to equal the patients of the Salpêtrière and other hospitals in
France--and very few amongst those who read, and even write, about
“occultism” and “super-normal phenomena” know the leading facts which
have been established in regard to this important branch of psychology.
The study of the natural history of the mind, its modes of activity,
and its defects and diseases is of fundamental importance--but its
results are often either unknown or greatly misunderstood by those
who have most need of such knowledge, namely those who, mistaking the
attitude of an ignorant child for that of “a candid inquirer,” try
to form a judgment as to the truth or untruth of stories of ghosts,
thought-transference, spirit-controls, crystal-gazing, divining-rods,
amulets, and the evil eye.
27. _Luminous Owls and Other Luminous Animals and Plants_
A correspondent lately described in a letter to a London newspaper
what he believed to have been “a luminous owl,” which was seen flying
about at night in Norfolk. He mentioned the well-known fact that the
dense greasy patch of feathers on the breast of the heron is said to
be luminous by many trustworthy observers. It is very probable that
it was some carnivorous or fish-eating bird, which was thus seen in a
luminous condition at night. The occurrence is much more in accordance
with known facts than most people would suppose to be the case.
Light, even strong light, is produced by many natural objects without
the accompaniment of heat. We usually expect not merely fire where
there is smoke, but heat--in fact, great heat, where there is light
or flame. Yet there are many instances to the contrary, and the word
“phosphorescence” is used to indicate a production of light without
heat in reference to the fact that phosphorus is luminous, even when
covered with water, although no appreciable heat accompanies the light
such as we are accustomed to observe in ordinary “combustion” or
burning.
There is more than one kind of phosphorescence. We separate the
phosphorescence which is due to the oxidation of peculiar fatty matters
in the bodies of plants and of animals (such as glow-worms) from that
which is caused by the breaking or heating of crystals (white arsenic
and apatite), or by longer or shorter exposure to the sun’s rays
(luminous paint), or by radio-activity, or by electrical discharges in
vacuum tubes.
The “luminous owl” of the above-mentioned correspondent and the
luminous breast of the heron probably owe their strange appearance
to the birds having smeared themselves with phosphorescent carrion or
dead fish, the luminosity of which is due to bacteria. The simplest
case of phosphorescence in living things is that of the almost
ubiquitous phosphorescent bacteria, minute microbes like those which
cause putrefaction. They can be obtained and cultivated from almost
any sample of sea water. A thin slice of meat placed in a shallow dish
of salt water, so as to be barely covered by the liquid, will in cool,
damp weather, almost certainly become covered with the growth of this
phosphorescent germ and appear brilliantly luminous. The populations
of seaside towns have often been terrified by all the meat in the
butchers’ shops suddenly becoming thus phosphorescent. The growth may
be cultivated in flasks of salt broth. I have prepared such flasks,
which, when shaken so as to introduce oxygen, give out a heatless
blaze of light of a greenish colour, brilliant enough to light up a
room. I once found a bone in a dog’s kennel which was brilliantly
phosphorescent owing to this bacterium. I kept it for several days
and showed it to Huxley as well as to other friends. A certain kind
of phosphorescent bacteria are parasitic in the blood of sandhoppers,
causing a disease which kills them. The diseased sandhoppers shine like
glow-worms. I have found them abundantly on the sea shore near Boulogne
and near Trouville, but not yet on the English coast. The bacteria
can be seen with the microscope and inoculated from diseased luminous
sandhoppers into healthy ones by using a needle to prick first the
diseased and then the healthy creature.
The animals of the sea are often provided with secreting organs,
producing a fatty body which can be oxidised and made luminous at the
pleasure of the animal. Thus many marine worms and minute sea-shrimps
give out brilliant flashes of light. Jelly-fish of many kinds, and the
minute noctiluca, no bigger than a pin’s head, and the three-horned
animalcule Ceratium tripos are the usual cause of the phosphorescence
of the sea on our own coast. Deep-sea fishes are provided with large
phosphorescent discs or plates on the surface of the body, which are
sometimes furnished with lenses like a bull’s-eye lantern. Glow-worms
and fire-flies and some tropical beetles are examples of insects which
have fatty phosphorescent organs which they can illuminate (oxidise)
at pleasure, under the control of the nervous system. Some of the West
Indian phosphorescent beetles are remarkable for having “lights” of
two different colours. In the marshes around Mantua the fire-flies
are so abundant at the end of June that the air for miles is full of
them, and the sight so extraordinary and beautiful as to be worth a
long journey to see. I have seen fire-flies as far north as Bonn on
the Rhine. Once I was nearly upset by a horse shying at a glow-worm on
a bank in Worcestershire. Some moulds and well-grown toadstools are
phosphorescent, and a phosphorescent earthworm, a peculiar species,
now well known, was first of all discovered in the South of Ireland
by the late Professor Allman. In the autumn I have often picked up
the phosphorescent centipede, which is remarkable for the fact that
the phosphorescent material is a kind of slime which exudes from the
body--the creature leaving thus a luminous trail behind it as it
crawls. The piddock, or pholas--a boring sort of mussel--has brilliant
phosphorescent glands, and the boys at Naples love to munch these
shell-fish at night, and then to alarm the passer-by by opening their
mouths, and showing a brilliant green light within. Cases are recorded,
but not recently, of persons suffering from tuberculosis becoming
phosphorescent; a possible, but certainly a rare, occurrence. Animal
and vegetable phosphorescence is varied in colour. The light emitted
is blue-green, green, yellow, orange, and even red in different cases.
It is always due to the oxidation of a separate fatty chemical body,
which can in many instances be extracted, then dried, and subsequently
made luminous by moistening with ether, in consequence of which
oxidation by the oxygen of the atmosphere is facilitated.
28. _Reminiscences of Lord Kelvin_
The late Lord Kelvin was one of the most fascinating personalities
in the learned world. He uttered with a delightful simplicity the
thoughts, however romantic and fanciful, which bubbled up in his
wonderful brain. It was because he was so much of a poet that he was
so great a man of science. Atoms and molecules and vortices, and the
vibrations and gyrations of ether, and “sorting demons” were all
pictured in his mind’s eye, and used as counters of thought to give
shape and the equivalent of tangible reality to his conceptions. By
such conceptions he was able to present to himself and his listeners
the complex mechanisms of crystals, of liquids, of gases, of electrical
and magnetic currents, and the endless astounding proceedings of rays
of light unsuspected by the ordinary man.
I think the last occasion on which he spoke in public was after Sir
David Gill’s brilliant address to the British Association at Leicester
last August. Lord Kelvin was sitting close to me on that occasion, and
I noticed that he never moved his gaze from the speaker. He followed
Sir David’s account of stars, whose distance is stated by the number
of years it takes for their light to travel to this earth, like an
enraptured schoolboy, and cheered when the evidence for the existence
of two great streams of movement of the heavenly bodies, in opposite
directions, going no one knows whither, coming no one knows whence,
was sketched to us by the lecturer. In proposing a vote of thanks to
Sir David Gill, Lord Kelvin burst into a sort of rhapsody, in which,
with unaffected enthusiasm, he declared that we had been taken on
a journey far more wonderful than that of Aladdin on the enchanted
carpet; we had been carried to the remotest stars and well-nigh round
the universe, and brought back safely to Leicester on the wings of
science, and the most marvellous thing about it all was that it is true!
A few weeks before this Lord Kelvin was at the dinner in celebration of
the jubilee of the foundation of the Chemical Society. In the speech
which he then made he referred to the painful accident of a year or
so ago which we had all so much regretted, when he had burnt his hand
accidentally in some experiments with phosphorus, and had had to carry
his arm in a sling for some weeks. “Lord Rayleigh, the president of
the Royal Society,” he said, “has just told us how, as a boy, he gave
proof of his devotion to chemical science by burning his fingers with
phosphorus--but I think my devotion must be considered greater than
his, for I burnt my fingers very badly with phosphorus only last year,
when I was 83 years old. It was at the end of April. My friends said
I was old enough to know better, and it should have happened, not at
the end of April, but on the first day, of that month.” Lord Kelvin
was associated in work in the sixties and seventies with another
splendid man, Tait, of Edinburgh, who, besides being a great professor
of “Natural Philosophy,” and joint author of the celebrated treatise
known as _Thomson and Tait_, was a great athlete--a golfer of the first
class, a first-rate billiard player, and a wise lover of good ale,
which he drank and gave to his friends to drink, whilst he discoursed
as few, if any, to my knowledge, can now do, of things philosophical,
mathematical, and humane.
29. _The So-called Jargon of Science_
It is often discussed as to whether science fails to obtain the
attention of the public and to excite intelligent interest, owing to
the obscure language which lecturers and writers use when attempting
to expound scientific views and discoveries to “the ordinary man,” or
whether the fault lies with the “ordinary man” himself, who is too
frivolous to bother about following carefully the words addressed to
him, and, moreover, has never learnt even the A B C of science at
school. It is certainly the case, as Professor Turner, the Oxford
professor of astronomy, has pointed out, that a popular lecturer could
tell his auditors a good deal more in an hour if they already had the
elements of his subject at their fingers’ ends than he can under the
existing state of neglect of school education in the natural sciences.
That, however, seems to be obvious enough, and does not touch the real
question.
I have had a long experience, both in lecturing myself and in
assisting in the training of others to lecture and also to inform
the uninstructed public by means of museum-labels and popular notes.
It seems to me that there are a large number of men who, even though
capable of expressing themselves clearly under usual circumstances,
yet fail to do so when trying to expound or to teach, in consequence
of three distinct faults, any one of which is enough to render their
discourse or writing hopelessly obscure to “the man in the street.”
These are, first, a kind of pride in using special terms and modes of
expression which infatuates the lecturer or writer, and leads him,
without reflection, to an attitude of mind expressed by saying, “That
is the correct statement about this matter, short and true. If you
don’t understand it, there are others who can. You can leave it alone;
it is not worth my while to spend time and trouble to explain further;
it is for you to give yourselves the trouble to find out what I mean.”
The second fault is a real incapacity (which occurs in many learned
men) to realise the state of mind of the uninstructed man, woman or
child who eagerly desires to be instructed: this is want of imagination
and want of sympathy. There is no cure for those who fail as teachers
for either of these two reasons.
The third fault is much more widely at work, and the most kindly
sympathetic lecturers and writers--but more especially lecturers--often
suffer from it and could easily amend their practice. It consists
in the attempt to tell the audience or reader too much--vastly
too much--in the limit of one hour, or within the space of a few
lines or pages. This failure is well-nigh universal. I have heard
a distinguished discoverer, an eloquent and able man, try to tell
a completely ignorant audience in one hour the results of years of
experiment and work by many men on the electrical currents observed
in nerves. The audience did not know what is meant by an electrical
current, nor anything about nerves, nor a single one of the technical
terms necessarily used by the lecturer. The task was an impossible one.
In six lectures it might have been accomplished, and great delight
and increase of understanding afforded to the listeners instead of
perplexity and a sense of their own incapacity and the hopeless
obscurity of science. That, I am convinced, is the real trouble, viz.,
the attempt to tell too much in a short time, the failure by the
lecturer to arrange his exposition in a series of well-considered,
definite steps, each exciting the desire to know more, and each
given sufficient time and experimental illustration or pictorial
demonstration to lodge its meaning and value safely and soundly in
the tender brain of the ignorant but willing listener. I am convinced
that there is in very many lecturers a tendency to try to crowd and
compress into one lecture what should occupy ten--if the willing and
intelligent but ignorant listener is to feel happy and is really
to understand what is said and done for his instruction. A special
difficulty also arises from the fact that the lecturer often feels
himself called upon to address and to say something to those among the
audience who already know a good deal about his subject, as well as to
make things clear to those who are absolute novices.
Some people have made this discussion the opportunity for attacking
on the one hand the English language, and on the other the use of
special names applied by men of science to special things and special
processes. We cannot at once change the English language, even did we
wish to do so. But the creation of special names to distinguish things
not distinguished from one another in common speech is a necessity. It
cannot be avoided. It is mere impatience and temper to call the names
and terms which are necessary as counters of thought “jargon.” No doubt
there may be in some lecturers and writers a tendency to excessive use
of special terms and names, but the real trouble in the matter arises
from the too rapid thrusting of a large number of such unfamiliar words
upon an untrained audience. If new words are introduced in moderation
they can be assimilated. They cannot be dispensed with altogether.
A correspondent lately complained to me that I wrote of the minute
creature which causes the sleeping sickness as a Trypanosome, whereas,
had I called it “a blood-parasite” he would have known what I meant,
and been able to follow my statement more easily. I am sorry to say
that I cannot agree with him. There are many kinds of blood-parasites;
there are the worms known as Filariæ, there are the vegetable microbes
known as bacteria and bacilli and spirilla, and there are minute
creatures of an animal nature called pyroplasma and trypanosoma
(beside some others). These must be distinguished from one another
if we are to understand anything about the causation of disease by
microbes. It would be mere muddling and confusion to simply call them
all by the same name, simply “blood parasite.” That would cause the
same sort of confusion as would occur if the Smiths or Browns of our
acquaintance had no Christian names by which we can separate each
member of the class from the others and assign to him his own special
qualities, opinions, and property. What some people call “scientific
jargon” is assuredly not a thing to be proud of or to mouth with a
sense of superiority. Nevertheless, it is absolutely necessary, and
must be introduced gently and considerately to the stranger who can
and will, if reasonably handled, appreciate the immeasurable advantage
of having distinct words to signify distinct things. That, after all,
is an elementary feature in all language. And just as the “jargon” of
a game, a sport, or a profession has a fascination for those who use
it, and forms a bond of union or special understanding between them,
so inevitably does the jargon of a branch of science flourish in the
thought and on the lips of those who devote themselves to that branch,
and bind them in a sort of freemasonry. We do not expect cricketers
or golfers to talk in plain English; why should we expect chemists or
naturalists to do so? After all, it is a question of moderation and of
gradually increasing the dose. The beginner must not be terrified by an
array of outlandish words.
30. _Rats and the Plague_
Rats! Who said rats? That is an important question, because the word
means different things to different people. To some persons “rats”
means simply “nonsense”! To Sir James Crichton Browne it means the
devastator of stores and the dread carrier of bubonic plague. To the
naturalist it means a group or natural cohort of small mammals similar
to our common rat and mouse, representatives of which are found in
every quarter of the globe and in almost every island of the sea. The
distinct “kinds” or “species” are numbered by the hundred. They are
extraordinarily alike, and can only be distinguished and classified
into proper “species” by careful examination and measurement. Mr.
Oldfield Thomas, of the Natural History Museum, has made a special
study of them. To give an idea of his work, it may be mentioned that
ninety different names had been given by previous writers to as many
apparently distinct kinds of rat occurring in India. But by careful
measurement and study of the relations to one another of these rats,
Mr. Thomas has reduced the number of really distinct Indian species of
rats and mice (for a mouse is only a smaller rat) to nineteen. What
we call in English water-rats, or water-voles, field-voles, and such
little foreign beasts as the lemming and the hamster, are very close to
rats in appearance, but are separated on account of clear differences
of structure from true rats and mice.
At a meeting in London the total destruction of “rats” was advocated.
Whether it was affirmed at the meeting, or was merely an error of
those who wrote and commented on the matter afterwards, I do not
know, but it was very generally stated in this connection that the
old Black rat (known to naturalists as Mus rattus) is quite extinct
in England, and that its place has been taken by the Norwegian, or
Grey rat (Mus decumanus), also called the Hanoverian rat, because it
became noticeable by its abundance in this country at the time of the
accession of the Hanoverian kings. The Black rat is not extinct in
England, not even very rare. Mr. Stendall lately sent me specimens
caught in his warehouse in the City of London, where they are
abundant. In many localities, _e.g._ Great Yarmouth, and in isolated
dwelling-places they occur, and even outnumber the Norwegian rat. A
most important and remarkable fact is that the rats which infest ships
are often all Black rats. The Black rat, or Alexandrine rat (as Mr.
Thomas calls it), lives in our houses, in the roof, in recesses of
woodwork. It is a house rat, whereas the Grey, or Norwegian rat, lives
in the sewers and the banks of ditches, and only comes up into the
basement of houses through defective building. The Grey rat has driven
out the water-voles from many river banks near towns, just as he has
to a great extent taken the place of the Black rat in houses where the
kitchen and food stores are close to and in communication with the
sewer!
The Black rat cannot be really distinguished by his blackness. That is
why some naturalists call him the Alexandrine rat, so as to avoid a
misleading implication. He is often of a bright yellowish-brown colour
along the back--with longer dark-brown hairs and a good deal of grey
elsewhere--quite like the Norwegian or Grey rat in colour. At the same
time he is often blackish, and frequently very black. The colour of
all these kinds of rats and mice can vary, according to the conditions
and colour surroundings in which they live. Black, white, sandy-brown,
or a mixture of spots of all three colours, or a uniform “mouse-brown”
tint, are (as most boys know) the possibilities revealed by allowing
them to breed in captivity. Nature selects accordingly the particular
tint which affords protection from observation by enemies in a given
locality.
The real distinction between the Black (Alexandrine) rat and the Grey
(Norwegian) rat is that the Black rat is smaller, has a tail longer
than its body (125 per cent.), and long and wide ears, which stand out
from the head. The Grey (Norwegian) rat is a larger, heavy-bodied rat,
with a tail shorter than its body (90 per cent.), and short ears. Both
these rats are common in India, but there is a third kind, which is
the commonest of the three in Calcutta, and is probably the one most
concerned in the dissemination of plague. It differs in some definite
features from both the Black rat and the Grey rat, although it is
very much like the latter in general appearance. It is called Nesokia
Bengalensis, or Mole-rat. It is a big rat--its tail is only 70 per
cent. the length of its body; the pads on the soles of its feet differ
from those of the two other rats; its fur is thin and bristly, and when
it is put into a cage it erects its bristles and spits! It is, like
the Black rat, a stable and granary rat, and makes burrows in which it
stores grain.
The rats of Calcutta have been carefully studied lately by Dr. Hossack,
in consequence of their connection with the bubonic plague. In the
older native parts of Calcutta, the Mole rat is twice as common as the
Norwegian Grey rat, and the Black rat not so abundant as the latter.
In the central European part of the town the Grey rat is commoner than
the Mole rat--because, apparently, the better-built houses do not
afford such facilities for burrowing. The Black rat is here also by a
good deal the most uncommon of the three. All these rats suffer from
the plague, die from it, and the fleas which lived in their fur leave
them as they get cold, and make their way on to human beings, whom
they consequently infect with the plague bacillus. This has now been
quite conclusively proved by the Indian doctors charged by Government
with the study of the causes of the plague. The plague bacillus--a
minute, rod-like organism, which grows in the blood and lymph, once
it has effected a lodgment, and there produces deadly poison--was
discovered some fourteen years ago, but it is only recently that the
plague bacillus has been shown to live in the intestine of the flea,
which sucks it up with the blood or other fluids of the rat on which it
lives. The flea, which readily goes to man, does not suffer from the
plague bacilli which it has gorged, but conveys them to man either by
its bite or by its excrement.
This being so, it becomes important to know all about the fleas of
rats. Quite unexpected facts have been discovered in regard to them.
In Europe a very large flea is found on the grey and the black rat.
This kind has not, I believe, ever been found on human beings or been
known to bite them. But in India, in the Philippines, and in the ports
of the Mediterranean, this northern rat-flea is rare, and its place is
taken by a smaller and more actively vagrant flea, which Mr. Charles
Rothschild (who is the great authority on fleas) found upon several
different kinds of small animals in Egypt. He named it “Pulex cheopis.”
This is the flea (and not our big northern rat-flea) which acts as
the carrier of plague-germs from rats to man in India. It appears
from experiments that the common flea of man (Pulex irritans) and the
cat-and-dog flea (Pulex felis), as well as the big northern rat-flea
(Ceratophyllus fasciatus), can harbour the plague-bacillus if fed on
plague-stricken animals, but there are no observations to show (as
there are about the “Cheops flea”) that they pass habitually from man
to rats and rats to men.