PATHOLOGY. 
i 
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retie powers, or capable of ftisnulating tlie aftion of the 
kidneys, is very great, efpecially from the vegetable 
world. Many of them, however, are very inefficacious ; 
and it is the common imperfection of the whole of this 
clafs to be very uncertain in their operation : fometimes 
the more feeble diuretics will fucceed, when the ftronger 
have failed ; and often, after every variety of kind and 
combination has been tried, the fecretion of urine remains 
unaltered. Digitalis, fquill, mercury, and cryftals of 
tartar, feparately or combined, are the mod efficacious of 
the clafs; but the alkalies both fixed and volatile, fome 
of the neutral falts, the nitrous ether, the^terebinthates, 
See. are by no means ufelefs as auxiliaries. There is per¬ 
haps no clafs of medicines, in which a combination of 
two or more fubftances, poffeffing fimilar powers, is fo 
frequently important, as in that of the diuretics. Thus 
the ufe of potafs, joined with bitter vegetables, is recom¬ 
mended by fir John Pringle, as an efficacious medicine : 
and, as the alkaline fubftances may be often prevented, 
by purging, from reaching the kidneys, fo their diuretic 
effeft may be often more certainly fecured by giving an 
opiate at the fame time, according to the practice of Dr. 
Mead. A combination of the fquill, with digitalis, and 
fome of the lefs purgative preparations of mercury, as 
the common blue pill, is occafionally very aflive in its 
diuretic operation ; and, in children, or in old and feeble 
people, the union of the fpirit of nitrous ether, or of other 
diuretic fubftances, with the bark, or other vegetable to¬ 
nics, appears to be often very ferviceable. 
Diuretics, moreover, receive great additional power 
from perfeft fol'ution ; and it was remarked by Cullen, 
that the union of diluents with thefe fubftances was pro- 
duftive of the beft effefts. Diuretics are moll generally 
had recourfe to for the purpofe of determining fluids to 
the kidneys which were liable to be effufed ; and indeed 
they have been fuppofed to aft an important part in re¬ 
moving them when that procefs had occurred. If the 
latter luppofition be admitted, we muft fuppofe that a 
diuretic pofl'efies immediately the power of promoting 
abforption ; and of that we have no direft evidence. On 
the other hand, that diuretics can prevent the further 
accumulation of effufions is a faft of which we have 
llrong inference, and which is accordant with the inex¬ 
plicable law of derivation fo generally obferved. 
Diaphoretics are thofe fubftances which promote in- 
fenfible perfpiration, or fweat. Their modus operandi 
may be inferred to arife, either by direft application, or 
by nervous confent. If diaphoretics are affimilated, pafs 
into the round of the circulation, and are applied 
direftly to the cutaneous veflels, they may produce 
increaled contraftion, or the reverfe : or otherwife, the 
powerful fympathy obferved between moft parts of the 
mucous expanfions, and efpecially between the ftomach 
and (kin, authorife us to believe, that the contraftion or 
dilatation of the veflels of the flein may be produced by 
nervous excitement, firlt im prefled on the ftomach, thence 
propagated to the nervous general communication, and 
iaftly to their veflels; or, in other words, the effeft may 
be produced by fympathy. 
The older praflitioners took great pains with thefe 
medicines: the fudorific plan of treatment was the 
fruitful fource of miliary eruptions, and a variety of 
troublefoine complaints. The ufe of diaphoretics is at 
prefent much reftrifted, particularly thofe which increafe 
the general circulation. 
There are two means, by which perfpiration may be 
induced, and the aftion of fudorific medicines promoted ; 
namely, by application to the (kin, and ingefta. When 
the flein is not in a ftate unfavourable to perfpiration, 
the application of heat to the furface of the body, with¬ 
out any affiftance from powers internally applied, is fuffi- 
cient to produce fweating; and the application of cold, 
i. e. the abftraftion of the heat, canalmoft certainly pre¬ 
vent the fame, though confiderable powers are employed 
within. Thus fweating may be obtained by the heat of 
the air, applied as in what is called the dry bath, or by 
increafing the heat of the furface by previous warm 
bathing, or by accumulating the warm effluvia of the 
body itfelf upon its furface. This laft may be done by 
covering up the body very clofely with fuch coverings as 
may both prevent the efcape of the warm effluvia ariling 
from them, and at the fame time prevent the accefs of 
external cold. But, farther to favour the diaphoretic 
aftion, a quantity of warm liquid may be taken into the 
ftomach, which not only excites the general circulation, 
but particularly, by confent of the veflels on the furface 
of the body with the ftomach, excites the aftion of thofe 
veflels which pour out fweat. The ufe of warm liquids 
alone, efpecially in the morning, while in bed, where 
there is a general difpofition to perfpiration, is in flight 
febrile cafes an ample fudorific. Thefe two means, of 
covering up the body clofely, and taking warm liquids 
into the ftomach, are what we call the fudorific regimen; 
which will often anfwer alone the purpofe of exciting 
diaphorefis ; is often neceflary to the operation of fudo¬ 
rific medicines; and will always render their operation 
more complete and permanent. Cullen's Mat. Med. vol. ii. 
The combination of opium with fudorific medicines is 
valuable in two ways : the opium aids the operation of 
the fudorific, on the one hand ; and, on the other, the 
fudorific, by determining to the fkin, renders the ano¬ 
dyne effeft of the opium more certain and complete, and 
prevents fome of its unpleafant influence on the head : 
for opium, given when the flein is dry, or not accompa¬ 
nied by perfpiration in the courfe of its operation, is very 
apt to occafion reftleflnefs rather than fleep, and to pro¬ 
duce a flight approach to delirium, by its influence on 
the brain : hence the acknowledged value of the combi¬ 
nation which is univerfally known by the name of Dover's 
powder, as a fafe and aftive diaphoretic and anodyne ; 
it confifts of opium combined with the diaphoretics, ipe¬ 
cacuanha, and fulphate of potafs. 
Guaiacum too has been much praifed for its fudorific 
properties: Dr. Cullen confidered it to be one of the 
moft valuable of the ftimulant diaphoretics, becaufe it 
affords a matter which paffes more entirely to the ex¬ 
treme veflels, and feems to ftimulate the exhalents more 
in proportion than it does the heart and great arteries. 
By this means it is both a more fafe and more effeftual 
fudorific than thofe which ftimulate the latter almoft 
only : but acute rheumatilin, or rheumatic fever, as it is 
called, is almoft the only acute difeafe in which it can 
be recommended ; and it is a difeafe in which the fweat¬ 
ing is fpontaneoufly profufe, and bears ftimulants better 
than phlegmonous inflammations. 
Emmenagogues. —It has not been thought neceflary 
to treat particularly of emmenagogues, as they are moil 
of them general ftimulants, and are fo uncertain in their 
aftion that they can fcarcely be viewed as ftimulators of 
the uterus in particular. 
A few other minor divifions, are alfo commonly 
made; as Errhines, which aft on the mucous membrane 
of the nofe, &c. but thefe coniift of fo very fmall a num¬ 
ber of the pharmacopceal articles, that the mention of 
the fubftances themfelves would be lefs tedious than their 
claffification. 
There are fome articles in the materia medica which 
have been denominated general Jlimulants , from their 
effeft on the fyftem at large. They are little ufed at 
prefent in the praftice of phyfic, but were ftrongly re¬ 
commended by Brown, and confequently came into 
very general approbation during the time that author’s 
theories were triumphant. They obtained this diftinc- 
tion partly becaufe Brown was praftically and individu¬ 
ally acquainted with the healthy feelings they excited, 
but moftly becaufe their ufe naturally grew out of his 
theory of debility and excitement before noticed. 
Moft of thefe fubftances appear to influence the body 
by means of the nervous fyftem ; for the rapidity with 
which their aftion is elicited cannot allow us to fuppofe 
their 
