only in terms of energy. It is, to our direct intuitions, resistance,
or inertia, that which requires energy in order that it may be made to
undergo change. Our static idea of physical solidity, or massiveness,
disappears on ultimate analysis. Molecules are made up of atoms, and
the atoms are assumed to have all the characters of matter: we could
not _see_ them, of course, even if we possessed all the magnifying
power that we wished, for they would be too small to reflect light.
Modern physical theory is compelled to regard atoms as complex, and
imagines them as being composed of moving electrons. The electron
is immaterial--it is the unit-charge of electricity. It is said to
possess mass, but mass is now understood to mean inertia. So long as
the electron is moving, it sets up a field of energy round it, and this
field--the electro-magnetic one--extends in all directions. Periodic
disturbances in it constitute radiation, and this radiation travels
with the velocity of light. It is because of the existence of this
field that we are _obliged_ to postulate the existence of an ether
of space. Unfamiliar to us until the discovery of Hertzian waves and
“wireless” telegraphy, this electro-magnetic radiation in space is now
accessible to our direct intuitions. We can initiate it by setting
electrons in motion, that is, by expending energy (producing the
sparking in the transmitters of the wireless telegraphy apparatus); and
we can stop it, if it is in existence, by absorbing the energy (in the
receivers of the wireless telegraphy apparatus). This is essentially
what we understand by the inertia of gross matter. We set a body in
motion by expending energy on it (the explosion of the powder in a
cartridge, which converts potential chemical energy into the kinetic
energy of the moving projectile); and we can stop a body which is in
motion by absorbing this energy of motion (by causing the projectile to
strike against a target, when the kinetic energy of its motion becomes
the kinetic energy of the heat of the arrested body).
Inertia is therefore the same thing whether it be the inertia of
visible, material bodies, or the inertia of invisible, material
molecules, or the inertia of the immaterial, non-tangible ether. It is
the condition that energy-changes must occur if anything accessible to
our observation is to change its state of rest or motion.
ENERGY
Energy is therefore indefinable. It is an elemental aspect of our
experience.
Nature to us is an aggregate of particles in motion. We have to speak
of massive particles, whether we call these visible material bodies,
or molecules, or atoms, or electrons, in order that we may describe
nature. We must employ the fiction of a _substantia physica_. We only
know the substance or matter in terms of energy; it is really the
latter that is known to us. It is the poverty of our language, or
rather it is the legacy of a materialistic age, that compels us to
speak of particles that move, rather than of motions as entities in
themselves.
Considering, then, the idea of particles in motion as a fiction
necessary for clear description, we can study energy. There is only
one kind, or form, of energy which presents itself to our aided or
unaided intuitions, that is kinetic energy. Bodies that move possess
this energy represented by their motion: they can be made to do work,
that is, their energy can be transformed into other forms of energy.
All things are in motion. A gas consists of molecules incessantly
moving with high velocity, and colliding and rebounding from each
other. The energy of a gas is the sum of one-half of the masses of all
the molecules, multiplied by the squares of the velocities of all the
molecules, that is, Σ1/2_mv_^2. This is also the kinetic energy of a
projectile, or of a planet revolving round the sun. Kinetic energy is
that of the uniform, unchanging motion of some entity possessing mass,
but we must extend our notion of mass so as to include immaterial,
imponderable entities such as electrons.
This energy cannot be destroyed or created--the law of conservation
of energy. This is a principle or mode of our thought. We are unable
scientifically or philosophically to think of an entity ceasing to be.
Dreams and phantoms show us entities which are real _while they last_,
but which cease to exist. If we do attempt to think of entities that
appear from, or disappear into, nothing, we surrender the notion of
reality. The more we think of it the more clearly we shall see that the
_things which we call real are the things which are conserved_.
Yet energy, to our immediate intuitions, seems to disappear. A flying
bullet strikes against a target and becomes flattened out into a
motionless piece of lead. A red-hot piece of iron cools down to the
temperature of its surroundings. A golf-ball driven up the side of
a hill comes to rest in the grass. A current of electricity passing
through water is used up, that is, electricity of a higher potential
is required to force the current through water than to force it through
thick copper wire. In all these cases we might think that energy is
lost, but we cannot believe this. The kinetic energy of the flying
bullet becomes transformed into the increase of the kinetic energy of
the molecules of the metal of which the bullet was composed; for the
latter becomes greatly heated when its flight is arrested and this
increased heat ought to be equal to the kinetic energy of the bullet
in flight. The red-hot piece of iron cools, and the kinetic energy of
its molecules becomes less and less, but this does not cease to exist,
for the energy is simply transferred by radiation and conduction to the
surrounding bodies, the temperature of which it raises. The golf-ball
driven up the hill comes to rest and loses its kinetic energy. Some
of this has been transferred to the air through which it passes, the
latter being heated very slightly; some of it is expended by friction
with the grass over which the ball rolls before coming to rest, and
this energy is traceable in heat-effects, or in mechanical effects,
but the rest of it apparently ceases to exist. But this would be
contradictory to the principle of conservation, and so we say that the
lost kinetic energy has become potential. The current of electricity
may heat the water through which it passes, and some of the energy
which seems to disappear is so to be traced, but the greater fraction
is apparently lost. A quantity of free hydrogen and oxygen is, however,
generated, and we say that the kinetic energy of the moving electrons
has become transformed into the potential chemical energy of the
gaseous mixture.
POTENTIAL ENERGY
Therefore, if energy disappears or appears, we do not say that it is
destroyed or is created: we invent potential energies, into which
we suppose that the energies in question have become transformed, in
order that we may still think of them as being subject to an _a priori_
principle of conservation. Although a particle of radium continually
generates heat, we do not therefore think of the first principle of
energetics as being invalidated, for we suppose that the energy which
thus appears was really potential in the atoms of radium. But it
was contrary to all our former experience of atoms that they should
contain any other energy than that of their own motion, and so the
further assumption was made that the atom, at least the atom of the
radio-active substance, is really complex, and not simple, as chemical
theory demands. It is made up of smaller particles, and possesses a
definite structure. In certain circumstances the atom may disintegrate,
and the energy which held together its particles, whether these were
simpler corpuscles or electrons, is given off as the heat which the
radio-active substance apparently generates. The potential energy of
the chemical atom is therefore a hypothesis which has been devised
in order to preserve the validity of the law of conservation, and
the reality of this hypothesis is being tested by investigation. If
we accept it as true, are the deductions made from it justified in
our experience? That is the test which must be satisfied in all the
hypotheses where potential energies are invented, and the potentials
are only real if the test is satisfactory. The golf ball at rest at
the top of the hill is a different entity from the golf ball at rest
at the bottom of the hill: it is capable of developing energy, for
a touch may cause it to roll down the hill, when most of the energy
which was expended in order to drive it to the top of the hill will
reappear in the form of the kinetic energy of motion of the ball. The
atoms of hydrogen and oxygen which were dissociated by the energy of
the electric current are different things from the atoms of hydrogen
and oxygen which are combined together to form the molecules of water.
Their state when the gases are in the elementary condition, or are
“free,” is that of molecules moving rapidly and incessantly, rebounding
from each other after colliding with each other: they possess energy of
position--potential energy--because they are separate from each other.
If they “combine,” as when a minute electric spark explodes the mixture
of gases, they tractate together, and remain in proximity to each
other, becoming molecules of water. The energy which became potential
in the gaseous mixture, when the electric energy of the current seemed
to disappear, now appears as the heat generated by the combustion,
that is, as the greatly increased kinetic energy of the molecules of
the gas (steam) which takes the place of the mixture of hydrogen and
oxygen. Previous to the explosion this gas was a mixture of molecules
of hydrogen and oxygen (2H↓{2} + 2O) at the ordinary temperature, but
after the explosion it consists of a smaller number of molecules at a
very much higher temperature.
What is “energy of position”? The golf ball at the bottom of the hill
was at a distance of _R_ feet from the centre of the earth, but at
the top of the hill it is at a distance of _R_ + 100 feet from the
centre of the earth. In the first case it was free to fall _R_ feet,
but in the second case it is free to fall _R_ + 100 feet. The atoms
of the constituent molecules of water occupy the position H - O - H,
the bonds (-) indicating that the atoms are very close together; but
when the water is decomposed by an electric current, the atoms occupy
the positions O - O + H - H + H - H, the (+) indicating that the atoms
are relatively far apart from each other. Now the golf ball and the
earth, or the atoms of hydrogen and oxygen, are physically the same
material entities, whether they are close together or far apart, yet
when the earth and the ball, or the atoms of oxygen and hydrogen,
are separated from each other, their “properties” are different from
what they are when they are close together. What is it that makes
the difference? It is that which is _between_ them. Is it, in the
last case, “the potential energy of chemical affinity”? This dreadful
phrase is actually used in a recent book on biology: “In the elements
carbon and oxygen, so long as they remain separate, a certain amount
of energy remains latent. When the carbon and oxygen atoms are allowed
to come together and unite, this potential energy of chemical affinity
is liberated as kinetic energy.” What is changed by the tractation and
pellation (the terms suggested by Soddy in place of the anthropomorphic
ones, “attraction” and “repulsion”)? It is the ether which has become
changed in some way. Potential energy resides therefore in the ether of
space.
ISOTHERMAL AND ADIABATIC CHANGES
Let us consider the changes which occur in a gas under the influence
of changes in temperature and pressure, premising that the remarks
which we have to make can be applied to bodies in the liquid and solid
conditions, with some necessary modifications. A gas, then, consists
of a very great number of particles, or molecules, in motion. These
molecules move in straight lines at very high velocities, and if
the envelope in which the gas is contained is a restricted one, the
molecules collide with each other, and with the walls of the envelope;
and, being assumed perfectly elastic, they rebound from each other,
and from the walls of the vessel, with the same velocity which they
had when they collided. The pressure of the gas (say that of steam at
a temperature of 110° C., and a pressure of 120 lbs. to the square
inch in a steam boiler) is the sum of the impacts of the molecules
on the walls of the containing vessel. When the temperature is high
the molecules are moving at a higher mean velocity than when the
temperature is lower, and their mean free path tends to become greater.
The volume of a certain mass of gas, that is, the volume occupied by a
certain very great number of molecules, is greater the higher is the
temperature, provided the envelope is one capable of yielding. If we
reduce the capacity of the envelope in which the gas is contained, the
pressure will rise, for the intrinsic energy of the gas is still the
same; but we have done work on it, and by the law of conservation this
work, or at least the energy represented by it, must still exist. It is
represented by the decreased length of free path of the molecules, and
this means that the impacts on the walls of the vessel will be greater
than they were. There is, therefore, a certain relation between the
volume of a gas and its pressure, and this relation can be represented
by an equation involving the temperature, the pressure, and the volume.
[Illustration: FIG. 29.]
The diagram represents the pressure and the volume of a gas when these
things change. There are two conditions, (1) when the heat developed
by the compression is allowed to escape through the walls of the vessel
to the outside, or when the heat lost in the expansion of the gas is
compensated by the conduction of heat through the walls of the vessel
from outside; and (2) when the heat developed is retained in the gas,
as when the latter is contained in a vessel the walls of which do not
conduct heat. The pressure of the gas is measured along the horizontal
axis, and the volume is measured along the vertical axis, and a curve
is drawn so that for any value of the pressure there is a corresponding
value of the volume. Thus the values of the pressures _p_ and _p_↓{1}
in the diagram correspond to the value of the volume _v_. The curve
relating the change of pressure with a corresponding change of volume
is, in general, that called a rectangular hyperbola. But there are
two kinds of such curves: (1) that which we obtain by plotting the
corresponding values of pressure and volume, when the temperature
of the gas remains constant throughout the series of changes, that
is, when the rise of temperature which would occur when the gas is
compressed is compensated by the conduction of this heat to the outside
of the vessel containing the gas. Such a series of changes of pressure
and volume is called an _isothermal_ one. (2) When the heat developed
by the compression of the gas is retained in the gas, as when the walls
of the vessel in which these changes are effected are such as do not
conduct heat: such a series of changes is called an adiabatic one.
Adiabatic curves are steeper than are isothermal ones.
THE CARNOT ENGINE
This is an imaginary mechanism which performs a certain cycle
of operations. It does not really exist, but the conception of
its operation is of the greatest value in the consideration of
energy-transformations, and it is for this reason that we discuss it
here.
Consider a gas, or some other substance capable of expanding or
contracting. It contains intrinsic energy, and it is capable of doing
work. Thus, since a gas can expand indefinitely it can be made to do
mechanical work. A mass of gas at a pressure _p_↓{1}, and having a
volume _v_↓{1}, and at a temperature _T_°, can do work by expanding
till its pressure is reduced to _p_, and its volume increased to _v_.
If it expands adiabatically its temperature will fall to _t_°. Let us
suppose that _t_° is the temperature of the surrounding medium: the
gas cannot therefore cool further, and we can obtain no more work from
it. If the gas is the substance which we wish to employ as the working
substance in the Carnot engine, we must therefore bring it back to the
condition represented by _A_. That is, we must raise its temperature to
_T_°, we must reduce its volume to _v_↓{1}, and we must increase its
pressure to _p_↓{1}.
[Illustration: FIG. 30.]
Thus the steam of an engine is (say) at a temperature of 110° C., and a
pressure of 120 lbs. to the square inch. When it has passed through the
cylinder and condenser it is water at a temperature of, say, 15° C.,
and it is at atmospheric pressure. We must, therefore, bring it back to
its former condition by heating this water in the boiler till it is
steam under the former conditions of temperature and pressure.
Therefore we must, in order to obtain a self-acting engine, cause the
working substance, and the mechanism of the engine, to perform a series
of cyclical operations.
The Carnot engine is a cylinder containing a gas called the working
substance _S_, and this gas can be brought into thermal contact with a
source of heat, or a refrigerator, that is, the gas can be heated or
cooled by a mechanism outside itself. The walls of the cylinder are
made of some substance which is a perfect non-conductor of heat, but
the bottom of the cylinder is made of a substance which conducts heat
perfectly. There is a piston in the cylinder which fits it closely,
but which moves up and down without friction. At the bottom of the
latter is a valve which can be turned so as to place the bottom of the
cylinder, and therefore the gas, in thermal contact with a reservoir
of heat (+), or a refrigerator (-). But when the valve is turned so
that the non-conducting part _O_ fills the bottom, the gas is perfectly
insulated, and heat can neither enter nor leave it.
[Illustration: FIG. 31.]
Such an engine is, of course, an imaginary one, since there can be no
mechanism in which there is not a certain amount of friction between
moving parts, and there are no substances which conduct or insulate
heat perfectly. The engine is, in fact, the _limit_ to a series of
engines each of which is supposed to be more perfect than the last one.
It is a fiction which is of considerable use in theoretical work.
THE CARNOT POSITIVE CYCLE
We have therefore a substance which can be heated by contact with a
hot body, and which can then expand, doing mechanical work by raising
a piston, and perhaps turning a flywheel, and on which work is then
done so that it returns to its original condition. This is a cycle of
operations. If we consider only the changes which occur in the working
substance we can represent these changes by a diagram.
[Illustration: FIG. 32.]
_First operation_, (1→2). We suppose that the valve is turned so that
the non-conducting plug closes the cylinder. The piston is in the
position II (Fig. 31). Heat cannot then enter or leave the gas. But the
latter already contains heat: it is at a temperature of _T_↓{2}°, so
that it can expand doing work. Let it expand, forcing up the piston.
During this operation the pressure of the gas will fall from a point
on the vertical axis opposite 1 to a point opposite 2, and its volume
will increase from a point on the horizontal axis beneath 1 to a point
beneath 2. It will cool because it has expanded, and no heat is allowed
to enter it during this act of expansion. The expansion is therefore
adiabatic; the temperature falls from _T_↓{2}° to _T_↓{1}°; and work is
done _by_ the gas.
_Second operation_, (2→3). The piston is now at the position I, that
is, at the upper end of its stroke, and we must bring it back again
to the lower end of the cylinder. The valve is turned so that the
bottom of the cylinder is placed in thermal communication with the
refrigerator (-), and the piston is pushed in to the position II. The
gas is therefore compressed until its volume decreases from a point
beneath 2 to a point beneath 3. As it is being compressed, heat is
generated and its temperature would rise, but as this heat is generated
it flows into the refrigerator, so that the temperature of the gas
remains the same during the operation. The contraction is therefore an
isothermal one; the temperature remains at _T_↓{1}°; and work is done
on the gas from outside.
_Third operation_, (3→4). But the piston is not at the lower end of
its stroke yet. We turn the valve so that the bottom of the cylinder
is closed by the non-conducting plug _O_, and then push in the piston
until it reaches the position III. The gas is still further compressed,
and this compression generates heat. But the heat cannot escape, so
that the temperature of the gas rises until it reaches _T_↓{2}°. The
contraction is therefore an adiabatic one. Work is done _on_ the gas.
_Fourth operation_, (4→1). The piston is now at the lower end of its
stroke. We turn the valve so that the bottom of the cylinder is placed
in communication with the source of heat (+). The gas expands from
the point beneath 4 to the point beneath 1, raising the piston to the
position II. This expansion of the gas would lower its temperature,
but it is in communication with the source of heat, and so it does
not cool, but draws heat from the source and remains at a constant
temperature, _T_↓{2}°. The expansion is therefore an isothermal one.
Work is done _by_ the gas.
This completes the cycle. But the gas is heated, and when the piston
is at position II, the valve is turned so as to close the cylinder by
the non-conducting plug _O_. The heat already contained in the gas
continues to expand, the latter doing more work, but this expansion
causes the temperature to fall from _T_↓{2}° to _T_↓{1}°. This is the
operation with which the cycle commenced.
Summarising the positive Carnot cycle, we see that the engine takes
heat from a source (+) and gives up part of this to a refrigerator (-),
(in an actual steam-engine heat is taken from the boiler and given up
to the condenser water). If we measure the quantity of heat taken from
the boiler in the steam which enters the cylinders we shall find that
this quantity of heat is greater than the quantity which is given up
to the condenser water. What becomes of the balance? It is converted
into the mechanical work of the engine. The Carnot engine therefore
takes a quantity of heat, _Q_↓{2}, from the source and gives up another
quantity of heat, _Q_↓{1}, to the refrigerator. We find that _Q_↓{2} is
greater than _Q_↓{1} and the balance, _Q_↓{2} - _Q_↓{1}, is represented
by the work done by the engine. Heat-energy falls from a state of high,
to a state of low potential, and is partly transformed into mechanical
work.
THE CARNOT NEGATIVE CYCLE
This is simply the positive cycle _reversed_. The reader should puzzle
it out for himself if he is not already familiar with it. It consists
of an adiabatic contraction 2→1, an isothermal contraction 1→4, an
adiabatic expansion 4→3, and an isothermal expansion 3→2. A quantity
of heat, _Q_↓{1}, is taken from the refrigerator at a temperature
_T_↓{1}°, and another quantity, _Q_↓{2}, is given up to the source at
a temperature _T_↓{2}°. But _Q_↓{2} is greater than _Q_↓{1}, and the
engine therefore gives up more heat than it receives, while, further,
heat flows from a body at a low temperature to another body at a higher
temperature. Where does the engine get this energy from? It gets it
because work is done _upon_ it by means of an outside agency, and all
of this work is converted into heat.
REVERSIBILITY
The Carnot engine and cycle are therefore perfectly reversible. Not
only can the engine turn heat into work, but it can turn work into
heat. This perfect, quantitative reversibility is, however, a property
of the imaginary mechanism only, and it does not exist in any actual
engine.
ENTROPY
Let us consider the cycle more closely. In the operation 4→1, which
is an isothermal expansion, there is a flow of heat-energy from the
source and a transformation of energy into work. The gas in the
condition represented by the point 4 had a certain pressure and a
certain volume. In the condition represented by the point 1, its
pressure has decreased, its volume has increased, and its temperature
is the same. Its physical condition has been changed, and to bring
it back into its former condition something must be done to it. Let,
then, the gas continue to expand without receiving any more heat, or
parting with any: that is, let it undergo the adiabatic expansion 1→2
until its temperature falls to that of the refrigerator, _T_↓{1}°. We
now compress the gas while keeping it at this temperature, that is,
we cause it to undergo the isothermal contraction 2→3, during which
operation it is giving up heat to the refrigerator, so that there is
again a flow of heat-energy. We then compress it still further without
allowing heat to escape from it, that is, we cause it to undergo the
adiabatic contraction 3→4. During this operation the gas rises in
temperature to _T_↓{2}°. It is now in the condition that it was when
the cycle commenced.
In this cycle of operations heat first entered, and then left the gas,
and with this entrance or rejection of heat, the condition of the
gas with respect to its power of doing work changed. We investigate
this flow of heat, and the concomitant change of properties of the
substance, with regard to which the flow took place, by forming the
concept called _entropy_. We make the convention that when heat enters
a substance the entropy of the latter increases, and when heat leaves
it its entropy decreases. We call the quantity of heat entering or
leaving a substance _Q_, and the temperature of the substance _T_. Then
_Q_/_T_ is proportional to the change of entropy of the substance when
the quantity of heat, _Q_, enters or leaves it.
Now it is a fact of our experience that heat can only flow, _of
itself_, from a hotter to a colder body. Consider two such bodies
forming an isolated system, the temperature of the hotter one being
_T_↓{2}°, and that of the colder one _T_↓{1}°. Let _Q_ units of heat
flow from the body at _T_↓{2}° to that at _T_↓{1}° no work being done.
Then the loss of entropy of the hotter body is _Q_/_T_↓{2}°, and the
gain of entropy of the colder body is _Q_/_T_↓{1}°. The nett change of
entropy of the system is _Q_/_T_↓{1}° - _Q_/_T_↓{2}°. Since _T_↓{2}°
is greater than _T_↓{1}°, _Q_/_T_↓{2}° is less than _Q_/_T_↓{1}°.
Therefore the expression _Q_/_T_↓{1}° - _Q_/_T_↓{2}° is positive,
that is, the entropy of the system, as a whole, has increased. When
heat flows from a hotter to a colder body the nett entropy of the two
bodies, therefore, increases.
But we can also cause heat to flow from a colder to a hotter body _by
effecting a compensatory energy-transformation_. Such a compensation
would not occur by itself in any system capable of effecting an
energy-transformation, if it is to be effected some external agency
must act on the transforming system. We can suppose it to happen in
a perfectly reversible imaginary mechanism. Suppose a Carnot engine
works in the positive direction, taking heat from a reservoir at
temperature _T_↓{2}°, and giving up part of this heat to a refrigerator
at _T_↓{1}°, and doing a certain amount of work _W_. Suppose that
this work is stored up, so to speak, say by raising a heavy weight,
which can then fall and actuate the same Carnot engine in the opposite
(negative) direction. The engine then exactly reverses its former
series of operations. The work it did is reconverted into heat, and as
much of this heat flows from the refrigerator into the source, that
is, from a colder to a hotter body, in the negative operations, as
flowed from the source to the refrigerator in the positive operations.
In this primary energy-transformation, combined with a compensatory
energy-transformation, there is no change of entropy. The mechanism is
an ideal one--the limit to an irreversible mechanism.
But--and now we appeal to experience and cease to work with ideal
mechanisms--the actual engine which we can design and work is one
in which there will be friction, in which some parts will conduct
heat imperfectly, and other parts will insulate heat imperfectly.
Let the friction generate _q_ units of heat, and let the quantity
of heat which is “wasted” by imperfect conduction and insulation
be _q_↓{1}. This heat will flow into the refrigerator, or will be
radiated or conducted to the surrounding medium, which we suppose to
be at the same temperature as the refrigerator. If, then, we divide
this total quantity of heat by the temperature _T_↓{1}°, we get (_q_
+ _q_↓{1})/_T_↓{1}° = _S_↓{1} as the quantity of entropy which is
generated as the result of the imperfections of the engine, in addition
to the quantity of entropy, _S_, which would be generated if the engine
were a perfect one. Both _S_ and _S_↓{1}_ are positive.
Also in the working of the engine in the negative direction a certain
quantity of entropy, _S_↓{1}, is generated for reasons similar to those
mentioned above.
The entropy generated when the engine works in the positive direction
is therefore _S_ + _S_↓{1}, and when it works negatively the quantity
generated is also _S_↓{1}. The entropy destroyed when the engine works
negatively is _S_. The total change of entropy is therefore 2_S_↓{1}
+ _S_ - _S_, that is, 2_S_↓{1}. In an actual energy-transformation
combined with a compensatory energy-transformation there is therefore
an increase of entropy.
We can generalise these statements so that they will apply
not only to a heat-engine but to all mechanisms which effect
energy-transformations. In all such transformations entropy is
generated. Therefore _the Entropy of the Universe tends to a maximum_.
AVAILABLE AND UNAVAILABLE ENERGY
Consider the Carnot engine as a perfect mechanism. It takes heat-energy
from a source at a temperature _T_↓{2}°, and it gives up heat to a
refrigerator at a temperature _T_↓{1}°_, _T_↓{2}° being greater than
_T_↓{1}°. In the adiabatic expansion 1→2 the gas continues to expand
until its temperature becomes equal to that of the refrigerator. It
cannot, then, expand and do work any longer, and thus the proportion
of the heat, _Q_↓{2}, received from the source, which can be converted
into work, depends on the difference of temperature _T_↓{2}° -
_T_↓{1}°. The greater is this difference the greater will be the
proportion of the heat-energy received which can be converted into
work. If the engine were a perfect one, and if the gas were also a
perfect one (that is a gas which would continue to expand according
to the equation for the adiabatic expansion of gases), and if the
refrigerator were absolutely cold, then _all_ the heat energy received
from the source could be converted into work.
We cannot produce a refrigerator of absolute temperature 0°, and
therefore only a certain proportion of the heat which is received by
the engine can be transformed into mechanical work. But this work can
be used to reverse the action of the engine, and thus the same fraction
of the total heat-energy which was given to the refrigerator can be
taken from it and given back to the source. The perfect engine is
therefore reversible without loss of available energy.
Now consider still the engine as a mechanism which takes heat from a
source and gives it to a refrigerator, but let it be an actual engine.
Instead of giving up a certain fraction of the heat received to the
refrigerator--a fraction equal to _Q_↓{1} (_T_↓{1}°/_T_↓{2}°), it
gives up rather more, because it is not a perfect mechanism, that is,
it generates friction, etc. Some of the heat received thus ceases
to be available for the performance of work; and passes into the
refrigerator. The fraction of the heat-energy which passes into the
refrigerator in the perfectly reversible engine was unavailable energy
in the conditions in which the mechanism worked, or was imagined to
work, but in the actual engine this fraction is increased. If we
divide the increase of unavailable energy by the temperature of the
refrigerator, the product is the increase of entropy generated in the
actual engine over that generated in the ideal engine. Because of this
reduction of available energy the actual engine is an irreversible
mechanism.
This is the connection between unavailable energy and entropy. In all
transformations some fraction of the transforming energy becomes heat,
and this heat flows by conduction and radiation into the surrounding
bodies. In general this heat simply raises the temperature of the
medium into which it flows, and becomes unavailable for further
transformations. With every transformation that occurs some part of the
energy involved becomes unavailable. Therefore although the sum of the
available and unavailable energy of the Universe remains constant, the
fraction of unavailable energy tends continually to a maximum.
INERT MATTER
We can see now what is indicated by Bergson’s “inert matter.” It is not
matter deprived of energy--such an expression has no meaning--_it is
energy which is unavailable for further transformations_.
The matter in which we choose to say that this energy is inherent has
become _inert_. Let us substitute for the Carnot engine the actual
steam-engine of a ship, the condenser of which is cooled by the sea
water which is taken in, and which is then heated and flows out again
into the sea. The heat derived from the source, that is, from the
furnace of the boiler where coal is burned to raise steam, thus passes
out into the sea. Now the heat capacity of the sea is so great that the
temperature of the water is not appreciably raised by this heat, which
drains into it from the engine: even if it were appreciably raised, the
heat would be conducted into the earth, or would be radiated out into
space, and would then raise the temperature of the material bodies of
the universe. But let all this heat remain in the sea. It then simply
raises the temperature of the water by an exceedingly small amount,
and the motions of the molecules become infinitesimally increased.
But the heat becomes equally distributed by conduction and convection
throughout the mass of the water in the sea, and as there are no
differences in adjacent parts there are no means whereby the energy
which thus passes into the sea can be again transformed.
A new order of things is the result of the processes we have indicated.
The segregated, available heat-energy of material bodies has become
transferred to the un-co-ordinated, diffuse, unavailable energies of
the molecules which compose these bodies. The transformations which we
can effect depend on the condition that the energy which we utilise
is that of aggregates of molecules which are in a different physical
condition, as regards this energy, from adjacent aggregates. But when
this energy becomes equally distributed among the molecules of all the
aggregates, the matter in which it inheres becomes inert. If we could,
by a sorting process like that of Maxwell’s hypothetical demons, a
process which does not expend the energy with which it deals, separate
the molecules which were moving slowly from those which were moving
more quickly, we could make this energy again available. But it must
clearly be understood that our physics is the physics not of individual
molecules, but of aggregates of molecules.
INDEX
Absolute, Driesch’s theory of, 47.
Acceleration (in physics), 355.
Acquired characters induced by the environment, 216;
a means of transformism, 220;
evidence of transmission scanty, 225;
transmission not inconceivable, 226.
Actions, categories of, and consciousness, 282;
deliberative, 283;
mechanistic hypothesis of, 157;
stereotyped, 283;
at a distance, 304.
Activation of the ovum, 176.
Adaptability, indicative of dominance, 258.
Adaptation, 217;
and acquired characters, 219;
and changes of morphology and function, 219;
not inherited, 220;
causes of, 239.
Adaptive response, 219.
Adiabatic changes, 361.
Aggregates, molecular, 353.
Algæ, distribution of, 260.
Allelomorphs, Mendelian, 231.
Alternation of generations, 175.
Amido-substances, 88.
Anabolism, 88.
Anatomical parts, homologies of, 251.
Animal action, considered objectively, 278.
Animal and plant contrasted, 269.
Animality, 269.
Annectant forms of life, 253.
Annelids, morphology of, 248.
Anthropomorphism in theories of action, 148.
Anti-enzymes, 94.
Antitoxins, 36.
Ants, a dominant group, 260.
Appendix vermiformis, 250.
Approximation, standards of, 347.
Armoured animals, 263.
Arthropods, morphology of, 249;
a dominant group, 259;
distribution, 260;
musculature of, 275;
adaptations for mobility, 275;
limits to size of, 275.
Assimilation, 67.
Atoms, constitution of, 355;
arrangements of, 353.
Automatism of animals deduced from mechanistic theories, 280.
Autonomy in development, 322.
Available energy, 62;
and entropy, 374.
Bacteria, a dominant group, 259;
distribution, 259;
geological history, 259, 261;
morphology, 268;
metabolism, 266;
specialisation, 263;
parasitism, 259;
nitrogen, 73;
prototrophic, 119, 266;
paratrophic, 266;
putrefactive, 266;
fermentation, 266;
and Brownian movements, 119;
compensatory to plants, 267.
Bergson, 28;
creative evolution, 244;
duration, 154;
animals and plants, 78;
eye of Pecten, 234;
inert matter, 375;
infinitesimal analysis of the organism, 111;
kinematographic analysis, 110;
theory of intellectualism, 51;
memory, 156;
morphological themes, 250;
theory of pain, 281;
theory of perception, 7, 10;
the vital impetus, 318.
Biology, systematic, 201, 203.
Biophors, 132;
size of, 183;
growth of, 185.
Biotic energy, 325.
Borelli and animal mechanism, 125.
Brownian movement, 118;
significance of, 119.
Bryan and thermodynamics, 62.
Bud-formation, 165.
Calculus, infinitesimal, 25, 115, 350.
Calorimetric experiments, 65, 68.
Capacity-energy factors, 61.
Carnot’s cycle, 69, 78, 113;
negative, 368;
description of, 363, 366;
compared with plant metabolism, 75;
compared with the organism, 73.
Catalysis, 90;
universality of, 91.
Catalysts, characters of, 91.
Categories of organisms, 209.
Central nervous system, specialisation of, 273;
a switchboard, 273;
evolution of, parallel with evolution of muscular system, 281.
Chance in evolution, 237.
Chemical affinity, 361.
Chemical energy, degradation of, 75.
Chemical reactions, direction of, 78;
exothermic, 86;
explosive, 86;
similar in organic and inorganic systems, 78.
Chemical synthesis, involve vital activity, 318.
Chemistry, medieval, 125.
Chlorophyll, 69.
Chlorophyllian organisms, 88;
metabolism of, 265;
a dominant group, 259;
essential morphology of, 268;
distribution of, 260.
Chromatin of the nucleus, 130;
the material basis of inheritance, 182.
Chromosomes, 130, 182, 183.
Classification of organisms, 209.
Classificatory systems, are artificial arrangements, 289;
suggest evolutionary process, 210.
Clausius, 54;
and Carnot’s Law, 113.
Cœlenterates, morphology of, 248.
Cœlomate animals, 256.
Colloidal platinum, 91.
Colloids, 107.
Colonial organisms, 164.
Comparative anatomy, task of, 251.
Compensatory energy-transformations effected by life, 309.
Conjugation, 173;
and heredity, 176;
a stimulus to growth, 175.
Consciousness involves analysis of the environment, 11;
analysis of, is an arbitrary process, 12;
a feeling of normality, 6;
a part of crude sensation, 40;
simplified by reasoning, 41;
an intensive multiplicity, 303;
degree of, is parallel to development of sensori-motor system, 280;
not existent outside ourselves, 278;
not a function of chemico-physical mechanism, 160;
intense in difficultly performed operations, 281;
and activity of cerebral cortex, 281;
absent in parasites, 291.
Conservation a test of reality, 357.
Conservation of energy, 52;
in organisms, 83.
Conservation of structure, 253, 256.
Constants, mathematical, 344.
Continuity of cells in embryo, 171.
Contractility, 100;
muscular, 103.
Co-ordinates, systems of, 23.
Corals, 164.
Cosmic evolution, 314;
is a tendency towards degradation of energy, 316.
Creation, special, 214.
Curvature, 27.
Curves, isothermal and adiabatic, 362.
Cuttle-fishes, 250.
Cytoplasm, 130.
Darwin, and natural selection, 221;
acquired characters are inherited, 220;
hypothesis of pangenesis, 181.
Death, is catastrophic katabolism, 340.
Degradation of energy, 81.
Deliberation and consciousness, 281.
Demons, Maxwell’s, 116.
Descartes and mechanism, 121;
the rational soul, 123, 318;
his physiology, 122;
his spiritualism, 124;
and animal automatism, 125.
Descent, collateral, 257.
Determinants in embryology, 132, 183;
arrangement of, 184;
latent in regenerative processes, 142.
Development, organisation in, 128;
parthenogenetic, 176;
reverses inorganic tendencies, 324;
impossibility of chemical hypotheses, 141;
is the assumption of a mosaic structure, 301;
blastula stage in, 129;
gastrula stage in, 130;
pluteus stage in, 140;
individual, 300.
Developmental systems prospective value of, 138;
prospective potency of, 138.
Diatoms, 163;
distribution of, 260.
Differential elements, 115.
Differentiation in development, 170.
Diffusion in the animal body, 95.
Digestion, 67;
chemistry of, 72.
Dinosaurs, an unsuccessful line of evolution, 275.
Dissipation of energy, 114;
in physical mechanisms, 59;
by the organism, 68, 79.
Distribution of organisms, 262;
limits to, 259;
indicative of dominance, 258.
Diversity, physical, 54;
effective and ineffective, 115.
Dominance in geological time, 258;
implies long geological history, 261;
Mendelian, 196.
Dominant organisms, 258, 259, 264.
Driesch natural selection, 229;
analytical definition of the organism, 331;
entelechy, 318;
experimental embryology, 134;
historical basis of reacting, 154;
logical proof of vitalism, 136;
proof of vitalism from behaviour, 153;
theory of the absolute, 47.
Duration, 28;
duration and time illustrated, 30;
illustrated by immunity, 35;
more than memory, 155;
a factor in responding, 155.
Ecdysis, 276.
Echinoderms, morphology of, 248.
Ectoderm, 177.
Effector organs, 158, 271.
_Élan vital_, 161.
Electromagnetism, 355.
Electrons, 304, 355.
Elimination, natural, 229.
Embryological stages compared with physical phases, 308.
Embryology, 127;
hypotheses of, 128;
physical hypotheses fail, 128;
experimental, 128;
suggests phylogenetic history, 213.
Emulsoids, 108.
Endoskeleton, 177, 276.
Energetics, first law of, 51;
second law of, 113.
Energy, 356;
available and unavailable, 55;
biotic, 325;
chemical, 61;
and causation, 54;
degradation of, 63;
dissipation of, 53;
electrical, 61;
forms of, 325;
kinetic, 52, 357;
mechanical, 60, 61;
potential, 53, 358;
of position, 360.
Energy-transformations, 54, 371;
anabolic, 89;
in the animal, 70;
compensatory, 88;
compensatory organic, 268;
irreversible, 59;
in physical mechanisms, 58;
in the plant, 71.
Engelmann, and the artificial muscle, 105.
Entelechy, 161, 318;
not energy, 329;
is power of direction, 329;
not spatial but acts into space, 330;
an intensive manifoldness, 330;
is arrangement, 323;
involves regulations, 323;
arrests inorganic happening, 327;
initiates chemical happening, 327;
compared with enzyme action, 327;
illustrated by analogy, 322.
Entropy, 54;
augmentation of, 75;
and Carnot engine, 369.
Environment, does not select variations, 235;
made by the organism, 236.
Enzymes, 90;
nature of, 92;
pancreatic, 93;
reversible, 93;
activation of, 92.
Enzyme activity, 93.
Epigenesis in development, 129.
Equilibrium, chemical, 102.
false, 86, 151.
Ether of space, 46, 304, 361;
potential energy resides in, 361.
Evolution tendencies of, 252, 264, 276, 295;
separation of tendencies, 296;
a transformation of intensive into extensive manifoldness, 309;
a dissociation of tendencies originally coalescent, 305;
increases diversity, 310;
segregates energy, 311;
compared with permutations and combinations, 301;
a series of phases in a transforming system, 298;
a logical hypothesis, 214;
parallel processes in, 234;
geological time inadequate for, 237;
side paths in, 262;
mechanistic hypotheses inadequate, 237;
cosmic, 214, 297, 314;
of the crust of the earth, 264.
Excretory products, 269.
Exoskeleton, 276.
Exothermic reactions, 86.
Experience and duration, 156.
Experimental biology proves evolution, 246.
Explosive reactions, 101.
Extension in space, 18.
Extinct groups, 263.
Fats, digestion of, 93.
Fecundity of animals, 179, 239.
Ferments, 92.
Fertilisation (in reproduction), 176.
Finalism, 216.
Fishes, distribution of, 261.
Fluctuating variations, 200.
Food-stuffs, absorption of, 89.
Force, 354.
Form, accidental and essential, 167, 353;
geological, 168;
crystalline, 168.
Frequency distributions, 22, 187, 350.
Frog, development of egg of, 131.
Functionality, 343;
in physical systems, 307.
Galvanotropism, 145.
Gases, compression of, 362;
kinetic theory of, 117, 361.
Gastrea-theory, 177;
illustrated, 255;
limitations of, 256.
Genera, stability of, 186.
Geometry, Cartesian, 25;
Euclidean, 19, 25;
perceptual and conceptual limits, 21.
Geotropism, 144.
Germ-cells, 175;
and soma, 179.
Germinal selection, 241.
Germ-layers, 177;
theory of, 256.
Germ-plasm, a mixture, 240;
stability of, 240.
Givenness, 47.
Gonads, 179.
Growth law of, in the organism, 172;
by accretion, 169;
by ecdysis, 276;
geometrical, 169;
physical, 167;
of crystals, 167;
and differentiation, 170;
variability of, 172.
Haeckel, the Gastrea-Theorie, 177, 254.
Harmonic analysis, 11.
Harvey, and the circulation of the blood, 121.
Heat, flow of, 117;
production of, in physical changes, 114.
Heliotropism, 144.
Heredity, 181.
Hertzian waves, 355.
Homoiothermic animals, 67.
Hormones, 225.
Human activity, tends to arrest dissipation of energy, 312.
Huxley, 84;
and mechanistic biology, 127;
and the physical basis of life, 113;
and mechanism, 106;
and universal mathematics, 215.
Hybrids, Mendelian, 196;
infertility of, 195;
between Linnean species, 194.
Hydra, regeneration of, 162.
Idants, 183.
Idealism founded on pure reasoning, 45;
of Berkeley, 45.
Ids, 183.
Immunity, 35.
Individual, 162;
definition of, 167.
Individuality, orders of, 163;
physical concept of, 165;
morphologically an artificial concept, 166;
in societies, 171.
Inertia, 354.
Infinity, a definition of, 342.
Inorganic happening abolishes diversity, 310.
Instinct, a problem for naturalists, 283;
an inheritable adaptation of behaviour, 287.
Instinct and intelligence, 283;
distinction not absolute, 294;
may coexist, 306.
Instinct and functioning, 286.
Instinctive actions not necessarily unconscious, 283;
not learned, 286;
not necessarily perfect, 284;
effective from the first, 285;
capable of improvement, 285.
Intelligent actions, non-inheritable adaptations of behaviour, 287;
involve deliberation, 50, 287;
involve conscious relations with the environment, 288;
involve use of tools, 284.
Intensity-factors, 61.
Intensive multiplicity, 303.
Irreversibility, 62.
Irritability, 100.
Isothermal changes, 361.
James, William (and academic philosophies), 80.
Jennings, and physiological states, 154;
behaviour of Protozoa, 293;
animal movements, 149;
the avoiding reaction, 149.
Katabolism, 90.
Kinases, 92.
Kinematographic analysis, 316.
Lamarck, hypotheses of evolution, 220.
Lamarckian inheritance, an inadequate cause of transformism, 227.
Lankester, acquired characters not inherited, 221.
Laplace, and universal mathematics, 215.
Laplacian mind, 299.
Larval stages, 170.
Latency (of characters), 195.
Lavoisier, and chemistry of the organism, 127.
Life and adaptation to physical conditions, 338;
and reversibility, 339;
a direction of energies, 341;
defined energetically, 337;
cosmic origin of, 338;
physical conditions for, 338;
limited in power, 306;
sparsity of, on the earth, 306;
tends to arrest dissipation of energy, 314;
its origin a pseudo-problem, 337.
Life-substance, the primitive, 301.
Locomotion, 258.
Loeb and the associative memory, 155;
and artificial parthenogenesis, 176;
mechanism and life, 127;
stereotropism, 19;
theory of tropisms, 144;
tropistic movements, 146;
theories of heredity, 181.
Limit, the mathematical, 346.
Limits to perceptual activity, 23.
Links, missing, 252.
Linnean species, 201.
Manifoldness, intensive, 302.
Mass, 353.
Mass action, 140.
Materialism, 85.
Mathematics, evades consideration of time, 35.
Matter, 353;
inert, 375;
notion of is an intuitive one, 352.
Maxwell, and sorting demons, 116, 377.
Mayow, and chemical physiology, 126.
Mechanical work, done by the animal, 67;
not done by the plant, 71.
Mechanism, organic and inorganic, 78;
the thermodynamic, 66;
radical, 215;
in life, 121.
Membranes, semi-permeable, 95.
Memory, 39;
a possible cerebral mechanism of, 158;
mechanistic hypotheses impossible, 157.
Mendelism, 196;
a logical hypothesis, 199;
terminology is a symbolism, 198;
analogy of unit characters with chemical radicles, 197;
transmission of characters of, 230.
Mesoderm, 177;
origin of, 255.
Metabolism, 37, 88, 209;
analytic, 269;
of animals, 65, 67;
constructive, 269;
destructive, 269;
direction of, 69;
in green plant, 70, 75;
intra-cellular, 99;
integration of its activities, 111;
rôle of oxygen in, 105;
specialisation of during evolution, 305;
synthetic, 269.
Metaphysics of science, 45.
Metazoan animals, 162.
Mitosis, 182.
Mobility, organic, 269;
structural adaptations tending to, 275.
Modifications of structure adaptive and non-adaptive, 251.
Molecules, 353;
size of, 116;
in a gas, 115;
aggregations of, 108.
Molluscs, morphology of, 249.
Morgan, and physico-chemical mechanisms, 128, 143.
Morphogenesis, 257.
Morphological evolution, tendencies of, 295.
Morphological structures degeneration of, 251;
suppression of, 250;
coalescence of, 250;
replacement of, 250;
specialisation of, 250;
change of function of, 251.
Morphology, 209;
a basis of classification, 210;
relates groups of organisms, 211;
distinctions of, not absolute, 285, 290;
generalised, 250;
suggests blood relationships, 213;
schemata of, 249, 291;
cannot be considered apart from physiology, 285.
Mosaic-theory of development, 131.
Motion not an intellectual concept, 27;
not considered in Euclidean or Cartesian geometry, 26;
bodily motion is absolute, 24;
outside ourselves is relative, 24.
Motor-habits, 38, 155.
Multicellular organisms, evolution of, 223.
Muscular contraction, 104;
metabolism in, 104;
heat production in, 104.
Muscular and nervous organs, 275.
Musculature and weight of body, 275.
Mutations, 189;
essential nature of, 193;
causes of, 200;
must be co-ordinated, 231;
physical model of, 192;
the material for selection, 230.
Nägeli, and autonomy in development, 160.
Natural selection, 228;
generality of, 229;
a slow process, 230.
Nebulæ, 315.
Nebular hypothesis, 296.
Nerve impulses, 100;
velocity of, 101;
integration of, 273.
Nervous system, 272;
in co-ordination of activities, 171;
paths in, 157.
Nervous activity, 107;
metabolism in, 107;
electric changes in, 107;
influence of metabolism on, 97.
Nothing, a pseudo-idea, 18.
Nucleus, evolution of, 222;
division of, 130, 182.
Ontogenetic stages, 255.
Orders of individuality, 171.
Organism, definition of, 331;
analysis of its activities, 109;
animal and plant, 76;
considered energetically, 77;
the dominant, 258;
a function of the environment, 216;
a mechanism, 51;
the primitive, 222;
a physico-chemical system, 65;
a thermodynamic mechanism, 104.
Organic chemical syntheses, 317.
Organisation in development, 137.
Organ-rudiments, 257.
Osmosis, 95, 99.
Ostracoderms, 291.
Ostwald on catalysis, 91.
Ovum, development of, 129;
maturation of, 198, 239;
an intensive manifoldness, 302.
Oxidases, 105.
Oxygen in metabolism, 69.
Pain, Bergson on, 281.
Palæontology, 210;
relates groups of organisms, 211.
Pangenesis, 181.
Paramœcium, division of, 173, 175;
responses of, 4.
Parasitism, 259;
tends to immobility, 290.
Parthenogenesis, 176;
artificial, 176.
Particles, 356.
Pecten, eye of, 233.
Perception
not merely physical stimulation, 7;
involves effector activity, 7;
involves deliberative action, 9;
arises from acting, 50;
and choice of response, 155;
is unfamiliar cerebral activity, 8;
skeletonises consciousness, 40.
Peridinians, 77, 163;
distribution of, 260.
Personal equation, 45.
Personality, 167;
an intuition, 167;
division of, 173;
is absolute, 48.
Pflüger, and experimental embryology, 131.
Phases in physical systems and organic systems, 321;
in transforming systems, 308.
Phenomenalism, 46.
Photosynthesis, 70, 76, 86.
Phototaxis, 144.
Phyla
animal, 247;
morphology of, 247;
relations between, 252;
ancestries of, 252.
Phylogenies, 253;
are summaries of morphological results, 254;
indicative of directions of evolution, 254;
criteria of, 253.
Phylogeny, 246.
Phylum, 210.
Physical basis of life, 84.
Physico-chemical reactions, 80;
are directed, 118;
the means of development and behaviour in the organism, 160.
Physico-psychical parallelism, 160.
Physics, a statistical science, 116, 377.
Physiology
Galenic, 122;
an analysis of organic activity, 120, 328.
Plants, geological history of, 261;
characterised by immobility, 277;
contrasted with animals, 277.
Platonic ideas, 204.
Platyhelminths, morphology of, 248.
Poikilothermic animals, 68.
Poincaré, and Brownian movement, 119.
Polar bodies, 198.
Polyzoa, 164.
Porifera, 248.
Potential, 61.
Potential energy, 58, 114.
Preformation an embryological hypothesis, 128.
Probability, 350.
Proteids, digestion of, 90.
Proto-forms, 254.
Protoplasm, nature of, 106;
artificial, 106;
disintegration of, 107;
activities of, 107;
similar in plant and animal, 294.
Protozoa, 247;
behaviour of, 293.
Pterodactyls, 274.
Races (in specific groups), 194.
Radiation, 355;
of sun, 51;
transformation of energy of, 57.
Radio-activity, 56, 359.
Reality, objective, 43.
Reception, 3;
organs of, 271;
by specialised sense-organs, 11.
Recessiveness, Mendelian, 196.
Reflex action, 4, 272;
concatenated, 150;
a complex series of actions, 6;
not necessarily accompanied by perception, 155;
the basis of instincts, 150;
a schematic description, 5;
in decapitated frog, 6;
frictionless cerebral activity, 8;
involves a limited part of the environment, 50.
Reflex arcs, 272.
Regeneration, 142;
in Hydra, 164;
in sea-urchin embryo, 164;
in Planaria, 164.
Regression, 189.
Reinke, and structure of protoplasm, 106.
Reintegration in development, 171.
Rejuvenescence, 175.
Releasing agencies, 157.
Reproduction, 167;
asexual, 175;
by brood-formation, 173;
by conjugation, 173;
sexual, 174;
by division, 172;
compared with minting machine, 242;
of the tissues, 180.
Responses of organisms, 217;
directed, 269;
of magnet, 279;
of green plant, 279.
Reversibility, physical, 369.
Rodewald, chemical nature of protoplasm, 106.
Roux, experimental embryology, 131;
development the production of a visible manifoldness, 307.
Saliva, secretion of, 96.
Salivary glands, metabolism of, 96.
Salivary secretion, not a purely mechanistic process, 112.
Sea, not really rich in life, 306.
Sea-urchin gastrula, 170.
Secretion described mechanistically, 98.
Secretion, psychical, 99.
Segmentation of the ovum, 129.
Selection, natural, 228;
from fluctuating variations, 189;
from mutations, 190.
Semon, mnemic hypothesis of heredity, 181.
Senescence, 175.
Sensation, 2;
analysis of, 13.
Sense-receptors and the idea of matter, 352.
Sensori-motor system, 270;
dominant in animals, 271, 273;
specialisation of, 271, 273;
essentially the same in all animals, 294;
absent in plants, 269;
vestigial in some parasites, 290.
Sexuality, 174.
Siphonophores, regeneration in, 163.
Size of animals, 274.
Skeleton of vertebrates, 276;
of arthropods, 276;
and mobility, 276.
Soddy, and chemical energy, 361.
Soma, 179;
evolution of, 223.
Space, form of, 18;
3-dimensional, 18;
3-dimensional space an intuition, 19;
2-dimensional, 19;
the form of, depends on modes of activity, 21, 25.
Species, are categories of structure, 201;
comparison with Platonic ideas, 204;
criteria of, 202;
elementary, 193;
are intellectual constructions, 203;
individuality of, 203;
Linnean, 201, 289;
are phases in an evolutionary flux, 206;
are families in the human sense, 208;
systematic, 201.
Specific organisation, stability of, 186.
Stahl, and the phlogistic hypothesis, 126;
and vitalism, 126.
Stimuli, elemental, 151;
physico-chemical, 151;
formative, 176;
complex auditory, 152;
integration of, 152;
individualised, 152, 270;
contractile, 103.
Stimulus and response, functionality of, 152.
Substantia physica, 46, 355.
Surface tension, 105, 106.
Suspensoids, 108.
Sylvius, the organism a chemical mechanism, 125.
Symbiosis, 77.
Symbiotic organisms, 88.
Synapses, in central nervous system, 158, 272.
Synthetic chemistry, 236, 317.
System, isolated, 63.
Systems in development
equipotential, 139;
harmonious equipotential, 139;
complex equipotential, 140.
Taxis, 144;
no perception in, 155.
Telegraphy, wireless, 355.
Temperature of sun, 56;
of space, 57.
Thermodynamics, 51;
1st law of, 51;
2nd law of, 54, 63, 309, 316;
and Maxwell’s demons, 118;
laws of subject to limitations, 115.
Thermodynamical mechanism, the organism not a, 69.
Thomson, W., dissipation of energy, 113.
Time a series of standard events, 28;
astronomical, 34;
time differentials, 34.
Tissues, evolution of, 223.
Tools, nature of, 285;
use of must be learned, 285;
bodily, 285.
Toxins, 36.
Transformism, 213.
Trematodes, larval stages of, 165.
Trial and error, 293;
in reasoning, 293;
a hypothesis of animal movements, 150.
Trigger reactions, 87.
Trilobites, an ancient group, 261.
Tropisms, 144;
in plants, 269, 279;
in moths, 280;
and natural selection, 147;
and movements of caterpillars, 146;
an inadequate basis for a theory of animal movements, 147.
Tunicates, suppressed notochord of, 250.
Unavailable energy and entropy, 375;
tendency to increase of, 375.
Unicellular organisms, energy-transformations in, 177.
Unit-characters, 230.
Van’t Hoff’s law, 218.
Variability, 172, 186;
continuous, 188;
discontinuous, 188;
examples of, 187;
and the environment, 189;
independent of the environment, 239;
and growth, 188;
tendencies of, 235.
Variation, rate of (mathematical), 344;
in biology, 186;
atavistic, 195;
direction of, 233;
fluctuating, 189;
must be co-ordinated, 231;
mathematical probability of co-ordination of 233;
the material for selection, 229;
origin of, 230;
selected by the organism, 237;
cause of, a pseudo-problem, 242;
arise de novo, 244.
Variables (mathematical), 343.
Varieties, specific, 194.
Vegetable life, 265.
Vertebrates, 249;
adaptations securing mobility, 275;
ancestry of, 253;
morphology of, 249;
a dominant group, 259;
distribution of, 260.
Verworn, and mechanism in life, 127.
Vesalius, anatomical school of, 121.
Vital activities, integration of, 128;
co-ordination of, 171.
de Vries and mutations, 191;
fluctuating variations inherited, 220.
Vital force, 318.
Van der Waal’s equation, 308.
Weber’s law, 16;
a quasi-mathematical relation, 17.
Weismann, hypothesis of heredity, 182;
hypothesis of germinal selection, 241;
hypothesis of development, 132;
mosaic-theory, 131;
preformation hypothesis, 133;
hypothesis of the germ-plasm, continuity of the germ-plasm, 181;
germinal changes inconceivable, 224;
size of biophors, 183;
origin of life, 339;
spontaneous generation a logical necessity, 339.
Weismannism, a series of logical hypotheses, 320;
physico-chemical analogies, and subsidiary hypotheses, 223.
Whales, an unsuccessful line of evolution, 274.
Whitehead, and mathematical reasoning, 347.
Wilson, mosaic-theory of development, 139.
Yerkes, and behaviour of crustacea, 293.
Zymogens, 92.
Zymoids, 94.
PRINTED BY
TURNBULL AND SPEARS,
EDINBURGH
Spelling corrections:
animo-acids → amino-acids
animo-substances → amino-substances
differen tkinds → different kinds
algae → algæ
organsim → organism (x2)
diffusbility → diffusibility
marjoity → majority
hythothesis → hypothesis
execretory → excretory
conconsidered → considered
End of Project Gutenberg's The philosophy of biology, by James Johnstone