THE FLUKE-WORM OF THE SHEEP

The livers of sheep which have fed in wet and marshy grounds, generally abound with these Worms. They are also occasionally found in the stomach and intestines; and are sometimes vomited up in brooks where the animals drink. When they are not numerous, the animal feels, or at least appears to feel, no inconvenience from them; but when they fill the biliary ducts, as they often do, the parts become swollen, and they are the source of fatal maladies. The disease called the rot, is supposed to be occasioned by them.

These Worms are found in the livers of other quadrupeds besides sheep.

OF THE TÆNIÆ, OR TAPE-WORMS +.

Tæniæ 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 purpose of producing disease in the animals

DESCRIPTION. This Worm is about an inch in length, and of a somewhat ovate form. The anterior part of the body is terminated by a small tube. It has a white line down the middle, and a spot in the centre of the body.

SYNONYMS. Fasciola hepatica. Linn.-Fasciole hépatique. Bos.-La Douve du Foie. Cuvier.-Flounders, in some parts of England.

+ The body in the Tape-worms is flat, and composed of numerous articulations; and the head has four orifices for suction, a little below the mouth, which is terminal, and continued by a short tube into two ventral canals. The mouth is generally crowned with a double series of retractile hooks or holders.

they inhabit; but rather, that nature has directed that no situation should be vacant, where the work of mul tiplying the species of living beings could be carried on. By thus allowing them to exist in each other, the sphere of increase is considerably 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 concomitants than the causes of disease.

The species of Tæniæ 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 Taenia solium, or Common Tape-worm, and rarely any other; the inhabitants of Switzerland the Tania 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 without such matter in its composition. Having no particular organs of sense, the touch is therefore the only evident source 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 in

testines 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.

THE COMMON TAPE-WORM*.

This animal inhabits the human intestines. Its head is furnished with a mouth, and with an apparatus for giving it a fixed situation. The body is composed of a great number of distinct pieces articulated together, each joint having an organ, by means of which it attaches itself to the inner coat of the intestine; and as these joints are sometimes exceedingly numerous, so of course will be the different points of attachment. The joints nearest the head are always small, and they become gradually enlarged as they are further removed from it, except towards the tail, where a few of the last joints become again diminished. The body is terminated by a small semi-circular joint, which has no opening.

The external parts are clothed with a fine membranelike cuticle, immediately under which is a thin layer of fibres, lying parallel to each other, and running in the direction of the length of the animal's body. In this direction all its motions are performed; whence we may conclude that these fibres perform the office of muscles.

The head has a rounded opening at its extremity, which is considered to be the mouth. This opening is continued, by a short duct, into two canals, which pass round every joint of the animal's body, and convey the aliment. The head is fixed to its place by means of two small tubercles, concave in the middle, that seem to serve the purpose of suckers. The alimentary canal passes along each side of the animal, sending a cross

* SYNONYMS. Tænia solium. Linn.--Tania cucurbitain. Bosc. Le Cucurbitain. Cuvier.-Tape-worm.

canal over the bottom of each joint, which connects the two lateral canals together. The internal structure of the joints is partly cellular, and partly vascular: the substance itself is white, and in its texture somewhat resembles the coagulated lymph of the human blood.

The food of the Tæniæ, requiring probably very little change before it becomes a part of their body, is taken in at the mouth, and, being thrown into the alimentary canal, is made to visit, in a general way, every part. The central structure of the vessels placed in each joint, seems calculated to absorb the fluid from the alimentary canal, for the purpose of sustaining and repairing the immediately adjacent parts: but there is in their bodies much cellular substance, into which no vessels enter. Such parts of the bodies of these animals, are possibly nourished by transudation of the alimentary fluid into their cells; or this may be effected by the capillary attraction of their fibres. As they have no excretory ducts, the decayed parts of their bodies are probably dissolved into a fluid, which transudes through the skin like perspiration, and for this purpose the skin is extremely porous.

The length of the present Tænia is from three to thirty feet; but some individuals have been known to reach sixty feet, and to be composed of several hundred joints.

When these worms produce a diseased state of body, those remedies (as drastic purges) are supposed to be the most effectual, that operate partly by irritating the external surface of their bodies, so as to make them quit their hold, and partly by violent contractions in the intestines, which may sometimes divide their bodies, or even destroy them by bruising. Electrical shocks, passed frequently through the abdomen, it is supposed, might be beneficial, as the lower orders of animals are in general easily destroyed by electrical shocks.

OF THE FILARIE, 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, however, have been discovered in the intestines. None of them have yet been found to infest the bodies of reptiles or fish.

THE INDIAN THREAD-WORM, OR GUINEA-WORM†.

This species is too commonly found both in the East and West Indies. It enters the naked feet of the slaves, occasions very troublesome itchings, and sometimes excites even fever and inflammation. It particularly attacks the muscles of the arms and legs, whence it can only be extracted by means of a piece of silk or thread tied round its head. But the greatest caution is necessary in this simple operation, lest the animal, by being strained too much, should break; for, if any part remain under the skin, it grows with redoubled vigour, and becomes a cruel and sometimes a fatal enemy.

Dampier tells us, that these worms are no thicker than a large brown thread, but, as he had been informed, are five or six yards long. "If they are broken in drawing out, that part which remains in the flesh will putrefy, be very painful, and endanger the patient's life, or at least the use of the limb; and I have known some

Their body is round, thread-shaped, and very smooth. The mouth is dilated, and has a roundish, concave lip.

+ DESCRIPTION. This worm is of a yellowish white colour, and frequently ten or twelve feet in length, although its thickness is not greater than that of a horse-hair.

SYNONYMS. Filaria Medinensis. Linn. Gmel.-Gordius Medinensis. Linn. Syst. Nat.-Dragoneau de Médine. -Le Ver de Médine. Cuvier.

Bosc.