URINARY CALCULI. 



not always proportioned to their fize. Subftances of dif- 

 ferent qualities enter into their compofition, and diverfify 

 their heavinefs. Thus, the falts which have filica for their 

 bafe, and which are very uncommon, render fuch calculi as 

 contain them the heavieft of all in proportion to their fize. 

 On the other hand, fome urinary falts cryftallize when pre- 

 cipitated : of this kind is the ammoniaco-magnefian phof- 

 phate, the cryftals of which frequently leave confiderable 

 interfpaces, which are not filled up by the fubfequent pre- 

 cipitations. 



The urinary falts, in calculous patients, are not conti- 

 nually precipitated in the fame quantities : in fome cafes, 

 indeed, the procefs appeai-s to be even fufpended tor a con- 

 fiderable time. Hence, a ftone of middling fize, already 

 formed, may increafe but very flovvly ; and it has atlually 

 happened, that a calculus, which could be plainly felt with 

 a found, has remained more than ten years in the bladder, 

 and yet, after all this time, been only of a moderate fize. 



According to Dr. Marcet, the form of urinary calcuh is 

 moftly fpheroidal, fometimes eg'^-fhaped, but often flattened 

 on two lides like an almond. P. 50. 



Sometimes the calculous matter, which defcends from the 

 kidneys, is in the form of minute fpherical grains, which 

 have a fingular tendency to unite either to each other, or to 

 calculi already lodged in the bladder. 



When there are feveral loofc calcuh in the bladder tog;c- 

 ther, they feldom lie long in contaft with each other, while 

 their fize is diminutive, but are inceffantly changing their 

 fituation as the patient moves about or alters the pofition of 

 his body. Hence, their increafe is at firll: regular and uni- 

 form ; but when they have attained a more confiderable fize, 

 or by their numbers campofe a large mafs, their relative 

 fituation is more permanent, and many of their furfaccs, 

 being in this manner ufually covered, no longer receive any 

 additional depofitions. Every other part of thefe calcidi, 

 however, goes on increafing. It is thus that Hones witii 

 furfaces correfponding to thole of other Hones are produced, 

 and which are aptly denominated by the French writers 

 "pierres afacettes." This (hape necelTarily indicates the pre- 

 fence of feveral calculi. A different form, however, is by 

 no means a certain criterion of the ftone being fingle. 



Calculi alfo occafionally occur which are angular, and 

 fometimes almoft cubic ; but, as Dr. Marcet obferyes, this 

 is a rare occurrence. The fame phyfician has likewife given 

 the engraving of a fpecies of calculus which fomewhat re- 

 fembles a pear, with a circular protuberance at its broader 

 end, apparently moulded in the neck of the bladder. 



This writer alfo particularly calls our attention to the 

 variety in the colours and furfaces of calcuh, which often 

 afford indications of their chemical nature. " When they 

 have a brownifh or fawn colour, fomewhat like mahogany 

 wood, with a fmooth though fometimes tubercnlated furface, 

 they almoft always confift of lithic acid. When cut open, 

 they appear to be formed of concenb-ic layers, fometimes 

 homogeneous, fometimes alternating with other fubftances. 

 The colour, however, cannot be confidered as a certain cri- 

 terion, fince other kinds of calculi may often be coloured in 

 the bladder in a fimilar manner, by bloody mucous or other 

 vitiated fecretions. 



" When calculi are white, or greyifii-white, they always 

 confift of earthy phofphates. This is particularly the cafe 

 with the fpecies called fufible. And when they are dark- 

 brown or almoft black, hard in their texture, and covered 

 with tubercles or protuberances, they are generally of the 

 fpecies which has been diftinguiftied by the name of mtdherry, 

 and confifts of oxalate of lime. 



" Calculi have fometimes an uneven cryftalline furface, 



ftudded with fhining tranfparent particles. This appearance 

 always denotes the prefence of the ammoniaco-magnefian 

 phofphate." Marcet, p. 52. 



A large calculus, efpecially when it has a rough irregular 

 furface, produces a great deal of irritation of the bladder, 

 which contrafts more clofely round it. The contaft, how- 

 ever, is remarked to be particularly exaft at the tranfverfe 

 line, which extends between the terminations of the two 

 ureters in the bladder, a part of this organ which generally 

 becomes more thickened than the reft. Sometime?, indeed, 

 the cavity of the bladder is almoft entirely effaced, and the 

 urine can be retained only a very Ihort time, or, if it be not 

 evacuated, it fpreads uniformly round the calculus, efpe- 

 cially above and below the above-defcribed tranfverfe projec- 

 tion, which is lefs yielding than other parts of this organ. 

 Hence, the furface of the ftone, towards the orifices of the 

 ureters, does not enlarge fo faft as the other fides of it, and 

 a circular groove is produced, giving- the foreign body the 

 fhape of a calabafii. Such calculi are generally very large, 

 and fometimes even of enormous fize. In the latter circum- 

 ftance, the foreign body fills the cavity of the bladder fo com- 

 pletely, that there is no fpace left for the lodgment of the 

 urine there, which fluid then generally paffes along a fort of 

 groove, fituated in a line reaching from the lower termina- 

 tion of the ureter to the neck of the bladder. This ilate is 

 of courfe accompanied with a complete incontinence. 



Urinary calculi are not always loofe and moveable in the 

 cavity of the bladder, being fometimes fixed in various vrays 

 to certain points of the circumference of this organ. 



1. When a calculus has reached that part of the lower 

 termination of the ureter, which paffes obhquely between 

 the coats of the bladder, it may obftruft the inferior orifice 

 of the canal, and produce an accumulation of urine above it. 

 The diltention thus arifing may lead to the formation of a 

 cavity betwixt the coats of the bladder, where the calculus 

 is lodged. In faft, calculi have fometimes been found 

 fixed in a cavity of this defcription, the infide of which 

 communicates both with the lower end of the ureter and 

 with the bladder. In fuch a fituation, calculi have alfo 

 been known to attain a confiderable fize. 



2. It fometimes happens, that an urinary calculus de- 

 fcends to the very bottom of the ureter, and one end of it 

 projefts fom.e way into the cavity of the bladder ; but the 

 other end cannot difengage itfelf from the tube. If things 

 remain in this ftate long, the confequence is, that the ftone 

 grows larger at its two extremities, while the part which is 

 clofely embraced bv the lower termination of the ureter 

 remains much narrower than the reft of the foreign body. 



3. Sometimes, in confequence of the diftention of the 

 urine or other caufes, the inner membrane of the bladder 

 protrudes between the fafciculi of its mufcular coat, in the 

 form of pouches or cyfts, which are of different fizes, and 

 occafionally numerous. SmaU calculi, after getting into 

 thefe cyfts, frequently attain a very large fize ; and as the 

 inner coat of the bladder more readily yields than the muf- 

 cular fibres admit of feparation, the fundus of fuch pouches 

 becomes capacious, while their orifice remains of a diminu- 

 tive fize. Hence, a very fmall part of a ftone thus encyfted 

 is naked in the cavity of the bladder, and fometimes the 

 whole of the extraneous body is concealed under a fort of 

 moveable fold of the mucous membrane. 



4. There are on record very authentic cafes, proving that 

 calculi, fome of which were of confiderable magnitude, have 

 been fixed and lodged in a cavity that coufifted of the upper 

 portion of the bladder, feparated from the reft of this vifcus 

 by a circular contraction. Difficult as it may be to account 

 for fuch fafts, the truth of them is unqueiliouable. 



5. The 



