Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/730

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Hits kinds ; fmce when we fee the multitudes of fmall fly-worms already living on any of theft fubftances, it is not to be known from all their fuccceding changes, whether they were pro- duced from the body of the parent-fly in thatfhte, or as eggs. To dillinguifh with certainty, whether a fly be oviparous or viviparous, the belt means is certainly to obferve. it in the in- ftant of its producing its eggs, or young ones, which ever they are ; but asljhat is a moment not eafily feized, its place may be fupplied ' either by opening the body of a female fly, di- ftc-nded and full of eggs cr young, and the arrangement and form of the bodies contained, will eafily determine the ob- server, whether he is to look on them as eggs, or embryo-ani- mals : But a yet more certain way is to take a fly which ap- pears ready to depofit its future progeny, and fqueezing its body, force out a part of what would naturally have been thrownout in a. little time, and it will be eafy to fee whether thefe are eggs or worms.

It is eafyto find about our houfes one of thefe fpecics of vivi- parous flies; the creature is always buzzing about the places where meat is kept, and loves to depofit her young as the common, blue flefh-fly does its eggs, on meat. Its way of carrying its wings is the fame with that of the blue fly, and its antenna; are of tbe fame form. It at leaft equals the blue fly in length, but its body is lefs thick, and is a little bent at the hinder part ; its colour is grey. Oil the corcelet this colour arifes from a feries of long but irregular afh-coloured lines ranged on a brown ground : A fimilar colour is alfo fcen on the upper part of the rings of the body ; but the grey fpots here are much fhorter than on the corcelet, and almolt fquare, and the colour between thefe is a {hining brown, which, in fome lights, has a caff of blue. Its legs are black ; its petty wings whitifh ; and its reticular eyes reddifh. When a female of this fpecies is taken on meat, and has not too flat a body, one may always expect the fuccefs of an at- tempt to find that fhe is big with living young. Taking a fly of this kind, and in this ftate, between ones fingers, and ob- ferying its hinder part, one fhall ufually fee a fmall and fome- what cylindric oblong body thruff. itfelf out, and move from fide to fide, and fometimes make many finuofities ; this will be found to become more and more long, as it is more and more difengaged from the body of the fly, and is indeed no other than a worm now firft appearing, and endeavouring to difengage itfelf from the body of its parent; a few moments now lets it at liberty ; and it is no fooner fallen off, than the end of another like worm appears at the fame apperture, and in a few moments gets its liberty, as the former did ; this is fucceeded by another, and fo on for ten, twenty, or fome- times many more ; and when the creature feems tohave done producing them, the flighteft prcfl'ure on the belly will fend out numbers more, and fometimes two or three are, by this means, forced out at the pafTage together. The aperture is naturally large, through which they are to pafs, and is, befide this, capable of great extenfion.

It is ufually the head of the worm that firft makes its appear- ance ; but this is not always the cafe; and efpecially where external prcfl'ure has been ufed, 'tis not uncommon for the hinder part of the worm to appear firft ; and when many of them have, by this means, been forced cut together, and the pafTage by this means is become enlarged, 'tis no uncommon thing for a number of them coming out together, to brina with them a part of the membrane in which they had been enclofed, while in the body of the parent-fly. The confideration, however, of the many animals of the in- fefi clafs, which are often found to breed and nourifh in their bodies worms, not their own offspring, but that of the eggs of other infeas lodged in their flefh, and eating them up alive, might lead one to doubt whether thefe worms, inftead of being the genuine offspring of the fly, were not a fet of cruel enemies which had been long devouring and preying on its en- trails ; and what might fomething favour this opinion, is, that the fly ufually dies foon after it has finifhed its depofiting them. But there needs no more to refute this error, than to give thefe new-born worms fome meat ; the eagernefs with which they bury themfelvcs in it, is a proof of their being in a condi- tion to eat, and that greedily ; whereas the worms bred in the bodies of infeas, from the eggs of other creatures, when they leave the body of the creature, have no farther occafion for food, but have nothing to do but to prepare for their transfor- mation. On the other hand, if one continues to obferve thefe worms produced from the fly, one fhall find that they behave in. all refpeQs like thofe produced from the eggs of the blue flefh-fiics ; they eat the meat to a certain time ; then having obtained their full growth, they leave the fubftance they had fed on, and run into the earth, where they are afterwards found in form of nymphs, enclofed in a fhell made of their own (kill ; and, at proper diflances of time, there are pro- duced from thefe, flies male and female ; the latter, in all re- fpeas perfeaiy like the parent-fly, from whofe body the worms had been feen to come.

There are, befide this fpecies, two other of the viviparous flies, which are not uncommon. Both 'thefe, in a great mea- sure, referable the former ; but their bodies are fhorter ; and, m the whole, they much more than the other approach to the

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form of the blue flefh-fly. They are alfo fmaller than the for- . mer fpecies ; the one of them, however, on the whole*'- is not much fo, and, though fhorter, yet is much thicker both in the corcelet and- body. They are both,, though fmaller than that kind, yet tolerably large flies, and are bigger than the common horfc-fly.

On the leaves of ivy alfo there are often feen, about autumn two other fpecies of viviparous flies, which are eafily diffin- guifhed fromaU the otheis. Thofe of one of thefe -fpecies are larger than the great blue flefh-fly, and have a fhorter and thicker body than that kind. The manner of carrying the wings is alfo the fame in both; but though both have antennse of the battledore kind., yet they are evidently diftihguilhed. by this, that the extremities of the one are lenticular, and .thofe of-the others prifmatic. Near the origin of each wing-thefe have a brownifh fp.ot, as have thofe oviparous flies: which ufually have in .their body only two large eggs at a time, and which are produced of the yellow worms, fo commonin cpw- dung. But thefe viviparous ones differ from thofe ; flies,! in that they arc larger, and of a deep, but dead brown j whereas the others are black, or nearly fo. i!T

The other fpecies is not much unlike this in form, but is fmaller, being not more than of the bignefs of the blue flefh- fly, and of a bluifh black ; fo that it might eafily be miltaken for one of the common flefh-fiies, were it not for the two brown fpots at the infertion of the wings ; and both this and the former fpecies are plainly diltinguilhed from the cow-dun^- fly before delcribcd, by their wanting the. gold-coloured down which that has on the fore-part of its head. Reaumur, Hift. Infect, vol. 4. p.405. feq.

ULCER (Cycl.)— Callous Ulcers. The cure of callous VU cers is attended with very great difficulties, and indeed no cure is to be expected, till the callus is perfectly extirpated. This is to be done three ways ; the mildeft of thefe, which is fuited to recent callufes, and fuch as are not yet become very hard, is by means of corrofive medicines, and of thefe the milder kinds are often fufficient ; burnt alum either rubbed on the parts alone, or applied with an equal part either of the com- mon digeftive or bafiHcon, will fometimes anfwer this purpofe in thefe cafes, as will alfo the /Egyptian ointment, to which a fmall quantity of red precipitate may be added occafionally. If the callus will not yield to thefe remedies, it muff, be attacked with the common cauftic, or with butter of antimony, or with a folution of quickfilver in fpiritof nitre. Another mild method of extirpating callofities we are alfo taught by Le Dran. This author advifes to apply, for four or five days, a planner made of the diachylon with the gums, and the mercurial plafter, with a quadruple proportion of mercun', mixed in equal quantities ; this is to be renewed mornine and night,, in order to foften the callous lips as much as poffible ; after this he makes numerous incifions, fo deep as to pafs quite through the fubftance of the callus, and flops the blood which flows from thefe with dry lint ; then the fame plafter is again applied, and fo laid on, that it may touch the naked in- cifed lips. After about four days of this treatment, the fcari- fications are again repeated, and this to a third or fourth time, if the callohty be not before deftroyed.

If callous Ulcers are attended with fiftulous finufes, thefe muffc always be laid open, before we can attempt to deftroy the callus, with any probability of fuccefs j after this they may be cured as before directed ; or, if the ufe of the knife be not fafe, or the patient dreads it too much, it will be proper to form tents, and thruft them up the finus, firft anointing them with the /Egyptian, or with Wurtz's brown ointment. By thefe methods a callus, that is not of long flanding, may be extirpated ; if the ends of the tents, laft mentioned, be touched with butter of antimony, red precipitate, or the infernal ftonc, the bufinefs, in that method, will be the more eafily effected ; and, in cafes of this kind, where the callus cannot be reached by the corrofive end of the tent, it is a very good method to inject into the finus either the phagedenic-water, or a folution of the /Egyptian or brown ointment in fpirit of wine. The opening of the finus fhould be then clofed, to keep in the in- jection as long as may be, and the operation frequently re- peated.

Sometimes, however, it is found abfolutely neceflary to ufe the knife, as in callous Ulcers, or fiftula?, that are of very- long ftanding, and that have formed variety of finufes, and when either nothing can be done by corrofive medicioes, or elfe that they tear and corrode the nerves, and bring on convul- fions, and other bad fymptoms, before they affect the callus. In thefe cafes the beft and fafeft way is to lay open the finus, taking care not to wound the nerves, tendons, and arteries ; and, after that, all the callufes may be eafily deftroyed by the common methods. Finally, if even this method fhould

. not have the defired effect ; and if the patient has a confidera- ble fhare both of ftrength and courage, and the fituation ofthe nerves and arteries is favourable, the callus parts muft be ail either entirely cut out with the knife, or burned away byrhe actual cautery. This operation, though a very painful one, is attended with this great good conkquimce, that it will -re- duce the moft inveterate callous Ulcer to the ftate oi a frefh wound i and unlefs a caries, or bad habit of body, ortheppx,


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