C H E M ] 
dant. This is conftantly found wit h the greateft part .of 
the before-mentioned fubftances in calculi. The uric 
acid alone is almolt entirely free from it, becaufe it is of 
itfelf a kind of peculiar organic compofition. But the 
earthy phofphats, the oxalat of lime, and the filex itfelf, 
never condenfe into calculous ftrata, plates, leaves, or 
cryftals, without borrowing from the urine a certain por¬ 
tion of animal matter, which is found in the ■whited: and 
mod: laliniform calculi. This matter is the caule of the 
fetid ftnell, of thefe concretions, and the black colour 
they obtain by calcination. 
Thefe difcoveries on the nature of calculi, led Four- 
croy and Vauquelin to undertake fome experiments for 
didolving them in the bladder by means of injedtions. 
They found that calculi compofed of uric acid and unit 
of ammoniac, dilfolved readily in water, which contained 
fo little cauflic alkali as not to caufe a dilagreeable fen- 
fation on the tongue. By very weak nitric and muriatic 
acids, they found they could diffolve fuch calculi, as were 
formed of ammoniaco-magnefian phofphat, calcareous 
phofphat, and oxalat of lime. 
Of Uric Acid. —This acid was formerly called the li- 
thic acid. It was difcovered by. Scheele; but Dr. Pearfon, 
in his Experiments on Calculi, publilhed in the Philofo- 
phical Tranfadlions of 1798, having fhewn the impro¬ 
priety of this term, the chemiifs have, in confequence, 
affixed to it the name of uric acid ; its combinations are 
called urats. 
We have already faid, that fome calculi are formed of 
the pure uric acid alone. This acid is always in the 
concrete form, and is not eafily foluble in water. Diftil- 
led in a retort, it is decornpoled, and partly fublimed. 
It decompofes the nitiic acid. It is completely decom- 
pofed, without fmell, in cauflic potafh weakened with 
water. If weak muriatic acid be added to the folution, 
the uric acid will be precipitated in cryltals. This acid 
unites with earths, alkalis, and metallic oxyds: it yields 
its bafes to the weakell vegetable acids, even to the car¬ 
bonic acid; therefore it is not foluble in alkaline car- 
bonats. 
OF the SALIVA, PANCREATIC JUICE, and GAS¬ 
TRIC JUICE. 
There is a great analogy between the faliva, and the 
pancreatic juice. The falivary glands, and the pancreas, 
have, in fact, a ftrudture entirely of the fame kind, and 
the ufe of the fluids, fecreted by thefe organs, appears to 
be the fame. Man. and quadrupeds, are the only animals 
in which the faliva exifts ; or at lead the falivary glands 
have not been oblerved in any other animals. No accu¬ 
rate chemical experiments have yet been made with thefe 
fluids. This circumftance may be attributed to the dif¬ 
ficulty of procuring them, even in very fmall quantities. 
It is only known, that the faliva is a very fluid juice, fepa- 
rated by the parotides, and many other glands, which con¬ 
tinually flows into the mouth, but molt abundantly during 
maftication. It appears to be of a faponaceous nature, 
impregnated with air, which renders it.frothy ; it leaves 
but a fmall refldue, when evaporated to drynefs ; but it 
forms, neverthelefs, certain falivary concretions in the 
palTages which convey it into the mouth. It appears to 
contain an ammoniacal fait, fince lime and cauflic fixed 
alkalis difengage from it a penetrating and urinous odour. 
Pringle, from experiment, concluded, that the faliva is 
very feptic, and that it favours digeflion, by exciting a 
commencement of putridity in the aliments, Spallan¬ 
zani, and many other modern phyficians, think, on the 
contrary, that it poffeffes the property of retarding and 
impeding putrefaftion. 
The gaftric juice is feparated by fmall glands, or the 
arterial extremities, which open into the internal tunic 
of the ftomach. The cefophagus likewife affords a fmall 
quantity, efpecially in the inferior region. Glands of 
conliderable magnitude are obferved in many birds, which 
open into very lenfible excretory duffs. Some modem 
1 
8 T R Y. 367 
philofophers have paid great attention to the gaftric juice. 
Spallanzini, Scopoli, Monch, Brugnatelli, Carminati, 
have, within die laft few years, examined the properties 
of this liquor. They colledled it in the ftomach of iheep 
and calves, by opening them, after having fuft'ered them 
to fall for fome time. They obtained it from carnivorous 
and gallinaceous birds, by caufing them to fwallow fpheres 
and tubes of metal, pierced with holes, and filled with 
very fine fiponge. Spallanzani examined the gaftric juice 
of his own ftomach, by procuring a vomit, or by fwalloiv- 
ing wooden tubes, filled with different fubftances, to 
judge of the effedt of the gaftric juice on each of them. 
The experiments with tubes had been before attempted 
by Reaumur. Goffe of Geneva had the courage to caufe 
himfelf to vomit a great number of times, by a procefs 
which is peculiar to himfelf, and conftfts in fwallowing 
the air. From all the modern obfervations, the gaftric 
juice appears to poffefs the following properties. 
It is the principal agent of digeftion, and changes the 
aliments into a kind of uniform foft pafte : it adls on the 
ftomach itfelf after the death of animals. Its eftedls fliew, 
that it is a folvent, but of that peculiar nature, that it 
diffolves animal and vegetable fubftances uniformly, and 
without exhibiting a ftronger affinity for the one than 
for the other. Far from being of the nature of a fer¬ 
ment, it is one of the moft powerful antifeptics we are 
acquainted with: and from the experiments of the phi¬ 
lofophers before cited, its nature appears to be eflentially 
different in the feveral dalles of animals. According to 
Brugnatelli, the gaftric juice of birds of prey, and grani- 
vorous birds, is very bitter, and compofed of a difen- 
gaged acid, refin, animal matter, and common fait; that 
of ruminating quadrupeds is very aqueous, turbid, and 
fait, containing ammoniac, an animal extradf, and com¬ 
mon fait. Morveau, having digefted portions of the in¬ 
ternal tunic of the ftomach of the calf in water, found 
that it has an acid character. Spallanzani thinks, that this 
charadler depends on the aliments, as he never found the 
acid gaftric juice in the ftomach of carnivorous animals, 
but always in thofe which feed on grain. Goffe made 
the fame obfervation on himfelf, after having ufed crude 
vegetables for a long time. Brugnatelli thinks, that the 
white matter, in the excrements of carnivorous birds, 
contains pholphoric acid; but Morveau obferves, that 
his experiments are not conclufive. Scoppuli found mu- 
riat of ammoniac, and fufpedts that the muriatic acid is 
produced by the vital power of animals; but no decifive 
fadt has been brought in fupport of this opinion ; every 
circumftance, on the contrary, tends to ffiew, that this 
acid comes from the food. Macquart and Vauquelin 
have found that the gaflric juices of the ox, calf, and 
ftieep, are conftantly poffeffed of an acid charadler; but 
it appears from their accurate experiments, that it is the 
dilengaged pholphoric acid which gives to them this 
charadler. They have alfo difcovered that thele juices 
alter and loon putrefy. The gaftric juice of carnivorous 
animals pofieffes the antifeptic qualities in the liigheft: 
degree. 
Hence it may be concluded, 1. That the gaftric juice 
is not well known ; z. That it appears to be different in 
feveral claffes of animals, and in the fame animal, accord¬ 
ing to the diverfity of food ; 3. That no proof has been 
brought to fliew that it is a peculiar acid, and that we 
(liould acknowledge the exiftence of a gaftric juice; 4. 
That its moft remarkable property conlilts in its great 
lblvent power, which extends even to bony and metallic 
fubftances; and it is even faid to be capable of attacking 
ftliceous ftones; an indifference or equal attradfion for 
the matter it adls on. Its very ftrong antifeptic quality, 
which it communicates to all the bodies it is mixed with, 
and which even puts a flop to putrefadHon, in fubftances 
which have already begun to be changed by that procefs, 
has excited a greater degree of attention than the others. 
Carminati, Jurine, and Toggai, have applied the gaftric 
juice on wounds. Carminati has even ufed it internally; 
and 
