longer useful in the general fyftem, as organized bodies; and it is then abfolutely neceffary, that their frame fhould be diffolv ed, and their elementary principles difperfed, in order to form nourishment for those beings that yet continue to live.'

The commutation, therefore, of this principle of cohesion, when in its fixed and strongly attracting ftate, into that of its proving a cause of their diffolution, in its elaftic and repellent one, really being, as our Author fuppofes, not eafily comprehended, he has judged it expedient to add to fuch proofs of it, as had been already publifhed, a new fet of experiments, from which he proposed to obtain additional light, in fome points of very great importance in the animal oeconomy. The number of experiments in this Effay are thirty-four. The first seven were made in order to discover the relative quantity of air fet free from different mixtures by fermentation; and do alfo fhew, what different alimentary mixtures or fubftances were difposed to ferment fooner or later than others, in the fame degree of heat. The eighth experiment fhews the perfect fweetening a bit of putrid mutton, impregnated with the vapour of fermenting wort. The ninth, (which includes a very ingenious and conclufive experiment of Dr. Black's) fhews the method of transferring air, from an effervefcent mixture, into another substance, adapted to receive and to fix it; and which having been before deprived of its former air, was, until transferring this, incapable of effervefcence, which is thus restored to it. The contrivance for effecting this, which is at once very simple and effectual, is rendered perfectly clear by an engraving.

The tenth experiment compares the fermentative power of the Saliva and the Bile; the first of which fermented two hours fooner than the laft, tho' the fermentation of this continued twice as long, and was still brifker than that of the spittle. The eleventh and twelfth are intended to enforce the eighteenth of Dr. Pringle's experiments; and prove, that bodies in a state of putrefaction are exciting ferments to fuch as are sweet; which fact has been fuppofed to obtain in carious teeth, &c.

The thirteenth was inftituted to prove the fermentative power of the Bark, on which Mr. Macbride fuppofes its efficacy greatly to depend: but this experiment feems fomewhat lefs conclufive to us, as the firft figns of the fermentation of the Bark, with the addition of human faliva, quickly difappeared, and was perfectly at reft eighteen hours after, tho' it had remained for fix hours in a moderate heat, being fuffered to cool the last twelve. Neither did any motion revive in this mixture, till full twenty hours after the addition of ox-gall, which at length appeared even in the cold; but, on the application of moderate hear, the fermentation

U 2

cacy

fermentation returned very brifkly, continuing fo for twentyfour hours, and throwing off great quantities of air. To be ingenuous, we acknowlege this attempt to account for the effiof the Bark from its fermentation, (efpecially when that occurred to it with more than ufual flownefs and difficulty) favoured to us of a common difpofition to account for plain effects by fome favourite theory, which fometimes ftrains very hard to reconcile them to it: fince the ftypticity of the Bark, and of its refin, feemed to us a more fimple and evident property, from whence to account for its ftrengthening virtues. And as fome former Phyfiologifts have fuppofed, (which our Author pretty exprefsly accedes to, page 59,) a vifceral fermentation excited by the concurrence of the pancreatic juice and the bile in the Duodenum; the Bark's fermenting fo little together with the former (fuppofed fo fimilar to the faliva) and the bile, and very little, if at all, with the faliva alone, rather fuggefted to us, that one drachm of powdered Bark, did not wholly prevent the effervefcence of half an ounce of faliva and as much bile, than that it was confiderably, if at all, active in exciting their fermentation. Neverthelefs, we fhall not omit, that our ingenious and affiduous Experimenter obferves here, that a further probability of the fermentation of this valuable drug will ap pear in another place. That it contains air, which may be rendered elaftic, without which there is no effervefcence, is highly probable.

The fourteenth, a moft ufeful experiment, was made to dif cover, whether wheat, barley, oats, or rice, were the fooneft fermented, and, confequently, the most readily digestible. The event was, that the rice and barley mixtures (all four being hutked, well boiled, fo as to burft the grain, and beat up with water and flesh) were in brifk motion after an hour's warmth; the mixture with the oats not till after four hours warmth; and that with the wheat, was ftill three or four hours later. But when he hence infers wheat to be the most indigeftible, he jur dicioufly adds, page 58- But at the fame time we fee, that this property in wheat, renders it by much the fittest of all the Farinacea tor the making of bread; as it appears to have firmnels fufficient to enable it to bear fome degree of fermentation in the baking, and yet retain enough of its fubftance to undergo the alimentary fermentation afterwards in the body.'

The fifteenth experiment confifted in exciting an efferve-fcence, by pouring an ounce of lemon-juice on a drachm of falt "of wormwood in a cylindrical glass; and then confining, in the imprifoned air generated by the effervefcence, a live sparrow, which expired in lefs than half a minutes the fame death hayng occurred, within the fame fhort period, to another, put by

Dr.

Dr. Hales, into the air he had generated from heart of oak. Mr. Macbride here again expatiates on the good effects this. air may nevertheless produce in the ftomach and inteftines, however deadly in the lungs; and inftances the very frequent and fafe practice of giving Patients the aforefaid mixture of Riverius, in the very act of ebullition, which abundantly demonstrates it. And our Author's arguments and authorities here, for the blood's being fupplied with air through the chyliferous paffages, rather than from the lungs, as fome other Phyfiologifts have fuppofed, collaterally fupport the fame opinion.

The fixteenth experiment was contrived to difcover, whether the fixed air would pafs from a putrefying animal fubftance, into a caustic volatile alkali, fuch as fpirit of falt ammoniac with quick-lime, fo as to render this cauftic alkali mild and effervefcent. For the introduction of air into this liquid, of which it was before deprived by the quick-lime, proves fuch an analogous diluter of it, as water does of an inflammable vinous fpirit, The event of the trial was, that the spirit of falt ammoniac with quick-lime, after imbibing the air emitted from putrid Alefh, effervefced with an acid, which before its reforption of air it could not.

The four fubfequent experiments, to the twentieth inclufive, were made to difcover, whether bodies become putrid from the access of air, as fuppofed to communicate fome cause of putridity to them; or whether they become putrid, in confequence of the lofs of fome principle they before contained. The event was, that in repeated trials with different bits of beef and mutton, the morfels having been put in vacuo, under a cup with the bottom inverted on wet leather, and the air pumped out of it, in the open air, and in a cup which was filled up with melted fuet→→ that the meat in the exhaufted receiver, that under the cup, and that in the open air, tho' confiderably dried, became putrid in fixty hours; while that inclofed within the melted fuet was perfectly fweet. A fresh egg confined in the receiver for a week, had then contracted a fetid or putrid fmell; at which time it was broke, and next morning was quite putrid and offenfive; nor was its yolk near fo firm as that of another egg of the fame laying, which had been exposed to the open air, and continued perfectly fweet. But in the twenty-firft experiment, Mr. Macbride having inclosed, in a more compleat vacuum than he had procured before, one morfel of fweet fresh mutton, and put another of the fame bulk under a glafs, at the end of forty-eight hours he found that inclosed within the perfect vacuum sweet, and the other putrid. Hence he fuppofes the affertion of bodies not becoming readily putrid, "when perfealy excluded from the external air, may be true; notwithstanding the event of the

U 3

four

four preceding experiments; fince he had not been able to effect fo compleat a vacuum in the glafs receiver, as in the hollow metallic hemispheres. Yet he reasonably infers these former experiments inconteftibly to prove, that removing the pressure of the atmosphere to a certain degree, does facilitate the escape of the fixed air (his cementing principle) from bodies.

The twenty-fecond experiment to the twenty-fifth inclufive, were repetitions of fome of Dr. Pringle's, with refpect to septic and antiseptic fubftances; and Mr. Macbride's ingenious and rational deductions from them, ftrongly coincide with the theory of his aërial cement, and are very obviously applicable to the fubject of his fourth Effay, the Scurvy.

The remaining experiments in this Effay, from the twenty-fixth to the thirty-fourth, were intended to investigate, whether putrid animal fubftances ought to be regarded as alkaline. The experiment number twenty-fix, answered in the affirmative, with refpect to the putrid blood and ferum together, after keeping them two months; and N° 27, with regard to the spirit diftilled from it. The event of N° 28, was in the negative, with refpect to the putrid bile of an ox. By No 30, the putrid human bile raised no ebullition with strong spirit of vitriol; but the diftilled spirit of it, gave the alcaline greennefs to fyrup of violets; precipitated a folution of fublimate; and heightened the blue colour of paper tinged with radish scrapings; yet, notwithstanding thefe ftrong tokens of an alkaline nature, it effervefced but very obfcurely on the affufion of strong fpirit of vitriol, It may be queried here, whether the different diet of the man, and of the quadruped, conduced to the confiderable difference of the operation of the fpirit of the putrid human and brutal bile? The four laft experiments are pretty fimilar to thefe; and the whole induce our affiduous Investigator to join with Neuman in saying, that as foon as an animal fubftance begins to putrefy, it also begins to difcover an alkaline quality; and that the volatile matter now produced in it, may be feparated by diftillation, in a very gentle warmth. We may be certain our Author was particularly accurate in conducting these experiments, the effect of which has obliged him to diffent, though very philofophically and politely, with Dr. Pringle and Dr. Lewis, with regard to the alcalefcence of putrid fleshy fubftances: fome Gentlemen of knowlege in chemistry being prefent at his diftillation of such substances, all of whom feemed fatisfied, that these two eminent Phyficians have been mifled in this matter; and probably from inferring, that fince alkalies had been found by experiment to refift putrefaction, putrid animal fubftances must be very little, if at all, alkaline. But on this occafion our Author very judiciously diftinguishes, that the

principle

principle on which this action of alkaline falts depends, has nothing to do in particular with alkali, that being common to all faline bodies whatever, as falts.

The Effay on the refpective Powers, &c. of the different Antifeptics, is not lefs curious than the former, and affords many ftill more practical fuggeftions. It contains one short table of the effects of five different acids tried as antiseptics, by fresh mutton remaining in them from one to four days. A fecond brief table exhibits the different antifeptic powers of spirits of vitriol, of hartfhorn, of a lixivium of tartar, and of a neutral mixture; fimple water being the common ftandard in all these experiments. A third table fhews the force of four acids, that of the tartar being omitted, as correctors of putrefaction; the flesh immerfed in them, on this occafion, being first rendered foft and putrid, by its ftanding four days in water moderately hot. A fourth table gives the effects of fix different fermented liquors, tried as fweeteners of putrid flesh. The experiments in this Effay are twenty-five, which concur very coherently with the ingenious arguments deduced from them, in establishing the Author's general propofition. But as the account of this curious and important treatise has infenfibly, and, yet we think, unavoidably fwelled upon us, we are obliged to retrench nuch of what appears both ftriking and entertaining to us, in this Effay, to join our Author in the following very pertinent and material query, with the answer to and reflection on it, as they occur, page 149.

But here it may be demanded, what can these experiment prove, with regard to the restoration of putrid fluids, in a liv ing body? Is it poffible to faturate thefe humours with fuch a quantity of air, as will be fufficient to correct their sharpness, reRore their confiftence, and bring back their fweetnefs?

To this it may with fafety be replied, that it is not only poffible, but that it is, perhaps, the only way by which this change can be produced.

For we have feen, that there is a deception in regard to both acids and alkalies, when we fuppofe them to restore sweetnefs to a putrid animal fubftance; that the firft, so far from giving foundness to fuch kind of fubftances, do in reality deAroy their texture; and that the fecond only change the nature, but do not restore the original sweetness.'

What he fays, page 151, is another very interefting query, relating to the fame topic; where, after admitting the certain power of alkalies to refift and correct putrefaction in dead bodies, he very rationally adds- But whether, upon the prefumption of

U4

this