to consist only of a simple intestine, com posed of a fine and very delicate membrane, which is always filled with an orange-coloured liquor.

The motion of these worms is serpentine, in no respect resembling that of the earth-worm, with which they have sometimes been ignorantly confounded. The latter has the power of contracting and extending 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 it with considerable force.

These worms bring forth their young from

eggs.

The Vermicular Ascaris is very common in the intestines of children. The number in which this animal is produced exceeds all bounds, 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.

They bring forth their young alive. The female has, at the distance of about an eighth of an inch from the head, a small aperture, through which the offspring are protruded. Dr. Hooper, in the Memoirs of the Medical Society of London, informs us, that he has seen upwards of a hundred young ones escape through this

t

aperture, all alive, and active, several hours after the death of the mother.

The present species are sometimes known by the appellation of the maw or thread-worms.

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, as it has been stated, are sometimes vomited up in brooks where the animals drink. Whilst they are in small numbers, the animal feels, or at least appears to feel, no inconvenience from thein; but when they fill the biliary ducts, as they oftentimes do, the parts become swollen, and they become the source of fatal maladies. The disease called the rot, is supposed to be occasioned by them.

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

THE TENIA 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 purpose of producing disease in the animals they inhabit, but rather, that nature has directed that no situation should be vacant, where the work of multiplying the species of living beings could be carried on. By thus allowing them to exist within 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 at all 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 Tania 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 EngĴand have the Tania Solium, or common tape worm, and rarely any other: the inhabitants of Switzerland the Tania lata, &c.

The mode of increase or propagation of Tæniæ, appears to be principally by eggs; and there is reason to believe that these eggs, as well as those of other intestinal worms, are so constructed, as not to be easily destroyed. From this circumstance, we may suppose them to pass along the circulating vessels of other animals. We cannot easily explain the phænomena of worms being found in the eggs of fowls, and in the intestines of a fœtus before birth, except by supposing the eggs 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.

THE head of this animal 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 jointed 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 by which the animal fastens itself to any spot. 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 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 affected by the capillary attraction of their fibres.

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