320 INTRODUCTORY LECTURE. 
heart as indicated by the pulse, upon the temperature of the 
body, upon the secretions, and in fine upon all the healthy 
functions. Note all these effects carefully as you observe 
them; but at the same time be very cautious not to confound 
those changes in the system which may result from mental 
influence, or from the operation of ordinary or accidental 
causes, with those which are the genuine product of the medi- 
cine. Do not be satisfied with a single trial in each case, but 
repeat it with varying circumstances till there can no longer 
be a doubt of the actual effect produced. 
When you have sufficiently convinced yourselves of the ef- 
ficiency of the medicine, and ascertained its peculiar physiolo- 
gical action, you are next to apply it to the treatment of dis- 
ease; and here the same caution is requisite not to allow 
yourselves to be misguided by the influence of various dis- 
turbing agencies, nor to make hasty conclusions from one or 
a few trials. There is nothing in relation to which we are 
more apt to draw false inferences than the action of medicine 
in disease. Most complaints have a tendency to spontaneous 
cure, and will in general go on sooner or later to recovery, 
without the use, and often notwithstanding the use of medi- 
cine. In such cases, the last drug administered is apt to have 
the credit of the cure, though all its operation may have been 
to protract this result. There are a thousand causes which 
operate on the system in disease giving rise to changes not an- 
ticipated, which, without due caution, may be ascribed to the 
remedies employed. Against all these sources of error you 
must be on your guard, and above all against your own hopes, 
which will act powerfully in causing you to see things as you 
wish them. 
Other points which will require investigation are the part 
or parts of the plant most effective, its relations to the usual 
menstrua employed in pharmacy, as water and alcohol, the 
best mode of administration, and the dose. Its composition 
and general chemical relations are also important objects of 
inquiry; but few medical men, and none who have not devot- 
ed an especial attention to practical chemistry, are capable of 
