcd by tbo fact that 
its flbrM flwell np and become indlBtiugnisliable when 
irmitA with dilute acetic acid, and by the fact that it 



tr»4 



TOM aVMAS BODT. 



Tbe 




jieliU ge\*tm «bn bailed in «at«r. 

•ad in the btmn, which is toniM) into gelsttn br socfa 
trMtment ia kmnra a> tMOagem, Glw m inpnre gdatio 
<rirf«jo«d tram tandom sod li|«n«ito, and calfa-lbot 
Jelljr, M often rooamoBeodcd to Jnralidj , i» t pnrpr form of 
the iMn« rabctance obtaioed by bmlJiig tb« bx4 of cm1v», 
which ounUin the teodunji of many moadea panrritig bom 
tho h^g lo the foot. 





rut. A 



no. 13a. 



■pan. 



■.—WMM nhraof eoniuirllT* llmie, hichlr ErnkKnillHl. TIif duoIi^bIaI 
mv •■•D nliiHlia uirl ii|ii>mu4iik qiiuillD'iliiijii'd. an> hvh lii-ni uiil 
j tlie PDrfue ol tba biinitliHor tllirr*. 
IM.— Yailmr eluUo UiWMi nutftilllsd •Iter 11* (llirM haiv bsva b>m 



Zlaatlo Tlaaue. Tbi» \a almoat invariably mixed in some 
jtrupiirl ion i» all epocimcns of wliito fibrouii liuiic. oven 
jlift imrvul. Rnoh lu* tiii> uiitluiiK of m1lM-l(-^; Init in eortain 
])liii'Cx il fxifU iiliiiost tiloiii'. :i<i fui- vxiiiii|)]<) in tho liga- 
liK-liU {lig<iinfHia fulijfintt) In'tu'TOii tho a)vb«)i of tlit^ 
vnrl<>ltni', niid in the I'nuts of tlic Urger ni'icrics. In ^nad- 
ni])Oil(i il forms thv great ligiimonl alroiuly n-forrcd to (]i. 
tU), whidi ho]]i« to iiuatiiiu tho h«M]. This tiusue, in 



cossBcTirn-riBsus conpvscLss. 105 

mass, is of a doll jellow color anil estromcly extciwible and 
ela^tiu; when purest nmirly as much so ns n piece of indiu- 
rnhber. Sometimes it appears under the mici'<Mcope to Ix; 
mode tip of (Itliciitc mGinbranoi!, but moiit ofu-ii it is in the 
form of fibres (Fig- -Wrt) which aro coarser than thojo of 
white flbrona tissue und frenuently branch and unite. It 
is unaffected by ucetic nctd and docs not yiold gelatin wboii 
boiled. 

Connective-Tissue CorpuscloB, The fibres of white fl- 
brons tissue, whernTcr it is found, are united into bundles 
by a structureless ground mattTial known as the Miiuf»t »ulf- 
stance, which also invL'sts aaah bundle, or skein as we may 
call it, with ii ddit^ate coatiu^'. In thi* git'iind siib- 
Doo are numerous cArilies, branched and tlattened in 




FM. M.— CDnnonlnvUnniD eoipuiicbw, 

'tttUMtter, and often intercmtimunieating by their 
la those CAvitics li<! nudcuu>d maescsof proto- 
plasm (f^g. 44), frciiueiitlr also branched, known m the 
fonneciiiv-tivf«0 rvrpuxrUs. These it i^ wliii.'h build tip 
tlie tissue, each coll in the course of development forming 
around it 11 quantity of inloii'i-tliiliir liuhntjuKv, which sub- 
sequently becomes flbrillated in gi-eat part, the rciniiinder 
forming the cement. The cells do not quite All the cavi- 
ties in which they lie. and tho«o opening into others 1>y 
their offsets there !» formed a K>t of minute lubes nimify- 
ing through the connective tissues; and (niiifc tJie«e in 
turn permeate nearly all the Body) pervading all the organs. 
In theao cell cavities and their brunches the lymph flows 
before it enters definite lymphatic vessels, and they are nc 



IM 



rOK BTJXAy BODY. 



oordingly known lu lymph canaticuli. Id addition to the 
fixed bianclif(Uoni)cct.iv)>.iissueciir|iin'dos King in LhocurJ- 
ti«-« of I lie ground- substance there are often found oUiKr 
cell*, when living ronuoctiro tiwue is examined by llie micro- 
soopo. Tbesp polls nuit-h roj«ml>lc while blood coi-pinrck*. 
and iirobflbly are such which have bored through llie walls 
of tile finpr lili">ii-v(!s<«jlB. They ca^ep alwut aluug Ihc 
canaliculi by means of their facility of omceboid inuvomcul, 
and are known i\» the "wandering cells." I>uring in- 
flftmniation at any point their number iu that region is 
greatly increnscd. 

Subsidiary ViuiotioB of Conneotive Tissue. In various 
parts of ihe Boily are coniiective-li^-'iic sLriicturcs which 
have not undergone tlie tyjiicid dcv('!oj>aieiit, hut have de- 
parted from it in one way or anoiher. The cells having 
formed a non-fibritbted IntercclUilar »iib»tanee around 
Uicin, dereloiiRicnt may go no fanherand the inncB remain 
permanently as the jeilg4ik« connrctive Itttne; or, as in 
the vitreous humor of theoyo (Clwii. XXXI.). the eolls 
huving formed the soft mnlrix, mny disappear and leave the 
latter only. In other cauvs the intercellular substanoo 
ditappcara and the cflU hiaiiehitig, and joining by the ends 
of their brandios, form a network ihcnisolves, nucleated or 
not ftt the point« answering to the centre of each originally 
aeparuto cell. Thin lukiioiil cnnnf^inv tisgtte is fonud 
videly distributed in the Body especially iu connection 
with the lymphatic Kyxtcm, and forming a »ippurling 
framework for the iinipcr nervous elements in the hmin 
nud spinal oord. In other c:tscs the colU almorit alone con- 
stitute the tissup, becoming Qattonod. closely Rtted at their 
edges, and united by n very small nmount of cement sult- 
Btanoe. Membranes formed in this way lie tionoath layers 
of epithelium in many plaees iind are known am basvmtiit 
numbrarteji, and the flmtened tvlls which line joints and the 
serous cavities seem really to be closely apposed flattened! 
connect ive-lii^suc <.■■.> iimsclos. 

ElaaUo Cartilage, and Pibro-Oartllage. y>'e may now 
return to cartilages and consider those forms wliich are 
mode up of more or low true oartilnge mixed with more or 



tXTEHARrWVLAR VAKr/LAOSS. !07 

lou oi*nnet!tiv« liatnie of one kind or miother. The cnriU 
lagei of the car and iiosc and some others huvc their matrix 
pervAded l)y tine branching tibrcs of jfllow olasllc tisaie, 
which fonn iiclwurkK uronnd thi* gii>ii{tj> uf citrtiliige tolU. 
ijadi iniriilngtvi »■« iilijiblt? imd luii^h and ]>0B«<Mi idso twn- 
oidenible extensibility anil cla^icity. Tliey are kn<iwn ati 
(iatiie or, from their t-olor, as tftUate cartUagtt. Elscwiiere, 
i-»|)eciullr in tlit wirlilugc* whiuh lie between the hones in 
saxae jointj), we llud forms whiph have \\\e niiitiix inrvaUed 
hy while Jibrtms listw find known iis Jibro-carlitaijr''. For 
example the artioular c-arljliige on the end of ihu lower jaw 




ha Ih w m h III* JcilBt of itae lafFT Jut Hhnslnc IM InlcmnlciilW 
m, wall IM iriUMlftl cavil J on niJi liOc at IL 

dnesmtt t-ume into dirovt con tat't with that coveringits socket 
on theekull. but l.ving1>otwcenl]iotn'oinUi« joint (Fig. 45) 
in itXkiHirriirliruhir fihyo-cHrlihi'jf : fiinilur call i la geo exist 
in the knte-joint; imil the inictrei-tohitil di*kH arc also mude 
up of this timiie. Both eWiiucwIilii^^ and fibro'Ciirtilagu 
often lihude off insensilily into piire elaittic or pure white 
librous eonnectivc tiMnitt. 

Homologieeof theSupportingTissuoB. Bone, f-artilage, 
•AuA ''Himi'i'tive li.-^iie idt ii;.'!'!'!' in ln'oiiil gti'uelui-al cbarao- 
tert, and in tlu' umv In which they are applied in the Itmly. 
la each of them the cells which have built up the tissue. 



108 



rUK UVitAA- itODY. 



with niR^ oxceptioiiit, furra uii inconxpicnotut pari of it in 
iUi fully develuped sUle. Itiu t-iuaf tiutcH »f it cuuHistiug 
of iiitei'cclhilnr «iil>»iiiriw. Tii hviilJue cartjlage« this ItUier 
ie nut Gbrilbli'd; but tlic^ uiuliluges pass in^n^ibl^' in vu- 
riotw re^ons of the Buily inUi olustiu or Ubio-eai'tlla^, and 
these Uttvr Id turn iiilu clastic or Bbrou« (»iuuoctive tU6ue. 
Tliu IiibiuIIk of bone, too, wbeu |)ecled off u bone wftened 
iti YuaA and examined with a Ten' bigb raagniriiiig jwwcr, 
are seen to be penailed by line tibros. Struct iirally, there- 
fore, one lsu draw uo hunl and fust lino between these tia- 
tav*, l^iuimine is true of tbeii'i::bemiL-ulcoin|icu>itioii; bono 
and white libroua tieswe contain a subBrance (rollagcn) 
which is converted into ^latiu when boiled in water; and 
in old {K^oplc many cartiliigc!^ bcirouic burdened by the de- 
pwt in their matrix of the ttanif lime mIIa nliich give itx 
hardne«fi to bone. Further, the deTelopuieiital histoiy of 
all of tWin IB much ulilif. In very early life ouch in repre- 
sented by cells only : these torraan intermediate subsluicc, 
and thitf ttnbw.'ijnently may become GbriI1ut«d. or calcified, 
or both. Finally tliey all agree in manifesting in health nn 
gifut physiological activity, their use in the Body de|)end- 
ing upuu the mechanical pmportiCH of their inlcrcellular 
substance. 

The close nlliaacc of all three is further shown by the 
freiiueiiii'y with «hidi they replace one another. All the 
bones and ciirtilagos of lbi> adult are nt firet repre:^enlcd 
only by collections of connoctiTe tissue. Before or after 
birib thif i^i in i>omo cnscH eulwtitntcd by bone directly (as 
in Ibe cii^c of thi; collar-bone and llic boum on Ww root of 
the skull), while in other cjim's carlila^' suppluulH the con- 
nective ItBtiue, to bo aficrwiinl^ in iiiaiiy itlaccs replaced by 
bone., while eUowhpre it remaiun thronghmit life. 

Moreover in dillercnt adtdt animalri we often lind the 
«une part bony in one, cartilaginous in a Bccoud, and com- 
posed of connective tissue in a third: cto that these tisKUuM 
not only ivpn-*unt one another at difleivjit stages in the 
life of ilie same animal but [n'rinancnlly Ihrouglioitt the 
whole life of dilfcretit animals. Low in the oninuU scale 



nraiESB of orowzxo skbletox. 



109 



we find tlifin all represented merel; b; oella with struc- 
tnrelcaH intfU'oelliilar substance: » lilllc higher in the Bcule 
th« latter U'comi^s (itirillatcd iind fomis distinct oonneoUve 
tissue. I" I !io highest -Wo//u#/--}t(8e©Zoolo{^},ii8thecuttl6- 
SahM, this is purtlv repliicod hy cnrtiliigi-, and the eome 
iR true of thu liiwiint lUhtin; whik- in soiuo oUicr fl?hes and 
the remaining Vertebmtes, we Hnd more or lw« bone ap- 
|>caring in place of the originul coDiiectiyc ti.s»iic ur ctirti- 
lagB. 

From llic nimilarity of tJinir modes of develojtment and 
fundamental gtructure. the tmnsitioual forms which exist 
between them, and the freiiucncy witli which they repl«(« 
one unoth«r, hiiitologista class all three (bone, cartilage, and 
fionnectlTe tissue) togutiiiT as hinnologouf tissues and re- 
gard thi^m HS diftorcntiationa of the same original struc- 
ture. 

Hygiemo Remarks. Since in the new-bom infant many 
ports wbitjh will ultimately become bone, corwi^t (HiIv of cnr- 
tila^. the young child roquiR>s food which sJiall contain a 
targe proportion of the lime wdla which hto used in building 
np bone. Nature provides this in the milk, which \a rich iti 
fluob Balte(eccChiip. X.\.), and no other food ciui thoroughly 
replace it. If the m»ther'« health be mich xa to render it 
nnwiae for her to nurse her infant, the best enibHtitute, 
apart from u wrt-nurse, will Ixt wiw's milk diluted with one 
fourth its volume of water. Arrowroi>t. corn-flour, and 
other starchy foods will not do alone, wince theyiu-o all defi- 
cient in the required nalti*, and many infanta thongh given 
food abundant in qaautity are really Klarvcd, ^inco theii' fund 
docs not contain the Hnbtitances reijuisite for Iheir he^dthy 
developmcnU 

At birth even those honcji uf n child which are most ossi- 
fied am oftt'n not rontinuous masses of ofl«(wus tissue. In 
Uie humerus (or exatnjilo the shaft »f the bone '» well 
(Msified and so is each end. but bctwi^vn the shafts and each 
of the articular extremities there still reinaiiut a cartilagi- 
nous layer, and at those points the hone increases in length, 
new cartilage being formed and replaced by JL The bone 




110 



THE nxniAS BODT. 



iiiCTWiM* in thickness by new oRieoiis tiiv^ie fonnccl beneath 
ilie periosteum. The enmv thing i« trnouf the boiiwof tbf 
)eg. On acouimt of the largely c-m-tiloginon* Mid imperfecliv 
kiiit mate of its boues, it is crael to etK-oura^ a yonn^ chili 
to walk Ih'VoiuI iti' etrciigcb, and nmy kwl Ut "iHiw-lcgit" 
or otbor ]«;riitatii^iit di--<Uirtiun!t. Nevcnhclejw heiv iis «Isk- 
wliM'e ill theajiiiual body, moderate exercise promotes tho 
growth of the tiiwiiCJi voucerDtMl, and it \» nrarly m bad to 
whocl a rbild abitiit forever iu a baby-carriage as to force 
it to walk beyond its gtreugth. 

The kvt rule in to let n h^idrby child iimc iU lirab« when 
it tfv^i indintxl, but not by praise or blame to incite it to 
eQortA which arc beyond iti> ago, and m Mcrilicv iU healthy 
growth to the vnnity ot [uircnl or imri*. 

The final knitting togctluT of tiic bony artitnilar ends 
with the shaft of many Ihiuch takev plucv only i'oni[iAni- 
tivcly hiU' in life, and Uie Hge at which it oocura varies 
miii>li iu (iiffcront bono?. Cicnpmllr qwaking, n layer of 
ciu'liUgi' renuiinx Iwtwivn tht; Klmft and Iho omUi of the 
bone, luilil the luticr has attained it« f nil adult length. To 
tnkva fowenunjiK^: the lonir articular extremity of the 
humeruK only bt-cumcd cuntiutniUit with the chaft by Ixjny 
tiKMio in llw cixtei-nlh or seventeenlh y<-ar of life. The 
np]ier arliculur extremity only joiiu the shaft by bony con- 
tinuity in the twcntielli year. The upjier end of the femur 
joinc Ihi' vhuft by lione from Iho sevi^nteunth (o the Dini*- 
lin-iith year, and the lower end during the twcniieth. In 
the tibia Iho ujiper extremity and the filmft unite in the 
twraty-fir^t year, and tlie lower «nd and the ithaft in tlio 
eightconth or nineteenth: while in the tibiila the upper end 
joiiw Ihe fhaft in the twcntv-fiinrlh year, and tliH lower 
end in the twi'iity-llr:>l. The sejiurato vcrtrbnit of thu 
Bacnim aiv only unitt-d to form one bone in the twenty-ti/th 
ymr of lito; and the ilinni. JM-hinm. and puhiii Hmt« to 
form the nx i»»timiii'ilHm abuut the Hiime |H'ri(Kl. U|i to 
abnnt twenty-live thin Ihe skileion i- not tirndy "knit," 
and is ini-iipiible, withont ri«k of injnry, of bearing stmina 
which it might afterwards meet with impunity. To let 



FATOBLLS. 



in 



Inds of sixteen w serenteen r»w hikI t«k« other exercise in 
f'letily ia oti« Ihitig. inxl » good ono; l>tit to ulUiu tla-rn ti' 
imdeix" tilt' o^'^'oi^ Dod prolungetl su-aiu of truiniiig fur 
Hiid rowing a rave is qnito Huotber, uiid not dcroid of 
i-itik. 

Adipom TisBUfl. {''iitt^ suln^taiicoa of several kindj ox- 
Kl iti i-i>iiAidt!ral>le quautily iti t\\v human Itody in health, 
fioine Hd mimite iiropIpt« fluiitiii}; in Lhe hudiljr liquids nr 
ituhedded in wioux cells, but iii<ut in NiKciul ccDh, neurlv 
tilled u-itli fnl, and colk-oled into ntasaen with itnpporting 
iiud imtriljve imil*, i,.> form rulipoM ti«sue. In fuel «1- 
inost in every spot where the widelj dlstribnted are<»- 
htr tis^uo i^ found, thero \a ndiiKise Umuo in greater or 
!«(» jtroportion along with it. Contudcmlik- <|iiuntitic« ex- 
ist for exuni|iU' in the aiibcutaneous areolar tiwflne, eupt* 
ciuUy in t\w fi^iindo xex. giving the tigurt* of iho woman itfl 
general gracefnl roiindnihiit of coulotir when coiti|)iLrei:l witli 
that of the male. Uirge quantities coinmonh' lie in (h« 
abdominal ciivily iiromid thv )>idn«}'fl; in the vve-sockel«, 
forming n ]jad for the eyeballs; in 
the mari'ow of hoiiDit; nrauud the 
joinLi, and no on. 

Examined with the microaoopp 
(Fig. 46) adipose tissue \f found to 
conMst of eiuiall vei<iclc« from 0.2 
mm. to 0.011 mm. dij,- to jj^ inch) 
in diameter, diistoit-d tugvther inln 
little masaea and bound toom-anolliH' 
bjr connective ti»sue and blood-ves- 
mIh whidi i n tort win V around them: 
in tJiis way iIh- littU- lingular miuwes 
which are seon in hwt auet are formed, each mass be- 
ing Ke]Mii-iitcd by a somewhat i-oarsvr partition of areo- 
lar from il.^ neighborx. The individual fat-cells m 
round or ovul except when r-loxely paokeil, when they 
)boooiD« iMilygonal. Each consists of ii delimle enve- 
'lope containing oily matter, which in lifit m liquid 
at the temjvenitui-e of tlie Dody. Besidoit the oily mat- 
ter, A nueU'iis is commonly prexont in each fat-cell: 




rio M - Fm (-.'11* with 



1 



lis 



rnn nuxAy bodt. 



und MiiDetime^ s thin Uver of proto)>Win fonnR a lin- 
iiig to the cell-wall. The oily matter coiuiBte of a. mixture 
of putniutiD, ok-in uud sUMTia, which are oumpoands of 
palmitici sleiu'ic uiid oloio aa\A» witb glycerine, throe 
nioIocuU's of the atiii hoiiigcombinoil with ono of glycerine, 
with the elimination of wut«r; as for example: 

3^C..n»0 )o) + C'|;:}o. = 3<C,.H..O) jo- 4- 3 HO, 



stearic acid. 



(lljorrlna. 



Sieoflu. 



WbW. 



CHAPTER IX. 



THK STRUCTCKE OF THE MOTOR ORGANS. 



Motion ia Aaiiaals and Plant*. If oue were asked «> 
point out tlic! niiwi dliliiictivt- |)n>|>crtY of iiv'ii^nnimal«,the 
answer would probably be. tlieiri>owerof esecmingsiiontane- 
ous movement (i. Attimalit as we commonly knoir Ihem are 
nrcij at nrM, wliiln trw.* mid iitniics move only whon noted 
apon by eitenjal forces, wliich are in moat cases readiiy ra- 
cognixublcu Even ut tlieir qiiR'k\<t tim<»i some kind of mo- 
tion is obsrrviiblo ill Mu- iiij^her animals. In oiirown Bod- 
ies dnriu;; the <Iciepest flk-cji the brcutliing inovcmonts and 
the beiit of the heart continue; llioir cessution is to an on- 
looker most obvioua sij^i of death. Here bowerer, as else- 
where iu Biolo)^-, we find that prveiKe bouu<laric« do not 

lOllit; at liny nito so far inf aniinaUund jilants are concerned 
■we cannot draw a hai-d and faet line between them with 
ruferetico to the presence or abwnco of uppiiroiitly »p»iita- 
aooo* motility. Many a flower closw in the evening to ex- 
pand again in tbe nioniing sun ; and in many plants compara- 
tively rapid and oxtencive movements can b« colled forth by a 
alight touch, which in itwlf ia quilc insufflcient to prodnoo 
mcehuuirally that amotnit of motion in the moss. TIil' 
Vcniw""' llylrap {Diomea muftcipnbi) for oxitmple has fine 
haim on iU leaves, and when tbe^ ai-e touched by an insect 
the Icuf oloios np so ae tu imprison the aninud, which Ic 
ubitMiueutly digested andabitorlH^ by the leaf. The higher 

'ptanta it is true have not the power of locomotion, they 
cannot cbonj^ their )>hu;c as the higher animals can; but 
00 the other hand eome of the lower animaU are ]>crnin- 

.noDtly fixed to one spot; and among the loweat plants many 
arc known which swim alxiut actively throngh the water in 



i 



11* 



THE HUMjy BODT. 



which they Uto. Tholo<vo«t DnimiiUnnd planteftre in fact 
llmijo wliidi Imve uinli-rgutie Itst^l ditTereiitialion in their 
develop in on I. and nhich therefore rcsenilik? piich uther in 
[iosn-s«iiig. ill u more ur U'»k initnifovt dv^rt-c, uU Iho fuiida- 
menial physiological ]>roportiea of that siniiile m\us of pni- 
to|il:i£m uhich formed tbcBtarting point of each individual. 
AVilh ttu" [iliysii'logical diviiiion of kbcir which tiik<-« phico 
in the higher forma wo find that, G|)i>akin^ broadly, plant!* 
especially di^vclop nutritiro li^ites, whili.< nnimulu are cliiir- 
uctoriw^d hy ihe high development of tiwiicj! with motor 
and irritahle properties; bo thai the preponderance of the:* 
latter is very marked wlit-n a complex auiiuiil, like adog 
or a mini, is compared with a onijilci plant, like upioe 
or a hickory. The higher animal poeseasoa in addition to 
greatly dcvc'lo])ed nuiritivc tiwiiw (wliioh differ only in 
doUil from those of the planu and conj^titiite whut are 
therefore often called oiynm of vft/eiative life), well-deYel- 
opctl 8]iontanRous, irritable and conlraulile ti«i>iie«r found 
mainly iu the nervous and muKculnr eysteiiM, and forming 
what have becu called the onjnna of animal life. Since 
thcHC place thv animal in close relalioiinhip uith the 6nr- 
roanding uiiirerEc. enabling slight external foivCR to axctte 
it, aud it ill turn to ncl upon external objects, they are aUo 
often djiokeii of oa oiijhiik of rrUilioH. In man they have a 
highor dovet"pmeut on the whole than in anyothcr animal, 
and give him his leading place iu the animate world, and 
his power of no largely controlling and dtroeting natnral 
forei-d for hi* own good, while the jdaiit ran only poMively 
strive to endure and make the best of what ha)ipcn4 Ut 
it; it hoA little or no inSucnoc in controlling the haf- 
ptntHff. 

AmoDboid Cells. The simplcet motor tisanAS in the adult 
Hiinmn ll>dy are Ibo am<elioid cells (I'ig. I'i) already de- 
lieribfd. which may be rej^rded as the slightly modified 
dcsccndunU of the nudilTerentiatcd cells which at one 
lime made up the whole Body. In Uie a<Uilt they are not 
atlachcd to olhcr parU, so that their changes of form only 
affect thcmtielvc!< and jirodncc no movements in the rest of 
the Dody. Hence with regard to the whole fnime tbey 




OIUATBD CBCL8. 



t»a liardl.v bn oalled motor tiasiiea, nnd eo are placed in s 
group bv tbemMlv«« anclcr Lbc Dame of iindifferfulialtd 

Cmiat«d Colls. Ah th« growing Body d«vi?loj)s from iia 
primitive i»iiii]ilioity vrc Riid ihat, tho cc-Hit lliitiig xom« u( 
the tnbcs and caviUos iu its inU'rlor uiidei^go a very r^ 
markabte change, by which each cell diOereutiiiics itself iiiU> 
n nutritive, niii) u highly Diolilo unil sponhirKsiiis portion. 
Such oellti iin« found for example lining llic wiinlpijio, aJid 
a namber are reprosonted ia Fig. 47. Kach has a conical 
form, ih* haw of the cone being turncil to the cavity of 
the air-tube, and contains an oval nucli-ns, with a nucleolar 
On the broader free end are a nnmher (about thirty on tho 
ATAragc) of oxtrenielv fin<! prooi-Mifs called cilia. During 
life these are in constant rapid move- 
mont, liubing to and fro in the li<iuid 
irbtcl) moiiitens lite interior of the 
psasage: and as the cells are very 
clmtcly jiHcki'd, a hit of (lie inner 8iir- 
taoe of the windpipe examined with 
a micruicopo, laok)tlike a field cf wheat 
or barley when the wind blowa over 
iL Each cilium strikes with moro 
force in onv dircLtiim llian in tho oiiposite, and u« tb(s di- 
rection of more powerful stroke is the same for all tho cilia 
on any one surface, Ihe gciiend revniH i< that the liijuid in 
irhieh th<y inuve i.-> driven une way. In the on»e of llio 
windpipe for example it is ilriven up towards tho throat, 
and the tvniu-ious liquid or muciu which t» thiiit swept 
aloug li Anally coughed or "hawked" up and got rid of, 
instead of acoumuUting in tho doejier air-pu«wigeit Bway 
down ill the ehi-st. 

These ceils afford an extremely interesting ci:ample of the 
dirinon of physiological cmploymenti. Eneh pn>cee<.bi from 
a eell which wus jirimitively e<|iiully motile, autmniitic, and 
nutritive in nil its partM. Itiit in the fully ilfV('l(>]>i.il i>lut4^ 
the nutritive dutiuo Imve been e;f|W('iiilIy u.t:<uniHl hy tho 
conical oell-body, while tho automatic and oontraciilo prop- 
orliM have been condensed, eo to spoak, in tluit modified 




l^io -ir.-CUlalHl mUl 



118 



THE HUM AS BOOT. 



portion of the primitive protoploamic miug, which forms Ihp 
oOia. These, being eappUed with food by the rest of tho 
cell, BTt' niiii-<l ubovtt the viilgur cvirc« of life iind have tho 
0|)|Mirtui)tty to devote their whole attention to the perfonn- 
uQce of automatic morcmeuU; which iire nccordiugly far 
more nipid aod preoiiw than tiiow executed hy the whole 
wll iKifore any division of labor had occurred in it. 

That the movements depend upon the KtruL-tiiro and com- 
po«itiui) of the uells tlicmiclvcs, and not ujiwn iiitluencoM 
neat'hing them fiiini the nervous or other tiseties, ia proved 
by the fact that they cuntiutic fvr a long time in uoLalcd 
cells, removed aod phKi-d in a liquid, as blood ecmm, which 
docs not nltw their physical oonBtiiution. In cold-blooded 
animals, aa ttirllcs, whutw cunstitnont tJMUcx fr('<{iieiitly 
retain their individual vitality long after that bond of union 
has been destroyed which constitutes the life of the whole 
nnimnl as distinct from the livcii of its different tjmips, ihd 
ciliated wlU in the windpipe have been found still ut worV 
three weeks after the gencrul death of the animal. 

The Uuaclos. Thwto arc the main mutor orgonH ; their 
general ajiix-arnnco is well known to every one in the lean 
of biilclicr's nimt. Wliilo tmeebold cells con only more 
thcmiiclvAA, and (nl least in the Human Body) oiliuti.xI 
celU the layer of liquid with which they may ha|){>en to be 
in oontuct, the majority of the inUHcles, being tixed to tlie 
akeleton, can, by alterations in their form, bring nbout 
changw in the form and positiou of nearly all parlu of the 
Body. ITith the Kkcletou and Jointtt, they constitute pre- 
eminently the organs of motion and locomotion, and are 
Kwrvrned by the nervous syslem which regulates theirnctir- 
ily. In ftMrt Kkoleton, muscle!', uud nervous cyrtcni are 
correlated parts: the de^e of osefuluejis of any one of 
tbem largely depends upon the more or less oomi>lete de- 
velopment of the oihern. Mun'n Iiifbly endiiwod n-nses and 
his )>iiwers of reBeeiion and reason w^iiild be of litlle use to 
him. were his muscle* less littcd io cam' out the dictates of 
his will or hi.i joitil.4 k-.<s numerous or mobile. All the 
mnsclcfl aiv under the control of the nervous system, but 
all are not gummed by it with tho co-oj>rration of will or 



FAltlSTISS OF MUBCr.E. 



IIT 



'cooMiouHnL'Ni; wune moriDg wilhout oiir having any direct 
knowledge of the fact. This is especially the case with cer- 
tain muM-l(u< nhicliuro not (ixtxl u> tlio flkobloii but ttur- 
ronnd caviiies or tabes in the Body, as the blood-Te&sek aiid 
the alimentary ciuml, and by their niovcmentt control thv 
potaage of subetaocea Uiraitgh llK-m. The foi-iiier gron]>, ur 
$idst<^ mtuelea, are also from Uieir mioroscoiiic cburactiT^ 

iknovm as striped mtiscUa, while the liitkr. or visrtral mux- 
etts. arc c)ill(^ tnuflriped or plain mittchs. Tiio akeltJlJil 
mnsclcti Iwing geiierallj more or lees Hiibject to the control 
of the will (as for example those moving the limbs) iirc 
frequently ifpwkfii uf uif vt'liinlary.An^ thovisceml nmsirka, 
vhicli change their form independently of the will, as int'ol- 
untartf. The hcart-muscio forms a sort of intcrmcdiiitv 
link ; it is not directly attached to the idccleton, but forma 
a hollow bag which drives on the blood contained in it and 
that quite involnntarily; but in its microMCopiu i^tnictiiiti It 
rawmble^ the skeletal TOluntarj muwlcR. The niu^<-h>« of 
respiration might perUaiw bo cited as unothor iiit«rincdiiilv 
gTtiiip. Thsj an rtripeil Kkcklul musolcs an<l, as we nil 
know, are to a ccrlmn extent subject to the will; any one 
can draw u deep breath when be chooses. Bat in ordinary 
quwt breathing we are qnite Qnoooscious of their working, 
and even when attention is turned to them the ]iower of 
control a limitvd; no ono can volnntiu-ily hold his breath 
lung enongh to suffocate himself. As wo shall i^vc Iicrciiftt^'r, 
moreover, anyone or all of the striped muscles of the Dody 

Imay be thrown into activity independently of or even 
^inst the will, as, to cite no other iM.-liitice», is seen in (he 
"fidgets" of nervoiisuesa and tbt> irrepressible trembliag of 

^txtTOUie terror; fu that the names volnntw^' and involun- 
tary are not good one*. The functional diffcrcncwe be- 
tween the two groups depend really more on the nervouii 
OODiicctions of cocht than upon any oesentiaj difTei'enco in 
the properties of tlie so-called voluntary or involuatary 
Bjuscular UiWties themselves. 
The Skeletal Muaoles. In its simplest form a alceletal 
sisteof It ri:d soU central part, called Ihc Mii/. which 

[iapor* at t-iuih end and there passe>s into one or mora denfto 





llfl 



THE BVilAy BODY. 




■white cords which ooiwirt nrarlr entirely of whito fibrous 
vuiincctiTO li^KUo. Thcite u-rniiniil conU are cnlled th« 
lendom of tho muscle and eene to ati:K'h :c to )uirU i>f the 
bouy or cii]'iiliigiiioii.< Mkclt-ton. tii Fig. 48 is fihown the 
Hwpsmatvls of thcann, wbioh lie^ in front »f the AHmerw. 
Its fleshy bctly, Bb. is seen to ditido ahnjc. and ciid there 
in two Uinduus, onct of which, lil, i* rixod to the i^»i;>nls, 
while the other joins the t«ndon of n nei^'hhoring mnj^-lu 
(tlio coraco-t/rachiiil) utid is ni^o ti vud iibovo to tlie shouldcr- 
blttle. Nctu- tlie elbow-joiut thi: niiiiiole is continuod into 
a single tendon, B', which is fixed to the rndius, but gin^t 
an ofFshoot, B", to tlic connoctivo-tiiuue mombniacs lyiug 
iiroiind the clhow-juint. 

The belly of every mnscio possesses the power of shorten* 
ing forcibly under certain conditions. In to dotnj^ it pulls 
u))on the tendons, whit^h being compoj^d of invxtcn«ible 
white libnins ti^^Mie IrnUHinit tho niovcmcnt to the haid 
porta to wbioh tiioy aro ulttichcd. just ns a pull itt one cud 
of rope may be made to act upon distant objccta to which 
the othfr end is tied. Tho Undonst «ro mcri-ly jxMEivo 
cords and iirc Aoinctimoo very h'iiK> ^ '"i* ioatauco in Lhv 
cnse of the muKclcs of the tingcn, tho beUieeof tiumy of 
which lie uwuy in tlic foreiirm. 

If tlie tendons at each end of a tnnscle were fixod to the 
same bone the muscle would clearly be able to produce no 
movement, unloHi by bending or breaking the bono; the 
probiiblu result in nioh a cnse would be that t!ie mueelo 
would be torn by its own efforts. In the Body, however, 
the two cndi! of a mti«clc nrc nlwnys attached to two differ- 
ent piei-c* of the skoletdn, between which wkh-c or Imb 
movement is ]icTmilted, itnd so when tjte mu^clo pulls it 
alters the relative putitiouft of the ]mrt« to whioli it« ten- 
dons are 6xed. In the gn-iit majority of ea«as a into joint 
liiM between the bonc-H un which the muscle con pull, and 
when the latter nnharl* it produces movement nt the 
joint, ilauy muscles even invsn over two joints and can 
produce movement at cither, as the biceps of the arm 
whii;h, fl.^ed at one end to the scapula lUid nt the other to 
the-mdins. can move the hone* at either the shoulder or 



I 



d 



itusoina oy arm. 



Ill 



iii\ 




130 



TUB am AN BOUT. 



elbow joint*. Where ii inu8c-l« \>wtv» over 8n nrticulution 
it is nearly always reduced to a narrow wndon; otlierwisw 
the bulky bdlics lyiug inroiind lUe joinu would mukv them 
extremelv pIuuisv and limil llieii- mobility. 

Origin and Insartion of MuhcIom. Almost invariably 
tbnt jiurt i'( [he i^ki-U^Loii lo wliiili ono ond of u tnusi-lo ia 
fixed is more eiiaily moved than ihe part on which it pulk 
by its other tendon. The ki8« movublc nttiichment of a 
muHcIo in willed its origin. Hid more movobk- its inwrtiort. 
Taking tor example the biceps of the aim, we find that 
when the belly of the muM^le contractK and pulls on its 
upper and loner tendons, it commonly mov(-g only the fore- 
arm, bending the elbow-joint as sliown in Fig. 49. The 




luiy olivuniiilaiii.'ia, UiaatbuH juUiI U QcxeJ wlira iliv roiwclo «uiilr«cCii. 

shoulder is so mtich moro 6rm that it scnt's as a fixed 
point, and to that end i* tbo origin of the muKclf, and tho 
forearm attachment. P, the inwrtion. It is clear, how- 
ever, tUiit thi^ distinction in tlic mobility of the points of 
fixation of the mn.4clo iit only rt-Iatire for, by cbaiigiiig the 
conditions, the insertion may become the Etutionary and 
origin tho moved ])oint ; us for iiistnnoo in going up a 
rojw "hand over hand." In that cu^e the nidinl end of 
the muscle ib fixed and tho eiioutdcr in moved through 
Bpuoo by it« c-i'ntrnt^tion. 

Slflbreat Forma of MuscIob. Many mnscles of tho 
Body huvD the simpln typical form of a belly tattering to n 



rOBitS OF MUSCLB. 



ISl 




single tcndoD »i <;im*I> end lut a. Fig. 50; but other* AmAo 
ai one end aod an? cfUled Itro-hnulfd or bicepg nuisclea; 
while some wm uvmi thrct-liiwifd (ir hirr/if juukIm. Oft 
tilt! oilwr linnd hoiu« muHcles huve ito tendon nt all ut oiip 
, eud, Uie he!ly running right np to thv iwiiit «f atiacbmenl; 
iind M>mf have no l«ndon iit eiitiertiid. In inanv miisele* 
H U^tidon rmi.s along one side and the libnts of the belly aiv 
at.tacljedobliijiiGlyioit: *iidi iiiiii»cleii(&, 
Fig. 511) are aillfd/Jcwwi/wrw or featb- 
er-Iike; or a tondon mnaobli'inidy down 
the middle of the mumble »iid hna the 
fibn^^ o( thu bcUy fixvd obliquely on 
each side of it (c. Fig, flO), forniin- :i 
biptftniform muscle: or even iwo tm- 
donn may run down the t)clly»nd «o form 
a tripeiiuij'nrm mntr.U'. In a few caaes ^pi^i inawie wioi ■ 
n tflndon is found in the middle of the g^^'tinVS^ if"2 

belly w »-cii .« at cftoh end of it; «nch e;;i;;;,-;K„,;i^"";':t '^Is 

muscles are called thgaMrie. A mti-^t-te |S'S^hX'Sc!>'« i?^ 
of this form (Fig. .jl) i« found in ion- •o"'"' <n."no luunjie, 

. , , , . , a liliKiuuilonu miudp. 

nection mth the lower jaw. It arixes 
by H tendon ailaehed to the base of the skull: from there 
its Dr^t belly nintt downwrtnU and forwards tu the neck by 
the side of the hyoid bone, where it ends in a tendon 
which piuws through a loop »ervin»; as a pulley. This iti 
succeeded by a second belly dircuUd u|)wanl() 

V towards the chin, where it ends in a tendon 
inserted into ilie lower jaw. lluniiing along 
tlie front of the belly from the |>chis to the 
chettt is A long muscle on each side of the 
middle line eidled the rerlti* tihdomimn : it 
is polggoiiriti, consisting of four bellira Mp* 
[wmtcl by Mhort tendons. 3fany muscles morvovor an 
not rounded but fomi wide llai niiiN*!*^, a* for oinmple 
the mnoi'lc Sa seen on the rentral eide of the shoulder-blade 
I in Fig. 48. 

Qioaa Struoture of a Musole. Hoverer the form of 
the likv^ileliil muscles and the ai'rangeinent of their tendons 
nay rary, the c^ro-cnliul litruoturo of nJl is the some. Each 



«,-A (11- 



I?2 




TIIS UVMAX BODY. 




cansista of a proper «irip*d muscular tiMve. whioli i» iu n<- 
ecntiul )Htrl, liiit whlt^h \» EiipjwrUfl bv t-oimecLjVc lissoe, 
DOiiniihcd liy l>l»»(l-vvK><tlti un<l lvii)|)h»l ittx, unl luu its ac- 
dvity ^r^rned by Derrra; «o that s grest varietjr of things 
fp to form llio coiiiplvic OT;g«ii. 

A XiKfse «licJilh of areolar ooniiet-'tire tianio, oiUod the 
fmimtfuiiiin, fiiTcIopa cash muscle, and from this parti- 
tioaa run ia oud cnbdivido liio Mljr into bundles or /««-t- 
ctiii which run from t«n<)oR to t«ndon, or for th« whole 
l«tigtb of th« muscle when it has no londons. The coarse- 
noM or finuncM of Itiitt;hiT% niKul depends upon the eize of 
tliCM primary fnadcnli, which dillers in difforcnL muecica 
of the same animal. Thc»o hirgcr fawicali are subdivided 

l>y finer coQn«otiTe-tis8tie 
membranes into 8 mall or 
ones (iis shown in Fig. 52, 
whidi rcprospiitfl a fewpri- 
uiiiry fnscicnli of a muscle 
uiid the MM'oiidary fasciculi 
into n-liioh (hew; arc di- 
ridoii), «'aoh of which coii- 

pcMMi of thf«« pniuiuy rwdciiU. A. mttsetilar nbra iHinnd to- 

DAtunl iliei 0. Ihi- nam* nuicnlflxl. .• , "^ - 

dKwiDKUwHPondarrtHeieuiioIwUcti gi'l hCF bv verj Hue C011< 

oped iji a clii«o network of microgcopio hlood • voesols. 
Whoro u muscle tuperH the filirm in iho fasciculi become 
lesH nnmerons, and when a tendon i^ forinocl disnppeur 
altogiither. leaving liUlo hut the connective tiiuue. 

nutology of Uuaole. For the present we need only 
Donceni oiirsohes with Iho mn&cnlarllhr<>)'. Knch of th«m is 
from vtghl to thirU-Hvo millimeters (^ lo IJ inch) lonj;. 
hut only from 0.f»S4 to O.WA nitti. (-,J5 t" ^X^ inch) in 
dittmeter in itx widctit ]Mirt, and tapering to a point at each 
end. Honco in long miisclcii with terminal tendons, no 
fibre ram* (he whole Imglh of a fiMcicnhiit, which may bo a 
foot or more long, hiic the (asciculiis is mode up of mnny 
tuoceraive fibres, the nnnv>w cud of oiicli litting in between 
tb» ends of tboeo which follow it. In short or pensiforn 





^ 



PLAJX MVSOVLAR TiSSOS. 

where tha faaciculi are short, the fibres m»y run 
the whole length of euvli of the lutt«r. 

£xatniiiiHl (JiirofuUy with a good miorosoope each fibre 
ii 8e«n lo jtossesa & very thin homogeneons sheiith or envel- 
ope, called {\w farcohmma, n'ithin which lies the csonlrttc- 
tih; porli'iii gf the fibre, b, which prcfieuts a striped appear- 
sDce as if composed of darker and dimmer allcniatlng 
bands (Fig. 53). During life this Niih«tiiiioe is very soft or 
semifluid, but after death it rapidly solidi- 
fies and death -stiffening, or rigor mortis, is 
produced. Bojiidc-s the cuiitruciile sub- 
Btaooe a nnml>er of oral nuclei, each sur- 
rounded by a little unmodified pru>oplii»in, 
lie in«iilc Ihe »arcolenun». Tlie latter is 
impei'forate except at one point where the 
central portion (or axU cylinder, ten Chap. 
XU.)of a nerve-fibre penetrates it, and 
ends in an expansion or end plale which is 
\a imincdiiito contact with the striated sub- 
stance. 

The larger hlood-reasels of a muscle run 
In Ul6 eoamer partitions of the connective 
tissue, and the liner ones He clo<!e around 
etch fibrv but entirely out&ido it« «urcolem- 



I 




lua. 



FiilM —a (innJl 

Klrvti of miuculor 
liiv liltrbty lunS' 
Iill1i->1. At n UiH 

cnutiDil and twUt. 
cd ao M to t*ar 
llacODMitSKhll* 
Uio looKher ur- 
colcqnlniB. « I ■ •■ 
wbar* M cloMily 
itpiilMlaUiiirn* 
katahf Invliillilii, 
ramaliia untom 
anil eonaplcDiMtt, 



Structure of the TTnfltrlped Muaolea. 
Of Ihwu the nuisciilur coiit of llie i^tontuch 
(Fig. M) ia a good example. Thr-y have no 
definite lendoua hut form expanded mem- 
braDessurroODdingeavitiM, »o Ihat lliey have 
no definite origin or insertion. Like the 
i>koletal muscles they consist of proper conlractilc elemeuts, 
with aocesanry connective tisane, hluud-vcssels, and nerrea. 
Their fibres, however, have a very diffei-ent microscopic 
siructuro. They present no striation bnt arc made up of 
elongated cells (Fig, .'i.j), bound togi'llnT by a small ([uan- 
^^ tity of cvnii-uting material. Each cell a lluttcned in one 
^ft plane and tapers off at each end; ia ita interior lied an 



I2i 



TBS BUMAX BODY. 




hare the iwwor of Kliort«iiin<{ in Uio direction of their long' 
axis, and so of climitiiHhing the capacity of tlio caTitii>s in 
tlic vulU of u-hicb they lie. 

\i Cardiac MusoiUar Tissue. Tluii con- 
/ siBtB of flatteued bmnciied cells which unite 
I to form II network, in the inl«rMtic«s of 
I which blood capillaries and oervc-flbres run. 
n The cells prcaent trunsvorse striutions, but 
" not so clixtiact lu those of the »kc)ela) nmi- 
cles, «nd are said to have no sari^olemma. 

TheChsmlstryofMuscularTifisue. The 
phomic'Jil structure of tlie living musciUar 
lilii-e is titikniiun, niim' all the nicihoiU of 
chcmioal analysis at present diseovei'cd dp- 
compose aiid kill it. It contnioa 75 per 
cent of water; niid. tunong olhor inor^nio 
eiinvlituentit. pliuHphaU-s and chloridca of 
pota^tiium, sodium, aii'l magnesium. When 
at rest a living miiHcIo '\» feebly alkaline, but 
after hard work, or when dying, this reaction 
iH reversed through the formation of sarco- 
Diuiicie«'uiiji. lactic ucid (CiHiOi). Mti^olcii contain email 
qutuititicfi of grajifl sngar and glycogen, and of orguiio 




I 




OBSMismr or musclk. 



135 



oitiogenona cryetalline com])otiiids, CH}iw!nllv ki-ciitiu 
(C>II*XiO>). Ai* in Ihu cam of all otiicir phj:si(>logiciillj' uc- 
ti»e tissueii. however, the main pimt ntortftu c<iii«(ilucuts of 
the muscular tSbrus iiro proteid substauces, und iL U probii- 
Me tUut like proloptmtn itj<(rif (gi. 'J4) the c^iciitial con- 
11*110111? part of the tisaue consUU of a couijilex body ooti- 
tainiDf! prol«id, carbohydnitc and fatty residues; and ihul 
dnring mu«.'ular work ihis In hrnkoi up yielding prot«ids, 
carbon dioxide, siu-eoluctic acid, with probably other 
tbiugs; for tliis hy[i<)thetical iiubi^lsnce, wliicb baa never 
vol been isoIiiKd, i\w imme inojim hiw bfen proiMJsod, 
TXie main proteid flubatance obtained from niuscleii is that ^ 
known as mymn, wliich is prepiired n* followf!. I'orfectly 
frmsh and still living muAclea arc cul oul from o. irog which 
lias just been killed by deirtruction of il^ brain and Rjiiiial 
oord, a proceeding which entirely deprivus the animal of 
eonficioiisiK-ibi and the power of u.4iug iU niuKilcs, hut. 
learea these latter nnalt4?red aud alive for some time. Tho 
excited muscles are thrown inio a vaisel cooled below 0° C. 
by a freexing mixture and so are frozon hard before any 
great chcmictd change IiM hud lime to iicciir in them. Tlio 
solidified uiiincles are then out up into thin slices, the hita 
thrown on a cooled filter and let gnuliuilly warm up to the 
frcexiu); point of water, with the addition of mimo ico-cold 
(1.5 \KT cent solution of common salt, (iradually a i<mall 
<|uantitj of a tenacious liipiid lilterx throujih which is at 
first alkaline to icsl-paper but soon sots into a jelly and 
bcoonieH acid. The coagulation and the acidity are due to 
! breaking up of the muwdo «ul>^tance intu the myosin 
id other bodies referred to above. At first tlie jelly is 
traii»iiarent. but soon the myosin becomes opa^jue and 
shrinks just like blood fibrin, H(|uecxiiig out a (juantity of 
iNifjc/^ spruni, and remaining itself as the wunih clot. 
JlyoKin thu'i prepared is insoluble iu water and in saturated 
solntton of common salt, but soluble in five or ten per cent 
waterjr Bolutious of the latter substance. When boiled it 
IS turned into ooagulnted proteid (p. 11) and becomes in- 
Mluhlo in dilute iu-iib<, in wliich llio original myo«iu was 
•ftlnble, being at the aame time, liowovor, convei-ted into 



i 



im 



TOE aU3IA2f BODT. 



anothor protcid, called gt/nionin, which was formerly eon- 
sidcnrii to be tlio originul jirott-id yiclilcil Ijv the musclea. 
S^niioiiin is i[i)i)liible iiiwmer but 6oluL>lc in dilute acidj) 
mill alkalica and its eolutioiu ore not coagulated bv 
boiling. 

Beef Tea and Liebig'0 Extract. From Lite aboro »lnt4!d 
factK it ifi ik-ar thuiwhin a, muscle is boiled in vrater its 
iDTosin is fuii^idati-d and left Ix^bind in llie meiil: cvon if 
cooking bocomnienced by soaking in cold water, ihe myosin 
still remains as it is ioKilulili? in cold water. Beef ten as 
ordinHrily mailo, th«n, contain?) tiiTlo hnt tbv flavoring 
matters and salts of the meat aud ^ome gelatin, the former 
makinff it dciejitively tante nx if it Yrerc a strong fdiition 
of the whole moat, whereas it containitbiit lidleof the most 
ntitritious protcid portions, which in au insipid shmnken 
form are left when the liquid ia striuned off. Varinnx pro- 
po»ils hnvo been mjulo with tho objoet of avoiding this 
and getting a really nutritive beef tcK; a« fur example 
chopping the niw meat fine and soaking it in sliong brine 
for some boiin» tct dissolTo out the itiyo>in; or cutractiug it 
with dilute a^'ids whieh tuni the myosin into itrntanin and 
disaoWe it, at the iumc time rendering it non-coagulable bjr 
heal when gntbsetjnently boiled. 9uch methods, hnweTer. 
make uniialatable coni]»ounda which invalids, as a rule, will 
not take. Bec-f tea is a slight i^liniiilunt but hardly a food 
and cannot he relied upon to keep np apalient'sstrongthfor 
any length of time. Licbirf's ertrart of timtl \i eiwentially 
a very strong hecf tea; containing much of the flavoring 
snbstaneDB of the meat, nearly all its sidts and tho crystal- 
line nitrogenous bmlies, such iis kreatin, which exist in 
moHe, but liardly any of its really nutritive parts. From 
its stimulating effects it iR often useful to pcmons in feeble 
health, but other food should he given with it. It may 
nW bo used on account of its flavor to add to the "atook" 
of soup imd (or similar purponcK; hut the erronoousnos^ of 
tho common belief that it is a highly nutritions food can- 
not 1)0 too strongly iui^istcd npon. Under the name of 
Kguid txiracfs ofmmt other substances have been pro|iaj-cd 





LIQUID BXTBACT OF MEAT. 



127 



hy Biibjectiag meat to cfacmicul processes in which it un- 
dergoes chuDges similar to those eiperienccd iu digestiou: 
the myosin is tlms rendered sohible in water and uncongu- 
lable by heat, and such extracts if properly prepared ate 
highly Qutritioas. The flavor may be improyed by adding 
a little of Liebig'a extract if desired. 



CHAPTER X. 



THE PKOPERTIES OF MUSCULAE TISSUE. 



Contractility. The oharact«riBtic phjsioluip'cal |in»jjerly 
I'f mii^i'iilui' Ui'.'^iii>, and that for which it is eniplu^'ed iu the 
Body, in the faculty possessed by iU fibres of ehort«uitig 
forcibly under certain eircumslimces. The direction iu 
which Lhitt Nhortuiung (h'C-ui'r is always that of Uie long axis 
of the libre, in both plain and striped miistlea, and it ia 
accmnpiinKi) hy an alninKt «(|Uivaleiit l.hicki'ciiiig in oLhcr 
diainetern, tiu tliat when a rouficte cootrueu it docu not 
shrivel up or diminish its bulk in any uppruciuble wuy; it 
«imp!y chiingff its furni. When a iniii>clc cunUiiuts it aleu 
beoomca hai'der and more ripid, especially if it ha* to over- 
come any resistunoo. This and tlic diunf^ of form can be 
well full by placing the fingern of one hand over Uie bicc|w 
inuHcle lying in front of the laimerus of the other arm. 
When the muscle is contracted so as to bend the elbow it 
can bo fult to «well out and liardea h« it «horI«n«. Evory 
iiclioolboy know."! that whiMi he appeals to another to " feel 
liis muscle" he contract the latter so ss to make it thicker 
and appareutly moiu nuu-Jiivv us well as haiiliT. In etattH>fi 
the prominencce oii the- surface, inducting the diu«c1im be- 
neath the skin, are made very conspicuous when violent 
effort ID rcproBcntcd, mo im to indicate that Ihuy are in vigor- 
ous action. In a miuicular llbie we Hiid no longer the itlow, 
irregular, and indeBnite chanpen of fonn seen m thenndif- 
forentialcd cclU of cjiily development; this is rcphiced 
by a precise, rapid, and definite change of form m one di- 
rection only. Muscular tissue rc|)rL'.«cnts a group of cells 
in the botlily comiuunity, wbidi liave taken up Iho udo ope- 
cial duty of executing changes of form, and m ]>roportion 



JtUSVULAR IRRITAmUTY. 



139 



aa \hey have fewer other tliingti lo Ao, they do thut better. 
This coHtr<K4Utly of the mu«alar fibres msy be best can- 
ccivwl by oonsuUTiiigciich to po^sWM two niilnrul sh»p(»: 
one, the sliit« of reat, in which the flbres are long an<i niir- 
row; and the other the state of activitv. in whith they are 
ebortvr and thicker: iiuilor ecrtniu condition! the ^bres 
t«od to pftRi, with coUKidemblc fortrc, from their resting to 
thur active fonn. and in ito doing Ihey move partfi attached 
to their tendorn-. When the state of activity passes off the 
(ibrctt siitTor thcinwolrcs to ho passively cxt^'iidod a^iin by 
any force pulling upon them, and they so regain their rest- 
ing sbnpc; and since in the Hving Body other parts ar« 
n«iarly invmiably put iiixin tiie itrctoh when any given 
muscle contracts, these by their elaatioity serve to pull the 
hitter back again to its primitive shape. No muscuUr 
fibre I* known to h«vethe jviwcrof actively exjiandingaft^r 
it has contracted: in the active slate it forcibly resists ei- 
Unsion. hut ouce the contraction is over it suffers itsetf 
readily to be palled out to ita resting form. 

Xrrttability. With that modifiutti<in of the primitive 
protoplasm nf an amoiboid cell which gives rise to a mus- 
cular fibre, with it^ grout contractility, there goes a loss of 
oilier priJiMTtiex. All truce of spontjuieity seems to disap- 
pear; muscles are not autam.ttic like native protoplasm or 
ciliated colls; tliey remain at rest unless directly excited 
from wiihout. The umnnnt of external change required 
to cxoiti! the hving muscular tibre at any moment is. bow- 
over, very ;<mall: in otiicr words, it tH highly irritable, t, 
v«iT little thing l)cing snftlcient to coll forth a powerful 
voiitmction. In theli\'ing Hiimiiii Body the exciting force, 
or fiimnlwn, acting upon n uiii.tcle Ik almomt invariably a 
H«rvi)u» impiihp. a molecular movement transmitted along 
the iiervc>ftbroK attached to it^ and ujisetting the eqaili- 
brinm of Ihc innsnh-- It I* through the nerves that the will 
acts npon the mnsclew, and accordingly injury lo tlie nerve 
of a part, jik tlic face or a linili, will L'uuse pnratysis of iU 
mascleA. They may still be there, intact niid <juit« ready 
to work, but there are no means of sending cnmmandfl to 
them, and so they remain permanently idle. Althfltigh n 



ISO 



TnF. BOMAX BODT. 



nerroue ImpnUe lis the natural phyBiolo<;ical muscular 
stimiilUM it i* not the only mm kmiwn. If ii miit-clo be 
vxjiosed ill a living animal and » sli;i:ht but suilileii up U^ 
given to it, or a hot bur be »tiddi.-ii]}' brought ncur It. or an 
electric nhock be sent ilirougti it, oi- ii drop of givot-rine or 
of solution of iinimooin bo placed on it. it nill contract; ho 
that in {idditioii li> \\\y ritilunil iicrvouji HiiniiiluH, mti<cle)i 
lire irritable und^r the iuHueuce of median icnl, tli^rniul, 
elei:ti'ical,aud chemicul stimuli. Oue condition of tliD of- 
fit-any of all of thorn \a that ibey shall act with some sud- 
dciiiiess; a very alowly increased pressure, eren if uUiniiili-lt 
very great, or a very sluwly ruiwd li'iniicnituic, or a slowly 
incrciucd electrical current pitted tlirough it, will uut ex- 
cite the muscle; although far less pressure, varmth, or 
electricity, more rapidly iiiijilwil would i-tiniulate it power- 
fully. It may perlmps still be objected that it ii nut proved 
that any of these stimuli exuito the muscular fibres, and 
that in all these cases it is possible that the muncle \* only 
excited through its nerves. For tlio various stimuli mimed 
ahovD also excilc iicrvew (i<l'c C]tn\'. XIII), and when hc ap- 
ply them to the muscle we may really Im; acting lln<t upon 
the fine nerve-ondings there, and only indirectly and 
through tho mediatiim uf these upon )ho musoulur librca. 
Tliat the muscular Hbres have a pui])ei- irritability of 
their own. independently of their nerve:*, is, however, sbowi: 
by the action of uertaio drugs — for example curari, » South 
American Indian arrow poison. ^Vhcu this substance ia 
iiitriiduced into a wound, all the tflriped muscle!- are 
Hpp[iri.'ntly iici-iiiiiod, and thp animtd die* "f siilToeatioD 
because of the ce.isation of the hrralhing movements. But 
tho poison doc* not roally act on the muscles themselves: 
it kills the miidclo Dorvov. but leaves the mti»cle iiilact; uimI 
it kills tin- very endings of the miiKcIe-nervc^ right down 
in the inusck- tlbrc^ themselves. Now after its admini>itni- 
tion wo still find that the rarioiis nuu-phyciolugicul stimuli 
referi'ed to above make the mnseloii oontraot just a^ 
powerfully [i« before the poisoning, so we must conclude tliat 
the muscle.' thenwelvcp are irritable in the absence of idl 
nerve etimuU^-or, what amouutu to tlie same thing, when 



A 




nil lh«ir nen-o-fibres have been poisoned. The experiment 
also sbuws tbat thf cmitmctilily vt a mti»dc is u property 
holonging lu ihqU, mid ih^t iU cont rut-ling force is nut 
tunwtltitig derived from the nerves Ktlaciied to iL Tlie 
nerTenlimulu^ §imply«cte like the electric dhock or sudden 
blow and arouses the niusolo to luunifcst u propurty which 
it iilroady pos«0£«os. The older ])hy«iologi.-n.* *i;ttiiig that 
inuaouhir )>araly«M foUowcd when the nervous nonncctiuii 
between a mtucle nnd I ho bruin v/aa interrupted, LuncUided 
that the nerves ^ave the muscles the jwwer of oontraotiug. 
niey !)f!ievtsi tliat in thu bruin there was a great store of 
a myjili^rioiiii thing c-allcd viiul «/'iriy*, mid Ihnl sonic of 
this was ejected frotu the brain along tJie nerve to tJie 
muwlfi. when tho Utter was to be set at work, and gave it 
its working [luwcr. Wc ixiw know that twh is nut the 
'cttdc, but that a mtiacie tiltro is a collection of highly irrita- 
ble material which can have it« c(|iiilibriiini upset in a 
deflnileway, eau/ingit todmnge its Kbapo. under the influ- 
«noo of slight di^uirbing foi'ces, one of which \a a nor- 
Tous imptilitt; luid aiiuo in l]iu Body no ulher kind of 
stimulus uiually i-eaches the muscle-'i, they remain at rest 
when their nerrons connections are severed. But the 
tntiA-liii |iHridy/.ed in this way can still, in the living Body, 
be ma<1e to ccmtriK't by sending ehcLricul shocks Uirongh 
Ihem. Physiologically, then, muscle is u contractile and 
trrilablo. hut n"t automatic tissue, 

A Simple Huaoular Oontraotion. ^tovt of the details 
i-onccraing tiio phymolofrical pnijit-rties nf mu^clee have 
l«vn Ktudicd on tUtov of cold-bKiixicd aniutalit. A frog's 
miisulc will retain all Etii living pro)K!rtiiM for some time 
nft4T removal from tJie body of the animal, and so can bo 
cxjieriineuted on with c-ji^e, while tlie masulcv nf a rabbit 
or cat soon die under thix''C eircumiitiuiceH. Enough has. 
however, been observed on the niuM^les of the higher ani- 
mals to Hh»w that ill all e."eiitiaU they iij^oo with thoae of 
the trog or tcri'»|iiii. 

AVIieii a single electric shock is sent tlirongh a miuele it 
ra{ndly Hhortons and then, if a weight he hanging on it, 
rapidly lengthoni* again. The wholo scri<-i( of phenomena 



J 



tf^r 



133 



TUB BUXAX BODY. 



from Iho [noin(>nt of stimulution until Ui« tnufclt* r^ainR 
its resting form is knowo ae» " simple mum^thr conlra'titm" 
or u " twitch." It occupies ill tlic frog xbout om- tenUi ot 
n seeond and is separable iota three ]><>rtioiiK. Phut, there 
elti«i[K'i^ a time, ufl«r the HtiDiiilulion uud beforo th4> coni- 
iiK'nuiTiifiit of tint shorl*niiig, wliicli i» kiiowi] an tlie " losi 
tinio" or the jtenod of Intent rja'trmUHt. Thi« lasts aboul 
one liimdredih of a, i^ecoiid, ami n-iireiiciita thv time dtirin); 
wliitli molecular cbimges preparatory to the ponlraotion iirc 
tiikiiig jiliice in the inuscto fibi-ps. Thi>D follows the short- 
ening, sit. first slow, tbtjH rapiit. then mIovht iijfiiiD up to a 
Diaxiinura, and occupying rather more than half of the ro- 
muiniug time; the elongation occupies tho remsiuder of the 
time t»ki!ii up in the eontriR-tion. In warin-blnoded ani- 
mals, the diinitioii of a !<ini)ik> niuHi'iilar contraction it. vvcn 
less than one tenth of a seoond and all its atages are (jnick- 
enert. Id any given aninnil, cold iiicrcjwcii the rime Uiken 
in a miiiicniAr eontrataion and aho impairs the contractile 
power, OS we tind in our ovm linibi; when "numbud" with 
cold. Modentto warmlh on the other hand (up t« near 
tJie point at which heat-rigor is produced) diminishes the 
duniti'in of the contraction; ho that ihu moU'i^iiIur changes 
in a inuM'ulnr fihro arc clearly eminently snsiejilible U) xlight 
cbitngea in its environment. The coalructility of u muscle 
does not depend upon a vital force, entirely distinct from 
orilinary itiaiiiiiiatu fniies. but upon an aiTangement of iIb 
material elements, which is only tnniniaincd under oor- 
ttiin conditions and is eminently modiliable by Llie Rur- 
roumlintp?, 

Physlolo^oal Tetanus. It is obvions that tho ordinarj- 
movements of the Body are not brought about by nuch tran- 
sient mu^cuhir cuiti'iietiimi' ii.>< lho.-<e (lo^^c-ribed in the hist 
iwra^rajih. Ki'on n wink lasts longer than one tenth of a 
second. Ourmuvomentsaru, in fact, due Lomorejirolonged 
oontntetiun>« which may ho dcwribed as consisting of several 
•iinjili' twitches fuHed tfgoiher. and known :is " itianir 
eoniraf lions"; it might l>e better to cidl thi'in "cum|>ound 
contractions," nnco the word tetanus haa long been used 
by pathologists to signify a diseased stale, such as occura 



unH V 

I 



iruBCVLAR rosniAOTroy. 



133 



str^Thninc poutoninguiKl iiyfiniphobJH, in which most of 
ih« miiacleji of thp Body are thrown into prolonged and 
powerful Involnntarj- contntctions. 

If. while II frog's mimric i« utilidlKiHeninguHclcr the in- 
ncuu« "f (iiie oli'Ptne siinc-k, nnother alimiiiiis bp given it. 
, will contrast a^'ain anil the now lontraction will be added 
on to that already exisling, wilhuiit unj porind of elongation 
occrnrring liclwocn tliem. While the muscle is still con- 
traoting under the intUience of the second stimulus a third 
electric tibock vnW make il contnurt inuro, and )<o on. until 
tho niusclo in i^hortcncd luc niui^h u.* i# jxiMible to it for that 
strength of MiinnluK. If now thi> stimuli Iw repeated at 
tho proper iuterraU, each new one will not prodace any 
further ghorkniDg, but. each acting on tho nin«clo before 
tho effect of tho last hat begun to piws off, the muscle will 
be kept in s state of permanent or ■' tetanic" contraction; 
tin d this can be maintHriicd, by continuing thoEtimnIi, nntil 
the organ bcgin^n to get exhausied or "fatigued" and it 
tjien oominem^-s to elongate in Kpito of the iftimulation. 
When OUT tnuscleji are fitimulated in (he Body, from the 
nervft-centres through tho niTve«. they receive from tho Ut- 
ter about 20 fliniuh in a tteeoiui, and m are thrown into 
tetania contractions. In other words, not even in the 
most rapid niovemeut* of the Body in a musclu made to 
expcnU) a simple muitL-ular contraction; it U itlwars n 
longer or a shorter tetanna. When very quick movemeDt* 
are c\eciit*'(l. ai^ in pi-rformmg rapid passages on the piano, 
tho rt^ult \t obtuilied by ciuitrinrting two opposing mtuctea 
and alicrmiiely xtrengtheuing and weakening a little the 
tetanus of cich. 

CauBOB ollecting tho Degree ol Uuscmlar Controctioa. 
The (-Mt-iil of sliorieniiig wlmli can lie niilnl fnrih in a 
muscle varies with the -timiilus. In the first place, a 
Klnglo stimulus con never niiine n mnxirle to contract so 
much list rapidly rtiwated ntimnli ol the some strength — 
since in the latter case we get, a? already eiplained, ceveml 
«itnpl(' contniction<> such as a cingle stimulus would call 
forth, piled on the top of one oiiothrr. With rery power- 
fnl repeated electrical stimuli a muscle can be made tg 



134 



THE HUilAX BODT. 



shorten t« one third uf its resting length, bnt in the Body 
tho strongest effort of the vrill nerer produces u contnkc- 
tion tir Mint e.\k'nt. Ajutrl from the ralC' of stimuliition. 
the strength of the MimulUH has Rome iufliiGtice, s greater 
Ktimiiliti) Clinging a gredt^r (M>ntrsction, but very soon a 
point ii reached after which incretuiing the titinuiliiii pro* 
dncea no increoaed contraction; the muscle has reached 
iu limit. The umuitiit of loiid curried bj the mn«cIo (or 
the rcsiHttince opposed to it-t ahoHonitig) )ii» also an influ- 
ence, and thiit in a Tery remarkable war. Suppose we 
have a tro^v culf-miiEclc. currying no weight, and tind that 
with a Htiwnliia of a certain Ntrenglh it shortenii two milli- 
meters (t"! inch). Then if we bang one gram (15.5 grains) 
on it and give it tbcMiiincslimtdu«, it will be found U> con- 
tract more, say four or Bvo miltimetei's, and so on, up to 
the poiot when it ciirricis eiglit or ten grams. After that 
iin iiKtri-:Lscd noighl will, with the 8am« ^limulim, cause u 
less contraction. So that up to a certain limit, resistance 
to the tihurlt^ning of the niu»clc maicee it mure able tu 
idiorttfii: the mere greater extension of the muscle due to 
the greater resistance opposed to it£ shortening, puts it into 
a state in which it \s able to cotilraul mure powirfitlly. 
Faiigiie diniini'>hcjthe working power of amnstU' ;ind rest 
restores it, esiwcially if the circndutiun of the blood be going 
on in it ut the f^tnuf time. A frog's mu«cle cut out of the 
body will, huwerer, be eansidernbly restored by a jferiod of 
ivst, i*cn although no blond flows through it. 

The Ueoaura of Uuaoular Work. The work done by 
u 111 iisi-lc ui n given contraeiKin. when it lifts a weight verti- 
cidly against gravity, is measured by the weight movtil, muN 
tijiliL'd by the di^tMncc through which it is moved. In the 
»bovc t-ate when the muscle contnictcd curnfing no loud it 
did very little work, lifting only ita own weight; when 
loaded with one gram and lifting it fire millimeters it did 
five grum-millimetei's of work, junt ii! an engineer would 
any an engine liiid done so many kilogrummeters or foot- 
pounds. If loaded with ten grams and lifting it six 
millitnetera it would do sixty gram-inillimeters of woik. 
£veQ after the weight becomes so great that tt is lifte4 



MVSCULAH WORE. 



las 



tliroagii a less di^tunc-c, llio work done bv the mnBcIo goen 
on lUcreusiiig, fur the bigger veiglit Iifleil more thiui cotu- 
pfiiMleA for tlic le^A dvslance through whioli it in mj^ctl. 
Fur i<xuii)]ilt!, if tho above miisclc wore loiuJcJ with fifty 
^ram<i it wouW niiivlitt lift th»t weight only 1.5 niiliimo- 
t«ra. but it woiikl thi!ii <lo seven ty-fiTi; graiii-miUimclors 
of irork, which la more thuii when it HfUi] ten grama six 
millimeters. A load in, however, at la^t readied with 
which tho miiMik* doc- less work, the lift bccomiug rorj- 
litlle indcorl, until iit lair the weight bocomtw ho grout that 
the mascle cannot lift it all and so does no work when 
etimulfltod. Starting then from Ihe time when the muscle 
eurriwl ii<i 1«im1 and <iiil no work, we pit** with increasing 
weightt, thmugh jilms^-ii in whieh it dav* moru and more 
work, untU with one particular load it doea the grcatwit 
tuQuunt possible to il with that Flimulutt: iiflcr ihnt. with 
lucreit^ng loitdti less work is done until fliiully a l»>-id if 
reached with which the muscle again does no work. What 
18 tmo of one mnHcIc iii at cotirMo ima of all, and what ix 
tine of work done ngninst gravity ia trne of nil muscular 
work, so that there is one precise loiu] with which a beast 
of bnrik'n or a man v:ui >\<) the grcalest ]"»-'il>le nraoinit of 
work in a day. With a lighter or lieavier load tho dixUmce 
through which it Ciin Im? moved will be more or hv% hut 
iho iieliud work done always Ii'h«. In tho living Boily, how- 
t'Tor, the working nf tho mnscles de|>endswmiich on other 
things, as the duo uL-tiun of tho circulatory and respiratory 
tyKtcmit ami tho nervoii'* energy or "grit" (upon which 
the titimitlittion of the ninnelo'* iIcpcn<iA) of ihe individual 
man or beast, that the greul.at amount of work obtainable 
M not a tiimpio mcchjiuieal problem n» it u with the excised 
muscle. 

Influence of the Form of the Muscle on Ita Working 
Power. The amount of work that any niusilp ciiii do dc- 
pi-mii of course hrp-ly ii|Mn it* phytiiolncicji! state; a 
licalthy weii-noiiii.-'lii'd inii>fli- can <io luoro than a dis- 
aitcii or eturveil one: hut nllowiu;; for sneh viiriutious the 
work which can be done by a minelc vuriex with its fonn. 
The thicker the muscles, thit is the greater the number of 



139 



TJIK aVMAN BODY 



fibres (irexciit in ft section miuie acrws the long u«6 uf the 
fiificiculi, the ^router tiic loud tliiii ciui be lilccd or Uie other 
rasiNiaiiee ihiit. am Iw overcome. On tho other liund. the 
esteut through wiiich a muscle can move a wi-ight in- 
creuses with the length of it* fu«cicnli. A mnsdu a foot in 
length can coiitrsict niort- ihan a nmselo six inrhes long, nnd 
so "wtiuld movo a twne throHjjjh a greater dirtance, pi-oTJded 
the resiBUince were not too gi-eat for its streiigtli. But if 
the Bhorlcr ninselo Inwi duublc tlii' lliicknww, iht-ii il conid 
lift twice tho weight that the lunger muM:le conld. We 
findin the Body muscles constrneted on hot h plans; someto 
have a great tango of ninvement. othere to ovorvome great 
rt'iiintiinw. In-side-'* ininuTou» iiitcrrnediiile frtrm* which 
canitiit he called cither long and alemler or short and thicki 
muiv »hort muscles for example ure not rpcciidly thick, 
but ftie ahort meivly beeiinso tlio piirw on which they 
sot lie near together. It tini>-t be borne in uiind, too. thai 
many a|i]>arcnLly long mii-rli' mv nnUly ftliurt Htont onvn — 
those namely in which a lemion runs down tJie eide or 
middle uf thi- miii>cle. and ban the fibres infcrted obliquely 
into il. Till- miiaele {ffatlrocnnniiin) in the enlf of the leg 
for instance (tig. 60, b) is ixmlly a short stont muscle, for 
itit working length deiicnds on the length of its fnttcicnli 
and these are short nnd ohlt(|ue, while il.H Inie rrojis-ncciioti 
ifthnt lit right aDglot! tothefa>!ciculi nnd is Tery large. The 
force with which u muwle can yhorieii in very gratt. A 
trog^'fl muscle of 1 square centimeter (0.30 inch) in section 
can juHt lift iSOO gram;* (1)8.5 ounces), and a human muscle 
of till' Hiiiiie ai'i-a inure Ihiui tiririt ux much. 

Muscular xniwticity. A clear distinction nuwl he tnndo 
between eluHtieitv laiA conLriu^lility. Elasticity is a physi- 
cal jironertj- of matter in virtue of which Tiirious budiee 
loud til iiMiimc or retain a certain sha|ie, and when re- 
moved from il foreibly. t^i return to it. When ■ »innii 
steel spring is stretched il will, if let go, "oontract" in a 
eorlain sense in virtue of its elasticity, but. wicli a, contrac- 
tion is clearly ijuile dillcrenl from h muscular contmclioii. 
The Bpring will only eonlriiet iin ii result of previous distor- 
lion; it Minnot originate a change of form, while the uus- 



A 



xmovLAR Kt-AftTTcrrr. 



187 



V 



de cnn actiTClrcontriK't orcliungu h* shnjHMclicn it stimulus 
iictfl upon ft, and that witimut lifing previously stn*U;ii(iL 
It dues not mDr«ly tend lo return to a Diitiirid Khapc from 
irhifli it hitt liciii renioveil, hut it nH*<iiiiic'M ii i|iiit(' doit 
iiaiiirii! i«li:i)ie, so tlitit phpiologtcal nontriu^tttity a » difTi-r- 
cnt thing from mere physical elasticity ; the essential differ- 
onoo being that the coiled tipring or a Htroiched band 
onlj giTc* Irnck mechanical work which htu idrciidy been 
iipent on it, while the miiiiclo iirigiiiHt<^» work independ- 
I'utly ot any previoois luechanical stretching. In addition 
to their conlractilily. howovor, miiaclcn arc liighly i-la«tic. 
If a fresh musol<> he hung up mid its length mea^nrcd.O' 
and then a weight be hung ui)on it. it will stretch jiiit likeV 
apicc« of iniliiui-ruhbvr, uiid wln-u tho weight if remnved, I 
provided it has mtt Iieen so great as to injure the muscle, ' 
the latter will rHum passively, without any stimulus oi 
active cinitri«:litin, Iw it« ()rigiiial form. In Ihc Body all 
the muscles are so uttached that they are usually a little 
ulretclii'd lioyond thoir nnlnrul reeling kngih; «o that when 
a limb is aitiputiiii-d the muscles divided iu the stam]) 
shrink away considerably. Ry lhi« i>tR'lchcd tttjilo of the 
Rtttin; oliwtic miifctuf two things are gitincd. In the lirvt 
place when the musi-le contracts it is already tant, there 
is no " slack" to bo hauled in before it pulls on the parts 
atlJicheil to itiit tendons: and, i>«condIy, n« wc have alrcaily 
aecn the working power of a musclo is inorcaiied by tho 
' presence of some resistance to its oontra<!tion, and this is 
always provided for from the first, by having the origin and 
inwrtion oF ihc miisolc »o far apiu^ as to bo pulling on 
It when it begins lo shorten. 

Pb7«iolo^ of Plain Muscular Tissue. What has hith- 
erto been said applies t-specially Iu the skeletal muscles; but 
ID the main it is trne of the unstriiKd muscles. These 
also aro irritable and contractile, hut their changes of form 
are much more slow than those of the striated flbrCR. 
tTpon stimntnlion. a longer period of latent excitement 
elapses before the contraction commences, and when finally 
this take* place it is extremely slow, very graduully attain- 
ing a maximum and then gradnally dying away again. 



138 



TSS BVItAy BODY. 



There itomt in tact bo bo tonic cjiiinccrioii liotwceii thnt ar* 
nu]g«mentof Die coutrdctile eiiltstanco which shows itself 
under tho mici^wstt^jic ii« »triiiiii)n iind iho |>uw(-r <>r riiiiiO 
contru<;ti»Ti, litniw we find that tho lieiiit, which la not a, 
fikclutiil or voluutury mueclc kit }ct otic that controt-tn ruji- 
idly, agreos willi Ihcn; in having ils fibiTs i^Iriuttii. 

Hygiene of tho Muscles, 'i'ho hoahhy working of tho 
moeck'S needs vf cuu»(; u hciihhy vtiiti? of tlic Body gcner- 
ally, 10 that they cball be KUj.iiliuil witli ]ini|n,T niatciiiiUi 
for growth and re^jair and have ihoir waiites ra()icny and 
efficiently removed. In uthur words, good food and puro 
air itro neGcasary for a vigorouH miiM-nhir Rystctii, u fact 
which trainers rccoffnine in iiwisiiii™ ujion a Hirict dietary, 
and in siijicr^iitiiig gcinjrally tho mode of life of those wlio 
lire to engage in athtelicioontosl^. 'Dtc miisideK fhuiild al»o 
not bo cxiimed l<i niiycon^idoniblo continued pressure since 
thin iuWilerea with the flou of blood and lymph througli 
them. 

luitat tm tho luiucloii thomwlvcv are directly ooDccnied, 
exercise is tlie necessary condition of tlicir bcvt dtvc]oi>- 
menU A miwik' which in permanently uniiaed degetieratoti 
und i« alisorln-d, little finally being' left bnl the conni-ctiTC 
liasiie ol tho organ nnd a few muscle flbivs filled with oil- 
drop*. Thi« \i well itcun in atfv^ of pai-»lysis dependent 
on injury to the nerves. In Kiich caMS the tnuirclefl at firet 
may themselves be perfectly healthy, but lying nnim-d fur 
wocks they riijiiilly alter aiid,liniLlly, n-hen the nervotis in- 
jury hiui been healed, Ihe muKck« may bo found incaiia- 
ble of fiiDttioiiul activity. The ]>liyE>ieian llieiefon' is ofleii 
uireful to avoiil till* by exercising the parulyxcd miiiH-lcf 
daily liy niLiiii* of elieirieiil "iliouk' fciiI through the jMirl. 
The same fiiet in iltuati-alc'l by tin- feeble and nii^lcd oondi- 
lion of the muscles of » limb which has been kept for wimc 
lime iti ^|ilrnt9. .^ftcr tho hitler have been removed it if 
only slowly, by judii-iotia and perniKtont exerei.-e. that the 
long idle mnsck's regain their former siwnnd power. Tho 
great muHclen of the "brawny ann" of tlie blacksmith or 
wreetler illnstrate the roverso fact, the growth of the mu»- 
altt by exercise. Exereiso, however, muit Ih' judicious; rt- 



A 



MUSCULAR KXKRCISB. 



1.19 



])«at<>dlj continued until exhaiistion it does harm; the period 
of repair it imt. KiiHIoifiii to nllow roplticement of the part* 
used in work, und the niuscloa iluis waste under tooviolenl. 
esercise as wilh l.w> lill-U'. Host should allornutv with work, 
Mid tliat ix-t^ularly. if henelit \a tu be obtained. Moreover 
violent escrcisQ should norer bi- suddenly undertaken hy 
one unused to it, not only lem. the niusclui jmUcr but be- 
oiiusti iiiu.wulur work greatly inereaacs tiio work of the heart, 
not only beeuusu nioi'e btncHl hus Up b<i wnt to the muack-a 
i^msolvcj^ but ihfv iiroiJui* great qiijiiititic« of curbon 
Fdioxide which must be carried off in the blood to the lungs 
for removal from tlii; ISmly. and ihc lu-arl must work harder 
to tsoud ihv hl(jod f.i.>«ier through the lungn uiid at the muus 
time the breathing be hu«[cned so lui to renew the air in 
those organs faster. Thu liiiwt evil result of throwing too 
Tioh'ut work on the heart and Jungs in this way, is repre- 
senied by hting "out of breath." which is advantageous 
inEomuch as it may lend to a ecs«atiou of the exertion. But 
much luorc serious, and sometimes permanent, injuncK of 
either cho circulatory or i-cspirutory organs may be caused 
by violent and iirolmiKed efforts without any previong train- 
ing. No general rule e»n be laid down as to the amount 
of eierciso to Ije taken; for a healthy man in huMineHs the 
ininiiiium would perhaps be represented by a daily walk of 
five miles. 

VorietieB of Exercise. In walking and running the 
moNck-st (ihiofly emjiluyed are those of the lower limbs nnd 
tniak. This is tnie al«o of rowing, which when good ia 
perfonned niucli more by the Ifgs than thearmn: eepecinlly 
«i»oc the inlroduetion of sliding seal* llcnco any of (hen 
exercises alone ie apt to leave the inuiicles of the chest and' 
»rniB ini pelf eel ly excroined. Indeed no one excrciso em- 
[jIdvh e<iiially or proportionately all the mnscles: and hcnoc 
g_>nnnnfl>ia in whiih various feats of ugilily arc practiced, 
so DA to call differeiii part^ into pl^y. have attained a grx-al 
popularity. It should K' hurne in mind however, that the 
legs especially need strength; while the U]>^«.-r liinLs, iu 
wiiicli delieaiy of movement, n» a rule, is more desirable 
tluin power, do not reipiit* such constant exertion; and llie 



140 



XBE UUMAX BOVr. 



fuel that gymn«!itir eTepcisoa are commonly coiriecl on hi 
iloor:! m a great drawback to thek value, Winn lliowciithor 
perniitB, out-of-door oiitrcisc is fur better than that carried 
ou in QTcii lliii U->1 vciililiitt'd itud lightuil gAmnosium. 
For tbode who arc mi fortauato as to posscHRa garden there 
is no better exorcise, at §uitubte Boafiona, thau an liour's 
iLuily digging in it; sineu thiit cdl« into play neiirly all tJie 
mitKcles of the Body: while nf gnmo^ the niodirn oiio of 
]ttwn tonnix is porlupn the best from a hygienic view that 
luLii ever been iiitriHlucedi uuce it not only demands great 
muwiulai- agility in every pm-t of ilie H'"ly. Inii Iruiiis the 
Imnd to work with the eye In away iliai walking, ninning, 
rowing and similar jjiirfuits do not. For the »(me reasons 
basehuli, cricket, ikkI boxing are exeellMiU 

Exercwe in Infiinoyiuid Childhood. Young children 
have not only to strt^ngt.hen lliuir nniHles by exercise but 
aUo lo learn to use them. Watch an infant trying to con- 
vey something to it« month, and you will «ec liow little 
control it liaa over iu muscles On tlie olher liand tho 
healthy infant 'n never at rcet when awake; it conHiantly 
throws its limbs around, gniJipH at nil objcetfi within Its 
reach, coili! itself alioiit, and so gradually leiinis to exer- 
cise ita powerB, It ia a good plan to leave every healthy 
child, more than a few montba old. several times daily on 
II lurgo ix'dorcvcn on a rug or carpcti'il fluor, wilh us lit Lie 
covering as Is safe and that a& loose as. possible, and let it 
wriggle about as it pleaeoe. In this way it will not only 
enjoy itself thoroughly, but gain strength and a knowledge 
of hiiw to use its limbs. To kex-p a lu-allhy child swathed 
uU diiy in tight and heavy clothes is croelty. 

When a little later tho infant commences to craw], it is 
safe to permit it as much as it wishes; but nnwise to tempt 
it wiion disinclined. The bones and muscles are still fee- 
btontid muy bo injured by too much work. Tho same is 
true iif commencing walking. 

From four or five to twelve years of i^ alraowt nny form 
of oxereise should be permiited, or even eiici>urageiJ. At 
this time, however, llie f|>iphyso» of niiiny bones me not 
Qrinly united to their shafts and so anything tending to 



MUSCULAR KXEBCI8R. 



141 



throw too grciit a Htntiii oti ILe jointii should be avoided. 
jVflcr thai njj to commencing manhood or iiiuidriJiood any 
fciud of outdoor excrc-ii^o for healthy imtpomr i* gimd, and 
girls »ro all the better for beinp allowed to join in their 
brothers' e|io:'t!(. Ilitif of the dcbilitv and goui^rul ill-hi-ulth 
of 80 manv of our vrimicn is dci>(>ndont uiimi dcfioiviit ux- 
orci« during childhood, and the day, which fortunatt-ly 
^eenia apji roue hint;, which will hoc doll* a* uukiiown lo, or 
as dcspiftnl hv, lindlhy ^iIk na healihy hoy^, will seo the be* 
^'nning of a great improroment in the lamina of the 
female portion of nnr popnlat)"n. 

Exerctae in ?outb .-(lioiiiil hy regiiliitcd largely by »w; 
not that womon art' to be shut np and made p:ile. delicate, 
and unfit to share thu duticj' or pnrticipatc fully in the 
pleasures of life: bnt the other calls on the ftrengtli of the 
adnlt womun render vigorous muscular work often nnad- 
vtMihle, c^pecinlly under oonditious where it is apt to hi 
followed by a chill. 

A healthy boy or yonng man may do nearly anj-thin^, 
but until twetitv-two or twenty-three very jirolongod elTurt 
is nnadviEable. The frame is ulill not linnly knit or as 
capable of endurance ii* it will i>iibi<f(|iiently bi-comc. 

(lirU shonid !«■ allowed to ride or pliiy rmt-dour gumoH 
in moderation, nnd in any case ehoutd not be crihbe<l in 
tight diayn or light boots. A flannel drew and i>roper 
lawn-tennis shoes are as noceRwry for the hi>ttlthy and wife 
enjoynieiit of an afternoon at that game bv a girl bh they 
nrc for her brother in the bn«c-))al1 field. Rowing is eitral- 
lentfor girls if there be any one to leach them to do it prop- 
eriy, with the leg; and bade and nol with the arms only, as 
woin«n iin' ko npt to row. I'mpitrly pnwtiocd it strengthena 
the back and improTps the carriage. 

Exorcise in Adult Lift. Up to fort}' a man niny carry 
on jafely the excreitu--* of yonlh, hut uflcr that sudden ef- 
forts should be avoided. A lad of twenty-one or no may, if 
trained, pafcly nin n qtiarler-mile race, bnt to a man of 
(orty-flTC it woidd Ih" dimgor<iU!i, for with the rigidity of 
the cartilages and blood-vessels which begins to show itjtelf 
ahniit tbiit time itppearx II diminished power of meeting a 



im 



TUB NCiUy BODT. 



Kudden Tiolmit ilcmitiiil. On tliu otlit-r )iiiii<l tlio man of 
thirl)' would inure safely than the lad of nincii <-ti or ivrcnty 
undertake one of the long-distiince wnlkiii^ imiKliw which 
luive liticiy been in vogiio; (lie prwlongod fff.n-t Monld Ik' 
less dimgorouE to him, though n *'ix dti}e' mulch with its 
nlliiiidiiitl lo^j of KltH^p oftnnol fuil to b(> mmo or ^ci» dun- 
^eruUH to any one. Probably for one euj^aged in adive 
liueinciS II walk of a cuuph'of miU-K to it in the morning 
niid t)UL-k iigiiiii in tii« uficrmion is ilie \n-*l und niokt uvail- 
abte esercide. The habit which AmericanH have eveijn h«re 
ucijnirc'd, of never walking when they can take a horR--i;;«r, 
iaccrliiinly dclrimenlal to the general beallli; though the 
estremeH of heat and cold to which we »re Bubjecl often 
i'cndcr it iiniiroidiiblo. 

For woinvu daring niiddio life tho »Mime rule* ai)ply: 
thirre Khould be some regular bat not fiolent daily ex- 
pi-cisc. 

In Old Age 'h(i needful amount of exercise is lew. and it 
i« Etiil iiKiix' miportiini to avoid eiiddcn or riolent elTuri. 

Exercise for Invalids. This jilmiild W r<*giiliit<i1 nnder 
medical udviw. for feeble persons gymnoatic excrciwH are- 
Q^peeinJIy valuable, i^ince from tbdr variety they pontiit of 
Rpleolion acoording to Uie coudition of Uie individual; aiid 
their aniount eun be eonveniently controlled. 

Troiaing. If imy |K-r»oii uttcmpt^ some iinni<nal cxvr- 
rice he Mon Rndi that lie IntwH breath, gets ]>erhniia a 
"Mitch in the side," and fecln hi* heart I)palingwith un- 
wonted violence. If he jwi-aeveres he will |irii!inbly faint — 
or vomit, tw is frci)iiL'ntiy seen in imi'erfectly Iraincd mmi 
ut ihc end of a hard hont-nice. llieso {ihenomcna iirr 
Mvoidcil by ciuvftil grndnal prepiirniion known iw "tmin- 
tng." Tlie immediate canse of lliem lies in disturhnncoH 
of the circulatory and 'x-j-piiutory orgiiitK, on which cxoeMlvo 
work !■*! brown, umi ihe fitrlhcr discussion of training muBt 
Ihi put-tponed for the pic-!eiiU 



•t 



CHAPTER XI. 



MOTION AND LOCOMOTION. 

The Special Physiology of the Husolea. Tlnring now 
oonsidcrcd sv[>ai'uk-ly the striictoro nnd propurtius iii goji- 
eral ot tlie akelclou, the joiriu, and llm masdca, wo nmr 
go on to couaider liow they all work togelher in the Bodv. 
The propurtio* of u muscli:' for CTimipIt; arc tveiywlicro tlie 
■ini«, but tlio uses of diiTorent niuticles iirc TC17 Tiu'ied, by 
reaaoaot the difloront parts with which they are contiected. 
Some are matclis* i>f ivxpiruitini, olhci^i of doglutiliou; 
tahay are known asfitxori btemise tliey bend joints, others 
w «Kfrji(«urs.bocan*o they stntightcii tliem, ntid k>> (jd. Tlii; 
det«n 111 tint ion of the exnot use uf uny luirliciilctr uiiixi-le ia 
known lui it« spfcinl pkytiolvyii, iis distingtiishud frutu ftn 
getunti pUfftiolotjif, or ]irr<j)or1ii'd m a iniisule wittiout refer- 
ence to its ase as a mueL-lo in a juu'ticular place. Thu uses 
wf those mnscK<« forming; part* of tliv phyniuhigical iiu'i-hiui- 
isint vonocrncd in hreathing and swallowing will Wsnidicd 
hereafter; for the prcsuut wo may consider lliu mn^lee 
which co-upcrale in DiuiiitAiiiiiig p(ii<1 iiic-^ of Itu! I^ody; tii 
producing niuvomente of it^ part^ with ivfcrcix-e to one 
another; and in proiluoitig locomotion or niovciiiout of the 
whole Uody wilh rc-feroDoo to its euvironiiicnt. 

In nmi'ly all case the slTipcd muscles carry out thoir 
fiiiiclioiiK witli thf! oo'opcrnliou of the ski'lctou, i^ince nearly 
all arc lUed to bones at each end and when they contmct 
primiuily move tliexc, aud only secondarily the soft porta 
attaohod tu litem. To this geiKiral rule tlicre are, huwvver, 
exceptions. Tho muscle for L'lample which lifts tlje upper 
oyclid aud opiin« the eye arig^M from bone at tho back of 
the orbit, but is inserted, not into bone, but into tlie eyelid 



14i 



TUB UCMAN BODY. 



directly ; and eimilnrly other muscles arising si Uie back 
ol tlie orbit iiie diiecily fis«J to the eyeball in front and 
eervQ to rutiilc il uii tlit- ]>itd of fat on whicb it \wi. Mtuiy 
fiK'iid triitmlp^ »^;iiii liuve tio direct iittuvliuK-nt whatever to 
boiios, !Wi for (!](aiu{ilc tliu muwlo {orbicularis ortt) which 
surrounda tho ni(iuth-M)>«nJtig and hj Ha <Hintriu:tion nar- 
rows it and paraca out tlie lijia; or the orbicularin ptilpe- 
brartitn which ^i^li1ll^1y earrounds the vyv* and when it 
oonlrat'lfl closes ihem. 

Levers in the Body. Wlictt tho tnuRcles serve to move 
bones the lutter are in nearly all case* tn bf regarded as 
leveni whone fulcra lie at tlio joint whore the movement 
takes i»lai'e. Eiaiii}ilo3 of all the three forme of lerora 
recognized in mechanics are found in Uif Human liody. 

Levers of the First Order. In this form (Fig. 58) tlio 
fulcrum or fixed point of support lies between th« ■•weight" 



i 



i 



Fid. M.^AlrvM-ot Ui^flrM ortpr /; rukmn; P. uoirer; 11', nsloaiiM or 

VDllgllL 

or rc<irtanccto be overcome, and ihe "power" or movinfc 
force, as sliown in the <biignim. Tlie dislaiicc Pf, from 
tho ])ower to ihe fulcrum, in railed ihe •' power.arni;" the 
distance FW is the weight-arm. When ]>owcr-arm and 
wei|;ht-nrm aiv ei|nal, ut i» the case in the heiini of un ordi- 
nary pair of scaler, no ineehnnioal udninlage in gained, nor 
is there any loss or gain in the dititajicc through which the 
weight is moved. For every inch tlirough which P is de- 
pn»Rod, ir wiil he raiBcd an e<jual dislniict'. When the 
])Ower-arni is longer than llic other, then a nnaiier force at 
P will riiiso a larger weight at H', llie gain being propor- 
tiouate lo the diflerenco in tJie lengtliK of the arm*. For 
example if Pf in twice us long as J-'H% then hidf a kilo- 
gram applied at /'will haluncc it whole kilotrrum at I)', and 



ifOTiox AJTD Looo-vorroy. 



140 



jiui more thmi half ii kilogmm notild lift it; bat for pverj- 
oontiiiK'tur through wbicli /* <lc«ceii4«cl, D' wouW oiil)' Iw 
Hft«d hair ii centiniittcr. On the other biiiitl wlien ibo 
wpigbt-nriii in » l<>Ter is longer thiin thi- {xiwer-onn. ttiero 
ill loM in fm-ce but n gttiu in the JiHiaiioe through which 
the weight is moved. 

Examples of thi- lirst form of lover uru not uuniorous in 
the Iluoimi Body. One is afforded in the nodding move- 
monU ol the head, the fulcrum bcin^ tlie nrticti bit ions 
between the :ckull and the utlux. AVhvn tlie cbin i» el«vat«d 
tli» power is applied to the skall, behind the falcrnin, by 
itiuall muscles passing from the vertebral column to the 
occiput; thi' reeiitance La the cxcesf in the weight of the 
part of the bead in front of the fiilcnim over that behind 
it, and is not fnvat. To depress the chin as in nodding 
does not nocoiteurily cult for any muKCnIsr effort, um tlie 
head will fall forward of itaelf if the muAcleit keeping it 
erect i-euEc to work, m those of nn who have fallen aKJeep 
during a dull discourse on ahot dity havoleamt. tf the chin 
however be depressed foniibly. as in the athletic feat of 
nupciiditig one'H itelf by the chin, the muscles paning from 
the ohext t^ the skull in front of the atlanto-occipital artjc- 
itlaliou lire calk-d int« play. AnotlitT Dxumple of the em- 
ployment of the drat form of lever in the Body is afforded 
by the curtsey with which » lady sidutcs another. In 
curtseying the trunk ii> bont forward ut th<! hip-joints, 
which form ihe fulcrum; the weight is that of Ihe trunk 
acting as if all concentrated at its centre of gnivity, which 
lies a bitle above the Micrum and behind the hip-joints; 
iind tho power iiiafforded by muscles pasiung from the thighi* 
to the fronl of the pelvig. 

Xaoven of tho Second Order. In thi^ form the weight 
or resistance is Iwiwccn ibo power and the fulcrum. The 
power-arm PFie always Imip'r thun the weight-arm WF, 
■ad so It compitnitivcly wcnk force can overcome u concid- 
•nbte reeiMance. llut it is diMidvantageowi so fnr m re- 
gards rapidity and extent of movement, for it is obvioua 
th&t when P is raised a cciCain dixUnee tCwil) be moved a lea 
•liatauuo io theoiuuu lime. As un example of the employ* 



14fi 



TUR IWMAS BODT. 



nicnt of juch Were (Fig. ST) in llie Body, «■<■ may tAke the 
m-t rtf standing on llie tocR. Here the foot represeiita tlie 
lever, the fulcrum is ut the oontuctof iu fore purt witli 



r 



w 



Fn. Vt.~K lnvur nf Ito MMMId Cl4«r. F, riiluRim ; f.poinv; IT. gcetsbt. 
Thp arrowH liidlonln Ih* rfhwetinn In which iIih foif** KCt. 



the ground : the woight i« thnt of the Body acting down 
through tho mifclfi-jointfl iit Tn. Fig. .1.*; iind the power is 
the great muHcle of the caJf acting by ita tendon inserted 
into the hi'cl-bone {Ca, Fig. 58). .Another example is 
afforded by holding up the thigh when one foot is kept 
rallied from the ground, a* m hopping on the other. Ilere 
the fulcrum id at tlii; hip-joint, the power ia applied at th« 



CD cn c 




Tm "* —TIM dtdlMni of tb* Awt from th» nntrr fld». nL worttM- via 
viitoli iLiplw-boiWBBmciilMB: Oi.|]wa>l«iie»iui»u>i>hldith>t«ait[ui(lmdo 
.i.-l,aliu of Um oaU nu»t( la loMitod ; JR. Uia moUiaiMl liciiM«r iha fltlh 
•Ikll. 



kncc-eap by n great mnocle {rtvlut fnnnriii) inserted there 
niid which arices from the pelvis: and the weight is that 
of the whnlf Iiwer linih iieting nt it* centre of gravity, 
which will lie Komewhero in the thigh between the hip and 



LEVERS m THE JiODT. 



147 



knee joinif, thnt is bolween the fulcrum aud the point of 
application of th« power. 

Iievera of the Tbird Order. In tliouc ( Fig. .^9) the 
[iijwer IS belweou i!ip fulcrum and the weight. In euch 
iuverx llic wuigbl-iirin ih tiltvuyii InngiT tliaii llic power- 
arm, Bu ilie jiiiwvr wurkj" ut ii nu^iliiiiiioil cliKudvoutugo, 
bat ewiftD<!>i.s und rungit of movcmont are gained. It \i 
llio lover most commonly used in tlie Human Body. For 
example, when the foreurm ie bout up towards the arm, 
the fulorum itt the elbow-joint. th« power io applied at the 
JDsertion of the bic-cps muftclc (Fig. -!!>•) into tho rudju« 
(and of another mmu'le not iypr<>.«uui«d in [,\w figure, the 
brachialia aniieita, into the ulna], and the weight u that 



"W 



Fio. U.— A iDier <it Ihe Uilrd order. F. tulcrum i P, power i H'. ml^t. 



of the forearm and hand, with whatever may be contained 
in the latter, acting at the centre of gravity of the whole 
somewhere on the distal side of the point of application of 
the power. lu the Bixty the power-arm is usually very 
abort 80 a« to gain Kpi^ud and range of niovomvnt, the mus- 
cles being powerful enough to still do their wurk in spit« 
of the meckimioLl dieadvantngo ut which they are thuft 
placed. The limbitarc ihuH made much mure ehupetTthan 
would be the oase were the power applied near or hfyoud 
the weight. 

It is of coureo only rarely that simple movomont« as 
those doHcribcd above take placo. In the grmt majority 
of thoite executed several or many muscles co-operate. 

The LoMH to tho Huaoloa Rrom ttio Direction of tliolr 
FuU. It is worthy of note that, owing to the oblique direo- 

*P.UOl 



148 



rUJ{ UUMAX BODT. 



lion in wliioh the mnjiGltia uro <;oiiiniuulv inserted into the 
bones, much of their force is tost so far m jn-Dducfiug niuvo- 
ment is couconu'd. SuppuHc Iho lug of wood in the dia- 
grttni (Fig. (iO) to be niijied by pulling <jji the ropo in Hic 
direction a ; it is dear at first that the rope will act nl u 
grout di«advuDtage; muxt uf the pull trauKinitted by it will 
beexert«d againitt the pivot on which the log hingdE, and 
only a small fi-aotion be available for vlovuting the l»tl«i'. 
But the more the log in lifted, a^ for exiiniple into the 
po«itjon indical^d by the dottctd Hue. the more utwftit will 
be the direction of the pull, nnd the more of it will be itiwut 
on the log und thv K^^ lui't nunvmlingly in merely iucroas- 
ing the pressure at the binge. If we now consider ihy ac- 
tion of tiie bicep« (Fig. Vi) in flexing thii elbow-joint, w« 
see tiimilurly tb&t the Htruighter thv Joint is, thv more ot 




Fin. ao.~DI<«mm UliuuMlug Uia dliadTO>aU«« of an obliqtii! puIL 

the pull of the mnscle is wasted. Boginuing with the ann 
t^lriLight, it works ut n gn>iit disadvantage, but as the fore- 
arm ii iiuiwl the conditions become more and more favor* 
able to iho muscle. Those who have practiced the g.vm- 
iiastio feat of raising onc'it nelf by hendinj^ the elbows when 
hanging by tlie baiuU from a horixontal bar, know pmoti- 
callylhatif the elbow-joint* are quite straight it la very 
hard ia Etlart; and thut, on the other hand, if tliey are kept 
a little flexed at tlie beginning the effort needed is much 



fOSTUBBS. 



I4» 



Imh; (he rciwon I>eing of course the mAro advanu^eons 
direction of traction by tlie lik-ejiH in the latter case. 

Experiment proves timt ili<! power with which ii muecle 
CdQ ooiilract in greiitc.ti ui the i?ommeiic<Ktuent of iC:^ shori- 
ening. the very time at which, vro havp jiut 6c«n, it works 
At most mcchunioKl dtsudvautiigt: iii iirnportiuu iw iti> force 
becomes Icm the conditional becnnie more favorable lo iL 
Theie is however, it is cletir. noiirly alniiTw » t.-on»<iderat>le 
loss of povrcr iii the working nf ihc* itkelutjil muiiulM, 
streiiglh being siicrificed for rariety, ea^, rapidity, extent, 
Hiiii (•!c;;:tmo of movement. 

PostuTXM. Thi; term poKturc ix applied to thoso posi- 
tionii of oi{niIibrinm of the Body whioh can be maintained 
for gome lime, such as sluudiug, fitting, or lying, com- 
pared with leaping, niniiing. or fulling. In all po.ittires 
the condition of stability in that the vertical line drawn 
rhrough the centre of gravity of the Body shall fail witliiii 
tb« \m\t of support afforded by objwte wiUi which it ie m 
oontacl: and tlie security of Ihe posture is proportionate to 
the extent of this base, for the wider it is, the l«e8 is the 
risk ot the perpendicular through the centre of gntvily tail- 
ing outside of it on alight displacement. 

The Erflot Posture. This Is pre-eminently character- 
istic of man. ht» whole skelclon Ix-ing nioditicil with rcfer- 
SDOG to it. Nevertheless the power of maintaining it iH 
only slowly learnt in the first years after birth. un<l for 
a long while it is unsafe. And tlmugh llnully we luurn to 
stand urect without cou»cioua attention, the maintenance 
of that p'Khire always requires the co-operatiou of many 
mnHCics, ccM}rdinutod by the nervous Kyittom. The infln- 
iHioe of the latter is shown l>y the faJl whioh follows a 
eovure blow on the head, which may nevertheless have frac- 
Hired no bonound injured no muscle: the "coneussion" of 
the brain, as wc -say/'Mtun^" the man, and until its <-lTccts 
have piifsed oS he cannot stand upright. In stimding 
with the aniiit sirntght by the sides and the fi-et together 
the eeiilre of gravity of the whole adult Body lies in the 
articulation between tlie sacrum and the last lumbar verte- 
bra, and the perpendicular drawn from it will rvucli the 



lAO 



TUB liVMAH BOOT. 



II 



u 



ground between the two feet, vitbin the bMts of mpfwrt 
alToiTlcd bf them. Witli the f«ct cloco together, howorer, 
the ))')«tDr« ia not vor^ stable, and in standiiifi; we com- 
moDly nuke it more m by slj^jhtlv separutm^ them so a« to 
incretise ihv !»».*■■. Tlii; m»rt' one foot 
is in front of the other Ific nioi-e swav 
iug back and forward will bo conipiiti 
bte with safety, and the grciilor llic 
lateral dijituiico (ie]itiniling them, the 
greater the lateral sway which u po&n- 
ble withont falling. ConseqnentlT' we 
see that a uiau about to make great 
moTementii with the iipjier part of hia 
Body, as in fencing or boxing, or a vA- 
dier ]>rc|)aring for the bayonet exercise, 
ulwara commences by thrnsling od« 
foot forwards obliqnoly, eo lu to increue 
his bans of support in both directions. 
The COM with which we can stand is 
largely dciwulcnt upon the way in 
which the head is nearly baknocd on 
tbt> top i>r the vertebral column, so that 
but little muscular effort is needed to 
k<>cp it upright. In the eame way the 
trunk ia almost balanced on the bip- 
joinU: but not (juitp, its centre of gi-av-' 
ity falling nithor behind them; so that 
just OS some musculnr effort is needed 
tokc«p the head from falling forwards, 
some ia needed to keep the trunk from 

_ _ toppling backwards at the hiiw. In a 

uui 'h!u^ 'iST'jki'M similar manner other mufcles are called 
Sirttf wp tSS']?!^ ""'« playat'otherjoints: as between the 
r«M«iidu«.B<-iy.r«*. vertehml eolnmn and the petris, and at 
the know iind ankles; and thuw a eortain rigidity, duo to 
muscular effort, ext<*ndji nil along Ihe orcct Body: which 
on account of the flexibility of its joint-i could not other- 
wise be balanced on ila feet a* n statue can. Beginning 
(Fig. fli) at llic ankle-joint, wo find it kept stiff in standing 



i 



n». «t, — r>l«cmm II- 
iwIm 
bJMk 



■nwrallDf Um muivlM 
(4r*Bn fa UUdi 




by Uioconibiia-d and balanced oonlniotion of tli« inu«cl«« 
piW0iug from the heel to the thigh, and from the dorHutn of 
the foot to tho iiliin-hoiio (Jibia). Others pulsing before 
aud bt-hind iho knee-joint keep it from yielding; and so at 
the bip-joint«: uml otbcni ugiiin lying in the walls of the 
abdomen and iilong the vert^brnl column, keep (he Intler 
rigid, and er«ct on the pelvii^; and Anally the Eiknl) h kept 
in position by tnuBL'tes padding from the etemnm and Ter- 
t«brnl cohiRiii to it, in front of and behind the occipital 
n>Ddyle«. 

LocomotioD includes all movements of tho whole Body 
in #pace, d<'|i(!iidi'iit on it.« oun nnixulnr eftortii: suchaa 
walking, runninf;, lenpiiip. and swimming. 

Walking. In walking t!ic Body never entirely quit« the 
ground, the hi>el of the iidvanccd fo(.t touching the groand 
in uch Btep before the toe of the re-tr foot leuvea it. The 
advanced limb supports tho Body, and Ihe foot in the rciir 
at tlie commencement of each Ktep, proiHl^ it. 

8up)>ueo a nutn standing with his hoels together to com- 
mence i'i walk, Ktopping ont with the left foot: the whole 
Body 13 at first inclined forwards; the morenient taking 
place mainly at the ankle-jointa. By this means the cen- 
tro of gnivity would ho thrown in front of tho ba«ofonnt'd 
by the feet and a fall on the face result, were not aimnlta- 
neoualy the left foot slightly raised by bending the knee 
and then swung forwards, tho toes just clear of the ground 
snd, in good walking, the sole nearly parallel lo it. When 
the «tcp is completed the left knee is straightened and th« 
•ele placed on the ground, the heel touching It llrst and, 
the baiie of support being thus widened from before back, 
a fall is prevented. Mejinwhilo the right leg la kept 
straight, but inchnes forwards above with the trunk when 
tliu lallcr advances, and na tJiia occurs the sole gradnally 
leave.t Ihe ground, commencing with the heel. When the 
step of the left leg i^i eumplcted (he great toe of the right 
alone is in contact with Ihe support. With this a piub is 
given which sends the trunk cm over the left leg which U 
now kept rigid, except at the ankle-joint; and the right 
knee being bent tliut limb ewini^s forwards, iXa foot juA 



Ibi 



TUB UVMAX BODT. 



clearing tUe ground ns iho left diil Ijoftnv. Tbe Body \» 
niiittiwhilii .tuiijiurii'd on llic loft foot iilono, liut wliCD tlic 
right completes Its siepllio kiu'cof timt. k'g U ftriiijihtcnod 
and the foot thuji jiluui], lici-l firM, im the gronmi, Mpan- 
wiiile tlie left foot baa been gradually learing the ground, 
and it« tucB ulono «ro ut llmt. inonn-nt iiji'tn ii : fmm these 
» push iit given, iw bvforo with the Hfclit foot, iind the knee 
being bent ao as to raino the foot, Ihe left leg swings for- 
wards at the hip-joint to make a fresh step. 

Dining ojurh (ttcp tho wliolo Body »wavi« up and down 
and a1ai> from side to nEdc. It \» htgliu^t at the moment 
wlicu tlio adrancing trtink is tertically over the foot Jiij)- 
portiiig iu and then sinks nutil Ihe moment when the ad- 
vancing foot tutichi's tiio ground, when it i." hiwt-rf. I-Vom 
tliis nionicnt it rises as itawingaforwiird on this foot, until 
it Is verliiwlly ovi-r it, and then sinks again until the other 
t<»iu-hcs the ground; and so on. At the same time, as ita 
weight Ia alternal^ily tranaferred fmm thy right to the left 
foot and e(ce versa, there is a alight lateral sway, coinmonljr 
moro marked in women than in men. and which when ex- 
cesaive pnidtiekui an ugly "waddling" gait. 

Tlio length of each atej) Is primarily dci)ondent oii the 
length of tho legs; but can bo controlled within wide lim- 
its by «iwdal munctilitr effort. In ciuj walking, litllc mus- 
cular work ia employed to carrj* the ifiir leg forwards after 
it has given ita push. When ita font is raised from tbe 
gnninil it cwingi! on like a pendulum; but in fa«t walking 
tbemuaeliiH jin.'i.-'ingin froiitof the hip-joint, fromlhe pel- 
vis to the limb, by their contraction forcibly carry the leg 
forwards. The easiest stop, that in which there is most 
economy of labor, is that in which the limb is let swing 
freely, and since a short ])endtiliiin au-inga fiisler than a 
longer, the UEitural step uf ehort-leggcd people is (juicker 
tluin that of long-legged «ne». 

In fiut walking tho advanred or mipporting leg a]«o 
aids in propuUion; the muHCles parsing in front of the 
ankle-joint contracting bo aa to pull the Body forwards 
over that fool and aid the push from then-ar foot, Honcv 
the fatigue and pain iu front of the aliin which in felt in 



I 



Ruyyiyo a.vd lsapiso. 



168 



pFoIonged v«ry fattt walking. From the faot that each 
foot reaches the grotiud heel first, hut leaTw it toe laet, the 
length nf (•aoli utriile ii< ioorrawd by the letigtli of tlie foot. 

Hanning, Iii.thiji iiindc of projcreaoion there is a mo- 
ment ill cadi *tfp when both feet nre off the ground, thu 
Bi>dy l>oinjf:Hii«nii]nirtcil in tin- nir. The twH alone come in 
contjict with t\w ground In e-ach step, and Ihe knee-joini 
is not straight when the foot reachea Ihc fjround. Wlu-n 
the rear foot in to leave the *ii|>pi>rl, iJie knee la suddenly 
sLrat^iiteued, and at Hie same time the ankle-joint is ex- 
tended so OS to push the toes forciblj on thu groniid and 
give th« whole Body u powerful pudi forwards and upwards. 
Inamediately after this the knee is greatly flexed and the 
foot rut^d from the ground, and this oecur* before the 
toes of the forwurd foot roach the lallPr. The swinging 
leg lu ir&vh 8t4-|> is violently pulled forwards and not suf- 
fcred to swing naturally as in walking. By this the rapid- 
ity of the siitrcwion uf sfepis is inircascd, iind at the mm* 
lime Ihe stride is made greater by llio sort of one-legged 
leap that occurs tlirough the jerk given hy the #traightcn- 
nig of the kni'i' of the rear leg just before It leaves the 
ground. 

Leaping. In this mode of progression the Budy is 
rallied comj'letely from thu ground for (i considerable 
period. In n powerfnl leap the ankles, knees, and hS]»- 
joints are all fle,\eii us a preparatory measure, so that the 
Body iiKsumcs a eroni-bing alldiidi'. The hceli?. next, are 
raised from the gi-onnd and the Boily balanced on the- toes. 
The centre of gravity of the Body i« then tlimwn forwards, 
and simullaneously the flexed joints are straighlenod. and 
by the rvwistanceof the ground. Ihe Budy reecives a propul- 
ition forwards; nuieh in ihe same way as a hall rebounds 
from a wall. Tlie arms are iit the same time Bwung fur- 
wardn. in leaping hack, the Bmly wnd arms are Inclined in 
that direction; and in jumiiing vcrtiLally Ihero is no lotiii- 
ing either way and the arms ai-c kept by the sides. 



CHAPTER XII. 

ANATOMY OF THK NERVOUS SYSTEM. 



Vtwve-Vnhka. In dissectiupthe Human Body numer- 
ous white cordi arc rmiTi<] wliidi at firsi. siglit, niiglit be 
tukcn for tendons. That they ai'e somotbing else however 
soon bceomo)! clear, hiuco a gnat niuny of them have no 
coDiKtctioi) with muKclesi iil nil, aud those which havti usuully 
enter somewhere into the belly of iJie musric iiiKl^iicl of be- 
ing fixed to itH cn(l.4 a* mOAl tcudoiiit uro, Tht-ge curd^ uro 
nurve-trunks: followed iu oup direction each (Fig. Hi) will 
be found to bivoik up into finer and liner branche-s until 
the mibdltisioni* bi-coniL' too vmull to bo followed without 
the aid of a microscope. Traced the other way the iruiik 
will iu most cruses bo found to increase by the tiriion of 
others with it, and ultimately to join u much larger mafis 
of dilTcrout Ktrueture, and from wliii'h i>tlier Hunks also 
epriiig, Tliis majis ie a ncrBe-ffntrc. That end of it nerve 
attauhcd to Iho ccntrL- le nalurally it« cenlral, and the other 
it« tlinlat or /leiip/itrat fiiil. Xcrvi-iuntrea, then, ;;ive ongin 
to uervc-trunka; these latter radiate all over the Body, 
nsuully branching and becoming smnlliT and smaller tu< 
tliey proceed from the centre; tht-y tlniilly become veri- 
irmull, and how tht-y ultimAtt'ly end is not in all caseti cer- 
tain, but it iti known lliat ttomc linvc sen^ie-organs at their 
termiuatione and other.i niutipulnr libre^s. The general «r- 
rangenifnt of the larger nenc-triniks of the Hody is shown 
in Fig. G3. Physically a wrw i» nol ?o lutigb or xtrong a^ 
u tviidon of the same eiw; it may readily be split up into 
longittidiiinl .itrand!<, each of which ooii»iiit« of a number 
of microscopic threads, the utriv-^pbreg, bound together by 
councclivo tifisuo. 



I 



ASAIVMY OF NBHV0U8 8YST8U. 




T» M— Pta>nimllliulT«ttiict^<'C^n'"*l*n«M-in>iil nf U.o p-n-^nmrrt^ln 




d 




TBK BUMAJf nODT. 



riexusm. Very frequentlj' eevera) neighboring n«n-( 
tniDk^i .-cjhI ii(T oonuniiiiiriitiiig bmiiclios to one another, 
each hmiuli I'liiTving liliri-^ TKim out' Irunk lo Uie otJicr. 
Such iiL'tworke ai-e called plexusf* {V\g.(>'^*),^\nA through 
the inlerch»ngi'» Inking pluci- in ihcm it ofltu hti{i]>ciii« 
that the distjil hranrlie« <if a nerve-trunk contain tihttA 
wlitch it does not possess ati it Icuvot the centre to uliich it 
is coi)iit;cr(id. 

Norre-Contreo. Th<! great majority of tho nervwt istco 
thcii' origin from the brain and gpinal cortl, which together 
form thet great i-jrebro-tpinal centre. Some, however, coni- 
meiici- in rounded or oval niiumcK which vury in wiu from tlmt 
of Uie kumcl of lu almond <]uwn to mioroi»co|iic dimenAionH, 
and which arc widely diotribnted in the Body. Each of 
these smajler aoatt^rod ccntree is called u yuiigUon, and th<- 
whole of them are arranged in three h-1«. A considcRibl* 
number of tb« largtwi vxv. uiiitvil directly to one another b; 
neriC'lninki, and alt^o give off nenw to various orgun^ 
cKiicciallj to the blood -v*-*wli^ and the viscera in the thonicio 
and abdominal cavilicH. Tlu-tw ganglia am) their bnmchoe 
form the aifvipalhelir nen'ou* si/*tnn, a» dis1iiigui«hed from 
the ccrebro-flpimd nervous Bvulein consisting of the brain 
and fljiinal cord luid the nerves springing from them. Of 
the remaining ganglia some ait- couiitelril nilh variotiji 
cerebrospinal trunks near their origin, while the rest, for 
the most part veirnmall and connected with the peripheral 
branch(« of sjTnpathetic or other nerves, are known ui! tlii' 
tiporaiiic gam/tia. 

The Cerebro-Spinal Contro and ita Uemt^ranea. Ly- 
ing in the xktdl in the brain uud in the neural canal of the 
vertebral cohmin the tpiuul rortl or xpinai men-row, the 
two being contiuuona through iheforajnen magNtim of tho 
occipital bone and forming ihe great cerebro- spinal nerve- 
centre. This centre ia bilateixlly symmetrical thi-oughout 
eswjit for slight diflerences on the surfaces of part* of tho 
brain, \vhieh arc often found in the higher raoca of mankind. 
llolh bruin and rpinal cord arc very ouft and easily cni^hed; 
I he connective tissue which pervades them being of the deli- 
cato retiform variety; oeoordiiigly Ixith an- placed in nearly 



• P. loa. 



d 



MKMIHtAXXS OF TUK ymtyfi-VKXTHHS 

A 

0(>m|>!<'tAly <<1o!°e<1 bixty oiiTitiea and 
are also envpl^iwd by membnuwH 
whicli giv« llidii conH«t«ni7 and 
Hup port. Tiiciie membratiea are 
tbr«o in number. Ext«niiilly is the 
4ura mitfer, very tough and ftirong 
uid comportt'cl of white fibrous and 
ebutic connuvtiri! tissues. In the 
cnnlum thin dura nuil«r adhorx!* 
bv its outer surface to the iitnide of 
tho skull, serring a« the periot^tcum 
of \\» bone»; tliiti » not the vivm 
in the rertebral column, where the 
dniu [niit«r fonns ii loom) sheath 
around the .ipinal cord and in only 
attached here and thai* to the aur- 
lOiiading buHM, whioh have a sop- 
ante pCl-JOttCtfum of thfirumi. Tlio 
innorraoist mombrane of the oerebro- 
■phul ooDtro, lying in immediate 
oootaot with tho propor iierroux 
ports, is ibo pia muler, also made 
Dp of vrhiti:! fibrouo tissue inter- 
woven vith elastic flbreo, hut Icm 
doooly than in the dura tnator, so 
u to form It tcKN dejiso and tongh 
membraae. The pia mater ood- 
tiuns many blood-vesteU which 
break up in it into small branches 
beforf entering the ncrTouii umss 
btOMUh. Covering the outitlde "f 
th« pu> mator i# a layer i-f flat 
ckwely fitting cells, a ^imiliir layer 
llnM the inside of the dura mater, 
■nd thoM) two layers are described 
M tlie third memi>ran<r cif the cere- 
brospinal centre, called the nrarh- 
natd. In lli« space betaeon the 
two layers of the arachnoid it iMt\- 
talned a amall quantity of watery 



1.17 



Kin. 03 —Tb* iipifuil oonl 



IAS 



TTTB BUM Air liODT. 



cereiro-gpinal liquid, l^rt of the eurfiK« of the brain it 
folded nnd tlic pi» iiiiitcr docs not dip down niul line the 
furrowa between llio foida but slretctiea dcrofa tbem: in the 
Epaces thus left there i« idau c^ntiiiucd sonic of llie ccrvbro- 
ejiiiinl liquid. 

The Spin^ Cord (Fig. G3) is neur); cvlindriool in form, 
loing hcmevor ft little- wider from *ido to sido thiin dorso- 
ventralh", and tajjf ring off itt, il8 iMistonnrfitid. Itsiivci- 
age diiimetor is about 19 miUinutcrs (} inch) and its 
length 0.43 meter (IT inches). Il weighs 4^.5 grsm^ 
(1( ounces). There is no marked limit bciwecn iho xjiinal 
oord and the brain, tlio one parsing gradually into tha 
other (Fig. 70*),but Uio coi-d 'i« afliitrHrily Miid to com- 
mence opposite the outer margin of the foranu-n ntngnum: 
from there it lutenda to the urticuhition between the first 
and wcond hiinhar vertebra*, where it nnrrowc off to a 
slender filflment, tho filum tarminale (cut off and repre- 
sented srparutely ut B in Fig. G3), which runs bovk to the 
end of tlie neurid canal behind the aacnim. In its courec 
the oord preaenta two expansion!, aij upper, 10, the Offr- 
wVa/ fn/rer'/ffwpn/, reuohingfrom the thinl eerviwd to the 
fir^'l dtiroiil vertebra', and a lower or lumhar enlargeinent, 
fl, opposite tho last do^!^uJ vertebra. 

Running along tho middle line un both the ventral and 
the dorenl iu(pi-ct.t of tho coid is n gmuve, mid a cross-sec- 
tion sliows that these grooves are the surface indications of 
fissurea which extend deeply into the cord (f, Fig. Si) aad 
nearly divide it into right and left halves. 

The nnkrior fisium (1. Fig. 64) is wider and ehallover 
Uiiin the posfrriof, 'i. The truiiiiVerin.' #velion, C, eliows 
also that tho siib»liuirc of the cord is not alike throughout, 
but thiit its whUf sniierllcial layers envelop a centnd gra^ 
SiOtfliiiff arranged somewhat in the fiirm of a cn)>itfll U. 
Kach half of the gray maltor is ereacciit.shapod, and tlio 
orescent^ are lumcd biwk to bark and united acmm the 
middle line by the ;irnti comtnismrf. The tips of each 
creneeiit are called its horns or rormta, and Ihe ventral, or 
avti-rior rornu, on each side is thicker and larger than tho 
pooterior. In lint ui-rvical and lumbar enlargements the 

•>. laa. 



SPISAL CORD. 



IS9 



protMittion of whit* to gray mutrer is greaU^r llmii ul«c- 
vbero ; and aa tbe coid ap{>roachG« the meduUa oblongata 
its ccntrul gny nuus bccttmc^ irregular iti form )iit<i bt-giu^ 
to UiMk up into tiniulli^r [KirttonsL If Uticit ho drawn on 
tJio tranHTerse fiection of the cord from the tip of each horn 
of the gray mntter t« the nearest point of tJie eurface, the 
white Bubslanco in each hdf will he divided iuto thrvo por- 




Fro, ftl^-Ttio JtplnjiJ (<Qrtl piui firrw-ro^tv- A.n Briuill fiorti"?! nf ttit ixipA 
Kmfrnin thei^nml glile ; /'. -i" "niof v-mi lalpmllj -. i .«. r.-«-u-rtlnn ntihn 
COM 1 D. Xbr IKO (voir <>r a tpiiinl nvft ; 1. miicri'ir ('■■tilrili rtwiitr : ■:, pvfttc- 
rtor(<tcTUl) Ibmpe ^ a, BurfAoefnvavD&loiii: tttv Unv iif allaoluncni of tliaant*^ 
rlor nwre-pjuU: l line uf oHkID of Uw iniimur rt«w ; ». kuirrvnr rooi I1tk> 
mmtiiof ■ vliud twrvi' : is pcnisriorraot nirim.-iiw : i.'. kuikUihi al UispiMt*- 
Tier root ; J. T.'dw Inu |ir1auu]r dlvltluiu uf Uiu iiorTtpdruuK fonand liy dw 
onloq of uw tiro rootf. 

tionfl: one between the anterior flsstiro and the anterior 
corau, and ciillvd the anterior white eotmnn ; one between 
the postei-ior fi^nre tuid the ]>osicrior cornu, uud called the 
po$ierivr wkUt column; while the remaining one lying in 
the hoUon- ill the crviscont luid between the two horns is tli« 
lateral rulumn. In addition to tlilj a certain amunnt of 
white substance crosaea the middle line at the bottom of 



160 



TBE nuHAS BODT. 



Uie iuit«riDr fisfiiire; this forma tlie anterior wkitf commu- 
jmrf. Thoro i* no posu-riur while cominiwure. tlw bottom 
of Uii" [Kifierior lii-ffiii-e being the only jwrtion of llic oord 
where tbc grav isiiljstiina.- is UDOOvt-md b)' whit«. RiuitUDg 
uloag tin' middle of the gray i.<omiiiis«tirc, for tbc wholo 
length of the cord, ia u tiny channel, just visible to the 
itniiidod cyu; it is kiiuwii us thv central canal {eanalis mh- 

The Spinul Mervee. Thirty-one pairs of spinal iierre- 
triitikM I'lilor the nouial ennui of tho vcrlcbriil column 
through the intcrTcrtebral foramius (p. 71). Kiicli di- 
vidca ill tlu' funimcii into a donuil and ventral portion 
known n--!<|iectjvely as Ijic po»lerior imd ank-rhr roots of 
the nerre (l> and S. Pi;;. C4), and thejie again xubdiride into 
finer bruiioheit which are uttaclicd to tho sides of the cord, 
the poateriiir root at the jioinl when- the )i(wlerior atid lfttx>- 
ral whitfl cohimns meet, and the anterior root at the janc- 
tion of the lateral and anterior columns^ At the linc^ on 
which the rootearc nttiichcd there Bresiipei"fipialfitiTowsou 
the Kiirfaoe i>f the oi>rd. *)ii each posterior root i» a «/"*"'' 
ynitylion (O', I'ig. 64), placed just before it joins the an- 
terior root to mak« up thu oommon norvc-tnink. Inime- 
diatfly after ita formation by the mixture of fibrea from 
both roola. the tnink divide* into a, «Riall postfrior prinutrtf 
iiml a hirger rtntfrior primarif branch {"f 1 l>. Fig. G4). 
The former brunches of the ajiinal nerves go for the most 
['urt to the ekin and mtixcle^on the hack, while the anterior 
primary branches form a «erie« of plesnsea from which the 
nerves for the aide* and vcntnil region of t)ic neck and 
trunk, Hud fi>r the limbi*, iirisv. 

Tho viu-ionA spinal nerves are named from the portions 
of the vertebral column through the intervcrtcliral forominn 
of which ilicy pa."* "uL: nnd il< a grnoi-al rule ewch nerve ii^ 
named from the vertebra in front of it. Fur cxiiniplu the 
nerve pawing out bclwcwi the fifth luid eixlh dor!<al verte- 
\iTK \* the "fifth (i'lrwil " nerve, and that tjetwecn the last 
dorsal and first lumbar vertehrfp. the "twelfth donud." 
In the cervical niglon. however, thin rule in not adhered to. 
The nerve ])a8sing out between the occipital bone and ths 



TtmSFiyAL SERVES. 



191 



KtJax in willcil the " flrin ccrviutl " nerve, tlijit botwccn the 
allaf ami «xi.^ the secoad, and eo on; that between sevenOi 
furriciil tinil tiijit lionui] vcrtcbrm being the " eighth coni- 
cal " iK'i'TL'. The tbirlv-one juairo of i<{iin»l uorviiv urc tlivit 
thus distributed: Scenical. 12 doraaJ, 5 Inmbar, & sacrul. 
[ind 1 oin;cyge«l; the liitlcr piiwiiig out Iwtwefii the »ucruni 
mid oticcyi. Since tho spinal cord ends oj>i>iisitet.ho u|i|)or 
lumbar vertfljiw while the gacrul and coccygeal nerree i»0S8 
nut from the ncurul canal much furtluT biurk, it i^i v\vav 
that the n>oKA of ihose twrveEt, on their way to unite in thf 
foi^umins of exit and form nerve-trunks, must run oblifjuely 
baekwurdri in the i^pinu) cutial for it considerable dist^tnci'. 
One liud^ in fact th^ neural canal iti the lumbar and nncrtil 
re^ona, behind the point where tho ^tinal cord has tapered 
off. occupied by a great bunch of nerre-roDta forming tho 
MO-LttDed " botfioV tail" or niwla equina. 

DistributioQ of tbe Spinal Hervea. It would be out 
of pluicc here togo into detiiil an ti) iho oxuet portioniiof 
th(; Body supplied by each spinal nen'e, bitt tJie fulhiwing 
general 8latoinont« may bo mode. The anterior primary 
brancliro of the first four cervical nenea form on each side 
the ftrvicfit piextia (Fig. 65) from which branchcfi an* enj>- 
plicil to the muscles and integument of tho mx'k: also to 
the outer ear and the back part of the Hcalp. The anterior 
primary branches of tho remaining cervicnl nerve and (be 
llrst doi-sal form the bntchUii pfrjruii, from whtoh the npper 
limb it supplied. The roota of the tranka whtoh form this 
plexus arise from the rervjcal enliiri^mcnt of the Ht>inal nord. 

From the fourlh and lifth cervicid nerves on each Bide, 
small branch(-.'< ari»e nu<l unite to moke the phrenic iterx-i 
(4, t'ig. <!5) which mua down thningli the chut and end* 
in the diiiphnigm. 

Theaninriiir primary branchM of the donsiil nerves, ex- 
ccpr, purl f[ the tirst nhioh enters the brachial plexiu. fonn 
nij jil^xiipi. Imt eiu'h runs along the posterior border of a rili 
and !^iipp!ic.< branches to tho ohost-Avalls, and Ibo lower ones 
U> fhw.' (if ihi- abdomen also. 

The 'interior |irJmary brunches of the four anterior lum- 
bar iierve« are united bv brniiclie« to form the (un^ar 



16S 



THE BVMAX BODY. 



plgzua. It tapplicK f.hp lower pitrt of the trunk, the but- 
tocks, the front of the thigh, ami mwJinl side of the leg. 

The sacral pk^us in formed by the antcrinr primary 
hranchcs of the fiflh lunihiir and the flr^t four mcntl 
nerves, which ntiite into ono grout cord uid eo form the 




VU. U— 1l)«c«r(leBliiDdl>reohlKlp)»ruw<>oron(?«l>l--nriti»ItnlT' 

'■rintic nerve, which is the lur;^Ht iu the Buciy uiiil, ruDcing 
down til the back uf ihu thigh, uude in bminhcs for the 
lower limb. The roots of the trnnks which form the sacral 
]ilciU8 arise from tho lumbar enlargement of the oonl. 




THK HRAnr. 



163 



The Bmin (Fig. 06) ie far larger than the spinal M>rd 
aud more conipl*;! in structure. It Wfiglix rni the average 
aboat Ulfi grama (50 ounces) in the adult male, and alimit 
155 gruitui (5.5 ounces) \east in tho fomak-. lu its simpler 
formti th« Tert«l>rat« braiu contiiRtN of three masseH, envli 
with Eubsidlary parts, foltowing one another in tmriw from 
l)cfi>rc bock, and known u the furo-brain, midbrain, and 
hind-brain ro«pcotiveIj. In man tho fore-brain, A, weighing i 




Fra. OA— I>iji|:r»m illuiilrutfJiff^lip* irnnfrrni n^liirlnnHli^ph at Ui« |iartj> ot Iha 
brain. .1. tun- bm-ia -. Ii, niM-l>nLiii : it, tfcrrbi-llum ; V. punt V^roJII i t>. mr- 
duUa obk>ii<iUA , O. C, uhI l> lof^UiBi oonaUtuts Uw Idnd-bMlu. 

abutit Vi\h grumH (44 ounces), \i nuicl) larger than all tho 
rest put tofjethcr «nd lajw over them l>ehind. It consists 
iniunly «f two hujr^ convoluted musseB. separntfd from one 
another bj a dee'}! median liseuro, untl known us the cei-ebral 
htmigphfreii. The imniciiKe proporlionnte sixe of these i* 
very cli;u'actoristic of the human brain, Beneath each 
cerebral homisjihere is an ol/actort/ lobe, inL-onspicuous in 
man btit often lurgcr than the cerebral henii«phereH, as in 
most ttAxti. Itiiried in Uio forO'hnun ou.eadi ividc are two 
' large gray masl^es, the corpora tlriala and optic thalami. 
The mid-brain forms a connecting idtbmnfl between the 
two other divisions and presente on iXt dorsal sido four 




104 



TUB UVMAA HODT. 



hcnuxplifirioal pntinencee, the corpora ^mttlriytmina. On 
ilj< Tenrral side il exhibits tnu o^iiiioyliiidrioal pillaru {neen 
under the ncno /I' in Fig. *')• «iid knowu at tlic crurti 
rtrtM. The hiod-bnuD coiui«l« of IbrtT miuii pitrU: on 
iw dorul side is llw cerpliellnm, B. Vi^. 66, consieting of n 
r^ji^, a J^,«»d II Mttlian lobe ; on the ventral side is the 
pojts Vnrtilii, ('. Fig. GG. uiid biliind the inrdulla nhhnffnta, 
I), Vig. CG. which is i-outiimouv with the- »|>iiial iH>rd. 

Id imturo the innin divisions of the brain ar« not sepa- 
rated so much as lias beon rcprviwiil«d in the diagram for 




Tta. m, — Hm brain from the left ildA. Ch. die embni] bnmliplieTea fonnli^ 
Iho main bulk ot \bt [ore-brain : nn. lh» pnul]i>[liiin ; ifo. Ihi- innlulla oMon- 
gau ; P. tin; iwi.i. ViuoUl j •, ibe flnuri' ii( itjivliw 



the Rake of cleaniei<D, bnt lio closo together m rcprcitoiitcd 
in Fig. 6?, only eome foldn of tho membranes estonding 
betwnon (hem; and Iht* mid-brnin ii» entirely fovorud in on 
it« diirfiiil iiApccU Nmrly <'Vi>rywhert! the mirfnce ut the 
brain is folded, the folds, known a»gifri itr eoHvolutioitg. 
bi-ing deeper and more numerous in the brain of man thim 
in thnt iif b>wfr animaU; and in the hnman i:p(^cii-)< mon: 
nitu'ki'd in the higher thiin in th*; \nwvr races. 

The brain like the spinal t-urd cuniiiHts of gruy und 
whit« nerToiis mattor but aomewliat differently arningbd, 
lor while the br«in, like tlie cunl. contains gray matter in 

■ P. loe. 



OSREBRAL rBXTRlCLSS. 



1«S 



iu interior, a grent part of ita earface is also ouvered with 
it. By the external coiivolntioiii' uf I lie oi.^n)beUnm and 
til c t^'tn^ lira) liftnisiihiiiFfii llin tiiirfaot) ovt^r wjjtdi tlii:< gray 
isut)iit.aii(,'0 is wpread U very maoti iiicreiL-icMl (smic Fig, t!S). 

The Ventrioles of the Brain. Tlie mitiiiie iciitral 
cauftl of tho spinal curii i*; I'uii I iiiiicd into t!io liraia ai:d 
expands tliere at M-voral [luinlii inio chambers known as the 
venlriftcji. Enleriiig ihe medulU oblongata it approaches 
its iipfwr surface and dilal«>4 into the fourth vrnlrieU, 
which haa a very thin riii)f. lopiKni uvor by llii- i-vn-lit-nuni. 
From ibe front of the fourtli ventriclo runs a luin'ow pa»- 




Fia. tH—A T>^l.-ul fwiildn •rniiB ih»ii-ivhTnI ).--in1iirl>rn,«, CrP. tUri—^t 
raUottm: 17. Uiv iiiil-Fri»r villi nr (lii> ritr'ii lalonti n^irlpl-M UiH cny n'MoU 
lr« Mifrlup !• ilw t—^mt tirifitnm, uii the l*fi •Lrtf iho lujuTfloUJ ttAT oiatlsr 
cavwctii)( lln- uoaiuliiuuiuii I* ntuded. 



urtgo {ihr a ttrtio ail ^uaritna vmlriealum) which enters 
aniithvr dilatation lying in tlu' middle lino near thi.- under 
side of the fore-brain (jiict above llie two ^nndl ronndod 
miL<«>s Mi-n botwi-eri tho iieiTcs // and /// i)i Imj;, TO) and 
known )w the third vtttlri'h. Fmm ihv. tliird venlricle 
two apertures (tlio foramena of Mgnm) l(wd into \\\t> fir»t 
and Kfrond, or lateral veHtriclm, one of which lies in eaeh 



I6e 



TBS UUMAS BOOT. 



of tha cerebral hemisi)horcs. The front ends of theae two 
Tcnt.riclcs xtxn seen in tliv VGrlical tranavcrso mciion of the 
brain rc|iresetittid in Fig. 68. 

The ventriclea contain a small amount of e«rebro-»pinal 
liquid and are Uncd bj cpiUidiuin which \* oiliuud in 
furly life 

jro;«. A frequent cause of apoplexy is a hemorrltage into 
one of the Ut^^ ventricles; tho outjiourcil blood accit- 
mulating and prcuing upon the cerebral hemisphereii tlu'Ir 
fuiictioRg an) suppressed and unconsciousne** produced. 
When a person is found in an apoplectic 111 therefore the 
bc«t thing to do \i to leave him perfectly quiet until medi- 
Oal aid is obtained: for any movement mny start afresh, 
bleeding into the yentricle which had been stopped by clot* 
formed in the mouth.s of the torn blooj-vcsscln- 

Seotiona of tho Brain. Having got a general ide4i of 
(Iio iiaru tiumpctHinjj tho braiu, the beat way to oompiete a 
knowlcdgi' i>f its anatomy is to study Motions taken in 
varioud dirccttuna. Two siuch are giren in Fig«. 08 mid GU. 
Fig. (19 represents the right half of a vertical section of the 
bruin, tiikon from hef ore buck in tliu middle line and viewed 
from the inner side. AIhivo, iho knife hos poawd between 
tho two cerebral hemispheres, in the longitudinal fitturc, 
witltotit cutting cither, and the convoluted inner surface of 
tho right ouo \» eecn. The lickle-i^haped must lowcrdown, 
CcV to VcV reprceoiilM tin- cui siirfaooof a ooonccttng band 
of vhito nen-ouB tissue called the corptts ealloaum, wliidi 
runs across the middle lino from one oorobnU hemisphere 
to the other and put^ ihem in coinniuiiication. SI, the 
septum lucidum, ia a thin membrane which forma tho inner 
wall of tho bitoral Tuutricle of the heuiispherc Bi-tweeu 
Uio two septa ludda on tliu sides (in the niilurol position 
iif the parlff) and the corpus ndloHum above is inclosed a 
iiitrrow Kpace known iis Ihe fifth vimlricle. It ie, however, 
i|Uite different from ihe remaining cerebral ventricW, not 
being II continiiiition of the csnidis eentrulis of the spintd 
cord. The cpiiLC bi'iiwrth the septum luciduni and tho 
hiick part of the rorpntt oulloKum is llio third ventricle, 
whieli, lying iu the middle Hue. has bern laid open in the 




HXVIAX SURFACE OF TEE BRAIN. 



167 



Mctton. It is deep from above down but narn>vr Irrnn side 
to eido. Fnmi ita uoder Hide n proloiigalion nine dowo to 
H, the pUiiitary bodff ; behind, ibe ei'/iteduei of Sylviut, 
A, is Been pwwing back from tho third to the (onrth von- 
triclp, T'y. At FM is the spcrttiro {foraviett of Monro) 
leiidin^ into the right lal^'ral rentricle. Crossing the third 
ventrido iind pulling the two halves of the fore-brain in 
direct commanicaiion are three i>inidl coiumissares. Con, 




Fin. W.—Ttio nifhl lialt uf Iha brttin i»i M«n on tw miidlKn iil<l« aftar a *MUon 
moiln tijrnugli iiii'orvaii lii ihn lulililti- llni-. V-i, r<-<iiR)i<rDini.-li5: iio. mnlulU 
elitoncala ; f' I"'!!! Varolii ; /f. oi'l i<^ ncnt^ i JApliiiluiiT bcdv ; {'iki. ante- 
rior coninil*4iir« . Fit, fonunou oC Hr'iijo ]r*4iiic UtMa tho Uilnl vrnirlo]?. In 
ih" pavltj wl HliLch tbo l«iv« cud at ttu- line A.lf llu. U> Um rlubt laii-ral v«D- 
trli'li' ; Oom. aott CMDmlmirr. ninninK te^oi >l<l<- to ad* et th* thlnl >'nlri<-l(s 
ill>i't«l \ cup. poMMlor lyimnilanra ; t/i. ntrTH ^vadrianrnttta i A. kqiis- 
ilucl of BrWtwl Fir itmr a t*rlia ad gvtrtum irfifr^cuhim ; C^ Mrolifdiucn { 
(MM-Vl*. curpiu oatluauni ; Al, nplum luridum. 

Com, and fvyi, knowii rrapcctivcl; as the anttrior, the 
vmtiitii (or «()/■/), mid tbejDM/mor. The mass .lot-n bound- 
ing It ^rcut part of the side of tlie third renthole and 
uniled to it3 follow hy the soft rouiiiistiure is tho optie 
thahimus. Ahdve the uijiicdiict is the email [nediuu boity 
Cn, called the pintal glaml, whii;li Oontaiii« no nervoua 
tiseaD, bat has an interest as being, according to Descartes, 



308 



TBJt JICXAy BODT. 



tlic mat of Uie snnl. Ikhiiid it onme the corpom ijtindri' 
ijtmina, Lq, ixaA nbovo the fourth ventricle the errtbHlum, 
f7hl, sliDwing the primaiy and tiecondnry liMuiT? on itc 
hurfiux' wbiili givoitssertiona branched »|)|)ear»n<H> knoirn 
MS the arbor vitip. Mo i» tlie medulla lAloiigoftt, and P tlie 
jionB Viiixilii. Tlio cannli^ ocnlniliH of iho K])inAl cord U 
rejii'i'scuted leading back from the fourth Tentriole. 

Pi^. G8 roprcisetit^ u vertii;ai transverse eection of the 
brain taken tlinnigh the fore jnirt of the corpus callosum 
(CVP) and idlngethor in front of the tliii-d vcntrkOe. It 
shows (lio foldings of the cerobnim and its iJiiperRciul layer 
of gray inilwlano;; tbo interior end; of the lateral ventri- 
cles, Vl, with a gray mass, the corpu* tlriutHm lying be- 
nwith and oa tho ontcr Bide of each. If the section had 
been tjikon A little farther back tho oplic Ihaiami would 
have b(*n found reaching tbo floor of puch ventricle. 

The Baao of tho Br&iu and tho Cranial ITervcB. 
Tw«Uv [luirs of nerves leave the skidl by tijwrLiiros in its 
lin*e, and are known as the eruniul nerves. Most of them 
sjiringfrom tho under side of the bniin.iutdsotht>yarpboiit 
etadied in conneetiim with the Imisp of tlinl organ, which is 
reju-eaented in Fig. "fl. The/M^/wir, or ol/ndory nerirf, 
spring from the under sides of the olfactory Iob««, /, ond 
pass out through tlie roof of the nunc. Thoy ore the nervex 
of MnclL The tfrtintt pnir. or opfir nrrvfif, 11, i^pring from 
the optic (halami and corpora (juadrigoniina and, under 
tlio name of the opUe (rartu, run down to the base of ilu' 
bruin where they appear parsing around the crura cerebri 
lis represented in the figure. In the middle line tlie two 
optic tnw'ljt unite to form tho upHr. rommUturt (seen in 
eection at //' id Fig. 69) from whioh an optic nerve pro- 
ceeds to ouch eyeball. Behind tho o]»tic coimiiiKSUix^' 1* 
j?ecn the eoniwd stnlk of the pHtilarv borlff or fiypophyniK 
rtrrhri {!{ in Kig. Gft). and still further liiiek a pair of 
btnitsjihericul masses, about tho size of split peas, known as 
the corpora nlbiranlin. 

All the remaining cranial nerves arise from the hind- 
bmtn. nie third pair {m/tltirrs oruli) arise from the front 
of the p»n« Varolii, and nn^ diKirlbtited to most of tlic 



ran cHASiAi, NUnvEs. 



109 



uiuaclee which more tfai) ejolxiU »nd also to that which 
lifts the u]>per «yeli<i. The four-sided space bounded by 
Uie optic tt'iK'tB and commitviira in fmiit and tlie third 
pair of iicrveti behind, and having on it the pituitary body 




Fta. TO.— Tho h««e «f the bnta. The ofrebml hcmliphem aro HMnmvr- 
lappiue *ll tlu r'-ti. /. ntUt-t'iry l.>1im ; II. opliu irai'l puuinic hi Iha opUe 

r/. iH# kIkIi Darrc -ir fih(lF>/-'ii* ; Vf/, ibi> nrTrnlh en toirUI nortte or jmHto 



ilHm ; fill, Uio kiulii'.iry ultvo or portio iHuUii : /X. Ilie UnUi or gteia»- 
plurjmnal ; X. [ho u-oiri iir piii'unioKiutiii.- or miriu ' XI. Ilw qilai * 
«wy I Trr, tb'i li}-|in|[iL<>Mkl : n>V, tlie llm mityictl ii[itiuil iwrvtt 



and the coi-jtoni albicuntia. Hes beneath the third ventricle, 
so Limt a jii-olx; puithucl in there would enter tliiit curity. 

The fourt)i pair of nenres, / V {paliefici), arise from tho 
fruut jNU-tuf liiQ roof ot th« fourth vvntricle. From therfl, 



ITO 



THE BVMAX BODY. 



each curls around a crus cerebri (tbe cvlimlrk'ttl muM seen 
bcueatli it in tlit- figuri*, niniiing from ttie puna Varolii to 
enter llii* uudcr surface of the cerpbral Iiemisjihcn-s) and 
iip]>eai'e on the bii«i of llic brain. £ach goes lo one muacli- 
tit iho iToball. 

The fifth (lair of nerres, V {triffeminalfi), resemble Ihc 
spinal uerves in having two roou; one of the»c in muoh 
larger Ihuu tlit; other an'l pOK«e»si-!4 a gunglion (the i!a«se- 
rian gaiu/lion) like the posterior root of ft Kpinnl nerro. 
Beyond the guogUon the two roots form a comnKm trunk 
which divides inlo three main branchoa. Of these, the 
o/)^/A((/mtc Ih the smallest and in nminlydixtribnt^^ to the 
mtiacles and ekin over the forehead and u|>pcr eyelid; bat 
rIbo giTCs brunches to the muL-<3US liuiiibraue lining the 
no8i^ And to the ititegumont over it. The second diviiiion 
(swpflnor nuixillary nerve) of the trigeminal gives hnuicheb 
to the skin over the U-mpV, fo the cheek between the eye- 
brow and the anfjio of the mouth, and to th« npper teeth; 
u well as to the inucons membiKne of the no^e, phnrynx, 
wift pitl&t« xnd roof of the m-nitb. The third di^iniou 
(inferior mnxiUnrti) is the largi-st branch of the trigemi- 
nal: it receiver some fibres from the turgor root nud all of 
thesmnllcr. It is distributed to tlio side of the bead and 
the external car, the lower lip and lower part of the face, 
the muoou.i membrane of the mouth and Uie iintcnor 
two thirds of the tongue, the lower teeth, the siUivary 
glands, and the muscles which move the lower Jaw in miu- 
licutton. 

The tirlh ;wir of emnial nerves {VI, Fig. 70) or ah- 
iluixnifs arise from the posterior margin of the pons Va- 
rolii, and each is distributed to one musulo of the eye- 
ball. 

The Mivn(h pitir {/anal tuirvsa), VII, apiH>ar also at 
the [losterior margin of the pong. They ora distributed 
to most of Die muscles of the fiicc and sculp. 

The eighth pair {iiHilitory ttervea) arise otoae to the 
facial. They are the m-rves of hearing and are dJEtribated 
entirely to the inlernol ejir. 

The ninth pair (plossnphariingeah), IX, arising close to 




THS C&ASIAL XSBVBS. 



the uuditonw. aro dixtrtbutml lu lliu niucous membnuie uf 
the pliarjnx, the post«riar |ttrt of tho t«>nga<>, nni] tha 
middle our. 

Thu if nth pair {pnevmoijagirie n^rvta or rei^i). X. wnm 
from the sides uf l\\e mtHliilia oblongatik Va\c\\ givcx 
branches to the pliuryns, ^\\9t aud stomach, the brvui. 
wiiidiii)>c uid lung», und \d thv li«urt. Th« rngiiK run« 
farther through the Body ihao any other oraiiial iiiTve. 

The ritventh pair {tpitutl ii/xfssfrg ntms), XI, do not 
arise mainly from tb« brain but by a number of roots at- 
tuclied to the hitfini] volumiiif of the conicnl {lurtion of the 
M])iiis] cord, betireen the anterior and jMutf^rior I'oots of the 
projier cervical epinid nerves. Each, however. ninB into 
the likull f^vity ulungxide of thu iipinid cord aud, getting a 
few fiUmciit^ from the mednlla oblongata, ))aases out along 
with the glostophsryngoul and pneumogastrlc nenes. Ont- 
«idc tlie skull it divides into two branches, one of which 
joins the pnettmoigastric trunk, while tJie other Is distrib- 
uted to muwles about the shoulder. 

Tha twellth pair of cranial nerrea {/ii/poffhiti). XII, 
wise from the sides of the mcilulla oblungitia; thoj «ro 
distributed mainly to the muscles of the tongue aud th» ' 
hyoid bone. 

Seep Origins of the Craolal Nerves. Tlic points re- 
ferred to above, iit which the viirionf cnniint iiervcD appear 
on the surface of the brain, uru known lU thiar Kiiporficiol 
origins. From them the nerves can bo traced for a looS or 
greater way in iho tinbstiuico of Uie hntin unlU each ia fol- 
lowed to one or more masses of gray matter, which con- 
stitute its proper starting-point and arc known as its </»/» 
origin. The deep ortgiix of all excopt tlie first and second 
und part of the eleventh lie in the medulla oblongata. 

The Ganglia and Communioatlons of tbo Cranial 
Verves. Beside.* the Oasserian gunglion above referred 
[<i. mutiy others are found in connection with the cmniiil 
nerves. Thus for example there \it one on each of the 
main divisions of the trigeminal, two are found on each 
ipnttumogastric and two in connection with the gtoeeo- 
pharyuguul. At those ganglia and eliwwhcro, the Tarious 



in 



THE nVMAX RODT. 



nerves ofl«n rcieivo brauclies from iiQigbl>i>niig cmuiiil -ir 
epinitl iierv«H, »» lliat very noon tiflor it loavna the biain 
hardly any one ifmaiiis free from lilircs derived from other 
bunks except llio olfftcUiry. "plic.Jiiid imditury ncrvo*. 
This often makes it difficult to say from where the nervps 
of a special )>art have come; for exani])le, tlio nerve-fibrea 
goiDg to tbo fiubmuxilltirj* salivary gluiid from the trigemi- 
nal leave the brain ltr«t in the fncial and only iiflrrwardit 
enter the fifth; and many of the flbrem going a]>|iiirent1y 
from the pneomogantric to the heart come origiiially fi-om 
the spinal accessory. 

The Sympathetic System. Tlie ganglia which form 
the main ecnircs t>f the smpathetic iicrvoua system lie in 
two rows (*, Fig, 2, and vij. Fig. 3), one on eillier itido of 
the bodies of the vcrlebrip. Each ganglion ia united by a 
nervc-triink with the one in front of it, and no two great 
chains arc forinod reaching from the base of the aknll to 
the ooccyx. In the trunk region these chains lie in the 
vcntnd cavity, thdr relHlive luwition in which is indicated 
by the dota eft in the diagrammatic transverae section re- 
{iiesciiUtd on p. 7 in Fig. 3. Tlic ganglia on lhc»o chains iiro 
forly-nino in number, vii;., twenty-four pairs, and a single 
one in front of the cocc)x in which both chains terminuta 
They are named from liio regions of the vertebral column 
near which tbey lie; there being three cervical, twelve 
donal, fonr Inmbar. nnd five sacral ptiira. 

Kticb sympHthelic gaugliun is united by C'mmimtm/in^ 
branehen with the neighboring spinal nerves, iiud near Oic 
Kkull with vurioua cranial nerves also; while from the gan- 
glia and their uniting cords ariso numerotis trunks, many 
of which, in the thoracic and abdominal cuvities, form 
plexueee, from which in turn non'CH ore given ofl to tlie 
viscera. These" plexuses freijuentty iioHseas nnmeroua small 
ganglia of their own; two of the most important \x\<i tlie 
mrf/iW^ffti-tij which lies on the dorsid side of the heart, 
and the »olar plexnt which lies in the abdominal cavity and 
supplies nerves to the atomacb, liver, kidneys, and intes- 
tines. Many of the sympatlictic nerves finally ond in the 
walls of lite hlood-vcasels of variuas organs. To the naked 



BisroLOOT OF yjisrEs. 



173 



th«)^ »ro commonly grujror lu coloi' than the cerebro* 
cpiiiiil ncrTGR. 

Tho Sporadic QangUo. Tlieae, for Uio most part rerj- 
mii)Ul«, m-rn;-it!Ui.rea iirfi found acattcrcii in nwirly all 
piirts of the Body. They are eapcciully ubmidiint in the 
neighborhood of swrtttory lisMUOK iind about bhiod-Tpsselfl, 
whilt! u v«ry imjioruuit wl is found in the heart, Nenea 
nnite tliem with Uio c«Tebro-»pinal and sympathetic cen- 
tres, and probably mnuy of them belong ])ri)perly to Uio 
inynipiithelic Byst^'m. 

The Histology of Nervo-Fibcda. Tho microscope shows 
tliut in luldiiion to connoctive ti^ue iind other accessory 
part«, »ach a* bhiiiil-v('M.si;ls. the nervoux iirgmiK eonlitin ti«- 
snes peculiar to themselves and known an nerve-Jibrts and 
n»rve-eellt. The cells urc found in the centres only; while 
the fibres, of which tli<:re arc two main variclios known as 
the wM(a and the^^ri^v, are found iti both trunks and ccn* 
trcs; tlie whito vBricty proflominatiiig in the cerobro-spinal 
noni'iw and in the white siibstani>c of tho centre*, and tbe 
gray in the sympathetic trunks and the ^ray portions of 
tlic ct-ntrul organs. 

If an ordiniiry cerebro-spinal ncrro-lnink bo examined 
it will be found to be envclopei! in a lo»iie»boalb of arc-ular 
connoetivo tis^ie. which forms a packing for it and unites 
it to neighboring purts. From this sheath, or perineurium, 
bands of connective tif«ue ])enetrut« the itervo and dirido 
it up into a number of smaller cords or funiruli, ranch 
iu< a musclo ix subdivided into fiLsciculi: caub funiculus 
has a sheath of its own called the nfurilfiiimrt, eoni|itiM>d 
of raveral concentric liiycrs of a delicate membrane, with- 
in which the true nervc-ilhres lie. Tbew, which would be 
nearly all of tiie white kind, consist of extremely delicate 
threads, about O.Ol'iS raillm. (niVr inch) in diameter, bat 
frcquonUy of a length which i« in proportion very great. 
Each nerve-fibre in fact, is continuona from a ner^o-centre 
to the organ in which it ends, so that the fibres, e.y. which 
IHiiw out through the Kacnil plexus luid then run on tlirongh 
the sciatic nerve and ll* brancboj lathe skin of tlie-toes, are 
tlinic ti> four feet long. If a perfectly fresh nerVv-Gbrc 



Hi 



run IWJUAy BODT. 



be examined with the mici-oiscop© it ]nv»ents th« appear. 
Auw ot a i»erfeclly homngciuvma g\as»y llin-iwi; tint whih ii 
acquire* a charafteristic double contour (Fig. ■!) from the 
cuagulaliou of n portion Of iti* Ku1»tai>pc. Ily proper Ireiit- 
inenl villi rcageiitii threr layiTH maf be bmiigiit into riow. 
Uutdido is a line traDxpar«nt eiiTclopo (1, Pi};. 73) called 
thv /jriiniliFV theath ; inside thid is a fully suljHlunci', %, 



\ 





Tta. Tt,- WhltvnpnV'Aliimnwn bIu^ rnnm-gJ rroin Ilip Bodf add itboa ihof 
bBvoMuUlnd (hFir iloublF con lour. 

Fm. A— PIOKmn illiumrliie llw Mniclura cf ■ ■*•(« or mAluIlului ■kti'*- 
;»!» t.l.pHmKlfDiluallii K;t,uw(luUa/]rriMMti;%«xlBGJilliulu. 

forming the nudutlarif ghaath (llii* coa^lation of whicli 
^ivcs Uio fibre tttt dmiblo border), and iu the centre in n 
core, the ajris cyliutln; 3, whii-h is uleariy the essoulial 
IHu-tof the filiru, t'xnvv iiour iU eitdiu;; tiie pninilive imd 
tnedullitrj Nhoaths- aic frpqueiitiy abKoiit. At inteiTolB of 
about Olio miilinioUrr (^ inch) along the 6brG arc found 
nuclei. TliMc are indicalionH of the pritnilivo celU whicli 
hx tbdr eloHf^ation, fadoD and other modi Beat tons hsve 



BI8T0L0Q r OF XSR VK-OBLLS. 



175 



hnilt np the nerve-fibre, uoil nroitiul oitch there is a small 
HDinunt i>f unm<«)ii!o<l pniioptninn. Tho nn-dulbirr vlimth 
is inteiTilpted hjilf nay belnecu ca4;h puir of niidei at a 
point, c-JtIlcd Uie *i"rie, which un-s«frj< to tlio uriginul bound- 
ary Iwtwecn the two oella. In the course of a n«nre-trnok 
itfl (ihrou rarely divide; when a l>ritii(li is girori off »>mo 
fibixi^ nuTolyM-)<arat<! from the roitt, ntiicli »« ■ iikein of ftik 
might be wparated ont at one end into smaller btindleia con- 
tniniiig foner tlirc«ds. 

Gray Norvo-PibroB. Some of thc:te nro m<rrcly white 
fihn-x which iiwir their periphend ends hare Io.=t their rae- 
dnltnry .*he»tii*; hut others Iihto no medtdlxry eheatli 
throughout their whole oourae, oonsisting merely of nn 
mis cylinder (often longitudinnlly etrinted) imd primitive 
nhejilli, with uuclei. Suob Gbrci* are c^jicciullyitbundniit in 
tho sympathetic trunks; and they alone are found in the 
olbctory nerve, tn the commnnicnting brunches bctweeu 
the svinpathetic gangliit aud the spinal nerves holh whitv 
and gray fibre?! arc found; tbo former being probably 
ceri'liro-apinal llbrefi pawiing into the sympallictic «y«lem, 
while the gray fibroa originate in the synipalhetic system 
and pass into the spinal cord. AnolliereUssof gray nervo- 
llbrcn may be called wrvf-fihrih: they are extmnely fino 
and rfetulc from the snbdirision of axis cyliuden, close to 
their final endings in many piirlii of tho Body, after t]iey 
havo already \(iii both primitive and nto<liil1ary sheaths. 
Many line jfriiy fibres exist in tho nervf-centrea. 

The Hlatology of Nervo-Cells. So for a* our knowl- 
edge at jiresent goes tlie only Mnictwres known with cer- 
tainty to be oonnetded wilh ibe i-eiitral ondM of nerve-fibre;t 
are ntrvr-ctlU, and thene tatter may therefore Iw regarded 
as the centra] organs of the ncrTe-fibres, However, many 
nervs-filircK havo not yet been traenl into continuity with 
iierve-eell*. and poflubly end in Ihe oentrefi in olher wiij-s. 

At I, Fig. 73, is shown a typieo} nerve-ocll iruch nn may 
be found in an anterior Imm of tbe gray matter of the 
spinal ei)r(l. Itconsirtsof the rcff /Wy, or cell protophisiN, 
in whieh is a large nucUtw conlaining a HHeteolu*, 1-V>ni 
the body of llw cell ari«o i)e%'end hninches, the groat nut- 



176 



TOE nVMAK BODY. 



jorily of which Biibdivitio nn<I form tine &«rv«-Gt>rc« in the 
gray Biibstaneo of the spioal cord. One process of the cell, 
howover, a, Jops imt hninoli. but id continued into Iho iin- 
terior root of a epinul nerve, acquiringainpdiillary and iirim- 
itiTL' shcutli ut b, und Ix-o' lining ihus liii> nxii cylinder of a 
aervfrfibre. Other norve-oells (us kIiowh at 2 and 4) do not 
possciifl the {ivL'uiiiiraiit-cylindcr proceiis: all their bniiiciics 
cither join tho branches of othei- celUt or enter a fluv nvt- 




ntl n— I>UTerDnI r<?rm* of nprviMWllB. 1. ■ mil. onr liruich (if which, a, 
bwomw Uie mlJ cyllutliT cifa usrre-fllnv : i. i«o cell* uiillol liy ■ prn<v*a,e: 
1. dlaonn C< Utm cdIIh vuilUil )>y hnuielm ulihuufuinitlirr. nml eooli Imvliii 
•u alUHzyllDdw pnoiWi : t. • inulUtular uull wll luiut au ulH-ylliiiliT proctsL 

work of gray nervo-tibrils. Most nerve-cella are larger 
than the niujoritj- of tho oilier wd)^ of the Body, their 
avi^ragu diameter in thy anterior horns of the gray 8iib- 
etance of the conl being 0.1 millimeter (j-^tt inch). In 
the posterior horns they are i^mallcr, and in the brain 
many minute nen'e-cctU arc found in addition to these 
larger om% In ganglia the celUasa rule ai-o more reg- 



I 

I 

i 

A 




MINVTB 8TRGCTVBS OP BPINAI. CORD. 



m 




nliir in outline than those depicted in Fig. 78, and hare 
fewer brHnchi-sf, mo«t n|iiKtaring indeed to have but two. 
Others Iiitr« t^^iideircribed sa ponessing only ono prooeat 
conn('ct«d with them, und Home with none, but tho ex* 
ietencc of these is doiiblfiil, ttinoo in separutiDg the cell^ for 
mk-nwcopio flXBinination the delicate procc*«w may readily 
be bi-oken off and §o escape detection. 

The Stnicturo orNerre-Oentrea. Theseconaistof whilt- 
wild grav iKTVfi-tHjrc-s, of nene-ceUs, and of cotinectirc 
tiasiio and blaod-TeKsek arranged in ditTerant ways in the 
different ccntrca. Gaiiiftia are collections of non'ivcclU 
and ncrvi^-flbrei*, itome of the latter being oonnented with 
the oelU, while others aoom merely to pags through the 
ganglion on their way to otlicr parts. Tho whole mass 
is enTcIopcd and eitpport^'d by other tif»uesi. An an illtix- 
trulioii of tlie atriicturo of a more complex aerre-ceutre 
we may study tho cpinal cord. 

Hi«tology of the Spinal Cord. If a thin tranfrcrM! t«o> 
tion of the spinal cord he examined with a microscope it 
will be found lo oxbihit the following piirta {Fig. 74). 
Enveloping the whole and adherent to the rert is tho deli- 
cate layer of coiinoctiro tissue forming the pt'a mater. 
This linen the anterior fituure, 1, and an olTMltoot from it 
flili up the posterior fl«snre, 8. Elsewhere fine btuid.^ of it 
run ill and ramify through the cord, enpporting the nerv- 
on«i clement^; gome of tho coamr of thciwftrcrvpnweiited 
at 6, 7, and elsewhere in the flgnre, but from thoio still 
finer procctwcji wiBe, as represented at «l and * in Fig. 75, 
and surronnd the individual nerve fibres and l-«11s. This 
nltinutte finest connective timue supporting the Denoas 
ttisnes directly, belongs to the retiform variety (p. 106), 
juad is c^lcd the neumgUa. In tho white columns, the 
cord (Fig. 7.^) will be seen to be mainly made ap of meduU 
lated iicrvu-fibrcs which run longitudinally and therefore 
appear in the trausvcrso wction iw circles, with a dot in 
tho centre, which is tho axis cylinder. At ( in Fig. 75 
theae fibrcx arc represented, the intermediate connective 
tiasne being omitted, while at a this latter alone in ropro- 
sentcd in order to sliow more olesrly ita arrangement. At 



178 



THK UVMAX BODT. 



tb« IptcU of tho ncrre-roole b»ri»>ntal white flbrfw aro 
found (0 and 10, Pig. 74, and a. Fig. "5) running into the 
pay muttor, «iid others oxiiil ut Die bottom of the anterior 
fietiirv, running from one aide of the cord to the other. 
In the gray enbstiuioe the same supporting network of con- 
nective tissuo is found, bnt in it the mitjority of the norve- 
fibrc4arcnon-meduI!ate>d, and at certain pointa uerve-oellv, 




n» N^AiMnnkBimiHscctbinot baitot (ho q)tii«l wnl muenUM abnur 
to dlHnctcn. I. luiurior dNnira : ■. poffmfor flaum i t. canaut omtro/ii ; 

i.piovi ' - '^- ■ ■ 

tMmp. 
rtUTDoC 



HDctcn. I. luiurior dMure : ■. poffmfor flauin ; >. aMoOi amtralit ; 
r vuiIn-i>iivi4"|iiuKliMieord; 4. T. undH of |ria nitUir pHHilnllnE Uip onrd 
iupp3nlnK <tH nerra flenonta : t. a pcoWriiHTaM : 1(1. l>iuiilWof tin ano- 
irai ; a. n. i. it. (. cmupa o( iwrxc-DelU lu (be icntf mailer. 



ffliohiw are totally absent in then-hile eubi^tHnce, arc found. 
One oolloctiuu of th«40 norvo-collis is soen nt e in Fig. T-1, 
and othcTH are repreaonted at a, tl,f, and eliwwherc. The 
iicrTe-Gbrce in the gray matter are for tho mosi peat 
brancheii of Ukwc <»1U («oo Fig. 73), and Hit thoy nuit« 
irttb one another finely they form a slruotnrally oontinuous 




BmTOLOOY OFHPtyM. COBD. 



in 



network through the whole grtty itutmtaiict!. Tfie fibres of 
ibe anterior root* of the spinal nerves cuter the gray mat- 
itr iind there l«M;omc continuons with the unbrttmht-d pro- 
ccas of a nerve-cell; the en<ling of tho poctoHor mot-fibrcn 
is not fiuito cirtwin, but they appear to break np and join 
the gray iii-twork clJreetty, without, the interrention of a 
*;elL In any ea.>e tlio fundamental fact remains that evcPi" 
nerve-Sbre joining the spinal cord is direclly or iudireolJy 
in continuity with the gray network and so with all tha 





rm. 73 — A -mill titi •■( thp •Fftlxn rrpmrnl^I In PIe TJmoir DinnnUlnl. a. 
a UuiiJle of Al>iy* from aa *n1*r1«jr niot poMtintt ilhroi^rU Uxv vr]iL(v iimIi«iulco 
on in >nr (O Uh* eTbt. Townnla iho risU ol Ilia nKi'i* ">» a*m-<lbn>* uf Ilia 
■iittiilor oolUBUi ban bava eiulUBd ■•> M to mmlar mniw ommpIcimhk \tf luii- 
portliuc cobdcuUt* tlMiM, 4t and •, niMi>b««thsD«rr»-ltbn«aloDean> iri'iv- 
wntHl; r. (oTvlofiltm pia main. 

Other flbrea of all the spinal norrPM. From tjio eides of the 
gray eubstiuice fibres continmilly \uii» out into tho nhilo 
portion and bcoome mod ill la ted; sonie of these enter the 
gray network agrtin at. anulhi.-r level ami so bring parts of 
tbo cord into ee)>eoianr close union, while others paaa on 
into tho bmin. At tho top of the neck, moreover, the 
gray matter of the cord i« continuous with that of the 
miKlutla oblongata and through it with tho rest of the 
brain, so that tier\'oiis distnrtxinces can pass by uDatomi- 
cally continuouH paths from one to tho other. 



CHAPTER XIII. 

THE GENERAL PnYSIOLOGY OF THE NERV- 
OUS SYSTKM. 



The Properties of the Nervous System. Oeneral Coii- 
sidenition*. If thu linger of arij mii- mux poet *(Jly touches 
It very liut object, paiu la Mt aii<i the hmid \% Kuddt^iily 
snatched »way; that is to say, sensation is aroused and ccr- 
tuin iQiiseloK lire cuu^ed to contract. If. however, the 
nerves passing from lhi> iirin to tho Rpinn) cord liiive t)e«n 
divided, or if they have been rendered incapable of activity 
by diBetuie, no sueh rcsnits follow. Puin is not Ihen felt on 
touching the hot body nor dovx tiny inotemenl of the Hmb 
occur; even more, under such circumHtanees the i-lronpest 
effort of the will of Uic individual will be nimbk^ to cause 
any movciuent of his hand. If, again, the nerves of the 
limb have uniujured connection with the i^pinul cord, bnt 
purtHof the latter, higlwr up, bctweon the bmln and the 
point of jimctiun of the nerves of ihe brachial plexus with 
the coi\I, are injured, then a sudden eontjtct with the hot 
body will cau^e the urtn to be snatched away, bnt no jiain 
or other senBation duo to the contact will be felt, nor can 
the will act upon the musele.q of the arm. From the com- 
pariHon of what happens in ifiich oiwej^ (which have been 
observed over and over again ujion wounded or diseased 
persons) with what occurs in the natural condition of 
things, several important conclusions may bo arrived at: 

1. The fMlinij of ^min dot* not rr*iiU in tlif burnt part 
itielf ; nlthoiigii that may be perfectly normal, no sensa- 
tion will be aroused by any ext<'rnal force acting upon it, 
if tho nervous cords uniting it with the centres bo pre- 
Tionaly divided. 

S. The hot body hait ortijinaied »orru change which, prO' 




OBKRHAl. PROPBRTtm OP NBRVBB. 



181 



aiong the 7l«rvfi-ln(»V*, ha* rrrlle/J a mntiHion of 
tittt&iVB-eeiUres whieh t.« accompaniei/ hy a Kemation, in 
this partictilur case n paiufnl one. This i« vlenr frtm the 
fud Unit rho Ions of i^nwtkjn inim<idialdy followa diyima 
o( the nerTea of the limb, but not the injary of any of its 
other pans: tinloss of Hiich u cliarnct^r an to cut oS the 
Buppiy of hliioil, when of cour-^e ilio neiTe.< «oon die, with 
tlie rest. Even, however, iome time after lying thu vessels 
wlitch curry blood to A limb one can ohswrve In eiiwrlmenta 
upon tho loner imiiiiuU that sciiaibihty is dtill retained if 
the nerves be not directly injunni. 

3. WhtH a nrri'T in thr tkin iJt fj^ieti by a iurn or other- 
wise i I dot» not directly call forth muscular eonlraetion*; 
for if so. touching the hot body would cuuse the limb to be 
moved cvi-n when the nerve i:t liiviilcd high up in the arm, 
and a» n matter of obsei'vation and experiment wc find 
that no Biirh rcetilt follows if the ncrve-fibroa have been 
cut in uny p:irl of Iheir wurse from l)ie burnt part to the* 
i<]>inal miirrow. It it therefore through the nerva-cenlrtti 
thai tk« f.ian!/^< (ransmxtted from the fxciteil part of tha 
akin i> rejlecltil or »ent baek, to act upon the mu^eiet. 

4. The lufit dcilnclion mnkes it probable that nfrv6-fihrr» 
mu«t pass from th* rnilre to mutcles it* toelt at front thf 
ttin to the criitrt. This is oonGrmod by the fact that if 
the nerves of the liinb be divided the will i8 nnablc to net 
upon its muscles, showing that these are excited to oon- 
tmct through the nwves. That the nerve-flbri?s concerned 
in arouidug sensation and muscular coni nu-l ioii!( arc dilTor- 
ent, is shown also by c:ucs ofdiseiiae in which the sensi- 
bility of the limb it lost whik- the power of voluntarily 
moving it remains, and by other ones in which the roverec 
is seen, objects touching the hand being felt while it can- 
not bo luiivcd by the will. We conchiili' then that cer- 
tain norve-lihrea when stimulated convey gomi>lhing (« 
turvott* impulM) to the oimlr&i, and that these when ex- 
cited may radiat« impnlaes tlirnugh other ncrv<-tihrc« to 
distant part*, the centre Sfrving as s cannectiiig link be- 
tween tlio tllircs which carry inip«l»fa fmni wJHioul tn, and 
those which convey them from within oaL 




va 



TOK UCMAX BODY. 



■1. Fnrtber we conrliidc Ihal Ihr tpituil eord ean aet at 
tm inttmudiar^ bfltcfrn tht fibTf» carryiruj i» ntrvout im- 
pulur and lho*t carrying Uum out, but that tnuatiotu am* 
not be arouMd bg im/miZhm reaeiir^ the itpinai rvrS onlg, 
n»r ka* the tt'iU it* seat thtre ; volition and eoHfeioursit** ar* 
litpemlriit HpOH sltUei of lA* brain. Ti)i>> fulKiw from Uic 
iiiii'dUH^ioUii moT<^iiieDU of the limb wbieli fullow I'timuln- 
liun of iU skin after sQcb injnr; to (be epinaJ rord tu pr«- 
vcnto tlic tnuimiM»ion of nvirotui impulsefi farther on 
(showing that the cord U a rv^ne centre), iind from (he 
iibspiic«. in fiDch cruses, of seoaation in tbe jisrt whoF«iii-rTM 
buT« bt-cD injiin^l, and the b»a of the power of Tolunturil; 
caaring it« lunacka to contract. 

fi. finally vro ronclodo that the spinal eord in aildiiion 
to being a centre for rtfitz eri\OK» nfrves al»o to trantmii 
onwiirtin JtrrvouK impuUtu to Ikf brain: a fact itbicb is con* 
flrint'tl by tho histological obAorrnlion lluil in addition to 
thi) iicrvo-riillK, which arc tbe characteri^lic constitnenta <rf 
nor^-e-cenlTp.". it contain« tbe eimply conductire n«rve- 
fihri.-9i. nmiiy of uhich paii on to tlic brain. In other 
words tho Rpinul cord, bosidec containing flbres which enter 
it from, and paM from it to, peripheral parte (Mjntaimr 
many which iinit« it li> other centrctf ; and connect the 
niriouM centres in it, a« thoi« for tb« arnu and legs, to- 
gel her. This i^ true not only of the spinal cord but of the 
hntJD (which coQtainif many fibres iinittiig diCerenl centres 
in ii),iiii-l ini)biil.]y of all iicrvf-cciitre.i. 

The Functions of Norvo-Conlres and Norve-Triinka. 
Frnin what iiiw been niiitcd in the ]>revi(iiis pniii^niphd it is 
rlear thiil wo may distinctly separate tbe nerre-lriinkB from 
the iiorTo-centres. Tbn fibrce tcrvc eimply to convey im- 
ixdi*?!! cither from wiUiout lo u centre or in the i'|i]iotitc 
(liivcliuii, whili! the wiitres conduct and do niiidi inure. 
Some, n^ the spinal cord.aro merely rtfiex cenlrtt, nnd have 
nothing tu do with stutc« of uonHcioumeMi. A inun with 
bi« Mpinnl onitl ent or diseased in tJie dor^l region will 
Kick violently if the eoles of hi»i feet bo tiukled. but will 
'eel iiulbing of the tickling, and if ho (lid not sec his legs 
woa}A not know that they were moving. Keflex centi'es 




4 




rCXCTTOXS OV liKHYR-CBSmES, 



1S3 



iDoreovor du ixit aci. as a rule. iutliSerciitly and casually, 
bat rcorraugo tJio impaUoa roaching thorn, so as to pra> 
doco ft pi«lcctiv« or in »oine way udvantagnoa* result. Inj 
(rthcr words, thtse centres, actinf; in health, commonly . 
ordinuU tho inuuming iin|>iil'i,v< luiil give riRn lo out.wiird- 
guiug itu{iiit»e!( which ]>roduce uu spjiarently jtiviiiktive 
resalt. The bnrnt band or the tickled foot, in the a1x;eQce 
of all CI 111 me ion sue**, arc *iitit«'lied away from Llic irritant, 
and fu(Hl chewed in the mouth excitca nervex there which 
act on a centre which clauses curtain colls in tho sulirary 
glauds to form and [luur into the month nioro saliva. In 
addition to the reflex centres we hare others, placed in the 
bruin, and which, when excited, canse in us various states 
of coniiL'iouHnoss, OS sennit iim«, emotions, and the will: 
i-oiiwruing thwe ctntrrt of fmi»ciou*nt»», however, our 
physiological knowledge is still very incomplete and so they 
are still largely groitjiwl hy psych ologistii according to their 
individual fancy. The brain also contains a gi'eat manj 
iiiijHjrtant rctlcx ccntrt^j, ait that for the inuHcled of xwullow 
ing, an act which goes on perfectly without our coneoious- 
sess at nil. In fact if wo pay attention to our cwsllowing 
TO fiiil to ])erform it aa well a« if we Ii>t the uervQ-ma«caUr 
a|i|iarutus alotie. To complete the statement of the (iiric* 
tiuus of the ncrvc-ci^ntrcs wo muKt probiibly add two other 
groups. The first of these is that of the autamatir ctntrtt, 
which are centres excited not directly by iierve-flbreti con- 
reyiiig impulmu to them, but in other way». For example 
tho hroathing movementci go on iude]>cudciitly of our eon- 
acioaaiiess, being dependentoustimnlationof aucr^-e-cenlro 
in tho brain by the blood which flow« through it (we Chap, 
XXVI.); and the beat of the heart is also dciK'ndciii (C!ia]>. 
XVil.) upon ncrvc-oentrc* the excitant of which is nil- 
known. The final group of iicrro-centrcs is represented 
l>y certain sporadic symjmthetic and ccrfliro.Kpinid gnnglitt 
which are not known to W- either reflex, automat ic. or con- 
rcions in function. Tiny inny be called ri-lnif and jnnr- 
l ion cetUrea, since in them probably an im}itilse enlering 
by one nonc-fibrc csoitcs a cell, which hy itjt coinmuni- 
eating branches arouses iiuiny others, and lliMC nnd out 



IM 



TUB ac^dy BOOT, 



impnlsn then by the manj* ncrve-flbres connected vitb 
them. By trnch menne & eint^lo nonc-iibrp ciin net upon 
ail extended R'gii)ri of the BihIv. In other rasw it seema 
likely (iial a feeble nerruus iminilse reaching an irritiible 
ncne-ceil excit^-s eliiingeit in tbi.<t cumjmrnbtc to ihouc [iixi-j 
(liii»4 ill It mii^do wlieii it U stiniulated: nml the cell bj 
ils (iiseliarji^e sends on reinforcoil uorvc iuipul»e« ulong lis 
other bnitidK'*. 

Excitant and Inhibitory If orves. The great innjnrity 
of the norre-tilneH of the Body when they convey nervoiui 
impnlHes to a pjirl nro,i.ie il to attiviiv; Ihey hto excitant 
fibre*. There is, however, in the Body another vei-j- ini- 
portnnt ect which nrreat the iiclivity of parts and which 
arc known iia inhihiforij nerve-fifirf*. Some "f these check 
the iietion of central nervous organs, and other* the work 
of perijiherul piirt*. For in^laneo tulcing u pinch of snufll 
will nntkt! most peraons sneeze; it excited centnilly acting 
fibres in the no^c, the^o excite a centro in the brain, 
and this in tnni neiids out impaUes by efferent fibres wliich 
cani«o vnriouB mnselea to contract. But it the skin of the 
upper lip bo pinebed immedialcly nfter taking the snuS, in 
most cases the roflex act of snecaing, which the Will alone 
could not prevent, will not take place. The afferent iin- 
pnlses conveyed fnjm ihe skin of Ihe lip Imve " inhibited" 
what wo may call tlio '-sncexing centi-e;" and afford nj 
therefore an example of inhibitory lihiw rhecking a centre^ 
On the oUior hand, the hoart is a muscular organ which 
goet on Iwating steadily tlironghuut life; but if the branches 
of the pneuraogu^tric nerve guing to it bi> excited, the beat 
of the hcartwill be stopped: it will ceaee to work and licina 
i-elaxed resting condition; in this we hjivoau instance of au 
inhibitory ncrvo checking tho activity of a peripheral organ. 

OlMBlfication of Nervfl-FibroB. Nearly all the nerve 
fibre* of I In- Itiidy f;dl into imi' of two great groups corro-^ 
^ponding to those which carry impulses to the centres 
and those which cnny them out from tho centres. 
Tlio former ai-e nilti'd offfrrnt or cfntripftul Jihrts and the 
lalter efferent or cuiiin/iii/ah Since the impulses reaching 
tho ccutrea through the aScront Sbnt geueroUy cause sen- 



OLASSIFWATXOX OP ABBVB-FfBRES. 



isr> 




eatlons they are often cidled seruory fibrf-t; und as many nf 
Uiuw wliicli van-y out impuW^ fi-oiii the centrcA excite 
tiiovcnieiila, tlier are fre(|ueutly called motor fibres; but 
ilie<ic \fun Dsiiif« uro bitd, eiuco even cxi-^liKling inhibi- 
tory nvrv<«, matty offeroat fibres are iiot sensoi'y and iiuiiiy 
efferent are not motor. 

We may distiuguish aanubdi visions of (»//'frcB^_/i'ftrM — the 
following groii|i». 1. Sensory fibres proj)vr, ilie exttitcment 
of wliicli \A followed by a soiiaation when they aro oon- 
iiocted with their brain-oentre. which sensatioii may or 
iniiy not give rise to a voluntary movement, 'i. Reflex 
fibres, the excitation of which may be attended with (xm- 
scioufiness but gives rise to involuntary efferent imjialaen. 
Thus for example light fatling on tbe eye cuuxes not only 
n sensation hut atiu) u niirrowiiig of the pupil, whicli is en- 
tirely independent of the control of the Will. No ah«olulo 
line can, however, fjc drawn bi'lwcou these fibres and those 
of the lait group: any sudden excitation, m an (LDOXpcctcd 
noixe, will ciiiiKe iin inrohuitury movement, while the same 
sannd if expected would cause a movement or not accord- 
ing iw was willed. 'A. ExcUa-molor JibrM. The oxcitatiou 
of these when reaching » nerve-centn'^ muses the stimula- 
tion of cSereDt fibres, but without the participatioQ of 
vol) 8cioii#u (>.'<.'<. During fatiting for inetnnco bile at-cnmu- 
latea in the galUhliuldvr and there remiiins until somo 
«i?nti-digested food passes from the stomach into the intes- 
tine. Thin IK acid, and stimulates nerves in Iho mucous 
membrane lining the iute:itine, and these convey an im- 
pulse to n centre, which in consequence seniln out impnlses 
to the niiisnilar coiil of the gidl-bliutder e]ku§ing it to con- 
tract and exiK-'l its eonteuta into the intesline: hnt of all 
this wo ure entirely nnconsoions. 4. Cpntro-ijihihUnrt/ 
flbn-ii. Wholiior these exist as a distinct class is at pre.sont 
(luiihlfid. It may be that they are only ordinari' sensoiy 
or rcSox fibres and that tlieinhibilion is due only to the in- 
terference (if two impulses roiiching a central organ at the 
eame time and impeding or hindering the full production 
of tho normal result of either. 
In tff»r«nt ntrm-fibrei physiologists aUo diGtiuguisb 



186 



THE JiVJlAA Boar. 



§eTcrtiI groiifis. 1. Motor fibre*, which are distribated to 
llif musolca aiid govern tlieii- conlnurtiunH. a. Vaso-motor 
fihres. These* ari.' doI logicjillv so^inrublc from wtLor motor 
libri^;>; but \\ws itrc diatributod to tlie louscleii of Uie blood- 
veaitels atid b_v go\i>niing tbc bloi>d->u|>ply of Vikrioiis jwrtji, 
iudiroctly prodiieo stit'li sfcondiiiy R*#uli!i m entirely oter- 
Mliuduw tbeir iiiirnary effect as uierely jirodiiciiig uiiuculur 
(•ontractiona. 3, Secvetory fibnu. These are distributed 
to the udls of till' Body nbicli form variouaUtjuidstuedliiit. 
u» thu Kulivti uiid tbegiUitriv juiou, uid urou«c thvm to na- 
tivity. Tbt! ealivitry glauda for imtttiice raity be made to 
form Balivu by etimukliiig uervea goitig to them, and the 
HUUf! iH tnit) of the coll- whiib form the ewcat ]>oured out 
\i\>im tiio sui-fiK'u of the Body. 4. Tnphic ntn'e-_^bru. 
Under thb head ai-e iiichidDd nerve -Hbr&ii which liave been 
sujijiotK'd to govern the nutrition of the vurioui; liesues, and 

ati to control their hctiltliy life. It k very doubtful, how- 
ever, if any auch nerve>libres exist, most of the facta cited 
to proTc their existence being otherwifie explicable. Kor 
inHtanco shingles is u disoneo charncUirised by an eruption 
on iJie akin along the line of oortnln nervca wliich run be- 
tween the rijjs; hnt il may ho dejiendcot upon (liKitut' of 
tJie Viiso-motor nerves which control the blood-supply of 
llio part. In other casc!! dtHciut's ascribed to injury of 
troithic nerves have been ehown to be due to injury 
of the senBory nerves of the jKirt, which having lost its 
feeling, is exposed to injurios fiom which it would otiicr- 
wtHc luivo been protected. On the other liaiid it may be 
aaid that secretory nerrea are trophic, nerves in the li'uc 
sense of the word, since when excited they cause the se- 
cretory cells to live in a special way (p. 400) and produLO 
KubKtnnccs whiih wbou uiiavtcil upon by their nerves they 
do not fiiriii. But if we call secretory nerves tro]>hic we 
muiit iiii'ludo uW under that name all other elTercnt 
nerves; the nutritive pntftve* going on in a niunuuliir 
Tibrc when at work are dilTereut from those in the same 
fibre when at reat, and the fcimc \s true of all other cells 
the activity of which is governed by m-rve-flbrefc 6. Prri- 
fih<>raUjf-acli7tg inhibitory nervts. 




NSRVE ftrmrTLr. 



187 



Intoroentral Nerve>FibraB. Tlicw. which do not oonvev 
im)>iiWs< Ui or fnnii peripheral |utrt»aii(l aerro-wntreii, hut 
connef't one centre with uiiother. form n final group in aJ- 
dition to elliTcut and iiffiTont ncrTt^Sbrui. Many of them 
conoect Ihe xparuilic iiii<i sviujuilhiaio ganglia with one 
another and with the cerebro-spinai centre, while otheia 
pittco tlifTercnt parts of thi< liitlcr in direct cominiiiiiuiitioti: 
m for iuHtuui^ difTon-ut |>;trt^ of Uio ^)itial <x»rd, the brain 
nnd the epiiud cDi'd. und the two hulres of the bmiii. 
Th«M fibres 01-0 of very grcfll importRucv. but m yet their 
conrso is imperfeclly knowD, 

Oeneml Tabic Wo m»y physioloftically classify nerve- 
fibres iW in tb© f'lllowing tubuhir form which i« founded 
upon the fucta above suited. 



?rtrT»>fltiiv<k 



PfripJienL 



ABmi'ciI. 



EITiTpnt. 



ScRMr;. 



r 

j Eidlo-iDotor. 
[ tohlUtftr)-* 

Motor. 
Vam-foalor. 
BcCTdory. 
Trijphii: t 
InhlUlory. 



Inwrcenlral j £'^7^[jJ^. 



Th9 Stimuli of NerTe-Fibrm. Xrrvo-fihn^s, llko uiun* 
tular fibres, poH-iu-tii no tiutonuiticity; acted uiwa by certain 
external forces or stimttli they ])ropiij;»t« » chitnge, which is 
known lis a nirvoiia impuW, fr»in the jioint iMiU-rl upon to 
llicir ends; bni Ihcy do not gciRTalo nervons impulses wiion 
)ett entirely to tbemsclvoa. Xormally. in the living Body 
the stimu]ii:< twls ini ii norve-ltbre at one of it« «ndit, being 
cither Home change in a nerro-eontro with which th« fibre 
JA connected {efferpot nerves) or somo chunee in ux organ 
attached tu the outer uid of the nerve (offt^iviit fibri'.<). 
Exporiment shoWH, however, that a nerve can be stimulated 
in any part of jt« oonrse; that it ii irritslilo all through its 



188 



TBS BVHAir BODY. 



extent. If, for example, the eoiatie of a, frog bo exposed in 
tlie ibigh ftinl diviile<}, it vrill bo found llwl. olwlric uliocks 
ui'iiliud lit the point of dirision to (he outer half of the 
uerve stimulate the motor Gbrvti in it, and cause the mus- 
cular Gbrctt of the leg to contract: and Himilarly eiich slioi-ks 
iiplilied to the cutcmi of the ceiitml half irriUte the affe- 
rent Ubrei- in it, »s ehown by tlic liigus of feeling exhibited 
by the anitmit. In inirselves too, we often hiive the oppor- 
tunity of observing that the sensory fibrea can be stimulated 
in their course at Komti di»tiinco from their end«. A blow 
iit the biiek of the clhow, at the point commonly known w 
the "funny bone" or the "crazy bone," compresses the 
ulnar nerve there agiunst tho subjiLCent hime, and starts 
nervtjus inijiulsea which make thfimseWes known by nevere 
tinghn;; jiain referred to tlie little and ring fingers to which 
the nerve is distributed. This shows not only that the 
ner^'o-Ilhrea con be irritated in tlieir course as well as at 
their ends, hut also that senmtions do not directly tell ns 
whore a nerve-fibro liiw been excited. No matter where in 
its course tiie impulse has lieen started we nnconsciously 
refer its origin to the peripheral end of tho iiffercnt nerve. 
General and Special Nerve Stimuli. Certain external 
forces cx*ite:i]l ncrve-fihii--^, and in any part of their course. 
TliCtte are known as ijeni'ml nervfi stimuli; otliera act only 
on the end organs of nene-librcs, and often only on one 
kind of end organ, and lu-nee cannot l>c nmdo to excite idl 
nervM: these latter are commonly known as tpma! tirrre 
titimuli. In reality they juo not i)ropcrly nerxe stimuli at 
all: but only Ihingw which S" iiffect the irritable tissues at- 
liichi'd to the ends of eerliiin nerve-fibres as to make \.\\v*v 
titwues in turn excite the nerves. For cxftmple lif[ht itself 
will not stimulate any nerve, not even the optic: but in the 
eye it elTecta changes (apparently of a chemical nature) 
by which substances of tho nature of general nerve stimuli 
lire pi'iiduc«d and the-sc stimulate the optic ncrve-tlbrcs. 
The ends of the nerves in the skin are not iicccssible to 
light nnr arc the proper end organs on which the light 
iicts there present, so light does nof, lead to the pimiuction 
of nervous impulses in thoin: but the optic nerve witbont 





XBRVB sraeuu. 



IBS 



fte peculiar «n<I or^ns would be jast as insensiblo to liglit 
a& these nre. Similiirlj tlio iioriul Tibnitii>ri« nhick affect 
us as Bounds, doiiol^titnulaccdimctlj theflbroftof thotiiidi- 
tory nenre. llioy act on t«rmintil organs in the ear. and 
ttuee tlien stimiilatci tb« fibres of tlio iutvo of hciiring, just 
OS tber would niiy otlier nerve which happened to be cun- 
iivcloii wilb Ibeni. 

Oenerol Nervo Stimuli. Those known are (I) etectrie 
currenl*: an clectrii^ ahock paAMd tlirough iiny piu-t ut 
any nervc-abre. powerfully excitea it, A aleady current, 
ptu^in;; through a nerve duos not stimulate it, hnt xaj\ 
KiidiU'n cliiiiigc ill Uiis, wbulhur nil iiierojwu or ii dt'cn>ase, 
does, A rery grmlual change in the amount of electricity 
pasting through s. nerre in » unit of time vrill not stimu- 
late it. (i) Mtrhanirtd /ttimuU. Any Kuddcn pressursl 
or traction, as a blow or a pull, will atininlnlc a ncrro-i 
fibre. On the other hund steady prinunrc, or prcsanro very 
slowly inori^uNod from a minimum, will nut cxeito the 
nervo. (3) Thermnl gtimvli. Any FUdiicn btMitin^ or cool- 
ing of a nerve, »» for iimtmice liringiug a Imt wiro close toi 
it, will stimulate; slow changes of tomi)orature will not. (4)* 
Chemical stimuli. Ifnny snbvtanccs wliich nlt«r the nene- 
flbre chemically, stimulate before killing it; thns dipping 
the cut end of a nerve into strong solution of common salt 
will excite it, but very slow chemical chaugo in a nerve 
faibto stimulate. 

In the case of all tbefie general stimuli it will be Rcen 
that tus one coudition of their eflicncy they must net with 
considerable itnddennewt. On the otiur hand too tmnnent 
inflneneed have no effect. An electric shock sent for only 
0.0A15 of a second through a nerve does not stimnbite 
it: Apparently the inertia of the nervo molecidcii iit loo 
great to be overcome by eo brief ini nution. So, also, toOi 
strong sulphuric acid and many other bodiot kill nervM' 
immediately, altering them so rapidly that they die without 
being fitimutated. 

Special Nerve Stimuli. These ajt already explained 
act only on particular nerves, not because one nerve is ca-i 
sculijilly different from another, but because their inHuenco ' 




190 



TBB UVJfA.y BODY. 



is excited through specix) ond orgune which are pecoliar to 
isomc ncrvM. Tlic^oaliimili are — (1) Chanjn'« occnrring in 
ix-uti'ul orgaDfl, of whose uaiurc we kiion^ next to nothing, 
hut Hiiich cxuito IIk' cfTi^retit nerve- lib ix-« connectcil wilh 
tlicni. Th« remuining speciitl stimuli acl i>n ulTt-rviiL Qlm-n 
timiiifch choaeoEO-urgans. Tiicyure — (3) LighUwhich brliie 
inU'rvuuliun of orgnnH Jii Uie<fTe«Kcit** theoiitiuncrvo. ("') 
Sound, which hy tlie iiuenreiitioii of organs iu tlic cur oxL'ilOH 
the auditory nerve. {3) Heat, which through end organs in 
the skin is nblo, by very slight ehiiiiges, to exciH' t«rtuin 
!UTV(-fJbR'»: suuh slight ohimges of l«!iujierul uru being 
efficient aa would lie qnit« incapable of acting »^ general 
nerve eriniuli without the proper end organs. (4) Chemicaf 
affetKieji, 'I'lione when exircmely feeble au<l incapable of 
iKting M geni-ral stimuli, can act ue apodal stimuli through 
Rpecint end oi^uuh tn the month and ixw (ta in taste and 
smell) itud prDljably in oiher parts of the nlimonturr tract, 
where very feeble acids and iitkalicK ncein nhio to excite 
certftin uerrcA, und refleily tlu-ough tJicm excite movements 
or stir up the oclU ooncerui-d in making the digestive 
liqnids; for cxamjile the contraction of the gall-bladder 
ulrcudy rt-ferred to. (5) Uechunicid stimuli when «u fvcblo 
03 to ho iiieffident as genond stimuli. Pre«*iire on the 
akin of the forehead or the back of the hand, ecjuul to .Otf'i 
gism (.03 grain) can he felt through the end nrguii* of 
the sensory fibres ihere, but would be [|uito incapable of 
BoUng M a gonentl stimulus in the absence of the^o. 

It will be noticed ns rvgardi llu; special stinuill of 
Afferent nerves that many of llivm iire mcriOy le^s degrees 
of general stimuli; the end organi) in skin, mouth,ni)d noiie 
are in fact excited by the same things as the itervi'-libre-K, 
hut are fur more irritable. Iu the luso of the hii^her 
senses, seeing and hearing, however, the end organs sei'Ui 
to differ eiiliriily in jii'ojierty from nerve-fibres, hcing 
excited by ixmorous and luminous vibrations which, so fitr 
as we know, will in no degree of intensity din^-tly excite 
norVB-fibres. To imiko an end oj-giui for reeognixing very 
Eilight pressures we may imagine all that woidd bo needed 




SPECIFIC SERVE EXENOIBS. 



Wl 



would be to expose directly a rerj deliciito cud branch of 
Uio axU oylindei', and this Heems in fact, to bo the case in 
tU« n«ni"c«i of the irauspai-eiit exposed }tart of the ejeball, if 
not in many otbcr jiaru of tlie external integunienl of tli« 
Body. Biu as axis cylinders ai-c t|uite uoirrilablt^ by light 
or soaiid ii more cxpuMure of iheiii would ht> iiscliiis in ihv 
pye or i-ai-, and in each case we tlnd accordingly a \ery 
complex apparatus developed, who»i- fuuctlou it is to, 
convert these- modc« of motion which do not excite nerrcf) 
into others which do. We might i?orapure it to 
cartridge, which contains not only " irriiable" gunjiowder' 
hat highly " irrititbic" detonating powdur, and tJic stimulus 
of tho blow from the hummer which would nut itself ignite 
the gunpowder, acting on tlie detonating iiowdcr (which 
repre^enU an "end organ"), cautiw it to give off a Kpuik 
which in turn vicit^a tlie gunpowder, which answers to the 
nerve -fibre, 

BpeoUlo Kerve Energies. We have already «pcu that « 
nervous impuUe propiigiitod along a nerve-iibi-e will give 
ri»c to different n-iilt^^ muordiiig «j< diUcrunt ncrre-flbrea 
are concerned. Traveling along one fibre it will arouse a 
fceuisation, along another a movpmcnl, along a third a k-- 
oretion. In addition we niny ol>!M>rvc readilr tliat tliene 
different rcttults may be produced by the same pbyeical 
force wh«n it acta upon different norvcM. Radiant energy, 
for example, falling into tho cy« canH«« a xenMition of 
eight, but falling npon the nkin one of heat, if any. The 
different r08u1l« which follow tlie slimnlntion ol diff«ront 
nerroB do not then dcjtciid upon differences in the physical 
forces oxcitiiig them. This is still further shown by Ike 
fact that dilTerent physical force*) acting upon the same 
nerre arouse the same kind of seuaation. I^ght reaching 
the eye causes » night aensution. but if the optic nerve be 
irritated by a blow on the oyelHtll a M-iiHation of light ia 
felt just as if actual light had stimnbled the nerve ends. 
So too when IJie optic iii-rre is cut Ijy the surgeon in ex- 
tirpating the eyeball, the palicnt ex|>onenee* the sensation 
nf a fliuh of light; and the same result follows if &u electric 




IM 



THE HUMAX BODY. 



uloug llie tllire. If the musolo wt-io cut away from the end 
of the nerve we could still dcli:tct ihnt a nervous impulse 
hud Iravclod from tbo point of Atimulatiou to tliat where 
the fibres vere divided, bv tnu;king the negative vari:itian. 
Now if wo uxiiinitic the jwri of Ihe nerve on the contrHl 
Kiile of ihv stimulated poiiu we tiiid ihiit n nogaUvc vnriu* 
tiou (and hence we conclude a nervous impulse) triivels that 
WAV too: it ElartA at the same moment as the efferent nega- 
tive variation »iid travelK in the same via\, but ihe inijmW 
of which it is a.e\ga produces no more effect Ihan the efferent 
impulse would after the muscle had been cut away; for it 
Aw* not rftiicli any muscular fibi-o, or >n'ii«ory or reflex centre, 
which it can arouse to activity. (1) The following experi- 
ment is. howBTer, more eonelusivc. If a rat's tnil be am- 
piiljited close lo the body of the uniinnl and he then trans- 
planted to the buck and sewn into the iikin there bv it^ 
Burrewend, it will prow in this new popition, with the 
broad end, which M'ait prcviotixly nttjiihed and ncunst the 
spinal coitl. now fi-ee and farthest from it. The tail, in 
other words, will ho upside down. After the wound has 
healed, the ucrve-flhres in the tail, or some of tlicni, attach 
themselves to the citl nervo-lihres in the wound of the 
tinck to which it wiu Irfmspluited, and the tail iigiiin he- 
comoB acnailive if the <'ud now free he pinched. Here one 
of two things must have occurred. Kither the afferent 
ncrvc-6brBS ill the tail which naturally carried impulse! 
fmm iltt tip up, now carry them in I he opposite dircetion 
from the bi-oad end to the tip. or the offeront nerve-fibre* 
which cyirricd motor impulses down the luil, now carry sen- 
sory impiil.-'i'^ nnd trttnsmit them to the sensory fibres in 
the IxK-k with which they have become continuous. If llio 
llrst, which is the mom probable hyjiotliiais, bo true, it 
is proved that afferent nerve-fibres can carry impulses in 
either direction: if the second be tnie it is still moi-e clear 
tli.-il there is no special peouliarity in a sensory uervous 
impulne when compiired with a motor. 

AITcrcnt and etTeront norvo-fibros then dilTer in no 
observalilc i)roperty. All arc alike in {acuity and theii 
different names simply imply that they hare different ter- 





aiMlLAJtlTY OF ALL SKItVH-FIBRBS. 



l»r> 




minal nr^'.iiH. Jvi^t as nil inn«;Ii-!i arc uliko iii general 
jiln-siologictl |>iMi'urti(», nnd dirti'r in «[>ecial fuiiotion 
;ici?oniing I" llio parts on which tlioT net, so are all ncrvc- 
libix-H alike in gencnll (jli_v«Io!i>gicnl pvojierl ic-s iikI diff<'r 
in upe-^iai fnnciion only ln'c^tusi; thej- are uttuclinl to npi!- 
cial tliinfr*. The i-iii'iiiil physiology at tuHoum nenea will 
hvroiiftcr lie considered in oonneotiou with iho working of 
vauloua media nii>tn« in the Body. If it Iw true thiil Uic 
grcwt tiiiMiviKi<in)i fif iilTfixnt nnd efforcnt flbrea have 
identiati pi-oiierties, it follows that this ia a forfiori Itws 
of tho minor liiilidiviitions of «iu;h, und that niuiilory, gUK* 
catorj, imd npLic ncrvo-flhrea are all alike, and all identic 
cal with raoior and Tn*>.motor and socretory nene-Gbrcs; 
and that tbcnenous impulEC w in nil cxvnet ttio Rimt' tiling. 
varying in intontiity in diflcrent ciutcii and in the rate at 
whioh olhera follow it in the same fibre, hut tlie «inie in 
kind. To pnt tho uuo more defiiiitety: Light otili<idL- the 
cje exists as etliftreat ribrationA, sound out.'<ide tho ear as 
vibrntions of tho air (commonly). Kudi kind of vibration 
«ct^ on a partieiitar ond organ in ey« or ear which ts 
adapted to be acted njmn by it, and in tnro tJieso end 
orgAiu sxcite the opUo und nnditnry ncrvflibreic tlioxo in 
oDDSoqtience trannroit impulses, which reaching different 
partit of the bruin excite thcni: the exciUnieut of one of 
these brain>eentre8 is asaociaccd with sonoroii* and of the 
other with risual sensution*. The nen-ons irapniM! in the 
two cMC4i« quite alike, at IctKt hs t<> i^nalily: thonghit may 
differ in rjnantity and rhythm, and the rcxitllingdiRcrence 
ill quality of the senEntiona cannot de|ii>nd on it, Tim 
iptiility diOoreacH in them cases must be prodnels of tho 
csTiiral ncrvotiH Hvatem. If we hiwl n octof copper wtro« wo 
aiiglit by i<enduig prcctielysimibu'eWtrio currents tbrniigfa 
ibem produce ¥«ry diSerent results if different things worn 
uiter]io«<'d in llictr nonnie. In ono cjwc the enrrent mi;;bt 
l)p sent tbrdiigh w:iter mid docompowt it, doing rhemic«l 
work: in another through the ooil of an eleetro-raagnct 
and raise a weight; in n third thronf^h a thin pintinnm 
wire and develop light and heat, und *n on: the nutidt 
depending on the termiuul organs, us wo may call tbem, 



IM 



THB ffVMAX BODY. 



of oatch wire. Or on tlie other hand we might gen- 
erate the currpnt in each wire ditTcrciitly, in one by » 
Daiiidl'ii CL-II, ill ii ticc<>ud hy a therma -electric machine, 
in a third hy the rotation oi a mugnet inBide a coil, but the 
currents in tho wiivs wuuhl ho i-woiitiully tiio winii;, u» tlit 
nervous impulses ava in a nervo-Bhi-e, No niaitcr how 
thoy liuvu bcf'n starlet and, protidcd their amount is the 
same, whether they produce eiuiihir or diseimilar results, 
dfjicuiin only on whether thi-y »ru cojiiietitod with flimilar 
or dissimihu' end organs. 

The NatoTo of a Ifervous Impulse. Sinc« between 
genec-orgaoa and sensory cvncres. and tlic«e htttrr and i\w 
muficlee. nervoiiB impulses are the only means of eonitnnni- 
eation, it is through Ihiin that wo urrivc at our ojiinionB 
coiioeniing the external universe and through them that 
we are ahio to act upon it; their ultimate nature is there- 
fore » mutlcr of great iiitcri'-tt, but one about which we 
unfortunately know very little. We cannot well ima- 
gine it auyliiing but a mode of motion of the molecules of 
tho iienrc-fibiv-s but beyond tlii» hypntheBU wo cannot g» 
far. In many points the iiheiiimena preaented hy norvc- 
fibree us trausmilterBuf disturhano^B lire like the phenom- 
•nu of wires aa tranajnitters of elw-trieJly, and when the 
phenomena of current electricity were firet obwnvd ihcro 
was a j;reut tendency, explaining oq« unknown hy another, 
to consider nervouH impulHC« moroly as electrical currents. 
The increase of our knowledge cuncoruing hoih nerves and 
electric current*, however, Iiaa made anoh an hypolhesis 
Rlmoet if not quite untenable, in the first place, nen-e- 
flbrcii are extremely bad conductors of doolriclly, so bad 
that it is impossible to suppose them u»ed in the Body far 
that purpose, and in the second pliuM!, merely physical con- 
tiuolty of n nervc-fibrc, «nch as would not interfere with 
tho passage of an electric current, will not suffice for Uie 
transmission of a uenons impulse. For instance it a damp 
stringbo tied around u nerve, or if it he cut and its twomotst 
end» placed in contact, no nervous impulse will be trans- 
mitted across the constricted or divided point, although 
an electrical current would pass readily. An electrical 



FUKCriOSB OF THE SPtXAL ROOTS. 



197 



lock mu}- be vuxA like nuiny oth«r etimuli to upaet Uiu 
equilibrium of the uitvo luoleeulefl utid aluri u ultvous iin- 
puUo. ninth Lheii traveU uloug th« libra, but in junt u dif-^ 
t«runl fmm th<- atiniulua exciting it, as a uiUscultir ooulruo 
tioi) li fntiTi the stimulue which callH it forth. 

The neives, however, have rortain iDt«re(!titig eleciricnl 
properties from the litudy of wliioli we Ivuni i>ome liltlo 
filwnit II iieriou* im^iiiliti-. Ax alreiniy itii'iitloned whcnetcr 
;i iiorvuuH im|)iilKe U surlud in a uene an electrical chuiigc, 
known an the " negative Tarlatioii" or "action currenl," is 
started at the same time, from the same point, and trarela , 
along the nerve at the mmi^ rate. Honec wo conclude that ' 
the n*w internal molecular arrang«menl in u norve-filiro 
wh!ch ooustitutea ibi active aa compared with itx resting 
#lHt«. IS ttUa one which change* the electrical properties of 
the >1hrc It i^ an outward tti^n and the only knuwii one 
ol the inuu-nal change. Now it is found that the oetion 
current traTels along iko ncrre (in Ihc frog) nt (hv mt« of 38 
meti-ra (9-i,00 feet) in a aecond and takes .0007 second to 
pjuts by a given point; accordingly at any one moment it 
rxu^ndH over ahoot IS mm. (0.720 inch) of the nerve- 
fibre. Sloreover, when flrat reaching a point it U very 
feeble, then rises to a maximum and gnidnally fades away 
ugnin. Taking it a« an indication of what is going on in 
the nerve, we majr asBnme tliat the nervous impulse U a 
molecular change of a waveltko chOfBCtor, rising from a 
minimum to u maximum, llicn gradually ceasing, and about 
18 millimelei-sin length. 

The Rate of Tranflmiiwion of n NervoUR Impulse. 
This OiUi be nii'iiiiurt'd iiiMi'vw~.ii way.*, and infiirnlnwi-r than 
that of electric eurrents. It sgre€« as above stated with 
that of the n^utive variation, being ^S motcn (93.00 fcot) 
|KT oceood in the motor nerves of a frog. In man it is 
iiiimewhat quicker. bcingS-lmelerB (108.24 feet) per second, 
ihat is about -^ of the ralo of Hie traDamtsjion of Aonnd' 
waves in air at zero. 

Fiinotioaa of the Spinal Norvo-Hoota. The great ma- 
jority of the birgcr nurvc-trunkK <j{ ilui Body ooutain both 
a9eruiit and diercot unrvc-libre^ If one be exi>osed in ita 



198 



TBB aUHAN BODY. 



conrseniid divided in ii living luiimnl, it will be found that 
irrilatiug its |)onplionil nluiiigi cuuxu^ )iiu».'nliir c-ciuti'iu;tionB, 
uiid piuohiijg its centrul £tuiu|i cauekw ai^iu ot KH-nvaxXon, 
allowing tbai the trunk coutaiccd boiL nioiuf and Keiitwry 
fibres. If the tninic bo followed awav from the centre, m 
it brt^iikfi up into suiRllcr iind Etiiiillcr briimlicH, it will Iki 
found tbut tliv!io loo arc mixvd uiilil very near ttit'ir und- 
inga, wliore iho vorv fin^t leniiinitl brniti-iuM tlu^c* to Uic 
end organs, whether niuscular tibros, secretory cells, or aen- 
(fory upjtnratuses, conutin only afferent or eflerent fibres. 
If the uurve-trimk bo one tliut arise!! frum the i<pinitl curd 
snd be cxninincd progressively back to its origin, it will 
utill 1)6 found mixed, up to the point where its fibres aopa- 
rato to enter either an untcritir or it pii«t«nor ncrvc-rooL 
Eaoh of these littler however i.* pure, all the efferent fibi-en 
of the spinal nerves leaving ihe cord by the anterior roota, 
iu)(] all the nSerent entering il by the iwgterior. Thit of 
course eoiild not bo told from exaniinaiion of tlie dead 
nerves since the best microscope fails to distinguish an 
fttfercnt from »n efferent fibrv, but in rc^ulily proved by 
experiments first ]>erfot'nied by Sir CImrtciii Bell. If an 
anterior root be cut and its outer end stimulated, the mue- 
oles of the partx to which the tnmk nliich Jt helps to forui 
18 distributed, will be made to contract, and the skin will 
bo mikde to sweat also if tlie root Iiuppen to bo one that 
containxMcrctory fibriMfor tiic swcat-gliuidx. On the other 
liand, if the oentral end of the root (that part of it atuichod 
to tbo cord) hv Htimulat^d no renull will follow, showing tint 
the root contains do mnaory, n^tles, or oxcito-niutur fihre«. 
M'itb the posterior roota the reverse is the case: if one of 
them be divided and its outer end stimnlated, no observeil 
resalt foUown, slinwing the ubseiico of nil efferent lihres; 
but stimulation of its central end will eanee either eigne 
of frcliiig. or reflux actions, or l>utb. We might comiiare a 
spinal nerve-trunk to a rojw niaiio up of green iiwd veil 
threads with at one end all tlio an-t-w threads collected into 
one Hkeiii und the red into another, vhich would rvpreoeut 
the roots. At ita fartlior end wo taty suppose the rope 
dividotl into finer cords, cacb of tlieae also oontaining 




COMMVSICATIOX Or ymVtl-CBSTSKS. 



I9fi 



nd and green threads down to tlte Tery finest bnindtMl 
ccaaasting \>t only u tw Dircsul^ anil thoM ull of ono kind 
cither red or green, ono rci)re»eiitiiig efrci<ent, the othor 
iifferont fibres. 

Tfaa Cranial NenroB. Most of those nro mixed aim, but 
w)lh one cxce|itioii (Uio tiflh ]iutir, the Kmall root of whieli 
IS efferent and the isr^e K!in;;linteci ono afferent) thoy do not 
present distinct motor uiiil tciinory tooU, like thuM of Iho 
spina) nvrveo. At their origin from tiio bruin most of them 
are either pnroly afferent or efferent, and the mixed char- 
acter which their trunks exhibit is duo to crofX-brunchM 
with neighboring nerves in which atTerent and elTereot 
flbros are interchanged. The oltactory. optic, and andi- 
tory nerves remain, however, pun^ly afferent in all their 
course, and othcra though not quite pure contain mainlT 
efferent fibres (m the facial) or mainly afferent (as the 
gloaao'phHry u gcal ) . 

The Interoommunioation of ITerve-Centrea. From the 
ttnatomieal arrangenieiil of tliu ntrvom sj'stcm it is clear 
dial it forma one continnouB whule. No ^iilNlivision of it 
is isolated from the rest, lint ncrvc-trunks ]iroeeeding from 
the centres in one direction bind them to varionit tiisiiea 
anil, procc*Mling in another, la other nerre-eentres; which 
in turn are niiile<t vrilli other tismteii and other centres. 
Since the pbynological character of a nerro-fihrc is iti< con- 
ductivity — ita power of propagating a disturbance when 
once its molecular equilibrium ims )>ot'n ujiMtt at any one 
point — it in obnous that through the nenuiis system any 
one pan of the Uudy, supplied with nerves, may react on all 
other piirta (with the excopUon of sndi as hairs and naih 
and cartilages, which arc not known to pomes* nervex) and 
exoitcchangesin them. Pre-eminently the nervous system 
forma a uniting iinntomical and phyxiologieal bond through 
tlie agency "f which nnjtyand order are prfxlneeil in the 
aclivitiw of different and distant jiarts. We may compare 
it to the Western Union Telugrsjih, the head office of 
which in Xew York would iviincsent tho brain and spinal 
cord; the more important central offiocs in other large 
citiw, the sjrm]Mithetio ganglia: and (he minor oflSces in 



!»0 



nnt ffCVAy bout. 



country stHtions the B])oradic giuij;li;i; while the tele- 
grapli-wirea, directly or indirectly uniting iili, would mrrp- 
epoiidtotlieucrvo<lnuikgc Junt aa information ittutedtdong 
Bomc oiillyiiig wire nwiy bo traaamiited to a contrul office, 
aud from it to othors, and then, ucx^ordin;; to what liuppoiit 
Uy it in the ccnLie, W slupjted there,or sproiid in nil direo- 
tions, or in one or two only, so may a nerToua disturbamc 
reacbiDg a centre by one nerve-trunk merely cxoitc changes 
in it or bo rudinlcd from it tlirmigh other Lruiiku moro 
or less widely over tlie Body and aronae varioua actiti- 
tits in iU other component tiiwucs. In common life tlui 
very frw|uonoy of thin uniling activity of the nei-voBs sys. 
tern is such that wo arc apt to entirely overlook it. We 
do not woniU'rhow Ihcsiglilnf piciwiuit fond will niakclho 
moulh water and the bund reach out for it; it seema as we 
say '* naturid*' and to need no (■):])lunutioD. But the eye 
itneir can exrite no detiire, cauHo the fleeretion of no »aliva, 
nvd the moremcut of no limb. Tho whole complies result 
depeitdx on the fact tlmt tho eye i« united by iheopiic 
nerve with the brain, aud that again by other nerves with 
saliva-forming cclKand with muecoUr fibre* of tliearm; 
anil through these a change excited by light billing into 
[he eye in enabled ti> produce changex in far removed or> 
gans and excite deaire, secretion and movement. In caaca 
of diMcaao Ihisuction exerted at a iliittnnco is more apt lu ex- 
cite our attention: vomiting is a very common symptom of 
certain brain diaeaaea and mo§t people know that ii dii^or- 
derad stomach will produce a hwidachc; while the piiiii 
consequent upon tho l)ip-diM)ii«o of children is usually felt 
not at the hip-joint but at the knee. 



CHAPTER 

THE AKATOMY OF THE HEAKT AND BLOOD- 
VESSELS. 



GenenU Statomont. During liTo tlio Wood is kejil flow- 
ing Willi great m|iidity tliroiigh ull parts of the Body (ex- 
cept tliGi few uoii-v:isciiIiiir tissues alriudy niviitioncd) in 
dcGnito |mlli3 }iroscril>ed for it by the lieftrt and blood- 
ressels. These putbs. wbicb tinder normal cireumstanccs 
it norer leaves, ouii»tiiiite ii continuous 
act of closed tube* (Fig. 7B) bcgiiiuing 
at and ending iigiiin iu ibi; bcurl, nnd 
Minplc only clo«e to tbut orgiin. £!««• 
wbcrc it is greiitly brancbed, the most 
iMinicmus nnd fiiicvt bcnuchct; (/ mid a) 
being the mpHlaries. 'i'be heart is e»- 
KOiiIiidly a bagiricli muscukr walls und 
intenmlly divided into four cbninbcrK 
(rf. ff. «./)- Those at one end((/nnd f) 
receive blood from vessels opening into 
tbem aud kuown aa the vfim. From 
tliore the blood passes on to the reinnii)- 
iBg efaftmbers (jp and/) whicii huTe ver)- 
powerfu! walU and, forcibly contnct- 
iiig, drive the blcod ont into vessels 
(i and b) which commiiniaito with 
Idem nnd ni-c known as the aiterirs. 
Tlio big artcricit divide into smaller; 
tbcfiO into smaller agiiiu (Fig. 77) until the branches be- 
00010 too smull to bo traced by tiie iiiuiidcd eye. nnd llie«o 
aniallest brancbej end in tbe capillaries, ibrotigb which the 
blood flows and enters the coniinciiecmcuts of the rfins; 




Fio. n.— Tba heart 
ftnd Iduod-tfBM'lii dia- 
RraBiiniilhalljr rvprv 
tanlcil . 




8oa 



TITK im.VAy BOOT. 



uQil those coavey it ugiiin to tho lieurt. At certain point 
ill the oourao of tho blnod-)i}illiA %'b1v«8 iirc jilucsd. whid 
prevent a back-flow. 'J'hia alternating rooeptioti uf blixw 
ttt unv Olid \}y tli« hourt iiud its ejection from the oilier gi 




Ra> TT.-^li» HtMlM or tlip han<). ibowinc tlia eemmtmlealloii* or &nuu 
mCMMOt dlSMCMMMrlHauiI ilii- naeteUDlIial lw<fif<*ai uKCriu'i <h" hirm 
(nuta; IhMVIwlnaail ia Uh- caplllaria* virtdb would <mlr b«ililtilc ir taai 
■UM- Jt. I)iti nufint arlenivB mlileb Ihii jiulae la unwUy fell M the inM i E 
itwnliHiriirtrr}'. 



on during life steadily about «eventT times in a minatt 
and «o keep the liquid constantly in motion. 

TIio vuBCiilar Bystt^m i« ci>nii)li'lely eloBed etcept at tw 
points where the lyniph-veKiiels open into tho veins {p. 339) 
there some lym|ih is poured in and mixi-d directly with thi 
blood. Acctirdingly everything which leaves the bloo( 



POSmOS OF TUB UEdBT. 



ao8 



k 



muit dosobyooxin^ throngh the walls of the blood-vessels, 
and «Ti}rything which «ntera it must do tlio «ime, cx(?ept 
mutters convejed in by the lymph iit the point* above 
Bicntioiu-d. This inlerchnnge through the walls of the 
Teasels tAkos pliK'c only in lh«> capillaries, which form A tori 
of irrigution svstem all through Ihc Body. The heart, 
art«ne«,andveiiuuro all merely arrangements for keepiug 
the capilkrio!' full and renewing the blood within them. 
It \* in the capilbrieH alone that the blood does its pby- 
sioloi^cil work. 

Tha Portion of the Heart. The heart (A. Fig. 1) Ii» 
inthecbeit inimediiilely al>or« the diaphi-ugm and oppo- 
aito the lower two tbirdx of the breast-bone. It itt eoniiitl 
in form with itd Insf or bro«diT tnd tiinied upwards and 
proji-cting a little on the righi of the sternum, while it« 
narrow end or apex, turned downwards, prajecUto the left 
of that bone, where it may be felt beating between the 
carlilugeii of the fifth and siith ribs. The position of the 
organ in the Body i« therefore oblicjae with reference to \\» 
loDg axis. It does not, however, lie on the left side as is 
so commonly >uppo«ed but very nearly in the middle line, 
will) the upper part inclined to the right, and the lower 
(which may be easier felt beating — hence the common 
belief) i" ihelcff. 

Tho Membrane* of tho Heart. The heart does not lie 
bare in the chcit but if Kurrounded bya loo«e bag compMcd 
of connective lis.iue and called the perirardituH. This bag. 
like the heart, iscomciit bnt turned the other way, its broad 
part heicg lowcul and attached to the upper i;iirfaee of the 
diaphragm. Internally it i.i lined bya smooth nerouf mem- 
bntne like thai lining the utxlominal cavity, and b similar 
layer (tho vim-^rul htt/tr of the jjerioiirdium) covers the out- 
aide of the heart itself, adhering closely to it. Each of the 
seroua layers is covered by a stratum of flat cells, and in the 
cpnoe between them is found a small quantity of liquid 
which moistens thecontiguouHsmrfacc^. and diminishes the 
friction which would otherwiBe occur daring the movemeottf 
of the heart, 
lutcrnallv Uie heart is aIm lined br a fibrous inem1>nin«. 




SM 



TUB J£VJfA.y BOUY. 




covered irith a single lajer of flsttenod (.-elU. and called tJ 
tmtocardiuin. Belwevit llie endovHrclhiDi aud tho visceral 
Iaycrvrilie}iericni'(liiim llicliiilkof ihe wall of ihc lii-iti'11ie!$ 
and IB madoiip mainly of ^Iripcd mii^culHr tissue (diHcriiifr 
Eomuwliut fruni thnl of tbe eki'letiiliiuiwk-iijjbutoonuecUve 
tiBsues, blood -vl'SkvIm. ucrvc-celU, mid u<.-rvi.-libri-a iiro nlw 
abundant in it. 

yote. Sometimes llie pcricnrdium becomes inflamed, 
thii; nffection being known its pcriL-iirdJli^. It is extiemelr 
apt to occur in ncntc rlieuinati>ini. titid great euro should 
bo taken never, even for a moment, except under mediciil 
advice, to expose ii puliont u> cold during tlint disease, 
since any cliill is tlien ciipecially apt to iiet up pciicanlitii. 
In the earlier Htagesof pericardiac inHummation the rubbing 
surfact'Ji on the outride of the lu-art and the inside of tl)« 
pericardium become roughened, and Uieir frirlion produces 
It sound whicb can be rcTOgnined llirouj^b the stethoscope: 
In later stugi's great ijnimlitir.f of liquid may ucoumiilatfi in 
tlie pericardium so aH to scriouiily impede the heart's 
bcut. 
The Cavltiea of the Hoart, On opening the heart (see 

diagiam, Fig. 78) it is 
found to be >>ubd)vidod 
by a longitudinal parti- 
tion or trptum into 
completely Rcpamted 
right iiud left halves, 
the )>ar(ilioii running 
I> from about Ihe middle 
of the base to a point a 
little on the right of 
the apex. Each of tho 
chumbore on lie sidea 

piagnm r»tir™«it!rn a MCtlon of the septum IS Mgaiu 

incompletely divided 
transversely, into a thinner baaal portion into which veins 
open, known us the auricle, and a thicker apical |ior- 
tion fi-om whieh arleric* arise, called the rgn/rielf. The 
heart thus consists of a right auricle and ventricle and n 




Fio, _ _.. _ 

Uiroufb tlitf Ijmui fmifi tiikM? lo np<<jr. 



BXIEfUOa OF TBB nKA«T. 



MO 



Iflit Muriclo uiid ventricle, eacli auricle oomintinicntiug bj 
wi auricula wniricular orifice wiUi (lio vvitcricl« uii lU owu 
ude. aud thorcisnutiiruci coiQuiunicstion whatever Ihrongh 
the scpliuu bctircou tbo opposite sides of the bearc. 'L'u 
get from one side to the ulli«r the Mood must leuve Lite 



**e C' S« »* 




rii>. n ~Th» lii«rt nnil ihv jnrwt Wi^-thuI MUcbMI to II. «««a bwn lb* 
wtAf tvt.f\t ltir> iriTnum Tim liTi c»1lM ukd tbo Tsawla tunaaoted wltli 
theta ars coli>rv-l rv-I : itw rij[lit Uack. AU. latl Uirfole : ^ili ttiKl jIJ; uie rtfllt 
Mill latt kuMi'uUr mipj-iJajM ; I'll. riKht milrfolo ; V; loft natrkdo i A», 
*oft« : .4b, liitiiiiiiitiFiM BrMrr : 0>. lafl oodiibod eutiUil turf: tii, lutt nib- 
eUnui arlnnr : i; njUn tniQk ol tbe pulmooarj uWtT. tuid '^ ■'><> '>• ■■• 
bninobn to tbo ilcbl kD'l laft luiwi ; <■. «uperlOr«cn* cava ; AiU nnil AH, tha 
rlffbn au4 Utt laoaailnata **l(u : pd Had p*. Ibertsliluul led pulmaiuur tqUu: 
trd and cn^ th* right and lafl ca>«nar)r aitaria*. 

heart and pn» through a sot of cupilliirie^, nx may readily 
bo seen br tracin;; the coar» of the veaaels in Fig. 76. 

The Heart as aeen ft-om ita Extorior. When the heart 
ia viewed from the nide turned lowurds the sternum (Fig. 
79) the two imriclei, A(d Mid At. arc MWn to bo sopitratwl 



% 



206 



■ THE nVMAH BOUT. 



by a deep groove from tlie ventricks. I'rf and V*. A more 
hIiuIIow furrow runs lietwopn the vpmriHce mid indiralc* 
the {)U:»iUui) ut lliu iuUriiul loiigiliitliiiul septum. On tht 




Fra. Mi'-Tlw hi«n vipwr-l (nvm It* ilonai tMperi. Aid, fIkIiI ourtoli- \ tU 
Inbilor f nun cBimi HI, njiiiot vein ; ^'c. connmrf >vln. TIif rMuUnltia lelCrm 
ot rTi(>ri>m<c hant llir nunc *lciiJa«Liion u In FlK, t% 

(lor-onl uj^pect of the heart (Fig. 80) eimilar points may be 
noted, and on one or olhcr of tlic two figui'cs tho great 
reiMols opening into the CBvitiea of the heart m&y be Keen. 
The pulmonary artery, P. urisw from Ihc right ventricle, 




IXTSRIOB OF TUB SMART. 



SOT 



£»d renr sooa divides into the right and left pulmonary 
artvric!!!, Pd nnd Ps. which brojik up Into smaller braiiche* 
a«d enUT the eorretpoiHiing liingTi. Opciiitig into the 
right auricle are two great veina (see also Fig. 78), a untl 
df known respoclivoly ac the upper and lower venm cava, 
nr "hollow" win*; so oatl(Ti by tho wlilcr anatomists be- 
oanse they are frequently found empty after death. Into 
the back of thr right auricle opens aUo another vein, 

Fr, RiillH the coroitary vein or Mnus, which lin:ig>- back 
blood chat has circulated in the walls of the heart it- 
self. Sjiringing fmni the left venlricle. and appearing 
from beneath the pulmonary artery when the heart is 
looked at from tho ventral side, is a great artery, the 
aorta. Aa. It forms an arch over tlio base of the heart 
Hnd then riin« down behind it at tlio bitok or the cbvst. 
From the convexity of Ibc arch of the aorta several great 
branches are givon off, Sni. V*, .ih; but before that, cioso 
lo tilt heart, the aorta gives off two coromnj arfen'ea, 
bmnchefl of whi^'h are wen at cril and cr» lying in the 
gronn over Ibe partition bettreen the ventriel<N<. imd which 
carry to the aubstanoe of the organ that blood wliii-h oomos 
hack through the coronary sinus. Into tho left anriole 
open two right and two left pnlmiitMr{/ tvins. p» and jul, 
which are formed by tJie union of smaller veins jiroceeding 
from the lungs. 

In thi' diagram Fig. 78 from which tho branches of the 
great vessels near the heart, hare been omitlW for tho 8ak« 
of olcnrnes«, the connection of the varions vessels with the 
chamhera of the heart can be ln'tter wen. njioning into 
rho right auricle are the auimrior and inferior vena* cavie 
(m and ci) and proceeding from the right ventricle the 

pulmonary arter;/. P. Opening into the loft auriclo arc 
the right and left jmlmonarT,' veins { pd and p«) and spring- 
ing fium the left ventricle the aorta, A. 

The Interior of tbo Heart. The c»mminiioation of 
each iiuricle with its ventricle is also represented diagram* 
matieally in Fig. T8. and the valve* which are present at 
those points and at the origin of the pulnionary iirlory and 
that of the aorta. Internally the anricles are for the most 



sw 



nor ttVMAX noDT. 



part Hinootli, but from earh & hollow poneb, the aurimbir 
appendage, projedji over tho biiw of the corresponding Ton- 
tnclo luf Kcoii at .-j</x and .-f« in Figs. ~0 a:id 80. ThcRC 
pouches huvo somewliut the nhupc of ii doj^'x oar and have 
given their namo to ihc whoi»> aiiri('l«. Thoir interior '\» 
rough I'll i!ii by mu^ailar cleviiiionH, ci'Vored hy endocardium, 
known as the fleshy voltimus {rolurmiai rumea). Ou Ihe 
inside of Uio ventricles (Fig. 81) ivimilar fleshy coluinn.i are 
very prominent. 

The Aurioulo-VentrionJar Valvee. Thc»c nre known 
M right and I'/i. or as tlif irit-uspid and mitral valers re- 
8|»cctivcly. The mitral valve (Fig. 81) con*ii<t« of two flaps 
of thi> cndocanlium lixed by their batio* to the inargiim of 
auriculo-vcutrictilar aportura and with their edges banging 
down into the ventride when the heart is empty. Thtt** 
unattached edges are not however fi-ee, but havo fixed to 
them a nuinbcr ol etout connectiTe-tlHue cortis, the eordw 
ttndinfit, which are flied l)eIow to ninsenhirelevnlion^, the 
fapiUary mvacU*, Myw and Mpl, on the interior of tlio 
vcntrii'lo. The wjnb are long enough to lot tho valve flaps 
rise into a horizontal position and so clo«o the ojioning bi^- 
twecn auricle and ventriele which lies between them, aiid 
p«esc8 up behind the o]H;iied aorta, Sp, rcpit-Mnled in the 
figure. The IricuKpid mice is like the mitral but witli 
three flaps instead of two. 

SflmUunBT Talres. Thcao arc kjx Jii number: three at 
Uie mouth of tho aorta, I'^g. 81, and throe, cpii to like tliem. 
at the mouth of tlie pulmonary arter)'. f^aoh is a strong 
ciMeejilic pouch fixed by its more cunwl border, and with 
its free edge tamed away from the heart. When Uie 
valves are in action these free edges meet across the VMsel 
•nd prevent bluod fri)m flowing biit'k into tho ventricle. 
In the middle of the free border of mob vulve ii< a little 
cartlhiginous nodule, tho airpu* A mntii. and on each Hide of 
tbia the edge of the valve is very thin and when it meeU 
its neighbor doubles upji^fainst it and bo secures the climure. 
The Arterial Sy«tom. All Ihe ttrtoncs of the Body 
arise either direeily or iiidiiieetty from the aorta or pulmo- 
nary arterj- and the great majority of them from the f<ir- 



I 



TBB ABTBBTS& 909 

mer naaei. Tbe pulmonary artery only carrieei blood to 
the lunge t« an<)i<rgo oxchonges with tbe air in ibem, after 
II lias circalated tbnHigh the Bod.v gonernllv. 
After making its arch tho aorta ountiuuo* buck throngh 




ut of lliK aorta laid op*B 



J/vw. lijil, the paplUary maaols. fwn thaU nppurnulian-aci-i Uftonltf 
ImWiBMr pfOMnJlMg lo Uie adecs of tba llapa of um inlti*) vni 



k 



... , —a,- — - -,- — vnlvr Tli?op««- 

IBVInioihwaurlctonMbatwmiilLMDllapa At Uw beatniilu ot IheMrWm 
MBS Ut IlirM pouch-ltM ■rmlluiur TUim. - 

tlie ulie!tt, giving ofl many branchvx on it« way. Piercing 
the dtapbtagm it enlcrn IIh! abdomen uod after snpplring 
the parts m and around that cavity witJi bnuiobec, it QacU 




«10 



J7/K nUMASf BODY. 



tfpfOKt^ th« last lumbar TOrtvbra by divi<tiiig into the right 
and l«/l commvn ilinc arUtriw, which carry blood to the 
lower limlu. We have then to conaider the bmiahesof the 
$xch of tho aortii, and tbo»c of tho drgcmdinj/ aorta, which 
Itttter is for (»>iivciii»iit.iu d«>ioribt'd bj tttinlomiitte as cvnitiHt- 
ing of the thoraHc aorta, extending from the end of the 
arch to the dia|>hnigni. and the ((Arfomind/ aorta, extending 
from the diaphnigni to the liiiat 8ubdivisioil of tlio vessel. 

fimnclied of the Arob of tho Aorta. From thiH arise 
first the coronary arteries {erd and m, FigB. 79 and 80) 
which spring closo i» the heart, jnet above two of the 
pouches of the ncmilunar valve, and carrj blood into tho 
Rubatauce of that organ. The remaining branches of the 
arch are three iu number, and all ariGc from it4 convexity. 
Thu rust, is ilu> innmniwih arltrg (Ah, Fig. TO), which is 
very short, immediately breaking np into the rtghi xnhda- 
vian artery, uod the right common carotid. Then comes 
the If/l common carotid, Cs, and finally Uie left tubelavian, 
Sti. 

Each tuhflavian arlery r»n« out to the arm on its own 
side and after giving oS a verlehral artny (which rnno up 
the neck to the head in the vertebral canal of the trannverso 
prooosMS of the cnrvicnl vertebra?), croe^tee the arm-pit mid 
takes there the name of tho nsillnry ar-ifry. Thia con- 
tinues down the arm as the brachial arlery, which, giving 
off brunches on its way, runs to the front of the arm, and 
ju.>it lnli)W the clbfiw-joint divide into the rndialand ulnar 
arteries, the lower ends of which are eei-n at A' and V in 
Fig. 77.* These supply the forearm and end in the hand 
by uniting in form an ai-ch, from which branches are given 
off to the tingr'rs. 

Thertrmmon fitrotid arterieg pass oat of the cheHtiiito the 
neck, ailing wliloh tbc-y ascend on Ilie sides of the windpi])e. 
Opiwsite the angle of tho lower jaw each divides into an 
intfriial and txternal carotid arlerij, right or left as tho 
case may be. Th^^ IuiUt ends mainly in branches for the 
face, Ecalp, and salivary glands, imc grnit snbdiviiiion uf it 
Willi a tortuous course, t\\e tnnparal artery, beingoften seen 
> thin persons on lliu t-ide of the brow. The in- 



•p.aoa. 



A 



TBB CAPILLARIES. 



Ml 



Icrnsl carotid aitery DDters tho fkull through an apertnre 
III ita base atitl supplies tho braiii, which il will be remem- 
bered also goU bliwd throiixi' the vertebral arlerioi. 

BranoJiea of the Thoracic Aorta. Tlicso am nnmerona 
but amall. Some. th« iiilfrrwtnl artmrs. niii out between 
the ribs snil »iipt''y ''"^ cbest-walU: othcis. the hromhinl 
arUrist, carry blood to the lungs for their noun«IiineDt, 
that carried to them hj Iho pulmonary «rlericii being 
brought there fur another ])arpoee: and a few other email 
branches are given to other neighboring parta. 

Bisncbes of tho Abdominal Aorta. Thtic are both 
Urge and numerous, supplying not only the wall of the 
posterior part of the trunk, but the iniporlunt orgaiuin the 
abdomin^ cavity. The larger are — tJie ealiac axis wliich 
xupjilic^ gtomiich, spleen, liver, and pancreas; tlie superior 
mt*eiiteric artery which ripplit* a great part of the intes- 
tine; the renal arlrrUs, one for each kidney; and finally 
tiie inferior mesenleric artery which itiip|ilieB iho rest ol 
tho int«stiue. Bedsides these the abdominal aorta givM off 
Tcry many smaller branches. 

Artarlea of the Lower Zalmbo. Kaoh common iliac di- 
vides into an internal and tzUrmit iltne artrry. The 
former mainly end* in branches to parts lying in the i>elvi.->, 
but the tatter passes into tho thigln and th^re takes the 
Qamf of the/pwinrfff arfertj. At first thin tic* «ii tlie ven- 
tral a:tj3ect of the limb, but low'er down passes hack round 
the femnr. and above the knee-joint, where it ia called the 
poplitfal ar/fri/. divide* fnto the anterior and posterior 
tibial artartn whieh supply the leg and fooL 

The CapiUorio*. As the arterioR are followed from the 
heart Iheir brandies iKt-ume smaller and Bmnllcr, and finally 
cannot be traced without the aid of a microscope, riti- 
matcly they j)a«! into the tapiUarirs, tlio wiUis of which 

Lare simpler than thfwe of the arteries, and which form 
very dose networks in nciiily all i«irlsof the Body; llicir 
immvnfie niunbiT compensating for tJii'ir smaller size. The 
aferage diameter of h cupillary ressel ia .016 mm. (nVr 
inch) so that only two or three bViod corpuscles can 
Uirough it abreast, and in many pnrts the; are so 



pasij 



313 



Tnm nuMAif hodt. 



tbftt • pin'e point could not ho insorwd between two of 
thetn. It is while flowing ia those delicate tubes that the 
blood dues its Dutritivu work, tlio arteries being mcnOy 
sapply-tubox for the capiilnric!>. 

The Veins. The lirst veins arise from the capillary net- 
works in various! organs, aniJ lik^^ the l»*t art«rifii are very 
small. They soon increase in size by union and so form 




i\*, man vfliiEUurjiDK blood bwili tram Uio iMWr. "™™«""'™''™™""- 

larger and larger trunks. Tliew in many placea lie near or 
alongside the main artery of tlio pnrt, hiit there are many 
more largo viina just beneath the skin than there ar« large 
' '" This is esiiecially the case in the limbs, the mun 
which arc itnperficial und can in many pertotu bo 



d 



THH FSnCS. 



218 



Bcvii IV fitint bino lines tliroagli th« i>t:tii. Fi^. 83 repre- 
aente the aira at the front of the eitmw'joiut aflci' the 
Kkiii mid Bubcutttoeous areolar tissue ami fat have bocD re- 




-Pt 



b«* 



fM,! 

BVNM 



n.— ThanipoMlclklnilaslntrMtof Ule«Uuw-]o(iit. jy.tandmoFUMpi 

; £1. bnuHi'aliJintFrnumUMUl W. Cf«wa<Br fcrw wmele : I. uiKdUa 

1 1.1, 4, nnnii linuiuliii U> tlM Kin J RbnehUI arUity *1<I' Itn iiiiaII 



KOOatnuDjIng n-lni ^ »|>, >->>uIuille «<dD : laajMdUc Mlu ; m', [umIIu rrln ; 
*, luncUwi at ■ dMp-tiing tpIii with iba oijhilfa 

moved. The brachiul urtery, B, colored red. is seen lying 
tolerably dw]) und iicL-ompiiriieil by tnn ^niull Teiitu {vmw 
comitw) whioh oomniuiiLcate by cross- branches. The ^raat ; 



21* 




me SCMA.1 Bovr. 



nudian ntrtt, 1, a bnndt of the bnchifti plexus which 
sopplt^a Ecvcnil musdM of th« forMrm uid huDd, the 8kin 
over a gmtt piirt uf the inalm, aitd t[i« thnH! iiini-r lingcn. 
is seen alongside the arterr. Tlie larger veins of ihe part 
are teen to fonn a more inpcrfivud netvcH-k, joiti«d here 
nnd there, at for inst«a<» at *, by bnovlics (rom deeper 
pttTtH. Several aniall nerro-braiicliee which sni^tj the xkiii 
(2. 3, 4) are seen among tlic«o vcin». It id from the Tessel, 
cep, called the cephalic vtin, just above the ]>oint irli«ni it 
croeees th« median nerve, that mi^goons muallj- bleed a 
patient. 

A great part of tli« blood of the lower tiinb u bronght 
back by the long taphenout mn. wliicii can be £e«n ninning 
bonc«(h tho skin from IIm; intivr Mde of tlw ankle to the 
top of tho thigh. All the blood which leaves the heart by 
the aorta, eitcept that flowing through the coronary arte- 
ries, u liiiully colltclcd into the superior aiid inferior vtna 
cava {as uid ct, Figi. 79 aad 80), and poured into the 
right anricle. The jugular trinx which run down the 
neck, carrying back tho blood which went out along thv 
carolid arteries, unite below with tlic arm-vein {mUiavian) 
to form on each eide an tnnominaU i>rt'n (Ati and Ad*, 
Fig. 79) and the innominatca unite to form tJie superior 
cava. Tho roronary-artery blood after flowing through the 
capillaries of tho heart itM-lf, aUo n^turu.i to Ihix nuriclo by 
the coronary vein*. 

Th« PolmoDary Circulation. Through tJiis the blood 
gels back to the h-ft t^itlt- of the hi-art and so into the aorta 
again. Tlic piilmonar}' artery, dividing into branches for 
each lung, ends in tho enpiUaries of tho<e organs. From 
these it is collected by the pnlmo&ary reins whicli carry it 
back to thelcft auricle, whence it passes to tlie left ventricle 
to recommence its flow through tlic Body generally. 

Tho Courao of the Blood. From what hn« bcvu nud it 
is clcur that ilie movement of the blood is a circulation. 
Sturliug from any one chamber of the heart it will in Umo 
return to it; but to do this it muKt pass through at l^st 
two sets of capillaries; one of these is connected with the 
aorta and the other with tho pulmonary artery, and in its 



POSTAL CIBCULATIOX 



SU 



' 



I .wcuit tbo bloo^ returns to tho lit-iirt twit-o. LcaviDg the 
Kft Mds it Ktuniii to the right, uuil leaving the right it 
returns to the left; luid Ihorcu noroud for it from one side 
o{ the heart to the other except through it onpilhtrv network. 
Moreover it aln-ays leaves from a vciiiricle through an 
artery, and returuN to an utirtdo through ■ Tcin. 

There i* then really only one circulation; but it is uot 
lUKiotiimon to speak of two. the Bow from the left .title of 
the heart to the right, through the Binly gencrully, being 
culled the fyxlamie circulation, and from the right to tho 
left, through tho luufrs, the pulimnar^ circulation. But 
«inw after completing either of thette alone tho blood in not 
again attho point from which it etHrted, but ie separated 
from it by the septum of thi> lu-jirt, neither is a " circulation" 
in the prii|)er sense of tho irord. 

The Portal Circulation. A eortain portion of the blood 
which leave* the h-ft ventriele of tho heart through the 
iiorta has to i)a>« through throe sots of caiiillaries before it 
con ugoia roturn there. Thi.t in tho portion which goes 
throngh the stomach, spleen, pancreas, and iitteetinee. 
Arier traveling tho capillaries of thOKc organs it \a ool* 
lected inlo the portal vrxn which enters the litar, and 
breaking up in it into finer and finer branches like an 
artery, ends in the viipillaries of thnt organ, forming tlic 
second «et which this Mood ]>a.-uii>^ through on ita course. 
From these it is collected by the hepatic vtina which pour 
It into tho inferior rena cava, which carrying it Xa tho right 
aoricle. it hadstilUopii.<'< through the pulmonary caiiillariet 
to get hack to the left side of the heart, The portal vein 
m the only one in tho Human Body which thus like an 
artery fe«ds a cAjiillary network, and the flow from tlio 
«tomiioh and inlestinoe through the liver to the vena cava 
is often spoken of »« lh(> /lortnl n'rculaHoH. 

Diagram of the Cinmlation. Since tlio two halres of 
tlie Ik-utI are actually cimtpletely sejiaraliv] from one 
another by nn impervioiis jiarlition. i^though ]>laced m 
proximity in the Bo<iy. we may conveniently represent the 
course of the blood us in the uc^-om ponying diagmni (Fig. 
84) in which the ri^ht and left halves of tlio heart are rep- 



sie 



TBK nrntAS BODY, 



l-CHCiilccl at difteront pointa in the rasmilar syswm. Such 
an arrcingemoiit innk&9 it clear llmt tfic Iicrirl i» rciillj two 
ptimi^ wnrking side by sidn, and e«cb euj;agt>d in fmviiig 
the blood to tbe other. Starting from llic left atiricle. ia, 
uid folluwing tbe flow we traoe it through the left vt-inri- 
de and along tbe brandicx of the 
aorlii inli> tlit'hViiU'iniccapilliiricA.sc; 
from thence it paises back llirougb 
tho igttemiu \eins, vc. Reaching 
the Hglitauridc, ra, it is Kcnl into 
the right ventricle, re, and thence 
through the pulmonary artery, pa, 
to the lung cajiillariew, /«■. from 
which the pnlmonary veiun. /if, car- 
ry it to the left atiride. which drives 
it into the left veniriclc, ^r.and this 
sgiiin into the 11Q1I.&, 

Arterial and Venoua Blood. The 
blood *\Kt\ fluwitig in llie piilmu- 
nory ca))illiiricH giveit up carbon diox- 
ide to tbe air and receives oi\-gen 
from it; and «nce ita coloring mut- 
ter (hicnioglobin) fonns a scnrlet 
^,F». d-wsw^ni of iM compound with oxjiren, it fl<iwH to 
ing Au u r-.™.. .. .(i.b-i.. tbo Kiv iiuriclp in the pnlmonary 

Oltl««ldPDl»l ■"lIlMwrilimrai . , - 1. 11 „,, - 

iniu wnwi.iiii,- r m, riitlit reins or a bright red color, Ihia 

■ad Mt baK "I ill'- lii'iirt, • '._-.' .-■ ', I 

I 1 „^,,„. folor it mainttunK iinln it reaches 
> V'rkic! tbo systemiti capillaries, but In tb^se 
'■."X^\e '■' 1°"*" '""''*' oxygen to the snrround- 
p!"pS- '"8 tissue* ^nd gains much earbon 
c". pui- dioxide from them. But the blood 
coloring matter which haj< lost its 
oxygen has a dark ptirple-black color, antl since this un- 
oxidiEcil or "reduced" hwmo^iobin is now in excees, the 
blowl reluni* to the heart by Iho venip cavti" of a dark 
|iiirple-red color. This color it keeps tinlil it rendie.i the 
lungs, when the rcdui'cd hn^mnghibin becomes iigain oxi- 
dised. The bright red blood, rich in oxygen and poor m 
oarboD dioxide, is known as " Hrtorial blood" and tbe dark 




OImmI otrCK^* Willi rn'i»piiin 
" "" ■ III,- ■■! I" 

«U«h are I- I-- 
nlflla thv a I I 
fn,rlO(wiri. :- . 

taa^MMir 

Mcln: o». ". 
«BplUM4m 
(M, pulmoiNi 
moiMry ui«iiiii>i 
miHHMT rauu. 




emjTCTmtE of tbb »ta>oi>- vessels. 



sir 



red a^ " tcqoub blood:" and it mnst be borne in mind that 
Uic t«riii# ItiiTC tliii (iixiitliar t<i?liTiieal moaning;, miJ t!utt 
the putmoiiary vtins coiit»tm ar/erial blood and tbo palmo- 
nary rirterifg, venom blood; thi> clinngo from ftrterial to 
veiiou.-< taking |)lace in the syat^mic capillaries, ftnd from 
venous to arterial in the puliiionitrv cajiilliiric-s. Thu 
(Ummbcr«»f Ibu iiearl itnd iIk- great Te^cU contaiiilng ar- 
terial blood are shaded red in Fig^ 79 and 80. 

The Structure of the Arteries. A large artery can by 
careful disaeetion hi- Mj)!iraU'd iulo three e(iat«; an inlrrtuil, 
middle and ouier. Thi! internal coat tears readily across 
the long HJti:i of the artery and oonairts of an inner lining 
of flattened nucleated ccUa, and of a raiisblc number of 
layers vompoKcd of membraneK or netivirkfi of elastic tissue, 
oatside this. The middle coat is m^de U|i of altc-rnating 
layvrs of elastic libru:! »nc! plain inu^c-nlar tissue; the for- 
mer running for the most gtart longitudinally and ihclattcr 
ocrosi tho long axiH of the tqsmI The outer coat is the 
toughent nnd slrongeiit of all and is mainly made up of 
vbit« SbrouB connective tissue but cootuine a considerable 
amount of eliutic tiMue alHOi. It gradually ithados off into 
u loose areolar tissue which forms the nkMth of the artery 
or the liinuii luii'rntitia, and padcK it between surrounding 
parld. The smaller arteries have all the ela^itlc olcmcnt« 
Ie£s developed. Tho internal coat is consequently thinner, 
itnd the middlu coat is made up mainly of involuntary mna- 
culur Sbrcs. Ait « result the large arteries iu« highly claft- 
tie, the aorta being physically much like a piece of indian- 
rubber tubing, while the smaller arteries are highly con- 
triiL'tile, in the phy^iolngind wnsc of tho word. 

Structure of the Capillaries, lu the smaller arteries 
the outer and middle cutttx gradually di^ajipeiir, and tho 
eliMtic layerit of the inner oout also go. Finally, in the 
capillaries ibe lining epithelium alono u left, with a 
more or less developed layer of coonective-tiasue oorpnacles 
around it, roprewntiug the remnant of the lunicaadven- 
titia. These vessels are thus extremely well adapled to al- 
low of filtration or diffusion taking plnuc tliruiigh their 
thin walla 




218 



raw BUM AX BODY. 



Struotoro of tho Voina. In these the same three prl- 
m^rv C"iiU .1-1 i:i thi> uiUHos raav he found: Ihe iuner iiml 
iDtddle coats are less d eve lopod wliilo tho outer one remaina 
thick, und iitiuailu up almost cntirclyof white fihrons tissue. 
Hcnoe venous walls are kuipIi thinner thiiii thasc of the 
corrosponding arlvrics, and tho veins collap^o when emplr 
wliiiu the Btonter artv^Hvs reniuin i>]Ktii. Hut Ihi; tcniiiity 
and toughness of their outer twata give the veins greut 
strength. 

Except the pnlmonarj- artery and the norta> which po:"- 
^»i^ the semilunar valvt^x al. tlu-ir ciirdiuc orif)i-cR, the 
arteried poBseas noralvoH. Many veins on the contrary have 
Nuch, formci] by «i-militnur pmiohcx of the inner coat, ut- 
taciicd hy one margin Jind having that turned towards the 
heart free. These valves, sometimes single, oftener in 
pair*, and Konielinies threu at one level, permit hlood (o 
flow only towards the heart, for a current in that direction 
(aa in the up]ier dijignim. Fig. 85) pm-iwe* Ihi.' valve eh)*o 
againiit the side of the vejisel and 
meets wiih n<i ohstniclion fruiu it, 
Should any hiick-tlow bo attempted, 
however, the current closes up the i 
valve and hars Jt^ own p)u>saf^ afl' 
tudiculvd In the lower figure. 
TJiese valves are most niimeroua 
in superficial veinfi and those of 
musoular parts. They are uVcnt 
in the venii' eava* and the portal' 
and jiuhnouary veins, TTsually the 
vein is a little diluted opposite a valve and henov in imrl.< 
where the valves are mimciriiiw geU a knotted look. On 
rotnpre«sing the forearm so as to sl.ip ilin flow in it^a snh- 
I'lUaiioous veinv and muse their dilatation, the points nt 
which valves ai-e placed can he rei'ogni;%d hy their swollen 
nplH-uranw. They are most frequeatly found where two 
veins communicate- 



Ft* RS,— nk^niin to lllm- 
Inii. (hv nioitc of •cTloi] ot 
ilii-vnlmof Uienlnn C ihu 
rnfiilinn. Md B, Van livart 
I'Ud ut tho TllWtl 



CHAPTER XV. 

THE WORKING OF THE HEART AXt) BLOOD- 
VESSELS. 



The Beat of the Heart. It is possible by methods known 
(o ]ihvi4iologiste to open th« chvsl of a liTing narcotized 
iiDimd, Buch III a nibbit, and a-e its heart at work, lUtcr- 
niiloiy ooiilracting nml dimiiiishitiK the cavitien williin it 
and relaxing and expnnding Ihi-ni. It is then obserred 
thut eucli Wftt coinP)eDOi>K at the months of the great reins; 
fMiD there runs over thp rest of the auriclta, and then 
over till' veiitricW; the auricles oommencing to dilute the 
moroent the veatrieloe coinmoDce to contract. Haying 
liiiiiilied llicir cvnliticiion, the ventricloo aloo comment l<> 
dilate and ho for sone time neither tbcy nor the anriclus 
ore contracting, but the whnle heart expimdin^. Theeon- 
Imction of any part of I he heart is kunwii as its sysfotf 
and the roliutiition as it« diantole. uu<l cince the two ^ides 
of the heart work aynehroD(>u«ly. the auricle* together and 
ihe rentricles together, we may dcwrilw a whole ■■cardiiic 
pf riod" or " heart-bi-iil" as made np MtcoeBsively of auricu- 
lar »i/t:tolf, vrnirtrii/'ir ittt»lolf. and pawe. This cyclt- in 
re])eated about seventy times a minute; and if the whole 
time occupicil by it be Mibdivided into 100 purti<. ah»ut 
9 of thcAo will he oocupiiil by the unricular NT^tole. about 
30 by the ventricular systole, and 61 hy the pansc: 
during more than half of life, therefore, the niuvelea of 
Iheheart areat rest. In lhe/wM«Pthe heart if taken be- 
tween the finger and thnmb feels soft and flabby but dnr- 
ing the systole it (especially in its veatriciihir portion) be- 
en mes hard itud rigid. 

Change of Form of the Heart. During its systole ' 



»0 



TOE nUMAX BODY. 



heart becomc-s ehortcr xui] niundor, mainly from a ohanjB;e 
ill Ukd shajm of the rentricks, A (.-roiis-sodtuii uf thi< lioart 
at the \i-MD uf tlioa^ hittttr during diustole wonlil be elli))ti> 
cn\ in aiitlirif. with its longdiamuttT from right to left: 
(luring the sy^loU' it i« inwre circiilur, tliv hmgaxiw of tlic 
elJipso bi't'i'iuiiig shorteued while ilie doi-su- ventral diameler 
niRiuin.-) little altered. At the aiimo time the length nf tho 
vonlridefl is Ifswiu'd, i\\v- apex uf the lioiurt approaching 
the buM and htreoming blunter and rounder. 

Tho Cardiac Impulse. The buiuau heart lies with it« 
ajK-x l.oiii'liing the ehciit-ffall between the fifUi and sixth 
ribs on the left eido uf the brea^t-bune. At cvcrj- Ih^i u 
sort of Ijip, known as tbo "wirdiae impiiW" or "aiH-it 
W-at," may bo ft-lt by the finger at thiit jidiiit. There is. 
however, uw aotuiil " tapping"' since the heart's apex never 
leaves the chiiit-wall. During the diacloli^ the soft vculri- 
clea yield to tho chost-wall where thoy touch it, but dur- 
ing the «v.4t«le they bivonio htird utiil tvtiKe and pUKli it out 
a little betweeti the ribs, and so oaiL-ie the ajiex beat, tiinue 
tho heart hticoiiii-K sliortor daring the ventriculur syetole it 
might bo HupjHwed that at that time the apex would move 
up a little in the cheft, Tliitt however is not the case, the 
ascent of the apex towards the bnfe of the ventricleH being 
compciiioited for by a tnovenii.'nt. of the whole heart in the 
opposite direction. If water he ptim])ed into an elastic 
tiil3e. already loliTiibly full, tliis will be difilonded nol only 
tninsversely bitt longitudinally. Thi* is what huppeiiit in 
the aorta; when the left ventricle oontiiielx and pumps blood 
forcibly into it, the oliuitie artery is elongated as well as 
widened, and thi.* lengthening of (hat limb of itti arch »i- 
laelied to the heart punhes the latlfr down towards the dia- 
phrugm, and compensates for the upward movement of the 
upex due to the shortening of the ventricles. Hence if tho 
expOK<d living heart be watched it appcnrs aa if during the 
Bvtttole the biwe of t]io heart moved towards the tip, nither 
than the reverse. 

Bvonta oocurriog within the Heart dtiring a Cardiac 
Period. Ijet us commence ill the end of the vcntricnliu' 
systole. At this moment the semilunar valves at the orifices 



A 



PRBNOMSyA OF TUB BEART8 SEAT. 



m 



of the aoru and the ptilmonarr artery are closed, bo thai no 
blood can Qow buck from those tc«^-1)!. Thu whole heitrt, 
however, in mti itiid disUntiiMi' ami viclda risidilv lo blood 
flowing into it from the jmlraonun' veins and the Ti-iiie 
cavfc; this pii»>cs on tliroti^li the ojiou mitnd iind tricti»|iidj 
Talves luid fillH up the dilnting v«ntridc«, va well lis tJiaJ 
uuriclfs. Aw tlii^ Ventricles fill, back cnrrenti* are set up 
along their walls and these carry up the flaps of the ralvea 
80 that by the end of the pitusc th«y kv iituirly cloKcd. At 
this moment tho unricles contract, and since tliis contrac- 
tion commences at and narrows tho monthti of tho reins 
oponiDg into them, and at the «umi> lime tho blond in 
thow vpAsek oi)[KiBe3 some resistance to a back-flow into 
them, while the still flabby and diluting ventricles ojijiose 
much 1l>ss rc«istHnce, thogvniM'ol result is lliut thecouLract- 
ing auricles send blood munly into the ventricles, and' 
hardlv anv back into the veins. At the ntm« time the in- 
creased direct current into the ventricles produces ft-grenler 
boclc current on th» sides, which, as tho uuricle« ceiute their 
contraction and the flllpd venlride^ become tonsc and proM'i 
on the blood inside them, completely close the anrioulo- 
veutricnhtr valves. That this incrciwod filling of the ven- 
tricles, due to auricular oontraotions, will close Uie valves i< 
seen ow-ily in a sheep's heart If the aiiriclca be carefully ' 
cut Hwny from Ihis so as to expose the mitral and tricuspid 
valves, and water be then poured from a little height into 
the ventricles, it will be seen ttiat aa these cavitie;^ sro filled 
the valvc-flups are floalcd up and close the oriflcos. 

The auricular contraction now ccusesand the vontricnlar 
commences. The blood in each venlricle is impri.ioncd 
l)Clwccn Uic unrtculo- ventricular v^vee behind and the 
semilunar valves in front. The former cannot yield on 
account of the corda> tendinee flzed to iJieir edges: tho 
temilun.irvHlvi.vf, on tho other hand, umopi'n outwards from 
the vei]tricle and let the blood pcuw on, but they iiiv kept 
tightly shut by the pressure of the blood on tlicir other 
Kides, jiii>t lis the lock-gates of a canal are by the pressure of 
Iho water on tlieni. In order toopen tho canal-gates water 
18 let in or out of Llio lock until it utand« at the same Ict^ 



TBE BVMAJf BODY. 



on each side of tdciii; but of course they might be forced 
opeu without this by upplyiug Eufficieot pawer to overcome; 
the higlKnr Hutci' [iro^i^iiii; on uiiv side. K i^ in lliiii latter 
wiij ihut the semilunar valves are opened. The contracting 
Teiiiricle tightens itii ^ip on the blood inside it and becomes 
rigid tr) tliti toiiuh. Aii it sqnecze« harder and harder, at 
last th<! pressure on the blood in it t)ecome.'^ grcnter ihan 
the prceaiiro exerted on the other side of the valves \.\\ iho 
blood iti the arteries, the Sap^ are i)iiiilicd open, mid the 
blood begins to paae out: the tentricle continues its con- 
tnK^iioQ imtil it hs» obliterated it« cavity tind coinjilclely 
emptied itjivlf. Then it commences to rohu and bloodj 
immediately to flow back into it from the highly stretched 
arteries. This back current, however, cnttlics the pockets 
of the Kemiliiiiiir valve*, driv«w them back and clows the 
valre eo as to form an impaesble boiTier; and so the blood 
which haa been iorced out of either vcQtriclc cannot flow 
directly buck ini'i il. 

Use of the Papillary Utiaoles. In order Ihat the con- 
tracting vonlricln* may not force blood buck into llie 
auricles it Is estsential that the Ihips of the mitial luid 
tricuspid valves be mainlined horizonlalty across the ojien- 
ings which they close, and be not pushed back into ihtt 
auricle^. At the commencement of the ventricular r)y»> 
tole this ia provided for by the uonlas tcndineee. wliich are 
of *iieli a length m to kec]> the edges of the flaps in appo-^ 
aitiOD, a paeition which is farther secured by the fact that 
each set of cordaj tendiacte (Fig. 81*) rudiuting from a 
point in the Teutricle, is not attached around I he edges of 
one flap but on the contiguous edges of two flaps, and so 
tends to pull them tof^hor. But as the contrueliug ven- 
tricles ciioi'teu, the cordte tendineie, if directly fixed t» 
tlicir interior, would bo slackonod and the valve-flaps 
pu«hi;d up into the uuriclu. The littlo papillary muscles 
prevent this. Shortening as the ventricnlar systole proceeds, 
thfty keep the cordrn taut and the viilvcs closed. 

Sounds of the Heart, tf the car Jh? placed on I he chest 

OTw the regiiin uf the heart during life, two dislinguish- 

ftble sounds will be heard during each cardiac cycle. They 

»re known jiesj'ectivelyastbo first aud second rounds of the 



■ P. aOB. 



d 




BTByTS Of A CABDUO CTOLR 



its 



I 



bMit. The firxt i» of lower pitch and lasis longer than the 
second nnd sliarper Boand: vooilly ttivir ohat«ct«r Riny be 
toloniblf imitated by tbo vonU IShb, diip. The cause of 
tbe second sound ia Uio rioijnire, or ae one might say the 
"clicking tip," of tbe scmilnDar tuIvos, ^niw it occitn) at 
the moniput of their clo«iiround ckw.i'ca if ilioy Iw" hooked 
back in h liririg animal. The origiu of the first «ouiid m 
Htill uncertain: it takes place dnriiig the ventricular syfWlc 
and i» probiibly dne to vibnition:) <.)f the ti^nse ventiicular 
wall al lliuL lime. It i# not due, aa bae been euppoecd. to 
tbe auriculo-ventricnlar ralvee. since it may *1ill be lieard 
tu a bvHtnig hvurt empty of btoud, and in which there could 
h« no olo»urc or tenHion of those ralres. In various forms 
of heart disease these sounds are modified or elouki-d by 
additional '■murmurs" whicharise when tbe cardiac oriruvs 
are roughened or narrowed or diluted, or tlic Talves ineffi- 
cient. By jwying attention to tlie character of the new 
tonnd then heard, the exact period in the c:irdiac cycle at 
which it occurs, and the rc^on of the chest-wait at which it 
is heard moiit di.4tiiictly, tltc phy«ioiaucau often get impor- 
tant information as to ila cause. 

Dlaf^mm of the Evonta of n Cardiac C70I0. In the 
following table tliC phciioiiicna of thi- iienrl's beat are Tti\t- 
TMonted with reference to the changes of form which are 
seen in an exposed working heart. Events in the i<amu 
Vertical cobunii on-iir ^imultjiiieaajilj; on the some horitou- 
tal line, from left to right, sneceesively. 




inpulM 

Awtonlo-tvqMe- 

uUir imlrva. , , . . 

SemnunarnUToi. 

SmuhU. 



9S4 



TOE IIVMAX BOOT. 



Fonotion of the Auridon. Tlie ventricles have to do 
the work of |iiiin|iinj; \\w lilixiil througli tin- blood- vessels. 
Accordingly their walla are fsir thicker and more muscular 
than thoiO of the auricles; itiid the ktfl vcniriole, wliieli hus 
lo force ihc Wood over tlio Body gi-iierally, is aloufer tliati 
the righl, which haa only to send blood around the coin- 
pamtivcly short pulmonary circuit. The circulation oT iho 
blood \i in fact mainluincd by Ihe ventricles, and we 
bave to incjuire what U the use of tlie auridea. Mot uu* 
frequently the heart's action is described as if the nuriclca 
first filled with blood and then oonlriiPted mid filled the 
ventricles; and then the latter contracted and drove the 
blood into the nrtcric*. From Ihc account givvu abovd, 
however, it will bo seen that the e^c-nls are not itcciirately 
BO repreBenf«d. but that during all the pause blood flows 
on through tho auriclw int« the vcnlnclv*, which latler 
are already neiirly full when the auricles contract; tbis con- 
traction merely complefing (heir filling and finishing the 
closnrc of the aurioulo-rentriculnr valves. The real use of 
Ihc uuriclo-iii is to alTord a reserroir into which the veins may 
empty while the c<iiii]mrativt;ly long-liwting TCMtiir^ular 
Qoutraction is taking place: they also largely control the 
Ribouiit of work done by the heart. 

If ibo heart consisted of the ventricle* only, with valves 
at Ihe points of entr>' and exit of the blood, the circulation 
could be maintained. During diai'tolci the vcnlnde would 
All from tho veins, and dnriog syslole empty into the ur. 
U'rii.^. But in order to aoconijilifh this, during Ihe systole 
the valves at the point of entry must be uhwiil, or (he teu- 
Irirltt would cmjjty itself into the veins as well as into the 
arteries; and this closure would necessitate n gwat loss of 
lime which might be utiliKcd for feeding the pump. 
Thi* ii iivwided by the iiurieles, which are really resei- 
voirs at tlio end of Ihe venoui! sysicmi cnlleclnig blood 
when tho ventricular jmnip \g. at work. When the ven- 
tricle-* relax, the bbmd entt'ring the auricles flows on 
into them: but previiiu.H!y, during the ^^^ of tho curdim; 
cyclo occupied by the ventricular systole, the auricles 
have accnmulaled blood, and when thov st loiit con> 





FCXCTIOy OF TOE AVRICLBS. 



325 



Intct thtj^Mud OD into tlw rentribUw tli'iH ftcouniuliitioti. 
Even were the flow from the voioa Btopiiod during the 
stiriculur oiniilntctioH Ihiit would be of cumpuriilivt-ly Uttic 
ooiuieqaenco, since that event ocoDpies an brief s time. 
But, although no doubt tiomewhst leseeoed, l\iv emptying 
of liio vciiii into thv hnirt iloos Dot itoctu to !)<.', in lieiiltli, 
eto|>iied while tiie auricle is contraciiug. For at that mo- 
nicnl ihe veutricle is n-Imcitig nnd it^cciTcs the blood from 
the aunok* under a 1(^ prcwiury than it eiilcm tho latWr 
from the veins. The heart iu fact consists of a ooQpIo of 
" tutii-pumps" — the uuriok-s — and u coupl« of "for<H'- 
puniiw" — tlie ventrii-k'j; and so wonderfully perfect idi the 
mechanism that the supply to the feed-pumps is never 
Mtoppod. The auric1e« are iiov«r empty, bt-ing supplied all 
the time of their cmitra^ttion, which ia never so great as to 
obliterate their caviliea; while the ventricles coiitaiu no 
blood at the end of thdr systole. 

The auriclcM al.«o govern to a, ccrtuti extent the amount 
Af work done by the veiitnclcR. ThcM Utter ooiitmct with 
more tlmn sufficient forov to completely drive out nil the 
blood contained In them. If the auricles contract more 
[loworfully and empty thcmselvc:! more oomplotidy at any 
given time, the ventnele-i will contain more blood at the 
commencement of iheir systole, and have pumped out more 
at its end. \ow m wo itliall m.'e in Chapter XVII., the 
contraction of the auncloa U under the control of tlio 
nervous system; and tJuough the auricles the whole work 
of the henrt. In fact the ventricles represent the hnite 
force concerned in maintaining the circulation, while 
IRC aiiricle-t arc part of a highly dcvelo(icd co>ordiniiting 
mechanism, by wliicb the rate of the circulation ia governed 
according to the needs of the whole Body ut Ihe time. 

The Work Done by the Heart. This can Iw calculntcd 
with a]>proiimate correclnesa. At each systole each ven- 
tricle sends out the same quantity of blood — ubont 180 
granui {6.3 ounoes); the pre*»ure excrU-d by the blood 
in the aoru against the semilunar valvo^ aud which the 
veutricle has to overcome is about that which would be ex- 
erted ou the tuune surface by a column of mercury 200 




336 



TUM UUMAJi BOb Y. 



iiiillimeterfi (S incbeK) liigh. Thu left -rentricle therefore 
driTiM out, neveiily time* in a iiiiiiut«, I«0 gnims (6.3 
oances) of blood agaiiuit ttii^ prcssuni. Siuc« the specific 
gravity of mcrcurj' is Vi.h un<l iliat uf blood may for prac* 
tical parpo»eH be taken as 1, the work of each stroke of the 
Tentncle is cciuivuU'ut to rui«iiig 180 grams (6.3 ounces) 
of blood aOO X 12.5 = 2300 millini. (8.2 feot); or one 
gnim 45(1 iuet«rs (one ounce 51.60 feet); or one kilo- 
gram 0.13 meters (one lb, 3.93 feet). Work ia iiieaiturGd 
by the aniotiDi of tnvTgy needed to raioo a di-fiiiite weight 
u given d!«tanoc iigaiiiot gravity at tho earth's Miii-fuce, tiie 
nnit, called a kilogrtimmeter, being either that necessary to 
raJKO one kilu^^nim onu meter, or, called n foul-ponnd. tltat 
uecossary to raiee one pound one foot. Expressed thus Ihu 
work of the left ventricle in one minute, when the keart'ii 
»t« 18 seventy strokes iu that time, i8 0.4S X 70 = 31.60 
kilogramineters (3.23x70 = 226.1 foot-pounds): in one 
bour it is 31.50 X 60= 1890 kilogrummeteni (^3G.l X 60 
= 13,5116 footpound))); and in tweuly-fonrhour* 16H0 x 24 
= 43,3C0 kilogrammeters (325,584 foot-poiindsj. The pres- 
snrein tho pulmonary artery against which the right ventricle 
works is about ]^ of that in the (lorta; hfiicc tbi'- veiitriilo 
in twenty-four hours will do one third a^ much work as the 
loft, at 15,120 kilogrammeters (108.ft28 foot pounds) and 
Adding this to the amount done by tlie left, we got as the 
total work of the ventricle in a day tho immense amounL 
of G0.4!i!OkilogiammeteTB(4M,llSfoot-pound«). If a man 
weighing 73 kilognune (165 lbs.J olimbcd up a mountain 
800 metere (2644 feet) high his skeletal mtiscles would 
probably be greatly fatigued at the end of the ascent, and 
yet in lifting his Body tliat height they would only have 
performed the amouut of work that the ventricleeof the 
heart do daily without fatigue. 

The Flow of tho Blood Outaido the Heart. The hloiHl 
leaves the heart intennittentiy and not in a regular stream, 
a quantity being forced out at each syntole of the ventn- 
cIm: boforo it reaches the cupillarieH, however, this rhythmic 
tnoTement is transformed into a steady flow as may readily 
be seen by examining under the niicroseopo thin trans- 



r 



BIOODPLOW AS assy WITH THE MtCRmvOPB. W7 



jiarent parU of vanons animaU, a.i the ire1> of a fnig'tr foot, 
u muDMv'e «Hr, or the tail of n kiiihII fi^h. In conHeqaeticc 
of the Btcadintiss with whieh iho cjiptlhiHos i«i)))|il}' the voiM« 
tlie Sow in these is also nnafleoted, directly, by each beat of 
the heart; if a TeiQ be cut thu blood vrolls otit uniformly, 
whik' » cut nrt4!ry sjmrls out not only with much moro 
force, but in jeta which are much more powerful at regu- 
lar intervals correitpondiug with thu Byatolvij of the von- 
triclci 

ThoCirculationof the Blood as Seen in the Frog'a Wob. 
There i.-« wo mm-e r^icimiiin^ ur iiiTiTiictive |iheuoniciiijn 
tliftn the circulattou of thu blood o* i«on witii the mim>- 
soope in the (hm nicmbmne between the toes of a frog:'(( 
hind limb. Upon focusing beneath the epidermis a net- 
worit of minute arteries. voinM and cApiUuric^, with Ihu blood 
tlowtu;; through tbcm, comes into view (Hg. Kf*). The 
artenea, a, are readily recognizedby the fact that the flow in 
them w fa«U'»t umi from larger \a iimall^r branches. TJin 
laltor are seen ending in capillaries, which form ni'twoHw, 
the channels of which urc ull nuiirly e<)unl in dixe. While 
in Uio vein* arising from the Lajiillary the How in from 
Huallcr to liirger irunka, and slower than in the ortorieti 
but faster than in the capillartee. 

Thu i-eason of the slower flow of the mpillAries Ja thst 
their united arm w cnntuderahly greater titan that of the 
iirlerii-ft supplying them, ao that the same qUAiitity of hlood 
flowing through them in a given time, has a wider channel 
to flow in mtd moves more slowly. The Hfou of Ihe veJTH 
is nnnller than thut of the capillaries but greater than 
that of the arleries, and lieui;i> the nite of movement in them 
IS alw intermediate. Almiwl nlwavM whe« an artery 
divides, the area of ilahrancheu) is* greater than that of the 
mam trunk, and so the arterial current becomes slower and 
slower from the henrt onwards. In the vein* nn the "ther 
hand, the area nf a trunk formed by the union of two or 
moro hranchi-s tit lesH than that of thu hnincliM together, 
and the flow bccomen (juicker and qnicker towarrls thtt 
heart. But even at the heart the united ctxtss-sections 
of the veins entering the auriclea in grcjiter than that of 



298 



THH nVMAJf BODY. 



th« Art«ric« Iraviiig the vcntriolcii, an Uiut, itincca« niQv]i 
Uliiod returns to the boart in a given time tta leaves it, the 
rate of the current in the ]>iilmuiiury vciiu and the xewe 
Cttvn is loiu tlutii it) the puImoiiitrT artery and auMii. Wv 
may represent the TOSCtUiir aytitein ;is a double cone, widening 
from the ventricles to tlio citiiillarifj and luirrowing from 
rlifr latter to the anricks. Jiiet aa water foreed in at li 
narrow end of this wauld flow iiuieke^t there and elowest 
at thowidi'fl jiart, m the \AihsA lliiwi* i|ui(;k<^!<l in tlie norta 
and slowest in tba capillaries, which form togetlier a much 
wider ehiinnd. 

The Axial Ourrent and the Inert Layer. If a Kmall 
artery in the fioj;'* wfb lie dnwly ex;iniini:<d it will be Jtwn 
that the rate of Ihiw \i not, the Hauic in nil {mrtti of iL In 
the centre is n very rupid carrcnt carrying along nil the red 
corpuscic" Hiiil known a* the axiiil *trtam, while n«ii- thti 
wall of the vesjwl the flow \» niiicli slower, ox indicated by the 
rate nt which tbe jiale blood corpuscloH are nirried along in 
iL Tbi« \»i\ purely )>lij'fical phenomenon. If any li<|uid be 
forcibly driven through a fine tnbe which it wets, water 
for instance tbrougb a glass tube, tJie otitcrmoi^t layer of the 
litjiiid will remain mutionlc«i in eoiitact with tbo tube; 
\hv next Ifiycr of molecules will move faster, the next 
fawter still; and so on until a very rapid current is fonnd 
in tbe centre. If solid bodicx, »» powdeied Ktiling-wax, 
bo suspended in the water, th<-;*e wilt nil be carried on 
in llie cenlnil fiwter current or iirial *trraiii. just as the 
red oorpuBelos are in the artery. The white oorpusoles. on 
Bceouut of their jiower of executing independent amshoid 
movement.4 »nd tboir consequent inegiilur form, get fre- 
quently pnMied nnt of the axial current, so that many of 
them fire found in the inert l«ycr. 

Internal Friction. It follows fi-om the above-stated 
fncts that there i* no nntieenhio frii-tion between the blood 
and the lining of the vessel tbrougb wbicb it flow»i; since 
tbe outomioiH. blood layer in contact with the wall of tbe 
vessel is almost, motionless. But there ia very great fric- 
tion between the different connentrie layers of the lif|nid. 
Bincc each of tliem is moving nt a different rate from tbotw 




TBB CAPILLAST CIRCVLATtOS. 



820 



• 



I MpOUi 



in contucl witli it on each side. This form of friction is 
known iu hydro-dymimiL'a u " JnU^rnHl friction" «ud it is 
of groiit impDrUrioe in the circulation of the blood. In- 
ternal friction increaaM very fast as the calibre of the 
tube through which the li'jiiid IIowm diTiiitii>lics: so that 
with tht) stmo thus of flow it ia dispro))ortiunatel; much 
greater in a small tube thau in n larger one. Hcnoo n 
giren (juutitilv of li'|uid forccti in a minute through ono 
largo liiW, would exjwrifince much leas resistance from in- 
ternal friction thau if sent in the same time through f«ur 
or five umallcr tubu^, thcuoilt^ trun^vvrsc sections of which 
were together equal to that of the single larger one. In 
the blood-vessels the increased total arcu, and couEoqnently 
slower flow, in the wnaller chniinvlu [larily counteracts i\\\» 
increase of internal friction, but only to a comparatively 
slight oxt«nt; so that the internal friction, and conse- 
quently th« rwstanco to the blood-flow, \i far greater in the 
capillariea than in the amall arteries, and in the «inall ar- 
t«rie« than in the Iarg« on«a. Practically w« may regard 
the arteries as tubes ending tn a sponge: the united areas 
of all the channels in the latter might be considerably 
larger tlutn that of tlic Kujiplying tubox, but the friction to 
be OTercome in the flow through tliem would be much 
greater. 

The ConToraion of the Intermittont into a ContinuouB 
Flow. Since the heart itend.t blood into the aorta inu-r- 
mittcntly. we have still to inquire how it is that the flow in 
tJie eapillaricv is continuous. In the larger arteries it is 
not, since wo can feel thorn dilating us the "pulff." by ap- 
plying the finger over the radial artery at the wrist, or the 
tcmpond nrliTy on the side of the brow. 

The first cxpUnalton which suggestii it*clf is that since 
the capiicity of the blood-TOSsels increases from the heart 
to the capillaries, an acceleration of the Bow during tho 
Tentricnlar contractiou which might be very manifest in 
the n')>scls Dcjir the he-art would become lesa and leas obvi- 
ous in the more dislant vckscIs. But if thiM wero so, then 
when the blood was collected again from the wide capillary 
sponge iolo the great veins nuar the heart, which together 



«80 



TBS aUMAS aODT. 



Rn.1 .V 



i 



uro v«r3r littie bigger tlian tbe aorta, vrn ought to find a 
pulse, but ve do not: the vcuoiih puUe which eoiuetiiiie« 
occurs hiiTing <iuilo a differeui cause, being due to s back- 
fiow fixjui tho Buriclen, ur ii checking of tlie on<flow into 
them, daring the canlluc s^iitole. The rhythmic flow 
oiiUKud hj \ha huurt is theivfore not merely ctoitlc«d in tbaH 
small arteries am] ca)>illaricii but abolished \a them. ^| 

U e can, however, readily contriTo conditions outride the 
Body under which im iDtenuiitent m|>ply is tra&sfortned 

into a coulinuoni) Bow, 8a 
[ici»e wc hate two TCRttelH, 
and H (Fig. SC), containing 
wiiter and connected below io 
two ways; through tlie tube 
a on wliich there is a pnmp 
provided with rnWes ko that 
it can only drive liquid (ram 
A tM B, niid through 6, 
which may be left wide open 
or Hiirrowcd by the cUtnp e, 
at will If the appanttus be 
left at rest the water will lie at the same level, d, iu each 
vesiael. If now we work the pump, at each stroke a cer- 
tain amount of water will be conveyed from .1 to ff, and 
as a result of the lowering of the level of liquid in A and 
it^ rigo in B, there will be immediately a return Bow from 
B to A through the tube A. A, in these circumstances, 
would represent the venous system, from which the heart 
constantly takes blood to pump it into B, representing tiie 
arterial system; and b would rcpren-nt the enpillary vessels 
through which tho return flow takes jilaoe: but, so far, wc 
Bliould hiivo as intermittent » flow through the capillaries, 
b, as throu;;h tho hoart-punip, a. \ow imiigiiie A to be 
narrowed at one point so as to o))[)o»c resistance to the 
back-flow, whilethepumpgoeson working steadily. There- 
salt will bo an accumulation of water in B, and a fall of it« 
level in ,1. But the more the difference of level in the two 
resiwls Increases, the greater is the force tending to drive 
nater back through b to A, and luorv will flow buck, under 




Fia. M 




VAVaS OF STKADT CAPILLABT BLOOD FLOW. 231 




(lie greater dilTcrence of pre«!tiire, in a gircn time, nntil iit 
Ijwt, whtn the water in B has readied a wrtaiii lerel. if. 
and thi»t in A hiw eorre^ipoiidingly fiillcn to d". the current 
through h Hill OitrrT bnok in one minute junt tio much wmtcr 
M the pnni{) Hcuds the other vny. and this back-fiow will 
Im nc*rly constant; il will not dc|H'iiil dirwtly upon the 
strokes of the pump but upon UiR head of water accumu- 
lated in B; which head of water will, it is true, be slightly 
increased at cueh iitroko of tlio pump, but the increase will 
be rcry small comparod with the whole driving force; and 
its influence will bo inappreciable. We tliiis gun the idea 
that an inoomplclc imiicdimcnt to the flow from the w 
teries to the veina (from Bio A in the diagram), such as ia 
afforded by internal friction in the cajHUiiries, may bring 
about condition!) wliicli will lead to a oteady flow through 
llio latter vessel*. 

Bat in the arterial system there can be no accumnlation 
of blood at a higher level than that in the veins, such as is 
snpposed in the above apparatus: and we mnst neit con- 
sider if tbo " head of water" eim be replaced by some other 
form of driving force. Il is in fact replaced by the elas- 
ticity of the large arteries Suppow an elastic bag in- 
stead of the vciMol B connected with Ibe pump, "a." If 
there be no resittancc to the back-flow the ouri-ent through 
A will be disoontinttons. But if resi»<tance be interpoiicd, 
then the clastic bag will become distended, since the pnmp 
sendi in a given time more liquid into it timn it parses 
back through b. Bnt the moi-e it becomeii distended the 
more will the bag ifquoezo tho litjnid inside and the faster 
will it ^nd that back to A, until at hut its squeeze is so pow- 
erful that in a minute or any other unit of time it tends 
buck into A m much us il receives. Thenceforth the 
li»ck-flow Ihvoogh b will be practically constant, being im- 
mediately dopondont npon the elastic reaction of the bug: 
and only indirectly npon the action of the pump which 
keeps it distended. Sudi n state of things represents very 
closely the phenomena occurring in the hlood-veseela. 
The highly elastic large artcric< are kept stretched with 
blood bv the heart; and the reaction of their elastic walK 



i9i 



TBS HUXAA' BOJ>r. 



Bt«udily sqQcezing on tbe blood in them, torcee it contina- 
otialy Ihi'ougti the #niu1l artprion iiikI eufilluries. The 
steady flow in the lattci' depends thus on two factoi-s: first, 
tbe elasticity of the lur^ urt«riec: and eecondly the re-1 
8i$t«nc« to their emptyiug, dc]iei)donl ti[)»ii intcnitil rHction 
in the small srtmeii and the i-itpiilaricf. which calls into 
play the cluticily of the huge tvk^cIh. Wciv the (-jiiiilliityj 
resistaiice or the arterial elasticity abseut tJie blood-tlow in} 
tho capilluricfi would hu rhythmic 



CHAPTER XVT. 

ABTERIAL PRESSURE. THE PUIjSB. 






~Vebor'a SchDma. Tt \« c1<-«r from the etatementa mode 
in tholiut ciiapier lliat it is the preMui-e exerted b; the el««- 
tic iirt«nea upon tbo blood iDsidc them which keeps up tli9 
flow through the cupillnrios, the ht-urt seniiij; to keep the 
bigftrlcHet tightiv tilled and solo cull ihc cliistic rcHetion of 
their walls lulo phiy. The whole circnlatioii de])cnd!i 
primarily of coun>o upon tho bcjit of the heart, but tJiis 
aixly iiidirecily goTcnia the t^pillury Buw, u»d siiico (h« 
lattOT IS the nim of the whole va^uliir apparatus it U of 
great iinportanco to know all abutil urtorial pressure; not 
only how great it is on che aTcrage but how it is altered in 
different vcsselM in vuriotu ciroumstiuioes go as to make the 
Dow through iJic capillaries of a gircn part the groiitor or 
Ics* according to circuu] stances; for, as blushing and pullor 
of the face (wlueh Irt-ijuenlly occur wiihuut nny change in 
tho skin elsewhere) prove, the quantitj' of blood flowing 
through a given part is not always the same, nor is it 
always iticreu^od or diminished in all part^ of the Uody at 
I he same time. Mo^t of what we know alxiut arte rial pres- 
sure has booQ ascertained by experimeats made upon tho 
lower Huimals, from which deductions are then made con- 
cerniuK what hajipens in man, tiinoe anutomy shows th»t the 
circulatory organs are arruiij;ed iijion the same plan in all 
the iiianimalia. A great deal can, however, be learnt by 
studying the flow of li<j«id« through ordinurr ehuHic tubes. 
Suppose Kc havo a set of such (Fig. S?) supplied at one 
point with a pump, r, prjtt»cMsing valvfi of entrj- and exit 
which open only in the direction indicatiKl by the arrt)vnt. 
tkiid tluil Uie whole system is slightly overfilled with liquid so 



234 



T/IK a UMAX aODT. 



that its elastic waUs aro slight!}' etretched. Th«M will in 
oonseijiieiioc press u{K)U tlio liquid iniiid« them and tbe| 
uoiouQl of this pressure will be indicated \ty tlio giiitges: 
so long as the piimi> l§ at rest it will bo the eamp every whenJ 
(and thereforo eqiiul in the gaages on B and -(), sintv 
liquid in a, ect of horiEontitl tubco communicating freelj'. 
ut tlicKO do ut D, always <)iittril>ute« iteelf so that the 
prcitxure upon it i» everywhere the Hitme. T^ct ihe pump 
e now contract once, and then dilate; during Ihe conlrac- 
tion it will empty itself into B mid during the dilntalion lill 
itself from A. Conwqacatly the prewture in B, indicatt-d 
by the gauge x, will rise and that in A will fall. But very 
rapidly tho liquid will rodiMribnte ilwlf from H to J 
through D, until il agntn exists everywhere under the »me 




preovre. Every time the pump worke there will occur a 
similar Mric^ of plienomcnu, uiid tlicro will he udishii'huiie« 
of equilibrium causing a wave to flow round the tubing; 
but thcro will ho no steady maintenance of a pressure on 
Uio Hide B greater than that in A. Now let the u)>por 
tube D he closed so that the liquid to g«t from B lo .1 must 
Uow through the narrow lower tulies D, which opjiose con- 
siderable ruHislanco to its pn»uige on account of their fre- 
quent branchiDgs and the grcJtt intL'inid frictiun in them; 
t]ieii if the pump workn fnqiiently enough there will be 
produced and maintained in if a praaaui-e cousidemhly higher 
tLan thut in A, which may even become negative. If, for 



WEBUJrS SCHEMA. 



235 



pxampic, the pump w«rks flO timta a luiauto and at each 
sirokf takes 180 cubic centimeUtrs of liquid (C ounces) from 
A nod drivi-» ii itiu> B, the ({luinlity «eiil ia ut ihv first 
stroke will not (on account of the resistance to its flow 
oflered bv the xmull bruuclicd tubes), lute all got bock into 
A before t)ic next ati-oke takcH plaoe, eciiding 180 mure 
cubic centimeters (6 ox.) into £. Conseq neatly nt each 
i>truko B will become mom and more distended and A more 
find more emptied, and the gauge x Till indioale u luucti 
higher pressure than that oa A. As Ji is more stretched, 
however, it sqnoezoe harder upon it« contcntJ*, until at last 
a time coiiic» when this squeeze is ponerful cnougli to force 
Uirough the small tubas juat 180 cubic centimctci^ (6 oz.) in 
a second. Then further uccuiniiUtioti in B ccusos. The 
pump »ends into it 10,800 cubic centimeters (360 oiincvs) 
in a minute at one end and it squeeses out exactly Uiat 
amount in the same time from it4 other end: and so long 
us the pump works steadily the pressure in B will not rise, 
Dor that in A full, any Dioro. But under such circumslanoes 
the flow through the small tubes will Iw nearly conxtant 
since it dejiends upon the difFercnco iu pressure prerailiug 
between B and A, and only indir«ctly upon tlm pump 
which M-rvcs simply to keep the pressure high in B and 
low in A. At each stroke of the pump it ia true tJiorc will 
boaslightiacroaseof pmsuro in £ due to the fi-cnh ISO 
cub. cent. (6 ox.) forced into it, but tliis increase will W 
butasmall fraction of the totid pressure and so have hut an 
insigiiittimut influence upon the rate of flow Uirough the 
siiiiiU connecting tubes. 

Arterial Pressure. The eondition of things juitt d«- 
scribod ri'preseutii very closely the phenomenu presented iu 
the blood-vascular system, in which the ventricle* of thv 
heart, irirh their uuricido-vi'ntrieiilar uiiil K-miluuiir valres. 
represent the pump, the smalliisL arteries and the capil- 
laries the resistance at D, the large arteries tJie dbstio 
tube ff, and the veins the tube A. The ventHcles con- 
stantly receiving blood through che Miiricl<!;i from the veino, 
Bend it into the arteries, which tind a ilifficiilty in emptying 
thcmscKu* through the capillaries, and ho blood nceumu- 



TOM SUMAS BOOT, 



236 



btM in UMn n«a Ih* tlwtiti i— twp «t tbe Mmdied ar- 

tarici tt aUt to aqnaew to a ntamto thcmgb the cspiSarm 
}nat tn moch bloo4 m the left fvnliridc pUBps bato tlie 
MorUk, Bud th« rigbt iaso the |MlaoB«j atterr, in ibe aune 
tin*. Aeoordinclf to a bviiig aniBal a ptiiuu gaage 
connected with aa nrtcn ahovs a mncfa bi^Mr pttsnra 
tbaa one Mnnecud with a lebi, and this pexBBtent differ- 
ence of protsore, otiljr iiHim—il bjr a flBaD fractioo of the 
whole at tsich heart-beat, keepe ap a Meady How frutn ihc 
arteriet to Uieveiiu. The heart keepe the «rterwestKlcli«d 
and the rtretched arteriea maintain the low throng the 
eaj>tllane«, and tiie oooetaocy of the carmit in tbexi de- 
pends on two faoton: (1) the rMiataaoe ex|>enenced br the 
blood in it^ 6ow from the roDtridee to the Tein?. atid (:£) 
tlio elaiiticity of the larf^r arteries which ullowit the blood 
to aMmmnUte in them nnder a high pressure, in oonso* 
ijiiPDco uf thin redstanoe^ 

Tho Arterial Proasure. This cannot be dint-tly iDea«- 
arod willi iH'ciiriujr in mun, bnt from mea^iuements made 
on othor aiiinialM it ia culculiiu-d l])ut in the hnman aorta 
itaaiomge i« eqna] to t]uit of a c<'>)uriii of mercury 200 
millimc^era (6 luvboii) high. Daring the eyetole it risea 
about 5inillimet«r« ((incli)nboir«lhi8aud during the panes 
foUa the MiiHo umuiinl hclow it. The prcsmire in tho vettai 
oavBon ihooUier bund is often ncgiitivc, the blood being, 
to tuw ordinary Inngniigc, often " tucked" out of thcni into 
(ho heart, and it rarely rises above 5 millimeters (( inch) of 
mcronry except under conditions {such as powerful mua- 
oular effoK a£oonipunied by holding the breath) which 
force bloiid on into llic vcnw cavie and, by impeding the 
pulmonary ciroulution, intrrri,ii'(! with the emptying i-f the 
right, iiiiriele. Ili-mn to muinlatn the Bow from the iiurta 
to tlip vena ciiva we hiive nn iivcriigc difference of prewure 
ei|UHl to SOO — ft= l(tr>milhnii'terrt(7i inches) of mercnrj-, 
ri^in^' I" ^i<^^ — ft = 20(i mm. (H iiuhcfi) during the ciirdioc 
nyii(i)k' and fulling tn 11"*» — 'i = liKi mm. (74 indict) dur- 
ing till' priiiso; but the Klight idtciiitionii. only ubtmt ^^ of 
the whole difference of iiorlicund vena cava pres§urefl which 
maindiin the blood-flaw, aro too slight to c«u«o nppredable 




4 

4 



ARTERIAL PRBSSVRB. 



MT 



rcbsngea in the rot« at tho carrent in the capillaries. 'Die 
[iro^fuie un ilio blood in the pulmonar>- artery U uUiut J of 
that in tliL- iturtii. 

Sinci- 1I11' liliiotl flows frcHU Iho aorta to its branches and 
from the.ti' to the capiUarico iind thcuc*' Uy thv vciiu, and 
liijiiids in ii set of uontiiiuoun tiilies finw (rum |»oinl» of 
grinttt-r to tliuae of lesa preasure, it la clear that the blood- 
pi-e-junro must constantly dimiulMh from the aorta to Itio 
right auricle; and cimilarlj- from the pulnumnry arl«ry to 
tho l«ft anride. At any point in fact tlie ])re!<iure ik pro* 
(Ktrtlonate to the resistance in front, and since the farther 
the blood has gono tho Ic8« of thU, duo to impediments at 
hninchiDgs and to iitt«nial friction, it has to overcome in 
tlnixhing its round, the pressure on tho blood always di- 
miniflhei* as we follow it from tho aorta to tho vcnse cavae. 
In the larger art«rie!i the foil of preitanrp iit gnwiual and 
small, since the amount of resistance met with in tho 
^K flow through them is but little. In the sma]] arteries and 
^V capillariea Uie redsiance pase«d by is (on account of tho 
great internal friction due to tlioir small ciilibre) veiy great, 
and oon80cin«nUy the fall of pre««nr« betwocn the medium- 
sised ftrtone«and the veins is rapid and conaiderablo. 

Hodifloatlona of Arterial Presauro by Changes in the 
Bato of the Heart's Beat. A litile couaiderultim will make 
it clear tliat the pres-inro prevailing at any time in a givon 
^K artery depends on two thingfs — the rate at uhich the vessel 
^f isSlled, i.t, uptmthoiimotmtof work done by IholM-nrl; and 
' the case or difficulty with which it i!< emptied, that is U|jon 

tJie resistaucD iu front. Iteturning to tho mtemof L-l:if- 
tic tubctf with a pump rcprMenlHl in Fig. 87, let qs snp< 
{lOse the pnmp to be driving ax before 10,800 cub. cent. 
^ (360 ox. ) iicr minuto into the tubes B and that these tttttor 
^^ are HO distended that they drive out just that i]uantiiy in 
^™ the same time. Under snoh condition" tho prcwnre at an** 
given point in B will remain constant, ajiurt from the email 
variations dcjwndent wpon each stroke of the pump. 
Now, huwever, let the latUir, while still wnding in ISO cub. 
\ ocTit. (i[ OX.) at each stroke, work 80 ioatead of 60 times a 
I minote and so send in that time 180 X 80 = 14,400 cub. 



TUE UUMAH ISVIiV. 




W8 



oeiit. (460 ciz.) instead of the former quanti^. This wU] 
load to an acciiniuiHtioii Ju B, sinoo iu siiuii-m: u uuty eui- 
fiLknt, ttgiiiiirt ihf reHistmice opposed to it, to scud out 10,- 
»()() cub. L'tmU (SCO oz.) iu a minute. B ciooeequeiiih- will 
beconifi more stretdied and the juxwurc \a it will rise. Ai" 
tliis tokL'K jiliicc, however, it wii! nqucuxe more )>oworfally 
on itM CLiiic«nte uutil at laiit itj^ dietenaion it Hnch that its 
tilasticity is able to futve out in a miuuti> through thi' tmull 
tubes />, 14,400 cub, wul. (4^0 oz.). Theiicefortli, no long 
08 the pump bcntii with the same force and at the sain« rate 
and tho [feriphcral resistance) rcmaiae thoHuuv, iius moan 
jircsBure in B will neither rlsi; iioi- full — B sending Into A 
in a minute as much aa c takea from it, and we would have 
a steady conditicu of thiugs with u higher mean iireaure 
in H than iH'foix^ 

On the other hand if tlie pump begins to work more 
alovly while the resistance remains the same, it is clear thai 
the moon pre^fsuro in B will full- If, for cxuinplc, the pumfi 
worka only forty times a minute and so sends in that time 
180 X 40 = 7200 cub. cent. (240 oz.) into B, which la m 
xtretclii'd that it itt equii-zin^ ont 10.800 cub. rani. (SdO 
ox.) in titut time, it i« clour thut B will griulually empty 
itsolf and its walls become less stretched and the prc^^itrc 
in it fall. Ah this takiti phu^c, howercr. it will force Ichh 
liijiiid in n minute through the small tube.«. until at last a 
pn-ssuro is roachpd at which the squeeze of B only sonde 
out 7^00 GUh. cent. (340 ox.) in a minntxi; mid thun the 
full of pressure will eeoso and a steady one will be main- 
ijiinrd. hut lower than hefore. 

A|>i>tying the same rciiwniDf; to the vascular syiftom we 
sec that (when the peripheral reniHttnu'c rcniuins unaltered), 
if the heart's force remains the same hut iurato iuLrpu^ea, 
urleriul jin'«*uro will ri«i to u ni-w IcvpI, while a slowing of 
tlie heart's beat will bring almiit :i full of |irL'.i.Hiiri'. 

Modifloations of Arlorial Presaure Depenctent on 
Cban^eo in tho Foroe of the Heart's Beat. Iti-turning 
iigiiin to Fig, 87; 6ii])posi> thut nliilo the rule of the pump 
remiLiii!! the same, its power niter* so that each timo it 
eeDds800cub. cent. (0.G oz.) iuMleitdof 180(6 oz.) and so in 



CffAXftEa m ARTERIAL PRESStmU. 



339 



s miiiur« 1-.;,0iKj cub. oent (394) oi.) instead of lO.BOO (3<H> 
ox.) — tlio t|iiaiitiiv which B it srrclcbcil ctiongh to Rrjiin^xe 
out in thut time. Wiitcr will in ('uiiM'i|iieii<H> ii«cumulatv in 
B until it bfiuiiinea utretched enongh io 5t|iic«M out 13.000 
cub. cent. (309 oz.) in a minute, nnd tlitnitfluulv pixtsiiiiTc 
at s neir uiid higltvr low] will ho niuintikinod. On the 
other band if tlie pump, etill beating ^ixtr times a minnte. 
works more feebly so as to send out only 160 cub. cent. (5.6 
OS.) at vuoh etroko, th<>ii fi> iquAOzing out ut Gntt more 
than it recoiT«8 in a given time, will gradually empty 
itself until it only presses bard enough upon '\ta cont«nlji 
to force 100 X 60 = 9600 cub. ounL (3311 oz.) out tn a 
minulo^ 

Similarly, if while the reoatance in tlte small arteries 
vnd capiUarii>» n-mains the niibo und al:>>i the hciirt's rato, 
Ibo [lower of the stroke of the latter alters, so that at each 
beat it sends more blood out than pruviondy, then arterial 
pressure will r)*e; while if the heart beat* mure feebly il 
will f»ll. 

UodiRoations of Arterial Pressure by Changes in the 
Peripheral ItOHiatanoo. Let Iho piimp c in Fig. HT $llll 
work steadily »icndiug 10,SO0 oul>. cent. (3G0 ox.) jwr ti>iii* 
itto into B and the reeistoneo incrtuuo, it is clear arterial 
prcswuro must ri.'<e. For B in only Btretched cnotigli to 
"jueeie oat in a minute the above quantity of liquid against 
tJio original rcdistauco and cannot at tlrsl Mind out that 
([Daiitity against the greater. Liquid will oonni'iiienily nc- 
cumuluto in it until ut Uet it beoomes stretched enmigh to 
send out 10,800 cub. ccnt.'(3G0 cnbic ox.) in u mintito 
tlkroagh the small tubes, in #pite of the grvator resistance 
to be overcome. A aew mean pressure at a bighcr level 
will thou bo establLgbed. K on the contrary the nsistiuioa 
diminishedi while the pump's work remains the same, then 
B will at first squeeze out in a minute mwn- than it rcpoiriit. 
iiiilil finally it« elki^tic pre»rurc is reduced to the jminl at 
which itii roocipti and lost's hitlunoe. uod a new and lower 
mean pressure will he ostabliiihi'd in B, 

So in the viuionliir sjslom iiirreiise uf the peripheml re- 
mtonco by narrowing of the <^\au\\ arteries will iaonose ar- 



340 



TEE BUXAN BODY 



tcriftl pi-o.«i<nre in nil parU Dcaror the ImtH. while dilatiition 
of the sniftll arteries wilJ have the contrary etTcct. 

Sumniary. Wo fiud thou that arterial jin-'ssnre at any 
moment isdcpondent upon — (l)lhenito of tli« heart's boat; 
(li) the qoantitT of bluud forced into tho artcriuti itt each 
beat; (3) tlio culihre of the Rmallcr veswla. All of these, ■ 
niid conse(|iientlT the capilliirr uireiiliilion which depends^ 
ii|hon arterial pressure, are under tho coutrol of the nerroua 
syKtcm (sw Chap. XVTI.). 

The Pul«e. When the I«ft Tontricle contracts it for 
a, wrtuiii imnmnt of bloot.1 iuto tho aorta, which is already' 
diKLendcd mid im u(;c<>iiiit of tho rctxlNlaiiii^o in fnmt oamiot 
empty itself so faat aa tho contracting ventricle fUb it. Aa 
a consequence its elastic walls )-ield still morc^— it enlarges 
both transversi'lv and longitudinally and if cxpi^ised in s 
living animal can be seen and felt to pulsate, swRlling out 
at eiieh iiyiitolo of the heart, an<i shrinking and getting rid 
o( the exoesB during the pttuw. A Bimilar phenomenon 
can bo observed in all the other large arteries, for just a» 
the contracting ventricle fills the aort« faster than it cmp- 
tJM (the whole |ieriod of tho diaxlnle of the heart being 
required for emptying tho aorta of the blood sent in 
during the fviitolc) so tho incrwieed tension in the aorta 
immodiaiely after the oiirdiao contraction, driven on sunn- 
of it« contents into ilit branches and fills these faster than 
thoy are einplying and so causes a dilatation of them also, 
which only gradiuUly di'(a)>t>cai'4 m the aortic tension falls 
before tho next systole, Uencp after each beat of the heart 
there isftsensibledilutation of 1^1 the Wgor arteries, knoH-n 
OS iheputat, which U'cumes lew and less marked at pnint^i 
on the smaller branchea farther from the heart, but which in 
licjillh ciui readily be recognised on any artery large enough 
t<i be felt liy tho finger through the akin, etc. The radial 
artery near tho wriet, for example, will always he felt tense 
by the linger, cinee it is kept overfilled by the heart in the 
way already describ<'il. But after each hcart-lxuit it Iie- 
comos moi-e rigid and dilates a little, the increased dislen- 
aio» and rigidity gradually diMappcurtug a« thu artery 
pastes on the excess of blood before tho next heart-beat. 



TSB PU18B. 



S41 




The palae Is then » n-ave of increa^ praanre started by 
tho vcnlru'iilar .'•j^tule, radiiiting rmm lliv nemiluiiur tuItcs 
over ihe ^irterial sysieni. uttd grtidiinJIy distt])iieariiig in 
the EDiullcr bmiiclK-A In tliv uurtii llie ]>uUo Is most uiiu'kcil, 
fur tbc rc»iMtiiiioc tiiei-e to tho trantimiEsion onwardti of iho 
bluod aeiit in by the heart id greatest, and the elastic tubo 
ID which it conseqnciiily atL'UitiiiluU-ti i» xhorUist. rd<I hu tha , 
iiii:iviii>c of procure iind the (lilulutinn vnti«oil arv- coii!iid(<r- ' 
able. Tht' aorta, however, gradtinlly mjuceKej out the cx> 
0633 blood ioto its brauchcfl and so this beooiucs distributed 
OTpT a wtdt-r nrDii, aiid those branches huriog less resietance 
iri (runt liiiil V-m a,w\ \ti» difHoulty io patutiilg it on; oi>nM» 
(jut^niiy the puisp-wave beconiefi less and lais conspieuoiis 
and finally nitogi'lhcr dirapppiirs Iwforc the capillaries are 
reacht'd. llie exccM of litinid In the whole Rrtoriiil mtetn 
alter a veiitrioular sjstoTo being too small to een§ibly raise 
Ihn mean prcssora once it has boon widely diKiribiitM 
over the elastic vessels, which is the ca»o by the tiino tlio 
vuTO has reached iho Bniiill braauhca which supply the ca- 
]>i!larle!t. 

The pnlBe-irave travels over the art«rial system nt the 
rate uf iiImui 9 tnoters (30.5 fL-et) in a second, commenriug 
al the wrist O.I59«ccoud«, and in the po»t4;nor tiliiiil artery 
al the ankle 0.193 seconds, after the ventrioulnr xyHole. 
The blood tt.(wtf does not of cmrsu tmvel as fast as th6j 
pulse- wave, fot that quantity sent into the aortn at each 
heart-beat does not immedtaU'ly rush on over tlie whole 
arterial system, but by raising the local pressure causes the 
vuMol tOK<|tu-cxe outfastcr than before some of the bloml it 
already coulains. and this enlcrJnf; its branches rni-cs Iho 
pressiii-e in them and catieos thorn to more quickly lill their 
bmucbi-^ ami niitw the prusurc in tlicm; the pulso-vAvc or 
wave of iiiorrtised pi-essnro is transmitted in thiawaymuch 
faster than any given ]>ortion of the blood. How tJie 
wave of tncrcHM'd i>ri'!tijiurc and the liquid travel at differ- 
cnl rates m:iy be mtido clearer perhaps by picturing what 
would hiip]>en if liquid were pumped into one end of an 
already full elastic tube, closed at the otlior end. 'At the 
dosed cad of the tube a dilatation and incroasod tension 



342 



TBS Hl'MAy BOOT. 



wonid be foil immc'diAtclf itiev eaoli Htrok« of tlic pnmp, 
uliliuiigh tlie lk|iud pumped in al the other end would havo 
remiuia'd abuitt il:^ )H>iiiL of t-iilrv; it would cuuw ihc pul- 
Mitioii uot bj flowlug uloug the tubo itMlf. but \ty giving n 
]iush to the li'|uid ulrctidy in it. If iustead of absoluk-ly 
duaiug the dixtsl eiiil of the tube one brought about a 
isttitf «( thiiigx more iiuitrlj' rviSL'iubbiig that found in tho 
urlcricii bj* altowing it ti> ein)>ty itself against a reeitttanoc, 
ea.^ through u utirruw o])ouing. tlic plicuomcua obisenred 
would Lot htf i-.wctitiiilly allcri'd; tin; inoi'eaw of prewuri- 
would travel aloug tho distended tube br faster than Uie 
liipiid in it. 

The pnlee being dependent on the heart's Bjstole, " feel- 
ing the puW of coutvo primai'ily give* a couvonlcnt mtruus 
of roitntiug the rat^ of hfiit of tliat organ. To the skilled 
luuch however it may tell a great deal ni<»«, aefor exam[de 
whfthcr it i* a rwidily compri.<4i»iible or "soft pulse'' ehow- 
iug a low arterial iiri'-iHiirc, or t^nae and rigid (" a hard 
]>uIh'") indicative of high ariorial pruKMurv, and soon. lu 
athiltd the normal pul^> rate may vary from eixty-tirc to 
et-'venty-five. lu the tamo individiud it it fiuler when 
Ktauding than wlitrti fitting, and when sitting than whtn 
lying down. Any excrciao iiiereiues iU rate temjiorarily 
Hud so doca escitomoQt; a eiek person's pulse should Dul 
theit'forB be felt whon lio is nervous or excited (lu the 
I>hy-4ici3n knows when he tries ISrst to get his patient oiilrii 
iind conlident), a** it is then diBicult to draw correct 
cuni-luHiuiiii from it. In children the pulse is qniok^r thun 
in iKiiilt?, and in old age slower than in middle life. • 

The Kate of tho Blood-Flow. As the vascular system 
becuUKW mure eupucioii.'s fium the aorlii lo tho capillaries 
the rate of flow in it becomes i)ri>portionately slowci', and 
as tbo tola! area of the chunnoLs dimiiiiiihcs again from the 
CHpillurien tuthc veiiie uaviu, sodoe^ tho nitc of lt»w quicken 
again, just as a river cunwnt slackens where it sprciidt< out, 
uud UuwtJ fodtv-r wlitTi- it i* <'inilliRtl to a narrower channel; 
afuet taken advantage of in tlio cuiMtriiolioti of K;ids" jetties 
at the month of the Misfiii^i])pt, tho object of wliieli is to 
make tho wat^T flow in a nan-ower clinnncl nnd so with a 



aSVOADARf AIDS f) THE CinCVLATlOS. S43 



more nijijil curretil. Aciiiiil measnreincnta k.* to the ruts 
of flotr in t4te arteries cunnot t)0 mado on man, but from 
cipcrimoDtx on lower unimiils il it ctUculutcil tliut in tlic 
human carotid iho t>l<H)d flows ubnnt 400 miUiinotor^ ( 111 
inohcs) (u n sccunJ. In the aipilludus tliB current travoN 
uiil^ from 0.5 to O.io mm. {^^ to iS Indi) in u vccoud. 
Tho total lime lakeii bv a portion of blood In getting from 
the uorla tiiroii<^li the carotid unit its brunclies, imd tho 
aipilturiu.% and (lien through vcnw to tho right uuridc, 
tluit is in j^oing round the Eystpniic circulation, \a about 
S3 seconds — of which time about uno eooond is spont in 
the cnpillurio*; cuoh {>cirtiuii of bhind on its coiirso from 
the last artery to tbe first rein passes through a length 
nf capillary which on tho Kvoragu is 0.5 mm. (^ inch). 
The nito of flow In the great veios ia about 100 turn. (4 
inches) in a second, but is aubjoct to coD^iderable t-aria* 
tioDH dcpcndi-nt un tho respiratory and other morvmeuts 
of tho Body (see below). 

Seoondary Cniuies of the Ciraulatlon. While the heart's 
beat is the great driving forto of the circulation, certain 
other things hiOp mure or lca» — tix. gravity, comprossiuu u( 
the vein^ and as|iir;itii)n of the thorax. .Ul of I hem are, 
howerer, qnit« subsidiary; experiment on the di-iid Body 
ebows that the injection of whipi>cd hlood into tbe aortn 
under a less force than that exerted by the loft vontrielo 
during life, i« more than sufDcicnt to drive it round and 
Luck by tho venie cavm. Not unfrciiucntly tbe statement 
is made in books that, probably, the sy.-<t«mi(; ntpillaries 
have an attructirc foroo for nrtorial blood and tho imluoiiary 
capilhirios for Tcnoua blood, but there is not tho 6light«iit 
evidcuoc of the correctness of »ueh a supjioditiou, nor any 
nei'ftssitv for making it. 

Tho Influeooe of Gravity. Under ordinorr circum- 
»Lauccs ihis ma_\ hi' ni-giccicd. since in partK i>f tho Body 
below tho level ol ilie heart it will assist the flow in the 
RTtcriu fuid impedeit e<)naUy in tin.' vein*, while th« reverse 
ialliccaoe in the upper parts of the Itody. Jncuruinuw^, 
however, il \s well to bear tho°o points in mind. A part 
"ooagulod"or gorged with blood should if possible be 



944 



THE BUUAX BODY. 



• 



raii-cd »o M to nmke the back-flow in its rcina easier; and 
sometimes whin tlit ht-arl U luiting fccWj- il may bu iiblo 
to drivo l)lof)(i along nrtoriea in wiiich grai itj iioljis, but not 
otliorwise. Acconliugty in a tendi-Dgj' to fuititing it is beat 
to li« duwn. luiJ iiiako ii easier for the heart to wend blood 
up to the brain, bluudlessiiees o! which is the cause of the 
lo!<a of c'onscivufiDf.-Ni in nfniuting>lit. In fact so long as 
tho bK^iilhiitg cnntinuca the aspimtiou of the thorax will 
keep up tho veaoiis flow {sec below), while, in the circum- 
stances siippoicod. a relight diminution in tho resistance oji- 
pii^id ti> the arterial flow may be of iuiporlauce. The head 
of a i>erson who baa fainted should accordingly never be 
raised until ho bu miduuhu-dly recovered, a fact rarely 
borno in mind hr Bpectators who commonly rusli at oiu* to 
lift any one whom they see full in tho street or el^owhere. 

The InlluenGS of Tnuudent Compression of the Teins. 
The valves of Ihe reins bcins; e« disposed as to permit only 
II flow tinvunh the tieiirt, \\\v.'.a cxteniiU pressure empties a 
vein it a><.ti^ta the circulation. Contimiona pri'saurc, OS by 
a tight garter, is of cnur.'^o hud mnoo it checks idl Babs&- 
qneiit flow through the vessel, but intennitUxit prcuoro, 
Huch as exerted on many veins by muscloij in the ordi- 
nary movements of Iho Body, ocU m & pump to force on 
Ihe blood in them. 

The valves of the veins have another use in diminishing 
tJie pressure on tho lower part of those vessels in many 
regions. If, for innUtuco, there were no rttlvos in the long 
KiphenouR vein (p. 3U) of the leg the weight of the whole 
column of blood in it, which in tho erect position wowld he 
about a meter (39 iiiche») high, would prpM on tho lower 
part of tho vcsdcl. Hut each set of vidves in it carries the 
weight of the column of blood between it and the next ."ct 
of valves above, and relieve* part* hHow, and so the weight 
of tho column of blood iit distribnted and doea not nil bear 
on any ono paint. 

Aapiration of tho Thorai. Whenever a breath is drawn 
tho pressnre of the air on the vcisols inside thi.' obe*t is di- 
minished, while that on the other vessels of the Bodyi* iin- 
aftectcd. In conneeinciiee blood tondsto flow into the cbeet. 



PROOFS or rais vmauLATTos. 



Mft 



It canitot, lioireT4-r, flow bank from the art«nes on itocouiit 
i)f the Bcmilanar valvea of the aorta, but it readily lapreseed, 
or iu common lan^ogp "sacked," Duih iiiU> tUo grcut 
vcinn close to the heart and iuto the right auricle of Iho 
latter. The details of thiH uctioii must be omitted until 
the rcepiratury mocbunistn hss hnvn (-oiicidercd. All parts 
of Uk' imlmddiiry circuit being within the tbonix, the 
rcninviitury movomcntjii do not infiiipnce it, except in so fnr 
OS the diatenaion or ootlapee of tlie lucgs influences the 
wilibrt' of their voskcIb. 

Thi> cnnsidoriihie influence of tlie re*pinitory mov«ni«nt» 
ujfon the venous circulation can lie readily observed. In 
Ihni pcrvons the jngiitor Tein in the neck can oftoa bo 
i^en to empty rapidly and collapi>e during m.<pi ration, and 
fill up fwtcr than il oniptic!* during expiimlion, Uin« exhib- 
iting a «ort of Tcnoiu pnlae. Ereiy one, too, knows that 
by making a violent and prolonged expiration, m exhibited 
for example by a child with whooping-cough, the flow 
in atl Uio TcinK of Uio hc-iul and nock mny bo chcoked, 
causing them to ewell up and hinder the cikpillarydrcula- 
tion until the penon becomes " black in ihe face,'' from iho 
engorgement of tlio (mall vc3«el8 with the dark-colored ve- 
nous blood. 

In dieeuKsof tho trlctupid valve another form of Tenons 
pulse U often iieon in the sujicrfieinl vein* of the neck, since 
at each contr.iction of the riglil vetiti-ido some blood is 
driven back thruugh tlio right auricle iuttt tlio veins. 

Proofe of the Oiroulatioa of the Blood. The older 
|iliyiiii-ili>gi)i[8 hulii'Vi-d tliiil (bo muvt'Dicnl of tho blond was 
all ebb and flow, tn und from ciu^h side of the heart, and ont 
and in by l>oth nrtoriea and veins. They hud no idea of n 
circuliition, bnt thouj^bt pure blood was formed ta thelungn 
and impure in tliu liver, and that thcHj partially mixed in 
the heart through minute jwres supposed to exist in the 
septum. Sorvetns, who vaa burnt ^ive by Calvin in 1353, 
Bret showe^l that thure was a continuous passage through 
the lungs from the [uilmoniuy lU'lery to tho pulmonary 
Toins, but the great Knglinhman Ilarvey fir«t, in K'cturu 
delivered iu the CoU«gu of I'hydcians of London aboat 



S48 



TBS aVMAK BODY. 




1616, demonstratrd tliat the movement of tlie blcwd wa»(i 
<-ontiiiiiini.« i!iri.'uliili(>ii il> wv row kuuW it, iiixl «o liiid tho 
foundation of modern l^ysiology. In hiti time, liaweT«r. 
ilio lapillurj \L««ulii httd Hot been discovwcJ, to tliiit al- 
llioiigli be w&« quite certain that tliu blood got eomckon' 
front the final branched of the uoria to the rudiolet of tlio 
teiitms sTstem, he did not exactly know how. 

The proof* of llie course of tho circulation are at preseul 
quite concluMve and inny be suniinvd \x\> m follows. (1 ) 
Blood injeoti'd into an arti'tyin tho dead Body will n^umi 
by a vein; but injected into a vein will nut pass back hy mi 
artery. (2) the anatomica] arrangement of tho valve* of 
the hoart aud of tho Tcinti Hhuwic ibul tliv hhiod can only 
flow /com the heart, through the aneries and buck /o the 
heart by the veins. (!}) A cut artery spuria from the cud 
next the heart, a cut vein bUwd* inort from Uio end 
farthest from tho lioart. (4) A portion of « vein wlien 
i-ttijiiicd fllU only from the end fartliest from the liciirL 
This experiment can be made on tJie Tcina uu the baek 
of Uie hand of any thin person, o«pcciidly if the vcstscU 
Iic Hrst gorged by holding the bund in a de|>endent posi- 
tion for a few soeonds. Select then a vein which runs 
for an inch or so withotit branching, place one linger on 
its di&tul end and th«n omptjr it np to \U next branch 
(where valvea iiKiially exist) by comprcBsing it from below 
up. Tho Teiiso! will thin bu found to remain empty as 
long a^ the linger it kept on it3 lower end, but will GU 
immediately wjieu it ia removed; which proves that the 
valvM prevent any tilling of Ibo vein from il< heart end 
bnckwards. (&) If A biind:ige Ix) placed around the ami, 
no astoclose the Riiperflcial veins but not tight enough tn 
occlude the deeper-seated ortorioe, the veins on tJie distal 
vide of the bandage will biTCOino gorgc-d tind tho»u ou itK 
proximal aide eniply, piiowiug aj^ain that the vcimi only 
roccivo blood from their ends turned toirarda the capilla- 
ries. (II) In the lower animnli! direct obi<iTvation with tlio 
microsco])e shows tho Meadr flow of blood from tlie arlc- 
rioe UirougU the capilluries to the voidk, but never in the 



oppoKitc direction. 



CHAPTER XVII. 

TEK REQULATIOX OF THE HEART AXD BU)OD- 
VKSSEL8 BY THJi NERVOUS SYSTEM. 



The Heed of Co-ordination. For the safe and liJimio- 
nioU8 working uf tin- (inuIatDry HiiiiiiruUiii it h oliritiu.ilf 
neceosary ihitt tiu-it.- im noma mode of mutnn) inlernction 
between tlie heart und the blood-veaselj: it the bt-urt beat 
and the arterita rtduxod or contnKtiMl, e»i'h without any 
reference to the other, no orderly capillary flow conid be 
maintained. To aticure thai. th(> nork done by the heart and 
Ijio rt'siittauco to ibe blood-flow offered in the vessola must 
at any given moment Ira c^irrotaCed: ao that the heart sliull 
not by too powerful uction over-d intend or perhaps burst 
the (imaU arteries, nor llie Ultor contraet too much and so, 
by nicreaein^ the peripheral re«i#tunco. raise the aortic pn»- 
iuro to a prmt heiglil and incrciuo nnihily the work to br 
done by the left ventricle iu forcing open the scmilnnar 
ralres. A^in, the lotiil iimount of blood in thu Body in 
not sufficient lo kcip nil its orgims »nj)]i]icd with the 
amount needful for the full eiercise of their activity at 
one time, and in the Body accordingly we nercr find nil 
ilx parts hard at work at the same moment. If when on« 
group of niii«cles was ret at work and needed an cxlni 
bIood-!>iip]ily. tlii.'4 wuK attained merely by increasing the 
heart's activity and keeping npa faster blood-flow every- 
where throiit;h the Body, there wonid be a clear waste <if 
force, ranch as if the chandeliers in a bonse vera so ar- 
ranged that when a larger flume wiw wanted rtl one burner 
It eouid only bo obtained by turning more gaa on at all the 
rest at tho same time; besides Die big tap at the git#-metcr 
regnlating the general supply of the hotixe, local taps at 



THK mnfAK JtOTtT 



mcl) burner are ret|nirod which regulate the gai-sapply bi 
each flamo indcpcmluutly u( the i*st. A similar arrange- 
niciit is found in the Body. Certain nerrcs coulrol the 
calibre of the arterins mppIvJng difTerPnt ingiin* mid, when 
thu hit top are sot at work, allow ihcir arterion lo dihiie and 
eo inci'cafie the amount of bbod flowing through them 
while the general circulation clRcwhere remains piaclioally 
unnllecled. The resting parts at any moment thus get 
juat enough bloi^id to nminlnin their heakhy uutrition and 
the working parbi get more; utid an certain organs come to 
rest and others arc set in activity, the arteries of th« one 
narrow and of the other dilute; la this way the dietri- 
bution of the blood in the Baly is undergoing constant 
changes, parts which at one time contain much blood at 
auodier having but little. Id addition, then, to nervous 
organ; rcgidating the work of the h<;urt and the arteries 
with reference to one another, we have to connidcr unothi-r 
set of viit-eiilar nerves which govern the lucid blood-supply 
of hirri III regions of tlio Body. 

The NervOB of tho Heart. The heart geta nerves from 
three soiirt*. (1) j-'i'oni ncrvc>H?ell« buried in its own sub- 
stance and known as its infrimtr ganglin. (i) From ihc 
te.nth pair (i>ncuniogastrics) of cranial nerves. (3) From 
the Hynipalhetio nervous syiitcm. Tho intrinsic ganglia 
keep the heart baling, and the other two seta of nerves 
control the rate and forci; of the beat, 

Tbo Intritiaio Heart-Ndryea. The ganglia of tho heart 
lie fur the moiit part in ihe partition between the anrieles 
and along the line of junction of the auricles and ventricles; 
a fow nrc found also in tho upper parts of the latter. From 
some of tliem arise nervo-JiUre-* which go to the muscles of 
the heart, while others are connected with the endings of 
the extrinsic nerves reaching tho organ ; and probably all 
ciimmiinieat* by a network of nervc-fihrei. 

The hciirt ik an automatic organ : its beat, like Uie 
movement of fllamentj« of a ciliated cell, depends on its 
own structure and properties and not on anything outside 
itself. Tliiti it provi'd hy tho fart that ilic hcjirt cut out of 
an animal which \vm jtut boca decapitated, and entirely ro- 



CAV8S OF Tits aSAKrs BEAT- 



«49 



moved from nil llic ro«t at th« body, will go uii bcutiog for 
some tiuie ; a time which is very short id tbe case of wiinii- 
blooded auinmU, this tiiuiu^^ u( wbich itic very noon when 
tbo blood-flow tbrougli them ceases but which niitv extend 
to houra or even dava iu the excised hejirl of frog or 
turtle, if it bo kept from drying iij). Still, whelhur the time 
of it« coiitiitiiunoc Im shorter or longer, tlio fact that tlitt 
hearl-be^t continues after complete excision of the orgiin 
pi'uT<.'» that it is not dependent on Miinuli reaching it from 
otlicr partA of the Body. In the ciliated cell we hud no 
differentiation into muscle and nerve — its contractile and 
automatic parts if separated ut ull were not optically distin- 
guishable and wc could only t>peak of tlie cell as Atill rettiin- 
ing both of those primitive protoplasmic properties. But 
in the heart, where we find distinct mneclw and nerves, th<> 
quc«tion Qftturally ariftc^ in which of thorn does tbo auto- 
matic power reside. We have already seen (Chap. X.) that 
muscles elMwhei'f^ po^te^s no uut^maticity : tbcy only con- 
tract under the influence of a recogniKable stiniulua, and 
though the muscular nbros of tbo heart do diSer somewhat 
from other muscular fibres in tbe Body, it iji^tillapnm ini< 
probablo that tlioy are automatic and ve are accordingly led 
rather to auppow that the stimulus resides in the ganglion- 
oells of the heart, especially Rincc wv know that itorve<«elU 
olsowbcro are automatic. EiiKriment confirms this snppo* 
•ition. If n frog's heart, removed from the body and still 
beating, bs cut into several pieces with a iiharp razor it will 
be found that, while bits of tbe anricles and the base of the 
rentriole go on beating, the apical portions of tbe ventricle 
lie at rest — ^not because tbe muscle there is dea<l and bati 
lost its contractility, for these bits if excited by any ex- 
traneoua muijcular stimulus will ntlll bc-ut. but because 
that i>art of the heart possoases no antomaticity. Nhw this 
Is just the pm-t of Ihc frog's heart that has no gangiiun-relU 
of i[« own, while the jiarta that go on beating are those 
which iK>6desa them : hence ve conclude that the stimulus 
origiiwtes in the ntTve-cvlls of the organ and it from them 
carried by its nerve-flbrcs to the uiusclw. The excitant of 
the uerre-cells boing still unknown we call tlicm uutomatio 



uo 



THE BUM AS BOUT. 



in the nwlricU'fl jihysioiogical sense of the word. The 
primiir}' cause of the hciirt's bwil lying thus in itself, wo bare 
noit to ee« how thi» beat is ooutralled from outride and co> 
ordinafod with the condition at the rest of the Body ut any 
given niitiiu*rit, 

ITervea Sloving tho Heart's Beat. Kach jitieiitniig»»- 
tric trunk sends seveml branehuft to Iho heart. Certain of 
thv»c contain tibrcs which when vxcit«d stoir, or even alto- 
gether stop, the bcitl of tho heart and xre hence known m 
the cardia-Miifiilory fibres. 

If one pneamo^trio tnink be divided &a it mns down 
the neck and its peripheral, or hiwer, end bo stimidaled 
feebly the hwirt'x hciU bcoomfc* le-*s frmnient, while a more 
powcrfnl sliinuktiou will completely stop it for a few 
seconds, as if its muscles were suddenly paralyzed. If the 
experiment be performed upon u nnrcrttizcd nnimid.lhc heart 
of which lit at the Sitme time exposed by ojiening Ihecbeet, 
it will beseen thatdiiring tho stoppajp" the heart lic« dabbj 
anil roluKcd in diottole; tho excitalion of tho nerve does 
not stop the heart's beat, na might perhaps bo supposed, by 
keeping it in a state of permanent tetanic conlnurtiou, but 
it annuls its contmctiomt and throws it into n »ltite of rest ; 
the nervft-fibrea concerned are not excitant but inhibitoiy, 
stopping instead of calling forth the uctivity of the part on 
which they act. A\'hcth('r their inflin-neo is oxerlcd di- 
rectly on the muscular tibres of the hcjirt or npon iti in- 
trinsic gimglia, ul)»lii>bing their automatic activity and eo 
onttingoU the stimnli which normdly radiate from them 
to the muscles, is not certainty known, but the lutLer view 
is pnilmbly ihc correct one. In any ciwe the full iiihibi- 
inry )Kiw<.'r usiually liuita only u shurt time ; even if Iho 
pneumogastric stimulation bo continued the heart will n]- 
inuHt always after a few seconds recover from iu inflnenoe 
und eommeuce to heal, again. 

These caniio-inhibiioiy Hbn>;i originate in a collection of 
nerve-cells in the medulla oblongata known aa the cardio- 
inhibitory cenlrt. Thi.* centre is automatic and a1w*ye in 
a slate of slight eicittition, feebly slimiiUting the fibrea 
proceeding from ii. and slightly slowing the heart's beat. 



CAJiDtAC SSaJBtTSON. 



S5l 



TbiB is shown b; Uio tact timt if bolh pncumogastrto nerrc^ 
bo cut ia th« neck the heart at onco begins to beat a little 
fiuter than before; the brake, eo to qwak, ho* been taken 
tiff it. 

The lofiudDoe upon Artanal Pressure of Inhibiting 
the Heart. If the heiirt bo entirely )ito;ij>L'<l urtciial pres- 
sure will of omirsc full very rapidlr, since the disttndoil 
iirlerial system will go on cmptTing itself throngh the capit- 
bries into the veing, n-ithotit rrcciring any fresh lupply nt 
it« cardiac end. So too if the heart be mudo to beat sinwc-r, 
bat with the same loruu iu euch stroke, it foDon-s from the 
foots pointed out in the lii«t chapter (p. 23S) that arterial 
pressure will fail to n new and lower IotoI. at which the 
dasttc artcrii-s are only «trotclicii enough to s(|ueej!0 ont in 
a minnte as much as they receive. As a matter of fact, 
when the heart is made to beat slower by weak pnenmo- 
gutric istimtilution each beat ia usually a little more power- 
ful than before. However, this extra force is not sufHcient 
to coinpL'ti.<ate entirely for the slower Tat« and to the gen- 
oral arterial pressure falls. 

tJae of the Cardio-Inhibitor; Hecbanism. Althongh 
the cjinUn-iiihihitory cciilrw is iuiioiii;iiio nnd always in a 
state of alight activity it is also givatly under the control of 
afferent nervo-fibre-# reaching it and which can arouse it to a 
niiieh greater degree, and so retlexly control the heart's beat. 
If a frug be rendcrt'd inveiDiible and its abdominal cavity 
opened, it uill be found that one or two smart \M\>i on the 
iutwtine will cause the heart to stop in diastole. If, how- 
ever, the pueumopistric nerves, or the spinal cord, or the 
anterior rool" of the npinal nerves, or the communicating 
branches between the sympathetic norre^of the aMomen 
and the spinal nerves, be cut previously, then striking the in- 
testine has no influence ii(H)D the heart; nor has it if the 
cardio-iiihibitor>' centre in the medulla oblongata 1>6 pre-* 
viou»ly destroyed, Wc tbn*gct evident I'lut the mochaili- 
n\\ stimulation of the intestinal nerves ttops the heart ro- 
llexly through the pneumognelrics. the afferent impolses 
traveling from the sympathetic into tli« spina] nnrvee and 
passing then up tlio epitud cord to the eardio-iubibit^Hy 



iat 



rUK aVMAX ROOT. 



43entre, where iliey nre reQectcd m efferent impulma downj 
the pneamogastric trunkii \a the }ii-art. In ninii uiid otberj 
mttmni&la similar ammgements exift, the afferent tibrca pass- ^ 
ingfromthealimetitjuTcnniil through lhe8oIarplexuB(pi.l7Sy I 
which lies behind iho ftomiurh. It ia \ty exciting them and I 
BO rcfloily stopping thp heart, that men are Bometimes killed] 
by a severe blow i>ii tbc iiliilomeu «r even occiteionnlh' by a I 
largo druugbt ui vorv cold water, the sudden cold acting asi 
a thermal ^timulas, through tho walls of the etomuch, on th» j 
nerre-fibrea outfiidc>. A hot and very thirety person rcquir—j 
ing a big drink should Iboreforc iiol l^tkc too (!old water— 'j 
or if be do(«, swallow it only a moathful at a time. 

The btood-vessels of the alimentary uinal lu-e very nnnicr- J 
ons and uijiui-ioai* and form one of the large-tt vascular iractaj 
of the whole Bo<ly, and through thf reflex mechanism aboTe'l 
describiHl wo wo how they mayconlml the heart'e bcat-T 
Probably if the heart is beating too freqnQntly and kcepinn 
Dp too high a pressure in them, the sympathetic Derv»>4 
fibn-K in their coals tiro fiiumliucd imd (hen. roflexly,j 
through tho cardio-iiihibitoiy centre eiow the heart's beat 
and lower the general urlcrlid pressure : and so we get oat 
co>ordinatiiig mecliauism by which the heart and blood-vc 
sels are made to work in unison. 

Some other afferent nerves are idso known to be in con 
nection with the card io^iuhibi lory centre For instanoCi 
some persons are made to faint by a etrong smell, tho olfao>j 
torj- nerve* exciting the cardio-iuliibitory centre and stop 
ping or greatly slowing tho heart. DdatJis from tho admin- 
istration of chloroform are also uiinally brought about iu tin 
ftamo way. tho vapor stimulating the Hcnsory nerves of it 
air-paasuges which then excite powerfully tho cardio-inhibt 
tory centre and slop the hearL 

Tho Accelerator Nerves of the Hoart. These originate 
in the spiud cord, from which tluy |>ms by communicatio| 
branches to the lowest oerrical and np]icr i3<>r*al fym-l 
pathetic ganglia and thence to tho heart. When stimii- 
lated tbey cause the heart to beat qnicker. but under what) 
conditions they arc employed in the physiologicui working 
of the Body is sot known. 



SKBVSS OF THE BLOOD- VBSSELS. 



253 



Th»HorveHOfthoBlood-Ve8MlB. The arteriesias already 
(Mtinted out, pu :?'<-;<.'' a iiiii.-i^ul^ir Cfuit uonipoettl of fibres 
arraugud ucroAn Uiom, so ibat their conlraclinn will narrow 
the T««*elfi- This coat \s most prominent in the smaller 
Tcaaels, those of t^o «ixe wliich go lo supply separate organs, 
bnt dimjipcitr again inthesnialleiitlimiiciicd which are about 
to divide into capillaries for the individnal tissue elements 
of an organ. TIimo vascular iniucl«tire under tlio control 
of certain nerves called vaso-motor (p. 18G) and these liitter 
can thtis govern the amount of blood ronching any organ at 
a given time. The vuso-motor nervvM of the artcrii's aro, 
like* thoj« of the heart, intrinsicand oxtrinaio. The intrin* 
sio flbi'e^ originate from ganglion-cella in tJio coats of the 
arteries or lying alongside them, while the extrinsic origi- 
nate from cells in the cerebro-spinal centre, from which 
they commonly pass into the syinpathotio ayatem before 
they reach tho ve-:<scl«. The intrinsic gunglia, like those of 
Uie heart, are automatic and tend to keep tlie muscular 
coats of the arteries in a constant stjite of feeble contrac- 
tion so that, apart from tlieir physical eliuticily, the arteries 
always hold a certain grip on the blood. The contraction, 
however, is as a rule persistent and steady, or ionic, insteiul 
of rhythmic like that of the heart, although dow r^iythmic 
contnctions have been seen to occur in some arteries. The 
difference probably depends rather on the kind of mnscle 
ooncerued in each case than on the gunglion^colls, since 
phiin muscuhir tissue, such as is found in the artertori, con- 
tracts so slowly and remains contracted so long when excited, 
that stimuli reaching it at intervals which would give a 
rhythmic beat in cnrdino muscle, would keep the arterial per- 
manently contracted or tetanized. As in the heart, the 
Hutivity of tho arterial intriusic nervou-i mcchunism is 
under the control of extrinsic nerves, certain of which, the 
ifuo-ennstrietort, answer to the accelerator nerves of the 
heart and increase the activity of tho intrinsic ganglia, 
while others, oorresponcling to the cardio-inhibitory fibrea, 
check the activity of the intrinaic vascular nerrw. 

The Vaao-Motor Ceatro. The vaso-constriotor extriouc 
arterial neives are nearly always in a state of tilight activity, 




3H 



TUB HUMAX BODT. 



theH 

''— c. 



kuoping the ftrtf ries niorecon»trie*t«d than thoy would 
tmder the influence of their intrinsic nerves alone. Aecord- 
inglyif they are cut>or panily^rcd. inttnyri'gion of llic Body 
its arteries dilate and it becomes fliisht^d wiUi bluod. Those, 
of the external ear. for example, run m llic cervical symj 
tbetic-, from the lower part of the neck wiiero they leiive 
•ptuni cord, until they reach the iirteriii! Itianches for 
ear and riin along the smaller twigs to it. If, therefore, 
the cerrical iiympathetie be divided on one side in an.j 
anvKthetixed rabbit, the ear on that tiide beeomen red and 
warm from the dilatation of its arteries and the cxlrii' 
amount of blood Howing through it. If, liowever, Ibat end 
of the cut nerve still attached to the ear be excited electri- 
cally or olherwiac, the ear arteries contract gradually untilj 
their jiiiswtge t* almost closed up. and the whole organ 
cornea oold and veryjKile, Although these vaso-consirictor" 
fibres are thus shown to pass through the eenical £ymi«-^j 
tlietie, other rxperiments show that they really originat^H 
in a grnnp of ner\'(--oells in the medulla olilon^ta. anel^^ 
from there run down the spina) cord to the lower part of 
the neck, where they pass out in the anterior roots of some 
^inal nerves and reach the sympathetic system. The enme i 
it true of nearly all extrinsic vuso-eon^lrietor ncrve-fibrea i 
in the Body. Some few possibly arise from centres in the 
Bpinal cord, but the gn'ut majority come primarily from 
tlie mednlla oblongata, and the collection of nervc-celU 
there from which they spring is known as the vn»o-motnr 
eentn; a better name would be the vaso-contlridor (tnire. 
Tho Control of tho Vaao-Motor Centre. The vaAO- 
tnotor centre is automatic; that is to say it maintoini^ a 
certain amount of activity of its own, independently of any 
stimnh reaching it through afferent norvc-fibres. Never- 
theless, like nearly all automatic nerve-centres, it 'a under 
reflex control, so that it« activity may be increased or le 
aened by aiferent itnpulscs conveyed to it. Nearly every mi 
sory nerve of the Body is in connection with it; anystimt 
Ins giving riKe to pnin. for example, excites it, and 
constricting the arteries, increnses the peripheral resist 
auce to the bluod-fluw and raises arterial premure. 



rA3fi-DTT.AT0R NRUVEB. 



3S5 



the other hund, ccrtitin titires convoying impaku from the 
bmrt inbibit the wntro and dilate Uio *rteriee, lower 
Wood-pressure, and diminish tlie reaiatance to be overcome 
bj the bcurt, Tiiwo librci! rnn iii branchve of the pneumo- 
g^rio, and are known &* the dvpMssor fibre*, or in certain 
animals, for example the rabbit, where they arc all colU-clcil 
into ODU brsiieh, lu the deprtator tifrve. If this nerve be 
tlivided and its cArdi^ic end mimiitnted no effect ia pro- 
duced, btit if it£ central end (that ttttll connected 
with tlie rest of the pnciimogiwtnc trunk aud through it 
with the medulla obi ong;ata) be. .uiranlated, arlcrial prcdsiire 
gitadually falls; this result being dependent upon a dilats* 
tiou of the umiill arteriea. and conxdiucnt diminution of 
the peripheral reaiiitaiice, following an inhibition of the 
Taao-motor centre brought about by the depre«!or norvo. 
Through the deprcfsor ucrvo tho heart can therefore influ- 
ence the calibre of the amall arteries and, by lowering 
aurtic prc«suro, diminish 'd» own work if need be. 

Blualung. The deitressor nervea control a gn^at part of 
tlie viMo-niotor centre, and so can bring about dilatation 
of a large niunlwr of artories— their influence ia called into 
play when genenil arterial presMiire i^i to be towered, but ii 
ludom for controlling local blood-supply. Tliis i« man- 
aged by other nfTeroiit norvoa. each «f which inhibits a 
small part only of the vaao-motor centre, governing the 
arterivw of a limited tract of the Body: the dibitation of 
thei^e increattex the amount of blood flowing through the 
particniar region to which they are distributed, but doea 
not aflfect the total reaistanco to the blood-flow euflSciontly 
to influence noticeably the general preaimre in the arterial 
«yi(t«m. In Idimhing, for example, under Ihc influence of 
an emotion, tliat part of the vaao-motor centre which Hup- 
plieM couxtrictor nervea to the arteries of the akin of the 
neck and face, is inhibited by nerve-Gbrc« proceeding from 
the eerebrnm to the modulln oblongata, and the face and 
neck eonMeipicntly become full of blood and flush up. 
Quite similar phenomena oeour under olhor oouditiona in 
many pari* of the Body, although when not visible on the 
surface wc do not nanallj- call them blushes. The mucous 



i 





THB HUMAN BODY. 



mombnuio Jiuing tko empty sLoHiat^li in pilid and itfi ar- 
teries contracted, but aa souq »a food enttrs tbe organ 
it becumos rod und full of blond; llio food «limiil»ting 
aSenant ncrve-fibriu tliuro, which iiiliibit llmt part of the 
vuso-niotor cunlre which governs the gastric artf^ric^ii. 

Taking Cold. This common disease is not unfnxjueat- 
ly Ciuisc4 through undiK' relics ciritenivtit of the vaso- 
motor cciitrv. Cold acting upon the skia stjmiiltiteji, through 
tJie afferent nerres, the region of the v«Ko-motor centre gov- 
eraiiig the skin arteries, and the latter become coatritctod, 
oa shown by the pallor of the sTirfae& This has a two-fold 
iDBueace — in the lirst place, more blood U thrown into in- 
terniil part^, and in the second, coiitniction uf the arte- 
ries over so mueli of Uio Body considerably raises the gen> 
eral blood-preesure. Consequently the veMOlti of intflrusl 
part« become OTcrgorgi-d or "vongested/'scoDdilion which 
readily passes into iiiUammation. Accordingly prolonged 
expomirc to cold or wel is apt to he followed by c»t«rrb or 
inllnmination of more or les§ of the respiratory tract caus- 
ing bronehttls, or of the iulcKlitii'r) ouiieing diarrhica. In 
fact the commou summer dinrrha-» i^ far morv often due 
to a chill of the surface, eansing intestinal catarrh, than to 
the fruits eutt n iu that season which are so often blamed 
for it. Tho htao. prercuttve m to wear, when ex))OGed to 
grmt changes of temp<-raturo, a woolen or at li^iuc a cotton 
garment over the trunk of the Body; linen is so good a 
conductor of heat that it permit* any irlmtige in the ext«r- 
nid t<^'mporature to act almost at once upon the surface of 
the Body. Aftor an uiiuvoidabU^ wpo*ure to cold or wH 
the thing to be done is of course to maintain the cutaneoiu 
circiiUtion; for this purpose movement should bo |M?raisted 
m, or a Ihick dry outer covering put on, until warm and 
dry clothing can be obtained. 

For healthy iK-reons a lemjwrary exposure to cold, aa a 
plunge in a balh, i^i good, since iu them the sudden contrac- 
tion of the cutnnoou); arteries soon passes oft and Is suc- 
oeeded hy n itilntation oaiivin>; u warm healthy glow on the 
surface If the bather remain Irin long in cold water, bow- 
over, tliiK reaction pusses uU and is sueceedud by u mtisn 




VAaasiLATOs yearse. 



«67 



L 



pcrauuot chilltDCW of the narfaoc, which mnT eren laet 
till day. The bath should therefore be hti Wfora this 
oeoars, bul no absulntc time can be stated, as the reaction 
IS more marked and lueU longer in ilroug persons, aud in 
those tued to cold bntbiiig, Uian in oUicra. 

Taso-Dllator Nerres. We bare already seen, in the caM 
of the i^loin:ki.'li, oni' mothoil by which » locally increased 
blood-supply may be bnMij^ht abatit in an organ while it is 
ntwork. Usually, however, in the Body thi« ix m.-iniigcd 
in anotlier way: by vaso-dilator nerves which inhibit or 
paratyxe. not the Tiigo-motor t-cntrc, but the intrinsic nerv- 
ous supply of the bloiid-vcjiseU The ncrvesof the skeletal 
mnscles for example contain two seta of fibres: one motor 
proper and the other vaso-dilator. Whon the muscle con- 
tracts in a reflex action or nnder the iullucticc of the will both 
seta of fibres are eicited; so that when the or^an is »l at 
work its arteries are «initiltanooui<ly dihitcd and more blood 
flows through it. Quite a siniiUr thing occurs iu the sali- 
vary glands. Their coUx, which form tho saliva, are aroused 
to activity by Rpccial nerve-fibres; but the gland nerve ako 
contains vaso-dilntor fibres which ^mnltaneously caufie a 
dilutatiou of the gland artery. Tlirough such arrauge- 
mcnt4 the distribution of the blood in tho Body at any 
moment is goTi'incd: so that working parts shall have 
•bundance and other part^ less, while at tho same time the 
general arterial pressure remains tho same on tho avorogo; 
since tho exponaion of a few gmall local bnincbea but little 
inflnenocs the total |>cripheral raiistanoe in (he viwcniar sys- 
tem. Moreover, commonly when one set of organs is at 
work with its ressels dilatcil, otliers arc at rest with their 
arteries comparatively oontracted, and so a goneml average 
btood-pressurt is mairitainod. Few pcratms, for example, 
foel inclined to do brain work after a heavy meal: for then 
a great part of the blood of the whole Body is led off into 
tho dilated vi^ssels of the digestive organs, and tho brain 
geta a smaller snpply. On the other hand, when the bniiu 
is at work its vessels are dilated ami often ilu' whole hrad 
flotbcd: and so ozcitement or hard thought aft«r a meal 
n lery apt to produce an attack of indigestion, by diverting 




S58 



Ttm nVMAS BOOT. 



th« blood from the abtloniinul organii where it onght to be 
at that lime. Yoang persons, whose organs have a. stipcr- 
abnndance oi energy enabling them to work uniler uufuTor- 
ttble conditions, are lens apt to suffer in such ways than 
their cldiTB. One wes boys running actively abont after 
ctiting, when older people itsv[ a deslrt! to jit ^uiot and ru- 
minat« — or eton go to i-Ieep. 



^ 



CHAPTER XVni. 

THE SECEETOKY TISSUES AND ORGANS. 

Definition. In a strict nease of tlie turnut «vcry pro- 
cv»6 in which substAnces aro 8(!p&rat4>d from the blood, 
vhothcr thej be xltered or nnalt«red. u ''eecret«r;" and 
every prodnct of socb asopamtion is a"t<ecrcti»n;" in this 
sense secretioiks wotild bo Hopunible into thnio olii«s<^. (1) 
Liquids or gwfcs traniiiiding on free Hurfacc» of the Iloily, 
whcahcr cxlernal or internal; (2) the liqnids (lymph) 
moistening the various tissues of the Body directly, filling 
the {Qter^tices hctvrecD tliem and not contained in definitely 
limited cuviticti ; (3) all the solid tiitsues of the Body tinov, 
lifter an early period of enibrjouic life, thoy are built up 
from niiiteriidsdorivcd from the blood. Secretions would 
tluiK come to inclnde all coti>l4tucntii of th« Body exco})! 
Uie blood itself but, while it ia well to boar in mind tluit 
the whole Body is in siith a wayderived from the blood, in 
practice the term secretion u given a narrower connota- 
tion, the solid tissues and tlielympb beinj; oxcludod; so that 
A secretion is a Diatvrial (liquid or gaseous) derived from the 
Uood and poured out on a f roc mirfacv, wh<.<thfr that of the 
general exterior or that of an intGrual cavity. Such tnie 
secretions fall into two classes; one in which the product 
is of no further use in the Body and i# nit^rely separated 
for ri?mnval. us the urine; and one in which Uie product is 
inittndod to be \iwi\, for instance as a sotrent In the diget> 
tion of food. The former group arc sometimes distin- 
guishcil a* exrrtiion* and tho latter as imreliont proper, but 
there is no real difference bclwocn them, the argann ami pro- 
oesaos concerned bciut; fiindumcnlally alike in each casp. A 
bettor division is mWtranimdata&xiA. secretions, ^itAaiwiaf 



m 



TBB mn/Alf BODY. 



tion being s product which contains oothing which did 
nut previoiifil J Kx\si in l1i« blood, and then in aucb <{aantit; 
as might be dcrivablo from it bv mvivly [ihyucal processes; 
whik' a sccrvliiin in addition to tiunsudntioQ elempiitH oon- 
tftiiis II epfdjir eUmfitt, due to llic gpecial iihysiolugical 
aetivit; of the 80cr«tDr}- organ; being cither Komethitig 
which docs not exini in the blood at all or something vhieh. 
exieting in the blood in «niull <|iiuiitity, ozists in the Kcut- 
tiun in KtiL'h a high projxjrtltm thut it must have bwn 
aclively picked u]) and couTojed tliere by the secretory 
tissues concerned. For ingtAncc, the giuHric jnico contains 
free hydrochloric acid which dupii not crist in the blood; 
and the urine contains so much ni-ea that we mtut suppose 
it« ccll« to Imvc a iit'ciilifir power of romtiving that body 
from the ISi^itidf flowing near tlioni. Thhi subdjvidon is 
also juetidable on histological grounds ; wherever there is 
a secreting surface it is covered with cells, but these where 
transndata are formed (as on the serous membranes) are 
more flat Ecalee, with little or no protcpltum remaining in 
them, while the cclU which line a tnic KCcroling wrgan are 
enboidal, 8]>1ierlcal, or columnar, and still retain, with 
their high physiological activity, a good deal of their primi- 
tive |iroioijlu«ni in a but slightly moditied stale. 

Organs of Socretion. The simplest form in which a 
secri'liiigorfjiHi >n'c:iir!t (.-J, Fig. 88) w that of u flat membrane 
provided wiili a layer of cells, a, on one side (that on which 
the secretion is poured out) and with a network of capil- 
lary blood-vessels, r, on the other. The dividing mem- 
brane, b, is known as the bawment membrane and is ufually 
made up of flat, closely Btling cunnective-t issue corpuscles: 
supporting it on ]ts deep side iii a Inyer of connective tissue. 
d, in which the blood-vessels and lymphatics arc supported. 
Snch simiilo forms of socrutlng surfaces are found on the 
scrou.i membranes but are not common; in most cases an 
extended area is re<|uirGd to fi>rm the necessary amount of 
secretion, and if this woi'e attained simply by spreading out 
plane surfaces, these from their number nnd extent would 
ba hard to pack conveniently in the Body. Aeeordingly in 
most cases, the greater area is attained by folding the 



FORMS Of OLASm. 



Ml 




no. n.— Fonn* of Elandt. A. nnloiplp Keratlne •urtero; it. lu npllhnllum i 
b, iHunawDt membruic; r. cs^arlM. It. A •ImpM Inbulur aland : V.twefnX- 



aMirfiui- Ini^rvunl hy piulnuliiij*. K. a. ilmiitr ncuaote Klaii<l. I) anil <>, 
IMUEKl lulMilar j^UciJii, F, a iMiiip4>imi1 mivinrwi* ClftluL lli Alt InJI B the 
FKpllUrloH »nr omi'UsJ (or ihp unkp -if i-rfMincw //, naif ot a liiiflil.i Jufcl 



«ped nuvtnoa* Kland ^ r. lU main iIul-i Tin- IniT •! by mUtokr hoa brvn utad 
nib for Uie iMueoient iDWnliranii aboic. uiil [or l»nuichN ot duct bploo 



S6S 



TUIC UUMAX BOOT. 



eecretiag surface in varioaa waya so that a large Rnrfacft cun 
be [iiickeii in a fliual) bulk, jii^-t as a. Chinese lantern vhen 
shut op occupiM iniidi \cm itfrace than whc-n extended, 
although \U luttuat t«urf»£e remuina of the aanie extent. lu 
K few cases the folding takce the form of protrusions into 
iho carity o£ the Bccrcling orgaTi as iiidicuU'd «l C, Fig. 88, 
and found on Mome fiyuoviiU membranes: but much more 
commonly the surface extension is attained in another vay, 
the basement memhraue, covered by its cpitheUum, bein^ 
pitted in or involuted as at B. Such a socrciing organ it 
known ns a gland. 

Forma of Olaods. In some cases the snrface invola- 
tionif are uniform in liiiimeter, or nearly so, throughout {b. 
Fig. 88). Such glands are known as tubular; examples 
are found in the lining coat of the Ktomach (Fig. 97*); also 
in the nkin (Fig.l^df), wliere llicy form ihc »Ktaf-giands. 
lu other cases the isToIntion swells oat at its deeper end aud 
bocomw more or less sacculated {E) ; ^uch ghiiid» are racfmoxe 
or adneua. The small glandii which form the oily matter 
poured out on the hairs (Fig. 119t) are of this type. In both 
kindi the lining cells near the deeper end are commonly 
different in cliai'aotev from the rest; and mound that part, 
of tho gland the blood-veseeht fonn a closer network. 
Tliesc deeper cells form the true Ricreling clemonto of tho 
gland, and the passage, lined with difTeront cells. leading 
from them to the surface, and serring merely to carry off 
tho secretion, is known as the glartd duct. When the duet 
ia undivided th(t glimd is timplr; but when, &e is more 
usual, it is branched and each brunch liiu> a true secreting 
part at its end. we get a compound gland, tubular (ff) or 
raoemofto (/■', H) as the ciwe may \n^. In such cases the 
main duct, into which the rest open, is often of con^idera- 
blo length, so that the secretion is poured out at some dis- 
tance hnm till' main mass of the gland. 

A fuUy formed gUind. H, thus comes to be a complex 
structure, consisting primarily of a duct, r, ductules, dd, 
and secreting recesses, w. The ducts and ductules are 
lijicd with epitbetinm wliich is nicrrly protective and differs 
in eliiiructer from the secreting epithelium which lines the 

•!' 3ie. i P. US. :P. 416. 



PnOCSSSSf CONCERXED Df SECRBTION. 



263 



^ 



do^wt {MUiii. SuiToundiiig eucb subdiTision and bind- 
\a$ it to ito Deighbor* is tiiQ gland utromn formed of con- 
nectire tissue, a lajer of which a\m comnuuily envelops 
the whole gliind, as its eapaule. Commoolj on lookiii|> at 
tbc Hurfacc of • large gland it u scoo to be 8oparutcd by 
partitionaofiu stroma, coarser llian the rest,into lobea, each 
of which answers to a main division of the primary duct; 
and the lobos arc uflcu «imilarly divided into enmllvr part« 
ovIobuUt. In the oonnectiTc tiaaiio between the luboa and 
lobules blood-vessels jwnetrate, to end in Hne i-upillary 
veeacls around the tcnniDal recesses. They never penc- 
trstt the baitement niembrnuc Lvrnpliutica and nervca 
take a similar course; bat tliero U reason to believe the 
ncrve-librcs penetrate the basement membrane and be- 
come (lircci.ly united wiih the wuix^ung cells. 

The FhyaioaL Frooeases in Seoretion. Prom the etrao- 
i.ure of n gland it is clear that all matter, derived from the 
blood and poured into its cavity, must pass not only through 
tlio viilLs o[ tilt* oipillnry blood-vcjui'It), but ol^d. by filtra- 
tion or dialysis, through the basement membi-sue and the 
lining epitlioliimi. By tiltratitm ix meant the passage of a 
fluid under pressure through the courier moctuuiical poix'-x 
of a membrane, as in the ordinary lilt«riDg processes uf a 
cbcniieail laboratory; and the higbiT the presxure un the 
liquid to lie liltered the greater the amount whieb, other 
things bemg oqual, will pass through in a given time. 
Since in tlie living Body the li<|uid jircsMiiro in tlie blood 
oapillaiies is nearly always higher than that oui«ide thetu, 
filtration is apt to take place everjn-berc to a greater or Um 
extent, and will be increaHcd in amount in any region br 
eircum«taiioo« raising blood-prcuure there, uiiddiniinisfaed 
by those lowering it. To a certain extent also the nature 
of the Ii<|uid llltered ha« an influence. True solutions, as 
tliose of salt in water, paM through unchanged; but solu- 
tions containing substances such as boiled starch or raw 
^SS albumen, which Kwell up greatly in water rather than 
truly dissolve, are altered by fliti'aiinn: tho fltlratu contain- 
ing less of the imperfectly dissolved body than the uufil- 
terod liquid. Tbo higher the preMuru the greater the pro- 



S94 



THE nrnAy bodt. 



portion of SDch substances which geta through; and ff 
Uie pnwnre ia dlight th« iri>t«r or other Eolrent may alone 
paM, learing all the rest bchiud on the filtor. Uodor 
moderate preaeare the blood maj thus lose b; filtration 
Hoch bodies onlvu water and salines; while aa increase of 
arU-rial [ireiwuro niaj lead to th« inMtage of albumcD mid 
Qbrinugen. t'nder heitithjrconditHnui, forexainple, the urine 
oootuiDB no albntuen, bat anjrthing increasing the capiltarr 
prcMture in tho kidn«vii will cud»o it to appear. Dialgtis 
or oaiHMiA bus already beeu considered (p. 43); by it sub- 
BtADceB pass through the intcrmfilcciiliu- pores of a mem- 
bnno indepcndciitlv of the pressure on either side, und for 
it« oroarrcDoe two li^iuidsof different chemtoaHtm^iitiition 
are required, one on each side of tho meinbniQe. At least 
if diSnsiou takes pluce, or is probable, between two exactly 
similar tohiti'>n^ the onuonnt and character of the fub- 
Btance4 pa^King opposite wars in a given time are exactly 
eqtuU, so that no chan^ \* produced by the diidirr<iK; wtiicli 
pructiotlly araounta to the same thing as if none occurred. 
When s solution in placed on one side <>f u membrane allow- 
ing of dialysis and ptire water on the other, il is found that 
for every iikjIcciiIo of the diwiolTed body that ]ia«ite« one 
way a dofiiiite amoniit of water, called the tndutmotic 
mjtiiPriletU ot that body, posses in the oppunlo direction. 
CryrtullitK! budicji a^ a rule (hiemoglobin is un exception) 
have a low endoflmoUo etjuivalent or are readily dialyzablc; 
while rolhiiU sach as gam and proteids, have a very high 
one, Ko that to get, by dialysis, a small amount of albumen 
through a membrane, a practically infinite amountof water 
must poBi the oUior way. Accordingly, if we find such 
bodies in a secretion we cannot suppose that thoy have been 
derived from the blood by osmosis 

Tho Cltemioal ProcesBss of SeorMloti. As shore point- 
ed out. »;firt;iin sRcrelioiiK, called tmnnidata. «ocm to bo pro- 
ducts of flllration and dialysis alone, cnntiiining only such 
Piibfltanocs aa those which are found in the blood )ilHsma, 
more or less altered in nltilivc rjuuntity by the ease or diffi- 
culty with which they severally xtu/vmA through tho layen 
met wiih on their way to the surface. But in many caaes 



TBK SPECIFIC KLBjaarrs of SBCBBTIOSS. 36S 



the fiompoaitioQ of a secretioa cuiaoi bo «ocoiitit«d for in 
tbiEway: it oontsm»ei>aio itpeci^etenutfl, dtlicraFiibstance 
whicl) dix>xnut i>xt:<L in The h]Qod at «U and miii-I therefore 
have beeii added by the secretJDf; mcnibniiic, or some 
iiudy which, nllhoii';h cxistiog iu tbo bkicd, dot!« hu iu siidi 
miniitv proportion comptirvd with thiit in which il U found 
in the Mcrclion, that fomo tipccial activity of the secreting 
r^lLs is indicalod; xome affinity in them for tlie«o hodic« by 
which they aetircly pick them up. 

Eueli bring celC we have seen, u the Mat of oonataiit 
chemical nclivily, biking up matcritd* from the medium 
About it, traiuiformmg and utilizing them, and sooner or 
luk-r restoring their elementj), differently combined, to the 
meiluim ugxin. By such mcuns it buildK uj> undmainlainit 
itj living RubNtanoe, and obltuna enirgy to oarry on its daily 
work. While this is true of all cells iu the Body, we find 
certain groups in which chemical metabolism is the promi- 
nent fact; colls which are (peoialixeii for this purpose just 
a» nitisctilur tibre is for contniction or a nerve-fibre for con- 
duction, and certain of th«so prominently M«toio{iofi«M(M, 
exist in tlie true gfauids and produce or collect tlie Bpeoiflc 
elemeuu of tbeir seoretiona. Their ohemical processes are 
no doubt primarily directed to tbolr own nutritivo matntA- 
nanco; they live primanly for tlieni.*olves, but their nutritive 
prooosscs are HUch that the bodieti formed in them and sent 
into the aeoretion are such as to bo useful to tlie rcit of the 
cells of the couimuuity; or the bodies which tliey apeolally 
collect, nud in a eertoun mn^e feed on, are those the re- 
mural ot which from the blood is eeseotial for the general 
'good. Their individual nutritive poculiantiu^are utilized 
foj the wulfiiri' of the whole Bmiy. 

The Mode of Aotivlty of Seoretory Cells. If we eon- 
sidei the tuples of activity of living celld in general, it be- 
comes clear that secretory colls may ))r»duoe the specific 
element of a secretion in either uf two ways. They may, 
MK u by-result of tbeir living phiy of force*, produco chemi- 
cal changes iu tbo sunounding medium; or they muy build 
ap certain siibetUDces in thomselves and then Kt them free 
M specific elements. Yeast, for example, in a ««cchai-ine 



^ 



«M 



TBH arVAX BODY. 



Bolutlon causes tlit* rciirrangcinciit into carbon dioxide, 
alcohol, glyi'ciiiio and succioio acid, of many fttomR of car- 
boD, tivdrogcu and oxygen which prcTioofily exiiite'd tu aagar; 
and which during the meUimorpliocitf wcro probablj not 
paewd through ihc living (^-11. How tb« luttt-r iivt« wo do 
not know with ceilainly, but most liki^Iy by pit:king ocrtJtiu 
nloms out of tho sugar mulcculti, und Icuriog the rest to 
full down into simpk-r compounds. On thuothor luuid, wc- 
find colls forming and atonn^ up in themselves large quan- 
titiea of eubgtanccs, which they afterwards liborute: starch, 
for inittancc, biding formed und laid by in mmiy fruit- 
cells, and afterwards rendered soluble and patuied out to 
nourish tlie young plant. 

Olfuid-eclls might n priori give riw to the s[)ecilic elo- 
raent3 of secretions in either of iheae ways and we bare to 
seek in which manner they work. Do they simply set 
«* fermcnls (howcn-r that is) npoti the surrounding 
medium; or do they form the s|>eL-iiil bodies which chamc- 
terize their eecretion, lirst wilhiu their own subdancc and 
th*n Itbt^ruto them, citlior di*iiitograting themselves or 
not ut the Munc time? At present there is a large and an 
increasing muss of endetice in fuTor of iLc Mi-ond ^'tew. 
There ia. no doubl. Bonui reiuon lo lielicve that every living 
cell can act mure or lens as a ferment upon certain solu- 
tions should tliey come into contact with it. Not always, 
of course, as on alcoholic firment, though oven tut rrgarcU 
that one formentatJve power iL wx ins viiry generally po«- 
Mated by vegetable cells, and there is some evidence that 
alcohol is normally produceit in small amount (and presum- 
ably by the fermentation uf sugar) under the iufluonce of 
ccrlttin uf tho living tistfuoH o^ tho Human Body. As re- 
gard* distinctively secretory oelU, however, the evidence is 
all the other way, and in manj oases we can sec the specific 
element collecting in the glund-celU before it is eet free in 
the secret ion. Forcxnmple, in the oil-gbiuilM of the Kkin 
(Chu]i. XXVll.) welind tbe secreting cells, at Qi^t granular, 
nucleated and protoplasmic, gradually undergoing changes 
by which their prolo]>bu!m di»ippeurs mid \t replaced by 
oil-droplets, ontil finally the whole cell falls to bita and it^ 



TBS ACTION OF OLAJUl) CELLS. 467 

detritos forms the secretion; the cells being repliwred by new 
ones coDRtimtU' furuiiKl williiii the j^litnd. In viioli cases 
tliv ^corctinn iii the ulliniato product of the cell life; tJi6 
result of tiegcneratiTc changvs of old ugo occurring in it. 

In other cii*i>.*, however, the Uljcralion of the spedfic 
element is not atteaded with tht? destruction of the secret* 
ing cell; i\s an cxitnipic wo may tjikc the ])ancrcae. which 
u a large ^Innd lying in the abdomen and forming a secre- 
tion Oiied in digestion. Among others, this secretion pos- 
sesses the power, under certain couditionH, of dissolving 
prot«ids and convening iheiii into dialyxidtle jieptoncfl 
(p. 11). This it owes to a specific element known as trgp- 
MH, the formation of which wjiltin the gland-cells can he 
traced with the micro8coi>c. 

The pancreiis, like the majority of the glands connected 
with the alimentary cunal, has an intermittent activity; 
det«rmin<-U by the i>ie>eii(;f or ahveucn of food in various 
piirts of tlie digestive tract. It the organ be taken from ft 
rect'iitiy killeii dog whieh has fiislcti thirty hours and, after 
proper prepuralion, be stained with carmine and examined 
microscopically, we get specimens of what we may call the 
"reeling gland "—s gland which ha>( not been secreting for 
some time. In theiie it will be 9>een that thccclU lining ihc 
secreting recesses present two verj' distinct zones; an onter 
next the biuoment membrane which does not combine wilh 
the ooloi'iug inatl«r and U granular, and an inner which is 
not granular but picks up the carmine. The granules wc 
shall llntl to be iiidiniUon;* of the prMcnce of a trypsin- 
yielding substance, formed in the cellH. 

If anotlier dog be kept fasting until be has a good uppe- 
lilc and be then allowed to cat as much meat na he will, he 
will commonly take »o much that the stomiirh will only bo 
emptied at the end of about twenty hours. This period 
may, so far as the pancreas is concerned, be divided into 
tiro. Prom the time the food enters the stomach and on 
for aboot ten hours, the gland secrete* nbundantly; after 
that the secretion dwindles, and by the end of the second 
t«n hoars has nearly ceiucd. We have, then, a time during 
which the pancreas is working hard, followed bj a period 



U8 



TBE BCM.iS BODT. 



in which its acririty is Tory littlo, bnt during which It is 
abiisduntty siijiiilipd with fcwd miiteriaU, The pflrifireiw 
t4ikou from ud uuiniiil lit the unci of tht firet period and 
jtroiiarcd for oiicrosoopic oxnmiiitttioii will be found dif- 
ftireut from that tiikeu from a dog kilUn) at the end of ihc 
eecoud digestion period, and also from thp Tc«ttng glniid. 
ToWiHils the end of tho period of uctivo work, the gland-cell* 
ar(> diminished in aize and the proportionn of the grunuhir 
and non-granular zones are quite altered. The latl«r now 
occupies most of the veil, whil« the gninnlar non-staininp 
innor xonv itt griMtly diminished. During Ihe itccrt-tion 
there is, therefore, a growth of tht iion-graoular and a dft- 
Rtmctionof the gnmnliir Konc: and the hitter procosit rather 
exceeding the former, iho whole wei-eling edl is diminished 
in 8iBe. During the second digeatiTe period, when secre- 
tion ie languid, exactly a rercrsc process luke* place. The 
cclb inci-casc in Biiie roiis to become larger Ihan those of 
the resting gUmd; and this giowlh in alinoiji cniii-elvdue 
to thegmnulor itone which now oi-cupicH mosi of the cell. 

These fact^ suggest that during secretion ihe granular 
part of the evils is used up: but that, siinnltuiicoiisly, the 
deeper non-gmniitiir xone, being formed from maioriaU 
yielded by tlie blood, grndii.illy gives riw to the granular. 
During active secretion the luTukiiig down of the lat- 
ter to yield the epoeific elements ODoan faster tlian ita re- 
genomtion; in a later period, howorer, when the secretion 
JB oearing, the whole cell gri)w.s and, es|>ecially, the granular 
Bone is formed faster than it is disintegrated; hence the 
great increase of Ihat part of the cell. If thin he so. then 
we ought to flud fiomo relationNbip between the digc«- 
five activily of an infiiflon or extract of the gland and the 
size of the granular zones of the cells: and it has been 
shown that such esist^; the quantity of trypiiin which ran 
be obliiined from a pancreas being projwrtionate to the 
H2e of thai portion of its cells. 

The trypsin, however, does not exist in the cidls ready 
formed, bnt only a bmly which yjeldst it under oert«n tar- 
cumstaneos, and called ttjmngm. 

If a perfectly fresh pancreas bo divided into halves and 





nmvEKCs OF ivsrvks ox ssoRsrioy. Mft 

on« portion immediatolj minced and extracted with glyoo- 
rine, wiiilc the other ia laid aside for twenly-four hours in 
u wnrni {ilaoc and then similarlj treated, it will Ik* found 
that the tirst t^lycerino extriK^t hiu> no )>oirrr of digesting 
proteida, whilti the seoond is very active. In other wonlfi 
the frfsh gland does not couluin trypain, bat only somi- 
tbing which yield* it under nome condition^: amon^; 
others, on being kepL The inaodre glyceririp oxiract of 
the froidk ghtntl is howfircr rich iuzj-mogon: for if « little 
acetic acid be added to it, trypsin is fomiM and ihv extract 
becomes powerfully digcttive. 

We may iheii sura op the life of pancreas ceil in tliis 
way. It grows by materials derived from the blood uud 
first laid doirn in tl>c Don-graniiJar none. Tliia latter, in 
the ordinary coarw} of the cell-life, gives rise to the grann- 
lar Kone: and in this is a store of inrniogcn produced by ' 
the nntritivc metaboUsms of the cull. When the gland 
secretes, the xymog«& \t converted into trypsin and set free 
in the (tocretion; but in the reetiag gbnd this irnn^forma- 
tiondoes not occnr. Pnring secretory activity Ihurcfore 
tbochitmicul procci<«^» Inking plnoo in the cell. Are different 
from thow at other periods; and we have next to consdder 
how this change in the mode of life of the cells is brought 
about 

Influence of the ITerroue System upon Secretion. 
When the gland is iicUve it is fuller of bluod than when at 
rc-'tt: tl^ aru-ric-'' uro dilitu-d mid iu capillario gorged so 
that it gcl^ a brighter pink color; this eitm blood-^uppty 
might be the pnmnry ciiiiR* of (he iillerwl mcUiboli«m. 
Again, tlie activity of the pancreas U under the iuQucncc 
of the nervous system, as evinced not only by the reflex 
secretion called forth when food i^ntem Ihe stonuich, but 
also by the fact that electrical Hiimulation of the medulla 
oblougiita will citui><' the glund ii> i>eeretc. The nervous 
system may. however, only act through the nerves governing 
the calibre of the gland artericR. and so but indirectly on 
the secreting celU: while on the other hand, it is possible 
that nervd-fibree act directly upon the gland-ocUs and, con- 
trolling tluir DOtriliv* proceaees, govern the production <rf 



vn 



THS nxmAN nODT. 



Hie trypsin. To decide between the relative importaoce gf 
these posaible agencies we must pass to the coneiderstion of 
otlicr glunda; siuoe the question can only be decided by 
cxiicriment upon the lower animiils. iind the petition of 
the pancreas and the difficulty of getting ut it« uimtoh with- 
out Buch (CTcre operations as upset the physdological condi* 
tion of the ammal. furnish obstacles to itu study which 
have not yet been overcome. 

In cerljtiu other glundit, however, we find concloUTC ovi- 
doncv uf a direct a<!tion of nerve-fibres upon the secreting 
elements. If the sciatic nerve of n cat be stimnlated elec- 
trically the bulls of it« feet will Kweitt. Under ordinair 
circumstaQCOS the^ become at the same time red and full 
of blood; but that this congestion is a factor of subsidiary 
importance u» regards secretion is proved by the facts that 
stimulation of the nerve is still ublc to ezciU! the glutid- 
cells and cause sweating in a liml) whiirh has been ampu- 
tated ten or liftven tninutes (and tu which therefore no eir* 
onlatory ohMiges can occur) and also by ttie eold owcats, 
■(rith a pallid skin, of phthisis and the death agonv. It is, 
however, with reference to the submaxillary and parotid 
salivary gUuds that our information ii* most ]ircciso. 

When Iho mouth is empty and the jaws at rest the sali- 
vary secretion is companitivcly small: but a sapid substance 
placed on the tongue will cause a copious flow. Tbo phe- 
nomen<m is closely comparable to the production of a reflei 
muscular contraction. A stimulus acting upon an irritable 
tii)sue excites tJirongh it certain alTcreiit ncrvo-fibrcB: IbcM 
excite a nerve-centre, which in turn stimulates efferent 
fibres; going to a muscle in the one case, to a gland in the 
other. It will be useful to contiidcr again for a moment 
what occurs in the case of the muscle, taking account only 
of the elTcront llbrcs iind the purld they act upon. 

When a munule in the Body Ia made to contract rcflexly, 
through its nerve, two events occur in it. One is the 
shortening of the muscular fibres; the other is the dilati^ 
tion of the muncular arteries; every muscular nerve oon* 
tains two sets of fibres, one m()tar and one vaso-dilator, 
Ud normally both act together. In this cuse. however, 



nmuKKCE OF yKRvss ON aBcntcrroy. vn 



it Is cinir lliitt the KCtiriticR of botli, thongh correlated, are 
AHetittallv indepeudent. Tbo cuntroctioii i« not dne to tlie 
greater blood-flow for, not mily cilu an eioiaed tuUHcle en- 
tirely dejirired of l>lood, he made to contract by stimiiluting 
itM nerves, but in an animal to which a sniidl do*c of ciiniri 
— the arrow poi«ou of certain South Amerivau Indians— hoa 
been given, Btimulntion of the nerve will cau^e the Toecu- 
lar dihilation but no moscnlur contraction: the curari jmr- 
idyzing the motx>r Gbre^, but, nuluM In lur^i^ doKi.^ leaving 
the TSiio-dilal^irii intact. The muscular fibrea themaelvea 
are qnite unacted npon by the poison, as evinced by their 
ready contrautiuu when directly stimulated by un cloctnfi 
sliock. 

Now let us return to the (uilivary glands and see how far 
the taais arc compiirable. The main nc-rve of tliv ^iibinax- 
iUary gland U known ax the chorda (ijvijiiiiii. It it be di- 
vided in a narcotiised dug, and a tube placed In the gland- 
duct', no saliva will bo found to How. Dut on <tinitilu1ing 
tbc periiilieral end uf the nerve (thai end still connected 
with the gland) an abundant secivtion iuVvn pliice. At 
the same time there is a great diluiiiliun of the arleriea of 
the organ, much more blood than before flowing throngh 
it in a given time: the chorda obviously then contains vhmo- 
dilator fibres. Now in this case it might very woll be that 
the proceM was different from that in n miiflole. It is con- 
ceivable that the sucretion may be but a filtration due to 
increased pre-^ure id the gland capillarioK, con^MHincnt 
on dilatation of the arteries supplying them. If a greater 
filtration into the lymph sjiaces of the gland took place, this 
liquid might then m«rely ooze on through theeecretiug colU 
into the commencing ducts and, as it piissed throngh, dis- 
solve out and carry on from the cells the specific orgitnie 
elements of the necretion. Of these, in the nubmaxillary 
of the dog lit li-tist, mucin \» the mort imjwrtant and 
abundant. That, however, the process is quite different, 
and that thorL' nre in the gland true secretory fibres in ad- 
dition to the vaso-dilutor, just as in the mnsole there are 
tmo motor fibres, is provinl by other experiments. 
If Uie flow of liquid from the excited gUnd were merely 




trt 



TtlK nUXAS BODY. 



tlie onteome of a filtration dependent on inenaaed blood 
|>re«nu« in it> th^n it ia cl«ar that t)ii> presnire of tbo 
vecntion in the duct could never Hac above the prenure in 
Uio blood-ve'^U of tbe gland. Now it is found, not onlv 
that the gland can be made to »cret« in n n-t^ntlj decapi- 
utcd nniniul, in which of connte there is no Mood-prrMnirc. 
but that, vhen the circulation b going on, the pressnra of 
the eecretion in the dnct can rise far beyond that in the 
^atid arteries. Obviotuly, thon^ the mcrvtion is no qnes- 
tion of mere (lltralion, «ince a liijiiid cannot filter against a 
higher preiware. Finally, the proof that the vascular dila- 
tation is quite a tnbsidiary phcnomonun has been com- 
pleted by sliowjng that we can pro<ln<M) nil the incrcMed 
blood-flow through the gland without getting any secretion 
— that just as in a muscle nonre wo cau. by enrart, paralyze 
the motor tilircio and leave the vaAo-dilatorfi intact, ao we 
c«i by atropin. tbe active principle of deadly night-shade, 
got tiimilur plicnomciiK in the gland. In an utro]>tn''l 
animal stimnlalion of tbe chorda prodncea vascniar dila- 
tation but not a drop of KOcrvtion. Briiit^ng blood to 
the cell* abandantly, will not innko tliom drink; wo must 
HMk lomething more in the chorda than the vaso^dilator 
flbrea — eome proper eocrptory fibres; that the poison acta 
npon them and not upon the glund-colls, is shown, as in 
the miiticlc by the fact rhnt the cells slJll are capable of 
activity when stimulated otherwise than through the 
chorda tympani. For eximi]>le, by stJmnlation of the sym- 
pathetic fibres going to the ginnd. 

80 fftr then we seem to have good evidence of a direct 
a^^tion of nen'e-fibres upon the glaiid-eoUs. But oven that 
is not the whiilo niattvr. It ii» extremely proWilo. if not 
certain, that there are two sets of secretory fibres in the 
glaiid-nervea: a set which so acls upon the colla as to ninVc 
them pasi on more abnndaully the tmn«iidation elem(<nt« 
of the secretion (the water and mineral imits), and another^ 
(juiteditforont. which jfiiTcriis tliechemical transformations 
of the colls DO M to maki' tlivm prodnco initrrin from matters 
previously stored in them, in a comparable way to the pro- 
duction of trypsin from xymogen in the active pane 



USFLVESCS OF XJSBVSB OS SBOBBTJOS. S73 

Tfa«se latter fibres may be called *'tropbio," eince thej 
directly control the cell mctuboUsm: while ibe fornKT may 
Iw chIKhI " tiiin sudatory" fibres. Some of Uie evidence 
which leads to this conduuou \» a little comjilex. but it is 
worth while to eonitider it briefly. In the first jilucc, on 
stiiiiuliitiriii iif llie oiiorda of an uneihauflted gland (that is 
a gland not over-fa limned by prcviouis work) the following 
{loiuUi can bo noted; — 

With increasing strengtJi of tJie Htimulus the (^nantity of 
the gecrctiun, that is of the water putired out io « unit 
of time, iiiereoM;.-'; at the name time the mineral saJtfl alao 
increa*ie, but more ra])idly, m that their percentage in a 
rapidly formed Kccretioii U grL^aler tbun In a more elowly 
formed, np to a certain Umtl. The |»erceDtuge of organic 
constituents of the secretion also increases up to a limit; 
but soou ccasee to riiie, or even fidb again, while the water 
and aattastill increate. Thiaof courvo '\t readily iuU-lIigible; 
since the water and salts can be derived continually from 
ttie blood, while the apecifio elements, coining from the 
gland-cetk, may be soon eiliausted; and so far the experi- 
ment givoJi no evidence of the existence of distinct nerve- 
fibres for the wilts and water, and for the Bjx-eillc elements; 
all vary together with the strength of the stimulus applied 
to the nerve. But undir slightly different circumstancM 
their quantities do not run parallel. The jiroportion of 
ttI>ocifiu elements in the secretion is largely dependent on 
whctlier the gland hiLf been previously excited or not. 
Prior stimulation, not carried oti of courso to exhaustion, 
largely inereases tlie percentage of organic matters in the 
secretion produced by a subsequent «timulatiou; but has no 
effect whatever on the quantity of water or salts. These 
nro governed outtrely by the strength of the second stimu- 
lation. Here, then, we find that under Kiinilarciroumstancw 
the transudatory and si>ecific elements of the secrctioD do 
not vary togotlier; and are therefore probably dependent 
upon different exciting causes. And the facts might lead 
us to suspect tliat there are in the chorda, beside* the vaso. 
dilator, two other sets of fibres: one governing the salts 
and water, and the other the Hpceifiu elemeutii of the sooce- 



271 



TRE nUMAX BODY. 



tion. Tlio CTidcnc* U, perhajw, not quiie conolusciTe, h 
experimenU upon tb« piuvtid glund «f thu dog put tlie 
matter beyond a doubt. 

Tlio Bubrnaxillnry glaiid reoeires fibres from tlie Bjmpft* 
thetic system, as well aa the chorda lympani bora the 
cerebro-s))ia!iI. Excitutioii of tbc liympiitbctic Ilbi^ii caUMM 
tho gland W werete, but the aaliva jiouwd out is difler> 
ent front thut following chorda gtimulation. which is 
in tlie dog abundant und compunitivoly poor lu organic 
ooDstituentB. und uocompHniod liy vusciilar dilntution: whilfi 
the " i^ympiithctic eiilivii," m it is eallt-d, is Iftss abundant, 
very rich in mucin, and accompanied with constriction of 
the gland arteries. According to Uie above vi«w wo 
might ifuj>i)oso that tho cliordu contaius muny tranando- 
tory and ft^w tropliic HbreH, and tho sympathetic many 
troj)hic and few trunsudatory. It might, however, well be 
objected that the greater richness in organic bodies of tlie 
sympathetic saliva waa reidly due to the small (juantity of 
blood reaching the gland, whon that ncr^o wae stimulated. 
This might alter tho niitritivo phenomeua of tbo oelU and 
caufle them to form muein in unusual abundance, in whidi 
caae the trojdiic influence of the nerve would bo only in- 
direct. Ex|ionmcnt«( on the pitmtid preclude this oxphm- 
ation. That gland like the submaxillary getit nirvc-fibroa 
from two sources: a cerebral und a sympathetic. The latter 
^ter the glaud along its Krtory, whilo tho former, origia- 
atiiig from the gloaso-pharyngeal, ma in a roundabout 
course to till.' gbmd. Stimnlatiou of the cerebral fibres 
causes an abundant secretion, rich in wuier and ludU, but 
with hardly any organic constituents. At ibe same time it 
produces diliitalion of the gland arteries. Stimulation of the 
qrmpathetic cutise." contraction of tlio parotid gland aLTteriee 
and no secretion at all. Xevertheless it canses great 
changes in the gland-ci-llM. If it bo first stimulated for s 
while und then the cerebral gland-iiorre, tho msultjng 
seoretion may bo ten times as rich in organio bodies as that 
obtained without jirevious Ktimulatinn of the eympHthetic; 
and a similar jihenomenon is observed if tho two ncrres be 
ctimuhili.'id ximultuiiooufly. So that the sympathetio aem. 




nmrBycE or xbrves o.v sEcasrioy. 275 



though tmabk of itself to catiw a secretion, brings about 
great chemicul chxngcs in the gUnd-ctlltt. It ts u dietinct 
trophic nerve. Thia conclusioa is oonfirmed by hiatoloxy. 
Soctions of tlic gliinU uf tor prolonged stiniiilntion of the sym- 
patlietio show itn oella to be quite altered in apjiearanpc, 
and in their tendency to combine witli carmine, when com- 
pared either with thoK« of tho resting gland or of the gknd 
which has teen made to secrete bj stimulating its glossio* 
pharyngeal brunch alone. 

Wi- liavc *tiil to mpot the objection that the i«nopnthvtic 
fibres may be only indirectly trophic, governing the meta- 
bolism of tho eellit through the bloud-rcssels. If this be 
so, ontting off or diminishing the hlood-i^upply of the 
gland, in any way. ought to have theeame result as stimula- 
tion of its ^ymimthetic flbroii. Expcriuicnt shows thnt 
sach u not the case uud reduces us to a direct trophic iuflii- 
6Doe of the n«n-e. When the art«nce art' closed and the 
cerebral gland-nerve stimnlated. it is found that thtt iier- 
oestage of organic coni«utueuts in the Kccrction is as low 
as usual; it remains almost exactly the same whether th« 
aitoriea arc open or dosed or have been previously 0]>en or 
oloaed. We mast conclude that the peculiar influence of 
the sympathotio does not depend upon its vaso-constrictor 
fibres. 

These observalions make it clear that the plmnomena of 
secretion iiru dv])cndcut on very complex conditions, at least 
in the salivary glands and presumably in all others. 
Primarily dependent upon Gltrution and dialysis from the 
blood-Tes8old and tlie pliysiological character of tho gland- 
cells, both of these factors are controlled by the uerrous 
system, the secretory tiiisuei> being no nioix' antomatic than 
the muscular; and the facts also give ug important evidence 
of power of the nervous system to influence cell nntritiou 
directly. 

Summary. By secretion is meant the separation of Much 
Bubstinu'L^ji from tlm blood iw (ire poured out on free enrfaces 
of the Body, whether external or inlernal. In \t» simplest 
form it \» merely a physical iiroc^x.t dependent on filtra- 
tion and dialysis; for example the eliminutiou of carbon 
dioxide from the uurlaoea of the lungs, und the vaieiy 



vn 



TBE HfTMAN BODY. 



liqnid poared out on t!ie surfaces of the BCroas membranes. 
Stivh socretioiiH am knowa us tramudata and tbcir umouut 
it onl; indireoUy controlled bj the DOrroni ^stem, tbrougb 
tho iaflnciice of the kttt^r upon t)l(^ circulution of the blood. 
The cells lining erudi Rurfuce^ are not nixiretun' UssiieH in 
any tnm seiue of tiie word, being increlT flat, innctire, thin 
MslCB {irotticting tho cTirfuces. In other ciuch the lining 
cells arc thicker. and a^dvelyooncerned in the prooem; they 
uro then ustiuUy spread over the receases of a much folded 
iiivmbrauv, so thut tho whole is rolled up into u compact 
organ called tt gland, th« socrctiou of which may contain 
only transudation ei&meut* (»» for cxniniile that of tho 
laobiymal glands which form t)ie tears) or may contain a 
tpecific element, formed in the glund by it« cello, in addition 
to tran.tudiiti<iu elemcntin. In cilher ca«e tho activity of 
the organ is directly influenced by the nervous sTstem, 
usually in a reflex manner (e.ff. the watering of the eye* 
when the eyeball in touched and the luiltva poured into the 
mouth vhen food is tasted) hut may abo be otherwise ex- 
cited, as for example tlio flow of toars andcr the influence 
of thiHMt changes of the central nervous itystem which are 
awooiated with sad emotions, or tJie watering of the mouth 
at the thongbt of dainty food. The nerreti going to such 
glaiid«r bejiides controlling their blood-vosaeb, act upon the 
glaod'Oells; one set governing the amount of transudation 
of water and salines which shall take place through tliem, 
and another (in tho ctuc of gluud^ producing Mccrctiond 
with one or more specific doraenls) eontrothng the prodno- 
tiou of these., by starting new chemical processes in the cells 
by wiiich a substunce built up in tliem during rest is con- 
vcrlc-d into Ihe KpeciBc element, which is Holuble in and 
carried oS by the transudation elementa. What tlie speci- 
flc element of gland shall be, or whether its secretion con- 
tain any, is dependent on the nature of its special cells; 
how much trau«udntion and how much spocific olemeiit 
shall be secreted at any time i^ controlled by Uie nervous 
systom; Just as the contmctility of a muscle depends on 
the endowments of muKculur tissue, and whi-ther it sliall 
rest or contract — and if the latter how |>oworiuily — upon 
iti uerre. 




CHAPTER XIX. 

THE I.NXOME .IND KXPESDITURE OP THE 
BODY. 



The Materinl Lobmb of the Body, All day long wliile 
life liLsU eatii of us is kwiiig soiucthiDg from bis Uody. 
Tho air breuthed into Dm longs bcconu'8 in them ludon 
with carbon dioxide and water vapor, which arc carried off 
vrith it when it is «xpircd. Th« tfkiu !« ug cotutantly giv- 
ing off inoixtiiro, the total quantity in twenty-four houra 
beini; a good deal, cvou when thu amount pitssed out at any 
one time ig so emull no to he cvaporak'il nt once and so doca 
not collocl as <lro]iA of visible pempiralion. The kidueys 
again nre con.^lantly at work separating water and certain 
cryetalline uitrogcucous bodies from the blood, along willi 
Hoiiic inincTid nUI^. The product of kidney ttclivity, how- 
ovor, not being forthwith carried to tho unrfaee but to 
a reservoir, in which it awumulatea and which is only 
emptiod at iiil«rvaU, Uio luitivity of tliosv organs appears 
»t Ilrst sight intennitlont. If to tlieae losses we add cer- 
tain otiier waste substances added to the andigeeted residue 
of thu foo<l piu>^i>(l oiil from the alimentary eanal, and the 
loRf of hairs and of dried cells from the surfaro of the skin, 
il is clear that tho total amount of nuitU>r removed from 
the Bixly ihtily if coiisidenibte. The aclual <[uuntity varieo 
with the individual, with the work done, and with thu 
nature of the food eaten; but tho following table gives 
llpproximat4)ly that of tJio more important doily matenol 
lusaes of an average imm. 



I 



Z7& 
a 

a 

» 

is 

B 

s 
s 

B 
H 

H 

a 

s 



:3 



!§ 






ii 



OB 

n 

>- 

i3 

i 

■4 



O 

(0 






'•a 



THE nVMAS liODY. 






S 



E 






1 



i 



O 
^ 






« ■> 



■0 






o 



i 



O O 19 

-♦ o «i 
<i rf « 



» lO o 
t g • 






s 

3 



3" 






« « "7 

s - S 



© o 



'3 



e 






c 

3 



=5 g 









THE DAILT LOSBSS OF TUS BOOT. 



979 




The living Body thus loeea dailv in round unmljcrs 4 
kilograms of mnttor (8 lbs.) uad, eiricc il ih unable to 
croalo new miiiUT, this Inm mu^t bo compon^atej fur from 
th« exU>.rior or the tissuan woald soon dwindlu awny alto- 
gether; or at least until th«y were »o impaired that !ife 
CAino to nn «nd. Aflcr dcnth thf looses voald be of ii ditfiT- 
ent kind, and their qiiaotity much more dependent ujion 
anrroundiiig conditions; but cxiopt under Tery tinuBDal 
ciri:iini8tuncos tlie irasting away would still oontinuo In tb« 
doud Body. Finally, the composition of tko daily wostoif 
of the living Body in tolerably conxtnnt; itdoca not simply j 
loao a qtianiity of rantt«r weighing so mnch, but a ccrtaiai 
aniounl of detinite kinds of matter, carbon, nitrogen, oxygeDaJ 
and so on; and these sttmo stibstancc« muKt be rc8toi«d to< 
U from otitaide, in order that life may be oontinned. To 
give one asking for broud a etonu might, no doubt, if it noro 
swallowed. c<im|K^n8ato In weight for the matter lio Io«t in' 
twenty-four hours; hot bread wonld be needed to keep 
him uliw. In otlicr vonK the Body not only reqniroa ft 
Rupply of matlor from outside, but a supply of certain 
definite kinds of matter. 

Tba Iioaaea oTtho Body in Energy. The daily expendi- 
ture of matter by the living Body U not th« only one: na 
eontinuoiuily it \oio» in some form or another «nergi/,ot 
the power of doing work; often a« nicchanivAl work «z- 
pciided in moving external objects, but even when at rcat 
vTieigy is constantly Iwing lo«t to the Body in the form of 
huil, by radiation and vondtiction to earroanding objects, 
by the evafioration of water from tJio lungs and ekin, and 
by removal in worm exoretions. Unless the Body can 
mnke energy it muKt therefore rooeive a certain supply of 
it also from the exterior, or it would very «ooi) ccnso toj 
carry on any of it« vita] work ; it would be unable tol 
move nud would oooldown to the tcmperiiture of ^un^jund-' 
ing objcota. The discoveries of thii« oeutury having siiowu 
ifast energy is as indestmctihie and nncroatahle (ace Phy- 
aies) as matter, we are led to look for the souives of the 
BQpply of it to the Body; and finding (hat the living Body 
daily receives it and dies when the supply is cut off, we no 



!fSO 



THB nUMAS BODY. 



longer supposp, with Iho older phvsiolopsto, that it. works 
by means of a ini^Mtnouft vital force cxieting in or cn^tcd 
by it; but that getting energy from th« oatside it utiliua 
itforita piirjiosos— for the performaDoe of its nutritiTO uud 
other living work— and llu-ii rcliinid it to the o.iterior 
in what Uw pliysicisU know as a d<>grjidiHl slatt-; that iii in 
a Icjts utilizable condition. While energy- like matter Xi m- 
destructible it is, nulilcfl matter, tranKmuttible; ironiHalwuTt 
iron and gold alwayt gold; neither can by any mcaiuv'hich 
we pojiscss be converted into any other form of inullcr: and 
HO tlie Body, needing earVm. hydrogen, oxygen, and nitro- 
gen to buihl it and to cover itd daily lostHU. must be enp- 
pUod with those very sabslaacee. As regards energy this 
is not the cuee. While the total amoant of it in the atu> 
Terse is constant, itii form is constantly subject to change — 
and Utat one in whteh it enters the Body neicd not bo tliat 
in which it cicisls while in it, nor that iu which itleaves iL 
Diiily toning heat and mechaiiieal work t)ic Body doe« not 
need, could not in fact much utilize euei^gy, supplied to it 
in tJieee formM; but it doe* noitl energy of tomo form and 
in amount equivalent to that which it lo«c8. 

The Consorvation of Energy. The forms of energy 
known to n» wv nut ii<-i>rly «■> numerous as the kindu of 
matter. Still we all know several of them; such a£ light, 
h«Bt, eoond, electricity, and mwhauical work; and nioctt. 
people uowftdaya know iliat some of tlic^e forms are inter- 
convertible, BO that direrlly or indirectly we c<m turn one 
into Bootbor. In i>iicb changes it ie found chat a definite 
amonnt of one kind alt>'a\-x di^ippeani to give rife (o u 
certain qnantJty of the oiher; or, in other words, tluit no 
much of (he fii-st form is equivalent to so much of Ihp 
second. In a Ktcam -engine, heat is produced in the fur- 
nace; when the engine is ut work all of this enejgy does 
not leuvc it ns heat; eome goes as mechanicul work, and the 
more work Iho engine doM the grcutcr is the difference be- 
tween the heat generated in the furnace and that leaving 
the machine:. If, however, we used the work for nibbing 
two rough surfaces together we could get the heat book 
again, and if (which of course is impossible in pntctioe} 



THE OONSERVATION OF EKBSOT. 



SSI 



'm^ could avoid aI) friction in ih<- moTinj; pitris of Ihe 
machine, tlio quantity thus restored would be exactly eqnal 
to the exoMM of the boat j^cncratcd lu tin' ftirnuci.! over thiit 
It«viiig tho engine. Having tamed some uf ilic heat into 
mechanical work we could thus turn the work buck into 
heat aguiu, and find it jieKl vxatHly llic ninuunt which 
KccniiHl lo$I. Or we might uae l)ie engine to drive an clvc- 
tro-mognetie machine and «o tarn part of the beat Ubor- 
utod in it« fiiruuoc Gr«t lato mochatiical work Hud this into 
electricity; and if we ohose to use the latter nilh tho 
pro]>er apparatns, we could turn more or lens of it into 
light, and so have a grout part vf lltu vucrg}' which ftrst 
became coni<picnoas ts )ie<tt in the engine furnace, now 
manifeate<l in the form of light at some disfaint point. In 
fact, starting with a given ijnuntity uf one kind of energy-, 
we may by jn'ojter contrivances turn all or Home of it into 
one or more olhcr forms; and if we collected all tho finaJ 
forms and rutriinsffirnuHl (hem into tho Kret, wo Bliould 
have exactly the amount of it which hud di.4iip)ieured whitn 
the other kinds a|ipeared. This law, that energy can 
change it« form but that its amoant is invariable, that it 
i.'Annot be created or dcntroyixl but Kiniph' trjinnnintcd, w 
known as the /(iw of the Constrvation of Hiitr'ii/ (see I'liy- 
sice), and, like tjio iDde«tmctil>ility of matter, lies at the 
Imsis of all ttolentific oouceptionri of the universi.!, whether 
ooDcernod with anituato or inanimate objects. 

Since all form« of energy arc inlcrconvertible it is con- 
venient in conijiaring iunutint.4 nt dilTereiit kindrt lo expresji 
them in terms of some one kind, by »tying how much of 
that atandai'd form tho given amount of the kind spoken 
of would give riae to it were all converted into it. Since 
the most easily mea-nivd form of energy u meehantod 
work tliis i« commonly taken as the standard form, and 
the ijuantitiea of othera are expressed by saying hon- great 
a distance against the force of gravity at the c»rth'it mi- 
face a given weight could be raided by the energ>' in nne«- 
tiou, if it were all s|H<nt In lifting the weight. The unit< 
of mechanical work being the kilogrammetor, or tlio foot- 
pound, tlio mechanical equivalent of any given kindof cner^ 



S8» 



TtlB aCMAN BOOT. 



J3 the nnmber of kilograinmotcrs or foot-j>ouii<ik of work its 
nnit qnantity woiilil iit^rform, if canverted into mechnnical 
work ttnti used to raiec a wctgiil. For ex»mi>li> tlio unit 
quantity of livut in that Dccesaiirj' to raise one kilograiu of 
water one degree centignidc in tcnuKTatiirc; or sometim&i, 
in bookft writteu in Englinh, tht- <iiiuiitil,v iie(*s«aiy to warm 
one poiuid of w»l*r one degree Fahn-nlioiU When iherv- 
furu we Kuy t.liut tlie nieclianical e<|iiivalenl of ht-:it is 433 
kilogrammetei'x wo mwia that the ijuuDtity of heat uhich 
would raisu on<! kilogram of wulvr in t«tnj>iTutiin; from 
4° 0. to 5° 0. would, if all turned into mechanical work, 
be able to raise one kilogi-am 4;'.'! meters ugniust the attrac- 
tion of the tyirili; and ooiiversfly that this nmottot of nie- 
ohanieol work if turned into heat would worm a kilogram 
of water one degree centigrade. The tneeliaaical equiva- 
lent of beat, taking the Fahrenheit thormomctric scale and 
using foet and pounda m measures, is I "2 foot-iw>unds. 

Potential and Kinetio Energy. At times energy- seems 
to be lost. Ordinaiily wo only ohserve it when it U doing 
work and producing some change in matter: butsometlmoa 
it ID at rc!*t. »lnn;tl awny rikI [iroduoing no ehaiign that 
we rceognixo and tlmH seems to have been destroyed. 
Energy at work is known as kiHttie eHerijif: energy at rest, 
not producing changes in matter, js called potenfiot energy. 
Supimse aelone pulli'd up by a string and left tuitpondbd 
in the air. We know a ccrlain amount of energy was 
used to lift it; bnt while it hangs wc have neither heat nor 
light nor mi\ohaiiic»l work to rcprvHMit it. Still tlieonergy 
i» not loal; wp know wo have only to cnt the string and 
the weight will fall, and striking sumutliiDg give ri«o tn 
boat. Or we may wind up a iijH'ing and keep it so by ii 
catch. In winding it up a certain amount of energy in 
tlie form of mechanical work wim used to alter the form 
of the spring. Unlil Uio ealch is removed this cnergj' re- 
mains stared away as potential energy: hut we know it is 
not lost. Once the Bjiring is let loose again it may drivo a 
clock or a wateli, and in bo doing will perform rignin just 
so much work as was spent in coiling it; and when the 
watch htte run down this energy* will all have been lumod 



POTENTIAL ESERQT OF CHEMICAL AFFUflTT. «83 



into othfir forniii — ^mninly hcitt developed in th« frinliou of 
the parts of the watch nKainst one another: bnt partly also 
ill produoiu^ niovfiuenUt tif the uir, » portion i>f which wo 
can readily obwrTO in the Bound of its licking. The law 
of thcconsorvatioD of oiiorgy docx not say. tbcii. Ibnt either 
the total potential orthctotalkinctit^ener^inihennivenie 
is constant in amount: but that the sum of the two is invar 
riable, while const«[itly un(lorg[>ing ehaiigi^s fnim kinetic 
to ]mt«ntiiil and vice versa: and from one form uf kinetic 
to aiioihei'. 

The Energy of Chemical Affinity. Between ovory two 
ohemital atoms wliicli arc cupiitilii of entorin.K into comhi- 
natiun liiero oxi^iiii a oi^rlaiii amount of potential ener^': 
when they unite this cuprgy is liberated, nnually in ihu form 
of heat, and oiuo thoy have oombined a certain tunonnt of 
kinetic cnor^ niii.^i ii.'ii(ffitit to jmll them apart ni^in; this 
being exactly the animint which w:is libeiiited when tJiey 
united. Tlio more stable the onnipound formed the more 
kinetic cnorg}' apiK-ars during its formation, and the more 
must Iw liiyeut to break it up agniii- One may imagine the 
separated atoms as two bails pnshed together by ppringd. 
tho sLrength of the ttpring being proportionate to tjie <ti^ 
grO0 of tlieir chemical affinity. Onco they are let loose 
and permitted to strike together the potential energy pre- 
Tiously ropresented by the oompressod springs dinappeam, 
and in its place wo hare the kinetic enei^y. reprt<onlod by 
the boat dereloped when tho balls slriko together. To 
pnll them apart again, against tlio springs, to tJioir oripnal 
positions, just so much mechanical work must bo spent as 
in the cipiivalent of that amoinit of heal which appeared 
wlien they struck: and thus kinetic energy will again be- 
come latent in breaking up the compounil roprcttentod by 
the two in otmtact. The energy liberated in chemical com- 
bination is the most imporlaut iiource of that nsed in our 
miiohinf!^: and also of that spent by the liWng Rody. 

The Belation betwoen tlio Hatters Bemoved from th« 
Body daily and the Energy Spent liy it. A working 
locomotive is, we know, eiinxUmlly losing matter to the 
exterior in the form of luhcs and gasemu products of com- 



777;? inmAy bodt. 



btuliou, tho latter Iwiiig niuinly carbon (linii<Ici xncfiratcr 
viipor. Tho engine aii^o expends energy, not only in the 
furni of heat rtuliuti'd to the air, but as incchiiuical work 
in drawing tlifl car* against llto reiislanee offi-nnl by (rio- 
lion or eomctimes, up an incline, by gravity. Nob- ihe en- 
gine-driver knows thai tbcro is a clow rolstion^hij) betueGu 
tho losses of malU-i' ami tho ex]>eiiditurc of oncr^y, so that 
in) lut* Id stoko his fiiniaoe more fnKjuontly and allow a 
greater draft' of uir ihrmigh it in going up a ffradionl 
than when ninning on the level. The more wurk the en- 
gine doc* the more coals and air it needs to make np for 
its gicatcr waste. If v.e 8wk the cause of tliis relation- 
ship bctweoii work and waste, tho Sr^t an.iwer naturally is 
tliat the engine is a machino the special object of which is 
to convert heat into meohaniad work, and so Die more 
work it has to do (lie nmre he-at is required for oonvemon, 
and coiif«ji|uently tho more coala must lie burnt. This. 
however, opens the quoittion of the source of tht heat — of 
all that vniit amount of kinetic vaergy which ia lihcralcd in 
the fnrnacc; and to answer this wo must consider in what 
fonns inatU-r and energy enter thu farnaco, since the 
onorfry liberated there must be carried in M)mchnw from 
outside. For present purposes eoids may be eonniderMl as 
consisting of carbon and hydrogen, hoih of which sub- 
stitncos tend l<i fonribly combine with oxygen at high tem- 
peratures, forming iu the one cuae carbon diu.xiile ami in 
the other water. The oiygon necessary to form these com- 
jiounds lieiug supplied by iho Hir entering th« fiiniaee, all 
Ihc jiotential energy of chemintl affinity whioh ex■i^U•d lie- 
twecu the uncomhlned elements becomes kinetic, and is 
liberated a.-* heat when the eombination takes phice. The 
energy titiliiied by liie engine is therefore itnpp!i<xl lo it in 
the form of potential eiiorgy. associated wilb ihc niio»m- 
bined fonim of matter wliicii nyich Ilic furnace. Once ihc 
carbon and hydrogen have combined with oxvgen they are 
DO longer of any use t»> libtriitjirs of energy; and tho coni- 
ponnds formed if retained in I he furnace would only clog 
It and impede farther (->imbiistion; they are therefore got 
rid of IU waete« through (tie smoke-st«ck. Tho engine. 



SOVRCSS OF ESKBOT. 



985 



^V in short, receives nncombined elements aeaociatod vith 
r potential energy; iind lo«o« combined elements {vliicb faavc 

I lost Uic energy' previouslir associated with them) und kinetio] 

R enoigy: it so to speak eopaiatM U»! eiicrgy from tlio mab-j 

I trr with which it wim connected and, titiliziug it, gela rid 

of th(^ cihttufited matter. The amount of kinetic energy 1 
liberated dnnog such chemical eombiiiutiuiut lk very great; 
:i kilogram of carbon tmiting wilh oxygen t« form car- 
Ixin dioxide aets free 8080 unita of heat, or calorioa. Dur- 
ing the combination of oxygen and hydrogen to fona^ 
wnWr even more energy- It liberated, one kilogram of hydro- 
gen when completely burnt h berating more than tliirty-four 
thouwind of the same units. The mechanieal equivalent 
^^ of this can bt- calciilalod if it ia remembered that one heat 
^H nnit = A'i'A kilogrutnmctcrH. 

^^ Tnrning now to the living Body wo find that Its income 

f lUid expenditure agree very dosuly with those of the etcam- 

' engine. It reeo)ve-'< from the exterior substances capable 

of entering into chemical union; these combine in it oiid 
liberate energ)'; and it loxeit kinelicenergyand the produotx 
of combination. I-Vomtlieoutaide it takes oxygen through 
llio lungs, and oxidimble substances (in the form of food«) 
llirou^h the alimentnry canal; these combine nnder !))» 
conditions prvrailing in the living cells just as the carbon 
and oxygen, whti-h will not unite at ordinary tempcratnrcH. 
combine under the conditions existing in Ihe furnitce of 
the engine; the energy Uberated is employed in work of the 
liodv, whili'tlio u«clUM products of conibiniition ure got 
rid of. 'I'o explain, then, the fact that our Bodies go on 
working WL- hfive no need to invoke some speeial mysterious 1 
pon-ct resident in them und capable of creating energy, a 
i'ilfit force having no relation witli other natural forces, 
*\w\\ at the older ]>hysiol<>g)sU used to imagine. The Body 
needs and gets a supply of energy from the exterior jui^t lu 
the sLeum-eugine does, food and air being to one what coals 
and air are to ibe other; each is u machine in which energy 
IK liberate] by chemical combinations nnd Ihen lived for 
special work; the chariurter of which depends upon the 
peculiitnticsof mechanism which atilizes it iu each case. 



TtiB BPilAy nODT. 



mii not upon any pcciilinrily in the energy ntiliMd or m 
its source. The Body is, however, a fai' more eooDOtnical 
iiiiu:lii[ic Uiuu any steum-cngine: of uU the energy liberated 
in tho Intu-r only ii ^nml) frnrtioii, tiboiil one eighth, is uee- 
fulty employed, while our Bodies can utilize for the perform- 
imcoof miiR'iiltir work ulonu oiiu fifth of thu whole vncrgy 
supplied to them; leaving out of account altogt-lher (he 
untritive and other work curried ou in them, und the heat 
lo*t from llieni. 

The Condltioiu of Oxldatioa in the LiTiog Body. AN 
though the gcnonil priueiploa npon which the Body and 
the flteani-enginc get their working jiowor are the tuinte, 
still in minor jioints very obviona differences Hre found 
between thoni. In the fir«t. place the could uf nn engine 
are oxidized only »t a rery high temperature, one whitli 
would be instantly fata) to our Bodies which, ulihouf^h 
wurm when wimimrod with the bnlk of iniininiiiie objeew, 
are veiy slow lirei- when compured with a ftirnncc. Ohem- 
istry and phjvic^, Lowercr, tvitch ue that this dilloicnoo i* 
quite unimimrtant so far im concerns the nmonnt of energy 
liberated. If magnesium wire be ignited in the air it will 
boGome white-hot, Ihintc. and leave iit iJie end of a few 
(Wconds only a certain ainoant of inconibnstible riift or 
mfigiitnin, which consists of the metal oambiited vith 
iisygon. The hent and light evolved in tJic process repro- 
Rent of oonr^o the en<'rgy which, in a j)otential form, viis 
associated with the magneeium and oxygen before their 
combination. We can. however, oxidize the mctul in a difler- 
I'lit woy, attended with no evolution of light and no very jx-r- 
ceptiblerise of temperature. If, for instance, we leave it in 
the air it will heomo gradtiidly turned into magnoeia with- 
uul having evei' hi'vn hot to the touch or luminous to the 
eye. The proi-ew will, hriwever, take dnys or weeks; and 
while in this slow oxidation just as muchenergjis liberated 
as in the former ea»o it now all lakes the form of heat; and 
iuiitead of being liberated in a «<horl time \» spread over a 
mucli longer one. as tJie gradual chemical combination tjikcs 
place. The slowly oxidixing magnesium is. therefore, at no 
moment noticeably hotsino* it Iomm iU boat to aurroaoding 



SOrtlCE Of BDDILr BfiEHUr. 



S»7 



ubjecte as fast as it is gencniwd. The oxidations ocomring 
in our BuJicj nro of lliis slow luDd. An oiinco of itrrow- 
toot oxidix«i] ill u Grc, uiiil in thv ntiniim Body, would 
liberate exactly as much ciierg\' fn one case as tho other, 
bnt the osidatiuu would take \AacP in a fcir minutes and 
ala Ligli tcmpcnitun- in the formtr, and tdowly. at a loner 
t«n]|>erature. in the latter. lu the second place, the cugiup 
dillers from the living Body in the fact that thi; oxidations 
in it nil tuke iilnce in a small itiea, tlio riirna{>e. and >o the 
temperatnro tlierc becomes very high: whik- in our Bodies 
the oxidffltJouH take place all over, in each of ilic living 
cells; tlicre is no oiio fiiruav« or hearth where ull ihcenerg; 
is liberated for the whole and transferred tJicuoe in one 
form or another to diatiuit ]>arl«: imd t.lij« is another reason 
why uooni^piirtof lln' BiMlyatljiins a very high tein[ieiatiire. 
The Fuol of the Bodj. This is clearly diUcrt'Ot from 
thai of un ordinary engine: no one could live by eating 
cuala. Thie difTcrcnce again is subsidiary: a gas-engine 
requires different fiud from an ordinary locomotiTc; and 
the Body raqnireaasomcwhatdilTeivnt onefromeither. It 
needs us foods, substaocefi which can, in the lirst ]ilnce, be 
absorbed from llio alimcnutry canal and carried to the 
various UHsues: and. in ihc! second, can there bo oxidiised 
at a low tem|teratiire or, jwrhapa more probably, can be 
coDTcrtcil bv tho living cells into cximpounds which can be 
so oxidir.cd. With some trivinl execption.i, all snbstancM 
which fiillill these conditions are complex chemical com- 
ponnds. and to iinileiMritnil tlicir utilimition in tho Body 
we roust extend a little the statements above made as to the 
liberation of energy in chemical combinations. Tho gon«ral 
law may be stated thus — Em'niy is Ubrraied whenvvtr ehmti' 
val vn'ion tal-es plare : ami whrnrver man stablr compounds 
ittv f'oriufti /rotii tugt g/attte »w*«, {» which the cortftitueHt 
nioma werf leiiM Jirinlg hfhl hifflher. Of the liberation by 
simple comhinatioQ we hare niready Keen an instance in the 
fixiitation of carbon in a furnace: but the union netnl not 
lie an oxidntii>n. Everyone known how hot tiuicklime 
beoorac!' when it is slaked; the water combining strongly 
with tlie lime, and energ}' being liberated in the form of 



288 



TjfE mm AX BODT. 



hout, during the propess. Of the Ubpnition of ciK'rgT by 
the breaking iluwii of a comiilex coniponnd, in whieli the 
atoms are only feebly united, into simpler and stabler ones, 
we got an example in tilcobolic fermcDtation. Dnriug thiit 
process grnpo nugiir is bmlicn down into nioro Miible oom- 
pouudtf, niiiiiily earbon dioiide and alcohol, while oxygen 
i.4 at the Kimo time taken up. To pull iipiirl the ciirbnn. 
liydrogcn and oxygen of the sugar molecule requires a cer- 
tain ei|K'nditure of kinetic energy: but in the simultaneous 
fonnittion of the new and stabler conipminds n greutvr 
amount of energy i* set free, and the dilTercnee appears lu 
beat, 80 that the brewer has to coal his vats with ice. It 
is by processes like this lalttr. rather tliiin by direct com- 
binntioiis, tbut moi't of the kinetic rnt-rgy of Ihe Bmij ti 
obtained; the complex proteids and fats and starcbes and 
sugar taken ss food being broken down (tistinlly with con- 
eoiniliint oxidatioD) into eiuiplcr and nuirc !«lHb1c (-am- 
pound;?. 

Oxidatloa by Suooeasive Steps. In the fnrnace of an 
oupinc tlic iixiilaMoii i;ikes place completely ul once. The 
onrbiin iuni liydrogrii leaving it, if it \t well maniigcd, ai'b 
each in the state of their most stable oxygen compound. 
But thir* lived not br so: we might first oxidize the carbon 
»o iLS 10 form carhon monoxide, CO. and get a certain 
amount of beat; and then oiidiEe the enrbon monoxide 
fiirlher so lu tii form carbon dioxide, COi, and got more 
beat. If we add togetber Ihe anunuit« of heat liberated in 
each stage, the sum will be exactly the ^luantity which would 
have been obtained if the iitrbcin had been oomplolely burnt 
to the state of carbon dioxide at flrrt. Every one who has 
f<tn(licd (.'heniistry will think of many similar cases. .\.« 
llie procew i* imporUut plmiolOKically we mjiy take an- 
other example: say the oxidation of iilcohol. This may be 
burnt oi>nii)lotely and directly, giving rise to carbon dioxide 
mid watci' — 



C.H.0 + O. 

I Alcohol. iOxitta. 



- 200. + 

It CtrboD dioxide. 



3H.0 

xmer. 



)Ht instead of thl^ we can oxidize the alcohol by stagec, 



uriuzATioy of rxbrot m thk bodt, 

getting at each stage only a compnrfttmly Rmul) iimount of 
heat evolved. By couibiiiing it tlnit with one atom of oxy> 
gon> wo gut aldohyde and vrator — 

C.H.O + = O.II4O + H'O 

I Akohol, I OI7KWI. I AMiihyile. 1 W«ler. 

Then wo add an atom of oiygt-n lo the aldehyde aiid get 
itcetic acid (TiDtgiM-)— 

C.H.O 4- = C.H.O1 

t AUeh^c. 1 Uxfsvo. 1 AcoUa add. 

And fioiiUy u-c may oxidize the acetic acid so as to get cur- 
bvu dioxide and water — 

C.HiOi + 0. = 200i + 3H.0 

We get, in either case, from oue molecule of alcohol, two of 
carbon dioxiik- and thiw t>f waUti-; mid nix atoms of ozygea 
oro taken tip. In each ata^e of the gradual oxidation . 
certniu amount of heat \» erolti'd; und thu mini of tlieae il^ 
exactly the amount which would have been evolved hj 
barning the alcohol compleli'ly ut once. 

The food taken into the Body i» for the most jiartoxi- 
dined in this gradual manner; the producia of imperfect 
oombuEtion in one «et of colls being rarricd off and more 
completely oxidixcd in another »ct, until the tinul pro> 
ducts, no longer capable of further oxidation in the Body, 
ore carried to the lung», or kiiliivyif, or skin, and got rid of, 
A great object of physiology is U» trace all intermediate 
eompouiida between the food whinli eiiU-rH and the wnstoi 
pntducts H-hich leave; to find out just how far cheminil' 
degnulatioh iitcarriud in ciK-h organ; and what HuhMtuncea 
are thuH formed in rarious part.s: but at piVMut this part 
of the science is very imperfect. 

The Utilization of Energy in the Living Body. In the . 
9teani.t!iij,'Liie ent'rgy is Ijbpruled as heat: huiik: of the heatJ 
'\B nsiid to evaporate water and expand the resulting rtc«*m;[ 
and then the Nti^nm to drive a pistou. But in the living] 
Body it is very pmhiible (iudoed ainiotit cerl^iiu) that »I 
gre^c part of the energ}- liberated by chemical transfor- 



390 



TffE HCMAX BODT. 



mstioDS doot) not first take the form of beat; though some 
of it does. Thivf, agniii, docs not afTet-t. tlic geiicnil prin- 
ciple: thu HOun« af energy is esseutuilly the esqig in both 
cncea; it iu merely the form which it takes thnt is dif- 
ferent. In ii gnlvBtiio wll energy i« libitratcd during the 
uuiou of xiuc and Gulphuric acid, and we may eo arrange 
matu^ra as to get this energy as heat; hut on the olhef 
band w(? may luad it off, aa u so-called galvanic current, 
iiiid use it lo drive a magneto-electric machine before it 
has taken the form of heat at all. In fitct, that beat may 
be used to do niediuuicnl work wo must reduce sonic of it. 
to a lowiT t«m|M?ralure: an engine needs a condi?nscr of 
some kind as well as a furnace: and. other lhiiig>( being 
equal, the cooler the condenser ihe greater the proportion 
uf Uie whole heat liberated in the furnnoe which can be 
nsed to do work. Now in a ninxele Uiere \i no ouiidtniwr; 
its temperature is uniform thrnnghout. So when it contranta 
and lifts a weight, the energy employed inui^t be liberated 
iu mmv other form than heat — itome form which the muscn- 
lar fibre can use without a condenser. 

Summary. The living Burly is continually lotting mat* 
t«r and expending energy. (>ii long as we regard it u» 
working by virtue of some vit^d force, the power of gener- 
ating which it ha.1 inherited, the waste i» dilllouU to 
account for, since it is far more than we cau imagine as due 
merely to wear and tear of the working purl«. When, 
however, we consider the nature of the income of the Body, 
and of its expenditure, from a chemico-phyncol point of 
Tiew, we get the clue to the piiKzle. The Body does not 
wiute because it work.-* but work* bccuuM) it wasteK. The 
working power is obtained bychenii<-al changes occun'ing 
in it, associated with the libenition o( energy which the 
living cells utilise; and the products of these chemicnl 
changes, being no longcravaibhlc as sources of energy, are 
passed oiiU The chemical changes concerned are niuinly 
the breaking down of complex and unliable chemical com- 
pounds into simpler and more i^talilc ones, with ooncomi- 
toat oxidation. Accordingly the material Iomos of the 



SOURCES OF RS8H0Y IX THIS BODY. 



Ml 



Body are highly or oonip1ct«Iy oxidised, tolembly «iinplfl 
clicmical oom)ionndfl: and its mttimal income is mainly 
uneombiiied oxygon, and oxidizublv vuImIhiiccs. llie former 
obtuiiied thruiigli tbo lungs, the latter thioagh the alimeii- 
t^kry caiial. In energy, its income i^ the potential energy 
ot nncombiiied or fcobly oomhiued clemcnu, which ure 
ciiptihio of Rumliiniiig or forming more iit:tble combinatioiii>; 
und its final expenditure, if kinetic energy idmoet entirely 
in the form of nKclinnicnl work and heat. GiTcn oxygen, 
nil oxidixahle bodies will not serve to keep the Body alive 
and working, bnt only those which (1) urc cspiktile of ah- 
Korption from the Hliiiienlurycunftl ainl (2) thi>M which nre 
oiidizablo at the tomperature of the Body under the influ- 
ence of protoplasm. Ju^t tus carbon and osygcn n'ill not 
uuito in the farnacc of an engine unless the "fife be 
lighted" by the application of u match but, when once 
f(«rle(l, tlie heat evolved at one point will Rerrc lo ojtrry on 
ibe conditions of eombuiution through the rest of the mass, 
m the oxidations of the Body only oci^ur undi-r ttpi'cial con- 
ditions; and these are transmitted from parent to ofl^pring. 
Every new Human Being starts il< a portion of jirotoplaiini 
.■<cjiarated from a parent and affording the condition* for 
those chomical combinations which supply to tiring matter 
itj< wiirking power : tlilti i^ervcs, like tlie energy of the 
burning part of a fire, to start similar procemes in other 
portion!! of malter. At present we know nothing tu physi- 
ology anr^wcring lo the muuh which light< a furnace; thou 
manifestations of energy which we call life arc handed > 
down from generation to generation, m tbo sacred ftre in 
tbe temple of Ve^ta from ono watcher to another. Science 
may at some time teach us how to hring tjie chemical con- 
stituents of protoplasm into that combination in which 
they poMcm Die faculty of xtarting oxidations under 
those conditions which cliaracteri/^ life; then we will have 
loarnt how lo strike tho vital match. For the present 
we must bo content lo study the propertiM of that form 
of matter which ]>a°aeBse3 living faculties; ciinn- tlicrc iM no 
satisfactory proof that it has ever been produced, within 



S99 



THE ffVJfAy BOPr. 



oar experience, apart from the influence of matter ulready 
living. How ihit vital npark fit^t originated, how mole- 
cules of carbon, hydrogen, Diirogen ami oxygen lirst iiniied 
with water and stilts to form proto])]a^m, we hitvc no scien- 
tific data to ground u ]Kifiitive opinion upon, and auoh at iro 
uiay have must rest upon other grounds. 



CHAPTER XX. 

FOODS. 



Foods aa Tissue Formers. Hitherto we hare considered 
food? nti'ii-ly .H.- linnrcen -^'f onorgy, but tliey arc iiW re- 
quired to build up the substance of the Body. From birth 
to manhood wo iuCTciisi; in bulk and weight, and that, not 
merely by iM;oumtilating wiiler iirid «uch mb!<laiioc8, bnt by 
fonniug moie bone, mora muacle, more hratn, and ao on, 
Crom miiteriuls whii;h nre not necessarily bone or musclo 
or ncrri; tis.*uc. .\!«ngjiide i>f the processus by which coin- 
plei subLttancofl are broken down and oxidixed and i-nergr 
libvratod, conKtniclivo procossoa take pla>ce by which new 
complex bodiea are formed from simpler subslnncc-^ taken 
BS food. A grciit part of the euergj- liberated in the Body is 
inflict utilised rir!«t for thin purpo.'>o, since to con>^tnietcom- 
plox unstable molecnlce, like those of protoplasm, from the 
simpler compoiuidt) lakuii into the Budvr needs on expendi- 
ture of kinetic energy. Even after full growth, when the 
Body ceaacd to gain weight, the same synthetic processes go 
on; the living tissues arc tt«»di]y broken down and con- 
stantly reounst meted, us we see illuBtmt<)d by llio condition 
of a man who has been elarred for some time, and who loses 
not only hi*! power of doing work and of maintaining his 
bodily ti-iu|i<'ratiii'e but also a great pari of hia living liasncR. 
If again fed pro|iorly ho soon makes new fat and new muscle 
*ttud roguina bis original mow. Another itliistrotion of the 
ooutinnance of constructive powers during the whole of life 
is aSoriiitd by the growth of I he niusules when uxerdsed 
propei'ly. 

Since tbo tissues, on ultimate analysis, yield mainly car- 
bon, hydrogen, nitrogen and oxygen, it might be suppofed 
(I priori that a supnlv of theee elements in the uncombjned 



tM 



TSB UVMAA aODT. 



st&te vould eerro us nmtoriul for the ooDBtnictJve forces of 
the Bud; to work witli. Experience, however, teaches un 
that this U not ibe case, but ibiii iho aniniHl body requires, 
for Ihu uiiMt jiiirl, liij^hly complex coiaiKiuuds for t.li« con- 
straction of new tissue elementa. All the actiTe Uasuca 
yield on iinulysU lurgr i]iinutitic« of proU^ds whicli, M 
pointed out in Chapler I., vntvr lUwavit into the Mnn-lureof 
protoplaam. Nov, so far as we know at present, t)ic iininial 
body is onable to build up proteids from simpler com- 
pounds of nitrogon, ullhoiigb whc-ii jfiven one variety of 
iheiii iicau convert thai our into others, and combine them 
with other things to form protopliiam. Hence proteidsarc 
un essential iirtidi' of diet, in order to rcpluw thai jiorlion 
of the living celU whioli is dnil) broken donn and elimi- 
nated m the form of ureii and other ivanie substances. 
Even albuminoids (p. 11), although so nearlj aJliod to pro- 
tcids, will not w>rvo to rqilaee th«ni entirely in o <lii-l; a 
man fed iU)undaiitly on gelatin, fats, and starcliea, would 
sUtrve as certainly, though not so quickly, as if he got no 
mtrogenous food at all; his tissue waste would not be made 
good, and lie Woidd at last be no more able to utilite the 
oncrgy-yiolding matcriaU «upp]iod to )iim, than a worn-out 
cleam-engine could employ the heat of a fire in it« furnara. 
So, too. the uuimul is unable to take the carbon for the 
Coiuitrnction of its tissues, froia such cimplc compounds u« 
carbon dioxide. Us conatructiTC power is limited to the 
utilization of the carbon conlainod in more complex and 
lc«x xtulile coni)>ounds, such aa proteids, fat«, or sugars. 

The main bulk of all nscfid foods must therefore be 
nuadu np of complex £ubstance:>, and of tln-se a part must 
Ik proteids, since Ihe Body can utilize nitrogon for tiasui' 
formation only when supplied witlt it in that form. The 
bodiiM> tliti« taken in arc i^ouuor or httcr brokou down int'^ 
Himpler and eliminated; some at once in order lo yield 
eucrgy, otbeiv only after having first been built up into 
piut of a living cell. The {lartial exceptions aSorded by 
such losses to the Body as milk for suckling the young, 
or the albuminous ami fatty bodies stored for the same 
purpose in the egg of a bird, art< only apparent; the eltemi- 



rooD OP pLAyrs. 



$«6' 



cal dcf^radation U onlj' postponecl, taking place in the body 
of the offgpriug iiutMd of that of th« poreot. Iii nil nuM 
animolg nro Ukos, ettentiallir, proteid consamers or w&ti«n, 
utd breakers down of complex bodies: the carbon, bydi'o- 
gen and nitruj{eii which cb«v tiike a^ foods in the form of 
coiDplcx unstable bodies, ultimatelT leaving them in the 
irimpler compound^!, carbon dioxide, wHltT, and uroa: 
which are incupublo uf either yielding energy or building 
tissnc for uny other animal and so of nerring it «« food. 
The fniftition immediately §nggeate itself. How, since animalx 
are constantly liri'iiking up l.hesc complex b'^dJes and can- 
not Ngain bnild them, is the supply kept up?* For«xam- 
ple,the supply of prot«ide, which cannot be made artifitially 
by any process which we know, and yet arc iiece«8ary food" 
(rtf mII jinimals. and daily destroyed by them. 

The Food of Flanta. \i regards our own Bodies the 
question at the end of the last paragra}di might j>erhi>ps be 
answered by saying that we get our proteids from the flesh 
of the other aniruak which we eat. BqI, then, wo have to 
account for the possession of ihem by those animaU; since 
they cannot make then from uron and ettrbon dioxide and 
water any more than we can. The animals caUtn get them. 
in fact, from plants n-hicli are the great proteid formers of 
ihc world, 90 that the moat oamivurous animal really de- 
ponds for iU most essential foods upon the vegetablo king- 
dom; the fox that devours a hiire in the long run liveis on 
the proteidsot the herbs that the hare had prerioudy eaten. 
All animals arc thus, in it cerlam sense, parasites; they 
only do half of their own nutritive work, ju«l the tiiiiil 
dtages. leaving all the rest to the vegetable kingdom aiul 
using the product.)! of its labor; and plants are able to nic«l 
this demand lieoause Ihcy can live on tho simple eompomids 
of carbon, hydrogen, and nitrogen eliminated by animals, 
building up out of them new complex snbsttinces which 
tuiimals can use ad food. A giron plant, supplied witli am- 
monia Aalts, carbon dioxide, water, and iiomc miuemls, will 
grow and build uplargeriuantitiesof proteids, fats, starches, 
and similar things; it will pull the sLahle compounds eli- 
minated by animals to pieces, and l>uild them up into oom- 



m 



rmi nuMAx budf. 



picx iin8tsbl« .)odics, ctkpabic of yidiliugoiivrgy when uguin 
itiokon down. However, to do such work, to lireak uji 
■table combiuutions nm) lunko from Ihotn lo^f $tuble. ne«dg 
a HUpply of kiiiclic energy, which (liita|)|ionrn in tlio procpss 
being storeil away as potential enerji^ in the new compound; 
and wo may ;ii-k wiu-iioe it, in thai llic planl gets the siijuily 
"f ouLTgy whi>-ii it thus utilizes for chemical eonstruftion. 
since its simple and highly oxidizi-d fuod^ cun yiekl it uom'. 
It hua bc«n proved that for this purpose IJie grcon plant 
uses iJie energy of aunlight: thoseof its cells whioh contain 
the snbstance cnllcd chhrophij} (Itaf grwn) have the power 
of ntihxing energy in the form of light for the ficrforra- 
aiipc of chemical work, just as a steam-engine can iitiliu: 
Iicjit for the performance of mechanical work. Kx|K(sed to 
light, and rcwiving carbon dioxide from the air. and water 
and amniuniii (which is produced by the decomposition of 
uroa) from tie soil, the plant builds them up again, with 
the elimination of oxygen, into complex bodies like those 
which animals broke down, with fixation of oxygen. 
Some of the bodies \\\\ii formod it u*i'i^ for its own growth 
and the fimiiiition of new protoplasm, jti»l uh iin animal 
doeit; but in sunlight it forms more than it uses, and the 
excess i^turcd uji iii its tissues ii" nued by animals. In the 
long mil, thon. all the cncrgj' spent by our Boilic* eome« 
through millions of niik's of spiicc from the sun: but lo 
sock the Boiirco "f its supply there would take us far out uf 
the domain of Physiology (see Astronomy). 

ITon-Oxidisabla Fooda. Renidc^ mir oxidixable foods, a 
large nunilH'r of necessary food materials ai-c not oxidiza- 
Me, or at least are not oxidized in the Dody. Typical in- 
Htiuicus ai-v ulTonlod by water and eommim Halt. The use 
of theHe is in great part physical: the water, for instaoee. 
disflohes materials in tho alimentary canal, and carries the 
solutions tliroiigh the walls of Ihe digestive tube into 
the blood and lymph veswls, so that they cun he carried 
fn)m part to jiart: uiid tt |iermtts intenhangeA to go on by 
diffusion. The saline* alno iiiltticnro the solubility aud 
ehciiiK-iil itiiori'liJitigos of oilier iliiiigs presi-nt with thuni. 
Serum ulbumcu, the chief proteid of the blood, for exiunple, 




XOXOSJDJZABLB FOODS. 



S97 



. 



U insoluble in pure water, but dissolree readily if a Hmftll 
quantity of neutral ealt« is pri'M-nt. Bc«i(k-» i<uch uses the 
non-oxiiluublu twU have probably olhem, iti whut wu nijij' 
crull machini>rj formation. In the salts which give their 
hardness to the bone^ niid tvoth, wu huvo hu example of 
Bach an t'lnjilojiiu-nl. of them: and to ft K^i* oxti.>nt the 
Mtn« niiiy be Irue of other tissues. The Uody, iu ftict, is 
not a mere store of pototitijil energy but somelliing more — 
it in a luiichino for the diitpowil of it in ccrtaiu WHy»; and, 
wherever pi-acticable, it is denrly adTantsgeous to have Ihe 
purely cncrgy-expL'uding purt» made of nou-oxidizuble mat- 
tura, unil Ko protected from change and the riece*.iity of 
frequent renewal. The Body \a a aelf-building trnd self- 
ropairin;; machine, and the inuloriid for thin building and 
repair must be suppiiH in the food, ad well aa the fuels, or 
oxidi'tahle foods, which yield ihe energy the machine ex- 
pends: and whilo experience shows lu, tlmt oven for ma- 
chinery conBtruction, oxidi/uble nutturH arc largvily needed, 

uevertlieless it isajpiiii to ruplaee tliem by non-oxidizable 
Muh^tanceK when possible: just ai< if praclicablu it would bo 
adrantageous to cotiiitruct »u engine out of materialfl whioh 
would Dot rust, although other conditions deurmine the 
wv of iron for the jp-enter jiart of it. 

Oe&nition of Foods. Foods may be defintd at mb- 
Mittncva whirh are ftiirii into ike alinttntanj vanal, and 
mkich, whm ahtorbeil froin it, xerve either to suppig matirial 
for the growth of the Hod ij, or for the r«plac*inent t^matier 
which kat been remotvd from it. either after oridatioa w 
mthout kavinff been oxidited. Foods U> replace i»atl«n 
wluch have been oxidized must be themselveij oxidizable; 
tbey are force t/merators, but may be and generally are also 
tissue formers; Jind are nearly always complex organic suIj- 
stHni-cit derived fruni other animal^; or from pUuitH. Foodn 
to re|ita>ce matters not oxidized in the Body aiv force ret/U' 
latoTt, and we for the most part tolerably eimjile inorganic 
oompontidit. Among the force rogulalow we must, how- 
ever, include certain organic foods which, although oxidized 
in the Body and serving a* liboratont of energy, yet produce 
effects totally disprupoiliunate to the energy tliey mii tree. 



W6 



THU UVMAK BODY. 



and for wliich effecU they arc ukcn. In other wordf, then 
iuQiiciiof us :iiimtili in oxciting certain ti&suas to lilieriit^* 
energy, or as iuhibitory agents cbeckiug the activity of 
pai'ts, is more marked tlian their direct action as force gen- 
erators. A/ fxuniplct, we Diuy lake condiments: mustAiil 
and peppor are not of much ii*e as m>ui«c« of cuorg)-, al- 
choagb they no doubt yield «ome; we take them for their 
dimulMting effect on thi- mouth and other parts of the 
alimentary caoal, l>y which they promote an incrciuicd Sow 
«t till! digiystivc secretions or an itnTcum^d appetite for 
food. Thein, again, theactive principle of tea and cotTce. is 
taken for its stimulating efFect on the nervous system, rather 
than for the amouut of energy which iii yielded by \U own 
oxidution. 

Conditions which a Food must FulflU. (1) A food 
mu!l t-(inli(in the elewciitx which it is to rephico in thu 
Body: but lliiil alone is not sufficient, TIio eleinenta leav- 
ing the Itody being usually derived from Ibebieaking down 
of complex Kubslanw^ in it, the food mnat contain them 
either in the form of Buch complex substances, or in forms 
which the Body can bui]d up into llicm. Vttn nitrogen 
and hydrogen iirc no uiC as foods, since they ore neither oxi- 
dixable under the conditions prevailing in the Body (and 
consequently cannot yield it energy), nor are they cnimblo 
of construction by it into its tissues. (3) Food after it 
has been swallowed ia still in a strict sense outside the 
Body; the alimentary cunal \* merely a tube running 
through it, and so long m food lies there it is nut forming 
any part of the Body proper, llcnce foods mu=t be capa- 
ble of absorption from the alimentary canal; either directly, 
or after they have Iwon ehiinged by the iiroceesett of digen- 
tion. Carlion, for example, is no use as a food, not merely 
because the Body could not build it up into it«own tissues, 
but because it eiinnot bo absorlied fi-om the alimentary 
iimal. (.3) Neilher the subelanw itself nor any of the 
products of its tnmsformtition in the Body must be inju- 
rious to the structure or activity of any organ. If so it ].« 
a poison, not a food. 

AiimentATV PrinolDles. What in common language we 



AUMBSTABT PRIXCIPLE8. 



299 



^ 



oomtnonly otll foocli are, in nearly all cwea, tnixtureit of 
nvcnil fimhlnffi; "i'ii i<ul>stiinc«» whidi wo not food» «t 
a]). Ki-jtail, for examjile, conlainH water, salts, gluten (a 
prot«!d), some fats, much starch, and a little sugar; all ti-uo 
fooclstiift:!: hat mixc<l with these Is a qunntitj of cellulose 
(the chief ohemiiial cunstittictit»f thowiilU which surround 
Tegotabte celU), and this is not a food siuco it is incapable 
of nbtorjitioti from lhonlimuntiir}'c»iiiil. Chcinioiil cxumi- 
nation of nil th» common artiolcis uf diet kIiowm that Uuj 
actual number of important foodstuffs is but amall: tliey 
arc ri;poul«d in vurionv prnjiorljumi in the different tbinga 
we oat, mixfrd viih Hmall (luaniities of different flavoring 
eubetancos. and so give as a pleasing variety iu our mGatx; 
but the cMCutial ifubstiineco arc much the same in the fare 
of the workman and in the "delicacies of the season." 
These primary foodstuffs, which are found repeated in so 
many differontfoodd, are known aa"a/im«t/ar_v/'/'ina/'/#^;" 
uid the phj^siologivol value of any article of dii^ depends 
on tliem far more than on the trace:! of flavoring mattors 
which cause certain things to be especially sought after and 
80 raise their market Taliio. The alimentary principles 
may be conveniently classified into proteidti, albuminoids, 
liydroearbons, carbohydrates, and inorganic bodies. 

Protoid Alimentary Pnnoiploa, Of the nitrogenous 
foirdi'tuffs tin- must importunt are proteidii; tlicv form an 
essential part of all <lti'l«, and are obtained lioth from 
animals and plants. The most common and abundimt arc 
myoain and syntonin ifhich exist in the lean of all meats; 
egg albumen; oadcin, found in milk and cheese; glntenand 
vegetable casein from rarions pl^nt«. 

Albuminoid Alimontary Principles. These also ooQ' 
lain nitmgcn. but cannot replace the protcids entirely at 
foods; though a man cim get on with lees proteids when lie 
haa some albnmiuoid'< in addition. The most important is 
gdatin, which is yielded by the white flbrons itKnio of 
animnl« when cooked. On the whole the albuminoids are 
not foods of higti valms and the ca]r»-foot jelly and such 
componnds. often ^rrn to invalids, have not nearly tbe 
uutxilivc value they are coiumunly Bupi>osed to pOBSBBB. 




300 



TUF. iiVMAS Bonr 



Hydrooarbon* ( ^li/« and OiU). Tbo most importunt 
are Kteikrin. piilitiHtin. murgiiriu mid "Win, whiHi cxi»t iJi 
Vitriolic |iro)iorLioiit in animal faUt and vegclable oUa; the 
more fluid coDtaiDiuR most oleiii. Butter cons isU chieflr of 
a (at known ibi butvrin. All an.' nnilral cumpoundH of ply- 
ceriiieand fatly aeida and. s}ieakiii^gi'Dcrally, any auch sub- 
stance which IS fufiibto ut tho tomiiLTutnro of the Body will 
serve fts a food. The suarln of beef and muLlon fat» in 
not by iUelf fusible at the body ipmjiftratiir<>, but is mixed 
in thoBo foods with so niudi olciii ^ to he melted in the 
ttlimonlury otnul. Bix-mwhx, on the ol!ii;r hand, is a fatty 
body which will not melt in the ioteBtines and ao paasca on 
unabsorbed: ultbough from it« compoMtion it would be 
usefnl u« a food could it be digostt'd. II. 'a convenient to 
diKtingui^h /fits projier (ihe adipose tiHsne of auinuil* 
consisting; of fatty com)>ound); inrliwed in albuminous cell- 
wallK) from inli, nr faltv bodiett which an' not m surrounded. 

Carbohydratofl. Thtw arc mainly of vegetable origin. 
The iuomL iinporliint arc starch, fuund iu nearly ull vege- 
tiiblc foods; dextrin; gums; i^ra/je^Hf^iir (into which Htarcli 
is converted during digestion): SlwA (nun tiigar. Sut/ar of 
mill- and g^ffi^of/cn are alimenlary prindploj of tlii« gnuip, 
derived from animals. All of them, like the fat^i. 0Diisi»t 
of carbon, hydrogen and oxygen; but tho percentage of 
oxygen in tlicin is much higher, there being one atom uf 
usvgen fi>r every two of hydrogen Iti their molecule. 

Inorgonio FoodA. Water; common mM»; and the clilo- 
ridee, phosphates, and sulphates of potahsium, muguiMiium 
nod calcium. Mure orlcssof lhc«o bodic«, or the materiula 
for their formation, exists in all ordinary articles of diet, 
u) that we do not swnJlow them in a separate form. Tho^- 
pliates, forexauplc, exist in nearly all animal and vegcuiblr 
foods; while other foods, as casein, contain phosphorus in 
uoinhiiiati'Uix which in tho Body yield it up to bo oiidineil 
to form jihosphorio acid. Tho same is true of suljdwtw, 
which are partially !^wallowed as such in various articled of 
diet, and are partly formed in the llody by the oxidation of 
the sulphur of various proteids. Oalcium saita aro abun- 
dunt in bread, and are also found in many drinking waters. 



FLUSH FOODS. 



801 



Water and tablo ealt form exceptions to the rule that in- 
Di^iiu bodieR are oaten impercapltUjr ulong with oilier 
IhmgH, siDCO the Body lows more of ciich daii}- Uma U usu- 
ally enpplted in thut hiiv. It. hsis, baweTcr, b«en main- 
taiued (hut iialt, n^ «iicb, h an unneoeesar}- luxury; and 
there seems some evidence that curtain itavage tribes It^e 
without more than they get in the meat and Tegetables 
they cat. Sueli tribes arc, however, aaid to siiiTer ei^jwcinlly 
from intestinal ]>artu)it4.-s; and Ihero U no doubt that to 
civilized man the absence of suit is a great deprivation. 

Mixed Poodfl. These, as already pointed out, include 
nenrly all common articlesf of diet; they contain more than 
one alimentary jtrinciple. Among them we find great 
diScrciioeji; some being rich iu proteidf, others in slarrh, 
others in fats, and soon. The formation of a^cicntiflc die- 
tary doponds on a knowledge of Uiese oharactfristics. The 
foodx eaten by man are, however, so varied that wo cannot 
do more than consider the most impurunl. 

Floah. Tbi», whether derived from bird, beast, or fish, 
consists essentially of the same thing* — muMcnlar fihrcit, 
tendons, SntM, blood-vowels, and nerves, tt contains eeverul 
prot«id8 and espeoially myosin; gelatin-yielding matters 
in tlio white librous tivtnc; steorin, pulnmtin, nuirgnrio, aod 
olein among the fat«; unil a nniall amount of carbohydrates 
in the form of glycogen and grajie sugar; also ituaitf, a 
kind of AnguT found only in mii>tcle«. FIvah also contains 
much water and a considerable number of nlinos, the most 
important and abnndant being potassium phoiiphate. Os- 
tHtiame it a cryHtallino nitrogenous body which gives much 
of ila tutleto flesh; and small qunntiti<w of varions similar 
substnnccs exiht in different kinds of meat. There is also 
more or le«ii yellow claslio tisane in flush; it is indigwlihlo 
and nselcea aa food. 

When meat is cooked its white Sbrons tissue is turned 
into gelatin, uud the wh«lu must livcomos thus softer anil 
more easily di^iniegiuted by the teeth. When boiled much 
of the proteid matt^irs of tho moat pass out into the broth, 
and Ukurc in pari coagulate and form the acuta : thi4 loss 
may be prevented in great ihitI, it il is not intended to use 




miitum mtf 




Omwiatnfar; 
tetca. BHiltria 



Mm ■'*^' 

f ivf# fofMtiif Mnt Mtar/ • 

Lfr<f"'>tj Hni4« f^ imiynn, » v rntfom a A «f batjric scitl and 
lywfftM, I* IJm milk It M dwnnMtcd io the funn of 
'jii.itiA kI/jImIm wltioli, (ur 1L« HMMt part, float np to the top 

' triiiTH Um Milk b bt nUnd aad than iona tbe avmn. Id 
llili mmIi f«i flru)*l«t If warTouaA*A hj • pellivlo of allnii&i- 
H'f'f* t»utl«r) lij' iliTjrrilnjf, tlioiioprlliolai iire broken npaod 
Mil' f'li •IP'i'IcU run Ifittolln'r !■> fuim tlie biittor. Casein is 

[tfiMitiitiU til WMiiT, nml tii lliiiiiillh ii ih iliMolvi'd by lbs 

'KlhitllpiM *iill<i )ini*i<iit. Wlii'ii milk U kopl lUi tugjuiita* 
httidU mill kUim riMi In tiu'Ui' iK<til, wlitvit lu'dtmlisM tbe 

,1iIIihIi mill |iiviil|>ll<tt<'« (lie i^aKoiii im i-Mrt/n. In chMHV 

IliMkltiK lliit|iitt»tn U •iHitliiily t>i'«i'i|tiiiit«>(l li_v tho ndilition 

tif Htt milil HHil <ltit> Wriu't Iwmit |trMnl out) it otutstitvtM 

tlltt tlinlH Ixilh i>f \\w ^>litHwnV 

V<««taMit V\h>«Iii l^t l)»w « l(r«i «klliifa> tlw bMt. In 

^\VW\ imiU II t>t>ti*>MU* l!I.N t^f )«lvMtW t«8«(sUn:fa, 46 uf 

«^(iA «hMM« Ww*l >i««w «ta ji^Mwiny. 




yvfJETABLB mops. 

sod pxpAndrd during linking, r<imiii cavitiM in itsndcun 
it u> "rise" and mak« "lighl bread/' which is n<rt onlj 
moro jiloasant to c:tt bnt more digeetiblo than heavy. Othnr 
cereals may conluii » larger pcrceiitago of starch but nonej 
hare so mnch gluten as wheat; vheo bread is made frontV 
thum llio nu bon dioxide gas c«c»p<4 to rttmlily trom the Iciui 
tcnocioiu dough that it does not expand the mass jiroperly. 
0am contaiufi in 1000 parts, ?0 of proteid*. 637 of starch, and 
£roni 50 to 87 of fats: much more tbiiii any othdr kind of 
grain. Riiy is jKJor in pri'leidK (■'Vfl \mTtA in lOUO) but rery 
rich in Blareb (S23 parts in lOOO), Ptag aad brans are rich 
in proteids {from THy to SCO parts in lUOO), and ounlaiu about 
half iht'ir ireight of starch. Polatiteg area poor food. They 
oontun a gr«at deal of wat«r and cellnlo<c. and only about 
13 part* of proteidsnmi 154 uf slarth in UKH). Othttr trv»li 
vegetablea, aa carrots, turnips and cabbaged, are valuable 
mainly for (huBalts thoycotitaiii: their weight is mainly duo 
to iirat«r, and thoy eonlain but little starch, protetds, 
or fatfi. Fnitts. like most fresh veigetsblfe, are mainly talu* 
able for thctrsidinc constituents, the other foodstuffs in ihem 
being only present in small pro)>ortion. Some form of 
fresh T«getabl« is, however, a nocesBarr article of diet; as 
•hown by the scurvy which used to proriiil among Milors 
before fresh vegetahlex or linio-juioe were supplied to them. 
Tho Oooklnc of Vogctablaa. Thigis of more importance 
even than the cooking of l!e*li, since in most the main ali- 
meotary principle is xtarch, and raw starch is difficult of 
digestion. In plants starch is nearly always stored up in 
tbe form of solid granules, which consist of alternating 
luyoni of iftarrA ctHnlon and ittarch granuIoM. The diges- 
tirc fluids turn (he Kturch into grape sugar which is snhiblo 
and can bo absorbed from thealimcntary canal, while starch 
itself cannot. Now these fluids act very slowly and imiter* 
fecdj on raw starch, and then only on the grannlooe; but 
when Ijoilcd. the starch granules swell op, and are more 
readily converted into grape sugar; and the starch cellulose 
issoallered that it toounilergoesthatchange. Whenflanrh 
is rousted it is turned into a substance known as soluble 
starch which is readily dissolved in the alimentary canal. 



^ 



804 



THE nVMAS nODT. 



Thvrc is therefore a sciontific foniidHtion for thu <;o[iiinon 
belief tbat the crui>t«f » luiif i* mure <)igei<tibl» than the 
cnnnb, aiiJ tmist than ordinarr bread, 

Aloobol. Tliere arc perhaps no common articles of 
diet coiiconiing which more coiitriwiicNirv statements havo 
Ik'CU made thaii alc!oho1io drinkfi. Thin de)i(!ndMupciti Itieir 
jiciiiliur position: according to quimtity or circumstances 
ak'cihol may be ii puixin or u food; and lU a food il mu^' be 
roganlvd cither a» a foroo regulator or a force generator. 
There is no doubt that alcohol in certain d.wes may be prop- 
perly called a foixl. If not munt limn two onncos (which 
would l>o c<>nt»iiiod in ulxiut four ouuih'm of whijtkcy or two 
quarts of lager boer) are taken in the twenty-four hours, it 
ia completely uiidixed in the Boily and excreted a^ water 
unil carbon dioxide. In thii* oxidation oner^y U of courcc 
liberated and can bo uciliued. Commonly, however, alco- 
hol \t not taken fur this purpose but, ae a force regulator, 
for it« iDducnce on Uio nvrvouR syHtcni or digestive organs, 
and it is in tliis capiicity that it becomes dangerous. For 
not only may it be taken in (juantities so preal that it is 
nut all oiidlxed m the Body but \* piussi>d Ihmugh il iwiiico- 
bol, or even that it act« as a narcotic poUon instead of a 
stimulant, hut whun taken in what is called moderuiion 
ihvrf can ho no doitbl Hint the oouittaut " whi]>ping up" of 
the flagging organs, if contmucd. must he dangerous to 
their integrity. Hence the daily ui^c of alcohol merely in 
mii-h cjuaiitilies as to produce slight exhihimtion or to facili- 
tate work \» by no meatia saSn; though in disease when the 
iFyi<teni wnut« rousing to nuikc Momc s]woial effort, the phy- 
aician cannot dispense with it or some other similarly act- 
ing substance. In fact, a^a force generator alcohol maybe 
iiidvaiiuigeously replaced by Other foods in neuirly all CAses; 
and Ihore m* no evidence thai il hel;):< in tlie conKtniction 
of the working tissuen. thougli its excissiTe use often leadii 
to an abnormal ai'Cumnlation of bt. Its proper use is hn 
a " whip," and oiio has no more riglit to use it to the 
hciillhy IJody than the lash to overdrive a willing horse. 
TIio physician is the proper person to determine whether it 
Is wauled under any given circumaloiiees. 



ALCOHOL. 



^ 



If alcohol ie to b« used as « dnilr article of diet it should 
lie txinie in inintl that when oonoGotratcd it coagulnti>8 tiic 
pmloidH of the cpUs of the etomnch with which it c«me§ in 
{.-outiic-t. III the name sort of way. Diotigli of coiirm' to u 
mni'h lewi degree, as it ahiivelsand drieiiii)) iin niiim.il pre- 
served in it. Dilute slcoholic drinks, such as claret aiui beer, 
lire thcrGforc fnr Icds baneful Uiitn whiskey or brandy, and 
tltew are wont of all in the almost undilnied fonn of moitt 
" mi'cd drinks." For tlin aunfl reason alcohol in iu; mure 
injurioiiH on an empty Htoniaeli than after u meal. When 
the fttoinach is full it u diluted, is mure slowly abwirbed, 
and, moroorer, t:ilurg«ly xitcA Upint-iuignluting thepixitcids 
of the food instead of those of the lining merobmne of the 
stomach. The old "llirec bottle" men who drank their 
port-wine after a heary dinner, g«t off far more »if«iy than 
the modern tippler who i« taking "nips" all day long, 
although the lutt«r may imbibe a smaller quantity of alco- 
hol in fh(T twenty four hours. By far the b«at way, Iiow. 
erer. is to avoid alcohol altogotlicr in health. If the facts 
lend u« to conclude, againut the extremiclK, that it is to * 
certain extent a food, u la nevertheless a dangerous out; 
even in what wo may cull "physiological " ([tianliMos, or 
euch aniiitinU as can he totally oxidized m the Body. 

Tho Advantago of a Hlxod Diot. The nccoeeary quan- 
tity of diiily food depends U|>on that of the mntcnal daily 
loet from the Bo<ly, and this viirica both in kind and 
amount with thi< imcrgy cxpendvd and the organs moat 
uticd. In children n certain cicesa beyond thii is lequircd 
to funiinh niiiterials fur growth. Although it is impossible 
to lay down with perfect acciiraoy how much dailv food any 
■ndindnal requires, still the average quantity niav be de- 
rived fram the l«1d« of daily luracs giren on page 278. 
which shows that a healthy man needs daily in iLu-iniitabIc 
forms about "itA gram*: (4230 grains) of carbon and Ifi 
grama (292 grains) of uitrujren. Thedailvloni^of lirdrogeit 
which is very groiit (353 grams or M38 grains), is nearly all 
that containeil in wnti'r which ha^ been dnink and. so to 
apesk, merely filtered tlirough the Body, after hannfr 
wiistod in the solution and tninaferenoe through it of ether 



3W 



Tat! nuHA.y .lonr 



BobsUuMeB. About 31)0 gramt (4S^ grsina) of ntcr 
(cxfnfaiitiiti^ 33.3 granu (fll3 );rainH) nt livilmgcn arc, how- 
ever, formed iu the Body b>* oxidntioo, and the lijdrogcn for 
this purpose mast bo supplied in the fonu of wmo oxidixa- 
blo foodstuff, whether proteHl, fat, or curlwtijdntc. The 
oxygen wanted is mainly received from the air through the 
tnngB, but some is token in the food. 

Sin«e pn>t«id frwdf contain curlfon, nitrogen and liydro- 
gen, life may be kept up on tliem alone, willi tla- newwary 
BaltH, water and oxygen; but such a form of feeding wonid 
lif anything hut econoiuieal. Oi-diiutry pn>U^id» contain in 
100 partA (p. 10) about M of carbon and Id of nitrogen, so 
a man fed on them alone would get abont 31 parts of carbon 
for every 1 of nitix'gvn. Hi« <iiijly loKseii are not in this 
ratio, but abuut lliul of 2i4 grams (42*^0 grains) of carbon 
to 'liO gratiu (308 grains) of nitrogen, or as 13.7 to 1; and 
po tfi gel eiKingli carbon from prdlcidii fur moK timn the 
u«oeaauy amonnt of nitrogen must be taken. Of dry 
proteida AST gmms (HllO grains) would yield iho necessaiy 
carbon, but would oanUm 79 grams (1217 gruin«) of 
nilroiton; cir four timw more than is necessary to cover the 
(tiiily IdBsea of that clement froDi the Body. Fed on a 
inirt'ly pruieid diet a man wnulij. tliertforc. hitvv to digest a 
viiHt c|iiu[iiity to get enough cuibon, and in eating and 
absorbing it, as well at iu goLling rid of iho extra nitrogen 
which ii^ iiKulcw to him, a great dcul of unneecMory labor 
tvotihl lie thrown upon tho various organs of his Body. 
Siniilnvlv. if II man were lo live on bread ulone he would 
bnideii hii organs with much useless work. For bread 
oontuiiis but little nitrogen in proportion to its carbon, and 
so. to gel enough of the former, far more carbon than wbb 
utilixcd would have to bo ciitcn, digested, and vlimiuattfd 
daily. 

Aecordingly, we find thai mankind in genera) employ a 
mixed du'l when they eau gil il. iixing richly protcid stib- 
Rtunccs to supply the nitn>gen ■jcu'ded. but deriving the 
mrbon mninly froni non-mlrogt-noiis fowls of the fatty or 
oarbohydrote groups, and so avoiding excess of eiUicr. For 
iustauou, h-un beef contains nhoiii | of its weight of dry 




ADVANTAGSOfA MIXED DIRT. 



807 



prat«id. whicli contains IS per <M>nt of nitrogen. Consc 
()u«nlly llic 13d grunii< ('^048 gruink) ^f proti^d which 
would be found in 532 graiun (1 lb. 3 oz.) of lean uxtat 
would mipply all the nitrogeo needed to compciiBate for a 
day's losses. But the prot«id contains 52 per cent of 
carbon, eo the amount of it in the above weight of fatless 
meat would bo 69 gTHni.< (1062 griuii«) of carbon, kuving 
S05 grama (3167 grains) to be got either from fati* or car 
bohydrates. The noceBssiry amount would be contained 
in about 256 grumx (3942 grainit) of ordinary fut« or 400 
gramii (7084 grains^ of starch; hence either of these, with 
the above quantity of lean meat, would form a far better 
diet, both for the purse and thcfy^tt^ni, than the meat ulone. 
As already jiointed out, nearly all common foods contain 
■BTsnl foodstuffs. Ordinary butcher's meat, for vzample. 
OOntalns nearly half lU weight of tat; and bread, bolides! 
proteids. contains starch, fats, and ^ugar. In none of them, 
however, are tJio foodsluQs mixed in thv pliytiiulogicatly 
beat projiortioDS, and the pi-aclice of employing several of 
thom at each meal or different ones at different meals 
during the day, ih Ihuii not only agreeable to tlie palate but 
in a high degree advantsgeons to the Body. The strict 
vegetarians who do not employ oven euch snbstanccR ae 
eggA, diee-ae, and milk, but confine themselTex to a purely 
vegetable diet (euch ax isalwajo ]>uurin protoids), daily (akc 
fw more carbon than Ihey reciuirc, and are to be congi-atn- 
lated on their excellent digestions which are able to stand 
the strain. Tlioso who u«c eggs, checso, etc, can of course 
get on very well, snice snch snbstanOM ore extremely rich 
in proteide. and supply the nitrogen needed without the 
nooessity of swallowing tlie viut bulk of food which must 
be eaten in order to get it from plants direotJy. 



CHAPTER XXI 

THE ALIMENTARY CANAL AXD ITS APPEN- 

UAGEii 



General Arrangement. The nlimentan- ciinnl is pswii- 
tially an mvoluU-il jiurtiou of the akiu, epociiilly set iijmrt 
for ubKur{>tion, mu! runiiiiig a tube which runs through 
fill; BiKly (Fig. 2); it com in un ten ten with ihp oilcrior ill 
three points (llic no,w. Mio mouth, and the aiial iiiJi'i-tiiiy). 
lit. wliiob this modified 8kiii, or mumus membrane, is con- 
tinuauH with tliL- gcncriil outer iDteguaient. Sujiporiiiig 
the lining nlmorptivu iiioinbntiic nrt- other Inyers vhii'li 
Ktrengtheti Ihe tube, and are also in pari miineiihir and, 
by their contmcliouit, eone to puss materials along it from 
one end to llio oUior. In the wallti of the <.'sna1 juv 
niimcnitiM Wood and lympliatic ■vpsswls which carrj- off the 
miitiorfi absorbed from its cavity; and tliere alHo ckisl in 
connect ion nil h it nunicrouif ^/»'iijk, whose function it if< tii 
pour iuto it viinyns frcrftiomt which exert n kuIvouI ioflii- 
cnee on sucli fondslulTa ti» would othcrwiHC cscaiw ftb»<ir|>- 
tion. Some of these glands are minute and imlwdded in 
the walls of the alimentary tulw itself, but olhcre (Kuch 
jiH the ^ulivnry ginndx) are larger and lie away from llic 
main channel, into which their products arc carried by ducts 
of various lengths. 

The alimentary tube is not uniform but presents several 
diUteiions on its course; nor is it straight, since, being much 
longer than the Body, it is j>ac)(cd unay by being coiled up 
in the abdominn! cavity. 

Subdtviaioua of the AUmentary Canal. The mouUi 
upenin); k'ad.< into a <-li:tnibcr containing the teeth and 
tongiicr iht- Movtk e/uimbcr or buMal eatnti/. This is sue- 




MOUTH CAVITT. 



S09 



cecJixl bj {\\K pharynx IT throat cavity, which dmtowk »t 

tlie top uf tliii ni'ctc into Utc guilH or agophnffus; this runs 

dowii tliroiigh lilt? tliorux aiid. piifsiiig through (lii- diii- 

phriigui. dilutes in tho uppur purt uf the abdomiiuil cavln 

into the s/owmrA. Dl-vuikI 

tlie stomach the channel ugain 

narrows to funn a long tun) 

greaily coik-d tiihe. the smalt 

intenline, which temiinali^K by 

opening iiito tbv hrsf inlM- 

tine, much shorter although 

wider than the small, and ter> 

tninatiiig hj un opening on 

theexUrior. 

The Mouth Cavity (Kig. 
S^) i* huunitud in fruiit and 
on the sida'i br the Uim vud 
checkg, below by the tongue, 
k, and aboTo by the paiatt; 
whii'h latter consistsof an an* 
Icrior piirt, /, supported hv 
bono and billed the hard pal- 
ate, and u posterior, /, «iu- 
tiiining no bone, and railed 
the fo/t palate. The two can 
i-c«dily be dietinguiirlied by 
applying the tip of ttiutungiie 
to the root of the nioulh and 
druwing il bHckwanls. Tho 
liurd pillule forms the parti- 
lion Iiutwcen the month, and 
nose. The soft palate ai-chc" 
down over the back of the 
nioutti, baiigiiig like ii ciir- 
luin lietween it and the phuiynx. a« ciin bo acen by holding 
the mouth open in front of a luuking-glaM. From tlie 
middle of i1«i free liordora vonieal prucei^, theuvtiia, bangD 
tluwii. 

The Teeth. Immediately within the cheeks and bj-s are 




Fio. aa -Tlif nitpulh. ii< -■• ■ml i>h« 
rynx. Willi t}v <^ijntw\H^"afFiti <it lUf 
iriilln mirl Inijni ■• viiManI by B 
mllon. > lUllB lo till' lv(1 of IIif nii- 
djao |>laELD of iliF bo^' ti, tcnrljr^l 
ofitiiiuD ; &. LOllvl ; c, «liiil|it|ri>; i^. 
lujmx -. <. vpillnm* -, / ton iinlUi- : 
p, openlDC it BiuU(dil«Ji tubp -. k. 
l-iiunw : rtlMd HJM* : n. Uur i^ir' 
■••ilJ bona (01 tba UM ot thf tJiuIli ti. 
Ilif' Itv paH <•! tb* cranial dhUji' ■ 
a ji. g. the tablnsw bonn of Ibc oul- 
H >«& o( ihe Wt bonrtl cbuiiHrr. 



310 



THE nUMAK BODY. 



two semicircles, formed by the borders of tli« tipjier and 
lower jjtw-bfinea, which arc covered by the gturu. except at 
intervaU along thoir cdgot where they (xiiiuua Mckcu in 
which the tticth arc implanted. During life two sets of 
tocth urc dovelojMiJ; the lirst or milk get appoaiBEOCHi iiftor 
birth and in shed during chi]dh<wd, wb«il tlie secoad 
or permanent set appears. 

Till' leelli differ iii minor points from oue Knother> bnt 
ill all three piirts are dixtinguishitblo; one, sccii in the 
niotiDi uud culled iho crown of the tootii; a second, im* 
bedded in the jaw-bone and called the rool ot fang; and 
between the two, embraced by the edge of the gum, in a 
narrowed }»ortion. the neck or cervix. From diffcrcnpes in 
their forms and use* the teeth *nj divided into inrisora, 
canUiea, bicn^iih, and molnrs, arranged in a dcHnite oi-der 
in earh Jaw, Beginning at the middle line we meet in 
each half of OJich juw with, sucop^isivply, two ineisors, ono 
canine, and two molars in the milk-sel; making twenty 
altogether in the two juwii. The teeth of the permanent 
BOt are thirty-two in niimher, eight in each half uf eiu<h 
jaw, via, — beginning at the middle line — two incisors, one 
vaninc, two bicuepids, and three molars. The bleu bpids, or 
premolari^, of the permanent «et ropinco tho milk molars, 
while the permanent molars are new teeth added on as tlic 
jaw grows, and not tnbetitating any of tho milk leeth. 
The hindmost permanent molara aie often eulled the wi*- 
dom teeth. 

CharoQtora of Individual Teeth. The incUtori (Fig. 
90) are adapted for cutting the food. Their crowns are 
chisel -shaped and have shaqi horizontal outting edgr^g, 
which become worn away by use so that they are bevelled 
oR behind in the upper row, and iu the opposite direction 
in the lower. Each hu^ a single long fang. Tho •Mninu 
(Fig. Dt) ore Mmovhut larger than the incisors. Their 
crowns are thick aad somewhat conical, having a central 
l>oint or cusp on tho cutting edge. In dogs, cats, and 
other carNivora the ranincs are very large and adapted for 
Mcizing and holding piey. Tho bicuspids or jirtmolara 
(Pi^. 93) ore rather shorter than tJie canines and their 



riTff TKKTIt. 



to. 



croirns w« somcvhat cul>oidal. Eacli hu tvo cusps, on 
ontcr towards th« cheek, and an inner on the side turned , 
towards the interior of ibc mouth. The fnng is compressed ' 
laterally, und hm usuitll)' a groove partially tubdJvJdiug it 





Fra.Ki 



Fnt. *l. 



r».n. 



m.M. 



no 01,— A nulnn urnyi- (doUl 

Iiliii 9«-A triaiH|)i'l i-iuUi ■mutrain lu auMr«id*i ttwlaavrciuti U,areoar4- 
ng^, nol viHlblp. 
via. W.-A aiol»r tooUi. 



into two. At its tip the sopamtioQ is ofton complete. 
The molnr trtlh or grimUn (Pig. 93) haro Inrge crowna 
with bixMM] iiirfuces, on which arc four or fire projecting 
tubercles, which roughen thorn uiid ni«ko thom bolter udapt- 
cil to (?ri»h the food. Eiu;h \\»a u:iua]ly KYentl luig*. The 
)Mi7^- tetth only differ in sub^idim- points from those of 
the sami? namL-s in the permanent set. 

The Strooture of a Tooth. If a tooth be broken open 
a cavity ijiteiiding through both crown and fung will be 
fonnd in it. This is lillcd during life with a soft vilkcuIut i 
palp, and hence is known m Iho "pulp cavity" (c. Fig.' 
M). The bard parts of the tooth dii>po»^ iiround Ibe pulp 
cavity consist of throe diOercnt tissues. Of these one im- 
mediately sTirrouiidfl the cavity and mdcM up most of tbo 
balk of the tooth; it is dentine {?, Fig. 94); covering the 
dentine on the crown is the eaamti (1, Fig. 94) and, on the 
hng, the ctmwU <3, V\p M}. 

The pulp cavity opens below by a narrow aperture at tin, 
tip of tho fang, or at the tip of each if the looih has more' 
than one. The pulp consisUt mainly of connective tissue, 
but its surface next the dentine is covered by a layer of 



n% 



THE ffrVAX nODT. 



oolutntiftr ooUsl Throiigh llic opening on the fang blond- 
Tessels and nenres enter the pulp. 
The dentine yields on diemii-al analysis the mno niaUi- 




^0- 04.— O^T-tipti ibrouftla a pn^niolar (■j-tUi »f ilic c&r MiFI Liiib4<Jdt<J Ui lt> 
MCkfC K riuimel^ K.deouiHii S.caaii-ni; 1. the Bum, l.ilia tnnn vl UiFliiwnr 
JHW 1 c, Uw pulij carlly. 

rials us bono bnl \« somen-hat harder, cMthj mattun) con- 
Btihitin^ Ti ]>er eent of it n« ngiimst 6(: per cent in bone. 
Doidtr the nticroecope it is rccogmxed hy iho floe dentinal 



THE Tosors. 



S18 



tvbulea which, radiating from the pulp caritr. perforate it 
tiirougfaotit. fiiiiiliy ending in niiniitt> hranchea which open 
into irregnliir Larilics, the inltr^hhuUtr rpiurt, uhiiii Iji- 
jtut beiioHth Ihc cnamrl or cement. At their vridest enAi, 
(Awn to the pulp cavitT, the dentinal tttbulcs are ouly 
ahont 0.005 millimeter (tVmt *' "" inch) in diameter. 
The ettiunt umucb Itkc bono in »tnictui-caui1ooiii[)<>iiiii<iu, 
posseadng laounie and cauulicali but rarelf anr Ilii^enilan 
canals. It u thickest at the tip of the fang and thins 
Kwvj towards lliOG«rT)s. Enamel iii the hardest tt.'^ue in 
the Body, yielding on analysis only from two per oent lo 
three per cent of orguiiiv Dinttcr, the Tc«t being mainly 
calcium phoHphate and carbonate. \i» hiHtologiiial ele- 
ments are minute hexagonal prisma, closely packed, and eet 
on vertically to the siirfiicc of the ^nbjui^ent dentine. It i^ 
thickest over the fit* end of the crown, until worn away bv 
n«e. Covering the enamel in nnwom teeth U a thin struc- 
tiireloes homy layer, the enamel atlirle. 

The Tongue (Fig. 95) ia n muscular orgau eoverod with 
a niiicKUf membrane, extremely mobile, and endowed not 
only with a delicate tactile aeitsibibty but with the ter- 
minal organs of the special sense of taste; it is attached 
by ild root to the hyoid bono. It« upper i>urfiice is covored 
with small emiiienceit or piipilltr, much like tho^e more 
highly derolopod on the tongue of a cat, where they are 
readily felt On tlio htiinaii tongue there are tbret^ kinds 
of papillie, the circHmvailale, the /unffi/orm, and the fill- 
form. The circnmrallate papillny, 1 and 'i, the largest 
and lottut nuinerouii, are from seven (o twelve in number 
and lie near the root of the tongue arranged in the form of 
a V wiih Its open angle turned forwards. Each is un elr- 
vuuon of the mucous membrane, covered by epithelium. 
and surrounded by a trench. On the sides of the papilla), 
imbedded in the epithelium, arc small oval bodies (Fig. 165) 
richly supplied with nerves and HUpposed to bo concerned 
in the sen^e of tasle. and hence ciiUed the tatte bvdf 
(Chap. XXXIV.). 'X\ie j'utujSform i>aptUa,'6, are ruunded 
elevations attached by somcwhut narrower stalks, and found 
all over Uio middle and fore pari of the upper surface of 



S14 



Tits BVMAN BOOT. 



the too^e. They are easily recognixi^d oa tfao tmog 
toagne by tht-ir bright red color. The Jiliform papillai, 
most nDDieroiis and smBlleflt, are scattered all ov«r ilie dor- 




FiO- M.-Tbp appermirf '■ ■ ■■( ^m r i iinmlliii* p«>lll»ri (.tun 

iTlniUi', 

Hiim of Uie tongue except nnr iu biieo, Bach is a aonical 
eminence coverod by a thick bomy Inyor of opitlioliunt. 
It is thwt p«i)illn* which are no highly developed on tlia 
tongue* of Carniwra, and wn-A thi-iu U> Rcrape bones cleaa 




TITS flAr.rrAnr 0LA!fi>8. 



815 



of CToii «iich tongli etniclnrc« m ligntnenU. Tnmed tigen 
have been known to draw blood by licking the liand of their 
muster. 

Nofe. In hwUth tli* tnrfuco of the toni^ic is moist, 
ODTered hy littlo '*fur," and in cltildhood of n red color. 
In adult life the nahinil color of the tongne is less r«d, ex- 
cept uruuiid titc ed;;vM iind tip; n bright red glistening: 
tongue being, then, uHUftllys symptom of diKeas& Whea' 
the dtgcstivv orgun^ iiro dernnged tho tongue is commonly 
covered with n tliiok yellowish fio»t, oom|>090«l of ti liltlo 
mucos, a few cells of epitbeliiuii Abed from the surface, and 
numerous micnjiMJopic orgHnisms known oe bacteria; and 
there i« frciiuently tt " liad ttwtc" in the mouili. Tho 
whole alimenlary mnoua membrane it) in close phyaio- 
logical relatiunship; and unythiDg disordering the Eto- 
UAcli i* likely lo prodnoc a " furred tongue," 

The Salivary Glands. The saliva, which is jwurcd into 
tho mwiitli iimi wliieli, iiiixt-il with tho secretion of minute 
glands imbedded in its lining meoihranc, moistena it, is 
m-eretcd by three i«iir>i of glands, the pnroUil, the »uhmaxiU 
inry and the mibli'iyurt!. The [mrotid (jlaiidH tie in front 
of the ear beliind the ramus of the lower jaw; cucli 8cuda 
its eecrotion into the mouth by a tube known m» SIfnon'x 
duct, which oroHWS ihcchetrk and opens opjioHite the second 
upper molar tooth. In the diwa^e known as ntumps tlio 
parotid gliiud^ aiv iiillamcd and enlarged. Tho »iil> maxillary 
glands lie between the halveii of the lower jaw-bone, near 
Its angles, and their duot« open beneath the t/ingiie near tli« 
middle line. Tho sublingual glamlK lie lieneiUh the floor 
of the mouth, covered by its muoous membrane, butweon 
the bock part of the tongue and the lower jaw-honc. Hik'Ii 
has many duets (8 le SO), «am« of whieh join the subtnasil ■ 
lary duct, while the rest ojwii separately in the floor of tlio 
mouth, 

The Fauces is the name given to the aperture which can 
be soon at tlie back of the month (Fig. 83), leading from it 
into the pharynx below the soft palate. It U bounded 
ftt)Ove by the soft palate and uvula, below by Pie root of tlifl 
tongue, and un the sideit by uiuveular elevations, ooverod 



816 



TIW aKn/Ay BODT. 



mucons membrane, which rcwh fi-om tlie soft palnto hi the 
tijiigiif. T!n.---<(! I'liivalions are tho jnUnm of Hie fauet*. 
Ka€h bifurcates below, and in Ihc hollow botmceii its divi- 
sions he* It tonsil (7, Fig D5), nsuft rounded body nboul Iho 
Hize ot nil iiliiioiid, and containing numeroos minute glands 
which form mucus 

iVo/0. Tho loDi^ilx not unfrcquontly bccomi) onlarged 
during II cold or son> throat, and then ]>reRfiing on the 
Kustuchian tube (Chap. XXXlII.)t which lends from tho 
pharynx to the midflli; ear, Veep it clowil nnd produce toin- 
poniry dciifuen.-i, Sometiraee the euUrfjement is permanent 
and cikuseii much Hnnovanco^ Tlic loiiifiU nui, houi'vcr, bo 
readily removed without danger, and this Ia the ti'catiii£iil 
uftUiiliy atlojitcd in such ciises. 

Tho Pharynx or Throat Cavity {Kig. 89). This por- 
tiun of the alimentary canal may he deaorlbcd bj< a coaical ' 
bap with its broud end turned iipwiirda tonurds ihe base of 
tho Kkiill, and iU onn'ow end dowowards itnd jiuiiKing intn 
the gullet. Its front i.s imperfect., prewnting apertures 
which k'ud into the nose, the mouth, and (through ihc 
lar^-nx and windpijic) into tho lungs. Kxccpt when foMl 
is being swalh^wcd the KofI palnte hang« down belween the 
mouth and phiiryns; during deglutition it in miwd into a 
horisontal position atid separates an npjier or rv»pirtifory 
portion of tho plnnynx from the rcitt. Through this 
U]ipor part, tlierefore, air alone passes, entering it from llie 
posterior ends of the two iici.4lril clianiburs; while through ih > 
lower portion both food mid uiv piiss one on it^ way to the 
gullet, 6, Fig. SB. the other throiigli the larynx, tl, to the 
windpipe, r ; when u tiiurscl of food " goeM the wrong 
way " it tnlten the latter onur«e. Openiug into the njiper 
imrlifin of the pharynx on each aide is an KustuL-hian tube. 
ff: so that the apertures li'iidiiiij out of it iiro seren in num- 
ber; the two posterior narcw, llic two Ku.'iluebinn tubeit, the 
fance*. the opening of Ihe larynx, and that of the gul- 
let. At tho root of the tongue, over the opening of the 
larynx, in a plate of oartJhtge, the r/ni/tfilHii, e, whieh eati be 
seen if the mouth is widely o]>eiied and the back of ihi' 
tongue pressed down by some sneli thing a« the handle of 




TBB STOMACH 



317 



u g))»»ii. DurJiif! Hvnllowiofctbe epiglottis in jircitwxl il»wn 
like n lid over thv a!r-tiil)c itiid hvl{);< to keep food or salivii 
from i-oa-niig it. In striK'ture tlip |)tiiiryiix ooii«i«t(i ceseii- 
linlly of a bH^ of connective tissue liiicd by mucous m«in- 
linine, and liavitij; mii*clC'.'< in hn wnllt which, by their oon- 
tiiictions. drive llic fooii on, 

Tho CEaophftguB or OuU«t i^ ■> tube comtncncing at iIk' 
lovrcr terminiiluin of tin- |ihiirjiix uiid wtiii-h, passing on 
thixiiigli lIii> neck un<1 ehv»l, eadx i» tJic Rlonuich belon* the 
iliapliiagin in (he neck it lies oloec behind tho Mind)iipr. 
li consisUof tlirec costs — iimucnuHniL'iiibriine within: next, 
u Mit>mucou# cnni of aivolarconnootive tisme; iind, outside, 
» moscnUr coul made up of tn-o luyers, an inner withtrans- 
verao mid au outer with longiludimilh- nrrungcd libres. In 
and beneath its mucous membi-ane nrc. numerous imall 
glands whose durts open into tho tube. 

The Stomaoh (Fig. 86) i:« nsomewlmt uoiiJoil bug placed 
trniiHversely in the upper pari of the abdominal cavity. Its 
lari^>r oiid is lunipil to 
the left and lies close 
lieneatli the ilmjihriigm; 
opening into its u]>[ier 
border, through the mr- 
diac orifice at a, i» ihe 
gullet, d. The uarrftwcr 
right end it liontinuoui' 
nt c witlt thcumnll inlCK' 
tine; the coinmunii-alion 
between tho two is Ihe 
fffllonr ortfirf. The py- 
loric end of the ^lomach 
lies lower in the abdomen 
than the citrdinc, and is 
separated from tho diaphrugin by the lirer (sec Pig. 1) 
The concave boi-der between tlio two orifices u known as 
Ihe small cnrvalun. and the convex as the ffreaf cttrtfilurf, 
of the stomiicli. PVoin tlio lalti-r hangs down a fold of 
peritoneum (ne, I-'ig. 1) known w the t/rtat onifnlum. It 
is spread over the rest of the abdominal conteutA like an 




no. M.—Tllr ffomtcb. d. lutriT (lad Ot 
liirKullsl: a,podtlaii ot lln' i-nnliiu apsr 
Inn' ; b, tbt fumliiai r, Ibt |')lonii: r. llic 
<v>inTnm<wnrnt ot tbi muill tuletHnc 
ihlanirn. fi. r. Ilic jprnt curtmim; br4wivD 
Ihe p) Innu uid d. ibt ItHrr canvturri. 



S18 



TBK UVMAS BODT. 



apron. Alter middle life naaoh fat freqaently acciimalates 
in the omentum, so that it jb largely responsible for the 
" fair round l>oUy with good cajwn lin'^." The protrueion 
h to llu^ left *i<le of the rardiac onfice. Fig. J)6, is l\w/un- 
dug or ijrmt t'ul de »ac. The Gize of the stomach varicM 
greatly with tlio amouut of food in it; jii§t after u modn- 
ruiv niciil il i» about ten inches lon^, by five wide at its 
briiadt'.Hi, pari. 

Btructuro of the Stomach. This organ has four coats, 
kuiiwu successively Irum without id &« llio serous, the mus- 
culiir, the i^nbmucoUE, and tlie mncons. llie *erDti» coat is 
formed by a reflexion of the peritoneum, a double fold of 
whioh i^lmgi! the Etomiu-h; uftisr u'parutingto envelop it the 
two laycrfi again unite and, hanging down beyond it, form 
the great omentum. The mii(sfK/flj-f:o(//(Fi';,3-l*) consists of 
uiiftriix-d niiw liar liwuettrriingi'ii in three layers: an outer, 
longitudinal, most developed aliout the eurvature-i; a circu- 
lar, evenly spread over llie wholu organ, except around tJie 
pyloric orifice where ii furniH a thick ring; and an inner, 
oblique and very incomplete, radiating from the cardiac 
orifice. The »u/intarvui< coiil tn mndo up of lax areolar 
tiK.'iucnnd bindi* loosi^ly ihe mucoujooat to the miiKOular, 
Tlie mi(cowit coat \s a moiet pink membrane which is 
iuehi«tic, and large enough to lincthe stonioth evenly when 
il is fully disti'uded. Accordingly, when the organ i« 
empty and shrunk, this coiit is thrown into folds. During 
digfistion the arteries supplying the stomach become dilated 
and, ils capillariofl being gorge<l, ita mucous membraiio is 
Ihei) much redder than when the organ is empty. 

The blood-vcBiiets of the stomach run to it between the 
folde of peritoneum which uling it. After giving off a 
few branches to the outer layers, most of the arterie* 
break up into small branches in the submncous coat, from 
which twigs proceed to cupply the close oapillury network 
of the miicouK membrane. The pneumogagtrie ttervm 
(p. ITl) end in the stomach, and it idso gets branches from 
the sympuihclie eystcm. 

Histology of tho Oastric Uncous Uombrane. Kxami* 
tuition of the inner surfiKe of the stomach wjih a hand 




BTttVOTCRB OF STOMACH. 



319 



kosthows it to be ooTered nith minute Hhallow pit«. Into 
these open the mouths of mintit« tubes, the gastric ffhtuU. 
wbicli arc cliwictv pncktil iiiiii! hr tide in the mucous 
m«nil>raiie: there being between Uiein only a Bniall amount 
of (ronnectiv* tissne, a clow network of lymph-chntmels, 
nncl eapillary bloocl-ve»eLs. Tbo wholo i^nrfoce of the 
rDncuufi nn-mbninc ii* lined by a single layer of columnar 
C)>itiioliuui cells (Fig, 07). These dip cIovtd and lino the 
tubular glands, being iu sonio (<.-#pc\;iitlly tliuM about the 
pyloric end of the Eitomnch) hut little modified In appear- 
ance (<:■. Fig. 97). In others ibo epiUielial celtii become 
»borttr Kud cubunlul, uiid 
have ixineath them [a luid b, 
Fig.97) a Moond incomplete 
layer of much litrger oval 
cslh, d. The glands of this 
aeoond kind are the most 
numerous, and hate been 
ealled p«p(ic ghimh fmm 
the idcu tiial ihey idone 
iormed p«psiM, theesscntiul 
digestive ingredient of the 
gastric juice; this is how- 
ever by no meanii certiiin. 
The peptic glands freciuently branch at their deeper 
ends. 

The PyloniB. H the slomiich bo opened it is seen that 
the mucous niembmnc i)rojecl« in a fold iiround the pyloric 
ori6ce and narrows it. This is due to n thick ring of the 
circular niUH^ular layer tliero developed, and forming a 
Kphinctfr musclr around tlie orifice, which in life, by its 
contraction, keeps the paassge to the nnall int«i(l)ni'4 cloned 
except wh<-ii portions of food ore to be passed on from 
the stomach to snooeeding division* of tho ftlimentorj' 
canal. 

A'off. The cardiac end of the stomach lying immedialely 
beneath the diaphragm, which hax the heart on its upper 
side, nver-distenaion of the ^lomaoh. due lo indigestion or 
flatulence, may inipcdctbcuclionof the thoracic organs, and 




|f|0. VT.—A tkin ■eotl™ IhrouKb IM 
RUtriC nuicaiw nwmbruiu, w-rjiMirll- 
cular bi Itn wrfiHw, nuwnllwl ■■>«■( 
ajdlkinvlna. a.>HmpI«rwpllGKliinil* 
6. ao«Dpouiul twMWBlkod^e.amn' 

wcoUa, 




ut 



thh nuyfAw bodt. 



ran-w fpelinjis of oppre»iioa in the plieot, or imlpfUtion of 
the heart. 

The Small Int«aline, rommenriiig at t)io j^j-Iorus, ends. 
;iftcr many witidiiig", in the largo, ti ia atom six nii-tcrs 
;iwcnty fi'Ct) long, and nbout five centimeters (two iiieiu-.«) 
wide nt its {gastric end, nan-owing to ahiait. two thirds of 
that width at its lower portion. Externallj- there are no 
lines of KiiMiTiaion on the mnall iiitoHtinc. hut snatomUlit 
arbitrai'ily describe it as consisting of three {»irt>; the lir^t 
twelve iiiL'hcfbuing the (2iiuK2m«t». thcxiieeoedingiwu tlfih:( 
of tbc remainder i\ie jejunum, and (lie ri'Ht iJio ihum. 

Like the stomach, the small intefitiiie ])OBseiies four eoatc: 
a serous, a nin»culHr, a euhmucous, and u mucauii. The 
fifrnuf cotrl is formed by a duplicitnre of the pfritonenm. 
hut ]>resents nothing answering to the great omentum; this 
double fold, clinging the iuKstJne as the «niult omentORi 
slings the titomach, is called the me^f-Htny. The mutciilar 
ruttt is composed of plain muscular tissue arnmgcd in two 
strata, an outer lougituditial. and an inner tramivcrse or 
rireular. The nubmuroun oat is like that of the Htomacli; 
oonsistiug of loose areolar ti.'vuc, binding together the mu- 
cous and mniicular coats, and forming a bed in which ihe 
Wwd and lymphatic Tcasfts (which reiith tlio intestine in 
the fold of the muHenti^ry) break np into minute brunches 
before entering llie mucous membriinc. 

Tbo UuoouB Coat of tho Small Intoatine. This is pink, 
sofi. and cxtriMiii'Iy viwctilar. It does not jireitcnt tcm)H>- 
rary or elfaceable folds like those of the stomach, but is, 
Ihrunghant a great portion of ita length, raised up into |>er- 
nianent tnnisversc folds in the form of cresoentic ridge«. 
each of which nins traiidvcrnely for a greater or Icm way 
round the Inlw (Fig. tt8). Tin'w fuldn are the valvuUf 
ronnivtnlf. They are tirst found about two incJiea from 
the pylorus, and are most thickly set and largest in tin- 
upper half of the jejunum, in ihc lnwcr half i>f wliit-h tiny 
become gradually less conspicuous ; and they liuaily disappear 
altogether about the middle of the ileum. The folds 
serve greatly to incn<n«c the xurfaoe of the mucous mem- 
brane both for absorption and secretion, and they also de> 



SMALL lyresiws. 



891 



lay the food Bomeirtial in it« postage,, since it most collect io 
the hollows bctwooii Dieiit. iiixl ui lie loiigiT i.>x})()fi.i(l to the 
action of the digeotivG ll'ijuids. KxuDiined cioseiy with the 
eye or. better, with u liuod Icdii. thu mucotu memhrane of 
the stunll intcctlDO is seen tn W tii>t Hnioolli hut ^hnggr, be- 
ing covered everj-where (both over llie yhIvuIjb conniventes 
:i!id between them) with clo*cly piuikcd miniitf [imccHScs, 
imndingiipsomcwhit like the " (iilc"<»i velvet, and known 
itn the rilli. Enoh villua ie from 0.5 to 0.7 miilimelers 
(^ to J*! inch) long; some arc conical and roanded, but 
tlic majority i»ro coinprfiwcd at the base i« out? dianivtor 
(Fig. 99). In utructure a villuii i^ somewhst complex. 
Corering it is a single layer of cohimniir epithelial cells, be- 
iiLttth which the villus may he rotfarded m luado up of a 




Cmiiicwork of coiincctive tissue supporting the more essen- 
tial oonstituentjt. \car the surface itt an inconipWti.^ layer 
of plain muscular tissue, continuous below with a muHoular 
layer found an Ihe deep side of Ihv mucous membrane. In 
the centre is an oD?hont of the lymphatic system ; «omc- 
(imos iu the form of a single vessel with a eWed dilated 
end. and sometimM lu a network formed by two muin ves- 
sels with cross- branches. During digmtton [heM> lym- 
phatics lire iilled with a milky white litiuid absorbed from 
the intctdinen and they are itccordingly called IJie tadtaia. 
Thoy (wmmunicate with larger branchcH in Uic Hiibmucoui 
ciml which end in tninkfi that pass out in the mesentery to 
join tlie main lymiihatio system. Finally, in cuch villa*, 



$ta 



TBS ffCVAX BODY. 



oaUido t)ic Iftcleitlx ttmi bciicuth th« mnscnlar Uyer, is a close 
netvork of biooii-vesacln. 

Opcnitig on the Bin-face of the flmall intestine, between 
thp basCR of tho villi, are email glands, the crypts of Liebtr- 
kHhn, Each is a )iim{i1e imbrnnohot] Milie lined liv n luycr 
of columnar cellB similar to that which covers the villi and 
the surface of llio mucous mombruoo between them. In 




na,Hl-~VUUot thcfnuJI liiloicintf; muffnldnJ about W ilii(n»>t«n. In Ihu 
MUuiid KKurellu) ■■di-al*. n. A. r. wlUlud •llli ohIW ln]n'll»n:'I, blood-TM- 
mW In Ih" riKl^t-luwd fitpirB (lio liHtMli Alone iirp nrpivwiiliMl. (Ul«l vtUi a 
dillk ItijectMD. TlH •pHb.Uuin ootoHhk ihe TlUi. (uid tbdr uiusuulat llbRB, ua 
omillM. 

strnotnre they greatly rosomblo tho mucouR glands of tho 
stAmach {•;. Fig. il?). In the duodenum are found other 
minutv glands, ths glands of Brunner. TLcy lie in the 
sahmacous coat Mid tend their ducta through thi; niuoous 
mcmbnn« to open on its inner side. 

The Large Intestine, forming the final portion of tin- 
aliincntary win!!], is iiliont 1.5 meters (fi feet) long, and 
Tftrifii in diwneter from ahoul 6 to < cenlimelcrK (SJ to IJ 
inches). Anatomists describe it im consisting of the eocum 
with the tvrmi/orm appendur, tho colon, and the rectum. 
Tbecmiill intestine docs not open into the ci>miuL'nc4.'mcnt 
of tbe latga but into its side, some distance from its clo«ed 



THE uvea. 



jm 



apper «nd, and th» cjecoro U tliat .port of the large intes- 
tine which exUnds beyond the ooDimuniciilJon. From it 
projccU tho tvrmi/orin appendix, a narrow tnbo not thicker 
lha» a cetlar peaci), and about 10 oeatimeters (4 inches) 
long. The colon cummoncox on the right Rtdo of thft 
nbdomiiuil cavity where llie itmnll interline cominunicatoa 
with llio large, runs np for Bome vaj* uu thut side (ascemt- 
ing eolon), then crosses the middle line (Iranin'vrte coht^ 
below the dUHiuivh, and turns down {iit»r«ndi>ig colon) 
on the left side and tUere makes an S-shapcd bend known 
M tite tigmoid fitXHit; (n^m thit the nctum, the t«rini> 
na] straight portion of the intestiiMi, proceeds to the aual 
opening, bj which the •limeutary canal oommuniculcs 
with tbe exterior. In ittnu-tui'o the large i»tc«tin« prewnta 
tho same coats m the small. The externa) slnuiim of the 
muKCular coat is not, howcrer, developed tiuiformly urciiiii] 
it, except on the rocttiin, but ocoiiri in three bitnds separated 
by inter^'als in which it is wanting. These bands being 
sliorter than the roitt of the tube cuniie it to be pnolcered, or 
9iicou1at'ed. between them. The tnucotis coat possesses no 
villi or valrnls conniventes, but is UKiiully thrown into 
eSuviihle foldi", like tho»o of the gt«ma«h but smaller. It 
contains numerous closely set ];Unds mnch like tbe crypta 
of Liobcrkiihn of the small ititcetine. 

Tho Itoo-Colic ValTo. Where tlie small intestine joimi 
the large there i* a vulve, farmed by two Qmps of tho mucous 
membrane sloping down into the colon, anil «« ditpoxcd as 
to allow mutters to pas* readily from the ileum into tbe 
large intestine but not the other way. 

The lAver. Besides the tivorctiiinii formed by the glands 
imbedded in its walls, the small intestine receives those of 
two otlier large gland);, the /irrr and pancrfa», which Ho 
in tho al]domi[ud cavity. Tbe dueta of bolli ojMm by a 
common aperture into the duodeniim about 10 centimeter* 
(4 inches) from the pylorus. 

Tbe liver it tho largut gland in flie Body, weighing from 
1400 to 1700 grams (50 tofii ounces), It is situated in the 
upper part of the abdominal cavity (/«, If, Pig. 1). rather 
more on tlie right than on th<' left adeand itnmediatoly below 




3S4 



THE BUMAA- SOI>y. 



llic (liH[ihragm, into the coneavity of which iU upper sur- 
face Ills; it i-eacUoa sctoks the muldlt- line above the pyloric 
end of the slainuoli. It U of <iftrk rt^<li»ili-browu color, 
will of a soft friiiblo tcxtiiro. A deep fissure lucomplotcly 
divides the or^Hii inlorji/htanH left lotiM. of which the riglit 
18 miicli the liu-giir; on iu under ourfiici; (Fig. H>0)itliiilloW(;r 
groovvB Riurk off BOToral minor lohes, It« njiper siirftico 
ia smooth and convex. The vesseln earning blood to the 
liver are the ^r/M/ tv.')/i, V'p, auA ll»r iinpatw artery; \mt\\ 
cnU-r it at a fissure (Mi> ^orM^^ure) on iv* under ^^ido, and 
tj>er« also a duct piw»ea out from each half of the orgiiu. 




Fm- 1(M.— Tlij- iin.li^r urirfnwit Hid Itii'i. rf. rlahi .ml' ! ; i.i.. i yi.hi'ijull.- 

iijii: IV, ihiUjiI tvIh: t'o. rwia mn. int-nnt; I«; ii -lim; fie 

r;>itli: (lur.i; fM, lu-patto duct : I/. v^'blmUn-. 

'riie'luulj*uni(vtofonn WiKhcitnlir dud, Dh, whieh mw'tc at. 
ail iH'uto angle, Ihc cffnlic dwi, {)/•, proceeding from thc- 
giill-bloddiT, Vf, a pear-shapod eacin which the bile, or gall, 
formed by the liier, aceiuniilntt'* when food is not being di- 
gested in the intestine. The fMinm/n hilf-durt, prh, fornuil 
by tlio union of the hoimtic and cystic dnots, opens intci 
Ihfi dnodenum. Tlio blood which enter* the liver by the 
piJilal vein and hepatic artery passes out bj the hepatic 
vtint, Vh, wiiich liaue iho puHterior hordar of the orgui 




lUSTOLOOT OF CtVER. 



S3fl 



to the 7ert«bral column, and there open into tho iufe- 
nor vena cava, Vr, just Iwfori) it puttees up lltrongk tho 
diupliruf^tn. 

The Structure of the Liver. On dcwelf ezsmioing 
the «urfucu uf tliu livi-r, Jl will bo goes to be marked out 
into mnall angular mvu.* from one tu twa millimctvrK (^ 
to ^ luch) in diameter. These are tlie onter aides uf the 
snpcrhvial layer ol u Tiwt number of minute polygonal 
KiMMW, or Idruhf., of which tho liver U bitiU up; iiimilar 
areas are seen on the surface of »nr •octiun made thrnugh 
tba orgau. Kuch lubulo (Fig. 101) coD&itica of a number of 




Tat. 101,— A lolnil* at Out llTCr. niAirnlflril. •botrlnir ihe honaUp ecUi ndlatcl; 
Bnosvd M^innd UMmntralliilmlL>iiular*clD.iu«lilMli>l>ukrcaplUtu1a bttei^ 
iMvit wnh IttMD. 



hfpalie ctlla supported bya close network of capillariea; 
and is separated from neighboring lubuloa by couiiectivo 
tissue, larger blood-resseb, and b'ranohca of the hopatio 
duct. Tlie hep<ilir flU are the proper tissue elements of 
tlio liror, all iho rest being subsidiary arrangomenti) for 
Uieir nutrition and protection. £ach is polygonal, nucl«- 
P at«d and very grtinuW, and ha8 a dinmvter of ubont .OSfi 

H millimeter {rffdis of an iuch). In each lobule they are ar- 

I rwiged in rows or strings, which int«rrammuuicut« and 

I form a network, in the uiiMhoii of vliir^h tho blood Gspilla- 



S»6 



THE nuifAK noDT 



ricit run. Covering the surfnoc at llie liver in k Uvur of tI)P 
{leriioneum, beneath which i£ a detisc connective-tissue 
layer, forming ihooi/ww/eo^G/iwoM. At the purtul fissure 
olT»eU fniin Uiiji t-njuitlu run in, nnd Iin« ennuis, /A; portal 
catttd», whii'li are tunneled tlirough t)io oi-ganA. Thci^e, 
liecaniing smaller and smaller aa they branch, 6iially bo- 
ixiinu iutliMtingui^tiiiblc cloee to the- ultim&te lobules. From 
their wslU anil from tliu external ca|isulc, uonuwcivc-liiisue 
partitions radiate in all directions tlirough the organ and 
«nj)pijrt it^f oilier parts. In each portnl canal lie lbrc« ves- 
sels—a branch of the [xirtul vein, a braoch of the h«)iatio 




Via Vft - .1 rniitl pnrrlon of tlin iFrrr, Injiried, ond mneuUleil about ivcnty 

dtAruvlci-v. Till MkihI vi^<«'1( [irv o^pmtDfo^t while ; ihr intin vtv^l In n loili- 
lotniU/ vi*lii, nv-.'i-- ii4L,' '.tu^ lEilTflJubular ^uIuh. vrlili'li tu turn ar* itoHTni tniui 
IW k-iii'illiirl'-* "I llii. I.iliiilm 



■rttTV, ami a bntiR'b of tho hepatic duct; the dirinon of 
the porta! vein luring iiiiicli the liirgest of llic three. Tlicsw 
vessels br^ up as tho jiortal eauals do, and *ll end in 
minute biiiiidii-s (irmmj the lobule* The blood carried in 
by the portal vein (which hiw iilreiidy oirciihiled through 
the capillaries of the stomach, spleen, intestines and pan- 
cnw) is tliu« c-onruyL'd to a tine vascular inlerlobtiiar 
plextia aronnd the liver lobalct, from which it flown ou 
tlirongh th« cnpilkrics (lobular pUaua) of the lobules them- 
selVM. Tltcdc (Fig. lOlJ uuito in tlm centjv of the lobule 



BEPATfO VtnCULATIOX. 



8«7 



I to form a nnall intralobular vnn, which carries the blood 

I out uxid [loura it into one ol tho branobes of origin of tho 




Fill. inL-^lw Mamach, naiiiTWM. Ilivr. mail iliiodniuiii, wtlb mit «<1lMnM 
of thv inull InUwtttc niicr ltu> mewnlcrr^ Ihv ttomwh uid Ifm' lis*e bsM 
turned up <k> u In eipoK tn■^ pu'tvat v. ((oinacli : D. V.cr . riuodiinuin : U 
*|dcaa ; P. pauicmu : it. nibt hldavy ; T. Mutiuiii ; 17, nll-blaililar ; - K, 
hopallc duet ; c uyaile duel ; r*. mmman lilh.>-ditcl : 1. aoHn : >. hi viiKrf 
Wa oonmatTi of ttip (tomiuh ; I. hopulc artpiy ; < ^«nlc anarr i a, (uprrlar 
B u mtoUsna unerj ; ^ lupurMr mManUfW rcui ; y. apkUe Mo : Tp. porMl 
vtln. 

hepatic rein, called thexm&fodH/ar vein. Euch of the l*tt«r 
bumiuirlubiiloiiOQipt/ingMoud into it, und if dissected out 



328 



TBB RtntAK nOI>T. 



with them (Fij. 102) would look jnmethlng like a brauM 
at 0. tree with applci* attw.'li<.-d to it by «hort etulk;-, rcpre- 
aenled by (.he Intralobular v«ini«. I'lic blood is finally cor- 
ried. aa above pointed oat, by the hepatic veins into the 
inXcrior vctia ciivn. The hepatic arterj. a branch of the 
ooellac axis {p. 211), cnda mauily in Oli^oiis oapaiile «iid 
the walls of the blood-vessels and bile-diicta. but some of 
it« Mood nuKifaes the lobular plexuses; it ull filially leaves 
the liver by tlie hepatic veins. 

The bil&4nct8 can be readily traced to the periphery of 
the lobules, and there ]>robnbly communicate with a minute 
network of commonoiug bi1c>duct« runiifying in the lobule 
between the hepatic ceils composing it. 

The Fanoreaa or Sweetbread. This is an elongated 
soft organ of a pinkisli vciinw oolor, lying along the greftl 
carrature of the Rtoma<^h. Ita right end is larger, and 
is embraced by the duodenum (Fig- 103), which there 
makeji a curve to the left. A duct traverses Llie glaod and 
join* the common bile-duct close to its intestinal opening. 
The pancrcaa fonn« a wnt«ry-looking evcrvtion which is of 
great impurUuico m digestJun. 



CHAPTER XXII. 



k 



THE LYMPHATIC SYSTEM AND THE DUCT- 
LESS U LANDS. 

The LrmphAtics or AbKorbonts form close networks in 
Dtairly ull p»ru of tlio Bodv. Mo«t orgitru, m hu been 
pointed out ({>. 62), poncu a sort of iiittrmtl Mkek-tuii mailv 
np of oonnectire tAssne, vhich oonsiaU mainly of bundles of 
Gbrofl^ ooitod together nnd covered in by n "cement'' sub- 
stitnce. Id tliia subsUnoe arc fonud numeroas caTitiee, 
asuallT branched, and commanicating with one another by 
tht'ir brjinclice. They freqacstly oonluin oonn«ctivo>liM)ue 
coqiusctes, which, however, do not coni)>l6tely fill them; 
iind they ihits, with their bmncheH, fonn n sot of intercom- 
muiiicRting cbaimelM known m the *'tirrou» uiMilUuU;" 
Ihmic lire filled with Ivmph aod conatitutL^ ibe origin of 
lymphatic veesela in many orgitnK. El»<;whcre the com- 
mencing lymi>hutics teem to bo merely intersUcea(factfM«) 
between tli<> constitaent tissnea of an organ; tbia is espe- 
cially tbe cafe in glands. Such »pm.«» diftcr from the »• 
rono caiialictili in lii-lti^ lined by a detinit« epithelium. 

Stmoture of Lymph- Veesels. Tbe htous cuuulicul i and 
h-mph-spaces open into better defined channeU, lined with 
n single layer of wnry-edged flattened epitbeljol cells. 
Theite fonn networks in most parta of the Body and am 
known as the It/mph capillarm. Th«y are usnally wider 
than blood cupillorii^ From the capilUry networks 
larger t<«m^Ls arise which in structure roHmblo reins, and 
have similar, litit more numenms, TalveB. 

Tho Thorado Duct. All the lympbatica end finally in 
two main trunks which open into the venous system on each 
sideof theuGck, at thepointof junction of the jugular and 



330 



TBK HUMAN BODY. 



subcUTiuL The trnnlc on the right side is mnch «m: 
than the oth«r and is knoim as the '* right lymphatic duct. 
It coUocU lymph tram lhi> right BJde of tlie thorux, fpoi 
tho right side of the head and nwk, and the right urm. 
The lymph from ull the rest of tlic Body is collected intal 
the thoracic duct. It cotnmcucc* ut the iippei' jiurl of th 
abdominal cavity in a dilated reservoir (Iho receptarnlutA. 
ehgli), into which the lacteals from the intentinvs, and th 
lymphaticK of tho mt of tlie lowor part of the Dodr, tfpvn^ 
Prom thence the thoracic duct, receiving tnhnuiricis on it4 
course, mna ap the thorax idoug^ide of the aorta and, paaa- 
ing on into the nMik, oodH on the li-ft side at the point 
ftlroadj indicated; receiving on its way thv main st«ma 
from the left arm and the left side of the head iitid neck. 
The thoracic duct, thus, hriugs buck much more lymph 
than the right lymphatic duct. 

Tho Serous Cavitiw. These are great depciidonciea of 
tho lymphatic liyHtoni and may bo I'egnrdod as largo iMUiue. 
Each of thcui (peritoneal, pleural, ariK^hnoidal aud peri- 
cardiac) is lined by n definite epithelioid layer of c1oe«-flt- 
tiog, boiagoual celljL At certain ]M>inl«, however, opcuings 
or atomata occur, surrounded by a ring of smidler o^ls, and 
letidtng into tabes which open into sabjaoent lymphatic 
Tcssels. The liquid moistening these cavities is, then, really 
lymph. 

The Lympbatio Olands. Ihe^e are roumlish masses in- 
terposed, at Tsrions points, on tbe course of tho iTOph-vow- 
sels. Thov are e«pcoinlly nnmerous in the mcsenteiy, groin, 
and neck. In the Utter position ihoy often inflame and 
give rise to aba-e«Hi«. especially in scmfulous )ionion>'; and 
atill nioro oflcn enlarge, harden, and become more or \t»» 
tender, so as to attract attention to them. In mmmon ]<ar- 
lance it it then frc<tucntly Maid that tbe person's *' kernels 
have come down,"ortbat he has "vraxingkernoU." Each 
lymphatic gland is enveloped in aconnerliirc-tii'iiue ca|»ulu, 
and is pcrviithHl hy a conncctivc-ti^no framewDrk. In the 
meshes of this lie numerouit lymph cnqiusdet, which appear 
to multiply there by division. " Afferent " lymphatie roa- 
mIs open into tho periphery of the so-called gland, and ef- 





VOmfKyi OF THE I.TUPB. 



»31 



» 



fcrent rtuisels ariiw in its ceatre. Heuco, tlie lymph in its 
flow tii»ior«a llic i«lhiliir g!an<! sulftttaiice, and iti itfl 
ix>nr»c picks up extra corpuBoIea which it ciurics on to i\w 
Mood, la the gland there iasclose D«tirurk of blood capil- 
laries. It is clonr that thcao orgmns are not glands at. nil, in 
th« proper »&mi« of the word. They ttn sotnetimcs called 
igmfkttiis ganglia; hot that sagge8t«»Iti]MConn«ctioD witJi 
nerve-centres. 

Tbe Movement of the Lymph. Thin is no doubt sonie- 
irhal irref^lfir iu ihu cummcndiig vciwoIh. but, on the whole, 
MtB on to (he larger trunkit «ud through Ihcm to the veioiL 
Id numr animals (as the frog) at pointa where the lymphatics 
Gommunicuto with the vein^, there uro found rogiilarlj 
contmc^lik- " Ivniph-hmru" whtoli Iwat with » rhythm inde- 
pendent of that of the hlood-!ieart, and pnmp the lymph 
into a vein. Id the tlnmun Body, however, there arc no 
such hearty imd the flow of the lymph is diipcndent on \^sa 
defliiite arrangements, h aeems to be maintained mainly 
by three things. (1) The pn.'wure on the blood plaHma in 
the oftpilUrieis is greater than tJiat in the great veins of the 
neck; henoe any plasma filtered through the capillary wallx 
will be under a prcMtiro which will tend to make it flow to 
the Tenons termiiiiition of the thoracic or the right lym- 
phatic duct, {'i) Ou accntint of the numerous valves in 
the lymphatic vessela (which all only allow the lymph to 
flow past them to larger vft^ela) any movement compreas- 
ing » lymph •V(\iiii;l will cause an onward flow of itscontf'Dte. 
The iullnence thuii exerted is very important. If a tube be 
put in a large lymph-vessel. «iy at the top of the leg of an 
nnimal, it will be wen that the lymph only flows out very 
slowly when the animat is iiuiet: but as soon m it moves 
its 1^ the flow is greatly accelerated. (3) Ilriring each 
inspiration the pressure on tlie thoracic duct is less than 
that in the lymphiitics in parhi of the Rixly outiiide Ihe 
thorns (aee Chap. .\ XI v.). Accordingly, at that lime, lymph 
is pressed, or, in conmion phraae, is "liucked.*' into the 
thoracic duct. During the succeeding expiration the prcs- 
snre on the thoracic duct liecomes greater again, and some 
of its contents are pressed ont: hnton account of the valves 



ssi 



Tinr mrxAN hodt. 



they can onlv go farwnrdM, that Is, towards the ending of 
the duct in (lie Y<tiii« uf the ii<>cV. 

I>aring digestion, moreovpr, the contnu;tion of th« xilli 
\ritl press on Iho lympli cir clivic; tind in cortaiii purtsof the 
Body gTBTity, of course, aids the flow, though it will impede 
it in others. 



The Spleen. There are in the Body sereml organs of 
siu-h cinisiiicralilp .ii/i\ iind nf m grciit cmislancy in ii lurgo 
number of veriohrate animals, IliiiC they would a jirinri 
Rp|>car to be of eunsidoriible functional importance. What 
their w»c imiy be i* utill, hovrever, unknown or uiiocriain. 
They are commonly sjioken of pollectively. along with the 
Ivinphiilic piuigliii, as th« dnc/lrim ijiandf; hnt they are not 
j^limd* in the proper seniMJ of Iho word. The splfn is the 
largest of them. It is a red orfian situated at the left end 
of the stomach and about 170 gram» (G o/..) in weight. 
Its sixe is however very yariuble; it i-nliirges diirinfr diges- 
tion and Khrinki ngiuii after it until (hi> next mwil. In 
malarial disea£e« it also booomes enlarged, frequently to a 
very great cxtvut, and then coustitiitiM I lie eo-eaJIcd "ague- 
cake." In struoture, the «i>leon consists of a eonncctiiTi- 
tissne aipntih, rtoh in elnstie fibres, and giving off proeCi!»cs 
which niniify through Hie or^iin and forin n framework for 
ila pulp. The latter contains nunjcroiu blood coqniwlos; 
Mid many IxHiics winch i^ccin to be red corpuscles in pro- 
cc» of decay or destniPtion. Hence the sjileen ha^s been 
vuppoited to be a sort of graverard for their bodies — a ]>laoo 
where they arc broken up and their materials utilized when 
ihev huve run their life cycle. Othera, however, nonfidcr 
ihut in the spleen new red blood corpuscles are pro- 
dncL'd from eoli)rU'!w; and i)tbcr*, again, Hint the main 
fniieliou of the organ is the fonn;ilion of snbslances which 
are curried off to tho etomuch .md pancreas, to be there 
finally clahorated into digestive ferments. The arlcrios 
of the spleen open directly into llic pulp cavities, from 
which the veins arise. On iheir walls are rounded whitish 
lioduiea about the size of a millet-seed, and known as tha 



rirnrm dxi> tbtrotd. 



I p"' 

I "g 



Ma^ighiatt corpHtcUa. Thej* resemble tiny lj'mi)h2tio 
glands in structure. 

Tbo Thymus \» An orgsii which ODly exuts in childhood. 
At birLli it is found lying around tli« windpipe, in the upper 
part of the cheat cavity and the lower jiiirt of the neck. It 
iiwreaaes in size until the end of the second yeur, and than 
OS to dwindle avay. It is grayish piuk in color, of « 
ift lextnre, Aud, in microscopic structure, resembles some- 
u'hat a lymphatic glund. Ueuoe its function has b««n sup- 
poacd to be Ihe formulign of new lymph curpuecles. The 
"sw<M:tbrt!ad" of butchers iH iiomctinics the pancreas aud 
'Diclimes the thymus of young auimab — neek and beUy 

tetbread. 

The Thyroid Body and the Suprarenal Capauloa. 
The furuier of ihe^- structures liea in the neck on Uie aides 
of aud below "Adam's apple."' It i» dark red-brown in 
color, and sometimes bcvouies very much i-nlaigid, lu in the 
diR^iec known as goitre. Thi^ enlargement a]>pears to be 
often due to drinking water coataiuingmagaceiun limestone 
ill solution. In Kngland, for instance, it is known od" Der- 
byshire neck" from beiogespociallyfrequentiD partsof that 
county, where the hills are mainly composod of magnestwi 
limestone rocks; and the name frcological formation is 
found in those districts of Switzerland where creitHum 
(one ot the symptums of which is an enlarged thyroid 
body) preraila. 

The suprare'tai iodita lie one over the top of e«ch kid- 
ney. Their us«, like clnit of the thyroid, is quite pro- 
blematical, in what is known as Addison's disease (in 
which the skin becomes of a bronn.' color) it iH said that 
tbe^e bodies are alteri'd; but it is very improbable that the 
change in them is the actoal cause, rather than another 
«ymplom, of Lho disMM*. 



CHAPTER XI. 

DIGESTION. 



The Ofajeot of Digestion. Of Die various toodeiuSs 
Bwatiowed, some me iilrejuly in solution and ready lo diiilv/.o 
at onco into tlic lymjiliiitiu? ;iud bluud-rc£»eli^ of thealitncn- 
taiy canal; otJierii, such a^ a lump of sugar, tliotigh not 
diasoh'od whoa put into the moutli, are readily soluble in 
the liquids found in the alioicnlary canal, »ud iK<od do fur- 
ther dige.uion. In tlio case of many moat imjiorlant food- 
vliifTH.Iiuweviir, Kpccial clicmieal cliangca have to bv u-rungbt, 
either wiUi the object of conrerting insoluble buditv iuUi 
aolublf, or iion-di^yzabl« into dialyxable, or both. The 
different secretions poarcd into the alimentary tube act in 
various ways upon differenl foodstuffjt, and at InAl gvt them 
into a static in vhich they can pass into the L-irculuting 
tni-dium and bo camod to uU parU of the Body. 

The Saliva. The Qi^t solvent that the food mvets with 
is the saliva, which, a^ found in the moulli, 'u a mixture of 
pure 8alivii, formed in parotid, submaxillary, and sublingiial 
^andn, with the mucus secreted by email glands of the oral 
mucous membrane. Thi« mixed saliva is a cotorlomi, cloudy, 
feebly idkaliuo liciuid, "ropy" from the mucin pivwnt in 
it, and usually containing air-bubbles. Pure saliva, aa ob- 
tained by putting ii Bno tube in the duct of one of the euli- 
vary glands, in ]vs» tenacious and containa nu iiupri>oncd 
air. 

The uses of tlio saliv* are for the most part pliysicitl and 
tncchanicul. It kocpa the mouth muist and allows us lo 
speak Tith comfort; mo^t youug orators know the distreaa 
occasioned by the suppi'cssion of the salivary secretion 
through ncrvouMiois, and the imi>orfccl efficacy under duch 



U8RS OF SAUVA. 



33S 



cirDumstmcca of tiie traditioiuU gluH of water placed be- 
side pablic speakers. The saliva, aW, enaMes um tu swallow 
Ary fool; Micb n tbing dm a cniokcr when chewed wciild 
gire rise uierelj- to a beap of dust, inipoi^iblv to «wiillow, 
wore uot the month carit; kept moist. This fact used to 
be taken adnuitugo of in the Enst Indian rice ordeal for 
the i]«t«otion of criminulx. Th* guilty [tenon, bclioviiig 
firinly that he cannot swaUoir the parehed rice giren him 
nnd Miru of di'tcction, is apt to have his salirary glaads 
paralysed by fear, and w> doe* actually become iiuablo to 
swallow the rice: while in those with clear consciences the 
nerroos ^stem, acting normally, excites the usual rctlex 
wcrotion, «nd the dry food causes no difficulty of degluti- 
tion. Tlie Ralira, also, dissoWea such bodies as salt and 
sugar, when t«kcn into the mouth in a solid form, and 
eiiablce nt tx) la^te tht-ni; undiKHolvcd 8iibstancei« are not 
ta.iti'd, a fact which any one can rerify for himself by 
wiping his tongue dry and placing a fragment of KUgitr 
upon it. No svectflcan will be felt nnul a Utile moisture 
liiu exuded and diiMolvocI ]>art of Hw inigar. 

In addition to such actions the i«iiliTa, boworor. exerta n 
flhomical one on an imporl.mt foodstuff. Starch (althongh 
it fiwell« np greatly in liot wiklcr) i« insoluble, and could 
not 1)0 iibsorbed from the alimentary oonal. The snlira 
oontain« a spouilic cleiaisnt, plyaHn, which ltn:i the iiowit 
of turning starch into the readily solnble and dialyzable 
gra]>e fiugar. In effecting this change the ptysliii is not 
altered: at least a very small amount of it can cause the 
oonverxion of a raat amount of starch, and it doftt not set^in 
to have its activity impaired in the process, being still rowly 
at tho end of it to net upon more. The stan-h \t made lo 
combine with tho elemenla of a molecule of water, and the 
ptyaltn remains bobiud as it was — 

C'H"0' + iro = C'lfO* 

BtoRih. Watpr. ilnp* miipm. 

Snbatsnces acting in this way, producing chemical 
changes withont being themselves noticeably allprcd. arc 
fonnd in many of the digc«iivo sccrotionx, and an' called 



J 



TBB BtrXAK BODT. 



pliarjTix, any food which has once entered it mast bo swal- 
lowed: tho ifetliuiiiif of the Iawcsa fonn» n Mrt of Rubicon; 
food that has passed it must coDtJnne its ooone to the 
stotDAch allhongh the swollowcr luu-nl immediately tliat ho 
was tttking p»i«on. The third iitage uf dogluUlion is that in 
whioh the food is pa«.iiii^ along the gullet, and is L-ompara- 
tivcly^low. Kveii liijukl siibfltjiuceii do iioi fall or flow down 
this tube, but have their passage controlled by il« mu)<cu)ar 
coats, whicli grip the euccCMivo portioiiK ewallowed and luu-i 
them on. Hut](:r thepOMibUity of pi-rforining tho apparently 
wonderful feat of drinking a gtam of water while standing 
upon the head, often exiiibited by jngglers: people forget- 
ting that one sfee the siunv thing done cviiy diiy by hor«en. 
and other na)nial!>, vhich drink with the pharjugeal i>n<l of 
tile gullet lower than the etomiich. The moTcmenU of the 
(E«ophagiis are of the kind known a« cermicular or peri- 
staltic. H« circular fibres (p. 31 T) con tiw;t behind tho moiwl 
and narrow the passage there; and the constriction then 
trareJe along to tho stomach, pushing tho food in front of 
iU Si mill ton comply the longitndinal fibicfi, at the pnint 
vhere the food-ma^ is at any niomL'Ut and imincdiately in 
front of thnt. contracting. Khortcn and widen the puvage. 
Tho QoatrlG Juioe. The food having entoivd the sto- 
mach U exposed to the action of the guetric jnice, which is a 
thin, colorliNw, or palo yellow liijuid, of n strongly iioid re- 
action. It conlaina as specific elcmenuy'r''ii hijib-achhrie 
acid (about .(>'i per cent), and an enzyme called jieptin 
which, in M^id liquids, has the power of conTcrtiug the or- 
dinary niiii-diiilyxable pmteidH which wv c-»t^ into the clo«eljr 
allied but dtnlyzahU- bodiea called jxfptoues. It alao dio- 
solvee Bolid pixiteidx, changing them too into poptoucc. 
Piluto acids will by thcmiM?lv08 produco tho same diaiigoit 
in the oour^o of vcvuial day», hut in tlic prceenoe of |ii>pHin 
and at tlio lemperatnre of the Body the couverfiion is far 
more ra))id. In neutral or alkaline media the pepeiu it: 
inactive; and cold check sits activity. Boiling destroys it. 
In addition to pepsin, gastrio juico contains another enxyme 
which lias the power of coagulating the cuj<«ia of milk, ua 
illiutraled by tlio u«o of " rennet," proporod from the mu- 



JUaSBTIOy IN THE BTOilAOIf. 



889 



9008 membrunc of tho cslfV digestive ttomnch, m checee- 
mtldng. TI16 acid (if llic natural gastric jiiic« miglii it«rH, 
it is tnte, cougulnto the cowin, but nvulralised gaatric 
JDice ftill poMC-MOj thiH ponor; uiid, uiioe pure soIuIjocm ot-\ 
pepsin do not, it must be dne toeome third body, vliicli has, 
however, nut jet been iKolntod. The curdled condition of 
tliu milk re^rg;itat«d so often hj infanta is, therefore, not 
any sign of a disordered etate of the etotnach, as norsea ' 
oommonly «uppo»e. It is iinliiral uiid projHT for milk to 
undergo tbia cliunj^e, before the pc)>iiin and acid of the 
gastric juice conTert ita caseiu into peptone. 

Qastrtc Digestion. The process of swallowing ia oon- 
liimou!*, but in the stomach the onwwrd progress of the 
f*jod ia stayed for some time. The pyloric sphincter, re- 
maiuing contmclod, closes the apertnre lending into the 
intustine, and the irregnlarly disiwsed musoular layers of 
the stomach keep its Eemi-tiquid coutenla in constant 
movement, muiulaiuing u sort of chiinilng by which all 
portions are brought into coiitact vitli the macoua incm- 
bmno and iboroughly mixed with the secretion of its glaods. 
The gelatin-yielding connective tissue of meats is dissolved 
away, and the proteid-contsining fibres, left loose, are dis- 
Hulved and turned into peptones The ulbiuninous walls 
of the fat-cells are dissolved and their oily contents Bet 
free; but the gastric jnice does not act njwn tho latter. 
Ceruiii mineral i^ults (as phosphate of lime, of which there 
is always some in bread) which arc infohiblo in water but 
solable in dilute acids, are also di«*ulve(l in the stomacli. 
On the other hand the gastric juice has icself no action 
upon starch, and since ptyalin does not act at all, or only 
imperfectly, in an acid mcditim, tho activity of tho saliva., 
in converting starch is stayed in Ihe stomach. By thesolnJ 
tion of tiiu white fibrous connective tissae, that disintoj 
tiou of animal tooiU cnmmcnocd by tlio teeth, is carried^ 
much further iu the stomach, and the foiHl-mass, niiiLcd 
with much gastric secretion, becomes redur^d to thecon- 
listonoy of a thick soup, usually of a grayish color, lu 
this state it is cmlled ehymf. This cautains, after an ordi-^ 
nary meal, a oonsiderablc quantity of peptones which 



TBB BmfAlT BOJ)T. 



va great part gradnallj dialvzot] into the blood and Ij-mpb: 
ticvessetsof tho gastric mucons in<-mbruno, »nd carried off, 
along with other di!»olved dialyiable biidici*, «uc)i uk s»lt« 
and sugar. Aftor the food has remainGd in the stomach 
eomu time (one ftud u half lo two hours) tho chjmo bcginii 
t(i be ]iaK!tod on into tho intestine in cnocesfiive portions. 
The pyloric sphincter relaxes at Jnterrals, and the rest 
of the stomach, contracting at tho samo moment, injects a 
ijtuintit}' of cliyme into the duodenum ; Lliitt \% repcutcil 
freiiucntly, the larger undigested fragments being at llrHt 
tinable to ]UkS8 the orifice. At the end of about three or 
four hoursftfttr n meal the »tomaeh iHiigiun quite empliod, 
the pjlorio sphincter linally relaxing to a greater extent 
and iillowing any !arj;cr iudigostible masses, which the gas- 
tric juice eauuol break down, to be aqueczed into t)i« intos- 
tinc. 

The Chylo. When the chyme passes into the duoden' 
it lind.'* pix'puration tnaile for it. The panorea<i Li in re6 
oonnectioQ with the stomach, and its nerves cause it to 
comnieiico secreting HO soon as food enters the latter; henco 
a quantity of its secretion is already aooumulated in tho 
intestine when food cuterM. Tho gulUbhuldcr is distended 
with bilo, teoreted m\w. the last moul; tin;* piusing dowa 
the hepatio duct has been turned back up the cystic duct 
{De, Fig. 100*)on account of Ihe olusnro of tho common 
bile-duct. The acid chyme, ntitnuliiling nerve-cmlingv ia' 
the duodenal mucous membrane, canses reflex oonlrac- 
tion of lite muKcuhir ooat of Ihc gall-bladder, and a relaxa- 
tion of the oriBce of the common bile-duct; and eo a gush 
of bile is j>onrcd out on the chyme. From ihia time on, 
botli liver and jiiincrcus continue secreting actirelr for 
eonio hourii, and pour their jiruditctH into tho intestine, 
Tho glands of Brunner and tho crypts of Lieberkiihn are 
also set at work, but cimcorning their physiology wc kuow 
very little. All of these secretions are alkaline, and they 
sufHee very soon to more than ncutralizo the acidity of the 
gastrio juice, and so to convert tho acid ckymt into alka- 
line diyU, which, after an ordinary meal, will contain a 
great variety of tilings: mucus derived from the alimen- 



•P.SM. 



A 



fAXCRKATW m9KSnO!T. 



Ml 



tary canal; ptraiin from thi< hiIitu; pepsin fmm the sto 
tnacli; wiiUtr, {utrtl}- swallowed and puUy derived from the 
Miiiivary und other secretions; the peculiar ooiiBlttueuU of 
the bile and piuicreatic juiocsudof llie inl««tinal sccrelioDs; 
some itndigi-stvd jiroteids; unchnnged starch; oils from the 
IiAm Mtcn; peptonea formed in the atonutch but not yet 
ubiu^rbed; possibly titilini-« and «ugnru'liich hjirc nitso i-^caped 
absorptioii in the nioiitaoh; and iadigcstible substancea 
Ukon with the food. 

The PanoTontio Secretion iK clear, watery, alknliu«, and 
much likk^ Milivit it) iipjiCitntiici*. The (iermaii!) call the 
paucreoa the ■■stKiomiuul fuUivary gland." In digestive 
properties, however, the pancreatic secretion is far more 
im{H3rtant than the nlivs, acting not only on sUirch but, 
alAo, on ]kroteidB and fats. On starch it acts like tlie saliva, 
bat more energetically. It produces changes in proteids 
similar to tho^o effei-led in the titoma^^i, hut by the ageni^y 
of a different ferment, trypsin: which differs from pepsin in 
nctinir only in iin alkaline inot^iul of an acid mediiim. On 
fats tl ha.1 a donhle oction. To a certain extent it breaks 
them np, with hydration, into free fattyacidaand glycerine; 
for example — 

■ (°-g;if;)' f 0. +3H.0 = 3(^^"""g } o ) +'^*«; [ 0. 



istrum 



1 Water 



J Stnrlc Bcld + J nlyoerloA. 



The fatty acid then combine* with »omo of the alkuli pres- 
ent to make a map, which being soluble in wal'jr is capihle 
of nb§orptinn. Olyceiinc, also, is soluble in witter and dialy- 
xalile. Tlie grmter part of the fats arc not, however, «o 
broken up, but are dmply mechanicidly separated into little 
droplets, which n-main NU#peiidod in the chyle and give it a 
whitish color, just as the crcam-droii.4 are siijipendcd in 
milk, or the olive-oil in mayonnaise sauce. This is effected 
by the help of a quantity of albnmin which exists dissolved 
in the pancreatic socretiou. In the stomach, the animal 
fata eaten hare lo<rt their cell-walls, and have become melted 
by the t<.-mporaturo to which they are exposed. Uenoe 
their oily [Kirt lloat4 free in the chyme when it enters the 




949 



THE tlVMAy HODT. 



duodenum. If oil be Hhaken up with water, the tvo chii- 
uot be got to mix; iuimcdiatoly thi> sbakiog ceases the oil 
Bottts up to th« to]>; l)tii if luinie raw egg be added, a creamy 
mixlui'u \a Ttwlilj foimed, in which the oil rcinaing for » 
long lime evenly Htupcudvd in the watery menstniuni. 
The reason of Ihis iit thai each oil-droplet becomes sor- 
rouuded by a delicati? pellicle of albumen, and i« thun pro- 
Teut«d from fusing with iU ui-ighbons tu mnke large drop^ 
which would Mion lloat lo the tup. Such u mixture is udled 
an emuhion, aud the albumin of the juinoreiitii,' secretion 
cmuUifica Uic oils ia the cliyh>, which becomes white (for tlie 
came reason as milk i< thxt color) Ijei-unw the innumerable 
ti&y nil-dropa lloating in it retlect all the light which faUa 
on iu surface. 

The pancreatic secretion tha> converts ttneh into grape 
flngar, dii>.->olves protcidii (if necc^an-) and converts them 
into peptones, emulsifies fata, and. to a certain extent, bi-eak^ 
them up into glycerine nnd fatty aciiU, wbioh latter are 
Mponitled by the alkalies present. 

Tho Bito. Iluman bile when quite fresh is a golden 
brown li-iuid; it bucomM groea when kept. As fonni-d in 
tbe liver it contains hardly any mucin, hut if it mnk«>t any 
stay in the gall-bladder it aequirea a great deal fiom the 
lining membmne of that fi»c, and bocomn very "ropy." 
It 18 alkaline in reaction and, bcMidcN coloring maltem, min- 
eral Baits, and wutcr, cunlatiL-i the sodium bolts of two nitro- 
genized ncid«, taurocholic and gii/choeholic, tho former pre- 
dominating iu humnu bile. 

PfiiteHkdfer'a IttU Tml, If a »ina!l fragment of oane 
sugar bo added to some bile, and theo a large quantitj of 
Klrong nilphiiric ncid, a briUiniit purple color in developed, 
by certain products of tho decomposition of it« acids; tho 
physician can in this way. in disease, detect their prcBtiifc 
in Uie urini) or Dtlicr woreliniiit of the Body. (JmfUn'n 
Bile Tt»l. 'The bile-coloring matters, treated with yellow 
nitric acid, go through a series of osidations, accompantwl 
with changes of color from ycllow-brawn to green, then to 
blue, violet, purjde, red, and dirty yellow, in euccesfiiou. 

Bile hn« no digMtire actiou npon starch or proteids. It 





DIGSenVB ACTION OF BllB. 

does not break up fata, but to a linut«d extent emuIsiCies 
them, though fnr Ices perfvctl}' iJitm tlio pancrcutJu Mtcre- 
tion. It t.4 axea (ioutrtiul if this^ nntion U exerted in the 
intestines at alL In many animaiH, afi in maa, the bilo nud 
pancreiitii-ductsopcn together into tho iloodvnum, m that, 
on killing them during digestion and finding emulaiDcd 
fats in the ohvle, it is imj>oaMhlo to say whether or uo i\ie 
l)il« hod a shore in the procvNt. In the mbbit, however, the 
jBDcrcatio diiot oyn?na into the iutestine about a foot furtbw 
from the stomach thim the bile-<Inct, and it is found that - 
if ft rabbit be killed nft^r being fed with oil, no milkv chjle 
is found down to ihe jwinl where the i>ancrcatic duct opens: 
In this auimtti, therefore, the bile alone does not emulsify 
fnt«, and, sinoo tlio bito is pretty much the Mime in it and 
other mammaU. it probably docs not emulsfy fats in tbem 
either. Prom the inertness of bdo with respect to most 
foodstiifT^ it hsA boon doul>t«Hl if it is of an; digestive uve 
at all, and whether it should not be regarded merely as an 
excretion, ponred into the alimentary uuial lo be got nd oL 
But tliere arc ntnny reasons against such a view. In tiie 
first pliK«, the entr^' of the bile into the upper end of the 
small intestine where it hiui to traverse a course of more 
than twenty feet before getting out of the Body, instead of 
itj being sent into the rectum cIimo to tlio final op<.-ning of 
Ihe alimeatary canal, maktu it probable that it has some 
function to fuliill in the intestine. MoreoTOr, a great part 
of tJio bile poured into the inlmlinc* is again absorbed from 
them, only u small part being finally excret«d; and thisaiKo 
seems to «hon' that jmrt of it ul leust, is secreted for some 
other jmriKbC tliim mure eliininution from the Body. One 
useis, no doubt, to assist, by its alkalinity, in overcoming the 
acidity of tlie eliyme, and so to allow the tryjisin of the 
]>anDreutio secretion to oict »]»'n jirot^-ids. Constipation le, 
alao, apt to occur in cases where the bile<dnot is tempunirily 
stopped, so that the hile probably helps to excite the con- 
tractiunH of tlio muscular cout^ nf the int<iitin<M; and it is 
said that nnder similar circumstances putrefactive decom- 
podtJooa ore extremely apt bu occur in the inteetJnuI oon- 
tonts. Apart from «ich secondary actions, howerer, th« 



J 



TBB ajTMAy BOPT. 



bile probably has some infliieiic-e in promoting tlio absorp- 
tioD of fats. If unoGuil of m-Jiiiillnry gliisstnbi', nioistciKid 
villi water, bo dip]>o(] in oil, the latter wilt not ai-ictitl in it, 
or but a abort way; but if the tnbo be moiHiened wiih bile, 
iustfttil i)f w«tor, tliu oil will tiscvnd highur in it. So, too, 
oil [ia»8i>Ji thrmighaplugof poroiiaclay kept moiKt wiLli bilo, 
under a much lower pressure thiuj througli one wot with 
wiiHT. Hence bile, bysouking thoojiillicliulcotlii liiiingthi! 
idtcHtine, ma; facilitate the pa^sn^e into the villi of oily Kub> 
stances. At any rate, experiment shows that if the bile be 
prevented from entering llie intestine ut a dog, the animal 
cats au vuonniiuK iimount of food compared with ibnt 
amonnt which it needed previously; and that of thi^ food 
K great proportion of the fatty purt^ puseee out of the ali- 
mentary canal uuubtiorbod. There ijt no donbt, therefore, 
thut the bill! Komehow aid-i in the absorption of fnln, b»t 
exactly how is uncertain. It« )ios«iblc action in exciting 
the mu8clc8 of tlif villi tn conlrHct will bo referred to pri?a- 
entl^. Bile precipitates from solution, not only pepsin, bat 
fttiy peptones cont'uinud in tlie cbyiQo which enters the in- 
testine from tlio Ktoniueh. 

The Intestinal Secretions or Suooub Entericus. This 
coi]t<ii<tjt o( ihe swivLions of the gl:uici.< of Hruiuier and the 
crypt« of LieborkflhiL It id ditllcult to obtain pure; in- 
deed the product of Brunner's glands ha^ never been ob- 
tatncd unmixeil. That of the eryptit of Livbcrkuhn is 
watery and alkaline, and poured out more abundantly diir* 
ing digestion than at other timea. It has no special action 
onatiirchcs, most pro teids. or on fats; but is said to dissolve 
blood fibrin and oonvert it into peptone, and to chaii^ocano 
into grape sugar, a transformation the objeet of which is 
not vciy clear, since cane sugar is itticif reiulily soluble and 
diffusible- 

Intostinal Digestion. Having considered separately the 
actions of iho sccicti^ns with which the food meets in thfti 
^mal) inle«tine we may now consider their combined effect. 

The neutralisation of th« cbymo, followed by \U convex 
sion into alkaline chyle, will prevent any further action of 
the pepdin on prolcidc, but will allow the plyaliu of the 



ZSTSBTIXAL DTGESTTOy. 



840 



lySra (the ndivity of whioli wua AUijipcd by tlio Kidity of 
the goAtrio juice) to recomnicnce its action upon Kiurcl). 
Moreover, in the stomach there is produced, alongside of tlie 
true poj>Loiic», A body oilled pttiupcptunc, which agrees very 
closely with Rvntonin (|i. 126) in i1^ properties, and this 
passes into the duodenum ia the chyme. As good as tlie 
bile moot* the chyme ii preoijiituto^ the pitrupvptone. and 
this carrifiB down with it any peptones which, liaving es- 
caped absorption in tho Htomooh, may he present; it alio 
precipittttCH tho pPi»*in. In confictjuvncc, one commonly 
finds, daring digeation, a stiolcy granular precipitate over 
the villi, and in the folds between the ^^alvul»• counivcnlea i 
of the duodenum. This ik *oiiti rcdi^olvcd by the pancre- 
atic BGorction, which also changes into peptones tlie pro- 
teids (usually a considerable proportion of Uiose eaten at a 
mud) which huv« passed throiigh tlic stomach unchanged, 
or in the form i*f parappptonefl. The conversion of starcb 
into grape sugar will go on rapidly under the inRiicncc of 
ihu iiiuiorofttic Bocrelioii. VnU will ho split uji and sapoiii- 
fiod to a certain extent, btit a far larger proportion will Iw 
emuUificd aud give the ebyli- a whitish ajiiwanmce. Cane 
sugar, which may have escaped absorption in tlie stomach, 
will be converted into grape sugar and ubsorbod, along witli 
any Kalinc>< which may, aWi, have hitherto encapcd. Kla«tio ' 
tissue from animal substances eaten, cellulose from plants, 
and mucin from the secretions of tho alimentary trttct> will 
all remain unchanged. 

AboorpUon fV«m tho Small Inteetine. The chyme leaT- ^ 
ing the atoraach in a ^!mt-li<{iiid nuL^>< which, Iwing niiicc<l 
in the duodenum with considerable qunntities of panci'eatic 
secretion and bile, is still further diluted. Thenceforth it 
gets Uie intestinal secretion added to it but, the absorption 
more than eonutcrbalauciiig thomhlition of li<jtii(l, the food- 
maaa beoomes more and more solid aa it ajiproaofaes tho 
ileo-colic valve. At the eamo time it become* poorer in 
nutritive coostituents, the«o being gmdunlly removed from 
it in its progreci; most dialyxe through ihe epithelium into 
tho subjacent blood and lynii)hatiu viHwels, and are carried 
oil. rnioso pBKsiug into the blood CBpilluries are taken by 



846 



THE mnrAX body. 



tlic portal Tinn to l)io liver; whiln those entering tlie bctciiU 
are carried into the left jugular rein by the ihoracic duct. 
Ah to which foodKttitTH gi> imv roiid and which tho oth<7. 
there i« still much doiibr; siigjirs pnihaWy go by tln^ porlal 
system, while thu fiits, mainly, if uot entirely, go through 
tho Inctcalit. How th« fats arc absorbed Is not clear, 
eince oils will not dialyxe through menibraiicti, iruch lU that 
litiuig tho int«etine, inoigtvned with watery liquids. Moet 
of them, howoYcr, certainty get inio the hicteul* osoUsandj 
not as soluble soaps; for one finds tbew Tef»pltt, in a digest^ 
inganimal, flltud with a beautifully wbito milky chyle; wliile 
at other periods their oont«nta are watery mid colorleas Uks^ 
the lymph elsewhere in the Body. The little faC-dropg i 
the emulsion formt^d in the intcfltino, go through the epi- 
thelial ccIIr and not between xhi-m. fnr during digc^ion 
oao finds these cells loaded with oil-dropleta. \ow the 
frwi ends of tlieso cells arc stritilcd and probably devoid of 
any definite eelUn-all. and it is jwssible that the intestinal 
movements siineeae oil-drops into them, which the cell then 
poMvs on to its dwper end and, thenoe, out into Ihu sub*j 
jaoent lyniph-ttpoom, which communicate with the centra}] 
lacteal of a villus. Possibly, too. the^e cells aru amteboid 
and can thru>>t out procemca from their free ends and' 
actively pick up the oil-drops. In the villus there arc all 
the aiiatoitiical arrangemcnlt! for n mechanism which ell 
actively rxiok up ituhxtances into it. Kiich is more or Ic 
elastic, and. moreover, its capilliiry nclwork when filled with 
blood will dixlcnd it. If ihercfoic Iho mii»culjir itratnai 
(p. 321] contracts and comprei^ses it, emptying its laoteals 
into the vessels lying deeper Jn the inttii>iinal wall, tho villtis 
will actively oipand again so soon as its muscles relax. 
In BO doing it could not fill iu lacleals f rom tlio docpcr vea- 
sL-ls, on account of tho valvcii in the latter, uud, aocwrdingly, 
would (end to draw into it.telf nmtitrialit from the intestines;^ 
much likeaspongere-eipandingiu water, after having been 
s<j[iee7.ed,dry. The li<iuid thus sucked up m;iy draw oil. 
drops with it, into the free ends of tho culU and between 
them; and by rc[)Ctilionfl of the proconit U poA^ible that 
contiiderable c[uautitie8 of lit^uid, with snspandod oil-drop^/ 



r 



DIGESTION IN TBS LABOR INTESTINE. 847 



might be carried into the »iUuB indcpeudontly of uny pro- 
emu qT dialvKis. Tho l>i!<- inoiiriening the tinrfacv of ihtt 
Tillas may facilitate tbe paaeage of oil, as it docH throngh a 
pAper filter or a plate of pliiKtor-of-Pim», and it U al»> twid 
t') irt;inulat« the contractionA of tho rilli; if so, its eflicocy 
in promoting the absorption of fats will be expliiined, in 
fpito of it* chemical InertneHs wilh rospt-ct to those bodieti. 

Digestion In tbe Large Intestine. The contructiotts of 
llie sninil int^-^tine drive on itK Lontiniiall}' diminishing 
t'ontenu, until ihoy reach the ileo-eolic vhItc, through which 
Ihoy are uUimatoly pre^ifod. .\b a rnle, when the muff 
«nt«rs th« large iutcstiao itK nutritiTo por1iiin<i have E>ccn 
almoat entirely abaorbod, and it ooniti^lfl merely of some 
water, with the indigestiblo portion of the food imd of the 
MCntionK of Uie nliinenlary ennui. It ciinliiin!i oellulog«. 
Hastio tiwnie, macin, and ramewhat altered bile pigments; 
commonly some fat if n large quantity has been «ut«n: and 
some utarch, if nv vcgelahl«a hare foniicd part of the diet. 
In its progress thnnigh the large inlestiite it loMW Dion^ 
water, and the digestion of starch and tliu ab»»rplion of 
fata is continued. Finally the n»idue, with some excrvtoir 
matters uddetl to it in the Urge intestine, coUcctn in the 
sigmoid fleiuro of the eolon and in the rvctnm, and is 
finally rent out of the Body from the Litter. 

Tbe Digestion of an Ordinary Uool. Wc may In^t aum 
ap llie fiu;t« stated in thin chiipter by coiiHiilcriiig the diges- 
tion of a oonimon moul; say a breakfast consisting of bread 
and butter, bcefetcitk, potatoes and milk. Many of these 
substances contain several alimentary principles ^nd. since 
theM are digested in diSerent ways and in different pnrta 
of the alimentary tnct, the first thing to bo done Ik to con- 
eider what are the proximate constlituents of each. We 
then separate tho mAtorials of the breakfast us in the fol> 
lowing table — 




TBS IIVMAX BODY. 



il 






"Ml Mil n I 









I 



IB! 



O I 1 t. 






§? 



1 1 






t| 



I i 




DIGEsrtOX 0#" A StBAL. 



849 






From fiucb u meul we may first ttcpuntle lh« clutiD, oeh 
hUoBC, iind oalciumsuli'hatf. *.t indigestible and passed out 
of the llody HI tlio r^iue ntute and in ihe tuimc iiiiiiutily us 
they entered il. Then lomc tiic «a!incH whicb need no 
8peciiU ilig«stiou, tmA. cither taken in solution or dis* 
solved in Ihe saliva or gastric jnicc, are ubsorU'd frum the 
lUDUtb. etomuch and inteiiciuea n-ithout further change. 
Cane and grape HUgars experience I he «ime fute, exoopt 
that any cane sugar reaching the intestines before abtorp- 
lion, is liable to be changed inlo grape sngar by the tucctu 
enierieu)!. Oalcinm phoaphate will he disrolved by the 
free acid in Ihe sbomiurh. yielding calcium chloride, whicb 
will be ubmrhed there or in ihc inu-iitine. SUireli will be 
partially eonTerted into grape sugar during ma^cation and 
deglutition, aad the sugar will be absorbed from the sto- 
mach. A great ]Mrt of the stjirch will, however, be passed 
on into the inteetiac unchanged, since the action of the 
iva is suspended iu ihu sl/omach; Jind its conversion will 
cumiilcteil liy ihv imiicreatic siipretion, and by the ptyalia 
of the saliva, which will recommence ils a<:(ivitT when the 
ehylo becomes alk;iliiic. The viiriuus proteids will he par- 
tiidly dissolved in the stomaeh andoonrcrled into peptonw, 
which will in part be absorbed there; the residue, with the 
undigested proteids, will be passed on to tho intestines. 
There the hile will jirecipitale the jx'jitones and pumpcp- 
tonea and, with Ihe paucroutic secretion, render tho chyme 
itlkntine, and itontop iheuetivity of the gastric pepsin. The 
pancreatic secretion will, however, rwli^olvo the precipi- 
tated pcptonup and the uncliau^cd protcids and porapeptone, 
and turn the latter into poptonea; thr*c will be absorbed m 
they pass along the small intestine; a small quantity perhaps 
pitiuing into the liirge intestine, to bo taken up there. 
The fats will remain unchanged until they enter the amnll 
intestine, cxoept that tho protoid cell-walte of the fats of 
the beefsteak will be dixsolvcd nway. In the small intes- 
tine these hodiea will be partially saponiSed, but mo(t will 
be emuUillcd and taken up into the lucteaU in that condi- 
tion. Uelatin, from the white Qbroui tisxuv of tlie beef* 



3S0 



THE BUilAK HODT. 



Bleak, win tinttorgo i;hiiiigi.<« in (ho ^tutuaoli and int 
uud bo (liK^ulvcd mill iiliHurbc-d. 

The aubaLuiicos loavitig liie aUmentary canat after eucIi a 
meal would be, primarilj, the indigoHtible cellulose and 
elastin, togothcr with eumc wiitor. But lliora might be in 
addition some imiibsorbcd fiit.", stiirch, mid *iUtA To tliis 
would ho uddi-d. in r.ho idimoiitary oitiiii, muoio, Bomc uf 
the fermenta at the digestive socretionn, eom* slightly 
nlU'rod bile pigmcutf, uiid other bodtoa excreted hy the 
largt! iiitejitine. 

Dyspepsia i-i tho L-ommon name of a iiumhor of dlMSfed 
couditiouii attmidud witit hiM» uf u]ij>otiLf! or troableeome 
digestion. Ueing usually nniittendod with acut« pain, and 
if it kill« at all doing so very slowly, it is pre-eminently 
suited for treatment by domoi'tic (jiiackcry. In reality, 
howerer, the immediate cause of the symptoms, and tfao 
treatment called for, may vary widely; and itrt detection 
and the choice of the )iro|M>r remedial agoDla often call for 
more than brdinun>- modiud «kill. A fi'W of the more com* 
uon forms of dye|)e|iiii» may Ik' mciitioiicd horc, with their 
proximate causes, uot in order to enable people to under- 
take the rajdi oxperimont of dosing Uiomsvlvcii, hut to nhow 
how wido a chxni::e thcri< \n tor any unRkllled treatment to 
mi&t itj> vnd, and do more harm tluiii good. 

Appetite u )>rimarily duo to a condition of the mucoui 
membrane of the stomach which, in health, oomes on after 
tt tihurt fujt, and slimnlntos it« i«nsory nerves: and logs of 
appetite may Iw due lu eilliur of several chunm. The dto- 
mach may be apatJietic and hick ita normal seDsibtiily, so 
Utal the empty couditiou does not act, as it normally doc«, 
aa a sufficient exoitant. When food is taken it is a further 
stimulus and may be enough; in such caaes "appetite 
conies with eating." A bitter before a mual ja useful as an 
appetiiEer to patients of this sort. On tlie other hand, tho 
stomach may bo too sensitive, and a Toructous npiwlite ho 
felt before ft meal, which i* replaeed by uauaea, or even 
vomiting, as soon aa a few mouihfnls have been ewidluwed; 
UiD extra sliinulut uf the fiml thi-u ovor-sLimtihi(e« the too 
irritable stomach, just aa a draught of mustard and worm 



mDIQBSTlOS. 



3M 



irnt«r will a licftUbj one. Tho proper treatment in snoh 
cases is a soothing one. When food is tukcn it ought to 
iti tnulnt« tlto Mtisorjr guitric ncn'C«, im lu to cxcito the reAox 
centres for the Recretoiy nerves, and for the dilatation of 
the blood-vessels, of the organ; if it does not, tl:o giirtrJc 
juico will be imperfectly secreted. In Miich castM ono mar 
Ktimnlate the occrotory iiorvtm by weak alkalies (p. 33'>), as 
Apollinaris wrater or a little citrbunutc of soda, before ineali;; 
or give drug!*, m utrycbiiiiK;, which itioroiwo the irritability 
of rellei nerve-centres. The va^teular dilatation may l>o 
helped by warm driukm. and this is probably the rafioiuilt 
of tlie glass of hot water after eating which ha* rew-ntly 
been in vogue; the usual cup of hot eoifee after dinner (the 
desirabiHty of which i» prorud by the oiisensus of civilizi^d 
mankind) is a more agroeaWe form of thu siinie aid to 
digestion. In statw of general debility, when tliu stomach 
ig loo feeble to secrete nnder any stimulation, the adminis- 
tration of weak acids and artificially prepared ))C)x<in i^ 
needed, so ad td supply gaxtrio juicct from oatsidc. until iho 
improved digestion strengtheiiK the stomach tip to the 
p4)int of being able to do its own work. 

Enough haa pndmbly been said to show that dyspeiwia 
is not a disease, bnt n symptom ni^cumpnnyin^' many jiatliu- 
logical ooiiditionn, nMjuiring special knowled;ie for their 
treatment. From its nature— depriving the Body of its 
proper nonHshment — it tends to intensify it*olf, and so 
ebotdd never bo ucglectedi "■ etilch in time saves nine. 



CHAPTER XXIV. 



TUK UKSPlUATOitY MKCUANISM. 



Dafinitioiie. The blood as it flows from tlio riglit TCii- 
tricle of iiii< heart, through the lungT*, to lliu loft uurivlc. 
lots* curb';ii (lioxiilv and gniati ox^vgt'ii. In tho Byatemic 
circaUtion exactly the reverse chaug(« tako pluce, oxygen 
leaviug the bluixl to mipply the liviiig tivxiii'S und viirlK)]! 
dioxide, )j«iicnitod in tiiein, j)iu<iiing back into the Mood 
cai>illai-ies. The oxygeu loss und carbou dioxide g&ia are 
aesociated iritli h change in the color of tho blood from 
bright iieiirlct to purple red, or from urt«rial to venous; and 
the opposite ohitngcs in the Inngx restore to the dark blood 
itM bright tiul. The whok* set of proeciww through which 
blood boeoiues venouii in tho {^-atcmic circulation and 
orlerial in the pulmonary — in other word* tlm procowes 
concerned iu the gusuouH reception. diMribntion and elimi- 
nation of the Body — constitute the function of reagiimtinn; 
80 much uf this m is eoncerued in the intcrchange» between 
the blood and iiir iK'ing known at f^tcmal rftptrationj 
while the interchanges occnrring in the aystemic capillaries, 
and tlie procosses in gener:d by which oxjgen is fixed and 
carbon dioxide formed by the living liuiacs, ore known u.* 
infernal rrfpU-alioH. When the term rei(|>ira(ion is used 
alone, without any limiting ndjectire, tJio i-xt«roal rwspini- 
tion only, is commonly mcanl. 

Bespiratorr Organs. 'J'lie blood being kept poor in 
oxj'gen and rirh to L')ti'i)ou clinxide by Ihc action of the liv- 
ing tissues, u certain umoiuit of gaseous intiri'hnuge will 
nearly always lake plm-c when il eoines into close proximity 
to the snrroandin}; moiiiuni; whether thix bo th« HttDos- 
phoro itMelf or walci' ownUiiiing air in soliition. When an 



RESPmATORT OBOAJTB. 



853 



^ 



to 



aaiinai '» snuUl there ar« often no special orfpuis for its ex> 
tortuil ro«))initiuii, \U guDontl eiuiaoo being «ufficienl (c«pe- 
oially in a<|uattc aniidalfl with a moist skin) to permit of all 
tbe gateouB cxchiin;;e that is n«c«asary. In the simplest 
creatures, isclcvd, lliurc a ovod no blood, t))C cell or celU 
oompoaing them lukiug up for themaelTee from their en- 
Tiroumeiit the oxygen which tliej need, and paeing oat 
into it Uieir carhon ijioiido wiwW; in olher words, Uierc iit 
no difTercntiatioQ of the eiienial and inlernal reepiralions. 
Wfien, howt'vor. an animal is larger many of its cells are so 
far from u tntc (urtiK'« that they cannot tran»uct this give- 
and'tske iricb the sorrouoding medium dir«ctly, and the 
blood, or some liquid ropresontin;; it iu this respect, serres 
Its n middluuiun Ixilweon the living tix-iiieH and the external 
oxygen; and then one aanally fiiida special respirahry or- 
yaiu d«Toh>ped, into which the blood is brought to roplnco 
it* oxygon loss and get rid of it^ eioess of carbon dioxide. 
In at^uatio animaU such organs take commonly tbe form 
of gills; thceo arc prntnuiona of the body orcr which u 
conittanl current of water, containing oxygen in Rolu- 
tion, is kept np; and in which blood capillaries form a 
close network immediately beneath the Aurfaoe. In air- 
breathing animals a dilTcrent arrangement is usually found. 
In some, as frogs, it is true, the skin is kept motiit and 
aorvcs as on imjwrlant re^tpinttory organ, largo quanli- 
tieti of venous blood being sent to it for aeration. But for 
the occufTL-Mceof tiiu nfcossary ga«ou8diBu*ion, the skin 
must bo kept very moist, and tliis, in a terrestrial animal, 
oeoesffltates a great amount of secretion by the cntaneons 
glands to compeosnto for cvug>'>rHtion; and accordingly in 
land animals the air is usually carried into the body by 
tubes with narrow external orifices, and so the dr^nng np of 
the breatbing surfaces is greatly dimiuishod; just as water 
in a bottle with a narrow mvk will dinappear much more 
slowly timn the aame amount ex|H>sc<l in an open dish. In 
insects (as bees, butterflies, and bui-tlL->; the air is earriod 
by tubes whieli i^plit up into extremuly tine branches and 
ramify all th.v. 'gh the btnly, even down t« the individual 
tissue elements, which thux cut}' on tlicir gntonos exeliaagcs 




3M 



Tn« BUilAS BODY. 



without the intervontinn of the blood. Bat in tlie great 
Diiijoritr.of iiir>itrciilUiiig ttuini»l« t)iu urrungemwtt ia dif- 
ferent; the air-tubc« Icadinf; from the exterior of tJic bodj' 
do nut Eubdividv into bninchtm which riimifyiill throttgb it, 
hut ojKii into one or mora large sacs to which thv vouoiis 
blood is brought, and m whoso walU it tlows through 
II close ciipilhirv network. Such n-.'^j)) nitory snot are called 
lungH, and it '\» a highly developed form of them which in 
vinpluycd in the IlnmiLD Bodv. 

The Air-Paaaages and Lungs. In our mrii Bodies some 
small amount uf rc^tipinktiou is carried on in the alimentar}' 

canal, iho air flwatlowed with 
food or Baliva nndergoiug gas- 
cuuii exchangeB with the blood 
in i)ie giwl.ric and intestinal mu- 
coue metubranfid. The amount 
of oxygen thuH obtnined by tlie 
blood is however very trivial, an 
is that Absorbed through tlie 
skin, covered m Jt is by its dry 
homy non-vamnilar ci>idcnni». 
^Vll the really eai'eulial gaseous 
iiiteri'liiinjp')' b«tw«on Ihe Body 
and the aiinospliero take place 
in tlio InngH. two large sac« (lu. 
Fig. 1) lying in tho thoracic 
cavity, Olio on each side of the 
lieitrl. Tu ilicee mcs the air is 
conveyiHl thmiigli a eaHim of 
passages. Kiiteriiig tlie pharynx 
through the nu^tril« or month, 
t^^i^^?"^S^^^,:- ii I"^'"'« «»t of ti"« hy ihc open- 
luna """"'"'""'""'"'"" '"fi •«"''''g into *''" larynx, or 

Yiiitre-htix {a. Fig. 104), lying in 
the upper pwt of the m-clc (llic cmniiiunicution of the two 
ia seen in Fig. 8!l); from llic liirynx passes back tlio 
/crtfrAoa or windpipe, &,wlii(;]i,uftori'ntoriug the chest cavity, 
diyidcs into the right and U/t bronchi, d. Each brouohua 
dindes np into soiullur nud smuUcr branches, called bran' 




Tut. UM.^ThflluonMid Itrp^ 
fmm llv*Treiit, Oa i* 



» n.m rmm llv* rreot, Oa UiB 
llw DKura the IWlnuiiMT 

•liao Uic ruailluftUonH ut Uiv bron - 



MO*-.* 

Ipft of 




STHVCTVRIS OF TIIK LVX08. 



8S5 




Fm. UW.— A nnuill hmnchliil lab*. 
iBIr-l vnMi wul nod ill Uiu lAn^il' 



ehialtubts, within tho lung on ilixxrn side; and thesmalleit 
bronchial tabes end in Kicculat«d dilutatioiK, tito alveoli of 
tlie lungs, the «ucvuliili<>ni( (Fig. 106) being the air-ctlU: 
liic wonj " cell" being here need 
in its primitive ecngo of a email 
cavity, and not in its later tech- 
nical signitloation of a morpho- 
logical unit of the Body. On 
l!io wiill« uf tlie air-oells the 
piiImoniuT oapillariea ramify, 
and it is in tlicm thai tlio iittvr- 
chuugcj of tho external reapira- 
lion tiikft |>laoe. 

Struoturo of the Traohee 
and Bronchi. The wimlpipe 
uiiiy readily be fdt in the middle ]inc of the neck, a Utile 
hcluw Adam's apple, aa a rigid vvliiidrica] mat^ It con- 
siiita fundnjnvntidly uf a fibroua tube in which cartilages 
are imbedded, so as io keep it from cullap-ting; and u lined 
internally liy a inticuiid nitfrnhrane covered by several luyem 
of epithdium cfU*, of which the BUpcrficial i< ciliated (Fig. 
4?). The cartilages imlHKliIod in tit wuIIh are impcrfoct 
rings, «ach somewhat Uie nhajte of a hoi-fituline and, Uio 
deficient part of eaeh ring being turned hwrk Hards, it conie« 
to pass tliat tho dvopor or donuti nd« of tlie wi»dpi{»o has 
no hard purtj< in it. Against this side the gullet lies, and 
ihc absence thereof the cartilages no donbt facilitates bwbI- 
lowing. The bronuhi rceemblc tlio windpipe in structure. 

The Structure of tho Lungs. These consist of thn 
hronchial IiiWh and tlnir tci'tiiinal dilatations; nomorons 
liluDd-TCRScK nerves and lymphatics; and an abundance of 
connective tli^uc, rich in o1a«lic llbrcs. binding all together. 
The bronchial tulwKriiiniry in alrcc-like manner (Fig. 104). 
In structure the larger ones resemble tho tntciieo, except 
that tho carlilagu ring:* are Dot regularly arranged so as lo 
havo tboir open paru all turned one way. As the tubes 
become smaller their oonstituenta thin away; the cartJIagoi 
beoamo loss frequent and finally disappear; the epithelium 
18 reducei] t» a single layer of eclU which, though stilt cUi' 




see 



TBK BUXAX BOOT, 




fttod, are mach shorU-r ttian the colunuur superficial cell 
layer of the larger (iiboi<. The tcrmiiiat nlveoli {a, a, Fig- 
lOti,) and the wr-celU, b, vhich open into tliea, have w«1b 
composed mwnly of tilmtw tiffWi nnd linod bj a siu{;1c- 

layer «f flat, non'C>liat«cl «pi- 
tlielitim.imiiiL-diiilcIf bcueiith 
whicli i* ft verjrclow netvr-.ik 
of cspilUirj blood - TPssoi:i. 
Tbo uir ciitcrinf: bv tlio broa- 
cIiiilI tube U tbus only sepo- 
rated from the blood by the 
thin capillary wall nnd the 
iliin qiilhelinm, botli of 
which ore moist, and well 
adapted t« ]>vnnit ga«coiu 
diffusion. 

Tbo PlouTft. Each lung 
is covered, except at one 
point, by an clastic serous 
munibrtmo which adhcre« 
tightly to it and ia called llie 
phura; that point at which 
the pleura is wanting i« called tlio roof of the lung and i« 
on its inner side; it is there that its bronchus, blood-TCUe1« 
snd noFTcs enter it. At the root of the lung the plenru 
turns back luid linca the inside of the cheat cuvity, as rep- 
rcMtDted by the dotted line in the diagram Fig. 1. I'lie 
part of the plenra attached to each lung is its viteerai, and 
that utt4iohcd to the chcMt-wall it« parietal iag«r. Each 
pleura thus forms a closed sac surrounding a /)/ir«rrf//Of'i/y. 
in which, during health, there ore found a few drops of 
lymph, keeping its eurfacos moUU Tliis loosens friction 
between the two layers during ihc moveinentji of the chest- 
walls and the lun^: for nil hough, to insure distinctness, 
lh« visceral and parietal layers of tho iiloura are represented 
in tho diii^am as not in contact, that h not the naturul 
condition of things; tho lungs are in life distended sa that 
the viweral pleura rubs against the jiarictal, and tho pleural 
cavity is practically obliterated. This is brought about bj 



F)a. lOa-Two alveoli or tli« lunif 
htslk)* nUK&Ulfd. b. 6. Ui* aiitrll*, 
ur hollo* protnUilOinM itiralwutiui. 
opi^nliw IdM IWcnilnlc**ay: c,i«r- 
tniDOl Eranvba at ft bivniUilal tube. 



war TOE luyea do sot coliapsb. 



3S7 



Ihc proxaure of the stmo«ph«re on the )ii«d« of the InngR, 
lliruii^h Ui« «ir-pttfiEsgO)i. The lung« uro vxtremely Haetic 
iiii<l dUtciiiiible, and when the chi^t cavity t!i |iorfrtniti>d 
each shrireb up jiiiit as an mditto-rubbcr bladder does when 
iCfi neck U opened: iho ttuu'on being that then the air 
prewet on the ouuido of each n'ith as much force aa il din^ 
on the inside. Tbe« two proeunM iicutnliziog one nn- 
other, tbcnt i» nothing Ui overcome the tendency of the 
iQDgs. to coIlu|i«e. So long m the chest-walla are whole, 
howerpr. ihe Iiings remain distended. The ptGuriU sac ie 
iiir-ti(.'iii uiid contains no air, and the pressure of the air 
around the Body U borne by the rigid walls of the cheet 
and prercntcd from reaching the lungs; consequently no 
atmospheric pressure isoxerted on their uut«idu». Oil thoir 
interior, howeTer, the atmosphere prcBsea with iU fall 
weight, equal (gee Physica) to about 90 conttgranut on a 
!)i|uare ccntimot«r (14.5 Iba. on the li'iuare inch), and this 
la far more than ^utGcient to distend the 
Iung8 no M to mwkc them completely lill 
all the parte <^ the thoraoJo oavity not 
occupied by other or:gtin8. Suppose A, 
(Pig. 107) to bo a bottle closed air-tight 
t)y a eork through which two tabca paas, 
one of which, 6, \eadi into un elastic bug, 
ft, and the other, c, provided with a stop- 
cock, opens freely below into the bottle. 
If the stop-oock, r, is open the air will 
enter the bi)il)e and press there on Uio 
outsiilc of the bag, ns well as on its in- 
side through b. The bag will therefore 
oollaptw, as the lungi^ do wlieu the chest cavity is opened. 
But if some air be Kuckiil out of c the pressure of I liat remain- 
ing in the bottle will diminish, while Uiat inside the bag 
will bo the Kime. and ihe U:\j will thus be Mown up, because 
iheatmo^plicric pressure on its interior will not be balanced 
by that on its exterior. At last, when alt (he air is sucked 
out of the boltte and the rloi>-oock on c clowd. the bag, if 
fluflleiently distensible, will be expanded until it completely 
fills the boiUe and proitwi again»t its inside, and the stat« 




t^D. im.— Dtagnun 
nioMivihw Ow pras- 
mm nuuondUp* of 



3S8 



THE nVMAN BODT. 



of things Tin thfln anaww to that niitnmllj foimil in the 
oheet. If the bottle wcro now increased in siae without 
lotting »ir iiitd it, thn bng woulil expimd titill mora, «o us to 
fill it, and in so doing would receive air from ouUidc 
through b; «nd if the bottle (bcii n>tuni«l to it« original 
«iztf, it^wullfl would press on the bag and ean^ il to ehrink 
and eipel some of its air Ihrongh h. Kiacttv Die «ame 
must of course happen, under similar circumstances, in the 
clic.*t, ihc vfindpijie answering to the tube b through which 
air enter* or leaves the elastic sac. 

The Baspiratory Uovementa. The air taken into the 
lungs oOiJii Ixtuiiit's imk'ii in tlifni with carbon dioxide, and 
at the same time loses much of it* oxyRen; these inter- 
chatigtv luking plavo mainly in the deep recesses of the 
ftlvetiJi, far from the exterior, and onlvcommunicatingwith 
it through a long tract of narrow tubes. The aivec»l«r iiir, 
thus liooonic unfit io any longer convert; venomt biocxl into 
arterial, could only very slowly be renewed by puwous dif- 
faB4on with the outer nir through the long utr-piL^ages— 
not nearly fast enough for the ny|iiiremenl»t of the Body, ax 
any one rciidily csiierienfes through the sensatjon of anffo- 
cation which follows holding the bn-nth for a very short 
timo. Ooniwqucntly, added on to the breathing lungs ia a 
T*^irtdory meektmiMm. by which the air within them is 
periodically mixed with fro^li air taken from the outride, 
and also the nir in t)ie ulveoli is Mirred up #o as to bring 
fresh laycm of it in contact with the watU of the air-oclU. 
This mixing is brought alwut by the breathing movements, 
consisting of reguinrly altcrnutiiig inxfilraliimif, during 
which the chest cavity is enlargtij and frcj<li air enters lh« 
lungs, and r^r pirn f ions, in which the cavity is diminished 
and nir expelled from the lungs. When the cliest is enlni^gctl 
the uir the lung^ ooutjtin immedJalcly dit^tondj* them so aa 
to fill the larger space; in so doing it become iiireSed and 
k'^'S dense than the external air; and since gnaoa flow from 
])oints of greater to those of low pressure, some ontaide air 
at once flows iu by the air-paseagefl and enters the Itings. 
In c\]iiration the n>Torso taken place. The chost CttTity, 
;]iti)inighing, presses on the lungti and makes the air ioaidfl 



MOVBMEHTB OF TilK TttORAX. 



359 




Fin liW - liLrutTun lo lllaslrala Uip ra 
try of nrr 1<> iliii Iuiik* wluia Uu tliarai^io 




Uicm dciuicr than the external air, and do eome passes out 

nntil an e<iuiljbrium of pre«>urt> ia restored. Tho chc«t, id 

fact> acts very mticli liko a bclluwit. Wlieu thv lidlowa tn 

opened air cntcr« in coii- 

s<-i[iifiiice of tlie rarofnotioD 

uf that in the interior, 

vhich 18 expanding 1^ till 

the larger space; and nrben 

tho bc'llow:! arc c1ofl«d 

again it is expellod. To 

make the be) lows quite 

like the lunps wo must, however, as in Fig 108, hare only 

one opening in (hem, tliiit of tho nozzle, for huth f h« «ntrT 

and exit of lh<> air; and l.liii* opening ithonid lend, not 

directly into the bellows cavity, but into an elastic Ijug 

lynijj in it, and tit'd to the inner i>nd of the noiuile-pipe. 

This sac would represent the lungs and the space between 

it« onttiidc, and the imtido of the bellow^ the pleural oavi- 

ties. 

We have nest to see how the eipansion and contnurtion 
of the che^t cavity uii; brought alioiiL 

The Stmcttire of the Thorax. The Ihoraeie cavity has 
II conicid form determined hy tlivshii|raof its skeleton (Fig. 
tO!t), its narrower end being turned iipwanK Dor^tdly, 
ventrally, and on the sides, it is su])parted hy the rigid 
fiiimework aflorded by the dorral vertebrae, tlie breael-boue, 
and the ribs. Uetween and over tb<.-MC lie inuitcW:<, and tlie 
whole is covered in. air-tig^it, by the skin externally, and the 
(larietal liiyeris of the pleura* inside. Above, it^ aperture is 
closed by miii-ctes and by various* organs piinsing Iwtwonn 
the th«ax and the nock: and below it \s bounded by ths 
iiaf^r^m, which forms a movable bottom to thu, other* 
wise, tolerably rigid box. In inspimtion tliis box is in- 
creased in alt its diameters— dorso-vontrally, laterally, and 
from above domii, 

Tlie Vertioal Enlargomonl of tho Thonuc, This is 
lirought about by the cunlructioii of the duiphrngm which 
(Figs. I and ltd) is a thin aheel-like muscle, with u libi-oiis 
membrane, serving as a tendon, in its centre. In real, the 



aeo 



TltB nUHAy BODY. 



diaphrugm is domo-chapcii, it« coucavity being tornGd 
towurda the abdomen. From llio tendon on the crown of 
the dome striped mnscuUtr fibres riwllate, downwarde and 
outwards, to nil t^iiv*; uik* (ire fixed \>y their inferior ends 
to the lower ribs, iho breast-bone, and the vertebral column. 
In expimtiuQ the lower lateral portions of the diaphragm 
lie dose ngnin»t the client- wallit. no Inug intervening betnit-n 
them. In iiis])irution the muscular fibrco, sborteniog, flst- 




Fn, ion— ThMkclclonof Ibcthnrnz. u. p. ocrtrliml wiliiinn; b.flnilribia, 
clavicle: if. tliint nb; i, ictr-nolit [(uml 

ten tli« dome and eo enlarge the tlioracic cavity at the ex* 
ponseof the abduminul; und ni the mxn^- time ite Intend 
portions am imlled away from the ohest-wallfi, leaving a 
^ace into which the lower ends of the lungs expand. The 
contraction of the diaphragm thiis iucrcaseit greatly thcsixo 
of the thorax chamber by adding to ita lowe.it and widest 
part. 

The Dorao-Teatral EDlorgement of the Thorax. The 
ribs on the whole slojie downwards {I, Fig. S5) from thfl 

^ebral column to the brcnet-bone, the elope being moet 




Htli BSl.AIMSUEST OF TUB TltOBAX. 



marked i» llie lower uueo. Uariog iuspiratiuii tlio breut- 
bgno ami tlie stcrDsl cads of Die riU stUicliod to it are 




Pio. Ua "na dlftphmrm (Mil rnrni bflotr. 

tattocl, ttiid io the <li»tttuof bctneeti the Htemiim uud the 
vertebral coluuin is iticrwued. Thiit Huh musi be ito will 
retidil)' bt ik'cu Uy exnmiriiii;; l)u' diAgrani Fjg. Ill, ivhera 
ab rapreeeatfi (he vertebral column, 
c Kiid <! tvo tWa, and H the stor- 
num. The i-«iilinumi* line* repre- 
sent thi- nuliiriil posiliun of the ribs 
at rest m ex])iraltoii, ttiid the dotted 
lines thu jwsition inin»tj>irattoQ. It 
ia clear tbiit when Ihcir lower end* 
we raised, eo as to make the hora lie 
in H iiiorc hori^onlal jilane, the ster- 
nnm '\» pushed uwar from the Kpiuc. 
mid fn the chest cAvily is invrea«cd 
doi-*o- v«itrally. The inspiratory 
elevation of the rib« \* muitilydiio to 
tho action of the acaleae and erltr- 
nal iHlfrcottal ii^uhcIm. TIib aculenc iiiiiscles. three on each 
side, arise from che cervind vertebrte uid are inserted into 




Tta. m.-DUdan llliu- 
muiuc ttv dons'Tciiinu tn- 
cnat Id the dl&iiim«rof Um 
tlionu when the Hba >ra 
ntwi. 




»l» 



ma RCMAs Bour. 



the uj)per ribs. Tlio cxiomiil intorcostaU (i'ift. llS. ^) Uo 
Wlwi'i-ii llic riliK mill fxlcml from tbc vcrltbrwl uttluinn to the 
costal cartilages; their fibres slope downwards and forwards. 
During nn inspiration tlio scaletictt cuntriiot mid fix thu 
ii[t[H'r riljs finnlv; llu'ii ilio cxU-niiil itiitrrtoKlidK xliortc-n 
and each raises the rib lielow it. The niiist^lo, in fact, 
icndit to pull together llio piiir of ribij iK'twccti which it 
Viv*, but )w the upper one of thc^-c i« Imld tight by the 




Flo, lie. IVrtlolmof tmrf r1h» of « rfog wllhUio munrfr* lif f r e wi tlieill. ■■«, 
TDUlrBl cuaii ut Ihf rlhi. lolnluK nl c iiie rib oiLnilnun. b. vhMta an IlKtd U 
cutlUcliiuu* ixmlcni. d, <a cbe Ktrmuiu. .1. n umaJ luirroonUI MuacI*, MM- i 
Ing MlHWD Uiu hli •.-«nll»«i'i>. wliorvllxUiiUnin-llnli-ft'ioMl. ^liMan. BanrMHl 
thu mldilla twi> tllHllu>.-itrnuliiit<-(riiHtnl iiiu-«Ih luulxvn dVMKrWd awB|-, Mt < 
aat«iU«pIity ibQiiiitnalKtili'binuicoienslbjrlL 



e(.'alcn<!« niid oilier niUKcle* above, tlio roeult is that the lower 
rib is pulled tip, and not the iipiwr down. In (his niiv the 
luwL'i- rihd lire riLiKod inuc-li mure thun tlio upper, for thn 
whole oslenml intei-c-ostul iiiiiflcle« on one «<ie may be ro- 
g^irdcd us one great muscle with many Wilies, each lielly 
MiparutMl from the next by a tendon, poproeontod by the 
rilk. Whun thu wholo mu«oiilin' ebcot \t (ixvd altove antl 




MECRANISM OF KSPIRATtON. 



863 



contracts, it ia clear that its lower end will bo raided more 
than any int«rnicdiuU' point, »in«f tlicrc is a greater lonjj^h 
<if poiitmclile tissue nbOTo it. The elevation of the rilts 
tends to diminish the vertical djamelcr of tlie chest; ihii is 
more thui coinpcnsuiod for by the sinmltaneous deecent of 
tho diaphragm. 

The Lateral Ealargement of the Cheat ii> mainly due 
to thi' diik[)hragiii. which, when it contracts, adds to the 
lo«-c;!t and widest part of the conical chert csvity. Some 
small widening is, howt^vcr, brought about hy « rotation of 
some of the middle ribs which, as tlioy are raised, roll round 
H little at thi-ir vertebnd arliculationn and twist their car- 
tilages. Each rib is curved and, if the bones be ciHcninod 
in their natural position in a skeleton, it will be seen that 
the most curved part lion Ik-Iow ilio level uf a straight line 
drawn from the Tert«bral to the sternal attachment of tlie 
bone. By the rotation of the rib, during tnepiratloD, this 
curved part is raised and tnrnod out, and the chest widened. 
The meehaniam can bo uuJerfitood by clasping tho hunda 
opposite tho lower end of the sternum and a few inches in 
front of it, with the elbows bent and pointing downwards. 
Each arm will then answer, in an exaggerated way, to a 
curved rib, and Iho claopod bauds to tho brca«t-hone. If 
the hands be simply raised a few inches by moTcnitint at the 
shoulder-join Is only, tbey will be separated farther from the 
front of Uie Body, and rib clovatiou and tho coocetiucnt 
dorso-ventral enlargement of the cavity surrounded will be 
represented. But if, simultaneously, the arms bo rotated tX 
the shoulder'joints so as to nuRc tbo elbows und tnni them 
out a little, it will be seen that the «paco enrronnded hy tho 
two arms is considerably increased from side to side, its tho 
cheat cavity is in inspiration by the similar clevatioQ of the 
most cnrved part or " angle" of the middle ribs. 

Bxpiratioa. To produce an ius]>iration roqnirea oon- 
sidorablo mtiscular effort. The ribs and sternum hare to 
bo raided; the clastic rib eartilugv" bent and somewhat 
twisted; the abdominal viscera pushed down; and the ab. 
dominal wall pu!<hed out to maiio room for them. In ei- 
piration, on the contrary, but litUo. if any, musoitlar effort 



ZM 



THE nVMAy B0D7. 



is Deeded. As eooq Hi the muaoloji wliich have mUcd the 
ribs and Btormim rpUi, these tend to return to their natut 
unconttmined positkin, hixI the rib c-ii't iliigca, nlso, to uii4 
twist themselTCK ftiid bring the ribs buck to their ixisiiion 
of rert; Ui« elastic abdominal wall presfes the contaiuod 
visc«ra against the under «ido of ihcdinphrugm, itnd pufhes 
tliat up ttgiiin aa wimi iw it-a musoular fibres ceow contnwrl 
ing. By tbi-ofi tntaiia the chest cavity is restored to it«l 
original capacitj uDd tho air sent out of tlie Inngo, ntlicr 
by the «la.*tipiiy of the jiarts which were stretched iu inspir* 
atinn, than by any sjieuial expinitory musflca. 

Forced Besplration. NVTicn a very dyep hrculh is drawn 
or Lxpiilltid, or when there is some imjicdimciit t» tbo enlry 
or exit of the air, a great many niiisctej take part in pro- 
ducing the rcJ^jiiriitory movvmfnlK, and ei]iiniti>in then bo- 
eoiuc.'', ill part, aa actively muscular axi. Thi> main cicpirM- 
t«rv muscles are the inhntal inlerconfala wliich lie beneath 
tho external between each pair of rilw (Fig. 112, /^), and 
have an opposite direction, their libres running wpwards 
and forwards. In forced expiration tlie lower ribs are fixe 
or pulled down by museles running in the abdominal widf 
from the pelvis to them and to the hreasl-bime. The in- 
ternal intercosluls then oontmcting, pull down the upper 
ribs and the sternum, and so diminisli tlio thontcii; carity 
d»r«i)- vent rally. At tho eume time, the contracted aMomi- 
nal muscles preM thewnllsof tbut cavity agxiust the viscera 
within it, and pnslitng tlicne up forcibly ngaiuvt tho din- 
pbrugin make it very convex towards the cheat, and so 
diminish the latter in its vertical diameter. In very violent 
expiration many other niuiolt'H may co-operate. ti!ndin<r lo 
fix points on which tliot>e muscl&'i which can directlydimin- 
isli the tlioracio cavity, pull. In violent inspiration, also, 
many extra muKclctf iiro called into play. Tlic neck is held 
rit'id In give the scaleneis a firm attachment; tho sbmilder- 
joint is held fixed and mtisclcs going from it to Uio cbest- 
wsll, and oommonly serving to move tlie arm, are tboD 
used to elevate the ribs; the head is held firm on tho vertc- 
hral column by tho mnsclcs going between the two, and 
then other muscles, which pasts from tbo collar-bono and 



p 



CAPAClTr OF TUB LUyOS. 



365 



it«rnniii to the skull, are nwd to poll up the former. The 
mUHclefl whtcli are thus called iuto pluy id luWrod but not 
in (juiet lireuthing ure aillvd extraordinary niusdti oj r«s- 
pira/ ion. 

The Beapiratory Sounds. The entry ftiid vxk of air 
are uccumpiLDiod hy rtuptratory souniU or uturmurs, 
which ouii be hcurd on applying tlie ear to the cheat nrstl. 
The character ot tbeoe sounds in different niid charuL'teristic 
over the tnuihcH, thv larj^or hroiicliiul tubcH, siid ii»rtiuDj| 
of lung from which targe bronchial tubes are absent. Thoy 
are variously modided in pulmonary uffoctioos and henoe 
the value ot auscitltaliun of the luiign in assiRllug the phy- 
Rieian tn form a Uiagiioal^ 

Tbe Capacity of the Lungs. Since the chest cavity 
never oven a[iproximatcly coiUji«c«, the lun^ ar3 nerer 
coiiiplvtcly ein|itied of air: the «paiM; limy have U> occupy 
is hirgcr in initpiration than during expiration but i» alwayn 
considemble, so that after u forced expiration they still con- 
tain a tar^e amount of air wliich can only he c-xpellvd from 
tliom by opening the pleural euvitics: then they oiiltrcly 
oolla|HH>, juat an the hug in Fig. 10? would if the bottle in- 
olosing it were broken. The capacity ot the chetit, and 
therefore of the lungs, variea much in different individutilg, 
but in a man of medium height there remains in the longs 
after the motit violcitl possible cspirAtion, al)(>iit 1640 cub. 
cent. (IDO cub. iiii;lie») of iiir, edited the residual air. 
After an ordinary expimiiun there will be in lulditioa to 
this about as much more supplemental air; the residual and 
supplemental together forming the stationary air. irhieh 
rcmninjt in t!ii> cho.t during ([uitrt breutliing. In an ordi- 
nary inapinitiun bOO uub. cent, (30 cub. incheit) of tiditl air 
ure liikei) in, and about the same iiinuunt is expelled in nat- 
nral expiration. By a forced insjnratiou about l(!l>0 cub. 
cvnt. (98 cub. inc-hes) of coinplemenlal air can Iw added to 
the tidal air. Aft«r u forced iusjiiratiun therefore the chest 
will contiun 1G40 + 1640 -f &00 -f 1600 = 5:1^1) cubic conti- 
meters (32*1 cubic inches) of air. The amount vhich can 
be t*kc» in by iho must Tioleut pu^tiblc iiiiiiiiration after 
the dtrongcet poasiblo expiration, that is, the supplemental, 




TBB B VAX BODT. 



tt<lal and comp]mt«otiil air togetiicr, i» knowii m tlie mtitJ 
cafHKtly. For & healthy man 1.7 metere (& feet S iiicli(») 
high It is about 3700 cub. ^nU (£!5 cub. incbea) 
and iucrcusoH GO cub. cent, for each additioDal ntntime 
tec of fitature; or about 9 cubic luobeB for each inch ot 
height. 

Tlio Qusntlt; of Air Breathed Doily. Knowing the 
<|Uantity of ^i Utkeu in itt exuih bn-ulh tuiij exjielkil agaio 
(aftei more or IciiS thuruugh mixtui-e vtiiii tbe Etatiomirj 
air) we haveonly Uiknow, in addition, Ihc- rate ut which the 
breathing moTemeiit« occur, to be able to calculate how 
much air piUdos through the Iuiig» in twenty-four bourju 
Tho average number «f respinition* in a minute U found 
bjr counting on pcrsunii sitting (guietly, and not knowing 
that their breathing rate in under obaerTatioii, to be tiflccu 
in a minute, lu each of these half a liter (30 cubic iiicboa) 
of air IS concerned; therefore U-.n x 15 x CO x 24 = lO.fiOO 
liters (374 cubic foet) i^ the quuntity of air breathed iiiidei' 
ordinary circumstuncos by each fcnmn in a day. 

Hjrglenio Bemarka. Since the diaphragm u-hen it con- 
tructa j)ii.-!i<:'3 (l>ju*ii the abdotninut vii^tTni benoutb it, Ihete 
hate to ninko room fur Iheiiiselvos by [miihliig out the .wfL 
front of Ilie nbdumiu whioh, accordingly, jirotrudes vfaen 
Uie diaphragm descendiN Ileucc breathing by tb« dia- 
phragm, being indicated on tbv CKteriur by moTcm«ntx of 
the abdomen, is uflcn cidli-d "ubdamiual respiration," a* 
distinguifihcd from breathing by the ribe, Dall<d ■' costal" 
or "chest breulhing." In bitth sexes the diaphnigmntic 
broathiug u the munt important, but, m a rule, niMi and 
children UHO the ribs Ic.-.:! titan adult women. Since both 
abdomen and cho&t alterualely expand and contruct tii 
healthy breathing onytliiug which iinpedee their five move* 
mciit is lo bo avoided; iind tho tight hieing whicli used to 
be thought elegant a few years back, and is «lill indulged 
In by Bomo who think a distorted form bciiuliful, uriously 
impedMOiie of the most important functions of the Body, 
leading, if notliing worse, to sliortnew of bi-eath and nn in- 
eapucity for musciihir exertion. In exlreine cases of tight 
Isioing some organs arc often directly injured, weaU of 



p 

Ah. 



ASPIRATION OF THE THORAX. 



367 



flbroDs tissue being, tor example, not utifi-eijueutl^- found 
developed on the liver, frviu the prv«aiire of the lower ribs 
forced Hgaiunt it by a tigbl cor»et. 

The Aspirotion of the Thonu. As already points out. 
to coiiwuueiioe of the ngid fiamonork which »iijipuru its 
walls, the external air ctuiuot prc#8 directly upon tlic con- 
tents of the thoracic carily. It xtiU, however, presses o» 
Iht'm indirocUy, through the lungs. Aoting on Ihc interior 
of the^e with a pressure e'jual to thut exerted oti thw Mint: 
area by a column of mercury 760 mm. {30 luches) high, it 
distends them, itnd pu!«hc« thetn against tlio inside of the 
chest-wn]l», the heart, the great thoracic blood-TesaeU, the 
thoracic dnct, and the other contents of the cavity. The 
pressare thus exerted is not etinul U> that of the vxtvrnul 
air, since some of the total air-pressare on the inside of the 
Inngs is used up in overcommg their oI»^ icily, and it is only 
the rciiidii^ which piuhes them against the Ihings outside 
lliem. In expiratioti this residue is about equal to that ex- 
erted by a cohimii of mercury 751 mm. {\ inch Icm tiioa be- 
fore) high. On most parts of the Body the atmospheric 
presntre con, however, act with full force. Pressmg on m 
limb it piub« the skin against the soft parts beneath, and 
then against the blood and lymph vessels among Uiem; 
and the yielding ulidomimd wallti do not, like the rigid 
tJiorocio vails, carry the atmospheric prcHtiire themselves 
bat transmit it lo the t-ontonts of the cavity. It than 
como« to pass that the blood ami lymph in mo»t parts of 
the Body are under a higher atmospheric pressure tlian in 
tho chuHt, and conooqiiontly them li'iuids tend to Sow into 
Uie thorax, until Ihe extra distension of tlie vessels in which 
Ihey there accumulate oompeuates for the less external 
pressui-c til which tho»o vcscels «re oxpoeod. An equili- 
brium would IJins very aoon be brought about were it n<H 
for the respiratory movements, in consequence of which the 
intra-thuriioic pressure i« ultc^ruately increased and dimin- 
i«hed,and the tlioi-ax eomc« to act as n sort of siiction-pump 
on the oontente of the vessels of the Uody outiido it; 
thus the respiratory movements oome to influence the cir- 
culation of the blood and the Huw of the lymph. 



^ 



TJIE nWAX BODY. 



Infiuence of the Renpimtory Hovomenta upon the 
Circulation. Sui'jiOi'u liiv v\\vv^\ in a uuiidilioii or iiuturnl 
cxpinition and the cxtprual pressure on the bifjod in the 
blood -TcfiiielH witliiii it. :uid m the heart, to have come, in 
ihc muiim-r jioinl^'tl oiil in the last puntgrnpli, into ctiuili- 
hriuiu with tlie atmospherit^ pressureou the blood-Tc«sol* of 
the neck und abdomen. If iiii iDi>jiirutiuD now occurs, the 
chiMt citvity being enhtrget] the procure on all of iu con- 
tents wUl be dimintBhed. In oonBeijnence, air enl^m the 
lungs from the windpipe, and blood enters the Tcuie cavs 
and the riglit auricle of the heart. Not only the lungs, 
then, but the right side of the heart, and the intra-llioracic 
portions of tbo systetoic veins leading to it, aro expanded 
during an in»[>iniliou; but the lungs being much the most 
diHtcnnible take far the greateat part in tilling up the in- 
ci'cased space. Tlic left side of the heart is Dot mneh in- 
fliionced ns it is filled from the pulmonary veins: and the 
mIioIc visiiH'Ia of the 1e!»cr circulation lying within lh« 
chr^tf and being all affected in the .tame way at the Banii> 
time, the blood-flow in them is not influenced by the aspi- 
mtiou of thf tbiirax. Dii't«iisioD of the liing« 8ccm«, how- 
cviir, to diminish the ciipn^ity of their Teasels, and ao to a 
(frinin extent the flow ii^ influenced; aethe lungs expand 
blood is forcH-d n\it of their vi^iwoU into the left auricle, and 
when thcyngJiiu contract their vessels fill up from the right 
ventricle. The pressure on the thoracicaorta being dimin- 
ished in inspiration, blood ti-nds to How back into it from 
the abdominal portion of the viimgI, but cannot enter the 
heart on account of the t>cmiluuar valTcn; and Ibe back-flow 
docs not in anynwe c-iiual the onflow dne to the beat of the 
heart; so the what happens in the aorta is but a slight 
slowing of the current. Tlie general remit of all this is 
that the eireulalioii in considerably nMtiRted. When Oie 
ncit expiration oocurs. and the pressure in the thorax again 
rises, air and blood both tend toboexpolled from the cavity. 
The aorta thiw regainf what it hmt during in.'<|iiratiftn; the 
pronfiurc on it is increased and it em]>ties itself faster into 
iu abdominal portion. The semilunar valves having pre- 



BFVECT or UKSPiaA TlOa ON SLOODFLO W. 369 



▼ented iiny rcgnrjfitation into the henrt, there i« neither 
gain uoi loaasu far ui it iti cunceiiicd. With the RVKteinic 
intTathoriu;ic vein* however, ihia is not the cus«; the extra 
blood euU-nng thera has aliviidy lu gri'iil purt gooe on bo- 
vund the tricuspid vnlve, mid uuiinot flow book during ex- 
piration; and the proxsiure in the anricle being constantly 
kept low by il;< uinptviug into iho vcniricle, the inereasod 
pro.t«iiri> on the veiis cavip tendit .ih much to send the Ijluod 
Oil into the heart, m buck into ihv exu^-thoracio veinii. 
Moreover, wlialcver blood lends to take the latter course 
naniioL do it eflectiially since, although the vciin; ciivii' 
thcincelvcs cuiiKiui no vulve.f, the more distant Teins which 
ojicii into them do, ConwquenUy, whatever extra blood 
ba«. to use the common phrase, been "sucked" into the 
intra-lhonioic vonip nivii- in inspiration and ha* not bccii 
r^cnt alrciuly on into the right TCntnele b(>fore ex|iinitii>n 
oocnrs. I3> on account of the venona valves, imprisoned in 
tlip cavie nnd(T an ImTiwt'd jiniiwurc daring cspiration; 
and ihis tends to make it dow faster into the auriele during 
the diastole of the lutler. How much tho alternating re^ 
pinitorj movement!! annial tlie renons flow ia Khown by the 
dilation of tho veins of the liead and neck which occurs 
when a person i« hohling his brwith; and the blackneea for 
the fwH-. rmni diiiteii.->iiin of the veinit and itngnntion of tli« 
capillary flow, whicli occurs duringa prolonged fit nf eongh- 
ing, which is a iwrics of oipirutory offorts without any in- 
g] I i rations. 

In still another way the aspiration of the thorax ii«Mist« 
the heart. The heart and lungs are both extensible, though 
in dillerriit degi-ecs and ettvh i*i ttretehed in the chest 
somewhat beyond it^ natural site; the one by the atmoe- 
pheric prcwtire ilirectly. the other by that pressure in- 
directly, exerted tltrimgh thi> blcHwl expii^cd to it in the 
oxtra-thoracic veins. Supposing, therefore, the heart nid- 
denly to shrink it would Icuvo more space in the clioirt to ho 
filled by the lung#, and thcj<e, acconlingly, at each cardiac 
sjHtolo expand a little lo fill the extra room, juift as theydu 
when tho apueo around Lhum is otherwise enlarged during 



8TO 



TBS BUXAK floor 




an inspiration. The oliwticitj of the Itings, however, 
CMiitic.* tJiem to rcaial ihisdiHtGniiion and oppose the cardiac 
systole. The matter may bv mudc c'k-;ki- l>y an arrangement 
like Lhut iu Fig. 113. J Li aa air-tight resHel with a tube. 
e, provided with a stop-cock, leading from it; & is a highly 
disteosiblo cluetic bag in free communication tliroiigh tl 
vfilh the fxtorior; and c. rcpreiteDtiii;; 
the heart, la a leas exlcnsible kuc. from 
which a tnbe leads and dips nnder 
water in the tckecI B. If air be 
pumped oiil. through r both bags will 
dilate, b filling with air, and c with 
water driven up by atmospheric pres- 
iure. Ultimately, if siifljcioMtly ex* 
tcnsililp, they would fill tlie whole 
space, the thinner walled, b, occupy- 
ing moot of iu If then the istop-cock 
be closed, things will remain in eqai- 
librinm, each bag Ktririnf; to cullapae 
and «a exerting a pull on the other, 
for if (shriDkHrinnBt expand and vtcr 
versa. If e suddcfily shrink, as the 
heart doea in itt< syRtolc, b will dilate; but iu< koou a« the 
tystolo of c ccaacM, b will shrink again and pull c out to 
its previous size. In the same way, after the cardiac sys- 
tole when the heart-walls relax, the hmgs pull them ont 
tgain and dilate the organ. The coiitractiug lit-Art thn» 
expends some of its work in overcoming the elasticity of the 
ItmgH. which oppuEcs their expansion to fill the space left 
by Uio «miilli<r heart; but during the dia^ole of the heart 
this work is utilised to pnl) ont its walls again, and draw 
blood iuto it. Since tJiu nonnid heart liae muscular power, 
and to »pare, for its systole, thjji arningcment, by whicli 
some of the work then spent is stored away to ARsi«t the 
diastole, which citnnot bo directly performed by cordioo 
muscles, is of scrvii'o to it on Iho w)iol«. It is a physio- 
logical though not a mechanical advantage; no work power 
is gained, hut what there is, is better distributed. 



Pio. na.-Dliifrnni Hln*- 
iratlu^ tlirr lurlucui-" »f ai>- 
ptrmllcin i>f (h.« thn^rnK cm 
vli* drDulUtod ot tlie 
blood. 



tXFLVeyOE OF RESPIRATION OX I.TMPUFLOW 371 

Influence of the Beaptration on the Lymph-Flow. 
During inspiration, when iitlni-tliDracic prc-wiirc i« lowiTcd, 
lymph is prciUHKl into the tlionicic tliKt from tho abdomi- 
nal i/mphaticft. In espiration, when thoraoic preesnre rises 
agiiin, the eitra Ijmph oaiinot flow back on accoant of the 
valve in the iv<i)phatic vessels, iwi] i* \8 oonsoquontly 
driven on to thz csrvicwl ending of the tiioracie d""*-. The 
breathing nioTemoiK.s tlius pump the lymuh on. 



CHAPTER XXV. 

TUli CHfiMISTBY OF KKSFIRATION. 



ITature of the Problem*. Tlio etudy of the rMpira- 
tiirj- (jriiirc*,* frmn ii (-licniuvil *tAui)|ii>inl hnn for it* uliject 
to discover, first, what aro. in kind aiid extent, ihe int*r- 
cbanges bctweoa tlio a'tr in the luugs iiiid tho bloud in pul- 
lD0itiU7 citi>illnri(M; and, in the Kt'ooml jiliu^e, Uiu nfttuni 
and amount of Uie corresponding gusonud chants betveen 
the rariuuH living tin^iic« and the blond in the systemic 
cajiilWica. Theae proce§scH are the reTenw of one anollicr 
and in the lung run baluuuo, llio blood losing as much car- 
bon dioxide gne in the pnlTnonary ciri-nlution a« it gaius in 
the oyrttemic, and gaining as much oxygen in Ihe foriniT 
a<i it loses in tbo Inlter. To thoroughly comprehend the 
matter it is, niorooror, necosMiry to know the physical and 
ckotoioal cnndittdna of thoHO gnaeft in the* Itinjid, In tlic 
blood, and in the tiwues generally; tor only so can we 
nnderstand butv it ix lliat in difTcront looalitk-e of the Dody 
such exactly ccmlrary priK.-oi'w^ (x-cnr. So far u» tJie proh- 
loma connected with Uie external i-espiration are eonocrned 
our knowledge is tolerably complete; bnt as regards Ihe 
intora:d n«piriition, taking place all through the Body, 
much has yet to be learnt; fur example, W4 know that a 
rouade at work gives more carbon dioxide to the blood than 
one at rest and tnkcK more oxygen fr»m it, but exactly how 
much of the one it glvea and of the other it tnki.'^ U only 
known approximately; as are also the conditions tiuder 
wbicli this greater interchange during the activity of the 
muHiilar tiruuie U cfTcclod: aud (xmccrQing nearly all the 
other tlstttien we know eren less than about mnsclo. Li fact, 
aa regards the Body as a whole, it is comparatively ca«y t^ 




¥ 



CBAXOR8 PROI>VCEt> IJS AJB ONCE BRKATOBD. 378 



fiiKl how great its gnseouH iiit«rchaiif;es with tlu! ur are 
during work nnd rc-^t, wukiDf^ mid Mkcping. while fssting 
or digei>ting, and so on; hnt w]ieii it cometi to lie decided 
what, organs are coiiTOrnod ia each cafe in producing the 
greater or lew exchtiiigc, and how much of the wbolo is due 
to each of thvia, the qneatton ia one far more difficult to 
aettk- mm\ slill vpry far from completely ansft-ePixl, 

The Changes produced in Air by being onea BrMtbed. 
ThcjW are fourfold — ehani^es in \l» temperature, in ita 
moisture, iu its cht'miail ci»ti]ior<ition, and it« volume. 

The air taken into the lunga is nearly always cooler than 
that «i])ired. which has a temperature of about 36" C. 
(97° ¥,). The temperature of a rouiu \* HKiuUlyalKMit8I''0. 
(70° P. ). Th(! warmer the intipired air the lea*, of oounte, the 
heat which ta lost to the Body in the breatJitng prooeas; ita 
average amount \» uLlcu1ut«d as about ctjoiil to 3.5 calories 
in tweuty-fonrhoum: aealorie (^ne Physics) being aA much 
heat a« will rai.te the temperature of one kilogram (3.2 iba) 
or water one dcgrw contignnJc (1.8° V,), 

The inspired air always contains more or leas water vapor, 
but ia rarely saturated: that is, rarely oontaina bo much but 
it can lake up mont without Mhowing it as mist; the wanner 
air ill. the more wat«r vapor it requires u>!«aliiratv it. The 
expired air is nearly suturalcil for the temperature at which 
it {fsivcot the Bmiy, an is readily !>hown by the water deposited 
wlivn it '\i alightly coated, as when a mirror iit breathed 
u|>on; or by the clonds seen isfuin^ from the nostrils on a 
frosty day, thciK! being duo to the faia iliat tho air, as loon 
a« it ia cooled, cannot hold all the water vapor which it took 
itp when warmcil in the RimIj. Air, th«refon).whcn brcalhcd 
once, gains water vapor and carrim it off froni the lungii; 
iho actual amount being snbject to variation with the t«m- 
peraliirc and ^turation of the insptrod air: th« oolor and 
driur this is. the more water will it gnin when hrca) Ix-il. 
On an average the amniitit thus carried oR iu twenty-four 
hours is alwut S.'W) grams (0 ounces). To evaporate tliia 
water in the lungs an amount of heat is required, wbivli 
disappears for this puqioso in the Ilody, to appear again 
nda it when the water vapor condenau (aoe Pbysias). 




174 THE HUMAS BODT. 

The amount of h«at tukon ufT iii tbia way during the day i^ 
Kboat 1.% calories. The totiil <Iiiily \om of hi-ut from th4 
Body through the langii is therefore 10.7 valurii%<, 3.5 it 
worming the iuA{>ired uir luul T.^ in eraponting water. 

TbD mo6t im|)orUiit cliongiM hrought about in th< 
ba'Kthed uir are those in its chcmlcHl composition. Pnn 
■if when ooni]>l«t«ly dried consiat in 100 parts of— 

Br Volumo. By WeliitiL 

Oxjgen aXB sa 

NltroB«D nil 17 

Ordinary >tmoBphor!c air oontains in addition 4 volt 
ofcarbon dioxide in 10,000. orO.Ol in 100, atiuantiry whirhj 
for practical purposes, may be neglected. When bi-catbedJ 
once, Eucli air gains rather more than 4 volumuit in 100 of j 
carbon dioxide, and hw* mlher mi're than .1 of oxygen. 
More accurately, 100 volumes of expired uir when dried con- 
sist of — 

Oxjf/na IM 

mttngen "HA 

OtrboQ dioild*^ 4.S 

The expired air also oontiuns volatile organic Knbstuocefl 
in quantities too minute for chemiud anulyxtf, hut readily i 
dctccl<-(] by tJio now upon coming into a close room it 
nb \\ih A number of persons have been collected. 

8iiico 10.800 liters (346 cubic fMt) of air arc breathed laJ 
tweiity-fotir hours and lose bA per cent of oiygcn, tha| 
total qtuintity of this gas taken up in the lungs daily it 
10,800x5.4* 100=683.2 liters (20.4 oubio feet). Onwi 
liter of osy?en nionsured at 0*C l^M" P. ) anil under a pressure 
e<)iiii) to one atmosphere, wcigho L4'1 grains (■eoCbemisUy), 
m the total weiglit of oxygen taken u]i by the laugs daily isJ 
683.3X 1.43 = 833.0 grams. 0r,nsingincb<«andgruin8ii»' 
standards, 44.5 cubic inches of oxygen ai tb« above tern-, 
)>cratnro and pressure weigh almost exactly 16 grains, so ■ 
the 20.4 cubie feet absorbed in the Ituigs duly weigh 20.4>^ 
X 1728 .*■ 44.6X16 = 12.618 grains. 

The amount of carbon dioxide excreted from the lun^* 



VKyrxLATToy. 



3« 



being 4.3 per cent of the volume of the air breatlietl 
daiU-, is— 10,800 X 4.3 ■*■ ll» = 4C4.4 litora (10.25 ciibie 
feet) lut'u.'iiirod nt the normal teinperatura and jirecfiiro. 
This volame weighs 910 granu, or 14,105 graius. 

If the expiriHl nir bo miioaurcd as it leiivux tlio Body ita 
bulk will be fouitd greater than that of the in9])irc<l air, 
since it not only has water rapor added to it, but u 
expuiidod iu couMOtiuonce of )t« higher tempcrattire. If, 
however, it be dried and reduced to tlio same temperature 
as the infipircd air ita roluiu« will bu found dimiiiit>hi>d, 
sinuo it hu lo«t 5.4 voluinefl \>«x oent of oxygon and 
gained only 4.3 of carbon dioxide. In round nnmbeis, 100 
volnmea of dry inspired nir at xi^ro, give 99 volumuj of dry 
expired air mea8urt;d ac the same tempt-rature and pre»* 
iure. 

Ventilation. Since at every brtatb some oxygon is taken 
from the mr and sumo carbon dioxide given to it, wcrv the 
HtcDDMphcrc around a liTing man not reacwcd Ito vould, at 
lant, be nnaMe to got from the uir the oxy^n he required; 
ht; would die of oxygL-n slarvation or be nuftKuUd, «« such a 
mode of death is c»lled, as rorely, though not quite eo fast, 
us if he were put under tli« receiver of an air-pump aud all 
the air iLTOuud him remnred. Hence the necessity of ven- 
tilation to supply fresh air in place of that breathed, and 
clearly the amount of fi-oi<h air re']ui#il« mum bu doUr- 
mined by the number of persona collected in a room; the 
Hiipiily which would be ample for oue person would be in- 
sufficient for two. Moreover lircs, ga«, and laiuixs, all u»o 
up the oxygon of the air and |^ve carbon dioxide to it, and 
heaoo calculation must be made for them in arranging for 
the ventilation of a building in which they are to be em- 
ployed. 

In order that air be unwholesome to breathe, it is by 
no means necciraary that it have lost so mnch of its oxygen 
as to make it difficnit for the Body to get what it wants of 
that gas. The evil results of insufficient air-supply are 
rarely, if over, due tn lhatcttu.4oeven in the worst vcntiluti'd 
rooms for, as we shall see in the next paragraph, the blood 
can take what oxygen it wants from nircontainingcompara^ 



87ft 



rns BUM AX noDT. 



Hid 

;^ 

ese 
ihose I 

rboS 



tlvely litUe of that gas. The heiidncbe and tironeinc 
which C0ID9 cm from sitting in n Imdiy rciiliiuU)d r<H>m, unci 
tlic Hiini of ouorgv and ;;eDeral iIJ-h<'altb nhicb resultfroi 
pcTiuanciitly living in such, uro doiwudont on a t-ioir poieoi 
ini; of the Kmly by tbe reabxorptioD of the tilings clinii> 
nntvd fpt>m the Inn^ in provioiw ros|)irations, Wbat these 
aic is not !M;oitrjit«ly known: they djubtii'M Ijclong t« those 
Tolatilc biiiiies mentioned above, an carried off in rninut 
quantities in each breath: einoe obscnation shows tiiat 
»ir becomes injurioiw long before the unionnt of ctu-l 
dioxide in it U sufficieut to do any harm. Breathing 
containing one or two per Mnt of that gas pixKinoed 
bj ordiniiry clii-miciil mcihods does no particular ii]jary-,| 
but hreathinjj air containing one per cent of it produc 
by reajiiratiou is decidedly injiinoiis, Itccaiise nf the otht 
things eent out of the lungs at the wimc time. Carbon 
dioxide itself, at k-uat in any sueh perntntiigo as is cut 
moiily found in » room, i« not poisonouo, ns nmid to 
believed, but, since it is tolerably easily estiniulcd in uirJ 
whilo the actually injurious substaticw evolved in breathy 
tng are not> ibo purity or foulness of the air in a nwni 
nsually detennined by finding tlie percentage of carljoi 
dioxide in it; but it must be borno in mind that to me 
much this mn«t have been produced by breathing; otlicr- 
vise the amount of it present is no guide to theqnantity of 
really iniportimt injurious Mib^lanciM present. Of coura 
when a great deel of carbon dioxide i^ present the air 
irrespirable: as for example somotime* at the bottom 
wells or brewing-vata. 

In one minute as we have Bcon (p, 360) .11 X 16 = 1A 
liccnt \<i.'i!ti cubic fed) of uirare breathed and vitiat<'<[ wit 
carbon dioxide to the extent of rather more than four jwr* 
cent; this, mixed with throe timi-'i its volume of ext«n)al 
air, would give thirty liters (a tinlc over one oubio foot) 
Titiatctl to the extent of one per cent, and such air is n^^j 
longer respirable for any length of time with safety. Tb^H 
renult of breathing it for an evening is headache and gpii^^ 
eral malaise; of breathing it for weeks or muntlis a lowered 
toiM of the whole liody — lesa power of irork, physical 




rSATILATJOS. 



877 



m^nliil. And Tew povcr of reetsting dUeuw; the ill effeota 
may not slinw tjiemselrc* iit once, and may acvordingl}- Iw 
ovciloiikc'I, ur i^onudered sciontitic fsnciea, bj ihu uaraleiiB; 
but tlifv lire there ready to iinmifeet Piemwives Dererthv- 
lets. In order to iinvo air to breathe in a fiiiHy pure 
state every man ulnmid bavo for his own allowance at, loiwt 
33,000 Hlers of spacA to U-giii with (about 800 cubit; foet) 
nod the arranjp-inunu for Tiriiilation should, at the very 
Iwwi, rtiiew this at the mt« at 30 litor* (one cubic foot) 
l»cr minute. The nose it, however, the be*l guide, and it 
IB found that at Icwrt Bve tinwa this supply of fn.-*h air ia 
necewury to keep free from any odor the room iniiabitcdby 
nno udnlU In the more recently conBtractcfl hoHpiialu, ta 
II retinU of experience, twia; the alxivo minimum cubic space 
\a allowed for each bed in a ward, and th« roplaecmGut of 
the old air .-tt a far more rapid rate, is also provided for. 

Vcntilaiion does not necessarily mi^n draughts of cold 
air, its ia too often anppo^. In wanning by indirect radia- 
tion it may readily bo secured by fixing, in addition to the 
registers from which the new warmed air rt-iwhoj the room, 
eorroc] Minding upcnings at the opposite side, by which tlw old 
air may |»S8 off to make room fur I lie (rt-nh. An oiwn fire 
in a room vill aliray« keep up a carrent of air through it, 
imd iHoue of the h<«ltliiest, though not tho most ecouotni* 
cal, methods of wanning an npartmont. 

HtovcH in a Mom, unless constantly supplied with fresh air 
from without, dry its air to an unvfholc*omB extont. If no 
ni>pliance for providing this supply exists in a room, it can 
usually be got, without a draufjht, by fixing a board about 
four inchea wide und^T the lowt-r wuih and nhutting the 
'vindow down on it. FroHh iitr then oomea in by tho open- 
ing betwecQ tho two taahes and in a current directi-d 
upwanU, which gnulmilly dltTnitCK )t«elf over tlie room with- 
out Iwiiig folt ag a draught at any one point. In tho 
method of heating by direct radiation, the apiiaratua em- 
ployed provides of itself no means of drawing fresh afr into 
n room, as the draught up the chimney of an ojien llrt-pliiee 
or of a Btove does; and therefore siM'cial itdet and outlet 
openings are Tcry ncvessary. Since few dooriand windows, 





376 



TBB tICJfAS BODT 



m 

sod , 

I 

I 



rortanately, fit quite tight, (reeh air gets oven into dosed 
rouiiij^ in tolorrttjift iitmiKiunfe for one or two inliiibitan 
if there be ontlpta for (he air alreadv m them, 

Cbangee undergone by tbe Blood in the Lungs, Tfa 
are tbe cxiuit revcrsi- 1>[ thoa- mhiliik-il hy the bresihcci 
— what iho air gains the biooO lo§es. and vi'rr irrta. Con- 
sequently, the blood lose* lieat. and water. aii<l cwrlw 
diosidu in the pwbiifniary capiltarie.*; and f;ain* osrge 
Tht!«c gains and losses sre accompanied bya change of col 
from the dark purple which Or' lilood «ihibils in the piiP 
tDonary arUiry, to the bright acarlct itpos8i>»M« in the pul- 
monary TcillH. 

The dependence of this color change upon the aceeas o! 
frcshairtofhcliingKwhilo the blood is flowing through ihem. 
can be readily demonstrated. If a rabbit be rendered 
naconscious by chloroform, and it* chest be opened, after a^j 
pair of bellows hu been connected with itv windpipe, it )j[H 
ecen that, so long as the bcDowg arc worked to keep up 
artificial respiration, (he blooO in the right sideof thebenrt 
(lU tccn through the thin auricle) and that in the pulrao^H 
nary artery, is dark colored, while that in the pulmontir^^ 
veins and the left auricle U bright ret]. Lcl, however, the 
nrtifioial rciipiration lie stop]>cd for a few Mgoiidf and, 
consequently, tlie renewid of the air iu the lungs (iiinrc nn 
animal cannot breathe for itM-lF when it^ elicft is opened), 
and Tory Roon tlie blood retunie to the left anricle as dark 
OS it left Uio right. In a very short time symptonu of 
cuSocation show thcmr^elvi'^ and tbe animal dies, unless 
the bfllow^t Imj ngnin K-t at work. 

The Blood Gosob. If fresh blood be rapidly expoiicd to 
wcompk'Icn vm-num Mean be obtained it givesod certain 
gueR, known a^ the gii«M of flif blood. These *re the samo 
in kind, but diHer in proportion, in venoua and artcrialj 
blood; tlii^re being more carbon dioxide and less oxy; 
obtainable from the venous blontl going to the ]iing« by 
pulmonary artery, than from the urCorial blood coining back' 
to the heart by the piilaiotuiry veins. The gai^cs given off 
by venous and arterial blood, measured under the norm: 
sure and at the normal tcmpomtnre (see fbysics 



iimo 
iria^l 

m 

laele^n 



THB HLOOD ffAfKa. 



8:9 



■ amoant toabont?? -votnmee for ererylOOToliunesof blood, 
^1 and in Uie iwo caaei arc aj follows — 

I 



Vcnou* nooiL 

Oxygen. 10 

CBibon dioxide. tO 

NiiTOjiea... ....._,.. S 



MtfUJStofld. 

SO 
GO 



It 18 impurtant to bear in mind that wliilo arterial blood 
contains some carbon dioxi do tbiit c»n bcrcmovvd by IJie 
air-pnmp. tynoiL: blood also contains some oxygen, remova- 
blo in tbv itiimc way; no that thv difference bvlwct-u tlio 
two i.* only one of dcgnic. Wht-n ait aninial in killed l>y 
piffocation, however, the lasi trace of oxygpo which can be 
yicldud up in a rucnum, diNtppe»rs from the blood before 
ihf heart ceases to beat. All the blood of mich an aitimal 
in what might be called suflocatiun blood; and has a far 
darker color thim ordinan- venoiL^ blood. 

The Cause of the Bright Color ofArtorial Blood. The 
ci>lor of the blood depends ou its red corpusuleii, eince pure 
blood plasma or blood senim is colorloM, or ut inoti a very 
fain t straw yellow. Hence the color cluingc whi<:h ilic blood 
ex])erienceA in circulating through the luugs must bo due 
to some change in its red corpuscles. Now. mioute solid 
bodies suspended in a li<jnid rellect more light when they 
are more dense, other ibingi' being ciiual; and tlio first 
thing that suggests itaelf as the caose of the change in 
color of the blood is that its rtnl cor)>UKclcH havo shrunk in 
tho pulmonary circulation, and st> rellect more light and 
give the blood a brighter took. This idea gains somo 
support from the fact that, as soon under tbe mici'oscope, 
the md blood corpuscles of some animal», as the frog, do 
••xpand duniewhat when exposed to carbon dioxide g»H and 
shi.nk up u little in oxygen. Itut that this w not the chiof 
cause of the color change is midily proved. By diluting 
blood with water the coloring matter of tlie red coqmscloti 
i-im be made to pass out of them and go int«> tolntion in ib« 
phiKmti (p. 16) and il tn found that such a solution, in which 
there can be no question as to tho rellccting powers of 
colored solid bodies msjicndod in it, is brighter red when 
supplied with oxygen tJiau when deprived of that gas. 




880 



TBS nVXAX nODT. 



This BUgg««(« Uint the c >1oring tnnttor or AaimoffiobiH 
the ted corpuscles combinefi with oxjgen to form > Miarl 
compounil, uiid when deprived of ttiatf^a^ Imaa durkeranj 
mono iiur|ili> ooloi-; and further oxpcrira^nts uonfirm this. 
Uiemoglobiii comblDcd with osvgen is Icnova at oxgh<rmo- 
ghbin RTid it is ou itx ]>r(^do[iiinanc« that tlie color o: 
arit rial hluod di>poudii. Utemoglohin uiioutnhincd with oxy* 
gen is Tfduetd hamoglobin; it predominates in voiiouii blood, 
and ix alone found in the blood of a fiutTwHtid niammul. 

Tho Laws Oovenung the Absorptioa of Ooaea by a 
Ziiquid. !>■ order to understand tho condition of the gaees 
in the blood liijuid it iit noiVKtiiry to nciill the goDoml luws 
in accordance with which liquids abtiorb ga«eR. Thej are 
■5 followx: — 

1. A giyen volume of ii liquid at a definite t«mperatnre 
if it absorbs any of a gas to which it in eijKisecI, and yet does 
not conibiDe chcmict^ty with it, lidcoe up a definite volume 
of (he gM. It the gas be comprefmcd tlic liquid will still, 
at the eitmotpni|>erature, take up tho HiimeTol time as before, 
l>ul now it take.1 up a greater weight; and a w^'ight esiictly 
as much greater an the pressure is great<?r. since one vohima 
of B gM under any pro*iiiro oontaitM exactly twice tut mucb 
of the gas by weight as the same volume under liulf th 
preHiuro, and Kuon. Alitrroraqunrt of water, for example, 
ex))iiiiod to the air will dissolve a corttiin ainouiit of oxygen. 
If the air {and therefore thoiixygt-n in it) be compressed t 
ODD fourth its bulk then the water will dt«t>olve exactly tb< 
Kami} volume of oxygen as before, but thia volume of thi 
compressed gns will contitin exactly four times as mncll 
oxygen us did th« wimo volume of tJie giw under the origi- 
nal pre^uur^-; and if now the pressure be again dimiiiinhtHl 
the oxygen will be given off exactly in proportion as i 
proasuro on the tuirfaco of the water decrea«*. Finally, 
when a com)ilot« viicuum i^ formed iilKtve the fltirfaco of the 
water it will bo found thiit the latter has given off all i 
dituolvcil oxy^eu. ThiK hiw, that the quimtily of a gaa 
solved by a liquid varies directly as tho jiressure of that 
on the surfm<o ol the liquid ia known as Dalton's law { 
Phyniw). 



-* 



i 








Tim SBsOHPTiox f)y oasbs or uqviDs. .tsi 

2. The amount of a jpu disioWed byaliquid defMnds. not 
on the totid pressure exerted by all the gsaee pressing on 
iu tturfaije, bur on the fraction of the tutui i>rGMnr« nhich 
.IS exerted by the piLrtitiular gus in ({iieiition. For example, 
the totiil utmosplicric pressure \s equnl to thxt of a oolnmn 
of mercury 7 liO mm. (3u iiiuhex) high. Hut IOOyoIiiukm 
iif ttir cuiituii) approximately t^> Toliimea of nitrogen and 
aOof oxygen: therefore \ of the tot^ pressure is due lo 
oiygpn imd f to nitrogea: and the amount of osygeo 
nbflorbod by water is Just the «tme its if all tlic tiitrugen 
were remored from the nir and iu total preafltire there* 
fore reduced to ^ of JfiO mm. (30 inchw;) of mercury; that 
ii to 152 mm. (6 indiof) of mercury preivMuic. It in only 
the fraction of the totul prepare exerted by the oxygen 
ttaelf which affects the quantity absorbed by water st any 
giTcn tompvrutnra. So, too. of ull Div atmospheric pressure 
I U due to nitrogen, and all the oxygen might be removi'd 
from the air without affecting the quantity of nitrogen 
wlitob would bi] ahititrbed from it by ii given vnlimie uf 
water. The atmois|iheri(r prcssiu'e would then be ( of 7i>0 
mm. of mercuri', or (JOS mm. {'H inchon), but it would all 
he due tonitrc^n pa — and beexaotlyeqnal toth« fraction 
of th« total pressure due to that gas before the oxygen waa 
lemoved from ihc air. When Movenil gaiMM are mixed to- 
jtethcr the fraclinn of the lolid pnumire exerted by each 
one w known as the partial pressure of that gaa; and it is 
thiii parti^ pressure whidi dotormiiic^t the amount of each 
indtTidunl g«« diMolved by a liquid. If a liijnid cxpo«(4 
lo the air for some time liad taken up all the oxygen and 
nitrogen it oould at the piirtiul proasnres of those gaaes in 
■he air, and wore thtrn put in an Rtmo«phoru in which tho 
oxygen liad nil lieen re|iIacod by nitrogen, it would now 
give off all itii oxygen since, idlhough the total git«c<)U8 
pressure on it wiw tho «3inc, no part of it wtis any lunger 
due to oi^gen; and at Uie same time it wonid take up \ 
more nitrogen, rince the whole gaaeona prepare ou its hof- 
boe waa now duo to that giia while bt-foiv only \ of th« 
total was exerted by it. If, on the contrary, Uie liquid were 
uxpoited to pure hydrogen auder a pressure of ono atmoc 



388 



IBW BV31AS BOOT 



pliere it would gire oS all its previoualj dissolved oxygen 
aod nitrogen, r^iiR'uiioEicuf itit)iro«»urcuii itssurfuce woiil 
now bo (liit> to llioAO guaes; and would take up lU! miic 
hydrogen as corraHjtaiuU'd to a prcssurcof Hiatgaa equal 
7fiO mill, of merciiiy (aO inclies). 

3. A liquid may be such as to combine chemically wi 
a gas. Thea the amount of the gas absoibcd i» indcpcD' 
dent of the partial prc^surt' of tlic gae on ttie surface of 1 
litiuiii. Tb«<iuuiitityttb»orU!d wilUk-poiid upon how muc 

Un- liipiiii (.'lui ."mi-! .■, iili. Or, u li<{uid may partly 

C(iiii])w«!il of iiii:L^. v,ij].li .-Jiii[ily dissolve a gm and {wi-U; 
of thiugs which cliemicaJly combine with it. Then t! 
amount of the gas taken up under a given partial press] 
will d«]>end on two tliingx; a certain portion, tlmt merely 
dissolved, will vary with the prcesiire of the gas in qneation; 
but another portion, tliat cbemicully combined, will remtuo 
Ihe same under different pre»«urc& The amount of this 
second portion depends only on the amount of the snb- 
sbmc^e in the liquid which can chcmicully combine with it, 
and ia totally iadependent of the partial presiure of tli< 
gas. 

4. Bodies are known which chemically combine witb 
certain ga^itis when the partial pre.i>^iirc of these is con^der- 
hI)1o; but the compounds Uuls formed are broken up, and 
the go^ liberated, when it4 partial pressure on the surfaoo 
of the liquid falls below a ceruiu limit. 

5. A membrane, moistened by a liquid in which a gais is 
soluble, does not eitseiitiaUy alter the laws of al^mrpUtui, b; 
» liquid on one side of it, of a gait present on its other side,> 
whether the abiiorption bo due to mere solution or 
chemical comltinatious or to bolb, 

The Absorption of Oxygen by the Blood. Applying 
the physical and chemical fact^ stated in the precedin 
paragraph to tlio blood, we And (hat the blood contains {1 
plasma, which simply dissolM-s ris;yg«n, uiid (a) hamoghbtHt 
which combines Willi it under some partial pressures o: 
that gas, but gives it up under lower. 

Bluod plasma or, what comes to the same thing, free! 
senun, ezpo«ed to the an', takes up no more oxygen tliau 



1 



ABSORPTIOS OF OXTGBX BT Tlff7 BLOOD. S83 



mnoh Vflt«r, that il aboat 3 Tolumes of the g^ for oroiy 
100 ot the liqnid, ThU qnantitjr obers Dalton's law. 

If insteiid of hlood twnim trc»li w)ii[>jH-il Moud be om- 
plovtxl. the quikutity of oxyg«n taken up is muoh gr«atfir; 
tlii» extra qnantity must therefore bo taken up by the red 
corpiucles (in poeM«sing which u'hi[i{wd blood alone diftc-rs 
from blood flcrnm) and it dooj not obey Dalton's law. If 
the partial preaaare of oxj'geu on tbo Biirfaoo of tlie 
whipped blo<^ bo doubled, only om muDh more oxygen will 
1k! titken up &s correspondB ta that dinalred ia the plasma; 
and if the partial proeeure of oxyg«n on it« Rurfiico bu re- 
dut-cd to one Imlf only a ri-ry stnall amount of oxygen {\ 
of thiit dls^iolved by the neruin) will ho girou uB. All the 
much larger qu:intity tuken up by tho rod vorpuxulcs will 
be nnaffcct^id iiiid muHt therefore b« chcmicslly oombined 
with something in them. Since 90 per cent of their dry 
weight it nuulo up by htemoglobin, and tlii* Uxiy wLeu pro- 
pared pure ii< found capable of oonibiuing with oxygen, there 
is no doubt that it ie the hiemoglohln in tbo circulating blood 
whiob carries around nearly all the oxygen found in it. 
The red corposoles are so many little pookagoa in which 
oxygon is rtowed awmy. 

The compound formed between o^gen and bsmo^olnii 
i>, bowoTcr. a very feeble one; .the two OMily wparute^ and 
always do m> whuti the ox};ri-it pretuiure in tbo liquid orgiu 
to which the oxyhiemoglobin ia exposed falls below 25 miU 
limotont of merctir)'. Ilence, in an air-pum)), the blood only 
given olT aome of its mnull portion of merely diitsolred oxy- 
gen, until the pressure fulls to about ( of an atmo«p1tero, 
that JB to ^ =s 125 mm. (5 iuchvs) of mercury, of whiob 
total pre^ure one fifth {iT* millimftient or I indi) \t due to 
the oxygen preeent. .Vs noon as tlua limit is reached the 
hfl'ino^lobiti gives up its oiygcn. 

Consequenoea of the Feooliar Way In which the 
Oxygen of the Blood is Hold. The first, and most im- 
{lortuol. in tlint Ihi- blood can lake up far more oxygen in 
the lungs than would otherwise be possible. Since blood 
Kmm 0X]>W0d to pure nxvfrcu lJik<!(i up only 'i viilumes for 
too, blood exposed to the air would take up \ only of that 




¥ 

h«^ 



TAK BOOT. 

amount at ordiuat'v t^mipemtiircH, nnd Htill loss nt the tem- 
pcraturo of the Body, were it not for ita liffimoglobiii. I 
tbe liingR even l«tu irould bo tukvu np, since the air in t 
air-cell^ of tliosc organs is poorer in oiygoii than the 
cxterniU uir: and coiueqiieutly the partial pre-ttiutx} of 
thut giLK in it IK lower. 1')ie U<litl uir taken in at each 
breath serves merely to renew directly the air in the big 
bronchi; the deeper oiiv examined the pulni9iiury air tbo 
letti oxygt'n mid more carbon dioxide would be found, 
till, in the layers fartJiest from the exterior and onlj rv-^^ 
newed by diSusion with the air of the large broDohi, it H^M 
octimntcd that thu oxygon only oxiHta in ttnch quantity that^^ 
its partial presaure is equal to 130 niiUimeteri! of mercury, 
instead of 152 as in ordinary air. In tJie eecotid plaoc, u 
iwvDiiDt of the way in whiub hoimogluhin combines wit 
oxygen, the qnantity of that gas taken up by the blvod i< 
independent of such variutions of it« partial prei^auTe in th< 
atnioDplicro an we are subjeoted to in daily IJfo. At i.lie top' 
of a hi];h mountain, for example, the almogpberic preiisii 
li grcuily diinliiiithed, but trtill wo can breatho freely and gotj 
all the oxygen we want. So long as the partial pretwure u; 
that gas rcmuiui< aboru 'iTt miltiinetrrs (1 inch) of mcrutiry, 
iJio itnionnt of it taken up by the blood will dopeud on how 
much bsemoglobiu there in in that Ii<{uid and not on ho 
much oxygen there ia in the air. So, too, breathing pure 
oxygi'ii under a pressure of one atmosphere, or air ooin- 
prc!«sed to j or } ite bulk, dooi! not increase the cjuautity of 
that gikj> tttkcn up by the blood, apart from the very EniolL' 
cstra quantity which would be dissolved by tlie pltkimft. 
■Ml the wide-spread Htatemonta found lus to the oxliilarutiu 
and excitement canned by breathing ]uire oxygen aiv, as a 
matter of fuct. erroneous, being founded on early cx{K!r> 
mcnta made with impure gas, and corrected by many eum- 
petent ob^rrera since. 

The General Oxy^n Interchanges in tho Blood. Wo 
miiy now try to di-piivt wlwt Uii|ii'i>iis u> the blood oxygen 
in a complete circulation. Su|>po!-e we have a quantity of 
arterial blood in the aorta. This, fn.«h from the lungs, will 
have it« Inemoglobiu almost fully combined wJth oxygen 







TIIK ULOfil) (lASKS. 



385 



and in tlio itale of uxviiiHniuglobin. In the blood itlu^nia 
Gomo mon; oivgeii will be diitiolved and hi> iiiucli iia itniiwors 
to tt ineuutu ot Uut giM equal to 13u mm. (5.2 inclteiij of 
mercury, which i« tliu imrtiiil |i]'o«e(trt' of oxygen in the 
pulmonary air-cvll^ 'VIuk ttmiioit of I lie gtm in I In? jiliuniu 
irill be moru thim auffiuicut to kecji tiio bwiuo^lobiu rrom 
j^tvin}; off iu itxyjg^a. JSupixmu tiiv blood iioir enters l\ie 
capillaries of a inusflir. I» tlielittuid nioitttening thisorgiin 
Ihi; oxygen (on>>iiiti i:( ulmoit nil. Hiuce the tissue tilvmfiiU 
are i^tv^dily takiitj; tlii^^itH ii[> from llie lymph ui-omid them. 
Coiisei|iiently, ibroiigh lhi> capdl^ry walls tia- pbufiuu will 
givuolf oxygon until tlii- t«u»ion of Ihut gurt iiiitfidli< bi'luw 
2J( nitlltiiiet«ra of mercury. Ininiedialely some of ihe oxy« 
lia>mo);lobin la decomposed, and lliL>o\ygeii lilicruUd i» di«- 
H)!^^! in the pluMiiu, anH from tlii-rf jijtaiii |)asHud on lo ihv 
lymph outride: mid so the teumou id the pla&nia is ouce 
more lotrurod luid muiv oxy tia'itu>gh)biii dccumpot«d. This 
Koes on MO long as the blood is in the c-apillaric^ of the 
iiiiimIu, or at any nito to long lu the maeculur fibres keep 
ou ukiiig oxygen from the tynijih bathing them; if they 
ccikw to do so of eourM the t«n<ion of that gaa in the iympli 
will «oon oome to 0(|iinl tliat in Ihit plMma: the latter will 
therefore ccuw lo yield oxygen to the formor; uiid so iimin- 
lain it« tcouou (by the oxygi^n roceivod from the lant <Ie- 
ooniptxcd oxyhmnnglobtn) at a |)uint whii'h will preren 
the lilieriitionof any morG oxygen from nudi ru<) cdrpiisolm 
IV hiive not y«t giron alt tht'irs up. The blood will ii>iw go 
on an onliiiary vcnoitn blood inUt the veina of the minclo 
and fto hiusk to the lung^ It will o»nitii*t of (I) pl'Ditmi 
with oxygon dissolved in it at a tension of about 'i:t inilli- 
metorx (1 inch)* of mercury, (i) A number of i-ed eor- 
puRokui couliuning i-ctlut-etl hwmoglohin. (ji) A luimher of 
red oorpnsclee containiof; oxyhD^moglobin. Or {jcrhapH tt!I 
»f tlu) rod corpuscW will mntjiin fomo reduoed and some 
'ixidiidl hiemoglobin. Tho reliitive |«itportion of reduced 
imd unreduced hemoglobin iiill ilc'iicud on how active the 
iiiiisclu iru-fy if it wurkoil while the blood Hnwod through it 
it will have used up moie oxygen, and the blood leaving it. 
will conseiiii'-iitly be muro TCnons, than if it rested. This 






wttel 

I ■iiillii m > Bef^ the pwiiil 

blood plMMB atMh kn^ oiigta wdl W 

bitcr. aad tto tCBM* a< ibu fM IB tke j 

nBMd afatr tt> li»it 1 gtntfc h M glil 

b. Hsoce, M fa« at the plMon grti aVTBOi tin* nd cor* 

pnadM wbicfc cnatMa tax ndmatd hcm^^alna rvb H. and 

•o iu ttj^n tmman m kapc dosm briav ifeat ia Ute oir- 

cdk ud aO tte liBMn^iii it atiAd. ThM Um 

atjgea icoBoa of ite flHB* TMca k> Una of tte ^H is Uw 

■ir«db; oa ihr imgca it ^Borlcd, and tW Uaod i 

(a tW left nnefe irf tba iMrt ia tfae 

tar aa lujgu ii sODCcnM^ aa vwo w ooHnMBBM lo xu 

iowit 

TbaCtotam Dioxida of Om Blood. TIm »ne gEsoal 
law* appiT to this at to tbs Uood mcjgtn. Tb« gas m 
panly MBdy <ri»nlw<ii aad paitiy in a Iwmq cfc— iwl «md* , 
Uaaboo bmIi Uka tW trf aijgts vitk h■■^^^l■■, bot 
tlw bodj vhb rtucb is cwmUiwa ia iha wa; czitce to tbo 
plaoaa ^id aot ta cfaand eorpoadw; «hia it a^bt n 
sec ovtaaly knows. Batfilw tfu^ aane ■<■« cvtuni 
dionde ■■ tuAlj eo^ h iaad and it oaly ^t^ «A an tb« 
•ddtCiiNi of a litf BB g er acid. The partial fttmatt at aahen 
dioiide ia tlM ptimnagj air-odli >• aboot 40iiua. (1.6 
iadtea) at menm i j. Ibweian the leaian of that ^a to 
the tiitliBoaai7 cqAuiei nut be mm than tht«. Oa 
the otbor band ita tiaacia in artrhal Uood most be 1m> ! 
thin that is the Ijnph aroond the tiamea; othmiae it 
eoeld itot eater the Uood in the apMaic ctrddatMa, wlucb 
itdao^aapravadbrtbebet tbatlMToli.«C««aoaiblood j 
gire off 90 of thia gM, aad 100 tdU. «< arterial onlr Ml I 

TbrnitrognKWQtaiaedintbeUoud ii,io&rM vekitow, 
ijnile tmimportanL ^^ 

Zntenanl BeapdntioiL. Aa to the amooat of 0l7g^| 
and ipf each rtnwto aad tbe qaaatitj of catboa dioxide pro- ' 
dated t7 it w« know bat litUe; the foUovias painU tent 
hovenr, tolerably oertaia: — 

1. Tlie aauoat of cartMO dionda prodaeed ia aa 




lyTERXAI. RRtPIItAriOX. 



887 



in a giv«n limo beam no constant ratio to the amount of 
oryifen taken ap by it EimiiltatieouBty. This U certainly 
true of miiTidc, for fixpcritnent ebows tbat muBcnlar work, 
while it oontinuee, leads to an elimination of carbon dtoxidd 
containinf; more oiyg^n than the total oxy^n taken ap 
from iho tungs in the same timo. The balnnco is of course 
iiufle u[) ill subsequent ])eriod» of rejit, when moro frw 
oxygen ia taken up than ia eliminated in combiuation 
doriog the same time. Moreonr, a Sroffa muscle exciHCd 
from the body nud put in an atmoHplicro containing no 
oxygen and made there to contract, will evolve with oiKh 
contraction considerable quantities of carbon dioiido— 
allhongh from thu coudiUonfl of the experiment it can 
receive from oataido ao uQcombined oxygen, and other 
experiments ehowtbat it conuinti none. Hence the liring 
muiiciilfLr tibre must contain aHubAiance whtdi i« dccom* 
posed during aotirity and yields carbon dioxide as one pro- 
dnot of decompouition; and this quite indBp^ndcnt of any 
simtiltMncouit direct oxidatiotL 

'2. What is true of muscle is probably true of most of 
the tissues. During rest they take up oxygen and fix it 
ID the form of oaniplex compounds, bodies which, like gun- 
powder, ore itwlily decomposed into nmpler, and in iiuch 
decunipii-sitiona liberate energy which is used by the work- 
ing tissue. One product of the decomposition is the 
highly oxidixed carbon dioxide, .^nd this is elimiiinUid; 
other products are leas oxidized, and possibly arc not elimi- 
natod but budt up agnin, wilh fresh oxygen takcii bom tha 
blood and fresh oarlwn from the food, into the decomposa- 
ble Bubfltanae. 

3. During the day a man gives off from his lungs more 
oxygen in i^arhon dioxide, Uiuu ho taki.-^ up by the wme 
organs from the air. During the night the reverse is the 
CMe. This, huwcvor, hiis nothing to do with the alternating 
periods of light and darkness, as it has in the ca«D of a 
green plant, which in the light evolves more oxygon than 
it oonsamE^ and in the dark the oontmTy. It depnds, 
rather, on (he fact that during the day more muscular effort 
is exsrted than at night, and tlie meals are then taken 



raw auuAy bopt. 



l'MmI ■^jgp"**^ The actirity of the miucles and Ute digestii 
' ghuids ia d«pendaut ou procoau* which give rise to a large 
jirmluotiftQ of carbon ditixide &aA, diintig rhc night, wbon 
both are at rest, more oxvgeo U taken up than U c^tuliiiiicd 
in the carbon dioxiilc olimiuuted. If ti man works nud 
t»kc« hi* inuulfl at ni^liI, and fllvi'iJit iti llii> lUy, the usnal 
mtii)Bof hJH gaeeous csf^hatigi* with the esterior are entirolj 
reversed. 

4. The amount of work that a muu'B orguug do, is not 
de)>cndent on the amount of oxygen supidicd to tlu-in, hiil 
the amount of oxygon uaed by him depends on bow much 
he OBCfl hia organs. The quantity of oxyj^m xupplied mu£t 
of course always be, at least, that required to prevent suffoca* 
tion; but an oi:oo«8 above this limit will not make the tissues 
work. Just as a man must have a OL'rliiiii amount of food 
to keep him idivo, m he must have a certain amount of 
oxygen; but as extra food will not ninke hi« tissues or Aim 
(who is physiologically the sum of all his ti.ssuw) work, 
ajiiirt from «onic stimuhiB to c\i-rtiiin. m it jb with oxygen. 
Highly arlerialixod blood, or an abnormal ammint of blooil, 
flowing through mi organ will nut arouse it to activity; 
the working organ, niuwcle (p. 'ib') or gland (p. 260), for ex- 
ample, ustudly getd more blood to su|(])ly it^ extra iiocds — 
ja«t as a healthy man who works will have a better apjio- 
tite than an idle one; bub Ui^ taking enure food by an idle 
man will not of itself make him more onergetie, so itcitlier 
will sending more arterial blood through an organ exoitc 
it to aclivity. 

6. The preceding statement is oonlirmcd by oximrinients 
which dhow tliut an oiiiniul ukcs no more oxygen in un hour 
when made to breathe that giu in a pure static, than when 
allowed to breathe ordiniiry uir. In i>tber wonis. the 
amount of o\\^t:a an animal oses (provided it gets thu 
minimum neecMar}' for health) is dc]K-ndeDt only on how 
much it uses ito tiftsne^ Tlic-iw (llio rvst in mostcascs liiih- 
ject to a certain amount of control from the nervous) de< 
termine their own activity, and this, in turn, how much 
oxygen tthall be used in the systemic circulatioa aud ro* 



mTKRNA L RE8PIRA TION. 



38» 



stored in tlic palmonary. In other words, the physiological ' 
work of an aoimul, which in turn is largely dependent upon 
how external forces act upon it, determines how much 
oxygen it uses daily: and not the Bup))ly of oxygen how 
mitch its tissue iictivity bIioII be, noless the supply ginka 
below the stiu-vution limit. 



CHAPTER XXVI. 

THE NERVOUS FACTORS OF THE RESPI 
TOltV MECIIAXISM. ASi'UYXIA. 



The BeBplratory Centre. 'I'he reainratory movements 
nrc tu u LTi-tJiiu eiteut uuJcr the oontml of tJie will; wa 
caa breathe tai^-r or tilowor, tliallowcr or mure dcojil;, as 
irv iri«h, und can also " hold the breath" for eome time— Imb 
the yolnutarf control thus exerted is limited in exteat;^ 
DO one mn commit suicide bv holding faU breath. In. 
ordioarjr ijuict br«ithtng the moTements are qtiite inTolnD- 
t«y; they go on perfectly withont the least attention ou 
our |wrt, aiid, u<n only in .«loc|i, but during the nnconsciotUi^ 
Dessof faintingorof ana|>o|ilecttcfit. Tbetiataral breath-^ 
ing moTem«ato are therefore cither reflex or antomatic 

Th« mnsde« concerned in prodncing the changi.-^; ia ths 
dtert vbtch lead to the entry or exit of air an? of the 
ordinary Mrip«.>d kind; and these, as wo lutTCHcen. unlycon- 
tnot in the Body under tho tufluonoc of the ncrreti going 
to them; the nerrea of the diaphragm are tlie two phrvuio 
n«rrc« (p. 161), om.- for each «idc of it; the oxtcnial intcr- 
fwatal mnaclea are su)iplied by certain bnuicliea of t)iv dor- 
sal spinal nence, called tho intercostal nerves, if tlio 
phrenic nerT<M bccut tho diaphragm (x>aiwait« contractions, 
and a similar paralysis of the external intcroostals follows 
aeotion of tho int«rc<>«^tal ncrvt-?. 

Since the iiutpiratory mu.-i:Uti only act when slimalalcd 
by nerrons iui)>uls8S reaching them, we have next to aiMik 
where these iinpulwfl originate; and exporimeot shows thab 
it is in the mtduVa Monifala. All the brain of a cat or » 
nhbil in fri>nt of the mmlnlla can be remored. and it will 
Mill go on hraiitung; and cliildrvn are Mntotimt* bom ' 





THE RssrmATOsr CByritR. 



891 



L 



tbo mednlla oblongata onlj-, the rest of the brain boiiig tin- 
devolo[ied. umi yet thoy brctttli« pcrfcctjy well. If, on the 
other httnd, tJie Hpinal it>rit Iw divided uninodistcly b<?)ow 
the incdalla of an animal all breathing movements of 
the chest cease at onoe. We conc-lude. therefore, that the 
nervoua impuWs railing f»rLli oontnictioiifi uf the re^iiira- 
tury niii«vlLvi iiriso in the medulla ublonguta, and tnircl 
down the -siiiiial cord and thence out along the ]>hi'eiiic iind 
iutei-oostat nerres. This ia conlirmed by the fiict that if 
th(! spinal cord be cut acrui« below the origin of Uiofoarth 
pair of eerviml spinal nerves (from which tJie phrenic* 
mainly arise) but above the first dorsid spinal nerres. 
tiiL' respiratory inovemeutit of tho diopliragin conlinuo but 
thoite of the intercostal musoles oeose; this phenomenon 
has sometimes been ob^^rrcd in men stabbed in the back, so 
an to dirids tho spinal cord in ihe region indicated. Finally, 
that the nervous impulses exciting the inspiratory masclea 
originato in tho medulla, is provod by Uio fact that if a 
BnuU) i>ortian of that organ, the eo-colled vital point, 1m 
dtvtroyed, all tho respiratory movemonl« coaso at once and 
forerer, althongh all the rest of the brain and S]>inal cor<l 
may bb left nninjured. This partof tho medulla is known 
MM the rexpiratmif ftnirt. 

In the above atntcments, for the sake of simplicity, atten- 
tion hua been chietty confined to tlie diaphragm and the 
intercostal mnsclM; but^rbat ia eaid of them is tnie of the 
respiratory innervation of all othoir breathing niiuK-Ies, 
whether expiratory or inspiratory, normal or extraordinary; 
in all CSM'H the impulse giving riw to a rc-«iiiratory move- 
ment starts from the centre plaoed in the medalla oblon- 
Sata. 

Is the Beaplratory CoatroRefloxf Since this eentro 
jBloes on working indepcnd<mtly of tho will we have next to 
inquire is it a refleit centre or not; are the efferent dia- 
{-hargC!! it aenda along the respiratory nerves duo to afferent 
impulses reaching it by centripetal nen-i'-fibrea; or doe.* it 
originate efferent nervous impulses indciieudentlyof esciti^ 
tion through afferent nerve*? 

We know, in the first place, that the respiratory centre i% 



392 



rim uuMAy boot. 



m 

iie 

1 

1 



largely nnder reflex coutrol; a diwh of ooM walci on tbe 
ekin, ttiQ irritntion of thu niual mucous membmno 
Kiiuif, or of the larviix by a foiirigii Imdy, will <^iu'h cHoac 
modificaiion in the ivjqiirator)' movementj* — along indrawn 
breath, a enoezc, or a cough. Hut, although thu* subject 
tn iiiflut>iioi.^« rcitchiiig it by uiTrrvut nerrcs, th« rcspintury 
centre eeetna e»«utially independent of nub. In man; 
itimaK ai; rabbit^s, (»nd in some tn^n.) marked bre^lhin 
iioyi;mfut.'< tuko place in the noMtrilK, which diluU; (Inrio, 
iniipiratioii ; aud when the spinal eord of a rabbit iscut cloM 
to the medulla, thiu cutting oH all afferent uervous im- 
pnlsQS to tjie respiratory cciitn; oxct^pt Mich m may reach 
it throit^'h RraniaJ nerve-s the re^iiratory mnremcntoof t 
noiitrilti Htill continue until death. The movements of 
riba and diaphragm of course ceaee. and bo the aniu. 
diea vor}' fiiion unices artilk-iiil ri'."]*! ration bo maintained^ 
Moretncr, if nftcr cutting tim npimil cord iw above dcBcri bod, 
all Blleri^iit cranial nervea be divided, au na to t'lil otT thfr 
i'('i>]iir»toiy contri; frcim all poi^ible itlTorcnt ucrvoue iU' 
pulses, the regular breathing movemejita of the nosiri 
continue It is, therefore, obrious that the nctirity uf tlio 
rci^piralory centre, however much it may bo eupable of 
moditieation through acnsory nerves, ia oaseutially tude- 
pcndcnt of them: in other word« Uiv uonnal reapirato! 
movcmenlii are not rcflox. 

What it is that Excites the Bespiratory Centre. The 
thing Ihat, abovt'ulIi)llK'i«, iiilliu-nccjt ibiTC!-]iiratory centra 
ia Uie greater or le«e Tenoaity of tlie blood flowing throug 
it. If thiB blood l» Torj- ricli in oiygcu and comparativcl 
poor in carbon dioxide the rcspimtory centre act§ but feebly, 
and the rcepinUiona arc ithallow. If, on the other hand, thi 
blood be highly vonona the respiratory muv<-niuntt) are mo 
rapid than normal, and forced, the extraordinary uiiiAcIcao: 
rcKpirution being cullod into play; thia stale of riolen 
labored respiration, due to deficient ai^nitiouof tlio blood, is 
called (lijupuwa. Normal quiet breathing \n fvpn<ra. If the 
blood be highly aerated, us by keeping np forced artificial 
mpiration for a time, nil rv«pir«turiF' morementa ceiwo; tbo 
highly oxygenated blood does not excite the respiratory 





fiTlMUIJiriOX OF TUB RESPrRATOIlV VESTRE. 3tl3 



n, uud tlieauimal therefare remains without breathing 
»t all for £ome tim«; tliia ooiiilitioii i* apiwa, llmiigli phy- 
eiciunK l>y the word ajitia-ii commonly ruesu mei\.-ly extivnio 
dyspocea. U an aiiinia} be mudo upnwio nod tlic artificial 
respimtion etuppud, it» tiloud, during tlio oc^tuilioii of tfao 
rMpiratory movcmi-iil-'i, gradually losing oxygen and recelT- 
ing carbon dioxide, passes into the sliito of ordinary blood 
and again stimulates the rtwpirutory centre, and tbo brcalli- 
ing niuv«ment« then reounimence. 

How it i* that hi|;fa!y venous blood enures great eiciia- 
tion of the re«piratory centre, and highly urtcriul t'C!>Nition 
of its aottTity, it nut ccrljunly known; but we may makt- tiic 
following provisional hypothesis. The chemical changes 
occurring in the respiratory centre giro rise to a substance 
or Kiilxtluiire^ whieh .itimnlat« ittt nerve-ccllii. When tho 
blood is ricUy supplied with oxygen this substance is oxi- 
dized and rojiiovcd ait fiut as it is foriniHl, and so thccontn- 
is not excited. Wlien the bluod. on the other hond. is nn- 
UBuaily poor in oxygen, lhi:i Simulating body aoenmiilatoi 
and the respiratory dici^harges become more jiowerftil. 
Under normal ciruuni«tanccs the blood oxygen is nut kept 
quite up to the point of cntiix>ly removing Ibis exciting 
subj^tjuiec, and the centre is stimulated so fur as to ])ro. 
ducc tbo natural brouLhitig movements but not the more 
forced ones of dyspnoHi. That thestimuIutingouuHc, what- 
ever it 'vs. acts upon the respiratory centre and not upon the 
various orgiitia of the Biidy and thnmgh their sensoiy 
nervoa, in turn, ujion the miilullu, is proved not ouly by the 
facts above cited showing that the respiratory centre con- 
tiuuce to act when all afferent nerves are cut off from it. 
but aIm) by oxpcnmontswliiehshovr that the circulation of 
veueu» bloud through ibu body of iin animal, while iit the 
same time ita respiratory centre is supplied with arterial 
blood, does not produu; dy^pnwu: while sending venous 
bltiod to the medulla and arterial to all the rest of the Hudy 
doM cause dyspnopa. 

WhyaietheBeapiratoryDiaohargoaBhythmlof Rvery 
complet* rc*pir:itory act cousisr* of au inspiration, an exj)i ra- 
tion and -J, pause; and then follows the inspiration of the 




Tus Btnus ftoor. 





I ^fUBt farathi^ Oen if ■» 
I tfa m a i^i a w a^ tk* |mr. The in-' 
t ■ tha oalf aetnc p«t f p. 3SS); flic e^f iimtino and 

. on BKUcnlv iiuLti \ it i mdi tocfv- 
faw^ w>tfa« rB M Min BO<ib«d»Bhuyrf ■gr— i M p afa B B 
froB tha ntpnatej ceatiBL Bat then, man- ask, if in 
iwith tha h]^b«Bi nadtin tha hrt paragr^A. 
' aottia M ewutaoU; hciag dated. wfaT is it 
■ot aln^i dflofaaipBf? whj doca it oslj and aat nn-nnw 
jfaJiMatiaterTab? Tto ^al ten, whieh ii a— «aPj Hat 
mmt aa that whjr tha heart bcala rii7th»eallj. hriong» to 
tha hi^»Hpoaa of W^wolop- aad no obIt at pnacnt be 
h r|»thnie aH y apntrad. Lai aa coMider, for a naaKnt, 
iwiliiiaij Machaaieal cuvBHataHoat nadar whiA a (teadj 
aqpif ia taiaad iats aa iataBitleat diaehtga. Sappooe 
a tdw eteaed v*tcr4^t b^ov br a hi^ed i&te, iriDch ia 
keptdrntbraepriiig. If a«eadTai«BSi«( TatertapDond 
iniotha tahafn»Bab(ne,thawatar*iUnBaBBtil itevrigbt 
ii abb to uHwi o ui a tha -pnmutt of tha aprin^. *ad tba 
plata vin than ba lorted do«a and wmc water Sow oob 
na aprtag viO thaa praaa tha platv op again, aod the vatvr 
BOcamnlate nntil its weight again force* (>|«d the bottom of 
the taba. and tbca* ia ■pother oatraib; koA m on. By 
ap p M illg a oeruin TCateaaM to tha exit w cnoM thus 
tarn a sleadT inflow iaio a ihnhmio ootJIow. Or, take tha 
ea»of a taba with one end iiniaefHed in water and a ataadjr 
atnam od air wst inio its other SDd. The air win emn^ 
froia the iaantened eod« not ta a atcad; coirent, but ia' 
■siea of bobUea. Ita pro a m e in the tnbe mmt 
aotO it i« able to orerooaie the oohMire forc« of the water, 
Bad then a babble borata forth; afMr tbia the air baa agata 
to f/A np the reqvisite preeeora in the tabe before another 
bt^Ue if ejvvted; and to the (vntiniioiu ntpply is trans' 
funaed tatu aa intenniiteni delirm'. Pbviiioto^cta eop- 
poae aoaMtbiag of the fame kind to oocar in th« reapira- 
tac7 eentia. Ita aerre-cella are aJwavs, under Uinial 
cireanutaaeea, being exdtad: but. to di«diikrgie a nervous 
inpolae alone (he efferent respimtovr wmx, tber have to 
ovennme a orrt«io reciatanoe. The nertoos un|>iilae« har* 






^ 



CAVSE OF THE BBSPJBAWRT HHYTHM. 396 

to accDmaUte, or " gain a h«ad," before they travel oat 
from tho centro, and, ufler their dt»chai:gv, lime i» required 
to attain once more the neoeesary Wei of irruption before a 
freali innervation is sent to tho mnscles. ThiM method of 
aooonnting for tlie n^sjtiratory rhythm iti known u the 
"rttistance theort/." If not sitogethor EatiafactorT it ia at 
least far prefcmhlo to tho oldvr mode of considering the 
'(uCMtion solred by tuwtiniing a rhyihmio chancier or prop- 
erty' of the respiratory ccnti-e. It girca a deflnito hfpothe- 
sis, which accords with what is knonn of general natural 
blur* ouUide of tlie Body, and the truUi or falniiy of which 
ean be tcfitod by experiment: and so serves very well to 
show how tcicntifii' differs from prr-scientlBcrOr mcdiiBTiLl, 
phywologj*. The iaiur wnn uonU'nt with ohserTing thinga 
in the Body and considered it explained a phenomenon 
when it gave it a qama. Now we call a plienomenon ex- 
plained, when wc liave found to what general category 
of natural lairs it can be redaced as a speciid example; 
and this reducing a siwnial caae lo a pnrtietihtr inunifi»ta- 
tion of souio one or more general properties of matter 
nirciidy known jx, (if eotiree, all that wo ever menu wln-n we 
Bay we explain anything. We explain the fall of an apple 
and the ri»c of tJio tides by referring them lo tlio elnes of 
general results of the Law of Gravitation; but Uic why of 
the law of graviuition we do not know at all; it is merelya 
fiKt which wo h»vo found out. So with regard to Physi- 
ology; we are working scientifically when wc try to reduce 
the activities of the living Body to gpecial uislanoes of 
muchauicnl, physical, or chemical laws otberwiae known to 
us, and unscientiUcully when we lose sight of that aim. 
Ccrtxiin vital phenomena, as those of blood-pre»iure. we ean 
thus explain, as much as wecan explain anything; others, m 
the rhythm of the respirator^,' raor«mcnts, wo can provision- 
ally explain, atlhoiigh not yet certain that our explHiia- 
tion \a the right one; and still othrrs. iw the iilK-nomenii of 
consciousness, we cannot explain at all, and possibly never 
will, by referring them to general pnipertirs of matter, 
since they may be proiicrtieg only of that particular kind of 



398 



TUB nVXAX BOOT. 



luitltiT called protoplttstn, and jterlisjid onlv of Bome ti 
tiej> uf it. 

The Belabon or the Pneutnogatitric IfervoR to Uid B6B- 
pirfttory Centre. We have iioxt to coimider if any ]>licno- 
mcim [in.-Ji'nloi hy the living Bi>d_v give support to the 
re-iistance theorr of the rcupiratori- rhythm. A Tory im- 
portant ooUntctsl prop to it is given b; the relation of the 
pn4-tnnoga«tric nerves to the nto uid force of the rcspin- 
lory moTcments. These nervea give branches to the lan-iix, 
tlio wiitdpiiKT, and ihc hings, in a<liliti<>n to nutncrouK otlif^ 
port*, and lui^hl therefore be Ha^iiecled to liavc sonietbing 
to do with breathing. That thoy are not concerned iu iu- 
flnenciiig the re^ipimtory niiiiioled directly \» Hhovn bj the 
fact that all of these musclea (exeejit certain Hmall ones in 
the Uryiix) contract se usual iu hmthing after both 
pneuinogiMtric nerrm have been divided. Still, tlie section 
of l>ath nervea has a oonsiderable influence on the reepira- 
tory movomente; ^tyhtcome slowtr and dttprr. Wo niBj" 
nnderstaud this byeuppoaing that the reastanoe to the di«- 
chargv# of tlie respiratory cvutrc it liable to variation. It 
may be increased, and then the discharges will be fewer and 
]H;gcr; or diminished, and then they will be more fri?>({ueut 
bat each one lesa powerful. If the iipnng, in the '\Wu<-\ nt- 
tiuQ need in the prcc«ding parajfrapb, be ntade .itronger, 
while the inflow of water to tbc tube rcmaJnir the same, the 
onlflowB will be less frequent but each one greater; and viet 
vrrKti. The effect of eevtion of the pneiimogaGtric Lrniik 
may, thervfortt, be explained if weiiuppuwiliat. nortnally. it 
carries np, from its lung brauohea, nervous impulaee which 
diminish the resistance to the dischur^s of the respiratory 
centre; wlwn the nerrMaro cut (hcM helping itnpul.cs arc 
l(«t to the centre, and its impulses mu^t gaiher more head 
before they break out. but will be greater when they do. 
This view is oonllnned by tlio fact tliat etimnlation of the 
oentml ends of the dirided pneumoga^trio*. if weak, brings 
back the retipirationM to their normal rate and force: if 
stronger ninhes Uiom more mpid and shallower; and when 
stronger still, abohHhct; the respiratory rhytltm altogether, 
with tJie inspiratory muj^dai in a steady state of feeble coo- 



I 

I 
■ 

I 



TUB KXflRATORY VRSTRS. 



S9T 



''ti'action. Tbftt is to my, th<i rvfiii(tuuu> to thv iltscbnrgPK uf 
till? ccDtro bi-iug entirely tiiken ait&y (which is equivalent 
U) llic total remoral of tbo spring m our oxumplc), the cvn- 
tra sends out uiiint«mipU.'d lud Don-rhj' thmic stimuli to 
cbe iuHpinitory muaclLW. 

Till- inKHimogHStrio oerve gives two branches to the larjox ; 
known respectirelyas the superior and inferior (refurr^nf) 
larynqeiil nerves; tbo action of thonv on tbo rffipirutory 
ci'ntrc le oppoiiito to that of the (ibreit front the 1ungH 
coming np in tlio main pticuiuo^'<l ric Inink. If the 
superior Inryngca] branch be divided and its central end 
Htimubtted, the reepiratiuna becomv less fro(|uent but each 
oucmoro powerful; hvncc this n«n'ci« aup]ioi<ed toincroose 
the ri.-iii«lancfl to tbc diMchargej of the re^pinitury centre. 
The iAm^, hnc to a lees degree, ia true of the inferior lurrn- 
gcal branch. 

The Expiratory Centre. Hitherto we liavo considered 
bnmthiii;; as due to the rbytJtmicallr alternating iK-t.irity 
and rott «{ un inspiratory centre — and »iich is the cim> tti 
normul i|tiiet breathing, in which tiio exiitrationH are pas- 
sivv. But in dyxpnosa oxpinition in u iiiii«cu1ar act, and 
so there ninst be a section of the res]iiratory centre control- 
ling the expiratory mnadea. This part of the rcispiratory 
centre, however, is Imx irritable than the inspirator}' part, 
and henoe when the bh>od is in a normal atate of a$ratitiii 
never get4 stimnbtted up to lliedisch]U';;nng point. Indysp- 
utiM tlie stimulus bei^'ime^ suflicient to e»u»e it also to 
diBohaife, but only after th« mdro irritable Junpiralory 
centre; henou the ospiration follows the inspiration. This 
niternntiun of activity w, moreover, jiromoted by the fact 
that the ]>neiiaiogiistrio n^rvo-ribr^-.t coining tip fnitn the 
lnngi< are of two kinds. The predominant sort are those 
already referred tn, which dimiuifh tliu rcttsttuioo to di«- 
eharge of the inspiratory centre, and perhaps also increase 
the reaiHlanci; to the oipimtory discharge. Tliis set is cx- 
oitecl when tlio lungit diniiui^h in hulk, ib* in unpiration; 
and when tbo whole nerro is stimulated electrically thi-y 
usiuilly gut the Iwtter of the other set, which carry up to 
the medulla iiupalses which inoremu the resistance to in- 



898 




rUE UCMAX BODY. 



epiratory dischai^ and diminisli tli»t to espinitoiy, and 
ftre sUmulated vben the lungs expand. Hence, every ex- 
pansion of the lungs (inHpiratiou) teods to promoto an 
ezpinttion, and every collup»c of the lungs (expiration) tends 
to {iroducc an iuHpiration; and so, throngh IJie pneurao- 
gastnc nerves, the respirntury moeliuniEm is Jargely 8«U' 
regulating. ^| 

AftphyxiB. Asphyxia is death from »uffociition, ori*flH 
of oxygen by the tissues. It may be brought abont in 
Tarious ways; as by strangulation, which pret-^nta the entry 
of air into the lungs; or by oi]>o«uro in an atmosphere con- 
taining no oxygen; or by putting an animal in a vacuum; 
or by making it breathe sir containing a gas which lia^ ii 
stronger affinity for hjcmoglobin thiiii oxygen has, and 
which, therefore, turuM the oxygen out of tho red corpUBclcs 
and takes its place. The gaaea whicli do the latter arv 
vcrj- interesting winuo tliey eervc to prorc concUisiTcly that 
the Body can only live by the oxygen carried round by the 
hiemoglobin of the rod corpuscles; that amount dissolved 
in IJie blood plunna being inMiflicicnl for its ne'cde. Of 
such gaseecarbon monoxide is the most important and brat 
Ktndiet); in tho favorite French mode of committing eoicide 
by stopping np all the ventitution holes of a room and 
burning charcoal ib it, it is poisoning by earbon 
which causes death. 

The Belations of Cartwn Monoxide to H»nio|^fl 
If aiTiitcd whipind blui"!, iir ti isoliUKm of oxyhnmngiobin. 
be exposed to a gai^eouH mixture containing carbun mon- 
oxide, the liquid will absorb tbe latter gaa and ^ve off 
o^gen. The amount of carbon monoxide taken np will 
(apart from a small amountdtsiwlvt'd in tho plasma) )>e inde- 
pendent of the jinrlial )>rvt»ure of that ga« in tlio giuoont 
mixture to which the blood is exposed; the <inaDtity absorbed 
dcjicuds on the quantity of hiL>moglobin in the litjuid, 
and is replaced by an e^iual volume of oxygen liberated. 
This equivalence of volume, of itMlf. proves that the phe- 
nomenon is due to the chcniical replacement of oxygen 
in some compound, by liie earhun monoxide; for if the 
carbon monoxide were merely dissolved in the liquid in 





OARBOy-XOXOXWe lL.H3IOOt.OBm. 



3»» 



proportion to it* (wrtrol pressure on the fiurface, it would 
turn out no oxygen; th« (|uaDtityof diwwlvcd gMM hold 
by n liquid being dcp<;ui]«nt only kii Uie partial ]irc8snre of 
astah indtviilual gox on iu •(iirfsce, and uiiufFc«tcd )jy 
tJiat of all others. During t!i« taking up uf oitrbiiii 
monoxide the blood chjinpw co\ot in ft way that can bo 
recogiiiKitil by 11 jmictici'deye; it bocoraea cherry red instead 
of scarlet. This showji that some new cfaemical coniimnnd 
hu been formed in it; omniinution wiUi the spectroscope 
conSrmB this, and shows the color change to be due to tbo 
formation of curbon-monoxido ba.-mogli)k)n which has a 
different color from ozybirnioglobiu. A dilute solution 
of rodnoed hiemuglobin absorbs all the raya of light in one 
region abont the grcfu of Ihc *(>lar »|>cclrinn (wc Pliygicn), 
audKOprodnccs thcicadurk baud; a thin layer of (he blood 
of ail asphyxiated animal doca the (oxav. Dilute solution 
of oxybiemoglobin ub»orbs the rays in two narrow ru^una 
of tlie solar Ki)eclruni nt the oonrinoa of tbe ydlbw 
and groen, and arlerial blood dws the same. Diliito 
K'>lulion of Cflrbon- monoxide ha'moglobin, or blood wliirh 
has been exposed to this gag, also absorbs the light in two 
narrow bundu of the solar e)ieotram; but these are neonHT 
the blue end of the epectrum tliait ttie alworption biindi 
of oryhiemoglobin. Fine WixkI sernm unturaCcd with oxy- 
gen giiKoi' with carbon monoiidodoe^ not specially absorb 
anypai-tof thes|K-ctruni; therefore the abitorption) when 
luemoglohin is present, must be due to chemical compounds 
of thon gaws with ibat bi:)dy. 

Since carbon-monoxido-hmmoglobin luw a bright red color, 
wo find in the Uodies of persons ]>oisoiicd by that gas, the 
blood all through tho Body cherry rod; the tissnee being 
unable to take carbon monoxide frnmbiemoglobin in tliu8y«- 
tL-niio circulation. Hence the curious fact that, whilo dcalh 
)K really due to asphyxia, the blood is almost the color of 
arterial blond, iiiittciul of TCry dark purple, as in ordinary 
oases of death by suffocation. ExpenmenU with animolg 
aliow Unit in poisoning by carbon monoxide pcnixtent ex- 
posare of the blood to oxygen, by mcuuiH of artificial n'^pi- 
ration, will cause the poisonous giu to bo slowly replaced 



L 



4UU 



Tim IIUMAX B<a>T. 



again by oi^gen; honoe if tbu heart has not yet 
«(o]>im;i1 bvsting, artiltcial reii|HntLtun, kvjit up imtu 
dhtnild be emploTecI for the restoration of persons ]ioifioned 
by carlion miiniixidi'. 

The Fhenomona of A^hyxia. An »oon as the oxygen 
in the liliMxi fnll» Ih'Iou' the normal amonni the limtthin^ M 
bcciimcH hurried and dooper, and the oil rjiimiinitri' miiM-k^ V 
of reepiration are calW into actirity. The d\ti]iiiipa ix>- 
comcM mom and more marked, and this in eepec^ially t)j«^ 
vaae nritli the expirations which, almost or ijuilc ]>»«¥iTelr^| 
performai in natural breathing, become violently mui'cu Inf. ~ 
At la^ nvarly nil t)ii^ uium>)eit in the Body arc set sti work; 
the rhytlimic charsoter of the reitpiratory acts ia lost, and 
general convalsionB occur, but. on the whole, the contnw- 
lions of the cxpimtury miiiiielc:< are mor« violent than thowt 
of the inspiratory. Thus undue irnnt of ozygvo at first 
merely brings about an iucroaaed actirity of the rettpirat^rr 
centre, und especiullr of its expiratoiy dirisjon which a iiol 
excited in DontuJ brrathing. Then it stimulates other por- 
tions (the conrnUiff trnfre) of lhi> medulla oblongata Bbo, 
and gives riHe to violent aud irregular muscular apssma. 
That the convulsions arc due to excitation of nerve-centres 
in the medulla (and not, aa might hv supposed, to poisoning 
of the miiiclw by the exiremdy venouit blixKl) is tihown by 
thofncu (l)that theydonot occur in the trunk of an aniroi^ 
when the spinal cM>n) him been divided in the neck so as to 
cut off the mu«cl« from the medulla; and (3) that they etil) 
occur if (the spinal cord remaining undirided) nU the 
parts of the brain in front of the medniht have been r«- , 
moved. 

The violent excitation of the ncrvc-centrea boob ezhansta . 
then), and all the more readily since their oxygen mpply 
(which they like all other ti^ue^ need in order to oouttnue 
their activity) ia cut off. The courulsiona therefore gradu- 
ally cease, and the animal becomes calm again, save for an 
ooeaMonol net of bmthiug when the oxygen want hocomea 
•0 great as to cause efRcieut Bii'iiutittion even of the dy^ng 
respiratory centre: these final movementa are inepira* 
tions and, becoming less and less frequent, at last cease. 




ABPBTXtA. 



401 



iind the itnimiil appears dead. H, however, itsrhcet be 
(>l>ened tiic heart will be fonnd goi^cl nilli oxtromdy dark 
Tcnoiu biood and making: >t« Wt fow siow feeble pnbaUioni. 
8» l»ng ti» tl bcutii artificial rospiration CHn rmlore the ani- 
tnitl, but once the heart hu finally Ktoppcd rcnioratioii '\» 
imposxiblc. Th<-i« are thns throe distiagniBhable Btajpea 
ill death from aeplivxia. (I) The stage of dyqi&ow. (2) 
Th««tagBof convulsioiw. (S) TIie»tjigcof cxhaimlion; the 
oonrulRions haTing ceaeod but then? being from time to 
time an inspiration. The did of tho ihini stage ooonra in 
a Rutniinnl about five minute* afier the oxv^cn fliipply has 
been totally cut oS. If the uspliyxia be dnc to delicicncy, 
and not uboolato want, of oxyguu of course all the »tagc« 
tske.kiii^'fT. 

Circulatory Changea in Asphyxia. During death bj 
raffboation ciiura^i eristic changes occur in the working of 
the heart and bloi^-rewwls. The hcnrt at first bcaia 
((Djeker, but vcrr soon, before the end of th« clyspDceic itBge, 
more slowly, tJioughi at tintt, more powerfully. This slowing 
ill duo to tlio fact that the unusual want of oxygen Icaila to 
stimuhition of the cardio-inhibitory centre in tlie modutU 
(p. 2&0) and thii). Iliroiigh tho pti«umogu»tric nerres. slows 
tiie heart'R bent. Soon, however, the want of oxygen aSecta 
the heart itself and it begina to Iwat more feebly, and ulao 
more slowly, from oxhnantion, until it* final stoppage. 
During the second and third stages the hoart and tho wnn 
ravffi become greatly overfilled with blood, because the 
violent muscular contractions facilitate the flow of blood 
to Uio heart, while its beats become too feeble to send it 
ont again. Tho oferfilling u most marked on the right 
side of the heart which rocoiTO« tlio todous blood from the 
Body generally. 

During the first and aecond stages of asphyxia arterial 
Iiressurs rigoc in a marked degree. This i« due to excitation 
of tlie raao-motor centre ()>. 2A4) by the venous blood, and 
the oonMquent constriction of the muHcnhu' coata of the 
arterieK and inoreaAt; of rlu^ )>eri[itieral reaistance. In the 
third stage the blood- pre^isu re falls very rapidly, because 
the feebly acting heart then fuit« to keep the arteries 




403 



raw HTMAy nonr. 



teoae, even althnnj^h their climiniHhiKl calibro groKtlr slovf 
tbo mte at w)iic)i thny empt; theiiiitolviiit into tlio capillii*j 
ries. 

Another mcilnllury rctiliT iiticliily oxt-itod during iispliy.i[fa| 
is tbat from wliioh proceed tlio iicrvo-filnx-s go^'p-miiigj 
Ihoso miisciditr fibres of tliu eyv whJc-h enJar^ the pupiL] 
Dining nuffoL-ation, tliei-pfore. the [lujiilti Wcome widely 
dilitlcd. At the eanio tinif? all reflex irritshiliiv is lo»t. and 
trmching the vvdm!! oitii.'>r-K no wink: the reflex centret* nil 
over Lhc! Body being rendered, thri>ugh want of oxygen, in- 
capable of acljvity. The same is tme of the higher nerre- \ 
centres; unecinxcimi«neN!' eonic^a on dnring the convnlttivo 
stage, wliirli. Iiorribte oa it looks, is iinsticuded irith suffer- 
ing. 

ModiBed RoBpimtory Movementa. SiohiHff is a deep 
limg-dniwii inspiniiion followed by a slioricr but oortr*t>ond- 
ingly large expiration. Yawning is similar, bnt the air ia 
mainly taken in 1>j the mouth im-tead of tlir no^c, and the 
lowerjaw is draTrn down in a eliaract«ri£tic manner. Ific- 
congh dependti npon a sudden onntnK'tion of the diaplinigm, 
while the aperture of the larynx closes; the enKring air. 
drawn tlirougli tho narrowing ojioning, caiim'ji the pi-ciiliar 
eonnd. Coughing coDbiets of a full inspiration followed by 
a violent and rapid expiration, during the firet part of which 
the larrnpeal opening ia kept cloeed: being aflcrwarda «ud* 
dcidy opcmd, the air iitsucs forth with a ^l^h. tending to 
carry out with it anything lodged in the wind|i>]ic or larynx. 
SnecztHff is much like cuughing, except that, while in a 
cough the Uthmuii of tlie fauces is held open and the air 
mainly passes out through the month, in sneering the 
fauces are eluiird and tho hliut io driven through tho 
nu»trilA. It is commonly excited by irritation of the ruMid 
mucous mombrano. bnt in many persons a sndden bright 
light falling into the eye will produeo a enecxe. Laughing 
consists of a tterles of short expirntiong following a aingla 
inspiration; the larynx ie oj»cn idl the time, and the voc^ 
oord«{Clmii.XXXVI,)arn »et in vibration. Crt/iitgis, phy-i 
dologically, much hke laughing and, as we all know, oQt 

ia passes into tho other. The acoomjumyitig oontfa^. 



MODIFIED SBSPIRATORT ItOVBMSJtTS. 



408 



tioDB of Ike fttce musics girinf^ csprcMaon to the ootiiit«ii- 
ODOC are, howercr, diiferont in tlio two. 

AU these modified rrapinitory acts are eaeentially reflex, 
but, with tho exception of hiecough, Uicr nre to a oorluiD 
extent, like nalurnl breathing, under the control of the 
«ill. Most of them. too. can be imitiited more or leas 
jierfcotlf bj voluntary iiiii^eular moveuicnUi; though u 
good stage sneuM or cough is rare. 




m 




CHAPTER XXVII. 

THE KIDNKY8 AND SKIN. 



General Arrangemont of the Urinary Orgaiu. These 
consist of (1) the itilnei/s, the glnnd.i whidi «ecret« tbe 
urino; (3) tho uretera or dticU of the kiduevs, wbicli carry 
their aecretjon to (3) tJio urimtry bladder, a reservoir in 
which it accutnu lutes mid from which it in rxjiclloil from 
timo to time (hruugh (4) an exit tube, the urefkra. Tlw 
general arrungcmcnt of the« jiarls, as seen from boliind, is 
BbowD in the ligiirx' oppOBiltf. The kidneys. R. lie in lh« 
durtal piirl of the lumbar region of tho ftbdominnl cavity, 
one on each side of the middle line. Ktich i» n hoIiiI mase, 
with a convex outer and a concaive inner border, and lU, 
ii|ipcr end a little larger tbiin the lower. From th«J 
abdoniinnl aorta. A, a rtnal artery, Ar, entorn tliu inn* 
border of each kidney, to break up within it ioto lincrl 
branches, ultimately ending in capillarint. The blood u 
collected from these into the remd vrxn*, Vr, one of whieh 
leaves each kidney and opens into the inferior vena csn, 
Vc From tho conriivo border of each kidney pTOceedj 
also llie ureter, U, a slender tube from 28 to 34 cm. (11 to 
I.^.A inehe«) long, ojiening below into the bliiddcr, Fm, on 
lis dorsal aspect, and near its lower end. Fi'om tbe 
bladder proceed* thetirelhni.ut t'n. The channel of each 
ureter juiwtes very oblii|Uely through Ibo wall of tfaft 
bladder to open into it; nccoidingly if tbe preesnre inwdt^ 
tbe latter organ rixCM nbove that of the liquid in the ureler>fl 
tlic widU of the oblique ptwsagv urc prctisod tngothor and 



iu — 

Lh«fl 

oeflH 
ncrV 



A 



Tas iiEXAL onoAjrs. 



405 




Kia, IK— 'IliO miikl orvKUH. Tt(>w«dfr«ni bfhInH. B. rbibt kUneyL J, «ona: 
Ar. riKbt rennJ artuty : Te, Inftrtor T«an ckiii ; I >, tii^ iriiol ToUi ; O, r1(U 
uivtari Vu. bloditw: I/O, «aiiunMM!om«ito( uretlirft. 



406 



it ia cloMd. ITeaslI; tlie bladder, wbifh b&n a thick coat 
at QDAtriped nnucnW xiaaae lined by « macuus membrane, 
is reUzed, and the nrine Sows readilj into it from the 
areteo. The oomiD«Dcemeiit of tbe aretbn being 1tr\'i 
etoaed by dartic tiasae aniuiul it (which cui Tolnntarilv be 
reinforced by muscles which oompreas the tube) tbe orinc 
lOeiuoiUatoi in the bladdGr. When thu Utter contncu and 
prcwet on iu oontenta, the nreten are closed in the vsy 
aboTe indicate. thi> ebitic fibres ekwiag the arelbral i^sit 
from the bladder are OTeroome, and the liquid forced 
oat. 

Vaked Bye Structuro of tho Kidneys. Hiem mgans 
have ezternallv a red-browD color, uhicb can be seeo 
tbrangb the transparent capguU of pcriionenm which en- 
Tclopa ibcm. Wben a vc<ctioR is carried thrungh a kidnej 
from its outer to iU inner border (Fig. 115) it is seeo that 
a de^p flarare, the Ai7im, leads inio tlio latter. In the hUnt 
tbr> nreter wideni out to form the ptJrU. which Lrwiko up 
again intoanumberofemtdler divisions, thecupe or cufirM. 
The cut surfuce of the kidney proper is iwen to oonsLit of 
two distinct iimrUs; an outer or corliml portion^ and an 
inner or nuJitllary. The medullary jmrtiou is leea r*d and 
more glisteotng to the eye, is finely striated iu a radial 
direction, and does not consist of one contiiinoiu' mass but 
of a ntimlwrof eonicsd portions, thc^^AmtW^ of MaJpighi, 
%', Qo^h of which is separated from its neighbors by un in- 
ward )irolongation,*, of tJio cortit-ul ituhrta»c«. TliiH, how- 
eTor, docs not reach U> the inner end of the pyramid, 
which projccU, u \Mt papiUa, into a calyx of the aroter. 
At its outer end each pynunid sepiirutes into i^nuillt^r (Mir- 
lions, the /)yre»ti<fs of F^mn, 2',Acpiimted by thin layer* 
of cortex and gradually spreading everyithere into tbe tal- 
ler. The cortical substance is redder and more grantilat 
lookingund less sliiiiy than tbe mcdullani-, and forms every- 
where the outer layer of the orgim next ite ciiimuIo, bceidus 
di]>ping in between the }>yramids in the way descriWd. 

Thu ronid artery divides in the hilus into branches (5) 
which ran into ttic ki<liii-ybclw<.-entho pymmids, givingoff 
a few twigs to the latter and ending finally in a much 



I 
I 

1 
I 



I 




msTOLoor OF tiik Kwynrs. 



«7 



riclMir TiucaUr n(^tworlt in (he cortex. The braQch«8 of 
the n-iml vein huvo u KimiUr enume. 

Tho Minuto Structure of the Kidney. Th« kidneys 
■re couipiiuud lubitlur gUmJ^ com]>o«ed essentially of 




Fia. MA -!v<'itiin Uimuiib Ih" n/ht klilnry f rnm tMoutu lo lU lDD*r bonlrr 
1, mnri; s, niniliillii-. !'.pVnimi(1r.t MalpiBbK a*, pynnld oT Fwraln i S.iu»ftll 
hnrnvbiv riF 'liL'iriuJ KFttcT<-<>><itln0lir(>rHTa the pjrraiiildai ^ «limKlio(UHt 
mul uMiT' : C. Uie palrls of Uui klJnirx ; C, nroMr. 

Lntiichet] inicTx>soopic itrifi/erDua tuMes. lined by epithe- 
lium, l*^!! tutnilc commi-iicoo »l ii naiall opening on » 
IHtpilla and from tliemv hiiii a very cumplcx oour«e to its 
othw extnunity. Ceiiitlly about twuntr oi>en. side by etdo. 
on o&e jw|iiUa. Uliere tliey have * diunvlvr of about 



40« 



TUB BVMAy BODY. 



0.126 mm. {^ inch). Rnnning into the pyramid turn 
tbU jtoint eufh tiilmlo divides several times. At firfit the 
briLiiohcii an; Kiuallor than the itmiii tiilxt; but &» soon aa 
they have tome down to about 0.04 mm. ((Jn inch) this 
diminution in »\w cciLtc^, and Uic diviition continuing 
while the tabtiles retain the itame diitmetor, the jiyraniid 
thiu getB, in part, it» conical form. tTltimatelv each branch 
nuu ■omcwhere outof tlie pyramid, either from it-A hmm or 
fide, into ibe cortex and there dilatea and it< twisted. It 
then uuTOWK and doubles bavk igatn into t)te p%Tamid and 
mnaaaa 8traighttiibetoward<ithe)>a{)il1ii,htit bcfuru reach- 
ing it makes a loop, and turifs back again an a straight tube 
to the bu»o of (he pyramid, where it once more entere the 
cortex, dilaU^s and hecomcH contorUvl, and then ends in 
a spherical capsnle. eontaiainga tuftof timall bUwd-veK«cl«. 
Or, frtlldwed tbi' oilier way, ciich inbtilc commences in the 
cortex with a globular dilatation, the Mnipighinn rapsule. 
From this it contJniiee ae a convoluted tubnle in tin 
cortex; thiH passca into a pvramid, becomes Ktraight> and 
nna on aa tbe de«cen<li»^ limb of a hop of Heitle. 'I'lim* 
ing at tbe loop, it continues m its tucmdin^ IttHi, und this 
passes out again into thooortex and becomes the convoluted 
juncHonnl tubule, which padaea a« a straight collecting 
iubtiie into the pyramid and there joins others to form an 
exerfton/ tubuh which opens on ttiu papilla. Throughout 
its coftnw tbe tubnle is lined by a single lajrer of epithelium 
cells differing in cbarucl^T in iu different eeclioni). All the 
tubes are bound togi^ther by conneotiTC tissue and blood- 
vessels to form the fr'u'id. 

The Blood-Plow through the Kidney. Hie (liml twigs 
of the renal artery in the cortex, giving off a few brancheji 
whioh end in a capillary network around the convoluted 
tubnlCK. lU'e continued as the afferent vsitelt of Hklpi- 
f hinn oapsules.the walls of which are doubled in before them 
(Fig. 116); iLcrc etich breaks up into a little knot of 
capillary vessels called the glamfirulut, from which ulti- 
malcly iiii «fferenl vengfl proceeds, and outride thu cnp^nlo 
this breaks up into a close capillary network among tlicoon- 
voIuIkI tubes. From the eupillarics the blood is collected 



I 




TUS BSNAL SECRBTIOX 



409 




Fia. 110.— !%« tennlnatlMi ot » 
orinlfnmii* Mbul*. Mtli II* atoBMnl- 
liw. iL I ftf itl<wenilu« or M^lahlglitoii 
lyirrpuwlc; b. Ill* ninvolutt^ «ii<llng 
o[thutiibiiln:rf. IUliiilnc*ptUiriluin| 



into the renal vein. UoM o( the blood flowing through the 
kidaey thus go&a through two meU of capillaricc; «no in the 
cspsulas, ftod a second formed 
by th« brcakiug np of tho 
i»fT»>rent \eia of the latlor. 
Tlie capillary network in the 
)iyniiiiiili< is tuiich li-w olow 
than that in thecortex, wbioh 
gives nuaoa to etisptct that 
mo«t of the secretory work of 
the kidneys is done in llie oa|>- 
aulcs and oonrolnted lubulc«. 
The pyramidal blood flows 
oidy through one vol of «i]ii]- 
larie", then; boinj^ no glome- 
ruli in th« kidney medulla. 

The Benal Seoretlon. Thix 
amount of thi? carried off 
from the Hodyin 24 hourn in 
nuhject to coUBiderable varia- 
tion, being c«|iocially dimiti- 
i«hed by anything wliich pi-i>- 
motea perspiration, and ini^reascd by conditions, a* cold to 
the surfoco. which diminitth tho nkin vierction. Ita avcri^co 
daily ciuantit; varies from 1:200 to KAO cuh. rpnt. (40 
to 60 fluid ounces). The urine in a clear amber-colored 
liquid, of a slightly ncid roacUon; \i» ir]imfic gravity is 
about 1010, being higher when the total quiinlity exrretcd 
is smalt than when it is greater, sincD the amount of solida 
dtuolved in it remains nearly tho fame in health; the 
changes in its bulk being dependent mainly on cliunges 
in llie amount of water separated from tho blood by the 
kidiK'Vih 

Koniial urine conxists, in 1000 purtH, of al>out dRO water 
and 40 Mlids. Tho hitler are mainly crTntalline nitro- 
genous boiliiM (urm and iirir arid), but fimutl •|tmuti(ic« of 
pigmenUs and of non-nilnigi-num^ orgiuiio biflicd are also 
present, and a considerable ({Uantity of mineral raits. The 
following table gives appixiximalcly, in tlio firvt uolnmu, the 



tloinvniliu: g, lli««jrpmit 
, th» blood -w*«f to fonnliMItliB Mtt 



:t. 



Id ItogloDwruluiL 



410 



TiTB mrvAy hody. 



avenge compointion of the nrine exorolod hi tveuty-toni 
houn exprc««e<l in grains ; in lii« aectjnd column the midp 
exprasaed in grain*. Tho lliinl column gives the compon- 
ti<Mi iA 1000 parts of nrino. 



1 OrlnalaMlHWia. 


UOOcnuiu. 


BJK>KI«tUL 


la mo part*. 




i«n.oo 

78.00 


SS.1M.00 
1116.00 


853.W 

•laoo 


Tbc lolUU caiihIhIii of — 


3100 
6.00 
0l4O 
100 

10-00 

a.oo 

«.0O 
TOO 
OlTS 
9LS0 
11.00 
0.25 
0.90 


SI 1.00 

7. 78 
&W 

ISlSO 

8I.0O 

toeioo 

u.00 
SS-IB 

tni.90 

8.80 
3.00 


\ S.OQ 


Unci Mid ((-Ml.N.O,).... 


0.S3 
0.!7 


KnMJabi 


10.88 




S-OB 
1 38 




S.00 




4.70 




O.0O 

1.70 




7.» 

0.11 




013 








7t.eo 


UIOlOO 


47.4i 



llw DriDe, howerer, trtin in beoltb is subject to ronsid- 
entble viiristion in composition; not onlr m ix^iirds tbe 
■mount <>f wiiUT in it, but also in its aolid oonr>li(ucnt«} 
tbe Istter are e.']>cciaUy modified by the ^nuatilir &ii4 iiatare 
of tbe food tiikon. 

100 Tolunica of urino contain in solution about 14 vol- 
umes of goa. r^onsistin^ of about 13 uf carbon dioxide, 1 
uf nilro^n, and uii-ro tntoos of oxyprt-n. 

Xeohanism of the Bonal Secretion. Thv kiduors, » 
««orctiiig orgiii)% c<>n»i><t of lu-<iiiitiiiirtpHrl(<; (1) tlieglomfr- 
rnli through whiob a Altration of wat«r, probably with O11I10 
in Boliilion. takes place; nnd {'I) iin actircly secn^tory nppa- 
ratns, fiirm«t1 by till p»ri8of thciirinifcfous tuhnlffl between 
their terminal cap^ulofl ami the collocling tiiV*!. AcponI- 
inglT. we find in the uriiic bodiw. as water mid common salt, 
vhich already exist in the blood and can be removed from it 



d 



BOURCES OF UnBA. 



411 



merely by ilialyHisorfiJtntion: and others (theRpocific ele- 
jn(^nts of tlifl wfiftion). oipt'oially urea, which are selected 
t)T tniule by it special activity of the renal gland-oeJIa. The 
loul quantity of the twonty-fonr hours' urine thuadopende 
largii>ly on the pnwiure iu the renal arteries, since the 
higher this is the greater will the umouut of filtered li<|uid 
l>e. Under ordinary pnuwiireK ituch Htibntanceit tw Nlbumen 
will not filter, but ibey do under higher; oneordingly in 
healthy conditions none of the albumen of Uie blood plasma 
pu^cH into the urine, but if the prx'ic<urein1bccapillarie«of 
the glumeruli is considerably raised it does; ita presence in 
the urine being tlie most prominent symptom of tbatdangCN 
oils class of maladies groiipti] together under tiio name of 
Brigkl't di»tn»e. Filtration in the glomeruli ia largely|)ro- 
motod by the fact that the uilibrc of the effert-nt vessel of eucb 
ia rather less thanlh»ti>f theuffiriMit; and thus the proeaora 
IU the Ihin-vrulled TeaacU of the Tascular tiift ts raised. 

The RSle of the Banal Epithelium. Water and erilinn 
bfiiig piu-se.l out mainly through the glomeruli, wo haxe 
now to consider what part the eccreting cells of Uie kidney 
play; and cvpcciuUy fts regards nm, the niOHt important 
constituent of the nriiie. Urea representa the final state 
in which the proteids taken into the Body from the alimen- 
tary eanal (or at least their nitrogen) leave, after having 
yielded up, by chemical i^haiigea, a certain amount of energy. 
In this process the proteids aru oxidiml and broken down 
into carbon dioxide and water and urea; and tho kidneys 
get rid of the latter. 

Since the Ufc aud activity of every tissue is accompanied 
by a breaking down of proteids (though not necessarily at 
once into urea, aa many intermediate stages may, and doubt- 
less do, occur in different tissues), there is no doubt that the 
main cheniit-al degradation of aHiuminou^ooiDiiounds tjikea 
pliieo ont^de the kidneys. Whether the final steps by 
which urea is formed occur in those organs or elsewhere is 
not yet certainly kimwn. According to one view the urea is 
carric<l to the kidney in the blood of the renal arivry, and 
there merelypicked np and {itts«<(l on bytheexcrotingoella; 
while, according to another, not ureu, but the pennl- 




412 



TBK BTMAT mODT, 



I 



«r pnMMl < l ig f i l «ti mi from vbidi Biw 
: BO the kidwvK ad iht final f< 
t is tkOMoipM. Th* ranlUof bluod 

ImI M Ite «%ale U rrnnir |>mTnI Ihrt' 
ia nBat«rteff7 Ua>d tkm in rcnsl-TeiB. 
libw4.«Udii]idiata>thtf ■nBbiMtn«d£iBiiw kidnen 
In deatb, too, fraa winwaewn of the noul mct>on, urea 
bfMind to aocBMalite tn tfatUood whieih wimld not be the 
CMC nnlcM it were narsan j furmed dw«ber« and car- 
fwd off hv tW kidiw^i. The vimle am qaoation. whtdi 
■ (MM of gnat iBipMtaBCT, will Tn; m«*> fnlhr omcidFrcd in 
Chapter XXTHL, ia oobbwcmm with ibe tiktvatkxy ol'fl 
nnrHxNi IB gEwnL 

dia Bkte wbic^ eoms Ibo vbole rxterior of tbe Bodv, 
OOUUtMrerrvlMireof twaduUDctbfcn'; anooUrr, tbrrw/ii^ 
ari}mlnitti>,anda(tccfHn-, tba<fenatj,raii'«ivrii. orrffrftrm. 
AblUceruducto tbeaccnmalatknof l)<faidLvtwi<cD th(.-*« 
two laven. Tbe Aai>« and uaiU am exoeanrelT deTeloped 
jiani' af [b« cpidcnnU. 

The Bpidarmis, Fig. 117. ooiuiitji of oelk, arrangi'd in 
manjr Lty«r«, and QDited bjr a smalt amoont of oemr'nting 
MbataoM. Tbe deepest Uvvr. d, i« eomposed of plon^tod 
irr columav celU, set on villi tbeir long axea porpendH-ulur 
to the dtrinm benvath. To it saroeMi seTeral atratji of 
nnndUh oella, h, which in tbo outer lay«n bvcome mon 
and more flattened in a pUo« parallel to tbe rarf!M-i>. Tha 
oill«nno«t epidermic etratam i« compoeed of matiT laverit of 
extremely flattened oelU from which iho naclej (I'Oiisjticu- 
oiu in tb« deeper lavera) have diiuppeared. Theme 8Ui>er- 
Htriol oeUs are doad and are cnnstantlv bcinf; sbed from tbe 
■iirfaee of the Body, white their place ia taken \>\ new ceUs, 
formcfl in the deeper Uyers, and pnstied uji to the mrfocc 
and flattened in their pragreai. Tlie cluinge in the form 
of Itie eells aa they travel outwurd.4 in otioompautcd bj 
diemical change*, and they finally oonstitnte a Bcmitntna- 
(tarentdry AornyWrn/NM, a, diHtiiict from thcdcejwr, more 
»[Mcine and softer MaipiffAian or muFoiui la^rr, b and 
d, of tha opidermie. Tlie eells of this kttcr are sototde in 
in acid; tliom of the hornj itmtum, not. 



TUK BPWBiaa& 



4n 



The roll* of mAterial wbich are peoled off tbe akin in the 
" dmmpooing" of the Turkifih bath, or by riibbini;; riih a 
rough Eowrl uftor an orHinMry vrarm buith. are the dead 
otit«r Hcati^ i>f the horny atniuini of tbo eptdermig. 







Ite 117.— A •evtlon thiuiHcti Uie eptdsnnUi. •omewlul dlBCrammftilr, blxhlT 

ggi a. tho Ii»ni)' Urar at thn riiiiUrmli; It. Uir n>U rnHmuni or Milpliflilan 
lAyttr, 'i. th" \tsvT^ colamfurt*|tt«l(-tinlc c#U« lb huiimllUii oonlact wtlli Uio 
mnalt, h, Uie diiKtar > (*rc«t-|[l<uid. 

In durk races ibe color of the skin depends mniuly on 
miiitito pi'jiwnt granuh3 lying id the duciior colU of tho 
liulpigbiiLii layer. 




<14 



TtTX BWJUi MfiT. 



VoUaod-TH^i vlnD|*i«k> artvtfceflpadennii. vhid 
M tn&aij Mnaikcd hjnmttmiantA from tiw BObjMou 
oaniuft. Rob iimn tlaw m into it uid end that 
uuiDg iW caU«, in nnoaa vmn. 

Tb«OofhtB»Catta Ton. «rftw Skin. Fi^. IIS, cob- 
tuu fandioiaitaOr of ■ eloae Mtwarit of dsstic ud white 
■kroai tiaBCL, wliidi, beeomiui: wider meebed bdow, pstsei 



. - V^ifK.^<'%jf*^v 




.-y 



rM.1l8^Aa(rltwUirou^(lia<A:iiiii*liiili(nlitBta(>a*milarllMDiL m,Ot 
•tnUum, and l>, )lAl|iWU*n layer of Uh- cphlcnnii; f. oanri^ >•■■■» Mk 
Mo. A Ivaa ueolar iIhhc. wlUi fM, /. la lUi mrstm : atii >ii illiHililMUnllWIW' 
m*. pm)*pUi« Iota iha epIdennlB vfalA b tnnukkd oa IbnOB. Vovauisfa 

lEnuliuUI; iiitu tlio nubcHtafuvtu areoiar ti«»u« (p. Vii) \ 
vrhicli Mttoclicit tliA skin luunely to |iiirte benoatli. In' 
Uonlng it is the eatia vera wliii-h U turned into leutber, il4 
white flbroiu tisiuo farming an iiL-»tii1>)o lud lou^li uura- 
[loiiiid with the tannin at the o:ik-burk cmiiluyvd. Wlivn-vrr 
tlirrc are lutin, biimltnt uf pluici miL-M^ultir tisHiid &ro found 
in Iho voriam; it contains iilso a close capillary network 




BAms. 



416 



nntnerous lym)>tiftti<n and nerrciL In ekaving, w 
' as tho rnioT koapi in tb« epKlcrmiii th^re is uo t>]e<H]- 
^ing', but II dt-vjiur out nhovTj ul »Dce the vaaculnrit.}' cif th« 
true skin. 
Tht' outer s)irfacE> of the coriatn i» almost orori'iiliere 
^tc<l iiil.u niiiitil« elvvntioiis, calK'd iJie popilla, on wliicli 
the epidermis is moulded, so that ila deep side presentH pits 
corrc^pundtng to the project ions of the dermis. lu Fig. 117 
ia a papilla of theroriunt ooutitininf^a knot of blood- vosecis, 
siipplicii by the small srtory, /. and baring the blood carrini 
oR from them hv the two liltio veins, g g. Other jkaiiilltt! 
conlsin no capillary loops but S]wcial organs connected 
vrilh ncrvisfibras, and supposed to be concoruod iu the sense 
of touch. On Iho palmur .iiirfact^ of tlie hand the dermic 
papillie are especially well deTeIope<l (as they are in most 
parts whuro thu Moec <\t touch ■» auute) and are frvijucntly 
tompniintl or branched at the tip. On tho front of the 
hand, they are arranged in rows: the ijpidcrmis fills up the 
hollows between the papilla* of tho same row, bat dip-i down 
bclweenadja<:entrows,and thus are prodnoed the epidermic 
rtdgi's seen on the iialnui. In many pluocH tUo eorinin \* 
furrowed, as opposite the fingcr-jointa and' ou the jialm. 
Klsewberc such furrowii aro commonly leM marked, but 
they cii*1 over the whole skin. The epidermic clottely 
follows all the hollows, and thus thoyare made visible from 
the surface. Tho wrinkles of old j»er*oii8 are duo to the 
absurjition of subcutsueous fat and of other sufl ]iarta 
beneath the skin, whieh. not shrinking itself ut tbu enme 
rate, bceoines thrown into fold*. 

Hairs. Each hair is a long fllamont of epidermis derel- 
oped on the top of a special dermic pupilla. sealed nt Ihe 
bottom iif ndepreanion reaching duwu from iheskin into the 
tisane beneath and called the hmr follicle. The [lonton of 
a hair bunod in the «kin is c-nllcd An root; this is succeeded 
Dyas/pMi which, inaunncruihair, tapers oQ to n/i»in^ The 
stem i« covered by a single bv<^rur overlapping n-ales form- 
ing the /lair cuticle; the pmjeoting edge.^ of thoMi soales 
axe directed towards tho top of t ho hair. Beneath the hair 
eatide oontc* tho cortex, mudo up of gfMtly olouguted oella 




41« 



TBB HC.VAS BODY. 




united to form fibres; and in the centre of the ahaft thflW 
b foond, in many hain, « mrtiuUa, nntde ap of moro or le» 
rounded ceilH. Theoolor of hair is mainly dcpeiideiic apon 
pigmeDt gnuiiileit lying bctwcoo tht^ Cbrcs of the corteiL 
AU hsin< eonlain si>me uir Mvitju, especiaiiy in tho medulla. 
Thoy are very abundant in white baire und cause the wbite- 
iioss by reflecting id] the mcidcnt light, ju«t lu ii liquid btnteo 
into fine foam looka vhilo because of the light reflected 
from the wsUa of all the little air cuTJticji in it. Id dark 
hiiirx t.lio air eiivitioii &ti.- few. 

Tiie hair follicle (Fig. 119) ia » narrow pit of the dermif, 
projecting down into tho Hubcntuneoiitt luroliir tituuo, ttud 
lined by an iuTolntion of the epidermis. At the boitom of tho 

follicle ia a papilla and the 
-A.^^^^^. epidermis turningupovcr 
this, beoomes oontinu<nu 
with th« Lair. On the 
papilla epidermic eel I a 
mull )}>ly rapidly so long u 
the hair is growing, and 
thu ivliolo hair ia there 
made np of roumliiih cclln. 
no, ikk-pmtm o( hk. iiain imtwdiini As theBe got puehed up by 
io.i>T- >><>wn »<d iwf iL.^ t.AUA-: b ti.a fre.di on» formcti boQoatli 
luur r"UiLi.M>iiisii *-/ tUfir eouimcucm "lem, 1116 Outermost injur 
«u.r«au..h.up. bccomi-fliittenod and form 

the hair enticlc; ReTcral snooeodiiig 1iiyi>rs dongnto and 
form the cortex; while, in hairs with a medulla, tho middle 
oelU retain pretty much their original form imd size. 
Pulled apart by the rlunguting corticttl cells, tticw ountral 
onoi th(^n form the medulla with it^ air cavities. The 
innermost layer of the epidermis, Uninp ihc fullicle, luis its 
cells projecting, with overlapping odgra turnod dowu- 
wardn. Accordingly these interlock with tho upward 
dir('cii>d edges of the celli' of the hair cuticle; ooni«e(|ucntly 
when a buir \» pulled out the e|iideruiiu lining of the follidn 
in UKu:iliy brought with it. Kn long a.t the derniie pn]iillK 
ia left intact a new hair will be formed, hut not otlx-rwine. 
iilviiiler buudlc-a of unKtnj>rd muiiiclu (c, Fig. lltl) mu from 




I 



I 



JTAILA 



417 



^ 



the d«nuia to the ado of the hair follicle*. Tho luttor are 
oblitjae]; impUuledin iht< «kin #0 that the hairs lie^oivii 
on the turfnce of the Body, and the tausclee are so fixed that, 
irhea they shorten, thvy croet the hair and ca)is« it to 
hriatle, as may be tc.cn in an angry cat, or sometimes in a 
Kreatly terrified mini. Opening into each hair follicle are 
u:<uali)' a eoiijile of sebaceoum gl»iid« (p. 418). Ilairs are 
found on all regioun of tlio «kiii except tho pulni« of the 
hands and the ttAon of the feet; the back of the last jihiilanx 
of Uio tlngcD) and toes, the upper eyelids, and one or two 
other regionB. 

Naila. KiKh nuillti A|>artuf the epidermiF. with its horny 
stiBtum greally developed. The hacls part of tho nail fits 
behind into a furrow of the dennij and is called it« root. 
The visible purt connists of a boit/, fixed to the dermis 
benealh (which forma the /'rri vf ti>t naif), and of a free edge. 
Near the root is a little urcu whit«r than the rest of the 
Bail and called the lunula. The whiteness ia due in part 
to the nail heing really mnre npuquc there and purtly to the 
fact that its Ijed, which seen through the nail causes ita 
pink color, is in this re^on Ivss vascular. 

Tlie jMirtion of tike corium on whioh the nail is formed 
is cfllled it« mttlrix. Behind, tliis forms a furrow lodging 
the root, and it is by now cells added on thiTo that tho nail 
grows in length. The part of the matrix lying b<'n«alhlhc 
body of the nail, and called its bed, is highly vaflcular and 
raised up into papilln which, except in the region of the 
lunnla, aroarrangcd in longitiidinul rowK, slightly diverging 
as they ran towards the tip of the finger or toe. It is by 
now ci'Ils formed on its bed and added to its under enrfaco 
that the nail grows in tliicknes*, as it is pushed forward by 
the new growth in length at its root. The free end of a 
nail is tlierefore its thickest part. If a nail is "ojuvl" in 
coiuieqiiencc of an iignry, or toni olf, a new one is produced, 
provided the matrix is left. 

The Glands of the Skin an of two kinds, the audari- 
pnri>u» or xw,;il fjlantU, and tho ttbaetOHS or oil plnnd*. 
The former belong to the tubular, the latter to ihe race- 
mose type. Xhatweat-yland*, Fig. Vid, lie in the subou- 



418 



rns nrjfAy Boor. 





-A aweat 



tanooos tiFsuo, whflro thoy form little globular ma«tca eoin- 
jiWcd vi a coiled tube. From the oni) » dtict (sometitntif 
double) lea<lg to the iturfiice, being 
ntiually q)inillj' coiled aa it paaim 
tbrougli the vpidermis. The secret-: 
iiig pnrt of the ffland oon«iets of ft] 
c<iniii-(rMTi;-lii<stio tube, continuous 
along the duel with the dermis; [ 
vithin thifl is a basement membraniy 
»nd the liiiul iu>crctorr lininj; consists 
of suvcnil hiycrs of ghind-collx. A 
olo§e capillaiy network intertwines 
irith tho coils of tho glnnd. Swcat- 
g1iind« *re found on all wgionn of the 
skin, but more closely set in sorae 
place«, as the palms of the hands uud 
Uio brow, than clsowherfc litere are 
altogether about two and a half miUioua 
of thorn opening on the surface of tiifl 
Body. 

The aeiateotu glands nearly alwaj's 
open into hair follicles, and are found 
wherever there are hairs. Euch con- 
sistd of a duct opening near tho month of a huir follicle and 
brunchingatit^othereud: tho final branches lead into globu- 
lar Eiecreling i<uccul»<, which, like the dnots, are lined with 
0]>itbelium. In the sacciik-s iho subatance of th« celle 
booomMchurgcHl with otl-ili'iiji^, the protoi)lasm disappearing; 
and finally the whole cell faliii to pieces, its detritus conetitut- 
jng tho eocretion. Nev cells arc. menuwhilo, formed to talce 
llie place of those destroyed. Uttiially two glanda are con- 
nected with each hair follicle, but tfaero may be tliroo or 
only one. A pair of scbnccotui glands ore repi'e«ented on 
the itidf» of ciich of the htur follicles in Fig. 119. 

Tho Skin Socretiona. Tho Kkin besides forming a pru- 
teclivo Covering and serving aa a »cnec-organ (Chap. 
XX.XIV.) also ]i1avs an important part in regulating the 
temperature of the Body, and, as nn excrrtory organ, 
■i-ying off cerUiin wiwlo product* from it. 



glflnd. d. iK.rny loviTof 
■-■iiiline; r, M *l|ilKhlnn 

Ifty^rL h, >l>^rmK The 

imbcMtyl In Uif (iiU'ii- 
tMnom tal.nre HMQlMda w 
thadaisilK 





1 



pERsptBA rioy. 419 

Tlio eurcut p»UFcd out by IIk- iiuc]ori)iiiroas glands is » 
t niiii<|mrent colorlew li<)aid, with & peculiar odor, vnniinj 
i» difiereiit rooca, and in the Bamo indiTiduid io diScrent 
rogioiu »t tlio Budv. It« quantity in tvciitj'four houn u 
.4u1iji>ct to great Tuiations, but UBtialljties Iwtwcen 700 and 
^000 ^ama (10,850 and Sl.iino gniiii^). Thti amount io in- 
Iliii!iicvd mainly by thft Burroundin;^ temperature, being 
greater when this is \i.\s}v, but it is also increased by other 
ihinga tending \» nu»<i the t«mi>cnitnrv of tbo Body, ax 
niiiflcular exerras& The sweiit may or may not evu]>i>rnle 
OS fast as it ia secreted; in Die former vuso it is kiiowu as 
ituen»ibh, in the )att«r as wnjtiM* pertpiraiion. B} far 
the in<»t passes oS in the insensible form, dro[M of sweat 
only accumulating vfhen the secretion u very profuse, or the 
surrounding atmo<i|ilien! so humid that it docs not rcadily 
take ap more moisture. The iierspiration U acid, and in 
1000 parts contains 9D0 of water to 10 of Eolids. Among 
the latter are found urea {I.fl in 1000), fatty ncids, sodium 
chloride, and other wiltii. In di^fiifcd condition of tho 
kiilncyx tbo urea may \te greatly iiicrea««d, the skiu snpplv- 
mtinting to a certiiin vxtent deficiencies of thoic organii. 

The ITerTous and Oiroulatory Factor* in tho Swoat 
BeccQtlOD. It UHud tu be bolicTed that an increased flow ut 
blood through the skin would mlAc* of itwLf to cause in- 
crciucd perspiration; but against this view arc the facts 
that, in terror for cxiimple, there may lie profuse awealiiig 
with a cold pallid skin; and ttuit in many febrile states the 
skin may l)C hot and its vessels full of blood, and yet tliere 
may be no sweating. 

Booent experimenta iihow that the eecrotory activity of 
the sw«at-glundi< it under the direct oontrol of nerve-fibres, 
nnd is only indirectly dependent on the blood-supply in 
their neighborhood. ■Stimulating tho sciatic nerve of tho 
freshly amputated leg of a cat will cause the balls of its 
feet to sweat, although there is no blood flowing through 
tho limb. On the other hand, if the sciatic nerve be cut, 
Bo as to paralyxo it. in a living animal, tlie rikin arteries di- 
late and the toot gets more blood and becomes warmer; 
but it does not sweat. The tmtU-fiirtt originate in oertaia 



^ 



ao 



TRB ITVurAS mi>7. 



swuat'Cttttru in tho spinal cord, wiikh mair eithvr be di< 
rectly excite*! br l>!"<)(i oi » higher leniperainre than usual 
flowing through iheni or, reflpxly, by warmth ncliiig on chc 
pxt«rior of tlie Body and islimnhiling the sensory nerves 
lli«r& Both of thci^o ugi'imioi* comnimily ahto exoito the 
va^o-dilntor nerre^ of tho sweating part, and bo the incressi'd 
liiood-supply goes along wilh the nccrelioii; but tie two 
phenomena sire fundiinu'iitHlly indepondenu 

The Sebaoeous Secretion. This in oily, seinillaid, and of 
a rijieciat odor. It couljiiiiK tibout SO per ccut of fat« (olcin 
and pidmaliu). It lubricates tlic Xwvw* and usually rendem 
them gUwsy, even in persons who uso none of the various 
compounds sold as ■'hair-uil." No doubt, too, it ge(a 
«|irusid miiro or Iosk over the skin and makes the cuticle lesfl 
iwrinonble by water. Water poured on a liealtby skin does 
not wet it readily but runs oS it, us " off a dack's back" 
though to a leis* marked degiee. 

Hygieiu of the Wsxa. The eebaceous secretion, and 
the s»Ud residue left by evaporating tiweaC, couiitantly 
form a solid film over the skin, which must tend to choke 
up the muulbs of the ewent-glandx (the Ho-callcd "porea"of 
the skiu) and impede their activity. Hence the valim to 
health of kotpiiig the skin cleun: a daily bath should lie 
taken by every one. Women cannot well wash their hair 
daily as it takes so long to dry, but a man should immerse 
his head when ho tak«r< his butb. As a general rale, soap 
■hould only be used occasionally; it in (juite unnccessuy for 
eleanlinCKs, except on ex|)o9ed parts of the Boily, if f rcqBCnl 
balbiiig is a habit and the skin be well rubbed afterwards 
until dry. Soap nearly nlwnyit conlnins an excess of alkali 
which in itself injures some skins, and. besides, \t ajit to com- 
bine chemically wilh the sebaceous secretion and carry il 
too freely away. Persons whoi'e skin will not stand soaji 
can find ii good substitute, forwattbiiig the bonds and face, 
in a httle conimoul. No doubt many folk go aboat in 
very good health with very little washing; contact with 
the clothos and other external objects ktcp* iM excretions 
from accumulating on the ekin to any very great extent. 
Bnt apart from the duty of personal cleanliness imposed on 



BA Till SO. 



431 



^ 



man tu a social animul in daily intercourse with othi-r», 
the mere (act llmt the bealthj Body cuii manage to gel 
aloug uudcr unfavorable conditions ti* no reason for exptw- 
iug it to them. A cloggod tkiii throws mvn work on tlto 
lunga and kidueya than their fair shnrc, ami tho eyil eou- 
seqacnces may be experienuwl miy duy when something cleo 
throwK another extra strain on iheni, 

Anituslii, a considerable jiortion of irhotw «kiii ha* been 
TamiKbfd, die within afew hours!. This n*ed to be thought 
due to poisoning by retained ingredients of the sweat. 
Bui tlie real cause of death teems to be «u exceEsire mdia- 
tion of heat from ihe surface of the body, which the vital 
oxidative pioceAacs cannot keep up uitb, eo the bodily tem- 
perature falls until it reaches a fatal point, about 20° 0. 
(^T.) fur rabbits. If the animal be packed in raw cotton 
or kept in an aimoHphere at a temperature of 30*0. (86^ F.) 
it will not die from the raroishing^ 

BatMng. The general Huhject of bsthing may bo con- 
siJoied lioro. Ono object of it k that above mentioned, to 
cleanse the skin; but it \» alito us^'fiil to Htreugthcn and 
invigorate the whole frame. For strong healthy pontons a 
cold bath is the best, except in extremely severe weather, 
when the temperature of the water should be raised to Iti" 
0. (about m" F.), at which it HtiU fmU quite cold to the 
surface. The first effoot of a cold bath is to oontriict all 
tho flkiu-vos«els and muko the surfaoo pallid. This U eoon 
fulUiwed by a rcucliun, in which Uie skin becomes red and 
congealed, and a glow of warmth \* tv\l in il. Tito projii-r 
time to come out is while this reaction la.'^ts, and after 
omeiMon it should bo promoted by a good nib. If the 
stay in the cold wal«ir be tuo prolongod the state of reaction 
paHsos off, the skin aguiii beoomea pallid, and the person 
prolubly feels cold, uncomfortable, and deprcitsed all day. 
Then halhing in injurious instead of benelk-ial; it loners 
inatcad of stimulating the activitioa of the Body. Uow 
long a slikv in the culd water mar be made willi benefit, 
depends greatly on thi^ iiidtridual; n vigorous man onn bear 
it and set up a healthy reaction after much longer immer- 
sion than iL feeble lino: mun'ovL^, b<.-ing ii;od to cold bathing 



4M 



TBS HUMAX BODY. 



renders a longer Btay ^e, und. of course, tho t«mpcniUire 
of the water has a grcal iiifliicnoc: waler catlei "cold'" 
mar vary uitUiii m-.y)- widp limits of tempcratnrD. as todi- 
caled by the tlierDiumeter: luid \\\v culdvr it is tlio vliorter 
is tJio dmci whivli it i» wise to reui&in in it. Feraons who 
in the oompiiralively warm water of Narraganeett dnr- 
iiig the summer months Btiiy with benefit imd pIcH^iiri' 
in ihc «eu, have to content Lk«nMclTc» witli a iiiiglc jitiinge 
on part^ of tho coatit whero the waler is colder. The 
uature of the wat«r has some inftoeuee; th^ salts contained 
in sca-wflter stimulate the skin-norvcs and promolt thr 
ufu-rglow. Manv pcr«on« who otiinot dlnnd a simple <^>ld 
frc:sli- water buih take oiid with iK-iieUt when fonieMiiincs are 
previously dissolved in the wat«r. The best for lliis purpose 
are probubU' those sold iu tho shops under the name of 
"*<?a-jiaU«." 

It is perfectly safe to bath« when warm, provided tho 
skin is not perspiring profusely, the notion commonly pre- 
vtilont to tho contrary notwithstanding. On the other 
hiind, no one should ontor a cold bath when feeling ehilly, 
■>r in a deprtw^od vitiil condition. It is not wiite to take n 
bath immediately afr^r a meal, since the afterglow tends to 
draw away too much blood from tho digestive oipins, which 
are then aotiTely at work. The best time for a long bath is 
about three hours afU>r breakfast; bat for an ordinary daily 
dip, hwling but n short time, tlicce is no butt«r period than 
on rising and while still warm frnm bed. 

Tho shower-bath abstracts less heat from tlie skin than 
nil onlinurj' cold bath and. at the «:inie time, gives it u 
grciuer lilimuhi.*: lu'nco it hiLt certHln mlruntage*. 

Persons in feeble he;iUh may diminish the shock to tlie 
syatvm by raising the tvuiperatiira of tho water they bathe 
ill up to any point at which it still feel:< coul lo the akin. 
Batliiog in water which feels warm is not advi^ble: it tends 
gfriionilly to diminish tliwital activity of tho Body. Uenoo 
warm baths should only bo taken uccusioually and for 
apvciul parposeo. 



CHAPTER XXVIII. 



KUTKITION. 



The Problems of Amm»l WutriUon. Wo have in pre- 
ceding chapUTS tnnfii oi^rlaiii imvwiiala, consjgliug of ttn»i» 
more or 1km cimugeO by diycstiuu, iuto the BotU from the 
alimentaiy canal, and oxygon into it from the lungs. Wo 
havo aW det«ct«d the clemeots thiia taken into tho Body 
in their pasaage out of it again bv lungs, kidneys and Hkin; 
and found ibitt for thu moat pitrt their cliemioal aUite waa 
ditferout from liiat in which they entered; the ditToreuce 
being eipresiible in geticml icrms b}' Buying Ibat mora 
oxidized foruut of matter leave the Body tliau cnlvr iU 
Wu luiv« now to consider what happL-ns to each food during 
tJie joumoy through the Body: i» it changed at all? in it 
oxidi^icd? if so where? whaC products does ita oxidation 
give rise to? la the oxidation direct and complete at onco 
or docA it occur in Kiicuoiwivo i>l«p»? Has the fond been 
Uflcd Unit to make part of « living tiajuo and i» this then 
oxidised; or bos it been oxidized without formtng part of a 
liring tisrao? if so, where? in the blood stream or ontaide 
of it? Finally, if the ch«mical changcii undergone in 
the Body are such as to liborate cncr^, how has tlii.^ enngr 
been ntilixcd? to maintain the tomperattiro of the Body or 
to give rise to muacuW work, or for other puq)o«c«? This 
is a long string of questions, the answers to many of wbioh 
Physiology liii'' ncill to seek. 

The Seat of the Oxidations of tho Body. According 
to older views oxidation mainly took place in the blood 
while flowing through the lungs. Those organs were con- 
tiidered a sort of funioce in whieh lieut wiw lilxrated by 
blood oxidation, and then distributed bv the oirculation. 



4-J4 



rnii BCMAy BOUT. 



Uul if i\m woru so the longs utight t<> bu lliu liottvst jtait:' 
of tlie Body, and the blood leaving th«m by tlie pulmonan' 
Toiiis much hotter tlmn that brought tu them by the pulmu- 
nftry nrtery afwr it liad bocii cooled liy warming M the lit'- 
Biics; and neither of tlie.% things \a true. A small amount 
of httut is liberated when bmnoglobin combines vith oxygen 
in the pulmonary ca]ii11iiric«, but IhoalTiHiticti thus saliHfted 
are so feeble that iHb energy liberated ia trivial id amounT 
when compared with that wt froo when this oxygen ^ubR*- 
qnently fonnR stabler componndx elttewhere^ It U now, more- 
oTcr, tolerably certain that hai-dly arty of this tatler class of 
oxidations otciira in the living circtiliiling blood at all; H» 
cells do, no doubt, use up some oxygen and net free some car- 
bun dioxide; but not enough to be detected by ordiQuy 
methods of anttly»i«. The pcrcentjigc of oxygen liberated in a 
vacuum by two spQciroena of tlie Wood of an animal, taken 
one from mi artery near the heart, and the other f loni u di«t4inl 
one, are ])raetii:ally the same; showing that dnring llie time 
occupidd in llowiug two or throe feot through an artery thi' 
blood u«y up no ajj]iix-ci«ble ([iiiiility of it* own oxygen; 
while in the short time occupied in its brief cupillani' tran&it 
it loses so much oxygen as to become renous, The differ- 
ence is exjitttincd by the fact tliat the blood givc« off oxygen 
ga« through the thin capillary walls to the surrouudin;; 
tisgaes; nnd in them the oiidulioii lakes place. ^Vs wc 
have already necn, a fieshly excised muiicle deprived of 
blood can still be made to contract; and for eome consider- 
able time if it be the muHclo of a cold-blooded animal. 
During iu eontnicfinn it evolves largo amounts of carbun 
dioxido, although the reciting fret^li muscle contains bordly 
any of that gas. Hero wc have direct evidence of oxidation 
tuking place In a living ti^Kue and in connection witli ita 
functional activity: and what is true of a muscle is prob- 
iibly true of all tissiit-s; the oxjdutionx which iiup|>ly (hem 
with pnergy fuke place within the living cells ihemselves. 
The «tatoment frequently ma<lo that the oxygen in the cir- 
culating blood exists an ozone, roots on no sufRcicnt baeij<; 
decomposing hemoglobin does seem to form oEono when 
expOHod t^ the air, but fresh blood yields do «igD of it. 



I 



87XTHEf»BS IS THIS PODT. 



4S6 



^ 



» 



ErperiiaenU iniuli; )>y atltling rariouii conibutitililc itub- 
«tance», as sugar, to fresh blood, also fail to jjrove the oc- 
Cttneu<* of imy oxidittion of "udi bi>iiioii in Ihiil lu|iiid. 

Tissue^BuUdlng and Knerg7-Yioldiiig Foodit. The 
Human Uody. lilio thut of other nninialti, is, on Uiii w)iul«, 
chemicaUy deist rut' tivc; it lakes in highly complex sub- 
stiiices M food, and eliminates their elemeuto in much 
simplei' comj>otinds, which cuu ugniii be built up to their 
onginsl oonditioii by plants. NeTertholesa the Bo»ly ha« 
cerlniii coustruciiTe powers; it, at least, builds up prutoplaam 
from proteids and other KubstanceK receivod frcim the 
exterior; and there in reiuton t,o believe it docs u good deal 
mort> of the '^me kind of work, though never an amount 
equaling its chemical dost ructions. Given one single pro- 
teid in it.s food, my egg albumen, the Ikxly uin do rory 
well; milking tierum albamen and fibrin factor.^ out of it 
for the blood, myosin for the muEcles. and so on: in such 
cases the original jirotoid mn«l hare been taken more or 
lees te pieooe, romod«;li'd, and built up agsiin by the living 
tisniea; and it is extremely donhtful if anything dttferent 
occurs in other citHCt, wlien the protoid eaten happens to be 
one fonnd in the i3ody. In fact, dnnng digestion the pro- 
teids are broken down someuhat, and turned into peptones; 
in this state they enter the blood and must sgain be built 
np into protflids, either tJiere or in the Rolid tis»iic«. 

The constructive powers of tlio Body nsed to he mtlicr 
too much ignored. Foods werodivided intoojutfitVay^and 
cotnbuttibU, the former nerving directly l" renew the organs 
or tissues ae they were used np. or to supply materials for 
growth; thiMO were mainly proteids and tats; no special 
ehemioal synthesis was thus supposed to take pbice, the 
living cults being DounxlK-d by iheroouption from outride of 
molecnlco similur to tho-e they had lost. Fat-eells grew 
by picking up fatty mulecnles, like Ihtir contents, received 
from the food; and protoplasmie tifttui'i; by the reception 
of roady-mado proteid molecules, needing no further 
manofacture in the cell. The combustible foods, on the 
other hand, wore the carbohydrates and aomo fats: these, 
according to the hypotJiesis, were incapable of being mad* 




446 



TBS nVXAK BOOT. 



into parts of ■ living ti»suo, nnd w(>t« tiimpljr bnmt nt on 
ill order tn maintain the bodilj wanntb. It Iinving been 
proved, however, tli.tt more fnt might aoctimuUt« in th 
\>l^^\y iif nil uiiimul ibaii vr«« 1«kt-n in it* taoA, ibis cxcc; 
was accounted for by siipjiosing it was due to excesH of com 
buBtiblc foodit, i-UDvcrtod into falj! and vtorvd away as oil 
droplets in TAriouii cells; bat not actually baitt up into tru< 
living odipoMt ti&fue. Liobig, somewhat eimilnrlr, cUifS' 
ullfoad< into plasUctConcvTiU'A in making n«v Iip^ucs, aiid' 
rtspiratory, directly oxidixed before tboy erer eon$liliitod' 
H tissne. The plaetic foods were (he proteidfl, but these 
nUo indirectly giivc rise to tho cnorg}' expended in mnecu- 
lar work, and to wmo hv&\: the proteid mnscular fibre 
being bniken first into a liigbly nitrogenous part (area, or 
some body well on the roatl to become urea) and a non* 
nitrogunixed richly hrdrocorbonous part; and thi^ latter 
was then oxidized and garo rise to beat. Several facta may 
be urged against this view — (1) Men in trojiieal elimutes 
live mainly on non-proteid foods, yet their chief nevds ara 
not heat production, but tissue formation and miucnlar 
work : according to Licbig's view tht'ir diet tihouM be 
mainly nitrogenous. (9) OamiToroua animala live on a 
diet very rich in protcid*, ucvorthelonf develop plenty of 
animal hi^at. and thai witboiil doing the excesciTA mujtcu- 
Inr work which, on Liebig's theory, mast flntt W gtm« 
through ill order to break up the proteids, with the produc- 
Hon of a non*axotJzed jwrt which could then be oxidized for 
beat-production. (3) Great muH^ular work can be dono on 
a diet )ioor in proteids; beasts of burden are for the moKt 
part herbi vorous. (4) Furlhor, we know exactly how much 
onergy ran ho liljerated by thooxidatton of prot«id« tu that 
atage nliiiib occnrs in the Body; and it is perfectly poiwiMc J 
to cetimale pretty accurately the amount of urea and urio^| 
jicid excreted in n given time; from their »nm the amount ^1 
of proteid oxidized and the unionut of energy liberated in 
lliat oxidation can be ealcnlate<l; if Ibis be done it is fonnd 
that, iK-Jtrly always, the muscular work dtmc during the 
same period represent* far more energy expended than could 
t yielded by the proteids broken down. 



^ 




SOimOK OF MV8CVLAR WORK. 



487 



The Souroo of tltd Bnergy Expended in Uiuculnr 
Work. Tliis iiicstion, wliivli wiw jiosljmned in tlie oliftii- 
\vx* douling willi Uio iniixcuhr tisiiaoii, on lU'Oniiiit of its 
importanoe dcmundH horc a. disGamon. It may be put thug: 
— Doasa miucli'-fibn; wurk by thv oxidiition of its proteidn, 
U0, by breaking tbem down into coiiipoundti wliich ure 
then removed from il smd conveyed out of the Body? or 
does it work by the energy lil>enated by iho oxidation of 
curboQ luid hydrogen componnda only? The prohieiii muy 
be attacked in two ways; first, by examining the eicretJoiui 
of a man, or other animal, dnnnf; work »iid reet; fotjonil. 
by examining dirtictly the <^hemieal cliaiig^-i prodticcd in a 
muaclewhca itcootracta. Both methods point to the same 
conclusioQ, viz. that proUtid oxidation is ii»t the eouroo of 
the mechanical energy ex]>ended by the Body. 

One gram (15.5 grains) of pun- albumun when completely 
burnt liborale*, iw heat, an amount of energy e<innl to 2117 
kilogram metci-a (15,270 foot-pounds). But in the Body 
]>roteids are not fully oxidized; part of their carbon is. to 
form carbon dioxide, and port of the hydrogen, to form 
water; but some carbon and hydrogCD pass oot, combined 
with nitrogen Rud oxygen, i» the incompletely oxidiiwd 
Ht«te of urea. Therefore all of the energy tlieoretically ob- 
tainable is not derived from jtrotcids in the Body: frum 
the above full nmonnt fur each gram of proteid we must 
lake the quantity carried oS in the urea, which will ho the 
amount liberated when thai urea is completely oxidised. 
Koc-h gram {15.5grnini*) of proteid oxidiiod in the Bndygivea 
i tit a gram (!>.\A grains) of urea; and )>inc« oiip gram of 
urea libemte«, on oxidation, energj- amounting to 034 kilo- 
grammetem (tiT40 f»ot-poundH) each gram of proteid 
oxidized, so fariui iti pouibi* in the Body, yidd« during the 
proccesi 3117-- ^*- = lB0i>.7 kilogrammeten> (13,Ji37 foot- 
INtundfi) of energy. Knowing that area carries off pructi- 
CHllyull IhonitTogon of protoide broken np in the Body, and 
contains 46.6 per cent of nitrogen, while protdda contain 
IC per cent, it Is eaay to find that each gram of nre« repre- 
tatWA thcdocompoMlinn of ahout3.BQgnim«of proteid and. 
therefore, the liberation of 3060.00 kilogrammcter« (36,933.0 



l^. 



496 



TSB mXMAN BODY. 



foot-^nnds) of enorgr. If, therefore, ire knov how macfa 
urea n niiin cxureUM during a given time, and how mscli 
tnochttuical work he does dnring the 9&mt: time, we can 
readily discover if the ]»tter coultl posaibly liare boeii done 
by the energy eot free by ]>rot<'id doctimposition. Let ns 
take ft 8i>ccinl cnse. Fick and Wii<l(«cnu», two Gcrmnu 
obgcrrers, climbed the Faulhorn mountain, which i« iari6 
meters (about 6415 foct) high. Fick weighed CG kilogramia 
and, therefore, in lifting hi» Body alone, did during tho 
iisceiit 120,096 kilogram niet«rs {93S,0;3 foot-pounds) of 
work. WialecenuB, who wciglicd "6 kilogramx, did similarty 
148.656 kilognuneU'rs (1,073,296 fout-pound») of work. 
But during the ascent, and for five honra afterwards, Fick 

reted urine containing urea iimiwcring only to 37.17 
38 of proU'id, and Wislecenns ure* nnswcring to 37 

laai. Siuoe each ^am of proteid broken up in the Body 
liberates 1S05.7 kilognunmetcm (13,037 foot-pounds) of 
energy, tlio amount that Kick could pos-tibly have obtained 
from auch a source w 1805.7 X 37.17 = C7,U7 kilogram- 
meters (484,584 foot-{K)uuda), and Wisk-ccnna 1805.7 X 37 
= 66,810 kilogrammeters. If to the muBculnr work done 
in actually raising thoir bodies, wc add that done simul- 
taneously by the heart nnd the respiratory muscles, and in 
snoh nioveraents of the limbs as iiere not actually concerned 
in liling their weighl, we should have, at len^ to double 
the above tulal muscular vrurk done; and the Amount of 
energy liboitited meanwhile by proteid oxidation, beoomct 
utterly inadequate fur ita execution. It is thus clear that 
mnscnUr work in not wholly done at the expense of the 
oxidation of muscle proteid, and it is rer^' prubublo that 
none is so done under ordinary circumstances, for the urea 
excretion during roi^t is about m grent as that during 
work, if the diet remain the same: if the work is very 
violent, asinlong-disUmoe walking matches, the urea quan- 
tity 18 Bomctimcs temiiororily mixed but this lucrcaso, 
which no doubt represents an abnormal wear and tear of 
musele-flbre, is probably independent of the liberation of 
energy in the form in which u muscle fan use it, more 
taking the form of heat; and is, moreover, coinpcn- 




UltKti .t-YD MUSGULAlt WORE. 



4S9 



autM foriift«rvari]«by»cIiminiiilii><l nrea cxvrctiotL Thus, 
hourly, before the asoent Fioh and Wialecenna each ex* 
crated on the avcri)^ about 4 ^rums (C3 grains) of urea; 
during tb« a«'ctil tictwi'ccn 7 ami 8 graiiui (108-121 grain*;): 
hut during tbc Mubiequent 16 boun, irhon any nrca formed 
in the work woald certainly bftve reached tho urine, only 
nn average of almut -1 grutnii {Xti.Ti grains) per hour. 

It may alill bo objoclad. howpver, that a good deal of the 
muacle work may be done by thw onorg)" of oxidised muscle 
proteid; that tho amount of this oiidatian occurring in » 
muacle during rest or ordinary work is pretty conxtant and 
simply takes different forniti in the two caM?:*, iniioh m ft 
#t«am-engin« with itt funmnce in full blaat will bum as 
much coal when working as when renting, bat in the former 
caae lose all the energ;v' gcuci'atcd in tlie form of hrat, and 
in the latter partly aa miHihanioal work. Tims tho want of 
increase in urea daring muscular activity would be explained, 
while still a good deul of iit iliaiWn cncrgj- might come from 
proteid di^radtttioD. But if tliia wore eo, th<rn the work- 
ing Body should eliminate no more carbon dioxide than the 
resting; the amount of chemical chaiigca in ilA mnttcles 
being by hypothesis the same, the carbon dioxide eliminated 
should not bo increawd. Exporimeut, huwerer, shows 
that it is, and that to a T«ry Iiu-go extent, even when tho 
work done is quite moderate and falls within the limits 
which could bo performed by tho normal prot^^id degrada- 
tion of tho Bocly. Quite eaay work doubles tho carbon 
dioxide excret<>d in twenty-four hoars, and in a short period 
of very hard work it may rise to Are times the amount 
eliminated during rest. Since theiiren is not incrensecl, or but 
very slightly innrcascd, at tbesame tjmcthis carbon dioiido 
oinnot be due to increased proteid metamorjihosis; and 
it therefore indicates that a niuficle works by the uxi<hition 
of carbonaceouii non-nitrogenous compounds. Since all 
the carbon com|Kiunds oxidized in tho Body contain hydro- 
gen this olemunt i^ also no doubt oiidixod during muKi-u- 
lar work; but ila estimation is difficult and has not been 
attempted, because the Body oontainf so much water ready 
funned that a large quantity ts always ready for incrawcd 



i 



490 



TBR HUM Ay FODT. 



eTBpontioD £roiii the lungs and skin, when«Tcr thfl roepira* 
lioii.iarequicketii^d, ikithevareby eiorcist It, tliii», isTPry 
(lillicult t^> K»y lioir much of thu extra witlcr eliminated 
from th« llody during work 'u due merely la this cauite and 
liow much to increased hydrogen oxidation. 

The coQcIusion wo ure U-d to ii>, thvii, tliulnrnuBcIc works 
l>y the oxidation mainly, if not entirely, of carbon and 
hydrogen; much aa a steam-engiiio docs: the proteid con- 
Ktituciits of the muKolo itn*wcr roughly to the metallic jmrta 
of the engine, to the machinery using the enei^' liberated 
hy the ondations, but in itself only euflering wear and tear 
bearing do direct proportion to the work done; tut an cngiofl 
may rnat> m muxcle proteid may and doea oxidize, but not 
to BHpply the organ with energy for nsc. This conclasion, 
arrived ut by a liludy of the cxi-nl ioiiH of the whol* Boily, is 
confirmed liy the rc^ulU obtained by the chemical study of 
a eingle muscle. A freah frog's muscle {which agrees in all 
t'ltsentinl points with a manV) contain* priicUcailly no car- 
bon dioxide, yet, made to work in a Yaciium, gives off that 
gas, and more the moru it wiirkx. Some carbon dioxide tn 
therefore formed in tlie working muDclc. If the maeclc, 
after contracting aa long aa it will, bo thrown into doath 
rigor it givc« vB more curbon dioxide; and if taken per- 
fectly fresh and sent into riffor mortis without contracting 
it gires off carbon dioxide niso, in amount exactly equal to 
the fwtn of that which it would have given off in two sttigoe, 
if flr^t worked and then sent into rigor. The mufide must, 
therefore, contain a certain store of a carbon-dioxido-yield- 
ing body, and the dccom intuition of thi^! U associated with 
the occurrence both of muscular activity and death stiffen- 
ing. Simitar things are true of the acid simultaneously 
develoiK-'d ; llio mii«clo when it works produces some «irco- 
laetio acid, and when Ihroun into rigor mortis still more. 
No increase of area or krcatiu or any similar product of 
nitrogenous decomposition is found in a worked mu#clu 
when compared wilh a rested one, but the total carlioliy- 
dratca are rather less in the former. Theise facts make it 
clear that muscular work is not done at the eipuuso of 
proteid oxidation; and we liaw already ticen (p. 3tiT) that 




cnswrsrsr op worktxu vusaris. 



481 



th« oxjgco u luiiKcIc iiiwtt in contracting u not taken np bj 
it ftt tha time it is nsed, §inco a loDscle containing no oxy- 
gen will Btillcontnict and evolve carbon dioxide in a vaetinm. 
It is probable that th^oliemiealphciiomoiui ocuurrlngiiicon' 
tnotion and rigor are e^sentiiillj the same; the death stiffen- 
ing resulta when ttiey oceur to an extreme degree. Pro- 
visionally ouo may oxpluiti tlicfiuUu followM — A muscle in 
the Body tiUce* up fr.itn tiio bl<Mid, oxygen, protuids, and 
non-nitrogenons (earhohydrate or fatty) substances. These 
it buildd up intx) ii highly complex and TOry niii^tuble com- 
pound, comparable, fur I'xiimple, to niiro-giyeerine. Wlieii 
tlie muscle ia utinmlated this fulls down into simpler sub- 
etsiicea in which Btronger affiniliea arc eatiiflied; among 
these uT« carbon dioxide and «»rci>luvtic acid and s prol^id 
(myosin). The energy liberated is thus independent of 
any Bimultanemiii taking tip of oxygen; the imiouut poKfiiblo 
depemlH only ou how miieh of the dcci>mpo»ible body exists 
in the muscle. Under natural conditions the carbon 
dioxide ia carried off in the blood nnd p(!rhupji the surco- 
lactic acid aUn, the latter to be elsewhere oxidized further 
to form water and more carbon dioxidi'. Tiie myo«ia 
remains in the muiiclo-fibro and i« combined with mora 
oxygen, and compounds of carbon and hydrogen taken from 
the blood, and bnilt up into tbo ungtable energy-yielding 
body again; nons of it, under ordinary circtum«tancu, 
Icaros tbo muscle. If, hoivever, the blood-supply be defi- 
cient, the myosin clots [p. ri5) before this refititntion takes 
place and it cannot then be rebuilt; and in excessive work 
the sume thing partially occurs, the decomposition occur- 
ring faster than the recumpoNition; the clotted myosin is 
then broken «p into simpler bodies and yields a certain 
monsseof Ihenrea excreted. In rigor mor/t> all the myosin 
ptmet into the clotted statue and oansni the rigidity. A 
working miiitcle takes np more oxygen from the blood than a 
resting one. a* is shown by a oompnrison of the gases of its 
venouM blood in the two cases: this oxygen HKMiiniplion is 
not necessarily proportionate to the carbon-dioxide elimina- 
tion at the nimo time; for the latter depends on the break- 
ing down of a body already aocnmnlated in tlie mnsde dur> 




43S 



TBS nUMAK BOOT. 



ing rest, and this brMlcin; down may oooor fui4>r thn 
recoiwtruction. We are thns enabltid, also, to omit' retail d 
bow, daring exercise, the cKrlton dioxide eToWed itom the 
luDgs may contain more oxygen than that taken up at tho 
Mine lime; for it is lar^ly oxvgen preriondy stored dur- 
ing rest, that then apjMan in the carbon dioxidfl of tiie ex- 
pired air. 

Are any Foods Bespiratory in Iiiebig's Sonao of the 
Term? Wc find, \\\vn, Ihiit LiubigV cliissitiiTnlion uf foods 
cannot bcaocepted in an absolute sense. Thereianodouht 
that the sul><^t3ncc bntkra doi*-n in muMoljir contraction is 
proper living m»M-iil»r ti««u(-; and if thij {it* protcid con> 
Btituent being retained) be reconstmcted from fooda con- 
taining DO nitrogen (whether carbohydrates or fata) then 
the term j?^tu/ic or tii^ao-fomiing nuinnt bo restricted to 
the proteidfi of Uie diet. We mn^ mlher conclude that 
any alimentary principle containing carbon may be used to 
replAce the oiidizcd carbon, iintl any contaitiing hydrogen 
to re]itiu-i> the oxidized hydrogen, of a tissne; and »a e^in 
DOD-proteid foods may be plastic. A certain proportion of 
the foodi< dtgc«ted may perhaps be oxidized to yiHd energy, 
before they erer form part of a tiEsne; and so corre»[Kind 
pretty mnch to IJchig'a rwpimtory foods; hut no hard and 
fiut hnc atn be drawn, making all proleid foods plaatio 
and all oxidizable non-jiroteid foods reepiratory. 

Luzua Consumption. Xotonly, acabovejwintodoat, may 
non-nitrogcnoiH foods be plastic, but it is et-rljiin that if 
uny foods are oxidized at onoc before being oi-gauize<l into 
H tisnte. proteidsarc tiiidfr certain circiimi<lance«; namely, 
when they are contained in cxocfm in a dit't. If an anunal 
bo starred it ii* found that its non-nitrogenous tissues go 
first; an inMtinJdt-ntty fed animal Inee^ it^ fat lirvt. and it it 
ultimately dJui' "f slarviUion, ie f"iiiid to have lost 1*7 per cent 
of its adtpo^ tissue and only about 30 ]wr cent of it« 
proteid-rich mnscular tisane, and ulniost none of ita brun 
and spinal cord; all of conrse rc<^koned by their dry weigbt. 
It is tlins clour th»t thc^ proteidii of tlie tiiauex resist oxida- 
tion much betl<>r than fat does. But, on the other hand, if 
\ well-fed animal be given a very rich proteid diet all tJie 



i 




sovnctis Of vitF.A. 



433 



iiitrogeti of it£ food rmtppcura in it« urinr, mid thot wlieo 
it is UyJDg np ful; so ilutl tlieu we get a state of things in 
which proteids are broken up more eaeil> thuii fat*. This 
indicates Ihut proteid in the Body may exbt under two 
ooixlitions; onv, when it forma pari of a living tifisne and is 
protected to a ^at exU'nt from oxidation, and auothiT, in 
wbiob it ia oxidized with nuulinciet and is prGsamabl) in a 
difFerant condilinn from the 61-st, and not yet built up into 
part of a living cell. The uh- of prutviils for direct oxidiit iou 
is known as Itixtif innyumplittn; liow far ii occurn nnder 
ofdinary cireiiinstanccs will be conBidered presently. The 
main point now to be homo in mind u that wbilv all orgwiic 
nou-nitrogenons food^ cannot 1>c called renpiiatori/. neither 
can proteidfl under all circncostanccs be called plastic in 
Liiebig's sen«t. 

The Antecedents of Urea. In the long run iJie pro- 
genitors ot the urea I'XL-re ted from the Body arc the proteids 
taken in thu food: but it remains still to be oonitiditrvtl 
what intermediate steptt tht-se tako before excretion tn tbt> 
unuc; and whether urea ilaclf is Qnally formed iu the kill- 
aeyB or merely separated by them from the blood. 

In i>ocking untcocdeiit« of urea one niiturally turns first 
to tlie muscles, which form by far the largest iiiiln< of pro- 
t«id tissues in tho Body. Analysis shows that they alwuyx 
contain kreatin. a body iDtcrmediato vhemically between 
protvid» and nrea. Theqnantityof tbiiiin musolCAis prac- 
tically uiintfocted by work, and is from 0.^ to 0.4 per cent. 
Stnoc it ig> nuulily soluble and dialyzable, and Ibei-efore fit- 
ted to pass mpidly oat of the musi-lcs into the blood stream, 
il is a (uir conclusion that a good deul of it is formed in 
the mnscles daily and carried oO from them. Kifiitin, 
too, oxiAlit ill tlie bruin, and ])robaLily tlivro, and elsewhere 
in the nei'Tons ^«tem. is produced by cbemioid degrada- 
tion of protoplimn: Ihc spleen tdso contains a good deal of 
kreatin, and so do many glands. This substance would 
therefore seem to be conntaittly prodnced in considerable 
'pmntities by tho proUipln-Jinic tissues generally: and since 
it belongs to a group of iiitriigcnoiis compounds which the 
Body is unable to utiiixe for reconstruction into pi-otaids, 



434 



TUK BUM AX BODT. 



it mnot be carried off somehow. The nrine. however, oo" 
tains very littk- kreatiii. or iu immeiliuU' derivative, krea- 
tinin, utid what it docs contain depends miiiniy on lh« 
f«cding, aince it varies with the diet and vanishcB during 
starvation; eo it is probnhic thitt this Hnbatance is con- 
Tcrtwl inl« iiri'ii and pxorcied in that form. This oonver- 
sion must occur ebewhert- thmi in the muBcles, which con- 
tain no ureu; iilwi, very little, if any, fz\6U in the brain. 

Where Ihe kreatin is finally changed into ure» i« doulxt- 
tul. It may bo in the kidno-* by the renal epithelium, 
or it muy Iw el.<ewherf, and the nrea produced be merely 
picked up from Uie blood and pas-ied out by the kidney- 
cells; or both may owjur; histologically the dieitinctly 
«icret"ryej>ith«liumtiof thcconvohiteil part«of the tubak* 
and of Henle's loopii, differ so much as to .tnggeX on en- 
tirely different function for tlicm. 

On thi! whole, the evidenee *eems to show that urea is 
merely separated and not produced in the kidueys; a priori 
ih\* is more probtible, siuiv in Ihe degrudiKion of kreatin to 
yield urea energj- is liberated and lliis might very well Iw 
ntilizcd in some organ; whil» if the process took place in 
the kidney tubules the fon-e sel free would bo vrwtcd. 
The blood always contains urea, and renal-artery blood 
apparently more than rcniil-vpin blood, which shows that 
nrea ib removed from the blood in the kidneys. Moreover, 
if ft mammary kidneys be extirpated urea accumulates in 
its blood, which could not be the ease if urea were nor- 
mally only produce*! in the kidneys; and if nr«i be injected 
into a vein it ts rapidly picked up and carried off in the 
urine, showing that the kidney-ccIU have a i>clective power 
with respect to it. 

Whilv the urcn ri^utttng from further cbaDges in the 
kreatin formed in the ti^^^nes is n measure of the wear 
and tear of their protoplasm, part of the nrea excreted 
haa probably a differenl source; being duo to the oxidation 
of proteids, as energy liberators or ix-spiratory foods, before 
they have over formed u li^ne. When jdenty of proteid 
food is taken the urea eseretion is hirgely increiased and 
very rapidly, within n conple of huura for example, 




LUXVS COSSUMPTION. 



43& 



and before we can well suppose the proteids eaten to baT« 
been bitilt up into tUsii», tiixl ikwua in turn broken down; in 
fact there need be, mid umially U, under such drcnuiiitancc« 
DO sign ot any special activity of any group of tissuce, auch 
u one would eipoct to i^r« if the urea always came from t)ie 
breaking down of formed histological elements. TIiim urea 
is thu8 indicative of a atiliiation of pmteids for other thau 
plastic purposes; and tho esmo fact is indicated by the 
storage of carlMin and elimination of all the nitrogen of the 
food (p. 444) wheD s diet very rich in protcid ntimcutarj' 
jmnciples is taken. Thi.4 luxut comumption may be coni- 
jiared to tlie paying out of gold by a merchant instead of 
gre4>nbitck!i when he has an abnndftnoo of both. Only the 
gold can bo luod for certain pnrpoaes, aa acltling foreign 
debtii, bnt any quaotity above that needed for euch a pur- 
pose is harder to slore than the paper money and not so 
conTeuieiit to handle; ho it ia paid ont in preference to 
the paper money, which is really somewhat 1p!-s valuable, as 
aniilable at par only for the Heltlemeiit of domestic debtj). 
Xa artifloial pancreatic digestions, when long carried on, 
two bodies, called Icucin and tyrosin, ar« produced from 
proteids. It is found that when lenein is giren to an 
animal in ita food it reappeani in the urine as nrea; so 
the Body can turn lenein into that snbatanre, Uence a 
possible sonrcc of some of tlio luxiis-mnsmnption urea is 
leucin produced during intestinal digestion; and thin in 
Tery likely turned Into urea in the tiver. At any rate 
the liver, to which the portal vein might carry alt leucin 
IhuK formed, contains urea, which nooUiergtnnd does; mid 
when the liver is greatly altered, as in phosphorus poinnn* 
ingand the diiwuHC known a* iK>iitc yellow atrophy, urea 
almost entirely disappears b-omthe urine. This latter fart 
itoom><to point to a tinal production of tirea in thellTttr, whal- 
ever its immediate antecedents may be; whether muscle 
kreatin, or intestinal leucin. or excess of peptones in the 
diet. The Iatt«r might {wrhaps be broken up there into a 
nitrogonmiH part (urL'a)and anon-nitrogenoua part; and we 
shall And that a non-nitrogenous snbfltanoe (glycogen) is 
stored in the livor. 




438 



TffB BViiAN Bonr. 



Protoid Starrction and Overfbeding. Wlien an ani-1 
luul i--> Kit OR ioud detkionl iti )irutt;id.-i, or ooDtjiining none 
of tbem at all, ite urea excretion Mis verj: rapidly during 
the firal day or two, hut llieii much mono elowly until 
dcatli: tlicrc in thua indicated a double source of urea, a jiarl 
rssiilling from tistiuo ivc»r and tear, and altvare present; and 
II {mi't ix'nttlting from Ihc breaking down of proteids iiut 
liuilt ap into tissae, and ceasing when the amonnt of thia 
]>rotoid in llio Body {in liie ijlood for exiimpio) falls U-low 
a certain limit a» a reMilt of tliQ f<tarvation. Ah tho 
nitrogen-stiu-ved Body wastes, its bulk of proteid tiMoet 
is slowly reiliicud and the nrea resulting from their degrad- 
ation dimitiiaheii also, liova well proteid built up into a 
tiKKUo resists removal is shown by tho fact« already men- 
tioned (p. 49'i) &* to the relativfi losses of the proteid' 
and proteid-poor tissasB in sturralion. 

On tlie other hand, if an animal be taken while 
and losing weight and have a Ktnall amount of llr«li giv«ii 
it, il will continue to lojie weight, and more urea thaii 
before will appear iii the urine; increased proteid diet in- 
cn-aBoa the protvid metamurphoitis. and the animal atill 
lost-i, though less rapidly than it did. A little more pmU^id 
still invreast^s protvid metamorphosis in the Ixxly, and 
the urea elimination, and ro on for Bome time; but each 
incremout of prot«id in the food increases the nitrog«noni< 
mctaniorplic)»is somewhat le-M than the last did, until. 
Anally, a point ia reached at which the nitrogep cge«ta and 
ingesta balance; in a dog thU occurs when it gets duly 
ff il8 weight of meat, and uo other solid food. More food 
if llum given is at fimt stored up and the animal increawii in 
weight: but very soon tbc grcali?r wt-ur iind tear of the 
larger ma'.-' of li.'iKties shows itaeU as increased una ex- 
cretion; a^in the egesta and ingesta balance, and the ani- 
mal comes to a new weight equilibrium at the higher level. 
More meat now can<>e:< a n-jietltion of the )>heuomenon: ut 
Qn^t Increase of tissue, and nitrogen storage; and then a 
oeesation of tlie gain in weighty and an excretion in Iwenty- 
fonr boufK of all the nitrogen taken. And so on, until tho 
animal refnsee to eat any more. 



I 



I 




8T0RA0S TISSUES, 



437 



These factn BPcm, Tcry clearly, to show that [>rotoidx can- 
not be bnilt ap quickly into tUsuc«. Meat given to the 
Ktarnog unimnl hiL» it» [irotvidi^ nt ftr»t, ox^ u]> iiiuiuly in 
luxvtcoiwumption — while a little is Etored us tissae, though 
at first Dot enough to coiuiterbulouoc the dnily titwuc waste. 
When a good dcnl more prot«id is p\e\\ llina answers to 
thu nitrogen excretion during sturrution. the animal builds 
ii|> as much into liring tiseuce n£ it breaks down in the vitfiJ 
nrocesseBof tb««e, the rent going in iH^rvaconsumption; ilthtu 
ni'ithiT gHiim nor loseit. Moro jiniicid does not all apitcar in 
the urine at once: some is tuod to build up new tissue, but 
only slowly: thon, ar(«risoinc day>, tlieincri>McdniotAboIigni 
of the inercftM'd flesh balances the excess of nitro^n in the 
diet, and equilibrium is again attained. But. all through, it 
»cen)s ck-ar thai the tissue formation tititlownnd grailimt; 
and so it becomes additionally probable that the increased 
urea excretion soon after a meal is not due to rapidly in- 
or«Med tissue formation and degradation, but to a more 
direct prot«id oxidnhon. 

The Storage Tissues. Every healthy cell of the Body 
contuioe at any momi'til sumo little excess of materia] hud 
by in it^lf, uhove what is TttiuiriHl for its immcdiato necet- 
aities. The capacity of ooutraoting. and tJie concomitant 
evolution of carbon dioxide, exhibiteil by an excUod tnusele 
in a Tacuum, aeem to sliow that even oxygen, of which 
wann-blowled animals have but a small rc«ervo, may be 
■tored up in the living tisjucs in such fonnfi that they can 
utilize it, even when the air-pump faihi to extract auy from 
thorn. But in addilion to the supplies for immediate spend- 
ing, contained in all the cvlU, we find itpecial food roeervofl 
in the Body, on which any of the tii^aea can call at ncvd. 
TheHf, c>.«puciully the oxygen and prulvid resorves, are found 
largely in the blood. Special oxygen storago i», however, 
l-endured unnecessary by the faot that the Body can, 
except under very uunsual cirenm»t«ncca, get mure from 
the air at any time, ho thequuniily i^f Ihi* niibtiliiiice laid 
by is only small; hence death from a!(|>hyxia follows teiy 
i-apidly when the air-pOMagcs arc i^toppod, while, on accouni 
of the i-eservca laid up, death from other forms of ularva- 



^ 



438 



TUE JTrXA.r BOOT. 



tion is ft mach slower occurroncR. Prat«i<li), aHm, w« hate 
leximt from the etuAy of muKcle, are probably but litcle con- 
cerned in energy-production in tho ti««tic«. Spenkiiig 
broadly, the work of i\n- Body is carried on by the oxidation 
of carbon and hydrugcii, and wo God in (Jic Body, lit conv- 
epondcncQ with this fact, two great Gtoreboaees of fatty and 
curbuhvdruto foods, which iwrve lo >iupply the mntcrtulK for 
the perrormanc<! of work and the maintenance of the IxKtily 
temperature in ihe interTals between meals, and during 
longer periodx of KtarTation. One Huch store, that of car- 
bohydntc matt^rlal, i* found in the liver-oeUs; the other, 
or fatty reserve, is found in the adi])ose tissue. That euch 
i>nh»taiicc« are trtn- re«TVi.», not foi- any Kjiecial local [>ut[hwo 
but for the uae of the Hody Reiieraily. is shown by the way 
tlicy disapiwar in dtarvution; the liver rt«crvciu ufewdayv, 
and the fat «ioinewhal later and more iilowly, but very Iai;gely 
before any of the other tissues havp been seriously aSected. 
By using these accuniuliitcd ntatlora the Body oan work 
and keep wumi during serunil days of more or leesdeficiflat 
feeding: and thcfalli-ran animiil 18 at tlio l>cgiDningof i 
Bton'ntion |)eriud tlio longer will it live; which would not 
be the case could not its fat be utilized by the working 
tieeuos. nylH-nialinganiinuls prorethe «amc thing; bears, 
before llioir winter sleep, are very fat, and at the end of it 
commonly very thiu; while their muscular and norvona 
systomi! arc not notii'ealilydiniiniiihed in mo^. During the 
whole winter, then, the energy needed to keep the heart and 
respiratory muscle* at work, and to maintikin the tcmpeni- 
turo of the body, must hare been obtained from the oiida< 
tion of the fit ro8er%e with whitii the animal start«d. 

Qlyoogeu. It may ]>erliupEi Imvf etruck the render a» 
cui'i»uit that so large an organ as the liver should be aet 
apart for the formation of so comparatively uuimiKirtant a 
digcittive secretion lu the bile; and weru i\m the ;<ol« utte of 
the liver the size of the organ would certainly be anomalous. 
The muin fiiiiction of tho liver is. however, ijuito a diSoreut 
one. the formation and storage of a carbohydrate called 
ffltfcoffen, from tho abundant food materials carried through 
it by the jKirtul win after a meal; in the ttmes botwMn 



I 





GirCOGHS. 



4n 



this 



■abttaikoe ia Utcn <Io)ed out graduaHy, and went, 
round th« Bod; in th« blood. U a livor be cut op two or 
thrco hours aft«r retnovui from tho body of u hcaltliy well- 
fed animal, and thoroughly cxtjacteil with water, it will 
yield tip much grape sugar. If, on the other hand, a per- 
fectly frcith liTcr bo hwilcd rapidly to the tcmpcraturo of 
boihu^ water, and then pounded up and extracted, it irill 
yield a milky solution, containing httle grape sugar but 
much glycogen: a eubstauco which uhciuicully \\\\» the iwmc 
empirical formula aa starch (CtUioOi). and in other ways 
is closely allied to that body. The salivary and pancroutie 
w'croUou* rupiiil} comcrl il into sugar, ujt they do Starch, 
the elements of a moleoul« of wat«r being taken up at the 
same time — 

CHioO. 4- n.O = C.HmO. 

(lijvoitfu- WbI**. Olu 



The same traniiformatioD \» rapidly effected by fermenta 
present in the blood and liver, and hence the first thing to 
be done in preparing g^ycogoi \t to heat the organ at once 
to a temperature high enough to destroy theee ferments. 
Pun' glytiogen is » vhite amorphous inodorous powder, 
reailily soluble in water, forming an opalescent milky solu- 
tion; intohiblo in alcohol, and giv^ing with iodine a red 
coloration which ditappoarc on licntiiig and roappeors on 
cooling again. 

About four per cent of glycogen can be obtained from 
the lirer of a wttll -nourished animu) (dog or rabbit). This 
fur the human liver, which woighH alwtit lAOO grams (53 ox. ), 
would give about GO grams (2. 1 ok.) of glycogen ivt any one 
moment. The quantity actually formed daily ii, however, 
much in excess of that, nince glycogen is constMttly being 
removed from the liver and carried elsewhere, while a fn>i>h 
supply IS formed lu the organ. Its qnantity is anbject, also, 
10 con«idemble fluctuations; being ^rfat^at about two houni 
afier a good m«il. iind falling from llmt time until the next 
digestion period commenee^. when it IwginH to rise antil it 
retttains ils maximum. When a warm-blooded animid 
is starved the glycogen entirely ditappears from ils liver in 
the coarse of four or five days. Glycogen is, thus, clearly 




440 



THS nUMAJf BODY. 





being con^tAoHr xxteA tip, and its maintenance hi normal, 
qmntitT dopendit on food. 

Th« Source aud DestmatioD of Liver Olycoseo. 
fuodd :a'L' not equally cflicaciou^ in keeping up the Moclt 
glycogen in the liver; fats bv tliemsclvee are tieelees; pro-' 
Uidi by themselves girc u liltle; hut hv far tha raad \t 
formed on a diet rich in Htarch and su^: so it vonid aecin 
tb»t glycogen \» mainly formed from cnrbohydratc materi 
absorbed from the alimenliiry canal and carried to t 
hepatic cells by the portal win. These materials 
mainly gliicoifc, siitoc tlii- Fl:ireh eaten is changed into 
Rub^tance before abHor]>li<ni. Thi# riew of the matter 
enpported by seTerat (act*. (I) Grapo sugar if it ein 
in the bluod in nbovoHcerUiin ^nndl pcrceDl»g« pneees out 
by the kidacvs and appears in the urine, eonstituting t 
chnracteriittic sj-mptom <\i the disease called diabflas. I 
kealtii, liowever, CTen nfter a meal very rioh in oirbohi 
dnitcw, no eiigar ii))peui'E in the urine; so that the liir] 
quanttl^y of it ub«or))fd from th« itUmcntary canul, within 
brief time under such circumstances, must be ^Lopped 
eomewhcre before it reaches (he general blood carrent. (S) 
Oluooee injected into one of the g«uei-»l vein* of «n nnimal. 
if in any quantity, soon appears in the urine; b&t the nuse 
amount injected into the portal rein, or one of ite radide*, 
cnufloe no diabetes, but iin acciimulittion of glycogen io 
the lirer. We may therefore conclude that the grape xugar 
aheorbed from the alimentury cauul in taken by the portal 
Toin to the liver: there stayed und converted into glyoogen; 
which if! then more slowly parsed on into the h«])atie 
TciuH during the intervalu between meals. Thus in spile 
of the intervals which clupKe holweeu meals the carbo> 
hydmtfl content of the blood is kept pretty constant: dur- 
ing digpstion it id not suffered to rise very high, nor du; 
ing ordinary periods of fasting to fall very much below t 
averiige. 

In what form glycogen leaves the liver is not certain: 
it might be dissolved out and carried oft as sneii, 
previously turned again into glucose and sent on in that 
form; since the bloml and the liver both seem to contni 



nal 

4 



mi 

I 





0LrCO6BK 



441 



» 



^ 



ferments capable of otiangiog glycogen into gloonsv the 
latter Tiew is the more probuhlc. j\jialrscs of port;il 
iiiid licpulic Moods, mudc with the ricw of doiortniiiing 
whether more augur was carried out of the liver duiiug 
fofltiug thau into it, aru conltiuting. Tho maiu ^t, bow- 
ever, rviiiuinn that iiomehow thiK cartKihydral^ ixMcrvo in 
the Ijver is eteadily carried oIT to he lued eUewhei-e: and 
■Dbaal ^^IjlCQgMl (bus un«n-cn« prcltv uiiich to vegetahlc 
'itarob, wbioh, unda in the green leaves, is diKgoWed and 
carried sway by the sup currents to distant and not green 
imrUt (m the gTUtn« o( corn or tuh«rs of u potato, which 
cannot make starch for ihemselvea) and in them is agii'm 
laid down in the furiu of solid ^arch grains, which are 
subsequently dissolved and nscd tor the growlh of the ger- 
minating seed or potato. Reasons haro already been given 
(p. 423) for believing that tho corbohydruto leaving the 
liver is not oxidized in the blood, but first after it bus passed 
out of that into a living tissue. Among thcee tho mtiiKOc»ut 
lead iocm to got some, «iieo a frc«h muKcle »U ayscotilains 
ID, and ovun in normal amount when an animal is 
inrrcd for nomc tmic; the nitiiiolo-tibrvs then, so to speak, 
lulling on the balance with their hanker (tho liver) so long 
i>s there is any. Whea s mnscle contracts thiA glycogen 
disapjMMrs and Home glueofo appcam, but not an amount 
equivalent to tlie glycogen nsed up; aothat the working 
muscle would appear, probably for its repair after each con- 
traction (»ee p. 431), to titilixo this subft&nce. 
Uow it 18 that the glycogen, which ia so rapidly con- 
:rt«d into giape sugar by tho liver ferment after death, 
ipc-i micli rapid convcrxion during life hiu not bocu 
satJH flic tori ly anAwcred. Two possible reasons readily fng- 
geat t!ii.-m«.-lves; the liver ferment may be only prodiici'd 
by dying hepatic cells; or the glycogen in tlio living cell 
may not exist free, bat combined with other portions of the 
ci'll Kuhstanco so as to bo protecttMi; while, after dealii, 
poal'mnrtMtt changes may rapitlly liberate it in a condition 
to he acted upon by tho formcnU 

I>labot«a. The study of this disease throws some light 
npon the history of glycogen. Two distinct varieties of it 



mu» 
^ traci 




MS 



TRB UUMAS BODT. 




are known; one in wbiofa sugir appears in the nrtne onlj 
when the jMitivnt take« cartiuliydrate foods; the other in 
which it is still excreted when he Uikes no socb ioodi, ani 
must therefore form cagurin his Body from Rubglnnow not 
all chemiciillyalliod to it. The mo*t probable source of tl: 
aogitr in the latter case is proteids; since eoinc glycogen 
found in the livers of animnU fed on prot«ide only, while fiit« 
iduiiegivvnoneof it. In^omccomplex way iheproletd mole' 
cule woald appear to split up in the liver into u highly nitro- 
gonizcd part (iiroa or an anlccodont of urea) and u uon- 
azotixed part, glycogen. On this riow the more severe form 
of diabetes would be due to an inorewed activity of a normal 
proteid-deoom posing function of the hepatic cells; and 
eomcliincH the urea and ingar in (he urine of diabetics 
rise and fall together, thu.i seeming to indicate a com- 
mtinity of origin. Diabetes dependent on carbohydrate 
food might tic produced in seTcral ways. The liver-cellB 
might cease to stop the sngar and, letting it all pass on into 
the general circulation, KutTei- ii. to rii^eto snchn iiercenlago 
in the blood after a meat, that it attained the proportion in 
which the kidneys paes it out: or the tissues might coaeeto 
nae their natural amount »f sugar, and tliis. sent on Kleadily 
out of the liver, at last rise in the blood to the point of ei- 
crction. Or the liver might transfunn (into glucioso) and 
pass on its glycogen fiuter Uian the other tinncfl nsed it, 
uud 80 diabetes might arise; bnt this would only be tern* 
porary, lasting until the hver stock was used up by the 
rnjiid conversion. Artificially wo can, in fact, jirodnce 
diabetes in several of these waya; cnron poisoning, for ex- 
ample, piinilyxiiig the motor nerves, makes the skeletal 
musclcB lie complelt'ly at nsrt, and «o dimintMhos the glyco- 
gen consumption of the Body and producc^sdiabetes. Car- 
bon munoxido poisoning produces diabetes also, prestunably 
by checking bmlily oxidation. Finally, pricking a certiiin 
«pot ill the medulla oblongata causes a t«m]>orary dial>ctcii. 
This may be due to the fact that the operation injurea 
that part of the viiso-nuiL>ir centre which controls the mus- 
cular coat of the hepatic arterj-: Ibis artery, then dilating, 
CBirri<4 so muoli blood through tlio lircr that an exocM of 



ID 

I 



\ 



DXOCM Ol H 



FATS. 



443 



gtycogt^D \t tunicd into glncose in agiven time, and carried oS 
by tlie hepatic reins. If the Bplanchnic ncrvci be out ihe 
whole tfteries of thc(ibdouii]uIviM.xm<lilHteitniI ii»diftbet«8 
follows, beoauflc so many vesaets being dilated a gre*t par- 
of the blood of the Body accumulates in them, and theic it 
no Dvticeubly incren^ed flow tbroiigh the liver. Others, 
hiiwcTer. maintain that the " piqurt" diabetes (as that due 
to pricking the mcdiillu ifi called) is duo to irritation of 
trophic neno-fibres origiiLating there, and governing the 
rate at which the lirer-cells produce glycogen or convert it 
into glacoee. This latter view, though perhaps the lot 
commonly accepted, is probably the more correct. The 
hepatic cells do not merely hold btwk gluooae carried 
through the liver to that it isi there to be wa«hcd oat by a 
greater blood-flow, but they feed on gineose and proteids 
and make glycogen; and this is later converted into glucose 
and carried off. Glycogen is thus comparable to the zymo- 
gen of the puncrcat and other glands (Chup. XVUL); and 
the traugformfttton of such hoAxtt into the specific element 
of a secretion wo have alreiiidy ><ecn to bo directly under tlio 
contjol of the nervous system, and almost entirely or ([Uite 
inde])endent of tho blood-flow. 

The History of Fata. While gljcog«ii forms a roMtrre 
store of miiterinl tliut is subject to rapid alt^ratioDa, detor* 
mined by meal-times, the fats arc much more stablc;*tbeir 
(lei'iods of fluctuation are regulated by days, woclis, or 
mouths of good or had nutrition, and during starvation they 
arc not so readily, or at lea-it so rapidly, cidhxl upon as tti« 
hepatic glycogen. If wc carry on the simile by which we 
compared tlie rcMrx'e in each cell to pocket-money (p. 31), 
the glycogen vonid answer somewhat to a bahince on the 
right side with a man's bimker; while th(> fat wonld 
represent assets or seciiritlejt not «'■ mpidly realixahle: iw 
capital in bnsino«!, or the cargoes atlout iu the argosicft of 
Antonio, the "Merchant of Vonioe." Fat, in fact, is 
slowly laid down in fat-cells'and Mirroiindod in thaso by a 
cvll-vrall, and, being itjfolf insulnble in blood phuroa or 
lymph, it most undergo chemical changes, which no doubt 



W4 




TBB UVitAS ItOOr. 




require eoroe time, before it can be taken into the blood 
and nrried off Xt> olli«r parts. 

When adipose titwne is developing it is teen that ondi 
fercntiuted colls in the connectiTe tissues (espedatly areolar 
show mimito oil-<lro|» in their protopltisuu. These inc 
in siKe and, iiUimately, fuse together and fonti odo larger, 
uil-ilnipli'ti while moHt of tlio original protoplasm di^H 
npjK-uix. ^fl 

Tbo oilv matter would thus aecm dtie to a chemical 
metamorpliom of the cell protopUsm, during which it gives 
riw to a non-AXOtiiivd fatty residue which remains behind, 
and » highly nitrogenous ])ari which is fivried off. £^^| 
many parts of thi* Body prulojila^mic masaee are subject t^^ 
a Mimilur hut \vl»^ ooniplcie mcuniorphnsis; fatty degenera- 
tion of the heart, for cxmnple, is a more or less ext4>nKii 
rephiccmcnt of the proper substance of it« mascnlar fibr 
by fut-droplctii; and the cream of milk and the oily matter 
of the sebaceons secretion are due to a nmilar fatty 
degonenitjon in gland-colU. Morcovflr, careful feeding ez> 
]>i-riinoitt4' nndoabu-dly show that fat can oome from 
teids; when nu animal is rery richly supplied with tb 
all the nitrogen taken in tbcm reappears in ita exeoretiot 
but all the carbon does not! it is in part stored in the Body:' 
and, since siicli feeding produces bat little glycogen, this i 
carbtDi cjiii only be stored a8 fat. ^H 

While Ihcrc is, then, no doubt that some fut may haTe i^^ 
pmteid origin, it is not ccrtiiin that all htxa such. During 
dlpcKlion a great deal of fat i» ordinarily uhsorbod, in n 
chciiiicully unchanged slate, from the alimentary CADal; il_ 
is merely emulsilii'd and carried off in minute drops by 
chyie to he ponred into the blood: and this fat might 
directly deposited, w, such, in adipose tissue. There 
however, good reasons for supposing ihnt all the fat in the' 
Itddy if ninnufactnrcd. The fat of a man, of adog, andofi 
eat varies in the proportions of palmatin, stearin, margnrii 
and ulcin in it; and vanosiu just the^iimeway if all be fed < 
the Mime kind of food, which could not bo the cn*e if 
fat cateu were &imply dcjiosiled iindmngod. Moreover, if 
an animal be fed on a diet oontainlng uno kind of fat oaljf- 



pro^H 

theaS 

»odT:~ 



d; il^ 

''J 

the 
of^ 

:i 





OHtOOf OF FATS. 



4U 



Wiy olein, but a very slightly inercii*od percentage of Uiiit 
particular fatty sulntunco i* foiitid in iu adijw^e tiMUc, 
which goes to Mhov thnt if faCD come Imm fnt« eatea, the«c 
latter are Qrat pnlled to bits by th« living cHIa mid built up 
iigaia into the tornuiiurTniil to tli« animal: ra that> eveo with 
fatty food, the fal<t atored up aecm to )>c iii most part 
niunufiM;turiKl in the Body. 

In filill another w»y ii in proved that fats can be constructed 
in Iho Body. In animalu fed for «luug)iter, the total fat 
stored up in tlii-iii during the process is greatly in excess 
of that taken with th^ir food during the Rime tim<% For ex- 
iimple. a fattening pig may tttoro up nearly five huudred 
jKirL.* of fitt for every hundred i» its food, and this fat 
muHt he made from protctd^urcarbohydriiten. Whether it 
cnu eome from thu lattor in siill ]>erhaps an oj>en question; 
for, while all fatieumg foods are rich in starch or similar 
bodies, there are comtiderablo chemical difflcnltics in sup* 
posing an origin of fata from anch; and it is on the whole 
mare probable that they «iniply act by sjmring fruiii umo 
fata simultaneously fonned or stored in the body, and 
which would hare othervrisu been called u[ion. They make 
glycogen, kud this shetu-nt the fats. Liebig, indeed, iiiarciy 
eeVbnited discut^iou. maintained that fats were formed 
from carbohydrates. He ifhowed that a cow gave out more 
IjiUtcr in it« milk than it received fat4 iu ita loud; and 
Hiiber, the blind uaturaliist. showed that bees Milt miule 
wax (a fatty body) fur a time when fed ou pure su;:iii': and 
itidolluitely when fed ou honey. U'liiW-iiuently, for a long 
time, an origin of fat« from carbobydruies was' 8n|)po9ed to 
be proved; but tlieir posKible origin from protcids (a possi- 
bility now shown to be a certaiaty) was neglected, and the 
validity of the above proofs of tlieir carbohydrate origin is 
thii« u]ii*i.!l. The cow may have made its butter from proteitU; 
the bees, fed on sugar, their wax for a time from prateids 
in their bodies already; and, indotinitely, when fed on honey, 
fniiti the protcids in Uiat sulmtunce. Moreover, tuiiunis 
(ducks) fed ou abundant rice, which oontatn« much oarbo> 
hydrate but very Uttle pioteid or fot. remain loon; wliile i( 
some fat bo aildcd tliey lay up faL 




«M 



THE aUMAS SODT. 






PenKino who fiittCD «atlle for Ihc batch«r fiticl tb«t t! 
fowls uiwful for tlie purpose all coutaio protcids, carbob; 
dratas, and futs, and tliat rapid futt«Ding is ouly obtain' 
with fLH>d« oonUiiniiig » g<>od deal of tal; m oiluilte, milk.' 
or Indian ooru. Taking all the facte into account wc eh. 
|>robably not be irrong in concluding that nearly all 
bodily fat is mannfactured either from fate or proteidsf 
from fuLt ca«i«r tiian from anyihiug clw. but vben mtidi 
protcid \s cat4!n i»ome is mode fmni it iiloo. CurUibydrate* 
alone do not fatten; the animal body cannot make its pal- 
matin, etCfOatof th«m. ^Novertheless th«y are, indirectly, 
important fatt-t-ning foods when given with othere, miicg. 
being oxidiiEed instead of it, ihey protect the fat formed. 

I>iet«tio8. That "one man's meat may bo UDothi 
man's puittou" itt a fumiliar aaying. and one thai, uo dou 
exprenes a certain amount of trtith; bnt the difleren 
probably depeotls on the varying digestive powers of indi-' 
TidaaU ratJier than on peculiarities in their Uwe of eel 
nutritton; uU need pretty mach the same amoimt of p 
loidH. fata, aiid carboliydrut«s for encli kilogram of hod; 
weight; but all cannot digest the aame varieties of th< 
equully well : while many foods have peculiar, almost 
poittonoui, elTccta on some penuns. A good many pco 
are made ill by mutton, which tlie majority digest belt< 
than beef. 

The proper diet, too, will necessarily vary, at least aa 
amonnt.with the work done; whether it should varj' in kind 
with the nature of the work is not so certain. Provided a 
num gets enough protoids to bobmce those lost in the weta and 
li'orof his tissues, it probably matters little whether hegotit 
for oxidation and the liberation of energy either fats or car- 
liohyd rules:, or even excess of proteids themselves; imy one of 
the tliree will allow him to work cithorhis brain or his niusdctf, 
and to maintain his temperature. Proteids, however, are 
wasteful foods for mere euerg)--yieldiDgpurpuEes: inthefir^t 
place, they arc more costly than the otlicrs; secondly, they 
ore incompletely oxidized in the Body; and, thirdly. It is 
probably iiiuro laborious to the svirtem to get rid of urea thiin 
of the carbon dioxjile and wutvr, which alone arc yielded bv 



i 

I 

lOSt 




DIBTETICS. 



447 



Jon of t»U and carbohydrates. Betireen fata and 
carbohydrates similar considerations lead to a uttv of t h« Utter 
when practicable: itaich is mure easily utihxed in the Body 
tlian fati*, SA shown by the manner in which it protects the 
latter from oiidalioti; and a given weight of starch fully 
oxidiKod tu ihe Rudy will liberate one and a half times as much 
energy as the same amount of butter, while it costs cousider- 
ably lew than half Uie monov. Prohubly, loo, rtarch is 
more easily digested than fats; at least by many people: 
children especially are apt to be fond of starch; or sac- 
chariuo food« and to lo»t)io tttU; and the appetite in snch 
cases is a good guide. As a race, too, the American people 
differ markedly from the English in their lore of sweet 
foods of all kindif; whether thi« \« corrclatpd with their 
cluiract«rintiti activity, calling for .aome food that can be 
rapidly used, is an interesting question, to wbieb. however, 
It would be rash to give at prviient nn nfllrniatiTe answer. 

Tt is cieiir. tliercforc, that no general rales for every one'ii 
diet can bo laid down; but slill on brood principles the 
iMst diet would be that which conlatncd jiiiit the nmonut of 
proteid nece^^ary for tissue repair, nnd so much carbo- 
hydrates as could be well digested, the bulancc needed, it 
any, being iiia<le up by fats. Such a food would be tbe 
cbeapcet; that is tbe supplying of it would call for less of 
the time nnd ciii^rgy of the nation umng it, and leave more 
work to spare for other pnrsuits than food production — 
for all tlic uris wbtch miike life ngreoahlc and worth living, 
and which elevate iiivili/.oil man al>ore the merely nuilerial 
lifu of the savage whose time is devoted tocatching and eat- 
ing. Wo have high authority tor saying that man does 
not live by bread alone; m other wordit hiii highest develnp- 
ment is impossibla when he is totally absorbed in " keeping 
iKidy and soul together," and the more labor that can be 
xjiiired from getting ciiaiiglt food the better chance has he, 
it he use his leisure rightly, of becoming a more worthy 
man. While there is. thu!<. a thcorelicidly best diet, it is 
nevrrthelesit imponsiblo to say what that is for each indi- 
vidual; but what the genenti exjierience is may be approxi- 
mately gathered by taking an avenige of the dietaries of u 




us 



TBS UfitAS ttftD r 



anmber of poblic itutitntiaiu hi wbich tbe health of nuinv 
p«(^lo is mainUunM w wonomicslly mt ixwsible. Such an 
examination made br HoleoehoU, gii«a as ai itfi result a diet 
oontaiiuoK dwlj 

P ro ttM ^.... to fiwna OF 4&'> mitis. 

PkU fli ** or I.MO " 

AmfluUi. «M " or «.tt> " 

ftilts. » " or *e8 " 

Valor. 3B0O " or 41400 '■ 

PMpI« ID GWT circnmstancM t«k« u a ral« mora prot«idB 
asd fata aad lew anivloids; and XbU selectiou, wh«n » 
choioo is ponible, probably uidicatM Uutt ndi « diet is the 
lietter one: the proteadt in tbe abofe table aeem eqwotally 
d eflai tn t 



r 



CHAPTER XXIX. 
THE pRonrrrioN and RE<;rLATiON of tue 

HEAT OF THK BODY. 

Cold, and Warm-Blooded Animalft. All anitiia)». iin 
long as tbej are alive. iiri> ilii' «i«t "f chemical changefl by 
which heat iHlibeniUil; hviiotrall tfiui to IWKumorhat warmer 
titan their ordinary jurroandiniirH, though Uiediffercnoema)' 
Dot be noticeable nnlea the heat prodiicljon is considerable. 
A frog or a tish \» a litllo hotter thiui the nir or water ia 
which it Urea, but not mtich; the little beat that it pro- 
dncos i« lo«t. by nidijitiDn or cundnction, almo«t at onco. 
Hence such animals have no proper temperaturo of thttir 
own; OD a warm <lay they an warm, on a cold day <^)td, 
and are accordingly known as changiabh-trmperalurfd 
(poikilO'lhermoHs) or.in ordinary langna^, " rcihl-blocidtjd" 
animals. Man and other mammalx, a« woll m birds, on the 
i-oiitrury, ant th« aeat of vi-ry active chemical changes by 
which mneb heat n produced, and so niaintnin u lolcnibly 
uniform temperature of their own, much as a fire does 
whether it bo burning in a warm or a cold room: the licat 
pmduclinn at any given time Italancing the \<i*9 a nor- 
mid body temperature is maintained, niid usually one cotI' 
.-•idcrubly higher ihiui that of the medium in which they 
live; snch animals are therefore known as animaU of con- 
stant temperature {bomo-tkfrmona). or more commonly 
" warm-blooded" animnU. The hitter name, however, does 
not property express tJie facts; a lizard tiaxking in the sun 
on a warm summer's day may be nearly as hot as a man 
usually is; but on the oold day the lixard becomes cold, 
while the average lem|wrattiro of the healthy Human Body 



450 



THE Bun/Ay ttOttT. 



i«, within a degree, the same in wintor or Bammcr; wil^iii 
the arctic circle or un Oic ui^mttor. fl 

Moderate wariuth accelerates protoplasmic aotiTity; com-" 
pare a fro^ dormant m the viuter with the eamo animal 
Motive in the warm miintlm: vhat in tmo of the whole 
frog ia true of each of its living cells, Ita mueclea contract 
more rapidly when varmctl. and the whito corpuscles of its 
hlixxl wlieii heated up to the tfmpentture of the Human 
Ho(Jy aio seen (with the microscope) to exhibit mnch more 
luuivo anid'^Ktid niov<im«ut« than they do at thv tompcm- 
liire (if frogV blood. In summer a frog or other void- 
blooded animal iisea much more oxygen and evolves much 
m»rc carbon dioxide than in winti^^r, us rhown not only bv 
direct mea^Qremeiitii of its gasoouR exchanged, hut h\ tin- 
fact that in winter a frog can live a long time after its 
Imign have bwn rcmovoA (being able U.\ hreHth<- vnfliclciitJy 
through itt moist skin), while in warm weather it dieaot 
nttphyiia very soon aft«r the same Ios<. The warmer 
weaiher putj< iu tiHSues in a more active state; and so the 
amount of work the animal doi-s, and therefore the amotmt 
of oxygon it needa, depeii<l to » great oxtent upon the tem- 
perature of the medium in which it is Uving. With the 
warm-blooded animal the reverse ia the case. It always 
keeps up ita U-mporaliire to tJiat at which it« tissaea live ^ 
best, and accordingly in cold weather uses more oxygna «]idfl 
seto free more carbon dioxide because it needs a more aclivo 
internal conihiiKtion to conipi'nsnte f«ir its greater loss of 
heat to the exterior. In fact the living tiwues of » man 
may be compared to hothoase plants, living in an artifici- 
ally maiiitttiiifd tempcmlure; but thoy differ from the 
pjiints in ihe fact that they themselves are the smts of \ho 
coinhiiKtioiiH by whiuh the tumponiture is kejit up. Since. 
within wide limits, the Human Body retains the eame tem- 
[wrature no matter whether it be in cold or warm surround- 
ings, it is clear that ii must poEeeta an ucciinite arrangement 
for hfiiit regulation; cither by controlling the production of f 
heat in it. or the loss of heat from it, or both. " 

The Temporaturo of tho Body. The jiarts of the Body 
are alt eithir in contact with one another directly or, if 



ttm 




BOVSCES OF BODILY BEAT. 



4M 



not, Rt l«a^t indirectly tbrougb the blood, which, Dowirig 
(lom part to part, curries fa«Ht from wimiiur to colder 
n^om. TIiiu, althoDj^h at ono time one graup of musclee 
BIR7 eq>eciaU)- work, liberating bcnEl, and nt otber times 
nuother, or the miuc>1c« mny be ut rc«it nad tlic glunds the 
soat of active oxidation, ihe t«ni)>crat.ure of the whole Body 
U k«pt pretty much the santek ' The akin, bovcTor, which 
ia is direct con ttict with «xt«rual liodic«, uxually colder than 
itself, is cooler than the internal orgariii; its teniiturat iire in 
health is from M" to 37" C. (96.8-98.5° F.). being warmer 
in more protected partif, w ttie hollow of the armpit. In 
iRtemul orgBJiK, a» the liver and brain, the temperitturc \* 
higher; about 43' C. (107' F.) in health. lu the Innga, 
though there \» a corlaln i]uantJty of heat liliemted when 
oxjgen combiner with hieniogI<^iD, this is more than 
counterbalanced by los3 of the beat carried ont by the ex- 
pined air, and that umhI npinerapontliug the water carried 
out in the breath; 80 blood returned to the heaurt by the 
pulmoDur}' vein:! Is fl!ghtly colder tliau that curried from 
the right side of the heart to the lungs. 

The Sources of Animal Heat. These are two-fold; 
dircei ami indirect. Heat ia directly produced wherever 
oxidation is taking place; so that all thi; living ti^Hue^t at 
rest produce hvui ad tlie reitidt of the chemical changes sup- 
plying tliem with energy for the mitiutennnce of their 
vitality; and whenever an organ ia active and ita chemical 
metamorphosed are increawd it becomes hotter: a scenting 
ghmd or a contracting muscle is wanner than a resting one. 
Indirectly, heat w developed by the transformatioD of other 
forms of energy; mainly mechanioal work, but, to a less 
extent, also of electricity. All movements of parts of the 
Body which do uot move it in space or move external objects, 
are transformed intw heat within it; and the energy they 
represent i« lost in that form. Ererr cnrdinc contraction 
BeU the blood in movom<>nl. and this motion is for the most 
part turned into heat within the Body by friction within 
the blood-vowelK. The same tnuiRformation of energy- occurs 
with respect to the movementa of the alimentary oaool, ex- 
cept in «o far lu they expel miittern from the Body; ond 




■152 



TUB UUMjy BOlfT. 



erery maec]e in «ontractiu^ baa part of tb« roecbstii««l 
energy cxgx'ndud by it ttirno] into host by friclion Kgninitt 
neighburing jKiru. Similarly the raoTenients of cilis mi<1 
of amoeboid celU are (or liie tuogt part converted iii the 
Uody into hoiit. The miiscW and nerve* uro uW tbo MMtcl 
of niJitiifo.iUlionA of eleelricity, which, thoug;h small in 
amount, for the most part 'do not leare the Body in that 
form bul nro lirst lonvvrU'cl intu hc4tt. A c«rtaui amoiint 
of heiit ia alao carried into the Body vitii hot foods and _ 
drinks. H 

The Energy Lout by the Body in Twenty-four Hour*. 
Practically fe]<fakiii^, lUi' Uudv only liwc-s energy in iwo 
formii; as heat and nu'chnn teal work: by 8]}plying conduo- 
torn to diflerjrnl parts ut il.i surface «mall umuuiits of elec- 
tricity can be carried off. but the amnuiii in (juite trivial iu 
comparifon with the total daily energy expenditure. Dar- 
ing ruui]>k-le re.it, that is when no more work in done than 
that nece&^ary for the maintenance of life, nearly all the 
lo$4 t»ke« the form of heal. The abwtlnle amount of this 
will vary with the surrounding temperature and other con- 
ditions, but on un average a man loses, during a day of 
re£t. '^7U0 calorie»; that iir enongh to raii^e ilW kilogranu 
(5040 lbs.) of water from 0' tol^C. (from 32" to 33.8° F.);;| 
otherwise ex|ire»»cd. this iimonnt of heut would hoi] S7 kiloa 
(59.4 Ib¥.) of ico-culd water. Thin docs not ijuite rvprcecnt 
all the energy lost by the Body iu that time: since a Mnal) 
proportion is loatas mechanical work in moving the clothes 
nnd air by the respiratory movemcntjs, and even by the 
lioat of tlic h<iart, which at each systole pushes out th« 
chesi-wnll a little and moves the things in contact with it. ' 
The working Body liberates and loses mncfa more enorgy;.M 
part as mechanicul work done on uiternul objects, ]iart as 
increased heat iitdialod nr conducted from the anrface, or 
canied off by the eipirt^d air in the (juinkened respirations. 
Every one knowji ihut lie bcLDniet warmer when ho tiikca 
exercise, and measui-enients made on men show that the 
heat prodnceil and li>sl in i iliiv <.f moderate work is about 
one third greater than 'Ii.u in ji ibiy of rest. The follow- 
ing table gives moro accurate numbers — 



I 



UODtLT BA'KHOr lAmT PHH DAY. 



4&3 



n*7BfB)«t 



Day ot Work. 



BanMlm. SLwpshn. BcMHbn. WorkSlim Se«p«lm 



__, . / ia.«w FWi.-ib. \ 

■■" V I"** "nil* / 



__.,/ l<,»>)^ih-lb. \ 



The mechanical work done on the working daj, repre- 
sented in addition an expenditure of energy of 313,344 
kilogrammeters, which is eqiial to Wi calories. Of the ox- 
eeaa heat in the working diiy, {xnrl i« directly produced by 
the increased chemical ch»ii)rt-« in the quicker working heart 
Hnd respimtory muitclcM, and the other mtisclea set at work; 
while part in indirectly dae to heat arising from increased 
friction in the blood-vessels as the blood is drivun fiiritcr 
anmnd them, and ti> friction i>f the variniis mii^cle'i nt^vA. 
The STerage cardiac work in twenty-four hours is about 
60.000 kilojrntDitnetvni ; that of the respiratory mnsclea 
about M.ooo ; anil *ino© nearly all of both is turned tinully 
into heat within the Body, we hare 74,0Ull kilognimmeters 
of encrg}- uuiwi-ring to about 174 calories (C7tt6 Fith.-lb. 
nuite) indireotl; produced in the resting Body daily from 
thoie sonrG«s. 

Of 100 part* of heat lo«t from tlio ruling Body, abont 
V3 are carried olT in radiation or oondnction from the skin. 
14.5 are carrioci off in evaporation from tbo skin. 

7.8 " " " " " " lungs. 

3.0 " " " expired lur. 

l.S " " ** in the eicretions. 

In a day of iiTeragu work, of every 100 parts of energy lost 
in any form from the Body — 

1-3 go as heat in the excreta. 

3-4 in heating the expired air. 
20-30 in evaporating water from tlie Innga and «kin. 
60-75 in heat radiated or conducted from the surfaces and 
in external merbaiiical WMik. 

The Superiority of the Body aa a Working Uachine, 
During I'ight hours of work, we tind (table ut lop of page) 
tlieBudy loses 21 69. ft calories of euorgjiis heat; and can do 




I 



TBM BCMAM M»r 




at ifae total 



toaWiiliiiiii. 8a of all 
lit a Ite ti^ Antl-iBST talni tfi<! 
«vfc; dm M a mr Wp proportion 
OMTf;' fifdei, hmmg m aacfa hif^er per- 
pna by M Ji— 17 — dri— ■ The bat 
m atOiB a aiAaBied wocfc ooljr nlmat 
|i^ of Um M^ e —nj nasted in then utd Iwt fnim 
tben ID agnfs tine; tfe icnsiadar m bsHmitted directlv 
abcu bo lite exterior, aad 11 laK lotbetBgm^ fur all tu^fiil 
P«T** ^ 

BiiCMwy for the c»ntniBHiK« uf liie life of a wmna-blrKxIed 
aainal; cboaU tbe icnptfatnn rua abvn cerUio limits 
cbemiol cfaanget, iiHxn|iatAle willi Gfe. wear in the tis- 
«M ; for enrnpfe at aboot 49" O. <U0* K.) the muEliM be- 
gin to bacoMic rigid. Ob tlie otlMr hoad dcmUt eunes if the 
Bodj be cooled down to about Ift** C (W F.). Hence the 
need for meane of fetting lid d iumi best, and of protM- 
tioa from *u«MBt« MoGBg: fiOier end mav be g&ijwd in 
tTo imji; bf- altering the rate at which beat, ia loot or ihut 
at which it it prodoced. Am rvgaid« heot-loo, br br tbc 
■Bo«t important regaUtjng organ it the ikin: nnder ordi- 
oarjr drcamrtaitcee nearly 90 per cent of tbe total lu-»t gircn 
off from tb« Bodj ia 24 boon goea hj the ddn <?3 hy radi- 
attoo and conduction, t4.5 bjer^toratioa; see iii>oTe table). 
Thin Umb mar be ooutrolled — 

1. Vty fiotking: Wi> natarally wearmore in raid and InN iu 
wnmi weather ; ibe effect of clotbn being, of miiree, not td 
warm tbe Bodr bat to diminish the rate at ahich tlie beat 
formed in it u loM. 

i. locROoed tempeTolnre of therarrouadinvmpdiuro in* 
crc«M« tbo aotirity of tbe benrt and lnng». .\ hii£lenc«l 
oircnlation bjr itself doee not m» almtdy pointed ont (p. 38S) 
incnaae the general tinne actirity of the Braly. or the oxida- 
tion* oocorring in it, and, so, ojiart frum i\u- KitrdiT working 
lieuii il>M>1f. dnc! not influence IIk- umotint of XxcM \\\n-n.ivt\ in 
l)if IfaMtvdnringagiven time: but (he more rtipid bluod-flow 
Ibrougb tbo nkin eorries more of that Unid thniugh thij) cool 
Mrfaoe Mid iocreaaee the loss of beat in that way. Tbe 



I 
I 

I 



I 

I 

I 

me ^ 




r£.\fPKltATL'/tK-liEatrLAriON IX THE BOOT. 455 



quickened rM[Hnition«, too. incnuHe the ovnporatiitri of water 
in the lun^ and, ibuH, the loda of heat. 

3. Warinlh <lircctly tlilnles the skin-Teesels and cold cou- 
triict« thctii. In a viirm room the rv(>scl» on the 8ui'tiu.>e 
dttiit« as iiiiourti hy iU redne^, vhiln in n cold ntinosphere 
ihey contract and tlie skin becomes pale. But the more 
hl'HKl th:it flows ihrotigh the »kin the gi-uatiu* will bo the 
lirat Io«t from the surface — and mm verta, 

4. Ueat iudaces sweating and cold checks it ; the heat 
appean to act, partly, itflexly in exciUng the swcut-controt 
fntm which theseoretory nerves for the sudoriparnufi glands 
arise, and, partly, direcllyon thosecentrea, which arc ihiown 
inlo activity, at li-aet in health, m i^oon a« the Icmjfcruturv of 
the blood is raised, [u fever of cotirsie we may have a h:gh 
tompcrattiro with a dry non-sweating skin. The more sweat 
there is pmireil ont, the more heat is used ap iu eTaporaling 
it and tlie more the Body is cooled. 

6. Our EensatioDE indnce us to odd to or diminish the 
heal in the Dndy according to circumatancei; as by cold or 
warm baths, and iced or hoi drinks. 

Aa regards tvmporahirv-rogiilati'in by modifjnng the rata 
of bMt production in the Body the following pointjiRiaybo 
noted; on the whole such regulation is far leas important 
ihnn that brought about by cbang»> in Uie rate of Iom, Hince 
iJie necessary vital work of the Body alwayx neociuitatea 
tile ccintinnance of oniilativu prooe^ws which liberate a tol- 
erably large ipiantity of lK^ut, The Boily cannot therefore 
be cooled hy diminiiihing iiiieb oxidatinno ; nor on the other 
band can it bo safely warmed by largely inei-easinj; lliem. 
Still, witbni certain limits, the he*t production may b-ion- 
ti'olbd in several waya^ 

1. CoM lucreases hnnger; and increarad ingcirtion of food 
nicr<.>JisD^ bodily oxidation n* Hhown by the greater amount 
of carbon dioxide excreted in the hours snccvniing a meal. 
This increase is probably due to the activity into which ifao 
digestive organK are thrown. 

i. Cold inclines to voluntary exercise: warmth to mnecn- 
tar idlenew; and the more the mmtolea are worked the more 
heat is produced in the Body, 




4i9 



THE nVMAX BOOT. 



3. Cold tends to produce involuDtory musoolar more- 
mentj), uiid eu inuntujM'd ticut production; us cbatt«ring 
of the Iccth and shivering. 

A. Cold applied to the skin increases the bodily chemical 
metamori>h»"'CJ< and so h<?at. i)riKl«ction. At U-aet ihc torn- 
pcriiture in tlie armpil rises at first on entering a cold bath, 
though thL' heat carried off from t he surface soon overbalaDces 
its iucreaj!i'd pnKluction. The phunomcnoii nuiy, however, 
bo ex))laiiied iu another wsy. the rise being attributed to a 
siiddeu dimitiutiou of 1o8« from more exposed parts o( the 
ekin, dependent on eontraction of the cutaneous artericfl. 
In some ca«?8, howorer, the temporarj- rise is accompanied 
by an incrcawid excretion of ctkrhon dioxide, irhicli wonld 
indicate tlint tlie surface cooling doe§ really increase th« 
oxidations of the Body. 

n. Certain driig^, a^ »alicylio acid, and perhaps qninine, 
dimtaisb ihe heat production of the Body. Their modo ol 
action is still obscure. 

On the whole, howercr, the direct hott-rcgulating me- 
chanisms of the Uuman Body itself are not very efficient, 
especially as protoetiont against exrastive cooling. Man 
needs to lupplemeni them by tlie u«e of clothing, fuel, and 
exercise. 

Local Temperatures. Although, by the means above 
described, a wonderfully nnifonn bodily temperature is 
maintaintd, and by the circulating blood all parts ar« kept 
at nearly the same warmth, variations in hoih respects do 
oocnr. The amingemont^ for ec|nalii!ation are not by any 
meiutx folly efficient. Kxtcrnnl pai-ts, a* the Kkin, the lungs 
(which are really external in the sense of being in contact 
with the air), the mouth, and the uose chambers, are nlwaj's 
cooler than internal; and even all parts of the skin have 
not the same temperature. =ncb hollows as the armpit being 
warmer than more cx])oi<cd regions. On the otlier hand, 
a «>creting gland or a working muscle becomes warmer, for 
the time, than the rest of the Bixly, because more heat is 
libenited in it than is curried off by the blood flowing 
through. In such orgiins the venous blood tearing is warmer 
than the urteriul coming t<> llitm; whih' the reverse is the 



I 



I 



p 



TBSRMIO A-ESrSS. 



487 



case with part«, like Uic «kin, in wliiob the blood it cooled. 
Au organ colder than tlie blood is ot cuuree w»rnied bj- 
&D iucrea^ in itecircnlatiun, us tvtn in Uio local rite of Usm- 
perattiro in tlio nkJii of ihe face in bluabing. 

Tbermlo leervea. All nerves, anch at motor or secre- 
tory, which eiin throw working tis^utiM into activit}' tu-u in 
u ccrtuin Minso thormio norres: since they cicite inorctL«ed 
oxiiliitioii and heat prodnction in tho parte under their con- 
trol. A trap, purely thermic nerve wonld l>e one which 
iucreotKid tliu heat production in a tissue without otherwiM 
throwing it into activity; and whi'thcr such exist is still 
aodccided. Certain phenomena of di^ii-Hu, however, Kcm 
to render thi>ir existence probable. If wo return for a 
moment to our former poniparison of the working Body to 
n »team-cngiuL>, such ncrres might be roganled uk agencies 
incrcanng it« rale of ruKting without netting it at work. 
The oxidation of Uic iron would develop some heat, but by 
proceistes oseleaa to the steam-engiue. although such are, 
in modemtion, essential to living cellci; the vitulity of 
these even when »t rest, seoms to neceaeitate a constant, 
if «maU, brenking down of it« gubxlanoe. Id an ainoibotd 
ci!ll no doubt such processes occur ifutte independently of 
the nervous system; but in more dilTeri'^ntittted tissues they 
may bo controlled by it. Just a* » mn.^'cle doci not nor- 
mally contract unless excited through its nerve, although 
a white blood corposcto does, so may the natural nutritive 
prooowM of tho ma«cte-flbre iu m renting condition \k de- 
pendent on the nerves going bo it. If thesu be ;thnonunlly 
excit«d the muscle will brcuk down it« protoplasm faster 
than it con^tructH it, and cotiixtquently waste; at the 
same time the increased chemical degradation of its sub- 
stance will elevate it« tcm]>emturc. Febrile conditionK, in 
which many tissues waste, without any unusual manifesta- 
tion of their normal physiological activity, would thus lie 
rwidily acoouute"! for h<i due to gupcrexcitation of the 
tliermif nerves. Moreover, it is fonnd that lesions or sec- 
tions of the spinal i-ord are followed by a rise in tho tem- 
perature of thoiw part<« of the Body iiupplied witJi nerve* 
arising below the diseased or dinded portion. Now 



458 



THE bVitAy BODY. 



division of the spinal cord in two waja tends to lower the 
temperuturo of purtu bduw thv injun': in the first place, 
ill!) innHolcs are paralyzed and tio a great aotiroe of hvat JA 
cnt off: And in the second, the va»»-motor ncrvea truTeling 
down from the nu'dulla'y centre are cut, and bcnn* thi- 
ekiii aneriea behind the sectiou dilate and carry m<iK' MikmI 
to 111 u surfiiice to he cuukd. Tu explain tlie riecof tem- 
poratnre it has therefore been eonclitded that then- are 
true thermic ecutre* in the gpinul cord, which centres, like 
oUiore in that organ (Oliap, XXW.), are held in check ut 
inhibited by brain-eentres; when the controlling influence 
of the latter is rcmoTed the former may excite excessive oxida- 
tions in the tisfiii« k> whidi Ihi^y arc dir'tribtited. and so 
produce the ri»e of temppraturc. The pntcif, however, i« 
not corojtlete: for the raised temperature may, after all, be 
due merely to an cxce»ive supply of blood, warmed else- 
where in tiie Itody, to the dilated Hkin-veRRoK 

Clothing. To man. «a social animal, endowed with 
monil (I'i'litigs, clolhiiig \\«g certain untd in the intercutt 
of morality; but for such piirpoeee the amount necessary is 
not great, w we tliid in mnny tribes living in warm climates. 
Kxcept in tropical regions. howeTer. clothing lia^ in addi- 
tion an iniporiunt physiological luse in regulating the bodily 
temtwrature. While the majority of other warm-lilnoded 
animals have coats of their own. formed of luiir^ or feathem, 
over mo^t of man'ii Body his capillary coating is merely nidi- 
mcntoiT and ha« lost all pbyKiulogical impvrlnnco; andsu 
he has to protect himitelf by artificial garments, which 
his esUietic sense has led him to utilise also for pur|]oses of 
iid'iniment. Here, however, wc miut confine onrsclvtv to 
clothes from a physiological point of view. In civilised 
societies every one is required to cover most of his llody 
with Romcthing. and the iini-stiun ix what i« the bcl 
coTpring; the answer will vary, of course, with the rlimatir 
condition)! of the country dwelt in. In warm regions, 
clothing, in gcneial terms, should allow free nidiatioii or 
conduction of heat from the surface; in cold it should do 
the revente: aud in tcmjiurate climute«, with vaiying tem- 
peratures, it slionld Tory with the seoaon. If the surface 



CIOTHISO. 



4511 



of the Bod)' Ixi osjiosod so that cnrronts of air can freclv 
trarerse it much more beat will be csnietl off (uuder 
ttiD«o hbuhI conditiouH in irlitch the air i« cxtoler than \\w 
Kkiii) tiiuii if a MMttionikry Uycr of air be nmiiitiiinod in coo- 
tact with the sartace. Aa erery one knows, a "draught" 
cools much taaUsr ihun air of thu Mtino tcmperutare not in 
motion. All clothing, therefore, k*n(t« to k<*i> up the 
reiiipenilurii of Ihe Body by checking Ihe miovral t>f iJic 
layer of HJr in contact wilh it. Ajuirt from thi!<, lioweTcr, 
clotliM fall iuto two great gn>[ijw; thfuo which are good, and 
those which are bad, condnctora of heat. The former allow 
ohaogw in the external lein|jeratiire to cool or heat nii)idly 
the air Etratum in uctuul cuntiKrt with the Body, while ihe 
latter only permit these ehangeii to act more iilowly. Of 
Lhe niateriaU used for clothes, linen \e s good conductor; 
calico not quite to good; and silk, wool, and fur are bad 
vonduutore. 

Whenever the snrfaoe of Ihe Body w suddenly chilled 
the i<kin-V0)tulH are contracted and thix-io of inlcrnwl 
part-t reflexly diliilod ; hencv tDternal orginia tend to 
become ••ongeslfl. a onidilion wbich readily jiofwcs inlo Ihe 
difieikscd ilaie known a* injlanimaiion. When hot, ihercfoit', 
the most anitdTi»nblo thing to do, w to sit in a draught, 
throw (iff the plolhing, or in other ways to strive lo get md- 
denly cooled. Moroorer, while in the American Rnninifrit 
is tolerably safe to weiu' goiHl. conducting gnmunt^, and few 
people toko eold tlieu, this is by no nieang ^fe in ihe 
spring or autumn, when Uie temperature of the air is apt 
to vary oonsiderably within the course of ii day. A person 
going out, clad only for a warm morning, may have to re- 
turn in a very much colder evening; and if bis ctnthc« he nor 
such aa to )>revout a sudden snrfiuw chill, will gel off lighlly 
if he only " tako" one of the colds so prevalent at Ihosc 
gciwon«. In the great majority of casoe, no doubt, he KufTcn! 
nothing wnrw-. hut many ])pr»in((, eHiK.-<'i(Uly <>f the fcnuile 
sex, often u-fjuiro far more nrioiis discasm. When sadden 
changes of temperature are at alt probable, even if the pro- 
THiliug weather be vrarm, the truuk of the Body should 
bo always protcet«d by some tolerablyclose-fitling garment 




MO 



THE UUMAS BODY. 



of noii'Gondactitig malerial. Those whose nlcins are irri- 
tstwl l>y iiiiyLliiiig bat linen ithould wtuir immcdiutcly out- 
ode the under-gannentd a jacket of iiilken or woolen 
mauriat. In inidwintor oompgurstivelj f«v people take 
cold, bccauM all thcti wear tliick and noocODduottiig cloth- 
ing of some kind. 



CHAPTER XXX. 



SENSATION AND SBNSJ!-ORGANS. 



LI 

I mtu 



The Sut^sotive Fuuotions of the HerfouB System. 
Chan^'o^ in iiiiwiy partd of ouv Bodies ure nccompatiied or 
followed by thoite stales of eoDsciousnuu wliicli wo cull sen- 
fotums. All *wh doiisitivf parts are in connection, direct 
or indirect, with the brain, by cert^n afferent nerre-fibmi 
ciilled »emortf. Since uH feeling \6 lost in any region of the 
Biidy when this connecting puth w «eTcrod, il is clear thnt 
all scniuitiouH, whatever Uieir primary eicitiog cause, ilto 
finally dependent on conditions of the OL-ntnil nvrvoiu «ys- 
lem. Hitherto we ha»e studied this »» its activities are 
rereoled tJirongti movemente which it excites or prevents; 
we have Mcn it, directly or refleily, cnuKe tnunolcH to con- 
tract, glandfi to secrete, or tJie pulsations of the heart to 
oease; we bavo Ttowed it oltjKfivelg, as a motion-rogtiltiting 
appanitnt. Now we have t*; turn to another side iind oou> 
sii^ it (or porta of it) as influencing the states of coDscioua- 
noas of its poaMBsor: tbis study "f the »uhj'fffive nclivities 
"f the oerrotu system is one of much greater difBculty. 

[t may be objected that considerations conoerning stales 

feeling buro no proper place in n tiealiM ou Anatomy 
Physiology; that, since we cannot form the beginning 

a conception bow a oortain state of the nervous system 
cacuing the feeling rcdnoas, another U>e feeling hluenesa, and 
a third the emotion anger, all examination of mental phe- 
nomena should be excluded from the scionoen dealing with 
the structure and properties of living thingji. But, altliougfa 
wo cannot imagine how a narrous state (neurotU) gives ri«u 
(o a conscious state (/uyeAww), we do know this, that dia- 
Uuot pbauooMQa of oonsdousnew never oome under our 



4«S 



TSE uuMAs honr. 



"-1 



ob«emtion ai>art from « ncrvuus EVEtem, and bo are prt- 
BBmsbljT, in »<'iiii- wnj, f'tidowmontt) of ii; wcbtc, therefore, 
JuRtified in calUog (bem properties of the nervoiu tiyvtcm; 
wid their exaruination, espcciallj' »iih n-Kjicct to wh. 
ner\'^[>ar[s are conccmeil with different meiiiul Ktaliv, am 
vhat changes in the former arc associated with given phe- 
nomeoa in th« lMt«r, forma projjcrly a \a.n of I'liysiology. 
Wh«th«r niaaM« of pmlupUMn, More the differentiation of 
definite Dent^-titeaes, pone— aome ill-dcfiiicd sort of cuti- 
tciousoess, lu they poM^ wt indefinite contractility before 
they have been modified into mnscnJar fibres, may for the 
present he left undixrided: though thow who uvi-ept the doc- 
trine of evoluiion will be inchned to assent to Ute proposition. 

While, however, the PhysiologJEt has a right to be beard 
on queetjous relating to our meiitul facultin, it i« ucvcr- 
tiMden tirao tlint miuiy laws of thought have been eiitji> 
blifthed. concerning which our present knowledge of the 
1hv« of llie nervoitfl syntein givcHUBOoduo; the •cicnce of 
Psychology has thus a well-founded claim to an independent 
existence. Bat, in ta far lut its reenlltt lu-o confined merely 
to the «iiocc«fiionA and connectionn of mentul «1aI««, aaeatAh* 
linhcd by olisenation. they are meielydeecniilions, and mil J 
c\pliination« in uxcienti^c eenao: we know that so mauj ■ 
ni<-nlal iili^noniena have neoetwary material nnteoedcnla and 
concomilautx in nerrone changes, that we are jiiiilified in 
belit'Ting thai all huTc snch, and in continuing to c^i^^k for 
them. Wc do not know at all how an civetrio current aeal 
round a bar of soft iron makes it magnetic; we only know 
tiittt the one change is accompanied by the other: ''ot wc 
my wo hnvv cxpluined tlie mngnoli«m of a pioct of iron if 
wc liave found an electric current circulating around it. 
Similarly, we do not know haw a nerrous change causes a 
munlal state, but we have not explained tlie mental state 
until we hare found the nervous state associated with it 
and how tliut nervous slate was produced. 

Sx yi'l it 18 only witli roitiifct to some of the 
I tnti^s of ooii«ciousres3 that we know much of the q< 
phyjiiolo^cal antecedents, and among these our sensutiouH 
aiv the best investigated. Ak regards sueh mental pheno- 



1 with It 

simplestM 
nooceearyfl 
ensutiouH " 
pheno- 

A 




SBysATTOy .LVO OROASS OF SPECIAL SSyHK. 468 



metia w) tho Ajtwciation of IdcM, and Mctiior}', pbysiu- 
logj can givfi xm some ligltt; bat «o far lu others, such aa tbc 
Will and the Kmotiotu, are conceniod. it has at present little 
to offer. Tho phcuoinviia of Seiimtioii, therefore, occupy 
at present a much larger jiurtiun of phyHioIo^ciJ workii 
than all other mental fai;lf* |nit together. 

Common Sensation and Organa or Special Senso. A 
aenaory norro Is one which, when stiroulitied, uimu.hi.i, oi' 
majr arooae, a nmsaiion in its posaeasor. The KtimiiluDl h 
in all oases some form of motion, molar (e.g. mochaiiical 
preasore) or molecular (as ethereal vibrations or oliemicid 
ohaugw). Since all our nerves Ho irithiu onr Bodic-'i a^ 
ciroumsofibed by the skin, and are excited within (hem, one 
might, a prion be inclined lo siippom.' thiit the oauao of all 
MDaationa would appear lo be within onr Bodies themselvoK; 
that the thing /eil would boa modilied portion of ihofiuUr. 
Thia i^ the case with regard to inan^ Mneationii; a head- 
ache, toothache, or earache gives ua no idea of any external 
object; il merel; suggcdta to oitch of tu a particular 
alate of a aenntive portion of mi/Ml/. As regardu many 
aematioDs, bowoTer. this is not w. they snggintt to um ex- 
t«raal cauMe, toprnpcrtimof which imdnot to stales uf our 
Bodies, wcuitcrihe Ihein; and bo they lead us to thcconception 
of an external universe. A knife laid on tlie skin j>r<Hlnvcs 
change! in it whicli lead us to think not of a HUiti- of our 
itkin, hut of stalcii of some object ontside the skin; we 
believe we feela cold heavy hard thing in contact with it. 
NcTcrtlielbM we have no consofy nerve* going into the knife 
and informing ns directly of its condition; wliat we really 
foci arc tht' tUijdiScations of onr Body prodiicorl by it, 
although we irt'existibly think of them att properties of the 
knife — of some ubjeot that is no part of onr Body, and not as 
slates of the latter itself. Lot now the knife cut through 
the Rkin; we fool no more kniff, but experieni^ /miM, 
which we thmk of as a condition of ourselves. We do not 
saj the knife is pitinfnl, but that onr finger is, and yet we 
have, so far as scnMtion goo^. as much reiL«oii lo call the 
knife painful as oold. Applied one way it produced locid 
changes arousing a sensution of cold, and in anoUier local 





n 

tborla- 
brfl 

iobjtrU If 

.ytitbrnmajjoritj 

>tb» 

1 BoC IB the bcauL 

A UiNr M Ae iMdc «r IW dUv-JMBt. uijuii^ Um tdnw 
Bcmv fniaea mattmk^iod !■■*> b>l«Miu» of ting- 
S^maihtd UtOmMagtn ts vUci the eadt of the film 
g^ IViw wnh iM fBt i ii d Ba^hiwfaifay in thwr 
flBfsn nd IMI ln( ^tar thqr hnshaea hat, if the nenrt- 
trmka ta the elaa|> Winilitcd. Taeqlua joch CkU we 
maA beach «■ the piMmdef nFjv^Milacr, ud so the; rao- 
iMilbefa%4ilBaMidhcfe;lNit thr; era MonBonlj aecnbed 
tathenMjteof esperiMMe. The«fcnU«f EfchmtMi^ 
tu thek in the greet Bejori^ of inrie aeae the muoi^ bn- 
palMi vhicfa excite a gi<ia taccHe wwliwi. for example, 
hare acted npoo the tip of a Anger. ThewaaeiioagDee vben 
(be tugrr u rmtrted, aod nrtniM when it k tejilKicd; and 
the ejt mafirau the contart of ttw rstrmal ubjivt with the 
fii^pr-Up when we get the tactiW •«t?attuQ in quMtion. 
U'c thu!) cMDP firm]}- to aasDciate a paniralar region of tl 




qcAuriKs oy i*iixsATwy& 



U5 



ekin with ■ givon tenntion, and whenever afterwardn the 
tsarW'flbi'es coming from tlw finger are otimuliitvil, no mat- 
ter wlwre, we oacribo thi- orij^iti of the acuitaiiuu lu suiui^ 
thing acting on iho finger-tip. 

The Diflbrenoea between Bensationa. In botli groii|Mi 
of iieiiMilioit?. ibofJi.' di'nvtd t]ii'"iif;li urgims of Hptcinl 
senee uud thoi^o due to ur^nttof oouiniou f>unNition, wedi«- 
tingiiinh kiiid# whii-h lU'c iibsoluiely distiiii^t for our con* 
sciousse&'i. and not conii)amWe tnculslly. We can never 
got c-<;nf)i»od bctwoou n sight, ii KKutid, and n touch, nor Ix- 
twecii )iaiti, hunger, and nauaeii; nor c^iii wc conijiarc liu-m 
with one &aalber; each a »ui geHgri*. The fundamental 
difference which lhn£ sepanttea one eensaUon from another 
IK 'xl» tn'idality. Sen»ations of the aatne modality niuv difftr; 
Imt ihey shade impereeptibly into one another, and luv C(«n- 
parable between theiii«elvi-4 in two ways. Firet. as regtirda 
qitaliitf; while a high and a low pitched noUt uri; both 
auditory senaationH. they are ncverthe1c«a diSercnt ami yot 
inlcUigibly cuinpurnMei and jin uru bltie and rt-d objects. 
In the seoond pUoe, seiuations of tlie siune modality are 
diHtinguishahle and comparable us to amount or mtftisift/: 
we raadily recognise and oompuro « loud and a wmk i^oiiiiil 
of the same pitrh: a bri{;ht nod feeble lightot the «atno 
color; un avute and a (>ltght pain of the same general chiir- 
aoter. Oar Renmtion* thuM differ in the three a«i)Cot« of 
Vio^nlity, quality wtt/iitt tkt mme modalittf, and tnUiuity. 
Certain eensations alKo differ in what U kuown na the 
"local fign" a liiBori'nce by which wo tell a touch on one 
]>arl of the okin from a similar touch on another; or an ob- 
ject exciting one port of the eye from an object like it, but 
in a different location in spaoo and oxoiling anuUier part of 
the visual Rurfaoe. 

Aa regards modality, we commonly distingiiiMh five 
Rcnxes, thiw of wight. Round, touch, ta«tc, and iimclt; it '\» 
duubtful whether temperature should not be added. The 
Tiirictiot of common fleuMttion are also several: for example, 
piiin, hunger, Mtioty, thinit, nausea, fnA/niV, bifn-ftre {tvtA- 
ing "good"), fatigue. The muscular uenM stands on the 
intermediate line between qteciul and common BCHKatJoiu; 




486 



THE UCVAX BODT. 



we gather by it how miieh our viinous masolee on* em- 
timcied, and ao Ituim the ]M>sition of v»riniig jmrts <>r the 
Body, oi] the one baud, and the resistance oppofiotl to budily 
iiiutfUM^ul hy vstciiiiil objt-cU, on Khv. other. In fact, we 
ouinot draw a sharp line between the sjteraaJ aoneee and 
common suniiutiou«: uU the Body, we conclude from ol>- 
(LTvutioiu OH liie lower animate, !«, ut hu early stage of i\& 
derelopmvnU sensitive; very aoun iU odi;! sopanle them- 
selveH into an outer layer oxpoeed to the action of external 
foroee and an inner layer prot«ct«d from tiwm: and eome 
of the former ocIIh bcconieespec)ullyii<*N^i7tt'P. From them, 
iw dcTclopnicnl jirocmdii «Mn« are .voparutfd and baried be- 
neath the ^iirfuot! to become the bi-ain and i;]>inal cord; of 
thoM} which remain snperficiut, some are modified so that 
they (in the eye) hecomv Mipocially excited by «Uicreal T-i> 
bralidiiK; iit]ii.-rK (in the ear) become especially reajxinsve 
to sound vihrutions; others to slight chemicid changes (in 
nioutb and nose), and othcn (in the «liiu) to vanationa 
in press nro or temperature. 

All our sensatiouA are thus Diodifications of one common 
prjmnry iion^iliility, rcproMiitcd hy that of the i^kin, or 
rutbcr by the primitiTe representative of the ^kiu in audi 
an luiimal as th(> Ilydni (wo Zoolog)'). Tlio cutaneons een- 
fiatioiis, being h-* (HiT(-n.'ntiHt«d, shade off mon> readily into 
thu eoinmou Hensibiljly of the other living tissues than do 
the luitiriticij of the highly (li He rcn tinted cells in the c^vfl 
and oar. W« find, aooonlingly, that while a poircrfal prc^ " 
Mins or a high lompemture acting on the skin rewlilv 
aniiuk^i* iifion^'ationof pinn, that this is not the cfuw with tlie 
mure specialixud visual and auditory organA. Their supcr-cs- 
citeiiK'nt may bo disagreeable, but never passes into pniti, in 
the onliiiary scn:>e of the w<inl. Simihu'ly the dpocialskin 
lie iisat ions, touch and temperuturo, may sumetimM l*e god- 
fouiiiied, while .-i sound and a sight cannot I»e: the me- 
diiUti) of tiip li'w mtidificd skin-scuses is lo** complete. The 
stiiilt of comparative miatomy and dcvdopmcnt thits thowi 
that the irriud'li- jKirt; of uur seu^e-organa are bnt special dif- 
ferent i;itioii.-i of the pHniiuy cxteriiiil layer of cells oovering 
the Body when it is very young. Some of them beoome nerre 



I 




.frBVCTVBH OF aESSK-OR0AN8. 



40? 



end oi-^nH iii the e;e, oUien eaA orj^rw in th« Mr, and so 
or; while others, letss cbaiigic), rcmiiin id the »\.\u si» orgutiR 
of touc]l Aild t«in|<frntiirc; mid utt, from a funeral exlciior 
surface responding e(|ual1<r readily to many extenml nittitnil 
forctt«. wo get u siirfiivc modiQcd «> that its variona parts 
r<.-K[KitKl with different degrees of readiness to difTcix'nt ex- 
ternal forces; iiitd the»e inoditio<l parts contititu to the essen- 
tial |K>rtinn« of <inr urgniis of i^pwial iwntie. Erery sense 
oi^;aD thus comes to hare a special relatiouithip to some one 
nataml force or fvnn of ener*^* — iv » HpecikJly irritable 
mechanism by which t>uch n fori'c ii^ enabled to excite sen- 
xory nerrea; and i*. inoreovLir. commonly supplemented by 
orrangementa which, in the ordinary circunieUnces of life. 
prcTeiit other forces from stiniuluiing the norves connected 
with ii. Not all natund foroc^ Imve sense-organs with ref- 
erence to them deTi' loped in the Human Body; for exam- 
ple, wo iiHve no organ standing i» electrical chianges in the 
same relation that the eye docji to light or the car to 
gonnd. 

The Eseentlal Struoturo of a Sense-Organ. In every 
sense-org^u the fundamental purt ia Uiua one or more t>ui 
organ*, which arc highly irritable tissue* (p. 31), bo oou> 
structed and so placed aa to be noi-mally acted on by some 
one of ihc modi's of motion met with in tho uxtenial world. 
A sensory appamtiu rotiuinut in addition at leosta brain-cen- 
tre, and a aendory nerre-flbre connecting this with the ter- 
minal a])puratus; but one commonly finds accessory parts 
added. In tho eye, f.g. , wc b«v« arrangcmonte for bringing 
to a focus the light rays which are to act on the end 
orgnn.t of llic nerve-Hbrcs: and in the ear are foand simihir 
subsidiary part*, tr» cimdiict «imorou9 ribrntions to Uie end 
iippariitus of the auditory nerve. 

Seeing and hearing arc the two most specialized senses; 
the stimuli uflually aroiuing them are peculiar and <iuitc 
distinct from tlie group of general nerve stimuli (see p. 188), 
while those most frc(|nently, or naturally, acting upon our 
other Eenii&-orgaiis arc not su peculiar: they are forces wliioh 
act as gcDoral nerve stimuli when directly applied to nemy- 
flbres. The end organs, however, as alroadv pointed out 



4t» 



Tim nVMAX BOOT. 



(]). IfKt), so incnuue the sen^tiven«w n( tW imrto oontain- 
ing thom Ihiit dugrcvs of change in the exciting force9« 
which wouli] he totally uimblo to ALtmnliilo ncnp-filire 
tbemselToa an> appreciated. Thew tcrniinal npparatUB 
uro therefore » truly mechnnisms floabling changes, vhicl 
would not otherwiw Btiniiilut« norvM, to exctt« them, W'] 
are thfi end oi'giiiiH in the eye or e-ar. 

The CBUBOof ttio Hodality of our SonsMions. Seeinff ^ 
that the i-xitirnal forees ti^ually exciting our dllTtfrent octi- 
eations diSor. und thut th<; ccniutionH do also, we might atJ 
liret be luditicd to Ix-lieve Uint the lutt«r dilTeretice de-i 
pcndc'J on the former: thai hrightti<-iutdifTer(>d from lond- 
notu hecaose light was diSerent from sound. In oth( 
words, we are apt to tliink thut each Eeosstion dcriTeJi it 
Hpecific chftroctcr from aorae property of il« external phy»i- 
cal antecedent, and that our sensationR answer in Home way 
to, and re})refient more or leas accurately, properties of the 
forms of energj- arousing them. It is, however, quite eatt 
to kIiow that we have no HufRoJent logical warrant for siicli| 
a belief. Light falling into the eye causes a senntion ' 
Inminosity, u feeling belonging to the tUusI group 
modality; utid, sinoo nsaally nothing el»c «;(citc« snchl 
feelings and li^ht entering the healthy eye aln-nyi) do«s' 
we como to believe that the phyvicid agent light !« somo- 
tbing like onr sensation of luminosity. Bnt, its we hare 
already seen (p. 191). no matter how we stimulate (he optic , 
nerve we still get visual wnsalionH; cloiic the eyes and pr<ur| 
with a iiDgiT-nuil on one eyelid; a m-n.'uilion of toacb 
aroused where the finger meet§ the skiu; but the proMnr 
on the eyeball distorts it and stimulutee the optic nerfo 
(ibrfH in it al«o, and Ihc result iK n luminonM patch seeo'l 
ill front of the eye in ntieh a poaition as a bright body must' 
occupy in space to radiate light to thut part of the cxpan* 
sion of the optic nerve. Finding, then, the same kind of 
Mcnxiitiou, a visual one, produced by the totally dtfTercntl 
oatisee, pressure and light, we uro led to donbt if the dif-j 
fcnmoes of modality in our semtutiunN depend upon the dif- 
ferences of the natnral forces arousing them; and tin 
doubt is strengthenetl wlieu weliiid utill other forces (p. 191] 





WHT OUR SBS8ATI0X8 DIPTSR. 



499 



giving nse to risiia! senBations. Bat then.since light and 
pressnre, clcctricil v nnd cutting, all ciiuhc visuiil sotieations, 
vc have no valid rea«oD for suppotrting tliat light, more than 
either of the others, u really in any way like our sensation . 
of light: or that Hight-foeling diScrH from sound-feeling 
beraase objeotivoly I'ght differs from .tounil. Tb<.^ vyc is un 
organ eipecially set apart to be excited by light, and accord- 
ingly so fixed as to baTc it« nerve-fibres far more often ox- 
cileil by thut fiirra of force than l>y any ot)ier; but the fact 
that light sensations can be othemife aroused shows plainly 
tliat their kind orchametiT hait nothing directly to do with 
any projxjrty of light. Just as by pinching or hcnting or 
galvanizing amotornerro we can maketho muscles attached 
to it contract, and the contraction h&t nothing in common 
with the esoitant, so the visnal aenaation, as such, \« iudv- 
pendent of the stimulus arousing it and, of itaelf, t«ll8^ 
ns nothing couocriiiug the kind of (stimulus which has ^ 
operated. 

Diflerences in kind between external forces being thiia 
eliminated ai jiosaiMe causes of the modatttiM of our eea- 
satiunii, ne next naturally fall hack apon differences in the 
ecnse-organa thcmdelrcs. They do undoubtedly differ both 
in gross and microscopic structure, and tlie fact that pre»- 
Biiro on tho closed eye arouses a touch-feeling where th« 
sktnisoompressod, and asight-focling where the optic nerve 
is might well be due to the fact that a jHirijihenil touch- 
organ w)is diffcn^nt fn>ni a jwriphera! eight-organ, and tho 
mine force might therefore imidiioc lotjilly (lifTcrcnt efFocts 
on them and so cause different kinds of feelings, Hou-ever, 
hero al.^ closer vxamination shows that we must Beek far* 
ther. Ejeustition is not products] in a senBen^rgsn, bnt far 
away from it in llio bruin; the organ is merely an apparatuti 
for gcnonitiiig iicrvouit impul^^^ If the optic nerves be 
divided, no matter how pcrfout tlie eyeballs, no amount of 
light will aroufc visual sensations; if the spinal cord Iw cut 
in tho middle of the back no pressure on the feet will canse 
ft tactile or oilier fueling; though the skin, and its uervw 
and the lower half of the spinal cord be «]] intaot. In all 
ca«tss we Gad that if the ncrve-itatbs between a tvcusiT-orgau 




4n) 



TfW UCMAS BODT. 



« 



and the brain be wvered no stimulation of the organ will 
uill forth u MmsUiou. The final production of Uiid clvarh* 
depends, then, on aometliing occurring in the brain, and bu 
the kind of a i«ueatioti U preeitmablv dependent tipon brain 
«Tont« mlher than on occitiTenu-« in sciiMsorgane. 8tiU it 
might be that »>mcthiiig in tiie wnaeKirgan canaed one Ben> 
Hition to differ from annihcr. Each organ niightexcite the 
brain in a different wit^ and caum? a different eenR»(ion,afid 
BO our aeniationB differ becauseonrwnt^-organtidid. HuchH 
viev ia, however, negatived bjr obeerrations which ehow that 
perfectly chanicta-i«tic acnntion* nui be fell in the absence 
of the Heiiiuvorgana through whtoh they are normally ex- 
cited. Persons whoce eyeballs have been removed by the 
sorgcon, or completely destroyed bj-discaeo. hare frefjuenlly 
afterward^i definite and unmi-^takaltle viHnal sensations, qaite 
as characteriKiic as those which they had while still posMO!- 
ing thi; Tt»ii:il end organs. The tuctilc sonsatioii« felt in 
amputated limbs, referred to above, afford another example 
of the ume fact The perKoiix Ktitl/nr/ things touching tbeir 
legs or lying between their long-lo&t loea; and the sen- 
sations are distinctly laeiilt and not in any way lc» different 
flroin vinial or auditory iwDsatiomi tlian are the tonch-feel- 
inga following stimnhttion of those parts of the skin vhich 
are still posses^. It it. (hen, ole-^r lliut the modality of our 
MDiation* id to bo sought deegier than in properties of the 
end organs of the nerves of each sense. 

Pi-djK-rtios of externa) forcM and proportica of pcripbo* 
ml tKTvo-organs being exoladed as causes of differences in 
kind of ^nsutioii, we come next lo fJie eentwry nervo*flbre« 
theniivlvtt)'. \t it brcouw optic nervt^-tibres are different 
from auditory nerve-fibree that himinons sensations arr 
different from eonorous?' This q»e«tion most bo aa«vcnd 
in Uie negative, for we hare already (p. 193) seen reason lo 
Iwlieve that all nerve-fibres are alike in essentis) straolnrr 
and that their pr»pcrties are everywhere theiuinie; tliat all 
ihcy do \s to tnuinmit "nervous impulso*" when pxdlc<i. 
and that, no matter what the < -cilant, these impulses nn 
molecnlar muvemenU, always idikc in kind, tliough thfv 
Qiay differ in amoiuit utd io nto ol snocewon. Sii 




Wlir OCR SBXSATTOXS tUFFBR. 171 

flUtti drflU^ns optic norre doos is to eeni iivn'otis impiilseii 
to the brain, ami ull that the anditoi^ and guAUilory and 
touch and olfactory uerve-Sbrca do is the same, and thcae 
ioipitl^j UFO nil alike in kind, wo cjuinot vxpliun thi; diffor- 
eDce in qnality of vi.ttial and other sensations by uuy dif> 
fervncu in proiwrty of the nerve-trunks conccrnL-d. any more 
tlian wo conld attempt to explain thcfaut^lHitt, inoucwieo, 
an electric current sent through a thin platinum wire henta 
it, and, in another, <ent through ii solution uf a «alt decom- 
poser it, by o&iiiniing that the diOeient resnlts dcjicad on 
diOoTBDCos in the conducting copper wiiea, which may be 
absolutely the tame iu the two eueoB. 

We are thus driven to coix^lude that our sensations 
primarily differ bccuui^ different central nerre-organs in 
the bruin are concern<?d in thisir production. That just as 
an eHerent nerve-fibre will, when stimulated, caiue a itecre- 
tion if it go to a gland-uell, and a L-ontrac-tiun of it to go 
to a muitole- fibre, so an optic nerve- libro, carrying impulited to 
one bnin apparatus and exciting it, will ciiuso a visual 
Musation. and a gustutoty ncr^'o-Sbre, oonnvclcd with 
another brain-centre, a ta^te sensation. In other worda, 
onr kinds of sensation depend fundamentally on the proper- 
ties of our own c«rohnd nervoun system. For each special 
sense we have a nervous apparatus with its ))criph«rttl 
terminal organs, norrc-fibres, and brain-centres; and the 
excitement of this apparatna, no matter in what way, causes 
a sensation of a given modality, determined by the proper- 
lies of it« central portion. Usnally the apparatus is excited 
by one particular force acting first on its peripheral organs, 
but it may be arou&ed by stimulating ila nerve-fihrus 
directly or, as in certain diseased states (delirium), or under 
the action of certain drugs, by direct excitation of Ihccenlree. 
The sensations of dreamx, frequently so vivid, aiid halliioi- 
nations, are also probably in many ca^i dne to direct 
excitation of the central organs of sensory apparatusee, 
though no doubt aluo often due to peripheral stimulation. 
But no matter how or where the apparatus is excited, pro- 
Tided a sensation is produced it is always of the modality 
of that sense apparatus. 




*n 



THE BCUAS Honr 



I 



It u pombb) that the gen«ru] «tnterocnt in the hut purs- 
(nph needs fumo limiution. While in wnsesor distinttl 
modality, iliiitchiinu^tormubeaacribedoiitT to brain propttr- 
iita (ao that we may bepretty «iirethiit am»n, the inner end 
of whoae optic nerve was in pbrsiolo^csJ eontinaity with 
tli« outer end of \m aaditoiT, und the innor end ot bis ^m 
auditor; with the outer end of \\i* optio, might bntr a p>c-^| 
tna' and wo a symphony), yet. perhaps, differences in the 
rbvcbm or intenHity of ofTen-nt ucrrouKimpnlEes may cause ^_ 
diSerences in modality in le«j differentiated senses. TlinsH 
contact with a cold soft object may bo felt as heat, 
thought to bo due to tbc approiu^h of n warm body; and m 
from ancb cases we mast perhaps conchtde thai touch an<l.^| 
temperuturFi depend on excitations in different ways of oi»c ^ 
and the same bmin-oentrc; inipul^'K of n certain rhythm 
producing a sensation of heat, and those of another (deter, 
mined by the different lieat and touch end organs) canning 
a tactile sciiKation. if this be «o, however, heat and toviA 
would be but extreme varieties of one kind of unsatioo, 
and compomble to yellow and blue. Again, a iMnvy pref^ 
sure, graduniiy increased, aroueea sensations irhich paesitn- 
perccptibly from touch to pain, and tlie result may be dne 
to the fact that regnlar and oiderly afferent impalaM, 
determined tliron^h tactile rer^-e-eudin^, excite tlie centre 
in ono way; while irregular, di*ortleriy, and violent, excited 
when the nerve-trunks beneath the skin are directly stimn- 
lated. may cause a different sensation: much as Ibe same 
muEtcal notes combined in one order eau;^ pleMnre bnt in 
another are disajireenble, causing a sort of pain, allhougb 
the same brain-oentrea are stimulated in the two catee. 
ITio pain from a heavy weight may, howerer, be merely di» 
to the fact that >t excites the nerves very powerfally aud 
gives rise to impulses which radiate farther in the brain than 
those caueitig touch 8CD8ations, and .to excite new centrsor 
the modality of which is a jtain fenealioD. 

However differences in noni-oiw rhythm may aeconat for 
minor differences in scnnalion, it remuiui* clear that the 
diaracters of our sensatiood are crestioos of our own orgao- 



FKCUXEBS LAW. 



478 



iHin; tlwy depctid on pmiwrticB of our Bodies and not on 
propertiea of exteniul things, except in w lax as these may 
or nwy not bo iiduptvd to arouve our differi'Dt Hpiisorj 
apparatuses to aoiifity. From the kind of the senaatioii we 
cannot, therefore, argiic m to tho nature of tlio excitant: we 
have no moro warnnit for «uppo»i»g that light a liko onr 
seiiitatioii of light than that the knife that cuts ua Ls like 
our sensation of [>ftin. All that wo know with certainty \s 
stiitos of our own cuuMcioiuncss, and although from the»c wo 
form working hrpothcMS ax to an external aniTerse, ret, 
granting it-, wo haw no means of acc|airing any real knonU 
edge as to the properties of things ubmit U8. What wo 
want In know, however, for tho priurtical puritoKca of life 
ia, not what things art, but bow to nse them for our adTaa- 
tago, or to prerent them from acting to our disadvuntAgc; 
and our xcnfcs eniiMc u* to do thin sufficiontly well. 

The Psyoho-Fbysioal Law. Although oursensationsnro, 
in modnliiy or kind, indcpondontof the force exciting them, 
thoy are not m in degree or intensity, at loa«t within «tr- 
t-iin limiti. We cannot measure the amount of a scnHalion 
and express it in foot-pounds or calorics, but wo can got a 
Kort of unit by determining how email n diJIen'noQ in Bon- 
aationcanbe])eroetTcd. Supposing tfaissmalleet perocptiblfl 
difference to be constant within the range of the same eense, 
(which ix not proved,) it i^ found that it i*, pnxlueed by dif- 
ferent amount.i of stimuli, meaiiarcd objectively oa forcM; 
and that there exists in some cases a relation between the two 
which can be oxpresHcd in numben^ Tht incrfoat o/sHm- 
ulvs nff^nriri/ to /troduce the fumUfMl pef^ptilti" ckang* in 
a tetitilioH i* proportional to the atrength of the stimulus 
ttlrmdy ading: for example, th« heavier a iire^fHro already 
noting on the tikin the more muitt it be increased ordimin- 
iiihed in order tliat the increase or diminution may be felt. 
Expressed in another way the facts may bo put thus: snp- 
poHC three degrees of Ftlmnlnlion to bear to one another ob- 
jectively the ratios 10, 100, 1000, then their eahjective ef- 
fects, or the amounts of sensation aroused by them, will be 
rupectivoly «a 1, S, 3; in other words, the seHsation in- 




474 



TUB aVMAS BODY. 




creatna proporUotiaffIg to ths logarithm of the strength of 
ttimnlHg. EiuimpltM of tliii*, wliicti lis kuowu u« " H>^r'. 
or "Ftthnft'f psjirlio-phytical tate" will be licreaftc: 
pointed out, and are readily obscrvuble iu duilr life: ye 
have, for example, ii luniinown iieiiitiiiioii of eertiiin iurvnrii 
when u ligli ted candle is broughi intoadnrkrooiu; Ihi^scm 
eatiou ia not doubled when m n-coud ouidlo le brought ini 
and is hardly uftcclcd at all by a third. Tim law t» onl 
true, however (and then but apprciximntely). for seosatioiiB' 
of medium intendty; it t« applicablv, for exumplu. to light 
»eiiNitiuiix of all dcgTees between tboae arouited by the ligli 
of u eandle and ordinary clear daylight: but it iii not in: 
for lumiDosities to feeble u« only to be seen ftt all witli diffi- 
oully, or HO bright lu to be dazzling. 

B<uiide^ their yariations in intenfiity, dependent on roriu- 
tions in the etrength of liic Rtimnltis, our sensations aisii 
vary wilh the irritability of the flen.sory uppamtus itself; 
which is not constant from time to time or ^ni pcrMin to 
jwrson. In Lho above alatemontj the condition of the sense- 
organ and its nervons connections is presumed to remain 
the same tliroiighoiil. 

Percepuons. I" every Hiiution we haro to carefnlly 
di»ting\iisb between the pure sensation and certain jndg- 
niontAfomidcdnponiL: we tuirc to dittinguiah between whul 
we really feel and what we Uiink we feci; and very often 
Brnily btOiCTo we do foci when wo do not. 

The niOJtt important of thcitc judgments Js that which] 
leads us to ascribe certain eensiilions, those arouMd tbrongh 
organii of sitecJol Bcn^c, to external objects — thut out«r 
reference of our sciisatiaus which leads \u to form ideal 
eoncerning the exisloiico, form, position, and properties uf 
extenml lliiiigs. Stub rcprcMUtations as these, foundixl un 
our senses, are called pereepttont. Since tho» always imptr 
come mental activity in addition to a mere feeling, tJteir 
full di:icuxsion belongs to the dumiiin of Psychology. Phy- 
Bologj, however, is concerned wiih them w> fur as it can 
^doterminu the conditions of stimulation and nenroeis 
under which a given mental repru«eiitation conoeming a 
sensation is made. Ic is quite oerluin tliat we can fed 






I 



can fed^ 



PKnCKPTTOyS. 



475 



bnt statfiB of oar«elTe«, bat, u alrcadj pointed 
Hire no hcsifatiou in saying we fw! a liuitl or u 
cold, a rough or smooth body. When we look at a distant 
object wo neually muko no drmui* to suying that wc jwrccivo 
it. Wliat wv rciill}' feci \*, however, the change produced bv 
il in our eyoaL There are no parUof onr Bddios reaching 
to a tnv or n houses mile oH — and ycl wi- st'<;in to ft'cl Nil 
tJio while tliiit we are looking at iIm> tree or the liouse and 
feeling them, and not merely experiencing modifications of 
oiir own eyeti or bruini<. Whvu rctidiug wn /<W that what 
wc mtlly Ace \a the book; and yet the existence of the book 
ita jadgniont founded on a state of our Body, which alone 
is what wo truly feel. 

We bavo Iho Kame experience in oUier caaes, for example 
with regard to touch. 

Uairs are quite iii)icnMib)L>, but arc imbo<lded in the een- 
Bitiro *kiu, wltiob a excited when they are moved. But if 
the lip of a htur be touched by some external objc<^ we be- 
lieve we feol tho cuntaci st \M icuensible eod, uiid not in 
the Rcnaitivo skin at its root 80, the hard ]uirt«i of t]io 
toeth arc iosennblo; yet wlioo we rub them together we refer 
thoMtttuf tho Kensation aroused to the points where they 
touch one another, and not to the sensitive part.t aninnd 
the jackets where thoRcn^ory none impulse is really started. 

Slill nioro. wo niiiy rofcr tactile nensiili'iri*, not merely to 
the dii^tid ends of insenxible bodies iiuplsntcd in thettkin. 
but to the far ends of things which arc not pails of our 
Bodies at all; for innunoe, the distant end of a rod held 
betWMD the finger and a table. We then believe we fee) 
touch or preesare in two places; one where the rod touches 
onr finger, and tho other where it comes in contact with 
the table. Wo have, eimiiltaneouitly, iteninttons at two 
places separated by the length of the rod. If we hold tho rod 
immovably on the table we feol only its end next the lin- 
ger. If we could fix it immovably on tho finger while the 
other end was movable on the t^ble, wo would lose tho ten- 
aatioii at Uie finger and only believe we felt the preesaro 
whero the rod touched the tJible. When a tooth is touched 
with a rod we oat; feol the coutaot at its end, nnlen it 10 




in 



THE nrTMAJF BODY. 



looce in iU *ock«t; and then vc get two BCiuatioiu on 
toRohiDg its free eud with a foreign body. 

This iiTcsijitihk niciittii t«n(len«j' l« refer ccrUin of <mr 
stntcs ot feeling to cansu outside of our Bodico, and ettiur 
)D contact with them or scpurutcd from thorn by a certain 
qiaoe. is known us the phenomenon of [lie cxirtHtic refer- 
mtcB 0/ our wnsaiions. 

The discussion of it« origin belongs properly to Paychol- 
ogy. and it will biulHoe here to point out thut it seems tar^W 
to (U-]iend on the fact that the seaeat ion." ex triiiiiically referred 
can be modified by niOTcmcnti of our Bodi«& Hanger, 
thirst, and touthacho nil rcninin the Kume whether we turn 
to th« right or left, or move away from the phKe wo are 
filiinding in, But u sound U altered. We And that in a 
certjiin poi^ition of tlie head it is heiird more hy the right 
ear thiiu the Itft; hnt on tnrning round the rererw is the 
can; and half way round the loudness in each car i« the 
same. Hence wc are led, by mental laws ontside of the 
physiological domain, to ^lupuot that itscAuae is not in oiir 
Body, but outride of it; and dqicnds not on a condition of 
the Body but on something else. And thit is c-onfinned 
when going in one direction we find the sound incncMed. 
and in the otlicr that it is diminii<hi.'d. This im)^ies thai 
wc have a knowIedgB of our niovenienU, aud this w« gain 
tJirough the mngcular sense. It const itnteit the mictiTe ade 
of onr Bonsory life, associated witli the changes we produce 
in external things; and is correliued and conlmstcd with 
Uie passive side, in which other things prodnce aensationi 
by acting upmi u;*. 

As regards onr common scnRalions we Snd something ot 
the same kind. The more readily they can be modified by 
movement the more definitely do we localize them in tpacv, 
though iu thtit <:a*v within the Body inst«iid of outside it. 
Hunger and nausea can be altered by pressure on tJie pit 
of the stomuch; thirst hy moistening the throat with water; 
the desire for oxygen (I'e^piration-liunger) bymoremenUof 
the cheiit; and so we more ur \w» dcthiitely ascribe theee 
sensations to conditions of those parts of the Body. Other 
. een^ntionK, n* depivi>sion, anxiety, and eo on, ar« not 



I 



SSXSORT lU.USIOHS. 



477 



moditlablft by any particnUr moTcmcnt, and vt sppMr to 
us rather as mental iMs*, |>ure and aimpte, Uiao bodily 

Sonsory niaslonB. " I must belieTs my own cyc«" and 
"we can't aU'uy« bcUove onr KcnM«" are two cxprev- 
«ions fn^qiiviilly hoard, ntid.cach expreesing a trnth. No 
doubt a Meit^tion in itself \a an absolntfi iurantrori-rtible 
fact: if I feel redness or hotnos? I do feci it and that is an 
end of the matter: Iwt if I go beyond tb« fact of uy having 
a certain sensation and conclude from it o^ to propc>rti«fl 
of something eke — if I form njud^mt from my geHtativn 
— I may b« totally wrung; and in so br be unable to 
belioTO my eyeii or skin. Suoh judgments are almost 
inettricably woren up with many of onr HenMtions, and so 
clodoly Uiat we cannot readily separate the two; not even 
when we know that the judgment is erroneous. 

For example, the moon when rising or setting, appears 
biggor than wh«n high in the heavens — we seem to feel 
dimJtIjtiutit an>ti«e<i more seiiDattMn, and yet we know 
certainly that it docs not. With a body of a given brightnem 
the amount of eliango prodnccd in the end organs of the 
eye will depend on the size of the imago formed in the 
eye, prcgrided the aomo part of its sensory surface is acted 
upon. Xow the sixo of this imago depcndo on Iho distance 
of the object; it is smaller the farther off it is and biggor 
the nearer, and meoaurements show that the area of the 
sonsitivo surface uffectod by the image of the rising moon 
is no bigger than that affected by it when oTerhcnd. Why 
then do we, even after we know this, see it bigger ? Tho 
reason is that when tho moon is near the horizon wc imagine, 
unconacioosly and irresistibly, that it u farther off; fvon 
Mtrmioraers who know perfectly that it is not, cannot help 
forming this unconscious and orronoous jtidgmenl — and to 
thera the moon appears in consvqticnoe larger when near the 
horixon, just us it does to lo«8 well-informed mortals. lu fact 
we have u conception of the sky over which the moon trav- 
els, not aa a half sphere but as somewhat flattened, and 
henco when tho moon is at the liorixon we nnoonseioualy 
jadgo that it is farther off than when overhead. But any 





CHAPTER XXXI. 

AS AN OPTICAL INSTBITMENT. 

Struolure of an Eye. Every visual organ 

a( A nervuus c.\i>HUiiioa, provided with 

« iif wtikli light is trnablcd to oxcit« 

nntt cx|)o«eid to Uie toctet »t objccttro 

Mosioii is culled a retina. Bj- iUetf, 

would giro DO TitiuMl seDiuitions referable 

AUi^nijU (ibjecu; it would nihMo iU 

;l|t from darkucss, more light tnnn lea 

m \i» liiglilv dovcWpcd forms) light of 

;t> ' 'licr color; but that would be ull. 

1148 we oould uulytcll a printed 

k ixit) bj lIic Tiua that, bt'ing parti}- covered 

Hr*, (which n'llcct lesw light,) it would cxdu> 

liM |>owcrfully than the spotless white 

irdor Uiut dtHtioct objects mid not mcrul}' 

ity inuy bo tocu, «»me amiiigciiicnt is 

bring all light entering the ejne from 

ifnona «urfuM> to a foetu uj^in on one 

•urface. If A aiid /i (Fig. 131) Iw 

'on H bUok Biirface. A', and rr be a retina, 

lit divorcing from A would fall equally on 

nuua and «xcilo it all a littk; to with nij-g 

Jt, Thu MMiHitlioti arouited, sappoBiug thr 

itinn with tlio rest of tho nerrone vixuul 

ltd be uui< of a c^urtaiu aniotint of r«d light 

f, tliu rot] sjHitA, a-t definite objects, would 

iuhle. If, however, a convex glus Ions 

]iul in fi-oni of the retina, ir. wilt chu^ to 

lu a single jMint all the rays fi-ont A fulling 



478 



TUB nCMAK BODY. 



« 



body which vxciUMt lli« Mint; extent of tho senutiro ntr&oc 
of tbe ojc ft) a great dislunce that another doe» ut lv«», tnu»t 
be larger thaii thc> lutlcr; und eu wc coucludu Ihui tlic mouii 
Vt the horiKou is lurgcr lliitn llie moon in the utiiitb, and 
are reiuly to declare ib&t we see it so. 

So. nguiu, a liinall bit of liglit gray )>aperonavhit«ebeet 
lookd gray: but placed on a large bright green enrfsce it 
looks purple: and on a bright red surface looks bliie-gnwn. 
A« lb« wimo bit of gray piipcr \« xbifti'd fruin one to the 
other we see it nhange its color: it arouse* in ub different 
fe«liDge, orfi'olings which we interpret differently, although 
objcotively the light reflected from it remains tbe Hime. 
Similarly a raedium-tiixed man alongside of a very tull odb 
appears short, but when walking with a very short one, tall. 

fjiR'b evT(>iie»us perceptions as tbe«e are known as sensory 
iltusioaa; and we ought to be oonstantly on guurcl oguinst 
them. 



CHAPTER XXXI. 

THE EYE AS AN OPTICAL INSTBUMENT. 

The EsaeQliol Struotore of an Bye. Every j'vsaal organ 
L'OQaisU prinuirilv of u nervous oipftusiou, provided with 
end orguus by iuo<uii> of wtiicli light is cuubled to excite 
ncrvoiu im])ulw4, and exposed to the moe«t» of objcctiTo 
light; anch an ox(»iUiiiiou U cidled a relina. By it»elf, 
however, a rotina woakl give no tIxhuI sonsatioas referable 
to distinctly limited external objecU; it would caable it« 
potttiiiOT to telt light from darkaess, more light from le»« 
light, and (at kmt in itN highly dcrclopiil forms; li^ht of 
one color from light of another color; but that would tm all. 
Wore our eyea merely retiuw wi' t'ould only tcU a priiUeil 
page from a blank one by tJie tuat tliat, tK-ing[Kirtly covered 
with black loitorK, (which reflect less light,) it would cxdte 
our visual ofgan lesa powerfully thau the spotless whit« 
page would. In order that di«tiiiot obJeoUt tuid nut merely 
degrees of Inininoflity may be seen, iwme amngemont ia 
needed which shall bring all light entering the eye from 
one point of a luminous surface to a /ocua again on one 
(TOiut of tho wnsitive surface. If A and /I (Fig. 181) Iw 
two rod jipota on a black enrfaoe. A', and rr be a retina, 
then ruyii of light diverging from A would fall equally on 
all parUt of the retina and excite it all a little; »o with riyts 
starting fi-om /I. The sensation aroused, supposing the 
retina iu cotineclion with the net of the oerrous Tieual 
iipparnlit^ would be one of a curtain amount of red light 
reaching the eye: the red ii]Kitii, aa deDnite objects, wonld 
bo mdiHilnguii^hiibte. If, howoTor, a convex glass lens 
/. (Fig. lii) be put in front of tlie retina, it will cauw to 
conrerge again to « single point all the rays from A falling 



*» 




TBM BTHAjr BOUT. 



npoD it; M. too, vitb the ran from B: and if tlwfiKaU d» 
tanoe (see Phnio) af Uw lens be properly adjartod tli» 
pointa of coDTcr^nce will botli lie on the retiiutt tb»t lor 




m. m. - IHwrw nuMmMt tte taiMacteea of TMan <r«|i a rMlok «lia^ J 
KBaBrfM*eN*Mckaf» nro^ot^ jtaad 8. r r.t^B tti<lw. Tkn dlnanta 

ra^ from A aX a, and ttiat for rajs from B fA b, TbaJ 
■Muitire rarface voalA then only 1m excited at rwn limite 
and ■cpiintt«d )><>inU \>j ihv rud liglit ^manuring frum tkil 
KpotA; coaeequontly only soiDo of its end orgaos and nerT6- 




Fn> Its.— Illuilratlns Utr iiMof > lm<miclvtnRili>nnl)erTilnaIliiMM«. ^.AI 
K. r F. MliiFle. V» X. B UcniiTt^ Iriu an I'Uivl Ibkl li linu;* tn • Rwoi to ] 
thi- inlnu u wmI I> uf Uu< rrUna, nj* nt llclil iliictiriiiK trtAn A mod B rv I 

niiixw u-uuld hv Rtimnlated nnd the rosult would be tbC' 
rooogniUoii of two twpariitc nnl ubj«i-t8. In otir oycn aro 
found cortaiii refnic/ing media wliivli lio in front of tbo 
retina nm) ukc t)ie place of tlic Itm I. in Vig Hi. Tliat ' 
portion of physiology which trealfl of the physiail noliun of 
liOM) nimliu, or in other wonls of Ihe ere as an optiuitl in- 
iment, is known as Uii- iHo/ilricg of the eye. 
The Appendagos of the B^e. The eyvbaU itself oon- 
Hislji o( the retina and iTfraclinj;; media, together uith 
lupporting and Dutiilive strtictures and other accessory 




TUa HYKUUA 



m. 



upjuii^ttues, as., for cxntnple, some oontrolling cbo ligbt- 
convergiriK power ot the mcdtu, nud others reguUting the 
gizp of tlm aiHtrtitro (paptf) by whicli light i-uUitm. Out- 
lide the tnll Lie muAclets which \ma% about its movenaonUi. 
and othor piirU serving to protect it. 

Eucli orbit in u pvrniDid»l uavity occapiod br coDncctirc 
tisAiie, miisclce, blood-reiisela and oerres, and in gre^t |mi'l by 
fat, wliicb forms a wit cusliiou on which the back of the 
«jcball li«H HDd rolU during it* movement*. The conteuta 
of tho orbit being for Uko moat part incamprefsible, the eye 
caiinot bo drawn into itR socket. It aimply rotaUis there, 
as the bead of the fomnr does in the acetubtdani. When 
the blood -TCBst'ls uro gorgi'<l, liowevor. the nytlialln may Iw 
oansed to protrnde {as in Htrangulation). and when tlie ves- 
sels empty it roccdp-s somcvrhtit, an is commonly seen after 
death. The front of tlie eye \i <:-xp).im,'d for tho purpose of 
allowing light to reach i(, but ean be eoTored up by the 
»gttids, which axe folds of int«gument, moTablo by mu»clm 
and stnogthened by plates of fibro-cartJUge. At Uio edge 
of 6a4.'h eyelid the skin which oovera iUi out«ido i» turned 
in, and booomos continuous with a mucous membrane, the 
coitjttnetiivt, wtiicli lines the in»idc of cnnb lid, and also 
corers all the front ot the eyeball as a closely adherent 
kyor. 

The np]>er eyelid is larger and more mobile tluin the 
lower, and when the eye is closed covers all ila trauHpuent 
part. It ha8 a xjiccial muscle to raise it, the leeator paipt- 
hnt suptriori*. Tho eyes are closed by n flat circtibir aun- 
c\e,i\ieorbicutari»palpebrartim,v\nw^i, lyingon and around 
Ihe lids, immediately beneath the skin, surrounds the aper- 
ture between them. At their out-er and inner angle* {cati- 
iki) tb« eyelidfi ari> nnitod, and the apparent size of the eye 
dopenda ui>on tin- iiitvi-val l>etwwn the canthi, the eyeball 
ttwif being nearly of the snme sixo in all persons. Near 
the inner cantbus tho lino of tho edge of each eyelid 
(■hangc« it« direction mid bcoomKi more horiEonlal. At 
this point is found a6m:itl eminence, iiic lacbrymal papilla, 
on Oid-h lid. For mo«t of Uicirexlcrt the inner surfaces 
of the eyelids are in contact with the outsiiio of tho eye- 



L^ 



483 



TUE mXAX BODY. 



ball bat, near their inner eaAs, a red vertical fold of oon- 
junctin, the semilunar fold {plica sent ilnnnri)t) intcrvvnoK, 
Thi« ia a remnunl of the third eyolid, nr niciUaiing 
Membrane, found lai^ly developed in uunv animals, as 
birds, in wbioh it can be dravn all over ttio cxiweed part 
uf th« ejBbalL Quito in thu inner corner is a r«ddi£h elo- 
vatiou, the mrunritla la^Jiri/maU/t, caumkI by u oolli-ction of 
eobuceous glands imbedded in thcfomilnnar fold. Opening 
along tlie edge of each «yelid arc from twenty to thirty 
minute conii-nnnd Mbaoeoits glands, called the ^[eibomtan 
follirlca. Their secretion ia itnmetime* abnormully nbnn- 
diitil, and ihfii appears as a yellowish mailer along Ihr 
cdgL'H of the eyelidis which often dries in the night and 
canses the lid» to be glue<l logetbcr in the morning. The 
ejfflaxhes are sJiort ourrcd hairs, arranged in one or two 
rows rtlong each lid where the skin joins the conjnnctira. 

The Xtaobrynml Apparatus cunxi»l« nf the tenr-gland tn 
each orbit, tiie ducts which ctirry iu sccrotion to the npper 
«]vltd, and the onnulH by which thi^, tinlcw when exowwivc, 
is carried off from the front of the eye without running 
down orcr the face. The lachrymal or tear gland, nbonl 
the t-m of an atmimd, licx in the u)>pcr and outer port uf 
the orbit, near t)io front end. It is a compoond nicemow 
gland, from which twelve or fourteen ducia run and open 
in ft rnw nt the outer corner of the upjicr eyelid. Thfl to- 
cretioQ there poured out is spread evenly over the eipoeed 
part of the e}'o by iho movements of winking, and kecjw it 
moinl; finally it )« dminod off by two laehrytnal mnaU, one 
of whidi opens by a small pore {punctum laekrtfittalu) on 
each lachrymnl pnpilla. The aperture of the lower ninal 
con bo readily ttcen by examining the oorrcspimding papilla 
in front of a lookins-plass. The canals run inwards and 
open into llio lachriinwl fr, which lie:? ju«t ontatido the r\o»t, 
ill a hiillow where the lochn-mal and superior maxillary 
bonee {L and J/r, Fig. 2C)* meet. From the sac the neuat 
tinrt iinwcedii to ojien into the noee-chambcr below the in* 
ferior turbinate bone {q, Fig. 89, p. 309). 

Tears arc conr^JUitly being secreted, hut ordinarily in 

•Page 71 



I 




MUSCffKlf OF THB BTKBALL. 



483 



<]iuintit; aa to be drninfid oft int» tfa« nom, from 
which thoy flow into the pharym and are HWitllowed. 
Wheu tho luciiiymal ducts ore Blopiwd np, however, their 
oonttnuid jiro^eucc niiikoM iUelf UD|itcH#»nlh- felt, and mny 
need the aid of a Burgcon u> ilear thi! jiii^dage. In weepiHf/ 
the fiocretion is iucreiwod, and then not only more of it en- 
U'W tho noei', Imt gimm llown down the oheck?, Tli« frr- 
qnent swallowing niovemenis of a crying child, sometimes 
Hpokei) of ae "gulping down his passion,'' arc due to the 
need of Bwallowing tiiv extra tour* which reach the phuryox. 




Fro. m— Tlw^rehtlldtrvl Iticlr miivl'ww •cm vlwn ihn iMf << DM WbU 
luu bMU rvmnnd kul tri» rm in iLecnviiv hni ^l^n pniilr clMtMMnT* On 
Uw >lgh( dde (h« mptiior Rctiw mutcls liiu bnn ciic mi^. a, wtMnwl »a- 
lu; *; anpHior (««ui>: I. iDtsmnl rin.-im; t. tutwrior oblliiue. 

The MuBcloa of the Eye (Fig- IW). The eyeball is 
«lilu-i'otditliiiri<i'niandultjiched behind totheopticnerTO.R, 
fiomewhat as a cherry might tic toathickxiiilk. On it« outside 
are inserted the tendons nf MxmiiKch^H, fonrx/nri^A/and two 
oblique. The straight muscles lie, one {nuperior rtftuti), », 
above, one {infrrior reclHn) below, one {external rfrlux), a, 
oatside, andone(iWnrNM/ri"-fi<j'),), inudo the eyeball, ilach 
arises behind from the bony ranrffin of the foramen ihrouj^h 
which the optio nerve ctitei-« the orbiL la tlie figure, 





TffE ffUMAx Bca>r. 



4U 



vhicb reprewnts tIicorbitfiO]>ene(lfroin abore. tho anperior 
rcctuRor till- rij^ht «iil(! hif ln'cu romovul. The *«jwrrior 
obliqut or pulley (trochUar) viumle, t, arises behind iiror 
the xtmight miucloa tiud forms outeriurlj a tendon, 
V, whicli jiiij^ti tlirough n llbro*c«rUlag)iiuuB ring, or 
puUey, placed at ibe notch in tiie frontal bone, where it 
Ifoundit Biii>criorl_v llic front end of the orbit. The tendon 
then toTRH back An<3 is itucrlcd into tlie c^ebuJl betirccn 
thenpper and onler recti mmifllea. Tlio inferior oHiqiu 
mtucla dws ii<it iuIm^, like tbv rvti, nt the buck of the orbit, 
but near its front at the inner Ride, clotw to the laclit^'inal 
Bac. It pas&ea thence ontwarda and backwards beneatli the 
eyeball lo be iueertod into its outer and posterior part 

The inner, nppcr, and Iowerittr;iightniu«:lc*, the inferior 
oblique, and Ihe elevator of the upper lid are aop)i]i<.-<l by 
branches of tho tiiinl cranial niTvo (ttce p. 168). The siilh 
cranial none giH-x lo tbo onivr mctus; and the fourth to 
tho #ui)crior obliciue. 

The eye may be moved from side to side; np or down; 
oblicjucly, tliat is neither truly vertically nor horixonlally, 
but partly bolb; or, finally, it may bo rutatcd on its antero- 
poetorior axiib Tho obli<|ue iui>ven)eitt« are always accom- 
panied byaelighlamonntof ruifltion. AVhcn the glnaco il 
tnrned to t}ic Itft, the left oilornal rectus and the riglit id- 
temul contraot, and riV« wrta; vlicn tip, berth sujierior reoti; 
when down, both the inferior. The^periuroblitpiu mitsde 
noting alone will roll the front of the ere downnurdd and 
outwanls with a certain tunouut of rotation; the inferior 
oblique docs the rercr«c. In obliijtio movfineutd two of 
the recti are coDCCi-Qcd, an upper or lower u-itli an inner 
or ontcr; at the same time one of the oblique also alu-ay« 
oontiBcts. Movements of rotation rarely, U ever, oocnr 
alone. 

The natural oorohincd movcnicntd of tho cyc« by which 
both are directed eimaltaneouiJy towards the same point 
dfpe)ids on the aecurate adjustment of ail its nervo-mnscn- 
lar upparattis. When tlie co-urdiniiiiou is deficient the 
]>er8on is laud to s^um/. A left external nquM would he 
osoBod by paralysis of Uie inner rectus of tjljat cj'e, for then. 



4 




irh«n Qi^'Ml^l tutd been turned out by ihi> oxtvraal reo- 
iiu, it voaHl not be brought buck ugsiia to \is median 
position. A left infernal tquiiU wimlil W chumhI, viinilarly, 
bjf panlysis of llio Viti extcnml rectu.*; and probably by 
diSMM of tlio xixtb cninial uervc or it£ broin-ccutrefi. 
Dropping of the upjwr eyelid {pt(ms) iodicateii poralysia of 




nAlHr'naMten'talllnlKirlionUlHvUonrranibrtnrebu*. I. HrlaroUc: 
IL jmellaB «t mimrwk ■nd porne*; 1. cornfa: *. ft, onnJaoMIra: i poawirlor 
f4Ml?Uf*rof conuM: 7. cllUir maacii-: in. chontld: II. 13 cUiari ptti - 1 ww; 
It, IxU: A. iMIiu: Id. uiHln ncm>; 17. arwrr dhMtShk trtluu m »|'iu: mirrr^ 1)^ 
toia* onlnUiiL I**, nwon •rhnre •nvamy pan or n-ilim -tmIh: ;.-. t<iiii|iciiicinr 
llnnMnt: ttbipla«<tln ibacwulcf rstttaad Uie llnafronStpoincaion: M, 
ItoaaBorior pan uT (be byaloul niemMBM: aiLt!.ai»m fSmcei ou Ota iBmi 
npotnMta UMlln* of MUrhmMit uoand R of Ihe ti u ptamarr Unmnil; 9>. 
Tltranw humor; MK uilvrtorcliuobeiof luiutuuiihuiiiDr; tl, pOMcnor dumber 
of aqpiMUJ bunurr. 

ita elevator moscli) (p. 481), itnd ifiofl^naseriouH symptom, 
on pointing to Jiiii?aso of the brain-parts from whiHi it in 
innerrntcd. 

Tha Globe of the Eye it <ni tliu whole Kpheioiilal, but 
coiiiiisls uf pn-jj;iiiciitA of iwo»|i!iereit{.i('eFig. VH^, a porliou 
of a sphere of smaller radius forming; its anterior liiuiHpiiretit 
part and Wing £«t on to tlio front of Jls postorior segment, 
which ie port of a larger sphere, l-'rom bttfore Imck it 



4se 



TUB suit AN BODT. 



meositree about 3?. 5 millinK'torK {-f^ inch), nnd from «de 
to «i<la about "i's mllliraeiGra (1 inch). Kxcepi when looking 
ut near objectd^ the untero-poetonor axes of the eyeballa are 
DiiHrtf jwrnUelt bat tho optic norres diverge considerablv 
(Fig. 1^); oaoh joins it3oyeba]l, not at Uieoontre, bulutxnit 
3.5 mm. (^ff inch) on the naeaX side of t!ie postenor end of 
iU auturo-poAterior 11X18. lu gcnond torm;! tho eyeball ma> 
be described as consistiug of three wa/« and three n/rari- 
iag media. 

The outer coat, 1 and 3, Fig. 134, consigtd of tho tcUrolir 
and the cornea, the lattt>r being transparent and situated in 
front; tho former in npuijuu und whit« «tid coTere the btu-k 
and rides of the globe and [Wrt of Uic front, where it i* f«vu 
between the eyelidH as the tr/nU of the eye, Botli are 
tougb and strong, being coinjKtsed of dvn^e^onnectivv tis- 
fioe. The whit« of the eye and the cornea are alw cOTt-rcd 
over by n thin layer of the conjunctira. 4 and 5. Behind 
tho proper connectivo-tissiic luyi-r, 3, of the cornea is n thiu 
ctnictim^onK iiicmhrantr, 6, lined innide by a single layer of 
epithelial cells; it i« culled the membrane of Dtacrmet, or 
pOffeniir fingiir hit«r. 

Tiie w?eond coat consiats of the choroid, 9. 10. the ciliari/ 
proc^Mes, 11, III, and tho I'njt. 14. The rkoroid irun^slK 
maiiityiif bloml-ves^la su|iporled by loose connective tiBsne 
oontnining numert»i«eorpu«df!t. wUitb iji it* inner luyeiu are 
richly filled with diwk bruwu «r black jiigment granule:*. 
Towards the front of the eyeball, where it begins to dimin- 
ish in diamotor, thochoroidi* thrown iutoplulu, \\wdiiayy 
procftsiM, 11, 12, 13. Beyond these it oontinnas as the t>i>, 
which forma the colored jiart of the eye which w seen 
tliroiigh tho cornea; ami Jn the coHtre of it this a cirviihir 
aperture, thf pupil: so tho second coat does not, tike the 
onter one, completoly envelop tho ball. In tho iris art' 
two »t:l* of plain inui*uii!iir libr**; a circular around (he 
margin of the pupil and narrowing it when they contra<-t; 
the other »ct radiate from the inner to the outer margin of 
the iris and by their conlructioii dilate the pupil. Thi> 
pigment in the iris is yellow, or of lighter or darker 
brown, according to the color of tho cy«, and more or leas 



BlfiTOLOOr OF HBTjyA. 



is: 




abanAimt mcorAing BS the eve u Mack, brovn, or gn;. In 
biae ores the piji^cnt U contincl to the deepor Isrera and 
modified in tint by light. ab.-<cirpticin in tho tiut«rior color- 
}tm «trala through which the light passes. 

The third co:it of tho cvc. ihf retina, 15, u its eaaential 
]M>rti(in. boing th« jurt in winch tho li^jhl j-rodnom those 
change; that girt rise to impnUcs in the optic nerve It 
in* still less com pluti- c'Dvelopo thtin the itcoond tnuic, ex- 
tending fonrards only aa far 03 the commeuocinflnt vfth« 
ciliary i>rocesses. at least in itjt tTjiical form. It is extremely 
soft ftiid delicate and, vrhon trp^h, tranHpan^nL Usually 
whuu ui oyi> is wjH-iH\l it lotAs isilorlciu; but by Inking 
proper prccautionti tlie natural purple color of sunie of ila 
outer layers can be seen. Its mo«t external layer, more- 
over, is compoaod of black pigment eelliL On iU inner 
jrarfacc two pMta, different from the rest, can be seen in a 
eye. One is the point of entry of the optic nerve, 
16, the fibres of whicli, pcniitrating the iiclcrotic and 
choroid, Hpread ont in the retina. At this place the retina 
is whiter than elsewherv and pr«««nt« un elevation, the 
optic mound. Tlic other peculiar region is the j/«lhie tpol 
{macuia luiea), 18, which lies nearly at tlie posterior end of 
theaxii! of the eyeball and tbercforo outride Uie optic mound; 
m its centre the I'Otma is thinner than olsewhtre and eo a 
pit(/ovea ctntraltir), 18, is formed. This appear* black, the 
tjiinned retina there allowing the choroid to be seen through 
it more clearly than elsewhere. In Fig. liS is reprosenu-rl 
the loft retina as seen from tho front, the elliptiosl darker 
patch abont the centre b«mg tho yellow spot, and the 
whito circle on one tide, the optic mound. The To««d« of 
the retina arise from an art«ry (17, Fig. 124) which runs 
in with the optic nerve and from which branches diverge 
as shown in Fig. 115. 

Tho Uicroaoopio Struotnro of the Retina. A rtimplificd 
stratum, rontmiiiitis with the proper retina, imd formed of 

layer of nucle«teil columnar eolls is continued over the 
oliarr prooeaeea: elsewhere the membrane hu» a vciy €om< 
plox stractnrc and a mdion taken, except at the yellow 
spot or tlie optic mound, showii ten layers, jiarlJy Kotory 



488 



run aVMAS BOOT 



apparatoses and oerre-tumies, and partly teotmary sbiM^ 
tores. 

Beginning (Fig. 124) on Iho inner side vo find, first, tiiP 
intvrnal limiting membrane, I, a thin ittnictarvU'M Uycr. 
Kcxt comet the nerw^fibrt layer, 3, formed bj radiating 
fibre* of the optio ncrrc; third, tlio iterce-etU tat/er, 3: 




Pra^ 181— Tlinli-nfttlBkaallVWId Vhnxi if Uia trout fUiot ltM*7abkU 
vlth tba leu and •uraonaluineriNmviaaml- 



fourtJi, the iwww mohtiulitr lat/cr, i, consisting partlj of 
Tvry flDe nttrvc-tibnls, and Uir^uly of connective tinuc; 
fifth, the imur granular lagor, D, cuinpo«ed of nnolcatcd 
i'cll«. with a small amount of protoplasm at eacb end, and 
a tiunloolus. Thc«o granulet, or ut any mtc the majority 
of them, littvc an intier procett running to the inner 
molecular layer and an onter running to, 6, the oitar 
moUeular layer, which is thinner thun the inner. Then 
comes, eerenth, the rod and cvne fibre layer, 7, or outer 
granular kyor; compoaed of tJiick and thin fibres on encli 
of which is a consplcnuus nucleits with n nncleolas. Next 
is Iho thin fvrlfrH(tl Untiling membraite, 8. perforated by 
nporttircH through which the rods and conea, 9, of tho ninth 
hiyer join the librci of the scrcnth. Ontaide of all, next 
the choroid, \* the pigtnenUirn lat/er, 10. In addition, oer- 



maroLoor of usrj/fA. 



46S 



lain fibres niu vertically through the nitba from the inner 
to Uio out«r limiting iiu'iiibi-uiie; Ihey are known as th« 
radial ftbrw of MiilUr obU give off lateral bniDvhcs, which 
are eepccially nnmcroiu in the moleculur layers. 




Fro. 1W-A MCtlon UrooBII dls nUnn r 
1, in cciiit»cl will) Uia hynloTd lOFmh^ri. i 
rhonMil. I. laivmal llaUUmt tuemDnrir 



.Liir.Ti.ir or Innn" n\rfiw^ 

III t ' - " . .1 '-ht* 

.. _ ■.!■■■ I .. 11 

Uvrr; *. loner molMUlor lavw; », Inu.-i- . i .i ..r i.. .. : . i., r i„..i,. ninr 

Itjvr: 7. aui»« KranoUr bjar; A«xt<fnuJ iiiiuiiiiK nwahiiiiiDL V.rgdiiJ-iilodit* 
Itfer; 10, pl^maat'Uall laj«r. 



On account of the way Id u-hJoh the mipporting and e«(ii>n- 
Liul {iart« are )Qt«rwoveu id the retina it is not etny to track 



*m 



TBF. nujtA.\ aoDY. 



the latter through it. "Vie ehall find, faoirtn-er (Ch»|i^ 
XXXIl.)- thftt light Jiret wAs ujion the rod and ootit' Ixvcr, 
tiiivcreiug nil tlut Uiioknea of iiiucr elrula of tho Ktioit to 
reach this, before it cui start those chaiigGii w)ii<;h retmlt in 
TiBUsl eenffiitiiius; and it is thorctore probable thut the rods 
iind cones mx id dinx;! vimliuuitj wjtli tho optic nerve- 
lihrcK. The limiting »ioiiihriin«-j<, with the fibres of MiiUer 
und iheir branobeo, are uudoubtedl}' iu:ooAi«iry. 

Kfich rod and cone consieta of an otiitr and an xtrntr 
Mgmeni. TIk- mitcr^cginMiUuf hoihti'iid (o split up tnuis- 
vi-rwiy into iliskm and ure very tiiniil«r, i-xcept. that thutw of 
the t'hU are lunger Utun thone of thcconetaiiddo not taper 
as tljo latter do. The inner segmental of the concaaro 
ewollen, while thoee of the rods are narrow and Dearly cy> 
hiidricAl. Overmij«t of tho rt-tinii tlw nidis are longi-r and 
mnuh more nnnierous than the cones, but near the cihaiy 
p:-oce»M» they coiiso bt-foro tbo cone* do, and ia Iho yellow 
*{»>% clongalol coins alono iii« fwund. In this n-giun th« 
nliole retina U much modified; at ita margin all the layers 
are thickened hut c^pcciallj the nerve-coll layer, which ia 
here tw w nn-cu. Ihii-k, while elsewhere the cclla are found 
ill bill one or two atratn. All the tibros also are obliijne, 
reaching Id to become cuntin<iiini< with tho cones of the 
ceiiti-iil pit, which are long, slondor iiud very eloK-ly packed. 
In tho fovea itself all t!ie hiyer», except that of the cones, 
Uiinawur. and m the dcprcmion U piHidnccd. The foveais 
the Rcat of nmsL acute rision; when wc look at an object 
we always turn our eyee so that tliw light proceeding from 
it Bludl be foeuNtcd on iIhh sjiot. Where the optic nerve 
ontei':', all thchiyersbut the nerve-fibre layer, which iu very 
thick, and the incemal limiting m«'mbraue, are abeent. 

The blood-veiuclH of Lhu retina ho in the nerve-fllnv and 
nfine-oell lavera. 

The BefraoUng Uodia of the Kyo ure, in sncceesioii from 
before back, the niritfa, ilic rir/iirous Junior, tho crg/talHru 
hiif, ami Die vHrmua humor. 

Tho tn/tKwtf hiuni>r lills ihe space betwwn tiie front of 
the lens, SHJ, and liio hru-lc of tho cornea. This xpaoe ts in- 
completely divided by the iris into an anterior chamber, 



«8W nHfV ACTING MEIilA OF TUB BTR 491 



9, niid a posterior. 3] (Fig. ItM). Cliemicallv, the aque- 

bumor conKiHtx of w»t<<r hokiing in solution u emull 

l}aat of solid niait«r3. nminly rammoa salL 

!DbB erytlaiUne lena (^S, i&, 'il) u colorless, transparent, 

nnd Incoiirex, with its anterior Hiirfacc! Ir^i curved thmi 

poiiterior. It is BniTonndi'd bjii capHiile.and theiiinvr 

^odgvof Iho iris lies invoutiu-t with il in front. In coititiai- 

enoe it ia soft, but its central latere are ratlicr tnoro dense 

tliiin the outer. 

• Tlio I'ilrcous humor is a soft jelly, cnreloped in a thin 
itapxulc, the ht/aloid tnembrane. In front, this mouibrujie 
split* into tiro layers, one of which, %%, pa^ncK on to be 
fixed to the lens n little in front of its etlgp. This layer i* 
known axWiQ turpfMinry liffainent of fhe lent; its line of at- 
tachment around that organ is not stntlglit hut ainuouii 
as represented by the cui-ved line between 28 and 36 in !*ig. 
^1 124. The 1^)1100 botwccu the two lityer« into which the 
^Llijaloid splits in the canal of Pel it. The vitreous humor 
^P'MnilAj! mninlyof W)it«r and cimtnins enmo «ilt8,a little 
H^ allyumin, mid some mitciit. tl t.t divided up, by ddioalu 
V membranes, into ooni]iairtnieuta in which ita more li([nid 
portion* aro ini)>nKon«d. 

The Ciliai7 Uuaole. Running around the evebHlI 
nliLTo the c'ornfii join« the sclerotic is a little rein culled 
the canal of Schltmm; il is H-cn in veetion nt 8 in Fig. \HA. 
Lying on the inner udc of this cuiud, ju»t whciv the iris 
and the ciliary prooeosea meet, Uierc is some plain muscular 
tissue, imbedded miiinly tn the middle coat of the eyeball 

I and forming Hie ciliari/ ntNJidf, which oonsistKof a radtal 
and II eireular portion. The radial part is much the larger, 
and arises in frontfrom the inner surface of the sclerotic; the 
fibres pass book, Hpmadiiig out as tliey go, and are insfrted 
into the front of the choroid opiKwite the ciliarj- processes. 
The circuhir part of the mnaole lies around the outer rim of 
the )ni>. The nmtniction of the eilinrymnscle tend* lo pull 
forward (radial fibres) and |»res* inward (circular libres) the 
I front p»rt of tho choroid, lo which the buck piirt of ilic siih- 
^B pensoryUgament of the leiui ill closely attached. In this way 
H tho tension exerted on the lens bjits ligament is dimiDi«hcd. 



in 



rare" nvHAS nonr 



Tho FroportioH of Light. Uvforo procwding to Uie 
tl-aAj of the cvc a& an optical iiiiitmment, it is ncocsouy to 
recall bricHy certain properties of light, 

Liglit 18 conudcned »■ a form »f inovcmon t of the purl iclc« 
of un h^'pothetical medium, orolher, Uio ^ ihmtions being in 
liliines at right angles to the line of propagation of the 
light When » fUnw i» throim into n pond n i^Dnes of 
circahir wavea travel from that point in ii horhoHtal tltrtC' 
lion over the water, while the particles of water thcmselTea 
move up and •fotcit, and eaaw the Eurfnco inequalities 
which wescensthe vaTeH. Somewhat eiaiilikrly, lighl>wnTM 
spread out from a luminons point, bnt in the same medinm 
travel oiiunlly in nil dircctionsflo that the point is surrounded 
by abella of Rpherical warcit, imttcnd nf rings of circidiir 
waves traveling in one plane only, as (how on the surface 
of the water. Stiirtiog from a luminous point light 
would travel in all dirccticiUJt ainug the radii of a sphere of 
which the point is the centre; the Eight proimgatt-d along 
ono Hiicli radiiix is vaWcd a. ray. nnd in tiich my the etbpceal 
particles swing from side to side in a phmo perpend iciihir 
to the direction of the toy. Taking a particle on a&j^ raj 
it would 8wing ft«ide a certain distaDoe from it, then back 
to it a{(nin. and acroj^ for a certain distanoo on the other 
Bide; and then haek to its original position un the line of 
the ray. Snob a moremcnt is an okHMioh, and takes a 
certain time; in lights of certain ViaAstiwpttriodnif/oiifrilia' 
lioit are all the suDte, no matter how groat the extvnt or 
amplitudt of the o«ciIlatioii ; jnnt i\* a given pendulum will 
always complete it« swing in the same time no in»iti<i 
whether its Hwingri be grcnt or small. Light compo6»l of 
rars in which the periods of oscillation are all equal \a 
raited Hionocitromaiic or nimplf Ughl, whilo light made of a 
niixtnrc of oAciUalions of different periods is called mixtd 
or eompound light. 

If monochromatic light is eteadily emitted from a point, 
then, at certain distances along a ray, we ci>me to particles 
ill the same /'Anjtf of oscillation, say at their greatest dis- 
tanee from their position of rcKt; jnM a* in'the oonocntria 
waves seen on the water after throwing in a stone vewonld 




PROPF.HTlflS OF JJOHT. 



498 



; any radius meet, at iaterval¥, wttli vnier mimtd most 

llorizoDtuI |)I;iiH-ii« therr»/<»f ftvave. ordejtrened 

it as tlie ft'tHow of a wwvc The di^Unco along 

lie luy from crest to crest is called a leavtAenyth luid \t 

laln-iiys lite tmtM in any s^xen Eimplo light; bat differs in 

IdtfTorent-colorcd lights; ihe briefer llielimvof anoocillatian 

ttlio less th& wave-length. 

When light fiilU on a polished enrfaoc separating two 
I trans])are»t media, as air and glux, purt of it is refitfied 
or turned back into the first medium; part goes on into 
the «cuun[l indlinm. iind ik oomni'tnly deriated from iu 
original course or re/rnetcd. The original ray falling in tJie 
surface is the incident ruy. 
hetAB(Pig. 127) be the 

Panrfaoo of aeparation; a x the 
incident ray; and CD the 
porpendiouliur or norm;il to 
the mrfaoe at the puint of 
incidonoe: ax (7 will thonho 
the anjrfo of incidence. Then 
the re6«eted ray mulcM un 
anglt of rtfiftiioH with the 
nomial which is exjual to 
the ungln of incidence; and 
the rclli'Ctwl my lic« iu 
the same plane as the inci- 
dent ray and the normal to 
tJifl fiurfae« at x. The ixr 
ted ray lies also iu the 
>mo plutv to. Die normal and 



t 


/ 


.It 

/ 


r/ 


D 





uoni 



no. XT.-' EHNnm llliutnltaK Clw 
rrfmflluD of UicM- -tB. inrfftM or 

mirfftce mX (bv point n\ inctdcTtcc. t; 
at. Inulitaat x*i .td. rctncinl ray. If 
Ih* HOOBd mwdium ba ilnuBrlluii llin 

am: 3ff, retrwMrf nr< " nn- Hvcud 
nudlum u Inn relrwilTc ihon iha 
flrnrt. The rtdenoa me !■ noi rrpr*- 
■fnlnl. but w«uhl nuk* ui luiKl* vlth 
C'Rllul I»tb«kn||l*nxC- 

tbc incident ray, but does not continue in it« original diree- 
tii>n, zf\ if the medium below AB \^ denser than tJiat 
ahoto it. tiio refracted my is bent iu the direction xd 
nearer tlic normal, and making with it an angU of rffrae' 
(ion, Dzd, Hmallcr [ban the angle of incidence, axC. If, 
on the contrary, the second medium be Icm dense than tho 
first, the refracted ray ig is bent iinny from the normal, 
and makes an angle of refraction. Dxg, greater than the 
Angle of incidence. The nitiu of the xiiic of the unglo of 



iU 



TBK fltTM.V ROOT. 



iDcidfiK'C t» tl)«l of thu uiiglo of refrHCtton te ulwars t&fl ' 
atni for Uti» nunc two mcdtn with light of tli« Ntmc nsve- 
lengtlL When the first tnedium is air tlie ratio of llie sin« 
of the ungle of refraction to that of the angle of incideura 
is cullud thu refrttciivc imk-x of ihu Kcc^iid mediiiin. The • 
greater thla refractife index the more is th« refracted mj 
deviated from iu original conrse. Itajrs which fall pcrpen- 1 
ilicularly on tlic surfacoof (Hipiinitioa of two media pause on 
without refraction. 

The shorter I he oscillation jMjriods of )ight>rayfi tlie more] 
tJic)' are dvviat«d bv refractiuu. IImici) mixed light when 




Fro. m— nacrun tIlu(iniiciKiiwdiipoKi«oof mlxMlllglitbraprtan. 

sent through a prism is Kprviul out, and dconrnposed into ' 
iU simple eoiiKtitucDt*. I-'or let a x (Kig. 12U) bo » my of 
mixed light composed of a aet of short and a Mt of long 
ethereal vravM. When it fidk on the surfnoe A B vi 
the prism, that portion which ent«ra will be refracted 
towards the normal ED, but the short wnvofl more than the 
longer. Hence tJie former will take the direction xy, and 
the latter the direction xt. On emerging from the prism 
both mvs will again be refraetod. but now from the nor- 
mule Fy and O t. since the light i« pa-t^ing from a denser to I 
a nuvr medium. But again the ray j y, made tip of shorter 
waves, wouhl be muat deviated, m in the direction y r, and 



BKFRACTION BT CSXSSS. 



195 



the long WATCii leas, in the direction i r. If a ecrecn were 
put at S JH. we Kould receive va it ut xejmratc jHiintti, v luid 
r, Ihi; two uin[ile lighlj which vere mixed together in tiio 
oomiKiund incident ray ax. Such a sepamtion of light-rajs 
IB called dispfrtion. 

Onliniiry tvhite light, xunh as that of the sao, ia com* 
)iosed of ethereal vihraiiona of all po^ible lengths. Ueuoe 
u'hcn such light is evnt through u prism it givctt a (.'ontin- 
nou« bund of llght-ray», known as the Kolar spetirum, 
reaching from the least refracted to the most refnicted and 
«hurlc!t. The cxotiptiwmt to this «l«l<-moiit dtiu u> Frauen- 
hofvr'« litic« (see Phj^-iHcfl) are unessential for our prewnt 
purpose. All of the simple lights into which the com))ouud 
£oIur light in thus depurated do not, however, excite in us 
riaoal senwiious when they fall into the eye, but only cor- 
tuin middle onee. If solar light were used with the prism. 
Pig. Its, certain least refracted myo between r and S would 
not be seen, nor the mo*t refracted between v and S; while 
botvcoQ t< and r wonld stretch & luminous band exciting iti 
UH the Mries of colors red (due t« the le:ist refracted visible 
rayt), suceoMively through oruiige, yellow, green, bright 
blue, and indigo, to violet, which latter in the (en«ation 
arouaed by the most Tefrang:ible visible rays. The fitill 
•liorter wavet beyond the violet, are known mainly by their 
ohemioal effects and make up what are culled the aettnie 
rai/t; tlie longer inrisiblc wavct. I>oyoiid iho red, exert a 
liowcrful heating inSueucGtinduompoac- the t/ifrmal or dark 
httal rays. The eye, a?i au organ for making known to us 
the existence of ethereul ribnit ioiLr, hat, therefore, ouly a 
limited range. 

B«CHK)tlon of Light by LfiDses. In the eye the refract- 
ing media hiivu thi- form of tenaeH thicker in the centre 
than towards the iKirij)hery; and we may here confine our- 
eelvoa therefore to snob amprrsintj 1«ii»m. U simple light 
from a point A, Fig. ITi, fall on micIi a lens its raye, 
emerging on the other side, will take new directions ufuir 
retraction and meet anew at a point, a. after which they again 
direi^ge. If a screen, r r, bo held at a it will therefore 
receive an image of the luminous point A. For evary con- 



TBB BVXAS BODT. 




IM h*«Mi(nn M an Imic* tv > 



Terging lens tlicre is Eocfa a point behind it at which the 
raj'i* from a given point in front of it meet: the point of 
meeting ia ai]le<I the conjujfaU focv* of the point from 
which the nys etart. U instead of a Inminous point n 
InminoHH object he placed in front of the lens an image of 
the object will ho formed at a o<.-rt(iin distance behind it, for 
all rajc proceeding from one point of the object will meet 
tn the conjugate focDH of that point behind. The imu^ 
i« iQTcrted, u8 can be readilv seen from Fig. 139. All rap 

from tlie point A of the object 
meet at the point a of the 
image: tho«o from Bui b, and 
tho^e from intermediate pointa 
at intermediate posittons. If 
the fiingle lens were replaced 
\*j HCTera] combined eo aa to 
form an optical system tin 
general result would ho the Mmo, provided the tytltm 
were thicker in the centre tbao at its peripheij. 

The Oamorft Obacum, i\» tistvl by pliotognpher«, is nn 
ioBtmmuDl nhicit eencs to illnitrate the formation of 
imagee by converging ey^tema of lenses. It consi«t< of a 
box blackened inside and hiiving on itx front face a tube 
containing the lenses; the j>a<ilerior wall is mode of grounil 
gblB. If the front of the insii-ument bo directed on ex- 
tertor objects, inverted and dlmini^ihed images of them will 
be formed on the ground glaan;