and other infections, are no doubt best dealt with by excluding them
from access to the human body when that is possible. But once they
have effected a lodgment and commenced to multiply in the blood or
tissues, it is still possible to get at them by means of drugs, which
poison them without injuring their human victim. Thus quinine has been
of enormous service in checking the ravages of the malaria parasite,
and really in Great Britain has exterminated “ague,” which is the
English name for malaria. Many experiments have been made during the
last two years, with the view of finding some drug which will, in like
manner, destroy the trypanosomes which have established themselves in
the blood and lymph-passages of the human body, and are slowly killing
their victim with sleeping sickness. An arsenic compound, “atoxyl,”
has been found effective when injected into the patient’s body, and
according to Dr. Koch, who returned last year from Uganda, he has
found nothing better than this treatment, discovered by Dr. Thomas
and Dr. Breinl, of the Liverpool School of Tropical Medicine, three
years ago. Dr. Plimmer and Dr. Thomson, who have been experimenting
in London for the Royal Society, have found a drug which is more
effective than atoxyl in destroying certain trypanosomes which attack
rats, and is now being tried in the treatment of sleeping sickness.
This is the tartrate of sodium and antimony--a salt corresponding to
the well-known tartar emetic, with this difference, that it contains
sodium instead of potassium. It seems that this sodium variety of
tartar emetic is very destructive to trypanosomes in the blood and
lymph, and has no injurious effect of a lowering nature, such as occurs
when the potassium salt is used. As the antimony drug is far cheaper
than atoxyl, it will be possible to apply it freely to horses and
cattle suffering from “nagana” and “surra,” which are diseases due to
trypanosomes of a special kind. Two white men who had become infected
by the trypanosome of sleeping sickness in West Africa have been
treated with the new drug in London, and the parasites have completely
disappeared from their blood in consequence, though it remains to be
seen whether a permanent cure has been effected. One cannot imagine a
situation of more thrilling interest than that existing in the nursing
home where those two victims were given a strong hope of escape from
what seemed to be certain death, whilst the fate of thousands of
African natives, similarly infected, was hanging in the balance! After
six months from the date of treatment the report is satisfactory. The
parasites have not yet re-appeared (July, 1908) in the two patients
treated in November.
14. _Tsetse-Flies and Disease_
Dr. Koch appears to have been questioned on his return to Europe by
some journalists as to the results of his study of sleeping sickness
during the past year and a half in Uganda. It was already known (three
years ago), from the observations of Professor Minchin, Dr. Gray,
and Dr. Tulloch (the Royal Society’s observers in Uganda), that the
tsetse-fly in Uganda sucks the blood of crocodiles, also of fishes
and of hippopotami. Dr. Koch confirms this observation. Minchin also
observed a trypanosome in the blood of the crocodile differing from
that of sleeping sickness. Whether crocodiles help, in an important
degree, to keep tsetse-flies alive in the regions where they occur,
by offering them a ready meal of blood, is uncertain. So far as the
facts are known, they do not lead to the belief that the crocodile is a
“reservoir host” for the trypanosome of sleeping sickness.
“Reservoir-host” is a very useful and expressive name for animals
which can tolerate or support a parasite in their blood which is
deadly to other animals. The parasite flourishes in abundance in the
reservoir-host with entire satisfaction to both host and guest. But
a blood-sucking fly or gnat, of promiscuous tastes in the matter
of blood, comes along, sucks the reservoir-host a bit, and then
goes off for another meal to a susceptible animal, into which it
introduces the parasite now adhering to its already blood-smeared
proboscis or beak. Such a history was first established by Bruce in
regard to the trypanosome parasite which causes the deadly nagana
disease in the “fly-belts” of South Africa. The big game animals are
reservoir-hosts to this parasite, from which they are carried by the
tsetse-fly to horses, mules, and dogs, which, being of foreign origin,
are not tolerant of it, but are killed by the poison to which its
multiplication in their blood gives rise. Thus, too, native children,
both in Africa and the East Indies, appear to be tolerant of the
malaria parasite, and act as reservoir-hosts from which the spot-winged
gnats suck and distribute the parasite to the non-tolerant, susceptible
adult natives and white men.
The tsetse-flies are little bigger than the common house-fly, and
bite, or rather stab, very rapidly after alighting on the skin. The
study of flies and gnats, and other blood-sucking insects, has
become extremely important, and has been carried on with great energy
by many specialists since it became known that these insects play
such a terribly important part in the causation of disease. At the
Natural History Museum I received (in response to a circular issued
at my request by H.M. Government) thousands of specimens of gnats
(mosquitoes) from all parts of the world, and some hundreds of new
species have been described in a series of volumes by Professor F. V.
Theobald, published by the trustees. Other volumes are in preparation
illustrating the blood-sucking flies of various regions of the world,
and one concerning those of the British Islands has already appeared.
The common gnat, the spot-winged gnat, and the tsetse-fly--as well as
the microscopic parasites causing malaria and sleeping sickness--are
illustrated by greatly enlarged models--very carefully executed under
my direction, which are exhibited in the central hall of the museum.
It is a curious fact that the coloured races of men--especially those
of Africa--have little or no objection to being bitten by flies. They
seem to accept the attention of flies and ticks with indifference.
The men sleep in the day under trees, and are willing food-supply to
the insects. The eyelids of children are literally inhabited by flies
in some countries, and the folds of the skin of fat adults hide whole
rows of fast-holding ticks. But the white man does not willingly permit
either fly, flea, or gnat to settle on him. He is (or has been),
nevertheless, unwisely tolerant of house-flies in his habitations, and
the poorer and less cleanly population are in large proportion infested
with wingless insects. The newly established knowledge that certain
flies (glossina or tsetse-fly) are the carriers of sleeping sickness,
that gnats are the carriers of malaria and of yellow fever, that fleas
are the carriers of the plague, and that certain kinds of ticks are the
carriers of cattle-fevers and dog-fevers, and probably of some obscure
fevers of man, must make us all more anxious than we were about contact
with insect life. For ages popular tradition has ascribed diseases of
one kind and another in various parts of the world to the bites of
flies. But actually it is little more than fifty years ago since it
was really shown that deadly germs or parasites existed which could
be, and actually are, carried by flies from one animal to another, and
introduced into the blood by the flies’ stab. This was first shown in
regard to the bacterium of splenic fever (or anthrax, or wool-sorters’
disease), a blood-disease of cattle which is transferred by the big,
fiercely-biting “horse-flies” (tabanus), from animals to man, and is
invariably fatal. Another bacterial disease, “pernicious œdema,” is
inflicted on man in the same way. These cases were exceptional, and
it is only quite recently that the agency of flies and fleas in great
epidemics, and in diseases causing thousands of deaths every year in
well-known regions, has been discovered.
15. _Monkeys and Fleas_
The wingless parasites known as pediculi are not known as active
agents in spreading disease germs, probably because they do not
readily transfer themselves from one animal to another. It is in this
connection a really remarkable fact that monkeys are not infested by
fleas, and that only in few cases and not in many kinds have pediculi
or acari been observed. In this respect the lower races of men (and
even the higher) seem to have fallen away from a grade of excellence
attained by their despised quadrumanous cousins. When this fact as
to the freedom of monkeys from insect parasites is mentioned, those
who have watched monkeys in captivity will immediately say, “Surely I
have seen monkeys carefully picking insects from one another’s fur.”
The fact is that it is this very habit of “picking” which prevents
monkeys from harbouring fleas. Whereas a dog or a cat can only scratch,
the monkey has an opposible thumb and delicately sensitive fingers.
That which has become the hand of man, with all its marvellous skill
and efficiency, has been elaborated in its early stages as a means
for keeping the hair clean. When monkeys are seen carefully removing
something with finger and thumb from their own or their companion’s
hair, it is not an insect but a little piece of fatty secretion and
scurf which is thus removed. The habit, which seems to be general in
all kinds of monkeys, even with the anthropoids, such as the chimpanzee
and the orang, has of course been efficient in removing any parasitic
insects which may at one time have infested monkeys--all other furry
animals are liberally supplied with them, as also are birds--but is
now preventive of any re-establishment of such visitors. The popular
judgment of the monkey’s habit is similar to that of the Japanese Aino,
who remarked to a traveller who arranged to have a bath in his room
every day that he must be a very dirty man to require it.
16. _The Jigger Flea_
One flea is recorded as having been once taken on an anthropoid ape (a
gorilla), and is the “jigger,” Pulex penetrans. This is a very serious
pest, the history of which shows how man himself opens up the path
by which dangerous diseases spread. The jigger-flea was originally
known only in the South American tropics. It spread from there to the
West Indies in the last century. It burrows into the skin, usually
between the toes, but elsewhere also, and causes an abscess and sore
as big and deep as a hazel-nut. Several such cavities at a time are
dangerous, and often lead to blood-poisoning and death. Europeans avoid
the burrowing of the jigger by having their toes carefully examined
every morning, but black men are less careful. From the West Indies,
about thirty years ago, the jigger was carried in ships to West Africa.
There it flourished and spread from village to village across Central
Africa, decimating the population. It appears to have been carried to
a large extent by dogs, in whose skin it flourishes. It has now passed
through Africa to India, and we shall no doubt soon hear of its having
completed the circuit of the globe.
A great many kinds of fleas are known, many furry animals having their
own special species, which does not leave them to take up its dwelling
on other kinds of animal. The common rat has a large flea of its own,
which apparently is not the flea which carries the plague from rats
to men. It is a “wandering” flea which does this, namely, the Cheops
flea. This flea, common in the East but unknown in colder regions, does
not stay as one could wish it to do--on the rat; but travels about
visiting human beings and dogs, and so carries the plague bacillus
from rats to men. In the absence of these fleas plague would be a
rat-disease unknown in men. It is probable that we do not nowadays live
so thoroughly cheek-by-jowl with rats in Western Europe as formerly,
so that even if rats infected with plague and harbouring the Eastern
Cheops flea arrive in our docks, the wandering flea is too far off to
reach us in our modern houses.
17. _Public Estimate of the Value of Science_
The Royal Society, the full title of which is The Royal Society of
London for the Promotion of Natural Knowledge, has its anniversary
meeting and dinner on St. Andrew’s Day. The health of the medallists
of the year 1907 was given from the chair by Lord Rayleigh, and they
replied one by one to the toast. Professor Michelsen, of Chicago,
received what is considered the greatest honour the society has to
bestow--the Copley Medal (founded more than two hundred years ago) for
his researches on light. He related in his speech how he had tried
to interest a wealthy business man in the experiments going on in
his laboratory, in the hope that his friend might be moved to give
pecuniary aid for the provision of new apparatus. One by one, he showed
his delicate instruments and explained their uses; no impression was
produced. At last he explained how the bright lines of the spectrum of
flame, coloured by incandescent elements (such as theatre-goers know
as red fire, green fire, blue fire, &c.), can be recognised by means
of the spectroscope in the light of the sun--proving the presence of
the metals and other elements of this earth in that remote body. He
especially explained and showed his friend the experiments by which
sodium, the metal of which caustic soda is the “rust,” is thus proved
to be present in the sun. At last his friend spoke. He said: “Who the
---- cares if there is sodium in the sun?” Professor Michelsen did not
tell the fellows of the Royal Society how he replied to that abrupt
inquiry.
A more encouraging speech was that of Lord Fitzmaurice, the
Under-Secretary of State for Foreign Affairs, who replied to the toast
of the guests. He declared, in so many words, “It is every day becoming
more and more certain that science is the master.” He said that in
his own business as a diplomatist he found that the chief matters
which he had to discuss and decide depended on scientific knowledge
and the information and guidance given to him and his colleagues by
scientific men. In the beginning of the eighteenth century the British
Government had sent a bishop and a poet to negotiate the Treaty of
Utrecht. But neither would be of any use in modern diplomacy. What they
always had to seek at the present day was the aid of the scientific
departments of the Navy or the Army, or of the Royal Society. Such
matters as the relative merits of a Channel tunnel or a Channel ferry,
the limitations of territory by land, by sea, or above the land in
the air, the international agreements as to measures for checking the
spread of disease or of insect pests, and, indeed, most matters which
had come before him since he had been in office, had to be decided by
the scientific experts. He did not propose that diplomatists should at
once vacate their posts and endeavour to secure the occupation of them
by men of science, but he thought that at no distant date such a course
would be considered not only reasonable, but necessary!
18. _The Common House-fly and Others_
The common house-fly is not so innocent as he looks, but really a dirty
little thing. He has not a sharp beak-like proboscis, and cannot stab,
but he has a soft, dabbing proboscis, which he pushes on to every kind
of filth as well as walking with his six legs on such matter. Then he
comes and wipes off minute particles and germs on to our food, our
lips, our fingers, and faces. It is quite certain that he, and others
allied to him, are thus the means of spreading typhoid fever in camps
where there are open latrines and open larders and mess tables. The
house-fly breeds from a maggot, just as the blue-bottle or blow-fly
does, but very few people have ever seen or recognised the maggot of
the house-fly. The reason is that it lays its eggs in horse dung, and
the grubs are hatched in the muck-heaps of stables. That is also the
reason why it is much less numerous in London than it used to be,
since stables and mews are now fewer and cleaner than they were. It is
also the reason why the house-fly abounds in ill-kept country inns and
farmhouses. Its breeding ground is just outside the window.
There is not only one common house-fly in this country: there are
three kinds, in addition to the blue-bottle or blow-fly, which is
distinguished at once by its great size and blue colour, and lays its
eggs in carrion. Late in the year you may often see what would pass for
young or starveling house-flies going about among the others. This is
a distinct species, the Homalomyia canicularis of entomologists. The
third kind only to be distinguished by careful examination with the aid
of a magnifying glass, is Anthomyia radicum. Both these are much less
abundant than the common house-fly (Musca domestica), with which they
almost always occur. Their breeding habits are similar to those of the
common house-fly.
A fourth kind of fly is invariably mistaken for the common house-fly
when it is noticed, as it sometimes is, in consequence of the sharp
stab which it inflicts. As recently as the beginning of November last
year I was “bitten” or pricked by one of this fourth kind in a London
club. They are common enough on the sea shore in autumn, and may be
a severe nuisance. People generally take them for common house-flies
which have lost their temper in the hot weather and give way to the
bad habit of “biting” out of sheer exasperation. Really, of course,
a house-fly could not stab or prick with its broad-ended proboscis.
The fly in question, which looks almost exactly like a well-grown
house-fly, but possesses a sharp and business-like beak or proboscis,
is known to scientific men as Stomoxys calcitrans. There are many
kinds of Stomoxys scattered all over the world, and it is probable,
though not actually proved, that they carry parasites such as the
trypanosomes of horse and cattle diseases from one animal to another,
as do the species of Glossina or tsetse-fly.
But we have yet to learn more about these flies and the parasites
they transfer. In the case of the gnat, it has been discovered that
the malaria parasite is swallowed by the gnat, and multiplies in
it, producing thousands of spores in its blood, and it is these
spores which the gnat hands or rather “mouths” on to man. No such
multiplication of the trypanosome in the tsetse-fly (Glossina) is
known. The tsetse-fly passes on the trypanosome as it received it, and
yet it seems as though it is not any and every biting fly which can
pass on the trypanosome of nagana, or of sleeping sickness, but only
the particular species of tsetse-fly. Perhaps it is a case of greater
abundance, the tsetse-flies being the obvious and dangerous carriers of
trypanosome disease where they occur, on account of their abundance and
the fierceness and celerity of their attack. It is almost certain that
in India, Burma, and South America some other flies must transfer the
trypanosomes from animal to animal, causing the diseases known as surra
and mal de caderas, because no tsetse-flies--that is to say, no flies
of the genus Glossina--occur in those countries, and no other mode of
transference, except by some blood-sucking insect, seems probable.
Ants in Africa are carriers of infection, and possibly also in London
kitchens, where a little red ant sometimes abounds. The black beetle or
cockroach is a creature to be got rid of, as it is very probable that
it spreads certain kinds of infection over food and dishes during the
hours of “revelry by night” which kind-hearted people allow it to enjoy
in their kitchens.
19. _Cerebral Inhibition_
The best golf-player does not think, as he plays his stroke, of the
hundred-and-one muscular contractions which, accurately co-ordinated,
result in his making a fine drive or a perfect approach; nor does the
pianist examine the order of movement of his fingers. His “sub-liminal
self,” his “unconscious cerebration,” attends to these details without
his conscious intervention, and all the better for the absence of
what the nerve-physiologists call “cerebral inhibition”--that is to
say, the delay or arrest due to the sending round of the message or
order to the muscles by way of the higher brain-centres, instead of
letting it go directly from a lower centre without the intervention
of the seats of attention and consciousness. The sneezing caused in
most people by a pinch of ordinary snuff can be rendered impossible by
“cerebral inhibition,” set up by a wager with the snuff-taking victim
that he will fail to sneeze in three minutes, however much snuff he
may take. His attention to the mechanism of the anticipated sneeze,
and his desire for it, inhibit the whole apparatus. So long as you can
make him anxious to sneeze and fix his attention on the effort to do
so, by a judicious exhortation at intervals, he will not succeed in
sneezing. When the three minutes are up, and you both have ceased to
be interested in the matter, he will probably sneeze unexpectedly and
sharply. I was set on to this train of thought by a recent visit to an
exhibition of photographs.
There were many very interesting illustrations of the application of
photography to scientific investigation. Among others I saw a fine
enlarged photograph of the common millipede (Julus terrestris), and my
desire was renewed to have a bioscopic film-series of the movements
of this creature’s legs. Some years ago I attempted to analyse, and
published an account of, the regular rhythmic movement of the legs
of millipedes. I found that the “phases” of forward and backward
swing are presented in groups of twelve pairs of legs, each pair of
legs being in the same phase of movement as the twelfth pair beyond
it. But instantaneous photography would give complete certainty about
the movement in this case, and in the case of the even more beautiful
“rippling” movement of the legs of some of the marine worms. Some
kindly photographer might take up the investigation and prepare a
series of films. The problem is raised and the effects of “cerebral
inhibition” described in a little poem which I am told we owe to the
author of “Lorna Doone.” As it is not widely known, I give it here as a
record of “cerebral inhibition”:
“A centipede was happy ’til
One day a toad in fun
Said, ‘Pray which leg moves after which?’
This raised her doubts to such a pitch
She fell exhausted in the ditch,
Not knowing how to run.”
The point, of course, is that she could execute the complex movement of
her legs well enough until her brain was set to work and her conscious
attention given to the matter. Then “cerebral inhibition” took place
and she broke down.
20. _Colour-photography and Photographs of Mars_
There were admirable photographs of wild birds and their nests, and of
insects and plants in this exhibition. I saw the new Lumière coloured
transparent photographs thrown by a lantern on the screen, and could
distinguish the dots of red, green, and violet colour on what, at
a little distance, appeared to be a brilliantly white part of the
picture (the shirt collar of a “sitter”), just as one sees a mosaic of
coloured dots in the blazing sunlight of the pictures painted by the
French school of so-called “vibristes” (Monod and others). Perhaps the
most remarkable of these photographs was a set of prints from untouched
photographs of the planet Mars, executed in July 1907 by Professor
Perceval Lowell at his observatory in Arizona.
The Mars photographs are each about as big as a dried pea (that is
the biggest size possible with the feeble light reflected by Mars),
but “several of the canals,” says Mr. Lowell, “are distinctly visible
on the photographs, and one has been photographed double.” I should
have liked to examine these photographs in a good light with a lens.
The statement quoted means that the canals in Mars can no longer
be regarded as due to errors of eyesight and imagination, and that
the annual doubling or formation of a second canal parallel to what
was earlier in the year a single canal, is actually recorded by a
disinterested, impartial photographic plate. Are these canals the work
of intelligent inhabitants of Mars? I will not venture to say in reply
more than this, that I have never heard any other explanation of their
occurrence. But that, of course, still leaves the matter open.
21. _Origin of Names by Errors in Copying_
A curious illustration of a mistake perpetuated by a clerical error is
the title of Viscount Glerawly. The title was intended to have been
Glenawly, but the bad writing of a clerk converted the “n” into an “r,”
and the name having been so entered in the patent of nobility, or some
such document, could not be altered. The same thing has happened to
the mammoth. His proper native name is “mammont,” but “mont” became
“mout,” and then “moth.” A similar clerical error is responsible for
the name Gavial, which is applied to the long, narrow-nosed crocodile
of India, both as a scientific name (Gavialis) and colloquially.
Really the “v” is due to a misreading of an “r,” the creature’s native
name being Garial. It was so written down and sent home by an early
explorer, but his handwriting being wanting in clearness, the word was
copied as Gavial and the scientific patent issued in that name.
22. _False News as to Extinct Monsters_
The tendency of English newspapers to bedeck themselves every now
and again with rank absurdities copied from American rubbish-sheets
is a disease. On no subject outside the field of natural history and
medicine would any editor dream of printing the stuff which does duty
as “news” in regard to these departments--stuff which has not even the
semblance of being carefully concocted, but yet is found “good enough”
to circulate as serious information.