24 
DIURETICS AND THEIR USES. 
duced. In the case of indirect diuretics, however, the fact is 
different, their effects being caused through the system 
generally, rather than by any positive action on the glands 
themselves. Some of these produce diuresis secondarily, 
the primary effect being manifested on the absorbent system 
generally, whereby the blood becomes charged with water, 
and the kidneys are then called upon to excrete it from the 
blood. Mercury and iodine, were adduced as examples of 
this class. Other indirect diuretics act primarily on the 
stomach, and secondarily upon the kidneys, this end being 
accomplished either by lessening arterial action, and thereby 
promoting absorption, or by increasing the quality of the 
blood, and so causing the kidneys to share in the general 
improvement of the body. Examples of this kind are seen 
in digitalis and the preparations of iron. The beneficial 
effects of digitalis in cases of dropsy were then discussed, as 
was also the necessity of relieving the portal system in cases 
where the liver and its veins were gorged and congested, 
before we could hope to rouse the renal glands to increased 
action. Colchicum, mercury, and taraxacum were instanced 
as examples of diuretics acting indirectly by relieving the 
portal system, if congestion be present. The circumstances 
modifying the action of diuretics were stated to be — 1. The 
state of the skin, a profuse perspiration preventing the estab- 
lishment of a full diuresis. 2. Active catharsis suspends the 
operation of diuretics by diverting the fluid of the system 
from the -kidneys to the intestinal glands; a good instance 
of the kind being seen in Asiatic cholera, in which the 
kidneys do not act, simply because all the fluid of the body 
is drained off by the stomach and intestines. 3. No obstruc- 
tion must exist in the course of the intestinal canal to prevent 
the flow of the-medicine swallowed, as shown by Dr. Barlow. 
4. If there be extensive disorganization of the kidney, the 
due secretion of urine cannot take place. 5 . If the anasarca 
or ascites be very extensive, the pressure consequent upon it, 
acting upon the veins and lymphatics, prevents the absorp- 
tion of the remedies, and of the fluid to be evacuated. In 
these cases, tapping or puncturation of the limbs must first 
be resorted to, and then, the pressure being removed, the 
kidneys are more easily stimulated by the action of diu- 
retics. The subject of the dilution of the saline diuretics 
was then alluded to, and as their absorption was considered 
to depend upon the ordinary principles of endosmose and 
exosmose, the opinion that to be absorbed, and to act as 
diuretics, they must be so far diluted as to be below the 
specific gravity of the serum of the blood, was upheld; other- 
