TRANSCRIBER'S NOTE: Italic text is denoted by _underscores_ and bold
text by =equal signs=.
THE
PHILOSOPHY OF HEALTH;
OR,
AN EXPOSITION
OF THE
PHYSICAL AND MENTAL CONSTITUTION
OF MAN,
WITH A VIEW TO THE PROMOTION OF
HUMAN LONGEVITY AND HAPPINESS.
BY
SOUTHWOOD SMITH, M.D.,
_Physician to the London Fever Hospital, to the Eastern Dispensary,
and to the Jews' Hospital._
IN TWO VOLUMES. VOL. I.
_THIRD EDITION._
LONDON:
C. COX, 12, KING WILLIAM STREET, STRAND.
1847.
London: Printed by W. CLOWES and SONS, Stamford Street.
CONTENTS OF VOL. I.
INTRODUCTION Page 1
CHAPTER I.
Characters by which living beings are distinguished
from inorganic bodies—Characters by which
animals are distinguished from plants—Actions
common to plants and animals—Actions peculiar
to animals—Actions included in the ORGANIC
circle—Actions included in the ANIMAL
circle—Organs and functions defined—Action of
physical agents on organized structures—Processes
of supply, and processes of waste—Reasons why the
structure of the animal is more complex than that
of the plant 13
CHAPTER II.
Two distinct lives combined in the
animal—Characters of the apparatus of the organic
life—Characters of the apparatus of the animal
life—Characteristic differences in the action of
each—Progress of life—Progress of death 51
CHAPTER III.
Ultimate object of organization and life—Sources
of pleasure—Special provision by which the
organic organs influence consciousness and afford
pleasure—Point at which the organic organs cease
to affect consciousness and why—The animal
appetites: the senses: the intellectual faculties:
the selfish and sympathetic affections: the moral
faculty—Pleasure the direct, the ordinary,
and the gratuitous result of the action of the
organs—Pleasure conducive to the development
of the organs, and to the continuance of their
action—Progress of human knowledge—Progress of
human happiness 73
CHAPTER IV.
Relation between the physical condition
and happiness, and between happiness and
longevity—Longevity a good, and why—Epochs of
life—The age of maturity the only one that admits
of extension—Proof of this from physiology—Proof
from statistics—Explanation of terms—Life a
fluctuating quantity—Amount of it possessed in
ancient Rome: in modern Europe: at present in
England among the mass of the people and among the
higher classes 106
CHAPTER V.
Ultimate elements of which the body is composed—
Proximate principles—Fluids and solids—Primary tissues—
Combinations—Results—Organs, systems, apparatus—
Form of the body—Division into head, trunk, and
extremities—Structure and function of each—Regions—
Seats of the more important internal organs 148
CHAPTER VI.
Of the blood—Physical characters of the blood:
colour, fluidity, specific gravity, temperature;
quantity—Process of coagulation—Constituents of
the blood; proportions —Constituents of the body
contained in the blood—Vital properties of the
blood—Practical applications 334
CHAPTER VII.
Of the circulation—Vessels connected with the
heart; chambers of the heart—Position of the
heart—Pulmonic circle; systemic circle—Structure
of the heart, artery, and vein—Consequences
of the discovery of the circulation to the
discoverer—Action of the heart; sounds occasioned
by its different movements—Contraction;
dilatation—Disposition and action of the
valves—Powers that move the blood—Force of
the heart—Action of the arterial tubes; the
pulse; action of the capillaries; action of the
veins—Self-moving power of the blood—Vital
endowment of the capillaries; functions—Practical
applications 357
FOOTNOTES. 408
INTRODUCTION.
The object of the present work is to give a brief and plain account
of the structure and functions of the body, chiefly with reference
to health and disease. This is intended to be introductory to an
account of the constitution of the mind, chiefly with reference to
the development and direction of its powers. There is a natural
connexion between these subjects, and an advantage in studying them
in their natural order. Structure must be known before function can
be understood: hence the science of physiology is based on that of
anatomy. The mind is dependent on the body: hence an acquaintance with
the physiology of the body should precede the study of the physiology
of the mind. The constitution of the mind must be understood before its
powers and affections can be properly developed and directed: hence a
knowledge of the physiology of the mind is essential to a sound view of
education and morals.
In the execution of the first part of this work, that which relates
to the organization of the body, a formidable difficulty presents
itself at the outset. The explanation of structure is easy when the
part described can be seen. The teacher of anatomy finds no difficulty
in communicating to the student a clear and exact knowledge of the
structure of an organ; because, by the aid of dissection, he resolves
the various complex substances, of which it is built up, into their
constituent parts, and demonstrates the relation of these elementary
parts to each other. But the case is different with him who attempts
to convey a knowledge of the structure of an organ merely by the
description of it. The best conceived and executed drawing is a
most inadequate substitute for the object itself. It is impossible
wholly to remove this difficulty: what can be done, by the aid of
plates, to lessen it, is here attempted. A time may come when the
objects themselves will be more generally accessible: meanwhile, the
description now given of the chief organs of the body may facilitate
the study of their structure to those who have an opportunity of
examining the organs themselves, and will, it is hoped, enable every
reader at once to understand much of their action.
Physical science has become the subject of popular attention, and
men of the highest endowments, who have devoted their lives to the
cultivation of this department of knowledge, conceive that they can
make no better use of the treasures they have accumulated, than that of
diffusing them. Of this part of the great field of knowledge, to make
"the rough places plain, and the crooked places straight," is deemed a
labour second in importance only to that of extending the boundaries of
the field itself. But no attempt has hitherto been made to exhibit a
clear and comprehensive view of the phenomena of life; the organization
upon which those phenomena depend; the physical agents essential
to their production, and the laws, as far as they have yet been
discovered, according to which those agents act. The consequence is,
that people in general, not excepting the educated class, are wholly
ignorant of the structure and action of the organs of their own bodies,
the circumstances which are conducive to their own health, the agents
which ordinarily produce disease, and the means by which the operation
of such agents may be avoided or counteracted; and they can hardly be
said to possess more information relative to the connexion between the
organization of the body and the qualities of the mind, the physical
condition and the mental state; the laws which regulate the production,
combination, and succession of the trains of pleasurable and painful
thought, and the rules deducible from those laws, having for their
object such a determination of voluntary human conduct, as may secure
the pleasurable and avoid the painful.
Yet nothing would seem a fitter study for man than the nature of man in
this sense of the term. A knowledge of the structure and functions of
the body is admitted to be indispensable to whoever undertakes, as the
business of his profession, to protect those organs from injury, and to
restore their action to a sound state when it has become disordered;
but surely some knowledge of this kind may be useful to those who
have no intention to practise physic, or to perform operations in
surgery; may be useful to every human being, to enable him to take a
rational care of his health, to make him observant of his own altered
sensations, as indications of approaching sickness; to give him the
power of communicating intelligibly with his medical adviser respecting
the seat and the succession of those signs of disordered function, and
to dispose and qualify him to co-operate with his physician in the use
of the means employed to avert impending danger, or to remove actual
disease.
But if to every human being occasions must continually occur, when
knowledge of this kind would be useful, the possession of it seems
peculiarly necessary to those who have the exclusive care of infancy,
almost the entire care of childhood, a great part of the care of
the sick, and whose ignorance, not the less mischievous because its
activity is induced by affection, constantly endangers, and often
defeats, the best concerted measures of the physician.
The bodily organization and the mental powers of the child depend
mainly on the management of the infant; and the intellectual and
moral aptitudes and qualities of the man have their origin in the
predominant states of sensation, at a period far earlier in the history
of the human being than is commonly imagined. The period of infancy is
divided by physiologists into two epochs; the first, commencing from
birth, extends to the seventh month: the second, commencing from the
seventh month, extends to the end of the second year, at which time
the period of infancy ceases, and that of childhood begins. The first
epoch of infancy is remarkable for the rapidity of the development
of the organs of the body: the processes of growth are in extreme
activity; the formative predominates over the sentient life, the chief
object of the action of the former being to prepare the apparatus
of the latter. The second epoch of infancy is remarkable for the
development of the perceptive powers. The physical organization of
the brain, which still advances with rapidity, is now capable of a
greater energy, and a wider range of function. Sensation becomes more
exact and varied; the intellectual faculties are in almost constant
operation; speech commences, the sign, and, to a certain extent, the
cause of the growing strength of the mental powers; the capacity of
voluntary locomotion is acquired, while passion, emotion, affection,
come into play with such constancy and energy, as to exert over the
whole economy of the now irritable and plastic creature a prodigious
influence for good or evil. If it be, indeed, possible to make correct
moral perception, feeling, and conduct, a part of human nature, as much
a part of it as any sensation or propensity—if this be possible for
every individual of the human race, without exception, to an extent
which would render _all_ more eminently and consistently virtuous than
_any_ are at present (and of the possibility of this, the conviction
is the strongest in the acutest minds which have studied this subject
the most profoundly), preparation for the accomplishment of this object
must be commenced at this epoch. But if preparation for this object
be really commenced, it implies, on the part of those who engage in
the undertaking, some degree of knowledge; knowledge of the physical
and mental constitution of the individual to be influenced; knowledge
of the mode, in which circumstances must be so modified in adaptation
to the nature of the individual being, as to produce upon it, with
uniformity and certainty, a given result. The theory of human society,
according to its present institutions, supposes that this knowledge is
possessed by the mother; and it supposes, further, that this adaptation
will actually take place in the domestic circle through her agency.
Hence the presumed advantage of having the eye of the mother always
upon the child; hence the apprehension of evil so general, I had almost
said instinctive, whenever it is proposed to take the infant, for the
purpose of systematic physical and mental discipline, from beyond the
sphere of maternal influence. But society, which thus presumes that
the mother will possess the power and the disposition to do this, what
expedients has it devised to endow her with the former, and to secure
the formation of the latter? I appeal to every woman whose eye may
rest on these pages. I ask of you, what has ever been done for you to
enable you to understand the physical and mental constitution of that
human nature, the care of which is imposed upon you? In what part of
the course of your education was instruction of this kind introduced?
Over how large a portion of your education did it extend? Who were
your teachers? What have you profited by their lessons? What progress
have you made in the acquisition of the requisite information? Were
you at this moment to undertake the guidance of a new-born infant to
health, knowledge, goodness, and happiness, how would you set about
the task? How would you regulate the influence of external agents upon
its delicate, tender, and highly-irritable organs, in such a manner
as to obtain from them healthful stimulation, and avoid destructive
excitement? What natural and moral objects would you select as the best
adapted to exercise and develope its opening faculties? What feelings
would you check, and what cherish? How would you excite aims; how would
you apply motives? How would you avail yourself of pleasure as a final
end, or as the means to some further end? And how would you deal with
the no less formidable instrument of pain? What is your own physical,
intellectual, and moral state, as specially fitting you for this
office? What is the measure of your own self-control, without a large
portion of which no human being ever yet exerted over the infant mind
any considerable influence for good? There is no philosopher, however
profound his knowledge, no instructor, however varied and extended his
experience, who would not enter upon this task with an apprehension
proportioned to his knowledge and experience; but knowledge which men
acquire only after years of study, habits which are generated in men
only as the result of long-continued discipline, are expected to come
to you spontaneously, to be born with you, to require on your part no
culture, and to need no sustaining influence.
But, indeed, it is a most inadequate expression of the fact, to say
that the communication of the knowledge, and the formation of the
habits which are necessary to the due performance of the duties of
women, constitute no essential part of their education: the direct
tendency of a great part of their education is to produce and foster
opinions, feelings, and tastes, which positively disqualify them for
the performance of their duties. All would be well if the marriage
ceremony, which transforms the girl into the wife, conferred upon the
wife the qualities which should be possessed by the mother. But it is
rare to find a person capable of the least difficult part of education,
namely, that of communicating instruction, even after diligent study,
with a direct view to teaching; yet an ordinary girl, brought up in
the ordinary mode, in the ordinary domestic circle, is intrusted with
the direction and control of the first impressions that are made upon
the human being, and the momentous, physical, intellectual, and moral
results that arise out of those impressions!
I am sensible of the total inadequacy of any remedy for this
evil, short of a modification of our domestic institutions. Mere
information, however complete the communication of it, can do little
beyond affording a clearer conception of the end in view, and of
the means fitted to secure it. Even this little, however, would be
something gained; and the hope of contributing, in some degree, to
the furtherance of this object, has supplied one of the main motives
for undertaking the present work. Meantime, women are the earliest
teachers; they must be nurses; they can be neither, without the risk
of doing incalculable mischief, unless they have some understanding
of the subjects about to be treated of. On these grounds I rest their
_obligation_ to study them; and I look upon that notion of delicacy,
which would exclude them from knowledge calculated, in an extraordinary
degree, to open, exalt, and purify their minds, and to fit them for the
performance of their duties, as alike degrading to those to whom it
affects to show respect, and debasing to the mind that entertains it.
Though each part of this work will be made as complete in itself as
the author is capable of rendering it, and to that extent independent
of any other part, yet there will be found to be a strict connexion
between the several portions of the whole; and greatly as the topics
included in the latter differ from those which form the earlier
subjects, the advantage of having studied the former before the latter
are entered on, will be felt precisely as the word _study_ can be
justly applied to the operation of the mind on such matters.
In the expository portion of the work I have not been anxious to
abstain from the employment of technical terms, when a decidedly useful
purpose was to be obtained by the introduction of them; but I have been
very careful to use no such term without assigning the exact meaning
of it. A technical term unexplained is a dark spot on the field of
knowledge; explained, it is a clear and steady light.
In order really to understand the states of health and disease,
an acquaintance with the nature of organization, and of the vital
processes of which it is the seat and the instrument, is indispensable:
it is for this reason that the exposition of structure and function,
attempted in this first part of the work, is somewhat full; but there
cannot be a question that, if it accomplish its object, it will not
only enable the account of health and disease in the subsequent part of
it to be much more brief, but that it will, at the same time, render
that account more intelligible, exact, and practical.
S. S.
THE
PHILOSOPHY OF HEALTH.
CHAPTER I.
Characters by which living beings are distinguished
from inorganic bodies—Characters by which animals are
distinguished from plants—Actions common to plants and
animals—Actions peculiar to animals—Actions included in the
organic circle—Actions included in the animal circle—Organs
and functions defined—Action of physical agents on
organized structures—Processes of supply, and processes
of waste—Reasons why the structure of the animal is more
complex than that of the plant.
The distinction between a living being and an inorganic body,
between a plant and a stone, is, that the plant carries on a number
of processes which are not performed by the stone. The plant absorbs
food, converts its food into its own proper substance, arranges this
substance into bark, wood, vessels, leaves, and other organized
structures; grows, arrives at maturity, and decays; generates and
maintains a certain degree of heat; derives from a parent the primary
structure and the first impulse upon which these varied actions depend;
gives origin to a new being similar to itself, and, after a certain
time, terminates its existence in death.
No such phenomena are exhibited by the stone; it neither absorbs
food, nor arranges the matter of which it is composed into organized
structure; nor grows, nor decays, nor generates heat, nor derives its
existence from a parent, nor gives origin to a new being, nor dies.
Nothing analogous to the processes by which these results are produced,
is observable in any body that is destitute of life; all of them are
carried on by every living creature. These processes are, therefore,
denominated vital, and, being peculiar to the state of life, they
afford characters by which the living being is distinguished from the
inorganic body.
In like manner the distinction between an animal and a plant is, that
the animal possesses properties of which the plant is destitute. It is
endowed with two new and superior powers, to which there is nothing
analogous in the plant; namely, the power of sensation, and the power
of voluntary motion; the capacity of feeling, and the capacity of
moving from place to place as its feeling prompts. The animal, like
the plant, receives food, transforms its food into its own proper
substance, builds this substance up into structure, generates, and
maintains a certain temperature, derives its existence from a parent,
produces an offspring like itself, and terminates its existence in
death. Up to this point the vital phenomena exhibited by both orders of
living creatures are alike: but at this point the vital processes of
the plant terminate, while those of the animal are extended and exalted
by the exercise of the distinct and superior endowments of sensation
and voluntary motion. To feel, and to move spontaneously, in accordance
with that feeling, are properties possessed by the animal, but not by
the plant; and therefore these properties afford characters by which
the animal is distinguished from the plant.
The two great classes of living beings perform, then, two distinct
sets of actions: the first set is common to all living creatures; the
second is peculiar to one class: the first set is indispensable to
life; the second is necessary only to one kind of life, namely, the
animal. The actions included in the first set, being common to all
living or organized creatures, are called ORGANIC; the actions included
in the second class, belonging only to one part of living or organized
creatures, namely, animals, are called ANIMAL. The ORGANIC actions
consist of the processes by which the existence of the living being is
maintained, and the perpetuation of its species secured: the ANIMAL
actions consist of the processes by which the living being is rendered
percipient, and capable of spontaneous motion. The ORGANIC processes
comprehend those of nutrition, respiration, circulation, secretion,
excretion, and reproduction; the first five relate to the maintenance
of the life of the individual being; the last to the perpetuation of
its species. The ANIMAL processes comprehend those of sensation and
of voluntary motion, often denominated processes of relation, because
they put the individual being in communication with the external
world. There is no vital action performed by any living creature
which may not be included in one or other of these processes, or in
some modification of some one of them. There is no action performed
by any inorganic body which possesses even a remote analogy to either
of these vital processes. The line of demarcation between the organic
and the inorganic world is, therefore, clear and broad; and the line
of demarcation between the two great divisions of the organic world,
between the inanimate and the animate, that is, between plants and
animals, is no less decided: for, of the two sets of actions which have
been enumerated, the one, as has just been stated, is common to the
whole class of living beings, while the second set is peculiar to one
division of that class. The plant performs only the organic actions:
all the vital phenomena it exhibits are included in this single circle;
it is, therefore, said to possess only organic life: but the animal
performs both organic and animal actions, and is therefore said to
possess both organic and animal life.
Both the organic and the animal actions are accomplished by means
of certain instruments, that is, organized bodies which possess a
definite structure, and which are moulded into a peculiar form. Such
an instrument is called an organ, and the action of an organ is called
its function. The leaf of the plant is an organ, and the conversion
of sap by the leaf into the proper juice of the plant, by the process
called respiration, is the function of this organ. The liver of the
animal is an organ; and the conversion of the blood that circulates
through it into bile, by the process of secretion, is its function. The
brain is an organ; the sentient nerve in communication with it is also
an organ. The extremity of the sentient nerve receives an impression
from an external object, and conveys it to the brain, where it becomes
a sensation. The transmission of the impression is the function of
the nerve; the conversion of the impression into a sensation is the
function of the brain.
The living body consists of a congeries of these instruments or
organs: the constituent matter of these organs is always partly in a
fluid and partly in a solid state. Of the fluids and solids which thus
invariably enter in combination into the composition of the organs, the
fluids may be regarded as the primary and essential elements, for they
are the source and the support of the solids. There is no solid which
is not formed out of a fluid; no solid which does not always contain,
as a constituent part of it, some fluid, and none which is capable of
maintaining its integrity without a continual supply of fluids.
Whatever be the intimate composition of the fluids out of which the
solids are formed, the investigation of which is more difficult than
that of the solids and the nature of which is therefore less clearly
ascertained, it is certain that all the matter which enters into
the composition of the solid is disposed in a definite order. It is
this disposition of the constituent matter of the living solid in a
definite order that constitutes the arrangement so characteristic of
all living substance. Definite arrangements are combined in definite
modes, and the result is what is termed organization. From varied
arrangements result different kinds of organized substances, each
endowed with different properties, and exhibiting peculiar characters.
By the recombination of these several kinds of organized substances,
in different proportions and different modes, are formed the special
instruments, or organs, of which we have just spoken; while it is the
combining, or the building up of these different organized substances
into organs, that constitutes structure.
In the living body, not only is each distinct organ alive, but, with
exceptions so slight that they need not be noticed here, every solid
which enters into the composition of the organ is endowed with vital
properties. This is probably the case with the primary substances or
tissues which compose the several organs of the plant; but that the
animal solids are alive is indubitable; nay, the evidence is complete,
that many even of the animal fluids possess vitality. The blood in the
animal is as truly alive as the brain, and the bone as the flesh. The
organized body, considered as a whole, is the seat of life; but life
also resides in almost every component part of it.
Yet the matter out of which these living substances is formed is not
alive. By processes of which we know nothing, or, at least, of which
we see only the first steps,—matter, wholly destitute of life, is
converted into living substance. The inorganic matter, which is the
subject of this wonderful transformation, is resolvable into a very
few elementary substances. In the plant, these substances consist of
three only, namely, oxygen, hydrogen, and carbon. The first two are
aëriform or gaseous bodies; the last is a solid substance, and it is of
this that the plant is chiefly composed: hence the basis of the plant
is a solid. The elementary bodies, into which all animal substance is
resolvable, are four, namely, azote, oxygen, hydrogen, and carbon.
Into every animal fluid and solid this new substance azote enters so
largely, that it may be considered as the fundamental and distinctive
element of the animal organization: hence the basis of the animal is
an aëriform or gaseous fluid. The animal is composed of air, the plant
of solid matter; and this difference in their elementary nature gives
origin to several distinctive characters between the plant and the
animal, in addition to those which have been already stated.
Thus the characters of the plant are solidity, hardness, fixedness, and
durability; while the animal is comparatively fluid, soft, volatile,
and perishable; and the reason is now manifest. The basis of the animal
being an aëriform fluid, its consistence is softer than that of the
plant, the basis of which is a firm solid; and, at the same time, the
component elements of the animal being more numerous than those of the
plant, and the fluidity of these elements, and of the compounds they
form, greatly favouring their action and reaction on each other and on
external agents, the animal body is more volatile and perishable during
life, and more readily decomposed after death.
It has been stated, that the object of every structure or organ
of the living body, is the performance of some special action or
function,—the ultimate object of the fluids being the production of
the solids; the ultimate object of the solids being the formation of
organs; the ultimate object of organs being the performance of actions
or functions; while it is in the performance of actions or functions
that life consists. Functions carried on by organs; organs in action;
special organs performing definite actions, this it is that constitutes
the state of life. Every particle of matter which enters into the
composition of the living body has thus its own place, forming, or
destined to form, a constituent part of some organ; every organ has
its own action; all the organs of the body form the body; and all
the actions of all the organs constitute the aggregate of the vital
phenomena.
Every organ is excited to action, or its function is called into
operation by means of some external body. The external bodies capable
of exciting and maintaining the functions of living organs, consist
of a definite class. Because these bodies belong to that department
of science which is called physical, they are termed physical agents.
They are air, water, heat, cold, electricity, and light. Without the
living organ, the physical agent can excite no vital action: without
the physical agent, the living organ can carry on no vital process.
The plant cannot perform the vital process of respiration without the
leaf, nor, with the leaf, without air. The physical agent acts upon the
living organ; the living organ reacts upon the physical agent, and the
action between both is definite. In the lung of the animal a certain
principle of the air unites, in definite proportions, with a certain
principle of the blood; the oxygen of the air combines with the carbon
of the blood; the air is changed by the abstraction of its oxygen;
the blood is changed by the abstraction of its carbon. Atmospheric
air goes to the lung, but atmospheric air does not return from the
lung; it is converted into a new substance by the action of the organ:
it is changed into carbonic acid by the union of a given quantity of
oxygen, which it transmits to the organ, with a given quantity of
carbon which the organ conveys to it. Venous blood goes to the lung,
but venous blood does not return from the lung; it is converted, by
the instrumentality of the organ, into a new substance, into arterial
blood, by giving to the air carbon, and by receiving from the air
oxygen. In this manner the change in the physical agent is definite and
uniform; and the change in the living substance is equally definite and
uniform.
It is this determinate interchange of action between the living organ
and the physical agent that constitutes what is termed a vital process.
All vital processes are carried on by living organs; the materials
employed in all vital processes are physical agents; the processes
themselves are vital functions. All the changes produced by all the
organs of the plant upon physical agents, and all the changes produced
by all physical agents upon the organs of the plant, constitute all
the vital processes of the plant—comprehend the whole sum of its
vital phenomena. The root, the trunk, the woody substance, the bark,
the ascending vessels bearing sap, the descending vessels bearing
secreted fluids, the leaves, the flowers, these are the living organs
of the plant. Air, water, heat, cold, electricity, light, these are the
physical agents which produce in these organs definite changes, and
which are themselves changed by them in definite modes; and the whole
of these changes, taken together, comprehend the circle of actions, or
the range of functions performed by this living being.
In the state of life, during the interchange of action which thus
incessantly goes on between physical agents and vital organs, the
laws to which inorganic matter is subject are resisted, controlled,
and modified. Physical and chemical attractions are brought under the
influence of a new and superior agency, with the laws of which we are
imperfectly acquainted, but the operation of which we see, and which we
call the agency of life. Air, water, heat, electricity, are physical
agents, which subvert the most intimate combinations of inorganic
bodies, resolving them into their simple elements, and recombining
these elements in various modes, and thus forming new bodies, endowed
with totally different properties; but the physical and chemical
agencies by which these changes are wrought in the inorganic, are
resisted, controlled, and modified by the living body: resisted, for
these physical agents do not decompose the living body; controlled
and modified, for the living body converts these very agents into the
material for sustaining its own existence Of all the phenomena included
in that circle of actions which we designate by the general term life,
this power of resisting the effects universally produced by physical
agents on inorganic matter, and of bringing these very agents under
subjection to a new order of laws, is one of the most essential and
distinctive.
All vital processes are processes of supply, or processes of waste. By
every vital action performed by the organized body, some portion of its
constituent matter is expended. Numerous vital actions are constantly
carried on for the sole purpose of compensating this expenditure. Every
moment old particles are carried out of the system; every moment new
particles are introduced into it. The matter of which the organized,
and more especially the animal, body is composed, is thus in a state
of perpetual flux; and in a certain space of time it is completely
changed, so that of all the matter that constitutes the animal body at
a given point of time, not a single particle remains at another point
of time at a given distance.
All the wants of the economy of the plant are satisfied by a due
supply of air, water, heat, cold, electricity, and light. Some of
these physical agents constitute the crude aliment of the plant;
others produce in this aliment a series of changes, by which it is
converted from crude aliment into proper nutriment, while others act
as stimulants, by which movements are excited, the ultimate object of
which is the distribution of the nutriment to the various parts of the
economy of the plant.
The same physical agents are indispensable to the support of the animal
body; but the animal cannot be sustained by these physical agents
alone; for the maintenance of animal life, in some shape or other,
vegetable or animal matter, or both in a certain state of combination,
must be superadded: hence another distinction between the plant and the
animal,—the necessity, on the part of the animal, of an elaborated
aliment to maintain its existence. By the vital processes of its
economy, the plant converts inorganic into organic matter; by the vital
processes of its economy, the animal converts matter, already rendered
organic, into its own proper substance. The plant is thus purveyor to
the animal: but it is more than purveyor to it; for while it provides,
it also prepares its food; it saves the animal one process, that of
the transmutation of inorganic into organic matter. The ultimate end,
or the final cause of the vital processes performed by the first class
of living beings, is thus the elaboration of aliment for the second:
the inferior life is spent in ministering, and the great object of its
being is to minister to the existence of the superior.
At the point at which organization commences structure is so simple
that there is no manifest distinction of organs. Several functions are
performed apparently by one single organized substance. The lowest
plants and the lowest animals are equally without any separate organs,
as far as it is in our power to distinguish them, for carrying on the
vital actions they perform. An organized tissue, apparently of an
homogeneous nature, containing fluid matter, is all that can be made
out by which the most simply-constructed plant carries on its single
set, and by which the most simply-constructed animal carries on its
double set, of actions. But this simplicity of structure exists only
at the very commencement of the organized world. Every advancement in
the scale of organization is indicated by the construction of organs
manifestly separate for the performance of individual functions;
and, invariably, the higher the being, the more complete is this
separation of function from function, and, consequently, the greater
the multiplication of organs, and the more elaborate and complex the
structure;—and hence another distinction between the plant and the
animal. The simplicity of the structure of the plant is in striking
contrast to the complexity of the structure of the animal; and this
difference is not arbitrary; it is a matter of absolute necessity, and
the reason of this necessity it will be instructive to contemplate.
The plant, as has been shown, performs only one set of functions, the
organic; while the animal performs two sets of functions, the organic
and the animal. The animal, then, performs more functions than the
plant, and functions of a higher order; it carries on its functions
with a greater degree of energy; its functions have a more extended
range, and all its functions bear a certain relation to each other,
maintaining an harmonious action. The number, the superiority, the
relation, the range, and the energy of the functions performed by
the animal are, then, so many conditions, which render it absolutely
indispensable that it should possess a greater complexity of structure
than the plant.
1. To build up structure is to create, to arrange, and to connect
organs. Organs are the instruments by which functions are performed,
and without the instrument there can be no action. With as many
more organs than the plant possesses the animal must, therefore, be
provided, as are necessary to carry on the additional functions it
performs. Organs, for its organic functions, it must have as well as
the plant; but to these must be superadded organs of another class, for
which the plant has no need, namely, organs for its animal functions.
Two sets of organs must, therefore, be provided for the animal, while
the plant requires but one.
2. Some functions performed by the animal are of a higher order than
any performed by the plant, and the superior function requires a higher
organization. The construction of an organ is complex as its action is
elevated; the instrument is elaborately prepared in proportion to the
nobleness of its office.
[Illustration: Fig. I.]
[Illustration: Fig. II.]
[Illustration: Fig. III.]
[Illustration: Fig. IV.]
3. But this is not all; for the addition of a superior function
requires not only the addition of an organ having a corresponding
superiority of structure, but it requires, further, that a certain
elevation of structure should be communicated to all the organs of
all the inferior functions, on account of the relation which it is
necessary to establish between function and function. Unless the organ
of an inferior function be constructed with a perfection corresponding
to that of the organ of a superior function, the inferior will be
incapable of working in harmony with the superior. Take, for example,
the inferior function of nutrition: nutrition is an organic function
equally necessary to the plant and to the animal, and requiring in
both organs for performing it; but this function cannot be performed
in the animal by organs as simple as suffice for the plant. Nutrition,
in the plant, is carried on in the following mode:—The root of the
plant is divided, like the trunk, into numerous branches (fig. I. 1).
These branches divide and subdivide into smaller and smaller branches,
until at last they reach an extreme degree of minuteness (fig. I. 2 2).
The smallest of these divisions, called, from their hair-like tenuity,
_capillary_ (fig. I. 2 2), are provided with a peculiar structure,
which is endowed with a specific function. In most plants this peculiar
structure is found at the terminal point of the rootlet (fig. I. 2 2);
but in some plants the capillary branches of the rootlets are provided
with distinct bodies (fig. II. 1 2), scarcely to be discerned when
the root has been removed some time from the soil, and has become dry
(fig. II. 2 2); but which, in a few minutes after the root has been
plunged in water, provided the plant be still alive, become turgid with
fluid, and, consequently, distinctly visible (fig. II. 1 1 1). These
bodies, when they exist, or the terminal point of the rootlet when
these bodies are absent, are termed _spongeolæ_, or spongeoles; and the
structure and function of the organ, in both cases, are conceived to
be precisely the same. In both the organ consists of a minute cellular
structure. Fig. III. 1, shows this structure as it appears when the
object is magnified. The office of this organ is to absorb the aliment
of the plant from the soil; and so great is its absorbing power, that,
as is proved by direct experiment, it absorbs the colouring molecules
of liquids, though these molecules will not enter the ordinary pores,
which are of much greater magnitude. With the spongeoles are connected
vessels which pass through the substance of the stem or trunk to the
leaf. Fig. III. 2, shows these tubes springing from the cellular
structure of the spongeole, and passing up to the stem or trunk. Fig.
IV. 2, exhibits a magnified view of the appearance of the mouths of
these tubes on making an horizontal section of the spongeole. Fig. V.
1 1 1, exhibits a view of these tubes passing to the leaf. Figs. VI.
and VII. 1 1 1 1, show these vessels spread out upon, and ramifying
through, the leaf. The crude aliment, borne by these tubes to the leaf,
is there converted into proper nutriment; and from the leaf, when
duly elaborated, this proper nutriment is carried out by ducts to the
various organs of the plant, in order to supply them with the aliment
they need.
[Illustration: Fig. V.]
Now, for carrying on the process of nutrition in this mode, there
must be organs to absorb the crude aliment, organs to convey the crude
aliment to the laboratory, the leaf, in which it is converted into
proper nutriment; and, finally, organs for carrying out this proper
nutriment to the system. Complication of structure, to this extent, is
indispensable; and, accordingly, with spongeolæ, with sap-vessels, with
leaves, with distributive ducts, the plant is provided. Without all the
parts of this apparatus it could not carry on its function: any further
complication would be useless.
[Illustration: Fig. VI.]
But, suppose a new and superior function to be added to the plant;
suppose it to be endowed with the power of locomotion, what would be
the consequence of communicating to it this higher power? That its
former state of simplicity would no longer suffice for the inferior
function. Why? because the exercise of the superior would interrupt
the action of the inferior function. Nutrition by imbibition, and
the exercise of locomotion, cannot go on simultaneously in the same
being. The plant is fixed in the soil by its roots; and from this, its
state of immobility, results this most important consequence, that its
spongeolæ are always in contact with its food.
[Illustration: Fig. VII.]
[Illustration: Fig. VIII.]
But we may imagine a plant not fixed to the soil; a plant so
constituted as to be capable of moving from place to place; such a
plant would not be always in contact with its food, and therefore, as
it exercised its faculty of locomotion, it could not but interrupt
or suspend its function of nutrition. In a being capable of carrying
on these two functions simultaneously, the entire apparatus of the
function of nutrition must then be modified. Instead of having
spongeolæ fixed immovably in the earth, and spread out in a soil
adapted to transmit to these organs nutrient matter in a state fitted
for absorption, it must be provided with a reservoir for containing
its food, in order that it may carry its aliment about with it in
all its changes of place. And such is the modification uniformly
found in all animals: an internal reservoir for containing its food
is provided, perhaps, for every animal without exception. Even the
simplest and minutest creatures with which the microscope has made
us acquainted, the lowest tribes of the Infusoria (fig. VIII.), the
sentient, self-moving cellules, placed at the very bottom of the
animal scale, possess this modification of structure. For a long
time it was conceived that these minute and simple creatures were
without distinction of parts, that they had no separate organs for the
reception and digestion of their food; that they absorbed their aliment
through the porous tissue of which their body is composed; that thus,
instead of having a separate stomach, their entire body is a stomach,
and instead of having even as much as a separate organ for absorption,
like the more perfect plant, the whole body might be considered as a
single spongeole.
But, by a simple and beautiful experiment, a German physiologist
has shown the incorrectness of this opinion, and has established the
fact, that the distinction between the plant and the animal, here
contended for, is found even at the very lowest point of the animal
scale. Like other physiologists, conceiving that the difficulty of
discovering the structure of the lower tribes of the animalculi
might be owing to the transparency or the tissues of which they are
composed, it struck Ehrenberg, that if he could feed them with coloured
substances, he might obtain some insight into their organization.
In his first endeavours to accomplish this object he failed, for he
employed the pigments in ordinary use; but either the animals would not
touch aliment thus adulterated, or those that did so were instantly
killed. It then occurred to him, that these colours are adulterated
with lead and other substances, in all probability noxious to the
little subjects of his experiment. "What I require," said he, "is some
vegetable or animal colouring matter perfectly pure." He then tried
perfectly pure indigo and perfectly pure carmine. His success was
now complete: in a minute or two, after mixing with their food pure
vegetable colouring matter, he observed in the interior of the body of
these creatures minute spots of a definite figure, and of the colour
of the pigment employed (fig. VIII. 1 1 1 1). The form and magnitude
of these spots were different in different tribes, but the same in the
same individual, and even in the same species (fig. IX. 1 1, fig. X.
1 1). No other parts of the body were tinged with the colour, though
the animals remained in the coloured fluid for days together. This was
decisive. This physiologist had now obtained an instrument capable of
revealing to him the interior organization of a class of beings, the
structure of which had heretofore been wholly unknown. On applying
it to the MONAS TERMO (fig. VIII.), the animated point, or cellule,
which stands at the bottom of the animal scale, he discovered, in the
posterior portion of its body, several coloured spots which constitute
its stomachs (fig. VIII. 1 1 1 1). The different situations and
different forms of the stomach in different tribes of these creatures,
are represented by the coloured portions (fig. VIII. 1, fig. IX. 1,
fig. X. 1), in which the currents of fluid flowing to their mouths
are seen (fig. IX. 2, fig. X. 2). These experiments go far towards
establishing the fact, that every animal, even the very lowest, has an
external mouth and an internal stomach, and that it takes its food by
an act of volition.
[Illustration: Fig. IX.]
[Illustration: Fig. X.]
But if the proof of this must be admitted to be still imperfect
with regard to the lowest tribes of animals, it is certain that, as
we ascend in the scale of organization, the nutritive apparatus is
uniformly arranged in this mode. Every animal of every class large
enough to be distinctly visible, and the structure of which is not
rendered inappreciable by the transparency of its solids and fluids, is
manifestly provided with a distinct internal reservoir for containing
its food. On the internal surface of this reservoir open the mouths of
vessels, minute in size but countless in number, which absorb the food
from the stomach.
Fig. XI. shows these vessels opening on the inner surface of the
stomach, the white points representing their mouths, turgid with the
food they have absorbed. Fig. XII. exhibits magnified views of the same
vessels, the points representing their open mouths, and the lines the
vessels themselves in continuation with their mouths. Fig. XIII. shows
the appearance of the inner surface of the intestine soon after the
animal has taken food; the smaller white lines (1 1 1 1) representing
the absorbent vessels full of digested food, and the larger lines (2 2
2 2) the trunks of the absorbent vessels formed by the union of many of
the smaller.
[Illustration: Fig. XI.]
[Illustration: Fig. XII.]
From this account, it is clear that the absorbing vessels of the
stomach perform an office precisely analogous to that of the spongeoles
of the root. What the soil is to the plant, the stomach is to the
animal. The absorbing vessels diffused through the stomach, as long
as the stomach contains food, are in exactly the same condition as
the spongeoles of the root spread out in the soil; and the absorbing
vessels of the stomach are as much and as constantly in contact with
the aliment, which it is their office to take into the system, as the
spongeoles of the root. Such, then, is the expedient adopted to render
the function of nutrition compatible with the function of locomotion.
A reservoir of food is placed in the interior of the animal, provided
with absorbent vessels which are always in contact with the aliment. In
this mode, contact with aliment is not disturbed by continual change of
place; the organic process is not interrupted by the exercise of the
animal function.
[Illustration: Fig. XIII.]
But the more elaborate organization which it is necessary to impart
to the apparatus of the inferior function, in consequence of the
communication of a superior faculty, is not completed simply by the
addition of this new organ, the stomach. Other complications are
indispensable; for if food be contained in an isolated organ, placed in
the interior of the body, means must be provided for conveying the food
into this organ; hence the necessity of an apparatus for deglutition.
Moreover, the food having been conveyed to the stomach, and having
undergone there the requisite changes, means must next be provided for
conveying it from the stomach to the other parts of the body; hence
the necessity of an apparatus for the circulation. But food, however
elaborately prepared by the stomach, is incapable of nourishing the
body, until it has been submitted to the action of atmospheric air;
hence the necessity of an additional apparatus, either for conveying
food to the air, or for transmitting air to the food, or for bringing
both the food and the air into contact in the same organ. And, when
structure after structure has been built up, in order to carry on this
extended series of processes, the number of provisions required is
not even yet complete; for of the most nutritious fond the whole mass
is not nutritive; and even the whole of that portion of it which is
actually applied to the purpose of nutrition, becomes, after a time,
worn out, and must be removed from the system; hence the necessity of a
further apparatus for excretion.
That nutrition and locomotion may go on together, it is clear, then,
that there must be provided a distinct apparatus for containing
food, a distinct apparatus for deglutition, a distinct apparatus for
circulation, a distinct apparatus for respiration, a distinct apparatus
for excretion, and so on; and that, in this manner, the communication
of a single function of a superior order renders a modification not
merely of one but of many inferior functions absolutely indispensable,
in order to adjust the one to the other, and to enable them to act in
harmony.
But the necessary complication of structure does not stop even here;
for the communication of one function of a superior order imposes
the necessity of communicating still another. Locomotion cannot be
exercised without perception; sensation is indispensable to volition,
and volition, of course, to voluntary motion. A being endowed with
the power of moving from place to place, without possessing the power
of perceiving external objects, must be speedily destroyed. The
communication of sensation to a creature fixed immovably to a single
spot, conscious of the approach of bodies, but incapable of avoiding
their contact, would be not only useless but pernicious, since it
would be to make a costly provision for the production of pain, and
nothing else; but the communication of locomotion without sensation
would be as unwisely defective, as the former would be perniciously
expensive; since it would be to endow a being with a faculty, the
exercise of which would be fatal to it for the want of a second faculty
to guide the first. Nor could the possession of locomotion, without the
further possession of sensation, be otherwise than fatal, for another
reason. Consciousness is not necessary to nutrition as performed by
the plant, but it is indispensable to nutrition as performed by the
animal: for if the food of the animal be not always on the same spot
with itself; if it be under the necessity of searching for it, and of
conveying it, when found, into the interior of its body, it must, of
course, possess the power of perceiving it when within its reach, and
of apprehending and appropriating it by an act of volition, of none of
which actions is it capable without the possession of sensation. Again,
then, we see that, in order to secure harmonious action, function must
be put in relation with function. In order to prevent jarring and
mutually-destructive action, function must be superadded to function,
and throughout the animal creation the complication of structure, which
is necessary for the accomplishment of these ends, is given without
parsimony, but without profusion: nothing is given which is not needed,
nothing is withheld which is required.
4. As we ascend in the scale of organization, numerous functions being
carried on, and numerous organs constructed for performing them, it
is obvious that the range of each function must be proportionally
extended; the range necessarily increasing with the multiplication
of organ and function: and this is another cause of the unavoidable
complication of structure. Slight consideration will suffice to show
the necessary connexion between an extended range of action and
complication of structure. Take, as an example, the organic function
of respiration: respiration is the function by which air is brought
into contact with food; it is the completion of digestion. The sole
end of all the apparatus that belongs to this function is to bring the
air and the food into a certain degree of proximity. Now, when all the
substances that enter into the composition of the body of an animal are
slight, delicate, and permeable to air (as in fig. XIV.), and when the
body is always surrounded by air, air must at all times be in contact
with the particular organ that contains the food, no less than with
the general system to which the food is distributed. In this case, to
construct a separate apparatus for containing air would be useless,
because wherever food is, there air must be, since it constantly
permeates every part of the body.
[Illustration: Fig. XIV.]
When, on the other hand, the tissues are so firm and dense as to be
impermeable; when they are folded into bulky and complex organs, and
when these organs are placed in situations to which the external air
cannot reach, the construction of a separate apparatus for respiration
is indispensable. The respiratory apparatus consists either of organs
for carrying air to the food, or of organs for carrying food to the
air. The one or the other is adopted, according to the nature of the
body. If the size of the animal be small; if the tissues which form
the solid portion of its body be delicate in texture; if, at the same
time, the wants of its economy require that its food should be highly
aërated (for there is the closest connexion between energy of function
and perfect aëration of the food), an apparatus of sufficient magnitude
to aërate the food in a high degree would occupy the entire bulk of the
body. In such a case, it is easier to carry air to the food than food
to the air; it is better to make the entire body a respiratory organ,
than to construct a respiratory organ disproportioned to the magnitude
of the body. Air-tubes diffused through every part of the body, and
opening on its external surface, would obviously afford to every point
of the system an easy access of air. By an expedient of this kind the
system might be highly aërated, while the respiratory apparatus would
occupy but a comparatively small space; the function might be performed
on an extended scale, while there would be no necessity for encumbering
a minute body with a bulky organ. And this is the mode in which
respiration is carried on in large tribes of creatures, whose body
is small in size and delicate in texture, and the functions of whose
economy are performed with energy (fig. XV.).
[Illustration: Fig. XV.
The Achilles Butterfly of South America (_Papilio Achilles_),
showing the tracheæ on the upper and under side of the wings.]
But this contrivance will not do when the animal is of large
magnitude; when its body is divided into numerous compartments; when
these compartments extend far beneath the external surface; when
important organs are placed in deeply-seated cavities; and when
the substances that compose the organs are dense, hard, thick, and
convoluted. To construct air-tubes of the requisite diameter and
length, always open, always in a condition to permit the ingress and
egress of an adequate current of air to and from the remotest nook and
corner of a body such as this, would be difficult, if not impossible.
At all events, it is easier, in such a case, to carry the food to the
air, than the air to the food. But, for the accomplishment of this
purpose, what is necessary? An organ for containing food; an organ
for containing air; vessels to carry food to and from the receptacle
of the aliment; vessels to carry air to and from the receptacle of
the air; expedients to expose a stream of food to a current of air;
and, finally, tubes to carry out to the system the product of this
complicated operation. Accordingly, a reservoir of food and a reservoir
of air; an apparatus by which both are conveyed to their respective
receptacles; and an apparatus by which both are brought into contact
sufficiently close to admit of their mutual action, are all combined
in the lung of the animal, and in the mechanism by which its movements
are effected. The object is accomplished, but the apparatus by which it
is effected is as complex in structure as it is efficient in action;
the result simple; the means by which the result is secured, highly
complicated.
And if this be true of an inferior or organic function, it is still
more strikingly true of a superior or animal function. The relation is
still stricter between the complexity of the apparatus of sensation and
the range of feeling, than between the complexity of the apparatus of
respiration and the range of the respiratory process. The greater the
number of the senses, the greater the number of the organs of sense;
the more accurate and varied the impressions conveyed by each, the more
complex the structure of the instrument by which they are communicated;
the more extended the range of the intellectual operations, the larger
the bulk of the brain, the greater the number of its distinct parts,
and the more exquisite their organization. From the point of the animal
scale, at which the brain first becomes distinctly visible, up to man,
the basis of the organ is the same; but, as the range of its function
extends, part after part is superadded, and the structure of each part
becomes progressively more and more complex. The evidence of this,
afforded by comparative anatomy, is irresistible, and the interest
connected with the study of it can scarcely be exceeded.
5. In the last place, structure is complex in proportion to the
energy of function. The greater the power with which voluntary motion
is capable of being exerted, the higher the organization of the
apparatus by which it is performed; the more compact and dense the
shell, the cartilage, the bone, the firmer the fibre of the muscle,
and, in general, the greater its comparative bulk. The wing of the
eagle is as much more developed than the wing of the wren, as its
flight is higher, and its speed swifter. The muscles which give to the
tiger the rapidity and strength of its spring possess a more intense
organization than those which slowly move on the tardigrade sloth. The
structure of the brain of man is more exquisite than that of the fish,
as his perceptions are more acute, and capable of greater combination,
comprehension, and continuity.
Thus we see that the organization of the animal is more complex than
that of the plant, not from an arbitrary disposition, but from absolute
necessity. The few and simple functions performed by the plant require
only the few and simple organs with which it is provided: the numerous
and complicated functions performed by the animal require its numerous
and complicated organs: the plant, simple as it is in structure, is
destitute of no organ required by the nature of its economy; the
animal, complex as it is in structure, is in possession of no organ
which it could dispense with: from the one, nothing is withheld which
is needed; to the other, nothing is given which is superfluous: in the
one, there is economy without niggardliness; in the other, munificence
without waste.