IV

THE PRESENT CONDITION OF ORGANIC

NATURE.

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

lectures 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 the 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, the 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.

[Illustration: FIG. 32.]

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. 32). Here

would be the upper part of the animal--that great mass of bones that we

spoke of as the spine (_a_, Fig. 32). Here I should have the alimentary

canal (_b_, Fig. 32). Here I should have the heart (_c_, Fig. 32); 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. 32), and in the lower tube (_d d_, Fig. 32), 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. 32). 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. 33). 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. 32, 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. 32), so the primary structure of every tissue may be

represented by a mass of cells (Fig. 33).

[Illustration: FIG. 33.]

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.

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.

[Illustration: INORGANIC WORLD.