The =Giant Palisade Worm=, or =Strongyle=, (_Eustrongylus gigas_).
Female from a foot to thirty-nine inches long, and as much as two-fifths
of an inch thick. Male six to sixteen inches long; reddish. Lives in the
cavity (pelvis) of the kidneys in horses, oxen, dogs, and man; causes
degeneration of the kidneys, with blood in the urine, nervous diseases,
and disturbance of the feelings and intelligence.
[Illustration:
FIG. 129.—Tail of male _Strongylus armatus_, strongly magnified.
]
The =Armed Palisade Worm=, or =Strongyle= (_Strongylus armatus_),
four-fifths of an inch to two inches long, one twenty-fifth to
one-twelfth of an inch thick; reddish brown. Taken into the gut of the
horse with the drinking water as a young, minute worm, it bores through
the walls of this organ into the blood-vessels branching there. Later on
it bores into the walls of the larger arteries of the hinder part of the
body, especially into those which carry blood to the wall of the gut
(particularly anterior mesenteric artery). At those parts of the
arterial walls where it collects in large numbers, swellings (aneurisms)
are produced, varying from the size of a pea to that of a hen’s egg. A
constriction is often developed quite close to this swelling, and a plug
of fibrin may also be formed within the artery, so that the circulation
in the wall of the gut is greatly hindered. As a result of this the
glands and muscles in the wall of the digestive tube refuse their
office, so that regular digestion and onward movement of the food do not
take place. This leads to colic. As soon as the strongyloid larvæ have
become adult, they pass from the walls of the arteries into their
cavities, and are carried by the blood-stream to the walls of the gut,
which they penetrate in order to reach its cavity, where (cæcum and
large intestine) they pair, after which the female lays eggs, which are
carried to the exterior in the dung. The quickly hatched young seek
water, mud, or damp earth, where they live until, by some means (_e.g._
with the drinking water) they manage to enter the gut of a horse or
(more often) ass. _Preventive Measure_: Horses and asses must not be
allowed to drink stagnant water.
The =Stomach Palisade Worm=, or =Strongyle of the Sheep= (_Strongylus
contortus_). Male one-half to two-thirds of an inch, female
three-quarters to four-fifths of an inch long; whitish or reddish,
somewhat coiled at both ends. The disease of the stomach, and diarrhœa,
which affect lambs, usually in spring, and result from the presence of
these worms in large numbers in the true or fourth stomach, lead to
emaciation, weakness, and poverty of blood. Development unknown.
Nutritious food will cure lambs which are not very badly infested, but
hastens the death of those which are.
The =Lung Worm= of Lambs (_Strongylus filaria_). Male an inch, female as
much as three and a half inches long, thread-shaped, white or yellowish.
It appears that the young worms are taken into the stomach of a lamb (or
sheep) with the drinking water; they are found there in May, June, and
July. They quickly climb back into the throat, from which they get into
the windpipe and its branches. There they penetrate the mucous membrane,
where, until they have reached the sexual stage, they are found imbedded
in small swellings, which they quit at the end of winter or the
beginning of the next spring, if their host lives so long. The female
bears living young, which as very minute worms may be met with by the
hundred in the mucous lining the windpipe and its branches. A direct
transference of the parasite from one sheep to another does not take
place, since the young born in the mucus secreted by the walls of the
air-tubes must first live and grow for some time in water or slime
before they are able to undergo further development in the body of a
sheep or lamb. The fate, however, of the young worms which pass to the
exterior in the mucus is not yet sufficiently known. _Symptoms of
Disease_: Running of slime from the nose, difficulty of breathing,
cough, emaciation, poverty of blood. Death ensues in from two to four
months. Recovery only of very strong individuals infested by
comparatively few parasites, most of which they cough out. _Preventive
Measures_: In regions where the evil is very prevalent the young sheep
must not be allowed to go into the meadows. If it is impossible to keep
them penned in, a little food and water may be given before sending them
to pasture in the morning. In this way the danger of infection will be
somewhat lessened, since it is then less likely that the animals will
eagerly betake themselves to pools and ditches in order to quench their
thirst. Since during the months May to July the young worms (most
probably taken in with the water drunk) are found in the stomach, it is
good during this time to give vermifuges to the lambs and sheep. For
medicines a veterinary surgeon should be consulted.
The =Small-tailed Palisade Worm=, or =Strongyle= (_Strongylus
micrurus_). Thread-shaped; male one and two-fifths, female two and
two-fifths to two and four-fifths of an inch long; lives in oxen
(especially calves) in swellings of the arteries, also in the windpipe
and its branches. Severe bronchitis.
Family: =Trichotrachelidæ= (_Whip Worms_).
Small, slender, elongated worms, with the anus or, in the male, cloacal
aperture at the hinder end of the body; the latter, however, is not—as
in palisade worms—surrounded by an umbrella or cup-shaped expansion.
Here belongs:
=The Trichina= (_Trichina spiralis_).
[Illustration:
FIG. 130.—Encapsuled Muscle Trichinæ in flesh, strongly magnified.
]
[Illustration:
FIG. 131.—Male Intestinal Trichina, strongly magnified.
]
In the sexual condition this lives as a minute worm (male
one-seventeenth, female one-eighth to one-sixth of an inch long), the
so-called “intestinal trichina,” in the gut of human beings and
carnivorous mammals. In this situation it brings forth living young
(some fifteen hundred in number), and the multiplication is enhanced by
the fact that of the very numerous trichinæ found in the gut there are,
on the average, about twelve females to every male. The young trichinæ
bore into the walls of the gut, and are carried by the blood-stream into
the muscles. At first each little worm extends itself longitudinally in
a muscle fibre, but, as it gets larger, curves and becomes spirally
twisted, so that the sheath (sarcolemma) of the fibre is bulged more and
more outwards. The growth of the young trichina is very rapid—an
individual only ¹⁄₂₅₀ of an inch long before leaving the gut may attain
the length of one twenty-fifth of an inch in fourteen days. It then
grows no more, and the sheath of the muscle fibre gradually thickens to
form a capsule or cyst. Later on, in about a year, lime is deposited in
the capsule. The “muscle trichinæ” retain their vitality for several
years. If now the host of the muscle trichina is devoured by any other
mammal, the capsule is digested in the stomach of the latter, and the
once more liberated worm becomes a sexually mature “intestinal trichina”
in a few days. The pig is the ordinary host of trichinæ, which (without
the intervention of any other host) can be permanently parasitic in this
domestic animal, since pigs often devour swine’s flesh. They often
enough devour even their own young, and, especially in large
slaughterhouses, swine are often fed with the offal of their companions.
The trichinæ also spread through the body of any living being (men,
rats) which eats trichinous pork. The trichinæ thus introduced cause, in
the human subject, a dangerous or even fatal disease known as
_trichinosis_. The size of this book does not permit me to describe the
symptoms of this complaint in man. Pigs suffer much less from the
parasite; they may even contain an enormous number of trichinæ in their
muscles without being noticeably ill. Symptoms of disease, however,
often appear more or less clearly. A short time after eating the
trichinous meat the appetite of the pigs is bad; they appear in bad
spirits; the tail straightens out, and they often remain standing with
bent limbs and arched backs. There may be, in addition, pains in the
abdomen, diarrhœa, and fever. Later on, when the trichinæ have settled
down in the muscles, the pigs suffer from stiffness in the legs and
tenderness in the loins; they often cry out in pain. After this,
however, health and appetite may return, and they can be fattened.
Trichinous swine therefore appear quite sound, and are slaughtered in
due course. The trichinæ in the pig are found most abundantly in the
diaphragm, the masticatory, eye-, and other muscles of the head, also in
those of the neck, larynx, abdomen, and loins. The fore part is more
infested by trichinæ than the hinder part, but in very bad cases they
are found everywhere, even in the hams. _Remedies_: (1) The swine must
be prevented, as far as possible, from taking up trichinæ, and therefore
must never be given the offal from other slaughtered swine. The flesh of
trichinous swine should be burnt, and not buried, lest dogs or other
animals should eat it and spread trichinosis. (2) Care must be taken
that no trichinous pork is eaten by human beings (microscopic
examination; meat inspection). Pork (or sausages) must never be used raw
or half cooked. Trichinæ are killed by a temperature of 140° to 150° F.
The _inside_ of the piece of meat must be exposed to this temperature.
Family: =Filaridæ= (_Slender Thread Worms_).
Elongated and thread-shaped. Round mouth. Do not infest the gut or other
cavities, but the tissues of the body, chiefly connective tissue. None
of the species require notice here.
Family: =Ascaridæ= (_Round Worms_).
Relatively shorter than the worms of the preceding family. Mouth
triangular, surrounded by three teatshaped lips. In the male the hinder
end of the body is usually bent in a hook-like manner. The anus is not
placed quite at the hind end of the body. All the species inhabit the
alimentary canal (Cf. p. 211).
=Horse Worm= (_Ascaris megalocephala_). Male six to eight, female twelve
to seventeen inches long; sometimes occurs in great balls, causing
stoppage.
=Round Worm of Cat= (_Ascaris mystax_). Male two to two and two-fifths,
female four and four-fifths to five and one-fifth inches long; in the
intestines of the cat. _Ascaris marginata_ infests the dog.
=Pinworm= (_Oxyuris curvula_). Male one-fourth to one-third, female one
and four-fifths of an inch long. In the rectum of the horse, causing
persistent itching.
Family: =Anguillulidæ= (_Eelworms_).
Extremely small, thin-skinned; lay only a few relatively large eggs,
which develop very quickly. With few exceptions either earth eelworms
(_i.e._ live in decomposing organic matter or humus soil) or as plant
parasites leading to characteristic diseases of wild and cultivated
forms. All these parasitic forms have a “mouth spine.” This structure,
found in the mouth cavity, is very sharp and pointed in front, and can
be worked forwards and backwards so as to penetrate the cell walls of
plants. A mouth spine is not only found in the species which infest
plant tissues (several species of _Tylenchus_ and _Aphelenchus_, as well
as all the known species of _Heterodera_), but also in those forms
living free in the earth which bore into the exterior of plant roots
(the remaining species of _Tylenchus_ and _Aphelenchus_, _Dorylaimus_,
etc.). In all cases an eelworm, devoid of a spine, is not a plant
parasite. I will only deal with those parasites by which well-known
destructive diseases of cultivated plants are caused. These belong to
the genera _Tylenchus_ and _Heterodera_. The first remain eel-shaped
throughout life, but the adult females of the latter swell out
considerably and become lemon- or pear-shaped.
The =Stem Eelworm= (_Tylenchus devastatrix_).
Length one-thirtieth to one-fifteenth of an inch long, usually of
intermediate size; the two sexes of approximately equal length. Live and
reproduce in various cultivated plants (_e.g._, rye, oats, stored
onions, hyacinths, buckwheat, potatoes, clover, fuller’s teasel) and
wild plants (_e.g._, _Poa annua_, _Anthoxanthum odoratum_, _Dipsacus
silvestris_, _Polygonum persicaria_), but not to the same extent in all.
It must also be added that eelworms of which the progenitors have
developed for a considerable number of generations in the same plant,
are not easily transferred to another kind of plant, or at any rate do
not multiply vigorously there. Eelworms, of which the ancestors have
lived for many years exclusively in rye, or alternately in rye and
buckwheat, do not readily pass over to seedling onions, and first only
reproduce in them to a small extent. The eelworms live only in stems,
branches, and leaves, never in roots. In the places where they have
penetrated the plant tissues an abnormal growth in thickness of the
parts involved takes place, while the growth in length is either much
diminished or even entirely stopped. Also the chlorophyll disappears
sooner or later from the attacked spots, and rapid death generally
ensues. Since only those parts of an organ which are inhabited by a
large number of eelworms swell much, it is obvious that cracks are often
developed in the stems and leaves concerned. It is further easily seen
that the species and constitution of the infested plants will have an
important influence on the progress of the disease caused by the
eelworms. But since several generations of this parasite succeed one
another during the same year, the resulting malformation is usually very
considerable. “Clover sickness” is probably due to this eelworm.
I will treat in somewhat greater detail the =Eelworm Disease= of rye,
which is largely prevalent in Westphalia and the Rhine provinces, and
had already made its appearance, in the latter at least, at the
beginning of the century.
The eelworms producing the disease migrate into the soil on the ripening
or death of the grain, and later on go back to the new young rye plants
or to other plants in which they can live, as the case may be. It is
therefore clear that (1) where this disease exists the soil is infected
for a time, and (2), the eelworm disease of rye principally appears in
regions where the culture of rye is carried on to excess. Germination of
the seed corn goes on quite normally in infected fields, and it is only
exceptionally that anything particular is noticed in the young plants of
winter rye during autumn and winter. The disease appears at the
beginning of spring. Some plants soon become yellow and die: others
appear to grow very luxuriantly; they possess a beautiful bluish-green
colour and seem very healthy; later on they develop enormously in
breadth, and each separate plant covers a relatively large area. The
base of the stem swells abnormally, so that the plant looks as if it
bore below an onion projecting above the ground. This is caused by the
lower joints of the haulm remaining very short and thickening
considerably, causing the leaf-sheaths which surround the base of the
stem to become thicker and broader than usual. The feeble development of
roots is also characteristic. The leaves generally remain short, but get
very thick; they often become wavy, and may even appear frilled. All the
leaves, however, are not crumpled in this way; a few remain quite
normal, while others are small and grass-like, but thick (Fig. 132).
Later on, the tip of the haulm and the ear often do not come out of the
leaf-sheaths; in other plants the ear may appear, but remains small and
deformed as well as the rest of the haulm, while the grains which
develop are small. A number of shoots, however, may develop normally and
bear fruit. Badly infested plants quickly die, some at the very
beginning of spring, others later.
[Illustration:
FIG. 132.—Rye plant in the later stage of the Eelworm disease.
]
Where the disease is very bad it may easily be recognized by its
characteristic distribution. A number of bare places are noticed in
spring on the infected fields; round about these places still living but
badly diseased plants may be noticed, and the symptoms of attack are
less obvious the further one goes from the bald spots.
On the death of the rye plants the eelworms mostly travel back to the
soil, but sundry eggs and larvæ stop in the dried-up remains. Rye straw
may further infect a diseased field by getting into farmyard manure and
being brought back again with it; for the eelworms (at any rate as eggs
and larvæ) are killed neither by drying nor by the action of dung and
other decaying substances. Strongly infected spots (bare patches) on an
infested field are usually the places where dung containing diseased
rye-straw has lain for some time. From such centres the spreading of the
eelworms takes place: (1) _actively_ by the migration of the worms, (2)
_passively_ by rain, the feet of labourers, the hoofs of horses, field
implements, etc.; also (on loose soils) by the wind, which not only
blows about particles of earth, but also the dried-up larvæ which are
always found on the surface of the ground. As the eelworms multiply very
rapidly whenever they are in the plants, and as the means of
distribution are very numerous, the disease spreads with great rapidity.
_Remedies._—Proper rotation; limitation of the culture of rye, growing
in place of it carrots, turnips, or lupines. Now and then (but not too
frequently), potatoes, buckwheat, clover, and oats may be cultivated in
the fields affected, at any rate before sowing rye again. Abundant
manuring, especially with sulphates of potash, ammonia, and iron. Deep
cultivation of the soil, since the eelworms find no food in the deeper,
damper layers of the soil, nor can they pass into the dried condition,
and so must die.
=Oats= suffer from eelworms just in the same way as rye.
=Clover Sickness= is marked by short stunted shoots, and whitish rounded
buds, often remaining closed; also by the whitish colour and abnormal
thickening of the shoots and buds.
=Eelworm Disease of Potatoes.=—Crumpling and small growth of the parts
above ground. In many cases there may even be no potatoes at all, or
only small ones, poor in starch, though sometimes they may be tolerably
large. On the surface of the tubers there are discoloured rotten spots,
not penetrating deeply, and usually (but not always) at the attached
end. These dark patches contain the eelworms.
=Eelworm Disease of Buckwheat.=—Joints of the stem for the most part
much thickened, but abnormally short. In many cases a large amount of
branching in the lower part of the stem, usually at a place where it
bears a nodular swelling. Branches generally short. There may be twists
and bends in the stem and branches. Often, but not always, the formation
of flowers and fruit is stopped. The thickened parts of the stem are
brittle; they contain the eelworms in their interior.
The =Wheat Eelworm= (_Tylenchus scandens_ = _T. tritici_).
[Illustration:
FIG. 133.—Ear Cockles of Wheat; the third shows the eelworm larvæ on
its cut surface.
]
Length of the male about one-twelfth of an inch, of the female one-tenth
to one-fifth of an inch (according to the size of the galls in which the
eelworms develop). The wheat eelworm is the cause of “ear cockles,” also
known as “peppercorns” and “purples.” In several parts of the ear short
thick dark brown galls (Fig. 133), resembling the seeds of corn-cockle,
are found instead of wheat grains. Inside the thick brown shell there is
a yellowish white mass, containing hundreds or even thousands of eelworm
larvæ (one thirty-first to one twenty-seventh of an inch long). These
are quite dry and rigid, but gradually revive on moistening, even if the
black galls have remained twenty years in the dried-up condition. When
the wheat is ripe the dark-walled galls are gathered in with the crop,
and in many cases are sown again with the sound grains. The brown shell
then decays, and the eelworm larvæ leave the gall, travelling to a
neighbouring wheat seedling, where they live between leaf-sheath and
haulm, also penetrating into the terminal bud. The haulm of a wheat
plant infested by many eelworms remains relatively short, the leaves are
often sharply bent and have wavy margins. Wheat plants thus infested
closely resemble rye plants diseased in a similar way, but are much less
deformed. This is because the wheat eelworms do not reproduce till they
reach the ear, and there is consequently only one generation per year,
while several generations of eelworms succeed one another in the same
rye plant. The eelworms quickly travel from all parts of the plants into
the ears, and get into the rudiments of the flowers, causing them to
swell up like bladders, and their walls to become first dark green, and
then dark brown. Sixteen to twenty eelworms are present in the lowest
flowers of the ear, ten to twelve in those higher up (and therefore
smaller), and four to six in the topmost (smallest) ones. Soon after
entering the flowers the eelworms become sexually mature, and lay eggs
(600 to 1600), from which are developed the larvæ that inhabit later on
the cockle-seed like galls. The disease is known in England, Germany,
France, and Italy, and is especially harmful in Saxony, where it
sometimes attacks a quarter of the wheat crop. _Remedies_: Either there
should be no ear cockles in the seed corn, or else the eelworms should
be destroyed in them. The infested grain may either be put through a
sieve, or else soaked for twenty-four hours in weak sulphuric acid (one
pint strong acid to thirty-three gallons of water), when many of the
galls float and can be skimmed off, while the eelworms are killed in
those which sink.
[Illustration: