NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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May 6th.—There is but little fsecal matter to be seen. The
ground has been freely turned up by small beetles. A number
of pediculi are to be seen, also one or two other insects. Spe-
cimens of these were dissected, but neither eggs npr embryos
could be found within them. A number of rhabdites embryos
have hatched out.
May 9th.—Well-developed rhabdites present. A setige-
rous annelid dissected, contained one or two embryos differ-
ing in no way from those which had not met with this fate, but,
at the same time, apparently none the worse for it.
May 27th.—Mature rhabdites still present, but not in
large numbers; sluggish undeveloped embryos present in large
numbers.
June 5th.—Embryos plentiful, though a couple of dry
days has dried the surface considerably. Still one or two
mature specimens present.
July 8th.—Numerous sluggish non-sexual embryos
present, but no mature rhabdites.
July llth.—Examined with the same result, except that
one or two sexually differentiated, but yet not mature, speci-
mens were met with.
July 2Gth.—A quantity of ftecal matter from a healthy
person carefully examined, and found free from ova, mixed
with water and poured over the surface of the cultivation.
July 22nd.—All offensiveness has disappeared, principally
through the agency of small caleopetra; mature rhabdites
present in considerable numbers.
August llth.—Numerous embryos in the resting stage,
but no mature rhabdites.
August 12th.—Again examined with the same result.
August 14th.—Again examined with the same result.
A fresh dressing of healthy fasces applied.
August 15th.—Numerous rhabditea in the stage of sexual
differentiation, preceding maturity, present.
August 17tli.—Mature rhabdites in large numbers, also
very young ones, obviously just hatched.
August 20th.—Rhabdites in large numbers still present.
The result of the two fresh supplies of nutritive matter has been
to so greatly increase the number of embryos present that twenty
were counted in a morsel of earth not as large as a pea.
August 28th.—No mature rhabdites, but only small em-
bryos as yet without sexual differentiation present.
I look upon the facts established by these observations
as by far the most important result of my investigation. It
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shows that a patch of ground on which feecal matter has been
deposited by a person suffering from the disease, may remain
infected for many months, and that the accident of a fresh
deposit of fsecal matter, even from a healthy person, may
enormously increase its infectiveness, and indefinitely prolong
it. No one who knows anything of the habits of natives will
doubt for a moment that the revivication of infected spots, by
a fresh supply of nourishment, must be an accident constantly
happening in practice, as each family usually confines its atten-
tion to a small patch of ground, every part of which must be
used as a place of deposit again and again, in the course of the
year. Further, as a spot may remain infected for months after
all signs of defilement have passed away, there is nothing to
prevent the villagers from using the infected earth for cleansing
eating-utensils, and for all the other numerous purposes to which
mud and earth are turned in native domestic economy. Most
important of all, it shows that there is no limit whatever to the
time the infection may hang about an inhabited place, as,
though it is to be supposed that a time will ultimately come
when the resting embryos in my cultivations will succumb,
and pay the debt of nature, yet, at any moment before this takes
place, a fresh supply of fecal matter would suffice to start it
off on a fresh lease of life ; and under the conditions of life subsist-
ing in an Assamese village, this must, as has been pointed out,
occur again and again.
EFFECT OF SUPPLY OF OXYGEN.—In all stages, the em-
bryos exhibit a strong preference for situations in which
the air supply is of the freest; if we examine a cultivation, all
of them will be found quite on the surface. In the deeper
portions of cultivations, whether in the laboratory or in the
open, the ova either do not hatch out, or else the embryos
quickly work their way to the surface. Owing to this, cultiva-
tions in the open are always much more fruitful than those
undertaken in the laboratory, because, in addition to the freer
supply of air, the busy .operations of beetles, and other insects
turn up the soil into a fine light powder, and largely increases
the depth to which air can penetrate, in this way, more than
compensating for the nutritive matter which they consume.
Owing no doubt to this cause, ova placed in water, for example
in a test tube, hatch out much more slowly than those spread
out on sand or garden soil, and when hatched out, the embryos
fail to undergo complete development. Lively as their move-
ments are in water, they are quite incapable of raising them-
selves in it, and, on account of their relatively high specific
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gravity, sink to tlie bottom with great rapidity, and remain
there. In spite of this, embryos, at any rate such as have been
reared in sand cultivations, will live for weeks in a considerable
depth of water. A depth of a foot, however, was the greatest I
have been able to arrange for,conyeniently, but even at this small
depth, however well supplied with nourishment, though able to
exist in a resting state, they will neither breed nor develop. In
very shallow trays of water they will continue to develop for a
short, time, but, even here, soon come to a standstill. Evidently,
water is not their proper habitat, which indeed is to be found
only in defiled soil. Even in shallow trays, embryos in water died
out altogether in from two to three months, whereas, as we have
seen, the degree of longevity of embryos in sand cultivations has
not yet been reached. As might be expected from the con-
finement of the embryos to the surface of a cultivation, burial
of infected fasces will entirely prevent development, and not only
so, but brings about the death of the ova so that when unearthed
and exposed to the air, no development takes place.
The following experiments well illustrates this.
Experiment 20.—May 2nd.—A wide tube 9 inches in length
was taken, and closed air-tight at one end Avith an India-rubber
stopper. Some fsecal matter from a patient in the Shillong
dispensary, which was ascertained to contain Dochmius ova
in large numbers, was mixed with sand and water exactly as
in making the usual cultivations, and placed at the bottom of
the tube, i.e., lying upon the stopper. Over this was placed
damp sand until the tube was filled to the mouth, and a piece
of coarse muslin tied over all. By this means it was easy,
by removing the stopper, to examine the buried cultivation
without disturbance, and with only a very short exposure to the
air. At the same time, a check experiment of a cultivation of
the same rascal matter, conducted in the usual way, was made.
May 8th.—Check experiment swarming with embryos.
June 3rd.—Withdrew the stopper, and examined the
buried cultivation. It exhibited not a sign of iiematode life.
By close examination under higher powers, some bodies,
which appeared to be degenerated ova, were made out. The
tube was now inverted, and the surface, which was still
sufiiciently damp, was left exposed to the air. The check
experiment still contained abundance of embryos.
June 12th.—No embryos can be made out, nor did any
appear at any subsequent time, although the surface was kept
damp for a long time. At the date of writing, August 30th,
the check experiment still contains numerous embryos.
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It was found that dry sand or earth was just as effectual
in preventing all development as damp sand. The practical
importance of these results cannot be over-rated, as it clearly
shows that burial in trenches, as practised in the usual plan of
dry earth conservancy will be quite sufficient to render the
infective matter absolutely innocuous, and that, once buried,
there is no reason to fear any subsequent infection either
through drinking-water, or by means of any other vehicle.
INFLUENCE OP MOISTURE.—A certain amount of moisture
is essential to the well-being of the rhabdites. The most
favourable state of things is when the soil is moist enough to
hold together, but yet not sodden ; extreme conditions of either
dryness or moisture being unfavourable. On the other hand,
although their development is thereby arrested, they can retain
their vitality, in spite of drying, for considerable periods. I have
by me, a cultivation which has been repeatedly allowed to
become powder-dry and to remain so for weeks together, and
which yet, a few hours after damping, shows abundance of lively
embryos. If, however, the dessication be carried to an extreme
degree, the embryos are thereby killed.
A portion of a cultivation rich in active embryos was chemi-
cally dried, without the aid of heat, by being placed under a bell-
glass, along with a vessel containing concentrated sulphuric acid.
After a week, the material was removed to the open air,
and moistened freely with water. Many embryos could be
made out, quite shrunken and showing no signs of life. After
several days in water they had swollen out somewhat, and were
commencing to decompose, but showed no signs of vitality.
The direct rays of the sun, if allowed to act for a considerable
time seem, to have the same effect. A great proportion of my
earlier observations were made on an accidental cultivation
which existed outside the dead-house of the charitable dispen-
sary at Gauhdti. The piece of ground in question was a steep
bank, which received the outflow of the mortuary drain. Over
this drain the washing operation involved in the search for
parasites was usually conducted, and accordingly the ground
outside had been freely irrigated with water, carrying with it
large numbers of ova. During the whole of the cold weather,
the ground remained continuously moist from the heavy morning
fogs, and afforded an unfailing supply of embryos, in all
stages of growth. It was just at the end of the cold season
that I left Gauhati, and, on my return, the bank had been
subjected continuously to the action of the sun during the brief
duration of the Assam dry season.
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Not a trace of embryos could now be found, and, that they
were killed outright, is evident from the fact that, during a
recent visit, after the rains had been falling for months, the
ground was still as barren of nematodes as if it had never
been infected. The situation was, however, singularly exposed,
and received the full glare of all the sunlight that could be
got, so that the conditions were exceptional for Assam, where
the dense vegetation, which always is encouraged round houses,
must render a sufficently intense dessication to ensure the
death of the embryos a most exceptional occurrence, and it
is just in the shady bamboo, and plantain-groves about the
houses that infection is commonest and most dangerous.
This observation has an important practical bearing, as it
offers us a ready method of disinfecting sites, by clearing them as
thoroughly as possible at the end of the cold season, and leaving
the bare surface exposed to the sun throughout the dry hot
weather. It shows too, that the spread of the disease in very dry
climates, such as the Punjab, is extremely improbable, even
should it be introduced into such localities, as there would only
be a few months in the year during which infection of the soil
would be possible, and the whole infected area would be
quickly rendered harmless, once the short period of damp weather
was past. On the other hand, the toleration exhibited by the em-
bryos for moderate degrees of drying must be the source of
an added danger in climates where dessication can rarely go
to an extreme extent, for it is evident that the partially dried
embryos must often form a constituent of village dust, and
get carried by the agency of the wind to new sites, where
chance may at any time find them the nourishment necessary
to start a new focus of infection. On the whole, it seems
probable that rhabditic dochmii possess the power of resisting
dessication in as great a degree as any nematode, for they will
resist ordinary drying for very prolonged periods, and I can-
not recall any notice of experiments on other nematodes where
they have been subjected to actual chemical drying.
INFLUENCE OF HEAT.—The extent to which the develop-
ment of the embryos is influenced by the temperature of the
air has already been touched on. It remains to notice the
influence of higher temperatures.
A series of experiments was instituted to determine the
temperature at which infected faecal matter would be rendered
sterile (as far as concerns the development of doc/imius rhab-
dites). These experiments demonstrated that any temperature
exceeding 140° F. is fatal alike to ova and embryos. At inter-
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mediate temperatures, such as 120°-130° development is re-
tarded, much in the same way as by cold, but not put a stop to.
A very short exposure to a temperature exceeding 140°, for
example, by raising the water bath to 150°, and then removing
the lamp, and allowing it to cool naturally, was quite suffi-
cient for the purpose. It may be noted that in hot dry
climates, such as the Punjab, the temperature of the surface of
the soil must not unfrequently reach this limit during the day.
Throughout this series of experiments, check observations to
test the infectedness of the fseeal matter employed were
uniformly carried out.
INFLUENCE OF CHEMICAL AGENTS.—Perchloride of mercury,
thymol, carbolic acid, &c., were tried, but only proved fatal
when employed in such considerable strength as to render
their employment too expensive to be practicable, except in .the
disinfection of dejecta in hospitals, &c. Of these, per chloride
of mercury is by far the most efficient, the addition of an equal
bulk of 2 per thousand solution being quite sufficient to put a
stop to all development of embryos. Viewing the known
carelessness of sweepers and other hospital servants, I think
this precaution should always be taken in hospitals where cases
of anchylostomiasis are under treatment, especially as solution
of this strength costs so little that there can be no objection to
the adoption of the plan on the score of expense.
INFLUENCE OF LIGHT.—The more natural the surroundings
of an experiment, the more rapid and abundant will be the
development of the ova into embryos and mature rhabclites,
and I have a general impression that the influence of light may
have something to say in the markedly better results obtained
in experiments conducted in the open air, over those carried
out under laboratory conditions. At the same time, that
complete development to the adult rhabditic stage and their
reproduction may take place- in complete darkness is a fact that
has been demonstrated, during the present investigation, by a
large number of experiments, so that the influence of light is,
at any rate, not essential.
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VIII.—THE METHOD OF INFECTION BY THE PARASITE.
Having now considered the life history of the parasite, and
the circumstances that are favourable or hostile to its develop-
ment, the path, or paths, by which the infection is carried to
human beings, remains to be discussed.
In the first place, it must be remembered that the ova
themselves are never the infecting agent. Apart from
theoretical or rather comparative considerations, which are
entirely against the possibility of direct infection by the ova
of species possessing a free' stage, the circumstance that
embryos are never found in the faeces, however prolonged con-
stipation may have been, is alone sufficient to prove this. In
other words, the intestine does not offer suitable conditions
for even the hatching out, let alone the development of the eggs
produced by the parasite, and, as the other conditions of food
and temperature are quite favourable, it may be presumed
that the wanting factor is a sufficient supply of oxygen, an
agent which, as we have already seen, exercises a most potent
influence on all stages of its development.
It is the hatched-out embryos, and these alone, that are
in a fit condition to develop into the entozoic stage of the worm,
and, from the analogy of other similar parasites, it is more
than probable that the embryos hatched out from parasitic
eggs are innocuous, and that it is only the progeny of the
free stage that is capable of infecting.
Another matter that is certain is that the embryos must
gain access to their human hosts by the mouth, and so must be
introduced either with the food or drink, or perhaps, in certain
instances, by the fingers, when casually introduced into the
mouth for other purposes than eating.
Hitherto, it has always been assumed that the parasite
gained access to the intestinal canal through the agency of
drinking-water, but this opinion has been based rather upon
a priori considerations than upon the observation of actual
facts, and, though I have no doubt it occasionally occurs,
I am personally inclined to believe that drinking-water forms
a quite exceptional vehicle of infection. In the first place, out
pf the very large number of examinations of drinking-water
from infected places, in collecting which I in many instances
was at pains to stir up the mud, so as to favour the discovery
of embryos as much as possible, I have only once met with
any sign of Dochmius embryos, and even in this case, as
the specimen was a much-decomposed female, and not one
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of the very characteristic males, it is quite possible that it
may have belonged to a harmless and non-parasitic species.
I can only say that it was a rhabdites, agreeing in
general size and appearance with those of our species.
Now, were drinking water the usual vehicle, it is probable that
it would have been met with often, in large numbers, and not
an isolated specimen, once only.
Again, the physical peculiarities of the embryos are entire-
ly unfavourable to such an occurrence. Supposing them, as
indeed the ynot unfrequently must do, to gain access to a well,
they would at once sink to the bottom of it, and become
entangled in the mud, and, when we remember what clear
water may be commonly drawn from wells very muddy at the
bottom, it must be seen that, unless they happen to
be taken during their very rapid passage to the bottom,
their mixture with water actually taken for drinking must,
in the case of wells, be a most exceptional occurrence. Infec-
tion by water taken from running streams must be still more
exceptional, for the immense dilution that infected drainage must
at once undergo, must render the chances against even a single
embryo being contained in the few ounces of water drunk
during the day very small, for, prolific as these nematodes are,
the numbers produced are in no way comparable to those of
bacteria, such as those of typhoid fever, where the immense
number and infinite smallness of the infective organisms renders
the infection of large volumes of water not only possible, but
common. In the case of large rivers, such as the Brahmaputra,
water carriage of infection is well nigh inconceivable, for it must
be remembered that the introduction of single embryos would
do no appreciable harm, and that, unlike the bacteria, they are
quite unable to breed there like within the human subject, so
that every worm found parasitic must have been separately
introduced from without. Such being the case, how can drink-
ing-water have been the vehicle of infection in the already
cited instance of the village of Paru, whose only possible source
of drinking-water is the river Brahmaputra, the main current
of which sweeps by, within a few yards of its houses. On the
other hand, bhils offer much more favourable opportunities
for the conveyance of contagion, but, even here, the natural
habit of avoiding scooping up more of the mud than can be
helped must operate to render its carriage in water taken for
drinking very rare.
The habit which natives have of washing out their
mouths with water which they have just stirred up by
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bathing in it must, however, offer exceptional opportunities for
infection by the agency of water, especially as they nearly
always ease themselves on the very brink of the water in which
they propose to bathe. In pools employed for this purpose, I
have repeatedly met with undoubted Dochmius embryos, and
have little doubt that this habit is an occasional source of infec-
tion, although the people always stated that they did not use
the water for drinking. It is improbable, however, that this
will account for more than a very small proportion of cases, and,
in numbers of villages, although very badly infected, there is
no opportunity for its occurrence this way. For example, in
Paru the people bathe in the river, the rapid current of which
would instantly carry away embryos that might get into it.
If water, then, be, at best, a very exceptional vehicle of infection,
what, it may be asked, is the usual way in which the disease
is contracted ? To answer this question, we should first ascer-
tain in what situations infective embryos are to be found
in the largest numbers. These situations, I must most empha-
tically repeat, are neither wells nor pools, nor collections of
water of any kind, situations which I have, moreover, experi-
mentally proved to be entirely unfavourable to the life of the
embryos, but the surface of the soil near dwellings, which,
as we have seen, offers by far the most favourable situation
for their development.
In most parts of India, the villagers, however dirty
their habits, make a custom of going to some little distance
from their houses to relieve nature. As the}^ generally choose
the banks of the nearest nullali and so render inevitable
the defilement of their water-supply, this habit is, from
a general sanitary point of view, even worse than that of the
Assamese. One naturally expected that in this matter their
habits would resemble those of other Indians, but I was sur-
prised to find, from careful personal observation, that they
rarely trouble themselves to go more than a few yards from
their own doors. It is not uncommon to find the younger men
conform to the Indian habit, but old men, women, and children,
and especially the sick, will not move more than a stone's-throw
from their huts. After all, it is but natural that a man scarcely
able to move from the weakness brought about by anchylosto-
miasis, and often tormented by diarrhoea, should not trouble
himself to tax his strength by going to any considerable distance,
especially as his ideas of decency in this matter are, at the best,
quite rudimentary. Owing to such habits, a broad circle of
ground round the hut of a patient affected with anchylostomiasis