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the blood pafles thro' their fubftance with difficulty, and in but very fmall quantity, fince the loWnefs of the fides of the lungs, the largenefs of the thymus* and the arch formed by the dia- phragm cannot but keep them in a continual ftate of com- ureflion. This compreflion of the lungs does that to the pul- monary arteries, that a ligature would do, which ftiould pre- vent a part of the blood puffing thro' thofe arteries at every fyftole of the heart, and cannot fuffer them to become depref- fed, or to part at every fuch fyftole in the time required for it, with more than perhaps, a fourth, a third, or the half of that blood, which they ufe to receive at every pulfation. It is eafy to conceive, that the blood thus left behind in the veflels of the lungs from one pulfation to another, and mixed with the new blood of ftill fucceeding pulfations, muft, in thus accumulating itfelf by degrees, more and more feparate and diftend the fides of the veflels, and more augment their dia- meters, than would have been the cafe, if from the beginning the ramifications of the arterial veflels of the lungs had been more perfectly empty : for tho' at every pulfation, there pafles certainly from the trunk of the artery, but a fmall quantity of blood into the ramifications of the veflels of the lungs, yet this fmall quantity added to the excefs of the former pulfations, and mixed with them, muft in procefs of time, form a little mafs, and produce an extenflon and confiderable bulk in the veflels.
It is not difficult to conceive that the compreflion of the pul- monary veflels will make its effects fenftble at greater diftances than barely the extent of thofe veflels, and that indeed not on- ly to the foramen ovale, but alfo to the left ventricle of the heart and to the aorta ; that the blood which is carried back by the reflux toward the foramen ovale, muft naturally become lefs and lefs, as the new born infant enjoys the benefit of refpi- ration, and the blood of the two pulmonary arteries, finds its accefs as eafy as it was before difficult ; and finally, that of all the blood which arrives every inftant at the heart, there will be only a fmall part that will make its way thro' the lungs; the greater quantity, while the foramen ovale remains yet open, finding itfelf a much fhorter paflage, by means of that aper- ture, and of the yet open arterial canal.
It is evident therefore, from all that has been obferved, that the foramen ovale, and the canal of communication in the fcetus are in reality, no other than a fort of fubfidiary parts to the lungs, formed only for a certain time, and to become u^- ]efs, and difappear when the act of refpiration has given the turn to the circulation of the blood, which it is to retain thro' the whole life of the animal. Memoirs Acad. Scien. Par. 1739.
Dr. Trew does not agree with Monfieur Mery's hypothefis, which he has minutely examined, and affirms, that the mem- brane of the foramen ovale is fo placed as to permit the blood to pafs freely from the right auricle to the left, during the diaftole of the auricles, but never from the left auricle to the right. Phil. Tranf. N J . 457. Sea. 7.
The foramen ovale has fometimes been found open in adults. See Phil. Tranf. N°. 460. Sect. 5.
FORCE, in mechanics. See the Appendix.
FORCEPS (Cycl.) — Mr. Monro defcribes and gives a figure of a forceps, the mouth of which has on each fide two fmall {harp teeth, which apply clofc to one another, when it is fhut. This forceps when fhut may be fafely introduced into a gun- fhot wound, and the blades being immediately opened behind the bullet, the teeth will pierce into the lead, and hold it fa ft enough to bring it out, tho' they are not advanced fo far as the largeft part of it. Med. EflEdinb. vol.5, art. 41.
FORCING, in the wine trade, a term ufed by the wine-coop- ers for the fining down wines, and rendering them fit for im- mediate draught. See Fining.
The principal inconvenience of the common way of fining down the white wines by ifinglafs, and the red by whites of eggs, is the flow nefs of the operation; thefe ingredients not performing their office in lefs than a week, or fometimes a fortnight, according as the weather proves favourable, cloudy, or clear, windy or calm: this appears to be matter of con- ftant obfervatlon. But the wine merchant frequently requires a method that (hall, with certainty, make the wines fit for tafting in a few hours. A method of this kind there is, but it is kept in few hands a valuable fecret. Perhaps it depends up- on a prudent ufe of a tartarized fpirit of wine, and the com- mon forcing, as occafion is, along with gypfum, as the prin- cipal ; all which are to be well ftirred about in the wine, for half an hour before it is fuffered to reft. Shaw's Lectures, p. 208.
Forcing, among gardiners, is ufed for producing ripe fruits from trees before their natural feafon. The method of doing it is this ; a wall ftiould be erected ten foot high ; a border muft be mark- ed out on the fouth fide of it, of about four foot wide, and fome flakes muft be fattened into the ground all along the edge of the border ; thefe fhould be four inches thick. They are in- tended to reft the glafs lights upon, which are to Hope backwards to the wall, to flicker the fruit as there fhall be occafion; and there muft be at each end a door to open either way ac- Su PPL. Vol, I,
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cording as the wind blows. The frame fhould be made move- able along the wall, that when a tree has been fined one year the frame may be removed to another, and fo on, that the trees may be each of them forced only once in three years, at which rate they will laft a long time. They muft be alwats well grown trees that are chofen for fining, for young ones are foon deftroyed, and the fruit that is produced from them, is never fo well tafted. The fruits moft proper for this management are the avant, or fmall white nutmeg, the albermarle, the early Newington, and the brown nutmeg peaches ; Mr. Fairchild's early, and the elrugo and Newing- ton neflarins ; the mafculine apricot, and the may-duke and may-cherry. For grapes, the white and black Tweet-water, are the propereft ; and of goofebcrries, the Dutch-white, the Dutch early-green, and the walnut-goofeberry ; and the large large Dutch white, and large Dutch red currants. The dung before it is laid to the wall fhould belaid together on a heap for five or fix days, that it may heat uniformly thro', and when thus prepared, it muft be laid four foot thick at the bafe of the wail, and go doping up, till it is two foo' thick at the top. It muft be laid at Ieaft within three or four inches of the top of the wall, and when it finks, as it will fink two or three feet, frefh dung muft be laid ; for the firft heat will do little more, than juft fwell the bloflbm buds. The covering the trees with glafl'es is of great fen-ice, but they ftiould be taken off to admit the benefit of gentle fhowers to the trees, and the doors at the ends fhould be either left intire- ly open, or one or both of them opened, and a mat hung be- fore them, at once to let the air circulate and to keep out the frofts.
The dung is never to be applied till toward the end of No- vember, and three changes of it will be fufficient to ripen the cherries, which will be very fine in February. As to the apri- cots, grapes, neflarmes, peaches and plumbs, if the weather be milder, the glafies are to be opened to let in funfhine or gentle fhowers.
If a row or two of fcarlet ftrawberries be planted at the back of the frame, they will ripen in February, or the beginning of March ; the vines will bloflbm in April, and the grapes will be ripe in June.
It fhould be carefully obferved not to place early and late ri- pening fruits together, becaufe the heat neceffary to force the late ones will be of great injury to the early ones, after they have fruited.
The mafculine apricot will be ripe in the beginning of April, the early neflarines will be ripe about the fame time, and the forward fort of plumbs by the latter end of that month. Goofeberries will have fruits fit for tarts in January or Febru- ary, and will ripen in March, and currants will have ripe fruit in April.
The trees need not be planted fo diftant at thefe walls as at others, for they do not flioot fo freely as in the open air : nine feet aliinder is fufficient. They ftiould be pruned about three weeks before the heat is applied. Miller's Gard. Diet. FOREFANG,or Forefehc, in our old writers, is the taking of provifion from any one in fairs or markets, before the king's purveyors are ferved with necefliiries for him. The word is Saxon, compounded of fere, ante, and fangen, prendere. I OREG AVEL, forgabuhm, in our old writers, is ufed for a
fmall referved rent in money, or quit-rent. FOREGOERS, in our old writers. The king's furveyors were thus called from thtir going before, to provide for his houfehold 36 Ed. III. 5. FOREHEAD. Wounds of the Forehead. After a wound in this partis cleanfed from grumous blood and extraneous bodies if any were left there, it ftiould be dreflid with balfam of Pe- ru, or fome other vulnerary ballam ; the lips of the wound are then to be kept together by long (lips of flicking plaifter, and over this a vulnerary plaifter is to be laid. Where the wound is large, thefe plaifters will not be fufficient to bring on an even cicatrix ; therefore to forward this end, the wound fhould be fprinkied with a compound powder of comfrey root and gum tragacanth and arabic, and with gum farcocolla in pow- der ; and then the plaifters, compreffes, and proper bandages are to be applied. The bloody future is never to be uled in any wound of the face if it can be avoided, becaufe the flitches increafe the number of the fears. If a wound of the forehead is made in a ftrait line, the uniting bandage will be of great fervice in forming a fine cicatrix : but if the forehead is wound- ed tranfverfely, and the fibres of the frontal mufcle are divi- ded, it occafions a great deformity ; for the power of lifting up the eye-brows, and of contracting the skin of the forehead ceafes. In this cafe after cleaning the wound, it is beft to unite it with a flitch or two, dreffing it with a vulnerary ballinn and laying on flicking plaifters, fecuring all wiih a proper bandage, and enjoining the patient to keep himltlf ftill. I n young and healthy perfons, the fibres of the mufclesjoin and unite when this method is ufed, without coming to a fuppura- tion. Hei/ler's Surg. 78.
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