Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/909

 PUT

PSEU DO- Fumaria^ in botany, a name ufed by fome for a fpe-

cies of Fumitory. See the article Fumaria, Suppl. PsEUDO-Z-o/aj, in botany, a name by which fome call the Guaiacana of Tournefort. See the article Guaiacana, Suppl. VsEUDO-Pibumum, in botany, the name given by Rivinus to

a fpecies of Lantana. See the article L ant an a, Suppl. fUDDiNG-grtfs, a name by which the pulegium, or penny- royal, a fpecies of mint, is called. Seethe articles Mentha and Mint, Suppl ViSDVixG-pipe-tree, theEnglifh name ofagermsof plants, called

by botanical writers Cajfia. See the article Cassia, Suppl. PUD£N-DUM-7V£,A a name ufed by Columna for the Aphro- dita, a genus of fea-infects. See the: article Aphrodit a, Append. ¥\3LEX~JquaticuS) the water-flea, a name fometimes ufed

for the water beetles. See the article Dytiscus, fupra. PULMONES-ffwr/?]/, in zoology, a name ufed by feveral au- thors for the JJrtica marines. See the article Urtica ma- rina, Suppl. PUMP [Cycl.) — The defcription of the Forcing-pump, given in the Cyclopaedia, is erroneous. This kind of Pump confifts of a barrel, in which there is a forcer, that is, a pifton, or embolus without a valve, which moves up and down in the barrel, This communicates with two pipes, the one called a j taking pipe, which goes down into the well, and the other called a forcing pipe, which goes upwards. There are two valves ; the one at any place of the fucking pipe, the other in the forcing pipe, both of which let the water go up, and hinder it from going down. Then when the forcer is moved upwards, as it rarifies the air in the fucking pipe (for the valve in the forcing pipe hinders the outward air, which prcfTes upon it, from going through) the water rifes in it, till after feveral ftrokes it comes to the forcer ; then at every time the forcer goes down, the water that is prefled downwards, being hindered from going through the valves of the fucking pipe, opens and goes through the valves in the forcing pipe. When the forcer goes up again, then the water in the forcing pipe Ihuts the valves there by its preiTure, and confequently the water in the well will rife up in the part or the forcing pipe, between that valve and the fucking pipe ; and the fame hap- pens at every motion of the forcer.

It is to be obferved in the Forcing-pump, that the nearer the forcer comes tp the well, the better it is. See Defagulhr's Courfe of Experim, Philof. p. 160, 161. ' As to the various kinds of Forcers, fee the article Forcer Append.

The Pump defcribed in the Cyclopaedia, under the name Forcing-pump, is properly a lifting-pump ; and the cdmmon Pump, which works by the preiTure of the air, is called a Sucking-pump. Dr. Dcfagulicrs, in his courfe of Experimental Philofophy, a has given a full account of the conftruotion of of all thefe kinds of Pumps, and of fome others more com- plex ; as alfo of their buckets, valves, and other parts belong- ing to them. [ * Vol. 2. p. 152, to r 66. J jAV-Pump. See the article AiR-pump, Cycl.

There are feveral inconveniencies attending hiK-pumps of the common form, tho' much improved from what they ufed to be formerly. Thefe inconveniencies are enumerated, and a me- thod fhewn to remedy them, by Mr. Smeaton, in the Phil. Tranf. Vol. 47. p. 415, feq.

This ingenious artift has fucceeded fo well in his conftruction of the Air-pump, as to be able to ratify air a thoufand times ; whereas the beft of the common Air-pumps, eftcemed ""ood in their kind, and in complete order, never rarified it above one hundred and forty times.

Mr. Smeaton's Air-pump acts alfo as a condenflng engine, by the very fimple apparatus of turning axock. So that this Air- pump is anuniveifal engine, for (hewing any effect arifmgfrom an alteration in the denfity or fpring of the air, and with a little addition may be made to mew the experiments of the air-fountain, wind-gun, &c. See the Phil. Tranf. loc. cit. p. 422, feq. PUMPELMOES, a name fometimes ufed for a fpecies of O-

range. See the article Orange, Suppl. PURGING-»af, or Phyfic-nut, the name by which fome call the Ricinoides, a dtftinct genus of plants. See the article

RlCINOlDES, Sltppl.

FVR?LE-wort, a name given to feveral fpecies of trefoil, of a purple colour. See the article Trefoil, Suppl.

VURSLAIN ( Suppl.) — Sm-Purslainj a name by which fome call two very different genufes of plants, the Atriplex and Cheno- podium. See the articles Atriplex and Chenopodium, Suppl.

PUTREFACTION (Suppl.) — It is an obfervation of Lord Bacon, that an inquiry into the means of preventing or flay- ing putrefailion, is of excellent ufe in phyfic. Dr. Pnngle has made a great many curious experiments and remarks on this fubject, which are publifbed by way of Appendix to his Obfervations on the Difeafes of the Army. Pitfrefaftion is one of the inftruments of nature, by which many great changes are brought about. With regard to me- dicine, we know that neither animal nor vegetable fubftances APPEND.

PUT

can become aliment without undergoing fome degree of Pa-

trefaclion. Many diftempers proceed from a deficiency of this aflion. The enfis of fevers feems to depend upon it : and even animal heat, according to Dr. Stevenfon, does the lame. See the article Heat, Suppl.

Now, that the concoction of the humours is nothing elfe but Putrefailion, feems probable from hence, that whenever they are in that ftate, they are always more fluid, and fitter to pafs through the fmaller veffels, where they floated before Again, the offenfivenefs of the fweats, or other excretions confequent on a crifis, is likewife a fure fign of a hi^h degree of corruption. The time of refolution or PutrtfaMmte- pends on the degree of heat, the habit of the patient, and on the part obftru&ed. Refolution is the Puirefatlion of the im- pacted humour only, but fuppuration implies a corruption of the veflels alfo. This manner of fpeaking, indeed, has been diluted, from the prejudice that nothing was putrid but what was offenfively fo ; whereas, in fa&, every fibre becoming more tern r, and humour thinner, may be confident -as pu- trid in fome degree, whether the change tends to the better health, or to the deftruction of the perfon, or whether it be- comes grateful or offenfive to the fenfes. Pringle, Obferv. on Difeaf. of the Army. p. 337.

Mr. Boyle has ufed the words fermentation and Putrefailion of the blood promifcuoufly, in his treatife on the human blood. Stahl and other celebrated chemifls likewife ufe the terms putrid ferment. See the article Ferment, Suppl. Putrefailion i» always found to generate air. Hence, though flefli, as well as blood, be fpecifically heavier than water, yet dead bodies are found to float, after- lying fome time at the bottom, from air generated in the bowels by Putrefailion. Now, as it has been found by experiments, that the blood and other animal fubftances begin to emit air, before they are fo far corrupted, as the fame frequently are in putrid difeafes, it is probable that feveral of the fym'ptoms in deep furfelts may be owing to the action of the confined air. As all the humours of animal bodies become thinner by Putre- failion, fo the folid or fibrous parts are thereby relaxed or ren- dered more tender. And hence the extraordinary bulk of the heart, liver, and fpleen, incident to perfons labouring un- der putrid difeafes, may be accounted for. It is remarkable, that in directions of people who die of the plague, the heart is almoft always found of an uncommon bignefs j and as to the fcurvy, the'liver and fpleen are fometimes inlarged tofuch a degree, that the tumour may be feen outwardly. Id. ibid, p. 391, feq.

It being a received opinion, that bodies become highly alkaline by Putrefailion, the Doctor made the following experiments, in order to difcovcr how far this might be true. The ferum of human blood putrified, made, with a folution offublimate, firft a turbid mixture, and afterwards a precipi- tation ; which is indeed one of the tells of an alkali, but not to be admitted here, fince the fame thing was done with the recent urine of a perfon in perfect: health, which is never accounted alkaline. The fame ferum did not tinge the fyrup of violets green, and made no cftervefcence when the fpirit of vitriol was poured upon it. The experiment was- twice made upon portions of different ferums, both highly putrid ; and once on water, in which corrupted fiefii had been fometime infufed ; and the molt that could be found was, that a reddifh call: having been previoufly given to the fyrup with an acid, this colour was rendered fainter, hut not deftroyed by the putrid humours. And as to effervefcence, the fpirit of vitriol being dropped into thofe liquors unmixed, and alfo diluted with water, the mixture was quiet, and only a few air-bubbles appeared on fhaking the glaffes.

Upon the whole, though there were fome marks of a latent alkali in the putrid ierum, they were fo very faint, that a quantity of water equal to that of the putrid liquors, mixed with only one drop of fpirit of haitfhorn, being put to the fame trial, fiiewed more of an alkaline nature, than any of the other.

It has alfo been a maxim, that all animal fubftances, after Putrefailion, being diftilled, fend forth a great quantity of volatile fait in the firft water; but Mr. Boyle found, that this held good only in urine ; and that in the diftillation of the ferum of human blood putrefied, the liquor which came over firft had little ftrength, either as to its fmell or tafte, and did not at firft eftervefce with an acid. And here it may be ob- ferved, that the chemifls have generally applied thofe proper- ties which they difcovercd in urine, to all the humours indif- ferently ; whereas, in fact, there is a great diverfity : for fome animal fubftances, fuch as urine, the bile, and the crauamentum of the blood, foon putrefy ; the ferum, the fahva, and the white of an egg, (lowly. Yet thofe that foon- eft corrupt, do not always arrive at the higheft degree of Putrefa£iion\ thus, the bile is fooneft corrupted, but the ranknefs of it is not to be compared to that of flrfti ; and the white of an egg is not only much lefs difpofed to putrify than the yolk, but when corrupted, yields a different and lefs often live fmell.

Do£f.or Pringle farther obferves, that it feems peculiar to ftale

urine to contain an alkaline fait, which, without diftillation,

2 L makes