URINARY CALCULI. 



moft heat rom a common blow-pipe, when it may be com- 

 pletely fufed. It appears to be more fufible than the phof- 

 phate of lime, which forms the bafis of bone ; a circum- 

 ftance which Dr. WoUafton afcribes to the latter containing 

 a larger quantity of lime. (Phil. Tranf. 1797.) Calculi, 

 altogether compofeJ of phofphate of lime, are rather un- 

 common : with this fubftance there arc ufually other ingre- 

 dients, efpecially the phofphates of magnefia and ammonia, 

 and lithic acid. 



3. Triple CalciAus, or Ammnniaco-magnefmn Phofphate 



The exiftence of this calculus in the inteilines of animals was 

 firft pointed out by Fourcroy ; but its being a conftituent 

 part of fome urinary calculi of the human fubjeft was ori- 

 ginally afcertained by Dr. Wollafton. ( Phil. Tranf. 1 797. ) 

 Calculous mafles, confifting folely of this fubftance, are 

 perhaps never met with ; but concretions often occur, in 

 which it obvioully prevails ; and, as Dr. Marcet obferves, 

 " this triple fait frequently appears alfo in the form of mi- 

 nute fparkling cryftals, difFufed over the furface, or between 

 the inteilines of other calculous laminje. Calculi, in which 

 this triple fait prevails, are generally whiter and lefs com- 

 paft than thofe of the former cLfs. When the blow-pipe 

 is applied, an ammoniacal fmell is perceived, the fragment 

 diminifhes in fi?e ; and if the heat be ftrongly urged, it 

 ultimately undergoes an imperfeft fufion, being reduced to 

 the ftate of phofphate of magnefia." (P. 69.) Dr. Wol- 

 lafton defcribes the form of the cryftals of this fait, as being 

 a fhort trilateral prifni, having one angle a right angle, and 

 the other two equal, terminated by a pyramid of three or 

 fix fides. Thefe cryftals, as Dr. Marcet has explained, are 

 but very fparingly foluble in water, but very readily in moft, 

 if not all, the acids ; and on precipitation, they realTume the 

 cryftalline form. From the folutions of thefe cryftals in 

 muriatic acid, fal ammoniac may be obtained by fubhmation. 

 Solutions of cauftic alkalies difengage ammonia from the 

 triple fait, the alkali combining with a portion of the phof- 

 plioric acid. 



4. The fufibh Calculus Mr. Tennant firft difcovered 



that this fubftance was different from the lithic acid, and 

 that, when urged by the blow-pipe, inftead of being nearly 

 confumed, a large part of it melted into a white vitreous 

 globule. The nature of the fufible calculus was afterwards 

 more fully inveftigated and explained by Dr. Wollafton. 

 (Phil. Tranf. 1797.) According to the excellent defcrip- 

 tion lately given of this calculus by Dr. Marcet, it is com- 

 monly whiter and more friable than any other fpecies. It 

 fotmetimes refembles a mafs of chalk, leaving a white duft 

 on the fingers, and feparates eafily into layers or laminx, 

 the interftices of which arc often ftudded with fparkhng 

 cryftals of tlie triple phofphate. At other times, it appears 

 in the form of a fpongy and very friable whitifti mafs, in 

 which the laminated ftrufture is not obvious. Calculi of 

 this kind often acquire a very large fize, and they are apt 

 to mould themfelves in the contrafted cavity of the bladder, 

 affuming a peculiarity of form, which Dr. Marcet has never 

 obferved in any of the other fpecies of calculi, and which 

 confifts in the ftone terminating, at its broader end, in a 

 kind of peduncle, correfponding to the neck of the bladder. 

 The chemical compofitiou of the fufible calculus is a mixture 

 of the triple phofphate and phofphate of lime. Thefe two 

 falts, which, when feparatc, are infulible, or nearly fo, when 

 mixed together and urged by the blow-pipe, eafily run into 

 a vitreous globule. The compofition of this fubftance, fays 

 Dr. Marcet, may be ftiewn in various ways. Thus, if it 

 be pulverized, and acetic acid poured upon it, the triple 

 cryftals will be readily diftblved, while the phofphate of 

 lime will fcarcely be aftcd upon j after which the muriatic 

 9 



acid will readily diflblve the latter phofphate, leaving a 

 ft'i^U refidue, confifting of lithic acid, a portion of which is 

 alv 'ays found mixed with the fufible calculus. 



It is an obfervation made by the fame interefting writer, 

 that many of the calculi which form round extraneous bodies 

 in the bladder, are of the fufible kind. The fame thing is 

 remarked with refpeft to the calculous matter fometimes de- 

 pofited between the prepuce and glans. For many other 

 particulars, refpefling the fufible calculus, we refer to Dr. 

 Marcet's Eftay and Dr. WoIIafton's paper in the Phil. 

 Tranf. 



5. Mulberry Calculus, or Oxalate of Lime This is moftly 



of a dark brown colour, and frequently its interior is grey. 

 Its furface is ufually uneven, prefenting tubercles more or 

 lefs prominent, frequently rounded, fometimes pointed, and 

 either rough or poliftied. It is very hard, dif&cult to faw, 

 and appears to confift of fucceilive unequal layers. Except- 

 ing the few ftones which contain a proportion of filica, it ia 

 the heavieft of the urinary concretions. Though this calcu- 

 lus has been named mulierry, from its refemblance to that 

 fruit, yet, as Dr. Marcet has obferved, there are many con- 

 cretions of this clafs which, far from having the mulberry 

 appearance, are remarkably fmooth and pale-coloured, as 

 may be feen in plate 8, fig. 6. of that gentleman's eflay. 



According to Mr. Brande, perfons who have voided this 

 fpecies of calculus, are much lefs liable to a return of the 

 complaint, than other patients who difcharge lithic calculi. 

 Phil. Tranf. 1808. 



With regard to chemical charafters (fays profeffor Mur- 

 ray), it is lefs affefted by the application of the ufual re- 

 agents than any other calculus. The pure alkaline folutions 

 have no effeft upon it, and the acids dilTolve it with great 

 difficulty. When it is reduced, however, to fine powder, 

 both muriatic and nitric acid diftblve it flowly. The folu- 

 tions of the alkaline carbonates decompofe it, as Fourcroy 

 and Vauquelin have obferved ; and this alfords us the eafieft 

 method of analyfing it. The calculus in powder being di- 

 gefted in the folution, carbonate of lime is foon formed, 

 which remains infoluble, and is eafily diftinguilhed by the 

 effervefcence produced by the addition of weak acetic acid, 

 while there is obtained in folution the compound of oxalic 

 acid with the alkah of the alkaline carbonate. From this, 

 the oxalic acid may be precipitated by the acetate of lead, or 

 of barytes ; and this oxalate, thus formed, may be after- 

 wards decompofed by lulphuric acid. Another method of 

 analyfing this calculus is by expofure to heat : its acid is 

 decompofed, and by raifing the heat fufficiently, pure lime 

 is obtained, amounting to about a third of the weight of 

 the calculus. According to Fourcroy and Vauquelin, the 

 oxalate of lime calculus contains more animal matter than 

 any other. This animal niaf ' :r appeared to them to be a 

 mixture of albumen and ure;. The compofition of a calcu- 

 lus of this fpecies, analyfec by Mr. Brande, was oxalate of 

 lime 65 grains, uric acid 16 grains, phofphate of lime 15 

 grains, animal matter 4 grains. 



6. The Cyflic Oxyd was firft defcribed by Dr. Wollafton 

 in the Phil. Tranf. for 1810. In external appearance, it 

 bears a greater refemblance to the triple phofphate of mag- 

 nefia, than any other fort of calculus. It is however more 

 compaft, and does not confift of diftinft laminae, but ap- 

 pears as one mafs confufedly cryftallized throughout its fub- 

 ftance. It has a yellowifti femi-tranfparency, and a peculiar 

 glifteaing luftre. Under the blow-pipe, it gives a fingularly 

 fetid fmell, quite diftinft from that of lithic acid, or the 

 fmell of prulfic acid. Diftilled in clofe veffels, it yields fetid 

 carbonate of ammonia, partly fluid and partly folid, a/id a 

 hea»y fetid oil ; and there remains a black fpongy coal, 



which 



