Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/986

 LEE

LEE

feet, and of a black colour, with various fpots and lines, and a mouth with three diftinct openings. The creature is common in {landing waters, and is in fre- quent ufe in the practice of phytic, often fupplying the ufe of the lancet in bleedings. The beft to be chofen for this ufe are the fmall ones, and of thofe, fuch as have the moft diftinct lines on their backs. Dale, Pharmac. p. 355. The hiftory of this animal, and the ftructure of its parts, by means of which it becomes ufeful to us, in fupplying very happily the place of the lancet, with every other par- ticular circumftance of its life and food, have been very accurately given by Mr. Morand, in the Memoirs of the Academy of Sciences in the year 1739- The more vulgarly known particulars of this animal are briefly mentioned by this gentleman ; fuch are the cu- taneous annules of its outer coat, the beautiful arrange- ment of the feveral rays, the colours, the pyramids, and points, with which it is ornamented ; the avidity with which this creature feizes the flefh of animals ; the manner of its applying its mouth ; the vermicular motion obferved within it while fucking, which refembles the common motion of deglution; the time they have been known to live in the water without any vifible food ; and the faculty they have in common with many other animals, of moving when cut into feveral pieces : Thefe the author fuppofcs already fuffi- ciently known, and panes on to what is lefs fo, the ftructure of its inner parts.

The part of this animal, by which it pierces the fkin of any creature to get at its blood, is generally called, fimply, its mouth, but it really confifts of five different parts, which are confounded under that general name. Thefe are two regular lips, a cavity, which is properly the mouth, certain inftruments to pierce with, others which ferve it for fucking, and finally a fort of throat, or cefophagus, through which it (wallows the blood. When the leech is in a ftatc of reft, its upper lip forms a regular femicircle, and the lower a portion of a much larger circle.

When the creature lengthens its head to move, the femi- circle of the upper lip becomes two oblique lines, the junc- tion of which makes a faliant angle, which the creature applies to whatever it would fix itfelf to. That angle is marked by a regular black (pot on the outer edge of the lip. The extreme foftneia of the fibres of this part makes it very fervictable to the animal, in that it readily aflumes any figure, according to the occafion of fiezing any thing folid, in order to move the reft of its body ; or on the flefh of an animal, to give opportunity to the piercing in- ftruments to exert their force and action. Whether it be for either of thefe purpofes, that the creature fixes its mouth, the two lips regularly fix, and make in this ftate a fort of acetabulum, like the hollow of the tail. This may be (esn in their fixing on the fides of a glafs veflel in which they are kept, and the mouth, or aperture be- tween the lips, is diftinctly feen. This mouth is formed, like the lips, of fuch extremely fupple fibres, that it takes the figure of the part to which it is applied, and fixes perfectly clofe to it. When the lips are fixed on the flefh, in order to fuck, this little mouth continues moveable under them, and fearches over the compafs of flefh, inclofed in the larger circle of the lips, for the fpot where it will be eafieft to draw much blood.

Within this mouth is placed the inftrument for the piercing the fkin, which is more than the mecr fucker of the gnat, or the like kind of flies; firfce the quantity of blood to be fucked, by the leech, is greatly larger, and the aperture of the veflel muft therefore alfo be larger. The fhape of this weapon may be difcovered by examining the wound it leaves. This is compofed of three cuts, making three rays, which uniting in a center, make equal angles one with another. This ftru&urc of the wound is moft diftinctly (cgi\ when the fwelling is gone down, and the fkin is clean j and this is ufually on the fourth day after the application. The three openings are then plainly feen not to be punctures, but abfolute wounds, or cuts, as if made by a fine lancet. In examining the creature, the organ, deftined for making the wound, is found to be placed between the aperture of the lips and the bottom of the mouth; and on cutting up the animal, and drawing the finger carefully over this part of it, there is felt a rough- nefs like that of a fine file, which evidently is owing to fome rough fubftance, of the hardnefs of bone. Thefe are, in reality, a number of fine and fharp teeth, and when ex- amined by a microfope, they are found to be difpofed in three feries on three ribs, or, as they may be called, jaws ; each of which is placed along the middle of a ftrong muf- cle of its own length ; and thefe correfponding regularly to a triangular opening, which the creature has in its mouth. When that has feized on a proper part for the getting blood, and is fixed, thefe mufcles exert their action, and ftrike in the teeth through the fkin.

Thefe are the inftruments which pierce the fkin, and the veflel which is to afford the blood, and for the receiving it into the body of the animal. There is between thefe rows of teeth, or in the common center of the mouth, a fmall

aperture ; and within this there is a little body to be difco- vered, which by its motion feems very plainly to be a tongue, and which probably acts as a pifton to take up the blood flowing from the triple wound, in the center of which it naturally ftands, while the larger circle of the lips, csV. per- form the office of the body of the pump, and the blood is eafily, by this means, conveyed into the body of the ani- mal.^ Finally, between the root of the tongue and the be- ginning of the ftomach, there is a fpace of two lines in length, in which it is eafy to difcover two different ar- rangements of fibres ; the one fet are flat and plain, the others are circular. Thefe evidently have a power of widen- ing or contracting the cavity of the pump, and by that means facilitate its office ; the plane ones contracting in length, to enlarge the capacity, and the circular ones de- termining the blood toward the ftomach, by their power of contracting the hollow, when the blood is received. The blood from hence enters into a membranaceous fort of fack, which ferves the animal for ftomach and guts, and occupies the greateft part of the body of the creature. If the air is admitted into the body by the mouth, it may be feen to make its way down a longitudinal canal, and fill, as it goes, a number of facks, or little bags, which are on each fide. Thefe veficules receive the blood, and becoming filled with it, fwell out the body of the animal to a great fize. It re- mains here many months, and nouriihes the creature, and if any^ thing is excreted from it, it muft be merely by an infeniible perfpiration ; fince the creature has no anus, fo far as can be yet difcovereed, nor any aperture which can fug- ply the place of one.

Leeches are able to live in oil ; and when removed out of this liquor into water again, they throw off" a tender fkin, or film, of the regular fhape of their body, and refembling the fkin of an eel in miniature. Their living in oil feems a proof, that their or-gans of refpiration are not placed on the outfide of their bodies, as they are in many fmall ani- mals, which therefore die on being only rubbed over with oil. But the leech feems to refpire by the mouth; and this may be the more plainly difcovered, if the water, in which it is kept, be gently heated, for then the animal being uneafy, breathes hard, and very vifibly.

The leech is a well known infect, common in waters, and ufed to draw blood in medicine* The common ftanding waters afford us two fpecies of this infect, a larger, called the horfe-leech, and a fmaller, diftinguifhed from this not only in fize, but by its whole furface, being covered with finally tubercles. The larger kind grow to five inches long, and is yellowifh on the belly, and black upon the back. It i£ divided, in the manner of the earth-worm, into a num- ber of annular joints, not lefs than an hundred, and is fmaller toward the mouth, than toward the tail. The fmaller kind has a broad ftreak of a greenifh black running down its back, and on each fide of that a reddifh line, and beyond thefe there are other lines formed of large black fpots. The belly is blackifh, with a caft of green. This is the kind that fhould be ufed in medicine, and is eafily diftinguifhed from the other. Mr. Ray obferves, that there are fometimes found great numbers of young leeches flicking in clufters to the belly of the old one.

We have on the coaft of Cornwall another infect, much approaching to the nature of the leech. It is about fix inches long, of a greyifh colour, fpotted with black, and is divided into about nineteen rings. It has a great number of a fort of tubercles on the body, and is ufually found full of blood, or of a fubftance refembling blood in colour. Ray's Hift. Infect, p. 3. Bleeding with Leeches. The method of bleeding by thefe animals was very early introduced into the practice of phy- fie. Leeches fhould always be chofen from clear and run- ning waters ; for thofe from ftagnant ones, and dirty ponds, feem to have fomething malignant in their bite. The fur- geons ufually chufe fuch as have flender heads, green lines on their backs, and bellies of a reddifh yellow. But from whatever waters thefe creatures have been taken, the bell method is to keep them many days in a glafs of water, changing it often, that they may cleanfe themfelves. Before the leech is applied to the fkin, it fhould be taken out of the water, and kept an hour in an empty cup, to drain itfelf, that it may thus be rendered thirfty and empty. They may be properly applied to the temples, or behind the ears, in diforders of the head, and to the veins of the rec- tum in the blind piles. And applied to this part alfo, they often prove of great fervice in haemorrhages, or fpittings of blood by the nofe, efpecially when thefe have been occa- fioned by a ftoppage of the ufual difcharges that way ; though where this is not the cafe, they do great fervice merely by revulfion.

Before the leech is applied, the fkin muft be well rubbed, till it become hot and red, and then either hold the leech by the tail to the part, or let it crawl of itfelf out of the cup upon it. By this means they readily lay hold ; but if they refufe, the blood of a chicken or pigeon fhould be rub- bed on the part ; and if that does not allure them, they muft be laid afide as ufelefs, and others taken in their ftead.

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