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I 



PHILOSOPHY OF HEAIJH; 



AN EXPOSITION 



HUMAN LONGEVITY AND HAPPINESS. 



SODTHWOOD SMITH, M.D., 

PAylJciiBi Iff Ite ii 



[K TWO VOLUUES. 




THIRD BDITION. 



LONDON: 

v.. COX, 13, KING WILLIAM STEEET, BTKIlSD. 

1847. 



/ Printed by William Cloweu and SoN*,SiMftt<«^^Me*\.. 



CONTENTS OF VOL. II. 



CHAPTER VIII. 

OF THE FUNCTION OF RESPIRATION. 

Respiration in the plant ; in the animal — Aquatic and 
aerial respiration — Apparatus of each traced through 
the lower to the higher classes of animals — Apparatus 
in man — ^Trachea, Bronchi, Air Vesicles — Pulmonary 
artery — Lungs — Respiratory motions : inspiration ; ex- 
piration — How in the former air and Mood flow to the 
lungs ; how in the latter air and blood flow from the lungs 
— Relation between respiration and circulation — Quan- 
tity of air and blood employed in each respiratory action—- 
Calculations founded on these estimates — Changes pro- 
duced by animal respiration on the air : changes produced 
by vegetable reiipiration on the air — Chani^es produced 
by respiration on the blood — Respiratory function of the 
liver — Uses of respiration - - - - Page 1 

CHAPTER IX. 

OF THE FUNCTION OF GENERATING HEAT. 

Of the temperature of living bodies — ^Temperatnre of 
plants — Power of plants to resist cold and endure heat 
—Power of generating heat — Temperature of animals — 
Warm-blooded and cold-blooded animHls — Temperature 
of the higher animals — Temperature of the diffierent 
parts of the animal body — Temperature of the humeA. 
body — Power of maintaining that tempetaiiitft %.\. «».^'x»^ 
po/nf, whether in intense cold, or intenBe YvefliX — '■^'x.\«'kv- 
ments which prove that this power \% a \Hia\ \«yii«t— 



IV CONTENTS. 

Kvidence that the power of generating heat is connected 
with the function of rettpiration — Analogy between 
respiration and combustion — Phenomena connected with 
the functions of the animal body, which prove that its 
power of generating heat is proportionate to the extent 
of its respiration — Theory of the production of animal 
heat — Influence of the nervous s3''stem in maintaining 
and regulating the process — Means by which cold is 
generated, and the temperature of the body kept at its 
own natural standard during exposure to an elevated 
temperature ----- Page 120 



CHAPTER X. 

OF THE FUNCTION OF DIGESTION. 

Process of assimilation in the plant ; in the animal — 
Digestive apparatus in the lower classes of animals ; in 
the higher classes ; in man — Digestive processes — Pre- 
hension, Mastication, lusalivatiou, Deglutition, Chymi- 
fication, Chylification, Absor})tion, Fecation — Structure 
and action of the organs by which these operations are 
performed — Ultimate results — Powers by which those 
results are accomplished — Two kinds of digestion, a 
lower and a higher; the former preparatoiy to the 
latter -.-.--- Page 159 

CHAPTER XI. 
OF THE FUNCTION OF SECRETION. 

Nature of the function — Why involved in obscurity — 
Basis of the apparatus consists of membrane — Arrange- 
ment of membrane into elementary secreting bodies — 
Cryptse, foUicles} caeca, and tubuli — Primary combina- 
tions of elementary bodies to form compound organs — 
Relation of the primary secreting organs to the blood- 
vessels and nerves — Glands, simple and compound — 
Their atructurt and office — Development of glands from 
their aimpleat form in the lowe&t aD\xaa\» io \.\i«\x iHQst 

complex form ia the highest animaU — ^D^NftVo^roauX. m 



CONTENTS. V 

the embn'o-^Niiraber and distributiou of the lecretiof^ 
organ8 — llow secretin)^ ort^ani act upon the blood — 
Degree in which the produos of secretion agree with, 
and differ from, the blood — Modes in which modifications 
of the 8«creting apparatus influence the products of secre- 
tion — Vital agent by which the function is controlled — 
Physical agent by which it is effected - - P^ge 279 



CHAPTER XII. 

OF THE FUNCTION OF ABSORPTION. 

Sridence of the process in the plant, in the animal — Ap- 
paratus general and special — Experiments which prove 
the absorbing power of blood-vessels and membrane — 
Decomposing and analysing properties of membrane-^ 
Endosmose and exosmose — Absorbing surfaces, pulmo- 
nary, digestive, and cutaneo\iH — Lacteal and lymphatic 
vessels — Absorbent glands — Mution of the tluid in the 
special absorbent vessels — Discovery of the lacteals 
and lymphatics — S{)ecific office performed by the several 
parts of the apparatus of absorptiim — Condition of the 
system on which the activity of the process depends— 
Uses of the function ----- Page 332 



CHAPTER XIII. 
OF THE FUNCTION OF EXCRETION. 

In "what excretion differs from secretion — ^Excretion in the 
plant — Quantity excreted bv the plant compared with 
that excreted by the animal — Organs of excretion in the 
human body — Organization of the skin — Excretory pro> 
cesses performed by it — Excretory processes of the lungs 
— Analogous processes of the liver — Use of the deposi- 
tion of fat — Function of the kidneys — Function q\ tVv«. 
Iar>fe mtestuieH — Compensating and 'V\eaLX\OM'ft «.^<\(^\a 
— Reasona why excretory processes we TkAcevanrj — ■ 

AdJuHtmenta - - « - , V«^^*^^^ 



VI CONTENTS. 

CHAPTER XIV. 

OF THE FUNCTION OF NUTRITION. 

Cumposition of the blood — Liquor sanguinis — Recent ac- 
count of the Htructure of the red particles — Furniatiou 
of the red particles in the incubated egg — Primary 
motion of the blood — Vivifying influence of the red 
particles — Influence of arterial and venous blood on 
animal and organic life — Formation of human blood — 
Course of the new constituents of the blood to the lungs 
— Space of time required for the complete conversion of 
chyle into blood after its first transmission through the 
lungs — Distribution of blood to the capillaries when 
duly concentrated and purified — Changes wrought upon 
the blood while it is traversing the capillaries — Evidence 
of an interchange of particles between the blood and 
the tissues — Phenomena attending the interchange — 
Nutrition, what, and how distinguished from digestion 
— How the constituents of the blood escape from the 
circulation — Designation of the general power to which 
vital phenomena are referrible — Conjoint influence of 
the capillaries and absorbents in building up structure 
— Influence of the organic nerves on the process — 
Physical agent by which the organic nerves operate — 
Conclusion - - - - - Page 422 



TH« 



PHILOSOPHY OF HEALTH. 



CHAPTER VIII. 

OF RESPIRATION. 



Retpiration in the plant; in the animal-»Aquatic and 
aiixial Tespiration— -Apparatus of each traced through 
the lower to the higher classes of animals — Apparatus 
in man — Trachea, Bronchi, Air Vesicles — Pulmonary 
artery — ^Lung — ^Respiratory motions: inspiration; ex- 
piration — How in the former air and hlood flow to the 
lung ; how in the latter air and hlood flow from the lung — 
Relation between respiration and circulation — Quantity 
of air and blood employed in each respiratory action 
— Calculations founded on these estimates — Changes 
produced by animal respiration on the air : changes pro- 
duced by vegetable respiration on the air — Changes pro- 
duced by respiration on the blood — Respiratory function 
of the liver — Uses of respiration. 

313. No organized being can live without food 
ixid no food can nourish without air. In all crea- 
tures the necessity for air is more urgent than 
that for food, for some can live days, and even 
weeks, without a fresh supply of food^ bu\. Xkcycv^ 
without a constant renewal of the air, 

VOL 11. ^ 



2 THE PHILOSOPHY OF HEALTH. 

314. The food having undergone the requisite 
preparation in the apparatus provided for its assi- 
milation, is brought into contact with the air, from 
which it abstracts certain principles, and to which 
it gives others in return. By this interchange of 
principles the composition of the food is changed : 
it acquires the qualities necessary for its combina- 
tion with the living body. The process by which 
the air is brought into contact with the food, and 
by which the food receives from the air the quaU- 
ties which fit it for becoming a constituent part 
of the living body, constitutes the function of 
respiration. 

315. In the plant, the air and the food meet in 
contact and react on each other in the leaf. The 
crude food of the plant having in its ascent from 
the root through the stalk, received successive 
additions of organic substances, by which its na- 
ture is assimilated to the chemical condition of the 
proper nutritive fluid of the plant (320 and 325), 
undergoes in the leaf a double process ; that of 
Digestion and that of Respiration. The upper 
surface of the leaf is a digestive apparatus, ana- 
logous to the stomach of the animal ; the under 
surface of the leaf is a respiratory apparatus, ana- 
logous to the lung of the animal. For the per- 
formance of this double function, incessantly 
carried on by the leaf, its organization is admira- 

bly adapted. 



APPARATUS IN IHI PLANT. 3 

316. The solid skeletoa of the le»f consisttof 

a net-work composed partly of woody fibres uid 

partly of spiral vessels which proceed from the 

stem, and which are called veins (fig. czzii. 1,3J. 

Pig. CXSIl. 




Vie« of the net-work which toriDi the solid (triicture of 
the leaf, and which consiits partljr of woody fihies, and 
putljof epiral veuela. I. Veuela of the upper siirfMu; 
2. vBiaels of the under Borfaee; 3. dinlribiition of the yea- 
■eU through the aabtUnce oC the leaf; 4. \nl«i*^*c»» 
between tbt ramalt ecaipied by paieQcbyiD«> (vi c«\V;^ax 



THE PHILDSOPHT O 



In the intenticaa between the veine ie diapoeed a 
quantity of cellular tismie, termed the pBcenchyma 
of the leaf (fig. cxiii. 4) : the whole is enveloped 
in a membrane, called the cuticle (fig. cxziii. ]), 



iiq. CXXIII. 




Vertical MCliim o! (he leaf b» it sppecni whea seen 
' hi(;hly ma^niSed under the micriMcape. 1. Crlls oF the 
eutidefilled with air; 2. double MriEH of cylimlrieal relli 
occupying the upper iutfac« of the leaf filleil with organic 
particlea ; 3. iiregular celli Saraiiag a teliculatrd t^tme 
occupying the under lurfaceof thelnf; 4. interspaces be- 
tween the cells, termed the intaceellular paeeagei or ail 
chamhera. 

which is fumtBhed with apertures denominated 
stomata, or Btomates (fig. cxsiv.). 

317. The cuticle consiBta of a layer of minute 
cellules, colourleBS, transpareot, without veaaela, 
without organic particlea of any kind, and pro- 
bMbfy Med with air (fig. cxxm. I"). T^iesa «&. 



STKDCTUHB OF TBI LKAF. 5 

lules Open externally, at certain portiont of the 

cuticle, by apeitures or passage* which constitute 

the itomates (Gg. cxxiv.), and which present tkc 

Fig. CXXIV. 




of them ie]>nHat«d 



appearance of areolce with a slit in the centre 
(fig. CXXIV.}. They form a kind of oval sphinct- 
ers, which are capable of opening or shutting, 
according to circumstances, and they are disposed 
on both surfaces of the leaf, hut most abundantly 
on the under surface, excepting in leaves which 
float on water, in which they are always on the 
upper surface only. 

318. The cellular tiasue or parenchyma, im- 
mediately beneath the cuticle, when examined in 
thin slices, and viewed under a microscope with a 
high magnifying power, presents a regular struc- 
ture disposed iu perfect order. It conml&,Qu{&& 
af^ter moAce, of jt 7syer, and sometime* o( Vwts 
tad even three layere, of resicles of an o\Aott¥,«i 



b THE PHILOSOPHY OF HEALTH. 

cylindrical form, placed perpendicularly to th 
surface of the leaf, set close to each other (fig 
cxxiii. 2), and fiUed with organic particles consti 
tuting the green matter which determines th 
colour of the leaf. On the under surface, oi 
the contrary, the vesicles, which are larger thai 
the cylindrical, are of an irregular figure, and ar 
placed in an horizontal direction, at such dis 
tances as to leave wide intervals between eacl 
other (fig. CXXIII. 3) ; yet uniting and anastomo 
«ing together, and thus forming a reticulated tie 
sue, presenting the appearance of a net with larg 
meshes (fig. cxxiii. 3). 

319. A leaf, then, consists of a double congerie 
of vesicles containing organic particles, penetrate 
by woody fibre and air vessels (which is probabl 
the true nature of the spiral vessels), the who! 
being enclosed within a hollow stratum of air-celli 

320. The crude sap, composed principally ( 
water, holding in solution carbonic acid, aceti 
acid, sugar, and a matter analogous to gum, i 
transmitted through the leaf-stalk to the cylindr 
cal vesicles of the upper surface of the leaf (fi^ 
CXXIII. 2). These vesicles exhale a large pr< 
portion of the water ; the evaporation of which i 
so powerfully assisted by the action of the sun' 
rays, that it would probably become excessive 
were it not for the perpendicular direction of tt 
cylindrical vesi(^t9^ (fig. cxxiii. 2) ; but in consc 

€juence of their being disposed peTp«ndicw\^.T\^ 



CHANGES EFFECTED IN THE SAP. 7 

the surface of the leaf, their ends only are pre- 
sented towards the heavens (fig. cxxiii. 2), and 
thus the main part of their surface is protected 
from the direct influence of the solar rays. The 
primary efi^ect of the evaporation carried on in the 
cylindrical vesicles, is the condensation of the 
oi^anic matters contained in the sap. 

321. At the same time that the cylindrical vesi- 
cles pour the superfluous water of the sap into 
the surrounding atmosphere, they ahstract from 
the atmosphere in return carhonic acid, which, to- 
gether with that already contained in the sap, is 
decomposed. The oxygen is evolved ; the carhon 
is retained. The physical agent hy which this 
chemical change, which constitutes the digestive 
process of the plant, is eflected, is the solar ray ; 
hence the vesicles which contain the fluid to he 
decomposed, are placed on the upper surface of 
the leafi where their contents are fully exposed to 
the action of the sun ; and hence also this process 
takes place only during the day, and most power- 
fully under the direct solar ray: hut although 
the direct influence of the sun he highly conducive 
to the process, yet it is not indispensable to it ; 
for it goes on in daylight although there he no 
sunshine. Light, then, would appear to he the 
physical agent which effects on the crude food of 
the plant a change analogous to that produced on 
the crude food of the animal by the juices of \\v«. 
stomach. 



8 THE PHILOSOPHY OF HEALTH. 

322. Afiter the sap has been elaborated in tho 
cylindrical vesicles, by the exhalation of its watery 
particles, by the condensation of its organic mat- 
ter, by the retention of carbon and the evolution 
of oxygen, it is transmitted to the reticulated vesi- 
cles of the under surface of the leaf (fig. cxxiii. 3), 
These vesicles, large, loose, and expanded, as they 
have an opposite ftinction to perform, are ar- 
ranged in a mode the very reverse of the cylin- 
drical : in such a manner as to present the great- 
est possible extent of surface to the sunrounding 
air (fig. CXXIII. 3) : at the same time the broad 
interspaces between them (fig. cxxiii. 4) are so 
many cavernous air-chambers into which the air is 
admitted through the stomates (fig. cxxiv.). The 
cylindrical vesicles, exposed to the direct rays of 
the sun, are protected by the closeness with which 
they are packed ; and by the small extent of sur- 
face they present to the heavens : the reticulated 
vesicles, whose function requires that they should 
have the freest possible exposure to the surround- 
ing air, are protected from the solar ray, first by 
their position on the under surface of the leaf ; and, 
secondly, by the dense and thick barrier formed by 
the stratum of cylindrical vesicles (fig. cxxui. 2). 

323. In the cvlindrical vesicles carbonic acid is 
decomposed ; in the reticulated vesicles, on the 
contrary, carbonic acid is re-formed. The oxygen 
reguired for this generation of carbonic acid is 

abstracted p&riiy from the suiroundm^ «aT \ \\v^ 



eONVERSION OF SAP INTO NUTUMENT. 9 

carbon is derived partly, perliaps, from the air, 
but chiefly from the digested sap, and the car- 
bonic acid, formed by the union of these elements, 
is evolved into the surrounding atmosphere. 

324. This operation, which is strictly analo* 
gous to that of respiration in the animal, in which 
carbonic acid is always generated and expired, is 
carried on chiefly in the night. In this manner, 
under the influence of the solar light, the leaf de- 
composes carbonic acid ; retains the carbon and 
returns the greater part of the oxygen to the air in 
a gaseous form. At night, in the ahsence of the 
solar ray, the leaf absorhs oxygen, combines this 
oxygen with the materials of the sap to produce 
carbonic acid, which, as soon as formed, is evolved 
into the surrounding air. The carbonic acid gas 
exhaled during the night is re-absorbed during 
the day and oxygen is evolved ; and this alternate 
action goes on without ceasing ; whence the plant 
deteriorates the air by night, by the abstraction of 
its oxygen and the exhalation of carbonic acid ; 
and purifies it by day by the evolution of oxygen 
and the abstraction of carbonic acid. 

325. The result of these chemical actions is the 
conversion of the crude sap into the proper nutri- 
tive juice of the plant. When it reaches the 
cylindrical vesicles, the sap is colourless, not co- 
agulablc, without globules, composed chiefly of 
water holding in solution carbonic aivd ^iC^Vvc, 
acids, sugar, gum, and several salts \ wYieTv\\.\^v3^^ 



10 THE PHILOSOPHY OF HEALTH. 

the reticulated vesicles it is a greenish fluid, partly 
coagulable and abounding yfith organic particles 
under the form of globules. Its chemical compo- 
sition is now wholly changed ; it consists of resin- 
ous matter, starch, gluten, and vegetable albumen. 
It is now thoroughly elaborated nutritive fluid; 
the proper food of the plant (cambium) ; rich in 
all the principles which are fitted to form vege- 
table secretions : it is to the plant what arterial 
blood is to the animal, and like the vital fluid 
formed in the lung, the cambium elaborated in 
the leaf, is transmitted to the different parts and 
organs of the plant to serve for their nutrition and 
development. 

326. The formation of this nutritive fluid by 
the plf.nt is a vital process, as necessary to the 
continuance of its existence, as the process of san- 
guification is necessary to the maintenance of the 
life of the animal. If the plant be deprived of its 
leaves, if the cold destroy, or the insect devour 
them, the nutrition of the plant is arrested ; the 
development of the flowers, the maturation of the 
fruit, the fecundation of the seeds, all are stopped 
at once, and the plant itself perishes. 

327. The proper nutritive juice of the plant, 
completed by the process of respiration, is formed 
by the elaboration of organic combinations of a 
higher nature than those afforded by the sap. 

Acid, sugar, gum (325) are converted into the 
. bigber organic compounds, TeBin, ^vxleu, ^XwOr.^ 



RSSPIRATION IN THB ANIMAL. 11 

albumen, probably by chemical processes, the re- 
sult of which is the inversion of the relative pro- 
portions of oxygen and carbon. In the organic 
matters contained in the sap, the proportion of 
oxygen, compared with that of carbon, is in ex- 
cess ; on the contrary, in the higher compounds 
contained in the cambium, the carbou preponde- 
rates : by the inversion of the relative proportions 
of these two elements, the organic compounds of 
a lower nature, appear to be changed into those of 
a higher ; to be brought into a chemical condition 
nearer to that of the proper substance of the plant ; 
a condition in which they receive the last degree 
of elaboration preparatory to their conversion into 
that substance. 

328. In the process of respiration in the ani- 
mal, as in the plant, parts of the digested aliment 
mix with the air ; parts of the air mix with the 
digested aliment ; and by this interchange of prin- 
ciples, the chemical composition of the aliment 
acquires the closest affinity to that of the animal 
body ; is rendered fit to combine with it ; fit to 
become a constituent part of it. 

329. The extent and complexity of the respira- 
tory apparatus in the animal, is in the direct ratio 
of the elevation of its structure and the activity of 
its function, to which the quantity of air consumed 
by it is always strictly proportionate. 

330. The proceaa of respiration in t\ie ^liVTsiii^. 
is ejected by two media, air and watei ', \>mXi ^>fc 



12 THE PHILOSOPHY OF HEALTH. 

only real agent is the air ; for the water contri- 
butes to the function only by the air contained ia 
it. Respiration by water is termed aquatic, that 
by the atmosphere, atmospheric or aerial respintf? 
tioQ. 

331 The quantity of air contained in water 
being small, aquatic is proportionally less ener- 
getic than aerial respiration; and, accordingly, 
the creatures placed at the bottom of the animal 
scale, having the simplest structure and the nar- 
rowest range of function, are all aquatic. 

332. Whatever the medium breathed, respira- 
tion in the animal is energetic in proportion to 
the extent of the respiratory surface exposed to 
the surrounding element. As the water-breathing 
animals successively rise in organization, their 
respiratory surface becomes more and more ex- 
tended, and a proportionally larger quantity of 
water is made to flow over it. It is the same in 
aerial respiration : the higher the animal, the 
greater the extent of its respiratory surface ; and 
the larger the bulk of air that acts upon it. 

333. Whatever the medium breathed, respira- 
tion is effected by the contact of fresh strata of 
the surrounding element with the respiratory sur- 
face. The mode in which this constant renewal 
of the strata is effected, is either by the motion of 
the body to and fro in the element; or by the 
creation of currents in it, which flow to the respi- 

ratorj surface, A main part of the «ti5>'\^%x^\.\i& oi 



BASIS OF THK RESPiUATORT APPARATUS. 13 

respiration consists of the expedients necessary to 
accomplish these two objects ; and that apparatus 
is simple, or complex, chiefly according to the ex 
tent of the mechanism requisite to eflect them. 

334. Whatever the mediimi breathed, the or- 
ganic tissue which constitutes the essential pan of 
the immediate organ of respiration is the skin. 
The primary tissue of which the skin is composed 
is the cellular (23 et seq.), which, organized into 
mucous membrane (33 et seq.), forms the essen- 
tial constituent of the skin (34). In all animals 
the skin covers both the external and the internal 
surfaces of the body (34). When forming the 
external envebp, this organ commonly retains the 
name of skin ; when forming the internal lining, 
it is generally called mucous membrane ; and in 
all animals, from the monad to man, either in the 
form of an external envelop, or an internal lining, 
or by both in conjunction, or by some localization 
and modification of both, the skin constitutes the 
immediate organ of respiration. In different 
classes of animals it is variously arranged, assumes 
various forms, and is placed in various situations, 
according to the medium breathed, and the facility 
of bringing its entire surface into contact with the 
surrounding element ; but in all, the organ and its 
office are the same : it is the modification only 
•—that modification being invariably and strictly 
9tdt^tatJon, which constitutes the wVvoVe ^Nex^Voj 
f/ihe Immediate organ of reBpiration. 



14 THE PHILOSOPHY OP HEALTH. 

335. At the commencement of the animal scale, 
in the countless tiibes of the polygastrica (vol. i. 
p. 34, et 8eq.)» respiration is effected through the 
delicate membrane which envelops the soft sub- 
stance of which their body is composed. The air 
contained in the water in which they live, pene- 
trating the porous external envelop, permeates 
every part of their body ; aSrates their nutritive 
juices; and converts them immediately into the 
very substance of their body. They are not yet 
covered with solid shells, nor with dense im- 
pervious-scales, nor with any hard material which 
would exclude the general respiratory influence of 
water, or render necessary any special expedient 
to bring their respiratory surface into contact with 
the element. 

336. But in some tribes even of these simple 
creatures there is visible by the microscope an 
afflux of their nutritive juices to the delicate pel- 
licle that envelops them, in the form of a vascular 
net-work, in which there appears to be a motion 
of fluids, probably the nutritive juices flowing in 
the only position of the body in which they could 
come into direct contact with the surrounding 
element. In some more highly advanced tribes, 
as in wheel animalcules, there is an obvious cir- 
culating system in vessels near the surface of the 
skin. In other tribes, the internal surface con- 
stitating the alimentary canal, is of g;reat extent 

and width, and forms numerous caN'\\.\e» ^Vv^ 



UODiriCATIOR IN TBI JUCMDtMO SCALK. 15 

are often dutended with water. In thia manner 
a portion of the intenial, aa welt aa the external 
Rurface is made cantributary to the function of 
respiration, and thia extended reapiration ia condu- 
cive to tlieir great and contioned activity, to 
their rapid development, and to the extraordinary 
futility of their races. 

331 . In creanirea somewhat higher in the acale, 
a portion of the external aurface is reflected in- 
wards in the form of a sac, with an external open- 
ing (lig. cxxv. I). In some meduue there are 

Hg. CXXV.— Jfr^H. 




1. The mouth; 11. Iheitomaeh; 3. Urge caaali going 
froin th« (tomach ; 4. imallai canala which fuim, !>. 
■ [ileiuD of reufli at Iha margin of th« diac Mrring 'oi 
reipiratioD ; 6. HtugiD of Ihe due. 
nnroeroat eae» of this kind, which ip4»% TO."«mfe 
antil they are separated only l)y dnu w^Va-^on^ 



IG THE PHILOSOPHY OF HEALTH. 

the cavities of the stomach. The water permeat-' 
ing and filling these sacs comes into contact witb 
an interior portion of the body, not to be reached 
through the external surface. At the margin of 
the disk (fig. cxxv. 6) there is spread out a deh- 
cate net- work of vessels (fig. cxxv. 5) ; these ves- 
sels communicate with small canals (fig. cxxv. 4) 
which open into larger canals (fig. cxxv. 3) that 
proceed directly from the stomach (fig. cxxv. 2). 
As the aliment is prepared by the stomach, it is 
transmitted thence by these communicating canals 
to the exterior net-work of vessels where it is 
aerated. 

338. As organization advances, as the compo- 
nent tissues of the body become more dense, and 
are moulded into more complex structures, when, 
moreover, these structures are placed deep in the 
interior of the body, far from the external envelop, 
and proportionally distant from the surrounding 
element, the respiratory apparatus necessarily in- 
creases in complexity. The first complication 
consists in the formation of minute, delicate, trans- 
parent tubes (fig. cxxvi. 5), which communicate 
with the external surfieice by a special organ (fig. 
cxxvi. 4) that conveys water into the interior of 
the body (fig. cxxvi. 5). By means of these ra- 
mifying water-tubes, upon the delicate walls of 
which the blood-vessels are spread out in minute 
and beautiful capillaries, the water is brought into 
immediate contact with the va&c>]t\aT «^«Xft.\s\. 



PftOaKBWITB OHfPLlOAViaN. 
Fig. CXXVI— 0eAifj(>irw. 




1. Houth; 2. lalivar^ taut; 3. mtealioa; 4. cloaca: 
!>' lamified tub«i, eoufeyug wmtai Im nipiiBtion ia(o th< 
bterloT of th« bodf. 

339. Next, in tbe ascending scale, the esternat 
envelop of the body is extended into a distinct 
additional or supplemental oi^an, by which the 
(imction of the skin is assieted. This additional 
organ is called branchia or gill. The simplest 
fomi of branchia caneists of folds or duplicaturea 
of skin, forming ramified tufta {fig. cxsvii. 1), 
which in general have a regular and often a Ejm- 
nietrical disposition on the estenia\ uutiace i,^%. 
cxxrii. t). Sometimes, as in the Tiat«T \K«aSB- 



Kit. <^»IVI,_i...,^^,„,^ 




PROGRESSIVE COMPLICATION* 19 

I. Respiratory tufts. 2. Artery and Tein, supplying the 
respiratory apparatus. 3. Dorsal Tessel. 

ing annelides, tliese tufts form a fan-like expan- 
sion around tlie head ; but at other times they 
are disposed in regular series along the whole 
extent of the body. 

340. Instead of branchise in the form of rami- 
fied tufts, the ascending series of animals, namely, 
the higher Crustacea, possess branchiae composed 
of numerous, delicate, thin laminae or leaves, 
divided from each other, yet placed in close prox- 
imity, like the teeth of a fine comb, whence this 
arrangement is termed pectinated. Over the 
blood-vessels of the system spread out on these 
delicate, fringed, pectinated leaves, the water is 
driven in constant streams. 

341. Still higher in the scale, as in molluscous 
animals, an internal sac is formed to which are 
sometimes attached numerous tufts ; but which 
at other times is itself plaited into beautifully dis- 
posed regular folds, crowded with blood-vessels 
and constantly bathed with fresh currents of 
water. 

342. In all these water-breathing creatures, 
respiration is effected, either by the progressive 
motion of the body through the water, or by the 
creation of currents which bring fresh strata of 
the fluid into contact with the respiratory sur- 

faces. Both objects are effected \)^ Ocv^ ^^\sv^.\xk- 



20 THE PHILOSOPBT OF HBALTB. 

struments, namely, mioute fibres having the ap- 
pearance of fine haiTB or bristles. These fibret 
which are called dtia, have in general an elon- 
gated, flattened, thin, and tapering furm (fig. 
cxxviii). Their number, position, and arrange- 
ment, are infinitely various. Sometimes, as in the 
poriferous animals, they are so minute that they 
cannot he rendered visible to the eye even by the 
microscope, although the evidence of their exist- 
ence and action is indubitable. Sometimes they 
Fig. CXXVIIL 




8ie of great size and strength, attached by distinct 
ligaments to the body and moved by powerful 
muscles, as in wheel animalcules. Sometimes, 
as in polypiferouB animals, they are disposed 
around the orifice of die polypes or upon the sides 
of the tentacula, the instruments by which the 
animal seizes its prey. Sometimes they are sym- 
metricaBy dhpOB^ in loDgituc\inBlseii<*tin\i.ft\\* 



CILTA. 21 

8ur£BM% of the body, as in the Beroe pileus ; at 
other times they are arranged in circles ; whenever 
there are branchue, they are disposed around the 
margin of the branchial apertures, and always 
OD the margins of the minute meshes which com- 
pose the branchiae themselves. 

343. In some cases the number of these cilia is 
immense. Each polype, for example, has usually 
twenty-two tentacula, and there are about fifty 
cilia on each side of a tentaculum, making two 
thousand two hundred cilia on each polype. As 
there are about one thousand eight hundred cells 
in each square inch of surface, and the branches 
of an ordinary specimen present about ten square 
inches of surface, we may estimate that an ordi-* 
nary specimen of this zoophite presents more 
than eighteen thousand polypes, three hundred 
and ninety-six thousand tentacula, and thirty- 
nine million six hundred thousand cilia. But 
other species contain more than ten times these 
numbers. Dr. Grant has calculated that there 
are about four hundred million cilia on a single 
Flustra foliacea. 

344. The motions of these cilia are regular, 
incessant, and when in full activity far too rapid 
to be distinguished by the eye even when assisted 
by the microscope. They are generally to be per- 
ceived only when their motions are comparatively 
feeble. They produce two effects. Iw ^mm^"^ 

capable of progressive motion, U\e^ Uam^oiX. \)cv<i 



22 THE PHILOSOPHY OF HEALTH. 

body through the water, while they constantly 
bring new strata of water into contact with the 
respiratory surface. In this case they are partly 
organs of locomotion, and partly organs subser- 
vient to respiration. On the other hand, in animsli 
which are not capable of moving from place to 
place, they create currents by which the respira- 
tory surface is constantly bathed with fresh 
streams of water. These currents are regular, 
constant, unceasing. Like some physical pheno- 
mena not depending on vitality, it is a continued 
stream as regular as the motions of rivers from 
their source to the ocean, or any other move- 
ments depending on the established order of 
things. Dr. Grant, to whom we are indebted for 
our knowledge of the true nature of these cur- 
rents, as well as of the instruments by which 
they are efifected, gives the following account of the 
observation which led to the discovery : — " I put," 
says he, ** a small branch of the spongia coalita, 
with some sea water into a watch-glass, under the 
microscope, and on reflecting the light of a candle 
through the fluid, I soon perceived that there was 
some intestine motion in the opaque particles float- 
ing through the water. On moving the watch- 
glass, so as to bring one of the apertures on the side 
of the sponge fully into view, I beheld, for the first 
time, the splendid spectacle of this living foun- 
taJn, vomiting forth from a cixculax c«^v\t^ an im- 
petuous torrent of liquid mallet, «a\^ \ixii^\a% 



ACTION OF CIUA. 23 

along in rapid succession opaque masses "^hich it 
strewed everywhere around. The beauty and 
novelty of such a scene in the animal kingdom 
long arrested my attention, but after twenty-five 
minutes of constant observation, I was obliged to 
withdraw my eye from fatigue, without having 
seen the torrent for one instant change its direc- 
tion, or diminish in the slightest degree the 
rapidity of its course. I continued to watch the 
same orifice, at short intervals, for five hours, 
sometimes observing it for a quarter of an hour at 
a time, hut still the stream rolled on with a con- 
stant and equal velocity." 

345. The simple expedients which have been 
described suffice for carrying on the function of 
respiration in the water-breathing invertebrata ; 
but in creatures that possess a vertebral column, 
and the more perfect skeleton of which it forms a 
part, there is a prodigious advancement in the 
organization of the whole body, of the nervous 
and muscular systems especially, the organs of 
the animal, as well as in all the organs of the 
organic life. A corresponding development of 
the function of respiration is indispensable. Ac- 
cordingly, a sudden and great development in the 
apparatus of this function is strikingly apparent 
in fishes, the lowest order of the vertebrata, in 
which the branchiae, though still preserving the 
Bame form as in the animals below t\ieni^«LX^\%x\y^ 
^mad complex organs. The brancln» oi fea\ifc^ *XS\ 



coniist of fringed folds of memtvane diaposed, u 
in the preceding closBei, ia lamiiuG or leaves (if- 
CJXiz. 5) ; but there are now commonly four tean 
of these leaves, on each side of the body, placed 
in close appiojdmation to each other, the scTeial 

Fig. CSXIX. — Diagram ijf lite JpparaluM af ih, Circf 
taliam and Beipiralim in lit Fiik. 




1. Auricle (Sinrie) cf the heart. 2. VentikU (liuglc) of 
the heart. 3. Trunk of the btanchial artery. 4. Diii- 
tion of the biBnchial arlery (;oiiig to the branchin or triUi. 
5. IxaTOi of the braDchia. 6. Brucbial veina, which 
leturalbe blood from tlie biaachin, and unite to form. 7. 
theMoiii, by the divisioo of vhidi Aw MtiaA«& \il.A& n 
€»raed oat to the tnrtem. 



BRANCHIiE. 25 

leaves being divided into minute fibres, which are 
set close like the barbs of a feather, or the teeth 
of a fine comb (fig. cxxix. 5). Each leaf rests 
either on a cartilaginous or a bony arch, which 
exactly resembles the rib of the more perfect ske- 
leton, and performs a strictly analogous function ; 
for these arches are capable of alternately sepa- 
rating from, and of approximating to, each other, 
and these alternate motions are effected by appro- 
priate muscles. As these movements of separar 
tion or approximation take place, the branchiae 
are either opened or closed, and their surface pro- 
portionally expanded or contracted. Upon these 
leaves (fig. cxxix. 5) the veins (347) of the system 
(fig. CXXIX. 4) are spread out in a state of capil- 
lary division of extreme minuteness, forming a 
net-work of vessels of extreme tenuity and deli- 
cacy. So prodigiously is the surface increased for 
the expansion of these vessels by the leaf-like dis- 
])osition of the branchiae, that it is computed that 
the branchial surface of the skate is at least equal 
to the surface of the whole human body. 

346. Through this extended surface the whole 
blood of the system must circulate, and every 
point of it must be unceasingly bathed with fresh 
streams of water. To generate the force neces- 
sary for the accomplishment of these objects, an 
increase of power must be communicated both to 
the circulating and to the respiratory appai^Xw^. 

Neither the contractile power of the \efesA* \i^ 
VOL, jj. ^ 



26 THE PHILOSOPHY OF HBALTU. 

which in some of the simpler animals the nutri- 
tive fluid is put in motion, nor the contraction of 
the rudimentary heart by which in creatures some- 
what higher in the scale a more decided impulse 
is given to the blood, are sufficient. A muscular 
heart, capable of acting with great power, is now 
constructed, which is placed in such a position as 
to enable it to propel with velocity the whole blood 
of the body through the myriads of capillary ves- 
sels that crowd every point of the surface of the 
branchial leaflets. To bring the watei with 
the requisite degree of force into contact with 
this flowing stream, the apparatus of cilia is 
wholly inadequate. The water entering by the 
mouth, is driven with force, by the powerful mus- 
cles of the thorax, through apertures that lead to 
the branchial cavities. At the instant that the 
branchial leaves receive the currents of water 
through the appropriate apertures, the cartilagi- 
nous or bony arches which sustain the leaves, 
separate to some distance from each other, and to 
that extent expand the leaves and proportionally 
increase the surface exposed to the water : at the 
same time, the rush of water through the leaves 
unfolds and separates each of the thousand mi- 
nute filaments of which they are composed, so 
that they all receive the full action of the fluid as 
it flows over them. 

34*7. After the venous blood of the system has 
been thus exposed to the action oi lYve T^^vc^xarj 



AUXILIARY ORGANS OP RBSPIRATION. 27 

ruedium, it is taken up by the vessels called the 
branchial veins (6g. cxxix. 6), which for the 
reason assigned (372) are functionally arteries, 
as the branchial artery (fig. cxxix. 4) is func- 
tionally a vein. The branchial veins uniting toge- 
ther form the great arterial trunk of the system, 
(fig. CXXIX. 7) by which the aerated blood is car- 
ried out to every part of the body. 

348. But as if even this extent of apparatus 
were insufficient to afford the amount of respira- 
tion required by the system of the fish, the entire 
surface of its body, which in general is naked and 
highly vascular, respires like the branchiae. More- 
over, many fishes swallow large draughts of air, 
by which they aerate the mucous surface of their 
alimentary canal, which also is highly vascular ; 
and still further, numerous tribes of these animals 
are provided with a distinct additional organ, a 
bag placed along the middle of the back filled 
with air. Commonly this air bag communicates 
with some part of the alimentary canal near the 
stomach, by means of a short wide canal termed 
the ductus pneumaticus, but sometimes it forms a 
simple shut sac without any manifest opening; 
at other times it is divided and subdivided in a 
perfectly regular manner, forming extended rami- 
fied tubes ; while at other times its ramifications 
present the appearance of so many pulmonary 
cells. It is the rudiment of the compVex.\\rci^ Qfc\. 
tAe higher vertebrata, and it assiftta Te%^*vcvv.\!\oxv \ 

c '2 



28 T0e 

although since in some tribes it contains uot atmo- 
spheric air but azote, it is without doubt eubBerrieiil 
to other uses in the economy of the animal. 

349. In water-breathing animals, from the low- 
est to the highest, it is then manifest that a gpeui] 
apparatus is provided for, couBtantly renewingtbc 
stieams of water that are brought into conlwl 
with their respiratory surface. 

350. It is the same in aerial respiration. In 
the aimplest form of aerial respiration the app*- 
ralUB consists of minute bags or eacs, placed com- 
monly in pairs along the back, which open fo 
the admisaion of the air on the external surface, 
by small orifices called epiracula or spiracle* 

rig.CXXX.-7Vnr*M. 



tba aJimeaUiy esa aJ 



lag in form of Tsdufram ths Kfiiacles ro 4. 



TRACHEiB. 29 

^fig. cxxz. 2), at the sides of the body. In the 
»mmon earth-worm there are no less than one 
lundred and twenty of these minute air vesicles, 
:ach of which is provided with an external open- 
ng placed between the segments of the body. In 
he leech, the number is reduced to sixteen on 
tach side, which open externally by the same 
lumber of minute orifices. Over the internal 
urface of these air vesicles the blood of the 
ystem is distributed in minute and delicate ca- 
)illaries; and is capable of being aSrated by 
whichever medium may pass through the external 
orifices, whether water or air. 

351. In this simple apparatus is apparent the 
udiment of the more perfect atirial respiration by 
he organs termed tracheae, minute air tubes which 
amify like blood-vessels through the body (fig. 
;xxx. 3). These air tubes open on the external 
urface by distinct apertures termed spiracula 
ir spiracles (fig. exxx. 2), which are commonh 
)laced in rows on each side of the body (fig. exxx. 
I), with distinct prominent edges (fig. exxx. 2), 
ften surrounded with hairs; sometimes guarded 
>y valves to prevent the entrance of extraneous 
todies, and capable of being opened and closed by 
auscles specially provided for that purpose. These 
ubes, as they proceed from the spiracles to be dis- 
ributed to the diflFerent organs of the body, often 
iresent the appearance of radii (ftg. cxml. 'X^^ 
id when traced to their terminations w^ tewxA 



30 THE PHILOSOPHY OF HEALTH. 

to end in vesicles of various sizes and dgures, but 
commonly of an elongated and oblong form. These 
minute vesicles, when examined by the microscope, 
are seen to afford still minuter ramifications, which 
are ultimately lost in the tissues of the body. 

352. The tracheae are composed of three tu- 
nics, the external dense, white and shining ; the 
internal soft and mucous, lietween which is placed 
a middle tunic, dense, firm, elastic, and coiled into 
a spiral. By this arrangement the tube is con- 
stantly kept in a state of expansion, and is there- 
fore always open to the access of air. A great 
part of the blood of the body, in the extensive 
class of creatures provided with this form of re- 
spiratory apparatus, including the almost count- 
less tribes of insects, is not contained in distinct 
vessels, but is diffused by transudation through the 
several organs and tissues of the body. All the 
creatures of this class live in air, and possess great 
activity ; they therefore require a high degree of 
respiration ; yet they are commonly small in size, 
and often some portions of their body consist of 
exceedingly dense and firm textures; hence to 
have localized the function of respiration, by 
placing the seat of it in a single organ, would 
have been impossible, on account of the dispro- 
portionate magnitude which such an organ must 
have possessed ; in this case it was easier to carry 
the air to the blood, than the blood to the air, and 
accordingly tht air is carried lo l\vfe \i\oci^, ^xv^^ 



riiLMONic ucs. 31 

Fig. CXXXI.— JI(Vtra/«rjr Organ oflkt Setrfiim. 




I. Spiraclea. 2. iDttgument oT one half of tho body 
turneid back. 3. Branchuloigans. 4. Celli oi pouchm in 
vhieh they are lodged, a. One of Iba leipiratoij orgtui 

branchial leaflets, acd pteientmi; the peclinated appcac- 
ance deitribed in the iexX. 

like the blood in creaturea of higUei oi^a.miW.\ti\i, 
ia digued through every part of tVw K^«lem. 



32 TBE PHiLOSOPHT n 

353. The nest advancement in the aBceDdin; 
scale is, by a alep which obviously connects thi't 
higher class with the claeses below and above it. 
It consists of distinct cells, termed pulmonic can- 
ties (6g. cxxsi. 4), which communicate externDll; 
by spiracula (fig. csxzi. 1), like tracheae (351)i 
but which ere lined internaliy by a. soft and deli- 
cate membrane plaited into folds, disposed tilfc the 
teeth of n comb (pectinated) (fig, ckxki. a), pre- 
senting a striking analogy to the structure of gills 
(345), and therefore called by the French wrilere 
pneumo-branchiBS. These cavities have the inter- 
nal f(irm of an aquatic organ, but they perform 
the function of air -breathing sacs. In scorpions 
(fig. cxasi. 1) and spiders, this form of the appa- 
ratus is seen in its simplest condition ; in the 
slug and snail it is more highly developed : for iu 
these latter animals a rounded aperture, placed 

Fig, CXX\ll.—^pp-rel>H •/ R»pirali»n in Ikt Frog. 




1 . Trmehea. 2. Vesicu\i I Innp. a. 



TXSICULAK LUNCm. 33 

near the head, and guarded hy a sphincter moBcle, 
that alternately dilates and contracts, leads to a 
single cavity, which is lined with a membrane 
delicately folded, and overspread with a beautiful 
net-work of pulmonary blood-vessels. 

354. Passing from this to the lowest order of 
the air-breathing vertebrata (fig. cxxxii.), the 
apparatus is perfectly analogous, but more deve- 
loped. In the reptile, this air-breathing sac, 
which now constitutes a true and proper lung, 
instead of being simple and undivided, is formed 
by numerous septa, which traverse each other in 
all directions, into vesicles or cells (fig. cxxxii. 2), 
which proportionally enlarge the surface for the 
distribution of blood-vessels. In the Batrachian 
reptile, as the frog, salamander, newt, &c. (fig. 
CXXXII.) > the vesicles, comparatively few in num- 
ber, are of large size, and as thin and delicate 
as soap-bubbles. In the ophidian reptile, as the 
serpent, the sac is large and elongated, but divided 
only in the upper and back part into vesicles ; 
while in the Saurian reptiles, as the crocodile, 
lizard, chamelion, &c., the sac is comparatively 
small, but subdivided into very minute vesicles, 
bearing a close analogy to the more perfectly or- 
ganized lung of the higher animals. 

355. In birds, the next order of vertebrata (fig. 
cxxxiii.), as in insects, the class of invertebrated 
animals which are formed for flight (352)) the 
respiratory organs extend through the gTe».lei "^wtX. 



THE PHILOBOPBT OF B 




RBSPIRATORT APPARATUS IN TRB BIRD. 3& 

'• The Trachea. 2. The lunp;*. 3. Aperturw through 
^hich air passes into, 4. Air cells of the body. 5. A 
brittle passed from one of the air cells of the body, to 
Uie cayity contaiaing the lungs. 6. A bristle psMed 
from the cayity of the thigh>boae into another air cell of 
the body. 

of the body (fig. cxxxiii. 4). The lungB (fig. 
cxxxiii. 2), which still consist of a single pul- 
monic sac on each side (fig. cxxxiii. 2), are 
divided into cells^ minute compared with those of 
the reptile, yet large compared with those of the 
quadruped ; at the same time numerous air sacs, 
similar in structure to those of the lungs, but 
of larger size, are distributed over different parts of 
the body (fig. cxxxiii. 4) yWhich communicate with 
the air cells of the lungs Tfig* cxxxiii. 3) ; while 
of these larger sacs, several communicate also with 
the bones (fig. cxxxiii. 6), so as to fill with air 
those cavities which in othei animals are occupied 
with marrow. 

356. In the mammalia, the highest order of the 
vertebrata, respiration is less extended through the 
system, and is concentrated in a single organ, the 
lung, which, though comparatively smaller in bulk 
than in some of the lower classes, is far more de- 
veloped in structure. The lung in this class con- 
sists of a membranous bag, divided into an im- 
mense number of distinct vesicles or cells, in the 
closest possible proximity with each other, yet not 
communicatiagf and presenting, ftom \SaKVt tkv 
rjutencBB, a vast extent, of inteiuA ^vat^i:^, TKi% 



TBB PHILOSOPHY O 



bag is confined to a dietinct cavity of the trunk) 
the thorax (fig. csxxiv.), completely sepanted 
from the abdomen by the muscular partition, die 
diaphragm (fig. cxxzit. 10). This organ no 



rig. CXXXIV. 




I. He Ttacbes. 2. Th« ri)^t lung, 3, The left lung. 
4, Fiisncei, dividing each luag into, !i. Large poitioDi 
tenned lab«i. 6. Smaller diviskiuB teniiid fgbulei. 7. 
Pericardmni. 8. Heart. 9. Aoita. \(t. Ou^^m^ib h^&. 
rating the emvitjr •/ tha thorax train &at ol l^ tlbJUxmB. 



EBSPIItATORT APPARATUS IN If AN. 31 

;er Beods down cells into the abdomen, nor 
ibranous tubes into the bones ; but is con* 
rated within the thorax along with the heart 

czxxiv. 2, 3, 8). In all the orders of this 
, the development and concentration of the 
1 are in strict proportion to tlie perfection of 
general organization. 

»7. In man there are two pulmonary bags (fig. 
CIV. 2, 3), of nearly equal size, which, toge- 
with the hearty completely fill the large cavity 
le thorax (fig. cxxxrv.), their external sur- 
being everywhere in immediate contact with 
horacic walls. One of these bags is placed on 
ight side of the body, constituting the right 

(fig. cxxxiv. 2)9 and the other on the left, 
ituting the left lung (fig. cxxxiv. 3). Each 

is divided by deep fissures, into large por- 

called lobes (figs, cxxxiv. 4, and cxxxv. 
of which there are three belonging to the 
, and two to the left lung. Each lobe is 
ivided into innumerable smaller parts termed 
es (figs. CXXXIV. 6, and cxxxv. 6), while the 
es successively diminish in size until they 
inate in minute vesicles that constitute the 

bulk of the organ (fig. cxxxv. 8). 
8. The complete centralization of the respi- 
y function which thus takes place in man, 
;rs the apparatus exceedingly complex both 
;count of the expedients which axe li^ii.^'sww^ 
ain the requisite extent of svirfa^'b, Va \}cv<& 



38 THE PHtU>M>PHr OT HEALTH. 

imall allotted space, and to tmng into crodct 
within that epace the fluids that are to act on 
each other. 

359. The apparatuB conusts of avewel tocany 
the air to the blood; a vesael to carry the Wood 
to the air ; an organ in which the air and the 
blood meet ; end an organization by nhich both 
flnida are put in motion. The vestel that carria 
the air to the blood ia the windpipe (Gg. cxn*. 
Fig. CXXXV.-rTnpo/ f*c Air TVii imd iMg. 




I. The laiyni. i. Trachea. 3. Right bronchus. 4. 
Left brondiiii. i. Left lung ; the fitsurei denuled by tha 
(wo linei which meet st 6, diiidiag it into three lobsi, 
tnd the taalkl linei on it> auttate voailimv; tt« AiiU™. ot 
tie Jobea iato JobulM. 7. Luge \woiiehiB.\ to."oe», ^-^Kv- 
nute brooclml fubef terminabiig ic "- 



,o tha «i cbVUik i™^"*. 



TBB WIND-PIPE. 39 

I) 2) ; the vessel that carries the blood to the air 
u the pulmonary artery (6g. cxl. 1) ; the organ 
in which the blood and the air meet is the lung 
(Hg. cxxxv. 5) ; the organization which puts the 
air in motion, is the structure of bones, cartilage 
and muscles, called the thorax (figs. cxli. and 
cxLvi.)) Ai^d the engine that communicates motion 
to the blood is the right ventricle of the heart 
(fig. cxii. 5). 

360. The windpipe is a tube which extends 
from the mouth and nostrils to the lung (figs. 
CLiii. 1, 9, and cxxxv. 2, 5). It is attached to 
the back part of the tongue (fig. clii. 2, 9), 
and passes down the neck immediately before 
the esophagus, or the tube which leads to the 
stomach (fig. cliii. 9, 12). 

361. In the different parts of its course the 
windpipe is differently constructed, performs dif- 
ferent offices, and receives different names accord- 
ing to the diversity of its structure and function. 
The first division of it is called the larynx (fig. 
cxxxv. i.)> the second the trachea (fig. cxxxv. 
2), the third the bronchi (figs, cxxxv. 3, 4, 7, and 
cxxxv II.), and the fourth the air vesicles or cells 
(figs, cxxxv. 8, and cxxxviii. 2). 

362. The first portion of the windpipe called 
the larynx (figs, cxxxv. and cxxxvi.), constitutes 
the organ of the voice. It is situated at the upper 
and fore part of the neck (fig. cliii. 7, 9))\misi<^- 
diatelf under the bone to which the root oi \)ao 



tongue, called the oe hyoides C6gB. cliii. 6, tw 
cxxzvi. 1), is attached. The larynx forma 
very complex atructure, and is compoeed of 



I.Tb« 01 hfoides 

2. Thyroid urtilage. 

3. Cricoid MrltJage. 4. 
Arytenoid cartilogeii 
separated from each 
other. 5. Epiglottis. 
6. Opening of the 
glottii. 7. Termina- 
tion of tba cartilaKi- 
noui rings of ihg tra- 
chea. 8. The liga- 
mentoui portion of 



com luiface and fol- 
licle!, with the ante- 
rior porlion of the 
cartilaginoui ring! ap- 
pearing thioogli it. 




THB KPIGLOTTI8. 



variety of cartilages, muscles, ligaments, mem- 
branes, and mucous glands (fig. czxxvi. 2, 3, 4, 
5). At its upper part is a narrow opening of a 
triangular figure called the glottis (fig. cxxxvi. 
6), by which air is admitted to and from the lung. 
Immediately above this opening is placed the 
cartilage, which obtains its name from its situation, 
epiglcUis (fig. cxxxvi. 5), which is attached to 
the root of the tongue (fig. cliii. 6, 7), and which 
may be distinctly seen in the living body by press- 
ing down the tongue. 

363. The Epiglottis is highly elastic, and is an 
agent of no inconsiderable importance in respira- 
tion, d^lutition, and speaking. In respiration it 
breaks the current of air which rushes to the lungs 
through the mouth and nostrils, and prevents it 
Tom flowing to the delicate air cells with too great 
degree of force. During the action of deglu- 
tion the epiglottis is carried completely over the 
ottis (fig. CLiii. 6, 7, 8), partly because it is 
^cessarily forced backwards, when tlie tongue 
sses backwards in delivering the food to the 
arynx (fig. cliii. 6, 7, 8, 10), partly because it is 
ried backwards by certain minute muscles which 
directly upon it, and perhaps also partly in 
sequence of its own peculiar irritability. The 
lent the action of deglutition has been per- 
ed the epiglottis springs from the aperture of 
;lottis, puTtly by its own elasticil^, «iTv(i y^xJc^ 
e return of the tongue to its foTxaex -^o^vNJvoxv. 



42 



THE PHILOSOPHY OF HEALTH. 



During the act of speaking the column of air which 
is expelled from the lung, which rushes through 
the glottis, and which thus forms the voice, strikes 
against the epiglottis, and the voice hecomes there- 
by in some degree modified. 

364. The second portion ofthe windpipe termed 
the trachea (fig. cxxxv. 2), commences at the 
under part of the larjnx (fig. cxxxv. 1), and ex- 
tends as far as the third dorsal verte]bra, opposite 

Fig. CXXXVII. 



Vi«w of the trachea, showin^if, first, the division of the 

tube into the right and left bronchus, and the subdivision 

of the bronchi into the bronchiol tubes ; and secondly, the 

m^/nZ^raoous and cart ilnginouB tUsue« ot nvYAc^ vYtA ^x^«a 

IS composed. 



THE TRACHKA. 43 

to which it divides into two branches which 
are termed the hronchi (fig. cxxrzy. 3, 4, and 
czxxvii.). One of these branches, called the 
right bronchus, goes to the right lung ; the other 
branch, called the left bronchus, goes to the left 
lung (fig. cxxxv. 3, 4). 

365. The trachea of man, like the tracheie of the 
air-breathing insect (351), is composed of three 
tissues. These tissues differ essentially from each 
other in nature, and are widely different in form 
and arrangement. They consist of membrane, 
muscle, and cartilage. 

366. The membranous portion of the human 
trachea consists of three coats, the cellular (fig. 
cxxxvii.). the ligamentous (fig. cxxxvi. 8), and 
the mucous (fig. cxxxvi. 9). From the cellular 
and ligamentous coats the tube receives its 
strength, and in some degree its elasticity ; and 
the mucous coat constitutes the chief seat of the 
respiratory function. Between the ligamentous 
and mucous coats are placed two sets of mus- 
cular fibres ; the first, the external set, passes in a 
circular direction around the tube ; the second set, 
placed immediately beneath the circular, is dis- 
posed longitudinally, and collected into bundles. 
The office of the circular fibres is to diminish the 
calibre of the tube, and that of the longitudinal 
is to diminish its length. 

367. As the tracheae of the insecl w^ Ve\»\. ^^xw- 
Btantly open for the free admiawon oi ive \yj '^\^ 



44 THE PHILOSOPHY OF HEALTH. 

middle membranous tunic, dense, firm, elastic, and 
coiled into a spiral (351), so, for the accomplish- 
ment of the same purpose, there are placed be- 
tween the membranous coats of the human trachea 
delicate rings of the more highly organized sub- 
stance, cartilage (35). These cartilaginous rings 
amount in the entire course of the tube to sixteen 
or eighteen in number (fig. cxxxv. 2) ; each ca^ 
tilage being about a line in breadth, and the fourth 
of a line in thickness. They never form complete 
circles, but only a large segment of a circle (fig. 
cxxxvi. 7); the circle is incomplete behind (fig. 
cxxxvi. 7, 9), because there the esophagus is in 
direct contact with the trachea (fig. cliii. 9, 12), 
and instead of dense and firm cartilage, a soft and 
yielding substance is placed in this situation, in 
order that there may be no impediment to the free 
dilatation of the esophagus during the passage of 
the food. 

368. The point at which the bronchi enter the 
substance of the lung is called the root of the lung 
(fig. cxxxv. 3, 4). As soon as the bronchi begin 
to divide and ramify within the lung each carti- 
lage, instead of preserving its crescent shape, is 
divided into two or three separate pieces, which 
nevertheless are still so disposed as to keep the 
tube open. With the progressive diminution in 
the size of the bronchial branches, their cartilages 
become less numerous, and are placed at greater 
{//sconces from each other, unl\\ «i\. \eTvw>;)cv ^^\5wi 



THE AIR VESICLES 45 

bronchi terminate in the vesicles, th% cartilages 
wholly disappear ; and with the decreasing num- 
ber and size of the cartilages, the thickness of the 
cellular, ligamentous, and muscular coats of the 
bronchi also lessens, until at the points where the 
cartilages disappear, the muscular and mucous 
tunics, now reduced to a state of extreme tenuity, 
alone remain. The essential constituent of the 
air vesicles, then, is the mucous membrane ; but 
there is reason to suppose that the muscular 
tunic is likewise continued over these vesicles. 

369. It has been stated that the tracheae of the 
insect terminate in the different tissues of its body 
by minute vesicles of an oblong form. The termi- 
nation of the bronchi in the human lung presents 
a strikingly analogous appearance. Malpighi, who 
with extraordinary talent and success devoted his 
life to the investigation of the minute structures of 
the various organs of the human body, represents 
the mucous membrane of the bronchial tubes as 
terminating in minute vesicles of unequal size : and 
Reisseissen, who has more recently resumed the 
inquiry and examined this structure with extreme 
care, agrees with Malpighi in stating that the 
bronchial tubes at their terminal points expand 
into minute, delicate, membranous vesicles of a 
cylindrical and somewhat rounded figure (fig. 
cxxxviii. 2). The bronchial tubes do not divide 
to any great degree of minutenefis (ti.%. C!LX5LN\w, 
Oj hut terminate Bomewhat abrupl\^ \u\)cv^N^ivSv«i» 



46 THK PBiix)3oraT or health. 



<6g. cxxx«tii.2), which though minute are large 
enough to be TiBible to the naked eye (fig. 
cxzsvtii. 2). Viewed in connexion with the 
bronchial tubes at their terminiiil points, the ve- 
sicles present a cluetered appearance, not onlike 
clufitera of currantE attached to theii stem (fig* 
czxxviit. 2). 



FiR. CXXXVIII, 




370. In the inseet, for the reason ass^ned 
(351 ), these vesicles are diffused over the system, 
afirating every point of the body'; in mao they are 
concentrated in the lung i yet by their minuteness, 
and by the mode in which they are arranged, they 
present in the small apace occupied by this wgan, 
BO estended a surface that Hales, representiug the 
size of each vesicle at the lOOdtb part of an inch 
in diameter, estimates the amount of surface fur> 
aiMbed by tbetn collectively at ^,W)0 w^an 



thb air tksiclh. 
Fir. CXL. 




]. The inchwt. 2. Tbe nght and lenbroncbui ; the l«n 
bronchiu khowing iti diviaion into imullei and tmaller 
brauchei in the lung, and Ihe ullimate tmniDatiun ut the 
bfaneheH iD Uw air Vraiclea. 3. RiKbt aiiriele of the hestt. 

4. liefl auricle, b. Right lentricle. 6. The aorta arising from 
tbe left TeDtricle, the lefl vr-ntrclu being in thii diagram 
caneealed by the right 7. Pulmoaary artery ari)ing from 
the righi vintri.'lr and dividing into, B. The right, and 
9. The left branch. The latter in tfta dividing into aniBner 
and amaller brandiei, and ultimatBly terminating ou the 
ail Teiiclea. 10. Branchis of one uf the pulmonary voini 
proceeding from the tetrainatiuna of the ijulmonaiy artery 
on the air nesielea, where together they farm the net-work 
of mneU leimed the Ret^ Mirabile. U. Trunk. o( itw 
vein on its way to the left auricla ol fte \mrt- Yi- 
Superior nuu ea™. 13. Jnferjar vena cava, \4, X« Nsiifiie* 
mrgaiSed. 15. .Biood-vesaelB dUtributed u^u Xtven^- 



48 THE PHILOSOPHY OF HEALTH. 

inches. Keil estimating the number of the ve* 
sides at 174,000,000, calculates the surface they 
present, at 21,906 square inches. Leiberkuhn at 
150 cubic feet; and, according to Monro, it is 
thirty times the surface of the human body. 

371. Such is the structure of the vessel that 
carries the air to the blood, and such is the mode 
of its distribution. 

The vessel that conveys the blood to the air 
is the pulmonary artery, the great vessel which 
springs from the right ventricle of the heart (fig. 
CXL. 5). 

The pulmonary artery soon after it issues 
from the right ventricle of the heart divides into 
two branches (fig. cxl. 7, 8, 9), one for each 
lung (fig. CXL. 8, 9). Each branch of the pul- 
monary artery as soon as it enters its corre- 
sponding lung (fig. CXL. 9) divides and ramifies 
through the organ in a manner precisely simi- 
lar to the bronchial tubes. Every branch of the 
artery is in contact with a corresponding branch 
of the bronchus (fig. cxl. 2), divides as it divides, 
and accurately tracks its course throughout (fig. 
CXL. 2), until the ultimate divisions of the artery 
at length reach the ultimate vesicles of the bron- 
chus (fig. CXL. 2, 10), upon the dehcate walls of 
which the capillary arteries rest, expand, and 
ramify, forming a net- work of vessels, so complex 
that the anatomist who first observed it, named it 
the Rete Mirahile^ the woivdeiixxV T\e.\.-^atVL^ ^\i<Sk 



THB RBTE MIRABILB 49 

it is still called the Rete Mirahile Malpighi^ or 
the Reie Vasc%Uo9um MalpigM (fig. cxl. 2, 9, 
10). 

372. The blood which has finished its circula- 
tion through the system, returned by the great 
systemic veins (fig. cxl. 12, 13), to the right side 
of the heart (fig. cxl. 3), is driven by the right 
ventricle (fig. cxl. 5), into the pulmonary artery 
(fig. CXL. 1); by the branches of which (fig. 
CXL. 8, 9) it is distributed to the air vesicles 
of the lungs : consequently the right heart of 
man bears precisely the same relation to the 
lungs, that the single heart of the fish bears to the 
branchiae ; the former is a pulmonic, as the latter 
is a branchial heart ; one half of the double heart 
of the more highly organized creature is employed 
to circulate the venous blood of the system 
through the lungs, as the whole of the single heart 
of the less highly organized animal, is employed to 
propel the blood through the branchiae (368). 
From the capillary branches of the pulmonary 
artery in the Rete Mirabile (fig. cxl. 9), arises 
another set of vessels termed the pulmonary veins 
(fig. cxl. 10), which receive the blood from the 
venous vessels spread out on the air vesicles : for 
the pulmonary artery is functionally a vein, since 
it contains venous blood, though it is nominally an 
artery because it carries blood from the heart (269); 
and in like manner the pulmonai-y veins aie fvsAv^i' 

VOL. !!• Tk 



50 THE PHILOSOPHY OF HEALTH. 

tionally arteries since they contain arterial blood, 
though they are nominally veins because they 
carry blood to the heart (212). The branches of 
the pulmonary arteries are larger in size and 
greater in number than those of the pulmonary 
veins, the reverse of what is observed in any other 
part of the body ; because the pulmonary artery 
contains the blood which is to be acted upon by 
the air, while the pulmonary veins merely receive 
the blood which has been acted upon by the air, 
and the former ramifies more minutely than the 
latter, in order that the air may act on a larger 
surface of blood. 

37^. In the Rete Mirabile the junction of the 
air-vessel with the blood-vessel is accomplished. 
The combination of these two sets of vessels con- 
stitutes the lung ; for the lung is composed of air- 
vessels and blood-vessels united, and sustained by 
cellular tissue, and inclosed in the thin but firm 
membrane called the pleura (104 and 105). 

3l4. Such is the arrangement of that part of 
the respiratory apparatus which contains the fluids 
that are to act on each other. The object of the 
remaining portion of it is to produce the move- 
ments which are necessary to bring the fluids into 
contact. This is accomplished by the mechanism 
and action of the thorax and diaphragm (figs, cxli- 
and cxxxiv. 10). 
875. These organs, which mvan^fclY «ict in con- 



MOTiOMS or KSSPIRATIOlf. 51 

cert, are so conttructed and disposed, that when in 
action they give to the chest two alternate motions, 
one that by which its capacity is enlarged ; and 
the other that by which it is diminished. These 
alternate movements are called the motions of 
respiration. The motion by which the capacity 
of the chest is enlarged is termed the action of 
inspiration, and that by which it is diminished the 
action of expiration. 

376. The action of inspiration, or that by which 
the capacity of the chest is enlarged, is effected 
by the combined movements of the thorax and 
diaphragm ; by the ascent of the thorax and by the 
descent of the diaphri^m. 

377. The osseous portion of the thorax, which 
has been fully described (69 et seq.)^ consists of 
the spinal column (fig. czu. 1), the ribs with their 
cartilages (fig. cxli. 2, 8), and the sternum (fig. 
CXLT. 4). The soft portion of the thorax consists of 
muscles and membrane (figs, cxlii., cxlvi., and 
cxjLvii.), together with the common integuments of^ 
the body. The chief boundaries of the cavity of the 
thorax before, behind, and at the sides, are osseous, 
being formed before by the sternum and the car- 
tUages of the ribs (fig. cxli. 4, 3) ; behind by the 
spinal column and the necks of the ribs (fig. cxli. 
1,2); and at the sides by the bodies of the ribs. 
Below the boundary is muscular, being formed b^ 
the diaphragm (Bg, cxliii. 3). 



52 THE PHILOSOPHY OF H£ALTH. 

378. Externally the thorax is convex and en- 
veloped by muscle and skin ; internally it is con- 
cave (fig. cxLiii. 1), and lined by a continuation 
of the same membrane which envelops the lungs, 
the pleura (104). But that portion of the pleura 
which lines the internal wall of the thorax is called 
the costal pleura (pleura costalis), in contradistinC' 
tion to that which envelopes the iungs, which is 
termed the pulmonary pleura, or pleura pulmo- 
nalis (104). By the costal pleura, a thin but 
firm and strong membrane, smooth, polished, and 
like all the membranes of its class (serous mem- 
brane 30, et seq.)y kept in a state of perpetual 
moisture and suppleness, by a fluid secreted at its 
surface, the movements of the thorax are facili- 
tated, at the same time that they are prevented 
from injuring the delicate organs contained in it. 

379. The moveable parts of the osseous portion 
of the thorax are the ribs and sternum. The ribs, 
though by one extremity tied with exceeding firm- 
ness to the spinal column by ligaments specially 
constructed, and admirably adapted for that pur- 
pose (%s. Lvi. I, and lyii. 1), and though at- 
tached at their other extremity by their cartilages 
to the sternum (fig. lviii.), are capable of three 
motions, an upward, an outward, and a downward 
motion. 

380. The ribs form a series of moveable arches, 
lAe convexity of the archea bein^ OMl^SLtds^ and 



CXLL — fttw tf lilt 



friit* rf th* 'lUram. 




column. S. Rilii. 3. Ctrtitagei of rlb>. 4. 



1 being diepoaed in an oblique direction 
2). Tie first rib springs fiom ft» ^«i- 



54 THE PHILOSOPHY OF HEALTH. 

tebral column at nearly a right angle (fig. cxli. 
2) ; the acuteness of this angle increases in suc- 
cession as the ribs descend from the first to the 
last (fig. cxLi. 2) ; in this manner each rib is 
inclined obliquely outwards and downwards, and 
the obliquity thus given to the general direction of 
the ribs augments progressively from above down- 
wards (fig. CXLI. 2). 

381. In consequence of this conformation and 
arrangement of the ribs, every degree of motion 
which is communicated to them, necessarily in- 
fluences the capacity of the space ihey enclose. 
If they are moved upwards they must enlarge that 
space at the sides, because the intervals between 
each other will be increased (fig. cxli. 2) ; 
and from behind forwards, because the distance 
between the spinal column and the sternum (the 
sternum being protruded forwards with their carti- 
laginous extremities) (fig. cxli. 3, 4), will be in- 
creased. If, on the other hand, they are moved 
downwards, the capacity of the thorax will be pro- 
portionally diminished in every direction (fig. 

CXLI.)* 

382, One part of the action of inspiration con- 
sists, then, of this ascent of the ribs. The as- 
cent of the ribs is effected by the contraction of a 
double layer of muscles called the intercostal (fig. 
cxLii.), placed in succession between each rib ; 

and which communicate thia motvoti in the ibl- 



INTBRCOBTAL MUSCLES. 55 

lowing mode. The first rib is fixed; the secoDiI 
rib is moTeable, but Icm moveable than the third, 
the third than tfae fourth, and so on through tbe 
series : consequently the contrBCtion of the inter- 
costal muscles (figs, cxlii. and cxlvi. 2) must 

Fig. CXLIL 




View of ih.* inlereintal muadet wliich fill up Ihe inlenpacei 
WweaD the lilM. Theae muiclts coniiiat of e double 
Uyct uf Bbrei, the exterosl and Ihe internal, nhUlv CRm 
or intUMct «sei other. 



56 THE PHILOSOPHY OF HEALTH. 

elevate the whole series, because the upper ribs 
afford fixed points for the action of the muscles; 
and so, when all these muscles contract together, 
they necessarily pull the more moveable arches 
upwards towards the more fixed (figs. cxm. and 

CXLVI. 2). 

383. But from the oblique direction of the ribs, 
they cannot ascend without at the same time pro- 
truding forwards their anterior extremities (fig. 
cxLi.). Those extremities being attached to the 
sternum, which forms the anterior wall of the 
thorax, they cannot be protruded forwards without 
at the same time carrying the sternum forwards 
with them (fig. cxli.). Thus, by this two-fold 
motion of the ribs, an upward and consequently 
an outward motion, the capacity of the thorax is 
increased from behind forwards, that is, in its 
small diameter. 

384. Such is the part of the action, in inspira- 
tion, performed by the motion of the ribs. The 
remaining part of that action, by far the most 
important, consists of the enlargement of the 
capacity of the thorax from above downwards, or 
in its long diameter. This is effected by the de- 
scent of the diaphragm (fig. cxliii.). 

385. The diaphragm is a circular muscle, form- 
ing a complete but moveable partition between the 
thorax and the abdomen (figs, cxxxiv. 10, and 
CXLIII. 3), When not in action \tA u^^i surface 



DIAPHRAGM. 57 

forms an arcb (figs. czun. 4, and cxlv. 1), the 
convexity of which is towards the thorax (figs, 
GXI.III. 4, and cxlv. 1), and reaches as high as 
the fourth rib (fig. gzly. 1) ; its under surface, 
or that towards the abdomen, is concave (figs, 
cxxxiv. 10, and cxlv. 1). Its central portion is 
tendinous (fig. cxliit. 4). This central tendi- 
nous portion of the diaphragm, which is in appo- 
sition with the heart (fig. cxxxiv. 8), and firmly 
attached to the pericardium (fig. cxxxiv. 7), is 
nearly if not quite immoveable : it is only the lateral 
or muscular portions (figp czuii, 4) that are ca- 
pable of motion. Its central portion is constructed 
of dense and firm tendon, and is immoveable, pri- 
marily, in order to afford one of the two fixed 
points (the ribs affording the other fixed point), 
essential to the action of the muscular fibres that 
constitute its lateral or moveable portions ; and 
secondarily, in order to afford a support to the 
heart, which rests upon this central tendon. 
Thus, in consequence of this tendon being ren- 
dered absolutely fixed, the motions of the dia- 
phragm are completely prevented firom incom- 
moding the motions of the heart ; the function of 
respiration from interfering with the function of 
the circulation. 

386. During the action of inspiration the mus* 
cular or lateral portions of the diaphragm contract 
(fig. cxLiii. 3); its muscular fibie^ ^qxV^w 



Fig. CXLin^Piry if lir Ditg)iratm. 




of the dtqihragm. 

themselTei, and are approximated tawards tbe 
cenml tendon (fig. cxutt. 2) ; the couKqnence 
is that the whole muecle descends (Rg. cxi.iv. 
I) ; paflBea from the fourth to below the seventh 
rih (fig. cxLiv.), loses its arched fonn and pre- 
sentB the appearance of an oblique plane (^. 
cxLiv.). At the aame time the muaclea of the 
abdomen are protruded forwards (fig. cxliv. 2), 



DIAPBKAGM 




Fif. 144—1, Di&plingni is iti itale of gnUtti dearent 
in ihtpintioD. 3. Munclen of the alidoniea, shuwng the 
extent uf thtir piotruuOD in the actloa oCinB^itstion. Fi*;. 
US.— 1. Duptuagm inthesUle ofita ^reBleit Anceni ia 
e^ratioQ. 2. HukIbi af the abdonwn ia actma furciDg 
the riacen uid disphrtigin upwaidi. 

and tbe viscera contained in its cavity are pushed 
downwards. The result of theae moveroeots ie, 
that the capacity of the thorax is enlarged by all 
the space that intervenes between v\ie fo^t^Vi t^^ 



60 THE PHILOSOPHY OF HEALTH, 

(fig. cxLv. 1 ), and the lowest point of the oblique 
plane formed by the diaphragm (fig. cxliv. 1), 
together with all that gained by the protrusion of 
the walls of the abdomen and the descent of its 
viscera (fig. cxliv. 2). 

387. By the action of the intercostal muscles, 
then, the capacity of the thorax is enlarged at the 
sides and from behind forward, or in its short 
diameter ; by the action of the diaphragm, the 
capacity of the thorax is enlarged from above 
downwards, or in its long diameter ; by the com- 
bined action of both, the capacity of the thorax is 
enlarged in every direction, and thtu the motion of 
inspiration is completed. 

388. Expiration, the respiratory motion which 
alternates with that of inspiration, consists of the 
diminution of the capacity of the thorax, which is 
effected by the converse motions of the same organs; 
that is, by the descent of the ribs and the ascent 
of the diaphragm. 

389. By the descent of the ribs, the capacity of 
the thorax is diminished in its short diameter, be- 
cause by this motion, the oblique arches of the 
ribs are approximated to each other and to the 
spinal column, and the sternum is also approxi- 
mated to the spinal column. The descent of the 
ribs is effected first by the elasticity of their carti* 
lages (fig. cxli. 2). When the intercostal musclei 
relax^ the force which raised the ribs ceases to be 



DIAPHEAGM. 61 

applied, and that moment the elasticity of the car- 
tilages comes into play, and carries the ribs down 
wards. Secondly, by the contraction of the abdo- 
minal muscles (tigs. cxlv. 2, and cxlvi. 6, 7, 8)» 
the direct e£fect of which is to pull the ribs down- 
wards (fig. CXLVI. 6, 7, 8). 

390. By the ascent of the diaphragm the ca- 
pacity of the thorax is diminished in its long 
diameter (fig. cxlv. 1). When the diaphragm 
ascends, it changes from the figure of an oblique 
plane (fig. cxliv. 1), re-assumes its arched form 
(fig. CXLV. 1), and reaches as high as the fourth 
rib (fig. CXLV. 1). At the same time the abdominal 
muscles contract (fig. cxlv. 2), and are car- 
ried inwards towards the spinal column (fig. 
CXLV. 2). The result of these movements is, that 
the capacity of the thorax is diminished by all the 
space that intervenes between the lowest point of 
the oblique plane formed by the diaphragm and 
the fourth rib (fig. cxlv. 1), and by all the abdo- 
minal space lost by the contraction of the muscles 
of the abdomen (fig. cxlv. 2). 

391. The first step necessary to the ascent of 
the diaphragm is the relaxation of its muscu- 
lar fibres. As soon as these fibres are in a 
state of relaxation, that is, when the organ has 
changed from an active to a completely passive 
state, the powerful muscles of the abdomen (fig. 
cxLvi- 6, 7, 8) contract^ and pusb tbe iiMomVcAX. 



kxpiration and inspiration. 63 

called the Intereostmlt. 3. SabcUviot. 4. The bone 
called the ClaviCie. 5. The muscle cal>ed the Serratut 
Magnus Amicus. 6. Obliquius Ezternus. 7. Rectus. 
8. Obliquius Internos. 



viscera and the diaphragm with them upwards 
towards the cavity of the chest (6g. cxlv. 2) ; and 
thus, by the descent of the ribs and the ascent of 
the diaphragm, the capacity of the thorax is dimi- 
nished in every direction, and the motion of expi- 
ration ia completed. 

392. Such is the mechanism by which the 
capacity of the thorax is alternately enlarged and 
diminished in the two alternate states of inspi- 
ration and expiration, and the mechanism thus 
adjusted works in the following mode. 

393. Expiration succeeding to the state of in- 
spiration, the ribs descend, the diaphragm ascends, 
the capacity of the thorax lessens, and the com- 
pressed lungs are forced within the smallest pos- 
sible space. Then, inspiration, succeeding to the 
state of expiration, the ribs ascend and the dia- 
phragm descends ; the capacity of the thorax is 
enlarged, and the lungs freed from their pressure 
expand and fill the greater space obtained. In 
about a second and a half after the state of inspi- 
ration has been induced, that of expiration re- 
commences ; the motion of inspiration occupying 
about double the time of the motion of expiration, 
and these alternate conditions succeed each otK^t 

ID a regular and uniform course, da^ wci^ tL\^\.^ 



64 THE PHILOSOPHY OF HEALTH. 

during our sleeping and our waking hours to the 
end of life. 

394. As long as the function, is performed in a 
perfectly natural manner, a given number of these 
alternate movements takes place in a certain time, 
constituting what is termed the rythm of the respi- 
ratory motions. These motions perfectly regular in 
number and time, are likewise, in the natural statQ 
of the function, performed only with a certain 
degree of energy ; but they are variously modified 
at the command of the will; in obedience to 
numerous sensations and emotions; in the per- 
formance of a great variety of complex actions, and 
in different states of disease. These modifying 
circumstances may cause the action of inspiration 
to be more full and deep, and that of expiration 
to be more forcible and complete than natural ; or 
they may cause both movements to be shorter and 
quicker than common: hence the distinction of 
respiration into ordinary and extraordinary. 

395. In ordinary respiration, that is, when the 
respiratory motions are perfectly calm and easy, the 
ascent and descent of the ribs are scarcely percep- 
tible ; the action is confined almost exclusively to 
the ascent and descent of the diaphragm. In this 
condition the only action of the intercostal muscles 
is to fix the ribs, and thus to afford one of the two 
^ed points which have been shown (385) to be 
essential to the action of the diaphragm. But in 

extraordinary respiration, that ys^, '^\ie.ti <sa^9\\sk- 



BXTRAORDiNAHT RESPIRATION. 65 

atances happen in the economy which require 
that those motions should be extended, auxiliary 
sources can be put in requisition. There are 
many powerful musdeH situated al>out the breast, 
shoulder and back (fii^. czlvi. and czlvii.); 
which are capable of elevating the ribs and pro- 
truding tlie sternum to a very considerable extent 
(figs. cxLvi. 1, 2, 3, 5 ; and cxlvii. 1, 2, 3). 
'Where, for example, i\\e fullest iuvpiration which 
it is possible to take is required, the bones of the 
shoulder and shoulder-joint are firmly fixed by 
resting the hands upon the knees, and then every 
muscle which has the slightest connexion with the 
thorax, either before or behind, capable of raising 
the ribs, is added to the inspiratory apparatus (figs. 
cxLiv. and cxlvii.) ; at the same time that the 
abdominal muscles are relaxed to the utmost de- 
gree, in order to facilitate the ascent of the ribs 
and the descent of the diaphragm (figs, cxliv. 2, 
and CXLVI. 6, 1, 8). If, on the contrary, the fullest 
possible expiration is required, the abdominal 
muscles contract most forcibly (fig. cxlv. 2), 
and every other muscle which is capable of still 
farther depressing the ribs and of elevating the 
diaphragm (fig. cxlvi. 6, 7, 8) is called into in- 
tense action. By these forcible and extraordi- 
nary efforts the thorax may be enlarged or dimi- 
nished double its ordinary capacity. 
396. Such are the mechanism and «LCl\o\kQ^\.\v& 



THB PUILOSOPBr o 



FiK-CXLVII^nnv^MMe/MidUo* oncspaUr qToMul- 
ing in e/evaliMg lit S^t and praimding lie SfrnMiM, « 
ilala o/ ciinmrdinarji rttpiraliim. 




powers whicl) communicate to the thorax, tbe mo- 
tions b; which ite cap&city is alternately enlaTj;ed 
and dimiDished, and by which the requisite im- 
pulse is communicated to the fluids which flow to 
and from the htngs in the different states of respi- 



FLOW OF AIR TO THE LUNG IN INSPIRATION. 67 

ration ; that is, by which air and blood flow to the 
lungs in the action of inspiration, and from the 
lungs in the action of expiration. 

397. The mode in which air is transmitted to 
the lungs by the dilatation of the thorax, in the 
action of inspiration, is the following. The lungs 
are in direct contact with the inner surface of the 
thorax, and follow passively all its movements. 
When the 7olume of the lungs is reduced to its 
minimum by the diminished capacity of the 
thorax, in the state of expiration, they still contain 
a certain bulk of air. As their volume increases 
with the enlarging capacity of the thorax in the 
state of inspiration, this bulk of air having to 
occupy a greater space expands. By this expan- 
sion of the air in the interior of the lungs, it be- 
comes rarer than the external air. Between the 
rarified air within the lungs, and the dense exter- 
nal air, there is a direct communication by the 
nostrils, mouth, trachea, larynx, and bronchi. In 
consequence of its greater weight, the dense ex- 
ternal air rushes through these openings and 
tubes to the lungs and fills the air vesicles, the 
current continuing to flow until an equilibrium is 
established between the density of the air within 
the lungs and the density of the external air ; and 
thus there is established the flow (ft a current of 
fresh air to the air vesicles. 

398. The external air which, in obedk,wcAi \<^ 



68 THB PHILOSOPBT OF HEALTH. 

the physical law that regulates its motion, thus 
rushes to the lung in order to fill the partial 
vacuum created by the dilatation of the thorax in 
inspiration, produces, in passing to the air vesicles, 
a pecuhar sound. When the lungs are perfectly 
healthy, and the respiration is performed in a 
natural manner, if the ear be apphed to any part of 
the chest, a slight noise can be distinguished both 
in the action of inspiration and that of expiration. 
A soft murmur, somewhat resembling the sound 
produced by the deep inspirations occasionally 
made by a person profoundly sleeping This sound, 
though appreciable even by the naked ear, and 
though produced many times every minute, in 
every healthy human being from the first moment 
of the existence of the first man, had never been 
heard, or at least never attended to, until fibout 
twenty years ago, when it was observed by accident. 
A physician, Dr. Laennec, of Paris, having occa- 
sion to examine a young female labouring under, 
as he supposed, some disease of the heart, and 
scrupling to follow his first impulse to apply his 
ear to the chest, chanced to recollect that solid 
bodies have the power of conducting sounds better 
than the air. Thereupon he procured a quire of 
paper, rolled it up tightly, tied it, and then ap- 
plied one extremity to the patient's chest and the 
other to his ear. Profiting by the result, which 
wBSy that he could hear the beating of the heart 



FLOW OF BLOOD TO THE LUNG JN INSPIRATION. 69 

infinitely more distinctly than he could possibly 
feel it by the hand, he substituted for this first 
rude instrument a wooden cylinder, which he called 
a stethescope or chest inspector. The attentive 
and practised use of this instrument is found tu be 
capable of revealing to the ear all that is passing 
in the chest almost as clearly and certainly as it 
would be visible to the eye, were the walls of the 
chest and the tissues of its organs transparent. 
Besides the entrance of the air into the lung in 
inspiration, and its exit in expiration, even the 
motion of the blood in the heart, and in the great 
blood-vessels, are rendered by this instrunient dis- 
tinctly manifest to sense ; and as the ear which 
has once become famihar with the natural sounds 
produced by these operations in the state uf health, 
can detect the slightest deviation occasioned by 
disease, the practical application of this discovery 
has already efiPected for the pathology of the chest, 
what the discovery of the circulation of the blood 
has accomplished for the physiology of the body. 

399. At the instant that the expanding lung 
admits the current of air, it receives a stream of 
blood. The air rushes through the trachea to the 
air vesicles impelled by its own weight ; the blood 
flows through the trunks of the pulmonary artery 
to its capillary branches, spread out on the walls 
of the air vesicles, driven by the contraction of the 
right ventricle of the heart A current of cit wid 
a stream of blood are thus brou^Yvt \u\a %o ^Q%i^ 



70 THE PHILOSOrHT OF HEA1«TH. 

an approximation that nothing intervenes between 
the two fluids, but the fine membranes of which 
the air vesicles and the capillary branches of the 
pulmonary artery are composed, and these mem- 
branes being pervious to the air, the air comes 
into direct contact with the blood ; the two fluids 
re-act on each otherj and in this manner is ac- 
complished the ultimate object of the acdon of 
inspiration. 

400. On the other hand, by the action oi ex- 
piration, the bulk of the lung is diminished ; the 
air vesicles are compressed, and a portion of the 
air they contained, forced out of them by the 
collapse of the lung, is received by the brondii, 
transmitted to the trachea, and ultimately con- 
veyed out of the system by the nostrils and mouth. 

401. At the same instant that a portion of air 
is thus expelled from the lung and carried out of 
the system, a stream of blood, namely, blood which 
has been acted upon by the air, arterial blood, is pro- 
pelled from the lung and is borne by the pulmonary 
veins to the left side of the heart, to be transmitted 
to the system (fig. cxl. 10, 11)4). In this manner, 
by the simultaneous expulsion from the lung of a 
current of air and a stream of blood is accomplished 
the ultimate object of the action of expiration. 

402. That blood flows to the lung during the 
action of inspiration, and is expelled from it during 
the action of expiration, is established by direct 

experiment. 



PROOFS. 71 

403. If the great Tenel which returns the blood 
from the head to the heart, called the jugular Yein» 
be exposed to view in a living animal, it 10 seen to 
be alternately filled and emptied according to the 
different states of inspiration and expiration. 

It becomes nearly empty at the moment of in- 
spiration, because at that moment the venous 
stream is hurried forward to the right chambers 
of the heart, which in consequence of the general 
dilatation of the chest are now expanded to receive 
it. This may be rendered still more strikingly 
manifest to the eye. If a glass tube, blown at the 
middle into a globular form, be inserted by its ex- 
tremities into the jugular vein of a living animal 
in such a manner that the venous stream must 
pass through this globe, it is found that the globe 
becomes nearly empty during inspiration, and 
nearly full during expiration ; empty during in- 
spiration, because, during this action the blood 
flows forwards to the right chambers of the heart ; 
full during expiration, because during this action 
the venous stream, retarded in its passage through 
the lung, its motion becomes so slow in the jugular 
vein that there is time for its accumulation in the 
glass globe. In the artery, on the contrary, in 
which the course of the current is the reverse of 
that in the vein, the opposite result takes place. In 
the carotid artery the stream is seen to be feeble 
and scanty during inspiration, bulfoic\\A^%.'vA^\!J\. 
daring expiration, and if the artery \ie ^\N*\^<t^ ^'fc 



72 THE PHILOSOPHY OF HEALTH. 

jet of blood that issues from it absolutely stops 
during the action of inspiration; and the AiUa 
and deeper the inspiration the longer is the inter- 
val between the jets, while ic is during the action 
of expiration that the jet is full and strong. 

404. In the course of some experiments per- 
formed by Dr. Dill and myself with a view to Vh 
certain with greater precision the relation betwe^ 
respiration and circulation, we observed a pheno- 
menon which places these points in a still more 
clear and striking light. We happened to divide 
a lugular vein. We saw that the vessel ceased to 
bleed during inspiration, and that it began to 
bleed copiously the moment expiration commenced; 
the reverse of what uniformly happens in the en- 
tire state of the vessel. The reason is, that the 
division of the vein cuts off its communication with 
the lung, removes it from the influence of respira- 
tion, brings it under the influence, the sole in- 
fluence of the powers that move the arterial current, 
and consequently reverses its natural condition, 
and so reverses the manner in which its current 
flows ; affording a beautiful illustration of the 
influence of the two actions of respiration on the 
two sets of blood- vessels concerned in the function. 
405. It is then the venous system that is im- 
mediately related to inspiration, and the arterial to 
expiration. Each respiratory action exerts a spe- 
cific influence over its own sanguiferous system, 
and tbeinButnce of the one aeUoxi \&\^ii^\«:>«^x«ft 



BLOOD TRANSMITTBD IN INSPIRATION. 73 

of that of the other, as the two currents they work 
flow in opposite directions. The lungs, in inspira- 
tion, expand and receiye the utenous stream ; in ex- 
piration, collapse and expel the arterial stream. 
The expansion of the lungs in inspiration is thus 
simultaneous with the dilatation of the heart : 
during the inspiratory action hoth organs receive 
their hlood. The collapse of the lungs in expira- 
tion is simultaneous with the contraction of the 
heart: during the expiratory action both organs 
expel their blood. 

406. We are thus enabled to form a clear and 
exact conception of the mechanism and action of 
both parts of this complicated function. Almost 
all the points connected with the systemic cir- 
culation were established upwards of three hun- 
dred years ago (219), but many points con- 
nected with the pulmonic circulation have been 
established only recently. Our knowledge of the 
phenomena of both, and of their mutual relation 
and dependence, has been slowly increasing, and is 
at length tolerably complete ; and now that we 
understand the exact ojffice and working of each, 
we see that the action of the one is not only in 
harmony with that of the othef, but co-operates 
with it, and renders it perfect. 

401. But although the main points relative to 
the influence of inspiration and expiration ov^r the 
pulmonary circulation may be said to be uuv^ex- 
BtilJjr admitted, BtilJ physiologists axe not ^\t!^ ^& 

VOL, II, ^ 



74 THB rillLOSOPHT OP BEALTB- 

to the relative quantities of blood which are trans- 
mitted through the lungs during these differenl 
respiratory states. All are agreed that the state 
of inspiration is favourable to the passage of the 
blood through the lungs : some maintain that this 
expansion of the lungs in inspiration is essential 
to the pulmonary circulation. There is the like 
general consent that the state of expiration retards 
rhe flow of blood through the lungs ; by many it 
is conceived that it completely stops the current. 
By these physiologists it is supposed that, dmii^ 
the action of expiration, the lungs are in a state 
of collapse; that they contain a comparatively 
small portion of air ; that in this state the air 
vesicles are so compressed, and the pulmonary 
blood-vessels so coiled up, that the lungs are abso- 
lutely impermeable, and consequently, that whea 
the blood arrives at the right chambers of the 
heart, it is incapable of making its way to tbe left. 
This, according to a prevalent theory, is the im- 
mediate cause of death in asphyxia, the state of 
the system induced by suspended respiration, u 
in drowning, hanging, and suffocation. Death 
takes place in this condition of the system, it is 
argued, because the circulation of the blood b 
arrested at the right side of the heart, cannot per- 
meate the lungs, and consequently cannot reach 
the left ventricle, to be sent out to supply ibe 
organs of the body. 
408. This opinion, 'wYucVi a\i^%3» %X %JiiX 'wn 



BLOOD TKANSMITTBD Itf INSPIRATION. 75 

to be fmYoored by nmnerouB obserrations and ex- 
periments, has been shown to be fallacious by a 
series of decisive experiments, performed by Dr. 
Dill and myself, undertaken, as has been stated 
(404), with the object of ascertaining, in a more 
exact manner than had hitherto been done, the 
relation between the circulation and respiration. 
The previously ascertained fact that the heart 
continues to beat and the blood to flow several 
minutes after the complete suspension of the re- 
spiration, or after apparent death, afforded us the 
means of pursuing our research. The details of 
these experiments are given elsewhere : it is suffi- 
cient to state in this place the main results. 

409. As a standard of comparison, the quan- 
tity of blood which flows through the lungs after 
apparent death, when the lungs remain in a per- 
fectly natural state, was preriously ascertained. 
ft was found, after death produced in an animal 
by a blow on the head, that blood continued to be 
transmitted through the lungs for the space of 
twenty-flve minutes after the complete cessation 
of respiration. There passed through the lungs 
in all five ounces and two drachms of blood. 

410. Respiration was now suspended the in- 
stant after a perfectly natural and easy imtpiration ; 
there flowed through the lungs four ounces and 
five drachms of blood. 

411. RespiratioD was next suspeiide^ \\i^ Vcir 
gtanttifter a perfectly natural and easy cxpra^ou \ 



76 THE PHILOSOPHY OF HEALTH. 

there flowed through the lungs two ounces and 
seven drachms of hlood. 

412. When the trachea of an animal is closed 
by the pressure of a cord in suspension, or when 
an animal is immersed under water, it makes t 
succession of violent expirations, by which a large 
quantity of air is forced out of the lungs. Hence, 
when the lungs of an animal that has perished by 
hanging or drowning, are examined, they are 
always found much reduced in bulk; so much 
reduced in bulk as to have suggested the theory 
that the extreme collapse of the lungs and their 
consequent impermeability, is the cause of death 
in this condition of the system. On bringing this 
theory to the test of experiment, it was found that 
blood continued to flow through the lungs after 
apparent death from suspension, for the space of 
eleven minutes, and that there passed through in 
all five ounces of blood. The comparatively larger 
quantity transmitted in this case than when the 
inspiration and expiration were perfectly natural, 
was owing to the larger size of the animal. In 
the experiments made with a view to ascertain the 
relative proportions of blood transmitted through 
the lungs in the states of natural inspiration and 
expiration, the animals were chosen as nearly as 
possible of the same size, and were much smaller 
than the former. 

413. On examining the quantity of blood that 
passed through the lunga ai^i ^^«L\)[i ixvnsi %»}> 



BLOOD TRANSMITTBO IN BXPIRATION. 77 

mersion, it was found to be very nearly the same 
as that which was transmitted after death from 
suspension. 

414. But the lungs may be brought to a much 
greater degree of collapse than that to which they 
are reduced in hanging and drowning. By intro- 
ducing an exhausting syringe into the trachea, a 
much larger quantity of air may be drawn out of 
the lungs than they are capable of expelling by the 
most violent efforts of expiration. When, in this 
mode, the lungs had been reduced to the greatest 
possible degree of collapse, and had been exhausted 
of all the air that could be drawn out of them, 
there flowed through them two ounces of blood. 

415. Such are the results when the lungs are 
reduced successively from the moderate degree of 
collapse incident to a perfectly natural expiration, 
to the great degree of collapse incident to sus- 
pension and submersion, and the most extreme 
degree of collapse which it is possible to induce 
by exhaustion. 

416. When the phenomena that take place in 
the opposite condition of the lungs were investi- 
gated, results were obtained which present a 
striking contrast to those which have been stated. 
On forcing into the lungs the largest quantity of 
air which they are capable of containing without 
the rupture of the air vesicles, and in thi<» manner 
communicating to them the great^^t dvi^^"^ ^'l 



78 THE PHILOSOPHY OF HEALTH. 

dilatation compatible with their integrity, it was 
found that in this state there passed through them 
only three drachms of blood. 

417. But on fiilly distending the lungs with 
water instead of air, the pulmonary circulation 
was instantaneously and completely arrested ; they 
were incapable of transmitting a single drop of 
blood. On cutting the aorta across, as in all the 
preceding experiments, not a particle of blood was 
obtained, excepting what issued at a single jet, 
and which consisted only of the blood contained 
in the vessel at the moment the respiration was 
stopped. 

418. From these experiments it follows-— 

1. That the state of inspiration is favorable to 
the passage of the blood through the lungs. In 
the dilatation of inspiration they transmitted nearly 
double the quantity that passed in the collapse 
of expiration ; or, as four ounces and five drachms 
are to two ounces and seven drachms (410 and 
411). 

2. That no d^ree of collapse to which the 
lungs can be reduced is capable of wholly stop- 
ping the flow of the blood through them. In the 
collapse of suspension and submersion they trans- 
mitted as much blood, with the exception of two 
drachms, as when death was produced by a blow 
on the head (412 and 409). In the greatest de- 

gree of collapse capable of being produced by an 



AIR &BCBIVED IN INSPIRATION. 79 

exhausting syringe, they transmitted half as much 
as in the collapse of suspension and suhmersiun 
(414 and 412). 

3. That it is only a moderate degree of 
dilatation that is favorahle to the transmission o< 
the blood through the lungs. When the lungs 
are over-distended with air, they are capable of 
transmitting only an exceedingly small quantity 
of blood (416) ; when they are fully distendecl 
with water, they are incapable of transmitting a 
single drop of blood (417). In fact they can 
contain only a certain quantity of air and blood ; 
and when either of these fluids preponderates, it 
can only be by the proportionate exclusion of the 
other. It will appear hereafter that these results 
are capable of applications of the highest interest 
and importance in the explanation of numeroub 
phenomena of health and of disease. 

419. Physiologists have laboured with great 
diligence to determine the exact quantity of air 
and blood which enters and which flows from the 
lung at each of the actions of respiration, and 
they have succeeded in obtaining tolerably precise 
results. 

420. The quantity of air capable of being re- 
ceived into the lungs of an adult man, in sounci 
health, at an inspiration, is determined with cor- 
rectness by an instrument constructed by Mr. 
Green y analagous to one suggested by Mr. Aber- 
nethy. It comiBU of a tin trough, «Jao\\\. ^ \wN 



80 



THE PHIIX>SOPRY OF HEALTH. 



square, and six inches deep, three parts of whic 
are filled with water, into this trough is plaa 
» three-gallon glass jar, open at the bottom, an 
graduated at the side into pints, half-pints, & 
To the upper end of the jar a flexible tube 
affixed, having at its connexion a stop-cock. Tl 
lungs being emptied, as in the ordinary action 
expiration, and the mouth applied to the end < 
the flexible tube, the nostrils being closed by tl 
pressure of the fingers, the air is drawn out of tl 
jar into the lungs by the ordinary action of insf 
ration. When as much air is thus drawn into tl 
lungs as the air vesicles will hold, the stop-coi 
is closed, and the quantity of air inspired is ascc 
tained by the rise of the water, the level of tl 
water corresponding with the indications mark 
on the side of the jar. 

421. The quantity of air which a person by 
voluntary effort can inspire at one time is foun 
as might have been anticipated, to be different 
every different individual. These varieties depen 
among other causes, on the greater or less develo 
ment of the trunk, on the presence or absence 
disease in the chest, on the d^ree in which t 
lung is emptied of air by expiration previously 
inspiration, and on the energy of the inspiratc 
effort. The greatest volume of air hitherto fou 
to have been received by the lung, on the m< 
powerful inspiration, is nine pints and a quart 
The Mvenge quantity wlucb tbie Vim^ vt^ c%i^ 



AIR BXPBLLBO IN BXPIAATION. 81 

of receiving in perBona in g^ood health, and free 
from the accumulation of fiit about the cheat, ap- 
pears to be from five to seven pints. The latter 
is about the aven^ quantity capable of being in- 
spired by public singers. 

422. But these measurements relate to the 
greatest volume of air which the lungs are capable 
of receiving, on the most forcible inspiration which 
it is possible to make, after they have been emp- 
tied by forcible expiration, and consequently 
express the quantity received in extraordinary, not 
in ordinary inspiration. The quantity received at 
ah inspiration easy, natural, and free from any 
great effort, may be two pints and a half; but the 
quantity received at an ordinary inspiration, made 
without any effort at all, is, according to former 
observations which referred to Winchester mea- 
sure, about one pint. 

423. The quantity of air expelled from the 
lung by an ordinary expiration is probably a very 
little less than that received by an ordinary inspi- 
ration (456). 

424. No one is able by a voluntary effort to 
expel the whole contents of the lungs. Obser- 
vation and experiment lead to the conclusion that 
the lungs, when moderately distended, contain at 
a medium about twelve pints of air. As one pint 
is inhaled at an ordinary inspiration, and some- 
what less than the same volume is expelled at au 
urdinajj expiration (456)9 there remam "^^^XiV 



82 TSS PHffiOSOPHT OF SSALTS. 

la ihe lungs^ mA a minimum, ^ffvea pints «f air. 
There is one act of resptration to four pukationi of 
the heart; and« as in the ordinary state of lieaith 
there ai!e seyentj-^wo pulsations, so there are 
eighteen respirations in a minute, or 25,920 in the 
twenty-f^wjr houiis* 

425. Ahoui two oufiees of hlood are noeified 
hy Ae heart at each dilataiion of the aurides; 
about ihe same qiuantity is expelled from it at 
each eostraotion of its sresatricles ; consequently, ai 
the heart dilates and oontracts 8eirenty*twe times 
in a minute, it sends thus often to the limga, these 
to he acted upon by the tk, t<wo ounces of blood. It 
is eadmated by Haller that 1X),527 grains of Uoad 
ooeupy the same space as 10,000 grains of vaier, 
so that if one cnihie inch of water weigh 253 grains, 
the aame bulk of biood will weigh 2664 grainta. 

426. It is ordinarily estimated that on an 
average one circuit of t^ blood is perfomied in 
150 Ekeconds; but it is shown (451 aad 452) that 
the .^antity of air always present in the lungs 
contains precisely a sufficient quantity of oxygen 
to oxygenate the blood, while flowing at the ladi- 
nary rate of 72 contractions of the heart per 
minute, for the exact space of 160 seconds. It is 
there£9re highly probable that this interval of 
time, 160 seconds, is the exact period in which 
^kt blood performs one circuit, and not 150 
seconds, as former observations had assigned. If 

this he BO, then 540 circuits a.T« "^fisdoTm^^ >Ri «^ 



jtiBt Alfa BLOOD ni tbb lungs. 83 

twtixty^fonaf hours ; that is, there are three com- 
plete circulations of the blood through the body in 
every eight mmute* of time. 

427. But it has been shown (425) that the 
weight of the blood is to that of water as 1.0527 is 
to unity, and that consequently 10^521 grains of 
blood are in yoliune the same as 10/)00 grains of 
water. 

428. From this it results that if in the human 
adnlt two ounces of blood are propelled into the 
hmgs at each contraction of the heart, that is, 12 
times in a minute, there are in the whole body 
precisely 384 ounces, or 24 pounds avoirdupois, 
which measure 692.0657 cubic inches, or within 
one cubic inch of 20 imperial pints, which measure 
693.1847 cubic inches. 

429. By an elaborate series of calculations 
from these data Mr. Finlaison has deduced the 
following general results :— 

1. As there are four pulsations to one respira- 
tion (424), there are 6 ounces of blood, measuring 
14.418 cubic inches, presented to 10.5843 grains 
of air, measuring 34.24105 cubic inches. 

2. The whole contents of the lungs is equal to 
a volume of very nearly 411 cubic inches full of 
air, weighing 127 grains^ of which 29.18132 grains 
are oxygen. 

3. In the space of five-sixth parts of one 
second of time, two ounces, or 960 grains weight 



84 THE PHILOSOPHY OF HEALTH. 

of blood, measuring 3f or 3.60451 cubic inches, 
are presented for aSration. 

4. Therefore the air contained in the lungs is 
114 times the bulk of the blood presented, while 
the weight of the blood so presented is 7^ times as 
great as the weight of the air contained. 

5. In one minute of time the fresh air inspired 
amounts to 61&i- cubic inches, or as nearly as may 
be 18 pints, weighing 190j^ grains. 

6. In one hour the quantity inspired amounts 
to 1066-1 pints, or 2 hogsheads, 20 gallons, and 
10| pints, weighing 23f ounces and 31 grains. 

7. In one day it amounts to 57 hogsheads, 
1 gallon, and 7}- pints, weighing 57 1^ ounces and 
25 grains (454). 

8. To this volume of air there are presented 
for aSration in one minute of time 144 ounces of 
blood, in volume 259j^ cubic inches, which is 
within 18 cubic inches of an imperial gallon. 

9. In one hour 540 pounds avoirdupois, mea- 
suring 449^ pints, or I hogshead and 1^ pints ;— 
and 

10. In the twenty-four hours, in weight 12,960 
pounds ; in bulk 10,7^2^ pints, that is, 24 hogs- 
heads and 4 gallons. 

11. Thus, in round numbers, there flow to the 
human lungs every minute nearly 18 pints of air 
(besides the 12 pints constantly in the air vesicles) 
MDd nearly 8 pints of blood ; but in the space of 



CHANGES PRODUCBO OPON THE AIR 85 

twenty-four hours, upwards of 57 hogsheads of air 
and 24 hogsheads of blood. 

430. Provision cannot have been made for 
bringing into contact such immense quantities of 
air and blood, unless important changes are to be 
produced in both fluids ; and accordingly it is 
found that the air is essentially changed by its 
contact with the blood, and the blood by its con- 
tact with the air. 

431. Chemistry has demonstrated the changes 
eifected in the air. Common atmospheric air is 
a compound body, consisting of pure air and 
of certain substances diflnsed in it. Pure air 
is composed of two gases, azote and oxygen, 
always combined in fixed proportions. The 
substances diffused in pure air, and which are 
in variable quantity, are aqueous vapour and 
carbonic acid gas. These latter substances form 
no part of the chemical agents essentially con- 
cerned in the process of respiration. The only 
constituents of the air which are essentially con- 
cerned in the process of respiration are the t^'o 
gases, azote and oxygen, the union of which, in 
definite proportions, constitutes pure air. But of 
these two gases each does not perform the same 
part in the function of respiration, nor is each 
equally necessary to the support of life. 

- 432. If a living animal be placed in a vessel 
full of atmospheric air, and if all coinm\imt«L\.vw\ 
7f the atmosphere with the vesBel be "pi^NeTAfc^, 



S6 THE PHILOSOPHY OF HEALTH. 

the animal in a givea time perishes. If an animal 
be placed in a vessel full of azote, after a giyen 
time it equally perishes ; but if an animal be 
placed in a vessel full of oxygen, not only is the 
fbnetion of respiration carried on with fJEor greater 
energy than in atmospheric abr, but the! animal 
lives a much longer time than in the same bulk 
of the latter fluid. If twenty cubic inches of pure 
oxygen be capable of sustaining the life of an 
animal far the space of fourteen minutes, it can 
support life in the same bulk of atmospherie ab 
only six minutes ; and if its respration be ccmfined 
to either of these gases, after they have been 
already respired by another animal of the same 
species, the former will live only four minuter! ; 
that is, not longer than when entirdy deprived of 
air. It follows that the gas which givea to 
atmospheric air ita chief power of stwtaining life 
is oxygen. 

433. Accordingly it is proved that no animal^ 
from the lowest to the highest, ia capable of aus- 
fainiiig life unless a certain proportion of Oxyg^ 
be present in the fluid which it respires. WhelJiev 
it breathe by the skin, by gills, or by Imiga, 
whether the respiratory medium be water or air, 
the presence of oxygen is alike indispensable. Yet 
the life of no animal can be sustained by pure 
oxygen. If azote be not mixed with oxygen, evils 
itre produced in the economy which sooner or \$iet 
prove fttUh On the e^iket \i«tid,*ii VX^^ ^xnr^nt^oMt. 



CHANGES PEODUCJBD VTOV THE AIR. 87 

9tf (H^geu bfs dimlnbbed beyond a ceKain point, 
dbrowtiBefSy torpor^ and death result Not oxygen 
alonc^ then 9 but oxygen conbined ^th azote, in 
tke prop<]irtion in which nature has united these 
two flttids to form the atmospliere of the globe, is 
in dispe aaable ito animal existence. 

434* When the same portion of atmospheric 
iiir is repeatedly respired by an animal, the oxygen 
contained in it gradually disappears, the gas 
lessening with every successive respiration, until 
at last so small a quantity remains that it is no 
longer capable of sustaining the life of an animal 
of that class. When respiration has deprived the 
lur of its Qxygta to such an extent, that it can no 
longer support animal life, the air is said to be 
o^nrnvrififi ; but, correctly speaking, it is merely 
iphan^d in composition^ in the proportions in 
which its constituents are combined ; consequently 
4lie effset of respiratioB is to alter the chemical 
imposition of the air. - 

435. The essential change tliat takes place 
cousists in the diminution of the oxygen and the 
jbMn^case of the carbonic acid. When inspired, 
Atmospheric air goes to the lungs loaded with 
Oixygen; when expired, it returns loaded with 
carbonic acid That the air which returns from 
the lungs is loaded with carbonic acid, may be 
rendered manifest even to the eye. If a person 
breathe through a tube into water holding lime in 
Bolutiop, the carbonic acid contained m li^fc «sl- 



88 TUK PHILOSOPUT OP BBALTH. 

pired air will unite with the lime and form a 
white powder analogous to chalk (carbonate of 
lime), which being insoluble, becomes visible. 

436. On the other hand, the diminution of 
oxygen is demonstrated by chemical analysis. If 
100 parts of atmospheric air be successively 
respired, until it is no longer capable of supporting 
life, and if it be then subjected to analysis, it ii 
found that in place of being composed of 19 parts 
azote, 21 oxygen, and a variable quantity of car- 
bonic acid, sometimes amounting to half a grain 
per cent., it consists of 17 parts azote, and 23 
carbonic acid. The oxygen is gone, and is re- 
placed by 23 parts of carbonic acid ; at least this 
is the ordinary estimate ; but different experimen- 
talists differ somewhat in their account of tiie 
absolute quantity of oxygen that disappears, and 
of carbonic acid that is generated. 

437. Whatever estimates of the oxygen con- 
sumed, and of the carbonic acid generated, be 
adopted, they can be taken only as medium quan- 
tities. Dr. Edwards has demonstrated that the 
absolute quantity of oxygen consumed in a given 
time is constantly varying, not only in animals of 
different species, but even in the same animal under 
different circumstances ; insomuch, that there are 
scarcely two hours in the day in which the same 
individual expends precisely the same quantity. 
The nature and degree of the exercise taken 

during the observation, tlie coiid\\ioTi ci VltA xsaxyii^ 



CHANGES PRODUCED VTOS THE AIR. 89 

he state of the health, the kind of food, the tem- 
perature of the air, and innumerable other causes 
naterially influence the quantity of oxygen con- 
lumed. When, for example, the hourly consump- 
tion of oxygen, at the temperature of 54° Fahren- 
heit, amounted to 1345 cubic inches,* it fell, at 
the temperature of 79^, to 1210 cubic inches. 
During the process of digestion more is consumed 
than when the stomach is empty ; more is required 
when the diet is animal than when it is vegetable, 
and more when the body and mind are active than 
when at rest 

438. With regard to the carbonic acid, Dr. Prout 
has recently made the remarkable discovery, not 
only that the generation of this gas differs accord- 
ing to different circumstances, and more especially 
according to particular states of the system ; but 
that the quantity of it which is produced regularly 
varies at particular periods of the day. The quan- 
tity generated is always more abundant during the 
day than during the night. About daybreak it 
begins to increase; continues to do so until noon, 
when it comes to its maximum, and then decreases 
until sunset. The maximum quantity generated 
at noon exceeds the minimum by about one-fifth of 
the" whole. If from any cause the relative quantity 
be either increased or diminished above or below 
the ordinary maximum or minimum, it is invariably 

* The otdinary con8umpii(m of oxygen la, tot ttn ^^>i^\.^ 
JPOS cubic ineheB per hour (/iAA), 



90 THE PHILOSOPHY OF HEALTH. I 

diminisbed or increased Id an equal propovtkm 
during some subsequent diurnal period. The tb- I 
solute quantity generated is materially diminished 
by the operation of any debilitating cause, such ai 
low diet, protracted fasting, or long-continaed 
exercise, depressing passions and the like. Few 
circumstances of any kind increase the quantity 
produced, and*those only in a slight degree. 

439. The changes produced by respiration od 
the other constituent of the air, azote, appear at 
first view to be extremely variable. By numerouB 
and accurate experiments it is established that the 
quantity of this gas is at one time increased ; at 
another diminished, and at another unchanged. 
It is probable that there is a constant absorption 
and exhalation of it ; and that the apparent irregu- 
larity is the result of the preponderance of the one 
process over the other. When absorption prepon- 
derates, a smaller quantity is found in the air ex- 
pired than in that inspired : when exhalation pre- 
ponderates, a lai^r quantity is expired than in- 
spired; and when the absorption and exhalation 
are equal, just as much is expired as inspired, and 
consequently there appears to be no absorption 
at all. 

440. Such are the phenomena of respiration, 

as far as the labours of physiolc^sts has succeeded 

in ascertaining them, up to the present time. But 

as the estimates of the quantity of air and blood 

contained in the lunga were TaVhtx xoaXicet^ ^\ ^^> 



CALCULATIONS. 91 

jectiire than of demonstration, and as the quantity 
of oxygen consumed, of carbonic acid generated, 
and of azote absorbed, appeared still not to be 
determined with exactness, I requested Mr. Fin- 
laison to apply his power of calculation to the 
investigation of this subject, taking as the basis of 
his calculations the facts positively and precisely 
ascertained by experiment and analysis. This he 
has done with great care, and has obtained the 
following results. 

441. It was formerly estimated that the weight 
of pure atmospheric air is 305,000 grains troy for 
one million of cubic inches ; but the latest autho- 
rities assign it to be 310,117 grains. Of this 
weight of one million of cubic inches of pure air. 
The weight of the oxygen is - - - 71,809.3 
The weight of the azote is 238,307.7 



Total 310,117.0 

442. But common atmospheric air in its ordi- 
nary state contains in 1000 cubic inches, 
Of pure air 989 

Of the vapour of water - - - 10 

Of carbonic acid gas 1 

Ten inches of pure air are equal in weight to 
nine of oxygen. 

Eight inches of azote are equal in weight to 
seven of oxygen. 

The specific gravity of carbonic add \% \A ^^m^ 
lirat iterate of 15,211 to 10,000. 



92 THE PHILOSOPHY OF HEALTH. 

The specific gravity of the vapour of water is to 
pure air as 6,230 to 10,000. It follows that a 
million of cubic inches of air in its ordinary state 
weigh 309,111^ grains. 

Carbonic acid gas is composed of oxygen and 
pure carbon in the proportion of eight grains of 
oxygen to three of carbon out of every eleven 
grains of carbonic acid. 

443. Though during particular portions in the 
twenty-four hours, under circumstances which in- 
fluence variously the actions of life (437 and 438), 
the quantity of the oxygen consumed, of carbonic 
acid generated, and of azote absorbed, vary (436 to 
439), yet it is probable that the daily consumption, 
reproduction, and absorption of these gases, is pretty 
much the same one day with another. The expe- 
riments of Dr. Edwards clearly show that while 
these quantities vary to such an extent, vihea 
the observation embraces only a short interval, as 
to be scarcely ever the same hour by hour, yet that 
they lessen as the interval extends, until at length 
a nearly exact equilibrium is established. 

444. Experimental philosophers have not ob- 
tained precisely the same results as to the quan- 
tities consumed and reproduced of these respective 
gases. At present, therefore, we can only ap- 
proximate to the exact amount by taking the 
average of their observations. The following are 
the results of the principal experiments which 



9> 



CALCULATIONS. 93 

have been instituted. The quantity of uxygen 

consumed by an adult man in twenty-four hours 

is, according to 

Menzes 51,840 

Lavoisier 46,048 

Davy 45,504 

Allen and Pepys 39,534 

The mean of all which is, 45,131.5 inches. 

445. In like manner the quantity of carbonic 
acid generated in the same time is, according to 

Davy - 38,304 cubic inches. 

Allen and Pepys - 38,232 
Thermean of which is, 38,268 

The weight of 38,268 inches of carbonic acid 
gas is 18,130. 14*74 grains troy ; and the weight of 
45,731 j^ inches of oxygen is 15,157.9131 grains 
troy. 

Now this weight of oxygen must have been 
derived from the decomposition of 221,882 cubic 
inches of common atmospheric air. 

446. It has been shown that, iu the state of 
health, one contraction of the heart propels to the 
lungs two ounces of blood ; that this action of the 
heart is repeated 72 times in one minute ; that to 
every four actions of the heart there is one action 
of respiration; that consequently there are 18 
respirations in a minute, and 25,920 in the twenty- 
four hours. 

447. From these premises it results that at 



94 THE PHILOSOPHY OT HSAITH. 

each action of the heart there it decompoaed of 
the air inspired, 8.5603 cubic inchea, that ia, a 
quarter of a pint within one- tenth of a cubic inch, 
— ^the quarter of u pint imperial measure being 
8.6648 cubic inches. 

448. Previous observation had assigned one 
pint as the volume of air ordinarily inhaled at a 
single inspiration. We now see that the quantity 
decomposed is a quarter of a pint. It is, then, an 
absolute truth, that of the whole volume of air 
inspired, one-fourth part only is decomposed, and 
that three-fourths, af^er having been difiused 
through the air vesicles of the lungs, are expired 
without change. 

449. Observation had also assigned 12 pints 
of air as the volume constantly present in the 

lungs, — that is, 415.9108 cubic inches. 

The truth seems to be, 

that forty-eight times the 

quantity decomposed is 

constantly present,namely, 410.8926 cubic inches. 

The difiference is only - - 4.0182 cubic inches* 

which difference weighs less than 1-)- grains troy. 

450. It is then concluded that the real con- 
tents of the lungs is a volume of 410.8926 cubic 
inches, which is exactly the 540th part of 221,882 
cubic inches, being the whole volume decomposed 
in twenty-four hours. But 160 seconds is alto 
exactly the 540th part of the number of seconds 

in twenty-foar hours. 



CALCULATIONS. 95 

451. Of the whole weight of oxygen consumed 
1 twenty-four hours - - - - 15,757.9131 grains, 
he 540th part, or the propor- 
ion of 160 seconds, is • - - 29.18132 ,» 
nd 410.8926 cuhic inches of 
tmospheric air, which, as 
bove, is the contents of the 
angs, contain of oxygen the 
ame weight 29.18132 „ 

452. Then, if respiration were suddenly 
topped, proyision is made by the quantity of air 
klways retained in the lungs for the oxygenation 
if the blood while flowing at the ordinary rate of 
[2 strokes per minute, for the exact space of 160 
seconds, and for not one instant longer. 

453. This interval of time, then, as has been 
itated (426), is very probably the time in which 
he blood performs one circuit, not 150 seconds. 
Then 540 circuits are performed in the twenty- 
bur hours, or 3 circuits in every eight minutes. 
E^om this estimate has been deduced the quantity 
»f blood contained in the whole body of the human 
idult (428). 

454. The air inspired in twenty-four hours con- 
ains as under : — 

enbio inchM. graiM trojr. 
Jndeeompoted, and to be 
Kturned unrhanged 665,646 805.7S8.833. Common air, 

^ b« dMompoMd, containing in 
•olutlvn 

Pare atmospheric air.... 219.441 { m;^!!^'. mSS^ 

Vmpoar of water 2,Stl9 428.^a6, \ avout , 

CMTboaie acid gaa SSS 105.130 , CaiXsouVi wa^ 

'^*^'^ 887,588 a74j345.U\, Ot •XWVoi^*. 



Jkilk i. Weight i. Lg^dknt.. 



86 THE PHILOSOPBT OF HEALTH. 

This is, in bulk, 25,607i imperial pints, or 51 
hogsheads, 1 gallon, and 7i pints, and in weight 
57 1^ ounces and 25 grains. 

455. Now, although the air expired, in conse- 
quence of its recomposition, may have undergone 
changes in bulk, yet it seems agreeable to all ana- 
logy to suppose that its weight will remain the same 
as the weight inhaled. This, however, is not 
asserted as a truth, but only assumed, in order to 
show the result of such a theory. 

456. Then the air expired in twenty-four houn 
will be as follows : — 

Balk ic We^t m 

cubic locbet. grains troy. 

Given outundecomposed 

as before 665,646 205,758.833 

Recomposed carbonic 

acid gas 38,268 18,130.141 

Azote liberated - - - - 165,927 50,027.405 

Vapour of water as before 2,2 1 9 428.726 

Total - . 872,060 274,345.111 
weighing as before, but less in bulk by 446} 
pints : so that for every 100,000 inches expired 
there were inspired 101,774 cubic inches. 

457. When from the weight of 

carbonic acid gas thus expired, viz., 18,130.147 
we deduct the small portion inhaled 

in solution with the air - - - - - 105.130 



The remainder is - - - - IB^Q25.017 



CALCULATIONS. 97 

3 constituent parts of which are, 

xygen deriyed from the air 13,109.104 



d pure carbon derived from the 

>lood being the diflference 4,915.913 

us in the compass of twenty-four hours the 

od has produced 10 ounces and 116 grains 

y nearly of pure carbon. 

158. Now, from the oxygen con- Grains. 

ned in twenty-four hours as above 15,757.913 

sduct the weight restored in the 

form of carbonic acid gas 13,109.104 



le remainder must have been ab- 
sorbed into the blood 2,648.809 

It the weight of carbon given out 

being as above 4,915.913 



lere is still an excess given out weighing 2,267 . 1 04 
459. Some azote, however, is absorbed into 
e blood (439) as well as the above ascertained 
lantity of oxygen, 
le weight of azote so absorbed must 

be precisely 2,267.104 

the theory be true, that equal weights 
are expired and inspired. In 
which case, as the weight of the 
azote of the air inspired was, as 
shown above - -- 5^3\.^^^ 

VOL, il. V 



98 THE PUILOSOPHt OP HKALTH. 

While the azote expired could only 
have weighed 50,027.405 



The difference would have been ab- 
sorbed 2,267.104 

And thus the weight of carbon discharged by the 
blood is precisely compensated by the united 
weight of the oxygen and azote which it has ab- 
sorbed. 

460. Since it appears to be a general truth 
that one quarter of the air respired is decomposed, 
and that the volume of air continually present in 
the lungs is sufficient for that consumption of 
oxygen which is requisite in 160 seconds of time, 
if that volume he^ as is apparent, 48 Umes the 
quantity decomposed out of a single respiration, 
no error in the quantity of oxygen Consumed in 
the twentv-four hours, which we have assumed, 
will affect the time of 160 seconds. For there 
being 1 8 X 60 X 24 respirations, and 60 x 60 X 24 
seconds of time in the twenty-four hours, the 48t]i 
part of the first, and the 160th part of the last 
product is equally the 540th part of the whole, 
whatever it may be. 

461. But if the time in which a circuit of the 
blood is performed be, as is most evident, identical 
with the time in which the whole volume of air in 
the lungs is decomposed, and if such period of 
time were, as the old observers have assigned, 150 



6SNXRAL RESULTS. 99 

econds, then it would follow that only 45 times the 
uantity of air decomposed at a breath is present in 
he lungs, amounting to 385^ cubic inches, and that 
he whole blood in the body is 24 ounces less than on 
he supposition of 160 seconds, that is to say, only 
(60 ounces, or 22j^ pounds avoirdupois. Because 
he 45th part of 18 X 60 x 24 is the same as the 
.50th part of 60 x 60 X 24 ; in each it is the 56'7th 
mrt of the whole. 

462. From the whole of these observations 
ind calculations the following general results are 
leduced : — 

1 . The volume of air ordinarily present in the 
ungs is very nearly twelve pints (449). 

2. The volume of air received by the lungs at 
in ordinary inspiration is one pint (422). 

3. The volume of air expelled from the lungs 
it an ordinary expiration is a very little less than 
>ne pint (456). 

4. Of the volume of air received by the lungs 
it one inspiration, only one-fourth part is decom- 
MMed at one action of the heart (447). 

5. The fourth part of the volume of air received 
»y the lungs at one inspiration, and decomposed at 
)ne action of the heart, is so decomposed in the 
ive-sixth parts of one second of time (429.3). 

6. The time in which a circuit of blood is per- 
brmed is identical with the time in which the 
^hole volume of air in the lungs is decomi^^d 
461). 

v2 



100 THE PHILOSOPHY OF HEALTH. 

7. The whole volume of air decomposed in 
twenty-four hours is 221,882 cubic inches, exactly 
540 times the volume of the contents of the lungs; 
160 seconds being also exactly the 540th part of 
the number of seconds in twenty-four hours (450). 

8. The quantity of the blood that flows to the 
lungs to be acted upon by the air at one action of 
the heart is two ounces (425). 

9. This quantity of blood is acted upon by the 
air in the five -sixth parts of one second of time 
(429.3). 

10. One circuit of the blood is performed in 
160 seconds of time. Three circuits are performed 
every eight minutes ; 540 circuits are performed 
in the twenty-four hours (453). 

11. The quantity of blood in the whole body 
of the human adult is 24 pounds avoirdupois, or 
20 pints imperial measure (428). 

12. In the space of twenty-four hours, 57 
hogsheads of air flow to the lungs (429.7). 

13. In the same space of time 24 hogsheads of 
blood are presented in the lungs to this quantity of 
air (424.10). 

14. In the mutual action that takes place 
between these quantities of air and blood, the air 
loses 15,757.9131 grains, or 328i ounces of oxygen, 
and the blood 10 ounces and 116 grains of carbon 
(445). 

15. The blood, while circulating through the 
lungBj permanently retainft «n^ cvm&« \sXs^ ^^ 



GENERAL RESULTS. 101 

ystem — of oxygen, 2,648,809 grams; and of 
zote, 2,267,104 grains (458). 

16 The ultimate results are two : — 

Ist. While the chemical composition of the 
ilood is essentially changed, its weight amidst all 
hese complicated actions is maintained steadily 
he same; for the weight of carhon which is dis- 
harged hy the blood is precisely compensated by 
he united weight of the oxygen and azote which 
t absorbs (459). 

2ndly. The distribution of quantities is uni- 
ersally by proportions or multiples. Thus, of the 
ir inspired, one measure is decomposed and three 
neasures are returned unchanged : of the air de- 
omposed at a single inspiration, there are always 
a store in the lungs precisely forty-eight measures; 
.nd so on in many other cases. The proportions are 
lot arithmetical, but geometrical When we com- 
lare arithmetical quantities with each other, we 
ay that one quantity is by so much greater than 
nother ; when we compare geometrical quantities, 
ve say that one quantity is so many times greater 
han another. From this adoption in the distri- 
mtion of quantities of geometrical proportions it 
esults that whatever be the size of the animal the 
alios remain uniformly the same, and that thus one 
.nd the same law is adapted to the vital agencies 
>f living beings under every possible diversity of 
nagnitude and drcumstance. 

463. Such are the interesting and VmpoTV\i.Ti\. 



102 THE PHILOSOPHY OF HBALTH. 

properties and relations dedncible from the pheno* 
mena of respiration. The disappearance of oxygen 
aod azote from the air inspired, and the replace- 
ment of the oxygen that disappears by the produc- 
tion of carbonic acid, and of the azote by the exha- 
lation of azote, in which, as we have seen, the 
great changes wrought by respiration on the air 
consist, are essentially the same in all animals, 
whatever the medium breathed, and whatever the 
rank of the animal in the scale of organization. 
In all, the proportion of the oxygen of the in- 
spired air is diminished; — in all, carbonic acid gas 
is produced. Comparing, then, the ultimate result 
of the function of respiration in the two great 
classes of living beings, it follows that the plant 
and the animal produce directly opposite changes in 
the chemical constitution of the air. The carbonic 
acid produced by the animal is decomposed by the 
plant, which retains the carbon in its own system 
and returns the oxygen to the air. On the other 
hand, the oxygen evolved by the plant is absorbed 
by the animal, which in its turn exhales carbonic 
acid for the re-absorption of the plant. 

464. Thus the two great classes of organized 
beings renovate the air for each other, and maintain 
it in a state of perpetual purity. The plant, it is 
true, absorbs oxygen during the night as well as 
the animal ; but the quantity which it gives off in 
the day more than compenAa.t«« for that which it 
abatracta in the absence of \\|^\\l. T\»%Vxi\fcxt»SQRi% 



COMPBHSATIKG ACTIONS. 103 

bas been recently established by an extended 
a of experiments instituted by l^rofessoi 
)eney* for the express purpose of inTcstigating 
point. 

i5. From the general tenor of these experi- 
B, it appears that, in fine weather and as long 
e plant is healthy, it adds to the atmosphere 
mount of oxygen not only sufficient to com- 
ate for the quantity it abstracts in the absence 
;ht, but to counterpoise the effects produced 
le respiration of the whole animal kingdom, 
result of one of these experiments will convey 
conception of the amount of oxygen evolved, 
antity of leaves about fifly in number were en- 
d in a jar of air ; the surface of all the leaves 
I together was calculated ut about three 
red square inches; by the action of these 
8 on the carbonic acid introduced into the jar, 
: was added to the air contained in it no less 
twenty-six cubic inches of oxygen. As there 
eason to conclude that the evolution of oxygen, 
e circumstances under which this experiment 
performed, was considerably less than it would 
been in the open air, several plants were in- 
iced into the same jar of air in pretty quick 

>n the Action of Leaves upon Plants, and of Plants 
the Atmosphere, by Charles Daubeney, M.D. F.R.S., 
Bsor of Chemistry and Botany in the University of 
d. Philosophical Transactions of the RoyalSocV^V) (^^ 
m, for the y9%i 1836. Part I. 



104 TBE PHILOSOPHY OF BBALTB. 

succesBion : the amount of oxygen now evolved was 
increased from twenty-one to thirty-nine per cent, 
and prohahly had not even then attained the limit 
to which the increase of this constituent might 
have been brought. From the proportions of the 
constituent elements of carbonic acid gas (442) it 
necessarily follows that, by the mere process of 
decomposition, out of every eleven grains of car- 
bonic acid gas eight grains of oxygen must be 
liberated, three grains of carbon being retained by 
the plant, and consequently that eight grains of 
oxygen must be restored to the atmosphere, less 
only by so much as the plant itself may absorb. 
How great, then, must be the production of oxygen 
by an entire tree under favourable circumstances; 
that is, when animal respiration and animal putre- 
faction present to it an abundant supply of car- 
bonic acid on which to act ! 

466. This influence, says Professor Daubeney,i8 
not exerted exclusively by plants of any particular 
kind or description. I have found it alike in the 
monocotyledonous and dycotyledonous; in such 
as thrive in sunshine and those which prefer the 
shade ; in the aquatic as well as in those of a more 
complicated organization. How low in the scale 
of vegetable life this power extends is not yet ex- 
actly ascertained ; the point at which it stops is 
probably that at which there ceases to be leaves, 

467. From the whole, then, it appears that the 
/unctions of the plant have a %ts\c\. Tfe\«i>i\wi Vi^Oo**fe 



CHANGES PRODUCED UPON THE BLOOD. 105 

;he animal ; that the plant, created to afford 
Bittence to the animal, derives its nutriment 
Q principles which the animal rejects as excre- 
ititious, and that the vegetable and animal 
^oms are so beautifully adjusted, that the very 
itence of the plant depends upon its perpetual 
traction of that, without the removal of which 
existence of the animal could not be maintained. 
68. The changes produced upon the blood 
the action of respiration are no less striking 
. important than those produced upon the air. 
I blood contained in the pulmonary artery, 
ous blood (fig. 140-7. )* is of a purple or mo- 
a red colour : the moment the air transmitted 
the blood by the bronchial tubes comes into 
tact with it, in the rete mirabile (fig. 140-10.), 
\ purple blood is converted into blood of a bright 
rlet colour. Precisely the same change is prov- 
ed upon the blood by its contact with the air out 
he body. If a clot of venous blood be introduced 
» a vessel of air, the clot 8))eedily passes from a 
pie to a scarlet colour ; and if the air contained 
the vessel be analyzed, it is found that a large 
tion of its oxygen has disappeared, and that the 
gen is replaced by a proportionate quantity of 
bonic acid. If the clot be exposed to pure 
gen, this change takes place more rapidly and 
k grater extent ; if to air containing no oxygen, 
change of colour takes place. 
^9. The elemenU of the blood upcm ^Vvi^ ^ 



106 THE PHILOSOPHY OF HSAI.TH. 

portion of the air exerts its action are carbon and 
hydrogen. The oxygen of the air unites with the 
carbon of the blood and forms carbonic acid, and 
this gas is expelled from the system by the actioa 
of expiration. The constituent of the blood which 
affords carbon to the air would appear to be chiefly 
the red particles. The other portion of the oxygea 
of the air unites with the hydrogen which is ex* 
pelled with the carbonic acid in the form of aqueous 
vapour The direct and immediate effect of the 
action of respiration upon the blood is then to 
free it from a quantity of carbon and hydrogen* 

470. Physiologists are not agreed whether the 
union of the oxygen of the air with the carbon d 
the blood takes place in the lungs or in the system. 
Some experimentalists maintain that the oxjgeo 
which disappears from the air, and that which is 
contained in the carbonic acid, are exactly eqni- 
yalent, so that no oxygen can be absorbed. 
According to this view, which has been cleailj 
shown to be incorrect (459), the effect of r^ 
spiration is merely to bum the carbon of the 
blood, just as the oxygen of the air bums wood 
in a common fire, the result of this combustion 
being the generation of carbonic acid, which is 
expelled from the system the moment it is formed. 

471. The theory of Dr. Crawford is essentially 
the same, which supposes that venous blood con- 
taina a j)eculiar compound of carbon and hydrogen, 

termed hydro-ccarbony tbe eVemenVa ol ^\ii<^ \asMt 



AESPIBATORT FUNCTIOM OF THS LIVER. 101 

the lungs with the oxygen of the air, fonning 
iter with the one and carbonic acid with the 
lier. Mr. Cooper, for many years past, has 
aght the same doctrine in his lectures, without 
y knowledge of the fact that Crawford had 
ggested a similar modifi'^ation of bis theory. 
472. It is now established that more oxygen 
lappears than is accounted for by the amount of 
rbonic acid that is generated. The experiments 
Dr. Edwards had already shown this in so deci- 
e a manner that physiologists almost uniyersally 
mitted it as an ascertained fact. The calcula* 
ns of Mr. Finlaison, to whom the opinions of 
ysiologists on this point were unknown, haye 
w determined the precise amount of oxygen 
44 et seq.)y and the probable amount of azote 
59) absorbed. By many physiologists it is sup- 
■ed that the oxygen retained by the lungs, as 
ig as it remains in this organ, enters only into a 
itt of loose combination with the blood ; that in 
Is state of loose combination, it is carried from 
i lungs into the general system ; and that it is 
ly in the system that the union becomes inti- 
ite and complete. According to this yiew, the 
QgB are merely the portal by which the sub- 
mces employed in respiration are receiyed and 
(charged, the essential changes induced taking 
loe in the system. That it is through the lungs 
at the oxygen required by the system ifti^xiwi^^^ 
sn opinion fovokded on ezpeTinieTvt!^ no \t%% 



108 THE PHILOSOPHT OF HBAI.TH, 

exact than decisiye ; it is in accordance with the 
most probable theory of the production and dis- 
tribution of animal heat (chap, ix.) ; and the pre- 
ponderance of evidence in its favour is so great that, 
in the present state of oiu* knowledge, it may be con- 
sidered as established ; but it will appear hereafter 
that the lungs are by no means passive in the pro- 
cess, and that, physiologically considered, they as 
truly constitute a gland secreting carbonic acid gas 
as the liver is a gland secreting bile. 

473. Such are the main facts which have been 
ascertained relative to respiration, as far as this 
function is performed by the lungs. But the Uver 
is a respiratory organ as well as the lungs. It de- 
carbonizes the blood. It carries on this process 
to such an extent, that some physiologists are of 
opinion that the liver is the chief organ by which 
the decarbonization of the blood is effected. The 
following considerations show that whatever be die 
relative amount of its action, the liver powerfully 
co-operates with the lungs in the performance of a 
respiratory function. 

1. The liver, like the lungs, is a receptacle of ve- 
nous blood; blood loaded with carbon. The 
great venous trunk which ramifies through the 
lungs is the pulmonary artery, containing all the 
blood which has finished its circuit through the 
system. The great venous trunk which ramifies 
through the liver is the vena portse^ containing all 
the blood which has finished it& c\ie\)i\.V\iTo\x^^tt 



IBSPI&ATORT FUNCTION OF THB LIVER. 109 

atus of digestion. The liver is a secreting 

Ly distinguished from every other secreting 

1 by elaborating its peculiar secretion from 

as blood. Carbon is abstracted from the 

lus blood that flows through the lungs in the 

1 of carbonic acid ; carbon is abstracted from 

venous blood that flows through the liver in the 

m of bile. 

2. All aliment, but more especially vegetable food, 
ntains a large portion of carbon, more it would 

^»pear than the lungs can evolve. The excess is se- 
reted from the blood by the liver, in the form of 
eiin, colouring matter, fatty matter, mucus, and 
the princii)al constituents of the bile. All these 
substances contain a hirge proportion of carbon. 
After accomplishing certain secondary purposes in 
the process of digestion, these biliary matters, 
loaded with carbon, are carried out of the system 
together with the non-nutrient portion of the ali- 
ment. In the decarbonizing process performed 
by the lungs and the liver, the chief diflt;rence 
would seem, then, to be in the mode in which the 
carbon that is separated is carried out of the system. 
In the lungs it is evolved, as has been stated, in 
union with oxygen in the form of carbonic acid ; 
m the liver, in union with hydrogen in the form 
of resin and fatty matter. 

3. Accordingly, in tracing the organization of 
the animal body from the commencem^xiX ^i \2cv( 



110 THB PBILOSOPHT OF HaAX^TB. 

scale, it is found that among tiie distinct vdA 
special organs that are formed, the liver is one of 
the very first. It would appear to be constructed 
as soon as the economy of the animal requires a 
higher degree of respiration than can be effected 
by the nearly homogeneous substance of whidi, 
Tery low down in the scale, the body is com- 
posed. 1 11 variably through the whole animal series, 
the magnitude of the liver is in the inverse rido 
to that of the lungs. The larger, the more perfectly 
developed the lu^gs, the smaller the liver ; and con- 
versely, the lai^er the liver tbe smaller and the leis 
perfectly developed the lungs. This is so unifoim 
that it may be considered as a law of the animal 
economy. In the highly organized warm-blooded 
animal, with its large lungs, divided into numeroua 
lobes, and each lobe composed of minute vesiclei 
respiring only air, the magnitude of the liver com- 
pared with that of the body is small. In the less 
bighly organized animal of the same class, with 
its smaller and less perfectly developed lung, res- 
piring partly air and partly water, the liver in- 
creases as the lung diminishes in size. In the 
reptile with its little vesicular lung, divided into 
large cells, the liver is pi^oportionally of greater 
magnitude. In the fish which has no lung, but 
which respires by the less highly organized gill, 
and only in the medium of water, the proportionate 
size of the liver is still greater ; but in the moUus- 



RESPIRATORY FUNCTIOM OF THB UYER. Ill 

cooB animal, in which the lung or the gill is still 
leia perfectly developed, the hulk of the liver is 
prodigious. 

4. In all animals the quantity of venous hlood 
which is sent to the liver increases, as that trans- 
mitted to the lung diminishes. In the higher 
animal the great venous trunk which ramifies 
through the liver (the vena pOTtse) is formed hy 
the veins of the stomach, intestines, spleen, and 
pancreas, which are the only organs that transmit 
their hlood to the liver. In the reptile, besides all 
these organs, the hind legs, the pelvis, the tail, the 
intercostal veins forming the venaazygos and in some 
orders of this class, even the kidneys also send 
their blood to the liver ; but in the fish, in addition 
to all the preceding organs, the apparatus of re- 
production likewise transmits its blood to the liver. 
The very formation of the venous system in the 
dififerent classes of animals seems thus to point to 
the liver as a compensating and supplementary 
organ to the lung. 

5. The permanent organs in the lower animal 
are a type of the transitory forms through which 
the organs of the higher animal pass in the pro- 
gress of their growth. Thus the liver of the 
human foetus is of such a disproportionate size, as 
to approximate it closely to that of the fish or of 
the reptile. After the birth of the human embryo^ 
respiration is effected in part by the lutv^-, VroXXs^- 
fyre birth the hmg is inactive, no avt TWk.c)n^%\X\ 



y 



112 



THE PHILOSOPHY OF HEALTH. 



it contributes nothing to respiration; the de 
bonizing action of the blood is accomplished, 
by the lung, but by the liver ; hence the prodig 
bulk of the foetal liver and its activity in the b( 
tion of bile, and especially towards the L 
months of pregnancy, when all the organs 
greatly advanced in size and completeness. 

6. Pathology confirms the evidence derived i 
comparative anatomy and physiology. Whei 
function of the lung is interrupted by disease, 
activity of the liver is increased. In inflammi 
of the lung (pneumonia) ; in the depositio: 
adventitious matter in the lung (tubercles)^ 
which the air vesicles are compressed and ob 
rated, the lung loses the power of decarboni 
the blood in proportion to the extent and sevi 
of the disease with which it is affected. In 
case the secretion of bile is increased. In dise 
of the heart the liver is enlarged. In the mo 
caeruleus (516) the liver retains through life 
foetal state of disproportion. 

7» In the last place, there is a striking illui 
tion of the respiratory action of the liver, in 
vicarious office which it performs for the I 
during the heat of summer in cold, and all 
year round in hot climates. In the heat of s 
mer, and more especially in the intense and cons 
heat of a warm climate, in consequence of the 
refaction of the air, respiration by the lung is 
active and efficient than m t\vfe mtk^Kt ^\V^ 



USB8 OF RBSPIBATIOK. 1 13 

climate. During the exposure of the hody to this 
long-contmued heat, there is a tendency to the ac- 
cumulation of carbon in the blood. An actual ac- 
cumulation is prevented, by an increased activity 
in the secretion of bile, to which the liver is sti- 
mulated by the heat. In order to obtain the ma- 
terial for the formation of this unusual quantity of 
bile, it abstracts carbon largely from the blood ; 
to this extent it compensates for the diminished 
efficiency of the lung, and thus removes through 
the vena portse that superfluous carbon which 
would otherwise have been excreted through the 
pulmonary artery. 

474. Taking life in its most extended sense, 
as comprehending both the circles it includes, the 
organic and the animal (vol. i. chap. 2), it may be 
said to have three great centres, of which two re- 
late to the organic, and the third to the animal 
life (vol. i. chap. 2). The two centres which relate 
to the organic life are the systems of respiration 
and circulation ; the third, which relates to the 
animal life, is the nervous system. Of the organic 
life, the lungs and the heart are the primary 
seats ; of the animal, the brain and the spinal 
cord. Between each the bond of union is so 
close, that any lesion of the one influences the 
other, and neither can exist without the support 
of all. They form a triple chain, the breaking of 
a single link of which destroys the whole. 

475. But of these three great ceiiXie^ qI \\l^^ 



114 THE PHILOSOPHY OF HEALTH. 

upon which all the other vital phenomena depend, 
the most essential is respiration ; hence, to con* 
sider the relation of this function to the others, ii 
to take the most comprehensive view of the uses 
which respiration serves in the economy. 

416. The first and most important use of the 

function of respiration is to maintain the action of 

the organs of the animal life. It has been shown 

(vol. i. chap. 2) that the organic is subservient to 

the animal life, and that to build up the apparatus 

of the latter, and to maintain it in a condition fit 

for performing its functions, is the final end of the 

former. The direct and the immediate efiect of 

the suspension of respiration is the abolition of 

both functions of the animal life — sensation and 

voluntary motion. If a ligature be placed around 

the trachea of a living animal so as completely to 

exclude all access of air to the lungs, and if the 

carotid artery be then opened, and the blood 

allowed to How, the bright scarlet-coloured blood 

contained in the artery is observed gradually to 

change to a purple hue. The exact point of time 

at which this change begins may be noted. It 

is seen to assume a darker tinge at the end of half 

a minute ; at the end of one minute its colour is 

still darker, and at the end of one minute and a 

half, or at most two minutes (426), it is no longer 

possible to distinguish it from venous blood. As 

Boon as this change of colour begins to be visible 

the animal becomes uneasy \ \iia %.^\X».^<aiiVcL<ct&vu»^ 



USB8 OF EBSn&ATION. 115 

•8 the colour deepens ; and when it becomes com'' 
pletely dark, that instant the animal falls down 
insensible. If in this state of insensibility air be 
readmitted to the lungs, the dark colour of the blood 
rapidly changes to a bright scarlet, and instantly 
sensation and consciousness return. But if, on the 
contrary, the exclusion of the air be continued for 
the space of three minutes from the 6rst closing of 
the trachea, the animal not only remains to all ap- 
pearance dead, but in general no means are 
capable of recovering him from the state of insen- 
sibility ; and if the exclusion of the air be pro- 
tracted to four minutes, apparent passes into real 
death, and recovery is no longer possible. It 
follows that one of the conditions essential to the 
exercise of the function of the brain is, that this 
organ receive a due supply of arterial blood. 

471. The second use of the function of respi- 
ration is to afford blood capable of maintaining 
the muscles in a condition fit for the performance 
of their peculiar office, that of contractility. The 
closure of the trachea not only abolishes sensation, 
but the power of voluntary motion : sensation 
and motion are lost at once : on the re -admission 
of air to the lungs, both functions are regained at 
once : it follows that the process of respiration is 
as essential to the action of the muscle as to that 
of the brain. **By arterial blood," says Young, 
" the muscles are furnished with a stote o^ \.\n».\. 
unknown principle hy whicli they ait iciAct^ 



1 16 THE PHILOSOPHY OF HEALTH. 

capable of contracting." ^ The oxygen absorbed 
by the blood," says Spalanzani, ^* unites with the 
muscular fibres and endows them with their coa- 
tractility.'* It is more correct to say, respiratioii 
takes carbon from the blood and gives it oxygen, 
and by this means endows the blood with the 
power of maintaining the contractility of the 
muscular fibre. 

478. But respiration is as essential to the 
action of the organs of the organic life as to those 
of the animal. In a short time after the respi- 
ration ceases ; the circulation stops. When the 
blood is no longer changed in the lungs, it soon 
loses all power of motion in the system ; because 
venous blood paralyses the muscular fibres of the 
heart as of the arm. When the left ventricle of 
the heart sends out venous blood to the system, it 
propels it into its own nutrient arteries, as well as 
into the other arteries of the body ; into the coro- 
nary arteries^ as well as into the other branches of 
the aorta; the heart loses its contractility, for 
the same reason as every muscle under the like 
privation ; because venous instead of arterial blood 
flows in its nutrient arteries ; and the circulation 
stops when the heart is no longer contractile, 
because the engine is destroyed that works the 
current. 

479. Venous blood consists of chyle, the nutri- 
tive fluid formed from the aliment ; of lymph, a 

£uid composed of organic paTl\c\t^ v\i\c\i\».V\si% 



USES OF ME8PIRATI0N. 117 

ormed an actual part of the solid Btnicturea 

jody, are now returning to the lungs to 

i higher elaboration ; and of blood which, 

completed its circuit through the system, 

;re given off its nutrient and received excre- 

lOUB matter, is now returning to the lungs 

luration and renovation. These commingled 

on parting in the lungs with carbonic acid 

^ater, and on receiving in return oxygen and 

, are converted into arterial blood ; that it, 

i more coagulable than venous, and richer in 

men, fibrin, and red particles, the proximate 

.nic principles of all animal structures. The 

. and pure stream thus formed is sent out to 

various tissues and organs, from which, as it 

¥B to them, they abstract the materials adapted 

their own peculiar form, composition, and vital 

lowments. By the reception of these materials 

organs are rendered capable of performing the 

il actions which it is their office to accomplish. 

d thus the processes of digestion, absorption, 

retion, nutrition, formation, reproduction, all the 

cesses included in the great organic circle, no 

( than muscular action and nervous energy, de- 

id on receiving a due supply of arterial blood. 

these actions, like the faculties of the animal 

, cease totally and for ever in a few minutes after 

formation of this vital fluid has been stopped 

the suspension of respiration. 

\80. In the last place, the deput^liTk^ ^\^^t 



1 18 THE PHILOSOPHY OF HEALTH. 

effected by respiration is necessary to prevent tbe 
decomposition of the blood, and eventually that of 
the body. The first step in the spontaneous de- 
composition of animal matter consista in the km 
of a portion of its carbon, which, uniting with the 
oxygen of the atmosphere, forma carbonic add; 
precisely the same thing that takea place in thn 
process of respiration. The bodies of all auimali, 
of worms, insects, fishes, birds, and mammalia, de- 
oxidate the air and load it with carbonic acid ate 
death, some of them nearly as much as during Hft; 
and this before any visible marks of decompositioD 
can be traced. It is probable that the came 
which more immediately operates in preventiiig 
the decomposition of the body is the abstraction 
of a part of the carbon of the blood ; that were 
these carbonaceous particles allowed to accumulate, 
they would produce a tendency to decomposition, 
which would terminate in complete disorganization; 
and consequently, that one main object of the 
process of respiration is to afford blood not only 
capable of nourishing and sustaining the organs, 
but of maintaining their integrity, by removing 
noxious matter, the presence of which would sub- 
vert their composition and lead to their entire 
decomposition. 

481. The ultimate object of respiration, then, 

is to prepare and to preserve in a state of purity a 

fluid capable of affording to all the parts of the 

body the materials necessary to TCi^w\:K!L\i "Csl^m 



USES OF RB8PIRATI0N. 119 

;ndowinent8. By the exhalation of oxygen 

^ater, and the absorption of carbon, under 

igency of light, the plant elaborates such 

id from its nutritive sap, and out of this 

3rated sap forms temiary combinations, the 

nic elements of all Tegetable solids. By 

absorption of oxygen and azote, and the ex- 

ation of carbonic acid and water, probably 

ier the influence of electricity, conducted and 

plated by the nervous system, the animal 

sborates such a fluid from its aliment, and 

It of this elaborated fluid forms quaternary 

ombinations, albumen, and fibrin, the organic 

elements of all animal solids. 



CHAPTER IX. 

Of the temperature of living bodies — ^Temperature of 
plants — Power of plants to resist cold and endure heat— 
Power of generating heat — ^Temperature of animals- 
Warm-blooded and cold-blooded animals— Temperatme 
of the higher animals — Temperature of the diibmit 
parts of the animal body — ^Temperature of the human 
body — Power of maintaining that temperature at a fixed 
point whether in intense cold or intense heat — ^Experi- 
ments which prove that this power is a vital powei^— 
Evidence that the power of generating heat is connected 
with the function of respiration — Analogy betweci 
respiration and combustion — Phenomena conne^ed with 
the functions of the animal body, which prove that its 
power of generating heat is proportionate to the extent 
of its respiration — Theory of the production of animal 
heat — Influence of the nervous system in maintaining 
and regulating the process — Means by which cold is 
generated, and the temperature of the body kept at its 
own natural standard during exposure to an elevated 
temperature. 

482. Closely connected with the function of 
respiration, is the power which all living beings 
possess of resisting within a certain range the 
influence of external temperature. The plant is 
warmer than the surrounditv^ %.vt Vck mtLter^ and 
colder in summer. A theTmomeXet ^^^Aftdi^x^CuL 



TEMPERATURE OF PLANTS. 121 

)ottoin of a hole bored into the centre of a living 
ree, precaution being taken to keep o£f as much 
IS possible all external influence either of heat 
)r cold, does not rise and fall according to the 
changes of external temperature ; but rises when 
he external air is cold, and falls when it is 
varm. Thus, in a cold day in spring, the wind 
)eing north, at six o'clock in the evening, the teni- 
lerature of the external air being 47°, that of a 
ree was 55°. On another cold day in the same 
Donth, there being snow and hail, and the wind in 
he north-east, at six o'clock in the evening, the 
iztemal temperature being 39°, that of the tree 
ma 45°. On the contrary, in one experiment, 
rhen the temperature of the air was 57^°, that of 
he tree was only 55°; and when the temperature 
•f the air was 62°, that of the tree was 56°. 

483. These experiments afford an explanation 
f circumstances familiar to common observation. 
ilvery one has noticed that the snow which falls 
n grass and trees melts rapidly, while that on 
be adjoining gravel walks often remains a long 
ime unthawed. Moist dead sticks are constantly 
)und frozen hard in the same garden with tender 
rowing twigs, which are not in the least degree 
fleeted by the frost. Every winter in our own 
limate tender herbaceous plants resist degrees of 
old which freeze large bodies of water. 

484. But the colder, and the waTiaev V\ie cXv 
mte, the more strikingly does the plant eisjMXV^vi^ 

VOL, I J, Q 



122 THE PHILOSOPHY OF HEALTH. 

the power with which it is endowed of reeistiDg 
external temperature. In the northern parts of 
America the temperature is often 50^ below zero; 
yet, though exposed to this intense degree of cold, 
the spruce fir, the birch, the juniper, &c. presenre 
their vitality uninjured. From numerous experi- 
ments which have been performed expressly with 
a view to ascertain this point, it is found that a 
plant which has been once frozen is invariably 
dead when thawed. It is also proved by direct 
experiment, that if the sap be removed from its 
proper vessels, it freezes at 32^, the ordinary 
freezing point. In the northern parts of America, 
then, the plant must preserve in its living vessels 
its sap from freezing, when exposed to a tempera- 
ture of 50^ below zero ; which sap out of these 
vessels would congeal at the ordinary freezing 
point ; that is, the plant of this climate is endowed 
with the power of resisting a degree of cold ranging 
from the ordinary freezing point to 50^ below zero ; 
a property which can be referred only to a vital 
power, by the operation of which the plant gene- 
rates within itself a degree of heat sufficient to 
counteract the external cold. 

485. The opposite faculty of resisting the in- 
fluence of external heat is exemplified by the 
trees and shrubs of tropical climates, often sur- 
rounded by a temperature of 104°, which they resist 
ju8t as the plant of the ivoTlheTTi clime resists the 
intense degrees of cold, to -w^iVcV \\.Sa «x^«w^. 



TKMPSRATVBX OF ANIlfALS. 123 

486. That the plant is endowed with the power 
of generating heat is demonstrated hy the phe- 
nomena which attend the performance of some of 
its vital processes, such as those of germination 
and flowering. During the germination of harley, 
the thermometer was observed to rise in the course 
of one night to 102°. The bulb of a thermometer 
applied to the surface of the spadix of an arum 
maculatum, indicated a temperature V higher 
than that of the external air; but in an arum 
cordifolium, at the Isle of France, a thermometer 
placed in the centre of five spadixes stood at 111°; 
and in the centre of twelve at 121°, though the 
temperature of the external air was only 66°. 

487. Animals indicate in a still more striking 
degree the power of generating heat. The lower 
tlie animal in the scale of organization, indeed, 
the nearer it approaches to the plant in the com- 
parative feebleness of this function. The heat of 
worms, insects, Crustacea, mollusca, jfishes, and 
amphibia, is commonly only two or three degrees 
above that of the medium in which they are im- 
mersed. Absolutely colder than the higher animals, 
they are at the same time incapable of resisting 
any considerable changes in the temperature of the 
surrounding medium, whether from heat to cold' 
or from cold to heat. The higher animals, on the 
contrary, maintain their heat steadily at a fixed 
point, or very nearly at a fixed point, Yio^CiN^x^'t 
temperature of the surrounding inediwTCL t$\»:^ 



124 THE PHILOSOPHY OF HEALTH. 

change. Hence animals are divided into two great 
classes, the cold-hlooded and the warm-blooded. 
The temperature of the cold-blooded is lower than 
that of the warm-blooded, and it varies with the 
heat of the surrounding medium ; the temperature 
of the warm-blooded is higher than that of the 
cold-blooded, and it remains nearly at the same 
fixed point, however the heat of the surrounding 
medium may change. 

488. The temperature natural to the higher 
animals differs somewhat according to their class. 
The temperature of the bird is the highest, and is 
pretty uniformly about 103° or 104°; that of the 
mammiferous quadruped is 100 or lOP; that of 
the human species is 97** or 98**. 

489. The temperature of the animal body is 
not precisely the same in every part of it. The 
ball of the thermometer introduced within the 
rectum of the dog stood at 100^ ; within the 
substance of the liver at 1 00| ; within the right 
ventricle of the heart at 101", and within the 
cavity of the stomach at 101^ In the brain of 
the lamb it stood at 104° ; in the rectum at 105°; 
in the right ventricle of the heart, and in the 
substance of the liver and of the lungs, at 106° ; 
Imd in the left ventricle of the heart at 101°. 

490. The temperature natural to the human 
body is 98^ When the human body is surrounded 
bjran atmosphere at the temperature of 30**, it must 

iave its heat rapidly extracted b^ t\i^ ^^^\ci^\\iTC!L\ 



POWBR OF RESISTING HE4T. 125 

yet the temperature of the hody, however long It 
remain exposed to such a degree of cold, does not 
sink, hut keeps steadily at its own standard. But 
animals which inhabit the polar regions are often 
exposed to a cold 40** below zero. The tempera- 
ture of Melville Island is so low during five 
months of the year that mercury congeals, and 
tlie temperature is sometimes 46** below zero; 
vet the musk oxen, the rein deer, the white hares, 
the polar foxes, and the white bears which abound 
in it maintain their temperature steadily at their 
own natural standard. 

491. The power which the higher animal pos- 
sesses of resisting heat is still more remarkable 
than its power of resisting cold. On taking rabbits 
and guinea-pigs from the temperature of 50**, and 
introducing them very rapidly to the temperature 
3f 90®; it was found that the animals acquired 
mly two or three degrees of heat. How different 
the result when the cold-blooded animal is sub« 
jected to the same experiment ! The temperature 
of the surrounding air being 45°, a thermometer 
introduced into the stomach of a frog rose to 49°. 
rhe frog being then put into an atmosphere made 
nrarm by heated water, and allowed to stay there 
;wenty minutes, the thermometer on being now 
ntroduced into the stomach rose to 64*'. 

492. But the human body may be actually 
placed in a temperature of 60** above that of bo\l\w^ 
rater, not only without BvatQimn^ the a\\g\v\j&^\. W 



126 THE PHILOSOPHY OF HEALTH. 

jury, but without having its own temperature raised 
excepting by two or three degrees. The attention 
of physiologists was first directed to this curiom 
fact by some remarkable circumstances related by 
the servants of a baker at Rochefbucault, who were 
in the habit of going into the heated ovens in order 
to prepare them for the reception of the loaves. In 
performing this service, the young women were 
sometimes exposed to a temperature as high as 278". 
It was stated that they could endure this interne 
heat for twelve minutes^ without any materisl 
inconvenience, provided they were careful not to 
touch the surface of the oven. Subsequently Drs. 
Fordyoe, Blagden, and others, with a view to as- 
certain the exact facts, entered a chamber, heated 
to a temperature much above that of boiling water, 
and some of the phenomena observed during these 
experiments are highly curious. 

493. In the first room entered by these experi- 
mentalists, the highest thermometer varied firom 
132** to 130°; the lowest stood at 119**. Dr. 
Fordyce having undressed in an adjoining cold 
chamber, went into the heat of 119**; in half a 
minute the water poured down in streams over his 
whole body, so as to keep that part of the floor 
where he stood constantly wet. Having remained 
here fifteen minutes, he went into the heat of 
130° ; at this time the heat of his body was 100**, 
and his pulse beat 126 times in a minute. While 
Dr. Fordjce stood in t\n& i^XmaXaqiix ^ ^^oic^sGOt. 



rOWSE OF KKSISTIKO HKAT. 127 

flask was brcn^ht in by his order, filled with water 
heated to 100% and a dry cloth with which he 
wiped the 8ur£u» of the flask qnite dry ; but it 
immediately became wet again, and streams of 
water pomred down its sides, which continued till 
the heat of the water within had risen to 122^, 
when Dr. Fordyoe went out of the room, after 
having remained fifteen minutes in a heat of 130^ : 
just before he left the room his pulse made 129 
beats in a minute ; but the heat under his tongue 
and in his hand did not exceed lOO"". 

494. In a subsequent experiment the chamber 
was entered when the thermometer stood above 
21 P. The air heated to this degree, says Dr. 
Blagden, felt unpleasantly hot; but was very 
bearable. Our most nneasy feeling was a sense 
of scorching in the face and legs; our legs par- 
ticularly sujflfered very much, by being exposed 
more fully than any other part to the body of the 
stove, heated red hot by the fire within. Our re- 
spiration was not at all a£fected ; it became neither 
quick nor laborious; the only difference was a 
want of that refreshing sensation which accom- 
panies a full inspiration of cool air. But the most 
striking effects proceeded from our power of pre- 
serving our natural temperature. Being now in a 
situation in which our bodies bore a very different 
relation to the surrounding atmosphere from that 
to which we had been accustomed, every moment 
pKBented a new phenomenon. "WYiexiesw '^^ 



128 THE PHILOSOPHY OF HEALTH. 

breathed on a thennometer, the quicksilver sank 
several d^rees. Every expiration, particularly if 
made with any degree of violence, gave a very 
pleasant impression of coolness to our nostrils, 
scorched before by the hot air rushing against 
them whenever we inspired. In the same manner 
our now cold breath agreeably cooled our fingers 
whenever it reached them. Upon touching my 
side, it felt cold like a corpse ; and yet the actual 
heat of my body, tried under my tongue, and by 
applying closely the thermometer to my skin, was 
98**, about a degree higher than its ordinary tem- 
perature. When the heat of the air b^an to 
approach the highest degree which this apparatus 
was capable of producing, our bodies in the room 
prevented it from rising any higher ; and when it 
had been previously raised above that point, inva- 
riably sunk it. Every experiment furnished proofs 
of this. Mr. Banks and Dr. Solander each found 
that his single body was sufficient to sink the 
quicksilver very fast, when the room was brought 
nearly to its maximum of heat. 

495. in a third series of experiments the tern* 
perature of the chamber was raised to the 260th 
degree. At this time, continues Dr. Blagden, 1 
went into the room, with the addition to my com- 
mon clothes of a pair of thick worsted stockings 
drawn over my shoes, and reaching some way 
above my knees. I also put on a pair of gloves, 
and held & cioth constantV^ 'bel^^u xk^ Id^c^ «3\d 



POWEE OF RXSI8TIMG HBAT. 129 

the BtOTe (necessary precautions against the scorch- 
ing of the red-hot iron). I remained eight minutes 
in this situation^ frequently walking ahout to all 
the different parts of the room, hut standing still 
most of the time in the coolest spot near the lowest 
Uiermometer. The air felt very hot, hut hy no 
means so as to give pain. I had nodouht of heing 
ahle to hear a much greater heat ; and all who 
went into the room were of the same opinion. I 
sweated, hut not very profusely. For seven minutes 
my breathing remained perfectly good ; but after 
that time, I began to feel an oppression in my 
lungs, attended with a sense of anxiety; which 
gradually increasing for the space of a minute, I 
thought it most prudent to end the experiment. 
My pulse, counted as soon as I came into the cool 
air, for the uneasy feeling rendered me incapable 
of examining it in the room, beat at the rate of 
144 pulsations in a minute, which is more than 
double its ordinary quickness. In the course of 
this experiment, and others of the same kind by 
several of the gentlemen present, some circum- 
stances occurred to us which had not been re* 
marked before. The heat, as might have been 
expected, felt most intense when we were in 
motion; and on the same principle, a blast of 
the heated air from a pair of bellows was scarcely 
to be borne: the sensation in both these cases 
exactly resembled that felt in our nostrils on in- 
epiratioB, It was observed that o\ii \>ie.«L\)[v ^\^ 



130 THE PHILOSOPHY OF HEALTH. 

not feel cool to our fingers unless held very near 
the mouth ; at a distance the cooling power of the 
hreath did not sufficiently compensate the effect 
of putting the air in motion, especially when we 
breathed with force. 

496. On going undressed into the room, the 
impression of the air was much more disagreeable 
than before ; but in five or six minutes, a profuse 
sweat broke out, which instantly relieved me. 
During all the experiments of this day, whenever 
I tried the heat of my body, the thermometer 
always came very nearly to the same point (the 
ordinary standard), not even one d^ree of differ- 
ence, as in our former experiments. 

497. To prove that there was no fallacy in the 
degree of heat shown by the thermometer, but 
that the air which we breathed was capable of 
producing all the well-known effects of such heat 
on inanimate matter, we put some eggs and a beef 
steak upon a tin frame, placed near the standard 
thermometer, and farther distant from the stove 
than the wall. In about thirty minutes the e^ 
were taken out roasted quite hard. In about 
forty-seven minutes the steak was not only dressed, 
but almost dry. Another beef steak was rather 
overdone in thirty-three minutes. In the evening 
when the heat was still greater, we blew upon a 
third steak with the bellows, which produced a 
visible change on its surface, and hastened its 



OWEX. OF RESISTING HEAT AND COLD. 131 

ng; the greatest part of it was pretty well 
in thirteen minutes. 

8. The human hody» then, may he exposed to 
aperature 50® below zero, without having its 
heat appreciably diminished ; it may be ex- 
id to a temperature 60** above that of boiling 
,er, without having its own heat increased he- 
ld two or three degrees; or, as appears from 
periments subsequently performed expressly to 
certain this point, from three to five degrees. 
1 the former case, the body must generate a 
egree of heat sufficient to compensate the great 
quantity of caloric which is every moment ab- 
stracted from it by the intensely-cold surrounding 
medium. In the latter case it must generate a 
degree of cold sufficient to counteract the great 
quantity of caloric which is every moment com- 
municated to it by the intensely-hot surrounding 
medium. 

499. Powers so wonderful and so opposite ap- 
peared to the physiologists of former times to be 
involved in such profound mystery, that they did 
Dot even attempt to investigate their nature, or 
trace their mode of operation ; but satisfied them- 
selves with referring them to some innate quality 
of the body, and with considering them as essential 
ittributes of life. And difficulties connected with 
the subject still remain, which the present state of 
knowledge does not permit us wholly to «uimQMTkti\ 



132 THE PHILOSOPHY OF HEALTH. 

but wc are able at least to refer these powers to 
their proper seat, and to trace some steps of tbe 
processes by which they produce results so won- 
derful and beautiful. 

500. It is certain that whatever be the ultimate 
physical processes by which the generation of heat 
and the production of cold are effected in the 
animal body, the phenomena are dependent on the 
condition of life. No such phenomena take place 
excepting in living bodies. This is illustrated in a 
striking manner by a series of experiments per- 
formed by Mr. Hunter. A part of the living 
human body was immersed in water gradually 
made warmer and warmer from lOO"" to 11 ST; 
precisely the same part of the body, dead, was im* 
mersed in the same water, and both parts, the 
living and the dead, were continued in this heat 
for some minutes. The dead part raised the ther- 
mometer to 114°; the living part raised it to no 
higher than 102^°. On applying the thermometer 
to the sides of the living part, the quicksilver im- 
mediately fell from 118® to 104**; on applying it 
close to the dead part, the thermometer did not 
fall above a single degree ; the living part acta* 
ally produced a cold space of water around it 
Hence in bathing in water, whether colder or 
warmer than the heat of the body, the water coon 
acquires the same temperature with that of the 
body; and, consequently, in a large bath the 
patient should move from pVae^ v.o ^^dic,^, ^\A\!& ^ 



I 



A VITAL FOWBR. 133 

small one there should be a constant succession 
of water of the intended heat. 

501. A fresh, that is, a living egg was put into 
cold water at about zero, frozen, and then allowed 
to thaw. By this process its vitality was destroyed, 
and consequently its power of resisting cold and 
heat lost. This thawed egg was next put into a 
cold mixture with an egg newly laid : the time 
required for freezing the fresh egg was seven mi- 
nutes and a half longer than that required for 
freezing the thawed egg. 

502. A new-laid egg was put into a cold atmo- 
sphere fluctuating between 17° and IS""; it took 
about half an hour to freeze ; but when thawed 
and put into an atmosphere at 25** (10® warmer), 
it froze in half the time. 

503. A fresh egg and one that had been frozen 
and thawed were put into a cold mixture at 15°; 
the thawed one soon came to 32**, and began to 
swell and congeal ; the fresh one sunk to 29^, and 
in twenty-five minutes after the dead one, it rose 
to 32®, and began to swell and freeze. 

504. The result of this experiment upon the 
fresh egg was similar to that of analogous experi- 
ments made upon the frog, eel, snail, &c. where life 
allowed the heat to be diminished 2° or 3*" below 
the freezing point, and then resisted all further 
decrease ; but the powers of life having been ex- 
pended by this exertion, the parts then froze like 
AfTf other dead animal matter* 



134 THE PHILOSOPHY OF HEALTH. 

505. The heat of the bird is increased some- 
what when it is prepared for incubation. Some 
c^gs were taken from under a sitting hen whose 
temperature was 104°, at the time when the chick 
was about three-parts formed. A hole was broken 
in the shell and the bulb of a thermometer intro- 
duced ; the quicksilver rose to 99^"*; but in some 
eggs that were addled it was proved that their heat 
was not so high by two degrees, so that the life of 
the living egg assisted to support its own temper* 
ature. 

506. These facts sufficiently show the depen- 
dence of the faculty of generating heat and of 
producing cold on the powers of life. But the 
processes by which, under the agency and control 
of the vital powers, these different results are 
effected, are various, and even opposite. 

507. The power of generating heat is con* 
nected in the closest manner with the function of 
respiration, and is directly dependent upon it. 
The evidence of this is indubitable. For — 

508. i. Respiration is combustion, and, like 
ordinary combustion, is attended with the produc- 
tion of heat. In ordinary combustion oxygen 
disappears, and a new compound is formed, con- 
sisting of oxygen combined with the combustible 
matter; that is, an oxidized body is generated. 
On burning a piece of iron wire in oxygen, the 
DXj^en disappears, and the iron increases in 

weight The oxygen combm^ft V\\\i >\v^ \ssR^ 



RESPIRATION AND COMBUSTION. 135 

forming a new product, oxide of iron, and the 
weight of this new substance is found on exami- 
nation to be exactly equal to the weight of the 
wire originally employed, added to the quantity of 
oxygen which has disappeared. 

509. It is precisely the same in respiration. 
In this process oxygen combines with combustible 
matter, carbon : the oxygen disappears, and a new 
body, carbonic acid, is generated. 

510. ii. One phenomenon which invariably 
Etccompanies the combination of oxygen with com- 
bustible matter is the extrication of heat. When- 
sver a substance passes from a rarer into a denser 
state ; when, for example, a gas is converted into 
I liquid or solid, or when a liquid solidifies, heat 
s evolved; because, according to the ordinary 
heory of combustion, the denser substance has a 
ess capacity for caloric than the rarer, and con- 
lequently in passing from a rare into a dense state, 
I quantity of caloric previously combined or latent 
rithin it is set free. The combined or latent 
aloric contained in a body is termed its specific 
aloric ; the caloric which is evolved on its change 
f state is named free or sensible caloric. 

511. The combination of oxygen with carbon, 
s in the combination of oxygen with combustible 
latter in every other instance, must be attended 
rith the evolution of heat. Though the product of 
he combustion, in the present case, be a ga«eow% 
jtfy; carbonic acid, atUl, according to t\ie OT^iiacrj 



136 THE PHILOSOPHY OF HEALTH. 

theory of combustion, carbonic acid has less spe- 
cific caloric, or less capacity for caloric, than 
oxygen ; and therefore in combining with carbon, 
a portion of its specific caloric becomes free or 
sensible, that is, heat is evolved. But whatever 
theory of combustion be adopted, the fact is cer- 
tain, that whenever oxygen combines with carbon 
to form carbonic acid, heat is evolved; not only in 
the rapid union which takes place in ordinary cont- 
bustion, but also in the slow combination which 
occurs in fermentation, putrefaction, and germi* 
nation ; in the latter of which processes, as in the 
malting of barley, the temperature rises as high as 
10°. The union of oxygen with carbon in the lungs 
during respiration must therefore necessarily pro- 
duce heat, just as it does in a charcoal fire, or in 
any other natural process in which this combina- 
tion takes place. 

512. iii. Numerous phenomena connected with 
the animal body show that its temperature is in 
strict proportion to the quantity of oxygen which 
is consumed in respiration, and to the quantity of 
carbonic acid which is formed by the union of 
oxygen and carbon during the process. 

513. In all animals whose respiratory organs 
are so constructed, that the consumption of oxygen 
and the consequent generation of carbonic add 
is minute in quantity, the production of heat is 
proportionably small. It has been shown (331 

e^ seq.)y that in almo&t tYie exi\)vi^ ^^<v& ^^ the 



PROPOETIONATB TO KSSPUUTIOH. 137 

invertebrata, the lespintory appumtus is oomp«i- 
ratively minute and imperfect; acoordingly, in 
these animals the power of generating heat is at 
the minimum. In the fish, though the respiratory 
apparatus be large, and though all the blood of the 
body circulate through it (345 ei 9eq.)y yet only a 
small quantity of air is brought into contact with 
the respiratory organ, merely the air contained in 
water. In the reptile, though it possess a true and 
proper lung, and respire air, yet only one half of 
the blood of its body circulates through the com- 
paratively small, imperfectly divided, and simply 
constructed air bag, which constitutes its respira- 
tory organ (354). Hence, the striking contrast 
exhibited between the temperature of these cold- 
blooded creatures and that of the mammiferous 
quadruped, whose lung, comparatively large, and 
composed of innumerable minute and closely-set 
air vesicles (fig. cxxxiv. and cxxxv.), presents 
to the air an immense extent of surface (370), and' 
the whole mass of whose blood incessantly tra- 
versing this surface, comes at every point into 
contact with the air (399). 

514. In the various tribes of warm-blooded 
animals, the elevation and uniformity of the tem- 
perature is strictly proportionate to the comparative 
magnitude of the lungs ; to the complexity of their 
structure ; to the minuteness and number of the air 
vesicles; and, consequently, to the quantity of 
oxygen consumed, and of carbonic add gexiW«Aj^» 



138 THE PHILOSOPHY OP UBAI.TH. 

515. In all animals with red blood there is i 
strict relation between the temperature of the body 
and the lightness or depth of the colour oi the 
blood ; invariably the deeper the colour, the higher 
the temperature. Thus, the blood of the fish and 
of the reptile is of a Hght, and that of the bird of 
an intense red colour. It has been shown (229) 
that the lightness or deepness of the cdbur of the 
blood depends on the quantity of red pardclei 
which it contains, and the chemical action between 
the air and the blood is carried on chiefly through 
the medium of the red particles. 

516. Even in the same animal, the tempera* 
ture differs at different times, according to the 
energy with which the process of respiration is 
carried on. When the circulation of the blood is 
sluggish and the respiration slow and feeble, the 
quantity of oxygen consumed is small, and the 
temperature low ; when, on the contrary, the cir- 
culation is rapid, and the respiration energetic, 
the quantity of oxygen consumed is large, and the 
temperature proportionably high. Whatever di- 
minishes the quantity of air that flows to the lungs, 
and the quantity of blood that circulates through 
them, diminishes the temperature. Malformation 
of the heart, in consequence of which a quantity of 
blood is sent to the system without passing through 
the lungs, as in the individuals termed Cerukans : 
disease of the lungs, by which the access of air to 

the air veaicka is obstiucted) aa \a «&'Oki£a^ %t( 



PROPORTIONATE TO RESPIRATION. 139 

morbid states inyariably attended with a dimi- 
nutioQ of the temperature. 

517. When a warm-blooded animal is placed 
in an elevated temperature, its consumption of 
oxygen is comparatively small ; when it is placed 
in a cold atmosp] ere, and the production of a large 
quantity of heat is necessary to maintain its tem- 
perature at its natural standard, its consumption 
of oxygen is proportionably large ; accordingly, it 
is established by direct experiment that the same 
animal consumes a much larger quantity of oxygen 
in winter than in summer. 

518. Due allowance being made for the differ- 
ence in their bulk, young animals consume less 
oxygen than adults ; and they have a less power 
of generating heat. Different species of young 
animals differ from each other in their power of 
generating heat, and the closest relation is ob- 
seirable between the difference in their power of 
consuming oxygen and that of generating heat* 
Puppies and kittens require so small a quantity of 
oxygen for supporting life, that they may be wholly 
deprived of this gas for twenty minutes, without 
material injury, while adult animals of the same 
species perish when deprived of it only for four 
minutes. As long as these young creatures retain 
the power of sustaining life for so protracted a 
period without oxygen, they are wholly incapable 
of maintainii^ their own temperature; on free 
exposure to air, even in summer, thelxe^A, oi xYira 



140 THE PHUX>SOPHT OF HEAITH. 

bodv sinka impidlY, and if this exposure be con- 
tinued long, they perish of cold. In like manner, 
young spanows and other birds which are naked 
when hatched, consume little oxygen, and are in- 
capable of maintaining their temperature ; but can 
support life when deprived of oxygen much longer 
than adult birds of the same species ; while young 
partridges which are able to retain their own tem- 
perature at the period of quitting the shell, die 
when deprived of oxygen as rapidly as the adult 
bird. 

519. The state of hvbemation illustrates in tlie 
same striking manner the relation between respi- 
ration and the generation of heat. One of the 
most remarkable phenomena connected with this 
curious state, is the reduction, sometimes even the 
apparent suspension, of respiration; and in all 
cases of hybernation, the respiratory function is 
performed in a feeble manner, and only at distant 
intervals. Exactly in proportion to the diminuticm 
of the respiration, is the reduction of the power of 
generating heat ; so that when the state of hyber- 
nation is established, the temperature of the ex- 
ternal parts of the body sinks nearly to that of the 
surrounding medium; while the internal parts, 
the blood, and the vital organs are only a degree 
or two higher. In experiments made to reduce an 
hybemating animal to a torpid state by cold arti- 
£da}}y produced, De Saissy found that he could 
aot bring on the state oi \i^\>em%.\aa\v \s^ \5ea 



PROPORTIONATE TO RESPIRATION. 141 

reduction of temperature alone, without also con- 
straining the respiration. 

520. These and other analogous facts ahun« 
lautly estabhsh the relation between the function 
)f respiration and that of calorification, and lead 
to the general conclusion that the generation of 
inimal heat is in the direct ratio of the quantity of 
ur and blood which are brought into contact, and 
Nrhicb act on each other in a given time. Yet an 
ittempt has recently been made by an ingenious 
physiologist* to disturb this induction, and to 
)how that the production of animal heat is not in 
;he direct ratio of the quantity of oxygen inhaled , 
t)ut in the inverse ratio of the quantity of blood 
exposed to this principle. This position is main- 
adned on the following grounds : — 

521. Inspiration favours the flow of blood to 
he lungs ; expiration retards it : consequently, if 
Tom any causes the inspirations preponderate in 
lumber and proportion over the expirations, a 
^ater quantity of blood than usual will be accu- 
nulated in the lungs. There are conditions of the 
tystem in which this preponderance of the inspi- 
-ations actually takes place; when the mind is 
inder the influence of certain emotions, for ex- 
imple, B& when it is depressed by anxiety and fear, 
[n this state the inspirations are more frequent 

* An Experimental Inquiry into the Laws which regu- 
ate the Phenomena of Qr^ranic and Auimal L\^«. um 
Teojifo Calvert Bsdland, M,D, 



142 THE PHILOSOPBY OP HEALTH. 

and more complete than the expirations ; it is a 
state of continual sighing. In like manner, in 
certain diseases, such as asthma, the inspirations 
greatly pveponderate both in frequency ai^eneigj 
over the expirations. In such conditions of the 
system the blood accumulates in pretematural 
quantity in all the internal organs; but mom 
especially in the lungs; and two consequences 
follow : first, there is a remarkable diminution in 
the energy of all the vital actions ; and secondly 
there is a proportionate diminution in the pro- 
duction of animal heat. 

522. On the contrary, as it is the effect of 
inspiration to facilitate the motion of the blood 
through the lungs, so it is the effect of expiratioo 
to retard it ; hence, when the expirations prepon- 
derate the opposite state of the S3rstem is induced; 
all the vital actions are performed with increased 
energy ; the heart beats with unusual vigor ; the 
pulse becomes quick and strong ; a hu^r quan- 
tity of blood is determined to the surface of the 
body, and this excited state of the system is always 
attended with an augmentation of the temperature. 
523. As in the first state there is a greater and 
in the second a smaller quantity of blood than 
natural contained in the lungs, the inference de- 
duced by Dr. Holland is, that the production of 
animal heat is in the inverse ratio of the quantity 
of blood exposed to oxygen. But this inference is 
neither logical nor sound. 



PROPORTIONATE TO RESPIRATION. 143 

524. If, as a comparison of all the phenomena 
of respiration exhibited throughout the entire range 
of the animal kingdom, shows the production of 
animal heat to be in the direct ratio of the quantities 
of air and blood which are brought into contact, 
and which re-act on each other, every phenomenon 
of respiration must be in harmony with this law, 
and, accordingly, when really understood, it is 
found to be so. 

525. Inspiration, by the dilatation of the tho- 
rax, and consequently of the lungs incident to that 
action, is favorable to the flow of blood to the lungs. 
But it is only a certain degree of dilatation of the 
lungs that is favorable to the flow of blood through 
them (40*7 et seq.). If the dilatation be carried 
beyond a certain point, the quantity of blood trans- 
mitted through the pulmonary tissue is diminished 
(406) ; if the dilatation be carried farther, the 
transmission of the blood may be wholly stopped 
(417). The quantity of the blood which flows to 
the lungs, and the quantity which circulates 
through them, are not then identical. So large a 
quantity may flow to them as to impede or retard or 
wholly stop the pulmonary circulation. In pro- 
portion to the accumulation of blood in the lung 
must necessarily be the distension of the pulmo- 
nary tissue ; in that proportion the lung must be 
approximated to its condition in the experiment in 
which it was distended with water C^^H^^ yi\veti\\. 
did not transmit a single particle of blood. ¥Mi\>^et , 



144 THE PHILOSOPHY OF HEALTH. 

Id proportion to the preternatural distenBion of 
the pulmonary tissue with blood must be the 
exclusion of air from the air vesicles for the lungs 
can contain only a certain quantity of blood and 
air (418.3), so that the blood can preponderate 
only by the exclusion of the air. 

526. In those states of the system, then, in 
which the preponderance of the inspirations induces 
a preternatural accumulation of blood in the lungs, 
the production of animal heat is diminished for a 
two-fold reason ; first, because the distension of 
the pulmonary tissue with blood retards the pul- 
monary circulation, and proportionally lessens the 
quantity of blood which is brought into contact 
with the iair ; and, secondly, because the distended 
blood-vessels compress the air vesicles, and so 
diminish the quantity of air which is brought into 
contact with the blood. 

527. It follows that the diminution of temper- 
ature which takes place in this condition of the 
system is not because the production of animal 
heat is in the inverse ratio of the quantity of blood 
which is exposed to oxygen ; but because from a 
twofold operation there is a diminution of the 
quantity of blood and of oxygen which are brought 
into contact. 

528. The reason is equally obvious why there 
is an increase of the temperature in those con- 
ditions of the system in which the expirations 

preponderate over the inap\m\.\0Ti^. "^Ba^^m^^^xi^ 



PSOFOATIOKATS TO RB8PIRATION. 145 

true, somewhat retards the circulation of the 
. through the lungs, but the preponderance of 
espiratory action does not raise the tempera^ 
oy the retardation of the flow of blood through 
lings, and the consequent diminution of the 
tity transmitted in a given time ; for though 
ation somewhat retards the circulation of the 
. through the branches of the pulmonary 
f^ it promotes its circulation through the 
:he8 of the pulmonary veins (fig. cxx. 10). 
indeed by the action of expiration that the 
ed blood is transmitted from the lungs to the 
leart to be sent out renovated to the system, 
ration has no influence whatever over the 
ion of the blood. Before the action of ex- 
ion takes place, the blood is already aerated, 
oflice of expiration is to remove from the 
m the air which has served for respiration, 
x> transmit to the^ystem the blood which has 
subjected to respiration. Consequently, in 
i states of the system in which the expirations 
mderate, the temperature is increased, not 
ise the expiratory actions, by lessening the 
tity of blood in the lungs, diminish the quan- 
ixposed to oxygen, but because they transmit 
e system oxygenated blood as rapidly as it is 
sd, that is, blood which either produces animal 
in the act of its formation, or which gene- 
it as it flows through the system. 



146 THE PHILOSOPBY OF HEALTH. 

529. These conditions establish the conclusion 
deduced, as has been stated, from the comparison 
of the phenomena of respiration exhibited through- 
out the entire range of the animal kingdom. But 
if the production of animal heat be really the 
result of combustion, if that combustion take place 
in the lung, and if the lung be thus the focus 
whence the heat radiates to every other part of 
the body, why is not the heat of this organ and of 
the parts in its immediate neighbourhood higher 
than the temperature of the rest of the body? 
Some of the internal organs are indeed a d^ee or 
two hotter than the general mass of the circulating 
blood (469), and among these the lung is ad- 
mitted to rank perhaps the very highest. But 
how can a quantity of caloric sufficient to mun- 
tain the heat of the body in a temperature of forty 
degrees below zero radiate from an organ the tem- 
perature of which is only two or three degrees 
above that of the body itself? It is estimated 
that, in every minute, during the calm respiration 
of a healthy man of ordinary stature, 26 * 6 cubic 
inches of carbonic acid, at the temperature of 
50° Fahr. are emitted, and that an equal volume of 
oxygen is withdrawn from the atmosphere. From 
these data it is calculated that, in an interval of 
twenty-four hours, not less than eleven ounces of 
carbon are consumed. Why is the iunjor, the seat 
oi this combustion, not only not greatly warmer 



TRBORT OF ANIMAL HBAT. 147 

than any other organ ; but why is it not even con- 
sumed by the fire which is thus incessantly burn- 
ing within it ? 

530. It has been shown (468 and 469) that when 
the carbon of the blood unites in the lung with the 
oxygen of the air, the nature of the blood, in con- 
sequence of the abstraction of carbon, undergoes 
an essential change, passing from venous into 
arterial. By an elaborate series of experiments, 
conducted with extraordinary care and skill, it 
would appear that arterial has a greater capacity 
for caloric than venous blood, in the proportion of 
114 '5 to 100. In consequence of this difference 
n the constitution of the two kinds of blood, the 
heat generated in the lung by the combustion of 
carbon, instead of being evolved or becoming sen- 
sible (510. ii.), and so raising the temperature of 
the organ, goes to satisfy the increased capacity for 
caloric of arterial blood, is spent, not in render- 
ing the fluid sensibly warmer, but in augmenting 
its specific caloric (510. ii.). Arterial blood is not 
increased in temperature,* but with its absolute 

* It is not a perfectly accurate statement that the 
temperature of venous and arterial blood is precisely the 
same. The latest and best experiments concur in showing 
that arterial blood, at least in the heart and the great 
arterial trunks, is one or two degrees warmer than venous 
blood. The weight of evidence from experiment is also in 
favour of the opinion, that the different parts of the body 
are somtwhai less warm as they recede from the lungs and 
lieurt ; but the difference ia so slight that it ma^ \)« ^v%« 
Ttg&rded in the general argfument* 

h2 



148 THE PHILOSOPHY OF HEALTH* 

quantity of caloric augmented, flows from the 
lung to the left heart (fig. czl. 10), and thence to 
the system (fig. cxl. 6). In the system, in every 
organ, at every point of the component tissue o^ 
every organ and at every moment of time, the 
blood repasses from the arterial to the venous 
state : by this transition its capacity for heat is 
diminished; the venous cannot retain in it the 
same quantity of caloric as the arterial blood, con- 
sequently a portion of caloric is extricated ; that 
which was latent becomes sensible, and caloric 
being set free the temperature is raised. In thii 
process the lung is not burnt, it is only rendered 
just sensibly warmer than any other part of the 
body, though it be the organ by which the whole 
mass of blood receives its caloric, because it is 
only in the capillary part of the systemic circula- 
tion, when the arterial blood again passes into the 
venous state, that the caloric acquired is liberated. 
In this manner, gently, steadily, uninterruptedly, 
an abundant, unceasing, and equable current of 
heat is distributed to every part and particle of the 
system. 

531. Such is the celebrated theory of animal 
heat suggested by Dr. Crawford, of which it has 
been justly said, that it affords one of the most 
beautiful specimens of the application of physical 
and chemical reasoning to the animal economy 
that has ever been presented to the world. 
532, The main poaitioxi on. ^\kv^ >&iaa t\i<»)rY 



THBORT OF ANIMAL HXAT. 149 

Tests — ihat arterial possesses a greater capacity 
for caloric than venous blood — professes to be 
founded on experiments wbich, though of a deli- 
cate and complex nature, are nevertheless uniform 
and decisive in their results. In consequence of 
their extreme interest and importance, these expe • 
riments have been subjected, by different physio- 
logists, to rigid examination, with a somewhat 
conflicting result. The greater number of experi- 
mentalists maintain that Crawford's experiments 
are correct in all the essential points, and that the 
objections which have been urged against them 
do not really affect them ; while others are of opi- 
nion that, even although it must, upon the whole, 
be admitted that the specific heat of arterial is 
greater than that of venous blood ; yet that the 
excess is 80 small as to be inadequate to account 
for the effects attributed to it. Dr. Davy's expe- 
riments, which of all that have been instituted are 
generally conceived to be the most unfavourable to 
the theory of Crawford, do not afford uniform re- 
sults. Three experiments out of four indicate a 
greater capacity in arterial than in venous blood ; 
in those in which the experimentalist himself 
places the most confidence, in the relative propor- 
tion of 913 to 903 ; while, according to Crawford, 
the relative proportion is 114*5 to 100. 

533. But when this subject is closely consi- 
dered, the discrepancy in question turns out to b^ 
of DO real consequence. There is a mod\&c^\iQXk 



150 THE PHILOSOPHY OF HEALTH. 

of the theory, which removes every difficulty, and 
dispenses with the necessity of any regard what- 
ever to the point in dispute. 

534. It has been shown (444 et seq^^ that during 
the process of respiration more oxygen disappears 
than is accounted for by the carbonic acid that it 
generated ; that this excess of oxygen is absorbed 
by the blood; and that in the lung the oxygen 
merely enters into a state of loose combination 
with the blood, the union being intimate and com- 
plete only in the system. The complete chemical 
combination of the oxygen with the carbon takes 
place, then, not in the lungs, but in the capillary 
arteries of the system; consequently it is only 
while flowing in capillary arteries that carbonic 
acid is formed ; that is, it is only in these vessels 
that the arterial combustion takes place: of 
course, therefore, it is only in these vessels that 
heat is extricated, and only from them that it can 
be communicated to the adjacent parts. Accord- 
ing to this view, wherever there is a capillary 
artery, the combustion of carbon incessantly goes 
on, and there caloric is as incessantly set free; 
but since there is not a point of any tissue, in which 
there are not capillary arteries, there is not a point 
from which caloric does not radiate. As soon as 
formed, carbonic acid passes from the capillary 
arteries into the capillary veins ; by the veins it is 
transmitted to the lungs ; and by the lungs it is ex* 
pelled from the system. T\ie T«a!L o^x«.\asisGa oir- 



IMFLUKNCE OV THE NK&VOUS SYSTEM. 151 

lied on in the lungs, then, are the transmission of 
oxygen and the extrication of carbonic acid ; but 
this organ is not the seat of the essential and ulti- 
mate part of the function ; it is merely the portal 
through which the elements employed in the pro- 
cess have their entrance and exit. Thus the ques- 
tion concerning the greater capacity of arterial 
•blood for caloric is of no importance whatever : 
the phenomena may be equally accounted for, 
whatever be, in this respect, the constitution of the 
blood. 

535. The result of the whole is, the complete 
establishment of the fact, that the production of 
heat in the animal body is a chemical operation, 
dependent on the combination of oxygen with car 
bon in the capillary arteries of the system ; that 
is, it is the result of the burning of charcoal at 
•every point of the body. 

536* The agent which maintains and regulates 
this internal fire is the nervous system. There is, 
•indeed, reason to suppose that the nervous system, 
in some mode or other, contributes to the actual 
production of animal heat. It is established by 
direct experiment, that the quantity of carbonic 
acid formed in the system is inadequate to the 
supply of the caloric expended by it ; that in a 
given time more heat is abstracted from the body 
by the surrounding medium, than can be accounted 
for by the consumption of the amount of carbonic 
Mcjd thrown off by the lungs during XVie «tt.iii& voX^t* 



152 THE PHILOSOPHY OF HEALTH. 

val. There is evidence that the source of thii 
additional heat is the nervous system. 

537. The influence exerted by the nenou 
system over the production of animal heat, u 
demonstrated by the fact^ established by nume- 
rous observations and experiments, that whii- 
ever weakens the nervous power, proportion- 
ally diminishes the capacity of producing heit 
For, 

1 . The destruction of a x)ortion of the spinal cord 
diminishes the temperature of an animal without, 
as £Eur as is ascertained, the disturbance of any other 
function. 

2. The privation of the heart and blood-vessels of 
the nervous influence, as by decapitation, - thou|^ 
the passage of the blood through the lungs and ib 
ordinary change from the venous to the arterial 
state be maintained by artificial respiration, greadj 
diminishes, if it do not altogether suspend, the 
generation of animal heat 

3. The abolition of sensibility by the administrtr 
tion of a narcotic poison, artificial respiration being 
maintained, as eflectually disturbs the generation of 
animal heat as decapitation; while the power of 
generating heat is restored, in the exact proportion 
to the return of the sensibility by the cessation of 
the action of the poison. 

4. The temperature of an organ is found, by 
direct experiment, to be diminished by the di- 

Fision of the nerves that v.xi'^i^V] \X^^Ti<cr«^\a^ 



IKFLUXNCX OF TBI MBRVOUfl BT8TBM. 153 

nfluence. The nerves that supply the horn were 
livided on one side of the hody in a young deer ; 
he other horn was left entire. The temperature 
)f the horn— the nerves of which had been di- 
vided — ^wBs found, after some hours, to be consi- 
Isrdbly diminished, and it continued diminished 
hr several days ; at length ita temperature was 
^stored. On ezaminii^ the horn about ten days 
liter the operation had been performed, the divided 
aervea were found to be connected by a newly- 
fbrmed substance; thus apparently accounting 
for the loss of temperature in the £rst instance, 
sad for its subsequent restoration. 

538. But although these and other analogous 
bets prove, beyond all question, the important 
uifluence of the nervous system over the develop- 
ment of animal heat, yet the mod^ in which that 
influence operates is not ascertained. Its action 
may be either direct or indirect. The nerves may 
possess some specific power of generating heat, — 
extricating it immediately from the blood by a 
process analogous to secretion, — or they may 
evolve it indirectly by other operations, as by 
some of the processes of nutrition. Each hypo- 
thesis is maintained by able physiologists ; but 
the balance of evidence (as will appear hereafter) 
is greatly in favour of the opinion that the influ- 
ence of the nervous system over this process is 
altogether indirect. A beautiful illustration of 
this 20 afforded in the following opera'doTi) ^\i\Os\ 



154 THE PHILOSOPHY OF HEALTH. 

is going on, without ceasing, every instant during 
life. 

539. The skin which forms the exteml 
covering of the body is composed essentially of 
gelatin. No gelatin is contained in the blood; 
but the albumen of the blood is capable of being 
converted into gelatin by the addition of oxygen. 
Albumen is received by the capillary artery of the 
skin ; the blood, of which albumen forms so im- 
portant a constituent, contains a quantity d 
oxygen which it receives at the moment of inspi* 
ration, and which it retains in a state of loose 
combination (470 et seq.). Under the influenee 
probably of the organic nerve, the capillary artery 
chemically combines a portion of the free oxygra 
with the albumen of the blood, and gelatin is the 
result. In this process the albumen gives off 
carbon ; the blood affords oxygen ; the two 
elements unite; carbonic acid is formed; and, 
as in everv other instance in which carbonic 
acid is formed, heat is evolved. In this manner t 
fire is kindled, and is kept constantly bumingi 
where it is most needed to counteract the influ* 
ence of external cold, at the external surface of 
the body, 

540. Such are the main points which have 
been established in relation to the production and 
distribution of animal heat. But it has been 
shown that the living body is capable of bearing 

without injury a tempetaXxa^ \>^ "^VxOdl *tx ^ 



GENBRATION OF COLD. 155 

ipidly consumed when deprived of life. By what 
.cans does the vital power enable the body to 
saist the influence of such intense degrees of 

541. Two circumstances are observable when 
te body is placed in a temperature greatly higher 
lan its own. First, it can endure such a tem 
nrature only in the medium of air. Air can 
tsily be borne at the temperature of 260° ; 
|ueous vapour at the temperature of 130° few 
UTopeans are capable of enduring longer than 
reive minutes ; the peasants of Finland appear 
I be able to sustain it, for the space of half an 
[>ar, as high as 167°; but the hottest liquid 
ater-bath which any one seems to have been able 
» bear for the space of ten minutes, is the hottest 
iring at Bareges, the temperature of which is 
13^. But in heated air the quantity of heat in 
ctual contact with the body is much less than in 
le other media; because in proportion as the air 
I heated it is expanded, and in proportion as it is 
Kpanded the particles are diminished that come 
ito contact with the body. 

542. In the second place, the afflux of the 
older fluids from the central parts of the system 
> the surface may for a time exert some influence 
1 keeping down the temperature of the body, 
lut above all this, in the third place, a two-fold 
Tovision is made in the body itself for thft \^ 
uetion of its temperature when exi^t^o^ Xo m- 



156 THE PHIL060PHT OF HBALTH. 

tense degrees of heat ; by the one, the power ividi 
which it is endowed of produeing hest is dimi- 
nished; by the other, cold is poeitiydy gene* 
rated. 

543. It has been shown (517) that in pro- 
portion to the elevation of the temperature ts 
which the body is exposed the blood becomes leH 
▼enalized, and in the proportion in which thi 
blood retains its arterial character the consamptkiB 
of oxygen is diminished. Venous blood contain 
an excess of carbon, arterial blood an excess of 
oxygen. Conseqaently in proportion as the blood 
retains its arterial character it i^fords lesa caita 
for the combination of oxygen, that is lees inflam- 
mable matter. At an derated temperatore theie* 
fore there must, of necesuty, be a diminished pro- 
duction of heat within the body, since the blood 
contains a diminished quantity of combustiUt 
material. 

544. Moreover, in proportion to the eto- 
vation of the temperature to which the body io 
exposed, evaporation takes place from the entiis 
surface of the pulmonary vesicles. No experi* 
ments have been performed which enable the phy- 
siologist to ascertain precisely the quantity of 
vapour exhaled from the lungs in a given time« 
when the body is exposed to a given degree ol 
heat ; but both observation and experiment show 
that it is very great. The blood pours oat 
upon the whole surface oi X\v& ux ^t^sMdM % 



SBMEftATION OF COLD. 157 

[uantity of moiitare in the form of water : by 
he surrounding lur this water ia converted into 
apour: by the conversion of a fluid from the 
tatc of a liquid into that of vapour caloric is 
bsorbed: by the absorpdon of caloric cold is 
enerated, and that to such a degree that fluids 
zposed to the influence of evaporation may be 
roKen in the iatensest heat of summer. The 
ery process by which art, aided by science, 
ffords to the inhabitants of warm climates the 
oxury of ice, is that by which nature generates 
iold in the human lungs when the body is exposed 
o a temperature above its own. Not only, then, 
B the lung the instrument by which the body 
icquiies the power of evolving heat in greater or 
ess quantity in proportion to the demands of the 
tystem, but this very same organ, under a change 
>f circumstances, produces the directly contrary 
iffect, and actually generates cold. 

545. In the process of producing cold the 
(kin is a powerful auxiliary to the lungs. More 
luid is, indeed, evaporated from the surface of the 
ildn in the form of perspiration, than from the 
ungs in the form of vapour ; the cutaneous, like 
he pulmonary evaporation, increases in the ratio 
»f the temperature, and both co-operate in ab- 
stracting the excess of caloric. 

546. Finally, in proportion to the elevation of 
he temperature is the acceleration of the circu- 
Btion; the pulse ia augmented in po'^et) ^w^ 



158 THE PHILOSOPHY OF HEALTH. 

doubled or trebled in frequency (495) ; but in 
proportion to the rapidity of the circulation 'm 
the increase of the quantity of evaporable matter 
which is transmitted to the evaporating surfaces. 

547. From the whole it appears that by 
the combination of carbon and oxygen provision 
is made for the production of the greatest quantity 
of caloric that can at any time be required for the 
wants of the system ; that when a decreased evo- 
lution of heat is necessary a smaller quantity of 
carbon and oxygen is brought into union, and 
that when, from exposure to intense d^rees of 
heat, it is requisite for the maintenance of the 
temperature of the body at its own standard, that 
it should actually generate cold, it accomplishes 
this object by the evaporation of water. 



159 



CHAPTER X. 
OF THE FUNCTION OF DIGESTION. 

Process of Assimilation in tlie plant | in the animal^ 
Dig^stiYe apparatus in the lower classes of animals ; in 
the higher classes ; in man— -DigestiTe processes — Pre- 
hension, Mastication, Ins ally ation. Deglutition, Chy- 
mificationi Chyli&eation, Ahsorption, Fecation — Struc- 
ture and action of the organs hy which these operations 
are performed — Ultimate results — Powers hy which 
those results are accomplished — ^Two kinds of digestion, 
a lower and a higher ; the former preparatory to the 
latter, 

548. Digestion is the function by which the 
aliment is converted into nutriment. No food 
can nourish until it be converted into a fluid ana- 
logous in cliemical composition to that of the body 
by which it is assimilated. The conversion of 
the crude aliment into such a fluid is effected by 
a vital power peculiar to living beings, by which 
they subvert the constitution of other organized 
bodies, and cause them to assume their own. 
They accomplish this change by the agency of 
certain secretions which they elaborate in their 
own organs, and which they add to the substances 
they receive as aliment. By the action oC Wv^^^ 
secretioDB, the chemicsil com position ol V\v^viXv 



160 THE PHILOSOPHY OF HEALTH. 

meot is brought into a close affinity to that of the 
body which it nourishes. 

549. This change in the chemical composition 
of the aliment, by means of fluids secreted by the 
living bodies whick reeetre it^ is nanifett in. the 
plant as well as in the animal. The sap, as it 
issues from the root, is a colourless and limpid 
fluid ; it has a spedfic gravity a liule greater ^m 
that of water ; it has a sweetish taste ; it contains 
an acid which is sometimes free, and is either &e 
carbonic Qrthe acetic; but more commonly it is 
combined with lime or potass. To this crude 
sap, in thifc the first stage of its formatioDt vege- 
table secretions, sugar and nmcua, assimilative 
substances, are superadded, probably by the fibres 
•f the root. 

550. As the sap ascends in the stalk, a g^reater 
quantity and a greater number of these vegetable 
secretions are poured into it. In the ratio of its 
elevation it acquires sugar, mucus, albumen, and 
an azotized substance analogous to gluten. By 
the admixture of these assimilative secretionsi 
the crude sap is progressively assimilated nearer 
and nearer to the chemical composition of the 
proper nutritive fluid of the plant. Thus pre- 
pared, the sap passes to the leaf, in the upper 
surface of which it undergoes a process analogous 
to that of digestion in the animal (315), and is 
coDverted into proper nutrient matter. 

55L The plant can ou\^ Uk^ xrg^ \s^ iSowiir^ 



ASSIHILATION IN THE ANIMAL. 161 

tkm, liquid food; it never receiyes solid sub- 
Btances as aliment : it therefore needs no appa 
ratus for the division, solution, and fluidification 
of its food ; its sole work of assimilation consists 
in changing the innate affinities of liquid aliment. 
But animals which live on vegetable and animal 
substances have to modify, by their digestive 
juices, the affinities of organic solids : hence assi- 
milation in the animal must necessarily be a more 
complex operation than it is in the plant. 

552. Fixed immovably to the soil by its roots, 
the nutritive apparatus of the plant is always in 
contact with its food, which is slowly but un- 
unceasingly absorbed according to the wants of 
its system. But the animal endowed with the 
faculty of locomotion receives its aliment into the 
Interior of its body, that it may transport its food 
edong with it in all its changes of place; and 
that, as in the plant, its food may be always in 
contact with its nutritive apparatus. The interior 
Dutrition of the animal and the convei^ence of its 
Qutritive apparatus to the centre of its system, 
ind the exterior nutrition of the plant and the 
iivergence of its nutritive apparatus to the peri- 
pheral extremity of its body, are difierences in 
their mode of nutrition, connected with essential 
iifferences in the mode of life peculiar to the two 
)eing8. 

553. Plant-like animals have a plant-like 
node of nutrition. The tranration from \\i<& oxiic^ 



162 THE PHILOSOPHY OF HEALTH. 

class to the other is so gradual as to be almost in- 
sensible. Fixed to the same spot in the ocean as 
the tree to the land, the nutritive sur&ce of the 
poriferous animal is always in contact ¥rith the 
water, as the soil is ¥dth the external surface of 
the plant. The cellular substance of which the 
bag of the poriferous animal is composed is per- 
meated in all directions by ramifying and anasto- 
mosing canals, which, beginning by minute pores 
placed on the external surface, terminate in larger 
orifices, termed vents, which are fecal openings. 
These internal canals are incessantly traversed by 
streams of water, which enter through the minute, 
and are discharged through the larger orifices. 
By these currents the nutrient matter contained 
in the water is conveyed to every part of the bodj, 
and the streams that issue from the fecal orifices 
abound with minute fiocculent particles, the re- 
sidue of the digested matter. No separate part of 
the body is appropriated to the function of di- 
gestion any more than in the plant; there is 
merely a general absorbent surface ; the water is 
to this animal what the soil is to the plant ; its 
whole surface is a root ; every point of that sur- 
face is constantly in contact with its food, and 
every point is absorbent 

554. In the class above the porifera, the mar 
gins of the superficial pores are merely lengthened 
out into minute sacs, irrijtable and sentient, su]> 
rounded with vibratile dU^ (M^^. HlVi^ii^ «uai^ 



THB HTDRA. 163 

which are termed polypi, are so many little sto- 
machs, which select, seize, and digest the food 
brought to them in the currents of water created 
by the action of the cilia (344). 

Fig. CXLVIII.— /^y<^a rtridis. 




1. The Hydra with its tentacula expanded. 2. The ten- 
tacula. 3. The body of the Hydra. 4. Disc for attach- 
ment. 5. The Hydra in the act of creeping. 6. The 
Hydra with an animalcule in its digestive cavity. 

555. The fresh-water polype, the little hydra 
(fig. cxLviii. 1), is one of these minute sacs de- 
tached and endowed with the power of locomotion 
(fig. CXLVIII. 5), a sentient, self-moving digestive 
bag. Capable of swallowing animals many times 
ita own size, as the red-blooded worm, this little 
creature stretches its whole body like a thin 
elastic membrane over its prey, so as completely 
to alter its own Bbape, and the membiaiioxx^ %\i^^^ 



164 THE PHILOSOPHY OF HEALTH. 

stance of which it is composed becoming tranB- 
parent by the distention, allows the subsequent 
process to be distinctly seen. The red fluid of 
the worm, as the process of digestion advances, is 
slowly diffused over every part of the internal sur- 
face of the polype. The whole internal surfiBice of 
this minute self-moving bag is digestive ; a true 
and proper stomach (fig. cxlviii. 6). By dex- 
terous manipulation, this internal surfieuse may be 
rendered external, and the animal turned com- 
pletely inside out. Then the external begins to 
perform the ofiSce of the internal surface, carrying 
on the function of digestion, just as well as that 
which was primitively formed for it; while the 
originally digestive becomes the generative sur- 
face, for the creature buds from this surface, now 
the outer one ; a striking and instructive illustra- 
tion of the analogy between the external covering 
of the animal body or the skin, and its internal 
lining, or the mucous surface. 

556. In the monades (fig. cxlix.), and in all 

Fig. CXLIX. 




Oroup of If onades ; the dark «i^oU Va W^ \u\«n!cst ^C tibeh 



rOLTGi&TRICA. 165 

i lower animalcules, the digestive apparatus, 
(tead of forming the entire internal surface of 
i body, consists of numerous sacs, which con- 
tute so many separate stomachs, whence the 
me of the class, polygastrica. When empty, 
when filled with water, these digestive 
2a cannot he distinguished from the common 
Llular tissue of the body ; but on feeding the 
imals with coloured organic matter, minutely 
iused in water, the coloured particles readily 
ter the digestive sacs, and render apparent their 
"m and arrangement. In the minutest animal 
;herto appreciable, the monas termo, the 2000th 
rt of a line in diameter, four rounded sacs have 
en seen filled with coloured particles (fig.cxLix.)- 
Lch of these sacs, about the 6000th part of a 
le in diameter, opens by a narrow neck into a 
nnel-shaped mouth, surrounded with a single 
BV of long vibratite cilia, by the action of which 
e floating organic particles are brought within 
e reach of the mouth. In general, even in this 
Lss, an alimentary canal traverses the whole 
tent of the body, into which all the different 
iroachs open. Sometimes numerous branches 
oceed from the main trunks of the alimentary 
nal, hearing the nutritive matter to the different 
rts of the body (fig. cl. 2). Often, in order to 
tend the digestive surface, the alimentary canal 
produced, forming rounded enlargements called 
ical appendages, all of which act &« %o \xv«utc^ 



HK PHII^SOPHT OP BE ALTS 

Fig. CL— fimwAi HtfaUoa. 



1. Mouth. 2. AlimeDtujlulMl. X Sucker. 

additional Htomachs (Gg. cli. 3). In some iadi- 
viduali, obierred under favourable ciicuoiBtancce, 
nearly 200 of these ccecal stomachs, filled with 
coloured matter, have been counted, and there ma; 
have been many more uuBeen, because empty and 
collapsed. In the lowest tribes of this class there 
is but one orifice to the alimentary canal, the 
oral; the food entering, and the fecal matter 
passing out of the system by the same aperture ; 
but in the higher orders there is both an oral and 
an anal orihce, and the mouth and the anus are 
placed at opposite extremities of the body, as in 
the higher animals. 

557. Up to this point in the animal series the 

digestive sacs and the alimentary canal are merely 

cavities formed in the common cellular tissue of 

the body, without any lining membrane, without 

teelb, or without awj maltMmwv** I'm &«&%% 



CtBCAL APPENDAOBB. 



and preparii^ the tliment, and without b single 
gland, Bs ftirBBliBBbeen ascertained, to assist die 



Pig. CLI.—jlplirulila Jeu/n-ta. 




igettire process. All the aesimilati^e Ivmc^JOTia, 
w retjHntory as well as the digestive, a,"g^ox to 



168 THE PHILOSOPHY OF HEALTH. 

be performed by this single surface. But in the 
ascending scale not only is an apparatus appro- 
priated to digestion, perfectly distinct from that 
assigned to respiration, but even the stomach 
and the alimentary canal are separate organs, dis- 
tinguished from each other, both in structure and 
function. Still higher in the scale new organs are 
successively added, as the process becomes more 
complex and refined, in order to assist the main 
operations carried on in particular parts of the appa- 
ratus ; and as that apparatus approaches its highest 
degree of perfection, not only do the several parts 
of which it is composed increase in number and 
complexity, but each part becomes more and more 
isolated from the rest, a specific office being 
assigned to each in the division of labour that is 
made. Viewing, however, the digestive apparatus 
as a whole, whether simple or complex, whether 
consisting of a single uninterrupted surface, or 
divided into many separate portions, its nature is 
universally and invariably the same, and from the 
monad to man is endowed with analogous vital 
energies. 

558. Comparative anatomy, which has suc- 
ceeded in tracing through the different classes, 
orders, genera, and countless tribes of animals, the 
modifications in form and structure of the diges- 
tive apparatus, has shown that those modifications 
are invariably in strict .adaptation to the kind of 
food on which the appax&lMS S& ^^\.\xi«,d to act 



DIGESTIVE APPiUlATUS. 159 

and to the extent of the elaboration requisite to 
convert crude aliment into proper aninial sub- 
stance. To trace this adaptation through the 
rising and ever- varying series, is a most interest- 
ing and instructive study, not only exhibiting, in 
the very organs that elaborate its food, the phy* 
sical and even the mental qualities assigned by 
the hand of nature to each individual, but often- 
times shedding a clear and bright light on the 
complex structures of the highest and most per- 
fect organization. Striking and beautiful illus- 
trations are aflforded by these investigations of the 
principle formerly insisced on (vol. i. chap. i. 
p. 28, 3), that the communication of the higher 
faculties exalts the apparatus even of the very 
lowest processes, that the latter may work in har- 
mony with the former. In conformity with this 
principle, as the nobler endowments exalt the 
animal in the scale of organization, so even its 
very digestive apparatus becomes extended, iso- 
lated, complex and refined. 

559. The highest and most perfect form of 
the digestive apparatus is that which is disposed 
in a series of chambers in free communication 
with each . other. In these chambers the food 
undergoes a succession of changes, by which it is 
progressively assimilated to the nature of aniniul 
substance. This assimilation, however, is never 
effected by the sole agency of the cliambeia \.\v^tcv- 
selves; it is accouipUshedy to a great, ex^ltivX, \rj 

VOL, 7/. ^ 



170 THE PHILOSOPHY OF HEALTH. 

the influence of special organs placed in Ibe 
neighbourhood of the digestive chambers. In the 
lowest animal there is but one substance and 
one surface for every function ; in the highest, 
even for the performance of the lowest functioB, 
there is the combination of many substances which 
are arranged in complex modes. 

560. In man, the digestive chambers are five; 
the auxiliary organs are many. 

The first of these chambers is the cavity called 
the mouth ; the second is the bag termed the 
pharynx ; the pharynx communicates by the 
esophagus with the third chamber, the stomach; 
the fourth chamber consists of the convoluted 
tubes named the small intestines, and the fifth 
consists of the larger tubes, denominated the 
large intestines. The assistant organs are, first, 
numerous appendages to the mouth, namely, the 
tongue, the teeth, the salivary glands, and the 
muscles that work the jaws; and, secondly, ctf^ 
tain appendages to the small intestines, namely, 
the pancreas, the liver, the mesenteric glands, and 
the lacteal vessels. 

561. By the mouth the food is softened and 
reduced to a pulp ; by the tongue, materially aided 
by the soft palate, this pulp, when duly prepared, 
is transmitted to the pharynx; received by the 
pharynx, it is sent on to the esophagus ; by the 
esophaguSy it is conve-yed to tVv^ stomach ; in the 

stomach, it is converted mto n \\^^vXvw: ^\3\s!«»\ss&^ 



1IIGESTIVK PROCBSSBS. 171 

ailed cbyme; the chyme, passing from the sto- 
lach into the first portion of the small intestines^ 
) there converted into the substance called chyle ; 
fie chyle, carried slowly along the remaining por^ 
on of the small intestines, is successively absorbed 
y the lacteals; by the lacteals, it is conveyed 
irough the mesenteric glands to the thoracic duct, 
nd by the thoracic duct it is poured into the 
enous blood close to the heart By the large 
itestines the refuse matter is conveyed out of the 
^stem. 

562. The function of digestion consists, then, 
f the following processes : — 

1. Prehension. 2. Mastication. 3. Insaliva- 
ion. • 4. Deglutition. 5. Chymification. 6. Chy- 
ification. 7. Absorption. 8. Fecation. 

563. Prehension is the reception of the ali- 
Qent ; mastication is the mechanical comminution 
if it ; insalivation is the admixture of it with cer- 
ain juices poured into the mouth ; deglutition is 
he transmission of it, when duly moistened and 
livided, into the stomach ; chymification is the 
©uversion of it into chyme ; chylification is the 
inversion of the chyme into chyle ; absorption is 
he assumption of the chyle by the lacteals and 
he transmission of it into the blood, and fecation 
B the separation and discharge of the refuse 
natter. Each part of this extended apparatus is 
nodified in structure so as specially to ^t *\X ioi 

1 2 



172 THE PHILOSOPHY OF HEALTH. 

the performance of the office which is appropriated 
to it. 

564. The mouth is not merely the opening 
between the two lips, but consists of an oval cham- 
ber, bounded above by the upper jaw and the 
palate ; below by the tongue and the lower jaw; 
laterally by the cheeks ; behind by the soft pa- 
late ; and before by the lips. 

565. The upper and lower jaw, the palate 
bones, and the teeth, constitute the hard or the 
bony parts of the mouth. The soft parts consist 
of the lips, the cheeks, the soft palate, the tongue, 
and the mucous membrane which lines the whole. 

566. The lips and cheeks are composed prin- 
cipally of muscles, covered on the outside by the 
skin, and lined on the inside by the mucous mem- 
brane of the mouth. In the interspaces between 
the muscles is disposed a quantity of fat, which 
gives form to the face, facilitates the movements 
of the muscles, and protects the glands, blood- 
vessels, and nerves, with which all these organs 
are most abundantly supplied. 

567. The roof of the mouth, called the palate, 
consists partly of bony and partly of membranous 
substance. The bony part of the palate forms an 
arch in the upper jaw, the position of which in the 
erect posture is horizontal : the membranous part 
of the palate consists of the mucous membrane of 

the mouthy which avoids & eoN^Tin^ to the bony 
part of the palate. 



TBI UOtTTH. 173 

568. Fnim the posterior part of the bony arcl; 
nf the palate is Buspended, traneveraely, amoveablc 
partition, called the soft palate (Gg. clii. I and 2). 
which is composed of muscular fibres enclused in 
tlie mucouB membraneB of the mouth. No lees 
than ten distinct muscles enter into the compu- 




1. Aaturiuiarchaf ihv Mift palate. 2. Poaleriot arch, 3. 
Tun.ll. or amj^dulsa. 4. Uvula. 5. Co.nmuuiiatbn b-- 
tweouthe moutli uad pharyiiJi. C. The tuo^ue, l,tk.a- 
OrrJar Of nrnaus fuipills. 8 and 9. The up\.ei to4 \o«pt 
■» 'tiviiliag thu uontrila into (vu'i tWn\\j4S' 



114 THE Pail^SOPHT OF HKALTH. 

Fifi. CIJII,-^ ^t vifmo/llu Madh, BfciryM:, AW , *ii 




1. Mouth 2.ToBBue. 3. Section of the lower j,w. 4. 

^« 1ft .r,-' T.k'*!- 8.*hy™5Bl.„d 9^^ 
chea. 10.1.itenoroftheph.ry«. 11. Section of Ihe wll 
palata. 12. The eH.ph.gu,. 13. The interior of the ni^ 
A ■^* *-" 'i^^gj boae. dvvidmg it into three ch.,nW 
thophmrjax. 



THB FHARTMX. 




atteriar openiaj;;! of the now, cornmnnicatln)!; with tha 
•r part of the pharynx. 2. Poaterior lurrace of tb« 

palate. 3. Thv utida. 4. Back part of ttw mDiilh 
municaling with the pharynx. 5. The toneilK. 0. Back 

or root of the tongue. 7. Foiterior auilace of tha epi- 
tie. S. The laijiix. 9. The opening of the larynx into 
pharynx. 10. Cut edgei of the pharynx. II. Kso- 
^■, the continuation of thg phaiynx. 12. The Tra. 
1, continuation of tha larynx. 13, UubcIcs acting oo 
phaiyiou 

HI of the soft palate. These mviBcAn ue &\«- 
!d in each a manner that they lenitt ftift 



176 THE PHILOSOPHY OF HEALTH. 

organ capable of descending and of applying itself 
against the tongue (fig clii. 6), so as completely 
to close the passage between the month and the 
pharynx (figs. clii. 5, and cliv. 1), and of ascend- 
ing and carrying itself obliquely backwards to- 
wards the posterior wall of the pharynx, so as 
completely to close the passage between the 
pharynx and the nose (fig. cliv. 2, 1) ; hence 
this moveable partition performs the oflSce of a 
double valve, closing the passage from the mouth 
to the pharynx, and from the pharynx to the nose. 

569. From the centre of the soft palate hangs 
pendulous the conical-shaped body called the 
uvula (fig. CLII. 4), which consists of a small 
muscle enveloped in the mucous membrane of the 
mouth. The uvula assists in completing the valve 
formed by the soft palate (fig. cliv. 2, 3) ; it is 
also an important organ in the modulation of the 
voice. When destroyed by disease, both the de- 
glutition of the food and the sound of the voice 
become imperfect. 

570. The lateral edges of the soft palate se- 
parate into two layers, which enclose between 
them the bodies called the tonsils (fig. clii. 3), 
two glands commonly about the size of an almond. 
These organs co-operate with other glands in 
secreting the fluids of the mouth. 

571. The tongue (figs. clii. 6, and cliii. 2) 
is composed of six d\st\nct Tcwx^^cAa^ ewveloped in 

the mucous membrane o£ tVi^ tcvow\\v. TV^ 'Sa\^\ 



THB TONGUE. 171 

of these muscles are so interwoven with each 
other as to form an intricate net work ; and their 
number, arrangement, and exquisite organization 
render the organ capable of executing a sur- 
prising variety of movements with the most perfect 
precision^ and with a velocity of which the mind 
can scarcely form a conception: some of these 
movements being requisite to bring the aliment 
under the operation of mastication, and others to 
produce articulate speech. 

572. The tongue divided into base, apex, and 
dorsum, is supported by a bone called the hyoid 
bone (os hyoides) (figs, cxxxvi. 1, and cliii. 6), 
which, unlike any other bone of the body, is 
placed at a distance from the general skeleton, 
and completely imbedded in muscles. This sin- 
gularly posted and delicately constructed bone is 
not only connected with the tongue, but with 
many other highly important muscles, to which it 
affords a support and a lever. 

573. Each jaw is provided with sixteen teeth 
(fiig. CLV.), arranged with perfect uniformity, 
eight on each side of each jaw (fig. ci.v.) ; those 
of the one side exactly corresponding with those 
of the other (fig. clv.). The teeth, from the dif- 
ferences they present in their size, form, mode of 
connection with the jaw, and use, are divided into 
four classes, namely, on each side of each jaw, 
two incisors (figs. clvi. and clvh. 1, 2V, ow^ 
cuspid (figs, CLVI. and CLvii. 3) ; two \i\c\x%\i\^ 

1 3 



3[IX>SOPHT OP HEALTH. 



(figs. CLvi, and olvii. 4, 5) ; and three moln 
(figs. CLVI. and clvii. 6, 1, 8). 

FLg. CLV. 




A lateral view of the whole leriei of the teelli, ta n'n, 
■hawing the leUtiie eitualioD ofthaaeof the upper with 
those of the luwerjav. This figure and the follawinf; 
figuiea to 159, are copied from Mr. T. Bell's Kientific ud 
iwtructiTe work on the AaatOEoy, Phjalologj, aadDiHawt 
of the Teeth. 

574. The incisor, or cutting teeth, are situated 
a the front of the jaw ; that directly in the centre 
B called the central ; and the nest to it the lateitl 

ir (fig. CLV.), Their office, as their name 
importH, IE to cut the food, which they do, on the 
principle of shears or scisEurs. 

575. Standing next to the lateral incisor is the 
cuspid, canine, or eye-tooth (figs, clv., clvi., and 
CLVii.). It is the longest of all the teeth. It» 

office 18 to tear such 'pat\s oi We iool aa 9.te too 
bard to be readily diiide4\>"j \\i&\Tit\tm*. 



516. Next the cuapid u« tlie bicuflpid, two on 
each aide (fig. clt., cltii.)) m nuned from t'neir 




Fiiint or ratenial tinr of the upper teeth. 1. The leatnl 
innior. 2. The laletal iociwr. 3. The cuipid. 4. Thu 
firrt bicuKpid. 9. The sacond bicujpid. 6. The fint 
ataiia. 7. The mcodiI muUi. S. The Ihiid molar, oi dean 
wpieotin. 

being provided nith two distinct prominences or 
points. Their ofBce it to tear tough BubBtances 
preparatory to their trituration by the next aet. 

511- The molars, or the grinders, three on 
each tide (fig. clvi. and clvii.), provided with 
&ar or five prominences on the griadin^ &\uI«kk, 
with corrtaponding depressioni, >H\iic\v at% *« 



160 THE FRILOSOPHY OP BBALTB. 

BiTaag;ed that the elevations of those of the upper 
aie adapted to the concavities of those of the Iowa 
jaw, and the contrary. 

578. From the incieor to the molar teeth there 
Fig. CLVII, 




Iront view of Ihe lavre 
■L The WirtA inciscr. 3. Th. 
cuapid. 5. The swoDii Liuu 
7. The aecund molu'. S. The 



is a regular gradation in eize, form, and usCt the 
cuspid holding a middle place between the incisor 
and the bicuspid, and the bicuspid being ia 
every respect intermediate \>eWean the cuspid and 
■ *he molar. Thus the incisoT we «^^x«& ovivj W 



THE TEETH. 181 

cutting, the cuspid for teariug, the bicuspid partly 
for tearing and partly for grinding, and the molar 
solely for grinding. The incisor has only a single 
root, which is nearly round, and quite simple (fig. 
cLvii. 1,2); the cuspid has only a single root, but 
this is flattened and partially grooved (fig. clvii. 
3) ; even the bicuspid has only a single root, but 
this is commonly divided at its extremity, and is 
always so much grooved as to have the appear- 
ance of two fangs partially united, the body having 
two points instead of one, thus approaching it to 
the form of the molar (fig. clvii. 4, 5) ; and 
these last have always two, sometimes three, occa- 
sionally four roots, and their body is greatly in- 
creased in size, and ha9 a complete grinding sur- 
face (fig. CLVII. 6, 7, 8). 

579. In some animals whose food and habits 
require the utmost extension of the office of a par 
ticular class of teeth, a corresponding development 
of that class takes place. Thus in the camivora, 
as is strikingly seen in the tiger and the polar 
bear, the cuspid or canine teeth are prodigiously 
elongated and strengthened, in order to enable 
them to seize their food, and to tear it in pieces. 
On the other hand, in the rodentia,. or gnawing 
animals, as in the beaver, the incisors are exceed- 
ingly elongated ; while in the graminivora, and 
especially in the ruminantia, the molar teeth are 
by far the most developed. In each cas^ llait 
other kinds of teeth are of little compaTalVi^ vm- 



182 THE PHILOSOPHY OF HEALTH. 

portance; sometimes they are even altogether 
wanting. Thus the shark has only one kind of 
tooth, the incisor ; but of these there are several 
rows, and all of them the creature has the power 
of erecting at will. 

580. So intimately are these organs connected 
with the kind of food by which life is sustained, 
and the kind of food with the general habits of 
the animal, that an anatomist can teU the struc- 
ture of the digestive organs, the kind of nervous 
system, the physical and even the mental endow- 
ments ; that is, the exact point in the scale of organ- 
ization to which the animal belongs, merely by 
the inspection of the teeth. 

581. In man, the several classes of the teeth 
are so similarly developed, so perfectly equalized, 
and so identically constructed, that they may be 
considered as the true type from which all the 
other forms are deviations. 

582. For the accomplishment of their office the 
teeth must be endowed with prodigious strength : 
for the fulfilment of purposes immediately con- 
nected with the apparatus of digestion, it is ne- 
cessary that they should be placed in the neigh- 
bourhood of exceedingly soft, delicate, irritable, and 
sentient organs. That they may possess the re- 
quisite degree of strength, they are constructed 
chiefly of bone, the hardest organized substance. 

Bone, though not as sensvVAt «t"a f^ome other part? 
of the body, is neveTt\ie\e«.^ ^cviXartvX.. Tt^^ «si 



THE TBBTB. 183 

ployment of a sensitive body in the office of 
breaking down the hard substances used as food 
would be to change the act of eating from a 
pleasurable into a painful operation. It has been 
shown (vol. i. p. 84) that provision is made for 
supplying to the animal a never-failing source of 
enjoyment in the annexation of pleasurable sen- 
sations with the act of eating, and that, taking 
the whole of life into account, the sum of enjoy- 
ment secured by this provision is incalculable. 
But all this enjoyment might have been lost, 
might even have been changed into positive pain, 
nay, must have been changed into pain, but for 
adjustments numerous, minute, delicate, and, at 
first view, incompatible. 

583. Had a highly-organized and sensitive 
body been made the instrument of cutting, tearing, 
and breaking down the food, every tooth, every 
lime it comes in contact with the food, would pro- 
duce the exquisite pain now occasionally ex- 
perienced when a tooth is inflamed. Yet a body 
wholly inorganic and therefore insensible, could 
not perform the office of the instrument ; first, 
because a dead body cannot be placed in contact 
with living parts without producing irritation, dis- 
ease, and consequently pain; and, secondly, be- 
cause such a body being incapable of any process 
of nutrition, must speedily be worn away by fric- 
tion, and there could be no possibility of repairing 
ar of replacing it. The instrument in c\ne%\AWv^ 



Ib-i THE PHILOSOPHY OF HEALTH. 

then, must possess hardness, durability, and, to a 
certain extent, insensibility ; yet it must be capa* 
ble of forming an intimate union with sentient and 
vital organs, must be capable of becoming a con- 
stituent part of the living System. 

584. To communicate to it the requisite de- 
gree of hardness, the hard substance forming its 
basis is rendered so much harder than common 
bone that some physiologists have even doubted 
whether it be bone, whether it really possess a 
true organic structure. That there is no ground 
for such doubt the evidence is complete. For, 

1. The tooth, like bone in general, is composed 
partly of an earthy and partly of an animal sub- 
stance ; the earthy part being completely remov- 
able by maceration in an acid, and the animal 
portion by incineration, the tooth under each 
process retaining exactly its original form. 

2. The root of the tooth is covered exter- 
nally by periosteum ; its internal cavity is lined 
by a vascular and nervous membrane, and both 
structures are intimately connected with the sub- 
stance of the tooth. If these membranes really 
distribute their blood-vessels and nerves to the 
substance of the tooth, which there is no reason to 
doubt, the analogy is identical between the struc- 
ture of the teeth and that of bone. 

3. Though the blood-vessels of the teeth are so 
minute that they do not, under ordmary circum- 

5/aiices, admit the red psLxlVdeaolxJci^ WwA^wA. 



THE TEETH. 185 

ough no colouring matter hitherto employed in 
tificiftl injections has been able, on account of its 
ossness, to penetrate the dental vessels, yet diseise 
metimes accomplishes what art is incapable of 
fecting. In jaundice the bony substance of the 
3th is occasionally tinged with a bright yellow 
lour ; and in persons who have perished by a 
dlent death, in whom the circulation has been 
ddenly arrested, it is of a deep red colour, 
oreover, when the dentist files a tooth, no pain 
produced until the file reaches the bony sub- 
ance ; but the instant it begins to act upon this 
irt of the tooth, the sensation becomes sufficiently 
:ute. 

585. These facts demonstrate that the bony 
atter of the tooth, though modified to fit the in- 
niment for its office, is still a true and proper 
-ganized substance. 

586* Each tooth is divided into body, neck, 
id root (fig. cLviii. 1, 2, 3). The body is that 
irt of the tooth which is above the gum, the root 
lat part which is below the gum, and the neck 
lat part where the body and the root unite (fig. 
LViii). The body, the essential part, is the tooth 
roperly so called, the part which performs the 
hole work for which the instrument is con- 
Tucted, to the production and support of which 
il the other parts are subservient. 

587. Wheii a vertical section is madc^ m \\.\ft. 
'oth, it ia found to contaiu a cavity oi ccm^A^^x- 



THB FHILOSOPBT OP BEALTB. 
Fig.CLVlU. 




Views of difiacvnt kindi of tavth, thuwiog thair anitomi- 
cbI diviiiioD into, 1. Ttw budy or crowD. 2.11u£ui)[m 
luot. 3. TtM Deck. 

able size (fig. clis. 3), termed the dental cavitj, 
whicli, large in the bod; of the tooth, graduklt; 
diminishes through the whole leng;th of the root 

Tig. CLITL — Stcliwi of Tttth, exkibiling Iktir Sma^M. 




(Sg. ctix. 3). The AcBtiAc«'rt^ iaVvoftdthrough- 
oat with a thin. delic»te, and -^MCiiw uuK^mafc, 



INAMBL. 187 

tinued from that which lines the jaw. It con- 
ts a pulpy substance. This pulp, highly vas- 
a and exquisitely sensible, is composed almost 
[rely of blood-vessels and nerres, and is the 
rce whence the bony part of the tooth derives 
vitality, sensibility, and nutriment. The blood- 
lels and nerves that compose the pulp enter 

dental cavity through a minute hole at the 
remity of the root (fig. clix. 4). The mem- 
ne which lines the dental cavity is likewise 
tinued over the external surface of the root, so 
;o afford it a complete envelope. 
•88. Provision having been thus made for the 
finization of the tooth, for the support of its 
lity, and for its connexion with the living 
bem, over all that portion of it which is above 

gum, and which constitutes the essential part 
the instrument, there is poured a dense, hard, 
rganic, insensible, all but indestructible sub- 
loe, termed enamel (fig. clix. 2) ; a substance 
rganic, composed of earthy salts, principally 
«phate of lime with a slight trace of animal 
;ter : a substance of exceeding density, of a 
ky-white colour, semi-transparent, and consist- 

of minute fibrous crystals. The manner in 
ch this inorganic matter is arranged about the 
y of the tooth is worthy of notice. The crystals 
disposed in radii springing from the centre of the 
h (fig. cjLx. 3) ; 80 that the extremities oi \)[i<e^ 
taJs form the external surface of tYie tooXlti^ 



188 THK FHILOSOPBY OF BBALTB 

while the internal eztremitiec aie in c> 
the bony substance (fig. clx. 3). By tl 
ment a two-fold advantage is obtained ; 
Fig. CLX. 



Mit|nii£ed section of 

of ine tibra ■■ ciystalg con 

of the touth. 2. Buoy h 



is less apt to be worn down by friction, 
liable to accidental fracture. 

589. In this mannei ao instrumt 
stmcted possessing the requisite hardi 
bility, and inBeneibility ; yet organized 
truly an integrant portion of the living 
the eye or the heart. 

590. No less care is indicated in 
in constructing the instrument. It is 
situation not by one expedient, but by 

1. All along the margin of both jaw 

a bony arch, pierced with holes, which 

the sockets, called e.\'jeo\i, te ^^m; 

CLxi.). Each Bocket or ^4\w>\ms 




rASTSMINaS OF THt TIKTH. ISy 

there being one alveolus for each tooth (fig. 
Ci:ki.). The adaptation of the root to the 
■IveoluB is so exact, and the adhesion so clirae. 
that each root is fixed in its alveolus just as a nail 
IS fixed whea driven into & board. 

EV. CLXI. 




Upper jaw, ■hinriu); thu alieoli. 

2. The roots of the tooth, when there are more 
than ODC, deviate from a straight line (fig. clvi. 
6, 7. 8) ; and this deviation from parallelism, uii 
an obvious mechanical principle, adds to the firm 
nesB of the connexion. 

3. Adherent by one edge to the bony arch of 
the jaw, and by the other to the neck of the tooth, 
is « peculiar eubstance, dense, &no, merc^K(vya%, 
Jailed the gum, /ess hard than caruVa^e.WXTftvuii 



190 THE PHILOSOPHY OP HEALTH. 

harder than skin, or common membrane ; abound- 
ing with blood-vessels, yet but little sensible ; con- 
structed for the express purpose of assisting to fix 
the teeth in their situation. 

4. The dense and firm membrane covering the 
bony arch of the jaw is continued into each 
alveolus which it lines ; from the bottom of the 
alveolus this membrane is reflected over the root 
of the tooth, which it completely invests as far as 
the neck, where it terminates, and where the 
enamel begins : this membrane, like a tense and 
strong band, powerfully assists in fixing the 
tooth. 

5. Lastly, the vessels and nerves which enter 
at the extremity of the root, like so many strings, 
assist in tying it down ; hence, when in the pro- 
gress of age, all the other fastenings are removed, 
these strings hold the teeth so firmly to the bottom 
of the socket, that their removal always requires 
considerable force. 

591. But a dense substance like enamel, acting 
with force against so hard a substance as bone, 
would produce a jar which, propagated along the 
bones of the face and skull to the brain, would 
severely injure that tender organ, and effectually 
interfere with the comfort of eating. 

592. This evil is guarded against, 

1. By the structure of the alveoli (fig. clxii.), 
which are composed not oi Ciexv^^ «xv^ ^Q\fv>^act« but 
^ if loose and epongy bone (,^^.c\-^\\.^» T\s«.^iwr 



CAMCBM^TXi) mavcrvKX or altkoli. 191 
f^. CLXII. 




of the teeth. 



cellated arrangement of the oebcoub fibres is admi- 
rably adapted for absorbii^ vibrations and pre- 
venting their propagation (90). 

2. By the membTane vhich lines the sucket. 

3. By the membrane which coTers the root of 
the tooth ; and, 

4. By the ^m. 

These membranous substances, even more than 
the cancellated structure of the alveoli, absorb 
vibrations and counteract the communication of a 
shoclc to the bones of the face and head w^ftw 'Oe\« 
leetb act forcibly on hard materials; bo mttQ."3 



192 THE PHILOSOPHY OF HEALTH. 

and such nice adjustments go to secure enjoyment, 
nay to prevent exquisite pain, in the simple ope- 
ration of bringing the teeth into contact in the act 
of eating. 

593. The teeth in mastication are passive 
instruments put in motion by the jaws. The 
upper jaw is fixed, the lower only is movable. 
The lower jaw is capable of four different motions; 
depression, elevation, a motion forwards and back- 
wards, and partial rotation. These simple motions 

Fig. CLXIII Fiew of the Musclea of Moiiicaium, whict 

e/eveUe the lower jaw* 




1. The temporal muscle. 2. list insertion passing beneath. 

3. The zygoma. 4. The masseter muscle, its anterior 

portion reflected to show the insertion of the temporal 

The action of these powerful muscles is tu pull the luim 

jdw upwards with ^reat force against the upper jaw, and 

at the same time to draw it a,\\\.\.\«& iox'Nttx^^v^t backwards, 

According to the direction oi X'h'a ft\»\>s% ^il >i^«t \u>aaR2ixi^ 



HUSCLBB Of UABTICATION. 193 

npable, by combination, ot produciug variouB 
pound motions. Numerous miucles, some of 
1 endowed with prodigious power, are bo di»- 
d and combined as to be able, at the command 

Fig. CLXIV.— Jtf«ic/« o/lie Jaw, 




lion aC the if gomalic ftocrm of the tcmpord boue. 
ceoding plate of the luwer jaw removed to eipoae, 
.erDol pterygoid, and, 4. laternal ptc^Tygoid muacLes. 
etion of these muscles is to raise the lower iaw, and 
1 it obliquely towside the opposite side. Wnea both 

(□ maie the fore-teeth projeet beyond those uf the 
jaw. 

lition, to produce any of these motions that 
K required, simple or compound. 
1. By the combination, succeBHion, alter- 
1, and re/ietition of these mot\ora, "Oo^ Vs«^ 
ie to prodace upon the up^x JKW "iSi. "i^^ 



194 THE PHILOSOPHY OP HEALTH. 

variety of preeeure necessary for the mastication of 
the food. In this process the muscles of the 
tongue perform scarcely a less important part tban 
the muscles of the lower jaw. Some of its mvor 
cular fibres shorten the tongue, some give it 
breadth, others render it concave, and othen 
convex : so ample is the provision for moving this 
organ to different parts of the mouth and fauces, 
whether to bruise the softer parts of the aliment 
against the palate, to mix it with the saliva, or to 
place it under the pressure of the teeth. 

595. By the combined action of the muscles 
of the lower jaw and tongue, and that of the teeth, 
the food is bruised, cut, torn, and divided into 
minute fragments. This operation is of so much 
importance that the whole process of digestion is 
imperfect without it. It is proved by direct expe- 
riment that the stomach acts upon the aliment 
with a facility in some degree proportionate to the 
perfection with which it is masticated. If an 
animal swallow morsels of food of different bulks, 
and the stomach be examined after a given time, 
digestion is found to be the most advanced in the 
smallest pieces, which are often completely soft- 
ened, while the larger are scarcely acted upon 
at all. 

596. At the same time that, by the operation 
of mastication, the aliment undergoes mechanical 
division^ it imbibes a quanlVt^ oi ^vi\A.dftxvved firom 
varioua sources. 



SALIVAKT BUNDS. 19S 

1 . Vnm the membnne which linet the internal 
surface of the mouth, and which affords a covering 
to all the parts contained in it. 

2. From numerous minute glands placed in 
clusters about the cheeks, gums, lipi, palate, and 
tongue. Each of these glauds is furnished with 
its own little duct, which, piercing ihc mucous 
memlH'Hiie, opens into the cavity of the mouth. 
From tliese glands is derived the fluid with which 
the interior of the mouth it lubricated. It coniiats 
of a glutinous, adhesive, transparent fluid, of a 
light grey tint, salt taste, and slightly alkaline 
nature, termed mucus. 

Fit;. CLXV— Ftw if Ihi Parmid Glmd a<ilA Iht MuK/f 




I. PsroM gland. 2. Paratid dact. 3. HhweIvt muacl*. 
•I. Buccinstar. Ti. TrianguUriij, or dcprcuuT uf tin wo^ 
ot the nio-itb. 6. DrpreKiai of the Vqkui \\f . 1. CWixsM- 
ara. or drailarmiuebi of the movlCk. i, ^-aXx^^mita^' 



196 THE PHILOSOPHY OF HEALTH. 

or the distorter of the mouth, as in laaghin^. 9. IQeTator 
oi* the Single of the mouth. 10. Elevator of the upper lip, 
and win^ of the nose. 1 1 . Compressor of the cartila^ of 
the nose. 12. Orbicularis, or circular muscle of the eye- 
lids. 13. Occipito frontalis; elevator of the eye-lids; 
motor of the scalp, &c., an important muscle of ezpresaon. 
14. Tendinous portion of tho occipito frontalis. 16. Ele- 
vator of the ear. 

3. From six large glands placed symmetrically, 
three on each side, termed the salivary glands, 
namely, the parotid (fig. clxv. 1), situated before 
the ear ; the submaxillary (fig. cliii. 4), situated 
beneath the lower jaw ; and the sublingual (fig. 
CLIII. 5), situated immediately under the tongue. 
Each of these glands is provided with a duct 
(figs. CLXV. 2, and cliii. 4, 5), by which it pours 
the fluid it elaborates, called saliva, into the 
mouth. 

597. The other fluids of the mouth are always 
mixed with the saliva, and are all commonly in- 
cluded under that name. The secretion of these 
fluids is unceasing, and they pass into the stomach 
by successive acts of deglutition at nearly regular 
intervals ; so that the stomach, after it has been 
some time without food, contains a considerable 
quantity of these fluids. But they are chiefly 
needed during the operation of mastication, and 
two provisions are made for securing their flow in 
the greatest abundance at that time. 

598. First, the situation of the glands is such 
that they are all exposed to t\va wition of the 

muscles of mastication C^ga. ci.il\i\. *ii^ c.\axs^^ 



SALIVARY GLANDS. 197 

ion the glands are excited, a large 
^ood is deteimined to them, and the 
luid they secrete is proportionate to 
tf hlood they receive. Secondly, the 
iced under the influence of the mind, 
:ry thought, and still more the taste, 
od, acting upon them as an addi- 
us, causes an additional secretion, 
of fluid formed from these diflereut 
mixed with the food during the mas- 
. ordinary meal, is estimated at half 
lust commonly he more than this, 
case described by Dr. Gairdner, of 
1 which the esophagus had been cut 
as observed that from six to eight 
iiva were discharged during a meal, 
ed merely of broth injected through 
iophagus into the stomach, 
va is a frothy, watery fluid, in its 
: nearly insipid, and of a slightly 
re. It is composed of water, a pecu- 
substance called salivary matter, 
some, a little albumen, and several 
iuces important changes on the food, 
r, and the salts contained in it, it 
issolves the food ; and thus, while it 
ier to be swallowed, it prepares it for 
it changes it is to undergo. To this 
the assimilation of the (ood^iX^^isv^ 
te the first tendency \>y l\it ^JwASa^ 



198 THE PHILOSOPHY OF HBALTH. 

substances, the salivary, and the albuminous 
matter which it adds to it. From this, the com- 
mencement of the assimilative process to its com- 
pletion, animalized substances are successively 
added to the food which have the property of con- 
verting the food more and more into the nature of 
animal substance. 

600. Comminuted by the teeth, and softened 
by the saliva, the food is reduced to a pulp. In 
this pulp there is a complete admixture of all the 
alimentary substances with the assimilative matrer 
secreted from the blood, into the nature of which 
it is to be ultimately changed. The mass is at 
the same time brought to the temperature of the 
blood. 

601. As long as the operations of mastication 
and insalivation go on, the mouth forms a closed 
cavity from which the food cannot escape ; for the 
lips enclose it before, the cheeks at the sides, the 
tongue below, and the soft palate behind, the infe- 
rior edge of which being applied in close and firm 
contact with the base of the tongue, prevents 
all communication between the mouth and the 
pharynx. 

602. When, by mastication, the food is suffi- 
ciently divided, and by insalivation softened anc 
animalized to fit it for the future changes it is t 
undergo, it is collected by the tongue, and carrie 

by that organ to the back pari ol l\v^ mwiXV T 
soft palate (fig, clii. 1), obedveivl \»\)cv^ ^'cots? 



THE SOFT PALATB. 199 

of the duly prepared food, rises the instant it is 
touched by it, and afifords it a free passage to the 
pharynx (Bgs. cliii. 10, and cliv. 10). 

603. The pharynx (fig. cliii. 10), a muscular 
bag, immediately continuous with the moudi 
(fig. CLIII. 1), is a vestibule into which o|K'n 
several highly important organs. Before is the 
entrance to the windpipe, termed the glottis (Hg. 
CLIV. 9), leading directly to the larynx (fig. cliv. 8); 
at the sides are the mouths of two ducts, termed 
the Eustachian tubes, which lead to the internal 
part of the organ of hearing ; above are two en- 
trances to the nose (fig. cliv. 1^, and below is the 
passage to the stomach (fig. cliii. 12). 

604. Were the food to enter the Eustachian 
tubes or the nose, it would occasion great incon- 
venience ; were it to enter the glottis, it would 
cause death. It is prevented from entering the 
Eustachian tubes and the nose by the soft palatc- 
(fig. CLii. 1 and 2), which by the very act of 
rising to aflFord an opening from the mouth to the 
pharynx, is carried over the other apertures so as 
completely to close them. By the varied direction 
of the muscular fibres which enter into the com- 
position of this organ, it is enabled to execute the 
different and even opposite motions required in 
the performance of its important office. 

605. The food is prevented from entering the 
glottis partly by a cartilaginous v«Av^ (^^, c.\an •'V^^ 

termed the epiglottis, placed imm^iiJvsiX.^^ ^w^ 
the glottis, and attached to the xoot ^l \>afc V^fw^^ 



200 THE PHILOSOPHY OF HEALTH. 

(fig. CLiv. 6). In delivering the food to the 
pharynx the tongue passes hackwards (fig. cliv. 6). 
In passing backwards it pushes in the same direc- 
tion the epiglottis which is attached to it, and so 
necessarily carries it over the glottis, completely 
closing the aperture (fig. cliv. 9). At the same 
time the opening is still more securely closed by 
the glottis itself, in consequence of the powerful 
and simultaneous contraction of the muscles that 
act upon it in the production of the voice. It is 
proved, by direct experiment, that the spontaneous 
closure of the glottis is a more powerful agent in 
excluding the food from the larynx even than the 
depression of the epiglottis ; but both organs 
concur in producing the same result ; and a 
double security is provided against an event which 
would be fatal. 

606. It is deeply interesting to observe the 
part performed in these operations by sensation 
and volition, and the boundary at which their in- 
fluence terminates and consciousness itself is lost. 
Mastication, a voluntary operation, carried on by 
voluntary muscles, at the command of the will, ig 
attended with consciousness, always in the state o 
health of a pleasurable nature. To communicaf 
this consciousness, the tongue, the palate, the lip 
the cheeks, the soft palate, and even the pharyr 
are supplied with a prodigious number of senti 
nerves. The tongue especially ^ one of the n 
active agents in the operaUoii,\s «\r^^\\^^Vv 



POINT AT WHICH CONSCIOUSNESS CEASES. 201 

less than six nerves derived from three different 
sources. These nerves, spread out upon this 
organ, give to its upper surface a complete cover- 
ing, and some of them terminate in sentient ex- 
tremities visible to the naked eye. These sentient 
extremities, with which every point of the upper 
surface, but more especially the apex, is studded, 
constitute the bodies termed papillae, the immediate 
and special seat of the sense of taste. This sense 
is also diffused, though in a less exquisite degree, 
over the whole internal surface of the mouth. 
Close to the sense of taste is placed the seat of the 
kindred sense of smell. The business of both 
these senses is with the qualities of the food. 
Mastication at once brings out the qualities of the 
food and puts the food in contact with the organs 
that are to take cognizance of it. Mastication, a 
rough operation, capable of being r.ccompli8hed 
only by powerful instruments which act with force, 
is carried on in the very same spot with sensation, 
an exquisitely delicate operation, having its seat 
in sofl and tender structures, with which the ap- 
propriate objects are brought into contact only with 
the gentlest impulse. The agents of the coarse 
and the delicate, the forcible and the gentle 
operations are in close contact, yet they work 
together not only without obstruction, but with the 
most perfect subserviency and co-operation. 

607. The movements of ma»V\ea\Aoxv ^\^ Y^^- 
duced, and, until they have accoTo^v^'t'^ "^^ 



202 THE PHILOSOPHY OF HEALTH. 

objects of the operation, are repeated by successive 
acts of Tolition. To induce these acts, grateful 
sensations are excited by the contact of the food 
with the sentient nerves so liberally distributed 
over almost the whole of the apparatus. To the 
provision thus made for the production of plea- 
surable sensation, is superadded the necessity of 
direct and constant attention to the pleasure in- 
cluded in the gratification of the taste. It is justly 
observed by Dr. A. Combe, that without some 
d^ee of attention to the process of eating, and 
some distinct perception of its gratefulness, the 
food cannot be duly digested. When the mind is 
so absorbed as to be wholly unconscious of it, or 
even indifferent to it, the food is swallowed without 
mastication ; then it lies in the stomach for houri 
together without being acted upon by the gastric 
juice, and if this be done often, the stomach 
becomes so much disordered as to lose its power of 
digestion, and death is the inevitable result : so 
that not only is pleasurable sensation annexed to 
the reception of food, but the direct and con- 
tinuous consciousness of that pleasurable sensa- 
tion during the act of eating is made one of the 
conditions of the due performance of the digestive 
function. 

608. With the operation of mastication wad 
one part of the process of deglutition, immediatel* 
to be DotJcedf the agency of \o\\\.\oii «xk^ «ft.\isatio 
cease. Beyond this the iuncvvwi ol ^^^%5w» 



DEGLUTITION. 203 

wholly an organic process. In addition to the 
reasons assigned (vol. i. p. 55) why all the organic 
processes are placed alike beyond the cognizance 
of sense and the control of the will, there is this 
special reason why, in the function of digestion, 
they cease at the exact boundary assigned them. 

609. Every time the act of deglutition is per- 
formed the openings to the windpipe and to the 
nose are closed, so that during tliis operation all 
access of air to the lungs is stopped, consequently 
it is necessary that the passage of the food through 
the pharynx should be rapid. Mastication, a 
voluntary process, may be performed slowly or 
rapidly, perfectly or imperfectly, without serious 
mischief; but life depends on the passage of the 
food through the pharynx with extreme rapidity 
and with the nicest precision. It is therefore 
taken out of the province of volition and entrusted 
to organs which belong to the organic life, organs 
which carry on their operations with the steadi- 
ness, constancy, and exactness of bodies whose 
motions are determined by a physical law. 

610. No sooner does the duly- prepared food 
touch the soft palate than the whole apparatus of 
deglutition is instantly in motion. This movable 
partition suddenly rises to afford to the food a free 
passage to the pharynx. The pharynx itself, at 
the aame instant, rises to receive the morsel thrust 
towards it by the pressure of the totv^vx^*, ^\A orcw^ 
muBcle, the «tyio-pharyngeuft, Yr\vvcli eoTic\«% Vsk^ 



204 THE PHILOSOPHY OF HEALTH. 

producing this movement, seems specially in- 
tended, in addition, to expand the pharynx. Three 
muscles throw their fihres around the pharynx, 
termed its upper, middle, and lower constrictors, 
which, the moment the morsel reaches the pha- 
nmx, contract upon it, and embrace it firmly. At 
the same instant the larynx, closing its aperture, 
springs forward towards the base of the tongue, 
under which it is in a manner concealed, the 
additional shield of the epiglottis being simul- 
taneously thrown over the glottis. By this move- 
ment of the larynx, upwards and forwards, the 
course of the morsel across the dangerous passage 
is shortened. All these motions take place with 
such rapidity that Boerhaave said the action is 
convulsive. And now the food, firmly pressed by 
the pharynx, cannot return to the mouth, for the 
root of the tongue is there stopping up the pas- 
sage ; it cannot enter the Eustachian tubes or the 
nose, for the soft palate is there closing the aper- 
tures; it caimot enter the larynx, for a double 
guard is placed upon the glottis securing its firm 
closure. The food can advance in one direction 
only, the direction required, that which leads to 
the esophakgus. Well, therefore, on the con- 
templation of these complex structures and the 
omsent and harmony with which they act, might 
Paley say, '' In no apparatus put together by art 
do I know such muitiisiiwi& \3>se& %() a.i^tlY con- 
trived ma in the natuiai or^^ias^zAXioTi q*1 >^^\sq3&s3^ 



THB MOUTH AND APPENDAGES. 205 

1 and its appendages. In this small cavity 
lave teeth of different shape ; first, for cut- 
; secondly, for grinding ; muscles most arti- 
ily disposed for carrying on the compound 
ions of the lower jaw by which the mill is 
ked ; fountains of sahva springing up in dif- 
^nt parts of the cavity for the moistening of the 
>d while the mastication is going on ; glands to 
id the fountains ; a muscular contrivance in the 
ick part of the cavity for the guiding of the pre- 
ured aliment into its passage towards the stomach, 
nd for carrying it along that passage. In the 
nean time, and within the same cavity, is going 
3n other business wholly different, that of re- 
spiration and of speech. In addition, therefore, to 
all that has been mentioned, we have a passage 
opened from this same cavity of the mouth into 
the lungs for the admission of air, for the admis* 
aion of air exclusively of every other substance ; 
we have muscles, some in the larynx, and, without 
number, in the tongue, for the purpose of mo- 
dulating that air in its passage, with a variety, a 
compass, and a precision of which no other musical 
instrument is capable; and, lastly, we have a 
specific contrivance for dividing the pneumatic 
part from the mechanical, and for preventing 
one set of functions from interfering with the other. 
The mouth, with all these intentions to serve, is a 
single cavity; is one machine, 'wvlVv \\a ^^\» 
leither crowded nor con&ned, and ^^cNx \3»k^ 



206 THE PHILOSOPHY OF HEALTH. 

barrassed by the rest." It should be added, the 
mouth is also the immediate seat of one of the 
senses, and is in intimate communication with a 
second sense ; both these senses are always ex- 
cited while the principal business performed by 
the machine is carried on, and are necessarily 
excited by the very working of the machine, and 
the sensations induced in the natural and sound 
state of the apparatus are invariably pleasurable. 
611. The food is delivered by the pharynx to 
the esophagus (fig. cliii. 12), a tube composed 
partly of membrane and partly of muscle. Its 
muscular fibres consist of a double layer, an ex- 
ternal and an internal layer ; the external has a 
longitudinal direction ; the internal describes por- 
tions of a circle around the tube. By the contrac- 
tion of the longitudinal fibres the length, and by 
the contraction of the circular fibres, the diameter 
of the tube is diminished. Cellular membrane 
envelopes these layers of fibres externally, and 
mucous membrane covers them internally. Whea 
the tube is contracted, the mucous membrane is 
disposed in folds, which disappear when it ii 
dilated, and these folds allow of the expansion of 
the tube without injury to the delicate tissue that 
lines it. The food passes slowly along the eso- 
phagus urged towards the stomach, not by its own 
gravity, but by a force exerted upon it by the 
tube itselfy chiefly by the coivtTactiou of its cir- 
cular Bbres. Delivered at \eii%l\i \» \)afc «x«a»i^ 



TSB groMACB. 201 

the food ii incapable of retuniing into the eaopbk- 
gna IB eoniequence of the oblique direction in 
which the esophagus enters the atomach, the 
obliquity of its ratrtnce serving tEie office of a 
valTe. 

613. The stomach is a bag of an irregular 
oval shape (1^. clxvi.), capable, in the adult, 
of containing about three pints. It is placed trans- 
versel; across the upper part of tlie alidomen 
(fig. u. 7). It occupies the whole epigastric 
(Sg. cv. 3), and the greater part of the left 
hypochondriac regions (fig. cvii. 3). Above, it 
is in contact with the diaphragm, the arch of 




I. Ite nophmrui Inmiuting in the itonuch. 2. The 
cvdiu ori&ca. 3. The py lama. 4.Thii coinmencementiif 
the duodanum. S. The lurge cuivHiuin of thu eloniBch. 
6. ThB imall curriilure. 7. The lurga ™\njmi\^. ft.Tws 
tmmll uTtKiBtty. 9. Tlie laU|;itudiiie\ iiauKu\>x f&««m> 
10. Iha eirealar muKulair fibre*. 



THE STOMACH. 209 

(fig. CLxvi. 7), the esophagus opens by an aper- 
ture called the cardiac orifice (fig. clxvi. 2). At 
the right extremity, a second aperture called the 
pyloric orifice (fig. clxvii. 2), leads into the first 
intestine. 

614. Between the cardiac and the pyloric 
orifices are two curvatures, one above, called the 
smaller (fig. clxvi. 6), the other below, termed 
the larger curvature (fig. clxvi. 5). 

615. Like the esophagus, the stomach is com- 
posed of two layers of muscular fibres, the external 
longitudina] (fig. clxvi. 9), the internal circular 
[]fig;. clxvi. 10). By the contraction of the first 

extent of the stomach, from extremity to ex- 
dty, is diminished, or the organ is shortened ; 
*. '%y the contraction of the second the extent of the 
■tomach, from curvature to curvature, is dimi- 
nished, or the organ is narrowed. During di- 
gestion, by the contraction of these muscular 
fibres, the capacity of the stomach is changed 
alternately in both directions, whence a gentle 
motion is communicated to the aliment, which is 
thus brought in succession under the influence of 
the agent that acts upon it 

616. A thin but strong membrane, derived 
from the peritoneum, the membrane that lines the 
general cavity of the abdomen, forms the external 
tunic of the stomach ; hence its outer covering is 
called the peritonea] coat. 
61 7. The inner or mucous coat {!^%. ci;xv\\ . V^ , 



210 THE PHltABOPBT 

B direct continuation of the lining membrs 
the esophagus, is sometimes called &lso villoi 
account of the roinule bodies termed villi, 
which every point of its internal surface is atu 
It is these villi which give to this Burfa< 
pilous or velvety appearance. 

618. The mucous coat is far more exh 
than the other two, in consequence of its 
plaited into a number of folds (fig. clxvi 
termed rugee, which are so disposed as to pi 
the appearance of a net-wcrk. The object i 
rupe is to enlarge the space for the espami 




I. Stomach raised to eihiliit til poaleiinr iiiilkce, 

ionis. 3, DuoAvaiira. 4. Fftncieiia. Ei. Spltten. 6. 

auTlace oC tfi« liver. 7. Gall-UailAM, \Q «nin™aa » 

iirer. S. I.arge vesKelt pinceeiVvig tom- ^. k- 

truiik td>mpp\y ihe liver, gaU-bVaAia, «oni»t^4> 

IMaauaa. ami Ei<l>u>n. 



THE STOMACH. 211 

blood-vessels and nerves, and to admit of the 
occasional distension of the organ without injury 
to the delicate tissues of which it is composed. 

619. Immediately beneath the mucous coat are 
the mucous follicles which secrete the mucous 
fluid by which the inner surface of the organ is 
defended. These glandular bodies are extremely 
numerous, and vary considerably in diameter. 
The largest are towards the great extremity, the 
smaller towards the pylorus. 

620. Altogether different from the mucous 
secretion is another fluid, which also flows from the 
mucous surface, termed the gastric or the digestive 
juice, from its being the principal agent in the diges- 
tive process. By some anatomists the gastric juice 
is supposed to be secreted by minute glands placed 
between the mucous and the muscular coats, pro- 
vided with ducts which pierce the mucous coat, and 
which bear their fluid into the stomach precisely 
as the salivary glands carry the saliva into the 
mouth. It is certain that this is the case with 
some animals, as in certain birds, the ostrich for 
example, in which glands of considerable magni- 
tude, with ducts large enough to be visible, are 
seen to pour the digestive fluid into the stomach. 
But as no such glands have been discovered in the 
human stomach, it is generally conceived that in 
man the gastric juice is secreted by minute arteries 
expanded upon the villi. 

62 L All around the pyloric oti&ce (Ja^. cv.^N\\,*i^> 



212 THB PHtLSOPHT 

Fig. CLXIX 




is placed a thick, Btrong, and circular muide 
(6g. CLXViT. 2), termed, from its office, pylonu. 
It is about four times the thickness of the musculu 
coat of the stomach, and presents the appearance 
of a. prominent and even projecting band (fig. 
ciavu. 2). From the frequent action of iB 
fibres, the pylonis often looks as if a piece of pack- 
thread had been tied around it (fig. clsvi. 3). Ita 
office is, by the contraction of its fibres, to guud 
and close the opening from the stomach until the 
aliment has been duly acted upon by the digestive 
fluid. 
622. The quantity of blood sent to the atomach 
is greater than is epent upoa «n^ iA>i« or^n ex- 
cept the brain. The ^esaeXa oi ftva «^«iIIl»t^ VSi% 



BLOOD-VESSELS AND NERVES OF STOMACH. 213 

CLXix.) form two distinct layers, of which the 
external is distributed to the peritoneal and mus- 
cular coats, while the internal, after ramifying on 
the fine cellular tissue which unites the muscular 
and mucous tunics, penetrates the mucous coat, and 
is spent upon the villi, where it forms an exqui- 
sitely-delicate net-work. There is, moreover, an 
intimate vascular connexion between the spleen, 
pancreas and liver, and the stomach (6g. clxviii. 8, 
9). The arteries which supply all these organs spring 
from a common trunk, and there is the freest com- 
munication between them by anastomosing branches. 
623. Equally abundant is its supply of nerves, 
some of which are derived from the organic or 
non-sentient system, and others from the animal 
or sentient system. The organic nerves are 
spread out in countless numbers upon the great 
trunks of the arteries, so as to give them a com- 
plete envelope (fig. clxx. 3) ; these nerves, never 
quitting the arteries, accompany them in all their 
ramifications, and the fibril of the nerve is ulti- 
mately lost upon the capillary termination of the 
artery. It is by these organic nerves that the 
stomach is enabled to perform its organic func- 
tions, which, for the reason assigned (vol. i. p. 82), 
is placed beyond volition, and is without con- 
sciousness. By the nerves derived from the 
sentient system which mingle with the organic 
(fig. XVI.), the function of nutritioii \a \iiQV3L'^\. 
into relation with the perclpieiit "mmd, ^\A ^^ 



^14 THE PBILOSOPBT OF BBALTB. 

¥ig..CVXX.—ritw of Ike Orf one Ntrm ^ lit Si 




I. Under iiiifau of tke iiTer turned upi to bnng nli> 
view the anteiiDi lurftre of the atotaaA. 2. Gdll Uaddtt. 
3. Organic nvnea euirelniMnK the trnoki of the Uool- 
•assals. 4. tVlarie exltemity of the stomach and cobi- 
ineoceineDt of the duoiUnum. b. ConlTacti?d portion of 
the pylona. 6 Situat'ioa of VW Wii-fUa coutiactiM 
of the stomach, heie impe[(Bet.Vj tc^bkuV^- 1 > Qma 



NERVES OF THE STOMACH. 215 

mtde part of our sentient nature. By the coni" 
mixture of tliese two sets of nerves, derived from 
these two portions of the nervous system, though 
we have no direct consciousness of the digestive 
process — consciousness ceasing precisely at the 
point where the agency of volition stops (vol. i. p. 
82, et «eq.), yet pleasurable sensation results from 
the due performance of the function. Hence the 
feeling of buoyancy, exhilaration, and vigour, the 
pleasurable consciousness to which we give the 
name of health, when the action of the stomach is 
soand: hence the depression, listlessness, and 
debility, the painful consciousness which we call 
disease, when the action of the stomach is un- 
sound: hence, too, the influence of the mental 
state over the organic process ; the rapidity and 
perfection with which the stomach works when 
the mind is happy — ^when the repast is but the 
oocasion and accompaniment of the feast of reason 
and the ilow of soul ; the slowness and imper- 
fection with which the stomach works when the 
mind is harassed with care struggling against 
adrerae events ; or is in sorrow and without hope ; 
when the friend that sat by our side, and with 
whom we were wont to take sweet counsel, is 
gone, and therefore gone that which made it life 
to live. 

624. Renovation is the primary and essential 
oj£ce of the stomach, and its or^amc ii&\\^^ ^w- 
mble it to supply the ever-recuning -w^txvX^ o^ N>cv^ 



216 THE PHILOSOPHY OF HEALTH. 

BYstem. Gratification of appetite is a secondary 
and subordinate office of the stomach, and its 
sentient nerves enable it to produce the state of 
pleasurable consciousness when its organic func- 
tion is duly performed. By the double office thus 
assigned it, the stomach is rendered what Mr. 
Hunter named it, the centre of sympathies. . 

625. From the whole length of the great arch 
of the stomach, and partly also from the com- 
mencement of the duodenum (fig. clxx.), the 
peritoneal coat of the stomach is produced, form- 
ing a thin, delicate membranous bag, called the 
omentum, or cawl (fig. clxx. 7). The omentum 
extends from the great arch of the stomach to be- 
low the umbilicus, and completely covers a large 
portion of the anterior surface of the abdominal 
viscera (fig. clxx. 7). Between the two fine 
membranous layers of which it is composed is 
contained a quantity of fat, of which substance it 
serves as a reservoir, and by the transudation of 
which it appears to lubricate the intestines, and 
to assist in preventing their accretion. 

626. The food, on reaching the stomach, does 
not occupy indiflferently any portion of it, but is 
arranged in a peculiar manner always in one and 
the same part. If the stomach be observed in a 
living animal, or be inspected soon after death, it 
is seen that about a third of its length towards the 

pylorus 18 divided from theie^Xb^ the contraction 
of the circular fibries caWed liSafe Vwtt-^^»» ^»sDr 



ARRANGEMBNT OF FOOD IN STOMACH. 217 

traction (fig. clxx. 6). The stomach is thus di- 
vided into a cardiac and a pyloric portion (fig. 
CLXJC. 6). The food, when first received by the 
stomach, is always deposited in the cardiac por- 
tion, and is there arranged in a definite man- 
ner. The food first taken is placed outermost, 
that is, nearest the surface of the stomach ; the 
portion next taken is placed interior to the first, 
and so on in succession, until the food last taken 
occupies the centre of the mass. When new food 
is received before the old is completely digested, 
the two kinds are kept distinct, the new being 
always found in the centre of the old. 

627. Soon after the food has been thus arranged, 
a remarkable change takes place in the mucous 
membrane of the stomach. The blood-vessels 
become loaded with blood; its villi enlarge, 
and its cryptce, the minute cells between the 
rugse, overflow with fluid. This fluid is the 
gastric juice, which is secreted by the arterial 
capillaries now turgid with blood. The abun- 
dance of the secretion, which progressively in- 
creases as the digestion advances, is in proportion 
to the indigestibility of the food, and the quietude 
of the body after the repast. 

628. In the food itself no change is manifest fcr 
some time ; but at length that portion of it which 
is in immediate contact with the surface of the 
stomach begins to be slightly soileii^^. T\\\^ 
eoftening elowly but progressively \iieT^^"a»^^ \vix\A 

VOL, II, 



218 THE PHILOSOPHY OF HEALTH. 

the texture of the food, whatever it m 
been, is gradaally lost ; and ultimately tl 
solid portions of it are completely dissolves 

629. When a portion of food thus acl 
examined, it presents the appearance oi 
been corroded by a chemical agent. Tl 
of a hard-boiled egg looks exactly as ii 
been plunged in vin^ar or in a solution o 
The softened layer, as soon as the soft 
sufficiently advanced, is, by the action 
muscular coat of the stomach, detached 
towards the pylorus, and ultimately trai 
to the duodenum; then another portioi 
harder and undigested food is brought int 
diate contact with the stomach, becomes 
in its turn, and is in like manner detach 
this process goes on until the whole is diss 

630. The solvent power exerted by th 
juice is most apparent when the stomai 
animal is examined three or four hours a 
has been freely taken. At this period the 
of the food first in contact wiih the sto 
wholly dissolved and detached ; the port 
sequently brought into contact with the 
is in the process of solution, while the 
part remains very little changed. 

631. The dissolved and detached porti( 
food, from every part of the stomach flo^ 
but steadily beyond the hour-glass con 

or towards the pyloric exlieixivc^ VJ 



CBTMB. 219 

which not a particle of recent or undiBSolved food 
iB ever allowed to remain. The fluid, which thus 
accumulates in this portion of the stomach, is a 
new product, in which the sensible properties of 
the food, whatever may have been the variety of 
substances taken at the meal, are lost. This new 
product, which is termed chyme, is an homogeneous 
fluid, pultaceous, greyish, insipid, of a faint sweet- 
ish taste, and slightly acid. 

632. As soon as the chyme, by its gradual accu- 
mulation in the pyloric extremity amounts to about 
two or three ounces, the following phenomena 
take place. 

633. First, the intestine called duodenum, the 
organ immediately continuous with the stomach, 
contracts. The contraction of the duodenum is 
propagated to the pyloric end of the stomach. By 
the contraction of this portion of the stomach, the 
chyme is carried backwards from the pyloric into 
the cardiac extremity, where it does not remain, 
but quickly flows back again into the pyloric ex- 
tremity, which is now expanded to receive it. 
Soon the pyloric extremity begins again to con- 
tract ; but now the contraction, the reverse of the 
former, is in the direction of the duodenum ; in 
consequence of which, the chyme is propelled 
towards the pylorus. The pylorus, obedient to 
the demand of the chyme, relaxes, opens, and 
aflbrds to the fluid a free passage into \\i^ (iuvA^- 
num. As soon as the whole of ibe dxiV^ ^t^^^x^^ 

\.1 



220 THE PHILOSOPHY OF HEALTH. 

chyme has passed out of the stomach, the pylonw 
closes, and remains closed, until two or three 
ounces more are accumulated, when the same suc- 
cession of motions are renewed with the same re- 
sult ; and again cease to he again renewed, as 
long as the process of chymification goes on. 

634. When the stomach contains a large quan- 
tity of food, these motions are limited to the parts 
of the organ nearest the pylorus ; as it becomes 
empty, they extend ftirther along the stomach, 
until the great extremity itself is involved in them. 
These motions are always strongest towards the 
end of chymification. 

635. The stomach during chymification is a 
closed chamber ; its cardiac orifice is shut by the 
valved entrance of the esophagus, and its pyloric 
orifice by the contraction of the pylorus. 

636. The rapidity with which the process of 
chymification is carried on is diflferent according 
to the digestibility of the food, the bulk of the 
morsels swallowed, the quantity received by the 
stomach, the constitution of the individual, the 
state of the health, and above all, the class of the 
animal, for it is widely different in different classes. 
In the human stomach in about five hours after 
an ordinary meal the whole of the food is probably 
converted into chyme. 

637. The great agent in performing the pro- 
cess of chymification \» tW ^^^\x\a yiice. The 

evidence of this is com^\e\^ iox^ 



GASTRIC JUJCB. 221 

1. As soon as the food enters the stomach a 
large quantity of hlood is determined to the 
arteries, which secrete the gastric juice (627); 
and this fluid continues to be poured into the sto- 
mach in great abundance during the whole time 
the process goes on. 

2. The solvent power of this fluid is demon- 
strated by the fact that it sometimes dissolves the 
stomach itself, when death takes place suddenly 
durii^ the act of digestion in a sound and vigor- 
ous state of the digestive organs. 

3. On introducing into the stomach alimentary 
substances inclosed in metallic balls perforated 
with holes, or in pieces of porous cloth, it is found, 
on removing these bodies from the stomach, after a 
certain time, that the alimentary substances con- 
tained in them are as completely digested as if 
iliey had been in actual contact with the surface 
of the stomach; the metallic ball and the cloth 
remaining wholly unchanged. This experiment, 
which has been often performed with the same 
uniform result, was the first that led to the disco- 
very of the true nature of the digestive process. 

4. Though it be impossible to imitate out of the 
stomach all the circumstances under which the food 
is placed within it, yet, on procuring gastric juice 
from the stomachs of various animals, and mixing 
it with diflerent alimentary substances, it is found 
not only todisBolve them, but to coii\ct\.\)wewv\aX» 

if pultaceouB mass, closely Te«eixiV>\\xi\^ Oo^yccifc' 



222 THE PHILOSOPHY OF HEALTH. 

Gastric juice thuB procared was put into a glass 
tube with boiled beef, which had been masticated; 
the tube was then hermetically sealed, and ex- 
posed near the fire to a uniform heat : by the side 
of this tube was placed another, containing the 
same quantity of flesh immersed in water. In 
twelve hours, the flesh in the tube con taili- 
ng the gastric juice began to lose its fibrous 
structure ; in thirty-five hours it had nearly lost 
Its consistence, being reduced to a soft homo- 
geneous pultaceous mass. It experienced no fur- 
her change during the two following days. On 
the other hand, the flesh that had been immersed 
in water was putrid in sixteen hours. 

638. Since alimentary substances under the 
action of the stomach present precisely the 
appearance exhibited by bodies exposed to the 
influence of chemical agents, it appears that the 
gastric juice not only dissolves the food, but 
dissolves it by a chemical agency. Its action 
bears no proportion to the mechanical texture of 
bodies, nor to any of their physical properties. It 
acts upon the densest membrane, dissolves even 
bone itself; and yet produces no eflect on other 
substances of the most tender and delicate texture. 
On the skin of fruit, on the finest fibre of flax and 
cotton, it is incapable of making the slightest 
impression. In this selection of substances it 
perfectly resembles «l cYieimcaX ^«o\. ^\.\tl^ hf 
ehemical affinity. On c«t\aai «K^Mto»R^ '^ 



GASTRIC JUICE, 223 

action is unquestionably of a chemical nature. It 
occasions the coagulation of albuminous fluids ; it 
prevents the accession of putrefication ; it stops 
^e process after it has commenced. From the 
whole, it follows that the food in the stomach is 
converted into chyme by the agency of a fluid 
secreted by the inner surface of the stomach, and 
that this change is effected by a proper chemical 
action. 

639. It had been long ascertained that the 
gaatric juice contains an uncombined acid, and that 
if carbonate of lime be placed in a tube and intro- 
duced into the stomach, the carbonate is dissolved 
just as if it were put into weak vinegar. Several 
years ago, it was discovered by Dr. Prout that this 
free acid is muriatic acid. Some time after the pub- 
lication of Dr. Front's experiments, Chevreul and 
Leuret and Lassaigne in France obtained different 
results ; but Tiedemann and Gmelin, professors in 
the university of Heidelberg, in an extended series 
of experiments, arrived at precisely the same con- 
dusion as the English physiologist, and apparently 
without any previous knowledge of the researches 
of the latter. Tiedemann and Gmelin state, as 
the result of their experiments, that the clear ropy 
fluid, or the gastric juice obtained from the stomach 
flome time after it had been without food, is nearly 
or entirely destitute of acidity ; that the presence 
of food, or indeed of any stimuVu^ \a ^^ toxx!(:xs^^ 
membrane, causes the gastric jmcfc\ft\i^^w£v^^c»- 



rf^^' 








.;aestft>^^*'. *•' cop^o«* !„^ia-, »tA«»» 
*"" ,fttv«cc^^^ we «, if. ^** ,tot i*^' 
^' tat «> ^*^*fa\\ cot^***'" Iloff""** 

Xt 19 e'"' .A\ttietvt.a^ „ tha* " » at tine tei» 






CONSTITUENT OF THB GASTRIC JUICE. 225 

itest motion it divides into an insoluble mass, 
ecUy homogeneous and similar to the chyme 
lie stomach ;* a very close approximation to 
BLCtual digestive process, more especially when 

considered that it is not possible to imitate 
of the stomach several circumstances mate- 
y influencing chemical action under which the 

is placed within the stomach. 

11. Muriatic acid, the chemical agent by 
;h the stomach dissolves the food, is probably 
ined from the muriate of soda (common salt) 
ained in the blood. The soda, the basis of the 

would appear to be retained in the blood, to 
erve the alkaline condition essential to the 
itenance of the sound constitution of the blood, 
e the muriatic acid, disengaged from the soda 
he process of secretion, is poured into the 
lach to act upon the food. 

12. A remarkable confirmation of the correct- 
of the general conclusions to which observation 
experiment had thus enabled physiologists to 
re, is afforded by the case of a young soldier 
he American army, of the name of Alexis St. 
tin, who received a wound on the left side by 
accidental discharge of a musket. The charge, 
;h consisted of duck shot, and which was re- 
3d at the distance of one yard from the 
zle of the gun, entered the side posteriorly in 

7r,IL Thomson, British AnnaU o£Med\diiei^(^A*^ 

1.^ 



226 THE PHILOSOPHY OF HEALTH. 

an oblique direction, forward and inward ; blew 
off the integument and muscles to the size of a 
man's hand; fractured and carried away the 
anterior half of the sixth rib ; fractured the fifth 
rib ; lacerated the lower portion of the left lobe of 
the lungs ; lacerated the diaphragm, and perforated 
the stomach. 

643. Violent fever and extensive sloshing of 
the parts injured ensued, and the life of the yooog 
man was often in jeopardy, but he ultimately 
recovered. At the distance of about a year from 
the date of the accident, the injured parts had ill 
become sound, with the exception of the perfo* 
ration into the stomach, which never closed, bat 
left an aperture permanently open, two inches 
and a half in circumference. This aperture was 
situated about three inches to the left of the 
cardia, near the left superior termination of the 
great curvature. For some time the food could 
be retained only by constantly wearing a com- 
press and bandage ; but at length a small fold of 
the mucous coat of the stomach appeared, which 
increased until it completely filled the aperture 
and acted as a valve, so as effectually to prevent 
any efflux from within, while it admitted of being 
easily pushed back by the finger from without : 
when the stomach was nearly empty, it was easy 
to examine its cavity to the depth of five or six 
inches by artifiicial dislenaioiv \ Wv^ -^V^xv entirely 
empty^ the stomach waa «\^«^^ cotoXx^^Xr^ ^^ 



PAPILLJE OF STOMACH. 227 

he valve generally forced through the 
ther with a portion of the mucous 
iqual in bulk to a hen's egg. 
hanced that the admirable opportunity 
d of bringing the process of digestion, 
is carried on in the stomach, under the 
of sense, occurred to an observant 
)phical mind, and it was not lost.* 
ng are some of the curious and in- 
enomena observed. 

le inner coat of the stomach, in its 
healthy state, is of a light or pale pink 
ing in its hues according to its fuU, or 
. It is of a soft or velvet-like appear- 
, and is constantly covered with a very 
arent, viscid mucus, lining the whole 
he organ (619). 

mmediately beneath the mucous coat 
11 spheroidal, or oval-shaped glandular 
d which the mucous fluid appears to 

(619). 

y applying aliment or other irritants to 
I coat of the stomach, and observing the 
ugh a magnifying glass, innumerable 
d points, and very fine nervous or vas- 
llee are seen arising from the villous 
» and protruding through the mucous 

leots and Observations on th^ G«L%\.rv!C '^'^\\CA^ 
tyaiology of Digestion. By "W* "ft^axanoxA^ 
n in the U. S. Army. Boston. \%'^At* 



228 THE PHILOSOPHY OF HEALTp. 

coat, from which distils a pure, limpid, colourless, 
slightly viscid fluid (620). This fluid, thus ex- 
cited, is invariably distinctly acid (639, et geq,). 
The mucus of the stomach is less fluid, more viscid 
or albuminous, semi-opaque, sometimes a little 
saltish, and does not possess the slightest character 
of acidity (619). On applying the tongue to the 
mucous coat of the stomach in its empty, un» 
irritated state, no acid taste can be perceived. 
When food or other irritants have been applied 
to the villous membrane and the gastric papilln 
excited, the acid taste is immediately perceptible. 
The invariable eflect of applying aliment to the in* 
temal, but exposed part of the gastric membrane, is 
the exudation of the solvent fluid from the papillae. 
Though the aperture of these vessels cannot be 
seen even with the assistance of the best micro- 
scopes, yet the points from which the fluid issues 
are clearly indicated by the gradual appearance of 
innumerable very fine lucid specks rising through 
the transparent mucous coat, and seeming to 
burst and discharge themselves upon the very 
points of the papillae, diflusing a limpid thin fluid 
over the whole interior gastric surface. 

648. The fluid so discharged is absorbed by the 

aliment in contact; or collects in small drops, and 

trickles down the sides of the stomach to the more 

depending parts, and there mingles with the food, 

or whatever else may "be conXakkt^m \ikft gastric 

cavity. This flluid, ttie e^c\&xiX. twaafc ^i ^^gar 



EXPERIMENTS. 229 

tion, the true gastric juice \b secreted only when 
it is needed ; it is not accumulated in the inter- 
Tals of digestion, to be ready for the next meal ; it 
is seldom if ever discharged from its proper se- 
creting vessels, except when excited by the natural 
stimulus of aliment, the mechanical irritation of 
tubes, or other excitants. When aliment is re- 
ceived, the juice is given out in exact proportion 
to its requirements for solution, except when more 
food has been taken than is necessary for the 
wants of the system. 

649. On collecting this fluid, which it was 
easy to obtain, it was found to be transparent, in- 
odorous, saltish, and acidulous to the taste; it 
consisted of water, containing free muriatic and 
acetic acids, phosphates and muriates, with bases 
of potass, soda, magnesia, and lime, together with 
an animal matter soluble in cold, but insoluble in 
hot water. 

650. When a portion of liquid aliment, as a 
few spoonsful of soup, were introduced into the 
stomach at the external orifice, the rugae (fig. 
CLXvii. 1) immediately closed gently upon it; 
gradually difiused it through the gastric cavity, and 
prevented the entrance of a second quantity till this 
diffusion was effected ; then relaxation again took 
place, and admitted of a further supply. When 
solid food was introduced in the same manner, 
either in large pieces or finely dvv\di"&^, \!si^ ^•^\siRk 
"en tie contraction and graspiiig moXlvyas ^^et^ 



230 THE PHILOSOPHY OF HEALTH. 

excited, and continued from fifty to eighty seconds, 
80 as to prevent more from being introduced, 
without considerable force till the contraction was 
at an end. 

651. When the position of the body was such 
that the cardiac portion of the stomach was brought 
into view, and a morsel of food was swallowed in 
the natural mode, a similar contraction of the 
stomach, and closing of its fibres upon the bolus 
was invariably observed to take place; and till 
this was over, a second morsel could not be 
received without a considerable efibrt Hence, 
in addition to the other purposes accomplished 
by mastication, insalivation, ~ and deglutition, 
it is probable that these operations answer the 
further use of duly regulating the time for the ad- 
mission of successive portions of the food into the 
(tomach.* 

652. On watching the phenomena that tahe 
place on the contact of a portion of food with the 
stomach, the circumstances described (627) are 
seen ; the change in the mucous coat from a pak 
pink to a deep red colour, in consequence of the 
enlargement of the blood-vessels and their admis- 
sion of a greatly increased number of red particles i 
the undulating motion of the stomach, in conse* 

* See Dr. Andrew Combe on the Physiology of Di- 
ffestion, in whose work a fiill detail of this, instructirt 
ease 18 given. See al«o Ma^o^^OxxxXvu^ ^\'^\ic|«sAiCkQ 
4th EdiU Appendix* 



EXPERIMBNT8. 231 

qiience of the contraction of its muscular fibres, 
excited by the stimulus of food ; the distillation 
of the gastric juice from the enlarged and excited 
papillae; the continuous flow of this fluid until the 
complete solution of the food, when food is pre- 
sent ; and, on the contrary, the cessation of this 
discharge in a short time when it is produced by a 
mechanical irritant, as the bulb of a thermometer, 
although at first the gastric juice distil from the 
papillas, from the contact of such an irritant, just 
as when excited by the contact of food. 

653. On collecting the gastric juice and placing 
it in contact with an alimentary substance out of 
the stomach, its solution takes place more slowly, 
but not less completely, than when retained in the 
stomach. An ounce of this fluid was placed in a vial 
with a piece of boiled, recently salted beef, weighing 
three drachms ; the vial was then tightly corked, 
and immersed in water, raised to the temperature 
of 100^, previously ascertained to be the ordinary 
heat of the stomach. In forty minutes the process 
of solution had commenced on the surface of the 
beef. In fifty minutes the texture of the beef 
began to loosen and separate. In sixty minutes 
an opaque and cloudy fluid was formed. In one 
hour and a half the muscular fibres hung loose 
and unconnected, and floated about in shreds in 
the more fluid matter. In three hours the mus- 
cular fibres had diminished about ou^ \k»Xl« X'Ql 
6ve hours only a few remained \rad\a«o\N^^. ^^ 



232 THE PHILOSOPHY OF HEALTH. 

seven hours the muscular texture was no longer 
apparent ; and in nine hours the solution was 
completed. 

654. At the commencement of this experiment 
a piece of the same heef of equal weight and size 
was suspended within the stomach by means of 
a string. On examining this portion of beef at 
the end of half an hour, it was found to present 
precisely the same appearance as the piece in the 
vial; but on the removal of the string at the end 
of an hour and a half the beef had been com- 
pletely dissolved, and had disappeared, making a 
diflFerence of result in point of time of nearly seven 
hours. In both, the solution began on the surface, 
and agitation accelerated its progress by removing 
the external coating of chyme as fast as it was 
formed. 

655. An ordinary dinner having been taken, 
consisting of boiled salted beef, bread, potatoes, 
and turnips, with a gill of pure water for drink, a 
portion of the contents of the stomach was drawn off 
into an open-mouthed vial, twenty minutes after 
the meal. The vial was placed in a water-bath, 
maintained steadily at a temperature of 100^. It 
was continued in this temperature for five hours. 
At the end of that time the whole contents of the 
vial were dissolved. On comparing the solution 
with an equal quantity of chyme taken from tht 

stomach, little <t£fereiice coxAd \» distinguished 

between the two fluids, excei^^u^V^Ei^^.V\^^TMaflr 

/est that the digestive ptocesB W^ ^xQCftfc^^^^TSft^ 



BXPERIHENTS. 233 

moie rapidly in, than out of the stomach. 
>od, in this experiment, afler having remained 
utact with the stomach for the space of 

7 minutes, had imhibed a sufficient quantity 
•trie juice to complete its solution. 

>. Fifteen minutes afler half a pint of milk had 
introduced into the stomach, it presented the 
ranee of a fine loosely-coagulated substance 
[ with a semi-transparent whey-coloured fluid, 
chm of warm gastric juice poured into two 
ms of milk at a temperature of 100®, pro- 
. a precisely similar appearance in twenty 
;e8. In another experiment, when four 

8 of bread were given with a pint of milk, 
ilk was coagulated and the bread reduced to 
pulp in thirty minutes, and the whole was 

letely digested in two hours, 
r. When the albumen or white of two eggs 
wallowed on an empty stomach, small white 
began to be seen in about ten or fifteen 
j&s^ and the mixture soon assumed an opaque 
ih appearance. In an hour and a half the 
: had disappeared. Two drachms of albumen 
I with two of gastric juice out of the stomach 
went precisely the same changes, but in a 
irhat longer time. 

$. Dr. Beaumont's observations are adverse 
I opinion, founded on numerous expeTyn\&\i\&^ 
he food is arranged in the atoiiv«iCi\i Va. «i. ^^^- 
anner, and that a distinct Wne oi «e^«wJC\«^ 



234 THE PHILOSOPHY OF HEALTH. 

exists between old and new food (626). In 
the human stomach, according to the subject of 
these experiments, the ordinary course and direc- 
tion of the food are first from right to left along 
the small arch, and thence through the large curva- 
ture from left to right. The bolus as it enters the 
cardia turns to the left, passes the aperture, de- 
scends into the splenic extremity, and follows the 
great curvature towards the pyloric end. It 
then returns in the course of the smaller curva- 
ture, makes its appearance again at the aperture, 
in its descent into the great curvature, to perform 
similar revolutions. These revolutions are com- 
pleted in from one to three minutes. They are 
probably induced in a great measure by the cir- 
cular or transverse muscles of the stomach 
(615), as is indicated by the spiral motion of the 
stem of the thermometer, both in descending to the 
pyloric portion, and in ascending to the splenic 
These motions are slower at first than after chy- 
mification has considerably advanced. The whole 
contents of the stomach, until chymification be 
nearly complete, exhibit a heterogeneous mass of 
solids and fluids, hard and soft, coarse and fine, 
crude and chymified; all intimately mixed, and 
circulating promiscuously through the gastric 
cavity like the mixed contents of a closed vessdi 
gently agitated or turned in the hand. 
659. In attempting U) i^«a^ a lon^ glass thermo- 
meter through the apertuxe 'm\AO[v^Y^^'^ V^^f^°^ 



KXPERIMBNTS 235 

of the stomach, during the latter stages of digestion, 
a forcible contraction is perceived at the point of 
the hour-glass contraction of the stomach, and the 
bulb is stopped. In a short time there is a 
gentle relaxation, when the bulb passes without 
difficulty, and appears to be drawn quite forcibly, 
for three or four inches, towards the pyloric end. 
It is then released, and forced back, or suffered to 
rise again, at the same time giving to the tube a 
drcular or rather a spiral motion, and frequently 
revolving it quite over. These motions are distinctly 
indicated and strorgly felt in holding the end of 
the tube between the thumb and finger ; and it 
requires a pretty forcible grasp to prevent it from 
slipping from the hand, and being drawn suddenly 
down to the pyloric extremity. When the tube is 
left to its own directi(m at these periods of con- 
traction, it is drawn in, nearly its whole length, to 
the depth of ten inches ; and when drawn back 
requires considerable force, and gives to the fingers 
the sensation of a strong suction power, like draw- 
ing the piston from an exhausted tube. This 
ceases as soon as the relaxation occurs, and the 
tube rises again, of its own accord, three or four 
inches, when the bulb seems to be obstructed from 
rising further ; but if pulled up an inch or two 
through the stricture, it moves freely in all direc- 
tions in the cardiac portions, and mostly inclines 
to the splenic extremity, though noX. d\«»^Q\^^^ Xi^ 
makeita exit at the aperture. TV\e&e '^^c>3Xv»i \wir 



236 THE. PHILOSOPHY OF HEALTH. 

tions and contractions continue until the stomach 
is perfectly empty, and not a particle of food or 
chyme remains, when all becomes quiescent again. 

660. The chambers in which the remaining part 
of the digestive process is carried on are much 
less accessible, and no such favourable opportunity 
as that enjoyed by Dr. Beaumont has occurred of 
rendering their operations manifest to the eye. 
Nevertheless, the researches of physiologists have 
succeeded in disclosing, with almost equal exact- 
ness and certainty, the successive changes which 
the food undergoes even in these more hidden 
organs, that admit of no exposure during life 
without extreme danger. 

661. The chyme on passing through the pylorus 
is received into a chamber (fig. clxvii. 3) which 
forms the first portion of the small intestines. 
The small intestines, taken together, constitute a 
tube about four times the length of the body. This 
tube is conical, the base of the cone being towards 
the pylorus, and its apex at the valve of the 
colon, where the small intestines terminate in the 
large. From the pi^orus to the valve of the colon 
the small intestines diminish in capacity, in thick- 
ness, in vascularity, in the size of the villi, and in 
the depth and number of the valvulae conniventes. 

662. The first portion of the small intestine is 
termed the duodenum (fig. clxvii. 3). It is about 

twelve inches in letigt\\, w^^, wx^A^fefc ^^ ^.Vvoiach, 
which is capable oi coiv«i^ei«JoU Taa>Msii^ >x >^ 



Hnely tied down to the back by the peritoDeum, 
•hich imperfectly covers it The rest of the 
mall intestine is divided into two portions — the 




ridtd tadnBeeted. 



I bladder 10. Abdom\iu,\ im)ac\«« ^^ 



238 THE PHILOSOPHY OF HEALTH. 

upper two-fifthB of which are termed jejuiium, 
and the three lower ilium. 

663. The duodenum, the chamber which re- 
ceives the chyme from the pylorus, is a second 
stomach, which carries on the process commenced 
in the first. It is assisted in the performance of 
its function by two organs of considerable magni- 
tude, the pancreas and the liver. 

664. The pancreas is a conglomerate gland 
(fig. CLXxii. 5), of an elongated form, placed in 
the epigastric region, lying transversely across it, 
immediately behind the stomach (fig. clxxii. 1), 
and resting upon the spinal column (fig« clxxii. 
5). Its right extremity is attached to the duo- 
denum (fig. clxxii. 9), and its left to the spleen 
(fig. clxxii. 4). In external appearance it re- 
sembles the salivary glands, but it is of much 
larger size, and its weight, from four to six ounces, 
is three times greater than that of all the salivary 
glands together. It secretes a peculiar fluid 
called the pancreatic juice, which is carried into 
the duodenum by a tube named the pancreatic 
duct (fig. CLXvii. 7),. whidi opens into the duo- 
denum about four or five inches from its pyloric 
end (fig. CLXVII. 2). 

665. The liver, the largest and heaviest gland 
in the body, weighing about four pounds, is placed 
chiefly in the right hypochondriac region (fig. 

CLXXi. 3) ; but a poition o£ Sx e.iL\£iv^<&\x»iiv(eT8ely 
across the epigastric, "mlo X\ife\ei\.\K^v^Owso&wgi 




. Stomarh miseil. 2. Under tuitiee of In 
ladder. 4. Splevn. 5. Pancreai. G. Kldaeys. : 
n. 6. Uilnacy bladdw. 9. Portion oi 'in\e--\.\nt 
toiknuni. 10. Fortioa of iDteatloe c&Ue^ 



I. Q>ll 

Ure- 



ft 

1 



1^. 



a coT»«'° ,v. U^er * Gide» ^ ^ts 



I 
^ 




PANCRBATIC AND BIUABT JUICES. 241 

duct called the cystic (fig. clxvii. 10), and 

ly to the duodenum (fig. clxvii. 3) by a duct 

ied the choledoeh (fig. clxvii. 6), a common 

ik formed by the union of the cystic with the 

latic (fig. clxvii. 10 and 9). The choledoeh 

ct opens into the duodenum at the same point 

the pancreatic (fig. clxvii. 7), and generally 

f a common orifice. 

667. The duodenum, on receiving the chyme from 
le 9tomach, transmits it slowly along its surface, 
rhe kind of motion by which the chyme is borne 
ilong the surface of the duodenum is perfectly 
analogous to that by which it is transmitted from 
the stomach to the duodenum, irregular, some- 
times in one direction, and sometimes in another. 
at one time commencing in one part of the organ, 
at another time in another, always slow, but ulti- 
mately progressive. 

668. As the chyme slowly advances through the 
upper part of the duodenum, the biliary and the 
pancreatic juices slowly distil into the lower 
portion of the organ. The bile is seen to exude 
fix>m the choledoeh duct, not continually, but at 
intervals, a drop appearing at the orifice, and dif- 
fusing itself over the neighbouring surface, about 
twice in a minute, while the flow of the pancre- 
atic juice is still slower. 

669. No appreciable change takes place in the 
chyme until it reaches the orifice oi t\\e cYvviV^^^^ 
duct ' but 08 soon as it cornea in cohIblcV m>^ ^^ 



242 THE PHILOSOPHY OF HEALTH. 

portion of the duodenum, the chyme suddenly loses 
its own sensible properties, and acquires those of 
the bile, especially its colour and bitterness. But 
these properties are not long retained ; a sponta- 
neous change soon takes place in the compound. 
It separates into a white fluid and into a yellow pulp. 
The white fluid is the nutritive part of the ahment; 
the yellow pulp is the excrementitious matter. 

6^0. This white fluid, the proper product of the 
digestive process, as far as it has yet advanced, is 
called chyle. If any portion of oil or fat have 
been contained in the food, the chyle is of a milk- 
white colour ; if not, it is nearly transparent. It 
is of the consistence of cream, and it bears a close 
resemblance to cream in its sensible properties. 
It differs from chyme in being of a whiter colour, 
more pellucid, and of a thicker consistence: it 
differs also in its chemical nature, for, whereas 
chyme is a6id, chyle is alkaline. 

671. Three fluids are mixed with the chyme in 
the duodenum, each of which contributes to the con- 
version of the chyme into chyle. First, the secre- 
tion of the duodenum itself, a solvent analogous 
to the gastric juice. Secondly, the secretion of the 
pancreas, a watery fluid holding in solution 
highly important principles, namely, a large 
quantity of albumen, a matter resembling casein, 
osmazome, and diflerent salts. Thirdly, the secre- 
tion of the liver, a coia^owivd fL\iid^ consisting of 
^Bter, mucus^ and 8evet«iV^fec\iX\«x ^\x\Tsiii\fia&^s9^ 



USB OF TBB PANCREATIC JUICE. 243 

Qely, resin, cholesterine, picromel, cholic acid, a 
>uring matter, probably salivary matter, osma- 
16, casein, and many salts. 
172. There cannot be a question that the secre- 
i of the duodenum has a solvent power over the 
me analogous to that of the gastric juice. Some 
Biologists indeed maintain that the juice poured 
from the inner surface of the duodenum is as 
rerful a solvent as the gastric juice. It is 
ain that substances which have escaped chy- 
ication in the stomach undergo that process in 
duodenum, and that there is the closest analogy 
xreen the action of the duodenum on the chyme 
that of the stomach on the crude food 
•73. The pancreatic secretion adds to the 
me richly azotized animal substances, albumen, 
jin, osmazome (671), by which it is brought 
rer the chemical composition of the blood, and 
pared for its complete assimilation into it. 
i first addition of such assimilative matter, it 
been shown, is communicated by the salivary 
ids, but far more important additions are now 
plied from the pancreas. Hence the larger size 
le pancreas and the more copious secretion of 
pancreatic fluid, in herbivorous than in car- 
nrous animals ; hence the change produced in 
size of the pancreas by a long continued change 
be habits of an animal ; hence the smaller size 
he pancreas in the wild cat, wbic\i\\Nt'& -^V^^ 
nimal food, than in the domestic c«X, '^\C\Ocv 

M 1 



244 THE PHILOSOPHT OF HEALTH. 

lives partly on animal and partly on vegetable 
food. 

674. The bile, the most complex secretion in the 
body, accomplishes manifold purposes. 

1. Like the pancreatic secretion, it communicates 
to the chyle richly azotized animal substances, 
picromel, osmazome, and cholic acid (671); by 
the combination of which with the chyme, it is 
brought still nearer the chemical composition of 
the blood. These principles are manifestly united 
with the chylous portion of the chyme, since they 
are not discoverable in its excrementitious matter. 

2. Bile has the property of dissolving fat ; con- 
sequently, when oily or fatty matters are contained 
in the food, it powerfully assists in converting 
these substances into chyle. 

3. The excrementitious portion of the bik a 
highly stimulant. The contact of its bitter resin 
with the mucous membrane of the intestines 
excites the secretion of that membrane ; hence the 
extreme dryness of the excrementitious matter 
when the choledoch duct of an animal has been 
tied; and hence the same dryness of this matter in 
jaundice, when the bile, instead of being conveyed 
by its appropriate duct into the duodenum, is taken 
up by the absorbents, poured into the blood, and 
distributed over the system. 

4. The bitter resin of the bile stimulates to con- 
tract/on the fibres o{l\ieTa\»Gvi\w\x«iL\RQCthe intes- 
tines ; by thecontTactioivoi\)cie.%^^T«fc^^v5as3fc' 



USES OF THE BILK. 245 

nentitious matter is conveyed in due time out of 
;he body; hence the constipated state of the 
X)wel8 invariably induced when the secretion of 
;he bile is deficient, or when its natural course 
nto the intestines is obstructed. 

5. The excremcntitious portion of the bile exerts 
m antiseptic influence over the excrementitious 
portion of the food during its passage through 
he intestines. In animals in which the choledoch 
iuct has been tied, the excrementitious portion of 
he food is invariably found much further advanced 
n decay than in the natural state. This is also 
miformly the case in the human body in propor- 
ion as the secretion of the bile is deficient, or its 
Missage to the intestine is obstructed. 

675. Such appear to be the real purposes ac- 
lomplished by the bile in the process of digestion. 
Several uses have been assigned to it, in promot- 
ng this process, which it does not serve. Seeing 
he instantaneous change wrought in the chyme on 
t8 contact with the bile, it was reasonable to sup- 
pose that the main use of the bile was to convert 
hyme into chyle, a purpose apparently of sufficient 
mportance to account for the immense size of the 
;land constructed for its elaboration. The sound- 
less of this conclusion appeared to be established 
»Y direct experiment. Mr. Brodie placed a 
igature around the choledoch duct of aw aw\\ci<^\ 
her. the operation the animal ale a^ \\sv\^\ ov^ 
'Uing^ the aniinal some time after \l Yv«A \»k^x^ ^ 



246 THE PHILOSOPHY OF HEALTH. 

meal, and examining the body immediately after 
death, it was clear that chymification had gone on in 
the stomach just as when the choledoch duct was 
sound, but no chyle appeared to be contained 
either in the intestines or in the lacteals. In the 
lacteal s there was found only a transparent fluid, 
which was supposed to consist of lymph and of the 
watery portion of the chyme. Mr. Brodie's expe- 
riments seemed to be confirmed by those of Mr. 
Mayo, who arrived at the conclusion, that when 
the choledoch duct is tied, and the animal is exa- 
mined at various intervals after eating, no trace 
whatever of chyle is discoverable in the lacteal 
vessels. But these experimentalists inferred that 
no chyle existed in the intestines or lacteals, 
because there was present no fluid of a milk-white 
colour, a colour not essential to chyle, but de- 
pendent on the accident of oily or fatty matter 
having formed a portion of the food. These 
experiments have been repeated in Grermany by 
Tiedemann and Gmelin, and in France by Leuret 
and Lassaigne, who have invariably found, after 
tying the choledoch duct, nearly the same chylous 
principles, with the exception of those derived 
from the bile, as in animals perfectly sound ; and 
the English physiologists have since admitted that 
their German and French colaborateura have 
arrived at conclusions more correct than their own. 
676. The bile consiata \\ieTi^i \.^o ^ciSKt«i\.^x^ 
tiona; a iighly anima\ize^^oT\:\Qra,^\aOsi<iw^ 



USES OF THE BILE. 247' 

with the chyme and exalts its nature hy approxi- 
mating it to the condition of the blood ; and an ex- 
crementitious portion, which, after accomplishing 
certain specific uses, is carried out of the system 
with the undigested matter of the food. The excrc- 
mentitious portion of the bile, namely, the resin, the 
fat, the colouring principle, the mucus, the salts, 
constitute by far the largest portion of it. These 
constituents of the bile for the most part coniaiu 
a very large proportion of carbon and hydrogen, 
and the reasons have been already fully stated 
(473, et 8eq.) which favour the conclusion that the 
elimination of these substances under the form of 
bile is one most important mode of maintaining 
the purity of the blood, and that the liver is thus a 
proper respiratory organ, truly auxiliary to the 
lungs. It is a beautiful arrangement, and like one 
of the adjustments of nature, that the bile, the 
formation of which abstracts from the blood so 
large a portion of carbon and hydrogen as to main- 
tain the purity of the circulating mass and to 
counteract its putrescent tendency, acts on the 
excrementitious portion of the food, always highly 
putrescent, as a direct and powerful antiseptic ; 
that the very matter which is eliminated on 
account of the putrid taint it communicates to 
the blood, on its passage out of the body, stops 
the putrefaction of the substances which have 
been ministering to the repleniaVvmeAW. sil \N^^ 
bloods 

677. The chyle, thick, gluiiuowfi, blxi^l «AVw^^ 



248 THE PHILOSOPHY OF HEALTH. 

attaches itself with some degree of tenacity to the 
mucous surface of the duodenum. Nevertheless, 
by the successive contractions of the muscular 
fibres of the duodenum the fluid is slowly but 
progressively propelled forwards. The separation 
of the excrementitious matter becomes more com- 
plete, and consequently the chyle more pure as it 
advances, until, having traversed the course of the 
duodenum, it enters the second portion of the small 
intestines, the jejunum. 

678. The jejunum, so called because it is com- 
monly found empty, and the ilium, named from 
the number of its' convolutions, on account of 
their great length, are provided vtdth a distinct 
membrane to support them, and to retain them in 
their situation, termed the mesentery. 

679. The mesentery is a broad membrane com- 
posed of two layers of peritoneum. Between these 
two layers, at one extremity of the duplicatuie, is 
placed the intestines, while the other extremity is 
attached to the spinal column. The mesentery being 
much shorter than the intestines, the intestines 
are gathered or puckered upon the membrane, by 
which beautiful mechanical contrivance they are 
held in firm and close contact with each other, yet 
their convolutions cannot be entangled, nor can 
they be shaken from their place by the sudden 
and often violent movements of the body. It 

sometimea happens, in coxi»ei\vx«cic^^ ^\«r»s^ that 
rAe convolutions of theit\te%\kve^w^^\i^Xnsff&«st 
brtbeeffuBion of lyrop\i»aT\^t\iexi^>ci^^^^»a«w^ 



TBB SMALL INTESTINES. 249 

causes are capable of producing the severeat 
symptoms of obstruction in the bowels. 

680. The internal surface of the small intestines 
is distinguished, 

1. By the number of the mucous glands, which 
may be seen by a magnifying glass to consist 
partly of a prodigious numrber of the minutest 
follicles, not collected in groups, but equally scat- 
tered throughout ; and partly of glands of a larger 
dimension, disposed in groups at particular parts 
of the canal. 

2. By the increase in the number and size of 
the villi, of which there are about four thousand 
to the surface of a square inch. Like those of 
the stomach, the villi of the small intestine are 
composed of arteries, veins, nerves, and mucous 
ducts ; but to the villi of the small intestine, in 
length about one-fourth of a line, there is added a 
new vessel, the absorbent of the chyle, the lacteal 
(figs. 175 and 176), so named from the milk-like 
chylous fluid which it contains. 

3. By the great extension of the mucous coat 
obtained by the disposition of the membrane into 
the folds called valvulse conniventes (fig. clxxiii. )• 
These folds, which rarely extend through the whole 
circle of the intestine, are often joined by communi- 
cating folds (fig. CLXXIII.). The folds are broadest 
in the middle, and narrowest at the extreraU.\&% 
{fkg. CLxxni.). In general, they BlT^ ^XioxaX ^Xvcvs: 

and a half broad. One edgeoi \.\i^ io\^ *\^ V^o^^^ 



250 TBB PHILOSOPUT or HEALTH. 

but the other it fixed to the intestine (fig. CLXZiii). 

The office of these foH> i«, flret, without in- 

Fig. CLXXIII. 




creasing speu:e, to extend surface for the distri- 
bution of the villi; and, secondly, to retard the 
flow of the chyle, by opposing to its descent yalni 
BO canstnicted and disposed as, without airestiDg 
its progress, to moderate and regulate its coune, 
in order that time may be allowed for its absotp- 

681. The OEward flow of the chyle through 
the course of the small intestines is eGTected by the 
action of the double layer of muscular fibres, the 
circular and the longitudinal fasciculi which 
compose its muscular coat (fig. clxxiv.). The 
disposition of the muscular fibres of the ali- 
mentary canal in general, and of this part of it in 
particular, deserves special notice. The ordlnsij 
arrangement and action of muscular fibres would 
not /tape produced in ttaa c&m, vVt tind and de- 
cree of motion reqwed. T'cie maftiai\sa Smu* 
rAal compose the veamci\« oi OQt^tiiA »»» 



HUBCULAH COAT. 



accumulated and duposed, Uiat theii contractioi) 
wiginatea, and communicateB energetic itnpulee. 







> 



The muacles of the urn are so accumulated and 
dieptued that their contraction originates the like 
energetic impulse. Musclee so accumulated in 
the alimcntuy canal would have produced motion, 
indeed, but motion not only not accomplishing the 
end in view, but directly defeating it. In order 
to obtain '^he kind and degree of motion in this 
case required, the firm and thick muscle is attenu- 
ated into minute, delicate, and thready fibres, not 
concentrated in a bulky muse, so as to obtain by 
their accumulation a great degree of force; but 
opread out in such a manner as to form a thin and 
almost transparent coat. The tender &n«,% cnnv- 
pogiijg tbia delicate coat, bj the« (MttoWiiNa^N 



252 THE PHILOSOPHY OF HEALTH. 

produce two alternate, gentle, almost constant 
motions, called the peristaltic, from its resem- 
blance to the motion of the earth-worm, and the 
antiperistaltic. By the peristaltic action motion 
is begun at once in several parts of the canal. 
Whenever the chyle is applied in a certain quan- 
tity to any part of the intestines, that part contracts, 
and makes a firm point, towards which the por- 
tions both above and below are drawn, by means of 
the longitudinal fibres which shorten the canal, and 
at the same time dilate the under part. .By the 
antiperistaltic action, which is the exact reverse 
of the former, the chyle is turned over and over, 
and exposed to the orifices of the lacteal vessels ; 
while, by the motion of the chyle forwards and 
backwards, and backwards and forwards, produced 
by these two actions constantly alternating with 
each other, its slow, gentle, but ultimately pro- 
gressive course is secured. 

682. The chyle thus gently moved along the ex- 
tended surface of the jejunum and ilium, and still 
in its course acted upon in some degree by the 
secretions poured out upon the mucous membrane, 
successively disappears, until at the termination 
of the ilium (fig. clxxi. 5) there is scarcely any 
portion of it to be perceived. It is taken up by 
the vessels termed lacteals. 

683, The lacteal vessels (figs. 175 and 116), 
take their origin on tYvft ««t^«it^ ^i SJ^vr n^\L, by 

open mouths, too minule to \i^ V\«WV^ xa ^^ xsa^^ 



THE LACTEAL8. 253 

eye, but distinguishable under the microscope. 
These minute, pellucid tubes, wholly countless in 
number, are composed of membranous coats so 
thin and transparent that the milky colour of their 
contents, from which they derive their name, is 
visible through them, and yet they are firm and 
strong. They present a jointed appearance (figs. 
cixxvi. 4, and clxxvii. 7). Each joint denotes 
the situation of the valves with which they are pro- 
vided, and which are placed at regular distances 
along their entire course (fig. cxcii. 1 and 2). 
These valves, which are generally placed in pairs 
(fig. CXCII. 2), consist of a delicate fold of mem- 
brane of a semilunar form, one edge of which 
is fixed to the side of the vessel, while the other 
lies loose across its cavity (fig. cxcii. 2). So firm 
is this membrane, and so accurately does it per- 
form the office of a valve, that even after death it 
is capable of supportiug a column of mercury of 
considerable weight without giving way, and of 
preventing a retrograde course of the fluid. The 
lacteals are nourished by blood-vessels, and ani- 
mated by nerves, and it is conceived that they 
must be provided with muscular fibres, or some 
•analogous tissue, for they are obviously contractile, 
and it is by this contractile power that their con- 
tents are moved. The delicacy and transparency 
of the vessels, however, render it impossible to dis 
tinfiruish the different tissues whicb coiivpo^t \X\"evt 
walls. 



254 THE PBtLOSOPHT OF BEALTH. 

684. If the mucous coat of the Bnull intestmeB be 

examined some hours qfter a meal, the lacteals are 
Been turgid with chjle, covering its entire aurface 
(tig. CLZxv, 1). Thefte veBBcls, which are eome- 
times of such magnilude and in such numbers as 
entirely to conceal the ramifications of the blood- 
Fig. CLXXV. 




hours sfter a meaL I. The smaller tirnDches of tbe lac- 
tcxU, turjjid with chyle, Eav(niii|; the surfsce of the into' 
tiae. 2. Larger branches of tbe lacteals formed by the 



veggels, unite freely with each other, and fbnn • 
net-work, from the me»\v«» ol -^Vaiih ijroceed 
hrani:hes «liich,8acceB8we\^ \iTO,\i»%,lOTia\K*si^w* 



THB LACTEALS 



of a lai^r size (fig. clxxv. 2). These lurget 
branches perforate the mucous coat and ]inss for 
some wa.y between the mucous and tjie niiiBciilat 



Fig. CLXXVI. newofthe 




1, The ooiia. Z. Thoncic duel. 3. Eiteinal aurl'HFe of 
■ portion of bidbU mleitiue. 4. LBcteali apiicariii); on tlie 
eiLterital surface of the Lnttititjne after hiiving perforutrd all 
ila cuats. 5. MuHnleric j^landii uf the fiiat otiIit. [>. Me- 
■enteric glands of Ihti lecund order. 7. Keceptuclc for thi.- 
chyle. 8. Lymiihatic veuBclstuniiiiiatingin tliB recepticlo 
of the chjle, ot conHnencemeut of Ihe thoratic duct. 

tunics ; at length they perforate both tlie nmecular 
and the peritoneal coats, when, from having been 
on the inside of the intestine, ihev ii,tt oti 'iie, wiV 
mide of it (&g. clxxvi, 3, 4), aud a.iem'iViiiKiC^'i** 



256 THE PHILOSOPBT OF HEALTH. 

Fig. CLXXVII. 




■P^' "'^•'^ curae of tW Thinaac T>aiA (iohv iu orfeip n 
"' teraiinution. 1. LEicte&\ ieBw\» »n«i^m t,^ ^ 
aucoua aur&ce of tha iutcatmei. ' 1. miA <r^\ sI-bhek 



C0VK8K OF TBK LACTCALS. 257 

Stands. 3. Second order of mesentene fflands. 
?be gpreat trunks of the lacteais emerging from the me- 
«ric glands, and pouring their contents into — 5. The 
ptade of the chyle. 6. The g>eat tninka of the lym- 
tic or general absorbent system terminating m the 
ptade of the chyle. 7. The thoracic duct 8. Tenni- 
on of the thoracic duct at — ^9. The anffle formed by 
union of the internal jugular Tein with Uie subclaTian 
I. 

intestiae itself, between the layers of the mesen- 
r. All the different sets of lacteals converging 
[ uniting tc^ether, form an exceedingly compli- 
ed plexus of vessels within the fold of the 
sentery. Radiating from this plexus, the lacteals 
ance forwards until they reach the glands, called, 
n their being placed between the fold of the 
sentery, the mesenteric (figs, clzxvi. 5 and 6, 
I CLxxvii. 2 and 3) ; rounded, oval, pale- 
mred bodies, consisting of two sets, arranged 
a double row (figs, clxxvi. 5 and 6, and 
j[vii. 2 and 3) ; the set nearest the intestine 
. CLXXVII. 2) being considerably smaller than 
succeeding set (fig. clxxvii. 3). 
185. On reaching the first series of glands (fig. 
jcvii. 2), the lacteals penetrate the substance 
be gland, in the interior of which they communi- 
i with each other so freely, and form such innu- 
*able windings, that the gland seems to consist 
1 congeries of convoluted lacteals. Emerging 
a the first series of glands, the lacteals proceed 
heir course to the second series (J^\^. c\a's.^n\\.^> 
:b they penetrate, and in the mXenoT oi ^>kv^ 



258 THE PHILOSOPHY OF HEALTH. 

they present the same conyoluted appearance as 
in the first set. On pasung out of this second 
series of glands, the lacteals unite together, and 
compose successively larger and larger hranches, 
until at length they form two or three trunks 
(fig. CLxxvii. 4), which terminate in the small 
oval sac (fig. clxxvii. 5), termed the receptacle 
of the chyle (receptaeulum chyli). 

686. In this oval sac or receptacle of the chyle 
(fig. CLXXVII. 5), which rests upon the second or 
the first lumhar vertehra, also terminate the trunks 
of the general ahsorhent vessels of the system 
(fig. CLXXVII. 6), called from the lymph or the 
pellucid fluid which they contain, lymphatics, as 
the lacteals are named from the lactitious or milky 
appearance of their contends. 

681. The receptacle of the chyle produced 
forms the thoracic duct (fig. clxxvii. *?), a canal 
ahout three lines in diameter. This tube rests 
upon the spinal column, ascends on the right side 
of the aorta, passes through the aortic opening 
in the diaphragm (fig. cxxxiv. 9, 10), and 
enters into the chest. Here it forms a trans- 
parent tube about the size of a crow-quill; it 
rests upon the bodies of the dorsal vertebrae; it 
continues to ascend still on the right side of the 
aorta, until it reaches the sixth or fifth dorsal 
yertebra, when changing its direction, it passes 
obliquely over to the left «\d^ (Ja.%. c\;sxsiw AV 
From thiB point it contiuwaa *\\.?» ^wa^ \x^'^«:A.v 



couksb ov thb 

t left edde of the neck, ai high aa the eixth 
:al vertebra; when euddenty turning for- 
I and a littk downwardB, it temuiiBte* its 




) Thoracic Duef. 2. Lymphalio entering Uu ^aa^ 
) TBin laid open, ahowing the vaVje at fta tamixia^ 
tbedact. 4. The left internal iugu\M -itvtt, b.Toa 
xJatiaa vein. 6, The »Bin coi^^ iiuwai\ns^*- 



260 THE PHILOSOPHY OF HEALTH. 

formed by the noion of the internal jugular and lubclaTiaa 
Teins. 7. The right jugular vein. 8. The right subclir 
vian vein. 9. The superior cava formed by the union of 
the veins above. 10. The inferior cava formed by tke 
union of the veins below. 1 1. The two venae cavaB passing 
to the right auricle of the heart 12. The heart. 13. The 
pulmonary artery dividing into right and left branchei. 
14. The aorta. 

course in the angle formed by the union of the in- 
ternal jugular with the subclavian vein (fig- 
CLxxvii. 8, 9). At its termination in these great 
venous trunks are placed two valves, which pre- 
vent alike the return of the chyle, and the entrance 
of the blood into the duct (fig. clxxviii.). 

688. This account of the course of the thoracic 
duct is a description of the course of the chyle. 
Performing a double, circuitous, and slow circula- 
tion through the minute convoluted tubes of which 
the double series of mesenteric glands are com- 
posed, the chyle, in its receptaculura, is mixed 
with the contents of the lymphatic vessels, lymph 
(fig. CLXXYii. 6, 5), that is, organic matter brought 
from every siuface and tissue of the body. Both 
fluids, chyje and lymph, mixed and mingled, flow 
together into the thoracic duct, by which in the 
course traced (687) they are poured into the 
blood, just as the venous torrent is rushing to 
the heart (fig. clxxviii. 6, 9, 11). 

689. Thus, the final product of digestion, the 
chyh; particles of organized matter, the lymph; 
and venous blood, that \9>,\AqcA ^V\Oti\A& %lxeadY 
circulated through the ftNatfcm cwnxxKOi^^^ ^s» 



rUNGTION OP LARGB INTESTINES. 261 

together to the right heart, by which it is trans- 
mitted to the lungs, where all these different fluids 
are converted into one substance, arterial blood, to 
be by the left heart sent out to the system for its 
support. 

690. While these processes are going on, another 
and a very important function is performed by the 
remaining portion of the alimentary canal. It is 
the office of this part of the apparatus to carry out 
of the body that portion of the aliment which is 
incapable of being converted into chyle. The pre- 
paration of the excrementitious part of the aliment 
for its expulsion constitutes the process of fecation. 
The organs in which this process is carried on, and 
by which the excrementitious matter, when duly 
prepared for its removal, is conveyed from the body, 
are the large intestines. 

691. The large intestines (fig. clxxix.) consist 
of the cfiecum, the colon and the rectum (fig. 
CLXXIX.)* The caecum varies in length from two 
inches to six; the colon is about five feet in 
length, and the rectum is about eight inches. 

692. The ilium opens into the caecum (fig. 
CLXXIX. 8, 10), just as the esophagus opens into 
the stomach. At this point the ilium is elongated, 
forming two concentric folds which join at their 
horns, and between the folds are placed a number 
of muscular fibres. In this manner is constructed 
a valve, which is termed the valve oi \\v^ c^w^. 
It IB placed in a transverse direclion ^cto%>^ ^N^R- 



THK PHILOSOPHY OP HBAI.TB. 



into — ID. CKCum. 




I. 7. Du«- 

nteBtines dividioR 
12. ArchoFthe 

„ ^Qoid flexura here 

imperfectly cepreseDted. 15. Rectum. 

intestine, and its action as a valve is very com- 
plete. It admits of the free passage of theeon 
teate of the small iateetinea into the large, but it 

preveatB the returii ot&n^ ^goTtioaol 'Owumwk®* 

of the latter into the formei:. 



STRUCTUSB OF LARGE INTESTINES. 263 

693. The colon is distinguished hy its capacious 
size, its great length, and its longitudinal bands, 

Fig. CLXXX. 




Portion of the large intestine, showinj^ the arrangement of 
the muscular fibres. 1. The longitudinal fibres collected 
into bands, and forming larger fasciculi. 2. The circular 
fibres arranged as in the other intestines. 

'which consist of strong muscular fasciculi (fig. 
CLXXix .1 1 ). It is divided into an ascending portion 
'which occupies the right iliac and hypochondriac 
regions (fig. clxxix. 11); the transverse portion, 
called its arch, 'which is placed directly across the 
epigastric region (fig. clxxix. 12), a descending 
portion which occupies the left hypochondriac 
region (fig. clxxix. 13), and a fourth portion, 
which being curved somewhat like the italic letter 
5, is called the sigmoid flexure, which occupies the 
left iliac region (fig. clxxix. 14). The sigmoid 
flexure terminates in the last portion of the alimen- 
tary canal, called the rectum (fig. clxxix. 15V 
which is placed in the hollow of lYve ^«LCTM\xi^ ^w^^ 
which foUowB the curvature of th«Lt \iQTL^ ^^%* 



264 THE PHILOSOPHY OF HEALTH. 

XLV. 5). The circular fibres of the rectum are 
accumulated at the termination of the bowel t« 
form the internal sphincter of the anus. External 
to this is placed another set of fibres, which con- 
stitute the external sphincter. 

694. The mucous membrane of the large intestmes 
is disposed differently from that of the small intes- 
tines, and the mucous membrane of the colon still 
differently from that of the rectum. In the colon 
the mucous membrane, instead of being disposed 
in the form of valvulae conniventesy is so arranged 
as to divide its whole surface into minute apart- 
ments or cells by which the descent of the fecai 
matter is retarded still more than the descent of t}ie 
chyle by the valvulae conniventes. Some partidei 
of chyle do, however, continue to be separated 
from the fecal matter, even in the large intestines; 
and in order that nothing may be lost, a few val- 
vulae conniventes, with their lacteals, appear here 
also, while the cells of the colon, by retarding the 
descent of the fecal matter, allow time for the 
more complete separation and absofption of the 
chylous particles. 

695. In the rectum the mucous membrane is 
plaited into large transverse folds, which disappear 
as the fecal matter descends into the bowel, accu- 
mulates in it, and distends it; an arrangement 
which gives to this portion of the intestine its 

power of distension, so cVosel^ touwftcted with ow 
convenience and comfoTt. 



BAMOB OF SSN8ATI0N AND TOUTION. 365 

96. As soon as that portion of the alimentary 
ter which ig transmitted to the large intestines 
hes the colon it ceases to be alkaline, the dis- 
dve character of the contents of the small 
stines, and becomes acid, just as the whole 
lentary mass is acid at the commencement of 
stion in the stomach. It acquires albumen ; 
ases are no longer the same, for whereas pure 
rogen is contained in the small intestines, 
I is ever found in the large, but in the place of 
irbureted and sulphureted hydrogen ; and now 
the first time it receives its peculiar odour, 
t continues to descend, its fluid parts are pro- 
sively absorbed, so that it becomes more and 
e solid, until it reaches the rectum, when it is 
)8t dry. Here the accumulation of it goes on 
considerable extent^ the peristaltic action at 
excited by the distension of the rectum being, 
ould appear, counteracted by the contraction 
le external sphincter of the anus. When, how- 
, the distension of the bowel reaches a certain 
t, it produces a sensation which leads to the 
re to expel its contents. The bowel is now 
wn into action by an effort of the will, and 
action is powerfully assisted by the descent of 
diaphragm and the contraction of the abdo- 
il muscles, actions also induced by an effort 
he will. Thus the action of the first part of 
digestive apparatus, that which. \& coixTk&cXjd^ 
the reception and partly livitli t\i^ d.^^\)Xi^iA!(3rEi 
X, II, tsi 



266 THE PHILOSOPHY OF HEALTH. 

of the food, is attended with consciousness, and is 
placed under the control of the wilt; the main 
portion of the digestive apparatus, that in which 
the essential part of the digestive process is carried 
on, is without consciousness, and is placed beyond 
the inBuence of volition ; the last portion of the 
digestive apparatus, that connected with the expul- 
sion of the non-nutrient portion of the aliment, 
again acquires sensibility and consciousness, and 
is placed under the control of the will. The 
striking differences in the arrangement of the mus- 
cular fibres in these different parts of the appara- 
tus, in accordance with the widely different func- 
tion performed by them; the powerful muscles 
connected with the prehension, mastication and 
deglutition of the food ; the delicate and transpa- 
rent tissue of fibres forming the muscular coat of 
the stomach and small intestines ; the increase in 
the number and strength of the fibres of the large 
intestines, and the prodigious accession to them in 
the rectum, are adjustments not only exquisite and 
admirable in their own nature, but so indispensable 
to our well-being and comfort, that were the 
appropriate action of either to be suspended but 
for a short period, life would be extinguished, or 
if it could be protracted, it would be changed into 
a state of unbearable torment. 

697. From the preceding account of the structure 
and action of the apparalMa ot Aa^^^Uwv^ oyv a com- 
parison of all the ])henoTcveiv«i, \x ^^w^^v^^ xXvcX'^^ 



CHANGS OF FOOD INTO BLOOD. 261 

ive stages of the process are marked by the 
siye approximation of the food to the 
of the blood. The main constituents, of the 
re albumen, fibrin, an oily principle, and red 
IS. Even in the chyme there are (races of 
n, with globules, not indeed to be compared 
iber with the red particles of the blood, 
in size, and without colour, but still of an 
»us nature. In the chyle of the duodenum 
mtity of albumen is larger, there are traces 
Q, and of an oily matter, and the number of 
bules is increased. In the chvle, after its 
im the mesenteric glands, the albumen, the 
the oil, the globules, and more especially 

first and the last, are greatly increased, 
the chyle when it reaches the thoracic duct, 
)rinciples are so augmented, concentrated, 
)proximated to the state in which they 

1 the blood, that the chyle is now capable 
ergoing the characteristic process of the 

for as the blood, when drawn from a vein, 
oes spontaneous coagulation, so the chyle, 
irawn from the thoracic duct, separates into 
parts ; a solid substance or clot, which 
s at the bottom of the vessel; a fluid 
surrounds the clot ; and a thin layer of 
which is spread over the surface of the 
The solid substance is analogous to the 
and the fluid to the serura oi \)[v^ \A<i^^\ 
\e layer of matter whicYi is fti^ife^L^ oN«t \5ca 

1* 1 



268 THE PHILOSOPHY OF HEALTH. 

fluid is of an oily nature : moreoYer, the chyle, when 
in contact with the air, quickly changes to a red 
colour, and ahounds with minute particles oi 
various sizes, hut the largest of which is not yet 
equal to the diameter of the red particles of the 
hlood. 

698. The changes wrought upon the food, by 
which it is thus approximated to the chemical com- 
position of the hlood, are effected, as has been 
shown, partly hy the gastric and intestinal juices, 
and partly' hy matters comhined with the food 
highly animalized in their own nature, and en- 
dowed with assimilative properties, as the salivary 
secretion mixed with the food during mastication; 
the pancreatic and hiliary secretions mixed with 
the food during the conversion of the chyme into 
chyle ; and the mesenteric secretions mixed with 
the elaborated chyle of the mesenteric glands, and 
lastly, organized particles which have already 
formed a part of the living structures of the body 
mixed with the chyle under the form of lymph in 
the thoracic duct. 

699. The lymph, until lately regarded as ex- 
crementitious, is really highly animalized, partly 
combined with the chyle as its last and highest 
assimilative matter; whence the compound formed 
by the admixture of chyle and lymph is far more 
proximate to the blood than the purest and most 
concentrated chyle; andip^ilV^ i^turning with the 

chyle to the lungs, to tecewfe \)a.«^ «i ^^ixiA ^'s^ 
artdon, and thereby a \i\g\iet <^»5tta»^wi. 



UJiBORATION OF LTliPB. 269 

There is evidence that there is a series of 
specially provided for the elaboration of 
iph no less than of the chyle. There are 
manifestly connected with the digestive 
tus, to which physiologists have found it 
lely difficult to assign a specific office. These 
3 have a structure in some essential pomts 
; that structure is strikingly analogous to 
organization of glands : like glands, they 
ve a prodigious quantity of arterial blood, and 
supplied with a proportionate number of 
,nic nerves ; yet they are without an excretory 
t. The organs in question are the bodies 
ed the renal capsules, placed above the kidneys ; 
, thyroid and thymus glands situated in the neck, 
1 the spleen in close connexion with the stomach. 
701. These organs, however analogous in struc- 
e to glands, cannot, it has been argued, be 
reting organs, because they are destitute of an ex* 
tory duct, do not manifestly form from the blood 
J peculiar secretion, or, if they do, since there are 
means of detecting where it is conveyed, it is 
[>ossible to understand how it is appropriated, 
t if these organs collect, concentrate, and elabo- 
5 lymph, preparatory to its admixture with the 
rle and to its being sent a second time into the 
od to undergo a second process of depuration, 
y perform the function of glands; and their 
at of an excretory duct, which, liaa VviXk'wXo 
iered their office bo obscure, \^ ^jx^vvciX^ 



270 THE PHILOSOPHY OF HEALTH. 

for; they do not need distinct tubes for the 
transmission of any product of secretion; the 
lymphatic vessels which proceed from them and 
which convey the fluid they elaborate into the 
receptacle of the chyle, are their excretory ducts. 
That one of these organs, the spleen, is specially 
connected with the elaboration of the lymph, is 
manifest, both from its chemical nature and 
from the remarkable change which takes place 
in the chyle the moment the lymph from the 
spleen is mixed with it. Tiedemann and Gmelin 
state, as the uniform result of their observations 
and experiments, that the quantity of fibrin con- 
tained in the chyle is greatly increased, and that 
it actually acquires red particles as soon as the 
lymph from the spleen is mixed with it, and that 
the lymph from the spleen superabounds both 
with fibrin and with red particles. That the 
organs just enumerated, with the spleen, perform 
a similar fiinction, is inferred fi-om their being, like 
it, of a glandular structure, and without any 
excretory duct. If the spleen be really one of a 
circle of organs appropriated to a function such as 
is here supposed, a purpose is assigned to it ade- 
quate to its rank in the scale of organization; 
inferior to few, if its importance be estimated by 
the quantity of arterial blood with which it is 
supplied ; yet this is the organ for which Paley 
could find no bell&t \x^^ \Vmw\ \.\va.t of serving for 
package. 



DIGESTIVE POWERS. 271 

702. But in whatever mode the lymph be elaho- 
rated, it is certain that it consists of matter highly 
animalized, and that its most important principles*, 
its albumen, its fibrin, its globules, and even its 
salts, are in a chemical condition closely resem- 
bling that in which they exist in the blood. 

703. It will appear hereafter that all the proxi- 
mate principles of which the body is composed are 
reducible by analysis to three, namely, sugar, oil, 
and albumen : of these, sugar and oil are the least, 
and albumen the most highly organized. Every 
alimentary substance must contain at least one 
of these proximate principles, and in the various 
articles which compose an ordinary meal always 
two, and often all three, are afforded in abundance. 
From the phenomena which have been stated, it is 
clear that the digestive organs, in acting on these 
principles, exert the following powers. 

1. A solvent power. The first action of the 
stomach on the alimentary substances presented 
to it is to reduce them to a fluid state. No sub- 
stance is nutritious which is not a fluid, or 
capable of being reduced to a fluid. The stomach 
reduces alimentary substances to a fluid state by 
combining them with wat^r. Water enters into 
the composition of organized bodies in two states, 
as an essential and as an accidental element. A 
quantity of water is contained in sugar when re- 
duced to its dryest state; this water e«ixvxvft\ \\^. 
(dissipated without the decompositiou oi \)tv^ ^w^«:« \ 



272 THB PHILOSOPHY OF HEALTH 

it is therefore an essential constituent of the com- 
pound. Water is combined with sugar in its moist 
state : of this water much may be removed without 
destroying the essential properties of the sugar : 
this part of the water is therefore said to be an 
accidental constituent of the sugar. In most cases 
organized bodies contain water in both these 
forms ; and though it is commonly impossible to 
discriminate between the water that is essential 
and that which is accidental, yet the mode of 
union among the elements of bodies in these two 
states of their combination with water are essentially 
different. The stomach has the power of com* 
bining water with alimentary substances in both 
these forms. Thus fluid albumen, or white of ^, 
presented to the stomach is immediately coagulated 
or converted into a solid. Soon this solid begins 
to be softened, and the softening goes on until it is 
again reduced to a fluid. What was fluid albu- 
men in the white of egg is now fluid albumen in 
chyme ; but the albumen has undergone a remark- 
able change. Out of the stomach the albumen of 
the egg may be converted by heat into a firm solid; 
but the albumen of the chyme is capable of being 
converted only into a loose and tender solid. In 
passing from its state in the egg to its state in the 
chyme, the albumen has combined with a portion 
of water which has entered as an essential ingre- 
dient into its compositioii. B^ \,\vv& combination 
the compound is reduced itoift.^\kaX.Ta»:^\sfc «»^^ 



DIGESTIVE POWERS. 273 

a strong to a weak state. This is the first action 
exerted by the stomach on most alimentary sub- 
stances. They are changed finom a concentrated to 
a diluted, from a strong to a weak state : the power 
by which the stomach e£fect8 this change is called 
its reducing power, and the agent by which it 
accomplishes it is the gastric juice ; the essential, 
ingredient of which has been shown to be munatic 
acid, or chlorine (639, et seq,). The muriatic 
acid obtained from the common salt of the blood 
is poured in the form of gastric juice into the sto- 
mach, dissolves the food, combines it with water, 
reduces it from a concentrated solid to a dilute 
fluid ; and thus brings it into the condition proper 
for the subsequent part of the process. 

2. A converting power. Since whatever be 
the varieties of food, the chyme invariably forms a 
homogeneous fluid, the stomach must be endowed 
with the power of transforming the simple alimen- 
tary principles into one another; the saccharine 
into the oily, and the oily into the albuminous. 
The transformation of the saccharine into the 
oleaginous principle is traceable out of the body in 
the conversion of sugar into alcohol, which is 
essentially an oil. That the same transformation 
takes place within the body is indubitable. The 
oleagenous and the albuminous principles are 
already so nearly allied in nature to animal sub- 
stance that they do not need to undergo au^ e%%&\!L«> 
tin! change in tb&r composition. 



274 THE PHILOSOPHY OF HEALTH. 

3. A completing power. When the alimentary 
substances have been reduced and formed into 
chyme, when the chyme has been converted into 
chyle, and when the chyle absorbed by the lacteals 
is transmitted to the mesenteric glands, it undergoes 
during its passage through these organs a process 
the direct reverse of that to which it is subjected in the 
stomach ; for whereas it is the office of the stomach 
to combine the alimentary substances with water; 
it is one office of the mesenteric glands to remove 
the superfluous water of the chyle; to abstract 
whatever particles of matter may be contained in 
the compound which are not indispensable to it, 
and to concentrate its essential constituents ; and 
consequently these organs exert on the digested 
aliment a completing, in contradistinction to a 
reducing power. 

4. A vitalizing power. When sugar is con- 
verted into oil, when oil is converted into albu- 
men, when albumen, by the successive processes 
to which it is subjected is completed, that is, 
when the alimentary substances are made to 
approximate in the closest possible degree to the 
nature of animal substance, they must undergo 
a still further change, more wonderful than any of 
the preceding, and far more inscrutible; they 
must be endowed with vitality ; must be changed 
from dead into living matter. Living substance 
only 18 capable of iornvm^ ^ CQi^«,tituent part of 

living substance. T\ie "vAxvnv^Xfc ^ol\«\i ^^. "^^ 



TWO KINDS OF DIGESTION. 275 

digestive organs is the communication of life to 
the food, to which last and crowning process 
the reducing, converting, and completing pro- 
cesses are merely subordinate and preparatory. 
Of the agency by which this process is effected we 
are wholly ignorant ; we know that it goes on ; 
but the mode in which it is accomplished is veiled 
in inscrutable darkness. 

. 704. Blood is alive ; blood is formed from the 
food ; life is communicated to the food before it is 
mixed with the blood. The blood is essentially albu- 
men, which it contains in the form of albumen pro- 
perly so called, in that of fibrin, and in that of red 
particles. In the thoracic duct the strong albumen 
of the lymph is mixed with the weaker albumen of 
the chyle. At the point where the thoracic duct 
terminates in the venous system, lymph and chyle 
are mixed with venous blood, and all commingled 
are borne directly to the lungs. There the carbon 
with which the venous blood is loaded is expelled 
in the form of carbonic acid gas ; the particles of 
the lymph undergo some, as yet, unknown change, 
exalting their organization ; and the water hitherto 
held in chemical union with the weak albumen of 
the chyle, is separated and carried out of the sys- 
tem together with the carbonic acid gas in the 
form of aqueous vapour. By this removal of its 
aqueous particles the ultimate completion is given 
to the digested aliment ; and the weak and deli- 
cate albumen of the chyle is coiwett^^ VcAft ^^ 
Btrong and £rm albumen of the b\ood.. 



276 THE PHILOSOFHT OF HEALTH. 

705. It has been stated (539), that though 
gelatin enters abundantly into the composition of 
many tissues of the body, and performs most im- 
portant uses in the economy, it is never found in 
the blood ; that it is formed from the albumen of 
the blood by a reducing process, in consequence 
of which carbon is evolved, which unites with the 
free oxygen of the blood, forming carbonic acid, 
thus conducing, among other purposes, to the 
production of animal heat. It is equally remark- 
able, that though the lymphatics or absorbents 
arise in countless nimibers from every tissue of 
the body, and are endowed with the power of 
taking up every constituent particle of every 
organ, solid as well as fluid, yet gelatin is never 
found in the lymphatic vessels. The lymphatics 
contain only albumen in a form far more proxi- 
mate to the blood than that of the chyle ; conse- 
quently, before the gelatin of the body is taken up 
by the lymphatics, it must be reconverted into 
albumen; that is, the absorbed gelatin must 
undergo a process analogous to that which gelatin 
and other matters undergo in the stomach and 
duodenum ; it follows that the digestive process is 
not confined to the stomach and duodenum, but 
is carried on at every point of the body. Hence 
there are two processes of digestion, a crude and a 
refined process. The crude process is carried on in 
the sto/nach and duodenwrcv^ \xv -^ViyqK ^^i^ animal 
matter Im converted into \mti\r» w^^^'^axv^j.^^ ^^^'^^ 
however, possessing on\y i\ie\oHi^x.Vvi^^^^ <^^>^ 



FIJiST AKD SECOND PROCBSSK8. 277 

The capillary arteries receiving the substance thus 
prepared for them, build it up into structure per- 
haps the lowest and coarsest, the least organized, 
and capable of performing only the inferior func- 
tions. 

706. Capillary arteries in countless numbers 
terminate in the tissues in membraneless canals 
(304 and 310). Particles of the blood are seen to 
quit the arterial stream and to enter into the tissues, 
becoming a component part of them : other particles 
are seen to quit the tissues and to enter the current 
of the blood. The latter are probably organic 
particles, to which a certain degree of elaboration 
has been already given, now transmitted to the 
capillary veins, to be carried back to the lungs to 
undergo there a further depuration, fitting them 
on their return to the system for a higher organi- 
zation. 

707. Thus the lymphatic vesBels, analogous in 
so many other respects to the veins, are probably 
similar to them in this also — that they take up from 
the tissues particles already organized, in order to 
submit them to processes which communicate to 
them a progressively higher organization. The 
notion that the contents of the lymphatics consist 
of worn-out particles, capable of accomplishing no 
fiither purpose in the economy, is not tenable : — 

1. Because it is not analogous to the ordinary 
operations of nature to mix wholly excTe,iiv<e.iv\!\^Q»\x% 
matter with a substance for the pxodxxcXxoxv, ^«^- 



278 THE PHILOSOPHY OF HEALTH. 

boration, and perfection of which, she has con- 
structed such an expensive apparatus. 

2. Because, on the other hand, the admixture 
of matter already highly animalized with matter, 
as yet but imperfectly animalized, exalts the 
nature of the latter, and is conducive to its com- 
plete animalization. 

3. Because the lymph, almost wholly albu- 
minous, is already closely allied in nature to the 
blood ; it is, therefore, reasonable to infer, that it 
is matter passing through an advancing stage of 
purification and exaltation. 

4. Because this plan of progressive organization 
is in harmony with the ordinary operations of 
nature, in which there is traceable a successive 
ascent from the low to the high, the former being 
preparatory and necessary to the latter. The 
tender and delicate organs of animal life, the brain, 
the nerves, the apparatus of sense, the muscles, 
inasmuch as they perform the highest functions, 
probably require to be constructed of a more highly 
organized material, for the production of which 
the matter primarily derived from crude aliment 
is subjected to different processes, rising one above 
the other in delicacy and refinement ; by each of 
which it is made successively more and more 
perfect, until it acquires the highest qualities of 
living substance, and is capable of becoming the 
instrument of perfoTmrn^ its most exalted func- 

tione. 



2TO 



CHAPTER XI. 



OF SECRETION. 

Nature of the function — ^Why involved in obscurity — 
Basis of the apparatus consists of membrane — Arrange- 
ment of membrane into elementary secreting bodies — 
Crypts, follicles, caeca and tubuli — Primary combina- 
tions of elementary bodies to form compound organs — 
Relation of the primary secreting organs to the blood- 
vessels and nerves — Glands simple and compound — 
Their structure and office-— Development of glands from 
their simplest form in the lowest animals to their most 
complex form in the highest animals — Development in 
the embryo — Number and distribution of the secreting 
organs — How secreting organs act upon the blood — 
Degree in which the products of secretion agree 
with, and differ from, the blood — Modes in which 
modifications of the secreting apparatus influence the 
products of secretion — Vital agent by which the func- 
tion is controlled — Physical agent by which it is 
effected. 

708. Secretion is the function by which a substance, 
gaseous, liquid, or solid, is separated or formed 
from the nutritive fluid. It is a function as neces- 
sary to the plant as to the animal, and indispensable 
alike to the life of both. It is of ec\u»\. Vav^ortVa.^'^^ 



280 THE PHILOSOPHY OF HEA.LTH. 

to the preservation of the individual and to the 
perpetuation of the species. In all living beings 
secretions are separated from the nutritive fluid, 
and added to the aliment to assist in converting it 
into nutriment, and are separated from the nutri- 
ment to maintain the composition of the nutritive 
mass in a state fit for the continued performance 
of the act of nutrition, and to form the germ on 
the development of which the continuance of the 
species depends. 

709. The secretions of the plant, varied and abun- 
dant, are indispensable to its nourishment, growth, 
and fructification. The becretious of the animal 
more diversified, and far more constantly performed, 
increase in number and elaborateness in proportion 
to the range and intensity of the vital endowments 
and actions. In all animals high in the scale of 
organization, and especially in man, the products 
of secretion are vast in number, and exceedingly 
complex in nature, — membrane, muscle, brain, 
bone ; — the skin, the fat, the nail, the hair ; — ^water, 
milk, bile, wax, saliva, gastric juice ; — whatever 
substances enter as constituents into the corporeal 
structure; — whatever substances are specially 
produced, in order to perform some definite pur- 
pose in the economy ; — ^whatever substances arc 
separated from the mass, and carried out of the 
system on account of their useless or noxious pn^ 
pertiea : — ^all are derived iioxa \)tvfc xsw&tVtvve fluid, 



APPARATUS. 281 

the blood, and are formed from it by the process 
of secretion. 

'710. In this function are included the most 
secret and subtle processes of the vital economy, — 
the ultimate actions of the organic life. Of the real 
nature of those actions nothing definite is known ; 
and they are modified by agencies over which the 
art and skill of the experimentalist can exert no 
adequate control. It is not wonderful therefore 
that they should be involved in obscurity : never- 
theless, when all the phenomena are collected and 
compared, much of the mysteriousness in which 
the function appears at first view to be involved 
vanisbes. 

711. The apparatus of secretion is infinity varied 
in form : when examined in its complex combina- 
tions it appears inextricable in structure, but the 
diligence and skill of modem research have un- 
folded much of its mechanism, and enabled us to 
trace the successive steps by which it passes from 
its simple to its complex condition, 

112. To form an organ of secretion there must he 
an artery, a vein, a nerve, an absorbent, and a suffi- 
cient quantity of cellular tissue to allow of the free 
expansion of these vessels and of their complete 
intercommunication. Memhrane constitutes such 
an organ ; for membrane is composed of arteries, 
veins, nerves, and absorbents sustained and con- 
nected by cellular tissue. Hence Inem^il«afc c.wi- 



282 THE PHILOSOPHY OF HEALTH. 

stitutes a secreting organ, in its simplest form. 
The most important secreting membranes are the 
serous (30), the cutaneous (34), and the mucous 
(33). 

713. Serous membrane which lines the great 
cavities of the body, and which gives an external 
covering to the organs contained in them (fig. lx. 
a, c), forms an extensive secreting surface. Sy- 
novial membrane, or that which covers the internal 
surface of joints, and which constitutes an im- 
portant portion of the apparatus of locomotion, is 
essentially the same in structure and office. 

714. Cutaneous membrane, or the skin, which 
forms the external covering of the body, is an organ 
in which manifold secretions are constantly elabo- 
rated ; but the skin is only a modification of the 
membrane which lines the interior of the body, 
the mucous. Mucous membrane forms the basis 
of the secreting apparatus placed in the mouth, 
fauces, esophagus, stomach, and intestines in their 
whole extent ; of the secreting apparatus auxiliary 
to that of the alhnentary canal, namely, the pan- 
creas and the liver ; probably also of the mesen- 
teric, or lacteal glands, together with the vast 
system of lymphatic glands, and certainly of the 
glands of the larynx, trachea, bronchi and air 
vesicles of the lungs. Hence, while membrane 
forms the basis of the secreting apparatus in gene- 
ral, mucous membrane is far more extensively 



MEMBRANB. 283 

employed in its construction than any other form 
of membrane. 

115. 1. In the construction of the secreting ap- 
paratus, membrane disposed in the simplest form, 
constitutes merely a uniform, smooth, extended 
surface. Serous membrane is always disposed in 
this simple mode. The costal pleura which lines 
the internal surface of the walls of the chest 
(fig. Lx. a); the pulmonary pleura which is 
continued from the walls of the chest over the 
lungs (fig. LX. 5) ; the peritoneum which lines the 
internal surface of the cavity of the abdomen, and 
which is reflected over the viscera contained in it 
(fig. LX. c, and 6, 7, 8, &c.) ; the synovial mem- 
brane which covers all the articular surfaces ; the 
arachnoid membrane which envelopes the brain^ 
form simple continuous, serous, secreting surfaces > 
On the contrary, mucous membrane is never dis- 

Fig. GI.XXXI. 




A portion of the mucous surface of the intestines, showing 
some of the mucous glands which ) resent the ajipearanoe 
of fovse or crypts. 



284 THE PHILOSOPHY OF HEALTH. 

posed in this perfectly simple mode ; even when 
it forms a continuous surface, as in the lining, 
which it affords to the alimentary canals, it is more 
or less plaited into folds or rugae (fig. clxvii. 1). 

716. 2. The second disposition of memhrane in 
the construction of the secreting apparatus, is the 
depression of it into a minute pit or fova, called a 
crypt (cLxxxi.), which is sometimes inclosed on 
all sides, forming a cell or vesicle (fig. cxxxviii.). 

711. 3. Next, the vesicle, instead of heing 

Fig. CLXXXII. 
s 1 8 s 1 




Portion of the skin and cellular tissue, showing the sebft- 
ceous follicles, as seen under the microscope very highlj 
magnified. 1. The external surface of the follicles with the 
blood-vessels ramifying upon it. 2. Follicles laid open, 
showing the interior cavity into which the secreted fluid ii 
poured. 

rounded, is elongated into a peduncle or neck, not 
unlike the neck of a hottle (fig. clxxxii. 1). This 
pedunculated vesicle is called a follicle. 

718. 4. Then, the follicle is somewhat elongated, 
without neck and without terminal expansion 
(fig. CLXxxvi. 1) ; and this is called a csecum or 
pouch. 

119. 5. And, lastly, XJcia e«iCMXxv itself is elon- 



XLEMENTART FORMS. 285 

gated ; so that instead of presenting the appear- 
ance of a pouch, it rather resembles a tube (fig. 
CLXXxv. 1), and is accordingly named tubulum. 

720. In the construction of the secreting appa- 
ratus, membrane, then, may be said to be disposed 
into four elementary forms constituting cryptse or 
vesicles, follicles, caeca and tubuli. Membrane, 
disposed into these elementary forms, constitutes 
the simple bodies by the accumulation and the 
varied arrangement of which the compound organs 
are composed. There is no other known element 
which enters into the composition of the most 
complex secreting organ. 

721. One of these elementary bodies may exist 
as a simple organ, or many may be collected into a 
mass to form a compound organ. When single 
they are called solitary : when collected into a 
mass, aggregated. Each elementary body has a 
mode of aggregation peculiar to itself. Vesicles 
aggregate by clustering together (fig. cxzxviii.), 
and adhering as if by a common stem (fig. 
cxxxviii.); follicles by uniting at their orifices 
(fig. CLXXxiii.)) and forming masses which are 
disposed either in a linear direction (fig. clxxxiii.) 
or in fasciculi (fig. clxxxiv.) ; caeca by forming 
bundles, parallel or branched (fig. clxxxvi.); and 
tubuli by forming masses straight (fig. clxxxv.), 
tortuous or convoluted (figs, clxxxv. and clxxxix.) 

722. When a single elementary body^a^ «u N^\d<& 



286 



THE PHILOSOPHY OF HEALTH. 




Fig. CLXXXIir. 



tmiiM 



\mmm'i^'mismm 



Aggregated follicles disposed in a linear direction, here re- 
presented of their natural size, as seen near the mouth in 
the goose. 

or follicle, forms a distinct secreting organ, the 
matter secreted is elaborated at the inner surface of 

Fig. CLXXXIV. 







Conglomerated follicles. 



the organ (6g. clxxxii. 2), and is contained within 
its cavity. When needed it quits this cavity 
through the waWa oi l\ife N^«\cU>or at the orifice of 



n.niBMTART poRiu. 267 

>llicle, on the application of the appropriate 
luB. WhenanvunberofcryptaorTeUclei are 
;ated into cluaten, the mdividnal veuclea 
imea open hy distinct orificea into a common 
tacle OT SBC (Gg. clxxxiv.). When folliclea 
cgregated into a mass, and the mats ii dis- 

in a linear direction (fig. clzxxiii.), each 
; pours out its secreted matter by its own 

(fig. CLXxxiii.) ; but if conglomerated, into a 
on mass by a common orifice (fig. clxxxiv.}. 
.In like manner, in some very simple arrange- 
. of ccBCa and tubuli, each body opens by ita 
lisdnct orifice (fig. clxxxv. 2). But in the 



Fig. CLXXXV. 




t\ tubulL, opening by dutinet orificei into — 3. A 



288 TDB PHILOSOPHY OF HEALTH. 

more complex arrangementB of these bodies, it u 
iDdiepeneably necesMTj to modify this mode of 
parting with their contentB. When the elementary 
bodies are a^^p^gated into denae, thick masaes (6g. 
cuxzix.), when layer after layer of these maaaei 
containicg myriads of myriads of folliclee, oeca, m 
tubuli, are niperimposed one upon another, (% 
CLZXXix.), it is impoasible that each indiTidoil 

Fig. CLXXXVI. 




Branched cwea, diowiiif; — 1. The oeca lanaiDstiilgin— 
3. Eicretoty dueli which unite to foiin— 3. A emim^ 



8BCRXTIV6 CANALS. 289 

body can have a separate orifice. In this case a minute 
tabe springs from each body (fig. clzxxvi. 2) ; and 
a complete connexion is established between all the 
indiyiduals composing the mass by the free inter- 
communication of these tubes (fig. clxxxvi. 2). 
Of these tubes the minutest unite together, and form 
larger branches (fig. clxxxvi. 2) ; these larger 
branches again uniting form still larger branches 
(fig. CLXXXVI. 2), until, by their successive union, 
the branches form at length a single trunk (fig* 
CLXXXVI. 3), with which all the individual branches, 
whether great or small, communicate, and into 
which they all pour their contents (fig. clxxxii. 
2, 3). The bodies from which these tubes take 
their origin, and the minute tubes themselves, are 
called secreting canals (fig. clxxxii. 1,2); the 
common trunk formed by their union is termed the 
excretory duct (fig. clxxxii. 3). The secreting 
canals contain the secreted matter ; the excretory 
duct collects this matter, and convevs it to the 
part of the body in which it is appropriated to the 
specific purpose which it serves in the economy. 

724. The basis of the secreting canals consists, 
then, of membrane disposed in one or other of the 
elementary forms described (712, etseq.). These 
secreting canals constitute a peculiar system of 
Drgans wholly different from all the other organs of 
the body. The form of these organs, their structure 
8ind their relation to the blood-vessels and IveIN^%^ 

hare formed Bubjecta of laborious iuveati^'aXivoxv taA 
roL, ir, o 



290 THE PHILOSOPHY OF HEALTH. 

of keen controversy during several centuries. The 
honour of discovering the exact truth on these 
points is due to very recent researches. 

725. Malpighi, an Italian, who flourished at 
Bologna in the middle of the llth century, was the 
first to establish a special inquiry into the intimate 
structure of the secreting apparatus. After many 
years of laborious examination he arrived at the 
conclusion that a minute sac or follicle is invariably 
interposed between the termination of the capillary 
artery and the commencement of the excretory 
duct. According to him« the capillary artery con- 
veys the blood to the follicle, separates from the 
blood the substance secreted, and the excretory 
duct arising from one extremity of the follicle con- 
veys the secreted fluid, when duly prepared, to its 
destined situation. By injection, by dissection^ by 
the microscope, by experiment on living animals, 
and by the phenomena of disease, he conceived 
that he had demonstrated that this is the true 
structure of the secreting apparatus in its most 
complex form. This view was generally acquiesced 
in i?y his contemporaries and by succeeding anato- 
mists and physiologists; and in the time when 
Ruysh wrote was the received opinion. 

726. Ruysh, who flourished at Amsterdam, 
and '^as contemporary with Malpighi, but a 
younger man, and who published on the glands 
about twenty years after Malpighi, according to 

the account of HaWeic, " ^ysv^q^^ "^^T^dfixM pa- 



RELATION TO BLOOD-VESSELS. 291 

tience, with the assistance of his daughters, in 
rendering all his preparations elegant and beau- 
tiful, being equally skilled in the methods of 
softening, hardening, filling, and dr}ing." Of 
Rayah it was said that while others, in their 
anatomical preparations, merely exhibited the 
horrid features of death, he preserved the human 
body in all the freshness of life, even to the 
expression of the features. The fineness of his 
injections, the dexterity with which he unfolded 
the minute vessels, nerves, and absorbents, and 
exhibited their combinations and relations in the 
most deUcate structures, the skill with which he 
preserved his preparations in transparent fluids, 
and the elegance with which he displayed them in 
their natural forms and folds, excited universal 
admiration } and philosophers^ statesmen, princes, 
kings, all the learned and noble of the day, 
crowded to his museum. 

727. By his superior method of injecting, Ruysh 
conceived that he was able completely to disprove 
Malpighi's doctrine. He maintained that the 
bodies which Malpighi mistook for sacs or follicles 
are in reality convoluted vessels; that these 
vessels are capable of being completely unravelled ; 
that, when unfolded, their continuity with the 
excretory duct is perfectly demonstrated; that 
secretion is performed by the capillary artery 
itself, without the intervention of an^ o\\v«i crt%^iccs.\ 
fiDd that when the secreted «ubfe\.atvc^ \& ^>i^'^ 

o1 



292 THE PHILOSOPHY OP HBALTH. 

prepared, it is poured by the capillary directly 
into the excretory duct. 

728. Modern research has demonstrated that the 
opinion of Malpighi approaches nearer the truth 
than that of Ruysh, who appears to haye mistaken 
the secreting canals for the ultimate division of 
the arterial vessels. Malpighi, indeed, did not 
succeed in discovering the elementary bodies of 
which the secreting apparatus is composed ; but 
he arrived at the very verge of the truth. Profil- 
ing by the art which Ruysh brought to so much 
perfection, by the facts which Malpighi disclosed, 
and, above all, by the improved structure of the 
microscope, and the increased skill which has been 
acquired in the manipulation of the instrument, 
the modern physiologist is enabled to see what 
was formerly beyonct the cognizance of sense, and 
to demonstrate what before could only be matter 
of conjecture. Availing himself of these advan- 
tages with consummate skill, and applying himself 
to the task with indefatigable industry, Prdessor 
Miiller, of Berlin, has investigated the structare 
of the secreting apparatus in the whole animal 
kingdom, and has traced the progressive develop- 
ment of the several secreting organs through die 
entire animal series, from their simplest form in 
the lowest animal, to their most complex in the 
highest. 
729. From the leseaTf^^ oi xJKife ^li^siologist, 
And from the labouiaof ol\i«^^Vv& c.wx3to^iafc\i.«!^ 



RELATION TO BLOOD-TBSSBLS. 293 

contemporaries, who have engaged in the investi- 
gation with an ardour second only to his own, it is 
demonstrated that the secreting apparatus of the 
animal hody is disposed in one or other of the ele- 
mentary forms which have heen descrihed. The 
blood-vesseh are distributed upon the walls of 
these elementary bodies, whether simple crypt® 
follides, caeca, or tubuli, or whether these bodies 
are accumukted and combined into the largest 
and most complex series of secreting canals, just 
as the branches of the pulmonary artery are distri- 
buted upon the walls of the air-A^esicles in the rete 
mirabile of the lungs. The air- vesicles of the 
lungs are secreting organs, and afford an excellent 
example of the mode in which the blood-vessels 
are distributed upon the walls of the elementary 
secreting bodies. The arteries do not form con- 
tinuous tubes with the secreting bodies or their ex- 
cretory ducts, as was maintained by Ruysh ; nei- 
ther is the secreting body interposed between the 
termination of the artery and the commencement 
of the excretory duct, as was thought by Malpighi ; 
but the ultimate divisions of the arteries are spread 
out upon the walls of the secreting bodies, where 
they terminate in veins by a delicate vascular net- 
work (fig. CLXxxvii. 2). The minutest branch of 
the artery is always smaller than the minutest se- 
creting body on the walls of which it is distributed. 
According to Miiller, the arteries, spread o\x\. >r^wi 
the walls of the secreting bodies, fotra «^ ^vWCvcvcX 



294 THE PHILOSOPHY OF HEALTH. 

and peculiar system of vessels visible under the 
microscope. In the more complex secreting 
organs, immediately before reaching their distribu- 
tion upon the walls of the secreting canals, the 
ultimate divisions of the arteries form an intricate 
and delicate net- work (fig. clxxxvii. 2). When 
at length they reach the secreting canals the arte* 
ries no longer divide and subdivide, but are always 
of the same uniform size in the same secreting 
organ, though their magnitude is different in 
every different kind of secreting organ. These 
ultimate divisions of the arteries are the proper 

Fig. CLXXXVII. 




A thin portion of the surface of the kidney taken from 
the scianus, showing^ — I. The termination of the csca 
forming the uriniferous duct ; and — 2. A delicate TasciilAT 
net-work, consistinp^ of capillary hlood-vessels about to be 
distributed on the walls of the csca. 

capillary arteries. It is in these arteries that the 

changes are wrought upon the blood which it is 

the object of the various processes of secretion to 

effect. In the walls of these arteries there are 

visible no pores, no apertures, no open extremities 

by which the secreted f^mA.^'vV^TL iarKL^-^^tom the 

blood, is conveyed into t\ve c».n\\73 ^^ ^^ ^^^tioM^ 

canals; it probably pn^ae^ >^V^«^S^ ^^ ^^ ^ 



RELATION TO NERVES. 295 

le vessels into the secreting canals by the procesB 
r endosmose (804). 

730. Secreting organs are very abundantly sup- 
lied with nerves, which are derived for the most 
BLTt from the organic portion of the nervous system ; 
though for the reasons assigned (vol. i. p. 77, ei 
^q.) sentient nerves are mixed with the organic, 
lie more important secreting organs have each a 
istinct net-work or plexus of organic nerves, which 
irround the blood-vessels distributed to the organ, 
ig. CLxx. 3), and which envelopes more espe- 
lally the arterial trunks and their larger branches 
ig. CLXX. 3). From these plexuses nervous fila- 
lents spring in countless numbers (fig. clxx. 3), 
hich are spread out upon the w^lls of the arteries, 
ist as the arteries are spread out upon the walls 
r the secreting canals. The nerves never quit 
le arteries; are never spent upon the n)em- 
ranous matter which forms the basis of the 
!creting organ, but are lost upon the walls of 
le capillary arteries. The nerves uniformly in- 
rease in number and size as the arteries diminish 
i magnitude and as their capillary terminations 
ecome thinner and thinner. 

731. When the secreting apparatus consists of 
mply extended membrane, a close net-work of 
ipillary arteries with their accompanying nerves 

spread out over the whole extent of the secret- 
ig surface. This simple arrangemetvl \^ wiS^cvetsX. 

separate from the blood the siiHYiVe s^cteVkoa \^ 
s case required. 



296 THE PHILOSOPHY OF HEALTH. 

732. When the secreting apparatus consisU of 
simple cryptse, follicles, caeca, or tubuli, a nmilar 
net-work of capillary arteries and nerves is spread 
out on the sides of this more extended surface. 
The more elaborate secretion now formed is received 
into the iilterior of these organs, where it remaisi 
for some time, and whence it is ultimately con- 
veyed as it is needed by the actions of the system. 

733. But when the secreting apparatus consists 
of aggregates of cryptse, follicles, caeca, and tubuH, 
with their net-works uf arteries and nerves, a much 
more complex structure is built up, which b 
destined to perform a proportionably elaborate 
function. An aggregation of these secreting 
bodies into a large mass, enveloped in a common 
membrane, so as to form a distinct body of a sdid 
consistence, constitutes the organ termed a gland. 
Simply extended membrane, with its apparatus of 
arteries and nerves does not constitute a gland. 
Simple cryptie, follicles, caeca, and tubuli, with 
their larger apparatus of arteries and nerves, do not 
constitute a gland. The first is simply secreting 
surface ; the second are simply secreting crypICi 
follicles, caeca or tubuli; but when these bodiei 
are aggregated into dense and solid masses with 
an extended system of excretory ducts, and when 
the whole of this apparatus is inclosed in a proper 
membrane so as to form a distinct body, such a 
body IB termed a gland. 

734. Primary aggTe%a.^oT» ^i ^«ttfe ^Ksttiofi^ 
bodies constitute wbat \ft lexia^^ ^ ««ise«5«i6fc, 



GLANDS. 297 

that isy a simple gland ; auch are all the glands 
connected with the absorbent or lymphatic system. 
Secondary aggregates, or aggregates composed of 
simple glands, constitute what is termed a conglo • 
merate, that is, a compound gland ; such are all 
the organs commonly termed viscera, as the liver, 
the spleen, the pancreas, the kidney, and so on. 

735. The conglobate, or simple gland, being 
formed by the aggregation of crypUe, follicles, cseca, 
or tubuli, inclosed in a proper membrane, presents 
the appearance of a simple solid body, commonly 
of a rounded «r oblong form (fig. clxxvi. 516). 
On the contrary, the conglomerate or compound 
gland, being fonned by the aggregation of conglo- 
bate or simple glands, presents the appearance of a 
compound body composed of a congeries of masses 
(fig. CLXV. 1). The larger masses enveloped in 
their own proper membrane are termed lobes 
(fig. cxci.); the smaller masses, also enveloped in 
their own proper membrane, are termed lobules 
(fig. CXCI.); the lobules, when carefully exa- 
mined, are seen to be composed of still smaller 
masses, and these of masses yet more minute, 
until at length patient, laborious, and skilful dis- 
section brings into view the ultimate constituent 
elements, which are invariably found to consist of 
simple cryptse, follicles, cseca, or tubuli. 

736. Thus membrane having a specific arrange- 
ment of blood-vessels and nerves, from bem^ ^vcw^-^ 
extended, is folded into a few elemeivlaT'^ ioT\«v^\ 
the bodies which result constitute a\mp\e ^ectt^:vci^a 



298 THE PHILOSOPHY OF HEALTH. 

organs; these bodies collected together form, by 
their aggregation, ciomponnd organs ; the com- 
pound organs, uniting, form aggregates still more 
compound, until at length a structure is buik up 
highly elaborate and complex. But this complexity 
of combination and arrangement does not alter 
the constitution of the organs ; thcSir form varies, 
but their nature remains edsentially the same. All 
consist alike of membrane organized in a similur 
mode. The Complex contains no elenient not poi- 
ftessed by the simple gland, and the gland dontaini 
no element not possessed by the secreting surfitce. 
But there is thife diffetence in the complex OTgam. 
Every kind and degtee of change in the form of 
the secreting apparatus, from membrane simply 
^tended, to membrane coil^ up into the most 
complex glandj is attended with an accumulation 
and concentration of secteting surface. The crypt 
contains a larger extent of secreting surface than 
the simple membrane ; the follicle than the ciypt; 
the caecum than thii follicle ; and the tubulum than 
the csecum. A Certain atnotint of secreting sur&ce 
is gained by the disposition of the simple mem^ 
brane into the form of the crypt. The eolleedon 
of a number of crypts into a cluster doubles the 
extent of the secreting surface by the extent of 
every crypt that is added to the duster. The 
addition of every cluster doubles the whole extent 
of surface acquired b^ ^ «\tv^<& duster. But when 
stems spring as if itom ^^ wsckibswiXxvs^^ i&^ 
braBcbes spring ftoma^toesa-, ^^k«v«^^ai^\KWJ6•^ 



BTBIICTUaB AMD OFFICE. 2M 

from the large bi»9ches, and yet tmailer 
les from tha small in a aeriei^ which the eye, 
d by the most powerful microscope, is whdly 
( to trace ; when all the clusters thus formed 
Uected« and combined into a compact mass, 
;ricacy of which no art can cos^pktely onrayel, 
taat of surface obtained is altogether immea- 
e. How immense must be the extent of 
e thus acquired in such an oi^an as the 
1 lungs, in such a gland as the human 

[. In such a9 aggregation the concentration is 
qual to the accumulation ; the maximum of 
e is comprised in the ^linimum of ^ace, and 
lei^ a^d elaborateness oi the fimction of a 
ing organ is ujiiformiy proportionate to such 
sentration of its secreting substance. 
). Hence the complexity of the compound 
in the higher animals would appear to arise 
from the intricate arrangement of the immense 
of secreting matter concentrated in a small 
iss; hence also the pro^essively increased 
Lication indicated in the successive derelop* 
of the glandular system in the animal series. 
, for example, among the distinct organs 
d for the purpose of elaborating a iqpecific 
ion, being intimately connected with the 
sfl of digestion, one of the first is the salivary 
. Low down in the scale, in t\ie«xiSxci»im 
the £nt rudiment of a saliNsx^ \^&XkdL\% 
fie, k eooBista of a single ioWic\^ ^Vvi\^ 



300 THE PHILOSOPHY OF HEALTH. 

appears to serve the office of a gland. In an 
animal a little higher in structure, two, three, or 
four follicles combine to form a somewhat less 
simple organ. In an animal still higher in the 
series, a number of follicles are clustered together 
and form a much more complex oi^an ; and in this 
manner, as the organization of the animal becomei 
higher and higher, the complexity of the gland 
increases, until at length it is composed of a count- 
less number of follicles collected into clusters, the 
clusters disposed into lobes, the lobes subdivided 
into lobules, and the lobules into still smaller par- 
ticles, the ultimate elements of the glandular appa- 
ratus. In like manner, when the first rudiment 
of the liver is discoverable, it consists of a single 
pouch or caecum ; somewhat higher in the series, 
the organ is composed of two or more caeca distinct 
and free; and then, as its complexity increaaes 
with the perfection of the organization, cseca are 
accumulated upon caeca ; the aggregates so formed 
are closely compacted, disposed into lobes, divided 
into lobules, and subdivided into the ultimate pa^ 
tides of the glandular apparatus. So in a gland 
composed of tubuli, as the kidney, the organ in ita 
rudimentary state consists of a few straight tubuli: 
as its structure advances more tubuli are added: 
next, the increasing tubuli superimposed one upon 
another become tortuous; then the tubuli still 
Accumulating, become nolTnet^'^ \«ttaou8^ but con- 
volated; and last of a!i\» cwxtixXk^a >sx«s^wfi».^\ 
tubuU are closely compficted Voto ex^^^^T^sg.^ ^^* 



DBVBLOPHSNT OF QLAHDS. 301 

id masses. Unifonnly, the lower the animal 
lie timpler the organ, the lai^r and the more 
feat are the elementary parts of the gland ; 
J the higher animals these eUmentBry bodies 
a minute as to be altogether microscopical 
ng. CLXXXVIIl. 




^afcidsiiiidurtewii c«ea opening irfofti««Ji™ftTiH.»i^ 
euial, peifoiaiing the function otnu^i^ttX• 



THB PHlIX>aOPHT OF BBALTB. 




P«BJlgr to be dirthbuteAK.-'i.T^ato™^^^^^ 



'ai[ the uiiaiftuDoa ducta «\a^ 



k.-t<* 



DEVBLOraSHT OV GUiNDB. 303 

Bon teaetory duet called uret«r ^-B another portion 
le lame kidney, vhowing the extremely convoluted 
le of — 4. The uriniferous ducts. 5. The Mmaller excre- 
dacti, or secreting canals, conTerg^i; and uniting 
rm — 6. The common excretory duct called the ureter. 

their arrangement is so complex that it can 
nravelled only with extreme difficulty. 
)9. It is a striking confirmation of the correct- 
of this view of the structure of the glandular 
jratus, that whenever in the ascending series 
md appean for the first time in any class, the 
entary hodieaateso large, and are disposed in 
imple a mode, that a slight examination is 
:ient to demonstrate their primitive form, and 
nder it manifest that they eontist either of 
les, follieles, caeca, or tuhulri more or less 
^ted. This is seen in the obvious structurs 
inted by th^ liv^r, the panereaa^ the salivary 
is^ and the mammae, in the simple animals in 
h these organs first appear. Thus the liver 
limals loiw down in the acakr is manifestly 
losed of simple clustering follicles : in the 
he pancreas is composed of simple branched 
les ! in the bird, the salivary glands are com- 
l of simple parallel tubuli ; and in the cetacea 
breasts are composed of simple branched 

• 

1. 

0. But the microscope, by bringing the Suc- 
re development of the compound gland in the 
yo of the highei' animal under the co^itaxa^^ 
perfectly diBclofses the nature of iXACcnn^^V!' 



304 THE PUIIOSOPHT OF 

tion. Id tlie development of theiocubsted egg tnrj 
■tep of the ptt^eBBive foTiQation of the compoond 
gland is lendered visible to the eye. When thia pio- 
CCBS ifl carefully watched, it is seen that the pait of 
the gland firBt formeil is the excretory duct, wbich 
a|inrigs Irom the blastema, the common mau of 
matter out of v^ich all the o^sni ^re fpniwi' 
rig. CZG. 




A lobula oft elaiid in the pnwran <i dnelapingDt |i tf* 
ovum of the urd, u teeo under iha niieroicoK tiiowaf 
the oriiiin of Uie Bxentoij dueti ia the •emip^add ffl*- 
tinoui blaitema, uid the braocliing and foliitted aTTU|t- 
ment of the folUdei id which the cicntury duct* to 



From this duct the elementary parts of the gland 
bud just as bunches of grapes bud from the atalk. 
The buds, at first at considerable distances &aiii 
each other, app^ach iiewu aa they increase bj 
new growths, until at Xen^&i 'itfi'j wmw. -oSft mJm^ 



N TBK tMBRTO. 



ontact. The growth contmning, and the compact* 
«s8 of t^e lubBtance of the gland proporUonall; 
icremsing, the primitive form of the elementnry 




•eetioDof the livei in the lower animal in the|iiognw uf 
M««liipnant, ai lecD uiid«r the microscope, >hawinK the 
udimentaty diTiiioa iota lobet and lobutei, and the 
loiuatvd tcrmiDatioDs of tlia bilirerous ducts, or eylin- 
rieu acini TBiiously diipoied id a braacliiag and faliated 

odiea which compose it is ultimately loat. The 
abstance of the gland now appean to cmxGuX «il 
mjpact aolid matter, which is coTamotiVj Ustove^ 



306 THE PHILOSOPHY OF HEALTH. 

parenchyma. The component particles of this 
parenchymatous and apparently solid suhstancc 
present a clustered or grape-like appearance, from 
which they early obtained the name of acini, from 
the Latin word acinus, a berry. This term, origi- 
nally employed merely to express the clustered 
and branching appearance of the elementary parts 
of the gland, has since been used in widely dif- 
ferent senses. By some it has been employed to 
express solid glandular grains constituting a sup* 
posed distinct parenchymatous substance, differing 
in every different gland, ft is pow proved that iio 
such solid granular particles enter into the com- 
position of any gland in th,e i^iiimal kingdom. By 
others the term acini has been employed to express 
granular bodies composed pf blood-vessels, directly 
continuous with the excjceUtry ducts, and from 
which the excretory dncfs derive their origin. 
Recent investigation hag demonstrated that there is 
no continuity of ^he blood-vessels into the excre- 
tory duct either in the acini or in any other part 
of the gland. It is established that the blood- 
vessels are spread out upon the walls of the se- 
creting canals and do not form with them c6a- 
tinuous tubes. The bodies which have been mis- 
taken for granular particles, constituting the so 
called solid acini, are really the shut extremities 
of hollow follicles, cseca, or tubuli, which appear 
solid only from the c\oaeiieea^\\3a. -^hich they are 
compacted. When c«teWi)t^ ^\%^^^\».\ yss^ vx- 



IN THE EMBRYO. 307 

ed under the microscope, their real nature 
nes apparent, and this is also sometimes 
ble of being demonstrated by injection; for 
of these elementary bodies are vesicular, and 
be filled with mercury, when they present a 
dful appearance like clusters of diamonds ; or 
may be inflated with air, just as the air vesicles 
e lungs. 

:1. On watching the formation of the gland 
e development of the embryo, it would appear 
at first free streams of blood, or blood not 
lined in proper vessels, pass around the acini, 
hut extremities of the excretory ducts, or the 
ting canals. "So it would seem," says 
er, " when we examine the evolution of the 
and kidney in the embryo of the lower animal ; 
lie interstices of the canals appear bloody, 
)ut the slightest trace of the walls of blood- 
Is. I conceive that in the banning new 
tns arise in an amorphous mass (a mass 
)ut form), not bounded by proper parieties ; 
that soon walls are formed, which present 
ite boundaries to the streams, the density of 
substance around the streams gradually in- 
ing." It is in this manner that the con- 
>n is first established between the system of 
iary blood-vessels and that of the secreting 

IS. 

2. In its embryo state the compowoA. ^«xA oJv 
g;be8t animal consists of mere excieXox^ ^\Sl^\»^ 



308 THB PHILOSOPHY OF HBALTH. 

wonderfully similar to the simple secreting bodiei 
of the lowest classes. Bat in the higher animsl 
this simple form of the gland is transient: grt- 
dually, with the progressive eyolution of thi 
embryo, it passes into a more complex stmctuie; 
while in the lower animal the simple form of tbe 
gland remains permanently the same through thi 
whole term of life. 

743. Such are the main points which have been 
ascertained relative to the structure of the secrel- 
ing apparatus, which enters in one or other of iti 
forms, as a constituent element, into almost evecy 
part of the animal body. Wherever there is 
nutrition there b secretion, and wherever there it 
secretion there is one or other of these secreting 
bodies. How immense the number of these orgsni 
in the human body ! Every point in the interior 
of the walls that bound the great cavities is t 
secreting surface. Every point of the secretiDf 
surface that lines the alimentary canal, from its 
commencement to its termination, is studded witk 
distinct secreting organs. Every point of tiie 
skin is still more thickly studded with distinct 
secreting organs. By the naked eye, and still 
more distinctly with a lens, may be seen the pores 
through which the vapour that constitutes the in- 
sensible perspiration incessantly exudes. Next 
are the open mouths of myriads of sebacknis 
follicles that pour out u^n xk<^ %kin the oily 
matter which gives it Vis «jaYe\«t«» %xA ^^XMia\ 



ACTION VFOH THB BLOOD. 309 

ind besides all these, are the hairs, each the pro- 
luct of a secreting organ placed immediately 
leneath the skin. An attempt to count the num- 
>er of pores and hairs visible to the eye within 
lie compass of an inch, and thence to compute 
he number on the whole surface of the skin, may 
convey some conception of the amount of these 
irgans ; yet these form but a small part of the 
lecreting apparatus. The great Tisoera of the 
x)dy, the brain, the lungs, the liver, the pancreas, 
he spleen, are portions of it ; all the organs of 
he senses, the eyes, the ears, the nose, the tongue ; 
til the organs of locomotion ; every point of the 
lorface of every muscle, and a great part of the 
lurface and substance of the very bones are 
nrowded with secreting organs. 

744. Since every secreting organ is copiously 
(upplied with blood, it follows that a great part of 
he blood of the body is always circulating in 
lecreting organs ; and, indeed, it is to afford ma- 
erials for the action of these organs that the 
»lood itself is formed. 

745. How do these organs act upon the blood ? 
All that is known of the course of that portion 

»f the blood which flows through an organ of 
ecretion is, that it passes into arteries of extreme 
ainuteness, which are spread out upon the ex- 
emal walls of the elementary secreting bodies, 
ind which, as far as they can be traced, ^%»«^ \Si\A 
tpillary veias, — ^nowhere termmatVn^ \s^ o^'c^ 



310 TBB PHILOSOPHY OP HBALTH. 

mouths — ^nowhere presenting visible outlets or 
pores ; their contents probably transuding through 
their thin and tender coats by the process of en- 
dosmose. 

746. As it is flowing through these capillary 
arteries, the blood undergoes the transformatioDs 
effected by secretion, forming — 1 . The fluids, which 
are added to the aliment, and which accomplish its 
solution, and change it into chyme. 2. The fluids, 
which are added to the chyme to convert it into 
chyle, and both to chyle and lymph, to assist in 
their assimilation. 3. The fluids which, poured 
into the cavities, facilitate automatic or voluntary 
movements. 4. The fluids, which serve as the 
media to the organs of the senses by which ex- 
ternal objects are conveyed to the sentient extre- 
mities of the nerves for their excitement. 5. The 
fluids which, deposited at different points of the 
cellular tissue, when more aliment is received thao 
is needed, serve as reservoirs of nutriment to be 
absorbed when more aliment is required than can 
be afforded by the digestive organs. 6. The fluids 
which are subsequently to be converted into solids. 

7. The fluids which are eliminated from the com- 
mon mass, whether of fluids or solids, to be caJried 
out of the system as excrementitious substances. 

8. In addition to all these substances, which are 
indispensable to the preservation of the indivi- 
dualf those which ate T\e<iessary to the perpetaa- 

tion of the speciea. 



PRODUCTS OF SECRETION. 311 

74*7. In order to form any conception of the mode 
in which the secreting organs act upon the blood, so 
as to elaborate from it such diversified substances, 
it is necessary to consider the chemical composi- 
tion of the difiPbrent products of secretion, and 
the degrees in which they really differ from each 
other, and form the common mass of blood out of 
which they are eliminated. 

'748. By chemical analysis, it is established that 
all the substances which are formed from the blood 
by the process of secretion are either water, albu- 
men, mucus, jelly, fibrin, oil, resin, or salts ; and, 
consequently, that all the secretions are either 
Aqueous, albuminous, mucous, gelatinous, fibrin- 
ous, resinous, oleaginous, or saline. 

749. 1. Aqueous Secretions. — From the en- 
tite surface of the skin, and also from that of the 
lungs, there is constantly poured a quantity of 
water, derived from the blood, mixed with some 
animal matters, which, however^ are so minute in 
quantity, that they do not Communicate to the 
aqueous fluid any specific character. 

750. 2. Albuminous S£cretions. — All the 
close cavities, as the thorax, the abdomen, the peri- 
cardium, the ventricles of the brain, and even the 
interstices of the cellular tissue, are constantly 
moistened by a fluid which is termed serous, be- 
cause it is derived from the serum of th^ blood. 
This serous fluid consists of albumen vci «. ^>xA 
form, and it differs from the serum o£ l\ie \Aoo^ 



312 THE PHILOSOPHY OF BBALTH. 

cliiefly in contidniDg in equal volumes a smaller 
proportion of albumen. Membranes of all kindi 
consist essentially of coagulated albumen; and 
the albumen, as constituting these tiasuea, di&n 
from albumen as existing in the serum of tbe 
blood only in being unmixed with extraneoQt 
matter, and in being in a solid form. 

751. 3. Mucous Secretions. — As all thedoie 
cavities, or those which are protected from the ex- 
ternal air, are moistened with a serous fluid, m 
all the surfaces which are exposed to the externil 
air, as the mouth, the nostrils, the air-paaeaget, 
and the whole extent of the alimentary canal, ait 
moistened with a mucous fluid. Mucus does nU 
exist already formed in the blood. It is always 
the product of a gland. Some of the mucous 
glands are among the most elaborate of the body ; 
still the main action of the gland seems to be to 
coagulate the albumen of the blood, for tbe basis 
of mucous is coagulated albumen. The fluid that 
lubricates the mucous surfaces in their whole ex- 
tent, the saliva, the gastric juice, the tears, the 
essential part of the fluid formed in the testea and 
in the ovaria, are mucous secretions. Hence the 
most complex and elaborate functions of the body, 
respiration, digestion, reproduction, are intimatdy 
connected with the mucous secretions : neverthe- 
less, as far as regards their chemical nature, the 
mucous differ but slightly from the albuminous 
secretiouB ; and it iaipTo>a«iXAfc \ia»x. ^^v^v^S&s&s^ 



PRODUCTS OF SECRETION. 313 

In the secreting organ is sufficient to convert the 
one into the other. By the irritation of mercury 
on the salivary glands, the saliva, properly of a 
mucous, is SQmetimes converted into a sub&tancc 
of an albuminous nature ; and irritation in some 
of the serous membranes occasionally causes them 
to secrete a mucous fluid. 

752. 4. Gelatinous Secretions. — The proxi- 
mate principle termed jelly abounds plentifully in 
several of the solids of the body, and more espe- 
cially in the skin ; but jelly does not exist already 
formed in the blood. Yet it is not the product of 
a gland, neither is there any known organ by 
which it is formed. Out of the body albumen is 
capable of being converted into jelly by digestion 
in dilute nitric acid : this conversion is probably 
efifected by the addition of a portion of oxygen to 
the albumen. Albumen contains more carbon 
and less oxygen than jelly ; the proportions of 
hydrogen and nitrogen in both being nearly the 
same. According to MM. Gay Lussac and The- 
nard, the elements of albumen and jelly are, 

Carbon. Oxygen. Hydrogen. Nitrogen.' 

Albumen ... 52.883 23.872 7.54 15.765 
Jelly 47.881 27.207 7.914 16.988 

The conversion of albumen into jelly is incessantly 
going on in the system ; and the process accom- 
plishes most extended and important uses. In 
the lungs at the moment of iiisp\i«X\o\\. otk^^^'^ 

VOL, IT, Y 



314 THE PHILOSOPHY OF HEALTH. 

enters into the blood in a state of loose combina- 
tion ; but in the system, at every point where the 
conversion of albumen into jelly takes place, 
oxygen probably enters into a state of chemical 
combination with albumen; and the new proxi' 
mate principle, jelly, is the result. The agent by 
which this conversion is effected appears to be 
the capillary artery: the primary object of the 
action is the production of a material necessary for 
the formation of the tissues oi which jelly consti- 
tutes the basis, as the skin ; but a secondary and 
most important object is the production of animal 
heat ; the carbon that furnishes one material of 
the fire being given off by the albumen at the mo- 
ment of its transition into jelly ; and the oxygen 
that furnishes the other material of the fire being 
afforded to the blood at the moment of inspiration. 
This view affords a beautiful exposition of the 
reason why jelly forms so large a constituent of 
the skin in all animals. The great combustion of 
oxygen and carbon, the main fire that supports 
the temperature of the body, is placed where it 
is most needed, at the external surface. 

753. 5. Fibrinous Secretions. The pure mus- 
cular fibre, or the basis of the fiesh, is identical with 
the fibrin of the blood. It contains a larger pro- 
portion of nitrogen, the peculiar animal principle, 
and is consequently more highly animalized than 
the /)receding substances. It appears to be sim- 
ply discharged from t\i^ c\ic;v:^».^tv^ V^M^by the 



PRODUCTS OF SECRETION. 315 

capillary arteries, and deposited in its appropriate 
situation ; ho material change in its constitution 
being, it would seem, necessary to fit it for ite 
office. 

754. 6. Oleagbnous Secretions. — Fat of all 
kinds, which is found so eztensirely connected 
with the muscles, and with many of the viscera, 
and which is more or less difiiised through the 
whole extent of the Cellular tissue, marrow, iiiilk, 
and nervous and cerebral matter, are essentially 
of the same nature . the basis of them all is oil ; 
and oil exists already formed both in the chyle 
and in the blood. 

755. 7. Resinous Secretions.-— The peculiar 
substance forming the basis of bile, picromel; 
the peculiar substance forming the basis of urine, 
urea ; the peculiar substance connected with the 
muscular fibre, and forming a component part of 
almost all the solids and fiuids of the body, osma- 
zome, consists of a common principle — a resin, 
which exists already formed in the blood, and 
more especially in the serosity of the blood. 

756. 8. Saline Secretions.— The substances 
termed saline, namely, the acids, the alkalis, and 
the neutral and earthy salts, are disposed over every 
part of the system : they enter more or lees into 
all the constituents both of the solids and fluids ; 
they form more especially the phosphate of lime, 
the earthy matter of which bones are comi^Q%e.d\ 
and they all exkt already formed \ii t\i(t\i\ocA. 



316 THE PHILOSOPHY OF HEALTH. 

757, From this account, then, it appears, that 
hy chemical analysis, the blood is ascer- 
tained to contain water, albumen, fibrin, oil, resin, 
and various saline and earthy substances : it fol- 
lows, that, with the exception of the absence of 
jelly, the constituents of the body and the consti- 
tuents of the blood are nearly identical ; and it is 
probable that they will be found to be perfectly 
identical when their analysis shall have become 
complete. 

758. It is also manifest that in by far the greater 
number of cases the various substances of which 
the body is composed are simply separated from 
the nutritive fluid at the parts of the body at 
which they are deposited; and that, existing 
already formed in the blood, they are merely de- 
posited there, and not generated. Still, however, 
since it is certain that gelatin cannot be recog- 
nized in the blood, and since it is doubtful whe- 
ther some other substances found in different tex- 
tures and secretions really exist in the blood, it is 
necessary, in the present state of our knowledge, 
to suppose, that although most of the constituents 
of the living tissues are contained in the blood, 
yet that in some instances a material change is 
effected in their nature at the time and place of 
their escape from the circulation ; and that in 
these cases the secreted substances are not simple 
extractB from, but producta of^ the blood. 

759. It is by the api^ttXttX\i&v)i«ftR;cfe>sL^\v'^cA^>iGi9k 



MECHANICAL ARRANGEMRNT. 317 

separation, evolation, or re-formation, is effected 
Out of a fluid which contains, blended together, 
almost all the heterogeneous substances of which 
the body is built up, particular substances are 
selected from the common mass, and are deposited 
in certain parts, and only in certain parts. Al- 
though by the most careful examination of the 
structure of the apparatus, it is not possible to 
form a precise conception of the mode in which 
this separation is effected, yet we are enabled to 
perceive a number of contrivances which we can 
readily understand must conduce to the accom- 
plishment of the object. 

760. I. Of these, the most obvious is mecha- 
Bical Arrangement. 

761. In its passage to different organs the blood 
is propelled through canals of extreme minuteness : 
in every different case these canals differ from 
each other in size ; pass off from their respective 
trunks at different angles; possess different 
degrees of density ; are variously contorted, and 
are of various lengths. In some they are straight, 
in others convoluted; at one time branching, at 
another pencillated, and at another starry. The 
veins, too, in some cases, are almost straight, in 
others exceedingly tortuous, in others reticulated ; 
and the freedom of their C(mimunication with the 
arteries varies so much, that in some cases fine 
injections pass from the one set of vessels to iW 
other with the greatest facility, 'wVvAe^Ysx qNNx^^^ 



318 fHE PHILOSOPBt OF HEALTH. 

they pass with extreme difficulty. The conse- 
quence of these divers arrangements of the capil- 
lary blood-vessels is, that the current of the blood 
must necessarily flow in them with different 
degrees of velocity ; its particles must be placed 
at different distances from each other, and must 
be presented to each other in diflerent positioni 
and in widely different proportions. In no two 
secreting organs are any two of these conditions 
exactly ahke. In the lower orders of animals, in 
which secretion is seen in its simplest condition, 
the general nutritive fluid, elaborated and con- 
tained in a single internal cavity, appears to ftl^ 
nish a variety of products very different from itself) 
by a process hardly more complex than mere 
transudation through a living membrane. In the 
higher animals the different secreting organs may 
be considered, in part at least, as mechanical con* 
trivances adapted to carry on analogous transoda- 
tions — fine sieves or strainers diveraly censtmcted. 
A fluid containing such heterogeneous matters as 
the blood, held in combination by so slight aa 
affinity, slowly transuding through series of tubeit 
the mechanical arrangement of which is so varied, 
must yield a different substance in every diffierent 
case. Thus by simply filtering the blood a vast 
variety of products may be obtained, merely in con- 
sequence of a varied disposition of the minute 
tubes of which the filters a,t« ootc^^^ocied. 
762. 2. But ill the «ecQfn^^\M»%^>3i^ ifiw^ssjtos^ 



CHEMICAL ACTION. 319 

lechanical arrangement is calculated in a high 
ee to promote and to modify chemical action, 
contact or proximity of the particles of bodies, 
ixtent of surface which those particles pre- 

to each other, the space of time in which 
continue in contact, the degree of force 

which they impinge against each other, the 
ee of temperature to which they are exposed, 
ese, and circumstances such as these, are 
itions which exert the most powerful influence 

chemical decomposition and re-combination, 
the different secreting organs, as has been 
ni, the blood must necessarily pass through 
bIs having every conceivable diversity of 
leter: in those vessels it must consequently 

with corresponding differences of velocity. 
e of these diameters will admit one constituent 
ae blood, as one of the red particles; others 
be large enough to admit two or more of the 
[Mirticles abreast ; others may be so small as 
; incapable of admitting a single red particle, 
ivingonly the more fluid portions of the blood ; 
ime vessels these different constituents will be 
ae degree of proximity, in others in another ; 
>me they will remain long in contact, in others 

for an instant : it is obvi()us that from such 
rent conditions the chemical products may 
afiiiitely varied. 
53. Such is the composition of cVkem\^^\)^^\^%^ 

a great divermty of 8ubatance% Sa Q>a\»I\\isii^^ 



320 THE PHILOSOPHY OF HEALTH. 

merely by changing one condition, the proportions 
in which the elementary particles combine. 

764. Oxygen and nitrogen combined in one 
proportion form atmospheric air ; in another pro- 
portion, nitrous oxide ; in another, nitric oxide ; in 
a fourth, nitrous acid ; and in a fifth, nitric acid. 
Few secretions formed from the blood differ raore 
widely from each other than the products thus 
formed from these two elementary bodies. 

765. Urea consists of two prime equivalents of 
hydrogen, one of carbon, one of oxygen, and one of 
nitrogen. Remove one of the atoms of hydrogen, 
and take away the atom of nitrogen, urea is con- 
verted into sugar; combine with urea an addi- 
tional atom of carbon, it is changed into tithic 
acid. In like manner add a small quantity of 
water to feirina, it is converted into sugar ; to fibrin, 
it is changed into adipocere. From a reservoir 
containing a quantity of substances in the state of 
vinous fermentation, draw off portions of the 
liquor at different stages of the process^ and cause 
these to pass through tubes of various diameters 
and with various d^rees of velocity, there will he 
obtained at one time an unfermented syrup, at 
another, a fermenting fluid, at another, wine, at 
another, vinegar. Out of the body place the blood 
in a state of rest, it will spontaneously separate 
into serum and crassamentum, and the crassamen- 

tum will furthcT sepawilft m\ft ^\»tvci and red par- 
ticlea. Add to the servxm a ^ictXawv YJ^ii^sttL^l^^a^^ 



NERVOUS INFLUENCE. 321 

idll be coagulated into solid albumen ; add to 
I solid albumen another portion of acid, it will 
converted into jelly. Add a certain portion of 
1 to fibrin, it will be <;banged into adipose 
tter ; bring the acid into contact with the red 
tides, they will be converted into a substance 
sely resembling bile. If by the rough che«- 
itry which the art of man can conduct so great 
ariety <^ substances may be obtained out of a 
gle compound, it is not wonderful that a far 
ater variety should be produced by the delicate 
1 subtle chemistry of life. 
766. 3. But a third most important agent in the 
cess of secretion is some influence derived from 

nervous system. 

L It is proved, by direct experiment, that the 
truction of the nervous apparatus, or of any con- 
srabk portion of it, stops the process of secretion. 

experiments performed by Mr. Brodie, it is 
ertained that the secretion of the urine is bus* 
ided by the removal or destruction of the brain, 
ugh the circulation be maintained in its full 
our by surtificial respiration. 
2. The section, and still more the removal, of a 
tion of the sentient nerves of the stomach i(the 

vagum, or eighth pair), according to some ex- 
imentalists, deranges and impedes ; accorcUng to 
ers, totally arrests the process of digestion. 
). Other classes of phenomena illustrate in ^ 
king manner the infiuence oi l3a!t tatsvsvsa 



322 THR PHILOSOPHY OF HEALTH. 

system over the process of secretion. -The sight, 
nay, eren the thought of agreeable food, increases 
the secretions of the mouth. Pleasurable ideas 
excite, painful ideas destroy, the appetite for food ; 
probably, in the one case, by increasing, and, in 
the other, by suspending the aecretion of the gas- 
tric juice : the emotion of grief instantly causes a 
flow of tears ; that of fear, of urine ; the sight or 
thought of her child fills the maternal breasts with 
milk, while the removal of the cbild from the 
mother diminishes and ultimately stops the secre- 
tion. 

161. Even the imagination is capable of exerting 
a powerful influence over the process. A female 
who had a great aversion to calomel was taking 
that medicine in very small doses for some disease 
under which she was labouring. Some one told 
her that she was taking mercury : immediately she 
began to complain of soreness in the mouth; 
salivated profusely, and even put on the expression 
of countenance peculiar to a salivating person. 
On being persuaded that she had been misin- 
formed, the discharge instantly began to diminish, 
and ceased altogether in a single night Two days 
afterwards she was again told, on good authority, 
that calomel was contained in her medicines, upon 
which the salivation immediately began again, and 
was profuse. That this salivation was not pro- 
duced by the calomel, bwt "va^ the effect solely of 
the in^uence of imaginaXVou oxi xXv^^^^^x^ ^%^^ 



NERVOUS INFLUENCE. 323 

was proved by the absence of redness of the gums, 
which always takes place in mercurial salivation, 
and also by the absence of the peculiar fsetor, 
which is characteristic of the action of this metal 
on the system. 

768. The same influence is apparent even in the 
lower animals : exhibit food to a hungry dog, the 
saliva will pour from its mouth. Rob the nest of 
the bird of its eggs as soon as they are laid, the 
bird may be made to deposit eggs almost without 
end, though if the eggs are allowed to remain un- 
disturbed, it will lay only a certain number. The 
bird is led by instinct to continue to deposit eggs 
in the nest until a certain number is accumulated ; 
that is, a mental operation acts upon the ovarium, 
the secreting organ in which the eggs are formed, 
maintaining it in a state of active secretion for an 
indefinite period; whereas without that mental 
operation the secretion would be limited to a 
definite number. 

769. In all these cases it is probable that the vital 
agent by which the eflect is produced on the secret- 
ing organs is the organic nerve. Though the 
sentient part of the nervous system may in many 
cases be the part primarily acted on, yet there is 
reason to believe that the ultimate eflect is inva- 
riably produced on the organic part, the sentient 
nerves in this case acting on the organic, as in 
other cases the organic act on the sentient, in con- 
sequence of that intimate coniveuoTk. ^V\0(v^ i^x 



324 THE PHILOSOPHY OF HEALTH. 

the reason assigned (toL L p. 19), is estabLished 
between both parts of thia system. For, 

170. 1. The true objeet of the sentient part of 
the nervous system is to estaldii^ a relation be- 
tween the body and the external world ; the object 
of the organic part is to preside over the functions 
by which the body iia sustained and nourished, 
that is, over the processes of secretion^ 

171. 2. The nerves whkh are distributed to the 
secreting arteries, and which increase in number 
and size as the arteries become capiQary, are, for 
the moat part, derived from the organic portion of 
the nervous system (fig. clxx. 3). This anatomical 
arrangement clearly pointa to some physiological 
purpose, and indioatca the closeness of the relation 
between the function of the organic nerve and the 
ultimate action of the capillary artery. 

772. 3. It is demonstrated that the sentient part 
of the nervous system, though occasionally influ- 
encing and modifying secretion, is not indispenssble 
to it. In tracing the normal or regular develop- 
ment of the human fbatua, it ia foiind that the 
heart is constructed and is in full action before the 
brain and spinal cord, the central masses of the 
sentient part of the nervoua system, are in exist- 
ence; and that these masses are themselves 
built up by processes to which the action of the 
heart is indispensable ; eonsequently, innumerable 
acta of secretion must have taken place, those, for 



INFLUENCE OF THE NBRYOUS SYSTEM. *d25 

txample, which have been necessary to form the 
tifferent substances which enter into the compo • 
ition of the heart, before the brain and spinal 
»rd exist. In hke manner in the anormal or 
rregular development of the foetus, as in the pro- 
Loction of monsters, there may be not a vestige of 
lead, neck, brain or spinal cord, while there may 
)e a perfect heart, perfect lungs, perfect intestines, 
ind various portions even of the osseous system. 

773. However in the perfect animal secretion 
nay be under the influence of the brain and spinal 
x>rd, it is clear that, since the process can go on 
without them, it must be independent of them. It 
s a false induction from these facts drawn by 
(ome physiologists tliat secretion is independent of 
he nervous system. They do prove that it is 
ndependent of one pait of the nervous system, 
he sentient ; but it does not foUow that it is inde** 
>endent of the other part, the organic, 

774. 4. It is demonstrated that the (Organic part 
)f the nervous system is not only independent of the 
lentient part, but that it is even pre-existent to it. 
Researches into the development of the nervous 
lystem, as shown in the progressive growth of the 
betus of difieroat animab, have proved that the 
existence of the organic nerves is manifest long 
)efore that of the sentient ; that nerves are disco- 
rerable in the tissues, before the brain and the 
tpinal cord are formed; that as these mas&e«k 
"iecame risihle and grow, nervea s^xi^^% itocx^N^ 



326 THE PHILOSOPHY OP HEALTH 

tissues advance towards the central nervous masses, 
and at length unite with them ; but that this union 
does not take place until the development of the 
nervous system is considerably advanced. These 
curious and most instructive facts show that in the 
foetus, though the brain and spinal cord may 
have been destroyed or have been non-existent, 
yet that the organic nerves may have been in full 
action. After a communication has been once 
established between the two parts of the system, in- 
deed, the destruction of the brain or spinal cord may 
stop secretion, not because these organs are indis- 
pensable to secretion ; but because the destruction 
of one part of the system involves the death of the 
other, just as the organic life itself perishes soon 
after the destruction of the animaL 

715. The existence of the organic nerve is pro- 
bably simultaneous with that of the secreting 
artery : from the first to the last moment of life 
the nerve regulates the artery ; the influence of the 
one is indispensable to the operation of the other; 
and, by their conjoint action, the sentient nerve 
itself, as well as every other organ, is constructed. 
776. There is reason to believe that the physical 
agent by which the organic nerve influences se- 
cretion is electricity. The nerve appears to be the 
medium by which electrical fluid is conveyed to 
the secreting organs, and the nerve probably in- 
HucDces secretion b^ influencing chemical combi- 
oatioUf through the uiVeTNcoxSssa. ^\ ^iibML tw«!L 



BLBCTRICITT. 321 

powerful chemical agent. Thit ia rendered pro- 
bable by the observation of variout phenomena, 
and by the result of direct experiment. 

117. 1. It it proved tliat galvanic phenomena 
may be excited by the contact of the nerve and 
muscle in an animal recently dead. A galvanic pile 
may be constructed of alternate layers of nervous 
and muscular substance, or of nervous substance 
and other animal tissues. A secreting organ libe- 
rally supplied with organic nerve is probably then 
in its physical structure nothing but a galvanic ap- 
paratus. It is certain that some animals, as the 
raia torpedo, possess a special electrical apparatus 
composed essentially of nervous matter ; that the 
nerves which compose this apparatus correspond 
strictly with the organic nerves of the human 
body ; that they are distributed principally to the 
organs of digestion and secretion, and that they 
exert a powerful influence over these processes ; 
for, when the animal is frequently excited to 
give shocks, digestion appears to be completely 
arrested ; so that, after the animal's death, food 
swallowed some time previously is found wholly 
unchanged. 

778. 2. It is universally admitted that the nerves 
in all animals possess an extreme sensibility to the 
stimulus of electricity, and more especially to 
that form of it which is temipd galvanism. 

779. 3. Direct experiment proves that the atiiaw- 
Jii# of galvaniem may be made to pTod\xce. Vci >\\^ 



328 THE PHILOSOPHY OF HEALTH. 

living body precisely the same efifect as the Dervous 
influence. It has been stated, that the division 
of the par vagum, in the neck of a living animal, 
suspends the digestion of the food probably by 
stopping indirectly the secretion of the gastric 
juice. If after the division of the nerves, their 
lower ends, that is, that portion of the nerves 
which is still in communication vnth the stomach, 
but no longer in communication with the brain, be 
made to conduct galvanic fluid to the stomach, 
secretion goes on as fast as when the nerves are 
entire and conduct nervous influence. Dr. Wilson 
Philip having divided the par vagum in the neck 
of a living animal, coated a portion of the lower 
end of the nerves with tin foil, placed a silver 
plate over the stomach of the animal, and con- 
nected respectively the tin and silver with the 
opposite extremities of a galvanic apparatus. 
The result was that the animal remained entirely 
free from the distressing symptoms which had 
always before attended the division of the nerves, 
and that the process of digestion, which had been 
invariably suspended by this operation, now went 
on just as in the natural state of the stomach. On 
examining the stomach after death, the food was 
found perfectly digested, and afibrded a striking 
contrast to the state of the food contained in the 
stomach of a similar animal, in whom the nerves 
had been divided, Wt '^jVicii Wd not been sub- 
jected to the galvamc m^MfcxiCfc. 



£LECTRICITT. 329 

180. 4. On applying a low galvanic power to a 
saline solution contained in an organic membrane, 
Dr. WoUaston found that the galvanic fluid decom- 
posed the saline solution, and that the component 
parts of the solution transuded through the mem- 
brane; each constituent being separately attracted 
to the corresponding wire of the interrupted 
circuit. This experiment, says this acute and 
philosophical physiologist, illustrates in a very 
striking manner the agency of galvanism on the 
animal fluids. Thus the quality of the secreted 
fluid may probably enable us to judge of the 
electrical state of the organ which produces it ; as 
for example^ the general redundance of acid in 
urine, though secreted from blood that is known 
to be alkaline, appears to indicate in the kidney a 
state of positive electricity ; and since the propor- 
tion of alkali in bile seems to be greater than is 
contained in the blood of the same animal, it is 
not improbable that the secretory vessels in the 
liver may be comparatively negative. 

781. We may imagine, says Dr. Young, that at 
the division of a minute artery a nervous filament 
pierces it on one side, and affords a pole positively 
electrical, and another opposite filament a negative 
pole. Then the particles of oxygen and nitrogen 
contained in the blood, being most attracted by 
the positive point, tend towards the branch which 
is nearest to it ; while those of the hydrogen aivd 
carbon take the opposite channel ; w\^ XXv^X. X^^^*^ 



a30 THE PHILOSOPHY OF HEALTH. 

these portions may be again subdivided, if it be 
required; and tiie fluid thus analysed may be 
rccombined into new forms by the reunion of a 
certain number of each of the kinds of minute 
ramifications. In some cases the apparatus may 
he somewhat more simple than this ; in otben, 
perhaps, much more complicated ; but we cannot 
expect to trace the processes of Nature through 
every particular step ; we can only inquire into 
the general direction of the path she follows. 

782. Considerations such as these afford us a 
glimpse into the mode in which Nature conducts 
some of her most secret and subtile operations ; or 
rather into the immediate agency by which she 
effects them ; for, properly speaking, of the mode 
in which she works, we do not obtain the slightest 
insight, and even of her immediate agency our 
view, at least in the present state of our know- 
ledge, is indistinct and vague. By the study of the 
apparatus which she builds up, we can trace back 
her operations a step or two ; but in every case, 
at a certain point, the apparatus itself becomes so 
delicate as to elude our senses, and then of course 
we are necessarily at a stand. So, the rough 
materials with which she carries on her great 
work of secretion, by careful analysis we can 
separate into divers parts, and ascertain that 
each part possesses peculiar properties. The 
main channels by wYiVcVi ^Vt tow^-^^ >&«»fc \wicd 
ODBtitaents to the difteteivX ^wV^ ^^ S>ft&^«Hs^ 



ULTIMATE PROCESSES. 331 

ve can trace ; the delicate organn by which she 
iroduces on these rude materials her wonderful 
ransformations we can see ; but beyond the thresh- 
Id of these organs we cannot go. Why from 
ne common mass of fluid the same variety of 
leculiar substances are constantly separated, and 
ach in its respective place: why the kidney 
lever secretes milk, nor the liver urine, nor the 
reast bile: why membrane, and muscle, and 
one, and fat, and brain, are uniformly deposited 
1 the same precise situation : why these deposi- 
ons go on with uniformity, constancy and regu- 
trity ; and by what laws each process is controlled 
ad modified, we do not know. But though with 
'hatever diligence we investigate these operations, 
16 great problem remains, and probably ever 
ill remain unresolved, still it is both a pleasur- 
ble and a profitable labour to follow Nature in 
er path, to the extreme point to which it is pos- 
ble to trace her footstep; for the phenomena 
lemselves are often in the highest degree curious 
id interesting ; while their order and relation 
m seldom be so considered as to be understood, 
ithout the suggestion of practical applications of 
reat and permanent usefulness. 



OF THE FUNCTION OF ABSOl 

Hndeuee of the proMH in the plant, ia the i 
pantui f^aeral and ipecial — BiperimeDl* 
the abtorbiog power of blood-TeoeU uid i 
DeeompoiiDg and analjinDg pTopeitira of i 
Endomoie aod ooemou — Abioibing lUfC 
oaiy, digeili*e, and cntaneoui — Lftcteal an 
vetieli — Abiorbent glandi — MotioD of the 
ipeciol abioibent vnteli — Diicorerj of 
and Ijmphatict — Specific office perfonned b 
parte of the appuatui of abaorptiou— Con 
■jitem on which the actiiity of the procei 
Utei of the function. 

7B3. Absorption ii the function by 
teruid lubetanceB are received into the 
the component particles of the body ar 



BVIDENCB OF ABSORPTION. 333 

784. The plant in a humid atmosphere increases 
in weight The nutritive matter of the plant diffused 
in the soil is taken up by its capillary rootlets, or 
by the spongolae which are attached to them, and 
conveyed into the system. The fall of dew or rain 
upon leaves promotes the growth of the plant. 
Leaves placed on water are capable of preserving 
not only their own vitality, but that of the branches 
and twigs to which they are attached. These 
phenomena show that the process of absorption is 
carried on by the plant. 

785. The evidence of the absorbing power pos- 
sessed by the animal is still more striking. 

786. 1. If an animal be immersed in water the 
amount of which is ascertained by measure, its 
head being kept out of the water, so that none can 
enter the mouth, the body increases in weight and 
the water diminishes in quantity. If certain 
animals, as snails, are plunged in water impreg- 
nated with colouring matter, the fluids m the 
interior of their body soon acquire the colour of 
the water by which they are surrounded. Frogs, 
previously kept for some time in dry air, when 
placed in water, absorb a quantity equal in weight 
to their whole body. 

787. 2. In a humid atmosphere the animal in- 
creases in weight still more than the plant. 

788. 3. If a quantity of water be injected into 
any of the great cavities of the body, as into that of 



334 THE PHILOSOPHY OF HEALTH. 

the peritonenm, the whole of the fluid after t cer- 
tain time diaappears ; it is apontaneofiialy iem(i?cd. 

ISQ. 4. If in the progrest of disease a fluid be 
poored into any cayity of the body, as often bap- 
pens in dropsy, the whole of the fluid is removed, 
sometimes spontaneously and quite suddenly; bat 
more often slowly, under the influence of mediQ- 
nal agents. 

190. 5. Certain substances, whether applied to 
an external or an internal surfiK^ produce specifie 
effects on the system, just as when they are re- 
ceived into the stomach or injected into the blood- 
vessels. Mercury in mere contact with the skin, 
but more rapidly when the application is aided by 
friction, produces the same specific action upon 
the salivary glands, and the same general ackioi 
upon the system as when the preparation of the 
metal is received into the stoBiach. By the Ifte 
external and local appHcatton arsenic, opiniDy 
tobacco, and other narcotics produce their distiaet 
and peculiar effects on the nervous system, snd 
their remote and general efiects on the other syi- 
tems. 

791. 6. Tf an organ or tissue be deprived of non* 
rishment, it gradually diminishes in bulk, and at 
length wholly disappears from the system. By long- 
continued pressure, such as that occasioned by the 
pulsation of a diseased artery, as in aneurism, or 
hy the growth of a fleshy tumor, portions of the 



SVIDKNCE OF ABSORPTION. 335 

firmest and strongest muscle, nay, even of the most 
dense and compact bone, wholly disappear. At one 
time the fluids diminish in quantity, the flesh 
wastes, and the weight of the body ia reduced one 
half or more. Under other circumstances, while 
the state of the general S3rstem remains stationary, 
some particular part diminishes in size, or alto- 
gether disappears. 

792. 1. Healthy and strong men, engaged in 
hard labour and exposed to intense heat, sometimes 
lose, in the space of a single hour, upwards of five 
pounds of their weight. Though daily engaged 
for months together in this occupation at two dif- 
ferent periods of the day, for the space of an hour 
each time, and though consequently these men 
lose five pounds twice every day, yet when weighed 
at intervals of three, six, or nine months, it is 
found that the weight of the body remains sta- 
tionary, not varying, perhaps, more than a pound 
or two. It follows that the bodies of these men 
must absorb, twice every day, a quantity equal in 
weight to that which they lose. 

793. These phenomena depend on a power in- 
herent in the body, that of taking up and carrying 
into the system certain substances in contact with 
its surfaces, and of transporting from one part of 
its system to another its own component particles. 

194. Tlie apparatus by which these operations 
are carried on is general and special. 

795. The general apparatus consiata oi \^q^^- 



336 THE PHILOSOPHY OF HEALTH. 

vessels and membrane. The special appai 
consists of a peculiar system of vessels, namel) 
lacteals and lymphatics, together with the sy 
of glands termed conglobate. 

796. It is proved by direct experiment tha 
walls of Blood-vessels exert a power by which 
stances in contact with their external sm 
penetrate their tissue, reach their internal sur 
and mix with the mass of the circulating fl 
and that this property is possessed by all bl 
vessels, arteries and veins, great and small, < 
and living. 

797. If a portion of a vein or artery taken i 
the body be attached by either extremity to 
glass tubes in order to establish a current of w 
water in its interior, if the vein be then place 
a fluid slightly acidulated, and the fluid w 
flows through the vessel be collected in a fl 
this latter fluid becomes, in the space of a 
minutes, sensibly acid. In this experiment tl 
is no possibility of communication between 
current of warm water and the external aciduli 
fluid, consequently the latter must penetrate 
parietes of the vessel, that is, absorption n 
take place through its membranous walls. 

798. A striking experiment demonstrates the 
sorbing power of the living blood- vessels. I f the tr 
of a vein or artery be exposed in a living anii 
and a poisonous substance in solution be drop 

on the external feuiiact ol €\^«^^^ ^^ioaa 



ABSORBING POWER OF MEMBRANE. 337 

killed in a few minutes, just as when the poison 
18 injected into the blood-vessel itself. Analogous 
experiments on the minute blood-vessels not only 
show that they are endowed with the like absorb- 
ing power, but that their number, tenuity and 
extent, are conditions which greatly favour the 
activity of the process. 

799. Membrane is an organised substance 
abounding with blood-vessels. Whether the ab- 
sorbing power possessed by thi^ tissue be due 
only to these vessels^ or whether it be assisted 
in the operation by other agents not yet fully 
ascertained, it is certain that the absorbing power 
it exerts is highly curious and wonderful. 

800. An auimat membrane placed in contact 
with water becomes saturated with fluid : placed in 
contact with a compound fluid, as with water or 
spirit holding colouring matter in solution, the 
membrane actually decomposes the compound and 
resolves it into its elementary parts, just as ac- 
curately as can be done by the chemist If one 
extremity of a piece of membrane be placed in a 
vessel containing the tincture of iodine, for ex- 
ample, and the other extremity be kept out of the 
fluid, that portion of the membrane which is in 
immediate contact with the tincture acquires a 
perfectly dark colour, because the iodjne completely 
penetrates the substance of the me^ibranQ. This 
dark-coloured portion is bounded by a de^m^^ 
hne, above which the membTane ia -pexv^XY^A.^^ V^ 

VOL. JI. (^ 



338 TUB FHILOSOPHT OF HKAl.TH. 

a different part of the solution, by a pearly 
colourless fluid, the alcohol in which the iodine 
was suspended. Above this again there are traces 
of a still lighter coloured fluid, which is probably 
water. In like manner, if strips of membrane are 
placed in glasses containing port wine, the same 
analytical process is effected by the membrane. 
The colouring matter of the wine is imbibed by 
the lower portion of the membrane ; above this is 
the alcohol, and above this the water. 

801. These and many analogous experiments 
demonstrate that the process of absorption is 
accompanied with the further phenomena of de- 
composition and analysis ; and that membrane, at 
the very moment it imbibes certain compound sub- 
stances, resolves them into their constituent ele- 
ments. 

802. It is further established by numerous ex- 
periments that different compound substances are 
decomposed and absorbed by membrane with dif- 
ferent degrees of facility. If strips of membrane 
are placed in phials containing different kinds of 
fluids, one fluid rises only a line or two ; others 
rise to the height of many inches. There is in- 
dubitable evidence that analogous properties are 
possessed by living membrane ; that the mucous 
membrane of the stomach at the moment it 
imbibes, deconiposes and analyses the alimentary 

and medicinal Bw\»\»."Wie» Vn ^woXA-ct with its sur- 
face • Mid COUBCC^UfcXiVVj OttsXm ^ ^\v\xc\aSikTSKS&ir 



ENDOSMQSE. 339 

brane becomes a most important agent in carrying 
on the digestive process. 

803. But perhaps the most remarkable pro- 
perty possessed by membrane is that of estabb'sh- 
Ing in fluids in contact with its surfaces currents 
through its parietes, which proceed in opposite 
iirections, according to the different natures of the 
fluids, and more especially according to their dif- 
ferent densities. If small bladders composed of 
membrane are filled with a fluid of greater density 
:han water, and securely fastened, and then 
;hrown into water, they acquire weight and become 
jwollen and tense. If the experiment be reversed ; 
f the bladders be filled with water and immersed 
n a denser fluid, the denser fluid flows inwards to 
;he water, and the water passes from the interior 
mtwards. M. Dutrochet, who was led by accidenJ; 
.0 the observation of these phenomena, and who 
;aw at once the possible importance of this agency 
n some organic processes hitherto involved in 
;reat obscurity, commenced an extended series of 
xperiments with a view to ascertain the exact 
acts. He took the cseca of fowls, membranous 
lags already made to his hand, into which he in- 
roduced a quantity of fluid consisting of milk, 
bin syrup, or gum-arabic dissolved in water, 
laving securely tied the membranes, he placed 
be bags thus filled in water, and found that two 
pposite currents are established thiow^lft. XW. ^^^ 
^ the ceeca. The first and stTOiv^e^V. c,\vct^x^X. 



340 THE FrilLOSOPET OF UEALTH. 

that from without inwards, is formed by the flow 
of the external water towards the thicker fluid 
contained in the caeca; the sf^ond and weaker 
current, that from within outwards, is formed by 
the flow of the thicker interior fluid towards the 
external water. The first or the in-going current 
is termed endowiose, from £v3ov, intus, and wrftoQt 
impulsus, and the second or out-going current is 
termed exosmose^ from a similar combination of 
Greek words signifying an impulse outwards. 

804. The velocity and strength of these cur- 
rents are capable of exact admeasurement The 
amount of endosmose is measured by au apparatus 
termed an endosmometer, which consists of a 
small bottle, the bottom of which is taken out and 
the aperture closed by a piece of bladder. Into 
this bottle is poured some dense fluid ; the neck of 
the bottle is closed with a cork, through which a 
glass tube, fixed upon a graduated scale, is passed. 
The bottle is then placed in pure water. The 
water by endosmose penetrates the bottle iu 
various quantities according to the density of the 
fluid contained in its interior through the mem- 
brane closing its bottom. The dense fluid in the 
bottle, increased in quantity by the addition of the 
water, rises in the tube fitted to its neck, and the 
velocity of its ascent is the measure ci the velocity 
of the endosmose. 

805. The stren^Vv o^ ^^udosmose is measured 
bv a similar appaT^lus^'\xi^V\Oft. ^>NiQfc x^v^^^s: 



ENDOSMOSB. 341 

bent upon itself, and the ascending branch contain- 
ing a column of mercury which is raised by the fluid 
in the interior of the endosmoroeter, as the volume 
of this fluid is increased by the endosmose. By 
means of these two instruments it is found that 
the Telocity and strength of endosmose follow the 
same law, and that both are proportionate to the 
excess of the density of the fluid contained in the 
endosmometer above the density of water. By 
numerous experiments it is ascertained that by 
employing syrup of ordinary density (i. 33) an 
endosmose is obtained, the strength of which is 
capable of raising water more than 150 feet. 

8()6. But though diflerence of density is ne- 
cessary to the production of endosmose, yet nu- 
merous and decisive experiments show that the 
different natures of fluids, irrespective of their 
proportionate densities, materially influence the 
activity and energy of the process. Thus, if 
sugar-water and gum- water of the same density be 
placed in the same endosmometer, the former pro- 
duces endosmose with a velocity as seventeen and 
the latter only as eight. The endosmose produced 
by a solution of the sulphate of soda is double that 
produced by a solution of the hydro-chlorate of 
soda of the same density. A solution of albumen 
exerts an endosmose four times greater than a 
solution of gelatin of the same density. 

807. With organic fluids endosmose ^q«&q\n. 
witboat ceasing until the cbemicaV Tv».\.\a^ oS. "Oftft. 



342 THE PHILOSOPHY OF HEALTH. 

fluids becomes altered by putrefaction; butvitL 
alkalies, soluble salts, acids, and chemical agents 
in general, the endosmose excited is capable only 
of short continuance, because sucb agents enter 
into chemical combination with the organic tissue 
of the endosmometer, and thus destroy endosmose. 
808. It is remarkable that the direction of the 
endosmotic currents produced by y^etable mem- 
brane is the exact reverse of that produced by 
animal membrane imder precisely the same cir- 
cumstances. Thus oxalic acid, when separated 
from water by an animal membrane, invariably 
exhibits endosmose from the acid towards the 
water ; when separated by a vegetable membrane, 
from the water towards the acid : and the same is 
the case with the tartaric and citric acids, and with 
the sulphuric, the hydro-sulphuric, and the sul- 
phurous acids. I filled, says Dutrochet, a pod of the 
colutea arborescensy which being opened «t one end 
only, and forming a little bag, was readily attached 
by means of a ligature to a glass tube, with a solution 
of oxalic acid, and having plunged it into rain- 
water, endosmose was manifested by the ascent of 
the contained acid fluid in the tube, that is to say, 
the current flowed from the water towards the 
acid. The lower part of the leek {cdlium porrum) 
is enveloped or sheathed by the tubular petioles of 
the leaves. By slitting these cylindrical tubes 
down one side, ve^eU\i\^ w.cwAitanous webs of 
sumcient breadth amV sUtxv^VVi>ot>:\^Ns^^'^ 



ENDOSMOSE. 343 

reservoir of an endosmometer are readily obtained. 
An endosmometer, fitted with one of these vege- 
table membranes, having been filled with a solu- 
tion of oxalic acid and then plunged into rain- 
water, the included fluid rose gradually in the 
tube of the endosmometer, so that the endosmose 
was from the water towards the acid, the reverse 
of that which takes place when the endosmometer 
is furnished with an animal membrane. Vege- 
table membrane, then, at least with fluids con- 
taining a preponderance of acid, produces a current, 
the direction of which is the exact reverse of that 
produced by animal membrane. 

809. The bodies of organised beings are com- 
posed in great part of various fluids of diflerent 
density, saparated from each other by thin septa, 
precisely the conditions which are necessary to the 
production of endosmose. But such conditions 
never concur in inorganic bodies, whence inor- 
ganic bodies never exhibit endosmotic phenomena. 
Vegetable tissue of every kind consists of vast 
multitudes of aggregated cells intermingled with 
tubes. The parietes of these hollow organs are 
exceedingly delicate and thin ; the organs them> 
selves are at all times filled with fluids, the 
densities of which are infinitely various; conse- 
quently, by endosmose and exosmose, mutual in- 
terchanges of their contents incessantly go on; 
those contents brought into contact by currents 
moving now in one direction aivd uo^ m ^wvsiCcvfc^ 
DOW rapidly and now slowly ■mleTxam^'fe^ ^^^ "^^ 



344 THE PHILOSOPHY OF HEALTH. 

consequence of their admixture changes iu their 
chemical composition take place. It is hy these 
powers that water holding in solution nutneut 
matter diffused through the soil penetrates the 
spougeolte of the capillary rootlets, always filled 
with a denser fluid than the water contained in the 
soil, — ^that the energetic motion by which the sap 
ascends is generated, — that the ascending sap is 
attracted into fruits, always of greater density than 
the crude sap, — that buds are capable of emptying 
the tissue that surrounds them when they begin to 
gro^, and that almost all the phenomena con- 
nected with the motions of fluids in plants, and 
the chemical changes which those fluids undergo 
in consequence of this admixture, is effected. 
And there cannot be a question that analogous 
phenomena take place in the various cells, cavities, 
and minute capillary vessels of the animal hody. 

810. It is then established on induhitahle 
evidence that all animal tissues, without excep- 
tion, possess an inherent property by which they 
are capable of transmitting through their substance 
certain fluids, and even solids, convertible into 
fluids ; and that the great agent by which this 
transmission is effected is membranous tissue, 
whether in the form of blood-vessels or of 
proper membrane. By virtue of this property 
fluids and solids are absorbed, by the animal 
body, with whatever svuritiee at or^an they are 
w contact, wbelhet w\l\i sea wl\.«\s»S. w ^s^ 
internal surface, or with l\ie «^^, ^'t \w«s&cwx 



FULMONART ABSORBING SURFACE. 345 

the tongue, the stomach, the lungs, the liver, or 
the heart. 

811. But membrane is so disposed and modi- 
fied, in difTerent parts of the body, as to admit 
of the introduction of fluids and solids from the 
exterior to the interior of the system with widely 
different degrees of facility. There may be said 
to be in the human body three great absorbing 
surfaces, the pulmonary, the digestive, and the 
cutaneous, each highly important, but each en^ 
dowed with exceedingly difiPerent degrees of absorb- 
ing power. 

812. The pulmonary surface, for reasons which 
will be readily understood from what has been 
already stated relative to the structure of the air 
vesicles of the lungs, is by far the most active 
absorbing surface of the body. The mode in 
which the air vesicles are formed and disposed 
has been shown to be such as to give to the lungs 
an almost incredible extent of membranous sur- 
face, while the membrane of which the cells are 
composed is exceedingly fine and delicate. More- 
over, there is the freest possible communication 
between all the branches of the pulmonary vas- 
cular system, whether arteries or veins ; the 
distance between the lungs and the heart is short ; 
the course of the blood from the pulmonary ca- 
pillaries to the central engine that works the cir- 
culation is rapid, and the lungs we ^X iVv^ %»xsv^ 
time close to the central masses o? \\vfe w^Tsci\vfe 

system, with which indeed theN ore ^-e^^^^ ^'^ 



346 THE PHILOSOPHY OF HEALTH. 

direct communication by nerves of great mag- 
nitude and of most extensive distribution. These 
circumstances account for the wonderful rapidity 
with which substances are absorbed, when placed 
in contact with the pulmonary surface, and for 
the instantaneousness and intensity of the im- 
pression produced upon the system, when the 
substance thus introduced is of a deleterious 
nature. 

813. They also afford an explanation of a 
phenomenon not to have been credited without 
experience of the fact, that innoxious substances, 
introduced into the air cells of the lungs in mode- 
rate quantities produce no more inconvenience 
there than when taken into the stomach. A 
single drop of pure water, when in contact near the 
glottis with the same membrane that forms the 
air vesicles of the lungs, excites the most violent 
and spasmodic cough, and the smallest particle of 
a solid substance permanently remaining there 
occasions so much irritation that inevitable suffo- 
cation and death result. Yet so different is the 
sensibility of this membrane in different parts of 
its course, that while at the upper portion of the 
trachea it will not bear a drop of water without 
exciting violent disturbance, in the air vesicles it 
tolerates with only slight inconvenience a consi- 
derable quantity even of solid matter. An acci- 
dent of a nature «\xfl&ekiillY alarming, which 

occurred to Dessault, affoi^ «i %\x^Ti%'^>Mto%65SB. 

of this curious fact. tViVa tfe\cfexi^V.^^ «vK^B5«ii\sb^ 



PULMONARY ABSORBING SURFACE. 347 

eit a case in which the trachea and esophagus 
cut through. It was necessary to introduce 
»e through the divided esophagus into the 
ch, and to sustain the patient hy food intro- 
in this manner. On one occasion the tuhe, 
d of heing passed through the esophagus to 
tomachy was introduced into the trachea 
to the division of the bronchi. Several 
ions of soup were actually thrown into the 
before the mistake was discovered ; yet no 
sind even no dangerous consequences ensued« 
that period, in various experiments on ani' 
several substances of an innoxious nature 
been thrown into the lungs without pro- 
5 any inconvenience beyond slight disturb- 
)f the respiration and cough. The reason 
it after a short time the substances are ab- 
l by the membrane composing the air vesi- 
and are thus removed from the lungs and 
into the general circulating mass. At every 
of the pulmonary tissue there is a vascular 
ready to receive any substance imbibed by 
1 to carry it at once into the general current 
J circulation. 

[. Hence the instantaneousness and the 
ful energy with which poisons and other 
IS substances act upon the system when 
ht into contact with the pulmonary tissue. A 
3n of nux vomica injected iivto X3\^ X.t^Ocv^'a. 
jes death in a few seconds. K «a\^feV»ss^"^~ 



348 THE PHILOSOPHY OF HEALTH. 

ration of the concentrated prussic acid kills with the 
rapidity of a stroke of lightning. This acid in its 
concentrated form is so potent a poison, that it 
requires the most extreme care in the use of it, and 
more than one physiologist has been poisoned by it 
through the want of proper precaution while em- 
])loying it for the purpose oi experiment. If the 
nose of an animal be slowly passed over a bottle 
containing this poison, and the animal happen to 
inspire during the moment of the passage, it 
drops down dead instantaneously, just as when 
the poison is applied in the form of liquid to the 
tongue or the stomach. The vapour of chlorine 
possesses the property of arresting the poisonous 
effects of prussic acid, unless the latter be in- 
troduced into the system in a dose sufficiently 
strong to kill instantly; and, hence, when an 
animal is all but dead from the effects of prussic 
acid, it is sometimes suddenly restored to life by 
holding its mouth over the vapour of chlorine. 

815. Examples of the transmission of gaseous 
lK)dies through the pulmonary membrane hare 
lieen already fully described in the account of the 
passage of atmospheric air to the lungs, and of 
carbonic acid gas from the lungs, in natural re- 
spiration. But foreign substances may be mixed 
with or suspended in the atmospheric air, which 
it is the proper offiee of the pulmonary membrane 
to traxiBmit to the lun^, sud may be immediately 
carried with it into t!he c\w«A^>lvb%'b»a%. 'X^sas.^ 



ULMONART ABSORBING SURFACE. 349 

•sing through a recently-painted chamber 
le urine the odour of turpentine. The 
turpentine diffused through the chamber 
tted to the lungs with the inspired air, 
ig into the circulation through the pul-> 
nembrane, exhibits its effects in the 
tre rapidly than if it had been taken into 
:h, and thence absorbed, 
egetable and animal matter in a state of 
ition generates a poison, which when dif- 
the atmosphere, and transmitted to the 
le inspired air, produces various diseases 
3st destructive kind. The exhalations 
m marshes, bogs, and other uncultivated 
ained places, constitute a poison of a 

nature, which produces principally 
nt fever or ague. Exhalations accumu- 
close, ill-ventilated, and crowded apart- 
;he confined situations of densely-popu- 
^8, where no attention is paid to the 
'putref3ring and excrementitious matters, 

a poison chiefly of an animal nature, 
iduces continued fever of the typhoid 
It is proved by fatal experience that 
situations in which these putref3ring 
ided by heat and other peculiarities of 
:enerate a poison so intense and deadly 
;le inspiration of the air in which they 
d is capable of producing instantaneous 
\d that there are othet «v\Ai^\!\o\i% Ssx 



350 THE PHILOSOFHT OF fiLEAI.TH. 

which II less highly concentrated poison accu 
mulates, the inspiration of which for a few 
minutes produces a fever capable of destroyiof 
life in from two to twelve hours. In dirty aiul 
neglected ships, in which especially the bilge* 
water is allowed to remain uncleansed ; in damp, 
crowded, and filthy gaols ; in the crowded wards 
of .ill- ventilated hospitals filled with persons 
labouring under malignant surgical diseases, or 
some forms of typhus fever, an atmosphere n 
generated which caimot be breathed long, even by 
the most healthy and robust, without producing 
highly dangerous fever. 

817. The true nature of these poisonous exhala- 
tions is demonstrated by direct experiment If & 
quantity of the air in which they are difiused be 
collected, the vapour may be cond^sed by cold 
and other agents, and a residuum of vegetable 
or animal matter obtained, which is found to be 
highly putrescent, constituting a deadly poison. 
A minute quantity of this concentrated poison 
applied to an animal previously in sound health, 
destroys life with the most intense symptoms of 
malignant fever. If, for example, ten or twelve 
drops of a fluid containing this highly putrid 
matter be injected into the jugular vein of a dog^ 
the animal is seized with acute fever ; the action 
of the heart is inordinately excited, the respiration 
is accelerated, the beaX increased, the jmntra- 
tion of strength extrcnie> ^^ TDwacvjNKt ^s*^ 



TIVB ABSORBING SURFACE. 351 

hat the animal lies on the ground 
to stir or to make the slightest 
er a short time, it is actually seized 
▼omit, identical, in the nature of 
tuated with that which is thrown 
idual labouring under yellow fever, 
by varying the intensity and the 
)on thus obtained, to produce fever 
type, endowed with almost any 
;al power. These facts^ of which 
ations of the highest utility are 
made, may suffice to show the im- 
I pulmonary membrane as an ab- 
By the extent and energy of its 
r, it is one of the great portals of 
or of disease and death, 
estive surface is of much less extent 
onary) it is less vascular; it is 
I from the dentre of the circulating 
; is covered with a thick mucus^ 

adherent to it | hence its absorb- 
nthet so great as that of the pul- 
me, nor do noxious substances in 
afifect the system so rapidly. An 
erval commonly elapses between 
I of a poison into the stomach and 
the system. An emetic is com- 
r of an hour before it begins to 
c itself is generally half an hour> 

three quarteT« oi wii \kO\w^ ^i^- 



352 THE PUILOSOPHY OF UEALTfl, 

fore it produces any decided effect on the sys- 
tem : but at length a noxious substance, applied to 
any part of the digestive membrane is introduced 
into the circulating mass and produces its appio- 
priate effects on the system, just as when it is in 
contact with the pulmonary tissue. 

819. Over the external surface of the body or 
the skin, there is spread a thin layer of solid, 
inorganic, insensible matter, like a varnish of 
Indian rubber. The obvious efi^ct of such t 
barrier placed between the external surface of 
the body and external objects, is to mode 
rate the entrance of substances from without, 
and the transmission of substances from within, 
that is, to regulate both the absorbing and the 
exhaling power of the skin. Henoe the coropa- 
rative slowness with which substances enter the 
system by the cutaneous surface; the impunity 
with which the most deadly poise ns may remain 
for a time in contact with the skin, with which 
prussic acid, arsenic, corrosive sublimate, may be 
touched and even handled. The internal surface 
of the body is protected from the action of acrid 
substances introduced into the alimentary canal 
by a layer of mucua through which an irritant 
must penetrate before it can pain the sentient 
nerve or irritate the capillary vessel; but were 
not a still denser shield thrown over the external 
surface, pain, dlsea^e^ «lXl^ dsAlb. must inevitably 
result from the mete toxitwiX. q>1 \\3R!L\i\fidt\i^ 



CUTANEOUS ABSORBING SURFACE. 353 

which now are not only perfectly innoxious, 
)ab1e of ministering in a high degree to 
comfort and improvement. 

Immediately beneath the cuticle is a sur- 

vascular as it is sensitive, from which 
ion takes place with extreme rapidity, 
in very minute quantity introduced beneath 
cle kills in a few minutes. Arsenic applied 
aces from which the cuticle has been 
i by ulceration produces its poisonous 
upon the system just as surely as when 
ced into the stomach. The poisonous 
of small-pox and of cow-pox pladed in 

inappreciable quantity by the lancet 
L the cuticle produces in a given tiine its 
action upon the system. When, iii cer- 
Ltes of disease, with the view of bringing 
;em rapidly under the influence of a medi- 
;ent, the cuticle is removed by a blister, 
e exposed surface is moistened with a 
I of the substance whose action is re- 

the constitutional efiects are developed 
ch intensity, that if extreme care be not 
1 the employment of any deleterious sub- 
.n this mode thfe result is fatal in a few 
I. 

The phenomena which have been stated 
ifice to illustrate the absorbing power of 
cral tissues and surfaces of the bod^ \ \s^ 
ded to this, there is carried oxi va ^wc\I\c>SSKt 



354 THE PHILOSOPHY OP HEALTH. 

parts of the system a specific absorption for which 
a special apparatus is provided. 

822. The special apparatus of absorption, com* 
monly termed' the proper absorbent system, con- 
sists of the lacteal and lymphatic vessels and of 
the conglobate glands. The lacteals arise only 
from the intestines ; the lymphatics, it is pre- 
sumed, from every organ, tissue, and surface oi 
the body. Both sets of vessels possess a structure 
strikingly analogous to that of veins, the common 
agents of absorption. The coats of the lacteals 
and lymphatics are somewhat thinner and a good 
deal more transparent than those of veins; yet 
thin and delicate as th^y are, they possess consi* 
derable strength, for they are capable of bearing, 
without rupture, injections which distend them far 
beyond their natural magnitudie. 

I'V CXCII. 




An enlarged view of an absorbent veBsel. — 1. Kxteinal 
surface, with the jointed appearance ])roduced by the 
valve*. — 2. The same nw*A VbaA. ^^^wau showing th« 
arrangement of tbe viVN^i*. 



FROP£K ABSORBENT VE&SELS. 355 

When fully diBtended, these vessels pre- 
ointed appearance somewhat resembling a 
)f beads (fig. cxcii. 1). Each joint indi- 
e situation of a pair of valves (fig. czcii. 
lese valves are of a semilunar form, and 
posed of a fold of the inner coat of the 
fig. CXCII. 2). The convex side of the valve, 
acteals, is towards the intestines; in the 
tics towards the surfaces ; in both towards 
ins of the vessels. The valves allow the 
3 of the vessels to pass freely towards the 
runk of the system, but prevent any 
de motion towards the origins of the 

By continued pressure the resistance of 
es may be overcome, so that mercury may 
z to pass from the trunk into the branches, 
his is done in an absorbent truvk proceed- 
a certain organs, such as the liver, it is seen 

absorbents are distributed, arborescently, 
vast numbers that the surface of the viscus 
as if it were covered with a reticular sheet 
Lsilver. 

The internal coat of the small intestines 
Q shown to present a fleecy surface, crowded 
nute elevations called villi, which give this 
an appearance closely resembling the pile 
et. Each villus consists of an artery, a 
nerve, and a lacteal, united and sustairved 
Rte cellular tissue. Aftei a Tcvt«\. N^'e. \^^.- 



356 THB 

teals become bo turgid with chyle that they com- 
ptetely conceal the blood-veaaels and nerves, h 
that the Burface of the intestiDe preBcntB to the 
eye only a white masB, or a Burface thickly crowded 
with white spots (fig. cxciii.) 





FLg. cxcin. 









Appiiri 



626. When a portion of the intestine in thi> 

condition of the lacteal vessels is examined tmdei 

(he micruBcope, there is said to be yiuble on the 

Kg. CXCIV. 



LACTEALS. 351 

villus an oval vntcle, termed an ampullula (fig. 
cxctv.)- This vesicle is described as having en 
apertOK at ita apex, which it is conceived consti- 
tutes the open mouth of the lacteal, and through 
which the chyle !■ supposed to be teken up. 

821, Mr. Cruikshank, who particulBjly devoted 
himself to the study of this part of the ebsorbent 
system, states that he had an opportunity of eia- 
mining these vessels in a person who died sud- 
denly some hours after having taken a hearty 
meal, and who had been previously in sound health. 
" In some hundred villi," he says, " I saw the 
trunk of the lacteal beginning by radiated braaches 
(fig, cxcT.). The orifices of these radii were very 
distinct on the surface of the villus aa well as the 




View of villi, vilh ihelactKaliioiiuQKfioni thairsuifacu by 
upsn mouthi and laimiag ludUled bfSDchn. The surface 
of oBS of Omn Tilli ii repmented u entirtly while, fniiii 
tks Ucteali beio)^ n turgid with chyle u eom^UVftV) \E, 
obanuw tte'*'' on£ce« and their ndialinx ^wvcVfc*- 



358 THE PHILOSOPHY OP HEALTH. 

radii themselves (fig. cxcv.). There was but one 
trunk in each villus. The orifices on the villi of 
the jejunum, as Dr. Hunter said (when I asked 
him as he viewed them in the microscope hoir 
many he thought there might be) were about 
fifteen or twenty in each villus, and in some I MV 
them still more numerous" (fig. cxcv.). 

828. The course of the lacteals, from their 
origin in the villi to their termination in the 
thoracic duct, has been traced (687). It is 
conjectured that the lymphatics take their origin 
I'rom every point of the body, but it is admitted 
that they have not been actually seen even in 
every organ; still they have been found in so 
many that it is inferred that they really exist in all, 
and that in those in which they have not been 
hitherto detected they have eluded observation on 
account of their extreme delicacy and transparency 
and our imperfect means of examining them. 

829. Though, like veins, lymphatics anastomose 
freely with each other, yet they do not proceed 
from smaller to larger branches and from larger 
branches to trunks, but continue of nearly the 
same magnitude from their origin to their ter- 
mination. They are disposed in two sets, one of 
which always keeps near the. external surface of 
the body, and the other is deeply seated, accom- 
panying more especially the great trunks of the 

6/ood-ves8el8. 
830, In the human \>r»«VN e^etNi n^^s^ ^"«^«s^ 




flunks of »b«ir 
v\vn, 3. Highly msgnifiEd views ol Ibo 
« uf «bicli I he gland in ■u|>|«»kI tu coniiit 
I. Absuibent tgwcIs callrtl va»a iaferentia, 
the glaail. 3. AliBdrbent veiBtU emer)^U)( 
>d, culled rati effereDlin, mil tanning (4) a 
.. tXCVllI— 1. Tniuli of ab>orl*nl v«>*l 
od. 2. Oland apparently comiHisecl enlireljr 
veaseli. 3. Venelietou^iig from 1hei;laad 

y Tecogniaed either at a lacteal or a 
passes, in aome part of its course, 
conglobate or lymphatic gland (fig*. 
CVI1I.). These glandi, small, uat- 
lar or oval bodiea, reaemhUn^ Vkwca 
I enclosed in a dtBtlnct me,T(^nxi.w» 



360 THK PHIJX>SOPHY OP HEALTH. 

envelope. Their intimate structure has heen al- 
ready fully described (chap. xi.). They arc of 
various sizes, ranging from three to ten lines in 
diameter: they are placed in determinate parts 
of the body, and are grouped together in variom 
ways, being sometimes single, but more often col- 
lected in masses of considerable magnitude. Nu- 
merous absorbent vessels, termed vasa inferentiat 
enter the gland on the side remote from the heart 
(figs, cxcvii. 1 and ci^cvni. 1) ; a smaller number, 
called vasa efferentia, leave it on the side proxi- 
mate to the heart (fig. cxcvii. 3). If mercury be 
injected into the vasa inferentia (fig. cxcvi.), it 
is seen to pass into a series of cells of the cor- 
responding gland (fig. cxcvi. 3), and then to 
escape by the vasa efferentia ; but if the gland be 
more minutely injected, as by wax, all appearance 
of cells vanishes; the whole substance of the 
gland seems then to consist of convoluted ab- 
sorbents (fig. cxcviii. 2), irregularly dilated, and 
communicating with each other so intimately that 
every branch that leaves the gland appears to have 
been put in communication with every branch 
that entered it (fig. cxcviii. 1, 2, 3). 

831 . The motion of the fiuid within the absorbent 
vessels, though not rapid, is energetic If a 
ligature be placed around the thoracic duct in a 
living animal, the tube will swell and ultimately 
burst, from the ruplux^ of its cqat, in conse- 
quence of the force oi \)ft& ^veX.^\^^<(2bW ^iosfi. 



DISCOYBRT OF THB LACTKAL8. 361 

1 place below the ligature. If the thoracic 
in the neck of a dog be opened some houra 
the animal has taken a full meal, the chyle 

from the ressel in a full stream, and in 
»pace of five minutes half an ounce of the 
may be obtained. Yet this system of vessels 
fond the influence of the circulating blood : 
s no heart to propd it ; no current behind 
fs in rapid motion to urge it onwards ; it is 
fore inferred that it is moved by a vital con- 
le power inherent in the vessels, analogous 
' not identical with, muscular contractility, 
flow of blood through the arterial tubes is 
irsally believed to be effected, in part at least 
ch a contractile power, for this, among othei 
as, that if in a living animal the trunk of an 
r be laid bare, the mere exposure of it to the 
spheric air causes it to contract to such a 
e that its size becomes obviously and strik- 

diminished (298. !)• The same phenome- 
las been observed in the main trunk of the 
bent system. Tiedemann and Gmelin state 
in the course of their experiments they saw 
doracic duct contract from exposure to the 

2. The delicacy and transparency of the 
Is and lymphatics long concealed them from 
dew of the anatomist. The lacteals had 
d been occasionally seen in ancient. \ix!Ck&%»^ 
\eir o£Sce was altogether xrnktkorwTv, Va. N)aR 



362 THE PHILOSOPHY OF HEALTH. 

year 1563 Eustachius discovered the thoracic 
duct, but did not perceive its use. About half a 
century afterwards, in the year 1622, the lacteab 
were again on6 day by chance seen by Asellius, In 
Italy, while investigating the function of certnn 
nerves. Mistaking the lacteals for nervesj he it 
first paid no attention to them ; but soon observing 
that they did not pursue the same course as the 
nerves, and ** astonished at the novelty of the 
thing," he hesitated for some time in silence. 
Resolving in his mind the doubts and contro- 
versies of anatomists, of which it chanced timtbe 
had been reading the very day before^ in order to 
examine the matter further, ^* I took," he says, 
^ a sharp scalpel to cut one of these chords, but 
scarcely had I struck it when I found a liquor 
ifr\i\it as milk, or rather like cream, to leap out 
At this sight I could not contain myself for joy ; 
but turning to the by-standers, Alexander Tadinus 
and the senator S^ptaliiis, I cried out Edpiyral 
with Atchimedes ; and at the same time invited 
them to look at so rare and pleasing a spectacle, 
with the tiovelty of which they were nnich moved. 
But I wii's not lorrg pethiitted to enjoy it, for the 
dog now expired, and, wonderful to tell, at the 
same instant the whole of that astonishing series 
and congeries of vessels,' losing its brilliant white- 
ness, that fluid being gone,' in our very hands, 
and a/nlost before out e"^t*> %o c^«a\%hed and db- 
appeared that hardly «^ xe«!^^ hj^ V.^ '^ ^ 



DISCOVERT OF THE LYMPHATICS. 363 

most diligent search." The next day he procured 
another dog, hut could not discover the smallest 
white vessel. *' And now," he continues, " I 
hegan to he downcast in my mind, thinking to 
myself that what had heen ohserved in the first 
dog must he ranked among those rare things 
which, according to Galen, are sometimes seen in 
anatomy." But at length recollecting that the 
dog had heen opened ''athirst and unfed," he 
opened a third ** after feeding him to satiety ; and 
now everything was more manifest and hrilliant 
than in the first case." The zeal with which he 
followed out the clue he had obtained is indi- 
cated by the number of dogs, cats, lambs, hogs, 
and cows which he dissected, and by the state- 
ment that he even bought a horse and opened 
it alive; but, he adds, *'a living man, how 
ever, which Erasistratus and Herophilus of old 
did not fear to anatomize, I confess I did not 
open." 

833. Nearly thirty years elapsed before the 
lacteals, which were long thought to terminate in 
the liver, were traced to the thoracic duct ; and it 
was not until the year 1651, about eighty years 
after the discovery of Asellius, that the lymphatics 
were discovered, and that the whole of this 
portion of the absorbent system was brought 
to light. 

834. Taking together the whok oi \3tw<fe ^^t^^- 



364 THK PHILOSOPHY OF HEALTH. 

ratus of absorption, the specific office performed 
by its several parts seems to be as follows : — 

835. 1. It is established that the lacteak 
absorb chyle, and that they refuse to take up 
almost every other substance which can be pre- 
sented to them. Experimentalists are uniform io 
stating that however various the substances intro- 
duced into the stomach, it is exceedingly ran to 
find in the lacteals anything but chyle. Tbeie 
vessels appear to be endowed with a pectdiar sen- 
sibility, derived from the nervous system, by which 
they are rendered capable of exerting an elective 
power, readily absorbing some substances and 
absolutely rejecting others. 

836. 2. The lymphatics absorb a far greater 
variety of substances than the lacteals, but not 
all substances indiscriminately ; chiefly organized 
matter in a certain stage of purification ; particles 
passing through successive processes of refine- 
ment (707). 

837. 3. The blood-vessels, and more especialij 
the capillary veins, appear to absorb indiscri- 
minately all substances, however heterogeneous \ 
their nature, which are dissolved or dissolvable in j 
the fluids presented to thera. 

838. 4. The absorbent glands appear by 
various modes, either by removing superfluous 
and noxious matters, or by the addition of secreted 

substances "posseft«i»^ ^a^Yco^^Xvj^ '^roi^erties, ^o 



CONDITION NECESSARY TO ABSORPTION. 365 

appitudmate the fluid which flows through them 
more and more closely to the nature of the blood. 
Fatal effects result from the artificial infusion ot 
minute portions even of mild substances into the 
blood. Hence the extended and winding course 
which Nature causes the new matter formed from 
the food to undergo, even after its elaboration in 
the digestive apparatus, in order that, before it is 
albwed to mingle with the blood, its perfect puri- 
fication and assimilation may be secured. 

d39. The activity or inactivity of the process 
of absorption is mainly dependant on the emp- 
tiness or the plethora of the system. There is a 
point of saturation beyond which the absorbent 
▼essels, though in immediate and continued con- 
tact with absorbable matters, will take up no more 
The nearer the system to this point the less active 
the process; the further the system from this 
point the more active the process. Thus, when 
an animal whose vessels are full to saturation is 
immersed in water, or exposed to humid air, its 
body does not increase in weight, and there is no 
sensible diminution of the water ; but the longer 
an animal is kept without fluid, and the more it is 
exposed to the action of a dry air, the further its 
system is removed from the point of saturation, 
and exactly in that proportion, when it is brought 
in contact with water, is the diminution of the 
quantity of the fluid and the mcieft:^^ m \}cv& 
wdgbt of the body. This law expV^ixv^ xsvmv^ 



366 THE PHILOSOPHY OF HEALTH. 

circumstances of the animal economy, — why it is 
impossible to dilute the blood or any other animil 
fluid beyond a certain point, by any quantity of 
liquid which may be in contact with the external 
surface, or which may be taken into the stomach; 
why it is impossible to introduce nutrient matter 
into the system, beyond a certain point, by any 
quantity of food, which the digestive organs mij 
convert into chyle ; why, consequently, the bulk 
and weight of the body are incapable of indefinite 
increase ; why that bulk and weight are so rapidly 
regained after long abstinence ; and why the appe- 
tite is so keen, and the ordinary fulness and 
plumpness of the body are so soon restored, after 
recovery from fever and other acute diseases, when 
the digestive organs have been uninjured. 

840. Different portions of the absorbent appa- 
ratus accomplish specific uses. With the absorbent 
action of the capillary blood-vessels and of mem- 
branous surfaces every organic function, but more 
especially the processes of digestion and respira- 
tion, are intimately connected. 

841. The specific absorption carried on by the 
lacteals has for its object the introduction of new 
materials into the system, for the reparation of the 
losses which it is constantly sustaining by the 
unceasing actions of life. 

842. The sped^c absorption carried on by the 
ijmphatics haa a twoioV^ <^^^cX. Y\x^\^\hft intro- 
duction of paTtidea, yiVaeV Vv?^ ^^\^ Vsraa^ 

an integrant part ot lYie ^^^\.e«i,^^^Tv^^xm^^^^«^ 



USES OF THE FUNCTION. 367 

the blood, in order to subject them anew to the 
process of respiration, thereby affording them a 
second purification, and giving them new and 
higher properties ; and, secondly, the regulation 
of the growth of the body, and the communication 
uid preservation of its proper form. 

843. It is the office of the lacteals to reple- 
nish the blood by constantly pouring into it new 
matter, duly prepared for its conversion into the 
nutritive fluid. It is the office of the lymphatics 
to preside over the distribution of the blood as 
it is deposited in the system in the act of 
nutrition. The lymphatics are the architects 
which mould and fashion the body. They not 
only regulate the extension of the frame, but they 
retain each individual part in its exaQt position, 
and give to it its exact size and shape. Growth 
is not mere accretion, not simple distension ; it 
consists of a specific addition to every individual 
part, while all the parts retain the same exact 
relation to each other and to the whole. When a 
bone grows it does not increase in bulk by the 
mere accumulation of bony matter; but every 
osseous particle is so increased in length and 
breadth that the relative size of every part, and 
the general configuration of the whole organ, 
remain precisely the same. When a muscle 
grows, while the entire organ enlarges in bulk by 
the augmentation of every individwaV i^wX, ^"mScv 
part retains exactly its former "pTopoi\i\oxi% "kvA 



368 THE PHiiiOsopirr of health. 

its reladve connexions. When the brain grows a 
certain quantity of cerebral matter is added to 
every individual part, but at the same time the 
proportionate size and original form of each part, 
and the primitive configuration of the entire 
organ, are retained exactly the same. How is this 
effected ? By a totally new disposition of eveiy 
integrant particle of every part of every organ. 
New matter ia not deposited before the removal of 
the old : the lymphatic, in the very act (^removing 
the old, foshions a mould for the reception of the 
new, and then the capillary artery brings tiie new 
particle and deposits it with unerring exactness in 
the bed prepared for it. Thus, by removkig the 
old materials of the body in a determinate manner, 
and thereby fashioning a mould for the receptioa 
of the new, the lymphatics may be said, in the 
strictest senses to be the architects of the frame. 



369 



CHAPTER XIII. 



OF THE FUNCTION OF EXCRETION. 

la what excretion differs from secretion — Excretion in the 
plant — Quantity excrajted by the plant compared with 
that excreted by the animal — Organs of excretion in the 
human body — Oiganization of the skin — Excretory pro- 
cesses performed by it — Excretory processes of the lungs 
— Analogous processes of the liver — Use of the deposi- 
tion of fat — Function of the kidneys — Function of the 
lai^ intestine^— Compensating and vicarious actions 
•—Reasons why excretory pxoces^es are necessary — Ad- 
justments. 

844. The various matters contained in organ- 
ized bodies^ and even those which enter as consti- 
tuent elements into their composition, are con*- 
Btantly removed from the system, and thrown off 
into the external world. The matters thus re- 
jected are called excretions ; and the various 
processes by which their elimination is eflfecicd 
constitute a common function termed excretion. 

845. Excretion is the necessary consequence of 
the deterioration which all organized matter un- 
dergoes by the actions of ]ife. The matters 
removed by the process consist of the v«j&\& ^«x- 
ticlee of the body, oi the particles exipexv^e^ vcv \N\^ 

B. ^ 



370 THE PHILOSOPHY OF HEALTH. 

vital actions, as the aliment contains the particles 
which replenish the waste, and compensate the 
expenditure. 

846. The excretions are separated from the 
common organized mass hy processes perfectly 
analogous to those comprehended in the great 
function of secretion. Excretion is only a parti- 
cular fdrm of secretion : the difference between 
the two functions is, that, in the former, the 
matter eliminatcid being either noxious or useless, 
is separated for the sole purpose of being rejected; 
while, in the latter, the matter eliminated is 
destined to perform some useful purpose in the 
economy. Accotdingly, the products of excretion 
are termed excrementitious ; and those of secre- 
tion, recrementitious. 

841. The chief matters excreted by the plant 
are oxygen, carbonic acid, air, water^ in some 
few cases, under peculiar circumstances, ammonia 
and chlorine ; and in still rarer cases, during th^ 
night, poisonous substances, as carburetted hy- 
drogen, together with acrid, and even narcotic 
principles. 

848. The forms under which these excre^ons 
are eliminated are exceedingly various. Some- 
times the matter excreted is in the shape of gas, at 
other times it is in that of vapour, and at others 
in that of liquid. The chief gaseous exhala- 
tions are oxygen wi^ c,"w^xC\<c^c\d\ the vapor- 
ous exhalations cotvwiftX ^rvvicv^aS^-^ ^^^^^jw^Ns^.^^ 



EXCRETION IN THE PLANT. 37 1 

state of vapour; aid the liquid exhalations are 
either pure water, or water holding in combination 
sugar, mucilage, ai^d other proximate vegetable 
principles. Even the peculiar products formed by 
the vital actions of the plapt, as the volatile 
oils, the fixed oils, the baUams, the resins, and 
perhaps, with the exception of gum, sugar, starch, 
and lignine, all the substances formed out of the 
prpper juices of the plant, are true excretions; 
for these substances are fixed iinpiovably in the 
cells^ sacs, or tubes which secrete and contain 
them : they are not conBumed in the growth of 
^he plant ; they do j}ot appear to be applied to 
any useful purpose in the economy ; they are in- 
jurious, and even poisonous to the very plant in 
wliich they are formed when tajken up by the 
roots and combined with the sap : as long as they 
remain in the plant they are isolated in the indi- 
fidaal parts in whicl;i they are first deposited, 
.until ^,ith the advancing age of the plant they 
lose their aqueous ftart^icles, and are finally dried 
4ip^ they, therefore^ possess all the essential cha- 
racters of excrementit^ous substances. 

849. The organs by which these matters are 
excreted are the leaves, the flowers, the fruits, the 
roots, and certain bodies called glands. 

850. The gaseous and vaporous exhalations 
are effected chiefly by the leaves, which it has 
been shown (320 and 465), under live m^\)£.\^<(:.^ 
of the solar ray, are always pourm^ omX. «u Vi^^^^ 



372 THE PHILOSOPHY OF HEALTH. 

quantity of oxygen, and still larger quantities of 
fluid in the state of vapour. 

851. Similar matters are exhaled by the flowers 
either in the form of vapour or of liquid; and 
this exhalation commonly bears with it a peculiar 
odour, which proceeds from an essential oil, some- 
times evaporated with the pollen, and at other 
times secreted by glandular bodies which have 
their seat in the petals. 

852. Fruits, and especially green fruits, as 
raspberries, pears, apples, plums, apricots, figs, 
cherries, gooseberries, and grapes, pour out oxygen 
during the day, and carbonic acid gas during the 
night, and thus co-operate with leaves in carrying 
on the function of excretion. 

853. The more elaborate excretions contained 
in special receptacles, and formed by diverse 
organs from the proper juices of the plant, descend 
chiefly by the bark, and are poured by the roots 
into the soil. These excretions, if re-absorbed hy 
the roots, and re-introduccd into the system of the 
plant that has rejected them, poison that plant 
Consequently, two processes of deterioration are 
always going on in the soil ; first, the absorption 
of the nutrient matter contained in it; and, 
secondly, the accumulation of excrementitious 
matter constantly poured into it by the growing 
plant. By the addition of manure, the soil is re- 

pleniahed witb ftesYv xwXtvNan^ xckAX^xvols ; by a 
rotation of crops, it ia^\w\&sA^^wa.^w»s^ ^- 



EXCRETION IN THE PLANT. 373 

cretions. It is a remarkable and beautiful ad- 
justment, that excrementitious substances which 
are destructive to plants of one natural family, 
actually promote the growth of plants of a different 
species. Thus, if wheat be sown upon a tract of 
land proper for that grain, it may produce a good 
crop the first, the second, and perhaps even the 
third year, as long as the ground is what the 
farmers call in good heart. But, after a time, it 
will yield no more of that particular kind of corn. 
Barley it may still bear, and, after this, oats, and 
perhaps after these, pease, or some other species 
belonging to a different family. The excrementi- 
tious matter deposited in the soil by a preceding is 
absorbed by a succeeding crop; the matter ex- 
creted by the former serving as nutriment or 
stimulus to the latter. But though in this mode 
all noxious matter is removed from the soil, yet 
' the ground at last becomes quite barren, in conse- 
quence of having parted with all its nutrient par- 
ticles, and then it will yield tio more produce 
until it is supplied with a new fund of matter. 
This new matter is afforded by vegetable or ani- 
mal substances, in which| the principle of life 
having become extinct, the peculiar bond that 
held their particles together is dissolved^ Leaves, 
flowers, fruits, bark, roots; hair, skin, horns, 
hoofs, fat, muscle, bone, the blood itself, whatever 
has formed a part of the organized \)od^ ^ w.^^ 
dead, and repasaing through the "pToce^ft oi ^ec,wsv- 



314 THE PHILOSOPHY OF HEALTH. 

position, back to the simple physical elements, all 
its forms of beauty gone, and exhaling only mat- 
ters highly deleterious to animal life, mixed with 
the soil, are recom})ined into new products, spring 
up into new plants, ^nd thus re-appear under new 
forms of beauty, and afford fresh putriment to 
myriads of animals. The very refuse of tbe 
matters which have served as fopd and clothing to 
the inhabitants of the crowded city, and which, 
allowed to accumulate there, taint the air, and 
render it pestilential, promptly remoyed, and 
spread out on the surface of the surroui^diBg 
country, give it bealthfulness, clothe it with verr 
dure, a^d endow it with inexhaustible fertility. 

854. Th.e q^uantity of matter excreted by the 
plant is proportionate to the energy of its vital 
actioiis. Hence it is always greatest in spring, 
when the tender leaves are beginning to shoot; 
gradually diminishes as autump approaches ; and, 
at last, as the leaves turn yellow, and the vessels 
which connect the leaves with the stalk dry up 
and are closed, it aitnost wholly ceasea. 

855. It is copious in proportion to the number 
of the leaves, and to the extent of the surface they 
present. From experiments performed as long 
ago as the year 1699, by Woodward, it appears 
that, of the whole quantity of water absorbed by 
the plant, the least proportion exhaled to that 

retained is a« 46 oi ^^ \ft \ \ Vew xbmk^ cases it is 
as 100 or 200 to 1, axi^ Vli web& ti^QRN^^K^ m^ V 



KXCRETION IN THE PLANT. 375 

In one experiment, a pli^it which imbibed 2501 
grains of water, increased in weight only three 
grains and a half: hence the dampness and hu- 
midity of the air in all places in which trees and 
the larger vegetables abound ; more especially 
when the leaves are young, and most numerous 
and active ; and hence also the magnitude of the 
rivers in all extensive countries which are covered 
with forests. 

856. Exhalations Scslrcely appreciable in the 
night, is most abundant during the day under the 
influence of the solar light. If two plants of the 
same size are covered '^ith two glass bells, and 
dne be exposed to the sun's light, while the other 
is left in the shade, the inner surface of the former 
bell becoiiles dUvered with drop* of water, while 
that of the second remains perfectly dry. 

857. The absolute quantitjr of matter excreted 
by the plant is widely different in different spe- 
cies. According to Itales, in a sun-flower three 
feet and a half high, the leaves of which presented 
a surface of 5616 square! inches j or 39 square feet, 
the greatest quantity exhaled in twelve hours, 
during the day^ was one pound fourteen ounces 
avoirdupois ; the medium quantity one pound 
four ounccis. Ill a middle-sized cabbage, the 
greatest quaiitity exhaled ^v^as one pound nine 
ounces; the medium quantity one pound three 
ounces. In a vine, the greatest quantity es\v^^\ 
was six ounces ; the medium t|uant\ty £ivc owxvc^'^ 



376 THE PHILOSOPHY OF HEALTH. 

In a young apple tree having 163 leaves, the sur- 
face of which was equal to 15S9 square inches, or 
1 1 square feet, th^ greatest quantity exhaled was 
eleven ounces ; the medium quantity nine ounces. 
Martino calculated the quantity ei^haled by t 
cabbage, in the twenty- four hours, at tiRrenty- 
three ounces ; by a young mulberry-tree, eighteeo 
ounces ; ^nd, by a maize plant, seven drachms. 

858. Supposing the weight of the human body 
to be 160 pounds, and the weight of a sun-fiower 
3 pounds, the relative weights of the two bodies 
will be as 160 to 3, or as 53 to 1. The surface of 
such a human body is equal to 15 square feet, or 
2160 square inches; the surface pf the sun-flower 
is 5616 square inches, or as 26 to 10. The quanr 
lity perspired in the twenty-four hours by an ordi- 
nary-sized man, according to the estimate of Keill, 
is about thirty-one ounces. Allowing two ounces for 
the exhalatipn during the beginning and the eD4* 
ing of the jiight, the quantity exhaled by the plant, 
in the same time, is twenty-two ounces ; so that 
the perspiration of a man to that of a sua-flower 
is nearly as 141 to ICO, though the weight of the 
man to that of the sun-flower is ^s 53 to 1. Taking 
bulk for bulk, the planjt imbibes seventeen times 
more fresh fluid than the inan, partly, no doubt, 
for the reason assigned by Hales — because, " the 
fluid which is Altered through the roots of the 
piant is not near ^o i\\)\ ix«i\^\wi ^irith nutrient 
particles as the ch^\e yj\v\<^ e»X.«^ \iQfc\aRXw6ba. ^ 



KXCRSTION IN THE ANIMAL. 377 

\ animal ; the plknt, therefore, requires a much 
ger supply of fluid." 

B59. As soon in the animal series as organs 
! formed distinct from the homogeneous mass of 
ich the minute and simple beings placed at the 
:tom of the scale appear to consist, these organs 
I appropriated, at least in part, to the function 
excretion. In the human being, six organs 
:e a part, and are chiefly appropriated to this 
iction — ^namely, the skin, the lungs, the liver, 
: adipose tissue, the kidneys, and the intestinal 
lal. All these otgans serve other purposes in 
! economy ; but still the removal, in some spe- 
c form, of excrementitious matter from the 
tern, is a most important part of the office of 
h. 

360. The Ikhi (34), to which are assigned nu- 
rous and highly important offices, seems to be 
icially constructed for performing the function of 
:retion. It is composed of three layers, of which 

internal i6 called the cutis, or true skin ; the 
emal the cuticle, or scarf skin ; and the middle, 

which the other two are united, the rete 
cosum. The latter is indistinct, excepting in 

negro, in whom it is the seat of colour. 
^1. The cutis, or true skin, is a dense mem- 
,ne, composed of firm and strong fibres, inter- 
yen like a felt. Its internal surface is marked 
nutneroas depressions, which receive ^toc)&«&^:s» 
be adipose tissue beneath. Over its e^\.«txi«X 



378 THE PHILOSOPHY OF HEALTH. 

surfiace is spread a delicate and complex network 
of vessels, termed the vascular plexus, of such 
extent and capacity that, in the natural state 
of the circulation, a very large proportion of 
the whole hlood of the body is constantly 
flowing in these blood-ves9els of the cutis. A 
prodigious number of nerves accompany the 
cutaneous blood-vessels, some derived from the 
organic, and others from the sentieiit portion of 
the nervous pystem. The organic nerves endow 
the arteries with the power of performing the 
organic processes proper to the cutis, which are 
pripdpally of an excrementitious nature. The 
sentient nerves communicate to every point of the 
external surface of the cutis the exquisite degree 
of sensibility possessed by the skin. Innumer- 
able absorbent vessels terminate at the same 
points, with the capillary arteries and the sentient 
nerves. 

862. The extreme smoothness arid softness 
natural to the skin is conmiunicated to it by a 
number of follicles which are placed in the cutis, 
and are termed sebaceous, from the oily substance 
they secrete. It is the matter secreted by these 
organs which communicates to the animal body 
the odour peculiar to it, on which the scent 
depends. 

863. In many parts the cutis is perforated 
obliquely by hairft, ^\i\c\v %^incu%%tQtEw\v\>iV'^\s.nlb8 
beneath it, to wViicVi t\i^ ^gcwt^ ^^ ^'^ \«ss%. >». 



ORGANIZATION OF THE SKIN. 379 

confined. The human hair, which is hollow, 
consists of fine tubes filled with an oily matter. 
This matter is either of a black, red, yellow, or 
pale colour, as the hair is black, red, yellow, or 
white. 

864. The nails are products formed by the 
cutis, and are essentially the same as the cuticle. 

865. By long-continued boiling the cutis is 
resolvable into gelatin, which by evaporation 
becomes glue, and by combining with tannin and 
the extractive of oak bark is converted into 
leather. 

866. The third portion of the skin, the cuticle, 
is a thin, elastic membrane spread over the exter- 
nal surface of the cutis, from which it is easily 
detached, by the action of a blister in the living, 
and by the process of putrefaction in the dead 
body. It is without vessels and nerves, and con- 
sequently it is insensible and inorganic. It is 
formed as a secretion by the cutis, and is com- 
posed almost entirely of solid albumen. When 
any portion of it is removed, it is renewed with 
great rapidity. Since it is subject to constant 
waste from friction, and is much increased bv 
pressure, as is manifest in the palms of the hands 
and the soles of the feet, its formation must be 
continual ; yet even in the foetus it is thicker in 
the parts where pressure is ultimately to be made 
than in the other parts of the body. 

661. The cuticle is a sheath in w\vic\i \)cv^>oq^^ 



380 THI PHILOSOPHT OF HEALTH. 

is enclosed for the purpose of restraining the 
organic actions which take place at its surface, 
and for tempering the sentient impressions receiyed 
there. For restraining the organic actions it is 
fitted by the cohesion of its parts, which is such 
as to receive and transmit any fluid very slowly, as 
is manifest from the dryness of its surface when 
it is raised in a blister, and firotn the extreme rapi- 
dity with which the cutis dries, until it becomes as 
hard as parchment, when the cuticle is removed 
from it in the dead body. 

868. Diflused over every part and particle of 
the cutis is the seat of common sensation, that 
cognizance may be taken of the presence of 
external objects. Restricted to particular poiDts, 
the tips of the fingers, is the seat of one of the 
special senses, that of touch. Had the nenes 
which communicate to this extended surface its 
acute sensibility been placed in direct contact 
with external bodies, intolerable pain would hsTe 
been the result ; but by covering this sur&ce with 
an inorganic and insensible substance, yet so thin 
that it is a pellicle rather than a membrane, the 
organ of sense is shielded, while the delicacy of 
the sensation is not impaired. But the control of 
the organic process and the protection of the 
sentient nerve are not the only offices performed 
by the cuticle ; it serves further to hide what it is 
undesirable to have cwMiXaxiA:^ -oin^sw. ftJi that 
is beautiful in the \Aoo^«» wi ^\^x ^1 ^\afc>a. 



EXCaiTORT FUNCTION OF THB SKIN. 381 

rendered visible through the cuticle, in the bright 
and rosy hue of health, at the same time that 
every process, the sight of which would excite 
anxiety or terror, is effectually concealed. 

869. The skin, an organ of secretion, an 
organ of absorption, an organ of excretion, and 
an organ of sense, is thus the immediate seat 
of three organic processes and of one animal 
process. 

870. The chief excretion performed by the 
skin, in the human body, is commonly known 
under the name of perspiration. The perspiration 
is either sensible or insensible. Sensible perspi- 
ration is the liquid commonly called the sweat. 
Insensible perspiration consists of a vapour which, 
under the ordinary circumstances in which the 
body is placed, is invisible. The invisible vapour 
is constantly exhaling ; the visible liquid is only 
occasionally formed. The quantity of matter 
carried out of the system under the form of invi- 
sible vapour is much greater than that lost by the 
visible liquid. 

871. That a quantity of matter is incessantly 
passing off from the surfietce of the skin, under the 
form of an invisible vapour, is proved by the fol- 
lowing facts • — 

1 . If the hand and arm are enclosed in a glass 
jar, the inner surface of the glass soon becomes 
covered with moisture. 

2. If the tip of tiie finger be held a\. «)ao\\\. \X\^ 



382 THE PHILOSOPH7 OP HEALTH. 

twelfth of an inch from a mirror, or any other 
highly polished surface^ the surface rapidly hecomes 
dimmed by the vapour which condenses upon it 
in small drops, and which disappear on the 
removal of the finger. 

3. If the body be weighed at different periods, 
an accurate account being taken of the ingesta 
and the egesta, it is found to undergo a loss of 
weight sensibly greater than can be attributed to 
any of the visible discharges : this loss must be 
owing to the transmissioh of a quantity of matter 
out of the body, under the form of invisible 
vapout. 

872. The matters excreted under the form of 
perspiration are separated from the blood by a 
triie and proper secretion, hke the other secretions 
of the body. The process by which this is 
effected is called transudation. The matter of 
transudation deposited on the surface of the sldo 
by a vital function is removed from the body by 
evaporation, a physical process which consists of 
the conversion of a liquid into a vapour by the 
addition of heat. Consequently the process of 
perspiration is a cooling process, and it is chiefly 
by the increase of the perspiration that the body 
is enabled to bear the intense degrees of heat 
which it has been shown (491, et seq. ) to be 
capable of sustaining. Sittiiig one day in repose 
in the shade dunii^ tYve *vcv\.^tfflfc\kR».\. s^^ slu ^e- 
rican summet*© doj, x^^ ^^"^^ fe^^^ ^TK^xxswyfe. 



EVAPORATION. 383 

e\ery pore. Dr. Franklin happened to examine 
the temperature of his hody with a thermometer. 
fie found that the temperature of his body was 
several degrees lower than that of the surrounding 
air. The physiologists who exposed themselves 
in heated chambers, for the sake of ascertaining 
the greatest degree of heat which the human body 
is capable of enduring, perspired profusely during 
the experiment (495). The artisans who carry on 
their daily occupations in elevated temperatures 
perspire most profusely (884^61 seq.). Under such 
circumstances, caloric is communicated to the 
human body just as freely as to inorganic matter 
yet it does not injure the body, because it does 
not accumulate in the system, but is immediately 
expended in supplying the heat necessary to con- 
cert the water, which is poured out upon the skin, 
nto vapour. In this manner that surface of the 
K>dy at which, under ordinary circumstances, a 
arge portion of its animal heat is generated, is the 
'ery surface at which, under extraordinary circum- 
.tances, cold is generated^ and the heat of the sys- 
em positively reduced. 

873. The physical process of evaporation 
vould go on to a certain extent, though the vital 
unction of transudation did not exist, and does 
ro on in the dead body when the vital function is 
it an end. An organic tissue enclosing a liquid 
nay not be porous enough to give passage to a 
223gle drop of liquid, and yet sufficiently ^xowa. \ft 



384 THE PHILOSOPHY OF HEALTH. 

admit air. In this case the air in contact with the 
tissue dissolves the liquid in its interior, and' 
carries it off in the form of invisible vapour; 
hence liquids contained in organic bodies in contact 
with the air diminish in quantity by evap(»ra- 
tion. But if an animal be placed in air satu- 
rated with moisture, and of the same tanpera- 
ture as its own, the air can no longer deprive 
that animal of a single particle of its moi^ure : 
evaporation from the body, in such a condition 
of the air, is suppressed. On the other hand, 
when an animal is placed in air saturated 
with moisture, and of the same temperature 
as its own, so far is transudation from being 
suppressed, that the sweat streams from every 
part of the external surface of the body. By 
modifying the condition of the air, in regard 
to its hygrometrical state and its temperature, the 
result of the physical process and of the vital 
function may thus be separated from each other, 
and the amount of each may be ascertained with 
perfect exactness. Now, by numerous experi- 
ments on the cold-blooded vertebrata, placed under 
such conditions of the air, it is found that, in 
these animals, perspiration by evaporation is to 
that by transudation as 6 to 1. But since the 
human body presents to the air an immense extent 
of surface over which is constantly flowing a lai^ 
proportion of the w\ioVfc q^wji^yXtj q»\ W^^^^ <soutained 
in the cystem, the \o^«» ^yg >()cvfc ^^i\^«ftiL ^tsjrs®. 



TRANSUDATION. 385 

compared with that by the vital function must 
be still greater in man than in the cold-blooded 
animaL 

874. Taking together the average quantity of 
matter removed from the human body by both 
processes, or the whole loss of weight sustained 
from perspiration, on the comparison of the re- 
Bults of many observations, it is estimated to 
vary from twenty ounces in the twenty-four hours 
of the colder, to forty ounces in the warmer 
climates of Europe. Keill estimated it at thirty- 
one ounces. In the climate of Paris it is stated 
to be thirty ounces. 

875. By the delicate tests of modern che- 
mistry, various substances are found to be con- 
tained in the aqueous fluid which constitutes the 
great proportion of the matter of perspiration, 
namely, an acid, probably the lactic, a small pro- 
portion of animal matter, some alkaline and earthy 
salts, an oily or fatty substance, probably derived 
from the sebaceous follicles. All these matters are 
80 analogous to the constituents of the serum of 
the blood as to leave little ground for doubt that 
they are merely separated from this part of the 
blood as it is flowing through the complex net- 
work of vessels spread over the surface of the 
cutis (861). 

876. The skin, when in contact with the air, 
also separates a portion of caTbon fxota >i}cv^ 
blood, and to the extent in whicYi \\. ^ofe% \)wva» 

VOL, II. ^ 



386 THE PHILOSOPHY OF HEALTH. 

it is auxiliary to the lungs ; but the quantity of 
earbonic acid excreted by the skin is small and 
variable in amount. The primary office oi the 
skin as an organ of excretion is to relieve the 
blood of its superabimdant watery particles, thst 
is, to remove from the system its superfluous 
hydrogen. 

87*7. A full account has been given (359, 6t 
seq,) of the primary office of the lungs, which, it 
has been shown, is to decarbonize the blood. The 
details of the calculations have been stated (457), 
from which it is estimated that 10 ounces and 116 
grains of carbon are daily exhaled by the lungs under 
the form of carbonic acid ; and the reasons have 
been assigned which favour the conclusion thattbe 
carbonic acid expired is not formed immediatelj 
in the lungs by the combination of the oxygen of 
the atmospheric air with the carbon of the blood j 
but in the system, where the oxygen taken into 
the blood at the lungs unites with carbon, the 
carbonic acid resulting from the combination 
passing as soon as formed into the capillary veins. 
The blood contained in these vessels, thus become 
venous, returns to the lungs, where it gives off the 
carbonic acid accumulated, in it, and by that de- 
puration again assumes its arterial character. 

878. Some interesting experiments performed 

by Dr. Stevens appear to show that there exists a 

powerful attTaclioii \i^\7N^«.\i oxygen and carbonic 

acid, and that t\ve '^feiio\\a\^^^>^3^'^S&^wM{, 



EXCRBTORT FUNCTION OF THE LUNGS. 387 

through the hingB, is freed from its carhonic acid 
by virtne of that attraction. Chemists were so 
universally agreed that the carbon in carbonic acid 
is united with its maximum dose of oxygen, that 
the idea of an attraction between carbonic acid 
and oxygen appeared highly improbable. The 
evidence of the fact, however, is decisive. If a 
receiver, filled with carbonic acid, and closed by a 
piece of bladder, firmly tied over it, be exposed to 
the atmospheric air, the carbonic acid, notwith- 
standing its superior specific gravity, rapidly 
escapes, and does so without the exchange of an 
equivalent portion of atmospheric air ; the bladder 
is consequently forcibly depressed into the receiver. 
If the converse of this experiment be tried, and 
the receiver, containing atmospheric air, be tied 
over with a piece of bladder or thin leather, and 
then be immersed in carbonic acid, this gas will so 
abundantly penetrate the membrane and enter the 
receiver as to endanger its bursting. 

879. Dr. Stevens had repeated opportunities 
of verifying these facts, during a stay which he 
made at Saratoga, in the United States, the springs 
at which place liberate a large quantity of car- 
bonic acid. In the high rocks it often collects in 
considerable quantity and purity, and experiments 
on dogs and rabbits are often made for the enter- 
tainment of strangers, as at the Grotto del Cano, 
near Naples. This rock stands by \lae\i vci «u\(y« 
valley, through which there run two cvLttetiXa o^ 

s!2^ 



388 THE PHILOSOPHY OF HEALTH. 

water, the one fresh and superficial, the other 
beneath and charged with salts and carbonic acii 
A current of this water rises to some height in a 
cavity of the high rock, which appears to have 
been formed by a deposition of earthy salts from 
the water. It has a conical figure, the base of 
which is below the surface of the ground, and ii 
about nine feet in diameter. It rises about five 
feet from the ground, where it is truncated, and 
presents an aperture a foot in diameter. The 
water rises in general only about two feet above 
the ground, and in the three feet above the sur&ce 
of the water the liberated carbonic acid collects. 
By luting a large funnel over the aperture, car- 
bonic acid may be collected at the mouth of the 
funnel in indefinite quantities, of which Dr. Stevens 
availed himself to multiply and vary his experi- 
ments, the result of which appears to be, the com- 
plete establishment of the fact that there exists a 
powerful attraction between carbonic acid and 
oxygen. 

880. The application of this fact to the ex* 
planation of the phenomena of respiration is highly 
interesting. By virtue of this mutual attraction} 
two currents are established, which flow in opposite 
directions, through the membranous matter of the 
air-vesicles of the lungs and the pubnonary blood- 
vessels spread out upon their surface ; the oxygen 
o£ the air ftowa to t\v^\i\o^ ^^v.^njcti^d by its ca^ 
bonic acid, and tVve c«i>aQ>Ti\^ ^^\^ oJl "^oa^^^fsj^ 



EXCRBTORT FUNCTION OF THE LUNOS. 389 

flows to the air attracted by its oxygen. According 
to Dr. Stevens, the moment the blood parts with 
its carbonic acid it loses its dark colour, and 
becomes of a bright yermilion colour, for the fol- 
lowing reason : all acids impart a dark colour to 
the blood. With respect to most acids, this colour 
remains, although the added acid be ajfterwards 
saturated. Carbonic acid forms an exception, for 
on the removal of this aerial acid the blood resumes 
its bright and arterial colour. Alkalies, like acids, 
darken the colour of the blood, but salts produce a 
bright and vermilion colour when added to the 
colouring matter of the blood. When the blood 
loses its carbonic acid, the salts contained in the 
blood produce upon its colouring matter the ver- 
milion tint natural to the combination when the 
influence of the salts is not counteracted by the 
presence of a redundant acid. At the moment the 
venous blood gives up its carbonic acid it receives 
in exchange a portion of the inspired air, which is 
chiefly at the expense of the oxygen. It retains 
somewhat more oxygen than it yields back in the 
shape of carbonic acid. The reddened and oxy- 
genated blood, having returned to the heart, is 
difliised over the system, where it parts with its 
oxygen and combines with carbon, forming by the 
xmion carbonic acid ; the necessary result of this 
combination is the generation of animal heat in 
the exact proportion to the quantity oi tVie ca.i\>otcv& 
aad which is produced. The venowA \]\o^<» 



390 THE PB1LCMM>PHT OF HBALIS. 

which receives the carbonic acid as it is formed in 
the system, is darkened by its presence, which 
counteracts the effects of the salts of the blood 
upon its colouring matter. 

881. An account has been given (439 ) of the 
experiments, which prove that the lungs also con- 
stantly exhale a quantity of azote. 

882. It has been further shown (469) thit, 
together with the carbonic acid, which passes off in 
the inspired air, there is always present a quantity 
of aqueous vapour. This aqueous vapour is not 
visible at the ordinary temperature of the air in 
its ordinary hygrometric state, because the water is 
then dissolved in the air, and is carried off in the 
form of invisible vapour ; but it becomes aband- 
antly manifest at a low temperature, or when the 
air is loaded with moisture. By the removal of 
this aqueous vapour, the lungs assist the skin in 
the depuration of the blood. The water transpired 
by the lungs, like that perspired through the ddn, 
is separated from the blood by a true and proper 
secretion constituting the pulmonary transudation* 
It is commonly estimated that the lungs exhtle 
about one-third as much as the skin, or fifteen 
ounces daily. Dalton estimates it at twenty-four 
ounces. 

883. These estimates of the quantity of fluid 
lost by cutaneous and pulmonary transpiration 

relate to the quai\l\^e«\o«x «x V^t^ <st^ai«r; oxtenul 
temperatures in ^YiVcYi tJcie \w\flB»si\*2^\%^$asi^ 



QUANTITT LOST BT THB SKIN AND LUNGS. 391 

The quantity lost when the hody is exposed to an 
elevated temperature is prodigiously increased. 
It did not occur to the physiologists, whose experi- 
ments have been detailed (492, et seq.)^ to ascertain 
this by causing themselves to be accurately weighed 
immediately before they entered their heated cham- 
ber and immediately after they left it. Having 
heard that the loss daily sustained by the workmen 
employed in gas-works is very extraordinary, I 
endeavoured to ascertain the amount of it with 
exactness. This I have been enabled to accom- 
plish by the assistance of Mr. Monro, the mana- 
ger of the Phoenix Gas Works, and of Mr. Cooper. 
The following are the experiments by which this 
has been ascertained. 

ExpERiMBNT I. — November 18, 1836, at the 
Phoenix Gas Works, Bankside, London. 

884. Eight of the workmen regularly employed 
at this establishment in drawing and charging the 
retorts and in making up the fires, which labour 
they perform twice every day, commonly for the 
space of one hour, were accurately weighed in 
their clothes immediately before they began and 
after they had finished their work. On this occa- 
sion they continued at their work exactly three- 
quarters of an hour. In the interval between the 
first and second weighing, the men were allowed 
to partake of no solid or liqmd, i\oi \a '^vtX.^S^ 
ithen The day was bright and c\e«r, 'w\X)ci tk»kJcw 



392 THE PHILOSOPHY OF HEALTH. 

wind. The men worked in the open air, the tem- 
perature of which was 60° Farh. The barometer 
29° 25' to 29° 4'. 

Weight of the Men Weight of the Men 
before they began after they had fi- Lois, 
their work. lushed their work. 

cwt. qr. lbs. oz. cwt. or. lbs. os. lbs. (»■ 

Michael Griffiths....! 1 14 10 1 I IS S S 8 

JohnKenny 1 86 10 1 Si 1 S 9 

John Ives 1 14 S 1 11 8 8 10 

James Finnigao ....11 10 6 11 7 36 

Wiiliam Hummerson 10 84 4 10808 3 12 

Timothy Frawley.... I 1 8 10 1 1 4 IS 3 14 

Patrick Nearey 1 1 14 10 1 1 10 8 4 2 

Bryan Olynon 1 104 10 84 1 43 



Experiment II. — Nov. 25, 1836. 

885. Day foggy, with scarcely any wind. Tem- 
perature of the air 39° Farh., barometer 29" 8'. 
On this occasion the men continued at their labour 
one hour and a quarter. 

Before. After. Loss. 

cwt. qr. lbs. oz. cwt qr. lbs. oc lbs. oc. 

Patrick Murphy ....11 1087 S 014 

John Btodenck 1 094 1080 14 

Michael Macarthy...l 119 10 10 3 16 

Michael Griffiths .... 1 1 15 8 1 1 13 S 86 

James Fiunigan 1 118 4 119 18 88 

Bryan Duffy 1 1 11 13 119 2 12 

John Didderick 1 1115 1188 8 13 

Charles Cahell 1 145 1116 8 15 

886. Charles Cahell, the man who on this 
occasion lost the most, was weighed previously to 
the commencement of his work, with all his 
clothes off, excepting his shirt, which was kept 
dry and put on him again when weighed a second 

time at the end oi loi^ ^otV. ^^ ^«^& \.\skfficv im- 
mediately put into a Yiaxm\>«AXv ^.x. ^"^ ^«£*t!L..,'«^ 



IZPERIMENTS. 393 

there half an hour : he complained of being 
and faint, and when reweighed had gained 
. pound. 



Experiment III. — June 4, 1837. 

7. Day clear, with some wind. Temperature 

« 

Before. After. Lose. 

'cwt. qr. Ibt. os. cwt. qr. Iba. ot., lbs. ox. 

rt Bowers 1 1 19 1 1 17 SO 

imMalUns 1 180 1110 SO 

lesCaheU 1 ISO 1100 SO 

Kenny 1 0SS3 10 19 8 SIO 

BGlynon 1 S7 I S4 i S 13 

Haley 1 140 1114 SIS 

imin Faulkner...! 1 15 U I 1 13 8 14 

Ael Griffiths 1 188 1158 30 

Broderick I 046 03S78 4 14 

Didderick I 16 IS 111 10 5S 

^. The two last men worked in a very hot place 
le hour and ten minutes ; all the rest worked 
one hour. Michael Griffiths, as soon as he 
nished his work, was put into a bath at 98^, 
! he remained half an hour. He was re- 
icd on coming out of the bath, and had 
oz. 

h From these observations it appears that, 
ds the end of November, when the tempe- 
i of the external air was 39°, and the day 
)ggy and without wind, the greatest loss did 
mount to 3 lbs. (2 lbs. 15 oz.), the least 
7as 14 oz., and the average loss was 2 lbs. 

K In the middle of the aame montV, ^\L^\i 



394 THE PHILOSOPHY OF HEALTH. 

the temperature of the air was 60®, and the day 
was clear with much wind, the greatest loss was 
4 lbs. 3 oz., the least loss was 2 lbs. 8 oz., and the 
average loss was 3 lbs. 6 oz. 

891. In June, when the temperature of the 
external air was 60°, and the day exceedinglj 
bright and clear, without much wind, the greatest 
loss was 5 lbs. 2oz., the next greatest loss was 
4 lbs. 14 oz., the least loss was 2 lbs., aud the 
average loss was 2 lbs. 8 oz. 

892. The same individuals lose very different 
quantities at different times. Tlius, James Finnigan 
in the first experiment lost 3 lbs. 6 oz., in the 
second 2 lbs. 8 oz. Michael Griffiths in the first 
experiment lost 2 lbs. 8oz., in the second 2 lbs. 
6 oz., and in the third 3 lbs. ; while John Kenny 
in tlie first experiment lost 2 lbs. 9 oz., and in the 
third experiment, which was the second to which 
he was subjected, he lost very nearly the same, 
namely, 2 lbs. 10 oz. On the other hand, Bryan 
Glynon in the first experiment lost 41b8. 3oz., 
and in the third experiment, which was the second 
to which he was subjected, he lost no more than 
2 lbs. 12 oz. 

893. In one case, when a man who had lost 
2 lbs. 15 oz., the greatest quantity lost by any of 
the men examined during that day, was put into 
a hot bath at 95°, and reweighed on coming out 

of the bath, where \ie\v«L^ T^mvc«v^\ ^^^cUy half 
an iour, it was foxmd \)tMv.\. V^ \v^^ ^gfiLxw^WaJil^ x 



EXPERIMENTS. 395 

pound. On the other hand, when a man who had 
lost 3 lbs. was put into a hot bath at 98% and kept 
there for half an hour and reweighed, it was found 
that he had lost exactly half a pound. 

894. It was our intention to have pursued 
these experiments, with the view of ascertaining 
the influence of the hygrometrical state of the air 
on transpiration, as well as the absorbing power 
of the skin, under circumstances so favourable to 
the activity of that power, but the investigation 
has been unavoidably postponed. 

895. The results of these observations are as 
interesting in relation to absorption as to transpi- 
ration. Thus, James Finnigan, on the 18th of 
November, weighed, 

cwt 

before the experiment ... 1 
after the experiment . . 1 

having lost 

On the 25th of November he weighed 1 cwt. 
1 qr. 12 lbs. 4 oz., having gained in the interval 
1 lb. 14 oz. 

Michael Griffiths, on the 18th of November, 

cwt. qr. lbs. oz. 

oefore the experiment, weighed 1 I 14 10 
after the experiment ... 1 1 12 2 

having lost 2 8 

On the 25th of November, before the experiment, 
he weighed I cwt. 1 qr. 15 lbs. 8oz., having 



qr. 


lbs. 


oz. 


1 


10 


6 


1 


7 








3 


6 



S96 THE PHILOSOPHT OF HEALTH. 

gained 14 oz. ; but on the did of June be weighed 
1 cwt. 1 qr. 8 lbs. 8oz., having lost between the 
18th of November and the 3Td of June, 
6 lbs. 2 oz. 

896. John Kenny, on the 18th of November, 

before the experiment, weighed .1 26 10 
after the experiment .... 1 24 1 

having lost 2 9 

On June the 3rd he weighed 1 cwt. 22 lbs. 2oz., 
having gained in the interval 4 lbs. 8 oz. 

897. Bryan Glynon, November 18th, 

cwt. qr. Ibi. oi. 

before the experiment, weighed 11 4 
after the experiment ... 1 24 I 

having lost 4 3 

On the 3rd of June he weighed 1 cwt 27 lbs., 
having lost 1 lb. 4 oz. 

898. Thus, in the course of their ordhiary occu- 
pation, these men are in the habit of losing from 
2 lbs. to 5 lbs. and upwards twice a-aay; yet, 
when weighed at distant intervals, it is found that 
some have actually gained in weight and others 
have lost only a few pounds ; it follows that the 
activity of the daily absorption must be proper* 
tionate to that of the daily transpiration. 

899. According to the prevalent opinion, the liver 

is the cause of a large proportion of the maladies 

which afflict and de^txo^YraisAXklife. It certainly 



DIOBSnVB FUNCTION OV THB LtVBR. Sdl 

ircises an important influence over health and 
ease, the true reason of which is hut little 
lerstood hy those who attrihute most to its 
jncy. 

900. The liver is an organ of digestion and an 
;an of excretion. 

[t is an organ of digestion in a two-fold mode : 

1. By the secretion of a peculiar fluid, through 
i direct action of which chyme is converted into 
yle. The several phenomena attending this 
eration have hcen fully descrihed (668 et seq.). 

2. By subjecting alimentary matters which have 
en partly acted on by the stomach and intestines 
a second digestion. 

901. It has been shown (666) that the 
ins which return the blood from the digestive 
gans, the stomach, the intestines, and the me- 
ntery, together with the veins of the spleen, the 
lentum and the pancreas, instead of pursuing a 
rect course to the right side of the heart in 
der to transmit their contents by the shortest 
uteito the lungs, as is the case with all the other 
iins of the body, unite together and form a large 
link termed the vena portse, which enters the 
rer and ramifies through it in the manner of an 
tery. It has been further shown (666) that 
te bile is secreted from the venous blood con- 
ined in this vessel by its capillary branches 
)Tead out on ihe walls of the 'biliary ^w.cX.%^ ^^ 
Jjr known instance in the human "bod^ m^VvSa. 



398 THE PHILOSOPHY OF HEALTH, 

a secretion is formed from venous blood by venous 
capillaries; that the trunk of this vein, unlike 
that of any other, is encompassed with oiganic 
nerves, which accompany its subdivisions, and are 
spread out upon its capillary branches just as an 
organic nerve is spent upon an artery, and that 
thus, as this vessel performs the function of an 
artery, it has the structure and distribution of an 
artery. 

902. The veins which unite to form the vena 
portse take up, by their capillary branches, certain 
portions of the contents of their respective .organs, 
and bear those contents directly into the venous 
current. The capillary veins of the stomach take 
up certain parts of the contents of the stomach, it 
would appear the fluid substances received with 
the aliment more especially ; the capillary veins of 
the duodenum take up certain portions of the con- 
tents of the duodenum, and so on of the ca- 
pillary veinb of the spleen, intestines, and all 
the organs whose veins combine to form the vena 
portae. Further, branches of the absorbent ves- 
sels of these organs have been distinctly traced 
opening directly into the veins in their immediate 
neighbourhood. Certain products of digestion 
must, then, be constantly poured, both by the 
capillary veins and by the absorbent vessels of the 
digestiYe organs, into the blood of the vena portse. 
903, Accordin§\y, wi Vkt ^7L%m\\ii^\x<!«v of ani- 
mals 8O0D after a Tnea\, «tet^«>BA ^1 ^^sia^\»as«."^\ 



DIGESTIVE FUNCTION OF THE LIVER. 399 

chyle are often observed in the blood of the vena 
portie. It is further established by numerous 
experiments, that if alcohol, gamboge, indigo, and 
other odoriferous and colouring matters, are mixed 
with the food, their presence is manifest in the 
blood of the digestive organs, and more especially 
in the blood of the mesenteric veins and in that 
of the vena portse, while no trace of these sub- 
stances is ever found in the lacteals. 

904. The lacteals, it has been shown (835. 1), 
are special organs appropriated to the performance 
of a specific function, that of absorbing chyle. To 
fit them for this office, they are endowed with an 
elective power, by virtue of which they select, fi-om 
the alimentary mass, that portion of it only which 
is converted into chyle ; in a natural and healthy 
state they would appear to be incapable of absorb- 
ing any other substance excepting pure chyle. 
But in the digestive organs there is always present 
much nutritive matter not yet converted into pro- 
per chyle, and with this matter there are mixed 
foreign substances not strictly alimentary. These 
unassimilated matters and foreign substances, 
absorbed by the capillary veins or by the absorbent 
vessels, or by both, are conveyed directly into the 
vena portse, by which vessel they are transmitted 
to the liver, where they undergo a true and proper 
digestion. After undergoing this digestion in the 
liver, they are sent by a short course to lli^ V«ax\.^ 
wd thence to the lungs, where tlve^ %ie^««aK^^^^ 



I 

I 
400 THE PHILOSOPHY OF BBALTH. ' 

into, or at least commingled with, arterial blood, 
and, with arterial blood, are transmitted to the 
system. The substances subjected to this hepatic 
digestion, which is as real as that effected in thr 
stomach and duodenum, do not appear to enter 
the lacteals at all ; they have therefore a shorter 
course to traverse, and probably a proportionatelj 
less elaborate process to undergo, before their trans- 
mission to the lungs and their final entrance into 
the arterial system. 

905. What the particular substances are for 
which this slighter digestive process suffices is not 
known with certainty. There is, however, reason 
to suppose that they consist chiefly of liquids, 
while there is direct evidence that vinous and 
spirituous liquids enter the system through this 
shorter course; since these fluids are often 
abundantly manifest in the blood of the vena 
portae, when not the slightest trace of them can he 
detected in the lacteal vessels. 

906. According to this view, the liver is a 
second digestive apparatus, completing what the 
first commences, or effecting what that is incapa- 
ble of accomplishing ; and this view assigns the 
reason why certain fluids taken into the stomach 
sometimes appear in the secretions and excretions 
with such astonishing rapidity ; why the liver so 
constantly becomes diseased when highly stimu- 

J&ting substances. iioV. Y^o^tVj i»&s&ssqx»x^^ are 
mixed with the food, wvd mw. «b^«m^^ -^^^a^ 



EXCRBTORT FUNCTION OF THE LIVER. 401 

ardent spirits or the stronger wines are largely and 
habitually taken; why the sympathy is so inti- 
mate and intense between the stomach and the 
liver and the liver and the stomach, both in health 
and disease ; why in the ascending animal series 
the liver so soon appears after the stomach, and 
why the magnitude of the organ and the elaborate- 
ness of its structure progressively increase with 
the extension of the digestive apparatus and the 
corresponding complexity of the general organiz- 
ation. 

907. The second function performed by the 
liver is that of excretion. The excrementitious 
matter eliminated from the blood by the liver is 
contained in its peculiar secretion, the bile. The 
bile consists of two portions, an assimilative part 
which combines chemically with the chyle, purify- 
ing and exalting its nature; and an excremen- 
titious part which combines with the residue of 
the aliment. 

908. The excrementitious part of the bile con- 
tains a large proportion of carbon and hydrogen. 
Carbon and hydrogen abound in venous blood ; 
venous blood in large quantity is sent to the liver 
to afford the materials for the secretion of bile ; 
consequently, the more copious the secretion of 
bile the greater the quantity of carbon and hydro- 
gen abstracted from venous blood. It follows 
that, by this elimination of carbon and Vv^di^vy^x^. 



402 THE PHILOSOPHY OF HEALTH. 

from the blood, the liver is auxiliary, as an organ 
of excretion, to the skin and the lungs. 

909. But it is well worthy of remark, that 
although the liver at all times assists the skin and 
the lungs in carrying on the process of excretion, 
it does this most especially under circumstanoea 
which necessarily enfeeble the action of the cu- 
taneous and pulmonary organs. 

910. Less carbon is expelled from the lungs in 
summer than in winter; at a high than at a low 
temperature; consequently by a long-continued 
exposure to intense heat, as in the hot months of 
summer, and still more by a continual residence 
in a warm climate, an accumulation of carbon in 
the blood is favoured. A part of this excess is 
removed by the increased exhalation from the 
skin. The skin, however, is the chief outlet, not 
for carbon, but for hydrogen ; and accordingly by 
the increased perspiration hydrogen is large^ 
removed. Hydrogen and carbon compose ftt. 
The deposition of fat, could it go on to the requi- 
site extent, would afford an adequate consumption 
for the superabundant carbon ; but the formation 
of fat is prevented by the dissipation of the 
hydrogen. Under such circumstances, when the 
lungs cannot carry off the requisite quantity of 
carbon, nor the adipose tissue compensate for its 
diminished activity by the deposition of fat, the 

JiVer, taking on an mcwasfc^ ^Oassti^ ^ft&T^tea an 



BXCRSTION OF FAT. 403 

extxaordinary quantity of bile. In this manner 
the saperfluout carbon, instead of being removed 
in the ordinary mode, by the pulmonary artery 
through the lungs, under the form of carbonic 
acid gas, is excreted by the vena portee, through 
the liver, under the form of bile, while the super- 
abundant hydrogen is removed by the increased 
quantity of perspiration ; and thus the accumu- 
lation of these inflammable matters in the system 
16 effectually prevented. 

911. By the deposition of fat in the adipose 
tissue material assistance is afforded to the excre- 
tory action of the skin, the lungs, and the liver. 
Fat is composed essentially of carbon and hydro- 
gen ; it contains no nitrogen and very little oxygen. 
It is deposited whenever an excessive quantity of 
nutritive matter is poured into the blood, and 
especially when at the same time the different 
secretions and excretions ordinarily formed from 
the blood are diminished. The primary object of 
this deposition is to relieve the circulation of a 
load which would embarrass and ultimately stop 
the actions of life. It serves, however, a secondary 
purpose, that of forming a storehouse of nutritive 
matter, duly prepared for supplying the wants of 
the system, in case the body should be placed 
iinder circumstances in which the digestive organs 
eau no longer receive food or no longer convert it 
into chjle. 

912, TbuB hjbemating animals, ^\aOa. ^^ai. 



404 THE PUILOSOPHT OF HEALTH. 

many months without taking food, accumulate a 
store of fat before they fall into the state of torpor. 
Marmots and dormice subsist on this store during 
the winter, and hence, when spring awakens them 
from their torpor, they are always in a state (d 
extreme emaciation. Birds and other animals 
which live on food procured with difficulty in the 
winter, become unusually fat in the autumn. 

913. During fever and other acute diseaaes, 
when little food is received, and still less converted 
into chyle, the extreme emaciation which the body 
imdergoes is owing partly to the disappearance of 
the fat, which is taken up by the absorbents and 
carried into the blood, in order to compensate for 
the deficiency of nutrient matter supplied by the 
digestive organs. 

914. The chief depositories of the fat are 
those intersticial spaces of the body in which a 
certain quantity of soft but tenaceous substance is 
required to obviate pressure or to preserve sym- 
metry. A large quantity is also placed imme- 
diately beneath the skin; in the interstices of 
muscles; along the course of blood-vessels and 
nerves ; in the omentum, where it is spread 
like a covering over the viscera of the abdomen 
(fig. CLxx. 7 ) i in the mesentery and around the 
kidneys. 

915. Fat is a bad conductor of heat; conse- 
quently the layer wlaidi \s «^x^»A. w«t xW exter- 
na] surface immedia\.e\^ Aoeu^cC^i ^'^ ^\^^^ -^^ 



USES OF THE FAT. 405 

that which is collected in the interior of the 
smeutum, must he useful in preserving the heat 
}f the hody. Fat persons bear cold better than 
ean persons. Animals which inhabit the northern 
climates, and the fishes of the frozen seas, are 
mveloped in prodigious quantities of fat. Where 
:he accumulation of this substance would produce 
ieformity or interfere with function, as about the 
oints, in the eyelids, within the skull, not a par- 
icle is ever deposited. About the joints it would 
mpede motion ; in the eyelids it would render the 
*ace hideous and obstruct vision ; and within the 
jkull, a cavity completely filled with the brain, an 
)rgan impatient of the slightest pressure, had a 
iuhstance been placed, the quantity of which is 
iable to be suddenly trebled or quadrupled, 
changes in the system which now produce no in- 
5onvenience would have been fatal. Thus, while 
provision is made at once to exonerate the system 
Tom too great a load of nourishment, and to lay 
ip the superfluous matter, as in a magazine, to be 
-eady for future use, the most extreme care is 
aken to deposit the store in safe and convenient 
ituations. 

916. The excretory organs and processes, 
litherto considered, have for their object the 
'emoval from the blood of its superfluous carbon 
md hydrogen ; the element peculiar to the animal 
3odj^ Hzote, 18 eliminated by tlve \^<dLii€^^^ ^^i^« 



406 THE PHILOSOPHY OF HVALTH. 

dular organs which possess a highly complex 
structure. 

917. But hesides the remoyal of the super- 
fluous azote, the fluid secreted by the kidneyB 
would appear to be a general outlet for whatever 
is not required in the system, and for the remoTBl 
of which no specific apparatus is provided. Che« 
mical analysis shows that, in different states of 
the system, the £Dllowing substances are contained 
in this fluid : — water, free phosphoric acid, phos- 
phate of lime, phosphate of magnesia, floric add, 
uric acid, benzoic acid, lactic acid, urea, gelatin, 
albumen, lactate of ammonia, sulphate of potarii, 
sulphate of soda, fluate of lime, muriate of soda, 
phosphate of soda, phosphate of ammonia, sul- 
phur, and silex. 

918. This catalogue itself suggests the idea 
that when any matter employed in carrying on 
the functions is in excess, or when it has become 
decayed, or is decomposed and is not eliminated 
by any other excretory process, it is taken up by 
the absorbents, poured into the veins, and so 
conveyed in the course of the circulation to the 
kidneys, by which organs it is separated from thb 
blood, and thence by an appropriate apparatus 
carried out of the system. 

919. The specific matter secreted by the 
kidneys is that termed urea; a substance of a 

resinous nature, higYA^ wvysmXyl^^* CyoL^^haxac* 



BXCBBTORY FUNCTION OF THE KIDNEYS. 407 

by which the animal is diBtinguished from the 
it is its locomotion. The organ by which the 
nal is rendered capable of performing the 
ction of locomotion is muicle or flesh. The 
is of muscle is fibrin, and the basis of fibrin 
te. There must be in the animal body an 
ndant supply of fibrin, and consequently a 
portionate abundance of azote. Azote is intro- 
ed into the system partly by the food and 
tly by the lungs. That there may be a suffi- 
icy for all occasions, more is introduced than is 
sssary on ordinary occasions, and a special 
et is established for the excess through the 
(leys. 

120. Organs appropriated to the removal of 
stances from the blood, capable of becoming 
sterious by their accumulation, generally in a 
e of health perform their office so perfectly 
t the matters which it is their part to excrete 
eliminated almost as quickly as they enter the 
)d, so that they are seldom present in the cir- 
iting fluid in sufficient quantity to be detected 
the most delicate chemical tests. But by 
removal of the excretory organ, or by the 
pression of its function, the excretory matter 
iimulates in the blood, and is then readily 
scted. A decisive experiment disclosed that 
t is the case with regard to urea. The kidneys 
€ removed from a living animal. TVi^ q^t^- 
did not appear to be productive ol Tft».\«wa^^ 



408 THE PHILOSOFHT OF HEALTH. 

injury for some time; but at length symptoms 
denoting the presence of a poison in the blood 
arose, and the animal died. The blood was 
carefully examined after death. It was found to 
contain a much larger quantity than ordinary of 
the peculiar animal substance which enters into 
the composition of the serosity of the blood 
(225). On subjecting this substance to the 
action of various re-agents, and also on redacing 
it to its ultimate elements, it was found to re- 
semble urea; to be, in fact, nearly identical 
with urea as contained in the urine. From this 
experiment it became manifest that the source of 
the urea is the serosity of the blood. It is pro- 
bable that the chief office of the kidney is to sepa- 
rate the urea from the other ingredients of the 
blood, and to convey it to the organs which are 
destined to carry it out of the body. 

921. It is estimated that about a thousand 
ounces of blood pass through the kidneys in the 
space of an hour ; itself a sufficient indication of 
the importance of the excretion performed by this 
organ, and an adequate source of the matter actu- 
ally excreted, although, under ordinary circum- 
stances, distributed through the circulating mass 
in quantities so minute as to be almost inappre- 
ciable. 

922. From the power of absorption possessed 
by the veins of the ^XoTM^Oa. «xA VoXn^tkies, firom 

the connexion provedi to "^ eeXsi^^AXu&ww^ 



EXCRETORT FtTKCTION OF THE INTESTINES. 409 

be venous and absorbent systems, and from the 
iscovery of Lippi, that several absorbent branches 

I the abdomen terminate directly in the pelvis ol 
:ie kidney, that is now an established fact whicli 
ras long a conjecture, that there exists a short 
oute from the stomach to the kidneys, so that the 
xtreme rapidity with which certain substances 
aixed with the aliment appear in the fluid secreted 
J the kidneys is no longer a matter of wonder. 

923. Out of the body urea jiutrifies with great 
apidity. When retained in the system by the 
ztirpation of the kidney, or by placing a ligature 
Tound the ureter, such is the septic tendency 
iommunicated to the blood that signs of putres- 
ency become manifest even during life, and after 
leath all the soft parts of the body are reduced to 
. state of putrefaction with extreme rapidity. 
The suppression of the secretion in the human 
»ody, or the undue retention of the matter secreted, 
nduces fever of a malignant kind, in which the 
ymptoms that denote a highly putrid taint in the 
ystem are rapidly developed. But for the labour 
»f the kidney, then, a substance would accumulate 

II the blood, which would quickly lead to the de- 
omposition of the body. 

924. It has been shown that the mucous 
nembrane which lines the alimentary canal is 
tudded in its whole extent with glands, whicli 
ecrete from the blood a large quaiitXt^ oi ^ixiA, 

VOL, II, T 



410 THE PHILOSOPHY OF HEALTH, 

These secretions go on without interruption, iwhe- 
ther food be taken or not, so that there may be 
copious alvine evacuations though not a particle 
of food enter the stomach ; and the separation of 
the matter eliminated from the blood by this 
extended membrane can no more be dispensed 
with than that by the skin or the lungs. There 
is, too, a most intimate sympathy between the 
secretion of the membrane that lines the internal 
surface of the body and that carried on by its 
external covering ; any disorder of the one imme- 
diately and powerfully disturbs the natural course 
of the other : hence the diarrhoea, so often pro- 
duced by the application of cold to the external 
skin, and the diseases of the skin, so constantly 
connected with a disordered state of the mucous 
membrane of the intestines. 

925. It is the special office of the large intes- 
tines to prepare for its removal, and to carry out 
of the system the residue of the aliment, together 
with the excrementitious portion of the bile. 

926. It was calculated by Haller, that the different 
excretory organs remove from the system every 
twenty-four hours twenty pounds of matter. Of 
this total loss sustained daily by the human body, 
It was estimated that four pounds are removed by 
the skin, four pounds by the lungs, four pounds 
by the kidneys, and eight pounds by the intestinal 
csLu&U In ihia e«.\ivxu^X«i>^\i\^ \^ ^\]Aidered toi 



REJLATIYE PROPORTIONS* 41 1 

large, especially that by the intestinal canal, the 
quantity stated must be understood as denoting 
the maximum of each secretion. 

927. Supposing the ingestain twenty-four hours 
to be of food 6 pounds, or 96 ounces, and of 
oxygen retained in the system 4 ounces, in all 
100 ounces, it is estimated that the egesta will 
be, in twenty-four hours, by the skin, 34 ounces, 
by the lungs 17 ounces, by the intestines 6 ounces, 
by the kidneys 40 ounces, and by various other 
excretions 3 ounces, in all, 100 ounces. These 
calculations must of course be taken only as ap- 
proximations to the truth, and as ascribing rather 
the relative than the positive quantities of matter 
excreted. 

928. Whatever be the absolute quantity or the 
form of the excretions, it is clear, from the pre- 
ceding account, that there is constantly removed 
from the system by the skin a large portion of 
hydrogen and some carbon ; by the lungs a large 
portion of carbon and some hydrogen; by the 
liver a large portion of hydrogen and some car- 
bon ; by the kidneys a large portion of azote ; by 
the large intestines the residue of the aliment; 
while, by the deposition of fat, the surperabun- 
dant nutriment withdrawn from the current of the 
circulation is laid up in store in some safe part of 
the body. 

929. Most of the processes "w\nc\i \i«s^\ste^ ^^ 
9cribed are mutually compensa^ug %xi^ n\&«xv^>^^< 



412 THE FHII.OSOFHY OF HEALTH. 

Besides the office wbicb each habitually performs, 
it is capable of having its action occasionally in- 
creased, for the purpose of supplying the deficiency 
of one or more of its fellows. If perspiration by 
the skin languish, transudation by the lungs in- 
creases ; if neither the skin nor the lungs be able 
to remove the superfluous hydrogen and carbon, 
these inflammable substances are carried out of 
the system by the liver in an augmented secretion 
of bile. If the action of the liver be diminished, that 
of the kidney is increased ; and if the secretion of 
urine be suppressed, the secretion of bile is aug- 
mented. When the absorbents are oppressed by 
the quantity of fluid poured into the stomach, or 
when the system is at the point of saturation, 
and no absorption can go on^ the veins take up 
the superfluous liquids, pour them into the circu- 
lating current, and bear them to the kidneys, by 
which organs they are rapidly separated from the 
blood, and carried out of the body. The weak- 
ness of one organ is compensated by the strengtb 
of another ; the diminished activity of one process 
is equalized by the increased energy of some other 
to which it is allied in nature and linked by sym- 
pathy; and thus the evils which would result 
from the partial and temporary failure of an im- 
portant function are obviated by some vicarious 
iabour, until the enfeebled organ has recovered its 
tone, and the Ilatul«^. Wk»-^<^ '^i ^^^>ssAtian8 is 

refltored. 

930. The condU\oxv ta^c^a^vm^Vi ^^^^assSaa 



CONDITION OF EZC&EMENT1TI0V8 HATTER. 413 

particles of organized bodies, from their long 
continuance in the system, which induces the 
necessity for their excretion, is not known. The 
chemical elements of the excretions are the very 
same as those which constitute the organized tex- 
tures and the nourishment by which they are sus- 
tained. Carbon is the basis of the organized 
body; yet all living bodies, without exception, 
excrete carbon. Oxygen, hydrogen, and azote, 
also, virithout which life cannot be maintained, if 
retained in the system beyond a given time, are 
incompatible with the continuance of life. During 
the chemical changes which these elementary 
particles undergo, ia the course of the vital pro- 
cesses, they appear to enter into some combina- 
tion, which is no longer compatible with the pecu- 
liar mode in which they are disposed in organ- 
ized and living structures. And one such change, 
of a very remarkable nature, has been observed, 
which, it is conceived, has a considerable share in 
rendering their constant expulsion and renovation 
indispensable. 

931. Out of the condition of life the compo- 
nent elements of organized bodies readily combine 
so as to form crystals ; the peculiar combinations 
by which they form the constituent textures of 
organic structures are never crystalline. No 
crystal is ever seen in the seat of a living and 
growing vegetable cellule; no cr^«la\. H» ^^«^ 
found &a a constituent part of ainraaX TsiieaOotvxi^' 



414 THB PHILOSOFBT OF HEALTH. 

Whenever a crystal occurs in an organized body 
it is always the result either of disease or of some 
artificial process, or else it is an excretion separated 
from the nourishing fluid and the useful textures. 
Every one of these textures contains, even in its 
minutest parts, saline and earthy, as well as vege- 
table or animal, matter. Why do not these saline 
and earthy particles as readily combine to form 
crystals in the organic as they do in the inorganic 
body ? They never do. In the organic body these 
saline and earthy particles are always so arranged 
that they are diffused through the membranous 
fibres or cells, never concentrated in crystals. 

932. On the other hand, the elements con- 
taining the peculiar matters of excretion are 
generally in such a state of combination as readily 
to assume the crystalline form, either alone or in 
the simplest further combinations of which they 
are susceptible. It seems probable that this cir- 
cumstance may be, at least in part, the cause which 
necessitates their expulsion, and it is certain that 
some such general principle must determine the 
incompatibility of the matters of excretion with 
the life of the structures. 

933. The ultimate object of the processes in- 
cluded in the function of excretion is to maintain 
the nutritive fluid iu a certain chemical condition. 
Into the combinativoTi o€ the blood there most 

enter certain conatitawiXa^ %xA\Jci^^"fe \s^^ 
certain relative 1pto^ot^o^x%^wA\slx.^^'^^av \\ 



ULTIMATE OAJECT OF EXCRETION* 415 

the salts be diminished or in excess, if the fibrin, 
or the red particles, or the serum be abundant or 
defective beyond a certain degree, either the ne- 
cessary chemical elements are not present, or not 
present in the form necessary to their entering; 
into the requisite combinations; the result is, 
that a proper nutritive fluid is not formed, and 
consequently due nourishment is not afforded to 
the textures nor due stimulus to the moving 
powers ; there is either too much nutriment and 
stimulus or too little ; in the one case the machine 
is exhausted and worn out, and in the other it is 
clogged and stopped. 

934. The capillary arteries of the skin, and of 
all the other tissues into the composition of which 
gelatin enters as a constituent, necessarily pour 
carbon into the capillary veins at the moment 
they convert albimien into gelatin (539). The 
veins, receiving in their course more and more 
carbon from the arteries, at length become loaded 
with this element, and in order to get rid of the 
excess they bear it to the limgs, where it is expelled 
by the act of expiration under the form of carbonic 
acid gas. On the other hand the chyle, gradually 
becoming firmer and more condensed by the series 
of changes which it undergoes from its first forma- 
tion in the duodenum to its admixture with the 
lymph in the receptacle of the chyle, and with the 
blood in the subclavian vein, la Yv\XTi\fe^ \a x^^ 
ieart and thence to the lungs, vjYieT^ VX. ^^e» ^^ ^ 



416 THE PHILOSOPHY OP HEALTH. 

large portion of its watery particles, also by the 
act of expiration f under the form of aqueous 
vapour. This excretion of its watery particles is a 
necessary part of the process of completiou by 
which the weak albumen of the chyle is converted 
into the strong alhimien of the blood (703. 3). 
How completely analogous then is this excretory 
process in the plant and in the animal! How 
precisely the same is the action of the leaf and of 
the lung! The leaf dissipates the superfluous 
water of the crude sap, concentrates its organic 
principles, and brings it into the chemical con- 
dition which constitutes the proper juice of the 
plant ; the lung removes the superfluous water of 
the chyle, ooncentrates its organic principles, and 
completely assimilates its chemical nature into 
that of the blood. 

935. It is the same with every other process of 
excretion ; its uniform result is to alter the che- 
mical composition of the nutritive fluid, to restore 
it to a state of concentration and purity. Excre- 
tion then is appropriately termed a depiiratiug 
process. 

936. The effect of the suppression of excre- 
tion, when the suppression is complete, is appalling. 
Stop the respiration, that is, suspend the depurat- 
ing action of the lungs, carbon accumulates in the 
venous blood ; carbon mixes with the arterial 
blood ; in half a m\xw3L\a\)afc. W^^^ ^wdn^ in the 

arteries is evidentXy A»xYexit.^\ *mN!sa^-^3^«sNsB».^ 



ULTIMATE OBJECT OF EXCRETION. 417 

c minute it is of a dusky hue ; in a minute and a 
half it is quite black ; every particle of arterial 
blood has now disappeared^ and the whole mass is 
become venous. With the first appearance of the 
dusky hue great disturbance is produced in the 
system ; the instant it becomes dark sensibility is 
abolished ; in a few minutes after it is black the 
power of the heart is so enfeebled that it can no 
longer carry on the circulation, and in a few 
minutes more its action wholly ceases, and can 
never again be excited. The brain feels the poison 
first, and is first killed ; but the heart cannot long 
resist the fatal influence. 

937. Stop the excretion of the kidney by the 
extirpation of the organ, or the suppression of its 
secretion, urea accumulates in the blood; the 
poison, after a short time, begins to work ; fever is 
excited, and then, with fearful rapidity, fever is 
followed by coma, and coma by death. 

938. Stop the secretion of bile, a poison ac- 
cumulates in the blood as potent, producing in- 
sensibility and death as rapidly, as that generated 
by the suppression of the depurating action of the 
kidneys. 

939. Only obstruct the secretion of bile, merely 
prevent its due elimination from the blood, just in 
proportion to its suppression does the system 
suffer from languor, lassitude, and inaptitude fot 
every muscular and mental exertion. 

940^ How do the internal OTgan^ ^vikffet v4\v«ol 



418 THE PHILOSOPHY OF HEALTH. 

the excretion of the skin is deficient, and how 
numberless and hideoos are the diseases of the skin 
when the depurating process of the alimentary 
canal is suspended \ 

941. When, on the contrary, all these excre* 
tbns are well and duly performed, how regular and 
tranquil, yet how full and strong the flow of the dr- 
culatiug current ; how rich the stream poured by it 
into every organ ; how healthfully exciting its in- 
fluence on them all ; how gentle, how efficient, eyery 
organic action ;. how complete the absence of all 
note or sensible intimation that any such action is 
going on, yet how delicious the consciousness pro- 
duced by its soundness and vigour; how acute the 
sense, how bounding the motion, how quick the 
percipience ; how the pure blood mantles in the 
cheek and difiuses its sparkling colour over all 
the transparent complexion ; how the jocund 
spirits laugh from the eyes ; how the inteUectual 
and sympathizing mind beams forth from them 
with a higher and holier happiness ! How woor 
derfully beautiful is such a human body, and how 
magnificently endowed in its capacity to give and 
to receive enjoyment ! 

942. There are two adjustments, with r^^ard 

to the excretions, carried on by organized bodies, 

which can never be contemplated with sufficient 

adiniration. It iisa )Q«av i»L\!L^ ^hown (464 et seq,) 

that the relatioii eftt&>aYu^e^\«to«^^'^^Nw^ ^»A 

classes of organized \>^m%^ "v^ «^^ ^^^ "^^ « 



ADJUSTMENTS. 419 

crementitious matter of the plant is nutritious 

to the animal, and the e&crementiticms matter 

of the animal is nutritious to the plant; and, 

consequently, that the two orders of living heings 

maintain the world, which is given them as their 

inheritance, in a state of perpetual adaptation for 

the life and health of each other; the animal 

receiving healthy stimulation from that which is 

poisonous to the plant, and the plant being 

nourished by particles which the animal throws off 

as exhausted and useless. And this relation 

naturally suggests that so beautifully described by 

Milton : — 

Flow*rB and iheir fruit, 
Man's nourishment, by gradual scale sublimed 
To vital spirits aspire, to animal. 
To intellectual ; give both life and sense, 
Fancy and understanding ; whence the soul 
Reason receives. 

943. Secondly, the particles thrown off by 
<»rganized bodies are rendered, in the very act of 
their dissipation, subservient to purposes of utility 
and pleasure. How these poisonous elements are 
converted into the pabulum of life and health has 
been shown. To a being with the senses and 
faculties of man, how loathsome might these 
particles have been rendered diuring the period of 
their transition from one organized kingdom to 
the other ! And if disagreeable at all, how con- 
stantly forced upon his sense, wherever he might 
he, during every moment o£ "hia 'vi^L\\v% Vwx't'^^ 
au8t these objects of disgust \\«tve)aeeu\ ^>q^.Vs^ 



420 THE PHILOSOPHY OF HEALTH. 

does the matter actually stand? The excretions of 

the plant are the very particles that, poured 

'* Into the blissful field through gloves of myrrh, 
And flow'ring odours, cassia^ nard, and balm«'' 

create '* a wilderness of sweets." It is as these 

exhalations are passing off from the economy to 

which, if retained, they would be noxious (851), 

that they become 

'< Exhalations of all sweets 
That float o*er vale and upland ;" 

and which refresh and delight even more than the 
forms and colours of the "aery leaf" or "the 
bright consummate flower." 

944. And the human body, when the func- 
tions of its economy are sound and vigorous, is 
fresh and fragrant as the flower (862) ; and by 
that intellectual faculty by which man is capable 
of associating his conception of beauty and delight 
with whatever object has been the source of exqui- 
site gratification, the fragrance of the flower is 
but suggestive of what, to him, is inexpressibly 
sweeter and dearer. 

'^ As new waked from soundest sleep. 
Soft on the flow'ry herb I found me laid 
In balmy sweat, which with his beams the sun 

Soon dry'd 

By quick instinctive motion up I sprung, 

- And upright 



Stood on my feet- 



All things smiled 



With fragrance, and vrVWi \o^ tay h. art o*erflow*d. 
MyseU I then perused, waA\YDa!ia>j Vvxt^ 
Survey'd, and sometime* vieii\.,wiCi%w^^'c«sv^^ 
With supple joints, as V\Ne\>j N^%^^a^fteL. U.xv.^ 



ADJUSTMENTS. 421 

Fresh lily, 

'Tib her breathiog that 

Perfumes her chamber thus. Shaxspbauk. 

The very air 

With her sweet presence is impregnate richly, 
As in a mead that's fresh with youngest green 

Some fragrant shrub exhales 

Ambrosial odours 

Charming present sense* 
And sure of memory ; — so her person bears 
A natural balm — distilling incense. 

** Death of Marlowe/' by R. H. Hornb. 



422 



CHAPTER XIV. 



OF NUTRITION. 

Composition of the blood — Liquor sanguinis — Recent ac- 
count of the structure of the red particles — Formation 
of the red particles in the incubated egg — ^Primary 
motion of the blood — ^Vivifying influence of the red 
particles — Influence of arterial and venous blood on 
animal and organic life — Formation of human bloodr- 
Course of the new constituents of the blood to the lungs 
— Space of time required for the complete conversion of 
chyle into blood after its first transmission through the 
lungs — Distribution of blood to the capillaries whec 
duly concentrated and purified — Changes wrought upon 
the blood while it is traversing the capillariies — Evidence 
of an interchange of particles between the blood and 
the tissues— Phenomena attending the interchange^ 
Nutrition, what, and how distinguished from digestion 
— How the constituents of the blood escape from the 
circulation — Designation of the general power to which 
vital phenomena are referrible — Conjoint influence of 
the capillaries and absorbents in building up structure^ 
Influence of the organic nerves on the process- 
Physical agent by which the organic nerves operate— 
Conclusion. 

945. The ob^ecX. oi x^v^ ^\«^\&t ^-mx. ^€ the 
processes hitheno de^criXi^^Na xa ^^^^ ^^ ^>5n. 



THE LIQUOR SANGUINIS. 423 

live fiuid, and to briDg it to the requisite state of 
purity and strength. Recent researches into the 
composition of the nutritive fluid confirm the 
general correctness of the account already given 
of it. (211 et seq.) 

946. When examined as it is flowing in the 
finest vessels of a transparent part of the body, 
or immediately after it is abstracted from the 
trunk of a vein or artery, before coagulation 
(218) takes place, the blood is seen to consist of 
a colourless fluid, through which is diflused a 
countless number of minute solid particles of a 
red colour. The colourless fluid is called the 
liquor sanguinis, and the solid particles the blood 
corpuscles or the red particles. 

947. By the process of coagulation, the phe- 
nomena of which have been fully described 
(219 et 8eq,\ the blood spontaneously separates 
into a clear fluid of a yellow colour called serum 
or blood-water, and into a solid mass termed the 
clot or the crassamentum. The serum, which 
must be carefully distinguished from the liquor 
sanguinis, is the fluid formed from the blood by 
coagulation ; the liquor sanguinis is the fluid part 
3f the blood which exists before coagulation. 

948. The liquor sanguinis contains in solution 
a large quantity of animal matter, fibrin (228), 
which separates spontaneously in a solid form on 
'coagulation; the serum also contam« a c^vcl\!\\:^ ^i 
nJmal matter in solution, albumen C^^4l)^ "vVviJKv 



424 THE PHILOSOPHY OF HEALTH. 

does not separate in a solid form spontaneously, 
but only on the application of heat, acids, alcohol, 
&c. (224.) The animal matter, the fibrin, which 
separates spontaneously from the liquor sanguinis 
in a solid form, constitutes one part of the clot, 
and the other part of it consists of the red parti- 
cles which floated in the liquor sanguinis. 

949. Thus, by coagulation, the liquor san- 
guinis separates into a portion which ^ remains 
fluid, the serum ; and into a portion which becomes 
solid, the fibrin ; while the fibrin, as it is passing 
from the fluid to the solid state, entangles the red 
particles, and both together form the clot ; conse- 
quently the liquor sanguinis contains in solution 
two kinds of solid matter, fibrin and albumen; 
while the serum contains in solution only one 
kind of solid matter, albumen. 

950. The solution of fibrin in the liquor san- 
guinis, and its spontaneous solidification during 
the process of coagulation, has been shown by 
Professor MuUer in the following mode. Having 
carefully collected blood from the femoral artery 
of the frog, and also from the heart laid bare and 
incised, and having brought a drop of this puie 
blood under the microscope, and diluted it with 
serum, so that the red particles were separated 
from each other by distant intervals, he observed 
that there formed m \\i»&^ mtervals a coagulation 

of previously diBsoVve^ TftaXXKi^Vj ^\sv^*^^^!e^ 
rated red particleft vjeit cssKaR^^J^ Xan^sSiaRx. ^\ 



STKUCTUKK OF THE RBD PARTICLES. 425 

raising, with a Beedle, the coagulum occupying 
the intervening spaces, this solid matter was 
obtained free from red particles. The blood cor- 
puscles of the frog are rendered, by a powerful 
microscope, so large, that this operation may be 
performed with the greatest distinctness. In con- 
sequence of the minuteness of the red particles of 
human blood they pass, with the liquor sanguinis, 
through filtering-paper ; but those of the frog, 
being four times larger, are kept back by the 
filter, while the liquor sanguinis percolates through 
as a clear fluid, and then coagulates. This colour- 
less coagulum is so transparent that it is not even 
detected, after its formation, until it is raised out 
of the fluid with a needle. It gradually thickens 
and becomes white. It is the fibrin of the blood 
in its purest state. 

951. Professor Milller's account of the struc- 
ture of the red particles differs in a material point 
from that given (231 et seq,). He agrees that 
they are rounded bodies (fig. cxii. 1), generally 
of the same size, though some are seen larger 
than common, but never double the mean dia- 
meter; that they are always quite flat (232) ; that 
in a certain light they look as if they were hol- 
lowed out from the edges to the centre (fig. 
CXII. 1) ; but, he adds, 'Uhat this spot is a real 
depression, as some think, appears to me in the 
highest degree improbable; for 1 \i&.N^ %.\.\&sX 
convinced myself that the blood cot^m'^^'^ ^^ 



426 THB PHILOSOPHY OF HEALTH. 

man and the mammalia contain a very small 
nucleus of the diameter of the flat corpuscle. 
My ohservations prove heyond doubt that the 
blood corpuscles of frogs and salamanders (fig. 
cxii. 4) contain a nucleus entirely different in its 
chemical relations from the outer layer. With 
one of Frauenhofer's microscopes I have seen very 
distinctly, in the blood corpuscles of man an 
exceedingly small, round, well-defined nucleus, 
yellower and brighter than the transparent cir- 
cumference. When the blood corpuscles are 
mixed, under the microscope, with acetic acid, 
the shell is almost entirely dissolved, and these 
small nuclei, which are seen with great difficulty 
in human blood, remain, while those of the frog 
appear, very evidently the nuclei observed earUer 
in the blood corpuscles. In man, the nuclei 
within the corpuscles are so small, that the dia- 
meter does not exceed the thickness of the flat 
corpuscles." 

952. The enveloping capsule is stated to he 
soluble in water, while the internal nucleus is inso- 
luble ; but the capsule is not soluble in serum ; 
the albumen and the salts contained in the serum 
probably rendering it insoluble. The colouring 
matter of the capsule, which gives the red colour 
to the blood, is called hsematosin. Lecanu consi- 
ders the capsular «\\b«>taxice as a combination of a 
specific colourmg ina\X«t^ 'vVv^'Va. <:»^ 5^SckJ&s^ 
and of albumen ; WtlA^\^«t t^^«x^ \^. ^^ 'Sowk 



FIRST FORMATION OF TBB BLOOD. 427 

containing a quantity of iron. The latter phy- 
siologist states that the opinion of Brande, that the 
amount of iron in hsematosin is not greater than 
in serum and other animal substances, has been 
refuted by Berzelius and Engelhart. The iron is 
not an accidental ingredient obtained from the 
food ; for iron has been found in the blood of a 
new-born animal that has never even sucked. 
According to Berzelius the colouring matter of the 
blood contains a quantity of iron corresponding to 
somewhat more than a half per cent, its weight of 
metallic iron, and he thinks it most probable that 
the iron exists in the blood in the metallic state, 
and not as an oxide. 

953. By carefully watching the development 
of the chick in the incubated egg, the first forma- 
tion of the red particles can be distinctly seen. 
The blood in the new being, which is elaborated 
before the existence of the vessels that are to con- 
tain it, is formed from the substance of the germ 
or from that of the germinal membrane, and is 
augmented by the blood of the egg, which is the 
substance of the yolk. First, a number of gra- 
nules are produced from the substance of the 
yolk. These subsequently lose their granular 
appearance, and ' become translucent On the 
translucent ring is produced the nucleus of the 
blood corpuscles. When completely formed, the 
blood corpuscles of the bird, «* oi ^ ^'^ ^^-v- 
mab below the bird in the acate oi oi||,«xvyl'^^^^- 



428 THE PHILOSOPHY OF HEALTH. 

are of an elliptical figure, and quite flat (fig. czii. 
4, 5) ; but when first produced they ace rounded 
globules, not flat, and they gradually assume their 
proper and permanent form ; it is only on the ns& 
day of incubation that they b^;in to be elliptical, 
by the ninth day they are all elliptical (fig. cxii. 
4, 5). 

954. The substance of the fluid yolk is thus 
chained into blood without the action of any spe- 
cial organ ; for, as yet, no organs such as liTer, 
spleen, or lungs, exist. When the formation of 
the blood has arrived at a certain point, it begins 
to be in motion. The blood is seen to be in mo- 
tion before the heart can be observed to beat 
The germinal membrane arising out of the enlaiged 
germinal disk soon exhibits a thin upper layer 
(serous membrane) and a thicker under layei 
(mucous membrane). There is also formed in 
the middle of the germinal membrane around the 
appearing trace of the embryo a translucent space, 
the area pelliLcida, The exterior of the germinal 
membrane remains opaque, and this opaque por- 
tion becomes divided by a definite boundary into 
an external and internal annular space in from 
sixteen to twenty hours. This separation en- 
closes one part of the opaque portion of the ger- 
minal membrane, which surrounds the interior of 
translucent space of the germinal membrane, and 
18 termed area dciscuIoso, \sfec«x»fc ^Ow^ "^ks^A^ ^ad 
veBseh form the iniieT \wB!i.i oi^ema %^vi%. 



INFLUBNCB OF THB RED PARTICLES. 429 

955. As far as the area vasculosa extends, a 
mular layer is presented between the two layers 

the germinal membrane, which soon divides 
lO numerous granular isolated particles with 

nslucent intervals, in which the blood collects, 
St in the form of a yellowish, and then of a 
Idish fluid ; first distinctly in the periphery of 
i area vasculosa, from which it is seen to flow 
vards the heart before the heart beats. 

956. The blood exerts its vivifying influence 
iefly by the red particles. If an animal be 
id to fainting, and pure serum be injected into 

vessels, re-animation does not take place ; but 
:he blood of another animal of the same species 
injected, the animal which was apparently dead 
quires new life at every stroke. 

957. The fibrin may be removed from the 
>od without injuring the red particles. If the 
rin be abstracted, and a mixture of the red par- 
ies and the serum be brought to a proper tem- 
rature, and injected into the veins of an animal 
.d to fainting, re-animation is eflected. 

958. If the blood of an animal of another spe- 
s be injected whose red particles are of the same 
m, but of a different size, re-animation is in- 
id eflected, but the restoration is imperfect ; the 
;anic functions are oppressed, and languish, and 
ith takes place generally within the sixth day. 
e eame effects follow, if a mixlate oi «K?Evissi «x>i^ 



430 TBR PHILOSOFHT OF HEALTH. 

red particles of the blood of a different species be 
injected. 

959. If blood with circular particles be in- 
jected into the vessels of an animal whose blood 
corpuscles are elliptical, the most violent effects are 
instantly produced; such blood acts upon tbe 
nervous system like the strongest poisons ; and 
death usually follows with extreme rapidity after 
the injection of a very small quantity. Thus, if a 
few drops of the blood of the sheep be injected 
into the vessels of the bird, the bird is killed in- 
stantaneously. It is very remarkable, that the 
blood of the mammalia should be thus fatal to the 
bird. The effect cannot be dependent on any me- 
chanical principle. The injection of a fluid with 
particles, the diameter of which is greater than 
that of the capillary blood-vessels would of course 
destroy life by stopping the circulation ; but the 
blood corpuscles of the mammalia are much 
smaller than those ot the bird ; yet the pigeon is 
killed by a few drops of mammiferous blood ; and 
the blood of the fish is rapidly fatal to all the 
mammalia as well as to birds. 

960. It is manifest, both from observation and 
experiment, that arterial blood is far more neces- 
sary to the support of the animal than of the 
organic life. When in asphyxia the communica- 
tion of atmoapheiic air with the lungs is sus- 

pejided, the fimctioiia o^ ^^ \i\^M:i«x^^^isisKsa^aft^ 



INFLUENCE OF ARTERIAL BLOOD. 431 

bility and voluntary motion are lost tbe mo- 
. venous blood circulates in the arteries of the 

I. It has been shown (476), that if this 
continue, the animal life is destroyed in a 

ite and a half; but that the organic life is not 
iguished for many minutes, and sometimes 
5ven for several hours. 

II. It sometimes happens that the commu- 
ion between the pulmonary artery and the 
., and between the right and left auricle, 
h naturally exist in the foetus, is continued 

birth. In persons having this state of the 
ilation, called ceruleans, some portion of 
us blood is always mixed with arterial blood. 
lis case the various processes of secretion and 
ition, the entire circle of organic functions, are 
little disturbed ; while the animal functions 
leranged in a remarkable degree. The mind 
:ak and inactive, and the muscular power is 
eble, that the least exertion produces a sense 
ffocation ; and, if the muscular effort be con- 
id, occasions fainting, and even suspended 
nation. 

12. But while venous blood is in no case 
ble of supporting sensation and voluntary 
on, there are decided cases in which secretion 
fected, at least in part, from venous blood, as 
bile from the venous blood that circulates 
ugh the liver in man and a\\ X\i^ TCi<dxcaccQSxi&^ 



•032 THE PHILOSOPHY OF HEALTH. 

and the urine which is formed from venous blood 
in some of the lower orders of animals. 

963. The proper nutritive fluid of the human 
body is directly formed from chyle, lymph, and 
venous blood ; that is, partly from new matter in- 
troduced into the system from the external world, 
and partly from matter which has already formed 
a constituent part of the body. The new matter, 
the white chyle, is prepared partly by the action 
of the digestive fluids upon the food, and partly 
by tb^ addition to the digested food of highly 
animalized substances, endowed with assimilative 
properties, by which the product is progressively 
approximated to the chemical composition of the 
blood. The old matter consists partly of the clear 
lymph, contained in the lymph vessels, and de- 
rived from the interior of the organized parts, 
particles which have already formed an integrant 
portion of the tissues and oi^ans ; and partly of 
the dark venous blood, the residue of the proper 
nutritive fluid, after the latter has yielded to the 
system the new matter required by it, and has 
given ofl" from the system its superfluous and 
noxious particles. 

964. In the duodenum and jejunum the new 
matter, the chyle, contains albumen ; biit it is 
without coagulable fibrin : it acquires fibrin in the 
/jmph vessels otv \t^ "w^.^ ^^ *^® veins. 

965. In tlve ch:^\^ ^q\svs\s» «^\iwct% \sq1 the 



PROGABSSIVE ELABORATION. 43^ 

chyle corpuscles are white, are without an external 
envelop, are comparatively few in number, ate 
somewhat more than half the size of the blood 
corpuscles, and, like the nuclei of the latter, are 
insoluble in water. 

966. The fatty or oleaginous matter contained 
in the chyle is in a free state, not intimately com- 
bined. 

967. The chyle is alkaline, but is much less 
alkaline than the blood ; and the iron contained in 
the chyle is much less intimately combined than it 
is in the blood. 

968. Lymph contains in solution more animal 
matter than chyle, and the white globules are 
more abundant in lymph. But though lymph 
contain in solution more albumen and fibrin than 
chyle, it is not so richly loaded with these sub- 
.stances as blood. Still, however, the solution of 
albumen and fibrin in lymph approximates lymph 
so closely to the blood, that the lymph very much 
resembles the clear liquor sanguinis of which the 
blood consists when the red particles are ab- 
stracted from it. The colourless liquor sanguinis 
is the lymph of the blood. Lymph is blood with- 
out red particles ; and blood, lymph with red par- 
ticles. 

969. The chyle is transmitted into the lymph- 
vessels to mingle with the lymph before it flows 
into the veins to mingle with the blood. 

970. The commmg\td fluids, cli-^Xe «LXid\YH^>^^'* 

VOL. lU \3 



434 THE PHILOSOPHY OF HEALTH. 

pass into the blood very slowly, drop by diop. 
The regulation of the rapidity of the admixture 
seems to be the chief office of the valve placed at 
the termination of the thoracic duct. When the 
operation is observed in a living animal, it is seen 
that this valve prevents the new matter from dew- 
ing into the blood in a full stream. If in a dog 
of ordinary size that has recently eaten as much 
animal food as it chose, the thoracic duct be 
opened in the neck, the dog being alive, there will 
flow from the duct about half an ounce of fluid in 
five minutes (831) ; yet when this fluid reaches 
the termination of the duct only a few inches fur- 
ther on, it flows into the vein only drop by drop, 
at considerable intervals. One great object of 
pouring the chyle and lymph into the venous system 
so close to the heart (fig. clxxviii.)> and of causuog 
the commingled fluid to pass under the action of 
that powerful engine before it is transmitted to the 
lungs, seems to be, by the agitation to which it is 
subjected in the right auricle and ventricle to ac- 
complish the most perfect admixture possible be- 
tween the particles of the chyle and lymph and 
the red particles of the venous blood ; an object 
which would be counteracted by the too rapid 
entrance into the current of the circulation of the 
new and as yet imperfectly assimilated matter. 

971. After their due admixture by the power- 
ful action of the eii^vcie xJt^aX ^otV^ ^Jaa circulation, 
the commingled fLui^^ «.Te \.twvotxv^x^\\s^ '^^ca.t^ 
heart to the lungs. TYi^^ x\.^ ^^x«x^ ^^^^ ^^ 



CONVERSION OF CHYLE INTO BLOOD. 435 

the chyle and lymph is removed ; the composition 
of the albumen and fibrin is completed, these sub- 
stances being changed from a weak and loose into 
a strong and concentrated state ; the solid par- 
ticles are increased in number, augmented in size, 
and changed from a white into a red colour; 
carbon is given off; oxygen is absorbed ; azote is 
alternately inhaled and exhaled ; and the ultimate 
result is, that the three fluids — chyle, lymph, and 
venous blood — are converted into one homogeneous 
fluid, arterial blood, the proper nutrient fluid. 

972. The particles of the chyle and lymph, on 
mingling with the blood, are scattered through l^e 
mass, and become invisible, being apparently lost 
among the innumerable red corpuscles ; but it is 
not probable that the chyle is immediately con- 
verted into blood. If the coagulation of the blood 
be retarded by the addition of a small portion of 
the carbonate of potass, the red particles gradually 
sink some lines below the level of the fluid ; and 
the supernatent liquid is whitish, evidently from 
the chylous globules mingled with the blood. In 
ordinary coagulation, the chyle globules are in- 
cluded among the immense number of the red 
particles of the coagulmn, and are thus indistin- 
guishable ; but Ihere is reason to believe that the 
chyle is not converted into blood under at least 
from ten to twelve hours ; it is certain, that in that 
space of time after the completion of d\%t&<&\\vvcv^ 
the serum of the blood is fTeq[ueikt\3 %efetv \.o\i^ 

13 "l 



436 THE PHILOSOPHY OP HEALTH. 

milk-white, from the quantity of unassimilated 
chyle still contained in it 

973. How the red colour of the blood is ob- 
tained, and whence the capsules of the red par- 
ticles are derived, if these bodies really possess an 
external envelop, is wholly unknown. But it has 
been shown (953 and 955) that in incubation the 
blood is formed from the substance of the fluid 
yolk, without the action of any special organ; 
that at the period when the blood is first generated, 
no such organs as appear to influence the pro- 
duction of the blood in the adult are in existence ; 
it is, therefore, reasonable to infer that the forma-' 
tion of blood in the adult may not be so dependent 
on the action of special organs as is commonly 
supposed; and that the formation of blood from 
chyle^ of blood corpuscles from chyle corpuscles, 
may take place at all periods of life under the in- 
fluence of the same general vital conditions as it 
does in the incubated egg. 

974. What change the matter of the blood un- 
dergoes by respiration, whether it acquire some- 
thing without which it is incapable of maintaining 
life, or part with something the presence of which 
is incompatible with life, is equally unknown. We 
only know that the blood, during respiration, 
changes its colour ; but of the nature of the change 
produced upon its substance we are wholly iguo 

rant. In the piesent «Xate oil wa Wowledge, the 
ultimate fact is, t\iat V\\!tko>\\. \)afc <^«smi,^ ^^>^v 



DISTRIBUTION OF THE BLOOD. 437 

Upon the blood by respiration, the blood is inca- 
pable of maintaining life ; in fact, no proper nutri- 
ent fluid is formed. 

975. Once formed, the conservation of the 
proper proportions of tne composition of the blood 
is effected by the excr?cory processes already de- 
scribed ; by the remova* of its superfluous water 
by the lungs, skin, and kidneys ; by the removal 
of its superfluous carbon, azote, and oxygen by the 
lungs, liver, and kidneys ; by the removal of saline 
and mineral matters chiefly by the kidneys ; and 
Anally by the instantaneous removal of products of 
decomposition formed in the course of the organic 
uc'ions, chiefly, it would appear, by the kidneys. 

976. Once formed, and duly concentrated and 
purified, the blood is sent out by the left heart to 
the system. Dri' en by the heart through tne main 
trunks ar^i nranches of the aorta, the blood ulti- 
matelv reaches the capillary arteries, which do 
nor. iivide and subdivide indefinitely, but ulti- 
mately reach a point beyond which they no longer 
diminish in size. Not all of the same magnitude, 
some are large enough to admit of three or four 
of the red particles of the blood abreast ; the dia- 
meter of others is only sufficient to admit of two 
ot even of one ; others are capable of transmitting 
only the clear and transparent liquor sanguinis ; 
while in many cases the membranous tunics of the 
capillaries wholly disappear ; llae VJVocA xv^Vscv^'^ 

tiowain actual vessels, but is contame^ vsx^fe^v^" 



438 THE FHILOSOPHT OF HEALTH. 

Stance of the tissues in channels which it forms jA 
them for itself (304). 

977. Under the microscope, says Muller, the 
blood corpuscles are seen distinctly pouring firom 
the smallest ramifying arteries into vessels which 
grow no smaller. After leaving these, they again 
assemble in the origins of veins formed in collected 
branches. The blood corpuscles flow in the 
finest capillaries, one after another, and often in- 
terruptedly. They are colourless when they flow 
singly; accumulated more thickly, they appear 
yellow, and in still greater quantity, yellowish red 
or red. In animals that have lost their strength, 
the globules flow without stoppage : when the 
animal is weak and the motion is retarded, the 
globules move by starts; they move on, but go 
more rapidly by fits. In a still weaker animal 
they only advance during the impulse of the heart, 
and then fall back a little. When several arterial 
currents unite in an anastomosis, one current 
always predominates and traverses the anastomosis 
alone, to mingle its blood in the other currents. 
Thus the currents meet and divide in the reticulate 
capillaries till all are collected again in veins. 
Sometimes the direction of the current changes, 
when another current becomes stronger, and the 
previous leader weaker, according to the pressure 
exerted on the part. 
978. While t\ie >a\ocA S» ^Okss.^ \xv(^\:^vai^ the 
capillaries, its coVout c\i«L^^^% ^wb. ^\srw^\. ^aw^^ 



INTERCHANGE OF PARTICLES. 439 

to a dark red. This change in the colour of the 
bk)od is the certain sign that particles have been 
abstracted from the circulating mass, and have 
been applied to the formation and support of the 
fluid and solid parts through which the stream is 
flowing. Some physiologists have satisfied them* 
selves that they have seen the actual escape of 
particles from the circulating current ; that they 
have witnessed the immediate combination of those 
particles with the substance of the tissues, and 
even that they have beheld other particles quitting 
the tissues and mingling with the flowing blood. 
Other physiologists doubt whether the most patient 
observation, aided by the most skilful management 
of the best glasses, can ever have rendered such 
phenomena matters of sense. ** I imagined," says 
Mailer, " at an early period, that 1 had seen 
something like this in the setting circulation ; but 
by prolonging the observation I saw the globules 
move on if the current continued.'' 

979. But whether the human eye have ever 
actually seen or not an interchange of particles 
between the blood and the tissues, it is absolutely 
certain that such an interchange does take place. 
For,— 

1. Indubitable evidence has been stated (786, ef 
seq.) of continual absorption from all parts of the 
body, yet there is no loss of substance ; there must 
therefore of necessity be a propoTtioTitt.lb d^^i\^<cii\. 
2, Equal evidence has been adduc^a^ VJsfe*^ 



440 THE PHILOSOPHY OF HEALTH. 

that constant additions are made to the blood 
through the organs of digestion, yet the quantity 
of the blood in the body does not progressively and 
permanently increase ; it follows that a quantity 
must be abstracted from the blood proportionate to 
the quantity added to it. 

3. The human germ, from a scarcely visible 
point, by the successive additions of new matter 
progressively acquires the bulk of the adult man. 

4. Organs whose special office it is to abstract 
particles from the blood for the elaboration of 
specific secretions consist almost entirely of con- 
geries of blood-vessels. The agents are multiplied in 
proportion to the extent of the labour assigned them. 

5. Growth, which is merely excess of deposition 
above absorption, is active in proportion to the 
quantity of blood which circulates through the 
growing part in a given time. The blood-vessels 
o/ a growing part increase in number and augment 
in size is proportion to the rapidity of the growth. 
In morbid growth, it is sometimes sufficient to stop 
the process merely to tie the main trunks of the 
arteries distributed to the part. 

980. By every organ and every tissue ; by the 
membrane, the muscle, the bone; by the brain, 
the heart, the liver, the lungs, particles are ab- 
stracted from the countless streams that bathe 
thenij or that flow through them. In every case 
in which particVea aieX^xsA ^2a«XT^^\ft.^V^^\i8«ie 
the following phenomexv^i xiNw^ ^Vt^\— 



NUTRITION. 441 

1 . Only those constituents of the blood are ab- 
stracted by the tissue which are of the same che- 
mical nature as its own. 

2. The constituents of the blood abstracted by a 
tissue, identical in chemical composition with its 
own, are immediately incorporated into its substance. 

3. The constituents of the blood abstracted by a 
tissue, as they are incorporated into its substance, 
are not disposed fortuitously, but are arranged 
according to the specific organization of the tissue, 
.and thus receive its own peculiar structure. 

4. The constituents of the blood which thus 
receive the peculiar organization and structure of 
the tissue by which they are appropriated, acquire 
all its peculiar vital endowhients. 

981. It is manifest, then, that the tissues 
assimilate the blood just as the digestive fluids 
assimilate the aliment. And this is nutrition, the 
assimilation of the blood by the tissues and organs. 
Digestion is the conversion of the food into blood ; 
nutrition is the conversion of blood into living 
fluids and solids. 

982. For the reasons assigned (757 and 758), 
it is probable that the living fluids and solids, 
formed from the blood by the act of nutrition, are 
not generated at the parts of the body where they 
appear, but that, pre-existing in the blood, they 
are merely evolved at those parts. Hence the 
variety and complexity of the pToe^^«»^<& iot \iwt 
elaboration of the blood whic\iY\ave\iefc\x^^'s><i^^^^\ 



443 THB PHILOSOPHY OF HEALTH. 

and all of which appear to be indispensable Uf 
bring the blood to a proper state of purity and 
strength. The great effort of the system is pat 
forth in effecting the constitution of the blood. 
When the blood is once formed, all the rest of the 
work appears to be easy ; because, before it reaches 
any part of the organization which it is destined 
to support, the blood is already adapted, mechani- 
cally, chemically, and vitally, to afford that support. 
Still since there are cases, as in the production of 
gelatin, in which the substance does not appear to 
be pre-existent in the blood, we are under the 
necessity of supposing that a material change is 
effected in the constituents of the yital fluid at the 
time and place of their escape from the circulation. 

983. How the constituents of the blood escape 
from the circulation and incorporate themselves 
with the substance of the tissues there can be no 
difficulty in conceiving, wherever the capillaries 
terminate in membraneless canals, channels worked 
out for the reception of the nutrient stream by the 
force of the current itself; and in every case in 
which the capillaries, retaining their membranous 
tunics, remain true and proper vessels, their con* 
tents escape through their delicate walls by the 
process of endosmose (803), for which their 
structure appears to be admirably adapted. 

984. But m Ib^ ca^^llUry vessels there exists 
only blood . \3n\veT%%XV5 wv^ \sCT%xvi5J^^\sftSss«i ^lisft 
Wood pasBCB from un^et \>w^ \xAn>kw«. ^\ ^^ 



VITAL AFf IMITT. 443 

capillary yessela it has ceased to be blood. Arterial 
blood is conveyed by the carotid artery to the 
brain; but the cerebral arteries do not deposit 
blood, but brain. Arterial blood is conveyed by 
the capillary arteries to bone; bat the osseous 
capillaries do not deposit blood, but bone. Ar- 
terial blood'is conveyed by the muscular arteries to 
muscle, but the muscular capillaries do not de* 
posit blood but muscle. The blood conveyed by 
the capillaries of brain, bone, and muscle is the 
same; all comes alike from the systemic heart, 
and is alike conveyed to all tissues ; yet in the one 
it becomes brain, in the other bone, and in the 
third muscle. Out of one and the name fluid are 
manufactured cuticle, and membrane, and muscle, 
and brain, and bone ; the tears, the wax, the fat, 
the saliva, the gastric juice, the milk, the bile, all 
the fluids, and all the solids of the body (310). 

985. These phenomena are wholly inexplica- 
ble on any known mechanical principles. It is 
equally impossible to refer them to mere chemical 
agency, or to any properties of dead matter. We 
are therefore under the necessity of referring them 
to a principle which, for the sake of distinguishing 
it from anything mechanical or chemical, we term 
vital. As the actions which take place between 
the integrant particles of bodies, giving rise to 
chemical phenomena, are referred to one general 
principle, termed chemical affimtY) «o X\\^ ^Ocvksisl^ 
which take place in living bodieu, ^nyw^ ivas. n» 



444 THB PHILOSOPHY OF HKA.LTH. 

vital phenomena, may be referred to one general 
principal, termed vital affinity. The term expluns 
nothing, it is true, it merely expresses the general 
fact ; but still it is convenient to have a term for 
the expression of the fact. The property itself 
will ever remain an ultimate fact in physiology, 
however exactly the limits of its agency, and the 
laws according to which it modifies the mechanical 
and chemical relations of the substances subjected 
to its influence, may hereafter be ascertained ; just 
as chemical affinity will ever be an ultimate fact in 
physics, whatever discoveries may yet be made of 
the extent of its agency and of the conditions on 
which its action depends. 

986. It is then an ascertained fact, that there 
exists between the blood and the tissues a mutual 
reaction, not of a physical, but of a vital nature, 
in which the blood takes as active a part as the 
tissue, and the tissue as the blood ; the blood 
exerting a vital attraction on the tissue, and the 
tissue on the blood. We only express this ultimate 
fact when we say (and this is all we can do) that 
in every part of the body, by virtue of a vital 
affinity, the tissue attracts from the blood the 
molecules of matter appropriate to its chemical 
composition, and the blood attracts from the tissue 
the particles which, having served their purpose 
there, are destined to other uses in the economy ; 
or^ if wholly useVeaa, wee «Xiwst\ifc^ "vslX^ '^^ ^scbcwdlI 
of the circulation to \>^ ex^€^\^ it^m>(ia& v^^Masu 



ACTION OF THE PROPER ABSORBENTS. 445 

987. We can see how the particles of matter 
which are attracted hy the tissue from the blood 
are so deposited and disposed that the tissue always 
preserves its own shape, bulk, and relation to the 
surrounding tissues. This definite arrangement is 
the result of an action which has been already 
stated to be proper to the absorbent vessels. Pre- 
viously to the deposition of a new particle of matter 
by a capillary, an old particle is removed by an 
absorbent, either a lymphatic or a vein. In re- 
moving the old matter, the absorbent forms a mould 
into which the capillary deposits the new mole- 
cules; and the form of every tissue and organ 
depends on the kind of mould formed for the 
reception of its nutrient matter by the absorbent 
vessel. The absorbents are thus the architects of 
the system ; and the capillaries are both chemists 
which form the rough material employed in the 
structure, and masons which deposit and arrange it. 
The conjoint action of both sets of vessels is ne- 
cessary to the formation of the simplest tissue ; and 
it is by their united labour that the compound 
organs are built up out of the simple tissues. 

988. It is conjectured that the immediate living 
agents by which this vital attraction is exerted 
between the blood and the tissues are the organic 
nerves. These nerves consist of two sets, those 
which enter as constituents into the tissues and 
those which accompany the capillaries. It ho^ 
bec/j shown (304), that while tive TciEa^T^x^ssvia^ 



446 TBB PHILOSOPHY OP HXALTH. 

tunics of the capillaries diminish, the nervoua 
filaments -distributed to them increase; that the 
smaller and thinner the capillaries the greater the 
proportionate quantity of their nervous matter; and 
that this is most remarkably the case in organs of 
the greatest irritability. It is conceived that the 
capillaries, in consequence of the nervous structure 
which thus envelops them, exert upon the fluid 
which is flowing through them an influence per- 
fectly analogous to that of the secreting organ, in 
consequence of which similar particles are ab- 
stracted from the blood as those which compose the 
tissue in which the operation takes place. 

989. It is further conjectured that the physica] 
agent by which this action upon the blood is effected 
is the galvanic fluid. Dutrochet believes that he 
has actually formed muscular fibre from albumen 
by galvanism. He considers the red particles of 
the blood as pairs of electrical plates, and thinks 
that the nucleus is electronegative, and the capsule 
electropositive. Miiller has repeated and critically 
examined the interesting experiments of Dutrochet ; 
and while he arrives in many essential points at 
diflerent results, expresses the highest admiration 
of the ingenious manner in which this philosopher 
has sought to solve a great problem. ** If," says 
MQller, '* a drop of an aqueous solution of the yolk 
of egg (in which very small microscopic globules 
are suspended^ \>e ^«\N«Kvifc\^ >iNfc cwrrents dis- 
covered by DutTOc\veX.viW\\ifc <3a««r^^. 'Wft.^t»?t> 



PHYSICAL AGENT. 447 

proceeding from the copper or negative pole, iii 
which the alkali of the decomposed salt accu- 
mulates,' is transparent, from the solution of albu- 
men by the alkali. The wave, proceeding from 
the positive or zinc pole^ particularly in its circum- 
ference, is opaque, and white from the acid it con- 
tains. Both waves encounter, and exactly in the 
line of contact a linear coagulum is immediately 
produced, which assumes the form of the line of 
contact, and is curled at times as the edges of the 
waves are meeting. The meeting of both waves 
takes place with a lively motion, in the line of con- 
tact, when the deposition of coagulum takes place ; 
but as soon as the deposition of coagulum has 
occurred, all is tranquil, and not the least trace of 
motion is observed. It is therefore inconceivable 
how an observer of the first rank, like Dutrochet, 
can pronoimee this coagulated albumen contractile 
muscular fibre, generated by galvanism; it is 
nothing but coagulated albumen. This coagulum, 
besides, like the albumen which is deposited by 
galvanism round the zinc pole, has no consistence, 
but is composed of globules easily separated by 
stirring, and only precipitated in the line where 
the two waves meet without cohesion." 

990. But though science has not yet succeeded 
in ascertaining with certainty the physical agency 
to which the ultimate changes that take place in 
organized matter are to be referred, there cannot be 
a question that they are dependeivX. wi ^^'sx^'^ 



448 THE PHILOSOPHY OF HEALTH, 

agents; and the legitimate object of scientific 
inquiry is to discover what those agents are, and to 
ascertain the modifications they undergo by those 
vital affinities to the influence of which they are 
subjected. 

991. The discoveries which science has already 
made relative to the influence of certain physica' 
agents on particular organs, and to the influence of 
the whole circle of physical agents on the whole 
living economy, have added not a little to humaD 
power over human health and disease. But these 
agents also exert an influence scarcely less nior 
mentous on the entire apparatus and action of the 
animal life, so inseparably linked with the organic. 
An account will therefore be next given of the 
structure and function of the nervous and muscular 
systems. The exposition of these systems, which 
will be as brief as possible, will be followed by a 
full account of the action of physical agents od the 
whole of this complex and wonderful organization 
The detail of the ascertained phenomena will have 
a strict reference to the development of the physica 
and mental powers of the human being, and thereby 
a close and practical application will be attempted 
of physiology to the production and preservation of 
health. 



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