From the American Journal of Science and Arts, No. 2, Vol. 39. 
AN 
ACCOUNT 
OF A 
FILARIA IN A HORSE’S EYE, 
WITH 
REMARKS ON SIMILAR PHENOMENA, 
ANDTHIT 
MODE OF THEI& ORIGIN, 
BY CHARLES A. LEE, M. D., 
OF NEW YORK. ACCOUNT, &c. 
Read before the Lyceum of Natural History of New York 
The existence of parasitic worms in the interior of animals 
has been known from a very remote period. They are mention- 
ed by Hippocrates, Galen, Celsus, Pliny and other writers; and 
various speculations have been advanced in respect to their ori- 
gin. It is only however within modern times that they have re- 
ceived much attention from physicians and naturalists, except as 
to their agency in the production of disease. Many different gen- 
era and species have now been described by Linnseus, Rudolphi, 
Bremser, De Blainville, Cruvelhier and others, and arranged ac- 
cording to their several characters. Indeed so numerous have Account of a Filaria in a Horse’s Eye. 
3 
these animals become, that their study constitutes quite an im- 
portant branch of zoology. Large and important works have 
been written upon a single species of these parasites, and Dr. 
Nordmann of Germany has lately published a treatise on those 
that inhabit the eyes of the higher orders of animals. They 
may be arranged under two general divisions. 1. The Entozoa, 
or those which reside in the internal parts of the animal, and 2. 
Ectozoa, those which are confined to the external surface. The 
latter are chiefly insects, the former worms. 
Linnseus arranged the Entozoa according to the situation 
which they occupied: viz. such as are developed in cavities 
communicating with the external air, as intestinal worms ; and 
such as are imbedded in the very substance of organs, visceral 
worms. The classification of Rudolphi, however, is founded on 
the varieties of form, as Nematoides, Acanthocephala, Trematoda, 
Cestoides, Tcenia, and Cystica or hydatids. Cuvier divides them 
into two classes; one characterized by a digestive cavity, and the 
other by the parenchymatous structure. 
A horse is now being exhibited in this city whose right eye 
contains a vermiform animal, floating in the anterior chamber, 
between the iris and the cornea. It was first observed in Febru- 
ary last, when it was about half an inch in length ; since which 
time it has increased so as to measure at present about four inches, 
resembling a portion of white thread or bobbin, with an enlarge- 
ment at one extremity of half an inch or more in extent. The 
animal is confined, exclusively to the anterior chamber of the eye, 
in which it swims with the greatest ease and activity; doubling 
itself in every direction, and performing the most graceful and 
rapid evolutions. It seems remarkable that it should not pene- 
trate the iris, and visit the posterior chamber. Why it does not, 
it is impossible for me to explain. Its movements do not appear 
to excite any sensation in the horse, although a milky cloudiness 
in the aqueous humor, somewhat dims the vision of the eye in 
which it floats. This discoloration is believed by Mr. Camp, the 
owner of the horse, to be owing to the excreta of the parasite, 
which, he says, are evacuated about once in three weeks, when 
the eye appears much more clouded than at other times. This, 
however, is observed to subside considerably in the course of a 
few hours. Whether this be a fact, may well admit of a doubt. 
We think it more probable that the cloudiness is owing to the ef- 4 
Account of a Filaria in a Horse’s Eye. 
fusion of coagulable lymph, the result of inflammation of the 
vessels, caused by the presence of a foreign body. There is no 
doubt whatever that the discoloration exists in the aqueous hu- 
mor, and not in the cornea. A few weeks after the animal was 
first discovered, the conjunctiva was much injected; but since 
that time it has assumed its natural, healthy appearance, and now 
does not differ in the least from that of the other eye. There is 
nothing peculiar in the appearance of the horse, which is of the 
Eclipse family, and seven years old. Owing to the incessant and 
rapid motion of the worm, it is difficult to examine it with a mi- 
croscope, so as to determine with accuracy, its precise internal 
organization, yet it evidently belongs to the class Entozoa, order 
Nematoidea, genus Filaria, species Papillosa. The only oth- 
er genus which it resembles, is the Gordius of Linnseus; but 
as this belongs to the class Annelides, which have red blood, in- 
habit the water only, and are more filiform in shape, there is but 
little danger of confounding them together. 
We have stated that the Entozoa are so called because they 
inhabit the interior of other animals. Every kind of animal, in- 
deed, has been supposed to have its Entozoa, or internal parasites, 
which are peculiar to itself, just as it has its Ectozoa, or external 
ones. They not only infest the alimentary canal, and the ducts 
leading into it, but also the muscles, the cellular tissue, and the 
parenchymatous structure of the different organs, as the brain, 
liver, lungs, kidneys, &c. Indeed, it is now believed by many 
naturalists, that every different tissue and organ of the body has 
its peculiar parasite. Thus in man, -more than twenty different 
species of animals have been discovered in different parts of his 
body. In the brain, we find the Echinococus hominis ; in the 
liver, the Fasciola hepatica ; in the venous blood, the Linguatu- 
la venarum ; in the kidneys, the Strongylus gigas ; in the mus- 
cles, the Hydatigera cellulosa ; in the cellular tissue, the Filaria 
medinensis, or Guinea worm ; in the female ovaries, the Lingua- 
tula pinguicola ; in the intestines, the Tcenia solium, the Ascaris 
lumbricoides, &c.; and some attack infants only, as the Oxyurus 
vermicular is. 
Mr. Richard Owen, of England, has lately discovered that the 
human muscles of voluntary motion are sometimes the residence 
of very minute cysts of an oblong figure, in size and color bear- 
ing a strong resemblance to nits, or the young of pediculi. Account of a Filaria in a Horse's Eye. 
5 
These cysts appear, when examined with a lens, not exactly 
ovoid, but irregularly contracted towards one extremity, so as to 
form a kind of short neck. These are dispersed throughout the 
the muscles over the body, and are placed in the direction of the 
fibres, in the cellular membrane, immediately investing the mus- 
cular fibrillse, or the tendinous fibres to which they are attached. 
In a recent specimen, one and sometimes two thread-like worms 
may be seen, coiled up in each cyst. Mr. Owen regards this an- 
imal as closely allied to the eels which are found in paste and 
vinegar, and has given it the name of Trichina spiralis. It is 
very probable that some anomalous diseases may be occasioned 
by the great multiplication of these worms, while the cause is 
unsuspected and inexplicable. 
The most common worm met with in the different classes of 
animals, is the fluke, or Fasciola hepatica, which is sometimes 
also found in man. We find it in cattle, sheep, swine, and deer; 
in reptiles, fishes, and even worms of the largest kind; and it is 
this which occasions the disease called the rot in sheep. Leuwen- 
hoeck counted 870 of these animals in one liver. Hydatids are 
also found in sheep, in the brain and liver, and often carry off 
whole flocks. This is also met with in man, swine, deer and 
oxen, of which there are three different species, viz. cerebralis, 
vervecina, and ovilla. It is unnecessary however to go into de- 
tail, in relation to the different species of parasites which inhabit 
the different races of animals ; it must suffice to state, that they 
are extremely numerous,—that though some are common to sev- 
eral species, yet that, in general, each has its peculiar parasite;— 
and, moreover, that probably each texture and organ furnishes a 
habitation for a distinct race of inhabitants. To this it might be 
added, that many of these parasites have parasites of their own, 
so that they are literally paid in their own coin. 
It has been remarked that the Filaria belongs to the order Ne- 
matoidea of Rudolphi. This order embraces those animals whose 
external skin is more or less furnished with muscular fibres, and 
usually striated transversely; containing an abdominal cavity, in 
which is a distinct intestinal canal, extending nearly the whole 
length of the body. The intestine is connected with the neigh- 
boring parts and the general envelope of the body by numerous 
threads, considered by some writers as vessels for the conveyance 
of the nutritious fluid, and by others as trachea, but without suf- 6 
Account of a Filaria in a Horse's Eye. 
ficient proof of the fact. We can discover no true circulation in 
these animals, but in several there appear to be one or two nerv- 
ous cords, which surround the mouth, and extend the whole 
length of the body along the internal surface of the envelope. 
The intestine is for the most part straight and of considerable 
width; the esophagus is contracted, and in some species the 
stomach is distinctly developed. The animal is of both sexes 
and propagates by ova, which are extremely small. 
The Filaria is of a long, slender, filiform shape, and perfora- 
ted at the anterior extremity by a round oval aperture. Some 
species bear considerable resemblance to the Gordius, or hair- 
snake, which abounds in fresh-water brooks and ponds. It prin- 
cipally occurs within cavities which do not communicate exter- 
nally,—in the cellular membrane, the substance of the muscles, 
and different viscera, and occasionally in the eye. The follow- 
ing embrace a few of the more common species. 
1. Filaria medinensis, or Guinea worm, is the most common 
and best known species. It is found chiefly in warm climates, 
where it is often seen in the morning dew, sometimes ten or 
twelve feet long, and not thicker than a horse-hair. It is this 
species which insinuates itself under the skin, where it may be 
felt like a tense string. Here it burrows and grows to a length 
of several feet, without exciting great pain or uneasiness, until 
the skin is perforated by the animal. It is usually drawn out 
with great caution, by means of a piece of silk tied around its 
head. If it break by a too violent effort, the part remaining 
grows with redoubled vigor, and often occasions a fatal inflam- 
mation. When drawn out, it is found to be elastic, white, trans- 
parent, and contains a gelatinous substance. Though usually 
met with in the lower extremities, it sometimes occurs in the in- 
teguments of the head, neck and trunk, and Baron states that he 
saw two instances of it under the mucous membrane of the eye- 
ball. 
2. Filaria bronchicilis. This species is described by Treutler, 
and so named from its occurrence in the lungs of persons labor- 
ing under phthisis. It has also been called Hamularia lymphat- 
ica, and by Rudolphi, Haularia sub-comprcssa. This is also 
met with in the lungs of the inferior animals, especially when 
affected with tubercles. Dr. Hodgkin states that he often found 
the Filaria in the lungs of the boa constrictor. Account of a Filaria in a Horse’s Eye. 
7 
3. Filaria gracilis is found in apes and monkeys in great 
abundance. It grows to a length of ten or twelve inches, is 
about as thick as a fine thread, head obtuse, and tapering slightly 
at both extremities. 
4. Filaria attenuata. This species is found in the abdominal 
cavity of crows, also in the cornea of the eye of fishes. It is 
from one to six inches long, and obtuse at both extremities. 
5. Filaria obtusa inhabits the intestines of swallows. Its head 
is somewhat acute, tail obtuse, body comparatively thick and 
elastic, and has been found twelve inches in length. M. Ru- 
dolphi has traced out its intestinal canal and ovaries. 
6. Filaria truncata. This species is about five inches long, 
has a truncated head, a tail somewhat thick, obtuse, terminated 
by a very sharp point; inhabits the larva, or caterpillar of cer- 
tain species of moths. {Tinea padella.) 
7. Filaria ovale. This species formerly went under the name 
of Gordius piscium, (hair-worm of fishes,) because it is found in 
the liver of the carp. It is three or four inches in length; head 
oval; tapering forwards ; tail round. 
8. Filaria capsularia. From half an inch to an inch long, 
and resembles in thickness a middle-sized thread. The borders 
of the mouth are recurved, resembling, according to De Blain- 
ville, the mouth of a pudding-bag; tail obtuse, papilliform, and 
ending with a fine, sharp point. It occurs of both sexes, with a 
large intestinal canal and stomach. The female is more gross— 
often met with in the herring, in large quantities. It is very te- 
nacious of life, for Rudolphi states that he has known it live 
eight days in a dry place, and even to revive after having been 
long frozen in masses of ice. It is this species which Zeder and 
some other naturalists have formed into a genus, under the name 
of Capsularis. 
9. Filaria papillosa. The Filcdre equi of Gmelin, and the 
Gordius equinus of other writers. This is the species which in- 
habits the eye of the horse. It is from one to seven inches in 
length, and about one-third of a line in diameter. It is usually 
of a yellowish white or ash color,—sometimes of a brownish hue. 
Head slightly obtuse; mouth orbicular; neck studded with pa- 
pillae ; tail slender and curved. It occurs in different parts of the 
horse, chiefly in the muscles and intestinal canal, though it has 
been detected in the brain, as well as the aqueous humor of the 
eye. 8 
Account of a Filaria, in a Horse's Eye. 
M. De Blainville, in the Dictionnaire des Sciences Naturelles, 
describes twelve species of Filaria, and mentions thirty-one oth- 
ers, which are doubtful, and whose names are derived from the 
species of birds, fishes, quadrupeds, insects and reptiles which 
they inhabit. The points of difference among these do not ap- 
pear sufficient to constitute them into distinct species, with the 
exception, perhaps, of the four following, viz. coronata, acumin- 
ata, plicata and alata, which have been minutely described by 
Rudolphi and De Blainville. For our knowledge of the others, 
we are chiefly indebted to Lamarck and Roessel. The principal 
animals in which the Filaria has been detected are the vulture, 
eagle, falcon, oicl, swan, duck, stork, heron, lark, starling and 
linnet, among birds, and the horse, swine, ox, hare, weasel and 
lion, among quadrupeds; in numerous species of fishes, and cole- 
opterous insects, among the lower orders. 
Dr. Nordmann, in his work above referred to, states that he has 
detected the Filaria in the eye of a person affected with cataract, 
also a hydatid in the eye of a young woman. Ehrenberg agrees 
with Nordmann in opinion that cataract and some other diseases 
of the eye, are probably owing to an accumulation of these par- 
asitic animals. This writer has shown very satisfactorily that 
quadrupeds, birds, reptiles and fishes have each their eye-worms, 
which are, for the most part, peculiar to each species. Several of 
these are figured in his work ; among which, one that infests the 
eyes of different species of perch, is very conspicuous. In one 
instance he counted 360 of these in the eye of a single fish af- 
fected with cataract. “ This little animal,” says Kirby in his 
Bridgewater Treatise, “appears something related to the Planaria 
or pseudo-leech, and from Dr. Nordmann’s figures seems able, like 
it, to change its form. Underneath the body, at the anterior ex- 
tremity, is the mouth, and in the middle are what he denomin- 
ates two sucking-cups; these are prominent, and viewed laterally 
form a truncated cone; the anterior one is the smallest and least 
prominent, and more properly a sucker; the other probably has 
other functions, since he could never ascertain that it was used 
for prehension.” 
It is remarkable that these animals, small as they are, are in- 
fested with parasites of their own. These appear like minute 
brown dots or capsules, attached to the intestinal canal. When 
extracted and laid upon a smooth surface, these capsules burst, Account of a Filaria in a Horse’s Eye. 
9 
and disclose a great number of living animalcules, of the genus 
Monas. 
The accompanying magnified sketch will represent the form 
of this animal with sufficient exactness. 
Of the worms which Nordmann describes as infesting the eyes 
of fishes, five out of seven are attached to different species of 
perch. Kirby conjectures that as these constitute the most nu- 
merous body of predaceous fishes in rivers, the object of this sin- 
gular provision is to impair their organs of vision, so that the 
roach, dace, carp and tench tribes may not be entirely destroyed.* 
Achtheres percarum. 
Instances of the occurrence of Filaria in the human eye, have 
been recorded by different authors. In a late German medical 
periodical, (Zeitschrift fur die gesammte Medicin, Feb. 1839,) 
several cases of this kind have been recorded. Blot of Martinique 
saw two worms in active motion under the conjunctiva, which 
he removed by incision. One of these, which was sent to M. 
Blainville, was thread-shaped, thirty-eight millimetres long, with 
a black protuberance adapted for suction. Bajon, in 1768, observ- 
ed a Filaria in the eye of a negress, which kept in a continual ser- 
pentine motion without producing pain; but it caused a constant 
epiphora, or watery secretion. When an incision was made the 
worm went to another part, and was obliged to be secured by a 
* It is now a well ascertained fact that animals not only inhabit vegetables, but 
that vegetable growths are sometimes observed in the bodies of living animals. 
The most remarkable example of this, perhaps, is that of the “ vegetating wasp” 
of our Southern States and the West Indies. The insect, which is a species of 
Polystrix, is infested, while alive, with a parasitic fungus allied to Sphceria, which 
gradually increases so much in size as to destroy the life of the animal, which 
having deposited its eggs in the plant, perishes; when, in due time, a second gen- 
eration succeeds, which is cut off in the same manner, and so on. Similar instan- 
ces have been observed among other insects, in all stages of their development. 10 
Account of a Filaria in a Horse’s Eye. 
small forceps. In a second case the conjunctiva was more in- 
flamed, and the patient refused to submit to an operation. In 
Blot’s case above-mentioned, the worms were between the con- 
junctiva and the cornea, around and across which they traversed, 
producing stinging pains and nervous symptoms. The patient, 
an African negress, was unable to tell where she came from, or 
whether her fellow-country people were subject to similar affec- 
tions. The Cystericus cellulosa has also often been observed in 
the human eye, of which there is a case in the London Medical 
Gazette for Aug. 1833, where one was seen in the eye of a littlo 
girl six years old, under the conjimctiva resting on the sclerotica, 
and perfect in all its parts. 
The existence of Filaria in the eyes of horses in the East In- 
dies, is of frequent occurrence, as may be seen by consulting ail 
article in the Edinburgh Medical and Surgical Journal for Jan. 
1826. Bremser states that he saw three worms in the anterior 
chamber of the eye of a horse at the Veterinary School of Vien- 
na, in 1813. In the Bulletin des Sciences Medicates for Feb. 
1826, it is stated that Dequilleme saw several of these animals in 
the eye of a cow, and the case was published by Gohier, a vet- 
erinary teacher, in his memoirs. In the report of the proceedings 
of the Veterinary School at Lyons, in 1822, there is a case in 
which a knot of worms was seen in the eye of a mule. Some 
of these were extracted; no inflammation followed the operation, 
but a violent nervous agitation of the head and a turning of it to 
the left side, took place. In the same journal mention is made of 
a memoir read before the Medical Society of Calcutta, in which 
the writer states that the Strongylus armatus minor of Rudolphi, 
and the Filariapapillosa are frequently found in the eyes of horses 
in India, but much more so in the cellular membrane, particularly 
about the loins. The writer maintains that they make their way 
into the blood-vessels, and through them into the eye. Treutler 
says that he has seen the Strongylus armatus in aneurisms of the 
mesenteric artery of the horse, and Dr. Kennedy, in the Edin- 
burgh Phil. Transactions, describes a worm which he calls Asca- 
ris pellucidus, but which was doubtless the Filaria papillosa, 
as being common in the eyes of horses in the east. A common 
effect of these worms in the muscles of the loins is paralysis of Account of a Filaria in a Horse's Eye. 
11 
the hind legs.* The only case of the kind which has come to 
my knowledge, as having occurred in our own country, is record- 
ed in the second vol. of the Transactions of the American Philo- 
sophical Society. This volume contains two communications on 
the subject,—one by F. Hopkinson, Esq., entitled 11 Account of a 
ivorm in a horse’s eye f the other by John Morgan, M. D., “ Of 
a living snake in a living horse’s eye, and of other unusual pro- 
ductions of animals.” Mr. Hopkinson reports the case as fol- 
lows : “ A report prevailed last summer that a horse was to be 
seen which had a living serpent in one of his eyes. At first I 
disregarded this report, but numbers of my acquaintance who had 
been to see the horse, confirming the account, I had the curiosity 
to go myself, taking a friend along with me. The horse was 
kept in Arch street, and belonged to a free negro. I examined 
the eye with all the attention in my power, being no ways dispo- 
sed to credit the common report, but rather expecting to detect 
a fraud or vulgar prejudice ; I was much surprised, however, to 
see a real living worm within the ball of the horse’s eye. This 
worm was of a clear white color, in size and appearance much 
like a piece of fine bobbin ; it seemed to be from two and a half 
to three inches in length, which, however, could not be duly as- 
certained, its whole length never appearing at one time, but only 
such portion as could be seen through the iris, which was greatly 
dilated. The creature was in constant lively vermicular motion ; 
somtimes retiring so deep into the eye as to become totally invisi- 
ble, and at other times approaching so near to the iris as to become 
plainly and distinctly seen ; at least so much of it as was within 
the field of the iris. I could not distinguish its head, neither end 
being perfectly exhibited whilst I viewed it, and indeed its mo- 
tion was so brisk and constant, that so nice a scrutiny was not to 
be expected. The horse’s eye was exceedingly inflamed, swollen 
and running ; I mean the muscles contiguous to the eye-ball, and 
seemed to give him great pain, so that it was with much diffi- 
culty the eye could be kept open for more than a few seconds at a 
time; and I was obliged to watch favorable moments for a dis- 
* A singular case is reported by M. Cloquet, in the Archives Generates for Dec. 
1827, where a number of small worms were discovered in the eye of a man. On 
examination, they proved to be the larvae of the common fly, (Musca carnaria,) 
which had been deposited in the form of eggs on the eye while the man was 
aeleep. These afterwards hatched out, and the result was a total loss of vision. 12 
Account of a Filaria in a Horse's Eye. 
tinct view of his tormentor. I believe the horse was quite blind 
in that eye, for it appeared as if all the humors were confounded 
together, and that the worm had the whole orb to range in, which, 
however, was not of a diameter sufficient for the worm to extend 
its whole length, as far as I could discover. As this is a very un- 
common circumstance, and may affect some philosophical doc- 
trines, it is much to be lamented that the horse had not been pur- 
chased, and the eye dissected for better examination. That there 
was a living, self-moving worm wi thin the ball of the horse’s eye, 
free from all deception or mistake, I am most confident. How 
this worm got there, or if bred in so remarkable a place, where 
its parents came from, or how they contrived to deposit their se- 
men or convey their egg into the eye of an horse, I leave for oth- 
ers to determine.” 
The additional particulars communicated by Dr. Morgan, are 
that the horse was of a sorrel color, nine years old, and belonged 
to Dr. Dayton, near Elizabethtown, New Jersey. The first cir- 
cumstance which attracted the owner’s attention was, that from 
being very mild and gentle, the horse suddenly became vicious 
and unmanageable, and ran away and dashed the chair to pieces. 
When seen by Dr. Morgan the worm was about four inches in 
length, and “ as thick as a knitting-needle, or piece of common 
twine.” The aqueous humor was of a white, milky appearance, 
bordering on the color of a cataract, which was supposed to be 
owing to a breaking down of the vitreous humor, which had thus 
discolored the aqueous portion. The iris was thought to be de- 
stroyed, but this was doubtless a mistake. At this time the ani- 
mal passed freely from the anterior to the posterior chamber of 
the eye, and vice versa, which the Dr. supposed could not have 
happened unless the partition between had been broken down. 
But it so happens that there is no partition between the two ex- 
cept the thin membrane of the iris, through which there is an 
opening, the pupil, of sufficient size to permit a free passage. 
11 It may be presumed,” says the writer, “ that whatever might be 
the state of vision, that eye must be now blind. The lids are 
commonly closed, probably owing to pain excited in the eye by 
so troublesome a guest; but there is no blood-shot appearance on 
the cornea, though the surrounding parts, namely, the palpebree, are 
a little tumid. To get a view of the eye, the keeper commonly 
strikes the horse on its back with an open hand, at which, as if Account of a Filaria in a Horse’s Eye. 
13 
frightened, it opens the lid of the left, as well as widens the open- 
ing of the right eye, which continues disclosed but a short time; 
however, this gives an opportunity for inspection for five or six 
seconds of time together, and the blows must be repeated to keep 
the eye open when a person wishes to have a longer time for in- 
spection.” 
The similarity of this case to the one now exhibiting, is too 
obvious to need remark. In all their essential points there is al- 
most an exact correspondence, viz. the size, color, shape and ap- 
pearance of the worm; its incessant motion ; the cloudiness of 
the aqueous humor, and the partial blindness of the eye. In the 
case, however, reported by Mr. Hopkinson, the worm appeared 
to excite more sensation in the eye, and consequently produced a 
higher degree of inflammation. This no doubt was occasioned 
by its passing through the iris, and coming in contact with the 
expansion of the retina and the delicate ciliary processes ; where- 
as in the present case, the animal is confined exclusively to the 
anterior chamber of the eye, which is comparatively insensible. 
Origin.—It is a singular fact that some of the first physiolo- 
gists and helminthologists of the day, attribute the origin of in- 
testinal and visceral worms to spontaneous generation. Such is 
the opinion of Muller, Bremser, and most of the German physi- 
cians. The opinion of Linnaeus, that they were terrestrial or 
aquatic species, taken in with food or drink in the form of ova or 
germs, is now exploded, for, with the exception perhaps of the 
Filaria, we do not find the same species of worms which 
infest animal bodies, out of them. Indeed, Cruvelhier lays it 
down as an axiom, that worms, like the intestinal and vis- 
ceral, have never been met with out of the bodies of man and 
other animals, unless discharged from them; and the con- 
verse of this he holds to be no less true, viz. that no terrestrial 
or aquatic worms have ever been met with alive, in the bodies of 
men and other animals, unless they had been very recently intro- 
duced into them. We might then conclude, with confidence, that 
worms do not originate from without, but are generated within 
the body, were it not contended that these animals may have 
been introduced ab externo, but that in consequence of a change 
of situation and nutriment, their forms and characteristics are al- 
tered, as plants and animals are under similar circumstances, and 
as neuter bees are made prolific, on the loss of the queen bee, by 14 
Account of a Filaria in a Horse’s Eye. 
feeding in a particular manner. But if such transitions occur in 
worms, we should sometimes observe them while undergoing the 
process, for it would be contrary to all analogy to suppose that the 
change would be sudden. But we see no such transitions; we 
never find these animals “ half way between what they were and 
what they are.” No zoologist, not even Brcmser, who devoted 
twelve years o£ his life to the study of Entozoa, ever witnessed 
any such change; indeed, he states expressly, “ that after having 
diligently examined 15,000 specimens of worms in the Cabinet 
of Yienna, he never was for one moment at a loss to say which 
were intestinal worms and which were not.” If worms then ori- 
ginate within the body, how do they originate ?—what are the 
obstacles in the way of our adopting the theory of spontaneous 
generation ? In the first place, if they can be formed by the 
mere combination of inorganic elements, we may well ask, why 
they should be furnished with reproductive organs ? No such 
creations or combinations have ever been observed, and therefore 
the fact of their occurrence is a matter of mere supposition. The 
only argument on which this hypothesis may be said to rest, is 
our ignorance of the precise mode of their origin, and derives no 
support from analogy. 
If this theory be true, it is difficult to explain why the law 
should be confined to the lower classes of animals, and not also 
extend to the higher. By some fortuitous concourse of atoms, 
we should expect, occasionally, to see a man, a quadruped, or a 
bird, spring up from some dunghill, or fermenting vat; but this 
is a phenomenon which even Ovid never dreamed of. 
The production of certain species of vegetables was once as 
difficult to explain, as it now is to account for the origin of intes- 
tinal worms; but late investigations have removed these difficul- 
ties, and shown that they are propagated in the usual manner by 
seed or reproductive granules. Thus it is observed that white 
clover is ready to spring up on soils which have been rendered 
alkaline by the strewing of wood-ashes, or the burning of weeds; 
ground newly turned up by the plough is found to produce plants 
dissimilar to any in their neighborhood; parasitic fungi sprout up 
upon decaying organized substances, and even in the interior of 
cheese, &c. Dr. Good remarks that he “ has seen a hop-ground 
completely overrun and desolated by the Aphis kumuli, or hop 
green-louse, within twelve hours after a honey-dew (which is a Account of a Filaria in a Horse's Eye. 
15 
peculiar haze or mist, loaded with a poisonous miasm) has slowly 
swept through the plantation, and stimulated the leaves of the hop 
to the morbid secretion of a saccharine and viscid juice, which 
while it injures the young shoots by exhaustion, renders them a 
favorite resort for this insect, and a cherishing nidus for the myri- 
ads of little dots that are its eggs. The latter are hatched within 
forty eight hours after their deposit, and succeeded by hosts of 
other eggs of the same kind; or, if the blight take place in an 
early part of the autumn, by hosts of the young insects produced 
viviparously, for, in different seasons of the year, the Aphis breeds 
both ways.” The inference which Dr. Good deduces from these 
phenomena, is, that the atmosphere is freighted with myriads of 
insect eggs that elude our senses, and that such eggs when they 
meet with a proper bed are hatched in a few hours into a perfect 
form. In this manner, damp cellars are covered with Boletuses, 
Agarics, and other fungi, and walls and rocks with lichens and 
mosses. In these cases it is now fully ascertained, that the vegeta- 
ble is propagated by reproductive granules contained in the frond 
of the Alga, the spores of the higher Cryptogamia, the pileus, or 
cap of the Fungi, and the pollen of the anthers of the Pha?iero- 
garnia. 
If we adopt the theory of spontaneous generation, we not only 
are obliged to adopt the hypothesis of the Archeus, to direct its 
operations, but we shall be unable to account for the extinction 
of some races of organic beings ; we shall be unable to explain 
the limitation of the characters of different genera and species, 
to certain defined limits ; and we shall equally be at a loss to ac- 
count for the non-production of new genera and species. Why 
is it, on this hypothesis, that each species is produced of nearly a 
certain uniform size, neither larger or smaller ? And why is not 
the whole mass of matter operated upon by this spiritus mundi, 
changed into organized beings ? 
Because we cannot, in many cases, actually detect the ova or 
germs, it by no means follows that they do not be- 
cause we find a plant or an animal in some unusual Wfftat, we 
are not necessarily obliged to suppose that it could only have 
been brought into existence by spontaneous generation. It has 
been well observed, that “ there are very few, if any, facts taken 
in support of the doctrine of equivocal generation, but what may 
as equally, and perhaps as justly, be used to support the contrary 16 
Account of a Filaria in a Horse's Eye. 
opinion ; for it is not the obvious appearance of the organisms, 
whether vegetable or animal, that is disputed, but the cause of 
their appearance. A known organism appears in some unusual 
place from its previously known habitats, or an unknown one is 
observed in some locality never as yet minutely examined, or at 
least not made known that it has been examined; the advocates 
of spontaneous generation immediately say, that our doctrine is 
the right one is plainly evident, because here an organism has 
appeared which cannot be accounted for otherwise. Is assertion 
to take the place of positive facts ? and is not this mere assertion ? 
How can we prove that there were no germs of that type of or- 
ganisms in that place where we now observe the organism in 
question ? We find, when we begin to examine it, that it pro- 
duces germs itself; then by what parity of reasoning can we 
assert that it has sprung from matter without any previous germ, 
when we find, in every succeeding instance, a germ is always 
given for a succeeding organism ?” A full consideration of this 
subject would require an investigation into the nature of the 
vital principle and the vital powers, which our limits will not al- 
low ; we therefore dismiss the question, with the single remark 
that it is more in accordance with the dictates of sound philoso- 
phy, in all doubtful cases, to acknowledge our ignorance than to 
attempt to assign a cause to explain such extraordinary phenom- 
ena. 
Another theory has lately been advanced, which receives the 
support of some highly respectable names in physiology. It is 
that worms are produced within the body by some living process 
or function of the organism, analogous to the secretion of lymph 
upon a serous surface. An organized portion of matter is thus 
formed, under the influence of the vital principle of the original 
animal, which is afterwards thrown off and becomes a separate 
being, and capable of an independent existence. In answer to 
this hypothesis it is sufficient to say, that we have no proof what- 
ever of of such formations ; that they are contrary 
to all and will not explain the identity of characteristics 
which form the different genera and species. In short, it has no 
better foundation to rest upon than Bremser’s notion that intes- 
tinal worms are formed by the presence of semi-assimilated nu- 
tritious matter in the digestive tube. Account of a Filaria in a Horse’s Eye. 
17 
There remains, therefore, but one other theory, and that is the 
one which attributes the origin of intestinal and visceral worms, 
in all cases, to ova. Ehrenberg has clearly proved by his care- 
ful microscopical observations, that these animals have organs of 
reproduction clearly developed, and never deficient; indeed, sur- 
passing in development, for the most part, those of other organic 
systems; thus plainly pointing to a predominant cyclical develop- 
ment, in the same manner as we find in the higher organisms. 
Ehrenberg has also shown that the fecundity of these animals is 
most astonishing, each female producing thousands, if not millions 
of ova at a time. The same diligent and accurate observer states, 
that if we carefully examine animal bodies, whether of man or 
other animals, we shall, in nearly all cases, discover worms of 
some kind, and that we do not meet with more, he thinks is ow- 
ing to the great difficulties in the way of the development of the 
ova, among which the resistance of the vital principle is not the 
least. He therefore believes that the eggs of intestinal worms 
are taken into the circulation and carried into all parts of the body, 
but are developed only where the particular conditions requisite 
for this purpose are favorable. “ The smaller diameter of the 
finest vessels through which they have to pass,” he remarks, 
“ does not appear to me to present any important difficulty, be- 
cause these, as we see in every inflammation, become easily and 
quickly expanded as soon as they are irritated; and these eggs 
may, as excretive bodies, like every body which is foreign to our 
organism, act in an irritative manner, and may be taken up by 
the embouchures of the absorbents and be propelled along with 
increased activity through them ; that this is the case with mer- 
cury, pus and other matters, has been already received as an ob- 
served fact. It is even probable that the eggs of the Entozoa 
and their propulsion through the vascular system may be an im- 
portant morbid matter hitherto overlooked, and which causes a 
part of the phenomena comprehended under the name scrofula. 
In bodies which are particularly favorable to the development 
of worms, there must necessarily be an innumerable quantity of 
secreted eggs of these parasites, which, if they are not expelled 
by the intestinal canal or by the primce vice, must, as foreign bod- 
ies, produce disorders. If the absorption takes place entirely or 
for the most part in the lymphatics, it would occasion their gen- 
eral or sole influence upon that system. Obstructions in the 18 
Account of a Filaria in a Horse’s Eye. 
lymphatics, but especially in their reticular tissue, the glands, 
which lead to local congestions of lymph, inflammations, and 
morbid appearances of various kinds, become in this manner ve- 
ry easy of comprehension; and these assuredly deserve the at- 
tention of medical science, not as speculations, but as realities. 
Thousands of eggs of intestinal worms, whose existence in many 
bodies can not be denied, must perish, as they are rarely develop- 
ed in such great quantities from the difficulty of their attaining 
the place and conditions favorable for their development; while 
only some, very often none, ever actually attain those conditions. 
This relative proportion of the number of intestinal worms and 
of their eggs to the organs of the larger animals, is also found to 
exist. There are very often observed in animal dissections a 
small number of full-grown worms, filled with an innumerable 
quantity of eggs, without any young in their proximity; and I 
was often astonished to find in the considerable number of my 
dissections of animal bodies, (I have brought from Africa alone 
intestinal worms of 196 species of animals, all of which I have 
myself dissected, and of some from 40 to 50 individuals,) only a 
few alive, although these were completely filled with eggs. 
Thus from laborious observations this opinion has become more 
and more firmly fixed in my mind, that it is much more astonish- 
ing how the great fecundity of the Entozoa should be so limited 
by the living organs, than that it should be possible that living 
worms should inhabit them, and, considering their diffusion, es- 
cape observations which are generally superficial.” 
Such are the views of this very able naturalist on this diffi- 
cult subject, and I believe they are those which eventually will 
be generally adopted. In this manner can we only satisfactorily 
account for the existence of worms in the foetus of man and oth- 
er animals, and in the intestines of chickens and the young of 
other birds, which have just broken the shell; numerous instan- 
ces of which have been recorded by Rudolphi, Blumenbach and 
others. I see no great difficulty in the supposition that these 
ova are absorbed by the lacteals and lymphatics, and carried into 
the circulation, as they are known to be smaller than the particles 
of quicksilver, and the coloring matter of madder, &.c., which it 
is well known are constantly taken up and deposited in the bones 
and other tissues of the body. We believe then that it is in the 
highest degree probable, if not actually proved, that the minute Account of a Filaria in a Horse’s Eye. 
19 
ova are thus introduced into the blood, carried to every part, and 
there only hatched, where they meet with a suitable nidus or 
pabulum, and other circumstances are favorable to their develop- 
ment.* Thus are they transmitted from parent to offspring, and 
thus do we account for the fact that each species of animal has 
its own parasites. In this manner the ovum of the Filaria was 
deposited in the eye of the horse now exhibiting in this city, 
there hatched into existence, and where it may now be seen, 
reveling in an element which appears, so far as we can judge, to 
be highly congenial to its nature and habits. 
New York, June 24, 1840. 
Postscript. July 22, 1840.—Since writing the above I have 
seen numerous Filaria in eels and black-fish, chiefly on each side of 
the spine ; and the Ashmen inform me that they have seen them 
in the eyes of Ashes. Mr. A. Halsey also stated at the meeting 
of the Lyceum, after the above paper was read, that he had often 
seen Filaria in coleopterous and other insects. I have ascertained 
that they are extremely tenacious of life, and will not only bear 
freezing, but a temperature little inferior to that of boiling water, 
without depriving them of life. Professor Owen of London, the 
celebrated comparative anatomist, estimates the number of ova 
in one Ascaris lumbricoides which he examined, at 64,000,000. 
[Lancet, June.) The fecundity of the Filaria is probably not 
inferior. 
* “ A very curious disease of the eye has in a few instances been observed. The 
common symptoms of ophthalmia appear, as injection of the conjunctiva, dimness 
of the cornea, weeping and swelling of the cornea. These are properly attended 
to, but the inflammation increases; and on very close examination, a small white 
worm, about the size of a hair and an inch in length, is found swimming in the 
aqueous humor, or that fluid which is immediately behind the cornea. Now it is 
at once evident that the only way to get rid of or to destroy this worm, is to punc- 
ture the cornea and let it out; and this method has been resorted to. In some 
cases, however, not many days pass before another worm makes its appearance, 
and the operation is to be performed a second time, and the horse eventually loses 
that eye. A veterinary surgeon, M. Cbaigraud, who seems to have had most ex- 
perience about this, says that three or four days before the appearance of the 
worms, one or tico minute bodies, of a reddish white color, are seen at the bottom of 
the anterior chamber of the eye. He also says, that the disease appears about June, 
and is not seen after December. There is no difficulty about these animalcules get- 
ting into the eye, for there are undisputed instances of their passing through the 
smallest capillaries, and being found in almost every tissue.”—Youatt on Cattle, 
jp. 293.