calculi in the urethra, accordingly, are only fmall calculi which, pafling from the bladder, have been detained and lodged in the membranous part of that canal, and, there, have been expofed to the fame procefs of flow accretion, from the paffage of urine, which they would otherwife have undergone, from lying in the bladder expofed to the action of the fame fluid. One of the calculi of this defcription which Mr Brande examined, was of a fingular appearance. It was a perfect fphere, of about half an inch in diameter, coated with fmall regular cryftals of the ammoniacomagnesian phosphate in its purest state.

Our author clofed his experiments with examining the calculi of different animals. In the horfe, fheep, rhinoceros and rabbit, the calculi confifted of the phofphates in part, with animal matter and carbonate of lime. In the dog, no carbonate of lime was found; and, in the hog and ox, no phofphates,-the calculus being wholly compofed of carbonate of lime and animal matter. Not uric acid nor oxalate feems to have been detected in any of the fpecimens. Some of them were of a large fize: a calculus from an old dog weighed fixteen ounces.

From this induction, it is very evident that one conclufion may fafely be drawn-that, in moft inftances, the stone is connected with the formation of uric acid. Sometimes that acid forms calculi in the kidneys, which, after creating fufficient torment in that region, pafs into the bladder, and become the nuclei of ftill larger, more painful, and more fatal accretions of other fubftances; while, in many inftances, the fame acid continues to augment the mafs, either alone or combined with other fubftances. To prevent its formation, then, becomes a most important object; and both Mr Brande and Mr Home propofe, for this purpofe, the exhibition of fome alkaline earth, which may neutralize and carry it off. But, before adverting to this preventive remedy, we may notice the additional proofs adduced, in the papers now under review, to evince the hopelefonefs of any attempts to folve the ftones already formed, at leaft in the prefent flate of chemical science.

In arguing this point, Mr Brande (or, as Mr Home always terms him, Mr W. Brande) proceeds more by principle ;-his patron Mir Home comes forward to his protection with cafes. Mr Bode clearly fhows, that an alkali adminiftered to a calculous patkan tands no chance of reaching the uric concretion in a cauftic late; for the urine contains both phosphoric and carbonic acid uncombined. But experiment clearly thows, that neither carbonates nor fubcarbonates exert any fenfible action on uric acid: in other words (as we appic end), the aflinity of the uric acid for alkalies is weaker than inity of carbonic acid for the fame bodies: therefore, alkaline liquors cannot act as folvents of the

uric calculi. On the other hand, if acids be adminiftered with a view of attacking the phosphates, the formation of the uric acid is greatly favoured. This, Mr Brande's experiments have alfo taught him. And as for the injection of folvents through the urethra into the bladder, he juftly obferves, that although we were not ignorant (as we are) of the kind of calculus in each cafe, the frequent introduction of inftruments into the bladder, and the long continuance of the operation, would form infuperable obftacles to this mode of treatment, which, though recommended by great names, has always been fpeedily relinquished when tried.

Now come Mr Home's cases,-which plainly demonstrate, that where the use of alkaline medicines was supposed to have reliev ed the patient by dissolving the calculus, on examination no such effect was found to be produced. In two cases, where the violence of the complaint appeared to have subsided, the dissolution was taken for granted, and ascribed to alkaline medicines; but, on dissection, the calculi were found in great size, only imbedded in cysts, from the enlargement of the prostate gland, which often takes place late in life. In some instances, again, the increase of calculous concretions was found to proceed rapidly, while the patients were going on with courses of alkaline medicines. One person took these remedies for four or five years, and, at his death, the bladder was found nearly filled with light, spongy calculi of different sizes, no less than 35 in number. Another, who had taken soda, both mild and caustic, for some months, and then submitted to the operation on the symptoms increasing. was found to have a calculus, which was surrounded with a coat of triple phosphate, one tenth of an inch thick, the rest being a mixture of uric acid and phosphates; from whence it is fair to infer, that the alkali increased the formation of triple phosphate, though it checked the prc.'nction of uric acid. In a third case, of a very virulent nature, the exhibition of alkalies did not even prevent the formation of uric concretions. Mr Brande's experiments, however, in 1808, having rendered it highly probable that, in the great majority of cases, alkaline medicines would operate powerfully in checking the growth of uric calculi, by neutralizing the uric acid before it could form a concretion, this inquiry has lately been resumed by that industrious and skilful observer, with the aid and advice of Mr Home; and the result of their joint labours is given in the fourth of the papers examined at the head of this article.

Upon consultation with Mr Hatchett, they were led to fix tipon magnesia, in preference to the cther alkaline substances; and the event appears to have justified this very natural and judicious choice. Some preliminary trials showed, that the mild, safe, and

easily prepared earth in question, diminished the quantity of uric acid in urine, which contained a larger proportion of it than any of the alkalies, however copiously administered. But this point is of such primary importance, that we must notice the four cases in which a further examination of the matter was prosecuted.

The first was that of a gentleman sixty years old, who, apparently from the habit of drinking acid liquor, had acquired an uncommon tendency to secrete uric acid, and had his urine constantly mixed with that substance, in the form of red sand or crystals. He took, first, the subcarbonate of soda, and then of potash, without any amendment from the former, and with but a slight relief from the latter. His urine being previously examined, he was ordered to take fifteen grains of magnesia three times a day, and in a week the uric concretions diminished sensibly-in three weeks, they were only observed occasionally. The same medicine has been continued for eight months, and no calculi have been voided; nor has there been any material deposit in the urine. He has also been cured of heartburn, and other stomach complaints. Another gentleman, of about forty years of age, who suffered greatly from a similar complaint, and tried the alkalies in vain, has been wholly cured by a six weeks' course of magnesia, in the quantity of twenty grains every night and morning,' (we wish Mr Brande would say more distinctly whether he means twenty grains a day, or forty), without any change of regimen whatever. The third case, is that of a gentleman. forty-three years old, who has, for about a year, succeeded in driving away repeated attacks of the uric acid, by taking magnesia for a few weeks at a time, when the fit comes on. The fourth case is that of a more confirmed calculous tendency, which has nevertheless yielded, in a great degree, to the free use of magnesia; with this addition, that since the patient began it, he has been free from gout, contrary to his former habits.

The different qualities of magnesia and the alkalies thus obferved, led our author to make fome experiments on their refpective effects upon healthy urine. Subcarbonate of potash and foda occafioned a copious precipitation of the phosphates in the urine, during the first two hours after thefe falts were taken into the ftomach; and, after that, no further effect was produced. The fame alkalies, faturated with carbonic acid, threw down the phofphates lefs copiously and rapidly. Magnefia, administered in the fame circumstances, produced a much smaller and flower precipitation. Instead of this effect reaching its maximum in a quarter of an hour, as it did in the cafe of the alkalies, it did not reach that point in lefs than fix hours; and on this circumftance our author concludes, that its value in calculous diforders chietty

depends.

depends. Lime, either in the cauftic or mild form, produces a very flight effect; and its naufeous tafte, as well as the difficulty of administering it in fufficient quantities, manifeftly preclude its use in this disease. In one cafe, carbonic acid exhibited in aërated water, was found to keep the phosphates (which the urine was greatly charged with) in a state of folution; and, when left off, thofe falts were again voided in their folid fhape.

Thus far, then, we think, it may fafely be hoped, at least with as little risk of disappointment as ufually attends our fpeculations in medical science, that fome light has been thrown on the method of treating a difeafe, of all others which prey upon the body, the most inimical to the happinefs and comfort of man. Where the object is fo valuable, it is natural for us to feel uncommonly anxious and distrustful, as well as more than ufually eager in our wishes for its accomplishment. Instead, therefore, of being fatisfied with what Mr Brande and Mr Home have already effected, we would expect them to perfevere in their experimental inquiries-multiplying the number of their obfervations on real cafes-and, as it were, leaving no ftone unturned to attain the complete maftery of this great problem. Much will be done for medicine, if they fhould go no further than perfecting the preventive application of magnefia to the Uric calculus. A great number of calculous cafes, of the worst defeription, will be prevented, thofe, to wit, in which the ftone in the bladder is formed on a uric nucleus. Many others of the fame clafs will be greatly relieved. Thofe, in which compofite calculi confift partially of uric acid, and all that clafs of complaints with which the region of the kidneys is afflicted, by the uric concretions formed there, will be entirely removed. Should fuch a ftep in the healing art be made, we need fcarcely defpair of living to fee the phosphates themfelves attacked by it, and yielding to fome equally fimple and fafe remedy.

While we are, however, indulging in thefe vifions, and anticipating the final eradication of all calculous diforders, we unluckily caft our eye on the last of the papers which are now before us, and find, that Dr Woollafton has been difcovering a new fpecies of urinary calculus, at the very moment that his learned brethren were occupied in extirpating the already fufficiently numerous. fpecimens of the old catalogue. This new fpecies is extremely rare, our author having only met with it twice. It refembles the triple phosphate more than any other kind; but is more compact, and confits, not of lamina, but of a confufed mafs of cryitals, having a yellowish luftre and femitransparency; but it is formed of a peculiar fubftance. Dr Woollafton made as many experiments on this fubftance, as the limited quantity of it in his pof

L3

fellon

feflion would allow. When burnt, it gives a fmell quite peculiar to it'elf When diftilled, it gives a fetid carbonate of ammonia, and an animal oil, leaving a fpongy coal. It is readily diffolved by all the pure alkalies and by lime water-it is even folved by the carbonates of potafh and foda. The acids diffolve it alfo, except the citric, tartaric, and acetic. Neither water, alcohol, nor faturated carbonate of ammonia, diffolve this fingular fubftance. From its difpofition to unite with both acids and alkalies, Dr Woollafton fufpects it to be an oxide; which is confirmed by its forming carbonic acid in diftillation; that is to fay, if we take it for granted, as he seems to do, that this acid does not exist ready formed in the mafs. If it does contain oxygen, our author admits, it must be in a quantity infufficient to give it acid propertics: for it produces no effect on the colour of litmus paper. On the fuppofition of its being an oxide, and to diftinguish it from other bodies of that clafs, Dr Woollafton propofes to name it the cystic oxide, on account of its having hitherto been only found in the bladder.

This excellent chemift concludes his paper with fome curious obfervations on the connexion between the production of uric acid in birds, and their food. The white matter contained in their urine, and voided along with their dung, was found by M, Vauquelin to confit principally of that acid; and our author examined with fome care in what manner its quantity was affected by the diet of thofe animals. In the dung of a goofe fed on grafs, it only formed part;-in that of a pheafant fed on barJey, it amounted to;-in that of a hen which fed on infects as well as vegetable food, in a barn-yard, it was much more abundant, and mixed with lime. The folid part of the dung of a hawk fed wholly on flefh, was chiefly uric acid; and the evacuation of a gannet, feeding folely on fith, confifted altogether of urine; for the only folid parts were uric acid. It feems' (our author concludes) deferving of inquiry, what changes might be produced in the urine of any one animal by fuch alterations of its diet as its conftitution would permit; for, as far as any inference can be drawn from thefe varieties which naturally occur, it would appear that perions fubject to calculi confiiting of uric acid, as well as gouty perfons in whom there is always a redundance of the fame matter, have much reafon to prefer vegetable diet; but that the preference ufually given to fith above other kinds of animal food, is probably erroneous.'

The mention of Dr Woollafton's paper naturally leads us to reflect on the important fervices which this truly philofophical inquirer as formerly rendered to the branch of fcience now under confideration. It was his important difcovery of the nature

of