MATERIA MEDIC A. 
617 
greasy matter, or infused in water or vinegar, it is sometimes 
employed externally, in order to destroy vermin of different sorts 
on the skin. 
Third Class of Special Excitants, 
MEDICINES WHICH ACT MORE PARTICULARLY ON THE KIDNEYS, AND 
TEND TO INCREASE THE SECRETION OF URINE. 
Diuretics. 
Diuretics do not usually exercise any primitive general in¬ 
fluence ; that is to say, they do not primarily modify either the 
digestion or the circulation, or the greater part of the other 
functions. Their immediate effect does not extend beyond a 
simple diuresis. Under itheir influence the urine is not only 
increased in quantity, but often changed in quality; thus, after 
the use of turpentine, it strongly yields the odour of a violet. 
Diuretic medicine, in diminishing the aqueous part of the blood, 
gives a new activity to the interstitial absorption, and particularly 
to that which takes place in the areoise of the cellular tissue, and in 
the great splanchnic cavities. It is thus that we explain the species 
of revulsion which this medicine seems to produce in certain cases; 
for we cannot believe that the renal excitation which accompanies 
it is capable of being the only and essential cause of these phe¬ 
nomena. But, however that may be, diuretics are plainly in¬ 
dicated in most species of dropsy, in anasarca, in the rot in sheep, 
in oedema, in grease, and in many other cutaneous affections. 
There are some diuretics which, with moderate care, pass from 
the primse vise into the circulation, without producing any local 
irritation, and that can, therefore, be employed with advantage in 
the treatment of inflammatory diseases. Such are nitre, and 
other diuretic salts. But there are others more essentially irri¬ 
tating, such as resinous diuretics, and which would generally be 
prejudicial in such diseases. Although the first are rarely contra¬ 
indicated in an imperious manner, there are nevertheless some 
circumstances in which they can do much mischief. It is so in 
retention of urine, when we often see them aggravating the 
sufferings of the patient by increasing the quantity of that fluid, 
which ought not to be secreted at all, and the presence of which 
in the bladder makes us fear the most fatal accident every 
minute. It is bad practice, then, to have recourse to diuretic 
medicine in these cases; nor is it often employed in irritation of 
the urinal passages. If it is administered, it is of the mildest 
nature, and dissolved in a great quantity of bland fluid. This 
precaution is particularly important when the kidneys are the 
scat of inflammation ; for every cause of direct excitation of that 
part cannot then fail of aggravating the evil. 
