342 
CHI EM ICO- PII YSIO LOGICAL CONSIDERATIONS ON 
first place, whether it be on account of their certainty of opera- 
tion, or of their energetic and extensive influence in the animal 
economy. 
Under the denomination of diuretics are included all such me- 
dicines as act particularly on the urinary passages, which secretions 
and excretions they render more active. Their most usual and 
constant effect is to augment the quantity of urine furnished by 
the kidneys in any given time; but they often likewise produce 
urine modified in its chemical composition, as also some change, 
physiological or pathological, in the secretory apparatus over which 
they exert their influence. 
Diuresis or acceleration of the secretion is not produced by 
diuretic medicines alone. This secretion, in its physiological 
condition even, presents an activity exceeding variable, capable 
of being modified afresh, under other circumstances, by a mul- 
titude of causes. These causes are, hygienic (alimentation), 
physiological (greater or less activity of the skin), pathological 
(asthenic diseases of the kidneys), pharmaceutical (a great number 
of medicaments and poisons). We must also take account of the 
natural or accidental variations of the urinary secretion in order to 
comprehend clearly diuretic medication. 
Diuretics are furnished by all the three kingdoms of nature, 
which account for their chemical composition being so variable. 
They may be administered through the tegumental surface or 
through the veins. Cutaneous friction is sometimes employed for 
small animals, and drinks for the large herbivora. The solid form 
is only adapted for active diuretics. Solution in some suitable 
liquid best insures the operation of the generality of diuretics. 
Diuretic drinks are administered either cold or hot. When hot, 
they are apt to exert more action on the skin. In whatever way- 
diuretics enter the circulating medium, once mingled with the 
blood, they make their way by a sort of elective affinity to the 
kidneys, which they excite, or through which they become filtered 
in some way, and so make their exit out of the system. Through 
such special action, varied by each diuretic, it is that acceleration 
of the urinary secretion is produced. 
These medicaments possess nothing in common save their evi- 
dent effect, viz. diuresis. In regard to the medium through 
which they individually or in groups produce this effect, it is as 
variable as their chemical nature. This will come to be better 
understood when we shall have investigated the nature of the 
urinary secretion, such as physiological chemistry, in these recent 
days, has determined it. 
Physiologically, the urinary secretion is essentially excrernen- 
titious ; that is to say, that the matters which it separates from 
