firm; particularly that with the camomile, which was fo hard and dry, that it feemed incorruptible. Why the bark had not altogether the fame effect, was probably owing to its close texture.

6. I have also made fome attempts towards the sweetening of corrupted flesh, by means of mild fubftances; becaufe diftill'd fpirits, or ftrong acids, the only things known to answer this intention, were of two acrid and irritating a nature to be thoroughly useful, 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, fpongy, 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 infufion; and this I kept all the fummer, and have it ftill by me, quite sweet, and of a firm texture*. In like manner I have been able to fweeten several small pieces of putrid flefh, by repeated affufions of a strong decoction of the bark; and I constantly obferved, that not only the corrupted smell was removed, but a firmness reftored to the fibres.

Now, fince the bark parted with fo much of its virtue in water, it was natural to think it would still yield more in the body, when open'd by the Saliva and bile; and therefore it was by this antifeptic virtue it chiefly operated. From this principle we might account for its fuccefs 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 circumftances 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 moft after hot fummers, with a close and moist state of air. They begin at the end of fummer, and continue thro' autumn; being at the worst, when the atmosphere is moft loaded with

*This piece has been kept a twelvemonth in the fame liquor, and is still firm and uncorrupted.

the

the Effluvia of ftagnating water, render'd 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 thefe fevers. The heats difpofe the humours to acrimony; the putrid Effluvia are a ferment; and the fogs and dews, fo common to those climates, ftop perfpiration, and bring on a fever. The more these causes prevail, the eafier it is to trace this putrefaction of humours. The Naufea, Thirft, bitter Taste 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 feasons, the intermittents not only begin with fymptoms of a putrid fever, but, if unduly managed, eafily change into a putrid and malignant form, with livid fpots and blotches, and mortification of the bowels. But, as a thorough difcuffion of this queftion might carry us too far from our present 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 flesh, or the fibrous parts of animals; I fhould 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 tranfactions.

ART. IV. The Nature of the nervous Fluid, or animal Spirits demonftrated, with an introductory Preface. By Mal colm Flemyng, M. D. 8vo. Is. Millar.

TH

HE ingenious author of this differtation is hardy enough to affirm his demonstration of the nature of that moft exquifite animal fluid, whofe very existence has been denied by fome; while the precife Analyfis or compoVOL. VI.

fition

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 elastic vibration. Now tho' our author takes the existence of this nervous fluid, and, as we imagine, very juftly, for granted, we fhall 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 he obferves, "that the external or cortical part of the brain, which is manifeftly very vafcular, is continued to, and coheres 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 vafcular texture of the cortical part, were not hollow, but folid, they muft repell the blood by their folidity, and fo render its derivation there at least ufelefs. But as the medullary and cortical parts increase alike, their equal growth manifeftly points to one common caufe of it, to wit, the fuperior 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 vafcular."

The Phanomena 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 fhook 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 faftened to the great veffels and the Pericardium. Furthermore, the influence of an irritated nerve is never propagated upwards,

3

which

which is contrary to the nature of an elaftic chord, that communicates its tremors equally to both ends from the point of percuffion. This is, in fome measure, illuftrated from the known experiment on the phrenic nerve, which, being rubbed downwards, below the place of compreffion, renews the motions of the diaphragm, but rubbed upwards entirely ftops it; whence it feems evident, the progrefs of the nervous fluid is urged by one motion, and intercepted by the other." From thefe and fome other arguments he very rationally concludes it almost abfolutely certain, that the nervous fibres are hollow, and that they exercife their functions, not by their fpring, but by the motion of their proper fluids. Nor is the extreme fmallness of these canals, which no microscope can reach, an objection of any weight, with him, against the experiments above mentioned; nor the abfence of tumour in a nerve upon being tied, which, he affirms, is not altogether true, nor other arguments of the like nature, which, he thinks, only prove the imperfection of our fenfes, but avail nothing againft the actual prefence of nervous spirits."

To thefe folid arguments, from this great phyfician, Dr. Flemyng ingenioufly adds, that if the Hypothefts of the vibration of the nerves might be commodioufly applied to explain fenfation, it could nowife account for mufcular motion, or action, for what, faith he, hath trembling to do with traction or pulling?'

Dr. Flemyng's aflumption then, that the nerves are hollow canals, the fmalleft in the body, which contain and tranfmit a peculiar fluid, being rendered fo entirely probable, he proceeds to his firft Lemma, viz. that the animal folids confift of phlegm or water, of oyl, of a peculiar effential falt, and of earth, to which their ftability or firmnefs is owing.' He employs two or three pages to prove to his readers, in general, the certainty of thofe principles, which his medical and chemical ones will immediately allow him. And if he had added here, that the blood, that animal fluid, from which all the others are fecreted, was conftituted of the fame principles, tho' differently proportioned, as the Lemma would have been equally admittable, perhaps it would have been more comprehenfive, and not have had a less direct and immediate tendency to infer the principles of the nervous fluid fecreted from it. It might alfo have prevented an unphyfical reader's mifapprehending a paffage in the 16th page of this performance, where Dr. Flemyng defires to ob

E 2

ferve,

serve, that as the nerves are folid parts, that is, not fluid, they must be acknowledged to contain the fame principles with the other folid parts of the animal ftructure.'-From whence, as the folids and fluids may feem mentioned here in fome contradiftinction to each other, fome readers might fuppofe they confifted of different principles; which the doctor did not intend, having evinced the very reverfe in the progrefs of his work. In p. 24, 25. he says, the nerves are nourished principally by the nervous fluid; but that fluid cannot give to the nerves what it contains not itself.' And p. 38 he afks, what can the moft fubtile fluid in the animal body confift of, but the fame principles which conftitute the blood, out of which it is made?' And that this fimilarity, or even identity, of the principles of the animal folids and fluids is not mere affertion, we know from chemical Analyfis; and particularly from a late accurate one of animal flesh, and of the human blood and urine, made by the worthy and indefatigable Dr. Langrish, in his valuable treatife of the modern theory and practice of phyfic, where it appears, that the principles which the tendons and mufcles of an ox, and the blood and urine of a healthy man were refolvable into, were the fame, tho' in different proportions; with this only exception, that the folids afforded no fixt falt, as the fluids, and particularly the urine, did. Neither is it probable, that if found human flesh were eafily procurable for an Analyfis, the principles would have been different; tho' poffibly their proportions might vary a little; and perhaps the human fiefh might have afforded fome fixt falt, which the quadrupeds did not, the fixt falt from the fluids exhibiting the ufual Phanomena of fea-falt.

The doctor's fecond Lemma fuppofes, that the nutrition of the fmallest veffels in the animal body is fupplied, at leaft in a confiderable measure, if not principally, by the fluids or juices, which pervade their cavities. This appears fo rational in itself, and fo obvious to every perfon, who is furnished with a tolerable idea of the animal œconomy, that we fhall mention but two of the author's many arguments in fupport of it: the firft is its analogy with the general manner of nutrition in the other animal vessels, as acknowledged by the beft modern authors on that fubject, who allow a plaftic or nutritive quality in the fluids, which repairs the abrasions their friction has occafioned: the fecond is its not being agreeable to the fimple procedure of

Compare p. 53. 54. with 80, 81 and ga,

nature,