The Present Condition of Organic Nature / Huxley, Thomas Henry, 1825-1895

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Title:  The Present Condition of Organic Nature



Author:  Thomas H. Huxley



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EDITOR'S NOTE



Of the great thinkers of the nineteenth century, Thomas Henry Huxley,

son of an Ealing schoolmaster, was undoubtedly the most noteworthy. His

researches in biology, his contributions to scientific controversy, his

pungent criticisms of conventional beliefs and thoughts have probably

had greater influence than the work of any other English scientist. And

yet he was a "self-made" intellectualist. In spite of the fact that his

father was a schoolmaster he passed through no regular course of

education.  "I had," he said, "two years of a pandemonium of a school

(between eight and ten) and after that neither help nor sympathy in any

intellectual direction till I reached manhood."  When he was twelve a

craving for reading found satisfaction in Hutton's "Geology," and when

fifteen in Hamilton's "Logic."



At seventeen Huxley entered as a student at Charing Cross Hospital, and

three years later he was M.B. and the possessor of the gold medal for

anatomy and physiology.  An appointment as surgeon in the navy proved

to be the entry to Huxley's great scientific career, for he was

gazetted to the "Rattlesnake", commissioned for surveying work in

Torres Straits.  He was attracted by the teeming surface life of

tropical seas and his study of it was the commencement of that

revolution in scientific knowledge ultimately brought about by his

researches.



Thomas Henry Huxley was born at Ealing on May 4, 1825, and died at

Eastbourne June 29, 1895.







LECTURES AND ESSAYS BY T.H. HUXLEY









ON OUR KNOWLEDGE OF THE CAUSES OF THE PHENOMENA OF ORGANIC NATURE









NOTICE TO THE FIRST EDITION.



The Publisher of these interesting Lectures, having made an arrangement

for their publication with Mr. J. A. Mays, the Reporter, begs to append

the following note from Professor Huxley:--



"Mr. J. Aldous Mays, who is taking shorthand notes of my 'Lectures to

Working Men,' has asked me to allow him, on his own account, to print

those Notes for the use of my audience.  I willingly accede to this

request, on the understanding that a notice is prefixed to the effect

that I have no leisure to revise the Lectures, or to make alterations

in them, beyond the correction of any important error in a matter of

fact."









THE PRESENT CONDITION OF ORGANIC NATURE.



When it was my duty to consider what subject I would select for the six

lectures [*To Working Men, at the Museum of Practical Geology, 1863.]

which I shall now have the pleasure of delivering to you, it occurred

to me that I could not do better than endeavour to put before you in a

true light, or in what I might perhaps with more modesty call, that

which I conceive myself to be the true light, the position of a book

which has been more praised and more abused, perhaps, than any book

which has appeared for some years;--I mean Mr. Darwin's work on the

"Origin of Species".  That work, I doubt not, many of you have read;

for I know the inquiring spirit which is rife among you.  At any rate,

all of you will have heard of it,--some by one kind of report and some

by another kind of report; the attention of all and the curiosity of

all have been probably more or less excited on the subject of that

work.  All I can do, and all I shall attempt to do, is to put before

you that kind of judgment which has been formed by a man, who, of

course, is liable to judge erroneously; but, at any rate, of one whose

business and profession it is to form judgments upon questions of this

nature.



And here, as it will always happen when dealing with an extensive

subject, the greater part of my course--if, indeed, so small a number

of lectures can be properly called a course--must be devoted to

preliminary matters, or rather to a statement of those facts and of

those principles which the work itself dwells upon, and brings more or

less directly before us.  I have no right to suppose that all or any of

you are naturalists; and even if you were, the misconceptions and

misunderstandings prevalent even among naturalists on these matters

would make it desirable that I should take the course I now propose to

take,--that I should start from the beginning,--that I should endeavour

to point out what is the existing state of the organic world,--that I

should point out its past condition,--that I should state what is the

precise nature of the undertaking which Mr. Darwin has taken in hand;

that I should endeavour to show you what are the only methods by which

that undertaking can be brought to an issue, and to point out to you

how far the author of the work in question has satisfied those

conditions, how far he has not satisfied them, how far they are

satisfiable by man, and how far they are not satisfiable by man.



To-night, in taking up the first part of this question, I shall

endeavour to put before you a sort of broad notion of our knowledge of

the condition of the living world.  There are many ways of doing this.

I might deal with it pictorially and graphically.  Following the

example of Humboldt in his "Aspects of Nature", I might endeavour to

point out the infinite variety of organic life in every mode of its

existence, with reference to the variations of climate and the like;

and such an attempt would be fraught with interest to us all; but

considering the subject before us, such a course would not be that best

calculated to assist us.  In an argument of this kind we must go

further and dig deeper into the matter; we must endeavour to look into

the foundations of living Nature, if I may so say, and discover the

principles involved in some of her most secret operations.  I propose,

therefore, in the first place, to take some ordinary animal with which

you are all familiar, and, by easily comprehensible and obvious

examples drawn from it, to show what are the kind of problems which

living beings in general lay before us; and I shall then show you that

the same problems are laid open to us by all kinds of living beings.

But first, let me say in what sense I have used the words "organic

nature." In speaking of the causes which lead to our present knowledge

of organic nature, I have used it almost as an equivalent of the word

"living," and for this reason,--that in almost all living beings you

can distinguish several distinct portions set apart to do particular

things and work in a particular way.  These are termed "organs," and

the whole together is called "organic."  And as it is universally

characteristic of them, this term "organic" has been very conveniently

employed to denote the whole of living nature,--the whole of the plant

world, and the whole of the animal world.



Few animals can be more familiar to you than that whose skeleton is

shown on our diagram.  You need not bother yourselves with this "Equus

caballus" written under it; that is only the Latin name of it, and does

not make it any better.  It simply means the common Horse. Suppose we

wish to understand all about the Horse.  Our first object must be to

study the structure of the animal.  The whole of his body is inclosed

within a hide, a skin covered with hair; and if that hide or skin be

taken off, we find a great mass of flesh, or what is technically called

muscle, being the substance which by its power of contraction enables

the animal to move.  These muscles move the hard parts one upon the

other, and so give that strength and power of motion which renders the

Horse so useful to us in the performance of those services in which we

employ him.



And then, on separating and removing the whole of this skin and flesh,

you have a great series of bones, hard structures, bound together with

ligaments, and forming the skeleton which is represented here.



[FIGURE 1.  (Section through a horse.)



FIGURE 2.  (Section through a cell.)]



In that skeleton there are a number of parts to be recognized.  The

long series of bones, beginning from the skull and ending in the tail,

is called the spine, and those in front are the ribs; and then there

are two pairs of limbs, one before and one behind; and there are what

we all know as the fore-legs and the hind-legs.  If we pursue our

researches into the interior of this animal, we find within the

framework of the skeleton a great cavity, or rather, I should say, two

great cavities,--one cavity beginning in the skull and running through

the neck-bones, along the spine, and ending in the tail, containing the

brain and the spinal marrow, which are extremely important organs. The

second great cavity, commencing with the mouth, contains the gullet,

the stomach, the long intestine, and all the rest of those internal

apparatus which are essential for digestion; and then in the same great

cavity, there are lodged the heart and all the great vessels going from

it; and, besides that, the organs of respiration-- the lungs: and then

the kidneys, and the organs of reproduction, and so on.  Let us now

endeavour to reduce this notion of a horse that we now have, to some

such kind of simple expression as can be at once, and without

difficulty, retained in the mind, apart from all minor details.  If I

make a transverse section, that is, if I were to saw a dead horse

across, I should find that, if I left out the details, and supposing I

took my section through the anterior region, and through the

fore-limbs, I should have here this kind of section of the body (Fig.

1).  Here would be the upper part of the animal--that great mass of

bones that we spoke of as the spine (a, Fig. 1).  Here I should have

the alimentary canal (b, Fig. 1).  Here I should have the heart (c,

Fig. 1); and then you see, there would be a kind of double tube, the

whole being inclosed within the hide; the spinal marrow would be placed

in the upper tube (a, Fig. 1), and in the lower tube (d d, Fig.  1),

there would be the alimentary canal (b), and the heart (c); and here I

shall have the legs proceeding from each side.  For simplicity's sake,

I represent them merely as stumps (e e, Fig. 1). Now that is a

horse--as mathematicians would say--reduced to its most simple

expression.  Carry that in your minds, if you please, as a simplified

idea of the structure of the Horse.  The considerations which I have

now put before you belong to what we technically call the 'Anatomy' of

the Horse.  Now, suppose we go to work upon these several parts,--flesh

and hair, and skin and bone, and lay open these various organs with our

scalpels, and examine them by means of our magnifying- glasses, and see

what we can make of them.  We shall find that the flesh is made up of

bundles of strong fibres.  The brain and nerves, too, we shall find,

are made up of fibres, and these queer-looking things that are called

ganglionic corpuscles.  If we take a slice of the bone and examine it,

we shall find that it is very like this diagram of a section of the

bone of an ostrich, though differing, of course, in some details; and

if we take any part whatsoever of the tissue, and examine it, we shall

find it all has a minute structure, visible only under the microscope.

All these parts constitute microscopic anatomy or 'Histology.'  These

parts are constantly being changed; every part is constantly growing,

decaying, and being replaced during the life of the animal.  The tissue

is constantly replaced by new material; and if you go back to the young

state of the tissue in the case of muscle, or in the case of skin, or

any of the organs I have mentioned, you will find that they all come

under the same condition.  Every one of these microscopic filaments and

fibres (I now speak merely of the general character of the whole

process)-- every one of these parts--could be traced down to some

modification of a tissue which can be readily divided into little

particles of fleshy matter, of that substance which is composed of the

chemical elements, carbon, hydrogen, oxygen, and nitrogen, having such

a shape as this (Fig. 2).  These particles, into which all primitive

tissues break up, are called cells.  If I were to make a section of a

piece of the skin of my hand, I should find that it was made up of

these cells.  If I examine the fibres which form the various organs of

all living animals, I should find that all of them, at one time or

other, had been formed out of a substance consisting of similar

elements; so that you see, just as we reduced the whole body in the

gross to that sort of simple expression given in Fig. 1, so we may

reduce the whole of the microscopic structural elements to a form of

even greater simplicity; just as the plan of the whole body may be so

represented in a sense (Fig. 1), so the primary structure of every

tissue may be represented by a mass of cells (Fig. 2).



Having thus, in this sort of general way, sketched to you what I may

call, perhaps, the architecture of the body of the Horse (what we term

technically its Morphology), I must now turn to another aspect.  A

horse is not a mere dead structure: it is an active, living, working

machine.  Hitherto we have, as it were, been looking at a steam-engine

with the fires out, and nothing in the boiler; but the body of the

living animal is a beautifully-formed active machine, and every part

has its different work to do in the working of that machine, which is

what we call its life.  The Horse, if you see him after his day's work

is done, is cropping the grass in the fields, as it may be, or munching

the oats in his stable.  What is he doing?  His jaws are working as a

mill--and a very complex mill too--grinding the corn, or crushing the

grass to a pulp.  As soon as that operation has taken place, the food

is passed down to the stomach, and there it is mixed with the chemical

fluid called the gastric juice, a substance which has the peculiar

property of making soluble and dissolving out the nutritious matter in

the grass, and leaving behind those parts which are not nutritious; so

that you have, first, the mill, then a sort of chemical digester; and

then the food, thus partially dissolved, is carried back by the

muscular contractions of the intestines into the hinder parts of the

body, while the soluble portions are taken up into the blood.  The

blood is contained in a vast system of pipes, spreading through the

whole body, connected with a force pump,--the heart,--which, by its

position and by the contractions of its valves, keeps the blood

constantly circulating in one direction, never allowing it to rest; and

then, by means of this circulation of the blood, laden as it is with

the products of digestion, the skin, the flesh, the hair, and every

other part of the body, draws from it that which it wants, and every

one of these organs derives those materials which are necessary to

enable it to do its work.



The action of each of these organs, the performance of each of these

various duties, involve in their operation a continual absorption of

the matters necessary for their support, from the blood, and a constant

formation of waste products, which are returned to the blood, and

conveyed by it to the lungs and the kidneys, which are organs that have

allotted to them the office of extracting, separating, and getting rid

of these waste products; and thus the general nourishment, labour, and

repair of the whole machine is kept up with order and regularity.  But

not only is it a machine which feeds and appropriates to its own

support the nourishment necessary to its existence--it is an engine for

locomotive purposes.  The Horse desires to go from one place to

another; and to enable it to do this, it has those strong contractile

bundles of muscles attached to the bones of its limbs, which are put in

motion by means of a sort of telegraphic apparatus formed by the brain

and the great spinal cord running through the spine or backbone; and to

this spinal cord are attached a number of fibres termed nerves, which

proceed to all parts of the structure.  By means of these the eyes,

nose, tongue, and skin--all the organs of perception--transmit

impressions or sensations to the brain, which acts as a sort of great

central telegraph-office, receiving impressions and sending messages to

all parts of the body, and putting in motion the muscles necessary to

accomplish any movement that may be desired.  So that you have here an

extremely complex and beautifully-proportioned machine, with all its

parts working harmoniously together towards one common object--the

preservation of the life of the animal.



Now, note this: the Horse makes up its waste by feeding, and its food

is grass or oats, or perhaps other vegetable products; therefore, in

the long run, the source of all this complex machinery lies in the

vegetable kingdom.  But where does the grass, or the oat, or any other

plant, obtain this nourishing food-producing material?  At first it is

a little seed, which soon begins to draw into itself from the earth and

the surrounding air matters which in themselves contain no vital

properties whatever; it absorbs into its own substance water, an

inorganic body; it draws into its substance carbonic acid, an inorganic

matter; and ammonia, another inorganic matter, found in the air; and

then, by some wonderful chemical process, the details of which chemists

do not yet understand, though they are near foreshadowing them, it

combines them into one substance, which is known to us as 'Protein,' a

complex compound of carbon, hydrogen, oxygen, and nitrogen, which alone

possesses the property of manifesting vitality and of permanently

supporting animal life.  So that, you see, the waste products of the

animal economy, the effete materials which are continually being thrown

off by all living beings, in the form of organic matters, are

constantly replaced by supplies of the necessary repairing and

rebuilding materials drawn from the plants, which in their turn

manufacture them, so to speak, by a mysterious combination of those

same inorganic materials.



Let us trace out the history of the Horse in another direction.  After

a certain time, as the result of sickness or disease, the effect of

accident, or the consequence of old age, sooner or later, the animal

dies.  The multitudinous operations of this beautiful mechanism flag in

their performance, the Horse loses its vigour, and after passing

through the curious series of changes comprised in its formation and

preservation, it finally decays, and ends its life by going back into

that inorganic world from which all but an inappreciable fraction of

its substance was derived.  Its bones become mere carbonate and

phosphate of lime; the matter of its flesh, and of its other parts,

becomes, in the long run, converted into carbonic acid, into water, and

into ammonia.  You will now, perhaps, understand the curious relation

of the animal with the plant, of the organic with the inorganic world,

which is shown in this diagram (Fig. 3).



[FIGURE 3. (Diagram showing material relationship of the Vegetable,

Animal and Inorganic Worlds.)]



The plant gathers these inorganic materials together and makes them up

into its own substance.  The animal eats the plant and appropriates the

nutritious portions to its own sustenance, rejects and gets rid of the

useless matters; and, finally, the animal itself dies, and its whole

body is decomposed and returned into the inorganic world.  There is

thus a constant circulation from one to the other, a continual

formation of organic life from inorganic matters, and as constant a

return of the matter of living bodies to the inorganic world; so that

the materials of which our bodies are composed are largely, in all

probability, the substances which constituted the matter of long

extinct creations, but which have in the interval constituted a part of

the inorganic world.



Thus we come to the conclusion, strange at first sight, that the MATTER

constituting the living world is identical with that which forms the

inorganic world.  And not less true is it that, remarkable as are the

powers or, in other words, as are the FORCES which are exerted by

living beings, yet all these forces are either identical with those

which exist in the inorganic world, or they are convertible into them;

I mean in just the same sense as the researches of physical

philosophers have shown that heat is convertible into electricity, that

electricity is convertible into magnetism, magnetism into mechanical

force or chemical force, and any one of them with the other, each being

measurable in terms of the other,--even so, I say, that great law is

applicable to the living world.  Consider why is the skeleton of this

horse capable of supporting the masses of flesh and the various organs

forming the living body, unless it is because of the action of the same

forces of cohesion which combines together the particles of matter

composing this piece of chalk?  What is there in the muscular

contractile power of the animal but the force which is expressible, and

which is in a certain sense convertible, into the force of gravity

which it overcomes?  Or, if you go to more hidden processes, in what

does the process of digestion differ from those processes which are

carried on in the laboratory of the chemist?  Even if we take the most

recondite and most complex operations of animal life--those of the

nervous system, these of late years have been shown to be--I do not say

identical in any sense with the electrical processes--but this has been

shown, that they are in some way or other associated with them; that is

to say, that every amount of nervous action is accompanied by a certain

amount of electrical disturbance in the particles of the nerves in

which that nervous action is carried on. In this way the nervous action

is related to electricity in the same way that heat is related to

electricity; and the same sort of argument which demonstrates the two

latter to be related to one another shows that the nervous forces are

correlated to electricity; for the experiments of M. Dubois Reymond and

others have shown that whenever a nerve is in a state of excitement,

sending a message to the muscles or conveying an impression to the

brain, there is a disturbance of the electrical condition of that nerve

which does not exist at other times; and there are a number of other

facts and phenomena of that sort; so that we come to the broad

conclusion that not only as to living matter itself, but as to the

forces that matter exerts, there is a close relationship between the

organic and the inorganic world--the difference between them arising

from the diverse combination and disposition of identical forces, and

not from any primary diversity, so far as we can see.



I said just now that the Horse eventually died and became converted

into the same inorganic substances from whence all but an inappreciable

fraction of its substance demonstrably originated, so that the actual

wanderings of matter are as remarkable as the transmigrations of the

soul fabled by Indian tradition.  But before death has occurred, in the

one sex or the other, and in fact in both, certain products or parts of

the organism have been set free, certain parts of the organisms of the

two sexes have come into contact with one another, and from that

conjunction, from that union which then takes place, there results the

formation of a new being.  At stated times the mare, from a particular

part of the interior of her body, called the ovary, gets rid of a

minute particle of matter comparable in all essential respects with

that which we called a cell a little while since, which cell contains a

kind of nucleus in its centre, surrounded by a clear space and by a

viscid mass of protein substance (Fig. 2); and though it is different

in appearance from the eggs which we are mostly acquainted with, it is

really an egg.  After a time this minute particle of matter, which may

only be a small fraction of a grain in weight, undergoes a series of

changes,--wonderful, complex changes.  Finally, upon its surface there

is fashioned a little elevation, which afterwards becomes divided and

marked by a groove. The lateral boundaries of the groove extend upwards

and downwards, and at length give rise to a double tube.  In the upper

smaller tube the spinal marrow and brain are fashioned; in the lower,

the alimentary canal and heart; and at length two pairs of buds shoot

out at the sides of the body, which are the rudiments of the limbs.  In

fact a true drawing of a section of the embryo in this state would in

all essential respects resemble that diagram of a horse reduced to its

simplest expression, which I first placed before you (Fig. 1).



Slowly and gradually these changes take place.  The whole of the body,

at first, can be broken up into "cells," which become in one place

metamorphosed into muscle,--in another place into gristle and bone,--in

another place into fibrous tissue,--and in another into hair; every

part becoming gradually and slowly fashioned, as if there were an

artificer at work in each of these complex structures that we have

mentioned.  This embryo, as it is called, then passes into other

conditions.  I should tell you that there is a time when the embryos of

neither dog, nor horse, nor porpoise, nor monkey, nor man, can be

distinguished by any essential feature one from the other; there is a

time when they each and all of them resemble this one of the Dog.  But

as development advances, all the parts acquire their speciality, till

at length you have the embryo converted into the form of the parent

from which it started.  So that you see, this living animal, this

horse, begins its existence as a minute particle of nitrogenous matter,

which, being supplied with nutriment (derived, as I have shown, from

the inorganic world), grows up according to the special type and

construction of its parents, works and undergoes a constant waste, and

that waste is made good by nutriment derived from the inorganic world;

the waste given off in this way being directly added to the inorganic

world; and eventually the animal itself dies, and, by the process of

decomposition, its whole body is returned to those conditions of

inorganic matter in which its substance originated.



This, then, is that which is true of every living form, from the lowest

plant to the highest animal--to man himself.  You might define the life

of every one in exactly the same terms as those which I have now used;

the difference between the highest and the lowest being simply in the

complexity of the developmental changes, the variety of the structural

forms, the diversity of the physiological functions which are exerted

by each.



If I were to take an oak tree as a specimen of the plant world, I

should find that it originated in an acorn, which, too, commenced in a

cell; the acorn is placed in the ground, and it very speedily begins to

absorb the inorganic matters I have named, adds enormously to its bulk,

and we can see it, year after year, extending itself upward and

downward, attracting and appropriating to itself inorganic materials,

which it vivifies, and eventually, as it ripens, gives off its own

proper acorns, which again run the same course.  But I need not

multiply examples,--from the highest to the lowest the essential

features of life are the same, as I have described in each of these

cases.



So much, then, for these particular features of the organic world,

which you can understand and comprehend, so long as you confine

yourself to one sort of living being, and study that only.



But, as you know, horses are not the only living creatures in the

world; and again, horses, like all other animals, have certain

limits--are confined to a certain area on the surface of the earth on

which we live,--and, as that is the simpler matter, I may take that

first.  In its wild state, and before the discovery of America, when

the natural state of things was interfered with by the Spaniards, the

Horse was only to be found in parts of the earth which are known to

geographers as the Old World; that is to say, you might meet with

horses in Europe, Asia, or Africa; but there were none in Australia,

and there were none whatsoever in the whole continent of America, from

Labrador down to Cape Horn.  This is an empirical fact, and it is what

is called, stated in the way I have given it you, the 'Geographical

Distribution' of the Horse.



Why horses should be found in Europe, Asia, and Africa, and not in

America, is not obvious; the explanation that the conditions of life in

America are unfavourable to their existence, and that, therefore, they

had not been created there, evidently does not apply; for when the

invading Spaniards, or our own yeomen farmers, conveyed horses to these

countries for their own use, they were found to thrive well and

multiply very rapidly; and many are even now running wild in those

countries, and in a perfectly natural condition.  Now, suppose we were

to do for every animal what we have here done for the Horse,--that is,

to mark off and distinguish the particular district or region to which

each belonged; and supposing we tabulated all these results, that would

be called the Geographical Distribution of animals, while a

corresponding study of plants would yield as a result the Geographical

Distribution of plants.



I pass on from that now, as I merely wished to explain to you what I

meant by the use of the term 'Geographical Distribution.'  As I said,

there is another aspect, and a much more important one, and that is,

the relations of the various animals to one another.  The Horse is a

very well-defined matter-of-fact sort of animal, and we are all pretty

familiar with its structure.  I dare say it may have struck you, that

it resembles very much no other member of the animal kingdom, except

perhaps the Zebra or the Ass.  But let me ask you to look along these

diagrams.  Here is the skeleton of the Horse, and here the skeleton of

the Dog.  You will notice that we have in the Horse a skull, a backbone

and ribs, shoulder-blades and haunch-bones.  In the fore-limb, one

upper arm-bone, two fore arm-bones, wrist-bones (wrongly called knee),

and middle hand-bones, ending in the three bones of a finger, the last

of which is sheathed in the horny hoof of the fore-foot: in the

hind-limb, one thigh-bone, two leg-bones, anklebones, and middle

foot-bones, ending in the three bones of a toe, the last of which is

encased in the hoof of the hind-foot.  Now turn to the Dog's skeleton.

We find identically the same bones, but more of them, there being more

toes in each foot, and hence more toe-bones.



Well, that is a very curious thing!  The fact is that the Dog and the

Horse--when one gets a look at them without the outward impediments of

the skin--are found to be made in very much the same sort of fashion.

And if I were to make a transverse section of the Dog, I should find

the same organs that I have already shown you as forming parts of the

Horse.  Well, here is another skeleton--that of a kind of Lemur--you

see he has just the same bones; and if I were to make a transverse

section of it, it would be just the same again.  In your mind's eye

turn him round, so as to put his backbone in a position inclined

obliquely upwards and forwards, just as in the next three diagrams,

which represent the skeletons of an Orang, a Chimpanzee, a Gorilla, and

you find you have no trouble in identifying the bones throughout; and

lastly turn to the end of the series, the diagram representing a man's

skeleton, and still you find no great structural feature essentially

altered.  There are the same bones in the same relations. From the

Horse we pass on and on, with gradual steps, until we arrive at last at

the highest known forms.  On the other hand, take the other line of

diagrams, and pass from the Horse downwards in the scale to this fish;

and still, though the modifications are vastly greater, the essential

framework of the organization remains unchanged.  Here, for instance,

is a Porpoise: here is its strong backbone, with the cavity running

through it, which contains the spinal cord; here are the ribs, here the

shoulder blade; here is the little short upper-arm bone, here are the

two forearm bones, the wrist-bone, and the finger-bones.



Strange, is it not, that the Porpoise should have in this queer-

looking affair--its flapper (as it is called), the same fundamental

elements as the fore-leg of the Horse or the Dog, or the Ape or Man;

and here you will notice a very curious thing,--the hinder limbs are

absent.  Now, let us make another jump.  Let us go to the Codfish:

here you see is the forearm, in this large pectoral fin--carrying your

mind's eye onward from the flapper of the Porpoise.  And here you have

the hinder limbs restored in the shape of these ventral fins.  If I

were to make a transverse section of this, I should find just the same

organs that we have before noticed.  So that, you see, there comes out

this strange conclusion as the result of our investigations, that the

Horse, when examined and compared with other animals, is found by no

means to stand alone in nature; but that there are an enormous number

of other creatures which have backbones, ribs, and legs, and other

parts arranged in the same general manner, and in all their formation

exhibiting the same broad peculiarities.



I am sure that you cannot have followed me even in this extremely

elementary exposition of the structural relations of animals, without

seeing what I have been driving at all through, which is, to show you

that, step by step, naturalists have come to the idea of a unity of

plan, or conformity of construction, among animals which appeared at

first sight to be extremely dissimilar.



And here you have evidence of such a unity of plan among all the

animals which have backbones, and which we technically call

"Vertebrata".  But there are multitudes of other animals, such as

crabs, lobsters, spiders, and so on, which we term "Annulosa".  In

these I could not point out to you the parts that correspond with those

of the Horse,--the backbone, for instance,--as they are constructed

upon a very different principle, which is also common to all of them;

that is to say, the Lobster, the Spider, and the Centipede, have a

common plan running through their whole arrangement, in just the same

way that the Horse, the Dog, and the Porpoise assimilate to each other.



Yet other creatures--whelks, cuttlefishes, oysters, snails, and all

their tribe ("Mollusca")--resemble one another in the same way, but

differ from both "Vertebrata" and "Annulosa"; and the like is true of

the animals called "Coelenterata" (Polypes) and "Protozoa" (animalcules

and sponges).



Now, by pursuing this sort of comparison, naturalists have arrived at

the conviction that there are,--some think five, and some seven,--but

certainly not more than the latter number--and perhaps it is simpler to

assume five--distinct plans or constructions in the whole of the animal

world; and that the hundreds of thousands of species of creatures on

the surface of the earth, are all reducible to those five, or, at most,

seven, plans of organization.



But can we go no further than that?  When one has got so far, one is

tempted to go on a step and inquire whether we cannot go back yet

further and bring down the whole to modifications of one primordial

unit.  The anatomist cannot do this; but if he call to his aid the

study of development, he can do it.  For we shall find that, distinct

as those plans are, whether it be a porpoise or man, or lobster, or any

of those other kinds I have mentioned, every one begins its existence

with one and the same primitive form,--that of the egg, consisting, as

we have seen, of a nitrogenous substance, having a small particle or

nucleus in the centre of it.  Furthermore, the earlier changes of each

are substantially the same.  And it is in this that lies that true

"unity of organization" of the animal kingdom which has been guessed at

and fancied for many years; but which it has been left to the present

time to be demonstrated by the careful study of development. But is it

possible to go another step further still, and to show that in the same

way the whole of the organic world is reducible to one primitive

condition of form?  Is there among the plants the same primitive form

of organization, and is that identical with that of the animal

kingdom?  The reply to that question, too, is not uncertain or

doubtful.  It is now proved that every plant begins its existence under

the same form; that is to say, in that of a cell--a particle of

nitrogenous matter having substantially the same conditions.  So that

if you trace back the oak to its first germ, or a man, or a horse, or

lobster, or oyster, or any other animal you choose to name, you shall

find each and all of these commencing their existence in forms

essentially similar to each other: and, furthermore, that the first

processes of growth, and many of the subsequent modifications, are

essentially the same in principle in almost all.



In conclusion, let me, in a few words, recapitulate the positions which

I have laid down.  And you must understand that I have not been talking

mere theory; I have been speaking of matters which are as plainly

demonstrable as the commonest propositions of Euclid--of facts that

must form the basis of all speculations and beliefs in Biological

science.  We have gradually traced down all organic forms, or, in other

words, we have analyzed the present condition of animated nature, until

we found that each species took its origin in a form similar to that

under which all the others commence their existence.  We have found the

whole of the vast array of living forms, with which we are surrounded,

constantly growing, increasing, decaying and disappearing; the animal

constantly attracting, modifying, and applying to its sustenance the

matter of the vegetable kingdom, which derived its support from the

absorption and conversion of inorganic matter.  And so constant and

universal is this absorption, waste, and reproduction, that it may be

said with perfect certainty that there is left in no one of our bodies

at the present moment a millionth part of the matter of which they were

originally formed!  We have seen, again, that not only is the living

matter derived from the inorganic world, but that the forces of that

matter are all of them correlative with and convertible into those of

inorganic nature.



This, for our present purposes, is the best view of the present

condition of organic nature which I can lay before you: it gives you

the great outlines of a vast picture, which you must fill up by your

own study.



In the next lecture I shall endeavour in the same way to go back into

the past, and to sketch in the same broad manner the history of life in

epochs preceding our own.











End of The Project Gutenberg Etext of

The Present Condition of Organic Nature by Thomas H. Huxley