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^ ^C.^/^6^. 






HUMAN PHYSIOLOGY. 



A TREATISE 



HUMAN PHYSIOLOGY; 



- ■ bKSlOX^D rdtf t'HR uVb or 



STUDENTS AND PRACTITIONERS OF MEDICINE. 



JOHN C. DALTON. Jr.. M. D., 

FKOPUMK or rariioiour arr ■icsaaropic ahitomt m the cwLtBui op nnteiAKt ahd icMmn, 
SKw tokk; auniiB op tbk rew ioik acidimi up iiu>rcipk; op thm kbw tork 

PJLTHOLOOICALIOCIxrT; OP TRk AMKBtClV ACABEMT OP ARTi AKO aCIUiabI, 

■OfrrOR, MAM. ; ARD OP TBE BIOLOOICAI. DEPAKTHBHT OP THE 

ArADUlT OP RATCKAL KIERCU OP PHtLABELPBIA. 



Sittoatt CbitioB, ^tbistb anil ftnUigtli. 



V/ITH TWO HUNDRED AND SEVENTY-ONE ILLUSTRATIONS. 




PHILADELPHIA: 

BLANCHARD AND LEA. 

1861. 

1. 



Entered aooording to the Act of Congreas, in the ^e&r 1859, by 

BLANCHARD AND LEA, 

ia the Oflice of the Clerk of the DfEtrict Conrt of the United States in and for tlie 
Eastern DiBtrict of the State of PennBylTania. 



philadklpbia; 
colltks, pbinteb, 705 j*t»b street. 



F3^ 



TO MY FATHER, 

JOIN C. DALTON, M.D,, 

H0HA.OE Of HIS LONG AND SUCOESSfUL DEVOTION 

TO tHB 

8CIEN0E AND ABT OP MEDICINE, 

AMD IV 
GRATEriTL BBCOLLECTIOK 07 HIS PROTKSSIONAL PBICIPTS AMD IXAUPLS. 

18 BESPECTFtJLLT AND AFFECTIONATELY 

INSCRIBED. 



PREFACE TO THE SECOND EDITION. 



In preseoting a new edition of this work, the author desires to 
express his sincere acknowledgments to his professional brethren 
for the very favorable manner in which it was received at the 
time of its first appearance, two years ago. In the present edition, 
the author has endeavored to supply, as fully as possible, the 
deficiencies which, he is well aware, existed in the former volame. 
Some of these deficiencies were evident to his own mind, while 
others were indicated by the suggestions of judicious criticism. 
These suggestions, accordingly, have been adopted in all cases in 
which they appeared to be well founded, and not inconsistent with 
the general plan of the work. In those instances, on the other 
hand, in which the views «f the author on physiological questions 
seemed to him to be positively sustained by the results of observa* 
tton, he has retained these views unchanged in the present edition. 
At the same time, he has abstained, as before, from the lengthened 
discnssion of theoretical points, and has purposely avoided even 
the enumeration of new experiments and observations, wherever 
they have not materially affected the position of physiological 
doctrines ; for in a work like the present, it is not the object of 
the writer to give a detailed history of physiological science, but 
only such prominent and essential points in its development as 
will enable the reader fully to comprehend its actual condition at 
the present time. 

The principal additions and alterations which have thus been 
fonnd advisable are: — 

First, the introduction of an entire chapter devoted to the con- 
sideration of the Special Senses, which were only incidentally treated 
of in the former edition. 




Till 



SecoDd, the re- arrangement of ihe clmpter od ibo Cranial I^ervea^ 
and the iDtroduction of some new views and facts in regard to their 
physiology. 

Third, nn account of some new experimetits, original with the 
jiulhor, relating to the function of the CavUUum, and the conclu- 
sions to which they lead. 

Fourth, certain considerations respecting the general properties 
o? Scmaticti and MoU'on, as resident in the nervous system, which 
are important as an introduction to the more detailed study of 
these functions. 

Fifth, the introduction of a chapter on Imhililion and Exhalation^ 
and the functions of the Lymphatic System; including the study of 
cndosmoais and exosmosia, and their mode of action in the animal 
frame, the experiments of Dutrochot, Chevrenil, Gosselin, ^{attcucci, 
and others, on this subject, the constitution and circulation of the 
lymph and chyle, and, iSnally, a quantitative estimate of the entire 
procewcs of exudation and reabsorption, as taking place in the 
living body. 

Additions have also been made, in various parts, to the chapters 
on Secretiun, Excretion, the Circulation, and the functions of the 
Digestive Apparatus. In every instance, these alteration!) have 
been incorporated with the text in such a manner as to avoid, so 
far as possible, increasing unnecessarily the size of the book. 

Twenty-two new and original illustrations have been introduced 
into the present volume, of which number five replace others in 
the former edition, which were regarded as imperfect, either in 
design or execution. The remaining seventeen arc additional. 

It is hoped that the above alterations and additions will be found 
to be improvements, and that they will enable the work, in its pre- 
sent form, to accomplish more fully the object for which it was 
designed. 



H«w VoKx, I'thmary, 1S61. 




PREFACE TO THE FIRST EDITION, 



This yolnme is offered to the medical profession of the United 
States, as a text-book for students, and also as a means of commu- 
nicating, in a condensed form, such new facta and ideas in physio- 
logy, as have marked the progress of the science within a recent 
period. Many of these topics are of great practical importance to 
the medical man, as in6uencing, in various ways, his views on 
pathology and therapeutics ; and they are all of interest for the 
physician who desires to keep pace with the annual advance of his 
profession, as indicating the present position and extent of one of 
the most progressive of the departments of medicine. 

It has been the object of the author, more particularly, to pre- 
sent, at the same time with the conclusions which physiologists 
have been led to adopt on any particular subject, the experimental 
basis upon which those conclusions are founded; and he has en- 
deavored, so far as possible, to establish or corroborate them by 
original investigation, or by a repetition of the labors of others. 
This is more especially the case in that part of the book (Section - 
I.) devoted to the function of Nutrition ; and as a general thing, 
throughout the work, any statement of experimental facts, not 
expressly referred to the authority of some other writer, is given 
by the author as the result of direct personal observation. 

The illnstrations for the work have been prepared with special 
reference to the subject-matter ; and it is hoped that they will be 
found of such a character as materially to assist the student in 
comprehending the most important and intricate parts of the sub- 
ject It is more particularly in the departments of the Nervous 
System and Embryonic Development that simple, clear, and faithful 



X FBEPACE TO THE FIRST EDITIOX. 

illastrationa are indispensable for the proper understanding of tbe 
printed descriptions ; the latter being often necessarily somewhat 
intricate, and reqairing absolutely the assistauce of properly 
arranged figures and ' diagrams. Of the two hundred and 6 fly- 
four illostratioDS in the present volume, only eleven have been 
borrowed from other writers, to whom they will be found duly 
credited in the list of woodcuts. 

Of the remaining illustrations, prepared expressly for the pre- 
sent work, the drawings of anatomical structures, crystals, and 
microscopic views generally, were all taken from nature. The 
diagrams were arranged, for purposes of convenience, in such 
a manner as to illustrate known anatomical or physiological ap- 
pearances, in the most compact and intelligible form. 

Physiological questions which are in an altogether unsettled 
state, as well as purely hypothetical topics, have been purposely 
avoided, as not coming within the plan of this work, nor as calcu- 
lated to increase its usefulness. 

Nsw YoBK, January 1, ISSfi. 



CONTENTS. 



INTRODUCTION. 

PAOK 

DefinftloD of PhjBlology — lu mode of stnd; — Natare of Vital Phenomena — 
DiTltion of the subjeot . 33-43 



SECTION I. 
NUTRITION. 



CIIAPTER I. 

PBOXIMATB PRINCIPLES IN QENERAL. 

Definition of Proximate PriDclplea— Mode of tbeir oxtraction — Manner in which 
thej an suociated with eaeh other — Natnral variation in their relative 
qoaDtitiea— Three distinct clanes of proximate principles , , 45-92 

CHAPTER II. 

PEOXIMATE PRINCIPLES OF THE FIRST CLASS. 

Inoi^anlo Snixtanees — Water — Chloride of Sodiam — Chloride of Potassium — 
Phosphate of Lime — Carbonate of Lime — Carbonate of Soda — Phosphates of 
Hagne«ia, Soda, and Potassa — Inorganic proximate principles not altered in 
the body — Their disoharge— Nature of their fanctloa . . 53-62 

CHAPTER III. 

PROXIMATE PRINCIPLES OF THE SECOND CLASS. 

Stabch — Percentage of starch In different kinds uf food — Varieties of this 
sabsUncfl — Properties and reactions of ataroh — Its conversion into sugar — 
HnoAR — Varieties of Bngar*— Pbjsioal and chemical properties — Proportion 
in different kinds of food — Pats — Varieties— Properties and reactions of fat 
— tta crystallisation — Proportion Ib different kinds of food — Us condition in 
the body— Internal prodnotlOQ of fat — Origin and destination of proxtroate 
principles of this class ....... 63-78 



XII 



CO STENTS. 



CHAPTER IV. 



rsDXIHATB PKINLTipLBS OP TIIB TMIBO OLABS, 



rtot 



Qeneral oha.raotera of organio sabsUncn — Their alietnml cDuatilution — Hjrgtt>- 
Rcopic prci[Mfrti««— Co»giiittion — CftUi1v*ia — Fenn«n[ali<in — I'ntrrfiiction— 
Fibrin — Albmuwn— Caaeiu— Glolniline— PBi»iiii?— Fnuorenttiitt— MueosLoa- 
OBtelna— CAr(ilii(;ine — Muscatine — tliEmiitiue — MeUnlne — llilirdrdine — 
CrcwMiiift— Orlgiu Aud dcsLruulion uf pruximalo i>riiici|>lvs of llits clua 76~£8 



CHAPTER V. 

or rooD. 

Importance of Inorgnnic Hulwlnncni »« ingroilivnti of food — Of fnccharinp and 
starchj Dutwunoes — 0/ falty matlurs — lusufllcieDoy of (linitij NubnUnutM 
when Dsed alone — EfTooIa of iin rxcluaivn non-nitrogotions diet — Organic 
MabntanocN al«u in«iiflii:ipiit by IhornHxlres— Rx)>(-rini(inU of Mngnndift on 
exL'luiilve diet of i^elatine or flbHn — Pood riKiTiires to ooutatii jiU cUsa«fl of 
prositcate prinoiplvs — Cum pu* it inn of Tarivo> kinds of fuod — Dailjr iiQaulitjr 
of fitod r6i|alred b/ man — DlgeaUbitity of food— BlTiicl of oooking . i>V~Vi 



CHAPTER TI. 

DIOXSTIOK. 

If&tuM) (if digfRlIoii — DigeBtUe apparatus of fowl — Of ox— Of man — MAfrrci- 
Tion — Varieties of tsctli — Effect of uiattlcatioii — &ALivA~lt« comi>o9hion — 
Dall^ qnontitj |>r(Hluo«d — Ita aotiou on elsrcb — Etfuct of Ita Bnppression — 
Fnuatiun of tk« saliva — OAinTiiif' Ji-irs, and Stoxacm UiOKsnon — Struct um of 
gastrio maoon* inpuibrnii«^I>r. Bnauinout'a exiwriiuviita on St. Martin — 
ArliJluial gnalrio llBtalac — CotnpoMJlion mid properties of gastrio Jniue — Itg 
ootiflii on albuiiiiuuid lubeiaQoes— Ffri^tulliu aution of Hlouach — Tinio ra- 
qulrod for dignation — Dait^ qaantii}' of gastrio JaJce^Inflnem^M modifying 
iU MiKinitlon — Ivtb»tixal Jiticki, a»[> thr l>rniwTiOH or Suoab asd Stabch — 
FolUclee of intn»tln»^Prupi>rtiRii uf iulestinal juicv— PasicjiicATir. Jurcx, akd 
THE DiawTiuN OF Vat — Compoeltion and prop«rtt«e of pannreatic Juiow — Its 
action on oily matten — SuocoMiiv<g ohaogca iu int«Kt1iiiil digention — Tho large 
ioteatine and Its eonlenta ...... B9-144 



CHAPTEK VII. 

ABSORpriO.N. 

(^0!i«d folUolei and tIIK of small iDtealine — PeHslaltio notion— Absorption 
by WoodreMfla and lymphatic* — (^hyle— Lymph— AtwoHwnt aysteui — Lao- 
taB.la and lyiiiph«tl«a — Absorpliou of fat — lU ai'vumulatfou In ibe blood 
during digestion — Ila Goal deuotupoflilion atid disapp«aniua« . . 14&-157 



CONTENTS. Xlll 

CHAPTER VIII. 

TBB BIU. 

PAOl 
PfaTBical properties of the bile — Its eompoiitlon — Blllreidine — Cholesterin — 
Billu7 BBlts — Their mode of eitrMtlon — Cr7st«llisatloa — Qljko-ohoUtA of 
Bodft — Taaro-oh<^te of soda — BiliAry aalti In diferent Bpeoies of aclmAls 
and in man— Tests for bil»>-Tariatlona and fanctions of bile— Dallj qoan- 
tity — ^Tlme of Its disoharge into intestine — Its disappearance from the alE- 
mentaty eanal— Its reabaorptlon — Its ultimate decomposition . . 168-181 

CHAPTER IX. 

FOBHATION OF SUUAR IN THE LIVEB. 

Bxistenee of sngar In liver of all animals — Its percentage — Internal origin of 
lirer-aogar — its prodoctton after death — Oljoogenlc matter of the liver — Its 
properties and composition — Absorption of llrer-sngar hj hepatic veins — 
Its acenmolation la the blood daring digestion— Its final decomposition and 
disappearance ........ 182-189 

CHAPTER X. 

THE SPLEEN, 

CapsnIe of Sple«n — Variations In sise of the organ — Its internal stmotare — 
Halpighlan bodies of the spleen — Action of spleen on the blood — Effeat of 
iU extirpation ........ 190-194 

CHAPTER XI. 

THE BLOOD. 

Ran Olobdlbs of the blood— Their microscopic characters — Stmcture and com- 
position — Variations in size in different auimals — White Qlobdlbs of the 
blood— Independence of the two kinds of blood-globules — Plasma — Its com- 
position — Fibrin — Albumen — Fattj matte ns— Saline ingredients — Extractive 
matters — Coaoulatios or the Blood — Separation of clot and serum — Influ- 
ences hastening or retarding coagulation — Coagulation not a commencement 
of organiiation— Formation of buffjr coat — Entire quantitjr of blood lu bodf 

196-213 

CHAPTER XII. 

BE8PIRATION. 

Respiratory apparatus of aquatic and air-breathing animals — Structure of 
Inngs in human Bnbject-^&espirstory movements of chest — Of glottis — 
Changes in the a!r during respiration — Changes in the blood — Proportions 
of oxygen aud oarbonio acid, in venous and arterial blood— Solution of gases 
bj the blood-globules — Origin of carbonic acid in the blood— Its mode of 
production — Qaantitj of carbonlo acid exhaled from the body — Variations 
according to age, sex, temperature, &c. — Respiration by the skin 214-234 



XIV 



CONTENTS. 



CHAPTER XIII. 



ANIMAL BEAT. 



PMS 



SlandArtl ttrmptratarn of aniionU — Itovr miiiiitniiiri] — Pmriucliou of lit; at by 
VegrUbU*— Moilo of gendTBtion of animal livst — Theory of oombasifon — 
Objvoliona lo ibis theory— ^uoxSilatiua in vep^tablM during produi-tion of 
heal — dauiittipa of oxygen And cnrlronh acid In animals do not correspond 
wllh each other — Prmliiilifin of aoimtil best a local process — Duponiii on 
lb« c1i«tnical pbenoniena of nntrition ..... 235-24S 



CHAPTER XIV. 

THE CIRCt'l^Tlf>S. 

Circulatory spp&rstna of fleh — Of r»pill» — Of mammalians — Cnanw of blood 
tlirou^'h tbe b^arl — Action of tsIti^i^ — Sounds of li'uart— MotHnietit*'— Ini- 
puleu — Succvsfivu pubatlotM — Arlirriiil s>'8tffin — Mov«mvnt of blood Ilirougb 
IbA orlitrlna — Atteriul pnlso — Artbrir\l prusinru — Rapidity of arterial cimula- 
tion — The TAins— CaiMoa of movoinenl of l)loud in th» r(;!na — Rapidity of 
T«nouit i^nrrxnt— 'Onpi Mary cin;iilntioii— l'h»Tionieri& nn<i cjiniins of i-ApiLInry 
vlrvalation — Rapidity of entire oircnUtloo — Loo^lI rariatlona la diflpri'nt 
part* ^<J-2SB 

CHAPTER XV. 

IMBIBITION AND EXHALATION. — TIIR LTMPIIATIC SYSTEM. 

End«iinodlHanrl«xoinio)ilH — MorlouruxhitilllngtbeiD — Conditions Trbkh rei;ii> 
UIp ilii'ir activity — Katiiro of tbo mtirabrane — Rxtpnt of contact — ConBtitn- 
liiju of lliB Itiiuida— TeinpomturH— PrvMaurt)— NKtunt of vitduumuHli— lla 
coo'iitiniis in th* living body — Itn rapidity — Pbenoroena of «n<io8moiis la 
tho circulatiou— Tlia lyrophatioH— Tliuir origin— Confititiillou of tbw lymph 
and chylfl — Their qoanlity— Liqoidfl secreted and reabHorhod In tirenty-/onr 
lioon ......... 'J8a-^0& 



CHAPTER XVI. 

SECRETION. 

Katnr* of s«orelion — Tarlations in actirtty— Macna — SebBci>aaA matter — Ita 
varictin — Ferapiralinn — Struolore of pcrspirniory ^Innda — Compositioti nnd 
quantity of the penpEmtlon — Us use in regulating lliirauiiual tvuiperaturu — 
Tears — Uilk — iu acidiBcalign — Secretion of bile — Atiatoinioal peouliaiitles 

30tJ'322 



CONTENTS. XV 

CHAPTER XTII. 

EXCBBTION. 

Natnra of excretion — Exorementitioiu ■obstanoeB — Effect of their retention — 
Urea — Ita conroe — Conversion into c&rbon&te of ammonia— Dally qnantitjr 
of area — Creatine — Creatinine — Orate of soda — Urates of potasM and ammo- 
nia — General oharaoters of the nrlne — Its oompoaltion — Variationi — Aooi- 
denul ingredlenii of the nrine— Acid and alkaline fermentstiont— Final 
decompositiou of the urine ...... 323-346 



SECTION II. 
NEHVOUS SYSTEM. 

CHAPTER I. 

OENEBAL CHABACTEB AND FUHCTIONS OV THS NBBTOUS BTSTEH. 

Natore of the fnnotlon performed bj nervona system — ^Two kinds of nerrona 
tissae — Fibres of white sabsUnoe — Their minute itmctare — DIriaion and 
inoecnUtion of nerves — Oray Bnbatance — Nervons system of radiata — Of 
molinacs — Of artionlata — Of mammalia and human sabjeot — Structure of 
enoephalon — Connections of its different parte .... 347-369 

CHAPTER II. 

or NE&rous ibkitabilitt, and its mode or action. 

Irritability of mnscles— How exhibited — InSaences which exhaust and destroy 
it — Nervous irritability — How exhibited — Continnee after death — Exhaosted 
by repeated excitement — Inflnence of direct and inverse electrical carrents 
— Nervotu irritability distinct from mosoalar irritability — Nature of the 
a«TonB force — Its resemblauce to electricity — Differences between the two 

37l>-38l 

CHAPTER III. 

THE SPINAL CORD. 

Power of sensation — Power of motion— Distinct seat of sensation and motion 
in nervous system — Sensibility and excitability — Distinct seat of sensibility 
and excitability la spinal cord — Crossed action of spinal cord — Independent 
and associated action of motor and sensitive filaments — Reflex action of 
spinal cmd — How manifested during disease — Inflnence in health on 
sphincters, voluntary mnscles, urinary bladder, &c. . . 382 — 400 



iti 



CON'TKNTS. 



cuAPxnn IT. 



THE BRAIir. 



rAOE 



Seat of Nenitibilitjr itml ^scitabilitj in diflVrBiil pRrU nf tha «oo«ph&1oii— Oiru- 
toiy ^nngHfl — Optio th&lami — Corpora xtnatA — EI vm is pharos — Itemarkable 
eaacB oflnjury of hemlBp!i*rea — tilTBctof llielr removal — Imperfect dovelop- 
maiil in iilioW-^Axt'.'c cliiMri^n^Tlimiry of phwnoloij^ — Ci^rwhellnm — -KfFpct 
of lU Injury or r«ujoral — Coiuparalive durolopmenL in Jiffurvtil ctsssoft^ 
Tnb«rculn(|aa(lrtgt>niina — Tulii.Tannu1ar»^Medul]«ob]ungnta— Thre« kintis 
of reflex AOtlou In nerTgua B^stem ..... 401-429 

CHAPTER V. 

TBI! CttANIAL MERVKS. 

Olfiftclorj nerves — Optic ner^e* — Auditorj n«rTi>a — ClsHslflcation of cranEal 
norveB— Motor iierv9B~SenBiliv9 ncrvos — Motor oouli oooimuufG— PuthcU- 
co«— Mnlor exlonma— Fifth pair— Its s«n8ll>ilUjp — Effect of division — Intln- 
enon on nianticntion — Indnence on the or|^-nii of Ai^lit — Pacini nerve — Effect 
of it,K pMralysiR— UlDssO'phnrjn^enl ncrvi-— E'nnumniiaiilric— lis diHtribniion 
— Iiiflu>uni.>u on pbarynx nml (tuophngu* — On larvnx — On lungs — On RloiiiauU 
and diRestiou— Spinal accessory nerve — Hypoglossal . . . 430-461 



CHAPTER VI. 

THE gPECIAL BKySKS. 

General and Kppoial spn*it>ility — Sunttf of tniiRh in Iho *l(in and mneoas meni- 
bmuee — Nature of tlw speclsl s*nie! — Tabtk — Ajiparatua of this SfUSf^Its 
ooudllioiis — Its rosomblanoe to onlinnry naniialion— liijnry to Iho tasto in 
paralysis of :h« farial nerro — Suem.— Arrangement of nerves in nasa! pas- 
aagPM — ConiIiti-i>n« of tliis sonsi! — Uinliiiclion li.-twi'i'n odors nnJ irritating 
vapors — SiouT — Strnclure of tlie oyrball — Spt-cisl sensibility of ttiti rtttina— 
Action of thij Iwun^-Of the lrl» — CombiTind action of two i'y(«— Vivid nnlnrti 
nftlio visual Impressions — [iKAimro — Auditory apparatus — Action of mem- 
brAua tyiupnni — Of cluun of bonwt— Of ihoir musclus — Apprsuiation of the 
dlreellon of sonnd — Analogies of heiariTig with ordinary •«naAtion 4(11^-^97 



CHAPTER VII. 

srereM op the great sYMt'.vTiteTic. 

Ganglia of the (treat sympitlhotin — Distrlbtition of Ite Derv«8 — Sensibility and 
excitability of sympalhi'lic — Slujigish aotlou of tliii nBr*«p — Itif1n«nc« ov«r 
orfi;ana of aiwcial «iin!Hi — inevation of lemjieniture aftor division of sympa- 
thetic — t'ontraction of pnpil following the emno operation — Roflvx ■olions 
taking place ikruugh tlii» gruat syupalhetio .... 4CI6-S08 



CONTENTS. XVii 



SECTION III. 
KEPEODUCTION. 

CHAPTER I. 

OM TBB NATUBS OF RGPRODDCTION, AND THE OBIOIN OF PLANTS AND 

ANIMALS. 

PAOB 

ITitara Bod objects of the ftanction of r«pTOdD<.-tion — Uod« of its aocompltih- 
inent — By generation from parents — Spontaneoas g«n«ration — Hietaken in- 
stances of tliia mode of generation — Prodnetion of infosoria — Conditions of 
their derelopment — Schaltse's experiment on generation of infusoria — Pro- 
doction of animal and vegeuble parasites — EncTSted entosoa — Trichina 
spiralis — Tenia — Cysticeraas — Production of tnnia from o/stioeroas — Of 
cTSticeroas from eggs of tenia — Plants and animals always produced bj 
generation from parents ....... 609-523 

CHAPTER II. 

ON 8EXVAL QENERATION AND THE HODS OF ITS ACOOHPLISHHENT. 

Sexual apparatas of plants — Fecundation of the genn — Its derelopment into 
a new plant — Sexual apparatas of animals — Ovaries and testicles — Dni- 
seznal and bisuzaal species — Distinctive cliaracters of the two sexes 624-527 

CHAPTER III. 

ON TBS EOO, AND THE FEMALE GROANS OP GENERATION. 

Siifl and appearance of the egg — Vitelline membrane — Vitellus — Oerminative 
vesicle— Oerminative (pot — Ovaries— Graafian follicles — Oviducts — Female 
generative organs of frog — Orar; and oviduct of fowl — Changes in the egg, 
while passing through the oviduct — Complete fowl's egg — Utems and ova- 
ries of the sow — Female generative apparatus of the human snbject — Fal 
It^ian tubes — Body of the uterus — Cervix of the uterus . . 528-539 

CHAPTER IT. 

ON TBE SPERMATIC FLUID, AND THE MALE 0ROAN8 OF QENERATION. 

The spermatozoa — Their varieties in different species— Their movement— For- 
mation of spennatoEoa in the testicles — Accessory male organs of generation 
— 'Bpididymis— Vas deferens — Veslcnin seminales — Prostate — Cowper's 
glftnds — Function of spermatosoa — Physical conditions of fecundation 540-546 

2 



3tvin 



CONTESTS. 



CUAPTRR T. 

ox PERIODICAL OVULATION, AND TUB rCMOTlON OP MENSTRUATIOS. 

rAOR 
PaaioiMCAi, OvtrLATioK— Pnt^xistsnce of e^B In tlie OT«ri« of all aniinali— 
Tb«tr iDore&Bed duvvloi^ment at ike perioi) of pabertj' — Their Baccwslre 
rlpenlusaudporlodiualdisohArge — Discbarge of uggs lndt>i>(indnntly of xcxuaI 
lnt«rcoDrse — Itnplure of (IrAnflan fvllinlo. And expulsion of lli« eg^ — PUeuo- 
laoiia of mtTnitlion— MK^K-riiiTATiOK — C>orr«HpciniIeiiCD of niKnatrual periods 
nUI> pMtioiU of orulaliuu io tlia lownr aniitinls — Oiltaharas of egg daring 
iD«n>traal period — Conditions of Ha luipregualiou, anor luaving iho ovary 

&47-S53 

CHAPTER VI. 

ON TDK OORPUe LtTTBUM OF MENSTBUATCON AND PHliONANCy. 

Cnit?Cii Lcmnrif or Mejijitrdat[ox — Dfiicharg« of blood into the ruptnr«d GraaBan 
foLLlcle — Decoioriiallon of th« clot, and hvportroplij^ of tliti uviuliraiiv of tli« 
veslulo — CorpUff lutfiam of moiiRtrnAtion, at tli« oiid of Ihree w«eka — Yellow 
roloration of convolutitd wall — Corpus lut«)Uin of nnnKtruaUon at tlio end 
of fonrvMiks — ShrlrcIIing and condensation of Ita tliaiies — Itaoonditiun at 
thivmd of iiin«ir«*kN-^lts Jihal atrojib/ and dimajipciu'aDco— CaayiiH Lotkdii 
Of Pbbohancv — Its continued development aflar Iho third w «elc -^Appear ail V9 
at Ifac end of avaond moutb — Of fourth month — At the liirmiuation of preg- 
nancT — Its atrnphy and dEsapprtaraneo after doliTcry — Distinulirocliaracliira 
of 4X)rpo/a Uilea of menstruation and prcgnauoy . , , ^(30-569 



CHAPTER VII. 

ON THE DEVCl-OPMEM Of THE IMFKEGNATEU EGO. 

Segmentation of tho vltollne — Formation of blastodermic moiubrsno — Two 
layers of blaBlodermio membrane — Tliickening of external layer — Formation 
of priiuit!v« Iraee — ^Doriial platen— Alidominal platon— Clo«nr« ofdoranl and 
abdominol plat«s ou tlie uiedian lin« — FuruiutioD of intestine— Of muutli 
and auus — Of organs of locomotion — Continued dwelopmonf of organs, after 
loBving tho vgg ...,,,.. S74-5T1> 

CHAPTER Vni. 



TUB UMUILICAL VESICLE. 

Separation of vitelltne lao into two cnrllies— Closttro of abdominal walls, and 
formation of amlnlical TeiielK in fiab — Mode of its disappearance aftrr hatch* 
Ing— Umbilical rpnicl* iii haman emhryo— rormalion and growth of pediels 
— DUappuarnnce of uaibjlliial viMlelv during ruibryoulc life 6l^0-5S2 



CONTESTS. xix 

CHAPTER IX. 

AMNION AND ALLANTOIfr— DETELOPIfENT OF THE CHICK. 

PASI 

Necesiit7 for aocnioiy organs in the deTfllopment of birds &nd qaadnip«ds — 
Formation of ftmniotio folds— Their union and adhesion— Growth of allantoia 
from lower pwi of Intestine — Its Tasoalarit/ — Allantoia In the egg of the 
fowl — Respiration of the egg — Absorption of caloareooa matter from the 
shell — Ossiflcation of skeleton — Fraotnre of egg-shell — Casting off of amnion 
and allantoia ........ 683-691 



CHAPTER X. 

DETELOPHENT 07 THE EOO IN THE HUAUN SPECIES — FOBHATION 07 THE 

CHORION. 

Conrersion of allantoia into ehorion — Snbseqaent ohanges of the chorion — 
Its Tillofllties — Formation of bloodresscls in villofiitles — Action of villi of 
chorion in providing for nntritlon of ftstas — Proofs that the ohoriou is formed 
from the allantoia — Partial disappearance of villositiea of chorion, and 
changes in Its external surface ...... 692-697 



CHAPTER XI. 

DEVELOPMENT OF m'EBINE MUCOUS HEHBBAXE — FOBftlATION OF THE 

DECIDUA. 

Stracture of uterine mncoas membrane — Uterine tubules — Thickening of ate- 
rine mucous membrane after Impregnation — Deoidna vera — Entrance of egg 
Into atema — Decldoa reflexa— Incloeure of egg bj decidua reflexa — Union 
of chorion with decidoa — Changes in the relative development of different 
portions of chorion and decidua ..... 698-604 



CHAPTER XII. 

THE PLACENTA. 

Nonrishment of fcetus by maternal and foetal vessels — Arrangement of the 
vascular membranes In different species of animals — Membranes of foetal 
pig — Cotyledon of cow's uterus — Development of foetal tufts in human pla- 
centa — Development of uterine sinuses — Relation of fcet&l and maternal 
btoodvedaels In the placenta— .Prools that the maternal sinuses extend 
through the whole thickness of the plaoenta — Absorption and exhalation 
bj the placental vessels ...... 605-613 



XX CONTENTS. 

CHAPTER XIII. 

DISCHABOB OF THE OVUM, AND INVOLUTION Or THE UTERUS. 

PAOI 

EnlargemeDt of amniotio carltf — Contact of amnion and chorion — Amniotic 
flaid — Uovementa of fistiu — Union of deoidna rsra and refieza — Expnlsion 
of the OTura and diechar^e of decidaal membrane — Separation of the pla- 
centa — Formation of new mncona membrane nndemeath the old decidoa— 
Fatt^ degeneration and reconstrootlon of mnsontar walla of ntenu 614-620 

CHAPTER XIV. 

DEVELOPMENT OF THE EMBBYO — NBBV0U8 BYBTEH, 0B0AN8 OF SENSE, 
SKELETON AND LIMBS. 

Formation of spinal cord and cerebro-spinal axis — Three cerebral Teslclea— 
Hemispheres — Optto thalaml — Taberonla qsadrigemina — Cerebellnm — Ue- 
dnlla oblongata— Bye — PapiIUr; membrane — Skeleton — Chorda dorsalis — 
Bodies of the vertebra — Lamina and ribs — Spina bifida — Anterior and poa- 
terior extremities— Tail — Integnment — Hair — Vemiz oaaeosa — Exfoliation 
of epidermis ........ 621-627 

CHAPTER XV. 

DEVELOPMENT OF THE ALIMENTARY CANAL AND ITS APPENDAGES. 

Formation of intestine — Stomach — Daodennm — Conrolatlons of Intestine — 
Large and smalt tnteaUne — Capnt ccli and appendix Tennlformis — Umbl- 
Uoal hernia — Formation of nrinarj bladder — Urachns — Tesioo-rectal septum 
—Ferinenm—UTer— Secretion of bil»— Oaatrlo Juice— Meconium — OI;oo- 
genlc function of liver — Diabetes of fcetns — Pharynx and oosophagns — IHa- 
I^ragm — Diaphragmatic hernia — Heart and pericardium — Ectopia cordis — 
Development of the face ...... 628-637 

CHAPTER XVI. 

DEVELOPMENT OF THE KIDNEYS, WOLFFIAN BODIES, AND INTERNAL OROANS 

OF OENERATION. 

Wolffian bodies — Their striictnre — First appearance of kidneys — Growth of 
kidneys, and atrophy of Wollflan bodies — Testicles and ovaries— Descent of 
the testicles — Tunica vaginalis testis — Congenital ingainal hernia— Descent 
of the ovaries — Development of the ntema .... 638-647 



CONTESTS. XXI 

CHAPTER XVII. 

DBVELOPHENT OF THE CIRCUI.ATOBT APPARATUS. 

PAOB 

Pint, m vttfllline ciroalatioa — Are« TusonloBft— SiniiB tennlnaUB — YitalUne 
oircnUtlon of fiali — Arruigement of BrteriM snd veins In hod^ of fliBtiia — 
Second, or pUoental olrcaUtion— Omphalo-mesentorlc arteries and vein — 
Clrcnlatioa of the ambilloal Tssicle — Of the alUntois and placenta— Umbi- 
lical arteries and veinB — Third, or adnlt olronlatlon — Portal and pnlmonary 
sjsteins — Development of the arterial sjBtem — Development of the venons 
STStem — Changes in the hepatic olrcolation — Portal vein — Umbilical vein 
— Dnotos venosna — Changes In the oordlao oiroalatlon — Division of heart 
Into right and left cavities — Aorta and polmonar^ arter; — Dnctns arteriosus 
— Foramen ovale and Enstachian valve— Changes In olrcnlation at the pe- 
riod of birth 648-669 

CHAPTER XVIII. 

DEVELOPMENT OF THE BODT AFTER BIBTH. 

Condition of fffitns at birth — Gradual establishment of respiratlcoi — Inactlvltj 
of the animal fanctiona — Preponderance of refiex aotious in the oervons 
B78tem— Peonliarities in the action of dmgs on inbnt — Difference In relative 
sise of organs. In Infant and adnlt — Withering and separation of amblllcal 
cord — ExG[^iatIon of epidermis — First and second seta of teeth — Snbseqaent 
changes in oeseoTis, mnacnlar and tegnmentary sjetems, and general devel- 
<^ment of the bod^ ....... 670-673 



2* 



LIST OF ILLUSTRATIONS, 

ALL OF WHICH HATE BBE^T PHBPARED PROM ORIOIIfAL DBAWINOS, WITH TBS 
EZCBPTIOH OF TEK, CBEDITED TO THEIB AUTHORITIES. 



FIO. 

1. Fibala tied tn a knot, after maceration in a dilate auid 

2. Qrains of potato atarch . 

3. Starch grains of Bermada arrowroot 

4. Starch grains of wheat floar 
6. Starch grains of Indian com 

6. Starch grains from wall of lateral ventricle 

7. Stearlne .... 

8. Oteaginoos principles of hnmsn fat 

9. Human adipose tissne 

10. Chyle 

11. OIobnleB of coir'a milk 

12. Cells of costal cartilages 

13. Hepatic eeUs 

14. Urinlferotts tnbnles of dog 
16. Unscnlar fibres of human ntems 

16. Alimentary canal of fowl 

17. Compound stomach of oz 

18. Haman alimentary canal 

19. Sknll of rattlesnake . . From 

20. Skall of polar bear 

21. Bknll of the horse 

22. Molar tooth of the horse 

23. Human teeth — upper Jaw 

24. Buccal and glandular epithelium deposited from sallra 
26. Qastrio mucous membrane, viewed from above 

26. Oastric mucous membrane, in vertical section 

27. Hucoos membrane of pig's stomach 

28. Qaatric tubnles from pig's stomach, pyloric portion 

29. Qaetrio tubnles from pig's stomach, cardiac portion 

30. Confervoid vegetable, growing in gastric Jnlce . 

31. Follicles of Lieberkahn .... 

32. Brunuer's duodenal glands • . 

33. Contents of stomach, during digestion of meat . 

34. From duodenum of dog, during digestion of meat 
36. From middle of smalt intestine . 



From Rymer Jones 
Aohille Richard 



FAOB 

69 
64 
64 
65 
dS 
66 
71 
72 
74 
74 
76 
76 
76 
76 
77 
101, 

loa 

103 
106 
]06 
106 
106 
107 
108 
117 
117 
117 
« 118 
118 
124 
135 
136 
142 
142 
143 



XXIV 



LIST OF ILLU8TBAT10SS. 



Tia. 

36. From l&at qaarter of amaU intestiDe 

37. One ot the Bloied folIiolM of Pojrer's patches 

38. Olandnlia agtniaata .... 

39. SxtramitT' of intestinal villas 

40. Panisia's experiment on absorption by bloodvessels 

41. Chyle, from oommenoement of thoracic duct 

42. I^cteals, thoracic dact, &o. 

43. Lacteals and lymphatics .... 

44. Intestinal epithelinm. In Interrals of digestion . 

45. Intestinal epithelinm, daring digestion . 

46. Cholesterin ..... 

47. Ox-bile, oiyeUllIsed .... 

48. Qlyko-cholate of soda from ox-bile 

49. Olyko-oholate and tanro-cholate of soda, from ox-bile 

50. Dog's bile, orystalliud .... 

61. Haman bile, showing resinous matters . 

62. Crystalline and resinoas biliary snbstanoes, from clog's Intestine 

63. Duodenal fistula ..... 

64. Haman blood-glob ales .... 

65. The same, seen oat of focus 

66. The same, seen within the focas . 

67. The same, adhering together in rows 

68. The same, swollen by addition of water . 

69. The same, Bhrirelled by evaporation 

60. Blood-globnles of frog .... 

61. While globules of the blood 

62. Coagalated flbriu ..... 

63. Coagalated blood ..... 
64'. Coagalated blood, after separation of clot and sernm 

65. Recent coagalnm ..... 

66. Coagalated blood, clot buffed and cupped 

67. Head and gills of menobranchua . 

68. Lang of frog ..... 

69. Homan larynx, trachea, bronchi, and langs 

70. Single lobule of haman tang 

71. Diagram illustrating the respiratory movements 

72. Small bronchial tube .... 

73. Haman larynx, with glottis closed 

74. The same, with glottis open 
7A. Human larynx — posterior view 

76. Clrcnlation of flah .... 

77. Clrcnlation of reptiles .... 

78. Circalation of mammalians 

79. Human heart, anturior view 

80. Human heart, poaterior view 

81. Right auricle and ventricle, tricuspid valve opeu, arterial valves closed 

82. Right aaricle and ventricle, tricua^d valve closed, arterial valves open 

83. Course of blood throagh the heart . . . . . 

84. Illnstrating production of valvular sounds . , . . 
66- Heart of frog, in relaxation ...... 



paoa 
143 
146 
US 
140 
148 
160 
161 
153 
169 
16S 
160 
161 
161 
162 
165 
166 
172 
173 
196 
196 
197 
197 
199 
199 
202 
203 
206 
208 
209 
212 
212 
216 
216 
217 
217 
219 
221 
222 
232 
223 
247 
248 
249 
250 
250 
250 
251 
262 
256 
258 



LIST OF ILLUSTRATIONS. 



zxr 



no. 






rAom 


86. Heart of frog, in oontnotion ..... 


258 


87. SLiuple Eaop«il fibres 




258 


88. Bullock's h»firt, showing Hnperflcial mnsonl&r fibres 




259 


89. Left Teiitri<rlfl of ballock'a heart, showiog deep flbrei 




269 


90. Diagmm of oiroaUr fibres of the heart . 




260 


91. Coover^ng fibres of the apex of the heart 




260 


92. Arterf in pulsation .... 




265 


93. Carres of the arterial polsatioD 




267 


94. Volkmann's apparatoa . . . . >; 




. 271 


96. The same ..... 




271 


96. Vein, with Talrea open .... 


■ 


275 


97. Vein, with valres closed 




275 


98. Small arterj, with capillary bianvfaefl . 




. 277 


99. Caplllar7 network .... 




278 


100. Capillary circnlation .... 




279 


101. Diagram of the ciroolation 




287 


102. Follioles of a compound mnooas glandule . From Kblliker 809 


103. Meibomian glands .... From Ladovlc 311 


104. Perspiratorj gland . . . From Todd and Bowman 312 


105. Glandalar stractore of mamma .... 


315 


106. Coloatmm oorpnsoles .... 




316 


107. MUk-globulea .... 




317 


408. Division of poil&l vein iu liver 




320 


109. Lobule or liver ..... 




. 821 


110. Hepatic oells ..... 




322 


111. Urea .... From Lehmann (Fnnke's Atlas) 326 


112. Creatine .... From Lehmaon (Funke's Atlaa) 328 


lis. Creatinine . . . From Lehmano (Foake's Atlas) 329 


114. Urate of soda ....... 


. 330 


llfi. Urio aold 






. 336 


116. Oxalate of lime . 






. 342 


'117. Phosphate of magsesla and ammcmta 






344 


118. NerrODB filaments, from brain . 






3SI 


119. Nervoos filaments, from sciatic nerre 






. 362 


120. BiTlsioa of a nerre 






353 


121. InoBoalation of nerves . 






. 354 


122. Nerve cells 






354 


123. Nervoaa system of starfish 






355 


124. Nervous sfstem of spljsia 






367 


12S. NervoQS system of oentipede 






. 398 


126. Cerebro-spinal ajstem of man . 






. 361 


127. Spinal cord 






362 


128. Brain of aUlgator 






364 


129. Brain of rabbit .... 






365 


130. Medalla oblongata of hnman brain 






. 366 


131. Diagram of boman brain 






368 


132. Experiment showing irritability of muscles 




371 


133. Experiment showing irritability of nerve 




373 


134. Action of direct and inverse onrrenta 




376 


135. Diagram of spinal oord and nerves 


. 




386 



XXVI 



LIST OF ILLUSTBATIOVS. 



no. 

136. Spltul oord In Tertloal section . 

337. Bzperimeot, showing effect of poisons on neirea 

138. Pigeon, after removal of the hemispheres 

130. Aiteo children .... 

140. Brain In sita .... 

141. TransrerSR section of brain 

142. Pigeon, after removal of the cerebellnm 

143. Brain of htsltb/ pigeou In profile 

144. Brain of operated pigeon in profile 

145. Brain of heaUlij pig^eon, posterior Tiew 

146. Brain of operated pigeon, postenor Tiew 

147. Inferior sorfaoe of brain of ood . 

148. Inferior snrfaoe of brain of fowl 

149. Course of opticj nerres In man . 

150. Distribntion of fifth nerve npon the face 

151. Facial nerve .... 

152. PneuniogastriQ nerve . . • 

163. Diagnimof tongae 

164. DisLribntloD of uurvee In the nasal passages 

165. Vertical aeffition of e/eball 
156. Dispersion of rava of light 

167. Action of otTStalllne lens 

168. Mjropia ..... 

159. Presb/opts .... 

160. Vision at short distance 

161. Vision at long distance . 

162. Refraction of lateral rays 

163. Skall, as seen hj left eye 

164. Sknll, as seen bj right eye 

165. Human auditor/ appairnLun 

166. 3reat STrnpalheUc 

167. Cat, an«r dJrision of sympathetic in the aeok 

168. DifTereot kinds of infusoria 

169. Uxpsrimenl on Bpontauuoua generation . 

170. Trichina spiralis 

171. Tvnia 

172. Cjstioeroos, retracted . 

173. Cystioerons, unfolded 

174. Blossom of Convoltulus parparens 

175. Siofjle articulation of Taala craasicollis 

176. Human ovnm .... 

177. Ilaman ovum, mptared by pressare 

178. Female generative organs of frog 

179. Matare frogs' egg* 

180. Female generative organs of fowl 

181. Fowl's egg ... . 

182. Uteros and ovaries of the sow . 

183. Generative organs of hnman female 
164. Spermatosoa .... 
185. Graafian follicle .... 



From Sohaltie 



raoB 
393 
396 
40S 
410 
412 
413 
416 
417 
417 
417 
417 
420 
420 
421 
436 
441 
446 
467 
473 
477 
479 
479 
480 
480 
481 
481 
484 
486 
486 
491 
499 
606 
514 
616 
619 
620 
621 
621 
624 
625 
628 
529 
631 
532 
635 
536 
637 
538 
641 
652 



LIST OF ILLUSTBATIOHS. 



xxvu 



MO. FAOI 

186. Ovary with Graaflan follicle raptured . . . . • . 552 

187. Oraaftan folUole, raptarad and filled with blood . .661 

188. Corpus luteam, three weeks after menstraation . . 562 

189. Corpus lateum, four weeks after menatrnatioB . . . 663 

190. Corpus iQteum, otne weeks after menHtmation . . . 663 

191. Corpus tuteum of pregoancy, at end of second month . . 666 

192. Corpus lateum of pregnancy, at end of fourth month . . 666 

193. Corpus Inteum of pregnancj, at term ..... 667 

194. Segmentation of the Titellns . . . . . . 671 - 

195. Impregnated egg, showing embryonfo spot .... 674 

196. Impregnated egg, showing two layers of blastodermio memlimn« . 676 

197. Impregnated egg, farther advanced ..... 676 

198. Fk^'b egg, at an early period . . . . .676 

199. Egg of frog, in process of development ..... 576 

200. Bgg of frog, farther advanced . . . . .676 

201. Tadpole, fnHy developed . ... . .677 

202. Tadpole, changing into (nyg . . . . . .578 

203. Perfect frog ........ 678 

204. Egg of fish 580 

205. Young fish, with umbilical vesicle . . . . .681 

206. Human embryo, with umbilical vesicle .... 681 

207. Fecundated egg, showing formation of amnion .... 684 

208. Fecundated egg, showing commencement of allantols . . . 685 

209. Fecundated egg, with allantois nearly complete . . . 685 

210. Fecundated egg, with allantois fully formed . . .686 

211. Egg of fowl, showing area vasoulosa ..... 687 

212. Egg of fowl, showing allantois, amnion, &c. .... 588 

213. Human ovam, showing formation of chorion .... 692 

214. Hnman chorion ........ 694 

216. Villoslty of chorioii ....... 696 

216. Hnman ovam, at end of third month ..... 696 

217. Uterine mnoons membrane ...... 699 

218. Uterine tubules .599 

219. Impregnated nterns, showing formation of decldua , . 601 

220. Impregnated nterns, showing formation of deoidaa reflexa . . 601 

221. Impregnated nterns, with decldua reflexa complete 601 

222. Impregnated uterus, showing union of chorion and decldita . . 603 

223. Pregnant uterua, showing formation of placenta . . . 604 

224. Foetal pig, with membranes ...... 606 

225. Cotyledon of cow's uterus . . . . . .606 

226. Fteut tnft of hnman placenta ...... 609 

227. Vertical seotion of placenta ...... 609 

228. Haman ovum, at end of first month ..... 614 

229. Hnman ovum, at end of third month ..... 616 

230. Gravid human nterns and contents ..... 616 

231. Unscalar fibres of unimpregnated ateras .... 619 

232. Hnscttlar fibres of human nteras, ten days after parturition . . 619 

233. Muscular fibres of hnman nteras, three weeks after parturition . 620 

234. Formation of cerabro-npinal axis ..... 621 
236. Formation of cereliro-^pinai axis ..... 622 



XXVlll 



LIST or ILLCSTBATI0N8. 



Fia. 

236. Foetal pig, showing bniin and spinal cord 

237. Fcetal pig, showing brain and spinal oord 

238. Head of fcetal pig ... . 

239. Brain of adult pig ... . 

240. Formation of alimentary canal . 

241. Head of linman embryo, at twenty days 

242. Head of haman embryo, at end of sixth week . 

243. Head of human embryo, at end of second month 

244. Foetal pig, showing Wolffian bodies 

245. Foetal pig, showing first appearance of kidneys 
24S. Internal oi^ans of generation 

247. Internal oi^gans of generation 

248. Formation of tunica vaginalis testis 

249. Congenital inguinal hernia 

250. Egg of fowl, showing area vaeoQlosa 

251. Egg of flsh, showing vitelline clrcolatfoa 

2fi2. Young embryo and its vessels . . . 

263. Embryo and its vessels, farther advanced 
2M. Arterial system, embryonic form 

255. Arterial system, adnlt form . , 

256. Early condition of venoas system 

257. Venoas system, farther advanced 

253, Continued development of venous system 

259. Adnlt condition of venous system 

260. Early form of hepatic circnlation 

261. Hepatic circulation farther advanced . 

262. Hepatic circulation, during latter part of fcetal life 

263. Adult form of hepatic circnlation 

264. FceUl heart 

265. Foetal heart 

266. Fcetal heart 

267. Fcetal heart 

268. Heart of Infant . 

269. Heart of homan fcetus, showing Eastachian valve 

270. Circulation through the fceUI heart 

271. Adult circulation through the heart 



From Longet 



PASB 

622 
623 
623 
623 
629 
635 
636 
636 
638 
640 
640 
642 
643 
644 
649 
649 
650 
651 
653 
653 
666 
656 
656 
657 
698 
659 
659 
660 
661 
661 
661 
662 
662 
664 
665 
668 



HUMAN PHYSIOLOGY. 



INTRODUCTION. 

I. Physiologt is the study of the phenomena presented by 
organized bodies, animal and vegetable. 

These phenomena are different from those presented by inorganic 
substances. They require, for their production, the existence of 
peculiarly formed animal and vegetable organisms, as well as the 
presence of various external conditions, such as warmth, light, air, 
moisture, &c. 

They are accordingly more complicated than the phenomena of 
the inorganic world, and require for their study, not only a pre- 
vious acquaintance with the laws of chemistry and physics, bat, in 
addition, a careful examination of other characters which are peco- 
liar to them. 

These peculiar phenomena, by which we so readily distinguish 
living organisms from inanimate substances, are called Vitalpheno- 
mma, or the phenomena of Life. Physiology consequently includes 
the study of all these phenomena, in whatever order or species of 
organized body they may originate. 

We find, however, upon examination, that there are certain 
general characters by which the vital phenomena of vegetables re- 
semble each other, and by which they are distinguished from the 
vital phenomena of animals. Thus, vegetables absorb carbonic 
acid, and exhale oxygen ; animals absorb oxygen, and exhale car- 
bonic acid. Vegetables nourish themselves by the absorption of 
unorganized liquids and gases, as water, ammonia, saline solutions, 
&o. ; animals require for their support animal or vegetable sub- 
stances as food, such as meat, fruits, milk, &c. Physiology, then, 
3 



INTRODUCTIOy. 

is TiHtumlly tVivided into two parla, viz., Vegefjible Physiology, and 
Animal Ptiyaiology. 

Again, ihe different groups and specica of atiimaU, while ihey 
resemble each other in their general characters, are dislinguishcti 
by certain minor differences, botli nf structure and function, which 
require a special study. Thus, the physiology of fishes is not 
exactly the same with that of reptiles, nor the physiology of birds 
with that of quadrupeds. Among the warm-blooded quadrupeds, 
the carnivora absorb more oxygen, in proportion to the carbonic 
acjd exhaled, than the herbivora. Among the herbivorous quad- 
rupeds, the proccsjt of digestion is comparatively simple in the 
horse, while it is complicated in the ox, and other ruminating ani- 
mals. There is, therefore, a. special physioJogy for every distinct 
species of animal. 

Human Puvsioi.ogv treats of the vital phenomena of the human 
species. It is more practically important than the physiology of 
the lower animals, owing to its connection with humau pathology 
and LherapeuLicfi. But it cannot be made the exclusive subject of 
our study; for the specinl pliysiology of the human body canuot 
be properly understood without a previous acquaintance with the 
vital phenomena common to all animals, and to all vegetables; 
beside which, there are many physiological questions that require 
for their solution experiments and observations, which can only be 
made upon the lower animals. 

While the following treatise, therefore, has for its principal sub- 
ject the study of Humito Physiology, this will be illustrated, when- 
ever it may be required, by what we know in regard to the vital 
phenomena of vegetables and of the lower animals. 

H. Since Physiology is the study of the active phenomena of 
living bodies, it requires a previous acquaintance with their struc- 
ture, and with the substances of which they are composed; that is, 
with their anatomy. 

Anatomy, again, requires a previous acquaintance with inorganic 
Bub^taucejj; since some of these inorganic sub:>tancos enter into the 
composition of the body. Chloride of sodium, for example, water, 
and phosphate of lime, are component parts of the animal frame, 
and therefore require to be studtcl as such by the auatfjmisi. 
Now those inorganic substances, when placed under the requisite 
uxtortial conditiuus, present certain active phenomena, which are 
characteristic of thorn, and by which they may be recognized. 




INTRODUCTION. 



85 



Thus lime, dissolved in water, if brought into contact with car- 
bonic acid, ahcFB its condition, and takes part in the formation of 
nn insoluble substance, carbonate of lime, wliich ia thrown dowtr 
as a deposit. A knowledge of such chemical reactions as these ia 
necessary to the nn&tonitst, since it is by them that ho is enabled to 
recognize the inorganic substances, forming a part of the animal 
body. 

It is important to observe, however, that a knowledge of these 
reactions is necessary to the anatomist only in order to cnnble him 
to judge of the presence or ab.secice of the inorganic substances to 
which they belong. It is the object of the anatomist to make him- 
self acquainted with every constituent part of the body. Those 
parts, therefore, which cannot be recognized by their form and 
texture, he dlstinguislics by their chemical reactions. But after- 
ward, he has no occasion to decompose ilieni further, or to make 
them enter into new combinations; for he only wishes to know 
these substances as thetj exist in the body, and not as they may exist 
under other conditioDS. 

The unorganiz<;il substances which exist in the body as compo- 
nent pnrts of its structure, such as chloride of sodium, water, phos- 
phate of lime, &o, are called the proximate principles of tlie body. 
Mingled together in certain proportions, they make np the aniiniil 
Haids, and associated also in u solid fortn, they constitute the tissues 
and organs, and in this way make up the entire frame. 

Anatomy makes us acquaintc<) with all those component parts of 
the body, both solid and tluid. ft teaches us the structure of the 
body in a stale of rest ; that is, just as it would be after life had 
suddenly ceased, and before putrefaction had begun. On the other 
hand. Physiology is a description of the body in a state of activity. 
It shows us its movements, its growth, its reproduction, and the 
chemical changes which go on in its interior; and in order to com- 
prehend these, we must know, beforehand, its entire mechanical, 
tcxtural, and chemical structure. 

It is evident, therefore, that the description of the proximate prin- 
c^/a, or the chemical substances entering into the constitutiun of 
the body, is, strictly speaking, a part of Anatomy. But there are 
many reasons why this study is more conveniently pursued in con- 
nection with Physiology ; for some of the proximate principles are 
derived directly, as we shall hereafter show, from the external world, 
and some are formed from the elenients of the food in the process 
of digeatioD; while most of them undergo certain changes io the 



86 



INTRODUCTION. 



interior of tlie body, which result in the formation of new sub- 
stances; nil these active phenomena belonging neccHaurily to the 
domain of I*hysioIogy. 

The deacnptioD of the proximate prlociples of animals and vege- 
tables will therefore be introduced into the following pages. 

The description of the minute structures of the body, or Micro- 
gcopie Anatomy^ is also so closely connected with some parts of Phy- 
siology ns to make it convenient to speak of them together; and 
this will accordingly be doue, whenever the oature of the subject 
may make it desirable. 



III. The study of Physiology, like that of nil the other natural 
sciences, is a study of pheTiomena, and of pbeuomuna alont;. The 
fissential nature of the vital processes, and their ultimate caoses, 
are questions which are beyond the reach of the physiologist, and 
cannot be determined by the means of investigation which arc at 
his disposal. 

Conaeqaently, all efforts to solve them will only serve to tnislead 
the investigator, and to distract his attention from the real subject 
of examination. Much time hns been losi^ for example, in discuss- 
ing the probable reason why menstruation returns, in the human 
female, at the end of every four weeks. But the observation of 
ualure, which is our only means of scientific investigation, cannot 
throw any light on this point, but only shows us the fact thai men- 
struation does really reeur at the above periods, together with tho 
phenomena which accompany it, and the conditions under which it 
is hastened or retarded, and increased or diminished, in intensity, 
duratioD, Itc. If we employ ourselves, consequently, in the discus- 
sion of the reason above mentioned, wo shall only become involved 
in a network of hypothetical surmises, which can never lead to any 
definite result. Our lime, therefore, will be much more pro6tably 
devoted to the stuOy of the above phenomena, which can bo learned 
from nature, aud which constitute, afterward, a permanent acquisi- 
tion. • 

The physiologist, accordingly, confines himself strictly to the 
study of the vital phenomena, their characters, their frequency, 
their regularity or irregularity, aud the conditions under which 
they originate. 

When he has discovered that a certain phenomenon always takes 
plaoe in the presence of certain conditions, he has established what 
is called a general principle, or a Law of Physiology. 



tyTRODUCTION^ ^ 8T 

As, for example, vlien he bas ascertained that eensation and 
motion occupy distinct situations in every part of the nervoud 
system. 

This "Law," however, it mast be reraerabered, is not a discovery 
by itaelf, nor docs it give him any new infofTiiatioii, but is simply 
the expression, in couvenient and comprehensive language, of the 
facts with, which he was already previously acquainled. It is very 
dangerous, therefore, to make tbesd laws or general prinoiplea the 
subjects of our study instead of the vital phenomena, or to suppose 
that ihoy have any value, except as the expression of previously 
ascertained facta. Such a misconception wuuld lead to bad practi- 
cal results. For if we were to observe a phenomenon in discord* 
anco with a "law" or "principle," we might be led to neglect or 
misinterpret the phenomenon, in order to preserve the law. But 
this would be manifestly incorrect. For the law is not superior to 
the pbenomenoD, bntf on the contrary, depends upon it, and derives 
its whole authority from it. Such mistakes, however, have been 
repeatedly made iu Physiolog}', and have frequently retarded its 
advance. 

IV, There ia only one means by which Physiology can be 
studied: that is, the observation of nature. Jts phenomena cannot 
be reasoned out by themselves, nor inferred, by logical sequence, 
from any original principles, nor from any other set of pIienom,ena 
whatever. 

In Mathematics and Philosophy, on the other hand, certain truths 
are taken for granted, or perceived by intuition, and the remainder 
aflorward derived from them by a process of reasoning. But in 
Physiology, as in all the other natural sciences, there is no such 
starting |x>int, and it is impossible to judge of the character of a 
phenomenon until after it hss been observed. Thus, the only way 
to learn what action is exertetl by nitric iicid upon carbonate of 
soda is to put the two substances together, and observe the changes 
which take place; for there is nothing in the general characters of 
these two substance:) which cuuld guide us in anticipating the result. 

Neither can we infer the truths of Physiology from those of 
Anatomy, nor the truths of one part of Physiology from those of 
another part; but all must be ascertained directly and neparately 
by observation. 

For, although one department of natural science is almost always 
a necessary preliminary to the study of another, yet the facts of 



88 



IirrRODDCTIOX. 



the latter can Tiever be in the least degree inferred from Ifioae of the 
former, hut must be studied hy thevxselve*. 

Thus Oliemistry is essential to Anatomy, because certain sub- 
stances, as we have already shown, belonging to Cheniislry, such 
as chloride of sodium, occur as couslituuntii of tliu animal body. 
Chemistry tenches ua the composition, reactions, mode of crystal- 
lization, solubility, &e., of chloride of sodium; and if we did not 
know these, we could not extract it, or recognize it when extracted 
from the body. But, however well we might know the chemistry 
of this substance, we could never, on that account, infer \\s presence 
in the body or otherwise, nor in what quantities nor in what situa- 
tions it would present itself. These focta must be nscertained for 
themselves, by direct investigation, as a part of anatomy proper. 

So, again, the structure of the bo<ly in a atate of rest, or its 
anatumr, ia to be first understood; but its active phenomena or its 
physiology must then be aaccrtaincd by direct observation and 
experiment. The most intimate knowledge of the minute struc- 
ture of the muscular aud nervous libres could not teach us any- 
thing uf their phyatology. It ia ouly by cxperitncnt that we 
ascertain one of them to be contractile, the other sensitive. 

Many of the phenomena of life are chemical in their chaTficler, 
and it is requisite, therefore, that the physiologist know the ordi- 
nary chemical properties of the substances composing the animal 
frame. Uut no amount of previous chemical knowledge will 
enablo him to foretell the reactions of any chemical substance in 
Iha interior of the body; because the peculiar conditions under 
which it is there placed modify these reactions, as an elevation or 
depression of Icinpernture, or other e.\.ternal circumstance, might 
modify them outside the body. 

We must not, therefore, attempt to deduce the chemical pbe- 
iiomcna of physiology from any previously established facts, since 
these are no safe guide; but must study them by themselves, and 
depend for our knowledge of tbem upon direct observation alone. 



V. By the terra Yilol phenomena^ we mean those phenomena 
which nre manifested in the living body, and which are character- 
iatio of its functions. 

Some of these phenomena are physical or mechanical in their 

character; as, for example, the play of the articulating surface* 

upon each other, the balancing of the spinal column with its ap* 

ipendages, the action of the elastic ligaments. Nevertheless, these 



INTRODUCTION. 



phenomena, though strictly physiea! in character, are ollen entirely 
peouliur nnd different from those seen elsewhere, becauee the mc- 
cbanism of their produciioQ is peculiar in its details. Thus the 
humon voice and itu modulations are produced in the larynx, in 
accordance with the general physical laws of sound; but the 
arrangement of the clnstio and movable vocnl (jhords, and their 
relations with the columns of air above and below, the moiat and 
flexible mucous meinbraue, and the contractile mu&cles outside, are 
of such a special character that the entire apparatus, as well as the 
aounda producc<l by it, h peculiar; and ita action cannot be properly 
compared with that of any other known musical instrument. 

Id the same manner, the raovementa of the heart are so compli- 
cated and remarkable that they cuntiot be comprehended, oven by 
one who is acquainted with the anatomy of the organ, without a 
direct examination. This is not because there is anything esseo- 
llally obscure or mysterious in their nature, for they are purely 
mechanical in character ; but because their conditions are so pecu- 
liar, owing to the tortuous course of the muscular fibr&i, tlietr 
arrangement in interlacing layers, their attachments nnd relations, 
that their combined action produces an eflcct altogether peculiar, 
and one which is not similar to anything outside the living body. 

A very large and important class of the vital phenomena ore 
those of a chemical character. It ia one of the characteristics of 
living bodies that a succession of chemical actions, combinations 
and decern position;*, is constantly going on in their interior. It is 
one of the necessary conditions of the existence of every animal 
and every vegetable, that it should constantly absorb various sub- 
staooes from without, which undergo different chemical alterations 
ID its interior, and .ire finally discharged from it under other forms. 
If these changes bo prevented from taking place, life is immediately 
extinguished. Thus animals constantly absorb, on the one hand, 
water, o.xygen, salts, albumen, oil, sugar, &c^ and give up, on the 
other hand, to the surrounding media, carbonic acid, water, ammonia, 
ureu, and the like; while between these two extreme points, of ab* 
sorption and c.thnlation, iherc take place a multitude of diOerent 
irnnsfurmalions which are essential to the continuance of life. 

Some of these chemical actions are the same with those which 
are seen outside the body; but most of them are entirely peculiar, 
and do not take place, and cannot be made to take place, anywhere 
else. This, again, is not becuuso there is anything particula 
mysterious or extraordinary in their naturt^ but because tl 



40 



IVTEODCCTIOy. 



rlitions necessary for their accomplishment exist in tlie body, and 
do not exist elsewhere. All chemical phenomena are liable to be 
modified by surrounding conditions. Many reactions, for example, 
which will take plac« at a high temperature, will not tike place at 
a low temperature, and ri'ce versd. Some will take place in the light, 
but not in the' dark ; others will take place in the dark, but not in 
the light. If a hot concentrated solution of sulphate of soda be 
allowed to cool in contact with the atmosphere, it crystallizes; 
covered with a film of oil, it remains iluid. Beoausa a chemical 
reaction, therefore, takes place andcr one set of conditions, wc can- 
not be at all sure that it will also take place under others, which 
are dift'erent. 

The chemical conditions of the living body are exceedingly com- 
plicated. In the anlmul solids and fluids there are many subsuinoea 
mingled together in varying quantities, which modify or ititcrfero 
with each other's reactions. New substances are constantly eniering 
by absorption, and old ones leaving by exhalation; while the circQ- 
lating 6uids are constantly passing from one part of the body to 
AQOthcf) and coming in contact with different organs of diHcrent 
textore and composition. All these conditions are peculiar, and so 
modify the chemical actions taking place in the body, that they are 
unlike those met with anywhere else. 

If starch and iodine be mingled together in a watery solution, 
they unite with each other, and strike a deep opaque blue color! 
but if they be mingled in the blood, no such reaction takes place, 
because it is prevented by the presence of certain organic substances 
which interfere with it. 

If dead animal matter be ox]>{Mted to warmth, air, and moisture, 
it putrefies; but it' introduced into the living stomach, even after 
putrefaction has commenced, this process is arrested, because the 
fluids of the stomach cause the animal substance to undergo a 
peculiar transformation (digestion), after which the bloodvessels 
immwliatcly remove it by absorption. Thero are also certain sub- 
stances which make their appearance in the living body, both of 
animals and vegetables, and which cannot be formed elsewhere; 
such as Hbrin, albumen, casein, pneumic acid, the biliary salts, mor- 
phine, &e. These substances cannot be manufactured artilicitdly, 
simply because the necessary conditions cannot bo imitated. They 
require for their production the presence of a living organism. 

The chemical phenomena of the living body arc, therefore, not 
different in their nature from any other chemical phenomena; bat 



INTBODDCTIOW. 41 

they are different in their conditions nod in their resalts, and are 
consequently pecaliar and characteristic. 

Another set of vital phenomena are those which are manifested 
in the processes of reproduction and development. They are again 
entirely distinct from any phenomena which are exhibited by 
matter not endowed with life. An inorganic substance, even when 
it has a definite form, as, for example, a crystal of fluor spar, has 
no particular relation to any similar form which has preceded, or 
any other which is to follow it. On the other hand, every animal 
and every vegetable owes its origin to preceding animals or vege- 
tables of the same kind; and the manner in which this production 
takes place, and the different forms through which the new body 
successively passes in the course of its development, constitute the 
phenomena of reproduction. These phenomena are mostly depend- 
ent on the chemical processes of nutrition and growth, which take 
place in a particular direction and in a particular manner ; but their 
results, viz., the production of a connected series of different forms, 
constitute a separate class of phenomena, which cannot be explained 
in any manner by the preceding, and require, therefore, to be studied 
by themselves. 

Another set of vital phenomena are those which belong to the 
nervous system. These, like the processes of reprodoction and 
development, depend on the chemical changes of nutrition and 
growth. That is to say, if the nutritive processes did not go on in 
a healthy manner, and maintain the nervous system in a healthy 
condition, the peculiar phenomena which are characteristic of it 
could not take place. The nutritive processes are necessary condi- 
tions of the nervous phenomena. But there is no other connection 
between them; and the nervous phenomena themselves are distinct 
from all others, both in their nature and in the mode in which they 
are to be studied. 

A troublesome confusion might arise if we were to neglect the 
distinction that really exists between these different sets of phe- 
nomena, and confound them together under the expectation of 
thereby simplifying our studies. Since this can only be done by 
overlooking real points of difference, its effect will merely be to 
introduce erroneous ideas and suggest unfounded similarities, and 
will therefore inevitably retard our progress instead of advancing it. 

It has been sometimes maintained, for example, that all the vital 
phenomena, those of the nervous system included, are to be reduced 
to the chemical changes of nutrition, and that these again are to be 



4S 



TNTRODCCTIOy. 



regurded ns not at all diftbrent in any respect from tbe ordinary 
chemical cliangea taking place outside the body. Thia, however, 
is not only erroneous in theory, but conduces nUo to a vicious 
mode of study. For it draws away our attention from the phe- 
nomena themselves and their real characteristicfs and leads us to 
deduce one set of phenomena from what wo know of another; a 
method which wc have already shown to be unsafe and pernicioas. 
It has alfio beeu asserted that the plienomeua of the uervous 
system are identical with those of electricity; for no other reason 
than that there exist between them certain general rcBcmblancea. 
But when we examine the phenomena in detail, wc find that, beside 
the.se gencnil resemblances, there are many essenti:!! points of difl* 
similarity, which must be 8Up}>ressed and kept out uf sight in order 
to sustain the idea of the assnmed identity. This assumption is 
consequently a forced and unnaturnl one, and the simplicity which 
it was iutended to introduce into our physiological iheoriea is 
imaginary and deceptive, and is attained only by sacriQcing a part 
of those scientific truths, wbieh are alone the real object of our 
study. Wc -should avoid, therefore, mnking any such unfounded 
comparisons; for the theoretical simplicity which result? from them 
do€8 not compensate for the loss ofesseotial acientiCic details. 



VI. The study of Physiology is naturally divided into three dis- 
tinct Sections: — 

The first of these includes everything which relates to the Nutri- 
tion of the body in its widest sense. It comprises the history of 
the proximate principles, their source, the manner of their produc- 
tion, the proportions in which they exist in diflerent kinds of food 
and drink, the processes of rligestton and absorption, and the con- 
stitution of tbe circulating fluids; then tbe physical phenomena of 
the circulntion and tbe forces by which it is accomplished; the 
changes which tlie blood undergoes in diflTcrctit parts of the body; 
all the phenomena, both physical and chemical, of respiration; those 
of secretion and excretion, and the character and clestination of the 
secreted and excreted fluids. All these processes have reference to 
a common object, viz., the preservation of the internal structure and 
healthy organiisation of the individual. With certain modifications, 
they take place in vegetables as well as in animals, and aro conse- 
quently known by the name of the ve'jdative/tnKdons. 

Tlie Second Section, in tbe natural order of study, is devoted to 
tbe phenomena of tbe Nervol'S System. These phenomena are 



INTBODDCTIOy. 48 

QOt exhibited by vegetables, but belong exclusivelj to animal or- 
ganizations. They bring the animal body into relation with the 
externa] world, and preserve it from external dangers, by means of 
sensation, movement, consciousness, and volition. They are more 
particularly distinguished by the name of the animal functums. 

Lastly comes the study of the entire process of Reproduction. 
Its phenomena, again, with certain modifications, are met with in 
both animals and vegetables; and might, therefore, with some pro- 
priety, be included under the head of vegetative functions. But 
their distinguishing peculiarity is, that they have for their object 
the production of new organisms, which take the place of the old 
and remain after they have disappeared. These phenomena do 
not, therefore, relate to the preservation of the individual, but to 
that of the species; and any study which concerns the species 
comes properly after we have finished everything relating to the 
individual. 



SECTION I. 
NUTRITION. 



CHAPTEE I. 

PROXIMATE PRINCIPLES IN GENERAL. 

The study of Nuthition begins naturally with that of the proxi- 
mate principle, or the aubstaaces entering into the composition of 
the different parts of the body, and the different kinds of food. In 
examining the body, the anatomist finds that it is composed, first, 
of variona parts, which are easily recognized by the eye, and which 
occupy distinct situations. In the case of the human body, for 
example, a division is easily made of the entire frame into the 
head, neck, trunk, and extremities. Each of these regions, again, 
is found, on examination, to contain several distinct parts, or 
" organs," wbich require to be separated from each other by dissec- 
tion, and which are distinguished by their form, color, texture, and 
consistency. In a single limb, for example, every bone and every 
muscle constitutes a distinct organ. In the trunk, we have the 
heart, the lungs, the liver, spleen, kidneys, spinal cord, &c., each of 
which is also a distinct organ. When a number of organs, differing 
in size and form, but similar in texture, are found scattered through- 
out the entire frame, or a large portion of it, they form a connected 
set or order of parts, which is called a " system." Thua, all the 
muscles taken together constitute the muscular system; all the 
bones, the osseous system ; all the arteries, the arterial system. 
Several entirely different organs may also be connected with each 
other, so that their associated actions tend to accomplish a single 
object, and they then form an " apparatus." Thus the heart, arte* 
ries, capillaries, and veins, together, form the circalatory apparattu; 
the stomach, liver, pancreas, intestine, &c., the digestive apparatr 
Every organ, again, on microscopic examination, is seen to be m 



46 PBOXIHATE PRINCIPLES IN' QKNKBAL. 

up of minute bodies, of deBnite size and figure, which are so small 
as to be invisible to the naked eye, and which, after separation 
from each other, cannot be further subdivided without destroying 
their organization. They are, therefore, called "anatomical ele- 
ments." Thus, in the liver, there are hepatic cells, capillary blood- 
vessels, the fibres of Glisson's capsule, and the ultimate filaments 
of the hepatic nerves. Lastly, two or more kinds of anatomical 
elements, interwoven with each other in a particular manner, form 
a "tissue." Adipose vesicles, with capillaries and nerve tubes, 
form adipose tissue. White fibres and elastic fibres, with capillaries 
and nerve tubes, form areolar tissue. Thus the solid parts of the 
entire body are made up of anatomical elements, tissues, organs, 
systems, and apparatuses. Every organized frame, and even every 
apparatus, every organ, and every tissue, is made up of difierent 
parts, variously interwoven and connected with each other, and it 
is this character which constitutes its organization. 

But beside the above solid forms, there are also certain fluids, 
which are constantly present in various partsofthe body, and which, 
from their peculiar constitution, are termed "animal fluids." These 
fluids are just as much an essential part of the body as the solids. 
The blood and the lymph, for example, the pericardial and synovial 
fluids, the saliva, which always exists more or less abundantly in 
the ducts of the parotid gland, the bile in the biliary ducts and the 
gall-bladder : all these go to make up the entire body, and are quite 
as necessary to its structure as the muscles or the nerves. Now, if 
these fluids be examined, they are found to be made ap of many 
different substances, which are mingled together in certain propor- 
tions; these proportions being constantly maintained at or about 
the same standard by the natural processes of nutrition. Such a 
fluid is termed an organized fluid. It is organized by virtue of the 
numerous ingredients which enter into its composition, and the 
regular proportions in which these ingredients are maintained. 
Thus, in the plasma of the blood, we have albumen, fibrin, water, 
chlorides, carbonates, phosphates, &c. In the urine, we find water, 
urea, urate of soda, creatine, creatinine, coloring matter, suits, &o. 
These substances, which are mingled together so as to make up, in 
each instance, by their intimate union, a homogeneous liquid, are 
called the proximate principles of the animal fluid. 

In the solids, furthermore, even in those parts which are appa- 
rently homogeneous, there is the same mixture of different ingre- 
dients. In the hard substance of bone, for example, there is, first. 



PBOXIUATB PRItrciPLEg IN GKNKRAL. 



47 



water, which may be expoUed by evaporatioa ; second, phosphate 
and carbonatti of lime, wbicb may bo extracted by Ibe proper sol- 
vents; third, a peculiar animal matter, willi which these calcareous 
salts are in union; and foiirtli, various other saline substances, in 
special proportions. In the muscular tissue, there is chloride of 
poiasaium, Inetic acid, water, salw, albumen, and an animal matter 
termed musculine. The dil^erence in consistency betweou the solids 
and Huidtidces not, therefure, indicate any radical diflerenQe in their 
constitution. 13uih ore equally made up of proximate principles, 
mingled together in various proportions. 

It ia important to understand, however, exactly what arc proxi- 
mate principles, and what are not such; for since these principles 
are extracted from the animal sulidH nnc] fluids, and sepnrated from 
each other by the help of certain chemical manipulations, such as 
evaporation, solution, crystallization, and the like, it might be sup- 
posed that every substance which could be extracted from an orgao- 
izod solid or (luid, by chemical means, should be considered ns a 
proximate principle. That, liowever, is not the case. A proximate 
principle is properly defined to be ani/ subsiance, uhciher simple or 
compound, chemically speaking, which txi$tt, urvUr its own form, in Ute 
animal toUd or fluid, and which can be extracted by means which do 
not alter or destroy its chemical properties. Phosphate of lime, for 
example, is a proximate principle of bone, hut phosphoric acid is 
not so, since it does not exist as such in the bony tissue, but is 
produced only by the decompoaition of the calcareuua salt: still 
\iim ph<wphorus, wliich is obtained only by the decompo&itioa of 
the phosphoric acid. 

Proximate principles may, in fact^be said to exist in all solids or 
fluids of mixefJ composition, and may be extracted from them by 
the same moans as iu the case of the animal tissues or secretions. 
Thus, in a watery solution of sugar, we have two proximate prin- 
ciples, viz: first, the water, and second, the sugar. The water may 
be separated by evaporation and condensation, af\er which the 
sugar remains behind, in a crystalline form. These two substances 
have, therefore, been simply separated from each other by the [iro- 
cess of evaporation. They have aot been decomposed, nor their 
chemical properties altered. On the other hand, the oxygon and 
hydrogen of ilic water were not proximate principles of the original 
solution, and did not exist in it under their own formA, but only in 
a statoof uombinatiou; forming, in this cundttion, a fluid subsiance 
(water), endowed with sensible properties entirely di&reut from 



48 



PROXfHATB PRiyoiPLBS ty OSKERAt.. 



tlieira. If wo wish to aacertnin, accordingly, llie nature and proper- 
ties of a saccharine solution, it will afford us but little satisfaction to 
extract lis ultimate chemical elements; for its nature and properties 
depend not so uiucli ou the presence in it of the ultimate elements, 
oxygen, hydrogen, and carbon, as on the particninr forms of com- 
bination, viz., water and sugar, under which they are prej*ent. 

It is very essential, therefore, that in extracting the proximate 
principles from the animal body, only such means should be adopted 
as will isolate the substances already existing in the tissues and 
fluids, without decomposing them, or altering thetr nature. A 
neglect of this rule has been productive of much injury in the pur- 
suit of organic chemistry; for chemists, in subjecting the animal 
tissues to the action of acids and alkalieti, of prolonged boiling, or 
of too intense heat, have often obtained, at the end of the analysis, 
many substances which were erroneously described as proximate 
principles, while they were only the remains of an altered and dis- 
organized material. Thus, the fibrous tissues, if boiled steadily for 
thirty-six hours, di,=solve, for the most part, at the end of that time, 
in the boiling water; and on cooling the whole solution solidities 
into a homogeneous, jelly-like substance, which has received the 
name of ijtlatine. But this gelatine does not really exist in the body 
as a proximate principle, since the fibrous tissue which produces it 
i.-4 not at lirst soluble, even in boiling water, and its ingredients 
become altered and converteil into a gelatinous matter only by pro- 
longed ebullition. So, again, an animal substance containing ace- 
tates or lactates of soda or lime will, upon incineration in the open 
air, yield carbonates of the same bases, the organic acid having been 
destroyed, and replaced by carbonic acid; or sulphur and phospho- 
rus, in the animal tissue, may be converted by the same means into 
sulphuric and phosphoric acids, which, decomposing the alkalioe 
carbonates, become sulphates and phosphates. In either case, the 
analysis of the tissues, so conducted, will bo a deceptive one, and 
useless for all anatomical and physiological poTposes, because its 
real ingredients have been decomposed, and replaced by others, in 
the process of mauipialatiou. 

It is in this way that diiTerent chemists, operating upon the same 
aninml solid or fluid, by following dift'erent plans of analysis, have 
obtained difierent results; enumerating as ingredients of the body 
many artificially formed substances, which are not, in reality, 
proximate principles, thereby introducing much confusion into 
physiological chemistry. 



PBOXIMATE PRINCIPLES IN GENKBAL. 



49 



It is to b« kept constantly in view, in the examination of an 
animal tissue or fluiJ, that the object of the operation is simply the 
aepanUum of ita ingredimU from each other, and not iLeir decomposi- 
tion or ultimate analysis. Only tho simplest forma of clieraical 
manipulation should, therefore, be employed. Tho substance to 
bo examined should first be subjected to evaporation, in order to 
extract and estimate its water. This evaporation must be conducted 
at a heat not above 212° K., since a higher temperature would de* 
stroy or alter some of the animal ingredienlB. Then, from the 
dried residue, chloride of Hodiuin, alkaline sulpliatos, earhonauw, 
and phosphates may be extracted with water. Coloring matters 
may be separated by alcohol. Oils may be dissolved out by ether, 
&C. &C. When a chomicnl decomposition is unavoidable, it must 
be kept in sight and allerward coRrected. Thus the glyko-cholate 
of soda of tho bile is separated from certain other ingredients by 
precipitating it with acctalo of leacl, forming glyko-cholate of lead; 
but this is afterward decomposed, in its turn, by carbonate of soda, 
reproducing tho original glyko-cholate of soda. Sometimes it is 
impossible to extract a proximate principle in an entirely unaltered 
form. Thus the fibrin of the blood can be separated only by allow- 
ing it to coagulate; aod once coagulated, it is permanently altered, 
and can no longer present all iU urigiual characters of Quidity, kc, 
as it existed beforchaud in the blood. lu such instances as this,. 
we can only make allowance for an unavoidable dilBcuIty, aod be 
careful ihat tho subsUincc suffers no further alteration. By bearing 
Id mind the above considerations, we may form a tolerably correct 
estimate of the nature and quantity of all of the proximate princl- 
pl«B existing in the substance utider examination. 

The manner in which tho proximate principles are associated 
together, so as to form the animal tissues, is deserving of notice. 
In every animal solid and iluid, there is a considerable number oF 
proximate principles, which are jjresont in certain proportions, and 
which are so united with each other that the mixture presents a 
homogeneous appearance. But this union is of a complicated cha- 
racter; and the presence of each ingredient de[)endts to a certain 
extent, upon that of the others. Some of them, auch as the alkaline 
carbonates and phosphates, are iti solution directly in the water. 
Some, which are insoluble in water, arc held in .-mlution by ihe 
presence of other soluble substances. Thus, phosphate of lime is 
held in solution in the urioe by the biphoaphnte of soda. In the 
blood, it is dissolved by the albumen, which is itself fluid by union 



60 



PROXIMATE PRIXCIPLKS IN QXIVERAL, 



with the water. The same substance may be fluid in one part of 
the body, and solid in another part. Thus in the blood and secre- 
tions the water is fluid, and liulds in solulion other substances, both 
animal and mineral, while in the bones and cartilages il is solid 
not crystallized, as in the case of ice or of saline subalances which, 
contain water of crystallization, but amorphous and solid, by iho 
fact of its intimate union with the aoimal and saline ingiedients, 
which are abundant in quantity, and which are themselves present 
in the solid form. Again, the phosphate of lime in the blood is 
fluid by solution in the albumen ; but in the bones it forms a solid 
substance with the animal matter of the osseous tissue; and yet 
the union of the two is as intimate and homogeneous in the bones 
as in the blood. A proximate principle, therefore, never exists 
alone in any part of the body, l^t is always intimately associated 
with a number of others, by a kind of homogeneous mixture or 
solution. 

Every animal tissue and fluid contains a number of proximate 
principles which are present, as we have already mentioned, in 
certain characteristic proportions. Thus, water is present in very 
large quantity in the perspiration and the saliva, but in very small 
quantity in the bones and teeth. Chloride of sodium is compara- 
tively abundant in the blood and deficient in the muscles. On the 
pthcr hand, chloride of potaasiom ia more abundant in the muscles, 
less 90 in the blood. But these proportions, it is important to ob- fl 
serve, are nowhere absolute or iavariable. There is a great differ- 
ence, in this respect, between the chemical composition of an inor- i 
ganic substance and the anatomical constitution of an animal fluid. ^| 
The former ia always constant and definite; the latter is always " 
subject to certain variations. Thus, water is always composed of 
exactly the same relative quantities of oxygen and hydrogen; and 
if these proportions be altered in tho Icaat, it ihereby ceases to bo 
water, and is converted into some other substance. But in the 
urine, the proportions of water, urea, urate of soda, phosphates, 
&Q., vary within certain liiniUi in difl'erent individuals, and even ia 
the some individual, from one hour to another. This variation, 
which is almost constantly taking place, within the limits of health, i 
is characteristic of all the animal solids and fluids; for they ara S 
composed of different ingredients which arc supplied by absorption 
or formed in the iuleriur, and which are eonstautty given up again, 
under the same or dillerent forms, to the surrounding media by the 
unceasing activity of the vital processes. Every variation, then, 



I 



PBOXII(AT£ FBINCIPLES IN GENBBAL. 61 

in the general coodition of the body, as a whole, is accompanied by 
a corresponding variation, more or less pronounced, in the consti- 
tution of its different parts. This constitution is consequently of 
a very difl»rent character from the chemical constitution of an 
oxide or a salt. Whenever, therefore, we meet with the quantita- 
tive analysis of an animal fluid, in which the relative quantity of 
its different ingredients is represented in numbers, we must under- 
stand that such an analysis is always approximative, and-not abso- 
lute. 

The proximate principles are naturally divided into three differ- 
ent classes. 

The first of these classes comprises all the proximate principles 
which are purely inobganic in their nature. These principles are 
derived mostly from the exterior. They are found everywhere, in 
unorganized as well as in organized bodies; and they present them- 
selves under the same forms and with the same properties in the 
interior of the animal frame as elsewhere. They are crystallizable, 
and have a definite chemical composition. They comprise such 
substances as water, chloride of sodium, carbonate and phosphate 
of lime, &c. 

The second class of proximate priociples is known as CBTSTAL- 
UZABLE SUBSTANCES OF OBOANic OBioiN. This is the name given 
to them by Robin and Verdeil,' whose classification of the proxi- 
mate principles is the best which has yet been offered. They are 
crystallizable, as their name indicates, and have a definite chemical 
composition. They are said to be of "organic origin," because they 
first make their appearance in the interior of organized bodies, and 
are not found in external nature as the ingredients of inorganic 
substances. Such are the different kinds of sugar, oil, and starch. 

The third class comprises a very extensive and important order 
of proximate principles, which go by the name of the Oboanic 
Substances proper. They are sometimes known as "albuminoid" 
substances or "protein compounds." The name organic substances 
is given to them in consequence of the striking difference which 
exists between them and all the other ingredients of the body. The 
substances of the second class differ from those of the first by their 

> Cliiinle AnstomlqQM fit Phralologiqoe. Puis, 1663. 



62 PROXIMATE PBINOIPLBS IN OSNBBAL. 

exclusively organic origin, but they resemble the latter in their cry b- 
tallizability and their definite chemical composition ; in consequence 
of which their chemical InTestigation may be pursued in nearly 
the same manner, and their chemical changes expressed in nearly 
the same terms. But the proximate principles of the third class 
are in every respect peculiar. They have an exclusively organic 
origin ; not being found except as ingredients of living or recently 
dead animals or vegetables. They have not a definite chemical 
composition, and are consequently not crystallizable; and the forms 
which they present, and the chemical changes which they undergo 
ID the body, are such as cannot be expressed by ordinary chemical 
phraseology. This class includes such substances as albumen, 
fibrin, casein, Ac. 



PBOXIHATB PRINCIPLES OF THE FIRST CLASS. 53 



CHAPTER II. 

PROXIMATE PBINOIPLES OP THE FIRST CLASS. 

The proximate principles of the first class, or those of an inor- 
ganic nature, are very nameroos. Their most promioent characters 
have already been stated. They are all crystallizable, and have a 
definite chemical composition. They are met with extensively in 
the inorganic world, and form a large part of the crust of the earth. 
They occur abundantly in the different kinds of food and drink; 
and are necessary ing^redients of the food, since they are necessary 
ingredients of the animal frame. Some of them are found universally 
in all parts of the body, others are met with only in particular 
regions; bat there are hardly any which are not present at the 
same time in more than one animal solid or fluid. The following 
are the moat prominent of them, arranged in the order of their 
respective importance. 

1. "Water. — Water is universally present in all the tissues and 
fluids of the body. It is abundant in the blood and secretions, 
where its presence is indispensable in order to give them the fluidity 
which la necessary to the performance of their functions; for it 
is by the blood and secretions that new substances arc introduced 
into the body, and old ingredients discharged. And it is a neces- 
sary condition both of the introduction and discharge of substances 
naturally solid, that they assume, for the time being, a fluid form; 
water is therefore an essential ingredient of the fluids, for It holds 
their solid materials in solution, and enables them to pass and repass 
through the animal frame. 

But water is an ingredient also of the solids. For if we take a 
muscle or a cartilage, and expose It to a gentle heat in dry air, it 
loses water by evaporation, diminishes in size and weight, and be- 
comes dense and atiSl Even the bones and teeth lose water by 
evaporation in this way, though iu smaller quantity. In all these 
solid and semi-solid tissues, the water which they contain is oaeftal 



I 



fii 



PBOXIMATB PBlNOrPLES OF THE FIRST CLASS. 



37 


Bill) . 


. . S80 


100 


Milk 


. . B87 


130 


PancrMticJnic* 


. 900 


55f> 


nrlu« 


. 936 


760 


Lynpli , 


. 9flO 


76 B 


Oartrici Juica . 


. 878 


"AO 


Pvjitpi ration, 


. 980 


795 


galivs. . 


. 999 


805 







by giving them the special consistency which is characteristic of 
them, and which would be Io3t without it. Thus a tendon, in its 
natural condition, is white, glistening, and opaque; and though very 
strong, perfectly flexible. If its water be expelled by evaporation 
it beuoracB yellowish in color, shrivelled, semi-transparent, inflexi- 
ble, and totally unfit for performing iw mechanical functions. The 
aamo thing is true uf the akin, muscles, cartilages, &c. 

The following is a list, compiled by Uobin and Vertleil from 
various ob3er%'era, showing tho proportion of water per thousand 
parts, in different solidf* and fluids: — 

QvASTPn or Watbr n 1,000 pabt* ix 

Teeth 
Bon«a 
Curtilag* . 
Uosolei . 
Li^Amenlfi 
Brnin 

S/novUl duld 

According to the best calculations, water constitutes, in the 
human subject, between two-thirds and three-quarters of the entire 
weight fjf the body. 

The water which thus forms a part of the animal frame is derived 
from without. It is taken in the different kinds of driak, and olso 
forms an abundant ingredient in the various articles of food. For 
no articles of food are taken in an absolutely dry state, but all 
contain a larger or smaller quantity of water, which may readily 
be expelled by evaporation. The quantity of water, therefore, 
which is daily taken into the system, cauuot be ascertained in any 
case by simply measuring the quantity of drink, but its proportion 
in the solid food, taken at tho same timo, mnst also bo determined 
by experiment, and this ascertained quantity added to that which 
is taken in with the fluids. By measuring the quantity of fluid 
taken with the drink, and calculating in addition the proportion 
existing in the solid food, we have found that, for a healthy adult 
man, the ordinary quantity of water introduced per day, U a little 
over 4J pounds. 

After forming a part of tho animal solids and fluids, and taking 
part in the various physical and chemical processes of the body, tho 
water is again discharged; for iia presence in tho body, like that 
of all the other proximate principles, is not permanent, but only 



I 



i 



CBLOBIDK OF 80D1UU. 



65 



/temporary. After being taken in with the food and drink, it is 
IfBsociated with other principles in the fluids and solids, pFissing 
>ni the intestine to the blood, and fratn the blood to the tissues 
id secretions. It afterwsrd makes its exit from the body, from 
Ivhich it is discharged by fourdinereQt passages, viz., in a lit^uid 
Ifbrtn with the nrine and the feces, and in a gaseous form with tho 
)reath and the perspiration. Of all the water which is expelled in 
^kbis way, about 48 per cent is discharged with the urine and feces,' 
land about 52 per cent, by the lungs and skin. The researchos of 
' XaToisier and Seguiu, Valentin, and others, show that from a pound 
and a half to two pounds is discharged daily hy the skin, a little 
over one pound hy exhalation from tho Uings, and a little over two 
ponnds by tho urine. Both the absolute and relative amount dis- 
charged, both io a liquid and gaseous form, varies according to 
circumstances. There is parlicuhirJy a. compensating action in this 
respect between the kidneys and the skin, so that when the cutane- 
ous perspiration is very abundant tho urine is less so, and vice iiersd. 
The quantity of water exhaled from the lungs varies also with the 
state of the pulmonary circulation, and with the temperature and 
l^drjness of the atmosphere. The water is not discharged at any 
time in a state of purity, but is mingled in the urine and feces with 
nline substances which it holds in solution, and in the cutaneous 
kftnd pulmonary exhalations with animal vapors and odoriferous 
VBabetaDces of various kinds. In the perspiration it is also mingled 
with saline substances, which it leaves behiud on evaporation. 

2. Chloride of Sodium. — This substance is found, like water, 
throughout the different tissues and fluids of the budy. The ouly 
exception to this is perhaps the enamel of the teeth, where it has 
not yet been discovered. Its presence is imporuint in the body, as 
regulating the phenomena of endosraosis and exosmosis in different 
parts of the frame. For we know that a solution of commou salt 
^passea through aolmal membranes much less readily thou pure 
water; and tissues which have been desiccated will absorb pure 
water more abundantly than a saline solution. It must not be sup- 
posed, however, that the presence or absence of chloride of sodium, 
or its varying <iuautity in the animal fluids, is the only couditioQ 
which regulates their transudation through the animal membranes. 
The maDDor iu wbioh endosmosis and exosmosis take place ia the 



• Op. olt., ToU It. pp. 143 ind 14fl. 



56 



PROXIMATB PBISCTPLES OF THE FIRST OLAflS. 



animal frame depends upoa the relative quantity of all tlie ingre- 
dients of the fluids, as well as on the constitution of the solids 
thcmsclvM; and the chloride of sodium, as one iogredient among 
many, influences these phenomena to a great extent, though it does 
not regulate tbem exclusively. 

It exerts also an important influence on the solution of various 
other ingredients, with which it is associated. Thus, in the blood 
it increases the solubility of the albumen, and perhaps also of the 
earthy phosphates. The blood-globules, again, which become dis- 
integrated and dissolved in a solution of pure albumen, are main- 
tained in a state of integrity by the presence of a small quantity of 
chloride of sodium. 

It exists in the following proportions in several of the solids and 
fluids :' — 

QDAxn-TT or Ciimreiib ap Sotuvu ix 1,(>00 pxan ni tbs 



UoBotea 




3 


Btle 


3.S 


Banes 




2.6 


Blood . 


4.5 


Uilk 




1 


Uncafl . . 


« 


flAlivft 




1.& 


AqueoQi hantor . 


11 


Urine 




3 


VitreooB humor 


14 



In the blood tt is rather more abundant than all tho other saline 
ingredients taken together. 

Since chloride of sodium is so universally present in all parts of 
tho body, it is an important ingredient also of the food. It occurs, 
of course, in all animal food, in the quantities in which it naturally 
cxiatfl in the corresponding tissues; and in vegetable food also, 
though in smaller amount. Its proportion in muscular flesh, 
however, is much less than in tho blood and other fluids. Conse- 
i^ucntly, it is not supplied iu sulHcieut quantity as an ingredient of 
animal and vegetable food, but is taken also by itself as a condi- 
ment. There is no other sulMtance so universnlly used by all races 
and conditions of moo, as an addition to tho food, as chloride of 
ecdium. This custom does not simply depend on a fancy for grati- 
fying the palato, but is based upon an instinctive desire for a sub* 
ftancc which is necessary to the proper constitution of tho tissues 
and fluids. Even the herbivorous animals are greedy of it, and if 
freely supplied with it, are kept in a much better condition than 
when deprived of its use. 

The importance of chloride of sodium in this respect has been 
well demonstrated by BoussingauU, in his experiments on tbo 

■Robin nud V«rdL-il. 




OTtLDRIDB OF SODICM. 



57 



fattening of animals. These observatioua were made upon six 

.bullocks, Belected, ns nearly 05 possible, of the same age and vigor, 
ind subjected to comparative csperimcat, Tlicy were all flupplied 

'with aD abundance of nutritious food; but three of them (lot No. 

II) rewivcd also a little over 500 grains of salt each per day. The 
jmaiiiitig three (lot Ko. 2) received no salt, but iu other respects 

\ were treated like the first. The result of these esperimeDts is given 
by Boussingaalt as follows; — ' 

"Though salt administered with thp food has bat little effect in 
increaaiog the size of the animal, it appears to exert a favorable 
inOueoce upon his qualities and general aspect. Until the end of 
March (the experiment began in October) the two lots experimented 
on did not present any marked difference in their appearance ; but 
in the course of the following April, thia JiDerence became i^uite 
manifest, even to an unpractised eye. The lot No. 2 had thou been 
without salt for sis mooths. In the animals uf both lots the skin 
bad a fine and substantial texture, easily stretched and separated 

• from the ribs; but the hair, which was tarnished and disordered in 
the bullocks of the second lot, was etnootb and glistening in those 
of the Crst As the experiment went on, these characters became 
more marked; and at the beginning of October the animals of lot 
Ko. 2, after going without salt for an entire year, presented a rough 

find tangled hide, with patches here and there where the skin was 
entiroly uncovered. The bullocks of lot No. 1 retained, on the 
oontrary, the ordinary aspect of stall-fed animals. Their vivacity 
aod their frei^uent attempts :ii mounting contrasted strongly with 
the dull and unexcitablo a-spect presented by the others. No doubt, 
the first lot would have commanded a higher price in the market 
than the second." 

Chloride of sodium acts also in a favorable manner by exciting 
the digestive fluids, and assisting in this way the solution of the 
food. For food which is tasteless, however nutritious it may be in 
other respects, is taken with reluctance and digested with difficulty ; 
while the attractive flavor which is developed by cooking, and by 
the addition of salt and other condiments in proper proportion, 
excites the secretion of the saliva and gastric juice, and facilitates 
consequently the whole process of digestion. The chloride of 
sodium is then taken up by absorption from the intestine, and is 
deposited ia various quantities in diQerent parts of the body, 



I Chlmla AgHoolv, Pari*, IBM, p. 271. 



5S 



PROXIl 



flNClPLEd 



[B&T CLASS. 



It is discharged with the urine, mucus, cutaneous perspiration, 
ko., in solatioD ia the water of these lluids. According to the esti' 
mates of M. Barral,' a small quantity of chloride of Eodium dis- 
appears in the body ; siuce he finds by acciirate comparison that all 
the salt introduced with the food is not to be found in the excreted 
fluids, but tliat about ona-fiflh oCit remains unaccounted for. This 
portion is supposed to undergo a double decomposition in the blood 
with phosphate of potassa, forming chloride of poiasaium and phos- 
phate of soda. By far the greater part of the chloride of sodium, 
however, escapes under its own form with the secretions. 

S. Chloride op Potassium. — This subatiiuce is found in the 
muscles, the blood, tlie milk, the urine, aud various other fluids 
and tissues of ihe body. It is not so universally present as chlo- 
ride of sodium, and not so important as a proximate principle. 
In some parts of the body it i^ n^oro abundant than the latter salt, 
ID others less so. Thus, in the blood there ia mora ohloride of 
sodium than chloride of potassium, but in the muscles there is more 
chloride of potassium than chloride of sodium. This substance is 
always in a fluid form, by its ready solubility in water, and is easily 
separated by lixiviation. It is introduced mostly with the food, but 
is probably formed partly in the interior of the body from chloride 
of sodium by double decomposition, as already mentioned. It ia 
discharged with the mucus, the saliva, and the urioe. 

4. Phosphate of Lime. — This is perhaps the moat important 
of the mineral ingredients of the body next to chloride of sodium. 
It is met with universally, in every tissue and every fluid. Its 
quantity, however, varies very much in diBercnt parts, as will be 
seen by the following list: — 

QitAsriTT or Pbosi'rate or Tjimn ik l.niin i>ixt« ixtiib 
Enamel of tLe teeth , . 663 Uusolea . . . .3.1 

Dnitin* . . . . 6U Blood . . . .0,3 

Bo&M .... D60 Gastria Jaioe . . .0.' 

CArliLagAR ... 40 

It occurs also under different physical conditions. In the bones, 
teeth, ami cartilages it is solid, and gives to these tissues the resist- 
ance and solidity which are characteristic of them. The calcareous 
salt is not, however, in these instances, simply deposited mechani- 
cally in the substunceof the bone or cartilage as a granular powder, 

' Id Rvbip Kod Voriluil, op. oU., vol. !1. p. 193. 



PH08PHATB OF LIKB. 



fi« 



Fig. 1. 



but is tDtimately united with the animal matter of the tissaee, like 
a coloring matter in oolored glass, so as tu present a more or less 
homogeneous appearance. It can, however, be readily dissolved 
out by maceration in dilate muriatic acid, leaving behind the 
animal substance, which still retains the original fi^nn uf the bone 
or cartilage. It is not, therefore, united with the animal matter eo 
as to low its identity and form a new chemical substance, as where 
an acid combines with an alkali to form a sah, but in the same 
manner as salt unites with water in a saline solution, both sub- 
stances retaining their original character aud composition, but so 
intimately associated that they cannot be separated by mechanical 
means. 

In the blood, phosphate of lime is in a liquid form, notm-ith stand- 
ing its insolubility in water and in alkaline Suicts, being held in 
K>lution by the albuminous matters of the circulating liluid. lu the 
nrino, it is retained in aolntron by the bi-pht5:*phato of soda. 

lo all the solid tissues it is useful by giving to them their proper 
coDsisience and solidity. For example, in the ena- 
mel of the teeth, the hardest tissue of the body, it 
predominates very much over the animal matter, 
and is present in greater abundnnce there than in 
any other part of the frame. In the dentine, a 
softer tissue, it is in somewhat smaller quantity, 
and in the bones smaller still ; though in the hones 
it continues lo form more than one-half the entire 
mass of the osseous substance. The importance of 
phosphate of lime, in communicating to bones their 
natural stiflhess and consistency, may be readily 
shown by the alteration which they suffer from its 
remoTal. If a long bone be macerated tu dilute 
muriatic acid, the earthy salt, as already mentioi]<.':il, 
is entirely dissolved out, after which the bone loses 
its rigidity, and may be bent or twisted in any direc- 
tion without breaking. (Fig. 1.) 

Whenever the nutrition of the bene during life 
is interferod with from any pathological cause, so 
that its phosphate of lime becomes deficient in 
amount, a softening of the osseous tissue is the 
consequence, by which thu bones yield to external 
pressure, and become more or less distorted. (Oateo-malakia.) 

AAcr forming, for a time, a part of the tissues and fluids, the 



fl BrLA T [IB IB 

.1 anor. urtnr ma. 

KCltl. (FtiiIII ■ (pool. 

uifiu In ihn muiaum 

at LiM Coll. or I'brrf- 

cUq* aad SorgouiM.) 



60 



PROXIMATE PRTNCIPLGS OP THB FIRST OIiASS, 



phosphate of lime is discharged from the body by the uriuc, the 
perflpiration, mxicus, &c. Much the larger portion is discharge*! by 
the urine. A small quftntity also occurs in the feces, but this is pro- 
bftbly only the superflaous residue of what i$ taken in with the food. 

5. Cjlruokate of Lime. — Carbonate of lime is to be found in 
the bones, and sometimes in the urine. The concretions of the 
internal ear are almost entirely formed of it. It very probably 
occurs also in the blood, teeth, cartilages, and sebaceous matter; 
but its presence here la not quite certain, since it may have been 
produced from the lactate, or other organic combination, by the 
process of incineration. In tlie bones, it is in much smalier quan- 
tity iban the phosphate. Its solubility in the blood and the urine 
is accounted for by the presence of free carbonic acid, and also of 
chloride of potassium, both of which substances exert a solvent 
action on carbouatc of lime. 

6. Carbonate or Soda. — This substance exists in the bones, 
blood, saliva, lymph, and urine. As it is readily soluble in water, 
it naturally Bssumos the liquid form in the animal fluids. It is 
important principally as giving to the blood its alkalescent reaction, 
by which the solution of the albumen is facilitated, and various 
other chemico- physiological proceases in the blood accomplished. 
The alkalescence of the blood is, in fact, necessary to life; for it is 
found that, in the living animal, if a mineral acid bo gradually 
injected into the blood, so dilute as not to coagulate the albumen, 
death takes place before its alkaline reaction bos been completely 
neutralized.' 

The carbonate of soda of the blood is partly introduced as suob 
with the food ; but the greater part oF it is formed wilhtn the body 
by tliG decomposition of other salts, introduced with certain fruits 
and vegetables. These fruits and vegetables, such as apples, cher* 
ries, grapes, potatoes, &c., contain raalates, tartrates, and citrates 
of soda and potassa. Now, it has been often noticed that, after 
the use of acescent fruits and vegetables containing the above salts, 
the urine bocomea alkaline in reaction from the presence of the 
alkaline carbonates. Lehmann' found, by experiments upon his 
own person, that, within thirteen minutes after taking half an oonco 



I 



I 

■ 

I 



' CI. TVniAM. L>ectun?« on tbo Ulood ; roportod bjr W. F. Atleir, M. U. 
delpliU, 1854, p. 31. 
' rhj^lologlcnl Ch<;mlstrr. Philadelphia «d., vol. I. p. HJ. 



PbiU- 



PHOSPHATES OF MAGNESIA, SODA, AND POTASSA. 61 

of lactate of soda, the urine bad an alkaline reaction. He also ob- 
served that, if a solation of lactate of soda were injected into the 
jagDlar vein of a dog, the urine became alkaline at the end of fire, 
or, at the latest, of twelve minutes. The conversion of these salts 
into carbonates takes place, therefore, not in the intestine but in the 
blood. The same observer^ found that, in many persona living on 
a mixed diet, the urine became alkaline in two or three hours aft«r 
swallowing ten grains of acetate of soda. These salts, therefore, 
on being introduced into the animal body, are decomposed. Their 
organic acid Is destroyed and replaced by carbonic acid ; and they 
are then discharged under the form of carbonates of soda and potassa. 

7. Carbonate of Potassa.— This substance occurs in very 
nearly the same situations as the last. In the blood, however, it is 
in smaller quantity. It is mostly produced, as above stated, by 
the decomposition of the malate, tartrate, and citrate, iu the same 
manner as the carbonate of soda. Its function is also the same as 
that of the soda salt, and it is discharged in the same manner from 
the body. 

8. Phosphates or Magnesia, Soda, and Potassa.— All these 
substances exist universally in all the solids and fluids of the body, 
but in very small quantity. The phosphates of soda and potassa 
are easily dissolved in the animal fluids, owing to their ready solu- 
bility in water. The phosphate of magnesia is beld in solution in 
the blood by the alkaline chlorides and phosphates; in the urine, 
by the acid phosphate of soda. 

A peculiar relation exists between the alkaline phosphates and 
carbonates in differenl classes of animals. For while the fluids of 
carnivorous animals contain a preponderance of the phosphates, 
those of the herbivora contain a preponderance of the carbonates: 
a peculiarity readily understood when we recollect that muscular 
flesh and the animal tissues generally are comparatively abundant 
in phosphates; while vegeteble substances abound in salts of the 
organic acids, which give rise, as already described, by their decom- 
position in the blood, to the alkaline carbonates. 

The proximate principles included in the above list resemble 
each other not only in their inorganic origin, their crystallizability, 

> Ph7»iological Chemiptry, vol. il. p. 130. 



62 



PBOZIHATE PRTSTCIPLES OP TRS FIRST CLASS. 



flnd their definite chemical composition, but also id the part which 
thejr takti in the constitution of the animal fratiie. They are 
dtstiaguiahed in this respect, first, by being derived entirely from 
without. There are a Few exceptions to this rule ; aa, for example, 
in the case of the alkaline carbonates, which partly originate in 
the body from the decomposition of malates, tartrates, iic. These, 
however, are only exceptions; and in general, the proximate prin- 
ciples belonging to the first claai are introduced with the food, 
and taken up by the animal tissues in precisely the same form 
under which ihey occur in external nature. The carbonate of lime 
in the bones, tbe chloride of sodium in the blood and tissues, are 
the same substances which are met with in the calcareous rocks, 
and in solution in sea water. They do not sufl'er any chemical 
alteration in becoming constitocnt porta of the animal frame. 

They are equally exempt, as a general rule, from any alteration 
while they remain in the body, and during their passage tlirough 
it The exceptions to this rule are very few ; aa, for example, where 
a small part of the chloride of sodium suffers double decomposition 
with phosphate of potaasa, giving rise to chloride of potassium and 
phosphate uf soda; or where the phosphate of soda itself gives up 
a part of its base to an organic acid (uric), and is converted in this 
way into a bi-phosphate of soda. 

Nearly the whole of these substances, 6nally, are taken up un- 
changed from the tissues, and dischargetl unchanged with the excre- 
tions. Thus we find the piiosphato of lime and the chloride of so- 
dium, which were tnken in with the food, dischnrged again under 
the aarae form in the urine. They do not, therefore, for the moat 
part, participate directly in the chemical changes going on in the 
body; but only serve by their presence to enable those changes to 
be accomplished in the other ingredients of the animal frame, which 
are necessary to the process of nutrition. 



I 




PBOXIlfATE PBINCIFLS8 OF THE SECOND CLASS. 63 



CHAPTEE III. 

PROXIMATE PEINCIPLES OF THE SECOND CLASS. 

The proximate principles beloDging to the second class are 
divided into three principal groups, viz: starch, sugar, and oil. 
They are distinguished, in the first place, by their organic origin. 
Unlike the principles of the first class, they do not exist in 
external nature, but are only found as ingredients of organized 
bodies. They exist both in animals and in vegetables, though in 
somewhat diSferent proportions. All the substances belonging to 
this class have a definite chemical composition ; and are further 
distinguished by the fact that they are composed of oxygen, 
hydrogen, and carbon alone, without nitrogen, whence they are 
sometimes called the "non-nitrogenous" substances. 

1. Stabch (C„H,„0,o). — The first of these substances seems to 
form an exception to the general rule in a very important particu- 
lar, viz., that it is not crystallizable. Still, since it so closely 
resembles the rest in all its general properties, and since it is easily 
convertible into sugar, which is itself crystallizable, it is naturally 
included in the second class of proximate principles. Though not 
crystallizable, furthermore, it still assumes a distinct form, by 
which it differs from substances that are altogether amorphous. 

Starch occurs in some part or other of almost all the flowering 
plants. It ia very abundant in corn, wheat, rye, oats, and rice, in 
the parenchyma of the potato, in peas and beans, and in most 
vegetable substances used as food. It constitutes almost entirely 
the different preparations known as sago, tapioca, arrowroot, &c., 
which are nothing more than varieties of starch, extracted from 
different species of plants. 

The following is a list showing the percentage of starch occurring 
in different kinds of food : — ' 

■ Fereira on Food and Diet, New York, 1843, p. 39. 



PROXIHATS PRINCIPLB9 OP THE SECOND CLASS. 





QDAXTtTT or Starcb 


IR ]00 pARta iir 




BIM . 


. 85.07 


Wheat flour . 


. 66.ta 


Ma-ixo 


. 80.92 


Icnlnni] moM 


. 44.60 


BuUy meal . 


. 07.1 B 


Kidnej bean . 


. 3&.»4 


Rjr* meal 


. ei.07 


P9U 


. 32.45 


Ost meftl 


. B9.00 


Potato . 


. 15.70 



"When porificd from foreign 
powder, which gives rise to a pecu 



Fig- 2. 







o 



<0 



v^ 



o 



ORArs* or I*aTATt> Stahcm. 



substances, starch is a white, lighl 
tr cniclv]iug sonHation when 
rubbed between the fingers. 
It is not amorphous, as we 
have already slated, but is 
composed of solid grauules, 
which, while they have a 
general reserablanco to each 
other, differ somewhat in va- 
rious particulars. The starch 
grains of the potato (Fig, 2) 
vary considerably in size. 
The smallest bave a diameter 
of ToSoo. the largest ,J,> of 
an inch. Thoy are irregu- 
larly pear-shaped in form, 
and are marked by concen- 
tric lainirju), as if ttie matter 

of which they are composed had been deposited in successive layers. 

At one point on the surface of every starch grain, there is a minute 

pore or depression, called the 
^' ' hilv^, around which the cir- 

cular markiuga arearrauged 
in a concentric form. 

The starch granules of 
arrowroot (Fig. 3) are gene- 
rally smaller and more uui- 
form in st;ie, than thoso of 
the potato. They vary from 
ao'ofl to rU of an inch in 
diameter. They are elongated 
aud cylindrical ia form, and 
the concentric markings are 
less distinct than in the pre- 
ceding variety. The hilus 











SrAion OiAivt ot Bi«mbi>* Aakovtoor. 



STABCH. 



6S 



has here aometimea thti form of a circular pore, and sometimes that 
of a transverse fissare or slit. 

The grains of wheat starch (Fig. 4) are still smaller than those 
of arrowroot They vary 



from 



TODOO 



to .j^^of an inch 



Fig. 4. 




in diameter. They are , 
nearly circular in form, with 
a round or transverse hilus, 
but without any distinct 
appearance of lamination. 
Many of them are flattened 
or compressed laterally, so 
that they present a broad 
surface in one position, and 
a narrow edge when viewed 
in the opposite direction. 

The starch grains of In- 
dian corn (Fig. 6) are of 
nearly the same size with 
those of wheat dour. They are somewhat more irregular and 
angular in shape; and are oflen marked with crossed or radiating 
lines, as if from partial fracture. 

Starch is also an ingre- 
dient of the animal body. 
It was iSrst observed by 
Purkinje, and aflerward by 
Kolliker,' that certain bodies 
are to be found in the interior 
of the brain, about the late- 
ral ventricles, in the fornix, 
septum lucidum and other 
parts, which present a cer- 
tain resemblance to starch 
graiDS,and which have there- 
fore been called "corpora 
amylacea." Subsequently 
Virchow' corroborated the 
above observations, and Moert< 



Starch QBAiir* or Wsbat Fioub. 



Fig. 6. 




Starok Qmaimu or Imdiax Cos*. 



•rlacea to be 



■ Id Amerioui 



66 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 




St^kcb Osaik* fsom Wall op Latrbal 
TaSTaiCLEa; from ■ wamsn acml 3.^ 



really Bubstancea of a starcliy nature; since they exhibit the usual 
chemical reactions of vegetable starch. 
The starch granules of the human brain (Fig. 6) are transparent 

and colorless, like those from 
^" ' plants. They refract the light 

strongly, and vary in size 
from ^T'on to rT»„ of an 
inch. Their average is yb"!! 5 
of an inch. They are some- 
times rounded or oval, and 
sometimes angular in shape. 
They resemble considerably 
in appearance the starch 
granules of Indian corn. The 
largest of them present a 
very faint concentric lamina- 
tion, but the greater number 
are destitute of any such 
appearance. They have 
nearly always a distinct hilus, which is sometimes circular and 
sometimes slit-shaped. They are also often marked with delicate 
radiating lines and shadows. On the addition of iodine, they become 
colored, first purple, afterward of a deep blue. They are less firm 
in consistency than vegetable starch grains, and can be more readily 
disintegrated by pressing or rubbing them upon the glass. 

Starch, derived from all these different sources, has, so far as 
known, the same chemical composition, and may be recognized by 
the same tests. It is insoluble in cold water, but in boiling water 
its granules first swell, become gelatinous and opaline, then fuse 
with each other, and finally liquefy altogether, provided a sufficient 
quantity of water be present. After that, they cannot be made to 
resume their original form, but on cooling and drying merely solidify 
into a homogeneous mass or paste, more or less consistent, accord- 
ing to the quantity of water which remains in union with it. The 
starch is then said to be amorphous or "hydrated." By this process 
it is not essentially altered in its chemical properties, but only in 
its physical condition. Whether in granules, or in solution, or in 
an amorphous and hydrated state, it strikes a deep blue color on 
the addition of free iodine. 

Starch may be converted into sugar by three different methods. 
First, by boiling with a dilute acid. If stnrch be boiled with dilute 



8U6AB. 67 

DJtric, sulphuric, or muriatic acid during thirty-six hours, it first 
changes its opalescent appearance, and becomes colorless and trans- 
parent; losing at the same time its power of striking a blue color 
with iodine. After a time, it begins to acquire a sweet taste, and 
is finally altogether converted into a peculiar specie of sugar. 

Secondly, by contact with certain animal and vegetable sub- 
stances. Thus, boiled starch mixed with human saliva and kept 
at the temperature of 100° F., is converted in a few minntes into 
sugar. 

Thirdly, by the processes of nutrition and digestion in animals 
and vegetables. A large part of the starch stored up in seeds and 
other vegetable tissues is, at some period or other of the growth of 
the plant, converted into sugar by the molecular changes going on 
in the vegetable fabric. It is in this way, so far as we know, that 
all the sugar derived from vegetable sources has its origin. 

Starch, as a proximate principle, is more especially important as 
entering largely into the composition of many kinds of vegetable 
food. With these it is introduced into the alimentary canal, and 
there, during the process of digestion, is converted into sugar. 
Consequently, it does not appear in the blood, nor in any of the 
secreted fluids. 

2. Sugar. — This group of proximate principles includes a con- 
siderable number of substances, which differ in certain minor 
details, while they resemble each other in the following particulars: 
They are readily soluble in water, and crystallize more or less 
perfectly on evaporation; they have a distinct sweet taste; and 
finally, by the process of fermentation, they are converted into 
alcohol and carbonic acid. 

These substances are derived from both animal and vegetable 
sources. Those varieties of sugar which are most familiar to us 
are the following six, three of which are of vegetable and three of 
animal origin. 

Vegetable J o,,p^ ,„g„^ Ammal ) Li„„ugar, 

■°B""- [sugar of starch. ^"«*"' I Sugar of honey. 

The cane and grape sugars are held in solution in the juices of 
the plants from which they derive their name. Sugar of starch, or 
glucose, is produced by boiling starch for a long time with a dilute 
acid. Liver sugar and the sugar of milk are produced in the 
tissues of the liver and the mammary gland, and the sugnr of 



68 PROXIMATE PBIKCIPLBS 0? THE SBCOlfD CLASS. 

honey is prepared in some way by tlie bee from niiitcrials of vege- 
table origin. 

Those varieties differ but little in their ultimate chemical compo* 
ailion. The following formutie have been cslablishcd for three of 
them. 



Cane sugar 
Milk »ngi\T 
Olucaaa . 



=c^ii.*"« 

Cane sugar is sweeter than most of tlie other varieties, and more 
soluble in wntur. Some sugars, such as liver sugar and angar of 
hooey, crystallize only with great tlifficulty; but ihis is probably 
owing to their being mingled with other substances, from which it 
is diflicult to separate them completely. If they could be obtained! 
in a state of purity, they would doubtless crystallize as perfectly as 
cane sugar. The diflercnt sugars vary also in the readiness with 
which they undergo fermentation. Some of them, as grape sugar 
and liver sugar, enter into fermentation very promptly; others, 
auch as milk and cane sugar, with considerable didiculty. 

The nbove are not to be regarded as the only varieties of sugar- 
existing in nature. On the contrary, it is probable that nearly 
every different species of anima! and vegetable produces a distinct 
kind of sugar, differing slightly from the r«st in its degree of sweet- 
ness, its solubility, its crystallization, its aptitude for fertnentatioo, 
and perhaps in iLs elementary composition. Nevertheless, ihore is 
so close a resemblance between them that they are all properly 
regarded us belonging to a single group. 

The teat most commonly employed for detecting the presence of 
sugar is that known as Trammer's test. It depends upon the fact 
that the saccharine substances have the power of reducing the 
persalts of ooppcr when heated with them in au alkaline solution. 
The test is applied in the following mauuer; A very small quantity 
of sulphate of copper in solution should be added to the suspected' 
li(]uid, and the mixture then rendered distinctly alkaline by the 
addition of caustic potassa. The whole solution then takes a deep 
blue color. On boiling the mixture, if sugar be present, the in- 
soluble suboxide of copper is thrown down as an opaque red, 
yellow, or orange-colored deposit; otherwise no change of color 
takes place. 

This lest requires some precautions in ils application. In tho 
first place, it is not applicable to all varieties of sugar. Cane 
sugar, for example, when pure, has no power of reducing the salts 




' SUGAB. 69 

of copper, even when present in large quantity. Maple sugar, also, 
which resembles cane sugar in some other respects, reduces the 
copper, in Trommer's test, but slowly and imperfectly. Beet-root 
sugar, according to Bernard, presents the same peculiarity. If 
these sugars, however, be boiled for two or three minutes with a 
trace of sulphuric acid, they become converted into glucose, and 
acquire the power of reducing the salts of copper. Milk sugar, 
liver sugar, and sugar of honey, as well as grape sugar and glucose, 
all act promptly and perfectly with Trommer's test in their natural 
condition. 

Secondly, care must be taken to add to the saspected liquid only 
a small quantity of sulphate of copper, just sufficient to give to the 
whole a distinct blue tinge, afler the addition of the alkali. If a 
larger quantity of the copper salt be used, the sugar in solution 
may not be sufficient to reduce the whole of it ; and that which 
remains as a blue sulphate will mask the yellow color of.the sub- 
oxide thrown down as a deposit. By a little care, however, in 
managing the test, this source of error may be readily avoided. 

Thirdly, there are some albuminous substances which have the 
power of interfering with Trommer's test, and prevent the reduc- 
tion of the copper, even when sugar is present Certain animal 
matters, to be more particularly described hereafter, which are 
liable to be held in solution in the gastric juice, have this effect. 
This source of error may be avoided, and the substances in ques- 
tion eliminated when present, by treating the suspected fluid with 
animal charcoal, or by evaporating and extracting it with alcohol 
before the application of the test. 

A less convenient but somewhat more certain test for sugar is 
iha.% of /ermenlatton. The saccharine fluid is mixed with a little 
yeast, and kept at a temperature of 70° to 100° F. until the fer- 
menting process is completed. By this process, as already men- 
tioned, the sugar is converted into alcohol and carbonic acid. The 
gas, which ia given off in minute bubbles during fermentation, 
should be collected and examined. The remaining fluid is purifled 
by distillation and also subjected to examination. If the gas be 
fonnd to be carbonic acid, and the remaining fluid contain alcohol, 
there can be no doubt that sugar was present at the commencement 
of the operation. 

The following list shows the percentage of sugar in various 
articles of food.' 

' Ferelra, op. cit., p. 55. 



70 proxij^Tt^pbtnciplb^o^tii^bbcond class. 



(kFAJCTITT or SrOAB U 100 TAKf* IX 



Fist* . . 
Clierrie* 

l*UAI'h>>li 

Tamarlnili 
Purs . 
RpAta 

S<rc«t alinomla 
Bitrlpy infill . 



52.50 
18.13 

12.S0 

U.52 

fl.Ott 

3.00 

5.21 



W]ient Soar 
Rjre meal . 
ItiHinn inMtl 
P«ai . 
Cqw'b milk 
Am's lull It 
Iluiuan lailk 



4.20 to e.48 

3.2S 



Beaide the -^ugar, iherefore, which is taken into the nlimentftry 
cannt in a pure form, a large quantity is also introducer! as an in- 
gredient of tlie sweet -flavored fruits and vegetables. All the 
starchy substances of the food .ire also converted into sugar in the 
process of digestion. Two of the varieties ttf sugar, at leust, 
originate in the interior of the body, viz., sugar of milk and liver 
sugar. Tlie former exists in a solid form in the substance of the 
mammary gland^ from which it passes in solution into the milk. 
The liver sugar is found in the substance of the liver, and almost 
always also in iho blood of the hepatic veins. The sugar which is 
introduced with the food, aa well as that which is formed in the 
liver, disappears by decomposition in the aniiual Ouids, and does 
not appear in any of the e.Ycrctions. 

8. Fat3. — These substances, lifco the sugars, are derived from 

both animal and vegetable sources. There are three principal 

varieties of them, which may be considered as representing the 

class, viz : — 

Olalne « C^^ U^ 0„ 

MJiiB*rlDB = Ci^ n;j 0„ 

Bloiriiw =C,„H,„0„ 

The principal difterence between the oleaginous and saccharine 
substances, so far ns regards their ultimate chemical composition, 
is that in the sugars the oxygen and hydrogen always exist together 
in the proportion to form water; while in the fata the proportionsof 
carbon and hydrogen are nearly the same, but that of oxygen is 
considerably less. The fan arc all fluid at a high temperature, but 
assume the solid form on cooling. Stenrinu, which is the most 
BoUd of the three, liquefies only at 143*' F.; margarine at 118® F.: 
while oleine remains fluid considerably below 100"* F., and even 
very near the freezing point of water. The fats are all in.5olnble 
in water, but readily soluble in ether. When treated with a solu- 
tioQ of a caustic alkali, they ore decomposed, and as the result of 



tbe decompoAiiirtn therenre formed two new bodies; firsl, glycerine, 
wbicb is a oeutntl fluid aubstance, and secomlly, a fiitty acii^, vi/ : 
oleic, megoric, or stearic acid, corresponding to the ]i\ut\ uf fnt 
which liua Iwon used in iliu experimuiii. Th^ glye«rin» remains in 
a free stotc, while the fatty acid unites ^s'lih tlie alkali employed, 
forming an oieate, margnrate, or stearate. Tliis coiubinatiun i8 
termed a soap, and the process by wbicb iE is forniei] is culled 
Kij'oni/icalion. Tliis process, however, is not a simple dec;omposliion 
nf iho fatty bmly, aince it can only take placo iti iho presence of 
water; several equivalents of which unite with the elements of the 
fatty body, and enter into the composition of the glycerine, &c., so 
that the fatty acid and the glycerine together weigh more than tbe 
original fatty substance which was decomposed. It is not proper, 
therefore, to regard nn oleaginous body as formed by the union of a 
fatty acid with glycerine. Ft is formed, on the contrary, in all ^iro- 
babiUty, by the direct combination uf its ultiumle chemical elements. 
The diSerent kinds of oil, fat, lard, suet, &e., cx>ntaia the three 
oleaginous matters mentioned above, mingled together in difli-ront 
proportions. The more solid fata contain a larger quantity of 
alearine and margarine; the less consistent varieties, a larger pro- 
portion of uleinc. Neither of the oleaginous matters, stearine, 
margarino, or oleine, ever occur separately ; but in every fatty sub- 
stance ihey are mingled together, so that the more fluid of them hold 
in solution the more solid. 

Generally speakiug, in the !'>«. 7. 

living body, these fni.\turc8 
ire fluid or nearly so; for 
though both stearine and 
margarine are solid, when 
pure, at tbe onlinnry tem- 
perature of the body, lliey 
are held in solution, during 
life, by the olcine with which 
Ibey are associated. After 
death, however, aa the body 
cools, the stearino and mar- 
garine sometimes separate 
twm the mixture in a crys- 
lallinc form, since the oleine 
cao DO longer hold in sola- 
two so large a quantity of them as it had dissolved at a higher 
temperature. 



>^-- 



STIi4mia> cr/SlBUlml frnm n Warm jolnlloii la 



72 PEOXIHATE PElNCrPLBS Or THE SECOND CLASS. 

These substances cryslalliKO in very slender noodles, wliich arc 
aometiinea straiglit, but more often somewhat curved or wavy in 
their outlino. (Fig. 7.) 

They are always deposited in a more or less radiated form ; and 
liave sometimes a very elegant, branched, or arborescent arrange- 
iiiont. 

When in a fluid elate, the fatly aubstances present ihemselves 

under the form of drops or 



Rs.S. 



O 



O 



globules, which vary indefi- 
nitely in size, but which 
may be readily recognized 
by their oplical properties. 
They are circular in shape, 
and have a faint amber color, 
distinct in the largerglobules, 
leaa so in the smaller. They 
have a sharp, well defined 
oailine (Fig. 8); and as ihey 
refract the light strongly, 
and act therefore as double 
convex lenses, they present 
a brilliant ccntre,surrounded 
by a dark border. These 
marks will generally be 

sufficient to distin^uiah ihem under the microscope. 
The following lint aliowa the percentnge of oily matter present in 

various kinds of animal and vegetable food." 

QuAtrrnv or Fat iir 100 pakts ix 



o 



Or.KAiiiiiAyi PaiKi^iPi.ta lie He max F4t. 



FEIberta . 


60.00 


Ordinary moftt 


. U.30 


WttlimU 


60.00 


Liver of ihe ox 


. S.89 


CoooA-nuu . , 


47-00 


Cow's [uiLk , 


. 3.13 


OliVM . 


32.00 


Ilmnnn milk 


. 3.55 


I.itiseed . . . 


22.00 


Aasua' uiitlc . . 


. 0.11 


lliilinci com . . 


9.00 


Ijodta' milk . 


. s.3a 


Tolk of «ggs . 


28.00 







The oleaginous matters present a striking peculiarity as to the 
form under which ihcy exist in the animal body; a ])cculiarity 
which distinguishes them from oil the other proximate principles. 
The rest of the proximate principles are all intimately associated 
together by molecular anion, so us to form either clear solutions or 



■ F*r«]re, op. cit.,p. 81- 



FATS. 78 

homogeneous solids. Thus, the sugars of the blood are in solution 
io water, in company with the albumen, the phosphate of lime, 
chloride of sodium, and the like; all of them equally distributed 
throughout the entire mass of the fluid. In the bon^ and car- 
tilages, the animal matters and the calcareous salts are in similarly 
intimate union with each other; and in every other part of the 
body the animal and inorganic ingredients are united in the same 
way. But it is different with the fats. For, while the three prin- 
cipal varieties of oleaginous matter are always united with each 
other, they are not united with any of the other kinds of proximate 
principles ; that is, with water, saline substances, sugars, or albu- 
minous matters. Almost the only exception to this is in the nerv- 
ous tissue; in which, according to Robin and Yerdeil, the oily 
matters seem to be united with an albuminoid substance. Another 
exception is, perhaps, in the bile ; since some of the biliary salts 
have the power of dissolving a certain quantity of fat. Every- 
where else, instead of forming a homogeneous solid or fluid with 
the other proximate principles, the oleaginous matters are found 
in distinct masses or globules, which are suspended in serous fluids, 
interposed in the interstices between the anatomical elemeute, in- 
cluded in the interior of cells, or deposited in the substance of 
fibres or membranes. Even in the vegetable tissues, the oil is 
always deposited in this manner in distinct drops or granules. 

Owing to this fact, the oils can be easily extracted from the 
organized tissues by the employment of simply mechanical pro- 
cesses. The tissues, animal or vegetable, are merely cut into small 
pieces and subjected to pressure, by which the oil is forced out 
from the parts in which it was entangled, and separated, without 
any further manipulation, in a state of purity. A moderately 
elevated temperature facilitates the operation by increasing the 
fluidity of the oleaginous matter ; but no other chemical agency is 
required for its separation. Under the microscope, also, the oil- 
drops and granules can be readily perceived and distinguished 
from the remaining parts of the tissue, and can, moreover, be 
easily recognized by the dissolving action of ether, which acts 
upon them, as a general rule, without attacking the other proxi- 
mate principles. 

Oils are found, in the animal body, most abundantly in the 
adipose tissue. Here they are contained in the interior of the 
adipose vesicles, the cavities of which they entirely fill, in a state 



74 PROXIMATE PEiyCIPLBS OF TOE SKC< 



of health. 'rh( 



I'twiules 



IT«1 



Ks-9- 



Ni 



HCMAM ADiroii TitaVB. 



e 11 MJinewhflt 
cotnpreiwioii. (Fig. it.) Thev 
vary in diameter, in iho liii- 
mmi subject, Trom aJe*^ sio 
of nn inch, nml fire composeit 
of a tLiij, structureless ani- 
rniil membrane, forming n 
closctl sac, in the interior of 
which the oily matter la con- 
tiiincd. There is hmv, aucord • 
ingly, no union whatever of 
iho oil with the other proxi- 
mate principles, but only a 
mechanical inclusion of it in 
the interior of the vesicles. 
Somclimca, when ctnacialion 
19 going on, the oil partinlly 
disappears from the cavity of 
the adipose vesicle, and ita place is taken by a watery serum; but 
the eeruua and oily fluids always remain distinut, and occupy difler 
cnt parts of the cj]vity of the vesicle. 

In the chyle, the oleaginous matter is in a state of emulsicn or 
suspension in the form of minute pnrticles in a serous fluid. Its 

subdivision is hero more cora- 
Pig. 10. plele, nnd its molecules more 

minutc,lbciuanywhereolse in 
ihe boily. It presents the ap- 
pearance (if a fine granular 
dust, which has been known 
by the name of the "molecu* 
Inr base of the chyle." A 
few of these gronules are to 
be seen which mensure nt^flo 
of an inch in diameter; but 
they are generally much less 
than this, and the greater part 
are so small that they cannot 
be accurately measured. (I'ig. 
10.) For the same reason 
they do not present the bril- 
liant centre and dark border of the larger oil-globules ; but appear 



I 






CirTkr. front M>mm«n(ODi*aI ot ThonMla Dii«t, 
Fran Iha l>i:ig. 




FAT8. 



76 



bj traDHmitted light only as minute dark granules. The white 
color and opacity of the chyle, as of all other fatty emulsiooa, 
depend upon this molecular condition of the oily ingredients. The 
albumen, salts, &o^ which are in intimate union with each other, 
and in solution in the water, would alone make a colorless and 
transparent fluid; but the oily matters, suspended in distinct par- 
ticles, which have a different refractive power from the serous fluid, 
interfere with its transparency 
and give it the white color and 
opaque appearance which are 
characteristic of emulsions. 
The oleaginous nature of these 
particles is readily shown by 
their solubility in ether. 

In the milk, the oily matter 
occurs in larger masses than 
in the chyle. In cow's milk 
(Fig. IIX these oil-drops, or 
"milk-globulea," are not quite 
fluid, but have a pasty con- 
sistency, owing to the large 
qoantity of margarine which 
they contain, in proportion to 

the oleine. When forcibly amalgamated with each other and 
collected into a mass by prolonged beating or churning, they con- 
stitute butter. In cow's milk, 




OLOBCtLII OP COW'l HiLK. 



the globules vary somewhat 
in size, but their average 
diameter is f^^is of "i" inch. 
They are simply suspended 
io the serous fluid of the 
milk, and are not covered 
with any albuminous mem- 
brane. 

In the cells of the laryn- 
geal, tracheal, and costal car- 
tilages (Fig. 12), there is 
always more or less fat de- 
posited in the form of round- 
ed globules, somewhat similar 
to those of the milk. 



Fig. 12. 




CiLL* OrCotTAL CAITILAntl, CODtalalDgOll- 

Olobnlai. UamtD. 



76 PROXIMATE PBiyciPLBS OT THE SECOXD CLASS. 



Hsr«Tiv C1LI.A Hnman. 



In the glandalar cells of the liver, oil occurs coustantly, in a 

8tate of bealtli. It is hero deposilod in tho substance or the cell 

(Fig. 18), generally in smaller 
^' ^^- globules than the preceding. 

In some cases of disease, it 
accumulates in excessive 
quantity, and produces the 
state known as fatty degcnft- 
ralion of the liver. This is 
cunsaquL'Dtly only an aX' 
Rggeraled condition of that 
which normally exists in 
health. 

In the carnivorous animals, 
oil exists in considerable 
quantity in the convoluted 
portion of the uriniferous 
tubules. (Fig. 14.) It is here 

in the form of granules and rounded dropti, which sometirnes appear 

to fill nearly tlie whole calibre of the tubules. 
It is found also in the secreting cells of the sebaceous and other 

glandules, deptjsited in the 
Pig- 1^ same niaDocr as in those of 

the liver, but in smaller 
quantity. It exists, beside, 
in large proporLion, in a 
granular form, in the secre- 
tion of the sebaceous gland- 
iiles. 

It occurs nbnndantly in 
llie marrow of the bones, 
both under the form of free 
oil-globules and inclosed in 
the vesicles of adipose tissue. 
It is found inconsiderable 
quantity in the substance of 
the yellow wall of the corpna 
luteum, and is the immediate 

cause of the peculiar color of this lx>dy. 
It occurs also in the form of granules and oil-drops in the 

muscular (Ibrcs of the uterus (Fig. 15), in which il begins to be 



f^c 



raiaiFHKOL-i TEKViiBaor D«W, froai Cortical 
PunloD uf Kviapf, 




FATS. 



77 




->^ 




Hdicdlak Ftbrbiuf Hoham tTTBKDi, thrv* 
wMki ■.fter inrtvrtlloB. 



rieposited soon af^r delivery, and where it continues to be present 
daring the whole period of the resorption or involution of this organ. 

In all these instances, the oleaginous matters remain distinct in 
form and situation from the 
other ingredients of the ani- ^'8- !*■ 

mal frame, and are only me- 
chanically entangled among 
its fibres and cells, or im- 
bedded separately in their 
interior. 

A large part of the fat 
which is found in the body 
may be accounted for by that 
which is taken in with the 
food, since oily matter occurs 
in both animal and vegetable 
substances. Fat is, however, 
formed in the body, independ- 
ently of what is introduced 
with the food. This im- 
portant &ct has been deSnitely ascertained by the experiments of 
MM. Pumas and Milne- Edwards on bees,' M. Persoz on geese,* and 
finally by those of M. Boussingault on geese, ducks, and pigs.' The 
observers first ascertained the quantity of fat existing in the whole 
body at the commencement of the experiment. The animals were 
then subjected to a definite nutritious regimen, in which the 
quantity of fatty matter was duly ascertained by analysis. The 
experiments lasted for a period varying, in-different instances, from 
thirty-one days to eight months; after which the animals were 
killed and all their tissues examined. The result of these investi- 
gations showed that considerably more fat had been accumulated 
by the animal during the course of the experiment than could be 
accounted for by that which existed in the food; and placed it 
beyond a doubt that oleaginous substances may be, and actually 
are, formed in the interior of the animal body by the decomposition 
or metamorphosis of other proximate principles. 

It is not known from what proximate principles the fat is pro- 
duced, when it originates in this way in the interior of the body. 
Particular kinds of food certainly favor its production and accu- 



< Annales de Chim. et de Pfays., 3d series, vol. zfv. p. 400. ' Ibid., p. 408. 
*Chimie Agricole, Paris, 1854. 



78 PROXIMATE fRlNClPLKS OF THE SSCOKD CLA39. 



I 



I 

i 



mulfltion to a cotiaiderable (degree. It is well known, for instance, 
that in augnr-growiiig countries, as in Louisiann and tlie Wwl 
ladies, during the (mw weeks occupied in gatherings the cane nnd 
exlractiug tlie sugar, all the negroes employed on the phiniali'ins. 
nnd even the horses and cattte, ihat are allowed to feed freely on 
the saccharine juices, grow remarkably fat; and that they again lose 
their aiijierabundunt fleiih when the seiisun is past. Kven in these 
instances, however, it is not certain whether the saccharine substances 
are directly converted into fat, or vfhcther they are first assimilated 
and only afterward supply the materials lor its production. The 
abundant accuruulatioa of fat in certain regions of tb« body, and its ■ 
absence in others; nnd more particularly its constant occurrence in 
certain situaiinii.i to which it could not bu transported by the blood, 
as for example the interior of the cells of the costal cartilages, the 
substance of the muscular fibres of the nterus after parturition, &c., 
make it probable that under ordinary conditions the oily matter is 
formed by decomposition of the tissues upon the very spot where ii 
subsequently makes its appearance. 

In ih'6 female durinj^ lactation a large part of the oily matter 
introduced with the food, or formed in the body, is discharged with 
the milk, and goes to the support of tho infant. But in the female 
in the intervals of Inctntion, nnd in the male at all times, the oily 
matters almost entirely disappear by decomposition in the interior 
of the body; since the small quantity which is discharged with the 
sebaceous matter by the slcin bears only an insignificant proportion 
to that whicli is introduced daily with the footl. 

Tli« most important characteristic, in a physiological point of 
view, of ihc proximate principles of the second class, relates to their 
origin and their final deslinaliou. Not only arc they all of a purely 
organic origin, making their appearance first in the interior of vege- 
tables; but the sugars and the oils are formed also, to a certain ex- 
tent, in the bodies of animals; contioaing to make ihcir appearance 
when uo similar substances, or only an insulTicient quantity of them, 
have been taken with the food. Furihcrmorc, when introduced 
with the fofwl, or formed in the body and de])osited iu the tissues, 
these substances do not reappear in the secretions. They, therefore, 
for the most part disappear by decomposition in the interior of the 
body. They paw? through a series of changes by wiiicii their es- 
sential characters are destroyed; and they are finally replaced in 
the circulation by other substances, which are discharged with ibe 
CKcrclcd fluids. 




PROXIUATE I'RINCIPLES OF THE THIRD CLASS. 79 



CHAPTER IV. 

PROXIMATE PRINCIPLES OF THE THIRD CLASS. 

The sabstaDces belonging to this class are very important, and 
form by far the greater part of the entire mass of the body. They 
are derived both from animal and vegetable sources. They have 
been known by the name of the " protein compounds" and the 
"albuminoid substances." The name organic substances vr&a given 
to them by Robin and Yerdeil, by whom their distinguishing pro- 
perties were first accurately described. They have not only an 
organic origin, in common with the proximate principles of the 
eecond class, but their chemical constitution, their physical struc- 
ture and characters, and the changes which they undergo, are all so 
different from those met with in any other class, that the term "or- 
ganic substances" proper appears particularly appropriate to them. 

Their first peculiarity is that they are not cryatallizable. They 
always, when pure, assume an amorphous condition, which is some- 
times solid (organic substance of the bones), sometimes fluid (albu- 
men of the blood), and sometimes semi solid in consistency, midway 
between the solid and fluid cotidition (organic substance of the 
muscular fibre). 

Their chemical constitution differs from ihat of bodies of the 
second class, first in the fact that they all contain the four chemical 
elements, oxygen, hydrogen, carbon, and nitrogen ; while the 
starches, sugars, and oils are destitute of the last named ingredient. 
The organic matters have therefore been sometimes known by the 
name of the "nitrogenous substances," while the sugars, starch, and 
oils have been called "non-nitrogenous." Some of the organic mat- 
ters, viz., albumen, fibrin, and casein, contain sulphur also, as an in- 
gredient; and others, viz., the coloring matters, contain iron. The 
remainder consist of oxygen, hydrogen, carbon, and nitrogen alone. 

The most important peculiarity, however, of the organic sub- 
stances, relating to their chemical composition, is that it is not 
ilefinite. That is to say, they do not always contain precisely the 



80 PROXIMATE PRINCIPLES OF THE THIRD CLASS. 

snme proportions of oxygen, hydrogen, carbon, and nitrogen; but 
the relative qiiantiiies of these elements vary within certain limits, 
in diPlerent iiulividiiaU and at different limes, without modifying, in 
any essential degree, the peculiar properties of the animal matters 
which they uonatitute. This fact is altogether a special one, and 
charactorititic of organic sulcata nces. No snbstnnco having a definite 
chemical compoaiilon, like phosphate of lime, starch, or olein, can 
suffer the slightest change in its ultimate constitution without being, 
by that fact alone, totally altered in its essential properties. It 
phosphate of lime, for example, were to lose one or two equivalcnta 
of oxygen, an entire destruction of the salt would necessarily result^ 
and it would cense to be phosphate of lime. For its properties as a 
salt depend entirely upon its ultimate cheraital constitution ; and if 
the tatter be changed in any way, the former are necessarily lost. 

But ihe properties which dislinguiah the organic substances, and 
which make them important as ingredients of the body, do not 
depend immediately upon their ultimate chemical constitution, and 
are of a peculiar character; being such as are only manifested in 
the interior of the living organism. Albumen, therefore, though 
it may contain a few equivalents more or less of oxygen or nitrogen, 
docs not on that account cease to be albumen, so long as it retains 
its fluidity and its aptitude for nudcrgoing the procesjies of absorp- 
tion and transformation, which characterize it ns an ingredient of 
the living body. 

It is for this reason that considernhle discrepancy has existed at 
various times among chennsts as to the real ultimate composition 
of these substances, difterent experlmentera often obtaining differ- 
ent analytical results. This is not owing to any inaccuracy in the 
analyses, but to the fact thai the organic substance itself really has 
a different ultimate constitution at different times. The most ap- 
proved formula) are those which have been established by Liebig 
for the following substances: — 

i-'ibrin = Cj„H,eK„0„S, 

AlbDinon -- Cj„H,e,N„(J^ 

C"-'n = t^^ltmN^O^'*, 

Owing to the above mentioned variations, however, tho samo 
degree of importance does not attach to the quantitative ultimate 
analysis of an organic matter, as tu that of other substances. 

This absence of a deQnite chemical constitution, in tho organig sub- 
alaiicea is undoubtedly connected with their incapacity for crystalli- 
zation, it is also connected with another almost equally [>cculiHr 




OBOANIC SUBSTANCES. 81 

&ct, tIz^ tliat although the organic substances unite with acids and 
vith alkalies, they do not play the part of an acid towards the base, 
or of a base toward the acid; for the acid or alkaline reaction of 
the sabstance employed is not neutralized, but remains as strong 
after the combination as before. Furthermore, the union does not 
take place, so far as can be ascertained. Id any definite proportions. 
The organic substances have, in fact, no combining equivalent; and 
tbeir molecular reactions and the changes which they undergo in 
tbe body cannot therefore be expressed by the ordinary chemical 
phrases which are adapted to inorganic substances. Their true 
characters, as proximate principles, are accordingly to be sought 
for in other properties than those which depend upon their exact 
nltimate composition. 

One of these characters is that they are hygroscopic. As met with 
in difi^erent parts of the body, they present different degrees of con- 
sistency; some being nearly solid, others more or less fluid. But on 
being subjected to evaporation they all lose water, and are reduced 
to a perfectly solid form. If after this desiccation they be exposed 
to the contact of moisture, they again absorb water, swell, and 
regain their original mass and consistency. This phenomenon is 
quite different from that of capillary attraction, by which some in- 
organic substances become moistened when exposed to the contact 
of water; for in the latter case the water is simply entangled me- 
chanically in the meshes and pores of the inorganic body, while that 
which is absorbed by the organic matter is actually united with its 
sabstance, and diffused equally throughout its entire mass. Every 
organic matter is naturally united in this way with a certain quantity 
of water, some more and some less. Thus the albumen of the blood 
is in union with so much water that it has the fluid form, while the 
organic substance of cartilage contains less and is of a firmer con- 
sistency. The quantity of water contained in each organic sub- 
stance may be diminished by artificial desiccation, or by a deficient 
supply ; but neither of them can be made to take up more than a 
certain amount Thus if the albumen of the blood and the organic 
substance of cartilage be both reduced by evaporation to a similar 
degree of dryness and then placed in water, the albumen will absorb 
EG much as again to become fluid, but the cartilaginous substance 
ouly so much as to regain its usual nearly solid consistency. Even 
where the organic substance, therefore, as in the case of albumen, 
becomes fluid under these circumstances, it is not exactly a solution 
6 



PBOSIMATB PRTNCTPLBS OP THB THIRD CLASS. 
^ 

of it in waler, but only a reabsorption by it of tbat quantity of fluid 

witli wbicli it is naturally associated. 

Another peculiar pbenometion cbaracleristic of organic subf^tances 
is tbcir ooa^ihtion. Those which arc naturally fluid suddenly a8> 
suroe, under ceriain conditions, a solid or semi-solid consistency. 
They are then said to bn coagulated ; aud ailer coajjulalion lliey 
cannot bo made to resume their original condition. Thus fibrin 
coagulatea on being withdrawn from the blood veaacis, albumen on 
being subjected to the lemperature of boiling water, casein on being 
placed iu contact with an acid. When an orgsnic substance thus 
coagulates, the clmiige wbluh tnkus plucc is a peculiar one, aud has 
no resemblnnce to the precipitation of a solid substance from a 
watery solution. On the contrary, the organic substancu merely 
assumes a special condition; and in passing into the solid form it 
retains all the water with which it was previously united. Albumen, 
for example, after coagulation, retains the same quntility of water in 
union with it, which it held before. After coagulation, accordingly, 
this water may be driven off by evaporation, in the same manner 
as previously ; and on being again exposed to moisture, the organic 
matter will again absorb the same quantity, though it will not re- 
sumo the fluid form. 

By coagulation, an organic substance is permanently altered ; and 
though it may be afterwards dissolved by certain chemical ro-agcnis, 
as, for example, the caustic alkalies, it is not thereby restrired to its 
original condition, but only suffers a still further alteration. 

In many instances we are obliged to resort to coagulation in 
order to separaLo an organic substance from the other proximMe 
principles with which it is associated. This is the case, for example, 
with the fibrin of the blood, which is obtained in the form of floc- 
ciili, by beating freshly drawn blood with a bundle of rods. But 
when Bcparulcd in thi^ way, it is already in an unnatural condition, 
and no longer represents exactly ilie original fluid fibrin, as it ex- 
isted in the circulating blo»l. Nevertheless, this is the only mode 
in which it can be examined, as there are no means of bringing it 
back to its previous cuuditioTi. 

Another important property of the organic substances is that 
they readily excite, in other proximate principles and in each other, 
those peculiar indirect chemical ciiangcs which are termed catalyses 
OTcaialytic trana/orTnations. That is to say, they produce the changes 
referred to, not directly, by combining with the substance which 
suffers alteration, or with any of its ingredients; but simply by their 



I 



I 



I 
I 
I 




OROAKIC SUBSTANCES. 83 

presence, which induces the chemical change in an indirect manner. 
Thas, the organic sabstances of the intestinal fluids induce a cata- 
lytic action by which starch is converted into sugar. The albumen 
of the blood, by contact with the organic substance of the muscular 
fibre, is transformed into a substance similar to it. The entire 
proces of nutrition, so far as the organic matters are concerned, 
consists of such catalytic transformations. Many crystallizahle 
Bulstances, which when pure remain unaltered in the air, become 
changed if mingled with organic substances, even in small quantity. 
Thus the casein of milk, after being exposed for a short time to a 
warm atmosphere, becomes a catalytic body, and converts the sugar 
of the milk into lactic acid. In this change there is no loss nor 
addition of any chemical element, since lactic acid has precisely the 
same ultimate composition with sugar of milk. It is simply a 
transformation induced by the presence of tbe casein. Oily matters, 
which are entirely unalterable when pure, readily become rancid at 
warm temperatures, if mingled with an organic impurity. 

Fourthly, The organic substances, when beginning to undergo 
decay, induce in certain other substances the phenomenon oi fer- 
mentation. Thus, the mucus of the urinary bladder, after a short 
exposure to the atmosphere, causes the urea of the urine to be con- 
verted into carbonate of ammonia, with the development of gaseous 
bubbles. The organic matters of grape juice, under similar circum- 
stances, give rise to fermentation of the sugar, by which it is con- 
verted into alcohol and barbonic acid. 

Fifthly, The organic substances are the only ones capable of 
undergoing the process of putrefaction. This process is a compli- 
cated one, and is characterized by a gradual liquefaction of tbe ani- 
mal substance, by many mutual decompositions of the saline matters 
which are associated with it, and by the development of peculiarly 
fetid and unwholesome gases, among which are carbonic acid, 
nitrogen, sulphuretted, phosphoretted, and carburetted hydrogen, 
and ammoniacal vapors. Putrefaction takes place constantly after 
death, if the organic tissue be exposed to a moist atmosphere at a 
moderately warm temperature. It is much hastened by the presence 
of other organic substances, in which decomposition has already 
commenced. 

The organic substances are readily distinguished, by the above 

general characters, from all other kinds of proximate principles. 

•They are quite numerous; nearly every animal fluid and tissue 

containing at least one which is peculiar to itself. They have not 

as yet been all accurately described. The following list, however, 



PKOXniATE PKINCIPLES OF THE THIRD CLAS8. 



comprises the most important of them, and those with which we are i 
at present most thorntighly acquainted. The first seven are fluid,' 
or uearly so, and uilhvr colorless or of a faint yellowish tinge. 

1. Fibrin, — Fibrin is found in the blood; where it exists, in thi 
human subject, in the proportion of two to three parts per thousand. 
It is fluid, and mingled intimately with the other ingredients of the 
blood. It occur»^ also, but in much smallor quantity, in the lymph. 
It is distingniahed by what is called its "spontaneous" coagulation; 
that is, it coagulates un being withdniwn from the vessels, or on the 
occurrence of any stoppage to the circolation. It is rather mora 
abundant in the blood of some of the lower animals than in that of 
the human subject. In general, it is found in larger quantity ia 
the blood of the herbivora than in that of the carnivora. 



I 



2. Albumen. — Albumen occurs in the blood, the lymph, the 
fluid of the pericardium, end in that of the serous cavities gene* 
rally. It is also present in the fluid which may bo extracted by 
pressure from the muscular tissue. In the bloo<l it occurs in the 
proportion of about seventy-five parts per thousand. The while of 
egg, which usually goes by the same name, is not identical with the 
albumen of the blood, though it resembles it in some respects; it is 
properly a secretion from the mucous membrane uf the fowl's ovi- 
duct, and should bo considered as a distinct organic substance. 
Albumen coagulates on being raised to the temperature of l(iO° K.; 
and the coagulum, like that of all the other proximate principles, ia 
soluble in cauatic poinssn. It coagnlates also by contact with alco- 
hol, the mineral ncidSj ferrocyanide of potJissium in an acidulated 
solution, tannin, and the inctallic salts. The alcoholic coagulum, if 
separnted from the alcohol by washing, does not xedissolve in water. 
A very small quantity of albumen has been sometimes found in the 
saliva. 



I 



a. Casein. — This substance exists in milk, in the proportion of 
about forty puns per thousand. It coagulates by coatact with all _ 
the acids, mineral and organic; hut is not aflectcd by a boiling I 
temperature. It is coagulated also by the juices of the stomach. 
It is important as an article of food, being the principal organic 
ingredient in all the preparations of milk. In a coagulated form, it 
constitutes the difli^rcnt varietiea of cheese, which are more or less 
highly flavored with various oily matters remaining entangled in 
the coagulated ca»i>in. 




GLOBULINE.— HUCOSINE. 86 

What is called vegetable casein or "legumioe," is diflrereut from 
the casein of milk, and constitutes the organic Bubstance present in 
rarioos kinds of peas and beans. 

4. OLOBULiifB. — This is the organic substance forming the prin- 
cipal mass of the red globules of the blood. It is nearly fluid in 
its natural condition, and readily dissolves in water. It does not 
dissolve, however, in the serum of the blood; and the globules, 
therefore, retain their natural form and consistency, unless the 
serum be diluted with an excess of water. Globuline resembles 
albumen in coagulating at the temperature of boiling water. It is 
said to differ from it, however, in not being coagulated by contact 
with alcohol. 

5. Pbpsine. — This substance occurs as an ingredient in the gas- 
tric juice. It is not the same substance which Schwann extracted 
by maceration from the mucous membrane of the stomach, and 
which is regarded by Robin, Bernard, &c., as only an artificial pro- 
duct of the alteration of the gastric tissues. There seems no good 
reason, furthermore, why we should not designate by this name the 
oi^anic substance which really exists in the gastric juice. It occurs 
in this fluid in very small quantity, not over fifteen parts per 
thousand. It is coagulable by heat, and also by contact with alco- 
hol. But if the alcoholic coagalum be well washed, it is again 
soluble in a watery acidulated fluid. 

6. Pancreatine. — This is the organic substance of the pancreatic 
juice, where it occurs in great abunddnce. It coagulates by heat, 
and by contact with sulphate of magnesia in excess. In its natural 
condition it is fluid, but has a considerable degree of viscidity. 

7. Mdcosine is the organic substance which is found in the dif- 
ferent varieties of mucus, and which imparts to them their viscidity 
and other physical characters. Some of these mucous secretions 
are so mixed with other fluids, that their consistency is more or less 
diminished ; others which remain pure, like that secreted by the 
mucous follicles of the cervix uteri, have nearly a semi-solid con- 
BJstency. But little is known with regard to their other specific 
characters. 

The next three organic substances are solid or semi-solid in con- 
sistency. 



86 PROXIMATE PRINCIPLES OF THE THIRD CLASS. 

8. Osteins is the organic substance of the bones, in which it is 
associated with a large proportion of pkosphate of lime. It exists, 
in those bones which have been examined, in the proportion of 
about two hundred parts per thousand. It is this substance which 
by long boiling of the bones is transformed into gelatine or glue. 
In its natural condition, however, it is insoluble in water, even at 
the boiling temperature, and becomes soluble only afler it has been 
permanently altered by ebullition. 

9. Cartilag-ine. — This forms the organic ingredient of cartilage. 
Like that of the bones, it is altered by long boiling, and is converted 
into a peculiar kind of gelatine termed "chondrine." Chondrine 
differs from the gelatine of bones principally in being precipitated 
by acids and certain metallic salts which have no effect on the latter, 
Cartilagine, in its natural condition, is very solid, and is closely 
united with the calcareous salts. 

10. MuscDLlNE. — This substance forms the principal mass of the 
muscular fibre. It is semi-solid, and insoluble in water, but soluble 
in dilute muriatic acid, from which it may be again precipitated by 
neutralizing with an alkali. It closely resembles albumen in its 
chemical composition, and like it, contains, according to Soberer, 
two equivalents of sulphur. 

The four remaining organic substances form a somewhat peculiar 
group. They are the cohring matters of the body. They exist 
always in small quantity, compared with the other ingredients, but 
communicate to the tissues and fluids a very distinct coloratioo. 
They all contain iron as one of their ultimate elements. 

11. H^HATINE is the coloring matter of the red globules of the 
blood. It is nearly fluid like the globuline, and is united with it 
in a kind of mutual solution. It is much less abundant than the 
globuline, and exists in the proportion of about one part of hsBma- 
tine to seventeen parts of globuline. The following is the formula 
for its composition which is adopted by Lehmann: — 

Enmatine = C^^Bt^fi^Fe. 

When the blood-globules from any cause become disintegrated, the 
hsmatine is readily imbibed afler death by the walls of the blood- 
vessels and the neighboring parts, staining them of a deep red 
color. This coloration has sometimes been mistaken for an evidence 



HELANl!rE.— UB03ACINS. 87 

of arteritis; but is really a simple effect of post-roortera imbibition, 
as above stated. 

12. Mklanine. — This is tbe blackisb-brown coloriog matter 
whicb is found in the choroid coat of the eye, the iris, the hair, and 
more or less abundantly in the epidermis. So far as can be ascer- 
tained, tbe coloring matter is the same in all these situations. It is 
very abundant in the black and brown races, less so in the yellow 
and white, but is present to a certain extent in all. Even where 
the tinges produced are entirely different, as, for example, in brown 
and blue eyes, the coloring matter appears to be the same in cha- 
racter, and to vary only in its quantity and the mode of its arrange- 
ment; for the tinge of an animal tisane does not depend on its 
local pigment only, but also on the muscular fibres, fibres of areolar 
tissue, capillary bloodvessels, &c. All these ingredients of the 
tissue are partially transparent, and by their mutual interlacement 
and superposition modify more or less the effect of the pigment 
which is deposited below or among them. 

Melanine is insoluble in water and the dilute acids, but dissolves 
slowly in caustic potassa. Its ultimate composition resembles that 
of hsematine, but the proportion of iron is smaller. 

13. BlLTVERDlNB is the coloring matter of the bile. It is yellow 
by transmitted light, greenish by reflected light On exposure to 
the air in its natural fluid condition, it absorbs oxygen and assumes 
a bright grass green color. The same effect is produced by treating 
it with nitric acid or other oxidizing substances. It occurs in very 
small quantity in the bile, from which it may be extracted by pre- 
cipitating it with milk of lime (Robin), from which it is afterward 
separated by dissolving out the lime with muriatic acid. Obtained 
in this form, however, it is insoluble in water, having been coagu- 
lated by contact with the calcareous matter; and is not, therefore, 
precisely in its original condition. 

14. ITrosacine is the yellowish red coloring matter of the urine. 
It consists of the same ultimate elements as the other coloring mat- 
ters, but occurs in the urine in such minute quantity, that the 
relative proportion of its elements has never been determined. It 
readily adheres to insoluble matters when they are precipitated from 
the urine, and is consequently found almost always, to a greater or 
less extent, as an ingredient in urinary calculi formed of the urates 



88 



PROXIMATE PRIN0TPLE9 OF THB THIttD CLASS. 



or of uric auid. Wben tlio uratua are thrown down also in tlie form 

of a powder, as a urinary deposit, they are usually colored more or 
less deeply, according to the quantity of urosacine which is preci- 
pitated with them. 



The organic substances which exist in tho body require for their 
production un abundant supply of similar substances in the food. 
All highly nutritions articles of diet, therefore, contain more or less 
of these substances. Still, though nitrogenous matters must be 
abundantly supplied, under tsDnie form, from without, yet the par- 
ticular kinds of organic substances, charactcriatic of the tissues, are 
formed in the body by a iransfonnation of thuso whicli are intro- 
duced with the food. The organic matters derived from vegetables, 
though similar in their general characters to thoae existing in the 
animal bwly, are yet specifically diflerenl. The gluten of wheat, 
the legumine of peas and beans, are not the same with animal albu- 
men and fibrin. The only organic substances taken with animal 
food, as a general rule, are the albumen of eggs, the casein of milk, 
and the musculiuc of flesh; and even thu^c, in tho food of the 
human spooies, are so altered and coagulated by the process of 
cooking, as to lose their specific characters before being introduced 
into the alimentary canal. They are still further changed by the 
process of digestion, and are absorbed under another form into the 
blood. But from their subsequejit mctamorplmaes there arc formed, 
in the diS'erent parts of the body, ostcine, carlilagine, ha^matine, 
globuline, and all the other varieties of organic matter that cha- 
racteriise tho difierent tissues. These varieties, therefore, originate 
as such in the animal economy by tho catalytic changes which the 
ingredients of the blood undergo in nutrition. 

Only a very smalt quantity of organic matter is discharged 
with the excretions. The coloring matters of the bile and urine, 
and the mucus of the urinary bladder, are almost the only ones 
that find an exit from the body in this way. There is a minute 
qunritity of organic matter exhaled in a volatile form with the 
breath, and a little also, in all probability, from the cutaneoua sur- 
face. But tho entire quantity so discharged bears but a very small 
proportion to that which ia daily introduced with the food. The 
organic suKstanccs, therefore, arc decomposed in the interior of the 
body. They are transformed by the process of destructive assimi- 
lation, and their elements are fioally eliminated and discharged 
under other forma of combination. 



4 

I 




OF FOOD. 89 



CHAPTER V. 

OP POOD. 

Under the term "food" are included all those substances, solid 
and liquid, which are necessary to sustain the process of nutrition. 
The first act of this process is the absorption from without of all 
those materials which enter into the composition of the living frame, 
or of others which may be converted into them in the interior of 
the body. 

The proximate principles of the first class, or the "inorganic 
aubstances," require to be supplied in sufficient quantity to keep up 
the natural proportion in which they exist in the various solids and 
fluids. As we have found it to be characteristic of these substances, 
except in a few instances, that they suffer no alteration in the in* 
terior of the body, but, on the contrary, are absorbed, deposited in 
itsiiasue, and pass out of it aflerward unchanged, nearly every one 
of them requires to be present under its own proper form, and in 
sufficient quantity in the food. The alkaline carbonates, which 
are formed, as we have seen, by a decomposition of the malates, 
citrates and tartrates, constitute almost the only exception to this 
rule. 

Since water enters so largely into the composition of nearly every 
part of the body, it is equally important as an ingredient of the 
food. In the case of the human subject, it is probably the most 
important substance to be supplied with constancy and regularity, 
and the system suffers more rapidly when entirely deprived of 
fluids, than when the supply of solid food only is withdrawn. A 
man may pass eight or ten hours, for example, without solid food, 
and suffer little or no inconvenience; but if deprived of water for 
the same length of time, he becomes rapidly exhausted, and feels 
the deficiency in a very marked degree. Magendie found, in his 
experiments on dogs subjected to inanition,' that if the animals 

> Compteg Rendns, vol. xiif. p. 256. 



so 



'OOD. 



were suppHed with wntcr alone tlicy liveil six, eight, and even ten 
days longer than if they were depri?ed at the same time of both 
solid and liquid food. Chloride of sodium, also, is usually added 
to the food in considcrablo quiiutity, and roquirea to bo supplied 
with tolerable regularity; but the remaining inorganic maleriuls, 
such as calcareous aaltfi, the alkaline phosphatc^i, &c., occur oata- 
rally id sufficient quantity iu most of the articles which are used as 
food. 

The proKimate principles of the second class, so far as they con- 
stitute ingredients of the food, are naturally divided into two 
groups : Ist, the sugar, and 2d, the oily matters. Since starch is 
iilways converted iuto sugar iu the process of digesliou, it inny be 
included, as an alimetitary substance, in the same group with the 
sugars. There is a natural dcstro in the human species for both 
saccharine and oleaginous food. In the purely carnivorous animals, 
however, though no starch or Bugar be taken, yet the body is main- 
tained in a healthy condition. It has been supposed, therefore, that 
saccharine matters could not be absolutely nece6.<»ry ns food; the 
more so since it has been found, by the experiments of CI. Bernard, 
that, in carnivorous animals kept exclusively on a diet of £esb, 
sugar is still formed in the liver, as well a» in the mammary gland. 
The above conclusion, however, which has Lmjuu drawn from these 
facts, docs not apply practically to the human s[)ecics. The car- 
nivorous animals have no desire for vegetable food, while in the 
human s|]ecies there is a natural craving for it, which is almost 
universal. It niay be dispensed with for a few days, but not with 
impunity fur any great length of time. The experiment has often 
enough been tried, iu the treatment of diabetes, of confining th« 
patient to a strictly animal diet. It has been invariably found that, 
if this regimen be continued for some weeks, the desire for vegetable 
food on the part of the patient beeumes so imperative that the plan 
of treatment is unavoidably nbanduncd. 

A similar question has also arisen with regard to the oleaginous 
matters. Are these substances indispensable as ingredients of the 
food, or may they be replaced by other proxiiuala priuciples, such 
as starch or sugar? It has already been seen, from the experiments 
of Bousstngault and others, that a certain amount nf fat is produced 
in the body over and above that which is taken with the food ; and 
it appears also that a regimen abounding in saccharine substances 
IB favorable to the production of fat. It is allugether probable, 
therefore, that the materials for the production of fat may he 




OF FOOD. 91 

derived, under these circumstances, either directly or indirectly 
from saccharine matters. But saccharine mutters alone are not 
entirely sufficient M. Huber' thought he had demonstrated that 
bees fed on pure sugar would produce enough wax to show that 
the sugar could supply all that was necessary to the formation of 
the fatty matter of the wax. Dumaa and Milne-Edwards, however, 
in repeating Huber's experiments,' found that this was not the case. 
Bees, fed on pure sugar, soon cease to work, and sometimes perish 
in considerable numbers; but if fed with honey, which contains 
some waxy and other matters beside the sugar, they thrive upon 
it; and produce, in a given time, a much larger quantity of fat than 
was contained in the whole supply of food. 

The same thing was established by Boussingault with regard to 
starchy matters. He found that in fattening pigs, though the 
qnanlity of fat accumulated by the animal considerably exceeded 
that contained in the food, yet fat must enter to some extent into 
the composition of the food in order to maintain the animals in a 
good condition ; for pigs, fed on boiled potatoes alone (an article 
abounding in starch but nearly destitute of oily matter), fattened 
slowly and with great difficulty; while those fed on potatoes mixed 
with a greasy fluid fattened readily, and accumulated, as mentioned 
above, much more fat than was contained in the food. 

The apparent discrepancy between these facta may be easily ex- 
plained, when we recollect that, in order that the animal may become 
fattened, it is necessary that he be supplied not only with the 
materials of the fat itself, but also with everything else which is 
necessary to maintain the body in a healthy condition. Oleaginous 
matter is one of these necessary substances. The fats which are 
taken in with the food are not destined to be simply transported 
into the body and deposited there unchanged. On the contrary, 
they are altered and used up in the processes of digestion and 
nutrition; while the fats which appear in the body as constituents 
of the tissues are, in great part, of new formation, and are produced 
from materials derived, perhaps, from a variety of different sources. 

It is certain, then, that either one or the other of these two 
groups of substances, saccharine or oleaginous, must enter into the 
composition of the food ; and furthermore, that, though the oily 
matters may sometimes be produced in the body from the sugars, 

' Nataral Historj of Bees, Edlnboro', 1821, p. 330. 

' Aonalea de Chim. et de Pbys., 3d series, rol. zIt. p. 400. 



dS 



OP FOOD. 



it is also necessary for the perfect nutrition of the body that fat 
supplied, under its own form, with the food. For the human 
species, alao, it is natural to have lliem both associated in the 
alimentary materiiils. Tbey occur together iti most vegetable sub- 
stances, and there is a natural deeira for them both, as elements of 
the food. 

They are not, however, when alone, or even associated with each 
other, sufficient fur the nutrition of the animal body. Mageudie 
found that dogs, fed exclusively on starch or sugar, perished after a 
short time with symptoms of profound disturbance of the DutnttTfl 
functions. An exclusive diet of butter or lanl had a similar eSeot 
The animal became exceedingly debilitated, though without much 
emaciation; and oftt^r death, all the iuternal organs and tissues 
were found infiltrated with oil, Bouasingault' jierformed a similar 
osperinient, with a like result, upon a duck, whioli wafl kept upon 
an exclusive regimen of butler. "The duck received 1359 to 1500 
grains of butter every day. At the end of three weeks it died of 
inani'timt. The butter ouzed from every part of its body. The 
feathers looked ns though ihcy had been steeped in melted butter, 
and the body exhaled an unwholesome odor like that of butyric 
acid." 

Lehmaan was also led to the same result by some experiments 
which he performed upon himself for the purpossof ascertaining 
the eflecl produced on the urine by different kinds of food.* 
Thia observer confined himself first to a purely animal diet for 
three weelu, and afterwardit U) a purely vegetable oue for sixteen 
{lays, without suffering any marked inconvenience. lie then put 
himself upon a regimen consisting entirely of non-nitrogenous sub- 
stances, starch, sugar, gum, and oil, but was only able to continue 
this diet for two, or at most for three days, owing to the marked 
disturbance of the general health which rapidly supervened. The 
unpleasant symptoms, however, immediately disappeared on his 
return to an ordinary mixoii diet. The same fact has been esta< 
Wished more recently by Prof. Wm. A. IlammoDd,' in n series of 
experiments which he performed upon himself. He was euabled 
to live for ten days on a diet composed exclusively of boiled starch 
and water. Afler the thinl day, however, the general health began 



I 



I 



I Cliiini(t AgriootB, p. ISB. 

' Joamal fUr pfAktiacha Chemlo, rol. xxrii, p. 2.17. 

* Bzpnrimontjtl RwiaaTches, &e., being the rr'me Kstaj of Ili« Aiaerivatl M«d[c«I 
Anoolatlon Car \K^. 



OF FOOD. 88 

to deteriorate, and became very much disturbed before the termi- 
cation of the experiment. The prominent symptoms were debility, 
headache, pyrosis, and palpitation of the heart. After the starchy 
diet was abandoned, it required some days to restore the health to 
its usual condition. 

The proximate principles of the third class, or the organic sub- 
stances proper, enter so largely into the constitution of the animal 
tissues and fluids, that their importance, as elements of the food, is 
easily understood. No food can be long nutritious, unless a certain 
proportion of these substances be present in it. Since they are so 
abundant as ingredients of the body, their loss or absence from the 
food is felt more speedily and promptly than that of any other sub- 
stance except water. They have, therefore, sometimes received the 
name of "nutritious substances," in contradistinction to those of 
the second class, which contain no nitrogen, and which have been 
found by the experiments of Magendie and others to be insufficient 
for the support of life. The organic substances, however, when 
taken alone, are no more capable of supporting life indefinitely than 
the others. It was found in the experiments of the French "Gela- 
tine Commission"' that animals fed on pure fibrin and albumen, as 
well as those fed on gelatine, become after a short time much en- 
feebled, refuse the food which is offered to them, or take it with 
reluctance, and finally die of inanition. This result has been 
explained by supposing that these substances, when taken alone, 
excite after a time such disgust in the animal that they are either 
no longer taken, or if taken are not digested. But this disgust 
itself is simply an indication that the substances used are insufficient 
and finally useless as articles of food, and that the system demands 
instinctively other materials for its nourishment. 

The instinctive desire of animals for certain substances is the 
snreat indication that they are in reality required for the nutritive 
process; and on the other hand, the indifference or repugnauce 
manifested for injurious or useless substances, is an equal evidence 
of their unfltnws as articles of food. This repugnance is well de- 
scribed by Magendie, in the report of the commission above alluded 
to, while detailing the result of his investigations on the nutritive 
qualities of gelatine. "The result," he says, "of these first trials 
was that pure gelatine was not to the taste of the dogs experimented 
on. Some of them suffered the pangs of hunger with the gelatine 

< Comptea Reudos, 1841, vol. xiii. p. 267. 



OF FOOD. 



within their reach, and would not toach it; others tasted of it, Ijut 
would not eat ; others alill devoured a certain <]uantily of it once 
or twice, and then obstinately refused to make any further use of iU" 

In one instance, however, Magcndie succeeded in inducing a dog 
lo take n considerable quimtity of pure fibrin dnily throughout the 
whole course of the experiment; but notwitlisiandiiig this, the 
ftnimal became eomeiated like the others, and died at last with the 
same symptoms of inanition. 

The alimentary substances of the aecond class, however, viz., the 
Bugnra and the oils, have been aometimea thought less important 
than the albaminous matters, because they do not enter so largely 
or EO permanently into the compusitioti of the solid tissues. The 
saccharine matters, when taken as food, cannot be truccd farther 
than the blood. They undergo already, in the circulating fluid, 
somo change hy which their essential character is lost, and they 
cannot bo any longer recognized. The appearance of sugar in the 
niammary gland and the milk is only exceptional, and does not 
occur nt all in the male subject. The faLs are, it is true, very gene- 
rally distributed throughout the body, but it ie only in the brain 
and nervous matter that they exist intimately united with ihtt re> 
maining ingrcdlentKof the tissues. Elsewhere, as already mcntionod, 
they are deposited in distinct drops and granules, and so long as 
thoy remain in this condition must of course be inactive, so far as 
regards any chemical nutritive process. In this condition they 
seem to be lield in reserve^ ready to be absorbed by the blood, 
whenever they may be retjuircd for the purposes of nutrition. On 
being reabsorbed, however, as soon as they again enter the blood 
or unite intimately with the substance of the tissues, they at onoe 
change their condJliou and lose their former chemical constitution 
and propertiea. 

It is for these reasons that the albuminoid matters have been 
sometimes considered as the only "nutritious" HHbstance.% because 
they alone constitute under their own form a great part of the 
ingredients of the tissues, while the sugars and the oils rapidly dis* 
appear by decomposition. It has even been assumed that the pro- 
cess by which the sugar and the oils disappear is one of direct 
combustion or oxidation, and that they are destined solely lo be 
consumed in this way, not to enter at all into the composition of 
the tissues, but only to maintain the heat of the body by an inces- 
sant process of cumbustion in the blood. They have been therefore 
termed the "combustible" or "heat-producing"' elements, while tha 



4 



i 



I 




OF FOOD. 96 

albuminoid substances were known as tbe nutritious or "plastic" 
elements. 

This distinction, however, has no real foundation. In the first 
place, it is not at all certain that tbe sugars and the oils which dis- 
appear in the body are destroyed by combustion. This is merely 
an inference which has been made without any direct proof. All 
we know positively in regard to the matter is that these substances 
soon become so altered in the blood that they can no longer be 
recognized by their ordinary chemical properties; but we are still 
ignorant of the exact nature of the transformations which they 
nndergo. Furthermore, the difference between the sugars and the 
oils on the one hand, and the albuminoid substances on the other, 
so far as regards their decomposition and disappearance in the 
body, is only a difference in time. The albuminoid substances 
become transformed more slowly, the sugars and the oils more 
rapidly. Even if it should be ascertained hereafter that the sugars 
and tbe oils really do not unite at all with the solid tissues, but are 
entirely decomposed in tbe blood, this would not make them any 
less important as alimentary substances, since the blood is as 
essential a part of the body as the solid tissues, and its nutrition 
roust be provided for equally with theirs. 

It is evident, therefore, that no single proximate principle, nor 
even any one class of them alone, can be sufficient for the nutrition 
of the body ; but that the food, to be nourishing, ntust contain 
substances belonging to all the different groups of proximate prin- 
ciples. The albuminoid substances are first in importance because 
they constitute the largest part of the entire mass of the body; and 
exhaustion therefore follows more rapidly when they are withheld 
than when the animal is deprived of other kinds of alimentary 
matter. But starchy and oleaginous substances are also requisite; 
and the body feels the want of ihem sooner or later, though it may 
be plentifully supplied with albumen and fibrin. B'inally, the ia- 
organic saline matters, though in smaller quantity, are also neces- 
sary to the continuous maintenance of life. In order that the 
animal tissues and fiuids remain in a healthy condition and take 
their proper part in the functions of life, they must be supplied 
with all the ingredients necessary to their constitution ; and a man 
Diay be starved to death at last by depriving him of chloride of 
sodium or phosphate of lime just as surely, though not so rapidly, 
as if he were deprived of albumen or oil. 

In the different kinds of food, accordingly, which have been 



96 or POOD. 

adopted bj the universal and instinctive choice of man, the three 
different classes of proximate principles are all more or less abund- 
antly represented. In all of them there exists naturally a certain 
proportion of saline substances; and water and chloride of sodium 
are generally taken with them in addition. In milk, the first food 
supplied to the infant, we have casein which is an albuminoid 
substance, butter which represents the oily matters, and sugar of 
milk belonging to the saccharine group, together with water and 
saline matters, in the following proportions: — ' 

COXFOSITIOR OF CoW'B HILK. 

Water 87.02 

Casein 4.48 

Butter 3.13 

Sagar of milk 4.77 

Soda 

ChlorideB of potaaBinm and sodium 

PhosphateB of soda and potaasa 

PhoBpliate of lime ^ 0.60 

" magnesia 

Alkaline c&rbonates 

Iron, &o 



100.00 

In wheat flour, gluten is the albuminoid matter, sugar and starcli 
the non-U itrogenoua principles. 

CoMPOBtTion OP Wheat Floor, 
Glaten .... 10.2 Gum .... 2.8 

SUrch .... 72.8 Water .... 10.0 

Sugar . . . .4.2 

100.0 

The other cereal grains mostly contain oil in addition to the 
above, 

CojiPosiTios OP Dbisd Oatmbal. 

StaroU 59.00 

Bitter matter and sagar 8.25 

Oray albuminous matter 4.30 

Fatty oil 2.00 

Gum 2.50 

Husk, mixture, and loss 23.95 



100.00 



Eggs contain albumen and salts in the white, with the addition 
of oily matter in the yolk. 

' Tlie accompanying analyttes of various kindd of food are taken from Peretra 
on Food anil Di».t, New York, 1843. 



OF POOD. 97 

CoHPosmox or Boas. 

WhlU or Kw. Tolk of %s. 

Water .... 60.00 S3.78 

Albnm«& and maciu 15.28 12.75 

Yellow oil 28.7fi 

Salta .... 4.72 4.72 

100.00 lOO.OO 

In ordinary flesh or butcher's meat, we have the albuminoid 
matter of the muscular fibre and the fat of the adipose tissue. 

CoHPogmoir or Ordihaht Bdtchbb'b Hsat. 

w . J i^ f f . nr T ( Water .... 63.418 

Heat devoid of lilt 85.7 !„.,, „„ „„„ 

iSolidtnattar . . . 22.282 

Pat, eellalar tissue, Ac 14.300 

100.000 

From what baa been said above, it will easily be seen that the 
nutritious character of any substance, or its value as an article of 
food, does not d^end simply upon ita containing either one of the 
alimentary substances mentioned above in large quantity; but upon 
its containing them mingled together in such proportion as is 
requisite for the healthy nutrition of the body. What these pro- 
portions are cannot be determined from simple chemical analysis, 
nor from any other data than those derived from direct observation 
and experiment. 

The total quantity of food required by man has been variously 
estimated. It will necessarily vary, indeed, not only with the con- 
stitution and habits of the individual, but also with the quality of 
the food employed; since some articles, such as corn and meat, con- 
tain very much more alimentary material in the same bulk than 
fresh fruits or vegetables. Any estimate, therefore, of the total 
quantity should state also the kind of food used; otherwise, it will 
be altogether without value. From experiments performed while 
living on an exclusive diet of bread, fresh meat, and butter, with 
coffee and water for drink, we have found that the entire quantity 
of food required during twenty-four hours by a man in full health, 
and taking free exercise in the open air, is as follows: — 

Meat 16 oances or 1.00 lb. Avoiidapois. 

Bread 19 " " 1.19 " 

Butter or fet . .3* " " 0.22 " " 

Water 62flnidox. " 3.38 " " 

That is to say, rather less than two and a half pounds of solid food, 
and rather over three pints of liquid food. 

7 



98 



OP FOOD. 



Another necessary consideration, in estimating the value of any 
substance as an article of food, is its digestibility. A vegetable or 
animal tissue may contain an abundance uf albuminoid or starchy 
matter, but may be at the same time of such an unyielding consist- 
ency as to be insoluble in the digestive fluids, and therefore useless 
as an article uf food. Bones and cartilages, and the fibrea of yellow 
elastic tissue, are. indigestible, and therefore not nutritious. The 
flame remark may be rnado with regard to the riubstanees contained 
in woody fibre, and the hard coverings and kernels of various fruits. 
Everything, accordingly, which softens or disintegrates a hard ali- 
mecitary substance renders it more digestible, and so far increases 
its value as an article uf food. 

The preparation of food by cooking has a twofold object : first, 
to soften or disintegrate it, and second, to give it an attractive 
flavor. Many vegetable substances are so hard as to be entirely 
indigestible in a raw state. Kipe peas and beans, the differeut kinds 
of grain, and many roots am) fruits, require to be soflencd by boil- 
ing, or some other culinary process, before they 6^0 ready for use. 
With them, the principal change produced by cooking is an altera- 
tion in conaislCDcy. With most kinds ofanimal food, however, the 
effect is somewhat diflerent. In the case of muscular flesh, for ex- 
ample, the muscular fibres themselves are almost always more or 
leas hardened by boiling or roasting; but, at the same time, the 
fibrous tissue by which they are held together is golaiinized and 
softened, so that the muscular fibres are more easily separated from 
each other, and more readily attacked by the digestive fluids. But 
beside this, the organic substances contained in meat, which are all 
of them very insipid in the raw state, acquire, by the action of heat 
in cooking, a peculiar and agreeable flavor. This flavor excites 
the appetite aud stimulates the How of the digestive fluids, aud 
readers, in this way, the entire process of digestion more easy and 
cxpoilitiouB. 

The changes which the food undergoes in the interior of the body 
may be included under three different heads: first, digestion, or the 
preparatiuu of the food in the alimentary cunul; second, lissimilationy 
by which the elements of the food are converted into the animal 
tissues; and third, excretion, by which they are again decomposed, 
and finally discharged from the body. 



1 




DIGESTION'. 99 



CHAPTER VI. 

DIOE8TI0N. 

DiGKanoN is that process by which the food is redaced to a form 
in which it can be absorbed from the intestinal canal, and taken up 
hy the bloodvessels. This process does not occur in vegetables. 
For vegetables are dependent for their nutrition, mostly, if not 
entirely, upon a supply of inorganic substances, as water, saline 
matters, carbonic acid and ammonia. These materials constitute 
the food upon which'plants subsist, and are converted in their inte- 
rior into other substances, by the nutritive process. These mate- 
rials, farthermore, are constantly supplied to the vegetable under 
SQch a form as to be readily absorbed. Carbonic acid and ammonia 
exist in a gaseous form in the atmosphere, and are also to he found 
in solution, together with the requisite saline matters, in the water 
with which the soil is penetrated. All these substances, therefore, 
are at once ready for absorption, and do not require any preliminary 
modification. But with animals and man the case is different. 
Tliey cannot subsist upon these inorganic substances alone, but 
require for their support materials which have already been organ- 
ized, and which have previously constituted a part of animal or 
vegetable bodies. Their food is almost invariably solid or semi-solid 
at the time when it is taken, and insoluble in water. Meat, bread, 
fruits, vegetables, Sk., are all taken into the stomach in a solid and 
insoluble condition; and even those substances which are naturally 
fluid, such as milk, albumen, white of egg, are almost olways, in 
the human species, coagulated and solidified by the process of cook- 
ing, before being taken into the stomach. 

In animals, accordingly, the food requires to undergo a process 
of digestion, or liquefaction, before it can be absorbed. In all cases, 
the general characters of this process are the same. It consists 
essentially in the food being received into a canal, running through 
the body from mouth to anus, called the "alimentary canal," in 
which it comes in contact with certain digestive fluids, which act 



DIOESTIOX. 



Upon it in aucb n way as to liquefy and dissolve it. Tbeae fluids 
are secreted by the mucoua raembrftncof the alimentary canal, and 
by certain glandular organs situated in its neighborhood. Since the 
food always coaaisls, as we have already seen, of a mixture of vari- 
ous substanees, having diflerent physical and chemical properues, 
tho several digestive fluids arc also dillerent from each other; each 
one ot them exerting a peculiar action, which is more or leas con- 
fined to particular species of food. As the food pasaes through the 
intestine from above downward, those parta of it which become 
liquefied are successively removed by absorption, and taken up by 
the vessels; while the remaining portions, consisting of the indi- 
gestible matter, together with the refuse of the intestinal secretions, 
gradually ncquire a firmer consistency owing to the absorption of 
the fluids, and are finully discharged from the ititcstine under the 
form of feces. 

In different speciea of animals, however, the difference in their 
habits, in the constitution of their tissues, and in the character of 
their food, is accompanied with a corresponding variation in the 
anatomy of the digestive apparatus, and tht; character of the secreted 
flaids. As a general rule, the digestive apparatus of herbivoroaa 
flnimnls is more complex thnn that of the carnivora; since, in vege- 
table substances, the nutritious matters are often present in a very 
solid and unmanageable form^ as, for example, in raw starch and 
the cereal grains, and are nearly always entangled among vegetable 
cells and fibres of an indigcsiible character. In those instances 
where the food consists mostly of herbage, as grass, leaves, &c., the 
digestible matters bear only a small proportion to tho entire quan- 
tity; and a large mass of food must therefore be taken, in order 
that the requisite aniount of nutritious material may bo extracted 
from it. In such cases, ncuordingly, the alimentary canal is large 
and long; and is divided into many coropartmenta, In which 
different processes of disiutegratlou, tranisforuiatiou, and solution 
are corried on. 

In the common fowl, for instance (Fig. 1()), tlio food, which con- 
sists mostly of grains, and frequently of insects with hard, coria- 
ceous integument, first passes down the ccsopbagua (a) into a 
diverticulum or pouch (b) termed the crop. Here it remains for 
u time, mingled with a watery secretion in which the grains are 
macerated and softened. The food \a then carried fjirthcr down 
until it reaches a second dilatation (c), the proventriculus, or 
secreting stomach. The mucoua membrane here is thick and 



* 



« 




DIOBBTtoy. 



101 



glandular, and is provided wiih numerous ae- *^8* l"- 

|Creling foUicIefl or crypta. From ihem nn 

'»cid 6oid is poured out, by which tlie food is 

isabjected to further changes. It next passes 

[into iho gizzard (c£), or trituraLinji^ stomach, n 
CRTitj inclosed by thick, muscular walls, and 

[lined with a remarkably totigh and horny 

t«pitbolium. Here it is subjected lu the crush- 
ing and grinding action of the muscular pa- 
rietes, assisted by grains of sand and gmvel, 

^which the animal iuatinctivcly swallows with 
the food, by which it is so triturated and di«- 
int^rated, that it is reduced toa uniform pulp, 

■-Bpou which the digestive fluids can effectually 
Operate. The mass then passes Into the inies* 
tine (e), where it meets with the intestinal 

^iccs, which complete the process of solution; /| 
and from the intestinal cavity it is Gnally ab- 
sorbed in a liquid form, by the vessels of the 
mucouif membrane. 

la tfa« oXf again, the sheep, the camel, the 
deer, and all ruminating animals, there aro 
tour distinct stomachs through which tho 
(bod passes in succession; each lined with 
mocous membrane of a diOerent structure, 
and adapted to ]>crfcrm a difterent part in 
the digestive process. (Fig. 17.) When 6rat 

Itwallowed, tho food is received into the m- r/'"""~,f *^'"*'"- 
tneri, or paunch (t), a large sac, itself par- ..rwff«iiiii,.ii>inK>b, </ gu- 
tially divided by incomplete partitions, and TtZTTj^ZZt. 
lined by a mucous membrane thickly sot 
with long prominences or villi. Here it ac- 
cnmulates while the animal is feeding, aad is 
n:tained and macerated in its own Buiils. When the animal has 
finished browsing, and the process of rumination commences, the 
food IB regurgitated into the mouth by an inverted action of the 
muscularwalUof the paunch uud wsophagus, and slowly masticated. 
It then descends again along the oraophagus; but instead of enter- 
ing the first stomach, as before, it is turned ofi' by a muscular valve 
into the second stomach, or reticulum (c), which is distinguished 
by the intersecting folds of its [nucoas membrane, which give it 



ALIMHMTtaT CAVII. 



cs) lul«*'whlch optD Into iba 
InMilInc ■ «liiin dUMOM 
aboTO ll* ■•rnilDUloD, 



102 



mOESTIOX. 



ft honey-combed or reticulalod appearance. 

triturnttid 
Kg. 17. 



h 



CeiCMiCV* ilT«a4i'll np Os.— a. (Km- 

pbftgnt. b, Ttt,m*-a, or fir>i tcotakch. e. K«tl- 
cnlani. oriiMuiid. d, Omuu*, ur llilnl. «. AIhi- 
ni>«ui, urhiorlh, /. DoodpuniD. (From Rjnior 
JoB««.) 



Here ihe food, already 
in tlie mouth, and 
inixenl with the saliva, is further 
macerated in the fluids swallowed 
by the animnl, which always ac- 
cumulate in considerable qaan- 
tity in the reticulum. The next 
cavity is the omaaus, or " paalte- 
rium" ((/), in which the mucous 
menibraoe is arranged in longi- 
tudinal folds, alternately broad 
and narrow, lying parallel with 
each other, like the leaves of a 
book, eo that the extent of mucous 
surface, brought ia contact with 
iho food, is very much increased. 
The exit from this cavity leads 
directly into the abomaetuij or 
"rennet" (e), wliich is the troe 
digestive stomach, in which the mucous mcinhranc w softer, thicker, 
and more glandular than elsewhere, and in which an acid and 
highly solvent fluid is secreted. Then follows the ioteatinal canal 
with its various divisions and variations. 

In the carnivcra, on the other hand, the alimentary canal is 
shorter nnd narrower than in the preceding, and presents fewer 
complexities. The food, upou which these animals subsist, is sol^r 
than that of the herbivora, and less encumbered with indigestible 
matter; so that the procesit of its solution requires a less extensiye 
apparatus. 

In the human species, the food is naturally of a mixed cha* 
racter, containing both animal and vegetable substances. But the 
digestive apparatus in man resembles almost exactly that of the 
carnivora. Kor the vegetable matters which we take as food are, 
in the first place, artificially separated, to a great extent, from indi- 
gestible inipiirities; and secondly, they are so softened by the 
process of euoking as to become nearly or quite as easily digestiblfl 
as animal substances. 

In the human species, however, the process of digestion, tbough 
simpler than in the herbivora, is still complicated. The altmcDtary 
canal is here, also, divided into diJTerent compartments or cavities, 
vhich communicate with each other by narrow orifices. At its 



I 

I 
I 



I 



I 




DIOBSTIOir. 



108 



'rj 



A. 



s 



cominenoement (Fig. 18), we finO the cavity of the mouth, which is 

guarded at its posterior extremity by the muscular valve of the 

itthtnus of the faacea. 
[Through the pharynx and 
IcesophaguB (n), it commu- 
ites with the second 
tpartmeat, or the ato- 
laeA (b\ a flafk-shapud 
jrdtlntAtion, which is guarded 

II the cardiao and pyloric 
foriHccB by circular bnnds 
muscalar fibres. Then 
' comes the imall inleatine (f), 

diflbrent parts of which, 

ovfing to the varying atruc- 

lare of their raucous mem- 
branes, have received the 

different names of dnode- 

num, jejunum, and ileum. 

Id the duodenum, we have 

ibe orifices of the biltart/ 
Ijftnd pancreatic ducts (_/^ 3). 

finally, wc have the large 

pttattne (A, t,_;", k\ separated 

from the smaller by the 

fleo-c£ecal valve, and ter- 
minating, at its lower ex- 
tremity, by the ftnaj», at 

which ia situated a double 

sphincter, for the purpose 

of guarding ite orifice. 

Everywhere the alimentary 

canal is composed of a 

raacouB membrane and a 
.piuscQlar coat, with a layer 

of submucous nreulur tissue 

between the two. The mua* 

cular oont is everywhere 

composed of a double layer of longitudinal and transverse fibros, 

by the alternate contraction and relaxation of which the food is 

carried through the canal from above downward. The mucous 



-^^V 



V- 







UVN«)I ALIKIITlNt CkHAt. — a. CB««titnfii*. 
b. muoiiuib. e. CArdliu arlBm d. I'jrkrut. c HaiaU 
lBla*t>n*. /. llllliT/ dapl. f l^iiienaUo •lucl h ,\t. 
MDdliil colon. 1. Tnuirane calon. /. ifHeendtnc tv- 
lus. Jr. Reclum. 



104 



DIOKBTION. 



membraiifi presents, also, a ditTereiit stractore, and has different 
properties in different parts. In tUe mouth and cesopbagus, it ia 
sinooth, with a hard, whitish, and tessellated epithelium. This kind 
of epithelium tenniiiates abruptly at the cardiaa orifice of the 
stomach. The mucous raembranc of the gastric cavity is soft and 
gUudular, covered with a transparent, coluiunar epitheliuos, and 
thrown into minute folds or projections on its free Hurfaoe, which 
are sometimes reticulated with each other. In the small intestine, 
we find Urge transverse folds of mucous membrane, the valvula 
connhenlctf the minute viUosities which cover its surface, and the 
peculiar glandular atruuturea which it contains. Finally, in the 
large intestine, the mucous membrane is again difterent. It is hero 
smooth and shining, free front viUosities, and provided with a dif- 
ferent glandular apparatus. 

Furthermore, the digestive secretions, also, vary in these different 
regions. In its passage from above downward, the food meets 
with no less than five different digestive fluids. First it meets with 
the salivn in the cavity of the mouth; second, with the gastric Juice, 
in the stomach; third, with the iiVe; fourth, with the pancreatK 
Jiuid; find fifth, with the inteatinal juice. It is the most important 
cliaracteristic of the proceiw of digestion, as established by modern 
researches, that different elements of the food are digested in different 
parts of the alimentary cniin? hg the agency of different digestive Jluida. 
By tbeir action, the various ingredients of the alimentary mass are 
successively reduced to a fiuid condition, and are taken up by the 
vessels of the intestinal mucous membrane. 

The action which is exerted upon the food by the digestive 
fluids is not that of a simple chemical solution. It is a transforma- 
tion, by which iho ingredients of the food aru altered in character 
at the same time that they undergo the process of liquefaetioa. 
The uctive agent in producing this change is in every instance an 
organic matter, which enters as an ingredient into the digestive 
fluid; and which, by coming in contact with the food, eicerts upon 
it a catalytic action, and transforms \\s ingredients into other sub- 
stances. It 13 these newly formed aubaiaoces which are finally 
absorbed by the vessels, and mingled with the general current of 
the circulation. 

In our study of the process of digestion, tho different digestive 
fluids will be examined separately, and their action on the aliment- 
ary substances in the difi'ereut regions of the digestive apparatus 
successively investigated. 



* 




MASTICATION. 103 

Mastication. — In the first division of the alimentary canal, viz., 
the mouth, the food undergoes simultaneously two different opera- 
tioDS, viz., mastication and insalivation. Mastication consists in 
the catting and trituration of the food by the teeth, by the action 
of which it la reduced to a state of minute subdivision. This pro* 
ceas is entirely a mechanical one. It is necessary, in order to pre- 
pare the food for the subsequent action of the digestive fluids. As 
this action is chemical in its nature, it will be exerted more promptly 
and efficiently if the food be finely divided than if it be brought in 
contact with the digestive fluids in a solid mass. This is always 
the case when a solid body is subjected to the chemical action of a 
solvent fluid; since, by being broken up into minute particles, it 
offers a larger surface to the contact of the fluid, and is more readily 
attacked and dissolved or decomposed by it. 

In the structure of the teeth, and their physiological action, there 
are certain marked differences, corresponding with the habits of the 
animal, and the kind of food upon which it subsists. In fish and 
serpents, in which the food is swallowed entire, and in which the 
process of digestion, accordingly, is comparatively bIow, the teeth 
are simply organs of prehension. They have generally the form 
of sharp, curved spines, with their points set backward (Fig. 19), 
and arranged in a'double or triple row 
about the edges of the jaws, and sometimes J^ ^' ^^' 

covering the mucous surfaces of the mouth, 
tongue, and palate. They serve merely to 
retain the prey, and prevent its escape, 
after it has been seized by the animal. In 
the carnivorous quadrupeds, as those of 
the dog and cat kind, and other similar 
fiimilies, there are three different kinds of teeth adapted to different 
mechanical purposes. (Fig. 20.) First, the incisors, twelve in num- 
ber, situated at the anterior part of the jaw, six in the superior, 
and six in the inferior maxilla, of flattened form, and placed with 
their thin edges running from side to side. The incisors, as their 
name indicates, are adapted for dividing the food by a cutting 
motion, like that of a pair of shears. Behind them come the canine 
teeth, or tusks, one on each side of the upper and under jaw. 
These are long, curved, conical, and pointed; and are used as 
weapons of offence, and for laying hold of and retaining the prey. 
Lastly, the molars, eight or more in number on each side, are 
larger and broader than the incisors, and provided with serrated 




Skull or RATTLBiXAKi. 

(After AchlUe-Rlcbftrd } 



DIGKSTION. 



Fig. 20. 



edges, each presenting several sharp points, arranged generally in 
a direction parallel with the line of the jaw. In these animals, 

mastication is very imperfect, since 
the food is not ground up, but only 
pierceii and mangled by the action 
of the teeth before being swallowed 
into the stomach. In the berbi- 
vora, on the other hand, the inci- 
sors are present only in the lower 
jaw in the ruminating aiiiinaU, 
though iu the horse they are found 
in both the upper and lower max* 
ilia. (Fig. 21.) They are used merely 
for cutting off the bundles of grass 
or herbage, on which the animal kaih. The canines are either 
absent or slightly developed, and the real process of mastication is 



Sxtl.1. or rdLAK RtAK. AOteriltT 



Fig. 21. 



\ 



SSVLI. OF THS tlOttt. 



Fig. 22. 



performed altogether by the molars. Thaw are large and thick 
(Fig. 22), and present a broad, flat surface, diversified by variously 
folded and projecting ridges of enamel, with shal- 
low grooves, intervening between them. By the 
lateral robbing motion of the roughened surfaces 
^S/BHS pJl against each other, the food is eilectually eommi- 
I9q^2jI nuteti and reduced to a pulpy nia^. 
«^H^S^Rj In the human subject, the leeth eombine the 
^1^^^^^^ characters of those of the carnivora and the herbi- 
Mrtt-A* TcoTB or vora. (Fiff. 23.) The incisors (a), four in number 
taii»rrH« iQ each jaw, have, as in other mstaoces, & cutting 



4 
4 




SALirA. 



107 



\ 






jy- 



' .d 



KdsjI]| Tibtr — Vppo ikV>.—a. Iacl«4>r«. l^ Ch- 
ilian, f, AbUrtol mnlkn. J, Poal«r1a( uiulun. 



edge running from side to side. The canines (i), which are situnlcfl 
immediately behind the former, are much less prominent and 
pointed than in the carni' 

Tora, and differ less in I^s- S3. 

form from the inciBora on ff. 

the one hand, and the ^x^X. 
molars ou the other. The 
molars, again (e^^, nre 
thick and strong, and have 
compnrfttively fl.U sur* 
faces, like those of the her- 
bivora; butinstead of pre- 
senting curvilinear ridges, 
are covered with more or 
less conical eminences, 
tike those of the carnivora. 
In the human subject, 
therefore, the teeth are 

evidently adapted fur a mixed diet, consisting of both animal and 
vegetable food. Mastication is here as perfect aa it is in ihu horbi- 
Tora, though less prolonged and laborious; for the vegetable sub- 
stances used by man, as already remarked, are previously Bt*paratcd 
to a great extent from their impurities, and softened by cooking; 
so that they do not require, for their mastication, so extensive and 
powerful a triturating apparatus. Finally, animal substances arc 
more completely masticated in the human subject than they are in 
the carnivora, and their digestion is accordingly completed with 
greater rapidity. 

"We can easily estimate, from the facts above stated, the great 
importance, to the digcaiive process, of a tborough prelimiuary 
mastication. If the food be hastily swallowed in nndivided mosses, 
.jt must remain a long time undissolved in the stomach, where it 
rill beoome a source of irritation atid disturbance; but if reduced 
beforehand, by mastication, to a state of minute subdivision, it ia 
readily attacked by the digestive fluids, and becomes speedily and 
completely liqueiied. 



Saliva. — At the aame time that the food is masticated, it is mixed 
in the cavity of the mouth with the first of the digestive fluids, viz., 
the saliva. ITuman saliva, as it is obtained directly from the buc- 
cal cavity, is a colorless, slightly vi!<uid and alkaline fluid, with a 



108 



mCBSTIOIf. 



'I 



speciBo gravity of lOOo. When first discharged, it is frothy and 
opaline, holding in suspension minute, whiliiih fluceuli. On being 
allowed to stand for some hours in a cylindrical gloss vessel, an 
opaqne, whitish deposit collects Rt the bottom, while the supernnUnt 
fluid becomes clear. The deposit, when examined by the micro- 
scope (l''ig. 24), is seen to 
^" consist oi' abundant epithe- 

lium scales from the internal 
surface of the mouth, de- 

,^ ,^_ tached by mechanical iirita- 

:;€5 ■ :') 'rf^ \ lion, minute, roundish, gra- 
nular, nucleated cells, appa- 
rently epithelium fix>m the 
mucous follicles, a certain 
amount of granular matter, 
and a few oil-globules. The 
supernatant fluid has a fuinl 
bluish tinge, and becomes 
slightly opalescent by boil- 

DecflAt Ai.i,oi,A»ftoi.iii ip.Tw«LiF». -iih iRg, flud by thc addition of 
otMnur «Mi.rMdoii-,ioboi»;i.i».ii»4MMdi- niirio acid. Alcohol in ox- 

mtai froiD hamka nlivA. ... 

cess, causes the precipitation 
of abundant whitish flocculi. According to Bidder and Schmidt,' 
the composition of saliva is as follows: — 

CovroniTinx of Sauta. 

W«t*r 895.16 

Organto iaatt«r 1>34 

Sul)>liD-{*yaniil« of pota&slum 0.116 

rhosplmloa of soda, litno, and mAgnosin .9S 

CItloritlT'ti of sodium itnd poCtuislnm .64 

MlxtaraorvpHhaiiain 1.A3 

IOIMJ.00 

The organic substance present in the saliva has been occasionally 
known by the name of jttyaline. It is coagulable by alcohol, but 
not by u builiug teuiperulure. A very little albumen is also pre- 
sent, mingled with the ptyaline, and produces the opalesocnoo 
which appears in the saliva when raised to a boiling tomperatore. 
The sulpho-cyanogen may be detected by a solution of chloride of 
iron, which produces the characteristic red color of sulpbo-oyauide 



' V«r(lAuaiiigiHeft« und StoflVocluel. Lalpxig, I8S3. 



SALIVA. 109 

of iron. The alkaline reaction of the saliva varies in intensity 
during the day, l)ut is nearly always sufficiently distinct. 

The saliva is not a simple secretion, but a mixture of four dis- 
tinct fluids;, which differ from each other in the source from which 
they are derived, and in their physical and chemical properties. 
These secretions are, in the human subject, first, that of the parotid 
gland; second, that of the submaxillary; third, that of the sub- 
lingual; and fourth, that of the mucous follicles of the mouth. 
These difterent fluids have been comparatively studied, in the 
lower animals, by Bernard, Frerichs, and Bidder and Schmidt. 
The paroUd saliva is obtained in a state of purity from the dog by 
expoeing the duct of Steno where it crosses the masseter muscle, 
and introducing into it, through an artificial opening, a fine silver 
canula. The parotid saliva then runs directly from its external 
orifice, without being mixed with that of the other salivary glands. 
It is clear, limpid, and watery, without the slightest viscidity, and 
baa a faintly alkaline reaction. The submaxillary saliva is ob- 
tained in a similar manner, by inserting a canula into Wharton's 
duct. It differs from the parotid secretion, so far as its physical 
properties are concerned, chiefly in possessing a well-marked vis- 
cidity. It is alkaline in reaction. The sublingual saliva is also 
alkaline, colorless, and transparent, and possesses a greater degree 
of viscidity than that from the submaxillary. The mucous secre- 
tion of the follicles of the mouth, which forms properly a part of 
the saliva, is obtained by placing a ligature simultaneously on 
Wharton's and Steno's duets, and on that of the sublingual gland, 
so as to shut out from the mouth all the glandular salivary secre- 
tions, and then collecting the fluid secreted by the buccal mucous 
membrane. This fluid is very scanty, and much more viscid than 
either of the other secretions; so much so, that it cannot be poured 
out in drops when received in a glass vessel, but adheres strongly 
to the surface of the glass 

According to Bernard,' the principal distinction between these 
difierent salivary fluids resides in the character of the organic 
matter peculiar to each one. The organic ingredient of the parotid 
saliva is small in quantity, perfectly fluid, and analogous in some 
respects to albumen, since it coagulates by a boiling temperature. 
That of the submaxillary is moderately viscid, and has a tendency 
to solidify or gelatinize on cooling; while that of the sublingual 

• L«fODa de Physiolcgle Eip^rimentale, Paris, 1806, p. 93. 



110 



folsi 



and muooQs sccrfitions is exceaaivcly viscid, bot does not gelatinize 
at A low temperature. 

Tbe saliva proper consists, therefore, of a nearly bomogenoous 
mixture of all these dlfferonl secretions; of which that from the 
parotid is the moat abundant, that of ibc sublingual and of the 
mucous fullicles of tbe mouth tbe least so. Bidder and Schmidt 
obtained, from one of tbe parotid glanda of the dog, one hundred 
and thirty-six grains of fluid in an hour; from the submaxillary, 
eighty-seven grains; and from the raucous follicles of the mouth, 
after ligature of both Wharton's and Steao*s ducta, thirty-ouo 
grains. Tbe saliva, as a whole, is not secreted with uniform 
rapidity at all times. While fasting, and while the tongoe and 
jaws are at rest, it is supplied in but small quantity, just sufficient 
to keep the mucous membrane of the mouth moist and pliable. 
Any movement of the jaws, however, increases the rapidity of its 
flow. ]t is still more powerfully stimulated by the introduction of 
food, particularly thai which baa a decided lasto.or which requires 
an active movement of the jaws for its mastication, Tbe saliva is 
then poured out in abundance, and continues to be rapidly stxreted 
until tbe food is masticated and swallowed. 

A very curious fact has been observed by M. Colin, Professor of 
Anatomy and Physiology at the Veterinary School of Alfort," viz^ 
that in the borae and ass, as well as in tbe cow and other ruminat- 
ing animals, tbe parotid glands of the two opposite sides, during 
mastication, are never In active secretion at the same time; but 
that they alternate with e»di other, one remaining quicseont while 
the other in active, and vice vertd. In these animals, mastication is 
said to be uuilateral, that is, when the animal commences feeding 
or ruminnting, the food is triturated, for fifteen minutes or more, by 
tbo molars of one side only. Ii is then changed to the opposite 
side; and for the next fifteen minutes maslicalion is performed by 
the mulars of that aide only. It is then changed back again, and 
BO ou alternately, so that tbe direction of tbe lateral movements of 
the jaw may be reversed many times during the course of a meal. 
By cstnblisliing a salivary fistula simultaneously on each side, it is 
found thnt the flow of saliva corresponds with the direction of the 
masticatory movement. When tbe animal masticates on the right 
side, it is the right parotid which secretes actively, while but little 
saliva is supplied by tbe left; when mastication ia on tbe letl aide, 

< TraitC- do Pli^Biologlfl C<miparfe. Paris, 18M, p. 46S. 




SALIVA. Ill 

the left parotid pours out an abandance of flaid, while the right is 
nearly inactive.' It is probable, however, that this alternation of 
fanctioD does not exist, to the same extent at least, in man and the 
carnivora, in whom mastication is performed very nearly on both 
sides at once. 

Owing to the variations in the rapidity of its secretion, and also 
to the fact that it is not so readily excited by artificial means as 
by the presence of food, it becomes somewhat difficult to estimate 
the total qtioniiii/ of saliva secreted daily. The first attempt to do so 
was made by Mitscherlich,* who collected from two to three ounces 
in twenty-four hours from an accidental salivary fistula of Steno'a 
duct in the human subject; from which it was supposed that the 
total amount secreted by all the glands was from ten to twelve 
ounces daily. As this man was a hospital patient, however, and 
suffering from constitutional debility, the above calculation cannot 
be regarded as an accurate one, and accordingly Bidder and Schmidt' 
make a higher estimate. One of these observers, in experimenting 
upon himself, collected from the mouth in one hour, without using 
any artificial stimulus to the secretion, 1500 grains of saliva; and 
calculates, therefore, the amount secreted daily, making an allow- 
ance of seven hours for sleep, as not far from 25,000 grains, or 
about three and a half pounds avoirdupois. 

On repeating this experiment, however, we have not been able to 
collect from the mouth, without artificial stimulus, more than 566 
grains of saliva per hour. This quantity, however, may be greatly 
increased by the introduction into the mouth of any smooth un- 
irritating substance, as glass beads or the like; and during the 
mastication of food, the saliva is poured out in very much greater 
abundance. The very sight and odor of nutritious food, when the 
appetite is excited, will stimulate to a remarkable degree the fiow 
of saliva; and, as it is often expressed, "bring the water into the 
mouth." Any estimate, therefore, of the total quantity of saliva, 
based on the amount secreted in the intervals of mastication, would 
be a very imperfect one. We may make a tolerably accurate 
calculation, however, by ascertaining how much is really secreted 
during a meal, over and above that which is produced at other times. 
We have found, for example, by experiments performed for this 
purpose, that wheaten bread gains during complete mastication 55 
per cent, of its weight of saliva; and that fresh cooked meat gains, 

' Simon'i Cbemistr; of Mu. Pbila. ed., 1846, p. 295. > Op. cit., p. 14. 



112 



DIOESTIOW, 



under the same circumstances, 4S percent, of its weight. We Tiave 
already seen that the daily allowaikce of thei^j two substances, for a 
man in full healtli, is 19 ounces of bread, and 16 ounces of meat. 
The quantity of snliva, then, requirwi for the mastication of these 
two substances, is, for tbc bread 4,572 grains, and for the meat 3,860 
grains. If we now calculate ibe quantity secreted between meals 
as coatlnuing for 22 hours at 556 grains per hour, we have:— 

Saliva i«qnlr«d far maatlaation of brend = 4572 ffrains. 
" " " " '■ m«Bt = 3360 

•• HffcniM in InterraN of iii«aU = 12S32 " 

Totnl qnintity in twonty-four lionrs = 2(1164 grains; 

or rather less than 3 jiounda avoirdupois. 

Tlio mast important question, conuected with this subject, relates 
to the /unction of the saliva m the digestive process. A very remark- 
able property of this fluid ia that which waa discovered by Leuchs 
in Germany, viz., that it possesses the power of coDverting boiled 
starcli into sugar, if mixed with it in (!<iiial proportions, and kept 
for a short time at the temperature of 100° ¥. This phenomenon 
is one of catalysis, in which the starch is transformed into sugar by 
simple contact wiOi the organic substance contained in the saliva. 
This organic substance, according to the experiments of Mialhe,' 
may even be precipitated by alcohol, and kept in a dry state for an 
indefinite length of time without losing the power of converting 
starch into sugar, when again brought in contact with it in a state 
of solution. 

This uction of ordinary liuman saliva on boiled starch takes place 
somotimes with great rapidity. Traces of glucose may occaeiODally 
be detected in the mixture in one minute afYer the two substances 
have been brought in contact; and wo have even found that starch 
paste, introduced into the cavity of the mouth, if already at the 
temperature of 100° F., will yield traces of sugar at the end of half 
a minute. The rapidity, however, with which this action is mani- 
fested, vnrics very much, as was formerly noticed by Lehmann, at 
different times; owing, in all probability, to the varying constitution 
of the saliva itself. It is oUeu impossible, for example, to Hud any 
evidences of sugar, in the mi.xture of starch and saliva, under five, 
ten, or fifteen minutes; and it is frequently a longer time than this 
before the whole of the starch is completely transformed. Kven 
when the conversion of the starch commences very promptly, it is 



< Clilmlu sppUqnf-e h la rii^rsiologle et i, la Tli£rai>BUt[(|a«, Paris, ISStl, p. 43. 



SALIVA. 



118 



often a long time before it is finished. If a thin starch paste, for 
example, which contains no traces of sugar, be tnken into the motiib 
and tboroDglily mixed with the buccal secretions, it will o(\cn, as 
already mentioned, begin to show the reaction of sugar lu the course 
of half a minute ; but some of the starchy matter still remains, and 
will continue to manifest its characteristic reliction with iodine, for 
fifteen or twenty minutes, or even half an hour. 

The above action of the saliva on starch, according to the expe- 
riments of Mugendie, Beraard, Bidder and Schmidt, &c., does not 
reside in either the parotid, submnxillary or mucous secretions 
taken separately; but only in the mixed saliva, as it comes from 
the cavity of the mouth. The submnxillary and m ucous secretions, 
however, taken together, produce the chiinge; though neitherof them 
has any eflfectnloiie, nor even when mixed artiQcially with the saliva 
of the parotid. 

It was supposed, when this property of converting starch into 
sugar was 6rst discovered in ihe saliva, that it constitute the true 
physiological action of this secretion, and that the function of the 
fuliva was, in reality, the digestion and liquefaction of starchy 
substances. It was very soon noticed, however, by the French 
observers, that this property of the sniiva was rather an accidental 
than an essential one; and that, although starchy substances are* 
really converted into sugar, if mixed with saliva in a test-tube, 
yet they are not ailecttid by it to the same degree in the natural 
procosa of digestion. We have already mentioned the extremely 
variable activity of the saliva, in this respect, at different times; 
aud it must be recollected, also, that in digestion the food is not 
retained in tlic cavity of the mouth, but passes at once, af\cr mas- 
^ticalion, into the stomach. Several German observers, as Frerichs, 
facubowitsch, Bidder and Schmidt, maintained at 6rst that the 
saccharine conversion of starch, after being commencecl in the 
mouth, might be, and actually was, completed in the slomach. We 
have convinced ourselves, however, by frequent experiments, that 
tbia is not the case. If n dog, with a gastric fistula, be fed with a 
mixtare of meat and boiled starch, and portions of the fluid coo- 
tents of ibe stomach wlthdruwu ufierward through the H^tula, 
atarob is easily recognizable by its reaction with iodine for ten, 
Ifteen, and twenty minutes afterward. In forty-five minutes, it is 
liminished in quantity, and in one hour has usually altogether dis- 
^appeared ; but no sugar is to be detected at any time. Sometimes 
8 



114 



PIQBSTIOir. 



tbe sUruli disappears more rapidly than tliis; but at no time, accord- 
ing to our observations, is there any indication of the presence of 
sugar in tbe gastric Quids. Bidder and Schmidt hitve also concluded., 
from subsequent investigattona,' that the first experiments performed 
tmder iheir direction by Jaciibowitseb were erroneons; and it is 
DOW acknowledged by them, as well as by the French olMervera, 
that sugar cannot be detected in the ^tomacli, afler the introduction 
of starch, in any form or by any method. In the ordinary process 
of digestion, in fact, starchy matters do not remain long enough id 
ths mouth to be altered by tbe saliva, but pans at once into tbe sto- 
nuh. Here they meet with the gastric fluids, which become min- 
gled with thera, and prevent the change which would otherwise be 
cflcctcd by iho saliva. We have found .that the gastric juice will 
interfere, io this manner, with the action of the saliva in the test- 
lube, as well as in the stomach. If two mixtures be made, one of 
starch and saliva, the other of starch, saliva, and gastric juice, and 
lioth kept for 6fteen minntes at the temperature of 100° F., in the 
first mixture the starch will be promptly converted into sugar, while 
in the second no such change will take place. The above action, 
iherefure, of saliva on starch, though a curious and interesting pro- 
{torty, has no significance as to its physiological function, since it 
does not take place in the natural digestive process. We shall see 
hereafter that there are other means provided for tbe digestion of 
Bturchy matters, altogether indi-pendent of the action of the saliva. 
The true function of the saliva is altogether a physical one. Its 
action i.s simply to moisten the food and facilitate its mastication, 
as well as to lubricate the triturated moes, and assist its passage 
down the tesophagus. Food which is hard and dry, like crusts, 
crackers, &c., cannot he masticated and swallowed with readiness, 
unless moistened by someHuid. If the saliva, therefore, be prevented 
from entering the cavity of the mouth, its loss does not interfere 
directly with the chemical changes of the food in digestion, but only 
with its mechuuical preparation. Tliis is the result of direct ex[>eri- 
ments performed by various observers. Bidder and Schmidt,* after 
tying Steno'a duct, together with the coranion duct of the sub- 
maxillary and sublingual glands on both sides in the dog, found 
that the immediate eB'ect of such an operation was "a remarkable 
diminution of iholluids which exude upon the surfaces of the mouth; 
8o that these surfaces retained their natural moisture only so long 



* Op oit, p. T9. 




■Op. elt., p. 3. 



SALIVA. 116 

as the month waa closed, and readily became dry on exposure to 
contact with the air. Accordingly, deglutition became evidently 
difficult and laborious, not only for dry food, like bread, but even 
for that of a tolerably moist consistency, like fresh meat The 
animals also became very thirsty, and were constantly ready to 
drink." 

Bernard* also found that the only marked effect of cutting off 
the Qov of saliva from the mouth was a difficulty in the mechani- 
cal processes of mastication and deglutition. He first administered 
to a horse one pound of oats, in order to ascertain the rapidity with 
which mastication would naturally be accomplished. The above 
quantity of grain was thoroughly masticated and swallowed at the 
end of nine minutes. An opening had been previously made in 
the cBsophagus at the lower part of the neck, so that none of the 
food reached the stomach; but each mouthful, as it passed down the 
oesophagus, was received at the oesophageal opening and examined 
by the experimenter. The parotid duct on each side of the face 
was then divided, and another pound of oats given to the animal. 
Mastication and deglutition were both found to be immediately 
retarded. The alimentary masses passed down the oesophagus at 
longer intervals, and their interior was no longer moist and pasty, 
as before, but dry and brittle. Finally, at the end of twenty-five 
minutes, the animal had succeeded In masticating and swallowing 
only about three-quarters of the quantity which he had previously 
disposed of in nine minutes. 

It appears also, from the experiments of Magendie, Bernard, and 
Lassaigne, on horses and cows, that the quantity of saliva absorbed 
by the food during mastication is in direct proportion to its hard- 
new and dryness, but has no particular relation to its chemical 
qualities. These experiments were performed as follows: The oeso- 
phagus was opened at the lower part of the neck, and a ligature 
placed upon it, between the wound and the stomach. The animal 
was then supplied with a previously weighed quantity of food, and 
this, as it passed out by the oesophageal opening, was received into 
appropriate vessels and again weighed. The difference in weight, 
before and after swallowing, indicated the quantity of saliva absorbed 
by the food. The following table gives the results of some of Las- 
flaigne'a experiments,' performed upon a burse : — 

> Leifons ds Physiologie Exp^rimentale, Paris, 1856, p. 146. 
' Comptea Reuiiua, vol. xxi. p. 362. 



116 



DIOSSTION. 



KiRD OF Food bxplotbd. QtrAtmrT op Saiita lAuiBn. 

For IDO parts of haj there won ftbaorlwd 400 t>artfl mIIta. 

" barley meal " 1S« 

" oau " 113 " 

" graaDHtalksAnd Ic&res " 49 *' 

Tt is evident, from the above fucts, that the quantity of aalira 
produced has Dot so much to do with the chemical character of the 
food OB with its physical cotiditiou. Wheu Uie food is drj and 
hard, and requires much mastication, the saliva is secreted in 
abundance; when it is suft and moist, a smaller quantity of the 
sccrciion is poured out; and finally, when the food is taken in a 
fluid form, as soup or milk, or reduced to powder and moistened 
artificially with a very large quantity of water, it is not mixed at 
all with the saliva, but passes at once into the cavity of the stomach. 
Tbe abundant and wnti^ry fluid of tho parotid gland is moat aseful 
in assisting masLlcation; while the glairy and mucous secretion of 
the submaxillary gland and the muciparous follicles serve to labii- 
cate the exterior of the triturated mass, and facilitate its passage 
through the oesophagus. 

By tbe combined operation of tho two processes which tbe food 
undergoes in tbe cavity of the mouth, its preliminary preparation 
is acuotnplishod. It is triturated and disintegrated by the teeth, 
and, at the same lime, by the movements of the jaws, tongue, and 
cheeks, it is intimately mixed with the salivary fluids, until the 
whole is reduced to a soft, pasty mass, of the same consistency 
throughout. It is then carried backward by tbe semi-involuntary 
movements of the tongue into the pharynx, and conducted by the 
mascuUr contractions of the oesophagns into the stomach. 

Qastric Ji;icB, and Stomach Digestion.— The mucous mem- 
brano of the stomach is distinguished by its great vascularity 
and the abundant glandular apparatus with which it is provided. 
Its entire thickness is occopicd by certain glandular organs, the 
gastric tubules or follicles, which arc so closely sot as to leave 
almost no space between them except what is required for the 
capillary bloodvessels. The free surface of the gastric mucous 
membrane is not smooth, but is raised in minute ridges and pro- 
jecting eminences. In the cardiac portion (Fig. 25), these ridges 
are reticulated with each other, so as to include between them 
polygonal interspaces, each of which is encircled by a capillary 
network. In the pyloric portion (Fig. 26), the eminences are more 



LStRIC JDtCB, AKD BTOKACH DiniSTIOS'. 



or less pointed and cooical in form, and generally flattenal from 
side to side. Tbey contain each a capillary bloodveasel, which le- 



Fig. 2i. 



Fig. as. 



\ ■ 






BSek, Ouillae pofllon. Mafalllail TO dUmnlan. 

Pig. M rrw mibc* of QAirBiD Mtrrvni 1<«h*niss, vUwvil tn vvrtltwi *MiJaa ; ttvm 
n^i Btoaaek, PflDria portlan. Ua^DiSnl 43D dUnclvm. 

turns upon itself in a loop at the extremity of tlie projection, and 
commuaic-utes freely witb adjacent vessels. The gastric fulUcled are 
very difl'urent in difieretit 
p*rts of the stomach. In the *''*■ "'• 

pyloric portion (Fig. 27), tlicy 
are nearly straight, simple 
tabales, ,lo of an inch in 
diameter, easily separated 
from each other, lined with 
glandular epithelium, and ter- 
minating in blind extremities 
at the under surface of the 
maoous membrane. They are 
sometimes slightly branched, 
or provided with one or two 
rounded diverticula, a short 
distance above their termiii.v 
lion. They open on the free 
surface of the mucous mem- 
tmne, in the interspaces be- 
tween the projecting folds or villi. Among these tubular glandules 



PjrtDtIc portion: Tortlnl ■saltan ; ■hnwliiff i;<i>lrlo 
lubiil^s ■■•4, M (I, B «lu*fd fulJIcla. Hj^alAcd ;•) 
dl*iui>tiir>. 



118 



BIOESTIO!r. 



there is also found, in the gaalric mucous membrnne, another kind! 
of glandular organ, consisting of closed follicles, similar to the soli- 
tary glands of the small intestine. These follicles, wliich are not very 
numerous, arc seated in the lower part of iho mucoua membrane, 
and enveloped by the Ciocal extremities of the tubules. (Fig. 27, o.) 



Fig. 2S. 



Ftg.2». 



/ 



J 



J 



"-*:-f 



'*^^-' 



\ 



Pl( n, a««TiiicTciiiir-KBrRoaPtii'«!lT«HjrR, Pjrlorie puiltno, ibowlaj Ibalr Cxal 
Bxtrvdilllvt. AI a. Ilm lurn nslrrniiij of a rubul*, ttiowlag 1U C«Tll7 

Pig. S. UitiTKio TU'nui.Ki rK'>)i V lo'* Sraai'iMi CanllAc porlloB. At a, ft Ur^t takiU* 
dlrldlng Into two BtD^I obm. b Partlon nf «, [nlkola, mm •udwlan. c. It* Mnttal eaTHjr. 



1 



I 



In the cardiac portion of the stomach, the tubules are very wide 
in the stiperficiiil part of the mucous membrane, and liuod with 
large, distinctly marked cylinder epithelium cells. (Fig. 29.) In the 
deeper parts of the membrane they become branched and conside- 
rably reduced in size, from the point where the branching takes 
place to their termination bclow^ they are lined wilii small glandular 
epithelium cells, and closely bound together by intervening areolar ■ 
tissue, so as to present aomowhac the appearance of compound 
glandules. 

The bloodvessels which come up from the submucous layer of 
areolar tiasuo form a close plexus around alt these glandules, and 
provide the mucous membrane with an abundant supply of blood, 
lor the purposes both of secretion and absorption. 

That part of digestion which takes place in the stomach has 
always been regarded as nearly, if not quite, tlie most important 
part of the whole process. The first observers who made any 
approximation to a correct idea of gastric digestion were Heaumur 
and Spallaozani, who showed by various methods that the reduction 




eXSTRIC JUICB, AND BTOMAOHDTGHSTIOK. 



119 



and liqueraclion of Lh« food m tbe stomach, could uot be owing to 
mere contact with the gastric mucous membrane, or to compression 
by the muscular walla of the organ ; but that it must be attributed 
to a digestive fluid secreted hy the mucous membrane, which pene- 
trates the food and reduced it to u Quid form. They regarded this 
process as a simple chemical solution, and considered the gastric 
juice as a universal solvent for all alimentary substances. They 
succeeded even in obtaining some of this gastric juice, mingled 
probably with many impurities, by causing the animals upon which 
they experimented to swallow sponges attached to the ends of 
cords, by which they were afterward withdrawn, the fluids whieh 
they had absorbed being then expressed and examined. 

The first decisive experiments on this point, however, were those 
performed by Dr. Beaumont, of the U. S. Army, on the person of 
Alexia St. Muriin, a Canadinu boatman, who had a permanent gas- 
tric fistula, the result of an accidental gunshot wound. The musket, 
which was loaded with buckshot at the time of the accident, waa 
discharged, at the distance of a few feet from St. Martin's body, in 
such a. manner as to tear away the integument at the lower part of 
the lel\ chest, open the pleural cavity, and penetrate, through the 
lateral portion of the diaphragm, into the grent pouch of the stomach. 
After the integument and the pleural and peritoneal surfaces bad 
nnit«d and cicatrized, there remained a permanent opening, of about 
four-Gflhs of an inch in diameter, leading into the led extremity of 
the stomach, which was usually closed by a circular valve of pro- 
trading mucous membrane. This valve could be readily depressed 
at any time, so as to open the fistula and allow the contents of the 
stomach to be extracted for examination. 

Dr. Beaumont experimented upon this person at various intervals 
from the year 1826 to 1832.' He established during the course of 
bis examinations the following important facts: First, that the ac- 
tive agent in digestion is an acid fluid, secreted by the walls of the 
stomach; secondly, that this fluid \a poureii out by the glandular 
walls of the organ only daring digestion, and under the stimulus of 
the food; and 6nal]y, that it will exert its solvent action upon the 
food outside the body as well as in the stomach, if kept in glass 
phials upon a sand bath, at the temperature of 100^ F. He made 
also a variety of other interesting investigations as to the efTect 
of various kinds of stimulus on the secretion of the stomach, thd 



' EiprhiunDUi sad UbMrvatlOM upoo the Outric Juic«. Boston, 1^34. 



no 



DtOESTIOir. 



rapi<1ity with which the process of digestion takes place, the com- 
parative digestibility of various kinds of food, kc. &C. 

Since Dr. Beaumont's time it bos been ascertained that aimilar 
gu5tric fistula! may be produced at will on some of the lower animals 
by a simple operation; and the gastric juice has in this way been 
obtained, usually from the dog, by Blondlot, Schwann, Bernard, 
Lehmann and others. The siniplest and most expeditious modo 
of doing ihe opemlion is the best. An incision should be mado 
through the abdominal parieies in the median line, over the great 
curvature of the stomach. The anterior wall of the organ is then 
to be seized with a pair of hooked forceps, drawn out at the external 
wound, and opened with the point of a bistoury. A abort silver 
caniila, one-half to three-quarters of an inch in diameter, armed at 
each extremity with a narrow projecting rim or flange, i.i then in- 
serted into the wound in the stomach, the edges of which are fast- 
ened round the tube with a ligature in onler to prevent the escape 
of the gastric fluids into the peritoneal cavity. The stomach is then 
retumet^l to its place in the abdomen, nnd the canula allowed to re- 
main with its external flange resting upon the edges of the wound 
in the abdominal integuments, which are to be drawn together by 
sutures. The animal may be kept perfectly quiet, during the ope- 
ration, by the administration of ether or chloroform. In a few 
days the ligatures come away, the wounded peritoneal surfaces are 
united with each other, and the canula is retained in a permanent 
g»9tric flKtula; being prevented by its flaring extremities both from 
falling out of the abdomen and from being accidentally pushe<1 into 
the stomach. It is closed externally by a cork, which may be with- 
drawn at pleasure, and the contents of the stomach withdrawn for 
examination. 

Experiments conducted in thta manner confirm, in the mnin, the 
results obtained by Dr. Beaumont. Observations of this kind are 
in some respects, indeed, more satisfactory when made upon the 
lower aiiimaliH, than upon the human subject; since animals aro 
entirely under the control of the experimenter, and all sources of 
deception or mistake aro avoided, while the investigation is, at the 
same time, greatly facilitated by the simple character of their foo<l. 

The gastric juice, like the saliva, is secreted in considenible 
quantity only under the stimulus of recently ingested food. Dr. 
Beaumont states that it is entirely absent during the intervals of 
digestion; and that the stomach at that time contains no acid fluid, 
but only a little Qcntral or alkaline mucus. He was able to obtain 



OJISTBIC JDICK, ASD HTOMACH DIOSSTIOX. 



12X 



a snfficient quantity of gastric juice for examination, by genlly irri- 
tatiug the mucous membrane wiih a gum-ela«lic catbeter, ot ihe end 
of a gUss rod, and by collecting tbe secretioa as it raa in drops 
from the Sstula. On the inlroduction of food^ be found that the 
tnuooua membrane became turbid and reddened, a clear acid fluid 
ooUected everywhere in drops uriderneath the layer of mucus lin- 
iug the walls of tbe stomach, and was soon poured out abundantly 
into its cavity. We have found, buwuver, tliat tlm rule laid down 
by Dr. Beaumont in thin respect, tiiough correct in the main, is not 
invariable. The truth is, tbe irritability of tbe gastric mucous 
membrane, and the readiness with which the (low of gastric juice 
may be excited, varies conbiderably in diQ'erent auimala ; even ia 
those belonging to the same species. In experimenting with gastric 

iAatuIce on diflureoldogs, for example, we Iiave found in one instance, 
like Dr. Beaumont, that the gastric juice was always entirely absent 
in the intervals of digestion; the mucous membrane then present- 
ing invariably either a neutral or slightly alkaline reaction. In 
this animal, which was a perfectly healthy one, the secretion could 
not be excited by any artificial means, such as glass rods, metallic 
catheterA, and tbe like; but only by the natural stimulus of ingested 
food. We have even Been tough and indigestible pieces of tendon, 
introduced through the fistula, expelled again in a few minutes, ono 
tflcr the other, without exciting the Bow of a single drop of acid 
fiaid; while pieces of fresh meat, introduced in tbe same way, pro* 
duced at once an abundant supply. In other instances, on the con- 
trary, the introduction of metutlic catheters, iic, into the empty 
Btomacb has produced a scanty flow of gastric juice; and in experi- 
menting upon dogs that have been kept without food during various 
periods of time and then killed by section of the medulla oblongata, 
TO have usually, though not always, found the ga.stric mucous mem- 
brane to present a distinctly acid reaction, even after an abstinence 
of six, aoveo, or eight days. There is at no time, however, under 
these circumslances, auy considerable amount of Quid present ia 
the stomach; but only ju.st suiTicient to moisten the gastric mucous 
membrane, and give it an acid reaction. 

1*fae gastric juice, which is obtained by irritating the stomach 
with a metallic catheter, is clear, perfectly colorless, and acid in 
iRaelion. A suflicient quantity of it cannot be obtained by this 

ihod for any extended experiments; and for that purpose, the 
animal should be fed, after a fast of twenty-four hours, with fresh 
lean meat, a little hardened by short boiling, in order to coagulate 



122 



DIGESTION. 



Iha fluid? of the muscular tissue, and prevent their mixing with the 
gastric secretion. No efleet is usually fl|)parent within tlio first flvo 
mtnut<^ t.tw.r the introduction of the food. At the end of that time 
the gastric juice begins to flow; at first slowly, and in drops. It is 
then perfeytly colorless, but very soon acquires a alight amber 
tinge. It then begins to flow more freely, usually in drops, but 
oAen running for a few seconds in a continuous alrcam. In this 
way from ,5ij to Siias may be collected in the course of fifteen 
minutes. Afterward it becomes somewhat turbid with the debris 
of the food, which has begun to be diirintegrated; but from tbia it 
may be readily separated by filtration. After three hours, it oon- 
linuoa to run freely, but has become very much thickened, and 
even grumous in consistency, from the abundant admixture of 
alimentary debris. In six hours after the commencement of diges- 
tion it runs less freely, and in eight hours has become very scanty, 
though it continues to preserve the same physical appearances as 
before. It ceases to flow altogether in from nine to twelve hours, 
according to the quantity of food taken. 

For purposes of examination, the fluid drawn during the first 
fifteen minutes after feeding should be collected, and separated by 
filtration from accidental impurities. Obtained in this way, the 
gtotrio juice is a clear, watery fluid, without any appreciable vis- 
cidity, very distinctly acid to test paper, of a faint amber color, 
and with a specific gravity of lOlD. It becomes opalescent on 
boiling, owing to the coagulatron of its organic ingredients. The 
following is the composition of the gastric juice of the dog, based 
on a comparison of various analyses by Lehm.aan, aud Bidder and 
Schmidt:— 

CoMPuHTioa or Oahtiiic Jdicx. 

Wnt«r 078.00 

Organic mutter 16.00 

I<*clfG JUiiA 4,78 

Clilorldsof aodioin I.JO 

" " pi>iBH«iDni 1,08 

" " mlduin (KSO 

" " annmoninni 0.65 

I'houpbalv of limn 1.48 

" " mngcrsia 0M 

*' " ina 0.06 

lOW.OO 

In place of lactic acid, Bidder and Schmidt found, in most of their 
ar.aly.ws, hydrochloric acid. Lehmann admits that a small quantity 
of hydrochloric acid i» sometimes present, hut regards lactic acid 



I 



OASTBIO JUICB, AXn STOUACH DIOSSTIOIT. 



128 



08 much the most abundant aud important of the two. Kobin and 
, Venleil also regard the acid reaction of the gn»trio juice as due to 
lactic acid; and, finally, Bernard has shown,' by a serlea of well 
contrived experiments, that the free acid of the dog's gastric juice 
ia undoabtedly the lactic ; and that the hydrochloric acid obtained 
by distillation, is really produced by a docom position of the chlo- 
rides, which enter into the CGmpoattion of the fresh juice. 

The free acid is an extremely important ingralient of the gastric 

BecrettoD, and is, in fact, essential to its physiological properties; 

[for the gastric juice will not exert its solvent action upon the fuod, 

after it has been neutralized by the additioa of on alkali or &u 

.alkaline carbonate. 

The most important ingredient of the gastric juice, beside the 
acid, is its organic matter or "ferment," which is sometimes 
[IcnuwQ under the name of ptpsine. This name, "pepsine," was 
^originally given by Schwann to a substance which he obtiiinod 
[from the mucous membrane of the pig^s stomach, by macerating it 
in distilled water until a putrid odor began to be developed. The 
substance in question was precipitated from the watery infusion by 
the addition of alcohol, and dried; and if dissolveti afterward in 
adulated water, it was found to exert a solvent a<;tioa qu boiled 
white of egg. This substance, however, did not represent precisely 
the natural ingredient of the gastric secretion, and was probably a 
mixture of various matters, some of them the products of com- 
tnencing decomposition of the mucous membrane itself. The name 
pepsine, if it be used at all, should be applied to the organic matter 
which naturally occurs in solution in the gastric juice. It is alto- 
gether uncsseniial, in this respect, from what source it may be 
originally derived. It has been regarded by Bernard nod others, 
on somewhat insufficient groundu, as a product of the alteration of 
the mucus of the stomach. But whatever be its source, since it is 
always present in the secretion of the stomach, and takes an active 
part in the performance of its function, it can be regarded in no 
other light than as a real anatomical ingredient of the gastric juice, 
and as es.'-ential to its constitution. 

Pepsins is precipitated from its solution in the gastric juice by 
absolute alcohol, and by various metallic salts, but is not aflectcd 
by fernxyanidc of potassium. Tt is precipitated also, and coAgu- 
laled, by a boiling temperature; and the gastric juice, accordingly. 



Lvi.'ooa <!• Phjniitilouia Kxp£fimcnl«l«, IHirit, ISStf, p. 390. 



124 



DlQBSTtON'. 



after being boiled, becomes turbid, and loses altogether its power 
of dissolving alitneoiary substances. Gastric juice is also affected 
in a remarkable manner by being mingled with bile. We have 
found that four to six drops of dog 'a bile precipitate completely 
with 5j of gastric jaice from the same auiinal ; so that the whole uf 
the biliary coloring matter is thrown down as a deposit, and the 
filtered fluid is found to have lost entirely its digestive power, 
though it retuiiis an acid reaction. 

A very singular property of the gastric juice is its inaptitude /or 
putrefaction. It may be kept for an indeilnite length of lime in a 
common glass-stoppered bottle without developing any putrescent 
odor. A light deposit generally collects at the bottom, and a cod* 

fervoid vegetable growth or 
Kg. 30. " mould" otlen shows itaelf 

in the fluid afler it baa been 
kept for one or two weeks. 
This growth has the form of 
white, globular luasKcs, each 
of which is composed of deli- 
cate radiating branched fila* 
ment9(Fig.30); each lilament 
consisting of a row of elon- 
gated cells, like other vege- 
table growths of a similar 
nature. These growths, how- 
ever, are not accompanied by 
any puirefactive changes, and 
the gastric juice retains its 
acid reaction and its digestive 
properties for many months. 
By experimenting artificially with gastrio juioe on various ali- 
mentary substances, such M meat, boiled white of egg, &c., it la 
found, as Dr. Beaumont formerly observed, to exert a solvent action 
on these substances outside the body, as well as in the cavity of the 
stomach. This action is most energetic at the temperature of 100"* 
F. It gradually iliminishesin iiiiensity below that point, and cea&ea 
altogetbar near 32". If the temperature bo elevated above 100" 
the action also becomes enTeebled, and is entirely suspended about 
160°, or the temperature of coagulating aH>umun. Contrary to 
what was supposed, however, by Dr. Beaomont and his predcc«a* 
ftora, the gastric juice is not a universal solvent for all alimentary 



C»»rB>TOir Vau>T««i.K (ntwios In lh« Oa*- 
trie JhIm uf ih# Doc. the Abntt li«*o »u itiwiigt 
dlaoiernruri-TOCAur •» liicli. 



I 



I 
I 




OA3TBIC JUICE, AND STOMACH DIGESTION. 126 

snbstances, bat, on the contrary, aSecta only a single class of the 
proximate principles, viz., the albaminoid or organic snbstances. 
Neither starch nor oil, when digested in it at the temperatnre of 
the body, suffers the slightest chemical alteration. Fatty matters 
are simply melted by the heat, and starchy substances are only 
hydrated and gelatinized to a certain extent by the combined influ- 
ence of the warmth and moisture. Solid and semi-solid albuminoid 
matters, however, are at once attacked and liquefied by the diges- 
tive fluid. Pieces of coagulated white of egg suspended in it, in a 
test-tube, are gradually softened on their exterior, and their edges 
become pale and rounded. They grow thin and transparent; 
and their substance finally melts away, leaving a light scanty de- 
posit, which collects at the bottom of the test-tube. While the 
diuntegrating process is going on, it may almost always be noticed 
that minute, opaque spots show themselves in the substance of the 
liquefying albumen, indicating that certain parts of it are lera easily 
attacked than the rest ; and the deposit which remains at the bot- 
tom is probably also composed of some ingredient, not soluble in 
the gastric juice. If pieces of fresh meat be treated in the same 
manner, the areolar tissue entering into its composition is first 
dissolved, so that the muscular bundles become more distinct, and 
separate from each other. They gradually fall apart, and a little 
brownish deposit is at last all that remains at the bottom of the 
tube. If the hard, adipose tissue of beef or mutton be subjected 
to the same process, the walls of the fat vesicles and the inter- 
vening areolar tissue, together with the capillary bloodvessels, &C., 
are dissolved ; while the oily matters are set free from their en- 
velops, and collect in a white, opaque layer on the surface. In 
cheese, the casein is dissolved, and the oil which it contains set 
free. In bread, the gluten is digested, and the starch lefl un- 
changed. In milk, the casein Is first coagulated by contact with 
the acid gastric fluids, and aftierward slowly liquefied, like other 
albuminoid substances. 

The time required for the complete liquefaction of these sub- 
stances varies with the quantity of matter present, and with its state 
of cohesion. The process is hastened by occasionally shaking up 
the mixture, so as to separate the parts already disintegrated, and 
bring the gastric fluid into contact with fresh portions of the diges- 
tible substance. 

The liquefying process which the food undergoes in the gastrio 
juice is not a simple solution. It is a catalytic transformation. 



126 



DT0E9TI0TI. 



produced in the albuminoid subaiLancca by contact with the organic 
matter of the digealive fluid. This organic matter acts in a Bimilar 
manner to that of the catalytic bodies, or "ferments,"' generally. 
Its peculiarity is that, for ila active operation, it requires to be dia- 
solved in an acidulated fluid. In common with other ferments, it 
requires also a moderate degree of warmth; ita action being checked, 
both by a very low, and a very high temperature, hj its opera- 
tion the albuminoid matters of the food, whatever may have been 
their original character, are all, without distinction, converted into 
a new substance, viz., albuminose. This substance has the geiioral 
characters belonging to iho class of organic matters. ]t is oncryB* 
talliziible, and contains nitrogen as an ultimate element. It is pre- 
cipitated, like albumen, by an excess of alcohol, and by the metallic 
salts; but unlike albumen, is not aB'ected by nitric acid or a boil- 
ing temperature. It is freely soluble in water, and after it is once 
produced by the digestive proceas, remains in a fluid condition, 
and is ready to be absorbed by the veaaels. In this way, cawio, 
fibrin, masculine, gluten, iSw., are all reduced to the condition of 
albaminoae. By experimenting as above, with a mixture of food 
and gastric juica in teat tubes, we have found that the casein of 
cheese is entirely converted into albuminose, and dissolved under 
that form. A very considerable portion of raw white of egg, how- 
ever, dissolves in the gastric juice directly as albumen, and retains 
its property of coagulating by heat. Soft-boiled white of egg and 
raw meat are principally converted into albuminose; but at the 
same time, a small portion of albumen is also taken up unchanged. 

The above process is a true liquefaction of the albumiaoid eub- 
stances, and not a simple disintegration. If fresh meat be cut into 
small pieces, and artiticially digested in gastric juice in test-iubcs, 
at 100" h\, and the process assisted by occasional gentle agitation, 
the fluid continues to take up more and more of the digestible 
material for from eight to ten hours. At the cud of that time if it 
be separated and filtered, the iiltered fluid has a distinct, brownish 
color, and is saturated with dissolved animal matter. Its specific 
gravity is found to have increased from 1010 to 1020; and on the 
addition of alcohol it becomes turbid, with a very abundant whitish 
precipitate (albuminose). There is also a peculiar odor developed 
during this process, which reaeinblea that produced in the malting 
of barley. 

Albuminose, in solution in gastric juice, has several peculiar 
properties. One of the most remarkable of these is that it inter* 




OASTRIC JL'ICB, AND STOMACH DIGSSTION. 



121 



rith the operation of Trommer's test for grape sugar (uee 
iS). We first observed and described this peculiarity in 
ld&4,* but could not determine, at that time, upon what particular 
ingredient of the gastric Juice it dupeniled. A short time Bubw- 
quenily it was also noticed by M. Longet, in Paris, who published 
his observations in the Gazette Hdidomadaire for February 9th, 
185.V He altributcd the reaction not to the gastric juice itself^ 
but to the albucDinase held in solutioii by it. We have since found 
this explanation to be correct. Gastric juice obtained from the 
empty stomach uf the fasting aniinnl, by irritation with a nietallio 
catheter, which is clear and perfectly colorless, does not interfere 
in any way with Trommer's test; but if it be macerated for some 
huura in a test-tube with (inely chopped meat, at a tomperature of 
100°, it will then be found to have acquired the property in a 
marked degree. The reaclion therefore depends undoubtedly upon 
the presence of atbuminose in solution. As the gastric juice, drawn 
from the dog'g stomach half an hour or more aflcr the introduction 
of food, already contains some albuminose in solution, it prcsenta 
the same reaction. If such gastric juice be mixed with a small 
quantity of glucose, and Trommer's test applied, no peculiarity is 
obeervedon first dropping in the sulphate of copper; but on adding 
afterward the solution of pota&sa, the mixture takes a riuh purple hue, 
instead of the clear blue tinge which is presented under ordinary 
circumstances. On boiling, the color changes to claret, cherry red, 
and finally to a light yellow; but no oxide otcopperiadepotiited, and 
the fluid remains clear. If the albuminose be present only in small 
quantity, an incomplete reduction of the copper takes place, so that 
the mixture becomes opaline nnd cloudy, but still without any well 
marked deposit. This interference will take place when sugar is 
present in very large proportion. We have found that in a mix- 
tare of honey and gnstrio juice in equal volumes, no reducUon of 
copper takes place on the application of Trommer^a test. It is 
remarkable, however, that if such a mixture be previously diluted 
with an equal quantity of water, the interference does not take 
place, and the copper is deposited as usual. 

Usually this peculiar reaction, now that we are acquainted with 
its existence, will not practically prevent the detection of sugar, 



< Amtrietn Jonrn. M«k1. Boi., Oct. IH54, p. S19. 

' Kouvellw roo1)«rc1i«s reUlives fc t'a^ltoii du vuo gutriqne tnr )m BUbftlnuce* 
albaniooidM.— Coc. fhbtt. S Fccrier, Ig^S, p. 103. 



128 



DIOK8TIOH". 



wben present; since the presence of the sugar is ilistiDctly indi- 
cated b^ iho change of color, as above mentioned, from jmriile to 
yellow, though the copper may not be thrown down as a precipi- 
tate. All possibility of error, furthermore, ■ may be avoided by 
adopting ihe following precauiioiia. The purple color, already men- 
tioned, will, in the first place, serve to in<iicotc the presence of the 
albuminoid ingredient in the suspected fluid. The mixture should 
then be evaporated to dryness, and extracted with alcohol, in order 
to eliminate the animal matters. After ihat, a watery solution of 
the sugar contained tn the alcoholic extraol will react as usual with 
Trommer's teat, and reduce the oslde of copper without difficulty. 

Another remarkable property of gnstric jnioe containing albu- 
minose, which is not, however, peculiar to it, but common to many 
other animal fluids, is that of interfering with the mutual reaction 
of starch and iodine. If ^' of such gagtric juico be mixed with 3j' 
of iodine water, and boiled starch be subsequently added, no blue 
color ia produced ; though if a larger quantity of iodine water be 
added, or if the tincture be used instead of the aqueous soiutioo, 
the superabundant iodine then combines with the starch, and pro- 
duces the ordinary blue color. This property, like that describod 
above, is not poaacased by pure, colorless, gastric juice, taken from 
the empty stomach, but is acquired by it on being digested with h 
albuminoid substances. ■ 

Another important action which takes place tn the stomach, 
beside the secretion of ilie gastric juiw;, ia the jicnttaUie movtmrnt 
of the organ. This movement is accomplished by the alternate 
contraction and relaxation of the longitudinal and circular fibres 
of its muscular coat. The motion ia minutely described by Dr. 
Beaumont, who examined it both by watching the movements of 
the food through the gastric fistula, and also by introducing into 
the stomach the bulb and stem of a thermometer. According to 
his observations, when the food first pasaes into the stomach, and 
the secretioD of the gastric juice commences, the muscular coat, 
which was before quiescent, is excited and begins to contract act- 
ively. The contraction takes place in such a manner that the food, 
af^er entering the cardiac orifice of the sk)mach, is first carried to 
the left, into the great pouch of the organ, thence downward and 
along the great curvature to the pyloric portion. At a short distance 
from the pylorus, Dr. B. often found a circular constriction of the 
gastric parietea, by which the bulb of the thermometer was gently ■ 
grasped and drawn toward the pylorus, at the same time giving a 



I 




GASTRIC JUICE, AND STOUACn DIGESTION. 129 

twisting motion to the stem of the iDstrament, by which it was 
rotated in hia fingers. In a moment or two, however, this constric' 
tioD was relaxed, and the bulb of the thermometer again released, 
and carried together with the food along the small curvature of 
the 01^11 to its cardiac extremity. This circuit was repeated so 
long as any food remained in the stomach; but, as the liquefied 
portions were successively removed toward the end of digestion, it 
became less active, and at last ceased altogether when the stomach 
had become completely empty, and the organ returned to its ordi- 
nary quiescent condition. 

It is easy to observe the muscular action of the stomach during 
digestion in the dog, by the assistance of a gastric fistula, artificially 
established. If a metallic catheter be introduced through the fistula 
when the stomach is empty, it must usually be held carefully in 
place, or it will fall out by its own weight. But immediately upon 
the introduction of food, it can be felt that the catheter is grasped 
and retained with some force, by the contraction of the muscular 
coat. A twisting or rotatory motion of its extremity may also be 
frequently observed, similar to that described by Dr. Beaumont. 
This peristaltic action of the stomach, however, is a gentle one, 
and not at all active or violent in character. We have never seen, 
in opening the abdomen, any such energetic or extensive contrac- 
tioQS of the stomach, even when full of food, as may be easily 
excited in the small intestine by the mere contact of the atmosphere, 
or by pinching them with the blades of a forceps. This action of 
the stomach, nevertheless, though quite gentle, is snfiicient to pro 
dace % constant churning movement of the masticated food, by 
which it is carried back and forward to every part of the stomach, 
and rapidly incorporated with the gastric juice which is at the 
same time poured out by the mucous membrane; so that the 
digestive fiuid is made to penetrate equally every part of the ali- 
ntentary mass, and the digestion of all its albuminous ingredients 
goes on simultaneously. This gentle and continuous movement of 
the stomach is one which cannot be successfully imitated in experi- 
ments on artificial digestion with gastric juice in test-tubes; and 
consequently the process, under these circumstances, is never so 
rapid or so complete as when it takes place in the interior of the 
stomach. 

The length of time which is required for digestion varies in 
different species of animals. In the carnivora, a moderate meal of 
freah uncooked meat requires from nine to twelve hours for its 
9 



DtGttSTION. 

complete solution and disappearance from the stomach. According 
Co Dr. Beaumont, the average time required for digestion in the 
human subject is considerably less; varying from one hour to five 
hours and a half, according to the kind of food employed. This 
is probably owing to the more complete masticnlioD of the food 
wbich tnkes place in man, than in the carnivorous animals. By 
examining the coutentd of the stomach at various intervals after 
feeding, Dr. Beaumont made out a list, showing the comparative 
digestibility of diJTerent articles of food, of which the following are 
the most important: — 
Time required for digestion, according to Dr. BeaumoDt; — 

Kixp DP Food. Hocne. MiMrm. 

Pig'e feet 1 00 

Trip« 1 00 

Tront (brailMl) I 80 

Venison itoxk 1 3S 

Milk 2 00 

Roa»l«d tarke/ 2 80 

bM«f 8 00 

" luulton 3 IS 

Tval (broilcHl) 4 00 

Snit h«iof (ItoWcA-) 4 IS 

Roaattwl pork C IB 

The comparative digestibility of diffbrent substances varies more 
or lens in different individuals according to temperament; but the 
above list undoubtedly givea a correct average estimate of the time 
required for stomach digestion under ordinary conditions. 

A very intereating question is that which rcklcs to tl^ total 
qwaniity of gastric juice secreted daily. Whenever direct experi- 
ments have been p'erformed with a view of ascertaining this point, 
their results have given a considerably larger quantity than was 
anticipated. Bidder and Schmidt found that, in a dug weighing 
84 pounds, they were able to obtain by separate experiments, cod- 
sumtng in. all 12 hours, one pound and three-quarters of gastrio ■ 
juice. The total quantity, therefore, for 2i hours, in the same ani- 
mal, would be SJ pounds; and, by applying the same calculation to 
a man of medium size, the authors estimate the total daily quantity 
in the human subject as but little less than H pounds (av.). This 
estimate is probably not an exaggerated one. In order to deter- 
mine the question, however, if possible, in a different way, we 
adopted the following plan of experiment with the gaatric juice of 
the dog. It was iirst ascertained, by direct experiment, that the 




GASTRIC JUICE, AND STOVACH I>IOBSTION. 



131 



. lean meat of tbe bullock's hiiart loses, by complete desiccation, 
78 per cent, of its weight. 300 grains of such meat, cut into small 
pieces, were then digested for ten hours, in 3iss of gastric juice at 
100*^ F.; the mixture being thoroughly agitated as oflen as ever; 
hour, in order to insure the digestion ofaa large a quantity of meat 
as pussibie. The meat remaioiog undissolved wob then collected 
on a previously weighed tlltor, and evaporated to dryness. The 
dry residue weighed o5 grains. This represented, allowing for the 
loss by evaporation, 250 grains of the meat, in its natural moist 
condition ; 50 grains of meat were tlien dissolved by Jisa of gastrio 
juice, or 33} grains per ounce. 

From these data wo can form some idea of the large quantity of 
gutrio juice secreted in the dog during the process of digestion. 
Oue pound of meat is only a moderate meal for a medium-sized 
animal; and yet, to dissolve this quanUly, no less than thirteen pinis 
of gastric juice will bo necessary. This quantity, or any approxi- 
matioD to it, would be altogether incredible if we did not recollect 
that tbe gastric juice, as soon as it has dissolved its quota of food, 
i» immatiotefy reabsorbed, and again enters the circulation, together 
with the alimentary substances which it hulds iu solution. Tbe 
secretion and reabsorption of the gastric juice then go on simulta- 
neously; and the fluids which the blood loses by one process are 
iDoeaoLntly restored to it by the other. A very large quantity, 
therefore, of the secretion may be poured out during the digestion 
of a meal, at an ex|>enBe to the blood, at any one time, of only two 
or three ounces of fluid. The simplest investigation shows that 
llie gtutric juice does not accumulate in the stomach in any coa- 
eiderable quantity during digestion; but that it is gradually 
secreted so long as any food remains undissolved, each portion, as 
it ia digested, being disposed of by rea^xtorption, together with its 
solvent fluid. There is accordingly, during digestion, a constant 
circulation of tbe digestive Quids from the bloodvessels to the all- 
niOQtMry canal, and from the alimentary canal back again to the 
bloodvessels, 

That this circnlation really takes place is proved by the fol- 
lowing facts: First, if a dog be killed some hours after feeding, 
there is never more than a very small quantity of fluid found in 
the Btoinucti, just sufBcient to smear over and penetrate the half 
digested pieces of meat; and, secondly, in the living animal, gastric 
jaice, drawn from the fistula Ave or six hours afler digestion has 
been going on, contains little or no more organic matter in solution 



132 



DiaESTIOS. 



than that extracted fifteen to thirty minutes after the iritrodiiotion 
of fonii. It has evidently been freshly secreted; and, in order to 
obtain gastric juice saturated with alimentary matter, it must be 
artiflcially digested with food in test-tubes, where this constant ab- 
sorption and renovntinu cannat take place. 

An unnecessary difficulty has sometimes been felt in understand* 
iDg how it is that the gastric juice, which digests so readily all albu- 
minous substances, should oot destroy the walls of the stomach 
itself, which ara composed of similar materials. This, in fact, was 
brought forward at an early dny, as an insuperable objection to the 
doctrine of Reaumur and Spallnnzani, that digestion was a process 
of chemical solution performed by a digestive fluid. It was said 
to be impossible that a fluid capable ol' dissolving animal mutters 
should be secreted by tho walls of the stomach without attacking 
them also, and thus destroying the organ by which it was itself 
produced. Since that time, various complicated hypotheses have 
been framed, io order to reconcile these apparently contradictory 
facts. Tho true oxplanaLion, however, as we believe, lies in this — 
that the process of digestion is not a simple solution, but a catalytic 
transformation oF the nlimentary substances, pro^luced hy contact 
with the pepsine of the gastric juice. We know that nil the or- 
f^anic substances in the living tissues are constantly undergoing, in 
the process of nutrition, a scries of catalytic changes, which are 
characteristic of the vital operations, and which are determined by 
ihe organized materials with which they are in contact, and by all 
the other conditions present in the living organism. These changes, 
therefore, of nutrition, secretion, &c., necessarily exclude for the 
time all other catalyses, and take precedence of them. In the same 
way, any dead organic matter, exposed to warmth, air, and moist- 
ure, putrefies; but if immersed in gastric juice, at the same 
temperature, the putrefactive changes are stopped or altogether^ 
prevented, because the catalytic actions, excited by the gastric 
juice, take precedence of those which constitute putrefaction. For 
u similar reason, the organic ingredient of the gastric juice, which 
acts readily on dead animal matter, has no eftect on the living 
tissues of the stomach, because they are already sul^ect to other 
eatalytio intiuences, which exclude those of digestion, as well' as 
those of putrefaction. As soon as life departs, however, and the 
peculiar actions taking place in the living tissues come to an end 
with the stoppage of the circulation, the walls of the stomach are 
really jitlackcd by the gostric juice remaining in its cavity, and^i 




IHTESTIKAL JUIOSS, DIGESTION OF SUGAR, ETC. 138 

ara more or less completely digested aad liquefied. In the hun)an 
subject, it is rare to make an exaraioation of the body twenty four 
or thirty-six hours al^er death, without finding the mucoua mem- 
brane of the great pouch of the stomaoh more or less softcDed and 
disintegrated from this cause. Sometimes the mucous membrane 
is altogether destroyed, and the submucous cellular layer exposed; 
and occasionally, when death ha» taken place suddenly during 
active digestion, while the stomach contained an abundance of 
gastric juice, all the coats of the organ have been found destroyed, 
and a perforation produced leading iulo the peritoneal cavity. 
These post-mortem changes show that, after deuth, the gastric juice 
really dissolves the coaLs of the stomach without difllculty. But 
during life, the chemical changes of nutrition, which are going on 
in their tissues, protect them from its influence, and eflectually 
preserve their integrity. 

The secretion of the gastric juice is much influenced by nervous 
conditions. It was noticed by Dr. Beaumont, in his experiments 
upon St. Martin, that irritation of the temper, and other moral 
causes, would frequently diminibh or altogether suspend the supply 
of the gastric fluids. Any febrile action in the system, or any 
unusual fatigue, was liable to exert a similar effect Every one is 
aware how readily any mental disturbance, such as anxiety, anger, 
or vexation, will take away the appetite and interfere with diges- 
tion. Any nervous impression of this kind, occurring at the com- 
meneemeni of digestion, seems moreover to produce some change 
which haa a lasting efleot upon the process; for it is very ofleti 
noticed that when any annoyance, hurry, or anxiety occurs soon 
after the food has been taken, though it may last only for a few 
moments, the digestive process is not only liable to be suspended 
fur the time, but to be permanently disturbed during the entire 
day. In order that digestion, therefore, may go on properly in the 
stomaoh, food must bo taken only when the appetite demands it; 
it should also be thoroughly masticated at the outset; and, litmlly, 
both mind and body, particularly during the commencement of the 
process, should be free from any unusual or disagreeable excite- 
ment. 



iNTKsnsAL Juices, and the Digestion or Sugar and Starch. 
— From the stomach, those portions of the food which have not 
already suffered digestion pasj^ into the third division of the ali- 
mentary canal, viz^ the small intestine. As already mentioned, U 



1S4 



DIGESTION. 



is oa\y the albuminous matters which are digasted in the stomacli. 
Cane sugar, it is true, is stowly converted by the gastric juice, OQt- 
side the body, into glucose. Wo have found that ten grains of 
cane sugar, dissolved in 5sa of gastric juice, give traces of gluccwe 
at the end of two hours; and in three hours, the quantity of thia 
substance is considerable. It cannot be shown, however, that the 
gastric juice exerts this effect on sugar during onlinary digestion. 
If pure cnno sugar be giveu to a dog with a gastric Sstula, while I 
digestion of meat Is going on, it disappears in from two to three 
hours, without any glucose being delected in the fluids withdrawn 
from the stomach. It is, therefore, either directly absorbed under 
the form of cane sugar, or passes, lictle by little, into the duodenum, 
where the intestinal fluids at once convert it into glucose. 

It is equally certain that starchy matters are not digested in the 
stomach, but pass unchanged into the small intestine. Here they 
meet with the mixed intestinal fluids, which act at once upon the 
_8t«rch, and convert it rapidly into sugar. The intestinal fluids, 

ten from the duodenum of a recently kilted dog, exert this 
Iransforniing action upon starch with the greatest promptitude, if 
mixed with it in a test-tube and kept at the temperature of 100** F. 
Starch is converted into sugar by this means much more rapidly 
and certainly than by the siiliva; and experiment shows that Ibo 
intestinal fluids are the active agents in its digestion during life. 
If a dog be fed with a mixture of meat and boiled starch, and killed 
a short time afler the meal, the stomach is found to contain starch 
but no sugar; while in the small intostiiio there is an abundnnoe of 
sugar, and bnt little or no starch. If some observers have failed 
to detect sugar in the intestin« after feeding the animal with ■ 
starch, it is because they have delayed the examination until too 
late. For it is remarkable how rapidly starchy substances, if pre- 
viously disintegrated by boiling, are disposed of in the digestive 
process. If a dog, for example, be fed as above with boiled starch 
and meat, while some of the meat remains in the stomach for 
eight, nine, or ten hours, the starch begins immediately to pass into 
the intestine, where it is at once converted into sugar, and then as 
rapidly absorbed. The whole of the starch may be converted into 
sugar, and curnpletcly absorbed, in an hour's time. We have even 
found, at the end of threequarters of an hour, after a tolerably 
full meal of boiled starch and meat, that all trace of both starch 
and sugar had disappeared from both stomach and intestine. The 
rapidity with which this passage of the starch into the duodenum 




IXTESTISAL JPICSS, DIGESTION OF SD-GAB, ETC. 135 



lakes p1ac« varies, to some ext«iit, in different animals, according 
to the general activity of the digestive apparatus; but it ia always 
■ comparatively rapid process, when the starch is already liquefied 
and is administered in a pure form. There can be no doubt that 
the natural place for the digestion of starchy matters ia the small 
iuleatine, and that it is aocumplisbed by the action of the intestinnl 
juices. ' 

Our knowledge is not very complete with regard to the exact 
nature of the fluids by which this digestion of the starch is aocoro- 
plished. The juices taken from the duodenum are generally a 
mixture of three different eecretionB, viz., the bile, the pancreatio 
Quid, and the intestinal juice proper. Of these, the bilo may be 
led out of the question; since it does not, when in a pure state, 
exert any digestive action on starch. The pancreatic juice, on the 
plher hand, has the property 
of converting starch into su- Fig. 3i. 

gar; but it is not known 
whether this fluid be always 
present in the duodenum. 
The true inU»tinal Juice is the 
prodact of two sets of glan- 
dular organs, seated in the 
substance of or beneath the 
roacoua membrane, viz., the 
folliclefl of Lieherktihn and 
the glands of Brunuer. The 
first of these, orLieberkUhn'a 
(blliclcs (Fig. SI), are the most 
numerous. They are simple, 
nearly straight tubules, lined 
vith a continuation of the 

intftstinal epithelium, and somewhat similar in their appearance to 
the follicles of the pyloric portion of the stomach. They occupy 
the whole thickness of the mucous membrane, and arc found in 
great numbers throughout the entire length of the limaU aud large 
Intestine. 

The glands of Brunner (Fig. 82), or the dnodonal glandulo?, as 
they are sometimes called, are confined to the upper part of the duo- 
denum, where they exist as a closely set layer, in the deeper portion 
of the mucous membrane, extending downward a short distance from 
the pylorus. They are composed of a great number of rounded fol- 






iMtlD* of Dog. 



186 



DIOBSTTOy. 



•4 



\ 



■ 
I 



r.^' 



l^)r(lno of ap« of BnL'nsra'a 



Ddovkvai. 



licles, clustered round a central excretory duct. Each follicld 
consisla of a delicate membranous wall, lined with glandular 

epillielium, and covered on 
^'S- ^^' its surface with small, dis- 

tinctly marked nuclei. The 
follicles collected around 
each duct are bound together 
by a thin layer of areolar tis- 
sue, and covered with a plex- 
us of capillary bloodTeasels. 
The inleslinal juice, which 
is the secreted product of the 
above glandular organs, has 
been less successfully studied 
than the other digestiTfl ^H 
fluids, owing to the difficulty V 
of obtaining it in a pure 
state. The method nsualty 
adopted ha& been to make au 
opening in the abdomen of the living animal, take out a loop of intea- ^ 
tine, empty it by gentle pressure, and then to nhut off* a portion of ^| 
it from the rest of the intealinal cavity by a couple of ligatnrefl, 
situated six or eight inches apart; niYer which the loop is returned 
into the ab^lumen, and the external wound closed by sutures. 
After six or eight hours the animal is killed, and the fluid, which 
has collected in the isolated portion of intestine, taken out and ' 
examined. The above was the method adopted by FrerlchB. Bid- H 
dcr and Schmidt, in order to obtain pure intestinal juice, (trst tied 
the biliary and pancreatic ducts, so that both the bite and the pan- 
creatic juice should be shut out from the intestine, and then estab' 
lislied an intestinal listula below, from which they extracted the 
fluids which accumulated in the cavity of the gut. From the great 
abundance of the follicles of Lieberkiihn, we should expect to find 
the intestinal juice secreted in large quantity. It appears, however, 
in point of fact, to be quite scanty, as the quantity collected in the 
above manner by experimenters lias rarely been sulTicienl for a 
thorongh examiaation of its properties. It seems to resemble very 
closely, in its [>hysical characters, the secretion of the mucons fol- 
licles of the mouth. It is colorless and glassy in appearance, viscid 
and mucous in consistency, and has a distinct alkaline reaction. 



I 




PANCKEATIC JUICE, AND THE DIOBSTIOy OF FAT. 187 

Tt has the property M-hen pure, a8 well as when miaed witli otlier 
Bacretions, of rapidly converting starch into sugnr, at the tempe* 
TBtQre of the living body. 

Pakorkatic Juice, akd thk Digestion op Fat. — The only re- 
maioiDg ingredients uf the food that require digestion Are the oily 
matters. These are not affected, as we have already stated, by con- 
lad with the gastric juice; and examination ttbows, furthermore, 
that they arc not digested iti the stomach. So long as they remain 
in the cavity of this organ they arc unchanged in iheir essential 
properties. Tbey are merely melted by the warmth of the stomscb, 
and aet free by the solution of the vesicles, fibres, or capillary tubes 
in which they are contained, or among which they are entangled ; 
and are still readily discernible by the eye, floating in larger or 
smaller drops on the surface of the semi-Quid alimentary mass. 
Very soon, however, after its entrance into the intestine, the oily 
portion of the food loses its chsractoristic appearance, and is con- 
verted into a white, opaque emulaion, which is gradually absorbed. 
This emulsion is termed the chyU, and is always found io the small 
intestine during the digestion of fat, entangled among the valvulie 
coODiventos, and adhering to the surface of the villi. The digestion 
of the oil, however, and its conversion into chyle, does not take 
place at once upon its entrance into the duodenum, but only after 
it has passed the orifices of the pancreatic and biliary ducts. Since 
Ibeae ducts almost invariably open into the intestine at or near the 
same point, it was for a long ume dilTiuult to decide by wliieh of 
the two secretions the digestion of tho oil was accomplished. M. 
Bernard, however, first threw some light on this question by ex- 
perimenting 00 some of the lower animals, in which the two ducts 
open separately. In tbo rabbit, for oxamplo, the biliary duct opens 
OS usual just below the pylorus, while the pancreatic duct com- 
manicales with the intestine some eight or ten inches lower down. 
Bernard fed these animals with substances containing oil, or in- 
jected melted butter into the stomach; and, on killing them after- 
«rar<l, found that there was no chyle in the intestine between the 
opening of the biliary and pancreatio ducts, but that it was abun- 
dant immediately below the oriBco of tho latter. Above thia point, 
also, he found tlie lacteals empty or transparent, while below it 
ihey were full of white and opaque chyle, 'I'he result of these ex- 
pcrimeDls, wbich have since been confirmed by Prof. Samuel Jack- 



188 



DTOESTION. 



son, of Philadelpliia,' \vd to the conclusion tb&t tbe pancrentic fluid 
is the active agent in the digestion of oily eubstauces; and an ex- 
amination of the properties of thta secretion, when obtaineil in a 
pDre state from the living animal, fully conRrms the above opinioD. 

In order to obtain pancreatic jtiice from the dog, the animal 
must be etherizeil soon after digestion has commenced, an iucisioa 
made in the upper part of the abdomen, a little to the righc of the 
median line, and a loop of the diiodenam, together with th« lower 
extremity of the pancreas which lies adjacent to it, drawn oat at 
the external wound. The pancreatic ditct is then to be exposed 
and opened, and a smalt silver cauula inserted into it and secured 
by a ligature. The whole is then returned into the abdomen and 
the wound closed by autiirea, leaving only the end of the canula 
projecting from it. In the dog there are two panoreatio ducts, 
situated from half an inch to an inch apart The lower one of 
these, which is usually the larger of the two, is the one best adapted 
for the insertion of the canula. Aflcr the eftbcts of etherization 
have passed off, and the digestive process baa recommenced, the 
pancreatic juice begins to run from the oriBce of the canula, at firat 
very slowly and in drops. Sometimes the drops follow each other 
with rapidity far a few moments, and then an Interval occurs during 
which the secretion seems entirely suspended. After a time it re- 
comroencea, and continues to exhibit similar fluctuations daring 
the whole course of the experiment Its flow, however, is at all 
limes scanty, compared with tliuL of the gastric juice; and we have 
never been able to collect more than a little over two fluidonncCT 
and a half during a period of three hours, in a dog weighing not 
more than forty-fivu pounds. This is equivalent to about 364 
grains per hour; but aa the pancreatic juice in the dog ia accreted 
with freedom only during digestion, and as this process is in opera- 
lion not more than twelve hours out of the twenty-four, the entire 
amount of the secretion for the whole day, in the dog, may be esti- 
mated at 4,S(>y grains. This result, applied to a man weighing 140 
pounds, would give, as the total daily quantity of the pancreatic 
juice, about 18,104 grains, or 1.872 pounds avoirdupois. 

Pancreatic juice obtained by the above process is a clear, color- 
less, somewhat viscid fluid, with a distinct alkaline reaction. Its 
composition according to the analysis of Bidder and Schmidt, is aa 
follows ; — 

1 AmericAn Joam. Umi. Sci., Oct. ISM. 



I 
I 





PANCREATIC JCICB, AKD THB DIOESTIOX OF FAT. 



Coiipo6iTn»c or Pancibatic Jiricn. 

Watw »0.7« 

OiYuic matter (pAiMnMfDa) 00.38 

ChlorirlM of ■odium 7.S< 

Pr*aiM«U O.SS 

rii(MphAt«of sod» 0.4S 

fialplmu Df soda 0.10 

8>lphue of potuRA O.OS 

I L(m« 0.-''4 

CombiDiUons ot < MsKiicsla ....... 0,0$ 

loxidoofiroa 0.03 



lOliO.OO 



^^^ The most important ingredient of the panareatic juice is its 
" organic matter, or pancreatine. It will be seen that this is much 
I more flbuDdant in proportion to the other ingredients of the aecre* 
I tiun than ibe organic matter of any other dige«live fluid. It is 
coagulablo by heat; and the pancreatic juice uf\en solidiQee com- 
pletely OD boiling, like white ofogg, so that not a drop of fluid re- 
mains after it« coagulation. It ia precipitated, furthermore, by 
nitric acid aiul by alcohol, and also by sulphate of magnesia in 
excess. By tbid lu»t property, it may he dietinguishod from albu* 
men, which is not afTected by contact with sulphate of magnesia. 

Fresh pancreatic juice, brought into contact with oily matters at 
the temperature of the body, exerta upon them, as wa« Gnst noticed 
by Bernard, a very peculiar effect It disintegrates them, and re- 
duces them to a state of complete emulsion, so that t)ic mixture is 
Bt onc« converted Into a white, opaque, creamy-looking fluid. This 
effect is instantaneous and permanent, and only requires that tho 
two substances be well mixed by gentle agitation. It is singular 
that some of the German observers stiould deny that the pancreatto 
jnioe possesses the property of emulsioning fat, to a greater extent 
than the bile and some other digestive fluids: and should state that 
although, when shaken up with oil, outside the body, it reduces 
the oily particles to a slate uf extreme miuuteuesa, the emulsion 
is not permanent, and the oily particles "soon separate again on 
the aurfaoe."' We have frequently repeated this experiment with 
diSbreot apceimens of pancreatic juice obtained from the dog, and 
have never failed to see that the emulsion produced by it is by 
far more prompt and complete than that which takes place vr 
Baliva, gastric juioe, or bile. The effect produced by these fluii 

■ Lclunann's rbjr>lologioal Cheuilatrj. PhilMiii. Ad., TOl. I. p. SOT 



DIOESTIOy. 



M 



ID fact altogether inpignJficanL, in cornpnri»on witli the prompt and 
energetic action exerlei) bv the pancreutic jaiiie. The emnlsion 
produced with the latter accretion may be kept, lurtherinore, for at 
least twenty-four hours, according to our observations, without any 
appreciable separation of the oily particles, or a return to their 
original condition. 

The pancreatic juice, therefore, is peculiar in its action on oily 
substances, and reduces them at once to the condition of an emul< 
sioQ. The oil, in this process, does not suffer any chemical altera- 
tion, ll 13 notdGcotnposnd or saponiQed, to any appreciable extent. 
It ia aim p\y emulsioned ; that is, it is broken np into a state of initiuto 
subdivision, and retained in suspension, by contact with the organic 
matter of the pancreatic juice. That its cbeinical condition is not 
altered is shown by the fact that it is still soluble in ether, which 
will withdraw the greater part of the fat from a mixture of oil and 
pancreatic juice, as well as from the chyle in the interior of the 
intestine. In a state of cmulaion, the fat, furthermore, is cupable 
of being absorbed, and ita digeslioo may be then said to be accom- 
plished. 

We find, then, that the digestion of the food ia not a simple 
operation, but is made up of several different processes, which 
commence successively in different portions of the alimentary 
canal. In the first place, the food is subjected in the mouth to tha 
physical operations of mastication and insalivation. Reduced to a 
soft pulp and mixed abundantly with the saliva, it passes, secondly, 
into the stomach. Here it escitea the geeretion of the gastric juice, 
by the influence of which its chemical transformation and solution 
arc commenced. If the meal consist wholly or partially of mus- 
cular flesh, the first effect of the gastric juice is to diwiolve the 
intervening cellular substance, by whiuli the tisiiue is disintegrated 
and the muscular fibres separated from each other. Afterward 
the muscular fibres themselves become swollen and softened by 
the imbibition of the gastric fluid, and are finally di3integrated 
and liquefied. lu the small intestine, the pancreatic and intestinal 
juices convert the starchy ingredients of the food into sugar, and 
break up the fatty matters into a fine emulsion, by which they are 
converted into chyle. 

Although tho separate actions of these digestive 6uids, however, 
commence at different points of the alimentary canal, they after- 
ward go on simultaneously in the small intestine; and the changea 
which take place here, and which constitute the process of tn/esfi'mif 




I 



VHENOMESA OF INTESTINAL DIGESTION. 



141 



digestion^ Form at the same time one of tbe most complicated, and 
one of ilie moat important parts of the whole digestive function. 

The phenomeaa of inlostinal digt^sliun may be studied, iu the 
dog, by killing the animal at various periods after feeding, and 
examining the contents of the intestine. We have also auccecded, 
hy eatablishing in the same animal an artificial inteatinol fistula, 
in gaining still more satisfactory information on this point. The 
fistula may l>e established, for this purpose, by an operation precisely 
similar to that already described as employed for the production of 
a permanent fistula in the stomach. The stiver tube having been 
introduced into the lower part of the duodenum, the wound is 
allowed to heal, and the inCestiual secretions may then be with- 
drawn at will, and subjected to examiuatioa at dlfibrent periods 
daring digestion. 

By examining in this way, from lime to time, the intestinal 
fluids, it at once becomes manifest that the action of the gastric 
jaice, in the digestion of albuminoid substances, is not confined to 
the stomach, but continues after the food has passed into the intes- 
tine About half an hour after the ingestion of a meal, the gastric 
juice begins to pass into the duodenum, where it may be recognized 
by its strongly-marked acidity, and by ila peculiar action, already 
described, in interfering with Tromraer's test far grape sugar. It 
baa accordingly already dissolvcti some of the ingredients of the 
food while still in the stomach, and contains a certain quantity of 
albuminose in solution. It soon afterward, as it continues to pass 
into the duodenum, becomes mingled with the debris of muatular 
fibres, fat vesicles, and oil drops; substances which are easily 
recognizable under the microscope, and which produce a grayish 
turbidity in the fluid drawn from the fistula. 1'his turbid admix- 
ture grows constantly thiclcer from the second to the tenth or 
twelfth hour; after which the intestinal fluids become less abund- 
ant, and finally disappear almost entirely, as the process of diges- 
tion comes to an end. 

The piissage of disintegrated muscular tis3ue into the intestine 
may also be showo, as already mentioned, by killing the animal 
and examiutng the contents of the alimentary cauul. During the 
digestion of muscular fiesh and adipose tissue, the stomach con- 
tains masses of softened meot, smeared over with gastric juice, ami 
abo a moderate quantity of grayish, grumous fluid, with an acid 
reaction. This fluid contains muscular fibres, isolated from each 
other, and more or lesa disintegrated, by the action of the gastric 



142 



DIGESTION. 



< 



c^ 



cs- 



Cai'TEi'-r* or gTnii«rn ditriiki Pinsariox 
or HiAT. Crom (lie tluir.— a. Pal Vv^IcK fllloil wllh 
opaqaa, mlH. griiiiuUrfkl h,lt. Hid »r pirllkllj' di*- 
l&tdfMMd miurDlhr Dtira. e. Oil globnloa. 



juice. (Fig. 33.) The fat vesicles arc but IlttW or not nt all altered 
in the stomach, and there are only a few free oil globules to be 

seen Boatiag in the mixed 
** ■ fluids, contained in the cavity 

of the organ. Id the duode- 
num the muscular fibres are 
further disintegrated. (Fig. 
34.) They becomevery much 
broken up, pale and transpa- 
rent, but can still be recog* 
ni/.ed by the granuhir mark- 
ings and flLriaiiona which are 
chamoteristio of them. The 
fat vesicles also begin to 
become altered in the duode- 
nam. The solid granular fat 
of beef, and similar kinds of 
meat, becomes liquefied and 
emulsioncd; and appears un- 
der the form of free oil drops 
and fatty molocnlcs; while 
the fat vesicle itself is par- 
tially emptied, and becomes 
mure or less collapsed and 
shrivelled. In the middle 
and lower parts of the intes- 
tine (l*'iga. So and S6) these 
changes continue. The mun- 
oolar Sbres become conslanN 
ly more and more disinte- 
grated, and a large quantity 
of granular debris is pro- 
duced, which is at last also 
dissolved. The fat also pro- 
gressively disappears, and the 
vesicles may be seen in the 
lower part of the intestine, 
entirely collnpsed and empty. 

In this way the digestion of the different ingredienls of the food 
goes on in a continuous manner, from the stomach throughout the 
entire length of the small intestine. At the same time, it results 



Pig. M. 



« 



From Droiiasux or Vto, ptmiFo Dinva- 

TIfl!i or Ukat— <i t'tl Vuiklf, irllli It* ciiuiiiiila 
dlwIolablDg^. The Tcsl4'l« !■ IjaglimlDg to ulirlitfl kid 

Iha tu bTHkiDK Dp. 0,6 DltlDirgntod rautcnlH 
flbra. e, r. OH yiti>liult>. 




THS LAROB INTB8TINK AND ITS CONTENTS. 



143 




PioM Middle or Small Ist««ti si.— «, a. 
FaL Tmldes, attkrlj ampUed of their eonlentii. 

Fig. 36. 



in the production of three diifeFent sabstAnces, viz: Ist. Albami* 
nose, prodooed by the aotion of the gastric juice on the albuminoid 
matters; 2d. An oilj emul- 
aioD, produced by the action ^'k* ^*' 

of the.panoieatic juiceon fat; 
and, 8d. Sugar, produced from 
tfae traDBfonnatiDn of starch 
by the mixed intestinal fluids. 
These substaaces are then 
ready to be taken up into the 
circulation; and as the min- 
gled ingredients of the intes- 
tinal contents pass success- 
ively downward, through the 
dnodenam, jcijuaum, and ile- 
um, the products of digestion, 
together with the digestive 
aeoretioDS themselves, are gra- 
dually absorbed, one after 
another, by the vessels of the 
mnoous membrane, and car- 
ried away by the current of 
the circulaUon. 

The Large InUatine and its 
Omienta. — Throughout the 
amall intestine, as we have 
just seen, tfae secretions are 
intended exclusively or main- 
ly to act upon the food, to 
liquefy or disintegrate it, and 
to prepare it for absorption. 
But below the situation of the 
ileo-cfecal valve, and throngh- 
out the large intestine, the 
contents of the alimentary canal exhibit a different appearance, and 
are distinct in their color, odor, and consistency. This portion of 
the intestinal contents, or the feces, are not composed, for the most 
part, of the undigested remains of the food, but consist principally 
of animal substances excreted by the mucous membrane of the 
large intestine. These substances have not been very fully investi- 
gated; for although they are undoubtedly of great importance in 




Fboh laiit qiriMTiK op Small iNTBirtRB. 
-a, a. Fm TeilelM, qnlte empty uid ihrlTelled. 



144 



DIOBSTION. 



regard to llio preservation of healtli, yet the peculinr manner m 
which they aro discharged by ihc mucoua membrane and united 
with each other in the feces has interfered, to a great extent, with 
u thorough investigution of their physiological characters. I 

They have been examined, however, by various observers, but " 
more particularly by Dr. W. Marcet.' In the contents of the large 
intestine, Dr. Marcet foand that the most characteristio ingredient ■ 
was a peculiar neutral crystal lizable substance, termed ercretine. It 
crystal li/.L'S in radiated groups of foiir-sided prismatic needles. It 
is insoluble in water, but soluble in ether and slightly so in lUcohol. 
It fuses and burns at a high temperature. This substance is non- 
nitrogenous, and consists of carbon, hydrogen, oxygen, and sulphur, 
ID the following proportions: — 

C„H„O.S. 
It is thought to be present mostly in a free state, but partly in anioa 
with certain organic acids, as a saline componnd. 

Beside this substance, the feces contain a certain amount of fat, 
fatty acids, cholcsterine, and the reninnrtts of undigested food. 
Vegetable cells and fibres may ba detected and some debris of the 
disintegrated mu-scular fibres may almost always be found after a 
meal composed of animal and vegetable substances. But little 
absorption, accordingly, takes place in the large intestine. Its oflica 
is mainly confined to the separation and discharge of certain excre- 
mentitious substances. 



' Id American JouruAl of tlie Mudlcol SoienceB, JftDuar/, l&M. 



ABSORPTION. 



145 



CHAPTER VII. 



ABSORPTION. 



Beside the glands of Bninner 
already described, ibere are, in 
intestine, certain glandular* 
looking bodies which are 
termed "glandulRsoHtariro," 
and "glandulre agmimitio." 
The glaadulie solitariw are 
globular or ovoid bodies, 
about onelbirticth of an inch 
in diameter, situated partly 
in and partly beneath the in- 
testinal mucous membrane. 
Each glandule (Fig. 37) la 
formed of au investing cap- 
anle, closed on all sides, and 
containing in its interior a 
■oft pulpy mass, which con- 
mats of minute cellular bodiea, 
imbedded in a homogeneoua 
substance. The inclosed mass 
is penetrated by capillary 
bloodveseeU, which pass in 
through the investing cap- 
sale, inosculate freely with 
each other, and return upon 
tbemaelves in loops near the 
centre of the glandular body. 
There is no ejcteraal opening 
or duct; in fact, the contents 
of the vesicle, being pulpy 
and vascular, as already de- 
Bcri bod. are nob to be regarded 



and the follicles of Licbcrktihn. 
the inner part 

ng.37. 



the walls of the 



aV 



f-^i 



-^■ 



N 



r 



Pati;hii«. fTum Rtnall liitDiUB« of Df. UBfalBMl 

90 dlunrten. 

Ftg. 3S. 



\ "'f^ 



\ 



of Pl|. UafDiflrtlSndlaibolcri. 



10 



ABaORPTIOW. 



aa a i^ccretion, but as constituting a kind of solid glandular tissue. 
The glandulffl ogmiiialm (Fig. 38), or "Peyer's patclies," as they are 
sometimes cnlledj consist of aggregations of similar globular or 
ovoid bodies, found moat abundantly toward the lower extremity of 
tbe small intestine. Both the solitary and agmiiiate<l glandules are 
evidently connected with the lacteab and the system of the mesen- 
teric glands, which latter organs they resemble very much in their 
minute structure. They are probably to be reganled as the 6rat 
row of mesenteric glands, situated in the wall* of the iatestioal 
canal. 

Another set of organs, intimately connected with the process of 
absorption, are the villi o( the small intestine. These are conical 
vascular eminences of the mucous membrane, thickly set over the 
whole internal surface of the small intestine. In the upper portion of 
the intestine, they are fattened and tnanguhtr in form, resembling 
somewhat the conical projections of the pyloric portion of the sto- 
mach. In the lower part, they are long and filiform, and often 
slightly enlarged, or club-shaped at their free extremity (Kijj. 99), 

and frequently attaining the length of 
one thirty-fifth of an inch. They are 
covered externally with a layer of 
columnar epithelium, siinilar to that 
whiuh lines iKcj rest of the intestinal 



?ig. S9. 



of the commencing rootlets of the por- 
tal vein. In the central part of the vil- 
lus, and lying nearly in its axis, there 
is another vessel, with thinner and more 
the commencement of a lacteal. The 
precise manner in which the lacteal originates in the extremity of 
the villus is not known. It commences near the apex, either by a 



XxTSBMirr or iFTRtriFAt 
Tii.i.ri. from lb* Dog.— a. ItjtrroT 
•pIlItcllDni. 6. Hloo4Ti<»rL. a, Lult«l 
tomhI. 

tntDsparent walls, which is 



1 

I 



mucous membrane, and contain in their ■ 
interior two sets of vessels. The most 
superficial of these are the capillnry 
bloodvessels, which are supplied in each 
villus by a twig of the meaentoric 
artery, and which form, by their fre- 
quent inosculation, an exceedingly clow I 
and abundant network, almost imme- 
diately beneath the epithtrlial layer. 
They unite at the base of the villus, 
and form a minute vein, which is one 



I 




AB30KPTT0W. 



147 



blind extremity or by an irrej^ular plesus, pitssea, in a straight or 
somewlint wavy line, toward the base of the villus, and then be* 
comes contiDuous witb a small twig of the mesenteric lacteals. 

The villi are the active agents in the process of absorption. By 
their projecting form, and theirgreat abundance, they increase enor- 
mously the extent of surface over which the digested fluids come 
in contact with the intestinal mucous membrane, and increase, also, 
lo a cor responding degree, the energy with which absorption takes 
place. They hangout into the nutritious, semi-fluid mass contained 
in the intestinal cavity, as the roots of a tree penetrate the soil ; and 
they imbibe the liquefied portions of the food, with a rapidity which 
is in direct proportion to their extent of surface, and the activity of 
their circalation. 

The procaSB of absorption ia also hastened by the peristaltic 
moTemenis of the intestine. The muscular layer here, as in other 
partfl of the alimentary canal, is double, consisting of both circular 
and longitudinal 6brcs. The action of these fibres may be readily 
seoD by pinching the exposed intestine with the blades of a forceps. 
A contraction then takes place at the spot irritated, by which the 
intestine is reduced in diameter, its cavity obliterated, and its con- 
tents forced onward into the ancceeding portion of the alimentary 
canaL The local contraction then propagates ilaelf to the neighbor- 
ing parts, while the portion originally contracted becomes relaxed; 
so that a slow, continuous, creeping motion of the intestine ia pro- 
ducwl, by successive waves nf contraction and relaxation, which 
follow each other from above downward. At the same time, the 
loDgiludinal fibres have a similar alternating action, drawing the 
narrowed portions of intestine up and down, as they successively 
enter into contraction, or become relaxed in the intervals. The efiect 
of the whole is to produce a pecullor, writhing, worm-like, or 
"vermicular" motion, among the diRe rent coils of intestine. During 
life, the vermiL-alar or peristaltic motion of the intestine is excited 
by the presence of food undergoing digestion. By its action, the 
substanc<>3 which pass from the stomach into the intestine are 
steadily carried from above downward, ao as to traverse the entire 
loDgih of the small intestine, and to come in contact sueceissively 
with the whole extent of its mucous membrane. During this pas- 
sage, the abaorpiion of the digested food is c<mstantly going on. 
Its liquefied portions arc taken up by the villi of the mucous mem- 
brane, and successively disappear; so that, at the termination of the 
small intestine, there remains only the urtdigustible portion of the 



14! 



ABSOBPTTOSr. 



food, together, with the refuse of the intestinal secretions, 
pass through the ileo-csccal orifice into the large intestine, and thi 
liecome reduced to the condition of feces. 

The absorplioQ of the digested fluida is accomplished both by 
the bloodvessels and the Incteale. It was formerly euppoeed that 
the Iftcteala were the only agents in this process; bat it has nov 
been long known that this opinion was erroneous, and that the 
bloodvessels take at least an equal part in absorption, and are in 
some respecta the most active and important agents of the two. 
AbundatLt experiments have demonstrated nut only that sohible 
substances introduced into the intestine may be soon afterward 
detected in the blood of the portal vein, but that absorption ukes 
placu more rapidly aud abundantly by the bloodvessels than by 
the laoteala. The most decisive of these experiments were those 
performed by Paiiiz/.a on the ahlominal circulation.' This ob- 
eerver opened the abdomen of a horse, and drew out a fold of tho 
amalt intestine, eight or nine inches in length (Fig. 40, a, a), which 



Fig. 40. 




FjiauiA'* BirsatWKiT.— «tA IniMtlne. h. Point of llnlai«af mtMiilrrie T*1a. « Optnta^ 
In talntlna fur lairuducUon of polaob. d. Op*(il[)slBii»«Diaric *•)□ balilad lb* llgaiimL 

ho included between two ligatures. A ligature wns then placed (at 
5) upon the mesenteric vein receiving the blood from this portion 
of intestine; and, in order ihnt the circnlation might not be inter- 
rupted, an opening was made (at d) id the vein behind the ligature, I 

' In Mnttiiuaci'i L«ctiir«s on tbe Phjrsic!.! I'heDomeui of Living Ueinga, Pvniia'a 
•dltton, p. 83. 




ADSORPTIOK. 



149 



90 tbat ttie blood brought by the ineaonteric artery, afler circuluting 
in tho intestinal capillaries, possed out at tho opening, and v>a>* 
collecterl in a vessel for examination. Hydrocyanic acid was tlien 
introduced into the intestine by an opening at e, and almost imme- 
diately afterward its presence was detected in the venous bloo<l 
flowing from the orifice at d. The aniinnl, however, was uot pui- 
iH>ned, since tlic ncid wms prevented from gaining an entrance into 
the genera] circulation by the ligature at b. 

Panizza afterward varied this experiment in the following man- 
ner: Instead uf lying the nieseoteric vein, he simply compressed it. 
Then, hydrucyanic acid being introduced into the intestine, as above, 
no eflet.n wa-s prodiicc<l on the animal, so long as compression was 
inniutntned U|>on the vein. But as soon as the blood was allowed 
lo pass again through the vessels, symptoms of general poisoning 
at onco became manire»t. Ltistly, in a tliird experiment, ihu 8»mo 
observer removed all the nerves and lacteal vessels supplying the 
intestinal fold, leaving the bloodvessels alone untouched. Hydro- 
cyanic acid now being introduce<:l into the inte«tinc, found an 
entrance at once into tho general circulation, and tho animal was 
immediately poisoned. The bloodvessels, therefore, are not only 
capable of absorbing fluids from the intestine, but may even take 
ibem Dp more rapidly and abundantly than the lacteals. 

These two sets of vessels, however, do not absorb all the nliment- 
ary matters iDdiscriminately, It is one of the most important of 
the facts which have b^en established by modern researches on 
digestion that the diflerent substances, produced by ibe operation of 
the digestive fiuids on the food, pass into the circulation by different 
routes. The fatty matters are taken up by the lacteals under the form 
of chyle, while the saccharine and albuminous matters pass by ab- 
sorption into the portal vein. Accordingly, after the digestion of a 
meal containing starchy and animal matters mixed, albuminose and 
sugar are both found in the blood of the portal vein, while they can* 
Dot be detected, in any large quantity, in ibe contents of ihe lacteals. 
These aubstances, however, do not mingle at once with the general 
masB of the circulation, hut owing to the anatomical distribution of 
the portal vein, pass first through the capillary circululion of the 
liver. Soon after being introduced into the blood and coming in 
contact with its organic ingredient;), they become altered and con- 
verted, by catalytic trans t'unnat ion, into other substances. The 
albuminose passed into the condition of ordinary albumen, and 
probably also partly into that of fibrin; while the sugar rapidly 



150 



lBSORPTION. 



I 



■.ij.A.^V*, ■-,-. 



becomes decomposed, and loses its charactemtie propcrUea; so 
that, on arriving at the entrance of tlio general circulation, both 
these newly absorbed ingredients have become already assimilated 
to those which previously existed in the blood. 

The chyle in the intestine consiata, as we have already mentiooed, 
of oily matters which have not been chemically altered, but simply 
reduced to a state of emulsion. In chyle drawn from tbe laotesla 
or the thontcio duet (Fig. 41), it still presents itself in the same 

condition and retains all the 
^''S;*^" chemical propertiea of oil. 

Examined by the microscope, 
it is seen to exist under tha 
form of dne granules and 
moleculea, which present the 
ordinary appearances of oil 
in a state of minute subdtvi* 
sion. Tbe chyle, therefore, 
does not represent the entire 
product of the digestive pro- 
cess, but contains only the 
fatty substances, suspended 
by emulsion in a serous fluid. 
During the time that intes- 
tinal absorption is going on, 
after a meal containing fatty 
ingredients, the lacteaia may be seen as white, opaqne vessels, dis- 
tended with milky chyle, passing through the mesentery, and con- ■ 
verijing from its inteatinal border toward the receptaculum chyli, 
near the spinal column. During their course, thoy pass througb 
several successive rows of mesenteric glands, which also become 
turgid with chyle, while the process of digestion is going on. The 
lacteals then conduct the chyle to tbe receptaculum chyli, wheocifl 
it passes upward through the thoracic duct, and is Anally dis- 
charged, at tho tern^instion of this canal, into the left, subclavian 
vein. (fig. 42.) It is then mingled with tha returning current of 
venous blood, and passes into the right cavities of the heart. 

The lacteals, however, are not a special system of vessels by them> 
selvc>), but are siin ply & part of the great sytitom of " absorbent" or 
"lymphatic" vessels, which are to bo found everywhere in the integu- 
ments of the head, the parietes of the trunk, the upper and lower 
extremities, and in the muscular tissues and mucous membranes 



CHTt.* raoa covMsvemtiiT c» Tiiogijicie 

t>DeT, rroiti lh« Da«. — The molraiil** ruj Id aliv 
rrum l-IO.OOath of m Inch duirainrd- 



I 



I 




ABSORPTION. 



151 



thmaghout the hady. The walls uf ihese vessels are thinner and 
more transparent than thuso of the arteries and veins, and they are 
consequently less cnsily de- 
lected by ordinary dissection. Kg. 42. 
They originate in the tissues 
of the above-mentioned parts 
by on irregolnr plexus. They 
pass from the extremities to- 
ward the trunk, con vergingand 
uniting with each other like ihe 
veins, their principal branches 
talcing usually the same direc- 
tion with the nervesand blood- 
vessels, and passing, at various 
points in their course, through 
certain glandular bodies, the 
"lymphatic" or "absorbent" 
glands. The lymphatic glands, 
among which are included the 
mesentericglands, consist of an 
external layer of fibrous tissue 
and a contained pulp or paren- 
chyma. The investing layer 
of fibrous tissue sends off thin 
•eptA or laminro from its inter- 
nal surface, which penetrate 
the substance of the gland in 
every direction and unite with 
each other at various points. 
In this way they form an interlacing laminated framework, which 
divides the substance of the glund into numerous rounded spaces 
or alvuoli. These alveoli are not completely isolated, but commu- 
nicate with each other by narrow openings, where the intervening 
septa are incomplete. These cavities are filled with a soft, reddish 
pulp, which is penetrate'], according to Kulliker, like the solitary 
and agtninated glauds of the itite^tine, by a fine network of capil- 
lary bloodvessels. The solitary and agmtnated glands of the intes- 
tine are, therefore, closely analogous in their structure to the lyni- 
phatics. The former are to be regarded as simple, the latter as 
compound vascular glands. 
The arraugemcnt of the lymphatio vessels in the interior of the 



W./ . 



LicTtALa, TiinkAric DccT, kt.—n. Intm- 
lin*. t. V«Ba <»*■ Vatfrior. r, f. III|M koil laft 
■olicladaD T»la*. d. PuLal of opsolnf of Ukoracio 
4a«t Isiu Wtl anlwlK'Ika. 



152 



ABSORPTIOSr. 



glftntJs in not precisely understood. Ench lymphatic vessel, as 
enters ihe gland, breaks up into & number of minute ramifications, 
the voic affervitia; and other aimilar twigs, forming the vasi cfftr- 
eniia, pass off in the opposite direction^ from the farther side of the 
gland ; but the exact mode of communication between the two has 
not been definitely ascertained. The fluids, however, arriving by 
the vnsa afferentia, must pass in some way through the tissue of 
the gland, before they are carried away again by the vosq efferentita 
Frotn the lower extremities the lympliatio vessels enter the aWomcn 
at the groin and converge toward the receptaculum chyli, into 
which their fluid is discharged, and afterwar^I conveyed, by the 
thoracic duct, to the left subclaviau vein. 

The fluid which these vessels contain is called the b/mph. It is 
a colorless or slightly yellowisli transparent fluid, which is absorbed 
by ihc lymphatic vessels from the tissues in which they originate. 
So far as regards its compositiou, it is known to contain, beside, 
water and saline matters, a small quantity of ilbrin and albumeiu 
Its ingredienta are evidently derived from the metamorphosis of 
the tissues, and are returned to the centre of the circulation in 
order to be eliminated by excretion, or in order to undergo some 
new transforming or renovating process. Wo are ignorant, how- 
ever, with regard to the precise nature of their character and 
destination. 

The laoteals are simply that portion of the absorbents which 
originate in the mucous membrane of the small intestine. During 
the intervals of digestion, these vessels contain a colorless and 
transparent lymph, entirely similar lo that which is found in other 
parts of the absorbent system. After a meal containing only 
starchy or albuminoid substances, there is no apparent change in 
the character of their contents. But aller a meal containing fatty 
matters, these substances are taken up by the absorbents of the 
intestine, which th<>n become fJIled with the white chylous emul- 
sion, and assume the appearance of lacteals. (Fig. 43.) It is for 
this reason that lacteal vessels do not show themselves lapon the 
stomach nor upon the first few inches of the duodenum ; because 
oleiiginous matters, as we have seen, are not digested in the stomach, 
bat only after ihey have entered the intestine and pas-sed the orifice 
of the pancre.atic duct. 

The presence of chyle in the lacteals is, therefore, not a con- 
stant, but only a periodical phenomeaon. The fatty substances 
constituting the chyle begin to be absorbed during the process of 




154 



ABSORPTION. 



known. They are, at all events, so altered in the bIoo<1, while 
passing through the lungs, that they lose the fornri of a fatly cmul- 
aioQ, and are no longer to be recognized by the usual testa for 
oleaginous subatances. 

The absorption of fat from the intestine is not, however, excla- 
sively performed by the lacteala. Some of it is aljw taken up, 
uader the same form, by the bloodvessels. It has been aacertatned 
by the experiments of Bernard' thai the bliKid of iho mesenteric 
veins, in the carnivorous animaU, contains, during intestinal diges- 
tion, a considerable amount of fatty mntter in a state of mtnate 
subdivision. Other observers, also (Lehman n, Schultz, Simon), have 
found the bluud of the portal vein to be considerably riuber in fat 
than that of other veins, particularly while tntiistinal digestion is 
going on with activity. In birds, reptiles, and fish, furthermore, 
according to Bernard, the intestinal lymphatics are never 611ed 
with opaquecb^le, but only with a transparent lymph; so that these 
animals may be said to be destitute of lactcals, and in them the fatty 
substances, like other Qltmeniary materials, are taken up altogether 
by the bloodvessels. In quadrupedsf, on tlie other hand, and id 
the human subject, the absorption of fat is accomplished both by 
the bloodvessels and the laoteals. A certain portion is taken up 
by the former, while the BU[>crubun dance of the fatty emulsion is 
absorbed by the latter. 

A difficulty has long been experienced in accounting for the ab- 
sorption of fat from the intestine, owing to its being considered ns a 
non-endosmotic substance ; that is, as incapable, in iis free or undis- 
solved condition, of penetrating and passing through an animal 
membrane by endoismosis. It is stated, indeed, that if a fine oily 
emulsiun be placed on one side of an animal membrane in an endoa- 
momoter, and pure water on the other, the water will rearlily pene- 
trate the substance of the membrane, while the oily particles cinnot 
Ije made to pass, even under a high pressure. Though this be true, 
however, for pure water, it is not true for slightly alkaline Hutds, 
like the serum of the blood and the lymph. This has been de- 
monstrated by the experiments of Maiteucci, in which ho made 
&n emulsion with an alk.ilinc fluid containing 43 parts per thou- 
sand of caustic potassa. Such a solution has no perceptible alkaline 
taste, and its action on reddened litmus paper is about equal tu 



I 



I 

I 



' hti^ait dtt Phjii)ol(i)jiw Esp.:fiinniLtaln. f&riii, IbSO, p> 325. 




ABSUBPTIOir. 



166 



that of the lympli and chyle. If this emulsion were placed in an 
eodoamometer, tt^ether with a watery alkaline solution of similar 
strength, it was found that the oily particles penetrated through the 
animal membrane without much difficulty, and mingled with the fluid 
on the opposite side. Although, therefore, we cannot explain the 
exact mechanism of absorption in the case of fat, still we know 
that it is not in opposition to 
the ordtnary phenomena of ^*" **" 

eudosmosis ; for endosmosia 
will take place with a fatty 
emulsion, provided the fluids 
used in the experiment be 
slightly alkaline in reaction. 
It is, accordingly, by a pro- 
cess of endosmosis, or imbi- 
bition, that the villi take up 
the digested fatty snbstanoes. 
There are no open orifices 
or canals, into which the oil 
penetrates ; but it passes di- 
rectly into and through the 
Babstance of the villi. The '^""' 

epithelial cells covering the external surface of the vill us are the first 
active agents in this absorption. In the intervals of digestion (Fig. 
44) these oells are but slightly 




tuTKiTiirAL Epitbilidm; rroiD IbsDag.vhIl* 



granular and nearly trans- 
parent in appearance. But if 
examined during the diges- 
tion and absorption of fat 
(Fig. 45), their substance is 
seen to be crowded with oily 
particles, which they have 
taken up from the intestinal 
cavity by absorption. The 
oily matter then passes on- 
ward, penetrating deeper and 
deeper into the substance of 
the villus, until it is at lost 
received by the capillary ves- 
sels and lacteals in its centre. 



Fig. 45. 




IvriaTiNAL Bpithilidm; tnu th« "Dog, Ant' 
iag iIm dIgMilon of tu. 



1KB 



AHSOBPTrOW. 



' The fatty substances takoD up by the portal vein, like those nb- 
Horbed by the lauieals, do not at once enter the general circulation, 
but pasB first through the cnpillary system of the liver. Thence 
they are carried, with the blood of the hepatic vein, to the right 
side of the heart, and subsequently through the capillary system of 
the lungs. During this passage they become altered in character, 
as above described, and lose for tbo moHt part the distinguishing 
characteristics of oily matter, before they hare passed beyond the 
pulmonary circulation. 

But as digestion proceeds, an increasing quantity of fatty matter 
finds its way, by these two passoges, into the blood; and a time at 
last arrives when the whole of the fat so introduct-d is not destroyed 
during its passage through the lungs, lis absorption taking place 
at this lime more rapidly than its decomposition, it begins to ap- 
pear, in moderate quantity, in the blood of tbo general circulation ; 
and, lastly, when the intestinal absorption 13 at its point of greatest 
activity, it is found in considerable abundance throughout the 
eniire vascular system. At this period, some hours after the inf^es* 
tion of fond rich in oleaginous mattera, the blood of the general 
circulalion everywhere contains a superabundance of fat, derived 
from the digestive process. If blood be then drawn from the veins 
or arteries in any part of the body, it will present the peculiar 
appearance known as that of "chylous" or "milky" blood. AfWr 
the separation of the clot, the serum presents a turbid appearance; 
and the fatty substances, which it contains, rise to the top after a 
few hours, and cover its surface with a partially opaque and creamy- 
looking pellicle. This appearance has been occasionally observed 
in the human subject, particularly m bleeding for apoplectic attacks 
occurring after a full meal, and has been mistaken, in some instances, 
for a morbid phenomenon. It is, however, a perfectly natural one, 
and depends simply on the rapid absorption, at certain periods of 
digestion, of oleaginous substances from the intestine. It can be 
produced at will, at any time, iu the dog, by feeding him with fut 
meat, and drawing blood, seven or eight hours afterward, from the 
carotid artery or the jugular vein. 

This state of things continues for a varying length of time, ac- 
cording to the amount of oleaginous mattera contained in the food. 
When digestion is terminated, and the fat ceases to be introduced 
in unusual quantity into the circulation, its iransformation and 
decomposition continuing to take place in the blood, it disappears 
gradually from the veins, arteries, and capillaries of the general 



I 




ABSORPTION. 167 

Bystem ; and, finally, when the whole of the fat has been disposed 
of by the nutritive processes, the serum again becomes transparent, 
and the blood returns to its ordinary condition. 

In this manner the nutritive elements of the food, prepared for 
absorpttoD by the digestive process, are taken up into the circulation 
under the different forms of albuminose, sugar, and chyle, and accu- 
mulate as such, at certain times, in the blood. But these conditions 
are only temporary, or transitional. The nutritive materials soon 
pass, by catalytic transformation, into other forms, and become 
assimilated to the preexisting elements of the circulating fiuid. 
Thus they accomplish finally the whole object of digestion ; which 
is to replenish the blood by a supply of new materials from without. 
There are, however, two other intermediate processes, taking place 
partly in the liver and partly in the intestine, at about the same 
time, and having for their object the final preparation and perfec- 
tion of the circulating Quid. These two processes require to be 
studied, before we can pass on to the particular description of the 
blood, itself. They are: Ist, the secretion and reabsorption of the 
bile; and 2d, the production of sugar in the liver, and its subsO' 
quent decomposition in the blood. 



158 



THE BILE. 



CHAPTER Vlir. 



THE BILE. 

The bile is more easily obtained iu a stale of purity than any 
otlier of the secretions which find their way into the intestinal 
canal, owing to the existence of a gall-bladder in which it accu- 
mulates, and from which it may be readily obtained without any 
other admixture than the mucus of the gall-bladder itself. Not* 
withstanding thi8^ itj study Iiaa proved an unusually difficult one. 
This difficulty has resulted from the peculiar nature of the biliary 
ingredients, and the readiness with which they become altered by 
chemical manipulation ; and it is, accordingly, only quite recently 
that we liave arrived at a correct idea of its real constitution. 

The bile, as itcumcs from the gall-bladder, is a somewhat viscid 
and glutinous fluid, varying in color and specific gravity according 
to the species of animal from which it is obtained. Uuman bile is 
of a dark golden brown color, ox bile of a greenish yellow, pig's 
bile of a nearly clear yellow, and dog's bile of a deep brown. We 
have found iho specific gravity of human bile to be 1018, that of 
ox bile 1024, that of pig's bile 1030 to 1080. The reaction of the 
bile with teat-paper cannot easily be determined; since it has only 
a bleaching or decolorizing effect on litmus, and does not turn it 
either blue or red. It is probably either neutral or very slightly 
alkaline. A very characteristic physical property of the bile is 
that of frothing up into a soap-like foam when shaken in a test- 
tube, or when air is forcibly blown into it through a small glass 
tube or blowpipe. The bubbles of foam, thua produced, remaio fl 
for a long time without breaking, and adhere closely to each other 
and to the sides of the glass vessel. 

The fallowing is an analysis of the bile of the ox, based oq the 
calculations of Berzelius, Frerichs, and Lehmaun: — 





THB BILK. 159 

CoHFOflmoK or Ox Bilb. 

Water 886.00 

Otyko-choUte of soda i 

TmnMshoUta " " J ^**-^ 

BillrerdiDe 

Fata 

01«ates, margArstes, and atearates of soda and potasu 13.42 

Cholesterin 

Chloride of Bodinm 

Phosphate of soda 

" " lime 15.24 

" " magneflla 

Carbonatei of soda and potassa 

Hdviu of the gall-bladder 1.34 



1000.00 

BiLiVBBDrNS. — Of the above mentioned ingredients, btliverdine 
is pecaliar to the bile, and therefore important, though not pre- 
sent in large qnaotity. This is the coloring matter of the bile. 
It is, like the other coloring matters, an uncrystallizable organic 
Bobstance, containing nitrogen, and yielding to ultimate analysis a 
small quantity of iron. It exists in such small quantity in the bile 
that its exact proportion has never been determined. It is formed, 
80 far as can be ascertained, in the substance of the liver, and does 
not pre-exist in the blood. It may, however, be reabsorbed in 
cases of biliary obstruction, when it circulates with the blood and 
Btaina nearly all the tissues and fluids of the body, of a peculiar 
lemon yellow color. This is the symptom which is characteristic 
of jaundice. 

Gholxsterik (C„n„0). — This is a crystallizable substance which 
resembles the fats in many respects ; since it is destitute of nitrogen, 
readily inflammable, solnble in alcohol and ether, and entirely in- 
soluble in water. It is not saponifiable, however, by contact with 
the alkalies, and is distinguished on this account from the ordinary 
&tty substances. It occurs, in a crystalline form, mixed with color- 
ing matter, as an abundant ingredient in most biliary calculi ; and 
is found also in different regions of the body, forming a part of 
various morbid deposits. We have met with it in the fluid of 
hydrocele, and in the interior of many encysted tumors. The 
crystals of cholesterin (Fig. 46) have the form of very thin, color- 
less, transparent, rhomboidal plates, portions of which are oflen 
cutout by-lines of cleavage parallel to the sides of the crystal. 
They frequently occur deposited in layers, in which the outlines of 



160 



THB BILB. 



the subjacent cr^'stals show very distinctly througb the sabstance 



of those which are placed above. 
Fig. 43. 



r-i 



I 



r \ 



Cholesterin is not formed in the 
liver, but originates in the 
Biibstancfl of the braiD and 
nervous tissue, from which 
it mny bo extracted in lar^e 
qaantity by the action of 
alcohol. From these tissues 
it is absorbed by the blood, 
tlien conveyed to the liver, 
and discharged with the bile. 

The fatty substances and 
inorganio saline ingredients I 
of tho bile require no special 
description. 



Caoi:KiT(Bia, rraioko EarpiwITunur. 



BiLiABY Salts. — By far 
the most important and characteristic ingredients of this secretion 
are the two saline substances mentioned above aa ihe glyko-efiolatf 
and taurochoiate of soda. These substances were first discovered 
by Strecker, in 1848. iu the bite of tlio ox. They are both freely 
soluble in water and in alcohol, but insoluble in ether. One of 
them, the tauro-cholate, has the property, when ilaelf in soliition ■ 
in water, of dissolving a certain quantity of fat; and it is probably 
owing to this circunDstancc thai some free fat is present in the bile. 
The two biliary substances are obtained from ox bile in the follow- 
ing manner: — 

The bile is first evaporated to dryness by tho watcr-hath. Tho 
dry residue is then pulverized and treated with absolute alcohol, ia 
the proportion of at least 5j of alcohol to every five grains of dry 
residue. The filtered alcoholic solution has a clear yellowish color. 
It contains, beside the glyko-cholatc and inuro-cholate of soda, tha 
coloring matter and more or less of the fats originally present in ■ 
the bile. Oo the addition of a small quantity of ether, a dense, 
whitish precipitate is formed, which disappears again on agitating 
and thoroughly mixing the fluids. On the rcpeatwl addition of 
ether, the precipitate again falls down, and when the ether has been 
added in considerable excess, six to twelve times the volume of the 
alcoholic solution, the precipitate remains permanent, and the whole 
mixture is filled with a dense, whitish, opaque deposit, consisting 



I 




THB BILX. 



161 



of the gl^ko-cholatc and uinro-chokte of soda, thrown down under 
the form of heav^ flakes and granules, pari of which subside to 
the bottom of tlie tetjt-tubo, white part remain for a time in suspen- 
BiDD. Gradually these flakes and grannies unite with each other 
and fuHe together into clear, brownish-yellow, oily, or resinous* 
looking drops. At the bottom of the teftt-tubc, aflcr two or three 
hours, there is usually collected a nearly homogeneous layer of 
this deposit, while the Temainder continues to adhere to the sides 
of the glass, in small, circular, transparent dmps. The deposit is 
semi-fiuid in consistency, and sticky, like Canada balsam or half- 
melted resin; and it is on this account that the ingredients compos* 
ing it have been called the "resinous matters" of the bile. They 
have, however, no real oheraical relation with true resinous bodies, 
since they both contain nitrogen, and diflcr from resins also in 
other imjiorlant particulars. 

At the end of twelve to twenty-four hours, the glyko-ofaolate of 

soda begins to crjstalliae. The cryHlals radiate from various points 

in the resinous deposit, and shoot u[iward into the supernatant 

fluid, in white, silky bundles. (Fig. 47.) If some of thesw crystals 

Fig. 47. Fig. 48. 






Oif KD-ci>ii.AT» or »"Dt ta,ca Ox-iii.b, 

nR") iwo l^ltJ*' CT]ra(>itl1(>t!i>u. At llin ^urirr pari ol 
lli« tfnn Ilia prjciaU an nfttlna laia dr-^p*, tr*ta lb< 
oispvnllaa vf llio ctbtr *ud aliHitpllitu u( niuUlura 



be removed anil examined by the microscope, they are found to be 
of a very delicate aoiuular form, running to u Snely pointed 
extremity, and radiating, as already mentioned, from a central 
U 



102 



THE BItE. 



point. (Fig. 48.) As the ether evaporates, tlie crystals obsorb 
moisture from the air, and melt np mpidly into clear resinous 
drops; so that it is difficult to keep them under the micnMCope 
long enough for a correct drawing and measurement. Thecrystal- 
lizatioa ia the test-tube goes on aEler the first day, and tho crystals 
increase in quantity for three or four, or even five or six days, until 
the whole of the glyko-cholate of soda present has assumed ths 
solid form. The tauro-cholate, however, is UDCry stall izable, and 
remains in ao amorphous condition. If a portion of the deposit be 
DOW removed and examined by the microscope, it is seen that the 

crystals of glyko-cholate of 



I 



Fl„. 4!l. 



o 



O 



o 



o 



^o. 



O 



O 



Q 



I 



o 



o. 



soda have increased conside- 
rably in thickness (Fig. 49), 
so that their transverse dia- 
mutor may be readily esti- 
mated. The uncrysUUlizabte 
taufo-cbolate appears under 
the form of circular drops, 
varying considerably in size, 
clear, transparent, strongly 
refractive, and bounded by 
a dark, well-deGucd outline. 
These dropt are not to be distin- 
guiahed, by any of their optical 
}jro^^r(iei,/ivm<Hi-ghbulet, as 
they usually appear under 
the microacoi>e. They have ■ 
the same refractive power, 
tbe same dark outline and bright centre, and the same degree of 
consistency. They would consequently be liable at all times to be 
mistaken for oil-globules, were it not for the complete dissimilarity 
of their chemical properties. 

Both the glyko-cholate and tauro-cholate of soda are very freely 
soluble in water. If the mi.\ture of alcohol and ether be poured 
off and distilled water added, the deposit dissolves rapidly and 
completely, with a more or less distinct yellowish co3or, according 
to the proportion of coloring matter origiually present in the bile. 
The two biliary substaoces present in the watery solution may lie 
separated from each oilier by the following means. On the addi- 
tion of achate of lead, the glyko-choEate of soda is decomposed, ■ 
and precipitates as a glyko-cholate of lead. The precipitate, scpa- 



Gl.Tln-rH<iL17« A**t Ttirio-onoLjTK or 

Soda, r%l^» ox-niL*, afrar tlx •!•;«' cmialllu- 
iteO- Tlin gif ki.-rlii>lsU U urjiMlllaMl ; Uio Ikujo- 
«bo)M« la tn Buld drop*. 



I 




TBE filLB. 



16S 



r»te<l by 61lration from the remaining fluid, \S then decomposed in 
Luni by carbonate of soda, and the original glyko-cholato of soda 
reproduced. The filtered fluid which reinuins, aud which contiiios 
ihe tauro-cholatc of soda, is then treated with subac/tfale nf lead, 
which precipitates a taiiro-cholate of lend. This is aeparatod by 
filtration, crashed, and decomposed again by carbonate of soda, as 
in the former case. 

The two biliary substances in ox bile may, therefore, be dis* 
tinguished by their reactions with the aalw of lead. Both arc 
precipitable by the Bubacetate; but the glyko-cholate of soda is 
precipitable also by the acetate, while the tauro-cbolate in not so. 
If subacetate of lead, therefore, be added to the mixed watery solu- 
tion of Ihe two substancea, and the wiiolo filtered, the aubsequent 
addition of acetate of lead to the filtered floid will produce no pre- 
tipilate, because both the biliary matters have been entirely thrown 
[down with the deposit; but if the acetate of lead be first added, it 
fill precipflatc the glyko-cholale alone, and the tauro-cholatc may 
aderward be thrown down separately by the subacetate. 
These two substances, examined separately, have been found to 
leaeee the following propcrlicii: — 

QlyhydtohUe of eoda {NaO.C'j,H„NOj,) crystallizes, whan precipi- 

lied by ether from its alcoholic solution, in radiating bundles of 

ine white silky needles, as above described, it is composed of 

aaited with a peculiar acid of organic origin, viz., glyko-cholic 

r«ci'{^(C„H^NO,„I10]. This acid iacrystalli/.able and contains nitro- 

[fcn, as «hown by the above formula, which is that given by Lch- 

^tnann. If bolted for a long time with a dilute solution of potaasa, 

glyko-cholic acid is decomposed with the prmiuction of two new 

subslaiicos; the Aral a non-nitrogenous acid borly, choUc acid 

''(C.j^^OpjHO); the aecoad a nitrogenous neutral body, ghjeinc 

(CfHjNOJ. Ileooe the name, glyko-cholio acid, given to the 

original substance, as if it were a combination of oholic ucid with 

glycine. In reality, however, these two substances do not exist 

originally in the glyko-cholic acid, but are rather new combinations 

of its elements, produced by long boiling, in contact with potassa 

and water. They are not, therefore, to bo regarded as, iu nny way, 

natural ingredients of the bile, and do not throw any light on the 

real oonsiitution of glyko-cholic acid. 

lyxuro-ckolaU of $oda (NaO,C„n^,NS,On) is also a very abundant 
ingredient of the bile. It is said by Kobiii and Verdeil' that it is 



■ Clilmlv An&toiutiiUi; vt l'li,rnii>lt)>iiqai», vol- >i. p. 4?.^. 



164 



TITB BILE. 



not crystallizable, owing probably to its rot having been separated 
OS yet in a jjerfectly pure co^ndition. Lehmann stales, on tbe con- 
irary, that it may crystallize,' when kept for a long time in contact 
with ether. Wc have not been able to obtain this substance, how- 
ever, in a crystalline form. Its acicj conslhucni, ianro cfioUc acid, 
is a nitrogenous body, like glyko-cholic acid, but differs from the 
latter by containing in addition two equivalents of sulphur. By 
long tioiling in a dilute solution of potassa. it is decomposed with 
the prod ucilon of two other substances ; the first of them the san;e 
acid body mentioned above as derived from tho glyko-cholic, viz., 
ehoitc acid; and the second a new nitrogenous neutral body, via., 
lourim (C,II,NS,0,). The same remark holds good with regard to 
these two bodies, that wo have alreaily niadu in respect to the sup- 
posed constituonui of glyko-cholic acid. Neither cholic acid nor 
taurine can be properly regarded as really ingredicnta of tauro- 
cholie acid, but only as artificial products reaulting from its altera- 
tion and decomposition. 

Tho glykocholates and taurocholatea are formed, so far as wc 
know, exclusively in the liver; since they have not been found in 
the blood, nor in any other part of the body, in healthy animals; 
nor even, in the experiments of Kunde, Molesehott, and Lehmann 
on frogs,* afler the entire extirpation of the liver, and consequent 
suppression of the bile. These substances are, therefore, produced 
in the glandular cells of the liver, by transformation of some other 
of their ingredients. They are then exuded in a soluble form, as 
jiart of the bile, and finally discharged by the excretory hepatic 
ducts. 

The two substanoea described above as the tauro-cholalc and 
glyko-cholate of soda exist, properly speaking, only in the bile of 
the ox, where they were first discovered by Strecker. In examin* 
ing the biliary secretions of difl'erent species of animals, Streckor 
found so great a resemblance between them, that he was disposed 
to regard their ingredients as essentially the same. Having estab- 
lished the existence in ox-bile of two peculiar substances, one 
crystallizable and noo-3ulphuxous(glyko-cholate),the other uncrys- 
tnllizable and sulphurous (Uiuro-cholale), be was led to consider 
ihe bile in all species of animals as containing the same substances, 
and as differing only in the relative quantity in which the two 

' I'hyeiological Chomlilry, Phil, ed., T(*1. I. p. 20fl. 

• l..-liniaiiii'» I'hydidogical Clieiiiiitrv, t'ltil. wd., rol, 1. p. 4715. 



I 



4 

i 

\ 




THB BILL 



165 



Klg. 50. 



were preaent. TVie only excepiion to this was snpposed to be pig's 
bile, in which Strecker foond a peculiar organic acid, tlie "hyo- 
obotic" or "hjro-cbulinic" acid, in cumbinatiou wilb soda as a biistf. 

The above concluaioo of his, bonrever, was not entirely correct. 
It is true that tlio bile of nit animals, so far as examined, contains 
peculiar substances, which resemble each other in being freely 
soluble in wftter,8oluble in absolute alcohol.and insoluble in ether; 
and iu giving also a peculiar reaction with Pettcnkofer's test, to be 
desenbed presently. But, at the same time, these substances pre- 
sent certain ininordifTerences in difiorontnnimnla, which show thoin 
Dot to be identical. 

In dog's bile, for example, there are, as in ox-bile, two substances 
precipitoble by ether from their alcoholic solution ; one crystalliz- 
able, the othernot so. But the former of these substances crystallizes 
much more readily than the glyko-cholate ofsoda from ox-bile. Dog's 
bile will not unfrcqueiiily begin to crystallize freely iu five to six 
hours after precipitation by ether (Fig. 60); while 
in ox-hilc it is usually twelve, and of^en twenty- 
four or even forty-eight hours before crystalliza- 
tioD is fully established. But it is more particu- 
larly in their reaction with tha salts of luad thai. 
the diflerence between these Mubstances becomes 
manifest. For while the crystal lizable substance 
of ox-bite is precipitated by acetate of lead, th:it 
of dog's bile is not aflectcd by it. If dog's bile 
be evoi>oroted to dryness, e.xtracted with absolute 
alcohol, the alcoholic solution precipitated by 
ether, and the ether precipitate then dissolved 
io water, the addition of acetate of lead to the 
watery solution produces not the slightest tur- 
bidity. If subacetnte of lend be then added in 
exixa&t a copious precipitate fulls, composed of 
both the crystallizable and uncrystallizable sub- 
staooes. If the lead precipitate be then separated 
by filtration, washed, and decomposed, as above 
described, by carbonate of soda, the watery solu- 
tion will contain the re-formed soda salts of the 
bile. The wat*'ry solution may then be evaporated to dryness, 
extracted with abfiolute alcohol, and the alcoholic solution precipi- 
tated by ether; when the ether precipitate crystallizes partially 



no.i'aRii. p.«xlliw(- 
oit Willi alwalulaalfoliol 
■till iirirlpllaWd wlih 
MhM. 



1G6 



TBE BlLt;. 



Pig. 51. 



after a time, as in fresh bile. Both tKe biliary matters of dog's bile 
are therefore preci[>itable by ^ubacutatt; of Itjail, but neither of them 
by tbe acetate. Instead ofcalliDg tbein, eoDsequently, glyko-cholate 
and tatinj-diolate of suila, we shall apeak of tliem simply as the 
"crystalline" and "r&sinous" biliary siibstant^cs. 

In cat's bile, the biliary subatancee act very much as in dog's 
bile. The ether-preci|)itatu uf the alcohuliu soliiliou conlains here 
also a cryalallino and a rc^tnaus substance; both of which are 
precipitable from their watery soIuEioa by subacetate of lead, but 
neither of them by the auotate. 

In pig's bile, on the other hand, there is no crystallizable sub- 
stance, but tlio ethcr-procipiliite is altogether resinous in appear- 
ance. Notwithstanding this, its watery solution precipitates abun* 
dantly by both the acetate and subacetate of lead. 

In human bile, agaiu, there \a uo Qrystallizablo substance. We 
have found that the dried bilo, extracted with Absolute alcohol, 
makes a clear, brandy-red solution, which precipitates abundantly 
with other in cxccj«; but the ether- precipitate, if allowed to stand, 
shows no sign of crystallization, even at tbe end 
of three weeks. (Fig. 51.) If the resinous preci- 
pitate bo separated by deeanlation and dissolved 
in water, it precipitates, as in the case of pig's 
bile, by both the acetate and subacetate of lead, 
Tliia might, perhaps, be attributed to the pre- 
sence uf two ditl'ei'ent substances, as in ox-bile, 
one precipitated by the acetate, the other by the 
subacetate of lead. Such, however, is not the 
case. For if the watery solution be precipitated 
by the acetate of load and ihau filtered, the GItcreil 
fluid gives no precipitate afterward by tbe sub- 
acetate ; and if first precipitated by the subacetate, 
it gives no precipitate after filtration by the ace- 
tate. The entire biliary ingredients, therefore, of 
human bile are precipitated by both or cither of 
the salts oflead. 

Diflcrent kinds of bile vary also in other re- 
spects; as, for example, tbcir specific gravity, the 
depth and tinge of their ctdor, the quantity of fat 
which they contain, ic. &c. "We have already 
mentioned the variations iu color and specific gravity. The alco- 
holic solution of dried ox-bile, furllicruioro, does iiol precipiiate at 



IU- K * H B 1 1, n , «x- 

■lenliiil iDil |ir>irij>Hiil- 

pd 1)7 Mh«r. 



I 
I 
I 




TESTS FOR BII.H. 



187 



ill on ihe addition of walor; wbile that of Iiumnn bile, of pig's 
biie, ami of dog's bile precipitate nbundanlly with distilled wiiier, 
owing to t!ie quantity of fat which iliuy hold in solution. Those 
variationa, however, are of secondary importanoe oonipnred with 
thorn which we have already mentioned, and which show that the 
crystalline and resinous substauces in diHcrent kinds of bile, though 
resembling each other In very many respects, are yet in reality far 
from being idonticat. 



Tests fob Bir.K. — In investigating tlic physiology of any animal 
fluid it is, of course, ot the Brat importance to have a convenient 
find reliable teat by which its presenoo may be detected. For a. 
long time the only test emplnyeil in the case of bile, was that which 
depended on a change <y' wlor produced by oxidizing substance*. If 
the bile, for example, or a mixture containing bile, be exposed in 
an open glass vessel for a few hours, ihe upper layers of the fluid, 
which are in contact with the atmosphere, gradually assume a 
greenish tinge, which becomes deeper with the length of time which 
elapaea, and the quantity of bile existing in the fluid. Nitrie acid, 
added to a mixture of bile and shaken up, produces a dense preci- 
pitate which lakes & bright grass-green hue. Tincture of iodine 
produces the same change of color, when added in small quantity; 
and probably there are various other substances which would havo 
the same effect. It is by this test that the bile has so oflen been 
reoogniiied in the urine, f;erous effusions, the solid tissues, &c., in 
oaaea of jaundice. liut it is very insufhcient for anything like 
accurate investigation, since the appearances are produced simply 
by the action of an oxidizing agent on the coloring mutter of the 
bile. A green color produced by nitrio acid does not, therefore, 
indicate the presence of the biliary substances projier, but only of 
the biliverdine. On the other hand, if the coloring matter be ab- 
■ent, the biliary substances themselves cannot be detected by it 
For if the biliary substances of dog's bile be precipitated by ether 
from an alcoholic solution, dissolved in water and decolorized by 
nnicnal charcoal, the colorleas watery solution will then give no 
green color on the addition of nitric acid or tincture of iodine, 
though it may precipitate abundantly by subacetate of lead, and 
give tlio other reactions of the cryatalliue and resinous biliary 
maiters in a perfccity distinct manner. 

PtUerdofe/'a Teal, — This is undoubtedly the best test yet pro* 
poaed for the detection of the biliary substances. It consists tn 



Ifi8 



TBS BII.S.' 



i 



mixing with r watery solution of the bile, or of the hiliary sab 
stances, a little cane sugar, and then adding sulphuric acid to the 
mixture unlit a red, lake, or purple color is produced. A solution 
may be made of cane sugar, in the proportion of one part of sugar to 
four parts of water, and kept for use. One drop of this solution is 
mixed with the auspectcd fluid, and the sulphuric acid then imme- 
diately added. On 6r8t dropping in the sulphuric acid, a whitish 
jirecipitate falls, which is abundant in the cast! of ox-bile, less so in 
that of the dog. This precipitate redJsaolvea in a slight excess of 
sulphuric acid, which should then continue to be added until the 
mixture assumes a somewhat syrupy conaiatcncy and an opalescent 
look, owing to the devetopmenl of miuutu bubbles of air. A red 
color iheQ begins to show itself at the bottom of the test-tube, and 
afterward spreads through the mixture, until the whole fluid is of 
a clear, bright, cherry red. This color gradually changes to a lake, 
and finally to a deep, rich, opaque purple. If three or four vol- 
umes of water be then added to the mixture, a copious precipitate 
falls down, and the color is destroyed. 

A''ariou3 circumBtaaces modify, to some extent, the rapidity and 
distinctness with which the above changes are produced. If the 
biliary substances be present in large quantity, and nearly pure, 
the red color shows it<iclf at once alter adding an equal volume of 
sulphuric acid, aud almost immediately passed into a strong purple. 
If they be scanty, on the other hand, the red color may not show 
itself for seven or eight minutes, nor the purfde under twenty 
or twenty-five minutes. If foreign matters, again, not oF a biliary 
nature, be also present, they are apt to be acted on by the sulphuric ■ 
acid, and, by becoming discolored, interfere with the clearness and 
brilliancy of the tinges protlueed. Ou this account it is indispen- 
sable, in delicate examinntions, to evaporate the suspected fluid to 
dryness, extract the dry residue with absolute alcohol, precipitate 
the alcoholic solution with ether, and dissolve the ether-precipitate 
in water before applying the test. In this manner, all foreign sub- 
stances which might do harm will be eliminated, and the test will ' 
succeed without difficulty. 

It must not be forgotten, furthermore, that the sugar itself la 
liable to be acted on and discolored by sulphuric acid when added 
in excess, and may therefore by itself give rise to confusion. A little 
care and practice, however, will enable the experimenter to avoid 
all chance of deception from this source. When sulphuric acid is 
mixed with a watery solution containing cane sugar, after it has 



I 





TESTS FOR B!LB. 



169 



beeu added in considerable excess, a yellowtab color begins to show 
itself, owing to the commencing decomposition of ihe sugnn This 
color gradually deepens until it has become a dark, dingy, muddy 
brown; but there Is oever at anytime any clear red or purple 
oolor, unless biliary matters bo presunt. If the bile be present in 
but small quantity, the colors produced by it may be modified and 
(ibftcured by the dingy yellow and brown of the sugnr; but even 
this difficulty may be avoided by paying attention to the following 
precautions. In the first place, only very little augnr should be 
added to the suspected fluid. In the aecond place, the sulphuric 
acid should bo added very gradually, and the mixture closely 
watched to detect the first changes of color. If bile be present, the 
red color peculiar to it is always procluced before the yellowish 
tinge which indicates the decomposition of the sugar. When the 
biliary matters, therefore, are present in small quantity, the add!- 
tion of sulphuric acid should be stopped at that point, and the 
colors, though faint, will then remain clear, and give unmistokablc 
evidence of the presence of bile. 

I'he red color alone is not sufScient as an indication of bile. It 
is in fact only the commencement of the change which indicates the 
biliary matters. If these matters bo present, the color pa8.ses, as 
we have already mentioned, first into a lake, then into a purple; 
and it is this lake and purple color alone which can ba regarded as 
really characteristic of the biliary reaction. 

It is important to observe that Pettenkofer'a reaction ia produced 
by the presence of either or both of the biliary substances proper; 
and is not at all dependent on the coloring matter of the bile. For 
if the two biliary substances, crystalline and resinous, be extracted 
by the process above de9crlbe<l, and, after being dissolved in water, 
decolorized with animal charcoal, the watery aolution will still give 
Pettcnkofer's, reaction perfectly, though no coloring matter be pre- 
sent, and though no green tinge can be produced by the addition 
of nitric acid or tincture of iodine. If the two biliary aubstaDces 
be then separate^l from each other, and tested in distinct solutions, 
each floluiion will give the same reaction promptly and completely. 

Various objections have been urged against this test It has 
been stated to be uncertain and variable in its action. Hubio and 
Verdeil' say that its reactions "do not belong exclusively to thfi 
bile, and may therefore give rise to mistakes." Som'' 



170 



THB BILE. 



slnnccs and Tolatile oils (olein, oleic acid, nil of turpentine, ait 
caraway) have been 8tatffll to produce similnr red and violet colors, 
when treated with sugar aud sulphuric acid. These objections, 
however, have not much, if any, practical weight. The test no 
doubt rtfquires some care and practice in its application, aa we have 
already pointed out; but this is the case also, to a greater or le&s 
extent, with nearly all chemical tcsia, and particularly with those 
for substances of organic origin. No other substance is, in poinl 
of Tact, liable to be met with in the intestinal fluids or the bloody 
which would simulate the rcnctions of the biliary matters. Ws 
have found that the fatty matters of the chyle, taken from the tho- 
racic duel, do not give any coloration which would be mistaken for 
that of the bile. When the volatile oils (caraway and turpentine) 
are acted on by sulphuric acid, a red color is produced which afler- 
ward becomes brown and blackish, and a peculiar, tarry, empyreu- 
matic odor is developed at the same time; but we do not get the 
lake and purple colors spoken of above, finally, if the precaution 
be obiierved — ilrst of extracting the suspected matters with absolute 
alcohol, then precipitating with ether and dissolving the precipitate 
in water, no ambiguity could result from the presence of any of thd ■ 
above substances. 

Tettenkofer's test, then, if used with care, is extremely useful, 
and may lead to many valuable results. Indeed, oo other test than I 
this can be nt all relied on to determine the presence or absence of 
the biliary substances proper. ^ 



V.^RiATiONS .AND FUNCTIONS OP BitE. — With regard to the 
aitire qttant\(y of HU sfcreted daily, we have had no very positive 
knowledge, until the experiments of Bidder and Schmidt, published 
iu ltt52.' These experiments were performed on cats, dogs, sheep, 
and rabbits, in the following manner. The abdomen was o|>ened| 
and a ligature place*! upon the ductus coinmiinis eholedochus, sa 
as to prevent the bile finding its way into the intestine. An open- 
ing was then made in the fundus of the gall-bladder, by which 
the bile was discharged externally. The bile, so discharged, was 
received into previously weighed vessels, and its quantity accurately 
determined. Each observation usually occupied about two hours, 
during which period the temporary fluctuations occasionally observ- 
able iu the quantity of bile discharged were mutually correctod| so 



V«ril.ianEMa«rU! uixl SiolTnocliMl. L«l|iii£, ISflS. 



I 





VARIATIONS AND FUNCTIONS OF DILE. 171 

IT as the entire result was concerned. Tbo nttinriAl was then killet], 
weighed, and carefully examined, in order to make sure that the 
biliary duct had boon securely tied, and that no inflnmmntory alter* 
ttion had taken place in the abdominal organs. The obatirvations 
were made at very diiTerent periods after the lost meal, so as to 
determine the influence exerted by tlio digestive procc8fl upon the 
rapidity of the secretion. The average quantity of bile for twenty- 
four hours was then calculated from a comparison of the above 
results; and the quantity of iU solid ingredients wai^ also ascer- 
tained in each instance by evaporating n portion of the bile in the 
water bath, and weighing the dry residue. 

Bidder and Schmidt found in this way that the daily quantity 
of bile varied considerably in different species of animals. It was 
very much greater in the herbivorous animals used for experiment 
than in the carnivora. The results obtained by these observers 
are as follows:— 

For every pound weight of the entire body there is secreted 
daring 2i hours 

pBKaK Bite. Dsr Rbkiovb. 
Id llic eat ...... 10'.! jcrAJni. &.7Vi grn\a». 

" dog . . . . 1*1 " fl.916 " 

■ rtewp 179 " S.4H8 " 

- nhUt &58 " 17.S80 " 

Since, in the human subject, the digestive processes and the 
nutritive actions generally resemble those of ihe carnivora, rather 
iban those of the herbivora, it is probable that the daily quantity 
of bile in man is very similar to that in the carnivorous animals. 
If we apply to the human subject the average results obtained by 
Bidder and Schmidt from the cat and dog, we find that, in an adult 
man, weighing 140 pounds, the daily quantity of the bile will be 
certainly not lese than 16,9^0 grains, or very nearly 2^ pounds 
avoirdupois. 

It is a matter of great importance, in regard to the bile, as well 
the other intestinal fluids, to ascertain whether it be a eotisiant 

sretion, like the urine and perspirniion, or whether it bo intennil' 
IaU, like the gastric juice, and discharged only during the digestive 
procesB. In order to determitie this pointy we have performed the 
following scries of experiments on dogs. The animals were kept 
confined, and killed at various periods af^cr feeding, sometimes by 
the inoculation of woorara, sometimes by hydrocyanic acid, but 
most frequently by section of the medulla oblongata. The con- 



172 

tenia of the intestine were then collet^tciJ and exnmined. Tn »!! 

itistancos, the bile was alao taken from ihe gall-bladder, and treat«<l 

in the same way, for purposes of comparison. The intestinal con- 

tentaalwaya prcacnted some peculiaritiea of appearance when treated 

with alcohol and ether, owing probably to the presence of other 

BuK'itanees than the bile; but they always j^uve evidencM) of the 

presence of biliary matters um welt. The biliary substances could 

almost elwuys be recognized by the microscope in the etheri)reci' 

pitato of the alcoholic solution; the resinous substance, ander the 

form of rounded, oily-looking drops (Fig. 62), and the other, ander 

the form of crystalline groups, generally presenting the appearance 

of double bundlosuf slender, 
I'ig. 52. 1 ■ 1- I 1 1 

radiating, slightly curved or 

wavy, needle-shaped crys- 
tals. These substances, dis- 
solved in water, gave a pur- 
ple color with sugar and 
sulphuric acid. These ex- 
periments were tried after 
the animals had been kepi 
for one, two, three, five, six, 
seven, eight, and twelve 
days without fooil. The 
result showed that, la all 
these instances, bile was pre- 
sent in the small intestine. 
It is, therefore, plainly not 
an intermilteot secretion, 

nor one which is concerned exclusively in the digestive process; 

but its secretion is constant, and it continues to bo disehargc<l into 

the intestine for many days after the animal has been deprived of 

food. 

The next point of importance to he examined relates to the frme 
after feeding at wKidi the bile pojscj into the inUsllnc m the rftraltst 
atninJaiice. Bidder and Schmidt have already investigated this 
point in the following manner. They operated, as above dei^cribed, 
by tying the common bileduct, and then opening the fundus of the 
gall-bladder, so as Ut produce a biliary fistula, by which the whole 
of the bile was drawn of!'. By doing this operation, and collecting 
and weighing the Suid discharged at different periods, they came 



o, 








• TA><^l*i fnn BciibII iBtMlInn at Oaf. a/Ral two daj** 
IkatlBl. 



i 



i 








VARIATIONS AND yUNCTlONS OF BIT.B. 



173 



to the conclaaion that the Sow of bile begins tr> irtoreaee within ivro 
and a hair hours after the introduction of food into the stomach, 
but that it does not ren^^h its maximum of activity till the end of 
twelve or flftuen hours. Otlier observers, however, have obtained 
diflbrent results. Arnold,* for example, found the quantity to be 
largest soon aller meals, decroawing again after the fourth hour. 
Koilikcr and MUllcr,* again, found it largest between the sixth and 
eighth hours. Bidder and Schmidt's experiments, indeed, strictly 
qteaking, show only the titne at which the bile is most activuly 
Mcrctcd by the liver, but not when it is uotually discharged into 
the intestine. 

Oar own experiments, bearing on this point, were performed on 
dogs, by making a permanent 
duo<1enal listula, on the same "*' **' 

plan that gaatrio Hstulfe have so 
dh.tn been established for the 
examination of the gastric juice. 
(Fig. 53.) An incision was made 
throagh the abdominal watts, a 
short distance to the right of 
the medtan line, the floating 
portion of the daodenum drawn 
up toward the external wound, 
opened by a longitudinal inci- 
noQ, and a silver tube, armed 

>t each end with a narrow 

pmjevting collar or flange, in- 

Berled into tt by one extremity, 

five and a half inches below the 

p^'lurua, and two and a half 

inches below the orifice of the 

bwer pancreatic duct. The 

'iW extremity of the tube was 

Wl projecting from the external 

opening in the abdominal pa- 

rietes, the parts secured by suturea, and the wound allowed to heal, 

AlW cioatrization was complete, and the animal had entirely 

fKovcred his healthy condition and appetite, the iiitcslinal fiuids 

*ere drawa offal various intervals after feeding, and their contents 



:v 



DcDDiNAL. Kr<Tt)l.t.~Hi. Stomieh. b Duo< 
ilcuiiiii r, e. e ranriviu; lu inn durin xrs •r>fa 
oiioniof fntu llii i]ai>dBDUin, one ui-ir [lie orlAe* 
u( III* hlhur; duM. 4, Ihs mhar n >lii)n dUUiiec 
law<r down r. Sllrer tub« pitcluf itif<iugli (hi 
■lliliiinllilll •ralla taA a)>«iilD|r Inli] ttia iluuitannn, 



' til Au. Jqhri. HwI. Scl.,.Apri1. 1890. 



Ibid., April, 1657. 



1T4 



TQK BIT.G. 



oxamincd. Tbis operation, which is rather moredifftcull tbnn Ui 
of making a permanent gastric fistula, is oevertheleaa exceedingly 
useful when it succeeds, since it enables 119 to study, not only the 
lime and rate of the biliary discharge, bat also, as mentioned in a 
previous chapter (Chap. VI.), maay other extremely interesting 
tnattera connected with inteatinul digestion. 

In order to ascertain the absolute quantity of bile discharged 
into the intestine, and its variations during digestion, the duodenal 
fluids were drawn 0% for fifteen minutes at a time, at various 
periuda alter feeding, collected, weighed, and examined separately, 
as follows: each separate quantity was evaporated to dryness, ita 
dry residue extracted with absolute alcohol, the alcoholic solution 
precipitated with ether, and the ether- precipitate, regarded as repre- 
senting the amount of biliary matters present, dried, weighed, and 
then treated with Pettenkofer's test, in order to determine, as nearly 
as possible, their degree of purity or admixture. The result of 
these experiments is given in the following table. At the eigh- 
teenth hour so small a quantity of fluid was obtained, that the 
amount of its biliary ingredients was not ascertained. It reacted 
perfectly, however, with Petteiikofer's test, showing that bile 
really pre3ent. 



I 

I 



Tlmo ifK-r 


tttiaoll^r <if(llliil 


brf riwlcloo 


Qimnltlf of 


Pro("itlti«i of 


fri-Jlmg. 


Irj 1.1 tuiuutck. 


udutmo. 


bills ly luktlrfi 


III drjr ffikl^Bf*, 


Itntuc^dlAlul^ 


fi4i> grains 


33 grains 


lOgntina 


.30 


1 hour 


l.ltftO ■• 


105 " 


4 " 


.03 


8 boutv 


760 " 


60 " 


4 " 


.07 


6 '■ 


760 '* 


73 " 


34 •■ 


.06 


9 " 


HIHl " 


78 " 


4} " 


.08 ' 


IS " 


325 " 


23 " 


S* '■ 


.16 


16 " 


Ml " 


18 " 


4 " 


.82 


18 " 


^ 





^ 


^_ 


ai " 


384 " 


11 " 


J " 


.00 


24 .. 


lfi3 " 


M " 


31 '• 


.34 


25 " 


151 " 


6 » 


3 ♦' 


.«> 



From this it appears that the bile passes iulo the intestine in by 
far the largest quautity immediatuly afler feeding, and within the 
first hour. AHer that time its discharge remains pretty constant; 
not varying much from four grains of solid biliary matters every 
fideen niinutes, or sixteen grains per hour. Tbe animal used for 
the above observations weighed thirty-six and a half ponnds. ■ 

The next point to he ascertained with regard to this question is 
the following, viz: What hea>mes of the hie in its passage throxtijh 
the inlestiueP Our experiments, performed with a view of settling 





VARIATIONS ANP FCKCTIONS OF BILE. 



176 



(his point, wero tried on dogs. Tho animals were fed with fresh 
ineat,and then killed at varioas intervals after the meaU, the abdo- 
men openei3, lignlures placed upon the intestine at various points, 
Hud the contents of its upper, middle, and lower portions collected 
and examined Bepamtelj. The results thus obtained bIiow that, 
under ordinary circumstance^ the bile, which is quite abundant in 
the duodenam and upper part of the small iutestiae, dimiuisbes in 
quantity from above downward, and is not to be found in the large 
intestine. The entire quantity of the intestinal contents also dimi- 
nishes, and their consiatcney increases, as we approach the ileo- 
cecal valve ; and at tbe same time their color changes from a light 
yellow to a dark bronze or blackieth-groeo, which is always strongly 
pronounced in the IobI quarter of the smalt intestine. 

Tbe contents of tbe small and large intestine were furthermore 
evaporated to dryness, extracted with absolute alcohol, and tho 
alcoholic solutions precipitatud with ether; the quantity of ctber- 
precipilate being regarded as representing approximatively that of 
the biliary substances proper. The result showed that the quantity 
of this ether-precipitate is, both positively and relatively, very much 
toss in tbe large intestine than in tbe small. Its proportion to the 
entire solid contents is only one-fltlh or ono-sixth as great in iha 
large intestine as it is in the small. But even this inconsiderable 
quantity, found in contents of the large intestine, docs not con- 
sist of biliary matters; for tbe watery solutions being treated witb 
tagar and sulphuric acid, those from both tbe upper and lower 
portions of the small intestine always gave Pettenkofer'a reaction 
promptly and perfectly in less Uian a minute and a half; while in 
that from the large intestine no red or purple color was produced, 
even at tbe end of three hours. 

The small intetitine consequently contains, at all times, substances 
giving all the reactions of tbe biliary ingredients; wbilu in the 
coQients of the large intestine no such substances can be recognized 
'oy Pettcnkofcr's test. 

The biliary matters, therefore, disappear in their passage through 
the intestine. 



In endeavoring to ascertain what is the precise /unrtiOT of (he bile 
in Uic inCesChu:, our first object must be to determine what ])arl, if 
wy, it takes in the digestive process. Aa the liver is situated, like 
the salivary glands and the pancreas, in the immediate vicinity of 
ihe alimentary canal, and like tbero, discharges its secretion into 



176 



I 



I 



ihe cavity of the intestine, it seema at Brst natural to regard the 
bile na one of the digestive fluids. Wc have previously shown, 
however, that the digestion of nil the different elements of the food 
is provided for by other secrellona ; and furtliermore, if we exaniiQe 
experimentally the digestive power of bile on alimentary sabstaDces. 
we obtain only a negative result. Bile exerw no special actioD upon 
oithcr ftlburoinoid, starchy, or oleaginous matters, when mixed with 
them in test-tubes and kept at the temperature of 100° F. It baa 
iberefore, apparently, uq direct iufluence in the digeatiuD of iboBa 
substances. 

It is a very rcmarkuble fact, in this connection, that the bile pre- 
cipitates hy eonfact with the gastric juice. If four drops of dog'a bile 
be added to 5j of gastric juice from the same animal, a copious 1 
yellowish white precipitate fulls down, which contains the whole of 
the coloring matter of the bile which baa been added; and if the 
mixture be then filtered, the filtered fluid passes through quite 
colorless. Tbe gastric juice, however, still retains its acid reaction. I 
Tbis precipitation depends upon the presence of the biliary sub- 
stances proper, viz., the glyko-cholate and tauro-chulate of soda, and 
not upon that of the incidental ingredients of the bile. For if the 
bile be evaporated to dryness and the biliary substances extracted 
by alcohol and precipitated by ether, as above described, their 
watery solution will precipitate with gastric juice, in tbe same 
manner us fresh bile would do. 

Although the biliary matters, however, precipitate by contact 
with fresh gastric juice, iftc^ ilo hqI do so with gastric Juice which hoUU 
aUfuminose in solution. We have invariably found that if the gas- 
tric juice bo digested for several hours at the temperature of 100' 
F^ with boiled white of egg, the filtered fluid, which contains an 
abundance of albuminose, will no longer give the slightest precipi* 
tate on the addition of bile, or of a watery solution of tbe biliary 
substances, even in very large amount. The gastric juice and tbe 
bile, therefore, are not finally antagonistic to each other in the 
digestive process, though at first they produce a precipitate on 
being mingled together. 

It appears, however, from the experiments detailed above, that 
the secretion of the bile and its discharge into the intestine are not 
con6ned to the periods of digestion, but take place constantly, and 
continue even after tbe nnimal hEis been kept for many days with- 
out food. These facts would lead us to regard the bite as simply 
an extrementitious jiuid : contaiaing only ingredients resulting from 



4 





VABIATIONS AND FUNCTIONS OP BILB. 



177 




waste and disintegration of the animal lissucs, and not intended 
to perform any ]>articular function, digestive or otherwise, but 
merely to be eliminnted from the blood, and discharged from the 
eystom. The same view \a more or less supported, also, by the 
following facta, vig: — ■ 

1st. The bile is prodaced, unlike all the other animal nccretious, 
from venous blood; that i?, tlie blood of the portal veio, which has 
already become contaminated by circulation through the abdominal 
organs, and may be sup[>oscd to contain disorganized ami eiteie 
Jngredients; and 

2d. Its complete suppression produces, in the human nubject, 
)ma of poisoning of the nervous system, analogous to those 
fallow the suppression of the urine, or the stoppage of respi- 
ration, and the pnlient dies, usually in a comatose condition, at the 
end of ten or twelve dnys. 

The above circumstances, taken together, would combine to 
make it appear that the bile ia simply an uxcremeutitioua fluid, not 
necessary or useful as n secretion, but only destined like the urine, 
to be eliminated and discharged. Nevertheless, experiment has 
sbowQ that such is not tlie case; and that, in point of fact, it is 
necessary for the life of the animal, not only that the bile be aecreted 
attd discharged, but furthermore that it be discharged into tbd 
intestine, and pass through the tract of the alimentary ciinal. The 
most satisfactory experiments of this kind are those of Bidder and 
Schmidt,' in which they tied the common biliary duct in dogs, and 
theu established a permanent fistula in the fundus of the gall-bladder, 
through which the bile was allowed to flow by a free external urilice. 
In this manner the bile was effectually excluded from the intestine, 
but ai the same time was freely and wholly discharged from the 
body, by the artificial fistula. If the bile llierefore were simply an 
excrementitious fluid, itsdeletcrioua ingredients being alt eliminated 
as usual, the animals would not suffer any serious injury from this 
operulion. If, on the contrary, they were found to sufter or die in 
consequence of it, it would show that the bile has really some im- 
portant function to perfurrn in the inteistinal canal, and is not simply 
excrementitious in its nature. 

The result showed that the eflects of such an ex|)ennient were 
fatal to the animal. Four doga only survived the immediate eftects 
of the operation, and were aflerwar*.! frequently used for purposes 



178 



THE 13ILE. 



of cxporimcnt. One of them was an animal from wliicfa the apleen 
hnd been previously removed, and whose appetite, as usual after 
this operation, was morbitlly ravenous; his system, accordingly, 
being placed uoder such unnatural conditions as to make him an 
unfit subject for further experiment. In the second animal that 
survived, the communicution cf the biliary duct with the intestine 
became re-established after ci^^hteen days, and the experiment con* 
aequently had no result. In the remaining two animals, however, 
everything was sueccsaful. The fistula in the gall-bladder became 
permanently establislieJ ; and the bile-duct, as was proved subse- 
quently by post-mortem examination, remained completely closed, 
so that no bile found its way into the intestine. Both these ani- 
mals died ; one of them at the end of twenty-seven days, the other 
at iho end of thirty-six days. In both, the ayniptoms were nearly 
the same, viz., constant and progressive cmnciation, which proceeded 
to such a degree that nearly every trace of fat disappeared from the 
body. The loss of flesh amounted, in one case to more than two- 
fifths, and in the other to nearly one-half the entire weight of the 
animal. There was also a falling off of the hair, and an unusually 
disagreeable, putrescent odor in the feces and in the breath. Not- 
withstanding this, the appetite remained good. Digestion was not 
essentially interfered with, and iiono of the food was dischargiMl 
with the feces; bui there was much rumbling and gurgling in the 
intestines, and abundant discharge of flatus, more strongly marked 
in one instance than in the other. There was no pain; and death 
took place, at last, without any violent symptoms, but by a simple 
and gradual failure of the vital powers. 

now IB it, then, that although the bile bo not an active agent in 
digestion, its presence In the alimentary canal is still essential to 
life? What ofiice does it perform there, and bow U itiinally dis- 
posed of? 

We have already shown that the bile disappears in ita passage 
through the intestine. This disappearance may be explained in 
two diSisrent ways. First, the biliary matters may be actually re- 
absorbed from the intestine, and taken up by the bloodvessels; or 
secondly, they may be so altered and decomposed by the intestinal 
fluids as to lose the power of giving Pettenkofcr'a reaction with 
sugar and sulphuric acid, and so pass oft' with the feces in an 
insoluble form. Bidder and Schmidt' have Snally determined thi^ 

■ Op. cit.p. 217. 



I 

I 



i 



\ 

I 

I 




VARIATIONS AND FUNCTIONS OF BILK. 179 

point in a aatisfactory manner; and have demonstrated that the 
biliary substances are actually reabsorbed, by showing that the 
quantity of sulphur present in the feces is far inferior to that 
contained in the biliary ingredients as they are discharged into the 
intestine. 

These observers collected and analyzed all the feces passed, dur- 
ing five days, by a healthy dog, weighing 17.7 pounds. The entire 
fecal mass during this period weighed 1508.15 grains, 

CoDUinmg I ^•'«" 874.20 grains. 

I Solid reBidne 633.95 " 



IfiOS.lfi 



The solid residue was composed as follows: — 

Nentnl fat, soluble in ether . 43.710 grains. 

Fat, with traces of hilitnj matter . 77.035 " 

Alcohol extract with biliarj matter 58.900 containing 1.085 grs. of snlphnr. 

Sabatanoes not of a blliarj natare 

extracted by mariatio acid and 

hot aloohol .... 148.800 contolning 1.302 grs. of salphor. 

2.367 
Fatt/ acids with oxide of iron . 98.426 
Beaidne consisting of hair, sand, Ac, 207.080 

633.950 

Now, as it has already been shown that the dog secretes, daring 
21 hours, 6.916 grains of solid biliary matter for every pound weight 
of the whole body, the entire quantity of biliary matter secreted 
ID five days by the above animal, weighing 17.7 pounds, must have 
been 612.5 grains, or nearly as much as the whole weight of the 
dried feces. But furthermore, the natural proportion of sulphur 
in dog's bile (derived from the uncrystallizable biliary matter), is six' 
per cent of the dry residue. The 612.5 grains of dry bile, secreted 
daring five days, contained therefore 36.75 grains of sulphur. 
But the entire quantity of sulphur, existing in any form in the 
feces, was 5.952 grains ; and of this only 2.387 grains were derived 
from substances which could have been the products of biliary 
matters — the remainder being derived from the hairs which are 
always contained in abundance in the feces of the dog. That is, 
not more than one-fifleenth part of the sulphur, originally present 
io the bile, could be detected in the feces. As this is a simple 
chemical element, not decomposable by any known means, it must, 
accordingly, have been reabsorbed from the intestine. 

We have endeavored to complete the evidence thus furnished by 



180 



TUK J3ILK. 



Bidder and Schmidt, and to demonstrate dirvctly the reabsorptioiT 
of the biliar_v matterii, by searching for ihatn in the ingredients of 
the portal blood. We )iave examined, fur this purpose, the portal 
blood of dog3, killed ot vnrious periods after feeding. The animals 
were killed by section of the medulla oblongata, a ligature imme- 
ilialely placed on the portal vein, while the circulation ivas still 
active, and the requiBite quantity of blood collected by opening 
the vein. The blood was sometimes immediately evaporated to 
(Irync&s by the water bath. Sometimes It was coagulated by boil- 
ing in a porcelain capsule, over a spirit lamp, with water and an 
excess of sulphate of sodo, and the filtered watery solution after- 
ward examined. Hut moat frequently the blood, after being col- 
lected from the vein, was coagulated by the gradual addition of 
three times its volume of alcohol at nineiy-five per cent., stirring 
the mixture constantly, so as to make the coagulation gradual and 
uniform. It was then filtered, the moist tnasa remaining on the filter 
snbjected to strong pressure in a linen bag, by a porcelain press, 
and the fluid thus obtained added to that previously filtered. The 
entire spirituous solution was then evaporated to dryness, the dry 
residue extrocted with absolute alcohol, and the alcoholic soltition 
trcatcfl as usual, with ether, kc, to discover the proscncc of biliary 
mutters. In every instance, blood was taken at the same lime from 
the jugular vein, or the alxlominal vena cava, and treated in the 
same way for ])urpoae8 of comparison. 

We have examined the blood, in this way, one, four, six, nine, 
eleven and a half, twelve, and twenty hours after feeding. As the 
result of these examinations, we have fuund that in the venous 
blood, both of the portal vein iind of the general circulation, there 
exists a snb^nce soluble in water and absolute nleoliol, and pre- 
cipitflblc by ether from its alcoholic solution. This substance is 
often considerably more abundant in the portal blood than in that 
taken from the general veuoua system. It adheres closely to the 
sides of the gloss after precipitation, so that it is always diflicult, 
and often impoiwible, to obtain enough of it, mixed with ether, for 
microscopic examination. It dissolves, also, like the biliary sub- 
stances, with great readiness in water; but in no instance have we 
ever been able to ohtnia from it snch a satisfactory reaction with 
PetienUofer'a test, as would indicate the presence of bile. This is 
not because the reaction is masked, as might be suspected, by some 
of thy other ingredients of the Wood: for if at the same time, two 
drops of bile be adde<l to half an ounce of blood taken from the 



I 

t 

I 
I 
I 




VARIATIONS AND FUNCTIONS OF BILE. 181 

abdominal vena cava, and the two specimens treated alike, the ether- 
precipitate may be considerably more abundant in the case of the 
portal blood; and yet that from the blood of the vena cavo, dis- 
solved in water, will give Pettenkofer'a reaction for bile perfectly, 
while that of the portal blood will give no such reaction. 

Notwithstanding, then, the irresistible evidence afforded by the 
experiments of Bidder and Schmidt, that the biliary matters are 
really taken up by the portal blood, we have failed to recognize 
them there by Fetteukofer's test. They must accordingly undergo 
certain alterations in the intestine, previously to their absorption, 
80 that they no longer give the ordinary reaction of the biliary sub- 
stances. We cannot say, at present, precisely what these alterations 
are ; but they are evidently transformations of a catalytic nature, 
produced by the contact of the bile with the intestinal juices. 

The bile, therefore, is a secretion which has not yet accomplished 
its function when it is discharged from the liver and poured into the 
intestine. On the contrary, during its passage through the intestine 
it is still in the interior of the body, in contact with glandular sur- 
faces, and mingled with various organic substances, the ingredients 
of the intestinal fluids, which act upon it as catalytic bodies, and 
produce io it new transformations. This may account for the fact 
stated above, that the bile, though a constant and uninterrupted 
secretion, is nevertheless poured into the intestine in the greatest 
abundance immediately afler a hearty meal. This is not because it 
is to take any direct part in the digestion of the food; but because 
the intestinal fluids, being themselves present at that time in the 
greatest abundance, can then act upon and decompose the greatest 
quantity of bile. At all events, the biliary ingredients, afler being 
altered and transformed in the intestine, as they might be iu the 
interior of a glandular organ, re-enter the blood under some new 
form, and are carried away by the circulation, to complete their 
function in some other part of the body. 



162 



FORMATIOX 0? SCGAB IS THE LITSS. 



CHAPTER IX. 

FORMATION OP SUGAR IN THE LIVKR. 

Besidb the secretion of bile, the liver performs also ADOtber 
exceeiliiiyly important function, viz., the production (/ tiugar by a 
metaicKir^ihuiits of some of its orgaiuu ingredieuts. 

Under ordioary circumstances a considernble quantity of sac- 
charine matter is introduced with tlie food, or produced from 
starcliy subsUinces, by ilio digestive process, in the int^»8linal canal. 
In man and tbe herbivorous animals, accordingly, an abundant 
supply of sugar is derived from these sources; and, ns we Lave 
already shown, the sugar thus intro<luced is necessary for the proper 
support of the vital functions. For though the sacchnrino matter 
absorbed from the intestine is destroyed by decomposition soon 
after entering the circulation, yet the chemical changes by wbicH 
its deem nposi lion isoQ'cctcd arc themselves necessary for the proper 
■constitution of the blood, and the healthy nutrition of the tissues. 
Experin\ent shows, however,, that the system does not depend, for 
its supply of sugar, entirely upon external sources; but that sac- 
charine mutter la also produced independently, in the tissue of the 
liver, whatever may bo the nature of the food upon which the 
animal subsists. 

This important function was 5rat discovered by M. Claude Ber- 
nard' in 184d, and described by him under the name of the gluco- 
genic /unction of ike liver. 

It has long been known that sugar may bo abundantly fiecreted, 
under some circumstances, when no vegetable matters have been 
taken with the food. The milk, for example, of all animals, car- 
nivorous Ds well as herbivorous, contains a notable proportion of 
sugar; and the quantity thus secreted, during lactation, is in some 
instances very great. In the human subject, also, when suft'cring 
from diabetes, the amount of saccharine matter discharged with the 



■ Nonrellt) Fonctlon du Folo. I'arli, l$ft3. 



FOBMATION OF SUOAB IN THE LITER. 183 

Qrine has oftan appeared to be altogether out of proportion to that 
which could be accounted for by the vegetable substancefi taken as 
food. The experiments of Bernard, the moat important of which 
we have repeatedly confirmed, in common with other investigators, 
show that in these instances most of the sugar has an internal 
origin, and that it first makes its appearance in the tissue of the 
liver. 

If a camivoroas animal, as, for example, a dog or a cat, be fed 
for several days exclusively upon meat, and then killed, the liver 
alone of all the internal organs is found to contain sugar among its 
other ingredients. For this purpose, a portion of the organ should 
be cat into snuiU pieces, reduced to a pulp by grinding in a mortar 
with a little water, and the mixture coagulated by boiling with an 
excess of sulphate of soda, in order to precipitate the albuminous 
and coloring mattera. The filtered fluid will then reduce the oxide 
of copper, with great readiness, on the application of Trommer's 
test A decoction of the same tissue, mixed with a little yeast, will 
also give rise to fermentation, producing alcohol and carbonic acid, 
as is usual with saccharine solutions. On the contrary, the tissues 
of the spleen, the kidneys, the lungs, the muscles, &c., treated in 
the same way, give no indication of sugar, and do not reduce the 
salts of copper. Every other organ in the body may be entirely 
destitute of sugar, but the liver always contains it in considerable 
quantity, provided the animal be healthy. Even the blood of the 
portal vein, examined by a similar process, contains no saccharine 
element, and yet the tissue of the organ supplied by it shows an 
abundance of saccharine ingredients. 

It is remarkable for how long a time the liver will continue to 
exhibit the presence of sugar, al^r all external supplies of this 
substance have been cut off. Bernard kept two dogs under his own 
observation, one for a period of three, the other of eight months,' 
daring which period they were confined strictly to a diet of animal 
food (boiled calves' heads and tripe), and then killed. Upon exa- 
mination, the liver was found, in each instance, to contain a propor- 
tion of sugar fully equal to that present in the organ under ordinary 
circumstances. 

The sugar, therefore, which is found in the liver after death, is a 
normal ingredient of the hepatic tissue. It is not formed in other 
parts of the body, nor absorbed from the intestinal canal, hut takes 

> NooTellfl Fonotion du Foie, p. 50. 



184 FORMATION OF SCOAB IS THE LIVER. 

its origin in the liver ilat-lf; ii is produced, as a new formation,' 
by n secreting process in the tiaaue of the organ. 

The presence of sugar in the liver is common to all species of 
atiiinalfi, so far as is yet known. liernarJ found it invariably in 
monkeys, dogs, cats, rabbits, the horse, the ox, the goat, the sheep, 
in birdn, in reptiles, and in most kinds offish. It was onl/ in two 
apecies of Bah, viz., the eel and the ray (Muru-^na anguilla and Kaia 
batis), that he sometimes failed to discover it; but the failure in 
these instances was apparently owing to the commencing putres- 
cence of the tissue, by which the sugar bad probably boon destroyed. 
In the fresh liver of the human subject, examined after death from 
accidental violence, sugar wits found to be present in the proportion 
of 1.10 to 2.14 per cent, of the entire weight of the organ. 

The following list shows the average percentage of sugar present 
in the healthy Hvcr of man and different 9|)ccies of animals, accord* 
ing to the examinations of Bernard:— 

PxnCR-tTAait OP StRAB 15 TItB LtVBI. 

In Ttiaii .... I.'GS In ox . . . . 3.30 

" m<ink»jr . 2.15 " home .... 4.06 

'■ iJvf; . . . 1.3» " goat . . . 3,89 

•■ cal . . . . l.H " birds .... 1.49 

■' r-ibbil . . . 1.84 " KtpUles . . , 1.04 

" Bbei-p . . . 2.00 " lUli . . . . 1.4S 

With regard to the nature and properties of the liver sugar, it 
resembles very closely glucose, or the sugar of starch, the sugar of 
honey, and the sugar of milk, though it is not absoluiely identical 
with either one of them. lu solution reduces, as wc have seen, the 
salts of copper in Troinmer'a teat, and becomes colored brownwhen 
boiled with caustic polassn. It ferments very readily, also, when 
mixed with yeast and kejit at tho temperature of 70° to 100' V. 
It is distinguished from all the other sugars, according to Bernard,' 
by the readirvess with which it becomes decomposed in the blood— 
since cane sugar and beet root sugar, if injected into t!ie circulation 
of a living animal, pa.<:s through the system without sensible decom- 
position, and are discharged unchanged with the urine; sugar of 
milk and gJiicnse, if injected in moderate qiiantiiy, are decomposed 
in tilt: blood, but if introduced in greater abundance make tbeir 
appearance aUo in the urine; while n solution of liver sugar, though 
injected In much larger quantity than either of the others, may dia- 

( L«qoDB iv Plij'Biologie Ezptjrlcuentale. Paris, 1&S&, p. £13. 




FOBHATION OP SUOAB IN THE LIVER. 185 

appear altogether in the circulation, without passing ofT by the 
kidneys. 

This Bobstance is therefore a sugar of animal origin, similar in 
its properties to other varieties of saccharine matter, derived from 
different soarces. 

The sugar of the liver is not produced in the blood by a direct 
decomposition of the elements of the circulating 6uid in the vessels 
of the organ, but takes its origin in the solid substance of the hepatic 
tissue^ as a natural ingredient of its organic texture. The blood 
which may be pressed out from a liver recently extracted from the 
body, it is trae, contains sugar; but this sugar it has absorbed from 
the tissue of the organ in which itcirculates. This is demonstrated 
by the singular fact that the fresh liver of a recently killed animal, 
though it may be entirely drained of blood and of the sugar which 
it contained at the moment of death, will still continue for a certain 
time to produce a saGcharine substance. If such a liver be injected 
with water by the portal vein, and all the blood contained in its 
vessels washed out by the stream, the water which escapes by the 
hepatic vein will still be found to contain sugar. M. Bernard has 
found' that if all tbesugar contained in a fresh liver be extracted in 
this manner by a prolonged watery injection, so that neither the 
water which escapes by the hepatic vein, nor the substance of the 
liver itself, contain any further traces of sugar, and if the organ be 
then laid aside for twenty-four hours, both the tissue of the liver and 
the fluid which exudes from it will be found at the end of that time 
to have again become highly saccharine. The sugar, therefore, is 
evidently not produced in the blood circulating through the liver, 
but in the substance of the organ itself. Once having originated 
in the hepatic tissue, it is absorbed thence by the blood, and trans- 
ported by the circulation, as we shall hereafter show, to other parts 
of the body. 

The sugar which thus originates in the tissue of the liver, is pro- 
duced by a mntual decomposition and transformation of various 
other ingredients of the hepatic substance; these chemical changes 
being a part of the nutritive process by which the tissue of the 
organ is constantly sustained and nourished. There ia probably a 
aeries of several dififerent transformations which take place in this 
manner, the details of which are not yet known to us. It has been 
discovered, however, that one change at least precedes the final 

■ Gasette Bebdomxlftins, F&ris, Oct. S, 1855. 



FORMATION OF BDOAB IN THE LIVBR. 



production of saccharine matter; nnd that the sugar itself is pro- 
duced by the trjinsformution of another peculiar substaiiue, of oate- 
rior formation. This dtibstance, which precedes the formation of 
sugar, and which U itself produced in the tissue of the liver, is fl 
known by the name of gli^cogem'c matter, or glyco^cnc. 

Thia glycogenic matter may be extracted from the Uvcr tn the 
following manner. The organ is taken immediately from the body 
of the recently killed animal, cut into small pieceft, and coagulnied by 
being placed for a few minutes in boiling water. Thia is in order 
to prevent the albuminous liquids of the organ from acting upon 
the glycogenic matter and decomposing it at a medium tcraperalure. 
The coagulated tissue ia then drained, placed in a mortar, reduced 
to a piilp by bruising and grinding, and afterward boiled in dis- 
tilled water for a quarter of an hour, by which the glycogenic 
matter is extracted and held in solution by the boiling water. 

The liquid of decoction, which should be as ooncentrated as pos* 
dible, must then be expressed, strained, and filtered, after which it 
appears as a strongly opalescent fluid, of u slightly yellowish tinge. 
The glycogenic mailer whicli is held in solution may be prceipt- ^ 
tated by the addition to the filtered fluid of five times its volume H 
of alcohol. The precipitate, after being repeatedly washed with ' 
alcohol in order to remove sugar and biliary matters, may tlien be _ 
redissolved in distilled water. It may be precipitated from its H 
watery solution either by alouhul in excess or by crystal livable 
acetid acid, in both of which it ia entirely insoluble, and may be 
afterward kept in the dry state for an indefinite time without 1omQ| 
its properties. 

The glucogenic matter, obtnined in thia way, is regirded 
intermediate in it^ nature and properties between liyd rated starch 
and dextrine. Its ultimate eompo-sition, according to M. Pclouze,' 
is as follows: — 



I 



tarchV 






When brought into contact with iodine, it produces a coloration 
varying from violet to a deep, clear, maroon rod. It does not 
reduce the salts of copper in Troramer^s test, nor does it ferment 
when placed in contact with yeast at the pro]>er temperature. It , 
does not, therefore, of itself contain sugar. It may easily be con- fl 
verted into sngar, however, by contact with any of the animal ^\ 
ferments, as, for example, those contaiuod in the saliva or in the 



■ Jdarnat da Pb/«[i>logts. Vui*, 18S8, p. K2. 



FORMATION OF 8U0AE IN THE LIVER. 



187 



If a solation of glycogenic matter be mixed with fresh 
homan aaliva, and kept for a few mlnutea at the temperature of 
100° F^ the mixture will then be found to have acquired the power 
of reducing the salts of copper and of entering into ferraentation by 
contact with yeast. The glycogenio matter has therefore been, 
converted into sugar by a proce8S of catalysis, in the same manner 
as vegetable starch would be transformed uniJer similar conditions. 

The glycogenic mnttcr which is tbus dcatlncd to be converted 
into BUgar, is formed in the liver by the processes of nutrition. It 
may bo extracted, as we have seen above, from the hepatic tissue 
of carntvoroaa animals, and is equally present when lK(;y have been 
exclusively confined for many days to a meat diet. It is not in- 
troduced with the food ; for the fleshy meat of the herbivora does 
not contain it in appreciable qtiantity, though these animals so 
constantly take starchy substnnccs with their food. In them, the 
starchy matters are transformed into sugar by digestion, and the 
sugar 80 produced is rapidly destroyed after entering the circula- 
tion; so that usually neither saccharine nor starchy substances arc 
to be discovere<J in llio muscular tissue. M. Poggiale' found ihat 
in very many experiments, performed by a commission of iho 
French Academy for the purpose of examining this subject, glyco- 
genic matter was detected in ordinary butcher^s meat only once. 
"We have also fouud it to be absent from the fresh meat of the 
bullock's heart, when examined in the manner described above. 
Nevertheless, in dogs fed exclusively upon this food for eight days, 
glycogenic matter may be found in abundance in tho liver, while 
it does not exist in other parts of the body, as the spleen, kidney, 
lungs, &c. 

Furthermore, in a dog fed exclusively for eight days upon the 
fresh meat of the bullock's heart, and then killed four hours nfier 
a meal of (he same food, at which time intestinal absorption is 
going on in full vigor, the liver contains, as above mentioned, both 
glycogenic matter and sugar; but neither sugar nor glycogenic mat- 
ter can be found in the blood of the portal vein, when subjected to 
a similar examination. 

The glycogenic matter, accordiugly, does not originate from any 
externa] source, but is formed in the tissue of the liver; where it 
is s<x>n afterward trnnsformod into sugar, while still forming a pari 
of the substance of the orgau. 



• Joaninl Ae Ph/siotogle, PaHh, 1S58, jt. US. 



Tho formation of suj^nr in tlie liver is ihorofore a function com- 
posed of two dletincl and successive processes, viz: first, the forma- 
tion, in the hepatic tissue, of a glycogenic matter, having some 
resemblance to dextrine; and secondly, the conversion of this 
glycogenic matter into sugar, by a process of catalysis and trans- 
fprmation. 

The sugar thus produced in the substance of the liver is absorbed 
from it by the blood circulating in its vessels. The mechanism of 
this absorption is probably the same with that which goes on in 
other parts of the circulation. It is a process of transudation and 
eridodtnosis, by which the blood in the vessels takes up the saccha- 
rine flyids of the liver, during its passage through the organ. 
While the blootl of the portnl vein, therefore, in an animal fed 
exclusively upon meat, contains no sugar, the blood of the hepatic 
vein, ns it passes upward to the heart, is always rich, in saccharine 
ingredients. This difference can easily be demonstrated by exa- 
mining comparatively tbe two kinds of blood, portal and hepatic, 
from the recently killed animal. Tho blood in its passage tliroagh 
tho liver is found to have acquired a new ingredient, and shows, 
upon examination, all the properties of n saccharine liquid. 

The sugar produced in the liver is accordingly to be regarded as 
11 true secretion, formed by the glandular tissue of the organ, by a 
similar process to that of other glandular secretions. It differs 
from tho latter, not in the manner of its production, but only in 
the raiidff of its discharge. For while the biliary matters pro<luccd 
in the liver are absorbed by tlie hepatic ducts and conducted down- 
waixl to the gall-bladder and the intestine, the sugar is absorbed by 
the bloodvessels of the organ and carried upward, by the hepatic 
veins, toward the heart and tho general circulation. 

The production of fugar in the liver during health is a constant 
process, continuing, in many cases, for several days after the animal 
has been altogether deprived of fooil. Its activity, however, like 
that of moat othor secretions, is subject to periodical augmentation 
and diminution. Under ordinary circumstonces, the sugar, which 
is absorbed by the blood from the tiasoe of the liver, disappears 
very soon after entering the circulation. As the bile is trunsfomied 
in th(j intestine, so the sugar is decomposed in the blood. We are 
not yet acquainted, however, with the precise nature of the changes 
which it undergoes after entering the vascular system. It is very 
probable, according to the views of Lehmann and Kobin, that it is 
Bt first converted into lactic acid (C^UgO^), which decomposes in 



I 




FORUATIOy OF SUOAB IK THE LIVER. 189 

turn the alkaline carbonates, setting free carbonic acid, and forming 
lactates of soda and potassa. But whatever be the exact mode of 
ita transformation, it is certain that the sugar disappears rapidly; 
and while it exists in considerable quantity in the liver and in the 
blood of the hepatic veins and the right side of the heart, it is nut 
usually to be found in the pulmonary veins nor in the blood of the 
general circulation. 

About two and a half or three hours, however, after the ingestion 
of food, according to the investigations of Bernard, the circulation 
of blood through the portal system and the liver becomes consider- 
ably accelerated. A larger quantity of sugar is then produced in 
the liver and carried away from the organ by the hepatic veins; 
80 tbat a portion of it then escapes decomposition while passing 
through the lungs, and begins to appear in the blood of the arterial 
system. Soon aflerward it appears also in the blood of the capil- 
laries; and from four to six hours afler the commencement of 
digestion it is produced in the liver so much more rapidly ihan it 
is 4estroyed in the blood, that the surplus quantity circulates 
throughout the body, and the blood everywhere has a slightly sac- 
charine character. It does not, however, in the healthy condition, 
make its appearance in any of the secretions. 

After the sixth hour, this unusual activity of the sugar-producing 
foDCtion begins again to diminish ; and, the transformation of the 
sugar in the circulation going on as before, it gradually disappears 
as an ingredient of the blood. Finally, the ordinary equilibrium 
between its production and its decomposition is re-established, and 
it can no longer be found except in the liver and in that part of 
the circulatory system which is between the liver and the lungs. 
There is, therefore, a periodical increase in the amount of unde- 
cotnposed sugar in the blood, as we have already shown to be the 
fCase with the fatty matter absorbed during digestion; but this 
increase is soon followed by a corresponding diminution, and daring 
the greater portion of the time its decomposition keeps pace with 
its production, and it is consequently prevented from appearing in 
the blood of the general circulation. 

There are produced, accordingly, in the liver, two different secre- 
tioDB, viz., bile and sugar. Both of them originate by transforma- 
tion of the ingredients of the hepatic tissue, from which they are 
absorbed by two difl'erent sets of vessels. The bile is taken up by 
the biliary ducts, and by them discharged into the intestine; while 
the sugar is carried off by the hepatic veins, to be decomposed in the 
circulation, and become subservient to the nutrition of the blood. 



Tns 8PtEBX. 



CHAPTER X, 



THE SPLEEN 



Thb spleen is en exceedingly vascular organ, situated in the 
vicinity of the great pouch of" ilic stumncb ami supplieil abund- 
antly by branches of the caeliac axis, lis veins, like ihate of the 
digestive abdominal organs, form a part of the great portal system, 
and conduct the blood which has passed through it to the liver, 
before it mingles again with the general current of the circulation. 

The spleen is covered on its exterior by an investing membrane 
or capsule, which forms a protective sac, containing the soft pulp 
of which the greater part of the organ is composed. This capsule, 
in the spleen of the ox, is thick, whitish, and opaque, and is com- 
posed to a great extent of yellow elaatio tissue. It accordingly 
possesses, in a high degree, ihc physical properly of elasticity, and 
may be widely stretched without laceration; returning readily to^ 
its original size ns soon as the extending force is relaxed. fl 

In the carnivorous animals, on the other hand, the capsule of 
the spleen is thinner, and more colorless and transparent. It coo- 
tains here but very little elastic tissue, being composed mostly of 
amooth, involuntary muscular fibres, connected In layers by a little 
intervening areolar tissue. In ihft herbivorons animals, accordingly, 
the capsule of the spleen is simply elastic, while in the carnivoni it 
is contractile. M 

In both instances, however, the elastic and contractile properties 
of the capsule subserve u nearly similar purpose. There is every 
reason to believe that the spleen is subject to occasional and per- 
haps regular variations in sItic, owing to the varying condition of 
the abdominal circulation. Dr. William Dobson' found that the 
BlKe of the organ increased, from the third hour arier feeding up to 
the llfih; when it arrived at its maximum, gradually decreasing 
after that period. When these periodical congestions take placOi 



* In Gnj, on the Stmatan* and Use* ot tliA 5plc«n. London, 18M, p. 40. 



1 



TDK SPLEEK. 



191 



tbe orgnn bccomiDg torgid with blood, the capaule is distended ; 
nnd limits, by its resisting power, the degree of tumefaciion to 
which the spleen is liable. When the disturbing cause has again 
passed away, and tbe circulation is about to return to its ordinary 
condition, the elasticity of the capsule in tbe herbivora, ntid its con- 
tractility in the carnivora, compress the soft vascular tissue within, 
and reduce the organ to its original dimensions. This contractile 
action of the investing capsule can be readily ^een in the dog or 
the cut, by opening tbe abdomen while digetttiou is going on, ex- 
posing the spleen and removing it, afler ligature of its veasels. 
When Grst exposed, the organ is plump and rounded, and presents 
externally a smooth and shining surface. But as soon as it has 
been removed from the abdomen and its vessels divided, it begins 
to ountraet sensibly, becomes reduced in size, stifl', and resisting to 
the touch; while its surface, at the same time, becomes uniformly 
wrinkled, by the contraction of its muscular Rhnrs. 

In its interior, the substance of the spleen is traversed everywhere 
by slender and ribbondike cords of fibrous tissue, which radiate 
from the sheath of its principal arterial trunks, and lire finnlly 
attached to the internal surface of its investing cnpsnlc. These 
Sbrous cords, or traUculoe, as they are called, by their frequent 
branching and mutual interlacement, form a kind of skeleton or 
fratnework by which the soU splenic pulp is embraced, and the 
shape and integrity of the organ maintained. They are composed 
of similar elements to those of tht; investing capsule, viz., elastic 
tissue and involuntary nuiacular fibres, nniicd with each other by 
a varying quantity of the fibres of areolar tissue. 

The interstices between the trabeculte of the spleen are occupied 
by the splenic pulp; a soft, reddish substance, which contains, 
beside a few nerves and lymphaiirs, capillary bloodvessels in great 
profusion, and certain whitish globular bodies, which may be re> 
garded us the distinguishing anatomical elt^niuuts of the organ, and 
which are termed the Malpiyhmn bodies of ihe apleen. 

Tbe Malpighian bodies are very abundant, and are scattered 
tbroaghout the splenic pulp, being most frequently aitached to the 
sides, or at tbe point of bifurcation of some small artery. They 
■re readily visible to the naked eye in the spleen of the ox, upon a 
fresh section of tbe organ, as minute, whitish, rounded bodieit. which 
mav be separated, by careful manipulation, from tbe surrounding 
parts. In the carnivorous animals, on the other hand, and in the 
human subjeet, it is more difTici'It to distinguish them by the an* 



192 



THE SPLEEN, 



aided eye, though they always exist in the spleen in a healthy 
condition. Their average diameter, according to Kollikcr, is ,'5 of 
an inch. They consist of a closed sac, or capsule, containing in 
its interior a viscid, semi-solid mass of cell!!, cell-nuclei, and homo- 
gencous Kubstnncc. Each Malpigliiau body is covered, on its exte- 
rior, by a network of fine capillary bloodvessels; and it is now 
perfectly well settled, by the observations of various anatomists 
(Kultiker, Busk, Huxley, kc), that blooilvesseU also penetrate into 
the substance of the Malpighian body, and there form on interaal 
capillary plexus. 

The spleen is accordingly a glandular organ, analogous in its 
minute structure to the solitary nnd agmlnated glands of the mmall 
intestine, and to the lymphatic glnnds throughout the body. Like 
them, it is a gland without an excretory duct; and resembles, also, 
in this respect, the thyroid and thymus glands and the suprarenal 
capsules. All these organs hnve a structure which is evidently 
glandular in its nature, and yet the name of glands has been some- 
times refused to them because they have, as above menuoned, nn 
duct, and produce apparently no distinct secretion. We have 
already seen, however, that a secretion may bo produced in the 
interior of a glandular organ, like the sugar in the substance of the 
liver, and yet not be discharged by its excretory duct The veins 
of the gland, in this instance, perform t1ie part of excretory ducts. 
They absorb the new materials, and convey them, through the 
medium of the blood, to other parts of the body, where they suffer 
subsequent alterations, and are fiually decomposed in the circula- 
tion. 

The action of such organs is consequently to modify- the consti- 
tution ol' the blood. As the blood pnsscij through their tissue, it 
absorbs from the glandular substance certain materials which it did 
not previously contain, and which are necessary to the perfect con- 
stitution of the circulating fluid. The blood, as it paiwes out from 
the organ, has therelbre a diflerent composition from that which it 
possessed before its entrance; and on this account the name of vaa- 
cuiar gfands has been applied to all the glandular organs above 
mentioned, which are destitute of excretory ducts, and is eminently 
applicable to the spleen. 

The precise alteration, however, which is effected in the blood 
during its passngc through the splenic tissue, has not yet been 
discovered. Various hypotheses have been advanced from time to 
time, as to the processes which go on in this organ; many of them 



4 



4 



THB SPLKRS. 



103 



vague aod inde6nite in cbaracter, and some of tbem directly con- 
tradictory of each other. None, however, have yet been oflcred 
which are eotirely satiafactor^' iti themselves, or which rest on suf- 
ficiently reliable evidence. 

A very remarkable fact vrith regard to the spleea is that it may 
be eutircly removed in many of the lower animals, without iia lona 
producing any serious permanent injury. This experiment has 
been frequently performed by various observers, and we have our- 
selves repeated it several times with similar results. The organ 
niay be easily removed, in the dog or the cat, by drawing it out of 
the abdomen, through an opening in the mediun line, placing a few 
ligatures upon the vessels of the gastro-splonic omentum, and then 
dividing the vessels between the ligatures and the spleen. TLie 
wound usually heals without dilEcuIty; and if the animal be killed 
some weeks al^rward, the only remaining trace of the operation 
ia an adhesion of the omentum to the inner surface of tlie abdomi- 
nal parietes, at the situation of the original wound. 

The most constant and permanent effect of a removal of the 
spleen is an unusual increase of the appetite. This symptom we 
have obser^'ed in some instances to bo excessively developed; so 
that the animal would at all times throw himself, with an unnatural 
avidity, upon any kind of food offered him. We have seen a dog, 
subjected to this operation, afterward feed without hesitation upon 
the fiesh of other dogs; and even devour greedily the entrails, taken 
warm from the abdomen of the recently killetl animal. The food 
taken in this unusual quantity is, however, perfectly well digested; 
and the animal will often gain very perceptibly in weight. In one 
instance, a cat, in whom the unnatural appetite was marked though 
nut excessive, increased in weight from five to six pounds, iu the 
course of a little less than two months; and at the same time the 
fur became sleek and glossy, and there was a considerable improve* 
roent iu the general appearance of the animal. 

Another symptom, which usually follows removal of the spleen, 
is an unnatural ferocity of disposition. The animal will frequently 
attack others, of its own or a different species, without any appa- 
rent cause, and without any regard to the diflerence of size, strength, 
&c. This symptom is sometimes equally exuessive with that of an 
unoataral appetite; while in other instances it shows itself only in 
(xscasional outbursts of irritability and violence. 

I^eitber of the symptoms, however, which we have just de* 
acinbed, appears to exert any permanently injurious effect upon the 
IS 



THE aPLEEX, 



Bnitnal which bus been subjected to the operation; ami life raay be 
prolonged for an indeflnitc period, without nny serious disturbance 
of tlio nutritive process, afXcr tbe spleen baa been completely 
extirpated. 

We must accordingly regard t*he spleen, not as a eingle organ, 
but as associated with others, which may completely, or to a great 
extent, perform its functions after its entire removal. Wo have 
already noticed the similarity in struuture between tlie spleen and 
the mesenteric and lymphatic glands; a similarity which boa led 
some writers to regard them as more or leas closely nssociatetl with 
each other in function, and to consider the spleen as an unusually 
developed lymphatic or mesenteric glaod. It is true that this 
organ is provided with a comparatively scanty supply of lymphatic 
veasela; and the chyle, which is absorbed from the intestine, does 
not pass through the spleen, us it posses through the remaining 
mesenteric glands. Still, tbe physiological action of the spleen 
may correspond with that of tbe other lymphatic glands, so far as 
regards its influence on the bluod; and there can be little doubt 
that its function is shared, cither by them or by some other glan- 
dular organs, which become unnaturally active, and more or less 
perfectly supply its place afWr its complete removal. 



BLOOD-OLOfiULES. 105 



CHAPTER XI. 

THE BLOOD. 

Ths blood, as it exists in its Dstural condition, while circulating 
in the vessels, is a thick opaque flaic], varjiog in color in different 
parta of the body from a brilliant scarlet to a dark purple. It has 
a slightly alkaline reaction, and a specific gravity of 1055. It 
is not, however, an entirely homogeneous fluid, but is found on 
micnMCopic examination to consist, first, of a nearly colorless, 
transparent, alkaline fluid, termed the plasma, containing water, 
fibrin, albumen, salts, &c., in a state of mutual solution; and, 
secondly, of a large number of distinct cells, or corpuscles, the 
blood-globules, swimming freely in the liquid plasma. These glo- 
bnles, which are so small as not to be distinguished by the naked 
eye, by being mixed thus abundantly with the fluid plasma, give 
to the entire mass of the blood an opaque appearance and a uniform 
red color. 

Blood-globules. — On microscopic examination it is found that 
the globules of the blood are of two kinds, viz., red and white; of 
these the red are by far the most abundant. 

The red globules of the blood present, under the microscope, a 
perfectly circular outline and a smooth exterior. (Fig. 54.) Their 
size varies somewhat, in human blood, even in the same specimen. 
The greater number of them have a transvorse diameter of ^^'^p of 
an inch; but there are many smaller ones to be seen, which are 
not more than j^'^j or even ^^^j^ of an inch in diameter. Their 
form is that of a spheroid, very much flattened on its opposite 
surfaces, somewhat like a round biscuit, or a thick piece of money 
with rounded edges. The blood-globule accordingly, when seen 
Satwise, presents a comparatively broad surface and a circular out- 
liDe(a); but if it be made to roll over, it will present itself edge- 
vise during its rotation and assume the flattened form indicated at 
ft. The thickness of the globule, seen in this position, is about 



THB BLOOD. 



Pig. &4. 



Tiivv o^ )>° ioch, or a little less than o»o-fl(lh of ita transverso 
diameter. 

When the globules nre examined lying upon their broad sur- 
faces, it can be seen that these aurfaces are not exactly flat, but that 

there lii on each side a slight 
central depression, so tliat 
tho rounded edges of the 
blood-globule are evidently 
thtuker than its middle por- 
tion. Thia inecpinlily pru- 
ducca a remarkable optical 
effect. The substance of 
which the blood-globula is 
composed refracts light more 
strongly than the flnid plaa- 
Dia. Therefore, when exn- 
mined with the microecope, 
by transmitted light, the 
thick edges of the globules 
act US double convex lenses, 
and concentrate the light 
above the level of the flnid. Consequently, if the object-glass be 
carried upward by the adjusting screw of the microscope, and lifted 

away from the stage, so that 



*^/ 



@ © 



© 



O 






Fig. fiS. 



® 



••) 



tlie blood -globules fall be- 
yond its focus, their et^lges 
will appear brighter. But 
the central portion of each 
globule, being excavated on 
both sides, acts as a double 
concave lens, and disperses 
the light from a point below 
the level of the fluid. It, 
therefore, grows brighter as 
the object-glass is carried 
downward, and the object 
falls within its focus. An 
alternating appearance of the 
blood-glob ule3 may, there- 
fore, be produced by view- 
ing them first beyond and then within the focus of the instrument. 



® 



twjrouil tliv Tneui of Ihr iiiltfFiiii-iiiM 



lltlli< 



ri 



4 



BLOOD-OLOBULZa. 



197 




TmiAHK, iwD > lUtle wllbln the foenii. 



When bejood the focaa,-the globules will be seen with a bn'gbt 
rim and a dark centre. (Fig. 55.) When within it they will appear 
with a dark rim and a bright 
oent«». (Fig. 66.) "8- ««• 

The blood-globales accord- 
ingly hare the form, of a 
thickened diak with rounded 
edges and a doable central 
excavatioD. They have, con- 
sequently, been sometimea 
called "blood-disks," instead 
of blood-globulee. The term 
"disk," however, does not in- 
dicate their exact shape, any 
more than the other; and 
the term "blood-corpuscle," 
which is also sometimes used, 
does not indicate it at all. 
And altbongh the term "blood -globule" may not be precisely a 
correct one, still it is the most convenient; end need not give rise 
to any confusion, if we remember the real shape of the bodies de- 
rignated by it This term will, consequently, be employed when- 
ever we have occasion to 
speak of the blood-globules vig. S7. 

in the following pages. 
Within a minute alVer being 
placed under the microscope, 
the blood-globules, after a 
flactaating movement of 
abort duration, very often 
airaoge themselves in slight- 
ly curved rows or chains, in 
which they adhere to each 
other by their flat surfaces, 
presenting an appearance 
which has been aptly com- 
pared with that of rolls of 
coin. This is probably ow- 
ing merely to the coagulation 

of the blood, which takes place very rapidly when it is spread nut 
in thin layers and in contact with glass surfaces; and which, by 




BLODD'aLOBDLii >dberlD( logalbar, liks rolli 
of coin. 



THB HLOOD. 



compressing tlie globules, fi>rces them into such a position that they 
may occupy the least possible space. This position is cvidcntlj 
that in which ihey are ap^jlied to each other by their flat surfs 
as above described. 

The color of ihe bloixl- globules, when viewed by traosmil 
light and spread out in a thin Inyer, is a light amber or pale yellow. 
It ia, on the contrary, deep red when they are seen by reflected 
light, or piled together Jn eomparativeJy thick layers. When viewed 
singly, they are so transparent that the oullinesof those lying under- 
neath can be easily seen, showing through the substance of the 
superjacent globules. Their consistency is peculiar. They are not 
solid bodies, ns they have been sometimes inadvertently described; 
but on ttie contrary have a consistency which is very nearly fluid. 
They are in consequence exceedingly flexible, and easily elongated, 
bent, or otherwis« disioried by accidcnia! pressure, or in passing 
through the narrow currents of fluid which often establish them- 
selves accideatally in a drop of blood under microscopic examina- 
tion. This distortioD, however, is oidy temporary, and the globules 
regain their original shape, as soon as the accidental pressure is 
taken off. The peculiar flexibility and elasticity thus noticed are 
characteristic of the red globules of the blood, and may always 
serve to distinguish thorn from any other free cells which may bo 
found in the animal tissues or fluids. 

In structure the blood-globuIc.-? are homogeneous. They have 
been sometimes erroneously described as consisting of a closed 
vesicle or cell-wall, containing in its cavity some fluid or semi-fluid 
substance of a different character from that composing the wall of 
the vesicle itself. No such structure, however, is really to be seen 
in them. Kach blood-^dobule consists of a mass of organized uoi- 
lual substance, perfectly or nearly homogeneous in appearance, and 
of the aaino color, consistency and composition throughout. In 
some of the lower animals (birds, reptiles, fish) it contains also a 
granular nucleus, imbedded in the substance of the globule; but 
in no instance is there any distinction to be made out between an 
external cell-wall and an internal cavity. 

The appearance of the blood -globules is altered by the addition 
of various foreign substances. If water be addedf so as to dilute 
the plasma, the globules absorb it by imbibition, swell, lose their 
double central concavity and become paler. If a larger quantity 
of water be added, they finally dissolve and disappear altogether. 
When a moderate quantity of water is mixed with the blood, the 



I 



I 



BLOOD-OLOBULES. 



109 



Pig. 68. 




Bloop-o bOBDLEi, iwulleu bj the tmblblrloa of 

wftter. 



edges of the globules, being thicker than the central portionB, and 
absorbing water more abundantly, become turgid, and encroach 
gradually upon the central 
part. (Fig. 58.) It is very 
common to see the central 
d^ression, under these cir- 
cumstances, disappear on one 
Bide before it ia lost on the 
other, so that the globule, as 
it swells up, curls over to- 
wards one side, and assumes 
a peculiar cup-shaped form 
(a). This form may oflen be 
seen in blood-globules that 
have been soaking for some 
time in the urine, or in any 
other animal fluid of a less 
density than the plasma of 
the blood. Dilute acetic acid 

dissolves the blood-globules more promptly than water, and solu- 
tions of the caustic alkalies more promptly still. 

If a drop of blood be allowed partially to evaporate while unaer 
the microscope, the globules 
near the edges of the prepa- 
ration often diminish in size, 
and at the same time present 
a shrunken and crenated ap- 
pearance, as if minute gran- 
nies were projecting from 
their surfaces (Fig. 59); an 
effect apparently produced 
by the evaporation of part 
of their watery ingredients. 
For some unexplained rea- 
aon, however, a similar dis- 
tortion is often produced in 
some of the globules by the 
addition of certain other ani- 
mal fluids, as for example the 
saliva; and a few can even 
addition of pure water. 




Blood-olobulki, ihrDakeD, wtlh Ihelrmarglas 
crsDkled. 



be seen in this condition after the 



200 



THB BLOOD. 



The entire mass of the blood globules, in proportion to the rest 
of the circulating fluid^ can only be approximately measured by 
the eye in a microscupiu examination. In ordinary analyses the 
globules are usually estimated as amounting to about flflcen per 
cent., by weight, of the entire blood. This estimate, however, refers, 
properly speaking, not to the globules themselves, but only to their 
dry residue, aflor the water which they contain haa been lost by 
evaporation. It is easily seen, by examination with the microscope, 
that the globules, in their natural KOmi-fluid condition, are really 
much more abundant than this, and constitute fuUy one^ai/" the 
entire maatof ihe hlooil; that is, the intercellular fluid, or plasma, is 
not more abundant than the globules themselves which are sua* 
pendcd in it. When separated from the other ingredicnta of tho 
blood and examinetl by themselves, the globules are found, oo 
cording to Lehmaun, to present the following componilion : — 

03MPt)BtT[0K OP THE Bl,Oor>-OuteDLBa 1:1 l<kt(> PAKTS. 

Wdtfrr «B8.00 

Ulotmlliia 283.22^ 



H^-iaitCin« 

Fally EubfiUiicea 

Unrtplcrmincil (<-x(rAct)r«) maltera 

Chloride of sndiuiii . . 

** potnxaiuni 

Ptiii>phBt«s of Bod& >uil i>ol&»ia 
Sal|.liiit« " " 

I'lm^pliAio or \\m« . ( . 
" uifljio«ala 



1S.7S,; 
2.31 



8.1a 



iiK<u.m> 



I 



The most important of these ingredients is the ^hhuline. This 
is an organic substance, nearly fluid in its natural condition by 
union with water, and constituting the greater part of the mass of ■ 
the blood-globules. It is aolublc in water, but insoluble in the 
plasma of the blood, owing to the presence in that fluid of albumen 
and aaline matters. If the blood be largely diluted, however, the I 
gtobuline la dissolved, as already mentioned, and the blood globules 
are destroyed, tilobuline coagulates by heat; but, according to 
Robin and Verdeil, only becomes opalescent at liiQ°, and requires 
for its complete coagulation a temperature of 200° F. M 

The Ii(vmaUne i» the coloring matter of the globules. It is, like ^ 
globuline, an organic substance, but is present in much smallerquari- 
tity than the latter. It ia not contained in the form of a powder, 



BLOODQLOBULSS. 201 

mechanically deposited in the globaline, but the two substances are 
intimately mingled throughout the mass of the blood-globule, just 
as the fibrin and albumen are mingled in the plasma. Hjematine 
contains, like the other coloring matters, a small proportion of iroQ. 
This iron has been supposed to exist*under the form of an oxide; 
and to contribute directly in this way to the red color of the sub- 
stance in question. But it is now ascertained that although the 
iron 18 found in an oxidized form in the ashes of the blood-gobules 
afler they have been destroyed by heat, its oxidation probably takes 
place during the process of incineration. So far as we know, there- 
fore, the iron exists originally in the hsematiae as an ultimate 
element, directly combined with the other ingredients of this sub- 
stance, in the same manner as the carbon, the hydrogen, or the 
nitrogen. 

The blood-globules of all the warm blooded quadrupeds, with 
the exception of the family of the camelide, resemble those of the 
human species in shape and structure. They differ, however, some- 
what in size, being usually rather smaller than in man. There are 
bat two species in which they are known to be larger than in man, 
viz., the Indian elephant, in which they are ^^w °^ ^n inch, and 
the two-toed sloth (Bradypus didactylus), in which they are y^n of 
an inch in diameter. In the musk deer of Java they are smaller 
than in any other known species, measuring rather less than j^izv 
of an inch. The following is a list showing the size of the red 
globules of the blood in the principal mammalian species, taken 
from the measurement of Mr. Gulliver.' 





DlAHSTES OF 


Bbd Olobdlbs in thi 






Ape 


• si'ffi.of 


KU iDch. 


Cat 


- • »%•' 


an inch 


Hone . 


nVff 


u 




Fox . 


Tl'dO 


it 


Ox 


lAlf 


(1 




Wolf . 


jAit 


u 


Sheep. 


15'af 


II 




Elephant 


iVo» 


11 


Qoat . 


Bs'lIB 


u 




Red deer 


in'ffff 


It 


Dog . . 


5i'o 


u 




Husk deer 


• Lthvv 


u 



In all these instances the form and general appearance of the 
globules are the same. The only exception to this rule among the 
mammalians is in the family of the camelidse (camel, dromedary, 
lama), in which the globules present an oval outline instead of a 
circular one. In other respects they resemble the foregoing. 

Id the three remaining classes of vertebrate animals, viz., birds, 

> Id Works of William Uewson, Sydenham edition, London, 1846, p. 327. 



202 



THE BLOOD. 



reptiles and finh, the blood-globutey tlifler so mucli from the above 
that they can be rend'ily distinguished by microscopic examination. 
They are oval in fonn, urid contain a colorless granular nucleus 
imbedded,- In their substance. They are also considerably larger 
than the blood -globules of the maminalians, particularly iu the . 

cla.s3 or reptiles. In the frog 
Fig. 60. (Fig. 60) they measure Ta'oo 

of an inch in their long 
diameter ; and In J/«i'^m*i- _ 
ehita, the great water lizard | 
of the northern lakes, ^J« of 
an inch. Id Proteus anffui- 
nvs they attain the size, ac- 
cording to Dr. CarpeDter,' of 
jjf of an inch. 

Beside the corpuscles de- 
scribed above, there arc glo- 
bules of another kind found 
in the blood, viz., the white 
globules. These globulea are 
very much less Domeroua 
than thu red ; the proportioa 
Iwtwccn the two, in human blood, being one white to two or three 
hundred red globules. In reptiles, the relative quantity of the 
white globulea is greater, but they arc always considerably less 
abundant than the red. They difl'er also from the latter in shap^ 
size, color, and consialoncy. They arc globular in form, whilo or 
colorless, and instead of being homogeneous like the others, their 
Buhstanoe is filled everywhere with minute dark molecules, which 
give them a finely grnnukr appearance. (Fig. 54, c.) In size they 
are considerably larger than the red glubutes, being about gg'oo of 
an inch in diameter. Tliey are also more couRistcnt than the others, _ 
and do not so easily glide along in the minute currents of a drop of | 
blood under examination, but adhere readily to the surfaces of the 
glass. If treated with dilute acetic acid, they swell up and become 
smooth and circular in outlino; and at the same time a separation 
or partial congnlation seems to take place in the substance of wbtch 
they are composed, so that an irregular collection of granular 
matter shows itself in their interior, becoming more divided and 



BLuoD-aLoacLt* itr T*cn. 
■MB adgBwUB- l. Wlili*-|l»Uiilii. 



Blood lloltnl* 



I 




' Tht UEoroioopv »nd iu Burvlntiom, Fhlladvlpliin ediliOD, p. OOO. 




BLOOD-OLOBULSS. 



208 



brokea ap as the action of the acetio acid upon the globule is 
longer continued. (Fig. 61.) This collection of granular matter 
often assumes a curved or crescentic form, as at a, and sometimes 
various other irregular shapes. It does not indicate the existence 
of a nucleus in the white globule, but it is merely an appearance 
produced by the coagulating 
and disintegrating action of ^ig- ^^- 

aceticacid upon the substance 
of which it is composed. 

The chemical constitution 
of the white globules, as 
distinguished from the red, 
has never been determined; 
owing to the small quantity 
in which they occur, and the 
difficulty of separating tbcm 
fhim the others for purposes 
of analysis. 

The two kinds of blood- 
globalea, white and red, are 
to be regarded as distinct 
and independent anatomical 

fonuB. It has been sometimes supposed that the white globules 
were converted, by a gradual transformation, into the red. There 
ia, hovever, no direct evidence of this; as the transfurmation has 
never been seen to take place, either in the human subject or in 
the mammalia, nor even its intermediate stages satisfactorily ob- 
served. When, therefore, in default of any such direct evidence, 
we are reduced to the surmise which has been adopted by some 
lathois, viz., that the change " takes place too rapidly to be de- 
lected by our means of observation,'" it must be acknowledged 
tbat the above opinion has no solid foundation. It has been stated 
by some authors (Kdltiker, Gerlach) that in the blood of the 
bitracbian reptiles there are to be seen certain bodies intermediate 
in appearance between the white and the red globules, and which 
represent different stages of transition from one form to the other; 
bat this is not a fact which is generally acknowledged. We have 
repeatedly examined, with reference to this point, the fresh blood 
of the frog, as well as that of the menobranchus, in which the large 




Wbiti OkOiDLMa op tBB Blood; ftltend hj 
dilate iMtle kcld. 



K5Ulker, Handbnch der Oewebelehre, Leipzig, 1852, p. 582. 



204 



THE BLOOD. 



size of the globules would give every opportunity for detecting nny 
such changes, did they really exist; and it is cor unavoidable con- 
clusion from these observations, that there is no good evidence, evea 
in the blood of reptiles, of any sucli transfonnatioti taking place. 
There is simply, as in human blood, a certain variation in sise and 
opacity among the red globules; bat no such connection with, or 
resemhlaiice to, the white globules as to indicate a passage from one 
form to the other. The red and white globules are therefore to be 
regarded as distinct nnd independent anatomical elements. They 
are mingled together in the blood, just as capillary bloodvessels and 
nervesare mingled in areolar tissue; but there is noother connection 
between them, so far aa their formation is oonceraed, than that of 
Juxtaposition. 

Neither in it at all probable that tho red globules are produced or 
destroyed in any particular part of the body. One ground for the 
belief that these bodies were produced by a metamorphosis uf the 
white globules was a supposition that they were uontinually and 
rapidly destroyed somewhere in tho circuktion; end as this loss 
roost be aa rapidly counterbalanced by the formation of new glo- 
bules, and as no other probable source of their reproduction ap- 
peared, they were supposed to be produced by transformation of 
the white globules. But there is no reason for believing that the 
red globules of the blood are any less permanent, as anatomical 
forms, than the muscular fibres or the ncrvoos filaments. They 
undergo, it is true, like all the coastituent parts of the body, a 
constant interstitial metamorphosis. They absorb incessantly nu- 
tritions materials from the blood, and give up to the circulating 
fluid, at the same time, other substances which result from their 
internal waste and disintegration. But they do not, so far as we 
know, perish bodily in any part of the circulation. It is not the 
ajuitomical forms, &ay where, which undergo destruction and reno- 
vation in tho nutritive process; but only tki proximate principlea of 
rchieh theij are composed. The effect of this Interstitial nutrition, 
therefore, in the blood -globules as in the various solid tissues, is 
merely to maintain them iu a natural and healthy uonditioa of 
integrity. Their ingredients are incessantly altered, by transforma- 
tion and decomposition, as they pass through various parta of tb« 
vascular system; but the globules themselvea retain their form 
and texture, and still remain as constituent })arts of the circulaiiog 
fluid. 



1 



I 



I 



I 
I 




PLASMA. 



206 



6.55 



Plasma. — *V\iepJ<uma of the blood, according to Lehmann, haa 
l!fae foUowiog constitution:^ 

CoMmM-nox or trb Plahxa nr 1,00(1 paxt*. 

W»l*r &03.M 

Fibrin 406 

Aibanwn 76.84 

mtjr nuiura 1.72 

tTndotMiniiMd (vxtravtlre) matters 3.M 

Clilorldu of e'^liain 

" potaBsluni .... 

PhoaphKtM of imJa itnil potMU . 
Solphatmi " "... 

Pb(wpb*le of lime 

** nsgneilK .... 

lOOO.OO 

The above tngredienU are all intimately mingled in Uie blood- 
plasma, in a flaid form, by mutual solution; but they may be scpa- 
rated from each other for examination by appropriate means. The 
two iogretlients belonging to the class of organic subataoces are the 
fibrin and the albumen. 

The jlbn'n, though present in small quantity, is evidently an im- 
]tartant element in the constitution of the blood. It may be ob- 
tained in R tolerably pure form by gently stirring freshly drawn 
Wood with A glft*s rod or a bundle of twigs; upon which the fibrin 
coagulates^ and adheres to the twigs in the form of slender threads 
and flakes. The fibrin, lliuscongulated, is at lirst colored red by 
the haimatine of the bloo<l -globules entangled in it; but it may be 
vasheU colorless by a few hours' aonking in running water. The 
fibrin iheu presents itself 



under the form of nearly 
white threads and Hakes, 
luviog a semi-solid consist- 
eocy, and a oonsider&ble de< 
groe of elasticity. 

The oo&gulatioD of ftbrin 
lakes place in a peculiar 
■nanner. It does not solidify 
ia a perfectly bomogeneous 
max; but ifcxamincd by the 
microiscope in thin layers it 
M seen to have a fibroid or 
filamentous texture. In this 
condition it is said to be 
''fibrillat«d."(Fig.62.) The 



IN5. 62. 



Co*aitt.ATIDriaBllc,«b<)'«lBBlliat'rtnftl(r«iran. 
d I lino. 



filaments of wliich it is compaiiefl nre colorless and elastic, anrl when 
isolated are seen to be exceedingly minote, being not more than 
loltTB or even soSitd of an inch in diameter. They are in part 
arranged so as to lie parallel with each other; but are mora gene- 
rally interlaced in a kind of irregular network, crossing each other 
in every direction. On the addition of dilute acetic acid, they swell 
up and fuse together toto a homogeneous mass, but do not dissolve. 
They are often interspersed evtry where with minute granular mole- 
cules, which render their outlines more or less obscure. 

Once coagulated, 6brin is insoluble in water and can only be 
again liquefied by the action of an alkaline or atrongly saline solu- 
tion, or by prolonged boiliog at a very high temperature. These 
agents, however, produce a complete alteration in the properties of 
the Hbrin, and af\er being subjected to them it is no longer the 
same substance as before. 

The quantity of fibrin in the blood varies in different parts of the 
body. According to tho observations of various writers,' there is ■ 
more fibrin generally in arterial than in venous blood. The blood 
of the veins near the heart, again, contains a smaller proportion of 
6brin than those at a distance. The blood of the portal vein con- 
tains less than that of the jugular; and that of the hepatic vein less 
than that of tho purUil. 

The albumen is undoubtedly the most important ingredient of the 
plasma, judging both from its nature and the abundance in which 
it occurs. It congulates at once on being heated to 1U0° F., or by 
contact with alcohol, the mineral acids, the metallic salts, or with 
ferrocyanide of potassium in an acidulated solution. It exists natu* 
rally in the plasma in a fluid furm by reason of its union with 
water. The greater part of the water of the jjlasma^ in fact, is in 
union with the albumen; and wheu the albumen coagulates, the 
water remains united with it, and assumes at the same time the 
solid form. If the plasma of the blood, tliereforc, after tho removal 
of the fibrin, be exposed to the temperature of 160* F., it solidifies 
almost completely ; so that only a few drops of water remain that 
can be drained away from the coagulated mass. The phosphates 
of lime and magnesia are also held in solution principally by the 
alliumcn, and are retained by it in coagulation. 

The /any matters exist in the blood mostly in a saponified form, 
excepting soon afler the digestion of food rich in fat. At that 
period, as we have already mentioned, the emulsioned fat finds ita 

' Rftbin nnrt Verdell, op. dt., vftl. II. p. 208. 



I 



I 

I 




COAOPLATION OP THE BLOOD. 



207 



way into the btooJ, and circulates for a time unchanged, Aftar- 
ward it disappears as free fat, and rcmaina partly in the saponified 
ooodition. 

The aaline ingredients of the plaema arc of the same nature with 
those existing in the globules. The chlorides of sodium and [kjIas- 
siitcn, and the phospbatuts uf suda and putassa are the most abundant 
in both, while the sulphates are present only in minute quantity. 
The proportions in which the various salts are present are very dif- 
ferent, according to Lchmann,' in the blood-globules and in the 
plasma. Chloride of potassium is most abundant in the globules, 
chloride of sodium ia the plasma. The phosphates of soda and 
potassa are more abundant in the globuks than in tlic plasma. On 
the other band, the phosphntes of lime and magnesia are more 
Abundant in the plasma than in the globule.4. 

The substances known under the name of extraciive malters consist 
of a mixture of diftereni ingredients, belonging mostly to the class 
of organic substances, which have not yet been separated in a state 
of suHicienl purity to admit of their being thoroughly examiued 
and distiuguisbed from each other. They do not exist in great 
ubandance, but are undoubtedly uf conisiderable importanuu in the 
constitution of the blood. Beside the substancen enumerated in the 
above list, there are stilt others which occur in small quantity as 
ingredients of the blood. Among the most important are t1i<3 alka- 
line carbonales, which are held in solution in the serum. It has 
ttrcady been inenttoned that while the plin^phatCB are must abun- 
dant in the blood of the cnrnivora, the carbona;,cs are most abun- 
dant in that of the herbivora Thus liChmann* found carbonate of 
soda iu the blood of the ox in the proijorlion of 1.628 per thousand 
ports. There are also to be found, in solution in the blood, urea, 
urate of soda, creatine, cr&Uinine, sugar, &c.; all of them cryatalli&a- 
Mc aabstancea derived from the transformation of other ingredients 
of the blood, or of tlie tissues through which it circulates. The 
relative quantity, however, uf thette substances ia very minute, and 
bas not yet been determined with precision. 



Coagulation of the Blood. — A few moments after the blood 
!uis been withdrawn from the vessels, a remarkable phenomenon 
presents itself, viz., its coagulation or clotting. This process com- 
raenoes at nearly the same time throughout the whole mass of the 
Wood. The Wood becomes first somewhat diminished in fluidity, 



Op. dt.. vol. i. p. S46. 



• Op. olt., Tol. \. p. 393. 



SOS 



THE BLOOD. 



SO that it will not run over the edge of the vessel, wbeo slightly 
inclined; and Its surface may be genily depressed with the end of 
the finger or a glass rod. It then becomes rapidly thicker, and at 
last solidiBea into a uniformly red, opaque, consistent, gelatinoua 
mass, which takes the form of the vessel in which the blood was 
received. Its coagulation is then complete. The proceiw usually 
commences, in the cose of the human subject, in about fif^n mtn* 
ntca aflcr the blood has been drawn, and is completed in about 
twenty minutes. 

The coagulation of the blood is dependent entirely upon the 
presence of the fibrin. This fact has been demonstrated in various 
ways. In the first place, if frog's blood be filtered, so as to separaw 
the globules and leave ihem upon the filler, while the plasma is 
allowed to run through, the colorless 6tter«d fluid which contains 
the fibrin soon coagulates; while no coagulation takes place in the 
moist globules remaining on the filter. Again, if the freshly drawn 
blood be stirred with a bundle of rods, as we have already de- 
scribed above, the fibrin coagulates upon thcni by itiwlf, while the 
rest of the pInHnia, mixed with the globules, remains perfectly fluid. 
It is the fibrin, therefore, which, by iis own ooogulation, induces 
the solidification of the entire blood. As the fibrin is uniformly 
distributed throughout the blood, when its coagulation takes place 
the minute filaments whii:h make their appearance in it entangle 
in their meshea the globules and the albuminous fluids of the 
plasma. A very small quantity of fibrin, therefore, is sufficient to 
entangle by its coagulation all the fluid and semi-fluid parts of the 
blood, and convert the whole into a volomi* 
nous, trembling, jelly-like mass, which is 
known by the name of the "crassamentu 
or "clot" (Fig. 63.) 

A^ soon as the clot bas fairly formed, it 
begins to contract anddlminiBh in size. Ex- _ 
actly how this contraction of iho clot is pro- f 
duccd, we are unable lo say; but it is proba- 
bly a conlinuatioD of the same process by 
which itssolidificaLicn isat Gretaccumplisbed, 
or nt least one very similar to it. As the 
contraction proceeds, the albuminous fluids 
begin to be pressed out from the meahes in 
which they were cntaiiglud. A few isolated drops flrat appear on 
the surface of the clot. These drops soon increase in aise aad be- 



I 



Fig. 03. 



Bowl *f rMfntlj* Coiir^ 
i.<>Tin Blohh. (howiiif iho 
vbolv tnaiw uulFurinlj lalldl- 



COAOULAriOS OF TBK BLOOD. 



209 



Hg. 64. 



come more namerous. Tbej ran together and coalesce with c&ch 
other, as more nod more fluid exudes from the coagulated niaiw, 
antil the whole surface of the clot Ja covered with a thin l&yer of 
fluid. The clot at Qrst adhercii prcity stntngly to the sides of the 
voanel into which the blood was drawn ; but as its eoDtractioti goes 
on, iu edges arc separated, and the fluid continues to exude between 
it and the sides of the vessel. This exudation 
contiaues for ten or twelve hours; the clot 
growing constantly ftmallor and firmer, and 
the expressed floid more and more abundant. 

The globules, owing to their greater ooo' 
sistency, do not escape with the albuminous 
6uids, but remain entangled in the fibrinous 
coagulum. Finally, at the end of ten or 
twelve hours tbe whole of the blood has 
usually separated into two parta, vi;;., the chi, 
which is a red, opaque, dense and resisting, 
semi-solid mass, consisting of the fibrin and 
the blood globules; and the serum, which is a 
transparent, nearly colorless fluid, containing the water, albumen, 
and saline matters of the plasma. (Fig. M.) 

The change of the blood in coagulation may therefore be ex- 
pressed as follows: — 

Before coagulation the blood consists of 



Bowl <■( *'■.'» 11 11. « T r n 
Rl.<'<Mi. BCler lnvlro buur> ; 

■bijwinit tb* clot <;-iiirBCtfd 
luiil fl>i>llDg In tbo luld ■■ran 



111. Oujmrvat; lud 2d. Plamu — oonlittiiiag 



Al\er coagulation it is separated into 



?ibriD, 

Albnmen, 

Water, 

SjLlW. 



,_. _ . , , ( Fibrin and 

Ul. Clot, oontaining { 



lOlvbultis: 



{Allmiiimi, 
Vinlmt, 



The ooagulation of the blood is hastened or retarded by various 
physical conditions, which liave been studied with care by various 
observers, but more particularly by Kobin and Verdeil. The con- 
ditions which influence the rapidity of coagulation are as follows : 
First, the rapidity with which the blood is drawn from the vein, 
and the size of the orifice from which it flows. If blood be drawn 
rapidly, in a full titrcam, from a large orifice, it remains fluid for a 
comparatively long time; if it be drawn slowly, from a narrow 
orifice, it coagulates quickly. Thus it usually happens that in the 
li 



TRB BLOOD. 



4 



operation of venesection, the btoot] drawn immct^iatcly &hc.T the 
opening of the vein runs freely and coagulates slowly ; while that 
which is drawn toward the end of the operation, when the teusioa 
of the veins has been relieved and the blood trickles slowlj froni 
the wound, coiiguliites quickly. Secondly, the shape of the vessel 
into which the blood is received and the condition of ita internal 
surfiice. The greater the extent of sarface over which the bloo<l I 
comes in contact with the vessel, the more is ita coagulation 
hastened. Thus, if the blood be allowed to flow into a tull, narrow, 
cylindrical vessel, ur into a shallow plate, it coagulates more rapidly 
than if it be received into a hemispherical bowl, in which the ex- 
tent of surface 13 less, in proportiaa to the entire quautity of blood 
which it cotilain^. For the etame reason, coagulation takes p]ac« 
more rapidly in a vessel with a roughened internal surface, than Id 
one which is smooth and polished. The blood coagulates most 
rapidly when spread out in thin layers, and entangled among the 
fibres of cloth or sponges. For the same reason, also, hemorrhagu I 
continues longer from an incised wound than from a laccmt«d one; 
beoauae the bloody in flowing over the ragged edges of the hwe- 
rated bloodvessels and tissues, aolidides upon them readily, and thus 
blocks up the wound. 

In all these cases, there is an inverse relation between the rapidity 
of coagulation and the firmness of the clot. When coagulation 
takes place slowly, the clot afterward becomes small and dense, and 
the serum is abundant. When coagulation is rapid, there is bat 
little coDtraction of the coagutum, an imperfect separation of the 
serum, and the clot remains large, soft, and gelatinous. 

It is well known to practical physicians that a similar relation 
exists when the coagulation of the blood is hastened or retarded bv 
disease. In cases of lingering and exhausting illness, or in diseases 
of a typhoid or exantheniatous character, with much depression of 
the vital powers, the blood coagulates rapidly and the clot remains 
soft. In oases of active inflammatory disease, as pleurisy or pneu- 
monia, occurring in previously healthy subjects, the blood cctagutates 
slowly, and the clot becomes very firm. In every instance, the 
blood which has coagulated liquefies again at the oommeocement of 
putrefaction. 

The coagulation of the fibrin is not a commencement 0/ organizatiotu 
The filaments already described, which show themselves in the clot 
(Fig. (J2), are not, properly speaking, organized fibres, and are on- 
tirely difl'erent in their character from the fibres of areolar tissue, or 



i 



I 



I 




COAOtlLATIO.V OF TBE BLOOD. 



2U 



ajiy otber normal anatomvcal clementa. Tbey are simply the ulti- 
mate form which fibrin assumes in coagulating, just as albumen 
takes the form of granules under the same circumstances. The 
coagulation of fibrin does not differ in character from that of any 
other organic substance ; it merely differs in the physical conditions 
which give rise to it. All the cuagulable organic subcttanccs are 
naturally fluid, and coagulate only when they are placed under 
certain unusual conditions. But the particular conditions necea-' 
sary for coagolation vary with the different organic substances. 
Thns albumen coagulates by the application of heat. Casein, which 
ia not affected by heat, coagulates by contact with an acid body. 
Pancreatine, again, is coagulated by contact with sulphate of mag- 
nesia, which has no effect onalbumcTi. So fibrin, which ia naturally 
flaid, and which remains flold so long as it is circulating in the 
vessels, coagulates when it is withdrawn from them and brought in 
contact with unnatural surfaces. Its coagulation, therefore, ia no 
more "spontaneous," properly speaking, than that of any other 
organic substance. Still less does it indicate anything like organ- 
ization, or even a commencement of it. On the contrary, in the 
natural processes of nutrition, librin is assimilated by the tissues 
&nd takes part in their organization, only when it is absorbed by 
them from the bloodvessels in a fluid form. As uoon a.s it is utice 
coagulated by any meant!, it passes inu> an unimtural condition, and 
iiiiist he again liquefied and absorbed into the blood before it can 
bo animilated. 

As the fibrin, therefore, is maintained in its natural condition of 
fluidity by the movement of the circulating blood in the interior of 
the veAsela, anything which interferes with this circulation wilt in- 
duce ita coagulation. If a ligature be placed upon an artery in the 
living subject, the blood whiuh stagnates above the ligature coagu- 
Utes, justas it would do if entirely removed from the circulation. 
If the vessel be ruptured or lacerated, the blood which escapes from 
il into the areolar tissue coagulates, because here also it is with- 
drawn from the circulation. It coagulates also in the interior of 
the vessels aHer death owing to the same cause, viz: stoppage of 
the ciraulatioQ. During the last moments of life, when the flow of 
Mood through the cavities of the heart is impeded, the fibrin often 
toagulates, in greater or less abundance, upon the moving chords 
leadineae and the edges of the valves, just as it would do if with- 
drawn from the body and stirred with a bundle of twigs. In every 
instance, the coagulation of the fibrin is a morbid phenomenon, de- 
pendent on the cessatiuu or disturbance of the circulation. 



212 



THE BLOOD. 



Fif. (15. 



'^ 



CII»T Coik'H-LUa, ihnvl&g 
lb* gtaaior nccumuUlloii ot 

blood-slolinlH Bi tha boitou. 



If the blood be allowed to coagulate in a bowl, and the cloi be 
then divided by a vertical section, it will be seen that iui lower M 
portion is softer and of a deeper red than the upper. (Fig. 66.) 
This is because tbe globules, wbioh are of 
greater specific gruvity than the plasma, sink^ 
toward the bottom of the vessel before coagu- 
lation lakes place, and accumulate in the 
lower portion of tbe blood, This deposit 
the globules^ however, isi only partial ; be- 
cause they are soon ilxed and entangled by 
the solid raaas of the coagulom, and are thoa , 
retained in the position in which they bap- 
pen to be at the moment that coagulutioa 
takes place. 
If (he coagulation, however^ be delayed 
longer than usual, or if the globules sink more rapidly than ia cus- 
tomary, they will have time to subside entirely from the upper por- 
tion of the blood, leaving a layer at tbo surface which is cumpoeed 
of plasma alone. "When coagulation then lakes place, this api>er 
portion solidifies at the same time with the rest, and the clot then 
presents two diSerent portions, viz^ H lower portion of a dark red B 
color, in which the globules are accumulated, and an upper portion 
from which the globules have subsided, and which is of a grayish 
white color and partially transparent. This whitish layer on the 
surface of the clot is termed the "baffy coal;" and tbe blood pre- 
senting it ia said to be "huffed." It is an appeamnce which often 
presents itself in cases of acute inHammatory disease, in which the 
coagulation of the blood ia unuaaally retarded. 

When a clot with a bufty coat begin.s to contract, the contrac- 
tion takes place perfectly well to its upper 

' portion, but in the lower part it is impeded 

ymgf^^mm^^^ ^y '^^ presence of tbe globules which have 

^^■t^^^^Wj accumulated in large quantity at the bottom 

l^^k^^^nj of tbe clot. While the lower part of the 

V^^^^^Hf/ coagalum, therefore, remains voluminous, 

\^^^^/ and hardly separate.** from the sides of the 

vessel, its upper colorless portion diminiabea 

very much in size; and as its edges separate 

from tbo sides of the vessel, they curl over 

toward each other, so that the upper surface 

of the clot becomes more or less excavated or cup-shaped. (Fig. 66.) 



Bawt of Co «»i* i..(tt D 

bLiir«d And ca|tp<k(i 




COAGULATION OF THE BLOOD. 213 

The blood is then said to be "buffed and copped." These appear- 
ances do not present themselves underordinary conditions, but only 
when the blood has become altered by disease. 

The entire quantity of blood existing in the body has never been 
very accurately ascertained. It is not possible to extract the whole 
of it by opening the large Tesselsjsiace a certain portion will always 
remain in the cavities of the heart, in the veins, and in the capil- 
laries of the head and abdominal organs. The other methods 
which have been practised or proposed from time to time are all 
liable to some practical objection. We have accordiogly only 
heen able thos far to ascertain the minimum quantity of blood 
existing in the body. Weber aad Lehmann* ascertained as nearly 
as possible the quantity of blood in two criminals who suffered 
death by decapitation ; in both of which oases they obtained essen- 
tially similar results. The body weighed before decapitation 138 
ponnds avoirdupois. The blood which escaped from the vessels at 
the time of decapitation amounted to 12^7 pounds. In order to 
estimate the quantity of blood which remained in the vessels, the 
experimenters then injected the arteries of the head and trunk with 
vater, collected the watery fluid as it escaped from the veins, and 
isoertained how much solid matter it held in solution. This 
uooanted to 477.22 grains, which corresponded to 4.88 pounds of 
blood. The result of the experiment is therefore as follows : — 

Blood wUoh escaped from the TeSHels 12.27 ponnds. 

" ramsined In the bod7 4.38 " 



Wh(de qaantitj of blood in the llrtDg body, IH.tiS 

The weight of the blood, then, in proportion to the entire weight 
of the body, was as 1 : 8; and the body of a healthy mau, weighing 
140 poands, will therefore contain on the average at least 17J 
pounds of blood. 

' Ph^iiologioal Chemistry, rol. i. p. 638. 



214 



BKSPIBATION'. 



CHAPTER XII. 



RE8PIKATI0N. 



Ths blood as it circulates in the arterial system baa a bright 
scarlet color; but as It passes through the capillaries it gradQally 
becomes darker, and on iUs arrival in tlie vciiia its color m a deep 
purple, and in some parts of the body nearly black. There are, 
therefore, two kinds of blood in the body ; arterial blood, which ia 
of a bright color, and venous blood, which is dark. Now it is found 
that the dark-colore«] venous blood, wJiicli has been contaminated 
by passing through the capillaries, is unfit for further circulation. 
It in incapable, in this state, of supplying the organs with their 
healthy stimulus and nutrition, and has become, on the contrary, 
deleterious and poisonous. It is accordingly carried back to the 
heart by the veins, and thcnco sent to the lungs, where it is recon- 
verted into arterial blood. The process by which the venous blood 
is thus arterialized and renovated, is known as the process of 
respiration. M 

This process takes place very actively in the higher animals, and V 
probably does so to a greater or less extent in all animals without 
exception. Its csyentinl conditions are that the circulating fluid 
should be exposed to the influence of atmospheric air, or of an 
aerated fluid ; that is, of a fluid holding atmoepheric air or oxygen 
in Eoluiion. The respiratory apparatus consists essentially of a fl 
moist nnd permeable animal membrane, the respiratory membrane, 
with the bloodvessels on one side of it, and the air or aerated Said 
on the other. The blood and the air, consequently, do not come id 
direct contact with each other, but absorption and exhalation take 
place from one to the other through the thin membrane which lies 
between. 

The special anatomical arrangement of the respiratory apparatus 
differs in different species of animals. In most of those luhabiliog 
the water, the respiratory organs have the form of gitU or bronchia; 
that is, delicate filumcnious prolongations of some part of the 



I 




BE3PIRATIOX. 



215 



HcAO J.*it dib(.« or MlUnaBAVeira- 



iote^Tnent or mncous membranep, which contain an abundant 
sapply of bloodvessels, and wliich hang out freely into the sur- 
roaodiDg water. Id many kiads of aquatic lizards, as, for exam- 
ple, in menobtanchiui (Fig. H7), 

there are upon each side of the ^'B- ^'• 

neck three delicate feathery 
lafls of threadlike prolonga- 
tions from the mucous mem- 
brnne of the pharynx, which 
pass out through fissurea in 
the aide of the neck. Each 
taft is composed of a priu- 
cipal etom, upon whiuh the 
filaments are arranged in a 
pinnated form, like the plume upon the shafl of a feather. Each 
filament, when examined by itself, is seen to consist of a thiu, rib- 
bon-shaped fold of mucoua membranie, in the interior of which 
there is a plentiful network of minntc bloodvessels. The dark 
blood, as it comes into the filament from the branchial artery, is 
exposed to the iuduence of the water in which the 6]amenl is 
bathed, and as it circulates through the capillary network of the 
gills is reconverted into arterial blood. It is tlmn carried away by 
the branchial vein, and paitses into the general current of the cir- 
culation. The apparatus is further supplied with a cartilaginous 
framework, and a set of muscles by which the gills are gently waved 
about ID the surrounding water, and con»tnntty brought into con- 
lact with fresh portions of the aerated fluid. 

Uost of the aquatic animals breathe by gills similar in all their 
essential characters to those described above. In terrestrial and 
air-breathing animula, however, the respiratory apparatiis is situated 
internally. In thorn, the air ia made to petietrale into the interior 
of the body, into certain cavities or sacs called the lungit, which 
are Hoed with a vascular mucous membrane. In the salamanders, 
for example, which, though aquatic in their habita, are air-breathing 
animals, the lungs are two long cylindrical sacs, running nearly the 
entirv length of the body, commencing anteriorly by a communi- 
cation with the pharynx, and terminating by rounded extremities 
at the posterior part of the abdomen. These lungs, or air-sacs, 
bare a smooth internal surface; and the blood which circulates 
through their vessels ia arterialized by exposure to the air contained 
iu their cavities. The air ia forced into the lungs by a kind of 



218 



RBSriBATIOK. 



Fig, 68. 



swallowing movement, and is aUar a time regurgitated and dis- 
charged, in order to mnke room for a fresh supply. 

In frog«, turtles, serpenia, &c, the structure of the lung is a 
Httle more complicated, since rettpiratiou is more active iu tliesc 
animals, and a more perfect organ is requisite to accomplish the 
artenalization of ihc blood. In theao animals, the cavity of the 
lung, instead of being simple, ia divided by incomplete partitions 
into a number of smaller cavities or "cells.'* The cells all comma- 
nicate with the ceutral pulmonary cavity ; and the partitions, wbich 
join each other at various angles, are all composed of thin, pro- 
jecting folda of the lining membrane, with bloodvessels ramifying 
between tliem. (Kig. fi8.) By this arrangement, 
the extent of surface presented to the air by the 
pulmonary membrane is much increased, and the 
arterializatioD of the blood takes place with a 
corresponding degree of rapidity. 

In tbo human duhjeet, and in all the warm* 
blooded quadrupeds, the lungs are constructed 
on a pUn which is essentially similar to the 
above, and which differs from it only in the 
greater extent to which the pulmonary cavity is 
subdivided, and the surface of the respiratory 
membrane increased. The respiratory apparatus 
(Fig. 69) commences with the larynx, which 
communicates with the pharynx at the upper part of the neck. 
Then follows the trachea, a mtKnbranous tube with oartilaginous 
rings; which, upon its entrance into the chest, divides into the right 
and left bronchus. These ngnin divide successively into secondary 
and tertiary bronchi; the subdivision continuing, while the bron- 
chial tubes grow smaller and more numerous, and separate oon- 
stantly from each otber. As they diminish in size, the tubes grow 
more delicate in structure, and the cartilaginous rings and plates 
disappear from their walls. They are finally reduced, according to 
KOlliker, to the size of g'j of an inch in diameter; and aro com- 
posed only of a thin mucous membrane, lined with pavement epi- 
thelium, which rests upon an elustio iibmus layer. They are then 
known as the " ultimate bronchial tubes." 

Each ultimate bronchial tube terminates in a division or islet of 
the pulmonary tissue, about -^j of an inch in diameter, which is 
termed a "pulmonary lobule." Kach pulmonary lobulo resembles 
in its structure iliu entire frog's tung in miniature. It consists of a 



-^ 



^.z»a or Funn 
•fenwlBg It* Inlvnul Mir 



I 



RESPIRATION, 



217 



Pig. «d. 



-^ 



^ 



/c^ 



©^ 



W 






^'y 






^>;^, 



j^jj-- 



;o^ 



:i 






>-.';iJ 



-,*=iS'^ 



<M 






^^ 



i^ 



I 



'^^ 



Fig. TO. 



bfoachl, aarf ita dNUoa or Iba liut$t Into lobolaa. 

VAsculftr membrane inclosing a cavity; which cavity is ilividcrl 
iDto a large number of secoudnry compartments by thin septa or 
parlitions, which project from its internal surface, (Fig. 70.) These 
secondary cavitiea arc the ''pulmonary 
cells," or " vesicles." Each vesicle is about 
,', of ati inch in diameter; and is covered 
on its exterior with a close uetwork of ca- 
pillary bloodvessels, which dip down into 
ihc spaces between the adjacent vesicles, and 
expose ID this wny a double surface to the 
air which is contained in their cavities. 
Butweea the vesicles, and in the interstices 
between the lobules, there is a large (quan- 
tity of yellow clastic tissue, which gives 
Brmness and resiliency to the pulmonary 
structure. The pulmonary vesicles, accord. 
ing lo the observations of Kolliber. are ,», ui»n— n..m..*tn«.. 
lined everywhere with a layer of pavement «»"«»t"'» * c«»ii]roiiofcuie. 
epithelium, conUnuuus wiib ihat lu the dM. 



218 



nKSPIKATrOK. 



iiltimnta bronchial tubes. The whole extent of respiratory eur- 
liicc in both lungs bus been calculated by Ijicberkiihn' at fourt'^eal 
liundre«l square feet. It is plainly impossible to make a precisely 
accurate calculation of this extent; but there is every reason Ul 
believe that the estimate adopted by Licbcrkiihp, regarded as 
approximative, is not by any means an exaggerated one^ The 
great multiplication of the minute pulmonary vesicle^ and of the 
partitions between them, must evidently increase to an extraor- 
dinary degree the extent of surface over which the blood, spread 
out in a thin layer, is exposed to the action of the air. These ^ 
anatomical conditions arc, therefore, the most favorable for its rapid 
and complete arterialization. 



Rescikatohy Movkhents of tqk Cukst. — The air which la contl 
taine<] in the pulmonary lobules and vehicles becomes rapidly vitiai 
in the process of respiration, and requires therefore to be expelU 
and replaced by a fresh supply. This exchange or renovation of 
the air is effected by alternate movements of the chest, of expansion^ 
and collapse, which arc termed the "respiratory movements of the' 
chest." The expansion of the cheat is efttfCted by two seta of mus- 
cles, vis., first, the diaphragm, and, second, the intcroostals. While 
the diaphragm is in a state of relaxation, it has the form of a vaulted 
partition botween the tliornx and abdomen, the edges of which are 
nitached to the inferior extremity of the steniom, the inferior 
costal cartilages, the borders of the lower ribs and the bodies of 
the lumbar vertebne, while its convexity rises high into the cavity 
of the chest, as far as the level of the fifth rib. When the fibres 
of the diaphrogm contract, their curvature is necessarily dimi- 
nished; and they approximate a straight line, exactly in proportion 
to the extent of tlieir coutructioit. Consequently, the entire con- 
vexity of the diaphragm is diminished in the same proportion, 
and it descends toward the abdomen, enlarging the cavity of the 
chest from above downward. (Fig. 71.) At the same time the inter- 
costal muscles enlarge it in a lateral direction. For the ribs, artlf 
culated behind witti the bodies of the vertobrie, and joined in front' 
to the sternum by the flexible and elastic costal cartilages, are so 
arranged that, in a position of rest, their convexities look obliquely 
outward and downward. When the movement of inspiration is 
about to commeDce, the first rib is fixed by the contraction of tho; 



Ju Sliuou's Chvuiiitry of Miiii, Pliilaaa. «d., IS46, p. 109. 



BK8PIBAT0BT MOTBMENTB OF THE CHBST. 



219 



Fig. 71. 



scaleni muscles, aad the intercostal miiBcles then coDtracting siniul- 

taneoosly, the ribs are drawn upward. In this movement, as each 

rib rotates upon its articulation with the 

^inal column at one extremity, and with 

Uie sternum at the other, its convexity is 

neoeasarily carried outward at the same 

time that it is drawn upward, and the pa- 

rietes of the chest are, therefore, expanded 

laterally. The stemnm itself rises slightly 

with the same movement, and enlarges to 

some «xtent the antero-posterior diameter 

of the thorax. By the simultaneous action, 

therefore, of the diaphragm which descends, 

and of the intercostal mnacles which lift 

the ribs and the sternum, the cavity of the 

chest is expanded in every direction, and 

the air passes inward, through the trachea 

and bronchial tubes, by the simple force of 

aspiration. 

After the movement of inspiration is ac- 
complished, and the lungs are filled with 
lir, the diaphragm and intercostal mascles 
relax, and a movement of expiration takes 
plaoe, by which the chest is partially col- 
lapsed, and a portion of the air contained 
in the pulmonary cavity expelled. The 
movementofexpiration is entirely a passive 
one, and is accomplished by the action of ""•* •*!»» •*>« Ago™ of the ehe>t 

three diflerent forces. First, the abdominal Tbow iT. wm* wh« expsuded"** 
oigans, which have been pushed out of their 

osaal position by the descent of the diaphragm, fall backward by 
their own weight and carry upward the relaxed diaphragm before 
them. Secondly, the costal cartilages, which are slightly twisted 
oat of shape when the ribs are drawn upward, resume their natural 
pomtion as soon as the muscles are relaxed, and, drawing the ribs 
down again, compress the sides of the chest. Thirdly, the pul- 
monary tissue, as we have already remarked, is abundantly sup- 
plied with yellow elastic fibres, which retract by virtue of their 
own elasticity, in every part of the lungs, after they have been 
forcibly distended, and, compressing the pulmonary vesicles, drive 
oat a portion of the air which they contained. By the constant 




DllORlM ILLrilTBATIlia 
TBI RiBFiaATOKT HOTI- 

■ ■iTTi. — (I. C»t(7 ot iha eh««t. 
b, Dlapbragm. Tha dftrk anl- 



220 



BESPIBATION. 



recurrence of these alternating movemcnta of inspiration and expi- 
ration, rresh portions of air are constantly introduced into and 
cipcUcd from the chest. 

The nverage quantity of atmoepherio air, taken into and dis- 
charged from the lunge with each respiratory movement, is, ac- M 
cording to the resultaof various obeervers, twenty cubic inches, Ac ^ 
eighteen respirations per minute, this amounts to 860 cuhio inches 
of air inspired per minute, 21,600 cubic inches per hour, and 518,400 M 
cubic inches per day. But as the movemenla of respiration are 
increased both in extetit and rapidity by every muscular exertion, 
the entire (quantity of air daily used in respiration is not less than 
600.000 cubic inches, or 850 cubic feet. 

T]ie whole of the air in the chest, however, is not changed at each 
moveraent of respiration. On the contrary, a v«ry considerable ■ 
quatitity remains in the jtuUnoiinry cavity afler tho most complete 
expiration ; and even after tho lungs have been removed from the 
chest, they still contain a Urge qnantity of air which cannot be 
entirely displaced by any violence short of disintegrating and dia- 
organizing the pulmonary tissue, It is evident, therefore, thatoul; 
a comparatively small portion of the air In the lungs paHses in and 
out with each respiratory movement; and it will require several 
successive respirations before all the air in the chest can be entirely h 
changed. It has not been possible to ascertain with certainty the V 
exact proportion in volume which exists between the air which is 
iilteroatoly inspired and expired, or "tidal" air, and that which 
remains constantly in the chest, or "residual" air, as it is called. 
It has been estimated, however, by Dr. Carpenter,' from the report* 
of various observers, that the volume of inspired and expired air M 
varies from 10 to 13 per cent, of the entire quantity contained in V 
the chest. If this estimate be correct, it will require from eight to 
ten respirations to change the whole quantity of air in the cavity of 
the chest. 

It is evident, however, from the foregoing, that the inspirator; 
and expiratory movementa of the cheat cannot be BulHcieat to 
change the nir at all in the pulmonary lobules and vesicles. The 
air which ie drawn in with each inspiration penetrates only into 
the traches and bronchial tubes, until it occupies the place of that 
i^hlch was driven out by the last expiraiion. By the ordinary 
respiratory movements, therefore, only that small portion of 

• Boman Diytiologjr, I'hilitJn. iid., Hii, p. 300. 




BSSPIRATOKY MOVSUENTS OF THB OLOTTIB. 



221 



air lying nearest tbe exterior, in the tmohea and large bronchi, 
voald fluctuate backward and forward, without ever penetrating 
itito the deeper parts of the lung, were there no other means pro- 
vided for its renovation. There are, however, two other forces in 
plav for this purpose. The first of these is the diffusive power of 
tha gases themselves. The air remaining in the deeper parts of 
the cheat is richer in carbonic acid and poorer in oxygen than that 
which has been recently inspired ; and by the Uwa of gaseous dif- 
Aision there roust be a constant interchange of these gases between 
the pulmonary vesicles and the trachea, lending to mix tbem 
equally in all parta of the lung. This mutual dida^ion and inter- 
mixture of the gases will therefore tend to renovate, pariinlly at 
least, the air in the pulmonary lobules and vesicles. Secondly, the 
trachea and bronchial tube$ii down to thot^ even of the smallest 
size, are lined with a mucous membrane which is covered with 
ciliated epithelium. The movement of these cilia is found Lo be 
directed always from below upward; and, like ciliary motion 
wherever it occurs, it has the eflect of producing a current in the 
same direction, in the Kuids covering the mucous membrane. The 
sir in the tubes must purtici- 

pate, to a certain extent, in Pig- 73. 

this current, and a double 
stream of air therefore is estab- 
lished in each bronchial tube; 
one current passing from with- 
in outward along the walls of 
the tube, and a return current 
posing from without inward, «„,,«„„„.,, tp-.. .ho^n,.o,..,d 

along the central part of its kBdla<nnJcarr«n(, prodoMd b7«liurr mo^tioa. 

»»ity. (Fig. 72.) By this 

means a kind of aerial circulation is constantly maintained in the 
interior of the bronchial tubes; which, combined with the mutual 
diffusinn of the gases and the alternate expunt<ion and collapse of 
the chest, effectually accomplish the renovation of the air contained 
in all parts of the pulmonary cavity. 



Respiratory Moveiib.nt8 of the Glottis. — Beside the move* 
iDeols of expanaion and collapse already described, belonging to 
the chest, there are similar respiratory movements which take place 
in the larynx. If the respiratory passages be examined after death, 
in the state of collapse in which they are usually found, it wilt be 



222 



BESPIBATIOS'. 



noticed that the opening of the glottis is very much Btnaller than 
the cavity of the trachea below. The glottis itself preseots the 
appearaace of a narrow chink, while the passage for the inspired 
air widens in the lowtr part of the larynx, and to iho tmchea 
constitutes a spacious tube, nearly cylindrical in shape, and over 
half an inch in diameter. We have found, for inatanoe, that io 
the human subject the space included between the vocal chords 
has an area of only 0.15 to 0.1" square inch; while the calibre 
of the trachea in the middle of iw length is 0.45 square inch. 
This disproportion, however, which is so evident after death, doe* 
not exist during life. While respiration is going on, there is a ■ 
constant and regular movement of the vocal chords, synchronous 
with the inspiratory and expiratory movemente of the cheat, by 



Fig. 73. 



FlS- 74. 




la lU ordliur* tvint'Diocinmcaiidtiloa.'— <i. 

UaaU McllLuv*' o. i>|HDln( of Ue (Icitli, 



Tlie ■am-, villi llir (lulll* df«<ml by 
■•pnr».tt>)a of ihd Tncjil rliord* — 41- Voesl 
ebvrda. b. ThfiMd (&rlll>t«. et. ArfW- 
Hold «artlla(0*. o. (>iirulii( at Ik* (lalll*. 



which the size of the glottis is alternalely enlarged and diiiiinishod. 
At every inspiration, the glottis opens and allows the air to pass 
freely into the trachea; at every expiration it collapses, aod the 
air is driven out through it from below. These movements are 
called the " respiratory movements of the glottis." They correspond 11 
in every respect with those of the cheat, and are excited or retanled " 
by similar causes. Whenever the general inovemenia of respiration 
are hurried and labored, those of the glottis become accelerated and 
increased in intensity at the same time; and when the movemeats 
of the chest are slower or fainter than usual, owing to debility, 
coma, or the like, those of the glnllis are diminicihed in the sanie 
proportion. 



CHAN'OES IN THE AIR DURING RBSPIRATION. 



223 



Hg. 7ft. 



/ 



Id the respirelory motions of the glottis, as in those of the cheat, 
"the movement of inspiration is an active one, and Ihnt of expira- 
tion passive. In inspiratinn, the glottis 
is openoJ by contraction of the posterior 
crico-arytenoid muscles. {i'''g- "5.) 
These muscles originate from the po3> 
terior surface of the cricoid cartilage, 
near the median line; and tlieir 6bres, 
ranniog upward and outward, are in- 
serted into the external angle of the 
arytenoid cartilages. By the contrac- 
tion of these muscles, during the move- 
ment of iuspiratiou, the arytenoid car- 
tilagea are rotated upon their articula- 
tions with the cricoid, so that their 
anterior extremities are carried outward, 
and the vocal chords stretched and sepa- 
rate from each other. (Fig. 74.) In this 
way, the size of the gloitia may be in- 
creased from 0.15 to 0.27 square inch. 

In expiration, the posterior crico. 
arytenoid muscles are relaxed, and the elasticity of the vocal chords 
brings them back to their former position. 

The motions uf respiration consist, therefore, of two sets of move- 
ncnts : viz^ those of the chest, and those of the glottis. ThcJW move- 
ments, in the natural condition, correspond with each other both in 
time and intensity. It ia at the same time and by the same nervous 
ioiluencc, that the cheat expands to enlialc the air, while the glottis 
opens to admit it; and in expiration, the muscles of both chest and 
glottis are relaxed, while the elasticity of the tisanes, by a kind of 
passive coDtractiou, restores the parts to their origioal condition. 



Htm** Linr^x. ro*Tiriiiia 
vi(<r,— 11, ThrruU MtlllkM- ^ Bpl- 
glolUn. t>f. Arficnalil rartllagwi d. 
CrieJkd wirtiUp-. «. H««ioMor trttc- 
krjrtfuoM iniuclm. /. TrulMA. 



Chaitoes in thk Aib uukino Respi ratios.— The atmoapherio 
air, as it ia drawn into the cavity of the lungs, is a mixture of oxj' 
gen and nitrogen, in the proportion of ftboot21 per cent., by volume, 
of oxygen, to 79 per cent, of nitrogen. It also contains about one- 
twentieth per cent of carbonic acid, a varying quantity of watery 
vapor, and some traeeo of ammonia. The last named ingredients, 
^werer, are quite insignificant in comparison with the oxygen and 
oitrogen, which form the principal part of its mass. 
If collected and examined, afler passing through the lungs, the 



m 



KESPIRATIOK. 



nir is found to have become altered in the following essential pai 
ticiilflra, viz: — 

l8t. It has lost oxygen. 



bos 



ed carbonic acid. And 

Sd. It has abaorbed tlie vapor of water. 

Bcmde the two latter subatanccs, there are also exhaled with the 
expired air a very small quantity of nitrogen, over and above what 
was taken in with inspiration, and a little animal matter in a 
gasBoua form, which communicntes a slight but peculiar odor to 
the breath. The air is al»o somewhat elevated iu temperature, by 
contact with the pulmonary mucous membrane. 

The watery vapor, which ia exhaled with the breath, is given off 
by the pulmonary mucous nietnbrane, by which it is abeorbed from 
the blood. At ordinary temperatures it is transparent and invtai^ 
bio; but in cold weather it becomes partly condensed, on leaving 
the luDgs, :ind appears uuder the form of a cloudy vapor discharged 
with the breath. According to the researches of Yalonlio, the 
average quantity of water, exhaled daily from the lungs, ia 8100 
grains, or about Ij pound.s avoinlupois. 

By far the most important pnrt, however, of the changes suffered 
by the air in respiration, consists in its losa of oxygen, and its 
absorption of carbonic acid. 

According to the researches of Valentin, Vieronll, Regnault and 
Reiset, &c., the air loses during respiration, on an average, five pel 
cent, of its volume of oxygen. At each inspiration, thereforaj 
about one cubic inch of oxygen is removed from the air and ab- 
aorbed by the blood; and as we have seen that the entire dailji 
quantity of air used in n-spiration ia about 850 cubic feet, the entire 
quantity of oxygen thus consumed in twenty-four hours is not less 
than seventeen and a half cubic feet. This is, by weight, 
grains, or a little over one pound avoirdupois. 

The oxygen which ihua disappears from the inspired air is no{ 
entirely replaced in the carbonic acid exhaled; that is, there is less 
oxygen in the carbonic acid which is returned to the air by expint* 
tion than has been lost during inspiration. 

There is even more oxygen absorbed tlian is given off again in 
both the carbonic acid and aqueous vapor together, which ara 
exhaled from the lungs.^ There is, then, a constant disappearance 
of oxygen from the nir uaed iu reupiraliou, and a constant accumu 
latioD of carbonic acid. 



Lvhmanu's Pliytiolugiiml Clivmiatry, riiiUda. «d., vol. 11. p. 432. 



I'll i%:3a 
is noli 




CBAKOES IK TnE BLOOD DURINQ BESPIRATION. 226 

The proportion of oxygen which disappears in the interior of the 
hody, over and above that which is returned in the breath under 
Che form of carbonic acid, varies in different kinds of animals. In 
the herbivora, Jt is about 10 per cent of the whole amount of oxy- 
gen inspired ; in the carnivora, 20 or 25 per cent., and even more. 
It is a very remarkable fact, also, and an important one, as regards 
the theory of respiration, that, in the same animal, the proportion of 
oxygen absorbed, to that of carbonic acid exhaled, varies according 
to the quality of the food. In dogs, for instance, while fed on ani- 
mal food, according to the experiments of Regnault and Reiset, 26 
per cent, of the inspired oxygen disappeared in the body of the 
animal ; but when fed on starchy substances, all but 8 per cent. 
reappeared in the expired carbonic acid. It is already evident, 
therefore, from these facts, that the oxygen of the inspired air is 
not altogether employed in the formation of carbonic acid. 

Gbanoks in the BhooD DURING RESPIRATION. — If we pass from 
the consideration of the changes produced in the air by respiration 
to those which take place in the blood during the same process, we 
find, as might have been expected, that the latter correspond 
inversely with the former. The blood, in passing through the 
lungs, suffers the following alterations: — 
. 1st. Its color is changed from venous to arterial. 

2d. It absorbs oxygen. And 

8d. It exhales carbonic acid and the vapor of water. 

The interchange of gases, which takes place during respiration 
between the air and the blood, is a simple phenomenon of absorp- 
tion and exhalation. The inspired oxygen does not, as Lavoisier 
once supposed, immediately combine with carbon in the lungs, and 
return to the atmosphere under the form of carbonic acid. On the 
contrary, almost the first fact of importance which has been estab- 
lished by the examination of the blood in this respect is the fol- 
lowing, viz : that carbonic acid exists ready formed in the venous blood 
h^ore its entrance into the lungs; and, on the other hand, that tfie 
oxygen tokick is absorbed during respiration passes off" in a free state 
with the arteruil blood. The real process, as it takes place in the 
long, is, therefore, for the most part, as follows: The blood comes to 
the lungs already charged with carbonic acid. In passing through 
die pulmonary capillaries, it is exposed to the influence of the air 
in the cavity of the pulmonary cells, and a transudation of gases 
16 



226 



rBATioy. 



I 



lakes place through the moist animal mcmbrtines of the tang. 
Since the bkmd in the capillaries conUiins a larger proportion of 
carbonic acid than the air in the air-veaicles, a portion of this gds 
leaves the blood and passes out tlirough tho pulmonary membrane; J 
while the oxygen, being more nbundant in the air of the vesicles 
tbau in the circulating fluid, passes inward at the same Lime, and is 
condensed by the blood. 

In this double phenomenon of exhalation and absorption, which 
takes place in the lungs, both parti of the process are wjually 
neces-iary to life. It is essential for the constant activity and DUtri> 
tion of the tissues that they be steadily supplied with oxygen by the 
blood; and if this supply be cut oil', their functional activity ceases. 
On the other hand, the carbonic acid which is produced in tbe body 
bj tho processes uf nutrition becomes a poisonoua substance, if it 
be allowed to collect in large quantity. Under ordinary circum- 
stances, thu carbonic acid is removed by exbalatiou through the 
luQgs as fast as it is produced in the interior of the body; but if ■ 
respiration be suspended, or seriously impetlod, since the production 
of carbonic acid couiinues, while its elimination is prevented, it 
accumulates iti the blood and in the tissues, aud terminates life id a 
few moments, by a rapid dcterioraLioii of the circulating fluid, and 
more particularly by its poisonoua efleot on the nervous system. 

The deleterious effects of breathing in a confined space will 
therefore very soon become apparent. As respiration goes on, tho 
oxygen of the air constantly diminishes, and the carbonic acid, 
mingled with it by exhaliitiun, increases in quantity. Alter a time 
the air becomes accordingly so poor in oxygen that^ by tliat fact 
alone, it is incapable of supporting life. At the same time, the 
carbonic acid becomes so abuudant iu the air vesicles that it pre- 
vents the escape of that which already exists in the blood; and tha 
deleterious cfl'ect of its accumulation in the circulating Quid is 
added to that produced by u diminished supply of oxygen. An. 
increased proportion of carbonic acid in the atmosphere is therefore 
injurious iu a similar manner, although there may bu no dirainutioa 
of oxygen; since by its [ireseuce it impedes the elimination of the 
carbonic acid already formed in tbe blood, and induces tho poison- 
ous effects which result from its accnmulalioD. M 

Examination of the blood shows furthermore that the interchange " 
of gases ill tbe lungs is not comptote but only partial in its exteoL 
It results from tho experiments of Magendie, Magnus, and others, 
that both oxygen and carbonic acid are contained in both venous 



I 

I 
I 




CHAMOKS IN THB BLOOD DURINO BBSPIRATIOy. 227 

ind arterial blood. Magnas' foand that the proportion of oxygen 
to carbonic acid, by volame, in arterial blood was as 10 to 26; in 
Tenous blood as 10 to 40. The venous blood, then, as it arrives at 
the langs, still retains a remnant of the oxygen which it had pre- 
rionalj absorbed; and in passing through the pulmonary capil- 
laries it gives off only a part of the carbonic acid with which it has 
become charged in the general circulation. 

The oxygen and carbonic acid of the blood exist in a aUUe of 
mlutum in the circulating fluid, and not in a state of intimate chemi- 
cal combioaUoD. This is shown by the fact that both of these 
snbotanoes may be withdrawn from the blood by simple exhaustion 
with an air-pump, or by a stream of any other indifferent gas, such 
as hydrogen, which possesses sufficient physical displacing power. 
UagnuB found' that freshly drawn arterial blood yielded by simple 
agitation with carbonic acid more than 10 per cent of its volume 
of oxygen. The carbonic acid may also be expelled from venous 
blood by a current of pure oxygen, or of hydrogen, or, in great 
meaaare, by simple agitation with atmospheric air. There is some 
difficulty in determining, however, whether the carbonic acid of 
the blood be altogether in a free state, or whether it be partly in a 
state of loose chemical combination with a base, under the form of 
an alkaline bicarbonate. A solution of bicarbonate of soda itself 
will loae a portion of its carbonic acid, and become reduced to the 
oonditioD of a carbonate by simple exhaustion under the air-pump, 
or by agitation with pure hydrogen at the temperature of the body. 
Lehmann has found* that afler the expulsion of all the carbonic 
add removable by the air-pump and a current of hydrogen, there 
still remains, in ox's blood, 0.1628 per cent of carbonate of soda; 
and he estimates that this quantity is sufficient to have retained all 
the carbonic acid, previously given off, in the form of a bicarbonate. 
It makes little or no difference, however, so far as regards the pro- 
cess of respiration, whether the carbonic acid of the blood exist in 
an entirely free state, or ander the form of an alkaline bicarbonate ; 
since it may be readily removed from this combination, at the tem- 
peratore of the body, by contact with an indifferent gas. 

The oxygen and carbonic acid of the blood are in solution prin- 
cipally m the blood-ghbuka, and not in the plasma. The researches 
of Magnus have shown* that the blood holds in solution 2| times 

' la Lehmsnii, op. cit., vol. 1. p. 570. 

■ In Robin ind Terdell, op. olt, vol. tt. p. 34. 

' Op. cit., vol. 1. p. 393. 

* Ib Robin and Vonieil, op. cit., vol. ii. pp. 28—32. 



228 



IKSPIRATIOV. 



I 



i 



as much oxygen as pure water could dissolve at the same tempera- 
ture; ntid tbot while the aerum of the blood, separated from the 
globules, exerts no iiioro solvent power on oxygen than pnre water, 
deBbrinated blood, that i.s, the sorum and globules mixed, dissolves 
quite na much oxygen as the fresh blood itself. The same thing is 
true with regard tu tho carbonio acid. It is therefore the semi- 
fluid blood-globialcs which retain these two gases in soluUon; aod 
since the color of the blood depends entirely upon that of the glo- 
bules, it is easy to understand why the blood should alter its hue _ 
from purple to scarlet in passing through the lungs, where the I 
globules give up carbonic acid, and absorb a fresh quantity of 
oxygen. The above change may readily he produced outside the 
body. If freshly drawn venous blood be shaken in a bottle with 
pure oxygen, its color changes at once from purple to red ; and the 
same change will take place, though more slowly, if the blood bo 
simply agitated wilii atmospheric iiir. It is for this reason that the 
surfaca of defibrinated venous blood, and the exleraal parts of a 
dark-colored c5ot, exposed to the atmcsphcrc, become rapidly red- 
dened, while the internal portions retain their original color. 

The process of respiration, so far as we have considered it^ con- 
sists in an alternate interchange of carbonic acid and oxygen in the 
blood of the general and pulmonary circulations. In the pulmonary 
circulation, carbonic acid is given off and oxygen absorbed ; while 
in the general circulation the oxygen gradually disappears, and is 
replaced, in the venous blood, by carbonic acid. The oxygen which 
thus disappears from the blood iu the general circulation does not, 
for the most part, enter into direct combination in the blood itself. 
On the contrary, it exi.-its there, as we have already stated, in the 
form of a simple solution. It is absorbed, however, from the bluod 
of the capillary vessels, and becomes fixed in the subsUince of the 
vascular tiseues. The blixxl irmy be regarded, therefore, in this 
respect, as a circulating fluid, destined to transport oxygen from the 
lungs to the tissues; for it is the tissues themselves which finally 
appropriate the oxygen, and fix it in their substance. 



I 



The next important question which presents itself in the study 
of the respiratory process relates to (he origin of the cariromc acid in 
the ttnous hhmi. It was formerly supposed, when Lavoisier first 
discovered the changes produced in the air by respiration, that the 
production of the carbonic acid could be accounted for in a very 
simple manner. It was thouglit to be produced iu the lungs by a 




CHANGES IN THE BLOOD DCBINO BESPIBATION. 229 

direct union of the inspired oxygen with the carbon of the blood 
in the pnlmonarj vessels. It was found afterward, however, that 
this conld not be the case; since carbonic acid exists already formed 
in the blood, previously to its entrance into the langs. It was then 
imagined that the oxidation of carbon, and the consequent produc- 
tion of carbonic acid, took place in the capillaries of the general 
circnlation, since it could not be shown to take place in the lungs, 
nor between the lungs and the capillaries. The truth is, however, 
that no direct evidence exists of such a direct oxidation taking 
place anywhere. The formation of carbonic acid, as it is now 
understood, takes place in three different modes: 1st, in the lungs; 
2d, in the blood ; and 8d, in the tissues. 

First, in the lungs. There exists in the pulmonary tissue a pecu- 
liar acid substance, first described by Yerdei!' under the name of 
"pnenmic** or "pulmonic" acid. It is a crystallizable body, soluble 
in water, which is produced in the substanoe of the pulmonary 
tissue by transformation of some of its other ingredients, in the 
same manner as sugar is produced in the tissue of the liver. It is 
on account of the presence of this substance that the fresh tissue of 
the lung has usually an acid reaction to teet-paper, and that it has 
also the property, which has been noticed by several observers, of 
decomposiag the metallic cyanides, with the production of hydro- 
cyanic acid; a property not possessed by sections of areolar tissue, 
the internal surface of the skin, &c. &c. When the blood, there- 
fore, comes in contact with the pulmonary tissue, which is 
permeated everywhere by pneuoiic acid in a soluble form, its 
alkaline carbonates and bicarbonates, if any be present, are decom- 
posed with the production on the one hand of the pneumates of 
soda and potassa, and on the other of free carbonic acid, which is 
exhaled. M. Bernard has found* that if a solution of bicarbonate 
of soda be rapidly injected into the jugular vein of a rabbit, it 
becomes decomposed in the lungs with so rapid a development of 
carbonic acid, that the gas accumulates in the pulmonary tissue, 
and even in the pulmonary vessels and the cavities of the heart, to 
such an extent as to cause immediate death by stoppage of the 
circulation. In the normal condition, however, the carbonates and 
bicarbonates of the blood arrive so slowly at the lungs that as fast 
as they are decomposed there, the carbonic acid is readily exhaled 
by expiration, and produces no deleterious effect on the circulation. 

■ Robin and Verdell, op. cit., toI. li. p. 460. 

■ ArobiTflS G«n. de M6d., ztI. 222. 



sso 



SESPIRATTON. 



Secondly, m tke hlood. There is little doubt, altbougb tlie fact has 
not been directly proved, that some of the oxygen definitely dis- 
appears, and some of the carbonic acid is also formed, in the sub- 
stance of the blood -globules during their circulation. Since these 
globules are anatomical elements, and since they undoubtedly go 
through with nutritive processes ftnatogoiis to those which take 
place in the elements of the solid tissues, there is every reason for 
believing that they also require oxygen for their support, and that 
they produce ca>bonic acid as one of the results of their interstitial 
decompoailioo. While the oxygen and carbonic acid, therefore, 
oontained in the globules, arc for the most part trjmsi>orted by 
these bodies from the lungs to the tissues, and from the tissues back 
again to the lungs, they probably take part, also, to a certain extent, 
in the nutrition of the blood -globules thetnselves. 

Thirdly, m the tismes. This is by far the most iroportftnt soorcc 
of the carbonic acid in the blood. From the experimcDta of Spal- 
lanzani, W. Edwards, Marchand and others, the following very 
important fact hiis been established, viz., thot every organized tissue 
and even every organic substance, when in a recent ccndxliart, has On 
poicer of ah$orhing oxtjgeii and of exhaling carbonic add, 0. Llebig, 
for example,' found that frog's muscles, recently prepared and cora- 
pletely freed from blood, continued to absorb oxygen and discharge 
Oftrbonic acid. Similar experiments with other tissues have ted 
to a similar result. The interchange of gases, therefore, in the 
process of respiration, takes place mostly in the tissoes themselves, 
it is in their substance that the oxygen becomes fixed and assimi- 
lated, and that the carbonic acid lakes it« origin. As the blood in 
the lungs gives up its carbonic acid to the air, and absorbs oxygen 
from it, so in the general circulation it gives up ita oxygen to the 
tissues, and absorbs from them carbonic acid. 

We come lastly to examine the exact mode by which the car- 
bonic acid originatos in the animal tissues. Investigation shows 
that even here it is not produced htj a procats of oxidaiwji, or direct 
union of oxygen with the carbon of the tissues, but in some other and more 
indirect mode. This is proved by the fact that animals and fresb 
animal tiscues will continue to exhale carbonic acid in an atmo- 
sphere of hydrogen orof nitrogen, or even when placed in a vacuum. 
Marchand found* thai frogs would live for from half an hour to an 
hour ID pure hydrogen gas; and that during this time they exhaled 
even more carbonic acid thaa in atmospheric air, owing probably 



In Lehnumn, op. olt., rot. 11. p. 47^ 



> Ibid., p. 442. 



CHANaSfl IN THE BLOOD DURING RBSPIRATION. 2S1 

to the saperior displacing power of hjdrogen for carbonio acid. 
For while 16,600 grains' weight of frogs exhaled about 1.13 grain 
of carbonic acid per hoar in atmospheric air, they exhaled during 
the Bame time in pare hydrogen as much as 4.07 grains. The same 
observer found that frogs would recover on the admission of air 
after remaining for nearly half an hour in a nearly complete 
vacuum ; and that if they were killed by total abstraction of the 
air, 16,600 grains' weight of the animals were found to hare 
eliminated 9.8 grains of carbonio acid. The exhalation of carbonic 
acid by the tissues does not, therefore, depend directly upon the 
access of free oxygen. It cannot go on, it is true, for an inde6nite 
time, any more than the other vital processes, without the presence 
of oxygen. But it may continue long enough to show that the 
carbonio acid exhaled is not a direct product of oxidation, but that 
it originates, on the contrary, in all probability, by a decomposi- 
tion of the organic ingredients of the tissues, resulting in the pro- 
dactioD of carbonic acid on the one hand, and of various other 
sabstanceson the other, with which we are not yet fully acquainted; 
in very much the same manner as the decomposition of sugar 
daring fermentation gives rise to alcohol on the one hand and to 
carbonic acid on the other. The fermentation of sugar, when it has 
once commenced, does not require the continued access of air. It 
will go on in an atmosphere of hydrogen, or even when confined in 
a close vessel over mercury; since its carbonic acid is not produced 
by direct oxidation, but by a decomposition of the sugar already 
present For the same reason, carbonic acid will continue to be 
exhaled by living or recently dead animal tissues, even in an atmo- 
sphere of hydrogen, or in a vacuum. 

Carbonic acid makes its appearance, accordingly, in the tissues, 
as one product of their decomposition in the nutritive process. 
From them It is taken up by the blood, either in simple solution or 
in loose combination as a bicarbonate, transported by the circulation 
to the langa, and finally exhaled from the pulmonary mucous mem- 
brane in a gaseous form. 

The carbonic acid exhaled from the lungs should accordingly be 
studied by itself as one of the products of the animal organism, and 
its quantity ascertained in the different physiological conditions of 
the body. The expired air usually contains about four per cent, of 
its volume of carbonic acid. According to the researches of Vier- 
ordt,' which are regarded as the most accurate on this subject, an 

' In Lehmann, op. clt., vol. li. p. 439. 



S92 BESFlRATtOK. 

adult man gives off 1.62 cubic inch of carbonic acM with each nor-' 
inal expiration. Tbis aoiouats to very nearly 1,160 cubic inches 
per hour, or &A.een and a half cubic feet per day. Tbis quantity 
is, by weighty 10,740 grains, or a little over one pound and a half. 
The amount of carbonic acid exhaled, however, varies from Umo to 
time, according to many dlflerent circumstaaces; so that no sucb 
Gtttimate can repri^senL correctly its quaniity at all timea. These 
vnrintions have been very fully investigated by Andral and Gavar- 
ret,^ who found that the principal conditions modifying the amount 
of tbis gfts produceil were age, sex, constitution aod development. 
Tfiu variations were very marked io different individuals, notwith- 
standing that tlie experiments were made at the same period of the 
day, and with the subject as nearly as possible in the same condn 
lion. Thus they found that the quantity of carbonic acid exhaled 
per hour in five different individuals was as follows: — 

QdAXTRT op CAB301IB ACII> FEB ttWR. 

In Bubjoct No. !..■■■ 1^>^7 oabio inohM. 
" " " 2 . . . . . 970 " " 

" " " 3 1250 " •• 

" « " 4 1250 " " 

" " " 5 i5£ii " " 

With regard to the differeoce produced by age, it was found that 
from the period of eight years up to puberty the quantity of car- 
bonic acid increases constantly with the age. Thus a boy of eight 
years exhales, on the average, 684 cubic inches per hour; while a 
boy of fifteen years exhales 981 cubic inches in the same time. 
Boys exhale during this period more carbonic acid than girls of tb« 
same age. In males this augmentation of the quantity of carbonic 
acid continues till the twenty-6fth or thirtieth year, when it reacbes, 
on the average, 1398 cubic inches per hour. Its quantity then 
remains stationary for ten or fifteen years; then diminishes slightly 
from the fortieth to the sixtieth year ; and after sixty years dimi- 
oiahes in a marked degree, so that it may fall so low as 1038 cubic 
inches. In one superannuated person, 102 years of age, Andral 
and Gavarrct found the hourly quantity of carbonic acid to be 
only 665 cubic inches. 

In women, the increase of carbonic acid ceases at the period of 
puberty; and its production then remains constant until the cessa- 
tion of menstruation, about the fortieth or fortyfif^h year. At that 
time it increases agaiu until aAer iitly years, when it subsequently 

> AnnalH dn Cliiiiil« «t d« Fhanuaoiv, 1M3, toI. Till. p. 128. 



CHAKGKS IN THE BLOOD DURING RESPIRATION. 2SS 

dimiDiahes with the approach of old age, aa in men. Pregnancy, 
occurnng at aoj time in the above period, immediately produces a 
temporary increase in the quantity of carbonic acid. 

The strength of the constitution, and more particularly the <kve- 
JopmerU of the muaeuhr si/Mtem, was found to have a very great in- 
flaence in this respect; increasing the quantity of carbonic acid 
Tery much, in proportion to the weight of the individual. The 
largest production of carbonic acid observed was in a young man, 
26 years of age, whose frame presented a remarkably vigorous and 
athletic development, and who exhaled 1591 cubic inches per hour. 
This large quantity of carbonic acid, moreover, in well developed 
persons, is not owing simply to the size of the entire body, but 
particularly to the development of the muscular system, since an 
unaaaally large skeleton, or an abundant deposit of adipose tissue, 
is not accompanied by any such increase of the carbonic acid. 

Andral and Gavarret finally sum up the results of their investiga- 
tions as follows : — 

1. The quantity of carbonic acid exhaled from the lungs in a 
given time varies with the age, the sex, and the constitution of the 
aabject. 

2. In the male, as well as in the female, the quantity of carbonic 
acid varies according to the age; and that independently of the 
weight of the individual subjected to experiment. 

8. During all the periods of life, from that of eight years up to 
the most advanced age, the male and female may be distinguished 
by the different quantities of carbonic acid which they exhale in a 
given time. Other things being equal, the male exhales always a 
larger quantity than the female. This difference is particularly 
marked between the ages of 16 and 40 years, during which period 
the male usually exhales twice as much carbonic acid as the female. 

4. In the male, the quantity of carbonic acid increases constantly 
from eight to thirty years ; and the rate of this increase undergoes 
a rapid augmentation at the period of puberty. Beyond thirty 
years the exhalation of carbonic acid begins to decrease, and its 
diroination is more marked as the individual approaches extreme 
old age; so that near the termination of life, the quantity of carbonic 
aeid produced may be no greater than at the age often years. 

6. In the female, the exhalation of carbonic acid increases accord- 
ing to the same law as in the male, from the age of eight years 
antil puberty. But at the period of puberty, at the same time with 
the appearance of menstruation, the exhalation of carbonio wid, 



284 



IBSPIBATtOX. 



contrary to what happens in the male, ceases to increase; nod it 
afterward remains stationary so long as ibe menslrual periods recur 
with regularity. At the cessation of the meoses, the quantity of 
carbonic acid exhaled increases in a notable manner; then it de- 
creases again, as in the male, as the woman advances toward old age. 

6. During the whole period of pregnancy, the exhalalioo of car- 
bonic acid riseH, for the Lime, to the same ataudard as id women 
whose meases have ceased. 

7. In brjth sexes, and at all ages, the quantity of carbonic acid ia 
greater as the constitution is stronger, and the muscular system 
more fully developed. 

Prof. Scharling, in a similar series of Investigatioas,' found that 
the quantity of carbonic acid exhaled was greater during the diges- 
tion of food than in the fastiog condition. It is greater, alsp, in the 
waking state than during sleep: and in a stale of activity than in 
one of quietude. It is diminished, also, by fatigue, and by most 
conditluua which interfere with perfect health. 

The process of respiration is not altogether conGned to the longs, 
but the interchange of gases takes place, also, to some extent through 
the skin. It has been found, by inclnsing one of the limbs in an 
airtight case, that the air in which it is confined 1o.<h;s oxygen and 
gainfl in carbonic acid. By an experiment of this sort, performed by 
Prof. Scliarling,' it was ascerlained that the carbonic acid given off 
from the whole outaneous surface, in the human subject, is from 
one-sixiieih to one-thirtieth of that discharged during the same 
period from the lungs. In the true amphibious animals, that is, 
those which breathe by luugs, and can yet remain under water for 
an indctiinto period without injury [as frogs and salamanders), the 
respiratory function of the skin is very active. In these animals, 
the integument ia very vascular, moist, and flexible; and is covered, 
not with dry cuticle, but with a very thin and delicate layer of 
epithelium. It, therefore, presenLi all the conditions necessary for 
the accnmpHshmcTit of rcapiraiion; aiid while the animal remains 
beneath the surface, and the lungs are in & stale of inactivity, the 
exhalation and absorption of gases continue to take place through 
the skin, and the process of respiration goes on in a nearly unin* 
terrupted manner. 

1 Aniialtfi de CKImle et ie Phananole, vol, vlll. p. 4!l<t. 

■ In Cftrpenter'a Hanutu PbyticAogy, 11ill«la. rd , l£3», p. 308. 



ANIKAL HKAT. 286 



CHAPTER XIII. 

ANIMAL HEAT. 

Oss of the most important phenomeDa presented bj animals and 
▼egetablea is the property which they possess of maintaining, more 
or less constantly, a standard temperature, notwithstanding the 
external vicissitades of heat and cold to which they may be sub- 
jected. If a bar of iron, or a jar of water, be heated up to 100° or 
200° F., and then exposed to the air at 50° or 60°, it will imme- 
diately begin to lose heat by radiation and conduction; and this 
loss of heat will steadily continue, until, after a certain time, the 
temperature of the heated body has become reduced to that of the 
sarroanding atmosphere. It then remains stationary at this point, 
unless the temperature of the atmosphere should happen to rise or 
ftll: in which case, a similar change takes place in the inorganic 
body, its temperature remaining constant, or varying with that of 
the surrounding medium. 

With living animals, Uie case is different. If a thermometer be 
introduced into the stomach of a dog, or placed under the tongue 
of the human subject, it will indicate a temperature of 100** F., very 
nearly, whatever may be the condition of the surrounding atmo- 
sphere at the time. This internal temperature is the same in sum- 
mer and in winter. If the individual upon whom the experiment 
bas been tried be afterward exposed to a cold of zero, or even of 20° 
or 80° below zero, the thermometer introduced into the interior of 
the body will still stand at 100° F. As the body, during the whole 
period of its exposure, must have been losing hoat by radiation and 
conduction, like any inorganic mass, and has, notwithstanding, main- 
tained a constant temperature, it is plain that a certain amount of 
heat has been generated in the interior of the body by means of the 
vital processes, sufficient to compensate for the external loss. The 
internal beat, so produced, is known by the name of vital or animal 
heaL 

There are two classes of animals in which the production of vital 



2S6 



HEAT. 



heat takes place with such activity that their blood and internal 
organs are nearly always very much above the external temper- 
ature; and which are therefore called "warm-blooded aDimals." 
These are mammaHa and birds. Among the birds, some specieSi 
as the gull, have a temperature ns low as 100* F.; but in naojt of 
them, it is higher, sometimes reaching as high aa 110° or 111°. In 
the mammalians, to which class man belongs, the animal tempera- 
ti3re is never far from 100". In tlie seal and the Greenland whnle, 
it has been found to be 104°; and in the porpoise, which is an air- 
breathing animal, 99°.5. In the human subject tt is 98° to 100°. 
When the temperature of the air is below this, the external parts 
of the body, being moat exposed to the cooling influences of radia- 
tion and conduction, fall a little below the standard, and may indi- 
cate a temperature of 97°, or even several degrees below thia poinL 
Thus, on a very cold day, the thinner and more exposed parts, such 
as the nose, the ears, and the ends of Che fingers, may become 
cooled down considerably below the standard temperature, and may 
even be congealed, if the cold be severe; but the temperature of 
the internal organs and of the blood still remains the same uuder 
all ordinary exposures. 

If the cold be so intense and long continued as to affect tbe 
general temperature of the blood, it at once becomes fatal. It has 
been found that although a warm>blooded animal usually preserves 
its natural temperature when exposed to external cold, yet if tbe 
actual temperature of the blood become reduced by any means 
more than 5° or 6° below its natural standard, death inevitably 
results. The animal, under these circumstances, gradually becomes 
torpid and insensible, and all the vital operations finally cease. 
Bird»i, acconlingly, whose natund temperature is about 110°, die if 
the blood be cooled down to 100°, which is the natural temperature 
of the mammalia; and the mammolians die if their blood be cooled 
down below 94° or 95°. Each of these difterent classes has there- 
fore a natural temperature, at which the blood must be maintained 
in order to sustain life; and even the different species of aoimala, 
belonging to the same class, have each a specific temperature which 
is charade rislic of them, and which cannot be raised or lowered, to 
any coosiderable extent, without producing death. 

While in the birds and mammalians, however, the internal pro- 
duction of heat is so active, that their temperature is nearly always 
considerably above that of the surrounding media, and suffers but 
little variation; in reptiles end fish, on the other hand, its produc- 



ANIMAL HEAT. 



237 



tion is mnch less rapid, and tbe temperature of their bodies differs 
bat little from that of the air or water which tbej inhabit. Birds 
and mammaliaDS are therefore called "warm-blooded," and reptiles 
and fish "cold-blooded" aoimals. There is, however, no other dis- 
tiactioQ between them, in this respect, than one of degree. In 
reptiles and fish there is also an internal source of heat; only this 
is not so active as in the other classes. Kven in these animals a 
diflference is usually found to exist between the temperature of their 
bodies and that of the surrounding media. John Hunter, Sir 
Hamphrej Davy, Czermak, and others,' have found the temperature 
of Proteus anguinus to be 63*^.5, when that of the air was 56°.4; 
that of a fr9g 48°, in water at 44°.4; that of a serpent 88°.4t}, in 
air at 81^5; that of a tortoise 84^ in air at 79^6; and that of fish 
to be from 1**.7 to 2°.b above that of the surrounding water. 

The following list* shows the mean temperature belonging to 
animals of different classes and species. 



Bnos. 



Havmalia. 



Rbptilb. 



Asmkh. 










Ukah Tbhpsbatobx. 


SwaltoT 1110.25 


Heron . 










1110.2 


Raren ,~ 










108O.fi 


Pigeon . 










107O.6 


Fowl . 










106O.7 


. Gnll . 










lOOO.O 


' Sqaiml 










105O 


Goat . 










102O.6 


Cat 










101O.3 


Hare . 










100O.4 


Ox 










990.6 


Dog . 










930.4 


Han 










980.6 


. 'Ape 










950.9 


Toad . 










510.6 


Carp 










510.25 


. Tenoh . 










520.10 



FtBH. 



In the invertebrate animals, as a general rule, the internal heat 
is produced in too small quantity to be readily estimated. In some 
of the more active kinds, however, such as insects and arachnida, 
it is occasionally generated with such activity that it may be 
appreciated by the thermometer. Thus, the temperature of the 
butterfly, when in a state of excitement, is from 6° to 9° above 



■ Simon's Chemlatrr of Man, Philadelphia edition, p. 124. 

■ Ibid., i^. 123—126. 



AyiVAt n«AT. 



that of tlie air ; ani] that of the humble-bee Troni 3° to 10° higher 
than the exterior. Accordinjif to the experiments oF Mr. Kewport,* 
the interior of a hive of bees may have a temperature of 48°^, 
when the external atmosphere is at 34°^, even while the insects 
are quiet; but if they be exciteU, by tapping on the oolsido of the 
hive, it may rise to 102°. In all cases, while the insect is at rest, 
the temperature ig very moderate; but if kept in rapid motion in 
a con6necl space, it may generate heat enough to affect the thermo- 
meter sensibly, in the course of a few minutes. 

Even in vegetables a certain degree of heat-prod ocing power is 
occasionally manifest. Usually, the expoBed surface of a plant u 
so extensive in proportion to its mass, that whatever calonc may 
be generated is too rapidly lost by radiation and evaporation, to be 
appreciated by ordinary means. Under some circumstances, how- 
ever, it may accumulate to such an extent as to become readily 
perceptible. In tbe process of making, for example, when a large 
quantity of germinating grain is piled together in a mass, its ele- 
vated temperature may be readily distinguished, both by the hand 
and the thermometer. During the flowering process, also, an una- 
sual evolution of heat takes place in plants. The flowers of the 
geranium have been found to have a temperature of 87°, while 
that of the air was SI"] and the thermometer, placed in the centre 
of a clump of blossoms of arum cordifolium, has been seen to rise 
to 111®, and even 121°^ while the temperature of the external air 
was only 66°.' 

Dutrouhet has moreover found, by a series of very ingeirioos aod 
delicate experiments,' that nearly all parts of a living plant gene- 
rato a ccrutin amount of heat. The proper heat of the plant is 
usually so rapidly dissipated by the continuous evaporation of its 
fluids, that it ia mostly imperceptible by ordinary means; but if 
this evaporation be prevented, by keeping the air charged with 
watery vapor, the heat becomes sensible and can be appreciated by 
a delicate thermometer. Butrochet used for this purpose a thermo- 
electric apparatus, so constructed that an elevation of temperature 
of 1° F., in tUo substances examined, would produce a deviatiou in 
the needle of nearly nine degrees. By this means he found that he 
could appreciate, wttliout diflficulty, the proper temperature of tho 
plant. A certain amount of heat was constantly generated, during 

' Carpent»r'H Oenera-l dbA CompArntivo Phjsiolog^, I'hiladelpbia, tfiiSl, p. &I>2. 

• Cari>ent«r'B Gen. adiI Comp. Phjrttiologjr, p. 84ti, 

* AnnaJa dsi Sciencwi NftLnrvlLM, Sil aeriea, icil. p. 277> 



ANIUAL HBAT. 289 

the day, ia the greoQ stems, the leaves, the bads, and even the 
roots and fruit. The maximum temperature of these parts, above 
that of the sarroandiDg atmosphere, was sometimes a little over 
one-half a degree, Fahrenheit; though it was often considerably 
leas than thia. 

The dififerent parta of the vegetable fabric, therefore, generate 
different quantities of caloric. In the same manner, the heat- 
prodacing power is not equally active in different species of ani- 
mala; bat its existence ia nevertheless common to both animals 
and vegetables. 

With r^ard to the mode of generation of thia internal or vital 
beat, we may start with the assertion that its production depends 
upon changes of a chemical nature, and is so far to be regarded as 
a chemical phenomenon. The sources of heat which we meet with 
in external nature are of various kinds. Sometimes the heat is of 
a physical origin ; as, for example, that derived from the rays of 
the ann, the friction of solid substances, or the passage of electric 
currents. In other instances it ia produced by chemical changes ; 
and the most abundant and useful source of artificial heat is the 
oxidadon, or combustion, of carbon and carbonaceous compounds. 
Wood and coal, substances rich in carbon, are mostly nsed for thia 
purpose ; and charcoal, which is nearly pure carbon, is frequently 
employed by itaelC These substances, when burnt, or oxidized, 
evolve a lai^ amount of heat; and produce, as the result of their 
oxidation, carbonic acid. In order that the process may go on, it 
is of coarse necessary that oxygen, or atmospheric air, should have 
free access to the burning body; otherwise the combustion and 
evolution of heat cease, for want of a necessary agent in the chemi- 
cal combination. In all these instances, the quantity of heat gene- 
rated ia in direct proportion to the amount of oxidation ; and may 
be meaaured, either by the quantity of carbon consumed, or by that 
of carbonic acid produced. It may be made to go on, also, either 
rapidly or slowly, according to the abundance and purity in which 
oxygen ia auppHed to the carbonaceous substance. Thus, if char- 
coal be ignited in an atmosphere of pure oxygen, it barns rapidly 
and violently, raises the temperature to a high point, and is soon 
entirely consumed. On the other hand, if it be shut up in a close 
stove, to which the air is admitted but slowly, it produces only a 
slight elevation of temperature, and may require a much longer 
time for ita complete disappearance. Nevertheless, for the same 
quantity of carbon consumed, the amount of heat generated, and 



340 



AKIHAtr HBAT. 



that of carbonic acid produced, will be equal m the tvro cases. In 
one iu»laiiuti wu liavo » ra]Md cumbuBtioi), in the other a slow com- 
bustion ; the total effect being the same in both. 

Such is the mode in which heat is commonly produced by arU6- 
cial means. Its evolmion is here dependent upon two principal 
conditions, wbich ore essential to it, and by which it is always 
accompanied, viz., the coosumplion of oxygen, and the production 
of carbonic aeid. 

Now, since the two phenomena jast mentioned are presented 
also by the living body, and since they are accompanied here, too, 
by the production of animal hoai, it was vory natural to suppose 
that in the animal organization, as well as elsewhere, the internal 
heat must be owing to an oxidation or combustion of carbon. Ac- 
cording to Lavoisier, the oxygen taken into the lungs was sup- 
posed to combine immediately with the carbon of the pulmonary 
tissues and fluids, producing carbonic acid, and to be at once re- 
turned under that form to the atmosphere; the same quantity of 
heat resulting from the above process as would have been produced 
by the oxidation of a similar quantity of carbon in woo*) or coal. 
Accordingly, he regarded the lungs as a sort of stovo or furnace, 
by which the rest of the body was warmed, through the mediuna of 
the circulating blood. 

It was soon found, however, that this view was altogether erro- 
neous; for the slightest examination shows that the lungs are not 
perceptibly warmer than the rest of the body; and that the heat- 
producing power, whatever it may be, does not reside exclusively 
in the pulmouary tissue. Furthermore, Eubse<|ucnt investigations 
showetl the following very important facts, which wo have already 
mentioned, vi>:^ that the carbuoic auid is not formed in the lungs, 
but exists in the blood before its arrival in the pulmonary capilla* 
ries; and that the oxygen of the inspired air, so far from combining 
with carbon iu the luitgH, is taken up in solution by the blood- 
globules, and carried away by the current of the general circalation. 
It is evident, therefore, that this oxidation or combustion of the 
blood must take place, if at all, not in the lungs, but in the capiU 
larics of tbc various organs and tissues of the body. 

Liebig accordingly adopted Lavoisier's theory of the produotioQ 
of animal heat, with the above modification. He believed the heat 
of the anima! body to Iw produced by the oxidation or combustion 
of certain elements of the food while still circulating in the blood; 
these substances being converted into carbonic acid and water by 



AyiMAL BKAT. 



241 



the oxidatioD of tbeir ciirbon and hydrogen, and immediately ex- 
pelled from the body without ever Imving formed a part of the solid 
tissues. He therefore divided the food into two different classea of 
alimentary substances; viz,, 1st, the nitrogenous or plwilic elements, 
which are introduced in comparatively smoll quantity, and which 
Are to be actually converted into the substance of the tissues, such as 
albumen, muscular flesh, iic; and 2d, the hydi-o-carhons or rapiratory 
dements, such as sugar, starch, and fiit; which, according to his view, 
are taken into the blood solely to be burned, never being a^imilated 
or converted into the tissues, but only oxidised in tite circulation, 
sad immediately expelled, as al>ove. under the form of carbonic 
acid and water. He therefore regarded these elements of the food 
only Hs 60 much fuel ; destined simply to maintain the heat of the 
body, but taking no part in the proper function of nutrition. 

The above theory of nnimul heui has been vary generally adopted 
'l&d acknowledged by the medical profession until withiu a recent 
fwriod. A few years ago, however, some of its deficiencies and 
inconsistencies were pointeil out, by Lehmann in Germany, and by 
Kobin and Verdcil in France; and since that time it has begun to 
low ground and give place lo a different mode of explanation, more 
in accordance with the present state of physiological science. We 
believe it, in fact, U; be altogether erroneous; and incapable of 
explaining, in a satisfactory manner, the phenomena of animal heat, 
as exhibited by the living body. We shall now proc^icd to pass in 
review the principal objections to the theory of combustion, con- 
■idered as a physiological duetriud. 



L It is not stall ne^resAsry t^) rt^gard the evolution of beat as 

dependent solely on direct oxidation. This is only one of its 
sources, atf we see constantly in exlernal nature. The suu's raya, 
mechanical friction, electric currents, and more particularly a great 
variety of chemical action.", such as various saline combinations and 
decompositions, are all capable of producing heat; and even simple 
soluUons,such as the solution of caustic pota^isa in water, the mixture 
of Bolphurio acid and water,or of alcohol and water, will often pro- 
duce a very seusible elevation of lecnperature. Now we know that 
in the interior of the body a thousand diRereni actions of this 
nature are constantly going on; solutions, combinations and dccom- 
poaitioDS in endless variety, all of which, taken together, are amply 
soOicieot to account for the production of animal beat, provitletl the 
theory of combustion should be found insufficient or improbable. 
16 



242 



ANIMAL HEAT. 



II. In vcgctnbles tlicro is an internal production of he&t, as well 
as in animals; a fact which has been t'uUy (lemonstrnted by the 
experimenui of Diiirochet and others, already described. In vcge- 
tubleit, liuwever, Iho absorption of oxygen and exhalation of car- 
bonic ucid do not take place; excepting, to some extent, during the 
night. On iho contrary, t)ie diurnal prticess in vcgetablea, it is well 
known, is exactly the reverse of this. Under the influence of the 
solar light thty absorb carbonic acid and exhale oxygen. And it 
is exceedingly remarkable that, in Dulrocliet's experiments, be 
found that the evolution of heat by plants was always accompanied 
by the disappearance of carbonic acid and the exhalation of oxygen. 
Plants which, in the daylight, exhale oxygen and evolve heat, if 
placed in the dark, imn:tediately Wgin to absorb oxygen and exhale 
carbonic acid; and, at the same time, the evolution of heat is sus* 
pendcd. Dutrochet even found that the evolution of beat by plants 
presented u regular diurnal variation; and that its maximum of 
intensity was about the middle of the day, jusl at the time alien Ote 
absorption of carbonic acid a/id the exhalation of oxygen are going on 
iviih the grtalesl acUviiy. The proper heat of plants, therefore, can* 
uot be the result of oxidation or com bust ion, but must be dependent 
on an entirely diilerent process. 



I 
i 



III. In animals, the quantities of oxygen absorbed and of carbonic 
acid exhaled do not correspond with each other. Most frequently 
a certain amount of oxygen disappears in the boiiy, over and above 
that which is returned in the breath under the form of carbonic 
acid. This overplus of oxygen has been said to unite with the 
hydrogen of the food, so as to form water which also passes out 
by the tiings; but this is a pure assumption, resting on no direct 
evidence whatever, for wc have no experimental proof that any 
more watery vapor is exhaled from the lungs than is supplied by 
the fluids taken into the stomach. It is superfluous, therefore, to 
assume that any of it is produced by the oxidation of hydrogen. 

Furthermore, the pntporiion of overplus oxygen which disap- 
pears in the body, beside that which is exiialcd in the carbonic acid 
vf the breath, varies greatly in the same animal according to the 
quality of the food. Begiiault and Keiset' found that in dogs, fed 
on meat, the oxygen which reappeared under the form of carbonic 
acid was only 76 per cent, of the whole quantity absorbed; while 



I 



Aiiii&Ji;ii lid Chlinie el de Plj/MiiiU*, 3d 9«riv», xxvi. p. 428. 



AynrAL itbat. 24J 

in dogs fed on vegeutble substances it amountGd to over 90 per 
,eent lu some instaric<?j»,' where the animals (rabbiu and fowls) 
were fed on bread and grain exclusively, the projjortion of expired 
oxygen amounted to 101 or even 102 per cent.; that is, nvtreoxygm 
mWat actually eontained in the carbonic acidexhakd, Oian fuid been alh 
torbed in a/rce Btate/rom tfu almmphere. A portion, at least, of tbe 
carbonic acid must therefore have been produced by other means 
than direct oxidation. 

IV. It has already been shown, in a previous chapter, that the 
carbonic acid which is exhaled from the lungs is not primarily 
formed in the blood, but makes its appearance in the substance of 
tlie tissues themselves; and furthermore, that even here it does not 
originate by a direct oxidation, but rather by a process of decom- 
position, similar to that bv which sugar, in fermentntion, is resolved 
into alcohol and carbonic acid. We uoderatund frum this how to 
explain tbe singular fact alluded to in the last paragraph, viz., the 
ihnndant production of carbonic acid, under some circumstances, 
with a comparatively small supply of free oxygen. The statement 
made by Liebig, therefore, that starchy and oily matters taken with 
the food are immediately oxidized in the circulation without ever 
being aflsimilaled by the tissues, is without foundation. It never, 
in fact, rested on any other ground than a supposed probability; 
lud as we see that carbonic acid is abundantly produced in the 
body by other menns, we have no longer auy reasou for assuming, 
without direct evidence, the existence of a combustive process in 
the blood. 

y. l*he evolution of heat in the animal body is nut general, as it 
would be if it resulted from a combut^tion of the blooit ; but local, 
lince it takes place primarily in the substance of the tissues them- 
Belvea. Various causes will therefore produce a local elevation or 
depreosion of temperature, by modifying the nutritive chauges 
which take place in the tissues. Thus, in the celebrated experiment 
of Bernard, which we have often verified, division of the sympa- 
thetic nerve in the middle of the neck produces very soon u marked 
elevation of temperature in the corresponding side of the head and 
face. Local inflaminatii>n8, also, increase very sensibly the lenipcra- 
tare of the part in which they are seated, while that of the general 

> Aniwlvi de Chitnle rt <1« Khrtiqn*, M Mrf«*, nrl. pp. -iOD — ISl. 



244 



BSAT. 



mass of the blood is not nltered. Fiually it has been demonstrated 
by Bernard that in the natural state of the system there is a marked 
ditference ia the temperature of the different organs and of the blood 
returning from them.' The method adopted by this experimenter 
was to introduce, in the living anima}, the bulb of n fine thermo- 
meter successively into tlie bloodvessels entering and those leaving 
the various internal organs. The diAerence of temperature in those 
two situations showed whether the blood had lost or gained in heat 
while traversing the capillaries of the organ. Bernard found, in 
the iirst place, that the blood in passing through the lungs, so far 
from increasing, was absolutely diminished in temperature; the 
blood on the left side of the heart being sometimes a little more 
and sometimes a little less than one-third of a degree Fahr. lower 
than on the right side. This slight cooling of the blood in the 
lungs is owing simply to its exposure to the air through the pul- 
monary membrane, and to the vaporization of water which takes 
place in these organs. In the abdominal viscera, on the contrary, 
the blood i^ increaitcd in temperature. It is sensibly warmer in the 
portal vein than in the aorta; and very considerably warmer in the 
hepatic vein than in either the portal or the vena cava. The blood 
of the hepatic vein is in fact warmer than that of any other pars 
of the body. The production of heat, therefore, according to Ber- 
nard's observations, is more active in the liver than in any other 
portion of the system. As the chemical processes of nutrition are 
necessarily different in the diQ'erent tissues and organs, it la easy to 
understand why a specific amount of heat should be produced in 
each of them. A similar fact, it will be recollected, wns noticed by 
Dulrochet, in regard to the different parts of the vegetable orgau- 
iaation. 

TI. Animal he.it has been supposed to aland in a special relation 
to the production of carbonic acid, because in warm-blooded animals 
the respiratory process is more active than in those of a lower 
temperature; and because, in the same animal, au increase or 
diminution in tbe evolution of heat is aocompanied by a correspond- 
ing increase or diminution in the products of reapirntion. But 
this is also true of all the other excretory products of the body. An 
elevation of temperature is accompanied by an increased activity 
of ufl the nutritive processes. Not only carbonic acid, but the 



! 
I 



I 



■ Oiax«it« Il(-Ui<>n)adair«, Aug. 29 and Sw^i. 26, IttStJ. 




AN'IUaL HE.vT. 



245 



ingrdientsof the urine and the perspiration are flischargod in larger 
qaaiitity than usual. An increased supply of food also is required, 
as well as a larger quantity of oxygen ; and the digestive and 
secretory processes both go on, at the same time, with unusual 
acUvity. 



Animal heat, then, is a phenomenon which results from the 
simultaneoas activity of many diS'erent processes, taking place in 
many dtfTerent organs, and dependent, umloubtedly, on diflerent 
chemical changes in each one. The intruduetion of oxygen and 
the exhalation of carbonic acid have no direct connection with each 
other, but are only the beginning and the end of a long series of 
coDtinuoDS obangea, in which all the tiasuus of the body successively 
take a part. Their relation is precisely that which exists between 
the food introduced through the stomach, and the urinary ingre- 
dients eliminated by the kidneys. The tissues require for their 
nutrition a constant supply of solid and liquid food which Is intro- 
duced through the stomach, and of oxygen which is introduced 
through the lungs. The diaintegration and decomposition of the 
tissues give rise, on the one band, to urea, uric acid, &c., which are 
discharged with the urine, and on the other hand to carbonic ncld, 
which is exhaled fn.im the lungs. But the oxygen is not directly 
converted into carbonic acid, any more than the food is directly 
converted into urea and the urates. 

Animal tie:tt is nut to bo regarded, therefore, aa the result of a 
combuBtive process. There is no reason for believing that the 
greater part of the food is "burned^' in the circulation. It is, on 
the contrary, assimibted by the substance of the tissues; and these, 
in their subuequent disintegration, give rise to several excretory 
products, one of which is mrbonic acid. 

The numeroua cornbinationa and decomposition a which follow 
each other incessantly during the nutritive process, result in the 
production of an internal or vital heut, which is present in both 
animals and vegetables, and which varies in amount in different 
species, in the same individual at diiTerent times, and even io 
liSerent paria and organs of the same hotly. 



2i8 



THE CIRCULATION. 



CHAPTER XTV, 



THE CIRCULATION. 



The blood may be regarded aa a nutritious fluid, holding in 
solution all the ingro-lierit-s necensury for the formation of the 
tissues. In someaniiniila nnd vegetables, of the lowest organisation, 
such IIS infusorin, polypes, algie, and the like, neither blood nor 
circulntion is required; since all partaof the bcxly, Imviog a similar 
atruclure, absorb nourishment equally from the surrounding mcdin, 
and carry on nearly or quite the same chemical procesaea of growth 
and assimilation. In the higher animals and vegetables, however, 
as well as in the human subject, the case is different. lu them, the 
Btructure of the b*Kly ia cotnpnund. Diflerent organs, with widely 
difl'erent functions, are eituaietl in difl'erent parta of the frame; and 
each of these functions is more or less eaijential to the continued 
existence of the whole. In the intestine, for example, the procesd 
of digestion takes place; and the prepared ingredients of the food 
are thence abs<)ri>eil into the bloodvessuly, by which they are 
transported to distant tissues and organs. In the lungs, again, 
the blood absorbs oxygen which is afterward to be appropriated by 
the tt.HSuea; and carbuiiiu acid, which was produced in the tissues, 
is exhaled from tho lungs. In the liver, the kidneys, and the skin, 
other substances S'^ain are produced or eliminated, and these local 
proce.*«»es are all of them necessary to the preservation of the general 
organization. The circulating fluid is therefore, in the higher 
animals, a maaiis of tra»eporlaiwn, by which the substances pro* 
dueed in pariieular organs are dispersed throughout tho body, or 
by which substances produced generally in the tissues are conveyed 
to particular organs, in order to be eliminated and expelled. 

The circulatory appanitua consists of four diflbrcnt parts, viz: 
1st. Tho hfiart; a hollow, muscular organ, which receives the blood 
at one oriSce and drives it out, in successive impulses, at another. 
2d. The arteries; a series of branching tubes, which convey the 
blood from the heart to the different tissues and organs of the body. 




TDK HEABT. 



247 



3d. The capillarvfi; a aetwork of tnioutg inosculnting tubules, 
which are interwoven wiiU che substance of the tis»iies, and which 
hring the blood into iniimate contact with the cells (ind fibres of 
which they are oomposeti; and 4ih. The veins; a set of converg- 
ing vessels, destined to collect the blood from tfie capillaries, and 
return it to the heart. In uaub of these four dJtferurit part;) of the 
circalatory appnrataH, tho movement of ihe blood t8 peuuliar and 
dependent on special comlitiuns. It wi!l thcreiure require to be 
studied in each one of them separately. 



rilE HBART. 



^H The structure of the heart, and of the large vessels connected 
^BHth it, varie* onnsiderably in different clashes uf anitnaU, owing to 
^■he different arrangement of the respiratory organs. For the respi- 
^^atory apparatus being one of thij modt important in the boly, and 

the one most closelv connected 

by anatomical relations with *''?■ "^■ 

the orgOQH of circulation, the 

latter are neflessartly modifie-l 

in structure to <'orrca[>onrl with 

the former. In fish, for exam- 
ple (Fig. 76), the heart is an 

organ consisting of two princi- 
pal cavities: an ourlole (a) into 

which the blood is received from 

the central extremity of ihe 

vena cava, and a ventricle (&) 

into which the hlooil is driven 

by ihecontraction of the auricle. 

he ventricle is considerably 

arj^er and more powerful than 

the auricle, and by its contmc- 

tion drives the blood into the 

main artery supplying the gills. 

In the gills [cc) the blood is 

arterialized ; alYer which it is 

collected by the branchial veins. 

The»e veins unite upon the median line to form the aorta ('/) by 

wbtch the blood is Gimllv distributed throu;'huut the fratue. In 



rt 




C I «ri-L(TI n* nr Flan. — it. Aartcl*. *, 
Vratrlrln. «. UIIU. it Aiitta. M. Vm>(tariu 




24S 



THB CIRCrLATrOS. 



Fig. n. 



these nnimala ilic rcapiratory process is not a very active one; but 
llie sills, which are of small size, being the only respiratory organ*, 
nil the blood reiqulres to pass through them for purposes of aeration. 
The heart here ts a single organ, destined only to drive the blood 
(ram the terminution of the venoos oysLem to the capillariea of the 
gills. 

In reptiles, the heart Ih composed of two anriclee, placnl side by 
side, and one ventricle. (Fig. 77.) The vemu cava discharge their 

blood into the right auricle (a\ 
whence it passes into the ventricle 
(c). From the ventricle, a part of it 
is carried into the aorta and distri* 
butcd throughout the body, while a 
part is sent to the lungs through the 
pulmonary artery. Thearterioli^ed 
blood, returning from the lungs by 
the pulmonary vein, is disohargeil 
into the left auricle {b), and thence 
finto the ventricle (c), where it 
mingles with the venous blood 
which has just arrived by the venB 
cava.'. In the reptile, therefore, the 
ventricle is a common organ of pro- 
puUion, both for the lungs and for 
the general circulation. In these 
aniniaU the aeration of the blood lu 
the lungs is only partial; a certain 
portion of the blood which leaves 
the heart being carried to these organs, just as in the human subject, 
it is only a |)ortion of the b]oo<l which is i;arried to the kidney by 
the renal artery. This orrangetnent is suHlcient for the reptiles, 
because in many of theni, Huch as serpents and turtles, the lungs 
are muuh more extensive and eflicient, as respiratory organs, than 
the gills of fish; while in others, such as frogs and water-lizards, 
the integument itJ^elf, whiuh is nmist, smooth, and naked, takes an 
important share in the aeration of the bIoo<1. 

In quadru)>eds and the human species, however, the respi- 
ratory process is not only exceedingly active, but the luugs 
are, at the same time, the only organs in which the aeration uf 
the Wood can bo fully accomplished. In them, accordingly, we 
find the two circulations, general and pulmonary, entirely dis- 




Ci»''ct.«Tir>i« or KtrTii.ra —a. 
R1|til •ortcln A. L(<n norkk e Vcain«lt. 
4. iMBgi a. Aorl*- /, Vana Ckn. 



1 

i 



THE HBART. 



249 



thict from each uLher. (Fig. 78.) All the blood returning from 
tbe body by the veins must pa&a through the lungs before it is 
ftgaiD distribated throagh the 

arterial system. We have Plp' 78. 

therefore a double circula- 
tioD, and also a double henrt; 
the two sides of whiuh, 
though anited externally, 
are acparatA internally. The 
mammalian heart consists of 
B right auricle and ventricle 
(o, t), receiving the blood 
from the venn cava (i), and 
driving it to the lungs; and 
a lefl auricle and ventricle 
(/, y) receiving the bliKiil 
from the lungs nnd driving 
it outward through tbe Arte- 
rial systeou 

III the oomplete or double 
mammalian hearty the difler- 
ent parts of the organ present 
certain peculiarities and bear 

certain relations to each other, which it is necessary to understand 
before we can properly appreciate ila action and movements. The 
entire organ has a more or less conical form, its base being situntcd 
on the median line, directed upward and backward; the whole being 
suspended in the chest, and loosely fixed to the spinal column, by 
the great vesaela which enter an<l leave it at this point. The apex, 
on the contrary, is directed downward, forward, and to the left, sur- 
munded by the pericardium and the pericardial fluid, butcnpuhlo 
of a very free lateral and rotatory motion. The auricles, which 
have a smaller capacity and thinner walla than the ventriules, are 
situated at iho upper and pfisterior part of the organ (Figit. 79 and 
80); while the ventricles occupy its anterior and lower portions. 
The two ventricles, moreover, are not situated on the same plane, 
but tbe right ventricle occupies a poeiition somewhat in front and 
above that of the left; so that in an anterior view of the heart the 
greater portion of the lefl ventricle is concealed by the ri'^ht (Fig. 
79). and in a posterior view the greater portion of the right ven* 
tricle is concealed by the lefl (Fig. 80); while in both petitions the 



C[«ri'i.»T 111* 1 w M twit a Lr «i • — n. Rlchl 
■urfrla. A, Rlflii triiirioU. «. PuliniifiMjr ulvrjr. 
(t Lnnf*. t, Pulmvakry tfli. /. LafL karWI* f, 
L«rt r«iilr1cl«. h Aurta t VoBarBTii. 



THE HEART. 



S61 



pulmonary veins into the right and left auricles; the auriculo- 
ventricular oriBces leailing from tlie auricles into the vcDtricles; 
and the aortic and polmonary orifiaes lending from ibe ventricles 
into the aortic and pulmonary arteries respectively. 

The auricolo-ventriculnr. aortic and pulmonary orifices are fur- 
niahed with valves, which allow the blood to pass readily from the 
auricles to tbe ventrides, nod from the ventricles to the arteries, 
bat shut back, with the contmcttons of the organ, so as to prevent 
its return in an opposite direction. The course of the blood 
through the heart w. therefore, »s follows. From the vena cava it 
passes iolo the right auricle; and from the right auricle into the 
right ventricle. (Fig. 81.) On the contraction of the right ventricle, 
tbe tricuitpid valves shut back, provoiuiiig its return into the auricle 
(Fig, 82); and it is thus driven through the pulmonary artery to the 

rig. 83. 



I'*tr AriretiB AN* VKITRieLA: Iwrkalo-TMtrleulir ValrM«h»*d. ArlfTtal rilr«* orcD. 



iun^ Returning from the lungs, it enters the lefi auricle, theuce 
pwes into the left ventriclo, from which it is finally delivered into 
'lie aorta, and distributed throughout the body. (Fig. 83.) This 
n>ovement of the blood, however, through the cardiac cavities, is 
>ot a continuous and steady 6ow, but is accum))Iished by alternate 
contractions and relaxations of the muscular parietcs of the heart; 
M that with every i mpulse, successive portions of blood are received 
bj tlifl auriclts, delivered into the ventricles, and by them dis- 



262 



THK CIRCULATION. 



charged into the arteries. Each one of these successive avtionfi 
called u beat, or pulsation of the heart. 

Fi«. 63. 



Corn*! nr Itinon TtiaiiriiH thh IlKiiiir. — «, h %aiia caia, •wiirrMir uid lal 
t. Ktg)il ti-nirh^ln C PaltantiArj %tl*tj d I'ulmonarjr t*ib. c L*fl rgairtcle. /! Aorta. 

Each pulsation of tho heart is accompanied by certain important 
phenomena, which require to be studied in detail. These are tho 
tounds, tho movements, and the impulse, ^ 

The sounds of the heart are two in number. They can readily be 
heard by applying the ear over the cardiac region, when they are m 
found to be quite diU'erent from each other in position, in tone, and V 
in duration. They are distinguifibed aa the Jirst and «e<vri(/ Bounds 
of ihe lieHrt. The first sound is heard with the gM^tcat intenRity 
over the anterior surface of the heart, and more particularly over 
the i^fth rib and tho Bflh intercostal Rpac«. It is long, dull, and 
smothered in tone, and occupies otie<half the entire duration of ■ 
single beat. It corresponds in time with the impulse of the heart 
in the precordial region, and the stroke of the large arteries in the 
immediate vicinity of the chest. The second sound follows imme- 
diately upon the first. It is beard most distinctly at the situation 
of tho aortic and pulmonary valves, viz., over the sternum at the 
level of the third costal cartilage. It is short, sharp, and distinct 
in tone, and occupies only about one-qu.irtcr of the whole time of. 



1 




THE HEAKT. 253 

t palntion. It ia followed by an equal interval of Bilence ; after 
which the iirst sonnd again recurs. The whole time of a cardiac 
palsfttion may then be divided into four quarters, of which the first 
two are occupied by the first sound, the third by the second sound, 
and the fourth by an interval of silence, as follows:— 



Time of paluUon. 



3d ** Second Boand. 

4th " IntotTkl of silence. 



The oauM of the second sound is universally acknowledged to be 
the sadden dosnre and tension of the aortic and pulmonary valves. 
This &ot is cBtmblished by the following proofs: 1st, this soand is 
beard with perfect distinctness, as we have already mentioned, 
directly over the aitnation of the above-mentioned valves; 2d, the 
farther we reoede in any direction from this point, the fainter be- 
oomes the sonnet; and 6d, in experiments upon the living animal, 
(rfien repeated by different observers, it has been found that if a 
cn'nred needle be introduced into Uie base of the large vessels, so 
u to hook back the semilunar valves, the second sound at once dis- 
appears, and remains absent nntil the valve is again liberated. These 
valves consist of fibrous sheets, covered with a layer of endocardial 
epithqliam. They have the form of semilunar festoons, the free 
edge of which is directed away from the cavity of the ventricle, 
while the attached edge is fiutened to the inner surface of the base 
of the artery. While the blood is passing from the ventricle to the 
artery, these valves are thrown forward and relaxed; but when the 
artery reacts upon its contents they shut back, and their fibres, be* 
coming suddenly tense, yield a clear, characteristic, snapping sound. 
The production of the Jirst sound has been attributed by some 
writers to a combination of various causes; such as the rush of 
blood through the cardiac orifices, the muscular contraction of the 
parietes of the heart, the tension of the aurioulo-ventricular valves, 
the collision of the particles of blood with each other and with the 
sar&oeof the ventricle, iic. &c. We believe, however, with Andry' 
aad some others, that the first sound of the heart has a similar 
origin with the second; and that it is dependent altogether on the 
demre of the awicuh-ventricular valves. The reasons for this con- 
tloaon are the following : — 
lafc. The second sound is undoubtedly caused by the closure of 

' DiMuee of the Heart, Kneeland'a translation, fioatoii, Ii^, 



THE CIRCPI-ATrOH. 



the semilunar valves, and in the action of iho heart the shutting 
back of the two seta of valves allernale with each other precisely 
U clo the first and second sounds; and there is every probability, 
to say the least, tliat the sudden tension of the valvular fibres pro- 
Juoea a similar effect in each instance. 

2d. The &Tat sound is heard moat distinctly over the anteriorj 
surface of the venlricles, where the tendinous cords supporting thel 
Buriculo-ventriuutur valves are inserted, and where the sound pro- 
duced by the tension of these valves would be most readily cod- _ 
dact«d to the ear. f 

3d. There is no reason to believe that the cnrrent of blood 
through the cardiac onlices could give rise to an appreciable sound, 
so long as these onijcc»>r and the cavities to whiclt they lead, have 
their normal dimensions. An unnatural souffle may indeed origi- 
nate from this cause when the orifices of the heart arc dimioiahed 
in size, as by calcareous or fibrinous deposits; and it may also 
occur in cases of aneurism. A soufQo may even be produced aifl 
will in any one of the large arturi^s by pressing lirtnly upon" it 
with the end of a stethoscope, so as to diminish its calibre. But in 
all these instances, the abnormal sound occurs only in consequence 
of a disturbance in the natural relation existing between the volume 
of the blood and the size of tlie orifice through which it oassee. 
In the healthy heart, the different orifices of the organ arc in exact 
proportion to the quantity of the circulating blood ; and there is no 
more reason for believing that its paswage should give rise to a 
sound in the cardiac cavities than in the larger arteries or veioa. 

4th. The difl^erence in character between the two sounds of the 
heart depends, in all probability, on the different arrangement of 
the two sets of valves. The second sound is short, sharp, and dis- 
tinct, because the semilunar valves are short and narrow, superficialfl 
in their situation, and supported by the highly elastic, dense and 
fibroua bases of ihc aortic and pulmonary arteries. The first sound 
is dull and prolonged, because the auriculo-ventricular valves aral 
broad and deep-seated, an<l arc attached, by their long chordjsj 
tendineoe to the comparatively soU and yielding fleshy columns of 
the heart. The diBbrence between the first and second sounds can, 
in fact, be easily imitated, by simply snapping between the fingera 
two pieces of tape or ribbon, of the same te.\ture but of different 
lengths. (Fig. 64.) The short one will give out a distinct and sharp 
sound; the long one a comparatively dull and prolonged sound. 

Together with the first sound of the heart there is also to bo] 



"1 



THE HEART. 265 

lieard a slight /ric^i'on aovnd, produced by the collision of the point 
of the heart against the parietes of the chest. This sound, which is 
heard in the fiflh intercostal space, is very faint, and is more or less 

Fig. 64. 




nuked by the strong vaWular sound which occurs at the same 
time. It is different, however, in character from the latter, and 
may UBoally be distinguished from it by careful examination. 

The movemmta of the heart during the time of a pulsation are 
of m peculiar character, and have been very often erroneously 
deaoribed. lu fact altogether the best description of the move 
menta of the heart which has yet appeared, is that given by Wil- 
liam Harvey, in his celebrated work on the Motion of the Heart and 
Blood, published in 1628. He examined the motion of the heart 
by opening the chest of the living animal ; and though the same or 
■milar experiments have been frequently performed since his time, 
tbe descriptions given by subsequent observers have been for the 
most part singularly inferior to his, both in clearness and fidelity. 
The method which we have adopted for examining the motions of 
dte heart in the dog is as follows: The animal is first rendered 
insensible by ether, or by the inoculation of woorara. The latter 
mode is preferable, since a long-continued etherization seems to 
exert a sensibly depressing effect on the heart's action, which is 
not the case with woorara. The trachea is then exposed and 
opened just below the larynx, and the nozzle of a bellows inserted 
wd secured by ligature. Finally, the chest is opened on the me- 
disn line, its two sides widely separated, so as to expose the heart 
tnd lungs, the pericardium slit up and carefully cut away from its 
attachments, and the lungs inflated by insufflation through the 
trachea. By keeping up a steady artificial respiration, the move- 



256 



I 



ments of the hcnrt may he matie to continue, in favorable cases,! 
more than an hour: and its notions ma}' bo studied hy direct o\ 
viition, like those of any external organ. 

The examination, however, requires to be conducted with ccrtaia 
precautions, which are indispensable to success. When the heart 
is first exposed, its movements are so complicated, and recur with 
such rapidity, that it ia difficult to distinguish them perfectly from 
each other, and to avoid a certain degree of confusion. Singular 
ns it may seem, it is even dilTicnlt at first to determine what [wriixi 
in the lieart's pulsation corresponds to cootraction, and what tafl 
relaxation of the organ. We have even seen several medical men, 
watching together the pulsations of the same heart, unable to agree 
upon this point. It ia very evident, indeed, that several Knglish 
and continental observers have mistaken, in their examinations, tbe^ 
contraction for the relaxation, and the relaxation for the contrao* ■ 
tioQ. The 6rst point, therefore, which it is necessary to decide, in 
examining the aucceaaivo movements of a cardiac pulsation, ia thfr 
following, vi?,: Which is the con(ractio7i and wkicfi Uu relaxation of 
the venlriclfBT The method which we have adopted la to pass a 
small silver caniila directly through the parietes of the left ven- 
tricle into its cavity. The blood is then driven from the external 
oriflcG of the canula in interrupted jets; each jet indicating the 
time at which the ventricle contracts u[)on its contonta. The 
canulfl is then withdrawn, and the different muscular layers of the 
ventricular walla, crossing each other obliquely, dose the ofwning, ^ 
80 tliat there is little or no subsequent hemorrhage. f 

When the successive actions of contraction and relaxation have 
by this means been fairly recognized and distinguished from each 
other, the cardiac pulsations are seen to be characterized by the 
following phenomena. The changes in form and position of tbef 
entire heart are mainly dependent on those of the ventricles, which 
contract simultaneously with each other, and which constitute much 
the largest portion of the entire mass of the organ. ■ 

1. At the time of its contraction the heart hardens. This pheno- 
menon is exceedingly well marked, and ia easily appreciated by 
placing the finger upon the ventricles, or by grasping them between m 
the finger and thumb. The muscular fibres become swollen and 
indurated, and, if grasped by the hand, communicate the sensation 
of a somewhat sudden and powerful shock. It ia this forcible indu- 
ration of the heart, at the time of contraction, which has been mis- 
taken by some writers fur an active dilatation, and described 




TUB HEART. 267 

snch. It is, however, a pbenomenon precisely similar to that which 
takes place in the cootraction of a voluntary muscle, which becomes 
swollen and indurated at the same moment and in the same propor- 
tion that it dimiDisbes in length. 

2. At the time of contraction, the ventricles elongate and the 
point of the heart protrudes. Tbis phenomenon was very well 
described by Dr. Harvey.' "The heart," he says, "is erected, and 
risea upward to a point, bo tbat at tbis time it strikes against the 
breast and the pulse is felt externally." The elongation of the 
ventricles daring contraction has, however, been frequently denied 
by subsequent writers. The only modem observers, so far as we 
are aware, who have recognized its existence, are Drs. C. W. Pen- 
nock and £dward M. Moore, who performed a series of very careful 
and interesting experiments on the action of the heart, in Philadel- 
phia, in the year 1839.* These experimenters operated upon calves, 
sheep, and horses, by stunning the animal with a blow upon the 
bead, opening the chest, and keeping up artificial respiration. They 
observed an elongation of the ventricle at the time of contraction, 
and were even able to measure its extent by applying a shoemaker's 
rule to the heart while in active motion. We are able to corroborate 
entirely the statement of these observers by the result of our own 
experiments on dogs, rabbits, frogs, &c. The ventricular contrac- 
tion is on active movement, the relaxation entirely a passive one. 
When contraction occurs and a stream of blood is thrown out of 
the ventride, its sides approximate each other and its point elon- 
gates; 80 that the transverse diameter of the heart is diminished, 
and its longitudinal diameter increased. This can be readily felt 
by grasping the base of the heart and the origin of the large vessels 
gently between the first and middle fingers, and allowing the end 
of the thumb of the same hand to rest lightly upon its apex. 
With every contraction the thumb is sensibly lifted and separated 
trom the fingers, by a somewhat forcible elevation of the point of 
the heart 

The same thing can be seen, and even measured by the eye, 
in the following manner: If the heart of the frog or even of any 
small warm-blooded animal, as the rabbit, be rapidly removed from 
the chest, it will continue to beat for some minutes afterward ; and 
when the rhythmical pulsations have finally ceased, contractions 

■ Wnrki or William Harrer, H. D. Sjr/leTiham ed., Loudon, 1847, p. 21, 

■ PhlUdvlpblk Medical Kztmltivr, Ko. 44. 

17 



258 



THB CIBCULATIOIf. 



can ftill be rea<^ily exviled by touching the heart with the point 



the heart be now held by 



the 



A Steel neeille. II tbe t:eart tie now 
thumb anJ finger, with its puint diretiteU upward, it will be seen 
to have a pyramidal or conical form, representing very nearly in 
its outline an equilateral triangle (Fig. t>5); it^ base, while in a 
condition of rest, bulging out laleraJty, while the apex is compara- 
tively obtuse. 



a.vC'K^^ 



Pig. 85. 



Fi|. 8S. 








Ma^K* lit Fbo* 
In a MM* vt NilaXk- 
duB, 




0tji«T or Pfto* la uameilMu 



Vig. 87- 



y^^ ^ ...When the heart, held in tins position, is touched with the point _ 
p.'^f a needle (Fig. Btl), it atarta up, becomes inatanily narrower and f 
. . . longer, Ms sides approximating and its point rising to an acute 
fT angle. This contraction is immediately followed by a relaxation; 

rvL^^A. 1 the point of the heart sinks down, and its sides again bulge out- 
ward. H 
l^^l tX.^ i*«t us now see in what manner this change in the figure of the 
a i\ f V vcTitrides during contraction is produced. If the muscular fibres 

of the heart were arranged in the form of 
simple loopa, running parallel with the 
axis of the organ, the contraction of these 
fibres would merely have the effect of di- 
minishing the bv&u of the heart in every 
direction. This effect can be seen in the 
accompanying hypothetical diagram (Kig. 
87), where the white outline represents J 
8uch simple looped fibres in a state of re- 
laxation, and the dotted internal line indi- 
cates the form which ihey would take iafl 
contraction. In point of fact, however, 
. . , none of the muscular 6brea of the heart 

IkVli^ K ' run parallel to its longitudinal axis. They are diapoeed, on the 
contrary, in a direction partly spiral and partly circular. The inoai 
tibrcs surt from the base of the ventriclea, am' 




I 






Diagram »l Si]ir[.B LuariD 

Piaari, in tpUuiii.iii 1,1111 cii' 




TBE HEART. 



269 



towftrd the apex, curling round the heart in Buch a manner ag to 
pass over iU anterior surface in an obliquely spiral direction, from 
above downward, and from right to left. (Fig. 88.) They converge 

toward the point of the heart, curl* 
**»• *8* ing round the centre of itsapei, and 

then, changing their direclion, be- 
come deep-seated, run upward along 

Fig. 69. 








Larr VaxraiabK or 

Bci.L«eK'i H It ART, (bow. 
1b| tta Jmji abrM. 



the septum and internal surface of the ventricles, and terminate 
in the oolutnnsB curnea:), and in the inner border of the auriculo- 
ventricular ring. The deepest layers of fibres, on the contrary, ore 
wrapped round the vcntriclc.<J in a nearly circular direction (Kig. 
ts9); their pointn of origin and attachment being still the auriculo- 
ventricutar ring, aud the points of the fleshy columns. The entn^ 
arrangement of the muscular bundles may be readily seen in a 
heart which has been boiled for nx or eight bourn, ao as to soften 
the oonnecting areolar tissue, and enable the 6bn^us layers to be 
easily separated from each other. 

By far the greater part of the mass of the fibres have therefore 
a circular instead of a longitudinal direction. When they contmcty 
their action tends to draw the lateral walls of the ventricles together, 
and thus to diminish the transverse diameter of the heart; but as 
each muscular fibre becomes thickened in direct proportion to ite 
oontractioQ, their combined lateral swelling necessarily pushee out 
iho apex of the ventricle, and the heart elongates at the same time 
tbal its sides are drawn together. This effect is illustrated in the 
accompanying diagram (Fig. 90), where tlie white lines show the 
figure of the heart during relaxation, wilb the course of its circular 



260 




TBB CIECULATlOff. 



Fig. 9(1. 




til»|iiiiB ■•rriK<riAa Final* 
ar THE lliAKT, &M ibeK «Mt- 



fibres, while the dotted line shows the narrowed and dongated 
figure necessarily produced by their coutraclion. This phenomeaun, 

therefore, of tbe prutrusioa of the apex 
of tbe heart at the time of contniciiciD, is 
not only fully established by observaitoD. 
but is readily explained by the anfttomical 
structure of the orgsn. 

3. Simultaneously with the hardeaiag 
and elongation of the heart, its apex move 
slightly from lef^ to right, nod rotales also 
DpoD its own axis In tbe same directioa. 
Both these moTements result from tbe 
peculiar spiral arrangmnont of t^c cardiac 
fibres. If we refer again to tbe preceding: 
diagrams., we shall see that, provided the 
fibres were arranged in eimplo loogituJi- 
Tial loop9(Pig.87),theircontraction would 
merely have the effect of drawing the point of the heart directly 
upward in a straight line toward its base. On the other hand, if 
they were arranged together in a circular direction (Fig. 90), tbe 
apex would be simply protruded forward, also in a direct line, 
without deviating or twisting either to tbe 
right or to the left. But in point of Gut, 
the superficial fibres, as we have already 
described, run spindly, and curling round 
ihe point of the heart, turn inward towanl 
its base; so that if tbe apex of the organ be 
viewed externally, it will be seen that tbe 
super^cial fibres converge toward ita ceo- 
tral point in curved lines, as in Fig. 91. It 
13 well known that every curved tnuscalar 
fibre, at tbe time of its shortening, necMU- 
rity approximates more or less to • straigfat 
line. Its curvature is diminished in exact proportion to the exteol 
of its contraction; and if arranged in a spiral form, its coDtmctioa 
tends in the same degree to untwist the spiral. During the con- 
traction of the heart, therefore, its apex rotates on its own axis io 
tbe direction indicated by the arrows in Fig, 91, vIk., from left I^H 
right anteriorly, and from right to lell posteriorly. This prodatri^n 
a twisting movement of the apex in the above direction, whteb la 



Ffg. 91. 




(' . . > r > ■ 11 I ■ u P I > K r • -if 

lUK ArKxov ma IJiaiit, 





TUX HEART. 261 

▼ery perceptible to the eye at every pulsation of the heart, when 
expoeed in the living animal. 

4. The protrQBion of the point of the heart at the time of con- 
traction, together with its rotation upon ita axis from left; to right, 
brings the apex of the organ in contact with the parietes of the 
chest, and produces the shock or impulse of the heart, which is 
Teadily perceptible externally, both to the eye and to the touch. 
In the human subject, when in an erect position, the heart strikes 
the chest in the fiftib intercostal space, midway between the edge of 
the sternum and a line drawn perpendicularly downward from the 
left nipple. In a supine position of the body, the heart falls away 
from the anterior parietes of the chest so much that the impolse may 
disappear for the time altogether. This alternate recession and 
advance of the point of the heart, in relaxation and contraction, 
is provided for by the anatomical arrangement of the pericardium, 
tod the existence of the pericardial fluid. As the heart plays back- 
vard and forward, the pericardial fluid constantly follows its 
movements, receding as the heart advances, and advancing as the 
heart recedes. It fulflls, in this respect, the same purpose as the 
BfDovial fluid, and the folds of adipose tissue in the cavity of the 
Urge articalations; and allows the cardiac movements to take place 
to their fall extent without disturbing or injuring in any way the 
kdjacent organs. 

6. The rhylhm of the heart's pulsations is peculiar and somewhat 
complicated. Each pulsation is made up of a double series of con- 
tractions and relaxations. The two auricles contract together, and 
afterward the two ventricles; and in each case the contraction is 
immediately followed by a relaxation. The auricular contraction 
ia short and feeble, and occupies the first part of the time of a 
pulsation. The ventricular contraction is longer and more powerful, 
and occupies the latter part of the same period. Following the 
Tentricular contraction there comes a short interval of repose, afWr 
which the auricular contraction again recurs. The auricular and 
Tentricnlar contractions, however, do not alternate so distinctly 
vitb each other (like the strokes of the two pistons of a Are engine) 
aa we should be led to believe from the accounts which have been 
given by some observers. On the contrary, they are connected and 
oontinaous. The contraction, which commences at the auricle, is 
immediately propagated to the ventricle, and runs rapidly from the 
(mm of the heart to its apex, very much in the manner of a jyeri- 
italtic motion, except that it is more sudden and vigorous. 



292 



THE CIRCITLATION. 



William Harvey, again, gives a bettor acconnt of thia part of i 
hearths action than has been published by any subsequent writer. 
Tbc following exceedingly graphic and appropriate deacriptton, 
takea from his book, ahows that be derived bis koowlodgo, not ' 
from any secondary or hypothetical sources, but from direct and^ 
careful study of tbe phenomena in ibe living animal. H 

"First of all," he says,' "the auricle contracts, and in the coarac ' 
of its contraction throws the blood (which it coutains in ample 
quantity as the bead of the veius, the storehouse and cistern of Um 
blood) into the ventricle, which being filled, the heart raises itself 
straightway, makes all its ^bres tense, contracts the rentriclea, and 
performs a beat, by which beat it immediately sends the bloody 
supplied to it by the auricle, into the arteries; the right vcntricli 
sending its charge into the lungs by the vessel which is called veosl 
arteriosa, but which, in structure and function, and all things elw, 
is an artery; the \e(l veutricle seodiug ita charge into tbe aorta, ^ 
and tliroUjL^h thia by the arteries to the body at large. ^ 

"These two motions, one of the ventricles, another of the auricles^" 
take place consecutively, but in such a manner that there is a kind 
of harmony or rhythm preserved between them, the two concurring 
in such wise that bat one motion is apparent, especially in the 
warmer blooded animals, in which the movements in question ars 
rapid. Nor ia this for any other reason thao it is in a piece of 
machinery, in which, though one wheel gives motion to another, 
yet all the wheels seem to move simultaneously; or in thai 
mechanical contrivauce which is adapted to Bre-arms, where the 
trigger being touched, down comes the flint, strikes against tbe 
steel, elicits a spark, which falling atnung the powder, it is ignited, 
upon which the flame extends, enters the barrel, causes tbo explo- 
sion, propels tbe ball, and the mark is attained ; all of which inci* 
dents, by reason of the celerity with which they happen, seem to 
take place in the twinkling of an eye." 

The above description indicates precisely the manner in which 
tbe contraction uf the ventricle follows successively and yet cod- 
tinuoQsly upon that of the auricle. The entire action of the auricle 
and veutricles during a pulsation is accordingly as follows: Tbe 
contraction begins, as we have already stated, at the auricle. 
Thence it runs immediately forward to the ajKix of the heart. The 
entire ventricle contracts vigorously, its walls harden, its Bp« 



■pp. oil., p. 31. 



THI ABTBBIE8 AND THE ARTERIAL CIRCULATION. 263 

protrudes, strikes against tbe walls of tbe ohest, and twists from 
left to right, the anriculo-ventrioalar valves shut back, tbe first 
aoand is produced, aad tbe blood is driven into the aorta and 
polmonaiy artery. These pheuomena occupy about one-half the 
time of an entire pulsation. Then the ventricle is immediately 
relaxed, and a short period of repose ensues. During this period 
tbe blood flows in a steady stream from the large veins into the 
auricle, and through the auriculo-ventricular orifice into the ven- 
tricle; filling tbe ventricle, by a kind of paraive dilatation, about 
two-thirds or three-quarters full. Then the auricle contracts with a 
quick sharp motion, forces the last drop of blood into tbe ventricle, 
distending it to its full capacity, and then tbe ventricular contraction 
fidlowB, aa above described, driving the blood into the large arteries. 
These movements of contraction and relaxation continue to alter- 
nate with each other, and form, by their recurrence, tbe successive 
cardiac pulsations. 

THE ABTKRIBS AND THE ARTERIAL CIRCULATION. 

The arteries are a series of branching tubes which commence 
with the aorta and ramify throughout the body, distributing tbe 
blood to all tbe vascular organs. They are composed of three 
Qoata, viz: an internal homogeneous tunic, continuous with the 
mdocardium; a middle coat, composed of elastic and muscular 
'fibnn; and an external or "cellular" coat, composed of condensed 
layers of areolar tissue. The essential anatomical difference be- 
tween the larger and the smaller arteries consists in the structure 
of their middle coat In the smaller arteries this coat is composed 
tacdnsively of smooth muscular fibres, arranged in a circular man- 
ner around the vessel, like the circular fibres of the muscular coat 
of the intestine. In arteries of medium size the middle coat con- 
tuns both muscular and elastic fibres; while in those of the largest 
odibre it conaists of elastic tissue alone. The large arteries, ac- 
eordingly, possess a remarkable degree of elasticity and little or no 
eoDtractility; while the smaller are contractile, and but little or not 
It all elastic. 

It is found, by measuring the diameters of the successive arte- 
rial ramifications, that the combined area of alt tbe branches given 
off from a tmnk is somewhat greater than that of the original 
fsnal; and therefore that the combined area of all the small arte- 
nesmust be considembly larger than that of tbe aorta, from which 



THS CIRCULATION. 



1 
I 



the arterial Bystem origtDates. As the bloo(], coDseqaentlj, ia its 
passage from the heart outward, flowa sncccsfliveljr through larger 
and larger spoces, the rapidity of its circulation roust necessarily 
be diminished, in the same proportion as it recedes from the heart. 
It ia driven rapidly through the larger trunkft, more slowly through 
those of medium size, and more slowly alill as it approaches tho 
termination of the arterial system and the commencement of the 
capillaries. 

The movemeni of tfie itfood through the arteries is primarily caused 
by tho couinictionflof the heart; but is, at the same time, regulated 
and modified by the elasticity of the ressels. The mode in which 
the arterial circulation takes place is as follows. The arterial sys- 
tem is, as we have seen, a vast and connected ramificatiou of tabular 
canals, which may be regarded as a great vascular cavity, divided 
and subdivided from within outward by the successive branching 
of its vessels, but communicating freely with the heart and aorta 
nt one extremity, and with the capillary plexus at the other; 
and this vascular system is iilleii everywhere with the circulating 
fluid. At the time of the heurt'a contraction, the muscular walla of _ 
the ventricle act powerfully upon its fluid contents. The auricolo- I 
ventricular valves at the same time shutting back and preveating 
the blood from regurgitating into the ventricle, it is forced out 
through the aortic oriRce. A charge of blood is therefore driven 
into the arterial ramifications, distending their walls by the addi- 
tional quantity of fluid forced into their cavities. When the ven- 
tricle immediately ailerward relaxes, the active distending force is 
removed; and the elastic arterial walls, reacting upon their contenta, 
would force the blood back again into the heart, were it not for the 
semilunar valves, which shut together and close the aortic orifice. 
The blood is therefore urged onward, under the pressure of the ■ 
arterial elasticity, into the capillary system. When the arteries 
have thus again partially emptieil themselves, and returned to their 
original dinionsiun^, they are again distended by another contraction 
of the heart. In this manner a succession of impulses or distensions 
arc produced, which alternate with the reaction or subsidence of ibe 
vessels, and which £aa be felt throughout the body, wherever the 
arterial ramifications penetrate. This phenomenon is known by 
tho name of the arterial puhe. 

When the blood is thus driven by the cardiac pulsations into the 
arteries, the vesseU are not only distended laterally, but are olongate<l 
08 well as widened, and enlarged iu every direction. Particularly 



Tie. »2. 



THS ARTBRtBS AXD TBB A.BTERTAL OIBOULATION. 265 

when the vessel takes a curved or serpentine course, its elungatiou 
nnd the increase of its curvatures may be observed at every pulsa- 
tion. This may be seen, for example, in the temporal, or oven 
in the radial arteries, in emaciated persons. It ia also very well 
seen in the mesenteric arteries, when the abdomen is opened in the 
living animal. At every contraction of the heart the curves of 
the artery on each side become more strongly pronounced. (Fig. 
92.) The vessel even rises op partially out of its 
bed, particularly where it runs over a bony sur- 
face, as in the case of tlie radial artery. In old 
persons the curves of the vessels become perma- 
nently enlarged from frequent distension; and all 
the arteries tend to assume, with the advance of 
age, a more serpentine and even spiral course. 

But the arterial pulse has certain other pecu- 
liarities which deserve a special notice. In the 
first place, if we place one finger npon the chest 
at the situation of the apex of the heart, and an- 
other upon the carotid artery at the middle of 
the neck, we can distinguish little or no diflerctice 
)Q time between the two impulses. The diaten- EUn«.ti.jii nuj f«tt»- 
■ioQ of the carotid seems to take place at the '»"»'•'> A«T»iii ix 
aame mstant with the contraction ol the heart. 
But if the second finger be placed upon the temjjoral artery, instead 
of the carotid, there ia n perceptible interval between the two beats. 
The impulse of the temporal artery is felt a little later than that of 
the heart. In the same way the pulse of the radial artery at the 
wrist saems a little later than that of the carotid, and Unit of the 
posterior tibial at the nnklejointa little later than that of the radial. 
So that, the greater the distance from the heart at which the artery 
is examined, the later is the pulsation perceived by the Snger laid 
upon the vessel. 

But it has been conclusively shown, jmrticularly by the inverti- 
gations of M. Marey,* that this diSerence in time of the attcrial 
pulsations, in different parts of the body, is rather relative than 
absolute. By the contraction of the heart, the impulse is commu- 
nicated at the same instant to all parts of the arterial system; but 
the apparent diftercncc between them, in this respect, depends upon 
the fact, that, although all the arteries begin to be distended at the 



■ Dr. Brmra-S^nard'a jAumat <1« niTnielngio. April, 1859. 



THB CIBC^TLATIOH. 



aamo moment, yet those nearest the heart are distended suddenly 
and rnpidly, while for those at a distance, the distension takes place 
more alowly and gradually. Tlius the impulse given to the finger, 
which marka the cxindltion of maximum disteasioD of the vessel, 
occurs a little later at a distance from the heart, than in immediate 
proximity. 

This modification of the arterial pulse is produced in the follow- 
iog way : — 

The contraction of the left ventricle is a brusque, vigorous and 
sudden motion. The charge of blood, thus driven into the arterial 
system, meeting with a certain amount of resistance from the fluid 
already filling the vessels, does not instantly displace and force 
onward a quantity of Uood equal to its own mass, but a large 
proportioa of its force is used in expanding the distensible walls 
of the vessels. In the immediate neighborhood, therefore, the 
expansion of the arteries is sadden and momentary, like the con- 
traction of the heart itself. But this expansion requires for its 
completion a certain cxpetiditure, both of force and time; ao ihal 
at a little distance farther on, the vessel will neither be distended 
to the same degree nor with the same rapidity. At the more dis* 
tant point, accordingly, tiie arterial impulse will be less powerful 
and will arrive at its maximum more slowly. 

On the other band, when the heart beuomcs relaxed, the artery 
in its immediaco neighborboad contracts upon the blood by its own 
elasticity; and as its contraction at this time meets with no other 
resistance than that of the blood in the smaller vessels beyond, it 
drives a. portion of its own blood into them, and thua supplies these 
veaeels with a certain degree of diHteniling force even in the inter- 
vals of the heart's action. Thus the difference in size of the carotid 
artery, at the two perio<ls of the heart's contraction and its rclaxa^ 
tion, is very marked; for the degree of its distension is great when 
the heart coutraots, and its own reaction aflerward empties it of 
blood to a very considerable extent. But in the small bmnchca of 
the radial or ulnar artery, there is less distension at the time of the 
cardiac contraction, because thia force ha^t boon partly expended in 
overcoming the elasticity of the larger vessels; and there is less 
emptying of the vessel afterward, because it is atill kept partially 
filled by the reaction of the aorta and its larger branches. In other 
words, there is progressively less variation in 8i?:e, at the periods of 
distension and collapse, for the smaller and distant arteries than for 
those which are larger and nearer the heart. 



i 



FEBIES AlHl 



n"Al&tERlAL CIBOULATION. 267 



^f r, Marej bas illustrated these facta by ao exceedingly ingenious 
and efleutualcoutrivaoce. He attached to the pipe uf a small forcing 
pomp, to be worked by alteraate strokea of the piston, a long elastic 
tube open at the farther extremity. At differeot points upon this 
lube there rested little movable le^era, which were raised by tho 
distension of the tube whenever water was driven into it by the 
forcing pomp. Each lever carried upon its extremity a small pen- 
cil, which marked upon a strip of paper, revolving with uniform 
rapidity, the lines produced by its alternate elevation and depression. 
By these currea, therefore, both the extent and rapidity of distension 
of different parts of the clastic taho were accurately registered. 
Jhe curves thus produced were as follows: — 

Fig. 93. 



Cvavivo' '■■ AiTBit«L PiIL*Atlos, at lltnatniMl hy U Umr'i «sp«rlMaBl,'-t. lt«u 
Ifc* dUlADJIftf rwM, 1. Al ft dUUBM Itaoi IL 3. Still fltnli«t r*m&T«d. 



It will be seen that the whole lime of pulsation is everywhere of 
equal length, and that the distension everywhere begins at the same 
moment. But at the beginning of the tube the expansion is wide 
and ludden, and occupies only a sixth part of the entire pulsation, 
while all the rest is taken up by a slow reacliou. At the more 

€ole point*, however, the period of expansion becomes lunger 
that of collapse shorter; until at 8 the two periods are com- 
ely equali/.e<l, and the amount of expansion is at the same time 
reduced oue-balf. Thus, the farther the blood passes from the heart 
outward, the more uniform is its Bow, and the more moderate the 
distensiun of the arteries. 

Owing to the alternating contractions and relaxations of the heart, 
accordingly, the blood posses through the arteries, not in a steady 
stream, but iu a aeries of welling impulses; and the heraorrbaga 
from a wounded artery is readily distinguished from venous or 
capillary hemorrhage by the fact that the blood flows in successive 

t^, as well OS more rapidly and abundantly. If a puncture be 
ade in the walls of the ventricle, and a slender canuht introduces* 



268 



THB CIBCULATIOir. 



the flow of the blood through it is seen to be entirely intflrmitlent. 
A strong jet takes place at each ventricular contraction, and at each 
rehutation the flow is completely inlerrui)ted. If the puncture he 
made, however, in any of the large arteries near the heart, the 8ow 
of blood through the orifice is no longer intermittent, but ia con- 
tinuous; only it is very much stronger at the time of ventricular 
contraction, and diminishes, though it does not entirely cease, at 
the time of relaxation. If the blood were driven through a series 
of perfectly rigid and unyielding tubes, its flow would be every- 
where intermittent; and it would be delivered from an orifice situ- 
ated at any point, in perfectly interrupted jets. But the arteries 
are yielding and elastic; and this eliisticity, as we have already 
explained, moderates the force of the separate arterial pulsations, 
and gradually fuses them with each other. The interrupted or 
pulsating character of the arterial current, therefore, which is 
strongly pronounced in the immediate vicinity of the heart, becomes 
gradually lost and equalized, during its passage through the vessels, 
until in tbo smallest arteries it is nearly imperceptible. 

The same etlect of an elastic medium in ecjualixing the force of 
aa interrupted curront may be shown by fitting to the end of a 
common syringe a long glass or metallic tube. Whatever be the 
length of the inelastic tubing, the wnter which is thrown into one 
extremity of it by the syringe will be delivered from the other end 
in distinct jels, corresponding with the strokes of the piston ; but if 
the metallic tube bo replaced by one of India rubber, of sufBcieot 
length, the elasticity of this substance merges the farce of the sepa- 
rate impulses into each other, and the water is driven out from the 
farther extremity in a ccntiuuuus stream. 

The elasticity of tlie arteries, however, never entirely equalizes 
the force of the separate cardiac pulsations, since a pulsating cha- 
racter can be seen in the flow of the blood through even the smallest 
arteries, under the microscope; but this pulsating character dimi- 
nishes very considerably from the heart outward, and the current 
becomes much more continuous in the smaller vessels than in the 
larger. 

The primary cause, therefore, of the motion of the blood in the 
arteries is the contraction of the ventricles, which, by driving out 
the blood in interrupted impulses, distends at every stroke the 
whole arterial system. But the arterial pulse is not exactly syn- 
chronous everywhere with the beat of the heart; since a certain 
amount of time is required to propagate the blood-wave from the 



THE AATSRIES AKD THE ARmiAL CTItCri.ATTON. 269 



centre of the circulation oatwftrd. The pulse of the radial »n«ry 
at tbe wrist is perceptibly later than that of the heart; and the 
pulse of the [wstcrior tibial at the ankle, again, porocptiblv later 
than that at the wrist. The arterial ciroulation, acsordingly, is not 
an entirely aimplo phenomenon; but is made np of the combined 
effects of two different physical forces. In the first place, there is 
the elasticity of the entire arterial system, by which the blood is 
sabjected to a constant and uniform pressure, qoite independent of 
the action of the heart. Secondly, ihure is the alternating contntc- 
tioQ and relaxation of the heart, by which the blood is driven in 
rapid and successive impulses from the centre of the circalation, to 
be thence distributed throughout the body. 

The passage of the blood ihrou>;h the arterial system takes place 
under a certain degree of constant pressure. For these vessels being 
everywhere elastic, and filled with blood, they ct^nstantly t«:nd to 
react, more or less vigorously, nn-i to compress the circulating fluid 
which they contain. If any one of the arteries, aocordlngly, be 
opened in the living animal, and a glass tube inserted, the bIoo4i 
will immediately be seen to rise in the tube to a height of about 
five and a half or six feet, and will remain at that level; thus indi- 
cating tbe pressure to which it was subjected in the interior of the 
vessels. This constant pressure, wbicb is thus due to the reaction 
of the entire arterial system, is known as the arterial preMure. 

The degree of arterial pressure rnay be easily measured by con- 
necting the open artery, by a flexible tube, with a small reservoir 
of mercury, which is provided with a narrow upright glass tube, 
open at its upper extremity. When the bltxid, therefore, urged by] 
the reaction of the arterial walU, pre«ea upon the surface of the 
mercury in the receiver, the mercury rises in the upright lube, to 
a correspoudiug height. By the use of this instrument it is seen,' 
in tbs first place, that the arterial pressure is nearly the same all 
over the body. Since the cavity of the arterial system is every- 
where oontinooos, the pressure must necessarily be communicated, 
by the blood tn its interior, equally in all directions. Accordingly, 
the constant pressure is the same, or nearly so, in the larger an J tb« 
smaller arteries,, iu those nearest the heart, and those at a distance. 
This constant pressure averages, in the higher quadrupeds, sixi 
inches of mercury, which is equivalent to from five and a half to 
>ix feet of blood. 

It is also men, however, in employing such an instrument, that 
the level of the mercury, in tbe upright tube, ia not perfectly steady, 



270 



THB CIRCULATIOW. 



but rises and fslls with the pulsations of the henrt Thus, At ererj 
contraction of the ventricle, the mercury risea for about half art 
inch, an<i at every relaxation it falls to its previous leveL Thus the 
instrument becomes a inemture, not only for the constant pressareof 
the arteriefl, but also for the intermitting pressure of the heart; and 
on that account it has received the name of the cardiometer. It ia 
seen, accordingly, that each contraction of the heart ia superior in 
foroe to the reaction of ihe arteries by about one-twelfth; and these 
vessels are kept filled by a succession of cardiac pulsations, and 
discharge their oonteuts ia tura into the capiUaries, by their 
eliurtic reaction. 

The rapidity with which the blood circulates through the artet 
system is very great. Its velocity ia greatest in the immediate 
Detghborbuod of the heart, and diminitihes somowhai as tiie blood 
recedes farther and farther from the centre of the circulation. Tbii 
diminution in the rapidity of the arterial current is duo to the aufr 
cessive division of the aorta and its primary branches into amalldrj 
aad Hmaller ramifications, by which the total calibre of the arlerid' 
system, as we have already mentioned, is somewhat inoroased^ Thai 
blood, therefore, flowing through a larger space as it passes oacwapJ,! 
necessarily goes more slowly. At the same time the increased' 
extent of the arterial parietes wiih which the blood cornea ia ooo> 
tact, as well as the mechanical obstacle arising from the division of j 
the vessels and the separation of the streams, undoubtedly oontii- 
bute more or Ictis to retard the currents. The mechanical ubmdc,' 
however, arising from the friction of the blood against the wmllaof j 
the vessels, which would be very serious in the. case of water ortuaj 
similar fluid flowing through glass or metallic tubes, has compaia* 
tively little eflect on the rapidity of the arterial oiroulattoo. TUa 
can readily be seen by microscopic examination of any tntnfiparefrt 
and vascular tissue. The internal surface of the arteries is so sniooUi 
and yielding, and the consistency of the circulating fluid so aeco* 
rately adapted to that of the vessels which contain it, thai the 
retarding eflecta of friction are reduced to a minimum, and the 
blood in flowing through the vessels meets with the least posaitde 
resistance. 

It is owing to this fact that the arterial circulation, though some- 
what slower toward the periphery than near the heart, yel retains 
a very remarkable vuluuily throughout; and even iu arteries of tb« 
minutest size it is so rapid that ihe shape of the blood-globules can- 
not be distinguished in it on microscopic examination, but only i 



THE ABTEBIB8 AND THE ARTBBIAL CIBCULATION. 271 

niDgled current shooting forward with increased velocity al every 
ardiac patsation. Volkmann, in Germany, has determined, by a 
■ory ingenious contrivance, ihe velocity of the current of blood in 
ome of the large sized arteries in dogs, horscii, and calves. The 
nstrument vhich he employed (Fig. 94) coDsisted of a roelallio 
yliuder (a), with a perfonitiun running from end to end, and cor- 
wponding in size with the artery to be examined. The artery was 
divided transversely, and its cardiac extremity fastened to the 
>er end (6) of the instrument, while its peripheral extremity was 



Kg. M. 



Fig. M. 



3^ 



TfttiM*|i«'« lrr*aATVt Hrntuahagiha ra»l4llrorih«BrtarikI«lr«itUlloB. 



ID ihe same manner to the lower end(e). The blood 

>rding1y still kept on itfl usual course; only pasMng for a short 

ince thnsugh the nrtificial lube (a), between the divided extremi- 

IDfthearlery. The instrument, however, was provided, il» shown 

|ihe aocompaitjring figures, with two transverse cylindrical plugs. 

perforated; and arranged in such a manner, that when, at a 



272 



THE CIBCULATION. 



given signal, tlio two plugs were suddenly turned in opposhal 
direciiutis, the stream of blood wuuld be lurited uut of its course? 
(Fig. 95), and made to traverse a long bcDt Lube of glass {d^d, d},. 
before again finding its way buck to the lower portion of the anerr. : 
In tbis way t!ie diatauce passed over by the blood in a given time 
oould be readily measured upon a scale attaubed to the side of the 
glass tube, Volkmann found, as the average result of his obser- 
vations, that the blood moves in the carotid arteries of warm-blouded 
qoadrupuds with a velocity of 12 inches per second. 



VENOUS CIRCULATIOIf. 

The veins, which collect the blood from the tisanes and return tt 
Co the heart, are composed, like the arteries, of three coats; an inner, 
middle, and exterior. In structure, they differ from the arteries in 
containing a much smaller qu&niity uf muiycular and clastic fibres, 
and a larger proportion of simple condensed areolar tissue. They 
are consequently more flaccid and comprciutiblc than the anerteia, 
and less elnalic nnd contractile. Tiiey are furthermore distin- 
guished, throughout the limbs, neck, and external portioDS of the 
head and trunk, by being provided with valves, consistingurBbrous 
she^ta arranged in the form of festoons, nnd so placed in the cavity 
of the vein as to allow the blood to pas.^ readily from the periphery 
toward the heart, while tbey prevent altogether its reflux in an 
opposite direction. 

Although the veins nre provided with walls which are very inach 
thinner und less elastic than those of the arteries, yet, contrary to 
what wc might expect, their capacity for resiiiance to pressure ift 
equal, or even superior, to that of the arterial tubes. Mllno Kd' 
wards' has coUoiuttid the results of various experiments, whieh show 
that iho veins will sometimes resist a pressure which is sufficient lo 
rupture the walla of the arteries. In one inst-inco the jugular vein 
8upporte<l, without breaking, a pressure equal lo a column of water 
im feet in height; and in another, the ili&u vein of a sheep resisted 
a pressure of more than four atmospheres. The portal vein was 
found capable of resisting a pressure of six atmospherea; and in 
one case, in which the aorta of a sheep was ruptured by a pressure 
of 158 pounds, the vena cava of the same animal supported a pren* 
BurO'equa] to 176 [wunda. 



■ Lacuna sur la I'hjr>ioloK[«, &n,, toI- It. p. 301. 




TBMOOS CIRCt'LATlOS. 



273 



This reaisuince of the veins is to be attributed to tlio Inr^o pro- 
portion of white fibrous tissae whteh enters into their composition ; 
tho same tissue whit-h forma nearly ihu whole of the tendon a nml 
fa-sciffi, aod which is Uistiuguished by its density and unyielding 
nature. 

The eUutteitt/ of the veins, however, ts much le^a ihnn thai of the 
arteries. When they are filled with blmul, ihey enlarge to a certain 
itixe, and cullape« again when the pressure is taken oft'; but they do 
not react by virtue of an elastic resilienoe, or, at least, only in a 
slight extent, as compared wiih the arteries. Aucordingly, when 
the arteries are out across, as we know, and emptied of blood, They 
still remain open and pervious, retaining the tubular form, on ac- 
count of the elaxticity of their walls; while, if tbu veins bu irvuted 
in the same way, their sides simply fall together and remain in con- 
tact wiih each other. 

Another peculiarity of the venous system is the afmti'hnre of 
the sejtarale thaimels. which it aQords, for the 6ow uf L>lood from 
the periphery towards the centre. I'he arteries pass directly from 
the heart outwant, each separate branch, as a general rule, going 
to a separate region, and supplying that part of the body wiih 
ftll the bloiNl which it re«iuires; so that the arterial system is kept 
oonsUintly filled to its entire capacity with the blood which passes 
through it. But that is not the case with the veins. In injeclet) 
preparations t>f the vascular system, we have often two, three, 
four, or even five veins, coming together from the snme region of" 
the body. Tlicre »re also abundant Inosculations between the ilif- 
ferent reins. The deep veins which accompany the brachial artery 
inosculate freely with onch other, and u\wi with the superficial veins 
of the arm. ]u the veins coming from the head, we have the ex- 
ternal jugular comiiii)ni(.-ating witti the thyroid veins, the anterior 
jugular, and the brachial veins. The external Bud internal jugulars 
communicate with each other, and the two thyroid veins also form 
ao abundant plexus in front of the trachea. 

Thus the blood, coming from the extremities toward the heart, 
flows, not in a single channel, but in many channels; and as the^ 
vhanuels commuuicale freely with eucli other, the blood passes some* 
times through one of them, and sometimes through another. 

The flow of bloixl through the veins is less powerful ami rogalar 
than that through the arteries. It depends ou the oombiue^l autU 
uf ibrev diflervDt forces. 
14 



274 



THE CIRCCLATION. 



1. Thtfmrx of aspiration of the thorax. — When the chest exjKtndis 

by the lifting of tlio rilw and the (keoent of the diaphragfn, its 
movement, of course, tends to dimintsb the pressure exerted upon 
its content^ and no has the effect of drawing into the thoracic cavity 
nil tlie fluids which cnn gain acces8 Ut it. The expanded cavity is 
prititipallj 6lled by the air, which passes in through the tmchea 
and fills the bronchial tubes and pulmonary vesicles. But the 
bIcKxl in the veins is also drawn into the chest at the same time and 
by the same force. This force of aspiration, exerted by the ex[>an- 
sion of the chest, is gentle and unlfurm in character, like the move- 
menta of respiration tht^mselves. Accordingly itH influence is ex* 
tended, without doubt, to the farthest extremities of the venous 
tiyHteiii, the blood being gently solicited toward the heart, at each 
expansion of the chest, without any visible alteration in the size of 
the veins, which are titled up from behind as fast aa they are emptied 
in front. 

But if the movement of inspimtion be sudden and violent, instead 
of gentle and ea8y,a diflFerenteffect is produced. For then the walla 
of the vt^im^ which are thin and lluccid, cannot retain their position, 
but collapse under the external pressure too rapidly to allow ibi 
biciud U) flow in from behind. In this vase, tfaenifuro, the vein ts 
simply emptied in the immediate neighborhood of the chesty bat 
ihe entire venous circulation is not assisted by the movement. 

The same difference in the effect of an easy and a V^iolent suction 
movement, may bo readily shown by attAohing to the nozzle of an 
nir-tight syringe a flexible elastic tube with thin walU, and placing 
the other extremity of the tul>e under water. If the piston of the 
i^yringo be now withdrawn with a gentle and gradual motion, the 
water will be readily drawn up into the tube, while the tabe itself 
suflers no visible change; but if the suction movement be made 
rapid and violent, the tube will collapse instantly under the pres- 
sure of (he air, and will fail to draw the water into its cavity. 

A similar effect shows itaelf in the living boi^y. If the jugular 
or siiltuiavinn vein be exposed in a dog or cat, it will be aeea that 
while the movements of respiration are natural and easy no fluc- 
tuation ill the vein can be perceived. But as soon aa the respira- 
tion becomes disturbed and tairartous, then at each inspiration the 
vein is collapsed and emptied; while during expiration, the chest 
being strongly compressed and the inwartl Sow of the blootl arreeted, 
the vein becomes turgid with blooil whiuh accumulates in it from 
behind. In young vhildren, also, the spasmodic raovements uf res- 



TEX^OUS CIRCl-LATtON. 



275 



pintion in crying prtvluce a similar tnrgescence and enj^orgoment 
of tlie large rein» during expiration, while iliey nre momentarily 
etiiptied (luring ihe hurried and forcible inspiration. 

In notural and quiet respiration, therefore, the movements of the 
chest hasten tind aasm the venous circulation; but in forced or 
laborious respiration, ihey do not assist and may even retanl its flow. 

2. The contradion of the vohintary rm'scles. — The veins wbich 
eoQvey the blood through the liinba, and the parielcs of the head 
and trunk, lie among voluniJiry muacles, which are more or less 
constantly in a state of alternate contraction and relaxation. At 
b every contraction these muscles become swollen latendly, and, of 
coarse, compress the veins whieh nrc situated between them. The 
bloo{l, driven out from the vein by this pressure, cannot regurgitate 
toward the capillaries, owing to the vulvcs, already described, which 
shut bock and prevent its reflux. It is accordingly forced onward 
towaitl the heart; and when the muscle relaxes and the vein is 
Liberated from pressure, it again fills up from behind, and the cir. 
eulation goes on as before. This force is a very elTicieot one In 
producing the venous circulation ; since the voluntary muscles are 
more or less active in every -position of the IkkIv, and tlie veins 
cunstanily liable to be compressed by them. It is on this nccouot 



Fig.se. 



Fig. VJ. 



V^ 



V«t« with vaIvw Djwa. 



bl.iuil |)AHlng nil \ij ■ Uinrml cbuDnal 



that the veins, in the external parts of the body, communicate sn 
freely with each other by transverse brnnches; in order that the 
eorrent of blood, which is momentarily excluded from one vein by 



276 



THE CITlCUtATIOX, 



the pressure of the muscles, mtiy readily And a passage througli 
otliers, whiuh communicate by cross branches witb ihe first. (Figs. 
96 and 97.) 

8. The /oree nf the capillary cirettia/ion. —Th'^s last cause oT tba ■ 
motion of tlie blood thrniigh ihe veins is the most important of all, 
1)8 it is the only oue wbicti is uoiiataiitly and uutversally active. In _ 
fish, for example, reupiratioti is performed alto^'clher by gilla; and f 
in reptiles the air is furce<l down into the lungs by a kind of deglu* 
litioii, injitciid of being drawn in by the expansion of the chest. In. h 
neiltier of these classes, therefore, can the movements of respiration 9 
assist meehanicoliy in the uiroulation of the blood. In the splsneh- 
nic cavities, again, of all the vertebrate animnls, the veins coming ■ 
from the internal organii, an, for example, the cerebral, pulmonaryi v 
portal, hepatic, and renal veins, are unprovided with valves; and 
the pns&aye of the blood through them cannot therefore be effected 
by any luieral prc&iure. Tlie circulation, however, constantly going 
on in the capillaries, everywhere tends to crowd the rsdiules of the 
veins with blood; and this visa lergo, or pressure from behind, fills 
the whole venous system by a constant and steady accumulation. 
So long, therefore, aa the veins are relieved of blood at their cardiac 
extremity by the regular pulsations of the bean, there is no back* 
ward pressure to oppose the impulse derived from the capillary cir 
eulation; and the movement of the blood through the veins continuea 
in a fitciidy and unifiirm course. ■ 

With regHrd to the rapiditi/ of the venous circuhtioii, do direct 
rcHtilta have been obtained by cxpfirimonL, Owing to the flaccidity 
of the venous purietes, and the readiness with which the flow offl 
bloo'l through them is difilurbcd, it is not possible to determine this 
point for the veins, in the same manner as it has been determined 
for the arteries. The only calculation which has been made in thia 
respect U based upon a coinjiartson of the total capacity of the 
nrterinl and venous systems. As the same blood which passes out- 
vf&rd through the arteries, passes inward again through the veins, 
the rapidity of its flow in each must be in inverse proportion to the 
capacity of the two sets of vessels. That is to t^y, a quantity of 
blood which would pasji in a given time, with a velocity of x, 
through un opening ec^ual to one square inch, would pass during 
ihe same time through an opening equal to two square inches, with 
ii velocity of j; and would recjuire, on the other hand, a velocity 
of 2 X, to pass in the same time through an opening equal to one- 
half a square inch. Now the cupneity of the entire venous system^ 





THB CAPILLaRT CIRCULATION. 



277 



I 



I 



THE CAPILLABT CIRCULATION. 



when distended by injection, is about twice as grent as that of the 
entire arterial system. During life, however, the venous system is 
at no time ao completely filled with blood as is the case with the 
arteries; and, making allowance for thu difference, wc find tliat thu 
entire quantity of venous blood is to the entire quantity of arterial 
blood nearly as three to two. The velocity of the venous blood, 
as compared with that of the arterial, is therefore as two to three; 
or about 8 inches per second. It will be tiiiderstood, however, that 
this calculation is altogether approximative, and not esnct; since 
the venous current varies, according to many diffcront circumstances, 
io different parts of the body; being slower near the cnpilluriea, 
and more rapid near the heart. It expresses, however, with suffi- 
cient accuracy, the relative velocity of the arterial and venous cur- 
rents, at corresponding parta of their course. 

■ The capillary bloodveasela are mjimte inosculating tubes, which 

■ permeate the vascular organs in every direction, ami bring the 
bloud into intimate contact with the substance of the tissuea. They 
an continuous with the terminal ramiUcations of the arteries on 
the one hand, and with the com- 
mencing rootlets of the veins on 
the other. They vary somewhat 
in aize in different orgnna, and in 
different species of animals; their 
average diameter in the human 
aabject being a tittle over , q'q J^ of 
an inch. They are composetl of 
a single, transparent, homogene- 
ous, somewhat elastic, tubular 
membrane, which is provided at 
varioufl intervals with fattened, 
oval nuclei. As the smaller arte- 
lies approach the capillaries, they 
dininiab constantly in size by 
Boeeeasive subdivision, and lose 
first their external or fibrous 
tunic. They are then composed 

only (if the internal or homogeneous cont, and the middle or muscu- 
lar. (Fig. 98, a.) The middle coat then diminishes in thicknea", 



J 



FIf. 98. 




lii>brMkln( ap iDlprapIUartw. tnm lhaj>Ai 
mattr. 



278 



TRIE 01ROVT.ATIOX. 



until it is reiluced to a single layer of circular, fusiform, nnstriped, 
tnuiKuIar fibres, which in their tura disappear altogether, ss the 
urtury inurgus at laat in the capillurius; leaving unly, as we have 
Qlready mentiuned, a simple, homogcneoas, nacleatud, tubular mem* 
branc, which is continuous with the internal arterial tunic. 

The capillaries are further distitiguitiheJ from both arteries and 
veins by their frequent inosculjiiion. The arteries constantly 
divide And subdivide, as they pasd from within outward; while 
the veins as constantly unite with each other to form larger and 
less numerous branches and trunks, as they pass from the circum* 
fenfnce toward the centre. But the capillaries simply inosculate 
with each otlicr in every diroction, in such a manner as to form an 
interlacing network or plexus, the eapiUary plertu (Kig. 99), which 
i* exceedingly rich and abundant in some organs, less so in others. 
'i'he spaces included between the meshes of the capillary network 
vary ul.so, in shiipe as well as in size, in diHi^rent parts of the body. 

In the muKCular i).4<)U6 thej 
^'8- ■"*■ form long paiallel'»graina; in 

the areolar tissue, irregular 
shapeless figures, corrBS[>ond* 
ing with the direction of the 
6brous bundles of which the 
tissue is composed. In the 
mucous membrane of the 
large intestine, the copillnrioa 
include hexagonal or nearly 
circular spaces, Inclosing the 
oriGces of the fullicle^ii. In 
the papillieof the tongue and 
of the skin, and in the tufts 
of the placenta, they are 
arranged In long spiral loops, 
and in the adipose tissue in wide meshes, among which the fat 
vesicles are entangled. 

The motivn of (he Hood in the cfptllariei mny be studied by 
examining under the microscope any Lranspai~eiil tiscme, of a 
sufficient degree of vascularity. One of the most convenient parts 
for this purpose is the web of the frog's foot When properly 
))repured and kept moistened by the occasional addition of water 
to the integument, the clrculntiou will go on in its vessels for an 
indefinite length of time. The blood can be seen entering the 



CAriLtlKT BvvwoKX DruB wabarrnj'* fiHif. 




THB CAPILLaST CIRCL'LATIoy. 



279 



field by ibe. smaller orteriea, shooting along through tbem vitb 
great rapidity and in successive itnpulses, and flowing off again by 
tbe veins at a somewhat sluvrer rate. In the capillaries themselves 
tbc circulation is considerably less rapid than ia either the arteries 
or the veins. It is also perfectly atendy and uninterrupted in its 
Dow. The blood passes along in a unit'orm and continuous cnrrent, 
without any apparent coniracliou or diluuitiou of tbe vessels, yery 
mach as if it were Sowing 

. , , , A Fl«. 100. 

through glass tubes. An- 
other very remarkable pe- 
culiarity of the capillary 
circulation is that it has no 
definite direction. The nu- 
merouij streams of which it 
is composed (l''ig. lOO) do 
not tend to the right or to 
the left, nor towar^l any one 
pBtticuJur jwint. On the 
contrary, they pass above 
nnd below each other, ai 
right angles to each otber^s 
course, or even in opposite 
ilircctions; ao that the blood, 
while in the caplHaries, merely circtilates promiscuously among 
the lissu&t, in such a manner as to come ioliniately iu contact with 
every part of tbeir substance. 

The motion of the white and r&\ globules in the circulating blood 
is also peculiar, and shows very distinctly the diflercnco in their 
consistency nnd other physical properties. In the larger vessels 
the rod globules are carried along in a dense column, in the central 
psrt of the stream; while near the edges of the vessel there is ii 
trans|uirent space occupiad only by the clear plasma of the blood, 
in which no red globules are to be seen. In iho smaller vcssetn, 
the globules pass along in a narrower column, two by two, ur 
following each other in single file. The nu.\ibility and serai-tluid 
consistency of these gh^bulcs arc here very apparent, from the 
readincas with which they become folded up, bent ur twisted in 
taming comers, and the ease with which they glide through minute 
branches of communication, smaller in diameter than themselves. 
Tbe white globules, on the other hand, flow more slowly und with 
greater difficulty through the vessels. They drag along the exteir- 




CAFILtAKT ClBCVL«TI«l Ik W«k Of fttg** IML 



S80 



THE CIRCUtjATlOS. 



nal portions of llie current, and are sometimes momentarily arrests 
Bppnreiitly adhering for a few seconds u> the intertint surfaoe of the 
vessel. Whenever the current is obstructed or retarded in any 
manner, t^e white globules accumukte in the affected portion, and 
become more numerous there in proportion to the red. 

It IB during the capillnry circulation that the blood serves for 
the nutrition of the vascular organs. Its fluid poniona slowly 
transude through the walU of the vcmcIs, and are absorbed by the 
tissues in such proportion as is requisite for their nourishmeot. 
The saline subslAuces enter at once into the composition of the 
surrounding parts, generally without undergoing any change. The 
phosphate of lime, for example, is taken up in large quantity by 
the bones and cartilages, and in smaller quantity by the softer parts ; 
while the chlorides of sodium and potasnium, the carbonates, sul- 
phates, kc^ are appropriated in special proportions by the diflerent 
tissues, according to the quantity necessary for their organizstioQ. 
The albuminous ingredients of the blood, on the other hand, are 
not only absorbed in a similar manner by the animal tissues, but at 
the same time are transformed by catalysis, and converted into new 
materials, characteristic of the different tissues. In this way are 
produced the musculine of the muscles, the osteioe of the bones, the 
<^a^tilagine of the cartilages, &.G. &.c. It is probable that this tmus- 
formation docs not take place in the interior of the vessels them- 
selves; but that the organic ingredients of the blood are absorbeil 
by the tissues, and at the same moment converted into new mate- 
rials, by contact with their substance. The blood in this way fur- 
nishes, directly or indirectly, all the materials necessary for the 
nutrition of the body. 

The physical condiiioDs which influence the movement of the 
bl'(K)d in the capillaries, are somewhat dilTerent from those which 
regulate the arterial and venoua circulations. Wo must remember 
that as the arteries jiassfrom tlie heart outward they subdivide and 
ramify to such an extent th.it the surface 0>f the arterial walls js 
very much increased, in proportion to the quantity of blood which 
they contain. It is on this account that the arterial pulsation is ^u 
much equal)7.ed at a distance from the heart, since the inHuence of 
the elasticity of the arterial coats is thus conataiitiy increased ft-oni 
within outward. But as these vessels finally reach the conlinea of 
the arterial system, having already been very much increjtsed in 
number and dirnintiiljed in si^&e, they then suddenly brt-ak up into 



THE CAPTLtAHY OIROULATIOS. 



281 



B terminal ramificitioti of still smaller and more numerous vessels, 
and BO lose themselves at last in the capillnry network. 

B; this 6n!il increase of the vasoular surface, the equalization of 
the beartV action is oompleted. There is no longer any intermitting 
or pulsatile character in the force which acts upon the circulating 
fluid; and the blood, accordingly, ia delivered from ilio arteries 
into the capillaries under a perfectly continuous and uniform pres- 
sure. 

This pressure is suflicieat to cause thft blood to pass with coa- 
giderable rapidity, through the capillary plexus, into the commence- 
ment of the veins. Thin fact was first demonstrated by Prof. 
Sbarpey,' of London, who employed an injecting syringe with a 
double nozzle, one extremity of which was connected with a mercu- 
rial gauge, while the other was inserted into the artery of a recently 
killed animal. When the syringe, filled with defibrinated blood, 
was fixed in this position and the vessels of the animal injected, the 
defibrinated blood would press with equal force npon the mercury 
in the gauge and upon the 6uid in the blood vessels; and thus it 
was easy to ascertain the exact amount of pressure required to force 
the defibrinated blood through the capillaries of the animal, and to 
make it return by the corresponding vein. In this way I*rof. 
Sharpey found that when the free end of the injecting tube was 
attached to the mesenteric artery of the dog, a pressure of 90 milli- 
metres of mercury cuused the blood to pass through the capillaries 
of the intestine and of the liver; and that under a pressure of 130 
millimetres, it flowed in a full stream from the divided, extremity 
of the vena cava. 

We have also performed a similar experiment on the vessels of 
the lower extremity. A full grown healthy dog was killed, and 
the lower extremity immediately injected with defibrinated blood, 
by the femoral artery, iu order to prevent coagulation in the smaller 
vessels. A syringe with a double flexible nozzle was then filled 
with defibrinated blood, and one extremity of its injecting tube 
attached to the femora) artery, the other to the mouthpiece of a 
cardiometcr. By making the injections, it was then found that the 
defibrinated blood ran from the femoral vein in a continuous stream 
under a pressure of 120 millimetres, and that it wosdisuharged very 
freely under a preasure of 180 millitncLrcs. 

Since, as we have already seen, the arieriat pressure upon the 



' Tmlil anil Uowtuin, rii^iiu!<i^iciil .^nAlnuiy and rii>«i><it<>^ uf Man, rol. ii, p. 



S&o. 



282 



rBE CIBCULATIOX. 



blood 18 equal to six inches, or 160 millimetres, of mercury, it ifl 
evident tliat this pressure is sufficient to propel the blood tbrougli 
tbo capillary circulation. 

Beside, the bluod is not alto^ther relieved from the influence of 
elasticity, afler it has left the arteries. For the cajilllaries them- 
selves are elastic, notwithstanding the delicate texture of tbeir 
walls; aod even tfae tissues of the organs which they travene 
possess^ in many instoDcea, a considerable share of elasticity, owing 
to the iDtnute elastic dbres which are scattered through their aub- 
stance. These elastic fibres are found in considerable quantity io 
the lungs, the spleen, the skin, the lubulat«d glands, and mure or 
less in the mucous membranes. They are abundant, of course, in 
the fibrous tissues of the extremities, in the faiscias, the tendons, and 
the intermuscular substance. 

In the experiment of injecting the ves?«cls of the lower extremity 
with dcEibrinatcd blood, it' the injection be stopped, tho blood does 
not instantly cease flowing from the extremity of the femoral vein, 
but continues for a short time, until the elasticity of the intervening 
parts is exhausted. 

The same thing may be observed even in the Uver. If the end 
of a water-pipe be inserted into the portal vein, tind the liver in- 
jected with water un<ler the pressure of a hydrant, the liquid will 
distend the vessels of the organ, and pass out by the hepatic veins. 
Bat if the portal vein be suddenly tied or compressed, so as to shut 
ofl" the pre:ssurc from behiud, the stream will continue to run, for 
several seconds afterward, from the hepatic vein, owing to the re- 
action of the organ itself u[>oii tho iluid contained in its vessels. 

As a general rule, also, the capillaries do not suffer any backward 
preftsure from the venous system. On the contrary, as wjon as the 
blood has been delivered into the veins, it is hurried onward toward 
the heart by the compression of the muscles and the action of the 
venous valves. 'The right side of Llie heart iLscIf continuet! the same 
process, by its regular contractions, and by the action of ila own 
valvular apparatus; so thai the blood is constantly lifted away from 
llic capillaries, by the muscular action of the surrounding parts. 

These are the most important of the mechanical influences under 
which the blood moves through the continuous round of the circu- 
lation. The heart, by its alternating contractiona aud relaxations, 
and by the backward play of its valves, continually urges the blood 
forward into the arterial system. The arteries, by their dilatable 
and elastic walls, convert the cardiac pulsations into a uniform and 



THE CAPILLARY CIUCULATIOX. 28S 

Steady pressure. Under this pressure, the blood passes through the 
capillary vessels; and it is then carried backward to the heart 
through the veins, assisted by the action of the muscles ami the 
respiratory movements of the chest 

At the same time there are certain phenomena which are very 
important in this respect, and which show that various local in- 
fluences will either excite or retard the capillary circulation in par- 
ticular parts, independently of the heart's action. The pallor or 
suffusion of the face under mental emotion, the congestion of the 
mucous membranes during the digestive process, the local and de- 
fined redness produced in the skin by an irritating application, are 
all instances of this sort. These phenomena are usually explained 
by the contraction or dilatation of the smaller arteries immediately 
supplying the part with blood, under tbe influence of nervous 
action. As we know that the smaller arteries are in fact provided 
with organic muscular fibres, this may undoubtedly have something 
to do with the local variations of the capillary circulation; but the 
precise manner in which these Lftects are produced is at present 
unknown. 

The rajmfity oi the circulation in the capillary vessels is much 
less than in the arteries or the veins. It may be measured, with a 
tolerable approach to accuracy, during the microscopic examination 
of transparent and vascular tissues, as, for example, the web of the 
Trog's foot, or the mesentery of the rat Tbe results obtained in 
this way by difTerent observers (Valentine, Weber, Volkmann, &c.) 
show that the rate of movement of the blood through the capil- 
laries is rather less than one-thirtieih of an inch per second; or not 
quite two inches per minute. Since the rapidity of the current, as 
we have mentioned above, must be in inverse ratio to the entire 
i-alibre of the vessels through which it moves, it follows that the 
united calibre of all the capillaries of the body must be from 350 to 
400 times greater than that of the arteries. It must not be sHp- 
jKMed from this, however, that tbe whole quantity of blood contained 
ill the capillaries at any one time is so much greater than that in 
the arteries; since, although the united calibre of the capillaries is 
very large, their length is very small. The effect of the anatomical 
Htructure of the capillary system is, tberefore, merely to disseminate 
u comparatively small quantity of blood over a very large space, so 
that the chemicu-phyaiological reactions, necessary to nutrition, may 
take place with promptitude and energy. Fur the same reason, 
iilthuugh the rate of movement uf the blood in these vesciela is very 



284 



THI OIRCDLATIOir. 



slow, yet as the distance to be passed over between the arteries nn^ 
veins is very small, the blood really requires but a short time to 
traverse the capillary system, and to commence its returning passage 
by the veins. 

OBNBRAI, COSSIDEl^ATIOXS. 

The rapidity with which the blood passes through the entire round 
nf the circulation is a point of great interest, and one wbiuh has 
received a considemble share of attention. The results of such 
experiment's, as have been tried, show that this rapidity is much 
greater than would have been anticipated. Bering, Poisseuille, and 
Matteucci,* have all experimented on this subject in the following 
manner. A solution of fcrrocyanide of potassium was injected 
into the right jugular vein of a horse, at the same time that a liga- 
ture was placed upon the corresponding vein on the left side, and 
an opening made in It above the ligature. The blood Bowing from 
the left jugular vein was then received in separate vessels, which 
were changed every five seconds, and the contents afterward exa- 
minutl. It was thus found that the blood drawn from the first to 
the twentieth second contained no traces of the ferrocyanide; but 
that which escaped from the vein at the end of from twenty to 
twenty-five seconds, showed unmistnltnble evidence of the presence 
of the foreign salt. The ferrocyanide of potassium must, therefore, 
during this time, have passed from the point of injection to the 
right side of the heart, thence to the lungs and through the pulmo- 
nary circulation, returned to the heart, passed out again through 
the arteries to the capillary system of the head and neck, and 
thonce have commenced its returning passage to the right side of 
the heart, through the jngulnr vein. 

By extending thei^e investigations to different animals, it was 
found that the duration of the circulatory movement varied, to 
some extent, with the size and species. In the larger quadrupeds, 
as a general rule, it was longer; in the smaller, the lime required 
was less. 

In tb« Horse,* tlin mean dtiration wu SS Moonda. 

■' Dog ' ' 16 ■■ 

" Omil " " " " 13 •' 

•• ¥hx " >i u u iij <• 

" Rabbil " " " .. 7 " 



' I'll viIor] Phmoiniiiiii or Livitii; n«)ngR, I'Mvln's trttiHlalion, Philmla. mI., 1MB, 
!>. 317. 

' Id Milou E<Ivar<ta, Logons sur Ia I'lijaiologlt^, Ae., fal. ir. p. 3(I4. 



I 
I 

I 




LOCAL TXKTATIOSS. 



286 



When these results were Arst publislied, it was thought to be 
doubtful whether the circulation were really as rapid as they would 
make it appear. It vra« thought that the saline matter which was 
iojevted, "travelled faster than the blood;" that it became "diftused" 
through the circulating fluid; that it transuded through dividing 
membranes; or parsed round to the point at which it was detected, 
by some short and irregular route. 

But none of these explanationa have ever been found to be cor- 
'rect. They are all really more improbable than the fact which 
they are intended to explain. The physical diffusion of liquids 
does not take place with such rapidity as that manifestaied by the 
circulation; and there is no other rouUs so likely to give passage to 
the injected fluid, aa the bloodvessels and the movement of the blood 
itael£ Beeide, the Qrst experiments of Poisseuille and others have 
not been since invalidated, in any cssontiiil pariicular. It was found, 
it is true, that certain other substances, injected at the same time 
with the saline matter, might hasten or retard the circulation to k 
certain degree. But thcso variations were noL very marked, and 
never exceeded the limits of from eigliteen bo forty-Gve seconds. 
There is no doubt that the blood itself makes the same circuit in 
▼erj nearly the same interval of time. 

The truth is, however, that we oannot fix upon any absolutely 
uniform rate which shnll express the time required by the entire 
blood to pass the round of the whole vascular system, and retuni 
to a given point. The circulation of the blood, far from being a 
Btmple phenomenon, like a current of water through a circular tube, 
is, on tbe contrary, extremely oompticaled in all its anatomical and 
physiological conditions; and it differs in rapidity, as well as in its 
physical and chemical phenomena, in diflcrent parts of the circa- 
Intory apparatus. We have already aeen how much the form of 
the capillary plexus varies in dtflerent organs. In some the vasoa- 
l&r network is close, in others comparatively open. In some its 
meshes are circular in shape, in others polygonal, in others reclan- 
gular. In some the vessels arc arranged in twisted loops, tn others 
they communicate by irregular but abundant inosculations. The 
mere distance at which an organ is situated from the heart must 
modify to some extent the time required for its blood to return 
again lo the centre of the circulation. The blood which psssas 
through the coronary arteries, for example, and tbe capillaries of 
the heart itself, must be reluroed to the right auricle in a compnr*- 
tively short time; while that which is curried by the carotids into 



S8« 



THE CIBCrLATIOT. 



the capillary system of ibe head and neck, to return by the JDguIar<i, 
will re<iuire a longer interval. That, again, which deicends by the 
abdominal aorta and its divisions to the tower extremities, ao'l 
which, after circulating through the tissues of the leg and foot, 
mounts upward ihrouj^h the whole course of the saphena, femoral, 
ilinc and abdominal veins, must be still longeron its way; white 
that which circulfltea through the abdominal digestive organs and 
is then collected by theportal system, to be again dispersed through 
the glandular tissue of the liver, requires undoubtedly a longer 
pericKl siill lo perform its double capillary circulation. The blood, 
therefore, arrives at the right side of the heart, from different parts 
of tho bwly, at successive intervals; and may pass severnl timeii 
through uue organ while performing a siuglo circulation through 
another. 

Furthermore, the chemical phenomena taking place in the blood 
and the tissues vary to a similnr extent in different oi^ns. The 
actions of transformation and decomposition, of nutrition and secre- 
tion, of endosniosis and cxosmosis, which go on simultaneously 
throughout the body, are yet extremely varied in their character, 
and produce a similar variation in the phenomena of the circula- 
lion. In one organ the blood loses more fluid than it absorbs; tu 
another it abttorbs more than it loses. The venous blood, conse' 
quoutly, has a different composition us it returns from different 
organs. lu the bniin and spinnl cord it gives up those ingredients 
necessairy for tho nutrition of the nervous matter, and absorbs cho- 
lesterine and other materials resulting from its waste; in the muscles 
it loses those substances necessary for the supply of the muscular 
tissue, and in the bones those which are requisite for the osseous 
system. Inthe parotid gland it yields the ingredients of the saliva; 
in the kidneys, those of the urine. In the intestine it absorbs in 
large quantity the nutritious elements of the digested fix)d ; and in 
the liver, gives up substances rlei^tined finally to produce the bile, 
nt the same time thai it absorbs sugar, which has been produced 
in the hepatic tissue. In the lungs, again, it is the elimination of 
carbonic acid and the absorption of oxygon that constitute its prin- 
cipal changes. It has been already remarked that the tempcraiure 
of the blood varies in different veins, acconling to the peculiar 
chemical and nutritive changes going on tn the organs from which 
they originate. Its color, even, which is also dependent on the 
chetnicnl and nuiritive aciinns taking place in the capillaries, varies 
in a similar manner. In the lungs, it changes from blue to red; 



I 

I 
I 



tOCAL rABTATT0:e8. 



Fl(. 101. 



in the capillaries of the general system, rrom red to blue. But its 

tin^e &\»j varies very consi'lembly in different parts of the general 

virculiition. The blood of ihe bcpaUc 

reina is darker than that of the femoral 

or brachial vein. In the renal veins 

it 13 verv much brighter than in the 

Teoa cava; and when the circulatioa 

through the kidneys is free, the bloud 

returning from ihem is nearly as red 

AS arterial blood. 

We must regard the citxjulotion of 
the blood, therefore, not as a simple 
process, but as made up of many difler- 
eDt circalAiionf>, going on simultjine* 
oasly iu diftorent organs. It baa been 
cuatomary to illustrate it, iu diagram, 
by a double circle, or figure of 8, of 
irhicb the upper arc is used to reprc- 
wntthe pulmonar}-. the lower the gen- 
eral circulation. This, however, gives 
but a very imperfect idea of the entire 
circolaiion, as it really takes place. It 
would be much more accurately re- 
prewDted by such a diagram as that 
in yig. 101, in which iia variations 
in different parts of the body are 
indicated in such a manner as to show, 
in some degree, the complicated cha- 
racter of its phenomena. The circula- 
tion is modified in these different parta, 
not only in its mechanism, but also in 
its rapidity and quantity, and in the 
natritive functions performed by the 
blood. In one part, it stimulates the 
nervoos centres and the organs of 
special sense; in others it supplies the 
fluid secretions, or the ingredients of 
the solid tissues. One portion, in 
passing through the digestive appara- 
tiu, absorbs the materials requisite 
for the nourishment of the bot^y: another, in circulating through 



PiKma of tl>« CiBCPt.irp<tv.— I 
ttoarl t Luiifs, 3. H**d mud nppvr 
• iiniiuUlH *. Bplr*a. A. lulanllna. O 
KI<lo«r 7. Law«r«Xlr«iDltl«*. S. Ufr. 



288 THK CIRCULATION. 

the luhga, exhales the carbonic acid which it has accumalated else- 
where, and absorbs the oxygen wbiah is afterward transported to 
distant tissues by the current of arterial blood. The phenomena of 
the circulation are even liable, as we have already seen, to periodical 
variations in the same organ ; increasing or diminishing in intensity 
with the condition of rest or activity of the whole body, or of the 
particular organ which is the subject of observation. 



lUBIBITIOir AKD ZZHALATIOX. 289 



CHAPTEB XV. 

IMBIBITION AND EXH ALATIO N.— THE LYMPHATIC 

SYSTEM. 

DiTRiNG the passage of the blood through the capillaries of the 
circalatory system, a very important series of changes takes place 
by which its ingredients are partly transferred to the tissues by 
exhalation, and at the same time replaced by others which the blood 
deiives by absorption from the adjacent parts. These phenomena 
depend upon the property, belonging to animal membranes, of 
imbibing or absorbing certain fiuid substances in a peculiar way. 
They are known more particularly as the phenomena of endoamosia 
and exoamosia. 

These phenomena may be demonstrated in the following way. If 
we take two different liquids, for example a solution of salt and an 
equal quantity of distilled water, and inclose them in a glass vessel 
with a fresh animal membrane stretched between, so that there is 
no direct communication from one to the other, the two liquids 
being in contact with opposite sides of the membrane, it will be 
found after a time that the liquids have become mixed, to a cer- 
tain extent, with each other. A part of the salt will have passed 
into the distilled water, giving it a saline taste; and a part of the 
water will have passed into the saline solution, making it more 
dilute than before. If the quantities of the two liquids, which 
have become so transferred, be measured, it will be found that a 
comparatively large quantity of the water has passed into the 
saline solution, and a comparatively small quantity of the saline 
solution has passed oat into the water. That is, the water passes 
inward to the salt more rapidly than the salt passes outward to the 
Tater. The consequence is, that an accumulation soon begins to 
■how itself on the side of the salt. The saline solution is increased 
in volume and diluted, while the water is diminished in volume, 
and acquires a saline ingredient This abundant passage of the 
water, through the membrane, to the salt, is called endoemosis; and 
19 



290 



IUBIB1TTOM AND BXHAt.ATTON. 



the more scanty passage of ihe snlt outward to the water is called 

The mode usually adopted for measuring the mpidity of eiidos- 
mosis is to take a glass vessel, ahaped somewhat like an inverted 
funnel, wide at the bottom and nnrrow at the top. The bottom of 
the vessel is cloaed by a thiu »nimal membrane, like the mucous 
membrane of an ux-bladder, whiub is stretcUiid tightly over it« edge 
and secured by a ligature, from the top of ihe vessel there rises 
a very narrow glaiw tube, open at its upper extremity. Wiien the 
instrument is thus prepared, it is filled with a solution of sngar 
and placed in a vessel of distilled water, so that the animal mem- 
brane, stretched across its mouth, shall be iu contact with pure 
water on one side and with the saccharine solution on the other. 
The water then passes in through the membrane, by endosmosis, J 
faster than the saccharine solution passes out. An accutnulation 
therefore takes place inside the vessel, and the level of the fluid 
rises in the upright tube. The height to which the fluid thus rises 
in a given time is a measure of the intensity of the endosmosis, and 
of its excess over exosmosis. By varyitjg the constitution of the 
two liquids, the arrangement of the membrane, kc, the variation 
in endosmottc action under different conditions may be easily^ 
ascertained. Such an instrument ia called an endoamomel^. ■ 

If the extremity of the upright tube be bent over, so as to point 
downward, as endosmoais continues to go on after the tube has 
become entirely filled by the rising of the fluid, the saccharine solu- 
tion will be discharged in drops I'rom the end of the tube, and fall 
back into the vase of water. A steady circulation will thus be 
kept up for a time by the force of endosmosis. The water still 
passes through the membrane, and accumulates in the endosroo- 
meter; but, as this is already full of Huid, the surplus immediately 
falls back into the outside vase, and thus a current is established, 
which will go on until the two li<^uids have bewme intimately 
mingled, 

Tlie conditions which influence the rapidity and extent of endos 
mosia have been most thoroughly investigated by Datrochet, who 
was the first to make a systematic cxamiDation of the subject. 

The first of these conditions is the freshness of the membrane itself. 
This is an indispensable requisite for the success of the experiment, 
A membrane that bus been dried and moi.stcncd again, or one that ■ 
has begun to putrefy, will not produce the desired effect. It ha»M 
been also found that if the membrane of the endosmometer be 



I 




THE LTUPHATIO BYSTEU. 291 

allowed to remain and soak in the fluids, after the column has risen 
to a certain height in the upright tube, it begins to desceod again 
as soon as putrefaction commences, and the two liquids finally sink 
to the same level. 

The next condition is the extent o/corUact between the membrane 
and the two liquids. The greater the extent of this contact, the 
more rapid and forcible is the current of endosmosis. An endos- 
mometer with a wide mouth will produce more effect than with a 
narrow one, though the volume of the liquid contained in it may be 
the same in both iustances. The action takes place at the surface 
of the membrane, and is proportionate to its extent. 

Another very important circumstance is the comtitution of the iico 
i^uida, and their relation to each other. As a general thing, if we 
use water and a saline solution in our experiments, endosmosis is 
more active, the more concentrated is the solution in the endosmo- 
meter. A larger quantity of water will pass inward toward a decse 
solution than toward one which is already dilute. But the force of 
endosmosis varies with different liquids, even when they are of the 
same density. Datrochet measured the force with which water 
passed through the mucous membrane of an ox-bladder into difl^er- 
ent solutions of the same density. He found that the force varies 
with different substances, as follows:' — 



BndMinoBU of Wftter, with k BOlation of albamen 
*• " " Bugsr . 

M » H gam 

« *• « golatine 



12 

11 

5 

8 

The position of Uie membrane also makes a difference. With some 
floids, endosmosis is more rapid when the membrane has its mucous 
surlHce in contact with the dense solution, and its dissected surface 
in contact with the water. With other substances the most favor- 
able position is the reverse. Matteucci found that, in using the 
macous membrane of the ox-bladder with water and a solution of 
sogar, if the mucous surface of the membrane were in contact with 
the saccharine solution, the liquid rose in the eudosmometer between 
four and five inches. But if the same surface were turned outward 
toward the water, the column of fluid was less than three inches in 
height. Bififerent membranes also act with different degrees of force. 
The effect produced is not the same with the integument of di£ferent 
animals, nor with mucous membranes taken from difierent parts of 
the body. 

> In Matteooei'a Lectnraa on the Physioal Phenomena of Living Betngt. Phllada., 
1848, p. 48. 



292 lUBIBITIOX AXO SXHALATIOy. 

(renorally speaking, endosmosia is more active when the temper- 
attire is moderately elevated. Dutrochet noticed that an endoamo- 
meter, containing a solution of gam, absorbed only one volume of 
water at a temperature of 82° Fabr, but absorbed three volumes 
at a temperature a little above 90°. Variations of temperature will 
sometimea even change the direction of the endosmoais altogether, 
particularly with dilute solutions of hydrochloric acid. Dutrochet 
fuun'l, for example,' llial when the endosinometer was filled with 
dilute hydrochloric acid and placed in distilled wntor, at the tem- 
perature of 50° F., endosmoais touk place from the acid to the water, 
if the density of the acid aolution were less than 1.020; but that it 
took place from the water to the acid, if its density were greater 
than this. On the other hand, at the temperature of 72° F., the 
current was from within outward when the density of the acid sola- 
tion was below l.OOS, and from without inward when it was above 
that point. 

Finally, the ^rewure which is exerted upon the fluids and the 
membrane favors their endosmosts. Fluids that pass aluwly under 
a low pressure will pass more rapidly with a higher one. Different 
liquids, too, require different degrees of pressure to make them 
pass the same metnbrane. Ljebig* has measured the pressure re- 
quired for several difl'erent liquids, in order to make them pasa 
through the same membrane. He found that this pressure was 

IsCMM or Hkxci-rt. 

For alcohol 92 

For oil 87 

Por flolntioa of e&lt 20 

Vnt water 13 

There are some cases in wliich endusmosis takes place without 
being accompanied by exosmosis. This occurs, for example, when 
we use water and albumen as the two liquids. For while water 
teadily passes in through the animal membrane, the albumen does 
not pass out- If an opening be made, for example, in the large 
end uf an egg, so as to oxpoise the shell -membrane, and the whole 
be then placed io a goblet of water, endosmosls will take place very 
freely from the water to the albumen, so as to distend the shell* 
mcmbratie and make it protrude, like a Keniia, from the opening in 
the shell. 13ut tlie albumen does not pass outward through the 
membrane, and the water in the goblet remains pure. AAer a time, 

' In Ullno Kdtrsrds, L^ons s-ar la Ptiralologle, &o., vol. t. p. llH. 
< In Uiugol'a TniU d« PbjnioIagi«, rol. i. ^ SHi. 



\ 





however, the accumulation of fluid in the inicrior bcoomos tio ex* 
cessive as to burst the shell -membrane, and then the two liquids 
become mixed indiacriraiiiately together. 

These are the principal conditions by which endosmoais is influ- 
eooed and regulated. Let us now see what is the nature of the 
process, and upon what its ]>henomcQ& depend. 

EndosmoHis is not dependent upon the simple force of diffusioa 
or admixture of two diQ'crant liquids. For sometimes, as in the 
case of albumen and water, all the ^uid passes in one direction and 
none in the oilier. It is true that the activity of the process de- 
pends very much, as wc have already seen, upun the difference in 
constitution of the two liquids. With water and a saline solution, 
for instance, the stronger the solution of suit, the more rapid is the 
eodosmosis of tlie water. And if two solutions of salt be used, 
with a membranous septam between them, cndnsmoais lalccs place 
from the weaker solution to the stronger^ and is proportionate io 
activity to the diftbrcnce in their densities. From this fact, Dutro- 
chet was at first led to believe that the direction of endosmosis was 
determined by the difference in density of the two liquids, and that 
the current of accumulation was always directed from the lighter 
liquid to the denser. But we now know that this is not the case. 
For though, with solutions of salt^ sugar, and the like, the current 
of endosmosis is from the lighter to the denser liquid; in other 
instances, it is the reverse. With water and alcohol, for example, 
endosmosis takes place, not from the alcohol to the water, but from 
the water to the alcohol; that is from the denser liquid tu the lighter. 
The diflerenco in density of the liquids, thurofore, is not the only 
condition which regulates the direction of the endosmotic current. 
In point of fact, the process of endosmosis docs not depend princi- 
pally upon the attraction of the two liqaids for each other, but 
apoo the aUraclion of tfte animal membrane /or the two liquids. The 
membrane is not a pasaive Ulter through which the liquids min}j;lc, 
hut it is the active agent which determines their passage. The 
membrane has the power of absorbing liquids, and of taking them 
up into its own substance. This power of absorption, belonging lo 
the membrane, depends upon the organic or albuminous ingredients 
of which it is composed; and, with difforeut animal substances, the 
power of absorption is dillereut. The tissue of cartilage, for exam- 
ple, will absorb more water, weight for weight, than that of the 
tendons; and the tissue of the cornea will absurb nearly twice as 
macb as that of cartilage. 



294 



IMIIIBTTTO:? AND EXnALATIOV. 



Beside, the potver of absorption of an animal membrane is dif- 
ferent for tiilTerent liquiris. Nearly all animal membranes absorb 
pure water more froety than a solution of salt. If a membrane, 
partly dried, be placed in a satorated saline solution, it will absorb 
tlie water in larger proportion than the salt, and a part of the salt 
will, iberefore, bo dcpoaJtod in the form of crystals on the surface 
of the membrane. 

Oily mattem, on the other hand, are usaally absorbed less readily 
than either water or salioe solutions. 

ChevTeuil haa investigated the absorbent power of different 
animal substances for diffure^nt liquids, by taking definite quanti- 
ties of the animal snbsiance and immersing it for twenty-foar 
hours in different liquids. At the end of that time, iho suhsuinoe 
was removed and weighed. Its increase in weight showed tbe 
quantity of liquid which it had absorbed. The rsisults whiah were 
obtained arc given in the following table: — * 



100 pAii-n OF 




Watbb. 


SAU^rfigGLcnox. 


Ou.. 


(,'artilngr, 




■ 2St parts. 


122 (larU. 




TeiiJoQ, 




178 ■• 


114 " 


S.G purtt. 


Eliistic ]igiita<<ut, 


absorb in 


148 " 


80 " 


7.2 " 


Coniiwi, 


24 hourn, 


-If:! - 


870 '■ 


9.1 " 


OrliliiKinoa* lig&ncnt, 




31S " 




8.2 " 


Dried flbfin, 




301 '■ 


154 " 





The same substance, therefore, will take up different quantities 
of water, saline solutions, and oil. 

Accordingly, when an animal membrane is placed in contact 
with two different liquids, it ab&i^rbs oue of them more abundantly 
than the other; and that which is absorbed in the greatest quantity 
is also diflfused most abundantly into the liquid on the opposite side 
of the membrane. A rapid endosmosi.s takes place in one direo- 
tion, and a slow exosmosis in the other. Consequently, the least 
absorbable Buid increases iu volume by the constant admijLture of 
that which is taken up more rapidly. 

The process of endosmoais, therefore, is essentially one of im. 
bibiiion or absorption of the liquid by an animal membrane, com- 
posed of organic ingredients. We have already shown, in do- 
scribing the organic proximate principles in a previous chapter, 
tbat these substances have the power of absorbing watery and 
serous fluids in a peculiar way. In cndosmosis, accordingly, the 



I 
I 



I 



■ la Loti|{vt'i Trail«d« Plij-aiotogi*, vol. 1. p. 3S3. 



THB tiTUPHAtlC 8T8TBU. 



296 



imbibed fluid penetrates the luembrnne by n kind of chemical 
combinatioD, and unites intimately with the substance of which its 
tissuea are composed. 

It is in this way that all imbibition and transudation take place 
in the living body. Under the most ordinary contlitions, the transu- 
dation of certain fluids is accomplished wilb great rapidity. Il has 
been shown by XI. tiosselin,' that if a watery solution of iodide of 
potassium be dropped upoti the cornea of a living rabbit, the 
iodine penetrates into the cornea, aqueous humor, iris, lens, sclerotic 
and vitreous body, in the course of eleven minutes; and that it 
will penetrate through the cornea into tLe aqueous humor in three 
minutes, and into the substance of the cornea in a minute and a 
half. In these experiments it was evident that ihe iodine actually 
passed into the deeper portions of the eye by simple endosmosis, 
snd was not transported by the vessels of the general circulation ; 
since no trace of it could bo found in the tissues of the upposiia 
eye, examined at the same time. 

Th« same observer allowed that the active principle of belladonna' 
penetrates the tissues of the eyeball in a similar manner. M. lios- 
selin applied a solution of sulphate of atropine to both eyes of two 
rabbits, ilnlf an hour afbcrwanl, the papik were dilated. Three 
quarters of an hour later, the aqueous humor was collected by 
puncturing the cornea with a trocar; and this aqueous humor, 
dropfied upon the eye of a cat, produced dilatation and immobility 
of the pupil in half an hour. These facts show that the aqueous 
humor of the aifccied eye actually contains atropine, which it 
absorbs from without through the cornea, and thU atropine then 
acts directly and locally upon the muscular fibres of the iris. 

But in all the vascular organs, tho processes of endosmosis and 
exosmosis are very much accelerated by two important conditions, 
Viz., first, the movcmeni of tho blood in circulating through the 
vessels, and secondly the minute diitsemination and distribution of 
these vessels through the tiiisue of the organs. 

The movement of a fluid in a continuous current always favors 
endosmoeis through the membrane with which it i^ in contact. For 
if the two liquids be stationary, on the opposite sides of an animal 
membrane, as soon as endosmosis commences they begin to a[)- 
proximal« in constitution to each other by mutual admixture; and, 
OS ibis admixture goes on, endosmosia of course becomes less active, 



' Qu*.-u« Butxlouiadnln, S«|)U T, UH. 



296 



IMBIBITIOy AKI> IXHALATIOy. 



and ceases entirely when the two liquids have become perfecU_ 
similar in comiwailion. But if one of the liquids be constantly 
renewed by a continuoas correot, those portions of it whicb have 
become oontaniiiiatcd are immediately carried away by the stream 
!ind replaced by I'resh portions in a alote of purity. Thus Uic 
diflereuce in coDJtltution of the two liquids is preserved, and 
traosudatioa will contiuue to take place between them with una- 
bated rapidity. 

Alaticucci demonstrated the effect of a current in facilitating 
endosmosis by attaching to the sLopcook of a glass rc^iurvoir filled 
with water, a portion of a vein also filled with water. The vein 
waa then immersed in a very dilute solution of hydrochloric acid. 
So long as tlie water remained stationary in the vein it did not give 
any indications of the presence of the acid, or did so only very 
slowly ; but if a current were allowed to pass through the vein by 
opening the stopcock of the reservoir, then the fluid runDiDg from 
its extremity almost immediately showed an acid reaction. 

The same thing may ho shown even more distinctly npon the 
living animal. If a solution of the extract of nux vomica be in- 
jected into the subcutaneous areolar tissue of the hind leg of two 
rabbits, in one of which the bloodvessels of the e,\treroily have 
been left free, while in the other they have been previously tied, 
80 as to atop the circulation in that part — in the first rabbit, the 
poison will be absorbed and will produce convulsions and death in 
the course of a few minutes; but in the second animal, owing t') the 
stoppage of the local circulation, absorption will be much retarded, 
and the poison will find ita way into the general circulation so 
slowly, and in such small quantities, that its speciBc effects will show 
themselves only at a late period, or even may not be produced at all. 

The anatomical arrangement of the bloodvessels and adjacent 
tisanes is the second important condition regulating cndoiiinosia 
and exoamosie. We have already seen that the network of capil- 
lary bloodvessels results from the excessive division and rami6cA* 
lion of the smaller arteries. The blood, therefore, as it leaves the 
arteries and enters the capillaries, is constantly divided into smaller 
and more numerous currents, which are 6nany disseminated in the 
most intricate manner throughout the snbstance of the organs aad 
tLHSues. Thus, the blood is brought into intimate contact with Iho 
surrounding tissues, over a com(niralively very large extent of sur- 
foce. It lias already been stated, as the result of Dutrochet's inves- 
tigations, that the activity of endosmosis is in direct proportion to 



I 



I 



I 

I 



1 





THE LTMPHATIC 8YSTEU. 



297 



the estent of surfnce over which the two liquids come in contact 
with the intervening membrane. It is very evident, therefore, that 
it win be very much facilitated by tb« anatomical distribution of 
the capillary blood vesseLs. 

It in in some of the glandular organs, however, that the transu- 
dation of fluids can be shown to take place with the greatest, rapi- 
dity. For in these organs the eihaling and absorbing surfaces are 
arranged in the form of minute ramifying tubes and follicles, which 
penetrate everywhere through the glanduliir t^ubstance; while the 
capillary bloodveiLsela form an ciiualty eoniplicated and abinidnnt 
network, situated between the adjacent follicles aud ducts. In this 
way, the union and interlncetnent of the glandular membrane, on 
the one hand, and the btuudveti^ela on the other, become exueed- 
ingly intricate and extensive: and the ingredients of the blood are 
almost instontaneoualy subjected, over a very large surface, to the 
influence of the glandular membrane. 

The rapidity of transudation through the glandular membranes 
has been shown in a very striking manner by Bernard.' This ob- 
server injected a solution of iodide of potassium into the duct of 
the parotid gland on the right side, in a living dog, and immediately 
afterward found iodine to be present in the saliva of the correspond- 
ing gland on the oppoitite Hide. In the few instants, therefore, re- 
quired to perform the experiment, tho salt of iodine must have 
been taken up by the glandular tissue on one side, carried by the 
blood of the general circulation to the opposite gland, and there 
tmnaudcd through the secreting membrane. 

We have also found the transudation of iodine through the 
glandular tissue to bo exceedingly rapid, by the Following experi- 
ment. The parotid duct was exposed and opened, upon one side, 
in a living dog, and a oanula inserted into it, and secured by liga- 
ture. The secretion of the parotid saliva was then excited, by in- 
trodacing a little vinegar into the mouth of the animal, aud the 
Baliva, thus obtained, found to be entirely destitute of iodine. A 
aolution of iodide of potassium being then injected into the jngu* 
lar veiu, and the parotid secretion again immediately excited by 
the introductioD of vinegar, as before, the aaliva first discharged 
IVom tha oanula showed evident traces of iodine, by striking a blue 
color on the addition of starch and nitric acid. 

Tht processes of exosmosis and eudosmosis, therefore, in the living 



* L»^[M di» Pliysiologf* ExpfaiuM-ntAto, Piria, 18S4, p. 107. 



29S 



IMBIBITION AND EXHALATION. 



1 



body, are regulated by tbe same conditions aa in artificial experi- 
ments, but tliey take place with infiuilcly greater rapidity, owing to 
tlie movement of the eirculai'ing blood, and tbe extent of contact 
oxiaiing between the bloodvessel and mljaccnt tissuejt. We havo 
alrendy seen that tlie absorption of the same fluid is accomplished 
with diiVtirent degretfs of rapidity by diHereiit animal substanoea. 
Accordingly, though the arterial blood is everywhere the same ia 
conipoflition, yet its different ingredients are imbibed in varjiny 
quantities by the diftercnt tissues. Thus, the cartilages absorb 
from the circulating fluid a Inrger proportion of phosphate of lime 
than the softer ti^uet;, and the bones a larger proportion than the 
cartilages; and the watery and saline ingredients generally are 
found in different quantities in difierent parts of the body. The 
same animal membrane, also, aa it has been shown by experiment, 
will imbibe diEferont substances with different degrees of facility. 
Thus, the blooi), for example, contains more chloride of sodium 
than chloride of potassium ; but the muscles, which it supplies with 
nourishment, contain more chloride of potassium than chloride of 
sodium. In this way, tbe proportion of each ingredient derived 
from the blood is determined, in each separate tissue, by its special 
absorbing or endosmotic power. M 

Furthermore, we have seen that, albumen, under ordinary eondi- V 
tions, is not endosmotic; that is, it will not pass by transudation 
through au animal membrane. l''or tbe same reason, the albumen 
of the blood, in the natural state of the circulation, is not exhaled 
from the secreting surfaces, but is retained within the circulatory 
Hyslem, while the watery and sa.Iine ingredients transude in varying 
quantities. But the degree o( pressure to which a tluid is subjected, 
has great influence in determining its endosmotic action. A sub- 
stance which passes but glowly under a low pressure, may pass 
much more rapidly if the force bo increased. Accordingly, we find 
that if the pressure upon the blood in the vessels be increased, by 
obstmctioQ to the venous current and backward congestion of Ihel 
capillaries, then not only the saline and watery parts of the blood 
pass out in larger quantities, but the albumen itself transudes, and 
infiltrates the neighboring parts. It is in this way that albumen 
makes its ap|7oarance in the urine, in consequence of obetruction to 
the renal circulation, and that local cedema or general anasarca 
may follow upon venous congestion in ^mrticular regions, or upon 
general disturbance of the circulation. 

The processes of imbibitiun and exudation, which thus take 



TEB LTHPHATIC BT8TSM. 209 

place incessantly throughout the body, are intimately connected 
with the action of the great absorbent or lymphatic system of ves- 
kIs, which is to be considered as secondary or complementary to 
that of the sanguiferous circulation. 

The lymphatics may be regarded as a system of vessels, com< 
menciag in the substance of the various tissues and organs, and 
endowed with the property of absorbing certain of their ingredi- 
CDtB, Tbeir commeocement has been demonstrated by injections, 
more particularly in the membranous parts of the body; viz., in 
the skin, the mucous membranes, the serous and synovial surfaces, 
and the inner tunic of the arteries and veins. They originate in 
these situations by vascular networks, not very unlike those of the 
capillary bloodvessels. Notwithstanding this resemblance in form 
between the capillary plexuses of the lymphatics and the blood- 
nssels, it is most probable that they are anatomically distinct from 
each other. It has been supposed, at various times, that there 
might be communications between them, and even that the lymph- 
atic plexus might be a direct continuation of that originating from 
the smaller arteries; but this has never been demonstrated, and it 
is now almost universally conceded that the anatomical evidence is 
in favor of a complete separation between the two vascular systems. 

Commencing in this way in the substance of the tissues, by a 
Tascalar network, the minute lymphatics unite gradually with each 
other to form larger vessels; and, after continuing their course for 
a certain distance from without inward, they enter and are distri- 
bated to the substance of the lymphatic glands. According to M. 
ColiD,* beside the more minute and convoluted vessels in each gland, 
there are always some larger branches which pass directly through 
ih substance, from the afferent to the efferent vessels ; so that only 
I portion of the lymph is distributed to its ultimate glandular 
plexus. This portion, however, in passing through the organ, is 
eridently subjected to some glandular influence, which mny serve 
to modify its composition. 

After passing through these glandular organs, the lymphatic 
Tesaels unite into two great trunks (Fig. 43): the thoracic duct, which 
collects the fluid from the absorbents of the lower extremities, the 
intestines and other abdominal organs, the chest, the left upper 
extremity, and the left side of the head and neck, and terminates 
in the left subclavian vein, at the junction of the internal jugular; 
and the right lymphatic duct, which collects the fluid from the right 

I nijsiolDgie oompxrfe di» Aoimauz domestiqnes, Paris, 165G, toL ii. p. G8. 



IHBIBITION AND EXHALATIOIf. 

opper extremity and right aide of the head and neclc, and joins the 
right subclavian vein at its junction with the corresponding jugular. 
Thus nearly all the lymph from the exterttal parts, and the whole 
of that from the abdominal organs, passes, by the thoracic duct^fl 
into the loft subclaviaa vein. I 

Wc already know that the lymphatic vessels are not to bo re- " 
garded as the exclusive agents of absorption. On the contrary, 
absorption takes place by the bloodvesselB even more rapidly nnd^ 
abundantly than by the lymphatics. Even the products of digea- ■ 
tion, including the chyle, are taken up from the intestine ia large f 
proportion by the bloodvessels, and are only in part absorbed by 
the lymphatics. But the main peculiarity of the lymphatic system h 
is that its vessels all pass in one direction, viz., from without inward, V 
and none from within outward. Consequently, there is no circula- 
tion of the lymph, strictly spenking, like that of the bloo<l, but ic^ 
is all supplied by exudation and absorption from the tissues. V 

The lymph has been obtained, in a state of purity, by various 
experimenters, by introducing n canula into the thoracic duct, at 
the root of the neck, or into large lymphatic trunks in other parts 
of the body. It has been obtained by Keea from the lacteal vessels 
and the lymphatics of the leg in the ass, by Colin from the Incteals 
and thoracic duct of the ox, and from the lymphatics of the neck 
in the horae. We have also obtained it, on several different occa- 
sions, from the thoracic duct of the dog and of the goat. fl 

The analysis of these fluids shows a remarkable similarity <aV 
constitution between them and the plasma of the blood. Tboy * 
contain water, fibrin, albumen, fatty matters, and the usual saline 
substancea of the animal fluids. At the same time, the lymph is 
very much poorer in albuminous ingredient than the blood. The 
following is an analysis, by Lassaigae,' of the Quid obtained from 
the thoracic duct of the cow: — 

W»t«r 9tf4.« 

Fibrin 0.9 

AlbQw^n 2S.0 

Kill 0.4 

Cliloridw of sodium 5.0 

C&rbonjita, 1 

I'hMliliAte B.nd I of Sodft 1.3 

Ual|>liitLti ) 

J'litMphate of Urns 0-fi 

IIKIO.0 

■ Cotin, ]'li7«iol'ii|{i<) cciinpAT^tt dva Aniuaanx domes Ui|aM, vol. II. p. 111. 




THE LTBCPHATIC BTSTEH. 801 

It thus appears that both the fibrin and the albninen of the blood 
tctnallj traDBode to a certain extent from the bloodvessels, even in 
the ordinarj condition of the circulatory system. Bat this transada- 
tion takes place in so small a quantity that the albnrainous matters 
are all taken ap again by the lymphatic vessels, and do not appear 
io the excreted fluids. 

The first important peculiarity which is noticed in regard to the 
floid of the lymphatic system, especially in the carnivorous animals, 
is that it varies very mnch, both in appearance and constitution, at 
different times. In the ruminating and graminivorous animals, 
sQch as the sheep, ox, goat, horse, &c., it is either opalescent in 
appearance, with a slight amber tinge, or nearly transparent and 
colorless. In the carnivorous animals, such as the dog and cat, it 
is also opaline and amber colored, in the intervals of digestion, but 
soon after feeding becomes of dense, opaque, milky white, and con- 
tinues to present that appearance until the processes of digestion 
and intestinal absorption are completed. It then regains its original 
aspect, and remaioa opaline or semi-transparent until digestion is 
again in progress. 

The cause of this variable constitution of the fluid discharged 
by the thoracic duct is the absorption of fatty substances from the 
intestine during digestion. Whenever fatty substances exist in con- 
liderable quantity in the food, they are reduced, by the process of 
digestion, to a white, creamy mixture of molecular fat, suspended 
in an albuminous menstruum. The mixture is then absorbed by 
the lymphatics of the mesentery, and transported by them through 
the thoracic duct to the subclavian vein. While this absorption is 
going on, therefore, the fluid of the thoracic dnct altera its appear* 
ance, becomes white and opaque, and is then called chyle; so that 
there are two different conditions in which the contents of the great 
tjmphatic trunks present different appearances. In the fasting 
condition, these vessels contain a semi-transparent, or opaline and 
nearly colorless lymph; and during digestion, an opaque, milky 
chyle. It is on this account that the lymphatics of the mesentery 
are called "lacteals." 

The chyle, accordingly, is nothing more than the lymph which 
is constantly absorbed by the lymphatic system everywhere, with 
the addition of more or lees fatty ingredients taken up from the 
intestine during the digestion of food. 
, The results of analysis show positively that the varying appear- 
ance of the lymphatic fluids is really due to this cause; for though 



302 litfilftlTtOK AVb EXBALATIOK. 

the clijle is also richer than the lymph in albumtnoas mattors, the 
principa] difference between iheni consists in the proportion of fat. 
This is shown by the following comparative anal^-sis of the ly mph 
uud chyia of llio ass, by Dr. Keea:'— 

LnrpH. Chylb. 

Water SBS.Se !K>2,37 

AlbuiQ«n 12.00 39. 1« 

Fibria 1.20 3.7i> 

Spirit sxtract 2.40 3.33 

Wfl.lsr extract 13.19 12.33 

Fat lr*o«. 36.01 

Balias uattor 9.85 7.11 

1,(>CW.00 1,«>U.<I0 

When a canula, accordingly, is introtluced into the thorncic duct 
at various periu<l!> after feeding, the fluid which la discharged varies 
considerably, both in appeamncc and quantity. We have foundfl 
that, in the dog, the fluid of the thoracic duct never becomes quite 
transparent, but retains a very marked opalitiu tinge even so late 
as eighteen hours afler feeding, and at least three days and a half 
after the introduction of fat food. Soon after feeding, however, as 
we have already seen, it becomes whitish and opaque, and remains 
so while digestion and absorption are in progress. It also becomes 
more abundant soon after the commencement of digestion, but J 
diminishesS again in quantity during its latter stages. We have™ 
found the lymph and chyle to be discharged from the thoracic duct, 
in the dog, in the following quantities per hour, at different periods 
of digestion. The quantities are calculated in proportion to the 
entire weight of the animal. 

Put Thoitiuxp Pakt». 

3^ honre aft«>r f«edinj 2.45 

7 " " " 2.20 

13 " " '• 0.99 

18 " ■' " 1.16 

I8J " » " 1.&9 

It would thus appear that the hourly quantity of lymph, 
diminishing during the latter stages of digestion, increases again 
somewhat, about the eighteenth hour, though it is still considera- 
bly less abundant than while digestion was in active progress. 

The lymph obtained from the thoracic duct at all periods uooga-j 
lates soon ai';er its wiibdrawal, owing to the fibrin which it coDtaioaJ 



< Id Colls, op. CLt.. Tcl. ii. p. 18. 



THB LYHPBATIC ST8TBH. 803 

in small qaantity, Afler coagulation, a separation takes place be- 
tween the clot and serum, precisely as in the case of blood. 

The movement of the Ijmph in the lymphatic vessels, from the 
extremities toward the heart, is accomplished by various forces. 
The first and most important of these forces is that by which the 
flaids are originally absorbed by the lymphatic capillaries. Through- 
oat the entire extent of the lymphatic system, an extensive process 
of endosmosis is incessantly going on, by which the ingredients of 
the lymph are imbibed from the surrounding tissues, and com- 
pelled to pass into the lymphatic vessels. The lymphatics are thus 
filled at their origin ; and, by mere force of accumulation, the fluids 
&re then compelled, as their absorption continues, to discharge 
tbemselves into the large veins in which the lymphatic trunks 
terminate. 

The movement of the fluids through the lymphatic system is 
also favored by the coniraction of the voluntary muscles and the 
respiratory motions of the chest. For as the lymphatic vessels are 
provided with valves, arranged like those of the veins, opening 
toward the heart and shutting backward toward the extremities, 
the alternate compression and relaxation of the adjacent muscles, 
and the expansion and collapse of the thoracic parietes, must have 
the same effect npon the movement of the lymph as upon that of 
the venous blood. By these difierent influences the chyle and 
l^mph are incessantly carried from without inward, and discharged, 
iQ a slow but continuous stream, into the returning current of the 
venous blood. 

The entire quantity of the lymph and chyle has been found, by 
tirect experiment, to be very much larger than was previously 
iDticipated. M. Colin^ measured the chyle discharged from the 
thoracic duct of an ox during twenty-four hours, and found it to 
exceed eighty pounds. In other experiments of the same kind, he 
obtained still larger quantities.* From two experiments on the 
horse, extending over a period of twelve hours each, he calculates 
the quantity of chyle and lymph in this animal as from twelve to 
fifteen thousand grains per hour, or between forty and fifly pounds 
per day. But in the ruminating animals, according to his observa- 
tions, the quantity is considerably greater. In an ordinary -sized 
cow, the smallestquantity obtained in an experiment extending over 

■ OsMtte Hebdomadaire, April, 24, 1857, p. 285. 

■ CoHd, op. cit., vol. ii. p. 100. 



304 



IXBIUtTEOH AND EXHALATIOy. 



I 
I 



a period of twelve hours, wns a liule over 9,000 gmina in 6fwe? 
minutes; that is, five poinuls an hour, or 120 pounds per day. In 
another experiment, with a young bull, he actually obtained a little 
over too pounds from a fistula of the thoracic duct, in twenty*foar 
hours. 

Wo hare also obtained siniilar results by experiments apoo the 
dog and goat. In a young kid, weighing fourteen pounds, we have 
obtained from the thoracic duct 1690 grains of lymph in three 
hours uud a half. This quantity would represent 540 grains in an 
hoitr, end 12,i}90 grains, or 1.85 pounds, in twenty-foar hoars; and 
in a ruminating animal weighing 1000 poands, this would corre- 
spond to 132 pounds of lymph and chyle discharged by the thoracic, 
duel in th« course of twenty-four hours. 

The average of alt the results obtained by us, in the dog, at dif- 
ferent periods after feeding, gives very nearly four and a half per 
cent, of the entire weight of the animal, as the total daily quantity 
ot lytnph and chyle. This is substantially the same result as that 
obtaiued by Colin, in the horse; and for a man weighing 140 
pounds, it would be equivalent to batweeu six and sis and a half 
pounds of lymph and chyle per day. ■ 

But of this quantity a considerable portion consists of the chyle 
which is absorbed from the intestines during the digestion of fatty 
substances. If we wish, therefore, to ascertain the total amount of ■ 
the lymph, separate from that of the chyle, the calculation should 
be based upon the quantity of fluid obtained, from the thoracic 
duct In the intervals of digestion, when no chyle is in process of 
absorption. We have seen that in the dog, eighteen hours after 
feeding, the lymph, which is at that time opaline and semi-transpa- 
rent, is discharged from the thoracic duct, in the counw of an boor, 
in a quantity equal to 1.15 parts per thousand of the entire weight 
of the aninial. In twenty-four hours this would amount to 27.6 
pans per thousand; and for a man weighing 140 pounds this would 
giva 3.864 pounds as the total daily quantity of the lymph alone. 

It will be seen, therefore, that the processes of c.Tudation and 
absorption, which go on in the interior of the body, produce a very 
aotive interchange or mtemal drculaiion of the animal iluidd, which 
may be considered as secondary to the circulation of the blood. 
For all the digestive fluids, as we have found, together with the bile 
discharged Into the intestine, are reabsorbed in the natural process 
of digestion and again enter the current of the circalation. These 
fluids, therefore, pass and repnss through the mucous membrane of 



I 




THE LYMPHATIC 8T8TEU. 805 

the alimentary canal and adjacent glands, becoming somewhat 
altered in constitation at each passage, but still serving to renovate 
alternately the constitution of the blood and the ingredients of the 
digestive secretions. Furthermore the elements of the blood itself 
also transude in part from the capillary vessels, and are again taken 
ap, by absorption, by the lymphatic vessels, to be finally restored 
to the retarniug current of the venous blood, in the immediate 
neighborhood of the heart. 

The daily quantity of all the fluids, thus secreted and reabsorbed 
daring twenty-four hoars, will enable us to estimate the activity 
with which endosmosis and exosmosis go on in the living body. 
In the following table, the quantities are all calculated for a man 
weighing 140 poands. 

SSCBBTED AND RbABSOBBID DITBtfO 24 BOtrBfl. 

Balira 20,164 grains, or ?..880 poondii. 



Outrio Jolos 98,000 " 


" 14.000 


Bile 16,940 " 


" 2.420 


PBDcreatio JnloB i;),104 " 


" 1.872 


lymph 27,048 " 


" 3.884 



26.036 

A little over twenty-five pounds, therefore, of the animal fluids 
tranaade through the internal membranes and are restored to the 
blood by reabsorption in the course of a single day. It is by this 
process that the natural constitution of the parts, though constantly 
changing, is still maintained in its normal condition by the move- 
ment of the circulating fluids, and the incessant renovation of their 
Dntritiona materials. 



20 



S06 



BSCRBTIOir. 



CHAPTER XVI. 



SECBETION. 



Wk liave already seen, in a previous chapter, how the elements of 
ihe blood are absorbed by the tiRsucs during the capillary circula- 
tion, and assimilated by ihem or converted into their own sub«Unce. 
Id this process, the inorganic or saline matter* are moelly tAkeo up 
unchanged, and are merely appropriated by the surrouiidin{; \viTts in 
particular quantities; while tho organic substances are transformed 
into new compounds, characteristic of tho different tiRSiies by whicb 
they are assimilated. In this way the varioos tissues of the body, 
though they have a difterent chemical composition from the blood, 
are nevertheless supplied by it with appropriate ingredients, and 
their nutrition cunstanlly maintained. 

Beside this process, which is known by the name of "assimila- 
tion," there is another somewhat giioilar to it, which lakes place in 
the different glandular organs, known as the process otKcntt'on. It 
is the object of tliis function to supply certain fiuids, differing in 
chemical constitution from the blood, which are required to assist 
in various physical and chemical actions going on in the body. 
These secreleii fluids, or "secretions," ait they are called, vary in 
consistency, density, color, quantity, ami reaction. Some of thera 
are thin and watery, like the tears and the perspiration; others arc 
viscid and glutinous, like mucus and ihe pancreatic fluid. They 
are alkaline tike the saliva, acid like the gastric juice, or neutral 
like tbe bile. Each secretion contains water and the inorganic soils 
of the blood, in varying proportions; and is furthermore distin- 
guished by the presence of some peculiar animal subslauce which 
does not exist in the blood, but which ia produced by the secreting 
action of the glandular organ. As the blood circulates through the 
capillaries of tho gland, its watery and saline constituents transude 
in certain quantities, and arc discharged into the excretory duct. 
At the same time, the glandular cells, which have themselves been 
nourished by the blood, produce a new substance by the catalytic 



SECRETION. 807 

traDsformation of their organic conatitaeots; and this new sal»taiice 
18 discharged also into the excretory duct and mingled with the 
other ingredients of the secreted fluid. A true secretion, therefore, 
is produced only in its own particular gland, and cannot be formed 
elsewhere, since the glandular cells of that organ are the only 
ones capable of producing its most characteristic ingredient. Thus 
pepsine is formed only in the tubules of the gastric mucous mem- 
brane, pancreatine only in the pancreas, taaro-cholate of soda only 
in the liver. 

One secreting gland, consequently, can never perform vicariously 
the office of another. Those instances which have been from time 
to time reported of such an unnatural action are not, properly 
speaking, instances of "vicarious secretion;" but only cases in 
which certain substances, already existing in the blood, have made 
their appearance in secretions to which they do not naturally belong. 
Thus cholesterine, which is produced in the brain and is taken up 
from it by the blood, usually passes out with the bile; but it may 
also appear in the fluid of hydrocele, or in inflammatory exuda- 
tions. The sugar, again, which is produced in the liver and taken 
Qp by the blood, when it accumulates in large quantity in the cir- 
culating fluid, may pass out with the urine. The coloring matter 
of the bile, in cases of biliary obstruction, may be reabsorbed, and 
BO make its appearance in the serous fluids, or even in the perspira* 
iaon. In these instances, however, the unnatural ingredient is not 
actually produced by the kidneys, or the perspiratory glands, but 
is merely supplied to them, already formed, by the blood. Cases 
of "vicarious menstruation" are simply capillary hemorrhages 
which take place from various mucous membranes, owing to tho 
general disturbance of the circulation in amenorrhoea. A true 
secretion, however, is always confined to the gland in which it 
natarally originates. 

The force by which the different secreted fluids Wte prepared in 
thQ glandular organs, and discharged into their ducts, is a peculiar 
one, and resident only in the glands themselves. It is not simply 
a process of filtration, in which the ingredients of the secretion 
exude from the bloodvessels by exosmosia under the influence of 
pressure; since the most characteristic of these ingredients, as we 
have idready mentioned, do not pre-exist in the blood, but are 
formed in the substance of the gland itself. Substances, even, 
which already exist in the blood in a soluble form, may not have 
the power of passing out through the glandular tissue. Bernard 



303 



lOKBTIO!^. 



has found* that ferrocyanitle of poUssium, when injected into tbe 
jugular vein, though it appears with great facility in tbe urine, 
dues not pass out with the saliva; and even that a solution of 
the same salt, injected into the duct of the parotid gland, is ab- 
sorbed, tnken up by the blood, and discharged with the urine; but 
does not appear in the saliva, even of the gland into wbiuh It bos 
been injected. Tlic force with which the secreted fluids accuinuUtc 
in the salivary dueta has also been shown by Ludwig's experi- 
ments' to be sometimes greater than the pressure in the bloodvu- 
sels. This author found, by applying mercurial gauges at tbe suae 
time to the duut of Stuno and to the artery of tbe parotid gland, thai 
the pressure in the duct from tho secreted saliva was considerablji 
greater than that in the artery from the circulating blood; so that 
the passage of the secreted fluids had really taken place id a direc- 
tion contrary to that which would have been caused by the simple 
influence of pre:isure. 

The process of secretion, therefore, ts one which depends upoa 
the peculiar anatomical and chemical conittitution of tbe glaDdaJar 
tissue Hud its secreting cells. These cells have the property of 
absorbing and transmitting from tho blood certain inorganic aod 
saline substances, and of producing, by chemical metnmorphosia, 
certain peculiar animal matters from their own tissue. These sob- 
stances are then mingled together, dis^Ivcd in the watery fluiiU 
of the secretion, and discharged simultaneously by tbe excretory 
duct. 

All the secreting organs vary in activity at diflToPent periods. 
Sometimes they are nearly al rest; while at certain periods ther 
become excited, under the influence of an occasional or periodical 
stimulus, and then pour out their secretion with great rapidity audio 
large quantity. The perspiration, for example, is usually ao slow); 
secreted that it evaporates us rapidly as it is poured out. and ibe 
surface of the Ain remains dry; but under the influence of unusual 
boilily exercise or mental excitement it is secreted much (aoa 
than it can evaporate, and the whole integument becomes covered 
with moisture. Tho gastric juice, again, in tho intervals of dlgosttou, 
is either not secreted at all, or is produceil in a nearly inappreciable 
quantity; but on the introduction of food into the stomach, it ii 
immediately poured out in Biach abundance, that between two awl 
three ounces may be collected in a quarter of an hour. 



■ l.r^D'tis da Phyilgloglti ExpdrltaeaUlv. 
■lLld.,p. lOtt. 



Paris, ISStf, lomu Ii. p. 9i> tt 1*9. 




1IUC09. 



809 



The priDcipol secretioQS met with in the animal body are as 
followa:— 



1. Uueaa. 

3. &«l<ftc«naft matter. 

3. Pcmpfration. 

4. Tli« iet.n. 

5. Th« niilk. 



«. Stlka. 

T. OMtric Jtiicf. 

8, Pancrt-atic Jnice. 

9. Int«*tituil juict. 
10. Bile. 



The last five of these fluids have already been described in the 
preceding chapters. We shal! therefore only require to examine 
at present tbe five following, viz^ mucus, sebaceous matter, per- 
spiration, the tears, and the milk, together with aome peculiarities 
in tbe secretion of the bile. 



ng. 102. 



1. Moccs. — Nearly all the mucous membranes are provided with 
follicles or glandulm, in which the mucus is prepared. Tliesc folli- 
cles are most abundant in the lining membrane of the mouth, nare>:, 
pharynx, oesophagua, trachea and bronchi, vagina, and male urethra. 
They are generally of a compound form, consisting of a number of 
secreting sacs or cavities, terminating at one end in a blind ex- 
tremity, and opening by tbe other into a common duct by which 
the secreted fluid is discharged. Each ultimate ficcreling sac or 
follicle is lined with glamUilar epithelium (fig. 102), and surround- 
ed on its external surface by a network of capillary bloodvessels. 
These vessels, penetrating deeply into the 
interstices between the fullicles, bring the 
blood nearly into contact with the epithelial 
cells lining its cavity. It is these cells 
which prepare the secretion, and discharge 
it afterward into the comtneucement of the 
excretory duct. 

The tnucus, produced in the manner 
above described, is a clear, colorless fluid, 
which is {K)ured out in larger or smaller 
quantity on the surface of the mucous 
membranes. Ii is distiiigui.-^hed from other aecretiona by its vis- 
cidity, which is its most marked physical property, and which 
depends on the presence of a peculiar animal matter, known under 
Uie name of muamne. When unmixed with other animal fluids, 
Uiis viscidity is so great that the mucus has nearly a semi-solid or 
gelatinous conaislency. Thus, the mucus of the mouth, when ob- 
tained onmixed with the secretions uf the salivary glands, is so 



FoLlir-Ll* or * C«M- 
rtttsa Mccnfla tiLtaOBl.*- 
Pram cIl« horaauiubloct. (AfUt 
Rntllkor >— n Mniilinntt at Ik* 
follkta. t, t. KptllwHuiD of llw 
tamo. 



810 SECBBTrON. 

toQgb and adhesive tbat the vessel containing it maybe tarned 
upsidti down wiibuut its ninniug out. Tbs mucus of the cervix 
uteri bos a similar Srm consistency, so as to block up tbe cavity 
of tbis part of tbe organ with a Bemi-A>Iid gelatinous mass. Muciifl 
is at the same time oxceeclitigly smooth and slippery to the touch, 
60 that it lubricates readily the surfaces upoo which it ta exuded, 
and facilitates the passage of foreign substances, while it defends 
the mucous membrane itself from injury. 

The coinpoaition of mucua, according to the analyses of Kasse,* 
is OS follows;— 

CoxriMiTiox w ]'ni.)i»»AftT HDctrn. 

W»t»r 955.53 

Animal mAtter 33.57 

fiLt £.8» 

Chlnritlvof •ixlIaTn 6.83 

Pfaotphiit«i of Boita aoil poiasMi 1-06 

Sulphatva » •- 0.<S 

CarbonaU.* " » (1.43 

low. TO 

The animal matter of mucus is insoluble in water; and conse- 
queuily mucus, wiien tJri^pped into water, does nut mix with it, but 
is merely broken up by agitation into getalinons threads and flakes, 
which subside afWr a time lo ibe bottom. It is misciWe, however, 
lo some extent, with other animal Buids, and may be incorporated 
with them, so as to become thinner and more dilute. It readily 
takes on putrefactive changes, and communicates thorn to other 
organic substances with which it may be in contact. 

The varieties of mucus found in diS'erent parts of the body are 
probably not identical in composition, hut differ a little in the cha- 
racter of their principal organic ingredient, as well as in the pro- 
portions of their saline constituents. The function of mucus is for 
the most part a physical one, viz., to lubricate the mucous surfaces, 
to deE'end them from injury, and to facilitate the t>assage of foreign 
Bubsunces through their cavities. 



2. Sebaceous Matter. — The sebaceous matter ia ilistinguished 

by containing a very large proportion of latty or oily ingrevlienls. 
There are three varieties of this secretion met with in the body, ■ 
viz., one produced by the .•sebaceous gland.^ of the skin, another 
by the ccruminoua glands of the external auditory meatus, and 
a third by the Meibomian glands of the eyelid. The sebaceous 



SIiuod'i Cli«&ii>trj' of Uaii, Fbilada., IMi!, p. 352. 



SEnAOSocra iiATTsn. Sll 

glands of tbe skin are found most abundantly in those parts which 
are thickly covered with haira, as well as on the face, the labia 
minora of the female generative organs, the gliins penis, and the 
prepuce. They consist aometimea of a simple follicle, or flask- 
shaped cavity, opening by a single orifice; but more frequently of 
R Dumber of such follicles grouped round a common excretory duct. 
The duet nearly always opens ju^it at the root of one of the hairs, 
which is smeared more or leas abundantly 
with its secretion. Each follicle, a^ in ihe ^^e- 1<*3- 

case of the mucous glandules, is lined 
with epithelium, and its cavity is filled 
with the secreltii) sebaceous matter. 

In the Meibomian glands oF the eye- ^^■nc-r> 
lid (Fig. 108), the follicles are ranged 
aloDg the sides of an excretory duct, 
situated just beneath the conjunctiva, on 
the posterior surface of the tarsus, and 
opening upon its free edge, a little be- ^^h Jt. a ^ « 
hind the roots of tho eyelashes. The 
ceruminoua glands of the external uuiU- 
lory meatus, again, have the form of long 
tubes, which terminate, at the lower part 
of the uitegumcnt lining the meatus, tii Lii4i.,tie. 
a globular coil, or convolution, covered 
externally by a network of capillary blood ve-^sels. 

The sebaceous matter of the skin has the following compositiun, 
according to Esenbeck.' 

CoMPoeiTCOS up SsBActoos Uattsb. 

AnfEiiiit nabntnncM 3&S 

FMt;^ iititl-n 3tiS 

Phv<|>li]|leuf litue 3t)0 

Cirin'iiito of liHie 21 

CAtboniile of miuptMlA Ifl 

Cittoriile of uxlinm i 

Acwtal«or«rNli, ^. { ^"^ 

lOOO 

Owing to the large proportion of stonrine in the fatly ingredicnta 

«if the sebaceous matters, they have n considernble Jegree of con- 

Bislency. Their office is to lubricate th« integument and the hair», 

to keep them sofl and pliable, and to prevent their drying up by 

' 8iinon'< CWmUlry of Uan, p. 379* 



SECRETIOy. 

too rapid cToporntion. When the sebaceous glands of the scalp 
are inactive or atrophied, the hairs become dry and brittle, are 
easily spHt or brokeD off, and finally cea$e growing altogether. 
Tho ccraminous matter of the ear is inteaded without doubt partly 
to obstruct the cavity of the meatus, awl by its glutinous consist- 
CDCy and strong odor to prevent amall insects from accidentally 
introducing themselves into the meatus. The secretion of the 
Meiboinian glands, by being smeared on the edges of the eyelids, 
prevents the tears from running over upon the cheeks, and confines 
them withiu the cavity of the lachrymal canata. 

8. Perspiration, — The perspiratory glands of the skin are scat- 
tered everywhere throughout the iulvguuient, being most abundant 
on the anterior portions of the body. They consist each of a slender 
tube, about ^jig of an inch in diamet^^r, lined with glandular epi- 
thelium, which penetrates nearly through the entire thicknesa of 
the skin, nnd terminates below in a globular coil, very siniilar in 

appearance to that of the cerumi- 
Fig. 104. nous glands of the ear. (Fig. 104.) 

A network of capillary vessels 
envelops the tubular coil and sup- 
plies the gland with the materials 
necessary to its secretion. 

These gland.s are very abundant 

iu some parts. On the posterior 

^~^4:^ portion of the trunk, the cheeks, 

(ifSS3S3!4^^ f^Y^^^J " V "^'"^ ^'^^ "^''^ "^ ^^^ thigh and leg 

there arc, according to Krause,' 
about 500 to the si^uare inob ; on 
the anterior part of the trunk, the 
forehead, the neck, the forearm, 
and the back of the hand and foot 
1000 to the square inch; and on 
the sole of the foot and the palm 
of the hand about 2700 in the same space. According to the same 
observer, the whole number of perspiratory glands is not leas than 
2,300,000, and the length of each tubular coil, when unravelled^ 
about Vk of an inch. The entire length of the glandular tubing 
must therefore be not leas than 158,000 inches, or about two miles 
and a half. 



};^ 



A I'lHIPI NITIIKI OLJlXn, W(tb til ■••■ 
IDMo.)— a. (iluidiulaTViLL b. PIpiui orTOHelt. 



• Eolliker, Hftiidbncli <l«r n«w«lw1«>ir«. Ulpiig, 1$S2, p. 147. 



i 



PXK3PIRAT10N. 81S 

It is easy to noderstAnd, therefore, that a very large quantity of 
fluid may be supplied tivm so extensive a glandular apparatus. It 
results from the researches of Lavoisier and Seguin* that the ave- 
rage quantity of fluid lost by cutaneous perspiration daring 24 
boars ia 18,600 grains, or nearly two pounds avoirdupois. A still 
larger quantity than this may be discharged during a shorter time, 
when the external temperature is high and the circulation active. 
Dr. Southwood Smith* found that the laborers employed in gas 
works lost sometimes as much as 8} pounds' weight, by both cuta- 
neous and pulmonary exhalation, in less than an hour. In these 
cases, as Seguin has shown, the amount of cutaneous transpiration 
is about twice as great as that which takes place through the lungs. 

The perspiration is a colorless watery fluid, generally with a 
distinctly acid reaction, and having a peculiar odor, which varies 
somewhat according to the part of the body from which the speci- 
men is obtained. Its chemical constitution, according to Ansel- 
mine,' is as follows : — 

COMFOfllTIOV OF TBI PBR8PIBATI05. 

Water 995.00 

Aninul nutten, with lime .10 

Balphfttes, and sobBtancea solable fo wat«r .... l.OS 

Chloiidaa of Bodiam and potassinm, and apirlt-extract . . 2.40 

A««tle aoid, acatatea, lactates, and aloohol-extraot 1.46 

1000.00 
The office of the cutaneous perspiration is principally to regulate 
the temperature of the body. We have already seen, in a preced- 
ing chapter, that the living body will maintain the temperature of 
lOO*' F., though subjected to a much lower temperature by the 
surrounding atmosphere, in consequence of the continued genera- 
tion of heat which takes place in its interior; and that if, by long 
continued or severe exposure, the blood become coaled down much 
below its natural standard, death inevitably results. But the body 
has also the power of resisting an unnaturally high temperature, 
as well as an unnaturally low one. If exposed to the influence of 
an atmosphere warmer than 100° F., the body does not become 
heated up to the temperature of the air, but remains at its natural 
standard. This is provided for by the action of the cutaneous 
glands, which are excited to unusual activity, and pour out a large 
quantity of watery flutf upon the skin. This fluid immediately 

' Hilno Edwarda, Lemons sar la Plijaiologie, &c., vol. ii. p. 623. 
' PhilOBoph; of Health, London, 1838, chap. zilL 
* Simon. Op. cit., p. 374. 



^14 



SSCRBTIO^r. ' 



evnporates, and in assuming the gaseous form caoses so macli heat 
to becotiio latent lliat ilie cutaneous surfaces are cooled down to 
their natural temperature. 

So long ns the air is dry, so that evaporation Trom the surface 
can go on rapidly, a very elevated teniperature can be borne with 
itiipuoity. The workmen of the sculptor Chantrey were in the 
habit, according to Dr. C'arpenttrr, uf entering a furnace in which 
the air was heated up to SoO'^ ; and other instances have been known 
in whiuh a temperature of 400° to 600° has been borne for a time 
without much incnnvenicnce. But If the air be saturated with 
moisture, and evaporation from the skin in this way retarded, the 
body soon becomes unnaturally warm; and if the exposure be long 
contlnueil, death is the result. It is easily seen that horses, when 
fast driven, sufTer much more from a warm and moist atmaiphere 
than from a warm and dry one. The experiments of Magendie and 
others have sbuwn' that quadrupeds eontined ia a dry atmosphere 
suffer at flrst but little inconvenience, even when the temperature 
ia much above that oF their own bodies; but as soon as the atmo- 
sphere is loaded with moisture, or the supply of perspiration is ex- 
hausted, the blood becomes heated, and the animal dies. Death 
follows in the^e eases as soon as the blood has become heated op to 
8** or 9® K., above its nnturol standard. The temperature of 110", 
therefore, which is the natural temperature of birds, is fotal to quad- 
rupeds; and we have found that frogs, whose natural temperature 
ia oO** or 00**, die very soon if they arc kept in water at 100" F. 

The amount of perspiration is liable to variation, &a wo have 
already intimated, from the variutli^ns in temperature of the sur- 
rounding olmosptiere. It is excited also by unusual muscular 
exertion, and increased or dirainiaheil by various nervous condi- 
tions, such as anxiety, irritation^ lassitude, or excitement. 

4. The Tears.— The tears are prot^uced by lobulated glands 
situated at the upper and outer part uf ihe orbit of the eye, and 
openitig, by frum six to twelve ducts, upon the surface of the con- 
junctiva, in the fold between the eyeball and the outer portion of 
the upper lid. The secretion is extremely watery in its composition, 
and contains only about one part per thousand of solid matters, 
consisting mostly of chloride of sodium ^nd animal extractive 
matter. The office of the lachrymal secretion is simply to keep the 



■ 



I 



■ fi««nanl, Lwclun* on lh« Blood. AlWe'a traiuUlltiD, p. S&. 



TUB MILE. 



315 



iurfoccs of iho cornea anU conjuDctiva muist aad poliahet^, and to 
preserve in this way the tranaparoncy of tbe parta. The tears, 
which arc constantly secreted, are spread out uniformly over the 
anterior part of the eyeball by the movement of the Uda in wink- 
ing, and are gradually conducted to the inner angle of the eye. 
Here they are taken up by the puncta lachryinalia, pas3 through 
the lachrymal canals, and are 6nally diacharged into the nasal pas- 
sages beneath the inferior turbinated bones. A constant supply of 
frodh ftuid id thua kept passing over the tran^tparent parta of the 
eyeball, and the bod re;sult3 avuided which would follow from iu 
aocamulation and putrefactive alteration. 

6. The Milk.— The mammary glands are conglomerate glands, 
resembling closely io their structure tlie pancreas, the salivary, and 
tbe lachrymal glands. They consist of nnmerous secreting sacs or 
follicles, grouped together in lobules, each lobule being supplied 
with a common excretory duct, which Joins those coming from 
»ljacent parts of the gland. 

(Fig. lOu.) In thia way, by Kig.ios. 

their succeaaivo union, they 

form larger branches and 

IraDJCfl, until they are reduced 

in Dumbers tofiome 15 or 20 

cylindrical ducts, the Uiciifer- 

€rvu duels, which open finally 

Ijy as many minute orilicea 

xi^>on the extremity of the 

nipple. 

Tbe secretion of the milk 

l>ecomes fairly established at 

t. he end of two or three days 

sKfter delivery, though the ni.*>»i-<.*B st«eoT«aaar u^ni*. 

k* reaata often contain a milky 

fluid during the latter part of pregnancy. At first the Quid dis- 
charged from the nipple is a yellowish turbid mixture, which is 

called the colostrum. It has the appcnrancc of lacing thinner than 
the milk, but chemical examinations have shown' that it really cod* 
Uitiaa larger amount of solid ingredienta than the perfect secre- 
tiuQ. When examined under the microscope it is seen to contain. 
Wide the tuilk-globults proper, a large amount of irregularly glu- 



M^'^ 



* Li<bat4na, op. cit., rol. H. p. U3. 



S16 



SBCRBTIOir. 



O^ 



»0 



CD 



o 



biilar or oval bodies, from j^j, to jSb of an inch in diameter, 

which are termed the "colostrum corpuscles." (Fig. 106.) Theie 

• bodies are more jellov and 
F'K* 106. opaque thau the true milk- 

globules, OS well as beingrer; 
mucli larger. They have a 
well defined outline, and ooo* 
flist apparently of a group of 
minute oily granules or glo- 
bules, imbedded in a mass 
of organic substance. The 
milk-globules at this time 
are less abundant ilian after- 
ward, and of larger size, 
measuring mostly from j^t 
^ Tg"oiF of an inch io dja* 
meter. 

At the eod of & day or 
two after its first appearance, 

the colostrum ceases to be discharged and is replaced by the troe 

milky secretion. 
The milk, as it is discharged from the nipple^ is a white^ opvjoe 

fluid, with a slightly alkaline reaction, and a specific gravitj of 

about 1030. Its proximate chemical constitution, aocordiog to 

Pcroira and Lchmann, is as follows: — 



O 



CvLDnrKi'H Con PI.-K- ■■«■. vti ti nitlk-flubiila 
A'«n ft ir«nia[i. one d^y kftei ddlHrf. 



Co)ir<MiTioii OF Cow'r Mii.i 

Wawr 

CaMio 

Butt«r 

Buj^ar 

So<i« 

Chloride* of flodinm xnul potasriinm . 
PbnspliatM rtf <iM(i anil patftua . 
Phoaphjile of lime 

« " magnMU 

" "Iron 

Altuline onrbonat«fl ■•.... 



S70.3 

31.3 

«.7 



«.» 



looa-ft 



Human milk ia distinguished from the above by containing leai 
casein, and a larger proportion of oily and saccharine iDgredieota 
The entire amount of solid ingredients is also somewhat less thu 
in cow's milk. 




THB MILK. 



S17 



Tlie catein is one of tbe moBt important ingredients of tbe milk. 
It is an extremul^ nutritious organic subHtanco, whidi is hekl in a 
fluiJ form by union wIlH the water of the Becretioo. Casein is not 
coagnlable by heat, and consequently, milk may be boiled without 
changing iu consistency to any considerable extent. It becomes 
a little thinner and more fluid during ebullition, owing to tbe melt- 
ing of its oleaginous ingredients; and a thin, membranous film 
forms upon ita surface, consisting probably of a very little albumen, 
which the milk contains, mingled with the caseiu. The addition of 
any of tbe acids, however, mineral, animal, or vegetable, at once 
coagulates the casein, and the milk becomca curdled. Milk is 
ooagulatcd, furthermore, by the ga^triu juice in the natural process 
of digestion, immediately afUr being taken into tlie stomach ; and 
if vomiting occur soon after a meal contaiuiug milk, it is throwu 
uff in the form of semi-solid, curd-like flakes. 

The mucous membrane of the calvc.4' stomach, or rennet, also 
has the power of coagulating casein ; and when milk has been 
curdled in this way, and it<t watery, saceharine, and inorganio in- 
gredients separated by mechanical pressure, it is converted into 
cheese. The peculiar flavor of tbe din'oreat variutlos of cheese 
depends on tbe quantity and quality of the oleaginous ingredients 
which have been entangled with the coagulated casein, and on the 
alterations which these sub- 

staooea have undergone by ^8- *o7. 

the lapse of ume and ex- 
posure to the atmosphere. 

The sugar and saline sub- 
stances of the milk are in 
fiolution, together with the 
casein and water, forming a 
clear, colorless, homogene- 
ous, serous fluid. The but- 
ter, or oleaginous ingredient, 
howercr, is suapended in 
this serous Huid in the form 
of miouta granules and 
globules, the true " milk- 
globules." (Fig. 107.) These 
gk)bules are nearly fluid at 
the terafierature of the body, and have a perfectly cirtiular out- 
line. In the perfect milk, they are very much more abundant and 



(0^0 



00 



o^-b 



?M 



80? 



cPo 






00 



pOQ 



'0», 



O D 



A 



^6)l9JPVfS^2o 



,000 



00 



^cfO^ 



p'O' 



t^°AloX'o'J:o°;&> 



09 



•b^, 



%? 



0«Q 



ooo?o o« 

"■ O O * * 






O 0, 



. Oft „ o o 



OSQ 



o 



CQ 



°6-o 
I O o 



iOo 



(our d>r* kXxdnltvMT. SMrtttom fuHj MiablliliBd. 



818 8KCRETI0K. 

smaller inside than in tbe colostrum; as the largest or them are' 
not over joVc of an inch in diameter, aiid the greater number 
about jnion of an inch. 

The following is the comf>08ition of the hotter of cow's milli, 
according to Kobin aod Verdeil : — 

Margarine 66 

OWw 30 

BuiyriBQ 2 

m 

It is iho last of these ingredients, the butjrine, which gives itidj 
peculiar flavor to the butter of milk. 

The railk-globoles hare sometimes been described as if each one 
were separately covered with n thin layer of coagalated casein or 
albumen. No such investing membrane, however, is to be seen. 
The milk-globules are simply small masses of semi-fluid fat, sus- 
pended by admixture in the watery and serous portions of tbe 
secretion, bo as to make an opaqae, whitish omolsion. They do 
not fuse together when they come in contact under the microscope, 
simply because they are not quite flnifl, but contain a large pro- 
portion of margarine, which is solid alonlinary temperatures of the 
body, and is only retained in a partially fluid form by tbe oleine 
with which it is associated. The globules may be made to fuse with 
each other, however, by simply heating the milk and subjecting it 
to gentle pressure between two slips of glass. ■ 

When fresh milk is allowed to remain at rest foi* twelve to twenty- ■ 
four hours, a large portion of its fatty matters rise to the surface, V 
and form there a dense and rich-looking yellowish-white layer, ihe 
cream, which may be removed, leaving the remainder still opaline, 
but less opaque than before, At the end of thirty-six to forty-eight 
hoars, if the weather be warm, the casein begins to take on s fl 
putrefactive change. In thia condition it exerts a catalytic action 9 
upon the other ingredients of the milk, and particularly upon the M 
sugar. A pure watery solution of niilk-sugar (Cj^„0^) may bef 
kept for an indefinite length of time, at ordinary temperatures, 
without undergoing any change. But if kept in contact with the 
partially altered casein, it Buftera a catalytic transformation, and is 
converted into lactic acid (Cgll^Oo). This unites with the free soda, ■ 
and decomposes the alkaline carbonates, forming tactiites of sodafl 
and potassa. After the ncutralizntioQ of these substances has beenfl 
accomplished^ the mitk loses its alkaline reaction and begins to tumfl 
sttur. The free lactic acid then coagulates the casein, and tbe milk 



SECRKTIOK OF THE BILE. 819 

ii curdled. The sltered organic matter also acta upon the olea- 
ginoos ingredieotB, which are partly decomposed; and the milk 
begins to give off a rancid odor, owing to the development of 
various volatile fatty acids, among which are butyric acid, and the 
like. These changes are very much hastened by a moderately 
elevated temperature, and also by a highly electric state of the 
atmosphere. 

The production of the milk, like that of other secretions, is liable 
to be much influenced by nervous impressions. It may be increased 
or diminished in quantity, or vitiated in quality by sudden emo- 
tions; and it is even said to have been sometimes so much altered 
in this way as to produce indigestion, diarrhcea, and convulsions in 
the infant. 

Simon found' that the constitution of the milk varies from day to 
day, owing to temporary causes; and that it undergoes also more 
permanent modidcationa, corresponding with the age of the infant 
He analyzed the milk of a nursing woman during a period of nearly 
six months, commencing with the second day after delivery, and 
repeating his examinations at intervals of eight or ten days. It 
appears, from these observations, that the casein is at first in small 
quantity; but that it increases during the first two months, and 
then attains a nearly uniform standard. The saline matters also 
increase in a nearly similar manner. The sugar, on the contrary, 
diminishes during the same period; so that it is less abundant in 
the third, fourth, fifth and sixth months, than it is in the first and 
second. These changes are undoubtedly connected with the in- 
creasing development of the infant, which requires a corresponding 
alteration in the character of the food supplied to it Finally, the 
qoandty of butter in the milk varies so much from day to day, 
owing to incidental causes, that it cannot be said to follow any 
r^ular course of increase or diminution. 

6. Secretion of the Bile. — The anatomical peculiarities in the 
rtructnre of the liver are such as to distinguish it in a marked 
degree from the other glandular organs. Its first peculiarity is 
that it is furnished principally with venous blood. For, although 
it receives its blood from the hepatic artery as well as from the 
portal vein, the quantity of arterial blood with which it is supplied 
u extremely small in comparison with that which it receives from 

' Op. cit,, p. 337. 



320 



SBCRBTIOX. 



the portal system. The blood which has circniatcd throngh tli4 
capillnries of the stomach, spleen, pancreas, and jnlestine is col' 
lected by the roots of the corresponding veins, and diacbarged into 
the portal rein, which enters the liver at tlio great transverse 
fissure of the organ. Immediately upon its entrance, the portal 
vein divides into two branches, right and left, which supply tlie 
corresponding portions of the liver; and these branches sucoesaa 
ively subdivide into »mnller twigs and ramiGcations, until they are 
reduced to the size^ according to KuUikcr, of f aVo "^ ^^ ''^^^^ '^ 
diameter. These veins, with tlieir terminal branches, are arranged 
in such a manner as to include between thero pentagonal or 
hexagonal spaces, or portions of the hepatic eubatance, ,"» to j'j 
of an inch in diameter in the human subject, which can readily be 
distinguished by the naked eye, bulb on the exterior of the organ 
and by the inspection of cut surfaces. The portions of hepatio 
substance included in this way between the terminal branches 

ot the portal vein (Fig. 108) 
''«'*°^' are termed the "acini" or 

"lobules" of the liver; and 
the terminal venous brauebes, 
occupying the spaces between 
the aOjacetit lobules, are the 
"interlobular" veins. In the 
spaces between the lobules 
we also 6Dd the minute 
branches of the hepatic ar- 
tery, and the commencing 
rootlets of the bepntic duds. 
Aa the portal vein, the he- 
patic artery, nod the hepatic 
duct enter the liver at the 
transverse fissure, they are 
closely invested by n fibrous 
sheath, termed Glisson's capsule, which accompanies ihem in their 
divisions and ramifications. In some of the lower animals, as in the 
pig, this sheath extends even to the interlobular spaces, iDcloeiog 
each lubule in a thin fibrous investment, by which it is distinctly 
separated from the neighboring p&rta. In the human subject, how- 
ever, Glisson's capflulc becomes gradually thinner as it penetrates 
the liver, and disappears altogether before reaching the interlobular 
spaces; so that here the lobules are nearly in contact with each 



Bimlllcadoa of PohTjII. Vma in llTfi— «. 
Twig vfiunsl vela b,6, tiiierlub(t1>Tr*(Da. r Adul, 




tS BILE. 



821 



other by their adjacent surfaces, being separated only by tbe inter- 
lobular veins and the minute branches of tbe hepatic artery and 
duct previously mentioned. 

From the sides of the interlobular veins, and also from their 
terminal extrcmilica, there are given off capillary vessels, which 
penetrate the substance of each lobule and couverge from its cir- 
cumrerence toward its centre, inosculating at the same time freely 
with each other, so as to form a minute vascular plexus, the 'iobu- 
lar" capillary plexus. (Fig. 109.) At the centre of each, lobule, the 

Pig. 109. 



UiBKLS nv LiTia, aliovlBj dUtrtbulion at bloadieaiMh; aiasnllloid t3(llaiaBl«ni.~4,(L t»- 
brtatalar wIbb. t. iDtrsUbatBr vain. c. f, e. Loticlkr npillar)r piioxtim <I, 4. T^lg* vf lbl«r- 



converging capillaries unite into a small vein (b), the "intralobu- 
lar" vein, which is one of tbe commencing rootlets of the hepatic 
vein. These rootlets, uoiting succosaively with each other, so an 
u> form larger and larger branches, Anally loave the liver at its 
poMterior edge, to empty into the ascending vena cava. 

Beside the capillary bloodveaacla of the lobular plexus, eacb 
acinus is made up of an abundance of minute cellular bodies, about 
(/oo of an iuch in diameter, tbe "hepatic cells." (Fig. 110.) These 
uelk have an irregularly pentagonal Bgure, and a soft consistency. 
They are composed of n homogeneous organic subntjince, in tbe 
midst of which arn imbedded a large number of minute granules, 
and generally several well defined oil-globules. There is also a 
round or oval nucleus, with a nucleolus, imbedded in the substance 
21 



822 



JJECRKTION. 



Fig. 110. 



of ihc ceH, sotnetvmea more or less obaourcd by the granales anc 
oil drops with which it ia surroanded. 

The exact modo io which these cclla are connected with the 
hepatic duel was for a long time the most obscure point ia tho'l 

minute nnatomj of the liver. 
It has now been ascertained, 
however, bythc researches of 
Dr. Leidy, of Philadelphia.' 
and Ur. Beale, of Londou,' 
that they are reallycontained 
in the interior of secreting 
tubules, which pass oft* from 
thesmaller hepatic dacts, and 
penetrate everywhere the 
substance of the lobulee. 
The cells fill nearly or com- 
pletely the whole cavity of 
the tubules, and the tubules 
themselves lie in close proxi- 
mity with each other, so as 
to leave no space between thera except that which is occupied by 
the capiltnry bloodveasela of the lobular plexus. 

These cells arc the active agents In accomplishing the function of 
the liver. It is by their influence that the blood which ia brought 
in contact with them supers certain changes which give rise to the 
secreted pruduct» of the organ. The ingredients of the bite first 
make their appearance in the substance of the cells. They aro J 
then, transuded from one to the other, until they are at last dis- 
charged into the small biliary ducts seated in the interlobular 
spaces. Kach lobule of the liver must accordingly bo regarded as 
a mass of secreting tubules, lined with glandular cells, an<l invested 
with a close network of capillary bloodvessels. It foilowi>, there- 
fore, from the abundant inosculation of the lobular capillaries, and 
the manner In which they are entangled with the hepatic tissue, 
that the blood, in passing through the circulation of ihe liver, 
comes into the most, intimate relation with the glandular cclU of 
the organ, and gives up to them the nutritious materials which are 
afkerward converted into the ingredients of the bile. 



BsPATic Crli.*. Ptsb Ibabamiio aiibJooL 



' Am^riraii J'jurtinl Itinl. Sci., Jaiiunrr, 1648. 

' tin ^tno I'liiiiU in llie Minute dnntom/ o( llie Liver. 



Loudon, l(>66. 



EXCRSTIOH. S23 



CHAPTER XVII. 

EXCRETION. 

Ws have now come to the last diviBion of the great nutritive 
fiiBCtion, viz., the process of excretion. In order to understand fairly 
the natnre of this process we must remember that all the component 
parts of a Uving oi^nism are necessarily in a state of constant 
change. It is one of the essential conditions of their existence and 
activity that they should go through wi^ this incessant transforma- 
tion and renovation of their component substances. Every living 
animal and vegetable, therefore, constantly absorbs certain materials 
from the exterior, which are modified and assimilated by the pro 
cess of nutrition, and converted into the natural ingredients of the 
organized tissues. But at the same time with this incessant growth 
and sapply, there goes on in the same tissues an equally incessant 
prooeaa of waste and decomposition. For though the elements of 
tbe food are absorbed by the tissues, and converted into musculine, 
usteine, hsematine and the like, they do not remain permanently in 
this condition, but almost immediately begin to pass over, by a con- 
Uhoance of the alterative process, into new forms and combinations, 
which are destiped to be expelled from the body, as others continue 
to be absorbed. Thus Spallanzani and Edwards found that every 
oi||;anized tissue not only absorbs oxygen from the atmosphere 
and fixes it in its own substance; but at the same time exhales 
carbonic acid, which has been produced by internal metamorphosis. 
This process, by which the ingredients of the organic tissues, al- 
nady formed, are decomposed and converted into new substances, 
IB called the process of Destructive Ammilation. 

Accordingly we find that certain substances are constantly mak- 
ing their appearance in the tissues and fluids of the body, which 
did not exist there originally, and which have not been introduced 
with the food, but which have been produced by the process of in- 
ternal metamorphosis. These substances represent the waste, or 
physiological detritus of the animal organism. They are the forms 



BTCRKTTOIT. 



under whicli those materials present themselves, which have once 
formed a part or the living tissue, but which have bcoomo altered 
by the incessant changes characteristic of organized bodies, and 
which are consequently no longer capable of exhibiting vital pro- 
perties, or of performing the vital functions. They are, therefore, 
destined to be removed and discharged from the animal frame, and 
are known accordingly by the name of Sxeremmtitious Substances. 

These excrementitioua aubsiances have peculiar characters by 
which ihey may be distinguished from the other ingredients of the 
living body; and they might, tberefure, be made to constitute a 
fourth claHs of proximate principles, in addition to the three which 
we hare enumerated in the preceding chapters. They are all sub- 
stances of definite chemical composition, and all susceptible of 
crystallization. Some of the most important of them contain nitro- 
gen, while a few are non-nitrogenous in their composition. They 
originate in tlie interior of living bodies, and are not found else- 
where, ejicept occasionally as the result of decomposition. They 
are nearly a1! suluble in water, and are soluble without exception in 
the animal fluids. They are formed in the substance of the tiasnea, 
from which tliey are absorbed by the blood, to be afterward conveyed 
by the circulating fluid to certaio excretory organs, particularly the 
kidneys, from which they are Hoally discharged and expelled from 
the body. This entire process, made up of the production of the 
cxcrcmenlitioQS substances, their absorption by the blood, and their 
linal elimination, is known aa the process of excretion. 

The importance of this process to the maintenance of life is readily 
shown by the injortons eAects which follow upon its disturbance. 
If the discharge of the excrementitious substances be in any way 
impeded or suspended, these substances accumulate, either in the 
blood or in the tissues, or in both. Id couaequence of this reteottoQ 
and accumulation, they become poisonous, and rapidly produce a 
derangement of the vital functions. Their influence is principally 
exerted upon the nervous system, through which they produce 
most frequently irritability, disturbance of the special senses^ deli- 
rium, insensibility, coma, and Bnally death. The readiness with 
which these efl'ecis are produced depends on the character of the 
excrementitious substance, and the rapidity with which it is pro- 
duced in the body. Thus, if the elimination of carbonic acid be 
stopped, by overloading the atmosphere with an abundance of the 
same gas, death takes place at the end of a few minutes; bat if the 
elimination of urea by the kidneys be checked, it requires three or 



H 



UREA. 826 

foar days to produce a fatal result. A fatal result, however, is cer- 
tain to follow, at the end of a longer or shorter time, if any one of 
these substanoes be compelled to remain in the body, and accumu- 
late in the animal tissues and fluids. 

The principal excrementttious substances known to exist in the 
hamao body are as follows: — 

1. Carbonloaeid C<^ 

2. CbolMtaiiae CjiHuO 

3. D«» C,H,NiO, 

4. CresUiM C^H^,0« 

b. CreatinfDa C,H,N,0, 

6. Crate of Bodft NaO,C,HN,Orf HO 

7. Drato of poUiia .... KO,C,HN,0( 

8. Urats of ammooia .... NH^OiSCtHNgOr^-HO 

Of these substances the first two have already been studied at 
eafficient length in the preceding chapters. We will merely repeat 
here that carbonic acid is produced in large quantity in nearly all 
the tissues of the body, from which it is absorbed by the blood, 
conveyed to the lungs, and there exhaled at the same time that 
oxygen is al»orbed. Cholesterine.is a non-saponifiable fatty sub- 
stance, originating in the brain and spinal cord, in the tissue of 
which organs it exists in the proportion of 68 parts per thousand. 
It is thence taken up by the blood, conveyed to the liver and dis- 
charged with the bile. Cholesterine is extremely insoluble in 
water, but is held in solution in the blood and the bile, by some of 
tbe other ingredients present in these animal fluids. 

The remaining excrementitious substances may be examined 
together with the more propriety, since they are all ingredients of 
anngle excretory fluid, viz., the urine. 

Ursa. — This is a neutral, crystallizable, nitrogenous substance, 
very readily soluble in water, and easily decomposed by various 
external influences. It occurs in the urine in the proportion of SO 
parts per thousand; in the blood, according to Picard,' in the pro- 
portion of 0.016 per thousand. The blood, however, is the source 
from which this sabstance is supplied to the urine; and it exists, 
accordingly, in but small quantity in the circulating fluid, for the 
reason that it is constantly drained off by the kidneys. But if tbe 
kidneys be extirpated, or the renal arteries tied, or the excretion 
of arine suspended by inflammation or otherwise, the urea then 

■ Id UilDfl Edwards, Le^na aar la Pbjaiologie, &c , vol. t. p. 297. 



326 



BXCRITIOI 



^ 



& 



l?,:i 



c:^/ 



accumulates in tTie blooti, and presents itself there in conaiderable 
quatiiity. It has bw;ti founO in the blood, under these cireom- 
sutuccs, in the [iroportion of 1.4 per thoufiand.' It is not yet known 

from what source the urea iafl 
^* ^^** originally derived; whether it 

be prcxluced in the blood itaclf, 
or whether it be formed in some 
of the solid tissues, and thcnco 
taken up by the blood. It has 
not yet been found, however, 
in any of the solid tiiauas, in a 
state of health. 

Urea isobtained most readily I 
from the urine. For this pur- 
pose the fresh urine is evapo- 
rated in the water bath until it] 
baa a syrupy consistency. It] 
is then mixed with an equal, 
volume of nitric acid, which] 
forms nitrate of urea. Thi.s salt, being lej» soluble than pure urca,j 
rapidly crystallizes, after which it is separated by 61tration from< 
the other ingredients. It is then dissolved in water and deoom-; 
posed by carbonate of lend, forming nitrate of lead which romalna 
in solution, and oarbonio acid which escapee. The solution is then 
evaporated, the urea dissolved out by alcohol, and finally crystal- 
lized iu a pure state. 

Urea has no tendency to spontaneous decomposition, and may 
be kept, when perfectly pure, in a dry Biato or dissolved in water, 
for an indefinite length of time. If the watery solution be boiled, _ 
however, the urea is converted, during the process of ebullition,'^ 
tato carbonate of aitimonia. One equivalent of urea unites with 
two equivalents of water, and becomes transformed into two equiva- , 
lents of carbonate of ammonia, as follows: — 



rB|4, pnnt-tDi] tnini ariar, ■nit cryitBlUml hj 



C,H,N,0,=L'r*». 



2 



Various impurities, also, by acting as catalytic bodies, wtU 
duco the same change, if water be present. Animal substances in 
a state of commencing decomposition are particularly liable to aet^ 



' Robiu uid Vvnlvit, col. U. p. fi02. 



UREA. 127 

iii this way. Tn order that the conversion of the urea be thus pro- 
dooed, it is necessary that the temperature of the mixture be not 
far from 70° to 100" F. 

The quantity of urea produced and discharged daily by a healthy 
adult is, according to the experiments of Lehmann, about 600 
grains. It Taries to some extent, like all the other secreted and 
<xcreted products, with the size and development of the body. 
XehmAtin, in experiments on his own person, found the average 
daily quantity to be 487 grains. Prof. William A. Hammond,' 
"who is a very large man, by similar experiments found it to be 
470 grains. Dr. John C. Draper* found it 40B grains. No urea is 
to be detected in the urine of very young childreu,-' bat it soon 
anakes ita appearance, and afterward increases in quantity with the 
development of the body. 

The daily quantity of urea varies also with the degree of mental 
and bodily activity. Lehmann and Hammond both found it very 
sensibly increased by muscular exertion and diminished by repose. 
It has been thought, from these facts, that this substance must be 
directly produced from disintegration of the muscular tissue. This, 
liowever, ia by no means certain ; since in a state of general bodily 
activity it is not only the urea, but the excretions generally, carbonic 
aoid, perspiration, &c^ which are increased in quantity simultane- 
ooaly. Hammond has also shown that continued mental applica- 
tion will raise the quantity of urea above its normal standard, 
though the muscular system remain comparatively inactive. 

The quantity of urea varies also with the nature of the food. 
Lehmann, by experiments on his own person, found that the quan- 
tity was larger while living exclusively on animal food than with 
a mixed or vegetable diet ; and that its quantity was smallest when 
confined to a diet of purely non-nitrogenous substances, as starch, 
wigar, and oil. The following table* gives the result of these ex- 
perimenta 

KiMD OF Food. Dailt Qdaktitt of Uhba. 

Animal 798 graiiu. 

Mixed 467 " 

Vrgetable 337 " 

Non-nitrogenooH 231 " 



t Amerioan Joarnal Ued. Sol., Jan., IHSS, and April, 1856. 
■ N«w York Jonrnal of Medicine, Harob, 1856. 

* Robin and Verdeil, vol. ii. p. 500. 

* Lebmann, op. oit., vol. ii. p. lt!3. 



5S8 



BXCHRTIOK. 



Finally, it has been sbowa by Dr. John C. Dmper' that there is 
also a diurnal variation in the norma] quantity of urea. A smaller 
quantity ib produced during the night than during the day; aod 
this difference exists even in patients who ere confined to the bed 
during the whole twenty-four hours, as in the case of a man under 
treatment for fracture of the leg. This ia probably owing to the 
greater activity, during the waking hours, of both the mental and 
digestive functions. More urea ia produced in the latter half than 
in the earlier half of the day; and the greatest quantity is dis- 
charged during the four hours from 6J to lOJ P. M. 

Urea exiata in the urine of the carnivorous and many of the 
herbivorous quadrupeds; but there is little or none to be found in 
that of birds and reptiles. 



Crsatine. — This is a neutral cryatallizable substance, found in 
the muscles, the blood, and the urine. It is soluble in water, very 

slightly soluble in alcohol, and 
Fig' 112> not at all m in ether. By boil- 

ing with an alkali, it is either 
converted into carbonic acid 
and ammonia, or is decomposed 
with the production of urea and 
an artificial nitrogenous crys- 
tallizable substance, termed sar- 
coaine. By being heated with 
strong acids, it loses two equiva- 
lents of water, and is oonverted 
into the substance next to be 
described, viz., creatinine. 

Creatine exists in the urine, 
in the human subject, in the 
proportion of about 1.25 parts, 
and in the muscles in the proportion of 0.67 parts per thousand. 
Its quantity In the blood has not been determined. In the muscu- 
lar tissue it is simply in solution in the interstitial fluid of the pariA, 
so that it may be extracted by simply cutting the muscle into 
small pieces, treating it with distilled water, and subjecting it to 
l>ressiirc. Creatine evidently originates in the muscular tissue, is 
absorbed llience by the blood, and is finally discharged with the 
urine. 

■ Lw. tAi. 




CNiiATi]i|[,crT>ln1Jlt*iirr.>u] bm trXnr 



(After 



I 
I 
I 

I 




CREATISIXl— CRATB OF SODA. 



Cbeatinink. — This is also a crystallizable sabstance. Tt differs 
in compoailion from creatine by containing two equivalents le«8 of 
the elements of water. It Is more soluble in water and in spirit 
than creatiue, and dissolves sliglitlj also in ether. It hru) a dis- 
tinctly flliiallnD reaction. It occurs, like crcaiino, in the muaclcA, 
the blood, and the urin6; and 

is undoubtedly first produced '*• US- 

in the muscular tlsfluo, to be 
discharged finally by the kid- 
neys. It is very possible that 
it originates, not directly from 
the muscles, but indirectly, by 
transformation of a part of the 
creatine; since it may be arti- 
ficially produce*!, as we have 
already mentionod, by trans- 
formation of the latter substance 
under the influence of strong 
acid?, and since, furthermore, 
vrbilecreatine is more abundant 
in the muscles than creatinine, 

in the urine, on the contrary, there is a larger quantity of creatinine 
than of creatine. Both these subHtnnccrs have been fouud in the 
muscles and in the urine of the lower animals. 



dl 






10 



^i 



lAfi^r IfbDiiioa.) 



■lOT 



Ubate or Soda. — As its name implies, this suKstance is a neu- 
tral salt, formed bj the union of soda, as a base, with a utlrogenoos 
inimal acid, viz., uric ncirf (CjUNjO^UO). Uric acid is sometimes 
i^Hiken of as though it were itself a proximnte principle, and a 
constituent of the urine; but it cannot properly be regarded as 
Rich, since it never occurs in a free state, in a natural condition of 
the fluids. When present, it has always been produced by decom- 
{Kpsition of the urate of soda. 

Urata of soda is readily soluble in hot water, from which a large 
portion again deposits on cooling. It io slightly soluble in alcohol. 
and insoluble iu ether. It crystallizes in small globular mas.=)e8, 
with projecting, curved, conical, wartlike excrescences. (Fig. 114,) 
It dissolves readily in the alkalies; and by most acid solutions it 
is decomposed, with the production of free uric acid. 

Urate of soda exists in the urine and in the blood. It is either 
produced originally in the blood, or is formed in some of the solid 



330 



BXCBBTIOK. 



tiKiQ&s, nnd alMorbed from them by the circulating fluicl. Il t» coo- 
statitly L'liiniuated by the kidneys, in company with the other ingre- 
dients uf the urine. The 
'''*■ ^**' average daily quantity of 

urate of soda diacharged by 
the healthy human subject Js, 
accord ingU) IxhTnann,aboot 
25 grains. This substance 
c^iats in the urine of the car- 
nivorous and omoivoroua 
animals, but not in that of 
the herbivora. In the latter, 
il is replaced by another sub* 
9tnnce, difTering somewhat 
from it iu couipositioii and 
properiie3, viz., hippurate of 
soda. The urine of herbi- 
vora, however, while stiU 
very young, and living upon the milk of the mother, has been found 
to contain urates. But when the young animal is weaned, and be- 
comes herbivorous, the urate of soda diaapijearB, and ia replaced by 
the hippurate. 



17»AT>ep Boti«; frnma arlntrr d«po>IL 



Urates of Potassa and Ammosia. — The urates of polassa awl 
aminonia resemble the preceding salt very closely ia their phy.iJo- 
logical relations. Thoy are formed in very much smaller quantity 
than the urate of eodn, and appear like it as ingredients of the urine. 

The siibsiances aV>ove enumerated closely resemble each other in 
their most striking and important characters. They alt contain 
nitrogen, are all crystallizable, and all readily soluble in water. 
They all ori^-inate in the interior of the body by the decomposition 
or catalytic tranaibrmntion of its organic ingredients, and are all 
conveyed by the blood Co the kidneys, to be finally expelled with 
the urine. These are the substances which represent, to a great 
extent, the fin.il tran-sformaiion of the organic or albuminoid in- 
gredients of the tissues. It has already been mentione<l, in a pre- 
vious chapter, that these organic or albuminoid substanoes are not 
discharged from the body, under their own form, in quantity at all 
proportionate to the abundance with which ihey are introduced. 
By far the greater part of the m.i3s of the frame is made up ofj 
organlu subdtiitices : albumen, niusculiue, ustelne, ko. tSimilar 



OKNKBAL CHABACTSBS OF THE URINE. SSI 

materials are taken daily in large qnaDtitj with the food, in order 
to supply the nutrition and waste of those already composing the 
^aes; and yet only a very insignificant quantity of similar 
material is expelled with the excretions. A minute proportion of 
Tolatile animal matter is exhaled with the breath, and a minute 
proportion also with the perspiration. A very small quantity is 
discharged under the form of mucus and coloring matter, with the 
orine and feces; but all these taken together are entirely insuffi- 
cient to account for the constant and rapid disappearance of organic 
matters in the interior of the body. These matters, in fact, before 
being discharged, are converted by catalysis and decomposition into 
new substances. Carbonic acid, under which form 3500 grains of 
carbon are daily expelled from the body, is one of these substances; 
the others are urea, creatine, creatinine, and the urates. 

We see, then, in what way the organic matters, in ceasing to form 
a part of the living body, lose their characteristic properties, and 
are converted into crystallizable substances, of definite chemical 
composition. It is a kind of retrograde metamorphosis, by which 
-they return more or less to the condition of ordinary inorganic 
materials. These excrementitious matters are themselves decom- 
posed, afler being expelled from the body, under the inBuence of 
the atmospheric air and moisture; so that the decomposition and 
destruction of the organic substance are at last complete. 

It will be seen, consequently, that the urine has a character 
altogether peculiar, and one which distinguishes it completely 
from every other animal fluid. All the others are either nutritive 
fluids, like the blood and milk, or are destined, like the secretions 
generally, to take some direct and essential part in the vital opera- 
tions. Many of them, like the gastric and pancreatic juices, are 
reabsorbed afler they have done their work, and again enter the 
current of the circulation. But the urine is merely a solution of 
excrementitious substances. Its materials exist beforehand in the 
circulation, and are simply drained away by the kidneys from 
the blood. There is a wide difiterence, accordingly, between the 
action of the kidneys and that of the true glandular organs, in 
which certain new and peculiar substances are produced by the 
action of the glandular tissue. The kidneys, on the contrary, do 
not seorete anything, properly speaking, and are not, therefore, 
glands. In their mode of action, so far as regards the excretory 
function, they have more resemblance to the lungs than to any 
other of the internal organs. But this resemblance is not complete; 



w 



KICBBTTOS. 



since tbc lungs perform a double Tunction, Absorbing oxygen at tbe 
same time tlint they exlinle carbonic acid. The kidneys alone are 
purely excretory in their olTice. The urino is noi intended to 
fulfil any function, mecbanical, chemical, or athervrise; but is des- 
tined only to bo eliminated and exp(;lle<1. Since it possesses so 
|xx:ulinr and impurlant a character, it will require to be carefully 
studied in detail. 

The un'ne is a clear, watery, amber-cotored fluid, with a distinct 
acid reaction. It has, while still warm, a peculiar odor, which dis- 
appears more or less completely on cooling, and returns when the 
urinu is gently heated. The ordinary quantity of urine discharged 
daily by a healthy adult is about Sxxxv, and its mean specific 
gravity, 1024. Both its total quantity, however, and its mean 
specific gravity are liable to vary somewhat from day to day, owing 
to the diflereitt proportions of water and solid ingredients entering 
into its constitution. Ordinarily the water of the urine is more 
tbau sufficient to bold all its solid matter in solution; and its pro- 
portion may therefore be diminished, by accidental causes without 
the urine becoming turbid by the formation of a deposit Under 
such circumstances, ic merely becomes deeper in color, and of a 
higher specific gravity. Thus, if a smaller quantity of water than 
usual be taken into the system with the drink, or if the fiuid ex- 
halations from the lungs and skin, or the intestinal discharges, be 
increased, a smaller quantity of water will necessarily pass off by 
the kidneys; and the urine will be diminished in quantity, while its 
specific gravity is increased. We have observed the urine lo be 
reduced in this way to eighteen or twenty ounces per day, its specific 
gravity rising at the same time to 1030. On the other hand, if the 
fluid ingesta be unusually abundant, or if the pcrspirntion be dimi- 
nished, the surplus quantity of water will pass off by the kidneys; so 
that the amount of urine in twenty-four hours may be increased to 
forty-five or forty-six ounces, and its specific gravity reduced at 
the same time lo 1020 or even I0L7. Under these conditions the 
total amount of solid matter discharged daily remains about the 
same. The changes above mentioned depend simply upon tbe 
fluctuating quantity of water, which may pass off by the kidneys 
in larger or smaller quantity, accordingto accidental circumstances. 
In these purely normal or physiological variations, thepcfore, the 
entire quantity of the urine and its mean specific gravity vary 
always in an inverse direction with regard to esch other; tbe former 
increasing while the latter diminishes, and vice vcrad. It^ however, it 



I 



I 



1 





DIUBNAL VARIATIONS OF THE URINE. 833 

sbould be found that both the quantity and specific gravity of the 
anoe were increased or diminished at the same time, or if either 
ODO were increased or diminished while the other remained station- 
ary, such an alteration would show an actual change in the total 
amount of solid ingredients, and would indicate an unnatural and 
pathological condition. This actually takes place in certain forms 
of disease. 

The amount of Tariation in the quantity of water, even, may be 
so great as to constitute by itself a pathological condition. Thus, 
in hysterical attacks there is sometimes a very abundant flow of 
limpid, nearly colorless urine, with a specific gravity not over 1U05 
or 1006. On the other hand, in the onset of febrile attacks, the 
quantity of water is oflen so much diminished that it is no longer 
sufficient to retain in solution all the solid ingredients of the urine, 
and the urate of soda is thrown down, after cooling, as a fine red 
or yellowish sediment. So long, however, as the variation is con- 
fined within strictly physiological limits, all the solid ingredients 
are held in solution, and the urine remains clear. 

There is also, in a state of health, a diurnal variation of the urine, 
both in regard to its specific gravity and its degree of acidity. 
The urine is generally discharged from the bladder five or six 
times during the twenty-four hours, and at each of these periods 
showB more or less variation in its physical characters. We have 
found that the urine which collects in the bladder during the 
night, and is first discharged in the morning, is usually dense, 
highly colored, of a strongly acid reaction, and a high specific 
gravity. That passed during the forenoon is pale, and of a low 
specific gravity, sometimes not more than 1018 or even 1015. It 
is at the same time neutral or slightly alkaline in reaction. Toward 
the middle of the day, its density and depth of color increase, and 
its acidity returns. All these properties become more strongly 
marked during the afternoon and evening, and toward night the 
urine is again deeply colored and strongly acid, and has a specific 
gravity of 1028 or 1030. 

The following instances will serve to show the general characters 
of this variation : — 

OBSBRVATins First. March 20th. 
Urine of IM discharge, acid, sp. gr. 1025. 
" 2d " alkaliae, " 1015. 

" 3d " neutral, " 1018. 

" 4th " acid, " 1018. 

" 5th " acid, " 1027. 



334 



EICBETIO:r. 



OHBBVATIOXStOONn. Sliirtk 21«(. 

Urino of Itt disohatgv, acl'l, ip. gr. 10S9. 

•* 2d '• nsBiral, - 1022. 

" 3A " TjfiitTfcl. " U'2a. 

» 4tb ■• add, " 1027. 

'■ 5th " nciii, " \0S0. 

TbcM variations do not always follow the [Kjrfectly regular 
courae nianifef^tcd in the above instances, since they are somewhat 
liable, as wo have already mentioned, to temporary modiGcation 
rrotn accidental causes during the day; but their geQeral teadeocy 
nearly always corresponds with that given above. 

It is evident, therefore, that whenever we wish to test the specific 
gravity and acidity of the urine in cases of disease, it will not be 
suQicieiU to examine any single specimen taken at random; but all 
the different portions discharged during the day should be collected 
and examined together. Otherwise, we should incur the risk of 
regarding as a permanently morbid symptom what tnight be 
nothing more than a purely accidental and temporary varialioa. 

The c^iemicat comtitution of the urine as it is discharged from the 
bladder, according tu the analyses of Derzelius, Lehmano, Becquerel, 
and others, is as follows: — 

CoMPosinox or TUX Uxixx. 

Wit« S3?.O0 

Vnx . , . • SO.tt) 

Crrntin« 1.Z& 

Cnatlnlii* . . . . • l.&O 

Drale of soda 

1.80,, 



Coloring m«ltnr and 1 
Mutu« 1 

Biplio?pliat<> of sohIa 
riuiapliste of Duxia 

" po1,-i««* 

" UiDD 

nilnriitrAof dioitlucn iiiid poUUKinm 7.80 

EulphntHii (iT soiIa rtml i>u[i.ihx .,..,.. 6.90 



.90 



13.45 



100U.OO 



We need not repeat that the proportionate quantity of thesBJ 
diflerent tngrcdicnlJfi, as given above, is not absolute, but only 
approximative; and that they vary, from time to time, within certain 
physiological limits^ like the ingredients of all other animal fluids. 

The urea, creatine, creatinine and urates have all been suffi- 



BBAGTIONS OF THE UBINB. • 886 

ciently described above. The macas and coloring matter, unlike 
tbe other ingredients of the urine, belong to the class of organic 
substances proper. Thej are both present, as may be seen by tbe 
analysis quoted above, in very small quantity. The coloring 
matter, or ttrosaeine, is in solution in a natural condition of the 
urine, but is apt to be entangled by any accidental deposits which 
may be thrown down, and more particularly by those consisting of 
tbe urates. These deposits, from being ofieu strongly colored red 
or pink by the urosacine thus thrown down with them, are known 
nnderthe name of "brick-dust" sediments. 

The mucus of the urine comes from the lining membrane of the 
urinary bladder. When first discharged it is not visible, owing to 
its being uniformly disseminated through tbe urine by mechanical 
agitation; but if the fluid be allowed to remain at rest for some 
"bouTS in a cylindrical glass vessel, the mucus collects at the bottom, 
xnd may then be seen as a light cottony cloud, interspersed often 
with minute semi-opaque points. It plays, as we shall hereafter 
see, a very important part in the subsequent fermentation and 
decomposition of the urine. 

Sij^iosphate of soda exists in the urine by direct solution, since it is 
Teadily soluble in water. It is this salt which gives to tbe urine its 
Acid reaction, as there is no free acid present in the recent condition. 
3t is probably derived from the neutral phosphate of soda in the 
Ttlood, which is decomposed by the uric acid at tbe time of its form- 
Ation; producing, on tbe one hand, a urate of soda, and converting 
a part of the neutral phosphate of soda into the acid biphospbate. 

The phosphates of lime and magnesia^ or the "earthy phcephates," 
ms they are called, exist in the urine by indirect solution. Though 
insoluble, or very nearly so, in pure water, they are held in solu- 
tion in the urine by the acid phosphate of soda, above described. 
*rhey are derived from the blood, in which they exist in considera- 
"ble quantity. When the urine is alkaline, these phosphates are 
deposited as a light-colored precipitate, and thus communicate n 
turbid appearance to tbe fluid. When tbe urine is neutral, they 
may still be held in solntion, to some extent, by the chloride of 
sodium, which has the property of dissolving a small quantity of 
phosphate of lime. . 

Tbe remaining ingredients, phosphates of soda and potassa, sul- 
phates and chlorides, are all derived from tbe blood, and are held 
directly in solution by tbe water of the urine. 
The urine, constituted by the above ingredients, forms, as we 



336 



BXCBETIOK. 



1 

i 



have already described, a clear amber-colored fluid, with a reacttoa 
for tht; most part distiactly acid, sometimes neutral, aod occasion- 
ally slightly alkaline. In its healthy canditioD it is affected by 
chemical and physical rcagcntit in the followmg manner. ■ 

Boiling the urine does not produce any visible change, provided 
its reactiou be acid. If It be neutral oralkiUitie, and ii^ at the same 
time, it contain a larj^or quantity than usual of the earthy phos- 
phates, it will become turbid on boiling; sinoe these salts are less 
soluble at a high than at a low temperature. 

The addition of nitric or other mineral acid produces at first only 
a slight darkening of the color, owing to the action of the acid upon 
tbo organic coloring matter of the urine. If the mixture, however, 
be allowed to stand for some time, the urates of soda, potasaa, &c., 
will be decomposed, and pure uric acid, which ia very insoluble, 
will be deposited in a crystalline form upon the sides and bottom 
of the glass vessel. The crystals of uric acid have most frequently 
tbo form of transparent rbomboidal plates, or oval lamina: with ■ 
pointed extremities. They are usually tinged of a ycHowish hoe 
by the coloring matter of the urintj which is united with them 
at the time of Ibeir deposit. They are frequently arranged inS 
radiated clusters, or small spheroidal masses, so as lu prcseai the 

appearance of minute calcu- 
^''S-^**' louB concretions, (Fig. 115.) 

The crystals vary very much 
in siso and regularity, ac- 
cording to the time occupied 
in their formation. 

If a free alkali, such as 
potnasa or soda, be added to 
the urine, so as to neutralize 
its acid reaction, it becomei 
immediately turbid from a 
deposit of the earthy phoa- 
pbaLes, which are insoluble 
in alkaline Huids. 

The addition of nitrate of 
baryta, chloride of barium, 
or Bubacetate of lead to heolthy urine, produces a dense procipi-, 
late, owing to the presence of the alkaline sulphates. 

Nitrate of silver produces a precipitate with the chlorides of 
sodium and potassium. 



. 



V»te AciD^ de)i<>*lit<l rrcDi urlDO. 



BBACTIONS OF THE URINE. 337 

Sabacetate of lead and nitrate of silver precipitate also tbe or- 
gaoic sabstances, maous and coloring matter, present in the arine. 
All the abore reactions, it will be seen, are owing to the presence 
of the natural ingredients of the nrine, and do not, therefore, indi- 
cate any abnormal condition of the excretion. 

Beside the properties mentioned above, the urine has several 
others which are of some importance, and which have not been 
aaually noticed in previous descriptions. It contains, among other 
ingredients, certain organic substances which have the power of 
interfering with the mutual reaction of starch and iodine, and even 
of decomposing the iodide of starch, af^r it has once been formed. 
^?ht8 peculiar action of the urine was first noticed and described 
Itj us in 1866.^ If 3j of iodine water be mixed with a solution 
of starch, it strikes an opaque blue color ; but if 5j of fresh urine 
"be afterward added to the mixture, the color is entirely destroyed 
a.t the end of four or live seconds. If fresh urine be mixed with 
f%>ar or five times its volume of iodine water, and starch be 
Bubseqaently added, no union takes place between the starch and 
iodine, and no blue color is produced. In these instances, the iodine 
unites with the animal matters of the urine in preference to com- 
Ixiaing with the starch, and is consequently prevented from striking 
its ordinary blue color with the latter. This interference occurs 
larhether the urine be acid or alkaline in reaction. In all cases in 
which iodine exists in the urine, as for example where it has been 
mdministered as a medicine, it is under the form of an organic com- 
bination; and in order to detect its presence by means of starch, a 
few drops of nitric acid must be added at the same time, so as to 
deetrby the organic matters, afler which the blue color immediately 
tppears, if iodine be present. This reaction with starch and iodine 
belongs also, to some extent, to most of the other animal fluids, as 
the saliva, gastric and pancreatic juices, serum of the bluod, &c.; 
bat it is most strongly marked in the urine. 

Another remarkable property of the urine, also dependent on its 
organic ingredients, is that of interfering with Trommer's test for 
grape sugar. If clarified honey be mixed with fresh urine, and sul- 
phate of copper with an excess of potassa be afterward added, the 
mixture takes a dingy, grayish blue color. On boiling, the color 
tains yellowish or yellowish brown, but the suboxide of copper is 
not deposited. In order to remove the organic matter and detect 

AiD«rii»ii Joarn&l U«d. Soi., April, 18&6. 

22 



888 EXCBETIOS". 

ibe sugar, ibo urine must be drst treated with an excess of animal 
charcoal and filtered. By tbta means the organic substances are 
retained upon the frlter, while thesugnr passes through in solution, 
and may then be detected as usual by Trommer's test, 

ACCIDEKTAL Inorediskts OP THB Ubins.— SlDCe tbc ufine, in 
its natural state, consists of materials which are already prepared in 
the blood, and which merely puas out through tlio kidneys by a 
kind of filtration, it is not stirprisiog that most medicinal and 
poisonous substances, introduced into the circulation, should be 
expelled from tho body by the same ehafinel. Those aubstanoes 
which tend to unite strongly with the animal matters, and to form 
with them insoluble compounds, such as the preparatiotis of iron, 
lead, silver, arsenic, mercury, &c., are least liable to appear in the 
urine. They may occasionally be detected in this fluid when they 
have been given in large doses, but when administered in moderate 
quantity are not usually lo be found there. Most other substances, 
however, accidentally present in the circulntion, pass off readily by 
tlie kidneys, either in their original form, or after undergoing cer- 
tain chemical modifications. 

The salts of the organic acids, such aa hctates^ acelales, Tnalates^ 
&c., of soda and pota,'*ia, when introduced into the circulation, are 
replaced by the carbonates of the same bases, and appear under 
that form in the urine. The urine accordingly becomes alkaline 
from the presence of the carbunntes, whenever the above sails have 
been taken in large quantity, or after the ingestion of fruits and 
vegetables which contain them. We have already spoken (Chap. IL) 
of the experiments of Lehmann, in which ho found the urine exhi- 
biting an alkaline ruaction, a very few minutes aft«r the administra- 
tion of lactates and acetates. In one instance, by experimenting 
upon a person with congenital extroversion of the biailder, in whom 
the orifices of the ureters were exposed,' he found that the urine 
became alkaline in the course of seven minutes after the ingestion 
of half an onnce of acetate of potassa. ■ 

The pure nlkalifs and their carbonates, according to the same ob- 
server, produce a similar effect. Bicarbonatoof [>ota;{sa, for example, 
administered in doses of two or three drachms, causes the urine 
to become neutral in from thirty to fortyfivc minutes, and alkaline 
in the course of an hour. It is in this way that certain " antical- 



■ Ph/siologloAl Cbemiati7, <rol. U. p. ISa. 



J 



ACCIDEyTAL INOBEDIENTS 0? THE UBINS. 

caloas" or "anti-lithic" nostruma operate, when given with a view 
of dissolving conoretions in the bladder. These remedies, which 
are asaally strongly alkaline, pass into the urine, and by giving it 
an alkaline reaction, produce a precipitation of the earthy phos- 
phates. Such a precipitate, however, so far from indicating the 
SQCcessful disint^ration and discharge of the calculus, can only 
tend to increase its size by additional deposits. 

Ferroeyanide of potassium^ when introduced into the circulation, 
appears readily in the urine. Bernard* observed that a solation of 
this salt, after being injected into the duct of the submaxillary 
glaod, could be detected in the urine at the end of twenty minutes. 
Iodine, in all its combinations, passes out by the same channel. 
We have found that after the administration of half a drachm of 
the syrup of iodine of iron, iodine appears in the urine at the end 
of thirty minutes, and continues to be present for nearly twenty- 
four hours. In the cose of two patients who had been taking iodide 
of potasfliam freely, one of them for two months, the other for six 
weeks, the urine still contaioed iodine at the end of three days 
After the anspension of the medicine. In three days and a half, 
liowever, it was no longer to be detected. Iodine appears alf>o, 
after being introduced into the circulation, both in the saliva and 
the perspiration. 

Quinine, when taken as a remedy, has also been detected in the 
^nrine. Sther passes out of the circulation in the same way. We 
liave observed the odor of this substance very perceptibly in the 
urine, after it bad been inhaled for the purpose of producing anses- 
tbesia. The bile-pigment passes into the urine in great abundance 
Id some cases of jaundice, so that the urine may have a deep yellow 
or yellowish brown tinge, and may even stain linen clothes, with 
"which it comes in contact, of a similar color. The saline biliary 
mbstanees, viz., glykocholate and tauro-cholate of soda, have occa- 
nonally, according to Lehmann, been also found in the urine. In 
these instances the biliary matters are reabsorbed from the hepatic 
ducts, and afterward conveyed by the blood to the kidneys. 

iSu^ar.— When sugar exists in unnatural quantity in the blood, 
it passes out with the urine. We have repeatedly found that if 
sugar be artificially introduced into the circulation in rabbits, or 
injected into the subcutaneous areolar tissue so as to be absorbed by 
the blood, it is soon discharged by the kidneys. It has been shown 

' LeqoQB d« Fhyaiologie Experimental e, 1856, p. 111. 



840 



KXCRETTOS". 



by Bernard' that the rapidity with which this subsfcmce appears in 
the urine under these circumainncea varies with the quantity in- 
jected and the kind of sugar used for the experiment. If a solution 
of 16 grains of glucose be injected into the areolar tissue of a rabbit 
weighing a little over two pounds, it is entirely destroyed in the 
circulation, and does not paaa out with the urine. A dose of 23 
grains, however, injected in the same way, appears in the urine at 
the end of two hours, 30 grains in an hour aud a hulf, 8^ grains to 
an hour, and 188 grains in fil\een minutes. Again, the kind of 
sugar used makes a diRerence in this respect. For while 15 grains 
of glucose may be injected without passing out by the kidneys, 
7^ grains of cane 8iig»r, introduced in the same way, fail U> be com- 
plelety destroyed in the circulatioo, and may be detected in the 
urine. In certain forms of disease (diabetes), where sugar accu- 
mulates in the blood, it is eliminaled by the same channel; and a 
aacchariue condition of the urine, accompanied by an iucreaw in 
its quantity and specific gravity, coustitutes the most characteristic 
feature of the disease. 

Finally, a^ufncn sometimes shows itself in the urine in conae- 
quence of various morbid conditions. Most acute inBammntioos 
of the icterual organs, as pneumonia, pleurisy, &c., are liable to be 
accompanied, at their outset, by a congestion of the kidneys, which 
produces a temporary exudation of the albutninuus elements of the 
blood. Albumen has been found in the urine, according to Simon, 
Becquerel, and others, in pericarditis, pneumonia, pleurisy, bron- 
ubitis, hepatitis, iuilaniinaliou of the brain, perlloaitis, metritis, &c. 
Wo have observed it, as a temporary condition, in pneumonia and 
after amputation of tlie thigh. Alljumitioua urine also occurs fre- 
quently in pregnant women, and in those affected with abdominal 
tumors, where the pressure upon the renal veins is sufficient to 
produce passive congestion of the kidneys. Whuu the renal con- 
gestion is spontaneous in its origin, and goes od to produce actual 
degenerution of the tissue of the kidneys, as in Bright's disease, the 
same symptom occurs, and remains as a permanent condition. In 
all such instances, however, as the above, where foreign ingredients 
exist in the uritie, these substauees do nut originate iu the kidneys 
themselves, but are derived from the blood, in the same manner as 
the tmtural ingredients of the excretion. 



Ii«(ODa do Ph^s. Bxp., ISbi, p. 214 e( Mf. 



ACID FEBUKNTATIOIT OF THE CRTlfE. 841 

Changes in the Ubine during Decomposition.— When the 
urine is allowed to remain exposed, afler its discharge, at ordinary 
temperatares, it becomes decomposed, afler a time, like any other 
animal fiuid; and this decomposition is characterized by certain 
changes which take place in a regular order of succession, as fol- 
lows:— 

After a few hours of repose, the mucus of the urine, as we have 
mentioned above, collects near the bottom of the vessel as a light, 
nearly transparent, cloudy layer. This macus, being an organio 
Bshetance, is liable to putrefaction; and if the temperature to which 
it is exposed be between 60** and 100° F., it soon becomes altered, and 
Gommnnicates these alterations more or less rapidly to the superna- 
tant fluid. The first of these changes is called the acid fermentation 
of the urine. It consists in the production of a free acid, usually 
lactic acid, from some of the undetermined animal matters con- 
tained in the excretion. This fermentation takes place very early; 
within the first twelve, twenty-four, or forty -eight hours, according 
to the elevation of the surrounding temperature. Perfectly fresh 
urine, as we have already stated, contains no free acid, its acid 
reaction with test paper being dependent entirely on the presence 
oS biphosphate of soda. Lactic acid nevertheless has been so fre- 
quently found in nearly fresh urine as to lead some eminent 
chemists (Berzelius, Lehmann) to regard it as a natural constituent 
of the excretion. It has been subsequently found, however, that 
urine, though entirely free from lactic acid when first passed, may 
frequently present traces of this substance afler some hours' expo- 
sure to the air. The lactic acid is undoubtedly formed, in these 
cases, by the decomposition of some animal substance contained in 
the urine. Its production in this way, though not constant, seems 
to be sufficiently frequent to be regarded as a normal process. 

In consequence of the presence of this acid, the urates are par- 
tially decomposed; and a crystalline deposit of free uric acid slowly 
takes place, in the same manner as if a little nitric or muriatic acid 
had been artificially mixed with the urine. It is for this reason 
that urine which is abundant in the urates frequently shows a de- 
posit of crystallized uric acid some hours after it has been passed, 
though it may have been perfectly free from deposit at the time 
of its emission. 

During the period of the "acid fermentation," there is reason to 
believe that oxalic acid is also sometimes produced, in a similar 
manner with the lactic. It is very certain that the deposit of oxa- 



S42 



BSCBITIOX, 



late of lime, far from being a dnngeroua or cron morbid symptom, 
aa it waa at one time regarded, is frequently preseni in perfectly 
oormal urine atler a. day or two of expusuru to the atmosphere. 
Wo have oflen observed it, under these cireumstances, n'hen no ■ 
morbid Hyniptoin cuulil bo detected in couoectiou either with the 
kidneys or with any other bodily organ. Now, whenever oxalic 
aoid is formed in the urine, it tnuat necessarily be deposited under 
the form of uxahite of lime: aioco this salt is entirely insoluble 
both in water and in the urine, even when heated to the boiling 
point. It is difficult to understand, therefore, when oxalate of lime 
La found as a deposit in the urine, how it can previously hare been 
held iu solatton. Ita oxalic acid is in all probability gradually 
formed, as we have said, in the urine itself; unitini;, as fast as it is 
produced, with the lime previously in aolution, and thus appearing 
asa crystallinedepoaitof oxalflteof lime. It is much more probable 
that tliits is the true explunatioo, since, in the cases to which we 
allude, the crystals of oxalate of lime grow, as it were, in the cloud 
of tnucus which cullecis at the bottom of the vessel, while the 
supernatant iluid remains clear. The^ crystals are of raioute size, 

transparent, and colorless, 
^'g- *i*- and have the form of regular 

octohedra, or double quad* 
rangular pyramids, united 
buseiobose. (Fig.116.) They 
mako their ap|>earance usu- 
ally about the commence* 
meiit of the second day, the 
urine at the satne time ooo> 
tinuing clear and retaining 
ita acid reaction. Thisdepo- 
sit is of freq^ueot occurrence 
when DO substance contaiu- 
iDg oxalic acid or oxalates 
has been taken with tbo food. 
At the end of some days 
thu cbauges above described 
come to nn end, and are succeeded by a diflerent process known as m 
the al^'afiiie/ermaitaU'on. This consists essentially in the docompo* 
sitiou or metamorphosis of the urea into carbonate of ammonia. 
As the ulLurution of the mucus advances, it loses the power of pro- 
ducing lactic and oxalic auidis aud becomes a ferment capable of 




J 
I 



OiiLJiTK vr LiaK; dfpoilirirrotDEiMilllijruHa*, 
dnrtcf lk« »ckd f«nit«DtMl«a. 




ALKALINE FKBHENTATION 07 THE URINE. 343 

acting by cataljsis apon the urea, add of exciting its decomposition 
as above. We hare already mentioned that urea may be converted 
into carbonate of ammonia by prolonged boiling or by contact 
with decomposing animal substances. In this conversion, the urea 
unites with the elements of two equivalents of water ; and conse- 
quently it is not susceptible of the transformation when in a dry 
state, but only when in solution or supplied with a sufficient quan- 
tity of moisture. The presence of mucns, in a state of incipient 
decomposition, is also necessary, to act the part of a catalytic 
body. Consequently if the urine, when first discharged, be passed 
through a enocession of close filters, so as to separate its mucus, it 
may be afterward kept, for an indefinite time, without alteration. 
Sat under ordinary circumstances, the mucus, as soon as its putre- 
&ition has commenced, excites the decomposition of the urea, and 
carbonate of ammonia begins to be developed. 

The first portions of the ammoniacal salt thus produced begin to 
neutralize the biphosphate of soda, so that the acid reaction of the 
urine diminishes in intensity. This reaction gradually becomes 
weaker, as the fermentation proceeds, until it at last disappears 
Altogether, and the urine becomes neutral. The production of 
carbonate of ammonia still continuing, the reaction of the fluid 
then becomes alkaline, and its alkalescence grows more strongly 
pronounced with the constant accumulation of the ammoniacal salt. 

The rapidity with which this alteration proceeds depends on the 
character of the urine, the quantity and quality of the mucus which 
it contains, and the elevation of the surrounding temperature. The 
urine passed early in the forenoon, which is often neutral at the 
time of its discharge, will of course become alkaline more readily 
than that which has at first a strongly acid reaction. In the summer, 
urine will become alkaline, if freely exposed, on the third, fourth, 
or fifth day; while in the winter, a specimen kept in a cool place 
may stilt be neutral at the end of flfleen days. In cases of paralysis 
of the bladder, on the other hand, accompanied with cystitis, where 
the mucus is increased in quantity and altered in quality, and the 
urine is retained in the bladder for ten or twelve hours at the tem- 
perature of the body, the change may go on much more rapidly, so 
that the urine may be distinctly alkaline and ammoniacal at the 
time of its discharge. In these cases, however, it is really acid 
when first secreted by the kidneys, and becomes alkaline while 
retained in the interior of the bladder. 

The first effect uf the alkaline condition of the urine, thus pro- 



344 



Bxcrkt:on. 



ducecl, 19 the precipitation of the earthy phosphates. These salts, 
being iciiiotuble in neutral and alkaline Huids, begin to precipitate us 
soon OS the natural acid reaction of the urine has fairly disappeared, 
and thus produce in the fluid a whitish turbidity. This precipitate 
slowly settles upon the sides and bottom of the vessel, or is partlv 
entaiigltKl with certain animal matters which rise to the surface and 
form a thin, opaline scum upon the urine. There are no crystals 
to be Heen at this time, but the deposit is entirely amorphous and 
granular in character. 

The next change consists in the production of two new double 
salts by the actiou of carbouate of aiomonia on the phosphates of 
soda and magnesia. Cue of these is the "triple phosphate," phos- 
phate of magnesia and ammonia (2MgO,NH,0,PO,+2HO), The 
other ia the phosphate of soda and ammonia (NaO,NH^O,HO,PO,+ 
8H0). The phosphate of magnesia and ammonia is formed from 
the phosphate of magnesia in the urine (3MgO,PO^+7HO) by 
ihe repbcement of one equivalent of magnesia by one of am- 
monia. The crystals of this salt ore verv elegant and charac- 
teristic. They show themselves throughout all parts of the mix- 
tare; growing gradually in the mucus at the bottom, adhering to 

the sides of the glass, and 
*^'^' "'^' scattered abundantly over 

the film which collects upon 
the surface. By their refract- 
ive power, they give to this 
l!lm a peculiar gliseeoiDg 
and iridesoeot appearance, 
■^- I which is nearly always visi- 

t^J^ ^^^ I ble at the end of six or seven 

days. The crystals are per* 
fectly colorless and transpa- 
rent, and have the form t>f 
triangular prisms, generally 
with bevelled extremities. 
(Fig. 117.) Frequently, also, 
their edges and angles are 
replaced by secondary facets. 
They are insoluble in alkalies, but are easily dissolved by acids, 
even in a very dilute form. At first they are of minute size, but 
gradually increase, so that after seven or eight days they may 
become visible to the naked eye. 



^ 



4e|i>'-lMd rruni li«alll>r UTlnv. JuKov klk4tlDt finneiL- 
lailuu. 



i 



i 



i 



i 



RBNOVATION BY NUTKITIVK PB0CE8S. 846 

The phosphate of soda and ammonia is formed, in a similar 
manner to the above, hy the union of ammonia with the phosphate 
of soda previously existing in the urine. Its crystals resemble 
very much those just described, except that their prisms are of a 
quadrangular form, or some figure derived from it. They are 
iDtermiDgled with the preceding in the putrefying urine, and are 
affected in the same way by chemical reagents. 

As the putrefaction of the urine continues, the carbonate of am- 

3nonia which is produced, afler saturating all the other ingredients 

Tfith which it is capable of entering into combination, begins to 

"be given off in a free form. The urine then acquires a strong 

■amrooniacal odor; and a piece of moistened test paper, held a little 

aibove its surface, will have its color immediately turned by the 

^kaline gas escaping from the fluid. This is the source of the 

^mmooiacal vapor which is so freely given off from stables and from 

«laDg heaps, or wherever urine is allowed to remain and decompose. 

^This process continues until all the urea has been destroyed, and 

"vntil the products of its decomposition have either united with 

«)tber substances, or have finally escaped in a gaseous form. 

Benotation op the Body by the Nutritive Pbocess. — "We 
v»n now estimate, from the foregoing details, the quantity of the 
different materials which are daily assimilated and decomposed by 
'fthe living body. For we have already seen how much food is 
'ftaken into the alimentary canal and absorbed by the blood after 
digestion, and how much oxygen is appropriated from the atmo- 
^}bere in the process of respiration. We have also learned the 
smount of carbonic acid evolved with the breath, and that of the 
-various excretory substances discharged from the body. The fol- 
lowing table shows the absolute quantity of these different ingre- 
dients of the ingesta and egesta, compiled from the results of direct 
experiment which have already been given in the foregoing pages. 

ABSORBSD SITBtKO 24 HOUBS. DtSOHABOSD DUKINa 24 HOUBS. 



Oxygen 


1.019 lbs. 


Carbonic acid 


1.535 lbs 


Water 


4.735 " 


AqneoiiB vapor 


1.155 « 


AlbamiDOiu nutter 


. .396 " 


Pnrapiratioii . 


1.930 " 


Starah 


.660 " 


Water of the urine 


2.020 " 


Fat . 


.220 " 


Urea and salts 


.110 " 


SalU . 


.040 " 


Feces . . 


.320 " 



7.070 7.070 

Bather more than seven pounds, therefore, are absorbed and dis- 



346 



EICTtBTlOIT. 



charged daily by tho licnlthy adult huTnnn sabjcct; and, for & man 
having tlio average weight of 140 pounda, a quantity of material, 
equal to the weight of the entire body, thus passes through the 
system in the course of twenty days, ■ 

It ia evident, also, that this is not a simple phenomenon of the 
passage, or Bltration, of foreign substAoccs throngh the animal _ 
frame. Tbe materials which are absorbed actually combine with f 
the tissues, and form a part of their substance; and it is only afler 
undergoing subsequent decomposition, that they finaUy make their 
appearance in the excretions. None of the solid ingredients of the 
food are discharged under their own form in the urine, viz., as I 
starch, Ikt, or albumen; but they are replaced by urea and other 
crystaHlzable substances, of a different nature. Even the carbonie 
acid exhaled by the breath, as experience has taught us, is not pro- 
duced by a direct oxidation of carbon; but originates by a steady 
process of decomposition, throughout the tissues of the body, some' 
what similar to that by which it is generated in the decomposition 
of sugar by fermentation. Tbese phenomena, therefore, indicate Stn 
actual change in the substance of which the brtdy is composed, and 
show that its entire ingredients are incessantly renewed under tha 
influence of the vital operations. 



SECTION II. 
NERYOUS SYSTEM. 

CHAPTER I. 

GENERAL STRUCTURE AND FUNCTIONS OF THE 
NERVOUS SYSTEM. 

Ik entering upon the study of the nervous system, we commence 
the examination of an entirely different order of phenomena from 
those which have thus far engaged our attention. Hitherto we 
have studied the physical and chemical actions taking place in the 
body and constituting together the process of nutrition. We have 
seen how the Inngs absorb and exhale different gases; how the 
stomach dissolves the food introduced into it, and how the tissues 
produce and destroy different substances by virtue of the varied 
transformations which take place in their interior. In all these 
instances, we have found each organ and each tissue possessing 
certain properties and performing certain functions, of a physical 
or chemical nature, which belong exclusively to it, and are cbarac- 
teriatic of its action. 

The foDctions of the nervous system, however, are neither phy- 
rical nor chemical in their nature. They do not correspond, in 
their mode of operation, with any known phenomena belonging to 
these two orders. The nervous system, on the contrary, acts only 
opon other organs, in some unexplained manner, so as to excite or 
modify the functions peculiar to them. It is not therefore an appa- 
ratus which acts for itself, but is intended entirely for the purpose 
of influencing, in an indirect manner, the action of other organs. 
Its object is to connect and associate the functions of different parts 
of the body, and to cause them to act in harmony with each other. 



84S 



GENERAL STBUCTCBB AJTD FDITCTIOITS 



This object may be more fully exemplified as folIowB:— 
Each organ and tissue in the body has certain properties peculiar^ 
to it, which maybe called into activity by the operation of a stimu- 
lus or exciting cause. This CAfiaciLy, which all the organs possess, 
of reacting under the influence of a stimulus, is called their excita- 
bility, or irritahility. We have often had occasion to notice this pro- 
perty of irritability, in experiments related in the foregoing pages. 
We have seen, for example, that if the heart of a frog, after being 
removed from the body, be touched with the point of a needle, it 
immediately contracts, and repeati the movement of an ordinary 
pulsation. If the leg of a frog bo separated from the thigh, its 
integument removed, and ihe polea of a galvanic battery brought 
in contact with the exposed surface of the muscle^, a violent con- 
traction takes place every time the electric circuit is completed,! 
In this itistanee, the stimulus to the muscles is supplied by the 
electric discharge, as, in the case of the ht^nrt above mentioned, it is 
supplied by the contact of the steel needle; and in both, a muscu- 
lar contraction is the immediate consequence. If we introduce a J 
metnllic catheter into the empty stomach of a dog through a gastrio ■ 
fistula, and gently irritate with it the mucous membrane, a secretion 
of gastric juice at once begins to take place; and if food be tatro- 
duced the fluid is poured out in still greater abutidance. We know 
also that if the integument be exposed to contact with a heated 
body, or to friction with an irritating liquid, an excitement of tha ■ 
ciruulntion is at once produced, which again passes away af^r the 
removal of the irritating cause. 

lu all these instances we Gnd that ihe organ which is called into- 
nctivity is excited by the direct application of some stimulus to its] 
own tissues. But this is not usually the manner in which the dif- 
ferent functions are excited during life. The stimulus which calls 
into action the organs of the living body is usually not direct, but 
indirect in its operation. Generally speaking, the organs which are 
situated in distant parts of the body are connectetl with each other 
by such A sympathy, that the activity of one is influenced by the 
condition of the others. The muscles, for example, are almost never 
called into action by an external stimulus operating directly upon 
tbeir own ilbrcs, but by one which is applied to some other organ, ■ 
either adjacent or remote. Thus the peristaltic action of the mus- 
cular coat of tlie intestine commences when the food is brought in 
ooTitact with its mucous membrane. The lachrymal gland is excited, 
to increased autivily by anything which causes irritation of tha- 



OF THE NERTOCS SYSTEM. 849 

oonjanctlTa. In all such instances, the physiological connection 
between two different organs is established throagh the medium of 
the nervous system. 

The function of the nervous system may therefore be defined, in 
the simplest terms, as follows: It is intended to associate the different 
parts <if the body in such a manner, that an action may be excited in one 
organ by means of a stimulus applied to another. 

The instances of this mode of action are exceedingly numerous. 
Thus, the light which falls upon the retina produces a contraction 
of the pupil. The presence of food in the stomach causes the gall- 
bladder to discharge its contents into the duodenum. The expul- 
sive eflforts of coughing are excited by a foreign body entangled in 
the glottis. 

It is easy to understand the great importance of this function, 
particularly in the higher animals and in man, whose organization 
is an exceedingly complicated one. For the different organs of 
tbe body, in order to preserve the integrity of the whole frame, 
most not only act and perform their functions, but they must act in 
harmony with each other, and at the right time, and in the right 
direction. The functions of circulation, of respiration, and of 
digestion, are so mutually dependent, that if their actions do not 
take place harmoniously, and in proper order, a serious disturb- 
ance must inevitably follow. When the muscular system is ex- 
cited by unusual exertion, the circulation is also quickened. The 
blood arrives more rapidly at the heart, and is sent in greater 
quantity to the lungs. If the movements of respiration were not 
accelerated at the same time, through the connections of the nerv- 
oas system, there would immediately follow deficiency of aeration, 
Taacular congestion, and derangement of the circulation. If the 
iris were dot stimulated to contract by the influence of the light 
falling on the retina, the delicate expansion of the optic nerve 
would be dazzled by any unusual brilliancy, and vision would bo 
obscured or confused. In all the higher animals, therefore, where 
the different functions of the body are performed by distinct organs, 
situated in different parts of the frame, it is necessary that their 
action sliould be thus regulated and harmonized by the operation 
of the nervous system. 

The manner in which this is accomplished is as follows: — 
The nervous system, however simple or however complicated it 
may be, consists always of two different kinds of tissue, which are 



850 



OHKERAL 8TBUCTUBB AND TCFCTIOyS 



distinguished From each other by their color, their structure, an 
their raode of aclioQ. One of theae is known as the tckite stihsiance^ 
or iUe fibrous {issue. It constitutes itie whole of the substance of the 
nervous trunks and branches, and is found in large quantity oa the . 
exterior of the spinnl cord, and in the central partA of the brain 
and cerebellum. In the latter situations, it is of a soil consistency, . 
like curdled cream, and of a uniform, opaque white color. In 
the trunks and branches of the nerves it has the same opaquB' 
white color, but is at the saiiio time of a firmer consistency, oiring 
to its being mingled with condensed areolar tissue. Examined hj 
the microscope, the white substance is seen to be composed every-' 
where of miuute fibres or filaments, the "ulliniate nervous fila- 
ments," running in a direction very nearly parallel with encb other. 
These filamenta are cylindrical in shape, and vary considerably in 
size. Those which ore met with in the spinal cord and tho brain 
ore the smallest, and have an average diameter of inhan of aa 
inch. In the trunks and branches of the nerves they average mSv 
of an inch. 

The structure of the ultimate nervou.<) filament is as foUowa: 
The exterior of each filament consists of a colorless, transparent 
tubular membraoe, which la seen with some diHicully in the oaturnl 
condition of the fibre, owing to the extreme delicacy of Its toxturo, 
and to its cavity being completely filled with a substance very 
aimilar to it in refractive power. In the interior of this tubular 
membrane there is contained a thick, semi-fluid nervous matter, 
which is white and gliuteuing by n-Hected light, and is called the 
"white substanco of Schwann." Finally, running longitudinally 
through the central piirt of each filament, is a narrow ribbon- 
shaped cord, of rather firm consistency, and of a iiemi-transpArent 
grayish color. This central portion is called the "axis cylinder," 
or the '^flattened baud." It is enveloped everywhere by the semi- 
fluid white subAtanco, and the whole ioveatod by tlie external tubu- 
lar membrane. ■ 

When nervous matter is prepared for the microscope and exa- 
mined by transmitted light, two remarkable appearances are ob- 
served in its filaments, produced by the contact of foreign aub- 
Rlances. In the first place the unequal pressure, to which the fila- 
menta are accidentally subjected in the process of dissection aod 
preparation, produces an irregularly bulging or varicose appearance 
in them at various points, owing to the readiness with which the 
semi-fluid white substance in tlicir interior is displaced in dt^rent 



OF THE NERVOUS 8TSTBU. 



861 




Nebtoci Filamekti from whlta inhaUnce of 
brain.— <!, a, a. Boft iDlwunee of th« fliamentii praued 
ont, And doatlut In irr^nUrlj ronnded drops. 



directions. (Fig. 118.) Sometimes spota may be Been here and 
there, where the nervous matter has been entirely pressed apart in 
the centre of a filament, so 

that there appears to be an ^'g- lis. 

entire break in its continuity, 
while the investing mem- 
brane may be still seen, pass- 
ing across from one portion 
to the other. When a nerr- 
408 filament is torn across 
imder the microscope and 
aobjected to pressure, a cer- 
'Sain quantity of the semi- 
^aid white substance id 
3}ressed out from its torn 
viztremity, and may be en- 
"•trely separated from it, so 
90 to present itself under the 
:ft)rm of irregularly rounded 
^rops of various sizes (a, a, 
«i;), scattered over the field of the microscope. The varicose appear- 
'^uce above alluded to is more frequently seen in the smaller nerv- 
^>iis filaments from the brain and spinal cord, owing to their soft 
«x}n8Utency and the readiness with which they yield to pressure. 

The second e£fect produced by the artificial preparation of the 
siervous matter is a partial coagulation of the white substance of 
Schwann. In its natural condition this substance has the same 
«x>n8istency throughout, and appears perfectly transparent and 
homogeneous by transmitted light. As soon, however, as the nerv- 
ous filament is removed from its natural situation, and brought in 
<»Dtact with air, water, or other unnatural fluids, the sofl substance 
Immediately under the investing membrane begins to coagulate. 
^t increases in consistency, and at the same time becomes more 
liighly refractive; so that it presents on each side, immediately 
underneath the investing membrane, a thin layer of a peculiar 
glistening aspect (Fig. 119.) At first, this change takes place 
only. in the outer portions of the white substance of Schwann. 
The coagulating process, however, subsequently goes on, and 
gradually advances from the edges of the filament toward its 
centre, until its entire thickness after a time presents the same 
appearance. The effect of this process can also be seen in those 



352 



GENERAL STRUCTUBI AND rCKCTtOyS 



N 



portions of the white substance which have hocn pressed out froai 
the ioterior of iho filameots, aod which float about iu the fonnof 

drops, (tig. 118, ii) These 
Fig. 119. drops are alwajs covered 

with a layer of coflgulaied 
material which is thicker 
and more opaque id propor- 
tion to tho length ot lime 
which has elapsed siooe the 
commcncenient of the alter* 
ation. 

The nervous filaments 
Kave essentially the same 
structure ia the brain and 
spioal cord as in the aervoiia 
trunks and branches; only 
they are of much sinallef 
size in the former than in 
the latter situation. In the 
nervottstrunksanil branches, 
however, outside the craniil 
and spiual cavities, ibers 
exists, superadded to the 
oervous filaments and interwoven with them, a large amount of 
condensed areolar or fibrous tissue, which protects them frooi 
injury, and gives to this portion of the nervous system a. peculiar 
density and resistance. This diflerencc in consistency between the 
whitt! tjubntaace of the nerves and tliat of the brain and spinal cofd 
is owing^ therefore, excluaively to the presence of ordinary fibrooa 
tissue in the nerves, while it is wanUng in the brain and spioal 
cord. The cousistency of the nervous filaments themselves is the 
same in each situation. 

The nervous filaments are arranged, in the nervous trunks aod 
branches, in a direction nearly parallel with each other. A certaia 
number of them are collected in the form of a bundle, which i* 
invested with a layer of Gbroua tissue, in which run the small 
bloodvcsseLa, destined for the nutrition of the nerve. These pri- 
mary bundles are again united into secondary, the secondary inu 
tertiary^ kc. A nerve, therefore, consists of a large bundle of ulti- 
mate filaments, associated with each other in larger or smaller 
packets, and bouud together by the investing fibrous layers. When 



(h«lr cuiciiJullon — At u. ilia loru vKlraialtJ of ■ 
nsrvoa* OUrnvoi iriih tbf ■«)■ cf liadnr {bt protrntllng 
rroni It Ai<'.ih« vlili«*nbii«ii»ii(Scliw*aiilii iiMrly 

■oparairil liy icrldcuUl niiii|iri'Hluii, but lb* all*- 
ofllail«r pKHti Mr«ui ib* nipluroj ponl^o. The vul- 
llua vt 111* iiil'iilkc inurnl-nni U hIihi »fva Hi c un Iha 
onNlil* i>r [1i* uarvun* BIkiuiiiiL 



OF THE XERTOVS 8T8TEV. 



853 



a nerve is said to becomo branched or "tlivided" in nny part of its 
course, tliis division merely implies that aomeof its filaments leare 
ttie bundles with which they were 
previously associated, and pursue ^s- 120. 

a different direction. (Fig. 1'2I>.) 
A nerve which originatesi, for ex- 
ample, from the spinal cord in the 
region of the neck, and runs down 
j the upper extremity, dividing and 
fflubdividing, to be finally diHtri- 
buted to the integument and mus- 
icles of the band, contains at its 
point of origin all the filaments 
into which it is afterward divided, 
and which are merely separated 
ai successive points from the 
roain bundle. The ultimate fila- 
taenia, accordiugly, are coutiau' 
ous throughout, and do not thom- 
' salves d ivide at any point between 
(beir origin and their final distri- 
bution. 

When a nerve, furthermore, is 

said to "iooeculate" with unotlior 

, nerve, as when the infra-orbital 

"EaotKulittes with the facial, or the 

cervical nerves inosculate with 

each other, this means simfily that some of the filaments composing 
the first nervous bundle separate from it, and cross over to form a 
part of the second, while some of those belonging to the second 
-orosa over and join the first (Fig. 121); but the individual filaments 
in each instance remain cuntinuous and preserve tbeir identity 
tliroughout. This fact is of great physiological importance; since 
the white or fibrous oerve-substaoce is everywhere simply an 
organ of transmission, It serves to convey the nervous impulse in 
■ various directions, from without inward, or from within outward; 
and as each nervous filament acts independently of the others, it 
will convey an impression or a slimnUis continuously from its 
origin to its termination, and will always have the same character 
aod function in every part of its course. 

The other variety of nervous inaltur is knuwu as the gray gtd>- 
2tt 



tll>l>ili<(l or ■ XlIKVII, •llnvllig pi»lliiti ilf 

ncrrcTi. Ininlf {n). and the lOpMVLlou at lu 
aI'DiBDta \>y, c, il, a). 



854 



GGN'GRAL STRUCTURE ASD FUKCTIOSB 



stance. It is sometimes called "cineritioiis mutter," and sometimes 
"vesicular aeurine." It is fuund in the centra] parljs of the spiDftl 



FIr 121. 



|l14.isOlllj(JiD|L of TSeRITEA. 



conl, at the base oF the brain in isolated masses, and is also spread 
out as a continuous layer on tliu external portions of tbe cerebrum 
and cerebellum. It also constitutes the substance of all the goo* 
glia of the great sympathetic. Examined by the microscope, it 

consists of vesicles or celU, of 



Pig. 123. 



ytMn Cii.ta, lal«rmis|lnd wHb llbm; fruni 
•rtallHaarffaclluB «f fat. 



various forms and sizes, im- 
bedded in a grayish, granular, 
intercelluUr substance, and 
contnining, also, very fre- 
queotly, granules of grayish 
pigmentary matter. It is to 
the presence of this granular 
pigment that this kind of 
nervous matter owes the ashy 
or "cioeritious" color from 
which it derives its name. 
The cells composing it vary 
in size, according to Kollikcr, 
from ,nff8 to loiF of ••» inch. 
Tlie largest of them have a 



OF THE XKBVOL'B 8TSTBM. 



8fi5 



very distinct nucleus and nucleolus. (Fig. 122.) Many of them ore 
provided with long processes or proje<>tions, uliicb are fiumeiitncs 
divided into two or three smaller brimches. These cella ore inter- 
mingled, in all the collections of gray matter, with nervous RlamenL*. 
and are eniAngled with their extremities in such a manner that tt 
is exoeedinglv diflicult to ascertain the exact nature of the anato- 
mical relations existing between iheni. It in certain that in some 
instance* the slender processes running out from the nervous veai- 
ekt become at last continuous with the Blamcnta; but it is not 
IcoowQ whether this be the case in all or even in a majority of 
iDstauces. The extremities of the filaments, however, are at all 
ercnts brought into very cloue relation with the vesicles or cells of 
the gray matter. 

Kvery collection of gray matter, whatever be its situation or 
relative size iu the nervous system, is called a gttngiion or nert<ma 
centre. Its function is to receive impressions conveyed to it by the 
nervous filaments, and to send out by them impulses which are to 
be transmitted to distant organs. The ganglia, therefore, originate 
nervous power, so to speak; while the filaments and the nerves 
only transmit it. Now we shall find that, in the Htructure of every 
nervous system, the ganglia are connected, first with the difleront 
or-gans, by bundles of filaments which arc called nerves; and 
s^^oodly with each other, by other bundles which are termed com- 
ntisdures. The entire system is accordingly made up of pauglia, 
**«rir», and comntissures. 

The simplest form of nervous system is probably that found in 
IV five-rayed starfish. This animal belonga to the type known 
*i radiata; that is, animals whose 
'■fgans radiate from a central point, Fig- 1'-^- 

so as to form a circular series of 
nniilar parts, each organ being ro- 
jieated at different points of the 
circumference. The starfish (Fig. 
123) consists of a central mass, 
with five arms or limbs radiating 
from iu In the centre is the mouth, 
and immediately beneath it the sto- 
mach or digestive cavity, which 
Rcnds prolongations into every one 
of the projecting limbs. There is 
also contained in each limb a portion it,BT«M bktbv ^r s? Airt.w. 



8&« 



OENCRAl. BTRUCTURE AVD 7CNCTI0N3 



uf the glandular and muscular systems, and the whole ia covered 
by a sensitive inleguinent. Tim nervuus aysteni consists of five, 
similar ganglia, situated in the central portion, at the base of thaij 
arms. These ganglia are connected with each other bycommts<| 
surea, so as to form a nervous collar or chain, surrounding 
onfiae of the digestive cavity. Kach ganglion also sends off nerTefl,!| 
iho lilaments of which are distributed to ibo organs contained -ti 
the corresponding limb. 

We have already stated that the proper function of the nervonfll 
system is lo enable a stimulus, acting upon one organ, to produoa] 
motion or excitemcut in another. This is ocoomplished, in lbs] 
starfish, in the following manner: — 

When any stimulus or irritation is applied to the integument of] 
one of the arms, it is transmitted by the nerves of the integumeatj 
to the ganglion situated near the mouth. Arrived here, it iaj 
received by the gray matter of the ganglion, and immcilialelj con-! 
verted into an impulse which is sent oat by other 61amenia to thai 
muscles of the corresponding limb; and a muscular contraction and 
movement consequently lake place. The muscles therefore contract 
in consequence of an irritation which has been applied to the skin. 
This is called the "reflex action" of the nervous system; because the, 
stimulus is first sent inwiird by the nerves of the integument, and' 
then returned or rellwtcd back from the ganglion u[k>d the masclea. 
It must be recollected that this action docs not neceasarily indicate 
nny sensation or volition, nor even any conaciousneas on the part of 
the animal. The function of the gray matter is simply to receive ^ 
the impulse conveyed to it, and to reflect or send back another; andlfl 
this may be accomplished altogether involuntarily, and without the 
existence of any conscious perception. 

Where the irritation applied to the integument is of an ordinary 
character and not very intense, it is simply rc6ected, as above 
described, from the corresponding ganglion back to the same limb. 
But if it bo of a peculiar character, or of greater intensity than usual, 
it may be also transmitted by the commissures to the neighboring 
ganglia; and so two, three, four, or even all five of the limbs may 
be set in motion by a stimulus applied to the Integument uf one of 
them. Now, as all the limbs of the animal have the same stmctuTe 
and contain the same organs, their action will also be the same; 
itnd the eflects of this communication of the stimulus from one to 
the other by means of commissures will be a repetition, or rather 
a Biinultiineuus ]>ruduciion of similar movements in different parts 



or THE 



867 



of the body. According to the character and intensity, therefore, 
of the original stimulus, it will be followed by a response from 
one, several, or all of llie diflerent parts of the animal frame. 

It will be seen also that there arc two kinds of nervous Hlaments, 
diCering esaentially in their functions. One set of these fibres run 
from the sensitive sarfacea to the ganglion, pnd convey the nervous 
impression inward. These are called sensitive fibres. The other 
set ran from the ganglion to the niusclea, and carry the nervous 
impression outward. These are called motor fibrea. 

In the starfish, where the body is composed of a repetition of simi- 
lar parts arranged round a common centre, and where all the liinba 
tre precisely alike in structure, the several ganglia compot'ing the 
nervous system are also similar to each other, and act in the same 
way. Bui in animals which are constructed ujvon a diflercnt plnn, 
and whose bodies are composed of distinct organs, situated in dif- 
ferent regions, we 6nd that the nervous ganglia, presiding over 
the function of these organs, preaeot a corresponding degree of 
dissimilarity. 

In AphjsitL, for example, which belongs to the type of mollasca, 
or sofi-bodied animals, the digestive apparatus consists of a mouth, 
an cesophaguB, a triple stomach, and a somewhat convoluted iniep- 
tine. The liver is large,' and placed on one side of the body, while 
the gills, in the form of vascular laminm, occupy the opposite side. 
There are both testicles and ovaries in the 
same animal, the male and female functions 
00-existir.g, as in many other invertebrate 
specie*. All the organs, furthermore, are 
here arranged without any reference lo a 
regular or symmetrical plan. I'he horty is 
oorered with a muscular mantle, which ex- 
pands at the ventral surface into a tolerably 
well developeil " foot," or organ of locomo- 
tion, by which the animal ia enabled to 
change its position and move from one 
locality to another 

The nervous system of this animal is con- 
structed Dpon a plan tx}rrespondii)g with 
that of the entire bo<ly. (Fig. 124.) There 5««Tr>p« tt*rxn or 
« a small ganglion (.) situated anteriorly, tZ-r^.,,:rTcZ 
which sends nerves to ihe commencement b^i «»<i«ii'^o. -1.3. i'*j*i ..r 
of the digestive apparatus, and is rcganled „i,„f r..ug;i«a. 



Fig. 124. 



358 



GENERAL STRUCTURE AXD FUNCTIONS 



Fig. 125. 



as the oesophageal or digestive franglion. Immediately behind 
a larger one (a) called the cephalic or cerebral ganglion, whict 
sends nerve* to the organs of special sen^e, and which is reganiei 
as the ^eut of volitiou and general Bcnsation fur the entire body, 
Following this is a pair of ganglia ().-i), ibe pedal or looomutcFr/ 
ganglia, which supply the muscular mantle and its fofit-like expaa- 
sioD, and which regulate the movement of these organs. Finallr, 
another gaoglion {*\ aiiuated at tbe p'tstcrior pare of the bodj, 
seuds nerves to the brunchiio or gills, and is termed the braochttl 
or respiratory ganglion. All these nervous centres are conDecled 
by commissures wiih the central or cerebral ganglion, and maj 
therefore act either independently or in association with each other, 
by means of these connecting fibres. 

Tn the third type of animals, uguin, viz , the orticula/tL, (he gaae* 
ral plnn of Btnicture of the body is diftercnt from the foregoing, 
and the nervous system is accordingly modified to correspond with 
ii. Tu these animals, the body ia compoaed of i 
number of rings or sections, whicb are articulated 
with each other in linear series. A very gocxi 
example of this type may bo found in tbeooo- 
mon ceutipcde, or scolopfndra. Here tbe bodyb 
composed of twenty-two successive and Dearly 
similar articulationa, each of which bos a pairo( 
legs attached, and contains a portion of the gUo- 
dular, respiratory, digestive and reproductive 
apparatuses. The animal, therefore, conaistaof a 
repetition of similar compound parts, arranged ia 
a longitudinal chain or series. The only exoep 
tions to this similarity are in the Srst and Usi 
articulations. The first is large, and ooataios 
the mouth; the lost is small, and contains tbc 
anus. The first articulation^ whicb is called tbe 
"head," ia also furnished with eyes, with anteooa^ 
and wiih a pair of jaws, or mandibles. 

The nervous system of the centipede (Kig. Xlh), 
corresponding in structure with tbe abore plaa, 
consists of a linear aeries of nearly equal ixiA 
similar ganglia arranged in paira, situated u{wfl 
tbe median line, along the ventral surface of ibe 
alimentary canal. Kach pair of ganglia is connected with the in- 
tegument uiid niusulcd of its own artiuuktiuu by auubiuve awl 



or t'liriPtPi- 



OP TBK NEBTOUS STSTEV. 



859 



motor 6IaTneDts; and trith those which precede and follow by a 
double cord o( longitudinal commissural iibrca. In the flrst articu- 
lation, moreover, or the head, the gAnglia are larger thao elsewhere, 
and send nerves to the anteonse and to the organs of special sense. 
This pair is termed the cerebral ganglion, or iho "brain." 

A reBex action may take place, in these animals, through either 
one or all of the ganglia composing the ncrroas chain. An im- 
prcitsion received by the integument of nny part of the body may 
be tntiismilled inwnrd to its own gaiigliou and thence reflected 
immediately outward, so as to produce a movement of the Wmhti 
belonging to that articulation alone; or it may be propagated, 
Ihroogh the longitudinal cammi»9urcs, forward or back, and pro- 
duce simuliaueous movements in several neighboring arliculalions; 
'Or, Gaully, it may be propagated quite up to the anterior pair of 
ganglia, or "brain," where its reception wiil be accompanied with 
oonaciousnesa, and a voluntary movement reflected back upon any 
or all of the limbs at once. The organs of special sense, also, com- 
municate directly wiLh the cerebral ganglia; and impressions con- 
veyed through them may accordingly give rise to movements in 
my distant part of the body. In these animals the ventral ganglia, 
or those which simply stand as a medium of commniiicntion be- 
tween the iotegumtut and the muscles, are nearly similar through- 
out; while the first pair, or those which receive the nerves of special 
sense, and which exercise a general controlling power over the rest 
of the nervous system, arc distinguished from the remainder by a 
well-marked preponderance in size. 

In the centipede it will be noticed that nearly all the organs and 
functions are distributed in an rajnal degree throughout the whole 
length of the body. The organs of special sense alone, with those 
of mastication and the functions of perception and volition, arc 
confined to the head. The ganglia occupying this part are there- 
fore the only qocs which are diatinguished by any exlemal pecu- 
liarities; the remainder being nearly uniform both in size and 
■ctivity. In some kinds of articulated animals, however, particular 
functions are concentrated, to a greater or less extent, in particular 
parts of the body; and the nervous ganglia which preside over 
them are modified in a corresponding manner. In the insects, 
tvT example, the body is divided into three distinct sections, viz: 
the head, containing the organs of prehension, tnaslicatioii, t.ict 
tod special sense; the chesl, upon which are concentrated the or- 
gans uflocomotion, the legs ami wiugn; and the abdomen, conuiin- 
ing the greater part of tho olimuuiary canal, together with the 



360 



GENERAL BTRL'CTURE AXU PITNCTIOKS 



glamliilar and generative organs. As tlie insects liave a greater 
ami)iint of intelligence and activity than the oentipcdca and other 
worm-like articulata, and as the organs of special sense are more 
perfect in them, the cerebral ganglia are als^j uDuaually developed, 
and are evidently compu»ud uf several pairs, connected by commis- 
sures aa as to form a compound mass. As the organs of locomo- 
tion, furthermore, instead of being distributed, as in the centipede, 
throughout the entire length of the animal, are concentrated u]>oii 
the cht'st, the locomolory ganglia also prepttnderatc ta size in this 
region of the body ; while the ganglia which preside over the secre- 
tory and generative functions arc situated together, in the cavity of 
the abdomen. 

All the above parts, however, are coiiaected, in the sanie manner 
08 previously described, wiih the anterior or cdrebral pair of guo- 
glia. In all articulate animals, moreover, the general arrangement 
of the body U symmetrical. The right side is, for the most part, 
precisely like the led, as well in the Internal organs aa in the ex- 
ternal covering and the looomotory appendages. The only marked 
variation between different parts of the body is in an anteropos- 
terior direction; owing to diCerent organs being concenlrated, in 
some cases, in the bead, chest, and abdomen. 

Finally, in the veriei*raie type of animiils, comprising man, the 
quadrupeds, birds, reptiles, and fish, the external parts of the body, 
Mgethcr with the tocomotory apparatus and the organs of special 
sense, are symmetrica), as in the articulate; but the internal organs, 
especially those concornod in the digestive and -secretory functions, 
nre ansynimetrical and irregular, as in the moUusca. The organs 
of respiration, however, are nearly symmetrical in the vertebrata, 
for the reason that the respiratory movements, upon which the 
function of these organs is immediately dependent, are performed 
by muscles belonging to the goneral looomotory ap|)aratuR. The 
nervous system of the venebrata partakes, accordingly, of the strac- 
tural arrangement of the organs under its control. That portion 
which presides over the locomolory, respiratory, sensitive, and in- 
tellectual functions forms a system by itself, called the cerebrospinal 
81/stem. This system is arranged in a manner very similar to that 
of the articulata. It is compo!*ed of two equal and symmetrical 
Italves, running along the median line of the body, the diQcrent 
parts of which are connected by transverse and longitudinal com- fl 
missiires. Its ganglia occupy the cavities of the cranium and the 
spinal cannl, and send out their ncrve^t through openings in the 
bony walla of iheie cavities. 



I 



I 

I 
\ 



I 




OF THE NERVOUB 8TSTIH. 



S61 



The other portioo of llie nervous system of vertebrata is that 
which presides over the functions of vegetative life. It is called 
the ganffUonie, or great symjyathetic ft/atem. Its ganglia arc situated 
anteriorly to the spinal column, in the visceral cavities of the body, 
and are connected, like the others, by transverse and longitudinal 
coromissures. This part of the oervous system is symmetrical ni 
the neck and thorax, but is unsymmetriual in the aUlonaen, where 
it attains its largest size and ila nuist comjilete development. 

The vertebrate animals, as a general rule, are very muoh superior 
to the other classes, in intelligence and activity, as well sa in the 
variety and complicated character of their motions; while their 
nutritive or vegetative function*, on the other band, are not particu- 
larly well developed. Accordingly we find that in th^eae animals 
the cerebro-spinal system of nerves preponderates very much, in 
importaooc and extern, over that of the great sympathetic. The 
quantity of nervous matter contained in the brain and spinal uor<l 
is, even in the lowest vertebrate animal, very much greater than 
that contained in the system of the 
great sympathetic; and this prepon- ^'B- *26. 

(lerance increases, in the higher 
classes, just in proportion to their «u- 

periority in intelligence, sensation, ^^^^^^, . - - ._ 
power of motion, and other func- ^^^^^B^^fl 
tions of a purely animal character. 

The spinal cord is very nearly 
alike in the dilfcrcni clas-^cs of ver- 
tebrate animals. It is a nearly 
cylindrical cord, running from one 
end of the spinal canal to the other, 
and oonoecied at its anterior ex- 
tremity with the ganglia of the 
brain. (Fig. 126.) It is divided, by 
an anterior and posterior median 
flssare, into two lateral halves, which 
still remain connected with each 
other by a central mass or commis- 
sure. Its inner portions are occupied 
by gray matter, which forms a con- 
tinuous ganglionic chain, running ct«i.»<.-.rr»*t.^T.rKi. »r «*.*. 
from one extremity of the cord to -' (-."brun.. inrr,wii.m, .r5.*spio.t 

' wti Biul BXTiM. t, 4. BrmcUlal ssit**, 

the Other. Its outer portions are s. a. bmai nonM 



862 



OBNKBAL STRVOTUBF. AND FVSCTIOXB 



composed of white substance, the filarnenta of which run fur the 
most part in a. longitudinal direction, connecting the different parts 
of the cord with each other, and the curd itself with tlw ganglia 
of the brain. 

The spinal nerves are given off from the spinal cord at regular 
intervals, and in symmetrical pairs; one pair to each successire ■ 
jHirtion of the body. Their filainents are distributed to the integu- 
ment nntl m usclcs of the corresponding regions. In serpents, where 
locomotion is performed by simple, filteroate, lateral movements 
of the spinal column, the spinal cord and its nerves are of the 
same size throughout. But in the other vertebrate classes, where 
there exist special organs of locomotion, such as fore and hind 
legs, wiitgs, and the like, the spinal cord is increased in size at 
the points where the nerves of these organs are given off; and the 
nerves themselves, which supply the limbs, are larger than those 
originntiog from other partu of the spinal cord. Thus, in th« hu- 
innn subject (Fig. 126), the cervical nervta, which go to the arms, 
and the sacral nerves, which are distributed to the legs, are larger 
than the dorsal and lumbar nerves. They form, also, by frequent 
inosculation, two remarkable plexuses, before entering their corre- 
sponding limbs, vi^., the brachial plexus above, and the sacral 
plexus below. The cord itself, moreover, presents two enlargentients 
at the point of origin of these ncrv&s, viz., the cervical enlargement 
from which the brachial nerves (4, *) are given off, and the lumbar 
enlargement from which the saoml nerves (», ») originate. 

ir the spinal cord be exaininct) in tnuisverse section (Fig. 127), 

it will be seen that the gray 
mutter in its central portion 
forms a double creecentic- 
shapcfl mass, with the oon- 
ciiviLy of the crescents turn- 
ed outward. The.*Kcrcsoentic 
masses of gray matter, occu- 
pying the two lateral halves 
of the cord, are nnited with 



FiB. 127. 




I 
I 

I 



Tr(u>K*rM> Si>riti>ii vrsrTiAi-Coap — ii, * 
ii«r*e>o^ rl(lit atiil ir(K >ldt. •hcirlii4 ibdr lw<i ruau. 
d. l)ri|[lu ..f aDlrtii'T null, «. Otifia oT pudsriui rooi. 



^H each other by a transverse fl 
, band of the same substance, 



which is calkil the grat/ 
oommisaurc of the cord. Di- 
rectly in front of this is a 
transverse band of white substance^ connecting iu u similar manner 



or TH8 NKBVOl'S STSTKX. 



868 



le white portions of the two lateral halves. It is called the white 
eommitsure of Ou cord. 

The spinal nerves originate from the conl on each side by two 
distinct nwts; one anterior, and one posterior. The anterior root 
(Fig. 1'27, d) arises from the surface of the cord near the extremity 
of the anterior peak of gray matter. The posterior root(«) origi* 
Dates at the point corresponding with the posterior peak of gray 
matter. Both roots ar« composed of a considerable number of 
ultimate nervous filaments, united with each other in parallel 
bundles. The posterior root is diaiinguished by the prej*ence of a 
small ganglion (c), which appears to be incorporated with it, and 
through which its Qbres pass. There is no such gnngUou on the 
anterior root. The two roots uitito with each other shortly after 
leaving the cavity of the spinal canal, and mingle their filaments 
in a single trunk. 

It will be Been, on referring to the diflgram (Fig. 127), that each 
lateral half of the apinal cord is divided into two portions, au 
anterior and a posterior portion. The posterior [wak of gray mat 
ter comes quite up to the aurfacc of the cord, and it is just at this 
point (e) that the posterior roots of the nerves have their origin 
The whole of the white substance iueluded between thin point and 
the posterior median fissure is called the posterwr column of the 
cord. That which is included beiwcou the same point and the 
anterior median fissure is the anterior column of tfie cord. The 
white auKstance of the cord may then be regarded as consisting 
for the roost part of four longitudinal bundles of nervous filament*, 
Tiz., the right and left anterior, and the right and left posterior 
columns. The posterior median fissure penetrates deeply into the 
substance of the cord, quite down to the gray matter, so thnt the 
posterior colunma appear entirely separated from each other in a 
transverse section; while the anterior median fissure is more shal- 
low and stops short of the gray matter, so that the anterior columns 
are connected with each other by the white commissure above men- 
tioned. 

By the encejJiaian we njean the wluile of that portion of the 
OArebro'Spinal system which is contained in the cranial cavity. It 
IB divided into three principal parts, vi;;., the cerebrum, cerebellum, 
and medulla oblongata. The anatomy of iheas parts, though some- 
what complicato<i, can be readily un<lerstood if it be recollected 
that they are simply a double serifs of uetvous ganglia, conturied u.'iih 
tach other and with the 9pi»al cord by Imnsverte and hn-jitttdinai 



864 



OKNERAI. BTRtTCTURE a:T1) FUyCTIOSS 



Pip. I2f. 



n^t 



commitaurea. The number and relative size of these ganglia, in 
diflerent kinds of animals, depend upon the perfection of the bodily 
organization in general, and nnoro especially on tbat of the intelli- 
gence and the special senses. They are moet readily described by 
commencing with the simpler furma and termiDatiDg with the more 
oomplex. 

The brain of the AUiyator (Fig. 128) consists of fire pair of 
ganglia, ranged one behind the other in the interior of the craniom. 
The first of ihcse arc two rounded nias8e«(i), lying juat above and 

behind the nasal cavities, which disiii- 
bute their nerves upon the Schneideriu 
mucoaa membrane. These arc tbeoJrt«- 
tori/ ^cotfflia. They are coDnectod wttit 
the rest of the braio by two long and 
slender commissures, the "olfactory con- 
miwiures.'' The next pair(i) are som*- 
what larger and of a triangular sbap^ 
when viewed from above downwanL 
They are termed the "cerebral ganglia," 
or the hemispherts. Immediately follow- 
ing them are two quadrangular niBsaes(i| 
which give origin to the optic nonres, and 
are therefore called the opti'e ganglia. 
They are termed also the "optic tuber* 
cles;^' and in some of the bighcr animals, 
where they present an imperfect division 
into four nearly equal parts, they are 
known as the "tuberculaquadrigeroina." 
Behind them, we have a single triangular collection of nervous 
matter (4), which is called the eerebellum. Finally, the upper por- 
tion of the cord, just behind and beneath the cerebellum, is aeeo to 
be enlarged and spread out laterally, so as to form a broad oblong 
mass (a), the medulla oblongata. It is from this latter portion of the 
brain that the pneumogastrie or respiratory nerves originate, aad 
its ganglia are therefore somctimcd term^ the "pneumogaatrie* or 
"respiratory" ganglia. 

It will be seen that the posterior columns of the oord, as they 
diverge laterally, in oriler to form tho medulla oblongata, leave b^ 
twecn them an open space, which is oootinuous with the posterior 
median fissure of the cord. This apaco ia known as the "foartli 
ventricle.'* It is panially covered in by the backward projtidioo 



Sbai:! or Ai.Lin jltoh.— I. UI- 
Opik loWrel**. 1. C«i«b«llUD. S. 



4 




OF TUE NtERVOUa SYSTEM. 



865 



of the cerebellum, but in the alligator is stilt sotnewhnt open pos- 
teriorly, presenting a kind of cliasm or gap between the two liiteral 
halves of the medolla oblongata. 

The successive gaoglin which conipnfte the bruin, being arranged 
in pairs aa above described, are separated from each other on the 
two sides by a longitudinal median fisanre, which ia continuous 
irith the posterior median tissure of the cord. In the broin of the 
Alligator this 6ssure appears to be interrupted at the cerebellum; 
but in the higher clasaea, where the lateral portions of the cerebel- 
lum arc more highly developed, as in the hnman subject (Kig. 126), 
they are also separated from each other posteriorly on the median 
Jine, and the longitudinal median fissure is complete throughout. 

In birds^ the hcmiapheres are of much larger size than in rep- 
tiles, and partially conceal the optic ganglia. The cerebellum, 
filso, is very well developed in this class, and presents on its sur- 
face 8 number uf transverse foldings or convolutions, by which 
the quantity of gray matter which it conlaina is considerably in- 
creased. The cerebellum here extends so far backward as almost 
completely to conceal the medulla oblongata and the fourth ventricle. 
In the (luadruprds, the hemispheres and cerebellum attain a still 
greater size in proportion to the remaining parts of the brain. 
There are also two other pairs 
of ganglia, situated beneath the 
liemispberes, and lietween them 
nnd the tubercula quadrigemina. 
Theae are the corpora striata in 
front and the cpiic Oialamx behind. 
In Fig. 1*29 is shown the brain of 
the rabbit, with the hemispbertrs 
laid open and turn(xl afii<)o, so as 
to show the inleraal parts in their 
natural situation. The olfactory 
ganglia are seen in front (i) con- 
nected with the remaining parts 
hy the olfactory commissures. 
The separation of the hemi^plieres 
(i, *) shows the corpora striata (i) 
and the optic thalami (<). Then 
come ibe tnbercula quadrigemina 
(•), which are here composed, as 
above mcntiunod, of four rounded masses, nearly equal in sise. 



Fig. 126. 



BH«l*or iliBDCT, rlrwe-l fr.nn nlxitr — 
I. lllfDDlar)' pDKtIa I K«ii>l*, hnroi. Iiinied 
K'ld*. 3. Ci.r^uta alrlnla. 1. I>|ill4 ll.aliiiHl. 
0. TnbMvnU i|iLiii]rl(«iu1UB. t. Caial«!Jam. 



366 



OSySBAL STRTCTIRE AMD FtIKCTION'8 



The cerebellum (•) in consiilerably enlargefl by the development of 
its laleml portions, and showa nn abundance of transverse convola- 
tiong. It conccaU from view the fourth ventricle and most of the 
medulla oblongata. 

In other species of quadrupeds the hemispheres increase in size 
so as to prujoct entirely over the olfactory ganglia in front, and to 
cover in the tubercula quadrigemina and the cerebellum behind. 
The Borface of the hemiRpheres also becomes covered with nume- 
rous convolutions, which are curvilinear and somewhat irregular 
in form and direction, insteojd of being transverse, like those of the 
cerobellum. In man, the development of the hcmi.'^pheres reaches 
its highest point; so that they preponderate altogether in size over 
the rest of the ganglia constituting the brain. Id the human brain, 
accordingly, when viewed from above downward, there is nothing 
to be seen but the convex surfacea of the hemispheres; and even 
in a posterior view, as seen in Fig. 126, they conceal everything 
bat a portion of the cerebellum. All the remainiDg parts, how- 
ever, exist even here, and have the same connections and relative 
eitUBtion as in other instances. They may be best studied in the 
following order. 

As the spinal cord, iti the human subject, passes upward into the 
cranial cavity, it enlarges into the medulla oblongata as already 
described. The medulla oblungnta presents on each side three pro- 
jections, two anterior and one pogterior. The middle projections 
on its anterior surface (Fig. V60, i, i), which 
Pig. 190. are called the ajitenor pymmidt, are the con- 

tinuution of the nnteriur columns of the 
cord. They pass onward, underneath the 
transverse fibres of the pons Varolii, run up. 
[i\f 'fsi r^ ward to the corpora striata, pass through 
these bodies, and radiate upwan) and outward 
from their external surface, to terminaie in 
the gray matter of the hemispheres. The 
projections immediately on the outside of 
the anterior pyramids, in the medulla ob- 
longata, arc the olivary bodies («, »). They 
contain in their interior a thin layer of 
gray matter folded upon itself, the functions 
and connections of which are but little un- 
deraUxHl, and are not, apparently, ol' very 
grent importance. 



yiprm llnr.niuiiTA 
«*r llriiH Bka'k. HBO. 
riur Tl»ir.— I, 1. Autetlor VT' 

3 3. KMIiroTin bodlfi. i D«- 
cu«B*llua (it Il>c ftnttnor m- 
liiBiaa. Thx mnliilli. obloDn- 
* k I* r»cn l*mili»<rd BboTg 
Lj- tliii Irsiuicru fiblM ul Lbe 
|><is« VaMllL 



OF THE NERVOUS 8TBTBM. 



867 



The anterior columns ot the cord present, al the lower part of the 
medulla oblongata, a reatarkable ihterchaage or crossing of Lheir 
fibres (4). The fibres of the left anterior column pass acniss the 
median line at ihts spot, and becoming continuous with the right 
anterior pyramid, ar« finally distributed to the right side of the 
cerebrum; while the 6bres of the right anterior column, passing 
over to ibo Icfl anterior pyramid, are distributed to the lufi aide of 
the cerebrum. Thia interchange or crossing of the nervous fibres 
is known as the decussation of the anterior columns 0/ the cord. 

The pofiterior columns of the cord, as they diverge on each side 

of the fourth ventricle, form the posterior and lateral projections of 

the medulla oblongata (*, a). They are sometimes called the "res- 

tiforra bodies," and are extremely important parts of the brain. 

They consist in great measure of the longitudinal i)lament« of 

the posterior columns, whii.'h pass upward and outward, and are 

<]iBtributed partly to the gray matter of the cerebellum. The 

remainder then pass forward, underneath the tubcrcula quadn- 

geminii, into and through the optic thntami; and radiating thence 

upward and outward, are distributed, like the continuation of the 

anterior columns, to the gray matter of the cerebrum. The resli- 

form bodies, hotrever, in passing upward to the cerebellum, arc 

supplied with some fibre* from the anterior columns of the cord, 

which, leaving the lower portion of the anterior pyramida, join the 

reatiform bodies, and are distributed with them to the cerebellum. 

Krom this dcocription it will be seen thnt both the cerebrum and 

the cerebellum arc supplied with Slaments from both the anterior 

and posterior column.-* of the cord. 

In the substance of each reatiform body, moreover, there is im- 
bedded a ganglion which gives origin to the pneumogastric nerve, 
and presides over the funcciont; of respiration. This ganglion is 
Eorroanded and covered by the longitudinal fibres passing upward 
from the cord to the cerebellum^ but may be discovered by cutting 
into the substance of the resliform body, in which it is buried. It 
is the first important ganglion met with, in dissecting the brain 
from below upward. 

While the anterior columns are passing beneath the pons Varolii, 
Ibey form, together with the continuation of the pcstcrior columns 
and the transverse fibres of the poas itsi^lf, a rounded prominence 
or tuberosity, which is known by the name of the tuber annuUirc. 
In the deeper portions of this protuberance there is situated, among 
the longitudinal fibres, another collection of gray matter, wliich 



SA8 



GXNBRAL STRUCTURE AND FPNCTIONS 



though not of large size, has very important functions and coaneo* 
tions. This is known iia the ^an'jiiim of the tuber atmntare. 

Situated almost immcfiintely ubovc these parts wo havo the cnr* 
pora striata in front, and the optic thalami behind, nearly eqnal id 
aize, and giving passage, aa above described, to the fibres of the 
anterior and posterior colnmns. Behind them stili, and on a littld 
lower level, are the tubercula qnadrigemina, giving origin to tha 
optic nerves. The olfactory ganglia rest upon the cribriform plat« 
of the ethmoid bone, and send the olfactory filaments through the 
perruratioQs in this plate, to be distributed upon the mucous mem- 
brane of the upper and middle turbinated bones. The cerebellum 
covers in the fourth ventricle and the posterior surface of the 
medulla oblongata; and finally the cerebrum, irhich has attained 
the si^e of the largest ganglion in the uraniol cavity, extends so far 
in all directions, forward, backward, and laterally, as to form a con- 
voluted arch or vault, completely covering all the reinainiog parla 
of the encephalon. 

The entire brnin may therefore be regarded as a connected aeries 
of gnnglia, the arrungeinent of which is shown in the accompany- 
ing diagram. (Fig. ISl.) These 



Pig. I3t, 




ganglia occur in the following 
order, counting fVom before back* 
ward: Ist, The olfactory gan- 
glia. 2d. The cerebrum or hemi- 
spheres. 3d. The corpora striata. 
4th. The optic thalami. 5th. The 
tul>ercula quadrigemina. 6tb. 
The cerebellum. 7ih. The gan- 
glion of the tuber annulare. And 
8lh. The ganglion of the medulla 

oblongata. Of these ganglia, M 
..».. «.»i »»» ■ 



I 



only the hemispheres and cere- 
bellum are convoluted, while iho 
remainder are smooth and round* 
ed or somewhat irregular ia 
shape. The course of the fibres 
ooming from the anterior and 
posterior columns of the cord is also to be seen in the accompany- 
ing figure. A portion uf the anterior fibres, we have already ob* 
served, pass upward aud backward, with the restiform bodies, to the 
cerebellum; while the remainder run forward through the tuber 



DIkfram irf II i- o * << H k 4 i ■ . In rertlntt nrr- 
Uau, abuirliig III* ■llnalloB of th* dtffpntnt ,pia- 
fll^ knd lh< covr*« nf Ihfi thrvt. I, tmat\'ity 
finfUnn. ]. Hdniaphaio 3 Corpiii ■irlaluni. 
4. Upllo IhaUmu*. l. Tabercnli qiuJrlfti&lQk 
B. OiabrllaiD. 7. IIivkIIiid of Inbcr ■ooaUrv 
9. OkaKlloaof nedullBablaant** 



I 




OF THE NERVOUS 8TSTEM. 869 

aoDolare and the corpus Btriatum, and then radiate to the gray 
matter of the cerebram. The posterior fibres, constitating the res- 
tiform body, are distributed partly to the cerebellum, and then pass 
forward, as previously described, underneath the tubercula quadri- 
gemina to the optic thalami, whence they are also finally distributed 
to the gray matter of the cerebrum. 

The cerebram and cerebellum, each of which is divided into two 
Jateral halves or "lobes," by the great longitudiqal fissure, are both 
provided with trausverse commissures, by which a connection is 
vatablished between their right and left sides. The great trans- 
verse commissure of the cerebrum is that layer of white substance 
-vhicb is situated at the bottom of the longitudioal fissure, and 
'vhioh is generally known by the name of the " corpus callosum." 
3t consists of nervous filaments, which originate iVom the gray 
xnatter of one hemisphere, converge to the centre, where they be- 
«M>iDe parallel, cross the median line, and are finally distributed to 
'She corresponding parts of the hemisphere upon the opposite side. 
TThe transverse commissure of the cerebellum is the pons Varolii. 
Hts fibres converge from the gray matter of the cerebellum on one 
aBide, and pass across to the opposite ; encircling the tuber annulare 
'^th a band of parallel curved fibres, to which the name of " pons 
"Varolii" has been given from their resemblance to an arched bridge. 
The cerebro-spiual system, therefore, consists of a series of gan- 
.^lia situated in the cranio-spinal cavities, connected with each other 
%y tranisverse and longitudinal commissures, and sending out nerves 
'fto the corresponding parts of the body. The spinal cord supplies 
"Khe int^nment and muscles of the neck, trunk, and extremities ; 
"^rhile the ganglia of the brain, beside supplying the corresponding 
^larts of the head, preside also over the organs of special sense, and 
^perform various other functions of a purely nervous character. 



24 



870 



OP ITBBVOrB TBBITABTLITT 



CHAPTER II. 



OF MEBVOUS IRRITABILITY AND ITS MODK OF 

ACTION. 

We have already meotioDed, io a previous citapter, that every 
organ in the body is enduwed with the property of irritabiUty: that 
is, the property of reacting In some peculiar manner wlicn subjected 
lo the action of a direct stimulus. Thus the irritability of a gland 
shows itself by increased secretion, that of the capillary vessels by 
congestion, that of the muscles by coutraetion. Now ibe irritability 
of the muscles, indicated as above by their contraction, is extremely 
serviceable as a means of stadying and exhibiting nervous pheno- 
tneoa. We shall therefore commence this cbapter by a study of 
some of the more important facts relating to muscular irritability. 

77ie irrilabitity of lite mxtsGies is a property inherent in dte mitscular 
fthrc itstlf. The existence of muscular irritability cannot be ex- 
plained by any known physical or chemical laws, so far as they 
relate to inorganic substances. It must be regarded simply as a 
peculiar property, directly dependent ou tlie structure and consti- 
tution of the muscular fibre; just as the property of emitting light 
belongs to phosphorus, or thai of combining with metals to oxygen. 
This property may be called iuto actiuu by various kinds of stimu- 
lus; OS by pinching the muscular fibre, or pricking it with the point 
of a needle, the application of an acid or alkaline solution, or the 
discharge of a galvanic buttery. All these irritating applications 
arc immediately followed by contraction of the muscular fibre. 
Tills contraction will even take place under the microscope, when 
the fibre is entirely isoktei), and removed from contact with any 
other tissue; showing tliat the properties of contraction and irrita- 
bility reside in the fibre itself, and are not communicated to it by 
other parts. 

Afum-uiar irntainlity cxmtinnea for a certain time after death. The 
stoppage of respiraiion and circulation does not at once destroy 
the vital properties of the tiasues, but nearly all of them retain 
these properties to a certain extent for some time afterward. It is 
only when the constitution of the tissues has become altered by 



AKD ITS HODB OP AGTIOIT. 



S71 



being deprived of blood, and by the consequent derangement of 
tbe nuiritivo process, tliat tliuir characteristic properties arc finally 
lost. Thus, in the mnscles, irritability and contractility may be 
easily shown to exist for a short lime after death by applying to the 
exposed muscular 5bre the same kind of stimulus that wo have 
already foand to affect it during life. It is easy to see, in the 
muscles of the ox, after the animal has been killed, flayed, and 
eTiscerated, different bundles of muscular fibres contracting irregu- 
larly for a long time, where they are exposed to the coniaet of the 
air. Even in the human subject the same phenontenoa may be 
seen in eases of amputation; the exposed musclesof the amputated 
limb frequently twitching and quivering for many minutes after 
their separation from the body. 

The duration of muscular irritability, after death, varies consi- 
derably in different classes of anirnuls. It disappears most rapidly 
in those whose circulation and respiration are naturally the most 
active; while it continues for a longer time in those whose circula- 
tion and respiration are sluggish. Thus in birds the muscular 
irritability continues only a few minutes after the death of the 
«ni[oal. In quadrupeds it lasts somewhat longer: while in reptiles 
it remains, under favorable circumstances, for many hours. The 
«aase of this difference is probably Ihut in birds and c^uadrupcds, 
th« tissues being very vascular, and the molecular clmnges of nu- 
trition going on with rapidity, ibe constitution of the muscular 
fibre becomes so rapidly altered after the circula- 
tion has ceased, that its irritability soon disappears. pi^, 132. 
^n reptiles, on the other hand, the tissues are less 
-vascular than in birds and quadrupeds, and all the 
nutrilivc changes go on more slowly. Kespiration 
and circalutioa can therefore be dispensed with for 
a longer period, before the constitution of the tig- 
sues becomes so much altered as to destroy albo- 

Lgether their vital properties. 
Owing to this peouliarity of the cold blooded 
uimals, their tissues may be used with great ad- 
vantage for purposes of experiment. If a frog's 
leg, for example, be separated from the body of 
tbe animal (Fig. 132), the skin removed, and the 
poles of a galvanic apparatus applied to the sur- f,o„-, i,,„, 
faoe of the muscle (a, b), a contraction takes place "^'^ i™'"* °' «»'- 
every time the circuit w completed and a discharge utUBi,ucu.»in,i. 



372 



or UTEBVOUS IBBITABILITT 



passed -througli the tissues of the limb. The leg of the frog, pre- 
pared in this way, may be employed for a long lime for the pur- 
pose of exbibitiog tlie e&'ect of various kinds of stimulus upon the 
musclea. AW iho mechanical and chemical irritants which w« 
have mentioned, pricking, pinching, cauterization, galvaniam, &A., 
act with more or less energy and promptitude, though the raoet^ 
efficient of all is the electric discharge. 

Continued irriiatipti exhausts llie irritahiUty of Oie m.useles. It ia 
found that the irritability of the muscles wears cat after death more 
rapidly if they bo artificially excited, than if they be allowed to 
remain at rest. During life, the only habitual excitant of mus* 
colar contraction ia the peculiar stimulus conveyed by the nervea>: 
Afler death this stimulus may be replaced or imitated, to a certain 
extent, by other irntanla; but their appHcation gradually exhausta 
the contractility of the muscle and hastens its final disappearance. 
Under ordinary circumstances, the post-mortem irritability of the 
moacle remains until the commencement of cadaveric rigidity. 
When this has become fairly eatablished, the muscles vrill no longer 
contract under the application of an artificial stimulus. 

Certain poisonous subatancca have the power of destroying the 
irritability of the muscles by a direct action upon their tissue. 
Sulphocyanide of potaasium, for example, introduced into the cir- 
culation in suflicient quantity to cause death, destroys entirely the 
muscular irritability, so that no contraction can afterward bo pro-l 
duced by the application of an external stimulant. 

Nervous Irn'iabilitij. —The irritability of the nerves is the pro- 
perty by which they may be excited by an external stimulus, so as 
to be called into activity and excite in their turn other organs to 
which their Diaments are dintributed. When a norvo is irritated, 
therefore, its power of reaction, or its irritability, can only be esti- 
mated, by the degree of excitement produced in the oi^n to which the 
nerve is distributed. A nerve running from the integument to the ■ 
brain produces, when irritated, a painful sensation; one distributed | 
to a glandular organ produces increased aeoretion; ooe distributed 
to a muscle produces contraction. Of all these effects, muscular 
contraction is found to be the best test and measure of nervous 
irritability, for purposes of experiment. Sensation cannot of course 
be relied on for thi? purpose, since both consciouanoas and volition 
are abolished at the time of death. The activity of the glandular 
organs, owing to the stoppage of the ciroulation, disappears aHaa 
very rapidly, or at least cannot readily be demonstratetl. The 



AND ITS HODB OF ACTION. 



873 



Fig. 133. 



oontractilitj of the muscles, however, lasts, as we have seen, for a 
considerable time after death, and may accordingly be employed 
with great readiness as a test of nervous irritability. The manner 
of its employment is as follows : — 

The leg of a frog is separated from the body and stripped of its 
integument; the sciatic nerve haying been previously dissected 
out and cut off at its point of emergence from the 
spinal canal, so that a considerable portion of it 
remains in conDection with the separated limb. 
(Fig. 183.) If the two poles of a galvanic appa- 
ratus be DOW placed in contact with different 
points (a h) of the exposed nerve, and a discharge 
allowed to pass between them, at the moment 
of discharge a sudden contraction takes place in 
the muBcles below. It will be seen that this ex- 
periment is altogether different from the one re- 
presented in Fig. 182. In that experiment the 
galvanic discharge is passed through the muscles 
Uhemselves, and acts upon them by direct stim- 
xi\uB. Here, however, the discharge passes only 
from a to 5 through the tissues of the nerve, and 
acts directly upon the nerve alone; while the 
iierTe, acting upon the muscles by its own pecu- 
liar agency, causes in this way a muscular con- 
'ftraction. It is evident that io order to produce 
'fthis effect, two conditions are equally essential : Ist. 
TTbe irritability of the muscles; and 2d. The irri- 
ability of the nerve. So long, therefore, as the 
■nuBcles are in a healthy condition, their contraction, under the 
inflaence of a stimulus applied to the nerve, demonstrates the irri- 
tability of the latter, and may be used as a convenient measure of 
its intensity. 

The irritability of the nerve continues aftxr death. The knowledge 
of this &ct follows from what has just been said with regard to ex- 
perimenting upon the frog's leg, prepared as above. The irrita- 
Inlity of the nerve, like that of the muscle, depends directly upon 
its aqatomical structure and constitution; and so long as these re- 
maiD unimpaired, the nerve will retain its vital properties, though 
respiration and circalatioa may have ceased. For the same reason, 
also, as that given above with regard to the muscles, nervous irri- 
tability lasts much longer after death in the cold-bloodeii than in 



FKoa'a Lia.wllh 
■dalle Derrs (If) ■!■ 
lachBd.— aA. Poletof 
gftlTkDie bdlterj, ap- 
plied Io nerve. 



874 



^ons iRRiTAQiLirr 



the warm-blowJeJ animals. Various artificial irritants may be em- 
ployed to call it into activity. TiDcliing or pricking the ei{.>0!«d 
nerve with steel instrumcnta, the applicatiou ofcntistic liquids, lad 
the passage of galvanic discharges, ill have this eQect The cUctrc 
current, however, is mnch the beat means to employ for this par 
pose, &inc« it is mom delicato in ita operation than the others, lal 
vrill continue to succeed for a longer time. 

The nerve is, inileed, so exceedingly senailive to the electric cur- 
rent, that it will respond to it when insensible to all other kinds of 
stimuliw. A frog's leg freshly prepared with the nerve fttttchtd, 
80 in t'ig. 13S, will react so readily whenever a discharge is pajsa) 
through tlie nerve, that it forms an extremely delicate instraraent 
for detecting the prc.<;enco of electric currents of low intensity, and 
has even been used for this purpose by N[atteucci, under the intnc 
of the "galvanosoopio frog." It is only necessary to introduce the 
nerve as part of the olectrio circuit; and if even a very feeble car- 
rent be present, it is at once betrayed by a muscular contraction. 

The superiority of electricity over other moons of exciting nerr- 
OQS action, audi aa mechanical violence or chemical agents, pnv 
bably depends upon tbe fact that the latter neoessarily alter and 
diaitiLe^rate more or less the euhstanco of the nerve, so that its irri- 
tability soon disappears. The electric current, on the other bind, 
excites the nervous irritability without any marked injury to the 
substance of the nervous fibre. Its action may, therefore, be cea- 
linued for a longer period. 

Xervous irritabUiOj^ tike that of the mumlea, u exhausted by rtfuaiid 
excitement. If a frog's leg be prepared aa above, with the srialic 
nerve altnched, and allowed to remain at rest in a damp and coot 
place, where its tissue will not become altered by desiccation, the 
nerve will remain irritable for many hours; but if it be excited, 
soon ader its separation from tlie body, by repeatetl galvanic shocks 
it soon begins to react witti diminished energy, and becomes gra- 
dually less and less irritable, until it at lost ceaaca to exhibit aaj 
further excitability. If it be now allowed to remain for a time at 
rent, itit irritability will be partially restored; and muscular contrao- 
tion will again ensue on the application of a stimulus to the nervr. 
Exhausted a second time, and a second time allowed to repose, it 
will again recover itself; and this may even be repeated sevend 
times in successiou. At each repetition, however, the recovery of 
nervous irritability is less complete, until it finally disappears alio- 
geiber, and can no longer be recalled. 



AVD ITS HODS or ACTION. 876 

Various accidental circa instances tend to diminish or destroy 
nervous irritability. The action of the woorara poison, for example, 
destroys at once the irritability of the nerves; so that in animaU 
killed by this substance, no muscular contraction takes place on 
irritating the nervous trunk. Severe and sudden mechanical inju- 
ries oi^n have the same effect ; as where death is produced by 
violent and extensive crushing or laceration of the body or limbs. 
Such an injury produces a general disturbance, or shocJc as it is 
called, which affects the entire nervous system, and destroys or 
saspends its irritability. The effects of such a nervous shock may 
frequently be seen in the human subject afler railroad accidents, 
where the patient, though very extensively injured, may remain 
for some hours without feeling the pain of his wounds. It is only 
after reaction has taken place, and the activity of the nerves has 
been restored, that the patient begins to be sensible of pain. 

It will oflen be found, on preparing the frog's leg for experiment 
as above, that immediately after the limb has been separated from 
the body and the integument removed, the nerve is destitute of 
irritability. Its vitality has been suspended by the violence in- 
flicted in the preparatory operation. In a few moments, however, 
if kept under favorable conditions, it recovers from the shock, and 
r^ins its natural irritability. 

The action of the galvanic current upon the nerve, as first shown 
hy the experiments of Matteucci, is in many respects peculiar. If 
ihe current be made to traverse the nerve in the natural direction 
of its fibres, viz., from its origin toward its distribution, as from a 
to 6 in Fig. 133, it is called the direct current If it be made to 
pass in the contrary direction, as from 6 to a, it is called the inverse 
CTurent. When the nerve is fresh and exceedingly irritable, a 
muscular contraction takes place at both the commencement and 
termination of the current, whether it be direct or inverse. But 
very soon afterward, when the activity of the nerve has become 
somewhat diminished, it will be found that contraction takes place 
only at the commencement of the direct and at the termination of the 
inver$e current. This may readily be shown by preparing the two 
legs of the same frog in such a manner that they remain connected 
with each other by the sciatic nerves and that portion of the spinal 
column from which these nerves take their origin. The two legs, 
BO prepared, should be placed each in a vessel of water, with the 
nervous connection hanging between. (Fig. 134.) If the positive 
pole, a, of the battery be now placed in the vessel which holds leg 



376 OF NEBTOUS IRBtTABILITT 

No. 1, and the Degatlve pole, i, in that ooDtaioing 1^ "So. % itwiQ 
be seen that the galvanic current will traverse the two legs in op- 
posite directions. In No. 1 it will pass in a direotion contrary to 
the course of ita nervous 6bres, that is, it will be for thia leg u 

Fig. 134. 




inverse current; while in No. 2 it will pass in the same direction 
with that of the nervous Bbres, that is, it will be for this leg a dutd 
current It will now be found that at the moment when the d^ 
cuit is completed, a contraction takes place in No. 2 by the direct 
current, while No. 1 remains at rest; but at the time the oircoit ii 
broken, a contraction is produced in No. 1 hy the inverse current, 
but no movement takes place in No. 2. A sncceaaion of alternate 
contractions may thus be produced in the two lega by repeatedly 
closing and opening the circuit If the position of the polea^ a, b, 
be reversed, the effects of the current will be changed in a oatr^ 
spending manner. 

Atler a nerve has become exhausted by the direct cnrrent, it it 
still sensitive to the inverse; and afler exhaustion by the invene, 
it is still sensitive to the direct It has even been found by Hat- 
teucci that after a nerve has been exhausted for the time by the direct 
current, the return of its irritability is hastened by the snbseqnest 
passage of the inverse current; so that it will become again sena- 
tive to the direct current sooner than if allowed to renudn at rat 
Nothing, accordingly, is so exciting to a ner^ as the passage of 
direct and inverse currents, alternating with each other in rapid 
succession. Such a mode of applying the electric stimulaa ia ^itt 
usually adopted in the galvanic machines used in medical praotiee^ 
for the treatment of certain paralytic affections. In these maohiiui, 




AND ITS MOD£ OP ACTION. 



877 



e electric circnit is alternately formed and broken with great 
rapidity, thus producing the greatest effect upon tbe nerves with 
the smallest expenditure of electricity. Such alternating currents, 
however, if rery powerful, exhaust the nervous irritability more 
rapidly nod completely than any other kind of irritation; and id 
an animal killed by the action of a battery used in this manner, the 
nerves may be found to be entirely destitute of irritability from the 
moment of death. 

The irri(a.hiUty c^ the r\erves xs distinct from that of the muactes; and 
the two may be destroyed or sospended independently of each other. 
When the frog's leg has been prepared and separated from the 
body, with the sciatic oerve attached, the muscles contract, as we 
have seen, whenever the nerve is irritated. The irritability of the 
nerve, therefoi-e, is manifesteil in this instance only through that of 
the mDaclc, and that of tbe muscle is called into action only through 
that of the nerve. The two properties may be separated from each 
other, however, by tbe action of iwwrara, which has the power, as 
first pointed out by Bernard, of destroying the irritability of the 
nerve without affecting that of the muscles. If a frog be poisoned 
by this subsLance, and the leg prepared as above, the poles of a 
galvanic battery applied to the uerve will produce no eflfect; show- 
ing that the nervous irritability has ceased to exist. But if the 
galvanic discharge be passed directly through the muscles, contmc- 
lion at once takes place. The muscular irritability has survived 
that of the nerves, and must therefore be regarded as essentially 
distinct frcnn it. 

It will bo recollected, on the other hand, that in cases of death 
from the action of sulphooyanide of potassium, the muscular irri- 
tability is itself destroyed; so that no contractions occur, even whea 
the galvanic discharge is nuwle to traverse tbe muscular tiiisue. 

There are, therefore, two kiuds of paralysis: first, « muscular 
paralysis, in which the muscular fibres themselves are directly 
aifcctcd; and second, a nervous paralysis, in which the affection is 
confined to the uervous filaments, the muscles retaining their natural 
properties, and being still capable of contracting under the iutlueuoo 
of a direct stimulaa. 

Nature of the Xervons Force. — It will readily be seen that the 

ous force, or the agency by which the nerve acts upon a muscle 

and causes its contraction, is entirely a peculiar one, and caunot be 

regarded as either chemical or mechanical in its nature. The force 

hich is exerted by a nerve in a state of activity is not directly 



01 a 

^^icrvi 



378 



rSBVODS IBRlTABIUTr 



appreciable in any vaj hy ihe senses, and can be judged of only 
by its eOtiOt in causing rnusoutar contrHCtiun. This peculiar vitality 
of the nerve, or, as it is sornetioies called, the " nervous force," does 
not precisely resemble in its operation any of the known physical 
forces. It Kfts, however, a partial rcaomblancc in some respects to 
eleulricity; and this lias been sulTicieiU tu lead soiuo writers iato lb« 
error of regarding the two as identioal, and of supposing electricity ■ 
to be rcully the force acting in the nerves, and ojicrating throngb 
them upon the muscles. The principal points of resemblance 
existing between the two forces, and which have been used la 
Bappurt of the above opinion, are the following : — 

1st. The identity of their effects upon the muscular fibre. 

2d. The rapidity and peculiarity of their action, by which the 
force is transmitted almost instantaneously to a distant point, with- 
out producing any visible effect on the intervening parts. 

Sd. The extreme sensibility of nerves to the electric current; aud 

4th. The phenomena of electrical fishes. 

As these considerations are of some importance in settling iho 
question which now occupies us, we shall examine them in succes* 
sion. 

let. The Identity of their Efffcla upon the Muscular Fibre. — It is' 
very true that the muscular fibre contracts under the influence of I 
electricity, as it does under that of the ncrroua force. Thts fact, 
however, does not show the identity of the two forces, but only 
thai they are both capableof producing one particular pheoomenoii; 
or that electricity may replace or imitate the nervous force in its 
action on the muscles. But there are various other agents, as we 
have already seen, both mechanical and chemical, which will pro- 
duce the same eStxi, when applied to tlie muscular tissue. Elec- 
tricity, therefore, is only one among several physical forces which 
resemble each other in this respect, but which are not oo that 
account to be regarded as identical. 

2d. The Jiapidtty amd I*eculiariltf tif Iheir Action, hy which the 
force is Iransmiittd almost inslaniauetmslt/ to a dislant pm'jity without 
producing any vi^sible effect on the I'n/eriwun^ parts. — This is a Tery 
remarkable and important character, both of the nervous force and 
of electricity. In neither case ia there any visible effect produced 
on the nervous or metallic fibre which acts as a conducting medium ; 
but the final action is exerted upon the substance or organ with 
which it IB in connection, ^o definite conclusion, however, can 
be properly derived from the rapidity of their traosmission, sinco. 



AKD ITS MODB OF ACTTON*. 



S7fi 



this rapidity has never been accurately measured in either instance. 
"We know that light and sound both travel with much greater 
rapidity than most other physical forces, and that electricity is more 

k-TBpid in its traDsmiaaion than either; but there is no evidenco that 
the velocity of the latter and that of the nervous force are the same. 
We can only say that in both instances the velocity is very great, 
without being able to compare them together with any degreA of 

[^cccQracy. The mode of traDsmisfion, moreover, alluded to above, 
is not peculiar to the two forces which are supposed to be identical. 
Light, for example, is transmitteii like them through conducting 
media, without producing in its passage any sensible eflect until it 
meets with a body capable of reflecting it. In the intcrvfll, there- 
fore, between the luminous body and the rejecting one, there ix 
the siCtne apparent want of action as in the nerve, between the point 
at which the irritation is applied and its termination in the mus 
cular tissue. 

Sd. The extreme SemibiHty of Nerve» to the Ekciric Current. — It 
has already been mentioned that the electric current is the most 
delicate of all the mean<i of irritation that may be applied to the 
nerve after death ; and that it may be uaed with less deleterious 
effect than any other. The evident reason for this, however, hap 

, already been given. Electricity is one among several physical 

''■j^uls by which the nerve may be artiticiiilly excited after death. 
It is Jess destructive to the nervous texture than any other, and 
consequently exhausts its vitality less rapidly. All these agents 
vary in the delicacy of their operation; and though the electric 
current happens to bo the rAoat ellicient of all, it is still simply an 
artificial irritant, like the rest, capable of imitating, in its own way, 
the natural stimulus of the nerve. 

4lb. The Pfterumenao/ Eiectrical Fishes. — It has been fully demon- 
Btrated that certain fish (gymnotus and torpedo) have the power of 
geoerating electricity, and of producing cloctrio discharges, which 
are ofVen sufficiently powerful to kilt small animals that may come 
within their reach. That the force generated by these animals is 
in reality electricity, is beyond a doubt. It is conducted by the 
same bodies which serve as conductors for electricity, and is stopped 
by those which are non-conductors of the same. All the ordinary 
phenomena produced by the electric current, viz: the heating and 
melting of a fine conducting wire, the induction of secondary 
carrenta and of magneti.sm, the decomposition of saline solutions, 
and even the electric spark, have all been produced by the force 



S80 



OP K1RT0U8 IRRITAB11.ITT 



geoeratcd by iliose animala. There is, accordingly, no room for' 
doubt as to its nature. 

This fact, however, is very far from demonstraUng the electric 
character of the nervous force in general. It ia, on the contrary, 
directly opposed to such a supposition; since the gymnotus and 
torpedo are capable of generating electricity simply because they 
have a special organ dtatined for tin's purpo$e. This organ, which is 
termed the "electrical organ," is peculiar to these 63h, and where 
it is absent, the power of generating electricity is absent also. The 
electrical organu of the gymnotus and torpedo occupy a considerable 
portion of the body, and are largely supplied with nerves which 
regulate tbclr function. If these nerves be divided, tie<l, or injured 
in any way, the electrical organ is weakened or paralyzed, just as 
the muscles would be if the nerves distributed to them were sub- 
jected to a similar violence. The electricity produced by these 
animals is not supplied by the nerves, but by a special generating 
organ, the action of which is regulated by nervous influcnco. 

The reasons quoted above, therefore, are quite iosufficieol for 
eslabUsbing any relation of identity between the nervous force and 
electricity. There are, moreover, certain well authenticated facts 
directly opposed to such a supposition, the most important of which 
arc the following: — 

The first is, that no electrical current has been aciuaUy foxmd to exist 
in an irriltUed nerve. The most conclusive ex|)eriments on this point 
are thoRO which were made by Longet and Matteucoi, in company 
with each other, at the veterinary scliuol of Alfort,' The galvano* 
meter employed in these investigations was constructed under the 
personal dircclionof the experimenters, and was of extreme delicacy. 
The oscillating needle was surrounded by 2500 turns of oonductiug 
wire, and the poles were each armed with a platinum plate, having 
an exposed surface of onc-aixth of a square inch. When the poles 
of the apparatus had been repeatedly immersed tn spring water, so 
that no further variation was produced from this source, the instru- 
ment was considered as ready for use. The sciatao nerve of a liv- 
ing horse was then exposed, and the poles of the galvanometer 
placed in contact with it^ in various positions, both diagonally and 
longitudinally, and at variouadeptha in its interior. The examina- 
tion was continued for a quarter of an hour, during which time the 
painful sensations of the animal were testilie{l by constant strog* 
gling movements of the limbs; showing that both the motor and 

■ LoDgot, TralU de Pbrsiologie.. P«li, l$£0, rol. U. p. 190. 



AND ITS ICODE 0? ACTION. 381 

sensitive filaments of the nerve were in a high state of activity. 
The conclusion, however, to which the experimenters were con- 
dncted was the following, viz: that "there was no constant and re- 
liable evidence of the existence of an electric current in the nerve." 

Secondly. The mode of conduction of the nervous force is different 
from that of electricity. The latter force, in order to exert its charac- 
teristic eSects, must be transmitted through isolated conductors, so 
arranged as to form a complete circuit No such circuit haa ever 
been shown to exist in the nervous system ; and the nerves them- 
selves, the only tissues capable of conducting the nervous force, are 
not particularly good conductors of electricity ; no better, for exam- 
ple, than the muscles or the areolar tissue. We know of nothing, 
therefore, which should prevent an electric current, passing through 
a nerve, &om being dispersed and lost among the adjacent tissues. 
This is not the case, however, with the natural stimulus conveyed 
by the nervous filament. 

Moreover the nerve, in order to conduct its own peculiar force, 
mast be in a state of complete integrity. If a ligature be applied 
to it, or if it be pinched or lacerated, the muscles to which it is dis- 
tributed are paralyzed for all voluntary motion, and yet it transmits 
the electric current as readily as before. If the nerve be divided, 
and its divided extremities replaced in apposition with each other, 
it will still act perfectly well as a conductor of electricity, though 
it is needless to say that its natural function is at once destroyed. 
The difference in the mode of conduction between the two forces 
may be shown in a still more striking manner, as follows. Let the 
nerve connected with a frog's leg be divided, and its two extremi- 
ties joined to each other by a piece of moist cotton thread. If the 
galvanic current be now passed through the detached portion of the 
nerve, no contraction will take place ; because the nervous force, 
excited in the detached portion, cannot be transmitted through the 
cotton thread to the remainder. But if one of the galvanic poles 
be applied above, and the other below the point of division, a con- 
traction is immediately produced; since the electric current is 
readily transmitted by the cotton thread, and excites the lower 
portion of the nerve, which is still in connection with the muscles. 

The nervous force, therefore, while it has some points of resem- 
blance with electricity, presents also certain features of dissimilarity 
which are equally important. It must be regarded accordingly as 
distinct in its nature from other known physical forces, and as 
kltogether peculiar to the nervous tissue in which it originates. 



383 



THE SPIN'At CORD. 



CHAPTER III. 



THE SPINAL CORD. 



^E have already seen that the spinal cord ia a long ganglion, 
covered with longitudinal bundles of nervous filameots, and occu- 
pying the cavity of the spinal canal. It sends out nerves which 
supply the mnscles and integument of at least nine-tenths of the 
whole body, viz^ those of the neck, trunk, and extremities. All 
theuo parts of the body are endowed with two very remarkable 
properties, the exercise of which depends, directly or indireoUy, I 
upon the integrity and activity of the spinal oord, viz^ the power 
of sensation and the power of motion. Both these properties are 
said to reside in the nervous system, because they are so readily 
influenced by its condition, and are so closely connected with its 
physiological action. Wo shall therefore commence the stcidy of 
the spinal cord with an examination of these two functiona, and of 
the situation which they occupy in the nervous system. 

SENSATloy.' — The power of sensation, or sensibilitt/, is the power 
by which we are enabled to receive imprefeions from external 
objects. These impressions are usually of such a nature that we 
can derive from them some information in regard to the qualitiea 
of external objects and the eHect which they may produce upon 
our own systems. Thus, by bringing a foreign body into contact 
with the skin, we feel that it is hard or soil, rough or smooth, cold 
or warm. We can distinguish the separate impressions produced 
by several bodies of a similar character, and we can perceive whe- 
ther either one of them, while in contact with the sbin, be at rest 
or in motion. This power, which is generally distributed over the 
extFernal integument, is dependent on the nervous filaments remi- 
fyitig in Its tissue. For if the nerves distributed to any part of the 
body be divided, the power of sensation in theoorrespondiag regioD 
is immediately lost. 

The sensibility, thus distributed over Ehe integument, varies in 



SENSATIOW. 



888 



ita acutcneas in different parts of the body. Thus, llie extrennlies 
of the fingers are more Hensitive to external impressions than the 
geDcral surface of the limbs and trunk. The surfaces of ilie fniKors 
which lie in contact with each other arc more sonaiiive than their 
doraal or palmar surfacos. The point of the tongue, the lips, and 
the orifices of most of the mucous passages are enduwud with a 
sensibility which is more acute than that of the general integument. 

If the impression to which these parts are subjected be harsh or 
violent in ita character, or of such a nature as to injure ihc texture 
of the iDttiguuient or itd nerves, it then produces a sensation of ;^rrL. 
U ia essential to notice, however, that the sensation of pain is not 
a mere exaggeration of ordinary senaitiva impressions, but is one 
of quite a difterent character, which is superadded to the others, or 
takes their place altogether. Just in proportion as the contact of a 
foreign body becomes painful, our ordinary perceptions of its phy- 
sical properties are blunted, and the sense of sufferitig predominates 
over ordinary sensibility. Thus if the integument be gently touched 
with the blade of a knife we easily feel that it is hani, cold, and 
smooth; but if an incision be made with it in the skin, we lose all 
distinct perception of these qualities and feel only the suflering 
produced by the incision. We perceive, also, the difference in 
Temperature between cold and warm substances brought in contact 
with the skin, so long as this difference is moderate in degree; but 
if the foreign bwly bo excessively cold or excessively hot, we can 
no longer appreciate its temperature by the touch, but only its 
injurious and destructive effect. Thus the sensation caused by 
touching frozen carbonic acid is the same with that producoil by a 
red-hot metal. Both substances blister the surface, but their actual 
lAmperatures cannot be distinguished. 

It is, therefore, a very important fact, in this connection, tbat the 
aensibiUty to pain is distinct from the power of orJinari/ smsation. This 
dirtinction was first fully established by M. Beau, of Paris, who has 
shown conclusively that the sensibility to pain may be diminished 
or suspended, while ordinary sensation remains. This is oflen seen 
'in patients who are partially under the influence of ether or cblo- 
r.roform. The etherization may be carried to such an extent that 
the patient may be quite insensible to the pain of a surgical opera- 
tion, and yet remain perfectly conscious, and even capable of feeling 
the incisions, ligatures, ice., though he does not suffer from tbem. 
It not unfrequentty happens, also, when opium has been adminis- 
tered for the relief of neuralgia, that the pain is completely abolished 



384 



THE SPIITJ 



by the inflaence of the drug, while the pntient retains completely 
his coDSuiousness aad his ordiiiary seiiaibtlity. 

In all cases, however, if the iDHueace of the narcotic be pushed 
to its extreme, both kinds of sensibility are suspended together, and ■ 
the patient becomes entirely nneonscious of external impreasioos. 

Motion. — Wherever muBOular tissue exists, in any part of the 
body, we find the jwwer of raotion, owing to iho contractility of 
the muscular fibres. But this power of motion, as we have already 
seen, is dependent on the nervous system. The excitement which ■ 
causes the contraction of the muscles is traosmitted to them by the 
nervous ijlamunts; and if the uerves supplying a muscle or a limb — 
be divided or seriously injured, these parts am at once paralyzed f 
and become incapable of voluntary movement. A nerve which, 
when irritated, acta directly npon a muscle, producing contraction, 
is said to be txciiahh; and its excitability, acting through the maa- 
ole, produces [notion in the part to which it I? distributed. ■ 

The excitability of various nerves, however, often acts during 
life upon other organs, beside the muscles; and the ultimate effect 
varies, of course, with the properties of the organ which ia acted 
upon. Thus, the nervous excitement transmitted to a muscle prO' 
duces contraction, white that transmitted to a gland produoee an 
increased secretion, and that conveyed to a vascular surface caasaBl 
congestion. In all such iniitances, the effect is produced by an' 
influence transmitted by a nerve directly to the organ which isj 
called into activity. 

But in all the external parts of the body muscular contraction 
is the most marked and palpable e£fect produced by ihc direct 
influence of nervous excitement. We find, therefore, that, so far 
as we have yet examined it, the nervous action shows itself princi*fl 
pally in two distinct and definite forraa; first, as si-nsthility, or the 
power of sensation, and second, as excilahUity, or the power of pro- 
ducing motion. 

DisTTNOT Seat or Sensation and Motion in the NEBTotJB' 
Ststsh. — Sensation and motion are usually the first functions 
which suffer by any injury inflicted on the nervous system. Aa a 
general rule, they are both suspended or impaired at the same time, 
and in a nearly equal degree. In a fainting fit, an attack of apo- 
plexy, concussion ur compression of the brain or spinal cord, or wM 
wound of any kind involving the nerves or nervous centres, insen- 



DISTINCT SKAT OF SENSATION AND MOTION. 886 

sibility and loss of motioa asaally appear aimultaneoasly. It is 
d)£5calt, therefore, under ordinary conditions, to trace oat the 
separate action of theae two functions, or to ascertain the precise 
sitoation occapied by each. 

This difficulty, however, may be removed by examiaing sepa- 
rately different parts of the nervous eystera. In the instances 
mentioned above, the injury which is inflicted is comparatively an 
extensive one, apd involves at the same time many adjacent parts. 
But instances sometimes occur in which the two functions, sensa* 
ttou and motion, are affected independently of each other, owing to 
the pecaliar character and situation of the injury inflicted. Sensa- 
tion may be impaired without loss of motion, and loss of motion 
may occur without injury to sensation. In tic douloureux, for 
example, we have an exceedingly painful affection of the sensitive 
parts of the face, without any impairment of its power of motion; 
and in facial paralysis we often see a complete loss of motion affect- 
ing one side of the face, while the sensibility of the part remains 
altogether unimpaired. 

The above facts first gave rise to the belief that sensation and 
motion might occupy distinct parts of the nervous system ; since it 
would otherwise be difficult to understand how the two could be 
affected independently of each other by anatomical lesions. It has 
accordingly been fully established, by the labors of Sir Charles Bell, 
Mttller, Fanizza, and Longet, that the two functions do in reality 
occupy distinct parts of the nervous system. 

If any one of the spinal nerves, in the living animal, afler being 
exposed at any part of its course outside the spinal canal, be divided, 
ligatured, bruised, or otherwise seriously injured, paralysis of motion 
and loss of sensation are immediately produced in that part of the 
body to which the nerve is distributed. If, on the other hand, the 
same nerve be pricked, galvanized, or otherwise gently irritated, a 
painful sensation and convulsive movements are produced in the 
same parts. The nerve is therefore said to be both sensitive and 
aoeUahk; sensitive, because irritation of its fibres produces a pain- 
fnl sensation, and excitable, because the same irritation causes mus* 
cular contraction in the parts below. 

The result of the experiment, however, will be different if it be 
tried upon the parts situated inside the spinal canal, and particularly 
upon the anterior and posterior roots of the spinal nerves. If an 
irritation be applied, for example, to the anterior root of a spinal 
nerve, in the living animal, convulsive movements are produced in 
26 



the parts below, bat there ia no painful sensation. The antenor" 
root BCtiordinglj is said to be excitable, bat not sensitiro. If Uie 
posterior root, on tho other luind, be irritated, acute pain is pro- 
duced, bill no convulsive movements. The posterior root is there- 
fore sensitive, but not excitable. A similar result is obtained by a 
complete division of the two roots. Division of the anterior root 
produces paralysis of motion^ but no insensibility; division of tho 
posterior root produces complete loss of sensibility, bat no mtiscuUr 
paralysiA. 

We have here, then, a separate localization of sensation and 
motion in the nervous system; and it is accordingly easy to under- 
stand how one may be impaired without injury to the other, or 
how both may be stmnlianeously affected, according to the situation 
and extent of the anatomical lesion. 

The two root;» of a spinal nerve dififer from each other, further* 
more, in their mode of transmitting the nervous impulse. If tho 
posterior root be divided (Fig. 135) at a, b, and an irritation applied 

Fig. u:>. 



I 
I 






Tk* pdtttrltfr (\x>t )> uep dlvtdod M a, b. 



to the separated extremity (n), no effect will be produced; but if 
the irritation be applied to the aitaeh^jd extremity (b), a painful 
sensation is immediately the resulL The nervous force, therefore, 
travels in the posterior root Irom without inward, but cannot pass 
from within outward. If the anterior root, on the other hand, bo 
divided at e, d, and its attached extremity (d) irritated, no eflect 
follows; but if the separated extremity (c) be irritated, convulsive 
movements instantly take place. The nervous force, consequently, 



SENSIBILITY AND KXClTAfilLlTT IN SPINAL CORD. 887 

trarels in the anterior root from within outward, bat cannot pass 
from withoDt ioward. 

The same thing is troe with regard to the transmission of sensa- 
tion and motion in the spinal nerves outside the spinal canal. If 
one of these nerves be divided in the living animal, and its attached 
extremity irritated, pain is produced, but do convulsive motion; if 
the irritation be applied to its separated extremity, muscular con- 
tractions follow, but no painful sensation. 

There are, therefore, two kinds of 6Iament8 in the spinal nerves, 
not distinguishable by the eye, but entirely distinct in their charac- 
ter and function, viz., the "sensitive" filaments, or those which 
convey sensation, and the "motor" filaments, or those which excite 
movement. These filaments are never confounded with each other 
in their action, nor can they perform each other's functions. The 
sensitive filaments convey the nervous force only in a centripetal, 
the motor only in a centrifngal direction. The former preside over 
sensation, and Lave nothing to do with motion; the latter preside 
over motion, and have nothing to do with sensation. Within the 
spinal canal the two kinds of filaments are separated from each 
other, constitating the anterior and posterior roots of each spinal 
nerve; but externally they are mingled together in a common 
tmok. While the anterior and posterior roots, therefore, are ex- 
clusively sensitive or exclusively motor, the spinal nerves beyond 
the junction of the roots are called mixed nerves, because they con- 
tain at the same time motor and sensitive filaments. The mixed 
nerves accordingly preside at the same time over the functions of 
movement and sensation. 

Distinct Sxat or Si£nsibility and Excitability in thb 
Spinal Cord. — Various experimenters have demonstrated the fact 
that difierent parts of the spinal cord, like the two roots of the 
spinal nerves, are separately endowed with sensibility and excita- 
bility. The anterior columns of the cord, like the anterior roots of 
the spinal nerves, are excitable but not sensitive; the posterior 
columns, like the posterior roots of the spinal nerves, are sensitive 
but not excitable. Accordingly, when the spinal canal is opened 
in the living animal, an irritation applied to the anterior columns 
of the cord produces immediately convalsions in the limbs below ; 
bat there is no indication of pain. On the other hand, signs of 
acate pain become manifest whenever the irritation is applied to 
the posterior column ; but no muscular contractions follow, other 



888 



THK SPIKAL COBD. 



than thot^e of a voluntary character. Longet has foand* that if the 
gpianl cord be exposed in the lumbar regioo aoil completely divide'l 
at that part by transverse section, the application of any irritant to 
the anterior surface of the separated portioD produces at once cod* 
Tulsions below; while if applied to the posterior colunins behind 
the point of division, it has no sensible ctTect whatever. Tbe an* 
terior and posterior colamns of tbe cord are accordingly, so fer, 
analogous in their propertit^a to the anterior and posterior roots of 
tbe spinal nerves, and are plainly composed, to a greater or leas ex- 
tent, of a continuation of their filaments, 

These filaments, derived from the anterior and posterior roots of 
tbe spinal nerves, pass upward through the spinal cord toward the 
brain. An irritation upplied to any part of the integument is then 
conveyed, along the sensitive filaments of the nerve and its pos- 
terior root, to the spinal cord ; then upward, along the longitudinal 
fibres of the cord to the brain, where it produces a sensation corres- 
ponding in character with the original irritation, A motor im* 
pulse, on the other hand, originating in tho brain, is trnnamitted 
downward, along the longitudinal fibres of the cord, passes outward 
by the anterior root of the spinal nerve, ond, following the motor 
filaments of the nerve through its trunk and branches, produces at 
lost a muscular contraction at the point of ita final distribution. 

Cbossed Action of the Spinal Cord. — As tbe anterior colun»n^ 
of the cord pass upward to join the medulla oblongata, a decussa- 
tioQ takes place between them, aa we have already mentioned in 
Chapter I. The fibres of the right anterior column pass over to 
the left side of the medulla oblongata, and so upward to the left side 
of the brain ; while the fibres of the left anterior column pass over 
to the right side of tbe medulla oblongata, and so upward to the right 
side of the brain. This decussation may be readily shown (aa in 
Fig. 130) by gently separating the anterior columns from each other, 
at the lower extremity of the medulla oblongata, where the decus- 
sating bundles may be seen crossing obliquely from side to side, at 
the bottom of the anterior median fissure. Below this point, the 
anterior columns remain distinct from each other on each side, and 
do not communicate by any further decussation. 

If the anterior columns of the spinal cord, therefore, be wounded 
at any point in the cervical, dorsal, or lumbar region, a pamlysis 



I 

I 
i 

I 
I 

I 
I 

I 

I 



* Traiie de Fh7Bioto«l», to), li. part 2, p. 8. 



# OBOSSKD ACTIOS OF THE SPINAL CORD. 889 

of ToIoDtary motion is produced in the Itmbs below, on the same 
dde with the injury. Bat if a similar lesion occur in the brain, the 
paralysis which results is on the opposite side of the body. Thus 
it has long been known that an abscess or an apoplectio hemorrhage 
on the right side of the brain will produce paralysis of the left side 
of the body; and injury of the left side of the brain will be fol* 
lowed by paralysis of the right side of the body. 

The spinal oord has also a crossed action in transmitting sensi- 
tive as well as motor impulses. It has been recently demonstrated 
by Dr. Brown-S^uard,' that the crossing of the sensitive fibres in 
the spinal oord does not take place, like that of the motor fibres, 
at its upper portion only, but throughout its entire length ; so that 
the sensitive fibres of the right spinal nerves, very soon after their 
entrance into the cord, pass over to the left side, and those of the 
left spinal nerves pass over to the right side. For if one lateral 
half of the spinal cord of a dog be divided in the dorsal region, 
the power of sensation remains upon the corresponding side of the 
body, but is lost upon the opposite side. It has been shown, fur- 
thermore, by the same observer,* that the sensitive fibres of the 
spinal nerves when they first enter the cord join the posterior 
oolumns, which are everywhere extremely sensitive; but that they 
very soon leave the posterior columns, and, passing through the 
oeotral parts of the cord, run upward to the opposite side of the 
brain. If the posterior columns, accordingly, be alone divided at 
any part of the spinal cord, sensibility is not destroyed in all the 
nerves behind the seat of injury, but only in those which enter the 
cord at the point of section; since the posterior columns consist 
of different nervous filaments, joining them constantly on one side 
from below, and leaving them on the other to pass upward toward 
the brain. 

The spinal cord has therefore a crossed action, both for sensation 
and motion; but the crossing of the motor filaments occurs only at 
the medulla oblongata, while that of the sensitive filaments takes 
place throughout the entire length of the cord itself. 

There are certiun important facts which still remain to be noticed, 
regarding the mode of action of the spinal cord and its nerves. 
They are as follows: — 

■ Ezperimeotal BMMrohes appllad to PhriiologT- and rathology. New York, 

ias3. 

■ lUm<rin lor U PhTiiologia de la Ho«lle iplaiin ; OaietU M6dfc«l« de Paria, 
1855. 



SDO 



THB 8Pi;f At. CORD. 



1. An irrilah'on apjAitd to a spinal nerve at the middle of itt ci»ir9€ 
produces the some effect as if it trat-ersed {($ entire tenglh. Thus, if the 
Bciaiic or median nerve be irritated at any part of its course, con- 
traction is produced in the mnscles to which these nerves are dis- 
tributed, just as if the impulse had originated as usual from the 
brain. Thia fact depends upon the character of the nervous fila- 
ments, as simple condactors. Wherever the impulse may originate, 
the final effect ia manifested only at the termination of the nerve. 
As the impulse in the motor nerves travels always in an outward 
direction, the effect is always produced at the muscular termination 
of the filaments, no matter how smiill or how large a portion of 
their length may have been engaged in transmitting the niimulua. 

If the irritation, again, be applied to a sensitive nerve in the 
middle of its course, the painful sensation is felt, not at the point 
of the nerve directly irritated, but in that portion of the integument 
to which its filaments are distributed. Thus, if the ulnar nervo be 
accidentally struck at the point where it lies behind the inner con- 
dyle of the horaerus, a sensation of tingling and numbness is pro- 
duced in the last two fingers of the corresponding hand. It is 
comroot) to hear patients who have suffered amputation complain nf 
painful sensations in the amputated limb, for weeks or months, anil 
sometimes even for years after the operation. They assert that 
they can feel the separated parts as distinctly ns if they were stiU 
attached to the body. This sensation, which is a real one and not 
fictitious, is owing to some irritation operating upon the divided 
extremities of the nerves in the cicatrized wound. Such nn irrita- 
tion, conveyed to the brain by the sensitive fibres, will produce 
precisely the same sensation us if the amputated parts were stiU 
present, and the irritation actually applied to them. 

It is on this account also that division of the trifacial nerve is 
not always effectual in the core of tic doalooreux. If the cause of 
the difficulty be acatcd upon the trunk of the nerve, between its 
point of emergence from the bones and its origin in the brain, it ts 
evident that division of the nerve upon the face will be of no 
avail; since the cause of irritation will still exist behind the point 
of section, and the same painful sensations will still be produced in 
the brain. 

2. The irritahilily of the motor filaments disappears from within out- 
ward^ thai of the sensitive JilamentB fmrn without inward. Immedi- 
ately after the separation of the frog's leg from the body, irritation 
of the nerve at any point produces muscular contraotion in the 



INDEPKNDENCE OP ITERVOUB FILAUENTS. 891 

limb below. As time elapses, however, and the irritability of the 
nerre diminishes, the galvanic current, in order to produce con- 
traction, most be applied at a point nearer its termination. Subse* 
qoently, the irritabilitj of the nerve is entirely lost in its upper 
portions, bat is retained in the parts situated lower down, from 
which it also, in tarn, afterward disappears; receding in this man- 
ner forther and farther toward the terminal distribution of the 
nerve, where it finally disappears altogether. 

On the other hand, sensibility disappears, at the time of death, 
first in the extremities. From them the numbness gradually creeps 
upward, invading successively the middle and upper portions of the 
limbs;, and the more distant portions of the trunk. The central 
parts are the last to become insensible. 

S. Eadi nervous filament acts independently of the rest throughout ita 
entire length, and doea not eommunioate ita irritation to thoae which are 
HI proximity with it. It is evident that this is true with regard to 
the nerves of sensation, from the fact that if the integument be 
touched with the point of a needle, the sensation is referred to that 
spot alone. Since the nervous filaments coming from it and the 
adjacent parts are all bound together in parallel bundles, to form 
the trank of the nerve, if any irritation were communicated from 
one sensitive filament to another, the sensation produced would be 
indefinite and diffused, whereas it is really confined to the spot irri- 
tated. If a frog's leg. furthermore, be prepared, with the sciatic 
nerve attached, a few of the fibres separated laterally from the 
nervous trunk for a portion of its length, and the poles of a galvanic 
battery applied to the separated portion, the contractions which 
follow in the leg will not be general, but will be confined to those 
moBcles in which the galvanized nervous fibres especially have 
their distribution. There are also various instances, in the body, 
of antagonistic muscles, which must act independently of each 
other, bat which are supplied with nerves from a common trunk. 
The superior and inferior straight muscles of the eyeball, for 
example, are both supplied by the motor oculi communis nerve. 
Extensor and flexor muscles, as, for example, those of the fingers, 
are often supplied by the same nerve, and yet act alternately with- 
out mutual interference. It is easy to see that if this were not the 
ease, confusion would constantly arise, both in the perception of 
sensations, and in the execution of movements. 

4. There are certain sensations which are excited simultaneously 
by the same causes, and which are termed associated eensaliona ; and 



S92 



THB 8PIKAL OOBDT 



there are also certain movements which take place simuItaQeouslj, 
and are called a$30cialed motKments, Id tbe fonuer iastance, one of 
the asaocintod sen^Lions is called up iinmodiatel^ upon the percep- 
tion of the other, without requiring any direct impulse of its own. ■ 
Thus, tickling the sole^ of the feet produces a peculiar sensation 
at tbe epigustrium. Nausea is oecasioned by cerLain disagreeable 
odors, or by rapid rotation of the body, so that the landscape seems 
to turn round. A striking example of associated movements, on 
the other hand, may bo found in tbe action of the muscles of the 
eyeball. Tbe eyeballs always accompany each other in their lateral 
motions, turning to the right or the lefl aide simultaneously. U is 
evident, however, that in producing this correspondence of motion, 
the lel^ internal rectus muscle must contract and relax together 
with the right external ; while a similar harmony of action must 
exist betweeu the right internal and the left external. The explana- 
tion of such singular correspuudencus catinot be found in the auato- 
mical arrangemeut of the muscles themselves, nor in that of the ■ 
nervoua filaments by which they are directly supplied, but must be 
looked for id some special endowment of the uervouii centres from 
which they originate. 



K^'LUX Action op thb Spinal Cokd. — The spinal cord, aa wa 
have thus far examined it, may be regarded simply as a great nerve; 
that is, as a buudle of motor and sensitive filaments, connecting 
the muscles and integumouL below with the brain above, and 
assisting, in this capacity, in the production of conscious sensation 
and voluntary motion. Beside its nervous filaments, however, it< 
contains also a largt) quantity of gray matter, and is, therefore^ 
itself a ganglionic centre, and capable of independent action as 
such. We shall now proceed to study it in its seoond capacity, as 
a distinct nervous centre. 

If a frog bo deuapilated, and the body allowed to remain at rest 
for a few moments, so as to recover from the depressing effects of 
shock upon the nervous system, it will be found tliat, although sen* 
sation and consciousness are destroyed, the power of motion siill 
remaiiis. If the skin of one of tbe feet be irritated by pinching it 
with a pair of forceps, tbe leg is immediately drawn up toward the 
body, as if to escape the cause of irritation. If the irritation applied 
to tbe foot be of slight intensity, the corresponding leg only will 
move; but if it bo more severe in character, motions will ofkeo be 
produced in the posterior extremity of the opposite side, and even 



BSFLEX ACTIOy OF THB SPINAL COBD. 



893 



in the two fore legft, at the fiamc time. These motions, it is import- 
ant to observe, are never spontaneous. The decapitated frog remains 
perfectly qaiescent if left to bimseir. It is only when some cause 
of irrttatioD is applied externally, that movements occur as above 
described. 

It will be seen that the character of these phenomena indicates 
the active operation of some part of the nervous system, and par- 
licalarly of some ganglionic centre. The irriUition is applied to 
the skin of the foot, and the muscles of tlio leg c^mtruct in conse- 
quence; shovring evidently the intermediate action of a nervous 
oonnecuon between the two. 

The effect in question is due to the activity of the spinal cord, 
operating aa a nervous centre. In ordur that the movements may 
take place as above, it is essential that both the integument and the 
mascles should be in communication with the spinal cord by nerv- 
ous filaments, and that the cord itself be in a state of integrity. If 
the sciatic nerve be divided in the upper pari of the thigh, irritation 
of the skin below is no longer followed by any muscular oontrao- 
tion. If eitlier the anterior or posterior roots of the nerve be 
divided, the same want of action results; and finally, if, the nerve 
aod its roots remaining entire, the spinal cord itself be broken up 
by a needle introduced into the spinal 
canal, the integument may then be 
irritated or mutilated to any extent, 
without exciting ihe least muscular 
contraction. It is evident, therefore, 
that the spinal oord acts, in this case, 
04 a oervoQs centre, through which 
the irritation applied to the skin is 
oommunicated to the muscles. The 
irritation first passes upward, aa shown 
in the accompanying diagram (Fig. 
136), along the sensitive fibres of the 
posterior root (o) to ihe gray matter 
of the cord, and is then reflectetl back, 
ilong the motor fibres of the anterior 
root (6), until it finally reaches the 

muscles, and produces a contraction. This action is known, accord* 
iogly, as the rtjiex action of the tj>miil cord. 

It will be remembered that this reflex action of the cord Is not 
ftocompanied by volition, nor even by any conscioa-i sensation. 



prft. I3<i. 



DUfmm »r firiSlLCoBft IK VSB- 
TlrAt. liic-Tiav, ahiivlBg rttint aMlDii. 

Mrtur tvut of tplaal nvrra. 



394 



THE SPISAL COED. 



The function of the spinal cord as a, nervoas centre is simply 
convert nn impression, received from tlicHkin, into a motor impul 
which is sent out again to the muscles. There is absolutely no 
fartlier Action than this; no exercise of will, consciousTiesa, or judg*fl 
ment. This action will therefore t;ike place perfectly well after 
the brain has been removed, and nfU;r the entire sympathetic Bf&> 
tern has also l>een taken away, provided only that the spinal cord 
and its nerves remain in a state of integrity. fl 

The existence of this reflex action after death is accordingly an ™ 
evidence of the continued activity of the spinal cord, just aa con- 
tractility is an evidence of the activity of the maacles, and irrita- 
bility of that of the nerves. Like the two last-mentioned pro[>crttea, 
also, it continues for a longer time after death in cold-blooded than 
in warm-blooded animals. It is for this reason that frogs and other 
reptiles are the most useful subjects for the study of these pheno- 
mena, aa for that of most others belonging to the nervous system. 

The irritability of the spinal cord, as manifested by tea reflex 
action, may be very much exaggerated by certain diseases, and by 
the operation of poisonous substances. Tetanus and poisoning by 
strychnine buth act in this way, by heightening the irritability of 
the spinal cord, and cautiing it to produce convulsive movements 
on the application of external stimulus. It has been observed that 
the convulsions in tetanus are rarely, if ever, spontaneous, but that 
they always require to be excited by some external cause, snch as 
the accidental movement of the bedclothes, the shutting of a door, 
or the sudden passAge of a current of air. Such slight canses of 
irritation, which would be entirely inadequate to excite involuntary 
movements in the healthy corvdition, act upon the spinal cord, when 
its irritability is heightened by disease, in such a manner as to pro*^ 
dace violent convulsions. H 

Similar appcamncca are to be aeen in animals poisoned by atrycb- 
nine. This substance acts upon tlio spinal cord and increases ila 
irritability, without materially affecting the functions of the brain. 
Ita effects will show themselves, consequently, without essential 
modification, after the head has been removed. If a decapitated 
frog be poisonctl with a moderate dose of .strychnine, the body and 
limbs will remain quiescent so long as there is no external source 
of excitement; but the limbs are at once thrown into convulsions 
by th'e slightest irrilaiion iippliud to the skin, as, for example, the 
contact of a hair or a feather, or even the jarring of the table on 
which the animal ia placed. That the convulsions in ca^es of 



BKFLKX ACTION OF THB SPINAL OOBD. 895 

poisoning hy Btrychnine are always of a reflex character, and nerer 
spontaneoaa, is shown by the roUowing fact first noticed by Ber- 
nard/ riz^ that if a frog be poisoned after division of the posterior 
roots of all the spinal nerves, while the anterior roots are left un- 
touched, death takes place as usual, but is not preceded by any con- 
Tulsioos. In this instance the convulsions are absent simply 
because, owing to the division of the posterior roots, external irri- 
tations cannot be communicated to the cord. 

The reflex action, above described, may be seen very distinctly 
in the human subject, in certain cases of disease of the spinal cord. 
If the upper portion of the cord be disintegrated by inflammatory 
softening, so that its middle and lower portions lose their natural 
oonnection with the brain, paralysis of volantary motion and loss of 
sensation ensue in all parts of the body below the seat of the ana- 
tomical lesion. Under these conditions, the patient is incapable of 
making any muscular exertion in the paralyzed parts, and is uncon- 
actons of any injury done to the integument in the same region. 
Notwithstanding this, if the soles of the feet be gently irritated 
with a feather, or with the point of a needle, a convulsive twitch- 
ing of the toes will often take place, and even retractile movements 
of the leg and thigh, altogether without the patient's knowledge. 
Sneh movements may frequently be excited by simply allowing 
the oool air to come suddenly in oontact with the lower extremities. 
We hare repeatedly witnessed these phenomena, in a case of dis- 
ease of the spinal cord where the paralysis and insensibility of the 
lower extremities were complete. M&ny other similar instances 
are reported by various authors. 

The existence of this reflex action of the cord has enabled the 
physiologist to ascertain several other important facts concerning 
the mode of operation of the nervous system. M. Bernard has 
demonstrated,' by a series of extremely ingenious experiments on 
the action of poisonous substances, 1st, that the irritability of the 
mnscles may be destroyed, while that of the nerves remains unal- 
tered; and 2d, that the motor and sensitive nervous filaments may 
he paralyzed independently of each other. The above facts are 
shown by the three following experiments: — 

1. In a living frog (Fig. 137), the sciatic nerve (i\0 is exposed in 

' Le^oiM anr In effets dM SnbtUnoM toxiqnes ot mMicam«nt«a9«s, Parii, 1867, 
^357. 
' liM., CUpi. 23 ud 21. 



see 



THB 8PINJIL CORD. 



IJ 




the back part of tho thigh, a^^er which a ligature ia passei] u 
neath ilaml ilrnwo tight around the hone and the remainitig soft' 
parta. In this way thu circulation is entirely cut off from the limb 
(rf), which remains in connection with the trunk only by means of 
the sciatic nerve. A solution of sulphocyanide of potassium is then 

introduced beneath the skin 
^t' ^^' of the back, at /, In sufficient 

quantity to produce its speci* 
fie effect. The poison ia then 
absorbed, aud ia carried by 
the circulation throughout the 
trunk and the three oxtrtinii| 
ticii a, b, c; while it is prM 
vented from entering the limb 
d, by the ligature which hM 
been placed about the thigM 
Sulphocyanide of potassium 
produces paralysis, as we have 
provtouftly mentioned, by a 
ing directly upon the raus 
lar tissue. Accordingly, a 
vanicdischargc passed throu, 
the limbs a, h, and c, produ< 
no contraction in them, wbi' 
the same stimulus, applied to 
d, Is followed by a strong and 
healthy reaction. But at the 
moment when the irritation 
is applied to the poisonet 
limbs 11, b, and e; though 
visible eft'ect Is produced 
them, an active movem 
takes plaoo in the heol^ 
limb, d. This can only 
owing to a reflex action of the spinal oord, originating in the in 
gument of a, b, and c, and transmitted, by sensitive and motor til 
montA, through the cord, to d While the mttecles 0/ Oie poiaom 
limh, t?teri/ore, have been dtrecthj paralyzed^ the nervee 0/ the sa\ 
parte havn r^aintd their irritability. 

2. If a frog be poisoned with woorara by simply placing t 
poison under the skin, no reflex action uf the spinul cord can 



BBFLBX ACTIOy OF THE SPINAL CORD. 807 

demonstrated after death. We bare already shown, from experi- 
ments detailed in Chapter II., that this sabstance destroys the irrita- 
bility of the motor Derves, without affecting that of the muscles. In 
the above instance, therefore, where the reflex action is abolished, its 
kwa may be owing to a paralysis of both motor and sensitive fila- 
ments, or to that of the motor filaments alone. The following experi- 
ment, however, shows that the motor filaments are the only ones 
affected. If a frog be prepared as in Fig. 187, and poisoned by the 
introdaction of woorara at /, when the limb d is irritated its own 
muscles react, while no movement takes place in a, 6, or c ; but if 
the irritation be applied to a, 6, or c, reflex movements are imme- 
diately prodaoed in dL In the poiaoned limbs, therf/ore, while the 
molor nerves have been paralyzed^ the sensitive filaments have retained 
Iheir irritqhilUy. 

8, If a frog be poisoned with strychnine, introduced underneath 
the skin in sufficient quantity, death takes place after general oon- 
TulsioDs, which are due, as we have seen above, to an unnatural 
excitability of the reflex action. This is followed, however, by a 
paralysis of sensibility, so that after death no reflex movements 
can be produced by irritating the skin or even the posterior roots 
of the spinal nerves. But if the anterior roots, or the motor nerves 
themselves be galvanized, contractions immediately take place in 
the corresponding muscles. In this case, there/ore^ the sensitive fila- 
Wienie have been paralyzed, while the motor filaments and the muscles 
have retained their irritability. 

We now come to investigate the reflex action of the spinal cord, 
as it takes place in a healthy condition during life. This action 
readily escapes notice, unless our attention be particularly directed 
to it, because the sensations which we are constantly receiving, and 
the many voluntary movements which are continually executed, 
lerve naturally to mask those nervous phenomena which take place 
without our immediate knowledge, and over which we exert no 
Toluntary control. Such phenomena, however, do constantly take 
place, and are of extreme physiological importance. If the surface 
of the skin, for example, be at any time unexpectedly brought in 
contact with a heated body, the injured part is often withdrawn by 
a rapid and convulsive movement, long before we feel the pain, or 
even fairly understand the cause of the involuntary act. If the 
body by any accident suddenly and unexpectedly loses its balance, 
the limbs are thrown into a position calculated to protect the ex- 
posed parts, and to break the fall, by a similar involuntary and in- 



898 



THE SPtXAL OOBD. 






sUntaneoua movcmetit The brain does not act in these cues, For 
there is no intentional character in the movement^ nor even any 
complete coQaciousness of its object Kverything indicata tluit u 
ii the immediate result of a simple reflex action of the spiokl oord. 

The cord exerts also an important and constant influence tipon 
the spkmclcr muscUt. The sphincter ani is habitually in a state of 
contraction, so that the contents of the intestine are not allowed to 
escape. VVhen any external irritation is applied to the iaiis,or 
whenever the feces present iliemselvcs internally, the sphincter 
contracts involuntarily, and the discharge of the feces ts preveoted. 
This habitual closure uf the sphincter depends on the reflex idiot 
of the spinal cord. It is entirely an involuntary act, and wiUcos- 
tinue, in the healthy condition, during p'rofoand sleep, ascomplde 
and efTiciutit as in the waking state. 

When the rectum, however, has become filled by the accu 
tion uf feces from above, the nervous action changes. Tfaeo 
impression produced on the mucous membrane of the dtsleadei 
rectum, conveyed to the spinal cord, causes at the same Umei* 
laxatioD of the sphincter and contraction of the rectum itaelf: m 
that a discharge of the feces consequently takes place. 

Now all theae actions are to some extent under the cootrolof 
sensation and volition. The distended state of the rectum is osuaHf 
accom|>anicd by a distinct sensation, and the resistaooe of ti» 
sphincter may be voLuntarily prolonged for a certain period, just u 
the respiratory movements, wbicli are usually involunuiry, ouij U 
intentionatly hastened or relan.]ed, or even temporarily saspeaiM 
But this voluntary power over the sphincter and the ractua a 
limited. After a time the involuntary impulse, growing n»« 
urgent with the increased distension of the rectum, becomes im 
sistible; and the di^K:ha^ge finally takes place by the simple nSei 
action of the spinal cord. 

If the f>pinal cord be injured in its middle or upper portions, tlK 
sensibility and voluntary action of the sphincter are lost, because lU 
connection with the brain has been destroyed. The evacoalMe 
then takes place at once, by the ordinary mechanism, as sooo u 
the rectum is filled, but without any knowledge on the part of Ur 
patient. The discbarges are then said to be "iovoluotary and on- 
conscious." 

If the irritability of the cord, on the other hand, be exaggeratst 
by disease, while its connection with the brain remains entire, the 
distcn.-4iiHi of the rectum a announced by the usual aensation, bot 




BEFLIX ACTION OF THI SPINAL CORD. 899 

die refiez impalse to eracuatioa is so urgent that it cannot be 
coDtrolled by the will, and the patient is compelled to allow it to 
take place at onoe. The discbarges are then said to be simply 
"iovolontary." 

Finally, if the substance of the spinal cord be extensively de- 
stroyed by accident or disease, the sphincter is permanently relaxed. 
The feces are then evacaated almost continnoasly, withoat any 
knowledge or control on the part of the patient as fast as they 
descend into the rectum from the upper portions of the intestine. 

Injury of the spinal cord produces a somewhat different effect on 
the urinary bladder. Its muscular fibres are directly paralyzed ; 
and the organ, being partially protected by elastic fibres, both at 
its own orifice and along the urethra, becomes gradually distended 
by urine from the kidneys. The urine then overcomes the elas- 
ticity of the protecting fibres, by simple force of accumulatiou, and 
afterward dribbles away as fast as it is excreted by the kidneys. 
Paralysis of the bladder, therefore, first causes a permanent disten- 
fooa of the organ, which is ailerward followed by a continuous, 
passive, and incomplete discharge of its contents. 

Injury of the spinal cord produces also an important, though 
probably an indirect effect on nutrition, secretion, animal heat, &c., 
in the paralyzed parts. Diseases of the cord which result in its 
softening or disintegration, are notoriously accompanied by consti- 
pation, often of an extremely obstinate character. In complete 
l)araplegia, also, the lower extremities become emaciated. The 
texture and consisteocy of the muscles are altered, and the animal 
temperature is considerably reduced. All such disturbances of 
nutrition, however, which almost invariably follow upon local para- 
lysis, are no doubt immediately owing to the inactive condition uf 
the muscles ; a condition which naturally induces debility of the 
circulation, and consequently of all those functions which are de- 
pendent upon it. 

It is less easy to explain the connection between injury of the 
spinal cord and inflammation of the urinary passages. It is, bow- 
ever, a matter of common observation among pathologists, that 
injury or disease of the cord, particularly in the dorsal and upper 
lamb«r regions, is soon followed by catarrhal indammution of the 
urinary passages. This gives rise to an abundant production of 
altered mucus, which in its turn, by causing an alkaline fermeuta- 
tion of the urine contained in the bladder, converts it into an irri- 



400 THK SFIKAL CORD. 

tat'mg and ammoniacal liquid, which reacts upon the mncous mem- 
brane and aggravates the previous inflammation. 

We find, therefore, that the spina] cord, in its character of a 
nervous centre, exerts a general protective action over the wbole 
body. It presides over the involuntary movements of the limbs 
and trunk ; it regulates the action of the sphincters, the rectum, 
and the bladder; while at the same time it exerts an indirect influ- 
ence on the nutritive changes in those parts which it supplies with 
nerves. 



THE BBAIN. 401 



CHAPTER IV. 

THE BRAIN. 

Bt the brain, or meepkaJon, as it is sometimes called, we mean all 
that portion of the nerroas system which is situated within the 
cavity of the cranium. It consists, as we have already shown, of 
a series of di&rent ganglia, connected with each other by transverse 
and longitudinal commissures. 

Since we have found the functions of sensation and motion, or 
sensibility and excitability, so distinctly separated in the spinal 
cord, we should expect to find the same distinction in the interior 
of the brain. These two properties have indeed been found to be 
distinct from each other, so far as they exist at all, in the encephalic 
mass; but it is a very remarkable fact that 'they are both confined 
to very small portions of the brain, in comparison with its entire 
bulk. According to the investigations of Longet, neither the 
olfactory ganglia, the corpora striata, the optic thalami, the tuber- 
cula quadrigemina, nor the white or gray substance of the cerebrum 
or the cerebellum, are in the least degree excitable. Mechanical 
irritation of these parts does not produce the slightest convulsive 
movement in the muscles below. The application of caustic liquids 
and the passage of galvanic currents are equally without effect. 
The only portions of the brain in which irritation is followed by 
convulsive movements are the anterior surface of the medulla ob- 
longata, the tuber annulare, and the lower partof the crura cerebri ; 
that is, the lower and ceutral parts of the brain, containing continu- 
ations of the anterior columns of the cord. On the other hand, 
neither the olfactory ganglia, the corpora striata, the tubercula 
quadrigemina nor the white or gray substance of the cerebrum or 
cerebellum, give rise, on being irritated, to any painful sensation. 
The only sensitive parts are the posterior surface of the medulla 
oblongata, the restiform bodies, the processus e cerebello ad testes, 
and the upper part of the crura cerebri; that is, those portions of 
the base of the brain which contain prolongations of the posterior 
columns of the cord. 
26 



40S 



TBK nBAlK. 



Tbo moat central portions of the nervoaa system, therefore, aa<1 
particularly tlie gray matter, are destitute of butb excitability an*! 
sensibility. It is only tlioso portiuDa which serve to conduct son- 
SQtiona and nervoua impulses that caa be excited by mechanical 
irrltaiion ; not the ganglionic centres themselves, which receive and j 
originate the nervous impressions. 

We shall now study in succession the difTereot ganglia of which 
the brain is composed. 

Olfactory Ganglia. — These gnnglia, which in some of the 
lower animals are very lai^e, corresponding in size with the ex- 
tent of the olfactory membrane and the acutenesa of the sense of 
smell, are very small in the human subject. They are situated ou 
the cribriform plate of the ethmoid bone, on each side of the criMa 
galli, just beneath the anterior lobes of the cerebrum. They send 
their nerves through the numerous perforations which exist in the _ 
ethmoid bone at this part, and are connected with the base of thefl 
bruin by two longitudinal commissures. The olfactory ganglia 
with their commissures are sometimes spoken of as the "olfactory 
nerves." They are not nerves, however, but ganglia, since they are 
mostly composed of gniy matter; and the term ''olfactory nerves'' 
can be properly applied only to the filaments which originate from 
them, and which are afterward spread out id ihe substance of the 
olfactory membrane. 

It has been found dilTicult to determine the function of tfaese^ 
ganglia by direct experiment on the lower animals. They may be 
destroyed by means of a strong nee(.lle introduced through the bones 
of the cranium ; but the signs of the presence or absence of the 
senae of smell, after such an operation, arc too indefinite to allow us 
to draw from them a decided conclusion. The anatomical distribo- 
tioD of their nerves, however, and the evident correspondence which 
exisld, in difierent species of auimul.-*, between their degree of de- 
velopment and that of the external olfactory organs, leaves no doubt 
as to their true function. They are the ganglia of the special een&u 
of smell, and arc not connected, in any appreciable degree, with 
ordinary sensibility, uor with the production of voluntary move- 
ments. 



Optic Tiialami. — These bodies are not, as their name would ^ 
imply, the ganglia of vision. Longet has found that the power of fl 
sight and the sensibility of the pupil both remain, in birds, after 



CORPORA STRIATA.— HCUISPHERB8. 408 

the optic thalami have beeo tboroaghly disorganized; and that arti- 
ficial irritation of the same ganglia has no e^t in producing 
either oontractton or dilatation of the papil. The optic thalami, 
however, aocording to the same observer, have a peculiar crossed 
action upon the voluntary movements. If both hemispheres and 
both optic thalami be removed in the rabbit, the animal is still 
capable of standing and of using hia limbs in progression. But if 
the right optic thalamus alone be removed, the animal fklls at once 
upon his left side; and if the left thalamus be destroyed, a similar 
debility is manifest on the right side of the body. In these in- 
stances there is no absolute paralysis of the side upon which the 
animal, falls, bat rather a simple want of balance between the two 
opposite sides. The exact mechanism of this peculiar functional 
disturbance is not well understood; and but little light has yet 
been thrown, either by direct experiment or by the facts of compa- 
rative anatomy, on the real function of the optio thalami. 

GoBPORA Striata. — The function of these ganglia is equally 
uncertain with that of the preceding. They are traversed, as we 
have already seen, by fibres coming from the anterior columns of 
the oord; and they are connected, by the continuation of these 
fibres, with the gray substance of the hemispheres. They have, 
therefore, in all probability, like the optic thalami, some connection 
with sensation and volition; but the precise nature of this connec- 
tion is at present altogether unknown. 

Hkmisphebrs. — The hemispheres, or the cerebral ganglia, con- 
stitute in the human subject about nine-tenths of the whole mass 
of the brain. Throughoat their whole extent they are entirely 
destitute, as we have already mentioned, of both sensibility and ex- 
citability. Both the white and gray substance may be wounded, 
burned, lacerated, crushed, or galvanized in the living animal, with- 
out exciting any convulsive movement or any apparent sensation. 
Iq the human subject a similar insensibility has been observed 
when the substance of the hemispheres has been exposed by acci- 
dental violence, or in the operation of trephining. 

Very severe mechanical injuries may also be inflicted upon the 
hemispheres, even in the human subject, without producing any 
directly fatal result One of the most remarkable instances of this 
fact is a case reported by Dr. William Detmold, of New York,' in 

' Am. JoDrn. of Mud. Scl., Jannarjr, 1S50. 



104 



TBE BRAIN. 



vrbich an nbscess in the anterior lobe of the brain was opened by an 
incision passing through the cerebral substance, nut only without 
any immediate bad eOect, but with great temporary reliel' to the 
patient. This was the caae of a laborer who was struck on the left 
side of the forehead by a piece of fulling timber, which produced a 
compound fracture of the skull at this part One or two pieces of 
boue afterward became separated and were removed, and the wound 
aubsequently healed. Nine weeks after the accident, however, 
headache and drowsiness cnme on ; and the latter symptom, becom- 
ing rapidly aggravated, soon terminated in complete stupor. At 
this lime, the existence of an abscess being suspected, the cicatrix, 
together with the adherent portion of the dura mater, was dissected 
away, several pieces of fractured bone removed, and the surface of 
the brain exposed. A knife was then passed into the cerebral sub- 
stance, making a wound one inch in length and half an inch in 
depth, when the abscess was reached and over two ounces of pus 
discharged. The patient immediately aroused from his comatose 
condition, so that he was able to speak; and in a few days reco- 
vered, to a very considerable extent, his cheerfulness, inielligenoe, 
and appetite. Subsequently, however, the collectiou of pus re- 
turned, accompanied by a renewal of the previous symptoms; and 
the patient finally died at the end of seven weeks from the lime of 
opening the abscess. 

Another and still more striking instance of recovery from severe 
injury of the brain is reported by Prof. H. J. Bigelow in the 
American Jounml of Afciical Sciences for July, 1S50. In this case, a 
pointed iron bar, thr,ee feet nod a half tn length, and one inch and a 
quarter in diameter, was driven through the patient's head by the 
premature blasting of a rock. The bar entered the left side of the 
face, just in froat of the angle of the jaw, and passed obliquely 
upward, inside tlie zygomatic arch and through the anterior port 
of the cranial cavity, emerging from the top of the fronWl bone on 
the median line, just in front of the point of union of the coronal 
and sagittal sutures. The patient was at first stuuued, but soon 
recovered himself so far as to be able to converse intelligently, rode 
home in a common cart, and with a little aaaistance walked upstairs 
to his room. He became delirious within two days after the aooi> 
dent, and subsequently remained partly delirious and partly coma- 
toae for about three weeks, lie then began to improve, and al the 
end of rather more than two months from the date of the injury, 
was able to walk about. At the end of sixteen months he was in 



HEUISPHERES. 



AOl 



perfect health, with the wounds healed, and with the mental and 
bodily functions entirely unimpaired, except that sight wns perma- 
nently lost in the nyQ of the injured side. 

The hemispheres, furthermore, are not the seat of sensation or of 
volition, nor are they immediately essential to the continuance of 
life. In quadrupedn, the complete removal of the hemispheres is 
Attended with so ranch hemorrhage that the operation is generally 
fatal from this cause within a few minutes. Id birds, however, it 
may be performed without any immediate danger to life. Longet 
has removed tlie hemispheres in pigeons and fowls, and has kept 
these animals afterward for several days, with most of the organic 
functions unimpaired. We have frequently performed the same 

cperiment upon pigeons, with a similarly favorable result. 

The effect of this mutilation is simply to plunge the animal into 
a Btata of profound stupor, in which he is almost entirely inatten- 
tive to surrounding objects. The bird remains sitting motionless 
upon his perch, or standing upon the ground, with the eyes dosed, 
and the head sunk between the shoulders. (Fig. 138.) The plu- 

Fig. 138. , 



>% A 



lis smooth and glossy, but ia uniformly expanded, by a kind 
Erection of the fonihera, bo that the bmly appears somewhat 
puffed out, and larger than natural. Occasionally the bird opens 
his eyes with a vacant stare, stretches his neck, perhaps shakes his 
bill once or twice, or smooths down the feathers upon his shoulders, 
and then relapses into his former apathetic condition. This state 
of immobility, however, is not accompanied by iho loss of sight, of 
hearing, or of ordinary sensibility. All these functions remain, as 



THE BRAiy. 



well as tliat of voluntary motion. If a pistol he discharged beliind 
tho hack of the animfti, he at once opens his ejes, roovea Iiia head 
half round, and gives evident aignsof having heard the report; but 
he immediately becomes quiet again, and paja no farther attention 
to it. Sight is also rL'tainetl, since the bin! will aometimcs fix its 
eye on a particular object, and watch it for several seconds together. 
^Longet hae even found that by moving a lighted candle before the 
anicnal's eyes in a dark place, the head of the bird will often follow 
the movements of the candle from side to side or in a circle, showing 
that tho impression of light '\a actually perceived by the sensoriuni. 
Ordinary sensnlion also remains, after removal of the hemispheres, 
together with voluntary motion. If the foot be pinched with k 
pair of foTxitipa, tlio bird becomes partially aroused, moves uneasily 
once or twice from side to side, and is evidently annoyed at the 
irritation. 

The animal is Atill capable, therefore, afWr removal of the hemi- 
spheres, of receiving sensations from external objects. But these 
sensations appear to make upon him no lasting impression. He is 
incapable of connecting with his perceptions any distinct succession 
of ideas. He hears, for example, the report of a pistol, but he is not 
alarmed by it; for the sound, though distinctly enough fwrceived, 
does not suggest any idea of danger or injury. There is accord- 
ingly no power of forming mental aasocialiona, nor of perceiving 
the relation between external objects. The memory, more particu- 
larly, is altogether destroyed, and the recollection of sensations is 
not retained from one moment to another. The limbs and muscles 
ore still under the control of the will; but the will itself is inactive, 
because apparently it lacks \is usual mental stimulus and direction. 
The powers which have been lost, therefore, by destruction of tho 
cerebral hemispheres, are altogether pf a mental or intellectual 
character; that is, the power of comparing with each other difterent 
ideas, and of perceiving the proper relation between them. 

The same result is well known to follow, in the human subject, 
from injury or disease of these parts. A disturbance of the mental 
powers has long been recognized as the ordinary con.sequence of 
Ic-iions of tho brain. In cases of impending apoplexy, for example, 
or of softening of the cerebral substance, among the earliest and 
most constant phenomena la a loss or impairment of the memory. 
The patient forgets the names of particular objects or of |)articular 
persons; or he is unable to calculate numbers with his usual facility. 
Uis mental derangement is ottcn shown in the undue estimate which ' 



HSUISPHSBES. 407 

he forms of passing events. He is no longer able to appreciate the 
trae relation between different objects and different phenomena. 
Thaa, he will show an exaggerated degree of solicitude about a 
tririal occnrrence, and will pay no attention to other matters of 
real importance. As the difficulty increases, he becomes careless 
of the directions and advice of bis attendants, and must be watched 
and managed like a child or an imbecile. After a certain period, 
he no longer appreciates the lapse of time, and even loses the dis- 
tinction between day and night. Finally, when the injury to the 
hemispheres is complete, the senses may still remain active and 
impressible, while the patient is completely deprived of intelligence, 
memory, and judgment. 

If we examine the comparative development of the hemispheres 
in different species of animals, and in different races of men, we 
shall find that the size of these ganglia corresponds very closely 
with the degree of intelligence possessed by the individual. We 
have already traced, in a preceding chapter, the gradual increase 
in size of the hemispheres in fish, reptil^ birds and quadrupeds: 
four classes of animals which may be arranged, with regard to the 
amount of intelligence possessed by each, in precisely the same 
order of succession. Among quadrupeds, the elephant has much 
the largest and most perfectly formed cerebrum, in proportion to 
the size of the entire body; and of all quadrupeds he is proverbially 
the most intelligent and the most teachable. It is important to 
observe, in this connection, that the kind of intelligence which 
cbaractenzes the elephant and some other of the lower animals, 
and which most nearly resembles that of man, is a teachable intelli- 
gence; a very different thing from the intelligence which depends 
upon instinct, such as that of insects, for example, or birds of pas- 
sage. Instinct is unvarying, and always does the same thing in the 
same manner, with endless repetition; but intelligence is a power 
which adapts itself to new circumstances, and enables its possessor, 
by comprehending and retaining new ideas, to profit by experience. 
It is this quality which distinguishes the higher classes of animals 
from the lower; and which, in a very much greater degree, con- 
stitutes the intellectual superiority of man himself. The size of 
the cerebrum in man is accordingly very much greater, in propor- 
tion to that of the entire body, than in any of the lower animals; 
while other parts of the brain, on the contrary, such as the olfactory 
ganglia or the optic tubercles, are frequently smaller in him than 
in them. For while man is superior in general intelligence to all 



408 



*HE BBAIK. 



the lower animals, he ia inferior to manjr of them in the acuteneas 
of the special senses. ■ 

As a general rule, also, the size of the cerebrum in dlflerent | 
races and in different individuals corresponds with the grade of 
their intelligence. The size of the cranium, oa compared urith that 
of the face, is smallest in the savage uegro and Indian tribes; larger 
in the civilized or semi-civilized Chinese, Malay, Arab^and Japan- ■ 
ese; while it is largest of at! in the enlightened European races. 
This diflfercnce in the development of the brain is not probably an 
effect of loQg-continued civilization or otherwise; but it is, on the 
contrary, the superiority in cerebral development which makes 
some races readily susceptible of civili/Jition, while others are 
either altogether incj^pabte of it, or can only advance in it to a 
certain limit. Although all races therefore may, perhaps, be said 
to start from the same level of absolute ignorance, yet after the ■ 
lapse of a certain time one race will have advanced further in | 
civilization than anotlier, owing to a auperior capacity for improve' 
ment, dependent on original organization. m 

The same thing is true with regard to different individuals. At m 
birth, all men are equally ignorant; and yet at the end of a certain 
period one will have acquired a very much greater intellectual 
power than another, even under similar conditions of training, 
education, dx. He has been able to accumulate more information 
from the same sources, and to use the same experience to better 
advantage than his utfsuciates; aud the result of this is a oertain 
intellectual superiority, which becomes still greater by its own 
exeroiae. Tbis superiority, it will be observed, lies not so much 
in the power of perceiving external objects and events, and of re- 
cognizing the connection between them, as in that of drawing con* 
olusiuns from one fact to another, and of adapting to new ootnbina- 
tions the knowledge which has already been acquired. 

It is this particular kind of intellectual did'erence, existing in a 
marked degree, between animals, races, and individuals, which cor- 
responds with the difference in development of the oerebrul heini* 
spheres. We have, thcroforo, evidence from three different sourees 
that the cerebral hemispheres are the seat of the reasoning powers, 
or of the Intellectual faculties proper. Firnt, when thew ganglia 
are removed, in tbe lower animals, the intellectual faculties are the 
only oues which are lost. Secondly, injury to these ganglia, in the 
humau subject, is fullowed by a eorresi>onding impairment of the 
aame faculties. Thirdly, in different species of animals, as well as 



HEUI8PHEBSS. 409 

in different races of men and in different individuals, the develop- 
ment of these faculties is in proportion to that of the cerebral 
hemispheres. 

When we say, however, that the hemispheres are the seat of the 
iDtellectnal facnlties, of memory, reason, judgment, and the like, 
we do not mean that these faculties are, strictly speaking, located 
in the sufaatance of the hemispheres, or that they belong directly to 
the matter of which the hemispheres are composed. The hemi* 
spherical ganglia are simply the instruments through which the 
int^ectual powers manifest themselres, and which are accordingly 
necessary to their operation. If these instruments be imperfect in 
stractnre, or be damaged in any manner by violence or disease, the 
manifestations of intelligence are affected in a corresponding degree. 
So far, therefore, as the mental faculties are the subject of physio- 
logical research and experiment, they are necessarily connected 
with the hemispherical ganglia; and the result of investigation 
shows this conneotion to be extremely intimate and important in 
its character. 

There are, however, various cireumstances which modify, in 
particular cases, the general rule given above, viz., that the lai^er 
the cerebrum the. greater the. intellectual superiority. The func- 
tional activity of the brain is 'modified, no doubt, by its texture aa 
well as by its size; and an increased excitability may compensate, 
partially or wholly, for a deficiency in bulk. This fact is some- 
times iUuBtrated in the case of idiots. There are instances where 
idiotic children with small brains are less imbecile and helpless 
than others with a larger development, owing to a certain vivacity 
and impressibility of organization which take the place, to a certain 
extent, of the purely intellectual faculties. 

This was the case, in a marked degree, with a pair of dwarfed 
and idiotic Central American children, who were exhibited some 
years ago in various parts of the United States, under the name of 
the " Aztec children." They were a boy and a girl, aged respectively 
about seven and five years. The boy was 2 feet 9} inches high, and 
weighed a little over 20 pounds. The girl was 2' feet 6} inches 
high, and weighed 17 pounds. Their bodies were tolerably well 
proportioned, but the cranial cavities, as shown by the accompany- 
ing portraits, were extremely small. 

The an tero- posterior diameter of the boy's head was only ^^ 
inches, the transverse diameter less than 4 inches. The antero- 
posterior diameter of the girl's head was 4^ inches, the transverse 



410 



ihaI 



diameter only SJ inches. The liabiia of these childreo, so far as 

regards feeding and taklug care of themselves, were those of chil- 



Fig. 139. 



'^ 






m^ 



AlTIc Cllll.nats.— TshMfrou lib. •( Sratind mtvq jmranrag*. 

dren two or three years of age. They were incapable of learning 
to Ifllk, and could only repeat a few isolated words. KotwithMAnd- 
ing, however, the extremely limited range of their intelleciti&l 
powers, these children were remarkably vivacious and excitable. 
While awake they were in almost constant motion, and any n«w 
objector toy presented to them immediately attracted their atten- 
tion, and evidonily awakened a lively curiosity. They were ac- 
cordingly easily influenced by proper management^ and understood 
readily the meaning of those who addressed them, so far as this 
meaning could be conveyed by gesticuUiion and the tones of ihe 
voice. Their expression and general appearance, though decidedly 
idiotic, were not at all disagreeable or repulsive; and they were 
mauh lesK troublesome to the persons who had them in charge than 
is oden the case with idiots possessing u larger cerebral development 

II may also be observed that the purely intellectual or reasoning 
powers are not the only element in llie mental superiority of cenaio 
races or of particular individuals over their assocutea. There ia 
also a certain rapidity of perception and strength of will which may 
sometimes overbalance greater intellectual acquirements and mure 
cultivated reasoning powers. Those, however, are diflerent facul- 
ties from the latter; and occupy, as we shall herealYer see, differeoC 
parts of the encephalon. 

A very remarkable physiological doctrino, dependent partly on 
the foregoing facts, was brought forward some years ago by Oall 
and Spurzheim, under the name of Phrenology. These observers 
recognized the fact that the intellectual powers are andoubttnlly 



HEUISPHEBES. 411 

■eated id the brain, and that the development of the brain is, as a 
general rale, in oorrespondeoce with the activity of these powers. 
They noticed also that in other parts of the nervoas system, different 
fanctioDS occapy different situations; and regarding the mind as 
made np of many distinct mental faculties, they conceived the idea 
that these different faculties might be seated in di&erent parts of 
the cerebral mass. If so, each separate portion of the brain would 
nndonl^tedly be more or leas developed in proportion to the activity 
of the mental trait or faculty residing in it. The shape of the head 
would then vary in different individuals, in accordance with their 
mental pecnliarittes ; and the character and endowments of the in- 
dividual might therefore be estimated from an examination of the 
elevations and depressions on the surface of the cranium. 

Accordingly, the authors of this doctrine endeavored, by examin- 
ing the heads of various individuals whose character was already 
known, to ascertain the location of the different mental faculties. 
In thia manner they finally succeeded, as they supposed, in accom- 
plishing their object; after which they prepared a chart, in which 
the snrface of the cranium was mapped out into some thirty or forty 
different regions, corresponding with as many different mental traits 
or faculties. With the assistance of this chart it was thought that 
phrenology might be practised as an art; and that, by one skilled 
in its application, the character of a stranger might be discovered 
by simply examining the external conformation of his head. 

We shall not expend much time in discussing the claims of phre- 
nology to rank aa a science or an. art, since we believe that it has 
of late years been almost wholly discarded by scientific men, owing 
to the very evident deficiencies of the basis upon which it was 
founded. Passing over, therefore, many minor details, we will 
merely point out, aa matters of physiological interest, the principal 
defects which must always prevent the establishment of phrenology 
as a science, and its application aa an art. 

First, though we have no reason for denying that different parts 
of the brain may be occupied by different intellectual faculties, 
there is no direct evidence which would show this to be the case. 
Phrenologists include, in those parts of the brain which they em- 
ploy for examination, both the cerebrum and cerebellum; and they 
justly regard the external parts of these bodies, viz., the layer of 
gray matter which occupies their surface, as the ganglionic portion 
in which must reside more especially the nervous functions which 
they possess. But this layer of gray matter, in each principal por- 



412 



TBB BRAIN. 



tiou of the brain, isconUiiuotiatliroug^iout. There is no anatomical 
division or limit between its different parti, like thate between 
the different ganglia in other portions of the nervous system; and 
consequently such divi»toDa of the cerebrum and cerebellum must 
be altogether arbitrary in ehziracter, and not dependent on auy 
anatomical batiis. 

Secondly, the only means of ascertaining tlie locatioa of the 
difterent menial traits, supposing them lo occupy different, part* of 
the brain, would be that adopted by Gall and Spurzheim, viz^ to 
make an aocurate comparison, in n sufficient number of oases, of the 
form of the head in individuals of known character. But the prac- 
tical difficulty of accomplishing this is very great. It requiros a 
long acquaintance and close observation to learn accurately the 
uharactor of a single person ; and it is in this kind of observation, 
more than in any other, that we are proverbially liable to mistakes. 
It is extremely improbable, therefore, that either Gall or Spurzheim 
could, in a single lifetime, have accomplished this comparison in so 
many instances as to furnish a reliable basis for the ooostructioo of 
a phreTtulugicuI chart. 

A still more serious practical difficulty, bowever, is the following. 
The different intellectual faculties being supposed to reside in the 
layer of gray substance constituting the surfaces of the cerebrum 
and cerebellum, they must of course be distributed throughout this 
layer, wherever it oxiata. Gall and Spurzheim located all the mental 
faculties in those parts of the brain which are accessible to external 
exploration. An examination «f different sections of the brain 
will show, however, that the greater portion of the gray substance 

is so placed, that its quantity cannot he 
Hg- 140. estimated by an external examination 

through the skull. The only portions 
which are expose^l to such an exainina- 
tiun are the upper and lateral portions 
V '.^-VA^^^i **^ t^® convexities of the hemispheres, 
together with tlie posterior edge and 
part of the uniler surface of the cere- 
bellum. (Fig. 140.) A very extensive 
portion of the corobrsl surface, however, 
remaiua concealed in such a manner that 
it cannot possibly be subjected to ex- 
amination, viz., the entire base of the 
braiu, with the under surface of the an- 






} 



D(aar»ie »[ ih* DsAiii m htd. 
■bowing til DM punlnii* wlikk >» ox- 
PVMi to •SBinluMlaD. 



HEHISCHSBBS. 



413 



Pig. Ml. 



tenor and middle lobes (i, s); the upper BarPace of the cerebellum 
(■) and the inferior surface of the posterior lobe of the cerebrum 
which covers it (4); that portion of the cerebellum situated above the 
medulla oblongata(a); and the two opposite convoluted surfaces in 
the fissure of Sylvius («, 7), where the anterior and middle lobes of 
the cerebram lie in contact with each other. The whole extent, 
also, of the cerebral surfaces which are opposed to each other in the 
great longitndinal fissure (Fig. 141), throughout its entire length, 
are equally protected by their position, and 
concealed from external examination. The 
whole of the convoluted surface of the brain 
most, however, be regarded as of equal im- 
portance in the distribution of the mental 
qualities; and yet it is evident that not 
more than one-third or one-quarter of this 
snrface is ao placed that it can be examined 
by external manipulation. It must further- 
more be recollected that the gray matter of 
the cerebrum and cerebellum is everywhere 
convoluted, and that the convolutions pene- 
trate to various depths in the substance of 
the brain. Even if we were able to feel, therefore, the external 
surface of the brain itself, it would not be the entire convolutions, 
but only their superficial edges, that we should really be able to 
examine. And yet the amount of gray matter contained in a given 
space depends quite as much upon the depth to which the convolu- 
tions penetrate, as npon the prominence of their edges. 

While phrenology, therefore, is partially founded upon acknow- 
ledged physiological facts, there are yet essentially deficiencies in 
its scientific basis, as well as insurmountable difilculties In the way 
of its practical application. 




TnniTerM laetioD of B ■ a i * , 
(howlng depth of great 1od(1- 
indlnftl BHore, kt a. 



Cebebelluh. — The cerebellum is the second ganglion of the 
encephalon, in respect to sizei If it be examined, moreover, in 
regard to the form and disposition of its convolutions, it will be 
seen that these are much more complicated and more numerous 
than in the cerebrum, and penetrate much deeper into its substance. 
Though the cerebellum therefore is smaller, as a whole, than the 
cerebrum, it contains, in proportion to its size, a much larger quan- 
tity of gray matter. 

In examining the comparative development of the brain, also, in 



4T4 



THE BltAtTT. 



different classes and species of aQimals, we find that tlie cerebellam 
Dearly always keeps paec, in ttiis respect^ with the cerebrum. These 
factfi wtiuhl lend us to regard it as a ganglion hardly secondary in 
importance to the cerebrum itself. 

Physiologists, however, have thug for failed to demonstrate the 
nature of its function with the same degree of precision as that of 
many other parts of the brain. The opinion of Gall, which located 
iu the cerebellum the sexual impulse and instincts, is at the present 
day generally abandoned; for the rcnson that it has not been found 
to be sufficiently supported by anatomical and experimental focU, 
many uf which ore indeed directly opposeil to it. The opiaioo 
which has of late years been received with the most favor is that 
first advocated by Klourens, which attributes to the cerebellum the 
power of associating or "co-ordinating" the diflcrent volunuiry 
movements. 

It is evident, indeed, that such a power does actually reside in 
Bome part of the nervous system. No movements arc effected by 
the independent contraction of single muscles; but always by 
several muscles acting in harmony with each other. The number 
and complicaliun of these associated movements vary in different 
classes of animals. In fish, for example, progression is accom- 
plished in the simplest possible manner, v'lv.., by the lateral flexion 
and extension of the vertebral column. In serpents it is much ttie 
same. In frogs, lizards, and turtles, on Iho other band, the four 
Jointed extremities come into piny, and the movements are some* 
what complicated. Tliey arc «till more so in birds and f^uadrnpeda; 
and Gually, in the human subject they become both varied and 
complicated in the highest degree. Even in maintaining the ordi- 
nary postures of standing and sitting, there are many diflerent mus- 
cles acting together, in each of which the degree of contraction, in 
order to preserve the balftoce of the body, must be accurately pro- 
portioned to that of the olhersi. In the motions of walking aad 
running, or in the still more delicate movements of the hands and 
fingers, this harmony of muscular action becomes still more evident, 
and is seen also to be absolutely indispensable to the efficiency of 
the muscular apparatus. 

The opinion which locates the above harmonizing or associating 
power in the cerebellum waa first suggested by the effects observed 
alYcr experimentally injuring or destroying this part of the braio. 
If the cerebellum be exposed in a living pigeon, and a portion of 
its substance removed, the animal exhibits at once a peculiar nn- 



CGREBBLLUV. 



416 



certainty io bis gait, and in tbe moTement of his wtngs. If the 
injury be more extensivu, he loses aliogetbor tlie power of flight, 
and can walk, or even stand, only with great difficulty. This is not 
owing to any actual paralysis, for the movements of the limbs are 
excee<iingly rapid ami energetic; but is due to a peculiar want of 
control over the muscular oon tractions*, precisely similar to that 
which is seen in a man in a state of intoxication. The movements 
of the legs and wings, though forcible and rapii'l, are confused and 
blundering; ao that the animnl cannot direct liis steps to any par- 
ticular spot, nor support himself in the ftir by flight, ilu reels and 
tumbles, but can neither walk nor fly, 

Kg. 142. 



.-^^i''* 



The senses aod intelligence at the same time are unimpaired. It 
is extremely curious, as first remarked by Longet, to compare the 
diflerent phenomena produced by removal of the ccrebrom and 
that of the cerebellum. If we do these operations upon two dif- 
fereot [Hgeons, and place the animals aide by side, it will be seen 
that the first pigeon, from whom the cerebrum only has been re- 
moved, remains standing firmly upon his feet, in a condition of 
complete repose; and that when aroused and compelled to stir, he 
moves sluggishly and unwillingly, but otherwise acts in n perfectly 
DBtural manner. The second pigeon, on the other hand, from 
whom the cerebellum only has been taken away, ia in a constant 
stale of agitation. He ia «asily terrified, and endeavors, frequently 
with viotcDt struggles, to escape the notice of those who are 



41G 



IS BRAiy. 



watching him; but bis movemeots are sprawling and unnatural, 
and are evidently no longer under tli« eflectual control of the will. 
(Fig. 142.) If the entire cerebellum be destroyed, the animal \m 
no longer capable of nssuming or retaining any nittaral poetnre. 
His legs and wings are almost constantly agitated with ineEIectual 
struggles, which are evidently voluntary in character, but are a; 
the same time altogether irregular and confused. Death generally ■ 
takes place after this operation within twenty-four hours. 

We have often performed the above operation, and always with 
the same eifect, Indeed there are few experiments that have been 
tried upon the nervoua system, which give results so uniform and 
so constant as this. Taken hy themselves, these reaultii would 
invariably sustain the theory of Flourcns, which, indeed, is founded 
entireiy upon them, ■ 

Dut we have met with another very important fact, in this respect, 
which has hitherto escaped notice. That ifi, that birds, which have 
lost their power of muscular co-ordination from injury of the cere- 
bellum, may rtcovtr this jiowcr in process o/timt, notwithstanding that 
a Urge portion of the cerebellum has been permanently removed. 
Usually such an operation upon the cerebellum, as we have men- 
tioned above, is fatal within twenty-fonr hours, probably on account M 
of the close proximity of the medulla oblongata. But in some ■ 
instances, the pigeons upon which we have operated have survived, 
and in these cases a re-establishment of the coordinating power I 
took place. 

In the first of these instances which was observed, about two- 
thirds of the cerebellum was taken away, by an opening in the 
posterior part of the cranium. Immediately after the operation, 
the animal showed all the usual eftbct^ of the operation, being 
incapable of flying, walking, or even standing still, but reeled and 
sprawled about in a perfectly hclplcM manner. In the course of five 
or six days, however, he had regained a very considerable control 
over his voluntary movomonts, and at the end of sixteen days bis 
power of muscular co-ordination was so nearly perfect, that its de- 
ficiency, if any existed, waa imperceptible. He was then killed; and 
on examination, it was found that hid cerebellum remained in oearly 
the same condition as immediately after the operation; about two- 
thinU of its substance being deficient, and no attempt having been 
made at its regeneration. The accompanying figures show cbo 
appearance of parts, iu this case, as compared with the brain of a 
healthy pigeon. 



CBBBBKLT.U1I. 



417 



Fig. 143. 



Hg. 144. 



We have also met with three other eases, similar to the above, in 
which about one-hair of the cerebellum waa removed by operation. , 





Bbaik «p Hialtbt PiaBoa— Proflla 
t1«w —I. HawUpbMa. 1 Optic tab«n)]«. S. 
Car*b«llBB 1. Optic ner*<>. S. Ufdulla cb- 

Fig. 145. 



Braiit of Opibatid Pkieob — / w'^^ 
Profile Tlew— «hDwiiif tlic muillulloii 
of cerebellum. 



■>^^ 



,V^J-C' 



Ftg. 146. 








c 



(,' 



/ 



BkAta nr Hbaltbt Piqkox— Paite> 
ifor rlcw. 



■ Oo 

Bbaik op Opbbatbd Piobob— 
PualarloT view — ■h<ivlii| (lie DiBllls- 
tloa of eerrbpllum. 



'U^' 







The loss of co-ordinating power, immediately after the operation, 
thongh leaa complete than in the instance above mentioned, was 
perfectly well marked in character; and in little more than a fort- 
night the animale had nearly or quite recovered the natural control 
of their motions. 

These instances show, accordingly, that a large portion of the 
oerebeUnm may be wanting without a corresponding deRciency of 
the co-ordinating power. If the theory of Flourens be correct, 
therefore, these cases can only be explained by supposing that 
those parts of the cerebellam which remain gradually become en- 
abled to supply the place of those which are removed. It is more 
probable, however, that the loss of co-ordinating power, which is 
immediately produced by taking away a considerable portion of 
this nervous centre, is to be regarded rather as the effect of the 
sudden injury to the eer^Uum aa a whole, than as due to the mere 
removal of a portion of its mass. 

Morbid alterations of the cerebellum, furthermore, particularly 
of a chronic nature, such as slow inflammations, abscesses, tumon:, 
&&, have often been observed in the human subject, without giving 
rise to any marked disturbance of the voluntary movements. 
27 



418 



THE BRMN. 



I 



Oil the otlicr liand, many facte derived from comparative anatomy 
seem to favor the opinion of Flourcna. If wc compare different 
classes of animals with each other, as &s\i with reptiles, or birds 
vilh quadrupeds, iu which the developmeut and actirity of the 
entire nervous system vary extremely, the results of the comparison 
will be often contradictory, liut if the comparison be made be- 
tvecn different species in which the general structure and plan of 
organization are similar, we often find the development of the cere- 
bellum tu correspond very clusety with the perfection and variety 
of the voluntary movements. The frog, for example, is an aquatic 
reptile, provided with anterior and posterior extremities; but its 
movement^, though rapid and vigorous, are exceedingly simple in 
character, consisting of little else than fluxion and extension of the 
posterior limbs. The cerebellum in this animal is exceedingly 
small, H8 compared with the rest of the brain; being nothing more 
than a thin, narrow ribbon of nervous matter, stretched across the 
upper part of the fourth ventricle. In the common turtle we have 
another aquatic reptile, where the movementsof swimming, diving, 
progression, &c., ore acconipliahed by the consentaneous action of 
anterior and posterior extremities, and where the motions of the 
head and neck are aUo much more varied than in the frog. In 
this instance the cervbellum is very much more highly developed 
than io the former. In the alligator, again, a reptile whose motions, 
both of the head, limbs, and tail, approach very closely to those of 
the quadrupeds, the cerebellum is still larger in proportion to the _ 
remaiiuDg ganglia of the encephalon. f 

The complete function of the cerebellum, accordingly, aa a nerv- 
ous centre, cannot be regarded as positively ascertained! ; but so far 
as we may rely on the results of direct experiment, this organ has 
evidently such an initmate and peculiar connection with the volao* 
tary movements, that a sudden and extensive injury inflicted upon 
\iR substance in always followed by an immediate, though temoo^^ 
rary, disturbance of the co-ordinating power. ^^^^ 

TUBSRCULA Qdadriobhika. — These bodies, DotwithstaodiDg 
their small aize, are very important in regard to their function. 
They give origin to the optic nerves, and preside, as ganglia, over 
the sense of sight; on which account they are also known by the 
name of the " optic ganglia." Their development corresponds very 
closely with that of the external organs of vision. Thus, they are 
large in Bab, reptiles, and birds, in which the eyeball is fur the 



TUBERCULA QUADBIOBHiyA. 419 

most part very large in proportion to the entire head ; and are small 
in qoadropeds and in man, where the eyeball is, comparatively 
speaking, of insignificant size. Direct experiment also shows the 
close oonaection between the tubercula quadrigemina and the sense 
of sight. Section of the optic nerve at any point between the 
retina and the taberclea, produces complete blindness ; and destruc- 
tion of the tuberoles themselves has the same effect Bat if the 
division be, made between the tubercles and the cerebrum, or if the 
cerebram itself be taken away while the tabercles are left un- 
toached, vision, as we have already seen, still remains. It is the 
tabercles, therefore, in which the impression of light is perceived. 
So long as these ganglia are uninjured and retain their connection 
with the eye, vision remains. As soon as this connection is cut 
o£^ or the ganglia themselves are injared, the power of vision ia 
destroyed. 

The tabercala quadrigemina not only serve as nervous centres 
for the perception of light, but a reflex action also takes place 
through them, by which the quantity of light admitted to the eye 
is regulated to suit the sensibility of the pupil. In darkness and 
in twilight, or wherever the light is obscure and feeble, the pupil 
is enlarged by a relaxation of its circular fibres, so as to admit as 
large a quantity of light as possible. On first coming into a dark 
room, accordingly, everything is nearly .invisible; but gradually, 
as the pupil dilates and as more light is admitted, objects begin to 
show themselves with greater distinctness, and at last we can see 
tolerably well in a place where we were at firat unable to perceive 
a single object. On the other hand, when the eye is exposed to an 
Quasnally brilliant light, the pupil contracts and shuts out so much 
of it as would be injurious to the retina. 

The above is a reflex action, in which the impression received by 
the retina is transmitted along the optic nerve to the tubercula 
qnadrigemina. From the tubercles, a motor impulse is then sent 
out through the motor nerves of the eye and the filaments dis- 
tributed to the iris, and a contraction of the pupil takes place in 
conaeqaenoe. The optic nerves act here as sensitive fibres, which 
convey the impression from the retina to the ganglion; and if 
they be irritated in any part of their course witb the point of a 
needle, the result is a contraction of the pupil. This influence is 
not communicated directly from the nerve to the iris, but is first 
sent inward to the tubercles, to be afterward reflected outward by 
the motor nerves. So long as the eyeball remains in connection 



420 



rs BKAIN. 



witli the brnin, mechariical irritation of tlie oplic nerve, as we have 
^hown above, causes contraotioo of the pupil; but if the nerve be 
divided, and the extremity which remains in connection with the 
eyeball be subjected lo irntation, no elTcct upon the pupil is pro- 
duced. 

The anatomical arrangement of the optic nerves, and the connec- 
tions of the optio tubercles, are modified in a remarkable degree in 
diflTerent animals, to corre8[>ond with the position of the two eyes. 
In fish, for example, the eyes are so placed, on opposite aides of the 
head, that their axes cannot be brought into parallelism with each 
other, and the two eyes can never bo directed together to the same 
object. In these animals, the opttc nerves cross each other at the 
base of the brain without any intermixture of their fibres; that 
from the right optic tubercle passing to the left eye, and that from 
the lefl optic tubercle passing to (he right eye. (Fig. 147.) The two 



I 



Pig. 147. 



Fig. 148. 



»r C<ii> — I Htcbi uplicai'rTa. 3 LvH 
•pit; Dvrtc X Klfhtopllc lulwrcl*. 4. 
Li«n 'ipilriati^rfl*. i. t. \Um\*tk*tm 

T. Ui^alla ubl,'il|Bii. 



IxrBNiflH 8rkr4''B or B<i«rs ap 
Fowl,,— I lll(M ••ptXiMT*. 1 un«p(k 

»plle catMMla. 0, * He u lap bans. 7. lU- 



nervous cords are here totally distinot from each other throughout 
their entire length ; and are only connected, at the point of cross- 
ing, by intervening areolar tissue. Impressions made on the right 
eye must therefore be perceived on the left side of the brain ; while 
those which enter the left eye arc conveyed to the right side of the 
braio. 



klNttlQEMIKA. 



421 



in birds, also, the axes of ihe two eyca are ao widelj divergent 
that ao ubject cannot be diBtioclIy id focas for both of them at the 
same time. The optic nerves are here utiilud, and apparently sol- 
ilered together, at their point of crossing: but the decusatioa of 
their fibres is nevertheless complete. (Fig. 148.) The nervous fila- 
ments coming fruiii the luft side pass altogether over to the right; 
and those coming from the right side pass over to the left. The 
result of direct experiment on the croaseil action of the tubercles in 
these animals corresponds with the anatomical arrangement of the 
nerroQs fibres. If one of the optic tubercles be destroyed in the 
pigeon, complete blindness is at once produced in the eye of the 
oppovite side; bat vision remains animpuired in ihe eye of the side 
on which the injury was inflictetL 

In the human subject, on the other hand, where the visual axes 
are parallel, and where both eyes are simultaneously directed to the 
same object, the optic nerves deuuasate with each other in such u 
manner as to form a oonnection between the two opposite sides, as 

Pig. 149. 



Cnvcxar Optic Kmvisiir M a«.— 1. 3. RlitlaodUn *r«bK]ti 1. T^triutiioh irf ApO* 
kima. i, t.^TubmulB lundrlfrmliia. 

well as between each tubercle and retina of the same nide. (Fig. 
149.) This decussation, which is somewhat complicnted, take-s place 



THB BRAiy. 



in the following manner. From each oi^lic tubercle three different 
bundles or " tracts" of nervous fibres are given off. One net pusaca 
ncroM transversely at the point of ilecassatlon, and, turning back- 
ward, t«rniinat«s in the tubercle of the opposite side; another, cross- 
ing diagonally, continues onward to tlie opposite eyeball; while a 
third passes directly forward to the eyeball of the same side. A 
fourth set of fibres, still, passes across, in front of the dccussaUon, 
from the retina of one eye to that of the opposite side. We have, 
therefore, by tliis arrangement, tlie two retinae, as well as the two 
optic tubercles, connected with each other by oomniissoral flbrcs; 
while each tubercle in, at the same time, connected both with its 
own retina and with that of the opposite side. Tt is undoubtedly 
owing to these connections that when, in the human subject, tbe 
eyes are directed iu their proper axes, the two relinu, as well as 
ihe two optic tubercles, act as a single organ. Vision is single, 
ibercfore, though there are two images upon the retinie. Double 
vision occurs only when the eyeballs are turned out of their proper 
direction, so that the parallelism of their axes is lost, and the image 
no longer falhi upon corresponding parts of the two relinra. 



I 

ible 
per 1 
age ■ 



I 



TcBKH AxNai.ABE.— The collection of gray matter imbedded in 
the deeper portions of the tuber anntilare occupies a situation near 
the central part of the brain, and lies directly in the course of the 
ascending fibres of the anterior and posterior columns of the cord. 
Tliia ganglion is immediately connected with the functions of sensa- 
tion and voluntary motion. We have already seen that these fuoo- 
tions arc not destroyed by taking away the cerebrum, and that they 
also remain after removal of the cerebellum. According to the ex- 
periments of Longet, even after complete removal of the olfactory 
ganglia, the cerebrum, cerebellum, optic tubercles, corpora striata 
and optic thalami, and when nothing remains in the cavity of the 
cranium but the tuber annulare and the medulla oblongata, ilie 
animal is still sensitive to external impressions, and will still en- 
deavor by voluntary movements to escape from a painful irritation. 
The sameobserver has found, however, that as soon as tbe ganglion 
of the tuber annulare is broken up, all manifestations of sensation 
and volition cease, and even consciousness no longer appears to M 
exist. The only movements which then follow external irritation 
are the oocaaional convulsive motions which are due to reflex action _ 
of the spinal cord, and which may be readily distinguished from 
those of a voluntary character. The animal, under these circum- 



KEDULLA OBLONGATA. 423 

stances, is to all appearance reduced to the condition of a dead 
body, except for Uie movements of respiration and circulation, 
which still go on for a certain time. The tuber annulare must 
therefore be regarded as the ganglion bj which impressions, con- 
veyed inward through the nerves, are first converted into conscious 
sensations; and in which the voluntary impalses originate, which 
stimulate the muscles to contraction. 

We must carefully distinguish, however, in this respect, a simple 
sensation from the ideas to which it gives origin in the mind, and 
the mere act of volition from the train of thought which leads to 
it. Both these purely mental operations take place, as we have 
seen, in the cerebrum ; for mere sensation and volition may exist 
independently of any intellectual action, as they may exist after 
the oerebmm has been destroyed. A sensation may be felt, for 
example, without our having the power of thoroughly appreciating 
it, or of referring it to its proper source. This condition ia oiWn 
experienced in a state of deep .sleep, when, the body being exposed 
to cold, or- accidentally placed in a constrained position, we feel a 
sense of snaring, without beiug able to understand its cause. We 
may even, under such circumstances, execute voluntary movements 
to escape the cause of annoyance; but these movements, not being 
directed by any active intelligence, fail of accomplishing their ob- 
ject. We therefore remain in a state of discomfort until, on awak- 
ening, the activity of the reason and judgment is restored, when the 
offending cause is at once removed. 

We distioguish, then, between the simple power of sensation, 
and the power of fully appreciating a sensitive impression and of 
drawing a conclusion from it. We distinguish also between the 
intellectual process which leads us to decide upon a voluntary 
movement, and the act of volition itself. The former must precede, 
the latter must follow. The former takes place, so far as experi- 
ment can show, in the cerebral hemispheres; the latter, in the gan- 
glion of the tuber annulare. 

UsDULLA Oblongata. — The last remaining ganglion of the en- 
cephalon Is that of the medulla oblongata. This ganglion, it will 
be remembered, is imbedded in the substance of the restiforra body, 
occnpying the lateral and posterior portions of the medulla, at the 
point of origin of the pneumogastric nerves. This portion of the 
brain has long been known to be particularly essential to the pre- 
servation of life; so that it has received the name of the "vital 



424 



BRACK. 



i 



point," or the " vital knot." All the other part-? of the brain mnv 
be injured or removed, as we bave already seen, without the imme* 
diate and oecesaary destractioQ of life ; but so aoon as the medulla 
oblongata is brokou up, and its ganglion destroyed, respiration 
oeascji iniitanLancouflly, and the circulation also aoon comes to an 
uod. Btfuioval of the medulla oblongata produces, therefore, as its 
intTnediate ami direct result, a stoppage of respiration; and deatb 
takes pince principally a^ a conscqueoce of ibis fact. 

Floureos and L<oiigcl have detertnined, with considerable accu* 
racy, the precise limits of this vital spot in the medulla obloognU. 
Flourens ascertained that in rabbits it extended from just above 
the origin of the pneuinogaatric nerve, to u level situated three lines 
and a half below this origin. In larger animals, its extent is pro* 
portionately increased. Longet ascertained, furthormoro, that the 
properties of the medulla were not the same throughout its entire 
thickness; but that its posterior and anterior parts might be de 
8troyt)d with comparative impunity, the peculiarly vita) spot being 
confined to theintermediftte portions. This vital point oocordingly 
is situated in the layer of gray matter, imbedded in the thickness 
of the reatiform bodies, which has been previously spoken of as 
giving origin to the pneumcgastric nerves. 

The precise nature of the connection between this ganglion and 
the function of respiration may be described as follows. Tha 
movements of rcspiratii^n, which tblluw each other with incessant 
regulnrity through the whole period of life, ore not voluntary 
movements. We may, to a certain e.xtent, hasten or retard them 
Bt will, but our power over thoin, even in ibis respect, is estremoly 
limited ; and in point of fact they are performed, during the greater 
part of the time, in a perftjctly quiet and regular manner, without 
our volition and even without our consciousness. They continue 
uninterruptedly through the deepest slumber, and even in a cou- 
diticui of intMinsibility from accident orditteosc. 

These movements are the result of a reflex action taking place 
through the mcdalla oblongata. The impression which gives rise 
to tbem originalee principally in the lungs, irom the accumulation 
of carbonic acid in the pulmonary vessels and air-cells, is trans- 
mitted by the pncumogastric nerves to the medulla, and is thence 
reflected back along the motor nerves to the respiratory mosoles. 
These muscles arc then called into action, producing an expansion 
of the chest. The impression eu conveyed to the medulla is usually 
uuperceived by the consciousness. It i^ generally converted directly 



VEDULLA OBLONGATA. 426 

ioto a motor impalw, without attrsoting oar attention or giving 
rise to any oonscioag sensation. Bespiration, accordingly, goes on 
perfectly well without oor interference and without our knowledge. 
The nerrona impression, however, conveyed to the medulla, though 
Qsnally imperceptible, may be made evident at any time by volao- 
tarily soqiending the respiration. As the carbonic acid begins to 
aocumnlate in the blood and in the lungs, a peculiar sensation makes 
itself felt, which grows stronger and stronger with every moment, 
and impels us to recommence the movements of inspiration. This 
peculiar sensatioo, entirely different in character from any other, is 
designated by the French under the name of "besoin de respirer." 
It becomes more argent and distressing, the longer respiration is 
soapended, until finally the impulse to expand the chest can no 
I<HigeT be resisted by any effort of the will. 

During ordinaiy respiration, therefore, each inspiratory move- 
ment is excited by the partial vitiation of the air contained in the 
langs. As soon as a new supply has been inhaled, the impulse to 
respire is satisfied, the muscles relax, and the chest collapses. In 
a few seconds the previous condition recurs and the same move- 
ments are repeated, producing in this way a regular alternation of 
inspirations and expirations. 

Since the movements of respiration are performed partly by the 
diaphragm and partly by the intercostal muscles, they will be 
differently modified by injuries of the nervous system, according to 
the spot at which the injury is indicted. If the spinal cord, for 
example, be divided or compressed in the lower part of the neck, 
all the intercostal muscles will be necessarily paralyzed, and respi- 
ration will then be performed entirely by the diaphragm. The 
ohest in these cases remaining motionless, and the abdomen alone 
rising and falling with the movements of the diaphragm, such 
respiration is called "abdominal" or "diaphragmatic" respiration. 
It is a common symptom of fracture of the spine in the lower 
cervical region. If the phrenic nerve, on the other hand, be 
divided, the diaphragm will be paralyzed, and respiration will then 
be performed sJtogether by the rising and falling of the ribs. It 
is then called "thoracic" or "costal" respiration. If the injury 
inflicted upon the spinal cord be above the origin of the second 
and third cervical nerves, both the phrenic and intercostal nerves 
are ai once paralyzed, and death necessarily takes place from suf- 
focation. The attempt at respiration, however, still continues in 
these cases, showing itself by ineffectuul inspiratory movements of 



426 



TRR BRAIEf. 



the mouth and noetrils. Finally^ if the medulln itself be broken up 
by a atoci instrument intnxluced through the foramen magnum, so 
as to destroy tho nervous centre in which the above reflex action 
takes place, both the power and the desire to breathe are at once 
taken away. No attemjit is m»de at inspiratioo, there is no strag- 
gle, and no appcaraiioe of suJlering. Tho animal dies simply by 
a want of aeration of the blood, which leads in a few moments to 
an arrest of the circulation. 

It is owing to the above action of the medulla oblongata that in* 
juries of this part are bo promptly and constantly fatal. When the 
"neck is broken," as in hanging or by sudden falls upon tho head, a 
rupture takes place of the transversa ligament of the atlas; the 
head, together with the first cervical vertebra, is allowed Ui slide 
forward, and the medulla is compressed between the odontoid pro- 
cess of the axis in front and the posterior part of the aroh of the 
atlas behind. In cases of apoplexy, where any part of the hemi- 
spheres, corpora striata, or optic thalami, is the seat of the hemor- 
rhage, the patient generally lives at leitst twelve hours; but if the 
liemorrhage take place into the medulla itself, or at the base uf the 
brain in its immediate neighborhood, so as to compress its sab- 
stance, death follows inatantoneously, and by the same mechanism M 
as where the medulla is inteniioivally destroyed. ■ 

An irregularity or want of correspondence in the movements of 
respiration is accordingly found to be one of the most threatening 
nf ail symptoms in an'eciiuna of the brain. A disturbance or sus- 
pension of the intellectual powers does not indicate neccssarilj any 
immediate danger to life. Even sensalioo and volition may be im- 
paired wilhuut serious and direct injury to the organic functions. 
These symptoms only indicate the threatening progress of the dis- 
ease, and show that ii is gradually approaching the vital centre. It ■ 
is common to see, however, as the medulla itself begins to be impli- 
cated, & paralysis first showing itself in the respiratory inovemeuts 
of the nostrils and lips, while those of the chest and abdomen stiU 
go on as uiiual. The cheeks are then drawn in with every inspira- 
tion and puffed out sluggishly with every expiration, the nostril* 
themselves sometimes participaliitg in these unnatural movements. 
A still more threatening symptom, and one which frequently pre- 
cedes death, is an irregulur, hesiuiting respiration, which sometimes 
attracts the attention of the physician, oven before tho remaining 
cerebral functions are seriously impaired. These phenomena de- 



HSDULLA OBLONGATA. 427 

pend on the coDnection between the Teiq)irator7 movements and the 
reflex action of the medulla oblongata. 

We have now, in studying the functions of varioaa puts of the 
cerebro-spinal sj^stem, become familiar with three different kinds of 
reflex action. 

The first ia that of the spinal cord. Here, there is no proper 
sensation and no direct consciousness of the act which is performed. 
It is simply a nervous impression, coming from the integament, 
and transformed by the gray matter of the spinal cord into a motor 
impalse destined for the muscles. This action will take place after 
the removal of the hemispheres and the abolition of conscioasness, 
as well as in the ordinary condition. The respiratory action of the 
medulla oblongata is of the same general character; that is, it is 
not necessarily connected with either volition or consciousness. 
The only peculiarity in this instance is that the original nervous 
impression is of a special character, and its influence is finally 
exerted upon a special muscular apparatus. Actions of this nature 
are termed, par excellence, reflex actions. 

The second kind of reflex action takes place in the tuber annu- 
lare. Here the nervous impression, which is conveyed inward 
frona the integument, instead of stopping at the spinal cord, passes 
onward to the tuber annulare, where it. first gives rise to a con- 
scious sensation; and this sensation Is immediately followed by a 
volantary act. Thus, if a crumb of bread fall into the larynx, the 
seoaation produced by it excites the movement of coughing. The 
seasations of hunger and thirst excite a desire for food and drink. 
The sexual impulse acts in precisely the same manner; the percep- 
tion of particnlar objects giving rise immediately to special desires 
of a sexual character. 

It will be observed, in these instances, that in the first place, 
the nervoos sensation must be actually perceived, in order to pro- 
duce its efl^t; and in the second place that the action which 
follows is wholly voluntary in character. But the most important 
peculiarity, in this respect, is that the voluntary impulse follows 
datctly upon the reoeipt of the sensation. There is no intermediate 
reasoning or intellectual process. We do not cough because we 
know that this is the most effectual way to clear the larynx ; but 
simply because we are impelled to do so by the sensation which is 
felt at the time. We do not take food or drink because we know 
that they are necessary to support life, much less because we under- 
stand the mode in which they accomplish this object; but merely 



428 



TUB BRAIN. 



because we desire thetn whenever we feel tlie sensatious of hunger 
and thirst. 

All actions of this nature are terme<l in«tineliv9. Tfae^r are Tolnn- 
iary in cbaraoter, but are performed blindly; that is, without any 
idea of the ultimate object to be acccmpliahed by them, and simply 
io consequence of the receipt of a particular sensation. Aocord- 
itigly experience, judgment, and adaptation have nothing to do with 
theae actions. Thus the bee builds bis cell on the plan of a mathe- 
matical figure, without performing any mathematical calculation. 
The silkworm wraps himself in a cocoon of his own spinning, 
certainly without knowing that it is to afford him shelter during 
the period of his metamorphoaia. The fowl incubates her eggs 
and keeps them at the proper temperature for development, simply 
because the sight of them creates in her a desire to do so. The 
habits of these animals, it is true, are so arranged by nature, thai 
such instinctive actions are always calculated to accomplish an 
ultimate object. But this calculation is not made by the animal 
himself, and does not form any part of his mental operations. 
There is consequently no improvement in the mode of performing 
such actions, and but little deviation under a variety of circum- 
stances. 

The third kind of reflex action requires the co-operation of the 
hemispheres. Here, the nervous impression is not only conveyed 
to the tuber annulare and converted into a sensation, but, still 
following upward the course of the fibres to the cerebrum, it there; 
gives rise to a special train of ideas. We understand then the 
external source of the sensation, tho manner in which it is calcu- 
lated to afTeci us, and how by our actions we may turn it to our 
advantage or otherwise. The action which follows, therefore, in 
these cases, is not simply voluntary, but reatonahle. It does not 
depend directly upon the external sensation, but upon an iutetlec- 
tual process which intervenes between the sensation and the voli- 
tion. These actions are distinguished, occordinj^ly, by a character 
of dcHiiite contrivance, and a conscious adaptation of means to 
ends; characteristics which do not belong to any other operations 
of the Dervoua ayatem. 

The possession of this kind of intolligcncso and reasoning power 
is not confined to the human species. We have already seen that 
there are many purely instinctive actions in man, as well as in 
animals. It is no less true that in the higher animals there is often 
the siime exercise of reasoning power as in man. Tho degree of 



XBDULtA OBLONGATA. 429 

this power is much leas in them than in him, bat its nature is the 
Bsnte. Wbenerer, in an animal, we see any action performed with 
the evident intentioa of aocompliahing a particular object, to which 
it is properly adapted, such an act is plainly the result of reason- 
ing powers, not essentially dififerent from our own. The establish- 
moDt of aentinelfl by gregarious animals, to warn the herd of the 
approach of danger, the reooUecdon uf punishment inflicted for a 
putioolar action, and the subseqaent avoidance or concealment of 
that action, the teachability of many animals, and their capacity of 
forming new habits or of improving the old ones, are all instances 
of the same kind of intellectual power, and are qaite different from 
instinct, strictly speaking. It is this faculty which especially pre* 
dominates over the others in the higher classes of animals, and 
which finally attains its maximum of development in the human 
species. 



430 



THE ORANIAt. NKRVBS. 



CHAPTER V. 



THE CRANIAL NEKTE9. 



Ix examining the cranial nerves, we shall find that although they 
at first seem quite diQ'erent in their distribution and properties _ 
rrum the spinal nerves, yet tfacy are in reality arranged for thef 
moBt part on the same plan, and may be studied in a similar 
manner. 

At the outset, however, we llnd that there are three of the ora- 
ninl nerves, commonly so called, whioh must be arranged in a class 
by themselves; since they have no character in common with the 
other nerves originating either from the brain or the spinal cord. 
These are the throe nerves of special sense; viz., the Otlactory, 
Optic, and Auditory. They are, properly speaking, not so much 
nerves as commissures, c^tnnecting ditlerent parts of the encephalic 
niAss with each other. They are neither sensitive nor motor, in 
the ordinary meaning of these terms; but are capable of conveying 
only the special senaation characteristic of the organ with which 
they are connected. 



Olfactobt Nerves.— We have already described the so called 
olfactory nerves as being in reality commissures, connecting the 
olfactory ganglia with the central parts of the brain. The moaaea 
situated upon the cribriform plate of the ethmoid bone are cooi> 
poaed of gray matter ; and even the filaments which they seod 
outward to be distributed in the Schneiderian mucous membrane, 
are gray and gelatinous in their texture, and quite different from 
the fibres of ordinary norvos. The olfactory nerves are not very 
well adapted for direct experiment. It is, however, at least certain 
with regard to them that they serve to convey the special seasniion i 
of smell; that their mechanical irritation doe» not give rise toj 
either pain or convulsions; and finally that their destruction,] 
together with that of the olfactory ganglia, does not occasion any i 
{Miraly^ii nor loss of ordiuary sensibility. 



THS CBANIAL VEBVBS. 481 

Oftio Nxbtxs. — We have ali^dj given some acconnt of these 
nerves and their deoassations, in coDnection with the history of the 
tubercula qnadrigemina. Thej oonsist of rounded bundles of white 
fibres, running between the tubercles and the retinsa. As the reti- 
nae themselves are membranous expansions consisting mostly of 
vesicular or cellular nervous matter, the optic nerves, or " tracts," 
must be regarded as commissures connecting the retinae with the 
tubercles. We have also seen that they serve, by some of their 
fibres, to connect the two retinae with each other, as well as the two 
tubercles with each other. 

The optio uerrea convey only the special impression of light from 
without inward, and give origin to the reflex action of the optic 
tubercles, by which the pupil is made to contract. According to 
Longet, the optic nerves are absolutely insensible to pain through- 
out their entire length. When a gal vanic current is passed through 
the eyeball, or when the retina is touched in operations upon the 
eye, the irritation has been found to produce the impression of lumi- 
nous sparks and flashes, instead of an ordinary painful sensation. 
The impression of colored rings or spots may be easily produced 
by compressing the eye in particular directions; and a sudden 
stroke upon the eyeball will often give rise to an apparent discharge 
of brilliant sparks. Division of the optic nerves produces complete 
blindness, but does not destroy ordinary sensibility in any part of 
the eye, nor occasion any muscular paralysis. 

AuDiTOBT Nkbtes. — The nervous expansion in the cavity of 
the internal ear contains, like the retina, vesicles or celts as well as 
fibres; and the auditory nerves are therefore to be regarded, like 
the optio and olfactory, as commissural in their character. They 
are also, like the preceding, destitute of ordinary sensibility. Ac- 
cording to Longet, they may be injured or destroyed without giving 
rise to any sensation of pain. They serve to convey to the brain 
the special sensation of sound, and seem incapable of transmitting 
any other. Longet* relates an experiment performed by Volta, in 
which, by passing a galvanic current through the ears, the observer 
experienced the sensation of an interrupted hissing noise, so long 
as the connection of the wires was maintained. Inflammations 
within the ear, or in its neighborhood, are oflen accompanied by 
the perception of various noises, like the ringing of bells, the 

■ TniH dtt Phjrsiologiv, toI. ii. p. 286. 



482 



TBB CRAXIAt, :«BRTaS. 



washing of the waves, the hamming of insects; sounda which have 
no external existence, but which are simulated by the morbid irri- 
tation of the auditory nerve. 

It is evident, from the facts detailed above, that the DerveH of 
special sense are neither motor or sensilive, properly speaking; 
and that they are distinct in their nature from the ordinary spinal 
nerves. 

The remainder of the cranial nerves, however, present the 
ordinary qualities belonging to the spinal nerves. Some of ihem 
are exclusively motor in character, olhcm exclusively sensitive; 
while most of them exhibit the two properties, to a certain extent, 
as mixed nerves. They may be conveniently arranged in three 
pairs, according to the regions in which they are distributed, cor- 
reBponding very closely with the motor and sensitive roots of the 
spina.! nerves. According to such a plan, the arrangement of the 
cranial nerves would be as follows: — 



Ca&RiAi. Nuthl 
X*rt*M of Special Stn-t. 
1. OUaclory. 2. OpUo. 3. Anililory. 
Molar Ker*«t. 
Motor oouli com. 
Palli«tloas 
Motor oc. uxl«rniis 
timall root ot fi'th |Mir 



Sontlllr* Xtr*«ii. 



Dl>tribaia4 to 



]»t FAIR. 



SdrAlR. 

M r*iB. 



H>'t'0^1o»8ILl 



Large root of &tti p»ir. Pmc«. 



Glirsm-phar^ngiNiL 
i'mtumogaatrio. 



Neck, &<f. 



The above arrangement of the cranial nerves is not absolutely 
perfect in all its details. Thus, while the hypoglossal supplies the 
muscles of the tongue alone, the glosso-pharyngeal sends part of ^ 
its sensitive fibres lo tlie tongue and part to the pharynx; and 
while the large root of the 6ih pair Is mostly distributed iu the 
face, one of its branches, v'xz^ the gustatory, is disthbaled to ihe ■ 
tongue. Notwithstanding these irregularities, however, the above 
division of the cranial nerves is in the main correct, and will be 
found extremely useful as an assistant in the study of their func' 
tions. 

There is no impropriety, moreover, in regarding all the motor 
branches distributed upon the face as one nerve; since even the 
anterior roots of the spinal nerves originate from the spinal cord, M 
each by several distinct filaments, whioh are associated into a single 



THK CBANIAL NSBTIS. 488 

bundle 011I7 at a certain distance from their point of origin. The 
mere fact that two nerves leave the cavity of the cranium by the 
same foramen does not indicate that they have the same or even a 
similar fdoction. Thus the facial and auditory both escape from 
the cavity of the cranium by the foramen auditorium internum, and 
yet we do not hesitate to regard them as entirely distinct in their 
nature and functions. It is the ultimate distribution of a nerve, 
and not its course through the bones of the skull, that indicates 
its physiological character and position. For while the ultimate 
distributioD of any particular nerve is always the same, its arrange- 
ment as to trunk and branches may vary, in different species 
of animals, with the anatomical arrangement of the bones of the 
skull. This is well illustrated by a fact first pointed out by Prof, 
Jeffries Wyman' in the anatomy of the nervous system of the 
bQllfh)g. In this animal, both the facial nerve and motor oculi 
eztemus, instead of arising as distinct nerves, are actually given 
off as branches of the 6th pair; while their ultimate distribution is 
the same as in other animals. All the motor and sensitive nerves 
distributed to the face are accordingly to be regarded as so many 
different branches of the same trunk ; varying sometimes in their 
course, but always the same in their ultimate distribution. 

The miAar nerves of the bead are in all re^>ects identical in their 
properties with the anterior roots of the spinal nerves. For, in the 
first place, they are distributed to muscles, and not to the integu- 
ment or to mucous membranes; secondly, their division causes 
maacnlar paralysis; and thinlly, mechanical irritation applied at 
their origin produces muscular contraction in the parts to which 
they are distributed, but does not give rise to a painful sensa- 
tion. In several instances, nevertheless, the motor nerves, though 
insensible at their origin, show a certain degree of sensibility when 
irritated after their exit from the skull, owing to fibres of com- 
munication which they receive from the purely sensitive nerves. 
In this respect they resemble the spinal nerves, the motor and 
sensitive filaments of which are at first distinct in the anterior 
and p<Mterior roots, but aderward mingle with each other, on 
leaving the cavity of the spinal canal. 

The three Mnntive nerves originating from the brain are the 
large root of the fifth pair, the glossopharyngeal, and the pneumo- 

■ HarTOoi StbUid of Rank pipieuB ; pabllshvd bj tlie Smithsonian Initltntioo. 
\rMliliigton, 1853. 

2a 



434 



IB ORASflJ 



Erves. 



gnstric It will be observctl tbnt, in all their essential propcrticB,' 
the J correspond witli the posterior roots of the spinal ner\-es. Uko j 
them they are inexoitable, but extremely sensitive. Irritated ati 
their polDt of origin, they give rise to acutely painful 8en^tioQ^ 
but to no convulsive movements. Secondly, if divide*! at the aame 
situation, the operation is followed by loss of Acnsibility in the 
parts to which they are distributed, without any disLurbance of the 
motive power. Each of these nerves, furthermore, liko the posta-, 
rior root of a spinal nerve, is provided with a ganglion througli 
which its fibres pass: the fiMx pair, with the Casserian ganglion, 
situated uear the inner extremity of the petrous portion of the tem- 
poral bone; the glosso- pharyngeal, with the ganglion of Andersch, 
situntoci in the jugular fos^^a; while the pnenmognstrte presents, 
just before its passage through the jugular foramen, a ganglion 
known as the ganglion of the pncumogastric nerve. Finally, the ■ 
aensitive fibres uf all these nerves, beyond the situation of their gao- f 
glia, are intermingled with others of a motor origin. The large root 
of the 6fth pair, which is exclusively sensitive, is accompanied by 
the fibres of the small root, which are exclusively motor. The 
glosso-pbaryngeal receives motor filaments from the facial and spi* ■ 
Dal accessory, becoming consequently a mixed nerve outside tbe 
cranial cavity ; while the pneumugnsLric i» joined by fibres from the 
spinal accessory and various other nerves of a motor character. 
These nerves, accordingly, are exclusively sensitive only at their ^ 
point of origin, Though they afterwurd retain the predominating " 
character of sensitive nerves, they are yet found, if irriUit«d In tbu 
middle of their course, to be intermingled with motor Qbrcs, and 
to have consequently acquired, to a certnin extent, the character of ■ 
mixed nerves. | 

The resemblance, therefore, between the cranial and spinal nerves 
is uompltite. 



MoTOE Oc0Li CJoMMPNis. — This nerve, which is sometimes known 
by the more convenient name of the ocuh-molariui, originates from 
the inner edge of the crus cerebri, passes into the cavity of ihej 
orbit by the sphenoidal fissure, and is distributed to the levator] 
pnlpcbra; suporioris, and to all the muscles moving the eyeball, 
except the external rectus and the superior oblique. Its irritation 
accordingly produces convulsive movements in these parts, and 
its division has the eQ'eci of paralyzing the muselcs to which it is 



FIFTH PAIR. 4S5 

diBtribnted. The superior eyelid falls down over the pupil, and 
cannot be raised, owing to the inaction of its levator musole, so 
tbat the eye appears oonstantly half shut This condition is known 
by the name of "ptosis." The movements of the eyeball are also 
nearly suspended, and permanent exteraal strabismus takes plac^ 
owing to the paralysis of the internal rectus muscle, while the ex- 
ternal reotns, animated by a different nerve, preserves its activity. 

Pathxticus. — This nerve, which supplies the superior oblique 
musole of the eyeball, is similar in its general properties to the pre- 
ceding. Its section causes paralysis of the above muscle, without 
any loss of sensibility. 

MoTOB ErmtNUS. — This nerve, the sixth pair, according to the 
usual anatomical arrangement, is distributed to the external rectus 
mnsole of the eyeball. Its division or injury by disease is followed 
by internal strabismus, owing to the unopposed action of the internal 
rectus mnacle. 

Fifth Pair. — This is one of the most important and remarkable 
in its properties of all the cranial nerves. It is the great sensitive 
nerve of the face, and of the adjoining mucona membranes. Its 
large root, after emerging from the outer and under surface of the 
pons Varolii, passes forward over the inner extremity of the petrous 
portion of the temporal bone. It there expands into a orescentic- 
ahaped swelling, containing a quantity of gray matter with which 
its fibres are intermingled, and which is known as the Oassertan 
ganglion. The fibres of the smaller root, passing forward in com- 
pany with the others, do not take any part in the formation of this 
ganglion, but may be seen passing beneath it as a distinct bundle, 
and continuing their course forward to the foramen ovale, through 
which they emerge from the skull. In front of the anterior and 
external border of the Gasserian ganglion, the fifth nerve separates 
into three principal divisions, viz., the ophthalmic, the superior 
maxillary, and the inferior maxillary. The first of these divisions, 
-viz., the ophthalmic, is so called because it passes through the orbit 
of the eye. It enters the sphenoidal fissure, and runs along the 
npper portion of the orbit, sending branches to the ophthalmic gan- 
glion of the sympathetic, to the lachrymal gland, the conjunctiva, 
and the mucous membrane of the lachrymal sac. It also sends ofi' 



483 



TnK ORA?riAL NERVES. 



R small br«ncli (nn 
Bogea nnd supplies 



tbe DMtl 1 



Kg. 160. 



branch) which penetrates i 
Q Schneicierian mucous membrane, it then 
emerges upon the Taco by the supra-orbiul foranmn, and is dtnri- 
butcd to the integument of the forehead and side of the head u kr 
back as the vertex. 

Tbe second division of this nerve, or the auperior maxilUrr,— 
passes out by the foramen rotundum, and runs along the litngrtO'^ 
dinal canal in ihc floor of the orbit, giving off brunches during it« 
passage to the teeth of the upper jaw and to the mnoous membniK 
of the antrum maxillare. It finally emerges upon the middle of the 
face by the infra-orbital foramen, and is distributed to tbe ial«ga- 
ment or ihe lower eyelid, noee, cheek, and upper lip. 

The third, or inferior maxillary division of the 6flh pair, whick 
is the largest of the three, leaves the cavity of the cranium by tSe 

foramen ovale. It comprises a on- 
sidcrablo portion of the large root 
of tbe nerve, and all the fibres of 
the small root. This divitioa is 
therefore a mixed nerve, contaioia; 
both motor and sensitive fibres, 
while the two former are cxclo- 
sively sensitive. It is distribaiaJ, 
accordingly, both to maacles ind 
to the sensitive surfaces. Soon afta 
emerging from ibc fommen ovalf 
it sends branches to tbe temporal 
muBcle, to the masaeter^ the buoci- 
nator, and to the internal and ex- 
ternal pterygoids ; that is, to tlie 
muscles which are particularly coe- 
oemed in the movements of the 
lower jaw. It also scndit sensitite 
filaments to the integument of tbr 
T^ernple, to that of a portion of the external ear and external ludi- 
lory meatus. The third division of the fifth pair, then passinu 
downward and forward, gives oft' a branch of considerable ««, tbe ' 
Hngiml branch, which is distributed to the maooas membrane of lbs j 
anterior two-thirds of the tongue, and which also sends filaments to 
the arches of the palate and to the mucous mernbmne of the cheek. 
The remaining portion of tbe third diviaion, after giving a to* 



Dtiminr-niis nF Piriii S titir. 

Cr"» TUB PiC«.— O. r*«»lUo ||lin|))llll. 

] llphibklmUdlrliloD. a. BnpvfWr biksU- 
liirjrdJTUlon 9. InfarluraikslllKrjr dliUluj,. 




FIFTH PATB. 4S7 

branches to the mylo-hjoid muscle and to the anterior belly of the 
digastric, then enters the inferior dental canal, sends filaments to 
the teeth of the lower jaw, emerges at the mental forameo, and is 
finally distributed to the integument of the chin, lower lip, and 
infiirior part of the face. 

This nerve is accordingly distributed to the sensitive aurfaces, 
that ifl, the integument and mucous membranes about the face, and 
to the muscles of maatioation. A few of its fibres are sent also to 
the superQcial muscles of the face, such as the buccinator and the 
orbicularis oris; but these fibres are sensitive in their character, 
and serve merely to impart to the muscles a certain degree of 
sensibility. It has been ascertained by Longet that if the various 
branches of this nerve be irritated by a galvanic current, no con- 
vulsive movements whatever are produced in those superficial 
muscles of the face, which it supplies with filaments; but if its 
smaller or non -ganglionic root be irritated in the same way, con- 
tractiona instantly follow in the muscles of mastication. 

The fifth pair is the most acutely sensitive nerve in the whole 
body. Its irritation by mechanical means always causes intense 
pain, and even though the animal be nearly unconscious from the 
influence of ether, any severe injury to its large root is almost 
invariably followed by cri«B which indicate the extreme sensibility 
of its fibres. 

If this nerve be completely divided, in the living animal, within 
the cranium, at the situation of the Gasserian ganglion, the operation 
is followed by total loss of sensibility in the skin of the face and in 
the adjacent mucous' membranes. The conjunctiva, upon the afiected 
side, is then completely insensible, and may be touched with the 
point of a needle or the blade of a knife, without exciting any un- 
easiness, and even without the consciousness of the animal. Probes 
and needles may be passed into the nostril, and the lips or the 
cheek may be pinched, pierced or cut, without exciting the least 
sign of sensibility. The animal is entirely indifierent to all me- 
chanical injuries upon the afiected side, though upon the opposite 
side the parts retain their natural sensibility. 

Owing to the paralysis of the lingual nerve, also, after this ope- 
ration, the tongue, in its anterior two-thirds, becomes insensible to 
ordinary irritations, and loses beside the power of taste. 

Another peculiar efiect of the division of the fifth pair depends 
upon the paralysis of its motor fibres, which are distributed, as we 



438 



THE CBANIAL NBRVES. 



menll 



have Been, to tbe mascles of mastication. Id m&uy of tbe lows 
nnimals, conaequcnLly, ihe movomeiita of mastication beoonw ei- 
ceedingly enfeebled upon the affected side. lo the cat, for example, 
an animal in which mastication is usuallj very tborougbl; per 
formed, this process becomes excessively laborious, so that the 
animal aflcr this operation cannot maslicato solid meat, bnt reqoirv 
to be fed with that which has already been cut in pieces. 

The fifth pai r, beside supplying the acnsibiliiy of the intega 
of the face, has a peculiar and important influence on the orgaas 
special sense. This influence appears to consist in some oonnectioa 
between the action of tbe fifth pair and tbe processes of nutrition; 
80 that when the former is injured, the latter very bood beoome 
deranged. For the perfect action of any one of the organs of 
special sense, two conditions are necessary: first, the sensibilitv of 
the special nerve belonging to it, and, secondly, the integrity of the 
component parts of the organ itself. Now as the nutrition of ihe 
organ is, to a certain extent, under the control of the fifth pair.uT 
serious injury to this nerve produces a derangement in the tiissnes 
of tbe organ, and consequently interferes with tbe due performaooe 
of its function. 

The mucous membrane of the nasal passages, for example, i> 
supplied by two different nerves; fi.rs», the olfactory, distributed 
throughout its upper portion, by which it is endowed with tbe 
special sense of smell ; and, secondly, tbe nasal branch of the Btik 
pair, distributed throughout its middle and lower portions, I7 
which it is supplied with ordinary sensibility. 

Since the fiflh pair, accordingly, supplies general sensibility to 
the nasal passages, this property will remain after tho special aaix 
of smell has been destroyed. If, however, the fifth pair ilseU hr 
divided, not only is general sensibility destroyed in the Scbnmderi«n 
mucous membrane, but a disturbance begins to take plaoe in IIk 
nutrition of its tissue, by which it is gradually rendered un6t for 
the perforoiancQ of its special function, and the power of smell is 
finally lost. The mucous membrane, under theae circumstaocai, 
becomes injected and swollen, and the nasal passage is obetnicwd 
by an accumulation of puriform mucus. According to Longet, tin 
raucous membrane also assumes a fungous consistency, and is liable 
to bleed at the slightest touch. The effect of this alteration is to 
blunt or altogether destroy the sense of amell. It is owing to a 
similar unnatural condition of the mucous membrane that tbe pow 




FIFTH FAIB. 439 

of smell is always more or less impaired in cases of coryza and 
ioflaenza. Tbe olfactory- nerves become inactive in consequence 
of tbe morbid alteration in tbeir mucous membrane, and in tbe 
secretions which cover it 

The influence of this nerve over tbe organ of vision is still more 
remarkable. It has been known for many years that division of 
the fifth pair within tbe cranium, or of its ophthalmic branch, is fol- 
lowed by an inflammation of the corresponding eye which usually 
goes on to complete and permanent destruction of tbe organ. 
Immediately after the operation, tbe pupil becomes contracted and 
tbe conjunctiva loses its sensibility. At the end of twenty-four 
hoars, the cornea begins to become opaline, and by the second 
day the conjunctiva is already inflamed and begins to discbarge a 
paralent secretion. The inflammation, after commencing in tbe 
conjunctiva, increases in intensity and soon spreads to tbe iris, 
which becomes covered with a layer of inflammatory exudation. 
Tbe cornea grows constantly more opaque, until it is at last 
altogether impermeable to light, and vision is consequently sua- 
ipended. Blindness, therefore, does not result in these instances 
from any direct affection of the optic nerve or of tbe retina, but is 
owing simply to opacity of tbe cornea. Sometimes the diseased 
action goes on until it results in ulceration of the cornea and dis- 
cbarge of the humors of the eye; sometimes, after the lapse of 
several days, the inflammatory appearances subside, and the eye is 
finally restored to its natural condition. 

It has been observed, however, that, although the above conse- 
quences always follow division of tbe fifth pair, when performed at 
the level of tbe Caaseriao ganglion, or between it and tbe eyeball, 
they are either much diminished in intensity or altogether wanting 
when the division is made at a point posterior to the ganglion. 
This circumstance has led to tbe belief that the influence of tbe fifth 
pair on the nutrition of tbe eyeball does not reside in its own proper 
fibres, but in some filaments of the sympathetic nerve which join 
tbe fifth pair at the level of the Casserian ganglion. If the section 
accordingly be made at this point, or in front of it, tbe fibres of the 
sympathetic will be divided with tbe others, and inflammation of 
the eye will result; but if tbe section be made behind the ganglion, 
the fibres of tbe sympathetic will escape division, and tbe injurious 
effects upon the eye will bo wanting. Such is tbe explanation 
usually given of tbe above-mentioned facts ; but tbe question has 
not as yet been determined in a positive manner. 



440 



lL kbstks. 



DiTision of tbe fifth pnir deatrojra also the genera! sensibility of 
the external auHitorjr mcsatus, the lining membrane of which ia 
supplied by its Glanients. In^nmmation of this membrane and its 
consequent alterations, it is well known, interfere seriously with 
the sense of hearing. It ia no uncommon oucurrcnco for an accu- 
mulation of cerumen to take place nfter inflummation of this part, 
so as to block up the auditory canal and produce partial or com- 
plete deafness. It has not been ascertained, however, whether 
division of the fifth pair is usuuUy luUowed by similar changes in 
this part. 

The lingual branch of the flflh pair supplies the anterior ex- 
tremity and middle portion of the tongue both with general sensi- 
bility and with the power of taste. The sensibility of the tongue 
is accordingly provided for by two difterent nerves; in its anterior 
two-thirds, by the lingual braituh of the llfih pair; in its posterior 
third, by the fibres of the glosso-pboryngeal. 

The facial branches of the fifth pair are the ordinary seat of lie 
douloureux. This affection is not ODfrequently conQned to either 
the supra-orbital, the infra-orbital, or the mental branch; and the 
pain may be accurately traced in the direction of their diverging 
fibres. It has already been mentioned that the painful sensations 
sometimes alao follow ihe course of the facial, owing to some sensi- 
tive Glanients which that nerve receives from the tiflh pair. 



I 

I 



I 



\ 



Facial. — This nerve was known to the older anatomisla as the 
"portio dura of the seventh pair." It leaves the cavity of the 
cranium by the internal auditory foramen, in company with the 
auditory nerve; and, as the Utter ia of a suffer consistency thou the 
former, they have received the names respectively of the ** porlio 
mollis" and *'[K>rlio dura" of the seventh pair. There is, however, 
no physiological connection between these two nerves; for while 
the auditory ia spread out in the cavity of the internal ear, the facial 
passes onward through the petrous portion of the temporal bone, 
emcr^(;a at the stylo-mastoid foramen, bends round beneath the 
external ear, and ptiSHus forward througli the substance of the 
parotid gland, forming a plexus, called the "pes anserinus," by the 
abundant inosculation of its different branches. It then sends its 
filaments forward in a diverging course, and is finatly distributed 
to the muscles of the external cor, to the frontalis and superciliaria 
muscles, to the orbicularis oculi, the compressors and dilators of 
the nares, the orbicularis oris, and to the elevators and deprcsaurs 



I 
I 
I 



TACIAL NERTK. 



m- 



?ig. 151. 



VAeiAi. ViKTi. 



of the lipe; lliat is, to the superficial musctes or the face, which are 
coDcerned in the prodaction of expression. (Fig. 161.) 

The facial, conseqaently, is the 
tor nerve of the face. It bcui 
nothing to do with traiifimiLting 
sensitive impressiona, since it hns 
been frequently shown that afler 
section of the QflU pair, the faciul 
reuuiaiDg entire, the sensibility of 
the &ce is completely lost; so that 
the integument may be cut, pricked, 
pierced, or lacerated, without any 
sign of pain being exhibited by the 
animal. The facial, therefore, dues 
not transmit sensation from these 
parts; aud its division, which was 
r&rmerly resorted lo in cases of 
lie douloureux, is accordingly alto- 
gether incapable of relieving nenralgic pains. 

This nerve, however, is directly connected with muscular action, 
since mechanical or galvanic irritation of its 6brea produces ooa- 
vulsivo twitching in the cars, nostrils, lips and cheeks. 

If the facial nerve be divided in one of the lower nnimnla, on, for 
example, in the cat, immediately after its emergence from the 
stylo-mastoid foramen, it will be found that complete muscular 
paralysis has occurreil in all those parts t*^ which the nerve is dis* 
tributed, while ihe power of sensation remains unimpaired. The 
animal is incapable of moving the car, which remains constantly in 
the same position. There is also incapacity of closing the eyelids, 
owing to paralysis of the orbicularis oculi, and the eye accordingly 
remains constantly open, even when the opposite) eye is closed; 
as during sleep, or in the act of winking. If the conjunctiva be 
touohcd, the animal fecl.4 the irritation, and endeavor^ to escape 
from it; but the eyeball is only drawn partially backward into the 
socket by the action of the recti muscles, and the third eyelid 
pushed partly across the cornea. The cotnploio cloanro of the eye 
is impossible. It will be observed, accordingly, that precisely oppo* 
site eftects are produced upon the eyeli<lB by paralysis of the ouulo- 
motorius nerve, and by that of the facial. In the fonnur instance, 
owing to the paralysis of the levator pulpebne superioris, the eve 
is always partially closed ; in the latter, owing to paralysis of thv 




E42 



THE CRAKIAL NEKVES, 



orbicularis, it Is always partUlJy open. The moveinenta of tbe 
tiarcs are atso suspended on the side oF the injury, nod if the angle 
of the :noulh Iw examined ou that aide, it will be found to hang 
dowQ lower than on the opposite side, and to be constantly partly 
open, owing to the parnlysis of the orbicularis oris and the eleva- 
tors of the angle of the mouth. 

These are the only inconveniences which follow the diviaion of 
the facial nerve in the cat, but in some otlier of the lower animals, 
where vahouii muscalar organs iq this region are particularly de- 
velopod, the oonsef|uouce8 are tnore trnubleaome. Thus, in the rabbit, 
the ear, upon the aifected aide, falls down, and cannot be raised or 
pointed in different directions; and as the movements of the ear 
are ioiportuut in tbetie animals, as aids to the bearing, the per- 
fection of this sense must be considerably impaired by paralysis of 
the facial nerve, In the horse, it has been noticed by Bernard,' 
that division of the facial on both sides is fatal by suiTocation. For 
this animal breathes exclusively through the nostrils, which open 
widely at the Liinu of iuitpiratiori, to allow the a^lrnissioD of air. If 
these movemonla be suspended, by paralysis of the facial nerve, the 
nmtrils immediately collapse, and the animal dies by suffocation. 

In the human subJMt, the facial nerve is occasionally paralyzed 
upon one side, sometimes from sympathetic irritation, sometimea 
ffoin organic disease in the potrouit portion of the temporal bone, 
or within the cranial cavity near the origin of the nerve. In either 
case, an extremely well-marked affection is the result, known as 
"faotal paralysis.'* This condition is chiefly characterized by an 
entire absence of expression on the alYected side of the face. The 
lower eyelid sinks downward, from paralysis of the orbicalarii 
muscle, and cannot be closed. 

The comer of the mouth also falls downward, and the whole 
lower part of the face ia drawn orer to the opposite side by the 
force of the antagonistic muscles. The lips are unable to retain 
the fluids of the mouth ; and the saliva dribbles away from between 
tbem, giving to the face a remarkably vacant and helpless appear- 
ance. 

The principal inconvenience, however, suffered by the human 
subject in facial paralysis, depends upon the want of action of ihe M 
muscles about the lips and cheek. In drinking, the fluids escope 

■ L«QOB8 >nr 1b I'hjnMogit et In pAtliologie da 6jr«Uia« Nvrveux, Pario, 1838, 
vol. il. p. 36. 



OLOSSO-PHABYirOEAL NEBTE. 448 

by the comer of the month, and io mastication the food has partly 
a tendenoy to escape by the same opening, and partly accumulates, 
on the a£focted side, between the gums and the cheek, owing to the 
paralysis of the buccinator muscle, which reoeires its motor fila- 
mentB from the fooial nerve. Thus, the action of all the superficial 
facial muscles is suspended, the expression of the face is destroyed, 
and the movementB of the lips and the prehension of the food 
seriously interfered with. 

Though the facial, however, be essentially a motor nerve, yet its 
principal branches distributed to the face have a certain degree of 
sensibility ; that is, when these branches are irritated in the middle 
of their course, the animal immediately gives evidence of a painful 
sensation. Longet has shown, by an extremely ingenious mode 
of experiment,' that this sensibility of the branches of the facial 
does not depend on any sensitive fibres of their own, but upon 
those which they derive /n?Tn inosculation ivith the JifO^ pair. He 
exposes, for example, the facial nerve in the dog, and, irritating Its 
principal branches one after the other, at each application of the 
irritant there are evident signs of pain. He then divides the facial 
nerve at its point of exit from the stylo-raastoid foramen, and 
finds that, after this operation, the sensibility of its branches still 
remains. The fibres, accordingly, upon which this sensibility 
depends, do not pass out with the trunk of the nerve, but are 
derived from some other source. The experimenter, then, upon 
another animal, divides the fiflh pair within the skull, leaving the 
&cial untouched; and afterward, on irritating as before the ex- 
posed branches of the latter nerve, he finds that its sensibility has 
entirely disappeared. It is by filaments, accordingly, derived from 
the fifth pair, that a certain degree of sensibility is communicated 
to the branches of the facial 

These facts account for the peculiar circumstance that, in cases 
of tic douloureux, the spasmodic pain sometimes follows exactly 
the course of the facial nerve, viz; from behind the ear forward 
upon the side of the face ; and yet the section of this nerve does not 
put an end to the neuralgia, but only causes paralysis of the facial 
muscles. 

Olosso-Phabyvoeal. — This nerve originates from the lateral 
portion of the medulla oblongata, passes outward, and enters the 

> Traits do Phjiiologie, vol. 11. pp. 354-357. 



4U 



THE CRAXIAl ICERVKS. 



posterior foramen Incorum in oompany with the pncumogastric ond 
spinal accessory. While in the jugular ibssa it presents a gangliform 
enlargement, culled the gntiglion of Attderscb, below the level of 
which it receive branchea of communication from the facial and 
the spinal accessory. It then runs downward and forward, and is 
distributed to the mucous membrane of the base of the tongue, 
pillars of the f&ace», suft palate, middle ear, and upper part of the 
pharynx. Jt also seuda some branches to the coustrictors of the 
pharynx and the neighboring muscles, Longet has foond this 
nerve at its origin to be exclusively nensitive ; but below the lercl 
of its ganglion it has been found by liim, as well as by varioos 
olbcr observers, to be both sensitive and motor, owing to the fibres 
of communication received from the motor nerves mentioned above. 
Its final dislributioD ia, however, as we have seen, principally to 
ttenBitivo surfaces. Thu principal olDce of this nerve is to impart 
the suiiBc of taste to the posterior third of the tongue, to which it is 
distributed. It also presides over the goneral sensibility of this 
part of the tongue, as well as that of the fauces and pharynx. 

Dr. John Kcid,' who has performed a great variety of experiments 
upon this nerve, cotncs to the following conclusions in regard to it. 
First, that it is essentially a sen.sitive nerve, since there are unequi* 
vocal signs of paiu when it is pricked, pinched, or cut. Second, 
that irritation of this nerve produces convulsive movements of ibe 
throat and lower part of the face; but that these movements are, in 
great measure, not direct, but reflex in their character, since they 
will take place equally well after the glossopharyngeal has been 
divided, if the irritation be applied to its cranial extremity. Third, 
that this nervo supplies the special sensibility of tasie to a portion 
of the tongue; but that it is not the excdtsUe nerve of this sense, 
since the power of taste remains, after it has been divided on both 
sides. 

There are certain reflex actions, furthermore, which take place 
through the medium of the glosso- pharyngeal nerve. After the 
food has been thoroughly masticated, it is carried, by the move- 
roenls of the tongue and sides of the mouth, through the fauces, 
and brought in contact with the muciius membrane of the pharynx. 
This produces an impression which, conveyed to the medulla 
oblongata by the QIaiuents of the glosso-pbaryngeal, excites the 



* III Todd's Cjcloptedto, of Aitmtam^ itn<l PlijRiolo^, artiuU C/oaM^/iAaryoym/ 
iVorvr. 



PNEUU0GA8TRTC NERTS. 446 

mascles of tbe f&oeea and pharynx by reflex action. The food is 
OODseqQently grasped by these muscles, without the concurrence of 
the will, and the process of deglutition is commenced. This action 
is not only involuntary, but it will frequently take place even in 
opposition to the will. The food, once past the isthmus of the fauces, 
is beyond the control of volition, and cannot be returned except by 
ooDVuIsive action, equally involuntary in its character. 

Natural stimulants, therefore, applied to the mucous membrane 
of the pharynx, excite deglutition; unnatural stimalauts, applied 
to the same part, excite vomiting. If the finger be introduced into 
tbe fiinces and pharynx, or if the mucous membrane of these parts 
be irritated by prolonged tickling with the end of a feather, the 
sensation of uausea, couveyed through the glosso- pharyngeal nerve, 
is sometimes so great as to produce immediate and copious vomit- 
ing. This method may oflen be successfully employed in cases of 
poisoning, when it is desirable to excite vomiting rapidly, and when 
emetic medicines are not at hand. 

Frkuiiooabtbic. — Owing to the numerous connections of the 
pnenmogsstric with other nerves, its varied and extensive distribu- 
tion, and the important character of its functions, this is properly 
regarded as one of the most remarkable nerves in the whole body. 
Owing to the wandering course of its fibres, which are distributed 
to no less than four different vital organs, viz., the heart, lungs, 
stomach and liver, as well as to several other parts of secondary 
importance, it has been often known by the name of the par vagum. 
Tbe pneumogastric arises, by a number of separate filaments, from 
the lateral portion of the medulla oblongata, in the groove between 
the olivary and restiform bodies. These filaments unite into a 
single trunk, which emerges from the cranium by the jugular fora- 
men, where it is provided with a longitudinal ganglionic swelling, 
the "ganglion of the pneumogastric nerve." Immediately below 
the level of this ganglion the nerve receives an important branch 
of communication from the spinal accessory, and afterward from 
the facial, the hypoglossal, and the anterior branches of the first 
and second cervicals. 

At its origin, the pneumogastric is exclusively a sensitive nerve. 
Irritated above the situation of its ganglion, it has been found to 
convey painful sensations alone: but if the irritation be applied at 
a lower level, it causes at the same time muscular contractions, 
owing to the filaments which it has received from the abuvc-men- 



440 



THB CRAKTAL NERVES. 



FiL-, 1.'.2. 



r'^r 



tinned motor nerves. It becomes, consequently, after emerging 
from the cranial cavity, a mixed nerve; and has accordingly, in 

nearly all its branches, a double distribu- 
tion, vis., to the mucous membranes and 
the moscular coat of the organs to which 
it belongs. 

The ordinary sensibility of the pneu- 
Tnogastric nerve, however, as all experi- 
menters have observed, is exceediogly 
dull, in comparisoo with that of the other 
soewitive cranial nerves. We have often 
divided this nerve in the middle of the 
neck, without any distinct manifestatioD 
uf pain being given by the animal; and 
though Bernard has found tbnt at some 
limes its sensibility is well marked, while 
lit others it is very indistinct, he is not 
ftble to soy upon what special physio- 
logical coQditloDs thiiidiQerence depends. 
While the ptieumogastrlo, however, it 
decidcflly deficient, as a general role, in 
ordinary sensibility, it possesses, as we 
shall see hereafter, n sensibility of a pecu- 
liar kind, wliieb is oxceedin^y important 
for the maintenance of the vital func- 
tions. 

In passing down the neck, this nerve 
rands braiiubes to the mucous membraae 
and muBculur coat of the pharynx, caso- 
phagus,and respiratory passages. Among 
ihe most important of these branches are 
the two laryngeal nerves, viz., the supe- 
rior and inferior. The superior laryngoal 
nerve, which is given off from the trunk 
of the pneiimognstric Just al\er it has emerged from the cavity of the 
skull, passes downwnrd and forward, penetrates the larynx by an 
opening in the side of the thyro-hyotd membrane, and is distributed 
to the mucous membrane of the larynx and glottis, and also to b 
single laryngeal rauscte, viz., the erico-thyrold. This branch is 
therefore partly muscular, but mostly sensitive in its distribution. 
The inferior laryngeal brunch is given off just after the pneumo- 



nin^mm at PaiiliK<i4i«aTat<T 
Vliiivt.«'lihlup<1ucii»Jbrui«li««. 
—I. Plturjn^ftl liraneli. 'i Piu|in- 
rlor luT/iiKaiil. X tnrnrlor tityu. 
gMkl. 4. riilgn»fi4r]r lntti<tLu*. ft. 
Sluniacli. <(. LWsi. 



PNECHOGASTBIC HSBTE. 447 

gastric has entered the cavity of tbe chest. It carves roand the 
sabclaviaa artery on the right side and the arch of the aorta on 
tbe left, and ascends in the groove between the trachea and oeso- 
phagns, to the larynx. It then enters the larynx between the 
cricoid cartilage and the posterior edge of the thyroid, and is dis- 
tributed to all the moscles of the larynx, with the exception of the 
crico-thyroid. This branch is, therefore, exclosively muscular in 
its distribution. 

The trunk of the pneumogastric, afler supplying tbe above 
branches, as well as sending numerous filaments to the trachea 
and cesopbaguB in the neck, gives off in the cbeet its pulmonary 
branches, which follow the bronchial tubes in the lungs to their 
minutest ramifications. It then passes into the abdomen and sup- 
plies the muscular and mucous layers of the stomach, ramifying 
over both the anterior and posterior surfaces of the organ ; afWr 
which its fibres spread out and are distributed to the liver, spleen, 
pancreas, and gall-bladder. 

Tbe functions of the pneumogastric will now be successively 
studied in the various organs to which it is distributed. 

Pharynx and (Eaoj^aguB. — The reflex action of deglutition, which 
has already been described as commencing in the upper part of the 
pharynx, by means of the glosso-pharyngeal, is continued in the 
lower portion of the pharynx and throughout the oesophagus by 
the aid of the pneumogastric. As the food is compressed by the 
superior constrictor muscle of the pharynx and forced downward, it 
excites the mucous membrane with which it is brought in contact 
and gives rise to another contraction of the middle conBtriclor. The 
lower constrictor is then brought into action in its turn in a similar 
manner; and a wave-like or peristaltic contraction is thence pro- 
pagated throughout the entire length of the oesophagus, by which 
the food is carried rapidly from above downward, and conducted at 
last to the stomach. Each successive portion of tbe mucous mem- 
brane, in this instance, receives in turn the stimulus of the food, 
and excites instantly its own muscles to contraction; so that the 
food passes rapidly from one end of the oesophagus to the other, by 
an action which is wholly reflex in character and entirely withdrawn 
from the control of the will. Section of tbe pneumogastric, or of 
its pharyngeal and casopbageal branches, destroys therefore at the 
same time the sensibility and the motive power of these parta. The 
food is no longer conveyed readily to the stomach, but accumulates 
in the paralyzed oesophagus, into which it is forced by the voluntary 



TRK CRAXIAL NBBVBS. 



movementfi of the mouth ami fauces, and by the continuerl actjon 
of the upper pnrt of the pharynx. 

It m«st be remembered that the general sensibility of the asso- 
phagua is very slight, as compared