« AnteriorContinuar »
with myrrh. As part of this fubftance diffolves in water, eight grains were made into an emulfion; but most of it fubfiding, I could not reckon on a folution of more than one or two grains; which nevertheless preferving the flesh longer than the standard, we may account the foluble part of myrrh perhaps about 30 times ftronger than fea-falt.
Aloes, Afa fetida, and the Terra Japonica, diffolved in the fame manner as myrrh, like it fubfided, and with the fame antifeptic force. But gum ammoniac and Sagapenum fhewed little of this virtue. Whether it was that they oppofed putrefaction lefs, or that all the antifeptic principle fell with the groffer parts to the bottom. Three grains of opium diffolved in water did not fubfide, and refifted putrefaction better than the falt. But I obferved that more air than usual was generated, and the flesh became tenderer than with any of the ftronger antiseptics.
Of all the refinous fubftances camphire refifted moft: two grains diffolved in one drop of spirit of wine, five grains of fugar, and two ounces of water exceeding the ftandard tho' during the infufion, moft of the camphire flew off, fwam a-top, or ftuck to the phial. Suppofe only the half loft, the remainder is at least 60 times stronger than falt; but if, as I imagine, the water fufpended not above a tenth part, then camphire will be 300 times more antifeptic than fea-falt. That nothing might be afcribed to the minute portion of the fpirit, used in this experiment, I made another folution of camphire in a drop or two of oil, and found this mixture lefs perfect, but ftill beyond the ftandard.
4. I made ftrong infufions of camomile flowers, and of Virginian fnake-root; and finding them both greatly be yond the standard, I gradually leffened the quantity of thefe materials, till I found five grains of either impart a virtue to water fuperior to 60 grains of falt. Now as we cannot suppose these weak infufions contained half a grain of the embalming part of thefe vegetables, it follows, that this must be at least 120 times more antifeptic than common falt.
I alfo made a frong decoction of the Bark, and infused a piece of flesh in two ounces of it ftrained; which flesh never corrupted, tho' it remained two or three days in the furnace, after the ftandard was putrid. In this time the decoction became gradually limpid, whilft the groffer parts fubfided: By which it appears, that a moft minute portion
of the bark intimately mixed with water (perhaps less than of the fnake-root, or camomile flowers) is poffeffed of a very extraordinary antifeptic force.
Befides thefe, pepper, ginger, faffron, contrayerva-root, -and galls, in the quantity of 5 grains each, as alfo 10 grains of dried fage, of rhubarb, and the root of wild valerian*, feparately infused, exceeded 60 grains of falt, mint, angelica, ground-ivy, fenna, green tea, red rofes, common wornwood, muftard, and horfe-radifh, were likewife infused, but in larger quantities, and proved more antifeptic than the standard. And as none of these can be supposed to yield in the water above a grain or two of the embalming principle, we may look upon them all as very powerful refifters of putrefaction. Farther, I made a trial with a decoction of white poppy-heads, and another with the expressed juice of lettuce, and found them both above the ftandard.
By these specimens we may now fee how extensive antifeptics are; fince, befides falts, fermented fpirits, fpices and acids, commonly known to have this property, many refins, aftringents, and refrigerants, are of the number; and even those plants called anti-acids, and fuppofed hafteners of putrefaction; of which clafs horfe-radifh is particularly antifeptic. And indeed after these trials, I expected to find all diffolvable fubftances endowed with fome dedree of this quality; till, upon further experiments, I perceived fome made no refiftance, and others promoted corruption. But before I enter upon that part of my subject, it will be proper to relate fome other experiments more nearly connected with the preceding.
5. Having feen how much more antifeptic thefe infufions were than fea-falt, I then tried whether plants would part with this virtue without infufion. For, this purpose, having three fmail and thin flices of the lean of beef, I rubbed one with the powder of the bark, another with fnake-root, and a third with camomile flowers. It was in the heat of fummer, yet, after keeping these pieces for feveral days, I found the flesh with the bark but little tainted, and the other two quite sweet. The fubftance of all the three was
*Tho' the experiment was only made with ten grains of the powder of this root, yet, confidering how long that quantity refifted putrefaction, we may reckon the valerian among the froneft antifeptics.
firm; particularly that with the comomile, which was fo hard and dry, that it seemed incorruptible. Why the bark had not altogether the fame effect, was probably owing to its close texture.
6. I have alfo made fome attempts towards the sweetening of corrupted flesh, by means of mild fubftances; because diftilled fpirits, or ftrong acids, the only things known to answer this intention, were of two acrid and irritating a nature to be thoroughly ufeful, when this correction was most wanted. As for falts, befides their acrimony, it is well known, that meat once tainted will not take falt.
A piece of flesh weighing two drachms, which in a former experiment had become putrid, and was therefore very tender, spongy, and fpecifically lighter than water, was thrown into a few ounces of the infufion of camomile flowers, after expreffing the air, to make it fink in the fluid: The infufion was renewed twice or thrice in as many days; when, perceiving the Fator gone, I put the flesh into a clean bottle, with a fresh infusion; and this I kept all the fummer, and have it still by me, quite sweet, and of a firm texture *. In like manner I have been able to sweeten feveral fmall pieces of putrid flesh, by repeated affufions of a ftrong decoction of the bark; and I conftantly observed, that not only the corrupted smell was removed, but a firmness restored to the fibres.
Now, fince the bark parted with so much of its virtue in water, it was natural to think it would ftill yield more in the body, when opened by the Saliva and bile; and therefore it was by this antifeptic virtue it chiefly operated. From this principle we might account for its fuccess in gangrenes, and in the low ftate of malignant fevers, when the humours are fo evidently putrid. And for intermittents, in which the bark is moft fpecific, were we to judge of their nature, from circumstances attending them in climates and feafons moft liable to the diftemper, we should affign putrefaction as a principal caufe. They are the great endemic of all marfhy countries, and rage molt after hot fummers, with a close and moift ftate of air. They begin at the end of fummer, and continue thro' autumn; being at the worft, when the atmosphere is most loaded with
*This piece has been kept twelvemonths in the fame liquor, and is ftill firm and uncorrupted.
the Effluvia of ftagnating water, rendered more putrid by vegetables and animal fubftances that rot in it. At fuch times all meats are quickly tainted; and dyfenteries, with other putrid diftempers, coincide with these fevers. The heats difpofe the humours to acrimony; the putrid Efluvia are a ferment; and the fogs and dews, fo common to those climates, ftop perfpiration, and bring on a fever. The more thefe caufes prevail, the easier it it is to trace this putrefaction of humours. The Naufea, Thirft, bitter Tafte of the mouth, and frequent evacuations of putrid bile, are common fymptoms and arguments for what is advanced. We fhall add, that in moift countries, in bad feafons, the intermittents not only begin with fymptoms of a putrid fever, but, if unduly managed, eafily change into a putrid and malignant form, with lived fpots and blotches, and mortification of the bowels. But, as a thorough difcuffion of this question might carry us too far from our prefent fubject, and be unfeasonable here, I fhall refer it to its proper place, and only remark, that whatever medicines (befides evacuations and the bark) have been found useful in the cure of intermittents, they are, fo far as I know, all highly antifeptic; fuch are, myrrh, camphire, camomile flowers, wormwood, tincture of rofes, alum with nutmeg, vitriolic or ftrong vegetable acids with aromatics.
Thus far, fays Dr. Pringle, I have only related my experiments upon flefh, or the fibrous parts of animals; I Thould next proceed to fhew, what effects antifeptics have upon the humours; for, though from analogy we may conclude, that whatever retards the corruption of the folids, or recovers them after they are tainted, will act fimilarly upon the fluids; yet, as this does not certainly follow, I judged it neceffary to make new trials; which, with fome experiments on the promoters of putrefaction, the reverse of the former, will be given in our next, from the fame number of the transactions.
ART. IV. The Nature of the nervous Fluid, or animal Sprits demonftrated, with an introductory Preface. By Macolm Flemyng. M. D. 8vo. 1 s. Millar.
HE ingenious author of this differtation is hardy enough to affirm his demonftration of the nature of that most exquifite animal fluid, whofe very exiftence has been denied by fome; while the precife Analysis or compo VOL, VI.
fition of it has been modeftly declined by many celebrated phyficians, who have nevertheless afferted the action of the nerves to refult immediately from the energy of a contained fluid, and not from any chord-like elaftic vibration. Now tho' our author takes the existence of this nervous fluid, and, as we imagine, very juftly, for granted, we shall beg leave to contract the excellent arguments of Dr. Haller for the fecretion of this fluid in the brain, from Dr. Flemyng's own quotation of him, for the fatisfaction of any of our medical readers, who might not have fully determined for themselves on this curious hypothetical fubject.
First then Dr. Haller obferves, that the external or cortical part of the brain, which is manifeftly very vascular, is continued to, and cohercs with, the internal medullary part: and as a great quantity of blood is inconteftably carried to the brain, by the carotid and vertebral arteries, if the fibres of the Medulla, which are inextricably connected with the vascular texture of the cortical part, were not hollow, but folid, they must repell the blood by their folidity, and fo render its derivation there at least useless. But as the medullary and cortical parts increase alike, their equal growth manifeftly points to one common cause of it, to wit, the superior force of the heart extending the blood-veffels; from whence the medullary, as well as cortical part of the brain, must be concluded to be vascular.'
The Phænomena of wounded nerves, he obferves, are inconfiftent with their elafticity. A nerve cut afunder does not retract its divided extremities towards the folid parts to which it adheres, but becomes rather longer, extruding its Medulla into a round tubercle. And if it hook on appulfe, like an elaftic chord, it fhould be compofed of hard fibres,. having their extremities fixed to fome firm bodies and bent, fince ftrings otherwife conftituted and difpofed are inelaftic and infonorous. But it is evident that all nerves are medullary and foft at their origin, as well as void of tenfion; fome being foft in every part, as the olfactory nerve, and the foft portion of the auditory nerve, where the greatest vibration might be expected, as it is the inftrument of hearing. And tho' they are hard in fome places, he affirms they grow foft in the Vifcera, the mufcles, and the fenfories, before they exert their functions: befides. which it is impoffible that fome nerves, in certain fituations, can tremble, as thofe of the heart, which are fastened to the great veffels and the Pericardium. Furthermore, the influence of an irritated nerve is never propagated upwards,