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SCIENCE PROGRESS

/IN THE TWENTIETH CENTURY

A QUARTERLY JOURNAL OF

SCIENTIFIC WORK

& THOUGHT

EDITOR

SIR RONALD ROSS, K.C.B., F.R.S., N.L.,
D.Sc, LL.D., M.D., F.R.C.S.

VOL. VII
1912— 1913

LONDON
JOHN MURRAY, ALBEMARLE STREET, W.

1913

aS". v. 57

^37

SCIENCE PROGRESS

TIDES AND THE RIGIDITY OF THE

EARTH

By prof. a. E. H. LOVE, F.R.S.

The publication of a third edition of Sir G. H. Darwin's well-
known semi-popular book on the Tides ^ affords an opportunity
of forming an estimate of the advances that have been made in
recent years in knowledge concerning all those geophysical
phenomena which either are directly due to the forces that
cause the tides or share with these direct effects some feature
rendering them amenable to discussion by similar methods.
Sir G. H. Darwin is the greatest living authority on these
questions and the fact that nearly one quarter of the third
edition of his book is either added or rewritten is sufficient
evidence that substantial advance has been made. This advance
is not confined to the theory but extends also to the methods of
observation and the devising of suitable instruments, besides
including a very great increase in the mass of records that are
available for the comparison of theoretical results with observed
facts. On the purely observational side, perhaps the greatest
novelty is to be found in the beginning of actual measurements
of the range of the tide in the open sea. On the purely
theoretical side, the modifications of Laplace's nebular hypothesis
which have been suggested by various writers are specially
attractive. But the advances that will prove most interesting to
many readers have been made by combining theoretical con-
siderations with observational results in regard to several
groups of phenomena from which conclusions have been drawn
as to the internal constitution of the Earth. We propose to
consider these matters in order.

* The Tides and Kindred Phenomena in the Solar Syste?ny by Sir George
Howard Darwin. Third Edition. London: John Murray, 1911.

2 SCIENCE PROGRESS

Tidal Oscillations in the Ocean

By the range of the tide at a place is meant the excess of the
depth of water available at high-water for floating a ship at
the place above the corresponding depth at low-water. Until
recently measurements of the range of the tide were made only
at places close to the coasts. They are, in fact, among the
results furnished by the use of a tide-gauge. It was supposed,
chiefly on theoretical grounds, that the range of the tide in the
open sea was much smaller. For a complete understanding of
the tides, it is desirable to ascertain the range in the open
ocean and in partially enclosed seas, such as the English
Channel, by direct observation. It appears that ordinary
methods of sounding are not available for this purpose and new
instruments have been specially devised, one by Captain Adolf
Mensing of the Imperial German Navy, the other by Admirals
Mostyn Field and Purey-Cust. The preliminary results obtained
by the use of the instrument due to the latter are very striking,
a range of tide in the Channel amounting to no less than
24 ft. having been measured at a place about midway between
Beachy Head and Dieppe. Systematic observations of this
kind may be expected to throw much light on the nature of
tidal oscillations. The extent to which the tide wave in the
Atlantic Ocean, for instance, is an oscillation generated in that
ocean by the direct action of the Sun and Moon, as contrasted
with a progressive wave, generated in the Pacific and Southern
Oceans and entering the Atlantic betweeen the promontories of
South Africa and South America, is in some degree a matter of
controversy. The systematic study of the tides in the open
ocean, as distinct from the ebb and flow along the coasts, may
be expected to go far towards settling the question; the whole
value of the method of cotidal lines, as developed by Airy and
Whewell, depends upon the answer that may be obtained.

Like other natural motions, the tidal oscillations of the ocean,
maintained by the attraction of the Sun and Moon, do not take
place without friction; and one effect which such friction can
bring about is a steady diminution in the speed of the Earth's
rotation. The friction of the tides which were in the past raised
by the Earth in the Moon, if the Moon once possessed oceans,
may in like manner have operated to diminish the speed of the
Moon's rotation ; this may be the reason why the Moon now

TIDES AND THE RIGIDITY OF THE EARTH 3

always presents the same face to the Earth. Tidal friction in
the Earth-Moon system can also cause the Moon to recede
from the Earth and it is possible that the Moon was once much
nearer to the Earth than it is now, even possible that it was
once part of the Earth. The theory of the effects which tidal
friction in such a system as that of the Earth and Moon— a
moderate-sized planet accompanied by an exceptionally large
satellite and revolving around the Sun— were traced in a
masterly manner by Sir G. H. Darwin in a series of memoirs
published some thirty years ago. The theory was necessarily
coloured to some extent by the then prevalent scientific ideas
concerning cosmogony, ideas derived mainly from Laplace's
nebular hypothesis. A perfectly natural chain of reasoning
leads directly from the discussion of the theory of the tides,
through tidal friction, to the most speculative regions of thought
as to the origin and evolution of planetary and stellar systems.

Evolution of Planetary Systems

Until recently Laplace's hypothesis held the field ; though
the authors of some modern theories might demur to such a
description, it still seems fair to describe all the more recent
hypotheses as modifications of that propounded by Laplace.
Darwin himself broke away somewhat from the Laplacian
doctrine when he suggested that the Moon became detached
from the Earth as a single satellite and not as a ring. J. H.
Jeans broke away still more when he suggested that gravita-
tional instability or the tendency of gravitating matter to
concentrate about local nuclei, rather than increased speed of
rotation due to cooling, might have been the cause of the
disintegration of the primitive nebula into detached masses.
But the modern revival of interest in the nebular hypothesis is
largely due to the criticisms levelled against it by T. C.
Chamberlin and F. R. Moulton and the propounding by them of
a view put forward as alternative and named the " planetesimal"
hypothesis. In this view the solar system is supposed to have
been developed from a spiral nebula, a type of celestial object
with which modern telescopes have made us familiar, consisting
of a central condensation from opposite parts of which there
emanate a pair of spiral arms. Such an object is supposed
to have originated from a single star through enormous tidal

4 SCIENCE PROGRESS

forces set up in it by passing near to another star. The
assumed partial disintegration thus effected in the parent star
and the mode in which subsequently aggregation of the ejected
matter into planets and satellites might have taken place offer
problems so intricate as to defy calculation ; the indications that
can be obtained certainly seem to suggest that we have in this
theory a modification of Laplace's free from many of the difficulties
inherent in his original form.

Earth Tides

The body of the Earth, on which the oceans rest, cannot
be absolutely rigid. No body is. It must be deformed more
or less by the attractions of the Sun and Moon. If we can find
out in what manner it is deformed and how much, we can draw
inferences in regard to its internal constitution. Thus there
arises the problem of earth-tides : How can such tides be ob-
served ? What conclusions in regard to the state of the matter
within the Earth can be drawn from the observations ? The
movement eludes direct observation. A tide-gauge can record
the rise of water above a marked level near a coast and other
instruments can do the same thing for the rise above a level
measured from the sea-bottom out at sea but the would-be
observer of earth-tides has no mark from which to measure.
His methods of observation must perforce be indirect. The
first attempts were directed to finding the actual height of the
so-called fortnightly tide. By the fortnightly tide is meant
a minute inequality in the tide-height, having a period of about
a fortnight, depending upon the inclination of the Moon's orbit
to the plane of the equator. The point at which the Moon
is overhead is not always or generally a point on the equator
but travels round and round the Earth in a sort of spiral path.
The whole spiral lies between two extreme turns, one the most
northerly, the other the most southerly, which, however, are
not fixed but vary in position from time to time. If we follow
the movement of the point, beginning at an instant when it
has an extreme northerly position, we find each successive turn of
the spiral lying to the south of the preceding turn, until at the
end of a fortnight an extreme southerly position is reached. After
this the path turns to the north and during the next fortnight
each successive turn of the spiral lies to the north of the pre-

TIDES AND THE RIGIDITY OF THE EARTH 5

ceding turn. This movement of the Moon causes an inequahty
in the tide-raising force with a period of a fortnight and this in-
equality in the force affects the observable height of the tide with
an inequality of the same period. It is as if, in addition to the
tide that comes in twice a day, there were a tiny tide that comes
in twice a month. The method of harmonic analysis of tidal
observations can draw out from a long series of observations
the amount of this tiny tide, just as a suitably tuned resonator
can pick out one of the component tones of a musical instrument
or of an orchestra. Now the amount which the fortnightly
oceanic tide would have if the Earth were absolutely rigid
can be calculated. The result that it may be calculated by
the so-called "equilibrium theory" was first asserted on
insufficient grounds, then denied on the basis of a more
rigorous investigation and finally proved by taking account
of a circumstance neglected in that investigation. The adven-
tures of this result form a curious chapter in the history of
science but must be omitted here. It is now w^ell established.
The comparison of the observed and calculated values is one of
the methods available for determining the height of earth-tides.
Clearly, if the observed value be nearly equal to the calculated,
the Earth yields but little ; if the observed value be much less
than the calculated, the Earth yields a good deal. In the
former case it is very stiff or of great rigidity, in the latter the
rigidity is small. If the Earth were fluid inside there should
be very little fortnightly tide. As a matter of fact, the observed
value is nearly two-thirds of the calculated. This result forms
an essential part of the famous argument invoked by Lord
Kelvin to prove that the Earth cannot consist of a molten fiery
core covered over with a thin solid crust.

This argument is greatly strengthened when it is found
to be confirmed by others derived from a study of other
phenomena than the fortnightly tide. The attraction of the
Moon tends to draw a pendulum to one side. The force
available for this purpose is not the full amount of the Moon's
attraction but the difference between the amounts of this
attraction at the centre of the Earth and at the place where
the pendulum is hung ; and of this difference the horizontal
component only can affect the direction in which the pendulum
hangs or the apparent vertical. The maximum amount of the
available force being only about one eleven-millionth of gravity,

6 SQIENCE PROGRESS

it is necessary to magnify the effect. This is done by using
a horizontal pendulum, that is to say, a pendulum free to
swing about a nearly vertical axis. The deflexion of the
pendulum measures the force acting upon it. If the Earth
were absolutely rigid, the Moon would act upon the pendulum
with a certain force, as above. It is necessary to take numerous
precautions to shield the pendulum from disturbances, such
as those due to draughts, to the heating of the soil by the Sun
during the day and its cooling at night, even to the tilting
of the floor by the weight of the observer. All these difficulties
were overcome by Dr. O. Hecker, who installed two horizontal
pendulums in an underground chamber at Potsdam and re-
corded their movements during several years. On analysing
his results, he showed that the actual movement of the pen-
dulum is about two-thirds of what it would be if the Earth
were absolutely rigid. Hecker's measurement of the lunar
deflexion of gravity is a very remarkable achievement. It
recalls and evidently confirms the result obtained by ana-
lysing tidal observations to pick out the fortnightly tide ; and
it has itself been confirmed by another series of experiments
with horizontal pendulums carried out by Dr. A. Orloff at
Dorpat. It is important to note that the deflexion of the pen-
dulum or at least that part of it which is periodic in half a lunar
day keeps time with the Moon.

The proper interpretation of these results is a matter of
some difficulty. The registering by the horizontal pendulum
of a deflexion less than that due to the Moon's force is evidence
that it is under the action of other forces which keep time with
the Moon ; and it is an immediate inference that these forces are
due to the deformation of the Earth by the Moon's tide-raising
force. This force alters very slightly the shape of the Earth,
elongating it towards the Moon and in the opposite direction
and flattening it all round at the places where the Moon is
near the horizon. The change of shape produces in the sup-
ports of instruments a slight tilt and consequently a horizontal
pendulum is subjected to a small force which may be described
as the "force due to tilting." It is easy to see that the force
due to tilting acts against the Moon's tide-raising force. But
this is not the only extra force which is exerted on the pendu-
lum. The elongation of the Earth in one direction, combined
with the flattening in all perpendicular directions, causes a

TIDES AND THE RIGIDITY OF THE EARTH 7

change in the attraction of the Earth or a genuine alteration
of gravity, due to the attractions of the tidal protuberances
and the loss of attraction that accompanies the tidal flattening.
This additional force, the genuine alteration of gravity, may
be described as the " change of attraction." It is easy to see
that it acts so as to reinforce the Moon's force. The observed
result is interpreted in the statement that the force due to
tilting exceeds the change of attraction by an amount equal
to about one-third of the Moon's force. Now if we knew the
force due to tilting, we should know how much the surface
is tilted and thence how much the Earth yields to the tide-
raising forces. If we knew the change of attraction, we
could then use the result obtained by observing the deflexion
of the horizontal pendulum to infer the force due to tilting
and thence, as before, find the amount by which the Earth
yields. But the pendulum result will not tell us how much
the Earth yields, because all it can possibly give is the
difference between two forces; what we want to know is the
magnitude of one of them. Observations of the fortnightly
tide cannot give us any additional information. They can
only tell us what the horizontal pendulum tells us.

The ambiguity of the interpretation to be put upon the
results obtained from observations of the fortnightly tide and
of the behaviour of horizontal pendulums should make us
cautious about accepting statements as to the rigidity of the
Earth, when such statements are founded upon observations
of these kinds only. It is true that Lord Kelvin proved long
ago that, if the Earth were homogeneous and incompressible,
it would have to be as rigid as steel to make the observable
height of the fortnightly tide as much as two-thirds of that
calculated by the equilibrium theory. The fact that the
observed height is of about this amount does not enable us
to infer that the actual Earth, which is neither homogeneous
nor incompressible, is as rigid as a ball of steel. To obtain
sufficient evidence for a judgment on this matter it is neces-
sary to have recourse to a different kind of observations and
the observations that have proved effective have to do with a
phenomenon that has no obvious relation to tides or the lunar
deflexion of gravity — the phenomenon of variation of latitude.
It has been known for a long time that the latitudes of places
on the Earth's surface are not quite fixed or, what comes to

8 SCIENCE PROGRESS

the same thing, that the North and South Poles are not quite
fixed points on the Earth's surface. It has become known
more recently that the Poles move in irregular paths about
mean positions, round which they circulate in a period of
about fourteen months. The period which this movement
would have if the Earth were an absolutely rigid body is well
known to be about ten months; one reason why the actual
periodic movement, with a fourteen-months' period, remained so
long undiscovered was that observers sought in their records
for traces of a ten-months' period. The lengthening of the
period from ten months to fourteen is due to the yielding of the
Earth. A movement of the Poles means a change of the instan-
taneous axis of rotation ; this is necessarily accompanied by a
change in the so-called " centrifugal force." The adjustment
of the Earth to rotation about one axis after another involves
a deformation, in exactly the same way as if it were subjected
to forces which are the differences between the centrifugal force
referred to the actual axis and the centrifugal force referred
to an axis passing through the mean positions of the Poles.
Exactly as in the case of tidal forces, the deformation implies
a tilting of the surface and a " change of attraction." The
lengthening of the period has been proved to depend upon
the change of attraction not upon the tilting of the surface ;
and the law according to which the change of attraction is
connected with the force causing deformation, in the case of
variation of latitude the inequality of centrifugal force, has
been made out. Further, it has been proved that the law
connecting the change of attraction with the force causing
deformation must be exactly the same, whether the force in
question be an inequality in centrifugal force or a tide-raising
force. The result is that from the period of variation of
latitude we can infer the change of attraction due to the tide-
raising forces.

To determine the actual height of earth-tides it only remains
to combine the results of observation in regard to variation of
latitude with those of horizontal pendulum experiments. The
change of attraction, the force due to tilting^ the amount of
the deformation have all been determined. But from this
information we cannot infer much more about the rigidity of
the Earth than that on the whole it is great. It is impossible
to fit all the observations by treating the Earth as a body

TIDES AND THE RIGIDITY OF THE EARTH 9

of one definite rigidity throughout. Being heterogeneous as
regards density it may be expected to be so in regard to
rigidity as well. It is perhaps not very surprising that it
should be possible to fit all the observations by the assump-
tion of a core of greater density enclosed in a crust of smaller
density, provided the core be stiffer than the crust ; and it is
interesting to note that, if the crust be taken to be about 1,000
miles thick and to have the average density of surface rocks,
whilst the core is taken to have the density of iron, the average
rigidity of the core, computed on the hypothesis of incom-
pressibility, must be nearly three times that of steel, whilst
the average rigidity of the crust, computed on the same
hypothesis, may be much less than that of steel and indeed
less than that of most hard rocks.

Rigidity of the Earth

The inference that the greater part of the body of the
Earth must be solid and very rigid has been confirmed in a
remarkable way by the results of seismological investigations ;
indeed, the perhaps unexpected conclusion that the inner parts
must be more rigid than the outer appears to be required as
part of the interpretation of seismic records. The systematic
recording by suitable instruments of seismic disturbances trans-
mitted to great distances has been practised for a relatively
short time but the results that have been obtained by means
of such records have already proved to be of the highest value
for Geophysics. When a great earthquake takes place it affects
seismographs all over the world ; the records always conform
to one type, a series of minute tremors being followed by a series
of much larger oscillations which subside gradually. When
the distinction between the preliminary tremors and the large
waves was first noticed, it was supposed by some writers that
they were to be classed respectively as longitudinal and trans-
verse waves, in accordance with the well-known physical
principle that waves transmitted through an elastic solid body
are of two types— waves of compression or rarefaction, charac-
terised by movement parallel to the direction of propagation ;
and waves of distortion, unaccompanied by change of volume,
characterised by movement transverse to the direction of propa-
gation. As the records accumulated and the theory of elasticity

lo SCIENCE PROGRESS

was improved, it was seen that this simple classification could
not be maintained. On the one hand it was found that the pre-
liminary tremors arrived at distant places at such times as
to indicate direct transmission through the body of the
Earth with a nearly constant velocity, whilst the larger waves
appeared to be transmitted over the surface of the Earth with
a smaller nearly constant velocity. Further, it was found that
both the preliminary tremors and the large waves were com-
posite. After the tremors have been going on during a few
minutes, a second series of tremors, showing certain charac-
teristic differences from the first, begin to be received, and the
result has been established that the movement is mainly longi-
tudinal in the first series, mainly transverse in the second.
Both series appear to travel through the body of the Earth with
nearly constant velocities. Again it has been found that the
large waves present a number of distinct phases, the most
important being an initial phase, in which the movement of
the ground is mainly horizontal and transverse to the direction
of propagation ; and a maximum phase, in which the horizontal
movement of the ground is mainly parallel to the direction of
propagation and is accompanied by considerable vertical move-
ment and a phase of subsidence.

Concurrently with the accumulation of seismic records and
the classification of the types of movement which they disclose,
there has been a considerable development of the physico-
mathematical theory by means of which an account of such
movements can be rendered. The first step was the discovery
by Lord Rayleigh of a third type of waves. A disturbance
set up in a solid body spreads out in a composite wave, which
gradually resolves itself into two waves, one of compression,
the other of distortion, with a peculiar type of motion between
the two. When the front of a wave reaches a bounding surface
reflexion takes place ; the reflected waves are in general com-
posite at first and resolve themselves gradually into pairs of
waves of the two special types. The effect of a bounding
surface is therefore to produce changes which may disguise
the simplicity of the resolution into the two types ; the result
which Lord Rayleigh found was that disturbances emerging
at the surface give rise to a distinct class of waves, which travel
over the surface with a nearly constant velocity and never affect
appreciably the matter at any considerable depth beneath the

TIDES AND THE RIGIDITY OF THE EARTH ii

surface. Waves of this type are characterised by a horizontal
movement parallel to the direction of propagation, accompanied
by considerable vertical movement. The conclusion that the
maximum phase of seismic movement must be transmitted by
v^aves of this type seems inevitable. The phase of subsidence
might be supposed to be due to the frittering away of the
energy through internal friction; doubtless this cause plays a
part but it has been proved by Prof. H. Lamb that waves
which spread over a surface, as distinguished from waves which
travel through a body, are always prolonged in a kind of " tail,"
showing a gradual diminution of intensity, quite independently
of any dissipation of the energy. The characteristic feature of
the initial phase of the large waves, viz. the transversality
of the horizontal displacement, can be explained only by taking
account of the heterogeneity of the Earth's substance. Waves
possessing this feature can travel through a superficial layer,
provided the rigidity of the subjacent material be greater than
that of the layer.

By regarding the Earth as made up of a nucleus and a
moderately thick superficial layer or crust and attributing
suitable mechanical properties to the nucleus and to the crust,
we can arrive at a fairly consistent representation of the various
phenomena. The first and second phases of the preliminary
tremors are, in this representation, taken to be due respectively
to compressional and distortional waves which travel through
the body of the Earth and emerge at the surface. The initial
phase of the large waves is taken to indicate the passage of
waves of transverse horizontal displacement transmitted through
the crust ; the maximum phase to indicate the passage over
the surface of waves of Lord Rayleigh's type ; and the phase
of subsidence to be the expression of the tails in which both
these types of waves would necessarily be prolonged. The
values to be attributed to the physical quantities by which
the state of the parts is specified are not completely determinate,
a change in the assumed density, for instance, being accom-
panied by a change in the inferred rigidity. But the indeter-
minateness is confined within relatively narrow limits. The
order of magnitude of the rigidity required in the nucleus
or at least in its more central portion is about three times
the rigidity of steel. This value may seem very large; but,
when we reflect upon the enormous pressures which must be

12 SCIENCE PROGRESS

developed within the Earth by the mutual gravitation of its
parts, it becomes less surprising. A similar value v^as inferred
by combining the result of horizontal pendulum experiments
w^ith the result of observations concerning variation of latitude.
The value required in the crust is about the average rigidity
of many kinds of granite and marble. The result that, for the
proper transmission of the initial phase of the large waves,
the rigidity should increase beneath the crust, points to a
gradual transition from the mechanical properties of the crust
to those of the nucleus, a thing probable enough. The general
result that the Earth as a whole is a very rigid body, not
a fluid body coated over with a thin solid crust, is so well
supported by the observations of the fortnightly tide, by the
experiments with horizontal pendulums, by the period of the
variation of latitude and by the interpretation of seismic records,
that it should by now be regarded as firmly established.

DR. PAVY AND DIABETES

By F. GOWLAND HOPKINS, M.A., M.B., D.Sc, F.R.S.

The death of Frederick William Pavy at the age of eighty-two
closed a remarkable career. It is not often that an exceedingly
busy professional man retains unimpaired, throughout a long
life, a vivid interest in the purely theoretical side of the problems
of his profession ; more usually intellectual relief is sought in
other fields. An eminent physician is rarely found busy at
once in practice and in the laboratory ; less often still are such
combined activities exercised over considerably more than half
a century ; and it is, I think, even more rarely that a scientific
worker, of any sort, is found content in his old age to struggle
with just those elusive and somewhat limited issues which
occupied him at the beginning of his career. The scientific
veteran usually comes to crave a more extensive area of action ;
if he have not left science for philosophy or affairs, his interests
are usually concerned with the wider aspects of his subject.
But Pavy, with fourscore years behind him and still a busy
consultant ever remained an active laboratory worker, faithful
to his original quest and as keen an inquirer as in his youth.

A few months before his death, he wrote to Prof. Armstrong
in the optimistic spirit which was characteristic of him. '* My
great object, before life comes to an end," he says, " is to elicit
all the useful knowledge I can bearing upon Diabetes " ; and he
speaks of his faith in the reality of the progress being made.
His latest colleague in research, Mr. Godden, tells me that,
to the very end, he would seize available moments between the
morning visits of his patients to enter his laboratory and watch
the progress of experiments. His afternoons were spent in
continuous experimental work at the physiological laboratories
of the London University and this routine was continued to
within a week of his last vacation, from which he returned with
but nine days of life left to him.

Pavy was born in 1829. Educated at the Merchant Taylors'
School, he entered as a student of Guy's Hospital in 1847. In

14 ' SCIENCE PROGRESS

1853 he obtained his Doctorate at the London University; his
first paper, entitled, '* Saccharine matter : its physiological rela-
tions in the animal mechanism," was published in the Guy's
Hospital Reports of the same year. It was the precursor of some
two-score of papers; the last of these has but just appeared and
was published posthumously. Almost any one of the long
series might well have received the title of the first. Pavy's
scientific interests w^ere indeed in one way extemely circum-
scribed : though other aspects of medicine and physiology
received attention from him intermittently, the subject which
really absorbed him was the metabolism of carbohydrates —
normal and erratic. Adolescent or aged, he remained devoted to
the problems of this domain. He was, of course, a specialist in
the treatment of diabetes and his professional fame ensured him,
during half a century, a lucrative consulting practice. But it must
not be supposed either that his interest in the metabolism of
carbohydrates arose merely from his professional needs or that
his labours as an investigator had anything whatever to do
with the desire to advertise his special knowledge : both began
before his practice took shape ; both lasted without abatement
long after his practice needed any prop whatever.

He once told me himself that it was an instinctive interest
in this particular aspect of physiology that led him to specialise
professionally. He was a great believer (as who should not
be?) in the value of pathological studies to the physiologist
and was apt to think that if physiologists could see as much
as he himself had seen of human diabetes they would more
readily accept his teachings concerning the normal fate of sugar
in the body.

It must be admitted that Pavy's special views did not, as a
matter of fact, conform to current opinion. In discussing them
I shall be bound, as a result of my own predilections, to take
more or less the standpoint of orthodoxy. But I write as one
personally indebted to the stimulus of Pavy's teachings and as
one who has seen physiology gain more from Pavy's work and
enthusiasm than from the writings of many who have kept step
with the majority.

Claude Bernard's Glycogenic Hypothesis

During the year in which he took his degree, Pavy paid
a visit to Paris; there he met Claude Bernard. Some few

DR. PAVY AND DIABETES 15

years earlier, this great physiologist had published his account
of the experiments which established belief in what is gener-
ally known as the glycogenic function of the liver; Pavy,
during his visit, doubtless received an account of the work at
first hand.

It is well to be clear with regard to the exact use of the
expression " glycogenic " as at first applied to the functions of
the liver. Bernard had set himself to explore the organs of the
body in the endeavour to locate the regions in which sugar is
utilised and destroyed. His hope was to discover what deficiency
might be responsible for the condition of diabetes and by
mitigating that deficiency to effect a cure of the disease. He
already knew that all carbohydrate food leaves the intestine in
the form of dextrose. The liver is an organ standing in the
path of transference from the intestine to the tissues and Bernard
first sought evidence for the destruction of the dextrose in that
organ. He found, however, that sugar was present in the
blood of the hepatic veins immediately beyond the liver during
the absorption of carbohydrate from the intestine. He then dis-
covered something more striking : that when the animal was
not taking carbohydrate but consuming flesh alone — no sugar,
therefore, flowing from gut to liver — sugar was still to be found
leaving the latter continuously and passing into the general
circulation beyond it. Claude Bernard held, therefore, that
sugar must be actually made in the liver.

All this was before he had discovered the nature of the
actual precursor of the sugar which leaves the liver and he
conceived at this time that the organ elaborated carbohydrate
from material which was not carbohydrate ; actually it " secreted "
sugar and was in a literal sense of the word "glycogenic."
Later, however, Bernard discovered that the precursor — at all
events, the main precursor — of hepatic sugar was itself a carbo-
hydrate, a polymerised sugar, in fact, which easily gave rise to
sugar under simple treatment. Its discoverer recognised the
physiological analogy of this substance with another complex
carbohydrate — the starch of plants— and though now known as
glycogen it has often been called "animal starch." The term
" glycogenic," as applied to the liver, now took on a somewhat
different aspect ; the organ is not in the main concerned in the
production of carbohydrate de novo but is a particularly
capacious storehouse of carbohydrate awaiting utilisation. Its

i6 SCIENCE PROGRESS

store of glycogen can be filled up when sugar is flowing from
the intestine and then drawn upon when demands arise, the
glycogen being reconverted into sugar and transported in this
form to the seats of utilisation.^

Bernard's discoveries thus provided physiology with a clear
and simple view concerning one fundamental aspect of the
metabolism of carbohydrates and this view is one which still
claims the suffrages of almost all. The facts in support of it
seem now, as we shall see, more cogent than they did to
Bernard's contemporaries.

Pavy's Antagonism to the Glycogenic Hypothesis

Yet Pavy dissented wholly from Bernard's point of view.
Every word that he spoke or wrote concerning the metabolism
of carbohydrates emphasised his antagonism to it ; throughout
his life he was engaged in marshalling facts which, in his belief,
proved it to be in error. To understand his teaching and the
drift of his work, it is very necessary to appreciate this
antagonism and how it arose. Before tracing its origin, how-
ever, it may be well to point out that Pavy's earlier views,
though they remained intact until quite the final period of his
life, were modified ultimately not a little by contact with the
work of others. Those who knew him ultimately are well
aware that during a long period he read but little of the
current literature. He was impatient of the dominance of
Bernard's views on the Continent and discus^'^^ his work
but little with his colleagues save when engaged in actual
polemics (which, it must be confessed, were somewhat of a
joy to him).

When still upon the active staff of Guy's, his purely
scientific work was confined within the four walls of his labora-
tory there. Subsequently (in the later nineties), when working
at the laboratories of the Colleges of Physicians and Surgeons,

* It might be termed therefore a "glycotactic," or, much more accurately, a
" glycodianomic organ {diavefxa). My colleague, Mr. E. Harrison of Trinity
College, who suggested the latter word, tells me that Plato speaks somewhere of
the lungs as the " Stewards of the Winds." " Steward of the Sugar " would so
exactly express the nature of the function of the liver that but for fear of pedantry
one would be inclined to call it " glycotamieutic."

DR. PAVY AND DIABETES 17

he came under influences ^ which led him to familiarise himself
with the work of others.

His attitude at the last, as displayed, for instance, in the
lectures delivered before the Royal College of Physicians in
1908, was further removed from his own earlier views and nearer
to that of the majority than he himself seemed to realise. He
developed, indeed, in these later years, a knack of weaving
a new weft of facts into the warp of his older views while
gradually removing the less durable threads from the latter.
In the end, though he seemed unable or unwilling to recognise
it, the material had become of almost orthodox pattern. He,
at any rate, believed to the very end that he had disproved
Bernard's original views and all that was based directly upon
them. His antagonism to the glycogenic doctrine was still
strongly expressed in his last published lectures.

I propose now to examine the reasons for this antagonism.
It was due in part to the interpretation he put upon his own
earliest experimental researches but more, I think, to the fact
that two preconceptions dominated his mind : one respecting
the nature of the renal functions, the other concerning the
fundamental nature of animal metabolism as a whole. Each of
these factors may be considered in turn.

Very shortly after his return from Paris, Pavy began to
work upon the carbohydrate question and was led to estimate
the amount of sugar in the blood of the right ventricle of
the heart when obtained from the living animal. He found —
and was greatly impressed by the observation — that, as a
matter of fa^^t, in life, this blood did not carry the excess of
sugar whicii Bernard had shown it might contain postmortem
nor that which apparently it ought to contain according to the
glycogenic doctrine. This led him to suspect that the supposed
excess of sugar in the liver was due to post-mortem changes.
After developing a technique for the avoidance of such changes,
he showed experimentally that there was no excess in the organ :
that if such be ever observed, it is only when the liver has suffered
damage at the hands of the operator. The glycogenic doctrine ^

^ I happen to know that in later life he was most grateful to Prof. Brodie and
to his own private assistant and colleague in research, Mr. Siau, for breaking down
at this time the habit he had acquired of isolating himself intellectually.

^ In its later form, that is to say. When Bernard first initiated it, the seat
of oxidation was supposed to be in the lungs.
2

i8 SCIENCE PROGRESS

further postulates that since sugar is transported from the liver
to the muscles and other tissues, where its oxidation takes
place, arterial blood should contain more sugar than venous.
Pavy's estimations failed to show such excess.

But if the liver contain no more sugar than other organs and
yield no sugar to the blood leaving it, if there be no transport
of sugar as such to the tissues, the glycogenic explanation fails.
Pavy felt that his researches proved all these negations and,
as I have said, disbelieved profoundly in Bernard's views to the
end of his life. His disbelief was supported by an argument
which for him was conclusive. Normal blood throughout the
body contains always a certain small proportion of sugar
(about one part in a thousand) and normal urine also contains
a definite though small amount. These circumstances have
been amply demonstrated by many observers but Pavy himself
took much trouble to obtain accurate quantitative data, both
from blood and urine. Now, in his view, any variation in the
amount of sugar in the former must be promptly indicated by
a corresponding variation in that of the latter. He held it was
impossible that a diffusible substance, such as sugar, with its
relatively small molecules, could fail to pass the kidney in
proportion to its concentration in the blood. But as he pointed
out, no such variations can be detected in the case of the healthy
person. At no time after a meal of carbohydrate is the condition
of the urine such as to indicate an increased excretion of sugar ;
therefore the constituents of that meal can never enter into
general circulation in the form of sugar.

In his criticism on the experimental work which was sup-
posed to support the glycogenic hypothesis by demonstrating
a special distribution of sugar in the circulation, Pavy was upon
strong ground. His own researches, even the earlier, were
made with the aid of better methods and in a more critical
spirit than those of his predecessors. If a belief that the
liver operates as a storehouse of available carbohydrates must
be based on the proof that on occasion sugar passes from it
into the blood, in such quantity that it may be detected
analytically, Pavy's work deprived that belief of foundation.
Those who still hold it are content to point out that the flow
of blood from liver to tissues is so rapid that the transport of
large quantities of sugar need cause but an infinitesimal per-
centage increase in the sample drawn off by the experimentalist

DR. PAVY AND DIABETES 19

for analysis, an increase which may well fall within the limits
of experimental error. Whilst, therefore, an experimental proof
of Bernard's theory cannot be obtained on these lines, a dis-
proof is equally impossible.

The arguments which Pavy based upon his view of the renal
function, though they seemed to him to appeal to common sense
and to be conclusive, were, on the other hand, essentially
a priori. That no increase of sugar takes place normally in
the urine as the result of a carbohydrate meal merely demon-
strates the perfection of the regulative activity of the liver :
the organ maintains the concentration of blood-sugar at a
value near to a mean, in spite of great fluctuations in the supply
from the intestine. On the glycogenic doctrine, fluctuations in
the demands of the tissues would, it is true, involve a fluctuating
output of sugar from the liver and any such fluctuations, Pavy
assumed, should be promptly registered by the kidney. This
assumption is not wholly valid, however. Increased demands
for sugar in individual organs may be met, in part or whole, by
increased velocity in the local blood flow rather than by increased
concentration of sugar in the blood. In many cases, again,
increase in the oxidation processes of the tissues in general
is associated with increased activity in the kidney itself (e.g.
in the adjustment of the body following a lowering of external
temperature) and this organ is one with a high-grade metabol-
ism, likely to utilise rather than to excrete any temporary
excess of sugar which passes it. Finally, though we know
that the kidney is extremely sensitive to increases of sugar
in the blood of above a certain amount, it is more than a mere
filter and we do not know that such small variations as might
be sufficient to cover the fluctuating demands of the tissues
would be registered in it.^

It is striking to find that a direct proof that sugar may
increase in the circulation without glycosuria, far more con-
vincing than such considerations as the above, was to be
furnished by the very last of Pavy's own work which came
to publication. In conjunction with Mr. Godden,* he injected
sugar into the venous circulation of rabbits— under conditions
which were more physiological than those of earlier experiments
of the same type ; and found that no less than 2 grammes of

^ Cf. E. Frank, Zeitsch, f. Physiol. Che^n. 70, 291 (191 1).
' Pavy and Godden, fourn. Physiol, xliii. 199 (191 1).

20 SCIENCE PROGRESS

dextrose per kilogramme of body-weight could be injected in the
course of fifty-five minutes without any trace of glycosuria being
noticeable. If we may transfer such figures to the case of a
man of average weight (70 kilos.) they mean that more than
150 grammes of sugar per hour or 3,600 grammes a day, at
least seven times the normal consumption of carbohydrate,
might enter the circulation without appearing in the urine.
To say the truth, such figures are startling and require further
investigation to explain them. It is hardly likely that they can
be legitimately applied to human physiology but they leave,
at any rate, a large margin of evidence on which to base our
belief that hepatic sugar may enter the circulation normally
in quantities sufficient to supply the maximum demands of the
tissues without inducing glycosuria as a necessary consequence.
How far Pavy would have adjusted his teaching to meet these
results, which were only published after his death, we cannot
tell ; as all his writings show how great was the importance he
attached to an argument which his very last experiments were to
undermine, the circumstances are not without a degree of pathos.

Pavy's own Hypothesis Concerning Assimilation : the
Lymphocytes as Carriers of the Food

To return to the discussion of his published views. If
the glycogenic hypothesis be wrong and sugar be not transported
from liver to tissues, if therefore the glycogen found in the
former be not a store of carbohydrate to be drawn upon by
the latter, what is the significance of its appearance after carbo-
hydrate has been consumed ? Being an insoluble, non-diffusible
form of carbohydrate, the formation of glycogen provides the
chemical mechanism for trapping the intestinal sugar which
must be prevented from entering the general circulation.
When, according to Pavy's earliest teaching, it disappears from
the liver, it undergoes constructive, not destructive, changes.
That sugar can be converted into fat in the body is a physio-
logical certitude and Pavy's original conception was that the
formation of glycogen was essentially the first step on the
way to such conversion. He was prepared, however, to believe
that some other assimilative path might be- open to it ; what he
felt to be certain was that it was never again broken down into
sugar. As his views developed they became more definite with

DR. PAVY AND DIABETES 21

regard to the immediate fate of carbohydrate in the body.
His teaching became even more dogmatic than before on the
point that the body must protect itself from the circulation
of free sugar ; he displayed, moreover, as was only logical
on his part, a strong antagonism to the current idea that protein
enters the blood broken down into its constituent amino-acids.
It seemed to him obvious that anything added to the blood
in such a way as to disturb its mean composition must circulate
in large molecular complexes, insusceptible of leaking through
the kidneys. He held, therefore, that the foodstuffs were
" assimilated " at the very earliest stage of their entry into
the body.

Two cellular mechanisms guard the portals of entry : fixed
epithelium cells, which line the intestinal wall ; free floating
cells (lymphocytes), which normally crowd the lymph spaces
of the intestinal villi but are susceptible of being transported
through lymphatic channels into the blood. Orthodox physio-
logy attaches many functions to the epithelium cells and among
them some of a synthetic nature. Pavy added another function.
He believed them to be capable of converting sugar directly
into fat and looked upon them as constituting the first line of
defence possessed by the body against the entry of diffusible
sugar. He held that he had actually seen this immediate
conversion of carbohydrate into fat in the intestinal wall of
the rabbit, though his observation, it must be confessed, is
not easy to repeat. Later on he attached much more weight
to the functions of the lymphocytes ; reading his later writings
in the order of their appearance, one realises that his faith in
the assimilative importance of these cells became more and
more vivid. In his last years, indeed, he found it difificult to
understand how any one could disagree with him on this point.
His faith certainly went far. Others have looked upon the
lymphocytes as important agents in the transport of protein
from the gut but Pavy took a bolder view : he conceived that
all the protein and carbohydrate eaten, all the supply meant for
the tissues as a whole, is first assimilated by the lymphocytes ;
only when there is marked excess of food to be dealt with
is the function of the liver as a second line of defence neces-
sarily called upon. This assimilation by the lymphocytes is
of the completest kind, leading to an actual growth of the cells,
proportionate to the amount of food absorbed ; even as yeast-

22 SCIENCE PROGRESS

cells grow upon a medium of sugar and nitrogenous matter,
so do the lymph-cells develop upon the sugar and peptone
provided by the intestine.

** Food that has been broken down and placed in a fit state
by digestion for absorption is at once dealt with at the seat
of absorption and rebuilt into an elaborated form. Dextrose
and peptone are alike recognisable at the seat of absorption
but both thereafter disappear. At the same time and at the
same spot, there is an active bioplasmic growth taking place
and bioplasm is known to feed upon dextrose and upon peptone.
The lymphocytes which constitute the growing material can
be followed from the villi into the absorbent vessels and
thence through the thoracic duct into the vascular system." ^
Once in the blood, the lymphocytes are broken down into in-
diffusible products which become available for the nutrition of
the tissues generally.

However startling and at variance with the trend of modern
physiological thought it may be, a theory propounded by so
acute a thinker must not be dismissed without examination.
Increase of lymphocytes in the blood, as a result of food
digestion, is a phenomenon long known and well established.
It is quantitative considerations alone which make Pavy's
theory difficult of acceptance. It is not, maybe, altogether
unthinkable that cells of the type of white blood corpuscles
should increase at the great rate postulated by the theory.
In the case of unicellular organisms multiplying by f" oion
great rates of increase have been observed when the conditions
for growth are favourable. But histologically the lymph-cell
does not by any means present in its nucleus the characters
which are associated with the process of rapid growth ; more-
over considerations of the quantities involved, even though we
can only estimate them approximately, seem to make the theory
quite inconsistent with the facts observed in the animal. An
adult man in the course of twenty-four hours eats some 600
grammes of protein and carbohydrate taken together. An
animal cell contains not less than 75 per cent, of water, so
that the actual mass of lymphocytic protoplasm that would
be formed from the day's dietary on Pavy's view would weigh
perhaps 2^ kilogrammes. Now a calculation indicates that the
total mass of white cells in the blood under average conditions

^ See the Lancet^ 1908, II. 1584.

DR. PAVY AND DIABETES 23

is of the order of from 5 to 6 grammes, so that if the
daily flow of lymph from the intestine really brought so large
a mass of lymphocytes into the blood, either the rate at which
they are destroyed must be almost inconceivably rapid or else
a meal would increase their numbers to a degree out of all
proportion to that observed.^

Pavy himself made an important discovery, which he felt
made it easy to believe in the temporary disappearance of the
carbohydrate of the day's diet in the bioplasm of lymphocytes.
Such a cell consists normally in the main of protein ; Pavy,
however, found that a carbohydrate constituent is always con-
tained in the molecules of proteins. We are to see that this
is a fact with qualifications ; but neglecting these for a moment,
it must be remembered that the protein in the diet, which
has to be assimilated, already contains its own proper pro-
portion of carbohydrate and a proper proportion of carbon
and nitrogen. To this, if we read our author literally, the
growing bioplasm of the intestinal leucocyte adds all the
carbohydrate of a mixed dietary, so that its composition
as it enters the blood-stream must be very different from
anything met with in a normal animal cell : the proteins of
the lymphocyte must contain some three or four per cent, of
nitrogen only, instead of fifteen or sixteen per cent. Otherwise
it must proceed from the intestine loaded with glycogen, a
condition which Pavy does not predicate and which histological
examination disproves.

I have assumed in the last few paragraphs, because Pavy
appears to assume it, that the lymphocyte could assimilate
all the material from the intestine and arrive in the blood
with the supply intact. This could not be the case actually ;
considerations respecting energy make it impossible. The
growth of living cells can never go on in such a way that
the total energy of the material consumed during growth is
stored in the material built up. Such rapid growth and
destruction of cells as the hypothesis under discussion calls
for is of such an exceptional kind that we have no data upon
which to base an estimation of the energy changes likely to
be involved ; but it is certain, I think, that the process would
involve a liberation of energy during the period in which food
is absorbed out of all proportion to that actually observed.
^ Cf. Halliburton, Lancet^ iQOQj Jan. 2.

24 SCIENCE PROGRESS

Such objections as I have urged against the lymphocyte
hypothesis of assimilation either did not occur to its author
or had no weight with him. In 1906 he states the matter
dogmatically thus : " Food into lymphocytes, lymphocytes into
proteids, proteids into tissue-substance may be taken as repre-
senting the chain of physiological connexions between the
food and the tissues."

Later Adjustments in Pavy's Views

I have spoken above of two preconceptions dominating
Pavy's mind. The first, concerning the relations of the blood
and the kidneys, has been dealt with ; the second was one
which made it possible for him to hold a view such as that
just discussed. He was one of those who held that chemical
changes in the material of the animal body occur only while
such material is in the strictest sense a part of the living
complex. The molecules that undergo change are molecules
that are in some way alive. Such an assumption involves
either a tendency to cease thinking about the phenomenon in
terms of structural organic chemistry altogether or a tendency
to use loose pseudo-chemical concepts of " living molecules
with stable central nuclei and active side-chains." This is not
the place to discuss so difficult a question as the chemical
constitution of bioplasm but it is important to point out that
the encouraging recent progress in biochemistry has been
associated with a recognition of the fact that the complex
tangle of chemical interactions involved in life is susceptible
of some experimental analysis into separate interactions which
may be studied by purely chemical methods ; secondl}^ (at least
to the minds of many), with a steady faith that full acquaintance
with such separate interactions will ultimately be followed by-
some knowledge of the manner in which they are co-ordinated
in the bioplasm. There are, indeed, chemical happenings in the
living cell itself which are to be looked upon as isolated from
the bioplasm, interactions which may be termed interplasmic
rather than intraplasmic. When an amoeba has ingested food
material, the digestive processes which go on, though intra-
cellular, are strictly interplasmic in the sense mentioned, as it
is to be supposed that suitable enzymes become operative
in the vacuole with which the food particle is quickly sur-

DR. PAVY AND DIABETES 25

rounded. Now, be it noted, it by no means follows that, even
in the case of the amoeba, all the digested food material is
" assimilated." Assimilation in the strict sense may, in the
case of ingested protein, for instance, be a highly selective
process even in unicellular organisms and other chemical
changes may follow mere hydrolysis in the vacuole. It is
clear that interactions may occur in interplasmic spaces less
obvious to the microscope than the large but temporary food
vacuole of the amoeba; it has been boldly suggested by
Hofmeister, in fact, that a tissue-cell may be a laboratory in
which a great number of isolated interactions precede, each
in its own locality. The colloid nature of the medium and
indiflfusibility of specific enzymes secure the localisation and
independence of the individual interactions. Such a view
may go too far and it cannot be claimed that physiological
thought has yet clarified itself in connexion with such matters
but it is of importance to recognise there is no necessity to
assume that " dead " matter must become " living " matter
before it suffers biochemical change. In a case which specially
interests us at the moment, that of sugar in its relation to
glycogen, there is full justification for the belief that the con-
version of either into the other involves no merging into an
unknown complex of bioplasm but only the progress in the one
direction or the other of a simple reversible interaction con-
ditioned by a specific enzyme. That some property of the
cell controls the direction of the interaction in a manner that
is largely unknown is a fact which must be admitted.

If we now consider Pavy's later teaching as to the part
played by the liver in the metabolism of carbohydrates, we
shall meet with an illustration of his more or less unconscious
adjustment to modern views. As already stated, he came to
think that when the intestinal mechanism is normal the liver
plays but a subordinate part in arresting unassimilated sugar. It
forms glycogen just as other organs form glycogen from the
complexes containing carbohydrate brought to it by the blood.
Because of its position and special activities it forms pro-
portionately more of this substance than do other organs.
When in 1894 he wrote his Physiology of Carbohydrates,
he had come to speak of the hepatic glycogen as a ** store " of
carbohydrate ; but, at this stage, he still appeared to view it as
stored by the liver for its own purposes, just as a yeast-cell

26 SCIENCE PROGRESS

or a muscle-fibre stores it. But by the time Carbohydrate
Metabolism and Diabetes was written (1906) he had come
nearer to Claude Bernard. " The seat of actual consumption
is in the muscles and therefore, in the case of its disappearance
{i.e. the disappearance of glycogen) from the liver, there must
be transport in some way or other through the circulating
system," though the transport is not in the form of free sugar.
A change from time to time in the language he uses when
discussing the action of the liver-cell illustrates the gradual
modification of his views. At one time we find only such
statements as that the bioplasmic complex of the cell " takes
on " sugar and " gives out " glycogen or fat. It might again
** take on " glycogen and " give out " fat ; only in the case of the
liver bioplasm there is no " giving out " of sugar. At this time,
in common with all or most writers, he made a sharp dis-
tinction between the powers of enzymes which could only
bring about degradations and those of the protoplasm itself,
which could induce synthetic and constructive changes. He
was clear at that time that the production of sugar observed
in the excised liver was due to the influence of an enzyme
exercising an activity which was essentially a post-mortem
phenomenon of no importance physiologically. In 1897-8 he
was engaged in a controversy on this point, in which he
showed, as always, great dialectical skill, from which, it must
be confessed, he emerged victorious as an experimentalist.
But neither he nor many others then realised what Goethe
appears to have realised w^hen he wrote in Wilhelm Meister's
Lehrjahren, " Nach dem Tode arbeiten sich die Krafte, die
vergebens nach ihren alten Bestimmungen zu w^irken suchen,
ab an der zerstSruUg der Telle die sie sonst belebten." ^

Pavy was after all as ready as most to realise later on, when
experimental work had clarified our views, that the enzymes
which, after disorganisation of the tissues containing them, pro-
duce results that are, quantitatively at any rate, unphysiological,
may be agents which " animate " the tissues when their work is
duly organised and orientated in intact cells. We find him {Car-
bohydrate Metabolism and Diabetes, p. 68) fully admitting subse-
quently that the process which precedes transport of carbohydrate
from liver to tissues is saccharification of the glycogen by the
diastatic enzyme ; only, once more, the sugar must not be
^ Quoted by M. Jacoby, Ergebenisse der Physiologie^ I. i. p. 239.

DR. PAVY AND DIABETES 27

supposed to wander in a state of freedom. As to the mechan-
ism of its transport, his views also showed developments. At
first, as we have seen, he denied the possibility of transport
altogether but in 1893 came his own discovery of what he
termed the "glucoside constitution of proteid matter," which
modified his views. It had been suspected at an earlier date
that the protein molecule yields something of a carbohydrate
nature upon hydrolysis and the work of Schiitzenberger had
given support to the belief. But Pavy came upon the fact
independently and his observations were more exact and went
much further than those which preceded them. They opened
indeed an interesting and important chapter in biochemistry.
It was shown that among the products of the complete hydro-
lyses of protein was a substance yielding a characteristic
cystalline derivative identical with the osazone of dextrose.
The quantity of this substance which can be obtained from
ovalbumen, the protein chiefly worked with, was considerable.
Here, then, felt Pavy, is the form in which sugar may be
transported in the blood without possibility of loss by way of
the kidney. He came, indeed, to attach the greatest impor-
tance to this protein-sugar, not only in relation to transport
but in connexion with other and more general phenomena of
the metabolism of carbohydrates. Quotations (1906) will define
his position both with regard to the mobilisation of liver gly-
cogen and its transport. The suggestion, he says, "presents
itself that sugar is taken on as a side-chain by a proteid con-
stituent of the blood and transported to the tissues where it is
taken off for subjection to utilisation " ; and then later, " Gly-
cogen is a storage material consisting of very large molecules
and therefore not adapted for shifting its position. I should
think that the first action that occurs is the breaking down of
its molecule into molecules of glycose which become instantly
taken on by the alluded-to molecules of the blood. There may
be concerted action between the breaking-down and taking-on
processes but that there is such an operation is rendered
probable by the fact that there is no show of sugar in con-
nexion with the occurrence. Enzyme action, it may be
considered, of necessity constitutes a part of the process. . . ."
But further study on the part of others showed that the facts
of the case are not quite such as can support these views with
regard to transport, at least, not in the definite sense in which

28 SCIENCE PROGRESS

they are formulated. Proteins are not glucosides. In the first
place, the group present in their molecule is not strictly a
carbohydrate group. What is really obtained on hydrolysis is
a nitrogenous derivative of dextrose (glucosamine). This sub-
stance contains an amino-group and so bears a relation to the
other constituents of protein — the amino-acids. Its constitu-
tion is such that it yields an osazone identical with that given
by dextrose, so that the evidence relied upon by Pavy to prove
the production of the latter was misleading. The substance
is not yielded by all proteins and is probably absent from the
molecules of typical blood proteins, the amount obtainable from
the serum-albumen being so small as to suggest that it arises
from some impurity. What is of special weight against Pavy's
views as regards its significance is the fact that glucosamine
does not behave as a carbohydrate in the body; it yields, for
instance, no glycogen to the liver.

With regard to transport, we find that, at the end, Pavy
was willing to simplify his views. He had been struck by a
paper by Bayliss dealing with " adsorption " as a preliminary
step to chemical action and seems to have decided that the
existence of a loose compound of circulating sugar with the
blood proteins will account for the failure of the latter to be
excreted.^ In the paper already mentioned as published after
his death he wrote : " After adsorption taking place, the sugar,
whilst recoverable (from the blood) by analysis, would be virtu-
ally holding a colloidal position and in this state would escape
being eliminated by the kidney."

I think it must be admitted that Pavy's final position with
regard to the function of the liver in the metabolism of carbo-
hydrates does not differ vitally from that of Claude Bernard nor
that of the present-day majority. He held, it is true, that
the liver does not deal with all the sugar absorbed from the
intestines but only with a part of it. He came to admit, however,
that the hepatic glycogen arises directly from the carbohydrate
of food, that it represents a store held in trust for the tissues
and that it is mobilised for transport by an enzyme which
converts it into sugar. The added view that during transport
it is not strictly free but forms a loose compound with the
blood proteins does not carry us far from the teaching of

' The view had been previously advanced by Otto Loewi, Archiv fiir exp.
Path, und Pharm. yS.\\\\. 410 (1902).

DR. PAVY AND DIABETES 29

Bernard, who, of course, had no reasons in his day to consider
such possibilities. It is by no means surprising that an in-
vestigator's views should be modified with the process of time
but it is striking to find that Pavy, in spite of his modified
attitude towards the facts, held to the end, as his latest writings
show, that the glycogenic doctrine is " mischievous." If in any
sense it be so, it is clearly not because it is in essence wrong
but because, as originally formulated and as generally under-
stood, it allots to the liver too large a share in the initial stages
of the metabolism of carbohydrates. When the matter is
narrowed down to this quantitative issue, Pavy's views are
seen to be special and, maybe (even if we cannot admit the
lymphocyte theory), are also right.

The Utilisation of Sugar in the Body

I have so far dealt with one aspect alone of the metabolism
of carbohydrades and have only discussed the fate of carbo-
hydrate of the body before its utilisation, as a source of energy
or otherwise, has begun. Of the processes associated with utilisa-
tion nothing has been said. When the views of Pavy are under
discussion, the attention is inevitably directed more particularly
to these earlier stages of metabolism, because he was himself
almost entirely preoccupied with them. He was concerned
to explain the nature of diabetes and he held that the ab-
normality producing that disease was to be sought among the
anabolic or assimilative stages of metabolism. In the diabetic
organism, he held, catabolic and oxidative processes may be
wholly normal. To him the question of right or wrong in the
metabolism of carbohydrates was in its broadest aspects a simple
one : the normal body converts its carbohydrates into complexes
immediately it receives them and sugar never circulates as such.
In the errant organism the initial synthetic assimilative functions
fail, sugar circulates as such and passes the kidney and this cir-
cumstance constitutes the essence of the diabetic condition. The
general view is more comphehensive. The error, it is held, may
also be on the other side of metabolism ; the body may be
diabetic because it fails to grip its sugar at the locus of utilisa-
tion. In any case, we have to consider that other region of
metabolism.

In 1889 von Mering and Minkowski presented a gift to

30 SCIENCE PROGRESS

physiology and pathology the great value of which they have
recognised though they have both experienced great difficulty
in learning how exactly to use it. These experimentalists
removed the pancreas from dogs and showed that its removal is
followed at once by a permanent condition of glycosuria. We
now realise fully that in the absence of some pancreatic function
the power to utilise sugar is completely absent from the tissues.
What exactly is the nature of that function ? In spite of much
endeavour the answer to this question is far from complete.
The general opinion, at any rate, is that it is exercised at
the seat of utilisation. An objective view is taken and
seems justified by experiment, that when an active tissue
element is to abstract energy from sugar, a tertium quid is
necessary to enable the former to get its chemical grip upon
the latter. This tertium quid is supplied in the internal secretion
of the pancreas and reaches the tissues by way of the blood.
Perhaps because scientific thought tends to run in ready-made
channels but also because of some experimental justification,
this view is made more definite by attributing to the pancreatic
factor the functions of an " amboceptor " — a conception and a
term derived from the literature of immunity. An amboceptor
is an agent which, by its ability to combine chemically with
each of two substances incapable of combining when alone,
completes a chemical system in such a way that the two sub-
stances are brought into interaction. This is essentially a
definition of a catalyst but the action of an amboceptor has
certain quantitative relations, which I must not stop to define
more closely, which put it in a special class of catalysts. A
current conception is that the pancreatic amboceptor brings
some enzymic mechanism of the tissues into relation with the
sugar. Until quite lately, at least, the evidence seemed to show
that it was directly concerned with the breakdown of sugar.
Pavy, when he came, somewhat late in the course of his teach-
ing, to express views as to the influence of the pancreas,
accepted the term amboceptor but modified the conception of its
action in a manner which was characteristic. It is, according to
him, an agent necessary for assimilation ; only in its presence
can sugar be so linked on to bioplasm as to undergo ultimately
the necessary building up into the living complex of lymphocytes
or liver-cells. In this connexion he himself carried out experi-
ments which showed that when pancreatic extracts are injected

DR. PAVY AND DIABETES 31

into the circulation, simultaneously with sugar, there is an
increase of what he termed the "amylose " carbohydrate of the
blood, a more complex substance than sugar itself. This pointed
to an influence upon synthetic rather than upon destructive or
oxidative changes. Now some confirmation of these results has
recently been obtained. When pancreatic tissue is ground up with
muscle tissue, better still, when an alcoholic extract of boiled
pancreas is mixed with muscle plasm and dextrose is added, the
sugar disappears from the mixture with considerable rapidity.^
The disappearance either does not occur or occurs much more
slowly, when the dextrose is in contact either with muscle alone
or with pancreas alone. What has been actually observed in
such experiments is a diminution in reducing power and this
has always been interpreted as meaning that the sugar under-
goes destruction. But it has been shown quite lately that, as a
matter of fact, the disappearance of the dextrose is due to its
condensation into a more complex sugar having a smaller reduc-
ing power.^ Here then, we find, at least in a limited sense,
a confirmation of Pavy's contentions ; for if experiments such as
those described really bear upon the physiological happenings
in the body, a synthesis of some sort would seem to precede the
utilisation of sugar by the tissues.^

Further inquiries into this point will lead us to consider
the more purely chemical side of the whole question and
that very small modicum of knowledge concerning it which
can be discussed in terms of molecular structure.

It must not be forgotten that though dextrose or grape sugar
is by far the most prominent physiological sugar, the animal

^ Otto Cohnheim, Zeitsch. xliii. 401 (1904); ib. xlvii. 253 (1906). Also Hall,
Amer. Journ. of Physiol, xviii. 283 (1907).

* Levene and IS/ltyer^ Journ. Biol. Chem. ix. 97 (191 1).

' Since the above was written, Knowlton and Starling have published (Proc.
Roy. Soc. Ixxxv. 218, 191 2) an account of experiments which demonstrate in a
striking manner the importance of the pancreatic function. The heart of an
animal made diabetic by removal of the pancreas is shown to leave unchanged
any sugar supplied to it by way of the circulation, while under similar experimental
conditions the heart of a normal animal uses the supply. When, however, a
pancreatic extract is added to the blood, the heart from the diabetic animal also
utilises the sugar. Such experiments show clearly that the pancreas influences
the processes of utilisation and is not concerned merely with the maintenance of
stability in carbohydrate deposits. They do not decide, however, whether oxida-
tion is directly accelerated or whether the pancreas promotes a process which
necessarily precedes oxidation.

SCIENCE PROGRESS

body possesses means of dealing with other simple carbohydrate
molecules. Hexose sugars isomeric with dextrose can suffer
metabolism. Fructose, mannose and galactose, for example,
are broken down in the body and, as a preliminary to further
change, can be converted into glycogen, the first-named sugar
almost as readily as dextrose itself. Now, the glycogen molecule
is an aggregate of a number of dextrose molecules and would
appear to be always the same substance, whatever simple
sugar has acted as its precursor. The physiological occurrence
of such a moulding of sugar molecules as this betokens raises
chemical considerations of no small interest. The biochemist
would miss his vocation if he were content in such cases to
resort to the magic of bioplasm as a sufficient explanation.
A description of the actual happenings in the definite terms
of chemical dynamics is his ultimate and perfectly reasonable
aim. To say merely that these sugars are " assimilable " and
therefore can be metabolised is to take an attitude towards the
operation of the bioplasm such as spectators take towards those
of the conjuror when he puts a golf-ball under a hat and later
displays a rabbit in its place. The physiological conversion of
one of the hexose sugars into another is comparatively easy
to understand now that it has been shown that dextrose,
fructose and mannose are mutually interconvertible in alkaline
aqueous solution. Starting with a solution of any one of them,
we find that after a time it contains all three in equilibrium.
By a process which ultimately involves an intramolecular
shifting of hydrogen atoms, though it is probably in essence
one of alternate hydration and dehydration, any one of these
sugars can assume an " enolic " or unsaturated form. This form
is the same in the case of all three sugars and from it all three
may be produced. The relationship will become clear when the
formulae of these carbohydrates are considered :

CHO

CH.OH

CH,.0]

HCOH

HOCH

COH

[OCH

HOCH

HCOH

CH2OH

CHjOH

Glucose.

Mannose.

Common enolic form.

Fructose.

The temperature and alkalinity of the body are not such as
would induce these changes with the required velocity and it

DR. PAVY AND DIABETES 33

is probable at least that they are determined by specific
enzymes. To some upset in the normal equilibrium of such
enzymic activity may be ascribed the fact that on rare occasions
fructose is excreted by individuals even when their diet contains
no carbohydrate which could yield fructose during digestion.
In such cases the normal direction of isomeric change would
appear to have suffered reversal, fructose being formed from
dextrose. For it is usually and very justifiably assumed that
normally, while dextrose is directly taken up by a cell, the
isomeric sugars are converted into dextrose before the metabolic
grip takes hold upon them. A certain speculation, however,
with regard to this matter may be excused. Yeasts can ferment
any of the above three sugars with approximately equal ease
and the fermentative breakdown in each case is on precisely
similar lines. It has been suggested that the reason for this
is that the fermentation starts with identical material in each
case— namely, the enol of the sugars produced by a preliminary
enzymic change.^ If this suggestion have any weight in con-
nexion with fermentation, it is justifiable to apply it to the
animal cell ; and if dextrose itself must be enolised before the
cell can condense it to glycogen or impress other changes upon
it, it is clearly possible that the metabolic failures responsible
for glycosuria may include a failure to enolise. The conversion
of any one of these related sugars to the enol form may perhaps
be conditioned by a distinct enzyme, so the interesting but very
obscure circumstance that diabetics can often utilise fructose
when their power to utilise an equal quantity of dextrose is
lost lends some support to the above conception. It must be
admitted, however, that it is essentially speculative.

We shall in any case clearly gain light upon the normal
metabolism of sugar if we can decide what precisely is absent
when, in conditions of clinical or experimental diabetes, the
body fails to oxidise that substance. The deficiency is by no
means the same in all varieties of diabetes or glycosuria and
the hope is reasonable that by the time we have classified these
varieties we shall know something of more than one of the
links in the chain of normal metabolic change. A fact of great
significance is that in spite of the failure to oxidise sugar, the
diabetic organism shows no failure in general oxidation power.

^ Cf. E. F. Armstrong, The Simple Carbohydrates and the Glucosides
(Longmans, 1910), pp. 52 et seq.

34 SCIENCE PROGRESS

During long periods, in spite of the escape of sugar from the
body, life in the diabetic is continued with combustion pro-
cesses in full vigour. This is an aspect of affairs which lent
a certain strength to Pavy's position. He writes scornfully of
those who speak as though diabetes were due to sugar failing
to be burnt in the system : ^* Nothing can be more gratuitous,
unfounded and misleading. There is not a particle of evidence
to show that defective oxidising power exists in connexion with
diabetes. The real fault is a condition antecedent to the oxidising
operation."

There are, indeed, many facts to suggest that sugar, when
normally burnt, is not burnt as sugar but that its oxidation
follows some previous change.

Consider the constitution of the sugar molecule :

H H H H
O O O

ill!

HOC — C — C — C — C — CH2OH

till

H H H H

If we were to assume that the free-molecule suffers oxidation
in the body and were to try to decide a priori the probable
steps involved in its oxidation, chemical and physiological
considerations would alike suggest the easily oxidisable alde-
hyde group ( — COH) as the first point for oxidative attack.
A deficiency in the diabetic might then be the absence of a
mechanism for oxidising this aldehyde group. Experimentally,
indeed, it has been found that if this group in sugar be oxidised
to a carboxyl (— COOH) group before it is administered to a
diabetic, then complete oxidation follows.
Gluconic acid —

H H H H

o 00

HOOC — C — C — C — C — CHsOH

' i ' '

H H H H

—is completely oxidised when the oxidation of sugar fails. But
it is no specific failure to deal with an aldehyde group that
stamps the diabetic, as he can equally well oxidise the substance
glycuronic acid, another primary oxidation product of sugar in

DR. PAVY AND DIABETES 35

which, however, the aldehyde group is intact and the group
(-CH2OH) oxidised—

H H H H

o 00

I I I I

HOC — C — C — C~C — COOH

III!

H O

H H H

So too, he can oxidise saccharic acid —

H H H H

000

I I I I

HOOC — C — C — C — C — COOH

I I I I

H H H H

— from which both these groups are absent. Of these closely
related substances only sugar itself is not oxidised.

These facts are in any case puzzling ; but with other facts
they make for the belief that what is absent in diabetes is not
an oxidative mechanism but a means to carry out a process
which, in the case of sugar, normally precedes oxidation in the
tissues. This process might be either a non-oxidative rupture
of the free molecule of sugar or it might be an event which
occurs while sugar is part of a complex.

In connexion with the former possibility certain experimen-
tal work has been supposed to show that animal cells deal with
the sugar in the way that the yeast-cell deals with it — that the
primary change is alcoholic fermentation and that what is sub-
mitted to actual oxidation is the alcohol. More recent and
more critical experimental studies greatly diminish the proba-
bility of this rather startling suggestion. But we are left with
more solid ground for a belief in another form of cleavage or
rather for a cleavage stopping short at what is possibly the
precursor of alcohol in yeast fermentations. It is certain that
lactic acid is formed in animal tissues and there is a strong
probability that it is formed from carbohydrate. What evidence
we have concerning the significance of its appearance is almost
entirely derived from a study of muscle metabolism.

In muscles lactic acid makes its appearance in appreciable
quantity only when the supply of oxygen is relatively de-
ficient. When such deficiency exists the acid appears in the
muscles of the living animal and is then, to some extent, excreted

36 SCIENCE PROGRESS

in the urine. The amount increases with the activity of the
muscles, the maximum being observed when strenuous mus-
cular work is done under conditions which interfere with
normal aeration through the lungs. Exertion at high altitudes,
where the oxygen tension of the atmosphere is low, has been
shown, for instance, to lead to an increase of lactic acid in the
blood. More precise information with regard to its signifi-
cance has been obtained by studying the processes which
occur in excised but still surviving muscles, especially in the
organs of cold-blooded animals, such as the frog, in which
chemical changes are slow and more easily analysed. In these,
the formation of lactic acid has been shown to be related
to the processes of surviving life. It ceases at a time when
the muscles no longer contract upon stimulation, so that the
production of the acid cannot be classed with post-mortem
changes. If the quiescent muscles are well supplied with
oxygen, lactic acid at no time appears in them in appre-
ciable quantity ; but if oxygen be available it accumulates
steadily up to the point of death. Now an excised muscle
can contract vigorously during a considerable period in the
complete absence of an oxygen supply. What then is the
source of energy under these conditions ? Since carbonic
acid is given off in the absence of a contemporary oxygen
supply, a belief, shared by Pavy, that the living tissues contain
" intramolecular oxygen " has long been held. Oxygen, it is
thought, is " built up " into the bioplasmic complex along with
oxidisable material. When energy is to be liberated there is
a change within the complex from less stable to more stable
configurations and oxidation products, especially carbon dioxide,
are produced. Recent critical experimental work has, in my
opinion, deprived this belief in intramolecular oxygen of all
foundation and I believe that its disappearance will mark an
advance in our understanding of living processes. The carbon
dioxide given off by a tissue when deprived of oxygen is
liberated from the alkaline carbonates, always present in tissues,
as the result of the accumulation of organic acids, of which
lactic acid is certainly the chief. Such carbon dioxide therefore
has no direct metabolic significance whatever.

A very instructive observation has shown that when a
muscle is made to pass from a quiescent condition to one of
active contraction in the absence of oxygen, there is no increase

DR. PAVY AND DIABETES 37

in the evolution of carbon dioxide at all proportionate to the
work done. No acceleration in its evolution is observed
beyond what is accounted for on the lines just mentioned.
But lactic acid does increase as a result of the contractions
and increases at a rate proportionate to the work done. Its
production is undoubtedly due to the processes which yield
energy to the contracting muscle. Now if an excised muscle
which has accumulated lactic acid as a result of oxygen defi-
ciency be given a supply of oxygen, its lactic acid proceeds to
disappear and if, as I have already stated, the oxygen supply
be adequate from the first the acid never accumulates, there
being proportionality between its formation and removal.
Upon such facts as these is based what I believe to be the
sound view that the energy of muscular activity is derived
from a non-oxidative molecular breakdown of which lactic acid
is a product. Upon this breakdown follows an oxidative re-
moval of the products which normally keeps pace with their
production. A careful study of the thermal relations of the
phenomena has largely justified this view.

Now if we were quite sure that the lactic acid which
appears in muscle were derived from sugar directly, we should
have clear evidence for the occurrence of that change in the
sugar molecule, preceding oxidation, which we were seeking in
order to explain the existence of a normal oxidative power in the
diabetic organisation side by side with its inability to oxidise
sugar. There is every probability that the lactic acid is derived
in some way from carbohydrate but the facts prevent our
taking a quite simple view of the relation. The derivation of
lactic acid from dextrose involves only a rearrangement of
atoms in the sugar molecule — CgHigOe = 2C3H6O3 — and the
change leads to a very small liberation of energy, some 3 per
cent, only of the total energy in the sugar being involved.
A calculation of the actual quantities concerned, however,
has led to the belief that the energy so liberated is, as a
matter of fact, sufficient to supply the contracting muscle with
its requirements ; but a very recent investigation into the
heat production of muscle during survival life points to the
fact that the actual precursor of the lactic acid must possess
at least 10 per cent, more energy than the acid itself^; dextrose,
as we have seen, contains only some 3 per cent. more.

^ A. V. Hill : private cotmnunication.

38 SCIENCE PROGRESS

Here we come to the end of our very imperfect knowledge
concerning these matters. We are left with the practical cer-
tainty that, in muscle, at any rate, if sugar be the source of
energy, it yields this energy not by a direct oxidation but by
a breakdown followed by oxidations. The former gives rise
to the rapid evolution of energy which is necessary for a
muscular contraction ; the latter, while evolving more massive
supplies of heat, in some unknown way yields energy for
winding up the machine again. At the same time it would
seem that the sugar molecule is not split while in a free state
but while in a complex containing more potential energy than
the carbohydrate itself. Unfortunately neither the few avail-
able facts concerning what happens in muscle nor any con-
siderations that can be based upon them give any hint as to
where the pancreatic factor intrudes into this chain of events.
There is an almost complete hiatus moreover between our
knowledge of muscle as a type of normal active tissue using
carbohydrate and our knowledge, such as it is, of the diabetic
condition. Confining our attention to one point — the probable
significance of lactic acid — it is of interest to know that in the
diabetic animal any lactic acid given by the mouth increases
the sugar in the urine. This suggests that the transformation
of the latter into the former is a reversible one.

Formation of Fat from Sugar

Dextrose has other relations in metabolism which I have
not yet dealt with. Very interesting is its conversion into
galactose, which, as a constituent of the milk-sugar molecule,
is formed continuously during the manufacture of milk by
the mammary gland. It is also found in the so-called cere-
brosides, complexes which can be separated from brain-tissue.
Unlike the other isomeric sugars, fructose and mannose, it
cannot be produced from dextrose by transformation through
a common enol form {supra) and it is very unlikely that the
change can be controlled by enzymic action. A tempting
view with regard to the occurrence of such purely configurative
molecular changes in the body is that of H. E. Armstrong,
who conceives that a pre-existing structure in the cell, acting
as a templet, moulds the precursor into the required form.

Dextrose is undoubtedly converted into fat in the body, as

DR. PAVY AND DIABETES 39

many carefully planned scientific experiments and thousands of
stock-raisers' balance-sheets have proved ; there is also little
doubt at the present time, though the fact has been much
disputed in the past, that the reverse change may occur and
sugar take origin from fat. As broad facts these transformations
are established but the chemical steps which are traversed
during their occurrence are as yet illuminated only by the faint
light of tentative researches. At one time, as I have already
pointed out, Pavy believed that a large portion, if not the whole,
of the carbohydrate eaten took this path of conversion into fat.
Later, like most others, he saw in the conversion a means of
disposing of carbohydrate in excess of current needs, by which
it could be stored for future use in a more stable form than
glycogen presents.

In disease, errors of metabolism may lead to an arrest of
this conversion simultaneously with an arrest in the utilisation
of sugar. This combination is found in ordinary severe diabetes
attended with emaciation. On the other hand the ability to
turn sugar into fat may, temporarily at least, remain normal
while the power to burn sugar is lost, a state of affairs which
leads to pathological obesity and is, as it were, a kind of
"masked " diabetes.

Only the younger school of chemical physiologists can be
said to have made any serious attempt to follow, in the body,
the molecular changes involved in this remarkable trans-
formation. Pavy, for instance, was preoccupied with other
aspects of the matter and was content, as we have seen, to let
his mind rest on the conception that the bioplasm of either the
intestinal-cell or the liver-cell takes up the sugar and gives
it out as fat.

Modern experimental work has unfortunately given us no
more than probabilities concerning the actual stages of the
transformation. It is a noteworthy point, however, that such
work as has been done justifies the present tendency of
physiological thought to look upon the intermediate production
of substances of quite small molecular weight as essential to the
accomplishment of such profound changes. Instead of that
view of metabolism which conceives of one substance as losing
its molecular identity in some vague complex to emerge again
later as quite another substance, we tend to think rather of
definite molecular transformations occurring in successive

40 SCIENCE PROGRESS

stages, which, however rapid, are isolated in time and, may be,
in place. One organ, we believe, may deal with some of the
stages and quite another organ with the later ones.

In connexion with the conversion of sugar into fat, attention
has recently become fixed upon the possibility that so simply
constituted a substance as acetic-aldehyde (CH3COH) is formed
upon the way. The aldehyde is formed by the partial oxidation
of dextrose or of its derivative, lactic acid, and may be supposed
to undergo condensation and to give rise to fatty acids. There
are suggestive, if not conclusive, experimental results in support
of this view ; it is also in accordance with the familiar but no less
remarkable fact that physiological fatty acids contain always an
even number of carbon atoms in their molecules. This would
clearly be the case if condensation of a two-carbon aldehyde
were responsible for their formation.

Formation of Sugar from Protein

That sugar takes origin from protein in the body is shown
by the quantitative study of certain physiological phenomena,
especially as they occur in carnivora. The fact is abundantly
evident in the phenomena of diabetes. In that condition as
experimentally induced and in the severer cases of the disease
in man, over half of the total energy contained in the protein of
the food appears in the excreted sugar. Whether this should be
taken as showing that so large a proportion as this normally
assumes the form of sugar, the diabetic error merely bringing
the sugar into view; or whether an abnormal breakdown is
involved in diabetes we cannot yet decide but from general
physiological considerations the former possibility is the more
likely.

The chemistry of the transformation is, perhaps, on the
whole, more easy to understand than that of sugar into fat,
though as little decided by experiment. The administration of
certain of the individual amino-acids which are contained in the
protein molecule has been shown to increase the sugar output in
diabetes ; and the whole mixture of them, as obtained after
hydrolysis of protein, yields as much sugar when administered
to a diabetic dog as does an equivalent weight of the intact
protein. Many are now working at this type of problem and
there is no reason why we should not arrive at a knowledge of

DR. PAVY AND DIABETES 41

the detailed steps in the transformation of amino-acids into
sugar.

Sugar, then, can be excreted in diabetes in large quantity,
when carbohydrate, as such, is completely absent from the diet
and even when there is no longer a store of glycogen in any of
the tissues. I find it very difficult to appraise exactly the attitude
of Pavy's mind towards these facts, which can scarcely be
reconciled with his view that purely assimilative errors so
predominate in the picture of diabetes. The patient, it is true,
in a great number of cases of the clincial disease, ceases, or
nearly ceases, to excrete sugar, when carbohydrate is, as far as
possible, removed from his diet, a method of treatment closely
associated with Pavy's name. In such cases it is easy to believe
that the error is solely on the side of assimilation. But Pavy
was from the first, of course, familiar with the severer forms of
the disease in which sugar continues to appear whatever the
dietary. Until the quantitative work of recent years had been
done there was no definite proof that, even in these cases,
the sugar arises directly from protein and Pavy seems to have
been slow to admit that there was any but an assimilative error
even in the severest cases. Eventually he writes of a " faulty
tissue-breakdown " ; but seems, in some way, to reconcile the
facts with his fundamental view, by assuming that the circulation
of unassimilated sugar, which alone is present in the earlier
stages of the disease, is the actual cause of the disordered kata-
bolism of protein which may be established later.^ When, in a
discussion concerning normal phenomena, he deals with the proof
that protein can yield sugar in the body in so large a quantity,
he merely uses it to support the view that sugar is incorporated
into protein during intestinal assimilation.^

A noteworthy circumstance characteristic of the diabetic
condition is that, though the tissues are bathed wuth a solution
of sugar stronger than that to which they are accustomed (for
in all forms of diabetes save that due to phloridzin, which is
dealt with later on, there is excess of sugar in the blood), there
is no inhibition of sugar-producing processes. One would
suppose, from considerations of chemical equilibrium, that these
processes would be automatically slowed. On purely teleo-
logical grounds and looking at the matter from the side of

* Carbohydrate Metabolism and Diabetes, pp. 114, 115 (1906).
2 Ibid. pp. 50-51.

42 SCIENCE PROGRESS

utilisation only, we can perhaps understand that if a process
which necessarily precedes utilisation {supra) be slowed by
a deficiency in the chemical mechanism, an effort to increase its
velocity by increasing the concentration round the cell would
follow. Von Noorden speaks of the cells in diabetes as con-
tinuously feeling the need of sugar, though surrounded by the
ample supply which they are unable to use. They still send
out, therefore, those normal chemical stimuli which lead to the
mobilisation of sugar and the supply continues in spite of the
failure to utilise it, Pavy rejected this conception of a "call"
made by sugar-hungry cells. So long indeed as diabetes
involves only a failure in assimilation of the carbohydrate eaten,
there is no need for any such assumption and, in any case, it is
not a very satisfactory one. But when a large production
of sugar from protein is established and continues, in spite
of the excess of sugar circulating, some explanation of the fact
seems called for.

Von Noorden's assumption, in so far as it involves a para-
doxical " call " for sugar when so much is available, is perhaps
unnecessary. We have seen that the diabetic organism liberates
approximately as much energy under given conditions as does
the normal organism under similar conditions. As this energy
in the case of the former is obtained to a very much smaller
extent from carbohydrate, it must be got from proteins and fat.
If now it be a normal thing, as most assume and as Von
Noorden assumes, for a certain fraction of the protein molecule
to pass through the stage of sugar during its breakdown in the
body, then that fraction is unavailable for the diabetic animal,
which in so far as it makes use ol protein to yield energy must
rely upon the residuum of the molecule which does not pass
through the sugar stage. But on the above assumption, the
breakdown which yields this residuum must also yield sugar,
even if it occur on perfectly normal lines. The call of the
tissues, therefore, is not for sugar but for energy and the con-
tinued mobilisation of sugar is a secondary phenomenon. Never-
theless, researches carried out during the last decade have led
to a belief on the part of many that neither inability, however
caused, of the liver to function in regulating the rise and fall
of glycogen, nor inability on the part of the tissues to utilise the
sugar brought to them, nor even a combination of these failures
will account for all the phenomena of diabetes, at any rate, as it

DR. PAVY AND DIABETES 43

is observed in its severest form in man. The view is being
forcibly expressed that the production of sugar in the body
is an independent variable, determined, it may be, by the
activity of specialised organs.

Temporary Glycosuria. The Latest Theories of Diabetes

No one who has any acquaintance with metabolism can
doubt that the normal utilisation of sugar is a process of a
nicely balanced nature which an extraordinary number and
variety of events can upset. Even the normal man has his limit
of tolerance for sugar and the degree of tolerance can be easily
modified. Temporary glycosuria may appear during many
departures from health which have nothing to do with diabetes.
It is induced by psychic strain or shock, by critical physiological
events, such as pregnancy, even by sudden exposure to cold.
It often follows as a secondary effect from the action ot certain
drugs on the body. But a condition of glycosuria which has
received special attention of late is that associated, not with the
absence or depression of an organic function but rather with
the hyper-functioning of certain organs; in particular, of the
thyroid, adrenal and pituitary bodies. I must not stop here to
consider the evidence for this association. I can only point out
that the facts have led to the conception that the normal
equilibrium of carbohydrate metabolism involves a balance
between factors, such as the activity of the glands just mentioned,
which are concerned with the " mobilisation " of sugar and
factors, such as the pancreatic function, which are concerned in
its utilisation. The balance may be upset from either of two
sides. The mobilisation of the sugar may be too rapid for
normal utilisation processes to deal with it or the power to
utilise it may diminish and so fail to cope with the normal
supply. In either case, glycosuria results and may be intensified
in certain cases, when there is at once over-production and
under-utilisation.

This conception, for which the school ol Von Noorden is
chiefly responsible, is at once the latest addition to our views
upon normal carbohydrate metabolism and the basis ot the
most recent theory of diabetes.

It is one of great interest but it cannot be said to be upon a
firm foundation yet. Although it is beyond question that the
internal secretions of the ductless glands just mentioned affect

44 SCIENCE PROGRESS

the adjustments of metabolism, it is by no means certain that
they influence the equilibrium of carbohydrate so greatly
as the theory demands. The discussion, at any rate, has taken
us away from the teachings of Pavy, who had but little oppor-
tunity of appraising so recent a view.

There is a form of glycosuria, experimentally induced, which
has been much made use of in laboratory studies but which
differs in a fundamental aspect from the vast majority of cases
of spontaneous diabetes. I must refer to it before closing be-
cause it occupied Pavy's attention and lent some support to his
views. When the substance phloridzin, a crystalline glucoside,
is administered to animals, intense glycosuria is induced. The
great difference between this and other forms of diabetes is in
the amount of sugar in the blood, which becomes less than normal
under the influence of the drug, instead of greater. Although
there is still obscurity with regard to the exact mechanism
of the action of this drug, there is no doubt that its seat is in the
kidney. The view with regard to phloridzin diabetes which has
been generally accepted is that of Von Mering, who discovered
the phenomenon. He held that the effect of the drug is to in-
crease the permeability of the kidneys for sugar. This leads to
a lowering of concentration in the blood and a liberation of
sugar from the organs to restore the deficiency. So long as the
drug is in action, this process is continuous and leads to a large
excretion of sugar.

It is clear, from what has gone before, that such a view
would not square with Pavy's fundamental conception. In
1903, in conjunction with Brodie and Siau, he published some
very interesting experiments which showed that a kidney
removed from the body and perfused with blood containing
phloridzin could excrete a quasi-urinary fluid containing more
sugar than was lost by the blood perfused. Other experiments
showed that if all the abdominal viscera were removed from an
anaesthetised animal with the exception of the kidneys, the in-
jection of phloridzin still produces a notable excretion of sugar.

Altogether these experiments seem to establish the fact that
sugar is formed in the kidney itself and Pavy's view was that
under the influence of the drug the renal cells acquire a
power of splitting off sugar from some complex in the blood.
Certainly these experiments offer the best evidence available
for the circulation of sugar in some definite combination.

DR. PAVY AND DIABETES 45

Pavy's Views too Limited but his Teaching still

Suggestive

In dealing with Pavy's teaching I have found it necessary
to point out that in some fundamentals it is incompatible, not
only with the views of the majority (which would be a small
matter) but also, as I believe, with physiological probabilities.
But I shall have given a wrong impression, however, if it be con-
cluded that Pavy held views devoid of basis or that what was
special in his teaching is now without significance. There remains
indeed much that should yet stimulate experimental research ;
it may even be said that quite the most recent experiments have
given results which, in a sense, support his special views.

The primary arrest of the sugar which leaves the intestine is
a process that is still not quite clear to us. Physiologists in placing
the seat of arrest wholly in the liver are faced with the re-
markable experimental fact that the establishment, in the dog,
of Eck's fistula, a proceeding which permits the blood flowing
from the intestine to enter the general circulation without
passing through the liver, is not followed by glycosuria, even
when the animal is digesting starch in abundance. One can-
not but feel, even if it be impossible to accept Pavy's theory
of local assimilation by the intestinal leucocytes, that such facts
warrant a further inquiry into the functions of the gut in
carbohydrate metabolism. As regards the form in which sugar
is carried by the blood, it seems clear that the greater portion
of it, if in any combination at all, is so loosely held as to be
liberated when the blood proteins are coagulated. The latest
observations agree, however, with those of Pavy, in showing
that some more complex carbohydrate also exists and there
is little doubt that the further study of this question, which he
was planning at the time of his death, would have been of
great value. We certainly do not yet possess full information
either as to the transport of carbohydrate or as to the signifi-
cance of that part which circulates in what Pavy called the
" amylose " form,

Pavy, when looking for those errors which lead to diabetes,
sought them, as we have seen, almost exclusively on the
assimilation or constructive side of metabolism. His views
were, we may say, too limited in this respect ; but quite recent
research seems to show that, during the last decade, too little

46 SCIENCE PROGRESS

attention has been given to the possibility of assimilative errors.
We have seen that there are now experimental grounds for
believing that the influence of the pancreas in carbohydrate
metabolism is exerted in connexion with some synthesis (of
which the formation of glycogen is possibly the first stage)
which precedes the final destruction of sugar in the body ; and
quite the last word upon metabolism, which Pavy would have
been pleased to hear, suggests that " carbohydrate in some
form or other is absolutely essential for the synthesis of protein
within the tissues." ^ Clearly we have not yet the knowledge
to appraise fully Pavy's views or any other views of a dogmatic
sort, concerning the metabolism of sugar or the significance of
diabetes.

It may shock many who are unfamiliar with the recent
literature of physiology and pathology to learn that so few
statements of a definite sort can be made with regard to so
fundamental a matter as the fate of a basal foodstuff in the
body. It may chill the heart of those who, at the beginning
of their career, think of working at such problems, to view
what seems the small harvest of Pavy's fifty years of labour.
But Pavy had no sense of failure and none should be felt by
those who have shared with him the attack upon these prob-
lems. If in this slight review speculations rather than facts
have been prominent it is because, under the influence of Pavy,
we have been considering the most intimate side of metabolism.
This, from its very nature, is a region where experimentation
is extraordinarily difficult and only recently has any serious
attempt to explore it been made. Twenty-five years ago our
equipment for the venture was most inadequate and the time
has been mainly spent in preparation. Any one who will con-
sider how much better we are equipped now will admit that
the years have been well spent.

Owing to the labours of Emil Fischer and others, our
knowledge of the pure chemistry of the simpler carbohydrates
is both extensive and precise, so that when we seek evidence
as to the course of molecular changes in the cell the possi-
bilities and probabilities are for the most part clearly before
us. But more than this : the moment the significance of intra-
cellular enzymes became manifest biochemists made haste to
* Cathcart, The Physiology of Protein Metabolism (Longmans, 191 2), p. 120.

DR. PAVY AND DIABETES 47

put our knowledge of the dynamics of enzymic action upon a
quantitative basis and have obtained information of the greatest
value for studies upon the living cell. In the case of inter-
actions which concern carbohydrates very important work has
been done, in this country especially, by Croft Hill and by H. E.
and E. F. Armstrong. We now know a great deal about the
course of such interactions when conditioned by enzymes and
such knowledge will make the experimental attack upon the
central problems of metabolism infinitely more profitable.

The present moment is marked by a revival of interest in
biological matters on the part of those who have high chemical
qualifications and this is an auspicious circumstance. It must
not, of course, be forgotten that results obtained in the chemical
laboratory only become biologically valid when they have been
checked in the animal and that our problems require the organised
efforts of many workers with diverse qualifications. Because
of the difficulties inherent in the complex conditions presented
by our special material, the problems call continually for
courage and patience— the courage and patience which charac-
terised the subject of this memoir, F. W. Pavy.

SIR J. J. THOMSON'S NEW METHOD OF
CHEMICAL ANALYSIS

By F. W. ASTON, B.A., B.Sc, A.I.C.

No observer of the progress of '' Molecular " Physics and
Chemistry during the past decade or so can fail to have been
struck by the extraordinarily intimate knowledge we have
acquired, especially recently, of Atoms and Molecules — the
individual units of complex matter. The results serve to
confirm the shrewd estimate made by a great scientific thinker
like the late Lord Kelvin that molecules are indeed almost incon-
ceivably small compared with the masses of matter affecting our
senses in everyday life. Thus the consensus of a variety of
methods shows that a thimbleful of the air we breathe contains
about a thousand million million million molecules, the average
diameter of each of these being one hundred-millionth of an inch ;
or to give a more practical illustration, a molecule of carbon in
the paper upon which this article is printed subtends to the •
reader's eye the same angle as would a normal human being I
at the distance of the moon. 1

To hope that an effect appreciable to our senses could be
produced by a body so minute as a molecule would therefore at
first sight seem absurd, yet this has been done in several notable
instances in a most convincing manner. Thus in the spinthari-
scope of Sir William Crookes we actually see the flash of light
caused by the impact of a single a ray (which is a charged
molecule of helium) upon a screen of zinc blende. Rutherford
and Geiger have shown the measurable " kick " of a delicate
electrometer due to the ionisation produced by a similar a ray.
Whilst C. T. R. Wilson, with the aid of an apparatus recently
exhibited at the Royal Society, has been able, in the most
beautiful manner possible, both to see and to photograph the
track of a single charged molecule.

The explanation of such large effects as these lies in the fact
that the charged molecule constituting an a ray is moving at \
so prodigious a velocity that in its collision with other material

THOMSON'S METHOD OF CHEMICAL ANALYSIS 49

particles it is able to set free a quantity of energy out of all
proportion to its mass ; it is this Kinetic Energy or power of

doing work, , which may be made appreciable by suf-
ficiently increasing the velocity factor v, although the mass
factor m may be inconceivably small. It is on this account that
the helium molecule of mass 6 x lO"^^ of a gramme, when moving
with a velocity 2 x 10^ cm., i.e. about 100,000 miles per second,
is capable of causing a flash of light appreciable to the eye when
it strikes a fluorescent screen.

The novel and remarkable method of chemical analysis which
is the subject of this article depends upon the fact that if we can
communicate high enough velocities to molecules they will be
able to produce appreciable and permanent effects when falling
upon suitable material ; also upon the fact that if such moving
molecules can be electrically charged they become amenable to
externally applied electric and magnetic forces and by their
movements under these forces can be made, in a phrase, to
weigh themselves. The method, indeed, is different from all other
chemical methods of determining molecular mass, in that it
deals with the individual molecule and not with large numbers.

It is the outcome of a long and exhaustive series of researches
upon the nature of Positive Electricity which Professor Sir
J. J. Thomson has been pursuing almost continually since he
revolutionised modern views on electricity by his classical
experiment with cathode rays, from which he inferred that
negative electricity occurs as definite units — corpuscles or
electrons — the mass of which is one eighteen-hundredth part of
that of an atom of hydrogen. The principal field of these
researches has lain in the so-called ** Canalstrahlen " or Rays of
Positive Electricity which Goldstein, as long ago as 1886,
observed in a vacuum tube provided with a perforated cathode.

These rays were investigated afterwards by Wien, who
showed that some of them at least carried a positive charge
and had a mass of molecular order : it has, however, been the
task of the head of the Cavendish Laboratory to explore, in
a detailed and accurate manner, this wide and complex field of
research. The subject of the present article is but a single off-
shoot of the work. It will be of interest to those who are
unable to follow the original papers on the subject to know the
method by which it has been demonstrated that just as light
4

SCIENCE PROGRESS

from a flame can be split up by a prism into a spectrum showing
the chemical constitution of that flame, so positive rays emerging
from a perforated cathode can be resolved, in like manner, so
that the several constituents of the gas in the discharge tube
become obvious.

In order to apply the method to a gas, its particles undergo
the follov^ing operations :

(i) they are given a definite charge of electricity;

(2) they have a high velocity impressed upon them in a
definite direction ;

(3) they are allowed to pass through an electric and a
magnetic field ;

(4) finally they fall upon a fluorescent screen, a photographic

Fig. I.

plate or some other suitable arrangement capable of recording
the exact positions of the impacts.

Fortunately the first two conditions are fulfilled at the same
time and automatically by submitting the gas to a high-tension
electric discharge at low pressure. The gas is "ionised" by this
treatment and the positive ions are projected with prodigious
velocity towards the cathode ; if this be pierced with a small
hole, so as to allow of their free passage, they will emerge on
the other side as a stream of positively charged particles which
may then be acted upon by the analysing fields.

It will be as well now to describe the particular form of
apparatus which has been found to give the most satisfactory
results. The main features are shown in the accompanying
diagram (fig. i). The discharge tube A, which is very similar

THOMSON'S METHOD OF CHEMICAL ANALYSIS 51

to an ordinary X-ray bulb, is a large spherical flask about
ij litres in capacity. Pushed into the neck of the flask and
closely fitting it is the cathode B : this is made of aluminium and
is so shaped that it presents to the bulb a hemispherical front
provided in the centre with a funnel-shaped depression. The
long, fine " canal-ray " tube extends from the bottom of this
depression. If carefully centred and fixed so that its hemi-
spherical head just projects into the bulb, this type of cathode
gives a very intense beam of positive rays down its axis, i.e.
into the " canal-ray" tube. The latter has been made in several
difl'erent ways : as the accuracy of the method depends on the
fineness of the emergent beam, it is essential that the tube should
be perfectly straight and extremely fine. The best results have
been obtained with brass or copper tubes drawn down until their
internal diameter was of the order of o'l mm. The fine tubes are
most carefully straightened — tested by sighting a bright light
through them— and mounted in a thick soft-iron tube (shown
black in the diagram), which not only protects them from injury
but also eff'ectually shields the rays passing through them from
external magnetic fields; the latter is a very important point,
as in so narrow and long a barrel — 80 mm. is a convenient
length — the smallest magnetic deflection would be sufficient to
drive the particles against the walls of the tube and so pre-
vent them from emerging. The cathode is kept cool during the
discharge by means of a small water-jacket C.

The anode of the discharge bulb is an aluminium rod Z),
which is generally placed for convenience in a side tube. In
order to ensure the gas under examination being as nearly pure
as possible and also to keep its pressure constant, a steady
stream of the gas is allowed to leak through an exceedingly fine
glass capillary tube E and after circulating through the
apparatus is pumped out at F by a Gaede rotating mercury
pump. By varying the speed of the pump and the pressure in
the gas-holder communicating with E, the pressure in the
discharge tube may be varied at will and maintained at any
desired value during considerable lengths of time. The pressure
is usually adjusted so that the discharge potential corresponds
to a spark-gap between brass balls 1-2 cm. apart in air, i.e.
30,000-50,000 volts. Positive ions, i.e. particles of gas carrying
a positive charge of electricity, are formed in A by the discharge
which is maintained by a large X-ray coil made by Cox. Under

52 SCIENCE PROGRESS

the influence of the enormous electric field, they attain corre-
spondingly high velocities and those which fall axially upon
the cathode pass through the narrow " canal-ray " tube and
emerge as a fine beam of ** canal-rays."

The charged particles travelling in a definite direction, at a
high velocity, are subjected to the analysing influence of electric
and magnetic forces by causing the beam to pass between the
pieces of soft iron P P' which are placed between the poles
MM' of a powerful electromagnet. P and P' constitute the pole
pieces of the magnet but are electrically insulated from it by thin
sheets of mica A^A^' and so can be raised to any desired electrical
potential difference by means of the leads shown in the figure.
As the rays pass between the faces of P P\ they are subjected
to the influence of electric and magnetic forces simultaneously
and after they have been analysed, in a manner to be described
later on, they enter the *' camera " G and finally impinge upon
the fluorescent screen or photographic plate H. In order that
the stray magnetic field may not interfere with the main discharge
in ^, shields of soft iron, //, are interposed between the magnet
and the bulb.

Fluorescent screens made of powdered Willemite were used
in all the earlier experiments but as these only show the impact
of the rays very faintly in a dark room and give no permanent
record, they are unsuitable for the purpose of accurate measure-
ments ; a notable advance in technique was made by the use
of photographic plates. When exposed to a beam of positive
rays, the surface of such a plate undergoes a chemical change of
a nature somewhat similar to that caused by actinic light and
may be developed in the ordinary way, a more or less intense
deposit of silver being formed wherever it has been struck by
.the rays. The plates which have been found to give the best
results are the well-known Sovereign brand made by the Im-
perial Plate Co. The most convenient way of exposing the
plate is to use a device which the writer has used previously in
other experiments requiring accurate movement of an object in
a high vacuum. It is roughly indicated in the accompanying
figure (fig. 2), which shows the complete camera. The photo-
graphic plate is placed in a light frame supported by a silk
thread ; the frame can be wound up and down by means of a
winch the axle of which works in an air-tight, ground joint.
While the pressure, etc., is being adjusted, the plate is kept at

THOMSON'S METHOD OF CHEMICAL ANALYSIS 53

the top of a light-tight metal case and as soon as the fluorescent
screen at A shows that the desired conditions have been
obtained the plate is lowered into the field of the rays and
a photograph taken. The exposures depend almost entirely on
the diameter of the canal-ray tube and vary from three minutes
to three hours. By the use of a long plate, as many as three
photos could be taken before it was necessary to destroy the
vacuum in the apparatus and introduce another plate. As it
is usually desirable, for reasons which will be explained, to

Fig. 2,

have as low a pressure as possible in the " camera," one or
two Dewar charcoal tubes are attached to it and are immersed
in liquid air while the photograph is being taken. As gas
can only enter through the long and fine canal-ray tube the
pressure in the camera may be very much lower than that in
the bulb.

The illustration facing p. 48, which is from a flashlight
photograph taken by Mr. Hayles, of the Cavendish Laboratory,
conveys a good idea of the actual appearance of an apparatus
set up by the writer with which a great many results were
obtained. On the extreme right can be seen part of the gas

54 SCIENCE PROGRESS

reservoir and just behind this the very fine capillary tube which
allows the gas to leak slowly into the discharge bulb shown
on the right of the large Du Bois electromagnet. In a cor-
responding position on the left of the latter is the "camera"
made of glass tube partially covered with paper ; this contains
the plate-holder and supports at the top the glass " winch " by
which the plate is raised or lowered. Behind the magnet may
be seen the Gaede pump and the induction coil. Attached
to the camera is the large Dewar charcoal bulb, which is
cooled by immersion in the vessel of liquid air ; the latter stands
on the table, together with an accurate ammeter for measur-
ing the current flowing through the magnet and a red
photographic lamp for use during the removal of the plate
when the exposure is ended.

The endeavour may now be made to explain, as briefly

Fig. 3.

and simply as possible, how by subjecting the moving charged
particle to an electric and a magnetic field, each at right
angles to its path, both the velocity and the mass of the
particle may be deduced.

Let A (fig. 3) be such a particle of mass m^ carrying a posi-
tive charge of electricity e and moving with velocity v in the
direction A B. If this particle be not influenced by electric or
magnetic forces, it will obey the ordinary laws of motion and
move in a straight line, striking a distant screen at a point B.
If, however, we cause it to pass through an electric field of
strength X between the plates P P\ it will be deflected away
from the positive and towards the negative plate in the plane
of the paper and finally strike the screen at some other point C,
the displacement B C = x being given by the equation :

If now the electric field be cut off and P P' made the poles
of a magnet of field strength //, the moving particle will be

THOMSON'S METHOD OF CHEMICAL ANALYSIS 55

deflected at right angles to the plane oj the paper a distance y
given by the equation :

y = k,

kxkz being constants depending solely on the dimensions and
form of the apparatus used.

If a continuous stream of particles, all of the same mass,
carrying the same charge (or what amounts to the same thing in
this case, having the same ratio mje of mass to charge) and
moving with the same velocity, strike the screen shown in
plan in fig. 4 — which is covered with a layer of powdered
Willemite, a substance that fluoresces strongly under the influ-
ence of the rays — a bright patch of light is produced at the
point By due to undeflected rays, when neither the potential

' p

^ (

Fig. 4. .

nor the magnet is on. The plates P P' being vertical, if the
electric field only be on, the spot will be deflected to C\ if the
magnetic field only be on, the spot will be deflected to D but
if both are on together to a point p of which the horizontal
and vertical displacements are x andjj; respectively. It is there-
fore only necessary to measure x andjv and from the equations
given above it follows that x is inversely proportional to the
kinetic energy of the particle y and inversely proportional to
its momentum j; and that

yjx is a measure of the velocity of the particle ;

y/^ „

7n
„ — or the ratio of mass to charge.

Now e can only exist as a multiple (and in general only a
small multiple) of the charge on a single corpuscle and all
the evidence up to now shows that this is invariable and

SCIENCE PROGRESS

indivisible. Thus if we have a beam of positive rays of constant
mass m but moving with velocities varying over a considerable
range, y^jx will be constant and the spot of light will be drawn
out into a parabola pp^ (fig. 5). When other rays having a
larger mass m^ but the same charge are introduced into the
beam, they appear as another parabola q q^ having a smaller
magnetic displacement. (If the range of kinetic energy be the
same for both particles the electric displacement will be the
same.) If any straight line p, q, n^ be drawn parallel to the

-..

/^q

^s^^

^.0*

V ^^^^fc^ 1

• *"

Fig. S.

magnetic axis O Y cutting the two parabolas and the electric
axis O -^ in />, ^, n^ it will be seen at once that

That is to say, the masses of two or more different particles can
be compared directly by merely measuring two lengths the ratio
of which is entirely independent of the form of the apparatus and
the experimental conditions.

This is really the fundamental principle on which the
method is based. A photograph is taken in which we can
identify at least one parabola as belonging to a set of par-
ticles of known mass ; all the other parabolas can then be
measured and compared with this one and their masses deduced.
In the case of the lighter particles, the hydrogen atom and the
hydrogen molecule are taken as the standards ; in the case of
heavier particles, the mercury atom is particularly useful as a
standard, as it is almost always present and for some reason at
present unexplained gives a very bright curve. In order that

THOMSON'S METHOD OF CHEMICAL ANALYSIS 57

there may be no possible doubt as to the identity of the H
and Hi parabolas, the absolute value of mle for these lines
has been determined and found to correspond to the values
obtained by electrolytic and other methods for the hydrogen
atom and molecule.

To return to the diagram (fig. 5), since OX is an imaginary
line and has no existence on the photograph, in order that
measurements may be made with greater convenience and
accuracy the magnetic field is reversed during the second half
of the exposure when — in the case we are considering — two
new parabolas will appear at r r^, 5 s\ due to m and m^ respec-
tively; the masses can be compared by the equation :

ni ~ qs^

/», q, r, s being any straight line cutting the curves approxi-
mately parallel to the magnetic axis. The measurements of
these lines is independent of zero determination and if the
curves are sharp can be carried out with considerable accuracy.

It has been shown that the electrical displacement is
inversely proportional to the kinetic energy of the particle.
Since this kinetic energy is simply dependent on and propor-
tional to the electrical potential through which the charged
particle fell before it reached the cathode and not upon its
mass, in general there will be a definite maximum kinetic
energy corresponding to the whole potential drop across the
Crookes' Dark Space in the discharge tube, with a correspond-
ing minimum displacement on the plate ; so that the parabolas
will end fairly sharply at points />, q, etc., equidistant from the
magnetic axis O Y. From the same reasoning it follows that,
the farther the parabola extends away from this limiting tip,
the larger must be the range of voltage through which the
particles forming it have fallen.

Such true parabolic curves as we have considered are
caused by positive rays which have retained their charge
unaltered throughout both the electric and magnetic field and
are termed Primary Positive Rays. Unfortunately a simple in-
terpretation of these is impossible, as the pressure in the
camera is seldom and in the canal-ray tube never entirely negli-
gible, so that owing to the intense ionising eff'ect of the rays
on the small amount of gas present in these localities free cor-

58 SCIENCE PROGRESS

puscles are always to be found there, the result being that
the behaviour of the positively charged particle is complicated
in the following ways :

It may pick up a single negative charge and becoming
neutral may pass the fields unaffected and strike the plate at
the origin O, the *' undeflected spot."

It may pick up yet another negative charge before emerg-
ing from the canal-ray tube and by retaining this throughout the
fields may become a Negative Primary Ray and give rise to
a parabola similar in all respects to the positive ones but in
the opposite quadrant, as shown in fig. 5 by dotted lines.

It may be changed from a neutral to a charged particle of
either sign or vice versa during its passage through the fields^
thereby giving rise to rays which do not strictly obey the
fundamental equations, as the values of X and H which affect
them will not be constant but will depend on the position of
their origin or destruction. These are called " Secondary Rays."
The effect of these rays on the photograph or screen is ex-
ceedingly complex ; indeed in the earlier experiments they
completely overshadowed the genuine primary rays, so that
it was only by designing apparatus in which the pressure in
the camera could be kept low that the primary rays could be
seen distinctly. Even with the apparatus in its present state,
it is impossible to eliminate them entirely, especially when gases
such as hydrogen or helium are present which are not com-
pletely absorbed by the cooled charcoal. Owing to the presence
of secondary rays, the greatest care must be taken in interpre-
ting the photographs, as the secondary rays may give parabolas
which under certain conditions are quite indistinguishable from
the true primary parabolas. Fortunately the relative positions
of these false curves are usually changed when the photograph
is repeated under slightly different experimental conditions. It
is then possible to detect them, as no such change in the
relative positions of the true primary parabolas is ever noticeable.
The object in maintaining the lowest available pressure in the
camera is to eliminate secondary rays as far as possible.

It will now be well to consider a few of the actual results
in detail. The accompanying plates are reproductions from the
original negatives and illustrate several typical cases. Plate I
was obtained with nitrogen (made from air) in the tube, the

Reduced in reproduction to three-quarters actual scale.

53]

THOMSON'S METHOD OF CHEMICAL ANALYSIS 59

magnetic deflection being small enough to show the two
hydrogen lines. It will be seen that there are five very bright
lines in each side of the magnetic zero ; if the most deflected
line be of mass unity, taking the squares of their relative
deflections, the other lines correspond to masses approximately
2, 14, 28, 200. The five lines are evidently due to the
hydrogen atom and molecule, to the nitrogen atom and
molecule and to the mercury atom respectively, each presumably
carrying a single charge.

All the parabolas end off approximately at the same distance
from the vertical axis through the bright undeflected spot : that
corresponding to the nitrogen atoms, however, has a distinct
** beak" or feebler continuation which ends half as far away and
therefore must be caused by particles having twice the kinetic
energy of those causing the brighter part. It is quite impossible
to suppose that these are due to nitrogen atoms which have
fallen through twice the voltage, as the actual maximum voltage
of the discharge tube never rose appreciably above that corres-
ponding to the tips of the other parabolas ; the most probable
explanation is that the atoms of nitrogen forming the extension
of the curve carried a double charge + 2e while coming up
to the cathode and therefore reached it with twice the normal
kinetic energy. If during their passage through the canal-
ray tube they picked up a single negative charge — ^, they
would emerge as atoms with a single positive charge and so would
fall upon the same parabola but at a distance half as far away
from the magnetic axis. If this view be correct, we might expect
some of these doubly charged atoms to retain both charges
throughout the fields ; they would then behave exactly as would
particles of mass 7 with a single charge + ^, as the position
of the parabola depends only on the ratio m\e. On looking for
such a parabola, it can be seen clearly between the nitrogen
atom and the hydrogen molecule, though it is naturally rather
faint. Similar evidence of doubly charged particles will be seen
in several of the other plates.

Though the negative in Plate I is a good one to reproduce
in print and to illustrate the general characteristics, it is by
no means the best type for actual measurement, as the lines
in it are much too thick and bright. It would be quite impossible
to reproduce satisfactorily the plates with which the best metrical
results have been obtained, as a line can be measured with great

6o SCIENCE PROGRESS

accuracy if the canal-ray tube be sufficiently fine even when it
is only just visible on the negative.

For measuring purposes the negative is clamped in a special
apparatus and a needle, mounted on a slider so that its point
just does not touch the gelatine, is moved across the parabolas
in a direction parallel to the magnetic axis O y (fig. 5); whenever
the needle lies exactly over a parabola, its position is read on
a vernier scale. In the case of a fine line the position can be
determined to about ^ mm.

In order to give some idea of the measurements which can
be made in this way, the actual records of an experiment with
a very fine canal-ray tube working satisfactorily may be quoted.

Gas in discharge tube air at about iIjj rnm. pressure. Poten-
tial on plates 166 volts. Current through magnet 2*00 amperes.
Exposure ij hours. Discharge potential equivalent to spark-
gap I J cm. in air; d\s the displacement in mm. from electrical
axis ; m is the corresponding mass obtained from the inverse
square of d expressed relatively to mercury as 200.

Probable cause of line.
Mercury atom with single charge.
Mercury atom with double charge.
Very faint line, possibly mercury with triple charge.
Very faint, probably CO2.
Nitrogen molecule (brightest line).
Oxygen atom.
Nitrogen atom.
Carbon atom.

Oxygen atom with double charge.
Nitrogen atom with double charge.
Carbon atom with double charge.
Hydrogen molecule.

(Carbon and its compounds were present as impurities derived
from the apparatus; these can only be eliminated with great
difficulty by prolonged washing with oxygen. Lines due to
such impurities are, as a rule, very faint in comparison with those
due to the gases known to be present in quantity.)

Here we have twelve distinct parabolas, not counting that
due to the hydrogen atom which has been thrown off the plate
by the large magnetic field. Of these all the bright ones fall
exactly on positions expected from the gas that filled the tube,
their masses agreeing with the generally accepted molecular
and atomic weights to about i per cent.

tn.

5'25

200

Hg4-

7-40

IOO-2

Hg++

9*15

64-6

Hg+++

11-30

43*0

co,+

14-05

28-0

N34-

18-50

16-0

0 +

19-70

I4-I

N +

21-50

11*9

c +

26-15

8-0

0++

28-1

6-98

N4-4-

30-35

5-98

C+4-

52-2

2-02

H24-

THOMSON'S METHOD OF CHEMICAL ANALYSIS 6i

A word of caution may well be given here in connexion with
the relative photographic intensities of the lines. These are
entirely misleading and incorrect, as one might very well expect
on seeing that in Plate I hydrogen gives almost the. brightest
lines in a tube supposed to contain practically pure air. A trust-
worthy electrical method has been devised recently by which
the true relative intensities of the lines can be deduced from the
total charges carried by the particles which give rise to them ;
the results show that a hydrogen line appearing on the plate
or screen as the brightest line of the set may really not be one
hundredth part as intense as the lines corresponding to the gas
with which the tube is filled.

From experiments already made by the electrical method,
we may say that roughly speaking the true intensities of lines
due to a given gas are proportional to the quantity of that gas
present, whilst the photographic intensity of lines of equal true
intensity is far greater in the case of those produced by particles
of lighter mass.

To readers interested in chemistry a short description of the
specific behaviour of a few individual elementary substances
may be of interest. To begin with, it is a fact of the very first
importance to the student of the nature of electricity that up to
now, though every possible scrutiny has been applied, no positive
ray having a smaller mass than that associated with a hydrogen
atom has been detected. Elements of lower atomic weight, if
present, make no appearance on the sensitised surfaces used to
record the rays, neither does it seem possible for the hydrogen
atom itself to carry more than one charge.

Hydrogen. — The lines due to Hi+ and H2+, largely no doubt
owing to their very exceptional photographic efficiency, appear
on practically every photograph taken of the part of the
magnetic spectrum which includes them. They can be elimin-
ated, however, by thoroughly rinsing out the tube with highly
purified oxygen. Oddly enough, considering the chemical
properties of the element, atomic hydrogen also appears
repeatedly with a negative charge, the negative parabola due
to the hydrogen atom being plainly visible in Plates I and
11. If hydrogen be mixed with a small percentage of some
other gas, such as nitrogen, a very remarkable line sometimes
makes its appearance which corresponds to a hypothetical

62 SCIENCE PROGRESS

substance H3+. A photograph showing this line is reproduced in
Plate II; though it is always faint when compared with Hi
and H2 the parabola is nevertheless genuine and has been
repeatedly obtained.

Oxygen. — This gas has probably been experimented with in
a more nearly pure state than any other, as it combines with all
the impurities given off by the apparatus forming compounds
which can be removed by means of liquid air. Plate III was
taken with this gas. Hi and H2 have practically disappeared
and nearly the whole of the intensity is in the lines correspond-
ing to + 16 and + 32, O and O2 respectively. There is a very
strong negative line 0_ at — 16. This 0_ line appears on
nearly all plates taken when oxygen is present, either free or in
combination. No negative corresponding to O2 has been de-
tected in highly purified oxygen but the line sometimes appears
when other gases are present. The very obvious extension
of the 0+ line in Plate III indicates the tendency of the oxygen
atom to take up a double charge.

Nitrogen appears as N++, N^. and N2+ ; it never gives a nega-
tive parabola. In some of the nitrogen photographs a faint line
is found at 42-43 which Prof. Thomson thinks may be due to
a compound N3 or N3H. If made from air, nitrogen shows the
argon line corresponding to mass 40.

Carbon appears as C++, C+ and C_ when compounds such as
the monoxide and dioxide are used. Plate IV, which represents
carbon monoxide, shows the negative O and C lines quite
clearly and also doubly charged positive ones. On using certain
organic compounds, a negative parabola corresponding to a
mass 24 is found, which seems to be due to a molecule
consisting of two carbon atoms carrying a single negative charge.

Organic compounds give very complex results but it is beyond
the scope of this article to discuss these. The case of methane,
CH4, however, is comparatively simple and of particular interest.
In the case of this gas, if a very narrow canal-ray tube be used,
a group of five distinct parabolas is observed differing from each
other by mass i and corresponding to C, CH, CH2, CH3 and
CH4 respectively, each carrying a single positive charge.

Chlorine and the other Halogens can be used in the form of
their compounds with hydrogen or carbon. They are princi-
pally of interest because, like oxygen, they give strong negative
atomic parabolas.

THOMSON'S METHOD OF CHEMICAL ANALYSIS 63

Helium is associated with a single very strong line of mass
4 corresponding to He+. As this gas cannot be removed from
the camera by the cooled charcoal the secondary effects are
usually very strong. Plate V shows the two faint hydrogen
lines and the bright helium line. This plate is an admirable
illustration of the danger of secondary rays. The apparent
parabola just inside the He parabola, which corresponds to a
mass 5 and might easily suggest a compound HeH, is really not a
primary at all. If the pressure in the camera be allowed to rise
rather higher, the effect shown in Plate VI is produced, bright
beams of secondaries of both signs being the only visible rays.

Mercury. — This element possesses quite peculiar interest
in connexion with these results. Its presence in the discharge
tube in small quantities is, of course, to be expected, as the
apparatus is exhausted by a mercury pump. Should mercury
not be required, it can be frozen out with liquid air ; in general,
however, its presence is an advantage, as the mercury line
cannot possibly be mistaken and gives a very valuable standard
for measurement. The presence of large quantities of certain
gases, notably oxygen and the halogens, involves its complete
disappearance. The behaviour of mercury is in two ways
quite inexplicable : in the first place, although the heaviest of
all the elements yet measured, its photographic efficiency seems
almost as great as that of the extremely light elements; and
what is still more unaccountable, its parabola invariably seems
to extend almost to the very origin itself and would require at
least three or four charges upon a single atom to account for
its enormous kinetic energy in the manner already indicated.
Nearly all the Plates here show its characteristic line quite
distinctly but Plate VII gives the most striking idea of its
beautiful parabolic form and remarkable appearance when the
strength of the magnetic field is made extremely high ; the
electrical displacement due to a single charge can be distinguished
as a bright *' bead " a short distance along it ; the head of the
other line (C0+) in the plate is in the same vertical line. This
mercury line 200 is almost always accompanied by the double
charged one corresponding to 100, which can be seen plainly
in Plate IV. Mercury is unique in that it is the only metallic
element, with the doubtful exception of potassium, which as
yet has given definite proof of its existence in positive rays.

Plate VIII, which was obtained from a mixture of hydrogen

64 SCIENCE PROGRESS

and oxygen under conditions of fairly high pressure in the
camera, has been included in order to give the reader some
idea of the extreme complexity of the secondary rays, which
in this particular instance form a perfect network of lines,
straight and curved. Out of five apparently distinct lines
on the negative side, only two, the Hi. and Oi_ lines, are
genuine. For a detailed discussion as to the origin and be-
haviour of secondary rays, the reader is referred to Prof.
Thomson's original papers on the subject which have been
published from time to time in the Philosophical Magazine.

From these few illustrations and brief descriptions, ideas of the
possibilities and limitations of the method will doubtless have
already been formed. As to the latter, some are obvious, such
as the fact that in order to apply the method to the determination
of atomic weights the substance analysed must exist in a state
of vapour and be able to support an electric discharge. There is,
however, another more subtle disability which is also known to
affect ordinary spectroscopic analyses of gases : this is that a
substance may be present in quite large quantities and yet its
characteristic lines may not be apparent. When it was stated
that mercury was the only metal so far clearly identified, it
must not be understood that it is from any lack of trying others.
As soon as the method was found to afford results of reason-
able accuracy. Sir J. J. Thomson endeavoured to apply it to
settle the much vexed question of the atomic weight of nickel,
the value generally accepted by chemists appearing incompatible
with the results obtained by physicists on studying the char-
acteristic radiation of the metal. But although nickel carbonyl
was passed through the tube and nickel chloride was vaporised
inside it, the plates obstinately refused to vouchsafe the least
indication of a nickel parabola and results with potassium were
very nearly as negative. It seems almost inconceivable that
these elements cannot exist as ions in the discharge tube but
it is quite possible that they are incapable of retaining their
charge after reaching the cathode and so are not analysable by
the method. Another less likely possibility which may shortly
be tested is that the parabolas are there but are incapable of
affecting the screen or the plate. From the point of view of
accuracy, the limitations of the method are almost entirely those
of apparatus, design and technique ; it is therefore to be
supposed that they will be removed as experience grows.

THOMSON'S METHOD OF CHEMICAL ANALYSIS 65

As regards the very special interest and possibilities of the
method, in the first place the sharpness of the parabolas
obtained, which appears to be only limited by the possible
fineness of the canal-ray tube, is the first rigorous and direct
proof of an article of scientific faith which has been accepted
during many years past without hesitation, namely, that the
individual molecules of any given substance all have identi-
cally the same mass.

The point which will probably appeal most strongly to
the imaginative mind is that connected with the almost incon-
ceivably short time necessary for a particle to exist in order
to register its mass. For since a moderate velocity for the
positive rays is 10^ cm. per second and 10 cm. is amply suf^cient
for them to gain their velocity and be deflected by the fields,
compounds which have an existence of but the ten-millionth
part of a second will infallibly be weighed on this impalpable
balance. Hence it is that we need not be surprised at finding
upon the plates lines corresponding to molecules found neither
in the heavens above nor the earth beneath ; nor need those
of us who are chemists hold up our hands in horror at such
unnatural and grotesque monsters of the world of molecules
as H3, CH, CH2, CH3, N3, etc., etc. Rather should we look
forward to this line of investigation as an extremely hopeful
field in which to study the actual mechanism of dissociation,
ionisation and chemical interaction. The method is applicable
to the most microscopic quantities of a substance at disposal.
That it has already yielded interesting results will, I hope,
be apparent from this very brief account; there seems to be
little reason to doubt that, as year by year the technique of the
experiments is improved, results of equal and greater importance
may be expected from it.

CONDITIONS OF CHEMICAL CHANGE

II. PHOTOCHEMICAL CHANGE IN GASES
Part II. Experimental^

By D. L. chapman, M.A.

In the preceding article, in which the views held by different
investigators on the mechanism of the interaction of chlorine
and hydrogen were explained and discussed more or less in
detail, it was indicated that the most favoured hypothesis
during several years preceding 1905 involved the assumption
that an intermediate complex was formed, containing chlorine,
hydrogen and water, of the type represented by the formula
[Cl2]x, [HsOjy, [H2I. It was supposed that this did not exist
in a freshly prepared mixture of chlorine and hydrogen but
was gradually produced when the mixture was exposed to light
and subsequently destroyed so as to form hydrogen chloride
and water, the production and decomposition taking place in
accordance with the law of mass. According to this view,
hydrogen chloride could not be generated in the system by the
direct interaction of molecules of chlorine and hydrogen but
only by the breaking-down of the unstable system in which they
were associated with water. It was claimed that by this explana-
tion it was possible to account satisfactorily for the accelerative
influence of moisture on the change and also for the initial inert
period which is generally observed when a mixture of freshly
prepared chlorine and hydrogen is exposed to light. Moreover,
the hypothesis supplied an intelligible account of another well-
known peculiarity of a mixture of chlorine and hydrogen,
namely, that when it has been exposed to light until the rate of
formation of hydrogen chloride is constant {i.e. until the con-
centration of the complex attains its maximum value) and is
then left in the dark during several hours, it regains in some

^ A description and diagram of an actinometer with which most of the ex-
periments on chlorine and hydrogen described in this article can be carried out
are given at the end of the article.

CONDITIONS OF CHEMICAL CHANGE 6^

measure its original property of temporary irresponsiveness to
stimulation by light. The explanation of this phenomenon,
which had received the name of " photochemical inducticm," was
supplied by the assumption that the complex is slowly broken
down in the dark into the substances from which it was built
up — chlorine, water and hydrogen. The hypothesis in question
was originally advanced by Mellor and afterwards modified by
Bevan so as to account for the fact discovered by Draper and
confirmed by Bevan that the inert period is of much shorter
duration when the chlorine is exposed to light before being
mixed with the hydrogen. The modification of the hypothesis
necessitated by the confirmation of Draper's observation was
obvious and simple. The complex must be formed in two
stages : in the first, water molecules become united with chlorine
molecules ; in the second, the complexes thus produced become
attached to molecules of hydrogen : the subsequent fate of the
final product depending, as stated above, on whether it be
permitted to break up in the light or in the dark. When
examined in the light of the qualitative facts on which it was
based, the hypothesis was not unconvincing. Bevan, moreover,
maintained that, by means of experiments on the formation by
expansion of clouds in moist chlorine and electrolytic gas, he
had obtained evidence of the existence of peculiar compounds
— presumably the postulated complex — which could act like
gaseous ions as condensation nuclei for steam.

The view that hypotheses based on the assumption of the
formation of intermediate complex compounds could adequately
account for the cardinal or subsidiary phenomena observed in
the study of the photochemical action of chlorine on hydrogen
was contested by Burgess and the writer at the Cambridge
meeting of the British Association in 1904 and also in the
Proceedings of the Chetnical Society^ for two distinct reasons.
The first objection was grounded on certain observations
relating to the preliminary inert period recorded by Draper and
confirmed by the authors. Under certain conditions when
electrolytic gas was exposed to light, no hydrogen chloride was
formed during a considerable period of time — sometimes in our
experiments exceeding two hours — and then the rate of formation
of the chloride rose in less than ten minutes to its maximum
value. This result was contrary to the requirements of
the intermediate complex hypotheses, according to any ol

68 SCIENCE PROGRESS

which the rate of diminution in volume of the electrolytic gas
ought to have increased gradually and steadily from zero to a
constant value. A second objection raised was that on repeating
Bevan's experiments on the formation of clouds in the rapidly
expanded gases, we failed to discover any facts which could not
be readily explained without invoking the aid of a new class of
condensation nuclei. Moreover Dyson and Harden {Trans,
Chem. Soc. 1903, 83, 29) had pointed out that the theory of an
intermediate compound could not be reconciled with the
** induction period " observed by them with an almost dry mix-
ture of chlorine and carbon monoxide. It was evident that the
hypothesis in question would have to be abandoned and that the
true cause of the " period of chemical induction " had not as yet
been disclosed. A systematic study of the conditions controlling
the manifestation of the inert period was therefore undertaken
in the hope of elucidating the cause of the phenomenon. It
was soon discovered that the source of the initial inertness of
the mixture resided as much in the liquid used in the actinometer
to absorb the hydrogen chloride as in the gas itself; moreover,
that the property of imparting inertness to the gas was possessed
in very different degrees by different liquids. Experiments on
the following lines had forced this conclusion upon us.

An actinometer, filled in the usual way with electrolytic
gas, was exposed to light until the maximum rate of inter-
action had been reached ; the duration of the induction period
was duly recorded. The actinometer was then shaken so
as to bring the liquid into intimate contact with the gas and
again exposed to light ; another inert period of shorter dura-
tion than the first was observed. On again shaking the
actinometer and then re-exposing it to light, a third induction
period shorter still than the second became manifest. By the
constant repetition of these operations the contents of the
actinometer were at length brought into such a condition that
no further indication of an induction period was noticeable on
shaking. The results show clearly enough that the cause of
the inertness resides in the liquid and can be communicated
to the gas and that it is destroyed on exposure of the
latter to light. A series of experiments was next performed
in which the absorbing liquids were aqueous solutions of
salts and mineral acids. In these circumstances, the induction
periods observed were often many times longer than when

CONDITIONS OF CHEMICAL CHANGE 69

distilled water had been used to dissolve the hydrogen chloride
produced in the interaction. An aqueous solution of a par-
ticular specimen of crystallised barium chloride was found to
be exceptionally effective in rendering chlorine inactive. Our
attention was next turned towards the discovery of all the
possible methods by which such aqueous solutions could be
rendered incapable of imparting inertness to electrolytic gas.
It was found that this could be best accompHshed by the simple
expedient of saturating the aqueous solution with chlorine and
then boiling the solution until as much as possible of the
chlorine had escaped. Attempts were next made to remove
the residue of chlorine from a solution which had been treated
in the above manner without at the same time introducing the
obscure agent which is capable of rendering electrolytic gas
temporarily insensitive to light, in order to provide ourselves
with the means of testing conclusively whether the agent in
question be a transitory and communicable property of the
salt — some substance produced from the pure salt — or simply
some foreign impurity contained in the original sample of the
salt. One of the methods adopted for removing the last trace
of chlorine from the boiled solution was to add a drop or two
of a solution of potassium iodide and then to remove the liberated
iodine with a solution of sodium thiosulphate ; the solution
from which the chlorine had been thus entirely removed was
incapable of imparting inertness to electrolytic gas nor did it
acquire the property on standing or on heating. We were
thus driven to the conclusion that the inhibitive agent was
neither an acquired property of the salt nor a substance
developed from the pure salt but some unknown, widely dis-
tributed impurity contained in the original sample of the salt.
Just as we were on the point of starting a series of experi-
ments with the object of concentrating and isolating the
impurity, a pure accident disclosed its identity. It was thought
that a method better than that just described of removing the
residue of chlorine from the boiled solution which had been
saturated with chlorine would be to add just sufficient ammonia
to destroy the chlorine ; on introducing the liquid treated in this
way into an actinometer which already contained a mixture
of chlorine and hydrogen and then exposing the actinometer
to light, an inert period of abnormally long duration was
observed. The widely distributed impurity present in many

70 SCIENCE PROGRESS

soluble crystalline salts, in mineral acids and in water, capable
of imparting to a mixture of chlorine and hydrogen the pro-
perty of temporary inertness towards light, was therefore very
probably ammonia. It was then discovered that the solutions
which previously had been found to induce the longest induc-
tion period were those which contained the greatest amount
of ammonia ; that ammonia-free water was incapable of ren-
dering chlorine inert ; moreover, that in relation to chlorine
and electrolytic gas, a dilute solution of ammonia corresponded
in every particular with the solution of crystallised barium
chloride previously examined. Now ammonia itself cannot
exist in the presence of chlorine, so that the actual substance
which induces the inertness of the mixture must be some
product of the interaction of chlorine and ammonia.^ Nitrogen
chloride would appear to be indicated as the cause by the
following experiment. A dilute solution of ammonia was
saturated with chlorine and divided into two portions ; 5 cc.
of the first portion were added to an actinometer containing
chlorine and hydrogen, which was then exposed to light ; the
induction period was long. From the second portion the
chlorine was removed by exhaustion and 5 cc. of the purified
liquid was introduced into a similar actinometer; the induc-
tion period w^as very short. Hence it follows that the com-
pound which is the immediate cause of the induction period
belongs to the class of substances which are volatile and
readily removable by exhaustion on account of their slight
solubility in water. Moreover, it is destroyed by light and
heat. Nitrogen chloride fulfils these conditions.

There v/as yet one outstanding fact which could not be
reconciled easily with the view that nitrogen chloride was the
sole cause of the induction period, the so-called phenomenon
of " deduction." When an actinometer containing electrolytic
gas and tap-water was exposed to light and shaken so as to
destroy the whole of the nitrogen chloride both in the gas and
in the liquid and the actinometer was left to stand in the dark
during several hours, it was generally found that the gas had
become inactive, i.e. that an initial inert period preceded steady
combination on re-exposure of the insolation vessel to light.
This behaviour could only be explained on the assumption
that the water contained some nitrogenous organic substance
* Manchester Memoirs^ Vol. XLIX. (1905), No. 13.

CONDITIONS OF CHEMICAL CHANGE 71

which was slowly decomposed at the ordinary temperature in
the dark and gave rise to the formation of nitrogen chloride.
In order to test this explanation an actinometer was con-
structed which could be charged and heated at a little over 100°.
When the heating had been continued during about twelve
hours the actinometer was allowed to cool and exposed to
light. Interaction at once set in and even after keeping the
actinometer in the dark during several weeks the photo-
chemical change was not preceded by a preliminary inert
period. The heating had destroyed the nitrogen chloride and
other substances from which nitrogen chloride could be de-
veloped by the action of chlorine. It was subsequently found
that inhibitors are formed slowly when chlorine acts on water
containing albumen.

The so-called induction period is therefore caused by the
presence in the gas of a powerful inhibitive impurity — nitrogen
chloride — which must be almost completely removed from the
gases before the chlorine and hydrogen can interact.

The facts detailed above were discovered and published early
in 1905 in the Proceedings oj the Royal Society and in the
Manchester Memoirs.

A year later it was suggested by Luther and Goldberg ^ — in a
paper in which our work was mentioned but curiously enough
not contested — that induction is essentially due to the contamina-
tion of the mixture of hydrogen and chlorine with oxygen. Any
one who peruses the papers of Bunsen and Roscoe, Bevan,
Mellor or those of the author and his collaborators will per-
ceive that such a suggestion cannot possibly be entertained.
Oxygen is not removed from a mixture of chlorine and hydro-
gen on exposure of the latter to light; if it be, the rate of
removal is so slow that the effect of its disappearance cannot
be detected by measurements of the velocity with which chlorine
and hydrogen interact.^

The most remarkable feature of the inhibitory influence
of nitrogen chloride is the enormous effect produced by an

* Zeitschr. Phys. Chem, 1906, 66, 43.

^ I take this opportunity of proclaiming the untenabiHty of Luther and Gold-
berg's suggestion, since the views of these authors on this question have been
accorded a prominent place in the new edition of Nernst's Theoretical Chemistry
and may through that source find their way into other text-books dealing with
the subject of photochemistry.

72 SCIENCE PROGRESS

exceedingly minute amount of the vapour. I estimate that a
sensitive mixture of chlorine and hydrogen which contains
one molecule of nitrogen chloride to 1,000,000 molecules of
chlorine and hydrogen is at least 100 times less sensitive
to light than a similar mixture which contains none ot the
vapour. The inhibitory effect of oxygen discovered by Bunsen
and Roscoe is surprisingly large but that of nitrogen chloride
is very many times greater. As photochemical changes are so
sensitive to the influence of common impurities, it is not
surprising that so little progress has been made in the eluci-
dation of the laws which control chemical transformations
induced by the agency of light.

It will now be convenient to relinquish for the present the
inquiry into the phenomenon of photochemical inhibition, in
order that we may pass on to the discussion of a question to
which an answer must be found before we can formulate any
views concerning the mechanism of the influence of light
in promoting certain chemical changes. When white light
traverses a mixture of chlorine and hydrogen, we know that
some of the rays are extinguished, since the emergent beam
is coloured. Is the whole of this abstracted light absorbed
by the one coloured constituent, chlorine, without the inter-
vention of the hydrogen ; or is a certain proportion of the
light extinguished as a result of the chemical change which is
proceeding, the amount being proportional to the change ?
More than one authority has asserted that the latter is the
correct view. Bunsen and Roscoe interpret some of their
experiments with the aid of the assumption that the absorbed
rays can be divided into two distinct parts, those which are
absorbed by the constituents of the mixture in virtue of the
optical properties of these and those which affect the chemical
changes. If this view were correct, a mixture of air and
chlorine in equal volumes would absorb less light than a
mixture in equivalent proportions of chlorine and hydrogen.
Bunsen and Roscoe claim to have shown experimentally that
such is the case ; but in order to interpret the results of their
experiments, they were compelled to assume that a formula
which is only strictly applicable to monochromatic light could
for all practical purposes be used to interpret the results ot
experiments performed with composite light. This objection
was fully realised by Bunsen and Roscoe at the time. Burgess

CONDITIONS OF CHEMICAL CHANGE 73

and the writer^ have submitted this important question to
re-examination, using an experimental method free from the
objection indicated above. Light from Harcourt's standard
pentane lamp, after it had traversed a column of a mixture of
equal volumes of chlorine and oxygen enclosed at atmospheric
pressure in a cylinder with transparent ends, was permitted
to fall on the insolation vessel of a Bunsen and Roscoe actino-
meter containing gas uncontaminated with any destructible
inhibitor ; the intensity of the light was then determined by
measuring the rate of interaction of the chlorine and hydrogen.
A mixture of chlorine and hydrogen in equal volumes and at
the same pressure was then substituted for the mixture of
chlorine and oxygen in the cylinder through which the light
passed before falling on the actinometer. The intensity of
the light proved to be the same in both cases. A mixture of
chlorine with an equal volume of hydrogen is therefore not
less transparent than a similar mixture of chlorine and oxygen.
The chemical change does not cause light to be absorbed ; it
is the light absorbed by the chlorine which stimulates the
molecules of the two gases to interact. Our conclusion that
an absorption of light does not occur as a direct result of a
chemical change has been confirmed recently by several workers
engaged on investigations relating to other photochemical
changes ^ and is, I believe, now generally accepted as true.

We were now in the possession of two fundamental facts
on which to base a working hypothesis. Firstly, the energy
which brings about the change is derived solely from the
light absorbed by the chlorine in virtue of the selective
absorption exercised by the latter ; secondly, certain impurities
have an enormous effect in retarding the interaction of the
chlorine and hydrogen. At the time when these two facts
were established, the investigation of R. W. Wood on the
resonance spectra of the elements was being carried on and
was attracting considerable attention. Wood's work had de-
monstrated the great complexity of the vibrations set up in the
atoms and molecules of the elements by the stimulating effect
of light and it was known that these vibrations could be pro-
foundly modified by traces of impurities. Influenced by these

^Journal Chem, Soc. 1906, 89, 1399.

* Winther, Zeitsch. wiss. Photochem. 1908, 8, 242 ; Weigert, ZeUsch,
^lektrochem. 1908, 596,

74 SCIENCE PROGRESS

considerations, we put forward the hypothesis^ that the light
which falls on the moist mixture of chlorine and hydrogen is
absorbed, in the first instance, by the coloured component
(the chlorine) and after it has been absorbed is degraded into
heat; during the process of degradation, the energy passes
through various forms. Now it is conceivable that the distri-
bution of the various kinds of vibration of which the degrading
energy is composed will depend in certain cases largely on
the presence in the system of even small quantities of foreign
bodies. A difference in the rate of chemical change might
clearly be expected as a result of a marked difference in the
character of the energy through which the light passes as it is
degraded into heat. We shall see below how far this view has
been confirmed by subsequent discoveries.

A statement had been made many years before this explana-
tion of the facts was put forward and had remained uncontested,
concerning the influence of the proportions of chlorine and
hydrogen on the rate of interaction of the gases, which, if true,
would have necessitated a profound modification, possibly a
complete abandonment, of our hypothesis. It had been an-
nounced, both by Draper and by Bunsen and Roscoe, that the
most sensitive mixture was one composed of exactly equivalent
proportions of the two gases, a slight excess of either having the
effect of reducing very appreciably the responsiveness of the
mixture to light. Bunsen and Roscoe assert that an excess of
three parts of hydrogen in a thousand reduces the rate of inter-
action from 100 to 37*8 and that one part of chlorine in a
hundred reduces it from 100 to 60. This effect required re-
investigation, especially as we suspected that there was a source
of error in Bunsen and Roscoe's experiment. Our experiments
were at first unsuccessful, owing no doubt to the circumstance
that the chlorine and hydrogen used to dilute the mixture con-
tained impurities. An appreciable retardation in the rate of
formation of hydrogen chloride was brought about by the
addition of a small quantity of either constituent to the electro-
lytic gas but its magnitude was variable. It was only after a
method had been devised for the preparation of chlorine and
hydrogen quite uncontaminated with destructible inhibitive |
impurity and containing very little oxygen that the experiments
furnished consistent results. These results demonstrated con-
* fourn. Chem, Soc. 1906, 89, 1433.

CONDITIONS OF CHEMICAL CHANGE 75

clusively that the addition of a small volume either of hydrogen
or of chlorine to a mixture of chlorine and hydrogen in equiva-
lent amounts did not appreciably affect the sensitiveness of the
mixture.^ It may here be mentioned that the hydrogen used by
Bunsen and Roscoe to dilute the mixture was prepared by the
electrolysis of dilute sulphuric acid and probably contained
oxygen derived from the electrolyte.

As we have already seen, the power of retarding the photo-
chemical interaction of chlorine and hydrogen had been shown
to be a property of two substances, oxygen and nitrogen
chloride, the effect of the latter being incomparably greater than
that of the former. The question arose, Is the property com-
mon in some degree to all substances or is it limited to a
special class of gases and vapours related in some unknown way
to chlorine ? To answer this question, the effect of adding
small amounts of a large number of volatile substances to
electrolytic gas had to be investigated. Accordingly an ap-
paratus was devised by means of which a measured volume of
the gases to be tested could be introduced into the insolation
vessel of an actinometer which contained a sensitive mixture of
chlorine and hydrogen. A series of experiments disclosed the
fact that the inhibitors belong to a special class of substances
and that substances outside this class exert an inappreciable
influence on the rate of interaction. Moreover, all the sub-
stances which were proved to retard the action at all were also
shown to be capable of exerting an inhibitive influence of
surprising magnitude. The inhibitors discovered were nitric
oxide, chlorine peroxide and ozone.^ In the case of nitric
oxide, it is not certain whether the true inhibitor is nitrosyl
chloride or peroxide of nitrogen. On entering the actinometer,
the nitric oxide would be converted almost immediately into
nitrosyl chloride but this compound would be acted upon,
perhaps very rapidly, by the water vapour present and con-
verted into nitrogen peroxide. Nitrosyl chloride undoubtedly
retards the interaction of dried chlorine and carbon monoxide ;
but it is doubtful if it can exist more than a short length of time
in the presence of moisture. It is not improbable, therefore,
that both nitrosyl chloride and nitrogen peroxide prevent the
interaction of chlorine and hydrogen. As might have been

^ Chapman and MacMahon, Trans. Cheni. Soc. 1909, 95, 135.
' Ibid.^ Trans, Chem, Soc. 1909, 95, 17 17, and 1 910, 97, 845.

^6 SCIENCE PROGRESS

predicted, the gaseous products of interaction of nitric oxide
and chlorine were gradually dissolved by the water in the
actinometer, so that the effect of adding the nitric oxide dis-
appeared after several days, even when the insolation vessel
was not exposed to light. In this respect, nitric oxide differs
in its behaviour from nitrogen chloride, which will remain for
months in the presence of moist chlorine and hydrogen and only
decomposes at an appreciable rate at a higher temperature or
under the influence of light. An idea of the magnitude of the
effect of nitric oxide can be gained from the following experi-
ment. A measure of nitric oxide, equal to -^js of the total
volume of the mixed gases, was admitted to the insolation
vessel : the mixture was exposed to the light of a glow lamp
during half an hour, in which period there was no detectable
movement of the index. If the original mixture had been
exposed to the light during the same length of time, about one-
third of the electrolytic gas would have been converted into
hydrogen chloride. After the illumination of half an hour,
the mixture was allowed to remain in the dark during two and a
half hours and then re-exposed to light ; during twenty-five
minutes there was no interaction. The actinometer was then
left during thirteen hours in the dark; on exposure to light
there was an instantaneous formation of hydrogen chloride.
The movement of the index was at first slow but it gradually
increased until the sensitiveness of the mixture was almost as
great as that observed before the nitric oxide had been added.

The inhibitory effects of chlorine dioxide and of ozone are
comparable with that of the product of interaction of chlorine
and nitric oxide. Even in the dark, the ozone completely dis-
appears after a few hours, owing to its extreme instability in
the presence of chlorine. The oxygen from the decomposition
of the ozone of course reduces the sensitiveness of the mixture
of chlorine and hydrogen but is not capable, like ozone, of
almost, if not completely, preventing the formation of hydrogen
chloride. The destruction of the ozone appears to take place
more rapidly in the light than in the dark.

The known inhibitors, therefore, are oxygen, nitrogen
chloride, nitrosyl chloride or nitrogen peroxide, chlorine peroxide
and ozone. They are all oxidising substances with moderately
unstable molecules, the one with the most stable molecule,
namely oxygen, being by far the weakest inhibitor. Chemically

CONDITIONS OF CHEMICAL CHANGE 77

inert substances such as carbon dioxide and nitrogen are in-
capable of reducing the rate of the photochemical process nor
has any reducing substance been discovered which possesses
inhibitory properties.

Chlorine monoxide and nitrous oxide, though oxidising
agents, exert no influence on the change. That chlorine
monoxide should be incapable of modifying the rate of inter-
action of moist chlorine and hydrogen is not astonishing, as
moist chlorine gas almost certainly contains a small proportion
of the lower oxide of chlorine : a solution of chlorine in water
consists largely of hypochlorous acid and it would be surprising
if the vapour of the latter substance were not to some extent
dissociated into chlorine monoxide and water vapour.^

Nitrous oxide, although usually classified as an oxidising
agent, since it supports combustion, is probably incapable of
parting with its oxygen at the ordinary temperature. There is,
in fact, reason to suppose that the molecules of this gas are so
stable that it may be regarded as an inert substance except at
elevated temperatures.

Oxygen, ozone, nitrogen chloride and nitrosyl chloride also
retard the interaction of chlorine and carbon monoxide, the
effect of the nitrosyl chloride being in this case permanent,
since it is not destroyed by light and no water is present to
effect its removal. Luther and Goldberg have shown that
oxygen retards the interaction of chlorine and benzene ; and in
a research which has not yet been published, Mr. R. Atkin has
found that some of the other substances which retard the inter-
action of chlorine and hydrogen act inhibitively towards the
union of chlorine and benzene. Each known inhibitor appears
to be capable of exerting a retarding influence on all photo-
chemical actions in which chlorine takes part.

We may here draw the attention of the reader to a remark-

' Either chlorine monoxide or hypochlorous acid may be an intermediate
product in the formation of hydrogen chloride from moist chlorine and hydrogen.
The course of the interaction would then be represented by the equations :

CI2 + H2O = HCl + HCIO (instantaneous)
2HCIO + H2 « 2H2O + HCl (photochemical)

The circumstance that an increase in the partial pressure ot the hypochlorous
acid makes no difference to the rate at which hydrogen chloride is produced can-
not at present be regarded as a valid objection to this view, as it is not improbable
that the rate of a photochemical change is regulated almost entirely by the rate
at which the light is absorbed and degraded.

78 SCIENCE PROGRESS

able parallelism (already indicated by F. H. Gee and the writer)
between the phenomenon of photochemical inhibition and that
of resonance inv^estigated during recent years by R. W. Wood.
Gee and the writer^ comment on this coincidence in the follow-
ing terms :

** Concerning the mechanism of the photochemical changes
under consideration, our own view is briefly this. Chlorine,
when it is absorbing light, preserves, for a time, the transformed
light energy in efficient forms which are gradually changed and
finally become the ordinary heat energy of the system, the rate
of degradation being considerably greater in the presence of
certain impurities. This efficient energy confers on the gas the
property of reacting with other substances for which it possesses
an affinity and therefore the presence of those impurities
which hasten the degradation of energy is a circumstance that
can only result in a reduction in the rate of a possible photo-
chemical change.

" It might be urged that if efficient energy is accumulated in
the chlorine in the manner assumed and that if consequently
the light is not instantly degraded to the state in which it
exists in the unilluminated system at the same temperature, it
ought to be possible to demonstrate the existence of this energy
in the illuminated gas by some physical means. The work of
R. W. Wood on the resonance spectra of the elements would
appear to have a direct bearing on this aspect of the question.
Five years ago it was shown by this investigator that iodine —
an element allied to chlorine — in the state of vapour emits a
green light when the rays from an arc-lamp act on it and that in
the presence of small quantities of oxygen the fluorescent light
is considerably reduced in intensity. At that time an unsuccess-
ful attempt was made to show that chlorine would fluoresce
under similar conditions. Quite recently Wood has returned to
the subject ^ and his latest results are such as to strengthen the
conviction that there is a close relationship between the pheno-
mena investigated by him and those observed in the study of
photochemistry. He has now shown that, when the pressure
IS sufficiently low, bromine vapour can be made to fluoresce,
a fact which very considerably increases the probability that
chlorine, exposed to light rays, will ultimately be shown to be
capable of retaining the absorbed energy in an efficient form for
a sufficient length of time to give rise to the phenomenon of
fluorescence. What is still more significant is the influence of
impurities on the fluorescence of iodine vapour. When the
vapour is excited by monochromatic light — the green light of

* Trans. Chem, Soc. 191 1, 99, 1727.

' Phil. Mag. 191 1 [vi], 21, 261, 309 and 314.

CONDITIONS OF CHEMICAL CHANGE 79

mercury — and the fluorescent light is analysed, it has been
found to consist of a number of lines, designated by Wood a
resonance spectrum. The line spectrum becomes a band
spectrum when helium is present in the vapour and at the same
time the proportion of light in the red to that in the green is
increased. The helium transforms and simultaneously degrades
the energy. Wood also finds that after the iodine vapour has
been mixed with the electro-negative gases chlorine or oxygen,
the degradation is so rapid that the fluorescence can no longer
be made manifest. Now all the gases which retard or prevent
the interaction of chlorine and hydrogen are likewise electro-
negative in character. This close coincidence would be most
remarkable if merely fortuitous but if, as we are disposed to
think, it arises from a causal connexion between the two classes
of phenomena, it could scarcely be disputed that it does afford
strong presumptive evidence in favour of the view that photo-
chemical inhibition results from the property possessed by the
inhibitor of degrading the energy essential to the progress ot
the chemical change. The fact (for which this communication
contains evidence) that the gases which behave as inhibitors
towards the action between chlorine and carbon monoxide are
also inhibitors in the case of the interaction of chlorine and
hydrogen, lends further support to the same view."

A direct and obvious consequence of the views that we
hold on the mode in which light brings about a chemical
transformation and on the nature of the influence of certain
impurities in modifying the action of the light is that the
impurities in question should not diminish the rate of the same
chemical change when the action is promoted by merely
elevating the temperature and the system is in thermal
equilibrium with all the surrounding objects from which it can
receive radiant energy. To put this conclusion to the test of
experiment, the interaction of chlorine and carbon monoxide
was the most suitable and nitrosyl chloride appeared to be
the best inhibitor, as it is capable of almost entirely preventing
the photochemical action but is not destroyed by light and
is stable at the temperature at which the thermal change
proceeds with a moderate velocity. An apparatus was con-
structed in which a mixture of equal volumes of chlorine and
carbon monoxide, enclosed in a glass bulb, could be kept at a
constant high temperature in an electric furnace and at the
same time exposed to light, the velocity of combination being
measured in the usual manner by the rate of contraction of
the contained gases. With the aid of this apparatus, it was

8o SCIENCE PROGRESS

demonstrated that nitrosyl chloride had no influence on the
thermal interaction of chlorine and carbon monoxide but that
at high, as well as low, temperatures, it reduced to a negligible
value the responsiveness of the mixture to light. The kind
of chemical inhibition under discussion is therefore essentially
and exclusively a photo-phenomenon. If a substance owed
its effectiveness as an inhibitor to its property of combining
with an unknown catalyst, instead of to its capacity to modify
and degrade the vibrational energy of the system, then we
should expect it to retard the thermochemical as well as the
photochemical change.

We shall now pass on to the consideration of the bearing
on the theory of the relation which has been found to subsist
between the partial pressure of the oxygen contained in a
mixture of chlorine and hydrogen and the sensitiveness of the
mixture to light. It has been shown that if the proportion
of oxygen be small, the sensitiveness {i.e. the velocity of
formation of hydrogen chloride for constant intensity of
illumination) is almost inversely proportional to the amount
of oxygen present in a given volume.^ This result is in
accordance with the assumptions that the degradation of the
vibrational energy which causes the interaction of the chlorine
and hydrogen is entirely effected by the oxygen and that the
rate of degradation is proportional to the concentration of the
oxygen. An interesting and obvious deduction from the
experimental result just stated is that if the relation continue
to hold for infinitely small concentrations of oxygen, a mixture
of chlorine and hydrogen entirely deprived of oxygen would
be infinitely sensitive. It has recently been shown that the
same relation does not hold between the sensitiveness of a
mixture of carbon monoxide and chlorine and the content
of oxygen if the value of the concentration of the oxygen be
large ; ^ when the partial pressure of the oxygen is relatively'
great, the doubling of the concentration has very little effect
on the sensitiveness of the mixture; thus, in the case of i
mixture which contained 25 per cent, of oxygen the sensitive
ness was 0745, whereas in one which contained 50 per cent, o ^
oxygen (the concentration of the chlorine and carbon monoxide
being the same) the sensitiveness was 0733. This resul

* Chapman, MacMahon, Trans. Chem. Soc. 1909, 95, 960.

* Chapman and Gee, Trans. Chem. Soc. 191 1, 99, 1726.

CONDITIONS OF CHEMICAL CHANGE 8i

points to the conclusion that a certain small proportion ot
the effective vibrational energy is not modified by the oxygen
molecules. For lower concentrations of oxygen the relation
found to hold for mixtures of chlorine, hydrogen and variable
small amounts of oxygen is approximated to. It would appear
that, as a first approximation, the sensitiveness of a mixture of
chlorine and carbon monoxide (and possibly also of a mixture
of chlorine and hydrogen) containing oxygen at different partial
pressures is given by the formula 5 = ^4- Bj[_0'], in which
A and B are constants and S and [O] are the sensitiveness and
concentration of oxygen respectively. If [O] be small, S is
so large that in comparison A becomes negligible and the

relation S = y) holds within the limits of experimental error;

but if [O] be large, S becomes almost equal to A. Further
experiments on the retardation of the photochemical interaction
of chlorine and hydrogen by oxygen are now in progress and
an attempt is being made to prepare chlorine and hydrogen
uncontaminated with oxygen.

It will be seen that some advance has been made in eluci-
dating the nature of the process which takes place when
chlorine and hydrogen or carbon monoxide interact under the
influence of light ; but what is of equal importance is the fact
that we are now in possession of sufficient information to
enable us to investigate, with reasonable hope of obtaining
results in which confidence can be placed, the important
question of the effect of the concentration of the interacting
substances on the rate of the chemical process.

A number of investigations on the displacement of equilibria
by the agency of light have been carried out during recent
years. A description of these has been omitted purposely from
the present article, our knowledge of the quantitative laws of
photochemistry, in the opinion of the writer, being at present
too vague and inexact to admit of the results of these re-
searches being discussed profitably.

In conclusion reference may be made to some of the effects
of ultraviolet light and the cathode rays. Ultraviolet light is
a much more efficient agent in promoting chemical changes
than visible light. Under its influence chemical transforma-
tions will proceed in colourless gases at an appreciable rate.
Light of short wave length owes its high efficiency to two
6

82 SCIENCE PROGRESS

causes — firstly, to the ease with which it is absorbed by nearly
all substances ; secondly, to the circumstance that being of
higher refrangibility a larger proportion of its energy is avail-
able for the performance of work.

In 1894 Ph. Lenard ^ showed that cathode rays which had
penetrated an aluminium window in a vacuum tube produced
ozone in the air through which they passed. Whether the
formation of ozone was due directly to the cathode rays or
indirectly to the ultraviolet light produced by the passage of
the cathode rays through air is doubtful. Lenard was unable
to detect any other chemical changes induced by the action of
this form of energy; electrolytic gas did not explode, carbon
disulphide did not burn, hydrogen sulphide was unchanged
and nitrogen and hydrogen did not interact when subjected to
the rays.

Lenard ^ also investigated somewhat exhaustively the effects
of ultraviolet light on gases. He showed, firstly, that under
the influence of light gases became conducting ; secondly, that
condensation nuclei were produced ; thirdly, that in the case
of oxygen ozone was formed. These effects were brought about
in air by light of wave-length o'oooi4 to g'oooiq mm., that is, only
by the rays of highest refrangibility to which air is compara-
tively opaque. Hydrogen was more transparent to ultraviolet
light than air and accordingly was unaffected by light of greater
wave-length than o*oooi6 mm. To the most chemically active
rays, air at atmospheric pressure was more opaque than rock-
salt, fluorspar or quartz. It is important that this relative
opacity of air should be borne in mind in the construction of any
apparatus to be used in the examination of the chemical effects
of rays and that air spaces in the path of the rays should be
avoided.

Closely connected with the above-mentioned work of Lenard
is an interesting research by E. Warburg,^ in which the dis-
charge of electricity through oxygen from a point was investi-
gated. Under different conditions the amount of ozone pro-
duced was from 1,000 to 93 times greater than the amount
which would have been found had its production been due
entirely to electrolysis. From this fact the necessary con-

^ Amt. Physik. 1894, 61, 225.

» Ibid. 1900, 70, 486.

' Sitzu7igsber. K. Akad. Wiss. Berlm^ 1903? ion.

CONDITIONS OF CHEMICAL CHANGE 83

elusion was drawn that ozone produced in the path of the
electric discharge results from the action of ultraviolet light
and cathode rays on oxygen, a view which received further
support from the circumstance that the amount of ozone formed
in a given time was roughly proportional to the intensity of
the light.

E. Warburg and E. Regener ^ were the first to demonstrate
that ultraviolet light could induce other chemical changes
besides the conversion of oxygen into ozone. As a source of
ultraviolet light they employed an electric spark between
aluminium electrodes. With their apparatus 2*2 per cent, of
oxygen at atmospheric pressure could be converted into ozone.
They found that ammonia, nitric oxide and nitrous oxide were
readily decomposed by the light.

S. Chadwick and J. E. Ramsbottom and the writer have
shown that the ultraviolet light emitted by a quartz mercury
lamp will bring about the interaction of oxygen and hydrogen
or carbon monoxide and effect the decomposition of carbon
dioxide into carbon monoxide and oxygen. As might be ex-
pected, the presence of moisture has a very marked effect
both on the union of carbon monoxide and oxygen and on
the decomposition of carbon dioxide. Its accelerative influence
on the one change, the combination of the carbon monoxide
and oxygen, is so much greater than that on the reverse
change, the decomposition of carbon dioxide, that although
dry carbon dioxide is decomposed to the extent of 46 per cent,
at a low pressure by ultraviolet light, it is scarcely affected
by the same agency when it contains moisture. When a
carefully desiccated mixture of carbon monoxide and oxygen
and a similar mixture in a moist condition are submitted to
the action of ultraviolet light of the same intensity, the rate
of contraction is the same in both cases ; but the contraction
in the first case is due mainly to the formation of ozone,
whereas in the second it is caused principally by the pro-
duction of carbon dioxide. A. Holt ^ has obtained very similar
results by decomposing carbon dioxide at a low pressure by
the silent discharge ; but at a higher pressure the results he
obtained were different from those furnished by our experi-
ments with ultraviolet light. He believed that the chemical

^ Sitzungsber. K. Akad. Wiss. Berlin^ 1904, 1228.
* Trans. Chem. Soc. 1909, 95, 34.

84 SCIENCE PROGRESS

effects of the silent discharge through gases at a low pressure
is mainly due to ultraviolet light, whilst at higher pressures
other agencies such as the cathodic rays come more promi-
nently into play.

Thorough investigations ol the action of ultraviolet light
on a mixture of carbon monoxide and steam and on a mixture
of hydrogen and oxygen would most probably furnish results
of considerable interest, especially as it has been shown
recently by W. Wieland ^ that formic acid is produced in
appreciable quantity by the interaction of carbon monoxide
and steam under certain conditions and F. Fischer and M. Wolf ^
have found that a very high percentage of hydrogen peroxide
may be produced by the action of the silent discharge on a
mixture of hydrogen and oxygen.^

Description of Actinometer

Most of the experiments on the photochemical interaction
of chlorine and hydrogen described above can be performed
with the aid of the apparatus shown in the accompanying figure.
The hydrogen and chlorine are prepared by the electrolysis oi
concentrated chlorhydric acid contained in the large U-tube
on the left of the figure. The electrodes A and C, of graphite,
are fused into hard glass tubes which are ground into the
narrow ends a and 7 of the two limbs of the U-tube. The
circuit is closed by touching the tops of the two graphite sticks
with the copper wires which convey the current. The hydrogen
and chlorine generated by the electrolysis of the acid escape
through the capillary tubes fused into the necks of the two limbs
of the U-tube. By turning the three-way taps c and a into the
right positions either the hydrogen and chlorine can be per-
mitted to escape through the tubes :vand j or conducted through
the taps b and d into the actinometer. The apparatus therefore
may be used to furnish a mixture of chlorine and hydrogen
in equivalent proportions or to prepare either of the gases
separately. The bottom of the U-tube is filled with glass beads
to prevent the movement of the saturated solution of chlorine

^ Berichte^ 191 2, 45, 681. ^ Ibia. 191 1, 44, 2956.

^ Both of these important discoveries are in complete harmony with Armstrong's
views on combustion. He has, in fact, predicted that the production of formic
acid would be found to be an intermediate stage in the combustion of moist
carbon monoxide.

CONDITIONS OF CHEMICAL CHANGE

in the anode limb towards the cathode : if this precaution be
not taken, the hydrogen evolved at the cathode is contaminated
with a large proportion of chlorine.

The gases enter the insolation chamber P of the actinometer
and after passing through the index tube m escape through the
water contained in the reservoir H. The insolation vessel P
is immersed in a bath of water provided with a glass window
through which it can be illuminated. The water-bath is kept
at a constant temperature by means of a delicate thermo-
regulator.

When P is exposed to light, the hydrogen and chlorine it

lOr^

contains are converted into hydrogen chloride, which dissolves
very rapidly in the water present. The consequent reduction
in volume is measured by the movement of the water in the
index tube m (to which a scale is attached) towards the insolation
vessel. In order to keep the pressure in H constant, the tube n
is connected with a large bottle filled with air which is placed
in the same water-bath as the insolation vessel.

The graduated tube Q is used to add measured quantities
of liquid to the insolation vessel P. The liquid is drawn
through the tube to the left of the three-way tap e into Q ; and
e is then turned so as to communicate with the insolation
vessel only and a measured quantity of liquid is forced by
pressure exerted through the tap / into the insolation vessel.

Z6 SCIENCE PROGRESS

If it be desired to investigate the effect of a gas on the rate
at which chlorine and hydrogen interact, a given quantity
of the gas can be admitted to the insolation v^essel by the
following procedure : The three-way taps b and d are turned
so that the tube z communicates only with the tube w and a
current of the gas to be used is passed in at z and out at w]
when all the electrolytic gas in the capillary tube between b and
d has been displaced, the three-way taps are turned so that the
tubes z and w are closed and the cell and actinometer are brought
into direct communication ; the gas contained in the capillary
tube between b and d is then driven into the insolation vessel
by means of a current of electrolytic gas.

THE STRUCTURE OF METALS

By CECIL H. DESCH, D.Sc, Ph.D.

The study of the structure of metals in relation to their physical
and mechanical properties is of quite recent origin. Apart
from a few isolated observations by Hooke and Reaumur, the
first to use the microscope in investigating metals was
H. C. Sorby, the brilliant Sheffield amateur who was a pioneer
in so many departments of research. The method of preparing
and examining metallic specimens devised by Sorby in 1864 is
in all essential respects the same as that in general use at the
present time, notwithstanding the many important improvements
of detail introduced by later workers. His unwearied patience
and skill in applying the microscope to the study of iron and
steel were attended with remarkable results ; nevertheless, his
work passed almost without notice and nearly twenty years
elapsed before any general attention was given to the subject.
Since that time, the advance of microscopical metallography has
been rapid and continuous, in regard both to the number of
workers and to the methods of investigation and interpretation.
The subject of metallography is not confined to the study of
metals and alloys by means of the microscope but includes
investigation by thermal, electrical, mechanical and other
methods into which it is not proposed to enter now.^ Reference
must also be made to text-books for details of the technique of
preparing and examining sections, merely noticing that, owing
to their opacity, metals have always to be examined by reflected
light. The object of the present article is to describe some of
the more important conclusions already established concerning
the internal structure of the principal metals and alloys of
technical importance and the connexion between structure
and practical utility. Appreciation of the value of the

^ See, for example, W. Guertler, Metallographies 2 vols., now in course of
publication (Berlin : Gebr. Borntraeger), or C. H. Desch, Metallography {Londion. :
Longmans, Green & Co., 1910).

88 SCIENCE PROGRESS

microscopical method is no longer confined to investigators
in the fields of inorganic and physical chemistry but is becoming
general among manufacturers and users of metals, examination
by means of the microscope now forming an essential part of
the routine in a large and increasing number of metallurgical
and engineering works.

The structure of solid metals is, in the main, crystalline. Of
cast and slowly cooled or annealed metals this is probably
strictly true, whilst rolled, drawn or otherwise cold-worked
metals are built up of material which is only in part crystalline
and in part glassy or amorphous. This difference of structure
gives rise to important differences of properties between the two
materials and it will be convenient to consider metals and alloys
in the thoroughly crystalline state before passing on to the
modifications brought about by mechanical work.

Technically, metals (using the term in its widest sense, to
include alloys) may be divided into two classes, from the point
of view of structure, namely, those w^hich are homogeneous
throughout and those which are composed of two or more
distinct crystalline constituents. The first class includes the
pure metallic elements and also a much more numerous group of
alloys, whilst the second class includes all other alloys. The
manner in which crystallisation is eff*ected in all members of the
first class is essentially the same and a description of the
process may serve as an introduction to the general problem.

The passage of a metal from the liquid to the solid state, like
that of any other crystalline substance, does not take place
simultaneously throughout the mass but begins at certain
nuclei, the number and distribution of these depending on the
nature of the substance and on the conditions of cooling. The
number of nuclei is greater when the liquid is cooled con-
siderably below its freezing-point before solidification begins
than when undercooling is reduced to a minimum. It has been
suggested that the number is also dependent on the degree of
heating to which the liquid has been previously subjected but
there does not seem to be experimental justification for such a
view, which is one also that it is difficult to accept on theoretical
grounds. The chief determining factor is certainly the degree
of undercooling.

The nuclei having once appeared, the further deposition of
solid matter takes place around them as centres ; not, however,

THE STRUCTURE OF METALS 89

equally in all directions, even when the temperature is maintained
as uniform as possible. The growth of a crystal in a mass of
fused metal does not, as a rule, resemble the growth of a crystal
of chrome alum in an undisturbed solution. Instead of a
perfect or almost perfect octahedron being formed by the
gradual addition of layer to layer, so that the shape is pre-
served as the crystal increases in size, the accretion of solid
metal takes place principally along certain axes, a skeleton
or crystallite being formed. This behaviour is characteristic of
metals.

In the case of certain salts, according to O. Lehmann,i
the first visible mass surrounding the nucleus may be an
octahedron ; during the subsequent growth the added matter is
not deposited uniformly over the surfaces of the octahedron but
becomes attached chiefly at the solid angles, so that the particle
becomes star-shaped. Further growth at the now sharpened
angles accentuates the difference from an octahedron, the form
of which soon disappears, its place being taken by needle-like
prolongations of the axes. The effect has been satisfactorily
explained by Lehmann, in the cases examined by him, as being
due to the rate of growth exceeding that at which the super-
saturation or undercooling in the immediate neighbourhood
can be equalised b}^ diffusion or convection ; it is not clear that
the same explanation will serve for slowly crystallising molten
metals. Whatever the cause may be, the skeletal mode of
growth is more frequent in metals than the normal mode of
accretion by successive layers.

Before the prolongations of the axes attain to any great
length, secondary axes make their appearance, in the form
of transverse growths parallel with the other axes of the original
crystalline particle ; these are followed in turn by tertiary
axes and others of a higher order. The skeleton therefore
becomes more complex and more closely packed, approaching
more and more nearly to a compact mass. Given a sufficient
supply of liquid metal, the process of " filling up " continues
until the numerous axial growths are in perfect contact and
the mode of formation of the crystallite has ceased to be
apparent. If, however, the supply of liquid be restricted or
if the closing up of the outer parts of the crystallite be complete
before the inner part is solid, cavities may be left which afford
^ Molekularphysik^ i. 326 (Leipzig, 1884).

90 SCIENCE PROGRESS

an indication by their form and distribution of the original
axial arrangement.

The growth in length of the axes and consequently the
growth in volume of the crystallite is not limited by the develop-
ment of external crystal faces but simply by the interference
of neighbouring crystallites. The mass of solid metal is ulti-
mately composed of polyhedral "grains"; each of these
represents the growth about a single primary nucleus, whilst
the degree of uniformity of their dimensions is an indication
of the regularity of distribution of the nuclei. The grains are
the units of crystalline structure in a homogeneous metal or alloy.
Their boundaries appear as polygons in a plane section through
the solid metal.

If we consider the common case of molten metal cooling in
an ingot mould, it is evident that the temperature of the mass
will fall most rapidly at the outer surfaces. The first nuclei
therefore make their appearance in contact with the walls of
the mould before the layers at a greater depth are sufficiently
undercooled to allow solid matter to separate. In consequence
of this distribution of the nuclei, the first crystallites grow
inwards from the surface. If the conditions of cooling are
uniform, these crystallites are approximately equally spaced
and tend to grow as parallel, elongated, more or less prismatic
masses recalling to a botanist the form of the " palisade
parenchyma " of a leaf. In a small ingot or in one which has
cooled with extreme slowness, these parallel crystallites may
extend so far inwards as to meet in the middle, whilst in
larger ingots or under more usual conditions of cooling they
merely form an outer layer, the interior being made up of
smaller crystallites without parallel orientation.

The typical structure of an ingot of pure metal as seen in a
transverse section is, then, a number of irregular polygons, of
which the outermost are parallel to one another and perpen-
dicular to the faces of the ingot, whilst those in the interior are
of approximately equal size and are not developed in any chief
direction. Naturally, as there is no chemical difference between
any one part of the section and any other, the structure is not
seen in a section which has merely been cut and polished but
in order to reveal it etching with a corrosive agent is necessary.
Thus, for example, a surface of copper may be etched with
nitric acid. The copper is attacked and its surface is roughened.

THE STRUCTURE OF METALS 91

Under a high magnification the roughening is seen to be due to
the formation of very numerous *' etch-figures" or hollows of
geometrical outline ; the form of these serves to give informa-
tion as to the crystalline system to which the metal belongs.
Within any one grain, the arrangement of the etch-figures is
strictly parallel but the orientation varies from grain to grain,
the result being that when light falls on the etched surface it is
reflected at different angles by different grains, so that one may
appear light and another dark in the field of the microscope.
The boundaries of the grains thus become visible as boundaries
of light and shade. Another circumstance contributes to render
the structure visible. Etching takes place more rapidly at the
boundaries than elsewhere, so that after a short time the grains
are separated by grooves which become broader and deeper on
longer etching. The cause of this phenomenon is not quite
clear. Traces of impurity would tend to accumulate at the
bounding surfaces of the polyhedral grains and would be re-
moved by etching ; but the effect is produced in the most care-
fully purified metals. It is most probable that the acid acts with
diff'erent degrees of rapidity along different planes in the crystal
— the fact that etch-figures are formed, indeed, points to such
a conclusion — and the junction between two grains of different
orientation may thus give rise to a difference of electrolytic
potential which is small but sufficient to produce an increased
action at the boundary. The photograph of iron containing
only very small quantities of impurities (** American ingot iron,"
really a mild steel almost free from carbon) shown in fig. i is
a typical example of the structure obtained on casting a homo-
geneous metal. The etching has been so light that the surfaces
of the crystal grains have hardly been roughened and the
structure has only been rendered visible on account of the etch-
ing at the junctions of the grains producing a fine groove which
is visible as a dark boundary line.

If, instead of a single metal, the mass under examination be
an alloy, cases may occur in which the structure observed in a
slowly cooled ingot does not differ from that just described.
Yellow brass, containing 70 per cent, of copper and 30 per cent,
of zinc, is an example of such an alloy. The brass contains
only a single micrographic constituent, as the copper is capable
of retaining the whole of the zinc in a state of uniform ad-
mixture. Apparent homogeneity in each crystal grain is reached,

92 SCIENCE PROGRESS

however, only slowly ; in specimens which have been cooled
comparatively rapidly from the molten state, as under ordin-
ary casting conditions, a distinct structure is visible under the
microscope. A section of an ingot of brass of this composition
is shown in fig. 2. The irregularly polygonal boundaries of the
crystal grains are seen as before but the area within each grain,
instead of being entirely uniform, as in the ingot iron, is
marked with " dendritic " patterns which are evidently of the
nature of the crystal skeletons described previously. They are
visible in the brass, although invisible in the iron, because the
alloy freezes in a manner which is somewhat different from
the freezing of a pure metal. The first particles of solid which
crystallise from the molten alloy are relatively richer in copper
than the liquid and the subsequent accretions to the original
nuclei contain a diminishing proportion of copper. There is
thus a distinct difference of composition between the material ot
which the primary and secondary axes are composed and that
with which the gaps between the axes are filled up. If an
etching-agent be used which attacks the portions richest in zinc
most readily, the parts of each crystal grain which are in
contact with the boundary are most etched and appear dark,
whilst the central axes appear as light " cores." This cored
structure is characteristic of cast homogeneous materials, in-
cluding brass, gun-metal and many of the special engineering
alloys. Theory teaches us that equilibrium is only reached
when the composition of the mass is rendered uniform through-
out by diffusion of one of the constituents from places of high
to those of lower concentration. This diffusion, however, has
to take place in a solid the internal viscosity of which is very
great and the equalisation of composition is therefore a slow
process. Annealing the alloy at a sufficiently high tempera-
ture greatly facilitates diffusion and a specimen of the same
brass after thorough annealing exhibits a perfectly homogeneous
structure in which no cores are to be seen. Fig. 3 represents
the same specimen as fig. 2 after heating to redness during
several hours. The light and dark areas are of the same com-
position and differ only in orientation.

Mechanical work produces a great distortion of the crystal
grains in metals and alloys of the above class and the outlines
of the broken and distorted grains may be barely distinguishable
in a thoroughly worked metal. Annealing brings about a

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THE STRUCTURE OF METALS 93

recrystallisation of the deformed material and a return, in great
measure, to the original structure of the casting. The forma-
tion of new crystals in the worked material, like the original
process of solidification, sets in from distinct centres or nuclei
and spreads outwards until the crystalline growths from neigh-
bouring centres meet and interfere, giving rise to crystal grains
as in the original process of solidification but the complex
interlocking of boundaries, which is so conspicuous a feature
of many cast metals, is less usual after annealing and an
approach to simple rectilinear polygonal forms is noticeable in
most worked and annealed metals, especially when they have
been subjected to a high temperature. If the metal be worked
mechanically before annealing, the crystals that are produced
are not simple but frequently twinned, the repeated twinning
being similar in effect to that observed in felspars in rock
sections. Fig. 4 represents a rolled and annealed specimen of
German silver, a homogeneous mixture of copper, nickel and
zinc ; both the rectilinear boundaries of the crystals and the
repeated twinning planes are apparent.

Another class of alloys, although crystallising from the
molten state in the form of a homogeneous solid, as in the
metals just described, undergoes such further changes in the
solid state that an entirely new structure is produced. To this
class belong most of the varieties of steel. All steels solidify
in the first instance in the form of crystal grains of uniform
composition, if certain minor impurities be, for the moment,
neglected. It is, however, rare that such a structure persists
during the process of cooling down to the ordinary tempera-
ture. Manganese steel, containing 13 per cent, of manganese
and I per cent, of carbon, which finds such important applica-
tions, on account of its resistance to abrasion, in crushing-
machinery, tramway crossings, etc., is an example of a steel
which retains its polygonal structure permanently ; but this is
quite an exceptional case. Ordinary carbon steels, from the
softest structural material to the hardest varieties of tool steel,
have undergone transformation to a greater or less extent, so
that the original polygonal grains have been more or less
resolved into a complex structure the principal constituents
of which are ferrite (iron alone or uniformly associated with
small quantities of silicon, manganese, phosphorus and other
elements but not carbon) and iron carbide or cementite^ FcgC.

94 SCIENCE PROGRESS

In a typical mild steel the mass of the metal is composed of
grains of ferrite between which lie patches of a material which
appears homogeneous under a low magnification but is really
an intimate mixture of ferrite and cementite. Fig. 5 represents
a section of a mild steel plate cut in the direction of rolling
and etched to show the structure. The arrangement of the
grains of ferrite is seen to follow the direction of rolling, whilst
the intervening patches of conglomerate are not sufficiently
magnified to reveal their internal structure. The manner in
which the pearlite and cementite are intermixed in this con-
glomerate varies with the heat-treatment to which the steel
is subjected. In steels quenched from a high temperature, the
carbide is in a state of ultramicroscopic subdivision termed
** emulsified carbide" by Arnold. It then becomes black on
etching and is commonly called troostite. If the cooling be less
rapid, the carbide becomes coarser and a granular conglomerate,
termed sorbite, is obtained. This condition is favourable to
toughness and is preferred in steel rails. Thoroughly annealed
steels contain the iron and carbide in a very finely laminated
form, like the surface of some diatoms or of mother-of-pearl
and hence termed pearlite. This, although generally regarded
as the typical condition of the conglomerate, is not physically
stable and if the annealing process be prolonged, the laminae
break up, the cementite becomes gathered into relatively coarse
granules, segregation continuing until the original finely divided
mixture has disappeared entirely and the steel no longer con-
tains any constituent but ferrite and isolated masses of cementite.
As each of these structures corresponds with a distinct set ol
physical and mechanical properties, the importance of the
microscopical examination of steel used as a structural material
is obvious.

A further example of the breaking-up of a homogeneous
solid during cooling may be taken from the alloys of copper
with zinc containing about 40 per cent, of the latter metal, to
which Muntz-metal and manganese bronze ^ belong. Like the

^ The necessity of a more systematic nomenclature of alloys is clearly seen
in this instance. Bronze is historically and in general usage an alloy of copper
and tin. Manganese bronze, however, is an alloy of copper and zinc to which
a minute quantity of manganese has been added to remove oxygen. Manganese
may be absent from the finished metal. Such absurdities are frequent in the
current technical nomenclature of alloys.

THE STRUCTURE OF METALS 95

lower brasses, these alloys solidify in the first place in the
form of a homogeneous mass of crystals but as the tempera-
ture falls changes take place in the solid, much as in the case
of an ordinary solution, new materials separating out. In this
instance the separated material is itself a homogeneous solid
containing relatively more copper than the original crystals.
By a convention which has been generally adopted in the case
of this and similar alloys, the new crystals are designated
the a- constituent, the prefix ^ being assigned to the material
of the original crystals and to that part of the ** mother
crystals" which remains after complete separation of the
excess. Alloys of this class have therefore a duplex structure,
the a-crystals being outlined on a (fig. 6) background of /3.
As the proportion of zinc in the alloys is increased, so the
proportion of a-crystals diminishes, until alloys containing
nearly 50 per cent, of zinc consist of homogeneous crystals of
the /^-constituent, which may be distinguished from the a-
crystals of which 70 : 30 brass is composed by its different
behaviour towards etching-agents and by the absence of the
cores which are so characteristic of brass in the cast con-
dition. A further increase of the proportion of zinc beyond
50 per cent, brings about the appearance of small bluish-white
crystals of the 7-constituent, which composes the whole alloy
when 61 per cent, of zinc is present. This substance is un-
doubtedly a definite compound, Cu2 Zug. It is exceedingly brittle
and its presence, even in small quantities, is fatal to the good
mechanical properties of the alloys. The proportion of zinc
which may be alloyed usefully with copper is therefore limited.

Each of these constituents has its special characteristics.
The a-crystals are remarkably tough and may be subjected to
very severe mechanical deformation without cracking. This
property reaches its maximum in the 70 : 30 alloy, which is
frequently known as " cartridge brass " from its use in the
manufacture of cartridge-cases in which process it is very
severely deformed by forcing through dies. The /5-crystals
are less tough and ductile but have a higher tensile strength ;
they are malleable at a high temperature, a property which is
not inherent in the alloys richer in copper. The presence
of a small quantity of the /3-form is essential if the alloy is
to be rolled while hot.

Both the a- and the 7-crystals are reincorporated to a very

96 SCIENCE PROGRESS

considerable extent by the /3-constituent when the temperature is
raised. By heating and rapidly quenching, therefore, most ol
the alloys of this series having a duplex structure may be
rendered homogeneous. Such treatment increases the tensile
strength of the alloys in question at the sacrifice of much of
their ductility. The quenched alloys are in a more or less
unstable condition and the duplex structure is restored by
annealing at a moderate temperature.

Aluminium forms alloys with copper which, in some cases,
resemble in a very striking manner those containing zinc but a
smaller quantity of aluminium is required to produce the effect.
Thus the proportions of the a- and /3-constituents in an alloy of
60 per cent. Cu and 40 per cent. Zn are almost the same as in an
alloy of 90 per cent, of copper and 10 per cent, of aluminium.
The latter is an alloy of very high technical value and is well
known under the name of aluminium bronze. As in the case
of the zinc alloys the 7-constituent, which appears when the
aluminium exceeds 12 per cent., is brittle and its presence is
fatal to the mechanical properties of the alloy.

The true bronzes are alloys of copper with tin to which
smaller quantities of other elements are very frequently added.
The a-constituent richest in copper resembles in all essential
properties the corresponding alloys with zinc and with
aluminium. Most technical tin bronzes, however, contain a
small proportion of the /3-constituent at high temperatures ; as
the temperature falls the /S-crystals become unstable and are re-
solved into a characteristic complex of finely divided a and a hard,
brilliantly white substance, the 8-constituent. Small areas of this
complex occur in many bronzes and form a large part of the hard
bronzes used for bearings. One of these areas is shown in fig. 7.

The resolution of the yS-constituent of tin bronzes into a
complex, which takes place on cooling below 500° and proceeds
rapidly to completion, has a remarkable parallel in the alloys of
copper and zinc, it having been shown quite recently ^ that the
/5-constituent in this case also is unstable when cooled below
470°, being resolved into a complex of a and 7. The main
difference lies in the velocity of transformation and of recrystal-
lisation. Even when the development of heat during cooling
has indicated that resolution into two constituents has taken
place, the products remain for some time in a state of such
* H. C. H. Carpenter,/. Inst. Metals^ 1912, 7, 70.

THE STRUCTURE OF METALS 97

extremely fine division as to be at the limits of microscopical
vision and prolonged annealing is necessary in order that
segregation may proceed far enough to give rise to a visibly
duplex structure. This interesting discovery has thrown much
light on the changes of properties undergone by these alloys
during heat-treatment and serves further to call attention to the
fact that the simplicity of constitution of some of our best known
alloys is only apparent and that subjection to long annealing
processes at a comparatively low temperature may produce very
far-reaching modifications of structure. In view of the extensive
use of alloys for engineering purposes in positions in which
they are exposed to the prolonged influence of temperatures
above that of the atmosphere, the technical importance of this
and similar observations is obvious.

A large proportion of the alloys in general use thus fall into
one of two classes from the point of view of crystalline structure.
The first class comprises alloys in which crystals of a single
type compose the whole of the alloy, which has thus, at least in
the annealed condition, the structure of a pure metal. This
class includes the true brasses, the alloys of copper with small
quantities of nickel, arsenic, manganese, iron and other metals,
used whenever toughness and resistance to high temperatures
are required, as in the fire-boxes of locomotives, the lower tin
bronzes, etc., Monel-metal (an alloy of copper and nickel, with
the latter in excess), German silver, manganese steel, nickel
steel and many other alloys, including the standard gold and
silver used for coinage. The second class, in which two types
of crystalline material are necessarily present as structural
constituents, includes Muntz-metal and manganese bronze, the
principal aluminium bronzes, naval brass and other similar
alloys. In most gun-metals and in bearing-bronzes, the one
material during coohng undergoes resolution into other con-
stituents and is therefore present as a complex. This is also
the case with carbon steels.

The class of alloys so frequently encountered in laboratory
investigations, in which the primary crystals are surrounded by
an eutectic alloy ,^ is relatively ol much less importance in technical

^ An eutectic alloy is an intimate mixture of two or more kinds of crystal
characterised by the fact that its melting point is lower than that of alloys
containing more of either the one or the other constituent and that it solidifies
at a definite temperature.

98 SCIENCE PROGRESS

practice. The most familiar technical examples occur amongst
the "white metals" used for the lining of bearings. The
essential qualities of such an alloy are sufficient hardness to
resist the rubbing action of the shaft and sufficient plasticity to
enable the lining to become adapted to the rubbing surface and
thus to correct any slight error of alignment or want of accuracy
in the shaping of the bearing originally present. These two
requirements are best met by an alloy in which primary crystals
of some hard material are embedded in a comparatively soft and
plastic ground-mass. The hard crystals are generally either of
antimony or of a compound ol tin and antimony, SnSb, which
forms very well-defined crystals of apparently cubical shape.
The plastic mass is an eutectic, generally, although not always,
containing lead as one of its components. Bearing-metals
usually contain more than two metals and a hard and brittle
compound of copper and tin is frequently present in small
quantities.

A different plan is adopted in the manufacture of *' plastic
bronzes," which also find considerable application as bearing-
metals. In these alloys copper hardened by the addition ot
either nickel or sulphur or of both forms a sponge the inter-
stices of which are filled with lead. Some tin is added to
produce partial miscibility in the liquid state but even with
this addition the alloy needs to be cast under specified
conditions to avoid separation into two layers. Crystalline
outlines are entirely absent from the micro-sections and the
structure is merely that of a meshwork of the harder metal
holding globules of the soft lead alloy. Such emulsion-like
solids are quite unmistakable when seen under the microscope.

Non-metallic elements only enter into consideration as
essential structural constituents in a few cases. The most
familiar of these is graphite in grey cast-iron or pig-iron. The
graphite is seen in the form of thin plates, usually curved and
appearing as lines where cut by the plane of the section. The
size of the plates and their distribution through the iron give
much information as to the mechanical properties that may be
expected from the material. A very finely divided variety of
graphite is met with in malleable castings as a product of de-
composition of the carbide. It is often regarded as amorphous
carbon but has been shown to be chemically identical with
graphite. Phosphorus is not visible in steel or in ordinary

THE STRUCTURE OF METALS 99

phosphor-bronze, the minute quantity which is actually present
being completely masked but ordinary grey cast-iron contains
an appreciable quantity of phosphorus in the form of iron
phosphide, FcaP, which is distinctly visible as a brilliantly white
constituent disposed in characteristic reticulated patterns which
represent the eutectic alloy that is the last portion of the cast-
iron to solidify on cooling from the molten state. Other non-
metallic elements occur principally as impurities and are there-
fore considered below.

The types briefly enumerated above comprise nearly all the
principal metals and alloys encountered in engineering practice,
with the exception of white pig-iron which has an eutectic
structure peculiar to itself — and of hardened steels — the complica-
tions of which are too intricate for discussion within the limits
of a short article. The variety in this instance is due to the
fact that hardened steels are not in a condition of chemical and
physical equilibrium and that many stages may be recognised in
the return to the stable condition. It is possible by examining
a polished and etched surface of such a steel to form an accurate
judgment of the heat-treatment to which the specimen has been
subjected. The newer " high-speed " tool steels, containing
chromium and tungsten or molybdenum as essential constitu-
ents, have structures differing considerably from those of carbon
steels and present difficulties of interpretation that have not yet
been overcome.

A metal or alloy which has been subjected to heat treat-
ment bears in its internal structure a record of its immediate
history and the interpretation of the record is one of the most
important applications of metallography to technical practice.
As an example, the influence of annealing on the microscopic
structure of mild steel may be considered. The temperature at
which annealing has taken place may be inferred, other things
being equal, from the average size of the crystal grains. It has
been found ^ that the rate of growth of the ferrite grains is a
maximum at slightly above 700°, growth being less rapid either
above or below that temperature. Prolonged annealing at 700°
produces an extremely coarse grain. When the proportion of
carbon is higher, as in the rail steel, containing 0*40 per cent, of
carbon, the ferrite forms *' cells," filled with sorbite or pearlite.

^ J. E. Stead, /. Iron and Steel Inst. 1898, i. 145 ; A. Joisten, Metallurgie
1910, 7, 456.

100 SCIENCE PROGRESS

The size of these cells is a measure of the heat-treatment which
the steel has undergone. This is explained by the behaviour of
such steel when heated above the recalescence point of 690°.
At a high temperature, the iron-carbide complex (sorbite or
pearlite) acts as a solvent for the ferrite of which the cell-walls
are composed ; the crystal grains thus produced grow, like the
grains of pure iron, during the annealing process. When the
steel is again cooled, the excess of ferrite is no longer held in a
homogeneous condition and becomes visible in the first instance
at the boundaries of the grains. The size of the cells is an
indication of the size of the crystal grains present at a high
temperature and is therefore either a measure of the tempera-
ture at which the steel has been annealed or, if that be known,
of the time during which the metal has been exposed to that
temperature. Further, the thickness of the cell-walls is an
indication of the rate of cooling, as the first deposition of
ferrite takes place at the boundaries of the original grains and
any ferrite subsequently deposited must appear in scattered
granules within the cell if cooling be rapid but become attached
to the cell-wall as an internal thickening if sufficient time be
given to allow of free diffusion through the solid mass ; a thin
cell-wall is therefore evidence of rapid cooling.^ If the com-
position of the steel and especially its carbon-content be known,
an inspection of the micro-sections gives a complete knowledge
of the heat-treatment to which the steel has been subjected,
knowledge which is ot the utmost value when rails are con-
cerned, the relationship between heat-treatment and the physical
and mechanical properties on which the life of the rail depends
being now well known.

The deposition of any substance present in excess during
the cooling of a homogeneous solid along the boundaries of the
crystal grains is not peculiar to steel. It is also observed in
alloys of the Muntz-metal class. An alloy of this kind, heated
to such a temperature as to be wholly or almost wholly con-
verted into the yS-constituent, has crystal grains of a size which
depends both on the time and temperature of annealing.
During cooling the a-constituent crystallises at the boundaries
of the grains and the extent to which thickening of the cell-walls
takes place by diffusion depends on the rate of cooling.

The last point to be considered in the present article is the
' See H. M. Howe, Internat. Zeiisck. Metallographies 191 2, 2, 13.

THE STRUCTURE OF METALS loi

influence of impurities on the structure. The most easily
recognised impurities are those which are not to be regarded
as true constituents of the alloys but rather as foreign matter
mechanically entangled. Dross in badly made brass is of this
character and some other metallic oxides often occur as
mechanical impurities. Thus molten aluminium becomes
covered with a peculiarly tough and resistant film or pellicle
of alumina which is not readily eliminated in the preparation
of aluminium alloys by fusion. Remelting is frequently
necessary to remove these films. Crystalline stannic oxide
remains obstinately entangled in molten tin bronze which has
not been sufficiently protected against oxidation and naturally
is a cause of brittleness. A slightly different position is occupied
by the slag and sulphides found in iron and steel, the impurities
in this case being liquid instead of solid at the moment of
entanglement in the molten metal. Masses of silicate slag,
drawn out into fibres in the direction of rolling, are char-
acteristic of wrought-iron bars, whilst oval globules of grey
manganese sulphide are found in mild steel, as in the middle
of the field in fig. 5. In the absence of manganese, however,
the sulphur in steel is present as ferrous sulphide, which has
much less tendency to agglomerate into such oval masses and
is commonly met with in the far more dangerous form of
thin films separating neighbouring crystal grains. Steel
containing ferrous sulphide is invariably red-short so that
microscopic cracks are developed in it during rolling.

Passing now to those impurities which are truly alloyed
with the metals under examination it is evident that elements
which become associated homogeneously with one or the
other of the primary constituents cannot be immediately
detected by the microscopical method, although occasionally
their presence may bring about some perceptible change in
the character of the crystals. For example, manganese is
miscible with iron and manganese carbide with iron carbide,
so that the structure of a mild steel is unchanged by the
introduction of manganese. On the other hand, when the
manganese is very much increased in quantity, as in certain
rich varieties of pig-iron, the increased coarseness of the
carbide crystals due to its presence gives a characteristic
aspect, both to the etched sections and to the fractured surface,
although no new structural constituent has made its appearance.

102 SCIENCE PROGRESS

If an impurity be present as a distinct constituent, its
detection by means of the microscope is not difficult. The
case of copper may be taken as an example. Highly purified
copper, such as is used for electrical purposes, exhibits the
typical structure of a pure metal. If, as is usually the case,
it has been rolled and subsequently annealed, the crystals
are polygonal with almost straight boundaries and show
repsated twinning. There is perfect contact between neighbour-
ing crystals. A small quantity of iron, nickel or arsenic does
not alter this structure appreciably but a very different effect
is produced by sulphur or oxygen. The sulphide or oxide is
visible in a polished section in the form of minute globules,
which have a characteristic blue colour by reflected light and
are therefore readily seen against the red background without
the application of any etching-agent. The examination is most
easily performed in the case of the cast metal. The fusible
eutectic, which is the last portion of the metal to solidify, is
then a mixture of copper with either cuprous oxide (CugO) or
cuprous sulphide (CugS) and occupies spaces between the
crystals. The eutectic, when present in any considerable
quantity, takes the form of globules or elongated rods of
the oxide or sulphide, the intervals between these being filled
with copper. In the micro-section, therefore, a dotted pattern
is seen between the crystals. As the proportion of impurity
becomes less, the eutectic occupies a smaller area and is at
last only recognisable as a narrow, discontinuous layer of
globules at the boundaries.

It sometimes happens that the eutectic alloy of a series
contains so little of the less fusible metal as to be practically
indistinguishable from the second metal. This is the case, for
example, in alloys of copper and bismuth. The eutectic point
lies so near to the bismuth end of the series that no structure
whatever can be detected in the most fusible portion of the
alloy, which has the properties of bismuth almost entirely free
from copper. Hence, an examination of copper contaminated
with bismuth but free from oxygen reveals crystals of copper,
usually much reduced in size, separated by a thin film of bis-
muth, as in fig. 8. It is evident that the presence of such a
highly brittle impurity, forming almost continuous layers be-
tween the crystals of the copper, must be a source of great
mechanical weakness ; in point of fact, the specimen represented

THE STRUCTURE OF METALS 103

cracked at the edges when an attempt was made to hammer
it out into a disc long before a specimen of pure copper
would have shown signs of failure. The effect of impurities
on the mechanical properties of copper is profoundly modified
by the simultaneous presence of oxygen, a fact well known
to metallurgists.

The detection of impurities is thus a very important part
of the work of the metallographist and the chemical and micro-
scopical methods supplement one another in a most valuable
way in indicating the properties that may be expected from
a given metal or alloy. It must not be forgotten, however,
that microscopical examination also gives information which
it is not in the power of any chemical analysis to yield — namely,
in respect to the heat-treatment that a metal has undergone,
on which its physical and mechanical properties so largely
depend. Widely different results may be obtained from two
specimens of identical chemical composition but the micro-
scopical method seldom fails to throw some light on the
difference. Naturally, the relation between structure and pro-
perties has not been by any means equally determined in the
case of all alloys and there are still many obscure and uncer-
tain points in the method. But both the technical details of
manipulation and the establishment of definite relations are
advancing rapidly and the microscope is becoming more and
more indispensable in all departments of metallurgy. Famili-
arity with the method is necessary in order to utilise its
indications and it is only possible in a short notice to touch
upon a few prominent points. The highly important subject
of the effect on metals of mechanical deformation is reserved
for a second article.

THEORIES AND PROBLEMS OF CANCER

PART II

By CHARLES WALKER, D.Sc, M.R.C.S., L.R.C.P.

Director of Research Department, Royal Glasgow Cancer Hospital

In order that the nature of the investigations dealt with in
these articles may be clear to the general reader, it is necessary
to say something about the character and varieties of malignant
grpwths. As was pointed out in the previous article, the cells
produced by the division of the ovum and subsequent genera-
tions of cells become arranged into two layers known as
epiblast and hypoblast ; groups of cells produced afterwards,
situated between these two layers, are known as the mesoblastic
layer. Different kinds of tissue are produced from these three
layers of cells. The skin is formed from epiblastic cells, the
lining of the alimentary canal from hypoblastic, the muscles
and bones from mesoblastic cells. Malignant growths may
occur in tissues composed of any of these three classes of cells ;
they are divided, however, into two great groups, carcinomata^
which arise in epiblastic or hypoblastic cells and sarcomata^
which arise in mesoblastic cells. Carcinoma includes epithe-
lioma, which is probably what was originally known as cancer.
It is practically question that all carcinomata are of the same
nature. Carcinoma is essentially a disease of middle and old
age ; sarcoma occurs chiefly in young individuals and children
may be born with it in an advanced stage. Authorities who
have studied the matter and are competent to judge are now
agreed that the phenomena involved in both carcinomata and
sarcomata are essentially similar in character and that like
problems have to be faced in either case. It seems probable
that the real difference is that one class of tissue is more subject
to certain changes at one period of life, the other class at
another period.

Abnormal growths of tissue — collections of cells— may be
roughly divided into two classes, benign and malignant. In text
books it is stated that one of the essential differences between

104

THEORIES AND PROBLEMS OF CANCER 105

these two classes is that malignant tumours tend to recur after
removal by operation, whereas benign tumours do not. This
statement is very misleading. Malignant tumours usually have
no well-defined margin and the cells composing them tend to
escape along various channels to surrounding or even distant
parts of the body ; therefore, at no stage can the surgeon be
certain that he has removed the whole of the cells which form
part of the malignant growth : the so-called recurrence is really
a multiplication of cells that have been left behind.

Another feature of malignant growths is the formation ol
secondary tumours — metastases — in some other part of the body,
brought about by cells of the primary growth having travelled
and multiplied in a new position. The cells of these secondary
growths partake, in a marked degree, of the characters of the
cells of the primary growth.

There can be but little doubt that there is sometimes an
insensible transition from benign to malignant tumours and that
it is impossible to say, at what particular time, in any given case,
a change from one to the other took place.

Malignant growths produce no primary symptoms in the
persons in whom they occur. All the symptoms and all the
damage produced by them are of a secondary nature, due to
pressure or some other mechanical action upon surrounding
parts of the body.

Having cleared up these points, I will proceed to deal with
the possibility of a specific parasite being the cause of cancer
and with the present condition of cancer research.

The Parasitic Theory

The discovery that so many diseases are due to micro-
organisms entering the body and multiplying there very
naturally led to a supposition that cancer was due to a similar
cause. The parasitic theory was most popular in the early
nineties but since then its adherents have diminished in numbers
with ever-increasing rapidity. It may be said at once that
very many "discoverers" of the cancer parasite have not had
the necessary knowledge and skill to conduct the investigations
they have entered upon and that a consideration of their
published work is neither profitable nor interesting. On the
other hand, men of acknowledged competence have strongly ad-
vocated the parasitic theory, though, as James Ewing says : ** The

io6 SCIENCE PROGRESS

whole basis, objective and theoretical, of the cancer parasite
has been traversed again and again with the uniform conclusion
by those who have finished the journey that the cancer parasite
is the cancer cell." ^ One of the only consistent and highly
competent exceptions, as far as I know, is Borrel ^ ; since he
admits that the fact that cancer can be taken from one indi-
vidual and grafted upon another proves nothing in favour of
the parasitic theory ; it is difficult to see, however, why he still
adheres to the idea of a parasite.

The motley throng which has in the past claimed the dis-
covery of the parasite of cancer consists mostly of the ignorant
but includes some very competent men. As has been frequently
pointed out, there are nearly as many different cancer parasites
as people who have claimed the discovery. Some claims are
so grotesque as not to be worth consideration, others have been
abandoned by their authors. It is probably not going too far
to state that, at the present time, no trained and competent
observer believes in any particular parasite except the one he
has himself discovered — which limits the supporters of parasites
to one man for each parasite.

It is necessary here only to consider the general grounds
of disbelief in any specific micro-organism as the cause of cancer.
Of course, it is not possible to take a definite stand and say that
cancer cannot be due to an organism but that it can be so
caused is eminently improbable.

As I shall show later, malignant growths may sometimes be
transferred from one individual to another by grafting small
portions of the tumour ; but in no case will the tumour cells
survive in an animal of another species or even of another
variety of the same species. We know of no parasitic micro-
organism in mammals of which this is true. In the case of
" wheat rusts," one or two varieties of wheat may be susceptible
to a particular variety of rust but all other kinds of wheat are
immune to this particular variety of parasite. Thus parasite X
may thrive on variety A of wheat but wheat B may be naturally
immune. There is a way, however, by which X may be
rendered capable of attacking B. Parasite X is able to live
in another variety of wheat C ; if it be allowed to live for some
time on C, it is found to be capable subsequently of living

* James Ewing, Archives of Internal Medicine^ vol. i. 1908.
' Borrel, Bull, de VInst, Pasteur^ 1907, v. 497, S45, 593, 641.

THEORIES AND PROBLEMS OF CANCER 107

on A. C is called the bridging species. Somewhat similar
attempts have been made in the case of cancer. Growths
originating in one breed of mice have been transferred with
difficulty from race to race(^.^. English, French, German, Danish)
but never survived when subsequently introduced into rats for
a longer period than it did before it had been passed through
two or more different races of mice. Consequently, if cancer be
caused by a parasite, there must be a different parasite for every
different kind of animal that suffers from cancer ; none of the
parasites must be able to survive in any species or variety of
animal except the one to which it belongs : yet all these different
parasites produce precisely the same results in the different
kinds of animals. All the parasites which we know to be
capable of causing the same disease in different kinds of
mammals are able to survive in a number of different species.

But this after all is one of the lesser difficulties in accepting
a parasite as the cause of cancer. Many of the points involved
in some of these difficulties are so technical that short of writing
a treatise on the general pathology of tumours, it would be impos-
sible to make them clear to the general reader. One or two
of the most striking examples must suffice.

Having gained an entrance to the system, though in some
cases parasitic micro-organisms may remain more or less
localised, when they extend their ravages upon their host to
different parts of the body they produce similar changes in
the cells and similar results whatever may be the tissue they
attack. Some parasites show a preference for particular parts
of the body or particular kinds of tissue, others do not. Malig-
nant growths occur in every tissue in the body with but few
exceptions, such as nervous tissue. When, however, a metas-
tasis, that is a secondary tumour or extension of the disease
to another part of the body, occurs in a person suffering from
cancer, this metastasis consists of cells similar in character to
the original or primary growth : it therefore must be supposed
that when the parasite gains entrance to the body of an animal,
it takes on a new power which enables it, when it passes to
another part of the body of its host, to transform the cells
of this other part and give them the characters of the
cells among which it lived at first in the body of this par-
ticular host. The only other alternative is to believe that
besides a different species of cancer parasite existing for

io8 SCIENCE PROGRESS

every species of animal subject to cancer, there is also a
different parasite for each of the many different kinds of
malignant growths. The different kinds of malignant growths
found in man are found also in other animals. For instance,
cancer of a gland is similar and has similar varieties in mice
and men, both microscopically and in general behaviour. It
would therefore be necessary to assume that the widely diver-
gent varieties of the cancer parasite in man have representa-
tives in the independent groups of parasites belonging to each
variety of animal.

Cancer of the uterus may arise during pregnancy but the
disease is not transferred to the offspring ; vice versa^ a child
may be born with malignant disease but the mother will be
free from it. This does not appear to be compatible with a
parasite which has such free powers of migration as a parasite
causing malignant growths must necessarily possess.

There are some parasites known to cause specific diseases,
which may also be among the causes of cancer. The parasite
of syphilis is an example. But to say this is not to suggest
that the parasite of syphilis or any other parasite is the cause
of cancer. That diseases and conditions producing chronic irri-
tation and inflammation and consequently an unusual multipli-
cation of the cells of a particular area should cause some of the
cells to pass out of somatic co-ordination and thus originate
a malignant growth, seems to be in every way in accordance
with what we know of cancer. A specific parasite is in no way
required in framing an adequate explanation and the difficulties
in the way of conceiving a micro-organism to be possessed of
the necessary qualities appear to be insuperable. The theory
of somatic co-ordination or cell autonomy, as set forth in the
last number of Science Progress, though affording a poorer
prospect of a speedy discovery of a cure, is compatible with all
the known facts. The conception of a parasite has been carried so
far, however, that a process has been described by which certain
bacteria multiply either in the body of the host or in artificial
cultures in such a way that exact representations are produced
of the minute structure of the individual cells and of the
arrangement of the groups of cells found in different kinds of
tissue.^ The author of the account certainly does not say

^ Marie Bra, Cultuj-e in Vitro des Cellules Canc&euses (Paris : A. Pcinat,
II, Rue Dupuytren, 1909).

THEORIES AND PROBLEMS OF CANCER 109

whether or not, when a group of these bacteria has multiplied
beyond the limit necessary to the imitation of one cell, the
process of cell division (mitosis) is imitated as the image of a
second cell is formed, which would be necessary as mitoses
are particularly numerous in many cancers. It is difficult to see
how evolution or any other process could have brought about
a case of mimicry which could only have been observed by
the individuals attacked by the organism since the invention
of the modern microscope. Mimicry which protects or other-
wise benefits the mimic can be understood. Mimicry such as
this is inconceivable. Various micro-organisms are frequently
found in cancer but these are found also in other diseased con-
ditions and they are not always present in cancer.

Experimental Investigations

During the past ten years a very large number of experi-
ments have been carried out with carcinomata occurring in
mice. One reason for this has been that some of these tumours
have been found to be transmissible — that is to say, on trans-
plantation from one mouse to another they grow in the new
hosts in a variable proportion of cases, the proportion of suc-
cessful transplantations being dependent upon several different
conditions.

An impression seems to exist that the present activity in
this particular branch of experimental work followed immedi-
ately upon the discovery that tumours could be transplanted.
This is not a correct impression. The activity is due to the
fact that public interest in cancer research took a practical turn
about ten or twelve years ago and that means were provided
for experimental work.

The first successful attempt to transplant a malignant tumour
from one individual to another appears to have been that made
by Novinsky, who transferred a cancer occurring in the nose
of a dog into two other dogs.^ He was followed by Wehr ^
and by Hanau,^ the former transplanting a sarcoma occurring in
a dog, the latter an epithelioma occurring in a rat. Morau,*
several years later, successfully transplanted a carcinoma in

* Centralbl.f. d. Med. Wissensch. Berl. 1876, xiv. 790.
' Arch.f. klin. Chir. Berl. 1889, xxxix. 226.

' Ibid. 1889, xxxix. 678.

* Arch, de Mid. Expir. et dAnat. Path. Paris, 1894, vi. 677.

no SCIENCE PROGRESS

mice and since then the number of successful transplantations
has been enormous. The obvious advantages of using so
small and cheap an animal adequately account for its popularity
for experimental purposes. Whether malignant growths are
really more common among mice than other mammals, as has
been suggested, is very doubtful. In the case of no other
animal have hundreds of thousands, perhaps millions, been
kept for the particular purpose of making observations upon
cancer and for breeding experiments. All that has been
suggested by the facts is that cancer is nearly as common as
it is in human beings and that, therefore, it may also be common
in other mammals, though we have no data at present upon
which to base a definite statement.

Some important points with regard to cancer have been
established by these experiments. Cancer is transmissible
from individual to individual but only through the transference
of the living cells of the growth from the individual in which
they originate to a suitable position in the body of another
individual. The cells of the growth, though they may live and
multiply for some time in a closely related animal,^ are only to
be established in an animal of the same variety of the same
species and the more nearly the animals are related to each
other, that is to say, the nearer their common ancestry, the
greater will be the percentage of successful graftings.^ It is
certain that these transplantation tumours grow from the trans-
planted cells and not from the cells of the new host.^

Successive generations of tumour, that is to say, successive
sojourns in fresh individuals as hosts, if the hosts are of the
same near ancestry, increases the percentage of successful graft-
ing. The rapid passage through successive hosts increases the
rapidity of the growth of the tumour.*

With regard to the experiments demonstrating this latter

^ Ehrlich, Arb. a. d. k. Inst. f. exp. Therap. zu Frankfurt ajM.^ Jena, 1905, i.
yy ; Apolant, Therap. der Gegenwart. Berlin u. Wien^ 1906, xlvii. 145 ; and
many others subsequently.

^ Jensen, Central./. Bakteriol. u. Parasit, Jena, 1903, xxxiv. 122; Haaland,
Bert. klin. Wohnschr. 1907, xliv. 713 ; and many others.

' Jensen, op. cit. ; Loeb, Journ. Med. Research^ Boston, 1901, vi. 28 ; and
very many others.

* Ehrhch and Apolant, " Beobachtungen iiber maligne Mausetumoren," Berl.
klin. Woch. 25, 1905, and ibid. " Experimentelle Beitrage zur Geschwulstlehre," 6
1906.

THEORIES AND PROBLEMS OF CANCER in

fact, the authors say that the results were due to the carrying
out of a definite plan, using a great number of animals and
transplanting as rapidly as possible. " Our object was to in-
crease the malignancy of the tumour cells to the maximum by
the continued systematic passage from animal to animal accord-
ing to the analogy of bacteriological technique." ^ Whether
another interpretation of these results is not more probable will
be considered later.

Bashford, Murray and Bowen ^ have observed alternations or
waves in the rate of growth and viability involving several
generations of the transplanted tumours with which they have
worked and they interpret this as being due to a rhythm in the
growth energy. Calkins records similar waves ^ but concludes
that they are due to some cause within the cancer cell itself and
considers that this cause is probably an intracellular parasite
such as Plasmodiophora brassicce. Apart from other considera-
tions which make it almost impossible to accept a parasite
as the probable cause of cancer, Calkins' paper shows such
intrinsic signs of carelessness that the observations described
in it cannot be taken as bearing much weight. Another in-
terpretation of the significance of these waves of growth will be
suggested shortly.

A general impression conveyed by a consideration of the
literature dealing with experiments upon these graftable mouse
cancers is that they differ to a large extent from primary
malignant growths occurring in the human subject. Metastases
or secondary growths are very rare. When they have been
described, they have generally followed only upon inoculation
with an emulsion of tumour cells and not upon the grafting of a
solid piece of tumour tissue. It must be obvious that the
former method is one that enables single cells to gain access to
a small blood-vessel and be carried to the lungs, where, if they
survive, a tumour will develop but only become noticeable later
than that formed at the site of inoculation. It is also almost
certain that when the emulsion is injected forcibly under the skin
or into the peritoneal cavity, isolated cells or groups of two or

' It has been demonstrated that a strain of certain disease-producing micro-
organisms may be rendered far more virulent by a rapid succession of inocula-
tions from animal to animal.

Proc. Roy. Soc. 1906, B. Ixxviii.

' Journ. Exper, Med. vol. x. 3, 1908.

112 SCIENCE PROGRESS

three cells must often be driven further from the bulk, be
scattered, in fact, and give rise to smaller tumours which become
noticeable later than the main tumour. It is remarkable that
practically all these secondary growths have been in the lungs,
though secondary growths in the lungs do not occur in the
ordinary course of primary carcinoma. These grafts have
always, in my experience, been enclosed in a definite capsule.
On following the sequence of events Irom a few hours after
grafting up to fourteen days, at first at intervals of twelve hours
and subsequently of twenty-four hours, I found that the in-
flammatory reaction in the surrounding tissues of the mouse
began almost at once : whilst not a single tumour cell which
had been introduced into the animal showed any sign of multi-
plication until twenty- four hours after grafting, the inflammatory
products had by this time completely surrouaded the graft.
Long before the cells of the graft had begun to multiply
actively, the inflammatory reaction had already cut them off"
eff'ectually from the surrounding tissues. The inflammation
was always in advance of the proliferation of the tumour cells.
This accounts for the rarity of metastases. I have but once
personally observed one in the many thousands of inoculated
mice I have examined except in those infected with emulsions
of tumour cells.

One of the most characteristic features ot primary malignant
growths is that when they are well established and have reached
a considerable size, their removal by operation is almost in-
variably followed by recurrence. Operations are completely suc-
cessful only when performed at an early stage. An operation is
often desirable in order to prolong life and to avoid unnecessary
suff'ering, when there is practically no chance of a complete cure.
With the graftable tumours in mice and rats, however, the case
is very difl'erent. I have just completed a series ot experiments
in which I have removed tumours from mice and rats. These
were in every instance large and well-established growths, in many
cases approaching in size that of the body of the animal from
which they were removed.^ In only eleven cases out of forty-
four has the tumour recurred and in these a second operation

^ In about 80 per cent, of the mice the peritoneum was involved and the
operation often included an incision in the peritoneum from the ribs to the pelvis,
besides the removal of a considerable portion of it. The two mouse tumours used
were of a particularly virulent kind.

THEORIES AND PROBLEMS OF CANCER 113

has been successful in every case. The recurrences are easily
explained through a small portion having been left in the first
operation. When a mouse weighs 30 grammes and a tumour
has to be dealt v^ith which perhaps is irregular in shape and
weighs from 15 to 20 grammes, requiring therefore a consider-
able amount of dissection to remove it, it is obvious that some
of the tumour cells may have been conveyed to the adjacent
tissues and left behind or that some outlying portion may have
been missed. Operations in rats have always been successful
in the first instance. In any case, as the second operation
to remove the remainder has invariably been successful, these
graftable secondary tumours must be placed in a category
different from that in which primary tumours are included.

The method of using emulsions instead of pieces of tumour
has been adopted by many observers. Bashford^ and others
have emphasised the need of using accurate doses of tumour
cells, stating that only thus can certain errors be eliminated.
However desirable accuracy of dosage may be, it cannot pos-
sibly be gained by using emulsions of cells, as only living cells
are effective. Even in a solid piece of tumour, there must be an
unknown number of dead and degenerating cells and many
must be killed outright and many more injured in the process
of preparing an emulsion. As it must be quite impossible to
estimate the proportion of living cells in a measured quantity
of emulsion even to within 50 or 75 per cent., I do not propose
to touch upon any experiments based upon accuracy of dosage
and have only referred to the method as being a possible source
of error with regard to the so-called metastases from inoculated
tumours.

It is curious that continual contemplation of little else than
these transmissible mouse tumours seems frequently to lead to
the adoption of methods really untrustworthy and very mislead-
ing for which intense accuracy is claimed. This is illustrated
by many of the papers dealing with the subject but by nothing
more clearly than by the drawings to scale of the outlines of
tumours in mice at various stages after inoculation given in the
Reports of the Imperial Cancer Research Fund. The accuracy
of the drawings in connexion with the accuracy of dosage
referred to above constitutes one of the most important factors

^ " Resistance and Susceptibility to Inoculated Cancer," Bashford, Murray
and Haaland, 3rd Scientific Report, Imperial Cancer Research Fund, 1908.
8

114 SCIENCE PROGRESS

in the general conclusions drawn from the experiments. Some
of the tumours and even small outgrowths from tumours
represented in great detail in these drawings are less in diameter
than the thickness of the mouse's skin. When it is realised that
even a stocking will alter the relative proportions of a foot,
ankle and leg and that the drawings referred to were made from
measurements taken through the mouse's skin, the value of the
details becomes more than questionable. When also the impos-
sibility of discriminating between minute collections of tumour
cells and the inflammatory tissue which is constantly present is
taken into consideration, it becomes obvious that the estimation
of size and of shape must always include elements of error which
vary inversely with the size of the tumour.

In primary cancer in man, a very marked feature is the in-
vasion of the surrounding tissues and the effect upon the general
health as the invasion interferes with the functions of the
body. This is particularly marked when ulceration and sepsis
occur. In the case of grafted mouse tumours the growth does
not invade the surrounding tissues, being cut off by the capsule.
Even if the surface of the tumour ulcerate and become septic,
the mouse does not generally seem to suffer in general health.
The septic products, cut off by the capsule, do not seem to be
absorbed to the same extent as they are in the case of cancer in
the human subject. Even when the tumour grows to a size
approaching that of the whole body of the mouse, general health
of the mouse frequently does not seem to be affected.

It has been suggested in previous passages that the cells
forming a malignant growth, having passed out of somatic
co-ordination and living upon the parent organism as parasites,
might in a sense be regarded as separate individuals. The
occurrence of meiotic phenomena and other considerations were
cited in support of this view ; most of the experiments just
enumerated upon transmissible mouse tumours may be inter-
preted in a way that emphasises it still further.

Variation, in so far as our knowledge goes, is an intrinsic
property of all living matter. Even two cells of the same organ
in the same individual are never the same morphologically. But
the differences extend beyond morphological features and include
potentialities of growth, resistance or susceptibility to stimuli
and other non-morphological characters. Moreover as existing

THEORIES AND PROBLEMS OF CANCER 115

cells vary from each other, so the cells produced by division
must vary from the cell that has produced them and from each
other. In these inoculation experiments we have therefore two
outstanding sets of variable potentialities : those of the individual
mice into which the tumour cells are introduced and those of
the cells themselves. Theoretically it should be possible to
select particular and obvious characters in either the hosts or
the tumour cells and with this idea in view I began some experi-
ments in selecting tumour cells which I am still continuing.
Though mice breed quickly, it would obviously be a more
lengthy, difficult and uncertain process to breed highly resistant
and highly susceptible races of mice. I used mice obtained
from the same source throughout the first series of experiments
and have repeated them with mice from an entirely different
source. The procedure was as follows : Twenty mice were
grafted at the same time with pieces of tumour of as nearly as
possible the same size. When two or three were large enough
to use for grafting, twenty more mice were grafted from the
largest. The process was carried on through several generations
as quickly as possible. On the other hand one of the most
slowly growing tumours was chosen at a later date from the
original batch of mice and was used to graft another twenty and
so on for several generations, selecting always a slowly growing
tumour. In this way I modified the rapidity of the growth and
produced three strains of tumour which developed at different
rates on the average. The differences between the rates of
growth were so very great as to be beyond explanation as the
result of chance. Selection also accounts for the fact that whilst,
when this tumour first came from Prof. Ehrlich's laboratory,
I succeeded in only about 30 per cent, of the graftings, the
percentage of successes increased in subsequent generations to
nearly 100. Working with another breed of mice, 1 have had
precisely the same experience.^

Other observers who have found that a tumour became more
visible after passing through a series of mice of the same breed
attribute this change to the acquirement of a power of resistance

' The first series of experiments was carried out in the Cancer Research
Laboratories in the University of Liverpool with mice bred in Essex. They
have been repeated with another breed of mice from Langside, Glasgow. The
figures of these experiments will be pubHshed shortly, being at present in the
hands of the Editors of the Journal of Pathology and Bacteriology.

ii6 SCIENCE PROGRESS

on the part of the tumour cells. A more probable explanation
seems to be that only those cells in the original graft that were
most resistant to the new environment survived to divide and
produce more cells. Of succeeding generations of cells, whether
in the same mouse or after having been transferred to another,
all which varied towards less resistance degenerated, whilst
those that varied towards greater resistance survived to transmit
the favourable variation to other cells, which varied in their
turn. This process of selection would go on until a race of cells
.almost entirely resistant to the environment was produced.
When the tumour cells are introduced to a new environment
in the shape of a new race of mice, the process would be gone
through again, unless of course the environment were so
unfavourable to begin with that none of the cells was sufficiently
resistant to survive. This interpretation seems to account for
the fact that Ehrlich and Apolant ^ were able to produce a very
rapidly growing tumour by a very quick succession of inocula-
tions— they were obviously obliged to use only the most rapidly
growing cells.^ It accounts for the fact noted by Jensen, that a
well-established tumour gives a higher percentage of successful
grafts than a young one.^ It explains why various parts of the
same tumour may give different results when grafted ^ and that
though tumour cells will not survive for long in an unsuitable
host, some of them survive and multiply when transferred back
to a suitable one.^ Unconscious selection also accounts for
the so-called rhythms of growth in Bashford's and Calkins'
experiments.

Bashford^ has suggested that another kind of selection
accounts for the production of strains of rapidly growing
tumours. He says : " In the light of the wide experience
gained, it can be asserted that the technique which consists
in the employment of large doses of tumour emulsion and rapid
passage was responsible for the selection of certain primary
tumours which survived the procedure and not for the in-
duction of a marked change in their rate ol growth." His

* Op. cit. 1905.

^ It of course applies equally to the method of producing a virulent strain of
bacteria referred to by these authors. (See previous reference.)
^ Jensen, op. cit. 1903.

* Bashford, Proc. Roy. Soc, B. vol. Ixxviii. 1906.

* Ehrlich, op. cit. 1905 ; Ehrlich and Apolant, op. cit. 1905.

* Fourth Scientific Report, Imperial Cancer Research Fund, 191 1.

THEORIES AND PROBLEMS OF CANCER 117

meaning is somewhat obscure but from the context he appears
to imply that as some tumours are more malignant than others,
the method followed had the effect of selecting the rapidly
growing tumours from among other tumours, because the less
rapidly growing tumours could not be successfully perpetuated
by the method used. The selection he suggests is that of
different kinds of primary growths and not of variations among
the cells of the same growth. He refers at some length to
variations among cancer cells but his remarks appear to apply
only to morphological characters. The mode of selection he
suggests might apply in a few particular points with regard
to some experiments. It is difficult to see how it can apply
to most of the experiments referred to here, which appear to
be adequately explained by the selection of variations in poten-
tialities occurring among the cells of the tumours and the
transmission of these variations in successive generations
of cells.

There are records of other observations which I think throw
some further light upon the difference between the behaviour
of transplanted tumours and that of primary growths from
which they are derived. These refer to the changes in the
histological characters of the growths from carcinoma to
sarcoma and vice versa and from a structure similar to that
of a primary cancer to that of a benign tumour. Considerable
interest was aroused in 1905 by the discovery in Ehrlich's
laboratory that in the tenth generation of transplantations of
a carcinoma in mice the characters of the tumour had altered
to a mixed sarcoma and carcinoma. In the thirteenth generation
this became a large spindle-celled sarcoma.^ A permanent
mixed tumour was also produced from the material of four
different strains all of which had originally been carcinomata.

The surprise aroused by these observations, however, was
somewhat uncalled for, as Loeb ^ had some years previously
recorded the change of a spindle-celled sarcoma occurring in
a rat to an endothelioma, a myxoma, alveolar sarcoma and
other forms of tumour upon transplantation to other rats.
Apolant^ claims to have followed the microscopical changes
in the development from carcinoma to sarcoma and describes

^ Ehrlich, Arb. a. d. k. Itistf. exp, Therap. zu Frankfurt ajM.., Jena, 1905, i. yy.

' Journ. Med. Research^ Boston, vi. 28, 1901.

^ Arb. a. d. k. Inst.f. exp. Therap. zu Frankfurt a\M.^ Jena, 1906, ii. 48.

ii8 SCIENCE PROGRESS

the cells of the sarcoma as being derived from those of the
stroma and not from the carcinomatous cells. Subsequently
Bashford ^ made similar claims with regard to a similar change
from carcinoma to sarcoma with another strain of tumours.

It is not made at all clear by these observers, however,
that the carcinomatous cells themselves do not take on the
characters of sarcoma, so the real point of their claim —
that the sarcoma develops from the stroma and not from the
carcinoma cells — remains very doubtful. Apolant ^ transformed
a carcinoma into a benign adenoma by transplanting it into
immunised mice.

In considering these observations, one realises that besides
the general effect upon the health of the animal and the other
points of difference already referred to between the trans-
planted tumours and primary cancer, there appears to be a
difference in the general history of the succeeding generations
of cells which form the growths. There is, I think, no record
of a primary carcinoma changing into a sarcoma or vice versa,
yet such changes in transplanted tumours were noted directly
they were brought under systematic observation.

It is quite clear that the conditions obtaining in a primary
cancer must be very different, in so far as the cells forming
them are concerned, from the conditions to which the cells
of the graft are subjected. The cells of the primary growth
are subjected to a minimum of selection by the environment,
as they or their immediate ancestors have arisen in the
identical environment in which they continue. Moreover,
they must act less as foreign bodies towards the surround-
ing tissues from which they arose than do cells introduced
from outside and so do not cause that inflammatory reaction
which is so marked a feature in tumours growing from grafts.
These considerations suggest an explanation of the invasive
nature of the primary growth as compared with the non-
invasiveness of those arising from grafts and for the rarity
or total absence of true metastases in mice bearing tumours
produced by inoculation. The more or less stringent selection
of those cells possessing high resistance to a change of en-
vironment which is involved in the transference to new hosts
is probably also sufficient to account for the other differences.

^ Berl. klin. Wohnschr. 1907, xliv. 1238.
^ Munchen Med. Wohnschr. 1907, liv. 1720.

THEORIES AND PROBLEMS OF CANCER 119

The cells forming the tumours produced after a long suc-
cession of graftings must possess some characters that were
not at all necessary to those forming the primary growth ;
they are able to resist a strange environment and the reaction
on the part of the cells of the host which does not exist at
all or only in a very slight degree in the case of a primary
cancer ; they go on multiplying during periods several times
as long as the period of life normal in the species of
animal in which the primary tumour originated from which
they were obtained ; and the cells produced after a number
of sojourns in strange hosts, involving a number of cell
generations many times greater than could possibly have
occurred had they remained in the original host, sometimes
exhibit very striking and obvious morphological differences
from the cells of the original primary tumour. In this con-
nexion it is well to bear in mind the facts relating to the
general potentiality of differentiation retained by the cells of
the soma.

It seems probable, from a theoretical point of view, that
the form of selection to which the cells are subjected in strains
of transmissible tumours must tend to preserve those in which
the potentiality for independent existence is greatest : that
the greater the number of cell generations produced away
from the environment in which the ancestral malignant cells
arose and the more numerous the different environments
through which the descendants have passed, the more similar
their characteristics should be to independent organisms. This
theoretical probability seems to be borne out by observed facts.

THE PLANET MARS

By JAMES H. WORTHINGTON

Before entering upon the subject of this article, it is advisable
that I should state in a few words why it has been written and
precisely how the information which it contains was obtained.
Being much impressed by what I had read of the Martian
features, as detected and portrayed by Lowell and SchiapareUi,
I determined to avail myself of the first opportunity, if possible,
to see for myself whether or no these features were real, because
they seemed to be too wonderful to be believed at second hand.
The opportunity came in 1909. Thanks to Lowell's hospitality
and kindness, I was able to study the planet at Flagstaff during
the opposition of that year and was fortunate enough to see
many of the canals and oases and to assure myself of their
reality. On returning to Europe in 1910, 1 found much scepticism
prevailing which I scarcely knew^ enough to refute. I therefore
attempted and partially succeeded in seeing the canals again at
Nice. This was in 191 1.

When the planet again approached opposition, I gladly
accepted Lowell's invitation to see more at Flagstaff and
accordingly spent two months there, observing the canals and
studying them in greater detail. I was able to confirm Lowell's
observations and by discussion with him to remove from my
mind many obstacles which stood in the way of accepting not
only the discoveries but also the explanations which he has
put forward.

Having had freedom to travel, I have been able, owing to the
courtesy shown to me by many astronomers on my journeys,
to study, with the aid of exceptional facilities, the effects of
climate upon the astronomical work — a factor the enormous
importance of which can scarcely be realised by those whose
experience is confined to a single country or even continent.

It seems to me therefore that I may be able to add a few

words of interest to the great mass of accounts which have

appeared recently upon this most engrossing subject.

120

THE PLANET MARS 121

From the earth no celestial body is more accessible to
observation than Mars, the moon alone excepted. To this
proximity is due, in large measure, the exceptional success
which has rewarded our study.

At the outset of this inquiry it should be remembered that
in space all positions are unique both in their conditions and
opportunities. It is therefore necessary, as far as possible, to
free our minds from the prejudices which are due to our
position and to study the details which have been revealed to
us with dispassionate coolness.

It being in the nature of man to seek his likeness, he seeks
it before all else, forgetting that when dealing with another
planet the one thing which is a priori probable is that he will
find much that is quite different and so he comes to consider
strangeness as one of the hall marks of truth in his discoveries.

Geomorphic ideas have led men into many errors. The
so-called seas of the moon have turned out to be the driest
of land and the greenish areas on Mars, at first so confidently
dubbed oceans, in the light of further research, appear not
to be fluid at all.

Thus are we taught to expect the unexpected, and to feel
no surprise when three centuries of patient study are rewarded
by its discovery in Mars.

With the invention of the telescope came the discovery of
the nature of the planets as comparatively cool bodies reflecting
to us the light of the sun — a discovery which was announced
in the famous anagram of Galileo :

Cynthiae figuras semulatur mater amorum.
(The mother of loves [Venus] imitates the phases of the moon.)

In later days his most distinguished compatriot Schiaparelli
might well have used his predecessor's words with equal
aptitude to express the result of recent work on Mars :

Haec immatura a me jam frustra leguntur.
(As yet I seek in vain to read the meaning of these incomplete observations.)

It fell to Galileo in the end to expound his epoch-making
discovery. The same justification came to Schiaparelli, for
though his eyes failed him, he lived to see through those of
his successors the confirmation, extension and interpretation
of his work.

122 SCIENCE PROGRESS

Soon after the discovery of the disc of Mars, came the
announcement from Huygens that the disc possessed surface
features from observation of w^hich he felt assured that, like
the earth, the planet rotated upon an axis. The marking which
revealed this fact is the nov^ well-known dusky wedge called
the Syrtis Major.

A little later increased telescopic power showed to the
old observers the white areas covering the poles of the planet
whose behaviour has turned out to be the master key to the
explanation of almost all the detail on the disc which subsequent
scrutiny has revealed.

But space does not permit me to follow historically all the
steps by which we have acquired our present knowledge of
the planet. Sufficient has been said to show that it has ad-
vanced pari passu with the power of optical instruments.

The investigators who preceded Schiaparelli laid the
foundations of areography, as the subject is named which
describes the configuration of the Martian surface features
— patches of colour, green and ochre, white and grey, which
cover the disc with their varied hues, making it appear like a
gigantic gleaming opal. On looking at Mars we perceive them
at once. Their outlines are well defined and have long since
been laid down in maps of the planet.

The delineation of these features was well-nigh complete
when Schiaparelli began his studies of the planet in 1877.
The opportunity then afforded was an exceptionally favourable
one, the planet being very near the earth when showing the
fully illumined face of opposition.

At this time the disc was so much dilated by its proximity
that with a magnifying power of only eighty diameters it
appeared in the telescope as big as that of the moon seen by
the unaided eye. Schiaparelli and the world alike were startled
on this occasion by the discovery of numerous dark lines criss-
crossing in the most unexpected fashion the ochre-coloured
regions of the planet.

Following the well-worn analogy of his predecessors — ot
land and sea areas on the planet — he christened these new
features " canali " or channels, which reckless translators at once
dubbed canals, a name implying more than the astronomer had
actually found on the planet.

At each subsequent opposition he succeeded in seeing them

THE PLANET MARS 123

again — and seeing them better with growing experience, he
added to their number and complexity the fact that many ot
them consisted of doublets the two component lines of which
were rigidly parallel.

Those who could not see the '' canali " at all very naturally
refused to give credence to them and began to suspect that they
were the illusions of their discoverer.

As first seen by Schiaparelli, they were not by any means
very regular but as his powers of discrimination increased with
practice, he perceived more and more clearly their linear and
geometric configuration.

To see these markings at all implies a very great advance in
the observer's art, as is proved by the fact that even to this day,
though their existence is no longer questionable or questioned,
there are few observers who have seen them as well as did their
discoverer more than thirty years ago.

The object of this article being to present concisely an
account of our present knowledge of the planet, we shall do
well to proceed at once to study the methods used by Lowell —
Schiaparelli's greatest successor — and the results which he has
obtained. Lowell has added more to our knowledge of the
planet than the sum total of all that we previously possessed. '

At his observatory the mathematical appearance of the
" canali " has been confirmed and the discovery of an equally
amazing and correlated system of spots— which he calls oases —
has been added.

Another advance was made by the detection in the green
areas of the uninterrupted continuance of the network of the
"canali," thus showing them to be limited in extent only by the
surface of the planet on which they occur.

In order to appreciate the weight ol conviction which these
discoveries carry, it is necessary to enter somewhat minutely
into the means and methods by which they have been achieved.
I shall therefore describe them as best I may.

It is often thought, by those unfamiliar with planetary
observations, that the larger the telescope the more detail it
should reveal; the first step therefore will be to remove this
cardinal misconception by a careful consideration of the optical
principles involved in the scrutiny of detail upon a planetary disc.

The problem may be succinctly stated as follows : Given a

124 SCIENCE PROGRESS

planetary disc, brilliantly illuminated as in Mars : required,
the aperture and magnifying power which will best reveal fine
detail upon its surface. It is necessary to digress at once to
inquire what happens when we turn the telescope upon a star.

The star disc seen in the telescope is a diffraction effect
produced by the lens. It is sufficient for the present purpose
to recall the fact that the larger the aperture of the lens, the
smaller is this diffraction disc ; but besides the disc there are
concentric rings surrounding it arranged in order of brightness,
the faintest visible being the outermost.

Now let us suppose that we wish to separate two bright
stars which are very close together. In a large telescope they
appear perhaps as two discs either in contact or overlapping
with their respective systems of diffraction rings interlacing.
The confusion apparent to the eye in this picture is further
increased by any unsteadiness in the air between us and the
star, which causes the two images to swim and flicker ; the rings
break and mingle, so that the observer is unable to see anything
clearly, the stars appearing as a single pool of boiling light.

The nature of the movements of the air must therefore be
considered. These consist of a series of ripples or waves
passing across the field of view, whose size may be estimated
from the nature of the disturbance they produce. An analogy
may illustrate the point.

Any one who has been out in a boat has seen the sea bottom
in the shallows on a calm day and noticed how the small objects
on the bottom — shells and stones— appear to swing about below
on account of the waves. This swaying does not disturb the
outlines of the small objects that are visible but merely produces
a general rhythmic motion. But if a little breeze ruffle the
surface of the water, the minute ripples immediately shatter the
image of shells and rock, leaving nothing visible but a confused
mass of colour.

Now the analogy between the watery ocean on the earth's
surface and the airy ocean above it leads us to expect kindred
disturbances ; whether we look down through the one or up
through the other, like Newton we may learn something from
the pebbles which fringe their mutual margin.

In looking through water — if the attention be confined to
a small area — no perceptible distortion of bottom detail is
produced by big waves. And so it is with the air also.

THE PLANET MARS 125

Telescopic vision is only concerned with those vibrations
which produce disturbance in its field.

Since aerial waves may be of any size up to many yards
long, it is obvious that their disturbing effects may be best
avoided by the use of a small telescope.

In practice it is found that when a telescope three inches in
diameter is used these disturbances are generally negligible.
Contrasting this small instrument with a three-foot telescope,
we see at once how much more we may expect to suffer. If it
be assumed that the air waves at the moment are a foot across,
then to the smaller instrument they are big waves of which
only part of one is in the field at any moment. They will
therefore produce general motion but being intrinsically small
the motion may well be imperceptible, both on account of its
minuteness and extreme rapidity.

The case is very different however in the larger instrument.
Here are waves much shorter than the diameter of the lens and
since every part of the lens contributes light to form the image
there are at the focus the integrated effect of three waves or
at least six different phases of disturbance superposed upon
one another and producing inextricable confusion.

In this case there is no general motion but instead a con-
tinuous blurring of the image. It therefore appears that since
air disturbance is inevitable it is best to seek that which is
longest and that which is least in amplitude. If the wave be
very big, it will produce only an occasional swaying motion of
the image which in no way disturbs the integrity of its parts.

We are now in a position to remove the first difficulty there
is in viewing the supposed double star — by stopping down the
telescope until the image is free from blurring and subject only
to general motion.

We accordingly stop down the telescope and the star now
presents the appearance of a peaceful, oblong patch of light,
somewhat fainter it is true and perhaps a little bigger but
something which will give our eye a chance.

The stars are not yet separate. The observer is still balked
of his aim — by reducing the aperture he has increased the star
discs, which now overlap the more and he seems to be in the
quandary of Alice in Wonderland when she had reduced herself
with the aid of the magic cake so as to get through the little
door in the passage and found that she could not then reach up

126 SCIENCE PROGRESS

to take the key off the glass table. She saw it clearly through
the glass, high above her diminished head. But Alice was not at
the end of her resources, nor is the astronomer. Alice reduced
herself still further and crept under the door and he may
further reduce the light of the stars and so see between them.
This time he uses a dark glass, the action of which is at once
apparent when the nature of the images is considered.

They are brightest at the centre and surrounded by fainter
interlacing rings which can well be dispensed with. The tinted
glass at once cuts off the light of the rings. It also dims the
central image equally all over so that only the brightest part in
the middle remains visible. The two middle points of the star
images are now seen neatly separated by the gap which
previously was filled with the light of their outer edges. So
the observer has achieved his purpose in an unexpected way
by reducing the light instead of increasing it.

This digression may appear at first sight to have little to
do with Mars but it is not irrelevant, for in the telescope
the disc of the planet is made up of an indefinite number of
luminous points each behaving in exactly the same way as the
two star discs first investigated. It is therefore easily seen
that the same methods must be used in separating the several
points upon his surface.

C)ne might at first suppose that the process might be con-
tinued indefinitely. But a limitation is set by the apparent
brilliance of the surface, because to see clearly the eye requires
a certain minimum of illumination ; above this minimum the
method may be applied whose importance has long been un-
accountably overlooked by many observers.

In the light of these facts it is easy to see that aperture plays
at best a secondary part in planetary observation, which is
restricted by the climatic difficulties by which we are so greatly
hampered on our earth.

Experience in many observatories has convinced me that
as yet there is not one which is so highly favoured in a matter
of climate as that of Lowell at Flagstaff, Arizona. At this
station (at an altitude ol a mile and a half above sea level), not
only is the air very steady and clear but there is actually less of
it and that only the best part left over the observer's head.

Here is then the best place to determine the limits of useful
aperture in planetary observation and the result to which

THE PLANET MARS 127

observers have been led here is both instructive and startling,
as they have found that, even under conditions so good as to
be incredible to those who have not seen them, no advantage
in definition is gained by dilating the aperture beyond eighteen
inches ; and when the conditions are less than the best, a very
perceptible loss of detail occurs.

It seems probable that until some better climate be found, no
very substantial advance can be made in the effective power of
our instruments but as yet so little is known of the conditions
prevailing in out-of-the-way localities that it is quite likely that
diligent search may reveal a better place. Meanwhile we must
console ourselves with the knowledge that the optician has done
all he can for the problem, having made telescopes much larger
than the astronomer can use profitably.

Having made this discovery, we must turn our thoughts
from the lens at the big end of the telescope to the man at the
small end, whose qualifications must now be examined.

Only those whose profession is the use of their eyes can
realise how much training is both necessary and possible and
how much the degree of proficiency attained depends upon the
nature of the training. Just as musicians are called upon to
learn different instruments, so astronomers are called upon to
view different objects.

There are two main divisions of visual astronomy — stellar
and planetary — differing from each other in as many essentials
as do fiddling and piano playing. In the case of a star, the
observer knows what he is seeking — namely a small disc of
light ; all he needs is to see that the star is there.

The case of a planet is different. The disc is there, it
cannot escape notice but we are not concerned with it but with
its parts. The glimpses of detail which our troubled atmosphere
permits us to obtain are but momentary and therefore one of
the first essentials is that the observer shall cultivate quickness
of perception as well as acuteness in discrimination. Herein
lies the fundamental difficulty of Martian observation which
only long practice can surmount.

When the conditions are not the best, only the very quick
observer will be able to see anything properly. The canals may
flash into sight repeatedly without the inexperienced observerever
perceiving them. He must wait for one of those rare occasions
when the detail is steadily visible during a second or two, in

128 SCIENCE PROGRESS

order to be assured of its reality. He will thus find out what
to seek and believe. It is an old story. To be discovered, a fact
must force an entrance into the stronghold of men's minds ;
when once it has achieved this it becomes a welcome guest.

This fact has been already exemplified in the case of Mars.
His satellites required a twenty-six inch telescope and persistent
care for their discovery but have often since been seen with
telescopes of less than half this size.

Although the more salient details of the disc of Mars may
be corroborated by any observer who has the needful practice
and patience, the discrimination and discovery of the more
intricate and minute parts require special qualifications which
few possess and practice cannot give them. I refer to the
intrinsic defining power of the observer's eye considered as an
instrument.

Lowell has pointed out that there are two useful extremes
in eyesight which cannot meet — defining power and sensitive-
ness to light. Suitable education of the eye assists by drawing
the two extremes nearer together but the possession of either
quality in a superlative degree excludes the other.

In the retina on which the image falls there is a structure
of rods and cones varying markedly in size and texture in
different eyes. Those having the finer texture have also the
greater defining power but are deficient in sensitiveness. A
photographic analogy may help. Rapid plates are more sen-
sitive to light and of coarser grain than the slower plates
which give a sharper picture. The increased definition on the
slower plate is due to the fact that the finer grain produces
less distortion of the detail which falls upon it.

To return to Mars. We find at once among observers of
the planet a striking contrast. Prof. Barnard, who by his
discovery of the fifth satellite of Jupiter (an object of excessive
faintness) proved the sensitiveness of his eye, finds himself
entirely unable to detect any of the " canah " which are so
evident to Lowell.

Of course some ot this discrepancy is due doubtless to
differences of climate and instrument but there remains a
residuum which can only be explained by a difference of eye-
sight. Fortunately for the elucidation of the problem many —
like the writer — possess e3^es intermediate between these two
extremes, so that to some extent they may share the discoveries

THE PLANET MARS 129

of both. Of this I may perhaps be permitted to quote an
instance.

Searching for canals at Flagstaff during the opposition of
1909, using a yellow screen before the eye-piece and an aperture
of 18 in., I was amazed, on glancing off the disc to the sur-
rounding sky, to see a minute point of light, which turned
out to be one of the satellites. Lowell, when his attention
was drawn to it, perceived it also. Canals were visible to
him which I could not see and the satellite which had escaped
his notice was evident to me.

There are many features visible on Mars which can only
be represented by drawings and to make these successfully
requires special qualifications of memory in the observer as
well as quick and acute vision. To be convinced on this
point it is only necessary to read the reports on the recent
eclipse of the sun, a phenomenon so fleeting as to serve our
purpose well.

As many readers may remember, this eclipse was just total
on the central line in Portugal during perhaps a second, cer-
tainly not much more. I quote from an observer who was
very near this central line. Referring to the orientation of
the solar crescent in mid-eclipse he says : " In the excitement
of the moment I did not see whether the crescent of the sun
as it passed from the left to the right side of the moon passed
below or above it." Again he says : '* As the event proved
we were too far south-east to be in the track of totality."

It is certain from his position that the crescent did pass
on one side only of the lunar disc. Further it is clear that
the passage of the crescent must have been comparatively
slow, occupying at least a large fraction of a second. Also
the observer was not without experience, as he was observing
a total eclipse for the fourth time. It is thereiore evident
that the omission which he so honestly admits was not one
of eyesight but of memory.

As has been said, the best views of Martian detail seldom
last a second. The positioning of this detail is of the same
order of difficulty as the observation quoted.

The next point which claims the attention of the observer
s his skill, which means command over the materials which
he uses. Many misconceptions of the appearance of Mars
9

130 SCIENCE PROGRESS

have arisen from the extreme difficulty of drawing the delicate
detail that is seen. We have only to look at various drawings
by different observers to be assured of this. Comparing the
drawings, it is difficult to believe them to be bona fide attempts
to portray the same object.

Lowell tells me that after twenty years of practice in this
particular work, he is quite unable to draw the canals of
Mars as they appear in the telescope. His practised hand
cannot trace lines on paper fine enough or straight enough
to represent them. It is therefore natural that the attempts
of less experienced observers should be but caricatures of the
planet which they strive to represent. It is, however, a relief
that the drawings made independently at Flagstaff do resemble
one another and the planet very closely, thus affording internal
evidence both of the reality of the features seen and the
accuracy of the representations.

Turning now to the method by which detail is detected,
we find that the process, unlike the announcement of the
discovery, is not a sudden one. Let us follow the observer
to the dome and trace his method. Armed with a suitable
dark glass and an appropriate aperture, as explained earlier,
he watches the planet carefully. Suddenly he is startled by
the appearance of some previously unknown marking which
flashes into sight but for a moment and is gone, leaving only a
vague impression of something being there. The hint so
obtained must be noted, for perhaps, later on, another and
another glimpse may be obtained which by their cumulative
effects assure us of the reality of the new feature.

This is the manner in which all the canals have been
discovered and just as accumulated observations establish
their numbers, so accumulated hints attest the existence of the
fainter markings, until a moment of perfect seeing shows them
in all their beauty with the fineness and fixity of a steel
engraving.

At first sight their elusiveness suggests an illusion, which
accordingly claims our attention next. Optical illusions may
be divided into two classes — those which are self-confessed and
obvious ; and those specious appearances of reality which may
deceive all but the most penetrating analysis.

As an illustration of the harmless class of illusion, irradiation

THE PLANET MARS 131

may be taken, which is the apparent enlargement of a bright disc
when seen against a dark background. By trial of the different
contrast effects to which this phenomenon is due, its laws may
be determined and its effect eliminated from observations which
it might otherwise vitiate.

An instance of the deceptive illusion is the often-quoted
power of the eye of integrating minute markings too small to
be severally visible. On looking at a mass of small specks too
small to be seen clearly apart, the eye has a strong tendency to
accept the specious appearance of these as lines and they cannot
be distinguished from realities except by the closest scrutiny
Happily this illusion is only possible under critical circum-
stances of distance on the narrow borderland between seeing
the dots as they are and not seeing any trace of them.

Now the lines which skilled observers have perceived on
Mars have been seen under many varied circumstances of
distance, illumination and instrument. It seems therefore
impossible that they can be due to this form of illusion. Also
it is certain that though a series of dots may masquerade as
lines, the converse action is inconceivable. Since also dots and
lines are visible on Mars at the same time — oases and canals —
the assumption of the reality of both seems warranted.

There is another illusion to which the double canals have
been, I think erroneously, assigned, namely double vision.
Why double vision should be specified I know not, for multiple
vision is equally possible. We all know that by imperfectly
focussing an object we may, under certain conditions, see it
double and if strong contrast occurs we may in the same way
induce multiple vision.

Now on Mars are many double canals but illusion suggests
that the most conspicuous should be double or multiple. On Mars
I know of many cases of faint canals which are double and
conspicuous ones that are single but none which are multiple.
The canals which appear double appear so from some cause on
the planet and not in the eye. They are alike indifferent to and
inexplicable by any illusion of the observer's eye and the
individuality of the behaviour quite definitely shows. It is
the failure to explain the Martian markings as the results of
illusion that assures us of their reality.

In this preliminary account I have but summarised the
methods and means, the illusions and difficulties which beset

132 SCIENCE PROGRESS

the path of the observer and so paved the v^ay for a description
of the detail which patient attention has disclosed ; this will be
given in a later article.

This preliminary discussion is needful because of the weird
oddity and utter strangeness of the features discovered ; unless
attested by methods of proven accuracy these would be quite
incredible and therefore liable to be regarded as the tricks of
fancy rather than as the discoveries of painstaking research.

VARIATIONS IN PASTURES

By C. T. GIMINGHAM
University of Bristol

A MOST important place is taken by pasture and meadow land
in British husbandry ; indeed, if the area of each crop grown
throughout the country be a measure of its relative importance,
grass comes before all others. Thus the annual returns of the
acreage of land permanently under grass in Great Britain have
shown a steady increase during the last sixty years, the area
having been enlarged since 1870 from 12,072,856 to 17,446,870
acres, an addition of 5,374,014 acres. In 191 1, the returns show
that of a total of 32,094,658 acres under crops of all kinds, the
area devoted to permanent grass was 2,799,082 acres in excess
of that occupied by all other kinds of crop put together. In
Ireland, the proportion of grass to arable land is almost exactly
two to one; and in some English counties the land is all but
entirely occupied by pasture : for example, Somersetshire in
191 1 returned 682,342 acres as under grass and only 170,451
acres as arable land. All these figures are exclusive of the
rough grass land catalogued as " Mountain and Heath Land
used for Grazing " which in Great Britain amounts to another
12,875,660 acres.

Much of the large area referred to is grass land of some-
what inferior quality, this being true especially of the part laid
down within recent years. Although some of the heavy clay
soils, too expensive to cultivate, in various parts of the country,
which were converted into permanent grass land are now
excellent pasture, yet most of the land was originally very poor
arable and having been allowed to fall down to grass without
special care or treatment is at present worth little for grazing
purposes. Under proper treatment, a good deal of the poorer
pasture land in the country is unquestionably open to consider-
able improvement ; well-planned practical experiments that

133

134 SCIENCE PROGRESS

have been carefully carried out have already afforded proof that
valuable results are to be obtained in this direction.^

In the present article, however, it is proposed to consider
purely scientific soil investigations and it must be admitted that,
on the whole, in England, up to the present, the amount of work
done on pasture soils and the special problems these afford are
not very considerable. All the important contributions to our
general knowledge of the factors governing soil fertility have
been the result of the study of arable soils, which so far have
almost monopolised attention. It is natural that arable soils
should have been first studied in detail ; but we have to recognise,
in applying the results to the case of soils which are permanently
occupied by grass, that a number of new conditions are intro-
duced which exert an influence in various directions on the
processes going forward in the soil and considerably modify the
nature of the problems with which we have to deal. It is most
important to know to what extent conclusions based on the
study of arable soils are directly applicable to the conditions
obtaining in pasture soils and whether the same methods of
investigation can be made use of in both cases.

In dealing with grass land, we have primarily to take
account of the fact that the soil is occupied by the crop con-
tinuously. What then is the effect of the long-continued action
of one character of growth upon the soil ? What differences
tloes the continuous presence of a crop make to a soil from the
biological, chemical and physical points of view ? There is
extremely little detailed knowledge available upon these points
and we can still scarcely do more than point out a few of the
possibilities and suggest some of the lines along which inves-
tigation is still needed.

In the first place, the continuous action of the roots of the
Same species of plants, always absorbing food and water, always
respiring and excreting, by its effect upon the atmosphere within
the soil and upon the soil itself, must certainly exert a direct
influence upon the nature of the living organisms — and especi-
ally of the bacterial flora. In what direction this influence acts
can be at present a matter of speculation only : it is possible
that it tends to make a more fixed and unvarying flora, one that

^ See especially the account of experiments on " The Influence on the Pro-
duction of Mutton of Manures applied to Pasture," by Somerville (Supplement
to \\it Journal of the Board of Agriculture^ vol. xvii. No. lo).

VARIATIONS IN PASTURES 135

does not undergo constantly the changes and fluctuations which
take place in arable soils. It would seem probable too that a
crop which is almost continually requiring food would render
impossible any considerable accumulation of readily available
plant food in the surface soil, such as takes place under certain
conditions in arable soils. In this connexion, it may be noted
that we are at present without precise knowledge as to the form
in which the pasture grasses take up their nitrogen. Recent
work on the assimilation of nitrogen by plants has shown that
perhaps many more types of compounds are available as
sources of nitrogen than was formerly supposed^ but almost
all the experimental work has been carried out with cereals and
leguminous plants. There is definite evidence, however, that
ammonium salts, as well as nitrates, can serve directly as food,
at all events for some species of pasture grasses. In the case of
the grass plots at the Rothamsted Experimental Station which
receive heavy dressings of ammonium salts annually, it has
been found ^ that nitrification takes place only to a very slight
extent and is probably confined to the immediate neighbourhood
of the scattered particles of calcium carbonate present in the
soil, since the soil generally is acid. None the less, on these
plots a fairly heavy crop of coarse grass is grown, consisting
almost entirely of three species — Holcus lanatus^ Alopecurus
pratensis and Arrenatherum avenaceum — forming tufts with bare
patches of peaty decayed vegetation here and there.

The continual occupation of the land by a crop undoubtedly
has a most important influence on the physical condition of the
soil. The surface of grass land is disturbed only to a minimum
extent and consequently its physical condition and texture are
quite different from that of a well-tilled arable field on the same
soil. This has far-reaching effects. The undisturbed condition
of the surface and consequent slight aeration have a large share
in determining what will be the predominant types of bacteria ;
and one of the evident results of the defect is that those types
are favoured which cause the decay of organic matter to proceed
much less quickly than in well-aerated soils ; and there is
always a certain accumulation of humus. This is especially
seen in grass land on heavy clay soils and on soils deficient in

^ See Hutchinson and Miller, Jour. Agric. Set. vol. iv. p. 282, for biblio-
graphy.

^ Hall, Miller and Gimingham, Proc. Roy. Soc. B. 80, 1908.

136 SCIENCE PROGRESS

lime. The importance of such an accumulation of humus in
modifying soil texture need not be enlarged upon.

In view of these and many other important factors, certain
questions at once arise. For example, does mechanical analysis,
which has given such valuable results in the study of arable
soils, afford equally useful indications in the case of pasture
soils ? Is chemical analysis a useful guide ? If so, can the
large number of data obtained from arable soils be taken as
standards ? And, to put the whole matter as briefly as possible,
how far, in considering pasture soils, must we modify our ideas
of the relative importance of the various factors which con-
stitute what may be termed the fertility of the soil ?

Such are shortly some of the more general questions. In
addition, a large number of local problems of considerable
complexity arise in connexion with pasture land and, as has
often happened in like cases, the detailed investigation of some
of these has served to throw light on the larger problems.

Pasture Soil Analyses, — The value of soil analysis as a guide
to the manurial treatment of poor pastures has been dealt with
by Wood and Berry ^ of the Cambridge University School of
Agriculture, in connexion with a series of experiments on
methods of improving poor grazing land ; the agricultural
results have been discussed by Middleton.- The soils from
a number of centres at which the experiments were carried out
were examined, in order to ascertain whether the results of the
soil analyses could be correlated with the results of the various
methods of treatment. Of the latter, the most important was
the remarkable improvement effected in almost all cases by the
use of basic slag ; but determinations of the total phosphate
present in the soils gave no indication of deficiency in phosphoric
acid. On the other hand, the figure for '* available " phosphates
{i.e. soluble in i per cent, citric acid) was of greater value and
appeared to be a trustworthy guide as to which soils might be
expected to respond to phosphatic manuring, " if for pasture
soils the limit below which * available ' phosphate may be
considered deficient is fixed as high as 0*02 per cent."

Other results indicated that the figures for total nitrogen,
total potash and lime were not of much help in determining the
best methods of manuring ; but if the soil contain not more

* Jour. Agric. Science^ vol. i. p. 114.
^ Ibid. vol. i. p. 122,

VARIATIONS IN PASTURES 137

than 0*01 per cent, potash soluble in i per cent, citric acid (avail-
able), the authors consider an application of potash salts is
likely to be useful. With regard to lime, unless a pasture soil
contain less than o'25 per cent, it seems improbable that liming
is necessary.

The mechanical composition of the soil is probably the
factor of prime importance to take into account in attempting
to improve poor pasturage. A fairly good mechanical condition
is essential: soils with a very high proportion of either the
coarsest or the finest grades of particles are never likely to make
really useful grazing land, whatever the manurial treatment.

A further paper by S. F. Armstrong^ (also from the Cambridge
School of Agriculture) deals primarily with the botanical and
chemical composition of the herbage of pastures and meadows
but includes observations on the soils of the grass lands
investigated. It was apparent that, at all events in the English
Midlands, the choicest grazing land was invariably associated
with soil rich in " available " phosphates ; here again the import-
ance of good physical condition and of an abundant supply of
" available " phosphoric acid for the production of good pasture
land is emphasised.

To what extent these conclusions hold good for pasture soils
generally can only be determined when we are in possession of
many more data on the subject.

Romney Marsh Soils. — An important local problem has
received attention in the very thorough investigation recently
carried out by Hall and RusselP of the Rothamsted Experi-
mental Station on the pasture soils of Romney Marsh.
Romney Marsh, which has an area of nearly 120 square miles,
is part of the large stretch of alluvial land which borders
much of the coasts of Kent and Sussex. It is only slightly
elevated above high-water mark but having been elaborately
drained is now dry and can no longer properly be called a
marsh. It is almost entirely grass land. In spring and summer
the fields are occupied by great numbers of sheep, as they
form some of the best grazing land in the south of England,
many of the pastures being famous for their richness. The best
land will fatten as many as ten sheep per acre during the sum-
mer without the aid of any artificial feeding ; but all the pastures

^ Jour. Agric, Science^ vol. ii. p. 283.
' Jbid, 1912, vol. iv. No, 4.

138 SCIENCE PROGRESS

are by no means equally good, adjoining fields, in some places,
showing extraordinary differences in feeding value. Land is
often found surrounding the most valuable fattening fields
which can only be used for breeding upon or that will just
keep sheep growing. The two types of land are referred to
as ** fatting" and *' non-fatting" pastures; the immediate object
of the work undertaken by Hall and Russell was to discover
the causes underlying the remarkable differences they exhibit.

Samples of the grass were obtained, at various centres, at
different times of the year, from fields representative of both
fatting and non-fatting pastures ; these were examined botanic-
ally and chemically. Samples of each foot of soil down to the
water level (usually about eight feet) were also taken and sub-
mitted to mechanical and chemical analysis ; moreover borings
were made to determine the water content of the soil at various
depths at different seasons, and during 1909 and 1910 regular
observations were made of the water level in the fields and of
the temperature at twelve feet and six feet below the surface.
By these means it was hoped to detect differences which might
lead to an explanation of the obvious differences in feeding
value between the two types of pasture.

The investigation of the botanical composition of the herbage
from the various fields showed that the most abundant grass was
Lolium perenne, which formed from one-third to four-fifths of
the total herbage on all the pastures ; Agrostis alba and vulgaris
were regular constituents up to 20 per cent. ; there was also
a fair proportion of white clover, though this is not evident
in the analyses, owing to the creeping habit of the plant, which
made it difficult to include it in the cut samples. The floral
type was on the whole remarkably similar in fatting and non-
fatting fields. No differences were brought to light by the
analyses which could at all account for the higher feeding value
of fatting fields.

There were, however, certain differences in the herbage
evident to the eye which were not brought out by the botanical
analyses. On the good land, the growth of grass was essentially
leafy and covered the ground much more effectively than on the
inferior land, where a marked tendency to the production of a
stemmy herbage with abundant flower-heads was noticeable.
This was seen very remarkably in one case, a non-fatting field
being covered with the yellow blossoms of buttercups when the

VARIATIONS IN PASTURES 139

adjoining fatting field showed none, though on analysis of the
herbage there proved to be almost exactly the same percentage
of the plant in both fields. The characteristic leafiness in the
one case and stemminess in the other was the chief difference
between the good and bad fields and was quite independent
of the floral type.

Three other differences more or less marked were noted —
in any pair of fields the good one had more clover in the
herbage, showed less tendency to burn in summer and probably
gave a slightly higher yield of grass.

The soils next claim attention. Speaking generally, the
surface soil in Romney Marsh is of a heavy, close-grained
type (though in a few places a lighter soil occurs) and is made up
largely of clay derived from the heavy soils of the Lower Wealden
strata which has been deposited as silt. The soils diff*ered a
good deal at the three selected centres in the Marsh at which
the investigations were carried out but as these differences
seemed to have no bearing on the present problem they need
not detain us. At centre No. i (Orgarswick) the soils proved
to be very uniform in mechanical composition to a considerable
depth and the fatting and non-fatting fields showed no signifi-
cant diff'erences in this respect. The soil was heavy, contain-
ing no coarse sand and about 25 per cent, of the clay fraction ;
below 7 ft. peat saturated with water was reached. Mechanical
analyses of the soils failed to reveal any reason for the
superiority of one field over another, poor and rich land
being almost identical in composition.

The water content of the soils of both fields at diff'erent
dates was always practically the same, the fatting field being
perhaps a little more moist in early summer and somewhat
dryer later on.

There was a small difference in the level of the water, this
being always higher in the fatting field. On the whole the soil
of the fatting field tended to keep a little dryer and to get rid
of its surface water rather more quickly and thoroughly. This
may probably be taken as indicating some difference in texture
not revealed by mechanical analysis. Diff'erences in soil tem-
perature were very slight but regular, the soil of the good
field proving to be a little warmer than the other.

Chemical analyses of the two soils gave very similar results ;
but a slightly higher percentage of nitrogen and phosphoric

140

SCIENCE PROGRESS

acid (especially the latter) was noted in the good soil. Lime
was present in abundance in the subsoil in both cases ; and,
quoting from the paper under review, " as regards the mechani-
cal and chemical composition, temperature and moisture deter-
minations, little can be found to discriminate between the two
soils and though some of the factors of production are slightly
better in the good soil the differences seem too small to be
significant."

Further examination, however, enabled the authors to account
to some extent for the difference in the type of growth of the
herbage observable in the fatting and non-fatting fields. The
soils of the good fields possess one marked characteristic : they
contain definitely more free ammonia and more nitrate in the
early part of the season, though the difference disappears
later. The accompanying table gives the figures obtained :

Nitrogen as Nitrate And Ammonia in parts per Million of

Dry Soil, 1910.

March i6.

May 13.

June 22.

September 14.

Nitrate.

Am-
monia,

Nitrate.

Am-
monia.

Nitrate.

Am-
monia.

Nitrate.

Am-
monia.

Orgarswick :
Surface soil. Fatting

,, Non-fatting

15-8
io"4

1 10
1 1*0

I4'6
8-9

7-0
30

1*4
3-0

—

58-4

60
220

MiDLEY :
Surface soil. Fatting

,, Non-fatting

12-4
6-3

—

24'2

6-5
2-8

6-4
27

—

15-4
217

—

Westbroke :
Surface soil. Fatting

,, Non-fatting

23-6
130

80
60

21-5

20-8

2-3

2"0

—

8-2

—

At the same time it was found that soil from the good field
underwent nitrification at a greater rate than that from the
bad field. These are the most significant differences observed.
It is evident that the better type of grass in the fatting fields
is produced as a result of a greater food supply, though the
floral type remains the same.

With minor divergencies, all the details given hold equally
for the soils of the other two centres, whether the physical
conditions of the soils in the pairs of fields were similar or
dissimilar. In the authors' words, "... the amount of nitrates
and ammonia in the good soils is always far above the quan-
tities found in the bad soils in the early part of the year. Here

VARIATIONS IN PASTURES 141

is probably the causal factor which accounts both for the greater
amount of growth on the fatting fields and its green, broad
leafy character. But accepting this more rapid production of
available nitrogen as the determining factor giving rise to the
herbage, it is still impossible to see from the other deter-
minations made why the formation of available nitrogen
compounds should be more rapid in the one case than in the
other. The difference apparently lies in the nature of the soil
organic matter."

From what has been said, it might be expected that the
chemical composition of the herbage from the two kinds of
fields would be markedly different especially as regards the
percentage of fibre ; but this proved not to be the case. The
amount of phosphoric acid and nitrogen is slightly higher
in the good that in the poor herbage but the difference is by
no means enough to account for the contrasts in feeding value.
The conclusion is reached that the ordinary methods of food
analysis need much refinement in order to give useful results
in such cases as this.

Attention should be drawn by this investigation to the
very important practical consideration that in dealing with
the feeding value of pasture grass it is necessary to distinguish
between the effect due to the botanical composition of the
herbage (the floral type) and that due to the habit of growth.
These are dependent on different sets of conditions. The
floral type is more influenced by local climate, situation and
management than by soil and may vary considerably on the
same field from year to year. The habit of growth in the
cases here dealt with appears to be chiefly determined by
the supply of nitrates and ammonia in the soil, i,e, by the
rate of decomposition of the organic matter.

From the point of view of the soil investigator the work
indicates forcibly the limitations of the methods of mechanical
analysis. Diff'erences in the physical properties and texture
of pasture soils exist which are not revealed by mechanical
analysis and, indeed, speaking widely, " soil analysis does not
give as clear indications with pasture soils as it does with
arable soils." This conclusion receives confirmation in some
work now to be referred to.

The Scouring^ Lands of Somerset. — A somewhat similar
^ Scouring is the farmer's word for acute diarrhoea in cattle.

142 SCIENCE PROGRESS

problem has recently been gone into anew by the present
writer/ This concerns a considerable area of pasture land
in the middle of Somersetshire in a district given up almost
entirely to dairy farming. Here again are marked differences
in the feeding value of closely adjoining pastures ; but in this
case the bad fields are actually injurious. In these particular
districts the herbage of much of the grazing land has the
property of causing cattle feeding there to be scoured very
seriously indeed at certain times of the year, such pastures
being known locally as " teart " or '* turt " land. Their presence
naturally lowers the value of the farms on which they are
situated, though the extent to which the scouring properties
of the herbage are developed varies greatly in different places ;
and good and bad fields are often intermixed in a very intricate
manner. Cows in milk suff'er most severely but all kinds of
cattle may be aff'ected ; lambs also are scoured badly, whilst
sheep and horses are, for the most part, exempt. The scouring
is usually most prevalent in the autumn — when cattle are feeding
on the aftermath — and as a rule the more abundant the growth
the more serious the trouble becomes, varying with the season.
Individual animals vary greatly in the degree to which they
may be affected.

Such scouring on the " teart " lands has been attributed to
a variety of causes, among them the presence of some particular
plant in the herbage and a bad water supply. Neither of these
explanations, however, can be substantiated.

Nor does the trouble suggest a specific disease and attempts
to isolate a responsible organism have proved abortive. Infec-
tion never travels from a '* teart " field to a neighbouring sound
field even though only a ditch may separate the two ; nor do
cattle transferred from " teart " to sound pastures ever bring
infection to healthy cattle with which they may come in contact.
The usual result of the application of manures to "teart"
pastures is to make matters worse as the growth is increased
and when large numbers of sheep are fed in these fields the
same result is noticed. On the other hand, the first two or
three sharp frosts remove all tendency to cause scouring from
the autumn herbage.

" Teart " land in Somerset is entirely confined to one
geological formation, the Lower Lias. The typical surface soil
^ Gimingham, Jour. Board of Agric. vol. xvii. 1910, p. 529.

VARIATIONS IN PASTURES 143

on the Lower Lias here is an extremely stiff unyielding clay,
blue or yellow lias clay subsoil being not far below. At the
same time, a considerable part of this district which lies
at a low elevation is covered by an alluvial deposit, varying
from a few inches to many feet in depth ; pastures on this
alluvial soil are invariably free from any tendency to cause
scouring even though the typical Lower Lias clay may lie not
far below the surface. The division between good and bad
land is in many places very sharp and affords an accurate
indication of the boundary between lias and alluvium. Where
the layer of alluvium is deep the differences in the surface
soils of the two kinds of fields are very obvious ; and even
where the soils are in most respects very similar the surface
of the good fields is noticeably darker in colour and looser in
texture and, further, the ground has an indefinably different
and more springy " feel " to the foot.

In order further to investigate this difference in texture
between sound and "teart" land, determinations of the densi-
ties ^ of some of the soils in situ were made. With few excep-
tions the surface soils of the sound fields show consistently a
definitely lower density than those of " teart " fields from the
same neighbourhoods. The sound soils have also a greater
capacity for holding moisture.

Ordinary chemical analysis of both types of soil has not
revealed anything that could account for the observed effects
and there is no obvious peculiarity in. the composition of the
"teart" fields. A large number of samples were also submitted to
mechanical analysis, the result being that all the soils, whether
from good or bad land, were found to be of the same general
type, so that the observed differences in physical condition and
texture cannot be accounted for by referring them to the
ultimate mechanical compositions of the soils.

These analyses have, however, brought out the fact that
there is, almost invariably, a considerably higher percentage of
organic matter in the good soils ; and there is no doubt that, to
a great extent, the dark colour, the texture and the different
appearance and '* feel " of the soil of these fields is due to the
influence of the higher proportion of organic matter on the
nature of the compound soil particles.

The only significant difference discoverable between sound
* Details are not yet published.

144 SCIENCE PROGRESS

and " teart " soils lies then in their physical condition. Hence
the production of scouring herbage must be determined to a
great extent at least by the special texture of the soil. How
then does the soil texture affect the physiological properties of
the herbage in this manner ? Chemical analysis has not so far
succeeded in demonstrating the presence of unusual substances
in the herbage to which the scouring might be attributed.
The ordinary methods of food analysis are not sufficiently
refined to detect such differences in feeding value as these ;
but there must necessarily be a difference somewhere in the
proximate constituents of grass from good and from scouring
fields. It can only be concluded that under the special soil
conditions some abnormal constituent is developed in the
herbage having a physiological action provocative of scouring ;
and further that the texture determines these special soil
conditions.

Some evidence is already forthcoming that modifications of
the soil texture remove the conditions giving rise to a scouring
herbage.

In the two investigations here summarised it is evident that
important differences in the textures of the respective types of
soils undoubtedly exist which were not indicated by the results
of the analysis ; and we cannot but draw the conclusion that
mechanical analysis according to our present methods is not
of the same value in the study of pasture soils as it has proved
to be in the case of arable soils. This is probably because
of the controlling influence exercised by the organic matter
in pasture soils and a place of primary importance must be
assigned to this constituent of the soil in determining the type
and composition of the herbage. Physical properties which,
from analogy with arable soils, might reasonably be inferred
from the results of mechanical analysis are, in the case of soils
permanently occupied by grass, often masked by the influence
of the organic matter present. No doubt the undisturbed con-
dition of the surface soil and the consequent slow rate of
decay of the humus accounts for this.

As to the manner in which the action becomes operative
we are at present entirely in the dark. Analyses of the herbage
by our present methods have led to nothing and it seems
probable that before it will be possible to throw much light
on this point we shall need to possess more delicate methods

VARIATIONS IN PASTURES 145

of food analysis and to know much more of the nature and
properties of the organic matter as it exists in pasture soils.

[I had an opportunity recently of visiting the Romney Marsh
pastures with Dr, Russell and was much struck by the remark-
able difference noticeable between adjacent fatting and not-
fatting fields. The evidence seems to be all but conclusive
that the difference has been induced, in course of time, rather
than there was a difference originally between the soils of the
two kinds of pasture. It should be noted that both have their
value and that both are required, as ewes with their lambs
cannot be kept on the fatting fields, the herbage of these affect-
ing the milk and making it in some way deleterious to the
lambs. The appearance of the two pastures is strikingly
different : the one has the rich, deep green colour characteristic
of grass fully provided with nitrogenous manure, whilst the
other has the pale appearance of nitrogen-starved grass.

The good graziers are most careful to keep so much stock
on the land constantly that the grass is fed off very close to
the ground ; the sheep are therefore fattened on very young
luscious herbage, whilst those on the not-fatting fields doubtless
partake of a growth of a more mature character.

There must be a very considerable difference in the com-
position and food value of the two kinds of herbage. The
statement that differences cannot be detected by analysis is
merely a confession of impotence — a confession that present
methods of analysis are not really of any value — and proof of
the need in which we stand of raising the status of agricul-
tural chemistry. Instead of requiring the merest modicum of
knowledge, this branch of chemistry is probably one which
needs more discriminative power than all the others put to-
gether and until we recognise this little progress will be made.

Although the number of species of plants on the two pas-
tures may be the same, it is obvious that there is a far more
luxuriant growth of clover on the fatting fields and that the
animals on these have more nitrogenous food at their disposal.

Apart from the organic elements, carbon, hydrogen, oxygen
and nitrogen, relatively little of value is removed by the fatten-
ing sheep from the land ; consequently this is constantly and
highly manured by their droppings. The sheep with lambs
apparently remove more from the soil and return less to it
10

146 SCIENCE PROGRESS

than the fattening sheep. It is not difficult to understand
therefore, bearing in mind that nitrogen is constantly assimi-
lated from the atmosphere by the clover, that the mere excessive
usage of the fatting pastures has led to their improvement and
that the difference in the contribution made by the tv^o classes
of stock to the land may v^ell have brought about the change
in the character of the pastures — apparently stock and land
have been in reciprocal relationship over a long period of
time. The investigation carried out by Hall and Russell appears
to be of special value from this point of view : by showing that
there is no reason to suppose that the actual soils of the two
kinds of pasture differ intrinsically to an extent sufficient to
account for the observed peculiarities and that the differences
are induced, in all probability, by rational usage, they have in
a measure foreshadowed means of improving pastures generally.

H. E. A.]

THE GENESIS OF LOGARITHMS

By ALLAN FERGUSON, B.Sc.
Assistant Lecturer in Physics in the University College of North Wales

In the historical development of mathematics the period covered
roughly by the seventeenth century must always, on two
counts, be held to be of primary importance, as this century
witnessed the birth of the fluxionary calculus and the discovery
of logarithms. It is proposed to deal with this latter discovery
in the present article. As the details of the discovery are of
remarkable interest to the mathematician, and as they are not
easily obtained and are couched in archaic language that is some-
what laborious reading, it seems that a restatement of the facts
may not be without interest and value.

In order to make the survey fairly complete a preliminary

discussion of the mathematical tables in use at the beginning
of the seventeenth century, together with a brief account of
the methods of computation adopted, will be given.

Confusion of diction and thought will be avoided if it be
remembered that what we call the ** trigonometrical ratios "
can be and were considered under two aspects— (i) that of
ratios, (2) that of lines. In (2), the older system, angles are
measured, by the arc swept out by a revolving line whose
length must be the same for all angles. Then in the figure
the line BM measured the sine of the arc A B, O M (the sine

147

148 SCIENCE PROGRESS

of the complementary arc) was the cosine, O T (which cuts the
circle) the secant; and so forth. So that the well-known theorem

sin 2<9 + cos ^6 = i

would be read by a mediaeval geometer as " The square of the
sine added to the square of the cosine gives the square of
the radius."

It is further to be noted that in the computation of tables,
the values of the trigonometrical functions were expressed
in integers ; so that when additional accuracy was required tables
of sines, etc., were computed on the assumption that the
** radius " was proportionately large. Thus, in the sixteenth
century, Rheticus computed tables for every ten seconds of
the first quadrant, taking the radius as 1,000,000,000,000,000;
whilst Pitiscus added to this table a few of the first sines
computed to the radius 10,000,000,000,000,000,000,000. This
manner of presentation is, of course, the mediaeval equivalent
of our modern phrase, " correct to so many places of decimals."

In more ancient times trigonometrical measurements of
angles were based upon the computation of the chord of double
the arc, that is to say, in the preceding figure the chord B B'
was put in relation to the arc A B. Thus in the first
century a.d. Menelaus defines the "nadir" of an arc to be
the right line subtending the double of the arc; a table of
such arcs and chords was constructed and exhibited by Ptolemy
in the second century a.d., in which the chords of various
arcs are calculated at intervals of half a degree. The relation
of the half-chord to the arc — what we should call the sine of
the arc — was known to the Greeks but its familiar use in
trigonometry is due to the Hindu mathematicians, whose
knowledge, through their Arab pupils, slowly filtered through
to th^ West.

The earliest trigonometric tables of note are those of
Johannes MuUer, commonly called Regiomontanus (1436-76),
who completed an earlier table of sines by Peurbach, in which
the radius was taken as 600,000 and the sines computed for
every minute of the quadrant. Afterwards, leaving the relics
of the sexagesimal notation implied in the above radius, he
made a fresh computation of the sines to every minute of the
quadrant, taking the radius as 1,000,000. We have also from
Regiomontanus a table of tangents— a table which he called

THE GENESIS OF LOGARITHMS 149

canon Joecundus'. — computed for every degree and to radius

100,000.

Barely mentioning the canon of sines given by Copernicus,
that of tangents by Reinhold (1553) and, about the same date,
of secants by Francis Maurolye, Abbot of Messina in Sicily,
v^e come to the striking work of Francis Vieta (i 540-1603),
without doubt the foremost algebraist of his day.

In a folio volume published at Paris in 1579 he gives
tables of sines, tangents and secants for every minute of the
quadrant to radius 100,000. And it is to be noted that he
regards the " trigonometrical ratios " not as being obtained
from a series of lines drawn in or about a circle but as being
obtained from a series of plane right-angled triangles in which
(i) the hypotenuse has the constant value 100,000, the other
two sides being variable and giving the values of the sine
and cosine; (2) the base has the constant value 100,000, when
the other two variable sides give the tangent and secant ;
(3) when the perpendicular is kept constant the variable sides
give the cotangent and cosecant.

A second table given by Vieta is something of a curiosity,
as in it he gives a canon of accurate sines, cosines, etc., ex-
pressed in integers and rational vulgar fractions. In general,
the numbers which express the trigonometrical ratios are
irrational but for certain particular angles the values are
rational; it is these values which are tabulated. The corre-
sponding angles are not given but in their place appears a
series of numbers called by Vieta numeri primi baseos. Let
one of these numbers be called p and let r be the constant
radius which, as before, is taken as 100,000, then, if r be taken
as the hypotenuse of the right-angled triangle, the sine or
perpendicular will be given by

the base or cosine will be

4+'

with similar expressions for the tangent and secant, cotangent

150 SCIENCE PROGRESS

and cosecant, when r is taken to represent the base and per-
pendicular respectively of the right-angled triangle.

Such expressions are clearly rational and by giving />, in
succession, different values the canon v;^e are discussing was
computed.

It should be mentioned that this work, which is of great
rarity, was published anonymously. Both Hutton and Montucla
agree in ascribing it to Vieta from internal evidence and from
the fact that Vieta repeatedly mentions it in his other works.

But perhaps the most massive of all such tables is that
computed by George Joachim Rheticus (1514-76), a pupil of
Copernicus and professor of mathematics at Wittenburg. The
work, which was published in 1596 by Valentine Otho, gives
tables of sines, tangents, secants, etc., computed to the radius
io^° and for every 10'' in the quadrant, together with their
differences. Theorems and explanations are given for the
construction of the canon to the radius 10^^ and, as in Vieta's
work before-mentioned, the trigonometrical ratios are con-
sidered as being represented by the sides of right-angled
triangles. The computations to the radius 10^^, which were
made proceeding by steps of 10'' and for every separate second
in the first and last degrees of the quadrant, were published in
161 3 by Pitiscus, who added to the canon a few sines calculated
to the radius lo^l

With the mention of Lansberg's tables (1591) and Pitiscus's
trigonometry (1599), our enumeration of the principal tables in
vogue at the beginning of the seventeenth century may be
considered to be fairly complete ; and now, remembering the
absence of all logarithmic aids to computation and considering the
large number of significant figures to which the calculations were
carried, one can well imagine what a slow, tedious and laborious
process was the construction of such tables. Rheticus, indeed,
in the compilation of his canon incurred an expense of thousands
of gulden, having a large staff of computers continuously
employed for a space of twelve years.

The methods used for computation were, of course, very
varied : I give here a brief analysis of one process, which will
serve as an example.

By the theorems of elementary geometry, the lengths of the
sides of a few of the regular figures inscribed in a circle of
given radius (lo^ io^° or whatever figure may be chosen) can

THE GENESIS OF LOGARITHMS

151

readily be calculated. The angles which these chords or sides
subtend at the centre of the circle are also known and clearly
half the length of any such chord will give the sine of half the
corresponding angle subtended by the chord. Thus in the
following table, taking radius as lo^ we have

Figure.

Arc.

Chord.

Half-
arc.

Half-chord or
sine of half-arc.

Triangle

120°

17320508

60°

8660254

Square .

90"

14142136

45"

7071068

Pentagon

72"

II755705

36^

5877853

Hexagon

60°

I 0000000

30^

5000000

Decagon

36"

6180340

18°

3090170

Quindecagon

24"

4158234

12°

20791 17

Now, knowing the sine of any angle, the sine of the half-
angle can be calculated by means of some such theorem as :

** The sum of the squares of the sine and versed sine equals
the square of double the sine of half the arc."

This is, of course, simply the equivalent of

sin *^ -f (i - cos 6f = 4 sin ' -

and gives sin - in terms of sin 6. And knowing the sine of any

angle, we arrive at the sine of the complementary angle by the
theorem :

" The square of the sine and the square of the sine of the
complement is equal to the square of the radius " ; i.e. simply

sin 2<9 -f cos ^6 = i.

Starting, then, with the sine of twelve degrees and continually
finding the sines of half-arcs, we obtain the following series
of tables :

Angle.

Sine.

Comp.

Sine.

12°

2079II7

78°

9781476

6°

1045285

84°

9945218

3: ,

523360

87°

9986295

1° 30'

261769

88° 30'

9996573

45'

130896

89° 15'

9999143

22' 30"

65449-4

II' 15"

32724-8

— ~~

Beginning with any of the complementary angles in table I and

152

SCIENCE PROGRESS

continually halving we have, taking, say, 84° and Sf as our
starting-points :

Angle.

Sine.

Comp.

Sine.

42''

6691306

48°

7431448

21°

3583679

69°

9335804

10° 30'

1822355

79° 30'

9832549

5° 15'

915016

K <

9958049

43° 30'

6883545

46° 30'

7253744

21° 45'

3705574

68° 15'

9288095

etc.

It is clear that this process can be extended largely by
continually taking one of the complementary sines as the
starting-point for the halving process ; and thus a large number
of the sines may be computed and tabulated.

Returning now to table I, we see that the sines of 22' 30''
and 11' 15'^ are, to the accuracy needed, in the same ratio as
their arcs, and thus sine i' is obtained by simply dividing
32,724'8 by 11 J, giving 2,909 as a result, and this is, of course,
exactly -^ of sine 45'; so, multiplying 2,909 by i, 2, 3, etc., we
have sine i\ sine 2', etc., up to sine 45'.

Theorems for the sums and differences of two sines were
known and these, combined with the theorems already given for
halving, doubling, etc., enabled the calculators to compute any
required sine from the knowledge of those given in the pre-
liminary tables and the sines of small arcs.

Usually the sines for the first 30'' and last 30° in the quadrant
were computed in this way. The remaining gap from 30° to 60''
was filled up by using the following theorem :

" The difference between the sines of two arcs that are
equally distant from 60" is equal to the sine of half the differences
of these arcs." That is, in modern notation

sin (60 + ^) - sin (60 - ^) = sin ^ (60 + ^ - 60 - 6) = sin 6

And hence

sin (60 - ^) = sin (60 + B) - sin B.

Now if e be less than 30°, sin (60 + 6) and sin 0 are by
hypothesis known ; and hence sin (60 — ^), which lies between
30° and 60°, is obtained by a simple subtraction.

The canon of sines (and also cosines) being thus completed

THE GENESIS OF LOGARITHMS 153

that of the tangents is obtained from the theorem "As cosine
is to sine, so is radius to tangent " — the equivalent of tan d =

^ — whilst, using theorems such as "The secant of an arc

cos d °

is equal to the sum of its tangent and the tangent of half its

complement," or " The secant of an arc is equal to the difference

between the tangent of that arc and the tangent of the arc

added to half its complement," the canon of secants is deduced

from that of tangents, by simple additions and subtractions.

Such, then, was the state and efficiency of the trigono-
metrical tables known to the mathematical world at the begin-
ning of the seventeenth century. The labour involved in such
computations as those that we have detailed above as well as
the increasing accuracy of astronomical observations gave rise
to a demand for a method of calculation which should materially
lessen such labours. That method was given to the world by
John Napier in the invention of logarithms. These aids to
calculation are looked upon as so much a matter of course at
the present day and are so strongl}^ associated with " powers,"
"indices" and what not, that the curious mode in which they
originated is apt to be lost sight of. In the writer's view this
is unfortunate. Nothing is more common than to hear and
read discussions as to whether the modern schoolboy shall be
taught to handle logarithmic tables before he is taught the
theory of indices and the subsequent deduction of logarithms
or not— some holding the latter view, others asserting that to
tell a boy he shall not use a table of logarithms until he knows
the theory of their construction is as inconsequent as to forbid
a boy's using his watch until he knows how to make one of
those useful articles. Yet the fact is never brought forward
that the discoverer of logarithms had not the ghost of a notion
of an index as we know it and that complete tables of logarithms,
the direct ancestors of those we use to-day, were printed and
in daily use close on a century before the days of Euler, who
was one of the first, if not the first, to look upon logarithms
as being indices of powers.

Of the life of the discoverer of logarithms few details are
known. Born in 1550 and living a life of retirement in a
country which was notably wild and lawless even in a lawless
age, the antiquary will find little that will help him to recon-
struct the daily life of John Napier. A great mass of Napier's

154 SCIENCE PROGRESS

papers perished in a fire which broke out in the house of one
of his descendants ; in consequence, Mark Napier's monumental
life of his ancestor is largely composed, so far as the facts of
the life go, of conjecture. What can be rescued from the mass
of hypothesis may be briefly condensed as follows: Born, as
stated above, in 1550, he was educated at St. Salvator's College,
St. Andrews. It is believed that he travelled on the Con-
tinent during several years but he was certainly at home again
in 1 571. Little is known of the details of his home life, save
that for years his attention was drawn, like Newton's, to specu-
lative theology. The results of these studies are shown in
his treatise, A Plaine Discovery of the Whole Revelation of
St. John, published in 1593. About this time he seems to have
made some progress towards his great discovery, for we are
told, on the authority of Kepler, that about this time Tycho
Brahe had heard from a Scottish correspondent that a canon
or table of such aids to computation was in process of con-
struction. The canon itself was not published until 1614, when
it appeared under the title of Mirifici Logarithmorum Canonis
Descriptio. Napier died in 1617; two years afterwards the
posthumous work Mirifici Canonis Logarithmorum Constructio
was published, which explains the manner in which Napier
constructed his canon.

It is a remarkable fact in the history of scientific discovery
that Napier's great work sprang, Minerva-like, in full per-
fection from the head of its discoverer. In the development
of the discovery of the infinitesimal calculus, we find all through
the seventeenth century foreshadowings in the writings of
Cavalieri, Roberval, Barrow and others of the comprehensive
calculus finally developed by Newton and Leibniz. But with
one solitary exception and that exception as old as the days
of Archimedes, we find nothing to show that Napier's dis-
covery was the culmination of a series of stages leading up to
that point. The discovery was almost perfectly self-contained.

The exception referred to above is to be found in Archimedes'
treatise Arenarius, an attempt to extend the cumbrous Greek
numerical notation so as to include integral numbers of
extremely large magnitude. With the structure of this treatise
we need not here concern ourselves. What is important to our
purpose is to note that Archimedes incidentally develops
therein some properties of geometrical progressions, one of

THE GENESIS OF LOGARITHMS 155

which contains the germ of Napier's great discovery. We
append a literal translation of the passage in question :

" It is also of some use to know this property. If a series
of numbers be arranged in a geometrical progression from
unity and any two of the terms of that progression be multiplied
together, the product will also be a term in the same pro-
gression ; and its place will be at the same distance from the
larger of the two factors that the lesser factor is from unity ;
and its distance from unity will be the same, minus one, that the
sum of the distances of the two factors from unity is distant
from unity. For, let A, B, C, D, E, F, G, //, /, K, L represent
any geometrical progression from unity, of which A is the
unity ; let D be multiplied by H, and let X represent the
product. Take L in the given progression, which is at the
same distance from H that D is from unity. It is to be demon-
strated that X is equal to Z,."

This proposition Archimedes proceeds to prove, giving also
the proof of the second proposition quoted in the above trans-
lation. Now this amounts to neither more nor less than
demonstrating that, given a geometrical progression, the pro-
duct of any two terms can be found without going through the
actual process of multiplication. The following would be
an equivalent method of stating the second of the above
propositions :

Take any geometrical progression starting from unity and
underneath each term write its " distance from unity," placing a
o underneath unity. Thus :

I, 2, 4, 8, 16, 32, 64, 128 .. .
01234567...

Then, to multiply 4 by 16, we add 2 and 4 together and look
up the number (64) above 6, which gives the required result.
It is to be noted that by starting the lower progression at o,
we get rid of the " minus one " of the proposition as quoted by
Archimedes.

But this — the study of the relation between an arithmetical
and a geometrical progression — is precisely the manner in which
the problem was approached by Napier. And his great insight
is shown, both in the manner in which he obtained a pro-
gression or series of geometrical progressions such that the
terms of the series were very near in value to the numbers in a
table of natural sines— for it is to be remembered that primarily
Napier was seeking for a table of logarithms of sines— and by

156 SCIENCE PROGRESS

the ingenious manner in which he conceived his related arithme-
tical and geometrical series to be developed.

This latter relation is treated in a manner which strongly
recalls Newton's subsequent development of the fluxionary
calculus and may fitly be described here, leaving the question of
the construction of the tables to be considered later. Trans-
lated into modern language and notation, Napier's treatment of
the problem proceeds thus :

A< — a -y > E < y > B

C < X > F D

Imagine two lines A B and C D, A B of length equal to the
radius, C D oi indefinite length. Let two points start simultane-
ously from A and C with the same initial velocity. But whilst
the velocity of C remains uniform, let that of A decrease in
such a way that at any stage of the journey, such as E, its
velocity is proportional to the distance E B yet to be described ;
when one point has reached E let the other be at E. Then CE
is called the logarithm of E B.

The length E B is taken as the sine of a given arc and A B

as the whole radius. It is clear, therefore, that the logarithm of

radius— that is, the logarithm of the sine of 90°— is zero and that

the logarithms increase as the sines decrease. The connexion

between Napierian logarithms and logarithms to the base e —

often wrongly called Napierian logarithms — may thus be

exhibited in modern notation :

By definition,

CF = logA^ EB,
i.e. X = logTv/.

Also, the velocity oi E = d ^^ ~2t ~ ^' ^^ hypothesis, since

Napier takes the constant of proportionality as unity.
Hence, integrating

To determine the integration constant we note that when
t z=i o^ y = a and therefore

k = - log« a.

Hence

/ -= 10g« 7

THE GENESIS OF LOGARITHMS 157

Now the initial velocity of C = Initial velocity of E = a
and the velocity of C is uniform.
Therefore

'ji — <^ and X — aty

the constant of integration vanishing, since x and / vanish
together. Hence

X . a

a is the radius, which Napier took as 10^ units in length.
So that we finally obtain

\o%Ny = 10' log, — -.

Now let us see how the actual tables constructed by Napier
were evolved. In the two rows of figures previously cited
the logarithms proceed in arithmetical progression, the numbers
in geometrical progression and such a geometrical progression
as we have cited shows increasingly large gaps. The problem
is to construct a series of numbers in geometrical progression
which shall yet be sufficiently close together to represent the
natural numbers or rather, in Napier's case, to represent the
sines of continually decreasing arcs, for, as has been said,
Napier's final object was the construction of a canon of
logarithms of sines. The manner in which this problem was
solved can best be demonstrated by a brief analysis of the
more important parts of Napier's posthumously published
work, the Construction which we now proceed to give.

The full title of this work, which was, as has been noted,
published posthumously in 1619, is, literally translated — "The
Construction of the Wonderful Canon of Logarithms ; and their
relations to their own natural numbers ; with an Appendix
as to the making of another and better kind of Logarithms.
To which are added Propositions for the solution of Spherical
Triangles by an easier method : with Notes on them and on
the above-mentioned Appendix by the learned Henry Briggs.

" By the Author and Inventor, John Napier, Baron of
Merchistoun, etc., in Scotland."

Both this work and the Descriptio are, curiously enough,
the most neglected of Napier's works. This neglect is, of

158 SCIENCE PROGRESS

course, mainly to be ascribed to the early introduction of the
more convenient tables computed to the base lo.

Three editions of the Descriptio were published in the years
1614, 1619 and 1620 respectively; an English translation by
Edward Wright was published in 1616; a retranslation, to-
gether with a table of hyperbolic logarithms, was published
in Edinburgh in 1857. A reprint of the Latin text is to be
found in the sixth volume of Baron Francis Maseres' massive
compilation entitled Scriptores Logarithmici. (Dates of publica-
tion 1 79 1- 1 807.)

The Constructio is much less accessible. After the first
(Edinburgh) edition of 1619 the only other edition of the
Latin text was printed at Lyons in 1620. In 1889, however,
a careful translation into English was issued by W. R. Mac-
donald, to which was added a very full and complete biblio-
graphy of Napier's published works.

The Constructio was printed in the form of a sequence of
propositions, some sixty in number. Starting with a definition
of progressions, both arithmetical and geometrical, Napier
lays down, in very clear fashion, various rules for obtaining
accuracy in computation, e.g. the taking of a large radius in
order to get a larger number of significant figures in the
numbers for both sines and logarithms ; and, equally important,
the annexing to the radius of a number of cyphers following
a decimal point, the figures following the decimal point being
discarded in the final tables. As Napier expresses himself in
Proposition IV., " Thus, in commencing to compute, instead
of 10,000,000 we put 10,000,000*0000000 lest the most minute error
should become very large by frequent multiplication."^

Then follows a clear discussion on the limits of accuracy
obtainable in adding, subtracting, multiplying and dividing
two numbers whose limits of accuracy are given and, beginning
with Proposition XIII., the methods of forming **easy" geo-
metrical progressions are carefully discussed.

Propositions XVI. — XXI. are concerned with the formation
of three tables of fundamental importance. The First Table
is a geometrical progression of 100 terms, of which radius
forms the first term, consecutive terms being in the proportion

I 0000000 radius

9999999 radius - i'

^ Construction Prop. IV.

THE GENESIS OF LOGARITHMS 159

This table is readily formed by subtracting '' from radius
with seven cyphers added ... its io,ooo,oooth part and from
the number thence arising its io,ooo,oooth part and so on."^
A specimen of part of the First Table, showing its construction,
is given in the accompanying figure.

First Table
(i) 1 0000000 '0000000

I'OOOOOOO

(2) 9999999*0000000
'9999999

(3) 9999998 'OOOOOO I

•9999998

(4) 9999997*0000003

•9999997

(5) 9999996*0000006
and so on, up to the looth term, which is
(100) 9999900*0004950

The Second Table is a geometrical progression of fifty
terms, radius (with six cyphers added) forming the first term,
the numbers being in the continued proportion of the first
term to the last term in the First Table ; that is, in the pro-
portion of 100,000 to 99,999. This table again may be formed
** with suf^cient exactness by adding six cyphers to radius and
continually subtracting from radius its ioo,oooth part in the
manner shown." ^

Second Table
(i) 10000000*000000

1 00 'OOOOOO

(2) 9999900*000000

99*999000

(3) 9999800*001000

99*998000

(4) 9999700*003000

99*997000

(5) 9999600*006000

and so on, up to the 50th term, which is
(50) 9995001 "222927^

The Third Table is much more extensive, consisting of
sixty-nine columns, each column containing twenty-one terms.

^ Construction Prop. XVI. ^ Ibid. Prop. XVII.

^ This number is erroneous {Vide Note B, Appendix).

i6o

SCIENCE PROGRESS

Considering any one column, the terms comprising it are in
the continued proportion of the first term to the last term in
the Second Table ; that is, in the proportion of 10,000 to 9,995.
The first term of the first column is radius " with four cyphers
added." The succeeding terms of the first column being in
the above ratio, are easily computed by methods strictly ana-
logous to those discussed in the formation of the First and
Second tables and the twenty-first term is found to be
9,900,473-5780.

The first numbers in each of the 69 columns are approxi-
mately in the proportion of the first term to the twenty-first
term of the first column, i.e. in the proportion of 100 to 99.
The numbers which head each of the columns are therefore
readily calculated and the remaining twenty terms in each
column are then easily filled in, as they form a descending
geometrical progression, of which the first term is given, con-
secutive terms being, as stated above, in the ratio of 10,000
to 9,995. Thus the table, when completed, has the form shown
below :

Third Table

Terms.

Column I.

Column II.

Column III.

etc. • - - till.

Column LXIX.

1 0000000 '0000

9900000*0000

9801000-0000

etc.

5048858-8900

999 5 000 0000

9895050*0000

9796099-5000

5046334*4605

9990002 '5000

9890102*4750

9791201-4503

etc.

5043811*2932

9985007-4987

9885157-4237

9786305*8495

5041289*3879

9980014*9950

9880214*8451

9781412*6967

etc.

50387687435

etc.

etc. up to the

etc.

up to

2 1 St term which

etc.

till

9900473-5780

9801468-8423

9703454* 1 539

etc.

4998609-4304

The net result of all these computations is that in the Third
Table we have, between radius and (approximately) half-radius,
interposed 6% numbers in the continued proportion of 100 to
99; and between each pair of these numbers we have inter-
posed twenty other terms in the continued proportion of
10,000 to 9,995. Also, between the first two numbers of the
Third Table, which are also the first and last of the Second
Table, we have interposed 48 numbers in the continued pro-
portion of 100,000 to 99,999. And, finally, between the first
two numbers of the Second Table, which are also the first
and the last of the First Table, are interposed 98 numbers

THE GENESIS OF LOGARITHMS i6i

in the continued proportion of 10,000,000 to 9,999,999. Thus
we have in these three tables a series of numbers in geometrical
progression, which numbers also coincide ver}^ nearly with
those in a table of natural sines from 90° to 30°.

It remains to show how, to each of these " natural " numbers,
Napier appended the corresponding " artificial " number or
logarithm.^ The portion of the Constructio (§§ XXII.-XXVI.)
immediately following the discussion of the formation of the
three tables given above is concerned with the definition of
logarithms which we have previously explained. Proposition

XXVII. proves, as before mentioned, that nothing is the
logarithm of radius {i.e. of the sine of 90°). Proposition

XXVIII. is of fundamental importance; as an illustration of
Napier's methods, we proceed to give his proof, as far as
possible in his own manner.

The proposition states that, if r be radius and 5 any given
sine, then the logarithm of 5 is greater than r — s and less than

(r — s) — .

0 T d S

S g

b c

Let T S represent radius, and let a pointy start from Z with
a velocity proportional to T S^ its velocity when at any point
d being proportional \.odS^ dS being taken to represent any
given sine s. Simultaneously with the departure of g from 7",
another point a moves from h with a uniform velocity equal
to the initial velocity of ^; if, then, when g is at d^ a is at c^
h c \s called the logarithm of dS.

In his proof of the proposition quoted above, Napier pro-
duces the line ST \.o o, so that o 5 is to TS as 7"S is to dS.

Hence it follows that oT \s equal to (r— s)— ; and since T d

is equal to r — 5, we have to prove that b c \s greater than Td
and less than 0 T. This Napier proves by assuming that the
moving point g starts from o, its velocity decreasing according
to the geometrical law in such a manner that when g arrives

* See Appendix C.

i62 SCIENCE PROGRESS

at T it has the velocity (proportional to T S)^ with which a
starts from h. In his own words : ^

" For in the same time that g is borne from o to T^ g is
borne from T to d^ because o 7" is such a part of o S as Td
is of T S and in the same time (by the definition of a logarithm)
is a borne from ^ to c; so that oT^ Td and be are distances
traversed in equal times; but since ^ when moving between
T and o is swifter than at 7", and between T and d slower but
at T equally swift with a ; it follows that o T the distance
traversed by g moving swiftly is greater and T d the dis-
tance traversed by g moving slowly is less than b c the
distance traversed by the point a with its medium motion, in
just the same moments of time ; the latter is, consequently, a
certain mean between the two former."

The proposition can, of course, be demonstrated by means
of the relation already proved that

from which we can easily show that

(f 5\
I -I 1

and expanding. When r is very nearly equal to s, the logarithm

of 5 is, therefore, very nearly equal to the arithmetic mean of

(v -\- s) (v ~~ s^
the limits, i.e. is very nearly equal to ^ — -.

This proposition Napier uses at once to find the logarithm

of the second term in the First Table, for, the first term being

radius, its logarithm is, by definition, zero ; and the logarithm

of the second term lying between the above limits lies therefore

, , J / \ ^ looooooo

between r — s ^ i '0000000 and (r — s) - = = I'ooooooi

s 9999999

and may therefore be taken with sufficient exactness as 1*00000005.
And this is also the common difference for the logarithms
of every number in the First Table; hence, multiplying this
common difference by 2, 3, etc., the logarithms are readily
appended to the 100 terms constituting the First Table.^

To proceed from the First to the Second Table, another

^ Co7istructio, Prop. XXVIII. ^ /^^v/. Prop. XXIX.-XXXIII.

THE GENESIS OF LOGARITHMS 163

proposition is employed, that, given two sines s^ and s.2, the
difference between the logarithms of the two sines lies between

the limits {s^ — S3) — and (5i — s^) — , which difference, if the

two sines differ but slightly, may be taken with sufficient accuracy
to be equal to the arithmetic mean of the above limits.^ This
proposition, which Napier proves in much the same manner as
the proposition quoted previously, may be verified readily by
putting

f f s

D = \o%N Si - logA^ Si = r log, — - r log, y = ?' log, y,

and putting D in the form

/ Si — s-,\ , / s. — s.A
D = r log, (i + — ^~-) = r log, (i - -^)

and expanding, the truth of the proposition is easily shown.

Now the last term of the First Table being 9,999,9000004950
and the second term of the Second Table 9,999,900, when these
numbers are substituted in the expression for the arithmetic
mean of the limits given above, it is found that the difference of
the logarithms of these two terms is, to the approximation
considered, '0004950 ; and, adding this number to the logarithm
of the last term of the First Table gives ioo'0005ooo at the
logarithm of the second term of the Second Table. Since the
logarithm of the first term of the Second Table is zero, this
number gives us also the common difference for all the terms in
the Second Table.

By a precisely similar process we can pass from the Second
Table to the first column of the Third Table and fill in the
logarithms of the twenty-one terms of this column. Then, using
the theorem again to pass from the twenty-first term of the first
column to the first term of the second column, we find that the
logarithm of this latter term is ioo503"3 ; this number, it must
be noticed, is the common difference of the logarithms of the
first terms of the first, second ... sixty-ninth columns, of the
second terms of the various columns, and so on; so that, knowing
the logarithms of all the terms of the first column and the
common difference between all terms on the same line in the
various columns, we can fill in the logarithms of all the terms
of the Third Table. The Third Table, with its logarithms so

1 Co7tstritctio, Prop. XXXIX.-XL.

l64

SCIENCE PROGRESS

appended, Napier calls the ** Radical Table"; a specimen of
the part of this table given in the Constructio is shown below : ^

The Radical Table

Column L

Column II.

etc.

up to

Column LXIX.

Natural Logar-
numbers. ithms.

Natural
numbers.

Logar-
ithms.

Natural
numbers.

Logar-
ithms.

lOOOOOOO'OOOO 'O

9995000*0000! 5001*2

999002*5000 10002*5

9985007*4987 150037

9980014*9950 i 20005*0

etc. up to etc. up to
9900473*5780 100025*0

9900000*0000
9895050*0000
9890102*4750
9885157*4237
9880214*8451

etc. up to
9801468*8423

100503-3
105504*6
110505*8
115507*1
120508-3
etc. up to
200528*2

5048858*8900
5046334*4605
5043811*2932
5041289*3879

5038768*7435

etc. up to
4998609-4034

6834225-8

6839227-1

6844228*3

6849229*6

6854230*8

etc. up to

6934250-8

With the help of this Radical Table it is an easy matter to
obtain the logarithm of any given sine, as, given the sine, the
number nearest to it in the Radical Table must be noted and by
the '' difference theorem " quoted above the difference between
the logarithms of the two numbers may be found. Adding
this difference to or subtracting it from the logarithm of the
number in the Radical Table at once gives the logarithm of the
given sine.

From this Radical Table, therefore, the logarithms of the sines
of all angles between 90° and 30° are computed. Further than
this we cannot go, without other assistance, as the natural
numbers in the Radical Table only go down to (about) half-radius,
which is the sine of 30^ It remains, then, to explain the methods
adopted by Napier in computing the logarithms of the sines of
the angles between 30° and 0°.

Two methods are indicated by means of which the com-
putation may be effected. In the first,^ the given sine x^ which,
by hypothesis, is the sine of some angle less than 30°, is
multiplied by some definite number ^, the number b being so
chosen that the product bx (^=y^ say) lies within the limits of the
Radical Table. This being so, the number nearest tojv is looked
up in the Radical Table and by the " difference theorem " earlier
quoted the logarithm oi y may be evaluated. Then, knowing
the logarithms oi y and of ^, the value of the logarithm of x is
obtained from the equation jv = b x.

In the second method,^ Napier utilises the proposition that
" As half-radius is to the sine of half a given arc, so is the sine

» Constructio, Prop. XLVII. » Ibid. Prop. LI.-LIV. ^ /^/^^ p^op. LV.

THE GENESIS OF LOGARITHMS 165

of the complement of the half-arc to the sine of the whole arc."
This is, of course, the Napierian equivalent of the trigono-
metrical theorem

sin 2^ = 2 sin 6 cos ^,

which equation, written in the form

. . sin 20

sin 6 = - — -■ — 7 a\i

2 sin (90 - dy

enables us at once to compute the logarithm of sin 0^ knowing
the logarithms of the sines oi 2 6 and of (90—^) ; choosing 6 so
that 2^, to begin with, lies within the limits of the Radical
Table, the table may be gradually extended so as to include the
logarithms of the sines of all angles from 30° to 0°. It is
further pointed out ^ that this method can be used for all angles
less than 45° ; so that the construction of the logarithms of the
sines of the angles between 45° and 30° is thereby rendered
much more simple, the use of the '* difference theorem " and the
Radical Table being avoided.

It is hoped that the preceding analysis will suffice to show
the uniqueness and originality of Napier's great discovery.
The publication of the Descriptio in 16 14 was hailed with an
amount of enthusiasm and the full credit of Napier's work
awarded to him with a unanimity seldom paralleled in the
annals of mathematical discovery. After the fashion of the
times, the enthusiasm of Napier's contemporaries found vent in
a number of laudatory poems, of which one by Thomas Bretnor
possesses sufficient merit, apart from its somewhat too-fervid
patriotic spirit, to bear reproduction to the extent of a couple
of verses :

"And bonnets vaile, you Germans ! Rheticus,
Reignoldus, Oswald, and John Regiomont,
Lansbergius, Finckius and Copernicus,
And thou, Pitiscus, from whose clearer font
We sucked have the sweet from Hellespont.
For were your labours ne'er composed so well
Great Napier's worth they could not parallel.

By thee great Lord we solve a tedious toyle,
In resolution of our trinall lines,
We need not now to carke, to care, or moile,
Sith from thy witty braine such splendor shines,
As dazels much the eyes of deepe divines.
Great the invention, greater is the praise,
Which thou unto thy nation hence doth raise."

^ Construction Prop. LVIII.

i66 SCIENCE PROGRESS

But the tables of Napierian logarithms had hardly seen the
light before proposals were put forward for altering the base to
the more convenient number lo also making zero the logarithm
of unity and unity the logarithm of lo, so that numbers and
their logarithms should increase and decrease together. In
giving an account of this change, Hutton, always learned and
usually extremely accurate, does less than justice to Napier, as
he assumes that Napier's part in recommending this important
alteration was practically nil and that jealousy of Napier's work
existed on the part of Briggs, which certainly seems to have no
foundation in fact. Mark Napier, in his Memoirs of John
Napier, successfully refutes Hutton's conclusions but " falls
into the opposite error of reducing Briggs to the level of a mere
computer."

Without going exhaustively into the evidence, it would seem
sufficient to say that, taking the words of both Napier and
Briggs at their face value, the change by which o became the
logarithm of radius and the logarithm of the tenth part of radius
became 10,000,000,000 was the separate and independent idea of
each writer ; and that Napier further suggested that o should
become the logarithm of unity and 10,000,000,000 that of the
whole sine.

Brigg's account of the matter is given in the preface to his
Arithmetica Logarithmica (1624) :

** . . . I myself, when expounding publicly in London their
doctrine to my auditors in Gresham College, remarked that it
would be much more convenient that o should stand for the
logarithm of the whole sine, as in the canon Mirificus, but that
the logarithm of the tenth part of the whole sine, that is to say,
5 degrees 24 minutes and 21 seconds, should be 10,000,000,000.
Concerning that matter I wrote immediately to the author
himself; and, as soon as the season of the year and my vacation
time of my public duties of instruction permitted, I took journey
to Edinburgh, where, being most hospitably received by him,
I lingered for a whole month. But as we held discourse
concerning this change in the system of logarithms, he said that
for a long time he had been sensible of the same thing and had
been anxious to accompHsh it,^ but that he had published those
he had already prepared, until he could construct tables more
convenient, if other weighty matters and his frail health would
permit him to do so. But he conceived that the change ought

* " Cum autem inter nos de horum mutatione sermo haberetur, ille se idem
dudum sensisse et cupivisse dicebat."

THE GENESIS OF LOGARITHMS 167

to be effected in this manner, that o should become the logarithm
of unity, and 10,000,000,000 that of the whole sine; which I
could not but admit was by far the most convenient of all.
So, rejecting those which I had already prepared, I commenced,
under his encouraging counsel, to ponder seriously about the
calculation of these tables."

The notably high characters of both Napier and Briggs,
the strong friendship which existed between the two writers
and the unqualified admiration and veneration which Briggs
ever shows of his master, justify us in taking these words
at their plain meaning ; it may be added that a more exhaustive
study of the evidence afforded serves to confirm the views
stated above.

It is not necessary here to go into any great detail con-
cerning the manner of computation of logarithms to the base 10,
as a clear account of some of the methods used is easily ac-
cessible in the article " Logarithms " in the Encyclopcedia
Britannica. Thus, for example, in computing the logarithm
of 5, given log i and log 10, the geometric mean of i (^)
and 10 {B) is taken, giving C— ^Z A B. Then, finding Z> = ^ B C^
E— v/ CZ), etc., we finally arrive at a mean which may be
made to approach as closely as we please to the value
S'ooooo. . . . And to every geometric mean there corresponds
a logarithm obtained by continually taking arithmetic means
of the logarithms in like manner, finally giving

log 5*000000 = '6989700.

A second method is outlined by Napier in the Appendix
to the Construdio. In his own words —

"... the Logarithm of any given number is the number
of places or figures which are contained in the result obtained
by raising the given number to the 1 0,000,000,000th power.

"Also if the index of the power be the Logarithm of 10
the number of places, less one, in the power or multiple, will
be the Logarithm of the root.

"Suppose it is asked what number is the Logarithm of 2.
I reply, the number of places in the result obtained by
multiplying together 10,000,000,000 of the number 2.

" But, you will say, the number obtained by multiplying
together 10,000,000,000 of the number 2 is innumerable. I
Feply, still the number of places in it, which I seek, is
numerable.

i68 SCIENCE PROGRESS

" Therefore, with 2 as the given root, and 10,000,000,000
as the index, seek for the number of places in the multiple,
and not for the multiple itself; and by our rule you will find
301,029,995, etc., to be the number of places sought, and the
Logarithm of the number 2."

A method used by Briggs for finding the logarithms of
small prime numbers, which depended upon the formation of
a large number of geometric means between unity and the
given prime number, is fully outlined in the article " Logarithms "
above-mentioned and needs no further discussion here.

By these methods Briggs computed the logarithms of all

integers from i to 20,000 and from 90,000 to 100,000 to 14

places of decimals. The gap from 20,000 to 90,000 was filled

by the calculations of Adrian Vlacq, who computed his

ogarithms to 10 places of decimals.

It is interesting to note that an abusive mention of Vlacq
by Milton in his Defensio secundo pro poptdo Aitglicano led
Vlacq to state simply and clearly the story of his life from
the age of 26. Any faithful account of one to whom mathe-
maticians are so much indebted — for the tables of Briggs and
Vlacq are the parents of all the logarithmic tables which
have succeeded them, no re-computation on such an extensive
scale having been made since — must necessarily possess great
interest, and '* one is almost inclined to pardon Milton his
abuse, seeing that thereby we are made acquainted with what
would otherwise probably have always remained a mystery." ^

Here an account of the genesis of logarithms may fitly
close. Several points of minor interest remain— a considera-
tion, for example, of Kepler's logarithmic tables, which differ
from Napier's in one point only ; in Napier's Table the arc of
the quadrant is divided into a definite equal number of parts,
so that the sines corresponding to these angles are, in general,
irrational numbers. In Kepler's table the radius is divided
into a definite number of equal parts, so that the sines are
rational numbers, the corresponding angles or arcs being
irrational.

Something might be said also of the very doubtful claim of
Joost Burgi (i 552-1632) to be an independent discoverer of
logarithms, a discussion '.of which may be found in several
of the standard histories of mathematics.

^ Glaisher, Phil. Mag. October 1872.

THE GENESIS OF LOGARITHMS 169

But, before concluding, one widespread error calls for notice.
In many text-books on trigonometry we find the statement
that, to avoid the inconvenience of printing negative charac-
teristics, the number 10 is always added to the logarithms of
sines, cosines, etc., thus giving the so-called logarithmic sines,
etc. This is by no means an exact statement of the facts. The
trigonometrical tables most in use at the beginning of the
seventeenth century were constructed, as previously explained, to
the radius lo^^ It follows, therefore, that the logarithm of radius
(the sine of 90°) is 10, with corresponding numbers having as
characteristics 9, 8, . . . etc., for the remaining sines. The
numbers, therefore, given as *' tabular logarithms " in a modern
book of tables are actual logarithms, the manner of printing
them having never been altered ; the modern conception of
the trigonometrical functions as ratios gives us, however,
unity as the sine of 90° ; consequently, the tabular logarithms
as printed are, in every case, too great by ten. It seems a
pity that the account of such an interesting remnant of seven-
teenth-century usage should be obscured by the usual '' expla-
nation " of trigonometrical text-books.

APPENDIX
Note A

The following short list of authorities consulted may be useful to those who
wish to pursue the subject further :

Napier, Mirifici Canonis Logarithmorum Descriptio. First edition, 1614.
A reprint is contained in vol. vi. of Baron Francis Maseres' compilation en-
titled Scriptores Logarithmici. English translations made by Edward Wright
(1616) and Herschell Filipowski (1857).

Napier, Mirifici Canonis Logarithmorum Constructio. First Edition, 1619.
English translation, together with an exhaustive bibliography of Napier's works i
made by W. R. Macdonald (1889).

HuTTON's Mathematical Tables. A full and for the most part accurate
historical introduction is prefixed to the earlier editions of the above Tables.
This introduction is reprinted in Hutton's Mathematical Tracts, vol. i. (1812).

Napier, Mark, Memoirs of John Napier of Merchiston (1834).

Encyclopaedia Britannica. Tenth edition. Articles Logarithms, Mathematical
Tables, Napier, etc.

MONTUCLA, Histoire des Mathematiques ; completed and published by
Lalande (i 799-1 802).

Fink, Geschichte der Elementar-Mathematik. English translation by Beman
and Smith (1903).

Cajori, a History of Mathematics.

170 SCIENCE PROGRESS

Ball, A Short History of Mathematics.
De Morgan, Trigonometry and Double Algebra.

Glaisher, Articles in the Philosophical Magazine for Oct. and Dec. 1872,
and May 1873.

Note B

The fiftieth term in Napier's Second Table, given as 9,995,001*222927 is
incorrect, the true value being 9,995,001 "224804.

This, of course, introduces a corresponding error into the logarithms attached
to the Radical Table, inasmuch as we have seen that the logarithm of the first
proportional in the Radical Table is obtained from the logarithm of the last
proportional in the Second Table by means of a theorem which involves the
difference of the proportionals ; and, one of the proportionals being in error,
the logarithm will also be incorrect. The magnitude of the error introduced
may be shown by noting that the logarithm of the last term in the Radical Table
is given as 6,934,250-8, its true value being 6,934,253'4 — an error of rather less
than one in 2^ millions.

The mistake, unnoticed by Hutton, seems to have been first pointed out by
Biot in 1835 and later in 1865 by Sang.

Note C

The derivation of the word logarithm is not without interest. Even when
we know that logarithm = Xoyav dpidnos = "the number of the ratios," the
modern mode of deriving logarithms as powers, and of computing logarithms
by means of series, is apt to render the meaning underlying the phrase
^'number of the ratios" somewhat obscure. But the originators of the word
looked at the subject of logarithms from the point of view of compounded
ratios. Suppose, then, that the ratio of 10 to i is compounded of, say, a
million small ratios or ratiunculse, each of which is, of course, the millionth
root of ten. Then the ratio of 2 to i is compounded of 301,030 of these
small ratios, so that the logarithm of 2 is given by the number of the ratios
or ratiunculas which is contained in the ratio of 2 to i. Hence the word
logarithm.

It may be noted that whilst Napier uses the word Logarithmus in the
Description published in 161 4, he uses, in the text of the posthumously published
Constructio, the phrase Numerus artificialis, or simply Artificialis, as opposed
to Numerus naturalis for the ordinary numbers. The term Logarithmus, how-
ever, is used in the title-page, headings and Appendix to the Cofistructio.

REVIEWS

The Disorders of Post-Natal Growth and Development. By Hastings
Gilford, F.R.C.S. [Pp. xxii + 727.] (London: Adlard & Son, 1911.
Price 15^. net.)

Mr. Gilford in this work propounds the novel thesis that all post-natal disease
is primarily inherent, though it may be aggravated by outside agencies : disease,
he contends, is the expression of an exaggeration of phases in the normal life-
history of cells.

A curious and not uninteresting faculty of looking on the wrong side of things
and a tendency to place effect before cause are the keys to the "theories " with
which the book abounds. Thus in dealing with the influence of heredity on
post-natal disorders, the statement is made that the characters latest acquired
are those most easily lost ; such elementary logic, of which examples abound
throughout the book, is contrary to the whole experience of practical stock-
raisers and of professed students of the principles of heredity.

The statement is often made that the constituent cells of essential organs are
capable of degenerating individually yet of continuing to live in altered and accord-
ing to the author more primitive forms : thus we read — " Cancer, cirrhotic liver,
acromegaly, though seemingly possessing nothing in common, are all examples
of the same morbid variation — i.e. a premature old age of groups of cells." It
is scarcely necessary to point out that so little is known as to the nature of
cancer that no such extreme statement can be justified ; cirrhosis of the liver
is well known to be the result of the replacement of dead liver-cells by fibrous
tissue after their degenerate remains have been removed by phagocytes ; and
it is accepted that acromegaly is due to interference with the internal secretion
of a part of the pituitary body. The exactness of the resemblance between these
conditions would seem hard to seek.

Again, we are told that fullness of blood and excess of red blood corpuscles
result in a tendency to apoplexy. It is not generally recognised that the rare
disease Polycythasmia Rubra quoted by the author in support of this statement
is alone responsible for death from cerebral haemorrhage or thrombosis.

As a final example of the author's peculiar views, aberrant growth may be
quoted. Abnormal growth is most excessive at the period of greatest relative
activity. Hence the astounding application : " We must look for hypertrophy
of the pylorus shortly after birth when the stomach, a new and untried organ,
comes first into use," springing at a bound, as the author says^ into activity.
Criticism of this flight of the imagination seems needless.

No doubt much labour has been expended by the author in compiling this
remarkable book ; it is to be regretted, however, that neglect to consider in-
ternal secretions of organs and the profound effect of bacterial infection render
the volume almost worthless. The book, one of great length, is clearly printed ;
the illustrations— few of which are original— are well reproduced ; and it is provided
with an exhaustive index.

R.
171

172 SCIENCE PROGRESS

Animal Life : Reptiles, Amphibia, Fishes and Lower Chordata. Edited by
J. T. Cunningham, M.A., F.Z.S. [Pp. xvi + 510, with four plates in
colour and numerous other illustrations.] (London : Methuen & Co. Price
los. dd. net.)

This volume, like others of the series, is written from an evolutionary point of
view, the section on Reptiles by Mr. Lydekker, F.R.S. ; that on Amphibia and
Fishes by Mr. Boulenger, F.R.S., and Mr. Cunningham ; and the remaining
sections on the Lampreys, Hag-Fishes, Sea-Squirts and other primitive or de-
generate relatives of the vertebrates by Prof. J. Arthur Thomsom — all well-known
specialists of eminence. It is well printed, admirably illustrated and not so over-
laden with china-clay that it cannot be held, though somewhat too heavy to handle
comfortably. The book is full of fascinating information and should not only
command a wide circle of adult readers but also be of real service in schools. No
better prize or gift-book could be given to an intelligent boy, especially to one
who has a taste for natural history. As the general editor of the series remarks
in his brief preface, " some of our neighbours assure us that ' Darwinism ' is dead !
If these pages show anything they show that the contrary is emphatically the
case ! ''

The Life of the Plant. By C. A. Timiriazeff. Translated from the revised
and corrected seventh Russian edition by Miss A. Cheremeheff. [Pp.
xvi -t- 355.] (London : Longmans, Green & Co. Price 7^. dd. net.)

In this book. Prof. Timiriazeff has reproduced a course of lectures he delivered in
Moscow in 1876 with the object, he says, "of informing the public," in a popular
way, of the then state of vegetable physiology. He appears to have been fully
conscious of the difficulty of the task he had undertaken— that it was necessary
that the author of such a review, as he expresses it, should " give up for a while
his usual point of view, that of a specialist ; and should, so to speak, step back a
little in order to see what science looks like at a distance." The book is worth its
cost for this precious sentence alone. Our writers of text-books, as a rule, have no
sense of perspective : if they would only step back at times and contemplate their
work from a distance, they might see how forbidding its appearance is to the
intelligent reader. One reason why science, at the present day, is making little
or no headway — why those who are set in authority over us are so lamentably
ignorant of its methods and of its teachings — is that its devotees, with few excep-
tions, are so steeped in their professional jargon that they are incapable of
expressing themselves in clear and simple terms that the multitude can under-
stand. We trust that the praiseworthy example set by a Russian writer will not
be without influence ; at least it will show that it is possible to deal with difficult
problems in a simple and attractive way.

The book is remarkable on account of the clearness and simplicity of its style
and also of the admirable series of apt experimental illustrations that are given in
explanation of the various processes considered. It is divided into ten chapters,
in which are discussed the external and internal structure of the plant ; the cell ;
the seed ; the root ; the leaf ; the stem ; growth ; the flower ; the plant and the
animal ; and the origin of organic forms. In a final chapter, the plant is considered
as a source of energy. The work of translation has been most admirably done.

In the English preface. Prof. Timiriazeff rightly protests against the alarming
spread of the " Reizphysiologie," with its morbid outgrowth of " Neovitalism "

REVIEWS 173

and " Phyto-psychology " and their natural corollary, anti-Darwinism. " I am as
firmly convinced," he says, " as I was forty years ago, that the ' mechanistic con-
ception ' and Darwinism have been bequeathed by the ' wonderful century ' to the
still infant science of plant physiology as the two sure guides for its further
evolution."

Here and there are passages to which objection can be taken as a little out of
date perhaps, if not incorrect ; such, however, are rare. The reference, at p. 167,
under osmotic pressure, to albumen and gum as being productive of the same effect
as sugar is a case in point. Clarity of argument and of statement, however, are
main characteristics of the work.

In these days, when so many are interested in the practice of horticulture,
such a book should meet with a most cordial reception from all who desire to gain
some understanding of the life history of plants ; it should also be of great service
in schools.

One of its chief advantages is that Prof Timiriazeff has known what to leave
out. He has not attempted to make details clear but has dealt broadly with the
various problems.

Monographs on Biochemistry. The Chemical Constitution of the Proteins.
Part I. Analysis. By R. H. A. Plimmer, D.Sc. Second edition.
[Pp. xii -i- 188.] Price 5.?. 6^. net.— The Physiology of Protein Meta-
bolism. By E. P. Cathcart, M.D., D.Sc. [Pp. viii + 142.] (Price
4^-. td. net.) London : Longmans, Green & Co.

Dr. Plimmer has increased the value of his now well-known monograph by
giving a more detailed description of the methods followed in analysing the
proteins and has brought his account up to date in other respects. Reference
is made in the preface to the astonishing activity displayed by Abderhalden.
Dr. Cathcart gives a Hst of no fewer than fifty communications published under
this worker's name up to the close of the year 1910. The two books under notice
serve to bring out very clearly the almost superficial character of much of the
work that has been done with proteins and the faults inherent in the German
method, which unfortunately involves placing tasks of the utmost difficulty, time
after time, in the untried and inexperienced hands of student operators. If we
are to progress, the work must be done in a more thorough manner in future, more
in accordance with the example set by the pioneer investigator in this field, Emil
Fischer and his distinguished American follower Osborne.

Dr. Cathcart's is probably the most valuable monograph published in the series
and is exceptionally well written. The subjects dealt with are the digestion and
absorption of proteins ; protein regeneration ; feeding experiments with products
of digestion free from biuret ; the removal of the amino-group ; influence of food
on the composition of the tissues ; protein requirements ; theories of protein
metabolism ; starvation ; and work. The work done in each of these chapters is
noted and considered — somewhat hastily, it must be confessed, but none the less
skilfully. The book has a fault which probably is inseparable from its size, too
little being said of the manner in which the investigations considered were con-
ducted to enable the reader to appraise their value as evidence. The vagueness
of the conclusions arrived at in most cases is very apparent. On this latter
account, the book will not appeal very strongly to the beginner ; but it will be
invaluable to the serious student in guiding him through the literature — much of

174 SCIENCE PROGRESS

which, perhaps, might now be burnt with advantage. It is to be regretted that
Dr. Cathcart has not given a crisp survey of the situation in a brief final chapter —
he perhaps errs on the side of modesty throughout the volume.

Spices. By Henry N. Ridley, M.A., C.M.G., F.R.S. [Pp. 449.] (Macmillan
& Co. Price Ss. 6c/. net.)

Few among the vegetable products used in everyday life have a more romantic
history than the spices, as they have played an important part from the very
earliest times, first in instigating exploration and then in causing the founding
of settlements. Most of the known spices are derived from the East — the Asiatic
tropics.

It is characteristic of the times that the public know little about spices — their
botanical origin, the methods of cultiv^ating them and, perhaps happily, the
frequency with which they are adulterated. The first two of these themes are-
very admirably treated in the work under notice and it may be recommended as
pleasant reading to those who are prepared to skip judiciously whenever the writer
lapses somewhat too freely into details regarding the methods of cultivation.
Even these sections are interesting, as showing the difficulties to be encountered
and, speaking broadly, the unscientific manner in which the cultivation of spices
is still carried on. The author is director of the Botanic Gardens of the Straits
Settlements and is therefore entitled to speak with authority on the subject he
deals with. Throughout the work, the commercial aspect is not overlooked and
careful statements are given of the cost of planting, upkeep and production of the
crop and of the probable return. The book is written primarily for use by planters
in all parts of the world and should prove very useful to them, as well as of interest
to the many who by force of circumstances have become interested in the plan-
tation industry of the Asiatic tropics. The spices considered are vanilla, nutmegs,
cloves, pimento, cinnamon, cassia bark, pepper, cardamoms, capsicum, coriander,
ginger and turmeric. The book might with advantage have been more fully
illustrated but it is attractively printed.

THE CONDITIONS OF RUSSIAN
AGRICULTURE

By J. VARGAS EYRE, Ph.D.

Excepting a few commercial travellers, not many Englishmen
go so far afield as to visit Russia in their wanderings. In a
measure this is because a belief prevails that travelling is
rendered almost intolerable by the overbearing attitude of the
police and other officials. Moreover little information is avail-
able, in the ordinary way, which bears the stamp of personal
knowledge and the prospect of having to find his own way and
shift for himself is not an inviting one to the tourist. In short,
want of knowledge of the country has led most people to regard
Russia with suspicion, if not as forbidden ground. The accounts
presented in the daily papers do not in any way tend to mitigate
the feelings of mistrust of the people which undoubtedly exist ; in
fact, our knowledge of Russia and the Russians is superficial
and often false and as we visit them so rarely and have so little
authentic information of their doings, this is not surprising.

Those who wish to learn what Russia is should go there
with an open mind ; they should visit the peasant, the village
and the small town but not the cities ; above all they should
avoid St. Petersburg, which is the headquarters of officialdom —
a city of " Tchin," beautiful but not RussiaUj The true Russia
is to be found away in the vast and silent plains, where dwell the
peasants, who form seventy-five per cent, of the entire population
— one hundred and twenty million souls, mostly engaged in
husbandry, thinly scattered over a vast Empire.

To understand the position of Russian agriculture, it is
necessary to acquire an understanding of the peasant and to
remember that servitude was abolished but fifty years ago. By
the emancipation of the serfs more than twenty-two million
people were delivered from bondage and a new era was opened
up. Millions of bondservants became peasant agriculturists on
the Communal System and thousands rented land for themselves.
Being a deeply religious people but steeped in superstition,
12 175

176 SCIENCE PROGRESS

having few requirements and knowing nothing of luxury, they
naturally made agriculture subservient to the enjoyment of their
freedom. Withheld from all knowledge of progress and pur-
posely kept ignorant, they were scarcely able to bear the burden
of their own existence, let alone fight for betterment. Conse-
quently, it cannot be said that the hopes of the pioneers of 1861
have been realised. The onus of failure must rest with the
clergy and the bureaucracy ; had it not been for the ignorance
and arrogance of a host of subordinate officials, the peasantry
would long since have been in a better condition ; as it is, they
remain a sad monument of the past — crushed and kept crushed.

As a class they are careless and lazy, accepting defeat by any
difficulty with a sigh of relief Circumstances of government
and conditions of climate have moulded them a listless people,
whose annual office it is merely to scratch over the ground, sow
seed and invoke the aid of the Almighty to afford them sufficient
supplies to tide them over from harvest to harvest.

Such are the majority of Russian agriculturists but a minority
are lifting themselves and among these the pessimism and apathy
that have so long prevailed are giving place to a spirit of hopeful
enterprise. Signs are not wanting, in fact, that Eastern languor
is departing before the encroaching influence of Western ideas.
In some districts, m.ore especially in the south and south-eastern
provinces, agriculture has been raised to quite a high level, the
people being no longer satisfied to supply only the bare neces-
saries of their own household or the requirements of the village
community; but on the whole, the standard of agriculture is
still very 'low, only about ten or tw^elve per cent, of peasant
farmers being able to afford to sell part of their produce.

The Russian Empire is so vast in extent and includes so
many varieties of soil and extremes of climate that to generalise
further would be to create a false impression. It is, however,
necessary to realise how great are the undeveloped agricultural
resources of the country and these forewords may assist readers
to view things Russian in their proper perspective.

In the north of Russia, forest extends for hundreds of miles
with scarcely' any interruption and it is said that the greater
part of the Iregion has not been explored by civilised man.
Winter continues through nearly eight months of the year, so
that it is doubtful whether any attempt will be made to carry on
farming operations against such heavy odds. To the south of

THE CONDITIONS OF RUSSIAN AGRICULTURE 177

this region, agriculture is practised but it is only of the most
primitive order. The soil is poor and the peasants have nothing
wherewith to enrich it. During nearly seven months out of the
twelve, the land is held in the grip of winter and much of the
open period is affected by cold rain. The land at present culti-
vated in the district is mostly farmed in small plots, which are
rented by the peasants, who work them as it suits their con-
venience. The plots are dotted about in the scrub, advantage
being taken of any natural shelter this offers and of favourable
variations in the soil. Owing to migration of the peasantry to
more congenial conditions, the northern parts of the country are
very sparsely populated; standing there beside one cultivated plot,
it is seldom possible to see another. When serfdom prevailed,
a far greater proportion of the land was under cultivation, so
that probably only the best is still worked. Ploughing is often
done entirely by human labour, the plough, a simple implement
of wood, being pulled and pushed across the small field by the
capable members of the household. Seldom is the land given
any dressing of manure, because cattle are scarce. Year after
year the same plot of land is scratched over and a crop raised ;
the miserable crop is sometimes a little better, sometimes a little
worse than usual but the peasant says nothing and accepts as
inevitable the small success which attends his labour. Generally
oats or barley are grown but the crops are very poor indeed
both as regards yield of grain and straw. It is a common thing
to see fully grown crops of oats standing no higher than ten or
twelve inches and carrying but little grain. Artificial manure is
seldom used because so few can afford the outlay ; the farmers
possessed of small capital who farm the very light soil between
Vologda and Moscow apply a dressing of some 3 cwt. of kainite
to the acre and reap a benefit of a 30 per cent, increased yield.

The best results are obtained with flax ; though not so adverse
to the production of good fibre crops, the climate is not suited
to the successful harvesting of seed. Much flax is grown in
the district of which Vologda is the centre, more especially in
the vicinity of the river Suhona, where, despite the poorness
of the soil, flax grows a good length and fibre is produced which
is the best raised in Russia and possibly second to none as
regards quality and strength.

Although it is recognised as being the best practice to ret
flax in water, there are many large areas where no water

178 SCIENCE PROGRESS

suited to the purpose is available. The freshly deseeded straw
is then spread thinly over the ground so as to allow alternate
dew, sunshine and rain to carry the process of decomposition
far enough to allow the fibre to be detached from the woody
part of the straw. The very nature of this process, depending
as it does upon favourable weather conditions, often gives rise
to a product of very low quality : nevertheless, in many parts
of Russia, this method of retting is the only one available and
enormous quantities of " dew-retted " flax are annually prepared.

Following a crop or two of rye, oats or barley, flax is often
raised year after year on the same land until the soil becomes so
impoverished that scarcely anything will grow on it. The land
is then allowed to lie fallow during a number of years, after
which the scrub is burnt off and the process repeated on the
freshly broken land.

Better conditions prevail in the western provinces, especially
in the Baltic Provinces of Livonia and Esthonia, a territory
which came under Russian authority at the beginning of the
eighteenth century. These provinces are inhabited principally
by Letts, who like the Esthes of Esthonia are in reality Finns
and are people possessing some energy and determination.
The usual practice among farmers in those districts is to autumn
plough, then sow winter grain and in the spring to sow and
harrow in the best grain. As a rule, the peasant grows what he
requires regardless of all other considerations ; consequently
the rotation adopted depends less upon his knowledge of matters
agricultural than upon his personal requirements. Only on
the larger estates — apparently those over a hundred acres — is
any regular course of rotation adopted ; judging from numerous
inquiries the following is accounted the best practice — fallow,
rye and clover, barley, flax, oats and fallow.

There is a growing belief that agricultural progress will depend
not so much on an increase in the acreage under cultivation
as on improvements in method being effected ; the feeling after
progress noticeable in the Baltic Provinces receives considerable
stimulation from the strong German and British community of
business people in Riga.

The good harvests of the last two or three years have put many
of the small farmers in a position to purchase modern implements
and at present there is a large demand for iron ploughs, small
winnowing machines and harvesting machines. The importation

3
O

tJO

THE CONDITIONS OF RUSSIAN AGRICULTURE 179

of agricultural machinery has increased enormously during quite
recent times. At some of the posting stations and local trading
centres a fair assortment of modern implements may be seen
and small machines of British, German and American manufac-
ture. German and American goods sell more readily than
British, not because of any superiority in quality or workman-
ship but simply because the German manufacturer ascertains
what is required and sends it, whilst the Englishman sends what
he is accustomed to make in the ordinary way regardless of any
particular local requirement.

Much of the western country is covered by forests which
extend as great arms across the land. Crops of potatoes,
barley, flax and oats occupy small patches of the open country.
Animal manure is very scarce, the soil is hungry and until
the financial position of the peasant farmers has been improved
by several more relatively good harvests they will not be able
to afford the outlay necessary on livestock or to purchase
artificial fertilisers.

Leaving Livonia and travelling eastward, the conditions
become more truly Russian. There is indeed some excuse for
the pride the Letts exhibit in speaking of a journey into the
next province — Pskov — as a journey into Russia. The country
loses in interest, there is less land under forest, the trees are
smaller and there is less cultivated land. The plots of arable
land resemble remote patches in a great garment.

In Russia proper the standard generally is lower than in the
Baltic Provinces, agriculture is more primitive, resembling that
of the north. Farming is extensively conducted on the triennial
system — winter grain, summer grain and fallow — although the
more intelligent adopt a six years' rotation, which includes
potatoes, flax, clover, oats, barley and fallow.

In the vicinity of the city of Pskov are two brothers, energetic
men, who have farmed a small property of their own during
many years past and it is interesting to note that both admit
that they are perfectly satisfied and pleased with their crops.
There is one feature of their farming which is not often met
with and which is of particular interest to flax growers who
insist on the need of a change of seed every year. These two
men always carefully select sufficient of their best crops to
furnish seed for sowing in the following year. They have grown
flax and other crops from the same strain of seed in this manner

i8o SCIENCE PROGRESS

during the last twenty years and their crops to-day are superior
to others in the district. This is not to be regarded as instancing
an improvement in the quality of flax seed for fibre production
but as showing how deterioration may be prevented. That
deterioration has taken place is beyond question and is admitted
by Russian farmers themselves. Generally speaking, i acre of land
at the present time yields 2 cwt. of finished flax fibre ; twenty-
five years ago the yield was 3J cwt — a loss of more than £2 per
acre to the peasant producer. Most countries, if not all, depend
upon Russia either directly or indirectly for their supply of flax
seed, so it is not surprising to hear universal complaints about
the decreasing yield of fibre from the flax crops.

In the west central provinces, the number of horses and
cattle kept by the peasantry is very small. When a household
does possess a cow, it becomes the duty of some old person or
of a child to accompany the animal throughout the day as it
goes browsing over waste places, so as to prevent it doing
damage by w^andering on to the unprotected fields. For similar
reasons, little children are sent out with the geese to wander with
them wherever they go and to bring them home again at dusk.

The governments of Pskov and the neighbouring govern-
ments of Livonia, Vitebsk, Smolensk and Tver constitute the
most important flax-growing area in the world. It is no
exaggeration to say that nearly the whole of the linen trade
depends upon this great flax district. It is not surprising
therefore to find that the keen cosmopolitan competition for
flax fibre is waking up the slothful peasant and that the Ministry
of Agriculture is endeavouring to improve present methods of
preparing flax.

The general practice with this crop is to pull the plants
before the seed has ripened and to tie them up into bundles, so that
all the roots are at one end. The next operation is to remove
the seed. Sometimes this is done in the field and the green
stems are at once retted in water; or the pulled flax maybe
dried and then deprived of its seed. By whichever method the
seed is obtained from the straw, it is finally dried artificially at
a fairly high temperature and then spread on a stone floor to be
threshed. Threshing often consists in a horse dragging a
wooden roller about over the seed so as to crush the " bolls,"
the seed being separated from the chafl* by repeatedly
screening in a draughty situation.

Removing Flax from Retting Pit.

Spreading Flax in the Province of Pskov.

[i8i

THE CONDITIONS OF RUSSIAN AGRICULTURE i8i

Most villages in Western Russia possess a common threshing-
floor and a specially constructed drying house fitted with a
fireplace, where the inhabitants can dry their crops. Not only is
the final drying of the flax seed carried out in a heated chamber
but grain crops in general are frequently so treated after having
been dried as far as possible out-of-doors. This artificial drying
operation often lasts for two or three days and, if the outdoor
conditions are not favourable to drying, a longer period is
necessary before the crop can be deprived of its moisture
sufficiently.

Dotted about at convenient places all over this part of the
country small pits may be seen in which water accumulates.
At the proper season of the year, these are used as pits for
retting flax. During early autumn, when the flax straw is taken
from the water and is spread on the land, so as to complete the
retting process, the whole countryside becomes covered with
flax. One may drive many miles and see scarcely a change in
the monotonous landscape ; everywhere flax, nothing but closely
arranged rows of retted straw spread over the country.

Further south in the same province, near the upper part of
the river Sheion and not far from Dedoviezy, is one of the three
stations for the promotion and improvement of flax cultivation
which have been established by the Ministry of Agriculture.
At this station various methods of retting are practised and the
application of artificial manure and the use of better appliances
are explained and demonstrated to those who desire to become
improved. Much rain falls in that district about harvest time
and in consequence considerable difficulty is experienced in
getting the crops up in proper condition. To overcome this
difficulty and to make the farmer less dependent upon the
weather, several drying sheds have been erected to receive the
crops. These are simply constructed sheds with open sides,
fitted with trellis shelves, so that the crop laid upon them is dried
equally both from below and from above. Flax and clover
dried in this manner are found to be superior to crops which
have been dried in the open subject to the inclement weather.
Clover dried under cover is beautifully sweet and fragrant and
the fibre obtained from flax straw allowed to dry in the shed is of
superior quality ; moreover the saving of good seed is made pos-
sible. So much success has attended the experiment that quite
a number of drying sheds are now in process of construction.

i82 SCIENCE PROGRESS

Journeying in a south-easterly direction the scenery im-
proves : instead of a vast almost treeless expanse, the country
becomes undulating and trees are in plenty. Much of the land
is covered by tall grass and silver birch trees grow in great
profusion. Villages are even less frequently seen and the
approach to them as well as their general appearance would
prompt strangers to give them a wide berth. It is, however,
worth while to seek a possible entrance, where the mud is
shallow, so as to have an opportunity of partaking of peasant
hospitality with one of the enterprising farmers of the district.

He will conduct his visitor to one of the log-built cottages
which are bunched together about a wide muddy track — to one of
larger size, perhaps, which besides a chimney boasts of some
ornamental woodwork about the window frames and is situated
close to several small sheds and an enclosure of apple trees.
Mounting a few rickety steps, the cottage is entered by a door
leading on to a small gangway alongside a central partition
which separates the farmer's living quarters from those of his
small collection of livestock — all under one roof.

Only a dim light prevails, just sufficient to make visible a
small loft above the gangway where there is a stock of hay and
straw, some baskets and a few sacks. Below, on the ground,
a horse is seen standing on a scanty litter of straw between a
pile of wood and the central partition of the cottage ; poultry,
pigs and maybe a calf will fill up the gaps between queer-looking
carts, agricultural implements and a quantity of odds and ends.
Leading from the gangway is a small room illuminated by means
of a tiny pane of glass. In this little place, on a raised hearth,
there is a cooking-stove of massive proportions, sundry cooking
pots and earthenware utensils. The atmosphere is hot, stuffy
with smoke and laden with various odours of animal and
vegetable origin. From this apartment the farmer's dwelling
proper is entered by a loosely hung door. It is a simply
furnished abode containing a few chairs, some boxes, a table or
two, several plants on a shelf before the window and a roughly
fashioned cupboard in one of the corners.

The main features of the room are the stove and the bed, both
in point of size and importance. The stove is a great brick and
stone structure which is stoked from the little room outside. It
is so built that part of its hot surface extends from the floor to
the ceiling in each room and generally a long broad seat forms

THE CONDITIONS OF RUSSIAN AGRICULTURE 183

part of the hot surface, so as to provide a comfortable couch
during the winter. The broad bed is usually built in a recess
between the stove and the central partition — certainly against
the stove — and is separated from the room by a tall screen which
is often pleasantly ornamented in a simple manner by some
dexterous work with an axe. There will probably be an
" ornament " under a glass shade occupying a place on a table
and some damp garments hung over a cord drying by the
stove. Sometimes as many as five ikons will be hung on
the wall and at least one small lamp will throw a faint light
upon their glittering surfaces.

Russians are kind hospitable folk and the simple farmer is
not behind his richer countrymen in the matter of entertaining
a guest, although the means at his disposal may be of the most
primitive kind. There are few things they like better than
manipulating the sizzling samovar and dispensing tea while the
wife produces rye-bread, honey, fruit and as a particular luxury
— some eggs. They offer all they have and sincerely hope it
will be accepted. Their soft eyes beam with pleasure when
they are sipping hot weak tea with a visitor at their little table.
Sugar is seldom used, the tea being sweetened to taste by
each person taking frequent mouthfuls of honey dug out from a
big lump of honeycomb by means of a small spoon.

In this simple manner the peasant farmers live, cultivating
flax and oats with which they trade and small quantities of rye,
hemp, clover and potatoes for their own use. Here and there
the Commune still survives, the village land, for which they
are taxed as a community, being divided up according to the
number of souls in the village at the time of division. This is
done by the Village Commune or Council of Elders, who not
only allot the ground to the inhabitants according to the
working ability of the various households but strictly supervise
its cultivation, deciding when to plough, when to sow, and when
to reap. So the peasant has no personal interest in the land, he
has only to carry out the communal instructions so as to avoid
trouble with the Elders. He may neither increase nor decrease
his agricultural task without the consent of the Commune,
neither may he seek employment elsewhere without their
permission : individual enterprise can find no place in a life
conducted under such circumstances.

A fair proportion of the country is covered by pine, birch

i84 SCIENCE PROGRESS

and acacia trees, whilst further east, on towards the Valdai
hills, extensive forests occupy much of the land. Frequently,
when passing along the clearways through the forest, large
clusters of acacia and birch trees may be seen growing
amongst the pines. These are pointed to by the peasants as
being places good for a habitation, as a patch of good land where
they would like to live. Several of these coveted patches may be
seen in process of preparation for farming : the trees having been
felled, the scrub and roots are burnt out ; after this, the land is
ploughed and probably the first crop sown will be flax. When
the plot is ready the peasant either builds himself a log cottage
on the spot or he removes one he may have elsewhere, transport-
ing the structure a few logs at a time by means of a small cart.

There is some fine rough woodland country about the Valdai
hills, wherein rise the small streams which unite at Selisharova to
form the river Volga, which flows in a south-easterly direction
to the town of Rshef. With the exception of some slight
differences in detail, it may be said that all small Russian towns
are alike. They consist of an amazing collection of two-storey
houses and shops, which are generally built of wood, situated
some distance from a railway but close to a river. In the midst
of the town will be a large church of pleasant outward appear-
ance and close beside an open market place. The roadways and
paths will be in a bad condition and everything appear to be in
a state of disrepair.

The best day to visit Rshef is on the Sabbath, market day, for
then Rshef is animated as well as muddy. Peasants come into
the little town from distant parts, bringing with them all kinds
of goods for sale. From soon after dawn until eight a.m., a steady
stream of pedestrians and small V-shaped carts come down the
main muddy street from the south and across the Volga by the
pontoon bridge from the north and up the river bank, all going
towards the market. Bags of grain and linseed, bales of flax
and baskets of apples form the major part of the traffic but the
merchandise exposed for sale on carts and on the ground
includes cattle, pigs, poultry, clothing, pottery, apples, baskets,
implements of wood, and other commodities. Merchants come
from afar to buy grain and fibre : indeed at certain seasons of
the year the competition is so great that agents go out to meet
these small carts as they approach the town ; business is done
at once and the sold goods are brought into Rshef. As would

THE CONDITIONS OF RUSSIAN AGRICULTURE 185

be expected, this anxiety on the part of dealers to purchase the
peasants' produce is arousing in them rather a pronounced
business propensity. Between half-past nine and ten o'clock
all the little shops are closed and trade stops while a service
is held in the church : afterwards the market proceeds until
two p.m., when trade ceases for the day — one might almost say
for the week. Rapidly the people leave the town, taking with
them various articles purchased at the shops and salt from
the barges on the river. Once more Rshef becomes a quiet
place : at night there is no light in the town and no sound to be
heard except from the watchman who walks about the dark
streets telling of his approach by swinging a noisy rattle and
showing his whereabouts by a lantern.

There are flax dealers from all over Europe congregated in
Rshef. At one small house there are six men of different
nationality living together ; they converse in German and each
man goes his own way, buying according to the instructions he
receives by telegram. Nearly all day long and part of the night
up to two o'clock telegrams arrive at that humble dwelling.
The slamming of doors, the heavy tread of messengers up and
down stairs and the word " telegram " all form part of the daily
existence of these buyers in Rshef,

Much if not all of the peasant produce, be it grain or fibre,
is very imperfectly cleaned. Their implements are primitive and
they use them carelessly. But a change is coming; it is already
noticeable in many places how mechanical devices are finding
favour and that they will bring an improved condition. The Mayor
of Rshef has been inquiring for suitable machines of simple con-
struction for cleaning flax, machines such as the peasants could
purchase and take to their homes. He knows what is required
and is seeking where he can procure machines suited to the
purpose. The replies to his inquiries are really significant of
the spirit in which trade is carried on with Russia. Those
received from British firms read, "We do not make such
machines " ; the replies from German firms read, '* We will make
the machines you require." With this difference of attitude in
mind, it is not difficult to understand why British goods are
being steadily ousted from the Russian market. It avails little
to gaze in wonderment at our ever-decreasing imports into
Russia when the fault lies with us for not studying the con-
ditions of Russian trade.

i86 SCIENCE PROGRESS

Between Rshef and Moscow there are extensive pine forests,
girt about and intermingled with beautiful groups of silver birch
and thorny acacia trees. The country is slightly undulating
and terminal moraines form quite a feature of the district.
Considerable quantities of apples are grown and cattle are to be
seen in great numbers, presumably because of the market for
meat and dairy produce afforded by Moscow. Apart from this
cause, the Government and the Provincial Councils have done
much to foster and develop this side of farming.

The remarkable and elegant city of Moscow, of which all
Russians are justly proud, possesses a great number of educa-
tional institutions. One of the most important is the large
Agricultural College, which is situated amid delightful sur-
roundings in a beech wood some little distance from the city.
The College is well attended and although the building and the
laboratories are extensive, so great is the bustle and stir that
the place seems to be overcrowded.

Eastward from Moscow a great featureless country is passed
through, where neither hedgerow nor tree breaks the monotony
of a desolate plain. Generally speaking the soil is light ; it
blows about as dust during the dry summer months and after
rain makes very disagreeable mud. The ways of communica-
tion are far worse than those found in the western provinces ;
there are few railways, and scarcely any roads. Irregular tracks
connect a village with its neighbourhood and may be seen as a
pair of wavy lines stretching across the country. Except in the
villages situated nearer to Moscow, the conditions under which
the peasantry live are extraordinarily low. In the more remote
parts poverty is to be seen on all sides, misery being written
everywhere and it is shocking to behold the conditions under
which some of the peasants exist.

The severity of the Russian winter is keenly felt by the
inhabitants of this flat unprotected region, where cold, searching
wind and snow sweep unmercifully across the plain. It is not
until the end of March that the snow begins to melt ; with the
advent of April warmer winds rid the earth of the last snow and
bring forth vegetation with exceptional rapidity. Cattle which
have survived the seven months' trial — poor starved beasts ! —
are driven to the grazing land and it is small wonder that the
release from winter is celebrated by a religious ceremony.
About the middle of April the land is prepared for summer

Diying-shccls near Dedoviezy.

Retting Hemp on the North Steppe.

[187

THE CONDITIONS OF RUSSIAN AGRICULTURE 187

grain ; that is to say it is shallow ploughed and the seed sown.
Seldom is the soil enriched by the addition of manure, because
there is little available; moreover, it not infrequently happens
that towards the end of winter, when the stock of fuel is
exhausted, part of the thatching from the roof, as well as the
manure that has been saved, is burned in the stove to keep the
cottage warm.

Agricultural work in connexion with summer grain proceeds
during six or seven weeks following St. George's Day and
during that time, as well as throughout the open season, the
peasant labours on the extensive grain-raising lands of the land-
owner, in lieu of paying him rent for the ground he works for
himself. When the spring sowing is completed the fallow land
is ploughed up and made ready for autumn sowing ; this takes
until about the end of June. Following this comes haymaking
and harvest commences about the middle of July, lasting until
the end of August. Hay is mown by small scythes and the
standing crops of grain are cut by reaping-hooks. Men reap
and women and children twist the bands and tie the crop into
small sheaves, which are subsequently carted to the village
threshing-floor, where the grain is removed in the old style by
means of the flail. During September winter grain is sown and
provision is made for the oncoming winter.

Into this programme of events there must be read the celebra-
tion of religious feasts and saints' days, all of which take time.
Russian peasants are not contented with fifty-two Sabbaths
during the year; they celebrate some 150 holy days in addition
and so great is their love of idleness that besides keeping the
holy da3^s of their own village they will frequently leave work
and go to the celebration of a saint's day in a neighbouring
place. This means that much of the available time during the
open months of the year is devoted to religious idleness.

Although the eastern provinces are primarily a grain-pro-
ducing district, some considerable quantity of flax is grown in
the north-east in the neighbourhood of Viatka and the organisa-
tion of co-operative societies in the district beside the Volga
between Yaroslavl and Kazan has made it possible for the
small farmers to carry on dairy farming profitably and to export
butter and large quantities of eggs. It may not be known
generally that about half the eggs imported into Great Britain
come from Russia, some thousand million annually.

i88 SCIENCE PROGRESS

The high road of Russia is the Volga, a vast traffic being
carried upon the slow-moving, turbid river. It is perhaps owing
to that traffic that better agricultural conditions obtain in the
Volga region ; with increasing herds of cattle, agriculture is
advancing and the conditions are becoming more stable. Deeper
ploughing, the use of iron ploughs and grain drills are all
making for better harvests.

The most important town in East Russia is Samara, the
centre of the greatest grain-producing district in Europe. Day
and night loads of wheat, oats and barley arrive there from
the remote parts of the vast cultivated area surrounding the
town. There is great activity in the docks and warehouses;
barge-loads of grain are towed up the river for exportation
from St. Petersburg and Riga.

A large proportion of the Russian-grown tobacco comes
from the province of Samara but the quality of the product is
not very good.

It is instructive to visit these more remote regions, to see
how great is the area of land already cultivated and the almost
equally great area not yet opened up to crops. The harvest is
enormous because of the greatness of the area occupied, not
because of large yields. As a rule the crop is small ; expressed
in bushels per acre the average is :

Winter wheat

. 14

Winter rye .

Oats

, 114

Spring wheat

. Hi

Spring rye .

Barley .

When these figures are compared with the following data
recording harvests from some of the Rothamsted plots it will be
seen how closely they approach the yield from unmanured land :

Unmanured. Dung. Complete artificial.

Average for five years .12 36 39 bushels of wheat

Already Russia exports more wheat than the United States,
so that when better methods of agriculture find place and when
some few more successful seasons enable the farmers to pur-
chase machinery and artificial manure, it is probable that
Russia will be able to meet all the European requirements
in the way of grain.

The severity of the winter is not felt by the young corn,
because the deep snow which covers the land protects the
crops from wind and frost. It is surprising to find that the

THE CONDITIONS OF RUSSIAN AGRICULTURE 189

more hardy crop, winter oats, does not seem to be grown,
nor is there any information to be had as to the reason.

In remote districts where little beside grain is cultivated
it is almost impossible to picture what the effect of crop failure
must mean ; the distress must be awful. Even at the present
time the terrible calamity of six years ago is still felt by the
peasantry, many of whom sacrificed all their belongings and
pawned their future labour in the struggle against starvation.
So poor were the crops of that year (1906) that only about
one-half of the grain sown was recovered at harvest. There
was nothing wherewith to pay taxes and nothing to live upon
during the winter and no reserve stock of grain in the district ;
thousands of people and cattle died from starvation.

Nearer to the Ural Mountains the country is far more
picturesque; it is undulating and well wooded, resembling
pleasant downland, affording a welcome contrast to the dreary
flat district to the immediate west. In the neighbourhood of
Ufa and Orenburg cattle-rearing has become quite an important
business and here again the organisation of co-operative societies
has proved a great benefit to the small farmers by enabling
them to export large quantities of butter. Villages are few
and far between ; indeed, in some parts, there seems to be
no population at all, though it is said there are about forty
inhabitants to the square mile.

To the west the broad Volga flows slowly towards the
Caspian Sea, passing through richer soil than in its northern
course ; but apart from this very noticeable improvement, there
is little to be seen which is different from other districts.
Besides cultivating wheat and other grain, horses, cattle and
sheep are extensively bred and as might be expected agriculture
is not conducted on such poverty-stricken lines. There are
quite a number of private estates where up-to-date farming
is practised ; some of them are of tremendous extent, embracing
many thousand acres of land under wheat ; horses and sheep
are bred on an equally large scale.

Continuing in a south-westerly direction, the renowned
Steppe region is reached, one might say the boundless Steppe,
because this rich band of soil stretches from the Carpathian
Mountains in the west far away eastward into Siberia ; in fact,
it is not quite known how far it does extend. The European
portion is a vast undulating plain, mostly covered by sweet

I90 SCIENCE PROGRESS

herbage, where there is not a tree to be seen and where droves
of horses roam about in almost a wild state. A journey across
this region resembles a sea voyage; the lines of the horizon
constantly retreat before the eyes without changing in aspect :
occasionally the view extends far away into the distance where
earth and sky merge together into an indefinite haze. Not a
tree is to be seen, scarcely a bush of respectable size to give
a touch of variety to the landscape. Although the soil is rich,
it is exceedingly light, lighter even than fine sand, so that one's
own conveyance raises in its wake a cloud of dark dust which
slowly drifts across the country.

Villages are more frequently met with than in other parts
of Russia ; they are cleaner and generally more orderly. As
no wood is available, the cottages are built of brick and stone
and are heavily thatched with straw : quite a contrast to the
rickety wooden structures which constitute a village in the
forest region. The climate is almost temperate, the soil
dark — nearly black — and very deep, producing good crops of
grain. There must be a wonderful future in store for this
fertile area. The condition of agriculture in the Steppe region
is advanced when compared with other parts of Russia ; already
the peasants have grasped the advantage of using machinery
and through the operation of credit associations they are now
able to purchase modern appliances. The Russian peasants
are not thrifty, they would seldom save sufficient to be able
to purchase a machine outright, so these associations will
probably play an important part in developing Russian agri-
culture. In many villages modern agricultural appliances are
to be seen amid primitive surroundings and during the month
of August, when harvest is in progress, the changing hum of
the steam threshing machine may be heard on most of the large
estates. The corn is cut and left in the field until threshing
commences, when a long stream of carts carry the sheaves from
the Steppe to the threshing machine. Numbers of women and
girls receive them, cut the bands and pass the sheaves on to
men who feed them into the machine while others stoke the
engine with the issuing straw. When threshing commences,
it is often carried right through to completion, lasting day and
night for several weeks on the large estates, great animation
prevailing ; indeed it is a wonderful and picturesque sight.

Extensive horse breeding is a feature of the north Steppe

THE CONDITIONS OF RUSSIAN AGRICULTURE 191

region : in one province, that of Voronezh, there are no less
than 230 breeding studs, and more than 370 studs in the
adjoining provinces of Tamboff and Orel. Towards the town
of Orel there is a Government Agricultural School where lads
from the surrounding villages may go to receive practical
instruction in farming. This establishment is managed on
good lines; the pupils are not taken from their humble sur-
roundings and placed in circumstances far in advance of that
of their homes. They live together, under proper supervision,
in a commodious building and they keep house for themselves,
taking it in turn to cook and to clean. They are shown how
to make use of the material at hand, be it indoors or out,
how to construct farm carts, wheels, tubs and so forth, so that
when they return home they become improvers instead of
grumbling talkers who cannot do anything for want of the
appliances upon which they have been taught to depend.
Dairy work, pig-breeding, poultry-farming, smithery and
harness-making all form parts of the course of instruction.

In some places agriculture is mainly carried on by the
womenfolk, the reason being that their household is capable
of cultivating more land than is at their disposal, so the men
go away to the towns and seek employment at hotels or practise
a handicraft while the women carry on the farming operations.
One of the most difficult in the north Steppe region is the
management of the hemp crop, which, like flax, requires much
judgment and labour and for this reason, although large
quantities of hemp are raised in Russia, it is a crop which is
generally grown in small plots.

In Russia hemp is grown both for seed and for fibre,
necessitating a separate treatment for the male plants and for
the female plants. The male plants come first to maturity and
are cut or pulled as soon as the stems show signs of changing
colour ; the female plants, which grow to a greater height, are left
standing for the seed to develop. At a later period, when the seed
is almost ripe these plants are also cut and after properly drying
them the seed is pulled off. Generally speaking the male plants
are spread on the ground and allowed to rot by the action of the
dew. The female plants yield a much coarser fibre and are sub-
mitted to a water retting process similar to the treatment of flax.
Rectangular pits are dug in the black earth in the vicinity of a
stream, so that water will accumulate there and bundles of the
13

192 SCIENCE PROGRESS

female stems are packed so as to occupy only the central portion
of the pit, leaving a free water space surrounding the hemp. A
little straw is scattered over the top and clods of earth are stacked
on the straw, so as to sink the hemp below the surface of the
water. When properly retted the bundles are withdrawn and
the stems spread out on the land to dry, the separation of the
fibre from the retted stems being carried on during the winter.

Besides hemp and the usual crops of grain, there is quite a
large quantity of tobacco grown on the rich dark soil of this
district, especially in the provinces of Tamboff, Poltava and
Tchernigoff, over 25,000 tons being produced annually in the last
named province. The quality of this tobacco crop is held to be
very superior to that grown in the neighbourhood of Samara.
Further north, at Orel, a busy little town about a night's journey
south of Moscow, the Government have started an establishment
where the cultivation of hemp may be studied. They have also
installed quite an instructive exhibit of all types of machinery
required in hemp cleaning and the manufacture of rope and twune.
The exhibit comprises both simple and complicated machines
and they are fitted up so that anybody can receive instruction in
working them. Every inducement is being used to encourage
people to work up the raw fibre instead of exporting it and to
improve the methods of cultivation ; but as the poorest class of
peasantry is concerned with hemp cultivation it is difficult to
effect any improvement. Those in charge of this station are
certainly firm believers in the use of machinery for everything
and enthusiastically point out the superiority of the British-
made goods. They would like to have more of the smaller
machines of the same high-class workmanship but find that the
British firms expect to have a large order placed with them at
once and are not willing to invite new business by supplying
small items.

The district known as the '* Pale " comprises most of the
south-western provinces extending from the Baltic Province of
Courland to the west shore of the Sea of Azov. Nearly 95 per
cent, of the Russian Jewish population live within this area but
only few occupy themselves with agriculture. The Jews are bad
farmers and generally lack inclination to take part in agriculture
except by dealing with the produce. It is a significant fact that
nearly all Russian dealers are Jews; in fact nearly 97 per cent.
of the grain dealers in the south-west provinces are of that race.

THE CONDITIONS OF RUSSIAN AGRICULTURE 193

In Poland and the north part of the " Pale," large quantities of
potatoes, apples and sugar-beet are grown in addition to the
more usual crops of grain. Further south, besides sugar-beet,
rye and wheat, maize is extensively cultivated ; tobacco growing
is largely carried on in the province of Bessarabia. Flax is
extensively grown as a seed crop in the southern part of the
Steppe region where the climate is warm. For the most part,
agricultural practices differ little from those which obtain in
similar regions, with the exception that farming is more intensive
and machinery plays an important part in all operations.

Owing to a number of distinct causes, such as better educa-
tion, mineral resources and the requirements of local industry,
the extreme south and the Caucasian provinces boast of still
better conditions of agriculture. In the Caucasus, Russian
husbandry is seen at its best; wheat, rye, sunflower, melons,
fruit, tobacco, tea and cotton are all raised in the district between
the Black Sea and the Caspian Sea. The horrors of famine are
unknown in this beautiful region because of the diversity of the
crops, as well as the steadying effect of horse-breeding; cattle and
small-stock raising allows of intensive cultivation being carried on.

The time will come when these more flourishing conditions
will extend over a large part of Russia instead of being confined
to a relatively small region ; indeed it is admitted that a great
change is setting in ; already there is evidence of this even in
the more remote parts of the Empire. Left to themselves the
peasants will not change but show them how to progress and
they will progress up to the hilt. At the present time, it may
be said truthfully that they are being shown how to progress.

The undoubted desire of the peasant is to become an inde-
pendent agriculturist, to own his own land ; to this end, assistance
is being given by the operation of the State Land Fund and the
Peasant Land Bank, which jointly work to bring about the
change. In recent years the State has done much to improve
the condition of the agriculturist, recognising in a practical
manner the valuable constructive work done by co-operative
societies. The possibilities that have been opened up and the pro-
gress that has been made in agricultural districts by the organisa-
tion of co-operative and credit societies are quite remarkable.
Judging from the present beneficial results, it would seem that
the Ministry of Agriculture looks well to the future when foster-
ing the growth of these institutions.

THE STRUCTURE OF METALS

THE INFLUENCE OF MECHANICAL TREATMENT

ON STRUCTURE

By CECIL H. DESCH, D.Sc, Ph.D.

The microscopic structures described in the former article^ were
those of cast metals and of worked metals which had been
sufficiently annealed to cancel the effects produced by the
mechanical treatment to which they had been subjected. The
mechanical treatment, such as forging, rolling, pressing or
wire-drawing, to which metals are usually subjected influences
in a most important manner the microscopic structure as well
as the mechanical properties of the metal ; as numerous
relationships between these properties and the structure have
been established, the examination of worked metals is a highly
important branch of the metallographer's activity. The subject
offers a wide field for future research, on account of the diversity
of mechanical conditions that come under consideration and the
minute and elusive character of some of the internal structural
changes to which they give rise.

One of the chief factors in determining structure is the tem-
perature at which the change of form of a metal by mechanical
means, such as rolling, is conducted. A mass of metal that is
forged or rolled at a bright red heat and then allowed to cool slowly
assumes a structure which is essentially that corresponding with
the annealed condition ; it may differ in several respects from
that of the same metal as cast, the difference being in the
arrangement of the micrographic constituents, however, not in
their nature or proportions. More rapid cooling may, of course,
disturb this equilibrium, as in the case of a cast alloy. On the
other hand, when the rolling or forging is carried out at a
considerably lower temperature, readjustment of the crystalline
structure may be impossible ; the cold metal then exhibits
unmistakable evidence of the treatment to which it has been

^ Science Progress, No. 25, p. 87.
194

THE STRUCTURE OF METALS 195

subjected. The effect of hot-rolling on steel has been referred
to in the former article (photograph 5), where it was shown
that the grains of iron and the areas of pearlite are elongated in
the direction of rolling. Such flow-structures are of frequent
occurrence in rolled metals, so that the direction which a
specimen originally occupied in the rod or plate from which it
was cut is readily determined by microscopical examination.
Naturally, enclosures of slag or sulphide and similar impurities
are also elongated in the direction of rolling when the tempera-
ture is so high that they are in a liquid or plastic state at the time.

A metal which has only been worked while hot has
properties which differ but little from those which the metal
possesses in a fully annealed state ; it differs from a cast metal
in being more compact and generally more uniformly crystal-
lised but the elastic properties are not greatly modified, except
in so far as they depend on the crystallisation.

The effect of mechanical work on the properties of a metal
becomes more pronounced as the temperature falls. So long as
the temperature of working is above a certain limit, different in
the case of each metal and alloy, internal strain is removed as
fast as it is produced by a process of recrystallisation whereby
the equilibrium is re-established. At lower temperatures this is
not the case : the properties of the metal undergo more or less
permanent alteration, until at the ordinary temperature nearly
all metals are very appreciably " hardened " by the process of
hammering, pressing, rolling or drawing into wire. The term
"hardening" here denotes a change in many properties which
are closely associated with one another. The actual minera-
logical hardness — that is, the resistance to scratching — as a rule
is little affected but the elasticity is increased and the ductility
diminished, whilst the electrical conductivity is also lessened
and important changes are produced in the electro-chemical and
thermo-electric properties. Such a metal is said to have been
" cold-worked," although the temperature of working may be
considerably above the atmospheric temperature provided that
it is below that at which recrystallisation occurs freely. The
crystals of such a metal as copper or 70 : 30 brass are crushed
and deformed, the extent of the deformation naturally varying
with the degree of cold-working, whilst the structure of alloys
containing two or more micrographic constituents becomes
extremely confused and small areas of an eutectic may be

196 SCIENCE PROGRESS

entirely indistinguishable. The detection of impurities by
means of the microscope is therefore far more difficult in
worked than in cast or annealed specimens. The effect on a
homogeneous alloy is well seen on etched surfaces of rolled
sheet brass. Still more severe distortion is seen in hard-drawn
wires, in spun sheet metal and in cold-pressed objects such as
cartridge cases.

The facts which have to be explained in the mechanical
deformation of metals are the plastic yielding of the crystal
grains, which distinguishes a metal from a material such as
sandstone — the grains of which are usually separated by
pressure before any great deformation of the stone as a whole
is produced — and the remarkable increase of hardness which is
the consequence of the cold-working of most metals. The two
properties, plastic yielding and increase of hardness, are
intimately connected but it is only in quite recent years that
either of them has been satisfactorily explained and several
points still remain obscure. Both properties depend on the
minute internal structure of the crystals.

Viewed in the gross, there is considerable analogy between
the behaviour of crystalline and of amorphous materials under
a mechanical stress sufficient to produce deformation. Thus,
if a rectangular block with polished surfaces be compressed
either uniformly over one face or locally by means of a knife-
edge, systems of lines appear on the remaining faces and these
lines have the same general form and direction whether the
material examined be wax, hard gelatin or metal. The arrange-
ment of lines can be calculated mathematically and is inde-
pendent of the nature of the material. The differences between
amorphous and crystalline materials become obvious whenever
the deformation is studied more minutely. Whilst a fracture
in an amorphous substance may occur in any direction indif-
ferently, a crystalline substance has definite planes of weakness
along which rupture takes place by preference. Moreover, an
amorphous substance may undergo considerable permanent
change of shape without the development of any fracture,
however minute, provided only that sufficient time be allowed
for the deforming force to exert its effect. Examples of this
are seen in the slow sagging of glass tubes supported only
at the ends and in the remarkable experiments with brittle
cobbler's wax which have been made familiar by Lord Kelvin.

THE STRUCTURE OF METALS 197

Time also plays a part in the deformation of the softer
metals but the mechanism of the process is quite different.
The bending of a stick of sealing-wax, for example, is not
accompanied by any obvious change in microscopic appearance ;
but even in the case of the softest metals, such as lead, the
structure is altered. Lead, in fact, is a convenient metal for
the study of the process. A smooth surface is prepared and
the metal is deformed, say by lightly bending between the
fingers. Examination under the microscope shows at once
that a change has taken place, the originally smooth surface
being crossed by very numerous lines arranged in parallel
groups ; unlike the systems of lines common to amorphous
and crystalline materials, to which reference has been made
above, these systems of microscopic lines do not bear any
necessary relation to the direction of the deforming force. On
the other hand, they are very evidently related to the crystalline
structure. Fig. i represents a surface of lead after bending;
it will be seen that a close parallelism is preserved by the lines
in each crystal but that their direction changes abruptly from
one crystal to its neighbour.

The lines thus developed have been termed " slip-bands "
by Ewing and Rosenhain ^ and the name has been generally
adopted. They are parallel with the cleavages of the metallic
crystals and their direction in any one grain seen under the
microscope depends on the crystalline orientation of that grain.
It has been found possible to show, by the direct examination
of a cross-section, after protecting the marked surface by
depositing a thick layer of copper on it by electrolysis, that
each line is really a minute step and that the surface on one
side of a line is at a different level from that on the other.^
The same conclusion may be reached by illuminating the
specimen obliquely and rotating the stage of the microscope;
it is then obvious that the lines disappear in certain positions
and flash out again on reaching such a position that they reflect
the incident beam into the tube of the microscope. As the lines
in any one grain flash out simultaneously whilst they are inde-
pendent of those in neighbouring grains, their dependence on
orientation is clear.

These facts furnish the explanation of slip-bands. They are

1 Phil. Trans. 1889, 193 A, 353.

^ W. Rosenhain, Jour?t. Iron and Steel Inst. 1906, ii. 189.

198 SCIENCE PROGRESS

due to the slipping of certain portions of the crystal over others
along the planes of weakness or cleavage planes. When the
stress in a crystal grain becomes too great for the metal to
yield elastically, slipping along these planes takes place and
the shape of the grain is changed not continuously as that
of a truly plastic substance v^ould be but by a series of
dislocations completely resembling in origin and appearance
the ** step-faults" of the geologist. After the formation of the
slip-bands, provided that no further change take place, the
internal structure of the crystal is not affected, since the dis-
placement of neighbouring portions of a crystal is only one
of translation. Hence, if we examine a polished surface on
which slip-bands are obvious and then remove a thin surface
layer by grinding and expose the crystalline structure by
etching, the slip-bands do not reappear. This fact distinguishes
them from the grosser changes of structure which are produced
by mechanical means under certain conditions and especially
from twinning. Twinning planes reappear after removal of
the surface and re-etching and are easily recognised when
once the manner in which they differ from slip-bands has
been appreciated. Both twinned lamellae and slip-bands may
be present in the same crystal, but whereas the latter are
universal in metals after cold-working, the former are less
frequent and are only developed abundantly in certain classes
of metals and alloys, of which austenitic steels (such as man-
ganese steel) and copper and its a-alloys, including yellow
brass, are familiar examples. The strained surface of lead in
fig. I shows twinning lamellae as well as slip-bands. Fig. 2
represents a cube of ingot iron after compression ; both slip-bands
and crystal boundaries are distinguishable, the latter having
been made visible by the strain without any etching process.

To produce slip-bands it is not necessary that the stress
applied should exceed the elastic limit of the specimen. A
crystalline metal, even if practically free from impurities, is
not a homogenous substance but is built up of distinct grains
aggregated to form a mass. When a stress is applied, it is
impossible that it should influence every grain equally and
it may readily happen that a few individual grains are stressed
by an amount exceeding the elastic limit whilst their neighbours
are under a much lower stress. Every slip along a cleavage
plane brings about a redistribution of stress, tending to make

Fig. I.

Fig. 2.

Fig. 3.

Fig. 4.

198]

THE STRUCTURE OF METALS 199

further slipping unnecessary unless the stress be increased.
In the case of progressively increasing stress, more and more
crystal grains are dislocated in turn and the constantly varying
direction of the local stresses causes the opening up of new
cleavages, so that a grain examined microscopically shoves
two or more intersecting systems of slip-bands corresponding
in direction with its systems of cleavage planes.

If this were all that happened, the hardening effect would
remain unaccounted for, as a mere translation of crystal elements
does not cause a change of properties. As a matter of fact a
more profound structural change occurs as soon as the amount
of cold-working is considerable. The slip-bands lose their
simple character and become broad and prominent on a smooth
surface. Etching no longer removes them completely ; a close
examination proves that the surfaces along which slipping
took place are now separated by a layer of material which
differs in some way, both chemically and physically, from the
unaltered crystals.

An explanation of the hardening of metals has been given
by Dr. G. T. Beilby,^ who has based his conclusions on observa-
tions of the effects produced by polishing. Whenever a metal
is subjected to friction a superficial layer is formed which
possesses peculiar physical and chemical properties, being
hard, isotropic and more active chemically than the original
metal. A similar layer may be formed in the interior of a
metal by cold-working. The first motion of translation along
a gliding plane may produce little effect but by repeated
rubbing a layer of the hard material is built up between the
two surfaces which hinders further slipping ; the process being
repeated on successive cleavage planes, eventually the whole
mass of the metal is appreciably hardened.

Hardening by cold-working cannot be continued indefinitely
but reaches a limit, which has a definite value in the case of
that particular metal under given conditions. Further stress
weakens the metal by causing rupture of the hard layer and
consequent separation of adjoining crystals. The effect is
often seen in hard-drawn wire. If the drawing be continued
too long the wire loses its strength ; if a longitudinal section
be examined, it is seen that only the outer shell is continuous,

^ Phil. Mag. 1904 [vi.], 8, 258 ; /. Inst. Metals, 191 1, 6, 5.

200 SCIENCE PROGRESS

whilst the inner core is broken into cylindrical fragments with
conical ends separated by distinct cavities.

It might be thought that this result would only be attained
when the whole of the metal had been converted into the hard
material but this is not the case. When a wire that is hard-
drawn as far as possible is examined, it is apparent that the
greater part is still composed of the original crystalline metal
but that the crystal grains have been reduced in size by
crushing and that each small grain is enclosed in a hard shell
of the modified material. Further slipping along cleavage
planes is hindered or prevented by this comparatively unyield-
ing, brittle casing. When a section of such a hardened rod
or wire is etched, the shell or casing is dissolved more readily
than the crystalline core, so that the structure becomes visible.

One of the most characteristic properties of the hard modifica-
tion produced by strain is its power of flowing. Thus in the
hard-drawn wire it envelops the unchanged cores, filling the
intercrystalline spaces without a break. This property is
most conveniently studied in the surface films produced by
polishing. Whilst the grinding of a metal surface with emery
or similar abrasives is simply a process of cutting, innumerable
fine grooves being produced, the subsequent process of polishing
with alumina or rouge is of a totally different character. Dr.
Beilby has shown that even in the case of such brittle metals
as bismuth or antimony the surface layer flows like a viscous
liquid under such treatment. The grooves are partly smoothed
out by removal of the intervening matter and partly filled up
or bridged over. Etching removes the altered film ; scratches
which had merely been bridged over during polishing reappear
on etching. This reappearance of " latent " scratches has long
been familiar to those who have examined etched sections.
Measurements made on polished crystals of calcite by an in-
genious chemical method show that the thickness of the surface
layer of modified material is of the order of 500-1000 /i/i,. A
pattern once developed in an alloy by etching may be obliterated
by polishing, in which case the gradual disappearance of the
structure as the altered material flows into the hollows may
be followed with great ease.

It is observations of this kind that have led to the con-
ception of the hardened modification of cold-worked and
polished metals as an undercooled liquid of high viscosity.

THE STRUCTURE OF METALS 201

This view is perfectly consistent with a high degree of brittle-
ness. Cobbler's wax is a typical example of a substance which
flows like a viscous liquid but yet is brittle under a suddenly
applied stress ; the combination of these two properties, at
first sight contradictory, is not uncommon. The amorphous,
isotropic character of the hard modification is fully in accordance
with such a view, which is further supported by considerations
of the following kind.

A modification which stands to the ordinary crystallised
metal in the relation of an undercooled liquid must be unstable
at all temperatures below the melting point. At the ordinary
temperature it is related to the crystalline metal as glass is
to the mixture of crystallised silicates which is formed from
it when it devitrifies or as vitreous silica is to quartz.
It may thus be expected to show, relatively to the crystals
of the same metal, a lower density and a greater activity
towards solvents and to exhibit a tendency to crystallisation
whenever the circumstances are favourable. These expecta-
tions are fulfilled. A cold-worked metal is actually of some-
what lower density than one that is fully annealed, although
the difference is small, as is natural in view of the fact that
the conversion always remains incomplete. The greater sen-
sitiveness of hardened metals to attack by chemical agents
has already been mentioned and is confirmed by determinations
of electrolytic potential, which show that a highly worked
metal always becomes the anode when coupled in an electro-
lyte with a piece of the same metal in an annealed condition.

The tendency to return to the crystalline form is also well
marked. The change takes place with extreme slowness at the
ordinary temperature but much more rapidly when the tempera-
ture is raised. At a certain point, termed the '* crystallisation
temperature " by Dr. Beilby, the return takes place suddenly ; the
progress of annealing may be followed by means of tests of
elasticity or still more conveniently by determinations of the
thermo-electric difference between the specimen and one of fully
annealed metal.

The tendency to recrystallise must be present in all cold-
worked metals even at atmospheric temperatures, although
greatly restrained by the internal viscosity. It usually becomes
evident, however, even under such unfavourable conditions, to
a sufficient extent to constitute a serious difficulty in technical

202 SCIENCE PROGRESS

practice. The "season-cracks" which develop in brass are due
to differences of stress existing in the inner and outer layers of
worked brass objects and are the outcome of the process of
spontaneous recrystallisation. Still more remarkable examples
are seen in objects of brass or German silver which have been
subjected to very severe cold-working in the shape of " spinning "
or pressing between dies. In thin articles such as brass lamp-
reservoirs numerous cracks are apt to develop which gradually
involve complete disintegration of the metal. This change pro-
ceeds more quickly in a warm than in a cold atmosphere ; it
has been described by Prof. Cohen ^ as " strain-disease," owing
to a remarkable similarity to the now well-known "tin plague"
which occurs in cold countries. The tin plague is due to the
change of ordinary white tin, which is unstable below i8°, into
grey tin and is propagated by contact with articles of grey tin.
So also the recrystallisation of severely strained metal is acceler-
ated by contact with the stable crystalline modification. In
some of the experiments a design was etched on a sheet of
metal in order to expose the crystalline structure by removing
the superficial fluxed layer and the clean surface was then
placed in close contact with another sheet of the same metal in
a cold-worked condition ; in the course of one or two days, at a
temperature of ioo° or upwards, the design was found to have
been transferred to the second sheet, the unstable modification
on the surface having reverted to the stable crystalline form.

The view was and frequently still is held by engineers and
others that a metal in use, especially when the load which it
carries varies in direction or intensity, tends to become more
coarsely crystalline ; in fact, failures of structures under stress
are very commonly attributed to crystallisation of the metal.
Growth of crystals takes place readily at high temperatures, to
such an extent that iron bars forming part of a furnace exposed
during several years to a' temperature favourable to crystallisa-
tion have sometimes been found, when the furnace has been
dismantled, to consist of only two or three large crystals. At
somewhat lower temperatures vibration has been found to
favour this process by facilitating the rearrangement of the solid
particles when the metal was initially in a condition not that
of equilibrium but there is no evidence that a thermally stable

^ E. Cohen and K. Inouiye, Zeitsch. physikal. Chem. 1910, 71, 301.

THE STRUCTURE OF METALS 203

metal undergoes any appreciable spontaneous change of the
kind at atmospheric temperatures, whether assisted by vibration
or not. There is some little evidence that vibration favours the
return of an unstable alloy to the stable state at the ordinary
temperatures but so far this case has not received much attention
from the practical point of view.

The evidence for the popular opinion as to the influence of
fatigue on metals rests entirely on the appearance of the frac-
tured surface. The appearance of fractures is constantly used
in practice as a means of judging of the coarseness of grain of a
metal and very useful results are obtained in skilled hands from
the comparison of specimens broken under precisely similar con-
ditions, although the accuracy of the method is naturally less than
that of microscopical examination. On the other hand, a single
piece of metal may give two entirely different types of fracture
if broken in two different ways, as by slow tension and by
sudden shock. A metal which breaks with a so-called " fibrous "
fracture in an ordinary testing machine may have a coarsely
crystalline fracture when broken by shock or by fatigue.

The manner in which fracture actually occurs 'has been
studied in detail by methods involving the fatigue of the metal.
For instance, a rectangular rod of steel may be fixed at one end
to a revolving shaft, whilst the other end is loaded by a weight
suspended by means of a stirrup passing over a polished sleeve.
The rod is thus subjected to a bending stress which varies
periodically in direction. By polishing and etching one surface
of the bar and interrupting the test at intervals, the course of
destruction of the specimen may be followed with the micro-
scope.^ The development of slip-bands begins in a few crystals
and gradually spreads to others, whilst at the same time new
systems of lines appear in the grains which were first affected.
As the alternations of stress are continued, the lines broaden,
indicating the formation of a layer of amorphous material of
appreciable thickness along the rubbing surfaces ; after a time
actual cracks become perceptible. The cracks always pass
through the amorphous films, not between the crystals (that
is, in such materials as soft steel, from which brittle inter-
crystalline eutectics are absent). A crack once started tends to
spread by localisation of stress at its ends but only a few of
the cracks which appear reach any great development, the
^ J. A. Ewing and J. C. W. Humfrey, Phil. Trans. 1902, 200 A, 241.

204 SCIENCE PROGRESS

others being arrested by meeting the crystal boundaries.
When it happens that the directions of the slip-bands in two
adjacent grains nearly coincide, it is possible for a crack to be
propagated and as every increase in its length produces a
further concentration of stress, a crack once extended over
several grains tends to spread to the exclusion of neighbouring
smaller cracks. Ultimately the crack spreads through the
whole rod with increasing velocity, owing to the increasing
intensification of local stress.

The "crystalline" fracture of metals broken by fatigue is
thus accounted for. The glistening facets which are usually
regarded as crystal faces are in reality cleavage planes exposed
by the process just described. When produced by simple
alternations of stress, such a fracture is not accompanied by
any marked deformation of crystal grains whilst a fracture
produced by slowly applied tensile or bending stress preceded
by great deformation has an entirely different character, the
crystals being drawn out and torn rather than snapped asunder.
In the well-known instance of wrought iron, the presence of
brittle slag bands causes fissility in one direction, so producing
the characteristic ** fibrous " fracture.

The brittleness occasionally exhibited by masses of mild
steel, such as boiler plates, is not revealed by the usual tests
involving the slow and continued application of stress. It is
possible for a metal to show the required strength and ductility
in a tensile test and yet to be so brittle that a sudden blow will
break it without previous yielding. In order to guard against
such accidents, a special form of test is required in which the
application of the stress is such as to cause fracture in the
manner just described, that is, by rupture of single crystals
along their cleavage planes. Such tests are of two kinds, the
one involving repeated alternations of stress and the other a
suddenly applied shock — both kinds are susceptible of many
different modifications. An alternating stress test may consist
in bending the test-piece to and fro or in alternately stretching
and compressing it, whilst a shock test may be made in a variety
of ways, by means of a falling weight, a swinging pendulum or
a revolving arm. The test-piece intended to be broken by shock
is generally notched to localise the stress. Although consider-
able differences of opinion exist as to the most suitable form of
test, it is certain that either of those mentioned gives a more

THE STRUCTURE OF METALS 205

accurate indication of the presence or absence of brittleness in
a specimen of steel than the ordinary tensile test.

Brittleness in steel may be due to the presence of impurities,
principally phosphorus, which has a remarkable effect in
coarsening the structure and developing the cleavages. The
influence of these dangerous elements is thoroughly well
understood and the control of metals by chemical analysis is
largely designed to guard against danger from this source.
Other less well understood factors remain, among them the
influence of nitrogen, to which some authorities have attributed
the brittleness which occasionally develops in mild steel plates
with age. This is a point which has not yet been fully investi-
gated, although certain remarkable changes of structure,
including the production of large and conspicuous cleavages,
have been recognised as associated with the presence of
nitrogen, which is apparently retained by the iron in the form
of a homogeneously distributed nitride. Apart from these
chemical conditions, the principal factor which determines the
toughness or brittleness of a given steel is the size of grain
and this is in turn dependent on the thermal treatment. Con-
sidering first a steel containing only a small proportion of
carbon, heating to a high temperature within the austenite
range, say to 1200° or 1300°, produces a coarse structure, the
size of the grain being approximately proportional to the
temperature and this coarseness is retained after cooling to
the ordinary temperature. In fact, the size of grain is a func-
tion of the maximum temperature to which the steel has been
exposed, provided that no mechanical work has been applied.
If, on the other hand, the metal be rolled or forged while hot, the
mechanical treatment breaks up the crystal grains while it
continues and the final size of grain is a function of the
"finishing" temperature and not of the maximum temperature.
Coarse crystallisation due to overheating is thus obliterated by
work, provided always that the metal has not been " burnt," in
which case the grains, separated by films of oxide, do not reunite
during cooling. Steels very low in carbon also become coarse
and brittle if annealed for a long time at a low temperature, the
growth of the grains being extremely rapid somewhat above
700°, as was shown in the previous article.

Steel which has been overheated or which has been annealed
for too long a period at a low temperature may be restored to

206 SCIENCE PROGRESS

a normal condition by heating until the austenitic region is
entered and then cooling. A fine grain is obtained in this way
and dangerously brittle steel, if not burnt, may thus be made
equal in quality to steel which has not been rendered coarse at
any time. The minimum temperature for the purpose varies
from 950° for very mild steels to 800° for hard steels.

When the proportion of carbon is somewhat greater, so that
the pearlite forms a considerable fraction of the entire mass, a
second factor enters, namely the condition of distribution of the
carbide. Rail steel containing about 0*45 per cent, of carbon
may be taken as an example. A slowly cooled or annealed rail
contains its carbide in the form of laminated pearlite. Prolonged
annealing not only causes an increase in the size of the grains
but if it be conducted at a temperature below that at which the
carbide is absorbed, it has the further effect of causing segre-
gation of the carbide, a final state of equilibrium being reached
only when the whole of the carbide has been gathered into
isolated masses which lie between the grains of ferrite. Such a
condition is eminently favourable to brittleness, on account of
the facility with which the cleavages opened in one grain can
be propagated. It has been found that the maximum toughness
is obtained when the steel is cooled so rapidly that the carbide,
instead of forming parallel laminae, remains in a minutely
granular state in the condition known as sorbite. Such a
condition may be obtained by a process of semi-chilling, in
which the cooling is not sufficiently rapid to harden [the steel
but is too rapid to allow the carbide to segregate.

Similar considerations apply to other metals and alloys.
Heating to a high temperature increases the size of the grains,
whilst hot-working destroys the large crystals, so that a fine-
grained structure may be obtained by selecting a suitable
finishing temperature. Fig. 3 represents a transverse section
cut from a rod of Muntz metal, which has been rolled hot and
has a fine grain, the a and /3 constituents being arranged very
uniformly, with little or no tendency to rectilinear groupings.
Fig. 4 represents a rod of the same alloy heated to 850° and slowly
cooled without applying work. The magnification is the same
in both cases. It is obvious that the size of grain has increased
enormously, whilst the a-crystals also show a strong tendency
to assume rectilinear forms and to become arranged parallel with
the cleavages of the /3-crystals from which they have separated.

THE STRUCTURE OF METALS 207

Such an alloy is far more brittle than the rolled specimen. If,
besides heating it to a high maximum temperature, the alloy be
quenched, so that it is entirely in the ^-condition, the brittleness
is enormously increased, the /3-grains being separated by
rectilinear boundaries without any a-constituent to produce
even a partial union.

The mechanical behaviour of metals at high temperatures also
has great technical importance. Such objects as the valves for
the admission and regulation of superheated steam or the plates
and stays of locomotive fire boxes are exposed to severe
mechanical stress at temperatures very considerably above that
of the atmosphere. It is well known to engineers that all
metals deteriorate in strength as the temperature increases but
satisfactory information on the subject is curiously scanty.
Generally speaking, the tensile strength, both of pure metals and
alloys, diminishes as the temperature rises. The ductility of
a cast or annealed metal also diminishes at first, whilst that of a
cold-worked metal increases, owing to progressive annealing.
At higher temperatures the ductility varies in an apparently
capricious manner, finally reaching zero at or near the melting
point. A number of factors are evidently concerned in the form
of the ductility curve and much work will be needed in order to
disentangle them.

The most satisfactory experiments of this kind are those
recently conducted at Liverpool by Mr. G. D. Bengough.^
Considering only the tensile stress under which a specimen
breaks, it appears from these tests that the stress falls as the
temperature is raised in a manner which is best represented by
two intersecting lines one of which is straight whilst the other
may be either straight or curved. The general condition pre-
sented by pure metals or homogeneous alloys is shown in fig. 5.
The line ABC represents the variation of strength with
the temperature of a cold-worked metal, whilst DBC represents
that of the same metal in a cast or hot-worked condition. The
change of direction at B is always well marked in the actual
curves. The point B is designated by Mr. Bengough the
*' temperature of complete recuperation." The curve AB is
evidently a range within which annealing of the cold-worked
metal, that is, recrystallisation of the amorphous modification,
is going on. It is suggested that our ordinary cast or hot-

^ Journ. Inst. Metals^ 191 2, 7, 123.
14

208

SCIENCE PROGRESS

worked metals contain a proportion, perhaps small, of the
amorphous material and that this accounts for the form of the
curve DB. On this view, a specimen composed exclusively of
crystalline material would exhibit a strictly linear change of
strength with temperature, as shown by the line EC. Beyond
B all three curves coincide ; B is therefore the highest tempera-
ture at which the amorphous modification can exist. This limit
lies at about 650" in the case of copper, 395° in that of
aluminium and at 710" in that of a homogeneous alloy
containing 80 per cent, of copper and 20 per cent, of nickel.

The hypothesis is ingenious but the continued existence of
the amorphous modification at such high temperatures is con-
trary to the evidence of experiments on the elasticity and
thermo-electric power of worked metals, which indicate lower

Fig. 5.

recrystallisation temperatures, about 250° for copper. The
sharpness of the break in the curve at B does not serve to
suggest that the point is merely the upper limit of a crystal-
lisation which sets in with great rapidity at a temperature 400°
lower and there are other difficulties which need further
elucidation.

In spite of the closeness with which the hypothesis of an
amorphous modification fits the facts, it has not met with
universal acceptance. The view also finds favour^ that con-
tinued cold-working involves merely a greater and greater
development of slip-bands, so that the individual crystalline
masses which remain unchanged in form become smaller and
smaller but without the appearance of any new form of
material.

^ O. Faust and G. Tammann, Zeiisch. physikal. Ckem. 1910, 75, 108.

THE STRUCTURE OF METALS 209

Prof. Tammann has recently applied this hypothesis in
detail to the explanation of the properties of hardened metals.
He rejects the assumption of an unstable amorphous state
on several grounds, of which the principal are the absence of
any permanent alteration in a metal when the pressure apphed
is equal in all directions and the fact that cold-working generally
produces a slight diminution of density, whilst the application
of an increased pressure might be expected to lead to the
formation of a denser rather than of a lighter modification.
The diminution of density is attributed to the formation of
minute gaps between different lamellae when the amount of
slipping and shearing becomes large. It is supposed that the
energy expended in causing slipping is stored in the crystal
and that thin lamellae are constantly tending to reunite to form
larger crystals ; the greater energy-content of the hardened
metal and its tendency to return to the normal condition of
coarse crystallisation are due to the same cause.

The diminished electrical conductivity of a metal which has
been hardened by drawing into wire is readily explained on
the hypothesis of an amorphous modification. If this be
rejected, the diminution must be attributed partly to internal
rupture of the material and partly to the effect of orientation
by sliding, it being assumed that the conductivity of a metal
is greater in the direction perpendicular to the principal
cleavage than parallel to it. There are obvious difficulties in
the way of such an explanation but it is supported by experi-
ments which show that drawn wires recover their conductivity
on annealing though severely twisted wires are rendered
permanently worse conductors. In the first case the effect
is due to reorientation of the crystals and a rise of temperature,
by allowing freer play to the capillary forces, brings about
recrystallisation, whilst in the twisted wire reorientation can-
not account for the lessened conductivity, which must be due
to cracks and therefore does not disappear on annealing. The
argument does not appear to' be conclusive and the writer
prefers the hypothesis of an amorphous material, especially
in consideration of the microscopical evidence from polished
and unpolished metals which is not discussed by Prof.
Tammann.

The theory of thin lamellae in metals, the number of which
^ Zeitsch. Elektrochem. 191 2, 18, 584.

2IO SCIENCE PROGRESS

is increased by cold-working, whilst subsequent annealing
produces reunion under the action of capillary forces, was
proposed as long ago as 1868 by Prof. G. Quincke,^ who has
since modified his views and now assumes that every metal,
even when pure, has a heterogeneous foam structure ^ and that
the cell-walls, which are chemically different from their contents,
modify the influence of mechanical work in displacing the
lamellae. In other respects his explanation of the phenomena
is in agreement with that of Prof. Tammann.

At the other extreme stands a remarkable hypothesis which
has been proposed recently as the outcome of important experi-
ments in the Geophysical Laboratory of Washington.^ The
hypothesis is to the effect that the flow of metals is due to
an actual melting. It is true that increase of hydrostatic
pressure has the effect of raising the melting-point of all but
a very few metals but it is contended that pressure producing
flow must have an entirely different effect. It has in fact been
shown, on theoretical grounds, that pressure must always
lower the melting-point if it be applied in such a way as to
act only on the solid while the liquid is free to escape ; ^ the
conclusion has been verified in the case of ice. If the heat
of fusion and the density of a metal at its melting-point are
known, it is possible to calculate the pressure which would
be necessary to melt a metal at atmospheric temperature. This
has been done and although the numbers obtained are very
large, the author of the memoir does not regard them as
impossibly so. The order in which the metals appear in such
a list coincides exactly with that of their elastic properties,
showing that the relation between melting-point and elasticity
is a real one whether the actual form of relation proposed
be correct or not. It is difficult to picture the manner in which
such melting can take place. It is true that the pressure
between two portions of metal on opposite sides of a cleavage
plane may be very much greater than the average pressure
on the metal under stress but the pressures demanded are
very large (1760 atmospheres in the case of lead and 14,000
atmospheres in that of silver at 27°, for example) and it would

^ Ber. Akad. Berlin^ 1868, 132.

' Proc. Roy. Soc. 1906, 78^, 60.

^ J. Johnston,/. Ainer. Chejn. Soc. 1912, 34, 788.

M. H. Poynting, Phil. Mag. 1887 [v.], 12, 32.

THE STRUCTURE OF METALS 211

appear to be impossible that such pressures could be confined
to the solid crystals.

The importance of a microscopical control of engineering
and structural materials will be obvious, even from this hasty
and incomplete sketch of the relation between structure and
properties. Whilst ultimate chemical analysis is of great
importance in controlling materials, there is much necessary
information that cannot be obtained by such means. Proximate
chemical analysis, which in some cases affords valuable informa-
tion, is almost in its infancy. Its absence is in a large measure
supplied by microscopical analysis, which permits a visual
separation of constituents. The highly important question
of crystalline arrangement within the metal is only to be
approached by microscopical means and although the complete
correlation of structure with mechanical properties may be
only an ideal towards which workers in metallography are
striving, the knowledge already available on this subject
suffices to make the microscope an indispensable auxiliary of
the balance and the testing machine in metallurgical work.

THE PLANET MARS
PART II

By JAMES H. WORTHINGTON

In the preceding article, I have explained the precautions that
are taken in observing this planet and have drawn attention to
various considerations which justify students of its features
in attaching reality to their observations, as well as in feeling
assured of the correctness of the arguments which they venture
to use.

The account is not complete nor can it be, as the subject is
one that is being developed almost daily ; but sufficient has been
said to illustrate the methods peculiar to the investigation.

The appearance of Mars in the telescope at Flagstaff, when
conditions are favourable and due precautions are taken to
stop down the instrument and to insert appropriate dark
glasses, is a most surprising revelation. The telescope presents
us with a disc of about five times the apparent diameter of
the full moon as seen by the naked eye : brilliantly lighted, it
shines with well-defined, delicately tinted patches of colour.

The snow cap is seen at the pole. Farther down the disc,
areas appear of a greenish-blue colour in which is visible a
v^ealth of minute stippled detail — too fine to be called features
but coarse enough to produce the impression of variation in
texture. These green areas are very clearly defined at their
edges and the better they are seen, the more clear-cut do they
appear to be. In addition to the green areas, there are ruddy
ochreous stretches extending over five-eighths of the surface of
the planet.

Thus far nothing new or startling is seen. But when, during
a few brief moments, the definition becomes perfect — and such
moments are infrequent — an amazing network of very fine lines,
arranged criss-cross-wise in perfect geometric fashion, is appar-
ent. These lines occur in all latitudes, alike over green and

212

THE PLANET MARS 213

ochreous areas ; they are the " canals " of which so much has
been heard.

In seeking an explanation of the general appearance of the
planet we may recall first that it is amply proved by spectro-
scopic study that the known chemical elements are the common
property of the visible universe. With a few exceptions,
perhaps, all the elements that exist in the stars are to be
found on the earth and vice versa. We therefore need have
no hesitation in drawing on terrestrial experience when in-
vestigating Mars, which differs from the earth mainly in being
more distant from the sun and of smaller mass. These two
differences alone suffice to explain most of the contrasts that
are evident on comparing the surface of Mars with that of
our earth.

Again the kinetic theory of gases provides a criterion by
which we may judge of the probability of the presence of an
atmosphere and its possible nature. According to this theory,
the molecules of all gases, at any given temperature, move with
velocities characteristic of each gas ; though the molecules of a
given gas move with varying velocities, both the mean and the
maximum speeds are functions of its molecular weight.

The power of a celestial body to retain a gaseous atmosphere
about itself depends at any given temperature upon the force of
gravity at its surface, the which force is a function of its size
and mass. This gravitational force is capable of controlling and
retaining particles or molecules which move with a speed less
than that which would be attained by a particle falling from
infinity to the surface of the planet under consideration ; this
velocity, for the sake of brevity, is called the critical velocity for
the planet because particles moving faster than this, in the right
direction, must inevitably fly off the planet and escape into space.

If it can be shown that the molecules of a given gas at the
surface of a planet would move with a maximum velocity higher
than the critical for a given planet, the conclusion is inevitable
that the planet cannot have permanently an atmosphere com-
posed of this gas.

An example or two will make the operation of this law clearer.
It has been found that the sun possesses an atmosphere largely
composed of hydrogen and this is in harmony with the fact that
the critical velocity at the sun's surface is something over three
hundred miles a second, whereas the maximum velocity of

214 SCIENCE PROGRESS

hydrogen molecules there is probably about 50 miles a second.
The earth has a lower critical velocity, namely 6'9 miles a
second, whilst the maximum velocity of the hydrogen molecules
at the mean temperature of the air would be about 7*4 miles
per second and but little hydrogen is found free in our atmo-
sphere. The critical velocity at the surface of Mars is about
3' I miles per second and the temperature, as we shall see, is
probably not so much below that of the earth as to make
it likely that gaseous hydrogen is a constituent of its atmo-
sphere though other gases whose maximum molecular velocities
are less than this may well be present.

On account of the weakness of gravity on Mars it is pro-
bable that though water may be scarce, yet the commoner
constituents of the earth's atmosphere whose molecular
velocities at its surface are all likely to be less than 3'i miles
per second may well be common. Among these gases are
those which make life possible here — namely water vapour,
oxygen, nitrogen and carbon dioxide. We need, therefore,
feel no surprise when appearances on Mars indicate the
presence of gases which are thus shown to be theoretically
possible. That there are other causes besides gravitational
weakness operating to rob the planet of a terrestrial atmo-
sphere cannot be doubted : diminished pressure of sunlight
is perhaps the most obvious. It appears therefore that we are
justified in concluding that the atmosphere of Mars may be
like our own, though less dense and that probably it is dis-
appearing gradually. It will be seen later that this conclusion
is amply corroborated by the detailed observations of the
surface features and their changes.

Our estimate of the temperature at the surface of Mars is
based upon the following considerations. The heating and
lighting power of the sun at the distance of Mars is about
half what it is on the earth ; but only about 40 per cent, of the
solar heat which the earth intercepts ever reaches the surface ;
the remaining 60 per cent, is thrown back into space by
our atmosphere. On Mars the conditions are very different.
Though the planet only receives 50 per cent, of the earth's
share, it retains a much greater proportion, for the low
albedo or reflecting power of Mars is an indication that
more than 80 per cent, of the incident light is retained and
hence it appears that the surface of the planet receives from

THE PLANET MARS 215

the sun at least as much as falls upon the surface of our
earth.

Now the average temperature of the surface of the earth is
about 60° F. It seems probable that Mars should not be much
colder. No doubt the thinness of the atmosphere of the planet
will have a chilling effect but it seems certain that the con-
ditions are such that winter and summer, frost and thaw, as
well as vital changes like those which occur on our earth,
are to be expected.

The low reflecting power of the planet itself is also evidence
that the atmosphere is scanty, though the strong whitish glare
on the limbs which there obliterates surface detail is clearly
seen in the middle of the disc and proves that there is an
atmosphere.

I come now to speak in greater detail of the markings of
the disc and the changes they undergo.

On Mars there are, roughly speaking, six different kinds of
markings — viz. :

Greenish areas ;

Ochreous areas ;

White areas near the poles ;

White areas which behave differently in the equatorial

regions ;
A network of extremely fine lines called " canali " ;
Small round dark spots forming knots in the network of
the "canah."

After duly noting the changes in which all these features
share, I shall attempt to outline an hypothesis which will
consistently account for all of them simultaneously.

The first features to be considered are the white patches
which, in their respective winters, are so conspicuous at the
poles. For many years it has been noticed that these polar
patches are smallest at the time when the summer heating of the
pole is greatest — a time corresponding to late July in the earth's
Northern Hemisphere — and that the maximum extent of white
occurs at midwinter. This in itself is an indication that the
material of which the caps are composed may be water.
As has been shown above, the temperature at the planet's
surface is such as to justify this view. I shall therefore assume
that the white patches consist of water and pass on to examine
other observations which have been made of their behaviour.

2i6 SCIENCE PROGRESS

The polar patch vanishes in the increasing heat of spring.
The blue strip which surrounds it is fluid, for it has been found
to polarise light and is exactly the colour of water. The blue
strip clings to the dwindling cap, just as pools form around
melting snow. When all the white is gone, a dark smudge as
of wet ground is seen in its place. By this time, the blue stuff
has also disappeared — has either flowed away or evaporated.

A recent discovery speaks accurately as to the temperature
prevailing round the pole in the later part of the summer, for
there appears at this time in the subpolar regions of the planet,
on the sunrise edge of the disc, a whitish patch which has
the unique property of being fixed. It is on the surface of
the planet but does not partake of its rotation. It is there-
fore a state through which the surface passes at this particular
hour of the morning. There can be no doubt that it is hoar-
frost. It may seem surprising that this should be visible but the
appearance is so striking as to show obviously and unmistakably
on many photographs of the planet.

When I first saw the patch I was so struck with its appearance
that I sought for evidence as to whether it had been seen prior
to the announcement of the discovery of its nature. I have
found many notes of white patches being observed in the
appropriate position the meaning of which was not divined at
the time. I need scarcely say that this discovery was made
at Flagstaff, where also the majority of the data used in this
paper were obtained.

Lowell has shown that this morning hoar-frost appears exactly
where it should do in the coldest part of the autumn hemisphere,
which is obviously not the pole but the place where the
increasing nights have become long enough to cause the land
to lose more heat than it receives daily from the sun.

The presence on Mars of water in all its three states being
indicated, it is natural to inquire what happens to it when it
leaves the pole. Most of the greenish areas lie in a belt
about the south temperate zone. When the snow at the
South Pole begins to melt, this zone of green proceeds to
darken, the wave of colour beginning in the southernmost part
and gradually spreading northwards. That this change may
be due to vegetation is evident. All circumstances are pro-
pitious. There is sufficient heat. Water is present to nourish
it. And all we know of the Martian atmosphere points to

THE PLANET MARS 217

its being one that could support plant growth. The colour
of the green areas is that of vegetation and the change to
green occurs at the right season. In the other hemisphere
the green areas, being in the grip of winter, are pale and faint.
This also is to be expected.

Granting that the water from the pole has moved down the
disc, it is natural to ask how it makes the journey. Accurate
measures made at Flagstaff prove that the shape of the planet
is such that fluids on its surface are in static equilibrium
and that water therefore could not flow naturally down
the parallels as it manifestly does. The conclusion is that
it is transported by some artificial means. We are thus led
to seek for evidence of artificial water channels. These the
** canah " supply. For the " canali " develop down the disc
equatorwards, their colour deepening ahead of the green
areas through which they run, thus proving that the water
reaches the regions through which they pass before it arrives
in the surrounding regions. The lines which we see are
presumably not the water channels merely but the strips of
country irrigated by them. The rapidity with which the
water progresses is indicated by the growth of the strips
and proof is obtained in this way that the development of
vegetation is not due to the perennial sunshine but to the
seasonal irrigation.

Wherever two canali cross, a minute dark spot or oasis
comes into view and in no other part of the planet do these
dark spots develop. The general appearance of the canals must
be noted. They all are perfectly direct and uniform in their
course; many are more than 1,000 miles long, one, the Eumenides
Orciis, being upwards of 3,000. The larger canals are all arcs
of great circles and are therefore the shortest possible courses
between the points they unite. Many are double, thin com-
ponents being rigidly parallel, though not alwa3^s equal in in-
tensity. All are uniform in width throughout their course, though
the width is individually characteristic of each canal — some being
strong lines, which are probably 30 miles wide, whilst the
fainter lines are the merest gossamer threads, visible with the
greatest difficulty and probably not more than a mile wide,
perhaps less.

Lowell's experiments on the visibility of distant telegraph
wires have shown that lines of this width should be visible.

2i8 SCIENCE PROGRESS

In all cases the width, which is itself imperceptible, is estimated
by the intensity. That there is a range of 30,000 per cent,
in the intensity proves that the larger canals are nowhere
near the limit of vision — a conclusion amply verified by the
fact that many of the larger ones are clearly visible on photo-
graphs of the planet. All these canali are equally geometrical
in their appearance and it is inconceivable to those who see
them that they are anything but the work of intellect. They
are just what our study of the planet's conditions have led
us to expect.

The existence of vegetation on Mars depends upon them
and conversely it is evident that the vegetation, for whose
production they were made, is a necessity to their makers.
It would be natural to suppose that on a planet capable only
of seasonal change due to water from either pole, each pole
would nourish its own hemisphere. That this is not so, is
another proof of artificial causes. For the vegetation caused
by Southern water spreads far into the opposite hemisphere —
defying all the laws of dynamics and symmetry.

Of the ochreous regions of the planet nothing has been said.
There is little to say, in fact, as they are as changeless as the
Sahara. In these regions only the parts near the poles show
any change and this is of a doubtful nature. The conclusion
seems inevitable that they are deserts. Their extent is most
telling — for they indicate that the planet has advanced far in
its course towards death and are evidence of that scarcity of
water which is the sign of advancing age in planets.

On the earth the same process of desiccation is going on.
There are two belts of desert. The most marked is the
northern one. Wherever there is land this desertism shows.
The Sahara, Arabia, Persia, Northern India and the Chinese
desert in the Old World and the deserts of Mexico and the
western part of the United States form links in this chain.
Historical and geological evidence points to the fact that the
belt is ever widening.

On Mars things have gone much further. Indeed water
can only reach the more genial parts of the planet by means
of the gigantic canal system which we are led to conclude
has been made there in self-defence by intelligence.

On earth the cry of humanity is for bread and the great
areas under wheat are perhaps the only changes which man

THE PLANET MARS 219

has brought into existence upon the earth's surface which are
big enough to be visible to instruments of the same order as
ours from a distance such as that at which Mars is situated.
On Mars, as on our earth, presumably the principal necessity
is water and it is the means employed there to bring water
into operation that has proved to us the existence of the
intelligence which wants it.

Like friends in need the two planets may become acquainted
through their necessities.

The canali are there and it must be admitted that they
have been made. It is therefore of interest to inquire what
are the difficulties which have been overcome. In like work on
earth, the chief difficulty is the mountainous nature of the
surface, which renders world-wide canalisation almost incon-
ceivable.

The first thing that strikes the observer of Mars is the
flatness of the surface. No mountainous markings have ever
been seen and yet if there were any they should be visible
on the terminator at sunrise or sunset by the shadow they
would cast. A hill 2,000 feet high would be quite visibly
indicated in this way. We are therefore warranted in saying
that there are none as big as this. Irregularities have
indeed been noticed on the terminator but they are only
explicable as high clouds or in some cases effects of con-
trast and irradiation due to differences of colouring of the
surface. Incidentally the flatness of the planet's surface,
which so clearly makes artificial canals easy of construction,
renders untenable one of the many theories which have
attempted to explain them as natural phenomena — volcanic
cracks in fact akin to those which radiate from many of the
larger craters on the moon.

On Mars there are no such craters and yet on the moon
the craters are more conspicuous than the cracks — except at the
time of the full — when the lighting is more favourable to
the one than the other. Besides all this the lunar cracks are
not straight and the canals of Mars are. Now there is every
reason to suppose that the moon and Mars are made of some-
what similar materials.

If both have cracked, there is no obvious reason why one
should crack crookedly and the other straightly. But whatever
we think of the method by which these two globes (which

220 SCIENCE PROGRESS

are not widely different in size) came into existence, it is
clear from Darwin's Tidal Theory that the moon is a frag-
ment broken away from Mother Earth, whereas Mars is an
independent planet.

It is very probable that the moon owes its volcanic features
to its terrestrial origin. Mars shows none of these rugged
characteristics. If the planet had ever possessed mountains,
these should be there still — for if we assume the green areas
at present containing vegetation to be the beds of departed
oceans, it is clear that like the moon Mars probably never
possessed water enough to wash the mountains away.

Lowell has calculated that if the particles of which Mars
is composed had fallen together under gravity the generated
heat of mass would probably be less than that of molten
iron — a temperature too low to cause much volcanic action.
The case is further emphasised by the fact that if the planet
grew gradually, it would be radiating heat and cooling layer
by layer as it grew.

Another suggestion will illustrate the quandary in which
those are placed who attempt to explain the obviously artificial
canali by other means. It has been suggested that the
canals might be in the nature of scars left by meteorites
grazing the surface. Apart from the fact that meteors would
require special training to produce any such effect, the
moon again helps, for it is open to the attack of more
meteorites than Mars, being nearer the sun, about which they
all revolve : yet no such canalisation is visible on her surface.
With the single exception of the valley of the Alps, no lunar
feature suggests this origin — and further if the valley of the
Alps be due to this course, its appearance shows that the effect
is quite different from any Martian marking, for it is at one
end an ill-defined scratch and in the middle a deep furrow.

To return to the canal builders. They have had no
mountains to contend with. Further, the force of gravity,
which limits work on earth, is less potent on Mars, being only
about 40 per cent, what it is on earth. The same muscular
effort would accomplish two and a half times as much work
in a day against it. But though we may feel sure of the
existence of intellect on Mars, we know nothing and need not
trouble much about its physical embodiment. It is quite evident
that the physical difficulties have been overcome.

THE PLANET MARS 221

One of them is directly deducible and throws an interesting
light on the nature of the water channels. Assuming that the
Martian atmosphere exerts a pressure of 2J inches of mercury
upon the surface — and it can scarcely be greater than this —
Lowell has shown that water could boil at a temperature of
111° F. As the solar energy falling on Mars is certainly not
much less than that which heats the rocks of the Sahara to at
least 130° F., it is clear that evaporation is much more rapid
there than here ; and consequently water travelling in an open
channel would evaporate long before it reached the tropics of
the planet, a journey which we know occupies several weeks.
It is therefore probable that the water is carried in something
akin to pipes and this is rendered the more plausible by the
fact that the water does not flow naturally but is driven, a
conclusion to which the shape of the planet has led us.

No apology is made for this last speculation. It is, I think,
directly justified by the observations and this one example
serves to illustrate the amount of detail which is possible in
constructing a picture of the happenings on the planet. Changes
speaking eloquently of activity are to be found among the
double canals, for they are not always double. The doubling
is seasonal in its nature but not entirely so, for there are canals
which sometimes double at the appropriate season and some-
times do not. That when they are not double their alter ego
is lying fallow is strongly suggested.

Instances of this kind might be greatly multiplied but space
does not permit.

There is yet another class of surface marking to be dealt
with — namely, the white spots which are seen in the equatorial
regions. They are intensely brilliant, often glistening but they
seem not to be snow, for they are often most conspicuous in the
height of the Martian summer ; and it has been noticed above
that they are not glaciated mountain tops. It seems natural
to surmise that they may be beds of salt left by the evaporated
seas. Their close association with the green areas strongly
suggests this explanation. As yet observational data are too
scanty to afford a firm base for conjecture but their increase
of brightness under a high sun forcibly suggests a mineral
origin. Further it may be remarked that vegetation would not
invade them but would probably be near them at the bottom
of the old marine depressions. A like instance on earth occurs

222 SCIENCE PROGRESS

in the Egyptian oasis of the Fayum, where the intensely salt
waters of the Birket el Kerum are within a few yards of some
of the most fertile land on earth.

To sum up :

Recent investigation of Mars has revealed to us a world of
great beauty but filled with signs of age, for it has evidently
reached that apocalyptic period when there is no more sea.
We have found reason to believe in the existence of a highly
developed and intelligent race making a last stand against the
increasing deserts of its world. The canals are evidences of
tremendous and united efforts to eke out the decreasing water
supply to the last drop. In this struggle we see, in some
sense, a forecast of what the earth also must come to in the
fullness of time.

We set out to learn about another planet. In return we
learn much of our own and incidentally our eyes are opened
to the demonstration of a truth long held by instinct, that we
are not alone in the cosmos — that other worlds beyond the
earth are no longer the dreams of fantastic poetry but firmly
established facts of observational science. We see how the
law of evolution which has shaped us to fit our surroundings
has fitted other creatures in another world to cope with
their special needs.

The falling apple led Newton to the law of gravity on the
moon. In the same way the appearance of sprouting vegetation
has led us step by step to recognise the law of evolution on
Mars — a world where, as on earth but with difTerences, winter
and summer, frost and snow, seedtime and harvest-time con-
tinue so long as there is water to support them.

No doubt the differences between Mars and the earth may
have led the thinkers on the former planet to be sure that no
intelligent being could exist on the earth owing to the reeking
wet and perennial clouds which enwrap it. But probably by
this time they too have abandoned the puerile and absurd idea
that they inhabit the only w^orld where intelligent life is possible.
It is well at least for us to realise not merely Man's place in
the universe but that of Mars also.

THEORIES AND PROBLEMS OF CANCER

PART III

By CHARLES WALKER, D.Sc, M.R.C.S., L.R.C.P.
Director of Research Department, Glasgow Royal Cancer Hospital

Having considered prevailing views of the nature of cancer and
the experimental work carried out in connexion with them, it
is now possible to draw general conclusions. The most pro-
bable explanation of the behaviour of the cells of which
malignant grow^ths consist is that owing to the operation of
some stimulus these are no longer subject to the co-ordinating
influence which, under normal conditions, regulates the relations
between the different groups of cells forming the body ; the
result is that the cancer cells live parasitically upon the organism.

Experimental work shows that the only way in which cancer
can be transferred from individual to individual is by transplant-
ing living cancer cells but to be successful the transplantation
must be effected in animals of the same species ; it is most easy
in the case of animals of the same race or breed and is more
difficult in proportion to the distance of relationship even within
the same species.

The parasitic theory — the theory that the disease is due to
a specific micro-organism — appears to be incompatible with
many of the well-known facts connected with cancer; though
many micro-organisms have been found in malignant growths,
it is evident that none of those described up to the present time
is found in all cancers and not in any other condition.

It is now necessary to deal with the present state of know-
ledge as to definite causes of cancer. To put the case briefly,
cancer is known to follow upon prolonged and more or less
continuous irritation and inflammation. It appears that in
cases in which the irritation and consequent inflammation is
slight, it must be continued during years before cancer develops.
Chimney sweeps' cancer appears to be due to the creases in
the skin being filled habitually with carbon ; minute particles
of carbon make their way between and even into the cells
and cause a certain amount of cell proliferation, which, in
15 223

224 SCIENCE PROGRESS

time, results in cancer. Persons who work with X-ray
apparatus have in some cases developed cancer in parts of
the body which have been continuously irritated and inflamed
for years by the action of the rays. The chronic irlflammation
accompanying syphilis is regarded by many, probably with
reason, as often resulting in cancer.

There is overwhelming evidence that cancer is commonly
incident to several different occupations and habits in all of
which chronic inflammation of some part of the body is involved,
cancer occurring in the part affected.

That cancer should follow upon prolonged inflammation is
compatible with the view that the cells have passed out of
somatic co-ordination. Apparently all the somatic or body
cells are destined to disintegrate within a limited space of
time. In some groups of cells — those forming the skin for
instance — the multiplication goes on actively throughout the
life of the organism ; in other groups, multiplication either
does not take place or is rare in the adult. Chronic inflam-
mation causes the groups of cells affected to multiply more than
they would under normal conditions. It seems probable that
the powers of normal proliferation of any given group of cells
included in the body are limited and that when a certain number
of cell generations have been produced the offspring tend to
escape from somatic co-ordination as a stage on the way towards
fertilisation. Having passed out of somatic co-ordination, the
cells possess novel properties and, as the experimental work
already described shows, are able to grow and multiply in a
suitable environment just like the cells of grafts or cuttings
of plants. The suitable environment is the body of the animal
in which they arose or a body similar to it; and they live
in it as separate individuals in a parasitic manner.

In every case in which a generally accepted cause of the
disease is apparent the cancer is external, that is upon or
near the surface of the body. It is quite likely that chronic
inflammation is the cause of internal cancer also and various
suggestions have been made on these lines. Chronic alcoholism
resulting in inflammation and the production of scar tissue in
the liver might well condition cancer, as also might chronic
inflammation of the Hning of the stomach. Primary cancer
of the liver is very rare, however. Cancer of the stomach is
common in men. Ulceration of the stomach is commonest

THEORIES AND PROBLEMS OF CANCER 225

in young women but the ulcers occur usually away from the
openings into and out of the stomach, while in men ulceration
usually occurs near the opening at which the food leaves the
stomach. Ulcers in the latter position are probably more
subject to continual irritation, which may account for cancer
of the stomach being common in men though it is rare in young
women. It is possible that diet, in the broad sense, may have
some connexion in these cases with the occurrence of cancer
but it is going much too far to suggest, as has been done,^ that
cancer is due to food and drink taken at a high temperature
and to the free use of wine, beer, spirits, flesh, coffee, tea and
tobacco. We may, I think, dismiss most of these from among
common causes of cancer. All the generally accepted causes
of external cancer involve irritation which is more or less
continuous and considerable in degree ; all are probably suf-
ficient to give rise to some local lesion and to keep up and
increase this lesion when it has once been established. Food
and drink if hot enough to produce such a result could
hardly be pleasant to take and we have no evidence to show
that numbers of people habitually take their food and drink
at a temperature which is unpleasant to themselves ; even if
they did so, the irritation would last at most but a few minutes
at a time at intervals of several hours, even supposing that
all food at every meal were taken at a very high temperature ;
the commonest site of cancer of the stomach would not be
reached until after the food had cooled. It is difficult to see
how meat can act in such a manner as to produce inflammation
similar in degree and nature to that produced by the various
irritants which are accepted as causes of external cancer.
Much the same may be said with regard to the other articles
of diet mentioned. Diet may be among the causes of cancer
but we have not sufficient evidence at present to say that it is.
Trustworthy statistics are available only in the case of some
of the most civilised countries and even then are insufficient and
unsatisfactory in many respects. If it were possible to compare
the death rate from cancer in populations which did and did
not use alcohol, meat and other articles of diet, by means of
equally trustworthy statistics, it would be reasonable to form
a definite opinion upon these points; but reports of missionaries
and medical officers serving abroad as to the frequency of cancer
^ Rollo Russell, Preventable C<r?;z^<?r (Longmans, London, 191 2).

226 SCIENCE PROGRESS

cannot be used for purposes of comparison with statistics dealing
with countries in which the whole population and causes of
death are registered. As far as we know, there is no community
of men existing under any kind of conditions in which cancer
does not occur and those races in which cancer is said to be
least common are generally those about which we know least.
Cancer is apparently as common or nearly as common among
mice as among men. Mice are the only animals which have
been kept in vast numbers in laboratories under careful obser-
vation for the purpose of cancer research.

Recently it has been suggested by Lazarus-Barlow that
there is a connexion between radium and cancer.^ He says :
** Radium appears to be found somewhat more frequently and
in larger though still minute quantity in carcinomatous than
in non-carcinomatous tissue ; but the point is not yet certain,
since in three instances in which carcinomatous and non-car-
cinomatous tissues were obtained from the same body and in
which radium was found, it was present in larger quantity in
the non-carcinomatous tissue."

A more suggestive set of figures are those given by this same
observer 2 in connexion with the occurrence of gallstones in
cancerous and non-cancerous cases. During the years 1900-4
inclusive, autopsies were made upon 1,448 individuals above
the age of 35 years : of these 699 were cancerous, 749 non-
malignant ; among the 749 non-malignant cases, gallstones were
found in 37, that is 4*94 per cent. The cases of cancer are
divided into those suffering from primary cancer of the gall-
bladder and those suffering from cancer in other parts of the
body. Amongst the 693 cases of cancer elsewhere than in
the gall-bladder, gallstones were found in 59, that is in 8*51
per cent. ; but gallstones were found in all the 6 cases of
primary cancer of the gall-bladder. The latter proportion may,
however, be too high, as Colwell,^ dealing with a period of 50
years, states that gallstones were discovered in only 27 out
of 31 cases of primary malignant disease of the gall-bladder
and bile passages at the Middlesex Hospital, that is to say
that gallstones were found in 87*1 per cent, of cases of primary
cancer of the gall-bladder. Lazarus-Barlow gives the following
figures as to the amount of radium, in the cases dealt with by

^ Arch. Middlesex Hosp. nth Report, Cancer Research Lab. 1912.
' Op. cit. 2 Arch. Middlesex Hosp. 4th Cancer Report, 1905.

THEORIES AND PROBLEMS OF CANCER 227

him, estimated per gramme of gallstone by the ether extraction
method and also by the incineration method :

Canes.

Frequency of

gall-stones

per cent.

Amount of radium per gramme
of gall-stone.

Ether extraction
method.

Incineration
method.

Non-malignant ....
Carcinoma primary at sites other

than gall-bladder .
Primary carcinoma of gall-bladder

4*94

8-51
100 or 87*1

I2'7X io~^°mgr.

47-9 »

3i4'3

OX io~'°mgr.

2-1

468 „

Granting the accuracy of the observations, there seems to
be no doubt as to the correlation between cancer and gallstones,
more particularly primary cancer of the gall-bladder. Also there
does not appear to be any doubt that in the gallstones occurring
in cases of cancer, again more particularly in cases of primary
cancer of the gall-bladder, a larger quantity of radium was pre-
sent in the malignant than in the non-malignant cases. But it
is difficult at present to see what the real significance of this
may be. Lazarus-Barlow suggests that radium is found more
frequently and in larger quantities in cancerous than in non-
cancerous tissues but does not show whether more radium is
present in the tissues generally of a cancerous than of a non-
cancerous subject. Is then the radium in the gallstones and
the frequency of the occurrence of gallstones in cases of cancer
secondary to the cancerous condition ; or is the presence of
radium the possible cause of the cancer? Neither supposition
involves the belief that gallstones in themselves or the presence
in them of radium are causes of cancer. Lazarus-Barlow claims
that the nucleus of a gallstone may collect radium ; it may be
that if an excess of radium in the tissues of the organism be
connected with cancer, this excess must exist for a long period
and is accentuated in the gallstones. These, however, are
speculations into which Lazarus-Barlow himself has not entered.
We know that in many cases cancer follow^s upon prolonged
irritation and that radium acts as an irritant but in the present
state of knowledge it is hardly safe to form a definite opinion
upon the matter.

Experimental Work bearing upon a Cure

We may dismiss the various advertised cancer cures without
any detailed comment : there is no evidence in favour of any

228 SCIENCE PROGRESS

of them which will bear scientific investigation. What I have
said with regard to diet as a possible cause of cancer applies
even more forcibly to diet as a cure. Diet 7nay be among the
causes of cancer but when once a group of cells has become
malignant, it is quite obvious that no change of diet can destroy
them. The cancer cells derive their nourishment from the cells
forming the body of the organism in which they exist. The
cancer cells have been shown experimentally to possess a
vitality at least as great as and in some respects greater than
that of the somatic cells, so any change of diet must affect the
cells through which the nourishment of the cancer cells passes
before it affects the cancer cells. There is nothing that suggests
that any particular form of diet could act upon the somatic
cells in such a manner as would cause them to produce any-
thing which would act in a selective manner upon the cancer
cells and cause them to die out without affecting any of the
other cells which form the body. Everything we know which
bears upon this point suggests that such an effect could not
be produced in such a manner. However, in spite of the
extraordinary improbability that diet could affect the growth
of cancer to any material extent, I made some experiments upon
mice suffering from cancer in order to make sure of this point.
Some were given a mixed diet of bread, water, milk and meat ;
others were kept upon a diet of rice and water only. According
to certain claims that have been made from time to time, meat
is one of the principal articles of diet which is to be avoided
in cases of cancer. The tumours in all these mice grew at
about the same rate. The great difference between the two
sets w^as that the mice fed on a mixed diet thrived whilst
those on a rice diet did not.

Radium and X-rays have been much used in cases of cancer
and in some cases have been successful ; there is, however,
no evidence to show that these exert any specific action upon
the cancer cells. The effect in both cases probably is to kill
the cells which are exposed to the treatment, whether they
be malignant cells or not. The form of malignant growth in
which such treatment has been most successful is rodent ulcer.
But rodent ulcer is successfully treated by purely mechanical
means such as scraping, though more scarring is thus pro-
duced. There is therefore nothing in the effect produced in
these cases which suggests selective action nor is there in

THEORIES AND PROBLEMS OF CANCER 229

the cases of small superficial cancers which are cured in the
same way. At the present time the only reasonable chance
of producing a cure is that afforded by the total removal of all
the cancerous cells. This can frequently be done successfully
in superficial cancers which are recognised early ; it is not
commonly possible in cases of internal cancer, which are gener-
ally not recognised until the cancerous cells have multiplied
and migrated to an extent which makes their total extirpation
an extraordinarily difficult if not an impossible achievement.
In connexion with reports of cures it must be remembered
that very occasionally a case of cancer recovers without treat-
ment and that a certain diagnosis is often impossible without
a microscopic examination of a portion of the growth. Even
when such an examination is possible the diagnosis is some-
times doubtful, as the chronic inflammatory condition seems to
merge almost insensibly into the malignant. Reported cures,
therefore, which are based entirely upon clinical evidence, are
to be received with considerable doubt, if indeed they be re-
ceived at all. Isolated recoveries following a certain line of
treatment must be regarded in the same way : serious con-
sideration can only be given if a number of recoveries follow
regularly upon a given treatment.

A great deal of experimental work has been done with
animals in the hope of discovering a means of dealing with
cancer in the human subject ; practically all of this work has
been carried out with cancers artificially produced by inocula-
tions similar to those described in the last article.

Certain kinds of resistance to the grafting of tumours usually
transmissible in mice have been demonstrated by a great many
observers. In 1889 Wehr^ recorded the spontaneous cure of some
of his transplanted tumours. Subsequently Gaylord and Clowes ^
reported recovery to have occurred from 20 per cent, of the Jensen
mouse tumours ; many others have reported similar occurrences.
Gaylord and Clowes also found that the mice which recovered
were immune to a further inoculation and that 10 out of 30
were resistant to a third and more virulent tumour. Ehrlich ^
was successful in immunising mice against malignant tumours
by inoculating with a non-malignant tumour. Others have

^ Arch. /. klin. Chir. Berlin, 1889, xxxix. 226.
^ Johns Hopkins Hosp. Bull. Baltimore, 1905.
' Arb. a. d. k, Inst, etc, 1906, viii. 481.

230 SCIENCE PROGRESS

failed to produce immunity in such a manner. Schone,^
Borrel and Bridre,^ Bashford^ and Tyzzer^ have shown that
inoculation with various normal tissue cells produces a variable
immunity to the subsequent inoculation of usually transmissible
tumours. Flexner and Jobling^ showed that from the tenth to
the thirteenth day after the inoculation of heated tumour cells,
the animals were more susceptible to inoculations with the
living cells of the same tumour, suggesting by this experiment
that a form of anaphylaxis was produced. Gaylord, Clowes and
Baeslack^ injected mice suffering from tumours with the serum
of immune mice. At first their results were highly satisfactory
and many of the tumours disappeared, whilst normal serum
produced no result. Subsequent experiments, however, were
not satisfactory. Beebe and Crile,^ having drawn off a large
proportion of the blood of some dogs bearing well-established
transplanted sarcomata, transfused large quantities of blood
from dogs that had resisted inoculation or recovered naturally ;
nine of the affected dogs recovered rapidly and completely. In
1908 I injected the serum of rats that had been subjected to re-
peated inoculations with the living cells of a rapidly growing
mouse-carcinoma into mice bearing well-established tumours of
the same strain ; the result was that in 80 per cent, of the mice
the tumours were completely absorbed. The serum of rats into
which the living cells of the mouse's testis had been injected
produced similar but less satisfactory results.^ Subsequent
experiments with these sera showed that they were highly
destructive to these particular tumour cells.^ These experiments
were confirmed up to a point by Bashford,^^ who showed that
while the mouse-tumour cells lived in untreated rats for some
time, they were rapidly destroyed in rats that had been
previously inoculated with the living cells of mouse tumour.
Ehrlich ^^ has explained the immunity to inoculation by means

^ MUnchen med. Wohnschr., 1907, liv. 2517.
' Bull, de rinst. Pasteur^ 1907, v. 605.

* Scientific Rep. Imper. Can. Res. Fund^ 1907.

* Journ. Med. Res. Boston, 1907, xvii. 155.

' Proc. Soc. Exper. Med. and Biol. 1907, iv. 156.

^ Med. News Philadel. Ixxxvi. 91, 1905.

' Proc. Soc. Exper. Med. and Biol., 1907, iv. 118.

8 Lancet, Sept. 12, 1908. ^ Ibid. April 9, 1910.

'^^ Proc. Roy. Soc, B, vol. Ixxxii. 19 10.

" Op. cit. 1905 ; Apolant, op. cit. 1906.

THEORIES AND PROBLEMS OF CANCER 231

of his hypothesis of " Atrepsia." In his opinion the immunity
is connected with the nutrition available for the tumour cells.
He found that when transferred for a short time to a rat and
then back to a mouse, the tumour cells continued to multiply
again with their original vigour; a continuance of this zigzag
method of transplantation did not render the tumour less trans-
missible in the mouse, though it would die out if left too long in
the rat. He assumed two kinds of atrepic immunity, both
dependent upon what he calls " X-stoff," which suppHes the
tumour cells with nutriment, either directly or indirectly. In
the one, in cases in which the tumour is in an animal similar to
that in which it originated, the " X-stoff" facilitates absorption ;
in the other, in cases in which the tumour is transferred to an
animal of another species, the part of the '* X-stoff" which is itself
carried over with the graft forms the nutriment of the tumour
cells and is soon consumed. The ** X-stoff," on this assumption,
must obviously be produced continuously when the tumour
cells, transferred to a similar animal, continue to grow in-
definitely but is used up gradually in cases of immunity. I have
kept a strain of tumour, given to me in 1906 by Prof Ehrlich,
growing in mice and have produced several hundreds of pounds
weight of it, without any changes taking place excepting such as
can be accounted for as the result of experimental treatment.

It seems quite in accord with other facts that mouse tumour
should die out when inoculated into rats, as many normal
mouse tissues have been shown to behave in the same way and
the same thing happens if normal tissue of one kind of animal be
introduced into another kind. The striking fact connected with
this is, that the cells from one species of animal will sometimes
multiply for a certain time in the bodies of another species
before they are destroyed but this appears to happen only when
the species are fairly nearly related. Jobling^ has shown that
transplanted pieces of a malignant growth from a human subject
continued to grow in monkeys during a maximum period of six-
teen days but failed entirely to grow in rats and mice. The new
environment evidently supports the transferred cells during a
time proportionate to its similarity to the natural environment.
If the new environment be so nearly alike to the original that the
most resistant cells survive, the action of selection may produce

* Monographs of the Rockefeller Inst, for Medical Research^ No. i, June 1910,
p. 120.

232 SCIENCE PROGRESS

a race of cells immune to it in the manner already indicated ;
on this supposition an " X-stoff " does not appear to be necessary
to explain the various phenomena observed.

The experiments under consideration may be divided into two
distinct groups : those in which the aim is to produce immunity
to subsequent inoculations ; and those which aim at curing
already existing tumours. The results in both cases are
evidently dependent upon the production in the body of the
animal of a specific reaction against particular kinds of tissue.
This reaction is shown best by the experiments demonstrating
that after the introduction into the body of the animal of living
cells which will be eliminated but slowly similar cells introduced
soon after are eliminated much more rapidly.^

The experiments showing the possibility of producing
immunity to subsequent inoculation do not suggest a possibility
of leading to anything that may be of practical value with
regard to the prevention or cure of cancer in the human subject.
Any preventive measures of this nature would have to be
applied to every human being for some time before the cancerous
age was reached and continued throughout life, as the immunity
is apparently only temporary. There is also another difficulty
which will be referred to later on.

The experiments in which already existing tumours have
been caused to disappear are on a different footing and at first
sight seem far more promising. Jobling^ has shown that the
cells of a malignant tumour from the human subject will live
and multiply during nearly as long a period in the body of a
monkey (Macacus) as do the cells of a mouse tumour in the rat,
a result which favours the view that the monkey's serum might be
rendered destructive in a selective manner to the cells of a
malignant growth in man in just the same way that rat serum
has been rendered destructive to the tumour cells of the mouse.
But it must be remembered that the experiments referred to
were performed upon transplanted tumours and it has been
shown that these tumours differ in many respects from primary
carcinomata.

Selection apparently has produced a race of cells in these
transplanted tumours which possess many more of the char-
acteristics of independent organisms than do primary cancers
and thus the tissues of the host have been caused to react
^ Walker, op. cit. 1908 and 1910 ; Bashford, op. cit. 1910. * Op. cit. 19 10.

THEORIES AND PROBLEMS OF CANCER 233

against them in a way in which they do not react against the
cells of a primary growth. It therefore seems probable that a
constituent of the serum destructive to these tumour cells would
be more easily produced and would be active to a greater
extent and perhaps in a different way from a serum active
toward the cells of a primary growth. Indeed, it seems likely
that it may be impossible to produce a serum active towards the
cells of a primary growth upon these principles. Moreover, it
seems very probable that the destructive capacity would only be
exhibited towards the particular race of tumour cells which had
produced the reaction, in which case it would be practically
impossible to apply the method to the human subject, a large
quantity of serum being necessary and a sufficient reaction
produced only after a number of inoculations of considerable
quantities of living cells into the secondary host. The same
criticisms apply to the results obtained in producing immunity
to subsequent inoculation with the transmissible tumours.

The experiments in which the rats were inoculated with the
cells of the mouse's testis, which afforded striking but less
satisfactory results than those in which the serum produced by
inoculating with the mouse tumour was used, avoid the sug-
gested difficulty with regard to the serum being active against
the cells of one particular tumour only. But this method is
inapplicable to man on account of the impossibility of obtaining
sufficient material from the human subject. Only living cells
are effective. In addition there is the insuperable difficulty of
obtaining the living cells of the human testis in sufficient
quantities and often enough. The cells of the testis do not die
immediately upon the death of the individual but practically all
are dead in about three hours.

Many attempts have been made to find chemical compounds
capable of exerting a selective action upon cancer cells— that is
to say, which will kill the cancer cells without materially in-
juring the rest of the body. Wassermann ^ has recorded the
effects produced by a preparation of selenium and eosin upon
cancerous tumours produced by inoculation in mice. The
preparation was introduced by intravenous injection directly
into the circulation and after a number of injections produced a
liquefaction of the tumours in the mice which survived the

^ " Beitrage zum Problem : Geschwiilste von der Blutbahn aus therapeutisch
zu beeinflussen," Deut, in. Woch. December 191 1.

234 SCIENCE PROGRESS

treatment. The treatment is stated not to have succeeded in
the cases in which the tumour was larger than a cherry and the
mortahty produced by it appears to have been about 70 per cent.
The theory of the treatment is based upon Ehrlich's statement
that tumour cells possess a much greater avidity for oxygen and
nourishment than do the cells of normal tissue.

Quite recently Neuberg, Caspari and Lohe have published
the results of somewhat similar experiments.^ These observers
attribute the selective action of the preparations they have used
to the presence in the tumour cells of certain enzymes which are
absent from the cells of the body tissues. They bring forward
in support of this view the rapid growth and the rapid degenera-
tion of the tumour cells. Rapid growth is a characteristic
feature of some strains of experimentally produced tumours in
mice and rats and as shown in the last number of Science
Progress may probably be produced in all by a process of
selection. Degeneration and death of the cells in the centre of
these tumours is probably a characteristic of all strains but it is
not of all kinds of malignant growths in the human subject,
though it is perhaps more common in some kinds than is usually
recognised. With regard to this point Ewing says^ that he
does not consider it has yet been proved that well-developed
tumour tissue undergoes autolysis more rapidly than an
equivalent normal tissue. As evidence to the contrary he
quotes the experiments by himself and Beebe ^ in which dog's
blood was passed by artificial circulation through test tubes
containing fragments of sarcoma from a dog. The fragments
remained alive during from eight to ten days ; fragments of
dog's liver and kidneys became necrotic and autolysed in forty-
eight hours under the same conditions.

Perhaps the most suggestive evidence with regard to the
existence of a specific ferment in tumour cells is provided by
the work of Beebe.^ From the purified nucleoproteids of cancer,
he prepared a serum which agglutinated the emulsified cells of
cancer and precipitated the nucleoproteids derived from this
source but acted very feebly and only when used in large pro-

' " Weiteres iiber Heilversuch an Geschwulstranken Tieren mittels tumoraffiner
Substanzen," Berl. klin. Woch. July 22, 191 2.

^ "Cancer Problems," Arch, of Internal Medicine^ vol. i. 1908.
^ Beebe and Ewing, Brit. Med. Journ. 1906, ii. 1559.
^ Quoted by Ewing in " Cancer Problems," op. ctt.

THEORIES AND PROBLEMS OF CANCER 235

portion on cells and nucleoproteids from normal tissue. These
experiments however, as far as I know, have not been repeated.

Neuberg and his collaborators apparently assume that the
peculiar characters of rapid growth and degeneration which
they attribute to the cells of malignant growths are due to the
presence in them of these abnormal enzymes ; their object has
been to produce some substance which will act only or to a
greater extent in the presence of the enzymes in question and
increase the degeneration to such an extent that all the tumour
cells will be destroyed. They have worked with compounds
of cobalt, silver, copper, platinum, gold and tin, obtaining the
best results with compounds of the first two. While claiming
that definite effects were produced upon the tumour cells by
hypodermic injections, they say that they did not effect actual
cures until they used intravenous injections.

In the case of these experiments, as in Wassermann's, the
tissues are described as undergoing degeneration, softening,
liquefaction and final disappearance. The useful dose of the
compounds is nearly as great as that which kills the animal
outright and must be injected into the circulation directly.
This latter point adds to the difficulty of the experiments, as
it is exceedingly difficult to inject a fluid into a vein in a mouse ;
moreover, as the operation has to be repeated frequently and
the difficulty is increased rather than diminished upon each
occasion, the experiment in each individual case may have
to be abandoned before completion. It is also to be regretted
that none of these investigators has given any definite informa-
tion either as to the constitution or as to the manner of
preparing the " compounds " they used, so that their experi-
ments cannot be confirmed nor is any kind of check upon them
possible ; nor can the work be carried on by other investigators
along varying lines from the new standpoint, as it probably
would be if the results they have recorded were confirmed.

The immediate effect of the "compounds" injected by
Neuberg and his collaborators is described as a contraction of
the blood-vessels of the body and a dilatation of those of the
tumour. This dilatation is so great that extravasations of blood
visible to the naked eye are numerous. In Wassermann's ex-
periments the injection of the selenium-eosin preparation was
described as turning the mouse pink all over immediately but
the pink coloration disappeared rapidly from the body and

236 SCIENCE PROGRESS

was concentrated in the tumour. These facts seem to suggest
that the action of the preparations under consideration may
possibly be to some extent mechanical and not due to any
selective action upon the tumour cells. We have seen that
there is no nerve supply to malignant growths. The dilatation
and contraction of blood-vessels is controlled by the nerves
and hence it is possible that when these poisonous substances
are introduced into the circulation the immediate result is the
contraction of the blood-vessels generally, excepting of course
those in the tumours, through their action upon the nervous
system. The blood-vessels and spaces in the tumour, owing
to the increased pressure produced by the contraction of the
vessels of the body, are forcibly dilated. The poisonous com-
pounds having been introduced directly into the blood stream
would thus act far more upon the tumour cells than upon
those in the body generally and as they are described as being
very unstable they would break down before the blood-vessels
of the body dilated. The fact that the doses that are effective
in producing the destruction of the tumour are so very nearly
those that result in the death of the animal is very suggestive
in view of this explanation. So is also the fact that though
it is reported that in the very few cases of spontaneous tumours
in animals upon which these preparations have been tried,
effusions of blood and softening have occurred more often than
not, no cures have been obtained. The animals have always
died before the tumour was destroyed.

As was explained in a previous article, the tumours pro-
duced in mice and rats by grafting become surrounded by a
capsule of inflammatory tissue before cell proliferation begins
among the tumour cells, so that these tumours are cut off from
the body of the animal in which they grow in a manner not
found to happen in a spontaneous primary cancer. This would
very probably, to a certain extent, confine the poisonous com-
pound to the tumour after it had been concentrated there
through the contraction of the blood-vessels of the body gener-
ally and the concomitant dilatation of the blood-vessels and
blood spaces of the tumour. That the blood-vessels of spon-
taneous tumours should become dilated in the same way is
what might be expected but in such cases there is lacking
that isolation of the tumour cells which forms so useful a
factor in success when the curative and lethal doses are very

THEORIES AND PROBLEMS OF CANCER 237

nearly balanced, as they are in the experiments under review.
What was said in the last article with regard to these graftable
mouse cancers having acquired some of the characters of
separate individuals not possessed by primary malignant
growths through the process of selection necessarily involved
in their propagation must also be borne in mind.

Neuberg and his collaborators attribute the failure of sub-
cutaneous injections to the other tissues having broken down
the unstable compounds they used before the tumour cells
were reached. The explanation with regard to the contraction
of the blood-vessels that I have just suggested seems to be as
satisfactory upon this point, as whilst contraction of the vessels
would probably be produced, though more slowly, by the
subcutaneous injections, the fluid would not be in the actual
blood stream from the moment of its introduction into the
system and so would not have a chance of being concentrated
immediately in the tumour.

Wassermann describes amorphous particles of selenium and
Neuberg and his collaborators amorphous particles of the
metals which were used as being discernible under the micro-
scope in the tumour cells. As the " compounds " they used
are described as very unstable they would probably break down
in any part of the body but being in greater quantity in the
tumour when first introduced more breaking down should
take place there than anywhere else.

A definite claim has been made recently to the successful
treatment of cancer by intravenous injections of colloidal
selenium.^ As far as I know, only one or two cases have
been treated in this manner, so that even a disappearance of
the tumours would mean no more than that there was no
direct evidence against the disappearance of the tumours being
connected with the injection of the selenium in the colloidal
form. I have tried colloidal selenium upon a number of mice
and rats bearing malignant tumours produced by grafting. No
effect was produced upon the tumours whether the colloid was
used alone or in conjunction with eosin. It is noteworthy that
whilst all the salts of selenium and combinations of selenium
and eosin which I have tried are very highly toxic, minute
doses killing mice or rats in a few minutes, selenium in the
colloidal form is not at all poisonous.

^ Societe Medical des Hopiteaux de Paris ^ February 14 and March i, 191 2.

238 SCIENCE PROGRESS

Conclusions

Having reviewed much of what has been done in the way
of attempts to cure cancer, the only conclusion to be arrived
at is that at the present time the only means available which
affords any reasonable chance for the patient is complete re-
moval by a surgical operation. Complete removal is generally
only possible in the very early stages and the only cases, as a
rule, in which there is a really good prospect of success are
superficial cancers which are diagnosed very early. In many
cases, however, much more may be done in the way of alleviation
and the prolongation of life under more comfortable conditions
than was formerly possible by surgical operations.

On the other hand, it should be thoroughly reahsed that
we have learned much concerning the nature of cancer during
the past ten years. Whilst none of the present lines of inquiry
seem to promise immediate success, the results already obtained
in following several of them serve to suggest the ultimate
discovery of one or more methods of curing a large number
at least, if not a great proportion, of cases of malignant disease.

It has been satisfactorily established that the only way in
which cancer can be transferred from individual to individual
is by the grafting of the living cancer cells in a suitable
position. Even when this is done, it is successful only in the
case of some particular tumours, as apparently all are not
transmissible ; and of graftings with usually transmissible
tumours only a certain proportion are successful.

It may be said therefore, with certainty, that cancer is neither
infectious nor contagious in the ordinary sense of these words
and that there is no risk of catching cancer from a cancer patient
unless in the highly improbable event of living cancer cells being
introduced into an accidental wound incurred by the surgeon
or his assistants during an operation.

THE DEATH-RATE OF EARTHQUAKES

By CHARLES DAVISON, Sc.D., F.G.S.

The destruction of Messina at the close of 1908 has made us
familiar with the immense loss of life that may be accomplished
within a few seconds by a great earthquake. The total number
of deaths is still unknown ; probably it will never be revealed but
it cannot fall far short of 100,000. Seldom has this number been
exceeded, though it has often been approached in other lands as
well as in Italy. Taking the latter country first, we may recall
the long series of earthquakes in 1783, when more than 30,000
lives were lost; and the Sicilian earthquake of 1693, when the
number rose to more than 58,000 according to Dr. Baratta and
to 93,000 according to Prof. Mercalli. Smaller but still con-
siderable figures were attained in other earthquakes, for instance,
2,313 in the Ischian earthquake of 1883, 6,240 in the Norcian
earthquake of 1703, 12,291 in the Neapolitan earthquake of 1857
and 15,000 in the Sicilian earthquake of 1169.

The Japanese records tell the same tale. In 1891, 7,273 lives
were lost during the great earthquake in the provinces of Mino
and Owari. Five years later, 27,000 persons were drowned at
Kamaishi and along the neighbouring coast by the sea-wave
following an earthquake. To the Japanese, this wave was more
costly in life than the whole war with China in 1894. Again,
30,000 persons were killed by the Kamakura earthquake of 1293
and the same number in Yechigo in 1828. But even these figures
were surpassed in 1703, when the death-roll is said to have risen
to 200,000, half of this number being in the district of Awa alone.
In other countries, to give only a few more instances, we find
that 50,000 were destroyed by the Lisbon earthquake of 1755,
40,000 in northern Persia in the same year, 60,000 in Cilicia in
1268, 100,000 in Pekin in 1731, 180,000 in India in 893, more than
80 per cent, of this number having been buried in the ruins of one
city, whilst 300,000 are said to have perished in the Indian earth-
quake of 1737. " As yet," wrote Humboldt in 1844, " there is no
manifestation of force known to us, including even the murderous
16 239

240 SCIENCE PROGRESS

inventions of our own race, by which a greater number of
people have been killed in the short space of a few minutes."

On the other hand, in some great earthquakes the loss of
life has been surprisingly small. At Charleston in 1886, only
twenty-seven were killed, though fifty-six more died afterwards
from cold and exposure. At San Francisco, twenty years later,
the earthquake was directly responsible for no more than 390
deaths; and the total number of lives lost at Kingston in 1907
is estimated at about 1,000.

In considering such statistics it is evident that the figures
furnish no real test of the destructive violence of an earth-
quake. Some of the greatest shocks for many years past are
those which have occurred in the sparsely inhabited regions
of central Asia. The disastrous character of the Messina earth-
quake was chiefly due to the presence of a large and ill-built
town near to its origin. The heavy death-rolls of earthquakes
in India and China are to be attributed to the dense population
of those countries. Consequently, instead of the death-roll, a
more accurate measure would be the death-rate or the pro-
portion deaths bear to the whole population. For instance, in
Charleston during the earthquake of 1886 and more recently
in San Francisco, the death-rate was considerably less than
I per cent. In the Ischian earthquake of 1881, it amounted to
2^ per cent, at Casamicciola. In the Andalusian earthquake
of 1884, the highest death-rate at any place was 9 per cent, and
in the Riviera earthquake of 1887 not more than 14 per cent.
Though attracting great attention from their occurrence in well-
known districts, these earthquakes belong to a group characterised
by a comparatively small loss of life.

In contrast with the above figures, many of the Italian earth-
quakes are characterised by an unusually high death-rate. In
the Ischian earthquake of 1883, the death-rate at Casamicciola
was 41 per cent. ; in the Sicilian earthquake of 1693, it rose to
50 per cent, at Ragusa and to 6^ per cent, at Catania; in the
Neapolitan earthquake of 1857, it was 50 per cent, at Saponara
and 71 per cent, at Montemurro ; in the first great Calabrian
earthquake of 1783, 59 per cent, at Bagnara and jy per cent, at
Terranova ; whilst in the Norcian earthquake of 1703, the
highest death-rate at any place was 81 per cent, at Avendita.
The corresponding figures for the Messina earthquake are not
yet accurately known; at Canitello the death-rate was 44

THE DEATH-RATE OF EARTHQUAKES 241

per cent, but in the lower part of Messina itself and Reggio
di Calabria the rates may well exceed any of those given above.

Among the conditions which determine whether the death-
rate due to an earthquake shall be high or low may be mentioned
the time of occurrence, the suddenness with which the shock
begins and the rapid succession of strong after-shocks. These
are all properties of the earthquake and beyond our control.
There are also others of no less consequence, which are governed
more or less by our own actions, such as the proximity of towns
to well-known seismic centres, the nature of the site selected —
whether on sloping or level ground, on a rocky or loose founda-
tion—and the nature of the buildings. I propose to consider
these conditions in detail, as it is only from a knowledge of such
conditions that we can expect to discover means of mitigating,
when we cannot altogether prevent, the disastrous effects of
great earthquakes.

The time of occurrence is one of the most important factors.
An earthquake which occurs at night is nearly always more
disastrous than one in the daytime. Not only are people
gathered indoors but, if asleep, they are unable to take
advantage of the brief warning that is sometimes given by
the preliminary sound or tremor. Among earthquakes with
a high death-rate may be mentioned the Messina earthquake
of 1908, which occurred at about 5.20 a.m., the Ischian earth-
quake of 1883 at 9.25 p.m., the Neapolitan earthquake of 1857
at 10.15 p.m., the Kangra and Dharmsala earthquake of 1905
shortly after 6 a.m. and the great Indian earthquake of 1737
at night. Among those with a low death-rate are the Assam
earthquake of 1897, which occurred at 5.15 p.m., the Ischian
earthquake of 1881 at 1.5 p.m., the Kingston earthquake of
1907 at 3.30 p.m., the Port Royal earthquake of 1692 and the
first Calabrian earthquake of 1783 which happened shortly
before and after noon. But even the daytime loses its advantage
when, owing to religious celebrations, many people are con-
gregated within doors. The Riviera earthquake of 1887, for
instance, took place on an Ash Wednesday morning at twenty
minutes past six. After a night spent in amusement, many
persons had lain down and were sleeping heavily; others had
risen early and were gathered together in churches. The
Caraccas earthquake of 18 12 occurred at 4.7 p.m. on Ascension
Day. " The procession of the day," says Humboldt, " had not

242 SCIENCE PROGRESS

yet begun to pass through the streets but the crowd was so
great within the churches that nearly three or four thousand
persons were crushed by the falling of the roofs."

The suddenness of onset of the shock is a second factor of
considerable importance. Almost invariably the shock is pre-
ceded by a deep rumbling sound accompanied by a faint tremor
which may last five or more seconds before the vibrations attain
a destructive strength ; the same sound precedes both weak
and strong shocks and at first affords no certain warning of
the disaster but in earthquake countries it is one that is always
heeded. ** If it had happened in the middle of the night," wrote
Darwin of the Concepcion earthquake of 1835, "the greater
number of the inhabitants . . . must have perished, instead of
less than a hundred ; as it was, the invariable practice of running
out of doors at the first trembling of the ground alone saved
them. In Concepcion each house or row of houses stood by itself,
a heap or line of ruins." To the same cause may be attributed
the comparatively small loss of life in such earthquakes as those
which destroyed Cumana in 1797 and Port Royal in 1692.

In many earthquakes, however, the warning given by the
earthquake sound is too brief to be of service. This was
the case, even with those who were awake, at Dharmsala
in 1905 and at Messina in 1908. In the Ischian earthquake
of 1883 sound and preliminary tremor were both absent within
the central district. So suddenly and with such intense violence
did the shock begin that survivors at Casamicciola found them-
selves beneath the ruins of their houses before they realised
that an earthquake had occurred.

The death-rate of an earthquake is often increased by the
rapid succession of strong after-shocks. In the central district
every great earthquake is followed by almost incessant tremors
among which stronger shocks are interspersed. The Riviera
earthquake of 1887 occurred at about 6.20 a.m. At 6.29 there
followed a second shock and at 8.51 a third of intermediate
strength. To these two shocks are attributed one-quarter of
the total amount of damage and also the small number of
wounded, many of those who lay buried in the ruins having
been killed by the subsequent overthrow of the shattered walls.
In this earthquake the number of persons wounded was only
72 per cent, of the number killed. The Neapolitan earthquake
of 1857 was succeeded after about an hour by another strong

THE DEATH-RATE OF EARTHQUAKES 243

shock and the number of wounded was only 14 per cent, of
the number killed. In the Andalusian earthquake of 1884 and
the Japanese earthquake of 1891, on the contrary, the number
of wounded was more than double that of the number killed.

Of the remaining conditions, the harmful effects of which
we can to a certain extent restrain, the most important is the
proximity of towns to well-known seismic centres. The unstable
regions of the earth have been determined on a large scale
by M. de Montessus de Ballore and Prof. J. Milne, the map
constructed by the former being based on all recorded shocks
and that of the latter on world-shaking earthquakes. The
dangerous zones of certain countries, such as Italy and Japan,
have also been carefully delineated. In Europe the large towns
are far removed as a rule from earthquake centres. Those
which have suffered most are Lisbon, Catania and Messina, in
addition to a number of small towns in the south-east of Spain,
in Ischia, Calabria, the Balkan peninsula, the Ionian Islands,
Crete and several islands in the Grecian archipelago. Other
countries are less fortunate. Off the west coast of South
America and especially from the tenth to the fortieth degree
of south latitude, the steeply shelving ocean-bed marks the site
of one of the most unstable portions of the globe. Nearly all
the larger towns on the coast — Callao, Lima, Arequipa, Iquique,
Copiapo, Coquimbo, Valparaiso, Concepcion and Valdivia —
have been destroyed at some time or other, most of them more
than once, several having suffered from the rush of the great
sea-waves as well as from the force of the shock. The shores
of the Pacific Ocean, indeed, are specially subject to seismic
disturbances throughout a great part of their extent. Of the
675 " world-shaking " earthquakes which have been studied
by Prof Milne during the eleven years 1899-1909, three-fifths
have originated in the five zones which border that ocean,
the greater number being submarine. Five other zones are
entirely oceanic but these and a sixth zone containing the West
Indian Islands include only one-fifth of the total number of
earthquakes, the remaining fifth originating in a great terrestrial
zone extending from Italy eastwards to the Himalayas.

The most important feature of these seismic zones from our
present point of view is that earthquakes shake particular
portions time after time, although they occur in other places
in the intervals. As on the west coast of South America, the

244 SCIENCE PROGRESS

same towns are repeatedly destroyed, either entirely or in
part. For instance, Reggio, Monteleone and Catanzaro have
been rebuilt several times ; also Antioch, Tripolis and Damascus
in Asia Minor ; Erivan, Tabriz and Meshed in Persia ; and
Cumana and Caraccas in Venezuela. Volcanic earthquakes,
however, such as those of Ischia, may be concentrated for
successive centuries within the same small areas.

To a very considerable extent, the destructiveness of a
shock depends on the nature of the ground, so that within the
area of a single town there may be many variations in the
amount of damage to the buildings. In the city of Tokyo,
there are two well-defined districts, one consisting of hard high
ground, the other of low soft ground, the intensity of the
earthquakes being much less on the former than on the latter.
In towns that are only partially destroyed, the distribution of
the damaged buildings illustrates the same law. At Charleston
in 1886, the injury to houses was greatest on low-lying ** made "
land ; and this was also the case twenty years later at San
Francisco and in 1908 in Sicily and Calabria. Even in the
non-destructive shocks of this country, local variations of
intensity depending on the nature of the ground are frequently
observed. Shocks are much less strongly felt in houses built
on the hard rocky ground of Malvern and Stirling than in
those situated on the plains at the hill-foot.

Important as the nature of the site undoubtedly is in an
earthquake country, the magnitude of the death-rate is affected
still more by the structure of the buildings. The defects which
are chiefly responsible for high death-rates could hardly be
illustrated more clearly than in many of the older cities of
Italy. In the Basilicata, the mediaeval towns and villages are
almost universally perched upon the summits and steep slopes
of hills and their spurs, the houses being built at the very
edge of precipices. The streets are narrow, sometimes only
five feet, not often more than fifteen feet, in width. The houses
are generally built of limestone and brick but the limestone is
seldom well-bedded and therefore cannot be raised in long flat
blocks. The mortar is poor from containing too much lime and
from the lack of a proper quality of sharp sand. Thus, even
the best walls, according to Mallet, consisted of " a coarse,
short-bedded, ill-laid rubble masonry, with great thickness of
mortar joints, very thick walls, without any attention to

THE DEATH-RATE OF EARTHQUAKES 245

thorough bonding whatever." The floors are heavy and the
roofs, which are hardly less massive, are covered with large
tiles secured, except at the ridges, by their own weight
alone.

Houses of this description were ill adapted to withstand
the rough shock of the Neapolitan earthquake of 1857. At
Saponara, where the death-rate amounted to 50 per cent, the
buildings, when shaken down, fell against and upon those
beneath them and thus increased the common ruin. When
Mallet, who investigated the earthquake with such skill,
reached the place, ** the summit and far down the slope all
round presented nothing but a rounded knoll — shadowless and
pale — of chalky stone and rubbish, without line or trace of street
remaining ; it might have seemed an abandoned stone quarry or
the rubbish of a chalk pit, save that its rounded and monotonous
outline was broken here and there by beams and blackened
timbers that, rooted in the rubbish, stood thrown up in wild
confusion against the sky-line like the gaunt arms of despair."

Though no doubt more firmly built, the houses of Messina
suffered greatly from their heavy stone floors and staircases.
" In some cases," writes a visitor to the city soon after the
earthquake, ** the whole centre of the house had fallen leaving
the empty case of the outer walls enclosing a heap of broken
rubbish. In others and these are more numerous, the main
walls fell outwards, leaving the core of the house exposed like
an open doll's house, with the floors intact. . . . But in most
cases the house had fallen entirely, leaving a shapeless mound."
Thus, almost universally, the floors and roof seem to have parted
from the walls, owing to the weight of the former and the
slightness of their connection with the walls. The streets were
so narrow, the greatest width not exceeding twelve yards, that
they were in many cases completely blocked by fallen masonry,
which rose to an average height of more than five yards ; so
that, even if people could have escaped from their houses, it
would only have been to die in the streets. In the Riviera,
again, the houses in some of the coast-towns are built of rounded
stones collected from the beach, bound by the poorest kind of
cement ; they are lofty in proportion to the foundation and
thickness of the walls and arches in the walls are common even
in the upper storeys and often abut against the walls without
any lateral support. In the private houses injured by the

246 SCIENCE PROGRESS

earthquake of 1887, it is estimated that more than 90 per cent,
of the dead bodies were found crushed beneath fallen arches.

Of the six conditions which govern the high death-rate of
earthquakes, we are chiefly concerned only with the last three.
We cannot in any way limit the time of occurrence of a great
earthquake nor can we prevent the rapid succession of strong
after-shocks. Fore-shocks when they occur and the preliminary
sound may provide early notice of the coming shock but, unfortun-
ately, they are characteristic of slight as well as of disastrous
earthquakes. Weak shocks may come alone and we cannot dis-
tinguish between such isolated tremors and the forerunners of a
catastrophe. Moreover, when they assume the latter aspect, the
interval that may elapse before the great shock comes is of
uncertain duration. It may be a few minutes or hours, it may
amount to days or weeks. The preliminary sound and tremor
differ in this respect. Both precede the shock by a few seconds ;
and except in large and lofty buildings a warning of even five
seconds may be sufficient. Pheasants and other birds are often
terrified by the early tremors of an earthquake ; but when kept
by the late Prof. Sekiya for the purpose they failed to serve as
satisfactory heralds. The deep earthquake-sound, again, is not
equally audible to all persons. It is so low that to some, who
are not in the least deaf to ordinary sounds, it is quite inaudible.
There is also reason to believe that races differ in their capacity
for hearing the earthquake-sound ; and it is possible that a
general deafness towards the earthquake-sound may result in
raising the death-rate. When this defect exists, it might perhaps
be remedied by the use of sensitive flames adjusted so as to
respond to the deepest sounds alone.

All attempts to issue earthquake-warnings have failed and
have deserved to fail, for the supposed forecasts have been
based on insufficient data. Without some knowledge of the
origin of earthquakes and of the movements which precede the
final catastrophe, such attempts were of necessity futile. But,
with the recent growth of our knowledge, it seems by no means
impossible that we may in time be able to provide rough fore-
casts of a coming shock. To be of service, such forecasts should
give the approximate time at which an earthquake may be ex-
pected and the region in which its severity will be chiefly
concentrated. To furnish both elements is at present beyond
our powers. But to give one only may be useful and of the

THE DEATH-RATE OF EARTHQUAKES 247

two elements it is of greater value to know the area that will be
mainly affected than the time when a shock will take place.
The time alone would be of little service, for sixty " world-
shaking " earthquakes occur on an average every year, so that
as a rule few weeks will pass by without the visit of an earth-
quake somewhere or other upon the globe.

What is required for the solution of this problem is more
definite knowledge than we at present possess of the operations
which precede the occurrence of a great earthquake. On this
subject, some light has been thrown by recent disasters. A
displacement of the earth's crust along a fracture more than two
hundred miles in length, like that which caused the Californian
earthquake of 1906, cannot be the work of an instant of time.
For many years, the strain must have been increasing until it
reached the point when rupture and sliding could no longer be
averted. By the erection of pillars along a line at right angles
to such a fracture and by careful observation subsequently of
their relative positions, the first deformations may be detected
and measured. Or, again, before a great movement can take
place, small obstacles to motion must be cleared away along the
surface of the fracture and every such removal must give rise
to a tremor more or less pronounced. The outlining of the
course of a fault by the centres of numerous slight shocks, as
happened before the Japanese earthquake of 1891, should reveal
the preparation that is being made for a great movement — a
movement which may, as in that case, take place within the
next two years.

For the present, it would seem advisable to direct attention to
those conditions which are partially within our control, so as to
lessen, if we cannot avert, the destructiveness of an earthquake
shock. In a few cases, there can be little doubt that the
Government should interfere and prohibit the rebuilding of a
town that has been frequently ruined. In permitting the re-
erection of Casamicciola after the Ischian earthquake of 1883,
the Italian Government incurred a grave responsibility, not-
withstanding all the precautions taken. Here, there is no
reason to suspect any migration of the seismic focus. Time
after time, the same small district has been the seat of renewed
shocks of increasing violence. The central volcano of Epomeo
may have been extinct during the historical period but outbursts
have occurred along radial fissures. The violent shocks which

248 SCIENCE PROGRESS

preceded the last eruption in 1302 were similar to those
which have occurred recently in the island and there is reason
to fear that the Ischian earthquakes of 1796, 1828, 1881 and 1883
are merely symptoms of underground activity which sooner or
later may result in forming a new lateral cone on the present
site of Casamicciola.

Of most towns, especially of those which lie along the coast,
the partial removal is all that can be considered. A harbour
like that of San Francisco, which has no rival for hundreds of
miles and which lies close to the shortest route from Panama to
Yokohama and Shanghai, cannot be transferred. Nor can those
along the western coast of South America, subject though they
be to the inrush of seismic sea-waves. The utmost that can be
attempted in such cases is to shift the residential quarters
farther inland, just as, after the earthquake of 1692, Port Royal
was maintained as a naval station while the town of Kingston
arose in place of that which sank beneath the sea. The removal
of a town, however, is a remedy so desperate that it will seldom
be entertained ; and as the recent experience of Kingston has
shown it may not be altogether effectual. We must, therefore,
as a rule, avail ourselves of the alternatives at our disposal and
endeavour to mitigate the effects of earthquakes by the choice of
suitable sites and modes of building.

As regards situation, it is clear that, in the absence of a
protecting sea-wall, low-lying land along shores that are liable
to be swept by seismic sea-waves should be avoided. All
buildings, especially lofty ones, should be erected on a rocky
foundation, never if otherwise possible on sand or gravel. Soft
friable beds resting on a slope of rock or forming the edge of a
cliff or steep river-bank are perhaps the worst of all foundations.
Not only is the shock more strongly felt on them than on the
adjoining rock but the beds as a whole may slide downwards or
forwards and be extensively fissured by the action of the shock.

In all cases, however, even in those in which an inferior site
cannot be avoided, the loss of life may be diminished by erecting
only houses that are adapted to withstand the strain of an
earthquake shock. To erect a building that is comparatively
earthquake-proof and at the same time fire-proof is merely a
question of expense. The walls must be very strong at the base
and as light towards the top as may be consistent with strength ;
they must be firmly braced together by iron rods from front to

THE DEATH-RATE OF EARTHQUAKES 249

back, from end to end and from foundation to roof, so that the
whole may vibrate practically as one mass. Public buildings
should be of this type ; but in the case of ordinary dwelling-
houses the expense of such methods would be prohibitive.
Fortunately, approximate safety in such cases may be secured
by other and less costly means. During his long and fruitful
residence in Japan, Prof. Milne determined the principal con-
ditions which should govern construction and the following
description of an ideal house is founded on the conclusions at
which he then arrived.

The houses are built in wide streets, with deep foundations
and are not as a rule more than two storeys high. The walls
are at once light and strong. They consist of a framework of
w^ooden beams, firmly braced together, the intervening spaces
being filled with light stone or hollow bricks. There are no
gable-ends and the corners of the houses are specially
strengthened. Nor are there any arches, except perhaps in the
cellars and then they are high, curve into the abutments and are
protected above by a lintel of wood or iron. The openings for
doors and windows in successive storeys are not placed in a
vertical line and are at some distance from the corners of the
house. The roofs are light and low-pitched and all tiles, if used,
are fixed by nails. The floor-beams in alternate storeys are at
right angles and penetrate nearly the whole thickness of the
walls. Chimneys, if forming part of the house, are short and
thick and without heavy ornamental copings ; if in the centre,
they penetrate the roof without touching it. Balconies are
altogether absent and the staircases, if connected with the main
walls, are light. No portions of the house are allowed to vibrate
separately from the rest and with different periods. The one
object throughout is to produce a light, strong and fairly elastic
house, which, in the day of trial, shall vibrate as a whole and,
while bending before the shock, shall yet endure.

How greatly such methods may contribute to the saving
of life has been admirably illustrated by Prof. Omori in his
recent report on the Messina earthquake. On October 28,
1 891, a violent earthquake devastated the provinces of Mino and
Owari in Japan. The shock was more than four times as strong
as the Messina earthquake and was felt over an area ten times
as great but the total number of victims was only 7,273. Not far
from the origin of the earthquake lies the city of Nagoya with a

250 SCIENCE PROGRESS

population in 1891 of 165,000. Here, though the intensity of
the shock was slightly greater than at Messina, only 190 persons
lost their lives instead of about 75,000 at the latter city. Thus,
taking the difference of population into account, the number of
persons killed in Messina was about 430 times as great as in
Nagoya ; or as Prof. Omori forcibly remarks, about 998 out
of every thousand persons killed in Messina fell victims to the
faulty construction of their houses.

THE. CHEMICAL ACTION OF LIGHT ON
ORGANIC COMPOUNDS

By W. a. DAVIS, B.Sc.

Without question the most important chemical change induced
by light is the transformation of carbon dioxide into sugars
and starch under the influence of the chlorophyll of green
leaves, involving as it does the absorption of much energy.
In most cases studied, light brings about a change involving
a loss of energy ; in the minor number of cases in which energy
is undoubtedly absorbed and its amount can be approximately
calculated, the absorption, expressed in thermal units, is ex-
ceedingly small : thus in the polymerisation of anthracene to
dianthracene, which has been studied by Luther and Weigert,^
the amount of energy absorbed, though greater than in most
other cases, is yet only about forty calories per gramme of
anthracene transformed. In the formation in the leaf of each
gramme of starch from carbon dioxide and water, an amount
of energy represented by 4,230 calories must be supplied ; this
is more than 100 times as great as that absorbed in any
other known photochemical change. The rapidity also of the
synthetic action effected in plant foliage is far greater than
that observed in the majority of other photochemical changes,
especially in comparison with those in which energy is ab-
sorbed. The assimilation of carbon in the plant is, in fact,
an unique phenomenon. The object aimed at in the present
article is to give an account of the experimental work which
has been carried out during the past few years, especially by
Professors Ciamician and Silber at Bologna, to obtain direct
information as to the general character of the changes brought
about in organic compounds by the action of light.^

' Zeit. Phys. Chem. 1905, 53, 416.

' Three monographs on the chemical action of light have been published
recently : (i) Die Chemische Wirkungen des Ltchts^ by Fritz Weigert (Ahrens'
Samtnlung Chemischer und Chemisch-technischer Vortrdge^ 191 1, vol. 17, pp.
183-296) ; this deals with the question mainly from the physical side. (2) Les
Actions chimiques de la Lumi^re^ an address delivered by Prof. Ciamician before
the Chem. Society of Paris {Bull. Soc. Ckim.^ 1908), in which his experiments up
to that date are discussed. (3) Pkotochefnie, by Joh. Plotnikow (Knapp, Halle-
a-Sa., 1910), a general treatise.

251

252 SCIENCE PROGRESS

The changes effected by light in carbon compounds may
be classified as follows :

(i) Oxidation and reduction (reciprocal),

(2) Autoxidation,

(3) Polymerisation,

(4) Condensation and synthesis,

(5) Isomeric and stereoisomeric change,

(6) Ring scission and hydrolysis,

(7) Two or more of these changes simultaneously.

All the transformations dealt with in this article occur only
under the influence of light : that this is true has been ascer-
tained in every case by a control experiment in which the
materials that were found to interact in light were left in
darkness during a period equal to that of the exposure to
the sun's rays without producing any positive result.

I. Oxidation and Reduction

The largest proportion of the changes studied are in this
class ; reciprocal oxidation and reduction of two substances,
one of which is oxidised at the expense of the other, appears,
in fact, to be the type of photochemical action most easily
brought about. In many cases the change effected consists
simply in the transference of one or more hydrogen atoms from
the one compound to the other. Thus in the first case studied
by Ciamician and Silber, in 1886,^ when a solution of quinone
in aqueous alcohol was exposed to light in sealed glass vessels
the yellow-coloured quinone disappeared, giving place to colour-
less quinol, an equivalent of aldehyde being produced at the same
time ; some quinhydrone was also formed by the interaction of
quinol and quinone.

QHXO2) + CH3 . CH, . OH -> CeHXOH)^ + CH3 . CHO

This work was not carried further at the time but in 1901 ^ it
was found that under similar conditions quinone was capable
of oxidising isopropylic alcohol to acetone, being itself, as before,
reduced to quinol. Tertiary butylic alcohol (trimethylcarbinol)
is also oxidised by quinone, quinol and quinhydrone being
formed as secondary products but the nature of the substances
into which the alcohol is converted is uncertain ; the action

^ Gazzetta Chijnica Italiana^ 1886, 16, 11 1.
2 Atti R. Accad. Lincei^ 1 901, 10, i. 92.

THE CHEMICAL ACTION OF LIGHT 253

takes place much more slowly than in the case of either of
the other alcohols.

Perhaps the most interesting of the oxidations effected by
quinone under the influence of light is that of the polyhydric
alcohols, such as glycerol, erythrol, ^-mannitol and dulcitol,
each of which loses two atoms of hydrogen and is converted
into the corresponding aldehyde.

These changes are striking in so far as previously they
were known to occur only under the influence of relatively
powerful oxidising agents, such as nitric acid or an alkaline
hypobromite. A particularly interesting case is the oxidation
of glucose by quinone in sunlight to glucosone, as follows :
CH^(OH) . CH(OH) . CH(OH) . CH(OH) . CH(OH) . CHO ->

Glucose.

CH-XOH) . [CH(OH)]3 . CO . CHO

Glucosone.

Other quinones behave with alcohols in the same way as
benzoquinone ; this is especially true of thymoquinone, which
in ordinary alcoholic solution gives thymoquinol and aldehyde.
The action of phenanthraquinone or isatin on alcohol takes
place, however, very slowly.

Formic acid is fairly rapidly oxidised by quinone in sun-
light to carbon dioxide, quinol being the other product.^ The
fatty acids (acetic and propionic acid) are only very slowly
affected and the nature of the products (other than quin-
hydrone) could not be ascertained. Hydroxy-acids (lactic,
malic and tartaric) are oxidised by quinone to carbon dioxide ;
the corresponding keto-acid could not be isolated.

But quinones are not the only compounds which are capable
of being reduced by alcohols under the influence of sunlight :
ketones and aldehydes are similarly affected, albeit, as a rule,
much more slowly and incompletely. In the case of the
parafhnoid ketones, the action is of a complex character (see
Section VII.) but is relatively simple in the case of benzenoid
ketones : thus, benzophenone (4 grm.), in presence of alcohol
(20 cc), is transformed in eight days almost completely into
benzopinacone : ^

CgHs CeHs CgHs

2 CO +C.H60 = HO.C C.OH + C^H.O

I I I

CgHs CfiHj CgHj

Benzopinacone.

^ Atti R. Accad. Lincei, 1901, 10, i. 92. ^ Ber. 1900, 33, 291 1.

254 SCIENCE PROGRESS

Acetophenone, in a similar manner, gives acetopinacone :

CeHj CgHs

I I

HO — G- C — OH

I I

CHj CH3

In these cases, the simple reduction to secondary alcohol is
masked by the tendency of two molecules of the latter tc
undergo oxidation to form a pinacone. Benzopinacone is alsc
largely formed when benzophenone is exposed to sunlight in
certain hydrocarbon solvents, such as toluene, ethylbenzene
and the xylenes but other changes also occur in such cases
(see Section VII.).^

Benzoin in alcoholic solution is reduced to hydrobenzoin
(its stereo-isomeride /5ohydrobenzoin being formed at the same
time) but a quantity of resin is also produced.^ The main
action, however, is that expressed by the equation :

QHs. CO . CH(OH) . C,H5 + QHeO = C,U, CH(OH). CH(OH). C,H, + C,H,0

When the diketone benzil, CeHg . CO . CO . CeHg is exposed
to light ^ in alcoholic or ethereal solution during a few hours, it
is partly reduced to benzoin, which combines with unchanged
benzil to form benzilbenzotn,

zCQHs . CO . CO . CU,) CsHs . CH(OH) . CO . CeHj,

a loose molecular compound which is resolved into its components
when melted or when boiled with benzene or alcohol. If the
action of light be prolonged, the benzilbenzoin which has
separated redissolves and a quantity of resin is formed together
with benzoin, benzil, benzoic acid and ethylic benzoate.^

The action of light on benzaldehyde is particularly striking
on account of the variety of products. The simplest product,^
obtained in alcoholic solution, is a mixture of the two
stereoisomeric hydrobenzoins formed by reduction, thus :

2CsH5 . CHO + C AO = C,H, . CH(OH) . CH(OH) . CeH^ + C^H.O

Hydrobenzoin,

A complex, polymerised form, (Ci4Hi402)4, of hydrobenzoin is
also produced. The polymerisation of benzaldehyde alone under

^ AUt i?. Accad. Lincei, 1910, 19, i. 645. * Ibid. 1901, 10, i. 92.

» Klinger, Ber. 1886, 19, 1862.

* Ciamician and Silber, A tti Lincei, 1903, 12, i. 235 ; Ber. 1903, 36, 1575.
^ Atti R. Accad. Lincei^ 1901, 10, i. 92.

THE CHEMICAL ACTION OF LIGHT 255

the influence of light is dealt with later (p. 266) ; the remarkable
self-reduction which takes place in presence of traces of iodine
is considered on p. 261.

Anisaldehyde behaves in alcoholic solution in the same
manner as benzaldehyde, giving rise to hydranisoin but the
action is much slower. The behaviour of vanillin/ on the other
hand, is quite special in its character, oxidation occurring when a
solution of the aldehyde in alcohol, ether or acetone is exposed
to light ; the product is dehydrovanillin, which can also be
obtained by the oxidation of vanillin with weak oxidising agents,
thus :
2CHO.C6H3(OMe)OH + 0 = H.,0 + CHO.C6H3(OH)(OMe).C«H3(OH)(OMe).CHO

Puxeddu ^ has recently shown that the photochemical

oxidation of vanillin does not depend on the presence of

atmospheric oxygen but takes place equally well in sealed tubes

when it is dissolved in benzene or toluene ; it is probably a

case of self-reduction in which vanillyl alcohol is also formed.

The action is always particularly rapid, dehydrovanillin beginning

to separate from the solution after ten minutes' insolation. It is

interesting that the ethylic and methylic ethers of vanillin

behave in an entirely different way. Thus when a solution of

methylvanillin or of ethylvanillin in alcohol, benzene, toluene or

acetic acid is exposed in sunlight, the corresponding vanillic

acid is formed :

OMe OMe

CHO COOH

Puxeddu gives a rather complex explanation of these changes
which involves the assumption that a dibenzylidene derivative
[in the case of the methylic ether, this has the structure
(OMe)2 . CfiHa . CH : CH . CgHg (OMe)2] is formed as intermediate
product ; but no trace of such a compound could be isolated.
It seems more probable that what really occurs is self-oxidation
involving the formation of the vanillic acid and the corresponding
vanillyl alcohol such as actually has been shown by Mascarelli to
take place in the case of benzaldehyde in presence of traces
of iodine (see p. 261).

When benzaldehyde dissolved in benzylic alcohol is exposed

* Atti R. Accad. Lincei, 1901, 10, i. 92. ' Ibid. 191 1, 20, ii- 718.

256 SCIENCE PROGRESS

to sunlight, hydrobenzoin and isohydrobenzoin are formed by
simple addition,^ thus :

C.H^CHO + CsH^CH^. OH = C«H,CH(OH) . CH(OH) . C,U,

but the action in this direction is far from quantitative and some
resin is formed.

Benzophenone and benzylic alcohol interact in a rather more
complex way^; the main product is benzopinacone, formed as
follows :

2C6H5 . CO . QH5+ QHsCH, . OH = (C,H5),C(0H) . C(OH)(C,H5), + C.H^ . CHO;

the benzaldehyde formed resinifies in part and is in part con-
verted into hydrobenzoins as above. In addition to these
changes, however, benzylic alcohol and benzophenone also give
rise to triphenylglycol :

^«^^>CO + QH5 . CH, . OH = ^«^J>C(OH) . CH <g«^=

Triphenylglycol.

As formic acid is so readily oxidised to carbon dioxide by
quinone in sunlight, it might be anticipated that benzophenone
would effect a similar change ; such, however, is not the case.

The action of ethylic alcohol on alloxan is very striking,^
alloxantin separating in quantity after a few weeks, the yield
after several months amounting to 35 per cent. Aldehyde is
also formed, the interaction being similar to that of quinone
and alcohol in which quinhydrone is formed ; the analogy is
strengthened by the fact that, according to Piloty and Finckh,^
alloxantin has not the structure that is generally assigned to it,

co<NH ; 88> c(OH) . c(OH) <co ; ^^> CO

but bears to alloxan the relation that quinhydrone bears to
quinone. The change may therefore be written :

2CO<^2 ; c§> CO + CH^O = C,H,0 +

CO^'^^'^^^aOU) O c-^C(OH).NHv^Q

Alloxantin.

In many of the changes above considered in which alcohol
plays a part, moist ether can be substituted for the alcohol with

* Atti R. Accad. TJncei^ 1903, 12, i. 235 ; Ber. 1903,86, 1575 and 1953.

* Annalen^ 1904, 333, 22.

THE CHEMICAL ACTION OF LIGHT 257

advantage. In fact as regards the action of light, the system
(C2H5)20 4- H2O seems to be equivalent to 2C2H5OH but it is more
effective and rapid in its action. A striking illustration of this fact
is found in the case of phenanthraquinone, v^hich is only slowly
affected by alcohol but is decolourised almost instantly when dis-
solved in moist ether on exposure to sunlight ; phenanthraquinol
is formed.^ Isatin also, which is hardly changed by alcohol,
gives hydrisatin in ethereal solution.^ In these cases acetalde-
hyde is formed, just as from alcohol itself. The action of dry
ether, however, is entirely different in character and gives rise to
synthetic changes, no aldehyde being formed (see Section VII.).
One of the most complex cases of reciprocal oxidation and
reduction is that which occurs when certain benzenoid nitro-
compounds are dissolved in a paraffinoid alcohol and the solutions
are exposed to sunlight during several months. The case of
nitrobenzene has been studied by Ciamician and Silber ' with great
care ; from their results they conclude that the photochemical
reduction takes place in successive simple stages as follows :

C«H,NO, -> [QH5NO] ^ C,H5NH(0H) -> QH5NH,

OH.CsH,.NH,

Aniline can always be isolated as well as />-aminophenol,
which, as shown by Bamberger, is undoubtedly a product of the
transformation of phenylhydroxylamine ; no doubt therefore the
latter is formed in the first instance. The fate of the alcohol
is uncertain ; the corresponding aldehyde can never be isolated.
Instead of this, quinaldine(a-methylquinoline) can be separated
in the case of ethylic alcohol, 2-methyl-3-ethylquinoHne in the
case of propylic alcohol and 2-isopropyl-3-isobutylquinoline in
that of isoamylic alcohol. These bases are formed in larger
quantity than aniline itself, which is the other principal con-
stituent of the basic fraction of the product ; and they are the
condensation products obtained by heating aniline and concen-
trated chlorhydric acid with acetaldehyde, propionaldehyde and
isovaleraldehyde, respectively, during several hours, in Doebner
and Miller's well-known method of synthesising quinoline bases.
The formation of the bases is without doubt, therefore, to be

1 Klinger, Ber. 1886, 19, 1862.

' Ciamician and Silber, Atti R. Accad. Lincet, 1901, 10, i. 92.
' Ber. 1886, 19, 2899 ; Attt /?. Accad. Ltncei, 1902, 11, i. 277, 1905 ; 14, ii. 375 ;
^^r. 1905, 38, 3813.

258 SCIENCE PROGRESS

attributed to the primary formation of the aldehyde in each
case. In the case of all three alcohols, the reduction of the
nitrobenzene is very incomplete, not exceeding lo per cent. ; it is
remarkable that methylic alcohol is almost without action on
nitrobenzene in sunlight. The majority of nitro-compounds too
are far less affected than nitrobenzene by the alcohols named
above. Of the three nitrotoluenes only the meta-compound
gives notable quantities of toluidine, whilst o- and m-dinitro-
benzene, the three nitranilines, picric acid and nitronaphthalene
remain unchanged.

In the foregoing case of the reduction of nitrobenzene by
alcohol, neither nitroso-benzene nor products formed from it,
such as azoxybenzene or hydroxyazobenzene, could be isolated ;
but when benzaldehyde and nitrobenzene are exposed to light
products are obtained which afford proof that in this case the
complete series of reduction stages :

CgHsNO^ -> QHsNO -» CeH5NH(OH) ^ QH5NH2

is passed through ; ^ the benzaldehyde is oxidised to benzoic
acid. The products actually isolated were benzanilide; benzoyl-
phenylhydroxylamine, C6H5N(OH). CO.CeHg ; dibenzoylphenyl-
hydroxylamine, C6H5N(OBz)CO. CaHs, and their products of
transformation : benzoyl-(?-aminophenol, OH . CqW^ . NHBz, and
dibenzoyl-/>-aminophenol, OBz. CgHs. NHBz, as well as azoxy-
benzene and o-hydroxyazobenzene.

Ciamician and Silber consider that the principal product,
dibenzoylphenylhydroxylamine, is formed directly from nitro-
benzene and benzaldehyde, thus :

a. QH5NO, + QHsCHO = QH.NO <^q ^ ^^

b. QH5NO<^^ (. jj^ + C«H,CHO = H,0 + C«HaN<^Q^2 'j^^^*

To understand the formation of the other compounds, it must
be admitted that nitrosobenzene is formed initially, C6H6NO2 +
C6H5CHO = CeH5COOH + C6H5NO. The further action of benzal-
dehyde on nitrosobenzene gives benzoylphenylhydroxylamine :

CeHsNO -H QH5CHO ^ C^HsN <^^ ^^^^

which is in turn reduced by benzaldehyde giving benzanilide :
C6H5N <^^ c H + CsHjCHO -» CeHsCOOH + C^HsN <^q ^^^^

^ Atti, R, Accad. Lincei^ 1905, 14, i. 265 ; Ber. 1905, 38, 1176.

THE CHEMICAL ACTION OF LIGHT 259

Azoxybenzene is derived from nitrosobenzene in the manner
experimentally demonstrated by Bamberger : in this case by the
intervention of benzoylphenylhydroxylamine :

CeHjNO 4- CeHsN <^^ c H = CeH^CO . OH + C.HsNO : ^C,W

Finally it has been shown by Knipscheer^ that azoxybenzene
is transformed under the influence of light into its isomeride
o-hydroxyazobenzene :

NO:N<(^ \ N:N / ^>

^ N — / ^ r^^^^ —

(no />-hydroxyazobenzene being formed in this case).

Very few other aldehydes are as active as benzaldehyde
in reducing nitrobenzene ; anisaldehyde alone produces a
similar series of changes. Salicylic, cinnamic and vanillic
aldehydes, piperonal and furfural are without action on nitro-
benzene and the same is true of the ketones, acetone and
acetophenone. A similar series of changes, giving rise to an
even more complex set of products, has been observed in the
case of nitrobenzene and benzaldehydephenylhydrazone.^

Intramolecular Oxidation

Several remarkable instances have been discovered in which
one group in a molecule is oxidised at the expense of another
under the influence of light. One of the most striking is
afforded by o-nitrobenzaldehyde,^ which is rapidly changed on
exposure to light into o-nitrosobenzoic acid. The change may
be regarded either as a case of intramolecular rearrangement
falling under Class V. ; or as an intermolecular action in which
two molecules of the same kind take part, thus :

/NO; CHO\ /NO

CeH / + >C,H4 = 2C6H /

\CHO NOo / \C0 . OH

* Angeli's formula for azoxybenzene.

' Froc. K. Akad. Wetensch. Amsterdam^ 1902, 5, 51.
' Ciusa, Gazzeiia, 36, ii. 94.

* Atti R. Accad. Lincei.^ 1901, 10, i. 228 ; Ber. 1901, 34, 2040.

26o SCIENCE PROGRESS

There is no evidence by which the question can yet be decided.
In view, however, of the relationship of this change with the
interaction of benzaldehyde and nitrobenzene discussed above it
will be considered in this section.

The transformation of nitrobenzaldehyde differs from the
photochemical changes hitherto discussed on account of the
extreme rapidity with which it takes place : whereas the majority
of the interactions considered need several weeks or even
months for completion and in most cases are very incomplete,
the rate at which o-nitrobenzaldehyde undergoes change is more
nearly comparable with that of ordinary photographic changes.
The nitroaldehyde is converted into the nitroso-acid even when
in the solid state, the colourless crystals becoming first green
but retaining their transparency and finally white and opaque
(Bruni and Callegari ^) ; in solution the transformation of the
aldehyde takes place so rapidly that, in a few hours, the tube
containing the liquid is full of crystals of the nitroso-acid.

A solution of (^-nitrobenzaldehyde in ethylic alcohol gives at
first ethylic nitrosobenzoate : as an alcoholic solution of (?-nitroso-
benzoic acid does not esterify on exposure to light, the action
probably takes place as follows : ^

QHXcSo + 2^^^^ -> C.UXc^'yOEt ^ CeH,<co OEt + ^^^"

\OEt

Some o-nitrosobenzoic acid, however, is always formed, as in
the case of indifferent solvents. Methylic alcohol gives methylic
nitrosobenzoate but isopropylic alcohol gives only o-nitroso-
benzoic acid. The influence of structure is also strikingly shown
in the fact that meta- and para-nitrobenzaldehyde do not undergo
a similar transformation. Moreover, no such change occurs in the
case of (?-nitrocinnamic aldehyde, NO2 . C6H4 . CH : CH . CHO ;
but most other ortho-nitro-aldehydes behave like o-nitro-
benzaldehyde. o-Nitropiperonal,^ for example, gives o-nitroso-
piperonylic acid :

2 :4-Dinitrobenzaldehyde gives o-nitroso-/>-nitrobenzoic acid*

* Atti R. Accad. Lincei, 1904, 13, i. 567.

* Bamberger and Elger, Ber. 1903, 36, 3645.
' Atli R. Accad. Lincei^ 1902, 11, i. 277.

* Colin and Friedlander, Ber. 1902, 35, 1265.

THE CHEMICAL ACTION OF LIGHT 261

and o-nitrobenzylideneaniline is transformed into the anilide of
o-nitrosobenzoic acid (44 per cent, yield after eight days).

^ „ /NO2 _^ ru /NO

UH4\cH : NPh "^ '-'«"\CO . NHPh

In the same way 4-chloro- or 4-bromo-2-nitrosobenzoic acid
can be prepared by exposure to light of solutions of 4-chloro-
or 4-bromo-2-nitrobenzaldehyde in benzene,^ whilst the ethylic
salts are obtained on exposing the alcoholic solutions. />-Chloro-
o-nitrobenzylideneaniline in toluene similarly gives 4--chloro-
2-nitrosobenzanilide.^

The nitroso-acids themselves undergo further change when
exposed to light, giving a complex mixture of products similar
to that obtained by Bamberger by the action of aqueous alkalies
on nitrosobenzene.^

A very striking instance of intermolecular oxidation-reduction
is the transformation of solid benzylidene-c?-nitroacetophenone
into indigotin under the influence of sunlight : the action is as
follows : *

OCO . CH : CH . QH5 02N<^

NO2 CeHs . CH : CH . Cok^

Unh;^ = ^<.coU

+ 2C«H5.C0.0H
-CO>s^

Indigotin.

The nitro-group supplies oxygen for the formation of the benzoic
acid.

With these changes may be classed the interesting trans-
formation, under the action of light and traces of iodine, of
benzaldehyde into benzylic benzoate, recently observed by
Mascarelli and Bosinelli.^ This result, which is fundamentally

* Sachs and Kempf, Ber. 1902, 35, 2704.

* Sachs and Kempf, Ber. 1903, 36, 3299. Sachs and Sichel, Bgr. 1904, 37,
1861.

' Compare Ciamician and Silber, A^/z B. Accad. Lincei^ 1902, 11, i. 277. Thus
ethylic nitrosobenzoate gives in alcoholic solution mainly ethylic-^-nitrobenzoate,
diethylic azoxybenzenedicarboxylate, CO:,Et . CgH^ .N.N. CeH^ . COaEt, with some

O
free azoxybenzenecarboxylic acid and ethylic anthranilate, NHj . CgH^. CO^Et.

* Engler and Dorant. Ber. 1895, 28, 2497.
' Gazzetta^ 191 2, 42, 82.

262 SCIENCE PROGRESS

the same as the well-known Cannizzaro transformation brought
about by alkalies,

QHs . CHO + CeHjCHO -> QH5CH, . OH + CgHi . CO . OH

is explained by Mascarelli as involving the formation of benzoyl
iodide, CeHs . CO . I, as an intermediate product ; although this
substance is not formed from benzaldehyde and iodine under
ordinary conditions, its production under the influence of sun-
light has been actually observed.

Exactly similar changes occur in the case of />-tolualdehyde,
which gives toluylic toluate when exposed to sunlight.^

The foregoing cases of internal oxidation-reduction are of
special interest when considered in reference to the changes
which occur in the foliage leaves of plants. The recent work
of Strakosch and others would indicate that dextrose is the first
sugar formed in the leaf of the sugar beet by photosynthesis ;
if this be so, its transformation into laevulose and hence into
cane sugar, in which form the sugar is stored in the root, is
a change closely analogous with the photo-chemical trans-
formation of the o-nitrobenzaldehydes.

CH2.OH CH3.OH

[CH.OHja [CH.OH]9

I -> I

CH.OH CO

I I

CHO CH2.OH

Dextrose Laevulose

II. AUTOXIDATIONS

The part played by light in conditioning the numerous cases
of ** autoxidation " which have lately attracted so much attention,
especially from Engler^ and Manchot, has as yet been little
investigated. From the point of view of the changes occurring
in plants, more especially those brought about by the so-called
oxydases^ such knowledge is particularly desirable. The recent
statement of Kernbaum^ that he has observed the decomposi-

^ Mascarelli and Russi, Gazzetta^ 19 12, 42, 92.

' See Engler andWeissberg, Kritische Studien iiber die Autoxydations vorgdnge,
Vieweg, 1903.

' Bull, Acad. Set. Cracovie, December, 191 1, 583.

THE CHEMICAL ACTION OF LIGHT 263

tion of water-vapour by sunlight into hydrogen and hydrogen
peroxide is suggestive from this standpoint.

It is well known that aldehydes undergo oxidation in the
air, especially rapidly in light, forming peroxides and finally
the corresponding acids; benzaldehyde especially behaves in
this way. Ketones also oxidise spontaneously in the air under
the action of light; acetone, for example, gives a mixture of
acetic and formic acids : ^

CH3.C0.CH, + 3O -> CH,.CO.OH -f H.CO.OH

Unsaturated compounds, such as stilbene,^ readily undergo
autoxidation under the influence of light; in the case of stil-
bene, the action occurs even when the solid is left in a desiccator
exposed to sunlight, benzaldehyde being first formed and finally
benzoic acid, a peroxide perhaps being produced as an inter-
mediate product :

C^Hs . CH O QHs . CH . O

II + II -> I I »» 2C6H5.CHO

CsHs.CH O CfiHs.CH.O

Stilbene Peroxide Benzaldehyde

A striking example of a somewhat similar character is that
observed by the writer ^ in the case of solid 3 : 6-dibromo-/3-
naphthaquinone, which is transformed almost quantitatively
when exposed to bright light into 3 :6-dibromo-2-hydroxy-i 14-
naphthaquinone (compare p. 266) :

+ 0

Brl^yX/Br
— OH _

0
/YNOH

Brl^y^S^Br
0

The well-known transformation of chloroform into carbonyl
chloride under the action of light is a somewhat similar case :

CHCI3 + O -> COCI2 + HCl

Some striking instances have recently been observed by
Ciamician and Silber* of the oxidation of such stable hydro-

* Atti R. Accad. Lincei, 1903, 13, i. 235 ; Ber. 1903, 36, 1575.
' Atti R. Accad. Lincet, 1903, 12, ii. 528 ; Ber. 1903, 36, 4266.

' Brit. Ass. Report, " Isomeric Naphthalene Derivatives," 1902.

* Atti R. Accad. Linceiy 191 1, 30, ii. 673.

264 SCIENCE PROGRESS

carbons as toluene, the xylenes and />-cymene by oxygen and
water under the influence of sunlight. Toluene is converted
into benzoic acid (small quantities of benzaldehyde being also
formed) ; the xylenes give the corresponding toluic acids (with
traces of the corresponding phthalic acids), whilst />-cymene
gives />-cuminic acid, CsHt^ . C6H4 . COOH, together with
/-hydroxyisopropylbenzoic acid, OH . CMcg . CeHi . CO2H and
^-propenylbenzoic acid, CH2 : CMe . C6H4 . CO2H.

Formic acid is formed as well in all cases. Oxidation does not
take place in darkness. It is interesting that the nitrotoluenes
do not undergo oxidation under the same conditions.

Neuberg ^ has recently shown that uranyl salts act catalyti-
cally in accelerating the oxidation by air of numerous organic
compounds exposed to sunlight ; iron salts act similarly.^ An
especially interesting case of oxidation brought about in this
way is that of benzoic acid to salicylic acid :

CeHsCO^H -> OH.CeH, .CO2H

The autoxidation of menthone is dealt with in Section VI.

III. Polymerisation

Among the earliest cases of photochemical action studied
were those which involve the pol3^merisation of unsaturated
compounds : thus acetylene is transformed into benzene, brom-
acetylene, CH : CBr, into sy^.-tribromobenzene, propiolic acid,
CH : C. CO2H, into trimesic acid (syw.-benzenetricarboxylic acid),
anthracene into dianthracene (Fritzche, 1866), whilst acridine,
anthranol and methylanthracene also give rise to polymeric
forms. In the case of anthracene, the action is reversible and
has been studied by Luther and Weigert^ from the physical
standpoint in considerable detail.

Thymoquinone was shown by Liebermann and Ilinski^ to
polymerise rapidly to dithymoquinone and this change was
further studied by Ciamician and Silberin 1886^ ; the conversion

^ Biochem. Zeitschr. 1908, 13, 305. * Ibid. 1910, 29, 279.

3 Luther and Weigert, Zeii. physikaL Chem. 1905, 63, 416 ; Weigert, ibid. 1908,
63, 458.

< Ber. 1877, 10, 2177 ; 1885, 18, 3193.
* Gazzetta, 1886, 16, ill.

THE CHEMICAL ACTION OF LIGHT 265

takes place in the solid thymoquinone, as when this is spread

out on the walls of a large flask (by dissolving in a minimum

of ether and then evaporating the solvent) it becomes colourless

on exposure to light. The polymerisation does not take place

in solutions of the quinone. From the point of view of

structure, it is interesting to note that although thymoquinone,

O : CgHaMePr^ : O, rapidly polymerises, /-xylylquinone, which

differs from it only by containing methyl in place of isopropyl,

is not susceptible to light. The same is true of durylquinone,

dibromothymoquinone and nitrosothymoljOH.NrCsHgMePr^iO.

In 1895 Bertram and Kursten ^ observed that when dry

cinnamic acid is exposed to sunlight, it is transformed into a

dipolymeride, a-truxillic acid :

CgHj . CH . CH . COjH
2C6H5 ; CH : CH . CO,H -> ( |

QHs . CH . CH . CO2H

This change, like that of thymoquinone, does not take place
in solution, if either alcohol or ether or acetone be used as
solvent ; but when cinnamic acid is suspended in paraldehyde it
is partly converted into its polymer. Stilbene, on the other
hand, dissolved in benzene (in absence of air, so as to prevent
autoxidation) is converted into distilbene : *

2Ci^Hi3 = (Ci4Hi2)2

If coumarin dissolved in absolute alcohol be exposed to light*
hydrodicoumarin is formed :

/CH:CH /CH2.C = C .CH2\

2CaH/ I -> CeH,< I I >CeH,

\0 .CO \0 .CO CO. 0/

CO.CH-CH.O

'III
(or possibly O CH-CH CO

V \/

CfiH^ C6H4

Dibenzylideneacetone, CHPh : CH . CO . CH : CHPh, resini-
fies under the influence of light giving a dimeric form.^ The
different behaviour of the isomers safrole and isosafrole,

^ Ber. 1895, 28, 387.

' Ciamician and Silber, Ber. 1902, 35, 4128 ; Atii R, Accad. Linceiy 1903, 12,
ii. 528 ; Ber. 1903, 36, 4266.

' Atti R. Accad. Lincei^ 1909, 18, i. 216 ; Ber. 1909, 42, 1386.

266

SCIENCE PROGRESS

methyleugenol and methylisoeugenol is shown in the following
scheme :

CHj . CH : CH2

\CH,

Safrole : not affected by one year's
exposure to light.

CH : CH . CH,

CH^.CHrCH,

Methyleugenol : not changed after
18 months.

CH:CH.CH,

^CH,

Isosafrole gives some di-isosafrole

ith

with much resin.

'OMe
OMe

Methylisoeugenol gives
di-methylisoeugenol.

A striking change, allied to polymerisation but accompanied
by elimination of hydrogen bromide, is that observed by the
writer ^ in the case of 3 : 6-dibromo-/3-naphthaquinone when
exposed in certain solvents (ethylic acetate, benzene or chloro-
form) to the action of light; this substance, which in the dry
state undergoes autoxidation (see p. 263), in presence of the
solvents named is transformed as follows :

HBr +

O
f^^^O Br

UU^

Purified benzaldehyde, exposed to light in the dry state
during two and a half years, in absence of air, is converted into
an amorphous material which is apparently a tetrameric form
(CHeO)..^

Small quantities of two trimeric forms ^ are also produced,
one of which was obtained by Mascarelli ^ as the principal

* Brit. Assoc. Report, Committee on Isomeric Naphthalene Derivatives,
1902.

' Ciamician and Silber, Atti R. Accad. Lincei, 1909, 18, i. 216 ; Ber. 1909, 42,
1386.

' Atti R. Accad. Lincei, 1911, 20> i. 881. * Gazzetta, 191 2, 42, i. 82.

THE CHEMICAL ACTION OF LIGHT 267

product (together with benzylic benzoate, see p. 261) on exposing
benzaldehyde containing traces of iodine to light. In the latter
case, only a small proportion of Ciamician and Silber's tetrameric
form could be isolated.

IV. Condensations and Syntheses

Closely allied with the changes involving polymerisation,
that is the union of like molecules, are those in which the action
involves the union of unlike molecules. Klinger in 1891 found
that benzaldehyde, which easily polymerises in sunlight, also
combines readily with other substances, such as quinone, under
the same influence. In the case of quinone ^ the action is as
follows :

O OH

>^C0 . C«H5

O OH

Dihydroxybenzophenone.

Acetaldehyde, in like manner, combines with quinone to form
dihydroxyacetophenone ^ (acetylquinol) :

O OH

.CO . CH,

+ QH3CH0 ->

r J+CH3.CH0 -> r J

O OH

Phenanthraquinone and benzaldehyde ^ interact as follows :

CO N-'^COH

+ CfiHsCHO ->
•CO J^ ^C . CO . CsHj

The addition of benzylic alcohol to benzophenone to form
triphenylglycol has already been dealt with in Section I.
Similar synthetic changes occur in the case of acetone in presence
of paraffinoid alcohols such as methylic and ethylic alcohol ; as
other changes also occur, these cases are dealt with in Section VII.

* Klinger and Standke, Ber. 1891, 24, 1340 ; Annalen, 249, 237,

* Klinger and Kolvenbach, Ber. 1898, 31, 12 14.

* Klinger and Standke, Ber. 1 891, 24, 1340 ; Annalen^ 249, 237.

268 SCIENCE PROGRESS

The action of acetone on isopropylic alcohol/ however, is
simple, consisting merely in a synthetic or additive change, a
pinacone being formed :

cSp>CO + 8S:>CH.OH -* CH.^C(OH).C(OH)<CH;

Pinacone.

Benrath ^ found that benzaldehyde combines with quinoline
and quinaldine to form compounds of the following structure :

From quinoline. From quinaldine.

CH (^^^ ^^

in, L 1 ^C . CH, . CH(OH) . QHs

N.CO.CfiHs N

The different character of the action in the two cases is very
striking. Benzaldehyde combines with cinnamic acid in still
another manner, a complex product being formed by elimina-
tion of carbon dioxide and hydrogen :

QH5.CHO OH.CO.CH iCH.CeHs

+ ->

CfiHs.CHO OH.CO.CH:CH. CsHs

C6H5.CO.CH.,.CH.C6H5

1 + H, + 2CO,

CeHs.CO.CH^.CH.QHs

In view of the production of hydrogen cyanide in the early
stages of plant growth, Ciamician and Silber have made a
number of experiments on the effect of light on the action of
hydrogen cyanide on aldehydes and ketones. Contrary to ex-
pectation, the cyanhydrol of aldehyde was not affected by light
but acetone^ in presence of hydrogen cyanide gave much
soluble gummy matter " recalling the peptones in chemical and
physical properties " together with a-hydroxybutyric acid,
OH.CMe2.CO2H, and its amide, OH . CMe2. CO . NH^, but
as main products :

CH3 CH-j CHq CH3

C .NHv C .NH2

I >CO and |

co.nhx CO. oh

Acetonylurea. a-Aminoisobutyric acid.

^ Atti R. Accad. Lincet, 191 1, 20, i. 714 ; Ber. 191 1, 44, 1280.

^ J.pr. Chem. 1906, 78, 383.

' Atti R, Accad. Linceiy 1906, 15, ii. 529; Ber. 1905, 38, 1671.

THE CHEMICAL ACTION OF LIGHT 269

It seems probable that the acetonylurea is formed by the further
change of a-hydroxybutyramide under the influence of forma-
mide (produced from the hydrogen cyanide by addition of water,
HCN + H2O = H . CO . NH2), as follows :

CH3 CH3 CH3 CH3

\/ OH NH,v \/

(CH3),C/ >C0 -> (CH3).C .NH\

\CO.NH, h/ I >CO + H,

co.nh/

a-Hydroxybutyramide. Formamide. Acetonylurea.

The formation of acetonylurea does not take place in darkness ;
the way in which the hydrogen liberated according to the
above equation is used up is not clear. a-Aminoisobutyric
acid is no doubt formed by hydrolysis of acetonylurea. Some
ammonic oxalate is also formed in the above case by hydrolysis
of hydrogen cyanide (or formamide), a change which also
involves liberation of hydrogen.

2H.CO.NH, = H2 + ONH,.CO.CO.ONH,

An interesting synthesis of a substance having alkaloidal
properties is described by Paterno and Maselli/ who, by ex-
posing acetophenone dissolved in alcoholic ammonia to bright
sunlight, obtained a crystalline compound, CisHisNg; apparently,
in the formation of this substance, two molecules of aceto-
phenone, two of ammonia and one of alcohol undergo condensa-
tion, water being eliminated.

Other syntheses are considered in Section VII.

V. Isomeric or Stereoisomeric Change

In the case of compounds containing an ethenoid linkage,
light brings about very frequently the transformation of one
stereoisomeric form into another. Wislicenus^ in 1895 observed
that in presence of traces of bromine maleic acid is rapidly
changed by sunlight into the more stable fumaric acid ; the same
change was found by Ciamician and Silber ^ to be brought about
by sunlight alone in either solid or dissolved maleic acid but
to take place more slowly in the absence of bromine. The
same is true of the analogous change of angelic into tiglic acid

* Gazzetia, 19 12, 42, i. 65.

' Ber. Verh. K. Ges. Leipzig^ 1895, 489.

' Atti R, Accad. Lincei^ 1903, 12, ii. 528 ; Ber. 1903, 36, 4266.

270 SCIENCE PROGRESS

and of isocrotonic acid (liquid) into crotonic acid (solid) (Wis-
licenus). In all these cases the modification of lower melting-
point and greater solubility is transformed by light into the
less soluble form melting at a higher temperature. When light
is excluded the changes referred to do not take place even in
presence of halogen. Thus, for example, when 2 grms. of maleic
acid is dissolved in water (5 c.c.) and a little bromine water is
added, crystals of fumaric acid separate within a minute when
the mixture is exposed to light but in darkness no separation
occurs after several hours. Iodine acts far less rapidly than
bromine in accelerating the photo-chemical change. The above
changes can be expressed by the equations :

H . C . CO2H H . C . CO2H

II -> II

H . C . CO2H CO2H . C . H

Maleic acid. Fumaric acid.

CH3 . C . H H . C . CH3

II -> li

CH3 C.CO.H CH3.C.C0,H

Angelic acid. Tiglic acid.

Similar results were obtained by Liebermann^ and may be
summarised as follows :

I. «//o-Furfuracrylic acid -> Furfuracrylic acid

C4H3O . C . H CHsO . CH

II -» II

HO.CO.C.H H.C.CO.OH

tnp. 103°. mp. 141°.

Change takes place slowly in benzene on exposure to sunlight
in absence of iodine. When iodine is present 90 per cent, is
converted in sunlight in fifteen minutes ; in darkness no action
occurs, even when iodine is present.

II. a//o-Cinnamic acid -> Cinnamic acid.

CgHs . CH H . C . CsHj

II II

CO2H . CH CO2H . C . H --

mp. 66°. mp. 133".

III. The most striking of all is the case of <a://o - cinnamy-
lideneacetic acid, CHPh :CH . CH : CH . CO2H. When dis-
solved in benzene the addition of 3 per cent, of its weight of
iodine causes the solution, on exposure to light, to set to a
crystalline mass of cinnamylideneacetic acid within three

» Ber, 1895, 28, I443-

THE CHEMICAL ACTION OF LIGHT

271

minutes ; 80 per cent, is converted in this time. In darkness,
even when iodine is present, no change occurs in six days.
Artificial light, such as that of a Welsbach burner, brings about
the transformation but more slowly.

In view of these facts, Ciamician and Silber studied the
behaviour towards light of some of the oximes which exist in
two stereoisomeric forms ; aw//-benzaldoxime and anti-piper ona\-
doxime are not affected by light but the three nitrobenzaldoximes,
m-nitroanisaldoxime and chlorobenzaldoxime are each trans-
formed into the stable isomeride of higher melting-point.^ The
case of o-nitrobenzaldoxime is particularly interesting, as in view
of the transformation of o-nitrobenzylideneaniline into o-nitroso-
benzanilide (observed by Sachs, see p. 261) and of o-nitrobenz-
aldehyde into nitrosobenzoic acid, it was to be anticipated that
o-nitrosobenzhydroxamic acid would be formed, thus :

NO2
r^CH :NOH

NO
-"^CO.NH.OH

Actually this change does not occur.

If a solution of sym-tribromodiazobenzene-5y;^-cyanide in
benzene be exposed to light, after three days the corresponding
anti-compound ^ is formed.

An important isomeric change brought about by light is that
which occurs in carvone, which is converted into a well-defined
new substance whose exact nature is still uncertain. The
change may be analogous with that undergone by the ethenoid
compounds considered above but an alternative possibility
is the following : ^

CH,

CH — CH,

CHo CH CH-)

CH2: C . CH3

I
CH = C

C.CH,

CH2

/
CH —

CHa

Carvone.

CH3
New form.

^ AUt R. Accad. Lincet, 1903, 12, ii. 528 ; Ber. 1903, 36, 4266. Ciusa, AtH
R. Accad, Lincei, 1906, 15, ii. 721.

^ Ciusa, Atti R. Accad. Lincei^ 1906, 15, ii. 136.

^ Ciamician and Silber, Atti R. Accad. Lincei^ 1908, 17, i. 576 ; Ber. 1908,
41, 1928.

272 SCIENCE PROGRESS

The behaviour of camphor and fenchone is dealt with in
Section VI.

The recent results of Stoermer^ are of great interest in
showing that the ultra-violet rays, in many instances, produce
effects which are the opposite of those brought about by
ordinary light. Thus when the stable, less fusible forms of com-
pounds containing an ethenoid linkage are exposed in benzene
or alcoholic solution to ultra-violet rays, they give rise to the
labile stereo-isomerides of lower melting-point. The following
changes take place from left to right in ultra-violet rays and
from right to left in sunlight :

Methylcoumaric acid ^ Mcthylcoumarinic acid.

Dimethyl ^-nitrocoumarate ^ Dimethyl ^-nitrocoumarinate.

Methoxycinnamic acid (or amide) ^ a//^-Methoxycinnamic acid (or amide),

Fumaric acid ^ Maleic acid.

In some instances, as for example the change of cinnamic acid
to isocinnamic acid and of methylic coumarate to coumarin, the
action is not reversible but takes place in one direction only.

In thisjplace it is not possible to do more than mention the
so-called '* phototropic" changes studied by Marckwald and
others.^ Such changes occur particularly in the case of certain
aldehyde-phenylhydrazones, which change in colour under the
influence of sunlight, the products formed regaining their
original colour when kept in darkness. No doubt a change of
structure is involved in the alteration. The same is true of the
fulgides ofjStobbe ^ of the general structure :

>C = C . CO^

R\ I I /^

>C = C . CO
R/

which undergo similar " phototropic " change. Schlenk and
Herzenstein * have observed a somewhat similar transformation

* Ber. 191 1, 44, 637.

» Marckwald, Zeit. physikal. Chem. 1899, 30, 140; Biltz, ibid. 30, 527 ; Padoa
and others, Atti R. Accad. Lincei^ 1910, 19, i. 490; ii. 302 ; 191 1, 20, i. 675 ; ii.
712.

* Zeit. FAektrochem. 1908, 13, 479.

* Bcf, 1910, 43, 3545.

THE CHEMICAL ACTION OF LIGHT 273

in the case of a mixture of derivatives of triphenylmethane with
the corresponding triphenylchloromethane, which in sunlight
becomes coloured owing to the formation of a triphenylmethyl
compound; this in darkness loses its colour owing to the
occurrence of the reverse change; for example

+ HCl

VI. Hydrolysis and Ring-Scission

One of the best-known cases of decomposition effected by
light is that of the paraffinoid carboxylic acids into carbon
dioxide and the corresponding hydrocarbon ; this change takes
place in presence of an uranium salt, which acts as a catalyst.
In this way, acetic, propionic and butyric acids give respect-
ively methane, ethane and propane.^ Succinic acid gives
propionic acid :

CHj.COjH CH,

CH2.C02H CH2.C03H

and pyrotartaric acid butyric acid ^ :

CH3 . CH . CO2H CH3 . CHo

i -> I

CH2.CO2H CH2.CO2H

In the absence of such catalysts, light alone brings about
striking hydrolytic effects. One of the most simple is the
transformation of wel acetone by sunlight into methane and
acetic acid ^ :

CH3 . CO . CH3 + HOH = CH, . CO . OH + CH4

and of methylethylketone into acetic acid and ethane*:

CH, . CO . C2H5 + H . OH = CH, . CO . OH + C,He

In these experiments, the air must be displaced by carbon

^ Seekamp, Annalen, 1862, 122, 115 ; Fay, Amer. Chem.J. 1896, 18, 269.

' Wisbar, Annalen, 1891, 262, 232. For the analyses of the mixed gases
(CO, CO2, CH4 and Hj) obtained in the decomposition by ultra-violet rays of many
organic substances such as alcohols, sugars, etc., see D. Berthelot and Gaudechon
{Compt. Rend. 1910, 151, 395 and 478).

^ Ciamician and Silber, Atti R. Accad. Lincei^ 1903, 12, i. 235 ; Ber. 1903,
36,1575-

* Atti R. Accad. Lincei^ 1907, 16, i. 835 ; Ber, 1907, 40, 2415.

274

SCIENCE PROGRESS

dioxide, otherwise oxidation occurs (Section I.) ; the action is
only partial, equilibrium being established when lo per cent,
of the ketone has been transformed.

Lsevulinic acid is hydrolysed ^ by water (ten volumes) in a
highly characteristic manner, methylic alcohol, formic acid and
propionic acid being the products, instead of acetic acid and
propionic acid as might have been anticipated :

CH3 i CO ; CH2 . CH2 . CO . OH + 2H0O -> CH3OH +

H.CO.OH -f CH3.CH2.CO2H

The behaviour of the cyclic ketones when exposed with
an excess of water (ten times the weight of the ketone) to the
action of sunlight is generally twofold in its character : usually
a fatty acid is formed, together with an unsaturated aldehyde.
In the case of cyclohexanone the changes that occur are : ^

CH2
i. H^C^/^^CHj

H2C

CH/

CH2.
ii. HX^.-'^CH

H2C

-f H2O -> CH3.CH2.CH2.CH2.CH2.CO.OH

H-Hexoic acid.

-> CH2 : CH . CH2 . CH2 . CH2 . CHO

Hexylene aldehyde.

CH,

0-Methylrv^/ohexanone under like conditions is changed as
follows :

CH2
i. H^Cz-'^CHMe

H.C

+ H2O -> CH3.CH2.CH2.CH,.CH2. CH2.CO2H

«-Heptoic acid (15 %).

ii. H,C/^CHMe

H.C

CHMe : CH . CH^ . CH2. CH^ . CHO

6-Heptenaldehyde (8 %).

CH.

In the latter case, the ring is spht only in the manner
indicated; no methyl-;^-butylacetic acid is formed, as would
be the case if splitting occurred between the CO and CH2, as
in the case of ^c/ohexanone.

» AUi R. Accad. Lincei, 1907, 16, i. 835 ; Ber. 1907, 40, 2415.
2 Atti R, Accad. Lincei, 1908, 17, i- I79 ; Ber. 1908, 41, 107 1.

THE CHEMICAL ACTION OF LIGHT

/-Methylcyc/ohexanone gives 7-methylhexoic acid :

275

CHMe
H2C,.--^CHa

H,Cl^^
CO

CH,

+ H2O -> CH3.CH2.CHMe.CH2.CH2.CO2H

with some heptenylic aldehyde, CHgiCH. CHMe. CH2.CH2.CHO.
Menthone ^ behaves as follows :

CHMea

H2C.

CH
OnCO

H2C

^^^^CH2
CHMe

CHMe-j

ii.

H2C

CH
/CKCO

H2C,

CH,
[Me

+ H2O -> CHMea . CH2 . CH2 . CH, . CHMe . CH^ . COjH

Wallach's decoic acid.

-> CHMCg . CH : CH . CH2 . CHMe . CH^ . CHO

New aldehyde isomeric with menthocitronellal.

When menthone is exposed to the action of water and
oxygen 2 conjointly, it undergoes oxidation as if it were sub-
mitted to the action of hydrogen peroxide :

CHMe^
CH.OH

CHMe

CH2 CH2.CO.OH

CHMe

CHMez

I
CO

CH2

CH2 CH..CO.OH

CHMe

The product is the keto-acid obtained by Arth by oxidising
menthol with chromic acid. The ring is split at the same
point as when air is excluded.

The behaviour of dihydrocarvone when exposed in aqueous
alcoholic solution to the action of light is interesting in com-
parison with that of carvone, which, as stated in Section V.,
gives rise to an isomeric form resembling camphor ; dihydro-

* Atti R. Ac cad. Lincei^ 1907, 16, i. 835 ; 1909, 18, i. 317 ; Ber. 1907, 40, 2415 ;
1909, 42, 1 5 10.

' Atti R. Accad. Lincei, 1909, 18, i. 317 ; Ber. 1909, 42, 15 10.

2/6

SCIENCE PROGRESS

carvone, on the other hand, gives rise^ to an acid and an
aldehyde, the ring being split in the manner already defined:

11.

CH, + H,0

CH3 CHj

\^
C

I
CH . CH2 , CO3H

► /

(acid CoHisOa)

H.C

H,C

CHa

CHMe

CH3 CH,

\^
C

I
CH

^.,0 CH2.CHO

(aldehyde, CioHigO)

CHMe

Camphor^ when exposed in aqueous alcoholic solution to
sunhght gives a mixture of campholenic aldehyde and a new
ketone isomeric with camphor itself. The action which occurs
is apparently as follows :

CH, CH CH2 CH2 CH . CH2 . CHO

CH.

CMe,

I
-CMe-

-CO

CMe,

I
CH = CMe

Campholenic aldehyde.

The formula assigned to the new ketone, from its behaviour
on oxidation, is

CHMe.

CH,

HC^^CO
CHMe

The ketone is the principal product. In this striking case of
isomeric change no hydrolysis appears to take place, the

^ Atti R. Accad. Lincei^ 1908, 17, i. 576 ; Ber. 1908, 41, 1928.
' Atti R. Accad. Lincei^ 191O) 19, i. 532.

THE CHEMICAL ACTION OF LIGHT 277

aldehyde being formed by the scission of the ring in a manner
analogous to that which occurs in the cases already considered.

Fenchone ^ is changed under the influence of light more slowly
but in a more far-reaching manner, carbon monoxide being
evolved and a resinous material formed the nature of which
is still uncertain.

The observations recorded on the changes of the cyclic
ketones considered above are of special interest from the point
of view of the production and transformation of odoriferous
principles in plants and the part they play in plant physiology.
Among other ketones studied by Ciamician and Silber the
following cases may be cited. Pinacolin gives butylene and
acetaldehyde :

Cris CHg

I I

CH3.C.CO.CH, -> CH^rC.CH, + CH3.CHO

CHs CH

Pinacolin. Butj'Iene Acetaldehyde,

Methylisobutylketone and the ketone methylheptenone
(CMca : CH . CH2 . CH2 . CO . CH3) do not undergo change
under the influence of light.

Mention may be made in this section of Neuberg's statement
that light is capable of causing the hydrolysis of disaccharides,
polysaccharides and glucosides dissolved in water containing
o"5 to I per cent, of uranyl salt.^

VII. Changes of Complex Character

When acetone (one part) mixed with methylic alcohol (two
parts) is exposed to sunlight during a year the principal pro-
duct is one formed by simple addition, viz. isobutylene glycol :

™')C0 + CH3.0H ^ OH.CMe2.CH,.OH

But isopropylic alcohol (reduction) and ethyleneglycol are also
formed, as follows:^

i. (CU,), CO 4- CH, OH = (CH3)o CH . OH + H . CHG
ii. CH, . OH + HCHO = OH . CH2 . CH^. OH

Glycol.

^ Atti R. Accad. Lincei^ 1910, 19, i. 532.
' Biochetn. Zeitschr. 1908, 13, 305.

' Atti R, Accad. Lincei^ 1910, 19, i. 364 ; 191 1, 20, i. 714 ; Ber. 1910, 43, 945
and 191 1, 44, 1280.

278 SCIENCE PROGRESS

In the same manner acetone and ethylic alcohol give as main
product, trimethylethyleneglycol :

(CH3)3CO + OH . CH2 . CH3 -> (CHa)^ C(OH) . CH(OH) . CH,

but isopropylic alcohol, acetaldehyde and dimethylethylene-

glycol are also formed as follows :

i. CH3.CO.CH3 + CH3.CH2.OH -> (CH3)2CH(OH) + CH,.CHO
ii. CH3.CH2.OH + CH3.CHO -> CH..CH(OH).CH(OH).CH,

The action of light on the methylic and ethylic alcohol solutions
of acetone is in striking contrast with its action on alcoholic solu-
tions of benzophenone or acetone ; in the latter case only benzo-
pinacone or acetopinacone are formed, by a process of reduction.

Acetone and ethylic ether ^ give isopropylic alcohol
(reduction) and a compound formed by their association,
OH . CMe2. CHMe . OEt, together with other substances not yet
investigated.

Acetophenone and ether ^ interact mainly in accordance with
the equation :

CeHs . CO . CH3+(C2H5),0 -> ^^^^^> C(OH) . CH <,^^^'

Some resin is formed but no acetopinacone, which is the
main product when alcohol is used in place of ether. This
behaviour is strikingly different from that of benzophenone
which gives with ether much benzopinacone (this is the sole
product when alcohol is used in place of ether) together with
the compound :

C.H^C(OH).CH<OEt

Benzophenone and benzenoid hydrocarbons also interact in

a striking manner. When toluene is used much benzopinacone

is produced together with some dibenzyl ; thus

Ph2 . C . OH CH2 . CfiHs
2Ph2 CO -f 2CH3 . CeHs -> I +1

Ph^ C.OH CH^.CsHs

but a considerable quantity of diphenyl benzylcarbinol is also
formed :

QH5> CO + CH3 . CsHs = ^«^'>C(OH) . CH^ . C^Hs

Exactly similar action occurs in the case of benzophenone and
ethylbenzene, ^-xylene and /-cymene (in this case the carbinol

^ Af^z R. Accad. Lincei^ 191 1, 20, i. 721. Compare Paterno and Chieffi,
Gazzetta, 19 10, 40, ii. 321.

^ Atii R. Accad. Lincel^ iQio, 19, i. 645. Compare Paterno and Chieffi,
GazzeitUy 1909, 39, ii. 415.

THE CHEMICAL ACTION OF LIGHT 279

was not isolated). Benzophenone and diphenylmethane^ give
aa/3y3-tetraphenylethanol,

Ph.CO + CH.Ph^ -> CPhaCOH) . CHPh^
Paraffins and hydrocarbons are transformed by benzophenone
in sunlight into unsaturated compounds which then combine
with the ketone ; the compounds formed are often complex.^

Photochemical action in relation to the refrangibility of the
active light. Here it is possible only very briefly to touch upon
this question. In an early series of experiments ^ Ciamician and
Silber, in 1902, showed that the photochemical results they had
obtained up to that date were due to the blue-violet rays and
were not produced by light of greater wave-length nor by the
heat-rays of the solar spectrum. In this respect, the changes
recorded were similar to ordinary photographic changes. On
the other hand, in the case of chlorophyll, photochemical change
is produced chiefly by the rays which are most strongly absorbed ;
the maximum activity is in the red between the lines B and C,
another maximum occurring in the blue near F, with a minimum
in the green corresponding with the transmitted rays.* In the
case of the red-tinted pigmented cells (Floridaceae) and yellow-
ish-brown (Diatomaceae), assimilation was proved by Engelmann
to be most active in that coloured light which was most com-
pletely absorbed by the pigment of the cell (** chromophyll ").

From the recent measurements of Brown and Escombe ^ of
the actual energy absorbed by the green leaf during the period
of assimilation it appears that under the most favourable condi-
tions nearly 100 per cent, of the total light-energy absorbed is
utilised in bringing about chemical change. The leaf seems, in
fact, to be an almost perfect photochemical machine ; moreover
the photochemical change produced in the leaf differs from all
others, not only as regards the enormous amount of energy
actually absorbed but in the fact that this energy is mainly
taken up from a portion of the spectrum which is usually in-
active photochemically : in other words, chlorophyll has pro-
perties which distinguish it from most other colouring matters.

' Paterno and Chieffi, Gazzetta^ 1909, 39, ii. 415.

' Compare Paterno and others, Atti R. Accad. Lincei^ 1909, 18, i. 104 ;
Gazzetta^ 1909, 39, i. 341, 449 ; ii. 415 ; 1910, 40, ii. 321.

^ Atti R. Accad. Lincei^ 1902, 11, ii. 145 ; Ber. 1902, 35, 3593.

* Engelmann, Bied. Centr. 1883, 174.

^ Brown and Escombe, Proc. Roy. Soc. 1905, 76 B, 29 (Bakerian Lecture);
see also Weigert, Che7n. Wirk. Lichts, p. 288.

HORTICULTURAL RESEARCH
I. THE PLANTING OF TREES

By spencer PICKERING, F.R.S.

More than seventy years ago the mind of one of our land-
owners in England became impressed with our ignorance of the
scientific principles on which the greatest industry of the
country— agriculture — was based and from small beginnings,
with plants grown in pots, this investigations grew till they
acquired a home in the Rothamsted Experiment Station^ the
prototype of all the experiment stations which have since been
established throughout the world. Following at a humble
distance, it was the object of those who founded the Woburn
Experimental Fruit Farm to attempt for horticulture what Lawes
and Gilbert had so ably succeeded in doing for agriculture.

There are few of us who cannot claim to be horticulturists in
the limited sense of having grown a few trees or shrubs ; even
such horticulture must have suggested to those of an inquiring
mind innumerable questions as to the why and the where-
fore of certain practices which are supposed to be right and of
others which are supposed to be wrong. Investigation, however,
requires time and money ; nothing would have been done in
the matter if it had not been that there are still landowners in
this country who take a broad-minded view of the duties of their
position and of their obligation to the cultivators of the land.
In founding the Woburn Fruit Farm in 1894, the present Duke
of Bedford was only acting up to the traditions of his prede-
cessors and it may be interesting to record that a hundred
years ago a former Duke was intimately associated with an
immediate ancestor (Coke of Norfolk) of the present writer in
raising the status of agriculture.

Exception has been taken more than once to the locality

in which the new station is situated ; Kentish fruit-growers, for

instance, insisting that it ought to have been established in

Kent, growers elsewhere advocating the claims of their own

280

HORTICULTURAL RESEARCH 281

counties : it is hardly to be expected, however, that any one
who takes so much interest in the problems of fruit-culture
as to found a station of this sort would establish it on other
people's property or anywhere remote from his own observation.
Owing to the specialisation to which fruit-growing has given
rise, it is a distinct advantage that a general experiment station
should not be connected with any particular fruit-growing
district : an independent central station, affiliated to subsidiary
stations in fruit-growing districts for the study of local problems
is, perhaps, the ideal arrangement. It must also be remembered
that exceptionally favourable conditions of soil, climate or
situation are just as disadvantageous for such stations as are
the reverse.

The scientific worker is rarely open to the accusation of
ignoring popular beliefs and traditions, for in many cases it is
found that these have a solid substratum of truth ; but the well
containing this truth is often very deep and requires a deal of
clearing out before anything of value is reached. Such beliefs
are common with horticulturists, who, as a class, must be
reckoned amongst the most conservative of men, ready to
adhere to whatever they have been taught in youth, as if it were
the accumulated wisdom of ages which no facts or demonstration
can upset. With them it is authority, not direct experiment,
which must settle disputed points ; a man who has grown trees
from boyhood, whose father has grown them before him, is a
prophet amongst the people, however limited his intelligence
may be. Of this spirit of opposition to inquiry and progress,
we have, not unnaturally, experienced the full force, for the
Woburn Farm directed its attention, in the first place, to
investigating the foundations on which horticultural practice
in various particulars was laid and the results in many cases
have not been favourable to accepted views.

Reproduction of Fruit-trees

Problems connected with the planting of trees were amongst
those to which our attention was first attracted. There are two
methods by which a tree reproduces its species in nature, the
one by bearing flowers which become fertilised with pollen
from the same or from a similar tree, thus producing seed which

282 SCIENCE PROGRESS

will germinate in the ground under favourable conditions and
eventually develop into a tree ; the other by throwing up from
the roots or the base of the stem shoots or suckers which
develop into new trunks capable of supplying the place of the
original stem when it decays. When the first is followed, the
tree produced is a new individual and in the case of cultivated
fruit-trees differs materially from the parent tree or trees,
generally showing a strong tendency to revert to the original
uncultivated type of its ancestors ; in the second case, the new
tree is really part of the parent and is, in consequence, similar to
it in every respect. Most of our cultivated fruit-trees, however,
show very little tendency to send up suckers from their roots ;
similarly, when a twig or young branch is cut from them and
planted, this will very rarely root itself and become a tree :
consequently other means of multiplying individuals of any
particular variety of fruit-tree have to be adopted. The method
usually followed, as is well known, is to ingraft a bud or a
shoot of the tree required on to some young fruit-tree or
" stock," as it is called, already established in the ground ;
when the bud or buds develop, they reproduce all the main
characteristics of the tree from which they were taken, the
roots of the stock serving onl}^ as a means of conducting
moisture and food from the ground to the tree. Yet the character
of the root-stock is not entirely without influence on the growth
arising from the bud and according as a low-growing bushy tree
or a tall growing standard tree is required different root-
stocks possessing corresponding characteristics are used. For
growing bush-apples and pears, the paradise {pomme de paradis)
and quince stocks, respectively, are used, as these readily form
a mass of fibrous roots which stretch out only a short distance
below the surface of the soil ; whereas for standard trees the
root-stock used is the crab or pear stock, consisting of young
trees obtained by sowing pips of the crab-apple or pear. The
roots formed by these latter are comparatively few in number
but are stronger and penetrate deeper into the soil than those
of the dwarfing stock. The general character of the roots of
these stock will be evident from the accompanying illustrations.
Such stocks, budded or grafted with cultivated varieties of
apples or pears, form the ** worked " trees which are planted
out from one to four years later to form orchards or fruit-
gardens.

Paradise.

Fig. I.

Crab.

^^B

i|g?

H¥^

..---.^^

282]

Quince.

Fig. 2.

Pear.

HORTICULTURAL RESEARCH

283

Root-growth

A root grows by elongation from the tips and unless such
elongation be in progress, either in the root itself or in laterals
arising from it, the root ceases to fulfil its functions and the
tree dies. The extension of a root depends solely on the
presence of certain cells which are capable of multiplying and
then elongating; these meristematic cells, as they are called,
form a small group situated at the end of the root-tip and are
protected from injury by certain outlying cells which constitute
the root-cap. The latter are continually rubbed off as the
root pushes its way through the soil and are continually
reproduced from the region containing the meristematic cells.

£ 72 vv.C

Fig. 3.
c, Central cylinder ; w, Wood vessels R, Cortex ; E, Epidermis ; H, Root-hairs ;

M, Root-tip ; K, Root-cap.

The whole root-tip is very minute, indeed microscopic, so that
it is impossible to lift a tree for the purpose of transplanting
it without breaking off most of the root-tips ; even if they are
not broken off, the unavoidable exposure to the air causes
them to dry up and to become useless : the continued existence
of a tree after transplanting must, therefore, depend on the
formation of new root-tips. There are no cells at the cut or
broken end of the root able to do this but there are cells
situated at intervals throughout the length of the roots which
are capable of becoming meristematic and of giving rise to new
root-tips, eventually forming new roots branching from the

284 SCIENCE PROGRESS

older one. These may be regarded as analogous to the dormant
buds on branches, which show no signs of developing into buds
unless the branches are cut back and deprived of those buds
which would normally continue the branch-growth. For the
development of the dormant root-buds, as they may be
termed, intimate contact between the roots and the damp soil
is essential ; consequently, in transplanting a tree, gardeners
always insist on the necessity of getting the earth well shaken
in amongst the roots and contend that if the soil be too wet and
sticky at the time to admit of this being done planting should
not be attempted. This, so far as it goes, is sound practice.
A number of trees were planted in soil which was in a good
working condition, others in the same soil made unworkable by
adding water ; these latter made only two-thirds as much growth
as the former during the four years following the planting.

Ramming

But much more intimate contact between the roots and soil
can be secured by ramming the soil round the tree, as in fixing
a gatepost, especially if the soil be wet at the time : this unusual
method of planting, which has so horrified orthodox horti-
culturists, has been proved beyond question to yield in nearly
every case better results than the most careful planting in
the ordinary way. Such revolutionary methods of planting
were not advocated without ample practical trial. The experi-
ments, which extended over many years, involved the planting
of nearly 2,000 fruit-trees and bushes of various descriptions,
half of which were planted in the orthodox manner and half
rammed : the plantations were made in nearly twenty different
soils, ranging from light sand to heavy clay, situated in eight
different counties ; moreover, the planting was carried out by
many experienced planters as well as by the horticulturists at our
own farm. The results showed, as might be expected, con-
siderable variation but, on the whole, a very strong balance
in favour of ramming : roughly summarised, this was the case
in 72 per cent, of the different sets of experiments, whereas in
only II per cent, were the results somewhat unfavourable, the
remaining 17 per cent, being ambiguous. The superior vigour
of the rammed trees was manifested in every respect ; not only
was a greater length of new wood formed in the succeeding
year but the shoots were stouter and the leaves larger than

Not rammed. Rammed.

Fig. 4.— Apple Trees.

Not rammed. Rammed.

Fig. 5. — Pear Trees.

[28s

HORTICULTURAL RESEARCH 285

those of the unrammed trees. The superiority in vigour, as
measured by the increased growth, amounted in many cases to
100 per cent, and in some cases to a great deal more ; an excess
of 50 per cent, may be taken as an average. That this was due
to increased root-formation was evident on lifting some of the
trees; instances are given in the accompanying figures.

One great advantage of this method of planting is that it
is not a fair-weather method but can be safely practised
however wet the soil may be and at a time when planting
in the ordinary way would be out of the question. Nor does
the ramming consist in merely patting the soil but of pounding
it till it is effectually puddled ; so much so that, in our soil, it
is quite possible, by stamping with the heel on the ground, to
recognise a tree which has been rammed, even two years after
the operation. That this consolidation of the soil is a bad
thing in itself cannot be doubted and if the whole of the ground
were treated in this way the results would probably be fatal ;
but in point of fact only a small portion of ground is rammed
and the roots soon spread into the looser soil beyond : the only
signs of a deleterious effect which have been noticed are that
during the first half of the season following the planting the
rammed trees are more backward than the unrammed ones,
their superiority not asserting itself till the end of the first
season, in some cases not till the second season. In one
instance only has ramming proved disastrous, that was in the
case of some trees planted in the London clay, at Merton,
where the absence of aeration affected the soil so much that
it became quite black and gave off hydrogen sulphide, which
killed the trees. In other heavy and clayey soils (the Woburn
farm itself is situated on the Oxford clay) no such deleterious
effect has been noticed and in most cases the beneficial results
of the ramming in heavy soils have been conspicuous. On the
other hand, in light sandy soils ramming has no effect, for the
simple reason that any consolidation of the soil effected by
this operation w411 have disappeared before the tree starts into
growth in the following spring.

Damaged Roots

In thus roughly ramming a tree into the ground some
mechanical damage must often be done to the roots; but this
is of little or no consequence, as may easily be realised when

286 SCIENCE PROGRESS

it is remembered that the life of the tree depends on the
formation of new roots, not on the preservation of the old ones.
Each item of damage and of supposed bad practice in planting
trees has been made the subject of separate experiments.
The general result of these has been to show that a certain
amount of damage to the roots is actually beneficial. It is
not very difficult to see the reason of this, for such damage
generally results in the new roots being formed from the
thicker and stronger parts of the old roots where the store of
reserve food is greater, so that the new roots develop more
vigorously. Thus, we have found the shortening of the old
roots to different extents to be of some slight advantage, so long
as not more than one-third of the whole length is removed :
greater shortening is detrimental. In the same way, the
removal of all the smaller roots of a less diameter than 2 mm.
is found to be beneficial (plums and pears were investigated)
but loss in vigour has followed the removal of those up to
4 mm. Most of the smaller roots, under ordinary conditions,
become too much dried up to recover their functions after
the tree has been replanted, consequently they die off: this
has been fully established by marking these roots by tying
pieces of silk round them and lifting the tree again at the end
of the first season : it is easily intelligible, therefore, that the
tree will be benefited by the removal of rootlets which in any
case will decay. Nothing more futile can be imagined than
the way in which gardeners carefully spread out and tend
these fibrous roots which are already virtually dead. However,
the store which is set on a tree which has a mass of fibrous
roots has this justification, that if a tree has sent out a good
mass of roots while in the nursery it is probable that it will do
so again after replanting in the orchard.

That the spreading out of the main roots and avoidance of all
injury has any beneficial effect has been disproved by actual
trial. In some cases trees were planted with their roots bent,
twisted and tied together tightly in a ball under the trees,
whilst in others the roots were lacerated to an extent far in
excess of any probable accidental laceration. It was found that
the number and vigour of the new roots formed was practically
unaffected by this treatment and that there was no detrimental
effect on the tree ; even slight benefit accrued in some cases.

Another point in which accepted rules find no justification in

HORTICULTURAL RESEARCH 287

practice is in the careful trimming of the broken ends of roots,
which is supposed to be essential, even to the extent of laying
down the law that the cut must be made in a certain direction.
This is founded, no doubt, on the erroneous idea that the cut end
of a root will grow when the tree is replanted, which it cannot
do for the simple reason that there are no meristematic cells
there capable of forming a new root-tip. Nor even do the
majority of new roots form near to the ends of the old ones : in a
large number of cases which were investigated, using apples on
the paradise stock, it was found that only 15 per cent, of the new
roots formed within a quarter of an inch from the old root-
ends, a like number started from the stem itself, the remaining
70 per cent, arose from the other parts of the main roots. More-
over a long straggling root will often fail to send out any new
rootlets, the root eventually dying in consequence ; or if rootlets
are sent out from near the end, these are of a feeble character.
Instances of this may be noticed on examining Figs. 4 and 5.
Whether the end of a broken root be trimmed or not appears
to make no difference to the welfare of the tree and to affect
only slightly the new root-formation from the particular root
which is broken or cut, the breaking, instead of cutting the root,
being merely tantamount to a little extra shortening.

It has thus been found that all the practices which are so
strenuously advocated as essential to the proper planting of a
tree are for the most part immaterial and may, even with some
shght advantage, be violated ; whilst as regards one of them,
ramming, the advantage in such violation is very considerable :
and this novel practice in planting is not only borne out by
strict experiment but is the rational consequence of what is
known as to the way in which roots are formed. It must be
admitted, however, that these experiments were not originally
based on any views as to what ought to be but arose from an
endeavour to demonstrate the necessity of following all the rules
prescribed for the " proper " planting of a tree. One set of trees
was planted with all the customary rules violated by way of
object lesson ; but instead of suffering from the treatment they
received, they flourished better than their carefully planted
neighbours. The results were set aside as accidental and fresh
plantations made in a similar way : this course was repeated four
times during six or seven years but always with the same result,
so that the fact had, perforce, to be accepted. Other more
19

288 SCIENCE PROGRESS

specialised experiments followed which served to account for
the results on the lines explained above.

The Proper Depth for Planting

Two questions of considerable importance remain to be
noticed in connexion with planting. These are the depth at
which a tree should be planted and the preparation of the soil
before planting. A safe practical rule is to plant the tree at the
depth at which it was growing in the nursery, this being easily
recognisable by the mark of the earth on the stem. In some
cases, however, purely for experimental purposes, we planted
trees with their roots buried to a much greater depth and were
surprised to find that these flourished much better than those
planted at the ordinary depth. These trees, however, were not
fruit-trees in the horticulturist's acceptation of the term but
young paradise stocks. The accompanying illustrations will
show what had happened and will serve to explain the apparently
anomalous results. In Figs. 6 and 7 are shown six of the stocks
as they were before planting and the same stocks as they
appeared when lifted two years afterwards. In this case they
had been planted with their roots 6 inches below the ground-
level, this being indicated by the horizontal line in the figures.
The root-system at the end of the two years is practically the
same as that in existence at planting but more developed. Fig. 7
represents six trees planted with their roots 24 inches below the
surface ; in this case the behaviour of the trees has been very
different : the original root-system has not developed and in
most instances has visibly shrunk, these roots and a portion of
the stem above them gradually dying ; but in their place there
has arisen from the stems higher up a new root-system and the
new roots composing it, having found abundance of stored
material for their nourishment, have developed strongly and, as
a consequence, the growth of the branches, also, has been much
more vigorous than in the case of the trees planted at the
ordinary depth. Similar, though less marked, effects followed
when the trees were planted 12 inches below the surface.

These experiments, by illustrating the vigour of new rootlets
arising from the thicker root-bearing portions of a tree, have an
important bearing on the explanation already given of the
results of careful and rough planting but they must not be inter-
preted as showing the advisability of planting an ordinary

] -. ' I

\ I 1 ■/ 1

k "^^^

Fig. 6.

288]

v^ — ^

Fig. 7.

288]

HORTICULTURAL RESEARCH 289

*' worked " fruit-tree at this depth in the soil. Quite the contrary.
The beneficial effects observed were due entirely to the fact that
these paradise stocks were capable of throwing out new roots
from their stems, whereas the stems of ordinary apple-trees have
in most cases no such power, so that if buried in the way
described, the original roots would die off as in the case of the
paradise stock but no fresh root-system would be formed in
substitution. Even when crab stocks were used in place of
paradise stocks, the results were found to be unfavourable, for
the crab stocks do not throw out roots as easily as do the
paradise stocks. It may be noticed, too, that the behaviour of
the individual paradise stocks varies considerably, one of the six
shown in Fig. 7 having made very little growth, because the stem,
for some reason or other, was incapable of producing new roots.

It is evident from these results that there is a particular depth
below the surface which is the most favourable for root-forma-
tion. This must vary with the nature of the soil and with the
habit of the plant but will generally be from 6 to 12 inches
below the level of the soil. This, as a rule, will be the best
depth at which to plant a young tree ; but small variations of,
for instance, 4 inches in either direction have been found to be
quite immaterial, for in such cases the new roots that are formed
have no difficulty in making their w^ay to the level at which they
flourish best.

High planting, in another sense, is sometimes adopted, the
roots being placed at the ground-level but covered up with earth
in the form of a mound 6 inches or more high. This is advan-
tageous if planting has to be done in a w^et locality. At present
we are investigating its effect as a means of minimising attacks
of canker : so far the practice seems to have led to good results
from this point of view but it would be premature to draw any
definite conclusions yet. As to its effect on the general behaviour
of the tree, this varies with the season, being, as might be
expected, good in a wet season and bad in a dry one. No one,
of course, would think of planting a tree in this way in a light
sandy soil.

Aeration of the Soil

The depth at which roots will flourish best is dependent, no
doubt, on the conditions prevailing in the soil with respect to air
and moisture. Aeration is necessary for the oxidation of organic
matter in the soil and of that thrown off from the roots, the

290 SCIENCE PROGRESS

carbonic acid thereby produced playing an important part in
rendering the mineral constituents of the soil soluble and
assimilable by the plant; aeration is also necessary for the
existence of the bacteria on which the plant is dependent for
its supply of soluble nitrogen. The importance of an air-supply
to the roots is rendered evident by the failure to grow plants in
water unless this be well aerated ; also, no surer way of damaging
or killing trees exists than that of allowing the soil to become
water-logged while they are in active growth. Thousands of
trees were killed in this way during the wet summer of 1903.
On the other hand, it is surprising how limited the supply
of air to the roots may be without interfering materially with
the growth of a tree. In some experiments at Woburn a
number of apple-trees were each surrounded by an iron drum,
3 feet in diameter, 18 inches deep; when this had been driven
down into the soil, the soil within the area enclosed by the
drum was covered with a 2-inch layer of cement. Each tree
was thus enclosed in a sort of tub and its roots could only
obtain such moisture and air as permeated through the stiff
clay subsoil 18 inches below the surface. Yet these trees
flourished during four years just as well as and even slightly
better than similar trees which were not enclosed ; and though
afterwards they began to fall behind-hand, owing to the ex-
haustion of the limited amount of soil available for their
growth, they are still — after thirteen years — fairly healthy trees.
Trees planted in towns, often with their roots covered by
paving-stones, afford familiar instances of the extent to which
they will thrive with a very limited access of air to their roots.
One very striking illustration may be noticed just outside
St. Pancras Station. The Midland Railway line passed over
a burial-ground in which there were some trees with stems
up to about a foot in diameter. This burial-ground was done
away with about twelve years ago and the ground made up
to the level of the railway line by dumping on to it some
13 feet of earth and rubbish: the trees were, consequently,
buried to this depth, leaving only their heads above ground :
yet they have continued to live and are still in a fairly flourishing
condition.

Trenching

The question of trenching or double-digging the soil pre-
paratory to planting fruit-trees is one of considerable importance

HORTICULTURAL RESEARCH 291

to growers, as it is a costly operation, especially in stiff soils
where it may be expected to do most good. The trenching
usually adopted (bastard trenching) consists in digging and
moving the first and second depths or spits of soil and breaking
up but not removing the third spit ; the second and first spits are
then put back into their original position. Ploughing with a sub-
soil plough is sometimes substituted for trenching. In vegetable
growing, trenching is generally understood to mean more than
this, a liberal supply of dung or refuse being buried in the
trench drawn out in the course of the digging ; this materially
alters the character of the soil. Trenching in its strict sense
has alone been investigated. The investigation embraced five
instances in different soils, fruit-trees being planted in the
trenched and untrenched ground and their behaviour examined.
At the same time the alteration effected in the soil by the
trenching was investigated by Dr. E. J. Russell, who determined
the water and nitrogen present in the various cases. The
results have not been quite completed yet but they are suffi-
ciently advanced to show that trenching has very little effect,
when measured either by the behaviour of the trees or by the
alteration in the soil. In many cases the effect has been nil
and whether it be appreciable or not seems to depend chiefly
on the character of the seasons following the trenching. In
any case, the beneficial effect is much too slight to compensate
the planter for the cost of the operation.

THE RELATION OF MIND AND BODY^

By J. S. HALDANE, M.D., LL.D., F.R.S.,
Fellow of New College and Reader in Physiology, University of Oxford

From our everyday standpoint a man or higher animal is a
personality consciously and purposively controlling, with
a certain amount of success, a surrounding physical environ-
ment. On closer examination, however, this conception appears
unsatisfactory : for the reactions between his body and the
environment are apparently physical and chemical in nature : the
body itself is apparently part of the physical and chemical world ;
the changes within it are apparently physical and chemical
changes, no break being noticeable indicative of any point at
which they are controlled by an independent mind or soul. Con-
sciousness seems, therefore, to be nothing but an accompaniment
of physical and chemical changes within the body.

The facts on which this conclusion depends appear at first
sight to be unassailable and to become more and more cogent
with every year of advance in physiological knowledge. Psy-
chologists thus tend to be driven into the position which has
come to be known as "parallelism " or "epiphenomenalism."

It is important to point out, at the outset of the discussion,
that if once we admit that the living body, whatever its pecu-
liarities, either forms part of or exists in a real physical world
of matter and energy, we are inevitably committed to the con-
clusion just indicated : for we can proceed to demonstrate
experimentally that the admitted physical and chemical con-
ditions determine all bodily activity, conscious or unconscious :
we can trace all perception and memory to the action of physical
stimuli ; and we can show that the working of the brain depends
on physical and chemical conditions. Cut off the oxygen supply
to the brain even for a few seconds and all evidence of con-
sciousness disappears completely, only reappearing again if

* A contribution, with some additions, to a discussion in the Physiological
Section of the British Association meeting at Dundee, 1912.

292

THE RELATION OF MIND AND BODY 293

the supply be quickly restored. Make some other minute
alteration in the chemical composition of the blood and a
man's behaviour is completely altered : he may be reduced to
below the level of a beast. We are in this way forced to admit
that if there be a soul, all its manifestations are dependent on
physical conditions ; and this being so, it seems scarcely worth
arguing whether, as the vitalists and (to use Dr. McDougall's
term) "animists" maintain, there is something else in a man
or animal apart from physical phenomena mysteriously accom-
panied by gleams of consciousness.

It is the premises of this argument which I wish to examine ;
indeed there must be examined with the utmost care if ever the
two sciences of biology and psychology are to be set on a firm
theoretical basis. Living, as we do, in a time when physical
conceptions are on all hands tacitly or explicitly assumed to
correspond to the reality of our visible universe, it is difficult
to obtain a popular hearing for any doubts on the subject; and
even from the philosophical side there comes the argument that,
unreal in ultimate analysis as the physical universe is, physical
conceptions are nevertheless the forms under which alone such
knowledge as we possess is possible.

Now it seems to me Very clear that in the case of living
organisms and their physiological environment, we cannot
express the observed facts by means of physical and chemical
conceptions but must and do have recourse to the conception
of organic unity ; and must use this conception as our funda-
mental working hypothesis just as the physicist uses the
conceptions of matter and energy. This means nothing less
than a definite break all along the line, including the environ-
ment, with the purely physical conception of nature. We may,
it is true, endeavour to give a physical description of the
phenomena of life ; but such attempted description cannot
express the main facts. ^ The time at my disposal does not

^ In his Address as President of the British Association Prof. Schafer deals
with " The Nature, Origin and Maintenance of Life " and defends the thesis that
"the problems of hfe are problems of matter." Needless to say, I am unable to
accept his general conclusions. It appears to me that he has failed to apprehend
correctly the general trend of biological advance, particularly during the last fifty
years ; and that he completely ignores the fundamental difficulties involved in
a physico-chemical conception of life. Living organisms are distinguished from
everything else that we at present know by the fact that they maintain and
reproduce themselves with their characteristic structure and activities. Nothing

294 SCIENCE PROGRESS

allow of my developing this position here ; but I may perhaps
refer to my address as President of the Physiological Section
of this Association in 1908. I will only venture to remark that
the position indicated involves a far more thorough departure
from mechanical explanations than that of the old vitalists or
their more recent representatives, although I am in agreement
with the position of the vitalists in their main criticisms of
what may be called, for the sake of shortness, " mechanistic "
biology. The vitalists cut the ground from under their feet by
accepting the physical conception of both the environment and
the body substance ; they cannot consistently escape from the
consequences of this acceptance. The conception of organic
unity implies a biological, as distinct from a physical, interpreta-
tion of environment as well as organism ; and the biological
interpretation is natural and necessary where biological facts
are concerned. The physical and the biological interpretations
are each theoretically applicable to the whole of Nature; but
neither can be actually applied completely, as only part of the
known facts correspond in either case. I feel no personal
doubts that the mechanistic biology, in spite of the great names
associated with it, including that of the distinguished President
of this Association, will soon be a thing of the past.

The conception of organic unity applies to the whole of what
may be called the " vegetative " aspect of life but takes us no

resembling this phenomenon is at present known to us in the inorganic world ;
and if, as we may confidently hope, similar phenomena are ultimately found in
what we at present call the inorganic world, our present conception of that world
as a mere world of matter will be completely altered. Prof. Schafer points to
the numerous physical and chemical processes which we can distinguish by
abstract thought within the living body ; he completely ignores the actual fact
of their maintenance in organic unity. The more detailed and exact our know-
ledge has become of the marvellous intricacies of structure and function within
the living body, the more difficult or rather the more completely impossible has
any physico-chemical theory of nutrition and reproduction become. The difficulty
stands out in its fullest prominence in connexion with the phenomena of repro-
duction and heredity. I can find in Prof. Schafer's address no serious attempt
to deal with this difficulty. He has much to say of the physics and chemistry
of colloid nitrogenous material and he makes play with the obsoleteness of the
distinction formerly drawn by chemists between " organic " and " inorganic "
chemistry ; but he ignores the evident differences between living organisms and
non-living material whether " organic " or " inorganic," colloid or crystalloid.
He also fails to see what constantly strikes me in my work as a physiologist, that
the advance of biology is everywhere hampered and confused by the physico-
chemical theory of life.

THE RELATION OF MIND AND BODY 295

further and no higher. A mere organism, regarded simply as
such, fulfils its biological destiny blindly and without evidence
of consciousness ; and just as physical conceptions are inade-
quate to express the phenomena of vegetative life, so are
biological conceptions inadequate to express the phenomena
of conscious existence.

What characterises any distinctively physiological or bio-
logical phenomenon is that whether it relate to the body or
to the environment it can only be interpreted as an element
in an organic whole constituted by the life of the organism.
Nevertheless much that we find in the living body and most that
we find outside it cannot be interpreted as organically deter-
mined. The advance of biology is constantly increasing the
sphere of the organic at the expense of the apparently inorganic ;
but the sphere of the inorganic increases just as rapidly.

In conscious life there comes in a quite new factor : for an
organism which perceives and wills, however dimly, is taking
into the unity of its own life the inorganic element. What is
perceived or willed is outside mere organic life and yet has a
determination or meaning in relation to the past, present and
future of the organism and cannot be adequately expressed as a
mere physical event. Perception and volition are always
"practical": their nature can only be expressed as elements in
the teleologically determined whole of a conscious personality.
It does not matter whether we approach this fact from the
psychological or the physiological side. From the psychological
side an isolated sensation or element of whatever kind in con-
sciousness is a meaningless abstraction : from the physiological
side an isolated physical stimulus or concomitant of sensation is
equally meaningless. When we speak of localisation of sensa-
tion we are only repeating empty words. The theoretical basis
of physiological psychology as ordinarily understood is wholly
unsatisfactory. We have scarcely even reached the threshold of
a true physiological treatment of the central nervous system :
for the present we have to content ourselves with a crude
physical treatment of the subject, in which physical metaphors
are everywhere substituted for experimentally ascertained facts.

The distinctive behaviour of men and conscious beings in
general cannot be interpreted except in terms of conscious
personalities living in an environment of their own percepts and
acts, which has grown with them and exists for them. In other

296 SCIENCE PROGRESS

words persons are real and no mere walking automata or
automata controlled by souls. The reasoning to the contrary is
based on the petitio principii that the physical interpretation of
the universe corresponds fully with reality. The physical
world is taken to be real by itself, though it is only real as part
of a known world and as no mere ** unearthly ballet of bloodless
categories " but the expression of concrete living personality.
It is on the basis of abstracting from the primary fact that the
physical world is known, that we build up an impossible theory
of the rest of our experience — impossible because it can give no
account of life or of knowledge and volition. It is only for our
own practical purposes that we separate off the physical world
from its relation to ourselves as the subjects for whom it exists ;
and the confusion arises from our forgetting this fact. In the
argument that all the conscious behaviour of a man or animal is
ultimately dependent on physical and chemical stimuli from the
environment, acting on the physical and chemical structure of
the body, the whole question is begged from the outset ; for the
assumed physical stimuli and physical structure do not behave
as such ; the facts do not fit into the assumption we have made
as to their nature. Stimuli and structure possess alike a
meaning — a determination as part of the unity which we
recognise as personality. We cannot separate the stimulus
from the consciousness of it. We are in presence of something
which cannot be expressed in physical terms. No amount of
tracing of paths of nervous connexion or localisation of function
will help us to a physical analysis of the unity of personality,
because the unity determines the whole and includes the
enviroment.

It is none the less true that apart from all attempts at a
physical analysis of personality, there is abundant room for
purely physical and physiological investigation of living
organisms, provided that it be clearly recognised that in these
investigations we are for our own practical purposes deliber-
ately leaving out of account certain aspects of the facts we
are investigating. This is, indeed, the case in all scientific in-
vestigation, whether mathematical, physical, physiological or
psychological.

We can, for example, proceed to measure, weigh and
describe in physical or chemical terms anything in connexion
with the living body ; but when we look closely we soon see that

THE RELATION OF MIND AND BODY 297

our data are, at best, of only a limited practical value. If we
weigh an animal or man, we obtain data which may be of great
practical value; but what are we weighing? It is not the
living body, because it includes the contents of the alimentary
canal and other cavities and perhaps the clothes : it also includes
deposits of fat, water and other material stored in the body,
either within or outside of living cells : also liquids such as the
blood plasm and lymph-deposits, of inorganic matter in the
bones and apparently lifeless organic matter in the connective
tissues and elsewhere. When we investigate metabolism or
chemical constitution of material or any other process or state
occurring in the body, similar questions have to be faced ; and
we begin to realise that in investigating biological questions
from the standpoint of physics and chemistry alone we are
dealing with a collection of abstractions from reality and that
we can do better by using a less abstract working hypothesis.

These physical investigations, like all scientific investiga-
tions, have nevertheless a very great practical value : for though
they are partial and one-sided they give us the best insight
we can for the time get as regards countless matters of detail
in our experience. The great mistake, leading to such con-
clusions as that living organism.s are physico-chemical mechan-
isms or that conscious behaviour is nothing but physico-chemical
change accompanied by consciousness, is to lose sight of the
wider point of view which shows us that in physical or indeed
any scientific investigation we are always dealing with partial
aspects of reality.

We can arrange the sciences in a certain order, according
as they deal with more or less abstract and one-sided aspects
of reality. The purely mathematical sciences come lowest in
this order ; next to them come the physical sciences ; then
biology ; whilst psychology and ethics deal iwith what is least
abstract. But if the mathematical sciences stand lowest in
one way, in another way they stand highest, as they have the
widest and most general field of application ; and all knowledge
and practice involve quantitative treatment.

Between body and mind there is no interaction, simply
because the body, more fully understood, is the mind. From
the physical and chemical standpoint a man is about 70 kilo-
grammes of material with a certain configuration, properties and
internal movements : this material consisting of a great variety

298 SCIENCE PROGRESS

of chemical compounds, interacting upon one another in various
ways. From the physiological standpoint the man is a living
organism blindly fulfilling its biological destiny. From the
psychological standpoint he is a person, the subject of purposive
knowledge and volition. The man as mere physical body or
organism is an evident fiction or abstraction from reality,
though a very necessary one for our imperfect knowledge. As a
conscious individual personality he is at least far less of a fiction.

The physical sciences, biology and psychology, go on their
several ways, accumulating knowledge which each science in-
terprets according to its own working hypotheses and subject to
the limitations of these hypotheses. Each lower science also
hands on what is relatively speaking raw material to the higher
one. The attempt to resolve the higher into the lower, as by
making mind dependent on body, is, however, foredoomed to
failure.

To sum up, the relation of body to mind is not that psychical
phenomena are the mere accompaniments of physical processes
in the body nor that there is interaction between body and an
incorporeal mind or soul but that body is conscious personality
looked at incompletely or abstractly. In other words, conscious
personality is the truth of the body and its environment ; and the
physical causes which seem at first sight to determine the mind
are only superficial appearances. This is merely another way of
saying that however little we understand it in detail our world
is a spiritual world.

We are not thereby committed to the absurd position that
the personality of the universe is a man's own individual per-
sonality coming into existence at a certain date and disappear-
ing again at a certain other date. Just as biological facts have
taught us that the life of each individual cell or organism is only
part of a wider life, so have ethical and religious facts shown
that the individual personality in its full realisation is the ex-
pression of divine personality, which alone can be the ultimate
truth of all existence. The individual personality, including
his ideas of the world and his ideals of conduct, is evidently a
** product of his time " — the expression of a wider personal life
which he only realises in living it and living it whole, confident
in his participation in it and ready to give up his mere individual
interests or even his life itself should his duty lead him to
do so.

THE RELATION OF MIND AND BODY 299

In drawing these conclusions I am only following on the
lines of great philosophers who have reached essentially the
same results. It is unfortunate that owing to faults on both
sides there has in recent times been so little real contact
between natural science and philosophy; but I hope that this
discussion in an assembly of men of science may prove a step
in promoting closer relations in future and once more bringing
these two great branches of human knowledge and endeavour
into living connexion.

SPECULATIONS ON THE ORIGIN OF LIFE
AND THE EVOLUTION OF LIVING
BEINGS^

By E. a. MINCHIN, F.R.S.

Any statements that can be made concerning the Origin of Life
must be, at the present time, of a purely speculative nature —
a speculation being defined as the logical process of drawing
from established data certain conclusions which cannot be
directly verified. Though the degree in which a speculation
approximates to the truth and commands our confidence in any
given case will depend entirely upon the nature of the evidence
by which it is supported, a proposition which cannot be directly
verified may nevertheless be based on evidence so strong that
it receives unhesitating assent from those who are able to
understand the premises and follow the reasoning. At the
opposite pole to such conclusions are those which cannot be
either proved or disproved and are therefore valueless ; as if,
for instance, one should attempt to discuss the configuration
of the other side of the moon or the nature of the inhabitants
of Mars. An intermediate class of speculative thought com-
prises discussions that are based upon a large body of established
facts though no two authorities may agree completely in interpret-
ing the facts : in such cases the conclusions drawn are neverthe-
less useful and are an aid to the advancement of science as they
serve to draw attention to points in which our knowledge is
weak or to indicate important lines of investigation which have
been neglected ; as an instance of such speculations, I may
cite the much-discussed question of the origin and ancestry of
vertebrates, a problem that may be discussed with profit though
it may never receive a solution which will command universal
assent.

^ Delivered as the Opening Address in a discussion on the Origin of Life, at
a joint meeting of the Botanical and Zoological Sections of the British Association,
Dundee, September lo, 191 2.

300

SPECULATIONS ON THE ORIGIN OF LIFE 301

I do not propose to attempt a definition of life, which, in
agreement with our President/ I regard as a practically
impossible task. The problem of the origin of terrestrial life
seems to me to admit of being resolved into two distinct
questions : first, assuming that the innumerable and immensely
varied forms of life now seen on the earth arose by a process of
gradual evolution from some original form of living substance
or primitive type of living being, to try to form an idea as to
what this earliest form of life was like ; secondly, when we have
reached a conclusion as to the nature of the primordial living
creature, to discuss the manner in which this primum vivens itself
originated and how it got its living and maintained its existence.
The first of these problems is one which, in my opinion, can be
discussed with profit, though not, I fear, with the hope of
drawing conclusions upon which all biologists will be agreed ;
the second appears to me to be scarcely ripe for discussion, the
data being at present altogether too inadequate to permit of our
arriving at results of real value. I will confine my introductory
remarks to these two questions and consider them in the order
indicated.

At the present time, I think I am right in saying, the
majority of those occupied with the study of living things
regard the cell as the vital unit, the primary form of living
being. One of our most prominent and valuable zoological
textbooks, the Traite de Zoologie Concrete of Delage and
Herouard, begins with the sentence *' Tout ce que vit n'est que
cellules." Living things, considered generally, are regarded by
most biologists either as single, individual cells or as built up
of many cells ; as Delage and Herouard express it, the cell is the
simplest protoplasmic organ which is capable either of living
alone or which requires only to be associated with others like
itself to form beings capable of independent life. Such state-
ments make it imperative to examine into the meaning and
application of the term '* cell."

The word "cell," as every one knows, is a term which we owe
to the botanists, since it was in plants that the cellular com-
position of the living body was first discovered. The term *' cell "
was first applied to the limiting membrane or cell-wall and
the fluid or viscid contents were regarded as of secondary
importance. Hence the primary meaning of the term " cell " was
^ See Prof. Schafer's Presidential Address, p. 3.

302 SCIENCE PROGRESS

what the word itself implies in ordinary language, a little box
or capsule, a small space enclosed in firm walls. But with
increased knowledge it became apparent that the fluid contents
were the essential living part of the cell and that the cell-wall
was of secondary importance, merely an adaptive product of
the contained living substance or protoplasm. Hence the word
*' cell," as used in biology, underwent a complete change in its
connotation and came to have a meaning altogether different
from that which the word has in common speech, often very
puzzling to those unacquainted with the technicalities of the
biological sciences, the cell being defined simply as a small
mass or corpuscle of the living substance which might either
surround itself with a cell-wall — the product of its own secretive
activity — or remain naked and without any protective envelope.
With still further advance in knowledge, it was found that in
every cell entering into the structure of an ordinary plant or
animal there was present at least one body of peculiar pro-
perties which was termed the nucleus ; on account of its
universal occurrence, as well as the peculiar relations it was
found to bear to the life of the organism, this body soon came
to be regarded as an essential component of the cell. Thus we
arrive at last at the now generall}^ accepted definition of the cell :
a vital unit consisting of an individualised mass of the living
substance protoplasm containing at least one nucleus.

We are arrived, then, at this point, that the unit-masses of
the living substance of which the bodies of ordinary animals and
plants are built up are themselves composed of at least two
essential parts. Using the term ** protoplasm " for the living
substance as a whole, we can assert that the protoplasm of an
ordinary cell is differentiated into two distinct components, the
cytoplasm or body-protoplasm and the nucleus. Here at once
the question arises, is this differentiation of the protoplasm a
primary characteristic of the living substance which was ex-
hibited by our hypothetical primum vivens oris it a differentiation
which was acquired in the course of evolution ? If the latter
alternative be the true one, is the nucleus or is the cytoplasm
the more primitive constituent of the living substance or are
they both to be regarded as derivatives of a substance yet more
primitive ? For my part, I cannot conceive that the earliest
living creature could have come into existence as a complete
cell, with nucleus and cytoplasm distinct and separate ; I am

SPECULATIONS ON THE ORI6IN OF LIFE 303

forced to believe that a condition in which a living body consisted
only of one form or type of living matter preceded that in which
the body was composed of two or more structural components.

It is, I think I may say, the most generally accepted notion
among biologists that the cytoplasmic substance of the cell (to
which the term "protoplasm" is often restricted) is to be regarded
as the primitive living matter. The earliest forms of life have
been supposed to be formless masses of protoplasm, without
nuclei, the so-called Monera of Haeckel. From such a condition
true cells are supposed to have arisen by individualisation of
the indefinite mass and acquisition of a specific form and size,
together with the differentiation of a nucleus, which on this
view would represent the oldest cell-organ but not an essential
or indispensable part of a living body. For my part, I find
myself obliged to dissent entirely from any such view.
Although a definite nucleus, a body of complex structure and
organisation, such as we find in the tissue-cells of animals and
plants, is undoubtedly to be regarded as a relatively late product
of evolution, I believe, nevertheless, that the nucleus contains
the oldest and most primitive elements of the living substance
and that the earliest forms of life consisted entirely of the
characteristic and essential material of the nucleus. In order
to elaborate this view further, I must discuss as briefly as
possible the nature and constitution of the nucleus.

In different cells the nucleus is seen to vary almost infinitely
in form, structure and composition ; but this diversity only
brings into greater relief the fact that common to all nuclei is
the presence amongst the contents of a peculiar substance
termed chromatin,^ which occurs in the form of granules or
masses distributed in various ways over the framework of the
nucleus. In addition to the chromatin contained within the
nucleus, however, there may also be grains of chromatin
scattered through the cytoplasm, so-called chromidia. In many
organisms, finally, a true nucleus may be temporarily absent,
the chromatin-substance being present only in the diff'used or
chromidial condition.

^ In the course of the discussion Prof. M. Hartog challenged me to give a
definition of chromatin ; I replied that I would almost as soon attempt to define
life Itself. I may add that I have discussed the question of the nature of chromatin
at greater length m my recently published work, An Introduction to the Study of
ihe Protozoa (Arnold, 191 2).
20

304 SCIENCE PROGRESS

The chromatin-substance receives its name from its peculiar
property of combining with certain dyes, whereby it can be
coloured selectively and differentiated more or less completely
from the rest of the protoplasm. The staining test is, however,
a very inadequate and untrustworthy method of recognising
the substance. Our conception of chromatin should rather be
founded upon its relations to the life of the organism as a
whole and to its vital activities ; these relations I can only indicate
very briefly and summarily, so far as they are known. To begin
with, the chromatin-substance is never absent from any known
organism, however minute or apparently simple in structure :
direct experiment has shown that a cell deprived of its nucleus
cannot maintain its life during any length of time and is unable
to initiate any of its characteristic vital activities. The repro-
duction of a cell or of a simple protoplasmic organism always
involves division into two or more parts and in this process
the chromatin-substance divides first and is partitioned amongst
the daughter-individuals. In many cells, the nucleus divides
by a very elaborate mechanism known as karyokinesis, which
ensures an exact quantitative and qualitative partition of the
chromatin between each of the two daughter-nuclei. Through-
out the series of living beings, wherever sexual phenomena are
observed, the sexual act consists essentially in the union of
chromatin from two distinct organisms ; the ascertained facts
of fertilisation and development have led to the belief which,
if not universal, is at least very widely spread among biologists,
that the chromatin-grains determine the characters of the off-
spring and are the carriers of hereditary tendencies and pro-
perties. In the internal economy of the cell, the special function
of the nucleus appears to be that of producing the peculiar
substances known as ferments or enzymes, substances which
perhaps more than any other are characteristic of living bodies.
These data, taken together, in my humble opinion constitute
a very strong case for regarding the nuclear substance, chro-
matin, as the all-important and essential constituent of living
organisms. Such a conclusion is greatly strengthened by the
fact that some of the minutest forms of life appear to consist
entirely or almost entirely of chromatin. Apart from the
Chlamydozoa, the true nature of which can hardly be said to
be established with certainty at present, many instances could
be cited of organisms or stages of organisms in which the body

SPECULATIONS ON THE ORIGIN OF LIFE 305

appears to consist of little or nothing more than chromatin, as
for example the spirochaetes (treponemes) parasitic in blood,
the male gametes of the malarial parasites, etc. It may be
urged against this statement that in such minute organisms
microscopic technique fails to reveal all details of structure and
that cytoplasmic elements may be present though invisible;
but at least this much can be said, that the more minute the
organism, the less evident, as a rule, is the presence of cyto-
plasmic structures, until in the very smallest the body appears
to consist mainly or even entirely of chromatin.

For these various reasons, I am unable to share the view
that the cytoplasmic substance of the cell is to be regarded as
the primum vivens of which the chromatin and the nucleus are
a secondary elaboration.^ Rightly or wrongly, I have been

^ The conclusion that the chromatin represents the primary living substance
of the protoplasm is one that has been reached by me mainly upon morphological
grounds ; it stands, therefore, urgently in need of support from other methods of
approaching the question and especially from the chemical side. In this con-
nexion, I may quote from a letter of the date August 17, 191 2, written to me by a
friend whom I know as yet only by correspondence, Dr. R. G. Eccles, of New
York, who makes some suggestions which I am not competent to criticise but
which seem to me extremely pertinent to the matter under consideration. Dr.
Eccles writes :

" If some of your biochemist friends could be induced to present Kossel's ideas
of the protamines in connexion with your paper it seems to me it would strengthen
your position. The protamines are the proteins most common in spermatozoa.
Chittenden refers to Kossel's views thus : * The basic protamines are undoubtedly
the simplest and lowest in the scale and it is quite probable, as suggested by
Kossel, that these substances constitute the nuclei of all proteins' {Pop. Set.
Monthly^ December 1904, p. 157). On the same subject Mann tells us that * Tho
radicles of which protamines are built up may be as numerous as they are in othei
albumins but there is less variety and each kind is repeated with great regularity
in the different protamines. Kossel believes the protamines to be the simplest
albumins' {Chem. of the Proteids^ p. 420).

"All proteins (albumins) are built out of amino-acids just as houses are built
of bricks or stones. There is one amino-acid, arginine, that constitutes 80 per
cent, of the protamine, salmine, from the spermatozoa of the salmon. Arginine
is the only amino-acid found in all proteins (albumins) {Chem. of Proteids^ p. 154).
It is the maximum constituent of the proteins of the nucleus and the minimum
constituent of the proteins of the cytoplasm. There are three amino-acids —
tyrosine, phenylamine and tryptophane— that reach their maximum in the
cytoplasm and their minimum in the nucleus. Some protamines seem to contain
none. Arginine belongs to the uncomplicated chain-series of carbon compounds
(aliphatic), whist the other three belong to the complex ring-series of carbon
compounds (aromatic). The aliphatic chains are the very simplest of carbon
compounds. The aromatic rings are complex and are only conceivable, genetically,
as arising from the aliphatic chains. It is thus seen that (i) the protein-molecules

3o6 SCIENCE PROGRESS

led to the conviction that the earliest forms of life were
extremely minute ultramicroscopic particles consisting of chro-
matin alone. I do not lay claim to any novelty in this view ;
I put it forward simply because I believe it to be true. In
the process of gradual evolution and adaptation to divers
conditions of existence these minute chromatin-particles formed
round themselves envelopes and coats of substance other than
chromatin and so gave rise to cytoplasmic elements. As the
body was thus increased in size, the next step would be an
increase in the number of granules of chromatin contained in
it. At this stage the bacterial type of organisation could have
arisen by the secretion of a firm membrane at the surface of
the body enclosing one or more grains of chromatin (chromidia)
in a small amount of cytoplasm. I am far from regarding the
bacteria as the earliest or simplest possible forms of life, as
some authorities seem to hold ; they appear to me rather to
represent a type of organisation which arose very early in the
evolution of living beings, long before the divergence into
animals and plants which dominates modern terrestrial life ; a
type in which the characteristic limiting membrane has in-
hibited further advance in evolution and has restricted their
structural differentiation within a narrow range. I consider
this at least a more feasible interpretation of the nature of
the bacteria than the view held by many that they are to be
derived from organisms primitively of cellular structure which
have become highly specialised for a parasitic or saprophytic
mode of life.

The absence, on the other hand, of a rigid membrane or
cuticle round the bodies of some of our imagined primitive
organisms would permit the formation of a greater amount of
cytoplasmic substance and an increase in the number of chroma-
tin-erains in a larger body. Thus would be possible an organism
of dimensions relatively large, indeed gigantic as compared with

of the nucleus, that are characteristic of the same, are simpler in construction than
the protein-molecules of the cytoplasm and, therefore, most likely more primitive ;
(2) that the protein-molecules of the cytoplasm, that are characteristic of it, are
more complex than those characteristic of the nucleus and less likely to be
primitive ; (3) that the amino-acid characteristic of the chief nuclear protein is an
open chain free from complexity, whist the amino-acids characteristic of the
cytoplasm are closed ring compounds that could only arise from chemical com-
pounds of the same type as that characteristic of the nucleus. These facts, I
believe, have an important bearing on your subject."

SPECULATIONS ON THE ORIGIN OF LIFE 30;

its earliest ancestors, though still microscopic to our limited
senses ; it would be a mass of cytoplasm containing numerous
chromidial grains and it is only in this sense that I can accept
Haeckel's Monera. The next step in evolution would be the
concentration and organisation of the scattered chromidia into a
definite compact structure, the nucleus ; with this step completed
the condition of the true cell would have been reached. Unless
the word " cell " is to become quite vague and meaningless, a mere
synonym of such terms as microbe or micro-organism, it should
in my opinion be restricted in its application to those organisms
which have reached the degree of structural complexity found in
the tissue-elements to which the term " cell" was originally applied
— that is to say, to organisms in which the protoplasm is differen-
tiated into cytoplasm and nucleus definitely marked off from one
another. By this criterion the Bacteria and their allies should
not be termed cells at all. For me the term "cell" connotes a stage
in the evolution of living beings which the Bacteria have not
reached.

The evolution of the cellular type of structure may be regarded
as the most momentous event in the evolution of living beings
on this globe. As I have pointed out elsewhere,^ the cell, in the
sense in which I use the word, should be regarded as the
starting-point in the evolution of the entire animal and vegetable
kingdoms, the elementary structural component of the bodies of
ordinary plants and animals. Moreover it is probable that the
peculiar phenomena of sex and sexual behaviour did not come
into existence until the cellular type of structure had been
evolved ; in my opinion, without sex there can be no true species
in living organisms.^

^ Presidential Address to the Quekett Microscopical Club, 191 1.

' In the course of the discussion, my views with regard to the fundamental
importance of chromatin in all living substance were criticised by Prof. MacDonald
on the ground that some of the most essential and important activities of the
human body were due to purely cytoplasmic structures, as for example all muscular
and nervous mechanisms. I am well aware that in the course of evolution of the
cell and of its adaptation to various functions, the cytoplasm becomes of great
importance and shows an amount of structural differentiation in excess of that
exhibited (visibly at least) in the nucleus. It is not necessary to take cells of the
human body as examples of this ; the ciliate infusoria furnish instances of cells
far more complicated in structure than any found in the human body. It seems to
me, however, that any attempt to gain a notion of the most primitive type of living
being must begin by seekmg to discover what, if anything, is common to all forms,
moods or shapes of life, rather than by dealing with the complex structures

308 SCIENCE PROGRESS

Having stated my views with regard to the nature of the
earhest forms of life, we may now consider briefly the possible
origin of the primitive living organism. Here, however, we find
ourselves at once on uncertain ground, where the obscurity
which the present state of our knowledge cannot penetrate
makes it as easy to frame vague hypotheses and speculations as
it is difficult to find any solid basis upon which to take a firm
stand. Almost all that we can do with any profit is to limit to a
certain extent the possibilities of the problem by means of certain
propositions, for the most part of a negative order and therefore
not a very sure foundation for deductions. Thus from the
conclusions of astronomers and physicists with regard to the
past history of our solar system, it appears highly probable that
the terrestrial globe was once an incandescent mass at a tempera-
ture very much higher than that at which life of any kind can
exist ; consequently there must have been a period at which
there could have been no living things on the earth. On the
other hand, from all scientific experience it appears to be an
established truth, so far as a negative proposition can ever be
established, that living things at the present time are produced
only as the offspring of pre-existing living things and do not
arise de novo. From these two propositions taken together, it
may be concluded that there must have been a period or epoch
of time during which terrestrial life originated. Then there
remain two possibilities, the first that life took origin on the
earth itself, the second that it was brought to our planet in some
way from without.

Biologists, I think, have generally been inclined to favour the
first of these views, namely, that terrestrial life was generated on
the earth itself; physicists, on the other hand (using the word
** physicist " in its widest sense), have been more prone to take the
view that living particles were wafted on to our planet from
interstellar space. It seems to me that the final word in the
matter will lie with the chemists. The main difficulties of the

presented by the most specialised types of living beings. In my opinion there is
only one thing common to all forms of life, to the bacterium as well as to man or
to the oak-tree, that is the chromatin-substance. Further, I do not think that
the evolution of living beings can be considered profitably from the highest forms
downwards and backwards ; it is best worked, in my opinion, in the direction it
must have taken — that is to say, from the simplest and apparently earliest forms of
life onwards to the more complex and specialised.

SPECULATIONS ON THE ORIGIN OF LIFE 309

problem are, first, to understand how the complex protein-com-
pounds of which living bodies are constituted could have arisen
in Nature ; secondly, given the primordial living thing, whatever
it was, how it could have maintained its existence on an
uninhabited earth — that is to say, what it could have fed on.
Both these questions are essentially chemical problems. If
living things first originated on the earth, the complex proteins
composing the living substance must have been synthesised by
some natural process as yet totally unknown ; and the same is
true a fortiori if living matter originated off* the earth. A
terrestrial synthesis of proteins makes the food-problem some-
what less difficult, since it may be supposed, as Lankester has
suggested, that the primtim vivens supported life on the compounds
produced as antecedent stages in its own evolution. On the
other hand, it is almost painful to think of a minute living
creature wafted from infinite space on to an absolutely barren
and sterile earth ; the imagination fails to conceive, with such
guidance as the present state of knowledge supplies, how it
could have got on at all. To obtain light on such questions
requires far greater knowledge than we possess at present, not
only of the chemistry of the proteins but also of the processes
of metabolism and the modes of life of the minuter organisms.
It is my conviction that there is a vast field as yet unexplored
in this direction and that in the future forms of life will be
discovered the very existence of which is as yet unsuspected.
Invisible forms of life are now known to exist the discovery of
which is due solely to the disturbances caused by them as
parasites of ourselves or of other organisms. Is it not then
equally possible that other invisible living things exist which, as
free-living organisms, produce in their environment effects not
as yet perceived by us ?

Many theories have been put forward at different times with
regard to the origin of terrestrial life.^ Without attempting to
give an account of them in any detail, I may summarise briefly
the possibilities that have been suggested. In the first place
there is the extreme view, represented by Arrhenius, that life
has had no origin in finite time but has existed from all eternity
and is coeval with matter and energy— that is to say, that in any
period of time to which we can throw our thoughts back,
matter, energy and life in some form existed in the universe.
^ See further my Presidential Address to the Quekett Microscopical Club, 1912

3IO SCIENCE PROGRESS

The acceptance of this view puts an end to any speculation on
the origin of life ; it then simply cannot be discussed at all.
On the other hand, the belief is far more prevalent, I think,
at least among biologists, that living matter in some form or
other arose at some time from that which was not living. In
that case there are two further possibilities : first, that life
originated on the globe only at some particular period of the
earth's history, under special conditions of some kind which
do not now exist ; secondly, that the conditions under
which life is generated exist always and that new life can be
produced in the present or future as well as in the past.

If life arose from not-living materials at any time on our
planet, its origin is a matter not only for discussion but for
investigation and experiment. For even if it arose under con-
ditions not existing now in Nature, there seems to be no reason
why such conditions should not be reproduced artificially.
On the other hand, it seems much more reasonable to suppose,
as pointed out by the President in his address, that the con-
ditions under which life first appeared on the earth were not
different from those now existing ; consequently, that if life has
arisen once de novo on the earth, it can do so again at any time,
past, present or future.

Why then do we not see new forms of life appearing on the
earth? In the first place, I doubt very much if we are ac-
quainted as yet with the simplest forms of life or should be
able to recognise them or be aware of their existence at their
first appearance. But apart from that, there is another thing
to be taken into consideration, as pointed out by Dr. F. J.
Allen at the meeting of the British Association in 1896, namely,
that if those substances, whatever they may be, which consti-
tute the simplest form of living matter or the transitional
stage between the living and the not-living were generated
now in Nature, they would almost certainly become the prey or
the food of some more highly specialised type of existing living
being. From this consideration it follows that the evolution of
life on the earth could have had only one starting-point. Just as
the dominance on the earth at the present time of an intelligent
animal, Man, would prevent the evolution of another animal
equally intelligent ; so, when once specialised types of living
beings had been evolved, a later generation and evolution of
life on the earth would have been impossible. In other words,

SPECULATIONS ON THE ORIGIN OF LIFE 311

the origin of the totality of living beings, as known to us, was a
historical event which cannot be repeated on the earth unless
by some means all existing terrestrial life be destroyed and a
fresh start permitted on the tabula rasa of the earth's surface.

But even if this conclusion be granted, the origin of life
would remain still a subject for investigation and experiment :
for if the conditions for generating new life exist in Nature, it is
conceivable that they can be reproduced in the laboratory ; and
if the only check to renewed generation of living matter in
Nature be the existence of specialised forms of living beings,
that is a check which could easily be removed in an artificial
environment.

It must, however, be pointed out that all these conclusions
are purely speculative and hypothetical, resting upon no sure
basis of established fact but assuming the occurrence of pro-
cesses of which, as yet, we know nothing whatever. In the
present state of scientific knowledge, our attitude towards the
problem of the origin of life must be one of expectancy, of hope
for more light in the future. At the point at which we stand it
is not possible to frame any hypothesis which can have greater
value than that of a pious belief. Whether it will ever be
possible to advance beyond this point in our speculations the
future alone can show.

THE ORIGIN OF LIFE : A CHEMIST'S

FANTASY

*' Behold, the beginning of philosophy is the observation of how men con-
tradict each other and the search whence cometh this contradiction and the
censure and mistrust of bare opinion. And it is an inquiry into that which
seems, whether it rightly seems ; and the discovery of a certain rule, even as
we have found a balance for weights and a plumb-line for straight and crooked.
This is the beginning of philosophy." — EPICTETUS.

The Presidential Address delivered recently to the British
Association at Dundee by Prof. Schafer and the subsequent
independent discussion, at a joint sitting of the Physiological
and Zoological Sections of the Association, of the subject
considered in the President's discourse will at least have served
as a corrective to the wave of vitalism that has passed over
society of late years, owing to the pervasive eloquence of Bergson
and other writers who have elected to discuss the problems
of life, mainly from the metaphysical and psychological points
of view, with little reference to the knowledge gained by
experimental inquiry.

As Prof. Schafer himself remarked, the problem of the
Origin of Life is at root a chemical problem. It is somewhat
surprising, therefore, that the chemists were not invited to join
in the debate at Dundee : judging from the remarks that fell
from several of the speakers, their sobering presence was by
no means unnecessary ; it is clear that, so long as biologists are
satisfied with the modicum of chemistry which is now held to
serve their purpose, they will never be able to escape from
the region of vague surmise.

On the Tuesday Prof. Macallum fancifully pictured the earth
as at one time " a gigantic laboratory where there had been
a play of tremendous forces, notably electricity, which might
have produced millions of times organisms that survived but a
few hours but in which also, by a favourable conjunction of
those forces, what we now call life might have come into exist-
ence." 1 think I heard him then refer to the great stores of

312

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 313

oil we now possess and imply that they came into existence
in those times. Chemists and geologists would be in agree-
ment, I believe, that these oils were formed at a somewhat
late geological epoch and that they are derived from fatty
materials laid down as remains of organisms.

Prof. Benjamin Moore, brimming over with biotic energy,
afterwards told us that " something more than structure was
necessary for life." He preferred a dynamic view which em-
braced energy, motion and change ... all the actions of the
cell were concerned with the liberation of energy and its trans-
formation into many forms. For the origin of life ... it was
necessary to start with the formation of organic bodies. The
colloids, which were large aggregates of molecules, began to
show the properties of dawning life but it was needful also
to get an energy transformer attached to the colloid. He also
insisted that " the problem was metaphysical at the present
moment, as through all the ages the process of life was going
on. As soon as the colloids got under the influence of sunlight
they started synthesising organic bodies. That process was
going on now."

In making such statements Prof. Moore allowed his imagi-
nation to run away with him ; his assertions cannot be justified.
Vague, sweeping generalities are out of place in such a dis-
cussion. Unless the steps be made clear, there can be no logic
in the argument.

No doubt something more than structure is necessary for
life. Nevertheless life is dependent on structure — just as is
the activity of the steam-engine. The steam-engine is essen-
tially a dynamic machine : it lives only when fuel is burnt
under its boiler ; but the energy liberated in combustion is
brought into action through the agency of a complex mechanism.
And it is worth noting that by a slight extension of this
mechanism the engine may be made to *' remember " and even
talk. Thus, if it be caused to draw a steel tape across the
magnetic pole of a telephone while the drum of the instrument
is being talked at, the message is taken down by the tape ;
if the tape be then drawn back in the reverse direction, the
drum of the telephone will speak and deliver the message
remembered in the tape. Surely such an analogy with life is
worth considering. Of course it will be said that the engine
is fashioned by an intelligence external to itself and if we

314 SCIENCE PROGRESS

suppose that life may have been self-constituted, to obtain a
hearing, we must discover the means of self-constitution.

Sir William Tilden, in a letter to The Times (September lo,
191 2), after referring to the various raw materials available on
the earth, remarks : " I venture to think that no chemist will
be prepared to suggest a process by which, from the inter-
action of such materials, anything approaching a substance of
the nature of a proteid could be formed or, if by a complex
series of changes a compound of this kind were conceivably
produced, that it would present the characters of living proto-
plasm." He appears to deprecate discussion of the problem,
judging from the concluding sentence of his letter:

**Far be it from any man of science to affirm that any given
set of phenomena is not a fit subject of inquiry and that there
is any limit to what may be revealed in answer to systematic
and well-directed investigation. In the present instance, how-
ever, it appears to me that this is not a field for the chemist
nor one in which chemistry is likely to aff'ord any assistance
whatever."

I agree with Sir William Tilden that Prof. Schafer's address
** leaves us exactly where we were " and that the " earlier
part of the discourse leaves open the question as to a criterion
by. which living may be distinguished from non-living matter."
But I cannot accept his statement that "we have at present,
therefore, no clear idea as to what life is and thereifore no
clear road open to the study of the conditions under which it
originated."

Like Prof Schafer, I do not find myself in the least helped
by the idea that life has originated elsewhere — by adopting such
a conclusion we only shift the difficulty a stage further back. I
agree too with Prof Minchin in thinking, that if life had reached us
from other worlds it would have found our earth unprepared to
receive it and would have been starved out of existence ; this
question of food supply has not been taken into consideration by
the advocates of the hypothesis. If there be life elsewhere, on
other worlds than ours, the probability is that it more or less
resembles life as we know it. To judge from spectroscopic
evidence, the materials of which our world consists are those
which constitute the cosmos. There is but one element in
which the potency of life can be said to exist — the element
carbon ; the complexities and variations which are met with in

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 315

animate material are only possible apparently in a material of
which carbon is the essential constituent. Carbon stands alone
among the elements. It is the only one known to us whose
atoms hang together in large numbers and can be arranged
in a great variety of patterns. The peculiarities of animate
matter may certainly be said to be in large measure determined
by the presence of carbon, though nitrogen and oxygen, of
course, play an all-important part. Our peculiarities may well
prove to be traceable ultimately to those of the elements of which
we are built — indeed it cannot well be otherwise — yet the
difference must be vast between elementary material and living
material. It is waste of time, I believe, to pay much attention to
the argument from analogy ; indeed I feel that Prof. Schafer
relied too much on analogy in the earlier part of his address.

As Dr. Haldane points out — " Living organisms are dis-
tinguished from everything else that we at present know by
the fact that they maintain and reproduce themselves with
their characteristic structure and activities. Nothing resembling
this phenomenon is at present known to us in the inorganic
world." I do not understand, however, why he goes on to say,
" and if, as we may confidently hope, similar phenomena are
ultimately found in what we at present call the inorganic world,
our present conception of that world as a mere world of matter
would be completely altered." Of course it would but the
eventuality is one that I, as a chemist, cannot contemplate as
possible ; far from having confident hope, I believe such
discovery to be out of the question.

Prof. Schafer says the contention is fallacious that growth and
reproduction are properties possessed only by living bodies and
refers to the growth of crystals — but in this and not a few other
cases, as I have said, he carries the argument from analogy too
far. The growth of crystals is a process of mere apposition of
like simple units, which become assembled, time after time, in
similar fashion like so many bricks ; and there is no limit to
crystal growth; given proper conditions, large crystals in-
evitably increase at the expense of the smaller similar crystals
present along with them in a solution — hence it is that occasion-
ally in Nature crystals are met with of huge size. The
multiplication of similar crystals is the consequence of the
presence of a multiplicity of nuclei in a solution ; nothing
corresponding to cell division is ever observed in cases of

3i6 SCIENCE PROGRESS

inorganic growth. Organic growth is clearly a process of
extreme complexity, one that involves the association by a
variety of operations of a whole series of diverse units.

It is impossible to regard demonstrations such as Leduc has
given with silica and other simple colloids as in any way
comparable with the phenomena of organic growth.

Moreover, Loeb's experiments are wrongly quoted by
Schafer as instances of sexual reproduction — what Loeb has
done has been to show that the life cycle may be started afresh
by the introduction of an excitant into the ovum and has thereby
shown that the process of fertilisation by the spermatozoon is
one in which at least two events are scored — the one being the
incorporation of male elements with female elements, whereby
biparental inheritance is secured ; the other the introduction of
an excitant (hormone) which conditions the renewal of the vital
cycle of the organism — but the development is that of an in-
complete being whose somatic cells lack half the normal
number of chromosomes.

Three years ago, in my iaddress to Section B of the British
Association at Winnipeg, I had the temerity to do what Sir
William Tilden says no chemist will be prepared to do — as
witness the following passage :

" The general similarity of structure throughout organised cre-
ation may well be conditioned primarily by properties inherent in
the materials of which all living things are composed — of carbon,
of oxygen, of nitrogen, of hydrogen, of phosphorus, of sulphur.
At some early period, however, the possibilities became limited
and directed processes became the order of the day. From that
time onward the chemistry prevailing in organic nature became
a far simpler chemistry than that of the laboratory ; the
possibilities were diminished, the certainties of a definite line of
action were increased. How this came about it is impossible to
say ; mere accident may have led to it. Thus we may assume
that some relatively simple asymmetric substance was produced
by the fortuitous occurrence of a change under conditions such
as obtain in our laboratories and that consequently the
enantiomorphous isomeric forms of equal opposite activity were
produced in equal amount. We may suppose that a pool con-
taining such material having been dried up dust of molecular
fineness was dispersed ; such dust falling into other similar pools
near the crystallisation point may well have conditioned the
separation of only one of the two isomeric forms present in the
liquid. A separation having been once effected in this manner,
assuming the substance to be one which could influence its own

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 317

formation, one form rather than the other might have been pro-
duced. An active substance thus generated and selected out
might then become the origin of a series of asymmetric syntheses.
How the complicated series of changes which constitute life may
have arisen we cannot even guess at present; but when we
contemplate the inherent simplicity of chemical change and bear
in mind that life seems but to depend on the simultaneous
occurrence of a series of changes of a somewhat diverse order, it
does not appear to be beyond the bounds of possibility to arrive
at a broad understanding of the method of life. Nor are we likely
to be misled into thinking that we can so arrange the conditions
as to control and reproduce it ; the series of lucky accidents
which seem to be required for arrangements of such complexity to
be entered upon is so infinitely great."

It is permissible now, perhaps, to enter somewhat more at
length into an explanation of the changes contemplated in this
passage.

Growth most certainly proceeds on determined lines —
" directive influences are the paramount influences at work in
building up living tissues " (Winnipeg address). What Prof.
Schafer has not pointed out, in contrasting the growth of
inorganic and of animal matter, is that Nature now works on
very narrow lines, making use of but little of the wealth of
material primarily at her disposal. Selective influences must
have been at work from the earliest stages of the evolution of
life onwards. It is in this respect perhaps more than any other
that the inorganic differs so greatly from the organic ; it is this
circumstance too more than any other which makes it so
improbable that life should arise frequently de novo from simple
materials not themselves the products of vital action.

To give an example, the hexose, glucose — a constituent of
every plant and animal — is one of sixteen isomeric compounds,
all represented by the formula

CHa(OH) . CH(OH) . CH(OH) . CH(OH) . CH(OH) . COH.

Of these sixteen compounds, fourteen have actually been pre-
pared in the laboratory and they differ considerably in
properties. The differences are due to the different distribution
in space of the H and OH groups relatively to the carbon
atoms. The sixteen compounds form eight pairs and as the
individual members of each pair have the power of rotating
polarised light in opposite directions, though to an equal

3i8 SCIENCE PROGRESS

extent, they may be said to be half right-hand and half
left-hand material.

Two other hexose sugars isomeric with glucose occur
naturally — galactose and mannose ; but the three compounds all
belong to the one series and all may be said to be right-hand
material.

Besides these three hexose sugars, plants also contain the
ketose, fructose, which is isomeric with glucose and differs from
it only in containing the CO group as the second instead of as
the terminal member in the chain of radicles composing the
molecule :

CH.(OH) . CH(OH) . CH(OH) . CH(OH) . CO . CH^ . OH.

Fructose is convertible into glucose and vice versa. Natural
fructose and glucose are both right-hand material. Nature
apparently is single-handed and can make and wear only right-
hand gloves.

It is possible to prepare such compounds in the laboratory
from the simplest materials, starting from carbonic acid —
CO(OH)2 — the compound from which the plant derives carbon.
By reduction this is first converted into formaldehyde, COH2.
When digested with weak alkali, this aldehyde is in part
converted into fructose ; the fructose that is formed, however, is
not merely the form which is found in plants but a mixture of
this with an equal proportion of the left-hand form. When the
chemist makes gloves, he usually cannot help making them in
pairs for both hands.

Some directive influence is clearly at work in the plant —
the formaldehyde molecules, which it undoubtedly makes use
of as primary building material, in some way become so ar-
ranged that when they interact they give only the right-hand
form of sugar ; there is reason to think, moreover, that the
action takes place only in this one direction — that the sugar is
the only product. My own belief is that the synthesis is
effected against a sugar template^ just as a brick arch is built
upon a wooden template curved as the arch is to be curved.

A similar argument -is applicable to the albuminoid or
protein matters derived from animal and vegetable materials ; in
fact, to nearly all the natural optically active substances : these
are all formed under directive influences. It is not improbable

^ Proceedings of the Royal Society^ 1904, vol. 73, 541.

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 319

that, excepting a few which presumably are products of retro-
grade changes, they are all of one type — right-hand material ;
and apparently they stand in close genetic connexion.

Prof. Minchin has difficulty, he says, in understanding how
the complex proteins could have arisen in Nature. But the
difficulty in accounting for these is no greater than that involved
in accounting for the formation of the sugars. The chief differ-
ence between the two classes of compound is that whereas the
sugars are composed of like simple units, the albuminoids consist
of unlike simple units, chiefly the various amino-acids. The
carbohydrate may be compared with a house built of bricks
alone, the albuminoids with a house built partly of bricks and
partly of stone slabs of various shapes and sizes ; the latter form
of construction permits of a greater variety of pattern but the
same building operations are involved in the use of the two kinds
of material : though the constructive units are different, in both
cases, the pieces are placed in position and fixed by means of
mortar in a similar way.

The directive influences at work and which preside over
synthetic operations in the plant and animal cell are un-
doubtedly the enzymes : these apparently serve as templates
and either promote synthesis by dehydration or the reverse
change of hydrolysis, according as the degree of concentration
is varied.

But how, it will be asked, could action have taken place in
times prior to the existence of enzymes? What are enzymes and
how did they arise ?

The activity of enzymes is comparable with that of acids and
alkalies, the former especially, with the exception that enzymes
act selectively; but whereas acids will hydrolyse every kind of
ethereal compound and are active in proportion to their strength
and the concentration of the solution in which they are
operative, enzymes will act only on particular compounds: hence
their special value as ** vital " agents. And the same distinction
is to be made with respect to the synthetic activity of the two
groups of agents.

At present our knowledge of enzymes is vague : we know
little of their structure. At most we can assert that they are
colloid materials and that in some way or other they are
adaptable to the compounds upon which they act. The picture '
I form of an enzyme is that of a minute droplet of jelly to which
21

320 SCIENCE PROGRESS

is attached a protuberance very closely resembling if not
identical with the group to which the enzyme can be affixed.
A geometer caterpillar attached by its hind legs to a twig, with
body raised so as to bring the mouth against a leaf on the twig,
affords a rough analogy, to my thinking, of the system within
which and within which alone an enzyme is active.

In the beginning of things, carbonic acid was doubtless
superabundant and reducing agents were not far to seek :
under such conditions formaldehyde may well have been an
abundant natural product. The production of fructose sugar, if
not of glucose, would be practically a necessary sequence to that
of formaldehyde.

But at this early stage, under natural conditions, gloves were
always made in pairs, left-hand and right-hand in equal
numbers ; by chance, somewhere, something happened by which
the balance was disturbed : some of the left-hand gloves were
destroyed perhaps.

It is well known that if a crystal be placed in a saturated
solution of its own substance, the surface molecules will attract
like molecules from the solution and the crystal will grow. It
is not unlikely that a substance may exercise attraction over
molecules which are its own proximate constituents — that
glucose, for example, may exercise a preferential attraction over
molecules of formaldehyde ; if such be the case, glucose may itself
serve to influence and promote the formation of glucose from
formaldehyde.

Granting such a possibility, if by some accident right-hand
molecules preponderated in a solution in which the conditions
were favourable to the synthesis of new molecules, the influence
of pattern would prevail and a larger proportion of right-hand
material would be formed. In course of time the left-hand
material would die out and only right-hand material would be
present — as in the world to-day. The argument is applicable
to compounds generally.

Even the formation of enzymes may be accounted for.
Under the influence of acid or alkali, colloid particles may
well have entered into association with this or that group.
But when once formed fortuitously enzymes probably would
become the models or templates upon which new molecules
would be formed, much after the manner of the dressmaker's
model upon which the dress bodice is fashioned.

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 321

But it will be said—" Granted even that simple substances
can be formed in such ways, surely it is impossible to account
for the production of protoplasm." No doubt, this is difficult,
especially as the thing we are asked to account for cannot be
defined. I am tempted here again to quote Epictetus :

"Whence then shall we make a beginning? If you will
consider this with me, I shall say first that you must attend
to the sense of words."

" So I do not now understand them ?"

" You do not."

" How^ then do I use them ?"

"As the unlettered use written words or as cattle use
appearances; for the use is one thing and understanding
another. But if you think you understand, then take my
w^ord you will and let us try ourselves whether we under-
stand it."

The word protoplasm means so little to most people, so
much to a few. It is the convenient cloak of an appalling
amount of ignorance — perhaps the scientific equivalent of the
" Don't'fidget, child," addressed to the too inquiring youngster or
the biological paraphrase of the older chemist's catalytic action.

Is protoplasm one or many things ? A medium or a sub-
stance. In saying that " Living substance or protoplasm takes
the form of a colloidal solution. In this solution the colloids
are associated with crystalloids which are either free in the
solution or attached to the molecules of the colloids," Prof.
Schafer scarcely helps us to a definition. Nor are his later
suggestions much more helpful. Speaking of the differential
septum by which living substance is usually surrounded, he
says : " This film serves the purpose of an osmotic membrane,
permitting of exchanges by diffusion between the colloid solu-
tion constituting the protoplasm and the circumambient medium
in which it lives. Other similar films or membranes occur in
the interior of protoplasm."

One thing only is certain— that protoplasm cannot be a
solution or anything approaching to a solution in character:
diverse structure it must have, structure of infinite delicacy and
complexity.

Judging from his reference to the simplicity of nuclear
material, it would seem that Prof. Schafer is prepared to
regard protoplasm as by no means very complex. But it is
inconceivable that the germ plasm, carrying within itself as

322 SCIENCE PROGRESS

it apparently does all the formative elements of the complete
organism, should be simple in structure. It must contain a
complete series of interconnected templates from which growth
can proceed. I have elsewhere stated that protoplasm may
be pictured as made up of a large number of curls, like a
judge's wig, all in communication through some centre, con-
nected here and there perhaps also by lateral bonds of union.
If such a point of view be accepted, it is possible to account
for the occurrence, in some sections, of the complex interchanges
which involve work being done upon the substances there
brought into interaction, the necessary energy being drawn
from some other part of the complex where the interchanges
involve a development of energy (Winnipeg Address).

My metaphorical wig as a whole may be taken as repre-
senting the racial type — the curls as corresponding to separate
characters.

I can imagine so complex a structure being formed by a
series of fortuitous accidents in course of time but taking into
account the extraordinary fixity of natural types, so well
expressed in Tennyson's lines :

So careful of the type she seems,
So careless of the single life,

it seems to me improbable that a like series of accidents should
recur. It is on grounds such as these that I cannot accord
my sympathy to statements such as Dr. Bastian has made and
that I cannot accept the suggestion put forward by Prof. Schafer
that life conceivably is arising de novo at the present day, let
alone that it is the easy process suggested so light-heartedly
by Prof. Moore. Where are the materials? Can we say that
they exist anywhere ?

It is useless for biologists to live in a higher empyrean of
their own and to disregard the minuter details which chemical
study alone can unravel : they will never be able to solve the
complex problems of life or even to grasp their significance
unless they pay more attention to the ways in which building
stones are shaped and mortar made and in which edifices are
gradually reared from such materials.

I have no desire to take exception to the general trend of
Prof. Schafer's address but I cannot help thinking that he
altogether underrates the complexity of vital chemical pro-

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 323

cesses ; while believing that, as he says, " we may fairly
conclude that all changes in living substance are brought
about by ordinary chemical and physical forces " and that
"at the best, vitalism explains nothing," I am in no way
prepared to underrate the difficulties before us in finding
satisfactory explanations of the Origin of Life.

I see no reason to suppose that life may be originating
de novo at the present time nor do I believe that we shall
ever succeed in effecting the synthesis of living matter.

With regard to Prof. Moore's statement that all the actions
of the cell are concerned with the liberation of energy and its
transformation into many forms — there is nothing to show that
the forms of energy that are operative during life are in any
way peculiar. Energy is inherent in matter : apparently its
primary form is that known to us as electrical energy; and
inasmuch as Faraday's dictum that chemical affinity and elec-
tricity are forms of the same power is incontrovertible, more-
over as electricity in its passage through matter is frittered
down into heat, the mechanical effects associated with life
are easily accounted for. As to the origin of consciousness
and of psychical phenomena generally, we know nothing — at
most we can assert that we arc conscious of consciousness.
The effects of consciousness may well be the outcome of
simple mechanical displacements of molecules such as take
place in the steel tape previously referred to in its passage
across a magnetic field varying in intensity. If nervous im-
pulses are conveyed not along continuous tracts but through
the agency of interdigitating fibres, a mere alteration in the
lengths of these fibres would condition a variation of the
impulse ; the actual conductivity of a continuous fibre would
vary also if chemical changes were to take place within its
substance. It is easy to see how chemical changes occurring
within a nerve or muscle cell would involve an alteration in
the osmotic state, which would necessarily be followed by the
influx or efflux of water, according as the alteration involved
an increase or diminution of the number ot molecules in
solution. Oscillatory hydraulic changes of this type may well
be at the bottom of both nervous and muscular activity in the
organism ; in fact, there is every reason to believe that we are
but hydraulic engines.

324 SCIENCE PROGRESS

According to Prof. Moore, the colloid shows the properties
of dawning life; whatever this may mean, I understand him to
say hat to make it live, it is necessary to get an energy trans-
former attached to it. It is surprising how little life there is in
those who live, how slowly lessons are learnt. The conditions
which determine the transformations of energy were laid down
generations ago by Faraday — but are disregarded to the present
day. There is little that is mysterious about them ; all that is
required is a proper arrangement of parts. To give an example,
a lump of zinc in diluted sulphuric acid constitutes a binary
system brimful of latent energy — of energy awaiting trans-
ormation but untransformable so long as the system remains
binary ; on coupling the conjoined metal and acid by means of
a relatively electronegative conductor, however, interaction at
once sets in, the metal attacks the acid and the acid the metal
and energy is set free — primarily as electricity, secondarily as
heat. Nothing can stop the transformation if the ternary
system be constituted. Apparently no special energy trans-
former is required but merely a proper arrangement of parts —
given the proper arrangement, action is bound to take place,
provided always that the system be one in which there is an
overplus of energy.

And here comes the rub. In the case of organisms, not a
few changes take place which can only occur if energy be
supplied. The assimilation of carbon by plants is a case in
point : ordinarily this is effected through the agency of sunlight;
but it is clear that in some cases, as in the fermentation of
sugar, for example, energy set free in a change taking place in
one part of a complex molecule may serve to make up a
deficiency preventing the spontaneous occurrence of a change
of the reverse order in another part of the molecule. It is an
important office of the protoplasmic complex apparently to
** negotiate " such exchange or transference of energy.

With reference to Dr. Haldane's statement that we cannot
express the observed facts by means of physical and chemical
conceptions but must have recourse to the conception of organic
unity — I am at a loss in the first place to understand what this
conception is, if it be inconsistent with chemical conceptions.
I am afraid the vague indeterminate phrases of the philosopher
make little appeal to the hard heart of the fact worshipper.

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 325

My position is that while we do not attempt to account for that
we do not understand or cannot express clearly, all that we do
understand is well within our compass to explain ; moreover,
that our power of understanding is growing every day.

I do not see how Prof. Schafer and those of us who are with
him can be said to have ignored the actual fact of the mainten-
ance in " organic unity " of the numerous physical and chemical
processes which we can distinguish within the living body.
It is far from being the fact that— "The more detailed and exact
our knowledge has become of the marvellous intricacies of
structure and function within the living body the more difficult
or rather the more completely impossible has any physico-
chemical theory of nutrition and reproduction become." Or that
" the difficulty stands out in its fullest prominence in connexion
with the phenomena of reproduction and heredity."

To make my meaning clear, let me go back to my wig.
Assuming the primordial wig to have come into existence
through a series of lucky, fortuitous accidents, assisted by
certain peculiarities inherent in the primary material and
favoured by the special conditions of the environment — wigs
have ever since been made much on the pattern of the first wig
though variations have taken place from time to time.

Each new wig is constructed on top of an old wig and when
a new wig is ready, " division " takes place and the new wig is
removed to a new ** cell " together with a supply of tools and
materials required for wig-making. According to the material
available, while the general pattern is maintained intact, varia-
tions may be introduced into individual curls. But two kinds
of wigs are to be thought of : simple wigs — male and female —
and compound wigs, the latter being made by superposing two
simple wigs after 'such alterations have been made in each
as to permit of their superposition : obviously, when the com-
pound wigs are separated and worn as simple wigs, the new
simple wigs differ somewhat from the old though they are very
like them in general character ; also it will be clear that all sorts
of combinations of simple wigs may be made.

Obviously my metaphorical wigs correspond to nuclei and
the tools and materials used in making them to the cytoplasmic
elements — assuming that the nucleus is the formative element
of the cell. Having thus put wigs on the green, I trust that
I have met the challenge given by Dr. Haldane and that it will

326 SCIENCE PROGRESS

be obvious that even the problems of reproduction and heredity,
if not those of immunity, may be dealt with from some such
point of view as that I have ventured to state.

The assertion has been made ^ recently that the scientific
world "is beginning on all sides to admit the necessity for
postulating the co-operation of some ' outside ' factor. Lodge
in England, Bergson in France and Driesch in German}^ are the
most conspicuous apostles of the new movement."

This is but one of the many such statements made of late.
An apostle after all is but a messenger and the character of a
message depends a good deal on the instruction the messenger
has received, though imagination may contribute a good deal
to its ultimate adornment. The messages delivered to the
public on such a subject are apt to be somewhat imaginary.
It is clear that they cannot be even an approximation to truth,
when no notice is taken by those who convey them of the
results achieved by the toiling workers in the distant adits of
the mine of science. Philosophers must go to school and
study in the purlieus of experimental science, if they desire to
speak with authority on these matters.

Here again I am served by the old Greek cynic — " The
beginning of philosophy, at least with those who lay hold of it
as they ought, is the consciousness of their own feebleness and
incapacity in respect of necessary things." Such sayings make
us wonder at the lack of appreciation displayed by the Sage of
Chelsea in making Sartor say : " The ' Enchiridion of Epictetus*
I had ever with me, often as my sole companion, and regret to
mention that the nourishment it yielded was trifling." But he
too was a philosopher.

After telling us that the cell is now defined as a vital unit
consisting of an individual mass of the living substance proto-
plasm containing at least one nucleus ; and that the proto-
plasm of an ordinary cell is differentiated into two distinct
components — the cytoplasm or body-plasm and the nucleus —
Prof. Minchin raises the question whether the cytoplasm or the
nucleus is to be regarded as the more primitive. He cannot
conceive, he says, that the earliest living creature could have
come into existence as a complex cell, with nucleus and cyto-
plasm distinct and separate ; and he is forced to believe that
^ " Involution " : by Lord Ernest Hamilton.

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 327

a condition in which a living body consisted only of one form or
type of living matter preceded that in which the body consisted
of two or more structural components.

The issue thus raised is an important one. Regarding the
cell as the vital unit, as ** the simplest protoplasmic organ which
is capable of living alone," in other words, capable of growing
and of reproducing itself, the question I venture to put is whether
life did not begin only when the cell was first constituted,
whether the materials formed prior to this period, however
complex, were not all incoordinated and therefore inanimate.

The term cell unfortunately has had somewhat different
meanings attached to it. At first, as Prof. Minchin tells us, only
the limiting membrane or cell wall was thought of, the fluid or
viscous contents being regarded as of secondary importance ;
the primary meaning, in fact, was that of a little box or capsule.
It then became apparent that the fluid contents were the essential
living part, the cell wall merely an adaptive product of the
contained living substance or protoplasm. Consequently, the
cell was defined as a small mass or corpuscle of the living sub-
stance, which might either surround itself with a cell wall or
remain naked and without any protective envelope. Further
advance involved the recognition of a nucleus as an essential
component of the cell.

I cannot think of a naked mass of protoplasm, call it chromatin
(stainable substance) or what you will, playing the part of an
organism ; at most, I imagine, it would function as yeast zymase
functions.

If it is to grow and be reproduced, the nuclear material must
be shut up along with the appropriate food materials and such
constructive appliances as are required to bring about the associa-
tion of the various elements entering into the structure of the
organism. The enclosure of the naked protoplasmic mass within
a differential septum (cell wall) through which only the simpler
food materials could gain an entry seems to me therefore a
necessary act in the evolution of life. From this point of view,
it matters little which came first — chromatin or cytoplasm.

The argument put forward by Mr. Eccles in support of the
contention that nuclear material is the more primitive, based on
the preponderance of the open chain derivative arginine in the
nucleus and of benzenoid derivatives such as tyrosine in the
cytoplasm, cannot be regarded as vaHd. The difference between

328 SCIENCE PROGRESS

open and closed chain compounds is not such that chemists can
regard one as more primitive than the other, except it be that the
open is the first to receive attention in the text books; and arginine
if not the most, is one of the most complex products hitherto
separated from albuminoid materials, far more so than tyrosine :

Arginme HN = C<^ j^^ ^^^ ^^^ ^^^ CH(NH,) . COOH
Tyrosine HO . QH, . CH^ . CH(NH2) . COOH

Arginine probably owes its value as a nuclear material to the
many points of attachment its nitrogen atoms offer — in other
words, to its complexity.

Professor Minchin would restrict the term cell to organisms
in which the protoplasm is differentiated into cytoplasm and
nucleus definitely marked off from one another and would there-
fore deny the term cell to Bacteria and their allies. But Bacteria
apparently consist of materials differing but little in complexity
from those met with in higher organisms and they contain a
variety of enzymes. The separation of the nucleus within a
special differential septum would appear merely to mark it off
as a separate factory within which special operations can be
carried on apart from those effected in the cytoplasm ; the
extrusion of nucleoli from the nucleus during the vegetative
stage is particularly significant from this point of view, especially
as the nucleoli within and without the nucleus stain differently.^
The differentiation of the nucleus therefore may be merely a
mark of a higher stage of organisation but to make the distinction
suggested between Bacteria and other forms appears to me to
be unjustifiable.

From the point of view I am advocating, every organism
must possess some kind of nucleus — visible or invisible : some
formative centre around which the various templates assemble
that are active in directing the growth of the organism. The
cell, in other words, is the unit factory and its definition should
be made independent of microscopic appearances.

To conclude. All speculation as to the Origin of Life must
savour of the academic ; it can have no very definite outcome
unless it be verified experimentally and at present it seems

^ See especially " Observations on the history and possible function of the
nucleoli in the vegetative cells of various animals and plants." By C. E. Walker
and Frances M. Tozer, Quart. Journ. Exp, Physiol. 1909, 2, 187.

THE ORIGIN OF LIFE: A CHEMIST'S FANTASY 329

improbable that such verification will be possible. But specula-
tion is none the less legitimate and desirable on account of the
fundamental issues to be considered.

In discussing the problems of heredity, in dealing with disease,
we are groping in the dark so long as we are ignorant of the
precise nature of the vital processes and of the minute details of
organic structure ; no effort should be spared therefore to unravel
these. The results of modern cytological inquiry are very
marvellous but unsatisfactory. We need to know far more of
living material, especially in the vegetative stage ; the chemist
has difficulty in accepting the findings of the morphologist at
their face value, he cannot avoid the feeling that not a few of the
*' structures " described may be artefacts bearing but a distant
resemblance to the living forms, as structure is usually brought
into evidence by staining and this cannot take place until the
differential septa of cells are broken down and rendered perme-
able ; so that the staining and fixing process is one that must be
attended with chemical changes, among which coagulation effects
are to be reckoned. But the appearances in many cases are too
definite, too wonderful, to be mere artefacts.

What is now needed is the combination of the eyes of the
cytologist with those of the chemist and with those of the physio-
logist, the collaboration of the student of external structure and
the student of function. Continued specialisation can only carry
us further away from the goal we are all striving at, though
vaguely — because we have no settled combined scheme of action.

H. E. A.

THE RESCUE OF FARADAY'S ELECTRO-
CHEMICAL RESEARCHES

Some enthusiastic believers in the soul-saving power of edu-
cation and in the possibility of imparting school-learning to
the masses generally may have dreamt of bringing science to
the doors of the public at large but it has remained for Messrs.
Dent & Son to make the actual experiment.

Instead of inviting some more or less obscure individual
to write a cheap, trashy text-book, with commendable foresight
they have republished, as one of the volumes in their well-
known Everyman's Library series, the whole of Faraday's
wonderful electrochemical researches communicated to the
Royal Society of London in the years 1833-4 and 1840 — that
is to say, Nos. Ill to VIII, XVI and XVII, in which the
foundations of electrochemical science were first laid down.
The reprint is from the issue in three volumes of Faraday's
papers published in 1839-55, in which foot-notes were added
to the original papers ; unfortunately the paragraphs have been
renumbered and dates are not attached.

Messrs. Dent & Son have rendered an invaluable service
to the cause of scientific education. It is to be hoped their
venture will meet with the recognition and success it deserves.

No happier choice could possibly have been made. Black's
short essay on Magnesia Alba (Alembic Club Reprints, No. I)
and these early memoirs of Faraday are the most conspicuous
examples of true scientific method it is possible to put before
the student — it is safe to say that the two books, costing to-
gether half a crown, are worth all the elementary text-books
on chemistry put together that are in use at the present day
in school or college.

We would counsel every serious student of science to
possess the volume — to study it line by line, paragraph by
paragraph, if only as a model of literary style and as an ex-
ample of clear, incisive, logical and purposeful writing. Whoever
learns to appreciate the lessons of truth that are conveyed in

330

FARADAY'S ELECTROCHEMICAL RESEARCHES 331

its pages should be fairly proof against the scientific immorality
characteristic of our time. Faraday's transparent honesty of
purpose, his marvellous gift of insight, his wonderfully philo-
sophical mind afford a striking contrast to the dogmatism and
narrowness of outlook which have prevailed of late years,
especially in the field which he was the first to cultivate :
unfortunately the details of his work have long been buried
in oblivion and the lessons to be learnt from him are in no
proper way brought home to the student.

Those who propose to study the memoirs should prepare
themselves by reading a life of the author. The introduction by
which the volume is prefaced is not one specially written for
the occasion but is taken from Tyndall's Faraday as a Dis-
coverer and is scarcely suitable. It is essential to know
something of the man to understand his work, to appreciate
his wonderful performances. His origin, the manner of his
introduction to the Royal Institution, the extraordinary way
in which he trained himself both as chemist and physicist,
before all things his character must all be considered in
connexion with his achievements.

The perfection of his literary style is altogether marvellous.
This is particularly noticeable in the first memoir in the
book — that dealing with the identity of electricities derived
from different sources. The simplicity and directness of the
questions put and at once tested experimentally, the swiftness
and sureness of the attack, the transparent honesty of purpose
maintained throughout the work are wonderful enough, taking
into account the state of knowledge at the time and Faraday's
previous experience; but the purity of diction and the lucid
and logical manner in which the work is described and the
argument developed are even more noteworthy. Polite letter-
writers have served their purpose in the past : if those who
aim at accomplishing scientific work take these memoirs of
Faraday as their model, far fewer complaints will be made in
future of the style of authors of papers on scientific subjects.

It is only necessary to call attention to a few of the plums
in the book. The memoir " On the power of metals and other
solids to induce the combination of gaseous bodies " is one that
should be studied by all who are interested in " catalytic "
phenomena. Little has been added to our knowledge of the sub-
ject which is not either contained or foreshadowed in this essay.

332 SCIENCE PROGRESS

The researches which led to the establishment of Faraday's
law, of course, are classic. The following statement, made in
paragraphs 254, 255 and 260, embodies practically all that can be
said even now, with any degree of conviction, of our knowledge
of the process of electrolysis :

254. " Passing to the consideration of electrochemical decom-
position, it appears to me that the effect is produced by an
internal corpuscular action exerted according to the direction of
the electric current and that it is due to a force either superadded
to or giving direction to the ordinary chemical affinity of the bodies
present. The body under decomposition may be considered as
a mass of acting particles, all those which are included in the
course of the electric current contributing to the final effect ;
and it is because the ordinary chemical affinity is relieved,
weakened or partly neutralised by the influence of the electric
current in one direction parallel to the course of the latter and
strengthened or added to in the opposite direction, that the
combining particles have a tendency to pass in opposite courses."

255. "In this view the effect is considered as essentially
dependent upon the mutual chemical affinity of the particles of
opposite kinds. . . ."

260. " I suppose that the effects are due to a modification, by
the electric current, of the chemical affinity of the particles
through or by which that current is passing, giving tnem the
power of acting more forcibly in one direction than in another
and consequently making them travel, by a series of successive
decompositions and recompositions, in opposite directions and
finally causing their expulsion or exclusion at the boundaries of
the body under decomposition, in the direction of the current. . . ."

The discussion " On the source of power in the voltaic pile,"
in which the contact hypothesis is discarded by Faraday, is one
that deserves renewed attention at the present time. Owing to
the fact that Lord Kelvin's great influence was exerted in favour
of direct contact action, the explanation has regained favour —
but it is very doubtful whether the arguments that have been put
forward in support of this view are valid : at least they require
reconsideration. But physicists are now so much concerned
with metaphysics that fundamental problems in electro-
chemistry appear no longer to interest them. The publication
of Faraday's early memoirs may serve, in some measure, to
redeem the situation ; sometimes in set words but always
implicitly he was an advocate of the doctrine that truth is the
one possible foundation of science.

STARCH: A CAPITAL DISCOVERY

It has long been established that starch, the first visible product
of the assimilation of carbon dioxide by plants, is resolved by
the enzymes known collectively as diastase into a mixture of
so-called dextrins and maltose, the isomeride of saccharose or
cane sugar ; acids have a similar effect but by their action the
starch is ultimately reduced to glucose. Starch is represented
empirically by the formula CgHioOs but it must be supposed that
a considerable number of such units are present in its mole-
cule, each derived from a molecule of glucose. The dextrins
apparently are all intermediate in complexity between starch
and maltose ; they are ill-characterised substances and with one
exception have been described as non-crystalline.

Needless to say, knowledge of the structure of starch is of
primary importance but chemists hitherto have met with little
success in their attempts to determine the manner in which the
Ce units are associated. At last, however, light is coming and
again we are helped by the humble Bacillus. It was pointed
out by F. Schardinger, in 1903, that crystalline products might
be obtained from starch by the action of certain Bacteria.
Schardinger then isolated the active organism {Bacillus macerans)
and with its aid succeeded in obtaining an a- and a /Q-dextrin,
which he described somewhat fully.^

Messrs. H. Pringsheim and H. Langhans, who have under-
taken the further study of these compounds, have arrived
recently at results of a striking character.^

Schardinger's a-dextrin dissolves in water to the extent of
17-9 and the /9-dextrin of 176 per cent, at the laboratory tempera-
ture. The /9-com pound is at least of the complexity indicated
by the formula (C6Hio05)6 ; cryoscopic determinations show that

^ F. Schardinger, Zeitschr. f. d. Untersuch. d. Nahrungs- u. Genussmittel, 6,
874(1903)- Wiener klinische IVocAensc^rzf / (igoi) Nt. S. Zentralbl. f. Bakterio-
logie und Parasitenkunde, II. Abt. 14, 772 (1905); 19, 161 (1907); 22,98(1909);
29, 188(1911).

' Berichte d. deut. chem. Ges. 191 2, 2533.

333

334 SCIENCE PROGRESS

the a-compound has the formula (CeHioOs)!. When digested
with acetic anhydride and zinc chloride, the two dextrins are
not only acetylated but both apparently yield derivatives of half
the original molecular complexity, the hexasaccharide giving
a non-acetylated trisaccharide and the tetrasaccharide a
hexacetylated disaccharide. The corresponding " saccharides,"
triamylose and diamylose, are obtained on displacing the acetyl
groups by hydrogen : both are crystalline.

Taking into account the composition of the Ce units — the
presence in each of only three hydroxyl groups and of OH2 less
than in glucose — and the fact that both compounds are without
action on Fehling's solution and do not exhibit the phenomena
known as mutarotation, the following formula is a not improbable
representation of the disaccharide :

I o ,

CH . CH(OH) . CH . CH . CH(OH) . CH,(OH)

o< >o

CH2(OH) . CH(OH) . CH . CH . CH(OH) . CH

! O !

It may be hoped that at no distant date, with the aid of data
such as the discovery under consideration affords and concep-
tions such as those introduced by Barlow and Pope, it will be
possible to arrive at a clear representation of the manner in which
the atoms are close-packed even in so complex a molecule as
that of starch.

THE MECHANISM OF INFECTION IN
TUBERCULOSIS

By R. R. ARMSTRONG, B.A., M.B., B.C. (Cantab.), M.R.C.S., L.R.C.P.
Registrar, Hospital for Sick Children, Great Ormond Street, London

*' Si Ton veut bien r^fldchir, d'unepart, aux differences de composition chimique,
meme qualitatives, qui peuvent exister entre deux esp^ces tres voisines, d'autre
part, a I'extraordinaire variete de matieres albuminoides qu'il est aujourd'hui
possible de concevoir, il ne paraitra pas excessif d'assimiler des especes animales
ou des varietes physiologiques d'une meme espece animale a des milieux de culture
varies, analogues k ceux qui m'ont servi pour I'^tude de la bacterie du sorbose,
ni d'expliquer I'immunit^ des unes et la receptivite des autres ^ I'egard d'un
microbe determine par une difference chimique ou seulement ster^ochimique de
leurs parties constituantes.

"Y a-t-il rien de plus suggestif ^ ce point de vue que ces deux bouillons de
levure formes des memes matieres organiques de toutes sortes, des memes bases
m^talliques, des memes acides, mais dont I'un renferme, en outre, de la sorbite et
I'autre de la dulcite ? Quand on y seme la bacterie du sorbose, le premier est
rapidement envahi ; la sorbite fait place a un corps nouveau, doue d'une grande
activite fonctionnelle ; les autres substances disparaissent en meme temps,
entrainees dans la nutrition du microbe. Le second, au contraire, resiste k
I'infection ; la bacterie, d'abord languissante, finit par y mourir sans transformer
ni la dulcite qu'on retrouve tout enti^re, ni, pour ainsi dire, aucune des autres
substances qui I'accompagnent.

*' II doit y avoir le plus qu'une image, peut-6tre un enseignement, dont il
faudra tenir compte dans la lutte contre certaines maladies.

"Apres la belle decouverte du serum antidiphterique, on avait pu croire
terminee I'^re nefaste des microbes pathog^nes, esperer I'arret definitif des
ravages exerces par la tuberculose, le cancer, etc. II n'y avait plus, semblait-il,
qu'k preparer, k I'exemple de Behring et de Roux, un serum contre chacun des
germes morbides. Malheureusement, il a dejk fallu revenir beaucoup sur ces
esp^rances.

" Toutes les maladies, comme toutes les cultures, ne se ressemblent pas. De-
pendant les unes et les autres de deux facteurs essentials : la semence et le
terrain, elles sont subordonn^es aux conditions de rencontre et de convenance de
ces deux facteurs.

"Si la maladie est, comme la culture spontan^e d'un vegetal parasite dans un
liquide ou un terrain vierge, une espece d'accident dont la frequence est limitde
par la rarete du germe, il devient possible, en faisant disparaitre I'organisme
Stranger qui a pris naissance, de revenir a I'etat normal et la proprete du terrain.
C'est ce qu'on peut faire k I'aide des serums dans le cas de la diphterie ou de
la peste.

22 335

336 SCIENCE PROGRESS

" Mais si, au contraire, le mal tient au ddveloppement d'un parasite dont le germe
est si extraordinairement repandu qu'il est impossible d'y soustraire le terrain de
culture, ne vaut-il pas mieux, au lieu de I'extirper sans cesse, agir sur le terrain
meme et le rendre impropre au developpement du parasite ?

" Envisag^e sous cette forme, la lutte centre la tuberculose trouverait peut-etre
a gagner. La medecine reconnait deja chez les individus arthritiques des
circonstances defavorables a revolution du bacille de Koch. N'est-ce pas le
moment d'etudier quelles sont ces circonstances, de chercher s'il n'y a pas la, au
fond, quelque cause d'ordre chimique, quelque chose qui rappelle I'un des bouillons
de tout h I'heure vis-k-vis de la bacterie du sorbose ? " — G. Bertrand (1906).

The Mechanism of Infection in Tuberculosis

A notable extension of the Public Health Act of 1875 made in
May 1911 renders the notification of pulmonary tuberculosis,
when diagnosed in hospital in-patients, a statutory obligation.
By an extension of this Order the notification of all cases of
pulmonary tuberculosis whenever and wherever diagnosed is
now recommended.

The Insurance Act, 191 2, with the terms of which most
people are tolerably familiar, makes provision for the treatment
of such cases in hospitals and goes so far as to provide for
the actual isolation of persons suffering from pulmonary
tuberculosis.

It is admitted by most observers that tuberculous infection,
at least in adults, is the result mainly of invasion by way of
inspired air of the respiratory tract; but it is equally well
known that the tubercle bacillus may gain entry by other
means. Milk contaminated with bacilli from tuberculous cows
and the flesh of animals which show evidence of tuberculosis
are considered to be potent sources of infection.

It is possible, however, that infection through the agency
of milk occupies a more prominent position in the public mind
than the frequency of its incidence warrants. So much, in fact,
has been written on this subject in the daily papers, so many
laws and bye-laws are in force to render the lives of unfortunate
cow-keepers, dairymen and milk-vendors burdensome, that
were it not that individual experience teaches each and all of
us that the danger is vastly over-rated, no sane person to-day
would ever drink raw milk.

Tuberculosis is no uncommon cause of death in young children.
As cows' milk is the staple food of the majority of infants during
the first year of life, a period when the relative death-rate is

MECHANISM OF INFECTION IN TUBERCULOSIS 337

high, by a somewhat questionable process of reasoning some
authorities have placed the blame upon the milk supply.

Inasmuch as our ideas are inevitably the result of impres-
sions received, the result of this insistence has been that not
only the majority of the thinking community but many phy-
sicians and even the Local Government Board authorities them-
selves are persuaded that at least in the case of young children
milk is the prime source of tuberculous infection.

Far more stringent regulations than those applied to milk
control the sale of meat for human food. Beasts showing any
evidence of tuberculosis and carcases in which tuberculous
lesions are present are rigorously condemned by the meat
inspectors.

Milk being entirely derived from bovine sources in our
country and meat very largely so, investigators directed their
attention at an early date to such differences as exist between
tubercle bacilli occurring in the ox and in man.

Distribution of Tuberculosis

No disease is more universally prevalent throughout the
animal kingdom than tuberculosis. A similar disease occurs
in reptiles ; birds also, especially in captivity, are prone to
tuberculous invasion and the avian bacillus has been found
to be possessed of definite characteristics; in fact, all animals
are susceptible to tuberculosis and in the collection of the
Zoological Society, as well as in similar menageries all over
Europe, no disease is more prevalent nor more fatal. Bovines
seem specially susceptible to pulmonary and abdominal tuber-
culosis and sometimes suffer from tuberculous disease of the udder.

Of the smaller mammals — mice, rats, guinea pigs, rabbits,
etc. — used in laboratories for inoculation experiments, the guinea
pig is very readily infected by tuberculous material.

It is scarcely necessary to refer to the great variation in
relative susceptibility to tuberculosis which is noticeable in the
different races of man. Europeans show a high degree of
natural and acquired immunity, whilst the liability to infection
of races which have no previous experience of the disease is
common knowledge. Thus the North American Indians are
said to have been decimated, indeed almost exterminated, by
tuberculosis ; the Sandwich Islanders afford another illustration

338 SCIENCE PROGRESS

of the disastrous activity of the disease when introduced amongst
peoples not previously exposed to its attacks.

On the other hand, the Jewish race is now possessed of a
high degree of natural immunity. Though it cannot be said
that tuberculosis does not attack Jews, the experience gained in
Out-patient Departments of Hospitals for Diseases of the Chest
affords unquestionable proof of the fact that pulmonary tuber-
culosis is of only occasional occurrence amongst them. When
met with in this race, moreover, the disease is rarely fatal but
assumes a chronic, i.e. a mild and slowly progressive form.

The statistics at my disposal of postmortems at the
Children's Hospital, Great Ormond Street, demonstrate equally
clearly the relative immunity from tuberculosis of the children
of Jewish parents. It is possible that the explanation of this
remarkable condition lies in the essentially urban character of
the Jewish race. Since the Fall of Jerusalem, at latest, the
Jews have lived in cities. Through the Middle Ages and
during the last century they have successfully encountered
persecution and squalor in the poorest quarters of the cities
of Europe and have flourished despite the slenderness of the
resources permitted them by the ruling race, owing to their
thrift and their aptitude as traders, in circumstances under
which the less careful indigenous population has gradually
succumbed. As a matter of fact, whilst tuberculosis is always
rife amongst slum populations, the Jewish members remain
practically immune. In fine, one is tempted to hazard the
suggestion that by a rigorous process of natural selection a
race has gradually been evolved possessing so high a degree
of resistance to tuberculosis that at the present day their
freedom from this disease justifies the statement that they are
naturally immune.

How far breast-feeding is responsible for the vigour of the
majority of Jewish children is open to discussion ; at all events,
their example is cited as a point in favour of cows' milk being the
cause of tuberculosis, breast-feeding being far less frequent or
prolonged amongst other races, notably the English.

Enough has been said to make clear the wide distribution of
tuberculosis in the animal kingdom and the extreme variation
in susceptibility to this disease shown by races subjected during
longer or shorter periods to its attacks, as well as the relatively
high mortality from tuberculosis in early life.

MECHANISM OF INFECTION IN TUBERCULOSIS 339

The Mechanism of Infection

Careful consideration of the mechanism of infection is clearly
of the first importance in view of the wide prevalence and heavy
mortality from tuberculosis. When such foods as milk and
meat are implicated as causes of the disease and not only the
health of the community but vast commercial interests are at
stake, the propriety of reviewing the evidence that milk and
meat are the carriers of infection is beyond question.

The matter may well be approached by considering the
lesions of tuberculosis, as they occur in man at the various stages
of his existence, under the varying conditions of function and
environment which attend infancy, adolescence, maturity and
old age.

Few generalisations are more remarkable than the freedom ot
infants from disease other than nutritional disorders during
the first year of life. Marked as this immunity is in breast-
fed infants, it is equally striking in those brought up by hand.

The suggestion has been advanced that by means of the
intimate apposition of foetal and maternal blood which attends
intra-uterine life, the growing embryo obtains from its mother
substances which serve to protect it from the attacks of patho-
genic micro-organisms in the early months of its existence.
These substances, it may be, are of the nature of anti-bodies,
which are preformed by the mother in response to infections
which she from time to time incurs ; or, perhaps, during the
nine months of its foetal existence, the child obtains doses of
the commonly occurring bacterial poisons by diffusion from the
maternal blood.

In response to the stimulation of these toxins, the child
prepares its own anti-bodies, the mother having, in the nature
of the case, previously tempered the virulence of the infection
below the minimum harmful dose by the exercise of her own
protective mechanisms. Even in uiero, cases are recorded of
foetal infection associated with advanced maternal tuberculosis
but these are extremely rare.

I would take this opportunity, however, of insisting that so
far as the acute infectious diseases of childhood are concerned,
milk is not a source of infection in infants, since in children up
to the age of one year they scarcely if ever occur. Furthermore
the epidemic diseases carried by milk are few. The infection of

340 SCIENCE PROGRESS

scarlet fever is frequently conveyed by milk ; that of diphtheria
sometimes ; that of measles {Morbilli) perhaps occasionally and
of German measles (Roteln) seldom. It is open to question if
chicken-pox can be conveyed by milk. Typhoid, it is well
known, is not infrequently attributable to the contamination of
milk with infected water.

Diphtheria is by no means uncommon in babies but more
frequently occurs as a nasal discharge than in its dangerous
membranous form ; in the nasal form of the disease, bacilli are
detected on bacteriological examination but there are no
symptoms other than the discharge. Tuberculosis affects
children of this age far less commonly than later in life and in
cases which I have seen there has commonly been an obvious
source of infection in a mother or attendant suffering from
pulmonary tuberculosis, often in an active form.

By far the commonest form of tubercle in children is that
involving infection of the glands of the neck ; but if postmortem
evidence be a fair guide, tubercle in the bifurcation gland — the
gland situated just below the bifurcation of the trachea into
the two main bronchi — is more common still, there being no
invasion of glands in the neck in many cases. Frequently the
bifurcation gland is the oldest focus found ; more frequently still
the gland is caseous, i.e. shows degeneration as the result of the
prolonged activity of tubercle bacilli.

Next in order may be placed tubercle in the abdominal
glands, particularly the mesenteric glands — the glands which
lie in the goffered, fan-shaped membrane by which the small
intestine is attached to the hinder body-wall — which are the
first to receive the lymph flowing from the gut.

Tubercle of the peritoneum is not uncommon.

Tubercle occurs frequently in bones — caries of the spine
being an outstanding example.

Tubercle of joints, particularly the knee and hip, is common
but it is to be noted that tubercle of the joints really begins not
in the joint but in the part of the bone which is growing most
actively, namely the epiphyseal end— either the upper or lower —
of the shaft of the bone ; it spreads thence to the joint.

A suggestive hypothesis bearing on the incidence of bone
lesions in children is that these parts are, as it w^ere, so busily
occupied with the work of growth and so highly specialised in
this connexion that they possess but little power of resisting

MECHANISM OF INFECTION IN TUBERCULOSIS 341

the attacks of pathogenic micro-organisms. Witness also the
extreme susceptibility of the periosteum of the thigh and shin
bones to acute streptococcal infections. Furthermore, the ends
of the long bones are richly supplied with blood moving through
wide spaces in a comparatively stagnant stream ; bacilli reaching
the bone by this route are pre-eminently liable to lodge amongst
the intricacies of the bony lattice which is being built into the
growing bone. These parts too in children are subject to direct
injury and this is true of the lower limbs to a greater extent than
the upper, a fact in correspondence with the more frequent
incidence of tuberculosis at the hip and knee.

There is no more remarkable nor uniformly fatal form of
tuberculosis in children than acute miliary tuberculosis. In
this disease, tubercle bacilli reach the blood stream in large
numbers and being carried to all parts of the body give rise to
tiny tuberculous foci scattered through every organ, hence the
term miliary— like millet seed. When the brain is also affected,
as is usually the case, we have the condition known as Acute
Hydrocephalus or " Water on the Brain " — called technically
Tuberculous Meningitis.

Much may be learnt from careful consideration of the exact
distribution of the tuberculous lesions in these cases and such
investigation is of special value, seeing that death within three
weeks, seldom longer, is their invariable consequence.

The determining factor in the invasion of the blood by
tubercle bacilli and its dissemination in the vital organs remains
a matter for conjecture. In no way is it correlated with the
number or extent of pre-existing lesions.

It has been my experience in making postmortem examina-
tions of cases of tuberculous meningitis that but one lymphatic
gland or group of glands has shown evidence of tuberculosis.
Occasionally this gland is to be found in the mesentery, in which
case it may be inferred that tubercle bacilli effected an entrance
through the gut : most frequently it occurs in the bifurcation
gland described above, which is often the only seat of tuberculous
infection.

The following case may be quoted in some detail in illustration :

A baby aged eleven months, which had always been fed at
its mother's breast, was brought to hospital with the story
that it had sustained a fall on its head fourteen days before
admission but neither at the time nor during the next few days

342 SCIENCE PROGRESS

seemed any the worse. About five days before bringing it to
the hospital, the mother had noted that though the child took the
breast as vigorously as ever, it vomited suddenly very soon
afterwards ; this sickness continued and the child became very
fretful, especially when disturbed ; later on it was drowsy.
She remarked that it was unusually constipated. The day
before the child was brought to hospital it was attacked by
severe convulsions : soon afterwards it appeared not to recognise
the mother and seemed unable to swallow its food. She herself
was in good health but her husband was suffering from phthisis,
A diagnosis of tuberculous meningitis was made. Despite
treatment, the infant became steadily worse and died a few days
later. At the postmortem, advanced tuberculous degeneration
(caseation) was found in the bifurcation gland. There were
large numbers of very recent, tiny miliary tuberculous
foci present in the lungs, brain and spleen corresponding
in their numerical incidence to the order given above. A
few tubercles were to be seen in the liver, very few in the
kidneys, none at all in the supra-renal nor the pancreas. In
the lower part of the small intestine a few very recent tiny
tuberculous ulcers were found. The heart showed no evidence
of tuberculosis ; the stomach also was unaffected.

The evidence that miliary tuberculosis is spread by the blood
stream and that the tubercle bacilli do settle in blood vessels is
so strong that for the purposes of this article it may be accepted
as proven. Accepting this hypothesis, it is interesting to review
the course of events from the time when the infant first sustained
an attack from tubercle bacilli till its death.

We may safel37 suppose that under the social conditions in
which persons of the hospital patient class live, the husband
shares their couch at night with wife and child. In such intimate
contact, the sleeping babe would inhale tubercle bacilli, as his
father lay wakeful and coughing through the night. It is my
belief, founded on considerations that I shall presently advance,
that tubercle bacilli so inhaled do not, in children at least, lodge
in the upper air passages in sufficient numbers to give rise to
lesions there but that they pass down the windpipe and are
carried along with the strong inspiratory air blast directly into
the ultimate air-cells of the lungs. Such is the known course
taken by bacilli or dust particles when injected into the trachea
under experimental conditions.

MECHANISM OF INFECTION IN TUBERCULOSIS 343

So relatively innocuous are the bacilli of tuberculosis and so
slight is the local disturbance to which they give rise that they
are not held up in the lung, as are the virulent organisms which
cause pneumonia. Becoming ingested by the cells which line
the air-chambers (alveoli) they are passed on into the lymphatics
of the lung and find their way to the glands lying at the
lung root, which act as filters for the lymphatic system. There
apparently they remain, either to be destroyed or perhaps, as in
the case under notice, to give rise to slow degenerative changes
in the gland substance ; the result is the formation of that curious
cheese-like or " caseous " material which is so characteristic of
tuberculous lesions.

The process of infection continues but the lymph-gland
filters prevent bacilli coming from the lungs from entering
the blood stream. As time goes on and the gland substance
is destroyed, bacilli either periodically find their way directly
into the blood coursing through the glands or pass perhaps
by way of the efferent lymphatic channels to the main lymph
ducts and thus reach the blood. The main lymph ducts in
such cases as this do occasionally show tuberculous lesions.

Under normal conditions the bacilli are destroyed in the
blood stream.

So far accurate investigation supports the picture we have
drawn. A day comes, however, when general resistance to
tuberculous invasion is lowered, either through chill or hunger
or by some such shock as the baby under notice received.

Or perhaps tubercle bacilli in the bifurcation gland give
rise to such destruction of tissue that the wall of a small artery
or vein in the gland becomes eroded or infected and tubercle
bacilli pass directly into the blood stream.

It is remarkable that Poirier has shown that veins from the
bifurcation glands — or, as he calls them, the inter-tracheo-
bronchial group— pass directly into the back of the great Inferior
Vena Cava, the main vein from the lower limbs and trunk and
thus enter the heart by the shortest possible route.

In either case, bacilli enter the blood stream in greater
numbers to find there far less resistance to their multiplication
or dissemination than under the conditions of health. Passing
into the venous blood from the bronchial glands directly into
the right auricle of the heart, they are hurried on in the heart's
blood stream into the right ventricle and pumped through the

344 SCIENCE PROGRESS

pulmonary artery into the lungs again. Most bacilli will lodge
where capillary vessels are smallest and the blood stream slow ;
consequently tubercles are found in greatest numbers at the
apex of each lung, where the movements of respiration expand
the lung least and where, therefore, blood is pressed out by the
lung with least force when this expands and the capillaries are
dilated less than elsewhere by lung relaxation during respiration.

But lung capillaries are wide and many tubercle bacilli
escape to return in the bright red oxygenated blood by the wide
pulmonary veins to the left auricle. From the left auricle, the
bacilli pass into the left ventricle and thence are swept in the
full current of arterial blood through wide channels without a
bend or branch by the internal carotid arteries to the brain. On
the base of the brain, the carotid artery bends suddenly to end
abruptly in branches, one of which, the largest — the middle
cerebral — continues the direct line of the carotid blood stream
and passing up the sylvian fissure supplies the surface of the brain.

It is precisely along this vessel that most tubercles are dis-
tributed in the variety of Meningitis which is under considera-
tion. Hard by the spot where the internal carotid springs from
the aorta the vertebral artery arises which supplies the upper
cervical portion of the spinal cord. Correspondingly, the
maximum incidence of tuberculous cerebro-spinal meningitis
falls on the anterior aspect of the cervical spinal cord.

Next in order of infection comes the spleen, itself the blood
filter, subserving a function in respect of the blood exactly
similar to that of the lymphatic glands on the lymph paths.
Elsewhere tubercles are found in all organs in which the blood
channels terminate in minute end-arteries — vessels having no
free communication with their fellows. Consequently miliary
tubercles are found under the capsule of the liver and kidneys.

In miliary tuberculosis I have never seen miliary tubercles
in the supra-renals nor in the pancreas, presumably because
these organs possess wide blood channels in free communi-
cation with each other, as is also the case in the limbs and
body wall.

Of particular interest in the case considered are the small
ulcers in the intestine unassociated with tuberculous deposit in
the intestinal glands.

Presumably, the baby had swallowed tubercle bacilh in
his saliva as well as breathed them into his lungs ; at the

MECHANISM OF INFECTION IN TUBERCULOSIS 345

end of his illness, when his resistance failed, these bacilli
effected a settlement in the intestinal wall and caused ulceration.
Sometimes but far less commonly it happens that the
primary focus from which tubercle bacilli find their way into
the blood is situate in a mesenteric gland, the resting-place of
tubercle bacilli which have reached it from the intestines. In
these cases, the distribution of the bacilli in the miliary tuber-
culosis which ensues still remains identical with that in the
case described — which originated in glands connected with the
respiratory system — and is amenable to a similar explanation.

Pulmonary tuberculosis or Phthisis Pulmonum is by no
means unknown even in very young children. Starting some-
times from a bronchial lymph gland, infected as I have
described, the bacilli attack the wall of an adjacent large air
tube and tubercle bacilli are sucked by the movements of
breathing to all parts of the lung on the affected side, there
giving rise to a tuberculous broncho-pneumonia.

It may happen too that tuberculosis will attack the lungs of a
child recovering from an attack of measles or of whooping-cough.
During adolescence — the years from twelve to eighteen —
attacks of tuberculosis are less frequent or severe. It would
seem that the weakly ones who are either born naturally
susceptible or are unduly subjected to infection from tubercle
bacilli have succumbed and that the survivors are relatively a
hardier race.

At this period of life the young human being becomes to
a large extent independent of its parents' efforts. Learning,
as experience grows, to safeguard himself from unnecessary
fatigue, delighting in a life spent in the open air, his natural
liking for good food in abundance is his surest defence against
an organism which flourishes best on bodies vitiated by star-
vation. At no time is he so keenl}'^ appreciative of all in his
surroundings that is conducive to enjoyment nor will he, at any
other time, experience such freedom from the cares of life and the
overwork which beset later years. Such factors as these are
valid means of defence against an organism certainly as old
as civilised humanity, which has been evolved on lines parallel
with the evolution of man himself, at one time successful in the
struggle, finding suitable soil in races before inexperienced, at
another spreading but slowly amongst peoples long accustomed
to its attacks.

346 SCIENCE PROGRESS

When early maturity is reached, the struggle for existence
becomes keener : overworked and underfed, shielded in many
ways from the invigorating influence of sunlight and fresh air,
both sexes then frequently succumb to the acute forms of
pulmonary tuberculosis.

Two factors inseparably correlated and mutually inter-
acting, namely a virulent infective strain coupled with a
greatly diminished resistance on the part of the host, are
responsible for the grave form of the disease met with under
these conditions.

By far the greater number of such cases of tuberculosis are
pulmonary and the distribution of the lesion usually at the
apices of the lungs may be accounted for by an hypothesis
similar to that above invoked to explain the distribution of
miliary tubercles in the lungs.

It is noteworthy however that in the common inhalation
form of pulmonary disease the lesion is not always accurately
at the apex of the lung but situate slightly below and to the
outer side.

The areas of lung affected earliest in the various lobes
correspond also with accuracy to the distribfution of the main
bronchi, as has recently been pointed out by Dr. Lees.

Diagnosis of Tuberculosis

Pulmonary tuberculosis in very many cases is amenable to
treatment and for this reason early diagnosis is of the first
importance. No surer method exists than the finding of
tubercle bacilli in the expectoration of a phthisical patient but
it is always to be feared that the disease is firmly established
when bacilli are present in sufficient numbers in the sputum to
be detected.

Many tests have been devised to ascertain the presence of a
tuberculous lesion : all are open to objection, particularly in
view of the extreme variation in response which individual
patients show and the consequent difficulty in forming an
accurate estimate of the extent of the lesion, the activity of
the infecting agent and the degree of response of the patient.

Most of the tests are not without risk, in that they are either
productive of immediate harmful effects or so lower the general
resistance of the patient that they may reactivate foci of the
disease previously quiescent. I have personal experience with

MECHANISM OF INFECTION IN TUBERCULOSIS 347

Von Pirquet's reaction alone. The test is carried out by
scarifying the skin and inoculating into the abrasion a small
quantity of Koch's *' Old Tuberculin." The agent is a filtered
glycerin-broth culture of tubercle bacilli from which the bacilli
have been removed by filtration. If the reaction be positive, the
skin in the neighbourhood becomes raised and red, forming a
** papule."

Certain cases of tuberculous infection do not respond to the
test. In miliary tuberculosis and in general tuberculosis, v^^hen
presumably the various defensive mechanisms of the sufferer are
completely overwhelmed by the disease, there is no reaction.

Many cases of abdominal tuberculosis and a large number
of children suffering from tuberculous disease of the spine also
fail to respond. The tubercle bacilli, in these conditions, give
rise to very prolonged illness in which there is little disturb-
ance in the general health of the patient. In consequence,
there seems to be no general reaction on the part of the
children. Von Pirquet's test failing in the absence of the
substances present in the blood of patients reacting to a
tuberculous infection which are responsible for the appearance
of a papule after inoculation.

Tuberculous pleurisy may be cited as an example of a
condition in which there is vigorous positive reaction. In this
disease the onset is sudden, the illness of relatively short
duration ending in recovery.

From these and other considerations based on observations
on the very large number of children suffering from the varied
forms of tuberculosis with which 1 have been associated, I am
inclined to the belief that in childhood, up to the age of ten
years, a positive Von Pirquet's tuberculin reaction indicates
not so much the presence or absence of tuberculosis but is
evidence not only that the patient has recently sustained an
infection from an active strain of tubercle bacilli but that he
is reacting vigorously against it.

In fact, it would seem that a positive reaction in a child suffer-
ing from tuberculosis is, for this reason, of favourable import.

After ten years of age the reaction is of little aid in
diagnosis.

In old age, tuberculosis is not infrequently secondary to
some pre-existing, often chronic, illness and determines its fatal
ending.

348 SCIENCE PROGRESS

Nature of Tuberculous Infection

Having very briefly summarised a few of the more important
results of tuberculous infection in man and indicated their
special incidence in organs and groups of organs at the several
periods of life, it remains to consider each of the several sources
of infection in light of the evidence adduced.

Clearly, tuberculous infection — other than infection of the
skin — enters the body by the air passages or the alimentary
system ; once in the lungs or intestine, the bacilli pass readily
through lymphatic channels and reach lymphatic glands, a
method of spread in many ways characteristic of children.

On the other hand, in adults, infection of the air passages
is common ; infection by way of the gut seldom occurs. Possibly,
the strongly acid character of the gastric juice is normally a
factor in promoting destruction of the bacilli.

When tuberculous ulceration of the intestine occurs in adults,
it is most usually due to infection by the bacilli swarming in
the sputum coughed up and swallowed by patients in the last
stages of pulmonary tuberculosis.

The two possible sources of infection, however, from ingested
food — particularly cows' milk — and inspired air are of import-
ance in children. Food taken into the mouth, after mastication,
is passed through the fauces into the oesophagus and swallowed,
passing across the tonsils on its way to the pharynx.

It is particularly worthy of note that advanced caseating
tuberculosis of the human tonsil is very rare, though caseation
of glands in the neck is by no means uncommon.

Now it has been pointed out by the Commissioners on
Tuberculosis that bacilli isolated from glands in the neck show
bovine'^ characters and in their opinion there is therefore pre-
sumptive evidence that the glands were infected from milk.

Furthermore, in 15 out of a series of 96 cases in children in

1 It should be clearly understood that by bacilli of bovine type is meant bacilli
difficult to cultivate on media in the laboratory, capable of producing fatal disease
rapidly when inoculated into animals ; it is in no way implied that the bacilli are
necessarily derived from oxen. The use of the term in this latter sense in
the Reports has not only misled the Commissioners, but has given fictitious
support to the view that milk is an effective source of tuberculosis in children.
No more unfortunate expression could have been used in discussing an issue
which turns entirely on the question whether or no organisms derived from
cattle have been introduced into the human system.

MECHANISM OF INFECTION IN TUBERCULOSIS 349

which the tonsils showed no signs of tuberculosis to the naked
eye, there was some microscopic evidence of tuberculosis.

Apparently it would seem that a strong case for tuberculous
infection through the agency of milk is hereby established. It
is not without significance, however, that though tuberculosis
is common during the first years of life, particularly in the
second and third years, advanced infection of glands in the
neck is far more rare than at later periods and is seldom present
unassociated with a much older lesion in the glands of the
respiratory tract.

Babies fed at breast or from the bottle must suck to obtain
their food and of necessity naturally breathe through their noses.
On the other hand, older children, from two years upwards,
soon become mouth-breathers.

Whereas air drawn in through the nose never comes into
contact with the tonsils, the reverse is the case in mouth-
breathers, who for this reason are constantly subject to tonsillar
infections.

We are confronted therefore with the fact that, at the age
when nose-breathing and milk-feeding are associated, infection
of the glands in the neck is undoubtedly rare, whilst later on,
when mouth-breathing is more frequent and milk no longer the
only diet, the glands in the neck are frequently invaded by
tubercle.

The evidence of tuberculosis in swine may be referred to
here as appropriate in this connexion. It is universally
admitted that swine are infected owing to their promiscuous
habits of feeding. They suffer from tuberculous ulceration of
the intestine and its associated lymphatic glands. They occa-
sionally show tuberculous tonsillitis and disease of the sub-
maxillary glands together with those which lie behind the
pharynx and in the upper part of the neck. A form of the
disease peculiar to swine is a tuberculosis spreading from
pharynx to mid-ear upwards into the brain. Clearly, therefore,
in cases in which the infection is definitely due to food, the
tonsil is frequently implicated.

On the other hand, dogs and horses, the associates of adult
man, who presumably derive tubercle bacilli from inhaled dust
and the spray distributed by tuberculous stable-hands in cough-
ing, show a large preponderance of infection of the respiratory
tract — in the case of dogs 75 per cent.

350 SCIENCE PROGRESS

Bovines suffer from both respiratory and intestinal tuber-
culosis. A form of tuberculous peritonitis and pleurisy to which
they are subject is known as grape disease and is comparable
with the forms of more chronic peritonitis in man. Large
masses of tuberculous material are found studded over the
peritoneum.

In about half the cases of bovine tuberculosis both forms of
tubercle are present : in one-third the lungs alone are affected.

In cattle the ovaries are affected rather more often than
the testicles, whereas in adult man disease of the testicles is
occasionally met with, whilst that of the ovaries is very rare.

Cattle are subject to tuberculosis of the joints. Tuberculosis
of the udder is a form of disease which is of particular interest
from its bearing on the infection of milk. In a series of German
experiments, it was found that 55 per cent, of the milk from
tuberculous udders was capable of producing infection in ex-
perimental animals. Calves fed on tuberculous milk succumb
to the disease and the calves of tuberculous mothers frequently
become infected.

The careful experiments of the Royal Commissioners ^
on Tuberculosis prove that calves suckled by cows suffering
from tuberculosis of the udder, produced experimentally by
injection into that organ of tubercle bacilli from either bovine
or human sources, always sustain infection of mesenteric glands
and sometimes ulceration of the intestine ; they occasionally
exhibit tuberculosis of the submaxillary and pharyngeal glands.

Calves fed on milk containing known quantities of tubercle
bacilli were proved to sustain similar lesions : the thoracic glands
being also affected in some cases.

When the dose was large and the strain one found to be
virulent in bovines, more extensive tuberculosis ensued, the
tonsils in these cases also being affected.

Whilst it cannot be denied that milk is a possible and some-
times an actual source of tuberculous infection, especially in
children, it does not necessarily follow that lesions of the in-
testine and its glands are a sequence of the ingestion of infected
food only.

In the experiments quoted, tubercle of the thoracic glands
sometimes occurred when tubercle bacilli could reach the calf

^ Second Interim Report, 1907. Compare Science Progress, No. 24, April
1912.

MECHANISM OF INFECTION IN TUBERCULOSIS 351

only in its food. It is at least possible that some bacilli, in such
cases, find a resting place in the mouth and are carried thence
in currents of inspired air to the thoracic viscera, eventually
reaching the thoracic glands.

Similarly it may readily be supposed that air-borne tubercle
bacilli, derived by children from their parents or their sur-
roundings, may sometimes be arrested in the saliva or dissolved
in the trachoeal mucus and again coughed into the mouth, there
to be swallowed, so reaching the intestinal tract.

The possibility that the intestine and its glands may be
infected in this manner is the more readily acceptable if it be
remembered that swallowed saliva does not excite the active
secretion of intestinal juices containing proteoclastic ferments
capable of digesting the bacilli.

On the other hand, when taken in food, tubercle bacilli are
subjected to the full activity of digestive ferments. In the one
case, we have a relatively concentrated suspension of bacilli in
saliva permitted to act on the surface of the intestine un-
restrained ; in the other, bacilli are not only diluted to a great
extent by admixture with food but are subjected to the des-
tructive action of digestive juices. So far then from tuberculous
milk being a necessary source, it would appear that conditions
for infection of the gut in children are most favourable when
food is absent.

It is not surprising, therefore, that though it is common
experience to find lesions in the digestive tract associated with
tuberculous infection of the lungs and thoracic glands, these
lesions are often neither so advanced nor so extensive as those
in the lungs.

Human and Bovine Sources of Infection

The exact nature of the mechanism of infection in young
children must remain uncertain if judged of on the evidence
afforded by considerations based on the incidence of the disease.
Some other means of estimating the characters of the infection
must be sought, if a clearer picture of the course of events is to
be obtained.

Such a means apparently is at hand in certain differences
which have long been known to exist between the majority of
strains of tubercle bacilli derived from human sources on the
23

352 SCIENCE PROGRESS

one hand and the majority obtained from bovine sources on
the other.

The human strains grow readily on artificial media outside
the body and when injected into animals produce lesions which
are neither severe nor acute ; bovine strains are often extremely
difficult to cultivate on artificial media but when injected into
animals produce widespread and rapidly fatal disease.

The elaborate investigations of the Royal Commission have
proved, as might have been anticipated, that tubercle bacilli
from either source show remarkable constancy in form and
behaviour during a number of generations, whether propagated
by passage from animal to animal of the same or different species
or by repeated subcultivations on artificial media.

There is, however, abundant intrinsic evidence in the
Report that the tubercle bacillus, stable as it is, shows almost
every mutation between the bovine type on the one hand and
the typical human variety on the other.

Bacilli from bovine sources produce in one calf lesions of a
mild or chronic type, in a second acute tuberculosis ; when the
infecting agent is passed from the chronic case into another calf,
acute lesions are produced, showing that there has been a
gradual increase in virulence of the bacilli.

Similarly, bacilli which at first are difficult to cultivate on
media w^ill flourish after repeated subcultivation where at first
they pined. In either case, the aptitude to flourish under one or
other set of conditions pre-existed in some, so that the organism
only required appropriate treatment to assume corresponding
characters.

It is specially noteworthy that bacilli of typical bovine
character have been isolated from human sources, whilst bacilli
have been obtained from oxen showing a variable degree of
virulence for animals and ready growth on media.

The bacilli from bovine sources show considerable con-
stancy of character. Bacilli from human sources often vary and
are placed in the Second Report of the Royal Commission
in three groups, one approximating in its character to the
typical bovine form, the second to the typical human form ;
the strains of "group three" manifest various mutations and
combinations of the characters accepted as typical in the two
strains together with a marked variability in cultures and when
inoculated into animals.

MECHANISM OF INFECTION IN TUBERCULOSIS 353

Bacilli from equine sources, whilst agreeing in their cultural
characters with the bovine type, give rise when inoculated into
animals to lesions of moderate severity such as are caused by
the so-called human bacillus.

There appears to be the strongest evidence, therefore, that
the bacilli of human and bovine tuberculosis are varieties of one
and the same organism.

Study of variation has been far more easy in the case of the
tubercle bacillus than in the case of other common pathogenic
micro-organisms. The slowness of its growth, the mild chronic
type of lesions which it causes, the delay which is apparent in
its response to altered surroundings are all reasons which have
led to an undue share of attention being given to characters
probably in themselves not essential which in more rapidly
growing bacteria escape notoriety.

So far as the discovery in a human lesion of bacilli either of
" bovine " or of " human " type can afford evidence of infection
from one or the other source, the position remains unchanged
from that which existed before the work of the Commission was
undertaken.

In view of the proven stability of the tubercle bacillus, it is
probable that a child suffering from tuberculosis due to bacilli
of " bovine " type may infect a number of other children and
give rise in them to tuberculosis due also to " bovine " bacilli.
In such secondary cases, it would be of little use to attack the
milk supply and neglect the obvious source of infection pro-
vided by the first sufferer.

Certain of the anomalous cases, in which the bacilli ex-
hibited both bovine and human characteristics, were attributed
by the Commission to a mixed infection with the two types of
organism.

In this connexion, the evidence of Von Pirquet's skin reaction
mentioned before is of interest.

In carrying out this test, it is customary to inoculate tuber-
culins/ro;;^ a bovine and a human source on separate sites. As
a result, in the vast majority of subjects, if a reaction occur, it is
positive to both human and bovine tuberculin. It is incredible
that in all cases a mixed infection should be operative.

In those cases in which one reaction or the other is alone
positive, there appears to be no clear correlation between the
site of the lesion and the type of reaction. Abdominal lesions

354 SCIENCE PROGRESS

or lesions apparently confined to the lungs when not either
positive or negative to both human and bovine tests are as
often positive to the human as to the bovine reaction.

Origin of Tuberculous Infection

In view of what has been said above it is difficult to avoid
the logical conclusion that the mechanism of infection in
children as in adults is in the main by way of the respiratory tract.
Children may become infected primarily by way of the
intestine but there are many possibilities in addition to those
afforded by infected food. Thus dirty fingers contaminated
with floor dust and particles of dried sputum containing
tubercle bacilli are immediately carried to the mouth of a
child ; or a tuberculous mother moistens with her lips the
child's rubber " comforter " and bacilli are thereby conveyed to
its intestinal canal.

Milk may be and no doubt is an occasional source of
tuberculous infection but the importance of giving attention
primarily to cows' milk rather than to other hygienic measures
for the prevention of consumption is undoubtedly over-rated.

No effort should be relaxed which will serve to promote the
provision of a pure milk supply from well-ordered dairies and
clean, well-ventilated, well-lighted cow-sheds ; at the same
time, the enormously greater probability of infection from
human sources, particularly from cases of pulmonary tuber-
culosis, cannot be exaggerated.

After all, to struggle against tuberculosis by means of
measures such as are now employed or foreshadowed by
legislation is at best a hopeless task. The evolution of man and
of the tubercle bacillus on mutually antagonistic lines seems
likely to proceed till the end of time; only by the gradual
establishment of natural immunity, built up step by step by
successive generations who have successfully sustained its
attacks, can freedom from the disease be at last attained.

Paradox though it may seem to be, by lessening the general
risk of infection of the community, the proposed isolation of
persons suffering from tuberculosis may actually retard rather
than assist the struggle against consumption.

What can and should be done is to place all individuals
from birth onwards under conditions most conducive to the

MECHANISM OF INFECTION IN TUBERCULOSIS 355

maintenance of good health, so that they may encounter
infection successfully, remembering always that overwork and
underfeeding are the surest preparation for the disease.

It is not impossible that the compulsory notification of
tuberculosis may have an effect perhaps undreamt of by its
promoters. The unfortunate patient branded as consumptive,
on the insufficient evidence afforded by the present means of
making a certain diagnosis of pulmonary tuberculosis, may
find himself in the position of a leper — more surely isolated by
the natural fears those who encounter him may have of incurring
the disease than by all the sanatoria that can be devised.

So far as children are concerned, the boiling of milk may
safely be regarded as of secondary importance so long as
windows are kept open and floors frequently scrubbed.

SCIENTIFIC PROBLEMS IN
RADIOTELEGRAPHY

By J. A. FLEMING, M.A., D.Sc, F.R.S.

The scientific questions that must be considered when any
branch of experimental work is carried beyond a laboratory
stage into the larger field of technical application are often
very interesting and instructive. Apart altogether from the
difficulties of conducting them on an enlarged scale or any
questions of utility or profit, entirely new problems are often
brought into view when we magnify the range or extent of
our operations. This is true particularly of the attempts made
to apply our knowledge of electromagnetic waves to long
distance wireless telegraphy.

After Hertz had shown us experimentally how to produce
Maxwell's electromagnetic waves and at one stroke given life to
the dry bones of certain mathematical equations familiar enough
to students of Maxwell's great treatise but otherwise " caviare
to the general," physicists all the world over entered with
unlimited delight upon the conquest of this new field of
research. Laboratory experiments on electromagnetic waves
became the order of the day but were carried on during five
years or more before the idea arose of utilising them for
telegraphic purposes. Sir William Crookes's remarkable fore-
cast in the Fortnightly Review in 1892 showed that the notion of
so using them had already been clearly formed ; moreover, had
the late Prof. D. E. Hughes not allowed himself to be dis-
couraged by criticism of some very original experiments he
showed to friends, radiotelegraphy might have been an established
fact before that date.

There is a wide gulf, however, between prognostications or
suggestive experiments and a practical invention. The real
invention or discovery which made possible an advance from
laboratory experiments with Hertzian waves to electric wave
telegraphy in any proper sense of the word was not merely an

356

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 357

improvement in the means of detecting these waves but the
invention of a radiator v^hich could project them far enough.

This important step in invention was made by Marconi when
he constructed a form of radiator consisting of a long, nearly
vertical wire insulated at its upper end and having its lower end
connected to one of a pair of spark balls, the other ball being
connected to the earth. What was not appreciated before his
time was that a vertically arranged Hertzian oscillator of great
length, say lOo feet or more, half buried in the earth had the
power of producing electromagnetic waves of great energy
which could travel over the earth or sea; also that a similar
aerial wire would absorb the radiation and enable it to be
detected. When once this clue to success had been provided,
the invention of details went on apace and by 1897 or so
apparatus for telegraphy without connecting wires over a range
of several miles had been fairly well perfected by Marconi,
whilst Lodge had also shown how the facts of electrical
resonance might be applied to preserve the privacy of communi-
cation and the isolation of stations. Leaving out of account
details of development and invention, for which special treatises
must be consulted, we may say that at the present time (191 2)
the greater part of all the wireless telegraphy in the world is
conducted substantially by means of the following appliances :
at every station there is a transmitter and a receiver, each of
which consists of three parts. The transmitter comprises : (i)
some means of producing a high-tension electric current,
whether by alternating current dynamo and transformer or
direct current dynamo and storage cells — or in the case of small
plants an induction coil and battery ; (ii) a condenser, which
may be a collection of Leyden jars or even a large air
condenser, which is charged to a high potential by the first-
named appliances and then discharged across a spark gap
several hundred times a second, (iii) This sudden discharge
of the condenser is sent through a coil of wire called an
oscillation transformer and is made to create other oscillations
of electricity in the third element called the *' antenna," which
is a long, nearly vertical wire, insulated at the upper end and
having its lower end in connexion with the earth or with other
wires laid either in or above the earth, called the balancing capa-
city. The antenna consists of a number of wires arranged in
fan-shape or else rising up and then bent down like the ribs of an

358 SCIENCE PROGRESS

umbrella; it may otherwise be made of a collection of wires
which rise up vertically for a certain distance and then extend
horizontally for a still greater length. Whatever its form, when
the condenser discharges take place, rapidly reversed electric
currents are set up in this antenna, each explosion of the con-
denser discharge producing a train or collection of such electrical
vibrations in it. The antenna may be regarded as a kind of
electrical organ-pipe in which electrical oscillations are produced
in place of aerial oscillations ; these vibrations create electro-
magnetic waves in the aether and these waves are projected
in every direction with the velocity of light.

In the condenser or dynamo circuit there is a key or inter-
rupter by which the trains of waves can be cut up into long
or short groups in accordance with the signals of the Morse
alphabet. The wireless transmitter is therefore a sort of light-
house sending out long and short flashes of electromagnetic
radiation which cannot affect the human eye but which do affect
the proper kind of sensitive receiver.

Turning then to the receiver we find it also consists of three
parts, viz. (i) a receiving antenna which may or may not be the
same as the sending antenna; this captures or absorbs the
incident electromagnetic waves, very feeble oscillatory electric
currents being set up in it which are a copy on a very reduced
scale of those in the sending antenna, (ii) These antenna
oscillations are caused, in turn, to induce others in a nearly
closed circuit comprising a receiving condenser which is tuned
to the antenna ; that is to say, it is arranged to have the same
natural period of electrical vibration. The energy picked up b}^
the receiving antenna is accumulated in this last circuit ; hence
electrical oscillations take place in this storing circuit which
are an exact imitation of those taking place in the distant
sending antenna and these are cut up into long and short
groups which are interpreted in accordance with the Morse
code. The third element in the receiver comprises the means
for making these signals visible or audible. At the present
time, the detectors in common use are the magnetic detector, the
glow-lamp or ionised gas detector and various forms of so-called
rectifying detector, the detector being associated with a tele-
phone. If a telephone receiver alone, of the ordinary magnetic
form, be connected across the terminals of the receiving con-
denser, no sound is produced in it unless the received electric

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 359

wave trains are extremely violent. The reason is that each train
of oscillations set up in the receiving antenna by the oscillatory
discharge of the condenser in the distant transmitting station
consists of a group of electrical oscillations gradually decreasing
in amplitude ; the successive oscillations are repeated at intervals
say of a millionth part of a second, some forty or fifty oscillations
forming the group or train. Electrical vibrations of this fre-
quency cannot affect the telephone, not merely because their
frequency lies beyond the limits of audition but because the
inductance or electrical inertia of the telephone coil is too great
to permit sufficient current to flow through it at this frequency
to move the diaphragm. If, however, we connect in series with
the telephone some device which either rectifies these oscillations
or permits movement of electricity only in one direction through
it, the group of decrescent vibrations is changed into a pro-
longed gush of electricity entirely in one direction. If these
gushes succeed each other at the rate of several hundred a
second, in passing through the telephone they give rise to a
musical note of the same frequency as that of the spark
discharges in the transmitter.

If these latter sequences of discharges are cut up into long
and short groups by a ke}^, a listener at the telephone would
hear a series of musical sounds of long or short duration,
which he could interpret alphabetically on the Morse code.
Many such rectifiers are now known. For instance, it is a
property of carborundum — an artificial crystalline carbide of
silicon made in the electric furnace — that an electric current
flows more easily in one direction through the crystal than in
another ; consequently, as the conductivity in different directions
is not the same, the crystal can act as a valve for electricity.

Accordingly, a crystal of carborundum joined in series with
a telephone provides a means of hearing electrical oscillations
if broken up into groups, the group frequency being preferably
about 500 per second.

G. W. Pierce has found that crystals of Hessite (a telluride
of silver) and Anatase (a native oxide of titanium) will act in
the same manner as carborundum. Again, it has been found
that a light contact between certain metals and non-metals is
a better electrical conductor in one direction than in the
opposite. G. W. Pickard has found that a contact between
steel and silicon has this property and L. W. Austin has shown

36o SCIENCE PROGRESS

that a contact between aluminium and tellurium will act in
the same manner.

A contact between copper and molybdenite, as G. W. Pierce
has shown, is likewise a rectifier, whilst Pickard has found
that a contact between zincite (a native oxide of zinc) and
chalcopyrite (copper pyrites) is an extremely good rectifier.
This rectification does not depend on thermoelectric action,
as the rectified current is generally in the direction opposite
to the current which would be produced by heating the junction.
R. H. Goddard has recently asserted that an oxide or sulphide
film of some kind is necessary for rectification and that the
contact between pure metals and pure non-metals in vacuo or
hydrogen is non-eff'ective as a rectifier.

It appears as if the film of oxide or sulphide or some
other impurities on the surface permits the passage of electrons
or ions through it more easily in one direction than the other
when the boundary surfaces are certain metals and non-metals.
In a large number of instances the direction of most easy
passage is such that electrons or negative ions seem to pass
more easily from the poor conductor (silicon, carbon, galena,
molybdenite, pyrites, etc.) to the good conductor (steel, copper
or gold) in contact with it but the tellurium-aluminium contact
is an exception to this rule. In any case, there is an asymmetry
of conduction at the boundary surface of many such contacts
between different classes of conductors which, when associated
in series with a telephone receiver, enables it to rectify trains
of electrical oscillations and to make audible groups of such
trains when coming at intervals of a few hundred a second.

The discovery of these rectifying contacts in the course of
the search made for radio-telegraphic receivers has not only
opened up questions of great interest in connexion with the
conductance of electricity but has made it clear how great is our
ignorance as yet concerning so familiar an operation as the
movement of electricity through conductors.

In addition to the crystalline or contact rectifiers referred
to, another type much used is the glow-lamp rectifier or oscilla-
tion valve, invented by the writer, which consists of a small
carbon filament glow-lamp having a metallic plate in its bulb
carried on a platinum wire sealed through the glass. When the
filament is incandescent, the space between it and the plate
has unilateral conductivity, negative electricity passing from

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 361

the filament to the plate but not in the opposite direction.
This property appears to be dependent on the fact that
electrons or negative ions are liberated from incandescent
carbon when it is at a high temperature.

A third much used detector is the magnetic detector of
Marconi, in which an endless band of hard iron wire is made
to pass near the poles of a couple of small horseshoe magnets
with similar poles in contiguity, the iron being embraced at
that spot by two coils ; one of these coils is in connexion
with a telephone receiver, the other coil is free to receive
electric oscillations from an antenna. The oscillations shake
up the iron and either cause it to lose its quality of magnetic
hysteresis or else promote an increased permeability or power
of acquiring it. In either case they alter the magnetic con-
dition of the iron within the secondary coil and hence cause
an electromotive force in the latter, which in turn causes a
sound in the telephone. This detector is simple and easily
managed and is largely used in ship installations. The need
for a form of detector which will record the signals has called
forth much ingenuity. The old forms of coherer and relay and
Morse printer, recording in dots and dashes on paper tape,
are now very little used, owing to the numerous adjustments
required and to their sensibility to external disturbances.
At present, in large stations, tlie Marconi Company use a form
of Einthoren string galvanometer joined in series with a
crystal or glow-lamp rectifier. The deflections of the fine
silvered quartz fibre in the strong magnetic field are recorded
by photography on a prepared tape, which is developed, fixed
and washed as it passes through the instrument and can record
signals at the rate of fifty words or more a minute.

Provided with these detectors and the associated antenna,
the radiotelegraphist is able to detect any and all sorts of
electric waves passing through space.

The atmosphere round the earth is the seat of natural
electrical disturbances which give rise to vagrant electric waves,
called atmospheric X's or strays, which are recorded on the
receivers used in competition with the message-bearing waves
sent out from transmitting stations in correspondence with the
receiver. In early days, when the coherer was used in con-
junction with the Morse printer as receiver, these atmospherics
were difficult to eliminate ; they gave rise to false signals, dots

362 SCIENCE PROGRESS

and dashes, which mingled with the inteUigible signals and
confused their meaning. Now-a-days, by the use of a high-
spark frequency, the intelligible signals have a high shrill
note in the telephone and it is therefore possible to distinguish
them from the lower clicks, knocks or squeaks produced in the
telephone by the atmospherics. And, in addition, better forms
of tuning circuits have been devised for getting rid of the more
highly damped atmospherics. A study of these atmospherics
will undoubtedly lead to the increase of our knowledge of
atmospheric electricity ; indeed, a considerable amount of
information on this subject has already been accumulated.
Natural electric waves are produced whenever a lightning dis-
charge takes place, as this is just of a nature to produce a
sudden disturbance in the aether like the wave caused in the
air by an explosion. But as these stray waves are always found
flying across country, whether local thunderstorms are going
or not, there must be some constant source from which they
come ; it may well be that they arise in the tropical regions of
the earth and are propagated to temperate zones. On the other
hand, although stray electric waves can nearly always be heard
in the telephone of a radiotelegraphic receiver, in our latitude
they are much more frequent by night than by day ; moreover,
Mr. Marconi and Dr. Eccles have noticed that they undergo
a very curious stoppage or suspension just about sunset and
sunrise. The latter investigator has described the twilight
course of these stray electric waves in England in the following
terms :

" Starting to listen (at the telephone) about a quarter of
an hour before sunset (in London) on a favourable afternoon
in late autumn or winter, the strays heard in the telephone are
few and feeble, as they have been all day; then at five minutes
after sunset a change sets in, the strays slowly get fewer and
fewer until at ten minutes after sunset a sudden distinct lull
occurs and lasts perhaps a minute. Often, at this period, there
is a complete and impressive silence. Then the strays begin
to come again and quickly gain in number and force and in
the course of a few minutes they settle down into the steady
stream of strong strays proper to the night."

In tropical countries great irregularities are noticeable but
broadly we may say that, at any place, these stray electric waves
are subject to regular diurnal variations something like those
of atmospheric electric potential or terrestrial magnetic force ;

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 363

moreover, irregular disturbances caused by local storms are
superposed upon these diurnal variations. Many of the stray
waves observed in England affect radiotelegraphic stations
hundreds of miles apart nearly simultaneously and therefore
cannot have their origin in England.

We have next to notice the diurnal variation in the strength
of artificial or message-bearing waves sent over long distances.
The fact was discovered by Marconi in 1902, in one of his
voyages across the Atlantic, that whilst by day he could (using
a certain receiver) only receive signals from his Cornwall station
at a distance of about 700 miles, he could receive similar signals
at a distance of 2,100 miles by night. The first hypothesis
suggested was that this was due to the discharging power of
daylight upon the sending antenna. The daylight effect, how-
ever, is only a long-distance effect and no such reduction in
the strength of day signals is noticed over short distances.
Hence it cannot be an effect produced merely ^n the sending
antenna. It was then suggested that the atmosphere became
ionised by the sunlight and that this was the cause of the
absorption of the electric waves. We can calculate the absorp-
tion due to any amount of assumed conductivity in the air when
long electric waves are passing through it and it is not difficult
to prove that the atmospheric conductivity which has been
observed at sea level or a few hundred or even thousand feet
above it is not sufficient to account for the observed diminution
of range of long electric waves by day as compared with night,
if it be attributed to mere absorption of wave energy, in other
words, to want of transparency due to some degree of conduc-
tivity in the air.

There is, however, another possible explanation. It is well
known that sound travels better with the wind than against it.
The late Sir George Stokes explained this as follows : When
the wind is blowing strongly, friction against the earth retards
it more at the surface than at higher levels. If then a plane
vertical sound wave-front be travelling against the wind, the
velocity of the wave will be more reduced at higher levels than
at the earth's surface. Hence the wave-front is no longer
vertical but slopes backward. The direction of propagation
of the wave being normal to the wave-front, the wave is tilted
upwards and the sound will pass above a distant point on the
terrestrial surface which it would otherwise reach if the wind

364 SCIENCE PROGRESS

were not blowing against it. A similar effect is possible in
connexion with electromagnetic waves passing through air.
It has been shown by Dr. Eccles that, on certain assumptions
as to the nature of the ions, an electromagnetic wave travels
faster in ionised air than in non-ionised air. It has also been
proved experimentally by the writer that air containing con-
densed moisture, in the form of water spherules, has a slightly
higher dielectric constant than dry air. Hence the wave
velocity is slightly less in moist than in dry air. Also, there is
experimental evidence for the statement that ultra-violet light
can ionise air and separate from the molecules positive and
negative ions. Owing to the rapid absorption of the ultra-violet
light of the sun by the atmosphere, this kind of ionisation is
principally confined to layers of air at a considerable height,
in fact above the level of ordinary clouds. We have then the
necessary conditions for producing a refractive effect. The
electromagnetic waves radiated from an antenna are sent off
with greatest intensity in a horizontal direction but radiation
takes place to some extent in directions elevated above the
horizontal. When these upward-trending waves reach the
ionised layer of the atmosphere, owing to the greater velocity
of the upper part of the wave-front, a refractive effect takes
place which bends them down again. The effect may be com-
pared with an inverted mirage effect, the layers of ionised air
corresponding to the layers of hot air and the layers of non-
ionised air to the cold air. Again if the atmosphere from any
cause become ionised in patches, such non-homogeneous air
would behave to electromagnetic waves as water full of bubbles
behaves to light; it would become more or less opaque and
break up the wave-front passing through it.

Before applying this theory in explanation of observed facts,
it will be well to turn attention for a moment to the fundamental
scientific question in connexion with long-distance radio-
telegraphy, viz. why is it possible to send electromagnetic waves
round the earth over long distances ? Suppose we consider an
analogy with light. If a luminous point of mathematical
dimensions were placed on the pole of a sphere one-quarter of
an inch in diameter, the radiant light would be diffracted to
a very small extent round the sphere but certainly not to such
a degree as to illuminate the sphere at its equator or even at
45° latitude.

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 365

Yet the length of these visible light waves bears the same re-
lation to the diameter of such a small sphere that radiotelegraphic
waves one kilometre in length bear to the diameter of the earth.
Hence it is by no means obvious that Transatlantic radio-
telegraphy is conducted in virtue of the diffraction of these long
waves. The matter has, however, been more carefully ex-
amined by mathematicians— by Lord Rayleigh, the late Prof.
Henri Poincare, Prof. H. M. Macdonald and Dr. Nicholson.
They have all come to the conclusion that radiotelegraphic
waves of even a kilometre or more in length cannot be
diffracted round the earth to an extent sufficient to account for
Mr. Marconi's long-distance wireless telegraphy. Hence our
fundamental problem is to find a valid reason for the pro-
pagation of these long electric waves in spite of the curvature
of the earth across the Atlantic or even, as achieved by
Mr. Marconi, from Ireland to South America, a distance of
6,000 miles or one-quarter of the way round the earth. A
mathematical discussion of the problem has made it tolerably
clear that if the earth were a ball of copper immersed only in
aether, no long-distance radiotelegraphy would be possible on
it. The waves generated at any place would soon glide off it
and be lost in space. The fact that we can conduct such
telegraphy on it over long distances is only due either to the
imperfect conductivity of the earth or to its possessing an
atmosphere of such a nature that electric waves created on it
are prevented by some means from rushing off it tangentially
into space. One explanation has been formulated by Prof.
A. Sommerfeld of Munich as the result of an elaborate
mathematical discussion of the problem of wave generation by
an oscillator at the boundary of two dielectrics of different kinds.
His conclusion is that, in the case of an oscillator at the
bounding surface of earth and air, there is not only an electro-
magnetic space wave radiated through the air but a surface
wave which travels along the bounding surface and is limited
to a small region on either side. There is a certain analogy
with a similar effect in the case of earthquakes, in which, as
investigation has shown, there are space waves travelling
through the earth and surface waves more or less confined to
the surface crust. Sommerfeld shows that these surface waves
would degrade in amplitude much less fast than the space
waves and would follow round the surface of the earth in spite

366 SCIENCE PROGRESS

of curvature and irregularities. His suggestion is that long-
distance wireless telegraphy is chiefly effected by such surface
waves. Although his analysis is no doubt valid, yet neverthe-
less the trend of experimental evidence seems to be against it.

If Sommerfeld's explanation were the true one, it is hard
to see why long-distance wireless telegraphy should either be so
much affected by daylight and by direction or exhibit the abnor-
malities with regard to wave length which it actually does.

There remains then one other assumption for which the
evidence is far from complete but which has been the ultimate
refuge of all those who have found it impossible to account for
the facts either on the basis of diffraction or on the hypothesis of
a surface wave. This assumption is that the upper levels of the
earth's atmosphere, say at a height of 60 to 100 miles, are
perpetually in a state of ionisation to such a degree as to render
it a fairly good conductor, possibly as good as dilute sulphuric
acid, at any rate sufficiently good to enable it to act as a
reflector for long electric waves.

Since pure wave diffraction is excluded as a possible
explanation of long-distance wireless telegraphy, we have to
fall back on one or other of two hypotheses, one of which
requires the production of surface waves in the crust of the
earth and the other refraction or reflection of waves in or by
the earth's atmosphere. As will be seen by what follows, the
abnormalities and irregularities of long-distance radiotelegraphy
seem to point to the determining cause of the bending of the
waves round the earth being something in the atmosphere
rather than in the earth. Yet, on the other hand, the existence
of surface waves is not disproved and there are some facts
which rather strongly support this latter supposition. The
experimental achievements and chief practical experience with
long electromagnetic waves which have to be explained are
therefore as follows : electric waves from i to 4 miles in
wave length can travel at least one quarter of the way round
the earth. This suggests at once the questions — Could they
travel half-way round ? Is wireless telegraphy between London
and New Zealand within the possibility of practice? In the
next place, there are great differences in the reduction of
amplitude experienced by such a wave when travelling by day
and by night over long distances; and certain extraordinary
variations in the strength of signals near sunrise and sunset.

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 367

Again, as observed by Mr. Marconi and his staff, there are
great differences in the facihty with which these waves are
propagated in different directions, as in some cases they
are more easily sent in north and south directions than in
east and west. Lastly, we have the same influence exerted by
daylight on the stray or natural waves as on the message-
bearing waves.

Under some conditions of the atmosphere, radiotelegraphic
apparatus intended for moderate distances will send or receive
over unusually great distances and these " freak transmissions,"
as they are called, are more likely due to some abnormal state
of the atmosphere than of the earth. Hence these vagaries of
transmission can hardly be explained merely by a surface wave
or by any regular process of transmission of wave energy.

It is clear that the unravelling of the knotty problems of
radiotelegraphy is bound up with a much more complete
insight into the structure of the eai:th's atmosphere. It is
indeed curious how, as progress takes place in science, blows
are continually struck at our complacent ignorance. Time was
when we all confidently thought the earth's atmosphere was
merely a mixture of oxygen and nitrogen with a dash of carbon
dioxide and some aqueous vapour ; then suddenly we learnt that
it contains argon, neon, helium, zcnon, krypton and perhaps
traces of several other gases. Radiotelegraphy is now teaching
us that it is of a still more complicated character and possesses
constituents which have the property of refracting, perhaps
reflecting and also absorbing, long electromagnetic waves in an
extraordinary manner.

Many of the mathematicians who have attacked this problem
of the bending of long electric waves round the earth have
fallen back on the hypothesis that there must exist at a high
level of the atmosphere a layer of rarefied gases which are so
much ionised that they form a very good conductor of electricity,
possibly as good as dilute sulphuric acid at its maximum con-
ductivity. This layer is assumed to have the property of
producing, by an inverted mirage effect, a reflection of long
electric waves. The hypothesis of long-distance transmission
that is then suggested is something as follows : When a radio-
telegraphic station is at work, the waves sent out horizontally
are diffracted to a small extent and may reach the receiving
stations at a very few hundred miles' distance directly. In
24

368 SCIENCE PROGRESS

addition to these horizontal radiations, rays are sent upwards
at various inclinations which impinge on the reflecting layer
and " illuminate " it, radiotelegraphically speaking, just as a
distant conflagration so far off" as to be below the horizon
illuminates clouds in the sky or " lights up " the sky, to use
Dr. Eccles's expression.

The suggestion is that, at very great distances, the waves
received, at least at night, are these reflected waves. In the day-
time, it is assumed that there is an additional ionisation, by ultra-
violet sunlight, of the air at still lower levels and that the effect
of this in accelerating the wave velocity of the upper part of
the wave front travelling through it is to bend down the rays
again earthwards, so as to make them fall short of the distant
receiving station. Perhaps also the interposition of the middle
layer of ionised air may reduce the perfection of the reflection
by the upper permanently ionised air. The two eff*ects com-
bined are postulated as an explanation of the reducing action
of daylight on radiotelegraphy. Since the sunlit half and
the dark half of the atmosphere are in diff'erent conditions
as regards ionisation, at the boundary line there will be a more
or less confused state which might be likened to a liquid in a
state of froth : hence the propagation of a wave across the
boundary line is accompanied by difficulties or obstructions
which do not affect transmission in the more homogeneous
night half or day half of the atmosphere.

Turning then to the facts of observation as regards the day
and night effects, some careful observations were made by
Messrs. Round and Tremellen at the Marconi Company's works
at Chelmsford last year, in July, which are recorded in a recent
issue (November 191 2) of The Marconigraph. They observed at
Chelmsford the strength of the signals sent out from the
Marconi station at Clifden in Ireland through a whole day and
night. Beginning say at midday, the strength of the signals
received at Chelmsford remained tolerably constant until about
an hour before sunset at Chelmsford. It then rose quickly to
about four times its day strength at a little after sunset at
Clifden. This rise was then followed by a sudden fall off" in
strength again, which reached a minimum about an hour after
sunset at Clifden. About an hour later a very sudden increase
in strength set in which carried up the signal strength to nine
or ten times its minimum day value ; this continued with

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 369

some irregular variations during the night. About an hour
before sunrise at Chelmsford, there was another sudden
decrease, followed by a rise and then a fall to normal day
strength soon after sunrise at Clifden. There is therefore one
maximum about sunset at Clifden and another at about sunrise
at Chelmsford.

Mr. Marconi pointed out in a Royal Institution lecture at the
same date that in Transatlantic radiotelegraphy the signals are
at their weakest when the boundary between day and night has
moved into a position about half-way between the two stations
on opposite sides of the Atlantic.

Other observers, such as G. W. Pickard, also have noticed
this curious dip or minimum in the signal strength curve at or
about sunrise and sunset. Similar variations are found to affect
the wave strength of the natural or stray waves. There are,
however, great variations in the phenomena due to wave
length and the position of the two stations in correspondence.
Hence we are very far yet from being able to lay down simple
general statements as to the facts or fit them to equally simple
explanations.

Thus in the case of the Transatlantic transmission during
the day, conducted with waves 4,000 metres in length and
passing from Nova Scotia to Ireland, Marconi states that the
waves yield strong and steady signals during the day at Clifden
(Ireland) which gradually decrease in strength after sunset,
reaching a minimum about i J hours afterwards ; they then
increase again until sunset at Cape Breton (Nova Scotia) and
attain later on a high maximum value. During the night they
vary a good deal in strength. Shortly before sunrise at Clifden
the signals grow stronger and decrease to a lower value about
two hours later ; they then return to normal day strength.

Beyond a distance of 4,000 miles, signals have only been
received by night but Mr. Marconi has remarked that it is
curious that the signals sent out from Clifden should only
have been detectable in Buenos Ayres by night, whereas in
Nova Scotia they are no stronger at night than in the day.
He has also noted the curious fact that whereas ships 1,000
miles from England off the south of Spain or round the coast
of Italy can nearly always communicate with post office stations
on the British coast by night, yet the same ships when at an
equal distance away in the Atlantic or to westward cannot

370 SCIENCE PROGRESS

communicate except with the aid of especially powerful
apparatus. It will be seen, therefore, that we have by no
means as yet even determined all the abnormalities of the
effects, far less reached a final explanation of them.

Ther^ are many geophysical facts which seem to indicate
that the upper layers of the earth's atmosphere are in a highly
conductive condition. We have in the first place the phenomena
of the Aurora, which is generally allowed to be an electrical
discharge and although its principal manifestation is in higher
latitudes, yet, as W. W. Campbell showed in 1895, the green
auroral line X 5, 770 can be seen on moonless nights in any
part of the sky. Then, again, we have Prof. Schuster's
conclusions from observations of terrestrial magnetism that the
greater part of the diurnal variation must be due to electric
currents in the upper atmosphere ; also the suggestions of
Arrhenius and of W. J. Humphreys that the outermost layers
of our atmosphere are kept permanently ionised either by
electrons shot out from the sun or by the bombardment of
cosmical dust. Prof. Schuster's conclusion is that at a height
of about 100 km. the atmosphere conductivity is of the order
of lO"^^ electromagnetic units, equivalent to 10,000 ohms per
centimetre cube ; Dr. Eccles, working from this basis, finds that
this conductivity would suffice to give sufficient refractive power
equivalent to reflection for radiotelegraphic waves.

Hence it appears as if a complete explanation of long-distance
radiotelegraphy and of the variations introduced by daylight
is intimately bound up with a knowledge of the state as regards
conductivity, dielectric constant and ionisation of the air at
very high levels. Our methods of direct exploration by balloons
are probably limited to altitudes of 7 or 8 miles, hence all our
knowledge of effects and states at a height of 40 or 50 miles
will have to be derived by inferences drawn from observations
of terrestrial magnetism, electricity and geophysics generally.

Furthermore, recent experiments by Dr. H. Lowy and others
have shown that electromagnetic waves may be used to explore
the crust of the earth and perhaps locate masses or veins of
metallic nature. A better knowledge of the function of the earth
in wireless telegraphy is therefore necessary as a basis for theory.

Sufficient will have been said in this article to show that
whilst radiotelegraphy has proved to be a weapon of enormous
value for supermarine intercommunication, for saving life at

SCIENTIFIC PROBLEMS IN RADIOTELEGRAPHY 371

sea and rendering more secure the position of those who have
to brave the perils of the deep, it has opened up scientific
questions of remarkable interest, which dovetail in with other
unsolved problems of terrestrial physics and invite the careful
consideration of expert students in many branches of physics.
It is curious how frequently the achievements of inventors
outrun all our powers of explaining the inventions in terms
of accepted knowledge. The unconscious cerebration of genius
attempts and succeeds but the exact reasons for success are
sometimes hard to find. Though we do not yet quite know
why it is possible to send electromagnetic waves across the
Atlantic, the fact that it can be done has increased to a most
valuable extent the means of communication on which the
conditions of our modern life and even our national welfare
incontestably depend.

X-RAYS AND CRYSTALS

By W. L. BRAGG, B.A.

Introductory Statement

Since ROntgen Rays were first discovered, many experiments
have been made to obtain with them some effect analogous to
the interference, diffraction and reflection of light waves but
till quite recently it could be said of all these experiments that
they gave a negative result. X-rays are scattered and absorbed
by bodies placed in their path but this scattering and absorption
have been found to depend merely on the nature of the atoms
of which the body consists and no evidence has hitherto been
forthcoming of any influence due to the chemical combination
or physical arrangement of these atoms. Such effects as inter-
ference and reflection demand a wave front covering a large
area, in order that the arrangement of lines in a grating or the
plane surface of a mirror may impress its nature on the wave.
It has seemed that an X-ray represents energy limited to so
small a volume as to be concerned merely with the nature
of single atoms traversed by it, so that it could not be reflected
by a mirror, however perfect the polish, because it had no means
of distinguishing between smooth and rough.

The experiments which form the subject of this article have
quite altered the aspect of the problem. An effect has been
obtained which shows that the regular arrangement of atoms
in a crystal makes its impress on the rays from an X-ray bulb
traversing the crystal. Not only is this so but the effect can be ex-
plained on any wave theory whatever, with suitable assumptions
about the wave lengths ; it is apparently due to the interference
of waves of the normal type having energy spread continuously
over a wave front. Except for their extremely small wave-
length, they are in all respects like waves of light and heat.
If these radiations are identical with the X-rays as investigated
by ionisation methods, there is the same paradox with regard
to their " corpuscular " and "wave" nature as there is in
the case of ultraviolet light. The transformation of X- into
cathode-rays and vice versa can be observed several times over

37*

X-RAYS AND CRYSTALS 373

with the rays from a bulb and it is almost incredible that the
reappearance of a definite amount of energy associated with
a cathode ray in these transformations should not be due to
the energy also being associated with the intermediate X-ray.
Yet this seems impossible when the energy of the X-ray is
spread over a wave front. However, the more paradoxical the
case seems, the more interesting it becomes ; indeed, there can be
no doubt that this new effect must go far towards solving that
puzzling problem, the nature of X-rays.

Electromagnetic waves are now known to us of all wave
lengths over a range of many octaves. When Hertz first obtained
the electromagnetic vibrations predicted by Maxwell in his theory
of light, there was a vast gap between the wave lengths corres-
ponding to the frequencies of his oscillators and those of visible
light, the former being something like a million times the
latter. This gap has now been narrowed until it can be said
to have been abolished. On the one hand, the investigation
of the spectrum of light from hot bodies has been pushed far
into the infra red, heat waves of longer and longer wave length
being discovered by means of a radiomicrometer. These long
waves are isolated by different methods, such as continued
reflection on a surface of rock salt or sylvite or by making use of
their strong refraction by quartz ; their wave length may be
found by interferometer methods. In this way, Rubens and
Wood have been able to show the existence of heat waves as
long as xV niiTi- in the radiation from a Welsbach burner.

On the other hand, by the use of improved forms of
oscillators, very much shorter electromagnetic waves have
been got than those which Hertz investigated. The shortest
waves as yet obtained have a w^ave length of 2 mm. Thus
there is hardly any gap left in the spectrum and one may now
say that all wave lengths greater than those of visible light
are at our command.

The wave length of visible light lies between 4 x lo"^ cm.
and 7 X 10-^ cm. and the known range of the spectrum extends
on the other side to the smaller waves composing ultraviolet
light, the region investigated photographically. Here waves as
short as i x lo"^ cm. have been found by Schumann and are
named after the discoverer. Until quite recently, the spectrum
as known to us has ended at this wave length.

374 SCIENCE PROGRESS

However, the experiments performed by Messrs. Friedrich,
Knipping and Laue have opened up a vast new range in the
spectrum never explored before. The paper in which they
announce their results appeared in June 191 2, in the Proceedings
of the Royal Bavarian Academy of Science. The effects which
they obtain can only be ascribed to waves of a length of the order
of one hundred millionth of a millimetre, the wave length being
small compared with the accepted radius of an atom !

When dealing with visible light, a diffraction grating is most
commonly used in order to split up the mixture of light of all
colours into components the wave length of which can be
measured. The effect produced by the diffraction grating is a
consequence of the regularity of its structure ; it is ruled with
lines at constant intervals which are greater than the wave
lengths of the light to be examined but of the same order of
magnitude. It is the interaction of this regular spacing of the
lines and that of a train of waves composing monochromatic
light which leads to the appearance of interference maxima and
minima. Now there are reasons to suppose that X-rays consist
of electromagnetic waves of very short wave length, something
of the order lO"^ cm. Laue came to the conclusion that if this
were so, it might be possible to get interference effects with these
short waves by using a crystal as a diffraction grating. The
atoms of a crystal are regularly arranged and on the whole the
intervals between them bear about the same relation to the wave
length 10-^ cm. as does the " constant" of a diffraction grating to
the wave length of visible light. To these waves a crystal is
really a most perfectly ruled grating. The experiments to test
this prediction were carried out by Friedrich and Knipping at
Laue's request : they obtained a positive result with the first
crystal they tried.

Since no way has yet been devised of obtaining a parallel
beam of X-rays corresponding to the parallel light which falls on
the grating in a spectroscope, an approximation to this must be
made. By a series of fine holes in screens of lead, the X-rays
from a bulb were stopped down till a very narrow pencil
I mm. in diameter was obtained.

This was allowed to fall on a small crystal of copper sulphate
and about 3 cm. from the crystal, in the direction away from the
bulb, a photographic plate was set perpendicular to the beam of
X-rays. The experimental arrangements are shown in fig. i.

A. Interference pattern obtained with a crystal of zinc blende, the direction of the
incident rays being parallel to a trigonal axis of the crystal.

B. Diagram representing the pattern obtained with the same crystal when the

incident rays are parallel to a cubic axis. In this diagram the fainter spots have

been made more distinct.

Fig. 2.

374J

X-RAYS AND CRYSTALS

375

This beam was by no means completely absorbed by the crystal ;
it traversed it to fall upon the plate and when the plate was
developed after several hours' exposure, the effect produced was
visible as a circular dark spot of much greater dimensions than
the cross section of the incident beam on account of slight
scattering of the rays. But besides this intense spot, there
appeared around it, on the plate, a series of much weaker spots
apparently arranged in a geometrical pattern. Fig. 2 shows two
typical crystallographs obtained with a crystal of zinc blende. By
altering the distance of the photographic plate from the crystal,

Fig. I.

A, Anticathode. Al, Aluminium window. Sj, S2, S3, S^, Stops. Or, Crystal. P, P, Photographic plate.
B, Light tight box. I, The incident beam. D, A diffracted beam.

the small spots could be made to close into or move out from the
big central one and it was clear that the3\ were formed by narrow
rectilinear pencils spreading from the piece of crystal. Some of
these pencils make quite large angles, as much as 40°, with the
direction of the undeviated ray. The spots hardly altered in
size as the distance of plate from crystal was increased, remain-
ing always of the same size as the smallest stop. Copper
sulphate forms triclinic crystals, belonging to one of the more
complicated systems ; in order to obtain results which could be
analysed more readily, a crystal was chosen which belongs to the

376 SCIENCE PROGRESS

more simple cubic system. As it seemed possible that the effect
was due to a secondary X-radiation, it was deemed advisable to
use a crystal containing one of the heavier metals which give
much secondary radiation ; for this reason zinc blende was the
crystal chosen.

Fig. 2B shows the result obtained when the beam of rays
traverses a crystal of zinc blende in the direction of a cubic axis
of symmetry, the interference pattern on the photographic plate
showing complete fourfold symmetry.

The interference maxima are little elliptical spots arranged
in a complicated geometrical pattern ; these spots represent
narrow rectilinear pencils spreading from the piece of crystal
traversed by the rays. From a knowledge of the position of one
of the spots on the plate and of the distance of the plate from the
crystal, it is easy to find the direction of the pencil which formed
the spot in question ; and taking the cubic axes of the crystal as
axes of reference, to define the direction in terms of the angles
made with the axes. As the incident waves pass through the
crystal, they act on the atoms which they meet, a secondary
wavelet spreading from each atom as a wave passes over it. If
the incident beam contain a train of waves of wave length X,
then in order that there should be an interference maximum in
a particular direction it is necessary that the train of wavelets
from every atom in the crystal should be in phase in that
direction.

To express this condition analytically, some assumption must
be made as to the arrangement of the centres from which the
secondary wavelets spread.

Laue regards these centres as forming a point system which
has for its pattern a little cube with a point at each corner. This
is the most simple cubic point system possible. Take for con-
venience axes of reference parallel to the cubic axes and origin
at the centre of one of the atoms, molecules or whatever it ma}^ be
that represents the diffracting unit; then the neighbouring atoms
will be equally spaced in all three directions OX, O Y, O Z.
Let the incident light be parallel to the axis OZ and the distance
between neighbouring atoms be a.

If we express the condition that the wavelets from the atom
at the origin should be in phase with those from its nearest
neighbours along OX, OY, OZ, we ensure that the wavelets
from all the atoms in the crystal are in phase.

X-RAYS AND CRYSTALS 377

This may readily be shown to be so if:

aa = hiX

a^ =hoX (I)

a(i-y) = h3X

where hi, ha, hg are integers and a, /3, 7 the cosines of the angles

which the direction considered makes with the cubic axes.

This is analogous to the equation which holds for a line

grating :

X sin ^ = nX

where n is the order of the spectrum ist, 2nd, 3rd, etc., a
the "constant" or interval between successive lines and 6 the
angle which the direction of the telescope axis makes with
the normal to the grating when a line of wave length \ lies on
the cross wire. It means that the wave from the atom at the
origin is hi and h^ wave lengths behind that from its neighbours
along O X and O Y respectively, hs ahead of that from its
neighbour along O Z.

These equations can at once be tested. By knowledge of the
position of a spot on the photographic plate, the a/3 7 of its pencil
can be calculated and since from equation (I)

a _ /3 _ I — y

h, h, ha

the values of a, yS, i —7, for the spot ought to be in a simple
numerical ratio. As a matter of fact, this is found to be so ; the
values of a, /3, i— 7 for spots are in ratios such as 1:3:1 or
1:9:3. In no case is it necessary to assume a number hi, hg or hg
greater than 10 in order to fit these values of a, jS, i —7 to a whole
number ratio. This affords strong confirmation to the theory
that the spots are due to interference.

The numbers hi, hg, hg are the most convenient parameters
with which to define an interference maximum. They give at
once the position of the spot on the photographic plate and the
wave length to which it corresponds.

By choosing for hi, hg, hg any three integers, one obtains the
position of a spot which ought to appear in the photograph, if
the incident radiation contain the wave length corresponding to
these three integers.

To each spot in the photograph in fig. 2 numbers hi, hg, hg
can be assigned in this way. If this be done and the numbers
corresponding to the most marked spots are arranged approxi-

378

SCIENCE PROGRESS

mately in the order of their intensities, some spots being much
darker than others, the following list is the result :

Table I

Each set of numbers in this table corresponds of course to four or eight spots
in the pattern, according as hi and h2 are equal or unequal.

Le. 5, 3, I represents ± 5 ± 3 i

± 3 ± 5 I
3, 3, I represents ± 3 ± 3 i

the pattern being of fourfold symmetry.

Though all the numbers are simple ones, it is not at once
obvious that they belong to any system. Why, for instance, should
there be spots in the photograph for which hi, hg, hg have values
I, 3, I ; I, 4, I ; I, 5, I ; I. 7) ^ ; and no spot corresponding to
1,6, I ? Also there are sets 2, 2, i ; 3, 3, i ; 5, 5, i ; but no set
4, 4, I. There are many similar gaps in the series. Again the
most intense spots are not given by the simplest value of hi, hg, hs
in this list, as would seem natural, these spots being analogous
to the spectra of low orders in the case of a diffraction grating,
which are generally the brightest. A theory of the effect must
attempt to explain these anomalies.

On considering equations (I), which for convenience are here

repeated :

a a = hiX

a^ =h2X

a(i-y) = h3\

it is clear that a knowledge of the numbers hi, hj^ hg to be assigned
to any spot determines the wave length of the radiation which
has at that point an interference maximum, as well as the direction
cosines of the pencil which forms it. There are three equations
to be satisfied. The values of a/37 represent only two variables
since they must obey the equation :

flS + ^3 + y3 = I

and therefore the value of \ must also be adjusted to satisfy the
equations. It is here that the action of a " three dimensional "
grating differs from that of a " one dimensional " grating like an

X-RAYS AND CRYSTALS 379

ordinary line grating. In the latter case every wave length can
form an interference maximum, in other v^ords, the grating can
give a continuous spectrum. In the former case two extra
conditions must be satisfied, only one more direction cosine is
available and now it is only certain wave lengths that can form
maxima at all.

A similar effect may be got with a line grating and white
light. If half-silvered parallel plates are placed in front of the
grating of a spectroscope, thus introducing an extra condition
for interference, a continuous spectrum is no longer obtained
when white light is focussed at the collimator, but in its place is
seen a line spectrum representing a series of definite wave
lengths. If for the line grating a cross grating were substituted
and for the collimator slit a small hole at its centre, the analogy
would be still closer.

If the photograph represent the most general pattern possible,
all values of hi, h2, hg ought to correspond to spots. This is of
course impossible ; consequently there must be some limit to the
values of hi, hg, hs and in a general way it may be said of the actual
photograph obtained that the larger these numbers are, the
fainter are the corresponding spots. But at any rate, it would
be expected that the spots in the photograph should correspond
to a list of numbers hi, hg, hg complete over a certain range. This
is not so and some explanation must be put forward to explain
why certain spots fail to appear.

The explanation which Laue suggests is this — that when a
spot corresponding to some simple set of numbers hi, ha, hs is
missing in the photograph, it is because there is absent from the
incident radiation that wave length which is the only one capable
of forming the spot in question. On the other hand, certain other
spots do actually appear, because the right wave lengths to form
them are available. In his paper, he shows that all the
prominent spots in the photograph can be explained as due to
five wave lengths which may be regarded as five broad lines in
the spectrum of the incident radiation. The lines must be broad
because the five definite wave lengths only satisfy the equation
approximately. This explanation is not very satisfactory. In
the first place it invokes the aid of five constants to explain the
pattern and in the second place these five wave lengths would
give many othenspots which, as a matter of fact, do not appear in
the photograph.

380

SCIENCE PROGRESS

There is another way of explaining why certain spots fail to
appear and I think that by its means the whole pattern may be
shown to be far more general than Laue considers it to be. The
point system in which the atoms are arranged for the purpose of
the above analysis is not the correct one.

Point systems of cubic symmetry have three elementary
forms. There is that taken by Laue which has, as element of its
pattern, points at the corners of a cube; another w^hich has points
at the corners and one at the cube centre ; a third with points at
the corners and also at the centres of the six cube faces. It
seems to me that it is this last system which is revealed as
characteristic of the structure of the zinc blende crystal by the
interference pattern. This different point system involves a

Fig. 3.

slight change in the analysis. Suppose, as before, that axes are
taken with origin at an atom and that the atom at the origin
send off a wavelet which is in the direction a, yS, 7, hi wave
lengths behind its neighbour along the x axis and so forth.
The distance between neighbouring atoms along the axis is
"a" as before but this is no longer the shortest distance
between atoms.

The arrangement of the atoms in the X Z and Y Z planes will
be as in fig. 3. The previous equations (I) ensure that all atoms
such as O, A, B, C, etc., shall emit wavelets in phase. We must
now express the condition that atoms at points such as D, F,
the extra atoms at the centres of cube faces should also emit
wavelets in phase with those from O.

The difference in phase of wavelets from D and O will be

X-RAYS AND CRYSTALS 381

I _1 ?i wave lengths, the co-ordinates of B being , — ; this

must be a whole number. In order that this may be so, the
numbers hi and hg must be both odd or both even. The same
condition must hold for hg and hg. This at once explains the
peculiarities of the list of numbers hi, hg, hg. Taking in that
list all the cases in which hg is unity, by the above rule hi and
h2 must be odd. It is now clear why in so many sets hi and
ha have odd values and are even in two cases only, i.e. i, 4,
I ; 2, 3, I. These last must now be written 2, 8, 2; 4, 6, 2 and
are comparatively complicated.

If the numbers hi, ha, hg in the table be reconsidered, assum-
ing this new arrangement of the "elements" of the crystal
grating, the reason of their selection becomes clear. Take the
sets of numbers which have h3 = unity. In the first place, by
calculating the corresponding wave lengths, they can be shown
to consist of every possible set of numbers which correspond to
wave lengths greater than a limiting value \ = '034a. In the
second place, sets corresponding to a wave length approaching
X = •o6a give the two very intense spots i, 5, i and 5, 3, i which
form a marked inner square in the photograph ; when the
wave length corresponding to a spot is greater or less than this
value, the spot is more faint, until spots corresponding to the
limiting wave length \ = •034a can hardly be seen. It is as if
the incident radiation had a continuous spectrum with a maxi-
mum intensity at the region \ = •o6a. If now the sets of
numbers having hg = 2 be considered, exactly similar results are
obtained. There are two very intense spots which may be
designated as 4, 6, 2 and 2, 8, 2, which have wave lengths
\= •013a and X = 0553, which form the outer square. But in
addition, there are others, such as 2, 4, 2 ; o, 6, 2 ; 4, 4, 2, which
are considerably fainter and have wave lengths further from the
maximum in the spectrum. The only difference between this
set and the one which has hg = i is that all the spots are com-
paratively fainter and that the range of wave lengths represented
is much reduced, there being now both an upper and a lower

limit to the values of -.

The same may be said of the sets of numbers which have

ha = 3, there being still fewer of these ; finally, only one very

weak spot is visible corresponding to parameters which have

382

SCIENCE PROGRESS

ha = 4. Below are tabulated the sets of parameters which
have hs equal to i, as typical of the other sets corresponding to
points in the photograph.

It can be seen how complete the pattern really is, every wave
length greater than X = *034a producing an interference maxi-
mum if there are values of hi, h2, ha to suit. One faint spot is
included here which is not in the former table. The vertical and
horizontal columns give the values of hi and hg respectively. In

the squares are set the values of — and stars denoting the

" magnitude " of the corresponding spot in the photograph,
according to an arbitrary scale :

^ * * + •

Table II
ha = I

h. = I

hi = 3

K = S

h, = 7

h, = 9

h2 = I

Off the
photograph

•178
*

•073

•039

•024
Invisible

^2= 3

•178
*

•104

•057

•034

•022
Invisible

h2= 5

'073

•057

•039
*

•027
Invisible

h2 = 7

•039
*

'034

•027

Invisible

hi = 9

*024

Invisible

•022
Invisible

Every spot to which can be assigned a value unity of hs is
represented in this table and it can be seen how complete the
scheme is. If, on the other hand, the table had been drawn up
on the assumption that when hs was unity hi and hg could
have any integral values without the restrictions explained
above, there would be either many unfilled squares or values
corresponding to weak spots mixed up with those corresponding

X-RAYS AND CRYSTALS 383

to intense spots. Similar tables may be drawn up for the other
values of hg.

If the point system selected be the correct one, it is of interest
to speculate what significance this has with regard to the
crystal structure. This question cannot be answered definitely
until results are forthcoming obtained with crystals of other
systems but it is interesting to note that there is already strong
evidence for associating this point system with a crystal such as
zinc blende. In the first place, zinc and sulphur have the same
valency and according to the theory of valency volumes of
Barlow and Pope the atoms should be arranged as if they were
spheres of equal volume in a system of closest packing con-
sistent with cubic symmetry. In order that this may be so,
the centres of the atoms must be arranged in this point system,
centres at the cube corners and at the middle of the cube faces.
Thus, if all the molecules of zinc and sulphur behaved in an
identical- manner towards the light waves, they would give the
interference maxima actually found to exist. Again, the same
point system is repeated, though on a diff'erent scale, when only
those atoms are considered which are identical in every respect
as regards chemical nature, their neighbours in the crystal and
so forth. In the arrangement of the atoms assigned by Barlow
and Pope to zinc blende and simJlar crystals of compounds of
two atoms having the same valency, atoms of one kind are
grouped together four at a time in little tetrahedra, these
tetrahedra being again arranged in this point system ; there-
fore identical atoms, one from each tetrahedron, have the de-
sired arrangement. The element of a grating is that which,
in the ideal case, repeats itself indefinitely without variation
and the crystallographs give evidence of the arrangement of
elements in the crystal. In a crystal such as zinc blende, it is
possible to class together a certain number of atoms of zinc
and sulphur in such way that the assemblage contains a speci-
men of zinc and sulphur atoms of all modifications and so that
the whole crystal may be built up by packing together these
assemblages. It is these which probably form the elements of
the crystal grating ; they form by repetition the crystal pattern.
The simplicity of the interference pattern seems to show that
it does not concern itself with the arrangement of atoms within
these assemblages. Whether this is so or whether the atoms
themselves are the grating elements might be settled by experi-
25

384 SCIENCE PROGRESS

meriting with crystals for which there is good ground to
suppose that the arrangement of the individual atoms differs
from that of the assemblages.

To pass to the physical aspect of the phenomena, the fact that
the interference pattern is complete over a wide range of wave
lengths means that the incident radiation is analogous to white
light. It is not only the photograph reproduced here which
supports this idea but in other cases, when the photographs
which Laue obtained admit of analysis, the results conform to it.
The way in which the crystal builds up from the incident
radiation of all wave lengths the monochromatic trains of waves
which form the spots can perhaps be best understood by
considering the effect from a slightly different point of view.
Since the radiation from the bulb is to contain all wave lengths,
it may be regarded as a series of irregular pulses in the ether,
that is to say, considered as a whole and not split up into its
monochromatic components. It is in this way that Schuster
treats diffraction of white light by a line grating. Pulses of
this kind ought to undergo specular reflection at a plane surface
in just the same way that light or heat rays do, if the plane
surface differ in any way from the surrounding medium and if
its " polish " be sufficiently good.

Taking advantage of the infinitely repeated pattern formed
by the atoms in a crystal, it is possible to classify them arbitrarily
as having their centres in sets of parallel planes. The simplest
of these planes are the cleavage planes of the crystal but, of
course, an infinite number of other ways are possible. When
the arrangement is made in a more complicated way, the planes
contain individually a very few atoms per unit area and are
crowded very close together ; on the other hand, the simple
cleavage planes are far apart and denSely packed with atoms.
The "polish" of these planes is almost perfect ; at any rate the
irregularities due to the atom centres lying off the planes are
small compared with atomic dimensions (io~^ cm.) and there-
fore these planes will be capable of reflecting waves of wave
lengths lo"^ cm. The spots in the interference pattern are
formed by the reflection of the incident beam in these planes in
the crystal.

When a single pulse is reflected in one of these sets of
parallel planes the atoms in any one plane only scatter a fraction
of the energy in the pulse. The wavelets from all the atoms in

X-RAYS AND CRYSTALS

385

one plane go to build up a reflected wave front and therefore,
as the incident pulse traverses the crystal, a train of reflected
waves — one from each plane — is formed, the pulses in the train
following each other at intervals of 2 d cos 0^ where d is the
distance between successive planes and 6 the angle of incidence.
These reflected pulses may be analysed by Fourier's theorem

into trains of waves of wave lengths X, -, -, -, where X—2 d cos 0.

234

Now though the pulses in]]the beam have been supposed to be
quite irregular, they possess some quality which is expressed
by saying that they have an average " breadth " of something
like io~® cm. If in the reflected train pulses follow each other

Fig. 4.

at intervals much smaller than this they will interfere and cut
each other out ; if, on the other hand, they follow each other at
long intervals, the trains will contain little energy per unit
length. Thus out of all the possible ways of dividing the crystal
into planes, a certain group will be selected, these being planes
for which the value 2 d cos 0 lies within a range of wave
lengths of the order of the average " breadth " of the pulses.

This way of looking at the interference must be analytically
exactly the same as that used by Laue. The numbers hi, ha, hg
in his analysis correspond to parameters defining one of these
methods of dividing the crystal into planes. For instance, a
spot in the photograph corresponds to the values 3, i, i of
hi, ha, hs. This means that (see fig. 4) the wavelet from the
atom at O is three wave lengths behind that from the atom at A,
one wave length ahead of that from C, in the direction of the

386 SCIENCE PROGRESS

interference maximum. Therefore, by going along a distance

-OA parallel to the X axis and up a distance - OC parallel to

the Z axis, an atom D is reached, the wavelet from which is
in phase with that from O, since

2 2 ^

The wavelet from E is also in phase with that from O, since

ih2--h3 = 0

2 ^ 2 *

and therefore when a pulse falls on these atoms the pulses from
the atoms O, D, E are all in phase in the direction of the
interference maximum ; that is to say, this is the direction in
which the pulse would be reflected from a plane O, D, E.

The advantage of this way of looking at the formation of the
spots is that it enables one to follow what happens when the
crystal is not placed symmetrically. If the crystal be tilted so
that the incident radiation does not pass along an axis of
symmetry, the spots of the pattern will all be displaced and
they will move as if they were reflections in planes fixed in the
crystal and tilting with it. This is shown very well by two
photographs which Laue published in his paper. The first shows
the effect obtained when a trigonal axis of symmetry of the
zinc blende was parallel to the incident beam (see fig. 2a); the rays
now making equal angles with the three cubic axes, a pattern of
threefold symmetry is the result ; the spots of this pattern are
reflections in planes of the crystal, some of the planes being the
same as those which give the spots in the pattern of fourfold
symmetry. In the second photograph, the crystal was tilted
though 3° from its normal position about an axis perpendicular
to one of the cube axes. The pattern is distorted exactly as it
would be if the spots were reflections ; it is also interesting
to notice that certain spots are very much changed in intensity.
If the angle of incidence of a pulse in a set of planes be altered,
the value of 2 d cos 0 alters accordingly and so the wave-
length of the reflected train may vary from a value characteristic
of intense spots to one characteristic of weak ones and vice versa. '
It was found before, in the case of the square pattern, that
intense spots corresponded to a wave length •o6a and this is
true of the two photographs considered here. One spot in

X-RAYS AND CRYSTALS 387

particular is hardly visible in the symmetrical pattern but
becomes the most intense of all when the crystal is tilted, because
its wave length is now right in the maximum of the spectrum.
If one imagines the crystal slowly tilted, the spots will be
in motion on the photographic plate and the wave length
continually changing. If only certain wave lengths were
present in the incident radiation, spots would be disappearing
and appearing all over the plate but as a matter of fact it can
be seen from the photographs that the process is quite con-
tinuous and so all wave lengths are present.

The ellipticity of the spots can be easily understood if the
pencils forming them are regarded as rays reflected in crystal
planes. It is a geometrical result of the fact that the incident
pencil is not strictly parallel but slightly conical. If a conical
bundle of rays be reflected in a slip of crystal, at right angles to
its axis, regarded as a pile of parallel plates, the rays will come
to an approximate line focus on the far side at a certain distance
from the crystal and the ellipticity of the spots is a result of this
tendency.

It was pointed out to me by Mr. C. T. R. Wilson that if
the interference phenomena could be regarded thus, it might
be possible to get a strong reflection in crystals which have
some very decided cleavage plane, this plane being presumably
thickly packed with atoms. To test this, a narrow beam of
X-rays was obtained by stops exactly as in Laue's experiments
and allowed to fall on a mica plate set so that the incidence was
almost glancing. A photographic plate was placed so that it
would receive both the transmitted beam and the reflected beam
if there were one.

It was found that in this way a well-marked reflected spot
appeared after a few minutes' exposure to quite a weak bulb,
whereas Friedrich and Knipping found it necessary to expose
the crystal during many hours to the most intense beam of
X-rays obtainable in order to get good results. The effect is
almost a surface efifect, quite thin plates of mica sufficing to give
full reflection ; it is possible that in this case the reflected radia-
tion is less penetrating and of greater wave length than that
forming the interference pattern with zinc blende. The rays
are, however, little absorbed by aluminium and black paper.
The reflected beam will, as before, consist of monochromatic
radiations, the wavelength depending on the angle of incidence

388 SCIENCE PROGRESS

and the distance apart of the cleavage planes in the mica. No
reflection has yet been obtained with an angle of incidence less
than 75° but there is no reason to suppose that this means any-
thing more than that the time of exposure was not long enough
for smaller angles.

When a somewhat longer exposure (30 minutes) is given to
the plate, subsidiary spots appear in a very characteristic manner.
In all the crystallographs taken with crystals of any system set
in any way, a certain feature of the arrangement of the spots can
be traced. There are generally several series of spots forming
well-marked ellipses passing through the big central spot.
These ellipses are nearly circular : they are in fact sections by
the photographic plate of circular cones which have the incident
pencil as one generator. The reason for their appearance is as
follows. The atoms of the crystal may be classed as having
their centres on parallel straight lines as well as in parallel
planes. Consider the crystal as divided in this way into a set
of parallel rows of atoms mclined at an angle to the direction of
the incident radiation. As an incident pulse passes over the
successive atoms of any one row, wavelets are emitted from each
atom in turn at equal intervals of time and these wavelets will
be all in phase in any direction lying on a circular cone having
the row of atoms as axis and the direction of the incident radia-
tion as one generator. In all these directions at least one con-
dition for interference is satisfied, so that the ellipse in which
the circular cone cuts the photographic plate gives a locus of
possible positions of interference maxima. The ellipses which
are so apparent in the crystallographs correspond in this way to
densely packed rows of atoms in the crystal. At the point where
two ellipses intersect, two conditions for interference are satisfied ;
the third is satisfied by the wave length and therefore a spot is
to be expected there. This effect is very apparent when the
beam is reflected from a slip of mica and a somewhat long
exposure given to the photographic plate. As well as the main
reflected spot, there are many others reflected from subsidiary
planes in the crystal. The greater number of these are arranged
on two ellipses which pass through the central spot and intersect
in the main reflection. They seem to correspond to a lattice
arrangement of atoms in the cleavage plane of the mica, the
atoms being at the intersections of two sets of parallel straight
lines. The atoms are therefore in rows in these two directions,

X-RAYS AND CRYSTALS 389

each direction being the axis of a cone which cuts the plate in
one of the elHpses.

There can be no doubt that these crystallographs must throw
a great deal of light on the physical nature of these short ether
waves. When an electron is shot into the anticathode of the
X-ray bulb and then brought up, there must be set up those
electro-magnetic pulses first supposed by Stokes to constitute
X-rays. It seems very probable that the waves here dealt with
are these electro-magnetic pulses and it will be of the greatest
interest to discover whether they are the same as the X-rays or
not. All that is known of them so far is that they are penetrat-
ing and act on a photographic plate. It is possible that there
may be in the rays from an X-ray bulb two components, waves
and corpuscles. The electro-magnetic pulses can be regularly
reflected, can interfere, can act on a photographic plate and
perhaps can be polarised. Their energy is spread uniformly
over a wave front. On the other hand, the facts of the emission
of characteristic secondary radiation from metals, of the equality
of the speed of electrons knocked out of atoms by X-rays and
the speed of the electrons which originally produced the rays in
the X-ray tube, seem to be explained far more simply by suppos-
ing the existence of a corpuscular radiation. These corpuscles
are represented by quanta of energy flying through space con-
tained in a small region of invariable volume. There is perhaps
the possibility of both these components having been hitherto
classed together as one. This is only conjecture but at any rate
it seems as if these experiments of Laue and his collaborators
may solve not only problems of crystal structure but also the
problem of the true nature of X-rays.

"MATHEMATICS AND CHEMISTRY":

A REPLY

By JAMES RIDDICK PARTINGTON, M.Sc.

In a recent issue of Science Progress (January 191 2) there is
contained a very interesting discussion on the relation between
mathematics and chemistry, between mathematicians and
chemists and between chemists and chemists, in which the
author, in addition to a criticism of the present conditions,
has given us what is very much more valuable, a suggestion of
what he considers to be a satisfactory method of remedying
their inherent faults. Since my text-book {Higher Mathematics
for Chemical Students: Methuen & Co., London, 191 1) has
been mentioned as the source of inspiration of the article and
as the author says explicitly that his statements ** may serve
to induce discussion or criticism," I may take this opportunity
of expressing my own views on what are undoubtedly matters
of increasing importance, viz. the utility of a knowledge of
mathematics to the chemist and the way in which he can
acquire that knowledge most profitably. Although the majority
of the statements made in Mr. Worley's essay are likely to
meet with hearty assent from any one who approaches the
subject without bias on either side, yet there are certain views
expressed which appear to be highly controversial and as such
call for discussion.

It would seem that the discussion must necessarily involve
the answering of questions such as the following :

(i) Is it desirable that chemists should be taught higher
mathematics?

(2) How much should they be taught ?

(3) In what way should the instruction be given ?

Besides these questions of pedagogic interest, there is also
the problem of the general relation between mathematics and
chemistry which has received due consideration in Mr. Worley's
paper. He has examined not only the relation between the
two sciences but also those between their followers. From

390

"MATHEMATICS AND CHEMISTRY": A REPLY 391

what he says of the latter, it would appear that things have
not improved very much since the time when Richter (1789)
made the statement which is quoted in my book (p. 5) : *'. . . the
most prominent chemists occupy themselves little with mathe-
matics and the mathematicians feel that they have little business
in the province of chemistry"; for we are now told that
** chemists, as a rule, know very little mathematics but even
when they have received what is considered to be a fair amount
of mathematical training they only too frequently find that their
knowledge is not sufficient to enable them to deal with the
practical problems that arise ; unfortunately, they also too often
find that the mathematician has not sufficient chemical know-
ledge and feeling to give them the assistance they need." The
advance probably lies in the raising of the standard of what
is considered to be a fair amount of mathematical training,
which is now certainl}^ higher than that which sufficed in
Richter's day.

This attitude the writer considers to be due to a real incom-
patibility of the chemical and mathematical habits of thought
a view which is reasonable enough in itself but which leads
him to what is clearly a fundamental error in natural philosophy.
After saying that " it must be admitted that chemical problems
are frequently of such a nature that it is impossible to be certain
of anything; the chemist frequently does not know what he
wants to prove nor indeed does he want to prove anything;
he wants merely to put a reasonable interpretation upon certain
experimental results," Mr. Worley tells us that ''chemical
properties are the expression of the reciprocal behaviour of
substances, not absolute quantities; on this account it is very
difficult to quantify such properties : often they can be felt but
not figured."

The word " feeling " or " feels " occurs in fact no fewer than
five times on the same page and it is quite clear that the author
is referring to that medieval doctrine of the Discrimination of
the Scientific Instinct which, although it should have received
its death-blow when Columbus circumnavigated the earth, is
apparently still very much alive. Does Mr. Worley seriously
ask us to believe that it is safe to rely on our feelings when
deciding a scientific problem ? One example 'of the results of
this procedure is given in my book (p. 4) ; at the risk of being
tedious to my readers I will add a few more. Could we reason-

392 SCIENCE PROGRESS

ably expect a physicist to ** feel " that there is a bright spot at
the centre of a circular shadow, that glass is a better conductor
of some kinds of electric currents than copper, that a surface
of separation between two perfectly transparent media is a
better reflector than polished opaque silver? Would any
chemist have those ** stirrings in the viscera" — as Professor
James put it — which would lead him to expect that " inert "
nitrogen could exist in a most active allotropic modification ;
or that, in spite of all that had been said about the cause of the
activity of substances in a " nascent " condition, the new mon-
atomic gases should be totally inert ? We know that there were
chemists who flatly contradicted the truth of the last example
and that solely on the evidence of their feelings. As a last
example we might take the question of the constitution of isatin,
which had been settled agreeably to the feelings of chemists
until Hartley and Dobbie showed that the actual facts were
exactly the opposite to what we should expect. It is undoubt-
edly true that chemists have made instinctive guesses which
have later on been shown to be quite incorrect. Some of the
guesses are bound to turn out right in any case on the theory
of probabilities but this is no justification for the use of guess-
work as a scientific method ; if scientists denied any validity to
the principle of the Discrimination of the Unscientific Instinct
in the time of Darwin, how can they defend their own use of
an identical principle now ?

When we come to deal with the three pedagogic questions,
we find that Mr. Worley has spared us the trouble of discussing
the first, for his paper leaves no doubt remaining that he recog-
nises the great value, both from a practical and from an
educational standpoint, which a mathematical education has
for a chemist.

In dealing with the second and third problems he is less
clear than could be wished. It is, of course, necessary to
make up our minds at the start not only what we are going
to teach but who is to be taught; the initial knowledge and
the future prospects of the student must always regulate the
course of any teaching that is going to be fair and straight-
forward, not merely the result of faddism or slavish adherence
to some pet educational doctrine. I wish to make it clear at
this point that I am not thinking, in referring to "the future
prospects " of the student, of his ultimately competing in any

"MATHEMATICS AND CHEMISTRY": A REPLY 393

examination, for I withhold my opinion of the value or otherwise
of examinations as being quite irrelevant.

The class of readers to whom my book is addressed is, I
think, made sufficiently clear in its title. It is not written for
experts. There is obviously a difference here which Mr. Worley
unfortunately does not keep clear. After stirring up our
sympathies for "the undergraduate struggling against various un-
necessary and unnatural obstacles to obtain a degree," he further
on leaves this unfortunate individual quite in the lurch and turns
his attention to the more dignified subject of *' the mathematical
requirements of the chemist for the purposes of investigation and
research." It must be confessed that by this sudden change of
attitude the writer to a great extent robbed us of those tender
feelings which he at first so successfully aroused. Although we
should pity that student, what really could be our attitude to-
wards one who had survived that iniquitous thing, " our present
educational system " and was still capable not merely of " in-
vestigation " but also of " research " ? He can surely be trusted
to look after himself and in the rest of this paper he will be
allowed to do so-

The answers to be given to the remaining questions are
largely matters of opinion and can most properly be left to the
judgment of the individual teacher. Since, however, Mr.
Worley has given us his opinions, it may be permitted to me to
express mine. The amount of mathematics which should be
taught to the chemical student varies, as has already been said,
with the future prospects of the latter. If he intend to devote
himself to synthetic organic chemistry, he will need only very
little, whereas if he be going to do original work in physical
chemistry, he will require more, although still not very much as
compared with the physicist. As a rough mean value, I am
inclined to indicate what is set out in my text-book, which may
therefore be taken as the expression of my opinion on this side.
Now the more important question how the student may with the
greatest advantage be taught the amount of mathematics which
has previously been decided is necessary and tentatively
sufficient for his requirements. Here Mr. Worley is again rather
indefinite, for he says that although "chemists are taught
mathematics without sufficient instructions in the way in which
the weapons put into their hands are to be used and especially
the way in which they are not to be used," yet " it would probably

394 SCIENCE PROGRESS

be vastly more satisfactory if the necessary parts of mathematics
were taught without attempting to deal with chemical problems,
with sufficient examples and exercises to make the student
proficient in the carrying out of the various processes and if
afterwards real chemical problems were dealt with thoroughly."
This can only be taken as meaning that the chemical student is
to have the following mathematical training :

(i) A course in pure mathematics, without any indication as
to what sort of use the material he is learning is afterwards
likely to be to him ; and (2) another course in which the material
is applied to chemical problems and in which the student is more
particularly told what he is not to do with his previously
acquired knowledge.

Now the first course corresponds with that which the chemical
student has been accustomed to receive ; it is one of those ** un-
necessary and unnatural obstacles " against which he has been
** struggling " and is all the less likely to be of real service for
the reason that " the chemical and mathematical habits of mind
are incompatible " and that " chemists as a class are never likely
to be mathematicians." It is my own opinion, supported by the
educational teachings of Herbart, that a mathematical process can
be most readily assimilated by such persons when it is presented
along with some chemical problem, just as the physical student
most readily learns the Calculus of Variations in connexion with
the Principle of Least Action, Fourier's series and integrals in
their application to the Conduction of Heat and the theory of
Probabilities as it appears in the Kinetic Theory of Gases. In
a text-book of mathematics in which the aim is to teach mathe-
matics and not chemistry, nothing can be gained by making the
examples too complicated. We do not usually begin our text-
books on dynamics by considering the effects of friction or
elasticity ; nor in teaching the student the theory of conduction
of heat do we insist on his trying his feeble strength directly on
an irregularly shaped and irregularly heated heterogeneous mass
cooling in draughts of air of various temperatures moving at
random over its surface, i.e. on real problems. Are we then to
be accused of deliberately trying to give " the impression that
(physical) problems are very much simpler and straightforward
than is really the case " ? I believe that Mr. Worley's accusation
that I have tried to do this in connexion with chemical problems
is unjust. It is true that in the book the simpler cases of mass

"MATHEMATICS AND CHEMISTRY": A REPLY 395

action are considered as well as the more complicated examples
but it is also made quite clear that ** there are cases in which n as
derived from velocity measurements does not agree with that
derived from the chemical equations " (p. 150), which apparently
is what Mr. Worley is telling us on p. 410 ; and further on more
space than usual is devoted to emphasising the uncertainty
which always attaches to the determination of the " order " of an
interaction by means of velocity measurements : " The view is
becoming more and more pronounced that reactions of higher
orders are very rare" (p. 152); "a chemical reaction is the re-
sultant of a large number of conditioning causes . . . and
therefore proceeds in a variety of ways and leads to a variety of
products. It is only in a few cases that we can say exactly how
a reaction proceeds in all its stages " (p. 246). I had hoped that
this would not have given rise to the opinion that there was any
attempt to make out that the whole matter is really simpler than
is actually the case and should have thought that it would have
been unnecessary for my critic to say that " the law of mass action
is a generalisation of an axiomatic nature, never apparently
obeyed exactly and incapable therefore of absolute proof; that
even if the correct assumptions are made with regard to the
number and nature of the interacting molecules there are many
disturbing factors, as a rule, that cannot be taken into account "
(p. 408). It would be interesting in the light of his statement
that the law of mass action is '* a generalisation of an axiomatic
nature," to ask the author if he knows the difference between a
generalisation and an axiom, as exemplified by the Second
Law of Thermodynamics and if he has ever heard of Willard
Gibb's thermodynamic demonstration of the law of mass action.
After what had been said on the tendency to superficiality
exhibited by existing text-books, it is not surprising to find the
author stating that " it is consequently highly desirable that the
mathematical treatment of a question, such, for instance, as that
of mass action, should be thorough, dealing with all the
difficulties that arise." One is tempted to ask if the writer has
found this method possible in practical teaching ?

Mr. Worley has also introduced some remarks on the theory
of solution into his paper. After exciting our imagination by a
moving picture in which a high edifice of " mathematical
jugglery " is to be '' razed to the ground," he makes us " shudder
to think of the terrific downfall should the foundations give

396 SCIENCE PROGRESS

way." We had almost begun to shudder when our fears were
calmed by a sudden cessation of superlatives and the author's
adding mildly, " such an occurrence is not impossible." Our
peace is not of long duration, for " we may find some day that
all the units of the solute are potentially active." When we
ponder a little time over the phrase " potentially active," we are
brought to a frame of mind in which it would cause us no
surprise to find " some day" that the units of the solute were
continuously distributed in discrete portions throughout the
solvent, in the form of microscopic, hard, spherical, soft cubes of
immense size. The author has in fact fallen in that last
paragraph — perhaps by reason of some unconscious psychical
process of suggestion due to the fact that the din of the last
" terrific downfall " is still ringing in his ears — into a trap which
one would think by this time had lost its deadliness. As this
does not appear to be the case, it may not be wholly useless to
repeat what has previously been said elsewhere in connexion
with the subject :

" The real fundamental proposition of the thermodynamic
theory of solution is contained in the assertion that the osmotic
pressure of a solution and every other property conditioned
solely by it, depend simply on the number of solute molecules
scattered through a given volume of solution and not at all on
the chemical nature of either solute or solvent or on the
relation between the latter, provided only that the solution is
dilute. The chemical properties of solutions, on the contrary,
depend not only on the number but also on the nature of the
dispersed particles and so are to a large extent conditioned
by the exact mode of connexion between the solvent and
solute."

" It seems necessary to emphasise this point because of the
fallacy, which unfortunately appears to be widely spread, that
there is some fatal incompatibility between the old qualitative
hydrate theory of solution and the new quantitative thermody-
namic theory of which van't Hoff was the pioneer. This view
has resulted from the one-sided outlook of the champions of
each theory and is certainly not a necessary consequence of the
fundamental basis of either. It is greatly to be desired that
writers of the theory of solution should distinguish clearly
which aspect of the subject belongs properly to their own
investigations and should refrain from attacking, on the basis
of irrelevant experiments, a theory which is quite immune from
the criticism which may reasonably be levelled against any
particular hypothetical view of the nature of solutions."

HORTICULTURAL RESEARCH
II. TREE PRUNING AND MANURING

By spencer PICKERING, F.R.S.

In the previous article an account was given of the results
obtained at Woburn in investigations of various problems
connected v^ith the planting of trees ; other experiments in-
volving the treatment of the tree after it has been planted will
be referred to in the present article.

Pruning

In the case of trees used for ornamental purposes, correct
pruning is a matter of taste and judgment, little more being
required than the removal of branches which interfere either
with the symmetry of the head or the shortening of branches
which project too far beyond their fellows. A similar attention
to symmetry is required in dealing with fruit trees but symmetry
is not the only desideratum : fruit-bearing and the production
of well-developed and ripened fruits should be the main object
in view. This is not the place to enter into all the techni-
calities of the art of pruning nor is this art always amenable
to investigation at an experiment station ; inquiry has to be
confined, at any rate in the first instance, to the main principles
governing the practice of pruning.

Under the head of pruning may be included all operations
which involve the use of the knife on branches or roots. It
is desirable to separate branch-pruning into four categories :
(i) the severe shortening of all the branches when the tree is
first planted, known as cutting back ; (2) the annual shortening
of the new twigs formed during the season, this being what
is generally meant by pruning; (3) the cutting out of badly
placed branches, especially those which cross or rub against
others, known as thinning; and (4) operations in summer
intended to arrest growth, such as pinching off the growing
tips of the twigs or half-breaking or twisting the ends of these

397

398 SCIENCE PROGRESS

twigs. The removal of some of the buds from trained trees,
in order to help the development of those which are left, is
also, properly speaking, a form of pruning, though it is generally
known as disbudding.

Cutting Back

The cutting off of about one-half or two-thirds of each
branch of a young tree when it is transplanted from the
nursery to the plantation is very generally recognised as being
the proper practice, though it is often omitted by the amateur,
who dislikes seeing his tree curtailed and learns too late that
such parsimony is false economy. The proper functioning of a
tree depends on the correct balancing of root-action to leaf-
action ; the one supplies the tree with water and food-material
derived from the soil, whilst the other is the channel through
which carbon is absorbed from the air : but as was explained in
the previous article, in transplanting a tree the existing root-
system is destroyed and a new root-system gradually has to
be evolved : the balance between roots and branches can only
be restored by curtailing the branches so as to adapt them
to the injured roots. This is the rationale of cutting back on
planting. The result of omitting the operation is very apparent,
especially during the first season and is often very serious.
Instead of forming good healthy leaves and a fair amount of
new growth, the leaves have been found to show a deficiency
of some 25 per cent, in size, little or no new wood being
formed. Photographs of two apple trees which were similar
when planted eighteen months previously are shown in figs, i
and 2 (the staff shown in the figures is divided into feet) ; these
give a fair idea of the results of the two forms of treatment. In
the case of plum trees, which commonly fruit precociously
after transplanting, if not cut back, the trees will often be so
exhausted as to be killed.

Although good horticulturists never question the advisability
of cutting back on planting, there is a considerable diversity of
opinion as to when this operation should be performed, some
advising that it be done at the time of planting, others at the
time when growth is starting in the spring, others again
advocating that it be deferred till one year after planting.
A number of somewhat elaborate experiments have been made
on this subject and it has been found that the time at which

t k;. I. — Cm back.

HORTICULTURAL RESEARCH 399

the cutting back is performed makes no difference whatever
so long as it is done before active growth sets in ; trees cut
back at various times between November (when they were
planted) and the middle of April (when they were beginning
to grow) all behaved in the same way : but when the cutting
back was deferred till July, it was seriously detrimental, the
trees showing a marked deficiency of growth and vitality
during each of the subsequent eight years. Rather than cut a
tree back in the summer, it is much better to defer the operation
altogether till the following winter. The effect of such delay,
however, is not good, though it varies considerably in different
cases. It cannot be good for a tree to remain, even for one
season, in the condition exhibited in fig. 2 ; and even if a tree
be cut back after the first year, one season's healthy growth
will have been lost. In some cases a tree treated thus will
continue to lag behind its fellows which were cut back on
planting, whilst in other cases it has been found that very
vigorous growth has followed the deferred cutting back, the
tree maintaining this vigorous habit of growth for several
years ; the result being that it has grown only, whilst it ought
to have been growing (though more moderately) and also
fruiting. In one plantation of apples where this deferred cutting
back had been adopted, the crop during the first five years
after planting was only one-quarter of that of similar trees
which had been cut back at once, though the trees themselves
were 10 per cent, greater in size than the latter. In another
case there was a deficiency of 40 per cent, of fruit during the

first eight years.

Branch-Pruning : Effect on Growth

There are various sayings current amongst horticulturists
embodying the idea that the more a tree is pruned, the more
it will grow. It is obvious that whatever truth there may be
in such an dea, it can only be true within certain limits ; now
direct experiment shows that these limits are very narrow
indeed. When the branches are cut away, the roots will be in
excess of the requirements of the tree and new branches will be
formed, the tree endeavouring, as it were, to repair the
injury. In the case of a tree which is old and has ceased to
grow or of one which has become stunted from other causes,
26

400 SCIENCE PROGRESS

the new wood which is thus made may rejuvenate the tree
and result in a healthy growth, which would never have occurred
had the old branches been left unpruned ; but in the case of a
tree already in a healthy condition the formation of new wood
to supply the place of that which has been cut away must
involve an extra tax being placed on the resources of the tree
and though the tree may do more work, the results will fall
short of those which would have been obtained without the
pruning. In other words, a young tree which is pruned heavily
every year must necessarily remain a smaller tree than one
which has not been pruned.

Various plantations of different varieties of apple trees on
the paradise stock have been grown side by side at Woburn
under different systems of branch-treatment. The normal
treatment consists of light pruning every year, involving the
removal of about one-third of the length of each new shoot
formed during the season ; whilst in other cases the pruning
is hard, two-thirds of the growth being removed ; in others,
again, there is no pruning. The trees are measured periodically.
The results leave no doubt that the less a tree is pruned
the bigger it becomes : the unpruned trees after five years
showed an excess of 33 per cent, in size over the moderately
pruned ones ; those which had been hard pruned showed a deficit
of 13 per cent. The differences naturally diminish as time
goes on, at any rate in cases in which the pruning is only
moderate ; for after ten years the unpruned trees showed an
excess of only 7 per cent, over the moderately pruned ones
and after fifteen years the difference was reduced to 2J per cent.
The deficiency in size produced by the hard pruning, however,
shows no reduction; from the 13 per cent, after five years it
became 18 per cent, after ten years and was again 13 per cent,
after fifteen years. Figs. 3 and 4 represent average specimens
of an unpruned and hard-pruned tree of Bramiley's Seedling
apple ten years after planting.

It is found that the deficiency in size of the hard-pruned
trees is more marked as regards the height and spread than as
regards the girth of stem ; the former showed, after five years, I
a deficiency of 21 to 24 per cent, but the latter one of only
9 per cent. : this is what might naturally be expected : therefore,
hard-pruning may be adopted as a means of making a tree
sturdier in proportion to its size than it would otherwise have

HORTICULTURAL RESEARCH 401

been, though the actual thickness of the stem and branches
may be less.

It might be suggested that, though a hard-pruned tree is
smaller than an unpruned one, it has really made more growth,
where allowance is made for the wood removed in the pruning;
but this is not the case, as was proved by comparing the recorded
weight of the prunings and the total weights of the trees when
some of these came to be removed. This point has also been
investigated in another way. Several trees were taken and on
each of them a number of straight shoots of exactly the same
size were selected, all 36 in. in length ; some of the shoots were
left unpruned, whilst others were cut back to a length of 24, 12
and 6 in. Fig. 5 shows one set of shoots at the end of the season
following this pruning. It is easy to see that the harder the
pruning has been the less is the growth which has taken place.
On the average the unpruned shoot increased five and a half
times more in weight than that which had been cut back to 6 in.
and the number and length of side shoots arising from it was
three times and twice as great, respectively : so that in no sense
had pruning favoured growth. Shoots cut back to intermediate
lengths gave intermediate values.

Effect on Fruiting

These experiments also afforded evidence on another im-
portant point, though this is scarcely visible in the figures :
the fruit-buds formed on the twigs were more numerous the
less the pruning, so much so that there were on the unpruned
twigs five and a half times as many fruit-buds as on those cut
back to 6 in.

The effect of pruning in reducing the fruiting power of trees
has been investigated more extensively in other experiments. In
one case a record of crops was available for this purpose obtained
from a ten years' trial of sixty dwarf apple trees grafted on the
paradise stock of each of three different varieties. The general
results for the first and second periods of five years are illus-
trated by the first two diagrams in fig. 6, from which it will
be seen that the weight of fruit obtained from the unpruned
trees is about double that obtained from the moderately pruned
or "normal" trees, whereas from the hard-pruned trees the
yield has been but little more than half of that from these

402

SCIENCE PROGRESS

normal trees. In another case there was a plantation consisting
of eight trees of each of 117 different varieties of apples, four
of each being on the crab stock and four on the paradise
stock. These trees had been treated in the same way till
they were seven years' old and then a difference was made
in pruning them, moderate pruning being continued with one
half and hard pruning adopted in the case of the rest. The
results of the cropping in the following season (all the varieties
did not bear fruit) are illustrated by the other diagrams in fig. 6
and bear similar evidence to that of the other experiments,

c
o

200

§■

-a
0

<♦-

:e t3

° 100

-p

<O0

■s

C
0

-0

•p

Q)
O

-P
CO

i.
(D

"a
o

-0

First
5 Years,

Second
5 Years.

53Vars. SOVars.
on Crab. Paradise,

Fig. 6. — Crops from trees pruned to different extents.

the hard pruning having reduced the yield to one-third of the
normal, this being equally the case whether the trees were on
the paradise or crab stock. These results refer to one season
only (1906) but the results have been similar in every succeeding
year up to the present date (1913). Of course, some instances i
occur every year in which the hard-pruned trees yield the
better crops but this is probably accidental, for no one variety
is found to do so uniformly in successive seasons.

The way in which fruiting is favoured by an absence of
pruning has received many striking illustrations at the Fruit

Fig. 3.— Unpruned.

Fig. 4. — Hard piuiicu.

402]

HORTICULTURAL RESEARCH 403

Farm during the last few years. All the shelter hedges there,
which are many hundreds of yards in length, consist of various
sorts of fruit trees : these are clipped after the manner of hedges
but in some cases a branch here and there has, for certain
purposes, been left uncut ; these uncut branches, especially in
the case of plums and damsons, are always loaded with fruit,
whilst the whole of the rest of the hedge is often quite bare.

One point which has caused us some surprise is that the
increase in crop produced by absence of pruning has not been
accompanied by any serious reduction in the size of the fruit.
Thus, taking the ten years' results with dwarf apple trees
previously quoted, the average size of the fruits from the un-
pruned trees was only 4 per cent, less than that of the fruit from
the moderately pruned ones ; that from the hard-pruned trees
being 18 per cent, greater. These differences would not
compensate for the much greater differences in the actual
weight of the crops, so what has been said as to the effect of
pruning on the weight of fruit obtained applies with almost equal
force to the value of that fruit.

Practical Application of the Results

It is thus established as a fundamental principle that the less
pruning there is the more will the tree grow and the more fruit
will it bear. There are, however, considerations which render
it advisable in practice not to dispense with pruning altogether.
While a young tree is growing the chief object of the grower
should be to condition its growth in such a way that when it
comes into bearing it should be able to carry its crop to the
greatest advantage : the branches should be evenly disposed and
should be far enough apart to admit light and air to the centre
of the tree ; none of these should cross or rub against another
and they should be stout enough to bear any reasonable weight
of fruit without being bent out of shape or broken. To attain
this end some pruning will be necessary, for, as has been
mentioned above, one effect of pruning is to make a tree
comparatively sturdier ; a branch will occasionally have to be
removed altogether, whilst others must be pruned hard so as
to restrict their extension in length until they have become
stout and strong. This will generally mean a certain but de-
creasing amount of pruning for five or six years after the tree

404 SCIENCE PROGRESS

has been planted, when the annual pruning may be reduced to
the removal of a few terminal inches of the twigs, which
generally consist of wood which has not ripened and would
probably give rise to feeble growth in the following year-
Combining these considerations with the general principle
mentioned above, we should say that, after the first cutting back
of the tree, pruning should be restricted to such an amount as is
necessary for the formation of good sturdy head to the tree.

What extent of pruning will be necessary to effect this will
vary very much with the nature of the particular tree. A
variety which is a strong grower and a shy bearer in its early
years will require very little pruning. The tree shown in fig. 3
is a variety of this sort (Bramley's Seedling). Although in this
particular instance no pruning whatever has been done, the tree
is fairly well formed and sturdy, being capable of carrying a
large crop of fruit : to a considerable extent it has pruned itself,
just as most forest trees do, branches originating and flourishing
only where they are wanted, that is, where there is enough light
and room for their free development. On the other hand, fig. 7
illustrates the result of not pruning a tree which is a less sturdy
grower (Stirling Castle) and bears heavy crops even when quite
young. The branches, as will be seen, are all bent out of shape
and when laden with fruit, much of this will be destroyed by
being on the ground or by being whipped off by the wind.

Instances of the harm done by the absence of pruning when a
tree is young may be seen in nearly any farm orchard through-
out the country and even in the plantations of growers in most
of the fruit-growing districts. But examples of over-pruning
are, perhaps, not less frequent and are generally to be found in
private gardens, where the stunted trees throw out every year
small forests of thin twigs, which are as regularly removed
and only serve the purpose of feeding a bonfire.

Pruning at different Times

It is often held that pruning should be done in the autumn
and that injury or loss of sap is likely to occur if it is done in
very cold weather. Such views appear to be ill-founded.
Pruning has been done in all states of the weather at Woburn
and no injury has ever been noticed, even in the severest frost.
One of the plantations there — a mixed plantation of a quarter

HORTICULTURAL RESEARCH 405

of an acre— was divided into three equal sections, one being
regularly pruned early in the autumn, the other in mid-winter,
the third in the spring ; during the eight years throughout
which the records extended, the three sections showed no
appreciable difference, the total values of the crops being in the
proportion of 109 : 94 : 100.

Summer Pruning

The results obtained at Woburn on summer pruning are
not yet complete and are still somewhat ambiguous. So far,
the performance of the ordinary annual pruning in summer
instead of in winter has led to no appreciable alteration in the
behaviour of the trees, either as regards their growth or their
fruiting. But under the general term "summer pruning" are
included other operations which fall short of actual pruning and
are generally followed by ordinary pruning at the end of the
season. These operations consist of anything which will check
the growth of the twigs and lead to the swelling of the buds
lower down on the stems. Sometimes the ends of the shoots are
pinched off; or the shoots may be partially broken and left
hanging on the trees ; or they may be twisted between the
thumb and fingers, so as to be injured. In many cases, no
doubt, the buds below the point of injury receive, in consequence,
a larger supply of nourishment than they would otherwise do
and they become converted into fruit-buds for the following
season. Such a result, however, is somewhat uncertain and is
dependent on the character of the weather following the
operation ; for if this favour vigorous growth, the buds which
should only have swelled will be forced into activity and the
result will be a mass of summer growth, consisting of short
twigs which will not ripen properly and will have to be cut
away in the winter.

Influence of the Age of the Tree

All that has been said above as regards pruning applies to
trees which are still in what may be termed the growing stage
and in some respects will have to be modified when it is a
question of older trees. This is so as regards the principle
that we get more growth according as the pruning is more
restricted. It must be recognised that with trees, as with
animals, there are certain periods in their life-history which

4o6 SCIENCE PROGRESS

are characterised by certain differences in behaviour. There
is, first, a period of rapid growth, when, in the case of a tree,
branch-formation is prominent, corresponding with the increase
of stature in the case of animals. In the second period branch-
formation becomes insignificant ; the tree has attained its limit
of size and such wood-formation as occurs goes to increase
the substance of the stem and branches already in existence.
This is the period of full bearing. Such new shoots as are
formed at the time are rather fruiting twigs than future
branches ; the general outline of such a tree will remain
practically unaltered during twenty or thirty years. It is only
when a branch is removed that anything approaching to branch-
formation will occur, the tree endeavouring, as it were, to
repair the damage done. The pruning of a tree at this stage,
therefore, will result in the formation of a greater length of new
wood than would otherwise have occurred. As an instance
may be quoted the results with tw^o similar fifteen-year-old
apple trees on the paradise stock : the one which was not
pruned formed twigs totalling 2,200 in. in length during
the season, whilst the other, which was pruned, gave growth
to twigs measuring 6,700 in.

It may be added that a third period in the life of a tree
may be recognised — that of senile decay— which is generally
characterised by a strenuous attempt to reproduce its species
before death, as evidenced by the bearing of heavy crops of
small fruit — worthless, however, from the point of view of the
grower — and by sending up of numerous suckers from the roots.

Method of Cutting the Branches

Of the technical details of pruning very little need be said
here. It is generally held to be of importance to prune back
to a bud which is pointing in the direction in which it is
desired that growth may extend ; in most cases this will be a
bud pointing outwards, so that the branches may spread apart
from each other, though some varieties of apples are so
straggling in their habit that the reverse is desirable. That
the position of the bud influences the direction of the growth
arising from it is, no doubt, true, though perhaps not to such
an extent as is generally supposed, for it is sometimes found
impossible to recognise the difference between similar trees
which have been pruned for many years to inside or outside

Fig. 5.

Fig. 7. — Unpruned precocious bearer.

406]

HORTICULTURAL RESEARCH 407

buds. In cases in which a difference has been made it was
found, also, that the trees pruned to the inside buds made the
greatest growth, due, no doubt, to the branches being closer
together and, therefore, getting more drawn up. Other details
which are insisted on — that the cut should be a slanting one and
as near a bud as possible— seem to be quite unimportant and to
make no difference to the well-being of the tree : when a branch
is cut a callus always forms at a bud and in a plane at right
angles to the branch ; any wood above it dies and is cut off
from communication with the living wood below by the callus.
These dead snags may be unsightly but they are not detri-
mental to the tree ; in our experiments on the subject, trees
pruned even two inches above a bud have always done better
than those pruned in the orthodox way, because, no doubt, the
bud is weakened by having the wood cut away close to it.

Root-Pruning

Wood-formation and fruiting are to a certain extent antago-
nistic to each other : a tree which is growing vigorously will
be too much exhausted in the process to bear heavily; by
putting a check on the growth, the cropping may be increased.
One method of doing this is by root-pruning. The tree, if
young, may be lifted bodily and the roots shortened ; or if
older, a trench may be dug down around it and all or some
of the roots pruned. The check thus given to a tree is a
serious one. In some plots of dwarf apple trees on paradise
stock root-pruning has been practised regularly since the trees
were planted. In one case this was done every fourth year,
with the result that, after fifteen years, the size of these trees
was only 75 per cent, of that of similar trees which had not
been root-pruned ; in a second case the trees were root-pruned
every other year and their size was reduced to 35 per cent,
of the unpruned trees ; whilst in a third case they were root-
pruned every year : these trees did not grow at all and after
about fifteen years were all dead. In the case of the least
severe treatment (pruned every fourth year), the trees bore
heavily, principally in the second year after the pruning ; but
owing to the reduction in size of the trees, the actual amount
of fruit borne was, on the average, only 44 per cent, of that
from similar trees which had not been root-pruned. Where the

4o8 SCIENCE PROGRESS

root-pruning was more frequent the total weight of fruit was
quite insignificant.

Evidently root-pruning is not an operation to be indulged
in except in extreme cases and then only sparingly, when, for
instance, a tree persists in making rampant growth and does
not flower. (The absence of fruit, be it noted, if the tree
has flowered, is not a case demanding root-pruning; it is
generally due to the flowers not having been properly
fertilised.) Root-pruning is rarely indulged in except in
private gardens ; in nine cases out of ten its practice there
is due to excessive branch-pruning. The effect of the latter is,
as has been seen, to reduce the fruiting, hence the necessity
of pruning the roots in order to restore the balance between
roots and branches. But it is not a very rational method of
treating a tree to injure it in one way and then injure it in
another to counterbalance the damage done. If there was less
branch-pruning we should hear very little about root-pruning.
In one general case only may it be inevitable, that of strong-
growing trees planted against a wall ; severe branch-pruning is
necessary, if the tree is to be confined to the wall and this will
entail a corresponding pruning of the roots.

Manuring

The most conspicuous features of the results obtained at
the Woburn Experimental Fruit Farm on the subject of the
manuring of fruit trees is the smallness of the effect produced
by any manures on apple and similar trees and the essential
difference between the requirements of these and of the smaller
fruits, such as gooseberries, currants and strawberries. Doubt-
less these results, as must be the case with all manurial
experiments, are largely dependent on the nature of the soil but
it must be borne in mind that the soil of the farm is by no means
of exceptional richness, as measured either by analysis or by
the behaviour of farm crops in it before it was converted into
a fruit farm. It was nothing more than agricultural land of
moderate fertility, which would probably be below the average
as a favourable soil for fruit growing ; the upper layer of good
soil is only about seven inches deep and below that there is a
very stiff clay subsoil, into which the roots of trees show a
great disinclination to penetrate and from which, therefore, they

HORTICULTURAL RESEARCH 409

can derive very little nourishment. Yet, in spite of this,
manure has had no effect on the trees.

There are twenty-one plots of dwarf apple trees devoted to
these experiments ; each contained originally eighteen trees but
the number has now been considerably reduced. They may be
divided into three groups : one lot receives a normal dressing
of manure, either artificial or natural, this normal dressing
consisting of twelve tons of stable manure to the acre or a
mixed chemical manure, probably equivalent thereto ; the second
group receives less than the normal or no manure at all ;
the third, more than the normal, up to ten times the ordinary
amount of artificials or two and a half times the ordinary amount
of dung : some of the plots receive artificials as well as dung.
These dressings have been applied every year since 1895.

Taking the records for the first ten years, during which the
plots contained their full complement of eighteen trees each,
those receiving extra manure prove to be only 37 per cent,
ahead of those receiving the normal amount ; the plots receiving
a deficit are also ahead of the latter but to the extent of only
07 per cent. These values apply to the combined results of
annual measurements of the leaf-size, triennial measurements
of the trees and annual records of the value of the crops. Each
of these sets of data gave very similar results. The average
difference of about 3 per cent, between the groups of plots
under the extreme differences of treatment is so small that it
may well be attributed to error. The observations have now
been continued with part of the trees during another seven
years and the average differences of these later records are even
less than those quoted above.

These results have been put to the test in two different
ways. One lot of trees embraced in the experiments was
removed after ten years but the manurial treatment of plots
was continued and farm crops were grown on them — potatoes
for two years and onions for one year ; and it was found that
on these crops the manures had the ordinary effect which they
have in other soils ; for instance, in one of the seasons the value
of the potatoes in the plots with excess of manure showed an
excess of 70 per cent, and that in the plots with deficit of
manure a deficit of 9 per cent., as compared with those receiving
moderate dressings. In the second place, the experiments with
apple trees were repeated in a very poor sandy soil and here

410 SCIENCE PROGRESS

the effect of manuring was very considerable, showing that the
method of experimentation was not in fault : the influence of
the treatment on the growth and fruiting of the trees began to
be appreciable after the first or second season and has become
more marked as time went on : thus in the seventh year after
planting the value of the crops from the trees receiving a
deficiency of manure was 40 per cent, below the normal and
that from those receiving extra manure was 30 per cent, above
the normal.

Whether or not manures will eventually have an effect on
the trees at the Fruit Farm is a matter of conjecture ; it is
certain that they have been quite unaffected by all that has
been applied to them during the past seventeen years. No
sweeping conclusion can, of course, be drawn from this that
such trees should never be manured ; but inasmuch as our field
does not appear to be exceptional, it seems certain that trees
would frequently exhibit a similar behaviour elsewhere and
that a grower would be wise before spending money in manure
to make sure, either by experiments on a small scale or by
considering the results obtained by his neighbours, whether
that manure is likely to be beneficial in his own case ; otherwise,
as with us, all his expenditure in dressing his land will be wasted.

Whilst manures have been thus ineffective on apple trees,
it is remarkable that, in this same soil, they have proved to be
absolutely essential to bush fruits. Thus with gooseberries,
plots containing four plants of each of forty-five different
varieties have received continuously different dressings. During
the first five years the crops from those receiving dung were
35 per cent, greater than those receiving no manure and the
superiority in the size of the fruits was very marked ; but
artificial manures had very little effect, at any rate, on the
cropping, the average yield from plots so treated being only
I per cent, above that from the unmanured plots. These
experiments have been continued for fifteen years and the plots
now are even more striking than they were at first ; for whilst
those which have received dung have 37 per cent, of the original
bushes planted in them still alive, the unmanured plots have
only 9 per cent, and those receiving artificials 23 per cent. The
fruit is now quite valueless except from the bushes receiving
dung.

The effect of varying the amount of the dressings was

HORTICULTURAL RESEARCH 411

interesting. Taking the first period of five years, an increase
in the dung from 12 to 30 tons per acre had no effect in
increasing the crops but it increased the growth considerably ;
with the 12 tons this growth was six times that in the un-
manured plot but with 30 tons it was ten times this quantity.
In subsequent years, however, this increased growth in the
early stages told on the cropping and the crops from the
heavily dressed bushes are now, after fifteen years, double to
treble those from the lightly dressed ones.

The effect of artificial manures on growth was similar to that
of dung but much less marked. When these artificials were
equivalent in supposed manurial value to the 30 tons of dung,
the growth was about 80 per cent, more than in the unmanured
plot but with artificials equivalent to only 12 tons of dung no
increase in growth was obtained.

Thus dung is essential to the well-being of gooseberries in
our soil and probably in all soils; the same has been found
to be the case with black and red currants and with raspberries.
With strawberries the results have been somewhat different,
for though they were benefited considerably by manuring, the
superiority of dung over artificials was not marked and in some
seasons was in favour of the one, in others of the other ; but
as regards the size of the fruits, there was a distinct balance
in favour of the dung.

The very different manurial requirements of fruit-trees and
bushes render it evident that, to obtain the most economical
results from this point of view, they should be grown separately
and not in mixed plantations ; other considerations, such as
economy of space, may often, however, necessitate modifications
of such an arrangement.

Measurement of Results

The problem as to the measurement of results in the case
of fruit-trees is by no means simple and was one of the first
which had to be attacked at Woburn. From a fruit grower's
point of view it is clear that the fruit borne should be the
criterion ; but it w^ould have to be the fruit borne during the
whole life of the tree ; as that may extend to fifty years or
more, such a method of measurement is hardly practicable.
The annual crops, it is true, must always be recorded, not only

412 SCIENCE PROGRESS

the total weight of the crops and the average size of the fruits
but these data must be supplemented with others less dependent
on climatic peculiarities and the chance depredations of insects!
etc. Measurements of growth must be made and growth is the
most important function of a young year, for the more it grows,
the larger will be the crops that it will be able to bear when
it comes to maturity. In experiments which are designed to
last only three or four years, the total increase in weight
of the tree may be determined ; for this purpose, as well as
to ensure uniformity, the trees are always weighed before
planting. When the experiment has to continue for a longer
time, other methods must be adopted. One of these is to
determine at intervals the general size of the trees by measur-
ing their height, the spread of the branches and the girth of
their stems. Another is to measure the total length of new
wood formed during the season, this being supplemented by
weighing the prunings. A third depends on determining the
relative size of the leaves : the sixth leaf from the end of each
shoot is removed and these leaves are dried and weighed. Occa-
sionally where the trees are small, the whole of the leaves are
removed and their weight determined.

The results obtained by these various methods have been
compared with each other, as well as with determinations of
the dry matter and nitrogen in the leaves; it is satisfactory
to find that they all show a substantial agreement : thus in each
of eight experiments eight different methods of measurement
were adopted and the order in which the experiment could
be arranged according to one of the methods was the same
as that obtaining in the case of the other seven, with only two
partial exceptions. Naturally, the actual magnitude of the
differences when measured by different features is not the
same, for some features will be more affected than others by
different treatment, e.g. the length of new wood formed varies
through greater limits than the size of the leaf. Where crops
have to be considered complication arises, for growth and
cropping are antagonistic to each other ; and such cases always
call for special discussion.

THE DISCUSSION ON ANIMAL
NUTRITION AT DUNDEE

Recorded by E. J. RUSSELL, D.Sc.

The new agricultural section of the British Association has
adopted the useful rule of holding at each meeting a discussion
on some important agricultural problem of local as well as
general interest. Animal nutrition was selected as the subject
for Dundee and the section was fortunate in being able to
bring together physiologists, agricultural chemists and practical
feeders, so that each party could present its particular point of
view for the consideration of the others. Unfortunately the
discussion on the origin of life somewhat interfered with the
attendance.

There can be no question as to the value of the discussion.
The problem has long been under investigation and each of
the three groups of workers had a considerable fund of
established fact to draw from. In general too, facts and data
familiar to one group were new to the others, so that in the
conversations that arose after the meeting it not infrequently
happened that a communication one group thought was lacking
in originality another group considered new and interest-
ing. The interest displayed in the discussion was real and
spontaneous, as indeed is almost always the case when a subject
has a human or practical side. But of chief importance was
the fact that men who are very differently occupied were
brought together and that a genuine attempt was made by all
to extend their several mental horizons. Agriculturists who
have remained faithful to the traditions handed down by an
older school of physiologists and have accumulated a large
body of data on the nutritive values of different foods were
able to assure the physiologists that none of the present methods
of evaluating foods gave results entirely in accordance with
the facts.

The physiologists had irrefutable evidence to offer that no
single scheme can completely express the value of foodstuffs :
neither the protein minimum and energy value nor the starch

413

414 SCIENCE PROGRESS

equivalent nor any other method affording more than an approxi-
mation to the truth. Great stress was laid on the subtle princi-
ples now considered essential to nutrition ; in fact, the meeting
was fast drifting into the position that all nutrition is a matter
of subtle principles when it was sharply pulled up by Dr.
Crowther, who delivered a spirited defence of starch equiva-
lents. Dr. Crowther declined to break off with the old love
till he knew more of the new and emphasised the marked services
rendered to agricultural chemistry by the admittedly imperfect
methods now on their trial. The agricultural chemist is under
the daily necessity of advising farmers as to the purchase of
feeding stuffs and it is futile to condemn methods which do
work in a way until new methods are forthcoming. The
position finally reached was that the nutrition of an animal
depends not only on the supply of carbohydrates, fats, proteins,
etc., of which the agricultural chemist already takes cognisance
but also on certain subtle compounds wanted probably only in
small quantity ; furthermore, that the molecular structure of
the compounds wanted in large quantity {e.g. the proteins) must
be considered. Although this perhaps represented no very
great advance, it was satisfactory to find that there was so close
an agreement between the views held by the physiologist, the
agricultural chemist and the practical farmer. It was still more
satisfactory to agricultural chemists to find that difficulties
which had arisen in the course of their animal nutrition work
are already under consideration by physiologists and apparently
in a fair way to being solved.

Such is a general impression of the result of discussion.
Before passing to the remarks of the various speakers, it
may be pointed out that the practical farmer long ago learnt
how to fatten animals and that he has a store of empirical
knowledge on the subject. Great stress is laid on regularity
of meals, quietness, etc. ; it is noteworthy indeed, as was
remarked at the meeting, that the details of the methods of
fattening bullocks given by one very successful farmer were
surprisingly similar to those adopted for human beings in sana-
toria. Thus the animals are regularly turned out at the same
hour each morning, fed with weighed quantities of food at
regular intervals, cleaned up and bedded for the night at a
definite hour ; and each one is kept under close observation.

The main difficulty in conducting experiments on the nutri-

ANIMAL NUTRITION DISCUSSION AT DUNDEE 415

tion of animals arises from the necessity of working with large
numbers; it is this circumstance that gives peculiar value to
the experimental work done by Mr. William Bruce, of the
Edinburgh and East of Scotland Agricultural College, whose
communication was the first taken.

THE VERDICT OF THE BULLOCK
(William Bruce)

The experiments to which this communication relates were
designed to test feeding stuffs and rations as used under the
ordinary conditions of farm practice. The object in view was
to provide practical guidance for the farmer rather than to
deal with any scientific questions with regard to animal nutri-
tion. Nevertheless, at least one point has emerged that is
closely connected with this subject.

It may be noted here that a special feature of these experi-
ments is the scale on which they have been carried out. With
the object of eliminating individual variation and reducing
the probable experimental error to a minimum, larger lots
of animals were employed than is usual in such work.
Besides this, some of the findings have been checked and
confirmed by repeating the trials.

As the experiments extend over eight seasons (1904-12),
it is impossible on the present occasion to discuss all the con-
clusions arrived at. Two issues which are of both practical and
scientific interest have therefore been singled out for discussion.
These are :

(i) The bearing of some of the results on the ''starch
equivalent " method for the valuation of feeding stuffs.

(2) A comparison of the value of the feeding stuffs as deter-
mined by the experiments.

The " starch equivalent " method of valuing a feeding stuff
consists in analysing the material under consideration and
multiplying the analytical results by digestibility co-efficients
which have been determined by digestion experiments with
the foodstuff in question. The figures so obtained for the
several digestible nutrients are then multiplied by their
respective energy values, starch being taken as unity.

The special point of the method lies in the attempt that is
then made to deduct from this total energy value a figure
27

4i6 SCIENCE PROGRESS

representing the amount of energy required for the digestion
of the nutrient material over and above that which v^ould have
been required had the nutrient been starch. The energy value
so deducted is supposed to be that necessary for dealing with
foodstuffs in which the percentage of fibre is considerable and
therefore the figure deducted represents the percentage of fibre
multiplied by a factor which varies from 0*29 to 0*58 according
to the character of the foodstuff". The values of feeding stuffs
are thus reduced to starch values or equivalents and expressed
in numbers that should indicate their relative value.

The method has been accepted generally as being by far the
best of the chemical methods that have been proposed for
valuing feeding stuffs and one naturally does not elect to
criticise it in any hostile spirit but rather the opposite. It
remains, however, to be seen how far it will apply to the
practice of feeding.

The first point of interest that was observed on studying the
results of the East of Scotland experiments from the standpoint
of starch equivalents was the fact that in a comparison of Bombay
and Egyptian cotton cakes, the former, although the poorer of
the two on analysis, gave consistently somewhat better results.

Between 1903-6, the value of Bombay cotton cake was
very thoroughly tested in three series of experiments which
were conducted in East Lothian in the winter feeding of half-
bred (Border-Leicester x Cheviot) hoggets. In each of the
three seasons the trials were carried out with six lots of sheep :
in the first, the lots contained thirty-eight animals ; in the
second and third twenty-two and thirty-two respectively were
used. They were folded on turnip land and each lot got as
much food as it would consume, subject to certain limitations
as to the quantity of the several items composing the respective
rations. The feeding began in December and was continued
during three to four months.

In the second season, Egyptian cotton cake was compared
with Bombay cotton cake. The details of this particular part
of the experiment are as follows :

Total roots consumed

„ hay „ ...

„ concentrated food consumed

„ live weight increase
Increase per head per week .

Egyptian

Bombay

cotton cake.

255^ cwt.

267^ cwt.

. 818 lb.

558 lb.

. 1,697 „

1,699 „

760 „

830 „

. 2325 „

2-539 »

ANIMAL NUTRITION DISCUSSION AT DUNDEE 417
The composition of the cakes was as follows :

Albuminoids.

Oil.

Carbohydrates.

Fibre.

Egyptian cake (per cent.) . 20*9

5'i

32'2

23-8

Bombay „ „ .19*0

5*4

35'o

22*3

It will be observed that the total quantities of food con-
sumed in this case are not the same and those acquainted with
the analysis of cotton cakes will also notice that the Bombay
cotton cake was rather above the average in composition.
But giving due weight to these two factors, the results were a
striking departure from what might been anticipated from
a comparison of the starch equivalents of the two rations.

In the following season an experiment in cattle feeding was
conducted in which two lots, each composed of eight carefully
selected two-3^ear-old fattening bullocks, were fed alike in every
respect except that one received Bombay cotton cake and the
other the same amount of Egyptian cotton cake. The analyses
of the two cakes used were as follows :

Albuminoids.

Oil.

Carbohydrates.

Fibre,

Egyptian cake (per cent.) . 22*5

4*9

32'9

21-5

Bombay „ „ . i8'6

3*4

35"2

22*2

The result of this experiment was that during equal periods
both lots made the same live weight increase, namely 290*5 lb.
per head or 2*07 lb. per head per day. Thus the Bombay
cotton cake, although shown by analysis to be a somewhat
poor sample, gave results equal to that obtained with the richer
Egyptian cotton cake.

These two experiments proved the value of Bombay cotton
cake as a feeding stuff and pretty clearly indicated that per
unit of nutriment it is more valuable than Egyptian cotton
cake.

Turning to a series of experiments undertaken in 1911-12,
for the purpose of comparing coconut cake and wheat bran
with linseed cake as foods for fattening cattle, we get a much
more definite case of departure from what might be anticipated
from the starch equivalent values. Three lots of fourteen
bullocks of about 1,000 lb. weight were fed in all respects alike
except that one got 4 lb. linseed cake, another 4 lb. coconut
cake and the third 4I lb. wheat bran per head per day. The
common basal ration was 90 lb. swedes, 12 lb. oat straw and
4 lb. Bombay cotton cake. The trials lasted 112 days: the

4i8 SCIENCE PROGRESS

quantities of the foods under trial and the results obtained were
briefly as follows :

Lot I. Lot n. Lot in.

Linseed cake. Coconut cake. Bran.

Tot il quantity .... 6,278 lb. 6,278 lb. 7,420 lb.

Starch equivalent (per cent) . 7235 793i 4276

Total starch equivalent . . 4,542 4,978 3,172

„ increase (14 cattle) . 3,5221b. 3,0871b. 3,1721b.

Increase per head per day . 2*27 „ I'gi „ 2*02 „

These figures are so remarkable that with the object of
ascertaining their suitability for comparison they have been
subjected to careful examination.

Scrutiny of the increase shows that the individual increases
are quite as good as can be expected. There are no notable
deviations. It may be mentioned that the cattle were fed as
six lots, each experiment being thus carried out in duplicate and
the fact that the results of the two series agree remarkably well
is evidence of trustworthiness. The probable error of the
gain has been calculated from Wood's figure of 14 per cent,
as the probable error of a single animal and are given below.
The actual probable error in these experiments appears to
be in the neighbourhood of 11 or 12 per cent, for a single
animal, so that the probable errors of the amounts gained are at
least not greater than those given. It may be noted that they
are small compared with the difference in the average daily
gain. They indicate for instance a 15 to i chance that the
daily gain of the linseed cake lot was at least 10 per cent,
greater than that of the coconut cake lot.

LotL Lotn. Lotm.

Linseed cake. Coconut cake. Wheat bran.

Starch value of basal ration . . 10*35 io'35 io*35

„ „ additional ration . 2*90 3*18 2*02

Daily gain (lb.) .... 2-27 ± '085 1*91 ± '07 2-02 ± '075

The total starch values and the relative efficiencies of the
three rations are :

Lot L Lot H. Lot HL

Linseed cake. Coconut cake. Wheat bran.

Starch value of total daily ration . . . 13*25 I3'53 12-37

Assumed necessary for maintenance . . 60 6'o 6'o

Starch value available for live weight increase . 7*25 7*53 6*37

Do. as percentage of ration No. I . . . 100 io3'9 ^7'9

Average daily gain as percentage of Lot I. . 100 84* i 89*0

In order to arrive at something which will represent approxi-
mately the starch value available for gain, the figure representing

ANIMAL NUTRITION DISCUSSION AT DUNDEE 419

the starch equivalent considered by Kellner to be necessary for
the maintenance of the cattle of the size used has been deducted.
This leaves a figure which represents the starch equivalent of
the ration which is available for maintenance in each case and
one would anticipate that the daily gain would be in propor-
tion to this figure. If this were so the coconut cake lot should
have made about 4 per cent, greater gain than the linseed
cake lot and the bran lot about 88 per cent, of the gain of the
linseed cake lot. Actually the bran lot made 89 per cent, of
the gain of the linseed cake lot, which must be regarded as
extremely close agreement with expectation ; but the coconut
cake lot made 16 per cent, less gain than the linseed cake lot.

The second point advanced for discussion is a means of
establishing a relationship between commercial values of
different feeding stuffs. Most experiments stop short at deter-
mining the relative value of feeding stuffs at the prices current
when the experiment is conducted ; consequently there is some
difficulty in applying the results, because the market prices of
feeding stuffs fluctuate and accordingly change in relation to
each other. The chief difficulty arises from the fact that the
price of a feeding stuff has to cover two things of importance
to the farmer, namely the consuming value and the manurial
value. An attempt to deal with this difficulty may be given in
concrete form. In seasons 1909-10 and 1910-11, a series of
cattle-feeding experiments was undertaken to determine the
value of soya bean cake by comparing it with linseed cake in
the winter feeding of cattle. A number of lots of cattle con-
sisting altogether of seventy-two animals were equally divided
and fed exactly alike in all respects except that the one half
got 4 lb. of linseed cake per head per day and the other received
4 lb. soya bean cake. In this way 6 tons i8f cwts. of the
two cakes were consumed. The increases were as follows :

Live Weight increase. Cost per cwt.

cwt. qr. lb. s. d.

Linseed cake 84 i 24 37 8^

Soya bean cake .... 78 o 5 35 sl

The difference in cost thus amounted to 2s. ^d. per cwt. live
weight increase in favour of the soya bean cake or 25s. id. per
ton of that food consumed.

The linseed cake cost £(^ 55. per ton and the soya bean cake
£^ 155.; when the value of their manurial residues, namely

420 SCIENCE PROGRESS

41S. and 52s., are deducted, the net food costs are 144s. and 83s.
respectively. But according to the results of the experiments,
the soya bean cake is worth 25s. more and therefore its relative
food value becomes 1085. when the food value of linseed cake is
144s. Thus the food value of soya bean cake was three-fourths
that of the linseed cake and its purchase value, taking linseed
cake at £<^ 55., would be \ (1855. — 415.) + 52s. = ;^8 per ton.

If the results of the coconut cake, bran and linseed cake
experiments already described are dealt with in the same way,
it will be found that the consuming value of both coconut cake
and bran is 62*6 per cent, that of linseed cake.

These experiments, so far as they go, indicate that compo-
sition and energy value are not the only things to be taken into
account in feeding. It appears that certain foods either have a
peculiar feeding value apart from that indicated by their compo-
sition or that certain substances combine to make a good ration
and other substances do not.'

THE DISCREPANCY BETWEEN THE RESULTS

ACTUALLY OBTAINED AND THOSE EXPECTED

FROM CHEMICAL ANALYSIS

(Dr. F. Gowland Hopkins)

It seems characteristic of the present moment in science that
fundamental conceptions, which we had looked upon as estab-
lished, concerning which our teaching had become dogmatic,
should prove to need revision.

The science of animal nutrition, though no one has pre-
tended that, in any of its departments, the data are exact, has
certainly developed its own quota of dogma.

We have long taught, for instance, that satisfactory criteria
of the efficiency of a dietary (assuming the presence of the
necessary inorganic constituents) are furnished by its content of
protein and energy considered solely from the quantitative
standpoint. A dietary, to be efficient for this or that animal, we
have taught, must contain a certain, rather vaguely known,
minimum of protein and a more exactly determined minimum of
total energy. We have commonly been content to evaluate the
protein by multiplying estimated nitrogen values by a numerical
factor; the energy from calculations based upon calorimetric

ANIMAL NUTRITION DISCUSSION AT DUNDEE 421

determination carried out with pure proteins, carbohydrates
and fats.

These data, which refer to the diet as raw material, must (we
have recognised) be qualified by determination of such variants
as digestibility, absorbability and the like ; but the amounts of
" available " protein and of " available " energy have remained
our sole essential criteria of efficiency in diets. That all the
assumptions implied in this limitation are become dogma is
seen when we read the latest writings of the highest
authorities.

Yet observations made during quite recent years (and I feel
that those just detailed for us come into the category) show that
our criteria and definitions have been incomplete. The food
supply of an animal may, as a matter of fact, contain protein in
sufficient amount, also abundant energy and yet may support
the animal inefficiently or fail altogether to support it : this,
too, when, to the best of our knowledge, the inorganic supply is
correctly adjusted.

We have learnt that the efficiency of the protein supply is
not to be defined by its amount alone. Ten or twelve years'
work upon the chemistry of " protein " carried out by Emil
Fischer and his school, as well as by others, has made it
abundantly clear that the term covers a multitude of substances
which, however closely related, differ so considerably that they
must have different nutritive values for the animal body. We
must for the future define an efficient protein supply in terms of
quality as well as quantity.

The nitrogen-free constituents of food we have been prone
to consider as sources of energy alone, as so much fuel. Since
Rubner has shown that fat and carbohydrate burn isodynami-
cally in the body, so that the place of a certain amount of
carbohydrate in a dietary can be supplied by a quantity of fat
containing its equivalent in energy, without affecting the
metabolic balance of the animal, we have troubled ourselves
but little about the relative amounts of carbohydrate and fat
present in a food mixture. Questions of convenience, digesti-
bility and the taste of the animal have, of course, intervened
to determine this ratio in practical cases ; but we have looked
upon the total energy as the one really essential factor. Yet
recent observations have proved abundantly that once an
animal is totally deprived of carbohydrate, no matter how much

422 SCIENCE PROGRESS

energy is at its disposal in the form of protein and fat, its
normal metabolism is undermined ; fats are incompletely burned,
all stability of protein metabolism disappears and health fails.
Carbohydrate, like protein, serves other purposes than that of
mere fuel and a minimum of the former is as necessary as a
minimum of the latter. The isodynamic law of Rubner holds
within limits only : carbohydrates and fats are not, an fond^
physiologically equivalent. One does not know how far this
fact may prove to have practical importance. Practical dietaries
probably all contain the necessary minimum of carbohydrate ;
but it is well to point out that for individual species an optimum
amount may exist not identical with the minimum. About this
we know nothing. It may quite well prove worth while to
determine more exactly the effect upon nutrition of altering the
carbohydrate : fat ratio during prolonged periods.

Apart from considerations relating to the better known
constituents of foods, we know from the work of the past year
or two that quite unsuspected factors are essential to the
normality of diet. An absence from the animal's diet of
substances to which it is accustomed in very small amount may
produce startling results. Feed a man on intact rice grains and
he does well. Supply him with decorticated polished rice alone
and he develops disease of the severest type. Restore a sub-
stance present in very minute amount in the cortex of the grain
and you restore nutritive power to the polished grain. Feed
a young animal on an artificial mixture of pure protein, fat,
carbohydrate and salts and it ceases to grow, even when the
amount consumed is quantitatively adequate. Add to the arti-
ficial dietary quite minute amounts of material extracted,
secundum artem^ from animal or vegetable tissues and it supports
growth quite normally.

It appears as though we shall have to extend our concepts
concerning efficiency in rations beyond the range of nutritive
values in the stricter sense and speak of the indispensable
" physiological actions " of certain constituents. Part of
dietetics is to become part of pharmacology!

I have avoided going into details with reference to this
matter, as others will follow me who are qualified to speak
concerning them. I have said enough to suggest that something
like a revolution is about to upset much of our dogmatic
teaching concerning animal nutrition. It is well, I think, that

ANIMAL NUTRITION DISCUSSION AT DUNDEE 423

the public should know how much there is yet to be done by
way of observation and experiment before our knowledge of this
important subject can be said to be in any way complete. How
far the newer conceptions that I have touched upon will
intrude into practice the future alone can tell. The united
efforts of the practical stock-breeder and of the laboratory investi-
gator will be required before the degree of their importance can
be determined.

ACTIVE CONSTITUENTS OF GRAIN
(Prof. Leonard Hill)

In order to test the worth of the claims made during a recent
newspaper agitation as to the superiority of standard bread,
we obtained a large number of young rats and mice, caged them
in lots of twenty in the same way and fed some lots on white,
some on standard and some on whole meal flour and
water. We soon found that white flour was not a food on
which life could be maintained, whilst standard or whole meal
flour proved to be very much better. White flour to which we
added the germ sufficed to maintain the animals in health and
in some cases through two or even three generations. The
fashion for standard bread has died away because people prefer
the colour and taste of white bread. White bread is a better
foil to other tastes and so adds to the pleasures of the palate.

White flour also bakes into a loaf of better quality. It is a
matter of indifference to most of us whether we eat white bread
and discard the active subtle principles in the outer layers of
the wheat berry, because we obtain these principles from meat,
milk, eggs, the growing tips of vegetables, etc. In the case of
slum children or the children of the Labrador fisher-folk, fed on
white bread and tea, however, it is a matter of great moment ;
such a diet is the cause of beri-beri (rampant in Labrador) and
probably of scurvy and contributes to other slum diseases.

Flack and I have succeeded, by adding an extract of bran
and sharps to the dough, in making a white loaf excellent in
taste and flavour and containing the principles necessary for
life. On this bread we have successfully fed pigeons, whilst the
birds in the control experiment fed on the best ordinary white
bread all died. There is no reason therefore why a white bread
should not be made containing the essential active substances.

424 SCIENCE PROGRESS

In speaking of these observations I wish to acknowledge the
priority of Dr. Gowland Hopkins, whose usual modesty had
prevented him from putting forward his own important con-
tributions to the subject. Ill health delayed Dr. Hopkins from
publishing work which showed the deficiency of white flour as
a life-sustaining food. I leave it to Dr. Casimir Funk to discuss
the chemical nature of these active substances which form so
small and so essential a part of foodstuffs. As these sub-
stances are destroyed by heating to 170° F. and are removed by
modern milling processes, it is obvious that great danger lies
in diets restricted to tinned food and white bread. Our supplies
of fresh natural foods must be maintained. Frightful suffering
and loss of life have been caused by the polishing of rice, a
milling process introduced merely to make the rice white and
please the eye of the buyer. This rice indeed has proved a
whited sepulchre and it has taken 3^ears of work to trace home
the causation of beri-beri to it.

AN EXPLANATION OF BERI-BERI

(Dr. Casimir Funk)

A substance has been isolated recently in what appears
to be a pure condition from rice-polishings, which it is sug-
gested should be named vitamine. It crystallises in colourless
needles, which melt at 233°; the results of the single analysis,
which the amount of material at my disposal permitted, indicated
the formula C17H20N2O7. The administration of this substance
(about o'02 grm.) to pigeons suffering from polyneutritis (beri-
beri) effected a rapid cure. The small proportion obtained,
however, did not allow of many such curing experiments being
performed and as the substance was not recrystallised doubts
of its purity might be entertained. A confirmation of these facts
was therefore absolutely necessary. In the first instance yeast,
which is known to be curative, was chosen as the source of
the material, as it was likely to give a better yield than
rice-polishings. It was of great interest to see whether yeast
contained the same substance as rice-polishings or only an
analogous compound. It was found possible to prepare a sub-
stance apparently identical with that present in rice-polishings.
The substance occurs in the fraction containing the pyrimidine
bases, which are, in fact, more or less precipitated by the agents
used in separating it.

ANIMAL NUTRITION DISCUSSION AT DUNDEE 425

Its curative effect was amply demonstrated by experiments
on pigeons, a dose of 2-4 cgm. being necessary.

The aqueous solution is neutral and not acted upon by
acids. On boiling with copper oxide no copper salt is formed
and therefore it is not an amino-acid. When recrystallised from
dilute alcohol the substance melts at 233°, which is the same as
that at which the curative substance from rice melts. As the
substances behave alike they must be considered to be identical.
It is precipitated in a pure state by mercuric acetate as well as
by silver nitrate but not by mercuric sulphate nor by the nitrate.

All these properties suggest that the curative substance is a
pyrimidine base analogous to uracil and thymine and that it is
probably a constituent of nucleic acid. On this view the two
nitrogens would be combined as in other pyrimidine bases in
the form of an ureide :

NH CO

I ' \

CO C— CH3 Thymine CO > CsHisOe Vitamine

NH CH NHX

Only a constitution of this kind would explain the neutral
character of the substance and its analogy with other pyrimidine
bases.

The curative substance was also isolated by analogous
methods from milk (this fact being very important in connexion
with infantile scurvy) and bran. Everything suggests that in
all these cases the curative substance is identically the same.
Further, a substance curing avian polyneuritis was found in
lime-juice, which is at present being more closely investigated.
These experiments throw an entirely new light on the physio-
logical importance of the nucleic substances.

MORE DIFFICULTIES FROM THE PRACTICAL SIDE

(Dr. David Wilson)

The values obtained by the methods in vogue are not a
sufficient indication of the relative feeding quality of home-
grown foods — grass, roots and fodders — which form the greater
part of farm rations. For example, analyses made of samples
of grass from five pastures gave the following indecisive results ^ :

^ Trans, Highland and Agric. Society^ 1894, pp. 411- 16.

426

SCIENCE PROGRESS

Reference numbers

s 4

Poorish but productive

pastures.

Fattening pastures.

Annual value of pastures

per acre

i6s.

20s.

26s.

60^.

70s.

In 100 parts dry matter

of grass.

Protein

1225

1 1 "37

ir6o

12*25

Amides, etc .

4-81

307

5'36

I 00

ro6

Ether extract

2*20

2'IO

375

395

457

Carbohydrates

50-69

52-31

46-47

52-35

51-62

Woody fibre .

19-85

1830

2r5o

1 9 90

20" 10

Ash ... .

1020

1285

ii"55

1 1 20

10*40

1 0000

1 00 00

Bullocks fed only on turnips and straw grown in certain
districts increase in weight as rapidly as they do in other
districts where they receive 4 lb. of good cake daily in addition.
Three sets of turnips obtained from different sources were
analysed by Aitken ^ ; each set consisted of two sacks dis-
tinguished by numbers only, the one containing good fattening
turnips, the other roots of very poor qualit}^ In every case
he selected the poor turnips as those likely to be best for
feeding. If analyses gave no information, the odds would be
7 to I against his making the wrong choice three times running.
Lawes,^ Warington,^ Hendrick ^ and Hall and Russell ^ may
be quoted as confirming this inadequacy of present methods on
which scientific values are now based ; as such methods are
inadequate to measure the feeding quality of the main part of
the ration, they cannot show the kind and quantity of cakes or
grains required to supplement an unknown deficiency.

Ingle ^ has tabulated and discussed British feeding experi-
ments, dealing with 989 cattle and 2,765 sheep. His graphs
compare separately " Digestible Protein," " Digestible Starch,"
"Total Digestible Matter" and ** Albuminoid Ratio" with
increase. If "Starch Equivalent " and ** Digestible Protein," as
ordinarily calculated, are actually a measure of feeding power,
such a large nuiflber of animals, viewed statistically, should

^ Trans. Highland and Agric. Society.^ 1889, p. 253, and 1893, p. 356 (foot).

^ Agric. Studenfs Gazette 1892, p. i.

^ Ibid. 1893, p. 6.

^ Trans. Highland and Agric . Soc, 191 1, p. 191.

^ Agricultural Science-, iv. pp. 366-70.

^ Trans. Highland and Agric. Soc. 1909, pp. 196-254, and 1910, pp. 168-257.

ANIMAL NUTRITION DISCUSSION AT DUNDEE 427

show some definite relation between these units and increase.
Some of Ingle's graphs do show a certain measure of correlation
but viewing the whole display in light of the law of error the
"Starch Equivalent" and "Digestible Protein" are correlated
with such widely different feeding effects that they must stand
for different things in the different rations.

Further, the conclusions drawn from such correlation as
exists in these graphs do not confirm Kellner's standard
rations. They indicate a lower protein requirement and show
no correlation whatever between " Albuminoid Ratio " and
increase in cattle or sheep.

The heterogeneous nature of all the analytical units on which
scientific feeding values are based seems a sufficient reason for
these failures.

An ordinary analysis gives :

(i) "Protein" or "Albuminoids." Every animal ration, to
be efficient, must contain a certain minimum of certain proteins.
But a minimum of specific proteins is a very different thing
from a minimum of insoluble and precipitated nitrogen multiplied
by six and a quarter. Even in a mixed ration, an animal may
have to consume a great superfluity of other proteins before
it obtains the necessary amount of specific proteins. The
various amounts of protein recommended by different authorities
and the great divergences in Ingle's charts indicate that this
difference in effect of a unit of mixed proteins frequently occurs
in practice.

(2) "Amides, etc.," account for a large proportion of the
nitrogen in home-grown foods. Theoretically different quantities
and kinds of concentrated food would have to be added to
turnips and straw according to the method adopted in evalu-
ating this group of varying composition and unknown function.

(3) " Ether Extract " is also a varying mixture. In young
grass only about 35 per cent, is fat ^ and all oil is not
linseed oil.

(4) " Carbohydrates " and " Fibre " are equally heterogeneous.
The "Fibre" of undecorticated cotton cake and of swedes and
the " Carbohydrates " of maize and wheat straw are, so far as
our analyses go, the same things. We are therefore entirely
dependent on average " digestibility" and " value "factors and in
the case of the foods most largely used here the " probable error "

^ Highland and Agric. Society Trans. 1889, p. 44.

428 SCIENCE PROGRESS

of these factors is great. The digestible protein in swedes is
given by Kellner as '3 per cent. ^ on the sole authority of an
experiment upon two sheep, one of which increased in weight
seven times as much as the other.^

The digestibility of the fibre in turnips varied from o to
100 per cent.,^ and that of protein in oat straw from 12 per cent,
to 50 per cent.^ The result of a " digestibility " or " value "
experiment is true only of the particular food, in the case of a
certain animal, under certain restricted ^ conditions and cannot
be usefully generalised by applying it to the mixed units of
ordinary analysis.

A farmer learns from experience how he must supplement
his own roots and fodders. Moreover the good cattleman studies
the individual animals and keeps their appetite fresh. " It is
the masters eye that fattens the cattle." His rations will fall
within certain limits and generally our present science is not
warranted in making these limits closer. The primary object
of research on feeding values in this country is not to inform
practical feeders how to construct their rations but to increase
the feeding quality of the foods we grow, which form the
main part of these rations. We know what an efficient measure
of the required quality did for the sugar-beet industry. If we
had an equally true measure of the feeding quality of home-
grown foods there is reason for hoping it would in some similar
degree benefit the agricultural industry. We could select,
breed, manure and cultivate with confidence and the tools which
got us increase of feeding quality would help us best to use it.

CERTAIN OIL FOODS

(Prof. Hendrick)

In most of the previous experiments on the substitution
of other fats for butter fat, cod liver oil has been used and
the opinion is consequently prevalent that this is the only oil
which can properly be used. The general purpose of the
experiments now described, in which calves were fed with

^ Scientific Feeding of Animals (Goodwin's Trans. 1909), p. 370.

' Bied. Centr. 20, pp. 12-19, and Chem. Soc. Abstracts, 1891, p. 595.

^ Scientific Feeding of Animals, p. 385.

' Ibid. p. 383.

' Highland and Agric. Soc. Trans. 1893, p. 344.

ANIMAL NUTRITION DISCUSSION AT DUNDEE 429

cotton seed oil as a substitute for butter fat, was to demon-
strate the practical economy of using separated milk and oil
in place of whole milk in feeding ordinary commercial calves.
Cotton seed oil was chosen as a comparatively cheap and easily
obtained vegetable oil which is extensively used in human food
and is known to be wholesome. Another reason why it was
chosen was that certain practical men, even of the intelligent
and educated class, were profoundly sceptical as to its value as
a food for calves. Their suspicion appeared to be based on the
general unsuitability of cotton cake as a food for young stock.

Three series of calves were fed during the experiments.
Each series consisted of three lots fed as follows :

Lot I. Whole milk till time of weaning.

Lot II. Whole milk till three to five weeks old, after which
either separated milk and cod liver oil or separated milk, cod
liver oil and a meal gruel were gradually substituted for whole
milk.

Lot III. Whole milk till three to five weeks old, then the
place of whole milk was gradually taken by separated milk,
cotton seed oil and a meal gruel.

After weaning, the calves were all treated similarly till about
two years old, when they were sent to the butcher fat. Records
of the weights were kept till the time of slaughter, when the
carcase weights and a report on the carcases by the butcher
were obtained.

The following table gives a summary of the results :

Lot I. Lot II. Lot III.

Whole milk. Cod liver oil. Cottonseed

Total number of calves .... 14 15 15

Average weight at start .... 1091b. 1131b. 1071b.

„ „ weaning • • • 3^9 » 290 „ 280 „

„ increase when weaned . . . 200 „ 177 „ 173 „
Average cost of feeding to time of weaning

(per calf) £3 ^9^- 3^- £i 7^- £1 S^- 9^-

Average cost of food per pound of increase . 482^. 1-83^. 179^.

„ weight when sent to butcher . 1,150*3 lb. 1,1171b. 1,078 '3 lb.

„ increase „ „ „ . 1,041-3 » 1,004 „ 97i'3 „

The table shows that there is little diff'erence, on the
average, between the increases made by calves fed with cotton
seed oil and those fed with cod liver oil. The cost of the cotton
seed oil feeding was slightly less. There did seem to be a
distinct difference in favour of the whole milk calves till the

430 SCIENCE PROGRESS

time of weaning ; after that there was no significant difference
and at the time of slaughter the differences between the lots
was so small as to be within the limits of experimental error.
So far as the evidence of these experiments goes, it shows that
cotton seed oil is as suitable as cod liver oil as a substitute
for butter fat in feeding calves.

I have long recognised that mere chemical analysis and
energy value or starch value do not tell all that is required
in order to enable us to determine the position and value of a
feeding stuff*. At one time and that not so long ago energy
values, albuminoid ratios and chemical analyses were looked
upon as almost the whole gospel of the nutrition of farm
animals ; this period of development is still the one represented
in the text-books of agriculture and agricultural chemistry.
Now it seems that the pendulum is swinging strongly over to
the other side and it is desirable to utter just one note of
warning. In the reaction against the overgrown claims of an
old school, do not let us go to the other extreme and lose hold
of what was true and right in their work. Although our
methods of food analysis are very imperfect and all our work
is vitiated by this and by the great individual variations which
occur in experiments with animals, still if there be one solid
basis of well-established fact which we hold on to as scienti-
fically sound and unassailable it is the energy values of food-
stuffs and nutrients. Moreover we are on sure, ground in
maintaining that energy values for the animal are the same
as for the inanimate machine, making due allowance for the
products of combustion obtained in each case.

THE MAGNITUDE OF THE ERROR IN NUTRITION

EXPERIMENTS

(Prof. R. A. Berry)

It is desirable to direct attention to the magnitude of the
experimental error in nutrition experiments on animals, dealing
especially with the case of pigs.

In an experiment carried out at the experiment station of
the West of Scotland Agricultural College in 191 1, in which
seventy-six large white pigs were used with an average initial 1
live weight of 77"6 lb. equally divided as to sex and all fed on
the same ration during fourteen weeks, the probable error for

ANIMAL NUTRITION DISCUSSION AT DUNDEE 431

one animal was i2"i per cent, of the live-weight increase. Calcu-
lating from the results of previous experiments extending over
the years 1905-8 and choosing only those lots which were
fed on the same or similar diets, numbering 102 pigs having an
average initial live weight of 97 lb., the probable error for one
pig works out to 137 per cent, of the live-weight increase.
Both sets of figures give practically normal frequency curves.
The differences mean that twenty-one or twenty-seven pigs
are necessary to determine with any degree of certainty a
difference of 10 per cent, between different foods and that thirty
or thirty-eight pigs are required to determine a difference of
10 per cent, in either direction. These differences, though not
large, point to the advisability, when calculating the probable
error, of taking into account age and weight of animal at com-
mencement of the experiment and of considering whether the
data are drawn from one complete experiment or from several
experiments extending over a number of years.

Fifty female pigs in the latter experiment gave a probable
error of 13*5 per cent, of the live-weight increase and fifty male
pigs 13*8 per cent.

Wood gives about 14 per cent, of the live-weight increase
on the probable error for cattle and sheep. His method of
calculation is followed here.

In connexion with the variation and sampling of oat straw,
using data from a hundred individual straw analyses, the pro-
bable error was very great and varied according to whether
it was calculated on the percentage of nitrogen, the total weight
of nitrogen or the dry matter of individual straws, respectively.
Except in the case of the total weight of nitrogen the frequency
curves were abnormal. Similar variations were found in the
probable error and frequency curves calculated on the different
constituents of the mangel.

A NOTE OF CAUTION
(Dr. Crowther)

From no part of his work has the agricultural chemist in
the past derived less real satisfaction than from his efforts to
harmonise farm practice in feeding animals with the views
dominant from time to time amongst physiologists as funda-
mental principles of animal nutrition.
28

432 SCIENCE PROGRESS

rlis diiticulties aris/e largely from the patent incompleteness
of physiological theory on the one hand, on the other from the
manifold imperfe'^^tions of the methods commonly used in deter-
mining the cor;,^ej^|. of utilisable nutrient matters in foods.

uring -jT^^j^y years past it has been the common practice to

ompar^^' the merits of different foods or rations in terms of
thei' ^

^r content of protein, fat, carbohydrates and " fibre," without

^Sking into account any quantitative differences in the make-up
of the materials comprised under these designations. It has
further been the custom to insist in the case of each class of
stock upon a definite " balance " being maintained between the
protein and non-protein constituents of the ration (" albuminoid
ratio") as a matter of fundamental importance. Fats, carbo-
hydrates and any excess of protein beyond the indispensable
minimum have been regarded as mutually interchangeable in
the proportions of their *' isodynamic equivalents." The appli-
cation of these views to farm practice, however, has met with
overwhelming difficulties from the start. There are difficulties
which any system will meet with necessarily, such as the great
variability in the composition of the foods that form the staple
of the ration and the individual variations in feeding capacity
between different animals. But even in cases in which these
general difficulties have been largely overcome, there has often
been a hopeless discordance between theory and practice.
Rations esteemed, from theoretical considerations, to be of equal
value, have frequently given widely different results in practice.
Albuminoid ratios condemned outright by theory have in
innumerable cases proved in practice to be in no whit inferior
to the optimum ratios of theory.

In the main, doubtless, the method has served the useful
purpose of correcting gross errors in feeding but its application
is so uncertain that it has never won the confidence of the
skilled feeder and voices have not been wanting to suggest
that theory has as yet little or nothing to offer in the way of
guidance to experienced practice.

Some explanation of the discrepancies has been suggested
by the results of recent research on nutrition. We realise now
clearly that all proteins are not to be treated as mutually
equivalent and that " amides " need often to be taken seriously
into account. We know further that the attainment of the full
nutritive value of certain foods is conditioned by the presence

ANIMAL NUTRITION DISCUSSION AT DUNDEE 433

in them of small quantities of an ingredient or ingredients
whose character has not yet been determined. Further we
have reason to believe that the interchange of fat and carbo-
hydrate is safe only so long as certain minimum amounts of
each are present in the ration. Lastly we may mention the
factor of palatability, which has been found to exercise an
influence, within certain limits, upon the nutritive efficiency
of foods consumed by farm stock.

Further blame for the discrepancies alluded to above might
easily be put upon the crudity of the analytical units in terms
of which the composition of foods is expressed.

Protein, carbohydrate and fibre, as commonly returned in
the analysis of foods, are not definite chemical individuals but
more or less complex groups of ingredients ; the amounts of these
present are arrived at, moreover, by methods which are not of a
high order of accuracy. In the case of "carbohydrates " indeed,
for want of a feasible method, no attempt at a direct determina-
tion is made but the amount is simply arrived at by difference.
Added to these shortcomings are the further crudities of the
estimation of digestibility. Of these only one need be mentioned
— the assumption that all material removed from the food during
its passage through the animal has been " usefully " digested.

In the face of all these complications and difficulties, it is
obviously impossible to devise any system of computing food
values that will give more than a rough estimate.

For the purposes of the farm, however, the rough estimate
will, in most cases, be sufficient and it would obviously be
foolish to abandon even the old method of arriving at such an
estimate, without further test of its value when modified in
accordance with the outcome of recent research.

It will be generally agreed that, provided it be satisfactory in
other respects, the nutritive value of a ration will be determined
by the amount it contains of assimilable protein, fat and carbo-
hydrate. Assuming that the ration is suited in bulk and
character to the animal and consists of sound foodstuffs, the
chief " other respects " that need to be satisfied will be, so far
as present knowledge informs us, the character of the proteins
and ''amides" present and the inclusion of the little-known
ingredients whose presence, though only in minute amount, is
essential for the efficient utihsation of the food in the body.

In a simple ration, .such as is often fed to pigs, there is risk

434 SCIENCE PROGRESS

that these last-named requirements may not be adequately
satisfied but it is probably only rarely, if ever, that such a diffi-
culty will arise with the more complex rations of roots, fodder
and concentrated foods commonly given to the other classes of
farm stock. With a basis of roots, hay or grass and straw —
given fair quality — no difficulty is ever experienced in devising
a ration on which " thrifty " animals will maintain a good rate of
growth, so that apparently these materials, as a rule, effectively
supplement any deficiencies of constitution in other foods with
which they are blended. We are probably committing no
serious error, therefore, in assuming that the nutritive value of
such rations is determined essentially by their content of
digestible protein, fat and carbohydrate and it remains to devise
a satisfactory method of evaluating this content for practical
purposes.

As yet only one method has been put forward which can be
said to rest upon a substantial basis of experimental investiga-
tion, viz. the method developed by Kellner, which for conveni-
ence may be referred to as the ** starch equivalent " method.^
This method is based upon the classical measurements by
Kellner of the value to the fattening adult ox of pure prepara-
tions of protein, oil and carbohydrate and also of a variety of
common feeding stuffs — in all, upwards of seventy experiments.
In these experiments the results of the feeding were gauged by
careful determinations of the gain of carbon and nitrogen by
the body and in every case the material under investigation was
compared directly with starch. In this way the relative values
(starch = i) to the fattening ox of the different nutrients when
fed separately in pure, easily digested state were found to be :

Digestible starch . = I'oo

„ fibre (cellulose) = i*oo

„ protein = 0*94

„ oil = 2'4i

In applying these values to the computation of the starch-
equivalents of ordinary foodstuffs, it is necessary to make allow-
ance for factors that tend to reduce the nutritive value of the
foodstuff, such as the labour of mastication, etc. In other words,
the " availability " (Wertigkeit) for productive purposes of the
digested matter must be taken into account.

' Kellner, Die Erndhrung der landwirtschaftlichen Nutztiere^ iv. Aufl. 393 ;
Goo6.w\n, Journal of the Board of Agriculture^ xviii. 721.

ANIMAL NUTRITION DISCUSSION AT DUNDEE 435

According to Kellner's measurements, this is rarely less than
95 per cent, in the case of easily digested foodstuffs but may be
as low as 30 per cent, in the case of tough, fibrous material, such
as wheatstraw. Such ''percentage availabilities" of a large
range of feeding stuffs have been tabulated by Kellner. In the
case of the more fibrous foods, however, he prefers to base his
correction of the theoretical starch equivalent upon the pro-
portion of crude fibre in the food, since it is this proportion that
largely determines the labour required for mastication and
digestion of the food.

A further difficulty in the computation of starch-equivalents
arises from the uncertainty as to the value which should be
attached to the non-protein nitrogenous ingredients of foods.
Kellner treated them as valueless for productive purposes but
this procedure perhaps hardly does full justice to these " amides."

It remains to be seen how this method will stand the test of
application in practice. Its validity can only be thoroughly
tested by the records of experiments, conducted upon a relatively
large scale, in which the exact consumption of digestible pro-
tein, fat, carbohydrate and fibre is recorded. Such experiments
have, as yet, been carried out but rarely in this country. A
very large number of carefully conducted feeding trials have
been carried out but in hardly a single case has any determina-
tion of digestibility been made and in the great majority of
cases information is lacking with regard to the composition of
the roots, hay, straw or other home-grown foods consumed by
the animals. Without this information, however, it is im-
possible to make any stringent test of the validity of the starch-
equivalent as a measure of nutritive value. All we can do is to
make a rough test by assuming for the home-grown foodstuffs —
of all foodstuffs the most variable in composition — an average
composition and digestibility, together with similar assumptions
with regard to the digestibility of any other foods of known
composition included in the ration.

It is not to be wondered at that the starch-equivalent
method has not survived with complete success every such
rough test that has been applied to it. Little weight can be
attached, however, to the results of such imperfect tests based
upon the results of one or two feeding trials. Of greater in-
terest is the comparison of the relative productive values of
foodstuffs as shown by their starch equivalents, with the

436

SCIENCE PROGRESS

average results obtained in feeding trials upon a large scale or
frequently repeated, such as those conducted in Denmark by
Fjord and Friis and in Sweden by Hansson.

The comparison with the Danish and Swedish results is the
more interesting in that the latter have reference to the relative
values of the foods in milk-production whereas Kellner's experi-
ments, upon which the method of computing the starch equiva-
lents is based, were measurements of fattening increase. Below
are given the equivalent quantities of a variety of foods of
different types, as deduced from their average starch equivalents,
alongside the corresponding data given in three separate tables
which are based solely upon practical feeding trials. In each
case, wheat is taken as the basis of comparison.

Equivalent Quantities of Food

From starch

equivalents

(Kellner's averages). ^

Danish
scale.*

MQller & Wendt's

scale ' (based upon

Swedish trials).

Lawes & Gilbert's
scale.*

Wheat .

Bran

1-25

Oil cake and similar

foods .

•9-11

•85-1

•9-11

Clover hay

2-5

Meadow hay .

2'5

2-6

Mangels ,

Turnips .

125

Straw

4-2

Green fodder .

7-9

7-5-11

Potatoes

3-8

8-5

With one exception (bran), the degree of concordance shown
in this comparison between the " theoretical " (starch equivalent)
feeding values and the " practical " feeding values is little less
than remarkable and it must be obvious, even to the layman,
that a method which, even when applied in somewhat rough
fashion, can give such an approximation to the results of prac-
tice, is worthy of a thorough and extended trial. There can be
little doubt that when its foundations have been more thoroughly
explored and the limits of its applicability more precisely de-
fined, it will become a permanent instrument in controlling
feeding practice on the farm.

^ Loc cit. pp. 582-93.

^ Jour7ial of the Board of Agriculture^ April 1905, 23.

^ Grundziige einer wirtschaftlichen Erndhrung der Milchkuhe^ Berlin, 1909.

* Journal of the Royal Agricultural Society^ 3rd Series, viii. 698 (1897).

THE SPECTRE OF VITALISM

By HUGH S. ELLIOT

I. Article by Dr. J. S. Haldane on "The Relation of Mind and Body," in Science

Progress, October 1912.
2 Presidential Address by Dr. J. S. Haldane to the Physiology Section of the

British Association, 1908.

3. Becquerel Memorial Lecture to the Chemical Society, 1912. By Sir Oliver

Lodge.

4. Article by Sir Oliver Lodge on "Life and Professor Schafer" in the Con-

temporary Review for October 191 2.

5. Article by Sir Oliver Lodge on " Uncommon Sense as a Substitute for Investi-

gation," in Bedrock for October 1912.

6. Science and Philosophy of the Organism. By Hans Driesch. (London : A. & C.

Black, 1908.)

7. Involution. By Lord Ernest Hamilton. (London : Mills & Boon, 191 2.)

8. On the Inheritance of Acquired Characters. By Eugenio Rignano. (Chicago :

Open Court Publishing Co., 191 1.)

9. Is the Mind a Coherer f By L. G. Sarjant. (London : George Allen & Co.,

1912.)

Men may be roughly classified into the two divisions of those
who believe in ghosts and those who do not. In old days
everybody believed in ghosts : everybody had his own private
ghost, which he gave up when he died : there were besides a
number of ghosts specially connected with departed personages;
and in addition to these, there was an army of ghosts on the
loose, so to speak, not specially connected with any human
individual. In short the ghost population vastly exceeded the
population of material human beings.

In modern times the population of ghosts has undergone
a very serious decline. A great many people do not believe
in them at all : and those who do no longer credit them with
the powers that their ancestors were supposed to possess. This
degeneration among ghosts has clearly been brought about
by the development of science : for the more we learn how
things happen, the more conscious do we become that ghosts
do not play the part in the causation of events that they were
supposed to play : indeed it is now somewhat widely believed
that ghosts play no part at all and that all events have material,

437

438 SCIENCE PROGRESS

not spiritual, causes. Yet it is well to remember that the
primitive impulse of mankind is to believe in ghosts : that, in
the absence of scientific explanations, spiritual '* explanations "
are commonly put forward and that even in the presence of
scientific explanations, a ghost is a shifty sort of character,
not easily driven finally out. The " will to believe" is so strong
that, even now, those who believe in ghosts of some sort or
other greatly exceed in number those who do not.

Among physiologists, those who believe in ghosts are called
vitalists and those who do not believe in ghosts are called
mechanists. The latter, who among physiologists are greatly
in the majority, affirm that all animal activities are due to
physical, chemical and mechanical forces acting in accordance
with laws the same as those which hold for the inorganic world.
The vitalists on the contrary declare that material forces alone
cannot account for all the manifestations of life, though they do
account for most of them : they say, however, there is a residue
of vital manifestations not so accountable and they throw what
they deem to be a flood of light over the whole situation, in
affirming that these vital manifestations are caused by a vital
force. The uneducated man apparently finds comfort in the
explanation. His propensity towards believing in ghosts
naturally disposes him to acquiesce in the presence of such
forces as ghosts might be expected to exert. It is now many
years ago since du Bois Reymond attempted to exorcise what
he aptly called the "spectre of vitalism": but that spectre in
an attenuated form still continues to haunt a few who have pre-
dispositions towards it. I have already elsewhere attempted
to refute the general doctrine of vitalism.^ My task here is
to review a certain number of recent publications which have
fallen from the pens of modern believers in ghosts.

The Views of Dr. Haldane

And first let me deal with the views of Dr. Haldane, as
stated in the October number of this review. There is indeed
nothing in it which can very easily be replied to : for Dr. Haldane
does not argue but confines himself to setting forth a series of
rather odd opinions, without furnishing the clue as to how he
came by them. The mechanistic theory therefore is in no way

* Bedrock^ October 191 2.

THE SPECTRE OF VITALISM 439

injured by his paper : except in so far as the authority of
Dr. Haldane's name may injure it. I venture however to
criticise a few of his utterances. " We cannot," he says,
"express the observed facts by means of physical and chemical
conceptions but must and do have recourse to the conception
of organic unity." What is that conception? Here is an
attempt to shift the required explanation from the ground of
science to metaphysics : which is virtually to abandon the
problem altogether. Then there follows the stock argument :
" Living organisms are distinguished from everything else that
we at present know by the fact that they maintain and reproduce
themselves with their characteristic structure and activities."
Even this argument is disputed by Prof. Schafer and others ;
but let us assume it to be the case: what follows? Has not
every substance its own peculiar properties which differentiate
it from other substances? The fundamental constituents of
protoplasm are bodies of immense molecular complexity : it
is to be expected therefore that such substances will display
properties different from those of inorganic substances. The
phenomena of growth occur, in crystals, in the most elementary
chemical substances. It may be true that there is small analogy
between crystal and organic growth. But there is also small
analogy between the substances considered. If such a simple
substance as sodium chloride possess the property of growth
under certain conditions, we need not be surprised that pro-
toplasmic substances possess a corresponding property in
immensely greater variety and complexity. The question at
issue is not whether growth and reproduction occur in the
inorganic realm : it is whether the complexity and variety of
these phenomena in the organic realm are such as to be totally
out of proportion to the molecular complexity and variety of
the substances built up in protoplasm. But these substances
are still unknown : and he would be a bold chemist who would
assert that their united formulae are too simple in character
to serve as foundation for the functional manifestations of
protoplasm. I confess I have alwa3^s been puzzled as to why
any one should attach the slightest importance to the argument
that living organisms have peculiarities different from those of
inorganic matter. That the substances in protoplasm have
properties not found in other substances surely bears in no
respect upon the question of vitalism and mechanism.

440 SCIENCE PROGRESS

The next quotation from Dr. Haldane on which comment
may be made is this : " In the argument that all the conscious
behaviour of a man or animal is ultimately dependent on
physical and chemical stimuli from the environment, acting on
the physical and chemical structure of the body, the whole
question is begged from the outset ; for the assumed physical
stimuli and physical structure do not behave as such." I do not
understand how the term '' behaviour " can be applied to stimuli
or structures : still less, as here alleged, how either a stimulus
or a structure can behave as though it were neither a stimulus
nor a structure but as something else — a ghost, no doubt. But
in any case, we may ask for further information as to how
the question is begged in arguing that conscious behaviour is
dependent on physical stimuli. That proposition may be either
true or untrue; but it is perfectly clear and straightforward
itself and begs nothing. Dr. Haldane's whole attitude is meta-
physical. Metaphysical questions may possibly here be begged :
I do not know whether they are and I certainly do not care.
Science will not stop, merely because ghostly questions are
begged ! *' The great mistake of mechanism," says Dr. Haldane,
"is to lose sight of the wider point of view which shows us
that in physical or indeed any scientific investigation we are
always dealing with partial aspects of reality." Since this
mistake is common to mechanism as well as every other
scientific theory, I suppose that mechanism, if proved, would
have the same sort of validity as other scientific truths : and
that is all we want. But the general type of the argument is
unsatisfactory : it is meeting a scientific theory with a meta-
physical refutation. If the scientific theory be untrue, it is
surely susceptible of a scientific refutation or criticism, at all
events. And so we go on : " Conscious personality is the truth
of the body and its environment." I have no idea what this
sentence means : nor how the body can have a truth. But
things get worse and worse: "Just as biological facts have
taught us that the life of each individual cell or organism is
only part of a wider life, so have ethical and religious facts
shown that the individual personality in its full realisation is
the expression of divine personality, which alone can be the
ultimate truth of all existence." If this is intended as hostile
to mechanism, it surely is the weakest of arguments. That the
divine personality is the truth of existence is the sort of thing

THE SPECTRE OF VITALISM 441

one finds in books on theology. Happily books on theology
are fast giving way to books on science. The sentence is
meaningless : and even if it were not, its logical basis of
" rehgious facts " is utterly flimsy. Let us not import into
the vitalistic controversy arguments founded in the rapidly
passing superstitions that are proper only to the childhood of
civilisation.

Dr. Haldane has given a more complete account of his views
in his presidential address to the Physiological Section of the
British Association in 1908. But here again, a critic can find
little to lay hold of: so elusive are Dr. Haldane's methods. He
uses in the main two arguments : (i) the argument from
teleology ; (2) the argument from the inadequacy of physico-
chemical explanations. With the teleological argument I have
dealt elsewhere^ and need only briefly recapitulate what I then
pointed out. Dr. Haldane puts the matter in some such form
as this : Physico-chemical laws act blindly in their operation ;
" purpose " is foreign to them and they are inadequate to express
purposefulness in events. But physiology shows a ** teleo-
logical ordering" of matter and energy. Every function is
nicely adapted to the needs of the organism and thus possesses
a purposefulness not to be explained by mechanical laws. The
argument fails because the premisses are erroneous : teleo-
logical events are not incompatible with mechanism ; a truth
that ought to be patent since the discovery of Natural Selection.
For here we have a teleological event — namely, evolution to-
wards increasing complexity of structure and specialisation of
function — following as a result of laws wholly mechanical :
namely, the extinction of the organisms least fitted to survive.
It is true that some biologists consider " natural selection "
inadequate to account for evolution. They have suggested
other factors ; but all these suggested factors are of a mechanical
nature. In short, there is almost universal agreement that
evolution is produced by mechanical causes. We must, then,
admit either that evolution is a blind, purposeless process; or, if
it have a purpose, that that purpose is expressible in mechanical
terms. In other words, there are not two kinds of events — the
purposeful and the unpurposeful. The " purposiveness " of an
event arises solely from our point of view ; it is not an attribute
of the object but of the subject. Any natural event may be

^ Bedrocky October 191 2.

442 SCIENCE PROGRESS

regarded as purposive if we orientate our minds in a certain
way towards it; but all natural events are none the less me-
chanical, physical, chemical, etc., in their causes and mode of
working. So, in referring to the teleological harmony of
the bodily functions. Dr. Haldane is only naming one of the
results which most biologists attribute to the blind operation of
natural selection. It is a striking example only because of the
extreme perfection of the adaptation between the organs of
the body. Not the extremest vitalist would deny that natural
selection, a mechanical factor, may bring about adaptation :
that the fauna of a country is adapted to the climate for the
simple reason that non-adapted varieties could not live. And
if adaptation of a simple kind be thus mechanically explicable,
if adaptation itself be a mere mechanical event, then vitalists
cannot look to it for arguments against mechanism.

Dr. Haldane's second argument is a very common one.
" The conceptions of physics and chemistry are insufficient to
enable us to understand physiological phenomena": hence we
must pass to some vitalistic theory. That argument has lain
at the base of every myth since the world began. Here is a
strange event : we do not see how natural forces could have
compassed it: therefore ghosts did it. It is the primitive ten-
dency to attribute animism to whatever we cannot understand.
I shall comment later upon this argument in connexion with
the work of Driesch. With reference to Dr. Haldane, I need
only refer further to his statement that biology "deals with
a deeper aspect of reality" than physics and protest once
more against the introduction of metaphysical conceptions into
science. " Reality " is not a stratified deposit into which we
may penetrate more or less deepl}^ : all scientific truths are
equally real for the man of science, those of physics not less so
than those of biology.

The Views of Hans Driesch

One of the most frequently quoted of all authorities in favour
of vitalism is Hans Driesch, whose Science and Philosophy of the
Organism is a deliberate attempt to re-establish that discredited
doctrine on a secure foundation. It will be necessary, there-
fore, to devote some space to the examination of his three proofs
of vitalism.

THE SPECTRE OF VITALISM 443

The first proof is introduced by a long account of the facts
of morphogenesis or the development of the individual organism.
Driesch commences with the fact that, if v^e go back early enough
in the history of an embryo, we reach a time when all its parts
are equally capable of giving rise to an adult organism : when, in
fact, there has been no differentiation of parts and each portion
of the embryo is as capable as any other portion of developing
into any of the specialised structures of an adult organism.
Any portion of an embryo which answers to this definition is
called by Driesch an equipotential system. If each embryonic
part be equally capable of developing into any of the varied adult
parts, what factors are they which control the development into
a harmonious whole? Driesch shows, in the first place, that
the absolute size of the system and the relative position of any
point in it are factors in accounting for the trend of develop-
ment. But he points out that they cannot alone explain de-
velopment: there remains the "prospective potency" of the
system — that is to say, its power of developing in certain
directions which terminate in the structure of an adult organism.
What is this potency ? Let us refer to it as E. Driesch then
considers every possibility that can be named as to the nature
of E. From the mechanistic point of view there are, he says,
three possibilities. There is, firstly, the possibility that " for-
mative stimuli " are sufficient to account for development ; there
is, secondly, the possibility of a chemical basis ; and there is,
thirdly, the possibility "of a real machine in the system," one
more or less resembling that suggested by Weismann. Driesch
takes two pages to refute the first possibility, four pages to refute
the second possibility and four pages to refute the third ; and the
very next page is headed by the legend, "Vitalism Proved."^
This startling announcement is founded on the following logical
process : There are four possibilities as to the nature of E ; it
may be either any one of the three already named or it may
be " a true element of nature." But it has been proved that it
is none of the three first named ; therefore it must be the fourth.
Henceforward it figures under the title of " entelechy."

I am aware that, in pausing to point out the sundry fallacies
involved in the above argument, I shall be casting reflections
on my reader's perspicacity. Nevertheless, since Driesch ap-

* The actual legend is " The autonomy of morphogenesis proved " : but
Driesch defines "autonomy of morphogenesis" as synonymous with "vitalism.'

444 SCIENCE PROGRESS

parently never has been answered and since many people
interpret silence as inability to reply, it is desirable to make a
few obvious criticisms.

The method is that which is sometimes called per exclusionem.
The first stage is to prove that there are only a limited number
of possible explanations of some phenomenon. The second stage
is to prove in turn that all these explanations except one are
false. It then follows that that one must be true. Fallacies
may enter at any step in the argument ; but they are most likely
to occur in the first stage. It must always be an exceedingly
difficult matter to prove that the range of possible explanations
is limited to four or five or any other number. It is difficult
to imagine a process by which one could make sure that no
alternative possibility had been overlooked : that all conceiv-
able theories have been marshalled in the field and that the
suggestion of any other theory at any future time in the history
of science is inconceivable. Yet, unless that be done, the whole
method lapses. The second stage presents a further oppor-
tunity for the introduction of fallacies. Each suggested ex-
planation that is refuted furnishes a loophole for error in the
refutation ; and a single error at any part of the argument
vitiates the whole. It is obvious, therefore, how untrustworthy
and difficult the method per exclusionem must always be. Has
Driesch recognised that untrustworthiness ? I have already
observed that he takes ten pages to dismiss the three possible
explanations which he suggests; that is, for the second stage.
But he has clean forgotten all about the first stage. The reader is
left in bewilderment to work out for himself why there should
only be four possible explanations of development ! Can I
suggest another ? I may be asked. The question is irrelevant.
It should be: Is it inconceivable that in the future history of
mankind any fifth alternative will ever be put forward ? And
to this there is surely only one imaginable answer : It is not
inconceivable.

In view of the hopeless instability of the foundations of
Driesch's argument, it would be a waste of time to insist on
the inadequacy of his refutations of the three alternatives so
summarily rejected. Let us move on to the fourth explanation,
''entelechy," which is left victorious in the field. I have called
it an explanation: though, so far from explaining anything, it
appears to me far more mystifying than the original problem.

THE SPECTRE OF VITALISM 445

Driesch defines it : he says it is an " intensive manifoldness."
But since he omits to mention what an " intensive manifold-
ness" is, we do not seem to be much advanced by the definition ;
I shall therefore use the word "entelechy" as being shorter
and not more incomprehensible than its definition. But I wish
to ask what we have learned by this explanation. At the outset
we started in ignorance of the etiological factors in develop-
ment ; we finish in an ignorance precisely as dense as that in
which we started. We have invoked entelechy but it is no more
than a rather pretentious name for our ignorance. Biologists
who talk about entelechy are animated by the same spirit that
led savage races to ascribe all unexplained phenomena to the
act of gods. To say that an event is caused by a god is not
in the l^ast an explanation of the event ; for our knowledge is
then no greater than if we said we did not know how the event
was caused : nor is our knowledge of development any greater
when we talk about entelechy, about *' intensive manifoldness "
or about **a true element of nature."

And yet this doctrine, if it be not over-full of meaning, is
none the less a dangerous one. The three rejected possibilities
of Driesch were mechanistic explanations : the one survivor,
" entelechy," is vitalistic. Since it is no more than a name for
the unknown truth that we seek, I see no reason why it should
be ranked as vitalistic. But it is so : that is the connotation
attached to it. Driesch, then, explains morphogenesis by
reference to certain known material factors acting in conjunc-
tion with a known vitalistic factor called entelechy. He
differs from other biologists in that they regard morpho-
genesis as due to the operation of certain known material
factors acting in conjunction with other material factors not
yet known nor furnished with a name. It would be interesting
to hear how the theory of cancer would be expressed in
terms of entelechy. Cancer is now regarded as due to the
failure of the organising power in an individual; that is, to
the failure of entelechy. Certain cells break loose from the
control of the organism and proceed to multiply riotously on
their own account, without the slightest reference to the needs
of the organism to which they are subjected in a healthy state.
Why they should thus break loose is hitherto quite unexplained.
But the conception of entelechy here calls up a horrible night-
mare. If individual development or morphogenesis be due to

446 SCIENCE PROGRESS

entelechy in conjunction with material factors, that aberration
of morphogenesis which we call cancer is as likely to be due to
an aberrant entelechy as to mere physical causes : more likely
indeed, for as one physical cause after another is suggested and
abandoned, the number of possible alternatives must be steadily
diminishing. Perhaps a time will come when some disciple of
Driesch will declare that, all physical causes having been proved
inadequate, the only remaining alternative — entelechy — must
per exclusionem be the true cause and thus found upon cancer
a new proof of vitalism. And if cancer be really due to a way-
ward entelechy, all hope of a cure or of therapeutics would, 1
presume, be gone. We may always hope to institute material
changes in the organism by physical means ; but such means
must be powerless to deal with an intangible ghostly factor like
entelechy — a ** true element of nature." We are here brought
face to face with the profound pessimism which follows upon
every kind of vitalism and spiritualism. All such phenomena
are necessarily beyond our control : when they take a course
opposed to us, we can only fold our arms and cry. How
different is the more materialistic outlook ! For when we know
that our means are not incommensurable with the ends to be
attained, hope need never be abandoned.

Driesch's second proof of vitalism is analogous to his first
proof The first rested upon the alleged impossibility of ex-
plaining individual development on the basis of mechanism ; the
second proof rests upon the alleged impossibility of explaining
inheritance on that basis. The egg-cell contains, somehow or
other, the potentiality of the structure of the entire future
organism. Driesch affirms that it is impossible to conceive
how, when it divides into two, each half can conserve the same
potentiality as the whole. " It is a mere absurdity," he says,
** to assume that a complicated machine, typically different in
the three dimensions of space, could be divided many many
times and in spite of that always be the whole ; therefore, there
cannot exist any sort of machine as the starting-point and basis
of development. Let us again apply the name entelechy to that
which lies at the very beginning of all individual morphogenesis.
Entelechy thus proves to be also that which may be said to lie
at the very root of inheritance." The whole argument is hope-
lessly inconsequent. Driesch's charge of absurdity lies really
not against the unknown mechanism of the process but against

THE SPECTRE OF VITALISM 447

the fact that an egg-cell can divide and still retain its potentiality
of development. However absurd that fact may be, it is true.
But surely few will be found to agree with the theory that
any physico-chemical action by which such a process could be
brought about is so inconceivable as to justify our parading the
process as a proof of vitalism. The great majority of biologists
do not regard a mechanistic explanation as being in the least
inconceivable ; on the contrary, they regard it as probable,
even as certain. Can Driesch, then, be serious in bringing
forward this process, without adding a single new fact, as proof
of vitalism ? Surely that is to beg the whole question from the
beginning. We might as well dispense with researches into
morphogenesis, declare at once that it is impossible to believe
we are machines and invoke this as a third proof of vitalism.
It would indeed be of equal cogency with the first two.

Nor is this very far removed from Driesch's actual procedure.
His third proof of vitalism is founded, like the first two, on the
difficulty of conceiving a mechanistic explanation of some
complex organic event. The concrete instance which he gives
is that of the different effect produced when one friend tells
another ** my brother is seriously ill " from that which would
have been produced if he had said " my mother is seriously ill."
The stimuli constituted by the sounds of these sentences are
closely alike. They differ in fact only in the substitution of m
for br. Yet the reaction of the listener is or may be altogether
different. If the mother and brother inhabit different parts of
the world, his thoughts will be carried to those parts ; and the
resulting trains of reflection set up in the two cases are far more
removed from one another than can be accounted for by so slight
a variation in the stimulus. No mere mechanical arrangement,
however complex (according to Driesch), could conceivably have
such a result. Driesch further strengthens the argument by
pointing out that, per contra, the sound stimulus may be radically
changed and yet the reaction remain unaltered. P^or the
sentence may be ** mon frere est severement malade" or " mein
Bruder ist ernstlich erkrankt." The result of either of these
would be the same as though they were spoken in English.
Thus, says Driesch, the result cannot be mechanically brought
about by the stimulus.

This argument amounts to saying that because we cannot
point out in detail how the machine works, it cannot therefore
29

448 SCIENCE PROGRESS

be a machine. For many of our human machines produce the
most widely different effects from closely similar stimuli. A
little button is pressed and a tiny electric bell may ring or a
20,000 tonner may be launched into the sea or a shock may
cause the death of a battalion. So also we frequently produce
the same result from widely different stimuli.

But let us consider this question more closely : let us take
Driesch's sentence and trace its physiological effects so far as
our knowledge extends. The phrase '' my mother is seriously
ill" first impinges upon the organism in the form of aerial
vibrations : it causes a certain specific motion of the molecules
of air which happen to be in contiguity with the tympanum.
The outer membrane is thus caused to vibrate and transmits
vibrations to the three auditory bones ; these act as light
levers and the vibrations which are carried along them cause,
so to speak, a tapping at the fenestra ovalis in the inner wall
of the tympanum. The fenestra, thus agitated, sets in motion
the fluid which bathes it on the inner side. The waves ensuing
in that fluid are propagated into the cochlea, pass through the
membrane of Reissner, then into more fluid, whence they reach
the basilar membrane. Here they produce an excitement
of the sensory hair-cells which gives rise to currents in the
auditory nerve. From the auditory nerve the currents are
carried away down the cochlear branch by several relays to the
posterior quadrigeminal and internal geniculate bodies, whence
fibres pass on again to the cerebral cortex.

Now I wish to point out that the whole process is proved to
be mechanical, so far as our laboratory methods enable us to
follow it. That difference between " mother " and " brother " is
in the first place represented by a different mode of molecular
vibration in the outer air. It is represented by a different mode
of vibration of the outer membrane of the tympanum, of the
auditory bones, of the inner membrane and of the fluids and
membranes of the cochlea. The nervous elements distributed
to the cochlea are so excessively numerous that they too record
the difference, which is thence carried into the brain. So far, the
whole process is known beyond question to be mechanical : the
machine to be one of almost incredible delicacy and complexity.

But however delicate and complex the auditory apparatus
may be, it is infinitely exceeded by the delicacy and complexity
of the brain into which the stimulus is carried. Physiologists

THE SPECTRE OF VITALISM 449

can trace the stimulus from the outer air to the auditory nerve :
but the infinite complexity which characterises the various
nuclei and nervous bodies to which it proceeds they cannot yet
trace. How then can we allow Driesch to make the a priori
assertion that no mechanism could account for the variations
in reactions to similar stimuli ? We have traced the stimulus
with a variety of changes of form through the auditory
machitte. We lose sight of its path only at the point where the
machine becomes so excessively complex, the paths of conduction
so infinite in number, that its progress can be traced no further.
And yet because the ultimate reaction is liable to extreme
variation with respect to the stimulus, we are asked to believe
that a mechanical procedure is impossible !

We may not know how a watch works : but we do not there-
upon deny that it is a machine (though savages do, by the way :
they think it is alive and the vitalists among them would no
doubt explain its action as due to a " horologic force "). I contend
that Driesch has not produced an atom of evidence in support of
his opinion that physical mechanism is inadequate to account for
the different mental associations set up by mechanically similar
stimuli. The original external stimulus in the form of molecular
vibrations of the air is transformed by the auditory machine into
vibrations of smaller amplitude and greater intensity, in order to
be transformable again into nerve currents. Driesch might well
say that such a transformation was inexplicable on mechanical
principles, had not the actual mechanism been discovered. But
if this machine be complex, its complexity is as nothing in com-
parison with that of the brain where the effects of the stimulus
operate. In short, the appearances are so strongly in favour of
a mechanical action, that it would be difficult to imagine any
other hypothesis. -- —

It becomes possible to account in part for Driesch's difficulty
in believing in a mechanical action, if we note that he already
begs the whole question by a false definition of a machine. He
says : ** Does it not contradict the very concept of a ' machine,'
i.e. a typical arrangement of parts built up for special purposes^ to
suppose that it originates by contingencies from without ? " His
argument, as I understand it, is that cerebral reactions to stimuli
are regulated largely by the previous stimuli or " experience" of
the brain and that, since this is a matter of chance and since
machines are things of definite purpose, cerebral action cannot

450 SCIENCE PROGRESS

be mechanical. To which, of course, the reply is that machines
are not necessarily " built up for special purposes " : that on the
contrary their essential action is in transforming energy or
transmitting power : and that they would be just as much
machines if that transformation had no purpose whatever.
What Driesch does is to define a "machine" in terms which
exclude the brain from his definition : and then to argue from
these premisses that the brain is not a machine. Well, no
mechanist ever said it was, in the sense defined by Driesch ! All
they have affirmed is that physical and chemical laws alone are in
operation : and that has nothing to do with any fancy conceptions
of the " purpose " of the machine.

Driesch's Science of the Organism is succeeded by his
Philosophy of the Organism. Vitalism and entelechy having
been established on a firm basis by scientific methods, a similar
result is achieved by metaphysical methods. I shall spare my
reader any account of this part of the work, firstly because (like
all metaphysics) it is indescribably dull, secondly because it
appears to me loaded with logical fallacies, thirdly because
however immaculate the metaphysics might be, however trium-
phant its proofs might appear, I should not think of believing or
attaching the slightest weight to any conclusion that might be
reached. The metaphysicians, like the theologians, have had
their say. Nothing in the world has ever been discovered by
metaphysical methods. No metaphysical *' truth " has ever been
found in all the thousands of years it has been sought. More-
over anything appears to be susceptible of" proof" bymetaphysics.
Hegel proved, as we know, that everything is the contrary of
what it is. I am credibly informed that certain modern philoso-
phers are of opinion that the part is (or may be) greater than the
whole. I am therefore by no means astonished to learn that
entelechy rests upon a firm metaphysical basis : and I am con-
tent to let it rest there undisturbed. I notice only that Driesch
proposes to ** establish vitalism " from " the organisation of
the Ego": that he has recourse to odd-sounding things like
"psychoids" to help him; that during the process it transpires
that every man has not merely one entelechy but a whole army
of entelechies— a hierarchy of entelechies ranged in authority
one above the other ; and that ultimately we meet with what I
am inclined to call the audacious statement that "life is explained":
explained by psychoids and entelechies !

THE SPECTRE OF VITALISM 451

Personally I greatly prefer the Bible explanation. Driesch
finally states that there are " three windows into the absolute " :
the thou, the ego and the it. I fear most people will find these
windows too thickly glazed to help them much. For myself I
confess I was completely puzzled as to what an " it " might be :
and was not greatly enlightened by the definition " the character
of givenness." But I merely mention these fatuities to provide
an example of what we may be reduced to, if we begin by
believing in vitalism.

Driesch is good enough to describe the opinions of those who
differ from him as " materialistic dogmatism " and adds in a lofty
manner that he has "nothing to do with dogmatism of any kind."
I fear this very superior attitude is not justified by the remainder
of the work. By " dogmatism " is usually meant the arrogant
expression of an unsupported assertion. Surely then it cannot
be applied to physiological mechanism — which is held by the
immense majority of physiologists, in contradiction to the wholly
unsupported assertion of vitalism. It is clear that Driesch uses
the term "dogmatism" as a conveniently stinking carcase to
fling at opponents. Indeed, in scarcely any branch of natural
science is it possible to express firm belief in some ascertained
truth without being called a dogmatist : and that too by people
who are prepared at any moment to believe in any rubbish
that comes along, without a particle of evidence ; moreover, to
cherish the idea with that bigoted and cursed obstinacy that
is commonly found in alliance with extreme ignorance.

To sum up, we find that the non-metaphysical arguments
against mechanism amount to this : " We cannot conceive how
mechanical forces could work such a result : therefore they
cannot : therefore vitalism is true." That is the entire substance
of Driesch's three proofs of vitalism. It is useless for me to
insist further on the fact that our inability to understand how a
process works is no argument in favour of its incapacity to work.
It is useless for me to name such discoveries as wireless
telegraphy or Rontgen rays, in evidence of the fact that physical
means may produce results that were a short time previously
held to be wholly impossible. And it is useless for this reason :
that any one who does not instantly perceive the futility of this
kind of logic is not likely to be converted by the most frappant
examples of its failure.

452 SCIENCE PROGRESS

The Views of Sir Oliver Lodge

Not by me at least ! Let me therefore pass on to the dictum of
one who is commonly classed as a friend of vitalism, Sir Oliver
Lodge. In a critical article upon the views of Prof. Schafer,
published in the Contemporary Review for October, Sir Oliver
makes a trenchant protest against founding positive doctrines
upon nescience or upon any kind of negation. The vitalist
position, as I have endeavoured to point out, is founded mainly
(with Driesch entirely) on the negative position that we cannot
imagine how mechanism could work. Sir Oliver is thinking
mainly of theologians ; but his criticism is equally cogent against
vitalists and the reason which he gives is equally applicable in
the two cases. " Theologians," he says, " have probably learnt
by this time that their central tenets should not be founded, even
partially, upon nescience or upon negations of any kind ; lest the
placid progress of positive knowledge should once more under-
mine their position and another discovery have to be scouted
with alarmed and violent anathemas."

But Sir Oliver, notwithstanding his admirable criticism of
the chief error in vitalist logic, is himself regrettably disposed
to explain away difficulties by the manufacture of metaphysical
entities. Criticising Prof. Schafer he says, " He realises his
limitations and definitely excludes the word ' soul ' from his
consideration ; thus proving himself to be in that respect not
only scientific, in the narrow sense, but genuinely philosophic."
I assume that Prof Schafer excluded the "soul" from his con-
sideration because he had other things more interesting to talk
about ; but it is very difficult to see how he is to be praised for
any special scientific virtue in choosing (as he was entitled to
do) those other subjects. Sir Oliver's suggestion is, of course,
that the " soul " is the concern of metaphysics and not of science ;
or if of science, not of biology but of psychology. And in a
sense he is right : in the same sense that a rattle is the concern
of a baby and not of a grown man. But if he means that there
can be any knowledge of " soul " or any statement about it
that is outside the domain of natural science, then he is wrong.
Science is knowledge organised and systematised ; all know-
ledge is of the nature of natural science. There is no knowledge
of the nature of metaphysics outside the range of natural science.
Hence, if the conception of a " soul " is to be accepted at all, it

THE SPECTRE OF VITALISM 453

would appear to be included rightly in the sphere of biology.
Many would claim it for psychology. Now psychology has for
a long time past been undergoing a transformation from being
a branch of metaphysics to being a branch of science. That
transformation is analogous to the process by which chemistry
developed from alchemy and astronomy from astrology. But it
is as yet very imperfectly emancipated. With certain modern
psychologists metaphysical whims have full play ; but from
another school metaphysics is tolerably successfully driven out.
There exists a truly scientific psychology ; and be it noted, this
is just the so-called " psychology without a soul." When we
really got to grips with the attempt to explain the properties of
mental states, it was found that the conception of a soul was
not of the slightest assistance. Not only did it provide no
intelligible explanation of anything but it proved to be an actual
impediment to rational discovery; in short, it was driven out
altogether. In view of the decease of this venerable ghost, it
is difficult to understand why Sir Oliver should be so charmed
with Prof. Schafer's omission to dilate upon it ; for piety suggests
that a funeral oration would have been appropriate to the
occasion.

Sir Oliver, I believe, founds his belief in souls very largely
on the phenomena of "psychical research"; which is certainly a
fragile foundation. I have no space to go into this discredited
sphere at present but I cannot resist drawing attention to a
recent article published by Sir Oliver in Bedrock. The question
is of ''cross-correspondences," the cases in which two persons
in remote localities are smitten by the same idea at the same
moment. Dr. Tuckett, who has given some attention to these
matters, came to the conclusion that " the coincidences of thought
and expression are sufficiently explained by the natural associa-
tion of ideas in minds preoccupied with the same themes."

To this Sir Oliver rejoins: "That is not the view to which
careful students of this subject hav^e been led. If I entered
into detail I might ask him why, for instance, Mrs. Verrall and
Mrs. Piper should in February 1907 have both been preoccupied
with the theme of a * laurel wreath ' and how Mrs. Piper knew —
for some part of her certainly knew— that Mrs. Verrall had
been so preoccupied." I agree this is a poser for Dr. Tuckett
and I should not be in the least surprised to hear that he broke
down completely in the attempt to explain why Mrs. Verrall

454 SCIENCE PROGRESS

and Mrs. Piper were both thinking of laurel wreaths. Perhaps
there was a Marathon race on at the time, perhaps there was
an article on laurels in the Daily Mail, perhaps they had been
reading classical poetry — a thousand suggestions occur to me
but I fail to see how the correct one would help us. In the
history of science w^e have often been struck with the number
of great discoveries which have been made simultaneously
by persons independently of one another, showing how the
thoughts of individuals are controlled by their times. Newton
and Leibnitz both thought of the differential calculus at the
same time ; Neptune was simultaneously discovered by Adams
and Leverrier, natural selection by Darwin and Wallace ;
Mendeleef and Lothar Meyer both hit upon the periodicity of
the properties of elements ; the true functions of the semi-
circular canals in the ear occurred simultaneously to Mach,
Breuer and Crum Brown; in 1904 two independent persons
thought of the possibility that ticks might carry the spirillum
of relapsing fever; and finally, in 1907 Mrs. Piper and Mrs.
Verrall were both thinking of laurel wreaths. Now all these
coincidences, except the last-named, are very interesting : a
valuable essay might be written on the social factors which
have brought about these simultaneous discoveries. But that
Mrs. Piper and Mrs. Verrall should both have been thinking of
laurel wreaths in February 1907 is neither interesting nor in
the least significant nor worth investigating whether it be true.
Why should they not both have been thinking of laurel wreaths ?
They must, I suppose, have been thinking of something or
other : the range of possible thoughts is not infinite — indeed
with most people it is singularly limited. It is tolerably certain,
a priori, that large numbers of people must always be thinking
of the same thing at the same moment. I cannot see, there-
fore, why anybody should be in the least disconcerted by the
information that Mrs. Piper and Mrs. Verrall were both thinking
of laurel wreaths in February 1907. Besides, perhaps they
were not ; mistakes will occur and it is much more likely that
one of these ladies made a mistake in trying to recall the subject
of her thoughts than that " psychical cross-correspondences "
are true. But, as I have already observed, there is no reason
to suppose that there was a mistake ; since the fact (if true)
bears no relation to the conclusion deduced from it by Sir Oliver.
In his Becquerel Memorial Lecture delivered before the

THE SPECTRE OF VITALISM 455

Chemical Society in October last, Sir Oliver adopts an ingenious
method of casting plausibility on the existence of ghosts and
spiritual events. He adduces a number of instances of the
materialising tendencies of science, with a view to showing that
the vague, ethereal conceptions of antiquity have given place to
definite material entities, previously unsuspected : his suggestion
being that as knowledge grows ghosts and phantoms will also
become materialised. He gives a variety of instances of this
materialising tendency : such as the recent attempt by Prof.
Callendar to resuscitate caloric or the material theory of heat ;
the substitution of material oxygen for its vague predecessor the
''acidifying principle"; the tracing of muscular fatigue to material
toxins ; the causation of malaria by the bite of a mosquito, " a
thing which can be crushed with the fingers "; and so on.

But whatever may be the modern tendency with regard to the
kind of entities dealt with by science, there surely can be no
questioning the fact that in the case of the phantasmagorical
entities of metaphysics the tendency is towards increasing
rarefaction and de-materialisation. The phantasms of the early
Greek philosophers were eminently materialistic. Democritus
conceived of the soul as made up of smooth round particles.
Thales traced the origin of the universe to the material substance
water. But by the time we have reached Plato, the concepts of
philosophy become entirely abstract and non-material. That
this is the necessary course of philosophic development, I have
attempted to show in my book Modern Science and the Illusions of
Prof. Bergson : for as science advances, the concrete entities of
the early philosophers become ever more subject to criticism. If
the soul consist of solid particles, science demands the liberty to
measure and weigh them. Thus spiritual existences can only
hold their own against advancing knowledge by becoming
always more ethereal and intangible. They elude the grasp of
science as they are de-materialised in proportion to the vigour
of scientific assault.

An exactly parallel development has taken place in modern
philosophy— where the concepts are now so abstract that only
the specially initiated can understand them. Already many of
the old phantasms have been refined out of existence altogether
and the rest are fast following. In theology, the same process
may be observed. In the middle ages, the soul was a thing of
definite human form and shape completely materialised ; that the

456 SCIENCE PROGRESS

devil had horns, hoofs and a tail was a belief questioned by few :
yet I understand that quite different conceptions now prevail in
theological circles. The tendency here again is opposite to that
alleged by Sir Oliver : it is all in the direction of extreme
de-materialisation. Need I amplify by reference to the
materialism of modern beliefs among primitive races? — how they
leave holes in their graves for the dead man's soul to fly in and
out ; or build mounds over the graves to keep the soul in ; how
they will not let their shadow fall upon a river, lest a crocodile
should eat it ; how they refuse to tell you their name, lest you
should steal it; how they treat diseases by thrashing the patient
and surrounding him with foul odours, in order that the ** evil
spirit" may find its habitat uncomfortable and take itself off.
Surely Sir Oliver has been most unfortunate in having recourse
to historical evolution as evidence of the future materialisation
of spirits. He appears to have confused two totally different
meanings of materialism : crude materialism and scientific
materialism. Crude materialism is that which allows the
existence of ghosts and spirits but says they are made of matter :
it differs only from spiritualism in regard to the kind of substance
of which the ghost is made and its greater or less refinement ;
scientific materialism, on the other hand, is a very modern
growth and has no truck at all with any such creatures. The
progress of philosophy is from crude materialism via innumerable
shades of spiritualism to scientific materialism or monism. The
ghost, originally material, cannot face science, with its balances
and test-tubes. It becomes ever more shadowy and refined ; as
the light of science spreads, it recedes further into dimness and
attempts to safeguard itself by ever-increasing vagueness and
obscurity ; and when its last lurking-holes are lit up, it fizzles
out altogether. In directing our attention to the historical
evolution of phantasms, Sir Oliver Lodge greatly injures the
cause of his proteges. To set against the innumerable ghosts of
the past which are extinct, can he mention one— one only — which
has become materialised and established its existence ?

Other Views

I need only mention shortly a few other works recently
published on the subject now before us. Eugenio Rignano
writes a book for the purpose of " explaining the inheritance of

THE SPECTRE OF VITALISM 457

acquired characters." The theory suggested is very elaborate
and would be interesting but for the circumstance that in point
of fact acquired characters are not found to be inherited. This
of course the author denies. He has undoubtedly spent great
pains and labour in presenting the subject to his readers : yet
his arguments are the old ones with which all biologists are
familiar. I find no new facts brought out : what is new is a
certain amount of a priori speculation. There has never been
any lack of a />non justifications for the inheritance of acquired
characters. Rignano's seems to me as good as any one else's :
though in view of the absence of evidence, this theory-building
is rather a waste of time. The author somewhat discredits his
judgment by affirming at the beginning of his book that the
principal object of biology is a search for the nature of the vital
principle.

The next book is one by Mr. L. G. Sarjant, entitled Is the
Mind a Coherer 1 Its opening sentence is somewhat startling:
'' Do you ever go out of your mind, reader?" A perusal of the
succeeding pages serves to suggest that the question would be
more pertinent if addressed to the author than to the reader.
After fifty pages we come to the point : " I ask you, reader, * Is
the mind a coherer ?' * I do not know,' you reply.' " In point
of fact, I reply that I do know : but suppose that I profess ignor-
ance, the author goes on to define a coherer, lest his readers
should not know what it is. He tells us that it is " an instru-
ment, an effect in which can be produced only and solely
declaring itself and fulfilling its purpose as an effect in coherence
when it bears witness to that similar effect, in a similar instru-
ment produced, which, howsoever produced, was of it the
exciting cause." On the next page he adds that although he
may be wrong in his interpretation of science, he is seeking, not
to be right or wrong but to be clear. The reader, now armed
with exact knowledge as to the nature of coherers, has no further
excuse for failing to understand the problem at issue. But alas !
I can find no facts in the remainder of the work bearing on the
question as to whether the mind is a coherer or not. It has
struck me however that the author's purpose is not that of
answering the question which he has raised but that he is
genuinely anxious to know whether or not the mind is a coherer
and has hit upon the present method of obtaining an answer. I

458 SCIENCE PROGRESS

beg, therefore, to inform him that the mind is not a coherer : and
I pass on to the next book.

In his work Involution^ Lord Ernest Hamilton takes "a
glimpse" at the "cosmic process." That ghmpse discloses to
him the existence of a new kind of ghost called a " Morion " very
similar to Driesch's entelechy. This particular spook appears
to me in nowise inferior to those of Driesch, Lodge or Bergson.^
But I think Lord Ernest has in many instances misinterpreted
modern opinions too favourably to his own views. He says that
" all humanity is groping for God," which is only true, if at all,
in a very metaphorical sense. He further asserts that ** all men
believe in a God," which is flatly untrue. He thinks that " the
history of species is the history of a gradual progressive ascent,''
which is not the case, whatever meaning we attach to the word
"ascent." He says that the doctrine of the ** interaction of an
outside intelligence with what are known as organisms " is now
rapidly gaining favour : and that " the chief reason for this change
of attitude is found in the complete failure of all attempted
explanations of life on materialistic lines." To this, I can only
reply that the 'belief mentioned is not ** rapidly gaining " favour
but rapidly losing it. Moreover I am not acquainted with any
attempt to explain life on materialistic lines within the last
quarter of a century and do not therefore see how they have
failed. Those who adopt what Lord Ernest is pleased to call the
materialistic view do not attempt to " explain life " as he and his
friends do. They are only astonished at the facile slurring over
the difficulty : whereby mystics imagine they have explained
life, by talking about morions, entelechies or psychoids.

Let it be recognised then that science will never permit an
" explanation " founded on the invention of new metaphysical
entities. Just as primitive peoples are apt to explain everything
they cannot understand by reference to the activities of a god,
so there still remains a strong mystical inclination to explain
"life" by reference to sundry ghosts and spectres to which

* It is noteworthy that Bergson has been appointed President of the Society
for Psychical Research for the current year ; he therefore may be looked upon as
the official head of the ghost-party. If I have made no mention of him in the
present article, it is because in my book Modern Science and the Illusions Oj
Prof. Bergson (Longmans) I said what I have to say from a scientific standpoint.

THE SPECTRE OF VITALISM 459

strange names are given — vital force being one of the common-
est. Not only is there no evidence whatever for the existence
of any such shadowy forms but if there were they would not
contribute one particle to an explanation : for such entities are
in themselves even more mysterious than the facts they are
called in to enlighten. The arguments by which Driesch and
the m3^stics support their views are precisely the same as those
by which primitive peoples advocate their gods. And not
primitive peoples only but the majority of our own society.
They see the trees and the grass growing and all kinds of
animals and plants : and they say, how can all this have come
to pass without the intervention of God? Just so, Driesch
contemplates the unexplained facts of organic development
and asks : How can all this have come to pass without the
intervention of entelechy ? By this method, there need remain
no obscurities in all the range of knowledge. For whenever
facts are unexplained, it is only necessary to invent a ghost, give
it a name and ask the " materialist " how he is going to explain
the facts without it. The materialist, on the other hand, will
regret the introduction of the new factor. In his view, the ghost,
even if established, makes the facts no easier to understand : the
mystery becomes ever more hopeless ; for the facts alone would
be simpler to explain than the facts plus the ghost. The
materialist will see in all this nothing but the overweening pride
of ignorance : a pride so great that it remains confident and
unabashed in the infinite regions of the unknown : an ignorance
so great as to suppose that the greatest mysteries of the universe
may be dissolved by recourse to ethereal " principles " built up
by man from among the ghosts and fairies which flit at large
through his untrained mind.

THE DANGERS OF SOCIALISTIC
LEGISLATION

By CHARLES WALKER, D.Sc, M.R.C.S., L.R.C.P.

No living organism, either animal or plant, is exactly like any
other living organism, no matter hov^ near the relationship may
be : in a litter of collie pups, no individual is exactly like either
of its parents ; nor are two individuals in the same litter exactly
alike. This is equally true of similar parts of the same organism :
no two leaves of an oak tree are exactly alike. Even when we
go down to the units of living matter, the cells, we find that no
two cells, even those forming parts of the same tissue or organ,
are ever exactly alike. It is then obvious that variability is a
common property of all living matter. Another property of
living matter, also universal, is that when organisms multiply or
produce young they produce organisms like themselves. Thus,
in spite of the differences already referred to in the case of a
litter of collie pups, the pups will be far more like each other
and like their parents than they will be like bulldogs or terriers.
This similarity extends to parts of organisms. An oak leaf,
though never exactly the same as other oak leaves, is far more
like them than are the leaves of any other kind of plant ; a liver
cell, though never exactly the same as other liver cells, is
incomparably more so than is any other kind of cell.

All this must be so readily realised by any one, even though
his knowledge and experience be of the slightest ; it is all so
easy of demonstration : that, in drawing attention to it, one risks
being classed among the apostles of the obvious. What
is perhaps not so obvious is that the evolution of living
organisms, animals and plants, is entirely dependent upon these
two properties of living matter. It is by the action of the
environment upon them that new characters, new species and
genera, the almost innumerable varieties of animals and plants
now existing in the world, have been produced. Of course, the
beginning must have been in some primitive form of living
matter of which we have as yet no knowledge but it is easy to

460

THE DANGERS OF SOCIALISTIC LEGISLATION 461

see how the process works by considering individual cases.
We will suppose a race of deer to be inhabiting a certain area.
Within this area are certain carnivora which prey upon them
but the deer can run faster than any of their enemies, who have
to depend upon cunning and surprises to catch them ; a new
species of carnivora, more speedy than any ot those already
there, migrates into this area : now some individual deer will be
able to run faster than the majority — for none is exactly like its
fellow — and only the faster will escape and produce young. The
next generation of deer will inherit their parents' characters with
variations, some towards greater, some towards less speed ; but
they will vary from a higher mean than the preceding genera-
tion : those with favourable variations will survive, those with
unfavourable variations will be killed. So things will go on,
each generation of deer becoming faster, until a racial mean is
reached in the characters involved in the quality of speed which
ensures a number of individuals escaping from the new and
unfavourable factor in the environment. This racial mean will
be kept up by the selection of inborn variations, those which
tend to lessen the speed of the animals being eliminated. In
this manner, either apparently new characters are produced or
existing characters are maintained at a high standard by natural
selection. Of course, if the selection be too stringent, a race or
species may be entirely exterminated before there has been time
for the new characters to be produced, as would have happened
had the new carnivora been so numerous and their speed so
great, in the case of our deer, that none of the deer had been
able to escape.

There is another matter which claims attention before the
consideration of the manner in which selection is acting at the
present time in the case of civilised man is taken in hand. This
is, that as soon as a character ceases to be the subject of selection
— in other words, as soon as the environment ceases to be detri
mental to those individuals who do not possess it or advantageous
to those who do — the character begins to disappear. A good
example of this is the blind cave fish, whose ancestors possessed
functional eyes, as is shown by the fact that they all possess
undeveloped eyes. Being useless in the dark, functional eyes,
however, give their possessors no advantage either in obtaining
food or in escaping from their enemies or in any other way.
Selection having ceased to act in the maintenance of this character

462 SCIENCE PROGRESS

in the cave fish, their power of sight has been lost. Innumerable
similar examples are available. Some characters disappear more
rapidly than others in, the absence of selection ; but there is no
need to discuss this point here.

There can be no doubt that mental as well as physical charac-
ters are subject to selection by the action of the environment.
Take the example of a pointer. Very likely a bulldog might be
taught to point but there cannot be the slightest doubt that
pointers generally are more easily taught to point than are bull-
dogs. The efficiency of pointers as pointers is maintained only
by the very stringent way in which selection is exercised by the
breeder ; their mental characters are just as much subject to
selection as the shape of their heads : those animals are most
sought after to breed from which have proved themselves to
possess the greatest power of displaying the mental characters
involved in pointing ; the characters involved in pointing have
been produced by selection from a common ancestor of the
pointer and the bulldog in comparatively recent times.

Among men, a very good example exists in the case of the
Jews. During hundreds of years, they were subjected to most
stringent selection — a selection which still continues to operate
to some extent in some countries. They were not allowed to
carry arms when every man went armed, so that any Jew who
showed any signs of combativeness or desire to resist oppression
by physical violence must have been eliminated at a very early
stage in his career and can have had but little chance either of
having or of bringing up children. Before they were dispersed
and subjected to this very stringent selection, the Jews were
probably the most quarrelsome, bloodthirsty and combative race
known to history. I think it would not be going too far to say
that they are now among the most peaceful. At the same time
the selection to which they were thus subjected has acted upon
their mental character in other ways. It was only by the exer-
cise of great intelligence that individuals were able to survive ;
the stupid must have been eliminated, only the clever could
escape. The result is that the Jews to-day probably possess a
higher average of intelligence than any other race in the world ;
but only in peaceful pursuits, for we do not hear of great soldiers
and sailors among them. I would here emphasise the fact that I
am speaking in general terms. I do not mean that there are no
combative or quarrelsome Jews but that on the average the race

THE DANGERS OF SOCIALISTIC LEGISLATION 463

is remarkably peaceful. I do not mean that there are no stupid
Jews but that on the average they rise higher in intellectual
pursuits, including the acquisition of riches, than do their
Gentile neighbours.

Now to apply all this to the consideration of socialistic
views and socialistic legislation. It is clear that the racial
standard of any character, mental or physical, must depend
entirely upon the stringency of selection to which the bulk of
the individuals of the race are subjected with regard to the
character. The race which can maintain itself with the least
effort will be the least industrious ; that which has never been
subjected to infection by a certain disease will be incomparably
more susceptible to it, if the infection be introduced into its
environment, than will a race that has been subjected to
infection during many generations. The characters of a race are
dependent entirely upon the existing environment and that
which has existed in the past, for the environment determines
the selection of those variations which give their possessors
an advantage over their fellows. In a civilised community,
mental qualities are sometimes of greater importance to the
individual than physical, within certain very obvious limits.
In this country the social conditions, during a long time past,
have been such that there has been a constant interchange
between the various classes. Unfavourable variations among
individuals of a higher class must cause a fall into a lower
class, which can only be checked by the occurrence of
favourable variations among the offspring ; the occurrence of
favourable variations will result in the individuals " bettering
themselves " and if these favourable variations are inherited
by the children, they in their turn will either maintain the
position gained by their parents or improve it if the favourable
variation have been increased. In cases where property and
position are by law inherited entirely or in overwhelming
proportion by the eldest son, the process of falling into a lower
class, in the case of the occurrence of unfavourable variations,
may be to some extent checked but the extent to which this
can happen and the number of individuals involved cannot
possibly be sufficient to produce an appreciable effect upon
the mean of the mental and physical characters of the race.
A cursory examination of the family histories of the present
members of the House of Peers, the class most protected in
30

464 SCIENCE PROGRESS

this way, will show how short is the time during which a
succession in the male line is maintained. On the other hand,
even in the case of the aristocracy, all but the eldest son in each
generation are dependent upon the maintenance of a certain
standard of efficiency; if unfavourable variations occur and
are handed on to the offspring, the individuals forming the
off-shoots — one should perhaps rather say the overwhelming
majority of the members — of these families must rapidly sink
to lower classes in the social scale. In the lowest class the
stringency of selection, particularly with regard to physical
characters, is very high, as is shown by the very high infant
mortality among other things. At the present time it is
probably far easier for individuals to rise from the lower
classes than was formerly the case and it is just as difficult
for individuals to remain in the higher classes and place
their children in positions similar to their own.

It must of course be realised that man is the supremely edu-
cable animal but this fact has unfortunately so impressed some
people who write upon social problems, that the inheritance of
mental capacities as distinct from superadded education has been
completely overlooked by them. No two boys in the same
class in a school will show precisely the same ability in
acquiring knowledge or skill. Moreover, one boy will very
likely be brilliant in mathematics but hopeless in some other
subject ; whilst the boy who is good in this other subject may
be incapable of attaining to any great efficiency in mathematics.
Probably all the class will be capable of attaining to a certain
degree of efficiency in any subject but the labour involved in
such attainment will vary in every case and some of them will
be unable to get beyond a comparatively low standard. The
various mental capacities are undoubtedly transmissible from
parents to offspring with variations towards increase or
decrease.

At the present time the selection of physical characters,
particularly among children, is most stringent in the lowest
class but it extends to all. In the case of all individuals there
is a continual competition by which the least efficient are
selected and placed under conditions under which the mor-
tality is highest. Of course, I do not for a moment contend
that there are no cases in which an individual, through an
unfortunate concatenation of circumstances, is kept in a position

THE DANGERS OF SOCIALISTIC LEGISLATION 465

not equivalent to his mental and physical efficiency ; but, as
a rule, there cannot be any doubt that the possessors of
favourable variations rise and that if these variations are handed
on to the children they continue the upward movement. The
converse is obviously true of unfavourable variations, particu-
larly when they are transmitted to the offspring. One excellent
feature of the process, from a biological point of view, is that
it is usually slow. An individual does not, as a rule, himself
rise directly from the lowest class to a high one and start his
children in life there ; for a substantial rise, several generations,
involving the continuance of favourable variations, are generally
necessary. The converse is true with regard to a fall. It is
far more probable that a high standard of capacity will recur
in the offspring of an individual whose ancestors, during many
generations, were of a high standard, though he himself varied
unfavourably, than that a high standard of capacity should
occur in the offspring of parents whose^ancestors, during many
generations, had never risen from the lowest class.

Now all the systems of socialism appear to me to aim at
mitigating the stringency of selection with regard to capacity.
The least that any of them aim at seems to make such provision
that every individual shall be able to live under healthy and
even comfortable and happy conditions and that all shall have
similar opportunities when starting in life. This involves a
limitation of selection, particularly in that the children of
efficient parents are not placed in a better position from which
to start than the children of inefficient parents. Competition
is selection in civilised communities and the ideal state of things
would be that all individuals who fail in this competition beyond
a certain point should be eliminated. On account of the senti-
mental feelings towards the individual which, in our country,
are concomitant with the advance of civilisation, active
measures in this direction are almost inconceivable. Hitherto,
a passive elimination of the inefficient has gone on to a con-
siderable extent, through the action of bad and insufficient food
and bad hygienic conditions generally upon the lowest classes
of society. There appears to be no doubt whatever that modern
legislation is removing this very necessary form of selection and
is giving us no protection in substitution for it. As it is impos-
sible to deal with many points in detail, I will select one or two
examples.

466 SCIENCE PROGRESS

Hitherto, unless individuals, particularly those in the lower
classes, considered the future to some extent, any unexpected
misfortune such as illness or unemployment placed them and
their children at a very considerable disadvantage ; the proba-
bility of having children or of successfully rearing those already
existing would be considerably diminished as compared with the
case of individuals who had foreseen the possibility of such
misfortunes and provided against them. Many of the lower
classes did so provide ; consequently there was a constant process
by which the provident became selected as against the improvi-
dent. Now, under the Insurance Act, the improvident are forced
to provide to some extent against unfavourable contingencies and
the process of selection is seriously interfered with in conse-
quence. The elimination of the improvident and their children
is to be prevented as far as the law can manage it. Much the
same criticism may be applied to the feeding of school children.

Not so very long ago lunatics were treated as criminals : the
treatment they received was such that recovery was wellnigh
impossible and the production of children was prevented. All
kinds of lunacy are not transmissible from parents to offspring ;
but most are and idiocy certainly is. The effect of modern
legislation with regard to lunatics and idiots is such that whilst
it is now made as difficult as possible to keep them under
restraint, they are treated in a way to improve their condition
and set at liberty upon temporary improvement ; they therefore
gain a renewed opportunity of perpetuating their kind. The
result is an increase in the number of lunatics, which increase is
progressing at such a rate that the public must inevitably be
frightened at no distant date ; the Government of the day will
then be forced to legislate afresh but it is to be feared that
sentiment will again intervene to prevent the introduction of
satisfactory measures.

One of the greatest dangers in the immediate future appears
to lie in thoughtless and sentimental legislation dealing with
disease. In some cases, there can be but little doubt that
legislation might do much towards the elimination of particular
diseases. In other cases it is almost certain that legislative
interference will be attended with a vast amount of harm and
with no possible chance of doing good. Those responsible for
this kind of legislation often appear to be either ignorant of the
complicated nature of the problems with which they are dealing

THE DANGERS OF SOCIALISTIC LEGISLATION 467

or to come to a conclusion without having devoted any considera-
tion at all to the consequences of their endeavours.

An amount of injury to the race which it is difficult to over-
estimate is likely to follow upon the recent legislation concerning
tuberculosis. The people of Northern Europe have been sub^
jected to a very stringent selection as regards tuberculosis during
several thousand years ; the selective process has become more
stringent of late years in proportion to the increase in the town
population. At the present time it is so stringent that, probably
every individual in Northern Europe, living in a town or even
in a village, is infected with tubercle many times during life. I
do not mean merely that the tubercle bacillus gains access to his
body and is immediately eliminated but that it becomes estab-
lished therein and multiplies, being eliminated only after some
time. The evidence that this happens is overwhelming. Thus
Ribbert has published the records of 5000 consecutive post-
mortem examinations of cases that died in general hospitals.^
Traces of tuberculosis were found in every one of these cases.
In all similar records of which I know, the lowest percentage of
cases in which traces of tuberculosis have been detected is
seventy-five. It has also been shown that very frequently the
signs that are met with of tubercular disease of the lungs of
long standing indicate very considerable and extensive damage
and destruction of tissue, not slight infection ; ^ yet such indivi-
duals have recovered from the disease and this has had no
permanent effect upon their health. Now it is well known that
when the tuberculosis bacillus is introduced among a race which
has had no previous experience of the disease many individuals
contract the disease and die of it rapidly under conditions which
would bring about a cure in susceptible European patients.

The explanation of this fact is quite simple. The relative
immunity of the European has been brought about by a process
precisely similar to that described in the case of the deer and the
carnivora. When the tubercle bacillus first appears, the different
individuals of the race will differ in their susceptibility to its
ravages, just as they differ in other characters. The least
susceptible will have an advantage over the more susceptible and
will have a greater chance of producing and rearing children.
Taking the average resistance of the race originally as o, some

^ Quoted by W. Osier, Principles and Practice of Medicine^ 1904.
' Brouardel, Trans. British Congress on Tuberculosis^ vol. i. 1902.

468 SCIENCE PROGRESS

of the individuals will have a greater resistance than the average
and these may be classed as + i. Others will have less — these
will be — I ; others will be o. In the next generation, however,
more children will have been produced and reared by the + i
individuals. Offspring inherit their parents' characters with
variations but this second generation will vary from a new
mean, + i ; some individuals will vary towards a greater, some
towards a less and some will inherit the character in the same
degree as their parents. We shall, therefore, have a generation
of individuals consisting of o, + i and + 2. Obviously, the + 2
class will have the greatest chance of surviving and rearing
children, so the next generation will vary again from a higher
mean, + 2. This process must continue as long as the tubercle
bacillus continues in the environment, until a very high degree
of immunity is attained by the race. Of course, variations away
from the average of racial immunity must continue to appear but
the standard of the race is maintained because these unfavourable
variations are eliminated. There is undoubted evidence that
tuberculosis existed in Egypt about 5000 years ago,^ so it is
practically certain that it occurred also in countries further north
which had communication with Egypt,^ at any rate indirectly,
where the conditions are as favourable to the tubercle bacillus as
they are unfavourable in Egypt. Northern Europeans have
therefore been subjected to selection during several thousand
years ; hence comes their comparative immunity. The effect of
recent legislation must certainly be to lower the standard of
immunity of the race, as the susceptible individuals are to be
taken in hand wholesale and kept alive to breed children, who
will vary in their immunity from a lower mean than that from
which their parents varied.

It is unfortunately inconceivable that the tubercle bacillus
can be eliminated altogether. It is able to survive in a dried-up
condition during a very considerable period of time and it is
probable that the inhalation of dried tubercle bacilli is a common
cause of pulmonary tuberculosis in the case of susceptible
individuals. Besides this, tuberculosis is probably as common
in cattle and perhaps other animals as it is in man. If, even in
spite of this wide distribution, the bacillus were eliminated in

* G. Elliot Smith and Wood Jones, Archceological Survey of Nubia^ Report for
1907-8, vol. ii. (Cairo, 1910).
' G. Elliot Smith, op. cit.

THE DANGERS OF SOCIALISTIC LEGISLATION 469

the British Isles, it is inconceivable that its introduction from
abroad could be prevented. Therefore, if susceptible individuals
are kept alive and allowed to breed in large numbers we must
expect serious ravages in the future, when the racial standard
has been lowered and a temporary concatenation of circumstances
favours the infection of a large number of individuals at the same
time. The nation whose racial standard is thus lowered by
legislative interference must eventually be supplanted by an
invading race which has continued to exist under conditions of
stringent selection. Under invasion I intend to include simply
the immigration of immune individuals.

The case of typhoid fever belongs to the class in which
legislative interference might bring about the suppression of
the disease. The micro-organism can only continue to live
under a comparatively limited set of conditions, which may
conceivably be eliminated.

Smallpox is in a rather different category. In this case, the
individual may be rendered, by artificial means, entirely or to
a large extent immune to the disease during the whole of his
life and that very easily. Unfortunately this is i the only case
in which a comparatively permanent immunity to a particular
disease can be produced early in life. The original legislation
enforcing vaccination upon every individual was wise. The
modern vice of sentimentality, which attaches so high a value to
the feelings of the individual but is regardless of the interests of
the community at large, has allowed any one who wishes to
refuse to allow his children to be vaccinated. We have already
experienced the consequences of this evasion in Gloucester and
other places and are likely to have further and more serious
demonstrations of the folly of our latter-day legislation in the
near future.

The legalisation and protection of trades unions are equally
disastrous in so far as these associations tend to equalise the
inferior and the superior workman. Anything that places the
unskilful and idle on the same footing as the skilful, hard-VN^orking
and steady man with regard to wages must tend to eliminate
to a great extent the selection of these desirable quahties. The
standard of efficiency to begin with may be that of the average
man but as there is no advantage to be gained in being above
the average, competition is interfered with; selection, in fact,
ceases to operate and though there is nothing in the environ-

470 SCIENCE PROGRESS

ment which can raise the average, all the factors tending to
make it fall remain ; fall, therefore, it certainly will. Many
employers of skilled labour who are competent judges upon this
point "are of opinion that the average has already fallen and is
continuing to fall. It does not appear that the so-called leaders
among the working classes are amongst the most diligent and
skilful at their various trades. The best men still have a practical
certainty of employment, at any rate in trades requiring skilled
labour ; many that I have met feel that they might be much
better off in the absence of union scales of wages, as doubtless
they would. But when the employer of skilled labour is obliged
to get a large quantity of work done for a certain sum — being
limited by the price he, in his turn, can obtain — he is obliged also
to pay a minimum if not a uniform wage ; the obvious result
must be that the least efficient man is paid more than he is
worth, the most efficient man less. From the point of view of
selection and the maintenance of a high standard of efficiency in
the race, there cannot be the slightest doubt that it would be
far better for the inefficient to be sweated and the efficient to be
paid too much. From the point of view of present-day sentiment,
the poor inefficient is to be saved from suffering and even from
discomfort at any cost. The cost must obviously be paid in
some form or other by the efficient and the ultimate result
must certainly be the lowering of the general efficiency of the
nation.

It is probable that the highest standard of efficiency is in the
professional and upper middle class generally, where selection
acts most quickl3^ Unfortunately, this class is the busiest ;
moreover, it is not often subject to the efforts of the agitator
and is not combined in a political sense. Men of this class con-
fine their attention to a great extent to their work and though in
them lies the overwhelming proportion of the mental capacity
of the nation, they play but a small part proportionately in the
government. Unfortunately, also, the sentimentality of the age
is as strongly developed in this class as in any other and
apparently no consideration is given by them to the ultimate
effects of indulgence in this weakness. Failures, including
criminals, as well as the children of failures are more and more
protected and kept alive to breed more failures. Failure in
competition for a livelihood means, in the overwhelming majority
of cases, that the individuals are so much below the average in

THE DANGERS OF SOCIALISTIC LEGISLATION 471

mental and physical capacity that it is necessary, if the racial
standard is to be maintained, that they should be eliminated or
at any rate should not produce children. There are exceptions
but it is better that the exceptions should suffer than that the
race should fail. Our intellectual and physical characters have
been produced by the action of natural selection upon inborn
variations. Unfavourable variations have been eliminated.
Elimination is necessarily unpleasant to the eliminated and
whilst to-day, horrified at the cruelty of the process going
on in our midst, we are preventing it by all the means in our
power, we are providing nothing to take its place. In the
absence of selection, characters must disappear ; inborn mental
capacities of every kind are just as much heritable as are arms
and legs. Any social legislation, therefore, which interferes
with the unpleasant process of the elimination of the unfit must
result in the diminution, if not in the disappearance, of those
characters which are so eminently necessary in the competition
between different nations — a competition that cannot be abolished
by anything that a single or even several nations can do.

THE DETECTION OF PREGNANCY

Under normal conditions, the substances entering the blood
stream, apart from the fats, are presumably the simple products
fashioned during digestion from the complex materials taken as
food ; they are either rebuilt into various tissues or gradually
utilised as sources of energy ; and in the latter case are finally
resolved almost entirely into carbon dioxide, ammonia and
v^ater.

Under the conditions of disease, more complex substances
may enter into circulation or the blood may become more or less
infected with micro-organisms. It is all-important to determine
what are the agencies at the disposal of the animal organism
whereby such intrusions are countered and rendered ineffective.
The body cells generally undoubtedly contain enzymes
capable of acting on albuminous materials, on carbohydrates
and on fats ; these are set free when the cells are subjected to
the action of hormones or to mechanical disruption. But fresh
blood plasma and serum, in the case of most animals, appear
to be without hydrolytic power.

Prof. Abderhalden, who has been an active worker in this
field of late years, has recently published an interesting account
of his views and experiments in book form.^

Observations have been carried out by injecting various
hydrolytes and after an interval observing the action of the
blood plasma or serum on the hydrolyte, normal plasma or
serum having been found to be without action. To ascertain
whether an effect had been produced, serum from the treated
animal was mixed with a solution of the hydrolyte and the
change in optical rotatory power which took place over an
interval of several hours was followed by means of the polari-
meter. A specially constructed short tube was used in carrying
out the observations, so as to permit of the use of small
quantities of material.

^ Schutzfermente des tierischen Organismus. Ei7i Beitrag zur Kenntnis der
Abwehrmassregeln des tierischen Organismus gegen korper-, blut- und zellfremde
Stoffe. Von Emil Abderhalden. (Berlin : Julius Springer, 1912 [pp. xii + no.)

472

THE DETECTION OF PREGNANCY 473

To quote a particular experiment. On each of two succes-
sive days, five grams of cane sugar was injected intravenously
into a dog and on the third day blood was withdrawn from the
animal and tested. In making the test, one cubic centimetre of
serum was mixed with one cubic centimetre of a lo per cent,
solution of cane sugar and 5 of physiological saline. The
initial rotatory power of the mixture was + o°'45 ; observations
made at intervals during forty-five hours showed a steady fall
in the rotatory power, which finally became — o^'S. In a second
experiment, in which ten cubic centimetres of a 5 per cent, solu-
tion of sugar was injected intravenously, the serum was found
to be active fifteen minutes after the injection. In the case of a
dog which had only received a single injection, the serum was
slightly active fourteen days afterwards; whilst that from one
which had received two injections subcutaneously was strongly
active nineteen days afterwards.

Similar results had been obtained previously by Weinland,
who had also made the remarkable observation that when either
milk sugar or soluble starch is substituted for cane sugar, the
blood acquires the power of hydrolysing cane sugar but that
these substances apparently do not provoke the appearance of
corresponding enzymes. Raffinose, a more complex sugar than
cane sugar, seems to be without action.

Similar observations have been made with albuminous sub-
stances and peptones — but the same remarkable result comes
out in these experiments : the response being a perfectly general
one, not specific, the blood plasma acquiring the power of
hydrolysing substances generally of the class to which the
hydrolyte used belongs, not this hydrolyte alone.

In view of the statement that it is possible to detect
invertase in blood plasma fifteen minutes after the subcutaneous
injection of cane sugar, Abderhalden's further statement is
remarkable that when albuminous materials are injected, it is
often many days before proteoclastic activity is fully developed.

It is obvious that much is yet to be learnt before it will be
possible to give a consistent explanation of the observations,
the evidence at present being far from decisive.

Perhaps the most interesting outcome of the work is that
relating to the peculiar condition of the blood in pregnancy
It is well known that during this period chorion cells pass from

474 SCIENCE PROGRESS

the ovum into the blood, of which they are not normal con-
stituents. Presumably means exist whereby these are destroyed.
Abderhalden finds that normal blood plasma and serum are
without action on the peptones prepared from human placenta
but that they are hydrolysed by blood plasma from pregnant
women and even from pregnant animals ; and in this case the
effect is specific, little or no action taking place either with
ordinary albuminous materials or with peptones prepared from
them. The effect is noticeable from the first month of
pregnancy to the close but disappears within eight days after
delivery.

To ascertain whether action had taken place, Abderhalden
originally used either the optical method or subjected the crude
mixture of peptone and plasma to diffusion and applied the
well-known biuret test to the diffusate. Recently an important
new test has been introduced.

In 1910, Dr. S. Ruhemann was led to prepare a substance to
which he gave the name triketohydrindene hydrate^ a compound
represented by the formula —

CbHXcC>C(OH),

This compound behaves in a most characteristic manner
with amino-compounds and when warmed with amino-acids
gives rise to coloured products : the test is an extraordinarily
sensitive one, so that if a solution containing a very minute
quantity of the keto-compound and of an amino-acid (glycine,
alanine, leucine, tyrosine, etc.) be warmed, a blue colour rapidly
makes its appearance.^

The proportion of amino-acids present in normal blood is
so minute that they cannot be detected in it by means of this
test but in pregnancy they are at once apparent. To apply the
test, a little of the serum is first subjected to diffusion,, as
peptones and proteins also give the blue colour ; the diffusate
is then warmed with a little of the keto-compound. No other
condition has been discovered in which the test gives positive
results — so that it is of great diagnostic value.

It has been the fashion of late — especially among physicists
— to decry the work of chemists and to stigmatise them as mere

^ Chem. Soc. Trans. ^ i9io> 2025.

THE DETECTION OF PREGNANCY 475

preparation-makers. Physicists unfortunately too often have
no proper knowledge even of the elements of chemistry let
alone of the higher walks of organic chemistry, so that they are
unable to appreciate the methods of the chemist and the progress
that is being made by his persistent efforts to discover new
paths by which the infinitely difficult problems of physiological
chemistry can be approached. We can put up with a very
large amount of dull work, if occasionally a discovery be made
so useful as that under notice is likely to prove. If special
colour tests applicable to particular diseases — syphilis and
tuberculosis, for example — could be devised, they would be of
the greatest value; as it is more than probable that different
diseases are attended with chemical changes special to each
disease, it is to be expected that simple tests may ultimately
be found that will at least facilitate diagnosis, if they do not
make it certain.

THE BLEACHING OF FLOUR

Satisfactory as is the increasing amount of interest taken by
legislative bodies in the purity of manufactured foods, it is to be
regretted that expert and scientific advice is not more often
sought before framing restrictive regulations ; in consequence,
measures not infrequently become law which are either un-
workable in practice or impose a grievous restriction on the
honest manufacturer ; and even, as in the case of milk and
butter, legally debase what was previously, in most cases, an
article of high quality. Our own Local Government Board
should be free from this criticism, since it is at pains to
anticipate legislation by reports prepared either by its own or
by co-opted experts. Admirable, however, as this plan should
be in theory, it has proved somewhat disappointing in practice.
There is an increasing tendency to take certain conclusions as
proved, even against the weight of scientific evidence and
contrary to the canons of scientific research. Such action can
only be regarded as a deplorable subversion of intelligence ;
taken in conjunction with the present-day exploitation of
science by company promoters and by advertisers of proprietary
foods and medicines, it is undoubtedly producing an adverse
effect on the public attitude towards science.

476 SCIENCE PROGRESS

The Local Government Board has recently issued the third
of a series of Reports ^ relating to the bleaching of flour, in
which experiments are described that have been made in the
Laboratories of the Board. In this pamphlet certain results are
described, almost without comment, which are directly at variance
with the conclusions arrived at in former Reports on the same
subject, so that it seems desirable to criticise the pronouncements
in detail.

In the former Reports (see Science Progress, April and
October 191 1) dogmatic statements were made as to the
injurious effects of bleaching flour — we are now favoured with
an account of experiments made to determine what bleaching
actually does to flour and the influence it has on the baking
qualities.

The immediate effect of bleaching flour is to destroy the
colouring matter. It has been suggested by Wesener that
the pigment present is identical with Carrotene, a yellow un-
saturated hydrocarbon which recent researches, more particularly
those of Willstatter, have shown to be widely distributed in
plants. To confirm this suggestion. Dr. Monier- Williams has
compared the absorption spectrum of carrotene with that of a
flour extract and finds the two to be identical. It appears that
elaborate spectroscopic apparatus was obtained and much time
spent in research before this conclusion was reached — would it
not have been easier to have made use of the facilities offered
by one or other of the many University laboratories in which
such apparatus has long been installed ? Pure carrotene was
prepared from other sources and the effect produced on it by
nitrogen peroxide compared with that of oxygen. Nitrogen
peroxide bleaches carrotene, products containing nitrogen
being formed. When exposed to the atmosphere, carrotene
becomes lighter in colour and absorbs oxygen ; no nitrite could
be detected in a sample (0*2 gramme) after such exposure.
It is assumed that the action of the two gases gives rise to
different products and hence that their action on flour is also
entirely dissimilar. It is a far step to take from the first to
the second of these statements on such slender evidence.

' Report to the Local Government Board on the nature of the colouring matter
of flour and its relation to processes of natural and artificial bleaching. By
Dr. G. W. Monier-Williams. Food Reports, No. 19. (London : Wyman & Sons.
Price 3^.)

THE BLEACHING OF FLOUR 477

In his previous Report, Dr. Monier-Williams made sweeping
assertions regarding the injurious effect of bleaching on flour.
He now produces experimental evidence to show that when
flour is exposed to the atmosphere, stored in calico bags under
conditions very similar to those which prevail in the retail trade,
it absorbs a minute proportion of nitrite from the air. The
quantity so absorbed was an amount equivalent to i*2 parts of
sodium nitrite per million, whereas commercially bleached flour
of the t3^pe manufactured in London did not contain more than
i'6 parts. The difference is so small that it is difficult to avoid
the conclusion that the same ultimate result is attained whether
the flour be bleached rapidly by artificial means or slowly by the
gradual absorption of nitrogen peroxide from the atmosphere.
This contention is dismissed in the Report because a sample of
pure carrotene did not absorb nitrite from the air. The power
flour, starch and similar materials have of absorbing all sorts of
things from the surrounding atmosphere is entirely ignored.

Not only does ordinary bleached flour absorb no further
nitrogen peroxide on exposure but highly bleached flour loses
most of its nitrite on prolonged storage and it is admitted that
'* under ordinary conditions of storage " there is ** an approximate
figure towards which the nitrite content of all samples, whether
highly bleached or unbleached, will eventually converge."

Hitherto the Local Government Board experts have been
silent as to the effect of bleaching on the baking qualities of
flour, though this is in reality the crux of the whole position.
No baker would use a flour if it had any effect on the quality of
his bread : the public are greater adepts at noticing such niceties
than is generally supposed. The services of Mr. Kirkland, of
the Borough Polytechnic, have now been called in to make
bread from flour subjected to different degrees of bleaching far
in excess of the commercial quantities. He reports that, with
the exception of the loaf from a flour containing 75 parts of
sodium nitrite per million, all the loaves were of excellent quality
and had no taste or smell !

Comment should be unnecessary. Dr. Monier-Williams
himself shows that his earlier conclusions were entirely
illogical and it is difficult to understand the attitude he took
up in his former report.

The whole question has been the subject of an important
legal case during 191 2 in connexion with a prosecution for flour

478 SCIENCE PROGRESS

bleaching. The experts for the prosecution concerned them-
selves with the effects of large amounts of nitrite ; the defence
was directed to flours as actually treated by a bleaching plant.
The judge found that commercially bleached flour cannot be
proved to be different from unbleached flour and that the result
of commercial bleaching was merely to alter the colour without
altering the nature, substance and quality of the flour so as to
render it a different article !

A remarkable aspect of the case was the attitude taken up by
some of the experts in deducing the behaviour of very small
quantities of a substance from what is known of the action of
large quantities. This method has been carried to exaggeration
by Dr. Wiley in America but that it is entirely fallacious few
scientific men will deny. In the first place, it ignores entirely
all possibility of selective action, such as is bound to occur when
an active agent is brought into contact with so complex a mixture
as flour ; secondly, scientific literature is full of well-authenti-
cated instances of the beneficial action of traces of substances
which in larger quantities act prejudicially ; much has been done
of late to put our knowledge of the mode of action of these small
quantities on a firm basis : it is therefore disconcerting to find
scientists of eminence adopting an attitude in the \yitness-box so
much at variance with proved fact as appears to have been the
case in the trial referred to.

In view of the foregoing considerations, if^ is obvious that
there is grave danger in basing action affecting interests so
great as those of the milling trade on the partial opinions of
persons who necessarily have only a limited knowledge and
experience of the practical side of the question at issue.

RADIOACTIVITY VISUALISED^

By C. T. R. WILSON, M.A., F.R.S.

The phenomena of radioactivity are known to be due to the
ejection from the atoms of the radioactive elements of two
kinds of particles which travel with enormous velocities :
(i) the alpha-particle, which is a positively charged helium
atom having a mass four times that of the hydrogen atom ;
(2) the beta-particle, which carries a negative charge only
half as large as the positive charge of the alpha-particle and
has a mass less than the 1700th part of the hydrogen atom.

The velocity of the fastest beta-particles approaches very
nearly to that of light, that of the alpha-particles being con-
siderably less but still exceeding 10,000 miles a second.

B}^ the action of Rontgen and other radiations, we can
cause electrons or corpuscles which are identical with the
beta-particles to be expelled from the atoms of any element
with velocities comparable with those with w^hich the alpha-
particles are ejected from radium.

The methods which have been used hitherto in the study
of the paths of these projectiles and of the effects produced
by them in their flight have been somewhat indirect. The
actual paths of individual particles have not been observed ;
it has been necessary to investigate the combined effects of a
large number of particles.

It is true it has been found possible by two different methods
to detect effects arising from the action of a single alpha-particle.
Thus Rutherford introduced a method in which effects due to
the ions set free along the path of a single alpha-particle could
be detected by an electrometer ; again in the Crookes spin-
tharoscope each alpha-particle causes a starlike point of light
to flash forth momentarily where it strikes the prepared screen.
But it has not been found possible by such methods to detect
effects arising from a single beta-particle.

^ A lecture delivered at the Royal Institution on the evening of Friday,
February 28, 191 3.

31 479

48o SCIENCE PROGRESS

It is plain that a great advance would be made if it were
possible to induce each alpha- or beta-particle to leave a visible
trail behind it along its whole course and to photograph this
trail. This is what is accomplished by the method now
described.

Each alpha- or beta-particle, in the course of its flight
through a gas like air, traverses large numbers of the atoms
of the gas. According to modern theories, such as those
developed by Sir J. J. Thomson and Rutherford, each atom
may be regarded as a sort of miniature solar system in which
the planets are represented by negatively charged corpuscles
or electrons ; the forces with which we are concerned being
of course electrical and not gravitational. When either an
alpha- or a beta-particle passes near one of the members ot
the system, there are forces tending to deviate the flying
particle from its otherwise straight course and to cause dis-
turbances in the path of the planetary electron ; these may be
violent enough to cause the electron to escape from the system.
An electron thus set free will become attached finally to some
other atomic system, which thus acquires a negative charge,
w^hilst the atom which has lost an electron has been left with
an excess of positive electricity. We thus get positively and
negatively charged atoms or ions.

Now a method of making visible the individual ions has
long been available. Molecules of water or of other vapours
attach themselves more readily to ions than to uncharged
atoms or molecules. Thus, in the absence of other nuclei on
which vapour can condense more readily, such as those called
dust particles by Aitken, it is possible to arrange that every
free ion shall act as a nucleus and cause the condensation of
water vapour, whilst none condenses elsewhere. Each invisible
ion may thus be converted into a visible water drop. The
supersaturated condition necessary in order that water vapour
may condense on the ions is most conveniently produced by the
sudden expansion of moist air.

The advance which I have recently succeeded in making
in the condensation method of studying ionisation is this.
The ions are now captured and converted into visible water
drops in the positions which they occupied immediately after
their liberation by the ionising agent; the cloud of drops is
then at once photographed. Thus the invisible trail of ions

RADIOACTIVITY VISUALISED

481

left behind along the course of any ionising particle is con-
verted into a visible line of cloud oi which a photograph is
secured. In this way a record is obtained of the path of each
projectile by making visible the atomic wreckage it has caused
in its passage through the air or other gas. In many cases
the individual ions produced along the tracks are visible in the

photographs.

In order that undistorted pictures showing the result of the
passage of the various rays may be obtained, it is essential
that the expansion should be effected without stirring up the
gas. This condition is secured by using a wide shallow cloud
chamber of which the floor can be made to drop suddenly and so
produce the desired increase of volume (fig. x).^

Fig. X.

It is hardly necessary to say that the cloud chamber must be
freed from dust particles and all nuclei on which water readily
condenses. This is easily done by repeated expansions, each
too small to cause condensation on the ions, any cloud formed
being always allowed to settle before making another ex-
pansion.

The cloud chamber must be free from ions other than those
produced by the ionising agent under investigation. Since
ions are always being produced even under normal conditions
within a closed vessel, it is necessary to maintain an electric
field between the top and bottom of the cloud chamber, so
that they may be removed as fast as they are produced.

^ The apparatus is described in ^% Proceedings of the Royal Society^ A., vol. 87
(1912), p. 277.

482 SCIENCE PROGRESS

One very practical point in connexion with the cloud chamber
remains to be mentioned. It is necessary that the interior
should be maintained in a nearly saturated condition and yet
that the roof and walls should be transparent and admit of a
clear and undistorted view of the contents. A glass vessel
containing moist air soon becomes coated internally with a
dew-like deposit of minute drops. This difficulty is completely
avoided by covering the inner surface of the glass with a film
of gelatine.

The moist gelatine under the plate-glass roof of the cloud
chamber forms a conducting film which is connected through
a marginal ring of tinfoil with one terminal of a battery of
cells, the other terminal being connected to the floor. In this
way, a nearly uniform vertical electric field is maintained be-
tween the roof and floor of the chamber. The floor is virtually
a pool of water made solid by the addition of gelatine and
blackened by means of ink so that it forms a dark background
for the clouds. It is supported by a glass plate which forms
the top of a hollow cylindrical plunger working in water.

As regards the actual mechanism for causing the sudden drop
of the floor of the cloud chamber, it is sufficient to state that
the space below the plunger can be put in communication,
through wide tubes, with an exhausted chamber by suddenly
opening a valve.

In order that the ionising particles should leave sharply
defined cloud trails, it is necessary that they should traverse
the moist gas immediately after this has been expanded while
the water vapour is still supersaturated to an extent consider-
ably exceeding the minimum which is required to cause
condensation on the positive ions (which are more difficult to
catch than the negative). Under these conditions, the ions lose
their mobility and grow into visible drops before they have
had time to diffuse appreciably away from the original track of
the ionising particle.

If the clouds formed by condensation on the ions are to be
photographed, it is necessary to expose them to an instantaneous
illumination of great intensity while the camera is in position.
The instantaneous illumination is obtained by a Leyden jar
discharge, the arrangement being essentially the same as that
used by Lord Rayleigh in photographing jets of water and by
Worthington in his study of the splash of a drop.

Fig. 2.

Fig. I,

Fig. 3.

Fig. 4.
PLATE I.

Fig. I. — Alpha-rays from radium.

Fig. 2. — Alpha-rays from radium ; the a-particles all traversed the air after its expansion.

Fig. 3. — Enlargement. of portion of Fig, 2.

Fig. 4. — Alpha-rays from radium emanation.

RADIOACTIVITY VISUALISED 483

I have, however, allowed the spark to traverse mercury vapour
at atmospheric pressure instead of air, the brightness being
thereby greatly increased.

The spark, of course, has to be suitably timed, so that the
cloud trails may be illuminated after the drops composing
them have grown sufficiently to scatter plenty of light but
before there has been any appreciable disturbance of the air by
convection currents.

Figs. I — 12 are pictures obtained by this method. It is
perhaps necessary to point out that they are all photographs
of clouds consisting of minute water drops condensed upon
ions, as many of the clouds have a very uncloudlike
appearance.

Fig. I is a photograph of the tracks of some alpha-particles
shot out from a minute quantity of radium placed within the
cloud chamber, the camera looking down through the plate-
glass roof. From the atoms of radium, alpha-particles are
continually being projected with velocities of many thousands
of miles per second, each producing more than 100,000 ions in
the course of its flight. Under ordinary conditions the trail of
ions left behind by each particle is invisible ; those formed
by particles which have traversed the supersaturated air of the
cloud chamber immediately after its expansion, however, are at
once converted into visible cloud trails. These form the sharply
defined spokes or rays of the picture. The more diffuse cloud
rays are the tracks of particles which have traversed the air
before its expansion, the ions having thus had time to wander
out of the original track before losing their mobility through
the condensation of water upon them. The electric field
maintained in the cloud chamber fixes a limit to the age and
hence to the diffuseness of the trails which are rendered visible ;
under the actual conditions any free ions would be driven by
the electric force to the roof or floor within less than a fifth of a
second after being set free. None of the ions made visible has
had a free existence exceeding this limit.

It is clear that an ionising particle, while traversing or even
passing near to an older trail of ions on which a cloud has
already formed, will not find the vapour supersaturated to the
extent necessary to cause condensation on the ions ; it will
therefore fail to leave a visible trail in this region. This is
doubtless the reason why the sharply defined trails only appear

484 SCIENCE PROGRESS

to begin at some distance from the source, the older trails being
most closely packed in the region around the source.

By means of a suitable shutter arrangement attached to the
floor of the cloud chamber, it is possible to prevent alpha-particles
from traversing the moist air till after the expansion. The
diffuse cloud trails are then absent from the photographs

(fig. 2).

The most remarkable feature of the tracks of the alpha-
particles is their general straightness. Sudden bends are to
be observed, hov^ever, practically all the rays being bent
within a millimetre or two of their ends. In this respect, as in
others, the photographs confirm the conclusions arrived at by
less direct methods.

In the next picture (fig. 3) an enlargement of two of the
tracks is shown, one of them having two sudden bends. The
path is otherwise straight except very near to its end. Now the
alpha-particle has thousands of encounters with atoms of
the gases of the air in each millimetre of its course by which
ionisation is brought about, as we know from measurements
made by the electrical method ; and in accordance with this,
the cloud particles (which are simply ions magnified by con-
densation of water) are so closely packed that they are not
separately visible in the photograph. It is remarkable that
only two encounters out of the many thousands occurring in
the course of its flight should succeed in deviating the particle
visibly from its course and that in these cases the deviation
should be quite large.

The alpha-particle, in passing near one of the electrons of
an atom, may impart to it sufficient energy to cause it to escape
from the atom, whilst on account of its own enormous
momentum it is not perceptibly deviated from its course.
We can thus understand the general straightness of the tracks.
The sudden deviations must be due to encounters of a special
kind ; according to Rutherford's view, such large deviations
would be caused by the alpha-particle passing near the centre
of the atom, where he supposes the positive charge to be
concentrated.

What is perhaps the most interesting feature of the
particular track I have been describing remains to be mentioned.
At the second of the two bends, there is a distinct spur which
one can hardly interpret otherwise than as being due to th^

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RADIOACTIVITY VISUALISED 485

recoil of the system which has caused the deviation of the
particle.

The next two photographs (figs. 4, 5) show the effect pro-
duced in the cloud chamber by a trace of radium emanation —
the radioactive gas which is the first product of the disintegra-
tion of radium. Each cloud ray is a visible record of the
conversion, by expulsion of an alpha-particle, of a single atom
of the emanation into an atom of the next member of the radio-
active series. Since the rays start in the gas, it is now possible
to get tracks which are complete from beginning to end. The
ends are distinguishable by the characteristic bend or hook.
At the beginning there is an enlarged head, where, moreover,
the cloud is of greater density ; this represents ionisation by the
recoil of the atom from which the alpha-particle has escaped.

It may be noticed there is a sudden bend in one of the rays
with which there is again associated a spur-like process.

Radioactive substances emit beta-particles as well as alpha-
particles. These produce comparatively few ions along their
tracks, which are thus much less conspicuous when converted
into visible cloud rays than those of the alpha-particles. They
are, in consequence, more difficult to photograph and they have
not appeared in any of the pictures shown thus far.

With suitable illumination, however, the droplets condensed
on the individual ions may be photographed, provided they are
not too closely packed. It is thus possible to study the path of
any ionising particle, however small the number of ions produced.

On account of the enormous velocities with which they are
emitted — closely approaching that of light— the beta-particles
are able to travel considerable distances in the air, distances
many times greater than the diameter of the cloud chamber. It
is therefore impossible to obtain a picture of the whole track of
a single beta-particle.

Here, on one plate (fig. 6) are shown the final portions of
the tracks of an alpha- and of a beta-particle. The beta-ray
shows much less intense ionisation, as indicated by the compara-
tive densities of the clouds ; and its devious path forms a great
contrast to the straightness of the alpha-ray.

The beta-particle, of course, is so much more readily diverted
from its course on account of its much smaller mass.

If, however, we catch the beta-particle at a sufficiently early
stage of its career, we find th^t its immense velocity compensates

486 SCIENCE PROGRESS

for its very small mass and its path may be sensibly straight for
distances of several centimetres, in spite of the very large number
of atoms which it must traverse. This is illustrated by the
next picture (fig. 7) in which is shown, in addition to the end of a
beta-ray, a portion of the trail left by a beta-particle while its
velocity was still very high ; it is noticeable that it is practically
straight. Another result of the high velocity is that very fev/
ions have been set free along its path ; for the faster the particle
traverses an atom the shorter is the time during which the
forces can act. The individual ions are readily distinguishable
in the photograph ; the droplets appear mainly in pairs (each
representing a positive and negative ion) but there are, in
addition, here and there, closely packed groups of twenty
or thirty.

In addition to the alpha- and beta-particles, radioactive bodies
emit an extremely penetrating type of ionising rays — the gamma-
rays — having properties similar to those of Rontgen rays. If
we expose the cloud chamber to this radiation (cutting out the
alpha- and beta-rays by a lead screen), we see on expansion
extremely fine threads of cloud crossing the vessel in all
directions. These are the tracks of beta-particles emitted
mainly from the walls of the vessel under the influence of the
gamma-rays. The whole of the ionisaation produced by
gamma-rays appears to be, as it were, secondary and due to
the beta-rays.

The remaining pictures illustrate some of the properties of
Rontgen rays.

In studying the nature of the process of the ionisation of air
by X-rays by means of the expansion apparatus, it is convenient
to use an instantaneous flash of the rays produced by sending
a single Leyden jar discharge through the Crookes tube. The
discharge is so timed that the rays pass through the cloud
chamber immediately after the expansion of the air, so that they
traverse it while it is supersaturated with water vapour. The
ions produced are thus at once fixed by the condensation of
water vapour upon them before any appreciable difl'usion has
occurred ; the illuminating spark is timed to pass a fraction of
a second later and so give an instantaneous photograph of the
clouds condensed on the ions.

Fig. 8 is a photograph showing the effect of such a flash

RADIOACTIVITY VISUALISED 487

of X-rays — the radiation being confined to a narrow cylindrical
beam by lead screens provided with apertures. The photograph
was obtained with the camera pointed horizontally through the
cloud chamber in a direction at right angles to the beam of
X-rays.

In the light of knowledge furnished by other methods, we
may interpret the picture in the following way. Under the
influence of the X-rays, an atom here and there in the path
of the cylindrical beam of X-rays has emitted a corpuscle or
beta-particle with velocity sufficient to enable it to traverse
several millimetres or even centimetres of air, ions being set
free along its path. It is the paths of these beta-particles or
cathode-rays which are made visible in the photographs. The
X-rays do not appear to produce any ionisation other than that
effected through the agency of the beta-rays excited by them, as
indeed Prof. Bragg has long maintained.

The only room for difference — apart from their mode of
origin — between the beta-rays produced by the action of X-rays
and those emitted spontaneously by the radioactive substances
lies in their initial velocity; for there is no lack of evidence
that all negatively charged corpuscles are alike, except in so
far as their properties are affected by their velocity. And in
fact, the tracks of the beta-particles or cathode-rays excited in
air by X-rays are indistinguishable from the end portions
of beta-ray tracks, such as are shown in figs. 6 and 7.

The tracks are far from straight and as the particle approaches
the end of its course the deviation becomes generally more and
more marked, the particle being more easily deflected the
smaller its velocity.

The departure from straightness is mainly of the nature of
a general curvature due to an accumulation of inappreciable
deflections at successive encounters ; sudden deviations through
large angles, the result of single encounters of a more effective
kind, also appear occasionally.

The number of ions produced per centimetre is known to
increase rapidly as the velocity of the cathode-ray particle
diminishes. This is shown by the increased density of the
clouds towards the ends of the tracks.

Fig. 9 is an enlargement of a portion of the track of a
beta-particle emitted in air exposed to X-rays. The individual
ions are clearly visible and may readily be counted ; the number

488 SCIENCE PROGRESS

per centimetre amounts to about i88 pairs, when reduced to
atmospheric pressure.

In taking the photograph shown in fig. lo the X-rays were
made to traverse the air before instead of after the expansion.
The ions liberated along the track of each cathode-ray were
thus free to move under the action of the vertical electric force
maintained in the cloud chamber, the positive travelling down-
wards, the negative upwards. Each trail w^as thus divided
into two portions, one consisting of negative, the other of
positive ions, before being converted into visible cloudlets
by expansion of the moist air; the ions of each trail have also
had time to be considerably scattered by diffusion.

The representations of X-ray clouds shown thus far have
all been from photographs taken with the camera pointed
horizontally and so placed that a magnified image was obtained.
The remaining photographs were obtained with the camera
pointed vertically downwards, the conditions being such that
the whole visible contents of a horizontal stratum of the cloud
chamber, about 2 cm. in thickness, were photographed just as
in the case of the alpha-ray pictures. Very intense illumination
is required to make the cathode-ray tracks visible in a picture
taken in this way and it is only recently that I have succeeded
in photographing them.

A thin sheet of copper was fixed in the centre of the cloud
chamber in the path of a narrow beam of X-rays, which was
made to traverse the supersaturated air of the cloud chamber
immediately after its expansion.

The absorption of X-rays by the copper is evident at a
glance (fig. 11) from the diff'erence of the density of the clouds
condensed on the incident and transmitted beams.

In passing through the copper the X-rays produce immense
numbers of cathode-rays which form dense clouds immediately
in front of and behind the copper plate. The clouds are not
quite in contact with the copper, the clear space next the plate
being due to the air becoming warmed by contact with the
copper before the passage of the rays, so that the ions fail to find
the supersaturation necessary for their growth into water drops.

From the researches of Barkla and others we know that
when exposed to X-rays the copper plate will emit secondary
rays — the homogeneous or characteristic or fluorescent rays of
copper. These will in turn c^use the air to eniit secondary

Fig. 9.

Fig. 10.

Fig. II. Fig. 12.

PLATE III.

Fig. 9. — Enlargement of portion of track of beta particle emitted in air exposed

to X-rays.
Fig. id. — Separation of positive and negative ions by an electric field in air

exposed to X-rays.
Fig. II. — X-ray beam incident or thin copper plate.
Fig, 12. — X-ray beam incident on thin copper plate, the less penetrating rays

having been intercepted before entering the cloud chamber.

488]

RADIOACTIVITY VISUALISED 489

cathode or beta-rays. The visible cloud trails left by these
are seen in the photograph (fig. 11). A photograph of this
kind shows at once the distribution of the secondary radiation
from a substance as well as the nature of the cathode-rays
produced by this radiation in the surrounding gas. The
cathode- or beta-rays produced in air by the copper-rays are
all much alike in length (about i mm.) ; this is in striking
contrast to the very varying length, ranging up to 2 or 3 cm.,
of those produced by the primary X-rays.

A photograph taken under similar circumstances with a
silver plate in place of the copper one shows similar effects,
but the cathode-rays produced in air by the silver-rays are
many times as long.

Some photographs were also taken with X-rays incident
upon the copper plate after their intensity had been reduced
by interposing a considerable thickness of aluminium. This
cuts out especially the less penetrating radiation. The individual
cathode-rays which start from the copper are now readily seen
(fig. 12); they were before too closely interlaced to be separ-
ately visible. The surprising feature of this photograph is the
great length of some of the cathode-rays emitted by both
copper and air exposed to the X-rays. Some of the tracks are
about 3 cm. in length when the air is at atmospheric pressure.

HORTICULTURAL RESEARCH
III. THE ACTION OF GRASS ON TREES

Bv SPENCER PICKERING, F.R.S.

Conspicuous among the results obtained at the Woburn Experi-
mental Fruit Farm are those relating to the effects produced by
growing grass above the roots of fruit trees. From the economic
point of view the question is naturally one of considerable
importance to the fruit grower but it presents a still more
important aspect in its bearing on the fundamental problems
of soil-fertility and the effect which one crop has on another.
The mere fact that if grass be grown above the roots of fruit
trees it has a deleterious effect seems to have been acknowledged
previously by some growers, though it was denied, indeed,
is still denied, by others. The chief reason for this divergence
of opinion lies, no doubt, in the fact that the effect produced by
grass varies greatly according to the nature of the soil and,
in some few cases, may even be negligible : in practice also the
grassing of land under fruit is generally carried out gradually,
a form of treatment which materially reduces the evil effects ;
moreover, grassing is hardly ever practised in such a way that
the grower has an opportunity of estimating by compara-
tive trials what the effect has really been.

In the case of many soils, when the grassing is done so as to
secure the maximum effect — for instance, when young trees are
planted either in land already grassed or in land which is laid
down to grass at once after the planting— the effect is practi-
cally always a fatal one. Fig. i shows two rows of standard
apple trees which were strictly similar at the time of planting ;
the one was grown in ground which was kept tilled, the other
in ground which was sown with grass after the trees were
planted and kept under grass. As will be seen, the result of
this difference in treatment has been to arrest practically all
growth. Another illustration is given in fig. 2 of similar dwarf
apple trees treated in the same way; the photographs in this

case were taken six years after the trees had been planted. The

490

S
o

-a

HORTICULTURAL RESEARCH 491

magnitude of the effect varies somewhat according to the variety
of apple dealt with but in all cases it is very great ; the effect is
equally or nearly as great in the case of pears, plums or
cherries and even in the case of forest trees, half a dozen kinds
of which have been investigated. Certain minor modifications
in the effect are noticed in some cases but it is not necessary to
specify these at present.

Unless the grass be allowed to act during so long a period
that the tree becomes permanently stunted, the tree will recover
its vigour as soon as the ground is cleaned ; in the same way, a
limited recovery begins at once when any of the roots pass
outside the grassed area. On the other hand, the grass-effect is
noticeable when even a very small proportion of the roots are
in grassed ground ; for instance, when only three or four ounces
of the roots of trees weighing 2 cwt. are under the grass.

It cannot be stated with certainty how far it is necessary to
clear the grass away from around the roots of trees so that
these may not be affected ; indeed, this must evidently depend
on the size and nature of the trees. In the case of freshly
planted young trees, a clear space three or four feet in
diameter may be advocated, though some benefit has been
noticed when the cleared circle was enlarged to six feet in
diameter ; on the other hand, benefit has been noticed even
when the grass was cleared away over a space extending only
six inches away from the stems.

The grass seed usually sown in the experiments was a
mixture supposed to be suitable for orchards in the particular
soil in which the trials were made ; but eighteen different sorts
of grass have been investigated separately in experiments made
with trees grown in pots and all have been found to have a
similar effect, though generally the effect has been more marked
in the case of the stronger growing grasses. Clover too has as
great a stunting effect as grass, the only difference being that
the foliage of the trees is not of the light, unhealthy colour
characteristic of trees grown under grass ; this difference,
doubtless, is due to the extra nitrogen supplied through the
agency of the nodules on the clover roots.

It was at first considered probable that the excessively
deleterious action of grass was due to its having been sown
around trees which had been freshly transplanted and, therefore,
were not established in the soil. But this was found not to be

492 SCIENCE PROGRESS

the case. A number of apple trees in a flourishing condition
which had been in the ground four years were selected and half
of them were grassed over ; the effect produced may be described
as instantaneous, for the grassed trees at once ceased to produce
any fresh growth and after two or three years the trees of one
of the varieties dealt with were all killed. A similar experiment
was subsequently made with a mixed plantation {i.e. one con-
sisting of standard and dwarf apple, pear and plum trees) which
had been established twelve years. The plantation was first
divided into halves, so that each half contained a similar col-
lection of trees ; on measurement the trees in these two sections
were found to be of equal vigour. One section was then laid
down to grass. The effect of this treatment was apparent
almost at once; and in three or four years the disturbance was
so serious that, in the case of some of the varieties, the trees
were actually killed ; others remained apparently unaffected
for some time but are now falling considerably behind those
in the tilled section.

The only case in which, in our particular soil, the action ot
grass seems to be modified is when the grass is allowed to
establish itself gradually during the course of several years.
The trees under such circumstances appear to adapt themselves
to the altering conditions, though even then they do not flourish
like those in tilled ground.

Many of the experiments on grassing trees have been made
also in the Harpenden soil ; though the effect produced there
is considerably less marked than at the Woburn Fruit Farm, it
is still very conspicuous and in some cases the grassing has been
fatal. In other localities, the effect of grass may be still less
marked but instances of its deleterious action may be observed
all over the country and in every class of soil. Only in one
instance which has come under our immediate observation has
there been no evident action and there seems to be no obvious
reason for this failure : it is certainly not because the tree-roots
have stretched down beyond the grass-roots, for both sets of
roots seem to be intermingled not far below the surface.

The visible effect of grass is not confined to the arrest
of growth ; it is also manifest in the altered colour of the leaves,
of the bark and of the fruit. The leaves are much paler than
those of healthy trees and assume their autumn tints quite
a fortnight before the normal time. The bark also is pale and

HORTICULTURAL RESEARCH 493

unhealthy in colour, whilst the fruit is evidently lacking in
green colouring matter, being either of a waxy yellow tint or
showing a strong red coloration. This latter may be an
advantage for market purposes and if the action of the grass
could be restricted, so as merely to affect the colour of the fruit
without seriously stunting the tree, it would be beneficial.
This can be done in some cases by having the grass over only
a small portion of the roots but the behaviour of different
varieties of trees and even of different individuals of the same
variety, differs too much to render such a method of culture
practicable.

The Water Supply

Naturally, the first explanation suggested was that the grass
abstracted from the soil the moisture and other food materials
required by the tree. Numerous experiments, however,
negatived such an explanation. That grass promotes evapora-
tion, rendering the soil drier than if the surface be kept tilled,
is well known ; but it was found that this drying effect did not
become appreciable until somewhat late in the year, whereas
the effect of grass on the trees is manifest even in the early
spring : moreover, in one season throughout which determina-
tions were made, the drying effect of the grass was never
so great that the amount of water in the soil was reduced below
the optimum amount for vegetation ; and yet the trees were
suffering severely. There is also the general consideration that
the grass effect is manifest in wet as much as in dry seasons
and that trees in tilled ground, even in the driest seasons,
do not show the same symptoms as trees suffering from grass.
It may further be added that in the original grassed plots at the
Fruit Farm, the soil contains actually more moisture than is
found in the neighbouring tilled plots : what the explanation of
this difference may be is not evident ; but it is clear that the
behaviour of the trees in these particular grass plots cannot be
due to a diminished water supply.

Further evidence of this fact was obtained by supplying trees
in grassed plots with additional moisture through pipes reaching
down to their roots ; it was thus ascertained that the effect of
the grass was not overcome even when the soil was kept so that
there was more moisture in it than in the neighbouring tilled
plots. Similar results have been obtained in other experiments

494 SCIENCE PROGRESS

in which trees were grown in pots, the condition of moistui*e

being so regulated that it was the same whether or no grass

was present.

The Food Supply

Similar experiments in pots supplied the most conclusive
evidence that the grass-effect is not explicable as a consequence
of the lack of the recognised food material of plants any more
than it is by lack of water. In some of these experiments the
grass-roots were effectually prevented from coming into contact
with the tree-roots by placing a layer of fine gauze about four
inches below the surface and adding all the water and food from
below, so that the tree obtained all that it wanted before any
reached the grass. In spite of this and in spite of the supply of
food being liberal, the tree suffered nearly as much from the
grass as when grown in the ordinary way without gauze, the
food being supplied from above.

General considerations are equally conclusive that the grass
effect is not due to lack of nourishment in the soil : thus the
grassed plots receive the same annual dressings of manure as do
the other plots and the grass, when cut, is not removed but
allowed to rot into the soil again, so that in the case of our original
grassed plots nothing will have been removed from the soil
during the last eighteen years other than the food material con-
tained in the one grass crop at present on the ground together
with the small amount of material removed by the feeble growth
of the trees ; whereas from the neighbouring tilled plot the
material removed has been that contained in the annual crop of
fruit and in the wood formed by the vigorously growing trees.
The grassed plot must evidently be richer in food than the tilled
plot : not only do analyses of the soil show that this is so but
when samples of soil are taken from these two plots and trees
are grown in them under similar conditions, it has been found
that those in the soil from the grassed plot flourished more than
twice as well as those in the soil from the tilled plot.

That the behaviour of the trees under grass is due to some
form of starvation cannot be doubted — the colour of the leaf is
itself proof of nitrogen starvation ; but it is starvation in a land
of plenty — due to the tree not being able to utilise the food which
is there, not to any deficiency in the supply of that food.

It has been suggested several times that if the grass were fed
off by sheep, as is the practice in the Kentish orchards, instead

HORTICULTURAL RESEARCH 495

of being cut, it would be found that it had no deleterious effect
on the trees. This was put to the test by making several small
plantations of standard apple trees in a portion of the farm which
had been laid down to grass several years before and penning
sheep on one of them. But during the two years throughout
which this experiment lasted, the trees thus treated suffered to
exactly the same extent as their neighbours in grassed land
where no sheep were kept. A similar experiment is now in
progress with fowls instead of sheep; the results during the
first season have been equally negative, except, perhaps, that the
foliage of the trees where fowls, are is somewhat darker. There
is one notable exception in the plantation, one of the trees show-
ing recovered growth : but in the case of this tree the grass
covering the roots has been practically eradicated by the fowls ;
an exception which may strictly be said to prove the rule.

Other Suggested Explanations

Other possible explanations have been sought in the direction
of alterations produced by the grass in the physical condition of
the soil, of alterations in aeration or the accumulation of carbon
dioxide, of alterations in the temperature or alkalinity and also
of alterations in bacterial contents. But without success.

Mechanical analysis of grassed and tilled soil failed to reveal
any alteration in the distribution of the finer particles by the
grass such as might give rise to the clogging of the roots by
accumulating at the root level; indeed, what alteration there was
has been in the opposite direction. The grassed soil also did not
appear to be alkaline and when soil was made alkaline artificially,
even strongly so, it did not affect the trees in the same way as
the grass did ; nor in the particular soil examined did it have
much effect on the distribution of the finer particles.

That absence of aeration cannot be assigned as the cause
seems to be fairly established by experiments described in a
former article with trees having their roots enclosed by an iron
drum with a layer of cement on the top ; this boxing up of the
tree was found to produce no effect comparable with that of
grass. It was also found in this experiment that the air below
the cement covering contained 50 per cent, more carbon dioxide
than air drawn from below the surface of tilled ground and more
than double the percentage of that in air drawn from grassed
32

496 SCIENCE PROGRESS

ground, so that it is evident that the grass-effect cannot be
explained by the presence of any excess of that gas in the soil.
Moreover, trees grow^n in soil into which a current of carbon
dioxide was led showed no alteration in behaviour.

The temperature of the soil under grass is on the average
somewhat lower than that of tilled ground : though during the
night it is slightly higher, in the daytime, under favourable
circumstances, it may be as much as io° F. lower. But the average
day excess during the summer would be only about 3° and as
this is less than differences observed in comparing one season
with another, it is clear that it will not account for the action ol
the grass ; added to which the grass-effect is equally apparent in
the case of plants grown in pots in a greenhouse where the
temperature of the soil in the various pots would be practically
identical.

The possibilities of the influence of bacteria on the results
have not yet been fully investigated but it is clear that the mere
number of these cannot be accepted as an explanation of the
grass-effect. The growth of grass is found generally to increase
the number of bacteria in the soil : in certain experiments, for
instance, the increase was from 2-3 to 9 million per gramme; but
we may still have as great an effect of grass on the tree as
occurred in this instance, when the bacterial contents is as low
as 2-5 million, this being the case when the tree and grass are
grown in sand instead of in earth.

The Question of Toxicity

A review of the whole of the facts relating to the effect of
grass on trees can leave very little doubt that the action is due
to some toxic effect, at any rate when this term is used in a wide
sense. The tree is not deprived by the grass of the food or
water necessary for its welfare ; these may be present in abun-
dance but it is incapable of utilising them : this is characteristic
of a toxic action. Long before all the evidence here alluded to
was obtained, such a conclusion was the one arrived at and to
those who have had trees suffering from grass constantly before
them, during many years, it would be difficult to arrive at any
other. A toxic action, however, does not necessarily mean that
the grass-roots excrete some substance which is poisonous to the
tree : there is a considerable amount of debris from the roots ol
grass while it is growing, which on decomposition might form

HORTICULTURAL RESEARCH 497

substances poisonous to the tree-roots ; or the poisonous effect
might be due to an alteration in the bacterial contents of the soil.

Independently of anything coming from the grass-roots or
resulting from their growth, it seemed possible that the grass
might abstract something from the soil and alter the proportions
of the constituents remaining so as to render the soil virtually
toxic. This suggestion, however, has been negatived by some
recent experiments in which the grass was grown in such a way
that it was impossible for it to draw anything out of the soil in
which the trees were growing. These trees were planted in
pots and the grass was grown in movable trays resting on the
soil in the pots ; the trays were perforated to allow of drainage
from them down to the trees but the holes were covered with
fine gauze to prevent the grass-roots from passing through and
thus there could be no passage of water upwards from the pots
to the trays. Yet in spite of this entire separation of the grass
from the tree, the grass-effect was still very noticeable and
caused a reduction of growth amounting to some 25 per cent.
These experiments have since been extended to a study of the
effect of grass on other plants besides trees and in every case
examined up to the present, a similar action has been observed :
in the case of barley the reduction of growth amounted to 15 per
cent. ; in that of tomatoes to 46 per cent. ; in that of mustard to
58 per cent, and in the case of tobacco to 71 per cent. Some of
the results in the last two cases are shown in fig. 3. One other
important point in connexion with these experiments should be
mentioned, that when the grass is grown in trays as in the
preceding experiments and the washings, instead of being allowed
to pass immediately to the tree-roots, are left for some time
exposed to the air before being used on the tree, their action,
instead of being hurtful, is decidedly beneficial ; apparently the
toxic substance is oxidised and converted into plant-food.

The proposition which has been made to account for these
facts— it cannot at present be termed more than a proposition —
is that the growth of grass and probably also of other crops,
gives rise, either directly or indirectly, to the formation of some
substance in the soil which is toxic towards plant-growth
but which, on oxidation, becomes harmless and when oxidised
serves to render the soil richer, probably both in organic matter
and nitrogen. While the grass is actually growing, there would
be a continuous supply of this toxin, which would prevent the

498 SCIENCE PROGRESS

plants from benefiting from the increased richness of the soil ;
but as soon as the grass were removed, the production of toxin
would cease and the previously grassed soil would be found to
be more fertile than soil which had never had grass growing in
it. This is in accordance with the behaviour of trees in soil from
grassed and tilled land, as mentioned above ; the accumulation
of nitrogen in grassed land is a fact which has been known now
for many years. It is probable, however, that no soil would
ever be quite free from the toxic substance, if such exist, which
is produced by the growth of grass.

The difficulty of examining the action of an easily oxidisable
substance by means of growing plants in soil containing it is
very great, because even the quickest growing plant takes a
considerable time to develop ; the question has been attacked,
therefore, by using the germination of seeds as a means of
investigation. It does not follow, of course, that a substance
which is toxic towards the germination of seeds is toxic also
tow^ards plant-growth but the results indicate that this is probably
so in the present case.

When soil is heated, the amount of soluble organic matter
and soluble nitrogenous matter is increased ; at the same time,
it becomes toxic, as shown by its effect on the germination of seeds.
The extent of this toxicity depends on the temperature ; different
seeds are affected to different extents and the results naturally are
also influenced by the nature of the soil dealt with. On heating
the soil to 150° C, the soluble organic matter is sometimes
increased over tenfold and the time which some seeds take to
germinate in the soil increased five or sixfold. When the soil is
heated to a lower temperature, the soluble matter and also the
toxic effect on seeds rapidly diminishes but the latter is recog-
nisable in soil heated to as low a temperature as 60° ; from the
general form of the curve obtained on plotting the various
results, it is probable that some such action exists (though it
may not'be measurable) in soil which has been heated only by the
sun, that is, to a temperature of about 30°, so that even so-called
unheated soil probably contains some of this toxic substance.
This conclusion is further supported by the fact that various ^
soils behave differently towards germinating seeds and that in j
nearly every case the seeds do not germinate so readily in soil
as they do in pure silica moistened with water.

It was ascertained that the treatment of soils with antiseptics,

HORTICULTURAL RESEARCH 499

such as carbon disulphide, chloroform, ether or benzene, produced
the same results as heating to a moderate temperature, the amount
of soluble matter in it being increased and the soil thereby
rendered slightly toxic to seeds. Such treatment was equivalent
in its effect to that produced by heating the soil to about 70° ;
and it was impossible to attribute this to any indirect action of
the antiseptic, through its modifying the bacterial growth in the
soil, for it was possible to complete the whole operation of treat-
ing the soil with the antiseptic, allowing this to evaporate and
obtaining an aqueous extract of the soil, within a period of from
20 to 60 minutes, during which time very little bacterial growth
could have occurred ; yet in this case the soluble organic matter
in the soil was found to have been increased by 61 per cent.
Moreover, after a soil has been treated with an antiseptic the
soluble matter in it decreases with the lapse of time : after
18 hours the original excess of 61 per cent, was reduced to about
35 per cent, and after five weeks to 16 per cent. : so that the
presence of the excess of soluble matter cannot be explained by
assuming it to be the product of the growth of bacteria : it is
evidently a direct product of the chemical action of the antiseptic
and it is, evidently also, a very unstable product.

The conditions under which the toxic substance in heated
soils is decomposed was then investigated. It was found that
when the soil was kept excluded from air, even in a thoroughly
wet condition, it remained unaltered, giving, after several months,
the original values for the soluble matter present and for
its toxic action towards germinating seeds. But if freely
exposed to air and kept moistened, the amount of soluble matter
rapidly decreased and at the same time it lost (in three months)
its toxic properties nearly entirely. A similar but much
slower change occurred when the soil was kept in a fairly
dry condition.

It is clear, therefore, that the toxic substance is of an easily
oxidisable nature and that it would soon be destroyed in any
ordinary cultural experiments, in which free exposure to air and
repeated watering have to be adopted. From the results obtained
with antiseptics, it further appears that the oxidation must
be very rapid at first, being considerably reduced even in a few
hours, though some of the toxin may persist, as shown by
the results with heated soil, after several months' exposure.
In spite, however, of the toxic effect having nearly disappeared

500 SCIENCE PROGRESS

at the end of this time, the soluble organic matter was still more
than double what it was in the unheated soil and this excess of
soluble matter, which is no longer toxic or is barely so, must
represent the presence of so much extra plant-food ; it is not
surprising, therefore, to find that plants flourish much better
after a time in soil which has been heated than in ordinary soil.

The occurrence of such changes in soil which has been
heated renders the investigation of its behaviour towards plant-
growth very difficult ; it is possible that the action of the
toxic substance present (if it be toxic towards plant-growth
as well as towards seed-germination) may be masked, by its
becoming decomposed before the plant can be grown ; the only
results which will follow from its presence will be an increase of
growth owing to the excess of soluble organic matter left in the
soil by its decomposition.

These two opposing factors are, as a matter of fact, recognis-
able in the results obtained when plants are grown in soil
which has been heated ; whether the one or the other pre-
dominate depends on the sensitiveness of the plant to the
action of the toxin and on the amount of the latter present.

Fig. 4 shows tomato and tobacco plants grown in soil heated
to 30° (so-called unheated soil), 60°, 80", 100°, 125° and 150°. The
presence of some toxic substance after heating to the higher
temperatures is placed beyond dispute by the dwarfed condition
of the plants in these cases, tobacco being evidently more
sensitive to this effect than the tomato. Photographs taken
at an earlier date show a much more marked effect than those
given here, whilst others taken later show less effect ; eventually,
before growth was completed, the toxic effect had almost
entirely disappeared and the beneficial effects of the products of
its oxidation had so far asserted themselves that the plants,
even in the most highly heated soils, had outstripped those
in the unheated soil.^ When the soil is heated to temperatures
of 100° or lower, owing to the smaller quantity of toxin present,
the effect persists during a still shorter period and even in the
early stages we get a stronger growth than in the unheated soil.

The disappearance of the toxic effect in the most highly

heated soils was further illustrated by growing a second crop of

these same plants in the samples of soil used for the first crops.

The results are shown in fig. 5. As will be seen, it is only in the

^ See Journal of Agricultural Science^ iii. 280.

Fig. 4. — Tobacco and tomatoes grown in soil heated to different temperatures.

First crop.

{From Journal of Agricultural Science.)

500]

IiG. 5.— Tobacco and tomatoes grown in soil heated to different temperatures.

Second crop.

(From Journal of Agricultural Science.)

fSot

HORTICULTURAL RESEARCH 501

case of tobacco that any indications of toxic action are still
visible and then only in the most highly heated soil.

Though the general results with all the plants examined
were similar to those here described, it was noticeable that the
toxic action was much less potent in the case of grasses than in
that of the other plants (tomatoes, tobacco and spinach), the
beneficial after-effect coming into evidence earlier and to a
greater extent.

These results fully justify the conclusion that the oxidisable
substance in heated soils which is toxic towards seeds, hindering
their germination, is toxic also towards plant-growth.

The experiments were further extended so as to establish
the identity of the action on trees with that on the other crops
mentioned : in the case of trees, if the trees are grown in the
ordinary way, the soil being fully exposed to air, owing to the
extended time required for growth nothing is observed but the
beneficial effects of the heating : but when the experiment is so
modified as to limit the access of air considerably, the toxic effect
is even observable. Small trees were grown in soil contained
in bottles the necks of which were closed, except for two open-
ings into which tubes plugged with cotton wool were inserted ;
the results of a series of experiments made in this way showed a
small increase of vigour of growth, not exceeding 10 per cent., in
the case of soils heated to temperatures up to 100* but a decrease,
up to 35 per cent., in the case of soils heated to 125° and 150°.

The connexion between the toxic action of heated soil and
the toxic action of grass on trees and other plants cannot
be said to have been established yet but there are one or two
facts which point to a possible identity. The soil which is toxic
while the grass is growing in it does not behave normally
as soon as the grass is removed ; but after it has been exposed
to the air, just like heated soils, it is more favourable to plant
growth than ungrassed soil and contains a larger amount of
soluble organic and nitrogenous matter. Another somewhat
remarkable point of similarity has been noticed : soils which
have been heated contain some oily or resinous substance which
renders them more difficult to wet than unheated soil. This
peculiarity becomes more marked as the temperature of heating
is higher ; different soils vary considerably in this, respect. The
peculiarity was so marked in one case that the soil could not be
thoroughly wetted after it bad been heated, even when left

502 SCIENCE PROGRESS

in contact with water during ten days. This oiliness is notice-
able, in many cases, in grassed soil, though to a less extent than
in heated soils: of fourteen pairs of different samples of soil,
one being taken from under grass and the other from tilled
ground immediately adjoining, eight showed that the grassed
soil was less readily whetted than the tilled soil.

The attempts made to discover a toxic action affecting the
germination of seeds in soil from grassed land have been un-
successful ; they showed that there was a small, though undoubted,
difference between the action of such soil and of soil from tilled
ground but in the opposite direction, the grassed soil being the
more favourable. In view of the readiness with which a small
proportion of the toxin will oxidise and produce favourable
results, this is not inconsistent with some toxin having been
present when the samples were taken ; but it cannot be used as
an argument that such was the case. The fact, however, that
there is some difference in action, whatever the direction
may be, is more favourable to such a view than if there were
no difference.

The increase of fertility produced by heating soil and by
treating it with antiseptics, has recently been put to practical
use in the case of soil used in greenhouses and hothouses and
an explanation of the result, differing from that detailed above,
has been given. According to the work of Russell and Hutchin-
son, when soil is heated to 50° or is treated with antiseptics, the
greater number of the bacteria present and all the protozoa
which feed on bacteria are killed, the result being that the
surviving bacteria are able to multiply without check and soon
outnumber those present in unheated soil and by this action a
corresponding increase in the supply of nitrogen available for
plant growth is brought about.

Without in any way controverting the evidence on which
this view rests, it seems impossible to accept it as the only
or even the principal explanation of the behaviour of plants
in heated soil. According to it, a maximum of fertility should be
observed in the case of soil heated to 50°, corresponding with the
temperature at which all the protozoa are killed and the injury
to the bacteria is incomplete : as the temperature of heating
is raised, the fertility should decrease or at any rate should take
longer to make its appearance, as a larger number of the
bacteria would have been killed ; and in the case of soils heated to

HORTICULTURAL RESEARCH

503

125° or above, in which all of them would have been killed, the
soil should be much less fertile than even unheated soils or any
increase in fertility which it exhibited would be of a very
irregular character, depending on chance reinoculation with
bacteria.

The results of growing plants in soils heated to different
temperatures do not tally with these requirements. Those
already alluded to are set out in fig. 6, the curve a b representing
those with tobacco, tomatoes and spinach, the curve a c repre-
senting those with three grasses. This latter has been some-
what smoothed, as the values were not very regular. Neither
of these curves shows a maximum at 50° : a b does show a

300

/-^

j^^ "^ "" "

100 — ^ —

so 100

Fig. 6.

ISO

maximum but this occurs at 100° and ac shows no maximum
at all. Moreover, neither curve shows any marked irregularity
from 125° to 150° or any tendency to give lower values than that
for the unheated soil : the results, in fact, seem to show that the
circumstances conditioning them are continuous from the lowest
to the highest temperature.

On the other hand these results are quite in harmony with
the chemical explanation given above of the effect of heating
soil— the formation of a toxic substance which becomes
oxidised to form a plant-food, different plants being sensitive
in different degrees to the toxic action. It is question-
able, however, whether the actual quantity of plant-food thus
Hberated by heating to the lower temperatures, up to, say, 100°,
is sufficient to explain the extra vigour of plants grown in such
soil; in such cases, no doubt, the bacterial explanation of
mcreased fertility becomes important. Both explanations are
probably correct but neither alone affords a full explanation
of the facts.

THE EXACT DETERMINATION OF ATOMIC
WEIGHTS BY PHYSICAL METHODS

By H. F. V. LITTLE, A.R.C.S., B.Sc.

The atomic weights of the elements are usually arrived at by
measuring their combining weights as precisely as refined
methods of chemical analysis or synthesis will allow and then
selecting those multiples which most nearly approach the
approximate atomic weights deduced with the aid of Avogadro's
theorem. This may be called the chemical method.

There is, however, an alternative method of arriving at exact
atomic weights, namely, to develop processes for the accurate
determination of molecular weights. This may be called
the physical method. The method has been developed during
the last twenty years ; the present article is devoted to the
consideration of the results that have been obtained.

With few exceptions, the only substances of which the
densities have been determined with a high degree of accuracy
are those which exist as gases at ordinary temperatures and
pressures ; these alone will be considered in the present article.
From the work of Rayleigh, Leduc, Morley, Gray and Guye
and his collaborators, it may be concluded that the methods of
preparing gases have been rendered so efficient and Regnault's
method of determining the densities of gases has been so
improved, that the densities of the commoner gases are now
known with an error not exceeding i part in 10,000. In
deducing molecular weights from these results, it is not
sufficient to assume the truth of Avogadro's hypothesis in its
primitive form ; the fact that Boyle's Law does not accurately
express the isothermal relationship between pressure and
volume in the case of any known gas and that the coefficients
ol expansion of gases are not exactly alike is proof that even
if, at some particular temperature and pressure, the relative
densities of gases were accurately proportional to their mole-
cular weights, at any other temperature and pressure this

504

DETERMINATION OF ATOMIC WEIGHTS 505

relationship would cease to be true. As a matter of fact, the
gramme-molecular volumes of gases, measured at the same
temperature and pressure, are only nearly very equal. It is
necessary to know the relative values of these magnitudes to
within at least i part in 10,000 if the results of density
measurements are to be utilised with advantage in the determina-
tion of molecular weights.

The problem may be stated algebraically in the following
manner. Let the weight of a normal litre of a gas — i.e. the weight
of the gas which occupies a volume of one litre at 0° C. and
under a pressure of 760 mm. of mercury at sea-level in lat. 45° —
be L grammes. If the gramme-molecular volume, at normal
temperature and pressure, of a perfect gas be R litres, then the
molecular weight M of the gas in question is not equal to RL
but is given by the equation

where X is a small fraction to be determined. For each gas,
there is a definite value of X ; and it is necessary to determine
the value of (i + X) with an accuracy of i in 10,000. Of the
various methods that have been proposed for the determination
of \ the three best known are (i) D. Berthelot's Limiting Density
Method^ (ii) P. Guye's Reduction of Critical Constants Method and
(iii) A. Leduc's Molecular Volume Method.

The Limiting Density Method

Boyle's Law does not accurately express the behaviour of
any known gas at ordinary temperatures and under pressures
of one or two atmospheres. If Vb denote the volume, under
the pressure pb, of a definite mass of a gas and Va its volume at
the same temperature as before and under another pressure pa,
we may write

i-2^ = aPV-pO (2)

The coefficient Ap^ is a measure of the average error per
atmosphere, over the range pa to pb, that is incurred by
assuming the validity of Boyle's Law for the gas (it is under-

5o6 SCIENCE PROGRESS

stood that pressures are expressed in atmospheres). Referring
to Fig. I (p. 509), it will be seen that

. Pb i_ p V - pbVb i_ EB

Pa ~ PaVa Pb - Pa ~ PaV* EC

Since the product pv is approximately constant, it therefore
follows that the coefficient Ap^ is (very nearly) proportional
to the slope of the chord BC of the curve ABCD joining the
joints B (pa, PaVa) and C (pb, PbVb).

In accordance with this definition of A^^ we have

pa'

A!=i -

PiV,

PoVo

It has been assumed by Rayleigh and Berthelot (3) that,
under extremely small pressures, Avogadro's hypothesis loses
its approximate character ; in other words, it is supposed that
at a definite temperature and under a common, indefinitely
small pressure, the molecular volumes of all gases are equal,
an assumption which forms the basis of the method of limiting
densities. The calculation of exact molecular weights by this
process was given by D. Berthelot (3) in 1898 in the following
manner :

Let the common molecular volume of two gases be Vo under
an indefinitely small pressure po and at the same temperature
T. When the pressure is increased to the finite value p, the
molecular volumes v and v' of the gases cease to be equal.
Applying equation 2 (p. 505), we have

v' = v,.&[i-A'P(p-p)]
The ratio of the molecular volumes is given by

^'"i-A'P^(p-Po)''i-p.A'P

since po is indefinitely small.

The molecular volumes of the gases at the temperature T
and under the pressure p are therefore proportional to

I - pA^ and i - pA'P

DETERMINATION OF ATOMIC WEIGHTS 507

Let the densities of the gases be L and U respectively at the
same temperature and pressure T and p. Then the molecular
weights M and M' are proportional to

(i - pAP)l and (i - pA'P)l'

A simplification may be effected in these expressions if we recall
the fact that the densities are always measured at 0° C. and
reduced to the values under normal pressure. By taking L
and U to represent the weights of the normal litre (p. 505) and
measuring pressures in atmospheres, the previous expressions
are reduced to

(i -A;)L and(i-A':)L'

Hence, if the weights of the normal litre of gases are
L, U, L" . . . , their molecular weights M, M', M'' ... are
related to these magnitudes by the equations

(i-a;)l-(i-a':)l'-(i-a":)l"- •• ^^^

in which Ao, A'o, A'Z . . . represent mean compressibility co-
efficients between zero and atmospheric pressures defined by
equation (2) on p. 505 and measured at 0° C.

Each of the fractions expressed in (3) above is equal to R,
the gramme-molecular volume of a perfect gas at normal tem-
perature and pressure. This is seen if it be assumed for the
moment that Ao is zero, in which case equation (3) gives

M/L = R or M = LR

for the supposed perfect gas of molecular weight M. Hence the
equalities (3) may be written

M = RL(i - A^), M' = RL'(i - A'^) (4)

It follows, then, from the preceding calculations, that it is
possible, from measurements of the weights of the normal litre
of gases and observations of their compressibilities at o^C, to
deduce their molecular weights and also the gramme-molecular
volume of a perfect gas.

Densities. — The densities actually required for the calculation
are densities referred to oxygen. Table I. gives these values at
N. T. P. and also the weights of the normal litre L (see p. 505)
and the critical data that will be required later on.

A few remarks upon these figures are necessary. A number

508

SCIENCE PROGRESS
Table I

Gas.

L02

Tc abs.

Pe atm.

Hydrogen

0-08986

0-06288

32-

19-4

Nitrogen .

1-25059

0-87515

128°

33*6

Carbon monoxide

125032

0-87496

I33'5°

35*5

Oxygen .

1*42900

I 00000

154*2°

50-8

Nitric oxide

1-34020

093786

I79"5°

71-2

Methane .

0-71680

0-50161

191-2°

54*9

Carbon dioxide

1-97678

1*38333

304*3°

72-9

Sulphur „

2-9266

2-0480

430-2°

77*95

Nitrous oxide .

1-97791

1*38412

311-8°

77*8

Hydrogen chloride

1-63915

1*14706

324-8°

83*6

Ammonia .

0-77082

053941

405*3°

109-6

Phosphine

1*5293

1-0702

324'3°

64*5

Ethane

1*3562

0-94906

308°

45-2

Hydrogen sulphide

1-5392

1-0771

373"

88-7

Methyl chloride

2*3045

I-6127

416*3°

65*85

„ oxide .

2-1096

1*4763

400-1°

of observers have determined directly densities with reference
to oxygen. The results are set out below, together with the
mean values that have been adopted here :

N2O

CO,

Rayleigh
Morley .
Guye
Gray
Leduc .

0-062892

0*062866

0-87517

0-87519
0*87508

0*87497
0-87495

0*93789
0-93782

1*38396
1*38397
1-38442

1*38336

i'38339
1*38324

Mean .

0-062879

087515

0*87496

0*93786

1*38412

1*38333

Rayleigh's figure for hydrogen has been omitted, as that
observer has recognised that it is too high, whilst Morley's
value of the density of oxygen has been used in calculating
Guye's results, since the value obtained for oxygen in Guye's
laboratory was recognised to be unsatisfactory. The mean
values have been converted into absolute densities by adopting
Morley's value of the absolute density of oxygen. As regards
the other figures in Table I., the value of L for ammonia is
the mean of those due to Guye and Pintza and Perman and
Davies and that for hydrogen chloride is the result obtained
by Gray and Burt ; the remaining values are those obtained in
Guye's laboratory (14, 16, 17, 19, 23, 24).

DETERMINATION OF ATOMIC WEIGHTS 509

Compressibilities. — The determination of the values of Ao, A'i . . .
is a problem that at the present time cannot be regarded as
solved in a perfectly satisfactory manner, except in the case of

a few gases. From the definition of AE^ given in equation
(2), it is clear that the value of A^ cannot be obtained directly
from compressibility measurements but must involve an extra-
polation from the lower pressure to zero pressure. The
uncertainty attaching to this process will be diminished in
proportion as the lowest pressure at which experimental
observations are made approaches zero ; but a limit is set to
the extent to which pa may be diminished by the fact that

since the absolute error in measuring a pressure is inversely
proportional to the magnitude of the latter, it eventually becomes
so great that experiments at lower pressures are worthless
owing to experimental errors.

The most direct and satisfactory method of determining AJ
is to realise experimentally the 0° C. isothermal of the gas for
pressures starting at one atmosphere and diminishing as far
as is consistent with trustworthy results. The results should
be expressed by stating the product pv as a function of the
pressure p and extrapolated to zero pressure for the value of
PoVo. The simplest plan is to extrapolate graphically.

Unfortunately, accurate data of this character are limited to
the cases of oxygen and hydrogen chloride, for which gases
the admirable experiments of Gray and Burt (20) are available.

510

SCIENCE PROGRESS

These observers determined the values of the product pv for
these gases from pb = 830 mm. to pa = 158 mm. Since it will
frequently be necessary in what follows to refer to diagrams in
which pv is plotted (as ordinate) against p (as abscissa), they
may be conveniently called compressibility diagrams. Gray
and Burt found that in the case of oxygen the compressibility
graph was a straight line whilst in that of hydrogen chloride a
slight but decided curvature was evident, the curve being con-
cave to the axes of co-ordinates as indicated in figs, i and 2.
The results for oxygen bear out what had been previously

2-Oahn.

known since the researches of Regnault on the subject, that
in the case of the difficultly liquefiable gases, pv may, with
sufficient accuracy, be regarded as a linear function of p for
pressures up to three or four atmospheres. Hence it is quite
simple to extrapolate to p = o for these gases. Algebraically, we
may say that AJ is a constant for values of p up to three or four;
and since in the case of these gases the numerical values of this
coefficient are very small and

A^ . A* • A^ • • ^ • — • ^

PoVo P.5V.5 PxVx

we may regard either Ao-5 or Al as being practically identical
with A'

DETERMINATION OF ATOMIC WEIGHTS 511

The various results that have been obtained for the difficultly
liquefiable gases are contained in the accompanying table :

Table II

Values of A

X 10*

Observer

CH4

Leduc and Sacerdote (2, 21)

- 61

+ 38

+ 53

+ 76

-f 106

+ 175

Rayleigh (12)

A0.5

—

Chappuis (7) . . .

—

Jacquerod and Scheuer (15)

Aoj

—

117

-—

Berthelot (13)

—

Gray and Burt (20)

—

~"~

Table III

N, CO

CH,

-56

+ 44 +60

+ 96

+ 114

+ 175

These values refer to the compressibilities at 0° C. ; it is
necessary to point out that Rayleigh's measurements and also
those of Leduc and Sacerdote were carried out at room tem-
peratures and hence their values had to be reduced to those
at 0° C. from theoretical considerations ; also that Berthelot has
merely stated his results without giving any details whatever.

In the calculations which follow, the following values will be
adopted :

Ao X lo^ at 0° C. .

To these may be added Gray and Burt's value for hydrogen
chloride deduced by graphically extrapolating the compressibility
curve from p = 180 mm. to p = o :

A^ at 0° C. for HCl = 743 x lo'^

The data for other gases are not very trustworthy and will
be considered later (p. 512).

Molecular Weights. — The foregoing data may now be used
in calculating molecular weights, for which purpose the equation
(P- 507)

M' L' ' I - A'o
is utilised. It is only necessary to substitute the numerical
values of L and AJ lor a gas and the values of M', U and A'i for
oxygen (viz. 32, 1*4290 and 96 x lo"^), to deduce the value of M.
Values of L/L' are given in Table L
33

n: SCIENCE PROGRESS

The results obtained are as follows :

Table IV

Gas. n, Nj CO O, NO CH, HCl

M . . 2-01 52 28-019 28'oo9 32 30*006 16*039 36*469

M (calc.) 2*oi6 28*020 28*000 32 30*010 16*032 36*468

To facilitate comparison, the values calculated from the
International Table of Atomic Weights are given in the last
line of the above table.

From the values of M just deduced (Table IV.), the follow-
ing series of atomic weights is easily constructed :

Table V

Atomic Weight (0

= 16).

Element.

From above

From International

Molec. Weights.

Table.

Hydrogen .

I *0076

1*008

Chlorine

. 35*461

35 "46

Nitrogen .

14*008

14*01

Carbon

12*009

I2*00

These results are discussed later.

Ofker Compressibility Determinations. — It has been already
mentioned that Gray and Burt (20) determined the values of pv
for hydrogen chloride over the range of pressure from 160
to 800 mm. ; and that they found that when the values were
plotted against the corresponding pressures they fell on a
decided curve. The nature of this curve will be fairly evident
from a consideration of the following results, deduced from
their experimental data :

Ao-s = 847 X io~^ ; hZls = 711 X io~5; Ar^ = 572 X io~^ ; A' = 743 x 10'^

Its form is evidently similar to that of the curves ABCD and
ACEG in figs, i and 2.

The compressibility curves for other easily liquefiable gases
are undoubtedly of this type, although there are few trustworthy
data concerning them. These consist, for the most part, of
a number of determinations of either PiVi/p-jV^ or p^v^/piVi for
various gases. In order to utilise these measurements in
calculating the values of A', it has been assumed either that the
compressibility graphs are straight lines or that their curvatures
may be deduced from theoretical considerations.

The values obtained on the first of these assumptions are
obviously too great, as they lead to values of poVo corresponding

DETERMINATION OF ATOMIC WEIGHTS 513

to the points H or J, as the case may be, instead of to the point
A (fig. 2). It is necessary, therefore, to consider the theoretical
views that have been appHed in making the requisite extra-
polations.

In the first place, it must be understood that the true form
of the initial portion AB of the curve (fig. 2) is unknown.
If Boyle's Law were a true statement within the limit, the curve
would of course be initially horizontal, i.e. the tangent to the
curve at A would be horizontal. On this assumption, it is
easy to account for the fact that the molecular weights obtained
for easily liquefiable gases by the limiting density method
are usually low ; the values of Ai would have been over-
estimated in the extrapolation. There are no experimental
data from which accurate estimates can be made of the slopes
of the compressibility curves at exceedingly low pressures ;
but the assumption that all compressibihty curves become
horizontal when p = o requires that, under very small pressures,
considerable changes in compressibility must occur in the
case of the difficultly liquefiable gases. The validity of Boyle's
Law as a " limit-law " is, however, not generally accepted ; the
slope of the compressibility curve at the origin is usually
regarded as being qualitatively in agreement with the observed
slope at atmospheric pressure. This is in accordance with
van der Waals' equation and it may be remarked that most
of the deductions from this equation are qualitatively correct,
even though quantitative agreement may be lacking.

In calculating the values of AJ for liquefiable gases, Berthelot
(6, 13) adopts van der Waals' equation as a basis. Choosing
the units so that pressures are expressed in atmospheres and
the limiting value of pv when p = o is unity at 0° C, the
compressibility of a gas at 0° C. may, according to this equation,
be deduced in the following manner:

(p+^^)(v-b) = i (6)

Neglecting the small term ab/v^ substituting for pb its
approximate value b/v and writing e for (a — b), this equation
may be written

pv = I - - (7)

i.e, the product pv is a linear function of the reciprocal of the
volume.

514 SCIENCE PROGRESS

Hence,

A^ = I - pivJpoVo = I - (i - e/v,) = e/vi
= e/(i - e/vO - e/(i - e)

with a sufficient approach to accuracy ; i.e.

Al = — ^ (8)

I - e '

Berthelot also gives equations deduced from van der Waals'
equation for other coefficients, viz. :

^' ~ I - 26 ' ^^ ~ I - 2-5e ' ^' ~ (I - 2e) (I - 3e) ^^^

and from these he arrives at the following relationships :

A * A-5 A*

A^=-^=— A^_ =_-^ (lo)

I + A] I -f I'sAf I + 4A^

by the use of which it is possible to obtain the value of Ao from
the results of compressibility measurements made at moderate
pressures (0-5 — 2 atmos.).

Before applying these formulae to the experimental data for
other gases, their application to the case of hydrogen chloride
may be considered. The value of A,] already quoted (p. 512)
leads to the following result :

Ao X I OS for H CI at o* C, from equation = 840

Actual value = 743

In this case, therefore, the value of Ao is greatly over-esti-
mated by formula (10). It is also interesting to utilise Gray and
Burt's results to test equation (7). For this purpose, the writer has
calculated the values of i/v and plotted them against pv values.
The points do not lie on a straight line ; the graph has a
curvature similar to that of the compressibility curve but not
so pronounced. The high value of Ao afforded by equation (10)
is therefore explained. The results are interesting also from
another point of view ; had the measurements extended only
down to 425 mm., it might very reasonably have been concluded
that equation (7) was accurate, when a linear extrapolation
would have given AJ = 863 x io~s (about), in agreement with
that deduced from equation (10) and much too high. This
brings out very clearly the danger attaching to extrapolation
over any considerable range of pressure ; in fact, linear extra-
polation of the results obtained between 158 and 265 mm. led

DETERMINATION OF ATOMIC WEIGHTS 515

to the value Al — 757 x io"s, which is a close approximation to
the actual value.

It appears, therefore, that Berthelot's method of calculating
leads to results for AJ in excess of the true values and con-
sequently to molecular weights that are under-estimated. The
results obtained by the application of equations (10) to the
available experimental data are given in the following table :

Table VI

Gas.

Leduc and

Sacerdote

(2, 21).

Chappuis
(7).

Rayleigh
(12).

Jacquerod

and Scheuer

(15).

Berthelot
(13)-

A^
676

A-5

A.^

CO2

N2O
HCl
CiHs
NH,
SO..
CH3CI

681

773

811

1254

2550
2739

678

786
1 194

2314
2468

694

666

744

661
739

1527
2386

1504
2330

688
764

2617

670
741

2374

676

751

2407

671

745

2351

All the values given above require to be multiplied by lO"^.
It should be mentioned also that Rayleigh's and Leduc and
Sacerdote's results were obtained at room temperatures and
corrected to 0° C. by theoretical formulae, the necessary
corrections being large. Also, it should be remarked that
Berthelot has merely stated his results without giving any
details.

Berthelot (13) also states values of A^ for the gases and
deduces from his results the values of e in equation (7). From
his figures, the following results have been calculated by
equation (8):

CO, NjO SO3

A^ X lo^ . . . 669 743 2363

These values naturally agree with those deduced above from
equation (10), since equations (10) and (8) rest on the same
theoretical basis.

Jacquerod and Scheuer (15) really carried out their measure-
ments between the pressures 800 mm. and 400 mm. and deduced
values for Ao in a different manner. The values of pbVb/PaVa,
when b = 400 mm, ^nd ^ = 200 mm. v^ere also determined and

5i6 SCIENCE PROGRESS

the required coefficients deduced by a " parabolic extra-
polation " of which no account is given. Their results were
as follows :

lOS • A4^ I05 • Aa^ I05 ' Aq

NH3. . . I 5531 I J526 J5J8 1521

^^' ' ' • { 2380 } ^3^^ ^^^° ^^^^

That their method of extrapolating gave too high results is
highly probable since their values of Ao are greater than those
deduced from their measurements by Berthelot's method and
given in Table VI, results which it has already been shown are
probably high. Moreover, their results are not sufficiently
exact to justify the extrapolation ; the difference between the
two values for Aj~ in the case of ammonia, is actually greater
than the difference between the values they adopt for A^^ and
Aa^. Jacquerod and Scheuer mention one source of un-
certainty in the results, namely, that due to condensation of gas
on the inner walls of the containing vessel, an error which was
experimentally determined and allowed for in Gray and Burt's
experiments on hydrogen chloride.

The uncertainty attaching to Jacquerod and Scheuer's
extrapolated values may be explained by reference to fig. 2.
These experimenters determined the position of the three
points F, D and B only, with the object of finding E and A;
and their method consisted in determining the relative positions
of F and D in one experiment with a certain mass of gas and
in determining the relative positions of D and B in another
experiment with a different mass of gas. Hence, assuming the
point F to be correctly placed, D may be in slight error with
reference to it, from the first experiment ; while B may be
slightly in error with reference to the (already slightly incorrect)
position of D, from the second experiment. There remains the
error incurred by assuming a parabolic relationship between pv I
and p. From the graphical point of view, Berthelot's method
consists in determining the position of A from the known
positions of only two points (E and G or E and C, as the case
may be) and an assumed relationship between pv and p.

Another method has also been used in arriving at the
requisite compressibility values. It is obvious that at constant
temperature the density of a gas which follows Boyle's Law

DETERMINATION OF ATOMIC WEIGHTS 517

would be directly proportional to its pressure. In no known
case, however, does this relationship hold ; and the extent to
which the measured densities deviate from the "theoretical"
can be used in deducing the value of AJ for the gas. Measure-
ments have been made by Baume (16) of the densities of sulphur
dioxide, methyl ether and methyl chloride at o°C. and at
pressures varying from 760 mm. to 311 mm. He has expressed
his results by means of the equation

pv = I + m (i - -j^j (")

in which Lp and L, denote the weights of a litre of gas at 0° C.
and under the pressures p and i atmos. respectively, m being
a constant. The pressure is expressed in atmospheres and at
N.T.P. the product pv = i. This method of extrapolation is
similar in principle to that expressed in equation (7).
The following values were obtained :

SO2 .... m = 0*02381

CH3CI . . . . m = 0*02215

According to Baume (16) and also to Guye (18), we have

m = Ao

This conclusion, however, is erroneous and is due to the fact
that Baume, in his paper, defines Ap^, in two different ways
which are not equivalent. As a matter of fact, we have from

equation (11),

PxVx = I and poVo = i + m,

and since, from equation (2),

Ao = I - PiVjpoVo,

it follows that

Ai=i-(i + mr = ^ (12)

The above values accordingly lead to the coefficients :

SO2 . . . . Ao = 0*02325

(CHsXO . . . =0*02587

CH3CI . , . =0*02167

which are much lower than those adopted by the Geneva
experimenters ; further, the agreement between the values for
sulphur dioxide obtained by this method and by that used by
Jacquerod and Scheuer (p. 516) vanishes. It will be noted,
however, that the figure for sulphur dioxide, obtained by

5i8

SCIENCE PROGRESS

correcting Baume's calculation, agrees well with that obtained
by applying Berthelot's method to Jacquerod and Scheuer's
compressibility measurements.

Excluding the values of AJ for ammonia and sulphur dioxide
given by Jacquerod and Scheuer, the preceding results may be
summed up as follows :

Table VII

Gas.

Ao X I05

Accurate Molecular
Weight.

CO,

N,0

NH3

SO2

(CH3).0

CH3CI

661 to 678

739 to 757

1 194

1504

2314 to 2374

2587
2167 to 2468

44*017 to 44*009
44*007 to 43'999

30*037

17*018
64*082 to 64*043

46*064
50*537 to 50*381

44000
44*020
30*048

I7'034
64*070
46*048
50484

The molecular weights corresponding to the extreme values
of Ao given in column 2 are given in column 3, whilst column 4
contains the molecular weights calculated from the International
Atomic Weights.

In view of the uncertainty attaching to these values, a
detailed discussion is unnecessary. It is, however, obvious
that the above values of M cannot afford accurate atomic weight
values. Further measurements of compressibilities at 0° C.
sufficiently comprehensive to reduce the uncertainty attaching
to the extrapolation to the smallest possible dimensions are

required ; Gray and Burt's method, which determines Ao from
first principles, as it were, is undoubtedly the best of those
hitherto used.

Reduction of Critical Constants Method

In this method of determining molecular weights, published
by Guye (9) in 1904, the requisite data, in addition to the normal
densities of gases, are their critical temperatures and pressures;
the determination of Al from compressibility measurements, a
difficult task as the preceding discussion has shown, is un-
necessary.

The fundamental formula is derived from van der Waals'
equation, which Guye applies in a form slightly different from
that used by Berthelot, Measuring pressures in atmospheres

DETERMINATION OF ATOMIC WEIGHTS 519

and choosing as the unit of volume the volume occupied by the
gas at N. T. P., van der Waals' equation becomes

(p + ^.)(v - b) = (I + a)(l - b)(i + at) (13)

where a — 1/273 and t = temperature in degrees Centigrade.
This is the equation used by Guye. Assuming the validity of
the fundamental assumption of the method of limiting densities
and also assuming that equation (13) represents the behaviour of
a gas between o and i atmos., Guye's fundamental formula
follows readily from equation (4) on p. 507, viz. :

M = RL(i - Ao) (4)

For, since

PoVo PoVo

at 0° C. with the preceding choice of units, the equation (4) may
be written

M = — . (14)

Also, at 0° C. equation (13) may be written

pv = (i + a) (i - b) + pb - -^ + ^r

and since, when p = o, v = 00, we have

PoVo = (i + a) (i - b).

Hence equation (14) becomes

M = ^ (15)

(i+a)(i-b) ^ ^^

which is Guye's formula.

Guye arrived at his formula in the following manner. It has
been shown by van der Waals (4) and independently by Guye
and Friderich (5) that the acceptance of van der Waals' equation
leads to the following result:

At normal temperature and pressure, the relative volumes
of different gases that contain equal numbers of molecules are
proportional to

(I + a)(i - b)' (i + a')(i - b')' (I + a")(i - b") * ' * '

the accents referring to different gases, the units being chosen
as previously described.

As the molecular weights (M, M', M" . , .) are proportional

520 SCIENCE PROGRESS

to the products of these expressions into the respective values
L, U, U' . . . , it follows that

M M' M"

L' ~ L"

= R (i6)

(i + a)(i - b) (I + a')(i - b') (i 4- a")(i - b")

corresponding to equations (3) on p. 507 ; it is obvious that each
fraction is equal to R (cf. p. 507). Hence,

RL RL' , ,

^ = (I + a)(i - b)' M' = (I 4. a-)(i - b-) <^ 5)

an expression for M identical with that previously obtained.

Guye adopts the value R = 22*41 2. The calculation of the

values of a and b depends upon a knowledge of Tc and pc the

critical temperature (absolute) and pressure of the gas. The

following equalities, connecting a, b, Tc and pc, can be deduced

from theoretical considerations in connexion with van der Waals'

equation :

_ ^ T = ^^ 8 X 273a . ,.

^^ ~ 27b=" ^ ^7bR = 27b(i + a)(i - b) ^^^^

By solving these equations, a and b may be expressed in
terms of Tc and pc, magnitudes which can be experimentally
determined. The calculation involves the solution of a cubic
equation and the numerical values of a and b are best obtained
by the ingenious method given by Haentschel (11). Values of b
calculated in this manner agree very well with those deduced
from the equation

T /T\»

b = o"ooo4496 — + o'oooooi835 f ~1

Pc Pc

given by Guye and Friderich ; this equation therefore affords a
simple means of approximating to b for any gas. All values of
a and b quoted later, however, have been calculated by solving
the necessary cubics.

Whilst the fundamental equation

22'4I2L (,7)

(i+a)(i-b)

has the theoretical significance that attaches to a deduction from
van der Waals' equation, it is, like van der Waals' equation
itself, only approximately correct and therefore Guye has
modified it. The modified equations, however, can only be
regarded as empirical, as will be seen subsequently.

DETERMINATION OF ATOMIC WEIGHTS 521

Let us consider how Guye modifies his equation in order to
deduce the molecular weights of readily liquefiahle gases. In
common with van der Waals, van Laar and others, he sup-
poses that the original van der Waals' equation can be made
to represent accurately the behaviour of a gas if the values of
a and b are assumed to vary with temperature and pressure.
Therefore, he regards the values of a and b calculated from
critical data as being valid at the critical temperature and pro-
poses two empirical equations from which to determine ap.x and
bp,T, the values of a and b at p, T. These equations are :

ap.. = a(^)-, bp., = b (i + ^)(i - ^-^-) (18)

fi being a constant common to all the gases. The values ao and
bo assumed by a and b at N. T. P. are therefore

ao = a(^f, bo = b(i+^?^^)(i-^Pe) (19)

Using these values, Guye calculates the molecular weights from
the equation

,, 22*412 L / _N

M = 7 ^-7 r-v (20)

(i+ao)(i-bo) ^

The empirical character of equations (18) is sufficient to
nullify the theoretical value of Guye's method. Moreover, the
demonstration that, at N.T. P., the relative volumes of different
gases that contain equal numbers of molecules are proportional
to expressions of the type 1/(1 + a)(i — b) is based upon the
assumption that b is independent of the pressure ; therefore
as soon as equation (18) for bp,T is accepted, the proof of formula
(15) becomes invalid.

The expression for bo is easily seen to be, at the best, of
limited application. In the cases of hydrogen, nitrogen and
carbon monoxide it gives negative values, an absurd result when
the theoretical meaning of bo is considered. Moreover, according
to formula (18) bp,T approaches ± 00 as the pressure approaches
zero.

As has been already mentioned, Guye only applies the
preceding calculations to the readily liquefiable gases. In order
to determine the numerical value of /3, he adopts carbon
dioxide as the standard gas and takes as the atomic weight of
carbon the value 12-002 deduced from gravimetric measurements
of the ratios C ; CQ^ and CO ; CO,. Hence M = 44'oo2 and

522

SCIENCE PROGRESS

accepting the values for L, Tc and pc given in Table I., it

follows that

^ = 0*003223

The molecular weights calculated from equations (16), (19) and
(20) are as follows (for values of L, Tc and pc refer to Table I.) :

Table VIII

a X 10^

b X 10^

ao X 10^

bo X 10^

Carbon dioxide ....

721

191

847

161

44*002

Nitrous oxide

719

185

878

156

44012

Ammonia .

859

170

1554

146

17036

Phosphine .

940

233

1217

214

33*935

Ethane

1209

314

1449

299

30-051

Hydrogen chloride

722

179

937

152

36-451

Hydrogen sulphide

900

194

1438

240

34*085

Sulphur dioxide .

—

2837

267

63*954

Methyl chloride .

—

2872

310

50*363

Methyl oxide

—

——

3111

382

46*030

In the case oi the difficultly liqueftahle gases, Guye uses a
simpler method of calculation. The molecular weights given by
equation (15) are found to be too low by amounts proportional
to the critical temperatures (absolute) of the gases; hence
instead of (15) Guye writes

(21)

^(i + a)(i - b) = R + mTc

where m is a constant for the gases and a and b are deduced by
means of equation (16). To determine the actual value of rn^
the numerical values of M, L, a, b and Tc for oxygen are
substituted in the equation (R equals 22*412 as before), the
result being that

m = 0*0000623.

The following table contains the results obtained by the

application of equations (16) and (21) to the data for the

difficultly liquefiable gases (values of L, Tc and pc are given

in Table I.) :

Table IX

a X 10*

b X lo'^

Hydrogen .

. 28-8

lyi

2*0150

Nitrogen .

. 275

174

28"oi3

Carbon monoxide

. 284

172

28*003

Oxygen

. 266

139

Nitric oxide

. 257

115

30 009

Metb^ije , , ,

' ^'J')

J 69

16*034

DETERMINATION OF ATOMIC WEIGHTS 523

From the values of M given in the last two tables, the
following atomic weights are readily obtained :

Table X

Hydrogen.

1*0075 from Hj.
Nitrogen.

14*007 from Ng.

14*009 „ NO.

14*012 „ N2O,

14*013 „ NH3.

14*010 = mean.

Chlorine.

35*436 from HCl.

Carbon.

12*003 fro"^ CO.
12*004 „ CH^.
1 2 '002 „ CO.J.
12*003 „ C^He.

12*003 = mean.

Phosphorus.

30*912 from PHj.
Sulphur.

22*070 from HjS.

31*954 „ SO,.

These results are discussed later.

It is convenient here to refer to another method of calculating
molecular weights, due to Berthelot, which also requires a
knowledge of L, Tc and pc. In the course of an elaborate
discussion of the compressibilities of gases between o and 3
atmospheres, based largely upon the experimental results
obtained by Chappuis, Berthelot (6) was led to propose a
characteristic equation for gases which is of the same form
as that given by van der Waals but in which a and b are not
constants. The values at N.T.P. according to Berthelot, are

a = lo-s X 2*071 X T3/p^, b = 10-4 X 2*575 x TJp^,
the units of pressure and volume being those already explained
(p. 513) in connexion with Berthelot's other method. Denoting
(a — b) by e, we have as before (p. 514)

Ao = e/i - e
and the calculation of molecular weights is made by the
"limiting-density," formula (5) on p. 511. Berthelot calls this
the ** indirect " method of limiting densities.

The following values of 10^. A^ are obtained from the critical
data given in Table I. :

Table XI

Gas.

lo^A^.

Gas.

Io^A^.

Gas.

10^ . A^.

Gas.

10'. Al.

CO
0.

- 39

+ 31

NO
CH,
CO,
N,0

103

174
698
709

CHe
HCl
NH,
PH3

1177

755
1177

974

SH,
SOj
CHCl
(CH)0

1116
2013
2152
2363

524 SCIENCE PROGRESS

In the case of the first ten gases mentioned in the preceding
table, the molecular weights calculated from the values of Al
given agree well with those derived from the International
Table of Atomic Weights but considerable discrepancies occur
in the case of the remaining gases.

Another equation deduced by Berthelot (6) should also be
mentioned, as it has given rise to some misunderstanding. The
equation is

TTJ/ • drr "" 128(9 1^ ~ ¥)

in which tt, v and 0 denote the ** reduced " pressure, volume and
abs. temperature of a gas {i.e. these magnitudes expressed as
fractions of the critical values). This equation is only valid

when TT is indefinitely small; in other words , - only gives

the slope of the compressibility curve at A (figs, i and 2).
This point has escaped the notice of Guye and his collaborators,
who quote the above equation in its equivalent form (at 0° C.)

A = 0-0002575 — ( — \ - i)
Pc V2732 '

and refer to it as Berthelot's indirect formula /or ^o- Such is,
of course, not the case ; the formula refers only to the limiting
value of A^^ when both pa and pb approach zero, a value
considerably smaller than AJ.

It was by utilising this formula that Rayleigh (12) reduced
his compressibility measurements to the values at 0° C.

The Molecular Volume Method

The method of molecular volumes was chronologically the
first of the methods described in this article (2). It will be
seen that while in principle it may be identified with the method
of limiting densities, yet with respect to the experimental data
necessary, viz. densities and critical constants, it resembles the
method of critical constants. Unlike the latter, however, it is
not a deduction from van der Waals' equation empirically
modified but rests on the broader basis of the Theorem of
Corresponding States.

The account here given is, in substance, that contained
in Leduc's latest memoir on the subject (21). The pressure,
molecular volume and absolute temperature of a perfect gas,

DETERMINATION OF ATOMIC WEIGHTS 525

i.e. one for which the laws of Boyle and Gay Lussac hold
exactly, are connected by the relationship

pV= KT

where K is a constant which, by Avogadro's theorem, has
the same value for all perfect gases. But no know^n gas is
perfect and if, at the temperature T and pressure p, the
molecular volume V of a gas be expressed by the equation

pV = KT (22)

the value of K' is not identical with K. By division,

K'/K = V'/V

The ratio VyV, i.e. the ratio of the molecular volume of a gas to
the molecular volume of a perfect gas at the same temperature
and pressure, will be called <^. Since, then, </> is equal to K'/K,
equation (22) may be written

pV = KT<^

or, if M be the molecular weight of the gas and v its specific
volume,

Mpv = KT0 (23)

which is Leduc's method of writing the equation. It must
be noted that, in this equation, </> is a variable quantity.
For the particular case of oxygen, we may write

32 pV02 = KT0O2

whence the molecular weight of a gas is seen to be given by the
equation

32
This in turn may be written

(24)

In this equation d and do^ denote the densities of the gas and
oxygen at the temperature T and pressure p, whilst </> and (^^^
refer to the same temperature and pressure.

It remains to indicate the manner in which Leduc arrives at
the values of <^ and (f>o^. Referring back to equation (23) and

32^

~ <po^y

,11

32"

526 SCIENCE PROGRESS

indicating by zero suffixes the values of the variables at
temperature T and at zero pressure,

Mp^v, = KT(/,, (25)

Hence, from (23) and (25),

pv _ 0

Leduc assumes that </)o is sensibly equal to i, i.e. at a common
temperature and under a common, indefinitely small pressure,
all gases have the same molecular volume. This is, of course,
the fundamental assumption of D. Berthelot's method. Hence,

<p = pv/p„v^

Further, Leduc assumes that over the range of a few atmospheres
pressure, the compressibility of a gas may be represented by the
equation

^ == ^ ~ D V == "^P + "P »

ro o

where m and n are small constants to be determined for each
gas.^ Hence,

<f) = I - mp - np',

,>. ^=,-n,p,(i)-np»(P-y (.6)

Leduc measures p in cms. of mercury and pc in atmospheres
and denotes p/pc by e, so that

(f) = I - mp^ . e - np^ . e= (27)

The values of m and n are arrived at by an application of the
theorem of corresponding states. At the same ^^ reduced'' tem-
perature and ^Weduced'' pressure, the molecular volumes of gases
are assumed to be eqiial. The " reduced " temperature and
"reduced" pressure of a substance are T/Tc and p/pc respec-
tively, i.e. the temperature and pressure expressed as fractions
of the critical values. Accordingly, for the same value of the
" reduced " pressure (or e), different gases give the same values
for ^ when at the same " reduced " temperature. Hence, in
equation (27), the coefficients mpc and npc must be functions
of the ** reduced " temperature only. Leduc calls the reciprocal

' If for ^ and ^02 in equation (24) the values I--E and I — Eog are inserted, it
will be immediately seen that the equation is identical with that derived from the^
method of limiting densities.

DETERMINATION OF ATOMIC WEIGHTS 527

01 the reduced temperature x ^^^ deduces two equations to
represent the values of mpc and npc as functions of %, within
the limits of experimental error. These equations are

10^ . mpc = iS'Ssx (2^^ - sf2x + 2 Vix - 0 ^^^^

and

loV np'c = 3-5x^(x - 0 (29)

which represent the results of Leduc's experiments on the com-
pressibilities of gases with great accuracy.^

The molecular volume method is applied in the following
manner. Given the density d of a gas at temperature T and
pressure p and given its critical temperature Tc and critical
pressure pc : required its molecular weight. Since pc is given
and X, which equals Tc/T, is also known, equations (28) and (29)
enable m and n to be calculated. Equation (27) then gives the
value of (j), as e, which equals p/pc, is also known. It is then
necessary to be able to calculate 0o,, the value for oxygen at
the same temperature T and pressur ^ p and the required
molecular weight follows from equation (24). In practice, T
and p are 273° and i atmos. respectively.

Leduc found that the theorem of corresponding states could
not be applied to certain gases, ie. that equations (28) and (29),
which give the correct values of m and n for a large number
of gases, do not give correct results in these particular cases.
These exceptional gases are ammonia, phosphine, hydrogen
sulphide and methylic ether. On the other hand, equations
(28) and (29) derived from data relating to substances gaseous
at the ordinary temperature and pressure may be successfully
applied to the calculation of A?, for toluene vapour at 129*6° C.,
the result being in excellent agreement with that obtained from
the experimental data of Ramsay and Steele (8).

Since equations (28) and (29) rest largely upon the com-
pressibility data of Leduc and Sacerdote and upon critical
constants which often differ a little from those hitherto employed
in this article, a detailed statement of the numerical results
obtained by this method is unnecessary, as the values would
not be directly comparable with those already deduced by other
methods. It is obvious that the results obtained by this

* Leduc deduced an expression for Ai, in terms of m and n and then sought
equations for m and n which would enable him to reproduce his experimental
values of Ai.

528 SCIENCE PROGRESS

method cannot differ sensibly from those obtained by the
limiting density method, except in so far as errors are incurred
in effecting extrapolations.

Leduc has arrived at the following atomic weights :
H = roo75, N = 14*006, C = 12-005, CI =35*45 (probably low).

Comparison of Atomic Weights derived (i) by Chemical
Analysis and (ii) by Physical Methods

The atomic weights deduced from the most trustworthy data
by the methods described in this article are as here tabulated :

Table XII

Density

Critical

Molecular

Limits.

Constants.

Volumes.

Hydrogen

1*0076

1*0075

Nitrogen

. i4"oo8

14*010

14*006

Carbon .

. 12*009

12*003

12*005

Chlorine

. 35'46i

35'436

35"45

The values for sulphur are unsatisfactory. The value for
phosphorus deduced by Guye's method is undoubtedly too
low and the same remark applies to Guye's value for chlorine.
These low values may possibly arise from a slight " association "
of hydrogen chloride and phosphine, the degree of association
varying between N.T. P. and the critical temperature and
pressure (22). Leduc (21) criticises his value for chlorine as
being, if anything, too low.

The atomic weight of carbon obtained by these methods
approximates closely to the result obtained from the best gravi-
metric work. The rather high value obtained by Berthelot's
method suggests that the compressibilities of carbon monoxide
and methane need revision, a conclusion that may also be drawn
from an inspection of the compressibility measurements given
on p. 511.

The atomic weight of hydrogen quoted above is in agreement
with the results of the best gravimetric work on the composition
of water but is distinctly an indication of the superior accuracy
of Morley's value (25) 1*0076 over that obtained subsequently by
Noyes (27), viz. 1*0078. Other considerations point to the same
conclusion.

Special interest attaches to the atomic weight of nitrogen, to
which the physical methods assign a value slightly lower than

DETERMINATION OF ATOMIC WEIGHTS 529

14*01. The value i4'oo3 was obtained by the physical method
as early as 1895 by Rayleigh and Ramsay (i) but the value
i4'04, derived mainly from the work of Stas, was published in
the International Table as late as 1906. Meanwhile, the low
figure was confirmed by Leduc (2), Berthelot (3), Guye and
his collaborators (10) and Gray, all using the physical method.
The first chemical work to yield the low value 14*01 was the
analysis of nitrous oxide by Guye and Bogdan (40) in 1904 and
after this result was confirmed by Gray's analysis of nitric oxide
(39), the value N = 14*01 was adopted in the International Table.
Ladenburg's discovery (26) in 1902 of an error in Stas's value
for the atomic weight of iodine was followed some years later by
the discovery, due to Richards and Wells (29), that Stas's value
for chlorine was in serious error. Since then, the values of
the fundamental atomic weights have been subjected to a most
careful revision, in the course of which the value 14*01 for
nitrogen has received further confirmation. The three following
ratios have been determined with the utmost care by Richards
and others (29, 30, 31) :

AgCl : Ag = 1*32867.
NH4CI : AgCl = 0-373217.
AgNOa : Ag = 1*57479.

From these results, assuming with Morley that H = i*oo76,i it is
easy to deduce that N = i4-oo9, 01 = 35*457, Ag=i07*88. The
value here given for silver was proposed by Guye (10) in 1905,
as a necessary consequence of adopting the value 14*01 for
nitrogen and has now been substituted for the old value 10793,
due to Stas.

To the analytical evidence in favour of N = 14*01 already
quoted, it is necessary to add the analysis of nitrogen peroxide
by Guye and Drouginine (36), from which the value 14*009 was
deduced, also the synthesis of the peroxide from nitric oxide and
oxygen, from which Wourtzel (38) deduced the value 14*007.

Turning to the atomic weight of chlorine, the value 35*457
derived above received the following confirmation. Firstly,
the ratios

LiClO, : LiCl = 2*50968

LiCl : Ag = 0-392997

established by Richards and Willard (3^), lead to CI = 35*454
' The assumption that H = 1*0078 leads to almost identical results.

530 SCIENCE PROGRESS

and Ag = 107*871. Secondly, the work of Richards and Staehler
(32) affords the ratio

K : CI = 1*102641

which, combined with Staehler and Meyer's ratio (37)

KCIO3 : KCl = 1*643819

leads to the value CI = 35*458-

The mean value CI = 35*456 derived from these gravimetric
results is in agreement with the value 35*461 deduced by Gray
and Burt, using the method of limiting densities ; and if Morley's
values for the density and atomic weight of hydrogen are
admitted, further confirmation is supplied by Edgar's syntheses
of hydrogen chloride (34), which give CI = 35*461 and Gray and
Burt's volumetric analyses of hydrogen chloride (20), which give
CI = 35*459. It should be mentioned, however, that Noyes and
Weber's syntheses of hydrogen chloride (28) supply the dis-
tinctly low value 35*452, whilst the analyses of nitrosyl chloride
by Guye and Fluss (35) furnish a decidedly high result,
viz. 35*466.

In conclusion, it would appear that the physical methods
have led to the deduction of several fundamental atomic
weights, which, in point of accuracy, compare favourably
with the values derived from the best chemical work that
has been accomplished. It is to be hoped that subsequent
research will add to their number : as has been already
indicated, a considerable amount of work still remains to be
done on the subject of gaseous compressibilities.

References

1. Rayleigh and Ramsay, Phil. Trans, 1895, 186, A, 187.

2. Leduc, Ann. chim.phys. 1898 (vii), 15, 5.

3. Berthelot, D., Compt. rend. 1898, 126, 954, 1030, 141 5 ; /. de physique, 1899,

8, 263 ; Zeitsch. Elektrochem. 1904, 10, 621.

4. Van der Waals, Continuity of the Liquid and Gaseous States, 2nd German

Ed. pt. i. p. 85.

5. Guye and Friderich, Arch. Soc.phys. et hist. nat. Geneve, 1900 (iv), 9, 505.

6. Berthelot, Travaux et Memoir es du Bureau des poids et inesures, 1903, 13.

7. Chappuis, ibid. 1903, 13.

8. Ramsay and Steele, Phil. Mag. 1903 (vi), 6, 492.

9. Guye, Compt. rend. 1904, 138, 1213 ; /. chim. phys. 1905, 3, 321.

10. Bull. Soc. chim. 1905, 33, i ; Chein. News, 1905, 92, 261, etc.

11. Haentschel, y4«;/.//^_/jz/^, 1905, 16, 565.

12. Rayleigh, Phil. Trans. 1905, 204, A, 351.

DETERMINATION OF ATOMIC WEIGHTS 531

13. Berthelot, Compt. rend. 1907, 144, 76, 194, 269, 352 ; 145, 317.

14. GUYE, /. chun. phys. 1907, 6, 203. A review of work done up to 1907 on

densities of gases.

15. and others, Mem. Soc. phys, et hist. nat. Genlve^ 1908, 35, 548-694.

16. Baume,/. chiin.phys. 1908, 6, i.

17. and Perrot, ibid. 1908, 6, 610.

18. GUYE, ibid. 1908, 6, 769. A review of all the physical methods published.

19. Baume and Perrot, ibid. 1909, 7, 369.

20. Gray and Burt, Chem. Soc. Trans. 1909, 95, 1633 ; Trans. Faraday Soc.

191 1, 7, 30.

21. Leduc, Ann. chim.phys. 1910 (viii), 19, 441.

22. Guye,/. chim.phys. 1910, 8, 222.

23. Ter Gazarian, ibid. 1909, 7, 337 ; 191 1, 9, loi.

24. Scheuer, ibid. 1910, 8, 289.

25. Morley, S7niihsonian Contributions^ 1895, No. 29.

26. Ladenburg, Ber. 1902, 35, 2275.

27. NOYES,/. Amer. Chejn. Soc. 1907, 29, 1718.

28. and Weber, ibid. 1908, 30, 13.

29. Richards and Wells, ibid. 1905, 27, 459.

30. and Forbes, ibid. 1907, 29, 808.

31. KOETHNER and TiEDE, ibid. 1909, 31, 6.

32. and Staehler, ibid. 1907, 29, 623.

33. and WiLLARD, ibid. 19 10, 32, 4.

34. Edgar, Phil. Trans. 1908, 209, A, i.

35. Guye and Fluss,/. chim.phys. 1908, 6, 732.

36. and Drouginine, ibid. 1910, 8, 473.

37. Staehler and Meyer, Zeitsch. anorg. Chem. 191 1, 71, 378.

38. Wourtzel, Compt. rend. 191 2, 154, 115.

39. Gray, Chem. Soc. Trans. 1905, 87, 1601.

40. Guye and Bogdan, Compt. rend. 1904, 138, 1494 ; /. chim.phys. 1905, 3, 537.

THE LOGIC OF DARWINISM

By ARCHER WILDE

By common consent, the great discovery of Darwin and Wallace
has long been considered to be as fully and finally established as
one of the most important of natural laws; their names are enrolled
among the immortals and their work forms the base upon which
all must take their stand who would peer yet further into the
secrets of life. Yet Darwinism still seems new and its bearings
even on strictly biological problems are far from being fully
worked out. It has been stated recently that " Biology to-day
teems with mutually incongruous opinions." The science has
hardly emerged from the state of ferment into which it was
thrown by a discovery which utterly subverted the old order
while necessarily supplying, at first, only the framework of the
new. There is therefore the less reason for surprise if, as I
shall attempt to show, the logical proof upon which the theory
of Natural Selection rests be not justly estimated by the
educated world at large. Some may perhaps ask — as long as
the theory is fully accepted, what does it matter upon what
grounds it may be based ? but I feel sure that more will agree
with the view that the great importance of the subject and its
intimate bearing upon social and political questions render
superfluous any apology for an endeavour to secure a fresh
survey of the ground on which Darwin built, if any reasonable
cause can be shown for it.

I have long held the opinion that the strength of Darwin's
argument has been seriously under-estimated in this — that the
theory is regarded as still awaiting the final proof afforded
by experiment. Whether or no this may be partly a lingering
effect of his great and possibly even excessive modesty is
an interesting question which I cannot now touch ; the fact
remains that, even among the most convinced supporters of the
theory of Natural Selection, it is common to find writers who
state or imply that the theory is susceptible, in this way, of
a higher kind of proof than it has yet received. For instance,

532

THE LOGIC OF DARWINISM 533

the able author of a little book on "Organic Evolution," written
a few years since for the instruction of the public, makes the
admission, in replying to objectors, that " we have not seen
natural selection at work " ; and he propounds the opinion that,
for final proof, we have to await the result of certain observa-
tions then being made by Prof. Weldon on crabs in Plymouth
Sound, which he regards or regarded, as far as they had
proceeded at the time of writing, as " very nearly tantamount to
experimental proof of the theory of natural selection." Other
quotations which I shall subsequently make show that this
opinion is still commonly accepted. The point which I shall
here endeavour to establish is that this attitude of mind is
mistaken : that the Darwinian theory has long since received
the highest proof possible — the proof of experiment — and is
incapable of further verification, except in the sense in which
the theory of gravitation is still being verified by the continual
accumulation of additional instances in which the phenomena of
nature are found to conform with the law.

Experiment differs from ordinary observation only in this,
that the phenomena observed are as far as possible kept under
control and isolated from the operation of the surrounding
forces of nature. Thus, instead of observing the effects pro-
duced by a particular acid upon a particular metal as these occur
in nature, which would be difficult if not impossible, we isolate
them both as far as possible and then bring them into contact
and observe their interaction. So, for instance, it is found that
the interaction of copper and sulphuric acid gives rise to the
beautiful blue vitriol of commerce. Now the domestication
of plants and animals, which began ages ago ; and the improve-
ment of breeds, which advanced gradually, in the course of
thousands of years, through unconscious to conscious selection,
until in recent times, especially since Darwin and Wallace
published their joint discovery, the deliberate improvement
of stock by selection of the most useful or most fancied strains
has become the common practice of every breeder : what are
these but the isolation and control of the phenomena of
reproduction in the organic world, attended as they are by
careful observation and usually by the maintenance, in modern
times, of a complete record of results ? What then does the
process amount to but one long series comprising an infinity of
individual experiments in proof of the Darwinian theory ? Not

534 SCIENCE PROGRESS

of course that the attempts were purposely made as experiments
in proof of any theory whatever. The guiding purpose has
always been man's own advantage : the fancier's love of his
hobby or the breeder's profit. But is it of the essence of
an experiment that it should be purposely made as such to
prove a theory? I think not. All that is really essential is
a sufficient control of the phenomena and a sufficient observa-
tion and the record of the sequence of events, all of which we
undoubtedly have. In a word, it is possible to prove theories
by experiment without knowing that we are doing so ; this
is what has been done. Breeding is the experimental produc-
tion of variety by the selection of variations.

To see the force of this contention, it is only necessary
to suppose that the human intellect, instead of being, as it is,
far stronger on the practical and inductive side than on the
theoretical and deductive, so that practice usually precedes
theory, had been stronger on the theoretical than on the
practical side and that in 1858, when the theory of Natural
Selection was enunciated, the practice of domestication of plants
and animals or rather, let us say, their improvement by selection,
had not been begun. What would biologists then have said ?
Clearly they would have reasoned : ** If this theory be true ;
if nature have indeed raised up highly developed and specialised
kinds of life from the simplest or from comparatively simple
forms by destroying out of each generation the weaker members
and reserving the stronger to continue the race ; if plants and
animals differ in their fitness to cope with their surroundings
and it be on the average the fitter that survive and multiply,
transmitting their superior fitness to their descendants : then
man too, in his comparatively limited way, even in the short
time at his disposal, must be able to produce proportionate
results. Therefore, if we breed our cows only from the best
milking cows and from bulls that are proved sires of good
milkers, if we set aside exceptionally large-grained specimens
of wheat as seeds for succeeding seasons, we shall be able
to improve both cattle and wheat, slowly no doubt but to
an indefinite extent in the selected characters. The experiment
is doubtless absurd but it is harmless and the failure to
produce results, say in the course of a century, will go some
way to disprove the theory and clear the air of this crack-
brained and pernicious nonsense." The proposal would

THE LOGIC OF DARWINISM 535

probably at first have been laughed out of court but afterwards
it might have been tried and would have met with an unexpected
degree of success ; and this would have been experimental proof
of the theory. Now, as the fact happens, it is just this sort
of experiment that has for ages been extensively and continuously
carried on by man in the process of domestication, that word
being used in its widest sense to include the cultivation of plants.
In what way and to what extent is the logical value of this series
of experiments affected by the fact that it began long before
Darwin was born ? I venture to think it is not affected at all.
So far as can be done in a few paragraphs, it may be well to
inquire in more detail what that process is and what it proves.
Its origin, deeply buried in antiquity, is to us mere matter of
surmise. It seems likely that it began not in any deliberate
subjugation of animals by men but in a partnership due to
mutual advantage. Probably wolves began to domesticate them-
selves with man as partners in the chase and scavengers to pick
up the offal and bones after that clever hunter had gorged
himself on his quarry, whilst men may have made a practice of
following the pack in full cry and coming in at the death to rob
them of their prey. Both practices would surely tend to the
evolution of the friendly dog out of the unfriendly wolf, by the
continual elimination of all such fiercer members of the pack as
turned on men or refused to give them way. But however
probable this may be, it is clear that no such surmises can be
cited as experimental proof of the theory, simply because of the
absence of all record of the facts. It is of the essence of such
proof that it should be founded not on surmise however probable
but on duly attested facts. Of these beginnings there are no
records but as we travel downwards through history records
begin to appear ; first perhaps in the shape of wall-pictures and
then in writings and finally in books, until at the other end of
the scale we reach such facts as are cited in the following passage
taken from Weismann's Evolution Theory (English translation),
vol. i. p. 38 : " Darwin says * The English judges decided that
the comb of the Spanish cock, which had previously hung
limply down, should stand erect and in five years this end was
achieved ; they ordained that hens should have beards and six
years later fifty-seven of the groups of hens exhibited at the
Crystal Palace in London were bearded.' " What is proved by
this double set of experiments or experiences ? Among others

536 SCIENCE PROGRESS

three points may be set down as well established : (i) The
variability of certain characters of the so-called Spanish variety
of the species Callus bankiva, namely the comb in the male and
the beard in the female. (2) That this variability is largely
independent of the other characters of the variety. These appear
to have been little if at all affected by the modification of the
chosen characters. (3) That the variations can be accumulated
in the same direction through several successive generations.
The large number of persons engaged in the double series of
experiments places these results of their concurrent testimony
beyond doubt. Putting them together we may say that they
prove the independent and cumulable variability of two par-
ticular characters of a particular variety of a particular species.
If, however, these experiments are taken, as they must be, with
hundreds of other series of experiments undertaken by other
breeders by which they effected changes in other characters of
the same variety of fowl, it will be seen that similar truths have
been established in regard to a great number of them. And if
these experiments again are taken with the experiments of thou-
sands of other breeders of various varieties of the same species,
it will be seen that the evidence of the independent and cumulable
variability of at all events every conspicuous character of the
domestic fowl is immense. Lastly Galliis bankiva is not the only
species which has been modified by domestication into divergent
varieties. If with the foregoing facts we consider the great
number of animals and plants in regard to which similar truths
have been established by similar experiments, the total evidence
of independent and cumulable variability in the characters of
organic beings becomes enormous and affords the best possible
ground for the belief that the rule applies to every part of organic
nature as a whole. The best possible ; for what more can be
proved by any expressly devised experiments in the case of
species still undomesticated ? Only that the rule applies to yet
one more species or rather to one or more of its characters ; a
difference in the quantity of proof, not in its kind. Now to prove
the existence of such variability throughout organic nature is to
establish Darwin's law, at least as far as it can be established by
experimental proof. For that it is in fact only or chiefly by this
means that life as we now see it has been evolved, can be proved
if at all only by appeal to the geological record ; it is matter of
inference from observation and not susceptible of experimental

THE LOGIC OF DARWINISM 537

proof. For my part then I cannot see that we have not here a
proof of the theory just as complete as if it had been devised by
scientists with all possible precautions and " controls " for the
express purpose of scientific demonstration. Indeed the process
must be much more conclusive than most experimental proofs,
on account of the enormous number and variety of instances in
which it has been tried and not found wanting. Those who
differ from this opinion may fairly be challenged to devise and
describe fully a crucial experiment or series of experiments
which shall finally prove or disprove the theory ; there will
then possibly be found those who can spare the time and
the means to put it into practice.

Suppose however it should be held that the interpretation I
have here given of the word experiment is too wide and that
to constitute an experiment properly so called definite and
conscious purpose is a requisite, what then ? In that case
all breeding and nursery gardening carried on since 1858 by
intelligent breeders and nurserymen who had read their Darwin,
with the deliberate purpose of improving their stock, must
still be regarded as experimental proof of the theory ; for it
cannot surely be vitiated as such by the fact that their chief
purpose has been to profit by the sale of improved stocks and
strains. The experimental production of artificial diamonds
in proof of a theory as to the manner of their formation
would not be held any less conclusive on account of the hope
of the experimenters that a valuable product would be obtained.

Such considerations incidentally go to show the profound
unreason of much of the early criticism of Darwinism. Darwin
argued mainly from the phenomena of domestication in plants
and animals (although indeed he also availed himself of all that
was known of them under natural conditions) that species were
proved to be artificially modifiable by means of selection for the
purpose of reproduction of slightly superior plants and animals
and must therefore also be modifiable and have been accordingly
modified in a state of nature, unless we were to suppose that
all the individuals of each species were of exactly equal fitness
to cope with their environments. Oh but, it was replied, you
cannot argue from the artificial conditions of domesticated
animals to their conditions in a state of nature. That, said the
then Duke of Argyll, is a " loose analogy." Man, was his
unexpressed assumption, is so much more powerful than Nature

538 SCIENCE PROGRESS

as to effect, in a few centuries, what Nature could not do in the
course of geological ages ; all sorts of things can be done by art
which are not done by Nature. He might just as well have
argued that the blue crystals, artificially produced from copper
and sulphuric acid, prove nothing regarding the behaviour of
such materials in Nature ; or he might even more plausibly
have asked what inferences could be drawn regarding natural
phenomena from the liquefaction of hydrogen under conditions
of cold and pressure which are not met in the natural world.
The truth is that this distinction between the natural and the
artificial, though no doubt it has its proper uses, is itself one of
the most artificial things in Nature and in matters biological is
often quite out of place. For what after all is man with all his
works but a part of Nature ? Those, no doubt, who with
Dr. Wallace at their head believe that at a certain stage of his
development a spirit must have been breathed into an inhuman
ape independently of the course of evolution in order to make
him man, may logically dispute this conclusion, as man's mind
in that case clearly contains a supernatural element, which
must also have had its effect upon all his works, so that neither
he nor they are entirely a part of the natural world. But those
who see in the human mind nothing but a development, however
great, of powers and faculties well indicated in the higher
animals, will readily agree that he is a part of Nature and
nothing more. Therefore as regards the evolution of animals
and plants, he is merely a more or less important part of the
environment ; to large animals a feature of ever-growing
importance — to too many kinds, it is to be feared, the sinister
omen of impending extinction ; to domestic plants and animals
the dominating feature of their surroundings and factor of their
lives ; but to deep-sea fishes a thing of remote if any con-
sequence. When the flat-footed ape appears on the scene or
at all events with the advent of the lethal variety called civilised
man, the environment of large animals undergoes a great and
rapid change and the qualities which before ensured their
survival become comparatively useless. Strength, speed,
wariness and ferocity now avail them little. Either they must
accommodate themselves to his purposes and become domesti-
cated or they must conceal themselves successfully to save
their skins or they must perish utterly — manet sors tertia ccedi.
The presence of man radically alters the environment and

THE LOGIC OF DARWINISM 539

therefore the conditions of survival and the qualities required
to secure it but that is all it does. Neither the animals that
accept man's yoke nor those that survive in spite of him are
withdrawn from the realm of nature or escape her law. Her
writ runs in byre and garden as well as in forest and plain.
The argument from domestication was not therefore an analogy
at all, still less a loose one. Improvements of stock by selective
breeding constituted in themselves the proof of the theory of
selection by demonstrating both the variability of species and
the fact that favourable variations do occur and are selected
and by accumulation may result in great modifications of any
part or character.

Not only so but in the phenomena of domestication it appears
to me we have the only possible complete experimental proof
of the theory, which therefore either has been or never can be
experimentally proved. That control of organic beings which
is requisite in order to constitute an experiment in the
phenomena of reproduction can only be obtained by what
amounts to domestication. The relation between observation
and experiment is similar to that between nature and art, so
that the element of art or artifice in domestication, far from
vitiating its results as a source of inference, is precisely what
makes them the proper material for final and conclusive proof.

In a word, man being a part of Nature, selection by man
does not merely prove but is natural selection and we have
*' seen natural selection at work." Nature acting by man's own
hand long ago began and has since in an ever-increasing degree
continued to select for survival those plants and animals which
are useful or pleasing to her simian pet and to destroy his
enemies.

Let us now turn to some fresher expression of opinion on
the subject than that above selected. " The theory " (of natural
selection), say Profs. Geddes and Thomson in their recent
popular hand-book on Evolution, "works well as an inter-
pretation but what we need is actual proof of discriminate
selection, actual evidence that survivors do survive in virtue of
particular qualities." Do not many cows survive in virtue of the
particular quality of giving a good supply of milk and many go
to the butcher by reason of their failure to do so ; have we
not here actual proof of discriminate selection ? As partly
satisfying their demand, the Professors go on to describe an

540 SCIENCE PROGRESS

experiment made by Mr. A. P. di Cesnola, who having exposed
some dozens of the two forms of Italian Mantis, green and
brown in colour, some in herbage which matched their colouring
and others in herbage which did not, found that the latter were
soon taken by birds whilst the former were left. Thus the
survival value of the protective colouring was distinctly proved
but not its cumulable inheritance from generation to genera-
tion nor the variability of the species nor the survival value
of small differences, of all of which we have ample proof in the
phenomena of domestication. As to the point that is proved,
far be it from me to detract from the cogency of the proof but
why is it more conclusive than any one of an infinite number
of experiments tried by humanity during hundreds, if not
thousands, of years by which they have unintentionally
demonstrated the survival value of this very character of colour
in other ways ? Colours have been points selected by breeders
and gardeners in the case of cattle, dogs, pigeons and numerous
flowers during centuries. In the one experiment, a few dozen
Mantis were demonstrated to have survived by virtue of colours
corresponding with their surroundings ; in the others, millions
of plants and animals have survived and have been selected as
progenitors of the future race by virtue of colours corresponding
with preconceived ideals of beauty in the minds of men. Nature
in both cases is the selector; in the one case her selective agents
were birds, in the other case men. In either case has the
possession of a particular colour been a favourable variation
determining the survival of a particular animal or plant in
competition with his fellows less fortunately endowed. Why
is the single experiment more cogent than the million ?

Again Dr. G. Archdall Reid is one of the ablest of present-
day exponents of organic evolution especially in relation to man
and his treatment of the subject of elimination by disease ought
to have and doubtless has gone far to dissipate the dense fog of
much loose writing on the supposed immunity of modern man
from Natural Selection. Yet he writes {Bedrock^ No. 2, p. 262) :
" It is necessary ... to ascertain whether Natural Selection
does really occur in Nature, to observe what kinds of variation
it selects and to discover the result, if any, of this selection. It
is useless to observe domesticated plants and animals ; they are
under artificial selection." But why does the fact that they are
under artificial selection make it useless to observe domesticated

THE LOGIC OF DARWINISM 541

species for this purpose ? I have given above some grounds
for thinking, that it is precisely this fact that makes them the
proper and the only possible material for experimental proof.
Domesticated races have not been withdrawn by man from the
operation of the active forces of organic nature. Her laws and
methods of nutrition, growth and reproduction have not been
essentially altered in their case. Had calves and puppies, peas
and cabbages in civilised countries ceased to be products of
Nature and become works of art like watches or pictures,
such expressions would be justified but hardly otherwise. It
seems to be forgotten that these species were wild before they
were tamed and that some of them at least have congeners yet
living in freedom from whom they have diverged under the
control of man. Such divergence is proof of the variability of
the wild species. In the course of some very effective criticism of
Mendelism, Dr. Reid points out that that school has no monopoly
of the method of experiment in the study of Biology and did not
therein initiate its use, which was practised by Darwin and others
before Mendelism was thought of; but if I may say so, he does
not go far enough. Ages probably have passed since some one
first consciously tried the experiment of breeding from the
fastest greyhounds with the deliberate object of improving the
race ; ages again before that men unconsciously did the same
thing by keeping the hounds they found most useful in the
chase and destroying or neglecting the rest, so that as a fact this
type of hound is said to be delineated in the wall-carvings of
ancient Egypt. This attitude towards the argument from
domesticated races seems the less defensible in Dr. Reid,
because he justly insists that, as of all animals the best known
to us is man, he is therefore the best subject for biological
speculation. For the like reason, that we know far more of them
than of wild animals and plants, domesticated species furnish
the second best materials for experiment and research. Indeed,
for the former purpose they are surely the more suitable, both
because they are much more amenable to control and because of
their far greater rapidity of reproduction. And it may be claimed
that this view is supported by the facts, for after all it was
from the domesticated races that Darwin chiefly drew the
data upon which he founded and, whether by analogy or as I
contend by proof positive, finally established his theory.

Upon the whole it seems that an incorrect and exaggerated

542 SCIENCE PROGRESS

estimate of the scope and nature of man's interference by
domestication in the process of evolution is widely current
and finds a footing even among the most enlightened evolu-
tionists. Theoretically Darwinism has put man in his proper
place in the world and killed the anthropocentric theory but in
practice the anthropocentric habit of mind dies harder and its
vestiges remain in our brains in spite of ourselves and influence
thought unawares. It seems to be vaguely supposed or un-
consciously assumed that by domestication a species is removed
from the operation of natural law but properl}^ regarded
domestication is nothing but a radical alteration of the en-
vironment, in which a new set of qualities, including some and
excluding others of the old set, constitute fitness and secure
survival. Beyond confinement and slaughter man does nothing
but select the variations which Nature, constant in nothing but
change, invariably presents. We may consider domestication
broadly as a kind of symbiosis, comparable with though widely
differing from other kinds occurring lower in the scale of life, in
which two species find it to their common advantage to live
in close companionship. If it be objected that, in this case, the
advantage is one-sided, the answer is that the domesticated
beast secures at least the main advantage of nutrition and
reproduction, whilst the cultivated plant may be said to secure
everything it would wish, if it could wish for anything. Like
enlightened merchants, they have found their own advantage in
supplying the needs of others ; or perhaps they are more like
the unenlightened, who do so unconsciously or even in spite of
themselves. And another answer is that there is no law of
nature that in symbiosis the advantages of the partnership must
be equal. Parasitism may be considered as a kind of symbiosis
in which they certainly are not so.

But, it may be said, breeders have never formed two species
out of one but only varieties which are always capable of inter-
breeding. The objection would have more weight if any one
could tell us what a species is. It is not denied that the
differences between domestic varieties of dogs and pigeons are
far more than enough to have constituted them separate species
or as some say even genera, if they had been found in a state of
nature ; whilst as for sterility, there are plenty of hybrids to
prove that it is not an essential but only an accidental feature ol
natural species ; and on the other hand, Darwin gave evidence

THE LOGIC OF DARWINISM 543

of the occurrence of sterility between varieties, evidence which
he considered it " impossible to resist." There is therefore, in
point of sterility, no real distinction between genus, species and
variety and the objection fails. The classification of animals
and plants depends or ought to depend always on the number
and extent of the differences in that assemblage of characters
which constitutes the organism as a whole, the degree of sterility
constituting only one difference among many.

It is probably in Darwin himself that the original source of
the error is to be found and I may fitly close my argument with
a condensed quotation from the Origin of Species which should,
I think, at the same time effect the final removal of any obscurity
about the point I have endeavoured to establish. The passage
occurs in Darwin's exposition of the principle which he " called
for the sake of brevity * Natural Selection,' " in the summary of
the fourth chapter : " If organic beings vary at all in the several
parts of their organisation and if there be, owing to the high rate
of increase of each species, a severe struggle for life at some age,
season or year, it would be an extraordinary fact if no variation
ever had occurred useful to each being's own welfare in the
same manner as so many variations have occurred useful to
man. But if useful variations do occur, assuredly individuals
thus characterised will have the best chance of being preserved
in the struggle for life and from the strong principle of inherit-
ance they will tend to produce offspring similarly characterised."
1 need hardly say, 1 do not quote this most moderate statement
for the purpose of dissent but my comment is this : that the
" many variations " which " have occurred useful to man " in
domesticated plants and animals are by that very fact *' varia-
tions useful to each being's own welfare," since they have given
"the individuals thus characterised the best chance of being
preserved," as is shown by the fact of their preservation and
such individuals do " produce offspring similarly characterised,"
so that the variations can be and have been accumulated from
generation to generation to produce an indefinite amount of
change. If this be so, the preservation of favoured races in the
struggle for life by means of Natural Selection and the con-
sequent production of new and more specialised forms widely
differing from the old is not a theory but an experimentally
proven fact.

THE MEASUREMENT OF OSMOTIC
PRESSURE BY DIRECT EXPERIMENT

By T. martin LOWRY, D.Sc.

A. Osmosis and Osmotic Pressure

As long ago as 1748 it was discovered by Nollet that a flow of
water took place through a membrane of pig's-bladder separating
alcohol from water. This observation was forgotten during
more than half a century, until it was redescribed in 1802 by
Parrot/ who also detected a similar flow when urine was used
instead of alcohol. Parrot recognised that a flow of liquid took
place simultaneously in both directions but that the velocities
differed so widely that a pressure might be developed, on one
side of the membrane, equivalent in some cases to a column
of water not less than 10 ft. in height. Quantitative measure-
ments made by Dutrochet (1827), to whom we owe the terms
exosmose and endosmose and by Vierordt (1848) showed that
the rate of flow depended on the nature of the membrane, on the
concentration of the solution and on the temperature; but
the factors determining the flow were too complex to allow of
any simple statements of the laws governing osmosis. One
of the first generalisations to be attempted was suggested by
Jolly in 1848, when he brought forward evidence to show that
a fixed ratio existed between the exosmosis or outward flow
of the salt through the membrane and the endosmosis or inward
flow of water into the solution. This ratio, the "endosmotic
equivalent," he supposed to be independent of the concentration
but further investigation showed that this was not the case.

Equally little progress was made when experiments were
carried out to determine the maximum " head " of liquid which
could be driven up by the osmotic flow of water into a solution.
It is true that one factor, the frictional resistance of the
membrane to the endosmotic flow, was now eliminated ; but
so long as an exosmotic flow still took place the " head " of

* See Walden, "Die Hauptdaten aus der Geschichte des Osmotischen Drucks
und der Osmotischen Losungstheorie," Bull. Acad. Set., St. Petersburg, 1912.

544

MEASUREMENT OF OSMOTIC PRESSURE 545

liquid or "osmotic pressure" was still dependent on the
individual properties of the particular membrane used. No
real progress could be made until this difficulty was overcome
by the discovery of " semi-permeable " membranes which would
stop completely the outward flow of the solute whilst still
permitting the solvent to pass inwards to the solution and
there develop the maximum osmotic pressure that was possible.
Such membranes were, in fact, discovered by Traube in 1865
in the form of floating films precipitated by the interaction of
two contiguous solutions. Traube then showed that if solutions
of copper sulphate and potassium ferrocyanide are brought
together, a floating membrane of copper ferrocyanide is pro-
duced which is permeable by water but impermeable by both
salts. According to the relative strengths of the two solutions,
water is drawn in one direction or the other through the
membrane which is so displaced that it always forms the
boundary between the two solutions. If the boundary expand
or if the membrane be broken, a fresh precipitate is at once
produced by the interaction of the two membrane-forming
solutions.

But whilst Traube's membranes possessed the property of
being semi-permeable, they were not suitable for quantitative
experiments, as they were incapable of supporting even the
smallest osmotic pressure. Great importance attaches there-
fore to the introduction by Pfeffer in 1876 of methods by
which Traube's membranes could be strengthened by pre-
cipitating them on linen or silk or parchment or best of all
in the pores of an unglazed porcelain battery-jar. With this
equipment, it was possible, for the first time, to make real
measurements of the maximum osmotic pressure set up in a
solution by the inflow of water through a semi-permeable
membrane. Even then, however, very few regularities were
discovered : the maximum pressure was found to be propor-
tional to the concentration of the solution but no indication
was obtained of any law by which the magnitude of the pressure
could be predicted.

B. Van't Hoff's Equation

In view of the obscurity in which the phenomena of osmosis
were involved, it would be difficult to exaggerate the dramatic
effect produced by the discovery, made by Van't HofT in 1887,

546 SCIENCE PROGRESS

that the gas-equation PV = RT could be applied directly to
solutions, if " osmotic pressure " were substituted for " gas
pressure." This remarkable generalisation appeared to illu-
minate a vast range of difficult and puzzling phenomena and
at the time of its introduction it was widely believed that the
problems of osmotic pressure and of solutions had for the most
part been finally solved.

Van't Hoffs conclusions were based on the measurements
which had been made by Pfeffer in the botanical laboratory at
Bonn about the year 1876. They were supported by a con-
sideration of cognate properties, such as the lowering of
vapour pressure and the depression of the freezing-point in
solutions, properties which had been studied by Raoult which
were now shown to be related thermodynamically to the
osmotic pressure. Using the somewhat scanty data then
available, Van't HofT showed that Boyle's Law could be
applied to solutions, since (as Pfeffer had found) the osmotic
pressure was proportional to the concentration of the solute and
therefore inversely proportional to the volume to which it was
diluted in the solution. He next discovered the fact (which
had been overlooked by Pfeffer) that the small temperature
coefficient of osmotic pressure is identical with the corresponding
coefficient in gases, so that osmotic pressure is (like gas-
pressure) directly proportional to the absolute temperature.
Having thus proved that osmotic pressure could be expressed
by the equation PV = RT, he calculated from Pfeffer's data the
value of the constant for a gramme-molecular proportion of sugar
and found that it was identical with the constant of the gas-
equation PV = RT. This equation could therefore be used
equally well to calculate the pressure of a gas or the osmotic
pressure of a solution.

The validity of the equation in the case of solvents other
than water and of solutes other than sugar was deduced from
the substantial identity, in the case of twelve solvents, of Raoult's
** Molecular lowering of the vapour pressure " with figures
calculated from the formula K = M/ioo (K = molecular lowering,
M = molecular weight) and of Raoult's " Molecular depression
of the freezing-point " with figures calculated from the formula
t = 0-02T7W (t = mol. depression, T = abs. temp, of fp., W=
latent heat of fusion) in the case of five solvents. As both
formulae were based on the assumption that osmotic pressure

MEASUREMENT OF OSMOTIC PRESSURE 547

obeyed the gas laws, the agreement afforded further proof of the
numerical agreement between the two sets of phenomena.

It must now be admitted that the evidence on which van't
Hoffs magnificent generalisation was based was of a very
inexact character. Thus, whilst Pfeffer's observations showed a
general tendency for osmotic pressure to increase with rising
temperature, the individual figures pursued a zig-zag course,
departing (in a range in which the whole change of osmotic
pressure was only 10 per cent.) by as much as 3 per cent,
from the smoothed values calculated by van't Hoff. Again,
in using Raoult's '* molecular depressions of the freezing-point "
as confirming his laws of osmotic pressure, van't Hoff^s figures
showed deviations up to 6 per cent., whilst the values for
the " molecular lowering of vapour pressure " showed differences
up to 10 per cent, between the observed and the calculated
values. The situation presents, indeed, many similarities to
the circumstances under which Dalton promulgated his atomic
theory on the basis of data so inaccurate that he was able
to recognise the presence of a single equivalent of nitrogen
both in nitric oxide and in ammonia, two compounds in which
the actual proportions differ no less than 50 per cent. ! But
in each case the generalisation was so bold and far-reaching
that its inherent truthfulness was at once recognised, in spite of
the inexact character of the evidence which could be produced
in its support. In the case of the atomic theory, Berzelius
and Stas carried out series of exact measurements which
established beyond all question the validity of the atomic theory
as an accurate expression of the laws of chemical combination.
In the case of van't Hoff's generalisation, measurements of
similar exactitude, made by Griffiths at Cambridge, proved that
the formula could be applied accurately to calculate the de-
pression of the freezing-point of water by cane sugar and by
potassium chloride at extreme dilutions. But all the accurate
measurements of osmotic pressure that have since been made
have gone to prove that, whilst van't Hoffs law may give
an exact representation of the properties of very dilute solutions,
it fails utterly to express the properties of solutions of even
moderate concentrations and is of value mainly in providing
a base line for the study of the deviations which they exhibit
from the requirements of this law.

The exact measurement of osmotic pressure is therefore

548 SCIENCE PROGRESS

a matter of very great importance both in order to determine
the actual magnitudes of the pressures and in order to provide
data for a theory of solutions which shall be applicable under
conditions other than those of ** infinite dilution."

It may be asserted emphatically that nothing, at the present
time, can take the place of direct measurements of osmotic
pressure carried out with the greatest care and exactitude.
Calculation fails utterly to represent the observations that have
been made : attempts to substitute indirect measurements for
direct measurements are almost equally useless : firstly, because
calculations are required which often involve approximations or
the use of constants of doubtful accuracy ; secondly, because it
is impossible to make isothermal measurements of the freezing-
point or boiling-point of a series of solutions, whilst vapour-
pressure measurements although made isothermally are usually
far from exact.

The foregoing statement will serve to explain the great
interest and importance which attaches to the exact measure-
ments of osmotic pressure which have been made during the
opening years of the present century by the Earl of Berkeley
and his colleagues in England and by Prof. H. N. Morse and his
colleagues in America. The American work, in its general
features, follows the methods used a quarter of a century before
by Pfeffer and will be described as a sequel to his work ; but ten
years of laborious experiment were required before all the main
sources of error were eliminated : the measurements extend
from decinormal to normal concentrations, whilst the range
of pressures is from 2 to 25 atmospheres and the range of
temperatures from 0° to 8o* C. The measurements of the Earl
of Berkeley and Mr. E. G. J. Hartley, which extended the range
of pressures up to 135 atmospheres, were carried out with a novel
type of apparatus, which will be described most conveniently in
the later part of the present article.

C. Pfeffer's Experiments

The experiments described in Pfeffer's Osmotische Unter-
suchungen (Leipzig, 1877) cover a very wide range of
phenomena. Observations were made of osmosis through
membranes of many kinds ; some of them were permeable
to the solute as well as to the solvent, others were permeable to
the solvent only. Experiments were made both on the rate of

MEASUREMENT OF OSMOTIC PRESSURE 549

osmosis under different conditions and on the maximum pressure
that could be set up by the osmotic flow. The most important
experiments were those in which this maximum osmotic pressure
was measured, using as a " semi-permeable " membrane the
precipitated films of copper ferrocyanide first described by

Fig. I.

Traube in 1865. These measurements were carried out with
the cells shown in fig. i.

Rigidity was conferred upon Traube's floating membranes
by depositing them first upon linen or silk but finally in the
walls of a porous battery-jar, a method that has been in use
through thirty-five years of subsequent work and has been proved
to be capable of furnishing membranes strong enough to resist

550 SCIENCE PROGRESS

pressures up to 150 atmospheres.^ The porous pot z was
46 mm. high and 16 mm. wide with walls i\ to 2 mm. thick.
The glass tubes v and / were joined to the porous pot by
two layers of shellac, the upper hard, the lower a little soft,
in order to make a sound joint. The softening of the shellac at
higher temperatures (up to 37°) was compensated by the
addition of a glass ring r filled with cement v/hich held the
apparatus rigidly together and by a layer of the same cement
above the shellac in the joints between v and / ; the cement used
was the well-known mixture of litharge and glycerol. Before
depositing the membrane the porous pot was extracted with
potash and with chlorhydric acid and freed from air by soaking
in water and evacuating with an air-pump. The pot was soaked
during several hours in a 3 per cent, solution of copper sulphate,
rinsed internally with water and partially dried with filter-
papers and by exposure to the air, then filled with a 3 per cent,
solution of potassium ferrocyanide and immersed again in the
copper-sulphate solution. After standing during twenty-four to
forty-eight hours the cell was closed and exposed to the pressure
due to the osmosis of the membrane-forming solutions ; twenty-
four to forty-eight hours later it was emptied, charged with
a 3 per cent, ferrocyanide containing ij per cent, of saltpetre
and exposed to the osmotic pressure of 3 atmospheres which
this solution develops or if necessary to the higher pressure
developed by a stronger solution. Membranes of Prussian blue
were prepared in the same way by using i\ per cent, ferric
chloride outside and 3 per cent, ferrocyanide inside the cell,
whilst membranes of calcium phosphate were prepared from a
3 per cent, solution of calcium chloride and a 6 per cent,
solution of disodium phosphate neutralised with sodium bicar-
bonate. Membranes of ferric hydroxide and ferric phosphate
were also tried.

It will be seen from the description that has been given not
only that Pfeffer's experiments were very extensive in their
range but that they were carried out with very considerable
care. It is, indeed, noteworthy that his methods were adopted
almost in toto by Morse twenty-five years later and that nearly
all the sources of error which the American workers strove so
long and so successfully to eliminate had been recognised (and

^ Pfeffer records pressures up to 436'8 cm., i.e. nearly 6 atmospheres, in the
case of a 3'3 per cent, solution of saltpetre in water,

MEASUREMENT OF OSMOTIC PRESSURE 551

to some extent guarded against) by Pfeffer; in particular, the
German botanist was aware of the errors due to leakage of the
solution through the membrane and to dilution of the solution
by inflowing water ; he saw the importance of using a manometer
of small bore and stoppers of slight compressibility in order to
diminish the inflow and actually invented the method of applying
pressure mechanically in order to reduce this factor to the
smallest possible dimensions.

The osmotic pressures developed in the apparatus were
measured by means of an air-manometer (fig. i) ; this had a
closed limb graduated over a range of 200 mm. and a short open
limb also graduated from the same zero and provided with a bulb
to act on a mercury reservoir. In order to secure rapid adjust-
ment, the bore of the tube was small, about r2 mm. ; the air was
renewed after every five experiments lest water should have
crept into it ; a joint at a, by which the long limb could be
disconnected, also served as a tap by which the manometer
could be cut off from the osmotic apparatus.

As is shown in the figure, the final sealing of the apparatus,
after it had been completely filled with solution, was effected by
fusing the capillary point of the glass tube shown at g ; the tube
g was then forced down a little, in order to hasten the attainment
of a steady pressure and reduce the quantity of water entering
the cell. The inflow of water into the most concentrated
solutions, due to the displacement of 100 mm. of mercury, was
about 0*1 1 c.c. on a total of i6c.c. ;the compression of the rubber
stoppers amounted to 0*05 c.c. at 2 atmospheres and 0*09 c.c. at
4 atmospheres ; but the total inflow can scarcely have exceeded
0*14 c.c. or less than i per cent, when the glass tube g was
pressed down after sealing.

The rubber stopper holding the tube g was wired down when
using higher pressures up to 7 atmospheres. Steady conditions
of temperature were secured by immersing the whole apparatus
in water or in a dilute solution of a membrane-former ; thus a
0*09 per cent, solution of copper nitrate was often used, a o*i
per cent, of ferrocyanide being placed inside the cell to balance it.

The concentrations of the solutions were checked by mea-
suring their densities both before and after they were used for
the osmotic experiments; in the case of sugar solutions the
polarimeter was used to check both the concentration and the
purity of the sugar. The substances examined were cane sugar,

552 SCIENCE PROGRESS

gum arable, dextrin, cream of tartar, Rochelle salt, saltpetre and
potassium sulphate.

D. Morse's Experiments

The experiments on osmotic pressure which have been
conducted at the Johns Hopkins University by Prof. H. N.
Morse and his co-workers have formed the subject of twenty-five
papers published in the American Chemical Journal horn 1901 to ,
191 1. But most of the essential features of the earlier papers
are described, with methods perfected and data corrected, in a
series of five papers which appeared in that journal in 191 1
under the heading '* The Relation of Osmotic Pressure to
Temperature." These five papers will long stand as one of the
monuments of Physical Science and may already be ranked
with the great classics of earlier generations. A sixth paper
dealing with the " Osmotic Pressure of Cane-Sugar Solutions
at High Temperatures " has appeared during the past year and
a further paper on this subject is promised. It will be con-
venient to describe in series the chief features of the apparatus
which enabled the American workers to reduce the measurement
of osmotic pressure from a rough approximation to an exact
routine.

I. The Manufacture of the Cells. — One of the most serious
difficulties in the measurement of osmotic pressure is to secure
suitable porous pots. This difficulty was encountered by Pfefi*er
but became of dominant importance in the more exact work of
the American investigators. At the end of four years they had
secured (from a batch of 100) only two cells with which they
could measure osmotic pressure with some degree of confi-
dence, whilst 25 or 30 answered the requirements moderately
well. A whole year spent in procuring and testing nearly 500
more cells from different makers revealed not one that was
suitable for the work and showed that the problem must be
transferred from the pottery to the laboratory.

The chief faults of the commercial cells were :

(i) Insufficient strength : only a few survived 30 atmospheres,
whilst most of them cracked at pressures below 20
atmospheres.

(2) " Air-blisters," communicating with each other and with
the interior of the wall, which gave rise to a series of
§ubsidiarv membranes in the interior of the wall,

MEASUREMENT OF OSMOTIC PRESSURE 553

(3) Unequal porosity even in the same cell, which caused the
membrane to wander towards the outer wall at every
locality of coarse texture.
The problem of making cells in which all the essential qualities
should be combined was finally solved by avoiding altogether
the use of ground feldspar as a binding material and selecting
as raw materials two natural! clays, one deficient in binding
material the other over-rich in that constituent ; these could
be mixed very intimately and never failed to give products
which were perfect in respect of uniform porosity. The carefully
prepared mixture was packed into a cylindrical steel mould and
subjected during fourteen to sixteen hours to a total pressure of
about 200 tons. From these cylinders cells were turned out on
the lathe, both the chuck and the cutting tools being of special
design ; the difficulty of this operation is shown by the fact that
at first 90 per cent, of the cells cracked in the kiln, a proportion
that has now been reduced by careful working to about 10 per
cent. After baking at about 1300° C. the pots were ground to
take the metal fittings and then glazed inside and out, from
the middle upwards, with a special glaze prepared by adding
sihca and feldspar to one of those used by potters for the better
grades of white tableware.

Fig. 2 shows the complete cell as fitted up for use at the
present time. The cell and the manometer are clamped to-
gether by means of a brass collar (i) and a brass nut (2), the
washer (3) being made of lead. The main brass cone (4) is pierced
with two holes for the manometer tube (5) and for the hollow
needle (6), which are both secured by means of Wood's metal at (7)
and later by a cone of the same metal at (i i). The joint between
the metal fittings and the pot is made by means of a rubber tube
(i2)|wound tightly at the upper and lower ends with twisted
shoemakers' thread (13, 14). The hollow needle (6) is nickel-
plated and brazed into a brass piece (8), which is bored and
threaded to fit the closing-plug (9); the grease-filled leather
packing at (10) makes a tight joint when screwed down.

2. The Manometers. — The form of manometer used in all the
later experiments on the influence of temperature on osmotic
pressure is shown in fig. 3. The bore is very small, from
0*45 to 072 mm. The advantages of narrow tubes are

{a) that the short mercury columns at the top of the
capillary are less liable to be displaced by tapping*

554

SCIENCE PROGRESS

(b) that the compression of the small volume of mercury

which they contain involves but little dilution of the
contents of the cell;

are required.

M (b)

(a) For moderate pressures.
(6) For high pressures.

Fig. 2. — Osmotic cell complete. Fig. 3. — Manometers.

On the other hand :

(d) the meniscus is more troublesome ;

(e) the capillary depression is large and varies so greatly

with the bore of the tube that it can only be deter-
mined by direct calibration;

MEASUREMENT OF OSMOTIC PRESSURE 555

(/) the movement of the mercury is much influenced by
impurities in the mercury or attached to the surface
of the glass.

An improved manometer, specially suitable for measuring
large pressures, has a capillary which is enlarged in the lower
part of the tube to sixteen times the normal sectional area ; this
leaves a much longer column of gas to be measured at the
higher pressures but has not been used in the present series of
measurements. The bulb (3) is intended to prevent the escape
of nitrogen from the calibrated portion of the tube when the
pressure is reduced ; the traps (i) and (2) serve to catch minute
particles of solution which are carried forward by the mercury
during fluctuations of pressure ; these traps effectually prevent
the disaster which results when such particles work their way
into the calibrated portion of the tube, compelling a dismantling
and cleaning of the whole apparatus. The short column of
mercury (4) at the top of the tube serves to prevent contamina-
tion of the nitrogen while the instrument is being closed and
afterwards keeps the gas out of the portion of the tube the cali-
bration of which has been affected to an unknown extent by fusing
off the ends. Two very fine marks are etched on each mano-
meter, one near the bottom of the calibrated portion of the
instrument and the other higher up : these are the only reference
lines, as any attempt at graduation would interfere with the
accurate location of the meniscus. The distance between the
two marks is known, so that when one is out of sight in
the bath, readings can be taken from the other line and then
referred back to the first.

The tubes are selected from large batches of the best
commercial qualities, one end of each selected tube being
marked and cut off so as to be available for sealing on to the
manometers if and when required. The tube is then calibrated,
either in a vertical or in a horizontal position or both, by means
of (a) a short thread of mercury of known weight, which is
measured in a series of positions along the tube and (b) a long
thread which fills the tube between the reference marks near the
ends of the tube and which is also weighed. The two weighings
do not give the same figure for the weight of mercury per
millimetre of the tube because of the curvature of the meniscus ;
but from the difference the volume-error due to the meniscus
can be calculated and applied to the subsequent readings of

556 SCIENCE PROGRESS

the manometer. The meniscus error thus determined is only
about three-fourths of that calculated for spherical surfaces ;
this may be due to the actual shape of the meniscus or perhaps
to a tendency to read the columns too short ; in either case the
same factors would probably appear in the reading of the
manometers and would be eliminated by taking the corrections
as found experimentally rather than by calculation. The
correction for the meniscus amounts to 0*141 per cent, in
decinormal solutions increasing to 1*07 per cent, in normal solu-
tions ; but it is believed that the difference of 25 per cent, between
the experimental and the calculated corrections is much greater
than the actual error in this correction ; in any case the
meniscus error is insignificant when dealing with temperature
coefficients.

The capillary depression of the mercury was determined by
direct comparison of the readings in the tube with those of a
wide tube into which mercury was driven up from the same
reservoir. The correction amounted to as much as 18 mm. or
0*023 atmosphere and was one of the most fertile sources of
error, since no relationship could be traced between the varia-
tions of capillarity and variation of bore. The same apparatus
was used to determine the volume of purified nitrogen finally
introduced into the manometer tube after sealing on to the bulbs,
etc., shown in fig. 3. In each case it was found that increased
errors appeared when using a calibrated tube or manometer
as a standard for direct comparison : in this case the readings
were affected by errors due to the irregular capillarity in both
instruments and it was found desirable (in spite of the increased
labour involved) to regard each manometer as an independent
standard. The labour involved in this essential and difficult
work is illustrated by the statement that " the whole time of
one of the authors of this paper is given up to the study of the
manometers which have been or are to be used in our measure-
ments of osmotic pressure."

3. The Regulation of Temperature. — Questions of exact regula-
tion of temperature are of altogether exceptional importance in
the measurement of osmotic pressure. In nearly every kind of
physical work it is sufficient that uniformity of temperature
shall prevail throughout the apparatus at the moment when
the readings are taken. But in dealing with osmotic
pressure any temporary fluctuation of temperature produces

MEASUREMENT OF OSMOTIC PRESSURE 557

effects which may persistduring many hours or even days after
the temperature has again been brought under control. This
must necessarily be the case, since the cooling of the cell
diminishes the volume of the contents, reduces the internal
pressure and permits v^ater to enter the cell, thereby causing
a local dilution which may persist during several days. Con-
versely, if the cell becomes heated when a condition of
equilibrium has been attained, the expansion of the contents
will drive water from the cell and concentrate the solution ; if
the dense concentrated liquid should sink to the bottom of the
cell, much time must be allowed for it to rise again by diffusion
and ultimately regain its normal concentration.

Similar conditions prevail when the cell is first closed.
Not only must pressure (approximately equal to the osmotic
pressure expected) be applied immediately to prevent water
from entering the cell and diluting the contents but this must
be done at the right temperature. The whole of the apparatus,
solutions, water, etc., must therefore be kept in a thermostat in
readiness for setting up.

The " thermometer-effects " due to fluctuations of temperature
were eliminated by using a series of thermostatic devices to
control the temperature of large water-baths and air spaces.
These were all constructed on one common principle : water or
air is passed rapidly (i) over a continuously cooled surface, then
(2) over a heated surface which is more efficient but is under the
control of a thermostat, (3) thence into or around the space
occupied by the apparatus, again over the cooled surface and
so on. Figs. 4 and 5, which show the thermostatic devices used
in the actual measurements of osmotic pressure, are typical of a
dozen such baths used for various purposes.

Fig. 4 shows the water-bath containing the cells. The
cooling surfaces 3, 8, 7, etc., are supplied with water from
the hydrant cooled, when necessary, before entering the bath
by passing it through a coil immersed in ice. The heating
surfaces 9 and 10 contain sockets for four lamps the current
through which is controlled by the mercury thermostat at i.
By means of the propeller shown on the left of the figure,
water is drawn out of the bath through the pipes 12 and 13,
brought back again through the pipe 14 and distributed through
the bath ; whilst outside the bath, in the short curved pipes
leading from 12 and 13 to 14, auxiliary gas-heating can be

S58

SCIENCE PROGRESS

applied to the water, when working at the higher tempera^'
tures, leaving only a small balance to be provided by theji
regulated electrical heating. Ample provision was made foil
driving enough water through the bath to keep the tempera-^
ture uniform from end to end : usually a circulation of 400 litresl
per minute was found to be ample. 4

Fig. 5 shows the arrangement of the air-space above th^
bath. This is provided with a system of pipes 7 throughl
which cold water can be circulated, a system of pipes m
through which either hot or cold water can be circulated and!
a series of four shaded lamps 3, 4, 5, 6, controlled by the!
mercury thermostat 10. A fan 9 driven by a motor providesi

Fig. 4. — Thermostat containing osmotic cells.

a vigorous circulation of air and also serves to keep the
manometers continually agitated.

Special apparatus has recently been introduced to secure a
steady temperature exactly at 0° but this need not now be
described in detail.

4. The Membranes. — The first membranes were formed in
the interior of the cell-walls but it became clear that with a
membrane so located it would not be possible to measure
osmotic pressures. In such a cell the minute pores between
the membrane and the inner wall would be choked with water,
which would require very long periods of time before it could
be displaced by the solution ; moreover, any temporary dilution
or concentration of the liquid in the pores, due to the displace-

MEASUREMENT OF OSMOTIC PRESSURE 559

ment of water through the membrane, would produce effects
which might last for a very long time. It was therefore
necessary to form the membrane on the inner wall of the cell,
an effect which could easily be produced by diminishing the
diameter of the pores. When, however, the texture was too fine
the membrane was not satisfactory, probably because it was
rooted with insufficient firmness to adhere properly to the
surface : it was also difiicult to develop a good membrane on a
cell from which an old membrane had been cleaned off.

The first step in preparing the cell was to displace the air in
the pores by water. This was effected by " electric endosmose."

Fig. 5. — A r-space above cells.

The cell was filled with a 0*005 normal solution of potassium
sulphate and was then immersed in a similar solution to
the lower edge of the glazed portion. By passing a current
inwards through the cell, water was drawn in continuously :
the cell was then rinsed and soaked and the same process
repeated with distilled water. In the later work, lithium
sulphate was substituted for potassium sulphate, as it was
found that " the quantities of water carried through the porous
walls of a cell, under identical conditions, are inversely propor-
tional to the relative velocities of the various kathions divided
by their respective valencies."

To deposit the membrane, the cell was set up with a
36

56o SCIENCE PROGRESS

cylindrical platinum kathode inside and a cylindrical copper
anode outside. Simultaneously, the interior was filled with
N/io ferrocyanide and the outer space with N/io copper sul-
phate. An electric current under a pressure of no volts was
applied during two or three hours until a maximum resistance
was reached, the interior being rinsed out with fresh ferro-
cyanide every two or three minutes to remove the alkali set
free by the electrolysis. The cell was then rinsed and soaked
during one to three days and the process repeated. It was
found essential to deposit the membrane at a temperature not
lower than that at which the cell was to be used ; similarly
it was advisable to measure the osmotic pressures first at
higher and afterwards at the lower temperatures. The mem-
branes were tested with weight-normal sugar solutions, with
membrane-formers of N/io concentration, the course of the
meniscus in the manometer being carefully watched to detect
irregularities of motion due to the breakage and repair of the
membrane in the pores. The electrolytic treatment and tests
were repeated over and over again until the behaviour of the
cell was satisfactory, the membrane-formers in the osmotic
tests being finally reduced to o'oi osmotically normal concentra-
tion. The minimum time required to form a cell was a month
but the operation often occupied three or four months, all the
essential operations being carried out in thermostats. In testing
the membranes it was not sufficient to secure steady pressures :
no reliance was placed upon a cell in which the maximum
pressure for the given concentration was not developed. When
the cell had been passed as satisfactory, no experiment was
accepted in which the concentration of the solution was not
perfectly maintained. This was found to be no mere ideal but
a test that could be applied rigidly to every measurement
recorded. In one experiment, a cell, not specially selected,
a constant pressure of 12*522 atmospheres was maintained during
sixty days, the range of fluctuation being almost exactly equal to
the range of atmospheric pressures during this period.

In a new cell the maximum osmotic pressure might be
reached in as little as six hours ; in an old cell, with a greatly
thickened membrane, as much as ten days might be required.
The old membranes were perfect in their osmotic qualities but
were rejected because of their slow action. This rendered
them tedious to use and greatly increased, the lag in recovering

MEASUREMENT OF OSMOTIC PRESSURE 561

from "thermometer effects" and "barometer effects" due to
small changes of temperature (rarely exceeding o'02° C.) and to
variations of atmospheric pressure ; these effects were very
serious in the case of dilute solutions, which could only be
examined in cells provided with the newest and most active
membranes and in periods of steady barometric pressure. The
problem of constructing a manostat for use in these experiments
is under consideration.

The most serious disaster in the whole course of the work
was an infection of the laboratory with Penicillium glaucum dur-
ing rebuilding operations on a lower floor, which necessitated^the
constant use of antiseptics during the whole of the subsequent
four years. The precautions used suggest the practice of a
bacteriological rather than of a chemical laboratory. The two
germicides which were most effective in destroying the spores
without injuring the membranes were thymol and gaseous
prussic acid ; all the solutions used in the measurements were
sterilised by the addition of thymol to o'ooi normal concen-
tration, saturated solutions being used for storing the cells
during the vacation. The mould seems to feed upon the
membranes. The first evidence of infection is usually the fact that
membranes which were previously rendering satisfactory service
show signs of leaking and fail to recover their fully semi-perme-
able character when resubjected to the membrane-forming process.

5. The Measurements. — The main results of the measurements
are summarised in Tables I. and II.

The upper part of each table shows the final measurements of
the osmotic pressure of cane-sugar solutions between 0° and 25°
as carried out in the years preceding 191 1. In this range the
ratio of osmotic pressure to " gas-pressure " is absolutely steady,
so that Gay Lussac's law may be applied rigidly. The observed
osmotic pressures exceed, however, the corresponding gas pres-
sures by an amount that ranges from 6 to 1 1*4 per cent. The ratios
in the case of the decinormal solutions rise in a somewhat
surprising manner and there is a further remarkable rise when
solutions of this concentration are examined at 0° ; as this is
within o"2° of the freezing-point of the solution it is possible
that the effect is in some way due to the polymerisation of the
solvent.

The lower part of the two tables shows the measurements
that have been made during 191 1 at temperatures above 25°

562

SCIENCE PROGRESS

1-1

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MEASUREMENT OF OSMOTIC PRESSURE 563

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564 SCIENCE PROGRESS

These measurements required the construction of a new series
of thermostats and were very costly in other ways on account of
the extreme brittleness of the heated glass. Thus whilst the
measurements at 30° were begun with an equipment of sixteen
manometers, the preparation of which had cost more than a
year's labour, not less than twelve of these were put out of
commission, half of them permanently, during the course of the
work between 60° and 80°.

The results, however, are both striking and important. As
soon as 25° is passed the ratio of osmotic pressure to gas
pressure begins to drop (in the case of the more dilute solutions
with perplexing rapidity), the result being that, in the case of
each of the ten concentrations examined, this ratio falls to unity
at some temperature below 80° C. In the case of the decinormal
solution this equality is maintained over the range from 30° to
60°; in the case of the more concentrated solutions, experiments
now in progress will show whether the ratio remains constant
at unity or whether it diminishes to some smaller figure.

E. Lord Berkeley's Experiments

The experiments of the Earl of Berkeley and Mr. E. G. J.
Hartley " On the Osmotic Pressures of some Concentrated
Aqueous Solutions" are published in the Philosophical Tran-
sactions for 1906 (A. 206, 481-507). Two additional papers " On
the Osmotic Pressures of Aqueous Solutions of Calcium Ferro-
cyanide " are published in the 1908 and 1909 volumes {Phil.
Trans. y 1908, A. 209, 177-203; 1909, A. 209, 319-36). Of these
three papers the first two dealt with osmotic pressures from 13
to 133 atmospheres, the third covered the region from 15
atmospheres downwards. It will be seen that the work on
concentrated solutions takes up and extends to regions of much
higher pressure the type of observation that was being made
by Mjrse and Eraser in America. In this region of high
pressures a considerable range of substances was examined,
including a number of metallic ferrocyanides. Most of the
measurements were made at one temperature, 0° C, the object
of the experiments being to determine the absolute values of the
osmotic pressures and not the temperature coefficients.

The Osmotic Apparatus. — This was of a different type from|
that used by Pfeffer and by Morse. The chief novelty consisted

MEASUREMENT OF OSMOTIC PRESSURE 565

in placing the membrane and the solution on the outside of a
porous tube instead of on the inside of a porous pot. The
apparatus is shown in Fig. 6.

AB is a porcelain tube, 15 cm. long, 2 cm. external diameter
and 1*2 cm. internal diameter with glazed ends, CC is a gun-
metal cage against the ends of which the dermatine rings DD
are compressed when the parts E and F of the outer gun-
metal vessel are screwed together, thus making a tight joint
with the tube. Another dermatine ring X provides a tight

Fig. 6. — Osmotic apparatus complete.

joint between E and F and allows the solution in EF to be com-
pressed without leakage. The water inside the porcelain tube
is enclosed between rubber stoppers KK, carrying the brass
tubes LL and compressed between the washers MM and the
nuts NN. One of these brass tubes carries a glass funnel and
tap, the other an open glass capillary or water-gauge, graduated
in millimetres and calibrated ; this capillary serves to show the
rate of flow of water through the membrane, either from
the water inside to the solution outside or under high
mechanical pressure from the solution to the water. Two

566

SCIENCE PROGRESS

curved metal tubes VV of larger diameter are clamped against
the ends of the brass case EF, the joint being made tight by a
rubber washer. The case EF is filled and the pressure trans-
mitted through the aperture at R, whilst the aperture at S
serves to empty the vessel.

The Pressure Apparatus. — The pressures were measured by
means of a dead-weight standard pressure-gauge, fig. 7. This
has two plungers, one supporting a series of weights, whilst
the other, actuated by a screw and wheel, compresses the
"steam cylinder" oil which lies between them. The plunger
supporting the weights, which forms the pressure-gauge of the
instrument, was kept slowly rotating by hand whenever it was
in use. The apparatus can be worked up to 136 atmospheres

• J f=cM>^

Fig. 7. — Pressure apparatus.

but as the sensibility is about 0*12 atmosphere throughout, the
percentage error is increased greatly at low pressures.

The Semi-permeable Membranes.— T o deposit the membranes
the porcelain tube was placed in a solution of copper sulphate
(50 grammes in a litre) in a desiccator and the air exhausted
during several days until no more bubbles appeared from the
tube ; the tube was then removed, wiped inside and out and
allowed to dry during three-quarters of an hour. After closing
the ends of the tube with rubber plugs carrying glass rods, it
was plunged with a spinning motion into a solution of potassium
ferrocyanide (42 grammes in a litre), allowed to soak and then
set up for electrolysis, the current being passed from a copper
electrode immersed in copper sulphate solution inside the tube
to a platinum electrode immersed in a ferrocyanide solution
outside the tube ; the platinum electrode was enclosed in a
porous pot to prevent the alkali liberated there from attacking

MEASUREMENT OF OSMOTIC PRESSURE 567

the membrane and the solution in the pot was frequently
changed. When at the end of about two hours, the resistance
of the tube had risen to a steady value, the tube was washed
and soaked with distilled water, during about ten days, until
every trace of copper sulphate had been washed away.

After washing, the loose ferrocyanide was rubbed off with
pumice-stone and the membrane remade electrolytically at
intervals of a few days until the resistance of the tube rose to
some 50,000 ohms. The tube was then tested in the osmotic
apparatus with a solution of cane sugar containing 660 grammes
in a litre and giving an osmotic pressure of about 100 atmo-
spheres. After washing, remaking and testing several times,
steady values for the osmotic pressure were reached; but
out of some 100 tubes of various makes which were tried only
two reached the highest state of efficiency, although over 400 elec-
trolyses were made. As a great improvement was effected when
the membranes were exposed to pressure, a special apparatus
was devised in which the electrolytic deposition of the
membrane could be carried out under a pressure of 130
atmospheres outside the tube and atmospheric pressure inside.
It was also found to be a great advantage to deposit the
membranes at 0° C. and to keep them at 0° C. until required for
measurements at this temperature.

The Measurements. — Three operations were involved in the
measurement of the ** equilibrium pressure," i.e. the hydrostatic
pressure which was required exactly to balance that set up
by osmosis.

{a) Guard-ring leak. As the semi-permeable membrane is
never quite on the surface of the porcelain tube, it is impossible
to get perfect contact between it and the dermatine packing ;
there is therefore always a leakage of the compressed solution
past these guard-rings. This leakage would not matter but for
the fact that the hydrostatic pressure on the solution gradually
diminishes as it oozes out until it finally escapes under a
pressure that is only atmospheric. Minute portions of the
membrane are therefore in contact with uncompressed solution
and through these water is steadily drawn from the tube into
the solution. This effect was reduced by making the guard-
rings overlap the ends of the tube and its magnitude was
rendered constant by filling the metallic extension-tubes VV
with solution so as to provide an ample reservoir of uncom-

568 SCIENCE PROGRESS

pressed solution. The extent of the guard-ring leak was
determined by filling the extension-tubes VV with solution
whilst the rest of the apparatus was charged with water both
inside and outside the membrane. In the final series of experi-
ments the guard-ring leak was reduced, from a rate equivalent
to that produced by a pressure of 2 or 3 atmospheres on
the solution, to a rate equivalent to only about 0*15 of an
atmosphere and therefore almost negligible.

(b) Determination of the turning-point. The chief operation
was to determine the pressure at which water just ceased to be
drawn from the porcelain-tube into the solution and com-
menced to flow in the opposite direction. After measuring the
guard-ring leak at 0° the space surrounding the porcelain-tube
was emptied, rinsed with solution and filled as quickly as
possible. The apparatus was then immersed again in ice and
pressure gradually applied by increments of about 10 atmospheres
until within 10 per cent, of the equilibrium pressure, when
smaller increments were applied at longer intervals until the
rate of flow was almost exactly equal to the guard-ring leak.
During the process of filling and before the pressure was
applied a small quantity of water was drawn through the
membrane into the solution, giving rise to a film of slightly
diluted solution on the surface of the tube ; by applying
pressure gradually in the manner described the excess of water
was driven out again and the solution restored to its original
concentration without damaging the membrane. Measurements
of the rate of flow with pressures a little above and a little
below the turning-point were made at intervals of an hour or
more until it was clear that a definite and steady value had
been reached.

(c) Solution-leak. At the close of the experiment the
apparatus was taken down but in such a way that the porce-
lain tube and its contents remained intact. After two days the
water in the tube was washed out and the sugar-content deter-
mined, this process being repeated until no more sugar could be
extracted from the interior of the tube. No attempt was made
in the later experiments to apply a correction for the greatly
reduced leakage of solution, which seemed to have no regular
influence on the " turning-point " : instead, all experiments were
rejected except those in which the leakage of sugar was proved
to be less than 0*0003 gramme, a stringent test which eliminated

MEASUREMENT OF OSMOTIC PRESSURE 569

all measurements except those made with two tubes of pre-
eminent excellence.

The Numerical Results. — The figures obtained in the measure-
ments of concentrated solutions were as follows :

Cane sugar

Dextrose

Galactose

Mannitol

• •

(recovered

) i

Concentration.

G/litre.

1 801
300*2
420-3
540-4
660-5
750-6

99-8
199-5
319-2
448-6
548-6
250
380
500
500
100
no
125

1395
26-77

43*97
67-51

100-78

13374
13-21
29-17

53*19

87-87

121-18

35*5
628

95-8
97*3
13*1
14-6
16-7

Pressure in

atmospheres.

12-45 (calc.)

51-9 (calc.)

The results are shown graphically in fig. 8, in which the
diagonal lines show the values calculated from van't Hoff's
equation.

Experiments on Calcium Ferrocyanide. — The experiments on
calcium ferrocyanide, published in 1908 and 1909, are note-
worthy as extending the measurements of osmotic pressure to
aqueous solutions of salts. In the case of the more concentrated
solutions the osmotic pressure was correlated with the vapour
pressure by means of a thermodynamic formula. In a formula
put forward by Prof. A. W. Porter the compressibility of the
solution and solvent were taken into account and these quan-
tities were therefore measured but deviations amounting to 2\
per cent, were found between the calculated and observed
values. A modified equation was therefore developed in which
the thermodynamic cycle was calculated for operations carried
out under atmospheric pressure instead of in a vacuum. The
deviations were then reduced to less than 0*5 per cent. ; but it
is noteworthy that the correct assumptions to be made in
working out the thermodynamic cycle were only determined

570

SCIENCE PROGRESS

after direct measurements of osmotic pressure and of vapour
pressure had been made. Here again then practice has served
as a guide to theory and direct measurements have alone proved
adequate to justify the validity of the formula in which the
thermodynamic relationships find expression.

In the paper on weak solutions of calcium ferrocyanide direct
measurements of osmotic pressure were correlated with measure-
ments of electrical conductivity. Once again the conditions

(a) Cane sugar.

lOO

c
u

1 25

500

ConcenCra/tion» in gra.mmes fser
liCrc of ooluCioi

150 300 450

ConcentrAtions in grammes per
litre of soluOion.

150 500 -tso 600

ConceriCr<a,tion» m grammes per
liCrg^ of solution.

''^^^

0 ■ i

ConcenC.ration& m ^r».mrr\Q^ per
li&re of solution.

{V) Dextrose. (</) Mannitol.

Fig. 8. — Influence of concentration on equilibrium pressure.

were too complex to be expressed by the simple formulas
usually applied to such solutions ; but with the help of the new
observations it was possible to find suitable assumptions by
means of which the experimental results could be expressed and
formulated.

F. Theoretical Considerations

On comparing the exact measured values of the osmotic
pressures, as recorded by Morse and by the Earl of Berkeley,
with those calculated from van't Hoffs equation, the latter is

MEASUREMENT OF OSMOTIC PRESSURE 571

seen to be capable of giving only a very approximate expres-
sion of the actual facts. In his latest paper Morse has shown
that at temperatures higher than atmospheric each solution in
turn reaches a point at which a modified form of van't Hoft's
equation gives a correct value for the osmotic pressure but it is
not yet clear whether this agreement is only momentary or
whether it persists over a large range of higher temperatures.
At temperatures from 0° to 25° the deviations recorded by Morse
amount to 6 to 12 per cent, even when using the modified form
of van't HofFs equation, whilst Lord Berkeley has recorded at
the freezing-point an osmotic pressure nearly three times as
great as the values calculated from the equation in its original
form.

The various attempts to calculate the osmotic pressures
of cane-sugar solutions are summed up by Findlay {Scientia
191 2) in the following table for 20° C. :

Table III

Weight
normal

Volume
normal
concen-
tration.

Osmotic
pressure
observed.

Osmotic pressure calculated according to
thermodynamic equation.

Error.

concen-
tration.

Van't
Hofr.

Morse.

Neglecting:
hydration.

Assuming
6H2O.

O'l
02

0-3
0-4
0-5
0*6
0*7
0*8
0-9

i*o

0*098
0*192
0*282
0*369
0-452
0-532

o*6io
0*684
0*756
0-825

2*59
5*06
7*61
10*14
12*75
I5'39
18*13
20*91
23*72
26*64

2'34

4'59

674

8-82

10-81

12*72

14-58
16-36
i8*o8
1973

2*39
478

9-56

11*95

I4'34
16*73
19*12
21*51
23*90

2*38
476
7-14

11*87
14*24
16*59
i8'94
21*29
23*64

2*40

7*40

12*54

17*93

23*52
26*42

0*19

0*21

0*20

0*20
0*22

The concentrations are shown (i) in gramme-molecules per 100
grammes of water and (2) in gramme-molecules per litre. The
observed osmotic pressures are shown in the third column,
whilst the remaining columns show the values calculated by
means of four different formulae.

Van't Hoffs equation PV = RT may be thrown into the form

RT RT n RT

RT n_

Vo N

V " Vo N ~ Vc

in which V° is the molecular volume of the solvent and x is the
ratio of the number of gramme-molecules n of the solute to

172 SCIENCE PROGRESS

the number of gramme-molecules N of the solvent in a givei
volume.

This equation is valid only for very dilute solutions an(
utterly fails to represent the experimental figures, e.g. in th<
case of the normal solution the observed and calculated figurei
are in the ratio 3 : 2 approximately.

The thermodynamic equation v^hich expresses the properties
of an ideal solution over the whole range of concentration takes
the form

P=^{-loge(i-^)}

= Y^-^ {i +i-^ + i-^ • • .}

This gives the figures shown in the sixth column. These
agree quite closely with those calculated by Morse from a
modified form of Van't Hoff's equation in which the con-
centrations are reckoned in gramme-molecules of sugar per 1000
grammes of water instead of per 1000 c.c. of solution. Morse's
equation may be written in the form

^ ~ Vo Vl - ;ir/

The close agreement of the values in columns 5 and 6 is
accounted for by the fact that the two equations differ only
by \x^ -\- \x^ . . . , quantities that are not important except at
very high concentrations.

But neither Morse's equation nor the thermodynamic
equation is completely satisfactory, as both are inaccurate to
the extent of some 10 per cent, throughout. The thermo-
dynamic equation is based on the assumptions that solvent and
solute mix without liberation of heat or change of volume
to form an incompressible solution in which the components
are present in their normal molecular form, without association,
dissociation or combination. Such a description cannot be
applied to a solution of cane sugar in water and ample ex-
planations are here forthcoming to account for the breakdown
of the thermodynamic formula. Foremost amongst these is the
explanation suggested by Morse and Eraser, that the sugar at
low temperature probably forms hydrates which break down
when the temperature is raised. The figures given in the seventh

MEASUREMENT OF OSMOTIC PRESSURE 573

column have been calculated on the assumption that the sugar
in the solution is present as C12H22O11, 6H20.^ A remarkable
result is seen on studying the list of errors tabulated in
column 8 ; although the calculated and observed figures are
even nov^ not in agreement, the error is quite steady through-
out at o'i9, 0*21, 0*21, o'20, 0*20, 0*22 atmosphere ; such a result
indicates that a formula has at last been arrived at which
expresses the properties of the solutions perfectly, with the
exception that some factor, the nature of which is still un-
disclosed, increases the observed values by one-fifth of an
atmosphere above those which have been calculated for the
hydrate C12H22O11, 6H2O.

In the above pages, the opinion has been asserted that
direct measurements of osmotic pressure are of such vital
importance that the enormous labour that has been expended
upon them has been both legitimate and fruitful. If the de-
tailed story of these arduous experiments serves to bring
home to readers some idea of the motives that inspired the
workers and of the difficulties that they had to overcome, the
purpose of the writer will have been fully carried out.

* The figures given by Findlay are for 5H2O ; his corrections have been
increased in the ratio 6 : 5 to give the figures tabulated in column 7 of the table.

THE COMPARATIVE ANATOMY OF THE
INTERNAL EAR IN VERTEBRATES

By R. H. BURNE

Every one is familiar with the streak, known as the lateral Hne,
upon the sides of fishes ; it can be observed any day upon the
fishmonger's slab. But it is perhaps not so universally known,
though a matter of common knowledge to any one at all
acquainted with comparative anatomy, that this line and
similar ones upon the head and face shelter a series of
cutaneous sense organs, of simple structure but unfortunately
at present of enigmatical function, known collectively as the
" organs of the lateral line."

In all probability it is in this system of sense organs of the
skin, peculiar to aquatic vertebrates, that we must look for the
birthplace of the ear. For in the first place, we have some
evidence ^ of a rough similarity in function between the two ;
in the second, there are certain anatomical peculiarities,^ par-
ticularly of the nerve supply, that indicate beyond all reasonable
question that the ear and the lateral-line organs belong to one
and the same sensory system and that the ear is only a lateral-
line sense organ specially set apart and so refined as to act, in the
first place, as an equilibrating organ for recording alterations
in the position of the body ; in the second, though possibly
only among terrestrial vertebrates, as an auditory organ
sensitive to vibrations of the surrounding medium too subtle
to be felt by the sense organs of the skin.

In this article an attempt is made to give a general idea of
our present knowledge, based upon the work of Retzius,^ of the
more important changes of structure that have accompanied
this elaboration and refinement of function.

To grasp the significance of the individual steps in the
process — for often the changes are in themselves insignificant —

* Parker, Bull. Bureau Fisheries^ 24, 1904, p. 185.

* Beard, Zool. Anz. vii. 1884, p. 142 ; hytxs^Jour. Morph. vi. 1892, p, i.
' Retzius, Das Ceh'67'organ der Wirbelthiere^ Stockholm, 188 1-4.

574

THE INTERNAL EAR IN VERTEBRATES 575

it is essential to have a working plan of the form and relative
positions of the different parts of the finished product to which
the evolutionary process has eventually led. Such a plan is
presented in fig. i, in which the chief parts of the left internal

fiXTETRNAL AMPULLA
ANTERIOR AMPULLA

LIG SPIRALS

Fig. I. — Left membranous labyrinth of man, seen from the mesial aspect.

The endolymph labyrinth has been left white, the cavities of the perilymph labyrinth dotted, A section is
supposed to have been cut out of the cochlea, to show the arrangement of the three cavities, scala
media or cochlear canal, scala vestibuli, scala tympani. (Based on Schoenemann.)

labyrinth of man are shown diagrammatically from the mesial
aspect. The diagram is based on the figures in Schoenemann's
atlas checked by a preparation of the human membranous
labyrinth made by Dr. Albert Gray and now in the Museum of
the College of Surgeons and by sundry preparations of the
37

576 SCIENCE PROGRESS

bony labyrinth. In studying this chart-diagram it is in the first
place essential to realise that in the membranous labyrinth
there are two absolutely distinct structures enclosed one
within the other. The inner part known as the endolymph
labyrinth is the actual sense organ — the seat of the sensory
elements in connexion with the filaments of the otic nerve. It
is left white in the diagram. The outer part (the perilymph
labyrinth^ forms a sheath to the endolymph labyrinth fitting it
tightly or loosely in different parts. In the diagram it is
represented as partly opened, its cavity being dotted.

This perilymph sheath is really no part of the sense organ
at all but is simply a portion of the mechanism by which
vibrations are conducted to the sense organ. The distinction
between these two parts cannot be too clearly recognised, for
in higher vertebrates and particularly in the cochlea of
mammals, parts of the outer sheath are so intimately blended
with the enclosed endolymph labyrinth that it is difficult
without reference to their past history as revealed by com-
parative anatomy to realise that they are not integral parts of
a single organ.

The endolymph labyrinth apart from its peril3^mph casing
can further be conveniently divided for study into two regions
physiologically distinct, the one, which forms practically the
entire labyrinth in aquatic vertebrates, being an organ for
equilibration, the other (peculiar to terrestrial vertebrates)
being specialised for audition. In fig. 2 these regions are
respectively represented by the parts of the labyrinth known
in man as vestibular — that is the semi-circular canals, utricle,
saccule and (in lower vertebrates) the lagena — on the one hand ;
and the cochlear canal or pars basilaris lagenae (the scala media
cochlece of human anatomy), on the other.

In tracing the evolution of the vestibular or equilibrating
part of the labyrinth, it will be unnecessary to consider the
perilymph sheath, for this only comes into prominence in
terrestrial vertebrates as an accessory to the auditory organ.

In every endolymph labyrinth, except only those of the
Lampreys and Hag-fishes, there are certain constant features
subject of course to minor variation but always recognisable.
Three semi-circular canals surmount and open into the saccular
chambers that form usually the bulk of the labyrinth. Each
canal has always at one end a swelling (fig. 2, AMP.) crossed

THE INTERNAL EAR IN VERTEBRATES 577

transversely by an upstanding ridge of sensory epithelium —
the canals and sensory ridges being so set that each lies
approximately in one of the three planes of space.

Upon the walls of the saccular chambers are three sensory
areas (fig. 2, dotted areas in Rec. utr., Sacculus and Lagena)
each covered by an otolith or mass of calcareous matter and
stated to lie, like the sense organs of the semicircular canals,
approximately in the three planes of space.

Act' tMOOUYMi

MACUt/^

ANT« CANAU

ANT: AMP-

HEC: UTR-.

N vn-R'SACC

PQST- fV T«UNK

Fig. 2. — A schematic left endolympli labyrinth seen from the mesial aspect, showing
all the chief structures ever found in this organ.

The nerve endings are dotted. The whole labyrinth, except the pars basilaris, constitutes the equilibrating
labyrinth (vestibular of man). The recessus utriculi, sacculus and lagena contain the three otolith
organs. The sense organ of the pars basilaris {viae, das.) constitutes the organ of Corti.

There are thus in the typical vestibular labyrinth two sets
of three sense organs so arranged that the members of each
set are aligned with some sort of accuracy in the three planes
of space — an arrangement approximating to that theoretically
the best for response to movements in any direction.

And as a matter of fact there is a mass of experimental
evidence from 1828 onwards^ to show that these sense organs
are concerned primarily in response to changes in the position

* Flourens, Mem. Ac. R. Sci. Inst. France\ t. 9, 1828, p. 455.

578 SCIENCE PROGRESS

of the body— the sense organs in the canals being probably
stimulated by the impingement against them of the fluid in the
canals displaced by rotational movements of the head, the
otolith organs being, in a similar way, stimulated by the drag or
pressure of the otoliths upon them during movements in direct
lines or through alteration in the resting position of the body.^

In land vertebrates, as we shall see later, an additional
sense organ arises between the sacculus and its lagenar appen-
dage (fig. 2, Mac. bas.) and undergoes progressive elaboration
to form in conjunction with parts of the perilymph system a
special auditory organ independent of the vestibular parts of
the labyrinth.

Such an organ as the above typical endolymph labyrinth,
even before the advent of the cochlea, is obviously very far
removed from a simple lateral-line sense organ but the relation-
ship between the two can be traced in the early development
of the ear.

At its first appearance ^ the ear, like many other epidermal
sense organs, is a little superficial thickening. Further growth
transforms this into a pit, w^hich sinks deeper and deeper into
the mesodermal tissues, becoming a long-necked flask, like one
of the isolated lateral-line organs of the skin, with a single area
of modified epithelium to represent the sense organ. This
may be considered to represent the lateral-line stage of the ear.

In most cases the flask now becomes nipped off* from the
surface and begins to develop characteristics peculiar to the ear.

The first indication of anything distinctive is the formation
of a narrow fold along the upper border of the vesicle.^ This
is the budding canal system and heralds the formation of the
two canals that lie in the vertical planes. The horizontal canal
in almost all cases appears later. This sequence in the canal
formation is particularly interesting, for in the few cases (Hag-
fishes and Lampreys) where there are only two canals, it is the
horizontal canal that is missing.*

Variation in the form and relative length and width of the
semi-circular canals is decidedly capricious ^ ; frequently a canal

* Lee,/(9«r. Physiol. 15, 1894, p. 311, and 17, 1894-5, p. 192.

* Krause, Handbuch der Entwicklungslehre^ L. 4 and 5, 1893.

' Krause, Arch. Mikr. Anat. Bd. 35, 1890, p. 287 ; Fleissig, Anat. Hfte. 37,
1908, p. 69.

* Tretjakoff, Anat. Anz. 32, 1908, p. 165.
' Wulf, Arch.f. Anat. 1901, p. 57.

THE INTERNAL EAR IN VERTEBRATES 579

does not even lie in the same plane throughout its length but
takes a sinuous course between one end and the other. The
facts, so far as we have them, seem to suggest that the course,
length and width of a canal are not of vital physiological im-
portance, provided that the sensory ridges and the stretch of
the canals leading to them are accurately aligned at right angles
to one another and in the three planes of space. The rest of
the canal, if approximately in the same plane, serves its purpose
by facilitating the flow of the endolymph across the sensory
ridge when the head rotates.

In the lowest fishes — the semi-parasitic Hags — the saccular
chamber into which the two ends of the combined vertical canals
open is single and has a single sensory area covered by a single
mass of calcareous material.

But in all other fishes most if not all of the chambers and
sense organs normal to the vestibular labyrinth are recognisable.
Interesting stages in the separation of the different parts may
be observed in many Sharks and other fishes, especially in the
Lamprey,^ the general tendency being towards a more complete
isolation of the different sense organs. In the Wolf-fish and
some other teleosteans, this tendency may, in fact, be carried
to such an extreme that the sacculus and lagena are completely
cut off and lie more than half an inch away from the rest of
the labyrinth.

Above the lowest fishes, all parts of the vestibular labyrinth
can be traced either in adult or embryonic life throughout the
whole Vertebrate Class, although in some cases one part, in
some another, may suffer degeneration. In all, however, there
are the three semi-circular canals lying in approximately the
same relative positions ; and in all, except in mammals other
than the monotremes, there are three sensory areas covered
by calcareous material.

In comparing the whole labyrinth of a fish with that of man,
for instance, it is plain that although in the fish all parts of the
human labyrinth except the cochlea are represented, they are
represented in excess, being vastly larger and more complete.
The vestibular or equilibrating labyrinth in man and all higher
vertebrates is, in fact, to a certain extent degenerated. This
fact requires some explanation if it indicate a diminution of
efficiency, for it entails no apparent loss of balancing power,
* Krause, Anat. Anz. 29, 1906, p. 257.

580 SCIENCE PROGRESS

One can only suppose, as has been suggested by some physio-
logists, that it is a more or less direct result of the greater
share taken in equilibration among higher vertebrates by sense
organs, other than the ear, of improved efficiency and power of
co-ordination.

On the other hand, when we consider the fact that in fishes
there are only those parts of the ear present to which, by
common consent, powers of equilibration alone are ascribed,
we are confronted by the interesting question whether it is
to be expected or rather whether there is any evidence to
show that fishes have any true sense of hearing, seeing that
in their ear there is no structure at all comparable to that by
which this function is performed in terrestrial vertebrates.

This is a question that has exercised the minds of naturalists
since very early days. It was one of the problems that engaged
John Hunter ^ in the eighteenth century but it appeared then
far more simple of solution than now, for it was taken for
granted that, if fish were sensitive to noises, the labyrinth, from
its resemblance to the human ear, without question must be the
organ affected ; further, no distinction was drawn between
coarse mechanical vibrations that can be felt and true molecular
sound vibrations that can only be heard.

Hunter attempted to solve the problem as presented to
him by a very simple experiment and was quite satisfied with
the result.

While serving with the army in Portugal, he chanced to be
watching a pond in which Gold-fish were swimming. To test
their sensitiveness to sound, he got a friend who was with him
to fire a gun screened from the fish by some bushes. No sooner
was the gun fired than the fishes .vanished into the mud at the
bottom of the pond.

Now this and similar experiments show that fish are sensitive
to shock or jar but that is all. They give no clue to their power
of true hearing nor as to whether the labyrinth is the organ
affected and if so what part of it is the actual receptive organ.

Since Hunter's day, experiments have been carried out with
the object of answering these questions but so far with per-
plexing and inconclusive results.

A few abstracts from some recent work on the subject will
show the position.

^ Hunter, Phil. Trans. 72, 1782, p. 379.

THE INTERNAL EAR IN VERTEBRATES 581

In 1895 KreidP made some experiments upon Gold-fish from
which he concluded that the fish ear was not sensitive to sound
or indeed to any vibration but that coarse vibrations were felt
by the skin.

He tested the fishes by means of vibrating rods plunged into
the water of the tank and with instruments of various sorts
sounded in the air. None of these vibrations elicited the least
response but the slightest jar to the water was responded to at
once — the response being quite independent of the presence or
absence of the ear but dependent on the full physiological
activity of the skin.

Similar results as to the total insensitiveness to musical
tones were obtained in 1907 by Lafite Dupont^ and Korner.^
Various kinds of fishes were tested with tuning-forks and
instruments specially constructed not to produce tangible
vibrations.

Thus it would seem to have been fairly settled that fishes
could not hear in the true sense of the word.

On the other hand Parker^ and subsequently Bigelow^ ob-
tained results from Minnows and Gold-fish the precise opposite
of those got by Kreidl. They found that the fish responded to
the vibrations of a tuning-fork when the ear was intact but that
when the ear was rendered inactive by cutting the otic nerve all
response ceased in spite of the fact that the skin remained in full
working order.

This is a surprising want of harmony in results obtained
by similar experiments upon the same species of fish. It can
perhaps be explained, as suggested by Bigelow, by the practical
difficulties that bar the removal of the whole ear by the method
of extraction used by Kreidl. And if, as seems likely, the lower
saccular chambers (sacculus and lagena) were left behind in his
experiments, his conclusion that the ear has no part in vibration
perception is vitiated.

All these experiments were performed on fish in captivity
and therefore in a somewhat abnormal state; but, in 1903,
Zenneck ^ carried out some very careful experiments upon fish

^ Kreidl, Arch.f. Physiol. 61, 1895, p. 450.

^ Lafite Dupont, C.R. Soc. Biol. Paris ^ 63, 1907, p. 710.

^ Korno^r, Arch, kydrobiol. Stuttgart, 2, 1906, p. 9.

'* Parker, Bull. U.S. Fish Co7nmissson, 22, 1902, p. 45.

^ Bigelow, A?ji. Nat. 38, 1904, p. 275.

® 2enneck, Arch. Physiol. 95, 1903, p. 346.

582 SCIENCE PROGRESS

living their ordinary natural life. The essential points of his
experiments were (i) the use of fish in their natural environ-
ments ; (2) the use of a powerful source for the sound (a bell
some 17 cm. in diameter); (3) great care in shielding the water in
which the fish were swimming from heavy mechanical vibrations
set up by the bell ; (4) the location of the source of sound in the
water.

The results of his experiments showed that the fish were
sensitive to the sound of the bell within a radius of some 8 to 10
yards.

Anyhow, after Parker had succeeded in satisfying himself
that the ear was sensitive to vibration, in 1908 he proceeded to
try to locate the actual receptive organ. ^ Taking the Squeteague,
a fish in which the sacculus is of very great size, he attempted
to put the great saccular sense-organ out of action by pinning
the otolith away from the sensory epithelium. Under these
conditions nearly all response to vibration was lost. Parker
therefore concluded that the otolith organs were the seat of a
vibration sense.

Further confirmation that the otolith organs respond to
sound is furnished by an important experiment by Piper.^
When the otoliths are exposed in the severed head of a Pike
and brought within range of the sound of a pipe, electrical
changes occur in the otic nerve such as are normally associated
with the passage of a nervous stimulus.

In addition to the above direct experimental evidence of a
generalised and dull auditory power in fishes, there is evidence
of an indirect circumstantial character that also points to the
same conclusion.

In the first place, many fishes, ^ particularly among the
Sciaenidae, Siluridae and Triglidae, make sounds which are quite
distinctive and sometimes remarkably loud. Possibly, in some
cases, these sounds are the by-products of some other
activity ; they may also be accompanied by mechanical vibra-
tions that can be felt. Whether the fish are also sensitive to the
true sound vibrations, it is almost impossible to say; the fact
that they make them, often as a secondary sexual action, favours
the assumption that they are also sensitive to them.

^ Parker, Bull. Bureau Fisheries U.S.A. 28, 1908.
' Piper, Miinch. med. Wochenschr. 53, 1906, p. 1785.
^ Tower, Annals JV.Y. 4-cad, Set, xviii. 1^08, p. 14^..

THE INTERNAL EAR IN VERTEBRATES 583

Then there are also those peculiar and intricate connexions
between the swim-bladder and the ear that are to be found
in Carps, Siluroids, Herrings and a few other bony fish.
These certainly, by their structure, suggest an organ for trans-
ference of vibrations. Though it is of course held by many,
including some, like the late Prof. T. W. Bridge, who have
made a very special study of these connexions, that they are
hydrostatic and serve to inform the fish of the condition of
tension in its swim-bladder and therefore of its depth in the
water, it should be borne in mind that they occur mainly in
bottom freshwater fishes who can have comparative little oppor-
tunity for alterations, in the depth at which they swim so great
as to be a vital matter. Unsatisfactory as the present condition
of the question of hearing in fishes undoubtedly is, the general
trend of the above evidence suggests that fishes are sensitive,
through the ear, to shock and jarring vibrations of any sort and
are also to some extent capable of hearing true sounds if the
sounds are sufficiently loud and are originated in the water.
The actual receptive organs for vibration are probably the
otolith organs.

We must now consider certain modifications that arise in
connexion with the equilibrating ear that ultimately lead to our
own organ of hearing — the cochlea and organ of Corti.

The first appearance of these modifications coincides with
the adoption of a terrestrial mode of life, which is quite what
one would expect, seeing that in air sound plays an infinitely
more important part in life than can be the case in the relatively
profound silences of the sea. It is not, therefore, matter for any
surprise that the organism responds to its new conditions and
attempts to form an organ more sensitive and accessible to
sound vibrations than is the deep-seated labyrinth of the fish.

This object has been attained by modifications in three
directions :

(i) By the formation of a direct path by which vibrations
may reach the capsule within which the ear lies (the tympanic
apparatus).

(2) By the provision of efficient means for directing the
vibrations after they have entered the ear capsule to certain
definite nerve endings.

(3) By an elaboration of the nerve endings themselves.
Pealing with the aeqonc} pf these Jipes of modification,

584 SCIENCE PROGRESS

it will be found that invariably the process has been of a
similar character.

Provision is always made by means of an open and definite
perilymph cavity for a direct and unimpeded passage for
vibrations between an opening in the outer skull wall (^fenestra
ovalis) and a similar opening elsewhere in the wall of the otic
capsule. This perilymph passage at a certain definite spot
or spots is separated from the cavity of the endolymph labyrinth
by tense drum-like thinnings of the labyrinth walls and near or
on these thinnings there is a nerve-ending which becomes very
highly specialised in the higher though simple in the lower
groups.

Thus in the simplest and most direct way provision is made
for unimpeded movements of the fluid around the endolymph
labyrinth and for the transference of these movements from the
perilymph to the endolymph at certain definite spots.

In the labyrinth of a fish, except for a thickening beneath the
sensory areas, the walls of each particular region are of fairly
uniform thickness or at least there is no sudden change from
thick to thin.

In the amphibia this is not so.^ Among them, except in the
lowest purely aquatic Urodeles, certain restricted areas of the
endolymph labyrinth wall are thinned down to the lining
epithelium, whilst around them the walls are suddenly thickened
like a frame.

These framed thinnings in the wall of the endolymph
labyrinth are the first sign of an auditory organ.

In amphibia where they first appear, there are three of them
which almost might be spoken of as tentative experiments in the
manufacture of an auditory instrument, for one of them only has I
apparently stood the test of experience, the one namely that
is situated in a special dilatation between the saccule and
the lagena.

This dilatation {pars basilaris lagence)^ with its thin area
stretched like a drum-head in its frame, at its first appearance
is inconspicuous enough but though so insignificant for the
moment, it is potentially of the very highest importance, for
it is from this paltry rudiment that the human cochlea with its
intricate powers of hearing has been evolved.

There is at first sight little in the structure of the pars
^ Harrison, Internat, Monthly Jour. Ami. 19, 1902, p. 221,

THE INTERNAL EAR IN VERTEBRATES 585

basilaris lagence of the amphibian to suggest the great coiled
cochlea that dominates the labyrinth of the mammal. But close
inspection in the light of a knowledge of this part of the ear in
reptiles and birds leaves no doubt that even when it first
appears, this pars basilaris has in it in rudiment some of the
most essential peculiarities of the cochlea.

In man and other mammals the cochlea, as every one knows,
consists throughout almost its entire length of three fluid-filled
channels — a central one (scala media) wedged in between two
others {scala vestibuli and S. tympani) (fig. i). The central
channel is a direct process of the endolymph labyrinth. It
is triangular in cross section, with the apex directed to the axis
of the cochlear spire, its base applied to the surrounding bony
envelope, one side (morphologically the outer) covered by the
scala vestibuli and the other (morphologically the mesial)
covered by the scala tympani. This third side consists partly
of a bony shelf [lamina spiralis) projecting from the axis of the
spire and partly of a thin membrane (membrana basilaris) tensely
stretched throughout the whole length of the cochlea between
the edge of the bony shelf and a corresponding fibrous ridge
{ligamentum spirale) projecting from the wall spoken of above as
the base of the triangle. Covering the axial half of the basilar
membrane is a strip of sensory epithelium of peculiarly intricate
structure, known as the organ of Corti.

These, from the point of view of comparative anatomy,
are the essential characters of the scala media or cochlear canal.

The two other scalae {S. vestibuli and tympani) are in open
communication at the apex of the cochlea. The scala vestibuli
is a continuation of the general perilymph space that lies
between ^the oval window and the vestibular parts of the
endolymph labyrinth. Just short of the tip of the scala media,
it passes into the scala tympani, which follows the scala
media to its base and there terminates in contact with the
membrane-covered round window. Near the round window
the scala tympani is connected with the brain cavity by a narrow
tube {canalis perilymphaticus). (Fig. i, Aqued. peril.)

The fluid in these two continuous perilymph scalae is thus
in a position to respond readily to every swing of the stapes in
the oval window and to transmit its movements to the sense
organ in the scala media. In fact these perilymph scalae are
parts of the mechanism for the transmission of vibrations to th^

586 SCIENCE PROGRESS

sense organ quite accessory to the sense organ itself. For our
present purpose the essential things to note are (i) the tense
but thin basilar membrane stretched from end to end of the
scala media, in a rigid frame (figs, i, 2, Mbr. bas.); (2) the
close relations of the basilar membrane to the brain cavity
and the exterior through the mediation of a definite perilymph
space {scala tympani).

These two characters are in fact the only ones to suggest
that the pars basilaris of the Amphibia is a cochlea in the
making. There is in this group of vertebrates no scala vestibuli
and no organ of Corti but there is a thin circular basilar
membrane framed in a cartilaginous thickening of the surround-
ing walls, and applied to the exposed (i.e. mesial) surface of this
basilar membrane is a little perilymph sac {scala tympani)
(fig. 3, amphibian, P. bas., Sc. tymp.) which is in close con-
nexion with the brain cavity and with the exterior on the one
hand and on the other by means of a tortuous but definite
tube (fig. 3, D. PLPH) with a great vestibular perilymph space
(Sp. sacc. fig. 3) lying between the fenestra ovalis (fig. 3,
f. ov) and the sacculus. At present there is no prolongation
of this vestibular perilymph chamber upon the outer surface
of the pars basilaris — no suggestion in fact of a scala vestibuli.
The sense organ of the pars basilaris at present lies near
but not upon the basilar membrane.

In this primitive condition of the auditory organ, there are
none of those refined peculiarities of structure that we are
accustomed to associate in the cochlea of higher vertebrates
with a power to analyse compound musical notes. There is no
specialisation of the sense organ such as we see in the organ of
Corti, no fibred structure of the basilar membrane and no
regular variation in size and number of the various elements of
which the different parts are composed. It is thus very doubtful
whether we should be justified in regarding these modified
tympanal areas in the endolymph labyrinth of the amphibia,
with their associated perilymph chambers, as anything more
than mechanisms for focussing vibrations upon certain sensory
areas.

But although we can scarcely credit amphibia, on structural
grounds, with a musical sense, there is every reason to suppose
that differences in the rapidity or complexity of the vibrations
beating upon the sense organs in the ear produce recognisable

THE INTERNAL EAR IN VERTEBRATES 587

differences in the character of the stimulations transmitted to
the brain.

Apart from any question of sound analysis, it is well recog-
nised that frogs have a very shrewd power of discrimination,^
as they respond with the greatest alacrity to the croaking of
their own species, whilst to other sounds even of the most
varied and alarming or seductive description they may remain
to all appearances deaf.

Among reptiles the cochlea makes great strides towards per-
fection. In the lowest forms it is scarcely present at all, in
crocodiles it is practically the same as in a bird. In all, however,
even the lowest, there is one very significant change : the sense
organ of the pars basilaris lies on the basilar membrane. This
is a difference that marks a distinct step towards the perfection
of the cochlea and possibly means the initiation of an entirely
new mode of stimulation. In any case, whatever the precise
physiological meaning, it is one of the distinctive anatomical
characters of the organ of Corti as opposed to an ordinary
sense organ of the labyrinth that it should rest actually upon a
thin, tense and probably vibratile membrane in the direct path
of vibrations passing across the scala media, not upon the sur-
rounding thick and stationary wall of the labyrinth.

In the further evolution of the cochlea, two tendencies may
be observed — one leading towards an increase in the length and
complexity of the scala media, particularly as concerns the
basilar membrane and the sense organ, the other making for
greater simplicity ^ of the perilymph spaces. The tendency to
elaboration results in an increase in the number and a regular
variation in the size of the sensory elements and of the various
structures associated with them ; the tendency to simplification
of the perilymph spaces ensures that the sense organ is sus-
pended in the direct and unimpeded path of movements
originating at the fenestra ovalis.

In reptiles the cochlear canal or pars basilaris lagenae can
be found in any condition between that of a lowly amphibian
and that of a bird. In different genera of snakes and lizards it
and its sense organ show a progressive increase in length cul-
minating in the tubular and slightly twisted cochlea of the

* Courtis, Am. Nat. 41, 1907, p. 677 ; Yevkes, /our. Comp. Neurol. 15, 1905,
p. 279.

' Gray, Proc. Roy. Soc. 80, 1908, p. 507.

SS3 SCIENCE PROGRESS

crocodile, with its long basilar membrane stretched in a corre-
spondingly elongated cartilaginous frame.

In all the reptiles, with the possible exception of the crocodiles,
the changes in the structure of the cochlea are apparently
quantitative rather than qualitative. The sense cells still have
the diffuse arrangement of those of an otolith organ. They
show no regularity in disposition or variations in size, nor
are they supported in any peculiar manner. In fact the sense
organ has as yet assumed none of the special features of the
organ of Corti.

It is curious how bird-like the cochlea of the crocodile is. It
stands quite apart from that of other reptiles and shows many
peculiarities of structure, insignificant in themselves but of the
greatest interest as the shadowy rudiments of important struc-
tures still to come. Thus, the basilar membrane is not only long
but differs in width in different parts and contains a layer of
stretched diagonal fibres ; the elements in the sense organ show
a distinct tendency towards orderly linear arrangement and a
structural differentiation amongst themselves ; the membrane
floating above the sense organ (tectorial membrane) is now for
the first time anchored along one edge to the supporting frame
of the basilar membrane, stretching out hood-like over the
surface of the sense organ.

All these slight changes are worthy of the closest attention
for they are in embryo characters peculiar to the cochlea in its
more perfect developments and indicate the rise among the
higher reptiles of an auditory organ not simply sensitive to
sound but probably to some extent capable of resolving com-
plex tones into their components and thus of judging the
musical quality of sound. Here in fact for the first time, in the
crocodiles and birds, we meet with an auditory organ of some-
thing the same kind as our own.

Although the cochlea in mammals is always unmistakably
mammalian, in the monotremes it has not yet shaken off all
traces of the reptile. While these traces are just in process
of elimination we may digress for a moment to reconsider and
complete their history.

The first is a small sense organ to which we have not
hitherto alluded. It is known as the macula neglecta (fig. 2, Mac.
ngl.) and was discovered by Retzius in many fishes. Although
present in most fishes, it reaches the height of its importance in

THE INTERNAL EAR IN VERTEBRATES 589

amphibia, where it is related to one of the experimental auditory
organs mentioned above. In reptiles and birds it again sinks
into insignificance ; in monotremes and possibly other mammals ^
it appears for a moment in the embryo ; in the adult it has gone.

Another interesting organ that disappears (at least function-
ally) in the mammals is the lagena. This chamber with its
otolith organ is first separated off from the sacculus among the
sharks. It is a conspicuous object in the labyrinth of bony fish.
In amphibia and most reptiles it still holds its own against the
encroachment of the growing pars basilaris which intervenes
between it and the sacculus. In birds it has become a mere
terminal appendage of the now preponderant pars basilaris. It
is still present as a sense organ in adult monotremes but in
other mammals it persists merely as the non-nervous tip of the
cochlear canal — a functionless vestige.

Other reptilian characters may be recognised in peculiarities
of the perilymph scalae and will be referred to again later.

Stripped of these surviving relics, the mammalian cochlea
very closely resembles that of man. Differences occur in the
length of the cochlear canal and in its mode of coiling^ but in all
essentials there is great uniformity and this is nowhere more
apparent than in the detailed structure of the sense organ — the
organ of Corti.^

This organ, which is absolutely characteristic of the ear of
mammals, has an extremely elaborate and definite construction
into which it is needless to enter now. It must suffice to em-
phasise certain essential peculiarities.

The cells that compose this sense organ have an absolutely
regular disposition. The sensory hair cells are set in parallel
rows from end to end of the cochlea.

All the elements — the sensory hair cells, the supporting
cells, the " Pillars of Corti " — increase regularly in both number
and size from the base of the cochlea to the apex. A similar
increase is noticeable in the size of the tectorial membrane that
floats above the sense organ and in the breadth of the basilar
membrane and therefore in the length of the transverse cords
of which it is composed.

^ Alexander, /^;za Denkschr.^ Bd. VI. Th. 2, 1904; Stutz, Morph. Jahrb. 44,
1912.

^ Gray, The Labyrmth of AIam??tals, vol. i. 1907, 22.

' Kolmer, Arch, tnikr, Anat, 70, 1907, p. 695, and 74, 1909, p. 259.

590 SCIENCE PROGRESS

These peculiarities are probably extremely important parts
of the mechanism by which complex tones are resolved into
their components and are essential to the due performance of
the higher functions of hearing. But before entering further
into this question we must return and study for a moment the
evolution of the perilymph spaces connected with the cochlea —
the scala vestibuli and tympani.

As mentioned above, the history of the perilymph spaces is
essentially one of simplification, as pointed out by Dr. Gray.
When we left these spaces in the amphibia (fig. 3, amphibian),
there was only a little rudiment of the scala tympani pressed
against the mesial surface of the basilar membrane but as yet no
signs of a scala vestibuli on the outer surface of the pars
basilaris. The scala tympani was nothing but a slight pro-
trusion from the side of a tube (fig. 3, D. PLPH.) that connects
the great perilymph chamber lying between the saccule and the
oval window (fig. 3, Sp. sacc.) with the cranial cavity and the
exterior. In reptiles the arrangement is essentially the same
(fi^- 3> reptilian) except for the advent of a scala vestibuli (Sc.
vest), which is represented by a downward prolongation of the
saccular perilymph chamber upon the outer surface of the pars
basilaris or cochlear canal. The two scalae, although present,
are not connected directly through their apices but indirectly
through the perilymph duct and the saccular perilymph chamber.

In crocodiles, so far as our information goes, in birds,
certainly, there is a direct connexion, though an imperfect one,
by means of a loose spongework of tissue that surrounds the
apex of the cochlear canal (fig. 3, Bird) and is in open connexion
with the cavities of both scalae. As soon as this direct con-
nexion appears the indirect connexion through the perilymph
duct is lost. Finally in monotremes a free passage (fig. 3,
monotreme, HLCTR) is opened up between the apex of the scala
vestibuli and the apex of the scala tympani and the two scalae
become a continuous tube running down the outer surface of
the cochlear canal from the vestibular perilymph space (foramen
ovale) and up the mesial surface to the foramen rotundum.

The loss of the perilymph duct in crocodiles and birds,
however, is not complete. A considerable part, somewhat
swollen, remains between the scala tympani and the cranial
cavity and the exterior (foramen rotundum), forming a definite
perilymph sac (fig. 3, SAC. PLPH). Very pronounced traces ol

THE INTERNAL EAR IN VERTEBRATES 591

SP-6ACC

SaCC Pl-PH

AMPH I BlANf

r ov

SC ; VEST

LIZA R D

VST

HLCTR;

^. OV;

ftC ■ V»T,

Bird

monotreme

SC vfcT

CARNIVORE

MAN

Fig. 3, — Four diagrams, based mainly on Mr. Harrison's and Dr. Gray's papers, illus-
trating the transformation of the perilymph spaces in Amphibia, Reptiles, Birds, and
Mammals.

The perilymph spaces are dotted, the endolymph labyrinth white. In each case the ear is the left in section,
seen from behind. The scala media of the cochlea is marked P. has (in amphibian), Cock. can. in the
rest ; the saccular chamber, SP. SACC. ; the connexion with the brain cavity, AQ. PLPH, or AQ. PL.
The open connexion between the two perilymph scalae in Monotreme is marked HLCTR.

this sac are present in adult raonotremes and it may still be
recognised in many of the lower mammals, sinking gradually
38

S92 SCIENCE PROGRESS

more and more into the general body of the scala tympani, till
at last the connexions with the brain cavity {canalis perilymph-
aticus) and the exterior {foramen rohmdum) become sessile upon
the wall of the scala tympani itself.^

So from the very simplest beginnings, by gradual elabora-
tion of the sense organ and simplification of the path by which
vibrations may reach it, our ear has reached its present form.
It is, however, one thing to pick a complex piece of mechanism
to pieces, quite another to explain its working. And that is
just the present position. The structure of the ear is fairly
well known, its action is still very obscure. At present there
are two classes of theory by which it is sought to explain the
mechanism of hearing: by one (the telephone theory) the
vibrations transmitted to the cochlea are supposed to act upon
the sense organ as a whole and the resolution of complex sound
is referred to the brain, by the other (the resonance theory)
the preliminary sorting is done by the ear. By the various
resonance theories, amongst which that of Helmholtz still holds
the field, the analysis of complex sounds is supposed to depend
on the sympathetic vibration of some part of the cochlea to each
particular note and the selective stimulation of corresponding
sensory cells of the organ of Corti.

Such theories rest upon the ordered distribution and
regular increase in length, size and number of the various
elements of the cochlea to which reference was recently made,
which is such a striking and remarkable feature in the anatomy
of this organ.

The parts most frequently regarded as the resonators are
the parallel cords lying in the basilar membrane upon which
the sense organ (the organ of Corti) rests, like piano-wires
stretched between the lamina spiralis and ligamentum spirale
(fig. I, Membr. bas.). Those cords that by their length and
degree of tension are in tune with any particular note vibrate in
unison with that note and tap the sensory hairs of the sense
cells resting upon them against the lower surface of the tectorial
membrane that floats like a hood above them.

This is the theory.
. Recently it has been questioned seriously whether the
basilar membrane and organ of Corti are by their structure
capable of acting as they should do upon this theory and

^ Gray, Froc. R. Soc. 1908, p. 521.

THE INTERNAL EAR IN VERTEBRATES 593

certainly a formidable array of difficulties can be raised on the
anatomical side.

It has, for instance, been said that the basilar membrane in
all its parts is too thick and too narrow^ to be set in sympathetic
vibration by sound, although as a matter of fact a model of the
basilar membrane, an indiarubber sheet 0*5 mm. broad, has
been made to vibrate in sympathy with a tuning fork. There
seems, therefore, to be no physical reason why the basilar
membrane should not be thrown into sympathetic vibrations
but recent histological research^ raises doubts whether the
fibres of the membrane are sufficiently free to vibrate inde-
pendently. Instead of lying more or less isolated and free in a
homogeneous semi-fluid bed, they are now shown to be bundles
of fibrous tissue loosely felted together at all points and thus
quite incapable of the individual movement generally assumed
to be necessary to satisfy the demands of the Helmholtz
theory.

But supposing the fibres are capable of sufficient individual
movement, it is maintained that their vibration would im-
mediately be damped by the soft tissues that cover both
surfaces^ of the basilar membrane.

Yet further objections may be urged with regard to the
number of the cords.

For the theory to hold good, it is necessary that there should
be fibres in sufficient quantit}'- and of sufficient variation in
length to resonate to every distinguishable note. Now we can
fairly gauge the hearing limits of certain birds by their powers
of mimicry. The parrot^ in particular has obviously an
extremely critical and discriminative ear with great appreciation
of the quality of sound. But in its cochlea there are only
some 1,200 cords in the basilar membrane^ with little or no
variation in length except towards the extreme base. Here
undoubtedly is a very formidable difficulty to the Helmholtz
theory, at least among birds.

Supposing, however, that the basilar membrane in mammals
is capable of doing all that is required of it under the theory, it

* Shambaugh, Am. Jour. Anat. 7, 1907, p. 247.

* Hardesty, Am. Jour. Anat, 8, 1908, p. 156.
' Kishi, Arch. ges. Physiol. 116, 1907, p. 121.
*■ Denker, Biol. Col. 26, 1906, p. 600.

^ In man there are some 24,000.

594 SCIENCE PROGRESS

has been shown recently that many of the elements that com-
pose the organ of Corti are more firmly united than was
supposed, too firmly to be capable of any individual movement ^ ;
finally it has been pointed out that in the pig parts of the sense
organ, apparently fully formed and functional, rest upon bone
and not upon the basilar membrane at all.^

All explanations of the working of the cochlea are so purely
a matter of speculation that it is necessarily difficult to prove
whether this or that objection is fatal to the Helmholtz or any
other theory.

Of course if a physicist can show that a membrane of the
size and thickness of the basilar membrane cannot possibly
vibrate in sympathy to musical tones there is an end of the
matter so far as it is concerned.

But short of this, the other objections just mentioned,
although matters for serious consideration, do not seem to be
necessarily fatal.

By a modification of the Helmholtz theory, Dr. Gray^
shows very conclusively that for the basilar membrane to act
as a resonant analyser, it is not by any means necessary that
single or even small groups of cords should alone vibrate for
each perceptible note.

On the contrary every note would produce sympathetic
vibration in a more or less extensive area of the basilar
membrane ; but in this area the part most accurately in tune
with the particular note would be in maximum vibration and
would give to the whole stimulation the colour of that par-
ticular note.

Although we may say, I think, that the Helmholtz theory
or some variant of it still holds the field as the orthodox ex-
planation of the action of the cochlea, an alternative resonance
theory, based on the structure of the tectorial membrane, has
recently been revived.

Prompted by the structural difficulties to the Helmholtz
theory that have just been mentioned, certain anatomists^ in
Japan and America insist that the tectorial membrane by its

^ Hardesty, Am. Jour. Anat. 8, 1908, p. 157.
^ Shambaugh, Am, Jour. Ajtat. 7, 1907, p. 247.
^ Gray ^ Jour. Anat. and Physiol. 34, 190x3, p. 324.

* Kishi, Arch.ges. Physiol. 116, 1907, p. 112 ; Shambaugh, Am. Jour. Anat. 7,
1907, p. 245 ; Hardesty, Am. Jour. Anat. 8, 1908, p. 109.

THE INTERNAL EAR IN VERTEBRATES 595

position, variation in size, fibrillar structure, low specific
gravity and extreme flexibility, is better fitted than the basilar
membrane to respond to every vibration of the endolymph and
to be set in motion in its different parts in sympathy with
notes of different rapidity and they maintain that it, not the
basilar membrane, is the active agent in the stimulation of
the sense-cells of the organ of Corti. The sense-cells do not
strike the tectorial membrane but the tectorial membrane strikes
the sense-cells.

The actual mode of stimulation of the auditory organ must
for the present remain undecided. There is, however, one and
that a fundamental question upon which it is possible to speak
with more certainty. There is evidence, both clinical and
experimental, to show that the cochlea is in itself, in some
way, a mechanical analyser of sound. For it is certainly
affected in different parts by notes of different pitch.

In cases of partial deafness (deafness to particular notes) it
has been shown by post-mortem examination that particular
parts only of the organ of Corti are destroyed.^ When the
deafness is to notes of high pitch it is the basal parts where
the elements of the cochlea are at their smallest and shortest,
when to notes of low pitch, the apical.

Similar results have recently been obtained by direct experi-
ments upon guinea pigs.^ Guinea pigs kept during long periods
under the influence of one note were found to have part of the
organ of Corti destroyed. The higher the note the nearer the
base of the cochlea was the spot.

One can therefore conclude with some degree of safet}^ that
the cochlea is the organ by which complex sound vibrations are
mechanically sorted and analysed. The perception and appre-
ciation of the results of this analysis depend of course upon
the brain. The ear can only furnish the brain with the raw
material of assorted stimulations; it depends upon the brain
by its innate powers and by practice to realise and appreciate
the shades of difference there are between these stimulations.

* Bezold, Z^-Z/j. /. Psych, u. Phys. d. Sinnesorgan^ 1896, xiii. ; Gruber, ^//^.
Wien. Med. Ztg. 1864, ix.

* Yoshii, Zeits.f. Ohrenheilk. 68-59, 1909, p. 240.

THE PROJECTED REVIVAL OF THE
FLAX INDUSTRY IN ENGLAND

By J. VARGAS EYRE, Ph.D.

Flax at the present time is worth nearly twice as much as it
was some eight or ten years ago and there seems to be little
chance of a return to the former level of prices. Apparently,
the increased cost of the raw fibre is due entirely to the
operation of natural economic conditions and cannot be attri-
buted to commercial manipulation. It is therefore not surprising
that attention is being directed to the question of the practic-
ability of reviving the flax industry in this country. More
particularly is this the case in view of the desire to encourage
a return to agricultural pursuits and to increase the number
of small holdings, flax being a crop which is better suited to
the conditions under which a small holder of land is placed
than to those of the farmer of a large acreage. Flax is a good
alternative crop and for this reason alone would be useful
as an addition to the usual rotation ; moreover, as weather
which suits flax grown as a fibre crop is not good for corn,
in a season in which cereals fail flax will probably succeed.

Judging from past experience it may be said that when
the difference between the price of wheat and the price of
flax is large, then the latter becomes a profitable crop in this
country. At the present time such conditions obtain. It is
noticeable also that the linen trade of Europe is dependent
upon the supply of middle and low quality fibre coming from
Russia and that the industrial and agricultural development of
this country is exercising a marked influence on the price
of flax and tends to keep the prices high for the following
reasons. Whilst the area under flax is not increasing, the
Russian linen industry is developing rapidly : already practi-
cally the whole of the best quality fibre grown in that country
is absorbed within the Russian Empire. The agricultural
development of Russia and the opening up of new areas to
wheat in Western Siberia and Asiatic Turkey have the effect

596 i

PROJECTED REVIVAL OF THE FLAX INDUSTRY 597

of reducing the profit attending wheat growing in other
countries and both these circumstances operate to make
the chance of successfully reviving the flax industry in our
country more favourable.

- The possibility of successfully reviving the industry has
been seriously considered by the Development Commissioners ;
indeed, the revival of both flax and hemp industries was
specifically mentioned in the Act of Parliament which brought
that advisory body into existence. During the past two
years much first-hand information has been gathered by
studying the subject of flax cultivation and fibre separation
in the chief flax-growing countries of Europe, namely Russia,
Holland, Belgium, France, Ireland, Austria-Hungary and
Germany and the information has been presented in the form
of a Report. Moreover, certain field experiments were con-
ducted last year in Bedfordshire, where, besides raising the
crop, retting experiments were made in tanks especially
constructed for the purpose.

The result of the inquiry made on behalf of the Develop-
ment Commissioners leaves no room for doubt that the
climate of this country is well suited to flax. The crop
makes no special demand for a particular class of soil, so
long as the land is properly prepared and suitably manured.
Light loam, however, may be said to be most favourable and
chalk least favourable, to a fibre crop. Large areas of suitable
land are to be found in Yorkshire and Somersetshire, as well
as in the midland and eastern counties. Flax can be grown
successfully as a fibre crop in this country and at the same
time the seed which it bears can be profitably saved ; indeed,
this is the practice which was formerly adopted. The flax crop
is somewhat more troublesome than the usual farm crops but
no dif^culty in its cultivation need be apprehended provided
practical information be placed at the disposal of farmers.
This could be done easily and there is every reason to believe
that good crops of flax would again be raised here if attention
were given to the work.

The somewhat complicated and troublesome operation of
separating the fibre is not considered to fall properly within
the province of the agriculturist. The labour at his disposal
is unskilled for the most part and he is able to give only
divided attention to the preparation of the fibre, whereas skilful

598 SCIENCE PROGRESS

handling and careful watching are necessary if good results are
to be achieved. The preparation of uniform fibre of good quality
should be the object in view, if the revival of the flax industry
is to be successful, because labour in this country is too costly
for low quality home-grown fibre to compete successfully with
that which is imported from Eastern Europe, where the labour
of preparation is disregarded when reckoning the cost of
production.

The possibility of cultivating and separating the fibre at a
profit cannot readily be decided ; there are many contingencies
which are difficult to evaluate and much that is hypothetical
enters into the problem. The general evidence obtained is un-
doubtedly favourable ; indeed, the opinion was expressed in the
Report to the Commissioners that practical trials on a moderate
commercial scale can alone afford the definite knowledge that
is required as to the degree of financial success that will attend
the production of flax fibre in this country. The possibilities
opened up, if the scheme proved successful, are held to be ample
justification for its serious trial. In this connexion it is very
noteworthy that the English flax industry existed longest in
those districts where there was a central retting depot to which
the harvested crop was carried and sold by farmers and, at the
present time, there is very reasonable foundation for the belief
that on these lines the flax industry could be successfully
revived.

Strong reason was found for the belief that the judicious
revival of the flax industry, managed according to improved
methods, would be productive of benefit to British agriculture and
would afford people an opportunity of finding regular employ-
ment in rural districts by creating a demand for skilled labour.

It has been recommended that one or more small retting
depots be established out of public funds in suitable localities —
for instance, in Yorkshire and in Somerset — each capable of
dealing with the produce of about one hundred acres. Such
establishments, managed on strictly business lines during a
few years and conducted as experimental stations, would
enable the required information to be gained as to whether
the cost of the after-processes of preparing the fibre can be
brought sufficiently low to make the flax crop once more a
profitable one to the farmers of Great Britain. This is
necessary because, although the re-establishment of flax as a

PROJECTED REVIVAL OF THE FLAX INDUSTRY 599

farm crop is the main object in view, it becomes necessary to
find a market for the straw and this involves organising the
after-treatment of the crop, namely the retting and cleaning.
It is with these operations that the chief difficulty is en-
countered.

The Commissioners have now had the Report on the
management of the flax industry before them and they have
received the recommendations contained therein favourably.
With the object of carrying out, in this country, the necessary
practical trials above mentioned, a society has been formed under
strict conditions of non-profit tradings in order that it may be
eligible for a grant from the Development Commissioners, who
are expressly empowered by the Act of Parliament which
established the Development Fund to encourage the cultivation
and preparation of flax and hemp in Great Britain.

In view of the interest which has been aroused already by

this line of action, the Commissioners have kindly given their

consent to the publication of the following resume of the Report

referred to.

Historical

Somewhat extensive flax growing and fibre production in
England is still within the memory of many people in certain
rural parts of the country ; but, at the present day, there is
little to indicate the extent of this lost industry. The names
of such places as Flaxton (Yorkshire), Little Steeping (Lincoln-
shire), Retford (Notts) and Flax-Bourton (Somerset) seem to
be some of the best evidence for locating the scene of flax
cultivation in the past. Separation of the fibre from the straw
was formerly part of the agricultural practice in England just
as it is in Russia at the present day, the cleansing and pre-
paration of the fibre providing work during the winter months
for the husbandman and his family.

Flax growing in England probably dates from the Roman
occupation, although practically no mention of it is to be found
in official records until a.d. 1175, when flax was included among
titheable articles, from which fact it is concluded that the culti-
vation of the crop had attained to considerable dimensions at
that time. In 1532, an Act of Parliament was passed which
compelled all persons holding tillage land to sow at least one
rood with flax for every sixty acres of such land occupied.
After thirty years, this law was made more stringent, a penalty

6oo SCIENCE PROGRESS

of £s being imposed upon persons not growing at least one
acre of flax for every sixty acres of land cultivated.

With the object of still further encouraging the growth of
flax in England, the tithe on this commodity was reduced
to 45. per acre in 1691 and in 1712 a bounty of one penny
per ell was given on all exported British-made sail cloth. In
1806 a bounty was offered for the importation of flax from
British Colonies and every efl'ort was made to increase the
production of fibre at home so as to supply the requirements
of the growing British industry more completely.

At that time flax was grown more or less in every part of
England and in many counties several thousand acres were
annually under this crop ; but the supply of raw material did
not keep pace with the home demand, as may be seen from
the Parliamentary Returns of that period, in which fairly large
imports of flax are recorded.

Flax sufl*ered considerable depreciation on the introduction
of cotton and the success obtained in spinning cotton fibre by
machinery led to a further reduction in the demand for linen, as
it was impossible for that material to compete with the low
price of cotton fabrics. About 1820 steam-driven flax-spinning
machinery became commercially successful and the demand for
flax fibre became greater inconsequence ; but, at that time, the
difl'erence in the value of a flax crop and of a wheat crop was
insufficient to induce the better farmers of this country to embark
again on the troublesome task of preparing the fibre. British
flax culture fell into discredit, apparently owing to the fact that
only low quality fibre was prepared and whilst the quantity
grown in England diminished, the amount imported became
steadily larger. To take one county as an example, in 18 10
between 4,000 and 5,000 acres of flax were grown in Dorset but
in 1850 the acreage under the crop had fallen to some 300 acres.

Writing in the Journal of the Royal Agricultural Society of
England in 1847, J. MacAdam states that the great markets for flax
supplying the spinning trade were Leeds, Belfast and Dundee ;
the finest yarns were made by English spinners, the great bulk
of medium yarns by Irish manufacturers, Scotland producing
the very coarsest. MacAdam advocated the more extensive
cultivation of flax in the United Kingdom and showed clearly
that a profit of ;^io per acre was obtainable at that time provided
cultivation were carried on in the proper manner.

PROJECTED REVIVAL OF THE FLAX INDUSTRY 6oi

There was a revival of English flax-growling about 1850 but
development v^as arrested by the greatly enhanced price of
corn, so that for the time being flax v^as outclassed as a farm
crop. Furthermore, following the Treaty of Paris in 1856 and
peace with Russia, very large quantities of cheap Russian fibre
came to British markets ; and this seems to have been the blow
from which English flax production has never properly re-
covered, although various attempts have been made to restart
the industry.

The custom of working large farms and the increased value
of produce requiring less attention and less skilled labour
occasioned a decline in the area devoted to flax and a marked
disinclination on the part of the agriculturist to do more than
grow the crop and harvest it. The establishment at this time of
depots at which the straw was received and worked up into
fibre mark a new stage in the history of English flax.

The adoption of the system of centralising the after-pro-
cesses led to a revival of the industry about i860, when con-
siderable quantities of flax were grown : in fact, in 1870 the area
devoted to flax in Great Britain was 23,957 acres, the greatest
area occupied by the crop in any year on record. About 1875
a succession of bad seasons was experienced in England ; this
circumstance and the keen competition of foreign flax fibre and
Manilla hemp, as well as the high price of wheat, caused many
farmers to cease growing flax and soon afterwards several works
were closed down. In 1876 flax w^orks were established at
Long Melford (Suffolk) and continued working during about
twenty years ; several smaller attempts were made to revive
the industry in Suffolk prior to 1888 but without success. To
judge from the quantity of straw dealt with annually, the most
prosperous mills were those at Selby and Staddlethorp in
Yorkshire. At the former, the crop from nearly 2,000 acres
was handled successfully but the quantity raised fell off con-
siderably, until in 1896 not more than a 500-acre crop was
dealt with at Selby and the mills at Staddlethorp had the crop
from barely 200 acres. It is, however, significant that both the
mills surviving in 1896 were conducted as central retteries and
that the principle of retting in tanks of warmed water had been
adopted. Since that time, flax has been grown as a fibre crop
only to a very small extent : small areas have been seen from
time to time both in Yorkshire and in Somerset ; in the latter

6o2 SCIENCE PROGRESS

county there is some grown still, which is dew-retted and
sold locally.

Agricultural Requirements

There is considerable diversity of opinion expressed as to
the particular soil which is best suited for the production of flax
as a fibre crop. It is frequently stated that a well-drained loam
gives the best results and rich loamy clays are considered to be
very suitable. Whilst on the one hand it is maintained that
good flax can only be raised on good rich soil, it is not in-
frequently asserted that the nature of the soil is of small
importance. From a general examination of the soil in the
principal European flax-growing areas the writer has formed
the opinion that there is much truth in all these statements :
apparently good flax can be raised on a great variety of soils
provided their texture be suitable. Very heavy clay is not
favourable for flax, neither is chalk and there is good evidence
for saying that soil which is very rich in humus is unfavourable,
also peaty moorland ; but almost any other ** clean " land which is
capable of producing good crops of grain will produce good
crops of flax.

The flax plant grows very rapidly, sending down a fine
filamentous root system as far beneath the surface of the soil as
the stem rises above it. The subsoil therefore must be of a
kind which will allow of root development to the full extent
and at the same time be sufficiently compact to offer a firm hold
for the plant : in fact, conditions which are most favourable to
the growth of wheat. It is of great importance to the production
of good uniform fibre that the plant should develop at a steady
rate and receive no check during growth — indeed, these con-
ditions are of paramount importance when flax is grown for
high quality fibre. Although rich land will produce what
appears to be a splendid crop of healthy tall plants, when they
are examined they are found to yield an amount of fibre not at
all in proportion to the luxuriance of growth and at the same
time to be of a lower value for spinning purposes. Although
stress is frequently laid upon the advisability of sowing flax on
rich soil, on strong deep loam, it is a singular circumstance that
most of the good flax grown is produced on very light soil,
often on sand.

Generally speaking, it may be said that in Ireland the best

PROJECTED REVIVAL OF THE FLAX INDUSTRY 603

flax comes from a gravel soil with gravel subsoil : in the north
of France excellent flax is grown on a very light sandy loam
and the soil of East Flanders is very similar to the French,
although it differs from it in containing a larger proportion of
sand and in being in a better condition owing to the high
cultivation that has so long prevailed in Belgium. The flax
soil of West Flanders is somewhat heavier than that of East
Flanders, as it contains a larger proportion of clay and in some
cases approaches the composition of the heavier marlish-loam
known in Holland as " Zeeklei." This is a deposit of sand rich
in clay which is widely distributed: it "weathers" readily,
forming a good porous firm soil and it may be said that flax
cultivation in Holland is confined to the regions of that
particular deposit.

The flax districts of Russia are so extensive that it is difficult
to formulate a general statement as to the class of soil yielding
the best crops. It may be said, however, the chief characteristic
is lightness, the soil being composed largely of sand. The poor,
sandy, scrub-land between Vologda and Tver produces flax of
excellent quality and when it is properly farmed and sown
remarkably good crops are raised. This type of soil extends
eastward as far as Viatka and Perm and the whole region is a
flax-growing area ; but in the western provinces of Pskoff,
Vitbesk, Livonia, Kurland and Kovno the soil is somewhat
heavier in consequence of the widely distributed moraine matter
in those regions.

Although flax is not a specially delicate crop to grow there
are several points in regard to its cultivation which require
unusual attention. One of the main factors which make for
success is the care with which the soil is prepared for the seed.
The importance of cultivating the land to a high degree of
firmness is to be emphasised, for therein lies much of the secret
of success. Not only must the soil be fine but it must be
firmly bedded. It would be ;diflicult to lay too great stress
upon the fact that the seed-bed must be deeply worked and
firm, with a shallow surface layer of fine soil to cover the seed.

Although flax has long been specially cultivated for the fibre
it bears, it is only comparatively recently that attempts have
been made to evolve a system of manuring the crop so as to
harvest better fibre. The growing period of flax is short; it
is only on the land about twelve to fourteen weeks and probably

6o4 SCIENCE PROGRESS

for that reason it requires its nutritive materials to be in such
a form that they are easily assimilable ; which means that the
application of manure can be made profitably only after a
thorough knowledge of the land has been acquired.

Flax is said to be a potash-feeding plant, requiring a good
supply of this soil constituent together with lime. Certainly
it does appear that this crop grows better on the new " Polder "
land in Holland than it does on the old, there being more
lime and potash in the soil recently reclaimed from the sea.

The place which flax is most suited to occupy in the scheme
of crop rotation is of course dependent upon the soil, upon
what is the most marketable produce and upon other varying
circumstances. It is certainly an unwise practice to grow flax
frequently on the same land, because a condition of soil sickness,
known as ** flax-sickness," sets in. Where the soil is rather
heavy, it is sometimes made to carry two or more crops
between a fdung manure and a flax crop : for instance, in
Friesland the land is well dunged for potatoes and the next
year sugar-beet is brought on by artificial manures ; in the
third year oats are grown with artificial manures ; in the
fourth, a suitable dressing of artificial manure is given for
a flax crop.

A very general practice in all countries is to sow flax after
oats or at any rate after some crop which will leave the land
as far as possible free from weeds. When the soil is poor in
nitrogen, the last oat crop is sown with clover and a clover
crop taken before flax is sown ; but where the soil is not
deficient in nitrogen, leguminous crops are kept well removed
from flax and a crop of chicory is taken between oats and flax.
Many people in Russia and Holland hold the opinion very
strongly that it is best to grow flax on land which has been
two or three years under grass.

It is probable that the conditions under which flax is grown
at the present time are not at all natural to the plant : the
production of tall, straight stems, with little seed and much
fibre, having been brought about by long cultivation under
particular conditions. The object of the flax-grower is to
produce long, uniform, slender stems carrying as much fibre as
possible and as little woody material as is compatible with
proper stem rigidity.

The actual growing period of flax extends over only about

PROJECTED REVIVAL OF THE FLAX INDUSTRY 605

ten weeks and of this time the early stages are the most critical.
When once started the plant grows rapidly, especially during
the month of June, when an increase of ij to ij in. occurs
during a period of twenty-four hours. Unless the soil is able
to retain a good supply of moisture or frequent light rain falls,
this rapid growth receives a check and this causes the fibre to
become coarse and irregular instead of increasing in length.

Quite a cool, temperate climate is best suited for the pro-
duction of a good fibre crop. It is noticeable how generally
flax-growing areas are situated near the sea coast, where the
crop benefits by the moist wind and the generally uniform
climate. Flax is grown extensively in Normandy, Brittany
and Picardy, in France ; in the northern part of Ireland ; over
an area extending about 50 miles inland from the Belgian
coast ; in Zeeland and the islands of South Holland, as well
as along the coast of Friesland and Groningen in North
Holland ; and extensively in the Baltic Provinces of Russia.
All these districts enjoy similar climatic conditions during the
growing period — namely, a rather low, even temperature, rather
high humidity and nearly equal rainfall.

Fibre grown in cool, moist regions is fine, silky and possesses
good spinning quality ; that produced in a district where the
summer is hot and dry is short, harsh and dry. This influence
of climate on the quality of the fibre was markedly shown in
the French and Belgian crops of 1910 and 191 1: the former
year being w^et and the latter unusually dry. Generally
speaking, the fibre from the 19 10 crop was long, firm, silky
and moist, whilst the fibre from the 191 1 crop was shorter,
stronger and somewhat harsh and dry. It may be said that
1910 gave a weft flax and 191 1 a warp flax.

It has been stated frequently that flax is an exhausting crop
for the land. All crops are exhausting, but in this case it is
intended to imply that flax removes more from the land than do
other crops. This opinion dates from very early times : flax
being stigmatised as a hurtful and exhausting crop by Greek
and Roman writers. At the present day, this belief finds
expression in some land agreements, wherein the tenant is
specifically prohibited from growing flax or is forbidden to
remove both the seed and the straw from the farm. Although
this belief has been contradicted from time to time, the evidence
refuting it has not received due credence because the fact

6o6

SCIENCE PROGRESS

remains that flax crops cannot be successfully grown at as
frequent intervals as other crops. In the light of the experi-
mental work of Snyder, Wolff, Hodge, Tretiakov and others,
there can be no doubt that flax removes, if not less, at any rate
not more, nutritive materials from the soil than other farm crops.
In this connexion, the work of Prof. Snyder is of particular
interest and it is from his results that the following table has
been compiled for the purpose of showing the comparative draft
of various crops upon the soil :

Pound

sof

Average crop

Crop.

in bushels.

Phosp. acid.

Potash.

Lime.

Silica.

Ash.

Wheat

174

315

Barley

216

Oats

205

30 tons

Mangels

225

105

450

1050

300

Potatoes

150

250

Flax

116

Among the points of interest which are brought out by this
table is the fact that a mangel crop is not a good crop to
precede flax because of the large withdrawal of nitrogen and
potash it occasions — substances upon which flax largely depends
for its rapid growth. It is evident also that a crop of flax is no
more exhausting to the soil than is an ordinary grain crop.

Other evidence contrary to the view that flax is a particularly
exhausting crop has been furnished from the North Dakota
Experimental Station, where it has been demonstrated that
better crops of wheat ^ can be raised after flax than after wheat.
When writing upon this subject Prof. Boiling cites the confirma-
tory work carried out at Poltava by Prof. Tretiakov, showing
the draft on the soil to be less for flax than for wheat, even
when water evaporation is taken into consideration.

Choice of S^ed

A number of forms of flax are cultivated at the present day
which exhibit differences sufficiently well marked for them
to be classified by some authorities into varieties of several
species. Flax, however, responds so markedly to a change

* It is not clear whether due allowance was made for the weeds which
presumably were left with the wheat crop and removed from the flax crop.

PROJECTED REVIVAL OF THE FLAX INDUSTRY 607

of climate or soil conditions that in some of these cases it is
difficult to regard the differences observed in the habit of the
plant as being due to conditions other than those of growth or
environment. The more important varieties which are grown
for fibre are :

1. Linum usiiatissimum vulgare blue flower.

„ J, „ album . . . white „

» » regale blue „

2. „ americanum album white „

3. „ hyemale romanum blue „

Some of these forms are undoubtedly better suited to
certain soils than are others ; for instance, on the heavier land
of Friesland the coarser-growing white flowering flax {L. usit.
van album) is exclusively grown, whereas on the adjacent new
" Polder " land the blue flax (Z. usit. vulgare) is found to be
more successful ; but in other regions, where white flowering
flax was formerly grown it has been found more profitable
now to grow the blue flowering variety. It is noteworthy
that Riga white flowering flax is less liable to disease and gives
a heavier return of fibre than Riga blue flowering flax, although
its quality, more especially in fineness, is not equal to that of
the latter.

Although in all other European countries emphasis is laid

upon the necessity of frequently changing flax seed, the country

from which the best flax seed is obtained — Russia — knows no

such necessity. In Russia, it is generally accepted that the best

seed for fibre production comes from the Baltic provinces and

the province of Pskoff and Vologda ; when occasion arises

Russian growers obtain seed from these districts for their own

use. The best fibre and the best flax seed are exported from

the provinces mentioned and the crops are almost invariably

grown from seed of the previous harvest, seed change not

being an agricultural consideration. In many cases the farmers

have had their seed in the family more than twenty years and

although at the present day the yields of fibre are smaller than

formerly, there is no such deterioration as is said to take place

in Holland and Belgium after growing from the same seed

successively during only four or five years. Generally speaking,

Russian seed undoubtedly gives a more uniform and more

healthy crop than any other, notwithstanding the fact that,

owing to increased railway facilities, the time has now passed

6o8 SCIENCE PROGRESS

when it was possible to say that reputed Pskoff seed came from
that province or that Riga seed came from the Baltic provinces.

It is a very noteworthy and general practice in the best flax
areas of Russia to dry the seed finally in an oven at a com-
paratively high temperature. Besides ensuring thorough drying,
this operation may possibly act beneficially in kiUing off
imperfectly developed and poor seeds, so that only those of a
uniform and high vitality remain. Certainly the process of
oven drying is beneficial, apart from the fact that it prevents
subsequent heating of the seed when in barrels during transit
and may account for the fact that Russian seed gives better crops
although the percentage of dead seeds is higher than in any other.
Not only has oven-heating been found advantageous to the sub-
sequent flax crop but if the seed be submitted to several degrees
of frost a similar result is observed ; it is no uncommon practice
for Russian peasants to expose their seed to the action of frost
with the object of improving the flax harvest raised therefrom.

As already mentioned, the general practice is to rely upon
Russia for the supply of flax seed to all countries, the imported
seed coming chiefly from the Baltic Provinces by way of Riga.
It is then grown in other countries for about three seasons,
giving rise to crops bearing seed which is known respectively as
" Riga-Child " and " Riga-Grandchild." Where the climate is
moist and dull, " original " Russian seed gives the best results ;
especially is this the case if the soil be light. Where the
prevailing atmospheric conditions are dry or the soil is some-
what heavy, better results are obtained by using '' Child " seed
although the crops raised therefrom are less uniform than those
from Russian seed. In Belgium, the best practice is to procure
" Dutch-Riga-Child " from some trustworthy source : the par-
ticular seed known to come from a good crop of fibre flax
grown in Holland the preceding year being the most highly
prized. Seed in Holland is ripened naturally in the field better
than in other countries and large quantities of " Dutch-Riga-
Child " are sown in Holland, Belgium, Ireland and France,
where, in many cases, it is sought after in preference to
Russian "original" seed.^

* Possibly this may be explained partly by the interesting and quite general
observation that whereas Russian " original " seed produces crops richer in fibre,
the " Child " seed shows its superiority in producing crops bearing fibre which is
finer and of better quality.

PROJECTED REVIVAL OF THE FLAX INDUSTRY 609

It is possible for those who collect Dutch-grown seed for
export to ascertain what the seed has done in the past and to
collect only the best for distribution to flax-growers ; and as
not more than 10 per cent, of the Dutch crop is grown from
seed other than that freshly imported from Riga, one can be
fairly certain that the seed is Dutch-Riga-Child when offered in
Holland under that name. In Russia, this is not yet possible ;
seed merchants have mostly to buy in small quantities from
agents or middlemen who collect smaller quantities from
peasant farmers. The Russian merchant has therefore to deal
with a great variety of types and is only able to grade his seed
according to general appearance, colour, shape, size, etc. and to
take care that *' Steppe " seed does not enter into his mixtures.
By long experience merchants have found that seed from a
region where there are certain conditions of climate is better
suited for exportation to one country than to another; for
example, seed from a very wet district does better in the drier
climate of Holland than in Ireland, whilst seed from a drier
region is better suited to the damp climate of the north of
Ireland. This kind of practical information stands the export
merchants in good stead and the accuracy of their judgment is
quite remarkable.

Sowing and After-Cultivation

In some quarters it is said to be an advantageous practice
to defer sowing flax seed until as late in the season as possible,
so as to allow the land to be cleaned of weed seedlings.
However true this may be in the case of certain lands where
weeds are plentiful, it must be questioned first whether flax is
a suitable crop in such cases ; moreover the advantages of this
practice are far outweighed by those attending early sowing.
The best advice is to sow as early as possible, as early as the
soil and weather will permit, so that the seed may germinate
slowly and have a good start while moisture is in the top soil.

Usually it is possible to sow on light soils at the commence-
ment of April, whereas the end of April is generally sufficiently
early for the heavier land such as occurs in Friesland but
varying influences have to be taken into account and only the
farmer can properly say when his land is in suitable condition.
The seed bed must be of fine tilth and it is best to sow on a
harrowed rather than on a rolled surface.

6io SCIENCE PROGRESS

For the production of a tall uniform flax crop it is necessary
to sow the seed somewhat thickly and although errors may be
made in the direction of sowing either too sparingly or too
freely, the fault is more often seen of sowing too thinly. This is
the worse error because it allows the plants to take on a
broader growth and to branch lower down the stem than would
be the case were they closer together. Thin sowing brings
about an increased yield of seed but the fibre, for which the
crop is grown, suffers in being coarser and shorter. The
thicker the crop is sown the taller will be the plants before
branching, consequently the yield of fibre will be greater and
it will be of a finer quality ; but of course there are limits to
this beyond which it is foolish to go.

Some of the highest rates of sowing in Ireland are from
if to 2 bushels per statute acre ; whereas in Holland and
Belgium as much as 3 bushels per statute acre are used. On
the very light soil in North Belgium 2 bushels of seed, 80 per
cent, germinating, are sown to the statute acre ; on the loam
soil in France 2J bushels and on the new Polder land of
Groningen as much as 3 bushels per statute acre.^

For the most part sowing is done by hand ; especially is this
the case in Ireland and Russia. It requires exceptionally calm
weather and great skill on the part of the sower to obtain
anything like an even distribution of the small, slippery seed.
A small portable distributing machine known as the Violin
(or Fiddle in England) is extensively used in Holland, Belgium
and also in Ireland. The machine is so called because of the
to-and-fro motion of a bow-like handle necessary to actuate
a distributing wheel which is fitted at the base of the small
reservoir containing the seed. This simple little machine is
carried under the left arm of the sower and is steadily worked
with the right hand as it is carried at a uniform pace over the
field. Much of the difficulty attending broadcast sowing has
been overcome by its use.

^ Before sowing it is advisable to test the germination of the seed, because in
some cases this varies rather widely. For example, Russian seed of which only
75 to 80 per cent, germinates will not go so far as Dutch seed of which 95 per
cent, germinates and this is approximately the extent to which differences are
found. Such tests, however, afford no criterion as to the value of the seed for
growing good crops and it must be remembered also that they are made under
conditions which are very different from those met with in the field, so that much
importance should not be attached to the results.

PROJECTED REVIVAL OF THE FLAX INDUSTRY 6ii

Few farmers show any inclination to drill the seed by
ordinary machines or by any modification of them, although
this method of sowing, besides ensuring even distribution, also
has the advantage of bedding the seed at a uniform depth. This
is a very important thing to achieve with flax because the
object is to raise a crop of great uniformity and when the seed
is deposited at varying depths irregular germination follows and
an irregular crop is the result. Flax must not be laid deeply
in the soil ; about half an inch is quite sufficient. After sowing,
the field is lightly harrowed crosswise and finally rolled Hghtly
so as to consolidate the surface, in order to bring moisture into
close contact with the seed and at the same time make the
surface of the field flat.

Weeds and Diseases

Well-farmed land is tolerably free from weeds and it is
possible by suitably cultivating during the previous season
to reduce weeds to a minimum. It must be observed, however,
that the nature of the conditions of flax cultivation and the
growth of the plant itself seem to be favourable to the growth
of weeds. In Holland and Belgium weeding is carefully and
thoroughly done by women and children, who go barefooted
about the field ; kneeling to weed, they go systematically
through the field twice and sometimes three times during the
months of May and June. Although the wage paid for this
class of labour is small (is. to is. 6d. per day of about twelve
hours), the cost of weeding in these countries when outside
labour has to be procured adds greatly to the cost of producing
the crop. Generally, however, the small farmers in those
countries have families sufficiently large to enable them to
provide most of the labour required for this purpose from their
own household.

This necessity for repeated hand-weeding is not recognised
in France nor in Ireland ; the farmers in those countries are
content to remove convolvulus and weeds which make a large
and bulky growth, such as thistles, dock and charlock. Excellent
flax crops are to be seen in Ireland and also in the north of
France, where some of the finest quality straw is raised and
taken to Belgium to be retted. The impression produced is
that the necessity for close hand-weeding as practised in
Holland and Belgium is somewhat over-estimated.

6i2 SCIENCE PROGRESS

Of the several diseases and pests which affect flax only quite
a few make themselves sufficiently prominent to call for mention
here : nor need they in any way cause the farmer anxiety. At
an early stage of growth, when the plants are only about
two inches above the ground, they are sometimes affected by a
fungoid disease known as ** yellowing " which is stated to be due
to the fungus Asterocystis radicis.

At a later stage of growth Flax Wilt is sometimes manifest ;
it is a disease attributed to the joint activity of several micro-
organisms of which the most definitely identified is Fusarimn
lini. This disease is hardly ever met with in Russia, although
it has long been known in Holland, Belgium and France.
Flax Rust {Melampsora lini) may become a serious trouble
in some localities where the wild purge-flax {Linum catharticum)
flourishes, this particular plant being somewhat commonly
affected by the disease.

Flax is subject to the ravages of several animal pests but
fortunately it suffers to no greater degree than do other farm
crops from similar causes. The grub of the silver Y-moth
{Pusia gamma) feeds upon the flax blossoms and the larva
of the two flies Thrips linaria Uzel and Haltica nemorum and
also the flax-flea-beetle {Longitarsus ater Fab.) may do con-
siderable damage to the young plants.

It has been found in Ireland that a certain local condition
of soil occasions a sparsity of some of the plant's requisites,
causing small areas of young flax to become yellow and of
sickly condition. Rain showers frequently revive such flax but
when no rain falls a light dressing of muriate of potash has the
effect of restoring the flax to a healthy condition. Save in
exceptional cases, it is not customary to apply top dressings to
flax but should a spell of dry weather retard the early growth of
the crop it is well to apply a light dressing of nitrate of soda ;
but it must be used with moderation and is only to be given
with the object of preventing the crop from receiving an early
check to its development. When once the flax crop has made a
good start it requires no more attention until about harvest time.

Harvesting

Only when the crop is grown expressly for seed is it allowed
to become quite ripe before being harvested. When grown for
the fibre it bears, the matter of harvesting seed is either entirely

PROJECTED REVIVAL OF THE FLAX INDUSTRY 613

neglected or it is only regarded as of secondary importance. It
undoubtedly detracts much from the value of the fibre if flax
straw be allowed to remain standing until the seed is ripe ; the
fibre thereby loses much in spinning quality, becoming dry and
inclined to brittleness, besides ultimately weighing less. The
cause of these differences is ascribed tentatively to the seed
depriving the plant of its oily sap for its own full development.

There are, however, but few districts where the seed borne
by the plant is entirely sacrificed. Sometimes this is done
in Belgium, where small quantities of flax are harvested almost
as soon as the crop comes into bloom with the specific pur-
pose of obtaining fibre of the very finest kind and of the
greatest possible elasticity and silkiness for the manufacture
of fine lace. Apart from such isolated instances it appears that
Ireland is the only flax-growing country where the asset the
seed affords is entirely disregarded.

To grow flax primarily for fibre and secondarily for seed
is certainly the most advantageous course to pursue and it
behoves the farmer to harvest his flax crop at a stage when
the seed is developed to the minimum extent for it to be of prac-
tical value, in order that the fibre may suff*er as little as possible.
It is everywhere agreed to be the best practice to harvest flax
when the lower part of the stem begins to change from green
to yellow — when about one-third of the stem has so changed
and when the leaves about half-way up the stem have changed
colour or fallen. At that stage, an examination of the seeds
within the capsule shows them to be just changing from a
full green colour to a brownish tint. These are the general
signs that the crop has matured sufficiently and harvest opera-
tions should commence at once. Eff'orts are made to get up
the crop as near the same stage of ripeness as possible ; no delay
is allowable, because during warm summer weather ripening
processes proceed rapidly.

When judging of the best method of harvesting flax it is
necessary to have in mind the fact that its value is greatly
reduced if the straws are not arranged parallel with one another
in a neat, uniform bundle — conditions which reduce the waste
occurring during the process of cleaning. The advantage of
these ideal conditions of harvesting therefore has to be
balanced against the cost of attaining to them.

The universal method of harvesting flax is to pull it from the

6i4 SCIENCE PROGRESS

ground by hand labour. This is due to the fact that no satis-
factory machine has yet been devised for pulHng it and it is
strenuously maintained to be a bad practice to cut it. Why
exactly this ban should be put upon cutting is not easy to
understand, because an examination of the root end of flax straw '
shows it to carry very little fibre indeed up to at least one inch
or an inch and a half above soil level, so that little fibre would
be wasted by close cutting the crop. Flax easily gets tangled
and cutting would certainly present difficulty for that reason
but this does not appear to be the reason for the statement that
flax must not be cut. The explanation seems to centre around
the belief that the cut ends of the fibres do not come together
kindly when being spun. The main advantage of pulling over
cutting seems to lie in getting up the crop more or less free
from weeds. Under certain conditions this certainly may be an
advantage but seeing that at a later stage, when the seed is
separated from the straw, an equally good opportunity is afforded
of getting rid of weeds and grading the straw into bundles of
uniform length, it seems to be doubtful economy to hand-pull
the crop.

Flax is pulled only during dry weather. It is grasped rather
low down on the stem in small handfuls and is pulled up with
as few weeds as possible, the earth is knocked off from the roots
against the puller's boot and, keeping the root ends level, a large
handful is accumulated until no more can be held. These
large handfuls are laid down on the ground for women to collect
together, " even up " and tie into larger bundles or sheaves
by twisting a few of the straws round them just below the
seed bolls.

The practice in the Russian flax-growing districts is to pull
the crop greener than in Holland and it is less carefully handled.
In the Baltic provinces, as the bundles are tied up they are
collected in a part of the field where a large knife is erected for
cutting off the seed bolls and for trimming up the sheaves
by slashing them down on to the knife.

In Ireland a somewhat different practice obtains ; the pullers
themselves lay the uprooted flax neatly across twisted rush
bands, until sufficient has been collected to tie up to form a
sheaf or as it is called locally, a " beet." As no attempt is made
to save the seed, there is no opportunity for *' evening up " the
sheaves after they are once made up, so it becomes of the greatest

PROJECTED REVIVAL OF THE FLAX INDUSTRY 615

importance to have the flax tied up uniformly in the first
instance.

There is much disagreement as to the merits of green-straw
retting over dry-straw retting, when regarded simply as a means
of preparing the best quality fibre, quite apart from the question
of saving seed, because it will be shown subsequently that in
either case the seed may be saved.

In Ireland, parts of Russia and certain localities in Belgium
green-straw retting is advocated as being the better method, the
fibre prepared in this way being, it is said, of superior quality ;
on the other hand, the best fibre of all comes from Belgium and
is prepared from straw which has been not only dried well but
has been kept until the following year before being retted. The
character of the growing season, the temperature and nature of
the water in which the straw is retted, all play a more prominent
part in determining what class of fibre will be obtained eventually,
so that it is difficult to ascribe distinctive merit to either method
of retting. Judging from information acquired in the different
districts, it may be that both methods have some particular
advantage ; possibly green-straw retting favours the production
of a fibre which is fine and more silky in character and the dry-
straw method produces a fibre which is stronger than the other
but the evidence in favour of this view is not very conclusive.

To allow the " after-ripening " of the seed to take place the
crop is left in the field to dry for a day or two. The Belgian
farmer then lays the sheaves uniformly in one direction so as to
build up a wall which is propped at frequent intervals to resist
wind pressure and roughly thatched with rye straw. By this
arrangement, the flax straw is protected from rain and from sun
and at the same time the wind has a fair chance of penetrating
the wall, so that after some seven or eight days it becomes
sufficiently dry for the seed to be removed. The custom in
Holland, especially in Groningen and Friesland, is somewhat
different from that in Belgium. In the former province, after
preliminary drying, the sheaves are built around a roughly
constructed wooden tripod, such as is used for drying clover;
they are then left for about a week for the seed to mature and
dry. In Friesland the sheaves are made up into small ricks,
which are protected at the top by a cloth covering or a light
thatch of green rushes.

In some parts of Russia, where the climate is wet, consider*

6i6 SCIENCE PROGRESS

able difficulty is experienced in drying the crop : rain and
inclement weather generally set in before the operation can be
accomplished in the ordinary way. To overcome this difficulty,
large drying sheds with open sides are erected which are fitted
with lattice shelves upon which the flax is laid as soon as it is
pulled. Again, in the neighbourhood of Rsheff, after the crop
is pulled and has been allowed to dry out of doors as far as the
climate allows, it is removed to a drying house, where it is
artificially dried in an oven before the seed is taken off.

There are numerous methods of separating the seed from
flax straw. Ordinary machine thrashing is strictly avoided, if
the straw is to be of much value for subsequent retting, because
this method occasions serious damage to the fibre. The method
most generally used is that known as " rippling," which is
effected by drawing the top part of the straw through a vertically
placed iron comb which does not allow the seed capsules to
pass between the closely arranged teeth. Men do the actual
rippling and women and children bring the sheaves, untie and
retie them again. To avoid loss of seed, rippling is carried out
over a large cloth spread upon the ground ; when the crop is
stored until the next year, the rippling is done in the barn in
which the straw is housed during the winter This operation of
rippling affords an excellent opportunity of taking out any
weeds as well as of grading the straw into bundles of approxi-
mately uniform length ready for steeping. Besides being a good
practical method of removing the seed, rippling has much in its
favour as a means of straightening out the straw and cleaning it
from short pieces as well as from weeds. Some go so far as
to say that this would be a profitable expenditure even if the
value of the seed alone did not completely cover the cost of
rippling.

¥\ax grown in Belgium is sometimes rippled as soon as it is
pulled or, after being well dried, the crop is deprived of the seeds
it carries by spreading it on an even stone floor and then beating
the top ends of the flax with flat wooden mallets. It is quite
the practice in West Flanders, especially during the winter
months, to effect the removal of the seed by this method.
Without having the advantage of straightening out and cleaning
the straw, this method of seed separation seems to necessitate
the employment of as much labour as does rippling ; moreover,
H is doubtful whether the seed does pot suffer under the tre^t-

Fig. I. — Harvesting flax: Bedfordshire, 1912.

Fig. 2. — Kippluig flax seed : Groningen.
PLATE I.

616I

PROJECTED REVIVAL OF THE FLAX INDUSTRY 617

ment. The one advantage seems to be that the seed is threshed
out and the capsules separated by the same operation.

In localities where flax straw is retted while in the green
state, as soon as it is pulled, a practice which obtains in the
neighbourhood of Lokern and St. Nicholas in Belgium, the seed
capsules are " rippled " off and then spread out on canvas in the
sun to dry.

The Russian methods of separating the seed from the straw
also vary. In the Baltic provinces and the Government of
Pskoff a modified form of "ripple" is employed, in which the teeth
are sharp knife blades which cut off seed-pods and the small
branches to which they are attached, leaving only the straight
stems. Different methods of removing the seed are practised in
other parts of Russia ; for example, the artificially dried flax
straw is taken by the root end in handfuls at a time and just the
top ends are passed between the butt ends of the revolving
wooden rollers fixed at such a distance apart that the straw is
practically untouched and yet close enough together to crush
the seed capsules and to free the seed without damaging it.

It has been mentioned already that the general practice in
Western Russia is to cut off the top branches and the seed
capsules from the flax straw ; these are collected together and
closely packed on a vertical drying frame erected in the field,
where they remain until the seeds within the capsules have
become of a uniform brown colour. After drying on these
frames out of doors, the seed is removed to a specially con-
structed drying shed, where it is heated to a fairly high tempera-
ture until quite dry : an operation which sometimes lasts during
two or three days if the out-of-doors conditions were not favour-
able to drying.

The seed is then spread rather thickly over a stone floor and
threshed, either with a flail, by simple machinery constructed of
wood ; or a horse is made to drag a grooved wooden roller about
the floor. Finally the seed is shifted and screened and then sold
to the local buyers, who pass it on with their other purchases
to people who properly clean and " grade it for export," what-
ever that may mean exactly.

In Holland it is customary to separate the seed from the
straw by hand labour during the winter months by rippling and
sometimes this is done by means of a machine known as a
"flax-brake." The seed is very carefully threshed out and

6i8 SCIENCE PROGRESS

cleaned and prepared for market by the farmer, who relies upon
his " Riga-Child " seed making a good price — there being a
large demand for this variety of seed by French, Irish and
Belgian growers. Most of the French and Belgian seed is sold
for oil.

Separation of the Fibre

Before the harvested straw can be of use to the spinner in
the customary way, it has to be put through several somewhat
complicated processes, including retting, breaking, scutching and
heckling. All these operations were carried out formerly by the
farmer who grew the straw ; but of late the tendency has been for
these subsequent operations to get into the hands of people who
specialise in one particular phase of fibre preparation.

It is now the more common practice for the farmer to sell
his standing crop, the purchaser deciding when to harvest and
himself taking off the seed. He then sells the straw to some-
body who rets it and then it passes into the hands of others
who have specialised in scutching and heckling; finally it is
bought by a dealer who sorts and grades his purchases and
sells in large quantities to the spinners. This procedure is
quite general in those districts where the higher qualities of
flax are produced and must be regarded as a consequence of
these subsequent processes requiring greater skill in carrying
them out than the average farmer is able to command.

The first of these after-processes, namely, retting, involves
the partial disintegration of the flax straw and for convenience
of reference the structure of a flax straw may be briefly de-
scribed here. When viewed in transverse section, it may be
considered as being composed of two parts or concentric rings :
a complex cellular system forming the outer ring and a cell
structure of greater simplicity forming the inner ring or woody
part of the stem. The valuable part of the straw, namely, the i
fibre, forms a series of irregular bundles almost on the outside*
of the stem, their exact position being between two thin par-
enchymatous layers, one of which is just beneath the epidermis
and the bounding cutica, the other being adjacent to the cam-
bium. This briefly describes the formation of the outer layer
the complex cellular system of which has to be partly broken
down before the bundles of fibre can be obtained in a useful
form. The inner part of the stem is made up of a ring of
woody material of more or less uniform character and with this

PROJECTED REVIVAL OF THE FLAX INDUSTRY 619

the fibre-winner has little to do. The long fibres composing the
** bundles" already mentioned are themselves made up of long
chains of shorter fibres which are held together and in position
by an inter-cellular gum or resin (pectose).

Successful separation of fibre from flax straw depends upon
the isolation of the long fibres without going so far as to weaken
the binding between the smaller, individual fibres composing
them. Up to the present time, this pectose decomposition has
been accomplished best by a natural fermentation process which
sets in when the damp straw is allowed to rot : a process which
now goes by the name of " retting."

Of the various ways of effecting this decomposition, the
simplest is that known as " dew-retting," the straw being spread
thinly in regular rows over the ground and alternate dew,
sunshine and rain allowed to carry the process forward until
the fibre is easily detachable from the wood. The very nature
of this process, depending as it does upon favourable weather
conditions, frequently gives rise to a product of low value :
nevertheless, in some districts, this method is the only one
which is possible and enormous quantities of dew-retted flax
are prepared annually. One acre of standing flax requires
nearly two acres of land over which to spread it and there it
remains for two or three weeks. It is then turned over care-
fully and left for three or four weeks longer, although the time
required depends upon prevailing weather conditions. Fibre from
dew-retted straw is usually of bad colour although it bleaches
well. Sometimes in Belgium, more often in Russia, winter
retting is practised, the flax straw remaining out in the field for
some months without suffering much harm and the fibre ulti-
mately obtained is of pale colour. In Western Europe only the
poorer qualities of straw are dew-retted : crops which are not
considered good enough to treat by other and more costly
methods.

A method of retting only seen in South Holland and East
Flanders is to pack the deseeded undried straw into long, narrow
ditches containing some two feet of water and then to cover the
whole mass with sufficient mud taken from the pit, so as to
completely immerse the straw and prevent it rising above the
liquid during retting. Like other fermentation processes, retting
proceeds more quickly during warm weather and as this method
is carried on immediately after harvesting the crop in July it

620 SCIENCE PROGRESS

only requires from eight to ten days for the straw to be suffi-
ciently decomposed. Experience tells when it should be
removed and then the people employed get into the pit and
carefully remove the bundles from the mud and water. Needless
to say the work is exceedingly unpleasant, more especially
because of the powerful stench which arises when the bundles
of straw are disturbed. After rinsing in cleaner water, the straw
is spread over a stubble field and there it remains for a month
or six weeks before it is dried and taken to the barn. The
small farmer carries out all these processes himself and although
his methods of cleaning the fibre are quite primitive the product
he obtains has a good name for softness and pliability. It is
dark in colour, inclining to blue — giving the name Blue Flax— but
it bleaches easily and is sought after for certain purposes.

Of the retting processes which are still carried out by the
farmer, " pond-retting" is the best. This is practised in Ireland,
France, Friesland and Russia with considerable success. It
involves placing the tied-up bundles of straw in water and
allowing them to remain there until properly retted. There are two
distinct methods of water-retting — the straw being either floated
or submerged : of these the former is the older and at the
present day is carried on only in Friesland. The bundles of
rippled and dried straw are floated on the surface of a fairly
large stretch of still water and every day they are turned over so
that the side which was uppermost and out of the water is placed
beneath the water next day. This turning is performed by men on
the bank, who use a small prong fixed to the end of a light pole.
By far the better method of pond-retting is to submerge the
straw completely. Probably there is no place where this is
carried out better than in some parts of Ireland and no place
where more good flax is sacrificed to this method than in Russia.
For the most part the retting ponds are simple excavations
in the ground with a clay bottom, although some few are
roughly paved or have boarded sides. It is almost universally
agreed that the best method of filling the retting ponds is to
arrange the bundles vertically or nearly so, one row deep,
with the root ends downwards. When the pond is completely
filled, a light covering of straw, tree foliage or other suitable
material is generally put over the flax and on the top of that
sufficient stones are arranged to submerge the entire mass
uniformly. The progress of retting is carefully watched

Fig. 3. — Retting tlax : Bedfordshire, 1912.

Fig. 4. — Retting flax : FrieslanJ.
PLATE II.

620]

PROJECTED REVIVAL OF THE FLAX INDUSTRY 621

especially towards the end of the operation, when the straw is
examined several times each day. The usual time for steeping
is from ten to twelve nights and when the adjudged point has been
reached the straw is carefully removed from the pond and spread
over grass land or opened out and stood upon end to dry.

When larger volumes of water are used or when the water is
allowed to flow slowly through the pond, the colour of the resultant
fibre is much paler ; and when retting is carried out at the shore
of a lake or river, the fibre obtained eventually is almost white.

For the production of high-class fibre, the method known
as ** double retting " stands before all others. It is practised
with greatest perfection in Belgium in the neighbourhood of
Courtrai, where since the middle of the last century flax has
been systematically double-retted in the River Lys. This
river is naturally adapted to retting inasmuch as the water is
very slow-moving and the river bank slopes gently down to
the water-edge. What probably is the cause of such successful
retting in this river in particular is the slow movement of the
water and the large amount of organic matter which it carries
from towns situated some distance above the portion of its
course devoted to retting. Bacterial development under these
circumstances, aided by the enormous quantity of flax which
is annually retted in the river, has resulted in the exception-
ally favourable conditions which obtain at the present day.

The Lys retting period lasts from April 15 to October 15 and
during that time the river is practically closed to traflic. For
some twenty miles on either side of Courtrai a continuous row
of retting crates or ** ballons " are to be seen packed close
together near to each bank of the river and remarkable acti-
vity prevails during the whole period. On the river bank the
straw is sorted into heaps of approximately equal length of
straw and the various heaps are made up into bundles which are
packed closely into the " ballons." Sacking is placed along
the open front, an ample covering of straw is spread over the
top and the "ballon" is then launched into the river and
weighted down by large stones so as to submerge the flax
straw. During the summer months the temperature of the
river water is about 20 to 25° C. and the first retting occupies
nearly a week. As fermentation proceeds the " ballon " rises
out of the water and therefore requires its weight of stones to
be adjusted from time to time.

622 SCIENCE PROGRESS

At the close of the first retting period the "ballons" are
hauled up on to the bank, the flax straw is taken to an adjacent
field where the bundles are opened and the straw arranged
on end in small open sheaves — ** steeples" — to dry. After about
three days the dried straw is collected together and is generally
given a rest-period of about one month before being sorted over
again, made up into bundles and retted in the river as in the
first instance. The second retting does not take so long as
the first retting, although the time necessary depends upon
several variable factors such as temperature, quality of original
straw, extent of first retting, etc. To determine precisely when
retting should be finally arrested requires very considerable
knowledge, aided by careful and repeated examinations of the
retting straw. When the conditions are satisfactory, the
"ballons" are taken from the river and the bundles of straw
are removed and dried after the manner already described.

This fermentation process of retting may be accelerated by
raising the temperature of the water in which the flax is steeped:
a fact which, although known long previously, was first made
use of practically by Schenk (1846) who devised a method of
retting flax straw in warmed water. Since then many establish-
ments have been organised and worked on this principle in
various countries including England and such retting establish-
ments, generally speaking, met with success. The chief
drawback to the successful working of many of them seems
to have been want of capital. It is of interest to find it re-
corded that in 1853 as many as twenty such retteries were at
work in Ireland alone and that, of the flax factories in England,
those which had adopted retting in warmed water at a central
depot were the last to close down. As recently as 1896 there
were two such retteries successfully working in Yorkshire.

It will serve no useful purpose to mention here all the various
modifications of Schenk's original scheme nor the vicissitudes
through which they passed. At the present time there are flax
retting depots at Bruges, Courtrai, Oenkerk and Appingadam
where retting in warmed water is successfully practised and the
fibre turned out is of good quality.

At the small factory near Courtrai flax straw is retted in
cemented tanks ; each one being fitted with a false bottom upon
which the bundles of straw stand and beneath which steam-pipes
are made to warm the water contained in the tank to 27 to 30* C.

PROJECTED REVIVAL OF THE FLAX INDUSTRY 623

The straw is twice retted and during each operation the water is
changed at least twice. At the retting station at Genkerk in
Friesland there are three pairs of retting tanks which are built
of stone and lined with wood and these also are fitted with
steam-pipes beneath a false bottom. The temperature of the
water is maintained at about 30° C. during about three days and
nights — until the straw is properly retted — then the water is
run off into a field drain and the straw is arranged in ** steeples "
to dry.

Near Bruges, there is a larger station than at Oenkerk,
where an almost identical plan is adopted ; the retting being
completed in seventy-two hours. Double-retting is practised at
Appingadam Central Rettery, where the retting tanks are
arranged in series or batteries of four. The tanks are made
of concrete and are each provided with an inlet at the bottom for
warmed water, overflow pipes and exit pipes and above each
battery of tanks there is a reservoir fitted with steam circulator
pipes where the required quantity of water is warmed prior to
entering the retting tanks.

Early in the nineteenth century retting was studied from the
biological side and it was soon established that it was primarily
a fermentation process : it was not, however, until much work
had been done on this subject that any further definite knowledge
was obtained. In 1868 Kolb put forward views regarding the
more exact nature of the retting process, namely, that it was
a pectin fermentation process whereby the insoluble inter-
cellular substance was removed as soluble products of fermenta-
tion, thus allowing the fibre to be separated.

This explanation was warmly contested by Tieghem and
others who supported the view that the process involved the
resolution of the cell structure and the dissolution of the
cellular membrane by a specific anaerobic organism. The
investigations of Fribes showed that the flax stems themselves
carry a definite anaerobic bacterium of somewhat large size
which is active towards the intercellular substance but which is
quite inactive towards cellulose ; this view is held at the present
day, although it is sometimes suggested that there are naturally
on the flax stems several species of bacteria which are concerned
in the retting.

The recent researches of Stormer (1904) and of Hoffmeister
(1905) show that the chief retting organism is not diflicult
40

624 SCIENCE PROGRESS

to isolate but, as at present understood, it is doubtful whether the
application of pure-culture methods of retting will be financially
possible on a technical scale.

Whatever the method of retting may be which necessitates
wetting the flax straw, before the fibre can be cleaned the retted
straw has to be thoroughly dried. This is effected either
by spreading the wet straw on suitable land or by stooking it up
on end to dry.

When properly dried the flax straw is gathered together,
tied in bundles and, as with all other stages of flax-handling,
great attention is given to making up the bundles evenly: all
straws should be straight and the ends should present a brush-like
appearance. At all stages great importance is attached to the
manner in which the flax is put up in bundles, because if
not well arranged considerable loss will result when the fibre
is cleaned. The dried straw is stored under cover of a barn or
under a good thatch until it is convenient to scutch and clean
it during the winter months.

This matter of adequately drying steeped flax is a serious
one for the management of retting depots, because, were it not
for the difficulty of drying the wet straw during inclement
weather, such depots could continue retting operations through-
out the year. As it is, land has to be set apart as drying ground
and used only during part of the year. Various attempts have
been made to dry the wet straw under cover, in a current
of warmed air and in warmed rooms but the amount of moisture
which has to be removed is so great that these methods have
not proved commercially successful. The wet straws lie in such
intimate contact one with another that the occluded water is diffi-
cult to remove. If some more open arrangement could be effected
the main difficulty of artificial drying would be overcome.

Before the process of cleaning the fibre is attempted, the
brittle, central woody part of the dry straw is broken up into
small pieces, so that the fibre may receive as little damage
as possible when being cleaned: this preliminary process is
known as " breaking." The machines used for this purpose
were formerly operated by hand and of very simple con-
struction, consisting of grooved wooden levers or single pairs
of fluted rollers between which the flax straw was passed and
repassed several times. In Russia, Hungary, Silesia and parts
of Friesland hand-breakers are still to be seen but it may be

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H^^-oiN*' . ■"'' ^-^^Sn^r:3r''Vi^lH

^l,^>^^HH|

,I3l«jIH

Fig. 5. — Retting flax in River Lys, near Courtrai, Belgium.

Fig. 6. — Belgian scutch mill.
PLATE III.

624]

PROJECTED REVIVAL OF THE FLAX INDUSTRY 625

said that these appliances have been entirely superseded
wherever the flax industry has attained a fairly high level.

Although the principle of the modern machines is much the
same as the old-fashioned ones, the " breaker " is now made with
many (eight or ten) pairs of metal rollers, some of which are
smooth to crush the straw flat, followed by many other pairs of
grooved rollers differently fluted : the object being to break up
the woody part of the stem and to remove mechanically as much
of it as possible at that stage without injuring the fibre. These
machines are driven by water, steam or other motive power and
ordinarily form part of the equipment of a flax-cleaning mill.
The straw is fed into the breaker at one end and received at the
other end by lads who handle the material carefully and lay
the broken straw in heaps ready for the cleaners.

After coming from the ** breaker," the broken-up woody part
of the straw — the shove — is separated from the fibre by a
mechanical beating operation known as scutching and, save
for some details, this is conducted on the principle of submitting
handfuls of broken straw to a beating by wooden blades which
are either wielded by the hand or are fixed to a rotating wheel.

As a household industry, scutching and cleaning fibre by
hand or by hand-driven machinery have quite disappeared
except in Russia and some of the more rural parts of Belgium.
These simple methods, which admit of varying the treatment at
will to suit the particular material dealt with, have much in
their favour from the point of view of preparing good fibre :
they have, however, been superseded for economic reasons.

The construction of a scutch mill is such that the revolving
beaters pass close in front of a rigid upright " stock " over
which the flax is firmly held and submitted to rapid beating in
a downward direction. The ease with which flax is scutched
depends largely upon whether the straw has been well or under-
retted : in Belgium, where flax is well retted, the scutching
blades are lightly fashioned and the rotating wheel carries more
blades than in Ireland, where flax is more often under-retted.

This briefly describes the operation of scutching as carried out
almost universally. The methods and appliances are primitive
and the treatment accorded the fibre is severe, yet more recent and
apparently improved devices for removing the shove have met
with but slight attention from those engaged in scutching.

In addition to the operations of retting which have been

626 SCIENCE PROGRESS

described already, various other methods of separating the fibre
have been advocated from time to time. Although it is not
exactly clear why they always fell into disuse, there seems
to be good evidence for concluding that it was owing to the
dry condition of the fibre obtained, to the removal of the
oily and strengthening matters from the fibre which give to it
a valuable spinning quality and also to the opposition offered by
the manufacturers and the trade generally to a new article.

Cost of Production

It is now so long since flax was grown as a field crop in
this country that little importance can be attached to the
recorded cost of production. Fifteen years ago the estimated
cost of this crop in Cambridgeshire, Lincolnshire and Suffolk
was said to be about £s per acre ; in Yorkshire a trifle less and
in the south of England a trifle more. It is probable that these
figures would not represent the cost at the present day owing to
the general increase in the cost of production that has taken
place during the last decade.

With regard to the preparation of the fibre the same argu-
ment applies ; moreover, the cost of retting is very variable :
frequently in two districts not far removed from one another,
the cost of retting in the one may be double that in the other.
Scutching is variously estimated to cost about ;^2 los. per acre of
straw grown but as this depends upon the skill of the scutchers
and the extent to which the straw has been retted, the cost of
this operation may vary considerably. The most trustworthy
information would be obtained from a central rettery where proper
records were kept and where the value of the product is recorded.
Unfortunately such data are not to be obtained from the few
depots in operation. The only indication of success upon which
reliance can be placed is the general appearance of the establish-
ment and the fact that some of them have been in operation for
about ten years, during which time modest profits have been made.

It has been mentioned already that during the past year
(1912) flax was grown in Bedfordshire as a fibre crop. Certain
experiments were made there with a view to getting practical
information regarding the successful handling of the crop both
in the field and during the after-processes. The field experiments
were made to include trials of varieties of seed procured in

PROJECTED REVIVAL OF THE FLAX INDUSTRY 627

Russia and in Holland and the effect of adding muriate of
potash at the time of sowing. Different methods of sowing the
seed were adopted and trials of different methods of harvesting
the crop were made.

Certain points of difference are said to be noticeable when
retting is conducted in cement-lined tanks as compared with
wood-lined tanks : the nature of the difference in the fibre pre-
pared from undried and from dried straw is not yet understood :
likewise the possibility of successfully treating the nauseous
tank effluent on a filter bed is unsolved. These and other
problems are of considerable importance when the question of
centralising retting operations is considered and it was with the
object of attempting to elucidate such problems that the experi-
mental tanks referred to were constructed.

So as to avoid having to attribute any success obtained with
the crop to exceptionally favourable soil, when selecting the
land care was observed not to choose that which was eminently
suitable to the flax crop but rather a soil which, if anything, was
adverse to its growth. An able farmer of good standing, who
farms gault land near to the chalk, was supplied with the different
varieties of seed and asked to do his best with the crop, one
of the reasons for making the trials being to ascertain what
difficulties would be encountered when employing labour which
was unfamiliar with the work.

The unusually dry weather during April seriously delayed
the sowing of the seed, in fact some of the plots were not sown
until well in May. Afterwards, the season became exceptionally
wet ; rain fell so frequently during August and September that
harvesting operations were interrupted and were often com-
pleted with difficulty, as was also the drying of the retted
straw.

Some difficulty was contemplated in getting the crop weeded
and pulled and in this there was no disappointment, although
the villagers displayed some anxiety to do their best and their
services became more useful as they became more familiar with
the work. No difficulty was experienced in getting female
labour in the fields, indeed, some women were glad to walk
nearly three miles to the work.

At no stage of the growth of the flax nor yet at the time of
harvest could any difference be observed between the part of
the plots which had received a dressing of muriate of potash

628 SCIENCE PROGRESS

and that which had not. Generally speaking the crops were
distinctly good, although in some places the consequence of
irregular germination was markedly shown.

With such frequent showers of rain falling, it was found
impossible to dry the crop when tied up into sheaves but this
was successfully accomplished by stretching a number of wires
the entire length of the field against which the flax was lodged
as soon as it was pulled. When sufficiently dry the flax was
then removed to the shelter of a large rick cloth where women
were engaged in rippling off the seed after the manner adopted
in Holland.

The deseeded straw was sorted over and tied up into bundles
and these were packed vertically in the retting tanks and over
them some hurdles were placed upon which rested a heavy piece
of timber to keep the bundles in position. Water was allowed to
enter the tanks from a neighbouring stream and then a sufficient
weight of large stones was distributed over the hurdles to keep
the entire mass uniformly submerged.

After about a week had elapsed the water in the tanks was
run out into a settling reservoir, fresh water was admitted from
the stream and the retting allowed to proceed. Although in the
first instance retting in the cement-lined tank commenced later
and proceeded at a slower rate than in the wood-lined tank,
after the first batch had been retted no such difference was
apparent. When the straw was sufficiently retted the tanks
were again emptied and the straw was removed to an adjacent
field where experiments on drying were made on the lines of
those practised in other countries.

The attempts made to construct a filter bed to purify the
tank effluent were not altogether satisfactory, although the
analyses of the liquor made before and after filtration indicated
the possibility of success attending further experiments.

The work done last year took more the form of a preliminary
trial of the more difficult operations of flax growing and fibre
separation, namely harvesting and retting ; experience was also
gained in carrying them out under very adverse circumstances.
It is anticipated that during the present year it will be possible
to make arrangements to study further the problem of purifying
the effluent and also to conduct more systematic experiments
with a view to ascertaining more exactly what would be the best
provision to make for establishing a small retting station.

THE STATE PROTECTION OF WILD

PLANTS

By a. R. HORWOOD
Leicester Museum ; Recorder, Plant Protection Section, Seldom e Society

If there be one direction in which the British Isles is particularly
behindhand, it is in the matter of preserving and protecting the
native flora. This is the more apparent v^hen it is observed that
Germany or rather, it should be said, Prussia, has a well-organised
State Department for this purpose, whilst we in England have
neglected to take any such precaution.

Nor is Prussia the only country that has reahsed the necessity
of giving State protection to wild plants, many other continental
nations having adopted this measure and America has also
realised its importance. As if to emphasise the need at home,
many of our own Colonies have already adopted temporary or
partial means of preservation or protection in special cases, by
establishing reservations and by other methods.

It is proposed to examine the peculiar circumstances which
make State protection necessary in this country and to describe
the temporary expedients resorted to already to prevent the
extermination of plants.

The principal causes at work contributing to the complete or
local extermination of wild plants are :

Smoke ; atmospheric abnormalities ; drainage ; cutting down
of woods ; desiccation ; drought ; cultivation ; building opera-
tions; sport; hawking and collecting; professional collecting;
nature-study operations.

Dealing seriatim with each of these major factors, the first,
smoke, is undoubtedly more potent than most of the others. In-
dustrial activities are continually enlarging the area of operations
in which the consumption of fuel is a necessary factor, the effect
being to transform completely the character of the open country
to the north-east of large towns and coalfields, in fact wherever
centres of industry have been established. Cryptogams more
especially, as I have shown elsewhere, have exhibited a marked

decrease in number and character all over the country.

629

630 SCIENCE PROGRESS

The effect of fog in London was described by Prof. F. W.
Oliver more than twenty years ago and G. Bailey has proved
that the same effect can be demonstrated as arising from the
aerial conditions in the Manchester district. Glasgow, Birming-
ham and Liverpool are other cities that are similarly affected by
the smoke evil.

Nor do these statements rest alone upon the authority
of those whom I have mentioned. Cryptogamists in all
parts of the British Isles bear testimony from their own
observations to the deleterious effect of smoke. A notable
instance is the Black Country, which is almost entirely denuded
of cryptogams. The smoke-clouds of Yorkshire can be seen at
a distance of thirty miles away and their effect is well known.

The atmosphere itself, apart from its accompanying impurities,
has undergone a change which has become particularly marked
during the last twenty years, these islands being much drier
than formerly.

One of the causes of the incidence of a drier era is un-
doubtedly drainage. We have only to mention the Fens as an
illustration of this process being carried out on a large scale to
demonstrate the extent to which a limited area in this country
has been drained of its inherent moisture but though less obvi-
ous elsewhere, drainage has produced a similar effect in all areas
brought under the conditions necessitated by modern methods
of cultivation.

The decrease of moisture, which is especially deleterious to
hygrophiles adapted to grow only under moist conditions, is
indirectly brought about also by the cutting down of trees or
woods. Thousands of acres of wood in Scotland, once used as
deer forests, have been cut down. In historic times, both England
and Ireland were extensively covered by tracts of forest ;
remnants of these are to be seen to-day in spots where ancient
oaks still linger and are pointed to as the trees under which
perhaps Druids once worshipped. Caesar's account of Britain
shows that Central England was once a wide region of primaeval
forest. To-day, with the exception of isolated forests — Sherwood,
Arden, Charnwood ^ — it is given up to a commonplace mesophytic
vegetation and consists largely of pasture or meadow-land.

Intimately allied to the last factor is the cultivation of land.

' Prof. H. Conwentz thought that not a remnant of indigenous woodland could
be found in this country.

THE STATE PROTECTION OF WILD PLANTS 631

The ridge and furrow of the midlands testify to the former
extent of cornlands and illustrate the purely local character of a
method of drainage which caused little more than local disturb-
ance of conditions without removing them. They allowed for
an alternation of xerophilous and hygrophilous plants without
driving out either class.

Where this primitive type of drainage alone persists, what
I have ventured to call " vestigial floras" or remnants or indica-
tions of the real natural plant-formations will be found surrounded
by a modern mesophytic type of vegetation. The insignificance
of the vestigial floras affords, in the field, an optical demonstra-
tion of the immensity of the changes wrought by this one factor
alone, the removal of water by drainage. Where, moreover,
land is drained by modern processes, by carrying the water by
drains to ditches, thence to streams, lastly to rivers and the sea
or lakes, the change is complete. There are not even traces of a
vestigial flora — there is in fact no aboriginal flora. Its place has
been taken by another type of flora.

If the grass-pastures alluded to are converted into cornfields,
there will be fresh changes. And a fresh race of alien plants
will impress itself upon the remnants of mesophytic vegetation.
This like the preceding phase will be artificial and from the
point of view of the continuance of natural plant-formations is
an instance of wholesale extermination on a very large scale.
And from the scientific point of view, extermination must be
examined in the light of the original not the derived or secondary
plant-formations.

Another important cause of disturbance and extinction is the
extension of building operations. The later extensions and
modifications of the City of London have brought about extra-
ordinary changes, as may be proved by comparing Curtis's
Flora Londinensis with the present flora. The increased
attention given to sanitary conditions leads to the alteration or
pulling down of old dwellings in old towns ; in this connexion
their very antiquity is the point of importance. Cryptogams,
particularly Lichens and Mosses, are especially addicted to
such habitats and are destroyed by the pulling down of old
buildings, whilst the erection of new buildings on fresh ground
involves the destruction of other habitats, since the sites
chosen are invariably the areas occupied by plants not found
elsewhere. This is especially the case where towns, as is often

632 SCIENCE PROGRESS

the case, are built on natural beauty-spots or on particularly
salubrious sites.

It is perhaps un-British to condemn anything which encour-
ages the love of sport but nowadays vast areas are given up
to recreation, whereby wild plants on the outskirts of towns
are exposed. This applies especially to golf. A certain
type of ground, suitable for golf-links, by an irony of
circumstances is very favourable to the growth of a class of
rare or local plants. And links are artificially treated, so that
the natural turf becomes altered in the process and all but the
soft grass tends to disappear. The proximity of golf-links to a
large city at once effaces the extensive flora that tracts suited for
links afford ; as an example, we may mention Barnes Common,
once noted for many uncommon wild-flowers. Racecourses
again are examples of the same correspondence between rare
plant habitats and natural features suited to sport. The old
racecourse at Leicester afforded before its conversion into a
sporting centre a station for the Mouse-tail, a particularly rare
plant in this county.

One of the most important factors of plant extermination,
because selective, is the practice of commercial hawking and
collecting. It is enough to offer, as an example of this class of
vandalism, the case of the Killarney Fern, which was sold in
Killarney as long ago as 1850 for five shillings a single root.
This and other cases of the kind in Ireland I have already
described elsewhere. And what applies to Ireland applies with
greater force, in regard to the extent of such ravages, in England,
Scotland and Wales. Moreover, ferns are not the only com-
modity in request but many other wild plants, especially the
beautiful ones, such as anemones, primroses, bluebells and
orchids come within the purview of the hawking fraternity.

To some extent the modern practice of taking holiday excur-
sions has been the cause, in the neighbourhood of holiday-resorts,
of the disappearance of the wild-flowers that used to adorn such
beauty-spots at the commencement of the holiday-making era.
This cause may appear unimportant to the uninitiated but
statistics show otherwise.

The districts around towns are not the only source of plunder
for this class of depredator, for hawkers and tourists alike invade
the more secluded spots where vegetation is luxuriant and tak(
toll of the rarities to be found in such haunts.

THE STATE PROTECTION OF WILD PLANTS 633

These people are not experienced in distinguishing between
allied species, nor do they know the habitats (it is to be hoped)
of the rarest plants, which is some satisfaction to the person
interested in the welfare of our native flora.

Perhaps the scientific collector is the person who does the
greatest harm. He possesses the intimate and expert knowledge
which enables him to go to the exact spot where rarities grow
and to discriminate between closely connected species, a difficult
task at best. Whilst the hawker causes wholesale extermination
of common plants usually the most beautiful, causing local
extinction, the scientific collector collects the rarities in the few
spots in which they grow and can ultimately bring about their
universal extinction.

The very general attention given at the present time in the
elementary schools to nature-study is another likely means by
which wild-flowers may be diminished in number. Having
regard to the normal desire of the teacher to inculcate a love of
nature and at the same time to impress upon his pupils the
necessity of regarding the beauties of the countryside as a
treasure not to be misused, it maybe hoped that there is not any
need to fear widespread difficulties from this cause; but the
possibility exists and must be guarded against, as the young
mind has no idea of taking thought for the future.

There are a considerable number of minor causes at work
contributing to bring about the diminution or extinction of
species, locally or universally, in the British Isles but it is not
our present purpose to consider these, as they have been dealt
with elsewhere. The consideration of the main causes enume-
rated is assuredly enough to make it necessary to discuss the
possible remedies that at present lie to hand.

The general character of many of the factors which lead to
the extinction of plants requires that any remedies that may be
introduced should be comprehensive, wholesale, effective and
permanent. Moreover no remedied measures will have any of
these qualities unless they also carry authority.

It is needless to suggest that the most effective means will be
the establishment of State protection.

It should be some incentive to us in this country to work
towards this ideal, that, as mentioned already, the Prussian
Government has a well-organised department of the State

634 SCIENCE PROGRESS

charged with the preservation and protection of natural monu-
ments. And we would ask, if this be possible in Prussia, can it
not also be made an accomplished fact in England ? The more
or less general adoption of some means of preservation by other
European and foreign nations, as well as by our own Colonies
should be reason for action on our part.

The present efforts to foster a movement towards the State
protection of plants have been primarily guided by the import-
ance of educating the public as to its need.

Towards the close of 1910 an arrangement was made whereby
the campaign which I had hitherto carried on personally was
made the special objective of a section of the Selborne Society.
The Society has always regarded the welfare of plant and
animal life as part of its programme from the commencement of
its career ; but hitherto its activities had found an outlet in other
channels.

At the suggestion of my friend and former tutor Prof. G. S.
Boulger, therefore, a section was initiated, called the Plant
Protection Section, with Dr. A. B. Rendle as Chairman, myself
as Recorder.

It is proposed to give a summary of the work and aims of
the section and at the same time to consider remedies that may
sooner or later be adopted for the factors of extinction discussed
in the previous section, taking them as before one by one.

With regard to the influence of smoke, it should be remem-
bered that there is a Smoke Abatement Society at work in a
great number of our industrial centres. It is not, however,
universal and has not yet acquired a national character. The
Black Country and the coalfields are exempt from the control of
any smoke regulations.

But in so far as private consumption of coal is concerned,
the tendency is rather towards economy and the adoption of
smokeless fuel. The construction of smokeless grates is receiv-
ing increased attention and herein lies some hope of the arrest
of the smoke evil.

The dryness of the atmosphere can be remedied in at least
one direction which will be productive of good in more than one
way. The cutting down of trees may be counteracted by
reafforestation — a practice on the increase.

It is a promising feature to note that the Woods and Forests
Department has at last recognised the necessity of training

THE STATE PROTECTION OF WILD PLANTS 635

foresters with a view to the proper care of our national forests.
This must have a beneficial effect upon the forests and wood-
lands in private hands by encouraging a wise and skilful super-
vision of those sources of fuel and moisture also. It is the
retention of the latter that we specially advocate here but as it
is intimately wrapped up with the preservation and establishment
of permanent woodlands the encouragement of the latter aspect
is the one to emphasise, because one of more direct economic
importance. The encouragement of the keeping of Arbor Day
has always been advocated by the Selborne Society and it is
now receiving wider recognition, so that children may be
impressed with a desire to be provident in this matter.

The desiccation which is due to drainage is a question which
is best dealt with by the advocacy of a general system of
irrigation. There can be no two opinions as to the value of this
practice and of the necessity of adopting it in this country,
especially since the recurrence of droughts periodically has
become an established fact. The necessary adaptation of
moisture-loving plants to xerophilous conditions can only be
controlled, to the advantage of the hygrophiles, which with
difficulty survive this artificial struggle for existence, by the
reservation of typical areas required by such hygrophilous
species ; and reservation is again a matter for State organisation.

Coming next to the increasing demolition of buildings,
especially ancient ones, it is a matter for satisfaction that in the
National Trust for the Preservation of Ancient Monuments and
places of natural beauty we have a body actively engaged in the
acquirement and preservation of such sites. Moreover, the
recent recognition of the value of the work done by the National
Trust by the State in the proffer of advice in such matters by
the Office of Works is a good augury for the future not only
of this phase of preservation of monuments but also for the
existence of a department for the protection and preservation of
all natural monuments, as in Prussia. That other bodies, such
as the Kyrle Society and Commons Preservation Society, as
well as the Footpath Associations, are receiving public support
on a wide scale shows that there is ample scope for optimism
in this direction.

Moreover the care of the highways is another matter requir-
ing urgent attention. Hedges and ditches of roadsides and
paths are being periodically despoiled of their beauty by the

636 SCIENCE PROGRESS

operations of the roadscraper, hedgecutter, macadamiser and
others. The influence of motor-cars which bespatter the high-
ways with dust and oil is another disquieting feature. In this
case the Plant Protection Section is endeavouring to elicit the
sympathy and support of the rural and urban district councils
to abolish the formal treatment of roads and to regulate the
motor traffic.

As to sport, it is necessary to arouse the interest of the great
landowners in the value of plant-life so that they may be led to
favour the subordination of golf-links made upon their property
to the natural features of the district and the preservation of
wild species of plants. The Selborne Society here again aims
at influencing both landowner and sportsman. In the case of
racecourses near towns, it is necessary to approach town
councils as to any encroachment of these upon natural features.
In the case of public parks, the parks committees need advice
as to the conversion of natural features into artificial recreation
grounds. In this, as in other matters, the active support of the
public is required.

To put a stop to the practice of hawking wild plants is a
work that can only be accomplished by the aid of the county
councils. Some of these, as in Essex, Devon, Surrey, have
already framed byelaws for the prevention of hawking on the
highways and property over which they have control. The
Selborne Society aims at obtaining the promise of every
county council to follow suit. Having accomplished this, it
will be an easy step to legislate, the next stage towards State
protection. By this means private property not under the
jurisdiction of the county councils would be safeguarded in
the same manner as the highways.

Already a Bill has been drawn up by Prof. Boulger, which
has the approval of Lord Avebury ; one of the next steps is to
introduce it into Parliament, on the first favourable occasion.

The vandalism of the hawker, of which more is heard than
of the other equally deleterious factors of extinction, can be
considerably prevented or controlled by the aid of the scientific
societies in the country. It is proposed to ask each of these
bodies to appoint one of their members to act as a corresponding
secretary and local representative, keeping the Section in touch
with local requirements and possibilities of support.

One of the m.ethods of opening the eyes of the public to the

THE STATE PROTECTION OF WILD PLANTS 637

gravity of the situation is to publish leaflets setting forth con-
cisely the losses in prospect and appealing to their common
sense to prevent the vandalism which goes on. Through
county councils and others fifty thousand such leaflets have
been distributed appealing " to the public " and " to teachers of
nature-study." Cards to be hung up in public places have also
been distributed. The assistance of the clergy and medical pro-
fession is to be enlisted in this work. The influence of the Press
in drawing public attention to the matter is also to be sought.

Another important means of strengthening the evidence for
the adoption of State protection in this country and of promoting
its realisation will be to secure the co-operation of affiliated
bodies, such as the British Association, Yorkshire Naturalists'
Union, South-Eastern Naturalists' Union and others. The attach-
ment of the Woods and Forests Department, the Board of Agri-
culture and Board of Works to the cause will further strengthen
the hands of those who wish to promote State protection.

The danger that may result from the pursuit of nature-study
is only to be counteracted by the co-operation of teachers and
the issue of leaflets discouraging excessive collecting. This has
already been done and we believe with beneficial effect. The
readiness with which the county councils undertook the work of
distribution promises well for the proposed appeal to them to frame
byelaws against hawking and in other ways help on the cause.

Over-collection in the schools may be guarded against by the
establishment of school-gardens, a step which in itself will
definitely encourage the study of botany.

Moreover museums are rapidly beginning to lay themselves
out to provide wildflower tables for the public by the aid of
which botanical study is given a direct stimulus and a certain
economy of material is secured, whilst at the same time quite as
much information is conveyed as when several separate collec-
tions are made in different schools.

Akin to this method is the formation of a wild garden in the
proximity of the school itself, the seeds sown being collected in
the district during the autumn of the previous year.

It is the opinion of the Plant Protection Section that, if these
and other methods are adopted, some, if not a great, measure of
success will follow the efforts to preserve the native flora of
the British Isles by the creation of a department of the State
to carry out proposals such as are made in this article.

FURTHER SPECULATIONS UPON THE
ORIGIN OF LIFE

By CHARLES WALKER, D.Sc.

The specialisation which has been the inevitable result of the
enormous increase in the general fund of knowledge during the
past sixty or seventy years is rendered very evident in the
recent discussion on the origin of living matter ; it appears to
be impossible, at the present time, for a man to possess more
than a superficial acquaintance with any branch of science
excepting that to which he has devoted himself particularly.
So great is the accumulation of recorded observations that, as
a rule, it is possible to keep up to date only in one section
af one of the great branches of scientific knowledge ; yet to
consider this problem properly it is necessary to call in the
help of biology and chemistry in some of their latest stages and
probably also physics.

It appears to me that in this discussion each biologist has
placed the solution of the problem where he sees the fewest
difficulties are to be faced; this moreover has not been where
his knowledge has been most detailed and intimate. Such a
course is a very natural one to adopt and I shall be obliged to
follow to some extent the example of better men and do the
same thing myself

Upon one point biologists seem to be more or less agreed —
that the problem is fundamentally one for the chemists.
Chemists, however, are not unanimous, I notice, that the bio-
logists have done enough of their share of the work to place
them in a position to state the problem in such a manner that
it can be handled by the chemists.

As has always been the case in such discussions, meta-
physical conceptions have been offered as explanations by
several biologists. Our knowledge of the properties of living
matter and of the possible conditions under which it may have
originated has always been hindered, never helped, by meta-
physical conceptions, from those propounded by the author od

638

SPECULATIONS UPON THE ORIGIN OF LIFE 639

the Book of Genesis down to those advanced by Driesch,
Bergson and others. I therefore propose to leave vitalistic
ideas alone and to begin by glancing at certain pertinent points
relating to some properties of living matter which are common
to the overwhelming majority of organisms belonging to both the
animal and vegetable kingdoms.

The unit of living matter, as far as we know, is the cell. I
will not at present try to give a comprehensive definition of a
cell but will deal, for the moment, only with that form in which
it is found in multicellular and the majority of unicellular
organisms both animal and vegetable.

The cell, in this sense, is a mass of protoplasm generally so
small as to be invisible to the naked eye. In some cases it is
surrounded by a covering, which apparently may be formed
from a secretion or excretion and have ceased to be a living
part of the cell ; or it may be a membrane formed from the
protoplasm which continues to live. In other cases, the cell
is said to possess no covering but there are many observed
facts which make this assumption unacceptable. Whether
there is or is not always either a membranous covering or a
layer of differentiated protoplasm which acts as such is not
material to the point of view from which I am dealing with the
subject under discussion.

Within the mass of protoplasm— the cell — is an area sur-
rounded by a membrane which differs in several ways from the
rest of the cell. This is the nucleus. The rest of the cell is
known as the cytoplasm. When cells are fixed and stained, it
is found that within the nucleus are collections of a substance
which has a great affinity for basic stains. On account of its
taking up stain very readily, this substance has been called
chromatin. Chromatin generally appears as minute granules,
sometimes collected together in masses of varying size, some-
times arranged in strings. The most usual form is a combination
of masses connected by a meshwork of strings. The chro-
matin appears to be always enclosed in an envelope of an
apparently homogeneous and not readily stainable substance
known as Hnin.

Within the nucleus are usually found either a single or
several more or less rounded bodies, the nucleoli. These
generally differ to some extent from the chromatin in their
behaviour towards stains.
41

640 SCIENCE PROGRESS

In the cytoplasm of cells, excepting those of the higher
plants, a pair of minute bodies known as centrosomes is found.
These bodies play an important part of which I shall have to
speak presently in cell division. They also appear frequently
to be connected with the motile appendages of cells. Besides
these there is a group of structures in the cytoplasm known as
chondriosomes, which are further subdivided according to their
structure and appearance.^ At present, however, we need only
consider them as a single group. Apart from certain phenomena
connected with chondriosomes which I shall deal with later, it
is only necessary to say that they give rise to the fundamental
material from which are formed the specific cytoplasmic sub-
stances found in the cells of various tissues, such as certain
parts of the striped muscle fibres and " prickles " in the cells of
the skin.^

Cells, as far as we know, have but one mode of origin and
that is from preexisting cells. The way in which cells divide is
by no means simple. The chromatin in the nucleus becomes
collected into a number of well-defined bodies, generally in the
form of U's and V's, which are known as chromosomes ; these
bodies divide individually, splitting lengthwise, thus ensuring a
division which is both quantitative and qualitative. While this is
happening, radiations appear in the cytoplasm around the cen-
trosomes, some of the radiations running between the two. The
centrosomes separate further and further apart, until they are
found at opposite poles of the cell with a spindle of radiations
extending between them. The nuclear membrane breaks up
and disappears, each chromosome becoming attached to one of
the spindle fibres. At the same time the cytoplasm takes an
hour-glass shape and the half of each chromosome travels
towards the opposite poles of the cell, so that when the con-i
striction in the middle of the hour-glass terminates in the
separation of the cell into two daughter cells, an exact repre-
sentative half of every original chromosome is present in each.

^ Meves, F., " Die Chondriosomen als Trager erblicher Anlagen. Cytologische
Studien am Hiihnerembryo," Arch. f. Mikro. Anat., Bd. 72, 1908.

^ Duesberg, J., " Les Chondriosomes des cellules embryonnaires du poulet, et
leur role dans la genese des myofibrilles," Arch. f. Zellforschung., Bd. iv. 1910 ;
Arnold, G., "On the Condition of Epidermal Fibrils in Epithelioma," Quart.
Journ. Micro. Science.^ vol. 57, part 3, Feb. 1912 ; Firket, J., " Recherches sur la
g^n^se des fibrilles epidermiques chez le poulet," Anat. A?iz.^ Bd. xxxviii. 191 1.

SPECULATIONS UPON THE ORIGIN OF LIFE 641

Every multicellular organism begins its existence as a single
cell, which in most cases is formed by the fusion of two cells,
one derived from each parent. This cell divides into two ; each
of these divides in turn and so on, until the whole body of the
organism is built up. Remembering what happens in cell
division, it is clear that every cell in the body, including those
that are to be cast off eventually to fuse with other cells and
form new individuals, must contain exact representatives of the
chromosomes contributed by the parents. This has led to the
very general assumption that the chromatin is the determinant
of the hereditary characters, the actual substance by which these
are conveyed.^ The sexual act is held to consist essentially in
the union of chromatin from two distinct organisms.^

With these views I disagree most emphatically. To begin
with, it seems quite possible that the chromatin is merely a
secretion of the linin. It waxes and wanes at different times in
the same cell, particularly during certain periods preceding
division. If, however, it be true that chromatin is only a
secretion of the linin, the same claims would doubtless be made
for the latter substance. Unfortunately we know but com-
paratively little concerning it, beyond the fact that it forms an
envelope around the chromosomes, around the masses of chrom-
atin in the nucleus when in the vegetative state, a meshwork
between these masses; also that it probably gives rise to the
nuclear membrane, in some cases at any rate. However, in
view of recent observations and experiments, neither linin nor
chromatin can be claimed as the sole or even chief means by
which hereditary characters are transmitted ; nor can the import-
ance of the fusion of two cells which constitutes sexual repro-
duction lie solely in union of the chromatin from two distinct
organisms.

It has been shown that the chondriosomes divide individually
just as do the chromosomes. This has been traced from the
first segmentation of the ovum up to a late stage. They are
carried in the cytoplasm of the sperm and fuse with those in the
ovum, eventually forming the specialised cytoplasmic structures

^ Strasburger, Hertwig, Kolliker, Weismann and others at different times have
advocated this view. See The Cell, Wilson, E. B., 1904 ; Heredity, Thomson,
J. A., 1908 ; Minchin, E. A , Science Progress, Oct. 1912.

* Weismann's theory of Amphimixis. Minchin, E. A., Science Progress,
Oct. 1912.

642 ' SCIENCE PROGRESS

found in the various kinds of somatic cells.^ Chondriosomes
have been demonstrated in every class of cell in which they
have been sought.^ Though often difficult to demonstrate,
owing to their not being easily stainable by the methods
generally used, I have been able to find them in every kind of
cell, animal or vegetable, in which I have looked for them.
Here then are cytoplasmic structures which are handed on from
cell generation to cell generation, for which claims as the
transmitters of some of the hereditary characters may be made
as logical as are those made for the chromosomes.

Enucleated eggs of one kind of animal have been fertilised
with the sperms of another kind and in spite of a total absence
of maternal chromatin and linin, the resulting embryos have
shown purely maternal characters.^ When certain parts of the
cytoplasm of the ovum are removed before segmentation, it has
been shown that in the resulting larva certain parts of the body
are absent.* This is most significant, for it must be realised that
as all the cells constituting the fully developed organism arise
from the single cell — the ovum — if the destruction of a certain
portion of the cytoplasm of this cell result in the non-appear-
ance of a certain group of cells in the developed organism, the
power of producing the particular differentiation found in the
group of cells involved must have been latent in the cytoplasm
and not in the nucleus.

^ Meves, F., 1908, op. cit. " Uber die Beteiligung der Plasochondrien
(Chondriosomes), an der Befruchtung des Eies von Ascaris megalocephala,"
Archiv fur Mikro. Anat. Bd. 76, 191 1 ; "Meves and Duesberg, Die Sperma-
tozytenteilungen bei der Hornine," Arch. f. Mikro. Anat.^ Bd. 71, 1908 ;
Duesberg, op. cit.^ 1910, " Sur la continuite des elements mito chondriaux des
cellules sexuelles et des chondriosomes des cellules embryonnaires," Anat. Anz.
Bd. 35, 1910; Arnold, op. cit.^ 1912 ; "The Role of the Chondriosomes in the
cells of the guinea pig's pancreas." Archiv. fiir Zellforsch.^ 8 Band 2 Heft, 191 2 ;
Firket, op. cit.., 191 1.

^ St. George, V. la Valette, " Spermatologische Beitrage," Arch. f. Mikro.
Anat. Bd. iii. 1886; Benda, C, Verh. d. phys. Ges. zu Berlift^ 1896-7, 1898-9; Ver. d.
anat. Ges. Kiel^ 1898 ; Hoven, H., Arch, de Biol.^ vol. xxv. 1910 ; Faure-Fremiet,
C. R. Soc. de Biol.^ 1909 ; Prenant, A., Joiirtt. de VAnat. et de la Phys.^ vol. xlvi,,
1910, and many others.

^ Godlewski, E., " Untersuchungen iiber die Bastardieruns der Echniden und
Crinoidenfamilie," Archiv fUr Entwicklungsmechanik^ Bd. 20, 1 906.

* Fischer, A., " Entwicklung und Organdifferenzieruns," Archiv fiir Ent-
wicklungsmechanikj Bd. 15, 1903; Wilson, E. B., "Experimental Studies on
Germinal Localisation," Journal of Experimental Zoology^ vol. i. 1904 ; and
many others.

SPECULATIONS UPON THE ORIGIN OF LIFE 643

It is therefore probable, if not certain, that chondriosomes
and perhaps other constituents of the cytoplasm play an
important part in the transmission of hereditary characters.
I do not for a moment mean to imply that the part played by
the chromosomes is not an important one. The point I wish
to make is that, at the present time, in view of recent work, no
one has any right to make the exclusive claims for them that
were considered justifiable in the past and which are still con-
sidered valid by perhaps the majority of biologists. I have
elsewhere given the details of a possible interpretation of the
relative parts played by the chromosomes and other portions of
the cell with regard to the transmission of hereditary characters ;
or, to speak more correctly, of the potentiality for developing
these characters.^ Here I only wish to show that this function
cannot possibly be confined to the chromatin.

The next point is the relative importance of nucleus and
cytoplasm. Here the very general opinion of biologists is that
the nucleus is of supreme importance, the cytoplasm playing but
a subsidiary part. With this opinion I am again at variance.
The nucleus qua nucleus is of no more importance than the
cytoplasm. Prof. Minchin says that a portion of cytoplasm
without nucleus cannot survive. Quite so, but it also seems
that neither can a portion of nucleus survive without cytoplasm.
Verworn, whose experiments upon the protozoa with regard to
this point are among the most important,^ came to the conclusion
that the one was as important as the other; neither could survive
alone, whilst from a small piece of nucleus together with a small
piece of cytoplasm a whole organism might be formed.

Much stress is laid upon the fact that in some cells, notably
sperms, the nucleus and its contained chromatin form so large
a part of the whole ; it is therefore concluded that the cytoplasm
is of little or no importance. In view of the facts I have already
adduced, I feel that the actual relative volumes of nucleus and
cytoplasm are not of fundamental importance with regard to
the subject under discussion. The nuclei of ova are as small
relatively to the whole cell as those of sperms are large. The
cytoplasm of the ovum has, of course, to provide nourishment
during a greater or less period of time after fertilisation and

^ Walker, C. E., "Hereditary Characters" (Arnold, London, 1910).
^ Verworn, M., "Die physiologische Bedeutung des Zellkerns," Archiv fiir
die ^esammte Physiologi2y\\. 1891,

644 SCIENCE PROGRESS

his accounts for some of the difference. But still there is a
certain proportion of cytoplasm in the sperm and that has
nothing to do except combine with the cytoplasm of the ovum.
With this cytoplasm go chondriosomes which fuse with the
chondriosomes of the ovum.^

Again, in many cells, the nucleus is so small in comparison
with the cytoplasm that it long escaped the notice of the micro-
scopist. So much so that we still read in histological descrip-
tions of a structure being "cellular" in contrast with adjacent
living structures and this in spite of the fact that all the
structures described are composed of cells and nothing but cells,
though the nuclei may be so small as to escape any but the
most careful examination. The relative bulk of nucleus to
cytoplasm would appear to be determined in each case by
adaptation to the immediate environment of the cell.

I am quite unable to accept the idea that the nucleus alone
produces enzymes. Digestion of particles that have been en-
gulfed always takes place in the cytoplasm and as I shall
describe shortly, there seems to be at times a special provision
against the cytoplasm having a chance of acting directly upon
the nucleus. All the phenomena that have been described as
taking place wuthin the cell as connected with the production
of enzymes occur in the cytoplasm and the granules which are
connected with these secretions are stated to be derived from
the chondriosomes, which in turn have been derived from the
chondriosomes of the gametes.

It is claimed that some organisms, particularly certain
bacteria, consist of nucleus only without cytoplasm. This I feel
is a somewhat dangerous claim. Cytoplasm has been de-
monstrated in many bacteria and when the methods of
preserving and staining bacteria become more refined, it seems
eminently probable that a thin layer, at least, will be found in
all. It is, after all, only a few years ago that parasitic protozoa
were always fixed by drying them upon a glass slide, generally
by means of violent heat. When the extraordinarily delicate
structure of these organisms is considered, it seems wonderful
that so much was discovered in spite of this barbarous method.
Bacteria are more resistent to rough treatment than are
protozoa but still it is too soon to make such a definite state-
ment as that some of them have no cytoplasm. Besides this,

^ Meves, F., 191 1, op. cit.

SPECULATIONS UPON THE ORIGIN OF LIFE 645

it is quite reasonable to regard bacteria and other uni-
cellular forms such as spirochsetes, in which the chromatin
appears to be excessive in proportion to the whole body, as
organisms specially modified from ancestors that were more
primitive for particular conditions of life. Moreover, some
cytoplasmic structures take basic stains in a manner very
similar or identical to the chromatin.

Perhaps the most important point of all regarding the
relations between nucleus and cytoplasm is the fact that we have
conditions in which there is no definite nucleus. At certain
stages in the life cycles of some organisms the chromatin is
distributed throughout the cell. It is probable, personally I
feel certain, that these small masses of chromatin are always
surrounded by linin but this does not affect my argument.
Also, when any cell divides in the manner described above,
it is obvious that the ground-substances of the nucleus and
of the C3^toplasm are inextricably mixed together. Round the
chromosomes there is always an envelope of linin and the same
or something of a similar nature may possibly exist in the case
of the chondriosomes. It is evident that the chromosomes, the
chondriosomes and the nucleus must be surrounded by some-
thing which is impervious to those substances present in the
cell which cause the disintegration of organic matter. It may
well be that this is a property of linin.

It therefore seems to me clear that a differentiation into
nucleus and cytoplasm is probably not indispensable for the
life of all cells. It would appear rather to be a differentia-
tion which has been brought about by natural selection from a
more primitive condition. This differentiation disappears
temporarily during division in all cells. Except during
division, an exchange of substance takes place between nucleus
and cytoplasm through the extrusion of the nucleoli. When
the cell is in a vegetative condition the nucleoli multiply con-
tinually and are extruded from the nucleus. The nuclear
membrane is pushed out in front of the migrating nucleolus and
closes up behind it as it passes. The staining reaction of the
nucleolus changes directly it reaches the cytoplasm.^ All
processes of digestion, absorption and of specific secretion,

* Walker, C. E., and Francis M. Tozer, "Observations on the History and
possible Function of the Nucleoli in the Vegetative Cells of various Animals
g^d Plants," Quart. Joiirn. of Exper. Ph^siolog^^ vol., ii. No. 1^ March i^o^.

646 SCIENCE PROGRESS

take place, as far as we can see under the microscope, in the
cytoplasm. The process by which the nucleoli are extruded is
such that the cytoplasmic substance which is capable of dis-
integrating organic matter does not get access to the nuclear
substance. It appears not improbable that the differentiation
into nucleus and cytoplasm is a definite separation of different
functions of the cell into different areas, just as the functions of
the liver and kidneys are a localisation of certain functions in
different areas of the body and different groups of cells. Both
are the outcome of more primitive conditions.

If these arguments are valid, then a differentiation into
nucleus and cytoplasm is not essential to life. All that appears
to be necessary is certain centres of activity existing in what
is apparently the only suitable medium — protoplasm.

This very vague statement takes us no further without some
enlargement. We have good evidence that there may be in cells
actual centres of activity of the most fundamental importance
which have no apparent morphological structure and can, in
fact, only be demonstrated indirectly. We saw, when con-
sidering the phenomena of cell division, that the centrosomes
formed the centres of two sets of radiations, the which radia-
tions formed the spindle fibres to which the chromosomes
became attached, the centrosomes forming the poles of the
division figure. No one who has studied cell division at all
adequately can have any doubt but that the centrosomes are the
centres of that energy which produces cell division. Yet in
the cells of the higher plants there are no centrosomes ! The
radiations appear and form the spindle. The process of division
is precisely the same as in other cells but at the centres of the
radiations are apparently structureless spaces. Within these
structureless spaces must be the centres of energy. We may,
I think, be sure that the chromosomes or collections of chromatin,
the nucleus when it exists and the chondriosomes must be
surrounded by a membrane which is impermeable to certain
substances and it is probable that this membrane is composed
of linin ; but what the most primitive state of these structures
may be we do not at present know.

What have we left which is absolutely necessary in the
constitution of living matter ? A complex substance composed
of carbon, oxygen, nitrogen, hydrogen, phosphorus and
sulphur, in which there must be centres of certain kinds of

SPECULATIONS UPON THE ORIGIN OF LIFE 647

activity. These centres may not be visible under any circum-
stances. Prof. Armstrong, in a previous number of Science
Progress, described from the chemist's point of view how
conditions under which matter of the nature of protoplasm
might have arisen. He spoke of " nuclei " arising but he uses
the term, I understand, in the way I use "centres of activity"
here. At any rate, I am afraid that biologists are likely to be
misled by a term which means to them something so very
different from what I understand is intended.

Knowing very little about enzymes, I am inclined to throw
the next step in our advance in the knowledge of the origin of
life upon them. Many if not all the phenomena connected with
life appear to be dependent upon their presence. It is for
the chemists to tell us of enzymes, which must certainly
be intimately connected with those centres of activity which
make the difference between living and dead protoplasm.

THE MYSTERY OF RADIOACTIVITY'

A DRAMATIC critic ends his notice of a recent play with the words,
" Radium, what crimes are committed in thy name !" We are
scarcely so far advanced as to commit what are recognised as
crimes in the name of the new " element " but not a few are
engaged in gulling an ever-gullible public into the belief that it
has magic virtues which make it a cure for all sorts of evils and
in setting an entirely fictitious value upon it — to serve commercial
ends. In thus acting, the medicine-men of to-day are but putting
new wine into the old bottles which they have inherited from
their very remote ancestors : some must know full well that
there is nothing to justify the faith they preach, though others
doubtless are the dupes of their own credulity and are fallen
victims to the desire to believe in the occult which appears to be
innate in us.^
The book under notice is one to be consulted by all who desire

^ The Interpretatio7i of Radium. By Frederick Soddy, M.A., F.R.S. Third
edition. [Pp. xvi -f 284, with illustrations.] (London : John Murray, 191 2.
Price 6^-. net.)

* The use made of Radium is in no small measure a justification of Samuel
Butler's criticism : " If people like being deceived — and this can hardly be doubted
— there can rarely have been a time during which they can have had more of the
wish than now — the literary, scientific and religious worlds vie with one another in
trying to gratify the public ! "

The effect of firing a profusion of bullets at a deal board would have is well known.
It would seem that this is the kind of effect produced by the various " rays "
emitted by Radium and that there is not the slightest reason to believe that it
acts in any specific manner, as a chemical agent would : it but destroys living tissues,
in the same way that X-rays, the rays from an electric arc lamp and strong sunlight
destroy them. It has been used with some measure of success, in place of the
surgeon's knife, to remove the surface form of cancerous growth known as rodent
ulcer ; but expert opinion favours the knife as far more certain, as it is difficult to
be sure that the whole of the cancerous tissue has been got rid of when radium is
used. It is more than difficult to believe that it can be effective in the case of deep-
seated growths. That the infinitesimal proportion of Radium present in natural
waters should have any useful effect is eminently improbable : those who encourage
the belief in its efficacy certainly have no evidence to rely on beyond that furnished
by their imagination. In most cases of disease, the factors leading to cure may b^
&o rLUjnerQua that it is impossible to single out one as the effective caus^..

64,8

THE MYSTERY OF RADIOACTIVITY 649

to understand what has been learnt of Radium and in what
respects its behaviour is remarkable. The story is more than
fascinating and it is told with remarkable lucidity, often rising
to eloquence, by Prof. Soddy — who is one of the most noted
workers on the subject of Radioactivity, the new branch of
chemistry and physics brought into existence through the
discovery of Radium. The present-day interpretation of Radium
that it is an element undergoing spontaneous disintegration, was
put forward in a series of joint communications to the Philoso-
phical Magazine of 1902 and 1903 by Professors Rutherford and
Soddy ; moreover, if report speak truly, Prof. Soddy was the
first to discover the production of Helium from Radium. In
reading the book, therefore, we are drawing inspiration from the
fountain head — and the stream is one which runs with quite
exceptional clearness and fulness.

The book consisted originally of the matter of six public
lectures delivered at Glasgow early in 1908 ; the present third
edition is much enlarged and brings the subject of Radioactivity
up to the middle of last year. It should be in the hands of every
student of physical science — and in every school library : no
person of intelligence should be able to read it without having
his imagination fired and a desire awakened in him to know more
of the wonders of science. The argument is developed so
gradually and so clearly that few will have difficulty in under-
standing it.

As Prof Soddy says, in discovering Radioactivity " science has
broken essentially new ground and has delved one distinct step
further down into the foundations of knowledge." But he goes
too far in making the statement that it is a new primary science
owing allegiance neither to physics nor chemistry as these
sciences were understood before its advent, because it is con-
cerned with a knowledge of the elementary atoms themselves of
a character so fundamental and intimate that the old laws of
physics and chemistry, concerned almost wholly with external
relationships, do not suffice.

The fact is. Prof. Soddy is pardonably carried away by his
enthusiasm and there are a number of over-statements, if not
inaccuracies, in his earlier chapters which he will do well to
modify in his next edition. Thus the one outstanding feature in
connexion with Radium and the property of Radioactivity which
it exhibits to an extraordinary degree, we are told (p. 24), is that

650 SCIENCE PROGRESS

" The radioactive substances evolve a perennial supply of energy
from year to year without stimulus and without exhaustion."

This is simply not true, as is fully shown later in the book —
why then start with so misleading a statement ? What too is a
perennial supply ? Gardening is so much in vogue in these
days that most people know what perennials are — plants which
the dealers say will live several years but which as often die
during the first. This doubtless is not the connotation Prof.
Soddy would select ; the accepted meaning, perpetual, is
incorrect. The word is again misused in Chap. III. A similar
confusing statement on p. 32 might also be modified with advan-
tage : it is undesirable in a scientific work to sacrifice accuracy
to rhetoric, rather is it necessary to follow the rigid Euclidian
method of argument throughout.

It is evident that in 1908 Prof. Soddy was irritated by the
criticisms which were passed when the full meaning of the new
discoveries was not yet apparent and the evidence could not
easily be appreciated — otherwise he would not have written (p. 5):
'' Natural conservatism and dislike of innovation appear in the
ranks of science more strongly than most people are aware.
Indeed science is no exception." Either this statement should
disappear from the next edition of the book or the position
should be correctly defined. The assertion that there is dislike
of innovation in the ranks of science is unjustifiable : we are
ever on the look-out for new things and prepared to welcome
the addition of an ascertained truth to the existing body of
knowledge ; the complaint commonly made of a fresh number of
a journal is that there is nothing new in it of interest. And it
conservatism be natural, as they are human beings, scientific
workers, like most other people, are by nature itecessarily
conservative. If men generally were not conservative, society
would have little stability. It is the first duty, moreover, of the
scientific worker to be critical and to deny belief until satisfactory
proof be given that he is justified in believing. It is just because
so few are critical and logical that there are so few, even in the
ranks of science, who deserve to be termed scientific — it is for
this reason also that science is making so little progress among
the people at large and that we can scarcely hope that it ever will
make much progress. In the ranks of Science, as in those of an
army, the majority are privates disciplined to do this or that
work and to accept instructions ; only the few are fit to exercise

THE MYSTERY OF RADIOACTIVITY 651

independent judgment. The fact that there is so little criticism
has also much to do with the slowness with which the knowledge
so hardly won by generations of workers is being codified and
properly utilised in developing a scientific conspectus.

In Radium a substance has been discovered which decom-
poses, apparently without rhyme or reason, at a perfectly
constant rate and in so doing gives out an amount of energy
altogether extraordinary in comparison with that given out in
any of the cases of chemical change known previously —
hundreds of times as much as can be derived from the com-
bustion of an equal weight of coal. And the process is a
very slow one in some of its stages, though very rapid in
others ; judging from the rate at which change is observed to
take place, about 2,500 years may be expected to elapse before
any given quantity is entirely dissipated.

If it be desired to form a picture of what is going on,
we may imagine a vast heap of similar live shell — shell
charged with an explosive — and that, in a given interval of
time, a certain proportion of these explode spontaneously but
without affecting the remainder; moreover, that in each
subsequent similar interval of time always the same propor-
tion of the remainder explode : obviously a smaller number
will be destroyed at each successive explosion. Such is the
behaviour of Radium. But to make the analogy complete,
the shell must be thought of as packed with shot together
with smaller shell; when these smaller shell escape, they in
turn explode and disperse both shot and shell. But the rates
at which the various smaller shell break down are difi'erent
from that at which the parent Radium shell explode. And the
radium shell, it is supposed, are derived from still more
complex shell — from Uranium, which breaks down so gradually
that its complete conversion is estimated to occupy eight
thousand million years.

When Radium was discovered, it was entered among the
chemical elements in the metallic class, because it behaved
like a metal in forming salts. When the further discovery
was made that its radioactivity was consequent on its resolu-
tion into other substances, a dream was fulfilled which
Mendeleeff had caused not a few chemists to dream by intro-
ducing the celebrated Periodic system of classification— a
system which meant, if it meant anything at all, that the

6S2 SCIENCE PROGRESS

substances regarded as elements — whether metallic or non-
metallic — because they could not be resolved by any of the
means at the chemist's disposal, were interrelated in such a
way that there must be some genetic connexion between them.
Now that it has been shown that three accepted elements of high
atomic weight, Uranium, Thorium and Radium, are not simple
substances, the probability that the elements generally are com-
posite in their nature becomes very great indeed.

Prof. Soddy would retain the term element even for Radium.
The question, *' How can an element or the atom of an element
change?" has given rise, he says, to many arguments of
etymological rather than scientific importance. But science is
only compatible with correct etymology — it is the duty of
science to be correct in word as in deed. Prof. Soddy
attempts to wriggle out of the difficulty in an interesting
manner by arranging that :

** You may, if you like, regard the Radium atom as a com-
pound of the atom of emanation and of the Helium atom which
result on its disintegration, as it certainly is such a compound
but you must make it quite clear that you do not mean a mere
chemical compound, which may at will be formed from and
decomposed into its constituents."

At the risk of being ranked as " a more or less random
critic of younger workers in radioactivity," seeing no reason
why even the younger worker should be spared from criticism,
I venture to urge that the argument is illogical.

There can be no question that, owing to the discoveries
under notice, the word element has now lost its significance
in chemistry and that the difficulty of defining it is consider-
able. We cannot base distinctions on degrees of stability,
as Prof. Soddy suggests should be done. But it is not easy to
find a substitute. Perhaps, in the future, we may come to
speak of chemical primaries^ metallic or non-metallic. At one
time, the term atom meant the unit quantity of any substance^
simple or compound ; it was customary to speak of the atom
of water, for example. But when physical conceptions became
paramount and Avogadro's theorem was accepted by chemists
as their guiding principle, it became customary to apply the term
molecule only to the kinetic or acting unit and to reserve the \
term atom for the ultimate elementary unit. Physicists, strangely
enough, have never followed chemists in thus giving a precise

THE MYSTERY OE RADIOACTIVITY 653

meaning to the terms molecule and atom ; it would be a retro-
grade step if chemists were to resume the old practice, especially
as two additional terms have been brought into use : that of
radicle^ applicable both to a single atom and to a group
of atoms capable of acting as a whole; and that of ion^ to
signify the radicle which is active in electrolysis. Moreover, in
nearly every case in which Prof. Soddy uses the term atom,
the correct term to use is molecule. The atom, it is true, will
become more than ever an ideal, if such reservation be made ;
but it is an ideal we need.

The properties of the radioactive elements are most sur-
prising in many ways. There have been chemists who have
expected doubtless that some day sufficiently powerful means
would be discovered enabling us to decompose elements;
no one had dreamt, however, of elements undergoing decom-
position spontaneously and thereby themselves affording the
long-expected proof of their composite nature ; and no one
probably had ever thought of the possibility of such a vast
amount of energy being stored up in a substance as is now
known to be stored up in Radium.

How are we to explain the change which it undergoes — is it
altogether without analogy, we may ask — is Prof. Soddy justi-
fied in asserting that the old laws of chemistry and physics do
not suffice ? Of late years, it has been the favourite doctrine of
those who dub themselves physical chemists that a great variety
of chemical changes are taking place unperceived at very slow
rates and that when such changes are caused to take place
rapidly by the intervention of a catalyst this but serves to
hasten the rate of change. The spontaneous decomposition of the
radioactive substances is not surprising from this point of view.

Nor is it surprising that the change should take place at a
constant rate — the behaviour of Radium, in fact, is simply that
characteristic of every changing substance : as chemical change
always takes place at some constant rate depending upon the
conditions. What is remarkable is that we are unable to in-
fluence the rate of change — either to retard it or to hasten it by
any of the means which are ordinarily effective. Furthermore
the amount of energy dissipated is phenomenally large. Where-
in lies the explanation of these peculiarities ?

The first stage in the decomposition of Radium involves the
formation of the so-called emanation and of Helium — which are

654 SCIENCE PROGRESS

two absolutely neutral substances apparently. It cannot be a
compound of such substances and yet they are obtained from
it : either or both must be present in it in some active form.
Many parallel cases are known to us. When nitrogen chloride
is exploded, it gives rise to nitrogen and chlorine gases, neither
of which can conceivably be present as such in the chloride : in
point of fact, there is every reason to believe that the molecule
of the chloride is resolved into its constituent *' atoms" and that
these then unite in new ways to form molecules : it is in this
last operation that the energy is liberated. Thus

2[NCl3 = N + CI + CI + Cl]
N + N = N2
3[C1 + Cl = CI2]

It is only necessary to suppose that the molecule of Helium
as we know it, like the molecule of nitrogen as we know it, is
composed of several "atoms" of — let us call \t—protohelium and
that the atoms of protohelium have intense affinity for one
another — an affinity so intense that it is far beyond anything we
have experienced in the case of any other element.

When argon was first described in 1895 by Rayleigh and
Ramsay, I ventured to assert such a view in explanation of its
apparently complete inactivity. What is true of argon, is
true doubtless of all its companions in air — helium, neon and
krypton.

In the light of my hypothesis, chemical primaries such as
Uranium, Thorium and Radium are comparable with the com-
plex hydrocarbons of the paraffin series represented generally
by the formula CnH2n + 2. When the paraffins are heated, they
are decomposed in a variety of ways : one way is that, time after
time, the elements of a molecule of hydrogen are removed, a
hydrocarbon being produced containing proportionately less
hydrogen ; thus

CnH2n + 2 = CnH2n + H2 i.

CiiH2n = CuHon - 2 + H2, CtC.

Such changes correspond to those which the radioactive
primaries undergo in losing the elements of a molecule of
helium time after time. But some of the immediate products in
the case of the h3^drocarbons are unstable and at once undergo
change into an isomeric substance ; this is a weightless change

THE MYSTERY OF RADIOACTIVITY 655

and corresponds, it may be supposed, to that which happens
when terms in the radioactive series are formed without any
apparent change in the weight of the molecule— changes in
which only /3 and 7 rays are given out.

Finally, we have to consider the rates at which Radium and
other radioactive materials undergo change— why the rate is
constant in each particular case. Why, as Radium decomposes
so slowly, does it decompose at all ; why does it not all blow up
suddenly, like an ordinary explosive? There is but one ex-
planation— that, like the other mere chemical compounds Prof.
Soddy speaks of so slightingly, it is always being decomposed
reversibly — into protohelium and something else, the which
products reunite more frequently than they part company and
escape, the protohelium after it has united with itself; the
Radium does not blow up, because of the intense affinity of
protohelium for its companion product of change ; for a similar
reason, heat is without influence on the rate of change and
there is no helium to be seen in the spectrum of Radium.

It would be surprising that Prof Soddy and other workers
have so long overlooked the potentialities of protohelium, were
it not human nature to have chief affection for one's own children :
to be blind to their faults and disinclined to seek virtues in
those of others. I venture, however, to suggest that it were
time to discard the fiction that the gases of the argon family are
monatomic molecules which has so long retarded progress.

Protohelium apparently is the wondrous material at the root
of radioactivity.

The terms of short life in the radioactive series are to be
regarded as compounds in which the affinity of the constituent
radicles for each other is slight. Radium or uranium even and
the most ephemeral of the radioactive products which it
furnishes may be contrasted the one with say sodium chloride
or carbonate, the other with nitrogen chloride or ammonium
carbonate: they are separated by a wider energy interval but
only in degree.

What has been said, it may be hoped, will in no way diminish

the attractiveness of Prof. Soddy's tale of wondrous scientific

achievement.

H. E. A.

REVIEWS

The Origin of Life : Being an account of Experiments with certain superheated
Saline Solutions in Hermetically Sealed Vessels. By H. Charlton
Bastian, M.D., F.R.S. Second Edition. [Pp. 98 with 12 plates.]
(London : Watts & Co., 1913. Price y. 6d. net.)

Dr. Charlton Bastian is nothing if not persistent. The volume under notice
is a second edition of his well-known essay, together with an appendix — termed
important on the title-page, this being a paper read by him, so recently as
November 19, 1912, before the Pathology section of the Royal Society of Medicine.
Apparently he has been spurred to this fresh effort by the discussion on the
Origin of Life which took place at the British Association in September last.

Dr. Bastian's essay is a pathetic document, as showing how easy it is for a man
to persuade himself into believing in the impossible. Not a few scientific workers
will be in full sympathy with him on account of the transparent sincerity of his
convictions, though they may refuse altogether to accept his experiments as
satisfactory. The essay contains his well-known indictment of the Royal Society,
who have declined to publish his papers. But he is wrong in regarding himself
as injured — the course he has taken in consequence of the refusal meted out to
him by " our premier scientific Society " has not only brought his fancied wrongs
prominently under notice but has secured far greater prominence for his views
than they would have had if they had been officially recorded. The Royal Society
has two kinds of archives — those which technically rank as such and its official
publications : it is well known that these latter are the highest form of decent
burial the scientific worker can achieve. They are to be found resting peacefully
on the shelves of the fellows and of public libraries but the evidence is conclusive
that they are rarely consulted here and that they are practically unknown abroad.
As self-erected monuments of industry and scientific precision, many of the
memoirs the volumes contain arc magnificent — but they rarely enter into practical
politics. Had the Royal Society desired to nip Dr. Bastian's heresies in the bud,
they would probably have ordered the publication of his communications in their
Transactions. In fact, Dr. Bastian has failed to realise that Huxley and Michael
Foster his follower were wags both and that their real object must have been to
give prominence to his views.

At present the Royal Society is suffering under the load of its traditions and
its superlative respectability but its inanition is deplorable. Some day it may
appreciate the sacred nature of the trust committed to it and once more become
a factor in the progress of science. Even papers such as Dr. Bastian's will be
accepted and read, fully and critically discussed and — if not withdrawn by
consent or request of the author — published together with the discussion, so
that all who run may read. The Society will then rank high by reason of the
sympathy which it will extend to all serious workers and its best safeguard will
be the reputation it will enjoy as a centre of unsparing but honest criticism ; in
that far-off time maybe science will have its golden days and will be honoured
as the protector of the public at large against false belief and pretence.

656

REVIEWS 65;

There Is much food for thought in Dr. Bastian's volume. It would be wrong
to say seriously that it is full of absurdities— and yet such an expression is almost
the only one that does justice to its argument. The immensity of the problem
considered is patent : Dr. Bastian's failure to appreciate the gravity of the issues
his contributions raise is only too obvious. Psychologically his attitude is one
that deserves most careful consideration— it illustrates both the difficulty that
attends the interpretation of the complexities of nature and our human tendency
to take ourselves seriously as capable exponents of her workings. Dr. Bastian
claims to have produced Torulce in his latest experiments from solutions con-
taining only, to each ounce of distilled water, either a few drops of a dilute solution
of sodium silicate together with about three times as many drops of liquor ferri
pernitratts or a few drops each of a dilute solution of sodium silicate and dilute
phosphoric acid together with a few grains of ammonia phosphate. In his latest
experiments, he used pure colloidal silica prepared by Graham's method in
place of the siUcate.

In opposing Dr. Bastian, Huxley doubtless was influenced mainly by his
feelings but sustained argument may now be substituted for his sledge-hammerism.
In the interval, we have learned much regarding the structure of the constituents
of the protoplasmic complex — the nature and functions of enzymes have been
made more or less clear to us — even simple organisms such as Dr. Bastian asks
us to believe were produced de novo in his tubes have been shown to be of
extraordinarily complex structure and capable of exercising both the synthetic and
analytic operations characteristic of organisms far higher in the scale — the chemist
has also discovered that Nature has developed extraordinary powers of selecting
out a certain limited set of materials for use in her building operations : those who
understand these things feel that it is simply inconceivable that life can ever arise
from materials such as Dr. Bastian has used and during times such as were
covered by his experiments. Bacteriologists have accumulated a vast fund of
experience : if the calling of living things into being were the easy process he
imagines, his observations would have been corroborated and his contentions
admitted over and over again.

With regret we must conclude that Dr. Bastian has never been a competent
critic of his own proceedings but he is in no way singular. Much of the so-called
research work of our time would never see daylight if those who perpetrate it were
better informed and sufficiently modest to be conscious of their inability to deal
with the tasks which they have had the temerity to undertake. This is the coming
difficulty in science ; the rank and file will continue to do good hoe and spade
work so long as they are prepared to subordinate themselves to competent leaders
but it will be possible to trust but the very few to deal with the more compre-
hensive problems or to base generalisations upon the scattered observations of the
multitude. It is in this direction, we may hope, a regenerate and virile Royal
Society will be able to serve the State— in promoting Natural Knowledge by
judiciously organising, criticising and controlling the exercise of scientific effort.

The Growth of Groups in the Animal Kingdom. By R. E. Lloyd, M.B., D.Sc.
(Longmans, Green & Co.)

Under an unassuming title this book conceals a most ambitious aim, no less than
an attempt to solve one of the root-problems of zoology, for the term "group"'
as defined by the author, is used to include everything from a sport represented
by two or three specimens to a new species and the question discussed under the

658 SCIENCE PROGRESS

caption of the "growth of groups " is nothing less than the origin of species. We
may say at once that, though we do not think that the author has succeeded in
his aim, he has certainly collected together some most interesting facts. The
discovery that plague was communicated to man by the rat-flea led the Govern-
ment of India to take measures to collect and destroy rats on a much larger scale
than anything of this kind that had been previously attempted ; it led further to
an investigation of the number and distribution of the varieties of rats found in
India. It was the privilege of the author to assist in these investigations and
from them were derived the ideas which are embodied in this book.

What Mr. Lloyd has been able to show is briefly this : (i) that Mus rattus, the
so-called " old English " black rat, is the dominant species over the greater part
of India ; (2) that this species exhibits marked colour varieties and that the most
frequent colour variety is not black but greyish brown, very similar in colour, in
fact, to the " common " rat of England, Mus norvegicus^ from which it, like all
varieties of Mus rattus^ is separated by a number of anatomical marks ; (3) that
these colour-varieties are sometimes confined to definite districts, such as moun-
tainous regions but sometimes occur in colonies in the heart of a population
consisting of the " normal " variety ; (4) that these colonies may be of any size,
from a "group" consisting of two or three individuals to assemblages of much
larger size which may include hundreds of individuals.

He shows further that there is evidence that practically the same variation
must have originated independently in widely different centres and that there is
some evidences that individuals of the same colour-variety have a tendency to
consort and mate together.

Mr. Lloyd is an ardent believer in the mutation theory of De Vries and, of
course, he sees in the distribution of these colour-varieties evidence in support
of that theory. According to him there can be no doubt at all that these colour
"mutants" have been born (through unknown causes) of "normal" parents and
have then proceeded to generate offspring like themselves, which have constituted
the group. It is in this way he imagines that new varieties and ultimately new
species have come into being. Mr. Lloyd has performed no breeding experi-
ments with his mutants and all his evidence consequently is indirect. Now all
who know the state of research into problems of heredity at the present day are
aware that nothing would give the orthodox Mendelian greater pleasure than to
assist at the birth of a new mutation and that the claim of De Vries to have done
so is gravely questioned by many of the most trustworthy workers in this field.
Mr. Lloyd seems to be totally unaware that the celebrated CEnothera Lamarckia^ta
labours under the suspicion of being a hybrid itself and that it is quite possible
that the various mutants to which it has given rise may be due to nothing but
the segregation of the different factors which have entered into its complicated
ancestry. If in the normal population of Mus rattus there exist several strains
of heredity which, for all we know, may have existed since Mus rattus was a
species at all ; further, if some of these strains are dominant over others, then
there will be always a sporadic appearance of apparent new varieties due to special
concatenation of circumstances which favour the appearance of recessive strains
in certain localities. On the fundamental question of the origin of a new mutation
his observations throw no new light.

We mentioned at the outset that we do not think that Mr. Lloyd had solved
the problem of the origin of species. Mr. Lloyd has some caustic comments to
make on the different conceptions of species held in practice by different types of
naturalist. He is certain that if some of the colour-varieties which he encountered

REVIEWS 659

had been sent home to museum specialists they would have been registered as
new species. Possibly he is right and yet too much blame must not be given
to those unfortunate but indispensable specialists. Possibly, like most conserva-
tive naturalists, they have the conception of a species as a group of animals
occupying a definite area, bound together by many constant characters and freely
interbreeding, ivhcse co?tstitution is adapted to the environmental circumstances
of that area. They would be the first to recognise that most of their specific
determinations, especially when they deal with collections of animals from un-
explored areas, are and must be provisional and would be ready to modify them
as soon as fresh evidence on the subject was available.

The real enigma in the origin of species is not the origin of slightly different
strains within the same stock but the origin of adaptations. On this subject,
as on what he conceives to be " Darwin's theory of selection," Mr. Lloyd has some
extraordinary remarks to make. It is, he thinks, of the essence of Darwin's
theory that variation should be small and should be chaotic, i.e. in all directions.
Further, he thinks that natural selection is an attempt to explain the unknowable,
i.e. adaptation.

It may surprise him to learn that Darwin was just as well acquainted with
the existence of "mutants" as De Vries and if he did not think that they had
been of importance in the formation of new species, it was not on account of any
philosophical objections to such an assumption but on account of many weighty
practical considerations which are set forth in detail in his works. As to vari-
ations being *' chaotic," Darwin, who spent a life-time in collecting all the
information he could about variation, was in a better position to judge than
Mr. Lloyd. He found that there was no part of an animal or plant which could
not be made to vary in any direction which man desired, as was evidenced by
the whimsical peculiarities of "fancy" strains of domestic animals and plants :
and it was a fair inference that if man could always find the variations he wanted,
they must occur sufficiently frequently to allow natural selection to modify a
species in any direction.

What hazy metaphysical notions Mr. Lloyd has in his head to permit of his
calling adaptation " unknowable," it is hard to guess. Adaptation is part of the
present order of nature, just as is the distribution of land and water and we have
reasons for believing that neither in its present form has existed from all eternity ;
and it is the function of science to explain the present from the past. Mr. Lloyd's
philosophical reflections are clothed in what he imagines to be an epigrammatic
style but we cannot think that such aphorisms as " Dissent is the outcome of a
difference of judgment which is inherent in the dissenter" add anything to the
forcefulness of his arguments.

In conclusion we cannot give Mr. Lloyd better advice than to engage in a

renewed and serious study of Darwin's works— more especially that entitled

The Variation of Anitnals and Plants under Domestication — and to weigh

carefully the concluding passages of that monumental work before putting forward

new ideas on the origin of species.

E. W. MacBride.

Sylviculture in the Tropics. By A. F. Brown. [Pp. 309, figs. 96. 8vo.]

(London: Macmillan, 1912.)
This refreshing work differs materially from other modern text-books of forestry
issued in this country. Of the latter, all the larger ones sufficiently accurate to be
worthy of consideration owe their publication— as does the book under review— to

660 SCIENCE PROGRESS

former ofificers of the Indian Forest Service, yet they are in the main adaptations
or actual translations of German works and deal specially with European forestry.
Mr. Brown's book deals with tropical sylviculture and contains much information
collected by the author during his wide experience in the forests of India, Ceylon
and the Sudan. Mr. Brown evidently recognises that in dealing with problems
outside the mere routine work of continental forestry it is essential to have a
special knowledge of trees and of the conditions under which they feed and grow ;
accordingly he makes use of his well-known acquaintance with systematic botany
and his evident study of plant cacology in the opening chapters, which are devoted
to the discussion of the factors influencing the existence of forests. Much of this
information will also be of interest to botanists, for we find here interesting facts
concerning trees occupying soils differing in constitution or moistness and in sites
differing in cHmate or altitude or exposure. The examples described are largely
taken from forests in the tropics of the Old World. Very varied are the matters
discussed ; for instance, the significance of depth of root in relation to resistance
to drought is exemplified by reference to Mr. R. S. Pearson's account of the
damage done to forests in the Madras Presidency during the drought of 1899-1900.
Among the suggestive facts that came within the author's range of observation
may be cited the remarkable germination of a viviparous Dipterocarp ( Vatica)
that grows in annually inundated sites in Ceylon. In the chapter deahng with
the living environment of trees the author gives interesting particulars and illus-
trative examples of matters varying from the succession of vegetation in forest
clearings to the kinds of seeds distributed by deer and elephants, the pollination of
parasitic Loranthaceae by birds, the damage done to forests by plagues of rats and
the intense dislike of elephants of white objects such as whitened posts or white-
barked trees, which are therefore wantonly destroyed by these animals. In the
chapter on " Man and Domestic Animals " Mr. Brown falls into the assumption,
which is by no means justified, that " in olden times . . . the greater part of the
globe was forest clad." An analysis of the climates of cold or dry deserts and
various grasslands renders it probable that " in olden times " there were always
immense areas not clad with forest. Yet the forester readily comes to Mr. Brown's
impression because he may have an exaggerated idea of the climatic change
induced by disforestation and in Europe he knows not only of wholesale destruc-
tion of forest by man and its degradation to heath or peat-bog but also of evidence
of the prehistoric existence of vast forests where bogs now prevail ; within the
tropics and subtropics the forester also sees the change of dense forest into open
savannah, grassland or waste area, induced by fire (perchance not due to man's
agency) possibly combined with the subsequent activity of grazing or browsing
animals. Instructive examples of such changes are described by Mr. Brown and
accounts are given of the forest-destroying powers of the goat and of the even
more destructive camel. To these two kinds of animals has been attributed the
disappearance of woodlands supposed to have existed formerly in the wadis of
Upper Egypt where desert now reigns. In connexion with the discussion on the
effect of fires the information is given that protection against fire has caused some
teak forests in Upper Burma to change into evergreen forest, in which teak can
no longer reproduce itself. Among the important factors influencing forests is
light and it seems a pity that Mr. Brown should not have given in his book some
discussion of its significance, since so much botanical work has been published
recently in regard to the amount of light required by various species of plants
including trees and the practice of forestry is so largely a matter of the proper
regulation of light.

REVIEWS 66i

The remaining sections of the book deal with practical operations of the
forester. The information is conveyed in a clear and interesting manner and
includes adequate recognition of necessary deviations from ordinary European
practice, for instance in connexion with the water supply in nurseries and the
making of coppice.

A number of instructive photographs and other illustrations add to the value
of this work, which may be recommended not only to foresters but to all engaged
in the cultivation of trees and shrubs within the tropics.

Percy Groom.

British Violets: A Monograph. By Mrs. E. S. Gregory. With an intro-
duction by E. Claridge Druce, M.A., F.L.S. [Pp. xxiii + 108^32 illustra-
tions.] (Cambridge : W. Heffer & Sons, Ld., 1912.)
Mrs. Gregory, whose work on the Eu-Violas is well known, has given us a
useful book on this sub-genus. The proof of the value of such a work is in the
using. The reviewer has worked through the long series of violets in his own
herbarium and has found that, in most cases, the descriptions, notes and figures
leave but little doubt as to the identification. The notes on distinctive features,
when given, are very helpful and it is rather to be regretted that in some cases
they are not more complete. For instance, it is doubtful whether var. pseudo-
mirabilis of V. Riviniana^ Reichb., could be determined with any certainty from
the account given.

There is, perhaps, a tendency to rely too implicitly on the opinion of conti-
nental botanists who have examined British specimens. In the preliminary
stages of the study of such a "critical" 'set of plants as these, it is generally
necessary to consult foreign experts but observation of plants in the field may
overrule the judgment of an absent authority — who knew nothing at first hand
of the habitat of the specimens under examination. Varieties of different species
often approximate in form, although the species are quite distinct. Hence
knowledge of the range of forms in any district may suggest the probability of
specific identity of very unlike plants — an identity at which the referee, seeing
only a few plants, could never guess. Indeed, a study of the range of form
possible for each clearly distinct species is urgently needed in all " critical "
groups.

No fewer than seventeen supposed hybrids are mentioned. Some hesitation
is perhaps natural in accepting all of these. Indeed the authoress herself expresses
doubt in some cases. The whole subject of hybrids in the British Flora is worthy
of careful study. Combination of the characters of two well-marked species,
especially if accompanied by sterility, may be good evidence and probably, in
general and under certain conditions, it is so but direct confirmatory evidence
from actual crossing is desirable. In particular, doubt may well be felt in
approaching such a name as V. canina x V. ladea x V, Riviniana (p. 96).

These remarks, however, are in no way intended to detract from the com-
mendation of the book. Mrs. Gregory did not set out to settle all the doubtful
points respecting the Violets. This would have required more than the twenty-
five years of study which she has devoted to the group. She intended to give
a clear working account of the violets occurring in this country and in this she
has very largely succeeded.

A special word of praise must be given to Miss Mills's drawings ; these are
numerous and very well executed. The photographs of herbarium specimens, too,
are clear and helpful,

662 SCIENCE PROGRESS

Monographs on Biochemistry. The Simple Carbohydrates and the Glucosides.
By E. Frankland Armstrong, D.Sc, Ph.D. Second Edition. [Pp. 171.]
(London : Longmans, Green & Co., 191 2. Price 5^-. net.)

One of the most gratifying signs of the success which has attended the series of
Monographs on Biochemistry is the fact that new editions of the earlier issues are
now appearing before the original programme of publication has been completed.
The scheme outlined by the editors, in the general introduction to the series, is
thus being faithfully adhered to and it is obvious that it is being appreciated.

In this second edition of his book, Dr. E. F. Armstrong has expanded and
modified the original work in a number of ways, the result being that the present
volume appeals forcibly both to the chemist and biologist. The task of selecting
the fundamental points of the chemistry of the sugar group from the voluminous
literature of this branch of research is in itself no easy one. To present the
facts in a natural and logical order, whilst keeping the theoretical aspects of the
subject in the foreground, is still more difficult and a careful review of the present
work justifies the opinion that Dr. Armstrong is to be congratulated warmly on
having produced a memoir of permanent value.

The opening chapter gives a clue to the spirit in which the book is written.
Dr. Armstrong is obviously of the opinion that the chemistry of the sugar group
can only be properly approached from the constitutional standpoint and in this
he is right. Throughout the book, the structure of the sugars and their related
compounds is dealt with in an exceedingly lucid manner and thus the work is
free from the reproach of being an empirical tabulation of compounds and their
properties.

Compared with the first edition, considerably more space has been devoted to
the phenomena of mutarotation and isomeric change ; the growing importance of
the biochemical relationships of the sugar group has also received due recognition
and a number of the rarer compounds have been fully described. The biblio-
graphy has been thoroughly revised and brought up to date.

The work should be valuable both to the organic chemist who is interested in
biochemical problems and to the biologist who desires to gain an insight into the
somewhat complex chemistry of the simple carbohydrates. The first edition of
the book has also, in the reviewer's experience, stood the test of being used as a
special text-book by students preparing for research work on sugars and the
present issue cannot fail to be more useful still in this respect.

There is one point in which future editions of this and other members of the
series might possibly be improved. That a highly specialised technique is re-
quired for work in the sugar group is well known and investigators new to this
work may well be discouraged by the practical difficulties encountered. The
suggestive manner in which Dr. Armstrong's book is written is likely to attract
new workers to this field and this desirable result would be greatly promoted if, in
future editions, he could find it possible to add a series of practical notes, derived
from his own experience, on the manipulation and purification of the sugar series.

J. C. I.

Electromagnetic Radiation and the Mechanical Reactions arising from it.

By G. A. SCHOTT, B.A., D.Sc, Professor of Applied Mathematics at Aberyst-
wyth. [Pp. xii + 330 and 7 appendices; 51 figs.] (Cambridge University
Press. Price iSs. net.)

The subject proposed for the Adams Prize Essay in 1908 was "The Radiation

REVIEWS

663

from Electric Systems or Ions in Accelerated Motion and the Mechanical Reac-
tions on their Motion which arise from it." The book under review is an extension
of the Prize Essay, most of the additional matter being introduced in seven
appendices occupying the last 125 pages. As might be anticipated from the title,
the essay is deductive and mathematical rather than constructive and physical.
The object of the author has been to establish mathematically the foundation for
any theory of matter based on the electron, whether it be the electron of Lorentz
or that of Bucherer or that of Abraham.

After a brief discussion of the fundamental equations of the Maxwell-Hertz-
Lorentz electron theory. Chapters II. and III. are devoted to the subject of
retarded potentials and the point potentials of Lienard and Wiechert. These
point potentials are discussed in Chapters IV., V. and VI. and applied to the
determination of the electromagnetic field in various special cases of the motion
of a point charge. In Chapter VII. the motion is assumed to have a single period
whilst in the following chapter more complicated periodic motions are considered
and in Chapter IX. non-periodic motions are dealt with. In Chapter VIII. there
is also a discussion of the precessional motion of a vibrating system, which is of
importance in the theory of the Zeeman effect. Chapter X. is devoted to the
field near the orbit of the vibrating charge, the next to the consideration of the
equations of motion of the moving charge itself and these are extended in
Chapter XII. to a group of electrons. The author states that the appendices
with the exception of the first, are mainly devoted to remedying the defects in
Chapters XI. and XII., which, owing to the shortness of time allowed for the
essay, were not treated at all adequately. The first appendix deals with the
Doppler effect.

Not the least pleasing feature of the book is the number of clear diagrams by
means of which the author illustrates and explains the mathematical processes and
results.

Vector analysis is used throughout and the distinguishing type and symbols
adopted are excellent.

The book is one which can be confidently recommended to all who know some-
thing of electromagnetic theory and the methods of vector analysis and wish to
understand the recent developments of the electron theory.

Electric Lighting— and Miscellaneous Applications of Electricity. A Text-
book for Technical Schools and Colleges. By William Suddards
Franklin. (New York: The Macmillan Company, 191 2.) [Pp. 299
ix, chaps., with 197 figures.

The title of this book is misleading, as less than 100 pages deal with electric
lighting. The contents are best described by the word " miscellaneous " in the
sub-title. The chapter contents are as follows: i, Costs and methods of charging;
2 and 3, wiring and transmission lines ; 4 to 7, photometry, lamps, illumination ;
8, electrolysis and batteries ; 9, telegraphs and telephones ; Appendix A, dielectric
stresses ; Appendix B, problems. Much of the material is good but the arrange-
ment is pecuUar and Appendix A gives one the impression of having introduction
by mistake. The practical data apply to American conditions and things almost
unknown here are given as standard practice.

Apart from such typographical errors as " killowatt " and " magdetite," we note
on p. 87 " two million ergs (or 0*2 of a watt) per second." The statement on
p. 229 that bridge duplex is specially prevalent in England is hardly correct.
Fig. 136 would not work with the batteries as arranged and Fig. 98 is ridiculous.

664 SCIENCE PROGRESS

Fig. 82 is borrowed from Mrs. Ayrton without a word of acknowledgment. A
very good point is the large number of references to papers and books on the
various subjects. The book is exceptionally well bound.

Outlines of Evolutionary Biology. By Arthur Dendy, D.Sc, F.R.S.
[Pp. ix + 454.] (London : Constable & Co., Ltd., 1912. Price 12s. 6d. net.)

Prof. Dendy's intention in writing this book evidently has been to purvey biology
for the million and badly enough it is wanted : mais I'homme propose et le bon
Dieu dispose. Will it serve the appointed purpose ? It has been most favourably
noticed by the Press but does this mean anything in these days of grace, now that
reviewing is a lost art and very few of those who have an opinion dare express it ?
Owing to the fact that the specialist too often lacks sense of proportion and is apt
to live a life apart and have no inkling of the depths of ignorance of those whom
he addresses, his opinion on a work intended for popular consumption may be of
less value than that of the ignoramus thirsting for information. It is therefore
permissible that a book such as that under notice should be criticised from the
point of view of those who have no special knowledge of its subject-matter and yet
are most anxious to learn ; indeed it would be much better if books were some-
times reviewed by those for whom they were written and not by those who
presume to understand them : if only we had the opinions of schoolboys and
schoolgirls on the works that are provided for their consumption, there would be
some chance of a chastened race of authors being evolved who would write books
worth reading, as if writers realised how often their productions are spoken
of in very uncomplimentary terms by juvenile readers who are forced to use
them, their self-sufficiency might be abated and they might eventually even be
overcome by some sense of modesty and retire from the field : those who " feel a
want" in the course of their educational ministrations would more often seek
comfort in some less harmful form of exercise than that of attempting to write a
book. When the new Socialism is estabHshed, no doubt such things will be pro-
vided against.

It is easy to agree with the opinions expressed by the author in the earlier part
of his preface. There is no doubt that biology, the fundamental science of living
things, is not properly encouraged by educational authorities in this country — but
is the fault entirely theirs ? Can the subject be taught satisfactorily in schools, is it
sufficiently developed .'' That attention is usually directed to the more special
branches no one will deny but is not this because of our more than relative
ignorance of the general subject ? Is it possible at present to write a book that
will be 0/ use — we desire to emphasise the " of use " — to those who have no
special biological training as well as to students who have taken the
ordinary first year's course and largely with a view to meet the requirements
of those who wish to familiarise themselves with the rapidly accumulating results
of biological investigation and the bearing of these results upon the problems
of life ?

It is only necessary to read through the opening chapter of Prof. Dendy's book
to realise how great the difficulties are : the author, like most zoologists it is to be
feared, obviously does not possess sufficient knowledge of chemistry and physics to
discuss the subject dealt with in it — the nature of life : to us it seems that when
the beginner has read through the chapter, he will know less than when he began :
like the frog in the fable, he will be puffed out with importance, as he will be

REVIEWS 665

equipped with sundry fine words and phrases but his mind— if he have one— will
be in a hopeless muddle.

At the end of eleven pages of terribly thin talk— there is no other term for it-
he will scarcely be comforted on hearing that " the ' soul ' of Descartes' philosophy
corresponds more or less closely with the ' vital force ' of some more recent writers
and the ' entelechy ' of others," especially as he is left without an explanation of
the blessed word entelechy.

To attempt to elucidate the nature of life in so brief a space is out of the question :
the whole chapter should be scrapped whenever a new edition of the book is pre-
pared. Until proper training has been given in things fundamental in chemistry
and physics, it will be impossible for students to grasp even the simplest concep-
tions of vital problems and the present-day biologist is certainly incompetent to
discuss the philosophy of so vast a subject as that of the nature of hfe, which is
admittedly an infinitely intricate nexus of complex chemical events. If we are
to write books that are to be of use to students, we must school ourselves to talk
only of things we can and do comprehend and they can understand.

The later chapters of the book are open to similar criticism, in so far as they do
not relate to matters specifically zoological, which are usually treated clearly and in
an interesting manner.

To refer to only a few points — surely it is undesirable even to mention to abso-
lute beginners the attempts that have been made to explain the dynamics of
mitosis — of which we are in absolute ignorance from A to Z, whatever cytologists
may say.

Variation and heredity, subjects of infinite importance, are dealt with in
sixty-two pages in Part III., chapters xi-xiv. : the treatment is of the kind to be
expected in articles of the popular magazine type ; no beginner could possibly
make much of the jumble of statements brought under notice. In this section,
the inheritance of acquired characters is dealt with in a way which makes it pretty
clear that the author is a believer in the doctrine : parenthetically we may say that
whatever the force of the arguments in its favour may be, we are convinced that if
there be one character that is not acquired it is the art of writing books success-
fully— this seems to be born in the very few.

The kind of logic used in dealing with the subject of inheritance will be apparent
from the following statement on the last page but one of the book :

" Man has indeed acquired a degree of control over his environment and over
his own destiny which distinguishes him from any of the lower animals but at the
same time the conditions of his life have become far more complex and the young,
at any rate in civilised communities, have to go through a long course of education
before they are fit to enter upon the struggle for existence on their own account.
Amongst the lower animals, all or almost all the faculties necessary for existence
are directly inherited from the parents, incorporated in the organism itself ; but
man inherits in this way only a relatively small proportion of the powers which he
requires to carry on his life. The greater part of human experience is of too
recent origin to have become heritable ; it has to be acquired afresh by education
in every generation and in this respect is strikingly contrasted with the instincts
of the lower animals."

Much of the difficulty in discussing this all-important subject arises probably
from the loose manner in which the term " acquired character " is used at the
present time. The untutored human being apparently is much like the exposed
photographic plate— the latent image is there but requires to be developed : it may

666 SCIENCE PROGRESS

be developed to various degrees of intensity but no development can bring out a
non-existent detail. A so-called " acquired character " may well be nothing more
than a developed character and not in any true sense one that is acquired. It is
as if a man found himself the possessor of various factories full of machines of
which he has little understanding : he sets to work and learns gradually to make
use of them ; sooner or later he is able to use some of the machines efficiently,
others he never makes use of, either because he cannot understand them or
because they were imperfect when they came into his possession or because he is
never called upon to set them in action, there being no demand for the articles
which can be made with their aid. He is even able to turn out new machines like
the old ones but is strictly limited to copying these, as the only templates at his
disposal are those from which they were made : willy-nilly therefore he is forced
to copy.

To be frank, we are of opinion that the author lacks not only the borderland
knowledge but also the critical power that is needed in writing such a book — the
power to take himself to task on every page and ask himself if he be not making a
fool of himself in stating this or that : without this, no one, in these days, should
attempt to write for babes and sucklings. Far too much is attempted and what is
written is put together far too loosely.

If the book were deprived of the cheap attempts at " philosophy " which
disfigure it and reduced to a common-sense account of the things which are
really known to zoologists, it would doubtless be of value — as the technical
descriptions are usually well written and well illustrated. As it stands, however,
it is a most misleading work — the student who had swallowed it as gospel would
only be a thing of shreds and patches, full of bombast and loose jargon but entirely
lacking in true understanding of the subject.

The book convinces us, in short, that educational authorities will be right in
giving but little encouragement to the teaching of general biology until it can be
placed on a logical footing. Loose scrappy talk must at all costs be kept out of
the schools.

It may be, however, that we are blaming the author for the faults of his
class and that what we have to object to is the way in which the biologists of our
time are prone to talk big of things of which they have no real understanding. By
wrapping up an endless number of factors in terms such as environment — by
speaking of stimuli without giving the least idea what a stimulus is and how it
acts — it is easy to produce a great impression of learning. It is noteworthy that
John Stirling, in a letter he wrote to the author on the appearance oi Sartor Resartus^
took exception to various new words Carlyle used — among others " environment " :
soul-satisfying as such epithets are, when analysed they amount to little : in the
end we must admit that we cannot yet ask a single clear question, let alone answer
one, about life.

INDEX TO VOL. VII

The entries in italics refer to reviews of books.

The names of the authors of papers are printed in capitals.

PAGE

Animal Kingdom., The Growth of Groups in the (R. E. Lloyd) . . 657
Animal Life : Reptiles., Amphibia., Fishes., and Lower Chordata (J. T. Cun-
ningham) 172

Animal Nutrition at Dundee, The Discussion on 413

The Verdict of the Bullock (William Bruce).

The Discrepancy between the Results actually Obtained and those
Expected from Chemical Analysis (Dr. F. G. Hopkins).

Active Constituents of Grain (Prof, Leonard Hill).

An Explanation of Beri-Beri (Dr. Casimir Funk).

More Difficulties from the Practical Side (Dr. David Wilson).

Certain Oil Foods (Prof. Hendrick).

The Magnitude of the Error in Nutrition Experiments (Prof. R. A.
Berry).

A Note of Caution (Dr. Crowther).
Armstrong, E. F. The Si7?tple Carbohydrates and the Glucosides . . 662
A[rmstrong], H. E. The Origin of Life : A Chemist's Fantasy . . 312

The Mystery of Radioactivity 648

Armstrong, R. R. The Mechanism of Infection in Tuberculosis . . 335
Aston, F. W. Sir J. J. Thomson's New Method of Chemical Analysis . 48
Atomic Weights, The Exact Determination of, by Physical Methods . 504

Bastian, H. Charlton. The Origin of Life 656

Biology, Outlines of Evolutionary {h. 'Dendy) 664

Bragg, W. L. X-Rays and Crystals 372

Brown, A. F. Sylviculture in the Tropics 659

BURNE, R. H. The Comparative Anatomy of the Internal Ear in Ver-
tebrates 574

Cancer, Theories and Problems of.— Part II '04

Part III 223

Carbohydrates, The Simple, and the Glucosides (E. F. Armstrong) . . 662
Cathcart, E. P. The Physiology of Protein Metabolism . . . .173
Chapman, D. L. Conditions of Chemical Change.— II. Photochemical

Change in Gases {continued) "^

667

668

INDEX TO VOL. VII

PAGB

Conditions of Chemical Change. — II. Photochemical Change in Gases

{continued) 66

Cunningham, J. T. Aniinal Life : Reptiles^ Amphibia^ Fishes, and Lower

Chordata 172

Darwinism, The Logic of

Davis, W. A. The Chemical Action of Light on Organic Compounds

Davison, Charles. The Death-Rate of Earthquakes

Dendy, A. Outlines of Evolutionary Biology .....

Desch, Cecil H. The Structure of Metals

The Influence of Mechanical Treatment on Structure of Metals

532
251

239
664

87
194

Ear, The Comparative Anatomy of the Internal, in Vertebrates . .574

Earthquakes, The Death-Rate of 239

Electric Lighting— and Miscellaneous Applications of Electricity (W. S.

Franklin) ............. 663

Elliott, Hugh S. The Spectre of Vitalism 437

Eyre, J. Vargas. The Conditions of Russian Agriculture . . .175
. The Projected Revival of the Flax Industry in England . . . 596

Faraday's Electrochemical Researches, The Rescue of
Ferguson, Allan. The Genesis of Logarithms
Flax Industry in England, The Projected Revival of the
Fleming, J. A. Scientific Problems in Radiotelegraphy

Flour, The Bleaching of

Franklin, W. S. Electric Lighting — and Miscellaneous Applications of
Electricity

330
147
596

356

475

663

Gilford, Hastings. The Disorders of Post- Natal Growth and Development 171

Gimingham, C. T. Variations in Pastures I33

Gregory, Mrs. E. S. British Violets : A Monograph .... 661

Haldane, J. S. The Relation of Mind and Body .
Hopkins, F. Gowland. Dr. Pavy and Diabetes
Horticultural Research. I. The Planting of Trees

„ „ II. Tree Pruning and Manuring .

„ „ III. The Action of Grass on Trees

HoRWOOD, A. R. The State Protection of Wild Plants .

292

280

397
490
629

Light, The Chemical Action of, on Organic Compounds . . . .251
Little, F. T. V. The Exact Determination of Atomic Weights by Phy-
sical Methods » . 5^4

INDEX TO VOL. Vll 669

PAGE

Lloyd, R. E. The Growth of Groups in the Animal Kingdom . . . 657

Logarithms, The Genesis of 147

Love, A. E. H. Tides and the Rigidity of the Earth . . . . i
LowRY, T. M. The Measurement of Osmotic Pressure by Direct Ex-
periment 544

Mars, The Planet 120

„ » Part II '212

Mathematics and Chemistry : A Reply 390

Metals, The Structure of 87

„ „ „ The Influence of Mechanical Treatment on

Structure 194

MiNCHiN, E. A. Speculations on the Origin of Life and the Evolution of

Living Beings 300

Mind and Body, The Relation of 292

Origin of Life, The (H. Charlton Bastian) 656

Origin of Life, The : A Chemist's Fantasy 312

„ „ Speculations on the, and the Evolution of Human Beings . 300

„ „ Further Speculations upon the 638

Osmotic Pressure, The Measurement of, by direct Experiment. . . . 544

Partington, J. R. Mathematics and Chemistry : A Reply . . .390

Pastures, Variations in 133

Pavy, Dr., and Diabetes 13

Pickering, Spencer. Horticultural Research. I. The Planting of Trees 280

„ „ „ „ II. Tree Pruning and

Manuring . . 397

„ „ „ „ III. The Action of Grass

on Trees . . 490

Plant, The Life of the (C. A. Timiriazeflf) 172

Plants, The State Protection of Wild 629

Plimmer, R. H. A. The Chemical Constitution of the Proteins. Part I.

Analysis 173

Post- Natal Growth and Develop77ient, The Disorders ^/ (Hastings Gilford) 171

Pregnancy, The Detection of 472

Protein Metabolism, The Physiology of {Y.. P. Cathcart) . . . .173

Proteins, The Chemical Constitution of. Part I. Analysis {K. H. A. Plimmer) 173

Radiation, Electro7nagnetic, and the Mechanical Reactions arising from it

(G. A. Schott) 662

Radioactivity Visualised 479

The Mystery of ^48

670

INDEX TO VOL. VII

Radiotelegraphy, Scientific Problems in . . . . . . . 356

Ridley, Henry N. Spices . . . . . . . . . .174

Russell, E. J. The Discussion on Animal Nutrition at Dundee . .413
Russian Agriculture, The Conditions of 175

Schott, G. A. Electromagnetic Radiation and the Mechanical Reactions
arising from it ...... .

Socialistic Legislation, The Dangers of . . .

spices (Henry N. Ridley)

Starch : A Capital Discovery . . . .
Sylviculture i?t the Tropics (A. F. Brown) .

Tides and the Rigidity of the Earth . .
Timiriazeff, C. A. The Life of the Plant .
Thomson's, Sir J. J., New Method of Chemical Analysis
Tuberculosis, The Mechanism of Infection in

VioletSj British : A Monograph (Mrs. E. S. Gregory)
Vitalism, The Spectre of

Walker, Charles. Theories and Problems of Cancer. Part H.

Part IT I

The Dangers of Socialistic Legislation

Further Speculations on the Origin of Life

Wilde, A. D. The Logic of Darwinism .
Wilson, C. T. R. Radioactivity Visualised
WORTHINGTON, James N. The Planet Mars .

Part TT

662
460
174

333
659

172
48

335

661
437

104

223
460
638
532

479
120
212

X-Rays and Crystals

372

Ptinicd, by Hazell, Watson & Viney, Ld., London and Aylesbury.

PLEASE DO NOT REMOVE

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Full text of "Science, technology and social responsibility : a discussion meeting organized by L. Wolpert, I. Nussey and A. MacDonald, and held at the Royal Society on Tuesday 16 March 1999"

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