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In the Linnean order of Intestina, the animals are simple, naked, and without limbs.
OF THE ASCARIDES.
The bodies of these worms are cylindrical, semi-transparent, and slender at each extremity. The head is furnished with three small vesicles. The intestines are generally spiral, and of a whitish color
. Although these worms have long been known to inhabit the stomach and intestines of men and animals, their origin and history seem enveloped in great obscurity. The difficulty of making satisfactory observations, and the want of favorable circumstances under which to attend to them, have hitherto presented insuperable obstacles to an intimate knowledge of their habits and economy.
In structure they are very simple, for being intended to subsist on already digested food, they are not furnished with any complicated organs. The denomination of Ascaris has been given to them from the circumstance of their being almost constantly in motion.
Some of the species are oviparous, and others produce living offspring
They are most abundant about the ileum, but they sometimes ascend into the stomach, and even creep out at the mouth and nostrils.
The motion of these worms is serpentine, and in no respect resembles that of the Earth-worm, with which they have sometimes been ignorantly confounded. The latter has the power of contracting and ex: tending its body, whilst the length of the Ascaris is never diminished. The head is always thrown forward, by the worm curling itself into circles, and suddenly extending its head with considerable force.
They are very common in the intestines of children ; and are sometimes found in the stomach. Their number exceeds all calculation, and they cause a most unpleasant sensation of itching, by piercing the skin in a slight degree, with their awl-shaped tails. Even newly-born children are not always free from them.
OF THE FASCIOLÆ, OR FLUKE-WORMS.
FLUKE-WORMS are often very numerous in the viscera of quadru. peds, birds, fishes, and reptiles. They are found in the stomach, the intestines, and the liver. Each individual has both the sexes united in itself. They are oviparous, and the ovaries are lateral.
Their body is oblong and flattish, and is furnished with two orifices, one of which is situated at the anterior extremity of the body, and the other at a little distance beneath it. The interior represents an in. testinal canal, which, after passing round the body, folds upon itself, and terminates at the second orifice.
The livers of sheep which have fed in wet and marshy grounds, generally abound with these worms. The disease called the rot, is sup. posed to be occasioned by them.
OF THE TÆNIÆ, OR TAPE-WORMS.
TENIE are worms that inhabit the bodies of different animals, where they are destined to feed upon juices already animalized. They are generally found in the alimentary canal, and usually about the upper part of it, where there is the greatest abundance of chyle, which seems to be their natural food.
We'are not to suppose that these Worms are created for the purposo of producing disease in the animals they inhabit: but rather, that Nature has directed that no situation should be v:cant, where the work of inultiplying the species of living beings could be carried on. Ву thus allowing them to exist in cach other, the sphere of increase is con. siderably enlarged. There is, however, little doubt, that worms, and more especially those of the present tribe, do sometimes produce diseases in the bodies they inhabit; but we are at the same time very certain, that worms do exist abundantly in many animals, without disturbing their functions, or annoying them in the slightest degree; and we ought to consider all these creatures rather as the concomi. tants than the causes of disease.
The species of Tænize are not confined singly to particular animals; men are subject to several different species, and even the people of particular countries and climates are subject to particular species of them. The people of England have the Tænice solium, or Common Tape-worm, and rarely any other; the inhabitants of Switzerland the Tcenic lata, &c.
These creatures are apparently possessed of few senses. Nothing resembling brain or nerves has been discovered in them; but, as they are highly sensible to stimuli, it is most reasonable to conclude, that they have a considerable portion of nervous matter in the composition of their bodies; that is, of such matter as is susceptible of stimuli. Indeed, we can scarcely imagine how any animal can even exist with out such matter in its composition. Ilaving no particular organs of
THREAD-WORMS-FURY TRIBE-HAIR-WORM TRIBE.
sense, the touch is therefore the only evident soạrce of intelligence which they possess.
The mode of increase or propagation of Tæniæ, appears to be principally by ova; and there is reason to believe that these ova, as well as those of other intestinal worms, are so constructed, as not easily to be destroyed. From this circumstance, we may suppose them to pass along the circulating vessels of other animals. We cannot easily explain the phenomena of worms being found in the eggs of fowls, and in the intestines of a foetus before birth, except by supposing their ova to have passed through the circulating vessels of the mother, and to have been by this means conveyed to the offspring.
OF THE FILARÆ, OR THREAD-WORMS.
THESE troublesome animals are found in the bodies of several kinds of quadrupeds, birds, and insects. Most of the species perforate the skin, immediately under which they lodge themselves ; a few, how. ever, have been discovered in the intestines. None of them have yet been found to infest the bodies of reptiles or fish.
THE FURY TRIBE.
OF this tribe only one species has hitherto been discovered. The body is linear, and of equal thickness throughout. It has on each side a single row of close-pressed reflected prickles.
In Finland, Bothnia, and the northern provinces of Sweden, says Linnæus, the people were often seized with an acute pain, confined to a mere point, in the face, or other exposed part of the body, which afterwards increased to a most excruciating degree, and sometimes
, even within a few hours after its commencement, proved fatal. This disorder was more particularly observed in Finland, especially about marshy places, and always in the autumn. At length it was discovered, that the pain instantly succeeded something which dropped out of the air, and almost in a moment penetrated and buried itself in the flesh. On more acute examination, the Fury was detected as the cause. This little worm creeps up the stalks
of sedge-grass and shrubs in the marshes, whence it is often carried off by the wind; and, if the naked parts of the skin of any person happen to be directly in its course, it immediately adheres and buries itself within.
OF THE GORDIUS, OR HAIR-WORM TRIBE.
THESE animals are inhabitants chiefly of stagnant waters. In their organization and structure they are extremely simple. Their bodies are round, thread-shaped, equal in thickness throughout, and smooth; and their interior consists of a canal, which extends from one ex. tremity of the body to the other.
COMMON HAIR-WORM-SEA LONG-WORM-EARTH-WORM. 1005
THE COMMON HAIR-WORM.
The popular name of this worm originated in the notion that it was produced from the hair of horses and other animals; a notion that is even yet prevalent among the common people. Its Linnean name of Gordius originated in the habit that it has of twisting itself into such peculiar contortions as to resemble a complicated Gordian knot. In this state it often continues for a considerable time, and then, slowly disengaging itself, extends its body to the full length.
It is common in our fresh waters, and particularly in such where the bottom is composed of soft clay, through which it is able to pass with great facility.
The Abbé Fontana kept a Hair-worm in a drawer for three years, at the expiration of which time it was perfectly dry and hard, and exhibited no signs of life; but, on putting it into water, it soon recovered its former vigor.
THE SEA LONG-WORM.
Such is the extreme length of these very extraordinary worms, that it is almost impossible to fix any bounds to it.
Some of the most intelli. gent of the fishermen, how. ever, assert, that they are upwards of thirty yards in length ; but Colonel Montagu is of opinion, that as many feet must be the utmost. None of the specimens which he saw appeared to exceed twenty feet.
The expansion and contraction of the Long-worms are very sur. prising. One of them, supposed to be nearly eight feet in length, was put alive into spirits, and it instantly contracted to about twelve inches, at the same time increasing to double its preceding bulk.
OF THE LUMBRICUS, OR EARTH.WORM TRIBE. THE Earth-worms have a round, annulated body, with generally an elevated fleshy belt near the head. Most of the species are rough, with minute concealed prickles, situated longitudinally, and have in the body a lateral aperture or pore.
Some of these worms bore into the earth, others live in mud, and others in the sand of the sea-shores. They are furnished with numerous prickles, which are short, and curved backward. These aid their movements in the ground. Their bodies, likewise, are covered with a viscid matter, which transudes through numerous pores, and assists their progress.
The most insignificant insects and reptiles are of much more impor. tance, and have much more influence in the economy of Nature, than the incurious are aware of; and, notwithstanding their minuteness,
they are mighty in their effects, from their numbers and fecundity Dew-worms, in appearance, constitute a small and despicable link in the chain of Nature; yet, if this link were destroyed, it would make a lamentable chasm. For, to say nothing of the many species of birds and quadrupeds that are supported by them, worms seem to be the great promoters of vegetation. They bore, perforate, and loosen the soil, and render it pervious to rains and the fibres of plants, by draw. ing straws and stalks of leaves and twigs into it; and chiefly, by throwing up infinite numbers of lumps called worm casts, which form a fine manure for
grass Gardeners and farmers express their detestation of worms, the former, because they render the walks unsightly, and make them much work; and the latter, because they imagine that worms eat their green corn.
But these men would find that the earth without worms would soon become cold, hard-bound, and void of fermentation; and consequently sterile. It should also be observed, that green corn, plants, and flowers, are not so much injured by worms, as by many species of insects in a larva state; and by unnoticed myriads of those small shell-less snails called slugs, which silently and imperceptibly make amazing havoc in the field and garden. Lands that are subject to frequent inundations are always poor; one great reason of this may be, because all the worms are drowned.
The body of the Dew-worm is formed of small rings, furnished with a set of muscles, which act in a spiral direction, and enable it, in the most complete manner possible, to penetrate into, or creep upon the earth. The motion of these creatures may be explained by a wire wound on a cylinder; where, when one end is drawn on and held fast, the other, if loosed, will immediately follow. These muscles enable them with great strength to dilate or contract their bodies. The annuli or rings are also each armed with small, stiff and sharp beards or prickles, which they have the power of opening out, or closing to their body. And under the skin is secreted a slimy matter, which they emit at the perforations between the rings, to lubricate the body, and facilitate their passage into the ground.
In winter these worms retire very deep into the earth, to secure themselves from being frozen. They do not become torpid during this season ; for often, in the intervals of mild weather, they are observed to throw up their casts, in the same manner as at other times of
OF THE LEECHES IN GENERAL.
The body of the Leech is oblong and truncate, or appears as if it were cut off at both ends. These animals are cartilaginous, and move by dilating the head and tail, and contracting themselves into the form of an arch.
Some species are viviparous; others are oviparous, and lay their eggs on aquatic plants or carry them under their belly. Each egg contains many young ones. Several of the smaller kinds may be multiplic:l by cutting.