PATHOLOGY. 
and Speedily emits a naufeous fmell from the evolution of 
ammonia. 
Moft authors haveconfidered a long-continued ufe of 
alkalies as the caufe of the phofphatic calculi ; but, when 
we conlider the unfrequency of this caufe,. vve fhould 
be inclined to put little ftrefs on its coincidence. This 
alfo is the opinion of Dr. Prout. This author allows 
that in a few cafes it may occur, but, as a general prin¬ 
ciple in the pathology of earthy depofitions from the 
urine, he considers it of no importance whatever. The 
real caufes of this ftate of difeafe are, he fays, either local 
or general. A large proportion of the cafes are owing to 
fome injury of the back. It is an old obfervation, that 
fuch injuries produce alkaline urine. Exceffive fatigue, 
Severe and protrafled debilitating palfions, are among the 
other general caufes of the affection, Its principal local 
caufes are irritations about the bladder or urethra , efpccially 
when operating for a conjider able length of time. This appears 
to be the leading feature in Dr. Prout’s views of the phof¬ 
phatic diathefis. It is certainly deferving of remark, that 
the fame view of the fubjefl had long ago been taken by 
Mr. Murray Forbes, who exprefsly dates, that, “when a 
foreign body gets into the bladder, it would operate bp ir¬ 
ritation, foas to occafion a redundancy of the phofphates.” 
The tranfition from the formation of lithic acid to the 
depofition of the phofphates is very curious. It takes 
place gradually through the lithate of ammonia, and is 
accompanied by the dil'appearance of the ufual colouring 
principle from the urine. The tranfition from the mul¬ 
berry-calculus to the phofphates takes place through a 
mixture of oxalate and carbonate of lime. The next 
layers are found to confift of the carbonate and phofphate 
of lime; and, ftill farther from the centre, the carbonate 
of lime difappears. Dr. Prout believes that wherever the 
change takes place ex abrupto, it is prefumable that fome 
time mull have elapfed between the depofition of the dif¬ 
ferent matters. It is a curious and important feature in 
the pathology of the urinary fyltem, that a decided depo¬ 
sition of the phofphates is never followed by a different 
depofite. 
When the depofition of the phofphates arrives at 
the magnitude of calculi, we have the three following 
kinds, as defcribed by chemical writers. 
Bone-earth, or phofphate of lime calculus .—This is of a 
pale brown colour, and fo fmooth as to appear polifhed. 
When fawn through, it is found very regularly lami¬ 
nated ; and the laminae, in general, adhere fo flightly to 
each other, as to Separate with eafe into concentric crufts. 
It diffolves entirely, though flowly, in muriatic or nitric 
acid. Expofed to the flame of the blow-pipe, it is at firft 
flightly charred, but foon becomes perfeftly white, re¬ 
taining its form, until urged with the utmoft heat from 
a common blow-pipe, when it may be completely fufed. 
It appears to be more fufible than the phofphate of lime, 
which forms the balls of bone ; a circumftance afcribed 
to the latter containing a larger quantity of lime. Cal¬ 
culi, altogether compofed of phofphate of lime, are rather 
uncommon. 
Triple calculus, or ammoniuco-magnefian phofphate .— 
Calculous maffes, confining folely of this fubftance, are 
perhaps never met with ; but concretions often occur, 
in which it obvioufly prevails; and, as Dr. Marcet ob- 
ferves, “this triple fait frequently appears alfo in the 
form of minute Sparkling cryftals, dift’ufed over the Sur¬ 
face, or between the interftices of other calculous laminse. 
Calculi, in which this triple fait prevails, are generally 
whiter and lefs compaft than thofe of the former clafs. 
When the blow-pipe is applied, an ammoniacal fmell is 
perceived, the fragment diminifhes in Size; and, if the 
heat be ftrongly urged, it ultimately undergoes an im¬ 
perfect fufion, being reduced to the ftate of phofphate of 
magnefia.” _ Dr. Wollafton defcribes the form of the 
cryftals of this fait, as beingd fhort trilateral prifm, having 
one angle a right angle, and the other two equal, termi¬ 
nated by a pyramid of three or fix Sides. Thefe cryftals 
349 
are but Sparingly Soluble in water, but very readily 
in moft, if not all, the acids; and on precipitation, they 
reaffume the cryftalline form. From the Solutions of thefe 
cryftals in muriatic acid, Sal ammoniac may be obtained 
by Sublimation. Solutions of cauftic alkalies difengage 
ammonia from the triple fait, the alkali combining with 
a portion of the phofphoric acid. 
Fufible calculus. —This is commonly whiter and more 
friable than any other Species. It Sometimes refembles a 
mafs of chalk, leaving a white duft on the fingers; and 
Separates ealily into layers or laminae, the interftices of 
which are often ftudded with Sparkling cryftals of the 
triple phofphate. At other times, it appears in the form 
of a Spongy and very-friable whitilh mafs, in which the 
laminated ftruflure is not obvious. Calculi of this kind 
often acquire a very large Size, and mould themfelves in 
the contracted cavity of the bladder, affuming that pear- 
fhaped form before alluded to, which Dr. Marcet has 
never obferved in any of the other Species of calculi, and 
which confifts in the ftone terminating, at its broader 
end, in a kind of peduncle, corresponding to the neck of 
the bladder. The chemical compofition of the fufible 
calculus is a mixture of the triple phofphate and phof¬ 
phate of lime. Thefe two Salts, which, when Separate, 
are infufible, or nearly lb, 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 ftiown in various ways. Thus, if it be pul verized, and 
acetic acid poured upon it, the triple cryftals will be 
readily dift'olved, while the phofphate of lime will Scarcely 
be aCted upon ; after which the muriatic acid will readily 
difl'olve the latter phofphate, leaving a Small refidue, 
confifting of lithic acid, a portion of which is always 
found mixed with the fufible calculus. 
The tendency to phofphatic depofition is cured with 
difficulty, especially in advanced cafes, when the aftual 
prefence of a ftone in the bladder forms a mechanical 
caufe of continued renal irritation. Even the French 
practitioners, fo Sanguine in their hopes of curing the 
lithic-acid depofitions by a vegetable diet and copious 
dilution, confefs their defpair in cafes of this kind. It 
may be remarked, however, that palliatives are particu¬ 
larly indicated. Large and frequent doles of opium may 
be given ; and it will be Some confolation to reflefl, that 
thefe medicines have Sometimes proved more than pal¬ 
liative; for that under a ftriCl attention to the ftate of 
the primae vise (and without this attention no medicine 
can do good), they have fufpended the depofition, and 
have reftored the patient, even though afflidled with ac¬ 
tual ftone, to a ftate of good health, by preventing the 
further morbid Secretion of the kidneys, and the conse¬ 
quent increafe of Size in the gravel or calculus. Befides 
this drug, Dr. Prout has prefcribed with good effeft a 
combination of uva urfi, muriatic acid, and hyofciamus, 
in the phofphatic diathefis. 
3. Mulberry Calculus, or Oxalate of Lime .—This is moft- 
ly of a dark-brown colour, and frequently its interior is 
grey. Its Surface is ufually uneven, presenting tubercles 
more or lefs prominent, frequently rounded, Sometimes 
pointed, and either rough or polifhed. It is very hard, 
difficult to Saw, and appears to confift of fucceffive une¬ 
qual layers. Excepting the few ftones which contain a 
proportion of Silica, it is the heavieft of the urinary con¬ 
cretions. The pure alkaline Solutions have no effeft upon 
this calculus, and the acids diffolve it with great difficulty. 
When it is reduced, however, to fine powder, both mu¬ 
riatic and nitric acids difl'olve it flowly. The Solutions 
of the alkaline carbonates decompofe it, as Fourcroy 
and Vauquelin have obferved; and this affords us the 
eafieft method of analyfing it. The calculus in powder 
being digefted in thfe Solution, carbonate of lime is Soon 
formed, which remains infoluble, and is eafily diftin- 
guifhed by the effervefcence produced by the addition of 
weak acetic acid, while there is obtained in Solution the 
compound of oxalic acid with the alkali of the alkaline 
carbonate. 
