of small insects on the patient's skin and linen. They were quick
in their motion, and so minute that it required some attention to
discover them. He took them at first for small Pediculi; but under
a lens they appeared to him rather to be a nondescript species of
Pulex[112]; yet the figure he gives has not the slightest likeness
to the latter genus, while it bears a striking resemblance to the
former. It is not clear whether his draughtsman meant to represent
the insect with six or with eight legs: if it had only six, it was
probably a Pediculus; but if it had eight, it would form a new genus
between the _Acarina_ and the hexapod _Aptera_. Dr. Bateman, in reply
to some queries put to him, at my request, by our common and lamented
friend Dr. Reeve, relates that he understood from Dr. Willan, in
conversation, that the insect in question jumped in its motion. This
circumstance he regards as conclusive against its being a Pediculus;
but such a consequence does not necessarily follow, since it not
seldom happens that insects of the same tribe or genus either have or
have not this faculty; for instance, compare _Scirtes_ with _Cyphon_,
small beetles, and _Acarus Scabiei_ with other _Acari_[113].
Dr. Willan has quoted with approbation two cases from Amatus
Lusitanus, which he seems to think correctly described as
Phthiriasis. In one of them, however, which terminated fatally, the
circumstances seem rather hyperbolically stated--I mean, where it is
said that two black servants had no other employment than carrying
baskets full of these insects to the sea!! Perhaps you will think I
draw largely upon your credulity if I call upon you to believe this;
I shall therefore leave you to act as you please.--Thus much for pure
Phthiriasis, which term ought to be confined to maladies produced
by _lice_. I shall only further observe, that as many species as
exist of these, which are the causes of disease, so many kinds of
Phthiriasis will there be.
_Acari_, or mites, are the next insect sources of disease in the human
species, and that not of one, but probably of many kinds both local and
general. They are distinguished from Pediculi not only by their form,
but also often by their situation, since they frequently establish
themselves under the cuticle. With respect to local disorders, Dr.
Adams conjectures that Acari may be the cause of certain cases of
_Ophthalmia_. Sir J. Banks, in a letter to that gentleman, relates that
some seamen belonging to the Endeavour brig, being tormented with a
severe itching round the extremities of the eyelids, one of them was
cured by an Otaheitan woman, who with two small splinters of bamboo
extracted from between the _cilia_ abundance of very minute lice, which
were scarcely visible without a lens, though their motion, when laid
on the thumb, was distinctly perceived. These insects were probably
synonymous with the _Ciron des paupières_ of Sauvages[114].--Le Jeune,
a French physician quoted in Mouffet, describes a case, in which what
seems a different species, since he calls them rather large, infested
the white of the eye, exciting an intolerable itching[115].--Dr. Mead,
from the _German Ephemerides_, gives an account of a woman suckling
her child, from whose breast proceeded very minute vermicles[116].
These were probably mites, and perhaps that species, which, from its
feeding upon milk, Linné denominates _Acarus Lactis_. The great author
last mentioned describes an insect, a native of America, under the
name of _Pediculus Ricinoides_, which, upon the authority of Rolander,
he informs us, gets into the feet of people as they walk, sucks their
blood, oviposits[117] in them, and so occasions very dangerous ulcers.
It would be an Acarus, he observes, but it has only six legs. Now
Hermann affirms, that some species of _Trombidium_ (a genus separated
by Fabricius from _Acarus_) have in no state more than six legs[118].
Others of the tribe of _Acarina_, and the insect in question amongst
the rest, may be similarly circumstanced; or those that Rolander
examined might have been larvæ, which in this tribe are usually
hexapods.
Linné appears to have been of opinion that many contagious diseases are
caused by mites[119]. How far he was justified in this opinion I shall
not here inquire; facts alone can decide the question, and observations
made by men acquainted with Entomology as well as the science of
diseases. Considerable deference and attention, however, are certainly
due to the sentiments of so great a naturalist, in whom these necessary
qualifications were united in no common degree. With respect to the
dysentery and the itch, he affirms that this had been manifested to his
eyes. You will wish probably to know the arguments that may be adduced
in confirmation of this opinion; I will therefore endeavour to satisfy
you as well as I am able. The following history given by Linné seems to
prove the dysentery connected with these animals.
Rolander, a student in Entomology, while he resided in the house of
the illustrious Swede, was attacked by the disease in question, which
quickly gave way to the usual remedies. Eight days after, it returned
again, and was as before soon removed. A third time, at the end of the
same period, he was seized with it. All the while he had been living
like the rest of the family, who had nevertheless escaped. This,
of course, occasioned no little inquiry into the cause of what had
happened. Linné, aware that Bartholinus had attributed the dysentery
to _insects_, which he professed to have seen, recommended it to his
pupil to examine his feces. Rolander, following this advice, discovered
in them innumerable animalcules, which upon a close examination proved
to be mites. It was next a question how he alone came to be singled
out by them; and thus he accounts for it. It was his habit not to
drink at his meals; but in the night, growing thirsty, he often sipped
some liquid out of a vessel made of juniper wood. Inspecting this very
narrowly, he observed, in the chinks between the ribs, a white line,
which, when viewed under a lens, he found to consist of innumerable
mites, precisely the same with those that he had voided. Various
experiments were tried with them, and a preparation of rhubarb was
found to destroy them most effectually. He afterwards discovered them
in vessels containing acids, and often under the bung of casks[120]. In
the instance here recorded, the dysentery, or diarrhœa, was evidently
produced by a species of mite, which Linné hence called _Acarus
Dysenteriæ_; but it would be going too far, I apprehend, to assert that
they are invariably the cause of that disease.
That _Scabies_, or the itch, is occasioned by a mite, is not a
doctrine peculiar to the moderns. Mouffet mentions Abinzoar, called
also Avenzoar, a celebrated Hispano-Arabian physician of Seville, who
flourished in the twelfth century, as the most ancient author that
notices it. He calls these mites little lice that creep under the skin
of the hands, legs, and feet, exciting pustules full of fluid[121].
Joubert, quoted by the same author, describes them under the name of
_Sirones_, as always being concealed beneath the epidermis, under which
they creep like moles, gnawing it, and causing a most troublesome
itching. It appears that Mouffet, or whoever was the author of that
part of the _Theatrum Insectorum_, was himself also well acquainted
with these animals, since he remarks that their habitation is not in
the pustule but near it: a remark afterwards confirmed by Linné[122],
and more recently by Dr. Adams[123]. In common with the former of these
authors, Mouffet further notices the effect of warmth upon them in
exciting motion[124]. Our intelligent countryman also observes that
they cannot be Pediculi, since they live under the cuticle, which lice
never do[125]. In the epistle dedicatory, the editor speaks also of
them as living in burrows which they have excavated in the skin near a
lake of water; from which if they be extracted with a needle and put
upon the nail, they show in the sun their red head and the feet with
which they walk[126]. And to close my _veteran_ authorities, Junius
thus explains the word Acarus, as I find him quoted in Gouldman's
useful dictionary, "A small worm, which eats under the skin, and makes
burrows in itching hands[127]."
In more modern times, microscopical figures have been added to
descriptions of the insect. Bonomo first furnished this valuable
species of elucidation. His figures, however, which are copied by
Baker in his work on the microscope, are far from accurate[128].
Those of De Geer and Dr. Adams are much more satisfactory, and
mutually confirm each other[129]. From them it is evident that the
same insect inhabits the scabies of Sweden and Madeira. Dr. Bateman,
in the letter before alluded to, informs his correspondent, that he
had seen that from Madeira, and gives it as his opinion, that there
cannot be a doubt of the existence of an _Acarus Scabiei_; an opinion
which he repeats in his late work on _Cutaneous Diseases_; and which,
according to Hermann[130], has been also rendered unquestionable by
Wichmann in his _Etiologie de la Gale_ (Hanovre 1786), a work I have
not had an opportunity of consulting. From all this we may regard the
point as so far settled, that an animal of this kind exists at least
as an occasional concomitant of scabies.
This fact being ascertained, a more complex inquiry remains, which
branches out into two distinct questions. Is scabies always produced
by these insects? Or, if this be not the case, Is the _animate_
scabies a distinct disease from the _inanimate_?
It is very remarkable that Linné, a physician as well as a
naturalist; and De Geer, one of the most accurate observers that ever
existed; should both assign the insect in question as the undoubted
cause of the _common_ scabies of their country; the one applying to
the disease he was speaking of the epithet of _communissima_, and
observing the fact to be notorious, (_cuique liquet_,) and the other
designating it by its well known French name "_La Gale_[131]." And is
it not equally remarkable that such men as John Hunter, Dr. Heberden,
Dr. Bateman, Dr. Adams, and Mr. Baker, should never, in this
country, have been able to meet with it? Did it indeed exist in our
common scabies, it seems impossible that it could have escaped the
observation of the two last of these gentlemen; Dr. Adams being so
well qualified to detect it from his observations in Madeira, and Mr.
Baker from his expertness in microscopical researches. Dr. Bateman,
in the letter above quoted, says, "I have hunted it with a good
magnifier, in many cases of itch, both in and near the pustules, and
in the red streaks or furrows, but always without success." In his
work on _Cutaneous Diseases_ he tells us, however, that he has seen
it, in one instance, when it had been taken from the diseased surface
by another practitioner. And though Dr. Willan in his book speaks
of the Acarus as the concomitant of this disease, yet his learned
friend just mentioned observes, that he admitted that it was not to
be found in ordinary cases, and indeed never seemed to have made up
his mind upon the subject. When I was at Norwich in 1812, Dr. Reeve
very kindly accompanied me to the House of Industry there, to examine
a patient whose body was very full of the pustules of this disorder;
but though we used a good magnifier, we could discover nothing like
an insect. I must observe, however, that our examination was made in
December, in severe weather, when the cold might, perhaps, render the
animal torpid, and less easy to be discovered.
From the above facts it seems fair to infer that this animal is not
invariably the cause of scabies, but that there are cases with which
it has no connexion. Now, from this inference, would not another
also follow, that the disease produced by the insect is specifically
distinct from that in which it cannot be found? Sauvages and Dr.
Adams are both of this opinion[132], the former assigning to it the
trivial name of _vermicularis_; and the latter proving, by very
satisfactory arguments, that it is different from the other. If they
were both _animate_ diseases, but derived from two distinct species
of animals, (for it seems not impossible that even our common itch
may be caused by a mite more minute than the other, and so more
difficult to find,) they would properly be considered as distinct
species; much more, therefore, if one be _animate_ and the other
_inanimate_. Nay this, I should think, would lead to a doubt whether
even their _genus_ were the same. I shall dismiss this part of my
subject with the mention of a discovery of Dr. Adams, which seems to
have escaped both Linné and De Geer--that the _Acarus Scabiei_ is
endowed with the faculty of leaping; (in this respect resembling the
insect found by Willan in _Prurigo senilis_ mentioned above;) for
which purpose its four posterior thighs are incrassated[133].
But besides these _Acarine_ diseases, there seems to be one (unless
with Linné we regard the plague as of this class[134]) more fearful
and fatal than them all. You will, perhaps, conjecture I am speaking
of that described by Aristotle and Sir E. Wilmot as the Phthiriasis,
and your conjecture will be right. But some think, and those men
of merited celebrity, that _mites_ have nothing to do in these and
similar cases, for that _maggots_ were the parasites mistaken for
lice. This, from the passage above quoted, appears to have been Dr.
Willan's opinion, to which, in the letter so often referred to, Dr.
Bateman subscribes; adding as a reason for excluding mites from being
concerned, that "they are too minute, and never have been seen in
such numbers as to be mistaken for lice." But both vary in size, some
of the former being larger than some of the latter. And allowing them
to be ever so minute, yet when they issue in swarms, as mites from a
cheese, they would be very visible, were it only from their motion.
Besides, as they are furnished with legs, their motions resemble
those of lice infinitely more than do the contortions of maggots. So
that a mite would be deemed a louse much sooner by an unentomological
observer than would a maggot. Whether mites have ever been seen in
such numbers as to be mistaken for lice, is the point in question;
and therefore, by itself, cannot be admitted for a valid argument.
Though _Acarus Scabiei_ does not appear to swarm in ordinary cases,
yet this is certainly no reason why other species may not do so.
Where it has once made a settlement, how incredibly, and in how
short a space of time, does the _Siro_ or cheese-mite multiply!
_Acarus Destructor_ and many other species are equally rapid in their
increase.--Millions of lice are said by Lafontaine, whom Hermann
calls a very exact describer, to show themselves in _Plica polonica_,
on the third day of the disease[135]; but whether the last-mentioned
author be correct in thinking it more probable that they are
mites[136], I have not the means of judging.
I shall now produce two instances where mites were evidently
concerned. Dr. Mead, from the _German Ephemerides_, relates the
miserable case of a French nobleman, from whose eyes, nostrils,
mouth, and urinary passage animalcules of a red colour, and
excessively minute, broke forth day and night, attended by the most
horrible and excruciating pains, and at length occasioned his death.
The account further says, that they were produced from his corrupted
blood. This was probably a fancy originating in their red colour:
but the whole history, whether we consider the size and colour of
the animals, or the places from which they issue, is inapplicable
to _larvæ_ or maggots, and agrees very well with _mites_, some of
which, particularly _Leptus autumnalis_, are of a bright red colour.
The other case, and a very similar one, is that recorded by Mouffet
of Lady Penruddock; concerning whom he expressly tells us, that
Acari swarmed in every part of her body--her head, eyes, nose, lips,
gums, the soles of her feet, &c., tormenting her day and night,
till, in spite of every remedy, all the flesh of her body being
consumed, she was at length relieved by death from this terrible
state of suffering. Mouffet attributes her disease to the _Acarus
Scabiei_; but from the symptoms and fatal result it seems to have
been a different and much more terrific animal. He supposes, in this
instance, the insect to have been generated by drinking goat's milk
too copiously. This, if correct, would lead to a conjecture that it
might have been the _A. Lactis_, L.
These cases I hope will satisfy you that mites, as well as lice,
are the cause of diseases in the human frame. This, indeed, as has
been before observed, is allowed on all hands with respect to that
of the itch; and it is, certainly, not more improbable that man
should be exposed to the attack of several species of this genus,
than that three or four kinds of Pediculus should infest him. If you
are convinced by what I have written, you will concur with me in
thinking that the one are as much entitled to give their name to the
disease which they produce as the other; and the term _Acariasis_, by
which, with due deference to medical men, I propose to distinguish
generically all acarine diseases, will not be refused its place
amongst your _Genera Morborum_.
I shall now proceed to the remaining class of diseases mistaken for
Phthiriasis; those, namely, which are produced by _larvæ_. There are
two terms employed by ancient authors, _Eulæ_ (Ευλαι) and _Scolex_
(Σκωληξ), which seem properly to denote larvæ; but there is often
such a want of precision in the language of writers unacquainted with
Natural History, that it is very difficult to make out what objects
they mean; and expressions which, strictly taken, should be understood
of larvæ, may probably sometimes have been used to denote the cause of
either the pedicular or acarine disease. _Eulæ_, which term, though
given by Hesychius as synonymous with _Scolex_, is by Plutarch used
as of different import[137], seems properly to mean those larvæ which
are generated in dead carcases, at least so Homer has more than once
applied it[138]: it is therefore a word of a much more restricted sense
than _Scolex_, which probably belongs to the larvæ of every order of
insects; for so Aristotle employs it, when he says that all insects
produce a _Scolex_, or are larviparous[139]. Yet when Homer compares
Harpalion stretched dead upon the ground to a _Scolex_[140], it should
seem as if he used the word for an earth-worm, which Aristotle commonly
calls by a figurative periphrasis, "Entrails of the earth[141]." In the
Holy Scriptures this word is used to signify larvæ which prey upon and
are the torment of living bodies[142]. It may on this account, perhaps,
be regarded as generally meaning such larvæ, to whatever order or genus
they belong.
Dr. Mead, therefore, is most probably right when he considers the
disease stated by the ancients to be caused by _Eulæ_ or _Scoleches_,
commonly translated worms, as distinct from Phthiriasis; and if so,
the inhuman Pheretima, who swarmed with _Eulæ_, and Herod Agrippa, who
was eaten of _Scoleches_[143], were probably neither of them destroyed
either by Pediculi or Acari, but by larvæ or maggots. And when Galen
prescribed a remedy for ulcers inhabited by _Scoleches_, observing that
animals similar to those generated by putrid substances are often found
in abscesses, he probably meant the same thing. The proper appellation
of this genus of diseases would be _Scolechiasis_.
This dissertation may perhaps appear to you rather prolix and
tedious: yet to settle the meaning of terms is of the first
importance. To inquire what ancient writers intended by the words
which they employ, and whether such as have been usually regarded as
synonymous are really so, may often furnish us with a clue to some
useful or interesting truth; and not seldom enable us to rescue their
reputation from much of the censure which has been inconsiderately
cast upon it. Because they did not know every thing, or so much as
we do, we are too apt to think that they knew nothing. That they
fell into very considerable errors, especially in subjects connected
with Natural History, cannot be denied; but then it ought to be
considered that they possessed scarcely any of those advantages by
which we are enabled to penetrate into nature's secrets. The want of
the microscope alone was an effectual bar to their progress in this
branch of science. Yet, in some instances, when they took a general
view of a subject, they appear to have had very correct ideas. This
observation particularly applies to the philosopher of Stagyra, whose
mighty mind and lyncean eye, in spite of those mists of prejudice
and fable that enveloped the age in which he lived, enabled him in
part to pierce through the gloom, and comprehend and behold the
fair outline that gives symmetry, grace and beauty to the whole of
nature's form, though he mistook, or was not able to trace out, her
less prominent features and minor lineaments.
* * * * *
It is now time to return from this long digression, which however is
closely connected with the subject of this letter, to the point from
which I deviated. Taking my leave of the disgusting animals which
gave rise to it, I proceed to call your attention to another of our
pygmy tormentors, (_Pulex irritans_,) which, in the opinion of some,
seems to have been regarded as an agreeable rather than a repulsive
object. "Dear miss," said a lively old lady to a friend of mine,
(who had the misfortune to be confined to her bed by a broken limb,
and was complaining that the fleas tormented her,) "don't you like
_fleas_? Well, I think they are the prettiest little merry things in
the world.--I never saw a dull flea in all my life." The celebrated
Willughby kept a favourite flea, which used at stated times to be
admitted to suck the palm of his hand; and enjoyed this privilege
for three months, when the cold killed it. And Dr. Townson, from
the encomium which he bestows upon these vigilant little vaulters,
as supplying the place of an alarum and driving us from the bed of
sloth, should seem to have regarded them with feelings much more
complacent than those of Dr. Clarke and his friends, when their hopes
of passing "one night free from the attacks of vermin" were changed
into despair by the information of the laughing Sheik, that "the
king of the fleas held his court at Tiberias:" or than those of MM.
Lewis and Clarke, who found them more tormenting than all the other
plagues of the Missouri country, where they sometimes compel even the
natives to shift their quarters. If you unhappily view them in this
unfavourable light, and have found ordinary methods unavailing for
ridding yourself of these unbidden guests; I can furnish you with a
_probatum est_ recipe, which the first-mentioned traveller tells us
the Hungarian shepherds (who seem to have been stupidly insensible to
their value as alarums) find completely effectual to put to flight
these insects and their neighbours the lice. This is not, as you may
be tempted to think, by a remarkable attention to cleanliness.--Quite
the reverse.--They grease their linen with hog's lard, and thus
render themselves disgusting even to fleas! If this does not satisfy,
I have another recipe in store for you. You may shoot at them with
a cannon, as report says did Christina queen of Sweden, whose piece
of artillery, of Lilliputian calibre, which was employed in this
warfare, is still exhibited in the arsenal of Stockholm[144]. But,
seriously, if you wish for an effectual remedy, that prescribed by
old Tusser, in the following lines, will answer your purpose:
"While wormwood hath seed, get a handfull or twaine,
To save against March, to make flea to refraine:
Where chamber is sweeped, and wormwood is strown,
No flea for his life dare abide to be known."