654 
ON THERAPEUTICS. 
The way in which medicines produce these new actions is 
not a profitable subject for discussion, as the only conclusion 
at which we can arrive is, that the action is dependent on the 
property of the agent; and however far we pursue the inquiry 
we come at last to this halting point. The nature of the action 
we decide by experiment; the cause of it can only be a 
matter of speculation, and to refer it to the property possessed 
by the agent is as definite and satisfactory a course as any 
other. Certain agents, then, are found to possess the pro¬ 
perty or power of producing effects on the healthy animal 
similar to those resulting from disease, and upon the character 
of those effects will depend the classification of the agents. 
By a somewhat singular coincidence, we find upon exami¬ 
nation, that all our medicines may be arranged in classes, 
corresponding to the number and character of the principal 
elements of disease ; for instance, we find class one to contain 
agents capable of increasing action; corresponding to the 
element “ Excess.” In class two, we have agents capable of 
depressing action; corresponding to the element “ Defect.” 
And in class three, we arrange agents capable of producing a 
change in the characterof a secretion or a structure; correspond¬ 
ing to the third elementofdisease, “ Perversion,”whichconsists 
in a change in the composition of any portion of the animal 
body. This arrangement only collects a number of medicinal 
agents in groups, without specifying their particular pro¬ 
perties, which are easily indicated by a subdivision. 
Medicines which are excitant in their effects may be divided 
into the following : 
Cathartics. 
Stimulants. 
Diuretics. 
Diaphoretics. 
Tonics. 
Counter-irritants. 
It is not of course contended that all these are stimulants 
in the ordinary sense of the word, because the very first sub¬ 
division includes drugs which are powerfully depletive; 
but by the designation excitants , is meant that the immediate 
and characteristic action is such upon some portion or function 
of the body ; and that consequently all medicines of the first 
class possess the property of inducing the element “ excess.” 
Medicines which are depressing in their action, may be 
subdivided into 
'Narcotics. Refrigerants. 
Sedatives. Astringents. 
These are all characterised by the property of diminishing 
action, and consequently in reference to some portion or 
function of the body they induce the element “defect.” 
