21 
The object of the Chemist being to ascertain the consti- 
tuents of all bodies, whether animal, vegetable, or mineral ; 
to investigate the way in which these constituents combine, 
and the nature of the compounds which they form ; his 
science must be admitted as indispensable as any for 
acquiring an accurate knowledge of natural bodies, more 
especially if we study them with a view to their employment 
as medicinal agents. These, as we have said, are seldom 
administered as afforded by nature, but undergo several opera- 
tions, some mechanical, others entirely chemical, constituting 
that branch of study called Pharmacy. For this, we require 
to be intimately acquainted with the laws of Chemistry, 
and the mutual action of bodies on each other, that we 
may not compound what are incongruous, or prescribe 
such as are incompatible. But the value of this science 
towards acquiring an accurate knowledge of Materia Medica 
is too well known to require being insisted on, whether we 
regard retrospective services or prospective aids. For I 
feel well assured, looking at the all-pervading grasp of 
Chemistry, and its recent achievements, that we shall every 
year be furnished with new agents and new forms, as well 
from the mineral, as from the vegetable kingdom ; more espe- 
cially if the chemical philosopher will subject to bis 
examination, not only those plants of which the uses are 
known, but the many others also which invite his atten- 
tion ; and to which he will be best, nay, easily guided, by 
attending to the Natural affinities of plants. 
But the most finished natural-historical description, the 
most accurate ascertainment of physical properties, the 
nicest analysis, or the most elegant preparation, form but 
a small, or, at least, only the preliminary portion of the 
duties which devolve upon the teacher or student of Materia 
Medica. For we have still to inquire, what are the 
Physiological action of medicines, or the changes effected by 
