URINARY CALCULI. 



which is much {miller than that left by lithic acrid. Water, 

 alcohol, acetic, tartaric, aiul citric acids, and faturated car- 

 bonate of ammonia, can only diffolve a very fliglit propor- 

 tion of it. The folvents of it, on the other hand, are 

 numerous ; as, for inftance, the muriatic, nitric, fulphuric, 

 phofphoric, and oxalic acids ; potalh, ioda, aiiinioiiia, and 

 lime-water, and even the neutral carbonates of potadi and 

 foda. When, therefore, it is intended to icparate it from 

 acids, the neutral carbonate of ammonia is beft adapted to 

 the purpofe, as it is not capable of rediffolving tlie precipi- 

 tate even when added in excefs ; and, for the fame reafon, 

 the acetic and citric acids are befl luited to precipitate it 

 from alkalies. 



In confequence of the difpolltion of this fpecies of cal- 

 culus to unite both with acids and alkalies, in common with 

 other oxyds, and the faft of its alfo containing oxygen, (as 

 is proved by the formation of carbonic acid in diRillation,) 

 Dr. WoUafton named it an oxyd, and the term c^ic was 

 added from its having been originally found only in the blad- 

 der in two examples. Dr. Marcet, however, has fubfe- 

 quently met with no lefs than three inftanccs of calculi 

 formed of cyftic oxyd, all of which were unqueftionably of 

 renai origin. 



7. Compound Calculi in dlftinB Layers. — Lithic ftrata fre- 

 quently alternate with layers of oxalate of lime, or with the 

 phofphates. Sometimes alfo the mulberry alternates with 

 the phofphates, and, in a few inftanccs, three or even four 

 fpecies of calculi occur in the fame Hone difpofed in diftinft 

 concentric lamins. For fpecimens of thefe fafts, we refer 

 to Dr. Marcet's interefting effay, in which varieties of fuch 

 calculi are correAly delineated and coloured. 



8. Compound Calculi -with their Ingredients intimately mixed. 

 — Under this title, Dr. Marcet comprehends certain calculi, 

 which have no charafteriftic feature, by which they can be 

 confidered as diftinftly belonging to any of the other clafles. 

 He obferves, that they may fometimes be recognized by 

 their more or lefs irregular figure, and their lefs determined 

 colour, by their being lefs diftinftly if at all ftratified, and 

 by their often pofTcfling a confiderable hardnefs. By chemi- 

 cal analyfis confufed refults are obtained. See Marcet's 

 Effay on the Chem. and Med. Hift. of Calc. Diforders, 

 p. 90. 



9. Calculi of the Projlate Gland. — The compofition of 

 thefe calculi is faid to have been firft explained by Dr. Wol- 

 lafton. (See Phil. Tranf. for 1797.) They all confift of 

 phofphate of lime, the earth not being redundant as in 

 bones. Their fize varies from that of a pin's head to that 

 of a hazel-nut. Their form is more or lefs fpheroidal, and 

 they are of a yellowilh-brown colour. 



Fourcroy has defcribcd a fpecies of urinary calculus, 

 which is charafterized by its being compofed of the urate 

 of ammonia. Dr. WoUafton, Mr. Brande, and Dr. Marcet 

 have not, however, fatisfaftorily afccrtained the prefence 

 of this fnbftance in any of the concretions which they havo 

 exammed. It is alfo to be rccollefted, that urea and the 

 triple phofphate, both of which afford ammonia, arc fre- 

 quently prefent in lithic calculi, and they may have given 

 rife to the analytical refults from which the cxiftence of urate 

 of ammonia has been inferred. Brande in Phil. Trar.f. 1808. 

 Marcet's ElTay, p. 93. 



Dr. Marcet has met with two fpecimens of urinary cal- 

 culi entirely different from any which have hitherto been 

 noticed. One of thefe he propofcs to name xanthic oxyd, 

 from |x»9of, yellonu, becaufe one of its moft charaftcriftic 

 properties is that of forming a lemon-coloured compound, 

 when aftcd upon by nitric acid. The chemical properties 

 of the other new calculus, mentioned by Dr. Marcet, cor- 



rcfpond to thofe of fibrine, and he therefore fuggpefts the 

 propriety of dillinguiftiing it by the tt^vmfbrinous. For a 

 particular defcription of thefe new fubftances, we refer to 

 this gentleman's effay. 



In addition to the remarks which have been off"ered in the 

 article Lithotcmv, on the fubjedl of lithontriptic medi- 

 cines, we mean to fay very little in the prefent place. Who- 

 ever ftudics the chemical properties of the' urine will learn, 

 that '• if any alkali (a few drops of ammonia for inftance) 

 be added to recent urine, a white cloud appears, and a fedi- 

 ment, confifting of phofphate of lime, with fome ammoniaco- 

 magnefian phofphate, fubfides, in the proportion of about two 

 grains of the precipitate from four ounces of urine. Lime- 

 water produces a precipitate of a fimilar kind, which is ftill 

 more copious ; for the lime, in combining with the excefs of 

 phofphoric, and perhaps alfo of lactic acid, not only precipi- 

 tates the phofphate of lime which thefe acids held in folution, 

 but it decompofes the other phofphates, thus generating an 

 additional quantity of the phofphate of lime, which is alfo 

 depofited. 



" If, on the contrary (fays Dr. Marcet), a fmall quantity 

 of any acid, either the phoiphoric, the muriatic, or, indeed, 

 even common vinegar, be added to recent healthy urine, and 

 the mixture be allowed to ftaud for one or two days, fmall 

 reddifh cryftalline particles of lithic acid will be gradually 

 depofited on the inner furface of the veflel. 



" It is on thefe two general fafts, that our principles of 

 chemical treatment ultimately reft. Whenever the lithic fe- 

 cretion predominates, the alkalies are the appropriate reme- 

 dies, and the acids, particularly the muriatic, are the agents 

 to be reforted to, when the calcareous or magnefian falts 

 prevail in the depofit." P. 147, 148. 



It is a fa£l perfeftly well afcertained, that the alkalies 

 taken into the ftomach reach the urinary paflages through the 

 medium of the circulation ; and it is alfo ftrongly fufpeAed, 

 that the acids likewife do fo, though this circumftance may 

 not be fo well proved. Unfortunately, the quantity of either 

 alkalies or acids, which thus mixes with the urine, is fo 

 fmall, that no imprefiion is made upon calculi of magnitude. 

 The experience of Dr. Marcet and others, however, has 

 clearly afcertained that fuch medicines are often capable of 

 checking a tendency to the formation of ftone, and fome- 

 times of bringing on a calculous depofit depending upon the 

 altered ftate of the fyftem. This writer, indeed, exjft-efTes 

 his decided opinion, that even fuppofing not an atom of 

 alkali or acid ever reached the bladder, ftill it would not be 

 unreafonable to expeft that thefe remedies may refpeftivcly 

 produce the defired changes during the firft ftages of alllmi- 

 lation, in one cafe by neutralizing any morbid excefs of acid 

 in the primse vix, and in the other by checking a tendency 

 to alkalcfcence, or otherwife difturbing thofe affinities which, 

 in the fubfcquent proceflcs of aftimilation and fecretion, give 

 rife to calculous affeAions. P. 153. 



When muriatic acid is prefcribed, from five to twenty-five 

 drops may be given two or three times a day, diluted with a 

 fufficient quantity of water. 



The beft way of taking the alkalies is by drinking foda- 

 watcr as a common beverage. It is afterted, however, on 

 the authority of fir G. Blane, that when the alkalies are 

 combined with citric acid, as in the ordinary faline draught, 

 they alfo have the cfft'ift of depriving tlie urine of its acid 

 properties. 



Dr. Marcet, with every appearance of probabihty, refers 

 to c.irbonic acid itfelf no folvent power, and he does not 

 even adopt Mr. Brande's opinion, th.it this acid paflTes into 

 the unne, when patients drink fluids which arc impregnated 

 with it. 



3X2 Sir 



