Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/625

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The increafe of this pernicious infect Is by eggs, and is (b very great, that Sellius, who has written a wliole folio of its hitteiy, computes there are in one parent more young at a time, than there are men in the eight largeit cities of Europe ; fo that it is no wonder that fo many of thefe creatures are found in the bottom of a fhip, when they have once feized upon it i the only wonder is, that there are not many more. When the bottom of a veffel, or any other piece of wood couftantly under water, is inhabited and injured by ever fo great a number of thefe worms, there is no iign of the da- mage to be perceived on the furface, nor are the creatures vi- able till the outer part of the wood is cut or broken away, then their flielly habitations come in fight ; thefe lie lb near the furface, however, as to have an eafy communication with the water, and there are a multitude or little perforations in the very furface through which the inhabitant infects throw out the extremities of their little fhelly horns. Thefe are of a red- difh colour, and may be diltinguiihed by an accurate obferver in form of fo many red prominent points j they all are re- tracted on the leaft touch, and are thrown out again as foon as all is quiet.. From thefe points, or the fmall apertures which give them a way out, are the cells of the Teredines to be traced. They are compufed of a pearly or fhelly matter, which forms a long tube with various windings and turnings, which marks the anode of the creature ; but which ulludly n.-ither adheres to the body of the animal, nor to the wood. Thefe cafes or tubes are always more or lefs loofe in the wood, and there is ever a large fpace within them, for the body of the animal to be furrounded every way with water. They are very imooth on the inner furface, and fomewhat rougher without j and are much harder and firmer in the cells of the older and larger animals, than in thole of the young ones. Thefe fhelly tubes are compofed of leveral rings, or annular parts j but thefe differ greatly in their length. There is an evident care in thefe creatures, as they are a re- public, never to hurt or injure one another's habitations ; and by this means each tubule or cafe is preferved entire, and in inch pieces of wood as have been found eaten by them into a fort of honeycomb, there never is feen a paffagc or commu- nication between any two of the tubules, tnough the woody matter between them often is not thicker than a piece of writing-paper.

The creature depofits its eggs on the outfide of the bottom of a ihip, or any other piece ot wood j the young worm hatched from this egg immediately eats its way into the wood, entering thus by a very minute hole, which is the reafon why the fur- face of wood ever fo much infeited with them fhevvs no fign of them j when they have made their way into the fubftance, they work forward in different directions, and when they find they approach one another, they turn fhort off, and di- rect their future courfe another way ; and to this feems ow- ing the twilled fhape of the tubules ; neither are thefe every where of the fame dimenftons, but are always wider where the head and the foleas-form fins are placed, than elfewhere ; a free motion of both thefe parts being extrenu-Iy neceffary to the well being of the animal.

The kind of wood in which thefe worms are lodged^ m.ikes a great difference in the appearance of their cells, as they work much more fpeedily and fuccefsfully in fome kinds, than in others. The fir and alder are the two kinds they feem to cat with the greatclt eafe, and in which they grow to the greateft fize. In the oak they feem to make but a very flow progrefs, and ufually appear very fmall and poorly nourifhed. The colour of their ihelly tubules is often brown in this wood ; which feems plainly owing to the effect of its juices. Although the head of this creature feems extremely well formed for the eating into any fubftancej yet the hardnefs of oak, and of fome other fpecies of wood in which thefe ani- mals are found, is fo great, that it feems fcarce credible that they could fairly h^ve eat their way into it. Reaumur has proved that fome kinds of fhell-filh have in part of their bodies a corrolive liquor ; and many have fuppofed the Teredo to have fuch a liquor, and by that means to deftroy the wood. But there are many reafons againft. this, as the exact and regular figure of the hole, the difficulty of corrod- ing wood, &e. Sellius refolves the whole into the mere repeated action of water. He fuppofes the whole body of the Teredo to be an hydraulic engine, which, as it is always furrounded with fea-water in its cells, takes in and throws out part of this as it pleafes ; and by continually difchargimr water with fome violence againft that part of the wood into which it would make its way* it is fuppofed by degrees either wholly to wear it away, or at leaft to fatten it in fuch a manner, as that it may be eafily gnawed away. By this means alfo the tracheal of. the wood and other vefiels, which in its growing ftate had ferved for its nutrition, are opened and enlarged, and make the way for wider holes much eafier than it would appear to any one who confidered the wood as one folid mafs.

When there comes an iron fpike, or other extraneous hard body in the way of one of thefe creatures in its courfe, it firft trys if it can eafily go round it, but if there appears any dif- ficulty in that, it continues its battery of water againft it, and either by continued induftry makes its way through it, Suptl. Vol. II.

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or perifhes in the attempt. The young ones when even but juft hatched from the egg, have this art of darting forth wa- ter, and by that means make their way, as well as by ero- fion into the wood.

One thing very remarkable 1% that the body of the Tereda when grown to a moderate fize becomes the habitation at pleafure of a vaft multitude of fmall fea-water infeas, which enter with the water into the cavity of the tubules, and are with it received into the body of the animal, and again thrown out againft the wood. In this, doubtlefs, many of them pe- rifh j but millions at a time are alfo to be feen, living perfectly at eafe in die belly of the creature.

The vaft increafe of thefe animals, and their fhelly tubules, naturally leads to a conlideration of the manner of their gene- ration ; and when we confider that each of thefe creatures is, from the time when it is produced from the egg, immediately lodged in a cell, in which it lives without the leaft poffibility of getting into that of another animal of its own kind, or receiving one of them into its own ; it is not eafy to account for the propagation of the fpecies in the common way. This, however, is foived by an accurate anatomical obfervation ot" the animals themfelves, fince in every individual the parts of generation of both fexes, and both the femen and ovula are found. Each individual therefore evidently ferves by it- felf for the propagation of the fpecies ; and this is probably very often the cale in earthworms, and other of the herma- phrodite animals. All the yet known kinds of thefe being foft-bodied ; and probably, though they often meet one ano- ther, and copulate in pairs, yet when they have not that op- portunity, the parts copulate in the individual; The eggs are found in great plenty in the bodies of thefe ani- mals in June, and are after this difcharged with the water into the lea, where the far greater part of them, doubtlefs, become food for other fmall animals ; and the few that come to good affix themfelves to any piece of wood they are warn- ed againlt, and there hatch and get into its fubftance in the manner of their parents.

Many other animals are great deftroyers of the eggs of the Teredo while they are fixed to the furface of the wood. The fcolopendrs marinae eat them in great abundance j thefhrimps alfo, and the pulmo marinus devour them. Poifonous ointments are alfo found to be of fome ufe in de- stroying them, on rubbing over the wood j fome have thought that burning the furface was an effectual way of preferving them, but this has been found to be otherwife. The fureit method of avoiding them in particular works, is the ufing bitter or very folid woods ; the firft kind they are found never to touch, and in the other they make but flow progrefs. Mix- tures of lime* fulphur, and collocynth, with pitch, for cover- ing over the furfaces of boards, &i, have been found of fome ule.

It feems very evident, that boards and other pieces of wood have been fubject to be eaten by thefe animals, from all times that we have any knowledge of; for the ftone called lapis Jy- ringoides is evidently no other than wood thus eaten, petrified by long lying in the earth, together with the tubuies of the worms. The maffes of this with the grain of wood yet plain in them, are common in many places among fea-fhelis, and other marine remains at great depths, and have evidently been brought thither in very diftant times, and before changes were made in the furface of the earth of which we have no accounts in our earlieft hiftories. SellH Hift. Natur. Te- redinis. TERENJABIM, in the materia medics of theantient Arabians, a word ufed to exprefs a kind of manna called by fome manna inajlichina-> from its round globules refembling the drops of maftic, and by the phylicians of many parts of the world at prefent manna ferftcutn. See the article Manna Per- Jicum.

Geoffroy indeed makes the Terniabin, or Terenjabin to be a kind of liquid manna ; but this is an error into which he has' been led by Bellonius, who, though a very cautious obferver in molt particulars, was evidently deceived in this, by the ac- counts of the monks of mount Sinai. Bellonius fays, that thefe monks collect a kind of liquid manna, which is called Tereniabin, and fold in the fhops at Cairo under that name ; and adds* that this is the met rofcidum of Galen^ and mel cedri- num of Hippocrates ; but it is very evident from the general confent of authors that this was not the fubftance called Te- reniabin by the Arabians, and now manna perficum. It feems indeed very probable, that this liquid manna collect- ed by thefe monks, is the fame fubftance called drofo- meli, and aeroynelt by Galen, and mel cedrinum by Hippo- crates (if there be no error in the text) though not the Te- reniab'in.

The defcription which Galen has left us of the mel rofcidum, and of the manner of collecting it on mount Sinai in his time, agrees very well with what Bellonius fays of it ; and thefe circumftances feem to be agreed upon by all authors in re- gard to it, but it does not appear that its ufe as a medicine was known any thing near fo early as in the days of Hippo- crates and Galen ; the Arabian phyficians feeming to have been the firft who brought it into general ufe as a purge. Galen takes notice of the metrofcidum^ or liquid manna, more G g g g «