In endeavouring to ascertain how the parasite entered the system I
inquired as to the water and food supply at Old Calabar, and my patient
informed me that at Iköröfiön, the mission station at which she resided,
the entire water-supply during the dry season was obtained from a spring
that bubbled up out of the ground close to the river. During the rains,
however, this spring might occasionally be covered by the swollen river,
but at that season the water-supply was derived from a tank in which the
rain was collected. The water used for drinking was always boiled, and
twice filtered. In washing her face she was specially careful to keep
her eyes well closed, and if at any time her eyes were sore she bathed
them with the drinking-water. These precautions she took, as it was a
popular belief among the natives that the worm gets access to the eyes
through the water with which the eyes are bathed. She further informed
me that the occurrence of this kind of worm in the eye is well known to
natives of Old Calabar, and they use a solution of salt and water as a
wash to scare them away. Mosquitos abounded at the station, and any water
left standing in a dish soon swarmed with their eggs. The fruit supply
consisted of mangos, Avocado pears, bananas, pineapples, oranges, and
custard-apples. No uncooked vegetables were used as food.
She herself had seen a number of instances of the worm in the eyes of
natives, and thus knew the nature of the affection when she had it
herself. It is said in Calabar that they are very difficult to capture.
She has never heard of the parasite piercing the skin or conjunctiva.
The ordinary guinea-worm (_Filaria medinesis_) under the skin is unknown
in Old Calabar. Miss H⸺ acted as dispenser for about a year during
the missionary’s absence, and never saw a case of it, nor heard of it
occurring during the whole of her residence there.
As a result of inquiry I found that other members of the Old Calabar
Mission had been affected with _Filaria loa_.
1. A lady, Mrs. M⸺, who for a time had resided with my patient at
Iköröfiön. She was in this country this year, but has returned to Old
Calabar. While in Scotland the worm was seen in her eye by my patient
Miss H⸺ and her sister, who is at present engaged in the study of
medicine. The latter saw the worm pass from the one eye to the other,
crossing the bridge of the nose under the skin.
2. Mrs. H⸺, the widow of a medical missionary to Old Calabar. I had the
opportunity of seeing this lady, and eliciting the following particulars.
She was three years in Old Calabar, from 1860 to 1863, at Old Town
Station. Here the water-supply was obtained from a spring which emerged
from the ground at a little distance from the river. Before use for
drinking the water was filtered through a porous stone basin, but it was
not boiled. The water for washing was not boiled or filtered, nor were
any precautions taken to prevent it coming in contact with the eyes.
During part of the time she was at Old Calabar she suffered from worm
in the eye, sometimes one, sometimes the other was affected, but never
both at the same time. She occasionally had a feeling as if the worm were
making its way under the skin at the root of the nose, in the eyelids,
or on the temple. The left eye was the one chiefly affected. She was
invalided home on account of intermittent fever. She did not suffer from
dysentery. The worms troubled her occasionally after her return home,
but they never came to the surface at a convenient time for removal till
in 1875, when her husband, Dr. H⸺, succeeded in removing a worm from her
left eye. She could not now recall the steps of the operation. About a
year later another worm was similarly removed by her husband—she thinks
from the same eye, and since then she has not experienced any symptoms of
filaria. These worms were preserved in spirits, but she fears were, after
some years, thrown away.
As in the case of my patient, Mrs. H⸺ noticed that the worms scarcely
troubled her at all during winter. It was only in warm weather they
were lively. Both ladies occasionally noticed that the worm lay for a
short time coiled up and motionless under the conjunctiva. When the
worm appeared on the surface Mrs. H⸺ experienced a “biting, nibbling
sensation” at the part where the worm was, and the eye became tender and
watery, so that she had to keep it closed, but it never produced any
severe inflammation. When not under the conjunctiva or skin she was not
aware of its presence.
3. The Rev. J. L⸺ went to Calabar in October, 1868, and returned in July,
1872. He often suffered from intermittent fever, on account of which he
was invalided, and by medical advice did not return. His recollection of
the time and circumstances of the appearance of the worm is now somewhat
faint, but he thinks it appeared during the latter part of his residence
in Old Calabar, and certainly troubled him after his return home. As far
as he remembers, one eye only, and he thinks the right, was affected,
but he cannot say with certainty. It only caused slight irritation, and
no severe inflammation. It affected the eyelids, he thinks, more than
the eye. He recalls one time in particular when, after preaching at
Musselburgh, he felt it wriggling under the skin of the upper lid, and
directed the attention of some friends to it, and they saw the movement
of the worm. The intervals at which it appeared were irregular, but
generally pretty long. He never felt the worm in any other part of the
body. As far as he can remember, the visits of the worm to the eye or
lids did not generally last long—at most two days. No attempt was made
to extract it, nor did any doctor see it. He has seen or felt nothing of
the worm for the last eight or nine years, at any rate. He did not notice
that the worm was influenced in its visits by the external temperature.
In addition to these cases among members of the Old Calabar Mission,
I may refer to the experience of Dr. Thompstone, who was for eighteen
months stationed at Opobo, on the delta of the Niger, and who is in this
country at present. He informs me that while he was at Opobo he saw two
cases of _Filaria loa_. In the one negro the parasite was situated in
the lower eyelid at the inner canthus close to the lachrymal sac—the
swelling in that region giving the appearance of dacryocystitis. He tried
to press out what he considered the contents of the distended sac, when
he observed the coiled-up worm to wriggle away into the orbit, and the
swelling disappeared.
In the other negro he observed the worm moving about under the
conjunctiva when he depressed the lower lid. The patient was affected
with slight conjunctivitis. Dr. Thompstone wished to undertake the
extraction of the parasite, but the patient declined operative
interference. While at Opobo he neither saw nor heard of other cases of
the affection. The water-supply for the native population there was very
polluted.
The literature on this subject is very scanty. As far as I have been
able to ascertain there have hitherto not been more than twenty cases
recorded, and in most of them the accounts given have been bald and short
in the extreme. I may, therefore, be permitted to give a short _résumé_
of what has been written regarding this filaria.
The first case recorded appears to be that observed by M. Bajon,[1] a
French surgeon, who for twelve years practised his profession in the
island of Cayenne and in Guiana. He reports that in July, 1768, the
captain of a ship from Guadalupe brought to him a young negress about
six or seven years of age, and asked him to examine one of her eyes, in
which a small worm, about the thickness of a fine sewing thread, could
be distinctly seen. It was about two inches in length. It cruised round
about the eyeball in the cellular tissue between the conjunctiva and
sclerotic. It moved in a tortuous oblique manner. The colour of the eye
was not changed, and the young negress said she felt no pain with the
movements of the worm, but she had an almost continual watering of the
eye.
On reflecting on the means he should employ to draw it out, he concluded
that if he made a minute aperture in the conjunctiva close to the head of
the small animal, and then stimulated it to move, it would emerge through
the opening. In carrying out this manœuvre, however, he found that in
place of escaping through the incision he had made, it passed by the side
of it, and went to the opposite surface of the eye. As this proceeding
did not succeed with him, he had recourse to the device of seizing the
worm by the middle with small forceps, along with the conjunctiva, then
making a small deep opening with a lancet by the side of its body, and
then introducing an ordinary needle, whereby he succeeded in drawing it
out doubled in two.
Again, in 1771, another young negress, a little older than the last,
was brought to M. Bajon suffering from painful inflammation of the
conjunctiva. On examination he observed a worm a little longer than in
the previous case, and which, like it, moved round about the eye between
the conjunctiva and sclerotic. He proposed to employ the same procedure
that succeeded in the other case, but the patient would not consent.
He considered that the worm was a dracunculus (dragonneau) similar to
those removed from other parts of the body in negroes, only finer and
shorter.
The next case recorded is one by M. Mongin, a surgeon at St. Domingo, in
the ‘Journal de Médecine’ for 1770, occurring in a negress who had for
twenty-four hours complained of severe pain in the eye with scarcely any
inflammation.
At first glance he saw a worm, which appeared to him to wriggle over the
globe, but on trying to seize it with forceps he found it to be between
the conjunctiva and sclerotic.
To remove it he incised the conjunctiva, and it emerged through the
opening. It was one and a half inches long, and the thickness of a violin
string, and of an ashy colour. It was larger at one end than at the
other, and very pointed at the two extremities. He was inclined to view
it as a worm of the blood (_ver sanguin_), as it did not appear to him
possible for it otherwise to get into that position without giving rise
to pain and inflammation at the part.
We have next several cases that were carefully observed and recorded by
M. Guyot, a French surgeon,[2] who had made many voyages to the Angola
coast of West Africa. The first case in which he discovered the filaria
was that of a negress in whom, after several examinations, he noticed a
ridge of the conjunctiva resembling a varicose vein, which induced him
to make minute openings over it to empty it. On pricking the elevated
conjunctiva with the point of a lancet he was surprised to observe the
projection disappear. The patient at the same time stated that she
felt something move in her eye, and that the movement was deep-seated.
He suspected that this could be nothing else than a roving worm (_ver
ambulant_), which sometimes appeared under the conjunctiva, sometimes
dived into the posterior parts of the eye. From inquiry he found that a
worm in the eye was common enough among natives of that land, and that
it was called a “loa,” and he consequently applied the term filaria loa
to the affection. He saw the worm on many occasions in the eye of the
negress, but whenever he touched the spot where it was it retreated to
the posterior parts of the orbit. On that voyage he saw several negroes
with this affection, for which he employed various collyria without
effect.
In 1777 he made another voyage to the coast of Angola. Having many
negroes on board the ship he renewed his researches, and found several
individuals affected with the disease. As no benefit had been derived
from the applications he had previously used he proposed to extract the
worm through a small opening in the conjunctiva. To effect this it was
necessary to fix the worm, to which end he employed dissecting forceps,
without, however, being able to seize it.
On another occasion he employed a ligature needle of medium size, with
which he pierced the conjunctiva by the side of the worm, and passed it
between the worm and the sclerotic, making it emerge at the opposite
side. By this manœuvre he was able to raise the fold of conjunctiva along
with the worm on the concavity of the needle. This fold he divided, and
drew out the worm without mutilation. The operation required to be done
very quickly, otherwise the worm escaped and disappeared, sometimes
for a very long time. Of five negroes upon whom he thus operated he
was only able to remove the worm twice. The worms were about fifteen
lines in length, and a little less thick than a violin string. He did
not think the worms were a species of dracunculus, for they were quite
white, firmer, and less long in proportion. He never saw the worm make an
opening for itself. In the seven voyages he had made to the Angola coast
he had never seen a negro affected with dracunculus. Other surgeons who
had sailed on these coasts assured him they also had seen no cases, which
made him conclude that the negroes of that country are not subject to
dracunculus. The cases on which he operated were healed in twenty-four
hours.
We next find M. Clot at a meeting of the Académie Royale des Sciences
in December, 1832, referring to the case of a negress, who suffered
from a dracunculus under the conjunctiva of the eye. It appeared now
and then gliding between the conjunctiva and sclerotic, lifting up the
conjunctiva. This case appears to be one that was seen by Dr. Roulin at
Monpox in America.
Another case is mentioned by Dr. Sigaud in his work on the ‘Climate and
Diseases of Brazil.’ He states he was witness in 1833 of the extraction,
by M. dos Santos, of a filaria situated in the orbit on the surface of
the sclerotic of a negress.
In 1838 Dr. Guyon made an interesting communication to the French Academy
of Sciences, in which he narrated the case of a young negress affected
with two filariæ, one in the right and the other in the left eye, but
occasionally both appeared in the same eye; the passage of the worm
from the one eye to the other occurring with great rapidity through the
cellular tissue under the skin at the root of the nose. The filariæ were
in different eyes when the operator (Dr. Blot of Martinique) extracted
the filaria from the left. Some hours after, when he returned to extract
the other worm, he found that it had passed to the left eye, from which
he extracted it by a fresh incision.
The first cases reported by an English surgeon were by Dr. Loney, a naval
surgeon, occurring in two Kroomen, whom he saw while cruising on the West
Coast of Africa during 1841-2. In both he succeeded in extracting the
parasite.[3]
Another case was observed by Dr. Mitchell at Trinidad in the person of a
young negress, in whom the worm appeared at long and uncertain intervals
for four or five years before he had the opportunity of seeing it. At
length in 1845 Dr. Mitchell saw the worm twisted like the letter S lying
motionless under the conjunctiva, midway between the edge of the cornea
and the inner canthus. Extraction of the worm was deferred to enable six
or seven of his medical brethren to observe so unusual an appearance,
with the result that when they assembled the following morning the
parasite had removed itself to deeper parts.[4]
A case is also recorded by Gervais and van Beneden,[5] in which M.
Lestrille succeeded in 1854 in extracting a filaria from a negress, and
Dr. Guyon once more, at a meeting of the French Academy of Sciences in
1864, exhibited another filaria, which had been removed by a French
naval surgeon from a negro of the Gaboon. The filaria was of unusual
size, measuring fifteen centimetres. Its length was such that the whole
of it could not be seen at one time below the conjunctiva, part always
remaining embedded in the deeper parts of the orbit.[6]
Dr. Morton[7] reports a case occurring in a negress residing at Gaboon
in West Africa, in which a native woman succeeded in extracting the
parasite. The worm, preserved in gin, had been sent to him by a
missionary, the Rev. Dr. Nassau, in the district, who informed him that
although he had been very many years in that country, and had often heard
of the parasite, this was the first specimen he had been able to secure.
The missionary himself appeared to be also affected with filaria, which,
however, did not appear on the eye, but could, he said, occasionally be
felt under the skin of the fingers, and once in the skin of the lower
eyelid, from which position he attempted himself to remove it with
scalpel and forceps, but he did not succeed, the worm wriggling away
across his cheek. The worm that was sent to Dr. Morton measured 16 mm.,
but was in too badly preserved a state to permit of accurate examination.
Lastly, in Dr. Davidson’s work on hygiene and diseases of warm climates
(p. 962) Dr. Manson, who writes the article on filaria, reports the case
of a negro who had been affected with _Filaria loa_, and in whose blood
he afterwards found the _Filaria diurna_, and raises the question whether
the _Filaria loa_ may not turn out to be the female parental form of the
_Filaria diurna_.
I am afraid we must confess that we are as yet very ignorant of many
points connected with the life history of the _Filaria loa_. With the
adult female parasite we have a limited acquaintance, but till now we
are ignorant of the appearance of the male worm. The larvæ have been
observed in the interior of the adult, but what their further course is,
what transmigration may occur, ere they reappear as fully formed filariæ
under the conjunctiva has yet to be discovered. The only observation that
bears at all upon this question is that made by Dr. Manson and reported
in Dr. Davidson’s work, that in one case of _Filaria loa_, the _Filaria
diurna_ was afterwards found in the blood. With the view of ascertaining
whether the _Filaria diurna_ was present in the blood of my patient
Miss H⸺, and also with the view of getting a report as to her general
medical condition, I got my friend Dr. Alexander Bruce to undertake the
examination.
It must, however, be borne in mind that in her case the filaria removed
proves to be a male, and, unless she were affected with the female
parasite as well, no embryos could be expected in the blood.
_Report by Dr. Alexander Bruce, October 16th, 1894._—“Miss H⸺,
missionary to Old Calabar, went there at the age of twenty-two,
has been out there ten years altogether; first was out for two
years, then furloughed for one year on account of an attack
of intermittent fever which turned her hair grey, but was not
otherwise very severe in type. Then she was out for four years
and home for one year on furlough. Then was out for seventeen
months, invalided home in January, 1894, for remittent fever,
gastritis, and a form of dysentery and great anæmia. The
remittent fever began in December, 1893, with delirium at
beginning, and fever which rose daily to 102° and 103° F.
She was sent to sea in ten days, and on the way home the
temperature on one occasion rose to 107°; this was reduced by
ice-pack. Improvement was slow, being retarded by the gastritis
and dysentery, and the tendency to pyrexia did not abate till
the end of June. The gastritis was indicated by intense pain
(agony, she called it) in swallowing anything, whether solid or
fluid. The bowels now move only once daily or less frequently,
and the motions are accompanied by small flakes of mucus
(formerly by blood). There was always great mental depression
during the attacks of dysentery.
“The arms became, since June, stiff and swollen, especially on
awakening from sleep (whether at night or during the day), and
the hands felt ‘numb,’ ‘dead,’ ‘as if asleep,’ or ‘as if they
didn’t belong to her.’
“She was so weak that she had to remain in bed till the
beginning of April. Since then, after a visit to Crieff, she
has improved rapidly, and can now walk two or three miles
easily. She now has a fairly good colour, has good appetite,
and no pain in the stomach. Examination of the circulatory
system shows absolutely nothing abnormal, no dilatation of
the ventricles, no arterial, valvular, or venous bruits. The
respiratory murmurs and the percussion note of the lungs are
normal. The liver is not, and the spleen is, just appreciably
enlarged. The blood flows readily from a prick in the finger;
it is rich red in colour. The red corpuscles are well-coloured,
well-formed, and form rouleaux readily. There is a slight
increase in the white corpuscles. Specimens of the blood drawn
at 9 a.m., 8 p.m., 9 p.m., 1 p.m., and dried on the slide
showed no evidence of filaria of any kind.
“The forearms presented, on the anterior and posterior aspects,
slight flattened doughy swellings, which had no definite
boundary and were not painful to pressure. There was no
alteration in the colour of the skin over them.”
We are still at a loss to account for the entrance of the worm into
the body. There are, I think, two different channels by which it might
possibly find access. First, by the passage of the embryo filariæ
directly through the conjunctiva, being brought in contact with the eye
in water used for washing the face or bathing the eye. This I think an
unlikely means of entrance, as in my patient special pains were taken to
avoid such a possibility, and yet she became affected with the disease,
and the power of the worm to penetrate skin or mucous membrane has never
been demonstrated. Second, by the swallowing of the embryo filariæ along
with articles of food or drink. Although in the case of my patient
excellent measures were taken to secure the purity of the water-supply,
and although the nature of the food was such as not readily to lend
itself to the conveyance of impurities, still I think recent researches,
made more particularly by Dr. Manson with regard to the development of
the _Filaria sanguinis_, render it probable that the ova of the _Filaria
loa_ are, as suggested by Dr. Manson, taken into the circulation of the
patient affected by the mature female parasite. That then some insect of
predatory habits, drawing its food-supply from this polluted stream,
becomes, in its turn, the host which supplies the necessary elements for
the further development of the parasite. This insect, in its turn dying,
deposits the embryo filariæ in water, which, being used for drinking
purposes, permits the parasite once more to affect man. Which the insect
is that probably plays the part of intermediate host is as yet unknown.
This view is purely hypothetical, but I think, reasoning from analogy,
the most probable one of the development of the _Filaria loa_.
The geographical distribution of this parasite appears to be a very
limited one, as almost all, if not all, of the persons affected, whose
cases have been reported, have either been natives of or been long
resident on a limited area of the West Coast of Africa, including
Congoland and Old Calabar. If Dr. Manson’s view as to the mode of
development of the worm be substantiated, then naturally the area of
the disease must necessarily be limited to the regions in which the
intermediate insect host is to be found.
The fully grown worm may, judging by some of the cases recorded, infest
the human subject for a good many years, and may yet not give rise to
any very serious symptoms. It possesses very considerable locomotive
powers. It is capable of wandering at will from one eye to the other, to
disappear into the deeper parts of the orbit, to wander under the skin of
the eyelids, and even to make excursions in the temporal region. These
seem to be the limits of its excursions. No doubt the Rev. Dr. Nassau
(the missionary at the Gaboon) had sometimes sensations of a filaria
under the skin of the fingers as well as under the skin of the eyelid,
but it is doubtful if this was a true case of _Filaria loa_, and even
then if the worm had made its way from the fingers to the eyelid. At the
same time it must be borne in mind that there are few regions of the body
in which the skin is so thin as in the eyelids, whereby the presence of
a small filamentous body can easily be discerned. The parasite might
readily move about under the coarser cutis of other parts and yet escape
detection.
The sensitiveness of the parasite to cold appears to be fully established
by the experience of my patient and Mrs. H⸺, and it is possible that a
prolonged residence in a cool climate may eventually prove fatal to the
worm, as seems to have occurred in the case of the Rev. J. L⸺. All the
cases previously recorded have occurred in negroes, but those I have
brought forward prove that Europeans are also susceptible to the attacks
of this worm.
I think I am warranted in saying that the disease is not very rare in
the district favoured by the parasite, as, although the number of cases
reported is small, the irregular intervals at which the worm comes to
the surface, and the slight irritation or annoyance its presence causes,
often prevent those affected seeking surgical advice; while it must be
admitted that medical assistance is not very readily procured in large
parts of the district where cases occur.
The interest connected with the elucidation of the obscure points in
the natural history of the worm will, I trust, stimulate those of our
profession residing on the West Coast of Africa to undertake the further
necessary investigations.
* * * * *
Remarks by Dr. PATRICK MANSON.—I have no hesitation in saying that I
consider the communication to which we have just listened from the
President to be one of the most important on the subject of filaria
loa that has been made for many years. Two or three years ago I had
an opportunity of examining the blood of a number of negroes from Old
Calabar in a missionary establishment and elsewhere, and I made the
interesting discovery that in 50 per cent. the blood contained the
embryos of a species of filaria—_Filaria perstans_—which were quite
different in their zoological characters from the filaria of the blood,
with which every one must now be familiar. While examining one of these
patients whose blood contained this new species of filaria I found
another species of bloodworm, whose anatomical features were similar
to those of the ordinary _Filaria sanguinis_, but which presented a
very great difference physiologically, inasmuch as contrary to what is
observed with the ordinary filaria, this one disappears at night and can
only be found in the blood during the daytime. This second new bloodworm
I therefore called _Filaria diurna_. Some time later, in a communication
which I had from Professor Leuckart, he told me he had been enabled to
examine the embryos in the uterus of an adult _Filaria loa_, and he sent
me a sketch of these embryos. On comparing this sketch with the _Filaria
diurna_, I came to the conclusion that they were practically identical,
and therefore that the filaria I had found in the blood of the negroes
might possibly be the embryos of _Filaria loa_. This opinion appeared to
me to be strengthened by the fact that this patient had previously had
a loa under the conjunctiva. I have very little doubt that the embryo
of _Filaria loa_ finds its way into the blood. Clinically, there is no
evidence of its attempting to find its way to the surface of the body,
and it is evident that there must be some arrangement by which it can
get out of the body, and so propagate its species by passing from one
person to another. From this and other considerations I consider that
it must be by way of the blood that the necessary escape is effected.
With the ordinary filaria it is now well known that the mosquito removes
it from the blood and acts the part of intermediate host, and I suppose
that a similar arrangement must exist in respect of the _Filaria loa_. On
inquiring of the Old Calabar negroes as to the blood-sucking insects of
the district, I learned that there was a particular fly which exists in
great numbers about the creeks, and was very annoying on account of its
pertinacity. I think this insect, which is also diurnal in its habits,
is probably the intermediate host for the _Filaria loa_, us the mosquito
is for the ordinary filaria. I do not believe that this individual worm
was the only _Filaria loa_ in the body of the patient whose history
we have just listened to. It became visible simply because it wandered
to a spot where it could be seen; elsewhere in the connective tissue
I opine there are others. The patient was first seen in February, and
whether sufficient time has intervened for the maturation of these
parasites and the evolution of their embryos I cannot say. None, it is
true, were found in the blood, but the specimen was a male, and from this
it is impossible to say what the degree of maturity the embryos of any
females present may be. I think the blood should be examined again, and
I would suggest that if possible a similar examination should be made
of the other members of the mission, and of the patients the President
referred to. The locomotive habits and sensibility to cold of this
parasite are particularly interesting in respect of the way in which
they subserve its interests, on which they certainly have a bearing.
The measurements of the _Filaria loa_ usually given, as ascertained
by looking over the literature of the subject, are from 17 mm. to 70
mm. The smaller measurements are explained by the author’s case; they
apply presumably to the male parasite, which in the filaridæ is almost
invariably smaller than the female. One measurement given, 15 cm., is
so enormous that I question the accuracy of the observation, or, if the
measurement were exact, it must have referred to some other parasite
than _Filaria loa_. With respect to the nature of the protrusions from
the body of the parasite under the microscope, one of them is certainly
the alimentary canal; the other is probably the testis ruptured in two.
One must be careful in coming to a conclusion about these and similar
connective-tissue parasites. There are four or five whose young inhabit
the human blood; and there are others whose young appear to have a
different history. Especially in West Africa do we find such parasites.
There is the guinea-worm, said, however, not to be found in Old Calabar;
it certainly is found in the neighbourhood; its name signifies an African
origin. There is the _Filaria perstans_, the _Filaria nocturna_, and
also a very minute bloodworm, _Filaria demarquayi_, the parental form
of which, as of _F. perstans_, has not yet been found. There is the
_Filaria volvulus_, which resembles the _Filaria loa_, in that it lives
in the subcutaneous cellular tissue. Not long ago Professor Magalhães,
of Rio Janeiro, described a species of filaria which he found in the
left ventricle of the heart, which is also probably a new species. It
follows, therefore, that before venturing on the diagnosis from specimens
of parasites found in the blood or connective tissues, usually more or
less mutilated, one requires to be very careful. One singular fact about
the _Filaria loa_ is that it will not live in the West Indies. It has
been introduced many times, but does not spread. It has been removed
from the eye there from imported negro slaves, but it has not become
acclimatised. In this respect it resembles very closely the _Filaria
medinensis_ (guinea-worm), which was introduced times without number
during the days of slave importation into the West Indies, yet it has
died out altogether except in one or two places, the island Curaçao and
a limited district in Brazil. This undoubtedly is in consequence of one
of two things; either the habits of the people, or the absence of the
proper intermediate host. In respect of the guinea-worm the intermediate
host is a fresh-water cyclops. I recently had a case in the Seamen’s
Hospital from which I was enabled to procure the embryos. This enabled
me to carry out some experiments which I would urge upon those who have
the opportunity to repeat. When the guinea-worm arrives at maturity a
little vesicle or bulla is formed on the ankle or foot. The vesicle
ruptures, and on careful examination you will see a small orifice in
the centre in which sometimes the head of the worm may be seen, but not
always. If you take a sponge and drop some cold water, not on, but in the
neighbourhood of this orifice, you will see the hole become filled with
a white grumous material, which under the microscope, and on adding a
little water, is seen to be a wriggling, writhing mass of embryos. The
application of water to the leg after an interval may lead to further
extrusion of embryos. This is a striking illustration of the curious way
nature has adapted the habits of the guinea-worm to its requirements.
The young guinea-worm lives in water, and probably for this reason the
mature worm descends to the feet or ankles, the parts of the human body
in tropical countries most often within reach of water. Having procured
in this way a supply of embryos, I tried to repeat the experiment
described by the Russian naturalist, Fedschenko, on the metamorphosis
of the embryos of the guinea-worm in its intermediate host. I obtained
some fresh-water cyclops and placed them in water with the embryos. After
five or six hours I took one of the cyclops and placed it under the
microscope, and I found the body-cavity to contain twenty or thirty of
the living and moving embryos. The next day, however, the cyclops were
all dead, but the contained embryos were all lively. Having still one or
two of the cyclops left I repeated the experiment, but, proceeding more
cautiously, placed only a few of the embryos in the water along with the
cyclops. After a few hours I removed the cyclops, and found that each
of them had two or three guinea-worm embryos coiled up or moving about
in their insides. Two of the cyclops I kept alive; one lived sixteen
days and the other five weeks, and during this time the embryos could
be seen moving and developing. At the end of five weeks I killed the
cyclops, and I found the guinea-worm embryos had undergone a certain
degree of development. The outer cuticle of the embryo had separated a
good deal from the body—ecdysis, and there were certain changes in the
alimentary canal. I have no doubt that had the cyclops been in a normal
condition as regards exposure to light and sun, the metamorphosis of the
guinea-worm inside the cyclops would have been completed. This shows
that it would be possible to introduce the guinea-worm into England if
we did not wear boots or shoes, and if we were in the habit of wading
about in pools and marshes as do the natives of West Africa. There would
be a discharge of the embryos into the water, and if less care were
taken about the purity of the water-supply, and supposing there to be no
adverse climatic influences, the worm would become common. This little
story about guinea-worms shows how these and similar parasites pass from
one man to another; and it shows how slight differences of habit, absence
of intermediate host, and so on, govern the distribution of a parasite
like _Filaria loa_. If you examine this _Filaria loa_ exhibited by the
President under the microscope, you will see that all over the skin there
are minute but regular bosses or protuberances. This occurs in certain
filariæ, but in no other human species so far as I am aware. These
protuberances, I have no doubt, have a bearing on the locomotive habits
of this particular parasite. I pass round a reproduction by Blanchard
from a book which carries us back a century further in the history of the
_Filaria loa_ than that given by Dr. Robertson. This book was written
by Pigafetta,[8] and it contains a picture showing a man drawing a
guinea-worm out of his leg, and a woman having a worm removed from the
eye, doubtless a _Filaria loa_.